ilitjrarp 


ANATOMY 

|)KSCRIITIVE  AND  APPLIED 


BY 

HENRY  GRAY,  F.R.S. 

FELLOW    OF   THE    ROYAL    COLLEGE   OF  SURGEONS;  LECTURER  ON  ANATOMY  AT   ST.    GEORGE's 
HOSPITAL  MEDICAL  SCHOOL,    LONDON 


A  NEW  AMERICAN 

FROM  THE  EICtHTEENTH  ENGLISH  EDITION 
THOROUGHLY  REVISED  AND  RE-EDITED 

AVITH  THE  BASLE  ANATOMICAL  NOMENCLATUEE 

IN  ENGLISH 


BY 

ROBERT  HOWDEN,  M.A.,  M.B.,  CM. 

PROFESSOR    OF    ANATOMY   IN  THE    UNIVERSITY    OF   DURHAM,    ENGLAND 


1I^u9trate^  wttb  1126  jeuQravinQS 


LEA  &  FEBIGER 

PHILADELPHIA   AND    NEW   YORK 
1913 


a  11 


Entered  according  to  the  Act  of  Congress,  in  the  3'ear  1913,  by 

LEA   &   FEBIGER 
in  the  Office  of  the  Librarian  of  Congress.     All  rights  reserved. 


THE   FIRST   EDITION    OF    THIS    WORK 


WAS    DEDICATED   TO 


SIR  BENJAMIN  COLLINS  BRODTE,  Bart.,  F.R.S.,  D.C.L. 

IN    ADMIRATION    OF 

HIS    GREAT   TALENTS 

AND    IN    REMEMBRANCE    OF 

MANY    ACTS    OF    KINDNESS    SHOWN   TO    THE    ORIGINAL 

AUTHOR    OF    THE    BOOK 

FROM   AN 

EARLY    PERIOD    OF    HIS    PROFESSIONAL    CAREER 


PREFACE. 


nnHE  outstanding  modification  in  the  text  of  this  edition  is  the  use  of  the  Basle 
nomenclature.  Except  in  one  or  two  instances,  this  nomenclature  has  been 
adopted  in  its  entirety;  in  most  cases  English  translations  of  the  Latin  terms 
are  employed,  but  in  those  cases  where  the  Latin  terms  have  become  fixed  by 
routine  usage  it  has  been  deemed  desirable  to  retain  them.  Where  the  Basle 
nomenclature  differs  materially  from  the  older  terminology,  the  latter  has  been 
added  in  brackets,  and  for  further  convenience  a  glossary  is  appended  showing 
(a)  the  terms  adopted  in  the  text,  (b)  the  Basle,  and  (c)  the  old  terminology. 

The  paragraphs  on  Surface  Anatomy,  which  in  previous  editions  were  appended 
separatel}^  to  the  descriptions  of  the  various  structures,  have  been  collected  and 
recast  into  a  special  chapter — an  arrangement  which  admits  of  more  easy  reference. 

The  section  on  Histology  has  been  shortened.  The  elementary  tissues  are 
described  in  it,  but  the  complex  tissues  are  considered  along  with,  the  organs  to 
which  they  are  specially  related.  The  whole  text  has  been  thoroughly  revised 
and,  where  necessary,  rewritten. 

About  two  hundred  new  engravings  have  been  added;  some  of  them  replace 
older  figures,  but  many  are  additional,  and  the  majority  are  drawn  from  original 
preparations. 

The  notes  on  Applied  Anatomy  have  been  revised  by  A.  J.  Jex-Blake,  jNI.A., 
M.B.,  B.Ch.,  F.R.C.P.,  Assistant  Physician  to  St.  George's  Hospital,  London, 
and  W.  Fedde  Fedden,  M.S.,  F.R.C.S.,  Assistant  Surgeon  and  Lecturer  on 
Surgical  Anatomy  in  St.  George's  Hospital,  London,  England. 

I  am  deeply  indebted  to  Dr.  J.  Ackworth  Menzies,  Lecturer  on  Physiology, 
and  to  Drs.  J.  Dunlop  Lickley  and  J.  C.  Boileau  Grant,  Demonstrators  of 
Anatomy  in  this  University.  Dr.  Menzies  revised  the  histological  part  of  the 
book,  and  furnished  a  number  of  microscopic  preparations  for  drawings.  Dr. 
Lickley  helped  to  revise  the  text,  arranged  the  chapter  on  Surface  Anatomy  and 
Surface  jNIarkings,  and  passed  the  book  through  the  press.  Dr.  Grant  prepared 
the  dissections  for  the  new  illustrations  and  assisted  in  the  revision  of  the  text. 

I  am  also  indebted  to  that  skilled  anatomical  artist  Mr.  Sydney  T.  Sewell, 
who  made  the  drawings  for  the  new  illustrations  and  who  spared  no  pains  to 
produce  clear  and  accurate  figures. 

ROBERT  HOWDEN. 

University  of  Durham  College  of  Medicine, 
Newcastle-upon-Tyne,  1913. 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 

Open  Knowledge  Commons 


http://www.archive.org/details/anatomydescripti1913gray 


PUBLISHPJRS'  NOTE. 


Books,  like  men,  have  characters  that  can  be  analyzed  to  a  certain  point,  but 
beyond  or  below  lies  a  quality,  subtle  as  life,  and  incapable  of  analysis  or  imitation, 
which  is  called  personality.  The  greater  the  author,  and  the  more  intense  his 
mental  action  in  creating  his  book,  the  more  it  partakes  of  this  element.  This 
principle,  so  clear  as  to  be  almost  axiomatic,  is  illustrated  to  the  fullest  extent 
in  the  work  in  hand.  Henry  Gray  combined  two  faculties,  either  one  sufficient 
to  make  his  name  famous.  He  was  a  great  anatomist  and  a  great  teacher.  He 
possessed  a  thorough  knowledge  of  anatomy  and  an  equal  insight  into  the  best 
methods  of  imparting  it  to  other  minds.  His  text  was  unequalled  in  clearness, 
and  he  united  with  it  a  series  of  incomparable  illustrations.  He  devised  the  method 
of  engraving  the  names  of  the  parts  directly  upon  them,  thereby  exliibiting  at  a 
glance  not  only  their  nomenclature,  but  also  their  position,  extent,  and  relations. 
His  work,  still  unique  in  this  respect,  was  also  the  first  to  employ  colors.  Summing 
all,  it  is  hardly  to  be  wondered  at  that  students  and  teachers  alike  find  their  labors 
reduced  and  the  permanence  of  knowledge  increased  by  the  use  of  this  book. 

On  its  original  appearance,  over  half  a  centur}'  ago,  Gray  immediately  took  the 
leading  place,  and  it  has  not  only  maintained  its  position  in  its  own  subject,  but 
has  also  become  the  best-known  work  in  all  medical  literature.  It  is  incomparably 
the  greatest  text-book  in  medicine,  measured  by  the  number  of  students  who  use 
it,  and  it  is  unique  also  in  being  the  one  work  which  is  certain  to  be  carried  from 
college  to  afford  guidance  in  the  basic  questions  underlying  practice. 

The  consequent  demand  is  evidenced  in  the  number  of  editions,  which  collec- 
tively represent  the  labors  of  many  of  the  leading  anatomists  since  the  early  death 
of  its  talented  author.  In  this  new  revision  every  line  has  been  carefully  considered, 
any  possible  obscurity  has  been  clarified,  the  latest  accessions  to  anatomical 
knowledge  have  been  introduced,  and  much  has  been  rewritten.  Care  has  been 
exercised  to  make  the  text  a  homogeneous,  sequential,  and  complete  presentation 
of  the  subject,  meeting  every  need  of  the  student,  physician,  or  surgeon. 

As  directions  are  given  for  dissecting,  this  volume  will  serve  every  requirement 
of  the  student  throughout  his  course.  The  Basle  Anatomical  Nomenclature  in 
English  has  been  used  in  the  text  and  on  the  engravings,  this  being  preferable  to 
the  Latin  form  in  the  judgment  of  such  eminent  anatomists  as  Professor  Howden 
and  Professor  ^Nlall.  A  Glossary  exhibiting  the  three  accepted  nomenclatures 
in  parallel  columns  will  be  found  a  great  convenience.  The  Table  of  Contents  is 
so  arranged  as  to  give  a  complete  conspectus  of  anatomy,  a  feature  of  obvious 
value.  The  whole  book  is  thoroughly'-  organized  in  its  headings  and  the  sequence 
of  subjects,  so  that  the  student  receives  his  knowledge  of  the  parts  in  their 
anatomical  dependence. 

As  a  teaching  instrument  the  new  Gray's  Anatomy  embodies  all  that  careful 
thought  and  unstinted  expenditure  can  combine  in  a  text-book. 


CONTENTS. 


HISTOLOGY. 


The  Animal  Cell. 


Protoplasm 
Nucleus    .... 
Reproduction  of  Cells 

Prophase 

Metaphase  . 

Anaphase 

Telophase 


Epithelium. 


Pavement    Epi- 


Simple  Epithelium   . 

Simple    Squamous 

thelium 

Columnar  or  Cylindrical  Epithelium 

Glandular  Epithelium        .... 

Ciliated  Epithelium 

Stratified  Epithelium 

Transitional  Epithelium 


Connective  Tissue. 

The  Connective  Tissues  Proper     .... 

Areolar  Tissue 

Adipose  Tissue 

White  Fibrous  Tissue 

Yellow  Elastic  Tissue 

Mucous  Tissue 

Retiform  or  Reticular  Tissue 

Basement  Membranes 

Vessels  and  Nerves  of  Connective  Tissue 

Pigment 

Applied  Anatomy 

Development  of  Connective  Tissue  . 


33 
34 
34 
35 
36 
36 
36 


37 

37 
37 
37 
37 
39 
40 


40 
40 
42 
43 
44 
44 
44 
45 
46 
46 
46 
47 


Cartilage 

Hyaline  Cartilage 

White  Fibrocartilage    .... 

Yellow  or  Elastic  Fibrocartilage 
Bone 

Structure  and  Physical  Properties 

Periosteum 

Marrow 

Vessels  and  Nerves  of  Bone    . 

Ossification 

Applied  Anatomj- 


The  Circulating  Fluids. 

Blood        

General  Composition  of  the  Blood 
Lymph 


The  Muscular  Tissue. 

Striped  or  Voluntary  Muscle   .... 

Vessels  and  Nerves  of  Striped  Muscle 
Unstriped  Plain  or  Involuntary  Muscle  . 
Cardiac  Muscular  Tissue      .      .  .      . 

Development  of  Muscle  Fibres 


47 
47 
49 
50 
50 
50 
51 
51 
52 
56 
59 


61 
61 
64 


64 
67 
67 
68 
69 


The  Nervous  Tissue. 

Neuroglia 70 

Nerve  Cells 70 

Nerve  Fibres 73 

Wallerian  Degeneration 76 

Non-medullated  Fibres 76 


EMBRYOLOGY. 


The  Ovum. 


Yolk   ...... 

Germinal  Vesicle 
Coverings  of  the  Ovum 
Maturation  of  the  Ovum 


The  Spermatozoon 

Fertilization  of  the  Ovum 

Segmentation  of  the  Fertilized  Oviun. 


The 


Formation    of    the 


Primitive    Streak 
Mesoderm 
Ectoderm 
Entoderm 
Mesoderm    . 


The  Neural  Groove  and  Tube 
The  Notochord  . 
The  Primitive  Segments 


Separation  of  the  Embryo  92 

The   Yolk-sac   ....        93 


Development  of  the  Fetal  Membranes  and  Placenta. 

The  Allantois 93 

The  Amnion 94 

The  Umbilical  Cord  and  Body-stalk  ...  96 

Implantation  or  Imbedding  of  the  Ovum      .  97 

The  Decidua  • 98 

The  Chorion 99 

The  Placenta 100 

Fetal  Portion 100 

Maternal  Portion 100 

Separation  of  the  Placenta                  .  101 


Development  of  the  Parieties. 

The  Skeleton 102 

The  Vertebral  Column 102 

The  Ribs 104 


12 


CONTENTS 


The  Skeleton— 

The  Sternum 105 

The  Skull 105 

The  Nose  and  Face Ill 

The  Limbs 113 

Development  of  the  Joints  115 

Development  of  the  Muscles  116 

Development  of  the  Skin,  Glands,  and 

Soft  Parts       .       .       .       .  116 

Development  of  the  Nervous  System  and  Sense 
Organs. 


The  Medulla  Spinalis 

The  Spinal  Nerves 

The  Brain 

The  Rhombencephalon  or  Hind-brain 

The  Mesencephalon  or  Mid-brain     . 

The  Prosencephalon  or  Fore-brain    . 
The  Diencephalon 
The  Telencephalon 
The  Cerebral  Nerves     . 
The  Sympathetic  System 

Chromaffin  Organs 
The  Suprarenal  Glands 
The  Nose       .... 

The  Eye 

The  Ear 


Development  of  the  Valvular  System. 


Further  Development  of  the  Heart 

The  Valves  of  the  Heart  . 
Further  Development  of  the  Arteries 

The  Anterior  Ventral  Aortse  . 

The  Aortic  Arches 

The  Dorsal  Aortse         .       .       . 
Further  Development  of  the  Veins 

The  Visceral  Veins 

The  Parietal  Veins 

Inferior  Vena  Cava 


117 
119 
120 
122 
125 
125 
126 
127 
132 
133 
133 
134 
134 
134 
138 


145 
151 
152 
152 
153 
154 
155 
155 
157 
157 


Peculiarities  of  the  Fetal  Heart     ....      161 
The  Lymphatic  Vessels 161 

Developmejit  of  the  Digestive  and  Respiratory 
Apparatus. 


The  Digestive  Tube 

The  Mouth        .      . 

The  Salivary  Glands 

The  Tongue       .       . 

The  Thyroid  Gland 

The  Palatine  Tonsils 

The  Thymus      .       . 

The  Parathyroid  Bodies 

The  Hjrpophysis  Cerebri 

Further  Development  of  the 
Tube 

The  Rectum  and  Anal  Canal 

The  Liver 

The  Pancreas    .... 

The  Spleen 

The  Respiratory  Organs 


D 


igestive 


Developinent  of  the  Body  Cavities 


162 
163 
164 
164 
165 
165 
165 
166 
166 

168 
172 
174 
175 
176 
176 

178 


Development  of  the   Urinary  and  Generative 
Organs. 


The 
The 


The 
The 


The 
The 
The 
The 
The 


and 


Pronephros  and  Wolffian  Duct    . 
Mesonephros,     Miillerian     Duct, 

Genital  Glands 

Ovary 

Testis 

Descent  of  the  Testes 
Descent  of  the  Ovaries      ... 
Metanephros  and  the  Permanent  Kidney 
Urinary  Bladder     .... 

Prostate 

External  Organs  of  Generation 
Urethra 


180 

180 
184 
186 
186 
187 
187 
188 
189 
190 
190 


The  Form  of  the  Embryo  at  Different  Stages 

of  its  Growth  .       .       .      :       .       .191 


OSTEOLOGY. 


Long  Bones  . 
Short  Bones  . 
Flat  Bones     . 
Irregular  Bones  . 
Surfaces  of  Bones 


The  Vertebral  Column. 
General  Characteristics  of  a  Vertebra. 


The  Cervical  Vertebrae 

The  First  Cervical  Vertebra  . 
The  Second  Cervical  Vertebra 
The  Seventh  Cervical  Vertebra 

The  Thoracic  Vertebra 

The  First  Thoracic  Vertebra 
The  Ninth  Thoracic  Vertebra 
The  Tenth  Thoracic  Vertebra 
The  Eleventh  Thoracic  Vertebra 
The  Twelfth  Thoracic  Vertebra 

The  Lumbar  Vertebrae 

The  Fifth  Lumbar  Vertebra  . 

The  Sacral  and  Coccygeal  Vertebrae 

The  Sacrum 

The  Coccyx • 

Ossification  of  the  Vertebral  Column 


The  Vertebral  Column  as  a  Whole. 


Curves 
Surfaces 


198 
199 
200 
201 
201 
203 
204 
204 
204 
204 
204 
205 
205 
206 
209 
210 


212 
213 


195  Base    .... 

196  Vertebral  Canal 
196    Applied  Anatomy 
196 
196 

The  Thorax. 

Boundaries 
The  Sternum 

Manubrium 
Body 

Xiphoid  Process 
The  Ribs 

Common  Characteristics  of  the  Ribs 
Peculiar  Ribs 
First  Rib 
Second  Rib 
Tenth  Rib 

Eleventh  and  Twelfth  Ribs 
The  Costal  Cartilages    .... 
Applied  Anatomy 


The  Skull. 
The  Cranial  Bones. 


The  Occipital  Bone 
The  Squama 
Lateral  Parts 
Basilar  Parts 

The  Parietal  Bone 


214 
214 
214 


216 
216 
216 
218 
220 
220 
221 
223 
223 
224 
224 
224 
224 
225 


227 
227 
229 
230 
231 


The  Frontal  Boue 

Sqiuiiua        .... 

Orbital  or  Horizontal  Par 
The  Temporal  Bone 

The  Squama 

Mastoid  Portion 

Petrous  Portion 

Tympanic  Part 

Styloid  Process 
The  Sphenoidal  Bone    . 

Body 

The  Great  Wings   . 

The  Small  ^^■in!J:s    . 

Pterygoid  Processes 

The  Sphenoidal  Concha? 
Ethmoidal  bono 

Crihrifonu  plate 

Pcrpciulicular  Plate 

Lal)\  rinth  or  Lateral  Mass 
Sutural  or  Wormian  Bones 
Applied  Anatomy 


The  Facial  Bones. 

The  Nasal  Bones 

The  Maxillte  (Upper  Jaw) 

The  Maxillary  Sinus  or  Antrum  of  High- 
more   259 

The  Zygomatic  Process 260 

The  Frontal  Process 260 

The  Alveolar  Process 260 

The  Palatine  Process 260 

Changes  Produced  in  the  Maxilla  by  Age  262 

The  Lacrimal  Bone 263 

The  Zygomatic  Bone 263 

The  Palatine  Bone 265 

The  Horizontal  Part 266 

The  Vertical  Part .266 

The  Pyramidal  Process  or  Tuberosity    .  267 

The  Orbital  Process 267 

The  Sphenoidal  Process 268 

The  Inferior  Nasal  Concha 268 

The  Vomer 269 

Applied  Anatomy 271 

The  Mandible  (Lower  Jaw)      .      .      .      .      .271 
Changes  Produced  in  the  Mandible  by 

A-e 275 

The  Hyoid  Bone 275 

Applied  Anatomy 277 


CONTENTS 

.      233 

The  Scapula 

.      234 

The  Spine 

.      235 

The  Acromion  .... 

.      237 

The  Coracoid  Process 

.      237 

Applied  Anatomy  . 

.      239 

The  Humerus 

241 

Upi)er  Extremity    . 

243 

The  Head      .  .       .       ■ 

244 

The  Anatomical  Neck 

.      245 

The  Greater  Tubercle 

24G 

The  Lesser  Tubercle 

.      248 

The  Body  or  Shaft     . 

249 

The  Lower  Extremity 

.      250 

Applied  Anatomy  . 

250 

The  Ulna 

.      251 

The  Upper  Extremity 

252 

The  Olecranon 

.      252 

The  Coronoid  Process 

253 

The  Semilunar  Notch 

255 

The  Radial  Notch 

.      255 

The  Body  or  Shaft       .      . 

The  Lower  Extremity 

The  Radius 

The  Upper  Extremity 

255 

The  Body  or  Shaft       .      . 

.      256 

The  Lower  Extremity 

13 


304 
306 
306 
307 
309 
309 
309 
309 
309 
309 
309 
311 
312 
313 
314 
315 
315 
315 
315 
318 
318 
318 
319 
320 
320 
321 


The  Exterior  of  the  Skull. 


Norma  Verticalis      .... 

Norma  Basalis 

Norma  Lateralis       .... 

The  Temporal  Fossa    . 

The  Infratemporal  Fossa 

The  Pterygopalatine  Fossa 
Norma  Occipitalis  .... 
Norma  Frontalis  ... 

The  Orbits  .  .      . 


The  Interior  of  the  Skull. 

Inner  Surface  of  the  Skull-cap 

Under  Surface  of  the  Base  of  the  Skull 

The  Anterior  Fossa 

The  Middle  Fossa 

The  Posterior  Fossa 
The  Nasal  Cavities 

Anterior  Nasal  Aperture 
Differences  in  the  Skull  Due  to  Age 
Sexual  Differences  in  the  Skull 
Craniology     .      .-     . 
Applied  Anatomy     .... 


The  Extremities. 

The  Bones  of  the   Uj^per  Extremity. 

The  Clavicle 

The  Sternal  Extremity  .... 
The  Acromial  Extremity  .... 
Applied  Anatomy 


277 
278 
281 
282 
283 
284 
284 
285 
286 


288 
288 
288 
290 
291 
292 
294 
294 
295 


Applied  Anatomy  of  the  Ulna  and  Radius    321 
The  Hand. 

The  Carpus 323 

Common  Characteristics  of  the  Carpal 

Bones 323 

Bones  of  the  Proximal  Row    ....  323 

The  Naviculaj-  Bone        ....  323 

The  Lunate  Bone 323 

The  Triangular  Bone       ....  324 

The  Pisiform  Bone 326 

Bones  of  the  Distal  Row         ....  326 

The  Greater  Multangular  Bone  326 

The  Lesser  Multangular  Bone   .  327 

The  Capitate  Bone 327 

The  Hamate  Bone 328 

The  Metacarpus 329 

Common  Characteristics  of  the  Meta- 
carpal Bones 329 

Characteristics  of  the  Individual  Meta- 
carpal Bones 329 

The  First  Metacarpal  Bone  329 

The  Second  Metacarpal  Bone          .  329 

The  Third  Metacarpal  Bone  330 

The  Fourth  Metacarpal  Bone    .  330 

The  Fifth  Metacarpal  Bone  330 

The  Phalanges  of  the  Hand 331 

Ossification  of  the  Bones  of  the  Hand     .  331 

Applied  Anatomy  of  the  Bones  of  the  Hand  332 

The  Bones  of  the  Lower  Extremity. 

The  Hip  Bone     . 
The  Ilium    . 

The  Body 

The  Ala 
The  Ischium 

The  Body 

The  Superior  Ramus 

The  Inferior  Ramus 
The  Pubis    .... 

The  Body         .      . 

The  Superior  Ramus 

The  Inferior  Ramus 
The  Acetabulum     . 

The  Obturator  Foramen 
The  Pelvis 


295  i  The  Greater  or  False  Pelvis 

297  ;  The  Lesser  or  True  Pelvis 

Axes 

Position  of  the  Pelvis 

Differences-  between  Male  and 
Pelves 

Applied  Anatomy  . 

The  Femur 

301  :  The  Upper  Extremity 

303  '  The  Head 

303  !  The  Neck  .... 

303  '  The  Trochanters  . 


Female 


333 
333 
333 
333 
336 
336 
337 
337 
337 
337 
337 
338 
339 
339 
340 
340 
340 
342 
342 

343 
344 
345 
345 
345 
345 
346 


14 


CONTENTS 


The  Femur — 

The  Bodv  or  Shaft, 348 

The  Lower  Extremity 349 

Applied  Anatomy         352 

The  PateUa 354 

Applied  Anatomy 355 

The  Tibia 355 

The  Upper  Extremity 355 

The  Body  or  Shaft 356 

The  Lower  Extremity 358 

The  Fibula 359 

The  Upper  Extremity  or  Head    .  359 

The  Body  or  Shaft 359 

The     Lower     Extremity     or     Lateral 

Malleolus 360 

Applied    Anatomy    of    the    Tibia    and 

Fibula 361 


The  Foot. 


The  Tarsus    .      . 
The  Calcaneus 


362 

362 


The  Tarsus— 

The  Talus 

The  Cuboid  Bone 

The  Navicular  Bone 

The  First  Cuneiform  Bone 
The  Second  Cuneiform  Bone 
The  Third  Cuneiform  Bone    . 

The  Metatarsus 

Common  Characteristics  of  the   Meta 

tarsal  Bones 

Characteristics  of  the  Individual  Meta 

tarsal  Bones 

The  First  Metatarsal  Bone  . 
The  Second  Metatarsal  Bone 
The  Third  Metatarsal  Bone 
The  Fourth  Metatarsal  Bone     . 
The  Fifth  Metatarsal  Bone 

The  Phalanges  of  the  Foot 

Ossification  of  the  Bones  of  the  Foot 
Comparison  of  the  Bones  of  the  Hand  and 

Foot 

Applied  Anatomy  of  the  Bones  of  the  Foot 
The  Sesamoid  Bones 


366 
367 
368 
369 
369 
370 
371 

371 

371 
371 
372 
372 
372 
372 
373 
374 

375 
375 
376 


SYXDESMOLOGY. 


Bone 379 

Articular  Cartilage 375 

Ligaments 379 


Classification  of  Joints. 

Synarthrosis 380 

Sutura 380 

Schindylesis 381 

Gomphosis 381 

Synchondrosis 381 

Amphlarthrosis 381 

Diathrosis 381 

Ginglimus 382 

Trochoid 382 

Condyloid 382 

Articulation  by  Reciprocal  Reception     .  382 

Enarthrosis 382 

Arthrodia 382 


The  Kind  of  Movement  Admitted  in  Joints. 

Gliding  Movement 383 

Angular  Movement  383 

Circumduction 383 

Rotation 383 

Ligamentous  Action  of  Muscles     ....  383 

Applied  Anatomy 383 


Articulations  of  the  Trunk. 

Articulations  of  the  Vertebral  Column     . 
Articulations  of  Vertebral  Bodies 

The    Anterior    Longitudinal    Liga- 
ment        

The    Posterior   Longitudinal   Liga 

ment 

The  Intervertebral   Fibrocartilages 

Structure 

Applied  Anatomy       .... 
Articulations  of  Vertebral  Arches 
The  Articular  Capsules   . 
The  Ligamenta  Flava 
The  Supraspinal  Ligament    . 
The  Ligamentum  Nuchae 
The  Interspinal  Ligaments  . 
The  Intertransverse  Ligaments 
Articulation  of  the  Atlas  with  the  Epistro 

pheus  or  Axis 

The  Articular  Capsules  .... 
The  Anterior  Atlantoaxial  Ligament 
The  Posterior  Atlantoaxial  Ligament 
The  Transverse  Ligament  of  the  Atlas 


384 
384 

384 

385 
385 
386 
386 
386 
386 
386 
387 
387 
387 
387 

388 
389 
389 
389 
389 


Articulations  of  the  Vertebral  Column  with 

the  Cranium 

Articulation    of    the    Atlas    with    the 

Occipital  Bone 

The  Articular  Capsules   ... 
The  Anterior  Atlantooccipital  Mem- 
brane        

The  Posterior  Atlantooccipital  Mem- 
brane       

The  Lateral  Ligaments   .... 
Ligaments  Connecting  the  Axis  with  the 

Occipital  Bone 

The  Membrana  Tectoria 

The  Alar  Ligaments 

Articulation  of  the  Mandible 

The  Artictdar  Capsule 

The  Temporomandibular  Ligament 
The  Sphenomandibular  Ligament 

The  Articular  Disk 

The  Stylomandibular  Ligament  . 

Applied  Anatomy 

Costovertebral  Articulations 

Articulations  of  the  Heads  of  the  Ribs  . 
The  Articular  Capsule     .... 
The  Radiate  Ligament    .... 
The  Interarticular  Ligament 
Costotransverse  Articulations 

The  Articular  Capsule     .... 
The  Anterior  Costotransverse  Liga- 
ment        

The  Posterior  Costotransverse  Liga- 
ment        

The  Ligament  of  the  Neck  of  the 

Rib 

The   Ligament   of  the   Tubercle   of 

the  Rib 

Sternocostal  Articulations 

The  Articular  Capsules 

The  Radiate  Sternocostal  Ligaments 
The    Interarticular    Sternocostal    Liga- 
ment   

The  Costoxiphoid  Ligaments 
Interchondral  Articulations    . 
Costochondral  Articulations  .... 
Articulation  of  the  Manubrium  and  Body  of 

the  Sternum 

Mechanism  of  the  Thorax       .  .       . 

Articulation  of  the  Vertebral  Column  with 

the  Pehris 

The  Iliolumbar  Ligament 

Articulations  of  the  Pehas 

Sacroiliac  Articulation 

The  Anterior  Sacroiliac  Ligament 

The  Posterior  Sacroiliac  Ligament 

The    Interosseous    Sacroiliac    Liga 

ment 


392 


392 
392 


392 


392 
392 

393 
393 
393 
393 
394 
394 
395 
395 
395 
396 
396 
396 
396 
396 
397 
397 
398 

398 

398 

399 

399 
399 
399 
399 

400 
401 
401 
401 

401 
401 

403 
404 
404 
404 

404 
404 

404 


CONTENTS 


15 


Articulations  of  the  Pelvis — ■ 

Ligaments  Connecting  the  Sacrum  and 

Ischium 404 

The  Sacrotuberous  Ligament  404 
The  Sacrospinous  Ligament  405 
Sacrococcygeal  Symphysis      ....  406 
The  Anterior  Sacrococcygeal  Liga- 
ment         406 

The  Posterior  Sacrococcygeal  Liga- 
ment         406 

The   Lateral   Sacrococcygeal    Liga- 
ment         406 

The  Interarticular  Ligaments    .  406 

The  Pubic  Symphysis 406 

The  Anterior  Pubic  Ligament  407 

The  Posterior  Pubic  Ligament  .  407 

The  Superior  Pubic  Ligament    .  407 

The  Arcuate  Pubic  Ligament  407 
The  Interpubic  Fribrocartilaginous 

Lamina 407 

Mechanism  of  the  Pelvis 408 


Articulations  of  the  Upper  Extremity. 


Liga 


Sternoclavicular  Articulation 

The  Articular  ("apsule 

The  Anterior  Sternoclavicular  Ligament 
The    Posterior    Sternoclavicular    Liga- 
ment   

The  Intercla\'icular  Ligament 
The  Costoclavicular  Ligament 
The  Articular  Disk      .      .      . 
Applied  Anatomy  .... 
Acromioclavicular  Articulation 
The  Articular  Capsule 
The    Superior    AcromioclaAdcul^r    Liga 

ment 

The    Inferior    Acromiocla'vdcular 

ment 

The  Articular  Disk      .... 
The  CoracoclaAdcular  Ligament  . 
The  Trapezoid  Ligament 
The  Conoid  Ligament 

Applied  Anatomy 

The  Ligaments  of  the  Scapula 

The  Coracoacromial  Ligament 
The  Superior  Transverse  Ligament 
The  Inferior  Transverse  Ligament 
Humeral  Ai-ticulation  or  Shoulder-joint 
The  Articular  Capsule 
The  Coracohumeral  Ligament 
Glenohumeral  Ligaments 
The  Transverse  Humeral  Ligament 
The  Glenoidal  Labrum 

Bursae 

Applied  Anatomy  . 

Elbow-joint 

The  Anterior  Ligament 

The  Posterior  Ligament 

The  Ulnar  Collateral  Ligament   . 

The  Radial  Collateral  Ligament 

Applied  Anatomy 

Radioulnar  Articulation 

Proximal  Radioulnar  Articulation 

The  Annular  Ligament   . 

Applied  Anatomy      .... 
Middle  Radioulnar  Union 

The  Oblique  Cord      .... 

The  Interosseous  Membrane 
Distal  Radioulnar  Articulation    . 

The  Volar  Radioulnar  Ligament 

The  Dorsal  Radioulnar  Ligament 

The  Articular  Disk    .... 
Radiocarpal  Articulation  or  Wrist-joint  . 
The  Volar  Radiocarpal  Ligament 
The  Dorsal  Radiocarpal  Ligament    . 
The  Ulnar  Collateral  Ligament  . 
The  Radial  Collateral  Ligament 

Applied  Anatomy 

Intercarpal  Articulations 

Articulations   of   the   Proximal   Row   of 
Carpal  Bones    .... 

The  Dorsal  Ligaments    . 

The  Volar  Ligaments 

The  Interosseous  Ligaments 


409 
410 
410 

410 
410 
410 
410 
411 
411 
411 

411 

412 
412 
412 
412 
412 
413 
413 
413 
413 
413 
414 
414 
415 
415 
415 
415 
415 
417 
418 
418 
418 
418 
419 
421 
422 
422 
422 
423 
423 
423 
423 
423 
424 
424 
424 
425 
426 
426 
426 
426 
426 
427 

427 
427 
427 
427 


Intercarpal  Articulations — 

Articulations    of    the     Distal     Row    of 
Carpal  Bones    .      . 
The  Dorsal  Ligaments 
The  Volar  Ligaments 
The  Interosseous  Ligaments 
Articulations     of     the     Two     Rows     of 
Carpal  Bones  with  Each  Other 
The  V'olar  Ligaments 
The  Dorsal  Ligaments 
The  Collateral  Ligaments 
Carpometacarpal  Articulations 

Carpometacarpal    Articulation    of    the 

Trunk       

Articulations  of  the  Other  Four  Meta- 
carpal Bones  with  the  Carpus 
The  Dorsal  Ligaments 
The  Volar  Ligaments 
The  Interosseous  Ligaments 
Intermetacarpal  Articulations 

The  Transverse  Metacarpal  Ligament 
Metacarpophalangeal  Articulations 

The  Volar  Ligaments 

The  Collateral  Ligaments 
Articulations  of  the  Digits        .... 


427 
427 
427 
427 

427 
428 
428 
428 
429 

429 

429 
429 
429 
429 
430 
430 
430 
430 
430 
431 


Articulations  of  the  Lower  Extremity. 

Coxal  Articulation  or  Hip-joint     ....  432 

The  Articular  Capsule 432 

The  Iliofemoral  Ligament       ....  433 

The  Pubocapsular  Ligament  433 

The  Ischiocapsular  Ligament  433 

The  Ligamentum  Teres  Femoris  434 

The  Glenoidal  Labrum 434 

The  Transverse  Acetabular  Ligament  434 

Applied  Anatomy 437 

The  Knee-joint 438 

The  Articular  Capsule 438 

The  Ligamentum  Patellae       ....  439 

The  Oblique  Popliteal  Ligament  439 

The  Tibial  Collateral  Ligament  ...  439 

The  Fibular  Collateral  Ligament  440 

The  Cruciate  Ligaments 441 

The  Anterior  Cruciate  Ligament     .  441 

The  Posterior  Cruciate  Ligament    .  441 

The  Menisci 441 

The  Medial  Meniscus      ....  442 

The  Lateral  Meniscus     ....  442 

The  Transverse  Ligament       ....  442 

Bursas 443 

Applied  Anatomy 446 

Articulations  between  the  Tibia  and  Fibula.  447 

Tibiofibular  Articulation         ....  448 

The  Articular  Capsule     ....  448 

The  Anterior  Ligament   ....  448 

The  Posterior  Ligament  448 

Interosseous  Membrane 448 

Tibiofibular  Syndesmosis        ....  448 

The  Anterior  Ligament   ....  448 

The  Posterior  Ligament        .       .  448 

The  Inferior  Transverse  Ligament  449 

The  Interosseous  Ligament  449 

Talocrural  Articulation  or  Ankle-joint  449 

The  Articular  Capsule 449 

The  Deltoid  Ligament 450 

The  Anterior  Talofibular  Ligament  450 

The  Posterior  Talofibular  Ligament        .  451 

The  Calcaneofibular  Ligament  451 

Applied  Anatomy 452 

Intertarsal  Articulations 452 

Talocalcaneal  Articulation      ....  452 
The  Articular  Capsule     ....  452 
The    Anterior    Talocalcaneal    Liga- 
ment   452 

The  Posterior  Talocalcaneal  Liga- 
ment         453 

The    Lateral    Talocalcaneal    Liga- 
ment         453 

The    Medial    Talocalcaneal    Liga- 
ment         453 

The   Interosseous   Talocalcaneal 

Ligament 453 

Talocalcaneona\"icular  Articulation  .  454 


16 


CONTENTS 


Intertarsal  Articulations — 

Talocalcaneonavicular  Articulat  ion — 
The  Articular  Capsule     .... 
The  Dorsal  Talonavicular  Ligament 
Calcaneocuboid  Articulation 
The  Articular  Capsule 
The   Dorsal   Calcaneocuboid   Liga- 
ment        

The  Bifurcated  Ligament 

The  Long  Plantar  Ligament 

The  Plantar  Calcaneocuboid  Liga 

ment 

The  Ligaments  Connecting  the  Calca- 
neus and  Navicular 
Tile   Plantar   Calcaneonavicular 

Ligament 

Applied  Anatomy 
Cuneonavicular  Articulation 
The  Dorsal  Ligaments 
The  Plantar  Ligaments  . 
Cuboideonavicular  Articulation  . 
The  Dorsal  Ligament 
The  Plantar  Ligament 


454 
454 
454 
454 

454 
454 
454 

454 

455 

455 
456 
456 
456 
456 
457 
457 
457 


Intertarsal  Articulations 

Cuboideonavicular  Articulation — 

The  Interosseous  Ligament 
Intercuneiform  and  (Juncocuboid  Art 

lation 

The  Dorsal  Ligaments 
The  Plantar  Ligaments  . 
The  Interosseous  Ligaments 
Applied  Anatomy 
Tarsometatarsal  Articulations 
The  Dorsal  Ligaments 
The  Plantar  Ligaments 
The  Interosseous  Ligaments  . 
Intermetatarsal  Articulations  . 
The  Dorsal  Ligaments 
The  Plantar  Ligaments     . 
The  Interosseous  Ligaments  . 
The  Transverse  Metatarsal  Ligament 
Metatarsophalangeal  Articulations 
The  Plantar  Ligaments     . 
The  Collateral  Ligaments 
Articulations  of  the  Digits 
Arches  of  the  Foot 


457 

457 
457 
457 
457 
457 
457 
457 
458 
458 
458 
458 
458 
458 
458 
459 
459 
459 
459 
459 


MYOLOGY. 


Applied  Anatomy  of  Muscles 462 


Tendons,  Aponeuroses,  and  Fascice. 


Tendons  . 

Aponeuroses 

Fasciae 


463 
463 
463 


The  Fasciae  and  Muscles  of  the  Head. 
The  Muscles  of  the  Scalp. 

Dissection 464 

The  Skin  of  the  Scalp 465 

The  Superficial  Fascia 465 

Epicranius 465 

Occipitalis        ...  ....  446 

Frontalis 466 

Galea  Aponeurotica  ...  466 

Applied  Anatomy 466 


The  Muscles  of  the  Eyelid. 


Dissection 
Orbicularis  Oculi 
Corrugator  . 


The  Muscles  of  the  Nose. 


Procerus  

Nasalis 

Depressor  Septi 
Dilator  Naris  Posterior 
Dilator  Naris  Anterior 


The  Muscles  of  the  Mouth. 


Dissection 

Quadratus  Labii  Superioris 

Caninus 

Zygomaticus 

Mentalis 

Quadratus  Labii  Inferioris 

Triangularis 

Buccinator 

Relations 

Pterygomandibular  Raphe 
Orbicularis  Oris  .... 
Risorius 


467 
467 
468 


469 
469 
469 
469 
469 


469 
469 
470 
470 
470 
470 
470 
470 
470 
471 
471 
472 


Masseter — 

Relations      .... 
Temporal  Fascia 

Dissection 

Temporalis 

Relations      .... 

Dissection    .... 

Pterygoideus  Externus 
Relations   . 

Pterygoideus  Internus 
Relations   . 


The  Muscles  of  Mastication. 


472 
473 
473 
473 
473 
474 
474 
474 
474 
474 


The  Fascia  and  Muscles  of  the  Antero- 

LATERAL    REGION    OF    THE    NecK. 


The  Superficial  Cervical  Muscle. 


Dissection 
Superficial  Fascia 
Platysma 


The  Lateral  Cervical  Muscles. 


The  Fascia  Colli  .      . 

Applied  Anatomy  . 
Sternocleidomastoideus 

Triangles  of  the  Neck 

Relations     .      .      .      . 

Applied  Anatomy  . 


The  Supra-  and  Infrahyoid  Muscles. 


Dissection 
Digastricus    . 

Relations 
Stylohyoideus 

The  Stylohyoid 
Mylohyoideus 

Relations 

Dissection    . 
Geniohyoideus 
Dissection 
Sternohyoideus   . 
Sternothyreoideus 
Thyreohyoideus 
Omohyoideus 


The  Anterior  Vertebral  Muscles. 


Ligament 

Parotideomasseteric  Fascia 

Masseter 


Longus  Colli 

Longus  Capitis   . 
472  i  Rectus  Capitis  Anterior 
472  !  Rectus  Capitis  Lateralis 


475 
475 
475 


476 
478 
478 

478 
478 
479 


480 
480 
481 
481 
481 
481 
481 
481 
481 
482 
482 
482 
482 
482 


483 
484 

484 
484 


CONTENTS 


17 


The  Lateral   Vertebral  Muscles. 


Scalenus  Anterior 
Relations 

Scalenus  Medius 
Relations 

Scalenus  Posterior 


484 
484 
484 
485 
485 


The  Fasci-k  and  Muscles  of  the  Trunk. 

The  Deep  Muscles  of  the  Back. 

Dissection  of  the  Muscles  of  the  Back  by 

Layers 485 

The  Lumbodorsal  Fascia 486 

Splenius  Capitis 486 

Splenius  Cervicis 487 

Sacrospinalis 488 

Iliocostalis  Lumborum 

Iliocostalis  Dorsi    . 

Iliocostalis  Cervicis 

Longissimus  Dorsi 

Lougissimus  Cervicis  .      .  .  488 

Longissimus  Capitis  .  489 

Spinalis  Dorsi    ....  489 

Spinalis  Cervicis     .  .  ...  489 

Spinalis  Capitis       .  .  489 

Semispinalis  Dorsi  ....  489 

Semispinalis  Cervicis 489 

Semispinalis  Capitis 489 

Multifidus 489 

Rotatores 490 

Interspinales 490 

Extensor  Coccygis  490 

Intertransversarii 490 

The  Suboccipital  Muscles. 

Rectus  Capitis  Posterior  Major     ....  491 

Rectus  Capitis  Posterior  Minor     ....  491 

Obliquus  Capitis  Inferior 491 

Obliquus  Capitis  Superior 491 

The  Suboccipital  Triangle 491 

Applied  Anatomj' 492 1 

The  Muscles  of  the  Thorax.  \ 

Intercostal  Fascia 492  j 

Intercostales 492 1 

Intercostales  Externi 492 

Intercostales  Interni 492  i 

Subcostales 492 

Transversus  Thoracis 492 

Levatores  Costarum 493  : 

Serratus  Posterior  Superior 493 

Serratus  Posterior  Inferior  493 

Diaphragma 493  i 

Medial  Lumbocostal  Arch  495  ; 

Lateral  Lumbocostal  Arch      ....  495  ' 

The  Crura 495 

The  Central  Tendon 495 

Openings  in  the  Diaphragma  495  ! 

Relations 496  I 

Mechanism  of  Respiration 497  i 

The  Muscles  and  Fasciae  of  the  Abdomen. 

The  Antero-lateral  Muscles  of  the  Abdomen  498 

Dissection 498 

The  Superficial  Fascia 49S 

Obliquus  Externus  Abdominis  .  499 

Aponeurosis       of       the       Obliquus 

Externus  Abdominis  .  499 
Subcutaneous  Inguinal  Ring  .  500 
The  Inter  crural  Fibres  501 
The  Inguinal  Ligament  501 
The  Lacunar  Ligament  502 
The  Reflected  Inguinal  Liga- 
ment      .-502 

Ligament  of  Cooper  502 

Dissection 503 

Obliquus  Internus  Abdominis  503 

Cremaster 504 

Dissection 504 


Tlie  Antero-lateral  Muscles  of  the  Abdomen— 

Transversus  Abdominis 504 

Inguinal  Aponeurotic  Falx  505 

Dissection 505 

Rectus  Al)doniinis 506 

Pyrainidalis 507 

The  Linca  Alba      ...  507 

The  Lineac  Semilunarcs 507 

The  Transversalis  Fascia        ...  508 

The  Abdominal  Inguinal  Ring  508 

The  Inguinal  Canal 508 

Extraperitoneal  Connective  Tissue    .  509 

The  Deep  Crural  Arch 509 

The  Posterior  Muscles  of  the  Abdomen  .  510 
The    Fascia    Covering    the    Quadratus 

Lumborum 510 

Quadratus  Lumborum 510 


The  Muscles  and  Fascice  of  the  Pelrt 


Pelvic  Fascia 
Levator  Ani  . 
Relations 
Coccygeus 


The  Muscles  and  Fascice  of  the  Perineum 


510 
513 
514 
514 


Muscles  of  the  Anal  Region 515 

The  Superficial  Fascia 515 

The  Deep  Fascia 515 

Ischiorectal  Fossa 515 

Applied  Anatomy 516 

The  Corrugator  Cutis  Ani  516 

Sphincter  Ani  Externus 516 

Sphincter  Ani  Internus 516 

The   Muscles  of  the   Urogenital   Region  in 

the  Male 517 

Superficial  Fascia 517 

The    Central    Tendinous    Point    of    the 

Perineum 518 

Bulbocavernosus 518 

Ischiocavernosus 518 

The  Deep  Fascia 519 

Transversus  Perinaei  Profundus  520 

Sphincter  Urethrae  Membranaceae  .  520 

The  Muscles  of  the  Urogenital  Region  in  the 

Female 520 

Transversus  Perinaei  Superficialis  520 

Bulbocavernosus 520 

Ischiocavernosus 521 

Transversus  Perinaei  Profundus  521 


The  Fascia  and  Muscles  of  the  Upper 
Extremity. 

The  Muscles  Connecting  the  Upper  Extreinity 
to  the   Vertebral  Column. 


Superficial  Fascia 
Deep  Fascia 
Trapezius 
Latissimus  Dorsi 
Rhomboideus  Major 
Rhomboideus  Minor 
Levator  Scapulae 


522 
522 
522 
524 
525 
525 
525 


The  Muscles  Connecting  the  Upper  Extremity  to 
the  Anterior  and  Lateral  Thoracic  Walls. 


Dissection  of  Pectoral  Region  and  Axilla 
Superficial  Fascia 

Applied  Anatomy 
Pectoralis  Major 

Relations 
Dissection 

Coracoclavicular  Fascia 
Pectoralis  Minor 

Relations 
Subclavius 

Relations 
Serratus  Anterior 

Relations 

Applied  Anatomy 


525 
526 
526 
526 

528 
528 
528 
528 
528 
528 
529 
529 
530 
530 


18 


CONTENTS 


The  Muscles  and  Fasciae  of  (he  Shoulder. 


The 


Dissection 530 

Deep  Fascia 530 

Deltoideus 530 

Relations 531 

Applied  Anatomy 531 

Dissection 531 

Subscapular  Fascia 531 

Subscapularis 531 

Dissection 532 

Supraspinatous  Fascia 532 

Supraspinatus 532 

Infraspinatous  Fascia 533 

Infraspinatus 533 

Teres  Minor 533 

Teres  Major 533 

The  Muscles  and  Fasciae  of  the  Arm. 

Dissection 533 

Brachial  Fascia 534 

Coracobrachialis 534 

Relations 534 

Biceps  Brachii 534 

Relations 535 

Brachialis 535 

Relations 535 

Applied  Anatomy 535 

Triceps  Brachii 535 

Applied  Anatomy 536 

The  Muscles  and  Fascia  of  the  Forearm. 

Dissection 536 

Antibrachial  Fascia '  536 

The  Volar  Antibrachial  Muscles    ....  537 

The  Superficial  Group 537 

Pronator  Teres 537 

Applied  Anatomy     ....  537 

Flexor  Carpi  Radialis      ....  537 

Palmaris  Longus 538 

Flexor  Carpi  Ulnaris        ...  539 

Flexor  Digitorum  Sublimis  539 

The  Deep  Group 539 

Dissection 539 

Flexor  Digitorum  Profundus      .       .  540 
Fibrous     Sheaths     of     the     Flexor 

Tendons 540 

Flexor  Pollicis  Longus  540 

Pronator  Quadratus 540 

The  Dorsal  Antibrachial  Muscles ....  542 

The  Superficial  Group 542 

Dissection 542 

Brachioradialis 542 

Extensor  Carpi  Radialis  Longus      .  542 

Extensor  Carpi  Radialis  Brevis  542 

Extensor  Digitorum  Communis  544 

Extensor  Digiti  Quinti  Proprius  544 

Extensor  Carpi  Ulnaris   ....  544 

Anconaeus 544 

The  Deep  Group 544 

Supinator 544 

Abductor  Pollicis  Longus  545 

Extensor  Pollicis  Brevis  545 

Extensor  Pollicis  Longus  545 

Extensor  Indicis  Proprius  546 

Applied  Anatomy 546 

The  Muscles  and  Fasciae  of  the  Hand. 

Dissection 546 

Volar  Carpal  Ligament 547 

Transverse  Carpal  Ligament 547 

The  Mucous  Sheaths  of  the  Tendons  on  the 

Front  of  the  Wrist 548 

Dorsal  Carpal  Ligament 550 

The  Mucous  Sheaths  of  the  Tendons  on  the 

Back  of  the  Wrist 550  ! 

Palmar  Aponeurosis 550    The 

Applied  Anatomy 551  | 

The  Lateral  Volar  Muscles 552 

Abductor  Pollicis  Brevis 552 

Opponens  Pollicis 553 

Flexor  Pollicis  Brevis 553 


The  Lateral  Volar  Muscles — 

Adductor  Pollicis  (Obliquus) 
Adductor  Pollicis  (Transversus) 

The  Medial  Volar  Muscles 
Palmaris  Brevis 
Abductor  Digiti  Quinti 
Flexor  Digiti  Quinti  Brevis 
Opponens  Digiti  Quinti 

The  Intermediate  Muscles 

Lumbricales       .... 

Interossei 

Interossei  Dorsales 
Interossei  Volares 

Applied    Anatomy    of    the    Muscles 
Upper  Extremity        .... 


of  the 


554 
554 
554 
554 
554 
554 
555 
555 
555 
555 
555 
556 

556 


The  Muscles  and  Fascia  of  the  Lower 
Extremity. 

The  Muscles  and  Fasciae  of  the  Iliac  Region. 

Dissection 559 

The  Fascia  Covering  the  Psoas  and  Iliacus  559 

Psoas  Major 560 

Relations 561 

Psoas  Minor 561 

Iliacus 561 

Relations 561 

Applied  Anatomy 562 


The 


The 


The  Muscles  and  Fascice  of  the  Thigh. 


Anterior  Femoral  Muscles 

Dissection    . 

Superficial  Fascia   . 

Deep  Fascia 

The  Fossa  Ovalis    . 

Tensor  Fasciae  Latae 

Sartorius 

Relations    . 
Quadriceps  Femoris 

Rectus  Femoris 

Vastus  Lateralis 

Vastus  Medialis 

Vastus  Intermedins 

Articularis  Genu  . 

Applied  Anatomy 
Medial  Femoral  Muscles 
Dissection    . 
Gracilis  .... 
Pectineus 

Relations    . 
Adductor  Longus    . 

Relations    . 
Adductor  Brevis 

Relations    . 
Adductor  Magnus 

Relations    . 
Applied  Anatomy  . 
Muscles  of  the  Gluteal  Region 
Dissection    . 
Glutaeus  Maximus 

BurssB   . 

Relations    . 
Dissection    . 
Glutaeus  Medius    . 
Glutaeus  Minimus 
Piriformis 

Relations    . 
Obturator  Membrane 
Dissection    . 
Obturator  Internus 

Relations    . 
Gemelli  .... 

Gemellus  Superior 

Gemellus  Inferior 
Quadratvis  Femoris 
Obturator  Externus 
Posterior  Femoral  Muscles 
Dissection    . 
Biceps  Femoris 
Semitendinosus 
Semimembranosus 
Applied  Anatomy  . 


562 
562 
562 
563 
564 
565 
565 
565 
565 
565 
566 
566 
566 
566 
567 
567 
567 
567 
567 
567 
567 
567 
568 
568 
568 
569 
569 
569 
569 
569 
570 
570 
570 
570 
570 
571 
571 
572 
572 
572 
573 
573 
573 
573 
573 
573 
574 
574 
574 
575 
575 
575 


CONTEXTS 


19 


The  Muscles  and  Fascia:  of  the  Log. 


The  Anterior  Crural  Muscles 

570 

Dissection    ... 

576 

Deep  Fascia      .      . 

57G 

Dissection 

570 

Tibialis  Anterior 

570 

Extensor  Hallucis  Longus                               577 

Extensor  DiKitorum  Longus                            577 

Peronaeus  Tertius        .      .                              57s 

The  Posterior  Crural  Muscles 

578 

Dissection 

578 

The  Superficial  Group 

578 

Gastrocnemius 

578 

Relations 

578 

Soleus 

579 

Relations. 

579 

Tendo  Calcaneus 

579 

Plantaris 

579 

The  Deep  Group     ... 

579 

Dissection         .... 

579 

Deep  Transverse  Fascia 

580 

Dissection        .... 

581 

Popliteus 

581 

Relations. 

581 

Flexor  Hallucis  Longus   . 

581 

Relations 

581 

Flexor  Digitorum  Longus 

581 

Relations 

582 

Tibialis  Posterior 

582 

Relations . 

582 

The  Lateral  Crural  Muscles 

582 

Dissection    .... 

582 

Peronaeus  Longus 

.      582 

Peronaeus  Bre\'is    . 

583 

Applied  Anatomy  . 

583 

The  Fascia:  Around  the  Ankle. 

Transverse  Crural  Ligament  584 

Cruciate  Crural  Ligament  584 

Laciniate  Ligament  585 

Peroneal  Retinacula       .      .  585 
Th(!  Mucous  Slieaths  of  the  Tendons  Around 

llu!  Ankle 586 

The  Muscles  and  Fascia;  uf  (he  Fool. 

The  Dorsal  Muscle  of  the  Foot  586 

Extensor  Digitorum  Brevis  580 

The  Plantar  Muscles  of  the  Foot  580 

Plantar  Aponeurosis  580 

The  First  Layer  587 

.    Dissection         .       .  587 

Abductor  Hallucis 587 

Flexor  Digitorum  Brevis  588 
Fibrous  Sheaths  of  the  Flexor 

Tendons 588 

Abductor  Digiti  Quinti    .  588 

Dissection 588 

The  Second  Layer  589 

Quadratus  Plantae  589 

Lumbricales 589 

Dissection 589 

The  Third  Layer 589 

Flexor  Hallucis  Brevis     ...  589 

Adductor  Hallucis 589 

Flexor  Digiti  Quinti  Brevis  590 

The  Fourth  Layer 590 

Interossei 590 

Interossei  Dorsales  ....  591 
Interossei  Plantares                    .591 
Applied    Anatomy    of    the    Muscles    of    the 

Lower  Extremity 592 


ANGIOLOGY. 


Structure  of  Arteries 
Capillaries   . 
Sinusoids 

Structure  of  Veins    . 


The  Thoracic  Cavity. 

The  Cavity  of  the  Thorax        .      .      . 
The  Upper  Opening  of  the  Thorax 
The  Lower  Opening  of  the  Thorax 

The  Pericardium. 

Structure  of  the  Pericardium   . 
Applied  Anatomy 

The  Heart. 

Size 

Component  Parts 


596 

Right  Atrium 

.     606 

598             Sinus  Venarum 

.     606 

599             Auricula 

.      606 

599    Dissection 

.      607 

Right  Ventricle 

.      608 

Dissection 

.      609 

Left  Atrium  . 

.      610 

Auricula 

.      610 

60n 

Dissection 

.      611 

001 

Left  Ventricle 

.      611 

001 

Ventricular  Septum 

612 

Structure  of  the  Heart 

.      613 

Applied  Anatomy 

614 

The  Cardiac  Cvcle  and  the  . 

Vctiont 

ot 

the 

601 

Valves 

.      615 

603 

Applied  Anatomy 

.      615 

Peculiarities  in  the  Vascular  Systein  in  the 
Fetus. 

604    Fetal  Circulation 616 

604    Changes  in  the  Vascular  System  at  Birth  618 


THE  ARTERIES. 


Applied  Anatomy 
The  Pulmonary  Artery 

Relations 

Applied  Anatomj'  . 


619 
620 
620 
621 


The  Arch  of  the  Aorta. 


The  Aorta. 
The  Ascending  Aorta. 


Relations 

Branches        

The  Coronary  Arteries 

Right  Coronarj^  Arterj- 
Left  Coronary  Artery 
Applied  Anatomy 


Relations        .       .       .       . 
Applied  Anatomj^     . 
The  Innominate  Artery 

Relations 

Branches 

Thj'reoidea  Ima 

Applied  Anatomy  . 


023 
024 
025 
025 
025 
626 
626 


622  The  Arteries  of  the  Head  and  Neck. 

622 

622  The  Common  Carotid  Artery. 
622 

623  Relations 627 

623  Pecuharities 628 


20 


CONTENTS 


Applied  Anatomy 

.      629 

The  External  Carotid  Artery  .... 

.      630 

Relations 

.      630 

Applied  Anatomy 

.      630 

Branches      

630 

Superior  Thyroid  Artery 

.      631 

Relations 

631 

Branches        

.      631 

Applied  Anatomy 

.      631  1 

Lingual  Artery 

.      631 

Relations 

.      632 

Branches        

632  1 

Applied  Anatomy 

.      632 

External  Maxillary  Artery    . 

.      633 

Relations 

.      633 

Branches        

.      634 

Peculiarities  .       . 

635 

Applied  Anatomy 

.      635 

Occipital  Artery 

.      635 

Course  and  Relations    . 

635 

Branches        

.      636 

Posterior  Auricular  Artery    . 

.      636 

Branches        

.      636 

Ascending  Pharyngeal  Artery 

.      637 

Branches        .... 

.      637 

Applied  Anatomy 

.      637 

Superficial  Temporal  Artery 

637 

Relations        .... 

.      637 

Branches        ... 

.      637 

Applied  Anatomy 

.      638 

Internal  Maxillary  Artery 

.      638 

Branches        .... 

.      639 

The  Triangles  of  the  Neck        .       . 

.      642 

Anterior  Triangle 

.      642 

Inferior  Carotid   or    Muscular 

Tri- 

angle 

.      643 

Superior   Carotid   or   Carotid 

Tri- 

angle 

.      643 

Submaxillary     or     Digastric 

Tri- 

angle 

.      644 

Suprahyoid  Triangle 

.      644 

Posterior  Triangle         .... 

644 

Occipital  Triangle 

645 

Subcla\ian  Triangle  . 

.      645 

The  Internal  Carotid  Artery    . 

645 

Course  and  Relations  .... 

.      645 

Cer\'ical  Portion 

.      646 

Petrous  Portion 

647 

Cavernous  Portion 

.      647 

Cerebral  Portion 

.       .      647 

Peculiarities 

.      .      647 

Applied  Anatomy  . 

.      .      647 

Branches      . 

.      .      648 

Caroticotympanic 

.      .      648 

Artery  of  the  Pterygoid  Canal 

.      .      648 

Cavernous 

.      .      648 

Hypophyseal 

.      .      648 

Anterior  Meningeal    . 

.      .      648 

Ophthalmic  artery 

.      .      648 

Branches        ... 

.      .      648 

Anterior  Cerebral  Artery 

.      .      651 

Branches        .... 

.      .      652 

Middle  Cerebral  Arterj' 

.      652 

Branches        .... 

.      .      653 

Posterior  Communicating  Arte 

ry    .      653 

Anterior  Choroid 

il  Artery    . 

.      .      653 

The  Arteries  of  the  Brain. 

The  Ganglionic  System       .... 
The  Cortical  Arterial  System  . 


654 

654 


The  Arteries  of  the  Upper  Extremity. 


The  Subclavian  Artery. 

First  Part  of  the  Right  Subclavian  Artery    .  655 

Relations 655 

First  Part  of  the  Left  Subclavian  Artery  655 

Relations 655 

Second  and  Third  Parts  of  the  Subclavian 

Artery 656 

Relations 656 

Relations 657 

Peculiarities 657 


Applied  Anatomy 657 

Branches 659 

Vertebral  Arterj^ 659 

Relations  .  659 

Branches   .      .  .  660 

Applied  Anatomy  661 

Thyrocervical  Trunk 662 

Branches 662 

Peculiarities 644 

Internal  Mammary  Artery  604 

Relations 664 

Branches 664 

The  Costoccrvical  Trunk        ...  666 

The  Axilla. 

Boundaries 667 

Contents 667 

Applied  Anatomj- 667 

The  Axillary  Artery 668 

Relations 668 

Applied  Anatomy 669 

Branches 670 

The  Highest  Thoracic  Arterj'     .  670 

The  Thoracoacromial  Artery  670 

The  Lateral  Thoracic  Artery  671 

The  Subscapular  Arterj^  671 
The  Posterior  Humeral  Circumflex 

Artery 671 

The  Anterior   Humeral   Circumflex 

Artery 672 

Peculiarities 672 

The  Brachial  Artery 672 

Relations 672 

The  Anticubital  Fossa 672 

Peculiarities 672 

Applied  Anatomy 673 

Branches 674 

The  Arteria  Profunda  Brachii  674 
The  Nutrient  Arterj-  ....  674 
The      Superior      Llnar      Collateral 

Artery 674 

The    Inferior   Ulnar   Collateral 

Artery 675 

Muscular  Branches 675 

The    Anastomosis  Around    the    Elbow- 
joint  675 

The  Radial  Artery 676 

Relations 676 

Peculiarities 676 

Applied  Anatomy 676 

Branches 678 

Radial  Recurrent  Artery  678 

Musciilar 678 

Volar  Carpal 678 

Superficial  Volar 678 

Dorsal  Carpal 678 

Arteria  Princeps  Pollicis        .  .      678 

Arteria  Volaris  Indicis  Radialis  679 

Deep  Volar  Arch 679 

Volar  Metacarpal  Arteries    .  679 

Perforating 679 

Recurrent 679 

The  Ulnar  Artery 679 

Relations 679 

Peculiarities 679 

Applied  Anatomy  ,       .  680 

Branches 680 

Anterior  Ulnar  Recurrent  Artery  .  680 
Posterior  Ulnar  Recurrent  Artery  .  680 
Common  Interosseous  Artery  680 

Muscular 682 

Volar  Carpal 682 

Dorsal  Carpal 682 

Deep  Volar  682 

Superficial  Volar 682 

Relations 682 

Applied  Anatomy     ....      682 


The  Arteries  of  the  Trunk. 
The  Descending  Aorta. 

The  Thoracic  Aorta 683 

Relations 683 

Peculiarities 6»3 


cox  TEXTS 


21 


The  Thoracic  Aort:^" 
Applied  Anatomy 
Branches 

Pericardial 
Bronchial   . 
CEsophaKcal 
Mediastinal 
Intercostal  Arteries    . 
Branches 
Applied  Anatomy 
Subcostal  Arteries 
Superior  Phrenic  . 
The  Abdominal  Aorta  . 

Relations 

Applied  Anatomy  . 

Branches      

The  Coeliac  Artery 

Relations 
The  Superior  Mesenteric  Artery 
Dissection 
Branches 
The  Inferior  Mesenteric  Artery 
Dissection 
Branches 
Applied  Anatomy 
The  ^liddle  Suprarenal  Arteries 
The  Renal  Arteries 
The  Internal  Spermatic  Arteries 
The  Ovarian  Arteries 
The  Inferior  Phrenic  Arteries 
The  Lumbar  Arteries 
The  iMiddle  Sacral  Artery 

The  Common  Iliac  Arteries. 
Peculiarities  .... 
AppUed  Anatomy 
The  Hj'pogastric  Artery 
Peculiarities 
Applied  Anatomy  . 
Branches 

Superior  Vesical  Artery 
^Middle  Vesical  ATter3^ 
Inferior  Vesical  Artery 
Middle  Hemorrhoidal  Artery 
Uterine  Artery 
Vaginal  Artery 
Obturator  Artery 
Branches 
Pectiliarities 
Internal  Pudendal  Artery 
Relations 
Peculiarities 
Branches 
Inferior  Gluteal  Ai'tery   . 

Branches 
Lateral  Sacral  Arteries 
Superior  Gluteal  Artery 
Apphed  Anatomy 
The  External  Ihac  Artery  . 

Relations 

Applied  Anatomy  .... 

Branches      

Inferior  Epigastric  Arterj 
Branches 
Peculiarities  . 
AppUed  Anatomy     . 
Deep  Iliac  Circumflex  Arterj 


683 
G85 
685 
685 
685 
685 
685 
686 
686 
686 
686 
686 
687 
687 
688 
688 
688 
691 
692 
692 
694 
695 
695 
696 
696 
696 
697 
697 
697 
698 
698 


700 
700 
700 
700 
701 
701 
701 
701 
701 
701 
701 
702 
702 
702 
703 
703 
703 
704 
704 
706 
706 
707 
707 
708 
70S 
708 
708 
709 
709 
709 
709 
710 
710 


Knee 


The  Arteries  of  the  Lower  Extremity. 
The  Femoral  Artery. 


The  Femoral  Sheath 
The  Femoral  Triangle 


710 
712 


The  Adductor  Canal  .... 
Relations  of  the  Femoral  Arterj-  . 
Peculiarities  of  the  Femoral  Artery 

Ajiplied  Anatomj' 

Branches        

Superficial  Epigastric  Artery 

Superficial  Iliac  Circumflex  Artery   . 

Superficial  External  Pudendal  Artery 

Deep  External  Pudendal  Artery 

Muscular 

Profunda  Femoris  Artery 
Relations   .... 
Peculiarities 
Branches    .... 

Highest  Genicular  Artery 


The  Popliteal  Fossa. 


Dissection 
Boundaries 
Contents 

The  Popliteal  Artery 
Relations 
Peculiarities 
Applied  Anatomj' 
Branches 

Superior  Muscular 
Sural  Arteries 
Cutaneous  Branches 
Superior  Genicular  Arteries 
Middle  Genicular  Artery- 
Inferior  Genicular  Arteries  . 
The    Anastomosis    Around    the 

joint 

The  Anterior  Tibial  Artery 

Relations 

Peculiarities 

Applied  Anatomy  .       . 

Branches      

Posterior  Tibial  Recurrent  Artery 

Fibular  Artery 

Anterior  Tibial  Recurrent  Arterj- 
Muscular  Branches    .... 
Anterior  Medial  Malleolar  Artery 
Anterior  Lateral  Malleolar  Ajrterj- 
The  Arteria  Dorsalis  Pedis 
Relations      .... 
Peculiarities 
Applied  Anatomy  . 
Branches      .... 

Lateral  Tarsal  Artery 
Medial  Tarsal  Artery 
Arcuate  Artery 
Deep  Plantar  Artery 
The  Posterior  Tibial  Artery 
Relations      .... 
Peculiarities 
Applied  Anatomy  . 
Branches      .... 
Peroneal  Artery    . 
Peculiarities  . 
Branches 
Nutrient  Artery    . 
Muscular  Branches 
Posterior  Medial  Malleolar  Arterj- 
Communicating  Branch 
Medial  Calcaneal  . 
Medial  Plantar  Artery 
Lateral  Plantar  Artery 
Applied  Anatomj" 
Branches 


THE  VEINS. 


The  Pulmonary  Veins      .  730 

The  Systemic  Veins. 

The  Veins  of  the  Heart. 

Coronary  Sinus 730 

Tributaries 730 


The  Veins  of  the  Head  and  Xeck. 

The  Veins  of  the  Exterior  of  the  Head  and 

Face 732 

The  Frontal  Vein 732 

The  Supraorbital  ^'ein 733 

The  Angtdar  Vein 733 

The  Anterior  Facial  Vein        ....  733 


22 


CONTENTS 


The  Veins  of  the  Exterior  of  the  Head  and 
Face — 
The  Anterior  Facial  Vein — 

Tributaries 733 

Applied  Anatomy 733 

The  Superficial  Temporal  Vein    .  733 

Tributaries 734 

The  Pterygoid  Plexus 734 

The  Internal  Maxillary  Vein                     .  734 

The  Posterior  Facial  Vein        ....  734 

The  Posterior  Auricular  Vein  734 

The  Occipital  Vein 734 

The  Veins  of  the  Xeck 734 

The  External  Jugular  Vein     ....  734 

Tributaries 735 

Applied  Anatomy                    .       .  736 

The  Posterior  External  Jugular  Vein  736 

The  Anterior  Jugular  Vein      ...  736 

The  Internal  Jugular  Vein             ...  736 

Tributaries                   736 

Applied  Anatomy 737 

The  Vertebral  Vein 738 

Tributaries 738 

The  Diploic  Veins 738 

The  Veins  of  the  Brain 739 

The  Cerebral  Veins 739 

The  External  Veins 739 

The  Superior  Cerebral  Vein  739 

The  Middle  Cerebral  Vein    .             .  739 

The  Inferior  Cerebral  Vein  .  739 

The  Internal  Cerebral  Veins  740 

The  Great  Cerebral  Vein  740 

The  Cerebellar  Veins 740 

The  Sinuses  of  the  Dura  Mater.    Ophthalmic 

Veins  and  Emissary  Veins        .             .  740 

The  Superior  Sagittal  Sinus   ....  740' 

Applied  Anatomy 741 

The  Inferior  Sagittal  Sinus     ....  741 

The  Straight  Sinus 741 

The  Transverse  Sinuses 742 

The  Occipital  Sinus 743 

The  Confluence  of  the  Sinuses  743 

The  Cavernous  Sinuses 744 

Applied  Anatomj- 745 

The  Ophthalmic  Veins                    .       .       .  745 

The  Superior  Ophthalmic  Vein        .  745 

The  Inferior  Ophthalmic  Vein   .  746 

The  Intercavernous  Sinuses    ...  746 

The  Superior  Petrosal  Sinus  ...  746 

The  Inferior  Petrosal  Sinus    ....  746 

The  Basilar  Plexus 746 

The  Emissary  Veins 746 

Applied  Anatomy 747 

The  Veins  of  the  Upper  Extremity  and 
Thorax. 

The  Superficial  Veins  of  the  Upper  Extremity  747 

Digital  Veins 747 

The  Cephalic  Vein        .             .       .  747 

The  Accessory  Cephalic  Vein  748 

The  Basilic  Vein 748 

The  Median  Antibrachial  Vein    .  749 

Applied  Anatomy 749 

The  Deep  Veins  of  the  Upper  Extremity  750 

Deep  Veins  of  the  Hand 750 

Deep  Veins  of  the  Forearm    ....  750 

The  Brachial  Veins 750 

The  AxUlary  Vein 750 

Applied  Anatomy 750 

The  SubclaA-ian  Vein 750 

Tributaries 751 

The  Veins  of  the  Thorax 751 

The  Innominate  Veins              .       .  751 

The  Right  Innominate  Vein       .       .  751 

The  Left  Innominate  Vein    .       .      .  751 

Tributaries 751 

Peculiarities 751 


The  Veins  of  the  Thorax — 

The  Internal  Mammary  Veins  751 

The  Inferior  Thyroid  Veins    .  751 

The  Highest  Intercostal  Vein  753 

The  Superior  Vena  Cava        .  753 

Relations 753 

The  Azygos  Vein 753 

Tributaries  753 

The  Hemiazygos  Veins  753 
The     Accessory     Hemiazygos 

Veins 753 

Applied  Anatomy 754 

The  Bronchial  Veins 754 

The  Veins  of  the  Vertebral  Column    .  754 

The  External  Vertebral  Venous  Plexuses  754 

The  Internal  Vertebral  Venous  Plexuses  755 

The  Basivertebral  Veins 755 

The  Veins  of  the  Medulla  Spinalis    .  755 


The  Veins  of  the  Lower  Extremity,  Abdomen, 
and  Pelvis. 


The  Superficial  Veins  of  the  Lower  Extremity 
The  Dorsal  Digital  Veins  . 
The  Great  Saphenous  Vein 

Tributaries 
The  Small  Saphenous  V  ein 
AppUed  Anatomy  . 
The  Deep  Veins  of  the  Lower  Extremity 
The  Plantar  Digital  Veins 
The  Posterior  Tibial  Veins 
The  Anterior  Tibial  Veins 

The  Popliteal  Vein 
The  Femoral  Vein 

The  Deep  Femoral  Vein 
The  Veins  of  the  Abdomen  and  Peh-is 
The  External  Iliac  Vein 

Tributaries 
The  Hypogastric  Veins 

Tributaries 
The  Hemorrhoidal  Plexus 
The  Pudendal  Plexus  . 
The  Vesical  Plexus 

AppKed  Anatomy 
The  Dorsal  Veins  of  the  Penis 
The  Uterine  Plexuses  . 
The  Vaginal  Plexuses 
The  Common  Iliac  Veins 

The  Middle  Sacral  Veins 
Peculiarities 
The  Inferior  Vena  Cava    . 
Relations    .... 
Peculiarities     . 
Applied  Anatomy 
Tributaries 

Lumbar  Veins 
Spermatic  Veins 

Applied  Anatomy 
I  Ovarian  Veins 

I  Renal  Veins  . 

Suprarenal  Veins 
\  Inferior  Phrenic  Veins 

Hepatic  Veins 


The  Portal  System  of  Veins. 

The  Portal  Vein        .... 
Tributaries         .... 
The  Lienal  Vein    . 

Tributaries 
The  Superior  Mesenteric  Vein 

Tributaries     . 
The  Coronary  Vein    . 
The  Pyloric  Vein 
The  Cystic  Vein   . 
The  Parumbilical  Veins 
■  AppUed  Anatomy  . 


THE  LYMPHATIC  SYSTEM. 


Structure  of  Lvmphatic  Vessels     ....  768 

The  Lymph  Glands 768 

Structure  of  Lymph  Glands   ....  769 

Applied  Anatomy 770 


The  Thoracic  Duct. 


The  Cisterna  Chyli 
Tributaries 


756 
756 
756 
756 
757 
757 
758 
758 
758 
758 
758 
758 
759 
759 
759 
760 
760 
760 
761 
761 
761 
761 
761 
761 
762 
762 
762 
762 
762 
762 
762 
762 
763 
763 
763 
763 
764 
764 
764 
764 
764 


764 
765 
765 
766 
766 
766 
766 
766 
767 
767 
767 


772 
772 


CONTENTS 


23 


The  Right  Lymphatic  Duct 
Tributaries 
Applied  Anatomy  . 


772 
773 
773 


Thk   Lymphatics  of  thk   Hkad,  Face,  and 

Neck. 

The  Lviiiph  Glands  of  the  Hoad  ...  774 

The  Occipital  Cilands 774 

The  Posterior  Auricular  Glauds  .  774 

The  Anterior  Auricular  Glands    .  775 

The  Parotid  Glands 775 

The  Facial  (Jhunls        .  ' 775 

The  Deep  Ivicial  Glands 775 

The  Lingual  Glands 775 

The  Retropharyngeal  Glands  .  776 

The  Lymphatic  Vessels  of  the  Scalp  .  776 
The  Lymphatic  Vessels  of  the  Auricula 

and  External  Acoustic  Meatus  776 

The  Lymphatic  Vessels  of  the  Face  776 
The    Lymphatic   Vessels   of   the    Nasal 

Cavities 776 

The  Lymphatic  Vessels  of  the  Mouth  .  777 
The  Lymphatic  Vessels  of  the  Palatine 

Tonsil 777 

The  Lymphatic  Vessels  of  the  Tongue     .  778 

The  Lymph  Glands  of  the  Neck   ....  778 

The  Submaxillary  Glands       .  778 

The  Submental  or  Suprahyoid  Glands   .  778 

The  Superficial  Cervical  Glands  .  778 

The  Anterior  Cervical  Glands      ...  778 

The  Deep  Cervical  Glands  .  .  .  .  .  778 
The  Lymphatic  Vessels  of  the  Skin  and 

Muscles  of  the  Neck 779 


The  Lymphatics  of  the  Upper  Extremity. 

The  Lymph  Glands  of  the  Upper  Extremity  779 

The  Superficial  Lvmph  Glands    .  .  779 

The  Deep  Lymph  Glands       ....  780 

The  Axillary  Glands        ....  780 

Applied  Anatomy 781 

The     Lymphatic     Vessels     of     the     Upper 

Extremity 781 

The  Superficial  Lymphatic  Vessels   .  781 

The  Deep  Lymphatic  Vessels        .  .  782 


The  Lymphatics  of  the  Lower  Extremity. 

The  Lymph  Glands  of  the  Lower  Extremity  782 

The  Anterior  Tibial  Gland      ....  782 

The  Popliteal  Glands 782 

The  Inguinal  Glands 783 

Applied  Anatomy 784 

The     Lvmphatic     Vessels     of     the     Lower 

Extremity 784 

The  Superficial  Lymphatic  Vessels  .  784 

The  Deep  Lymphatic  Vessels       .  .  785 


The  Lymphatics  of  the  Abdomen  and  Pelvis.  '  The 


The   Lymph   Glands   of   the   Abdomen   and 

Pelvis        .      .  • 

The  Parietal  Glands     .... 
The  External  Iliac  Glands    . 
The  Common  Iliac  Glands  . 
The  Epigastric  Glands     . 
The  Iliac  Circumflex  Glands 
The  Hypogastric  Glands 
The  Sacral  Glands 
The  Lumbar  Glands 
The  Lymphatic  Vessels  of  the  Abdomen 

Pelvis 

The  Superficial  Vessels 

The  Deep  Vessels  .... 

The     Lymphatic     Vessels     of     the 
Perineum  and  External  Genitals 


and 


785 
786 
786 
786 
786 
786 
786 
787 
787 

787 
787 
787 

787 


The  Jj.\iiiphatic  Vessels  of  the  Abdonieu  and 
Pelvis — 

Tiie  Visceral  Glands 787 

Tlie  Gastric  Glands 788 

The  JbriKilic  Glands         ....      788 

The  Pancreaticolienial  Glands   .  788 

The  Superior  Mesenteric  Glands  789 

The  Mesenteric  Glands  ....      789 

Ai)plied  Anatomy  789 

The  Ileocolic  Glands  789 

The  Mesocolic  Glands     .       .  791 

The  Inferior  Mesenteric  Glands  791 

The    Lymphatic   Vessels   of   the   Abdominal 

and  Pelvic  Viscera 791 

The  Lymphatic  Vessels  of  the  Subdia- 
phragmatic Portions  of  the  Digestive 

Tube 791 

The  Lymphatic  Vessels  of  the  Stomach  792 
The  Lymphatic  Vessels  of  the  Duodenum  792 
The  Lymphatic  Vessels  of  the  Jejunum 

and  Ileum 792 

The  Lj'-mphatic  Vessels  of  the  Vermiform 

Process  and  Cecum 792 

The  Lymphatic  Vessels  of  the  Colon  792 

The   Lymphatic   Vessels   of   the   Anus, 

Anal  Canal,  and  Rectum      ....     792 
The  Lymphatic  Vessels  of  the  Liver  792 
The    Lymphatic    Vessels    of    the    Gall- 
bladder  793 

The  Lymphatic  Vessels  of  the  Pancreas  793 
The  Lymphatic  Vessels  of  the  Spleen  and 

Suprarenal  Glands 793 

The  Lymphatic  Vessels  of  the  Urinary 

Organs 793 

The     Lymphatic     Vessels     of     the 

Kidney 793 

The  Lymphatic  Vessels  of  the  Ureter     793 
The     Lymphatic     Vessels     of     the 

Bladder        , 793 

The     Lymphatic     Vessels     of     the 

Prostate 794 

The     Lymphatic     Vessels     of     the 

Urethra 794 

The  Lymphatic  Vessels   of  the   Repro- 
ductive Organs 794 

The     Lvmphatic     Vessels     of     the 

Testes 794 

The     Lymphatic     Vessels     of     the 

Ductus  Deferens 794 

The  Lymphatic  Vessels  of  the  Ovary     795 
The     Lvmphatic     Vessels     of     the 

Uterine  Tube 795 

The     Lymphatic     Vessels     of     the 

Uterus 795 

The     Lymphatic     Vessels     of     the 
Vagina 795 


The  Lymphatics  of  the  Thorax. 

The  Parietal  Lymph  Glands 796 

The  Sternal  Glands 796 

The  Intercostal  Glands 797 

The  Diaphragmatic  Glands    ....  797 
Superficial   Lymphatic   Vessels    of    the 

Thoracic  Wall 797 

The  Lymphatic  Vessels  of  the  Mamma .  797 
The  Deep  Lymphatic  Vessels  of  the  Thoracic 

Wall 797 

The  Visceral  Lymph  Glands  798 

The  Anterior  Mediastinal  Glands  .  798 

The  Posterior  Mediastinal  Glands     .  798 

The  Tracheobronchial  Glands      ...  798 

Applied  Anatomy 798 

Lymphatic    Vessels    of    the    Thoracic 

Viscera 799 

The  Lymphatic  Vessels  of  the  Heart     .  799 

The  Lymphatic  Vessels  of  the  Lungs  799 

The  Lymphatic  Vessels  of  the  Pleura  800 

The  Lymphatic  Vessels  of  the  Thymus  800 
The   Lymphatic   Vessels    of    the    CEso- 

phagus 800 


The 


24 


CONTENTS 


NEUROLOGY. 


Structure    of    the    Peripheral    Nerves    and 
Ganglia 


SOI 


The  Medulla  Spinalis  or  Spinal  Cord. 


The 


Dissection 

Enlargements 

Fissures  and  Sulci 

The  Anterior  Median  Fissure 
The  Posterior  Median  Sulcus 
Internal    Structure     of    the     Medulla 

Spinalis 

The  Gray  Substance 

Structure  of  the  Gray  Substance 
The  White  Substance 
Nerve  Fasciculi 
Roots  of  the  Spinal  Nerves 
The  Anterior  Nerve  Root 
The  Posterior  Root 
Applied  Anatomy     .... 


The  Encephalon  or  Brain. 

Dissection 

General  Considerations  and  Di\-isions 

The  Rhombencephalon  or  Hind-brain. 

The  Medulla  Oblongata 

The  Anterior  Median  Fissure 
The  Posterior  Median  Fissure 
Internal     Structure     of     the     Medulla 

Oblongata 

The  Cerebrospinal  Fasciculi 

Gray    Substance    of    the    Medulla 

Oblongata    . 
Restiform  Bodies 
Formatio  Reticularis 
Applied  Anatomy 

The  Pons 

Structure      .... 
Applied  Anatomy  . 
The  Cerebellum 

Lobes  of  the  Cerebellum 
Internal  Structure  of  the  Cerebellum 
The  White  Substance 
Projection  Fibres 
The  Gray  Substance 
Microscopic     Appearance 
Cortex    . 
Applied  Anatomy  . 
The  Fourth  Ventricle    . 
Angles  .  _    . 

Lateral  Boundaries 
Choroid  Plexuses    . 
Openings  in  the  Roof 
Rhomboid  Fossa     . 


of     the 


805 


808 
808 


80S 
809 
810 
814 
814 
818 
819 
819 
820 


821 
821 


822 
822 
822 

826 
826 

829 
830 
832 
833 
833 
834 
836 
836 
836 
839 
839 
840 
842 

842 
844 
845 
845 
845 
846 
847 
847 


The  Dicncephalon — 
The  Optic  Tracts   . 
The  Third  Ventricle     .      . 
The  Interpeduncular  Fossa 
The  Telencephalon  .... 
The  Cereljrul  Hemispheres 

The  Longitudinal  Cerebral  Fissure   . 
The    Surfaces    of    the    Cerebral    Hemi- 
spheres      

The  Lateral  Cerebral  Fissure 
The  Central  Sulcus 
The  Parietooccipital  Fissure  . 
The  Calcarine  Fissure 
The  Cingulate  Sulcus 
The  Collateral  Fissure 
The  Sulcus  Circularis 
The  Lobes  of  the  Hemispheres 
The  Frontal  Lobe 
The  Parietal  Lobe 
The  Occipital  Lobe    . 
The  Temporal  Lobe  . 
The  Insula       .... 
The  Limbic  Lobe . 
The  Rliinencephalon 

The  Olfactory  Lobe    . 
The    Interior    of    the    Cerebral 
spheres   .... 
The  Corpus  CaUosum 
The  Lateral  Ventricles 
The  Fornix 

The  Interventricular  Foramen 
The  Anterior  Commissure 
The  Septum  Pellucidum . 
The  Choroid  Plexus  of  the 

Ventricle      .... 
Structure    of    the    Cerebral 
spheres  ... 
Structure  of  the  Cerebral  Cortex 
Special  Types  of  Cerebral  Cortex 
Weight  of  Encephalon  . 
Cerebral  Localization 
Applied  Anatomy     . 


Hemi- 


Lateral 
Hemi- 


863 
864 
865 
865 
865 
865 


867 
868 
868 
869 
869 
869 
869 
869 
869 
870 
871 
871 
873 
873 
874 
874 

875 
876 

877 
885 
887 
887 
887 

887 

889 
891 
893 
894 
894 
895 


The  Motor  and  Sensory  Tracts. 

The  Motor  Tract 89& 

The  Sensory  Tract 897 

Applied  Anatomy 89& 

The  Meninges  of  the  Brain  and  Medulla  Spinalis. 


The  Mesencephalon  or  Mid-brain. 

The  Cerebral  Peduncles 

Structure  of  the  Cerebral  Peduncles 
The  Gray  Substance 
The  White  Substance 
The  Corpora  Quadrigemina      .... 

Structure  of  the  Corpora  Quadrigemina 
The  Cerebral  Aqueduct 

The  Prosencephalon  or  Fore-brain. 


The  Diencephalon    . 

The  Thalamencephalon 

Structure   . 

Connections 
The  Metathalamus 
The  Epithalanius   . 
The  Hypothalamus 

Applied  Anatomy 
The  Optic  Chiasma 


849 
850 
851 
853 
854 
854 


855 
855 
856 
857 
858 
859 
860 
862 
862 


The  Dura  Mater 

The  Cerebral  Dura  Mater 

Processes    . 

Structure    . 
The  Spinal  Dura  Mater 

Structure    . 
The  Arachnoid    .... 
The  Cerebral  Part 
The  Spinal  Part      .       . 
Structure  .       . 

The  Subarachnoid  Cavity 
The  Subarachnoid  Cisternse 
The  Arachnoid  Granulations 

Structure    .       .       .  •   . 

The  Pia  Mater 

The  Cerebral  Pia  Mater    . 
The  Spinal  Pia  Mater 
The  Ligamentum  Denticulatum 
Applied  Anatomy  .... 


900 
900 
900 
902 
902 
903 
903 
903 
903 
904 
904 
904 
905 
906 
906 
906 
906 
907 
907 


The  Cerebral  Nerves. 
The  Olfactory  Nerves. 

Applied  Anatomy 909 

The  Optic  Nerve. 

The  Optic  Tract 909 

The  Optic  Chiasma 909 

Applied  Anatomy 911 


cox  TEXTS 


20 


The  Oculomotor  Nerve. 


Applied  Anatomy 

The   Trochlear  Nerve. 

Applied  Anatomy 

The  Trigeminal  Nerve. 

The  Semilunar  Ganglion 
The  Ophthalmic  Nerve 

The  Lacrimal  Nerve 

The  Frontal  Nerve 

The  Nasociliary  Nerve 

The  Ciliary  Ganglion  . 
The  Maxillarj'  Nerve 

Branches      .... 

The  Middle  Meningeal  Ncrv 
The  Zygomatic  Nerve 
The  Sphenopalatine. 
The  Posterior  Superior  Alveolar 
The  Middle  Superior  Alveolar 
The  Anterior  Superior  Alveolar 
The  Inferior  Palpebral 
The  External  Nasal   . 
The  Superior  Labial 
The  Sphenopalatine  Ganglion 
The  Mandibular  Nerve       .... 

Branches      

The  Nervus  Spinosus 
The  Internal  Pterygoid  Nerve 
The  Masseteric  Nerve 
The  Deep  Temporal  Nerves 
The  Buccinator  Nerve 
The  External  Pterygoid  Nerve 
The  Auriculotemporal  Nerve 
The  Lingual  Nerve 
The  Inferior  Alveolar  Nerve 
The  Otic  Ganglion     . 
The  Submaxillary  Ganglion 
Applied  Anatomy  of  the  Trigeminal  Nerve 
Trigeminal  Nerve  Reflexes       .... 


The  Abducent  Nerve. 

Applied  Anatomy 

The  Facial  Nerve. 


913 


914 


914 
915 
915 
916 
916 
917 
917 
917 
917 
917 
918 
918 
919 
919 
919 
919 
919 
919 
921 
921 
921 
921 
921 
922 
922 
922 
923 
923 
923 
924 
925 
925 
925 


929 


The  Ganglion  Nodosum — 
The  Auricular  Branch 
The  Pharyngeal  Branch    . 
The  Superior  Laryngeal  Nerve 
The  Recurrent  Nerve 
The  Superior  Cardiac  Branches 
The  Inferior  Cardiac  Branches 
The  Anterior  Bronchial  Branches 
The  Posterior  Bronchial  Branches 
The  CEsophageal  Branches 
The  Gastric  Branches 
The  Coeliac  Branches 
The  Hepatic  Branches 

Applied  Anatomy  of  the  Vagus  Nerve 

The  Accessory  Nerve. 

The  Cerebral  Part 

The  Spinal  Part 

Applied  Anatomy 


The  Greater  Superficial  Petrosal  Ner\-e   .  931 

The  Nerve  to  the  Stapedius 932 

The  Chorda  Tj-mpani  Nerve 932 

The  Posterior  Auricular  Nerve      ....  933 

The  Digastric  Branch 933 

The  Stylohyoid  Branch 933 

The  Temporal  Branches 933 

The  Zygomatic  Branches 933 

The  Buccal  Branches 933 

The  Mandibular  Branch 933 

The  Cer^-ical  Branch 933 

Applied  Anatomy 933 

The  Acoustic  Nerve. 

The  Vestibular  Root 935 

The  Cochlear  Root 935 

Applied  Anatomy 936 

The  Glossopharyngeal  Nerve. 

The  Superior  Ganglion -938 

The  Petrous  Ganglion 939 

The  Tympanic  Nerve 939 

The  Carotid  Branches 939 

The  Pharyngeal  Branches      ....  940 

The  Muscular  Branches 940 

The  Tonsillar  Branches 940 

The  Lingual  Branches 940 

The  Vagus  Nerve. 

The  Jugular  Ganglion 941 

The  Ganglion  Nodosum 941 

The  Meningeal  Branch 941 


The  Hypoglossal  Nerve. 


Branches  of  Communication 
Branches  of  Distribution     . 
The  Meningeal  Branches 
The  Descending  Ramus 
The  Thyrohyoid  Branch 
The  ^luscular  Branches 


The  Spinal  Nerves. 


941 
942 
942 
942 
942 
943 
943 
943 
943 
943 
943 
943 
943 


944 
945 
945 


946 

947 
947 
947 
947 
947 


Nerve  Roots 

.      948 

The  Anterior  Root 

.      948 

The  Posterior  Root      .       . 

.      948 

The  Spinal  Ganglia 

.      948 

Structure    .... 

.      949 

Applied  Anatomy  . 

.      950 

Di-\"isions  of  the  Spinal_ Nerves 

951 

The  Posterior  Di^nsions    . 

.      951 

The  Cervical  Nerves 

.      951 

The  Thoracic  Nerves 

.      952 

The  Lumbar  Nerves 

.      953 

The  Sacral  Nerves      . 

.      953 

The  Coccygeal  Nerve 

.     954 

The  Anterior  Di^^sions 

.      954 

The  Cervical  Nerves 

.      954 

The  Cervical  Plexus 

.      954 

Great  Auricular  Nerve 

.      956 

Cutaneous  Cer^-ical  N 

erve     957 

Supraclavicular  Nerve 

s           957 

Communicantes  Cer\d 

cales    957 

Phrenic  Nerve  . 

.      957 

Applied  Anatomy 

.      958 

The  Brachial  Plexus 

.      958 

Relations 

.      959 

Dorsal  Scapular  Nerv 

e     .      960 

Suprascapular  Nerve 

.      960 

Nerve  to  Subclavius 

.      960 

Long  Thoracic  Nerve 

.      960 

Anterior  Thoracic  Nei 

ves      961 

Subscaptilar  Nerves 

.      .     960 

Thoracodorsal  Nerve 

.      .     960 

Axillary  Nerve 

.      .     960 

Musculocutaneous  Ne 

rve       962 

Medial  Antibrachial  C 

uta- 

neous  Nerve 

.      .      964 

:Medial  Brachial  Cut 

1- 

neous  Nerve 

.       .      964 

Median  Nerve  . 

.      .     965 

Radial  Nerve    . 

.      .      968 

Applied  Anatomy  . 

.      .      970 

The  Thoracic  Nerves 

.      .     972 

First  Thoracic  Nerve     . 

.      .      972 

LTpper  Thoracic  Nerves 

.      .      972 

Lower  Thoracic  Nerves 

.      .     973 

Applied  Anatomj-     . 

.      .      974 

The  Lumbosacral  Plexus 

.      .      974 

The  Lumbar  Nerves 

.       .      974 

The  Lumbar  Plexus 

.       .      975 

Iliohypogastric  N 

erve     976 

Ilioinguinal  Nerv 

3      .      977 

Genitofem( 

jral 

Ne 

rve      977 

26 


COXTEXTS 


Divisions  of  the  Spinal  Nerves — 
The  Anterior  Divisions — 

The  Lumbosacral  Plexus — 
The  Lumbar  Nerves — 

The  Lumbar  Plexus — 

Lateral  Femoral  Cuta- 
neous Nerve 
Obturator  Nerve 
Accessory     Obturator 
Nerve     .... 
Femoral  Nerve 
Saphenous  Nerve. 
The    Sacral    and    Coccygeal 

Nerves 

The  Sacral  Plexus 
Relations 

Nerve  to  Quadratus 
Femoris     and 
Gemellus  Inferior 
Nerve   to   Obturator 
luternus   and    Ge- 
mellus Superior     . 
Nerve  to  Piriformis 
Superior      Gluteal 

Nerve   .... 

Inferior     Gluteal 

Nerve   .... 

Posterior       Femoral 

Cutaneous  Nerve 
Sciatic  Nerve 
Tibial  Nerve 
Lateral  Plantar  Nerve 
Common       Peroneal 
Nerve   .... 
Deep  Peroneal  Nerve 
Superficial    Peroneal 
Nerve   .... 
The  Pudendal  Plexus 

Perforating        Cuta- 
neous Nerve    . 
Pudendal  Nerve 
Anococcygeal  Nerve 
Applied  Anatomy  .... 

The  Sympathetic  Nerves. 

The  Sympathetic  Trunks 

Connections  -n-ith  the  Spinal  Nerves 


977 
979 


The  Cephalic  Portion  of  the  Sympathetic 
System. 

The  Internal  Carotid  Plexus        ....        996 
The  Cavernous  Plexus 996 

The  Cervical  Portion  of  the  Sympathetic 
System. 


980  The 
980 

981  The 

982  The 

982 
982 


Superior  Cervical  Ganglion 

.       .        997 

Branches    

.      .        997 

Middle  Cer\acal  Ganglion 

997 

Branches    

997 

Inferior  Cervical  Ganglion    . 

998 

Branches    

.      .        998 

984 


984 
984 


984 

985 

985 
986 

987 
989 

989 
990 

990 
991 

991 
991 
992 
992 


995 
995 


The 
The 
The 


The   Thoracic  Portion  of  the  Sympathetic 
System. 

Greater  Splanchnic  Nerve  ....  998 
Lesser  Splanchnic  Nerve  ....  999 
Lowest  Splanchnic  Nerve     ....        999 


The  Abdominal  Portion  of  the  Sympathetic 

System        ....      1001 

The  Pelvic  Portion  of  the  Sympathetic 

System        ....      1001 

The  Great  Plexuses  of  the  Symjjathetic  System. 


The  Cardiac  Plexus      . 

1001 

The  Coeliac  Plexus       .       . 

1002 

Phrenic  Plexus 

1003 

Hepatic  Plexus 

1004 

Lienal  Plexus 

1004 

Superior  Gastric  Plexus 

1004 

Suprarenal  Plexus 

1004 

Renal  Plexus  . 

1004 

Spermatic  Plexus 

1004 

Applied  Anatomv 

1004 

Superior  Alesenteric  Plexus 

1004 

Abdominal  Aortic  Plexus 

1004 

Inferior  Alesenteric  Plexus 

1005 

The  Hypogastric  Plexus    . 

1005 

The  Pehdc  Plexuses  . 

1005 

Applied  Anatomy 

1005 

THE  ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT. 


The  Peripheral  Organs  of  the  Special 
Senses. 

The  Organs  of  Taste. 

Structure 1007 

The  Organ  of  Smell. 

The  External  Nose 1008 

Structure 1008 

The  Nasal  Cavitv 1010 

The  Lateral  Wall 1010 

The  Medial  Wall 1012 

The  Mucous  Membrane        ....  1012 

Structure 1012 

The  Accessory  Sinuses  of  the  Nose  .       .  1014 

The  Frontal  Sinuses 1014 

The  Ethmoidal  Air  Cells       .       .       .       .  1014 

The  Sphenoidal  Sinuses 1014 

The  MaxUlary  Sinus 1015 

Applied  Anatomy  of  the  Nose      ....  1015 

The  Organ  of  Sight. 


The  Tunics  of  the  Eye 

The  Fibrous  Tunic 

The  Sclera     . 

Structure 

The  Cornea  . 

Structure 


1017 
1017 
1017 
1018 
1018 
1019 


The  Tunics  of  the  Eye — 

Dissection        .... 
The  Vascular  Tunic   . 

The  Choroid        .       . 

Structure 
Dissection 
The  Ciliary  Body     . 

Structure 
The  Iris    .... 

Structure 
Membrana  PupUlaris 
The  Retina      .... 
Structure 
The  Refracting  Media 
The  Aqueous  Humor 
The  Vitreous  Body    . 
The  Crystalline  Lens 
Structure 

Applied  Anatomy  of  the  Organ  of  Sight 
The  Accessory  Organs  of  the  Eye 
The  Ocular  Muscles  .... 

Dissection 

Levator  Palpebrae  Superioris 

The  Recti 

Obliquus  Oculi  Superior 
Obliquus  Oculi  Inferior 
The  Fascia  Bulb 
The  Orbital  Fascia 
Applied  Anatomy 
The  Eyebrows 
The  Eyelids     .      .      . 


1021 
1021 
1021 
1021 
1022 
1023 
1023 
1024 
1025 
1026 
1026 
1027 
1030 
1030 
1030 
1030 
1031 
1031 
1034 
1034 
1034 
1034 
1035 
1035 
1036 
1037 
1038 
1038 
1038 
1038 


CONTEXTS 


27 


The  Accessory  Organs  of  the  Eye — 
The  Eyelids — 

The    Lateral    Palpebral    Commis 

sure 

The  Eyelashes     .... 
Structure  of  the  Eyelids 
The  Tarsal  Glauds     .      . 

Sti'ucture 
The  Conjunctiva 

The  Palpebral  Portion 
The  Bulbar  Portion 
The  Lacrimal  Apparatus 
Tlie  Lacrimal  Gland 

Structure 
The  Lacrimal  Ducts 
The  Lacrimal  Sac 

Structure 
The  Nasolacrimal  Duct 
Applied  Anatomy 

The  Organ  of  Hearing. 

The  External  Ear 

The  Auricula  or  Pinna 

Structure 

The  External  Acoustic  Meatus 

Relations 

Applied  Anatomy       ... 
The  ]\Iiddle  Ear  or  Tvmpanic  Cavitv 
The  Tegumental  Wall  or  Roof  . 
The  Jugular  Wall  or  Floor    . 
The  Membranous  or  Lateral  Wall 
The  Tympanic  Membrane    . 

Structure 

The  Labyrinthic  or  Medial  Wall 
The  Mastoid  or  Posterior  Wall 
The  Carotid  or  Anterior  Wall    . 
The  Auditory  Tube    . 
The  Auditorv  Ossicles 

The  ]Malleus    .      .      . 

The  Incus 

The  Stapes 

Articulations  of  the  Auditory  Ossicles 

Ligaments  of  the  Ossicles 

The  Muscles  of  the  Tympanic  Cavity 


1038 
1038 
1039 
1040 
1040 
1040 
1040 
1041 
1041 
1041 
1041 
1041 
1042 
1042 
1042 
1042 


1043 
1044 
1044 
1046 
1047 
1048 
1049 
1049 
1049 
1049 
1050 
1050 
1050 
1051 
1052 
1052 
1053 
1053 
1054 
1054 
1054 
1054 
1055 


The  Auditory  Ossicles — 

The  Muscles  of  the  Tympanic  Cavity 
The  Tensor  Tympani 
The  Stapedius     ... 

Applied  Anatomy       .... 
The  Internal  Ear  or  Lal)yrint!<    . 

The  Osseous  Labyrinth  . 

The  Vestibule      .... 
The  Bony  Semicircular  Canals 
The  Cochlea        .... 

The  Membranous  Labyrinth 

The  Utricle 

The  Saccule 

The  Semicircular  Ducts 

Structure      .... 
The  Ductus  Cochlearis 
The  Basilar  Membrane 
Hair  Cells 

Applied  Anatomy       .... 


1055 
1055 
1056 
1057 
1057 
1058 
1058 
1059 
1061 
1062 
1062 
1062 
1063 
1063 
1065 
1067 
1068 


Peripheral  Terminations  of  Nerves  of  General 
Sensations. 


Free  Nerve-endings 

Special  End-organs 

End-bulbs  of  Krause    . 

Tactile  Corpuscles  of  Grandry 

Pacinian  Corpuscles     . 

Corpuscles  of  Golgi  and  Mazzoni 

Tactile  Corpuscles  of  Wagner  and  Meissner 

Neurotendinous  Spindles 

Neuromuscular  Spindles 

The  Comon  Integument. 

The  Epidermis,  Cuticle,  or  Scarf  Skin 

The  Corium,  Cutis  Vera,  Dermis,  or  True 

Skin 

The  Appendages  of  the  Skin. 

The  Nails 

The  Hairs 

The  Sebaceous  Glands       ...... 

The  Sudoriferous  or  Sweat  Glands    . 


1069 
1069 
1069 
1069 
1069 
1069 
1070 
1070 
1070 


1071 

1074 


1075 
1075 
1077 
1078 


SPLANCHNOLOGY. 


The  Respiratory  Apparatus. 


The  Pleura;. 


The  Larynx. 

The  Cartilages  of  the  Larynx 
The  Thyroid  Cartilage    . 
The  Cricoid  Cartilage 
The  Arytenoid  Cartilage 
The  Corniculate  Cartilages  . 
The  Cuneiform  Cartilages     . 
The  Epiglottis       .... 
Structure 

The  Ligaments  of  the  Larynx 
The  Extrinsic  Ligaments 
The  Intrinsic  Ligaments 

The  Interior  of  the  Larynx 
The  Ventricular  Folds 
The  Vocal  Folds  .... 
The  Ventricle  of  the  Larynx 
The  Rima  Glottidis    . 

The  Muscles  of  the  Larynx 
Cricothj-reoideus 
Cricoarytaenoideus  Posterior 
Cricoarj-taenoideus  Lateralis 
Arytaenoideus       .... 
Thyreoarvtaenoideus 


The  Trachea  and  Bronchi. 

Relations 

The  Right  Bronchus 

The  Left  Bronchus 

Structure      

Applied  Anatomy 


1079 
1080 
1081 
1081 
1081 
1082 
1082 
1082 
1082 
1082 
1083 
1085 
1085 
1086 
1086 
1087 
1088 
1088 
1088 
1088 
1088 
1089 


Reflections  of  the  Pleura  .... 

Pulmonary  Ligament 

Structure  of  Pleura                   ... 
Applied  Anatomy 

The  Mediastinal  Cavity 

Superior  Mediastinal  Cavity 
Anterior  Mediastinal  Cavity 
Middle  Mediastinal  Cavity    . 
Posterior  Mediastinal  Cavity 
Applied  Anatomy 


The  Lungs. 

The  Apex  of  the  Lungs 
The  Base  of  the  Lungs 
Surfaces  of  the  Lungs 
Borders  of  the  Lungs  . 
Fissures  and  Lobes  of  the  Lungs 
The  Root  of  the  Lung 
Divisions  of  the  Bronchi  . 
Structure  of  the  Lungs 
Applied  Anatomy  .... 


The  Digestive  Apparatus. 


1095 
1097 
1097 
1098 


1098 
1100 
1101 
1101 
1101 


1101 
1102 
1102 
1103 
1104 
1105 
1105 
1106 
1108 


„Q^  The  Mouth. 

1092  I  The  Vestibule  of  the  Mouth 1110 

1092  i  The  Mouth  Cavity  Proper 1110 

1092!  Structure IHO 

1093  The  Lips IHO 


28 


CONTEXTS 


The  Mouth  Cavity  Proper 

The  Labial  Glands 
The  Cheeks       .      .      . 

Structure    . 
The  Gums   .... 
Applied  Anatomy 
The  Palate  .... 
The  Hard  Palate 
The  Soft  Palate    . 
The  Palatine  Aponeurosis 
The  Muscles  of  the  Palate 

Levator  Veli  Palatini 

Tensor  Veli  Palatini 

Musculus  L"^^ilae 

Glossopalatinus  . 

Phar>'ngopalatinus  . 

Dissection 
Applied  Anatomy 

The  Teeth 

General  Characteristics  . 
The  Permanent  Teeth 

The  Canine  Teeth    . 

The  Premolar  or  Bicuspid  Teeth 

The  Molar  Teeth     . 
The  Deciduous  Teeth 
Structure  of  the  Teeth     . 
Development  of  the  Teeth 
Eruption  of  the  Teeth 
Applied  Anatomy 

The  Tongue 

The  Root  of  the  Tongue 
The  Apex  of  the  Tongue 
The  Dorsum  of  the  Tongue 
The  Papillae  of  the  Tongue 
The  Muscles  of  the  Tongue 

Genioglossus 

Hyoglossus     . 
Relations 

Chondroglossus 

Styloglossus  . 

Longitudinalis  Linguae  Superior 

Longitudinalis  Linguae  Inferior 

Transversus  Linguae 

Verticalis  Linguae    . 

Applied  Anatomy     . 
Structure  of  the  Tongue 
Glands  of  the  Tongue 
Applied  Anatomy       .... 

The  Salivarv  Glands 

The  Parotid  Gland     .... 

Structures  within  the  Gland 

The  Parotid  Duct    . 

Structure        

The  Submaxillarj'  Gland 

The  Submaxillarj-  Duct 
The  Sublingual  Gland 
Structure  of  the  Salivary  Gland 
Accessory  Glands       .... 
Applied  Anatomy  .      . 

The  Pharynx. 


The  Xasal  Part  of  the  Pharj'nx  . 
The  Oral  Part  of  the  Pharj-nx      . 
The  Palatine  Tonsils 

Structure 

Applied  Anatomy 
The  Laryngeal  Part  of  the  Pharynx 
The  Muscles  of  the  Pharynx 

Dissection 

Constrictor  Pharj^ngis  Inferior 

Relations        .... 
Constrictor  Pharj^ngis  Medius 

Relations        .... 
Constrictor  Pharyngis  Superior 

Relations        .... 
Stylopharj-ngeus  .... 
Salpingopharj'ngeus   . 
Structure  of  the  Pharynx 
Applied  Anatomy 


The  CEsopfuigus. 


Relations 
Applied  Anatomy 


1110 
1110 
1110 
1111 
1112 
1112 
1112 
1112 
1112 
1113 
1113 
1113 
1114 
1114 
1114 
1114 
1115 
1115 
1116 
1117 
1117 
Ills 
1118 
1118 
1119 
1121 
1124 
1125 
1125 
1126 
1126 
1126 
1127 
1128 
1129 
1129 
1129 
1130 
1130 
1130 
1130 
1130 
1130 
1130 
1131 
1131 
1132 
1133 
1133 
1135 
1135 
1135 
1135 
1136 
1137 
1137 
1138 
1138 


1139 
1139 
1139 
1141 
1141 
1141 
1141 
1141 
1141 
1142 
1142 
1142 
1142 
1142 
1142 
1143 
1143 
1143 


1144 
1146 


the    Omental 


of    the    Peri 


or  Appen 


The  Abdomen. 

Boundaries  of  the  Abdomen 

The  Apertures  in  the  Walls  of  the  Abdomen 
Regions  of  the  Abdomen 
The  Peritoneum 

Vertical  Dispositions  of  the  Main  Perl 

toneal  Cavity    . 
Vertical    Disposition    of 

Bursa      .... 
Horizontal    Disposition 
toneum 
In  the  Pelvis 
In  the  Lower  Abdomen 
In  the  Upper  Abdomen 
The  Omenta    . 
The  Mesenteries  . 
The  Peritoneal  Recesses  or  Fossae 
The  Duodenal  Fossae 
The  Cecal  Fossae 
The  Intersigmoid  Fossa 
Applied  Anatomy 

The  Stomach 

Openings  of  the  Stomach 
Curv'atures  of  the  Stomach 
Surfaces  of  the  Stomach 
Component  Parts  of  the  Stomach 
Position  of  the  Stomach 
Interior  of  the  Stomach 
Pyloric  Valve 
Structure  of  the  Stomach 
The  Gastric  Gland 
Applied  Anatomy 
The  Small  Intestine     . 
The  Duodenum 

Relations 
The  Jejunum  and  Ileum 
^kleckel's  Diverticulum 
Structure   .... 

The  Large  Intestine 
The  Cecum 

The  Vermiform  Process 
dix 
Structure 
The  Colic  Valve  . 
The  Colon        .... 

The  Ascending  Colon 
The  Transverse  Colon 
The  Descending  Colon 
The  Iliac  Colon 
The  Sigmoid  Colon 
The  Rectum    .... 

Relations  of  the  Rectum 
The  Anal  Canal 
Structure  of  the  Colon 
Applied  Anatomy  of  the  Intestines 
The  Liver    ...... 

Surfaces  of  the  Liver 
Fosste  of  the  Liver 
Lobes  of  the  Liver 
Ligaments  of  the  Liver    . 
Structure  of  the  Liver 
Excretory  Apparatus  of  the 
The  Hepatic  Duct    . 
The  Gall-bladder 
Relations 
Structure 
The  Common  Bile  Duct 
Relations 
Applied  Anatomy 
The  Pancreas    . 
Dissection 
Relations    . 
The  Pancreatic  Duct 
Structure    . 
Applied  Anatomy 


The  Urogenital  Appabatcs. 

The   Urinary  Organs. 

The  Kidneys 120& 

Relations 1207 

Surfaces 1207 


Liver 


CONTENTS 

29 

The  Kidneys- 

The  Fcm^ile  Geiiilal  Organs. 

Borders      

1209 

Extremities      . 

1209 

The  Ovaries 

1243 

Fixation  of  the  Kidney          .       .       .       . 

1209 

The  Epoophoron         

1244 

General  Structure  of  the  Kidney 

1210 

The  Paroophoron 

1245 

Applied  Anatomy 

1214 

Structure 

1245 

The  Ureters 

1216 

Vesicular  Ovarian  P^ollicles  . 

1245 

The  Ureter  Proper 

1216 

Applied  Anatomy       . 

1246 

Structure 

1217 

The  Uterine  Tube 

1247 

Applied  Anatomy 

1218 

Structure    ... 

1247 

The  Urinary  Bladder 

1218 

Applied  Anatomy                           .       . 

1247 

1218 

The  Uterus 

1248 

Tlip  Dii^tonHprl   T^InrlHpr 

1219 

The  Body 

1249 

The  Bladder  in  the  Child 

1220 

The  Cervix 

1249 

The  Female  Bladder 

1221 

The  Interior  of  the  Uterus   . 

1250 

The  Ligaments  of  the  Bladder 

1221 

The  Ligaments  of  the  Uterus 

1250 

The  Interior  of  the  Bladder 

1222 

Structure    

1252 

Structure 

1223 

Applied  Anatomy 

1254 

Applied  Anatomy 

1224 

The  Vagina 

1255 

The  Male  Urethra 

1225 

Relations   . 

1255 

The  Prostatic  Portion      .             . 

1225 

Structure 

1255 

1226 

The  External  Organs  . 

1256 

The  Cavernous  Portion  .... 

1226 

The  Mons  Pubis  . 

1256 

Structure 

1226 

The  Labia  Majora 

1256 

Applied  Anatomy 

1226 

The  Labia  Minora 

1257 

The  Female  Urethra 

1228 

The  Clitoris     .      . 

1257 

Structure 

1228 

The  Vestibule 

1257 

The  Bulb  of  the  Vestibule    .      . 

1257 

Th  Male  Genital  Organs. 

The  Greater  Vestibular  Glands 

1258 

The  Mammae 

1258 

The  Testes  and  their  Coverings  . 

1228 

The  Mammary  Papilla  or  Nipple    . 

1258 

The  Scrotum 

1228 

Structure 

1258 

The  Intercrural  Fascia    .... 

1229 

Applied  Anatomy 

1260 

The  Cremaster  Muscle    .... 

1229 

The  Infundibuliform  Fascia 

1229 

The  Tunica  Vaginalis       .... 

1229 

The  Ductless  Glands. 

The  Inguinal  Canal 

1229 

The  Spermatic  Cord        .... 

1229 

The  Thyroid  Gland. 

Structure  of  the  Spermatic  Cord 

1230 
1230 

Structure 

1262 

Applied  Anatomy 

Applied  Anatomy 

.      1263 

The  Testes  _ 

1230 

The  Epididymis        .... 
Appendages  of  the  Testis  and  Epi 

1231 

The  Parathyroid  Glands. 

didymis 

1231 
1231 
1232 

Structure            

1264 

The  Tunica  Vaginalis 
The  Tunica  Albuginea 

Applied  Anatomy 

1264 

The  Tunica  Vasculosa 

1232 

Structure 

1232 

The  Thymus. 

Applied  Anatomy     .... 

1234 

The  Ductus  Deferens 

1235 

Structure      

1264 

The  Ductuli  Aberrantes 

1236 

Applied  Anatomy 

1266 

Paradidj-mis 

1236 

Structure   

1236 

The  Spleen. 

The  Vesiculae  Seminales 

1236 

Structure 

1237 

Relations 

1266 

Applied  Anatomy 

1237 

Structure      

.      1267 

The  Ejaculatory  Ducts 

.      1237 

Applied  Anatomy 

1270 

Structure 

1237 

The  Penis 

.      1237 

The  Suprarenal  Glands. 

The  Corpora  Cavernosa  Penis   . 

.      1238 

The  Corpus  Cavernosum  Urethrae 

.      1238 

Relations      ......... 

.      1270 

.      1239 

Structure 

Applied  Anatomy 

1271 

Applied  Anatomy 

The  Prostate 

1240 
1241 

.      1272 

Structxire 

Applied  Anatomy 

1241 
1242 

The  Carotid  Skeins  . 

.      1273 

The  Bulbourethral  Glands             ... 

1243 

Structure    

.      1243 

The  Coccygeal  Skein  . 

1273 

SURFACE  ANATOMY  AND  SURFACE  MARKINGS. 

Surface  Anatomy  of  the  Head  and  Neck.  The  Cranium — 

Bony  Landmarks 

The  Bones 1275  The  Brain        .... 

The  Joints  and  Muscles 1276 !  Vessels 

The  Arteries 1278  I  The  Face 

External  Maxillary  Artery 
Surface  Markings  of  Special  Regions  of  the  Head  Trigeminal  Nerve 

and  Neck.  Parotid  Gland 

The  Nose 

The  Cranium 1279  The  Mouth 

The  Scalp 1279  The  Eye 


1279 
1280 
1282 
1282 
1282 
1283 
1283 
1284 
1284 
1287 


30 

CONTEXTS 

The  Ear 

1288    Descending  Colon 

1307 

The  Tympanic  Antrum 

1289 

Iliac  Colon  . 

1307 

The  Neck  " 

1289 

Liver 

1307 

Muscles 

1290 

Pancreas 

1307 

Arteries      ...             ... 

1290 

Spleen 

1307 

Veins 

1291 

Kidneys 

1308 

Nerves 

1291 

Ureters  . 

1308 

Submaxillary  Gland 

1291 

Vessels    . 
Nerves    . 

1309 
1309 

Surface  Anatomy  of  the  Back. 

Surface  Anatomy  of  the  Perineum. 

Bones 

1291 

Muscles 

1292 

Skin 

1309 

Bones 

1309 

Surface  Markings  of  the  Back. 

Muscles  and  Ligaments 

1309 

Bony  Landmarks 
Medulla  Spinalis 
Spinal  Nerves    . 


Surface  Anatomy  of  the  Thorax. 


1293  I  Surface  Markings  of  the  Perineum. 

1293 

1295    Rectum  and  Anal  Canal 1310 

Male  Urogenital  Organs 1310 

Female  Urogenital  Organs 1311 


Bones 

Muscles 
Mamma 


Surface  Markings  of  the  Thorax. 


Bonj'  Landmarks 

Diaphragma 

Surface  Lines 

PleuriBe 

Lungs 

Trachea 

CEsophagus 

Heart 

Arteries 

Veins    . 


Surface  Anatomy  of  the  Abdornen. 


Skin 

Bones 

Muscles 

Vessels 

Viscera 


Surface  Markings  of  the  Abdomen. 


Bony  Landmarks    . 

Muscles 

Surface  Lines 

Stomach 

Duodenum  . 

Small  Intestine 

Cecum  and  Vermiform  Process 

Ascending  Colon 

Transverse  Colon   . 


1295 
1295 
1296 


1296 
1297 
1297 
1297 
1298 
1299 
1299 
1299 
1300 
1300 


1301 
1301 
1301 
1301 
1301 


1303 
1303 
1303 
1305 
1306 
1306 
1307 
1307 
1307 


Surface  Anatomy  of  the  Upper  Extremity. 


Skin         .       . 

Bones 

Articulations 

Muscles 

Arteries 

Veins 

Nerves    . 


1312 
1313 
1315 
1315 
1318 
1318 
1318 


Surface  Markings  of  the  Upper  Extremity. 


Bony  Landmarks 

Articulations 

Muscles 

Mucous  Sheaths 

Arteries 

Nerves 


1319 
1319 
1319 
1319 
1320 
1323 


Surface  Anatomy  of  the  Lower  Extremity. 


Skin         .       . 

Bones 

Articulations 

Muscles 

Arteries 

Veins 

Nerves    . 


1323 
1324 
1325 
1326 
1328 
1329 
1329 


Surface  Markings  of  the  Lower  Extremity. 


Bony  Landmarks 

Articulations 

Muscles 

Arteries 

Veins 

Nerves    . 


1329 
1330 
1330 
1331 
1334 
1334 


INTRODUCTION. 


T^HE  term  human  anaiomy  comprises  a  consideration  of  the  various  structures 
which  make  up  the  human  organism.  In  a  restricted  sense  it  deals  merely 
with  the  parts  which  form  the  fully  developed  individual  and  which  can  be  ren- 
dered evident  to  the  naked  eye  by  various  methods  of  dissection.  Regarded  from 
such  a  standpoint  it  may  be  studied  by  two  methods:  (1)  the  various  structures 
may  be  separately  considered- — systematic  anatomy;  or  (2)  the  organs  and  tissues 
ma}'  be  studied  in  relation  to  one  another — topographical  or  regional  anatomy. 

It  is,  however,  of  much  advantage  to  add  to  the  facts  ascertained  by  naked- 
eye  dissection  those  obtained  by  the  use  of  the  microscope.  This  introduces 
two  fields  of  investigation,  viz.,  the  study  of  the  minute  structure  of  the  various 
component  parts  of  the  body — histology — and  the  study  of  the  human  organism 
in  its  immature  condition,  i.  e.,  the  various  stages  of  its  intrauterine  develop- 
ment from  the  fertilized  ovum  up  to  the  period  when  it  assumes  an  independent 
existence — embryology.  Owing  to  the  difficulty  of  obtaining  material  illustrating 
all  the  stages  of  this  early  development,  gaps  must  be  filled  up  by  observations 
on  the  development  of  lower  forms^ — comparative  embryology,  or  by  a  consideration 
of  adult  forms  in  the  line  of  human  ancestry — comparative  anatomy.  The  direct 
application  of  the  facts  of  human  anatomy  to  the  various  pathological  conditions 
which  may  occur  constitutes  the  subject  of  applied  anatomy.  Finally,  the  appre- 
ciation of  structures  on  or  immediately  underlying  the  surface  of  the  body  is 
frequently  made  the  subject  of  special  study — surface  anatomy. 

Systematic  Anatomy. — The  various  systems  of  which  the  human  body  is 
composed  are  grouped  under  the  following  headings: 

1.  Osteology — the  bony  system  or  skeleton. 

2.  Syndesmology — the  articulations  or  joints. 

3.  Myology — the  muscles.  With  the  description  of  the  muscles  it  is  convenient 
to  include  that  of  the  fasciae  which  are  so  intimately  connected  with  them. 

4.  Angiology — the  vascular  system,  comprising  the  heart,  bloodvessels,  lymphatic 
vessels,  and  lymph  glands. 

5.  Neurology — the  nervous  system.  The  organs  of  sense  may  be  included  in 
this  system. 

6.  Splanchnology  —  the  visceral  system.  Topographically  the  viscera  form 
two  groups,  viz.,  the  thoracic  viscera  and  the  abdominopelvic  viscera.  The 
heart,  a  thoracic  viscus,  is  best  considered  with  the  vascular  system.  The  rest 
of  the  viscera  may  be  grouped  according  to  their  functions:  {a)  the  respiratory 
apparatus;  (6)  the  digestive  apparatus;  and  (c)  the  urogenital  apparatus.  Strictly 
speaking,  the  third  subgroup  should  include  only  such  components  of  the 
urogenital  apparatus  as  are  included  within  the  abdominopehdc  cavity,  but  it 


32  INTRODUCTION 

is  convenient  to  study  under  this  heading  certain  parts  which  he  in  relation  to 
the  surface  of  the  body,  e.  g.,  the  testes  and  the  external  organs  of  generation. 

For  descriptive  purposes  the  body  is  supposed  to  be  in  the  erect  posture,  with 
the  arms  hanging  by  the  sides  and  the  palms  of  the  hands  directed  forward.  The 
median  plane  is  a  vertical  antero-posterior  plane,  passing  through  the  centre  of  the 
trunk.  This  plane  will  pass  approximately  through  the  sagittal  suture  of  the  skull, 
and  hence  any  plane  parallel  to  it  is  termed  a  sagittal  lAane.  A  vertical  plane  at 
right  angles  to  the  median  plane  passes,  roughly  speaking,  through  the  central 
part  of  the  coronal  suture  or  through  a  line  parallel  to  it;  such  a  plane  is  known  as 
a  frontal  plane  or  sometimes  as  a  coronal  plane.  A  plane  at  right  angles  to  both 
the  median  and  frontal  planes  is  termed  a  transverse  plane. 

The  terms  anterior  or  ventral,  and  j)osterior  or  dorsal,  are  employed  to  indicate 
the  relation  of  parts  to  the  front  or  back  of  the  body  or  limbs,  and  the  terms 
superior  or  cephalic,  and  inferior  or  caudal,  to  indicate  the  relative  levels  of  different 
structures;  structures  nearer  to  or  farther  from  the  median  plane  are  referred  to  as 
medial  or  lateral  respectively. 

The  terms  superficial  and  deep)  are  strictly  confined  to  descriptions  of  the 
relative  depth  from  the  surface  of  the  various  structures;  external  and  internal 
are  reserved  almost  entirel}'  for  describing  the  walls  of  cavities  or  of  hollow 
viscera.  In  the  case  of  the  limbs  the  words  proximal  and  distal  refer  to  the 
relative  distance  from  the  attached  end  of  the  limb. 


DESCRIPTIYE  AND  APPLIED  ANATOMY. 


HISTOLOGY. 


THE    ANIMAL    CELL    (Fig.  1). 

A  LL  the  tissues  and  organs  of  the  body  originate  from  a  microscopic  structure 
■^^  (the  fertilized  ovum),  which  consists  of  a  soft  jelly-like  material  enclosed  in  a 
membrane  and  containing  a  vesicle  or  small  spherical  body  inside  which  are  one 
or  more  denser  spots.  This  may  be  regarded  as  a  complete  cell.  All  the  solid 
tissiles  consist  largely  of  cells  essentially  similar  to  it  in  nature  but  differing  in 
external  form. 


Cell  wall 


Vacuole 


Centrosome  consisting  of  cen- 
trosphere  enclosing  two  cen- 
trioles 

~  Nucleolus 

Net-knot  of  chromatin  form- 
ing a  pseudo-nucleolus 
Chromatin  network 


Cell- inclusions  (paraplasm) 


Fig.   1. — Diagram  of  a  cell.     (Modified  froni  Wilson.) 

In  the  higher  organisms  a  cell  may  be  defined  as  "a  nucleated  mass  of  proto- 
plasm of  microscopic  size."  Its  two  essentials,  therefore,  are:  a  soft  jelly-like 
material,  similar  to  that  found  in  the  ovum,  and  usually  styled  protoplasm,  and  a 
small  spherical  body  imbedded  in  it,  and  termed  a  nucleus.  Some  of  the  unicellular 
protozoa  contain  no  nuclei  but  granular  particles  .which,  like  true  nuclei,  stain  with 
basic  d^'es.  The  other  constituents  of  the  ovum,  viz.,  its  limiting  membrane  and-- 
the  denser  spot  contained  in  the  nucleus,  called  the  nucleolus,  are  not  essential  to 
the  type  cell,  and  in  fact  many  cells  exist  without  them. 

Protoplasm  (cytoplasm)  is  a  material  probably  of  variable  constitution  during 
life,  but  yielding  on  its  disintegration  bodies  chiefly  of  proteid  nature.  Lecithin 
and  cholesterin  are  constantly  found  in  it,  as  well  as  inorganic  salts,  chief  among 
which  are  the  phosphates  and  chlorides  of  potassium,  sodium,  and  calcium.  It  is 
of  a  semifluid  viscid  consistence,  and  in  the  living  condition  appears  to  be  homo- 
3 


34  HISTOLOGY 

geneous  and  structureless.  When,  however,  cells  have  been  "fixed"  by  reagents 
a  fibrillar  or  granular  appearance  can  often  be  made  out  under  a  high  power  of  the 
microscope.  The  filjrils  are  usually  arranged  in  a  network  or  reticulum,  to  which 
the  term  spongioplasm  is  applied,  the  clear  substance  in  the  meshes  being  termed 
hyaloplasm.  A  granular  appearance  is  often  caused  by  the  knots  of  the  network; 
but,  in  addition  to  these,  protoplasm  frequently  contains  true  granules,  some  of 
which  are  proteid  in  nature  and  probably  essential  constituents;  others  are  fat, 
glycogen,  or  pigment  granules,  and  are  regarded  as  adventitious  material  taken  in 
from  without,  and  hence  are  styled  cell-inclusions  or  paraplasm.  The  size  and  shape 
of  the  meshes  of  the  spongioplasm  vary  in  different  cells  and  in  different  parts  of 
the  same  cell.  The  relative  amounts  of  spongioplasm  and  hyaloplasm  also  vary 
in  different  cells,  the  latter  preponderating  in  the  young  cell  and  the  former  in- 
creasing at  the  expense  of  the  hyaloplasm  as  the  cell  grows.  The  peripheral  layer 
of  a  cell  is  in  all  cases  modified,  either  by  the  formation  of  a  definite  cell  membrane 
as  in  the  ovum,  or  more  frequently  in  the  case  of  animal  cells,  by  a  transformation, 
probably  chemical  in  nature,  which  is  only  recognizable  by  the  fact  that  the  surface 
of  the  cell  behaves  as  a  semipermeable  membrane. 

Nucleus. — The  nucleus  is  a  minute  body,  imbedded  in  the  protoplasm,  and 
usually  of  a  spherical  or  oval  form,  its  size  having  little  relation  to  that  of  the  cell. 
It  is  surrounded  by  a  well-defined  wall,  the  nuclear  membrane;  this  encloses  the 
nuclear  substance  {nuclear  matrix),  which  is  composed  of  a  homogeneous  material 
or  karyoplasm  containing  a  network  or  karyomitome.  The  former  is  probably  of 
the  same  nature  as  the  hyaloplasm  of  the  cell,  but  the  latter,  which  forms  also  the 
wall  of  the  nucleus,  differs  from  the  spongioplasm  of  the  cell  substance.  It  con- 
sists of  fibres  or  filaments  arranged  in  a  reticular  manner.  These  filaments  are 
composed  of  a  homogeneous  material  known  as  linin,  which  stains  with  acid  dyes 
and  contains  embedded  in  its  substance  particles  which  have  a  strong  affinity 
for  basic  dyes.  These  basiphil  granules  have  been  named  chromatin  or  basichromatin 
and  owe  their  staining  properties  to  the  presence  of  nucleic  acid. 

^Yithin  the  nuclear  matrix  are  one  or  more  highly  refracting  bodies,  termed 
nucleoli,  connected  with  the  nuclear  membrane  by  the  nuclear  filaments.  They 
are  regarded  as  being  of  two  kinds.  Some  are  mere  local  condensations  ("  net- 
knots")  of  the  chromatin;  these  are  irregular  in  shape  and  are  termed  pseudo- 
nucleoli;  others  are  distinct  bodies  differing  from  the  pseudo-nucleoli  both  in  nature 
and  chemical  composition;  they  may  be  termed  true  nucleoli,  and  are  usually  found 
in  resting  cells.    The  true  nucleoli  are  oxyphil,  i.  e.,  they  stain  with  acid  dyes. 

Most  living  cells  contain,  in  addition  to  their  protoplasm  and  nucleus,  a  small 
particle  which  usually  lies  near  the  nucleus  and  is  termed  the  centrosome.  In  the 
middle  of  the  centrosome  is  a  minute  body  called  the  centriole,  and  surrounding  this 
is  a  clear  spherical  mass  known  as  the  centrosphere.  The  protoplasm  surround- 
ing the  centrosphere  is  frequently  arranged  in  radiating  fibrillar  rows  of  granules, 
forming  what  is  termed  the  attraction  sphere. 

Reproduction  of  Cells. — Reproduction  of  cells  is  effected  either  by  direct  or  by 
indirect  division.  In  reproduction  by  direct  division  the  nucleus  becomes  constricted 
in  its  centre,  assuming  an  hour-glass  shape,  and  then  divides  into  two.  This  is  fol- 
lowed by  a  cleavage  or  division  of  the  whole  protoplasmic  mass  of  the  cell;  and  thus 
two  daughter  cells  are  formed,  each  containing  a  nucleus.  These  daughter  cells  are 
at  first  smaller  than  the  original  mother  cell;  but  they  grow,  and  the  process 
may  be  repeated  in  them,  so  that  multiplication  may  take  place  rapidly.  Indirect 
divsion  or  karyokinesis  (karyomitosis)  has  been  observed  in  all  the  tissues — genera- 
tive cells,  epithelial  tissue,  connective  tissue,  muscular  tissue,  and  nerve  tissue. 
It  is  possible  that  cell  division  may  always  take  place  by  the  indirect  method,  and 
that  in  those  cases  in  which  direct  division  has  been  described  the  intermediate  stages 
may  not  have  been  seen,  owing  to  the  process  occurring  more  rapidly  than  usual. 


rilE  AXIMAL  CELL 


35 


The  process  of  indirect  cell  division  is  characterized  by  a  series  of  complex 
changes  in  the  nucleus,  leading  to  its  subdivision;  this  is  followed  by  cleavage 
of  tlie  cell  protoplasm.  Starting  with  the  nucleus  i)i  tlu>  quiescent  or  resting  stage, 
these  changes  may  be  briefly  grouped  under  the  f«iur  following  phases  (Fig.  2). 


I      ,' - 


^X^ 
3©^ 


VI 


^ 


^^^ 


r 


\t:i  ,.  - 


VIII  ..-■ 


Y 


Fig    2  —Diagram  showing  the  changes  which  occur  in  the  centrosomes  and  nucleus  of  a^ cell  in  the  i  recess  of  mitotic 
■     ■  division.     (Schafer.)     I  to  IV,  prophase;  T"  and  TT,  metaphase;  T  II  and  T  III,  anaph,  se. 

1.  Prophase.— The  nuclear  network  of  chromatin  filaments  assumes  the  form 
of  a  twisted  skein  or  spirem,  while  the  nuclear  membrane  and  nucleolus  disappear. 
The  convoluted  skein  of  chromatin  divides  into  a  definite  number  of  ^  -shaped 
segments  or  chromosomes.  The  number  of  chromosomes  varies  in  different  animals, 
but  is  constant  for  all  the  cells  in  an  animal  of  any  given  species;  in  man  the  number 
is  given  by  Flemming  and  Duesberg  as  twenty-four.^  Coincidently  with  or  pre- 
ceding these  changes  the  centriole,  which  usually  lies  by  the  side  of  the  nucleus, 
undergoes  subdivi'sion,  and  the  two  resulting  centrioles,  each  surrounded  by  a 
centrosphere,  are  seen  to  be  connected  by  a  spindle  of    delicate  achromatic  fibres 


1  Dr.  J.  Duesberg,  Anat.  Anz.,  Band  xsviii,  S.  475. 


36  HISTOLOGY 

the  achromatic  spindle.  The  centrioles  moN'e  away  from  each  other — one  toward 
either  extremity  of  the  nucleus — and  the  fibrils  of  the  achromatic  spindle  are  cor- 
respondingly lengthened.  A  line  encircling  the  spindle  midway  between  its  ex- 
tremities or  poles  is  named  the  equator,  and  around  this  the  V-shaped  chromosomes 
arrange  themselves  in  the  form  of  a  star,  thus  constituting  tlie  mother  star  or 
monaster. 

2.  Metaphase.  —  Each  \"-shaped  chromosome  now  undergoes  longitudinal 
cleavage  into  two  equal  parts  or  daughter  chromosomes,  the  cleavage  commencing 
at  the  apex  of  the  V  and  extending  along  its  di\'ergent  limbs.  The  daughter 
chromosomes,  thus  separated,  travel  in  opposite  directions  along  the  fibrils  of 
the  achromatic  spindle  toward  the  centrioles,  around  which  they  group  themselves, 
and  thus  two  star-like  figures  are  formed,  one  at  either  pole  of  the  achromatic 
spindle.    This  constitutes  the  diaster. 

3.  Anaphase. — The  daughter  chromosomes  now^  arrange  themselves  into  a 
skein  or  spirem,  and  eventually  form  the  network  of  chromatin  which  is  character- 
istic of  the  resting  nucleus.  The  nuclear  membrane  and  nucleolus  are  also  differ- 
entiated during  this  phase.  The  cell  protoplasm  begins  to  appear  constricted 
around  the  equator  of  the  achromatic  spindle,  where  double  rows  of  granules  are 
also  sometimes  seen.  The  constriction  deepens  and  the  original  cell  gradually 
becomes  divided. 

4.  Telophase. — In  this  stage  the  cell  is  completely  divided  into  two  new  cells, 
each  with  its  own  nucleus  and  centrosome,  which  assume  the  ordinary  positions 
occupied  b}'  such  structures  in  the  resting  stage. 

EPITHELIUM. 

All  the  surfaces  of  the  body — the  external  surface  of  the  skin,  the  internal 
surfaces  of  the  digestive,  respiratory,  and  genito-urinary  tracts,  the  closed  serous 
cavities,  the  inner  coats  of  the  vessels,  the  acini  and  ducts  of  all  secreting  and  ex- 
creting glands,  the  ventricles  of  the  brain  and  the  central  canal  of  the  medulla 
spinalis — are  covered  by  one  or  more  layers  of  simple  cells,  called  epithelium  or 
epithelial  cells.  These  cells  are  also  present  in  the  terminal  parts  of  the  organs 
of  special  sense,  and  in  some  other  structures,  such  as  the  hypophysis  cerebri 
and  the  thyroid  gland.  They  serve  various  purposes,  in  some  cases  forming  a 
protective  layer,  in  others  acting  as  agents  in  secretion  and  excretion,  and  again 
in  others  being  concerned  in  the  elaboration  of  the  organs  of  special  sense.  Thus, 
in  the  skin,  the  main  purpose  served  by  the  epithelium  (here  called  the  epidermis)  is 
that  of  protection.  iVs  the  surface  is  worn  away  by  the  agency  of  friction  new  cells 
are  supplied,  and  thus  the  true  skin  and  the  vessels  and  nerves  which  it  contains 
are  defended  from  damage.  In  the  gastro-intestinal  mucous  membrane  and  its 
glands,  the  epithelial  cells  appear  to  be  the  principal  agents  in  preparing  the  diges- 
tive secretions,  and  in  selecting  and  modifying  materials  for  absorption.  In  other 
situations  (as  the  nose,  fauces,  and  respiratory  passages)  an  important  office  of 
the  epithelial  cells  appears  to  be  to  maintain  an  equable  temperature  by  the 
moisture  with  which  they  keep  the  surface  always  slightly  lubricated.  In  the 
serous  cavities  they  also  keep  the  opposed  layers  moist,  and  thus  facilitate  their 
movements  on  each  other.  Finally,  in  all  internal  parts,  they  ensure  a  perfectly 
smooth  surface. 

Epithelium  consists  of  one  or  more  layers  of  cells  usually  supported  on  a  base- 
ment membrane  and  united  together  by  an  interstitial  cement  substance  which 
appears  to  be  similar  in  chemical  composition  to  the  matrix  or  ground  substance 
of  the  connective  tissues.  It  is  naturally  grouped  into  two  classes  according  as 
to  whether  there  is  a  single  layer  of  cells  (simple  epithelium),  or  more  than  one 
(stratified  epithelium  and  transitional  epithelium). 


EPITHELIUM 


37 


Simple  Epithelium. — The  (lill'eivnt  xaricties  of  simple  epithelium  are  squamous 
or  j)a\'euieut.  columnar,  glandular,  and  ciliated. 

Simple  Squamous  or  Pavement  Epithelium  (Fig.  3)  is  composed  of  flat,  nucleated 
scales  of  dill'erent  shapes,  usually  polygonal,  and  varying  in  size.  These  cells  fit 
together  by  their  edges,  like  the  tiles  of  a  mosiac  pax'ement.  The  nucleus  is  gen- 
erally flattened,  hut  may  be  spheroidal;  the  flattening  depends  upon  the  thinness 
of  the  cell.  The  protoplasm  of  the  cell  presents  a  fine  reticulum  or  honey-combed 
network,  which  gives  to  the  cell  the  appearance  of  granulation.  This  kind  of  epi- 
thelium forms  the  lining  of  the  air-sacs  of  the  lungs.  The  so-called  endothelium, 
\\hicli  covers  the  serous  membranes,  and  which  lines  the  heart,  bloodvessels,  and 
lymphatics,  is  also  of  the  pavement  type,  being  composed  of  a  single  layer  of 
flattened  transparent  squamous  cells,  joined  edge  to  edge  in  such  a  manner  as 
to  form  a  membrane  of  cells. 


ms — Stf^ 


Fig.  3. — Simple  pavement  epithelium. 


Fig.  4. — Columnar  epithelial  cells  of   the  rabbit's  intes- 
tine.    (Schafer.)     str,  striated  border;  n,  nucleus. 


Columnar  or  Cylindrical  Epithelium  (Fig.  4)  is  formed  of  cylindrical  or  rod-shaped 
cells  set  together  so  as  to  form  a  complete  layer,  resembling,  when  viewed  in  pro- 
file, a  palisade.  The  cells  have  a  prismatic  figure,  flattened  from  mutual  pressure, 
and  are  set  upright  on  the  surface  on  which  they  are  supported.  Their  protoplasm 
is  always  more  or  less  reticulated,  and  fine  longitudinal  striae  may  be  seen  in  it; 
the  nucleus  of  each  is  oval  in  shape  and  contains  an  intranuclear  network.  In 
the  case  of  the  intestinal  villi,  the  outer  free  border  of  each  of  these  cells  is  dis- 
tinctly marked  ofT  from  the  rest  of  the  protoplasm,  and  contains  well-defined 
vertical  striations.  Columnar  epithelium  covers  the  mucous  membrane  and 
nearly  the  whole  gastro-intestinal  tract  and  its  glands,  the  greater  part  of  the 
male  urethra,  the  ductus  deferens,  the  prostate,  the  bulbo-urethral  glands  of 
Cowper,  and  the  vestibular  glands  of  Bartholin.  In  a  modified  form  it  also 
covers  the  ovary. 

Goblet  or  chalice  cells  are  modified  columnar  cells.  The  goblet  cell  appears  to 
be  formed  by  an  alteration  in  shape  of  a  columnar  cell  (ciliated  or  otherwise)  con- 
sequent on  the  formation  of  granules,  w^hich  consist  of  a  substance  called  mucigen, 
in  the  interior  of  the  cell.  This  distends  the  upper  part  of  the  cell,  while  the  nucleus 
is  pressed  dow^n  toward  its  deep  part,  until  the  cell  bursts  and  the  mucus  is  dis- 
charged on  to  the  surface  of  the  mucous  membrane  (Fig.  5),  the  cell  then  assuming 
the  shape  of  an  open  cup  or  chalice. 

Glandular  Epithelium  (Fig.  6)  is  composed  of  polyhedral,  columnar,  or  cubical 
cells.  As  in  other  forms  of  epithelial  cells,  the  protoplasm  shows  a  fine  reticulum, 
which  gives  to  the  cells  the  appearance  of  granulation.  Granular  cells  are  found 
in  the  terminal  recesses  of  secreting  glands,  and  the  protoplasm  of  the  cells  usually 
contains  the  materials  which  the  cells  secrete. 

Ciliated  Epithelium  (Fig.  7)  generally  inclines  to  the  columnar  shape.  It  is  dis- 
tinguished by  the  presence  of  minute  processes,  like  hairs  or  eyelashes  (cilia) 
standing  up  from  the  free  surface.    The  cilia  (Fig.  8)  at  their  points  of  attachment 


38 


HISTOLOGY 


to  the  free  border  of  the  cell  possess  small  nodular  enlargements  (basal  knobs  of 
Engelmaiin) ;  within  the  cell  they  converge,  and  according  to  some  authorities  meet 
at  or  near  the  attraction  sphere.  If  the  cells  be  examined  during  life  or  immediately 
on  removal  from  the  living  body  (for  which  in  the  human  subject  the  removal 
of  a  nasal  polypus  offers  a  convenient  opportunity')  in  a  weak  solution  of  salt, 
the  cilia  will  be  seen  in  lashing  motion;  and  if  the  cells  be  separated,  they  will  often 
be  seen  to  be  moved  about  in  the  field  bv  this  ciliarv  action. 


'    %& 


Fro.  6. — Isolated  liver  cells  of  rabbit.      X  500. 


Fig.  5.— Goblet  cells  of  frog.      X  500. 


Fig.  7. — Ciliated  epithelium  from  trachea  of  kitten.      X  255. 


lifn'HrHHT"' Sasal  knobs 


Fig.  8. — Isolated  ciliated  cell  (semidiagrammatic). 


Fig.  9. — Stratified  epithelium  from  the  oesophagus. 


The  situations  in  which  ciliated  epithelium  is  found  in  the  human  body  are: 
the  respiratory  tract  from  the  nose  downward  to  the  smallest  ramifications  of 
the  bronchial  tubes,  except  the  lower  part  of  the  pharynx  and  the  surfaces  of 
the  vocal  folds;  the  tympanic  cavity  and  auditory  tube;  the  uterine  tube  and  the 
body  of  the  uterus;  the  vasa  efferentia,  coni  vasculosi  and  the  first  part  of  the 
ductus  deferens;  the  ventricles  of  the  brain  and  the  central  canal  of  the  medulla 
spinalis. 


EPITHELIUM 


39 


Stratified  Epithelium  (Fig.  9). — Stratificil  epithelium  consists  of  several  layers 
of  cells  varying  greatly  in  shape.  The  cells  of  the  deepest  layer  are  for  the  most 
part  columnar,  and  are  placed  vertically  on  the  basement  membrane;  above  these 
are  several  layers  of  polyhedral  cells,  which  as  they  approach  the  surface  become 
more  and  more  compressed,  until  the  superficial  ones  are  found  to  consist  of  flat- 
tened scales  (Fig.  10),  the  margins  of  which  overlap  one  another  so  as  to  present 
an  imbricated  appearance.  The  protoplasm  of  the  superficial  cells  is  completely 
converted  into  a  horny  substance  termed  keratin.  An  intermediate  body,  eleidin, 
is  often  present  in  the  deeper  layers  of  this  superficial  portion;  it  exists  in  the  form 
of  coarse  granules,  and  is  especially  well  seen  in  the  stratum  granulosum  of  the 
epidermis  (Fig.  11).  The  most  superficial  layers  lose  their  nuclei,  die,  and  are 
thrown  or  worn  oflF. 


Fig.   10.— Epithelial  cells  from  the  oral  cavity  of  man.     X  3.50.     a,  large;  h,  middle  sized;  c.  the  same  with  two  nuclei. 


Priclie-cells 
of  stratum  — ■< 
Malpighii 


Fig.   11. — Portion  of  epidermis  from  a  section  of  the  skin  of  the  finger.      (Ran\'ier.) 

The  cells  of  the  deeper  layers  of  stratified  squamous  epithelium  are  called  prickle 
cells;  they  possess  short,  fine  fibrils,  which  pass  from  their  margins  to  those  of 
neighboriiig  cells,  serving  to  connect  them  together.  They  are  not  closely  joined 
together  by  cement-substance,  but  are  separated  from  each  other  by  intercellular 
channels,  across  which  the  fibrils  may  be  seen  bridging.  When  a  cell  is  isolated, 
it  appears  to  be  covered  over  with  a  number  of  short  spines,  in  consequence  of  the 
fibrils  being  broken  through.  These  cells  were  first  described  by  Max  Schultze 
and  Virchow,  and  it  was  believed  by  them  that  the  cells  were  dovetailed  together. 
Martyn  subsequently  showed  that  this  was  not  the  case  and  that  the  prickles  were 
attached  to  each  other  by  their  apices;  and  Delepine  believes  the  prickles  to  be 
parts  of  fibrils  forming  internuclear  bundles  between  the  nuclei  of  the  cells  of  an 
epithelium  in  a  state  of  active  growth. 


40  HISTOLOGY 

Stratified  epithelium  is  found  in  the  skin,  in  the  conjunctiva,  in  the  nuicous 
membrane  of  the  nose,  excepting  the  olfactory  portion,  and  in  the  mucous  membrane 
of  the  mouth,  lower  part  of  the  pharynx,  and  oesophagus. 

Transitional  Epithelium. — Transitional  epithelium  occurs  in  the  ureters  and 
urinary  bladder.  Here  the  cells  of  the  most  superficial  layer  are  large  and  flat- 
tened, with  depressions  on  their  under 
surfaces,  to  fit  on  to  the  rounded  ends 
of  the  cells  of  the  second  layer,  which 
are  pear-shaped,  the  apices  touching  the 
basement  membrane.  Between  the 
tapering  points  of  the  cells  of  the  second 
layer  is  a  third  variety  of  cells  of  smaller 
size  than  those  of  the  other  two  layers 

Fig.   12.— Transitional  epithelium.  (Fig.   12). 


CONNECTIVE    TISSUES. 

The  term  connective  tissue  includes  a  number  of  tissues  which  support  and  con- 
nect the  other  tissues  of  the  body;  they  are  composed  of  cells  separated  from 
one  another  b}'  an  intercellular  material.  The  connective  tissues  may  differ  con- 
siderably from  each  other  in  appearance,  but  they  present  many  points  of  relation- 
ship, and  are,  moreover,  developed  from  the  same  layer  of  the  embryo,  the  meso- 
derm. They  are  divided  into  three  great  groups:  (1)  the  connective  tissues  proper, 
(2)  cartilage,  and  (3)  bone.  The  circulating  fluids,  although  functionally  and  prob- 
ably developmentally  different  from  the  others,  are  regarded  by  some  histologists 
as  a  form  of  connective  tissue,  and  are  dealt  with  therefore  in  this  section. 

The  Connective  Tissues  Proper. — Several  varieties  of  connective  tissue  are 
recognized:  (Ij  Areolar  tissue.  (2)  White  fibrous  tissue.  (3)  Yellow  elastic  tissue. 
(4)  Mucous  tissue.  (5)  Retiform  tissue.  They  are  all  composed  of  a  homogeneous 
matrix,  in  which  are  imbedded  cells  and  fibres — the  latter  of  two  kinds,  white, 
and  yellow  or  elastic.  The  distinction  between  the  different  varieties  depends 
upon  the  relative  preponderance  of  one  or  other  kind  of  fibre,  of  cells,  or  of 
matrix. 

Areolar  Tissue. — This  is  so  called  because  its  meshes  can  be  easily  distended 
with  air  or  fluid  and  thus  separated  into  areolae  or  spaces,  which  open  freely  into 
each  other.  Such  spaces,  however,  do  not  exist  in  the  natural  condition  of  the  body, 
the  whole  tissue  forming  one  unbroken  membrane  composed  of  a  number  of  inter- 
lacing fibres.  The  chief  use  of  areolar  tissue  is  to  bind  parts  together,  while  by 
the  laxity  of  its  fibres,  and  the  permeability  of  its  areolae,  it  allows  them  to  move 
on  each  other,  and  affords  a  ready  exit  for  inflammatory  and  other  effused  fluids. 
It  is  quite  the  most  extensively  distributed  of  all  the  tissues.  It  is  found  beneath 
the  skin  in  a  continuous  layer  all  over  the  body,  connecting  it  to  the  subjacent  parts. 
In  the  same  way  it  is  situated  beneath  the  mucous  and  serous  membranes.  It  is 
also  found  between  muscles,  vessels,  and  nerves,  forming  investing  sheaths  for 
them,  and  connecting  them  with  surrounding  structures.  In  addition  to  this  it 
is  present  in  the  interior  of  organs,  binding  together  the  ^'arious  lobes  and  lobules  of 
the  compound  glands,  the  various  coats  of  the  hollow  viscera,  the  fibres  of  muscles, 
etc.,  and  thus  forms  the  most  important  connecting  medium  of  the  various  struc- 
tures or  organs  of  which  the  body  is  made  up.  In  many  parts  the  areolae  or  inter- 
spaces of  areolar  tissue  are  occupied  by  fat  cells,  constituting  adipose  tissue,  which 
will  presently  be  described. 

Areolar  tissue  presents  to  the  naked  eye  an  appearance  somewhat  like  spun 
silk.     When  stretched  out,  it  is  seen  to  consist  of  delicate  soft  elastic  threads 


CONNECTIVE  TISSUES 


41 


interlacing  witli  each  other  in  every  direction,  and  forming  a  network  of  extreme 
deHcacy.  When  examined  nnder  the  microscope  (Fig.  13)  it  is  found  to  be  com- 
posed of  white  fibres  and  yellow  elastic  fibres  intercrossing  in  all  directions,  and 
united  together  by  a  homogeneous  cement  or  ground  substance,  the  matrix, 
showing  cell-si)aces  wherein  lie  the  connective  tissue  corpuscles;  these  contain  the 
protoplasm  out  of  which  the  whole  is  developed  and  regenerated. 


Plasma  cell 


White 
fibres 


Elastic 
fibres 


Fibrillaied 
cell 


Lamellar  cell 
Fig.   13. — Subcutaneous  tissue  from  a  young  rabbit. 


Highly   magnified.     (Schafer.) 


The  white  fibres  are  arranged  in  wavy  bands  or  bundles  of  minute  transparent 
homogeneous  filaments  or  fibrillse.  The  bundles  have  a  tendency  to  split  up 
longitudinally  or  send  off  slips  to  join  neighboring  bundles,  and  receive  others 
in  return,  but  the  individual  fibres  are  unbranched,  and  never  join  other  fibres. 
The  yellow  elastic  fibres  have  well-defined  outlines  and  are  considerably  larger 
in  size  than  the  white  fibrillse,  but  vary  much,  being  from  1  to  6 /x  in  diameter. 
They  form  bold  and  wide  curves,  branch,  and  freely  anastomose  with  each  other; 
they  are  homogeneous  in  appearance,  and  tend  to  curl  up,  especially  at  their 
broken  ends. 

The  cells  of  areolar  tissue  are  of  four  principal  kinds:  (1)  Flattened  lamellar 
cells,  which  may  be  either  branched  or  unbranched.  The  branched  lamellar  cells 
are  composed  of  clear  cytoplasm,  and  contain  oval  nuclei;  the  processes  of  these 
cells  may  unite  so  as  to  form  an  open  network,  as  in  the  cornea.  The  unbranched 
cells  are  joined  edge  to  edge  like  the  cells  of  an  epithelium;  the  "  tendon  cells,"  pres- 
ently to  be  described,  are  examples  of  this  variety.  (2)  Clasmatocytes,  large  irregular 
cells  characterized  by  the  presence  of  granules  or  vacuoles  in  their  protoplasm, 
and  containing  oval  nuclei.  (3)  Granule  cells  {MastzeUen) ,  which  are  ovoid  or 
spheroidal  in  shape.  They  are  formed  of  a  soft  protoplasm,  containing  granules 
which  are  basiphil  in  character.  (4)  Plasma  cells  of  Waldeyer,  usually  spheroidal 
and  distinguished  by  containing  a  vacuolated  protoplasm.    The  vacuoles  are  filled 


42 


HISTOLOGY 


with  fluid,  and  the  protoplasm  between  the  spaces  is  clear,  with  occasionally  a  few 
scattered  basiphil  granules. 

In  addition  to  these  four  typical  forms  of  connective-tissue  corpuscles,  areolar 
tissue  may  be  seen  to  possess  wandering  cells,  i.  e.,  leucocytes  which  have  emigrated 
from  the  neighboring  vessels;  in  some  instances,  as  in  the  choroid  coat  of  the  eye, 
cells  filled  with  granules  of  pigment  (pigment  cells)  are  found. 

The  cells  lie  in  spaces  in  the  ground  substance  between  the  bundles  of  fibres, 
and  these  spaces  may  be  brought  into  view  by  treating  the  tissue  with  nitrate  of 
silver  and  exposing  it  to  the  light.  This  will  color  the  ground  substance  and  leave 
the  cell-spaces  unstained. 

Adipose  Tissue. — In  almost  all  parts  of  the  body  the  ordinary  areolar  tissue 
contains  a  variable  quantity  of  fat.  The  principal  situations  where  it  is  not  found 
are  the  subcutaneous  tissue  of  the  eyelids,  of  the  penis  and  scrotum,  of  the  labia 
minora;  within  the  cavity  of  the  cranium;  and  in  the  lungs,  except  near  their 
roots.  The  distribution  of  adipose  tissue  is  not  uniform;  in  some  parts  it  is  in 
great  abundance,  as  in  the  subcutaneous  tissue,  especially  of  the  abdomen,  around 
the  kidneys,  and  in  some  other  situations.  Lastly,  fat  enters  largely  into  the  for- 
mation of  the  marrow  of  bones. 


Fig.  14. — Adipose  tissue.     Highly  magnified,     o,  star-like  appearance,  from  crystallization  of  fatty  acids. 


Adipose  tissue  consists  of  small  vesicles,  fat  cells,  lodged  in  the  meshes  of  areolar 
tissue.  Fat  cells  (Fig.  14)  vary  in  size,  but  are  of  about  the  average  diameter  of 
50m;  each  consists  of  an  exceedingly  delicate  protoplasmic  membrane,  filled  with 
fatty  matter,  which  is  liquid  during  life,  but  becomes  solidified  after  death.  They 
are  round  or  spherical  where  they  have  not  been  subjected  to  pressure;  otherwise 
they  assume  a  more  or  less  polygonal  outline.  A  nucleus  is  always  present  under 
the  cell  membrane  and  can  be  easily  demonstrated  by  staining  with  hematoxylin; 
in  the  natural  condition  it  is  so  compressed  by  the  contained  oily  matter  as  to  be 
scarcely  recognizable.  The  fat  cells  are  contained  in  clusters  in  the  areolae  of  fine 
connective  tissue,  and  are  held  together  mainly  by  the  network  of  capillary  blood- 
vessels which  is  distributed  to  them. 

Chemically  the  oily  material  in  the  cells  is  composed  of  the  fats,  olein,  palmitin, 
and  stearin,  which  are  glycerin  compounds  with  fatty  acids.  Sometimes  fat 
crystals  form  in  the  cells  after  death  (Fig.  14,  a).  By  boiling  the  tissue  in  ether  or 
strong  alcohol  the  fat  may  be  extracted  from  the  vesicles,  leaving  them  empty 
and  shrunken. 

Fat  may  be  first  detected  in  the  human  embryo  about  the  fourteenth  week. 
The  fat  cells  are  formed  bv  the  transformation  of  connective-tissue  corpuscles. 


CONNECTIVE  TISSUES 


43 


Small  droplets  of  oil  are  formed  in  the  protoplasm,  and  these  coalesce  to  produce  a 
larger  drop,  which  increases  until  it  distends  the  corpuscles,  the  remaining  proto- 
plasm and  the  nucleus  being  displaced  toward  the  periphery  of  the  cell  (Fig.  15). 


Fig.  15. — Development  of  fat.  (Kloiii  and  Xoble  Smith  ) 
a,  minute  artery ;  v,  minute  vein;  e,  capillary  bloodvessels 
in  the  course  of  formation ;  they  are  not  yet  completely  hol- 
lowed out,  there  being  still  left  in  them  protoplasmic  septa; 
the  ground  substance,  containing  numerous  nucleated  cells, 
some  of  which  are  more  distinctly  branched  and  flattened 
than  others,  and  appear  therefore  more  spindle-shaped. 


Fig.   16. 


-White  fibres  of  areolar  tissue.     X  400. 
(Sharpey.) 


ijlll, 


^^  9ii!|i' 


I     1      u 


Fig.  17. — Tendon  of  mouse's  tail,  stained 
with  [logwood,  showing  chains  of  cells  be- 
tween'"(the  tendon  bundles.  (From  Quain's 
"Anatomy."     E.  A.  Schafer.) 


Fig.   is. — Transverse  section  of  tendon  of  rat.      X  120. 


White  .Fibrous  Tissue  (Fig.  16)  is  a  true  connecting  structure,  and  serves  three 
purposes  in  the  animal  economy.  In  the  form  of  ligaments  it  binds  bones  together; 
in  the  form  of  tendons  it  connects  muscles  to  bones  or  other  structures;  and  it 
constitutes  investing  or  protecting  structures  to  various  organs  in  the  form  of 
membranes.  Examples  of  such  membranes  are  to  be  found  in  the  muscular  fasciae 
or  sheaths,  the  periosteum,  and  the  perichondrium;  the  investments  of  the  various 
glands  (such  as  the  tunica  albuginea  testis,  the  capsule  of  the  kidney,  etc.);  the 
investing  sheaths  of  the  nerves  (epineurium) ,  and  of  various  organs,  as  the  penis 
and  the  eye.    In  white  fibrous  tissue,  as  its  name  implies,  the  white  fibres  predomi- 


44 


HISTOLOGY 


nate;  the  matrix  is  apparent  only  as  a  cement-substance,  the  yellow  elastic  fibres 
are  comparatively  few,  while  the  tissue  cells  are  arranged  in  a  special  manner. 
It  presents  to  the  naked  eye  the  appearance  of  silvery  white  glistening  fibres, 
covered  over  with  a  quantity  of  loose  flocculent  tissue  which  binds  the  fibres 
together  and  carries  the  bloodvessels.  It  is  not  possessed  of  any  elasticity,  and  only 
the  very  slightest  extensibility;  it  is  exceedingly  strong,  so  that  upon  the  applica- 
tion of  any  external  violence,  a  bone  with  which  it  is  connected  may  fracture 
before  the  fibrous  tissue  gives  way.  In  ligaments  and  tendons  the  bundles  of  fibres 
run  parallel  with  each  other;  in  membranes  they  intersect  one  another.  The  cells 
found  in  white  fibrous  tissue  are  often  called  tendon  cells.  They  are  situated  on 
the  surfaces  of  groups  of  bundles  and  are  quadrangular  in  shape,  arranged  in  rows, 
in  single  file,  each  cell  being  separated  from  its  neighbors  by  a  narrow  line  of  cement- 
substance.    The  nucleus  is  generally  situated  at  one  end  of  the  cell,  the  nucleus 

of  the  adjoining  cell  being  in  close  proximity  to  it 
(Fig.  17).  The  tendon  cells  have  wing-like  processes 
which  pass  between  the  bundles  of  fibres,  giving  a  stel- 
late appearance  in  transverse  section  (Fig.  18).  Upon 
the  addition  of  acetic  acid  white  fibrous  tissue  swells 
up  into  a  glassy  looking  indistinguishable  mass.  When 
boiled  in  water  it  is  converted  almost  completely 
into  gelatin,  the  white  fibres  being  composed  of  the 
albuminoid  collagen,  which  is  often  regarded  as  the 
anhydride  of  gelatin. 

Yellow  Elastic  Tissue. — In  certain  parts  of  the  body  a 
tissue  is  found  which  when  viewed  in  mass  is  of  a 
yellowish  color,  and  is  possessed  of  great  elasticity,  so 
that  it  is  capable  of  considerable  extension,  and  when 
the  extending  force  is  withdrawn  returns  at  once  to  its 
original  condition.  This  is  yelloiv  elastic  tissue;  it  may 
be  regarded  as  a  connective  tissue  in  which  the  yellow 
elastic  fibres  have  developed  to  the  practical  exclusion 
of  the  other  elements.  It  is  found  in  the  ligamenta 
flava,  in  the  vocal  folds,  in  the  mucous  membrane  of  the  trachea  and  bronchi, 
in  the  coats  of  the  bloodvessels,  especially  the  larger  arteries,  and  to  a  very 
considerable  extent  in  the  hyothyroid,  cricothyroid,  and  stylohyoid  ligaments. 
It  is  also  found  in  the  ligamentum  nuchae  of  the  lower  animals  (Fig.  19).  In 
some  parts  where  the  fibres  are  broad  and  large  and  the  network  close,  the  tissue 
presents  the  appearance  of  a  membrane,  with  gaps  or  perforations  corresponding 
to  the  intervening  spaces.  This  is  to  be  found  in  the  inner  coat  of  the  arteries, 
and  to  it  the  name  of  fenestrated  membrane  has  been  given  by  Henle.  The  yellow 
elastic  fibres  remain  unaltered  by  acetic  acid;  chemically  they  are  composed  of 
the  albuminoid  body  elastin. 

Mucous  Tissue. — jMucous  tissue  exists  chiefly  in  the  "jelly  of  \Yharton,"  which 
forms  the  bulk  of  the  umbilical  cord,  but  is  also  found  in  other  situations  in  the 
fetus,  chiefly  as  a  stage  in  the  development  of  connective  tissue.  It  consists  of  a 
matrix,  largely  made  up  of  mucin,  in  which  are  nucleated  cells  with  branching 
and  anastomosing  processes  (Fig.  20).  Few  fibres  are  seen  in  typical  mucous  tissue, 
although  at  birth  the  umbilical  cord  shows  a  considerable  development  of  fibres. 
In  the  adult  the  vitreous  humor  of  the  eye  is  a  persistent  form  of  mucous  tissue, 
in  w^hich  there  are  no  fibres,  and  from  which  the  cells  have  disappeared,  leaving 
only  the  mucinous  ground  substance. 

Retiform  or  Reticular  Tissue  (Fig.  21)  is  found  extensively  in  many  parts  of  the 
body,  constituting  the  framework  of  some  organs  and  entering  into  the  construc- 
tion of  manv  mucous  membranes.     It  is  a  varietv  of  connective  tissue,  in  which 


Fig 


19. — Elastic  fibres. 
(Sharpey.) 


X   200. 


CONNECTIVE  TISSUES 


45 


the  intercellular  or  gound  substance  has,  in  great  measure,  disappeared,  and  is 
replaced  by  fluid.  It  is  apparently  composed  almost  entirely  of  extremely  fine 
bundles  of  white  fibrous  tissue,  forming  an  intricate  network,  and  chemically  it 
yields  gelatin.  The  fibres  are  covered  and  concealed  in  places  by  flattened  branched 
connective  tissue  cells.  In  many  situations  the  interstices  of  the  network  are  filled 
with  rounded  lymph-corpuscles,  and  the  tissue  is  then  termed  lymphoid  or  adenoid 
tissue. 


Fig.  20.— Mucous  tissue  from  the  umbilical  cord  of  the  human  fetus  of  four  months. 
■f 


Fig.  21. — Retiform  tissue,  from  a  lymph  gland. 

Basement  Membranes,  formerly  described  as  homogeneous  membranes,  are  in 
most  cases  really  a  form  of  connective  tissue.  They  constitute  the  supporting 
membrane,  or  membrana  propria,  on  which  is  placed  the  epithelium  of  mucous 
membranes  or  secreting  glands,  and  they  are  also  found  in  other  situations.    Bv 


46 


HISTOLOGY 


means  of  staining  with  nitrate  of  silver  they  may  be  shown  to  consist  usually  of 
flattened  cells  in  close  apposition,  and  joined  together  by  their  edges,  thus  forming 
an  example  of  an  epithelioid  arrangement  of  connective  tissue  cells.  In  some 
situations  the  cells,  instead  of  adhering  by  their  edges,  give  off  branching  processes 
which  join  with  similar  processes  of  other  cells,  and  so  form  a  network  rather  than 
a  continuous  membrane.  Some  basement  membranes  are  composed  of  elastic 
tissue,  as  in  the  cornea,  others  are  merely  condensed  matrix. 

Vessels  and  Nerves  of  Connective  Tissue. — The  bloodvessels  of  connective  tissue 
are  very  few — that  is  to  say,  there  are  few  actually  destined  for  the  tissue  itself, 
although  many  vessels  carrying  blood  to  other  structures  may  permeate  one  of  its 
forms,  the  areolar  tissue.  In  white  fibrous  tissue  the  bloodvessels  usually  run 
parallel  to  the  longitudinal  bundles  and  between  them,  sending  transverse  com- 
municating branches  across;  in  some  forms,  as  in  the  periosteum  and  dura  mater 
they  are  fairly  numerous.  In  yellow  elastic  tissue,  the  bloodvessels  also  run 
between  the  fibres,  and  do  not  penetrate  them.  Lymphatic  vessels  are  very  numer- 
ous in  most  forms  of  connective  tissue,  especially  in  the  areolar  tissue  beneath  the 
skin  and  the  mucous  and  serous  surfaces.  They  are  also  found  in  abundance  in 
the  sheaths  of  tendons,  as  well  as  in  the  tendons  themselves.  Nerves  are  to  be 
found  in  the  white  fibrous  tissue,  where  they  end  in  a  special  manner;  but  it  is 
doubtful  whether  any  nerves  end  in  areolar  tissue;  at  all  events,  they  have  not 
yet  been  demonstrated,  and  the  tissue  is  possessed  of  very  little  sensibility. 

Pigment. — In  various  parts  of  the  body  pigment  is  found;  most  frequently  in 
epithelial  cells  and  in  the  cells  of  connective  tissue.  Pigmented  epithelial  cells 
are  found  in  the  external  layer  of  the  retina,  on  the  posterior  surface  of  the  iris, 

in  the  olfactory  region  of  the  nose,  and  in 
the  membranous  labyrinth  of  the  ear.  Pig- 
ment is  likewise  found  in  the  cells  of  the 
deeper  laj'ers  of  the  cuticle  and  in  the  hairs; 
in  the  skin  of  the  colored  races  it  is  abun- 
dantly present,  but  in  the  white  races  it  is 
well-marked  only  in  the  areolee  around  the 
nipples  and  in  irregular  colored  patches. 

In  the  connective  tissue  cells  pigment  is 
frequently  met  with  in  the  lower  verte- 
brates. In  man  it  is  found  in  the  choroid 
coat  of  the  eye  (Fig.  22),  and  in  the  iris 
of  all  but  the  light  blue  eyes  and  the  albino. 
It  is  also  occasionally  met  with  in  the  cells 
of  retiform  tissue  and  in  the  pia  mater  of 
the  upper  part  of  the  medulla  spinalis.  The 
cells  are  characterized  by  their  large  size 
and  by  branched  processes,  w^hich  are  also 
filled  with  granules.  In  the  retina  the  pro- 
cesses of  the  cells  can  be  withdrawn  or  protruded  under  the  influence  of  light  in 
order  to  protect  the  delicate  rods  and  cones.  The  pigment  (melanin)  consists  of 
dark  brown  or  black  granules  of  very  small  size  closely  packed  together  within 
the  cells,  but  not  invading  the  nucleus.  Occasionally  the  pigment  is  yellow, 
and  when  occurring  in  the  cells  of  the  cuticle  constitutes  "freckles."  In  the 
retina  another  variety  of  pigment  occurs,  known  as  rhodopsin  or  visual  purple, 
which  is  bleached  on  exposure  to  light. 

Applied  Anatomy. — Abnormal  pigmentation  of  the  skin  may  be  congenital,  when  it  often  takes 
the  form  of  dark  brown  or  black  nevi  (moles),  scattered  over  a  greater  or  smaller  area  of  the 
body.  It  may  also  result  from  the  prolonged  consumption  of  various  drugs,  particularly  of 
salts  of  silver  or  arsenic,  being  most  marked  wherever  the  skin  is  exposed  to  the  action  of  light. 


Fig.  22. — Pigment  cells  from  the  choroid  coat  of  the 
eyeball. 


CONNECTIVE  TISSUES 


47 


Progressive  darkening  or  bronzing  of  tlic  skin  is  also  highlj'  suggestive  of  Addison's  disease,  which 
commonly  follows  destruction  or  tuberculosis  of  the  suprarenal  glands;  it  is  then  most  obvious 
in  regions  where  the  skin  is  normally  pigmented  or  is  subjected  to  pressure  or  irritation  from  the 
clothes.  Pigmentation  is  also  associated  with  certain  disorders  of  the  skin,  of  the  female  genitaUa, 
and  of  the  thyroid  gland,  and  with  the  later  stages  of  wasting  diseases  such  as  cancer  and  phthisis. 
It  does  not  yield  to  any  medical  treatment  as  a  rule. 

Development  of  Connective  Tissue. — Connective  tissue  is  developed  from  cells  of  the  meso- 
derm. Tlu'se  cells  nudtijjly  and  form  a  syncytium  containing  many  nuclei.  Later  the  proto- 
plasm increases  rapidly  in  amount,  and  in  the  vicinity  of  each  nucleus  is  differentiated  into  two 
pai'ts:  (1)  a  portion  sm-rounding  the  nucleus  and  forming  ultimately  the  cytoplasm  of  the  con- 
nective tissue  cell;  (2)  an  outlying  portion  in  which  fibrillation  takes  place.  Both  the  white  and 
the  yellow  elastic  fibres  are  laid  down  in  the  same  manner. 


Cartilage. — Cartilage  is  a  non-vascular  structure  which  is  found  in  various 
parts  of  the  body — in  adult  life  chiefly  in  the  joints,  in  the  parietes  of  the  thorax, 
and  in  various  tubes,  such  as  the  trachea  and  bronchi,  nose,  and  ears,  which  require 
to  be  kept  permanently  open.  In  the  fetus,  at  an  early  period,  the  greater  part 
of  the  skeleton  is  cartilaginous;  as  this  cartilage  is  afterward  replaced  by  bone, 
it  is  called  temporary,  in  contradistinction  to  that  which  remains  unossified  during 
the  whole  of  life,  and  is  called  permanent. 

Cartilage  is  di^'ided,  according  to  its  minute  structure,  into  hyaline  cartilage, 
white  fibrocartilage,  and  yellow  or  elastic  fibrocartilage.  Besides  these  varieties 
met  with  in  the  adult  human  subject,  there  is  a  variety  called  cellular  cartilage, 
which  consists  entirely,  or  almost  entirely,  of  cells,  separated  from  each  other  by 
their  capsules  only,  which  in  this  kind  of  cartilage  are  extremely  well-marked. 
Cellular  cartilage  is  found  in  the  external  ears  of  rats,  mice,  and  some  other  animals, 
and  is  present  in  the  notochord  of  the  human  embryo,  but  is  not  found  in  any 
other  human  structure.  The  various  cartilages  in  the  body  are  also  classified, 
according  to  their  functions  and  positions,  into  articular,  interarticular,  costal, 
and  membraniform. 

Hyaline  Cartilage. — Hyaline  cartilage  consists  of  a  gristly  mass  of  a  firm  consist- 
ence, but  of  considerable  elasticity  and  pearly  bluish  color.    Except  where  it  coats 
the  articular  ends  of  bones,  it  is  covered  externally  by  a  fibrous  membrane,  the 
perichondrium,  from  the  vessels  of 
which     it    imbibes    its    nutritive 
fluids,    being    itself    destitute    of 
bloodvessels.        It     contains      no 
nerves.     Its  intimate  structure  is 
very  simple.    If   a   thin   slice   be 
examined  under  the  microscope,  it 
will  be  found  to  consist  of  cells  of 
a    rounded    or     bluntly     angular 
form,   lying  in  groups  of  two  or 
more    in    a    granular   or    almost 
homogeneous    matrix     (Fig.    23). 

The  cells,  when  arranged  in  groups  of  two  or  more,  have  generally  straight  outlines 
where  they  are  in  contact  with  each  other,  and  in  the  rest  of  their  circumference 
are  rounded.  They  consist  of  clear  translucent  protoplasm  in  which  fine  inter- 
lacing filaments  and  minute  granules  are  sometimes  present;  imbedded  in  this 
are  one  or  two  round  nuclei,  having  the  usual  intranuclear  network.  The  cells 
are  contained  in  cavities  in  the  matrix,  called  cartilage  lacunae;  around  these  the 
matrix  is  arranged  in  concentric  lines,  as  if  it  had  been  formed  in  successive 
portions  around  the  cartilage  cells.  This  constitutes  the  so-called  capsule  of  the 
space.  Each  lacuna  is  generally  occupied  by  a  single  cell,  but  during  the  division 
of  the  cells  it  may  contain  two,  four,  or  eight  cells. 

The  matrix  is  transparent  and  apparently  without  structure,  or  else  presents  a 


Fig.  23. — Human  cartilage  cells  from  the  cricoid  cartilage. 
X  350 


48 


HISTOLOGY 


dimly  granular  appearance,  like  ground  glass.  Some  observers  have  shown  that 
the  matrix  of  hyaline  cartilage,  and  especially  of  the  articular  variety,  after  pro- 
longed maceration,  can  be  broken  up  into  fine  fibrils.  These  fibrils  are  probably 
of  the  same  nature,  chemically,  as  the  white  fibres  of  connective  tissue.  It  is 
believed  by  some  histologists  that  the  matrix  is  permeated  by  a  number  of  fine 
channels,  which  connect  the  lacunse  with  each  other,  and  that  these  canals  com- 
municate with  the  lymphatics  of  the  perichondrium,  and  thus  the  structure 
is  permeated  by  a  current  of  nutrient  fluid. 

Articular  cartilage,  costal  cartilage,  and  temporary  cartilage  are  all  of  the  hyaline 
variety.  They  present  differences  in  the  size,  shape,  and  arrangement  of  their 
cells. 

In  Articular  Cartilage  (Fig.  24),  which  shows  no  tendency  to  ossification,  the 
matrix  is  finely  granular;  the  cells  and  nuclei  are  small,  and  are  disposed  parallel 
to  the  surface  in  the  superficial  part,  while  nearer  to  the  bone  they  are  arranged  in 
vertical  rows.  Articular  cartilages  have  a  tendency  to  split  in  a  vertical  direction; 
in  disease  this  tendency  becomes  very  manifest.  The  free  surface  of  articular 
cartilage,  where  it  is  exposed  to  friction,  is  not  covered  by  perichondrium,  although 
a  layer  of  connective  tissue  continuous  with  that  of  the  synovial  membrane  can  be 


I  Superficial  flAiUened  cells 


'<t 


l*^)  I  Vertical  rows  of  cells 


^w . .  -^,- .      ^  Calcified  matrix 

V 

I 
— \  ertioil  beotion  of  articular  cartilage. 


Fig.  25. — Costal  cartilage  from  a  man,  aged 
seventy-six  years,  showing  the  development  of 
fibrous  structure  in  the  matrix.  In  several  por- 
tions of  the  specimen  two  or  three  generations  of 
cells  are  seen  enclosed  in  a  parent  cell  wall. 
Highly  magnified. 


traced  in  the  adult  over  a  small  part  of  its  circumference,  and  here  the  cartilage 
cells  are  more  or  less  branched  and  pass  insensibly  into  the  branched  connective 
tissue  corpuscles  of  the  synovial  membrane.  Articular  cartilage  forms  a  thin 
incrustation  upon  the  joint  surfaces  of  the  bones,  and  its  elasticity  enables  it  to 
break  the  force  of  concussions,  while  its  smoothness  affords  ease  and  freedom  of 
movement.  It  varies  in  thickness  according  to  the  shape  of  the  articular  surface 
on  which  it  lies;  where  this  is  convex  the  cartilage  is  thickest  at  the  centre,  the 
reverse  being  the  case  on  concave  articular  surfaces.  It  appears  to  derive  its 
nutriment  partly  from  the  vessels  of  the  neighboring  synovial  membrane  and 
partly  from  those  of  the  bone  upon  which  it  is  implanted.  Toynbee  has  shown 
that  the  minute  vessels  of  the  cancellous  tissue  as  they  approach  the  articular 
lamella  dilate  and  form  arches,  and  then  return  into  the  substance  of  the  bone. 

In  Costal  Cartilage  the  cells  and  nuclei  are  large,  and  the  matrix  has  a  tendency 
to  fibrous  striation,  especially  in  old  age  (Fig.  25).  In  the  thickest  parts  of  the 
costal  cartilages  a  few  large  vascular  channels  may  be  detected.     This  appears. 


CONNECTIVE  TISSUES 


49 


at  first  sight,  to  be  an  exception  to  the  statement  tliat  cartilage  is  a  non-vascular 
tissue,  but  is  not  so  really,  for  the  vessels  give  no  branches  to  the  cartilage  sub- 
stance itself,  and  the  channels  may  rather  be  looked  upon  as  involutions  of  the 
perichondrium.  The  xii)hoid  process  and  the  cartilages  of  the  nose,  larynx,  and 
trachea  (except  the  epiglottis  and  corniculate  cartilages  of  the  larynx,  which  are 
composed  of  elastic  fibrocartilage)  resemble  the  costal  cartilages  in  microscopic 
characteristics.  The  arytenoid  cartilage  of  the  larynx  shows  a  transition  from 
hyaline  cartilage  at  its  base  to  elastic  cartilage  at  the  apex. 

The  hyaline  cartilages,  especially  in  adult  and  advanced  life,  are  prone  to  calcify 
— that  is  to  say,  to  have  their  matrix  permeated  by  calcium  salts  without  any 
appearance  of  true  bone.  The  process  of  calcification  occurs  frequently,  in  such 
cartilages  as  those  of  the  trachea  and  in  the  costal  cartilages,  where  it  may  be 
succeeded  by  conversion  into  true  bone. 

White  Fibrocartilage. — White  fibrocartilage  consists  of  a  mixture  of  white  fibrous 
tissue  and  cartilaginous  tissue  in  various  proportions;  to  the  former  of  these  con- 
stituents it  owes  its  flexibility  and 
toughness,  and  to  the  latter  its 
elasticity.  When  examined  under 
the  microscope  it  is  found  to  be 
made  up  of  fibrous  connective 
tissue  arranged  in  bundles,  with 
cartilage  cells  between  the  bundles ; 
the  cells  to  a  certain  extent  re- 
semble tendon  cells,  but  may  be 
distinguished  from  them  by  being 


surrounded    by 
striated  area 
and  by   being 
26).    Thewhil/ 
mit   of    arranf 
groups — ^interai 
circumferentif' 

1.  The  1". 
plates,  of  a 


concentrically 
eilage  matrix 
ittened  (Fig. 
partilages  ad- 
.c  into  four 
',  connecting, 
stratiform. 


Fig.  26. — White  fibrocartilage  from  an.  intervertebral 
fibrocartilage. 


.icular  Fibrocartilages  {menisci)  are  flattened  fibrocartilaginous 
nd,  oval,  triangular,  or  sickle-like  form,  interposed  between  the 
articular  cartilages  of  certain  joints.  They  are  free  on  both  surfaces,  usually 
thinner  toward  the  centre  than  at  the  circumference,  and  held  in  position  by  the 
attachment  of  their  margins  and  extremities  to  the  surrounding  ligaments.  The 
synovial  membranes  of  the  joints  are  prolonged  over  them.  They  are  found 
in  the  temporomandibular,  sternoclavicular,  acromioclavicular,  wrist,  and  knee 
joints — i.  e.,  in  those  joints  which  are  most  exposed  to  violent  concussion  and 
subject  to  frequent  movement.  Their  uses  are  to  obliterate  the  intervals  between 
opposed  surfaces  in  their  various  motions;  to  increase  the  depths  of  the  articular 
surfaces  and  give  ease  to  the  gliding  movements;  to  moderate  the  effects  of  great 
pressure  and  deaden  the  intensity  of  the  shocks  to  which  the  parts  may  be  sub- 
jected. Humphry  has  pointed  out  that  these  interarticular  fibrocartilages  serve 
an  important  purpose  in  increasing  the  varieties  of  movement  in  a  joint.  Thus 
in  the  knee  joint  there  are  two  kinds  of  motion,  viz.,  angular  movement  and  rota- 
tion, although  it  is  a  hinge  joint,  in  which,  as  a  rule,  only  one  variety  of  motion 
is  permitted;  the  former  movement  takes  place  between  the  condyles  of  the  femur 
and  the  interarticular  cartilages,  the  latter  between  the  cartilages  and  the  head 
of  the  tibia.  So,  also,  in  the  temporomandibular  joint,  the  movements  of  opening 
and  shutting  the  mouth  take  place  between  the  fibrocartilage  and  the  mandible, 
the  grinding  movement  between  the  mandibular  fossa  and  the  fibrocartilage,  the 
latter  moving  with  the  mandible. 
4 


50 


HISTOLOGY 


2.  The  Connecting  Fibrocartilages  are  interposed  between  the  bony  surfaces  of 
those  joints  which  admit  of  only  sHght  mobihty,  as  between  the  bodies  of  the 
vertebrae.  They  form  disks  which  are  closely  adherent  to  the  opposed  surfaces. 
Each  disk  is  composed  of  concentric  rings  of  fibrous  tissue,  with  cartilaginous 
laminae  interposed,  the  former  tissue  predominating  toward  the  circumference, 
the  latter  toward  the  centre. 

3.  The  Circumferential  Fibrocartilages  consist  of  rims  of  fibrocartilage,  which 
surround  the  margins  of  some  of  the  articular  cavities,  e.  g.,  the  glenoidal  labrum 
of  the  hip,  and  of  the  shoulder;  they  serve -to  deepen  the  articular  cavities  and  to 
protect  their  edges. 

4.  The  Stratiform  Fibrocartilages  are  those  which  form  a  thin  coating  to  osseous 
grooves  through  which  the  tendons  of  certain  muscles  glide.  Small  masses  of  fibro- 
cartilage are  also  developed  in  the  tendons  of  some  muscles,  where  they  glide 
over  bones,  as  in  the  tendons  of  the  Peronaeus  longus  and  Tibialis  posterior. 

Yellow  or  Elastic  Fibrocartilage  is  found  in  the  human  body  in  the  auricles  of  the 
external  ear,  the  auditory  tubes,  the  corniculate  cartilages  of  the  larynx,  and  the 

epiglottis.  It  consists  of  cartilage 
cells  and  a  matrix,  the  latter  being 
pervaded  by  a  network  of  yellow 
elastic  fibres,  branching  and  anas- 
tomosing in  all  directions,  except 
immediately  around  each  cell,  where 
there  is  a  variable  amount  of  non- 
fibrillated  hyaline,  intercellular  sub- 
stance (Fig.  27) .  The  fibres  resem- 
ble those  of  yellow  elastic  tissue, 
both  in  appearance  and  in  being 
unaffected  by  acetic  acid;  and  ac- 
cording to  Rollett  their  continuity 
with  the  elastic  fibres  of  the  neigh- 
boring tissue  is  demonstrable. 

The  distinguishing  feature  of 
cartilage  chemically  is  that  it  yields 
on  boiling  a  substance  called  chon- 
drin,  very  similar  to  gelatin,  but 
differing  from  it  in  several  of  its 
reactions.  It  is  now  believed  that 
chondrin  is  not  a  simple  body,  but 
a  mixture  of  gelatin  with  mucinoid  substances,  chief  among  which,  perhaps,  is  a 
compound  termed  chondro-mucoid. 

Bone. — Structure  and  Physical  Properties. — Bone  is  one  of  the  hardest  structures 
of  the  animal  body;  it  possesses  also  a  certain  degree  of  toughness  and  elasticity. 
Its  color,  in  a  fresh  state,  is  pinkish- white  externally,  and  deep  red  within.  On 
examining  a  section  of  any  bone,  it  is  seen  to  be  composed  of  two  kinds  of  tissue, 
one  of  which  is  dense  in  texture,  like  ivory,  and  is  termed  compact  tissue;  the  other 
consists  of  slender  fibres  and  lamellae,  which  join  to  form  a  reticular  structure; 
this,  from  its  resemblance  to  lattice-work,  is  called  cancellous  tissue.  The  compact 
tissue  is  always  placed  on  the  exterior  of  the  bone,  the  cancellous  in  the  interior. 
The  relative  quantity  of  these  two  kinds  of  tissue  varies  in  different  bones,  and 
in  different  parts  of  the  same  bone,  according  as  strength  or  lightness  is  requisite. 
Close  examination  of  the  compact  tissue  shows  it  to  be  extremely  porous,  so  that 
the  difference  in  structure  between  it  and  the  cancellous  tissue  depends  merely 
upon  the  different  amount  of  solid  matter,  and  the  size  and  number  of  spaces  in 
each;  the  cavities  are  small  in  the  compact  tissue  and  the  solid  matter  between 


Cartilage  cell 


Hyaline  tnatrix 


Yellow  elastic 
fibres 


Fig.  27. — Yellow  or  elastic  fibrocartilage  from  epiglottis  of  cat. 


CONNECTIVE  TISSUES  51 

them  abundant,  while  in  tlie  cancellous  tissue  the  spaces  are  large  and  the  solid 
matter  is  in  smaller  quantity. 

Bone  during  life  is  permeated  by  vessels,  and  is  enclosed,  except  where  it  is 
coated  with  articular  cartilage,  in  a  fibrous  membrane,  the  periosteum,  by  means 
of  which  many  of  these  vessels  reach  the  hard  tissue.  If  the  periosteum  be  stripped 
from  the  surface  of  the  living  bone,  small  bleeding  points  are  seen  which  mark  the 
entrance  of  the  periosteal  vessels;  and  on  section  during  life  every  part  of  the 
bone  exudes  blood  from  the  minute  vessels  which  ramify  in  it.  The  interior  of 
each  of  the  long  bones  of  the  limbs  presents  a  cylindrical  cavity  filled  with  marrow 
and  lined  by  a  highly  vascular  areolar  structure,  called  the  medullary  membrane 
or  internal  periosteum. 

Periosteum.^The  periosteum  adheres  to  the  surface  of  each  of  the  bones  in 
nearly  eyery  part,  but  not  to  cartilaginous  extremities.  When  strong  tendons  or 
ligaments  are  attached  to  a  bone,  the  periosteum  is  incorporated  with  them.  It 
consists  of  two  layers  closely  united  together,  the  outer  one  formed  chiefly  of 
connective  tissue,  containing  occasionally  a  few  fat  cells;  the  inner  one,  of  elastic 
fibres  of  the  finer  kind,  forming  dense  membranous  networks,  which  can  be  again 
separated  into  several  layers.  In  young  bones  the  periosteum  is  thick  and  very 
vascular,  and  is  intimately  connected  at  either  end  of  the  bone  with  the  epiphysial 
cartilage,  but  less  closely  with  the  body  of  the  bone,  from  w^hich  it  is  separated  by 
a  layer  of  soft  tissue,  containing  a  number  of  granular  corpuscles  or  osteoblasts,  by 
which  ossification  proceeds  on  the  exterior  of  the  young  bone.  Later  in  life  the 
periosteum  is  thinner  and  less  vascular,  and  the  osteoblasts  are  converted  into  an 
epithelioid  layer  on  the  deep  surface  of  the  periosteum.  The  periosteum  serves 
as  a  nidus  for  the  ramification  of  the  vessels  previous  to  their  distribution  in  the 
bone;  hence  the  liability  of  bone  to  exfoliation  or  necrosis  when  denuded  of  this 
membrane  by  injury  or  disease.  Fine  nerves  and  lymphatics,  which  generally 
accompany  the  arteries,  may  also  be  demonstrated  in  the  periosteum. 

Marrow. — -The  marrow  not  only  fills  up  the  cylindrical  cavities  in  the  bodies  of 
the  long  bones,  but  also  occupies  the  spaces  of  the  cancellous  tissue  and  extends 
into  the  larger  bony  canals  (Haversian  canals)  which  contain  the  bloodvessels. 
It  differs  in  composition  in  different  bones.  In  the  bodies  of  the  long  bones  the 
marrow  is  of  a  yellow  color,  and  contains,  in  100  parts,  96  of  fat,  1  of  areolar  tissue 
and  vessels,  and  3  of  fluid  with  extractive  matter;  it  consists  of  a  basis  of  connective 
tissue  supporting  numerous  bloodvessels  and  cells,  most  of  w^iich  are  fat  cells 
but  some  are  "marrow  cells,"  such  as  occur  in  the  red  marrow  to  be  immediately 
described.  In  the  flat  and  short  bones,  in  the  articular  ends  of  the  long  bones, 
in  the  bodies  of  the  vertebree,  in  the  cranial  diploe,  and  in  the  sternum  and  ribs 
the  marrow  is  of  a  red  color,  and  contains,  in  100  parts,  75  of  water,  and  25  of  solid 
matter  consisting  of  cell-globulin,  nucleoprotein,  extractives,  salts,  and  only  a 
small  proportion  of  fat.  The  red  marrow  consists  of  a  small  quantity  of  connective 
tissue,  bloodvessels,  and  numerous  cells  (Fig.  28),  some  few  of  which  are  fat  cells, 
but  the  great  majority  are  roundish  nucleated  cells,  the  true  "marrow  cells" 
of  Kolliker.  These  marrow  cells  proper,  or  myelocytes,  resemble  in  appearance 
lymphoid  corpuscles,  and  like  them  are  amoeboid;  they  generally  have  a  hyaline 
protoplasm,  though  some  show  granules  either  oxyphil  or  basiphil  in  reaction. 
A  number  of  eosinophil  cells  are  also  present.  Among  the  marrow  cells  may  be 
seen  smaller  cells,  which  possess  a  slightly  pinkish  hue;  these  are  the  erythroblasts 
or  normoblasts,  from  which  the  red  corpuscles  of  the  adult  are  derived,  and  which 
may  be  regarded  as  descendants  of  the  nucleated  colored  corpuscles  of  the  embryo. 
Giant  cells  {myeloplaxes,  osteoclasts),  large,  multinucleated,  protoplasmic  masses, 
are  also  to  be  found  in  both  sorts  of  adult  marrow,  but  more  particularly  in  red 
marrow.  They  were  believed  by  Kolliker  to  be  concerned  in  the  absorption  of 
bone  matrix,  and  hence  the  name  w^hich  he  gave  to  them-^osteoclasts.     They 


52 


HISTOLOGY 


excavate  in  the  bone  small  shallow  pits  or  cavities,  which  are  named  Howship's 
foveolcE,  and  in  these  they  are  found  lying. 

Vessels  and  Nerves  of  Bone. — The  bloodvessels  of  bone  are  very  numerous.  Those 
of  the  compact  tissue  are  derived  from  a  close  and  dense  network  of  vessels  ramify- 
ing in  the  periosteum.  From  this  membrane  vessels  pass  into  the  minute  orifices 
in  the  compact  tissue,  and  run  through  the  canals  which  traverse  its  substance. 
The  cancellous  tissue  is  supplied  in  a  similar  way,  but  by  less  numerous  and  larger 
vessels,  which,  perforating  the  outer  compact  tissue,  are  distributed  to  the  cavities 
of  the  spongy  portion  of  the  bone.  In  the  long  bones,  numerous  apertures  may 
be  seen  at  the  ends  near  the  articular  surfaces;  some  of  these  give  passage  to  the 
arteries  of  the  larger  set  of  vessels  referred  to;  but  the  most  numerous  and  largest 
apertures  are  for  some  of  the  veins  of  the  cancellous  tissue,  which  emerge  apart 
from  the  arteries.  The  marrow  in  the  body  of  a  long  bone  is  supplied  by  one 
large  artery  (or  sometimes  more),  which  enters  the  bone  at  the  nutrient  foramen 


Normoblast  ivith  dividing  nucleus 


Myelocyte 


Erythrocyte  ---*« 


Myeloplaxe  •■--■ 


Myelocyte 


Fat 


Eosinophil 
cell 


C-^~  Normoblasts 


Myelocyte 
dividing 


-  Myelocyte 


Fat 


Fig.  28. — Human  bone  marrow.     Highly  magnified. 


(situated  in  most  cases  near  the  centre  of  the  body),  and  perforates  obliquely  the 
compact  structure.  The  medullary  or  nutrient  artery,  usually  accompanied  by  one 
or  two  veins,  sends  branches  upward  and  downward,  which  ramify  in  the  medul- 
lary membrane,  and  give  twigs  to  the  adjoining  canals.  The  ramifications  of  this 
vessel  anastomose  with  the  arteries  of  the  cancellous  and  compact  tissues.  In  most 
of  the  flat,  and  in  many  of  the  short  spongy  bones,  one  or  more  large  apertures  are 
observed,  which  transmit  to  the  central  parts  of  the  bone  vessels  corresponding  to 
the  nutrient  arteries  and  veins.  The  veins  emerge  from  the  long  bones  in  three 
places  (Kolliker) :  (1)  one  or  two  large  veins  accompany  the  artery;  (2)  numerous 
large  and  small  veins  emerge  at  the  articular  extremities;  (3)  many  small  veins 
pass  out  of  the  compact  substance.  In  the  flat  cranial  bones  the  veins  are  large, 
very  numerous,  and  run  in  tortuous  canals  in  the  diploic  tissue,  the  sides  of  the 
canals  being  formed  by  thin  lamellae  of  bone,  perforated  here  and  there  for  the 
passage  of  branches  from  the  adjacent  cancelli.  The  same  condition  is  also 
found  in  all  cancellous  tissue,  the  veins  being  enclosed  and  supported  by  osseous 


CONNECTIVE  TISSUES 


53 


material,  and  having  exceedingly  thin  coats.  When  a  bone  is  divided,  the  vessels 
remain  patulous,  and  do  not  contract  in  the  canals  in  which  they  are  contained. 
Lymphatic  vessels,  in  addition  to  those  found  in  the  periosteum,  have  been  traced 
by  Cruikshank  into  the  substance  of  bone,  and  Klein  describes  them  as  running  in 
the  Ha^'e^sian  canals.  Nerves  are  distributed  freely  to  the  periosteum,  and  accom- 
pany the  nutrient  arteries  into  the  interior  of  the  bone.  They  are  said  by  Kolliker 
to  be  most  numerous  in  the  articular  extremities  of  the  long  bones,  in  the  vertebrae, 
and  in  the  larger  flat  bones. 

Minute  Anatomy. — A  transverse  section  of  dense  bone  may  be  cut  with  a  saw 
and  ground  down  until  it  is  sufficiently  thin. 

If  this  be  examined  with  a  rather  low  power  the  bone  will  be  seen  to  be  mapped 
out  into  a  number  of  circular  districts  each  consisting  of  a  central  hole  surrounded 
by  a  number  of  concentric  rings.  These  districts  are  termed  Haversian  systems; 
the  central  hole  is  an  Haversian  canal,  and  the  rings  are  layers  of  bony  tissue 
arranged  concentrically  around  the  central  canal,  and  termed  lamellae.  More- 
over, on  closer  examination  it  will  be  found  that  between  these  lamellae,  and 
therefore  also  arranged  concentrically  around  the  central  canal,  are  a  number  of 


Fig.  29. — Transverse  section  of  compact  tissue  of  bone.     Magnified.     (Sharpey.) 


little  dark  spots,  the  lacunae,  and  that  these  lacunae  are  connected  with  each  other 
and  with  the  central  Haversian  canal  by  a  number  of  fine  dark  lines,  which  radiate 
like  the  spokes  of  a  wheel  and  are  called  canaliculi.  Filling  in  the  irregular  intervals 
which,  are  left  between  these  circular  systems  are  other  lamellae,  with  their  lacunae 
and  canaliculi  running  in  various  directions,  but  more  or  less  curved  (Fig.  29); 
they  are  termed  interstitial  lamellae.  Again,  other  lamellae,  found  on  the  surface 
of  the  bone,  are  arranged  parallel  to  its  circumference;  they  are  termed  circimi- 
ferential,  or  by  some  authors  primary  or  fundamental  lamellae,  to  distinguish  them 
from  those  laid  down  around  the  axes  of  the  Haversian  canals,  which  are  then 
termed  secondaiy  or  special  lamellae. 

The  Haversian  canals,  seen  in  a  transverse  section  of  bone  as  round  holes  at  or 
about  the  centre  of  each  Haversian  system,  may  be  demonstrated  to  be  true  canals 
if  a  longitudinal  section  be  made  (Fig.  30).  It  will  then  be  seen  that  the  canals 
run  parallel  with  the  longitudinal  axis  of  the  bone  for  a  short  distance  and  then 
branch  and  communicate.  They  vary  considerably  in  size,  some  being  as  much  as 
0.12  mm.  in  diameter;  the  average  size  is,  however,  about  0.05  mm.  Near  the 
medullary  cavity  the  canals  are  larger  than  those  near  the  surface  of  the  bone. 


54 


HISTOLOGY 


Each  canal  contains  one  or  two  bloodvessels,  with  a  small  quantity  of  delicate 
connective  tissue  and  some  nerve  filaments.  In  the  larger  ones  there  are  also 
lymphatic  vessels,  and  cells  with  branching  processes  which  communicate,  through 
the  canalculi,  with  the  branched  processes  of  certain  bone  cells  in  the  substance 
of  the  bone.  Those  canals  near  the  surface  of  the  bone  open  upon  it  by  minute 
orifices,  and  those  near  the  medullary  cavity  open  in  the  same  way  into  this  space, 
so  that  the  whole  of  the  bone  is  permeated  by  a  system  of  bloodvessels  running 
through  the  bony  canals  in  the  centres  of  the  Haversian  systems. 

The  lamellae  are  thin  plates  of  bony  tissue 
encircling  the  central  canal,  and  may  be  com- 
pared, for  the  sake  of  illustration,  to  a  number 
of  sheets  of  paper  pasted  one  over  another 
around  a  central  hollow  cylinder.  After 
macerating  a  piece  of  bone  in  dilute  mineral 
acid,  these  lamellae  may  be  stripped  off'  in  a 


i?^" 


Fig.  30! — Section  parallel  to  the  surface 
from  the  body  of  the  femur.  X  100.  o,  Haver- 
sian canals;  6,  lacunse  seen  from  the  side;  c, 
others  seen  from  the  surface  in  lamelte,  which 
are  cut  horizontally. 


Fig.  31. — Perforating  fibres,  human  parietal  bone,    decalcified. 
(H.  Miiller.)     a,  perforating  fibres  in  situ;  b,  fibres  drawn  out  of 

their  sockets;  c,  sockets. 


longitudinal  direction  as  thin  films.  If  one  of  these  be  examined  with  a  high  power 
of  the  microscope,  it  will  be  found  to  be  composed  of  a  finely  reticular  structure, 
made  up  of  very  slender  transparent  fibres,  decussating  obliquely;  and  coalescing 
at  the  points  of  intersection;  these  fibres  are  composed  of  fine  fibrils  identical  with 
those  of  white  connective  tissue.  The  intercellular  matrix  between  the  fibres  is 
impregnated  by  calcareous  deposit  which  the  acid  dissolves.  In  many  places  the 
various  lamellse  may  be  seen  to  be  held  together  by  tapering  fibres,  which  run 
obliquely  through  them,  pinning  or  bolting  them  together;  they  were  first  de- 
scribed by  Sharpey,  and  were  named  by  him  perforating  fibres  (Fig.  31). 

The  Lacunae  are  'situated  between  the  lamella,  and  consist  of  a  number  of  oblong 
spaces.  In  an  ordinary  microscopic  section,  viewed  by  transmitted  light,  they 
appear  as  fusiform  opaque  spots.  Each  lacuna  is  occupied  during  life  by  a  branched 
cell,  termed  a  bone-cell  or  bone-corpuscle,  the  processes  from  which  extend  into  the 
canal iculi  (Fig.  32). 

The  CanalicuU  are  exceedingly  minute  channels,  crossing  the  lamella?_  and  con- 
necting the  lacunge  with  neighboring  lacuna?  and  also  with  the  Haversian  canal. 
From  the  Haversian  canal  a  number  of  canaliculi  are  given  off,  which  radiate  from 
it,  and  open  into  the  first  set  of  lacunae  between  the  first  and  second  lamella. 
From  these  lacuna?  a  second  set  of  canaliculi  is  given  off;  these  run  outward  to  the 


CONNECTIVE  TISSUES 


55 


next  series  of  lacuna',  and  so  on  until  the  ])eriphery  of  the  Haversian  system  is 
reached;  here  the  canaliculi  given  oft'  from  the  last  series  of  lacunae  do  not  communi- 
cate with  the  lacumie  of  neighboring  Haversian  systems,  but  after  passing  outward 
for  a  short  distance  form  loops  and  return  to  their  own  lacunie.  Thus  every 
part  of  an  Haversian  system  is  sui)i)lied  with  nutrient  fluids  derived  from  the 
vessels  in  the  Haversian  canal  and  distributetl  through  the  canaliculi  and  lacunae. 

The  bone  cells  are  contained  in  the  lacunae, 
which,  liowe\er,  they  do  not  completely  fill. 
They  are  flattened  nucleated  branched  cells, 
homologous  with  those  of  connective  tissue;  the 
branches,  especially  in  young  bones,  pass  into 
the  canaliculi  from  the  lacunae. 

In  thin  plates  of  bone  (as  in  the  walls  of 
the  spaces  of  cancellous  tissue)  the  Haversian 
canals  are  absent,  and  the  canaliculi  open  into 
the  spaces  of  the  cancellous  tissue  (medullary 
spaces),  which  thus  have  the  same  function  as 
the  Haversian  canals. 

Chemical     Composition.— Bone     consists     of    an  Fig.  32.— Nucleated  bone    cells    and    their 

,              -I                        .  1                    _L      •     J  •         J    1  processes,  contained  in  the  bone  lacunae  and 

animal      and      an    earthy     part      intimately    com-  their  canalicuU  respectively.     From  a  section 

U  ■        J    X     _    j-1  through    the   vertebra    of    an    adult   mouse. 

bmed    tOgetlier.  (Klein  and  Noble  smith.) 


Eaversian  canal 

Done  corpuscle 


Bone  corpuscle 
between  inter- 
stitial lamellce 


Fig.  33. — Transverse  section  of  body  of  human  fibula,  decalcified.      X  250. 


The  animal  part  may  be  obtained  by  immersing  a  bone  for  a  considerable  time 
in  dilute  mineral  acid,  after  which  process  the  bone  comes  out  exactly  the  same 
shape  as  before,  but  perfectly  flexible,  so  that  a  long  bone  (one  of  the  ribs,  for 
example)  can  easily  be  tied  in  a  knot.  If  now  a  transverse  section  is  made 
(Fig.  33)  the  same  general  arrangement  of  the  Haversian  canals,  lamellae,  lacunae, 
and  canaliculi  is  seen. 

The  earthy  part  may  be  separately  obtained  by  calcination,  by  which  the 
animal  matter  is  completely  burnt  out.  The  bone  wdll  still  retain  its  original 
form,  but  it  will  be  white  and  brittle,  wall  have  lost  about  one-third  of  its  original 
weight,  and  wall  crumble  down  with  the  slightest  force.  The  earthy  matter  is 
composed  chiefly  of  calcium  phosphate,  forming  about  66.7  per  cent,  of  the  weight 


56 


HISTOLOGY 


of  the  bone;  it  confers  on  bone  its  hardness  and  rigidity,  while  the  animal  matter 
(ossein)  determines  its  tenacity. 

Ossification. — Some  bones  are  preceded  by  membrane,  such  as  those  forming 
the  roof  and  sides  of  the  skull ;  others,  such  as  the  bones  of  the  limbs,  are  preceded 
by  rods  of  cartilage.  Hence  two  kinds  of  ossification  are  described:  the  intra- 
membranous  and  the  intracartilaginous. 

Inteamembranous  Ossification. — In  the  case  of  bones  which  are  developed 
in  membrane,  no  cartilaginous  mould  precedes  the  appearance  of  the  bony  tissue. 
The  membrane  which  occupies  the  place  of  the  future  bone  is  of  the  nature  of  con- 
nective tissue,  and  ultimately  forms  the  periosteum;  it  is  composed  of  fibres  and 
granular  cells  in  a  matrix.  The  peripheral  portion  is  more  fibrous,  while,  in  the 
interior  the  cells  or  osteoblasts  predominate;  the  whole  tissue  is  richly  supplied  with 
bloodvessels.  At  the  outset  of  the  process  of  bone  formation  a  little  network 
of  spicules  is  noticed  radiating  from  the  point  or  centre  of  ossification.  These 
rays  consist  at  their  growing  points  of  a  network  of  fine  clear  fibres  and  granular 
corpuscles  with  an  intervening  ground  substance  (Fig.  34).    The  fibres  are  termed 


Union  of 
adjacent 
spicules 


Osteoblasts  ^^^  __ 


Osteogenetic 
fibres 


_  Calcified  deposit 
betweev  the  fibres 


Bony  spicules 


Fig.  34. — Part  of  the  growing  edge  of  the  developing  parietal  bone  of  a  fetal  cat.     (After  J.  Lawrence.) 


osteogenetic  fibres,  and  are  made  up  of  fine  fibrils  differing  little  from  those  of  white 
fibrous  tissue.  The  membrane  soon  assumes  a  dark  and  granular  appearance  from 
the  deposition  of  calcareous  granules  in  the  fibres  and  in  the  intervening  matrix, 
and  in  the  calcified  material  some  of  the  granular  corpuscles  or  osteoblasts  are 
enclosed.  By  the  fusion  of  the  calcareous  granules  the  tissue  again  assumes  a 
more  transparent  appearance,  but  the  fibres  are  no  longer  so  distinctly  seen. 
The  involved  osteoblasts  form  the  corpuscles  of  the  future  bone,  the  spaces  in 
which  they  are  enclosed  constituting  the  lacunae.  As  the  osteogenetic  fibres  grow 
out  to  the  periphery  they  continue  to  calcify,  and  give  rise  to  fresh  bone  spicules. 
Thus  a  network  of  bone  is  formed,  the  meshes  of  which  contain  the  bloodvessels 
and  a  delicate  connective  tissue  crowded  with  osteoblasts.  The  bony  trabeculse 
thicken  by  the  addition  of  fresh  layers  of  bone  formed  by  the  osteoblasts  on  their 
surface,  and  the  meshes  are  correspondingly  encroached  upon.  Subsequently 
successive  layers  of  bony  tissue  are  deposited  under  the  periosteum  and  around 
the  larger  vascular  channels  which  become  the  Haversian  canals,  so  that  the  bone 
increases  much  in  thickness. 


CONNECTIVE  TISSUES 


57 


Intercartil.\.ginous  Ossification. — Just  before  ossification  begins  the  mass  is 
entirely  cartilaginous,  and  in  a  long  bone,  which  may  be  taken  as  an  example,  the 
process  commences  in  the  centre  and  proceeds  toward  the  extremities,  which  for 
some  time  remain  cartilaginous.  Subsequently  a  similar  process  commences  in 
one  or  more  places  in  those  extremities  and  gradually  extends  through  them. 
The  extremities  do  not,  however,  become  joined  to  the  body  of  the  bone  by  bony 
tissue  until  growth  has  ceased ;  between  the  body  and  either  extremity  a  layer  of 
cartilaginous  tissue  termed  the  epiphysial  cartilage  persists  for  a  definite  period. 

The  first  step  in  the  ossification  of 
the  cartilage  is  that  the  cartilage  cells, 
at  the  point  where  ossification  is  com- 
mencing and  which  is  termed  a  centre 
of  ossification,  enlarge  and  arrange 
themselves  in  rows  (Fig.  35).  The 
matrix  in  which  they  are  imbedded 
increases  in  quantity,  so  that  the  cells 
become  further  separated  from  each 
other.  A  deposit  of  calcareous  material 
now  takes  place  in  this  matrix,  between 
the  rows  of  cells,  so  that  they  become 
separated  from  each  other  by  longi- 
tudinal columns  of  calcified  matrix, 
presenting  a  granular  and  opaque  ap- 
pearance. Here  and  there  the  matrix 
between  two  cells  of  the  same  row  also 
becomes  calcified,  and  transverse  bars 
of  calcified  substance  stretch  across 
from  one  calcareous  column  to  another. 
Thus  there  are  longitudinal  groups  of 
the  cartilage  cells  enclosed  in  oblong 
cavities,  the  walls  of  which  are  formed 
of  calcified  matrix  which  cuts  off  all 
nutrition  from  the  cells;  the  cells,  in 
consequence,  atrophy,  leaving  spaces 
called  the  primary  areolae. 

At  the  same  time  that  this  process 
is  going  on  in  the  centre  of  the  solid 
bar  of  cartilage,  certain  changes  are 
taking  place  on  its  surface.  This  is 
covered  by  a  very  vascular  membrane, 

J.1       _      •    1.       J   •                   ■•      1         •      •!        J.     j_i  Fig.  35. — Section  of    fetal  bone  of  cat.     ■!>.    Irruption 

tne  periCnondnUm,  entirely  similar  to  the  of  the  subperiosteal  tissue,     v-  Fibrous  layer  of  the  perios- 

pmhrvonir-     pnnnppfi\ra     fiQcnf^       nlr^nrl-^/  teum      o.   Layer  of  osteoblasts,     irn.  Subperiosteal  bony 

emoryomc     connective  ^  tissue       aireaay  deposit.     (From  Qualn's  "Anatomy,"  E.  a.  Schafer.) 

described  as  constituting  the  basis  of 

membrane  bone;  on  the  inner  surface  of  this — that  is  to  say,  on  the  surface  in 
contact  with  the  cartilage — are  gathered  the  formative  cells,  the  osteoblasts.  By 
the  agency  of  these  cells  a  thin  layer  of  bony  tissue  is  formed  between  the  peri- 
chondrium and  the  cartilage,  by  the  intramemhranous  mode  of  ossification  just 
described.  There  are  then,  in  this  first  stage  of  ossification,  two  processes  going 
on  simultaneously:  in  the  centre  of  the  cartilage  the  formation  of  a  number  of 
oblong  spaces,  formed  of  calcified  matrix  and  containing  the  withered  cartilage 
cells,  and  on  the  surface  of  the  cartilage  the  formation  of  a  layer  of  true  mem- 
brane bone.  The  second  stage  consists  in  the  prolongation  into  the  cartilage  of 
processes  of  the  deeper  or  osteogenetic  layer  of  the  perichondrium,  which  has 
now  become  periosteum  (Fig.  35,  ir).    The  processes  consist  of  bloodvessels  and 


5tM«. 


58 


HISTOLOGY 


cells — osteoblasts,  or  bone-formers,  and  osteoclasts,  or  bone-destroyers.     The  latter 

are  similar  to  the  giant  cells  (myeloplaxes)  found  in  marrow,  and  they  excavate 
passages  through  the  new-formed  bony  layer  by  absorption,  and  pass  through 
it  into  the  calcified  matrix  (Fig.  36).  Wherever  these  processes  come  in  con- 
tact with  the  calcified  walls  of  the  primary  areolae  they  absorb  them,  and  thus 
cause  a  fusion  of  the  original  cavities  and  the  formation  of  larger  spaces,  which 
are  termed  the  secondary  areolae  or  medullary  spaces.  These  secondary  spaces 
become  filled  with  embryonic  marrow,  consisting  of  osteoblasts  and  vessels,  derived, 

in  the  manner  described  above,  from  the 
osteogenetic  layer  of  the  periosteum  (Fig.  36). 
Thus  far  there  has  been  traced  the  forma- 
tion of  enlarged  spaces  (secondary  areolae), 
the  perforated  walls  of  which  are  still  formed 
by  calcified  cartilage  matrix,  containing  an 
embryonic  marrow  derived  from  the  processes 
sent  in  from  the  osteogenetic  layer  of  the 
periosteum,  and  consisting  of  bloodvessels  and 
osteoblasts.  The  walls  of  these  secondary 
areolae  are  at  this  time  of  only  inconsiderable 
thickness,  but  they  become  thickened  by  the 
deposition  of  layers  of  true  bone  on  their  sur- 
face. This  process  takes  place  in  the  follow- 
ing manner:  Some  of  the  osteoblasts  of  the 
embryonic  marrow,  after  undergoing  rapid 
division,  arrange  themselves  as  an  epithelioid 
layer  on  the  surface  of  the  wall  of  the  space 
(Fig.  37).  This  layer  of  osteoblasts  forms  a 
bony  stratum,  and  thus  the  wall  of  the  space 
becomes  gradually   covered   with   a   layer  of 


Osteoclasts- 


Fig.  36. — Part  of  a  longitudinal  section  of 
the  developing  femur  of  a  rabbit,  a.  Flattened 
cartilage  cells,  h.  Enlarged  cartUage  cells,  c, 
d.  Xewly  formed  bone.  e.  Osteoblasts.  /. 
Giant  cells  or  osteoclasts.  g,  h.  Shrunken 
cartilage  cells.  (From  "Atlas  of  Histology," 
Klein  and  Noble  Smith.) 


Osteoblasts 


Fig.  37. — Osteoblasts  and  osteoclasts  on  trabecula  of  lower  jaw  of 
calf  embryo.     (KolUker.; 


true  osseous  substance  in  which  some  of  the  bone-forming  cells  are  included  as 
bone  corpuscles.  The  next  stage  in  the  process  consists  in  the  removal  of  these 
primary  bone  spicules  by  the  osteoclasts.  One  of  these  giant  cells  may  be  found 
lying  in  a  Howship's  foveola  at  the  free  end  of  each  spicule.  The  removal  of  the 
primary  spicules  goes  on  j^^ri  -passu  with  the  formation  of  permanent  bone  by 
the  periosteum,  and  in  this  way  the  medullary  cavity  of  the  body  of  the  bone  is 
formed. 

This  series  of  changes  has  been  gradually  proceeding  toward  the  end  of  the  body 
of  the  bone,  so  that  in  the  ossifying  bone  all  the  changes  described  above  may 
be  seen  in  different  parts,  from  the  true  bone  at  the  centre  of  the  body  to  the  hyaline 
cartilage  at  the  extremities. 


CONNECTIVE  TISSUES  59 

AYhilc  the  ossification  of  tlie  cartilaginous  body  is  extending  toward  the  articular 
ends,  the  cartilage  immediately  in  advance  of  the  osseous  tissue  continues  to  grow 
until  the  length  of  the  adult  bone  is  reached. 

During  the  period  of  growth  the  articular  end,  or  epiphysis,  remains  for  some 
time  entirely  cartilaginous,  then  a  bony  centre  appears,  and  initiates  in  it  the 
process  of  intracartilaginous  ossification;  but  this  process  never  extends  to  any 
great  distance.  The  epiphysis  remains  separated  from  the  body  by  a  narrow 
cartilaginous  layer  for  a  definite  time.  This  layer  ultimately  ossifies,  the  distinc- 
tion between  body  and  epiphysis  is  obliterated,  and  the  bone  assumes  its  completed 
form  and  shape.  The  same  remarks  also  apply  to  such  processes  of  bone  as  are 
separately  ossified,  e.  g.,  the  trochanters  of  the  femur.  The  bones  therefore  con- 
tinue to  grow  until  the  body  has  acquired  its  full  stature.  They  increase  in  length 
b}'  ossification  continuing  to  extend  behind  the  epiphysial  cartilage,  which  goes 
on  growing  in  advance  of  the  ossifying  process.  They  increase  in  circumference 
by  deposition  of  new  bone,  from  the  deeper  layer  of  the  periosteum,  on  their  exter- 
nal surface,  and  at  the  same  time  an  absorption  takes  place  from  within,  by  which 
the  medullary  cavities  are  increased. 

The  permanent  bone  formed  by  the  periosteum  when  first  laid  down  is  cancellous 
in  structure.  Later  the  osteoblasts  contained  in  its  spaces  become  arranged  in 
the  concentric  layers  characteristic  of  the  Haversian  systems,  and  are  included 
as  bone  corpuscles. 

The  number  of  ossific  centres  varies  in  different  bones.  In  most  of  the  short 
bones  ossification  commences  at  a  single  point  near  the  centre,  and  proceeds  toward 
the  surface.  In  the  long  bones  there  is  a  central  point  of  ossification  for  the  body 
or  diaphysis:  and  one  or  more  for  each  extreinity,  the  epiphysis.  That  for  the 
body  is  the  first  to  appear.  The  times  of  union  of  the  epiphyses  with  the  body 
vary  inversely  with  the  dates  at  which  their  ossifications  began  (with  the  exception 
of  the  fibula)  and  regulate  the  direction  of  the  nutrient  arteries  of  the  bones.  Thus, 
the  nutrient  arteries  of  the  bones  of  the  arm  and  forearm  are  directed  toward 
the  elbow,  since  the  epiphyses  at  this  joint  become  united  to  the  bodies  before 
those  at  the  opposite  extremities.  In  the  lower  limb,  on  the  other  hand,  the 
nutrient  arteries  are  directed  away  from  the  knee:  that  is,  upward  in  the  femur, 
downward  in  the  tibia  and  fibula;  and  in  them  it  is  observed  that  the  upper  epiphysis 
of  the  femur,  and  the  lower  epiphyses  of  the  tibia  and  fibula,  unite  first  with  the 
bodies.  Where  there  is  only  one  epiphysis,  the  nutrient  artery  is  directed  toward 
the  other  end  of  the  bone;  as  toward  the  acromial  end  of  the  clavicle,  toward  the 
distal  ends  of  the  metacarpal  bone  of  the  thumb  and  the  metatarsal  bone  of  the 
great  toe,  and  toward  the  proximal  ends  of  the  other  metacarpal  and  metatarsal 
bones. 

Parsons^  groups  epiphyses  under  three  headings,  viz.:  (1)  pressure  epiphyses, 
appearing  at  the  articular  ends  of  the  bones  and  transmitting  "the  weight  of  the 
body  from  bone  to  bone;"  (2)  traction  epiphyses,  associated  with  the  insertion 
of  muscles  and  "originally  sesamoid  structures  though  not  necessarily  sesamoid 
bones;"  and  (3)  atavistic  epiphyses,  representing  parts  of  the  skeleton,  which  at 
one  time  formed  separate  bones,  but  which  have  lost  their  function,  "  and  only 
appear  as  separate  ossifications  in  early  life." 

Applied  Anatomy. — It  has  been  stated  above  that  the  bones  increase  firstty  in  length  bj^  ossifi- 
cation continuing  to  extend  in  the  epiphysial  cartilage,  which  goes  on  growing  in  advance  of  the 
ossifying  process;  and  secondly,  in  circumference  by  deposition  of  new  bone  from  the  deeper 
layer  of  the  periosteum,  on  the  external  sm-face. 

A  careful  study  of  osseous  development  is  of  the  very  greatest  utihty  in  the  proper  understand- 
ing of  bone  disease;  and,  moreover,  an  accm-ate  knowledge  of  the  blood  supply  of  a  long  bone 

1  Jour,  of  Anat.  and  Phys.,  vols,  xsxviii,  xxxix,  and  xlii. 


60  HISTOLOGY 

has  also  many  important  bearings.  The  outer  portion  of  the  compact  tissue  being  supphed  by 
periosteal  vessels,  which  reach  the  bone  through  muscular  attachments,  it  follows  that  where 
the  muscular  structures  are  well  developed,  and  therefore  amply  supphed  with  blood,  the  perios- 
teum will  also  be  well-nourished  and  the  bones  proportionately  well-developed  in  girth;  this  is 
well  seen  in  strong  muscular  men  with  well-marked  ridges  on  the  bones.  Conversely,  if  the  mus- 
cular development  be  poor,  the  bones  are  correspondingly  thin  and  hght,  and  if  from  any  cause 
a  hmb  has  been  paralyzed  from  early  childhood,  the  whole  of  the  bones  of  that  extremity  are 
remarkable  for  their  extreme  thinness — that  is  to  say,  the  periosteal  blood  supply  has  been  insuffi- 
cient to  nourish  that  membrane,  and  consequently  very  httle  fresh  osseous  tissue  has  been  added 
to  the  bones  from  the  outside. 

The  best  example  of  this  condition  is  seen  in  connection  with  the  disease  known  as  infantile 
paralysis,  where  a  hmb  becomes  paralyzed  at  a  very  early  period  of  childhood,  where  the  muscles 
become  flaccid  and  atonic,  and  where  the  blood  supply  is  in  consequence  very  greatly  diminished. 
In  such  cases,  although  the  hmb  does  continue  to  grow  in  length  from  the  epiphysial  lines,  its 
length  is  considerably  less  than  on  the  normal  side,  owing  to  the  imperfect  nutrition;  but  the 
most  striking  feature  about  all  the  long  bones  of  the  Umb  is  their  remarkable  tenuity,  little  or  no 
addition  having  been  made  to  their  circumferences. 

In  cases  where  the  periosteum  has  been  separated  from  the  compact  tissue  by  extensive  injury 
or  inflammatory  exudation,  necrosis  or  death  of  the  underlying  portion  of  bone  takes  place  owing 
to  its  blood  supply  having  been  cut  off,  and  the  dead  portion  or  sequestrum  has  to  be  separated 
and  subsequently  cast  off. 

Cases,  however,  occur  where  the  inflammatory  process  affects  the  whole  or  a  great  portion 
of  the  diaphysis  of  a  long  bone,  and  here  extensive  death  of  the  affected  portion  takes  place,  and 
the  condition  goes  by  the  name  of  acute  infective  periostitis.  Where  this  occurs  the  body  of  the 
bone  dies  very  rapidly,  especiaUy  if  the  single  nutrient  artery  be  thrombosed  at  the  same  time. 
The  pus  which  has  formed  beneath  the  periosteum  is  set  free  by  timely  incision,  or  bursts  on  the 
surface;  the  periosteum  then  falls  back  on  the  necrosed  diaphysis  and  rapidly  forms  a  layer  of 
new  periosteal  bone,  surrounding  the  sequestrum.  This  layer  is  called  the  involucrum,  and  the 
openings  in  it  through  which  the  pus  escapes  the  cloacce.  When  the  inflammatory  process  affects 
mainly  the  medullary  canal,  the  condition  is  spoken  of  as  osteomyelitis,  and  the  two  conditions 
very  frequently  coexist,  and  then  go  by  the  name  of  acute  infective  necrosis  of  bone  or  acute 
diaphysitis .  When  the  medullary  cavity  is  filled  with  pus,  septic  thrombosis  of  the  veins  in  the 
Haversian  canals  takes  place,  and  there  is  a  very  great  danger  of  septic  emboh  being  displaced 
and  carried  into  the  general  circulation,  thus  setting  up  a  fatal  pyemia.  In  fact,  pyemia  is  more 
frequently  due  to  septic  bone  conditions  than  to  any  other  cause. 

In  the  pre-antiseptic  days,  pyemia  frequently  resulted  from,  amputations,  where  the  medullary 
canal  of  a  long  bone  was  opened  by  the  saw  cut.  Osteomyehtis  ensued,  and  if  the  patient  sur- 
vived, a  tubular  sequestrum  of  the  divided  shaft  subsequently  separated. 

A  proper  knowledge  of  the  epiphyses  is  of  the  utmost  possible  importance,  and  greatly  simphfies 
many  of  the  problems  in  the  pathology  of  bone  disease. 

Speaking  generally,  the  long  bones  have  at  either  end  an  epiphysis  from  the  cartilage  of  which 
growth  occurs,  and  hence  the  body  of  the  bone  increases  in  length  from  both  ends.  In  every 
case,  however,  one  epiphysis  is  the  more  active,  and  also  continues  in  its  activity  for  a  longer 
time.  This  actively  growing  epiphysis  is  always  the  one  from  which  the  nutrient  foramen  in  the 
diaphysis  points,  and  it  imites  to  the  diaphysis  at  a  later  date.  It  follows,  therefore,  that  the 
increase  in  length  of  a  bone  is  largely  dependent  on  this  epiphysis,  and  hence  anything  which 
interferes  with  the  growth  from  this  epiphysial  hne  at  any  time  prior  to  the  union  of  the  epiphysis 
with  the  diaphysis  must  result  in  a  cessation  of  growth  in  length  of  that  bone.  Thus  when  deal- 
ing with  disease  in  the  neighborhood  of  this  actively  growing  epiphysis  very  great  care  should 
be  taken  not  to  excise  or  destroy  its  line  of  imion  with  the  diaphysis.  These  epiphyses  are  par- 
ticTilarly  prone  to  become  the  seat  of  tuberculous  disease,  which  especially  tends  to  attack  the 
soft,  highly  vascular  canceUous  tissue. 

Again,  the  actively  growing  epiphysial  plate  is  the  portion  of  a  long  bone  which  is  in  the  vast 
majority  of  cases  afTected  by  tumor  growth  in  bone,  whether  it  be  innocent  or  malignant,  the 
former  (e.  g.,  osteoma)  usually  appearing  about  puberty,  and  the  latter  (e.  g.,  sarcoma)  usually 
toward  the  end  of  the  active  period  of  epiphysial  growth. 

Epiphysial  growth,  moreover,  has  to  be  considered  by  the  surgeon  when  he  is  about  to  ampu- 
tate in  a  child.  If  the  amputation  is  being  performed  through  a  bone,  the  actively  growing 
epiphysis  of  which  is  at  the  upper  end,  and  which  will  continue  to  grow  for  several  years  (e.  g., 
humerus  and  tibia),  it  will  be  necessary  to  make  allowance  for  this  and  to  cut  the  flaps  long; 
as  otherwise,  owing  to  continued  growth,  the  sawn  end  of  the  bone  will  ultimately  project  through 
the  stump,  and  a  condition  known  as  "conical  stump"  wiU  result.  This  requires  removal  of  a 
further  portion  of  the  bone. 

An  inflammatory  condition  termed  acute  epiphysitis  also  occurs,  although  it  is  not  so  frequent 
as  the  acute  infective  conditions  of  the  diaphysis,  owing  to  the  freer  blood  supply  of  the  epiphysis; 


THE  CIRCULATING  FLUIDS 


61 


in  late  years  it  lias  been  shown  that  acute  epipliysitis  in  (children  is  very  frequently  the  result 
of  a  pneumococcal  infection,  and  it  may  pass  on  to  complete  separation  of  the  epiphysis.  In 
this  connection  it  is  worthy  of  note  that  some  of  the  epiphysial  lines  lie  entirely  within  the  cap- 
sules of  their  corresponding  joints,  in  other  cases  entirely  witliout  the  capsules;  and  it  must  follow 
that  in  the  former  case  epiphysial  disease,  acute  or  chronic,  becomes,  ipso  facto,  practically  synony- 
mous with  disease  of  that  joint.  The  best  examples  of  intra-articular  epiphyses  are  those  for  the 
head  of  the  femur  and  head  of  the  humerus,  and  the  vast  majority  of  all  cases  of  tuberculous  disease 
of  the  hip  start  as  a  tuberculous  epiphysitis  about  the  intra-articular  epiphysial  plate  of  the  femur; 
again  cases  of  acute  septic  arthritis  of  the  shoulder  or  hip  joints  generally  have  their  origins  in 
these  intra-articular  epiphysial  lines,  and  often  result  in  separation  of  the  affected  epiphysis. 
Those  of  the  other  class,  or  extra-articular  epiphyses,  when  diseased,  do  not  tend  to  involve  the 
neighboring  joint  so  readily;  and  it  should  be  the  surgeon's  duty  to  keep  the  disease  from  involv- 
ing the  joint.  For  example,  the  trochanteric  epiphysis  of  the  femur  is  extra-articular  as  regards 
the  hip-joint,  and  the  epiphysial  line  of  the  head  of  the  tibia  is  well  below  the  level  of  the  knee- 
joint,  and  should  a  chronic  tuberculous  abscess  form  in  the  latter  situation,  it  should  be  attacked 
from  the  outside  before  it  has  time  to  spread  up  and  involve  the  cartilage  of  the  head  of  the  tibia. 
It  is  therefore  of  great  surgical  interest  to  note  in  every  case  the  relations  which  the  various 
epiphysial  lines  bear  to  their  respective  joint  capsules. 

A  knowledge  of  the  exact  periods  when  the  epiphyses  become  joined  to  the  shaft  is  often  of 
great  importance  in  medicolegal  inquiries.  It  also  aids  the  surgeon  in  the  diagnosis  of  many  of 
the  injuries  to  which  the  joints  are  hable;  for  it  not  infrequently  happens  that,  on  the  apphcation 
of  severe  force  to  a  joint,  the  epiphysis  becomes  separated  from  the  diaphysis,  and  such  injuries 
may  be  mistaken  for  fracture  or  dislocation. 


THE   CIRCULATING   FLUIDS. 


The  circulating  fluids  of  the  body  are  the  blood  and  the  lymph. 

Blood. — The  blood  is  an  opaque,  rather  viscid  fluid,  of  a  bright  red  or  scarlet 
color  when  it  flows  from  the  arteries,  of  a  dark  red  or  purple  color  when  it  flows 
from  the  veins.  It  is  salt  to  the  taste,  and  has  a  peculiar  faint  odor  and  an  alkaline 
reaction.  Its  specific  gravity  is  about  1.06,  and  its  temperature  is  generally  about 
37°  C,  though  varying  slightly  in  different  parts  of  the  body. 

General  Composition  of  the  Blood. — Blood  consists  of  a  faintly  yellow  fluid,  the 
plasma  or  liquor  sanguinis,  in  which  are  suspended  numerous  minute  particles, 
the  blood  corpuscles,  the  majority  of  which  are  colored  and  give  to  the  blood  its 
red  tint.  If  a  drop  of  blood  be  placed  in  a  thin  layer  on  a  glass  slide  and  examined 
under  the  microscope,  a  number  of  these  corpuscles  will  be  seen  floating  in  the 
plasma. 

The    Blood    Corpuscles    are    of      /^^X    /<^IiX  M^^  ^^     b 

three  kinds:  (1)  colored  cor- 
puscles or  erythrocytes;  (2)  color- 
less corpuscles  or  leucocytes;  (3) 
blood  platelets. 

1.  Colored  or  red  corpuscles 
(erythrocytes) ,  when  examined 
under  the  microscope,  are  "seen 
to  be  circular  disks,  biconcave  in 
profile.  The  disk  has  no  nucleus, 
but,  in  consequence  of  its  bicon- 
cave shape,  presents,  according 
to  the  alterations  of  focus  under 
an  ordinary  high  power,  a  central 
part,  sometimes  bright,  sometimes 

dark,  which  has  the  appearance  of  a  nucleus  (Fig.  38,  a).  It  is  to  the  aggregation 
of  the  red  corpuscles  that  the  blood  owes  its  red  hue,  although  when  examined 
by  transmitted  light  their  color  appears  to  be  only  a  faint  reddish  yellow.  The 
corpuscles  vary  slightly  in  size  even  in  the  same  drop  of  blood,  but  the  average 


Fig.  38. — Human  red  blood  corpuscles.  Highly  magnified,  a. 
Seen  from  the  surface,  b.  Seen  in  profile  and  forming  rouleaux. 
c.  Rendered  spherical  by  water,  d.  Rendered  crenate  by  salt 
solution. 


62  HISTOLOGY 

diameter  of  each  is  about  7.5m/  and  the  thickness  about  2)u,  Besides  these  there 
are  found  certain  smaller  corpuscles  of  about  one-half  of  the  size  just  indicated; 
these  are  termed  microcytes,  and  are  very  scarce  in  normal  blood;  in  diseased  con- 
ditions (e.  g.,  anemiaj,  however,  they  are  more  numerous.  The  number  of  red 
corpuscles  in  the  blood  is  enormous;  between  4,000,000  and  5,000,000  are  con- 
tained in  a  cubic  millimetre.  Power  states  that  the  red  corpuscles  of  an  adult 
would  present  an  aggregate  surface  of  about  3000  square  yards. 

If  the  web  of  a  living  frog's  foot  be  spread  out  and  examined  under  the  micro- 
scope the  blood  is  seen  to  flow  in  a  continuous  stream  through  the  vessels,  and  the 
corpuscles  show  no  tendency  to  adhere  to  each  other  or  to  the  wall  of  the  vessel. 
Doubtless  the  same  is  the  case  in  the  human-  body;  but  when  human  blood  is  drawn 
and  examined  on  a  slide  without  reagents  the  corpuscles  tend  to  collect  into  heaps 
like  rouleaux  of  coins  (Fig.  38,  b).  It  has  been  suggested  that  this  phenomenon 
may  be  explained  by  alteration  in  surface  tension.  During  life  the  red  corpuscles 
may  be  seen  to  change  their  shape  under  pressure  so  as  to  adapt  themselves,  to 
some  extent,  to  the  size  of  the  vessel.  They  are,  however,  highly  elastic,  and 
speedily  recover  their  shape  when  the  pressure  is  removed.  They  are  readily 
influenced  by  the  medium  in  which  they  are  placed.  In  water  they  swell  up,  lose 
their  shape,  and  become  globular  (endosmosis)  (Fig.  38,  c).  Subsequently  the 
hemoglobin  is  dissolved  out,  and  the  envelope  can  barely  be  distinguished  as  a 
faint  circular  outline.  Solutions  of  salt  or  sugar,  denser  than  the  plasma,  give 
them  a  stellate  or  crenated  appearance  (exosmosis)  (Fig.  38,  d),  but  the  usual 
shape  may  be  restored  by  diluting  the  solution  to  the  same  tonicity  as  the  plasma. 
The  crenated  outline  may  be  produced  as  the  first  effect  of  the  passage  of  an  elec- 
tric shock:  subsequently,  if  sufficiently  strong,  the  shock  ruptures  the  envelope. 
A  solution  of  salt,  isotonic  with  the  plasma,  merely  separates  the  blood  corpuscles 
mechanically,  without  changing  their  shape.  Two  views  are  held  with  regard  to 
the  structure  of  the  erythrocytes.  The  older  view,  that  of  Rollett,  supposes  that 
the  corpuscle  consists  of  a  sponge  work  or  stroma  permeated  by  a  solution  of  hemo- 
globin. Schafer,  on  the  other  hand,  believes  that  the  hemoglobin  solution  is  con- 
tained within  an  envelope  or  membrane,  and  the  facts  stated  above  with  regard 
to  the  osmotic  behavior  of  the  erythrocyte  support  this  belief.  The  envelope 
consists  mainly  of  lecithin,  cholesterin,  and  nucleoprotein. 

The  colorless  corpuscles  or  leucocytes  are  of  various  sizes,  some  no  larger,  others 
smaller,  than  the  red  corpuscles,  In  human  blood,  however,  the  majority  are 
rather  larger  than  the  red  corpuscles,  and  measure  about  lO/i  in  diameter.  On  the 
average  from  7000  to  12,000  leucocytes  are  found  in  each  cubic  millimetre  of 
blood. 

They  consist  of  minute  masses  of  nucleated  protoplasm,  and  exhibit  several 
varieties,  which  are  differentiated  from  each  other  chiefly  by  the  occurrence  or 
non-occurrence  of  granules  in  their  protoplasm,  and  by  the  staining  reactions  of 
these  granules  when  present  (Fig.  39).  (1)  The  most  numerous  (60  per  cent.)  and 
important  are  irregular  in  shape,  possessed  of  the  power  of  amoeboid  movement, 
and  are  characterized  by  nuclei  which  often  consist  of  two  or  three  parts  (multi- 
partite) connected  together  by  fine  threads  of  chromatin.  The  protoplasm  is 
clear,  and  contains  a  number  of  very  fine  granules,  which  stain  with  acid  dyes, 
such  as  eosin,  or  with  neutral  dyes,  and  are  therefore  called  oxyphil  or  neutrophil 
(Fig.  39,  P).  These  cells  are  termed  the  poljnnorphonuclear  leucocytes.  (2)  A 
second  variety  comprises  from  1  to  4  per  cent,  of  the  leucocytes;  they  are  larger 
than  the  previous  kind,  and  are  made  up  of  coarsely  granular  protoplasm,  the 
granules  being  highly  refractile  and  grouped  around  single  nuclei  of  horse-shoe 
shape  (Fig.  39,  E).    The  granules  stain  deeply  with  eosin,  and  the  cells  are  there- 

'  A  micromillimetre  C")  is  1/1000  of  a  millimetre  or  1/25000  of  an  inch. 


THE  CIRCULATING  FLUIDS 


63 


fore  often  termed  eosinophil  corpuscles.  (3)  The  third  variety  is  called  the  hyaline 
cell  or  macrocyte  (Fig-.  39,  //).  This  is  usually  about  the  same  size  as  the  eosino- 
phil cell,  and,  when  at  rest,  is  spherical  in  shape  and  contains  a  single  round  6r 
oval  nucleus.  The  protoplasm  is  free  from  granules,  but  is  not  quite  transparent, 
having  the  appearance  of  ground  glass.  (4)  The  fourth  kind  of  colorless  corpuscle 
is  designated  the  lymphocyte  (Fig.  39,  i),  because  it  is  identical  with  the  cell  derived 
from  the  lymph  glands  or  other  lymphoid  tissue.  It  is  the  smallest  of  the  leuco- 
cytes, and  consists  chiefly  of  a  spheroidal  nucleus  with  a  very  little  surrounding 
protoplasm  of  a  homogeneous  nature;  it  is  regarded  as  the  immature  form  of  the 


Fig.  39. — Varieties  of  leucocytes  found  in  human  blood.     Highly  magnified. 

hyaline  cell.  The  third  and  fourth  varieties  together  constitute  from  20  to  30 
per  cent,  of  the  colorless  corpuscles,  but  of  these  two  varieties  the  lymphocj-tes 
are  by  far  the  more  numerous.  Leucoc^i:es  having  in  their  protoplasm  granules 
which  stain  with  basic  dyes  (basiphil)  have  been  described  as  occurring  in  human 
blood,  but  they  are  rareh'  found  except  in  disease. 

The  colorless  corpuscles  are  very  various  in  shape  in  living  blood  (Fig.  40), 
because  many  of  them  have  the  power  of  constantly  changing  their  form  by  pro- 
truding finger-shaped  or  filamentous  processes  of  their  substance,  by  which  they 
move  and  take  up  granules  from  the  surrounding  medium.  In  locomotion  the 
corpuscle  pushes  out  a  process  of  its  substance — a  pseudopodium,  as  it  is  called 

m  %  ^- 

Fig.  40. — Human  colorless  blood  corpuscle,  showing  its  successive  changes  of  outline  within  ten  minutes  when  kept 

moist  on  a  warm  stage.     (Schofield.) 

— and  then  shifts  the  rest  of  the  body  into  it.  In  the  same  way  w'hen  any  granule 
or  particle  comes  in  its  way  the  corpuscle  wraps  a  pseudopodium  around  it,  and  then 
withdraws  the  pseudopodium  with  the  contained  particle  into  its  own  substance. 
By  means  of  these  amoeboid  properties  the  cells  have  the  power  of  wandering 
or  emigrating  from  the  bloodvessels  by  penetrating  their  walls  and  thus  finding 
their  way  into  the  extravascular  spaces.  A  chemical  investigation  of  the  proto- 
plasm of  the  leucocytes  shows  the  presence  of  nucleoprotein  and  of  a  globulin. 
The  occurrence  of  small  amounts  of  fat,  lecithin,  and  glycogen  may  also  be 
demonstrated. 


64  HISTOLOGY 

The  blood  platelets  (Fig.  41)  are  discoid  or  irregularly  shaped,  colorless,  refractile 
bodies,  much  smaller  than  the  red  corpuscles.  Each  contains  a  central  chromatin 
mass  resembling  a  nucleus.  Blood  platelets  possess  the  power  of  amoeboid  move- 
ment. When  blood  is  shed  they  rapidly  disintegrate  and  form  granular  masses, 
setting  free  prothrombin  and  the  substance  called  by  Howell  thromboplastin.     It 

is  doubtful  whether  they  exist  normally  in  circulating 
blood. 

Lymph. — Lymph  is  a  transparent,  colorless,  or 
slightly  yellow  fluid,  which  is  conveyed  by  a  set  of 
vessels,  named  lymphatics,  into  the  blood.  These 
vessels  arise  in  nearly  all  parts  of  the  body  as  lymph 
capillaries.  They  take  up  the  fluid  which  has 
exuded  from  the  blood  capillaries  for  the  nourish- 
ment of  the  tissue  elements  and  return  it  into 
the  veins.  The  greater  number  of  these  lymphatics 
empty  themselves  into  one  main  duct,  the  thoracic 
duct,  which  passes  upward  along  the  front  of  the 
vertebral  column  and  opens  into  the  large  veins  on 
„     ^,     Di    J   w  w     Tj-  1,1         the  left  side  of  the  root  of  the  neck.    The  remainder 

Fig.  41. — Blood  platelets.     Highly  .  mi  i  •    i  i     • 

magnified.    (After  Kopsch.)  empty  thcmsclves  mto  a  smaller  duct  which  ends  m 

the  corresponding  veins  on  the  right  side  of  the  neck. 
Lymph  is  a  watery  fluid  of  specific  gravity  about  L015;  it  closely  resembles 
the  blood  plasma,  but  is  more  dilute.  When  it  is  examiner'  under  the  microscope, 
leucocytes  of  the  lymphocyte  class  are  found  floating  in  the  transparent  fluid; 
they  are  always  increased  in  number  after  the  passage  of  the  lymph  through 
lymphoid  tissue,  as  in  lymph  glands. 


THE   MUSCULAR   TISSUE. 

Muscular  tissue  is  composed  of  bundles  of  reddish  fibres  endowed  with  the  prop- 
erty of  contractility.  There  are  three  varieties  of  muscle:  (1)  transversely  striated 
fibres,  which  are  for  the  most  part  under  the  control  of  the  will,  although  some 
are  not  so,  such  as  the  muscles  of  the  pharynx  and  upper  part  of  the  oesophagus. 
This  variety  is  called  skeletal,  striped,  or  voluntary;  (2)  transversely  striated  cardiac 
fibres,  which  are  not  under  the  control  of  the  will;  (3)  plain  or  unstriped  fibres, 
which  are  involuntary  and  controlled  by  a  different  part  of  the  nervous  system 
from  that  which  controls  the  activity  of  the  voluntary  muscles;  such  are  the 
muscular  walls  of  the  stomach  and  intestine,  of  the  uterus  and  bladder,  of  the 
bloodvessels,  etc. 

Striped  or  Voluntary  Muscle. — Striped  or  voluntary  muscle  is  composed  of  bundles 
of  fibres  each  enclosed  in  a  delicate  web  called  the  perimysium  in  contradistinction 
to  the  sheath  of  areolar  tissue  which  invests  the  entire  muscle,  the  epimysium. 
The  bundles  are  termed  fasciculi;  they  are  prismatic  in  shape,  of  different  sizes 
in  different  muscles,  and  are  for  the  most  part  placed  parallel  to  one  another, 
though  they  have  a  tendency  to  converge  toward  their  tendinous  attachments. 
Each  fasciculus  is  made  up  of  a  strand  of  fibres,  which  also  run  parallel  with  each 
other,  and  are  separated  from  one  another  by  a  delicate  connective  tissue  derived 
from  the  perimysium  and  termed  endomysium.  This  does  not  form  the  sheath 
of  the  fibres,  but  serves  to  support  the  bloodvessels  and  nerves  ramifying  between 
them. 

A  muscular  fibre  may  be  said  to  consist  of  a  soft  contractile  substance,  enclosed 
in  a  tubular  sheath  named  by  Bowman  the  sarcolemma.  The  fibres  are  cylindrical 
or  prismatic  in  shape  (Fig.  42),  and  are  of  no  great  length,  not  exceeding,  as  a  rule, 


THE  MUSCULAR  TISSUE 


65 


40  inm.  Their  bretultli  varies  in  man  from  0.01  to  0.1  mm.  As  a  rule,  the  fibres 
do  not  divide  or  anastomose;  but  occasionally,  especially  in  the  tongue  and  facial 
muscles,  they  may  be  seen  to  divide  into  several  branches.  In  the  substance  of 
the  muscle,  the  fibres  end  by  tapering  extremities  which  are  joined  to  the  ends 
of  other  fibres  by  the  sarcolemma.  At  the  tendinous  end  of  the  muscle  the  sarco- 
lemma  appears  to  blend  with  a  small  bundle  of  fibres,  into  which  the  tendon 
becomes  subdivided,  while  the  muscular  substance  ends  abruptly  and  can  be 
readily  made  to  retract  from  the  point  of  junction.  The  areolar  tissue  between 
the  fibres  appear  to  be  prolonged  more  or  less  into  the  tendon,  so  as  to  form  a  kind 
of  sheath  around  the  tendon  bundles  for  a  longer  or  shorter  distance.  When 
muscular  fibres  are  attached  to  skin  or  mucous  membranes,  their  fibres  become 
continuous  with  those  of  the  areolar  tissue. 


^I'l^tS-" 


Fig.  42. — Transverse  section  of       'man  striped  muscle  fibres. 
X  255. 


Fig.  43. — Striped  muscle  fibres  from  tongue  of 
cat.      X  250. 


The  sarcolemma,  or  tubular  sheath  of  the  fibre,  is  a  transparent,  elastic,  and 
apparently  homogeneous  membrane  of  considerable  toughness,  so  that  it  some- 
times remains  entire  when  the  included  substance  is  ruptured.  On  the  internal 
surface  of  the  sarcolemma  in  mammalia,  and  also  in  the  substance  of  the  fibre 
in  frogs,  elongated  nuclei  are  seen,  and  in  connection  with  these  is  a  little  granular 
protoplasm. 

Upon  examination  of  a  voluntary  muscular  fibre  by  transmitted  light,  it  is 
found  to  be  marked  by  alternate  light  and  dark  bands  or  striae,  which  pass  trans- 
versely across  the  fibre  (Fig.  43).  When  examined  by  polarized  light  the  dark 
bands  are  found  to  be  doubly  refracting  (anisotropic),  while  the  clear  stripes  are 
singly  refracting  (isotropic) .  The  dark  and  light  bands  are  of  nearly  equal  breadth, 
and  alternate  with  great  regularity;  they  vary  in  breadth  from  about  1  to  2/i. 
If  the  surface  be  carefully  focussed,  rows  of  granules  will  be  detected  at  the  points 
of  junction  of  the  dark  and  light  bands,  and  very  fine  longitudinal  lines  may  be 
seen  running  through  the  dark  bands  and  joining  these  granules  together.  By 
treating  the  specimen  with  certain  reagents  {e.  g.,  chloride  of  gold)  fine  lines  may 
be  seen  running  transversely  between  the  granules  and  uniting  them  together. 
This  appearance  is  believed  to  be  due  to  a  reticulum  or  network  of  interstitial 
substance  lying  betw^een  the  contractile  portions  of  the  muscle.  The  longitudinal 
striation  gives  the  fibre  the  appearance  of  being  made  up  of  a  bundle  of  fibrils 
which  have  been  termed  sarcostyles  or  muscle  columns,  and  if  the  fibre  be  hardened 
in  alcohol,  it  can  be  broken  up  longitudinally  and  the  sarcostjdes  separated  from 
each  other  (Fig.  44.)  The  reticulum,  with  its  longitudinal  and  transverse  meshes, 
is  called  sarcoplasm. 


66 


HISTOLOGY 


In  a  transverse  section,  the  muscular  fibre  is  seen  to  be  divided  into  a  number 
of  areas,  called  the  areas  of  Cohnheim,  more  or  less  polyhedral  in  shape  and  con- 
sisting of  the  transversely  divided  sarcostyles,  surrounded  by  transparent  sarco- 
plasm  (Fig.  42). 

Upon  closer  examination,  and  by  somewhat  altering  the  focus,  the  appearances 
become  more  complicated,  and  are  susceptible  of  various  interpretations.     The 

transverse  striation,  which  in  Fig. 
43  appears  as  a  mere  alternation  of 
dark  and  light  bands,  is  resolved 
into  the  appearance  seen  in  Fig.  44, 
which  shows  a  series  of  broad  dark 
bands,  separated  by  light  bands, 
each  of  which  is  divided  into  two 
by  a  dark  dotted  line.  This  line  is 
termed  Dobie's  line  or  Krause's  mem- 
brane (Fig.  45,  k),  because  it  was 
believed  by  Krause  to  be  an  actual 
membrane,  continuous  with  the  sar- 
colemma,  and  dividing  the  light 
band  into  two  compartments.  In 
addition  to  the  membrane  of  Krause, 
fine  clear  lines  may  be  made  out, 
with  a  sufficiently  high  power,  cross- 
ing the  centre  of  the  dark  band; 
these  are  known  as  the  lines  of  Hensen 
(Fig.  45,  H). 

Schafer  has  worked  out  the  minute 
anatomy  of  muscular  fibre,  particu- 
larly in  the  wing  muscles  of  insects, 
which  are  peculiarly  adapted  for  this 
purpose  on  account  of  the  large  amount  of  interstitial  sarcoplasm  which  sepa- 
rates the  sarcostyles.  In  the  following  description  that  given  by  Schafer  will  be 
closely  followed. 


^    fig 


^SM    I 


Fig.  44. — A.  Portion  of  a  medium  sized  human  muscular 
fibre.  Magnified  nearly  800  diameters  B  Separated  bundles 
of  fibrils,  equallj-  magnified,  a,  a.  Larger,  and  b,  b,  smaller 
collections,  c.  Still  smaller,  d,  d.  The  smallest  which  could 
be  detached. 


S.E. 


H 


S.E. 


B 


Fig.  45. — Diagram  of  a  sarcomere.     (After  Schafer.)     A.  In  moderately  extended  condition.     B.  In  a  contracted 
condition,    k,  k.  Membranes  of  Krause.    H.  Line  or  plane  of  Hensen.      S.E.  Poriferous  sarcous  element. 

A  sarcostyle  may  be  said  to  be  made  up  of  successive  portions,  each  of  which 
is  termed  a  sarcomere.  The  sarcomere  is  situated  between  two  membranes  of  Krause 
and  consists  of  (1)  a  central  dark  part,  which  forms  a  portion  of  the  dark  band 
of  the  whole  fibre,  and  is  named  a  sarcous  element.  This  sarcous  element  really 
consists  of  two  parts,  superimposed  one  on  the  top  of  the  other,  and  when  the  fibre 
is  stretched  these  two  parts  become  separated  from  each  other  at  the  line  of  Hensen 


THE  MUSCULAR  TISSUE  67 

(Fig.  45,  A).  (2)  On  either  side  of  this  central  dark  portion  is  a  clear  layer,  most 
visible  when  the  fibre  is  extended;  this  is  situated  between  the  dark  centre  and  the 
membrane  of  Krause,  and  when  the  sarcomeres  are  joined  together  to  form  the 
sarcostyle,  constitutes  the  light  band  of  the  striated  muscular  fibre. 

AYhon  the  sarcostyle  is  extended,  the  clear  intervals  are  well-marked  and  plainly 
to  be  seen;  when,  on  the  other  hand,  the  sarcostyle  is  contracted,  that  is  to  say, 
when  the  muscle  is  in  a  state  of  contraction,  these  clear  portions  are  very  small 
or  they  may  have  disappeared  altogether  (Fig.  45,  B).  When  the  sarcostyle  is 
stretched  to  its  full  extent,  not  only  is  the  clear  portion  well-marked,  but  the  dark 
portion — the  sarcous  element — is  separated  into  its  two  constituents  along  the 
line  of  Hensen.  The  sarcous  element  does  not  lie  free  in  the  sarcomere,  for  when 
the  sarcostyle  is  stretched,  so  as  to  render  the  clear  portion  visible,  very  fine 
lines,  which  are  probably  septa,  may  be  seen  running  through  it  from  the  sarcous 
element  to  the  membrane  of  Krause. 

Schafer  explains  these  phenomena  in  the  following  way:  He  considers  that  each 
sarcous  element  is  made  up  of  a  number  of  longitudinal  channels,  which  open 
into  the  clear  part  toward  the  membrane  of  Krause  but  are  closed  at  the  line  of 
Hensen.  When  the  muscular  fibre  is  contracted  the  clear  part  of  the  muscular 
substance  is  driven  into  these  channels  or  tubes,  and  is  therefore  hidden  from 
sight,  but  at  the  same  time  it  swells  up  the  sarcous  element  and  widens  and  shortens 
the  sarcomere.  When,  on  the  other  hand,  the  fibre  is  extended,  this  clear  sub- 
stance is  driven  out  of  the  tubes  and  collects  between  the  sarcous  element  and 
the  membrane  of  Krause,  and  gives  the  appearance  of  the  light  part  between 
these  two  structures;  by  this  means  it  elongates  and  narrows  the  sarcomere. 

If  this  view  be  true,  it  is  a  matter  of  great  interest,  and,  as  Schafer  has  shown, 
harmonizes  the  contraction  of  muscle  with  the  amoeboid  action  of  protoplasm. 
In  an  amoeboid  cell,  there  is  a  framework  of  spongioplasm,  which  stains  with 
hematoxylin  and  similar  reagents,  enclosing  in  its  meshes  a  clear  substance,  hyalo- 
plasm, which  will  not  stain  with  these  reagents.  Under  stimulation  the  hyaloplasm 
passes  into  the  pores  X)f  the  spongioplasm;  without  stimulation  it  tends  to  pass 
out  as  in  the  formation  of  pseudopodia.  In  muscle  there  is  the  same  thing,  viz., 
a  framework  of  spongioplasm  staining  with  hematoxylin — the  substance  of  the 
sarcous  element — and  this  encloses  a  clear  hyaloplasm,  the  clear  substance  of 
the  sarcomere,  which  resists  staining  with  this  reagent.  During  contraction  of  the 
muscle — i.  e.,  stimulation — this  clear  substance  passes  into  the  pores  of  the  spongio- 
plasm; while  during  extension  of  the  muscle — i.  e.,  when  there  is  no  stimulation — 
it  tends  to  pass  out  of  the  spongioplasm. 

In  this  way  the  contraction  is  brought  about:  under  stimulation  the  proto- 
plasmic material  (the  clear  substance  of  the  sarcomere)  recedes  into  the  sarcous 
element,  causing  the  sarcomere  to  widen  out  and  shorten.  The  contraction  of  the 
muscle  is  merely  the  sum  total  of  this  widening  out  and  shortening  of  these  bodies. 

Vessels  and  Nerves  of  Striped  Muscle. — The  capillaries  or  striped  muscle  are 
very  abundant,  and  form  a  sort  of  rectangular  network,  the  branches  of  which  run 
longitudinally  in  the  endomysium  between  the  muscular  fibres,  and  are  joined  at 
short  intervals  by  transverse  anastomosing  branches.  In  the  red  muscles  of  the 
rabbit  dilatations  occur  on  the  transverse  branches  of  the  capillary  network.  The 
larger  vascular  channels,  arteries  and  veins,  are  found  only  in  the  perimysium, 
between  the  muscular  fasciculi.  Nerves  are  profusely  distributed  to  striped  muscle. 
Their  mode  of  termination  is  described  on  page  803.  The  existence  of  lymphatic 
vessels  in  striped  muscle  has  not  been  ascertained,  though  they  have  been  found  in 
tendons  and  in  the  sheaths  of  the  muscles. 

Unstriped,  Plain,  or  Involuntary  Muscle. — Unstriped,  plain,  or  involuntary  muscle 
is  found  in  the  following  situations :  in  the  lower  half  of  the  oesophagus  and  the 
whole  of  the  remainder  of  the  gastro-intestinal  tube;  in  the  trachea  and  bronchi; 


68 


HISTOLOGY 


in  the  gall-bladder  and  common  bile  duct;  in  the  large  ducts  of  the  salivary  and 
pancreatic  glands;  in  the  pelvis  and  calices  of  the  kidney,  the  ureter,  bladder, 
and  urethra;  in  the  female  sexual  organs — viz.,  the  ovary,  the  uterine  tubes,  the 
uterus  (enormously  developed  in  pregnancy),  the  vagina,  the  broad  ligaments,  and 
the  corpora  cavernosa  of  the  clitoris;  in  the  male  sexual  organs — viz.,  the  dartos 
of  the  scrotum,  the  ductus  deferens  and  epididymis,  the  vesiculae  seminales,  th'e 
prostate,  and  the  corpora  cavernosa  of  the  penis  and  urethra;  in  the  capsule  and 
trabeculse  of  the  spleen;  in  the  mucous  membranes,  forming  the  muscularis  mucosae; 

in  the  skin,  forming  the  Arrectores  pilorum,  and  also 
in  the  sweat  glands;  in  the  arteries,  veins,  and  lym- 
phatics; in  the  iris  and  the  ciliary  muscle. 

Plain  or  unstriped  muscle  is  made  up  of  spindle- 
shaped  cells,  called  contractile  fibre  cells,  collected  into 
bundles  and  held  together  by  a  cement  substance  (Fig. 
46).  These  bundles  are  further  aggregated  into  larger 
fasciculi,  or  flattened  bands,  and  bound  together  by 
ordinary  connective  tissue. 

The  contractile  fibre  cells  are  elongated,  spindle- 
shaped,  nucleated  cells  of  various  sizes,  averaging  from 
40  to  80m  in  length,  and  6  to  7 fx  in  breadth.  On 
transverse  section  they  are  more  or  less  polyhedral  in 
shape,  from  mutual  pressure.  Each  presents  a  faint 
longitudinal  striation  and  consists  of  an  elastic  cell  wall 
containing  a  central  bundle  of  fibrillse,  representing  the 
contractile  substance,  and  an  oval  or  rod-like  nucleus, 
which  includes,  within  a  membrane,  a  fine  net-work 
communicating  at  the  poles  of  the  nucleus  with  the 
contractile  fibres  (Klein).  The  fibres  are  attached  to 
one  another  by  a  certain  amount  of  interstitial  cement 
substance  which  reduces  nitrate*  of  silver,  but  in  some 
regions,  e.  g.,  the  muscular  coats  of  the  intestines,  the 
muscle  cells  are  also  connected  bj^  "bridges"  similar  to 
those  which  occur  in  the  prickle  cells  of  the  epidermis. 
Unstriped  muscle,  except  the  ciliary  muscle,  is  not  under 
the  control  of  the  will,  neither  is  the  contraction  rapid 
nor  does  it,  as  a  rule,  involve  the  whole  muscle,  as  is 
the  case  with  the  voluntary  muscles.  The  membranes 
which  are  composed  of  unstriped  muscle  slowly  contract 
in  a  part  of  their  extent,  generally  under  the  influence 
of  a  mechanical  stimulus,  as  that  of  distension  or  of 
cold ;  and  then  the  contracted  part  slowly  relaxes  while 
another  portion  of  the  membrane  takes  up  the  contrac- 
tion. This  peculiarity  of  action  is  most  strongly  marked 
in  the  intestines,  constituting  their  vermicular  motion. 
Cardiac  Muscular  Tissue. — The  fibres  of  the  heart  differ  very  remarkably  from 
those  of  other  striped  muscles.  They  are  smaller  by  one-third,  and  their  trans- 
verse striae  are  by  no  means  so  well-marked.  They  show  faint  longitudinal 
striation.  The  fibres  are  made  up  of  distinct  quadrangular  cells,  joined  end  to 
end  so  as  to  form  a  syncytium  (Fig.  47).  Each  cell  contains  a  clear  oval  nucleus, 
situated  near  its  centre.  The  extremities  of  the  cells  have  a  tendency  to  branch 
or  divide,  the  subdivisions  uniting  with  offsets  from  other  cells,  and  thus  producing 
an  anastomosis  of  the  fibres.  The  connective  tissue  between  the  bundles  of  fibres 
is  much  less  than  in  ordinary  striped  muscle,  and  no  sarcolemma  has  been  proved 
to  exist. 


Fig.  46. — Muscle  fibres  from 
small  intestine.  (Schafer.)  A. 
Complete  cell.  B.  Broken  cell 
showing  delicate  external  layer. 


THE  NERVOUS  TISSUE 


69 


Purkinje  Fibres  (Fig.  48). — Between  the  endocardium  and  the  ordinary  cardiac 
muscle  are  found,  imbedded  in  a  small  amount  of  connective  tissue,  peculiar  fibres 
known  as  Purkinje  fibres.  They  are  found  in  certain  mammals  and  in  birds,  and 
can  be  best  seen  in  the  sheep's  heart,  where  they  form  a  considerable  portion 
of  the  moderator  band  and  also  appear  as  gelatinous-looking  strands  on  the  inner 
walls  of  the  atria  and  ^'ent^icles.  They  also  occur  in  the  human  heart  associated 
with  the  terminal  distributions  of  the  bundle  of  His  (see  p.  614).  The  fibres  are 
very  much  larger  in  size  than  the  cardiac  cells  and  differ  from  them  in  several 
ways.  In  longitudinal  section  they  are  quadrilateral  in  shape,  being  about  twice 
as  long  as  they  are  broad.  The  central  portion  of  each  fibre  contains  one  or  more 
nuclei  and  is  made  up  of  granular  protoplasm,  with  no  indication  of  striations, 
while  the  peripheral  portion  is  clear  and  has  distinct  transverse  striations.  The 
fibres  are  intimately  connected  with  each  other,  possess  no  definite  sarcolemma, 
and  do  not  branch. 


.,— r^- re[^i=^ 


'^ 


Fig.  47. — Anastomosing  muscular  fibres  of  the  heart  seen 
in  a  longitudinal  section.  On  the  right  the  limits  of  the 
separate  cells  with  their  nuclei  are  exhibited  somewhat  dia- 
grammatically. 


Fig.  48. — Purkinje  fibres  from  the  sheep's  heart. 


The  Bundle  of  His  (see  p.  614)  is  composed  of  cells  which  differ  from  ordinary 
cardiac  muscle  cells  in  being  more  spindle-shaped.  They  are,  moreover,  more 
loosely  arranged  and  have  a  richer  vascular  supply  than  the  rest  of  the  heart 
muscle. 

Development  of  Muscle  Fibres. — Voluntary  muscular  fibres  are  developed  from  the  mesoderm, 
the  embryonic  cells  of  which  elongate,  show  multipHcation  of  nuclei,  and  eventually  become 
striated;  the  striation  is  first  obvious  at  the  side  of  the  fibres,  spreads  around  the  circumference, 
and  ultimately  extends  to  the  centre.  The  nuclei,  at  first  situated  centrally,  gradually  pass  out 
to  assume  their  final  position  immediately  beneath  the  sarcolemma.  In  the  case  of  involuntary 
muscle  the  mesodermal  cell  assumes  a  pointed  shape  at  the  extremities  and  becomes  flattened,  the 
nucleus  also  lengthening  out  to  its  permanent  rod-like  form. 


THE   NERVOUS   TISSUE. 

The  nervous  tissues  of  the  body  comprise  the  brain,  the  medulla  spinalis  or  spinal 
cord,  the  cerebral,  spinal,  and  sympathetic  nerves,  and  the  ganglia  connected  with 
them. 


70 


HISTOLOGY 


The  nervous  tissues  are  composed  of  nerve  cells  and  their  various  processes, 
together  with  a  supporting  tissue  called  neuroglia,  which,  however,  is  found  only 
in  the  brain  and  medulla  spinalis.  Certain  long  processes  of  the  nerve  cells  are  of 
special  importance,  and  it  is  convenient  to  consider  them  apart  from  the  cells; 
they  are  known  as  nerve  fibres. 

To  the  naked  eye  a  difference  is  obvious  between  certain  portions  of  the  brain 
and  medulla  spinalis,  viz.,  the  gray  substance  and  the  white  substance.  The  gray 
substance  is  largely  composed  of  nerve  cells,  while  the  white  substance  contains 
only  their  long  processes,  the  nerve  fibres.  It  is  in  the  former  that  nervous  impres- 
sions are  received,  stored,  and  transformed  into  efferent  impulses,  and  by  the  latter 
that  they  are  conducted.  Hence  the  gray  substance  forms  the  essential  constituent 
of  all  the  ganglionic  centres,  both  those  in  the  isolated  ganglia  and  those  aggregated 
in  the  brain  and  medulla  spinalis;  while  the  white  substance  forms  the  bulk  of  the 
commissural  portions  of  the  nerve  centres  and  the  peripheral  nerves. 


Fig.  49. — Neuroglia  cells  of  brain  shown  by  Golgi's  method.     (After  Andriezen.)     A.  Cell  with  branched  processes 

B.  Spider  cell  with  unbranched  processes. 


Neuroglia. — Neuroglia,  the  peculiar  ground  substance  in  which  are  imbedded  the 
true  nervous  constituents  of  the  brain  and  medulla  spinalis,  consists  of  cells  and 
fibres.  Some  of  the  cells  are  stellate  in  shape,  with  ill-defined  cell  body,  and  their 
fine  processes  become  neuroglia  fibres,  which  extend  radially  and  unbranched 
(Fig.  49,  B)  among  the  nerve  cells  and  fibres  which  they  aid  in  supporting.  Other 
cells  give  off  fibres  which  branch  repeatedly  (Fig.  49,  A).  Some  of  the  fibres  start 
from  the  epithelial  cells  lining  the  ventricles  of  the  brain  and  central  canal  of 
the  medulla  spinalis,  and  pass  through  the  nervous  tissue,  branching  repeatedly 
to  end  in  slight  enlargements  on  the  pia  mater.  Thus,  neuroglia  is  evidently  a 
connective  tissue  in  function  but  is  not  so  in  development;  it  is  ectodermal  in 
origin,  whereas  all  connective  tissues  are  mesodermal. 

Nerve  Cells  (Fig.  50). — Nerve  cells  are  largely  aggregated  in  the  gray  substance 
of  the  brain  and  medulla  spinalis,  but  smaller  collections  of  these  cells  also  form 
the  swellings,  called  ganglia,  seen  on  many  nerves.  These  latter  are  found  chiefly 
upon  the  spinal  and  cerebral  nerve  roots  and  in  connection  with  the  sympathetic 
nerves. 

The  nerve  cells  vaiy  in  shape  and  size,  and  have  one  or  more  processes.  They 
may  be  divided  for  purposes  of  description  into  three  groups,  according  to  the 
number  of  processes  which  they  possess:  (1)  Unipolar  cells,  which  are  found  in 
the  spinal  ganglia;  the  single  process,  after  a  short  course,  divides  in  a  T-shaped 


THE  NERVOUS  TISSUE 


71 


manner  (Fig.  50,  E).  (2)  Bipolar  cells,  also  found  in  the  spinal  ganglia  (Fig.  51), 
when  the  cells  are  in  an  embryonic  condition.  They  are  best  demonstrated  in  the 
spinal  ganglia  of  fish.     Sometimes  the  processes  come  off  from  opposite  poles  of 


Fig.  50. — Various  forms  of  nerve  cells.  A.  Pyramidal  cell.  B.  Small  multipolar  cell,  in  which  the  axon  quickly 
divides  into  numerous  branches.  C.  Small  fusiform  cell.  D  and  E.  Ganglion  cells  {E  shows  T-shaped  division  of 
axon),      ax.  Axon.     c.  Capsule. 


Sheath  of 
cell  body 


Nucleus 


Cell  protoplasm 


'~  Axon 


Nucleolus 


Fig.  52. — Motor  nerve  cell  from  ventral  horn  of  medulla 
spinalis  of  rabbit.  (After  Nissl.)  The  angular  and  spindle- 
shaped  Nissl  bodies  are  well  shown. 


the  cell,  and  the  cell  then  assumes  a  spindle 
shape;  in  other  cells  both  processes  emerge 
at  the  same  point.  In  some  cases  where 
two  fibres  are  apparently  connected  with  a 
cell,  one  of  the  fibres  is  really  derived  from 
an  adjoining  nerve  cell  and  is  passing  to 
end  in  a  ramification  around  the  ganglion 
cell,  or,  again,  it  may  be  coiled  spirally 
around  the  nerve  process  which  is  issuing 
from  the  cell.  (3)  Multipolar  cells,  which 
are  pyramidal  or  stellate  in  shape,  and 
characterized  by  their  large  size  and  by  the  numerous  processes  which  issue 
from  them.  The  processes  are  of  two  kinds:  one  of  them  is  termed  the  axis- 
cylinder  process  or  axon  because  it  becomes  the  axis-cylinder  of  a   nerve  fibre 


-Dendron 
Myelin  sheath 


Fig.  51. — Bipolar  nerve  cell  from  the  spinal  gan 
glion  of  the  pike.     (After  Kolliker.) 


HISTOLOGY 


(Figs.  52,  53,  54).  The  others  are  termed  the  protoplasmic  processes  or  dendrons; 
they  begin  to  divide  and  subdivide  as  soon  as  they  emerge  from  the  cell,  and 
finally  end  in  minute  twigs  and  become  lost  among  the  other  elements  of  the 
nervous  tissue. 

The  body  of  the  nerve  cell,  known  as  the  cyton,  consists  of  a  finely  fibrillated 
protoplasmic  material,  of  a  reddish  or  yellowish-brown  color,  which  occasionally 
presents  patches  of  a  deeper  tint,  caused  by  the  aggregation  of  pigment  granules 
at  one  side  of  the  nucleus,  as  in  the  substantia  nigra  and  locus  caeruleus  of  the 
brain.    The  protoplasm  also  contains  peculiar  angular  granules,  which  stain  deeply 


53. — Pyramidal  cell  from  the  cerebral  cortex 
of  a  mouse.    (After  Ramon  y  Cajal.) 


Fig  54  — Cell  of  Purkinje  from  the  cerebellum.  Golgi 
method.  (Cajal.)  a.  Axon.  b.  Collateral,  c  and  d. 
Dendrons. 


with  basic  dyes,  such  as  methylene  blue;  these  are  known  as  Nissl's  granules  (Fig. 
52).  Thev  extend  into  the  dendritic  processes  but  not  into  the  axis-cylinder;  the 
small  clear  area  at  the  point  of  exit  of  the  axon  is  termed  the  cone  of  origin.  These 
granules  disappear  {chromatolysis)  during  fatigue  or  after  prolonged  stimulation 
of  the  nerve  fibres  connected  with  the  cells.  They  are  supposed  to  represent  a 
store  of  nervous  energy,  and  in  various  mental  diseases  are  deficient  or  absent. 
The  nucleus  is,  as  a  rule,  a  large,  well-defined,  spherical  body,  often  presenting  an 
intranuclear  network,  and  containing  a  well-marked  nucleolus. 


THE  NERVOUS  TISSUE 


73 


In  addition  to  the  protoplasmic  network  described  above,  each  nerve  cell  may 
be  shown  to  have  delicate  neurofibrils  running  through  its  substance  (Fig.  55); 
these  fibrils  are  continuous  with  the  fibrils  of  the  axon,  and  are  believed  to 
convey  nerve  impulses.  Golgi  has  also  described  an  extracellular  network,  which 
is  probably  a  supporting  structure. 

Nerve  Fibres. — Xerve  fibres  are  found  universally  in  the  peripheral  nerves 
and  in  the  white  substance  of  the  brain  and  medulla  spinalis.  They  are  of  two 
kinds — viz.,  medullated  or  white  fibres,  and  non-medullated  or  gray  fibres. 


Fig.  55. — Nerve  cells  of  kitten,  showing  neurofibrils.    (Cajal.)    a.  Axon.    6.  Cyton.    c.  Nucleus,     d.  Neurofibrils. 

The  medullated  fibres  form  the  white  part  of  the  brain  and  medulla  spinalis,  and 
also  the  greater  part  of  every  cerebral  and  spinal  nerve,  and  give  to  these  structures 
their  opaque,  white  aspect.  When  perfectly  fresh  they  appear  to  be  homogeneous; 
but  soon  after  removal  from  the  body  each  fibre  presents,  when  examined  by  trans- 
mitted light,  a  double  outline  or  contour,  as  if  consisting  of  two  parts  (Fig.  56). 
The  central  portion  is  named  the  axis  -  cylinder ;  around  this  is  a  shea*h  of  fatty 
material,  staining  black  with  osmic  acid,  named  the  white  substance  of  Schwann 
or  medullary  sheath,  which  gives  to  the  fibre  its  double  contour,  and  the  whole 
is  enclosed  in  a  delicate  membrane,  the  neurolemma,  primitive  sheath,  or  nucleated 
sheath  of  Schwaim  (Fig.  58). 

The  axis-cylinder  is  the  essential  part  of  the  nerve  fibre,  and  is  always  present; 
the  medullary  sheath  and  the  neurolemma  are  occasionally  absent,  expecially  at 
the  origin  and  termination  of  the  nerve  fibre.  The  axis-cylinder  undergoes  no 
interruption  from  its  origin  in  the  nerve  centre  to  its  peripheral  termination,  and 


74 


HISTOLOGY 


must  be  regarded  as  a  direct  prolongation  of  a  nerve  cell.  It  constitutes  about 
one-half  or  one-third  of  the  nerve  fibre,  being  greater  in  proportion  in  the  fibres 
of  the  central  organs  than  in  those  of  the  nerves.  It  is  quite  transparent,  and  is 
therefore  indistinguishable  in  a  perfectly  fresh  and  natural  state  of  the  nerve. 
It  is  made  up  of  exceedingly  fine  fibrils,  which  stain  darkly  with  gold  chloride 


Fig.  56.— Medullated  nerve  fibres.     (Bidder 
and  Volkmann.) 


j-jQ  ,57_ — Longitudinal  and  transverse  sec- 
tions of  medullated  nerve  fibre  of  frog,  showing 
node  of  Ranvier,  medullary  segments  and  fibrils 
of  axis  cylinder.     Osmic  acid.     (Biedermann.) 


Fig.  58. — Diagram  of  medullated  nerve  fibres  stained 
with  osmic  acid,  '  X  425.  (Schiifer.)  R.  Nodes  of  Ran- 
vier.    a.  Neurolemma,     c.  Nucleus. 


(Fig.  57),  and  at  its  termination  may  be  seen  to  break  up  into  these  fibrilla.  The 
fibrillee  have  been  termed  the  primitive  fibrillse  of  Schultze.  The  axis-cylinder  is 
said  by  some  to  be  enveloped  in  a  special  reticular  sheath,  which  separates  it  from 
the  medullary  sheath,  and  is  composed  of  a  substance  called  neurokeratin.  The 
more  common  opinion  is  that  this  network  or  reticulum  is  contained  in  the  white 


THE  NERVOUS  TISSUE 


75 


matter  of  Schwann,  and  by  some  it  is    believed  to  be  produced  by  the  action  of 
the  reagents  employed  to  show  it. 

The  medullary  sheath,  or  white  matter  of  Schwami  (Fig.  57),  is  regarded  as  being  a 
fatty  matter  in  a  fluid  state,  which  insulates  and  i)r()tects  the  essential  part  of  the 
nerve — the  axis-cylinder.  It  varies  in  thickness,  in  some  forming  a  layer  of  extreme 
thinness,  so  as  to  be  scarcely  distinguishable,  in  others  forming  about  one-half  the 
nerve  jfibre.  The  variation  in  diameter  of  the  nerve  fibres  (from  2  to  16/x)  depends 
mainly  upon  the  amount  of  the  wdiite  substance,  though  the  axis  cylinder  also 
varies  within  certain  limits.  The  medullary  sheath  undergoes  interruptions  in  its 
continuity  at  regular  intervals,  giving  to  the  fibre  the  appearance  of  constriction 
at  these  points:  these  are  known  as  the  nodes  of  Ranvier  (Figs.  57  and  58).  The 
portion  of  nerve  fibre  between  two  nodes  is  called  an  internodal  segment.  The 
neurolemma  or  primitive  sheath  is  not  interrupted  at  the  nodes,  but  passes  over 
them  as  a  continuous  membrane.  If  the  fibre  be  treated  with  silver  nitrate  the 
reagent  penetrates  the  neurolemma  at  the  nodes,  and  on  exposure  to  light  reduction 
takes  place,  giving  rise  to  the  appearance  of  black  crosses,  Ranvier's  crosses,  on  the 
axis-cvlinder.    There  mav  also  be  seen  transverse  lines  bevond  the  nodes  termed 


I- 


Node  of 
Eanvier 


Frommann^s 
lines 


Fig.  59. — Medullated  nerve  fibres  stained  with  silver  nitrate. 


Fig.  60. — A  small  nervous  branch 
from  the  sympathetic  of  a  mammal. 
a.  Two  medullated  nerve  fibres  among 
a  number  of  gray  nerve   fibres,   h. 


Frommann's  lines  (Fig.  59) ;  the  significance  of  these  is  not  understood.  In  addi- 
tion to  these  interruptions  oblique  clefts  may  be  seen  in  the  medullary  sheath, 
subdividing  it  into  irregular  portions,  which  are  termed  medullary  segments,  or 
segments  of  Lantermann  (Fig.  57);  there  is  reason  to  believe  that  these  clefts  are 
artificially  produced  in  the  preparation  of  the  specimens.  Medullated  nerve 
fibres,  when  examined  in  the  fresh  condition,  frequently  present  a  beaded  or  vari- 
cose appearance:  this  is  due  to  manipulation  and  pressure  causing  the  oily  matter 
to  collect  into  drops;  and  in  consequence  of  the  extreme  delicacy  of  the  primitive 
sheath,  even  slight  pressure  wdll  cause  the  transudation  of  the  fatty  matter,  which 
collects  as  drops  of  oil  outside  the  membrane. 

The  neurolemma  or  primitive  sheath  presents  the  appearance  of  a  delicate, 
structureless  membrane.  Here  and  there  beneath  it,  and  situated  in  depressions 
in  the  white  matter  of  Schwann,  are  nuclei  surrounded  by  a  small  amount  of 
protoplasm.  The  nuclei  are  oval  and  somewhat  flattened,  and  bear  a  definite 
relation  to  the  nodes  of  Ranvier,  one  nucleus  generally  lying  in  the  centre  of  each 
internode.  The  primitive  sheath  is  not  present  in  all  medullated  nerve  fibres, 
being  absent  in  those  fibres  wdiich  are  found  in  the  brain  and  medulla  spinalis. 


76  HISTOLOGY 

Wallerian  Degeneration. — When  nerve  fibres  are  cut  across,  the  central  ends  of  the  fibres 
degenerate  as  far  as  the  first  node  of  Ranvier;  but  the  peripheral  ends  degenerate  simultaneously 
throughout  their  whole  length.  The  axons  break  up  into  fragments  and  become  surrounded  by 
drops  of  fatty  substance  which  are  formed  from  the  breaking  down  of  the  medullary  sheath. 
The  nuclei  of  the  primitive  sheath  proliferate,  and  finally  absorption  of  the  axons  and  fatty 
substance  occurs.  If  the  cut  ends  of  the  nerve  be  sutured  together  regeneration  of  the  nerve 
fibres  takes  place  by  the  downgrowth  of  axons  from  the  central  end  of  the  nerve.  At  one  time 
it  was  beheved  that  the  regeneration  was  peripheral  in  origin,  but  this  has  been  disproved,  the 
proUferated  nuclei  in  the  peripheral  portions  taking  part  merely  in  the  formation  of  the  so-called 
scaffolding  along  which  the  new  axons  pass. 

Non-meduUated  Fibres. — Most  of  the  fibres  of  the  sympathetic  system,  and 
some  of  the  cerebrospinal,  consist  of  the  gray  or  gelatinous  nerve  fibres  {fibres  of 
Remak)  (Fig.  60).  Each  of  these  consists  of  an  axis-cylinder  to  which  nuclei  are 
applied  at  intervals.  These  nuclei  are  believed  to  be  in  connection  with  a  delicate 
sheath  corresponding  with  the  neurolemma  of  the  meduUated  nerve  fibre.  In 
external  appearance  the  non-medullated  nerve  fibres  are  semitransparent  and  gray 
or  yellowish  gray.  The  individual  fibres  vary  in  size,  generally  averaging  about 
half  the  size  of  the  medullated  fibres. 


EMBRYOLOGY. 


rpHE  term  Embryology,  in  its  widest  sense,  is  applied  to  the  various  changes 
-*-  which  take  place  during  the  growth  of  an  animal  from  the  egg  to  the  adult 
condition:  it  is,  however,  usually'  restricted  to  the  phenomena  which  occur  before 
birth.  Embryology  may  be  studied  from  two  aspects:  (1)  that  of  ontogeny,  which 
deals  only  with  the  development  of  the  individual;  and  (2)  that  of  phylogeny, 
which  concerns  itself  with  the  evoluntionary  history  of  the  animal  kingdom. 

In  vertebrate  animals  the  development  of  a  new  being  can  only  take  place  when 
a  female  germ  cell  or  ovum  has  been  fertilized  by  a  male  germ  cell  or  spermatozoon. 
The  ovum  is  a  nucleated  cell,  and  all  the  complicated  changes  by  which  the  various 
tissues  and  organs  of  the  body  are  formed  from  it,  after  it  has  been  fertilized,  are 
the  result  of  two  general  processes,  viz.,  segmentation  and  differentiation  of  cells. 
Thus,  the  fertilized  ovum  undergoes  repeated  segmentation  into  a  number  of  cells 
which  at  first  closely  resemble  one  another,  but  are,  sooner  or  later,  differentiated 
into  two  groups:  (1)  somatic  cells,  the  function  of  which  is  to  build  up  the  various 
tissues  of  the  body;  and  (2)  germinal  cells,  which  become  imbedded  in  the  sexual 
glands — the  ovaries  in  the  female  and  the  testes  in  the  male — and  are  destined  for 
the  perpetuation  of  the  species. 

Having  regard  to  the  main  purpose  of  this  work,  it  is  impossible,  in  the  space 
available  in  this  section,  to  describe  fully,  or  illustrate  adequately,  all  the  phenom- 
ena which  occur  in  the  different  stages  of  the  development  of  the  human  body. 
Only  the  principal  facts  are  given,  and  the  student  is  referred  for  further  details 
to  one  or  other  of  the  text-books^  on  human  embryology. 

THE   OVUM. 

The  ova  are  developed  from  the  primitive  germ  cells  which  are  imbedded  in 
the  substance  of  the  ovaries.  Each  primitive  germ  cell  gives  rise,  by  repeated 
divisions,  to  a  number  of  smaller  cells  termed  cogonia,  from  which  the  ova  or 
primary  oocytes  are  developed. 

Human  ova  are  extremely  minute,  measuring  about  0.2  mm.  in  diameter,  and 
are  enclosed  within  the  egg  follicles  of  the  ovaries;  as  a  rule  each  follicle  contains 
a  single  ovum,  but  sometimes  two  or  more  are  present. ^  By  the  enlargement  and 
subsequent  rupture  of  a  follicle  at  the  surface  of  the  ovary,  an  ovum  is  liberated  and 
conveyed  by  the  uterine  tube  to  the  cavity  of  the  uterus.  Unless  it  be  fertilized 
it  undergoes  no  further  development  and  is  discharged  from  the  uterus,  but  if 
fertilization  take  place  it  is  retained  within  the  uterus  and  is  developed  into  a 
new  being. 

In  appearance  and  structure  the  ovum  (Fig.  61)  differs  little  from  an  ordinary 
cell,  but  distinctive  names  have  been  applied  to  its  several  parts;  thus,  the  cell 
substance  is  known  as  the  yolk  or  ooplasm,  the  nucleus  as  the  germinal  vesicle,  and 
the  nucleolus  as  the  germinal  spot.     The  ovum  is  enclosed  within  a  thick,  trans- 

1  JNIanual  of  Human  Embryology,  Keibel  and  Mall;  Handbuch  der  vergleichenden  und  experimentellen  Entwickel- 
ungslehre  der  Wirbeltiere,  Oskar  Hertwig;  Lehrbuch  der  Entwickelungsgeschichte,  Bonnet;  The  Physiology  of 
Reproduction,  Marshall. 

^  See  description  of  the  ovarj'  on  a  future  page. 


78 


EMBRYOLOGY 


parent  envelope,  the  zona  striata  or  zona  pellucida,  adhering  to  the  outer  surface 
of  which  are  several  layers  of  cells,  derived  from  those  of  the  follicle  and  collectively 
constituting  the  corona  radiata. 

Yolk. — The  yolk  comprises  (1)  the  cytoplasm  of  the  ordinary  animal  cell  witli  its 
spongioplasm  and  hyaloplasm;  this  is  frequently  termed  the  formative  yolk;  (2) 
the  nutritive  yolk  or  duetoplasm,  which  consists  of  numerous  rounded  granules  of 
fatty  and  albuminoid  substances  imbedded  in  the  cytoplasm.  In  the  mammalian 
ovum  the  nutritive  yolk  is  extremely  small  in  amount,  and  is  of  service  in  nourish- 
ing the  embryo  in  the  early  stages  of  its  development  only,  whereas  in  the  egg 
of  the  bird  there   is  sufficient  to  supply  the  chick  with    nutriment  throughout 


Fig.  61. — Human  ovum  examined  fresh  in  tlie  liquor  folliculi.  (Waldeyer.)  The  zona  pellucida  is  seen  as  a  thick 
clear  girdle  surrounded  by  the  cells  of  the  corona  radiata.  The  egg  itself  shows  a  central  granular  deutoplasmic  area 
and  a  peripheral  clear  layer,  and  encloses  the  germinal  vesicle,  in  which  is  seen  the  germinal  spot. 

the  whole  period  of  incubation.  The  nutritive  yolk  not  only  varies  in  amount, 
but  in  its  mode  of  distribution  within  the  egg;  thus,  in  some  animals  it  is  almost 
uniformly  distributed  throughout  the  cytoplasm;  in  some  it  is  centrally  placed  and 
is  surrounded  by  the  cytoplasm;  in  others  it  is  accumulated  at  the  lower  pole  of  the 
ovum,  while  the  cytoplasm  occupies  the  upper  pole.  A  centrosome  and  centriole 
are  present  and  lie  in  the  immediate  neighborhood  of  the  nucleus. 

Germinal  Vesicle. — The  germinal  vesicle  or  nucleus  is  a  large  spherical  body 
which  at  first  occupies  a  nearly  central  position,  but  becomes  eccentric  as  the  growth 
of  the  ovum  proceeds.  Its  structure  is  that  of  an  ordinary  cell-nucleus,  viz.,  it 
consists   of   a   reticulum  or  karyomitome,   the  meshes  of  which  are  filled  with 


THE  OVUM 


79 


karyoplasm,  while  coimected  with,  or  imhcdded  in,  tiie  reticuluin  are  a  number 
of  chromatin  masses  or  chromosomes,  which  may  present  the  appearance  of  a 
skein  or  may  assimie  the  form  of  rods  or  loops.  The  nucleus  is  enclosed  by  a 
delicate  nuclear  membrane,  and  contains  in  its  interior  a  well-defined  nucleolus 
or  germinal  spot. 

Coverings  of  the  Ovum. — The  zona  striata  or  zona  pellucida  (Fig.  (jlj  is  a  thick 
membrane,  which,  under  the  higher  powers  of  the  microscope,  is  seen  to  be  radially 
striated.  It  persists  for  some  time  after  fertilization  has  occurred,  and  may  serve 
for  protection  during  the  earlier  stages  of  segmentation.  It  is  not  yet  determined 
whether  the  zona  striata  is  a  product  of  the  cytoplasm  of  the  ovum  or  of  the  cells 
of  the  corona  radiata,  or  both. 

The  corona  radiata  (Fig.  61)  consists  or  two  or  three  strata  of  cells;  they  are 
derived  from  the  cells  of  the  follicle,  and  adhere  to  the  outer  surface  of  the  zona 
striata  when  the  ovum  is  set  free  from  the  follicle;  the  cells  are  radially  arranged 
around  the  zona,  those  of  the  innermost  layer  being  columnar  in  shape.  The 
cells  of  the  corona  radiata  soon  disappear;  in  some  animals  they  secrete,  or 
are  replaced  by,  a  layer  of  adhesive  protein,  which  may  assist  in  protecting  and 
nourishing  the  ovum. 

The  phenomena  attending  the  discharge  of  the  ova  from  the  follicles  belong 
more  to  the  ordinary  functions  of  the  ovary  than  to  the  general  subject  of  embry- 
ology, and  are  therefore  described  with  the  anatomy  of  the  ovaries.^ 


f.pn 


Fig.  62, — Formation  of  polar  bodies  in  Asterias  glacialis.  (Slightly  modified  from  Hertwig.)  In  I  the  polar  spindle 
{.sp)  has  advanced  to  the  surface  of  the  egg.  In  //  a  small  elevation  (pfei)  is  formed  which  receives  half  of  the  spindle. 
In  III  the  elevation  is  constricted  off,  forming  the  first  polar  body  (pb^),  and  a  second  spindle  is  formed.  In  IV  is 
seen  a  second  elevation  which  in  V  has  been  constricted  off  as  the  second  polar  body  (pfc^)  Out  of  the  remainder  of 
the  spindle  (/.pra  in  VI)  the  female  pronucleus  is  developed. 


Maturation  of  the  Ovum. — Before  an  ovum  can  be  fertilized  it  must  undergo 
a  process  of  maturation  or  ripening.  This  takes  place  previous  to  or  immediately 
after  its  escape  from  the  follicle,  and  consists  essentially  of  an  unequal  subdivision 
of  the  ovum  (Fig.  62)  first  into  two  and  then  into  four  cells.  Three  of  the  four 
cells  are  small,  incapable  of  further  development,  and  are  termed  polar  bodies  or 
polocytes,  while  the  fourth  is  large,  and  constitutes  the  mature  ovum.  The  process 
of  maturation  has  not  been  observed  in  the  human  ovum,  but  has  been  carefully 
studied  in  the  ova  of  some  of  the  lower  animals,  to  which  the  following  description 
applies. 

It  was  pointed  out  on  page  35  that  the  number  of  chromosomes  found  in  the 
nucleus  is  constant  for  all  the  cells  in  an  animal  of  any  given  species,  and  that  in 
man  the  number  is  probably  twenty-four.     This  applies  not  only  to  the  somatic 

1  See  description  of  the  ovary  on  a  future  page. 


80 


EMBRYOLOGY 


cells  but  to  the  primitive  ova  and  their  descendants.  For  the  purpose  of  illustrating 
the  process  of  maturation  a  species  may  be  taken  in  which  the  number  of  nuclear 
chromosomes  is  four  (Fig.  36).  If  an  ovum  from  such  be  observed  at  the  beginning 
of  the  maturation  process  it  will  be  seen  that  the  number  of  its  chromosomes  is 
apparently  reduced  to  two.  In  reality,  however,  the  number  is  doubled,  since 
each  chromosome  consists  of  four  granules  grouped  to  form  a  tetrad.  During  the 
metaphase  (see  page  36)  each  tetrad  divides  into  two  dyads,  which  are  equally 
distributed  between  the  nuclei  of  the  two  cells  formed  by  the  first  division  of  the 
ovum.  One  of  the  cells  is  almost  as  large  as  the  original  ovum,  and  is  named 
the  secondary  oocyte;  the  other  is  small,  and  is  termed  the  first  polar  body.  The 
secondary  oocyte  now  undergoes  subdivision,  during  which  each  dyad  divides  and 
contributes  a  single  chromosome  to  the  nucleus  of  each  of  the  two  resulting  cells. 


Primary  oocyte 


Primary  oocyte 
commencing 
muturdtion) 


Secondary 
oocyte 


First  'polar 
body 


/*e\  /^Q\  /*0\ 


Polar  bodies 
Fig.  63. — Diagram  showing  the  reduction  in  number  of  the  chromosomes  in  the  process  of  maturation  of  the  ovum. 

This  second  division  is  also  unequal,  producing  a  large  cell  which  constitutes  the 
mature  ovum,  and  a  small  cell,  the  second  polar  body.  The  first  polar  body  fre- 
quently divides  while  the  second  is  being  formed,  and  as  a  final  result  four  cells 
are  produced,  viz.,  the  mature  ovum  and  three  polar  bodies,  each  of  which  con- 
tains two  chromosomes,  i.  e.,  one-half  the  number  present  in  the  nuclei  of  the 
somatic  cells  of  members  of  the  same  species.  The  nucleus  of  the  mature  ovum 
is  termed  the  female  pronucleus. 


THE    SPERMATOZOON. 

The  spermatozoa  or  male  germ  cells  are  developed  in  the  testes  and  are  present 
in  enormous  numbers  in  the  seminal  fluid.  Each  consists  of  a  small  but  greatly 
modified  cell.  The  human  spermatozoon  possesses  a  head,  a  neck,  a  connecting 
piece  or  body,  and  a  tail  (Fig.  64). 

The  head  is  oval  or  elliptical,  but  flattened,  so  that  Avhen  viewed  in  profile 
it  is  pear-shaped.    Its  anterior  two-thirds  are  covered  by  a  layer  of  modified  proto- 


THE  SPERMATOZOON 


81 


plasm,  which  is  named  the  head-cap.  This,  in  some  animals,  e.  g.,  the  salanaander, 
is  prolonged  into  a  barbed  spear-like  process  or  perforator,  which  probably  facilitates 
the  entrance  of  the  spermatozoon  into  the  ovum.  The  posterior  part  of  the  head 
exliibits  an  affinity  for  certain  reagents,  and  presents  a  transversely  striated  appear- 
ance, being  crossed  by  three  or  four  dark  bands.  In  some  animals  a  central  rod- 
like  filament  extends  forward  for  about  two-thirds  of  the  length  of  the  head,  w^hile 
in  others  a  rounded  body  is  seen  near  its  centre.  The  head  contains  a  mass  of 
chromatin,  and  is  generally  regarded  as  the  nucleus  of  the  cell  surrounded  by  a 
thin  envelope. 


Head 


Connecting  piece 


•Perforator 


)  ycf/.- 


Tail'. 


Evd-picce  ■ 


Head-cap 


interior  centriole 
---'Posterior  centriole 


-Spiral  tliread 
-JlitocJioiidria  sheath 

Terminal  disc 
Axial  filainent 


Fig.  64.— Human  spermatozoon.      Diagrammatic.      A.  Surface  view.      B.  Profile  view, 
and  connecting  piece  are  more  mgnly  magmtied. 


In  C  the  head,  neck. 


The  neck  is  less  constricted  in  the  human  spermatozoon  than  m  those  of  some 
of  the  lower  animals.  The  anterior  centriole,  represented  by  two  or  three  rounded 
particles,  is  situated  at  the  junction  of  the  head  and  neck,  and  behind  it  is  a  band 
of  homogeneous  substance. 

The  connecting  piece  or  body  is  rod-like,  and  is  limited  behmd  by  a  terminal 
disk.  The  posterior  centriole  is  placed  at  the  junction  of  the  body  and  neck  and, 
like  the  anterior,  consists  of  two  or  three  rounded  particles.  From  this  centriole 
an  axial  filament,  surrounded  by  a  sheath,  runs  backward  through  the  body  and 
tail.  In  the  body  the  sheath  of  the  axial  filament  is  encircled  by  a  spiral  tliread, 
around  which  is  an  envelope  containing  mitochondria  granules,  and  termed  the 
mitochondria  sheath. 
6 


82  EMBRYOLOGY 

The  tail  is  of  great  length,  and  consists  of  the  axial  thread  or  filament,  sur- 
rounded by  its  sheath,  which  may  contain  a  spiral  thread  or  may  present  a  striated 
appearance.  The  terminal  jjortion  or  end-piece  of  the  tail  consists  of  the  axial 
filament  only. 

Krause  gives  the  length  of  the  human  spermatozoon  as  between  52^i  and  G2/Li, 
the  head  measuring  4  to  5/^,  the  connecting  piece  fV,  and  the  tail  from  41  ^  to  52 /i. 

By  virtue  of  their  tails,  which  act  as  propellers,  the  spermatozoa  are  capable  of 
free  movement,  and  if  placed  in  favorable  surroundings,  e.  g.,  in  the  female  pas- 
sages, will  retain  their  vitalit}'  and  power  of  fertilizing  for  several  days.  In  certain 
animals,  e.  g.,  bats,  it  has  been  proved  that  spermatozoa  retained  in  the  female 
passages  for  several  months  are  capable  of  fertilizing. 

Primary  oocyte  Primary  spermatocyte 


Secondary  f     ^  /^  ,^      \  /^       \  Sprrmdary 

oocyte      K        J  ">.^y  \        J  \       J  sptrrnatocytes 


Mature  /''~\ 
ovum  \         ) 


Polar  bodies  Spermatids 


Fig.  65. — Scheme  showing  analogies  in  the  process  of  maturation  of  the  ovum  and  the  development  of  the  spermatida 

(young  .spermatozoa). 

The  spermatozoa  are  developed  from  the  primitive  germ  cells  which  have  become 
imbedded  in  the  testes,  and  the  stages  of  their  development  are  very  similar  to  those 
of  the  maturation  of  the  ovum.  The  primary  germ  cells  undergo  division  and 
produce  a  number  of  cells  termed  spermatogonia,  and  from  these  the  primary 
spermatocytes  are  derived.  Each  primary-  spermatocyte  divides  into  two  secondary 
spermatocytes,  and  each  secondary  spermatocyte  into  two  spermatids  or  young 
spermatozoa;  from  this  it  will  be  seen  that  a  primary  spermatocyte  gives  rise  to 
four  spermatozoa.  On  comparing  this  process  with  that  of  the  maturation  of  the 
ovum  (Fig.  65;  it  will  be  observed  that  the  primary  spermatocyte  gives  rise  to 
two  cells,  the  secondary  spermatocytes,  and  the  primary  oocyte  to  two  cells,  the 
secondary  oocyte  and  the  first  polar  body.  Again,  the  two  secondary  sperma- 
tocytes by  their  subdivision  give  origin  to  four  spermatozoa,  and  the  secondary 
oocyte  and  first  polar  body  to  four  cells,  the  mature  ovum  and  three  polar  bodies. 
In  the  development  of  the  spermatozoa,  as  in  the  maturation  of  the  ovum,  there 
is  a  reduction  of  the  nuclear  chromosomes  to  one-half  of  those  present  in  the 
primary  spermatocyte.  But  here  the  similarity  ends,  for  it  must  be  noted  that 
the  four  spermatozoa  are  of  equal  size,  and  each  is  capable  of  fertilizing  a  mature 
ovum,  whereas  the  three  polar  bodies  are  not  only  very  much  smaller  than  the 
mature  ovum  but  are  incapable  of  further  development,  and  may  be  regarded  as 
abortive  ova. 

FERTILIZATION    OF    THE    OVUM. 

Fertilization  consists  in  the  union  of  the  spermatozoon  with  the  mature  ovum 
(Fig.  66j.    Nothing  is  known  regarding  the  fertilization  of  the  human  ovum,  but 


FERTILIZATION  OF  THE  OVUM 


83 


the  various  stages  of  the  process  have  been  studied  in  other  mammals,  and  from 
the  knowledge  so  obtained  it  is  believed  that  fertilization  of  the  human  ovum  takes 
place  in  the  lateral  or  ampuUary  part  of  the  uterine  tube,  and  the  ovum  is  then 
conveyed  along  the  tube  to  the  cavity  of  the  uterus — a  journey  probably  occupy- 
ing seven  or  eight  days  and  during  which  the  ovum  loses  its  corona  radiata  and  zona 
striata  and  undergoes  segmentation.  Sometimes  the  fertilized  ovum  is  arrested 
in  the  uterine  tube,  and  there  undergoes  development,  giving  rise  to  a  tubal  preg- 
nancy; or  it  may  fall  into  the  abdominal  cavity  and  produce  an  abdominal  preg- 
nancy. Occasionally  the  ovum  is  not  expelled  from  the  follicle  when  the  latter 
ruptures,  but  is  fertilized  within  the  follicle  and  produces  what  is  known  as  an 
ovarian  pregnancy.     Under  normal  conditions  only  one  spermatozoon  enters  the 


1.     Polar  bodies 
Female  pronucleus 

Male  pronucleus 


Female  pronuchiis 
Male  pronucleus 


Segmentntion 
nucleus 


-  Female  pro n ucleus 
Male  pronucleus 


Fused  pronuclei 


Segmentation 

nucleus 

[commencing 

division) 


Fig.  66. — The  process  of  fertilization  in  the  ovum  of  a  mouse.     (After  Sobotta.) 


yolk  and  takes  part  in  the  process  of  fertilization.  At  the  point  where  the  sperma- 
tozoon is  about  to  pierce,  the  yolk  is  drawn  out  into  a  conical  elevation,  termed 
the  cone  of  attraction.  As  soon  as  the  spermatozoon  has  entered  the  yolk,  the  per- 
ipheral portion  of  the  latter  is  transformed  into  a  membrane,  the  vitelline  membrane 
w^hich  prevents  the  passage  of  additional  spermatozoa.  Occasionally  a  second 
spermatozoon  may  enter  the  yolk,  thus  giving  rise  to  a  condition  of  polyspermy: 
when  this  occurs  the  ovum  usually  develops  in  an  abnormal  manner  and  gives  rise 
to  a  monstrosity.  Having  pierced  the  yolk,  the  spermatozoon  loses  its  tail,  while 
its  head  and  connecting  piece  assume  the  form  of  a  nucleus  containing  a  cluster  of 
chromosomes.  This  constitutes  the  male  pronucleus,  and  associated  with  it  there  are 
a  centriole  and  centrosome.  The  male  pronucleus  passes  more  deeply  into  the  yolk, 
and  coincidently  with  this  the  granules  of  the  cytoplasm  surrounding  it  becomes 
radially  arranged.    The  male  and  female  pronuclei  migrate  toward  each  other,  and, 


84 


EMBRYOLOGY 


meeting  near  the  centre  of  the  yolk,  fuse  to  form  a  new  nucleus,  the  segmentation 
nucleus,  which  therefore  contains  both  male  and  female  nuclear  substance;  the 
former  transmits  the  individualities  of  the  male  ancestors,  the  latter  those  of  the 
female  ancestors,  to  the  future  embryo.  By  the  union  of  the  male  and  female 
pronuclei  the  number  of  chromosomes,  is  restored  to  that  which  is  present  in  the 
nuclei  of  the  somatic  cells. 


SEGMENTATION    OF    THE   FERTILIZED    OVUM. 

The  early  segmentation  of  the  human  ovum  has  not  yet  been  observed,  but 
judging  from  what  is  known  to  occur  in  other  mammals  it  may  be  regarded  as 
certain  that  the  process  starts  immediately  after  the  ovum  has  been  fertilized, 
i.  e.,  while  the  ovum  is  in  the  uterine  tube.  The  segmentation  nucleus  exhibits 
the  usual  mitotic  changes,  and  these  are  succeeded  by  a  division  of  the  ovum  into 
two  cells  of  nearly  equal  size.^  The  process  is  repeated  again  and  again,  so  that 
the  two  cells  are  succeeded  by  four,  eight,  sixteen,  thirty-two,  and  so  on,  with  the 
result  that  a  mass  of  cells  is  found  within  the  zona  striata,  and  to  this  mass  the  term 


Fig.  67. — First  stages  of  segmentation  of  a  mammalian  ovum.  Semidiagrammatic.  (From  a  drawing  by  Allen 
Thomson.)  z.p.  Zona  striata,  p.gl.  Polar  bodies,  a.  Two-cell  stage.  6.  Four-cell  stage,  c.  Eight-ceU  stage. 
d,  e.  Morula  stage. 

morula  is  applied  (Fig.  67).  The  segmentation  of  the  mammalian  ovum  may  not 
take  place  in  the  regular  sequence  of  two,  four,  eight,  etc.,  since  one  of  the  two  first 
formed  cells  may  subdivide  more  rapidly  than  the  other,  giving  rise  to  a  three- 
or  a  five-cell  stage.  The  cells  of  the  morula  are  at  first  closely  aggregated,  but  soon 
they  become  arranged  into  an  outer  or  peripheral  layer,  the  trophoblast,  which 
does  not  contribute  to  the  formation  of  the  embryo  proper,  and  an  inner  cell-mass, 
from  which  the  embryo  is  developed.  Fluid  collects  between  the  trophoblast 
and  the  greater  part  of  the  inner  cell-mass,  and  thus  the  morula  is  converted  into 

1  In  the  mammalian  ova  the  nutritive  yolk  or  deutoplasm  is  small  in  amount  and  uniformly  distributed  through- 
out the  cytoplasm;  such  ova  undergo  complete  division  during  the  process  of  segmentation,  and  are  therefore  termed 
holoblastic.  In  the  ova  of  birds,  reptiles,  and  fishes  where  the  nutritive  yolk  forms  by  far  the  larger  portion  of  the 
egg,  the  cleavage  is  limited  to  the  formative  yolk,  and  is  therefore  only  partial;  such  ova  are  termed  meroblastic._  Again, 
it  has  been  observed,  in  some  of  the  lower  animals,  that  the  pronuclei  do  not  fuse  but  merely  he  in  apposition.  At 
the  commencement  of  the  segmentation  process  the  chromosomes  of  the  two  pronuclei  group  themselves  around  the 
equator  of  the  nuclear  spindle  and  then  divide;  an  equal  number  of  male  and  female  chromosomes  travel  to  the  opposite 
poles  of  the  spindle,  and  thus  the  male  and  female  pr9nuclei  subscribe  equal  shares  of  chromatin  to  the  nuclei  of  the 
two  cells  which  result  from  the  subdivision  of  the  fertihzed  ovum. 


SEGMENTATION  OF  THE  FERTILIZED  OVUM 


85 


a  vesicle,  the  blastodermic  vesicle  (Fig.  68).  The  inner  cell-mass  remains  in  con- 
tact, however,  with  the  trophoblast  at  one  pole  of  the  ovum;  this  is  named  the 
embryomic  pole,  since  it  indicates  the  situation  where  the  future  embryo  will  be 
de\'cluped.  The  cells  of  the  trophoblast  become  differentiated  into  two  strata:  an 
outer,  termed  the  syncytium  or  syncytiotrophoblast,  so  named  because  it  consists  of 
a  layer  of  protoplasm  studded  with  nuclei,  but  showing  no  evidence  of  subdivision 
into  cells;  and  an  inner  layer,  the  cjrtotrophoblast  or  layer  of  Langhans,  in  which 


Inner  cell-mass 

Entoderm 


Blastodermic  vesicle 


Trophoblast 


FlQ.  68. — Blastodermic  vesicle  of  Vespertilio  murinus.     (After  van  Beneden.) 
Inner  cell-mass       Trofhoblast 


Emhryonic  ectoderm        Entoderm 
Fig.  69. — Section  through  embryonic  disk  of  VespertUio  murinus.     (After  van  Beneden.) 


Maternal  bloodvessels 


Amniotic  cavity 


Syncytiotrophoblast 

Cytotrophoblast 


Embryonic  ectoderm       Entoderm 

Fig.  70. — Section  through  embryonic  area  of  Vespertilio  murinus  to  show  the  formation  of  the  amniotic  cavity. 

(After  van  Beneden,) 

the  cell  outlines  are  defined.  As  already  stated,  the  cells  of  the  trophoblast  do  not 
contribute  to  the  formation  of  the  embryo  proper;  they  form  the  ectoderm  of  the 
chorion  and  play  an  important  part  in  the  development  of  the  placenta.  On  the 
deep  surface  of  the  inner  cell-mass  a  layer  of  flattened  cells,  the  entoderm,  is  differ- 
entiated and  quickly  assumes  the  form  of  a  small  sac,  the  yolk-sac.  Spaces  appear 
between  the  remaining  cells  of  the  mass  (Fig.  69),  and  by  the  enlargement  and 
coalescence  of  these  spaces  a  cavity,  termed  the  amniotic  cavity  (Fig.  70),  is  gradually 


86 


EMBRYOLOGY 


developed.  The  floor  of  this  ca^•ity  is  formed  by  the  embryonic  disk  composed 
of  a  layer  of  prismatic  cells,  the  embryonic  ectoderm,  deri\ed  from  the  inner  cell- 
mass  and  lying  in  apposition  with  the  entoderm. 

The  Primitive  Streak;  Formation  of  the  Mesoderm. — The  embryonic  disk 
becomes  oval  and  then  pear-shaped,  the  wider  end  being  directed  forward.  Near 
the  narrow,  posterior  end  an  opaque  streak,  the  primitive 
streak  (Figs.  71  and  72),  makes  its  appearance  and  extends 
along  the  middle  of  the  disk  for  about  one-half  of  its 
length;  at  the  anterior  end  of  the  streak  there  is  a  knob- 
like thickening  termed  Hensen's  knot.  A  shallow  groove, 
the  primitive  groove,  appears  on  the  surface  of  the  streak, 
and  the  anterior  end  of  this  groove  communicates  by 
means  of  an  aperture,  the  blastopore,  with  the  yolk-sac. 
The  primitive  streak  is  produced  by  a  thickening  of  the 
axial  part  of  the  ectoderm,  the  cells  of  which  multiply, 
grow  downward,  and  blend  with  those  of  the  subjacent 
entoderm  (Fig.  73).  From  the  sides  of  the  primitive  streak 
a  third  layer  of  cells,  the  mesoderm,  extends  lateralward 
between  the  ectoderm  and  entoderm;  the  caudal  end  of 
the  primitive  streak  forms  the  cloacal  membrane. 
The  extension  of  the  mesoderm  takes  place  throughout  the  whole  of  the  embry- 
onic and  extra-embryonic  areas  of  the  ovum,  except  in  certain  regions.  One  of 
these  is  seen  immediately  in  front  of  the  neural  tube.  Here  the  mesoderm  extends 
forward  in  the  form  of  two  crescentic  masses,  which  meet  in  the  middle  line  so  as 


-Surface    view     of 
(After 


rabbit. 


Kolliker.)       arg.      Embryonic 
disk.     pr.  Primitive  streak 


Yolk- 


A')nnion 


Allatitois  in  body-stalk 


—  Notochord 


~~  Amnion 


y^ Neurenteric  canal 

Primitive  streak 


Fig. 


r2. — Surface  view  of  embryo  of  Hylobates  concolor.    (After  Selenka.)    The  amnion  has  been  opened  to  expose 

the  embryonic  disk. 


to  enclose  behind  them  an  area  which  is  devoid  of  mesoderm.  Over  this  area  the 
ectoderm  and  entoderm  come  into  direct  contact  wdth  each  other  and  constitute 
a  thin  membrane,  the  buccopharyngeal  membrane,  which  forms  a  septum  between 
the  primitive  mouth  and  pharynx.  In  front  of  the  buccopharyngeal  area,  where 
the  lateral  crescents  of  mesoderm  fuse  in  the  middle  line,  the  pericardium  is 


SEGMENTATION  OF  THE  FERTILIZED  OVUM 


87 


afterward  developed,  and  this  region  is  therefore  designated  the  pericardial  area.  A 
second  region  where  the  mesoderm  is  al)sent,  at  least  for  a  time,  is  that  imme- 
diately in  front  of  the  pericarchal  area.  This  is  termed  the  proamniotic  area,  and 
is  the  region  where  the  proairmion  is  developed;  in  man,  however,  a  proamnion  is 
apparently  never  formed.  A  third  region  is  at  the  hind  end  of  the  embryo  where 
the  ectoderm  and  entoderm  come  into  apposition  and  form  the  cloacal  membrane. 


^im^pi%f%% 


Fig.  73. — Series  of  transverse  sections  through  the  embryonic  disk  of  Tarsius.  (After  Hubrecht )  Section  I  passes 
through  the  disk,  in  front  of  Hensen's  knot  and  shows  only  the  ectoderrti  and  entoderm.  Sections//,  ///,  and  IV  pass 
through  Hensen's  knot,  which  is  seen  in  V  tapering  away  into  the  primitive  streak.  In  ///,  IV,  and  V  the  mesoderm 
is  seen  springing  from  the  keel-like  thickening  of  the  ectoderm,  which  in  ///  and  IV  is  observed  to  be  continuous  into 
the  entoderm. 

The  blastoderm  now"  consists  of  three  layers,  named  from  without  inward: 
ectoderm,  mesoderm,  and  entoderm;  each  has  distinctive  characteristics  and  gives 
rise  to  certain  tissues  of  the  bod3^^ 

Ectoderm. — ^The  ectoderm  consists  of  columnar  cells,  which  are,  however,  somewhat 
flattened  or  cubical  tow^ard  the  margin  of  the  embryonic  disk.  It  forms  the  whole 
of  the  nervous  system,  the  epidermis  of  the  skin,  the  lining  cells  of  the  sebaceous, 
sudoriferous,  and  mammary  glands,  the  hairs  and  nails,  the  epithelium  of  the  nose 
and  adjacent  air  sinuses,  and  that  of  the  cheeks  and  roof  of  the  mouth.  From  it 
also  are  derived  the  enamel  of  the  teeth,  and  the  anterior  lobe  of  the  hypophysis 
cerebri,  the  epithelium  of  the  cornea,  conjunctiva,  and  lacrimal  glands,  and  the 
neuro-epithelium  of  the  sense  organs. 

Entoderm. — The  entoderm  consists  at  first  of  flattened  cells,  which  subsequently 
become  columnar.  It  forms  the  epithelial  lining  of  the  whole  of  the  digestive  tube 
excepting  part  of  the  mouth  and  pharynx  and  the  terminal  part  of  the  rectum 

1  The  mode  of  formation  of  the  germ  layers  in  the  human  ovum  has  not  j'et  been  observed;  in  the  youngest  known 
human  ovum  (viz.,  that  described  by  Bryce  and  Teacher),  all  three  layers  are  already  present  and  the  mesoderm  is 
split  into  its  two  layers.  The  extra-embryonic  coelom  is  of  considerable  size,  and  scattered  mesodermal  strands  are 
seen  stretching  between  the  mesoderm  of  the  yolk-sac  and  that  of  the  chorion. 


EMBRYOLOGY 


(which  are  hned  by  involutions  of  the  ectoderm),  the  hning  cells  of  all  the  glands 
which  open  into  the  digestive  tube,  including  those  of  the  liver  and  pancreas, 
the  epithelium  of  the  auditory  tube  and  tympanic  cavit}-,  of  the  trachea,  bronchi, 
and  air  cells  of  the  lungs,  of  the  urinary  bladder  and  part  of  the  urethra,  and  that 
which  lines  the  follicles  of  the  thyroid  gland  and  thymus. 

Mesoderm. — The  mesoderm  consists  of  loosely  arranged  branched  cells  sur- 
rounded by  a  considerable  amount  of  intercellular  fluid.  From  it  the  remaining 
tissues  of  the  body  are  developed.  The  endothelial  lining  of  the  heart  and  blood- 
vessels and  the  blood  corpuscles  are,  however,  regarded  by  some  as  being  of  ento- 
dermal  origin. 


ect 
mes 


h 


Fig.  74. — A  series  of  transverse  sections  through  an  embryo  of  the  dog.  (After  Bonnet.)  Section  /  is  the  most 
anterior.  In  F  the  neural  plate  is  spread  out  nearly  flat.  The  series  shows  the  uprising  of  the  neural  folds  to  form  the 
neural  canal,  a.  Aortse.  c.  Intermediate  ceU  mass.  ect.  Ectoderm,  ent.  Entoderm,  h,  h.  Rudiments  of  endothelial 
heart  tubes.  In  III,  IV,  and  V  the  scattered  cells  represented  between  the  entoderm  and  splanchnic  layer  of  meso- 
derm are  the  vasoformative  cells  which  give  origin  in  front,  according  to  Bonnet,  to  the  heart  tubes,  h;  l.p.  Lateral 
plate  still  undivided  in  /,  //,  and  III;  in  JF  and  V  split  into  somatic  (sm)  and  splanchnic  (sp)  layers  of  mesoderm. 
mes.  Mesoderm,     p.  Pericardium,     so.  Primitive  segment. 

As  the  mesoderm  develops  between  the  ectoderm  and  entoderm  it  is  separated 
into  lateral  halves  by  the  neural  tube  and  notochord,  presently  to  be  described.  A 
longitudinal  groove  appears  on  the  dorsal  surface  of  either  half  and  divides  it  into 
a  medial  column,  the  paraxial  mesoderm,  lying  on  the  side  of  the  neural  tube,  and 
a  lateral  portion,  the  lateral  mesoderm.  The  mesoderm  in  the  floor  of  the  groove 
connects  the  paraxial  with  the  lateral  mesoderm  and  is  known  as  the  intermediate 
cell-mass;  in  it  the  genito-urinary  organs  are  developed.  The  lateral  mesoderm 
splits  into  two  layers,  an  outer  or  somatic,  which  becomes  applied  to  the  inner  surface 
of  the  ectoderm,  and  with  it  forms  the  somatopleure ;  and  an  inner  or  splanchnic, 
which  adheres  to  the  entoderm,  and  with  it  forms  the  splanchnopleure  (Fig.  74). 
The  space  between  the  two  layers  of  the  lateral  mesoderm  is  termed  the  coelom. 


THE  NEURAL  GROOVE  AXD  TUBE 


89 


THE  NEURAL  GROOVE  AND  TUBE. 

In  front  of  the  primitive  streak  two  longitiuiinal  ridges,  eaused  by  a  folding  up 
of  the  ectoderm,  make  their  appearance,  one  on  either  side  of  the  middle  line 
(Fig.  74).  These  are  named  the  neural  folds;  they  commence  some  little  distance 
behind  the  anterior  end  of  the  embryonic  disk,  where  they  are  continuous  with 
each  other,  and  from  there  gradually  extend  backward,  one  on  either  side  of  the 
anterior  end  of  the  primitive  streak.  Between  these  folds  is  a  shallow  median 
groove,  the  neural  groove  (Figs.  74,  75).  The  groove  gradually  deepens  as  the  neural 
folds  become  elevated,  and  ultimatel}^  the  folds  meet  and  coalesce  in  the  middle  line 
and  convert  the  groove  into  a  closed  tube,  the  neural  tube  or  canal  (Fig.  76),  the 
ectodermal  wall  of  which  forms  the  rudiment  of  the  nervous  system.  By  the 
coalescence  of  the  neural  folds  over  the  anterior  end  of  the  primitive  streak,  the 
blastopore  no  longer  opens  on  the  surface  but  into  the  closed  canal  of  the  neural 


J  oik,  bac 


Neurenteric  canal 

Primitive  streak 
Body-stalk 


Fig.    75. — Human  embryo — length,  2  mm.     Dorsal  view,  with  the  amnion  laid  open.     X  30.     (After  Graf  Spee.) 

tube,  and  thus  a  transitory  communication,  the  neurenteric  canal,  is  established 
between  the  neural  tube  and  the  primitive  digestive  tube.  The  coalescence  of  the 
neural  folds  occurs  first  in  the  region  of  the  hind-brain,  and  from  there  exterids 
forward  and  bacb^^ard;  toward  the  end  of  the  third  week  the  front  opening  (anterior 
neuropore)  of  the  tube  finally  closes  at  the  anterior  end  of  the  future  brain,  and 
forms  a  recess  which  is  in  contact,  for  a  time,  with  the  overlying  ectoderm;  the 
hinder  part  of  the  neural  groove  presents  for  a  time  a  rhomboidal  shape,  and  to  this 
expanded  portion  the  term  sinus  rhomboidalis  has  been  applied  (Fig.  76).  Before 
the  neural  groove  is  closed  a  ridge  of  ectodermal  cells  appears  along  the  prominent 
margin  of  each  neural  fold;  this  is  termed  the  neural  crest  or  ganglion  ridge,  and  from 
it  the  spinal  and  cerebral  nerve  ganglia  and  the  ganglia  of  the  sympathetic  nervous 
system  are  developed.  By  the  upward  growth  of  the  mesoderm  the  neural  tube 
is  ultimately  separated  from  the  overlying  ectoderm. 

The  cephalic  end  of  the  neural  groove  exhibits  several  dilatations,  which,  when 
the  tube  is  closed,  assume  the  form  of  three  vesicles;  these  constitute  the  three 
primary  cerebral  vesicles,  and  correspond  respectively  to  the  future  prosencephalon 


90 


EMBRYOLOGY 


(fore-brain),  mesencephalon  (mid-brain),  and  rhombencephalon  (^hind-brain j  (Fig. 
76).  The  walls  of  the  vesicles  are  developed  into  the  nervous  tissue  and  neuroglia 
of  the  brain,  and  their  cavities  are  modified  to  form  its  ventricles.  The  remainder 
of  the  tube  forms  the  medulla  spinalis  or  spinal  cord;  from  its  ectodermal  wall 
the  nervous  and  neuroglial  elements  of  the  medulla  spinalis  are  developed  while 
the  cavity  persists  as  the  central  canal. 


Head  fold  of  amnion  partlp 
covering  the  fore-brain 


2Iid-brain  -r 


Uind-hrain 


l^erve  ganglion 
Auditory  vesicle  - 


Vitelline  vein 


Fourteenth  primitive 
segment 


Paraxial  mesoderm 


Neural  fold, 


Sinus  rhomboidalis 


JRemains  of  primitive  streak 


HeaH 


Fig.   76. — Chick  embrv'O  of  thirty-three  hours'  incubation,  viewed  from  the  dorsal  aspect.     X  30. 
(From  Duval's  "Atlas  d'Embryologie."; 


THE  NOTOCHORD. 


The  notochord  (Fig.  77)  consists  of  a  rod  of  cells  situated  on  the  ventral  aspect 
of  the  neural  tube;  it  constitutes  the  foundation  of  the  axial  skeleton,  since  around 
it  the  segments  of  the  vertebral  column  are  formed.    Its  appearance  synchronizes 


THE  PRIM  in  VE  SEGMENTS 


91 


with  that  of  the  neural  tube.  On  the  ventral  aspect  of  the  neural  groove  an  axial 
thickening  of  the  entoderm  takes  place;  this  thickening  assumes  the  appearance 
of  a  furrow — the  chordal  furrow — the  margins  of  which  come  into  contact,  and  so 
convert  it  into  a  solid  rod  of  cells — the  notochord — which  is  then  separated  from 
the  entoderm.     It  extends  throughout  the  entire  length  of  the  future  vertebral 


Ectoderm  ., 


Neural  canal  Primitive    Wolffia7i 

segment    duct  Ccelom 


Somatic  mesoderm 


Entoderm  ^' 


Fig. 


Notochord  Aorta       Splanchnic  mesoderm 

-Transverse  section  of  a  chick  embryo  of  forty-five  hours'  incubation.     (Balfour.) 


column,  and  reaches  as  far  as  the  anterior  end  of  the  mid-brain,  where  it  ends  in 
a  hook-like  extremity  in  the  region  of  the  future  dorsum  sellae  of  the  sphenoid 
bone.  It  lies  at  first  between  the  neural  tube  and  the  entoderm  of  the  yolk-sac, 
but  soon  becomes  separated  from  them  by  the  mesoderm,  which  grows  medial- 
ward  and  surrounds  it.  From  the  mesoderm 
surrounding  the  neural  tube  and  notochord, 
the  skull  and  vertebral  column,  and  the 
membranes  of  the  brain  and  medulla  spinalis 
are  developed. 


THE   PRIMITIVE    SEGMENTS. 


Czit  edge  of  amnion 
Primitive  segments 


Tow^ard  the  end  of  the  second  week 
transverse  segmentation  of  the  paraxial 
mesoderm  begins,  and  it  is  converted  into 
a  series  of  well-defined,  more  or  less  cubical 
masses,  the  primitive  segments  (Figs.  76, 
77,  78),  which  occupy  the  entire  length  of 
the  trunk  on  either  side  of  the  middle  line 
from  the  occipital  region  of  the  head.  Each 
segment  contains  a  central  cavity — myocoel 
— ^w^hich,  however,  is  soon  filled  with  angular 
and  spindle-shaped  cells. 

The  primitive  segments  lie  immediately 
under  the  ectoderm  on  the  lateral  aspect  of 
the  neural  tube  and  notochord,  and  are  con- 
nected to  the  lateral  mesoderm  by  the  inter- 
mediate cell-mass.  Those  of  the  trunk  may 
be  arranged  in  the  following  groups,  viz.:  cervical  8,  thoracic  12,  lumbar  5, 
sacral  5,  and  coccygeal  from  5  to  8.  Those  of  the  occipital  region  of  the  head 
are  usually  described  as  being  four  in  number.  In  mammals  primitive  segments 
of  the  head  can  only  be  recognized  in  the  occipital  region,  but  a  study  of  the 
lower  vertebrates  leads  to  the  belief  that  they  are  present  also  in  the  anterior 
part  of  the  head,  and  that  altogether  nine  segments  are  represented  in  the 
cephalic   region. 


Yolk-sac 


Fig 


Neural  folds 


Neurenteric  canal 


Dorsum  of  human  embryo,    2.11   mm.  in 
length.     (After  Eternod.) 


92 


EMBRYOLOGY 


SEPARATION    OF    THE    EMBRYO. 

The  embryo  increases  rapidly  in  size,  but  the  circumference  of  the  embryonic 
disk,  or  Hne  of  meeting  of  the  embryonic  and  amniotic  parts  of  the  ectoderm,  is  of 
relatively  slow  growth  and  .gradually  comes  to  form  a  constriction  between  the 
embryo  and  the  greater  part  of  the  3^olk-sac.  By  means  of  this  constriction,  which 
corresponds  to  the  future  umbilicus,  a  small  part  of  the  yolk-sac  is  enclosed  within 
the  embryo  and  constitutes  the  primitive  digestive  tube. 

The  embryo  increases  more  rapidly  in  length  than  in  width,  and  its  cephalic  and 
caudal  ends  soon  extend  -beyond  the  corresponding  parts  of  the  circumference  of 
the  embryonic  disk  and  are  bent  in  a  ventral  direction  to  form  the  cephalic  and 
caudal  folds  respectively  (Figs.  84  and  85).    The  cephalic  fold  is  first  formed,  and 


Villi  of  chorion 


Amnion 
Embryo7iic  disc 


Bitdiment  of  heart 


Mesoder 


Chorion 

i"?"^  Mesoderm 

Body-stalk 
Primitive  streak 

Allantois 


toderm 


Bloodvessel 


Fig.  79. — Section  through  the  embryo  which  is  represented  in  Fig.  75.     (After  Graf  Spee.) 


as  the  proamniotic  area  (page  87)  lying  immediately  in  front  of  the  pericardial 
area  (page  87)  forms  the  anterior  limit  of  the  circumference  of  the  embryonic 
disk,  the  forward  growth  of  the  head  necessarily  carries  with  it  the  posterior  end 
of  the  pericardial  area,  so  that  this  area  and  the  buccopharyngeal  membrane  are 
folded  back  under  the  head  of  the  embryo  which  now  encloses  a  diverticulum  of  the 
yolk-sac  named  the  fore-gut.  The  caudal  end  of  the  embryo  is  at  first  connected 
to  the  chorion  by  a  band  of  mesoderm  called  the  body-stalk,  but  with  the  formation 
of  the  caudal  fold  the  body-stalk  assumes  a  ventral  position;  a  diverticulum  of  the 
yolk-sac  extends  into  the  tail  fold  and  is  termed  the  hind-gut.  Between  the  fore-gut 
and  the  hind-gut  there  exists  for  a  time  a  wide  opening  into  the  yolk-sac,  but  the 
latter  is  gradually  reduced  to  a  small  pear-shaped  sac  (sometimes  termed  the 
umbilical  vesicle),  and  the  channel  of  communication  is  at  the  same  time  narrowed 
and  elongated  to  form  a  tube  called  the  vitelline  duct. 


DEVELOPMENT  OF  THE  FETAL  MEMBRANES  AND  THE  PLACENTA     93 


THE   YOLK-SAC. 


The  yolk-sac  (Figs.  79  and  SO)  is  situated  on  the  ventral  aspect  of  the  embryo; 
it  is  lined  by  entoderm,  outside  of  which  is  a  layer  of  mesoderm.  It  is  filled  with 
fluid,  the  vitelline  fluid,  which  possibly  may  be  utilized  for  the  nourishment  of  the 
embryo  during  the  earlier  stages  of  its  existence.  Blood  is  conveyed  to  the  wall  of 
the  sac  by  the  primitive  aortae,  and  after  circulating  through  a  wide-meshed  capil- 
lary plexus,  is  returned  by  the  vitelline 

veins  to  the  tubular  heart  of  the  em-  Heart 

bryo.  This  constitutes  the  vitelline 
circulation,  and  by  means  of  it  nutri- 
tive material  is  absorbed  from  the 
yolk-sac  and  conveyed  to  the  embryo. 
At  the  end  of  the  fourth  week  the  yolk- 
sac  presents  the  appearance  of  a  small 
pear-shaped  vesicle  (umbilical  vesicle) 
opening  into  the  digestive  tube  by  a 
long  narrow  tube,  the  vitelline  duct. 
The  vesicle  can  be  seen  in  the  after- 
birth as  a  small,  somewhat  oval-shaped 
body  whose  diameter  varies  from  1 
mm.  to  5  mm.;  it  is  situated  between 
the  amnion  and  the  chorion  and  may 
lie  on  or  at  a  varying  distance  from 
the  placenta.     As    a   rule   the    duct 

undergoes  complete  obliteration  during  the  seventh  week,  but  in  about  three 
per  cent,  of  cases  its  proximal  part  persists  as  a  diverticulum  from  the  small 
intestine,  Meckel's  diverticulum,  which  is  situated  about  three  or  four  feet  above 
the  ileocolic  junction,  and  may  be  attached  by  a  fibrous  cord  to  the  abdominal 
wall  at  the  umbilicus.  Sometimes  a  narrowing  of  the  lumen  of  the  ileum  is  seen 
opposite  the  site  of  attachment  of  the  duct. 


Fig.  80.- 


Hind  limb 

Human  embryo  from  thirty-one  to  thirty-four 
days.     (His.) 


DEVELOPMENT    OF    THE    FETAL   MEMBRANES    AND    THE    PLACENTA. 

The  AUantois  (Figs.  82  to  85).— The  allantois  arises  as  a  tubular  diverticulum 
of  the  posterior  part  of  the  yolk-sac;  when  the  hind-gut  is  developed  the  allantois 
is  carried  backw^ard  with  it  and  then  opens  into  the  cloaca  or  terminal  part  of  the 
hind-gut:  it  grows  out  into  the  body-stalk,  a  mass  of  mesoderm  which  lies  below 
and  around  the  tail  end  of  the  embryo.  The  diverticulum  is  lined  by  entoderm 
and  covered  by  mesoderm,  and  in  the  latter  are  carried  the  allantoic  or  umbilical 
vessels. 

In  reptiles,  bhds,  and  many  mammals  the  allantois  becomes  expanded  into  a 
vesicle  which  projects  into  the  extra-embryonic  coelom.  If  its  finther  development 
be  traced  in  the  bnd,  it  is  seen  to  project  to  the  right  side  of  the  embryo,  and, 
gradually  expanding,  it  spreads  over  its  dorsal  surface  as  a  flattened  sac  between 
the  amnion  and  the  serosa,  and  extending  in  all  directions,  ultimately  surrounds 
the  yolk.  Its  outer  wall  becomes  applied  to  and  fuses  with  the  serosa,  which  lies 
immediately  inside  the  shell  membrane.  Blood  is  carried  to  the  allantoic  sac  by 
the  two  allantoic  or  umbilical  arteries,  which  are  continuous  with  the  primitive 
aortse,  and  after  circulating  through  the  allantoic  capillaries,  is  returned  to  the 
primitive  heart  by  the  two  umbilical  veins.  In  this  way  the  allantoic  cnculation, 
which  is  of  the  utmost  importance  in  connection  with  the  respiration  and  nutrition 


94 


EMBRYOLOGY 


of  the  chick,  is  estabHshed.  Oxygen  is  taken  from,  and  carbonic  acid  is  given  up 
to  the  atmosphere  through  the  egg-shell,  while  nutriti\'e  materials  are  at  the  same 
time  absorbed  by  the  blood  from  the  yolk. 

Amniotic  cavity 


Amniotic  cavity 
Yolk-sac 


Chorion 


Body-stalk 
Allantois 

Yolk-sac 


Chorion 


Fig.  81. — Diagram  showing  earliest  observed  stage 
of  human  ovum. 


Fig.  82. — Diagram    illustrating    early    formation 
allantois  and  differentiation  of  body-stalk. 


In  man  and  other  primates  the  nature  of  the  allantois  is  entirely  different  from 
that  just  described.  Here  it  exists  merely  as  a  narrow,  tubular  diverticulum  of  the 
hind-gut,  and  never  assumes  the  form  of  a  vesicle  outside  the  embryo.  With  the 
formation  of  the  amnion  the  embryo  is,  in  most  animals,  entirely  separated  from 
the  chorion,  and  is  only  again  united  to  it  when  the  allantoic  mesoderm  spreads 
over  and  becomes  applied  to  its  inner  surface.  The  human  embryo,  on  the  other 
hand,  as  was  pointed  out  by  His,  is  never  wholly  separated  from  the  chorion,  its 
tail  end  being  from  the  first  connected  with  the  chorion  by  means  of  a  thick  band 
of  mesoderm,  named  the  body-stalk  (Bauchstiel) ;  into  this  stalk  the  tube  of  the 
allantois  extends  (Fig.  79). 


Amniotic  cavity 
Embryo 

Body-stalk 


Placental 
villi 


Allantois 


Yolk-sac 


Chorion 


Heart 

Fig.  83. — Diagram  showing  later  stage  of  allan- 
toic development  with  commencing  constriction 
of  the  yolk-sac. 


Body-stalk 

Allantois 
Yolk-sac 

Heart 


Fore-gut 
Embryo 
Amniotic  cavity 

Fia.  84. — Diagram  showing  the  expansion  of  amnion 
and  delimitation  of  the  umbiUcus. 


The  Amnion. — The  amnion  is  a  membranous  sac  which  surrounds  and  protects 
the  embryo.  It  is  developed  in  reptiles,  birds,  and  mammals,  wdiich  are  hence 
called  "Amniota;"  but  not  in  amphibia  and  fishes,  which  are  consequently  termed 
"  Anamnia." 

In  the  human  embryo  the  earliest  stages  of  the  formation  of  the  amnion  have  not 
been  observed;  in  the  youngest  embryo  which  has  been  studied  the  amnion  was 
already  present  as  a  closed  sac  (Figs.  81  and  88),  and,  as  indicated  on  page  85, 


DEVELOPMENT  OF  THE  FETAL  MEMBRANES  AND  THE  PLACENTA     95 


appears  in  the  iiiiuT  cell-mass  as  a  cavity.  This  ca^•ity  is  roofed  in  by  a  single 
stratum  of  flattened,  ectodermal  cells,  the  amniotic  ectoderm,  and  its  floor  consists 
of  the  prismatic  ectoderm  of  the  embryonic  disk — the  continuity  between  the 
roof  and  floor  being  established  at 

the  margin  of  the  embryonic  disk.  placental  villi 

Outside  the  amniotic  ectoderm  is 
a  thin  layer  of  mesoderm,  which 
is  continuous  with  that  of  the 
somatopleure  and  is  connected  by 
the  body-stalk  with  the  meso- 
dermal lining  of  the  chorion. 

When  first  formed  the  amnion 
is  in  contact  with  the  body  of  the 
embryo,  but  about  the  fourth  or 
fifth  week  fluid  (liquor  amnii)  be- 
gins to  accumulate  within  it.  This 
fluid  increases  in  quantity  and 
causes  the  amnion  to  expand  and 
ultimately  to  adhere  to  the  inner 
surface  of  the  chorion,  so  that  the 
extra-embryonic  part  of  the  coelom 
is  obliterated.  The  liquor  amnii 
increases  in  quantity  up  to  the 
sixth  or  seventh  month  of  preg- 
nancy, after  which  it  diminishes 
somewhat;  at  the  end  of  preg- 
nancy it  amounts  to  about  1  litre.  It  allows  of  the  free  movements  of  the  fetus 
during  the  later  stages  of  pregnancy,  and  also  protects  it  by  diminishing  the  risk 
of  injury  from  without.     It  contains  less  than  2  per  cent,  of  solids,  consisting  of 


Yolk-sac 

Umbilical  cord 

Allantois 
Heart 
Digestive  tube 


Fig.  85. 


E^nbryo 

Amniotic  cavity 

-Diagram  illustrating  a  later  stage  in  the  development 
of  the  umbilical  cord. 


false  amnion  or  serosa 
\ 


villi  of 


Fig.  86. — Diagram  of  a  transverse  section,  showing  the  mode  of  formation  of  the  amnion  in  the  chick.  The  amniotic 
folds  have  nearly  united  in  the  middle  Une.  (From  Quain's  Anatomy.)  Ectoderm,  blue;  mesoderm,  red;  entoderm 
and  notochord,  black. 


urea  and  other  extractives,  inorganic  salts,  a  small  amount  of  protein,  and  frequently 
a  trace  of  sugar.  That  some  of  the  liquor  amnii  is  swallowed  by  the  fetus  is  proved 
by  the  fact  that  epidermal  debris  and  hairs  have  been  found  among  the  contents  of 
the  fetal  alimentarv  canal. 


96 


EMBRYOLOGY 


In  reptiles,  birds,  and  many  mammals  the  amnion  is  developed  in  the  following 
manner:  At  the  point  of  constriction  where  the  primitive  digestive  tube  of  the 
embryo  joins  the  yolk-sac  a  reflection  of  folding  upward  of  the  somatopleure  takes 
place.  This,  the  amniotic  fold  (Fig.  86),  first  makes  its  appearance  at  the  cephalic 
extremity,  and  subsequently  at  the  caudal  end  and  sides  of  the  embryo,  and  grad- 
ually rising  more  and  more,  its  different  parts  meet  and  fuse  over  the  dorsal  aspect 
of  the  embryo,  and  enclose  a  cavity,  the  amniotic  cavity.  After  the  fusion  of  the 
edges  of  the  amniotic  fold,  the  two  layers  of  the  fold  become  completely  separated, 
the  inner  forming  the  amnion,  the  outer  the  false  amnion  or  serosa.  The  space 
between  the  amnion  and  the  serosa  constitutes  the  extra-embryonic  coelom,  and 
for  a  time  communicates  with  the  embryonic  coelom. 


Somatic  mesoderm 


Splanchnic 
mesoderm 
Entoderm 


Vitelline  veim 


Amniotic  cavity 
Amnion 
Neural  groove 


Fig.  87. — Model  of  human  embrj-o  1.3  mm.  long.      (After  Eternod.) 


The  Umbilical  Cord  and  Body-stalk. — The  umbilical  cord  (Fig.  85)  attaches 
the  fetus  to  the  placenta;  its  length  at  full  time,  as  a  rule,  is  about  equal  to  the 
length  of  the  fetus,  i.  e.,  about  50  cm.,  but  it  may  be  greatly  diminished  or  increased. 
The  rudiment  of  the  umbilical  cord  is  represented  by  the  tissue  which  connects 
the  rapidly  growing  embryo  with  the  extra-embryonic  area  of  the  ovum.  Included 
in  this  tissue  are  the  body-stalk  and  the  vitelline  duct— the  former  containing  the 
allantoic  diverticulum  and  the  umbilical  vessels,  the  latter  forming  the  communica- 
tion between  the  digestive  tube  and  the  yolk-sac.  The  body-stalk  is  the  posterior 
segment  of  the  embryonic  area,  and  is  attached  to  the  chorion.  It  consists  of  a  plate 
of  mesoderm  covered  by  thickened  ectoderm  on  which  a  trace  of  the  neural  groove 
can  be  seen,  indicating  its  continuity  with  the  embryo.  Running  through  its 
mesoderm  are  the  two  umbilical  arteries  and  the  two  umbilical  veins,  together  with 
the  canal  of  the  allantois— the  last  being  lined  by  entoderm  (Fig.  87).  Its  dorsal 
surface  is  covered  by  the  amnion,  while  its  ventral  surface  is  bounded  by  the  extra- 
embryonic coelom,  and  is  in  contact  with  the  vitelline  duct  and  yolk-sac.  With 
the  rapid  elongation  of  the  embryo  and  the  formation  of  the  tail  fold,  the  body 
stalk  comes  to  lie  on  the  ventral  surface  of  the  embryo  (Figs.  84  and  85),  where 
its  mesoderm  blends  with  that  of  the  yolk-sac  and  the  vitelline  duct.  The  lateral 
leaves  of  somatopleure  then  grow  round  on  each  side,  and,  meeting  on  the  ventral 


DEVELOPMENT  OF  THE  FETAL  MEMBRANES  AND  THE  PLACENTA     97 

aspect  of  the  allantois,  enclose  the  viteUiiie  duct  and  vessels,  together  with  a  part 
of  the  extra-embryonic  coelom;  the  latter  is  ultimately  obliterated.  The  cord  is 
covered  by  a  layer  of  ectoderm  which  is  continuous  with  that  of  the  amnion,  and 
its  various  constitutents  are  enveloped  by  embryonic  gelatinous  tissue,  jelly  of 
Wharton.  The  vitelline  vessels  and  duct,  together  with  the  right  umbilical  vein, 
undergo  atrophy  and  disappear;  and  thus  the  cord,  at  birth,  contains  a  pair  of 
umbilical  arteries  and  one  (the  left)  umbilical  vein. 


a.e. 


Fig.  88. — ^Section  through  ovum  imbedded  in  the  uterine  decidua.  Semidiagrammatic.  (After  Peters.)  am. 
Amniotic  cavity,  b.c.  Blood-clot.  b.s.  Body-stalk,  ect.  Embryonic  ectoderm,  ent.  Entoderm.  Tries.  Mesoderm. 
m.v.  Maternal  vessels,    tr.  Trophoblast.    u.e.  Uterine  epithelium,    u.g.  Uterine  glands,    y.s.  Yolk-sac. 

Implantation  or  Imbedding  of  the  Ovum. — As  described  (page  82),  fertilization 
of  the  ovum  occurs  in  the  lateral  or  ampullary  end  of  the  uterine  tube  and  is 
immediately  followed  by  segmentation.  On  reaching  the  cavity  of  the  uterus  the 
segmented  ovum  adheres  like  a  parasite  to  the  uterine  mucous  membrane,  destroys 
the  epithelium  over  the  area  of  contact,  and  excavates  for  itself  a  cavity  in  the 
mucous  membrane  in  which  it  becomes  imbedded.  In  the  ovum  described  by 
Bryce  and  Teacher^  the  point  of  entrance  was  visible  as  a  small  gap  closed  by  a 
mass  of  fibrin  and  leucocytes;  in  the  ovum  described  by  Peters^  the  opening  was 
covered  by  a  mushroom-shaped  mass  of  fibrin  and  blood-clot  (Fig.  88),  the  narrow 
stalk  of  which  plugged  the  aperture  in  the  mucous  membrane.  Soon,  however, 
all  trace  of  the  opening  is  lost  and  the  ovum  is  then  completely  surrounded  by  the 
uterine  mucous  membrane. 

The  structure  actively  concerned  in  the  process  of  excavation  is  the  trophoblast 
of  the  ovum,  which  possesses  the  power  of  dissolving  and  absorbing  the  uterine 


^  Contribution  to  the  study  of  the  early  development  and  imbedding  of  the  human  ovum,  1908. 
-  Die  Einbettung  des  menschUchen  Eies,  1899. 


98 


EMBRYOLOGY 


Mucous  membrane 


Muscular  fibres 


Stratum  compactum 


tissues.  The  trophoblast  proliferates  rapidly  and  forms  a  network  of  branching 
processes  which  cover  the  entire  ovum  and  invade  and  destroy  the  maternal 
tissues  and  open  into  the  maternal  bloodvessels,  with  the  result  that  the  spaces 
in  the  trophoblastic  n£twork  are  filled  with  maternal  blood;  these  spaces  com- 
municate freely  with  one  another  and  become  greatly  distended  and  form  the 
intervillous  space. 

The  Decidua. — Before  the  fertilized  ovum  reaches  the  uterus,  the  mucous 
membrane  of  the  body  of  the  uterus  undergoes  important  changes  and  is  then 

known  as  the  decidua.  The  thickness 
and  vascularity  of  the  mucous  mem- 
brane are  greatly  increased;  its  glands 
are  elongated  and  open  on  its  free 
surface  by  funnel-shaped  orifices, 
while  their  deeper  portions  are  tortu- 
ous and  dilated  into  irregular  spaces. 
The  interglandular  tissue  is  also  in- 
creased in  quantity,  and  is  crowded 
with  large  round,  oval,  or  polygonal 
cells,  termed  decidual  cells.  These 
changes  are  well  advanced  by  the 
second  month  of  pregnancy,  when 
the  mucous  membrane  consists  of  the 
following  strata  (Fig.  89):  (1)  stratum 
compactum,  next  the  free  surface;  in 
this  the  uterine  glands  are  only 
slightly  expanded,  and  are  lined  by 
columnar  cells;  (2)  stratum  spongiosum, 
in  which  the  gland  tubes  are  greatly 
dilated  and  very  tortuous,  and  are 
ultimately  separated  from  one  another 
by  only  a  small  amount  of  inter- 
glandular tissue,  while  their  lining 
cells  are  flattened  or  cubical;  (3)  a 
thin  Unaltered  or  boundary  layer,  next 
the  uterine  muscular  fibres,  contain- 
ing the  deepest  parts  of  the  uterine 
glands,  which  are  not  dilated,  and 
are  lined  with  columnar  epithelium; 
it  is  from  this  epithelium  that  the 
epithelial  lining  of  the  uterus  is  re- 
generated after  pregnancy.  Distinc- 
tive names  are  applied  to  different 
portions  of  the  decidua.  The  part 
which  covers  in  the  ovum  is  named  the 
decidua  capsularis;  the  portion  which 
intervenes  between  the  ovum  and  the 
uterine  wall  is  named  the  decidua 
basalis  or  decidua  placentalis;  it  is  here 
that  the  placenta  is  subsequently 
developed.  The  part  of  the  decidua  which  lines  the  remainder  of  the  body  of  the 
uterus  is  known  as  the  decidua  vera  or  decidua  parietalis. 

Coincidently  with  the  grow^th  of  the  embryo,  the  decidua  capsularis  is  thinned 
and  extended  (Fig.  90)  and  the  space  between  it  and  the  decidua  vera  is  gradually 
obliterated,  so  that  by  the  third  month  of  pregnancy  the  two  are  in  contact.    By 


Stratum  spongiosum 


Unaltered  or 
boundary  layer 

Muscular  fibres 

Fig.  89. — Diagrammatic  sections  of  the  uterine  mucous 
membrane:  A.  The  non-pregnant  uterus.  B.  The  preg- 
nant uterus,  showing  the  thicltened  mucous  membrane 
and  the  altered  condition  of  the  uterine  glands.  (Kundrat 
and  Engelmann.) 


DEVELOPMENT  OF  THE  FETAL  MEMBRANES  AND  THE  PLACENTA     99 

the  fifth  month  of  pregnancy  the  deciduu  ('ai)sulari.s  has  jiractically  disappeared, 
wliile  during;  the  snc('ee<Hng  months  the  (k'cifhui  vera  also  undergoes  atrophy, 
owing  to  the  increased  pressure.  The  glands  of  the  stratum  compactum  are  oblit- 
erated, and  their  epithelium  is  lost.  In  the  stratum  spongiosum  the  glands  are 
compressed  and  appear  as  slit-like  fissures,  while  their  epithelium  undergoes  degen- 
eration. In  the  unaltered  or  boundary  layer,  however,  the  glandular  epithelium 
retains  a  columnar  or  cubical  form. 

The  Chorion  (Figs.  80  to  So). — The  chorion  consists  of  two  layers:  an  outer 
formed  by  the  primitive  ectoderm  or  trophoblast,  and  an  inner  by  the  somatic 
mesoderm;  with  this  latter  the  amnion  is  in  contact.  The  trophoblast  is  made 
up  of  an  internal  layer  of  cubical  or  prismatic  cells,  the  cytotrophoblast  or  layer 
of  Langhans,  and  an  external  layer  of  richly  nucleated  protoplasm  devoid  of  cell 
boundaries,  the  syncytiotrophoblast.  It  undergoes  rapid  proHferation  and  forms 
numerous  processes,  the  chorionic  villi,  which  invade  and  destroy  the  uterine 

Placental  villi  imbedded  in  the 

^Decidua  flacentalis 

Uterine  tube 


Allantois 


Umbilical  cord 
icith  its  con- 
tained vessels 


Non-placental  villi  im- 
hedded'  in  the  decidua 
capsularis 


Cavity  of  uterus 
Yolk-sac 

Cavity  of  amnion 

Decidua  vera 
or  parietalis 


Plug  of  mucus  in  the 
cervix  uteri 


Fig.  90. — Sectional  plan  of  the  gravid  uterus  in  the  third  and  fourth  month.     (Modified  from  Wagner.) 


decidua  and  at  the  same  time  absorb  from  it  nutritive  materials  for  the  growth 
of  the  embryo.  The  chorionic  villi  are  at  first  small  and  non-vascular,  and  consist 
of  trophoblast  only,  but  they  increase  in  size  and  ramify,  while  the  mesoderm, 
carrying  branches  of  the  umbilical  vessels,  grows  into  them,  and  in  this  way  they 
are  vascularized.  Blood  is  carried  to  the  villi  by  the  branches  of  the  umbilical 
arteries,  and  after  circulating  through  the  capillaries  of  the  villi,  is  returned  to 
the  embryo  by  the  umbilical  veins.  Until  about  the  end  of  the  second  month 
of  pregnancy  the  villi  cover  the  entire  chorion,  and  are  almost  uniform  in  size 
(Fig.  82),  but  after  this  they  develop  unequally.  The  greater  part  of  the  chorion 
is  in  contact  with  the  decidua  capsularis  (Fig.  90),  and  over  this  portion  the  villi, 
with  their  contained  vessels,  undergo  atrophy,  so  that  by  the  fourth  month  scarcely 
a  trace  of  them  is  left,  and  hence  this  part  of  the  chorion  becomes  smooth,  and  is 
named  the  chorion  laeve;  as  it  takes  no  share  in  the  formation  of  the  placenta,  it 
is  also  named  the  non-placental  part  of  the  chorion.  On  the  other  hand,  the  villi 
on  that  part  of  the  chorion  which  is  in  contact  with  the  decidua  placentalis  increase 


100 


EMBRYOLOGY 


greatly  in  size  and  complexity,  and  hence  this  part  is  named  the  chorion  frondosum 

(Fig.  85). 
The  Placenta. — The  placenta  connects  the  fetus  to  the  uterine  wall,  and  is  the 

organ  by  means  of  which  the  nutritive,  respiratory,  and  excretory  functions  of  the 

fetus  are  carried  on.    It  is  composed  of  fetal  and  maternal  portions 

Fetal  Portion. — The  fetal  portion  of  the  placenta  consists  of  the  yilli  of  the 

chorion  frondosum;  these  branch  repeatedly,   and  increase  enormously  in  size. 

These  greatly  ramified  yilli  are  sus- 
pended in  the  intervillous  space,  and 
are  bathed  in  maternal  blood,  which 
is  conveyed  to  the  space  by  the  uterine 
arteries  and  carried  away  by  the  uter- 
ine veins.  A  branch  of  an  umbilical 
artery  enters  each  villus  and  ends  in 
a  capillary  plexus  from  which  the 
blood  is  drained  by  a  tributary  of  the 
umbilical  vein.  The  vessels  of  the 
villus  are  surrounded  by  a  thin  layer 
of  mesoderm  consisting  of  gelatinous 
connective  tissue,  which  is  covered  by 
tw^o  strata  of  ectodermal  cells  derived 
from  the  trophoblast:  the  deeper 
stratum,  next  the  mesodermic  tissue, 
represents  the  cytotrophoblast  or  layer 
of  Langhans;  the  superficial,  in  contact 

with  the  maternal  blood,  the  syncytiotrophoblast  (Figs.  91  and  92).    After  the 

fifth  month  the  two  strata  of  cells  are  replaced  by  a  single  layer  of  somewhat 

flattened  cells. 


Fig.  91. — Diagram  to  illustrate  the  first  phase  of  the 
placenta.  (After  Peters.)  b.l.  Blood  lacuna,  ca.  Maternal 
capillary,  dc.  Decidua.  mes.  Mesoderm,  sy.  Syncytio- 
trophoblast.    tr.  Cytotrophoblast. 


mcp 


Fig.  92. — Diagram  to  illustrate  the  second  phase  of  the  placenta.  (After  Peters.)  The  mesodermic  core  has  now 
invaded  the  strands  of  the  trophoblast,  and  is  beginning  to  branch,  ca.  Maternal  capillary,  core.  Core  of  yiUus. 
fib.  Fibrinous  material  deposited  at  junction  of  trophoblast  with  decidua.  mcp.  Endothelium  of  maternal  capillary 
mes.  Mesoderm,    sy.  Syncytiotrophoblast.    vs.  Intervillous  space. 


Maternal  Portion. — The  maternal  portion  of  the  placenta  is  formed  by  the 
decidua  placentalis  containing  the  intervillous  space.  iVs  already  explained,  this 
space  is  produced  by  the  enlargement  and  intercommunication  of  the  spaces  in 
the  trophoblastic  network.  The  changes  involve  the  disappearance  of  the  greater 
portion  of  the  stratum  compactum,  but  the  deeper  part  of  this  layer  persists  and 
is  condensed  to  form  what  is  known  as  the  basal  plate.  Between  this  plate  and 
the  uterine  muscular  fibres  are  the  stratum  spongiosum  and  the  boundary  layer; 


DEVELOPMENT  OF  THE  FETAL   MEMBRANES  AND  THE  PLACENTA     101 


,        .  Umbilical 

Amnion     chorion    artery  Umbilical 
vein 


through  these  and  the  basal  phite  the  uterine  arteries  and  veins  pass  to  and  from 
the  intervillous  space.  The  endothelial  lining  of  the  uterine  vessels  ceases  at  the 
point  where  they  terminate  in  the  intervillous  space  which  is  lined  by  the  syncytio- 
trophoblast.  Portions  of  the  stratum  compactum  persist  and  are  condensed  to 
form  a  series  of  septa,  which  extend  from  the  basal  plate  through  the  thickness 
of  the  placenta  and  subdivide  it  into  the  lobules  or  cotyledons  seen  on  the  uterine 
surface  of  the  detached  placenta. 

The  fetal  and  maternal  blood  currents  traverse  the  placenta,  the  former  passing 
through  the  bloodvessels  of  the  placental  villi  and  the  latter  through  the  inter- 
vihous  space  (Fig.  93) .  The  two  currents  do  not  intermingle,  being  separated  from 
each  other  by  the  delicate  walls  of  the  villi.  Nevertheless,  the  fetal  blood  is  able 
to  absorb,  through  the  walls  of  the  villi,  oxygen  and  nutritive  materials  from  the 
maternal  blood,  and  give  up  to  the  latter  its  waste  products.  The  blood,  so  purified, 
is  carried  back  to  the  fetus  by  the  umbilical  vein.  It  w^ill  thus  be  seen  that  the 
placenta  not  onl}^  establishes  a  mechan- 
ical connection  between  the  mother 
and  the  fetus,  but  subserves  for  the 
latter  the  purposes  of  nutrition,  respi- 
ration, and  excretion.  In  favor  of  the 
view  that  the  placenta  possesses  certain 
selective  powders  may  be  mentioned  the 
fact  that  glucose  is  more  plentiful  in 
the  maternal  than  in  the  fetal  blood. 
It  is  interesting  to  note  also  that  the 
proportion  of  iron,  and  of  lime  and 
potash,  in  the  fetus  is  increased  during 
the  last  months  of  pregnancy.  Further, 
there  is  evidence  that  the  maternal  leu- 
cocytes may  migrate  into  the  fetal  blood, 
since  leucoc}i;es  are  much  more  numer- 
ous in  the  blood  of  the  umbilical  vein 
than  in  that  of  the  umbilical  arteries. 

The  placenta  is  usually  attached 
near  the  fundus  uteri,  and  more  fre- 
quently on  the  posterior  than  on  the 
anterior  wall  of  the  uterus.  It  may, 
however,  occupy  a  lower  position  and, 
in  rare  cases,  its  site  is  close  to  the 
orificium  internum  uteri,  which  it  may 
occlude,  thus  giving  rise  to  the  con- 
dition known  as  placenta  praeoia. 

Separation  of  the  Placenta. — After  the  child  is  born,  the  placenta  and  membranes 
are  expelled  from  the  uterus  as  the  after-birth.  The  separation  of  the  placenta  from 
the  uterine  wall  takes  place  through  the  stratum  spongiosum,  and  necessarily 
causes  rupture  of  the  uterine  vessels.  The  orifices  of  the  torn  vessels  are,  however, 
closed  by  the  firm  contraction  of  the  uterine  muscular  fibres,  and  thus  postpartum 
hemorrhage  is  controlled.  The  epithelial  lining  of  the  uterus  is  regenerated  by  the 
proliferation  and  extension  of  the  epithelium  which  lines  the  persistent  portions 
of  the  uterine  glands  in  the  unaltered  layer  of  the  decidua. 

The  expelled  placenta  appears  as  a  discoid  mass  which  weighs  about  450  gm. 
and  has  a  diameter  of  from  15  to  20  cm.  Its  average  thickness  is  about  3  cm., 
but  this  diminishes  rapidly  toward  the  circumference  of  the  disk,  which  is  continu- 
ous with  the  membranes.  Its  uterine  surface  is  divided  by  a  series  of  fissures  into 
lobules  or  cotyledons,  the  fissures  containing  the  remains  of  the  septa  which  extended 


Uterine  vein       Uterine  aHery 
Fig.  93. — Scheme  of  placental  circulation. 


102  EMBRYOLOGY- 

between  the  maternal  and  fetal  portions.  ]Most  of  these  septa  end  in  irregular 
or  pointed  processes;  others,  especially  those  near  the  edge  of  the  placenta,  pass 
through  its  thickness  and  are  attached  to  the  chorion.  In  the  early  months  these 
septa  convey  branches  of  the  uterine  arteries  which  open  into  the  intervillous 
space  on  the  surfaces  of  the  septa.  The  fetal  surface  of  the  placenta  is  smooth, 
being  closely  invested  by  the  amnion.  Seen  through  the  latter,  the  chorion  presents 
a  mottled  appearance,  consisting  of  gray,  purple,  or  yellowish  areas.  The  umbilical 
cord  is  usually  attached  near  the  centre  of  the  placenta,  but  may  be  inserted  any- 
where between  the  centre  and  the  margin ;  in  some  cases  it  is  inserted  into  the  mem- 
branes, i.  e.,  the  velamentous  insertion.  From  the  attachment  of  the  cord  the  larger 
branches  of  the  umbilical  A'essels  radiate  under  the  amnion,  the  veins  being  deeper 
and  larger  than  the  arteries.  The  remains  of  the  vitelline  duct  and  yolk-sac  may 
be  sometimes  observed  beneath  the  amnion,  close  to  the  cord,  the  former  as  an 
attenuated  thread,  the  latter  as  a  minute  sac. 

On  section,  the  placenta  presents  a  soft,  spongy  appearance,  caused  by  the 
greatly  branched  villi;  surrounding  them  is  a  varying  amount  of  maternal  blood 
giving  the  dark  red  color  to  the  placenta.  Many  of  the  larger  villi  extend  from 
the  chorionic  to  the  decidual  surface,  while  others  are  attached  to  the  septa  which 
separate  the  cotyledons;  but  the  great  majority  of  the  villi  hang  free  in  the  inter- 
villous space. 

The  further  growth  of  the  embryo  will  be  best  understood  from  a  description  of 
the  principal  facts  relating  to  the  development  of  the  chief  systems  of  which  the 
body  consists. 

DEVELOPMENT    OF    THE    PARIETES. 

The  Skeleton. — The  skeleton  is  of  mesodermal  origin,  and  may  be  divided  into 
{a)  that  of  the  trunk  (axial  skeleton),  comprising  the  vertebral  column,  skull,  ribs, 
and  sternum,  and  (b)  that  of  the  limbs  (appendicular  skeleton). 

The  Vertebral  Column. — The  notochord  (Fig.  77)  is  a  temporary  structure  and 
forms  a  central  axis,  around  which  the  segments  of  the  vertebral  column  are  devel- 
oped.^ It  is  derived  from  the  entoderm,  and  consists  of  a  rod  of  cells,  which  lies 
on  the  ventral  aspect  of  the  neural  tube  and  reaches  from  the  anterior  end  of  the 
mid-brain  to  the  extremity  of  the  tail.  On  either  side  of  it  is  a  column  of  paraxial 
mesoderm  which  becomes  subdivided  into  a  number  of  more  or  less  cubical  seg- 
ments, the  primitive  segments  (Figs.  77  and  78).  These  are  separated  from  one 
another  by  intersegmental  septa  and  are  arranged  symmetrically  on  either  side  of 
the  neural  tube  and  notochord:  to  every  segment  a  spinal  nerve  is  distributed. 
At  first  each  segment  contains  a  central  cavity,  the  myocoel,  but  this  is  soon  filled 
with  a  core  of  angular  and  spindle-shaped  cells.  The  cells  ,of  the  segment  become 
differentiated  into  three  groups,  which  form  respectively  the  cutis-plate  or  derma- 
tome, the  muscle-plate  or  myotome,  and  the  sclerotome  (Fig.  94).  The  cutis-plate 
is  placed  on  the  lateral  and  dorsal  aspect  of  the  myocoel,  and  from  it  the  true  skin 
of  the  corresponding  segment  is  derived;  the  muscle-plate  is  situated  on  the  medial 
side  of  the  cutis-plate  and  furnishes  the  muscles  of  the  segment.  The  cells  of  the 
sclerotome  are  largely  derived  from  those  forming  the  core  of  the  myocoel,  and  lie 
next  the  notochord.  Fusion  of  the  indi^'idual  sclerotomes  in  an  antero-posterior 
direction  soon  takes  place,  and  thus  a  continuous  strand  of  cells,  the  sclerotogenous 
layer,  is  formed  along  the  ventro-lateral  aspects  of  the  neural  tube.  The  cells  of 
this  layer  proliferate  rapidly,  and  extending  medialward  surround  the  notochord; 
at  the  same  time  they  grow  backward  on  the  lateral  aspects  of  the  neural  tube 
and  eventually  surround  it,  and  thus  the  notochord  and  neural  tube  are  enveloped 

'  In  the  amphioxus  the  notochord  persists  and  forms  the  only  representative  of  a  skeleton  in  that  animal. 


DEVELOPMENT  OF  THE  PARIETES 


103 


by  a  continuous  sheath  of  mesoderm,  which  is  termed  the  membranous  vertebral 
column.  In  this  mesoderm  the  original  segments  are  still  distinguishahle,  but  each 
is  now  differentiated  into 
two  portions,  an  anterior, 
consisting  of  loosely  arranged 
cells,  and  a  posterior,  of 
more  condensed  tissue  (Fig. 
95,  .1  and  B).  Between  the 
two  portions  the  rudiment 
of  the  intervertebral  fibro- 
cartilage  is  laid  down  (Fig. 
95,  C).  Cells  from  the  pos- 
terior mass  grow  into  the 
intervals  between  the  myo- 
tomes (Fig.  95,  B  and  C)  of 
the  corresponding  and  suc- 
ceeding segments,  and  extend 
both  dorsally  and  ventrally; 
the  dorsal  extensions  sur- 
round the  neural  tube  and 
represent  the  future  verte- 
bral arch,  while  the  ventral 
extend  into  the  body-wall 
as  the  costal  processes.  The 
hinder  part  of  the  posterior 
mass  joins  the  anterior  mass 
of  the  succeeding  segment 
to  form  the  vertebral  body. 
Each  vertebral  body  is  there- 
fore a  composite  of  two  segments,  being  formed  from  the  posterior  portion  of 
one  segment  and  the  anterior  part  of  that  immediately  behind  it.    The  vertebral 


Fig.  94. — Transverse  section  of  a  human  embryo  of  the  third  week 
to  show  the  differentiation  of  the  primitive  segment.  (KoUmann.)  ao. 
Aorta,  m.p.  Muscle-plate,  n.c.  Neural  canal,  sc.  Sclerotome,  s.p. 
cutis-plate. 


Myotome 

I     Anterior  portion  of  sclerotome 
Notochord 

Posterior  portion  of  sclerotome 
1  ntermyolomic  septum 
Costal  process 


::":>.■ 


7^ 


LVii^ 


Intervertebral 
fibrocartilage 

Notochord 


Fig.  95. — Scheme  showing  the  manner  in  which  each  vertebral  centrum  is  developed  from  portions  of  two  adjacent 

segments. 


and  costal  arches  are  derivatives  of  the  posterior  part  of  the  segment  in  front 
of  the  intersegmental  septum  with  which  they  are  associated. 


104 


EMBRYOLOGY 


This  stage  is  succeeded  by  that  of  the  cartilaginous  vertebral  column.  In  the 
fourth  week  two  cartilaginous  centres  make  their  aj^ijearancc,  one  on  either  side  of 
the  notochord;  these  extend  around  the  notochord  and  form  the  body  of  the  cartil- 
aginous vertebra.  A  second  pair  of  cartilaginous  foci  appear  in  the  lateral  parts  of 
the  vertebral  bow,  and  grow  backward  on  either  side  of  the  neural  tube  to  form 
the  cartilaginous  vertebral  arch,  and  a  separate  cartilaginous  centre  appears  for 
each  costal  process.  By  the  eighth  week  the  cartilaginous  arch  has  fused  with  the 
body,  and  in  the  fourth  month  the  two  halves  of  the  arch  are  joined  on  the  dorsal 
aspect  of  the  neural  tube.  The  spinous  process  is  developed  from  the  junction  of 
the  two  halves  of  the  vertebral  arch.  The  transverse  process  grows  out  from  the 
vertebral  arch  behind  the  costal  process. 

In  the  upper  cervical  vertebrae  a  band  of  mesodermal  tissue  connects  the  ends  of 
the  vertebral  arches  across  the  ventral  surfaces  of  the  intervertebral  fibrocartilages. 
This  is  termed  the  hypochordal  bar  or  brace;  in  all  except  the  first  it  is  transitory 
and  disappears  by  fusing  with  the  fibrocartilages.  In  the  atlas,  however,  the  entire 
bow  persists  and  undergoes  chondrification;  it  develops  into  the  anterior  arch  of  the 
bone,  while  the  cartilage  representing  the  body  of  the  atlas  forms  the  dens  or 
odontoid  process  which  fuses  with  the  body  of  the  second  cervical  vertebra. 


Anterior 

longitudinal 

ligamevt 


P  osier  io'rlong  it  udinal 

ligament 
Cartilaginous  end 

of  vertebral  body 

Nucleus  pidjjosus 

Intervertebral  fibro- 
cartilage 

Slight  enkirgemerii 
of  ivotocJiord  in 

the  cartilagirums 
vertebral  body 


Fig.  96. — Sagittal  section  through  an  intervertebral  fibrocartilage  and  adjacent  parts  of  two  vertebrsE  of  an  advanced 

sheep's  embrj-o.     (Kolliker.) 


The  portions  of  the  notochord  which  are  surrounded  by  the  bodies  of  the  verte- 
brse  atrophy,  and  ultimately  disappear,  while  those  which  lie  in  the  centres  of  the 
intervertebral  fibrocartilages  undergo  enlargement,  and  persist  throughout  life  as 
the  central  nucleus  pulposus  of  the  fibrocartilages  (Fig.  96). 

The  Ribs. — The  ribs  are  formed  from  the  ventral  or  costal  processes  of  the 
primitive  vertebral  bows,  the  processes  extending  between  the  muscle-plates.  In 
the  thoracic  region  of  the  vertebral  column  the  costal  processes  grow  lateralward  to 
form  a  series  of  arches,  the  primitive  costal  arches.  As  already  described,  the 
transverse  process  grows  out  behind  the  vertebral  end  of  each  arch.  It  is  at  first 
connected  to  the  costal  process  by  continuous  mesoderm,  but  this  becomes  differ- 
entiated later  to  form  the  costotransverse  ligament;  between  the  costal  process 
and  the  tip  of  the  transverse  process  the  costotransverse  joint  is  formed  by 
absorption.  The  costal  process  becomes  separated  from  the  vertebral  bow  by  the 
development  of  the  costocentral  joint.  In  the  cervical  vertebras  (Fig.  97)  the  trans- 
verse process  forms  the  posterior  boundary  of  the  foramen  transversarium,  while 
the  costal  process  corresponding  to  the  head  and  neck  of  the  rib  fuses  with  the 


DEVELOPMENT  OF  THE  PARIETES 


105 


body  of  the  vertebra,  and  forms  the  antero-lateral  boundary  of  the  foramen.  The 
distal  portions  of  the  primitive  costal  arches  remain  undeveloped;  occasionally 
the  arch  of  the  seventh  cervical  vertebra  undergoes  greater  development,  and  by 
the  formation  of  costovertebral  joints  is  separated  off  as  a  rib.  In  the  lumbar 
region  the  distal  portions  of  the  primitive  costal  arches  fail;  the  proximal  portions 
fuse  with  the  trans^'erse  processes  to  form  the  transverse  processes  of  descriptive 
anatomy.  Occasionally  a  movable  rib  is  developed  in  connection  with  the  first 
lumbar  ^•ertebra.  In  the  sacral  region  costal  processes  are  developed  only  in 
connection  with  the  upper  three,  or  it  may  be  four,  vertebrae;  the  processes  of 
adjacent  segments  fuse  with  one  another  to  form  the  lateral  parts  of  the  sacrum. 
The  coccygeal  vertehrce  are  devoid  of  costal  processes. 


CERVICAL 


LUMBAR 


THORACIC 


SACRAL 


Fig.  97. — Diagrams  showing  the  portions  of  the  adult  vertebrse  derived  respectively  from  the  bodies,  vertebral 
arches,  and  costal  processes  of  the  embryonic  vertebrae.  The  bodies  are  represented  in  yellow,  the  vertebral  arches 
in  red,  and  the  costal  processes  in  blue. 


The  Sternum. — ^The  ventral  ends  of  the  ribs  become  united  to  one  another  by  a 
longitudinal  bar  termed  the  sternal  plate,  and  opposite  the  first  seven  pairs  of  ribs 
these  sternal  plates  fuse  in  the  middle  line  to  form  the  manubrium  and  body  of  the 
sternum.  The  xiphoid  process  is  formed  by  a  backward  extension  of  the  sternal 
plates. 

The  Skull,- — Up  to  a  certain  stage  the  development  of  the  skull  corresponds  with 
that  of  the  vertebral  column;  but  it  is  modified  later  in  association  with  the  expan- 
sion of  the  brain-vesicles,  the  formation  of  the  organs  of  smell,  sight,  and  hearing, 
and  the  development  of  the  mouth  and  pharynx. 


106 


EMBRYOLOGY 


Fossa 
hypophyseos 


Mesoderm  of  base 
of  skull 


Parachordal 
cartilage 


The  notochord  extends  as  far  forward  as  the  anterior  end  of  the  mid-})rain,  and 
becomes  partly  surrounded  by  mesoderm  (Fig.  98).  The  posterior  part  of  this  meso- 
dermal investment  corresponds  with  the  basilar  part  of  the  occipital  bone,  and  shows 
a  subdivision  into  four  segments,  which  are  separated  by  the  roots  of  the  hypo- 
glossal nerve.    The  mesoderm  then  extends  over  the  brain-vesicles,  and  thus  the 

entire  brain  is  enclosed  by  a  mesodermal 
investment,  which  is  termed  the  membran- 
ous cranium.  From  the  inner  layer  of  this 
the  bones  of  the  skull  and  the  membranes 
of  the  brain  are  developed;  from  the  outer 
layer  the  muscles,  bloodvessels,  true  skin, 
and  subcutaneous  tissues  of  the  scalp.  In 
the  shark  and  dog-fish  this  membranous 
cranium  undergoes  complete  chondrifi- 
cation,  and  forms  the  cartilaginous  skull 
or  chondrocranium  of  these  animals.  In 
mammals,  on  the  other  hand;  the  process 
of  chondrification  is  limited  to  the  base 
of  the  skull — the  roof  and  sides  being 
covered  in  by  membrane.  Thus  the  bones 
of  the  base  of  the  skull  are  preceded  by 
cartilage,  those  of  the  roof  and  sides 
by  membrane.  The  posterior  part  of  the 
base  of  the  skull  is  developed  around 
the  notochord,  and  exhibits  a  segmented 
condition  analogous  to  that  of  the  vertebral  column,  while  the  anterior  part  arises 
in  front  of  the  notochord  and  shows  no  regular  segmentation.  The  base  of  the  skull 
may  therefore  be  divided  into  (a)  a  chordal  or  vertebral,  and  (6)  a  prechordal  or 
prevertebral  portion. 

Situation  of  olfactory  pit     Ethmoid  plate 

and  nasal     Olfactory  organ 


Anterior  arch  of  atlas 

Notochord 
Body  of  axis 

Third  cervical 
vertebra 


Fig.  98. — Sagittal   section  of  cephalic   end  of 
chord.    (Keibel.) 


Fossa 
hypophyseos 


Trahecula  _ 
cranii 

Situation  of 

auditory 

vesicle 

Parachordal ' 

cartilage 

Notochord' 


Extension  around 
olfactory  organ 
Foramina  for 
olfactory  nerves 

Eyeball 

Fossa 
hypophyseos 


--Basilar  plate 
--Auditory  vesicle 

Notochord 


Fig.  99. — Diagrams  of  the  cartilaginous  cranium.     (Wiedersheim.) 


In  the  lower  vertebrates  two  pairs  of  cartilages  are  developed,  viz.,  a  pair  of 
parachordal  cartilages,  one  on  either  side  of  the  notochord;  and  a  pair  of  pre- 
chordal cartilages,  the  trabeculae  cranii,  in  front  of  the  notochord  (Fig.  99).  The 
parachordal  cartilages  (Fig.  99)  unite  to  form  a  basilar  plate,  from  which  the  car- 
tilaginous part  of  the  occipital  bone  and  the  basi-sphenoid  are  developed.  On  the 
lateral  aspects  of  the  parachordal  cartilages  the  auditory  vesicles  are  situated. 


DEVELOPMENT  OF  THE  PARIETES 


\o: 


and  tlie  mesodt^rni  en('l()sin<>;  them  is  soon  converted  into  cartilage,  forming  the 
cartilaginous  ear-capsules.  These  cartiUiginous  ear-capsules,  which  are  of  an  oval 
shape,  fuse  with  the  sides  of  the  basilar  plate,  and  from  them  arise  the  petrous 
and  mastoid  portions  of  the  temporal  bones.  The  trabeculae  cranii  (Fig.  99)  are 
two  curved  bars  of  cartilage  which  embrace  the  hypophysis  cerebri;  their  posterior 
ends  soon  unite  with  the  basilar  ])late,  while  their  anterior  ends  join  to  form  the 
ethmoidal  plate,  which  extends  forward  between  the  fore-brain  and  the  olfactory 
pits.    Later  the  trabeculae  meet  and  fuse  below  the  hypophysis,  forming  the  floor 


Crista  galll 


Cribriform  plate 


MecheVs  cartilage 
Malleus 
Incus 

Int.  acoustic  meat. 

Jugular  foramen 

Fossa  subarcuata 


Canal  for  hypoglossal  nerve 


Small  wing  of  sphenoid 
Optic  foramen 

Great  wing  of 

sphenoid 

Sella  turcica 

Do7'sum  sellae 

Canal  for  facial 

nerve 

Ear  capsule 
—  Ductus  endol. 


Foramen  magnum 


Fig.   100. — Model  of  the  chondrocranium  of  a  human  embryo,  8  cm.  long. 

not  represented. 


(Hertwig.       The  membrane  bones  are 


of  the  fossa  hypophyseos  and  so  cutting  off  the  anterior  lobe  of  the  hypophysis 
from  the  stomodeum.  The  median  part  of  the  ethmoidal  plate  forms  the  bony 
and  cartilaginous  parts  of  the  nasal  septum.  From  the  lateral  margins  of  the 
trabeculae  cranii  three  processes  grow  out  on  either  side.  The  anterior  forms  the 
ethmoidal  labyrinth  and  the  lateral  and  alar  cartilages  of  the  nose;  the  middle 
gives  rise  to  the  small  wing  of  the  sphenoid,  while  from  the  posterior  the  great 
wing  and  lateral  pterygoid  plate  of  the  sphenoid  are  developed  (Figs.  100,  101). 
The  bones  of  the  vault  are  of  membranous  formation,  and  are  termed  dermal  or 
covering  bones.    They  are  partly  developed  from  the  mesoderm  of  the  membranous 


108 


EMBRYOLOGY 


cranium,  and  partly  from  that  which  lies  outside  the  entoderm  of  the  fore- 
gut.  They  comprise  the  upper  part  of  the  occipital  squama  (interparietal),  the 
squamse  and  tympanic  parts  of  the  temporals,  the  parietals,  the  frontal,  the  vomer, 
the  medial  pterj^goid  plates,  and  the  bones  of  the  face.  Some  of  them  remain 
distinct  throughout  life,  e.  g.,  parietal  and  frontal,  while  others  join  with  the  bones 
of  the  chondrocranium,  e.  g.,  interparietal,  squamse  of  temporals,  and  medial 
pterygoid  plates. 

Recent  observations  have  shown  that,  in  mammals,  the  basi-cranial  cartilage, 
both  in  the  chordal  and  prechordal  regions  of  the  base  of  the  skull,  is  developed 
as  a  single  plate  which  extends  from  behind  forward.  In  man,  however,  its  posterior 
part  shows  an  indication  of  being  developed  from  two  chondrifying  centres  which 
fuse  rapidly  in  front  and  below.  The  anterior  and  posterior  thirds  of  the  cartilage 
surround  the  notochord,  but  its  middle  third  lies  on  the  dorsal  aspect  of  the  noto- 
chord,  which  in  this  region  is  placed  between  the  cartilage  and  the  wall  of  the 
pharynx. 

Optic  foramen     Small  wing  of  sphenoid 


Great  wing  of  iphenoid 


Nasal 
capsule 


Vomer 


Palatine 
bone 


Mandible 


Thyroid  cart. 


Canal  for  hypoglossal 

nerve 


Fig.  101. 


-The  same  model  as  shown  in  Fig.  100  from  the  left  side.     Certain  of  the  membrane  bones  of  the  right  side 
are  represented  in  yellow. 


The  Branchial  or  Visceral  Arches  and  Pharyngeal  Pouches.— In  the  lateral  walls 
of  the  anterior  part  of  the  fore-gut  five  pharyngeal  pouches  appear  (Fig,  104) ;  each 
of  the  upper  four  pouches  is  prolonged  into  a  dorsal  and  a  ventral  diverticulum. 
Over  these  pouches  corresponding  indentations  of  the  ectoderm  occur,  forming  what 
are  known  as  the  branchial  or  outer  pharyngeal  grooves.  The  intervening  mesoderm 
is  pressed  aside  and  the  ectoderm  comes  for  a  time  into  contact  with  the  ento- 
dermal  lining  of  the  fore-gut,  and  the  two  layers  unite  along  the  floors  of  the 
grooves  to  form  thin  closing  membranes  between  the  fore-gut  and  the  exterior. 
Later  the  mesoderm  again  penetrates  between  the  entoderm  and  the  ectoderm. 
In  gill-bearing  animals  the  closing  membranes  disappear,  and  the  grooves  become 
complete  clefts,  the  gill-clefts,  opening  from  the  pharynx  on  to  the  exterior;  perfor- 
ation, however,  does  not  occur  in  birds  or  mammals.  The  grooves  separate  a 
series  of  rounded  bars  or  arches,  the  branchial  or  visceral  arches,  in  which  thickening 
of  the  mesoderm  takes  place  (Figs.  102  and  103).  The  dorsal  ends  of  these  arches 
are  attached  to  the  sides  of  the  head,  while  the  ventral  extremities  ultimately 
meet  in  the  middle  line  of  the  neck.     In  all,  six  arches  make  their  appearance, 


DEVELOPMENT  OF  THE  PARIETES 


109 


but  of  these  only  the  first  four  are  visible  externally.  The  first  arch  is  named  the 
mandibular,  and  the  second  the  hyoid;  the  others  have  no  distinctive  names. 
In  each  arch  a  cartilaginous  bar,  consisting  of  right  and  left  halves,  is  developed, 
and  with  each  of  these  there  is  one  of  the  primitive  aortic  arches. 


Mid-hrain 


Forc-hrain 
Stomodeum 
Muiidibal((r  arch 
Heart 


11  tnd-hrain 

Auditory  vesicle 


V  isceral 
arches 


Imnion  (cut) 


Olfactory  pit 
Maxillary  process 

Mandibular  arch 

Hyoid  aich      i 

Third  arch  " 


Fig.  102. — Embryo  between  eighteen  and  twenty-one 
days.     (His.) 


Fig.   103. — Head  end  of  human  embryo,  about  the  end 
of  the  fourth  week.    (From  model  by  Peter.) 


Lateral  tongue    Thyroid 
elevations     diverticulum 


The  mandibular  arch  lies  between  the  first  branchial  groove  and  the  stomodeum; 
from  it  are  developed  the  lower  lip,  the  mandible,  the  muscles  of  mastication, 
and  the  anterior  part  of  the  tongue.  Its  cartilaginous  bar  is  formed  by  what 
are  known  as  Meckel's  cartilages  (right  and  left)  (Fig.  105).  The  dorsal  ends  of 
these  cartilages  are  connected  with  the  ear- 
capsules  and  are  ossified  to  form  two  of  the 
bones  of  the  middle  ear,  the  malleus  and 
incus;  the  ventral  ends  meet  each  other  in 
the  region  of  the  symphysis  menti,  and  are 
usually  regarded  as  undergoing  ossification 
to  form  that  portion  of  the  mandible  which 
contains  the  incisor  teeth.  The  intervening 
part  of  the  cartilage  disappears;  the  portion 
immediately  adjacent  to  the  malleus  and 
incus  is  replaced  by  fibrous  membrane,  which 
constitutes  the  spheno-mandibular  ligament, 
while  from  the  connective  tissue  covering 
the  remainder  of  the  cartilage  the  greater 
part  of  the  mandible  is  ossified.    From  the 

dorsal  ends  of  the  mandibular  arch  a  triangular  process,  the  maxillary  process,  grows 
forward  on  either  side  and  forms  the  cheek  and  lateral  part  of  the  upper  lip.  The 
second  or  hyoid  arch  assists  in  forming  the  side  and  front  of  the  neck.  From  its 
cartilage  are  developed  the  styloid  process,  stylohyoid  ligament,  and  lesser  cornu 
of  the  hyoid  bone.  The  cartilage  of  the  third  arch  gives  origin  to  the  greater 
cornu  of  the  hyoid  bone.  The  ventral  ends  of  the  second  and  third  arches  unite 
with  those  of  the  opposite  side,  and  form  a  transverse  band,  from  which  the  body  of 


Fig. 


Entrance  to 
larynx 


104. — Floor  of  pharynx  of  embrvo  shown  in 
Fig.  103. 


no 


EMBRYOLOGY 


the  hyoid  bone  and  the  posterior  part  of  tlie  tongue  are  developed.  The  ventral 
portions  of  the  cartilages  of  the  fourth  and  fifth  arches  unite  to  form  the  thyroid 
cartilage;  from  the  cartilages  of  the  sixth  arch  the  cricoid  and  arytenoid  cartilages 
and  the  cartilages  of  the  trachea  are  developed.  The  mandibular  and  hyoid 
arches  grow  more  rapidly  than  those  behind  them,  with  the  result  that  the  latter 


Malleus 


Incus 


,,''  Tympanic  ring 
.'''Mandible 


_./Z- MeckeVs  cartilage 


-  Hyoid  hone 


Fig.   105. — Head  and  neck  of  a  human  embrvo  eighteen  weeks  old,  with  Meckel's  cartilage  and  hyoid  bar  exposed. 

(After  Kolliker.) 

become,  to  a  certain  extent,  telescoped  within  the  former,  and  a  deep  depression, 
the  sinus  cervicalis,  is  formed  on  either  side  of  the  neck.  This  sinus  is  bounded  in 
front  by  the  hyoid  arch,  and  behind  by  the  thoracic  wall;  it  is  ultimately  obliterated 
by  the  fusion  of  its  walls. 


Membranous  capsule  over  cerebral  hemisphere 
\ 


Fronto-nasal  process 


Stomodeum 


Lateral  nasal  process 

Eye 

Globular  process 
Maxillary  process 

Mandibular  arch 
Hyonuindibidar  cleft 

Fig.   106. — Under  surface  of  the  head  of  a  human  embryo  about  twenty-nine  days  old.     (After  His.) 

From  the  first  branchial  groove  the  concha  auriculae  and  external  acoustic 
meatus  are  developed,  while  around  the  groove  there  appear,  on  the  mandibular 
and  hyoid  arches,  a  number  of  swellings  from  which  the  auricula  or  pinna  is  formed. 
The  first  pharyngeal  pouch  is  prolonged  dorsally  to  form  the  auditory  tube  and  the 
tympanic  cavity;  the  closing  membrane  between  the  mandibular  and  hyoid  arches 


DEVELOPMENT  OF  THE  PARIETES 


111 


is  invaded  by  mesoderm,  and  forms  the  tympanic  membrane.  No  traces  of  the 
second,  third,  and  fourth  branchial  grooves  persist.  The  inner  part  of  the  second 
pliaryngeal  pouch  is  named  the  sinus  tonsillaris;  in  it  the  tonsil  is  developed,  above 
which  a  trace  of  the  sinus  persists  as  the  suj)rat()nsillar  fossa.  The  fossa  of  Rosen- 
miiller  or  lateral  recess  of  the  pharynx  is  by  some  regarded  as  a  persistent  part  of 
the  second  pharyngeal  pouch,  but  it  is  probably  developed  as  a  secondary  forma- 
tion. From  the  third  pharyngeal  pouch  the  thymus  arises  as  an  entodermal  diver- 
ticulum on  either  side,  and  from  the  fourth  pouches  small  diverticula  project  and 
become  incorporated  with  the  thymus,  but  in  man  these  diverticula  probably 
never  form  true  thymus  tissue.  The  parathyroids  also  arise  as  diverticula  from 
the  third  and  fourth  pouches.  From  the  fifth  pouches  the  ultimobranchial  bodies 
originate  and  are  enveloped  by  the  lateral  prolongations  of  the  median  thyroid 
rudiment;  they  do  not,  however,  form  true  thyroid  tissue,  nor  are  any  traces 
of  them  found  in  the  human  adult. 


Future  apex  of  nose 

Medial  nasal  'process 

Olfactory  pit 
Lateral  nasal  process 
Glcbular  process 
Maxillary  process 
Stomodeum 
Mandibular  arch 


Future  apex  of  iwse 

Medial  nasal  process 

Olfactory  pit 

Lateral  nasal  process 

Clohidar  process 
Maxillary  process 

Roof  of  plmrynx 
Hypophyseal  diverticidmn 

Dorsal  wall  of  pharynx 


Fig.  107. — Head  end  of  human  embryo  of  about  thirty 
to  thirty-one  days.     (From  model  bj^  Peter.) 


Fig.   108. — Same  embryo  as  shown  in  Fig.   107,  with  front 
wall  of  pharynx  removed. 


The  Nose  and  Face. — During  the  third  week  tw^o  areas  of  thickened  ectoderm,  the 
olfactory  areas,  appear  immediately  under  the  fore-brain  in  the  anterior  wall  of  the 
stomodeum,  one  on  either  side  of  a  region  termed  the  fronto-nasal  process  (Fig.  106). 
By  the  upgrowth  of  the  surrounding  parts  these  areas  are  converted  into  pits, 
the  olfactory  pits,  which  indent  the  fronto-nasal  process  and  divide  it  into  a 
medial  and  two  lateral  nasal  processes  (Fig.  107).  The  rounded  lateral  angles  of 
the  medial  process  constitute  the  globular  processes  of  His.  The  olfactory  pits  form 
the  rudiments  of  the  nasal  cavities,  and  from  their  ectodermal  lining  the  epithe- 
lium of  the  nasal  cavities,  with  the  exception  of  that  of  the  inferior  meatuses,  is 
deriA^ed.  The  globular  processes  are  prolonged  backward  as  plates,  termed  the  nasal 
laminae:  these  laminte  are  at  first  some  distance  apart,  but,  gradually  approach- 
ing, they  ultimately  fuse  and  form  the  nasal  septum;  the  processes  themselves 
meet  in  the  middle  line,  and  form  the  premaxillse  and  the  philtrum  or  central 
part  of  the  upper  lip  (Fig.  110).  The  depressed  part  of  the  medial  nasal  process 
between  the  globular  processes  forms  the  lower  part  of  the  nasal  septum  or 
columella;  while  above  this  is  seen  a  prominent  angle,  which  becomes  the  future 


112 


EMBRYOLOGY 


apex  (Figs.  107,  108),  and  still  higher  a  flat  area,  the  future  l>ri(lge,  of  the  nose. 
The  lateral  nasal  processes  form  the  alte  of  the  nose. 

Continuous  with  the  dorsal  end  of  the  mandibular  arch,  and  growing  forward 
from  its  cephalic  border,  is  a  triangular  process,  the  maxillary  process,  the  ventral 
extremity  of  which  is  separated  from  the  mandibular  arch  by  a  ^  shaped  notch 
(Fig.  106).  The  maxillary  process  forms  the  lateral  wall  and  floor  of  the  orbit, 
and  in  it  are  ossified  the  zygomatic  bone  and  the  greater  part  of  the  maxilla;  it 
meets  with  the  lateral  nasal  process,  from  which,  however,  it  is  separated  for  a 
time  by  a  groove,  the  naso-optic  furrow,  that  extend  from  the  furrow  encircling 
the  eyeball  to  the  olfactory  pit.  The  maxillary  processes  ultimately  fuse  with  the 
lateral  nasal  and  globular  processes,  and  form  the  lateral  parts  of  the  upper  lip 
and  the  posterior  boundaries  of  the  nares  (Figs.  109,  110).  From  the  third  to 
the  fifth  month  the  nares  are  filled  by  masses  of  epithelium,  on  the  breaking  down 
and  disappearance  of  which  the  permanent  openings  are  produced.  The  maxillary 
process  also  gives  rise  to  the  lower  portion  of  the  lateral  wall  of  the  nasal  cavity. 


Lateral  nasal  pro- 
cess 
Globular  processes 


Fig.  109. — Head  of  a  human  embryo  of 
about  eight  weeks,  in  which  the  nose  and 
mouth  are  formed.     (His.) 


Fig.   110. — Diagram  showing  the  regions  of  the  adult  face  and  neck 
related  to  the  fronto-nasal  process  and  the  branchial  arches. 


The  roof  of  the  nose  and  the  remaining  parts  of  the  lateral  wall,  viz.,  the  ethmoidal 
labyrinth,  the  inferior  nasal  concha,  the  lateral  cartilage,  and  the  lateral  crus  of 
the  alar  cartilage,  are  developed  in  the  lateral  nasal  process.  By  the  fusion  of  the 
maxillary  and  nasal  processes  in  the  roof  of  the  stomodeum  the  primitive  palate 
(Fig.  Ill)  is  formed,  and  the  olfactory  pits  extend  backward  above  it.  The  pos- 
terior end  of  each  pit  is  closed  by  an  epithelial  membrane,  the  bucconasal  membrane, 
formed  by  the  apposition  of  the  nasal  and  stomodeal  epithelium.  By  the  rupture 
of  these  membranes  the  primitive  choanse  or  openings  between  the  olfactory  pits 
and  the  stomodeum  are  established.  The  floor  of  the  nasal  cavity  is  completed 
by  the  development  of  a  pair  of  shelf-like  palatine  processes  which  extend  medial- 
ward  from  the  maxillary  processes  (Figs.  112  and  113);  these  coalesce  with  each 
other  in  the  middle  line,  and  constitute  the  entire  palate,  except  a  small  part  in 
front  which  is  formed  by  the  premaxillary  bones.  Two  apertures  persist  for  a  time 
between  the  palatine  processes  and  the  premaxillse  and  represent  the  permanent 
channels  which  in  the  lower  animals  connect  the  nose  and  mouth.  The  union  of 
the  parts  which  form  the  palate  commences  in  front,  the  premaxillary  and  palatine 
processes  joining  in  the  eighth  week,  while  the  region  of  the  future  hard  palate 
is  completed  by  the  ninth,  and  that  of  the  soft  palate  by  the  eleventh  week.    By 


DFA'ELOl'MEXT  OF  THE  I'AHIETES 


113 


the  t'onipletion  of  the  palate  tiie  permanent  choanae  are  formed  and  are  situated  a 
considerable  distance  behind  tlie  primitive  chc.ana-.  The  (k-formity  known  as 
cleft  palate  results  from  a  non-union  of  the  pahitiiit-  processes,  an<l  that  of  hare- 
lip throufi;h  a  non-union  of  tlie  maxillar\  and  <,dobuhir  processes  (see  pa^e  2\)\)). 
The  nasal  cavity  bec(_)mes  di\ided  by  a  \ertical  septum,  which  extends  downward 
and  backward  from  the  medial  nasal  process  and  nasal  laminae,  and  unites  below 
with  the  palatine  processes.     Tnt(.  this  septum  a  i)lat('  of  cartila^'c  extends  from 


\itrrs 


Primilive 
palate 


Fig.  111. 


Nasal 
cavity 


Bucconasal 
■mtmhranes 

-Primitive  palate  of  a  human  embryo  of  thirty-seven  to  thirty-eight  days.     (From  model  by  Peter.) 
On  the  left  side  the  lateral  wall  of  the  nasal  cavity  has  been  removed. 


the  under  aspect  of  the  ethmoid  plate  of  the  chodrocranium.  The  anterior  part 
of  this  cartilaginous  plate  persists  as  the  septal  cartilage  of  the  nose  and  the  medial 
crus  of  the  alar  cartilage,  but  the  posterior  and  upper  parts  are  replaced  by  the 
vomer  and  perpendicular  plate  of  the  ethmoid.  On  either  side  of  the  nasal  septum, 
at  its  lower  and  anterior  part,  the  ectoderm  is  invaginated  to  form  a  blind  pouch 
or  diverticulum,  which  extends  backward  and  upward  into  the  nasal  septimi  and 


Glchular  process 


Mouth  of  olfactory 
pit,  or  Jiaris 


Palatine  process  of 
globular  'process 

Palatine  part  of 
maxillary  proces 


Maxillary  frocesa 


Pharynx 


Fig.   112 — The  roof  of  the  mouth  of  a  human  embryo,  aged  about  two  and  a  half  months,  showing  the  mode  of 

formation  of  the  palate.     (His.) 


is  supported  by  a  curved  plate  of  cartilage.  These  pouches  form  the  rudiments  of 
the  vomero-nasal  organs  of  Jacobson,  which  open  below,  close  to  the  junction 
of  the  premaxillary  and  maxillary  bones. 

The  Limbs. — The  limbs  begin  to  make  their  appearance  in  the  third  week  as 
small  elevations  or  buds  at  the  side  of  the  trunk  (Fig.  114).  Prolongations  from 
the  muscle-  and  cutis-plates  of  several  primitive  segments  extend  into  each  bud, 
and  carrv  with  them  the  anterior  divisions  of  the  corresponding  spinal  nerves. 


114 


EMBRYOLOGY 


The  nerves  supplying  tlie  lim])s  indicate  the  innn})er  of  primitive  segments  which 
contribute  to  their  formation — the  upper  hmb  being  derived  from  seven,  viz., 
fourth  cervical  to  second  thoracic  inclusive,  and  the  lower  limb  from  ten,  viz., 
twelfth  thoracic  to  fourth  sacral  inclusive.  The  axial  part  of  the  mesoderm  of 
the  limb-bud  becomes  condensed  and  converted  into  its  cartilaginous  skeleton, 
and  by  the  ossification  of  this  the  bones  of  the  limbs  are  formed.  By  the  sixth 
week  the  three  chief  divisions  of  the  limbs  are  marked  off  by  furrows — the  upper 
into  arm,  forearm,  and  hand;  the  lower  into  thigh,  leg,  and  foot  (Fig.  115).  The 
limbs  are  at  first  directed  backward  nearly  parallel  to  the  long  axis  of  the  trunk, 
and  each  presents  two  surfaces  and  two  borders.  Of  the  surfaces,  one — the  future 
flexor  surface  of  the  limb — is  directed  ventrally;  the  other,  the  extensor  surface, 
dorsally;  one  border,  the  preaxial,  looks  forward  toward  the  cephalic  end  of  the 
embryo,  and  the  other,  the  postaxial,  backward  toward  the  caudal  end.  The  lateral 
epicondyle  of  the  humerus,  the  radius,  and  the  thumb  lie  along  the  preaxial  border 


^^>. 


%4. 


Lateral  part 
nasal  capsul 


Injerior  concha — ^  ;.tf!'>f^':;;  :/.V^-:.'^    f'-^-t-^    f;.  ."••■:-;■.  ■    .'- :'.  W'-'-  •.•.•-" 


Cartilage  of 
nasal  septuirk 


Inferior  meatus 

Vomeronasal 
cartilage 


Palatine  process 


Vomeronasal 
organ  of  Jacohson 


■  Inferior  meatus 


Cavity  of  mouth 


Fig.   113. — Frontal  section  of  nasal  cavities  of  a  human  embryo  28  mm.  long.     (Kollmann.) 


of  the  upper  limb ;  and  the  medial  epicondyle  of  the  femur,  the  tibia,  and  the  great 
toe  along  the  corresponding  border  of  the  lower  limb.  The  preaxial  part  is  derived 
from  the  anterior  segments,  the  postaxial  from  the  posterior  segments  of  the  limb- 
bud;  and  this  explains,  to  a  large  extent,  the  innervation  of  the  adult  limb,  the 
nerves  of  the  more  anterior  segments  being  distributed  along  the  preaxial  (radial 
or  tibial),  and  those  of  the  more  posterior  along  the  postaxial  (ulnar  or  fibular) 
border  of  the  limb.  The  limbs  next  undergo  a  rotation  or  torsion  through  an  angle 
of  90°  around  their  long  axes  the  rotation  being  effected  almost  entirely  at  the 
limb  girdles.  In  the  upper  limb  the  rotation  is  outward  and  forward;  in  the  lower 
limb,  inward  and  backward.  As  a  consequence  of  this  rotation  the  preaxial  (radial) 
border  of  the  fore-limb  is  directed  lateralward,  and  the  preaxial  (tibial)  border 
of  the  hind-limb  is  directed  medialward;  thus  the  flexor  surface  of  the  fore-limb 
is  turned  forward,  and  that  of  the  hind-limb  backward. 


DEVELOPMENT  OF  THE  JOISTS 


115 


DEVELOPMENT    OF    THE    JOINTS. 

The  mesuckTin  from  wliicli  tlie  dilt'crcnt  parts  of  tlio  skeleton  are  formed  at 
first  shows  no  differentiation  into  masses  corresponding  with  the  individual  bones. 
Thus  continuous  cores  of  mesoderm  form  the  axes  of  the  Hml)-l)uds  and  a  continu- 
ous cohnnii  of  mesotlerm  the  future  vertebral  column.  The  first  indications  of  the 
bones  and  joints  are  circumscribed  condensations  of  the  mesoderm;  these  condensed 
parts  become  chondrified  antl  finally  ossified  to  form  the  bones  of  the  skeleton. 
The  interN'ening  non-condensed  portions  consist  at  first  of  undifferentiated  meso- 
derm, which  may  develop  in  one  of  three  directions.  It  may  be  converted  into 
fibrous  tissue  as  in  the  case  of  the  skull  bones,  a  synarthrodia!  joint  being  the 
result,  or  it  may  become  partly  cartilaginous,  in  which  case  an  amphiarthrodial 
joint  is  formed.  Again,  it  may  become  looser  in  texture  and  a  cavity  ultimately 
appear  in  its  midst;  the  cells  lining  the  sides  of  this  cavity  form  a  synovial  mem- 
brane and  thus  a  diarthrodial  joint  is  developed. 


Hyoid  arch 
MamLhitlai  a)ch 

Maxillary  piocess 


Heart 


Foie-limb 


Fig.  114.- 


Hind-limb 


-Human  embryo  from  thirty-one  to  thirty- 
four  days.     (His.) 


Auricula 


Fore-limb 


Hind-limh 


Vmhilical  cord 

Fig.   115. — Embryo  of  about  six  weeks. 


(His.) 


The  tissue  surrounding  the  original  mesodermal  core  forms  fibrous  sheaths  for 
the  developing  bones,  i.  e.,  periosteum  and  perichondrium,  which  are  continued 
between  the  ends  of  the  bones  over  the  synovial  membrane  as  the  capsules  of  the 
joints.  These  capsules  are  not  of  uniform  thickness,  so  that  in  them  may  be 
recognized  especially  strengthened  band  which  are  described  as  ligaments.  This, 
however,  is  not  the  only  method  of  formation  of  ligaments.  In  some  cases  by 
modification  of,  or  derivations  from,  the  tendons  surrounding  the  joint,  additional 
ligamentous  bands  are  provided  to  further  strengthen  the  articulations. 

In  several  of  the  movable  joints  the  mesoderm  which  originally  existed  between 
the  ends  of  the  bones  does  not  become  completely  absorbed — a  portion  of  it 
persists  and  forms  an  articular  disk.  These  disks  may  be  intimately  associated  in 
their  development  with  the  muscles  surrounding  the  joint,  e.  g.,  the  menisci  of  the 
knee-joint,  or  with  cartilaginous  elements,  representatives  of  skeletal  structures, 
which  are  vestigial  in  human  anatomy,  e.  g.,  the  articular  disk  of  the  sterno- 
clavicular joint. 


116  EMBRYOLOGY 


DEVELOPMENT    OF    THE    MUSCLES. 


The  voluntary  muscles  are  developed  from  the  mycjtomes  of  the  primitive 
segments.  Portions  of  the  myotomes  retain  their  position  on  the  sides  of 
the  neural  tube,  where  they  may  remain  distinct  from  each  other  and  form 
the  short  muscles  of  the  vertebral  column,  or  fuse  with  corresponding  portions 
of  neighboring  myotomes  to  form  the  Sacrospinales  and  their  continuations. 
Other  portions  of  the  myotomes  extend  into  the  trunk  wall,  where  again  they 
may  retain  their  segmental  condition,  as  in  the  Intercostales,  or  may  fuse  with 
adjacent  segments  to  form  the  flat  muscles  of  the  abdominal  wall.  Finally,  por- 
tions of  the  myotomes  wander  into  the  limb-buds  and  there  undergo  fusions 
and  alterations  in  form  to  produce  the  limb  muscles.  The  original  segmental 
character  of  the  limb  muscles  is  therefore  lost,  but  their  segmental  nerve  supplies 
are  retained.  Some  of  the  limb  muscles  expand  and  migrate  secondarily  toward  the 
mid-dorsal  line,  e.  g.,  Trapezius  and  Latissimus  dorsi,  or  toward  the  mid-ventral 
line,  e.  g.,  Pectoralis  major.  Again,  muscles  may  migrate  in  a  cephalic  direction, 
e.  g.,  the  facial  muscles  which  are  derived  from  the  hyoid  arch,  or  in  a  caudal  direc- 
tion, e.  g.,  the  Serratus  anterior.  In  all  cases  the  muscles  carry  with  them  the 
segmental  nerves  of  the  myotomes  from  which  they  were  originally  derived;  two 
examples  of  this  will  suffice,  viz.,  the  Diaphragma,  which  is  derived  from  the  third 
and  fourth  and  the  Serratus  anterior,  from  the  fifth,  sixth,  and  seventh  cervical 
segments  as  is  indicated  by  their  nerves  of  supply.  In  man  and  the  higher  verte- 
brates many  of  the  derivatives  of  the  myotomes  degenerate  and  are  converted 
into  aponeuroses,  e.  g.,  galea  aponeurotica,  and  the  aponeuroses  of  the  abdominal 
muscles,  or  ligaments,  e.  g.,  sacrotuberous  ligament  and  fibular  collateral  ligament 
of  the  knee. 

The  involuntary  muscles  are  derived  from  the  splanchnopleure  mesoderm. 


DEVELOPMENT  OF  THE  SKIN,   GLANDS,  AND  SOFT  PARTS. 

The  epidermis  and  its  appendages,  consisting  of  the  hairs,  nails,  sebaceous  and 
sweat  glands,  are  developed  from  the  ectoderm,  while  the  corium  or  true  skin 
is  of  mesodermal  origin,  being  derived  from  the  cutis-plates  of  the  primitive  seg- 
ments. About  the  fifth  week  the  epidermis  consists  of  two  layers  of  cells,  the  deeper 
one  corresponding  to  the  rete  mucosum.  The  subcutaneous  fat  appears  about 
the  fourth  month,  and  the  papillae  of  the  true  skin  about  the  sixth.  A  considerable 
desquamation  of  epidermis  takes  place  during  fetal  life,  and  this  desquamated 
epidermis,  mixed  with  sebaceous  secretion,  constitutes  the  vemix  caseosa,  with 
which  the  skin  is  smeared  during  the  last  three  months  of  fetal  life.  The  nails 
are  formed  at  the  third  month,  and  begin  to  project  from  the  epidermis  about 
the  sixth.  The  hairs  appear  between  the  third  and  fourth  months  in  the  form  of 
solid  downgrowths  of  the  deeper  layer  of  the  epidermis,  the  growing  extremities 
of  which  become  inverted  by  papillary  projections  from  the  corium.  The  central 
cells  of  the  solid  downgrowths  undergo  alteration  to  form  the  hair,  while  the 
peripheral  cells  are  retained  to  form  the  lining  cells  of  the  hair-follicle.  About  the 
fifth  month  the  fetal  hairs  {lanugo)  appear,  first  on  the  head  and  then  on  the  other 
parts;  they  drop  off  after  birth,  and  give  place  to  the  permanent  hairs.  The  cellular 
structures  of  the  sudoriferous  and  sebaceous  glands  are  formed  from  the  ectoderm, 
while  the  connective  tissue  and  bloodvessels  are  derived  from  the  mesoderm. 

The  mamma  is  also  formed  partly  from  mesoderm  and  partly  from  ectoderm — 
its  bloodvessels  and  connective  tissue  being  derived  from  the  former,  its  cellular 
elements  from  the  latter.    Its  first  rudiment  is  seen. about  the  third  month,  in  the 


DEVELOPMEXT  OF  THE  XERVOVS  SYSTEM  AXD  SEXSE  ORGAXS     117 

form  of  a  lunnbtT  of  small  inward  projections  of  the  ectoderm,  which  invade  the 
mesoderm;  from  these,  secondary  tracts  of  cellular  elements  radiate  and  sub- 
sequently give  rise  to  the  epithelium  of  the  glandular  follicles  and  ducts.  The 
development  of  the  follicles,  however,  remains  imperfect,  except  in  the  parous 
female. 


DEVELOPMENT  OF  THE  NERVOUS  SYSTEM  AND  SENSE  ORGANS. 

The  entire  nervous  system  is  of  ectodermal  origin,  and  its  first  rudiment  is  seen 
in  the  neural  groove  which  extends  along  the  dorsal  aspect  of  the  embryo  (Fig. 
75).  By  the  elevation  and  ultimate  fusion  of  the  neural  folds,  the  groove  is  con- 
verted into  the  neural  tube  (Fig.  77).  The  anterior  end  of  the  neural  tube  becomes 
expanded  to  form  the  three  primary  brain- vesicles;  the  cavity  of  the  tube  is  sub- 
sequently modified  to  form  the  ventricular  cavities  of  the  brain,  and  the  central 
canal  of  the  medulla  spinalis ;  from  the  wall  the  nervous  elements  and  the  neuroglia 
of  the  brain  and  medulla  spinalis  are  developed. 


Eoof-plaie 

Oval  bundle 
Posterior  nerve  root 

Central  canal 
Ependynial  layer 

Mantle  layer 

Anterior  nerve-  rooUi 

■Marginal  layer 
Floor-plate 
Fig.  ,116. — Section  of  medulla  spinalis  of  a  four  weeks'  embryo.     (His.) 


The  Medulla  Spinalis. — J^t  first  the  wall  of  the  neural  tube  is  composed  of  a 
single  laj^er  of  columnar  ectodermal  cells.  Soon  the  side-walls  become  thickened, 
while  the  dorsal  and  ventral  parts  remain  thin,  and  are  named  the  roof-  and  floor- 
plates  (Figs.  116,  118).  A  transverse  section  of  the  tube  at  this  stage  presents 
an  oval  outline,  while  its  lumen  has  the  appearance  of  a  slit.  The  cells  which 
constitute  the  wall  of  the  tube  proliferate  rapidly,  lose  their  cell-boundaries  and 
form  a  syncytium.  This  syncytium  consists  at  first  of  dense  protoplasm  with 
closely  packed  nuclei,  but  later  it  opens  out  and  forms  a  looser  meshw^ork  with 
the  cellular  strands  arranged  in  a  radiating  manner  from  the  central  canal.  Three 
layers  may  now  be  defined — an  internal  or  ependymal,  an  intermediate  or  mantle, 
and  an  external  or  marginal.  The  ependymal  layer  is  ultimately  converted  into  the 
ependyma  of  the  central  canal;  the  processes  of  its  cells  pass  outward  toward 
the  periphery  of  the  medulla  spinalis.  The  marginal  layer  is  devoid  of  nuclei,  and 
later  forms  the  supporting  framework  for  the  white  funiculi  of  the  medulla  spinalis. 
The  mantle  layer  represents  the  whole  of  the  future  gray  columns  of  the  medulla 


118 


EMBRYOLOGY 


spinalis;  in  it  tlie  cells  are  differentiated  into  two  sets,  viz.,  (a)  spongioblasts  or 
young  neuroglia  cells,  and  (6)  germinal  cells,  which  are  the  parents  of  the  neuroblasts 
or  young  nerve  cells  (Fig.  117).  The  spongioblasts  are  at  first  connected  to  one 
another  by  filaments  of  the  syncytium;  in  these,  fibrils  are  developed,  so  that  as  the 


Germinal  cell 

Neuroblast 


Nuclei  of  spongioblasts 


'yncylium 


Fig.  117. 


-Transverse  section  of  the  medulla  spinalis  of  a  human  embryo  at  the  beginning  of  the  fourth  week. 
(After  His.)     The  left  edge  of  the  figure  corresponds  to  the  fining  of  the  central  canal. 


neuroglial  cells  become  defined  they  exhibit  their  characteristic  mature  appearance 
with  multiple  processes  proceeding  from  each  cell.  The  germinal  cells  are  large, 
round  or  oval,  and  first  make  their  appearance  between  the  ependymal  cells  on 
the  sides  of  the  central  canal.     They  increase  rapidly  in  number,  so  that  by  the 


Eoof-plate 

Alar  lamina 


Oval  bundle 


Posterior 

nerve-root 
Central  canal 

Ependymal 

layer 
Lateral 

funiculus 
Basal  lamina 


ntenor 
nerve-root 


Floor-plate 


Anterior  funiculus 


Fasciculus  gracilis  \Po.sterior 

Fasciculus  cuneatus)     funiculus 


-Post,  nerve-root 


Lateral 
funiculus 


Central  canal 


Anterior  funiculus 


B 


Fig.   118. — Transverse  sections  through  the  medullae  spinales  of  human  embryos.    A.  Aged  about  four  and  a  half 
weelis.     B.  Aged  about  three  months.     (His.) 


fourth  week  they  form  an  almost  continuous  layer  on  each  side  of  the  tube.  No 
germinal  cells  are  found  in  the  roof-  or  floor-plates;  the  roof-plate  retains,  in  certain 
regions  of  the  brain,  its  epithelial  character;  elsewhere,  its  cells  become  spongio- 
blasts.    By  subdivision  the  germinal  cells  give  rise  to  the  neuroblasts  or  young 


DEVELOPMENT  OF  THE  NERVOUS  SYSTEM  AND  SENSE  ORGANS     119 

nerve  cells,  which  migrate  outward  from  the  sides  of  the  central  canal  into  the 
mantle  layer  and  neural  crest,  and  at  the  same  time  become  pear-shaped;  the 
tapering  part  of  the  cell  undergoes  still  further  elongation,  and  forms  the  axis- 
cylinder  of  the  cell. 

The  lateral  walls  of  the  medulla  spinalis  contiiuie  to  increase  in  thickness,  and 
the  canal  widens  out  near  its  dorsal  extremity,  and  assumes  a  somewhat  lozenge- 
shaped  appearance.  The  widest  part  of  the  canal  serves  to  subdivide  the  lateral 
wall  of  the  neural  tube  into  a  dorsal  or  alar,  and  a  ventral  or  basal  lamina  (Fig.  118), 
a  subdivision  which  extends  forward  into  the  brain.  At  a  later  stage  the  ventral 
part  of  the  canal  widens  out,  while  the  dorsal  part  is  first  reduced  to  a  mere  slit 
and  then  becomes  obliterated  by  the  approximation  and  fusion  of  its  walls;  the 
ventral  part  of  the  canal  persists  and  forms  the  central  canal  of  the  adult  medulla 
spinalis.  The  caudal  end  of  the  canal  exhibits  a  conical  expansion  which  is  known 
as  the  terminal  ventricle. 

The  ^'entral  part  of  the  mantle  layer  becomes  thickened,  and  on  cross-section 
appears  as  a  triangular  patch  between  the  marginal  and  ependymal  layers.  This 
thickening  is  the  rudiment  of  the  anterior  column  of  gray  substance,  and  contains 
many  neuroblasts,  the  axis-cylinders  of  w^hich  pass  out  through  the  marginal  layer 
and  form  the  anterior  roots  of  the  spinal  nerves  (Figs.  116,  118).  The  thickening 
of  the  mantle  layer  gradually  extends  in  a  dorsal  direction,  and  forms  the  posterior 
column  of  gray  substance.  The  axons  of  many  of  the  neuroblasts  in  the  alar  lamina 
run  forward,  and  cross  in  the  floor-plate  to  the  opposite  side  of  the  medulla  spinalis; 
these  form  the  rudiment  of  the  anterior  white  commissure. 

About  the  end  of  the  fourth  week  nerve  fibres  begin  to  appear  in  the  marginal 
layer.  The  first  to  develop  are  the  short  intersegmental  fibres  from  the  neuro- 
blasts in  the  mantle  zone,  and  the  fibres  of  the  dorsal  nerve  roots  which  grow  into 
the  medulla  spinalis  from  the  cells  of  the  spinal  ganglia.  By  the  sixth  week  these 
dorsal  root  fibres  form  a  well-defined  oval  bundle  in  the  peripheral  part  of  the  alar 
lamina;  this  bundle  gradually  increases  in  size,  and  spreading  toward  the  middle 
line  forms  the  rudiment  of  the  posterior  funiculus.  The  long  intersegmental  fibres 
begin  to  appear  about  the  third  month  and  the  cerebrospinal  fibres  about  the  fifth 
month.  All  nerve  fibres  are  at  first  destitute  of  medullary  sheaths.  Different 
groups  of  fibres  receive  their  sheaths  at  different  times — the  dorsal  and  ventral 
nerve  roots  about  the  fifth  month,  the  cerebrospinal  fibres  after  the  ninth  month. 

By  the  growth  of  the  anterior  columns  of  gray  substance,  and  by  the  increase 
in  size  of  the  anterior  funiculi,  a  furrow  is  formed  between  the  lateral  halves  of  the 
cord  anteriorly;  this  gradually  deepens  to  form  the  anterior  median  fissure.  The 
mode  of  formation  of  the  posterior  septum  is  somewhat  uncertain.  Many  believe 
that  it  is  produced  by  the  growing  together  of  the  walls  of  the  posterior  part  of  the 
central  canal  and  by  the  development  from  its  ependymal  cells  of  a  septum  of 
fibrillated  tissue  which  separates  the  future  fvmiculi  graciles. 

Up  to  the  third  month  of  fetal  life  the  medulla  spinalis  occupies  the  entire 
length  of  the  vertebral  canal,  and  the  spinal  nerves  pass  outward  at  right  angles 
to  the  medulla  spinalis.  From  this  time  onward,  the  vertebral  column  grows  more 
rapidly  than  the  medulla  spinalis,  and  the  latter,  being  fixed  above  through  its 
continuity  wdth  the  brain,  gradually  assumes  a  higher  position  within  the  canal. 
By  the  sixth  month  its  lower  end  reaches  only  as  far  as  the  upper  end  of  the  sacrum ; 
at  birth  it  is  on  a  level  with  the  third  lumbar  vertebra,  and  in  the  adult  with  the 
lower  border  of  the  first  or  upper  border  of  the  second  lumbar  vertebra.  A  delicate 
filament,  the  filum  terminale,  extends  from  its  lower  end  as  far  as  the  coccyx. 

The  Spinal  Nerves.^ — Each  spinal  nerve  is  attached  to  the  medulla  spinalis  by 
an  anterior  or  ventral  and  a  posterior  or  dorsal  root. 

The  fibres  of  the  anterior  roots  are  formed  by  the  axons  of  the  neuroblasts 
which  lie  in  the  ventral  part  of  the  mantle  layer;  these  axons  grow  out  through  the 


120 


EMBRYOLOGY 


overlving  marginal  la^'e^  and  become   grouped   to  f(jrm  the  anterior  nerve  root 
(Fig. -117). 

The  fibres  of  the  posterior  roots  are  developed  from  the  cells  of  the  spinal  ganglia. 
Before  the  neural  groove  is  closed  to  form  the  neural  tube  a  ridge  of  ectodermal 
cells,  the  ganglion  ridge  or  neural  crest  (Fig.  119),  appears  along  the  prominent 
margin  of  each  neural  fold.  When  the  folds  meet  in  the  middle  line  the  two  gan- 
glion ridges  fuse  and  form  a  wedge-shaped  area  along  the  line  of  closure  of  the  tube. 
The  cells  of  this  area  proliferate  rapidly  opposite  the  primitive  segments  and  then 
migrate  in  a  lateral  and  ventral  direction  to  the  sides  of  the  neural  tube,  where  they 
ultimately  form  a  series  of  oval-shaped  masses,  the  future  spinal  ganglia.  These 
ganglia  are  arranged  symmetrically  on  the  two  sides  of  the  neural  tube  and,  except 
in  the  region  of  the  tail,  are  equal  in  number  to  the  primitive  segments.  The  cells 
of  the  ganglia,  like  the  cells  of  the  mantle  layer,  are  of  two  kinds,  viz.,  spongio- 
blasts and  neuroblasts.  The  spongioblasts  develop  into  the  neuroglial  cells  of  the 
ganglia.  The  neuroblasts  are  at  first  round  or  oval  in  shape,  but  soon  assume 
the  form  of  spindles  the  extremities  of  which  gradually  elongate  into  central  and 

peripheral  processes.  The  central 
processes  grow  medial  ward  and,  be- 
coming connected  with  the  neural 
tube,  constitute  the  fibres  of  the 
posterior  nerve  roots,  while  the  per- 
ipheral processes  grow  lateralward  to 
mingle  with  the  fibres  of  the  anterior 
root  in  the  spinal  nerve.  As  de- 
velopment proceeds  the 
bipolar  form  of  the  cells 
the  two  processes  become 
mated  until  they  ultimately  arise 
from  a  single  stem  in  a  T-shaped 
manner.  Only  in  the  ganglia  of  the 
acoustic  nerve  is  the  bipolar  form 
retained .  More  recent  observers  hold, 
however,  that  the  T-form  is  derived 
from  the  branching  of  a  single  pro- 
cess which  grows  out  from  the  cell. 
The  anterior  or  ventral  and  the  pos- 
terior or  dorsal  nerve  roots  join  imme- 
diately beyond  the  spinal  ganglion  to  form  the  spinal  nerve,  which  then  divides  into 
anterior,  posterior,  and  visceral  divisions.  The  anterior  and  posterior  divisions 
proceed  directly  to  their  areas  of  distribution  without  further  association  with 
ganglion  cells  (Fig.  120).  The  visceral  divisions  are  distributed  to  the  thoracic, 
abdominal,  and  pelvic  viscera,  to  reach  which  they  pass  through  the  sympathetic 
trunk,  and  many  of  the  fibres  form  arborizations  around  the  ganglion  cells  of  this 
trunk.  Visceral  branches  are  not  given  off  from  all  the  spinal  nerves;  they  form 
two  groups,  viz.,  (a)  thoracico-lumbar,  from  the  first  or  second  thoracic,  to  the 
second  or  third  lumbar  nerves;  and  (6)  pelvic,  from  the  second  and  third,  or 
third  and  fourth  sacral  nerves. 

The  Brain. — The  brain  is  developed  from  the  anterior  end  of  the  neural  tube, 
which  at  an  early  period  becomes  expanded  into  three  vesicles,  the  primary  cerebral 
vesicles  (Fig.  76).  These  are  marked  off  from  each  other  by  intervening  con- 
strictions, and  are  named  the  prosencephalon  or  fore-brain,  the  mesencephalon 
or  mid-brain,  and  the  rhombencephalon  or  hind-brain — the  last  being  continuous 
w^ith  the  medulla  spinalis.  As  the  result  of  unequal  growth  of  these  different 
parts  three  flexures  are  formed  and  the  embryonic  brain  becomes  bent  on  itself 


original 
changes; 
approxi- 


FiG.   119. — Two  stages  in  the  development  of  the  neural 
crest  in  the  human  embryo.     (Lenhossek.) 


DEVELOP m' EN T  OF  THE  NERVOUS  SYSTEM  AND  SENSE  ORGANS     121 

in  a  somewhat  zigzag  fasliion;  the  two  earliest  flexures  are  eoneave  ventrally 
and  are  assoeiated  with  corresponding  flexures  of  the  whole  head.  The  first  flexure 
appears  in  the  region  of  the  raid-brain,  and  is  named  the  ventral  cephalic  flexure 
(Fig.  125).  By  means  of  it  the  fore-brain  is  bent  in  a  ventral  direction  around 
the  anterior  end  of  the  notochord  and  fore-gut,  with  the  result  that  the  floor  of 
the  fore-brain  comes  to  lie  almost  parallel  with  that  of  the  hind-brain.  This 
flexure  causes  the  mid-brain  to  become,  for  a  time,  the  most  prominent  part  of 


A  udilory  vesicle 


Facial  and  acoustic  Ns. 
Trigeminal  N, 
Trochlear  N. 


Glossopluiryugeal  N. 
Vagus  N. 

Accessoi'y  N. 
Hypoglossal  N. 


Mesencephalon 
Octdomotor  N. 


Dienceplialon —  i- 


Cerebral 
hemisphere 


Froriep's 
ganglion 

•/•  Cervical 


Vitelline  loop  

Tail ' 


/.  Coccygeal  — V 


Sacral 


Fig.   120. — Reconstruction  of  peripheral  nerves  of  a  human  embryo  of  10.2  mm.     (After  His.)     The  abducent  nerve 
is  not  labelled,  but  is  seen  passing  forward  to  the  eye  under  the  mandibular  and  maxillary  nerves. 

the  brain,  since  its  dorsal  surface  corresponds  with  the  convexity  of  the  curve. 
The  second  bend  appears  at  the  junction  of  the  hind-brain  and  medulla  spinalis. 
This  is  termed  the  cervical  flexure  (Fig.  127),  and  increases  from  the  third  to  the 
end  of  the  fifth  week,  when  the  hind-brain  forms  nearly  a  right  angle  with  the 
medulla  spinalis;  after  the  fifth  week  erection  of  the  head  takes  place  and  the  cervi- 
cal flexure  diminishes  and  disappears.  The  third  bend  is  named  the  pontine  flexure 
(Fig.  127),  because  it  is  found  in  the  region  of  the  future  pons  Varoli.    It  differs 


122 


EMBRYOLOGY 


from  the  other  two  in  that  (a)  its  convexity  is  forward,  and  (6)  it  does  not  affect 
the  head.  The  lateral  walls  of  the  brain-tube,  like  those  of  the  medulla  spinalis, 
are  divided  bv  internal  furrows  into  alar  or  dorsal  and  basal  or  ventral  lamina? 
(Fig.  121). 


Fig.  121. — Diagram  to  illustrate  the  alar  and 
basal  laminae  of  brain  vesicles.     (His.) 


Eoof-plate 


Alar  lamina 

Furrow  between 
alar  and  ba-sal 
laminae 

Basal  lamina 


Vagus  nerve 
Hypoglossal  nerve 
Floor-plate 

Fig.   122. — Transverse  section  of  medulla  oblongata  of  human 
embryo.     X  32.     (Kollmann.) 


The  Rhombencephalon  or  Hind-brain. — The  cavity  of  the  hind-brain  becomes 
the  fourth  ventricle.  At  the  time  when  the  ventral  cephalic  flexure  makes  its 
appearance,  the  length  of  the  hind-brain  exceeds  the  combined  lengths  of  the  other 
two  vesicles.  Immediately  behind  the  mid-brain  it  exhibits  a  marked  constriction, 
the  isthmus  rhombencephali  (Fig.  125,  Isthmus),  which  is  best  seen  when  the  brain  is 
viewed  from  the  dorsal  aspect.    From  the  isthmus  the  anterior  medullary  velum 


Rhomhic  Up 


Vagus  nerve 


Hypoglossal  nerve 

Floor-plate 
Fig.   123. — Transverse  section  of  medulla  oblongata  of  human  embrj-o.     (After  His.) 


and  the  brachia  conjunctiva  of  the  cerebellum  are  formed.  It  is  customary  to 
divide  the  rest  of  the  hind-brain  into  two  parts,  viz.,  an  upper,  called  the  meten- 
cephalon,  and  a  lower,  the  myelencephalon.  The  cerebellum  is  developed  by  a 
thickening  of  the  roof,  and  the  pons  by  a  thickening  in  the  floor  and  lateral  walls 
of  the  metencephalon.     The  floor  and  lateral  walls  of  the  myelencephalon  are 


developSiext  of  the  xervous  system  AXD  SEXSE  ORGAXS    123 

thickened  to  form  the  ineduHa  oblongata;  its  roof  remains  thin,  and,  retaining  to 
a  great  extent  its  epithehal  nature,  is  expanded  in  a  hiteral  direction.  Later,  by 
the  growth  and  backward  extension  of  the  cerebelkim,  the  roof  is  folded  inward 
toward  the  cavity  of  the  fourth  ventricle;  it  assists  in  completing  the  dorsal  wall 
of  this  cavity,  and  is  also  invaginated  to  form  the  ependymal  covering  of  its  choroid 
plexuses.  Above  it  is  continuous  with  the  posterior  medullary  velum;  below,  with 
the  obex  and  liguhe. 


Taenia 
Rhombic  lip 


Fig.  124. — Hind-brain  of  a  human  embryo  of  three 
months — viewed  from  behind  and  partly  from  left  side. 
(From  model  by  His.) 


125. — Exterior  of  brain  of  human  embryo  of  four 
and  a  half  weeks.     (From  model  by  His.) 


The  development  of  the  medulla  oblongata  resembles  that  of  the  medulla  spinalis, 
but  at  the  same  time  exhibits  one  or  two  interesting  modifications.  On  transverse 
section  the  myelencephalon  at  an  early  stage  is  seen  to  consist  of  two  lateral  walls, 
connected  across  the  middle  line  by  floor-  and  roof-plates  (Figs.  122  and  123). 
Each  lateral  w^all  consists  of  an  alar  and  a  basal  lamina,  separated  by  an  internal 
furrow,  the  remains  of  which  are  represented  in  the  adult  brain  by  the  sulcus 
limitans  on  the  rhomboid  fossa.  The  contained  cavity  is  more  or  less  triangular 
in  outline,  the  base  being  formed  by  the  roof-plate,  which  is  thin  and  greatly 
expanded  transversely.  Pear-shaped  neuroblasts  are  developed  in  the  alar  and 
basal  laminae,  and  their  narrow  stalks  are  elongated  to  form  the  axis-cylinders  of 
the  nerve  fibres.  Opposite  the  furrow  or  boundary  between  the  alar  and  basal 
laminae  a  bundle  of  nerve  fibres  attaches  itself  to  the  outer  surface  of  the  alar 
lamina.  This  is  named  the  tractus  solitarius  (Fig.  123),  and  is  formed  by  the  sensory 
fibres  of  the  glossopharyngeal  and  vagus  nerves.  It  is  the  homologue  of  the  oval 
bundle  seen  in  the  medulla  spinalis,  and,  like  it,  is  developed  by  an  ingrowth  of 
fibres  from  the  ganglia  of  the  neural  crest.  At  first  it  is  applied  to  the  outer  surface 
of  the  alar  lamina,  but  it  soon  becomes  buried,  owing  to  the  growth  over  it  of  the 
neighboring  parts.  By  the  fifth  w^eek  the  dorsal  part  of  the  alar  lamina  bends 
in  a  lateral  direction  along  its  entire  length,  to  form  what  is  termed  the  rhombic 
lip  (Figs.  123,  124).    Within  a  few  days  this  lip  becomes  applied  to,  and  unites 


124 


EMBRYOLOGY 


with,  the  outer  surface  of  the  main  part  of  the  alar  lamina,  and  so  covers  in  the 
tractus  solitarius  and  also  the  spinal  root  of  the  trigeminal  nerve;  the  nodulus 
and  flocculus  of  the  cerebellum  are  developed  from  the  rhombic  lip. 

Neuroblasts  accumulate  in  the  mantle  layer;  those  in  the  basal  lamina  corre- 
spond with  the  cells  in  the  anterior  gray  column  of  the  medulla  spinalis,  and,  like 
them,  give  origin  to  motor  nerve  fibres;  in  the  medulla  oblongata  they  are,  however, 
arranged  in  groups  or  nuclei,  instead  of  forming  a  continuous  column.  From  the 
alar  lamina  and  its  rhombic  lip,  neuroblasts  migrate  into  the  basal  lamina,  and 
become  aggregated  to  form  the  olivary  nuclei,  while  many  send  their  axis-cylinders 
through  the  floor-plate  to  the  opposite  side,  and  thus  constitute  the  rudiment  of 
the  raphe  of  the  medulla  oblongata.  By  means  of  this  thickening  of  the  ventral 
portion,  the  motor  nuclei  are  buried  deeply  in  the  interior,  and,  in  the  adult,  are 
found  close  to  the  rhomboid  fossa.    This  is  still  further  accentuated:  (a)  by  the 

development  of  the  p^Tamids,  which 
are  formed  about  the  fourth  month 
by  the  downward  growth  of  the 
motor  fibres  from  the  cerebral  cortex ; 
and  (6)  by  the  fibres  which  pass  to 
and  from'  the  cerebellum.  On  the 
rhomboid  fossa  a  series  of  six  tem- 
porary furrows  appears;  these  are 
termed  the  rhombic  grooves.  They 
bear  a  definite  relationship  to  certain 
of  the  cerebral  nerves;  thus,  from 
before  backward  the  first  and  second 
grooves  overlie  the  nucleus  of  the 
trigeminal;  the  third,  the  nucleus  of 
the  facial;  the  fourth,  that  of  the  ab- 
ducent; the  fifth,  that  of  the  glosso- 
pharyngeal; and  the  sixth,  that  of 
the  vagus. 

The  pons  is  developed  from  the 
ventro-lateral  wall  of  the  meten- 
cephalon  by  a  process  similar  to  that 
which  has  been  described  for  the 
medulla  oblongata. 

The  cerebellum  is  developed  in 
the  roof  of  the  anterior  part  of 
the  hind-brain  (Figs.  124  to  129). 
The  alar  laminae  of  this  region 
become  thickened  to  form  two 
lateral  plates  which  soon  fuse  in  the  middle  line  and  produce  a  thick  lamina  which 
roofs  in  the  upper  part  of  the  cavity  of  the  hind-brain  vesicle;  this  constitutes 
the  rudiment  of  the  cerebellum,  the  outer  surface  of  which  is  originally  smooth 
and  convex.  The  fissures  of  the  cerebellum  appear  first  in  the  vermis  and  floccular 
region,  and  traces  of  them  are  found  during  the  third  month;  the  fissures  on  the 
cerebellar  hemispheres  do  not  appear  until  the  fifth  month.  The  primitive  fissures 
are  not  developed  in  the  order  of  their  relative  size  in  the  adult — thus  the  hori- 
zontal sulcus  in  the  fifth  month  is  merely  a  shallow  groove.  The  best  marked 
of  the  early  fissures  are:  (a)  the  fissura  prima  between  the  developing  culmen  and 
declive,  and  {h)  the  fissura  secunda  between  the  future  pyramid  and  uvula.  The 
flocculus  and  nodule  are  developed  from  the  rhombic  lip,  and  are  therefore  recog- 
nizable as  separate  portions  before  any  of  the  other  cerebellar  lobules.  The 
groove  produced  by  the  bending  over  of  the  rhombic  lip  is  here  known  as  the 


Ganglia  of  VII. 
and  VIII.  Ns. 

Auditory  vesicle 


Fig.   126.— Brain  of  human  embryo  of  four  and  a  half  weeks, 
showing  interior  of  fore-brain.   (From  model  by  His.) 


DF.VELOPMEXT  OF  THE  XERVOrS  SYSTE.\r  AXD  SEXSE  ORGANS     125 

floccular  fissure;  when  the  two  hiteral  walls  fuse,  the  right  and  left  Hoccular  fissures 
join  in  the  middle  line  and  their  central  part  becomes  the  post-nodular  fissure. 

On  the  ventricular  surface  of  the  cerebellar  lamina  a  transverse  furrow,  the 
incisura  fastigii,  appears,  and  deepens  to  form  the  tent-like  recess  of  the  roof  of  the 
fourth  ventricle.  The  rudiment  of  the  cerebellum  at  first  projects  in  a  dorsal 
direction ;  but,  by  the  backward  growth  of  the  cerebrum,  it  is  folded  downward  and 
somewhat  flattened,  and  the  thin  roof-plate  of  the  fourth  ventricle,  originally 
continuous  with  the  posterior  border  of  the  cerebellum,  is  projected  inward  toward 
the  cavity  of  the  ventricle. 

The  Mesencephalon  or  Mid-brain. — The  mid-brain  (Figs.  125  to  129)  exists  for  a 
time  as  a  thin-walled  cavity  of  some  size,  and  is  separated  from  the  isthmus  rhom- 
encephali  behind,  and  from  the  fore-brain  in  front,  by  slight  constrictions.  Its 
cavity  becomes  relatively  reduced  in  diameter,  and  forms  the  cerebral  aqueduct 
of  the  adult  brain.  Its  basal  laminae  increase  in  thickness  to  form  the  cerebral 
peduncles,  which  are  at  first  of  small  size,  but  rapidly  enlarge  after  the  fourth  month. 

Ganglion  hubenulce 

I 


Fig.   127. — Exterior  of  brain  of  human  embryo  of  five  weeks.     (From  model  by  His.) 


The  neuroblasts  of  these  laminae  are  grouped  in  relation  to  the  sides  and  floor 
of  the  cerebral  aqueduct,  and  constitute  the  nuclei  of  the  oculomotor  and  trochlear 
nerves,  and  of  the  mesencephalic  root  of  the  trigeminal  nerve.  By  a  similar 
thickening  process  its  alar  laminae  are  developed  into  the  quadrigeminal  lamina. 
The  dorsal  part  of  the  wall  for  a  time  undergoes  expansion,  and  presents  an  internal 
median  furrow  and  a  corresponding  external  ridge;  these,  however,  disappear, 
and  the  latter  is  replaced  by  a  groove.  Subsequently  two  oblique  furrows  extend 
medialward  and  backward,  and  the  thickened  lamina  is  thus  subdivided  into  the 
superior  and  inferior  colliculi. 

The  Prosencephalon  or  Fore-brain. — A  transverse  section  of  the  early  fore-brain 
shows  the  same  parts  as  are  displayed  in  similar  sections  of  the  medulla  spinalis 
and  medulla  oblongata,  viz.,  a  pair  of  thick  lateral  walls  connected  by  thin  floor- 
and  roof-plates.  Moreover,  each  lateral  wall  exhibits  a  division  into  a  dorsal  or 
alar  and  a  ventral  or  basal  lamina  separated  internally  by  a  furrow  termed  the  sulcus 


126 


EMBRYOLOGY 


of  Monro.  This  sulcus  ends  anteriorly  at  the  medial  end  of  the  optic  stalk,  and  in 
the  adult  brain  is  retained  as  a  slight  groove  extending  backwarrl  from  the  inter- 
ventricular foramen  to  the  cerebral  aqueduct. 

At  a  very  early  period — in  some  animals  before  the  closure  of  the  cranial  jjart  of 
the  neural  tube — two  lateral  diverticula,  the  optic  vesicles,  appear,  one  on  either 
side  of  the  fore-brain;  for  a  time  they  communicate  with  the  cavity  of  the  fore-})rain 
by  relatively  wide  openings.  The  peripheral  parts  of  the  vesicles  expand,  while 
the  proximal  parts  are  reduced  to  tubular  stalks,  the  optic  stalks.  The  optic  vesicle 
gives  rise  to  the  retina  and  the  epithelium  on  the  back  of  the  ciliary  body  and  iris; 
the  optic  stalk  is  invaded  by  nerve  fibres  to  form  the  optic  nerve.  The  fore-l)rain 
then  grows  forward,  and  from  the  alar  laminae  of  this  front  portion  the  cerebral 
hemispheres  originate  as  diverticula  which  rapidly  expand  to  form  two  large 
pouches,  one  on  either  side.  The  cavities  of  these  diverticula  are  the  rudiments  of 
the  lateral  ventricles;  they  communicate  with  the  median  part  of  the  fore-brain 
cavity  by  relatively  wide  openings,  which  ultimately  form  the  interventricular 


Recessus  infundibuli 

Tuber  cinereum 

Corpus  mmniliare 


Cervical  flexure 
Fig.   128. — Interior  of  brain  of  human  embryo  of  five  weeks.     (From  model  by  His.) 


foramen.  The  median  portion  of  the  wall  of  the  fore-brain  vesicle  consists  of  a 
thin  lamina,  the  lamina  terminalis  (Figs.  129,  132),  which  stretches  from  the 
interventricular  foramen  to  the  recess  at  the  base  of  the  optic  stalk.  The 
anterior  part  of  the  fore-brain,  including  the  rudiments  of  the  cerebral  hemi- 
spheres, is  named  the  telencephalon,  and  its  posterior  portion  is  termed  the 
diencephalon ;  both  of  these  contribute  to  the  formation  of  the  third  ventricle. 
The  Diencephalon. — From  the  alar  lamina  of  the  diencephalon,  the  thalamus, 
metathalamus,  and  epithalamus  are  developed.  The  thalamus  (Figs.  125  to  129) 
arises  as  a  thickening  which  involves  the  anterior  two-thirds  of  the  alar  lamina. 
The  two  thalami  are  visible,  for  a  time,  on  the  surface  of  the  brain,  but  are  subse- 
quently hidden  by  the  cerebral  hemispheres  w^hich  grow  backward  over  them. 
The  thalami  extend  medialward  and  gradually  narrow  the  cavity  between  them 
into  a  slit-like  aperture  which  forms  the  greater  part  of  the  third  ventricle;  their 
medial  surfaces  ultimately  adhere,  in  part,  to  each  other,  and  the  intermediate 


DEVELOPMENT  OF  THE  XERVOVS  SYSTEM  AXD  SEXSE  ORGANS     127 

mass  of  the  \eiitricle  is  developed  aert)ss  the  area  of  eontact.  The  metathalamus 
comprises  the  ^eiiieiihite  bodies  which  originate  as  sliglit  outward  bulgings  of  the 
alar  lamina.  In  the  adult  the  lateral  geniculate  body  appears  as  an  eminence  on 
the  lateral  part  of  the  posterior  end  of  the  thalamus,  while  the  medial  is  situated 
on  the  lateral  aspect  of  the  mesencephalon.  The  epithalamus  includes  the  pineal 
body,  the  posterior  commissure,  and  the  trigonum  habenulae.  The  pineal  body 
arises  as  an  upward  e\agination  of  the  roof-plate  immediately  in  front  of  the  mid- 
brain; this  evagination  becomes  solid  with  the  exception  of  its  proximal  part, 
which  persists  as  the  recessus  i)inealis.  In  lizards  the  pineal  evagination  is  elongated 
into  a  stalk,  and  its  peripheral  extremity  is  expanded  into  a  vesicle,  in  which  a 
ruilimentary  lens  and  retina  are  formed;  the  stalk  becomes  solid  and  nerve  fibres 
make  their  appearance  in  it,  so  that  in  these  animals  the  pineal  body  forms  a 
rudimentary  eye.  The  posterior  commissure  is  formed  by  the  ingrowth  of  fibres 
into  the  depression  behind  and  below  the  pineal  evagination,  and  the  trigonum 
habenulae  is  developed  in  front  of  the  pineal  recess. 


Choroidal  fissure 


Bypophysis 
Itecesstis  infundibidi 


Fig.   129. — Median  sagittal  section  of  brain  of  human  embrj-o  of  three  months.      (From  model  by  His.) 


From  the  basal  laminae  of  the  diencephalon  the  pars  mamillaria  hypothalami 
is  developed;  this  comprises  the  corpora  mamillaria  and  the  posterior  part  of  the 
tuber  cinereum.  The  corpora  mamillaria  arise  as  a  single  thickening,  which 
becomes  divided  into  two  by  a  median  furrow  during  the  third  month. 

The  roof-plate  of  the  diencephalon,  in  front  of  the  pineal  body,  remains  thin  and 
epithelial  in  character,  and  is  subsequently  invaginated  by  the  choroid  plexuses 
of  the  third  ventricle. 

The  Telencephalon. — This  consists  of  a  median  portion  and  two  lateral  diver- 
ticula. The  median  portion  forms  the  anterior  part  of  the  cavity  of  the  third 
ventricle,  and  is  closed  below  and  in  front  by  the  lamina  terminalis.  The  lateral 
diverticula  consist  of  outward  pouchings  of  the  alar  laminae;  the  cavities  represent 
the  lateral  ventricles,  and   their  walls  become  thickened  to  form  the  nervous 


128 


EMBRYOLOGY 


matter  of  the  cerebral  hemispheres.  The  roof-plate  of  the  telencephalon  remains 
thin,  and  is  continuous  in  front  with  the  lamina  terminalis  and  behind  with  the 
roof-plate  of  the  diencephalon.  In  the  basal  laminae  and  floor-plate  the  pars 
optica  hypothalami  is  developed;  this  comprises  the  anterior  part  of  the  tuber 
cinereum,  the  infundibulum  and  posterior  lobe  of  the  hypophysis,  and  the  optic 
chiasma.  The  anterior  part  of  the  tuber  cinereum  is  derived  from  the  posterior 
part  of  the  floor  of  the  telencephalon;  the  infundibulum  and  posterior  lobe  of  the 
hypophysis  arise  as  a  downward  diverticulum  from  the  floor.  The  most  dependent 
part  of  the  diverticulum  becomes  solid  and  forms  the  posterior  lobe  of  the  hypo- 
physis; the  anterior  lobe  of  the  hypophysis  is  developed  from  a  diverticulum  of  the 
ectodermal  lining  of  the  stomodeum  (page  166),  The  optic  chiasma  is  formed 
by  the  meeting  and  partial  decussation  of  the  optic  nerves,  which  subsequently 
grow  backward  as  the  optic  tracts  and  end  in  the  diencephalon. 

The  cerebral  hemispheres  arise  as  diverticula  of  the  alar  laminae  of  the  telen- 
cephalon (Figs.  125  to  129);  they  increase  rapidly  in  size  and  ultimately  overlap 
the  structures  developed  from  the  mid-  and  hind-brains.     This  great  expansion 

of  the  hemispheres  is  a  char- 
acteristic feature  of  the  brains 
of  mammals,  and  attains  its 
maximum  development  in 
the  brain  of  man.  Elliott- 
Smith  divides  each  cerebral 
hemisphere  into  three  funda- 
mental parts,  viz.,  the  rhinen- 
cephalon,  the  corpus  striatum, 
and  the  neopallium. 

The  rhinencephalon  (Fig. 
130)  represents  the  oldest 
part  of  the  telencephalon, 
and  forms  almost  the  whole 
of  the  hemisphere  in  fishes, 
amphibians,  and  reptiles.  In 
man  it  is  feebly  developed 
in  comparison  with  the  rest 
of  the  hemisphere,  and  com- 
prises the  following  parts, 
viz.,  the  olfactory  lobe  (con- 
sisting of  the  olfactory  tract  and  bulb  and  the  trigonum  olfactorium),  the  anterior 
perforated  substance,  the  septum  pellucidum,  the  subcallosal,  supracallosal,  and 
dentate  gyri,  the  fornix,  the  hippocampus,  and  the  uncus.  The  rhinencephalon 
appears  as  a  longitudinal  elevation,  with  a  corresponding  internal  furrow,  on  the 
under  surface  of  the  hemisphere  close  to  the  lamina  terminalis;  it  is  separated 
from  the  lateral  surface  of  the  hemisphere  by  a  furrow,  the  external  rhinal  fissure, 
and  is  continuous  behind  with  that  part  of  the  hemisphere,  which  will  ultimately 
form  the  anterior  end  of  the  temporal  lobe.  The  elevation  becomes  divided  by 
a  groove  into  an  anterior  and  a  posterior  part.  The  anterior  grows  forward  as 
a  hollow  stalk  the  lumen  of  which  is  continuous  with  the  anterior  part  of  the  ven- 
tricular cavity.  During  the  third  month  the  stalk  becomes  solid  and  forms  the 
rudiment  of  the  olfactory  bulb  and  tract;  a  strand  of  gelatinous  tissue  in  the  interior 
of  the  bulb  indicates  the  position  of  the  original  cavity.  From  the  posterior  part  the 
anterior  perforated  substance  and  the  pyriform  lobe  are  developed;  at  the  begin- 
ning of  the  fourth  month  the  latter  forms  a  curved  elevation  continuous  behind 
with  the  medial  surface  of  the  temporal  lobe,  and  consisting,  from  before  backward, 
of  the  gyrus  olfactorius  lateralis,  gyrus  ambiens,  and  gyrus  semilunaris,  parts  which 


Gyr.  olf.  med.    .— -^___^ 
Gyr.  olf.laL. J-r-tC 

Gyr.  ambiens 

Gyr.  diagonalis 

Gyr.  semilunaris 


Cerebellum 

Olive 


Fig.   130.- 


-Inferior  surface  of  brain  of   embrj'o   at   beginning  of   fourth 
month.     (From  Kollmann.) 


DEVELOPMENT  OF  THE  NERVOUS  SYSTEM  AND  SENSE  ORGANS     129 

in  the  adult  brain  are  represented  by  the  hiteral  root  of  the  olfactory  tract  and  the 
uncus.  The  position  and  connections  of  the  remaining  portions  of  the  rhinen- 
cephalon  are  described  with  the  anatomy  of  the  brain. 

The  corpus  striatum  (Figs.  126  and  128)  appears  in  the  fourth  week  as  a  triangular 
thickening  of  the  floor  of  the  telencephalon  between  the  optic  recess  and  the 
interventicular  foramen,  and  continuous  behind  with  the  thalamic  part  of  the 
diencephalon.  It  increases  in  size,  and  by  the  second  month  is  seen  as  a  swelling 
in  the  floor  of  the  future  lateral  ventricle;  this  swelling  reaches  as  far  as  the  posterior 
end  of  the  primitive  hemisphere,  and  when  this  part  of  the  hemisphere  grows 
backward  and  downward  to  form  the  temporal  lobe,  the  posterior  part  of  the  corpus 
striatum  is  carried  into  the  roof  of  the  inferior  horn  of  the  ventricle,  where  it  is 
seen  as  the  tail  of  the  caudate  nucleus  in  the  adult  brain.  During  the  fourth  and 
fifth  months  the  corpus  striatum  becomes  incompletely  subdivided  by  the  fibres  of 
the  internal  capsule  into  two  masses,  an  inner,  the  caudate  nucleus,  and  an  outer, 
the  lentiform  nucleus.  In  front,  the  corpus  striatum  is  continuous  with  the  anterior 
perforated  substance;  laterally  it  is  confluent  for  a  time  with  that  portion  of  the 
wall  of  the  vesicle  which  is  developed  into  the  insula,  but  this  continuity  is  sub- 
sequently interrupted  by  the  fibres  of  the  external  capsule. 

Falx  cerebri 


Hippocampal  fissure 

Cs.  Corpus  striatum.  '  Th.  Thalamus. 

Fig.   131. — Diagrammatic  coronal  section  of  brain  to  show  relations  of  neopallium.     (After  His.)     Cs.  Corpus  striatum. 

Th.  Thalamus. 

The  neopallium  (Fig.  131)  forms  the  remaining,  and  by  far  the  greater,  part  of  the 
cerebral  hemisphere.  It  consists,  at  an  early  stage,  of  a  relatively  large,  more  or 
less  hemispherical  cavity — the  primitive  lateral  ventricle — enclosed  by  a  thin  wall 
from  which  the  cortex  of  the  hemisphere  is  developed.  The  vesicle  expands  in  all 
directions,  but  more  especially  upward  and  backward,  so  that  by  the  third  month 
the  hemispheres  cover  the  diencephalon,  by  the  sixth  they  overlap  the  mid-brain, 
and  by  the  eighth  the  hind-brain. 

The  median  lamina  uniting  the  two  hemispheres  does  not  share  in  their  expan- 
sion, and  thus  the  hemispheres  are  separated  by  a  deep  cleft,  the  forerunner  of 
the  longitudinal  fissure,  and  this  cleft  is  occupied  by  a  septum  of  mesodermal 
tissue  which  constitutes  the  primitive  falx  cerebri.  Coincidently  with  the  expan- 
9 


130 


EMBRYOLOGY 


sion  of  the  vesicle,  its  cavity  is  drawn  out  into  three  prolongations  which  represent 
the  horns  of  the  future  lateral  ventricle;  the  hinder  end  of  the  vesicle  is  carried  down- 
ward and  forward  and  forms  the  inferior  horn;  the  posterior  horn  is  produced 
somewhat  later,  in  association  with  the  backward  growth  of  the  occipital  lobe  of 
the  hemisphere.  The  roof-plate  of  the  primitive  fore-brain  remains  thin  and  of  an 
epithelial  character;  it  is  invaginated  into  the  lateral  ventricle  along  the  medial 
wall  of  the  hemisphere.  This  invagination  constitutes  the  choroidal  fissure,  and 
extends  from  the  interventricular  foramen  to  the  posterior  end  of  the  vesicle.  Mes- 
odermal tissue,  continuous  with  that  of  the  primitive  falx  cerebri,  and  carrying 
bloodvessels  with  it,  spreads  between  the  two  layers  of  the  invaginated  fold  and 
forms  the  rudiment  of  the  tela  choroidea;  the  margins  of  the  tela  become  highly 
vascular  and  form  the  choroid  plexuses  which  for  some  months  almost  completely 
fill  the  ventricular  cavities;  the  tela  at  the  same  time  invaginates  the  epithelial 
roof  of  the  diencephalon  to  form  the  choroid  plexuses  of  the  third  ventricle.  By 
the  downward  and  forward  growth  of  the  posterior  end  of  the  vesicle  to  form  the 
temporal  lobe  the  choroidal  fissure  finally  reaches  from  the  interventricular  fora- 
men to  the  extremity  of  the  inferior  horn  of  the  ventricle. 


Gyrus  dentatus 
Taenia  thalami 


Tlialamus 


Choroidal  fissure 


Post,  commissure 


Corpora  quadrigemina 


Cerebral  aqueduct  — ,^- 
Cerebral  peduncle  ■   '     1 

— V  ™ 


Cerebellum 


IV.  ventricle 


Corpus  callosum 
Septum  pellucidum 
Anterior  commissure 


Mft--^^^^y^-  Lamina  terminalis 


Rhinencephalon 
Optic  cJiiasma 
Hypophysis 

\  III.  ventricle 
Pons 


r 

/\ Medulla  oblongata 


Fig.   132. — Median  sagittal  section  of  brain  of  human  embryo  of  four  months.     (Marchand.) 

Parallel  with  but  above  and  in  front  of  the  choroidal  fissure  the  medial  wall  of 
the  cerebral  vesicle  becomes  folded  outward  and  gives  rise  to  the  hippocampal 
fissure  on  the  medial  surface  and  to  a  corresponding  elevation,  the  hippocampus, 
within  the  ventricular  cavity.  The  gray  or  ganglionic  covering  of  the  wall  of  the 
vesicle  ends  at  the  inferior  margin  of  the  fissure  is  a  thickened  edge;  beneath  this 
the  marginal  or  reticular  layer  (future  white  substance)  is  exposed  and  its  lower 
thinned  edge  is  continuous  with  the  epithelial  invagination  covering  the  choroid 
plexus  (Fig.  131).  As  a  result  of  the  later  downward  and  forward  growth  of  the 
temporal  lobe  the  hippocampal  fissure  and  the  parts  associated  with  it  extend  from 
the  interventricular  foramen  to  the  end  of  the  inferior  horn  of  the  ventricle. 
The  thickened  edge  of  gray  substance  becomes  the  gyrus  dentatus,  the  fasciola 
cinerea  and  the  supra-  and  subcallosal  gyri,  while  the  free  edge  of  the  white  sub- 
stance forms  the  fimbria  hippocampi  and  the  body  and  crus  of  the  fornix.  The 
corpus  callosum  is  developed  within  the  arch  of  the  hippocampal  fissure,  and  the 
upper  part  of  the  fissure  forms,  in  the  adult  brain,  the  callosal  fissure  on  the  medial 
surface  of  the  hemisphere. 


DEVELOPMENT  OF  THE  NERVOUS  SYSTEM  AND  SENSE  ORGANS     131 


Parietal 
operculum 


The  Commissures  (Fig.  132). — The  development  of  the  posterior  commissure 
has  already  been  referred  to  (page  127).  The  great  commisssures  of  the  hemi- 
spheres, viz.,  the  corpus  callosum,  the  fornix,  and  anterior  commissure,  arise  from 
the  hmiina  terminahs.  About  the  fourth  month  a  small  thickening  appears  in 
this  lamina,  immediately  in  front  of  the  interventricular  foramen.  The  lower 
part  of  this  thickening  is  soon  constricted  off,  and  fibres  appear  in  it  to  form 
the  anterior  commissure.  The  upper  part  continues  to  grow  with  the  hemispheres, 
and  is  invaded  by  two  sets  of  fibres.  Transverse  fibres,  extending  between  the 
hemisjiheres,  pass  into  its  dorsal  part,  which  is  now  differentiated  as  the  corpus 
callosum  (in  rare  cases  the  corpus  callosum  is  not  developed).  Into  the  ventral 
part  longitudinal  fibres  from  the  hippocampus  pass  to  the  lamina  terminalis,  and 
through  that  structure  to  the  corpora  mamillaria;  these  fibres  constitute  the  fornix. 
A  small  portion,  lying  antero-inferiorly  between  the  corpus  callosum  and  fornix, 
is  not  invaded  by  the  commissural  fibres;  it  remains  thin,  and  later  a  cavity, 
the  cavit}'  of  the  septum  pellucidum,  forms  in  its  interior. 

Fissures  and  Sulci. — The  outer  surface  of  the  cerebral  hemisphere  is  at  first  smooth, 
but  later  it  exhibits  a  number  of  elevations  or  convolutions,  separated  from  each 
other  by  fissures  and  sulci,  most  of  which 
make  their  appearance  during  the  sixth 
or  seventh  months  of  fetal  life.  The 
term,  fissure  is  applied  to  such  grooves  as 
involve  the  entire  thickness  of  the  cere- 
bral wall,  and  thus  produce  correspond- 
ing eminences  in  the  ventricular  cavit}^ 
while  the  sulci  aflfect  only  the  superficial 
part  of  the  wall,  and  therefore  leave  no 
impressions  in  the  ventricle.  The  fissures 
comprise  the  choroidal  and  hippocampal 
already  described,  and  two  others,  viz., 
the  calcarine  and  collateral,  which  pro- 
duce- the  swellings  known  respectively 
as  the  calcar  avis  and  the  collateral 
eminence  in  the  ventricular  cavity.  Of 
the  sulci  the  following  may  be  referred 
to,  viz.,  the  central  sulcus  {fissure  of 
Rolando),  which  is  developed  in  two 
parts;  the  intraparietal  sulcus  in  four 
parts;  and  the  cingulate   sulcus  in  two 

or  three  parts.  The  lateral  cerebral  or  Sylvian  fissure  differs  from  all  the  other 
fissures  in  its  mode  of  development.  It  appears  about  the  third  month  as  a  depres- 
sion, the  Sylvian  fossa,  on  the  lateral  surface  of  the  hemisphere  (Fig.  133);  this 
fossa  corresponds  with  the  position  of  the  corpus  striatum,  and  its  fioor  is  moulded 
to  form  the  insula.  The  intimate  connection  which  exists  between  the  cortex 
of  the  insula  and  the  subjacent  corpus  striatum  prevents  this  part  of  the  hemis- 
phere wall  from  expanding  at  the  same  rate  as  the  portions  which  surround  it. 
The  neighboring  parts  of  the  hemisphere  therefore  gradually  grow  over  and  cover 
in  the  insula,  and  constitute  the  temporal,  parietal,  frontal,  and  orbital  opercula 
of  the  adult  brain.  The  frontal  and  orbital  opercula  are  the  last  to  form,  but  by  the 
end  of  the  first  year  after  birth  the  insula  is  completely  submerged  by  the  approxi- 
mation of  the  opercula.  The  fissures  separating  the  opposed  margins  of  the  oper- 
cula constitute  the  composite  lateral  cerebral  fissure. 

If  a  section  across  the  wall  of  the  hemisphere  about  the  sixth  week  be  examined 
microscopically  it  will  be  found  to  consist  of  a  thin  marginal  or  reticular  layer,  a 
thick  ependymal  layer,  and  a  thin  intervening  mantle  layer.    Neuroblasts  from  the 


Temporal  operculum 

Sylvian  fossa 
Frontal  operculum 

Fig.   133. — Outer  surface  of  cerebral  hemisphere  of 
human  embryo  of  about  five  months. 


132 


EMBRYOLOGY 


ependymal  and  mantle  layers  migrate  into  the  deep  part  of  the  marginal  layer  and 
form  the  cells  of  the  cerelDral  cortex.  The  nerve  fibres  which  form  the  underlying 
white  substance  of  the  hemispheres  consist  at  first  of  outgrowths  from  the  cells  of 
the  corpora  striata  and  thalami;  later  the  fibres  from  the  cells  of  the  cortex  are 
added.  Medullation  of  these  fibres  begins  about  the  time  of  birth  and  continues 
until  puberty. 

A  summary  of  the  parts  derived  from  the  brain  vesicles  is  given  in  the  following 
table : 


Rhombencephalon 
or  Hind-brain 


1.  Myelencephalon 


2.  Metencephalon 


Isthmus  rhomb- 
encephali 


Mesencephalon  or  Mid-brain 


Prosencephalon  or 
Fore-brain 


1.  Diencephalon 


2.  Telencephalon 


Medulla  oblongata 

Lower  part  of  fourth 
ventricle. 

Pons 

Cerebellum 

Intermediate  part  of  fourth 
ventricle. 

Anterior  medullary  velum 

Brachia  conjunctiva 
cerebelli. 

Upper  part  of  fourth 
ventricle. 

Cerebral  peduncles 

Lamina  quadrigemina 

Cerebral  aqueduct. 

Thalamus 

Metatbalamus 

Epithalamus 

Pars  mamillaria  hypo- 
thalami 

Posterior  part  of  third 
ventricle. 

Anterior  part  of  third 
ventricle 

Pars  optica  hypo- 
thalami 

Cerebral  hemispheres 

Lateral  ventricles 

Interventricular  foramen. 


The  Cerebral  Nerves. — With  the  exception  of  the  olfactory,  optic,  and  acoustic 
nerves,  which  will  be  especially  considered,  the  cerebral  nerves  are  developed  in  a 
similar  manner  to  the  spinal  nerves  (see  page  119).  The  sensory  or  afterent  nerves 
are  derived  from  the  cells  of  the  ganglion  rudiments  of  the  neural  crest.  The  cen- 
tral processes  of  these  cells  grow  into  the  brain  and  form  the  roots  of  the  nerves, 
while  the  peripheral  processes  extend  outward  and  constitute  their  fibres  of  dis- 
tribution (Fig.  120).  It  has  been  seen,  in  considering  the  development  of  the 
medulla  oblongata  (page  123),  that  the  tractus  solitarius  (Fig.  135),  derived  from 
the  fibres  which  grow  inward  from  the  ganglion  rudiments  of  the  glossopharyn- 
geal and  vagus  nerves,  is  the  homologue  of  the  oval  bundle  in  the  cord  which  had 
its  origin  in  the  posterior  nerve  roots.  The  motor  or  efferent  nerves  arise  as  out- 
growths of  the  neuroblasts  situated  in  the  basal  laminae  of  the  mid-  and  hind- 
brain.  While,  however,  the  spinal  motor  nerve  roots  arise  in  one  series  from  the 
basal  lamina,  the  cerebral  motor  nerves  are  grouped  into  two  sets,  according  as 
they  spring  from  the  medial  or  lateral  parts  of  the  basal  lamina.  To  the  former 
set  belong  the  oculomotor,  trochlear,  abducent,  and  hypoglossal  nerves;  to  the 


developmIent  of  the  nervous  system  and  sense  organs    133 

latter,  the  accessory  and  the  motor  fibres  of  the  tri^eiiiinal,  facial,  glossopharyn- 
geal, vagus  nerves  (Figs.  134,  135). 

The  Sympathetic  System. — The  ganglion  cells  of  the  sympathetic  system  are 
derived  from  the  cells  of  the  neural  crests.  As  these  crests  move  forward  along 
the  sides  of  the  neural  tube  and  become  segmented  off  to  form  the  spinal  ganglia, 
certain  cells  detach  themselves  from 
the  ventral  margins  of  the  crests 
and  migrate  toward  the  sides  of  the 
aorta,  where  some  of  them  are 
grouped  to  form  the  ganglia  of  the 
sympathetic  trunks,  while  others 
undergo  a  further  migration  and 
form  the  ganglia  of  the  prevertebral 
and  visceral  plexuses.  The  ciliary, 
sphenopalatine,  otic,  and  submax- 
illary ganglia  which  are  found  on 
the  branches  of  the  trigeminal  nerve 
are  formed  by  groups  of  cells  which 
have  migrated  from  the  part  of 
the  neural  crest  which  gives  rise 
to  the  semilunar  ganglion.  Some 
of  the  cells  of  the  ciliary  ganglion 
are  said  to  migrate  from  the 
neural  tube  along  the  oculomotor 


■Boof-plate 


'ilar  lamina 


Furrow  between 
alar  and  basal 
lamincB 

Basal  lamina 


Vagus  nerve 
Hypoglossal  nerve 
Floor-plate 

Fig.  134. — Transverse  section  of  medulla  oblongata  of 
human  embryo.     X  32.     (Kollmann.) 


nerve. 


Chromaffin  Organs. — The  tissue  from  which  the  sympathetic  ganglia  are  formed 
is  at  first  a  syncytium  of  cells  termed  sympatho-chromaffin  cells,  but  later  two 
kinds  of  cells  become  differentiated  from  it;  the  smaller  cells  (sympathoblasts) 
are  transformed  into  the  sympathetic  nerve  cells,  the  larger  become  chromafiin 
cells,  and,  separating  from  the  others,  accumulate  to  form  the  chromaffin  organs. 


Rhombic  lip 


Vagus  nerve 


Hypoglossal  nerve 

Floor-plate 
Fig.   135. — Transverse  section  of  medulla  oblongata  of  human  embryo.      (After  His.) 


In  the  gangliated  trunk  of  the  sympathetic  the  chromaffin  bodies  are  situated  in 
depressions  in  the  ganglia.  In  connection  with  certain,  but  not  all,  of  the  secondary 
plexuses  of  the  sympathetic  system  chromaffin  organs  are  found;  the  largest  mem- 
bers of  this  series  are  the  aortic  bodies,  which  lie  along  the  sides  of  the  abdominal 
aorta  between  the  superior  mesenteric  and  common  iliac  arteries;  to  this  group 


134 


EMBRYOLOGY 


belong  also  the  carotid  skeins.  After  birth  the  chromaffin  organs  degenerate 
and  can  no  longer  be  isolated  by  gross  dissection,  but  chromaffin  tissue  can  be 
recognized  with  the  microscope  in  the  sites  originally  occupied  by  them. 

The  Suprarenal  Glands. — Each  suprarenal  gland  consists  of  a  cortical  portion 
derived  from  the  coelomic  epithelium  and  a  medullary  portion  originally  composed 
of  sympatho-chromaffin  tissue.     The  cortical  portion  is  first  recognizable  about 


Cavity  of  fore-brain 


Invagination  of 

ectoderm  to  form 

lens  rudiment 


Pigmented  layer  of  retina 


Margin  of  optic  cup 


Nervous  layer  of  retina 
Optic  vesicle 


Fig.   136. — Transverse  section  of  head  of  chick  embryo  of  forty-eight  hours'  incubation.     (Duval.) 


the  beginning  of  the  fourth  week  as  a  series  of  buds  from  the  coelomic  cells  at  the  root 
of  the  mesentery.  Later  it  becomes  completely  separated  from  the  coelomic 
epithelium  and  forms  a  suprarenal  ridge  projecting  into  the  coelom  between  the 
mesonephros  and  the  root  of  the  mesentery.  Into  this  cortical  portion  cells  from 
the  neighboring  masses  of  sympatho-chromaffin  tissue  migrate  along  the  line  of 
its  central  vein  to  reach  and  form  the  medullary  portion  of  the  gland. 

The  Nose. — The  development  of 
Cavity  of  fore-brain      ^he    nose    has   already   been   con- 
sidered (pages  111,  112). 

The  olfactory  nerves  are  developed 
from  the  cells  of  the  ectoderm  which 
lines  the  olfactory  pits;  these  cells 
undergo  proliferation  and  give  rise 
to  what  are  termed  the  olfactory 
cells  of  the  nose.  The  axons  of  the 
olfactory  cells  grow  into  the  over- 
lying olfactory  bulb  and  form  the 
olfactory  nerves. 

The  Eye. — The  eyes  begin  to 
develop  as  a  pair  of  diverticula 
from  the  lateral  aspects  of  the  fore- 
brain.  These  diverticula  make  their 
appearance  before  the  closure  of  the 
anterior  end  of  the  neural  tube; 
after  the  closure  of  the  tube  they  are 
knowai  as  the  optic  vesicles.  They  project  toward  the  sides  of  the  head,  and  the 
peripheral  part  of  each  expands  to  form  a  hollow  bulb,  while  the  proximal  part 
remains  narrow  and  constitutes  the  optic  stalk  (Figs.  136,  137).  The  ectoderm 
overlying  the  bulb  becomes  thickened,  invaginated,  and  finally  severed  from  the 
ectodermal  covering  of  the  head  as  a  vesicle  of  cells,  the  lens  vesicle,  which  con- 
stitutes the  rudiment  of  the  crystalline  lens.  The  outer  wall  of  the  bulb  becomes 
thickened  and  invaginated,  and  the  bulb  is  thus  converted  into  a  cup,  the  optic  cup, 


Pigmented  layer 
of  retina 

Ectoderin 


Lens 

Nervous  layer  of 
retina 


Optic  stalk 


Fig.   137. — Transverse  section  of  head  of  chick  embrj'o  of 
fifty-two  hours'  incubation.     (Duval.) 


DEVELOPMENT  OF  THE  XERVOUS  SYSTEM  AND  SENSE  ORGANS     135 

consisting  of  two  strata  of  cells  (Fig.  137).  These  two  strata  are  continuous  with 
each  other  at  the  cup  margin,  which  ultimately  overlaps  the  front  of  the  lens  and 
reaches  as  far  forward  as  the  future  aperture  of  the  pupil.  The  invagination  is  not 
limited  to  the  outer  wall  of  the  bulb,  but  invoh-es  also  its  postero-inferior  surface 
and  extends  in  the  form  of  a  groove  for  some  distance  along  the  optic  stalk,  so  that, 
for  a  time,  a  gap  or  fissure,  the  choroidal  fissure,  exists  in  the  lower  part  of  the 
cup  (Fig.  138).  Through  the  groove  and  fissure  the  mesoderm  extends  into  the 
optic  stalk  and  cup,  and  in  this  mesoderm  a  blood\'essel  is  developed;  during  the 
seventh  week  the  groove  and  fissure  are  closed  and  the  vessel  forms  the  central 
artery  of  the  retina.  Sometimes  the  choroidal  fissure  persists,  and  wheii  this 
occurs  the  choroid  and  iris  in  the  region  of  the  fissure  remain  undeveloped,  giving 
rise  to  the  condition  known  as  colobonia  of  the  choroid  or  iris. 


TJialameiicepkalon  ■ — f 
Optic  stalk 


Telenceplmlon 
^       Ed^e  of  optic  cup 


Choroidal  fissure 


Arteria  centralis 
retinae 


Fig.   138. — Optic  cup  and  choroidal  fissure  seen  from  below,  from  a  human  embrj-o  of  about  four  weeks. 

(Kollmann.) 

The  retina  is  developed  from  the  optic  cup.  The  outer  stratum  of  the  cup 
persists  as  a  single  layer  of  cells  which  assume  a  columnar  shape,  acquire  pigment, 
and  form  the  pigmented  layer  of  the  retina;  the  pigment  first  appears  in  the  cells 
near  the  edge  of  the  cup.  The  cells  of  the  inner  stratum  proliferate  and  form  a 
layer  of  considerable  thickness  from  which  the  nervous  elements  and  the  susten- 
tacular  fibres  of  the  retina,  together  w^ith  a  portion  of  the  vitreous  body,  are 
developed.  In  that  portion  of  the  cup  which  overlaps  the  lens  the  inner  stratum  is 
not  differentiated  into  nervous  elements,  but  forms  a  layer  of  columnar  cells  which 
is  applied  to  the  pigmented  layer,  and  these  two  strata  form  the  pars  ciliaris  and 
pars  iridic  a  retinae. 

The  cells  of  the  inner  or  retinal  layer  of  the  optic  cup  become  differentiated  into  spongioblasts 
and  germinal  cells,  and  the  latter  by  their  subdivisions  give  rise  to  neuroblasts.  From  the  spongio- 
blasts the  sustentacular  fibres  of  Miiller,  the  outer  and  inner  limiting  membranes,  together  with 
the  groundwork  of  the  molecular  layers  of  the  retina  are  formed.  The  neuroblasts  become 
arranged  to  form  the  gangUonic  and  nuclear  layers.  The  layer  of  rods  and  cones  is  first  developed 
in  the  central  part  of  the  optic  cup,  and  from  there  gradually  extends  toward  the  cup  margin. 
All  the  layers  of  the  retina  are  completed  by  the  eighth  month  of  fetal  life. 

The  optic  stalk  is  converted  into  the  optic  nerve  by  the  obliteration  of  its  cavity 
and  the  growth  of  nerve  fibres  into  it.  ]\Iost  of  these  fibres  are  centripetal,  and 
grow  backward  into  the  optic  stalk  from  the  nerve  cells  of  the  retina,  but  a  few 
extend  in  the  opposite  direction  and  are  derived  from  nerve  cells  in  the  brain.  The 
fibres  of  the  optic  nerve  receive  their  medullary  sheaths  about  the  tenth  week  after 


136 


EMBRYOLOGY 


birth.  The  optic  chiasma  is  formed  by  the  meeting  and  partial  decussation  of  the 
fibres  of  the  two  optic  nerves.  Behind  the  chiasma  the  fibres  grow  backward  as 
the  optic  tracts  to  the  thalami  and  mesencephalon. 

The  crystalline  lens  is  developed  from  the  lens  \'esicle,  which  recedes  within  the 
margin  of  the  cup,  and  becomes  separated  from  the  overlying  ectoderm  by  mes- 
oderm. The  cells  forming  the  posterior  wall  of  the  vesicle  lengthen  and  are  con- 
verted into  the  lens  fibres,  which  grow  forward  and  fill  up  the  cavity  of  the  vesicle 
(Fig.  139).  ^  The  cells  forming  the  anterior  wall  retain  their  cellular  character,  and 
form  the  epithelium  on  the  anterior  surface  of  the  adult  lens.  By  the  second  month 
the  lens  is  invested  by  a  vascular  mesodermal  capsule,  the  capsula  vasciilosa  lentis ; 
the  bloodvessels  supplying  the  posterior  part  of  this  capsule  are  derived  from  the 
hyaloid  artery;  those  for  the  anterior  part  from  the  anterior  ciliary  arteries;  the 
portion  of  the  capsule  which  covers  the  front  of  the  lens  is  named  the  pupillary 


Rudiment  of  choroid y 

Rectus  muscle 

Optic  nerve 


Retina 

Pigm,ented  layer w 

Vitreous  body 
(shrunken)  • « 


Cornea 
Mernbrana  pupillaris 


Pari  ciham  and  pars  iridica  retinae 
Fig.   139. — Horizontal  section  through  the  ej-e  of  an  eighteen  days'  embryo  rabbit.      X  30.     (Kolliker.) 


membrane.  By  the  sixth  month  all  the  vessels  of  the  capsule  are  atrophied  except 
the  hyaloid  artery,  which  disappears  during  the  ninth  month;  the  position  of  this 
artery  is  indicated  in  the  adult  by  the  hyaloid  canal,  which  reaches  from  the  optic 
disk  to  the  posterior  surface  of  the  lens.  With  the  loss  of  its  bloodvessels  the  cap- 
sula vasculosa  lentis  disappears,  but  sometimes  the  pupillary  membrane  persists 
at  birth,  giving  rise  to  the  condition  termed  congenital  atresia  of  the  piipil. 

The  vitreous  body  is  developed  between  the  lens  and  the  optic  cup.  The  lens 
rudiment  and  the  optic  vesicle  are  at  first  in  contact  with  each  other,  but  after  the 
closure  of  the  lens  vesicle  and  the  formation  of  the  optic  cup  the  former  withdraws 
itself  from  the  retinal  layer  of  the  cup;  the  two,  however,  remain  connected  by  a  net- 
work of  delicate  protoplasmic  processes.  This  network,  derived  partly  from  the  cells 
of  the  lens  and  partly  from  those  of  the  retinal  layer  of  the  cup,  constitutes  the 
primitive  vitreous  body  (Figs.  140,  141).  At  first  these  protoplasmic  processes 
spring  from  the  whole  of  the  retinal  layer  of  the  cup,  but  later  are  limited  to  the 


DEVELOPMENT  OF  THE  NERVOUS  SYSTEM  AND  SENSE  ORGANS     137 

ciliary  region,  where  by  a  process  of  condensation  they  appear  to  form  the  zonula 
ciliaris.  The  mesoderm  which  enters  the  cup  through  the  choroidal  fissure  and 
around  the  equator  of  the  lens  becomes  intimately  united  with  this  reticular  tissue, 
and  contributes  to  form  the  vitreous  body,  which  is  therefore  derived  partly  from 
the  ectoderm  and  partly  from  the  mesoderm. 

Pig  III  c  nk'd     M  esode  riii  ul 

layer  of        'part  of  Rtuliment 

Upper  eyelid        retina    vitreous  body       of  sclera 


"=  <s>~   ■a. 


b  <.^-  ^^^'^^3s^%^^^^t-'^t€\ 


<S2t  l!g» 


-    o_^P„8>9?b%^c."'<^ 


CIS     <25» 
e3>    O    O'^^^a    ^   * 


fSS^'^tf     £S>     O 


Mesoderm 


Ectodermal    NervoiLs  layer 

part  of  of  retina 

vitreous  body 


Fig.  140. — Sagittal  section  of  eye  of  human  embryo  of  six  weeks.     (KoUmann.) 


The  anterior  chamber  of  the  eye  appears  as  a  cleft  in  the  mesoderm  separating 
the  lens  from  the  overlying  ectoderm.  The  layer  of  mesoderm  in  front  of  the  cleft 
forms  the  substantia  propria  of  the  cornea,  that  behind  the  cleft  the  stroma  of  the 
iris  and  the  pupillary  membrane.  The  fibres  of  the  ciliary  muscle  are  derived  from 
the  mesoderm,  but  those  of  the  Sphincter  and  Dilatator  pupillae  are  of  ectodermal 
origin,  being  developed  from  the  cells  of  the  pupillary  part  of  the  optic  cup. 

The  sclera  and  choroid  are  derived  from  the  mesoderm  surrounding  the  optic  cup. 

The  eyelids  are  formed  as  small  cutaneous  folds  (Figs.  139,  140),  which  about 
the  middle  of  the  third  month  come  together  and  unite  in  front  of  the  cornea. 
They  remain  united  until  about  the  end  of  the  sixth  month. 

The  lacrimal  sac  and  nasolacrimal  duct  result  from  a  thickening  of  the  ectoderm 
in  the  groove,  nasobptic  furrows,  between  the  lateral  nasal  and  maxillary  processes. 
This  thickening  forms  a  solid  cord  of  cells  which  sinks  into  the  mesoderm;  during 
the  third  month  the  central  cells  of  the  cord  break  down,  and  a  lumen,  the  naso- 
lacrimal duct,  is  established.    The  lacrimal  ducts  arise  as  buds  from  the  upper  part 


138 


EMBRYOLOGY 


of  the  cord  of  cells  and  secondarily  establish  openings  (puncta  lacrimalia)  on  the 
margins  of  the  lids.  The  epithelium  of  the  cornea  and  conjunctiva,  and  that  which 
lines  the  ducts  and  alveoli  of  the  lacrimal  gland,  are  of  ectodermal  origin,  as  are 
also  the  eyelashes  and  the  lining  cells  of  the  glands  which  ojjcn  on  the  lid-margins. 


Lens 


Blood-vessel 


Primitive 

vitreous 

hody 


Retina 


Outer  layer  of 
optic  cup' 


Fig    141. — Section  of  developing  eye  of  trout.      (Szily.) 


The  Ear. — The  first  rudiment  of  the  internal  ear  appears  shortly  after  that  of 
the  eye,  in  the  form  of  a  patch  of  thickened  ectoderm,  the  auditory  plate,  over  the 
region  of  the  hind-brain.  The  auditory  plate  becomes  depressed  and  converted 
into  the  auditory  pit  (Fig.  142).  The  mouth  of  the  pit  is  then  closed,  and  thus  a  shut 
sac,  the  auditory  vesicle,  is  formed  (Fig.  143) ;  from  it  the  epithelial  lining  of  the 


Cavity  of  hind-brain 


/   Auditory  pit 


Ectoderm 


Notochord 

Fig.  142. — Section  through  the  head  of  a  human 
embryo,  about  twelve  days  old,  in  the  region  of  the 
hind  brain.      (Kollmann.) 


Hind-brain 


Auditory 
vesicle 


Fig.  143. — Section  through  hind  brain  and  audi- 
tory vesiclesof  an  embryo  more  advanced  than  that 
of  Fig.  142.     (After  His.) 


membranous  labyrinth  is  derived.  The  vesicle  becomes  pear-shaped,  and  the  neck 
of  the  flask  is  obliterated  (Fig.  144).  From  the  vesicle  certain  diverticula  are  given 
off  which  form  the  various  parts  of  the  membranous  labyrinth.  One  from  the 
middle  part  forms  the  ductus  and  saccus  endolymphaticus,  another  from  the 
anterior  end  gradually  elongates,  and,  forming  a  tube  coiled  on  itself,  becomes  the 


DEVELOPMliXT  OF  THE  XERVOiS  SYSTEM  AXD  SEXSE  ORGAXS     139 

cochlear  duct,  the  vestibuhir  extremity  of  which  is  siibseciueutly  constricted  to  form 
the  canalis  reuniens.  Three  others  appear  as  (Usk-Hke  cNa^iiiatioiis  on  the  surface 
of  the  vesicle;  the  central  })arts  of  the  walls  of  the  disks  coalesce  and  disappear, 
while  the  jieripheral  portions  persist  to  form  the  semicircular  ducts;  of  these  the 


Aiiditory  vesicle 
Ductus  endo- 
lymphaiictis 


Saccns 
endohjmphnticus 


Superior  semi- 
circular duct 


Lateral  semicircular 
duct 

Posterior  semi- 
circular duct 


Rudiment  of  cochlear  duct 


Fig.  144. — Left  auditory  vesicle  of  a  human 
embryo  of  four  weeks,  seen  from  the  outer 
surface.     (W.  His,  Jr.) 


Fig. 


145. — Left  auditory  vesicle  of  a  human  embryo  of  five 
weeks,  seen  from  the  outer  surface.     (W.  His,  Jr.) 


superior  is  the  first  and  the  lateral  the  last  to  be  completed  (Figs.  145,  146).  The 
central  part  of  the  vesicle  represents  the  membranous  vestibule,  and  is  subdivided 
by  a  constriction  into  a  smaller  ventral  part,  the  saccule,  and  a  larger  dorsal  and 
posterior  part,  the  utricle.    This  subdivision  is  effected  by  a  fold  which  extends 


Ductus  endolymphaticus 


Ganglion 
cochleare 


Superior  seini- 
circular  duct 


Utricle 
Saccule 
Lateral  semi- 
circular duct 

Ductus  cochlearis 


Fig.   146. — Transverse  section  through  head  of  fetal  sheep,  in  the  region  of  the  labyrinth.      X  30.     (After  Boettcher.) 


deeply  into  the  proximal  part  of  the  ductus  endolymphaticus,  with  the  result  that 
the  utricle  and  saccule  ultimately  communicate  with  each  other  by  means  of  a 
Y-shaped  canal.  The  saccule  opens  into  the  cochlear  duct,  through  the  canalis 
reuniens,  and  the  semicircular  ducts  communicate  with  the  utricle  (Fig.  147). 


140 


EMBRYOLOGY 


The  mesodermal  tissue  surrounding  the  various  parts  of  the  epithelial  labyrinth 
is  converted  into  a  cartilaginous  ear-capsule,  and  this  is  finally  ossified  to  form  the 
bony  labyrinth.  Between  the  cartilaginous  capsule  and  the  epithelial  structures 
is  a  stratum  of  mesodermal  tissue  which  is  differentiated  into  three  layers,  viz., 


Fig.   147. — Left  membraaous  labyrinth  of  a  human  embryo  of  30  mm.      (From  model  by  W.  His,  Jr.) 

an^outer,  forming  the  periosteal  lining  of  the  bony  labyrinth;  an  inner,  in  direct 
contact  with  the  epithelial  structures;  and  an  intermediate,  consisting  of  gelatinous 
tissue :  by  the  absorption  of  this  latter  tissue  the  perilymphatic  spaces  are  developed. 
The  modiolus  and  osseous  spiral  lamina  of  the  cochlea  are  not  preformed  in  cartil- 
age but  are  ossified  directly  from  connective  tissue. 


Embryonic 
cotmective  tissue 


Cochlear  duct 


Ligamentmn  spirale 
Scala  tytnpani 


Epithelium  of  the  spiral 
organ  of  Corti 


Fig.   148. — Transverse  section  of  the  cochlear  duct  of  a  fetal  cat.      (After  Boettcher  and  Ayres.) 

The  middle  ear  and  auditory  tube  are  developed  from  the  first  pharyngeal  pouch. 
The  entodermal  lining  of  the  dorsal  end  of  this  pouch  is  in  contact  with  the  ecto- 
derm of  the  corresponding  pharyngeal  groove;  by  the  extension  of  the  mesoderm 
between  these  two  layers  the  tympanic  membrane  is  formed.    During  the  sixth  or 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM 


141 


seventh  month  the  tympanic  antrnm  appears  as  an  upward  and  backward  expan- 
sion of  the  tympanic  cavity.  With  regard  to  the  exact  mode  of  development  of 
the  ossicles  of  the  middle  ear  there  is  some  difference  of  opinion.  The  view  generally 
held  is  that  the  incus  and  malleus  are  developed  from  the  proximal  end  of  the 
mandibular  (Meckel's)  cartilage  (Fig.  105)  and  that  the  stapes  is  formed  from  the 
proximal  end  of  the  second  arch.  The  malleus,  with  the  exception  of  its  anterior 
process,  is  ossified  from  a  single  centre  which  appears  near  the  neck  of  the  bone; 
the  anterior  process  is  ossified  separately  in  membrane  and  joins  the  main  part 
of  the  bone  about  the  sixth  month  of  fetal  life.  The  incus  is  ossified  from  one  centre 
which  appears  in  the  upper  part  of  its  long  crus  and  ultimately  extends  into  its 
lenticular  process.  The  stapes  first  appears  as  a  ring  {annidus  stapedius)  encircling 
a  small  vessel,  the  stapedial  artery,  which  subsequently  undergoes  atrophy;  it  is 
ossified  from  a  single  centre  which  appears  in  its  base. 

The  external  acoustic  meatus  is  developed  from  the  first  branchial  groove.  The 
lower  part  of  this  groove  extends  inward  as  a  funnel-shaped  tube  (primary  meatus) 
from  which  the  cartilaginous  portion  and  a  small  part  of  the  roof  of  the  osseous 
portion  of  the  meatus  are  developed.  From  the  lower  part  of  the  funnel-shaped 
tube  an  epithelial  lamina  extends  downward 
and  inward  along  the  inferior  wall  of  the 
primitive  tympanic  cavity;  by  the  splitting  of 
this  lamina  the  inner  part  of  the  meatus  (sec- 
ondary meatus)  is  produced,  while  the  inner 
portion  of  the  lamina  forms  the  cutaneous 
stratum  of  the  tympanic  membrane.  The 
auricula  or  pinna  is  developed  by  the  gradual 
differentiation  of  six  tubercles  (Fig.  149)  which 
appear  around  the  margin  of  the  first  branchial 
groove.  Two  tubercles  appear  on  the  posterior 
edge  of  the  mandibular  arch;  these  represent 
the  rudiments  of  the  tragus  and  crus  helicis. 
Three  are  found  on  the  hj^oid  arch,  and  indi- 
cate, from  below  upward,  the  lobule,  antitragus, 
and  antihelix.  One  arises  above  the  groove, 
and  grows  downward  behind  the  antitragus 
and  antihelix;  from  it  and  its  downward  pro- 
longation the  upper  part  of  the  helix  and  the 
Cauda  helicis  are  developed   (Figs.  150,  151). 

Some  observers,  however,  maintain  that  the  lowest  tubercle  on  the  hyoid  arch 
becomes  the  antitragus,  and  that  the  lobule  is  developed  later  as  an  independent 
formation.  The  rudiment  of  the  acoustic  nerve  appears  about  the  end  of  the  third 
week  as  a  group  of  ganglion  cells  closely  applied  to  the  cephalic  edge  of  the  audi- 
tory vesicle.  Whether  these  cells  are  derived  from  the  ectoderm  adjoining  the 
auditory  vesicle,  or  have  migrated  from  the  wall  of  the  neural  tube,  is  as  yet  un- 
certain. Each  cell  gives  off  a  proximal  fibre  which  passes  into  the  neural  tube, 
and  a  distal  which  is  distributed  to  the  epithelial  cells  of  the  auditory  vesicle. 


Maiulibular  arch 


Maxillary  process 


Fig.  149. — Tubercles  from  which  the  different 
parts  of  the  auricula  are  developed.  (His.) 
1,  2.  Tubercles  on  mandibular  arch.  3.  Tuber- 
cle above  cleft.  3,  c.  Prolongation  of  3  down- 
ward. 4,  5,  6.  Tubercles  on  hyoid  arch.  o.v. 
Auditory  vesicle. 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM 

Bloodvessels  first  make  their  appearance  in  several  scattered  vascidar  areas 
(Fig.  152)  which  are  developed  simultaneously  between  the  entoderm  and  the  meso- 
derm of  the  yolk-sac,  i.  e.,  outside  the  body  of  the  embryo.^    Here  the  cells  become 


1  No  definite  statement  can  be  made  as  to  whether  the  earliest  vessels  are  derived  from  the  entoderm  of  the  yolk- 
sac  or  from  the  mesoderm  overlying  it;  the  most  recent  view  favors  the  entoderm  as  the  original  source  of  the  blood 
corpuscles  and  endothelium  of  the  vessels. 


142 


EMBRYOLOGY 


arranged  into  solid  strands  or  cords  which  join  to  form  a  close-meshed  network,  the 
area  vasculosa,  which  covers  the  whole  yolk-sac.     The  peripheral  cells  of  these 


Helix 


Cms  helicis 


Aniihehz 


Cms  helicis 


Tragus 


Anhtragus 
Mandible         Lobule  Tragus 


»Ueh 


Antihelix 


Antitragus 


Mandible       -^^^^^^^ 


Fig.   150. — Left  auriculse  of  human  embryos  estimated  at  thirty-five  and  thirty-eight  days  respectively. 

(After  His.) 


strands  become  flattened  and  joined  to  each  other  by  their  edges  to  form  the  endo- 
thelium of  the  walls  of  the  primitive  bloodvessels.    Fluid  collects  within  the  strands 

and  converts  them  into  tubes,  and  the  more 
centrally  situated  cells  of  the  cell-cords  are  thus 
pushed  to  the  sides  of  the  vessels  and  appear  as 
masses  of  loosely  arranged  cells  projecting  toward 
the  lumen  of  the  tube.  These  masses  are  termed 
blood  islands  (Fig.  153);  their  cells  are  detached 
to  form  the  blood  corpuscles.  The  earliest  blood- 
vessels, therefore,  are  formed  at  several  separate 
centres;  from  the  walls  of  these  vessels  buds  grow 
out,  become  vascularized  and  converted  into  new 
vessels,  and  join  with  those  of  neighboring  areas 
to  form  a  close  meshwork.  It  is  uncertain  whether 
the  vessels  within  the  body  of  the  embryo  are  ex- 
tensions from  this  network  (His)  or  whether  they 
are  of  new  formation.  Most  observers  agree, 
however,  that,  after  the  aortse  have  appeared, 
no  other  independent  vessels  are  laid  down,  i.  e.,  all  new  vessels  are  derived  from 
preexisting  ones. 


Antihelix 
—  Crus  helicis 

—  Antitragus 
Lobule 


Tragus 

.  2Iandible 
Fig     151  — \uricula  m  a  more  advanced 
stage   of    development    than    those    repre- 
sented in  Fig.  150. 


Mesoderm 


Blood  island 


Mesoderm 


Vascular  cells 


Entoderm 


Endothelial  wall 
of  vessel 


Entoderm 


Fig.   152. — Section  through  vascular  area  to  show  differ- 
entiation of  primitive  vascular  cells.     Diagrammatic. 


Fig.   153. — Section   through  developing  bloodvessel. 
Diagrammatic. 


The  red  and  the  colorless  corpuscles  of  the  blood  are  all  derived  from  the  nucleated 
cells  of  the  blood  islands — mesamoeboid  cells  of  Minot — and  the  earliest  blood 
corpuscles  are  thus  all  nucleated;  they  are  also  capable  of  subdivision  and  of 


bEVELOPMEXr  OF  THE   VASCULAR  SYSTEM 


143 


FiQ.  154. — Transverse  section  through  the  region  of  the  heart  in 
a  rabbit  embryo  of  nine  days.  X  80.  (Kolliker.)  j,  j.  Jugular 
veins,  ao.  Aorta,  ph.  Pharynx,  soni.  Somatopleure.  hi.  Proamnion. 
ect.  Ectoderm,  enl.  Entoderm,  p.  Pericardium,  spl.  .Splanchno- 
pleure.  ah.  Outer  wall  of  heart,  ih.  Endothelial  lining  of  heart,  e'. 
Septum  between  heart  tubes. 


executino-  amcrboid   movoinents.      Some   of  these   cells   acquire  coloring   matter 
{heiiKHjJobin);  their  nuclei  ilisintegrate  and  are  expelled  and  the  non-nucleated  red 
corpuscles  result.  Other  mesam- 
oeboid  cells  retain  their  nuclei;  7, 

some  remain  in  the  blood  as 
the  leucocytes;  others  wander 
out  into  the  tissues,  particularly 
into  the  liver,  lymphoid  tissues, 
and  marrow  of  the  bones,  where 
they  form  specialized  masses 
from  which  the  corpuscles  of 
the  blood  are  regenerated.  From 
the  mesamoeboid  cells  five  chief 
forms  are  derived:  (1)  erythro- 
cytes, (2)  lymphocytes,  (3)  finely 
granular  or  neutrophil  leuco- 
cytes, (4)  coarsely  granular  or 
eosinophil  leucocytes,  (5)  degen- 
erating or  basiphil  leucocytes. 

The  first  rudiment  of  the  heart 
appears  as  a  pair  of  tubular 
vessels  which  are  developed  in 
the  splanchnopleure  of  the  peri- 
cardial area  (Fig.  154).  These 
are  named  the  primitive  aortse, 
and  a  direct  continuity'  is  soon 
established  between  them  and 
the  vessels  of  the  yolk-sac.  Each 
receives  anteriorly  a  vein — the 
vitelline  vein — from  the  yolk-sac, 
and  is  prolonged  backw^ard  on 
the  lateral  aspect  of  the  noto- 
chord  under  the  name  of  the 
dorsal  aorta.  The  dorsal  aortse 
give  brandies  to  the  yolk-sac, 
and  are  continued  backward 
through  the  body-stalk  as  the 
umbilical  arteries  to  the  villi  of 
the  chorion. 

Eternod^  describes  the  circu- 
lation in  an  embryo  which  he 
estimated  to  be  about  thirteen 
days  old  (Fig.  155).  The  rudi- 
ment of  the  heart  is  situated 
immediately  below  the  fore-gut 
and  consists  of  a  short  stem.  It 
gives  oft'  two  vessels,  the  primi- 
tive aortse,  which  run  backward, 
one  on  either  side  of  the  noto- 
chord,   and  then  pass  into  the 

body-stalk  along  which  they  are  carried  to  the  chorion.    From  the  chorionic  villi 
the  blood  is  returned  by  a  pair  of  umbilical  veins  wliich  unite  in  the  body-stalk 


Umbilical . 


Umbilical 


Allantoic 
diverticulum 

Body-stalh 


Fig.  15.5. — Diagram  of  the  vascular  channels  in  a  human  embryo 
of  the  second  week.  (After  Eternod.)  The  red  lines  are  the  dorsal 
aortas  continued  into  the  umbiUcal  arteries.  The  red  dotted  lines 
are  the  ventral  aortse,  and  the  blue  dotted  Lines  the  vitelline  veins. 


Anat.  Anzeiger,  1899,  vol.  xv. 


144 


EMBRYOLOGY 


to  form  a  single  vessel  and  subsequently  encircle  the  mouth  of  the  yolk-sac  and 
open  into  the  heart.  At  the  junction  of  the  ;]>'olk-sac  and  body-stalk  each  vein 
is  joined  by  a  branch  from  the  vascular  plexus  of  the  yolk-sac.  From  his 
observations  it  seems  that,  in  the  human  embryo,  the  chorionic  circulation  is 
established  before  that  on  the  yolk-sac. 


Dorsal  aorta 

Primitive  jugular 

vein 


Amnion 

Cardinal  vein 

Dorsal  aorta 


Body-stalk 


Chorionic  villi 


Fig.   156. — Human  embryo  of  about  fourteen  days  old  with  yolk-sac.     (After  His.) 

By  the  forward  growth  and  flexure  of  the  head  the  pericardial  area  and  the 
anterior  portions  of  the  primitive  aortse  are  folded  backward  on  the  ventral  aspect 
of  the  fore-gut,  and  the  original  relation  of  the  somatopleure  and  splanchnopleure 


Fore-brain 


Bulbus  cordis 


Atrium  — 


Optic  vesicle 


Ventricle 


—   Vitelline  vei% 


Fig.  157. — Head  of  chick  embryo  of  about  thirtj -eight  hours'  uicubj,tiuu,  viewed  from  the  ventral  surface.     X  26. 

(Duval.) 


layers  of  the  pericardial  area  is  reversed.  Each  primitive  aorta  now  consists  of 
a  ventral  and  a  dorsal  part  connected  anteriorly  by  an  arch  (Fig.  156) ;  these  three 
parts  are  named  respectively  the  anterior  ventral  aorta,  the  dorsal  aorta,  and  the 
first  cephalic   arch.      The  vitelline  veins  which  enter  the  embrj^o  through  the 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM  145 

anterior  wall  of  the  umbilical  orifice  are  now  continuous  with  the  posterior  ends  of 
the  anterior  ventral  aorta.  With  the  formation  of  the  tail-fold  the  posterior  i)arts 
of  the  primitive  aortje  are  carried  forward  in  a  ventral  direction  to  form  the  pos- 
terior ventral  aortie  and  primary  caudal  arches.^  In  the  pericardial  region  the  two 
primitive  aortse  grow  together,  and  fuse  to  form  a  single  tubular  heart  (Fig.  157), 
the  i)osterior  end  of  which  receives  the  two  vitelline  veins,  while  from  its  anterior 
end  the  two  anterior  \'entral  aortae  emerge.-  The  first  cephalic  arches  pass  through 
the  mandibular  arches,  and  behind  them  five  additional  pairs  subsequently  develop, 
so  that  altogether  six  pairs  of  aortic  arches  are  formed;  the  fifth  arches  are  very 
transitory  vessels  connecting  the  ventral  aortae  wdth  the  dorsal  ends  of  the  sixth 
arches.  By  the  rhythmical  contraction  of  the  tubular  heart  the  blood  is  forced 
through  the  aortae  and  bloodvessels  of  the  vascular  area,  from  which  it  is  returned 
to  the  heart  by  the  vitelline  veins.  This  constitutes  the  vitelline  circulation  (Fig. 
156),  and  by  means  of  it  nutriment  is  absorbed  from  the  yolk  vitellus. 

The  vitelline  veins  at  first  open  separately  into  the  posterior  end  of  the  tubular 
heart,  but  after  a  time  their  terminal  portions  fuse  to  form  a  single  vessel.  The 
vitelline  \eins  ultimately  drain  the  blood  from  the  digestive  tube,  and  are  modified 
to  form  the  portal  vein.  This  is  caused  by  the  growth  of  the  liver,  which  interrupts 
their  direct  continuity  with  the  heart;  and  the  blood  returned  by  them  circulates 
through  the  liver  before  reaching  the  heart. 

With  the  atrophy  of  the  yolk-sac  the  vitelline  circulation  diminishes  and  ulti- 
mately ceases,  while  an  increasing  amount  of  blood  is  carried  through  the  umbilical 
arteries  to  the  villi  of  the  chorion.  Subsequently,  as  the  non-placental  chorionic 
villi  atrophy,  their  vessels  disappear;  and  then  the  umbilical  arteries  convey  the 
whole  of  their  contents  to  the  placenta,  whence  it  is  returned  to  the  heart  by  the 
umbilical  veins.  In  this  manner  the  placental  circulation  is  established,  and  by 
means  of  it  nutritive  materials  are  absorbed  from,  and  waste  products  given  up  to, 
the  maternal  blood. 

The  umbilical  veins,  like  the  vitelline,  undergo  interruption  in  the  developing 
liver,  and  the  blood  returned  by  them  passes  through  this  organ  before  reaching 
the  heart.  Ultimately  the  right  umbilical  vein  shrivels  up  and  disappears,  as  will 
be  explained  later  (page  156). 

During  the  occurrence  of  these  changes  great  alterations  take  place  in  the 
primitive  heart  and  bloodvessels. 

Further  Development  of  the  Heart. — Between  the  endothelial  lining  and  the 
outer  wall  of  the  heart  there  exists  for  a  time  an  intricate  trabecular  network  of 
mesodermal  tissue  from  which,  at  a  later  stage,  the  musculi  papillares,  chordae 
tendineae,  and  trabeculae  carneae  are  developed.  The  simple  tubular  heart,  already 
described,  becomes  elongated  and  bent  on  itself  so  as  to  form  an  S-shaped  loop, 
the  anterior  part  bending  to  the  right  and  the  posterior  part  to  the  left  (Fig.  157). 
The  intermediate  portion  arches  transversely  from  left  to  right,  and  then  turns 
sharply  forward  into  the  anterior  part  of  the  loop.  Slight  constrictions  make  their 
appearance  in  the  tube  and  divide  it  from  behind  forward  into  five  parts,  viz.: 
(1)  the  sinus  venosus;  (2)  the  primitive  atrium;  (3)  the  primitive  ventricle;  (4)  the 
bulbus  cordis,  and  (5)  the  truncus  arteriosus  (Figs.  158,  159).  The  constriction 
between  the  atrium  and  ventricle  constitutes  the  atrial  canal,  and  indicates  the  site 
of  the  future  atrioventricular  valves. 

The  sinus  venosus  is  at  first  situated  in  the  septum  transversum  (a  layer  of 
mesoderm  in  w^hich  the  liver  and  the  central  tendon  of  the  Diaphragma  are  devel- 
oped) behind  the  primitive  atrium,  and  is  formed  by  the  union  of  the  vitelline 
veins.  The  veins  or  ducts  of  Cuvier  from  the  body  of  the  embryo  and  the  umbilical 
veins  from  the  placenta  subsequently  open  into  it  (Fig.  160).    The  sinus  is  at  first 

*  Young  and  Robinson,  Journal  of  Anatomy  and  Physiology,  vol.  xxxii. 

'  In  most  fishes  and  in  the  amphibia  the  heart  originates  as  a  single  median  tube. 

10 


U6 


EMBRYOLOGY 


place  transversely,  and  opens  by  a  median  aperture  into  the  primitive  atrium. 
Soon,  however,  it  assumes  an  obhque  position,  and  becomes  crescentic  in  form;  its 
right  half  or  horn  increases  more  rapidly  than  the  left,  and  the  opening  into  the 
atrium  now  communicates  with  the  right  portion  of  the  atrial  ca^'ity.  The  right 
horn  and  transverse  portion  of  the  sinus  ultimately  become  incorporated  with  and 
form  a  part  of  the  adult  right  atrium,  the  line  of  union  between  it  and  the  auricula 


Bulbils  cordis 
Ventricle 

Airimti 
Si7ius  venosus 

Vitelline  vein 


Fig.  158. — Diagram  to  illustrate  the  simple  tubular 
condition  of  the  heart.  (Drawn  from  Ecker-Ziegler 
model.) 


Fig.   159. — Heart  of  human  embryo  of  about  fourteen 
days.      (From  model  by  His.) 


being  indicated  in  the  interior  of  the  atrium  hj  a  vertical  crest,  the  crista  terminalis 
of  His.  The  left  horn,  which  ultimately  receives  only  the  left  duct  of  Cuvier, 
persists  as  the  coronary  sinus  (Fig.  161).  The  vitelline  and  umbilical  veins  are  soon 
replaced  by  a  single  vessel,  the  inferior  vena  cava,  and  the  three  veins  (inferior  vena 
cava  and  right  and  left  Cuvierian  ducts)  open  into  the  dorsal  aspect  of  the  atrium 
by  a  common  slit-like  aperture  (Fig.  162).  The  upper  part  of  this  aperture  repre- 
sents the  opening  of  the  permanent  superior  vena  cava,  the  lower  that  of  the  inferior 


Maxillary  process 
Stomodeum 
Mandibular  arch 


Bulbus  cordis  — 


Ventricle 
Duct  of  Cuvier 

Cardinal  vein 


Atrium 

Bile-duct 
Umbilical  vein 


Fig.   160. — Heart  of  human  embryo  of  about  fifteen  days.      (Reconstruction  by  His.) 


vena  cava,  and  the  intermediate  part  the  orifice  of  the  coronary  sinus.  The  slit- 
like aperture  lies  obliquely,  and  is  guarded  by  two  halves,  the  right  and  left  venous 
valves;  above  the  opening  these  unite  with  each  other  and  are  continuous  with  a 
fold  named  the  septum  spurium;  below  the  opening  they  fuse  to  form  a  triangular 
thickening — the  spina  vestibuli.  The  right  venous  valve  is  retained;  a  small 
septum,  the  sinus  septum,  grows  from  the  posterior  wall  of  the  sinus  venosus  to  fuse 


d'evelopment  of  the  vascl  lar  system 


147 


with  the  valve  and  divide  it  into  two  i)arts — an  iii)j)er,  the  valve  of  the  inferior 
vena  cava,  and  a  lower,  the  \alve  of  the  coronary  sinus  (Fig.  105).    The  extreme 


Left  duel  of 
Curii  r 


Openincj  lata         lliijJtl  dad  of 
iitridni,  Cuvicr 


Fig.   161. — Dorsal  surface  of  heart  of  human  embryo  of  thirty-five  days.      (From  model  by  His.) 

tSeptum  spuriwm 
I       Opening  cf  sinics  vcnosus 
Left  venous  valve 

Septum  primutn 


Right  venous 
valve 


Spina  vestibul 

Posterior  endocard 
cushio 

Atrial  canal 


Septum  inferius 
Fig.   162. — Interior  of  dorsal  half  of  heart  from  a  human  embryo  of  about  thirty  da>-s.      (From  model  by  His.) 

upper  portion  of  the  right  venous  valve,  together  with  the  septum  spurium,  form 
the  crista  terminalis  already  mentioned.    The  upper  and  middle  thirds  of  the  left 


148 


EMBRYOLOGY 


venous  valve  disappear;  the  lower  third  is  continued  into  the  spina  vestibuli, 
and  later  fuses  with  the  septum  secundum  of  the  atria  and  takes  part  in  the  forma- 
tion of  the  limbus  fossae  ovalis. 


Eight  atrimn 
Bulhus  cordis 


—  Left  atrium 

-  Atrial  canal 

Ventricle 


Fig.   163. — Heart  showing  expansion  of  the  atria.      (Drawn  from  Ecker-Zeigler  model.) 

The  atrial  canal  is  at  first  a  short  straight  tube  connecting  the  atrial  with  the 
ventricular  portion  of  the  heart,  but  its  growth  is  relatively  slow,  and  it  becomes 
overlapped  by  the  atria  and  ventricles  so  that  its  position  on  the  surface  of  the  heart 
is  indicated  only  by  an  annular  constriction  (Fig.  163).  Its  lumen  is  reduced  to  a 
transverse  slit,  and  tw^o  thickenings  appear,  one  on  its  dorsal  and  another  on  its 

Septum  secundum 
Opening  of  coronary  sinus         j      Spina  vestibuli  fused  with 
Septum  ■spurium      j         j  septum,  primum 


Bight  venous 

Right  atrioventricidnr 
opening 


atrioventricular 
opening 
Septum  intermedium 


Srptmii  i)iffrius 
Fig.    164. — Interior  of  dorsal  half  of  heart  of  human  embryo  of  about  thirty-five  days.     (From  model  by  His.) 


ventral  wall.  These  thickenings,  or  endocardial  cushions  (Fig.  162)  as  they  are 
termed,  project  into  the  canal,  and,  meeting  in  the  middle  line,  unite  to  form  the 
septum  intermedium  which  divides  the  canal  into  two  channels,  the  future  right  and 
left  atrioventricular  orifices. 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM 


149 


The  primitive  atrium  grows  rapidly  and  partially  encircles  the  bulbus  cordis; 
the  groove  against  whicii  the  bulbus  cordis  lies  is  the  first  indication  of  a  division 
into  right  and  left  atria.  The  cavity  of  the  primitive  atrium  becomes  subdivided 
into  right  and  loft  chambers  by  a  septum,  the  septiim  primum  (Fig.  1G2),  which 
grows  downward  into  the  cavity.  For  a  time  the  atria  communicates  with  each 
other  by  an  opening,  the  ostium  primum  of  Born,  below  the  free  margin  of  the  septum. 
This  opening  is  closed  by  the  union  of  the  septum  primum  with  the  septum  inter- 
medium, and  the  communication  between  the  atria  is  reestal)lished  through  an 
opening  which  is  dcvcl()i)cd  in  the  upper  part  of  the  septum  primum;  this  opening 
is  known  as  the  foramen  ovale  {ostiiini  secundum  of  Born)  and  persists  until  birth. 
A  second  septum,  the  septum  secundum  (Figs.  164,  165),  semilunar  in  shape,  grows 
downward  from  the  upper  wall  of  the  atrium  immediately  to  the  right  of  the 
primary  septum  and  foramen  ovale.  Shortly  after  birth  it  fuses  with  the  primary 
septum,  and  by  this  means  the  foramen  ovale  is  closed,  but  sometimes  the  fusion 
is  incomplete  and  the  upper  part  of  the  foramen  remains  patent.    The  limbus  fossae 


Left  duel  of  Cuviej 


Opening  of  coronanj 
sinus 


roramen  ovale 
Probe  in  aorta 
Aortic  septum 


^Scptivm 

intermedium 


Septum 
inferius 


Fig.   165. — Same  heart  as  in  Fig.  164,  opened  on  right  side.      (From  model  by  His.) 


ovalis  denotes  the  free  margin  of  the  septum  secundum.  Issuing  from  each  lung 
is  a  pair  of  pulmonary  veins;  each  pair  unites  to  form  a  single  vessel,  and  these  in 
turn  join  in  a  common  trunk  which  opens  into  the  left  atrium.  Subsequently 
the  common  trunk  and  the  two  vessels  forming  it  expand  and  form  the  vestibule 
or  greater  part  of  the  atrium,  the  expansion  reaching  as  far  as  the  openings  of  the 
four  vessels,  so  that  in  the  adult  all  four  veins  open  separately  into  the  left  atrium. 

The  primitive  ventricle  becomes  divided  by  a  septum,  the  septum  inferius  or 
ventricular  septum  (Figs.  162,  164,  165),  which  grows  upward  from  the  lower  part 
of  the  ventricle,  its  position  being  indicated  on  the  surface  of  the  heart  by  a  furrow. 
Its  dorsal  part  increases  more  rapidly  than  its  ventral  portion,  and  fuses  with  the 
dorsal  part  of  the  septum  intermedium.  For  a  time  an  interventricular  foramen 
exists  above  its  ventral  portion  (Fig.  165),  but  this  foramen  is  ultimately  closed  by 
the  fusion  of  the  aortic  septum  with  the  ventricular  septum. 

When  the  heart  assumes  its  S-shaped  form  the  bulbus  cordis  lies  ventral  to  and 
in  front  of  the  primitive  ventricle.  The  adjacent  walls  of  the  bulbus  cordis  and 
ventricle  approximate,  fuse,  and  finally  disappear,  and  the  bulbus  cordis  now 


150 


EMBRYOLOGY 


communicates  freely  with  the  riglit  \entricle,  while  the  junction  of  the  hulbus  with 
the  truncus  arteriosus  is  brought  directly  ventral  to  and  applied  to  the  atrial  canal. 


Fig.   166. — Diagrams  to  illustrate  the  transformation  of  the  bulbus  cordis.     (Keith.)     Ao.  Truncus  arteriosus. 
Au.  Atrium.     B.  Bulbus  cordis.     RV.  Right  ventricle.     LV.  Left  ventricle.     P.  Pulmonary  artery. 

By  the  upgrowth  of  the  ventricular  septum  the  bulbus  cordis  is  in  great  measure 
separated  from  the  left  ventricle,  but  remains  an  integral  part  of  the  right  ventricle, 
of  which  it  forms  the  infundibulum  (Fig.  166). 


Aortic  septum 


Common  atrio- 
ventr  icular  aperture 


Right  ^ 
ventricle 


Septum  Left 

inferius         ventricle 


Aortic  septum 


Pulmonary 
artery 


Aorta 


Eight  atrio- 
ventricular 
orifice 


Bight 
ventricle 


Left  atrio- 
ventricular 
orifice 


Left 
ventricle 


Septum  inferius 
Fig.  167. — Diagrams  to  show  the  development  of  the  septum  of  the  aortic  bulb  and  of  the  ventricles.      (Born.) 


The  truncus  arteriosus  and  bulbus  cordis  are  divided  by  the  aortic  septum  (Fig. 
167).     This  makes  its  appearance  in  three  portions.     (1)  Two  distal  ridge-like 


Aorta 


Aorta 


Aorta 


Pulmonary  artery 


Pulmo- 
nary artery 


Pulmonary  artery 


Fig.   168. — Transverse  sections  through  the  aortic  bulb  to  show  the  growth  of  the  aortic  septum.     The  lowest 
section  is  on  the  left,  the  highest  on  the  right  of  the  figure.      (After  His.) 


thickenings  project  into  the  lumen  of  the  tube;  these  increase  in  size,  and  ultimately 
meet  and  fuse  to  form  a  septum,  which  takes  a  spiral  course  toward  the  proximal 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM 


151 


end  of  the  truncus  arteriosus.  It  divides  the  distal  part  of  the  truncus  into  two 
vessels,  the  aorta  and  i)uhn()nary  artery,  which  lie  side  by  side  above,  but  near 
the  heart  the  puhnouary  artery  is  in  front  of  the  aorta.  (2)  Four  endocardial 
cnsliions  appear  in  the  proximal  i)art  of  the  truncus  arteriosus  in  the  region  of  the 
future  semilunar  valves;  the  manner  in  which  these  are  related  to  the  aortic  septum 
is  described  below.  (3)  Two  endocardial  thickenings — anterior  and  posterior — 
develop  in  the  bulbns  cordis  and  unite  to  form  a  short  septum;  this  joins  above  with 
the  aortic  septum  and  below  with  the  ventricular  septum.  The  septum  grows  down 
into  the  ventricle  as  an  oblique  partition,  which  ultimately  blends  with  the  ven- 
tricular septum  in  such  a  way  as  to  bring  the  bulbus  cordis  into  communication 
with  the  pulmonary  artery,  and  through  the  latter  with  the  sixth  pair  of  aortic 
arches;  while  the  left  ventricle  is  brought  into  continuity  with  the  aorta,  which 
communicates  with  the  remaining  aortic  arches. 


Second  aortic  arch 
Third  aortic  arch 


First  aortic  arch 


Atulitory  vesicle 


Primitive  jugular  vein 
Fourth  aortic  arch 

Sixth  aortic  arch 
Dorsal  aorta 


Cardinal  vein 


Digestive  tiibe 


Himl-gut 


Vnibilical  vein 


Olfactory  pit 


Maxillary  process 
First  branchial  groove 
Mandibular  arch 

Bulbus  cordis 
A  trinm 
Duct  of  Cuvier 
Ventricle 


Vitelline  vein 
Yolk-sac 


Allantois 
Unibilical  artery 


Fig.   169. — Profile  view  of  a  human  embryo  estimated  at  twenty  or  twenty-one  days  old.     (After  His.) 


The  Valves  of  the  Heart. — The  atrioventricular  valves  are  developed  in  relation  to 
the  atrial  canal.  By  the  upward  expansion  of  the  bases  of  the  ventricles  the  canal 
becomes  invaginated  into  the  ventricular  cavities.  The  invaginated  margin  forms 
the  rudiments  of  the  lateral  cusps  of  the  atrioventricular  valves;  the  mesial  or 
septal  cusps  of  the  valves  are  developed  as  downward  prolongations  of  the  septum 
intermedium  (Fig.  164).  The  aortic  and  pulmonary  semilunar  valves  are  formed 
from  four  endocardial  thickenings — an  anterior,  a  posterior,  and  two  lateral — 


152 


EMBRYOLOGY 


which  appear  at  the  proximal  end  of  the  truncus  arteriosus.  As  the  aortic  septum 
grows  downward  it  divides  each  of  the  lateral  thickenings  into  two,  thus  giving 
rise  to  six  thickenings — the  rudiments  of  the  semilunar  valves — three  at  the  aortic 
and  three  at  the  pulmonary  orifice  (Fig.  1G8). 

Further  Development  of  the  Arteries.— Recent  observations  show  that  practi- 
cally none  of  the  main  vessels  of  the  adult  arise  as  such  in  the  embryo.  In  the  site 
of  each  vessel  a  capillary  network  forms,  and  by  the  enlargement  of  definite  paths 
in  this  the  larger  arteries  and  veins  are  developed.  The  branches  of  the  main 
arteries  are  not  always  simple  modifications  of  the  vessels  of  the  capillary  network, 
but  may  arise  as  new  outgrowths  from  the  enlarged  stem. 

EocUrnal  carotid 

Ventral  aorta 


— j Internal  carotid 

Common  carotid 

Aortic  arch 


Right  subclavian 
artery 


Might  pulmonary 
artery 


Ductus  arteriosus 
Vertebral  artery 

Subclavian  artery 


Trunk  of  pulmonary 
artery 


Left  pulmonary  artery 


Fig.   170. — Scheme  of  the  aortic  arches  and  their  destination.     (Modified  from  KoUmann.) 


It  has  been  seen  (page  145)  that  each  primitive  aorta  consists  of  a  ventral  and 
a  dorsal  part  which  are  continuous  through  the  first  aortic  arch .  The  dorsal  aortse 
at  first  run  backward  separately  on  either  side  of  the  notochord,  but  about  the 
third  week  they  fuse  from  about  the  level  of  the  fourth  thoracic  to  that  of  the  fourth 
lumbar  segment  to  form  a  single  trunk,  the  descending  aorta.  The  first  aortic 
arches  run  through  the  mandibular  arches,  and  behind  them  five  additional  pairs 
are  developed  within  the  visceral  arches;  so  that,  in  all,  six  pairs  of  aortic  arches 
are  formed  (Figs.  169,  170).  The  first  and  second  arches  pass  between  the  ventral 
and  dorsal  aortse,  while  the  others  arise  at  first  by  a  common  trunk  from  the  truncus 
arteriosus,  but  end  separately  in  the  dorsal  aortse.  As  the  neck  elongates,  the 
ventral  aortse  are  drawn  out,  and  the  third  and  fourth  arches  arise  directly  from 
these  vessels. 

In  fishes  these  arches  persist  and  give  off  branches  to  the  gills,  in  which  the 
blood  is  oxygenated.  In  mammals  some  of  them  remain  as  permanent  structures, 
while  others  disappear  or  become  obliterated  (Fig.  170). 

The  Anterior  Ventral  Aortse. — These  persist  on  both  sides.  The  right  forms  (a) 
the  innominate  artery,  (6)  the  right  common  and  external  carotid  arteries.  The 
left  gives  rise  to  (a)  the  short  portion  of  the  aortic  arch,  which  reaches  from  the 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM 


153 


origin  of  the  innominate  artery  to  that  of  the  left  common  carotid  artery;  (h)  the 
left  common  and  external  carotid  arteries. 

The  Aortic  Arches. — The  first  and  second  arches  disappear  early,  but  the  dorsal 
end  of  the  second  gives  origin  to  the  stapedial  artery  (Fig.  171),  a  vessel  which 
atrophies  in  man  but  persists  in  some  mammals.  It  passes  through  the  ring  of  the 
stapes  and  divides  into  supraorbital,  infraorbital,  and  mandibular  branches  which 
follow  the  three  divisions  of  the  trigeminal  nerve.  The  infraorbital  and  man- 
dibular arise  from  a  common  stem,  the  terminal  part  of  which  anastomoses  with 


Post,  cerebral  a. 


Ant.  cerebral  a. 

Supraorbital  br. 
of  stapedial  a. 

Trigeminal  nerve 


Maxillary  nerve 
Infraorbital  a. 


Stapedial  a. 


Mandibular  ? 

Mandibidar  a. 
Ext.  max.  a. 

Lingual  a. 
Sup.  thyroid  a. 

Common  carotid  a. 


Int.  carotid  a. 


Aortic  ar 

Pulmonary  arch 

Pulmonary  art. 

Dorsal  aorta 

Fig.   171. — Diagram  showing  the  origins  of  the  main  branches  of  the  carotid  arteries.     (Founded  on  Tandler.) 


the  external  carotid.  On  the  obliteration  of  the  stapedial  artery  this  anastomosis 
enlarges  and  forms  the  internal  maxillary  artery,  and  the  branches  of  the  stapedial 
artery  are  now  branches  of  this  vessel.  The  common  stem  of  the  infraorbital  and 
mandibular  branches  passes  between  the  two  roots  of  the  auriculotemporal  nerve 
and  becomes  the  middle  meningeal  artery;  the  original  supraorbital  branch  of  the 
stapedial  is  represented  by  the  orbital  twigs  of  the  middle  meningeal.  The  third 
aortic  arch  constitutes  the  commencement  of  the  internal  carotid  artery,  and  is 
therefore  named  the  carotid  arch.  The  fourth  right  arch  forms  the  right  sub- 
clavian as  far  as  the  origin  of  its  internal  mammary  branch;  while  the  fourth  left 
arch  constitutes  the  arch  of  the  aorta  between  the  origin  of  the  left  carotid  artery 
and  the  termination  of  the  ductus  arteriosus.  The  fifth  arch  disappears  on  both 
sides.    The  sixth  right  arch  disappears;  the  sixth  left  arch  gives  off  the  pulmonary 


154  EMBRYOLOGY 

arteries  and  forms  the  ductus  arteriosus;  this  duct  remains  pervious  during  the 
whole  of  fetal  life,  but  is  obliterated  a  few  days  after  birth.  His  showed  that  in  the 
early  embryo  the  right  and  left  arches  each  gives  a  branch  to  the  lungs,  but  that 
later  both  pulmonary  arteries  take  origin  from  the  left  arch. 

The  Dorsal  Aortse. — In  front  of  the  third  aortic  arches  the  dorsal  aortae  persist 
and  form  the  continuations  of  the  internal  carotid  arteries;  these  arteries  pass  to  the 
brain  and  each  divides  into  an  anterior  and  a  posterior  branch,  the  former  giving 
off  the  ophthalmic  and  the  anterior  and  middle  cerebral  arteries,  while  the  latter 
turns  back  and  joins  the  cerebral  part  of  the  vertebral  artery.  Behind  the  third 
arch  the  right  dorsal  aorta  disappears  as  far  as  the  point  where  the  two  dorsal 
aortse  fuse  to  form  the  descending  aorta.  The  part  of  the  left  dorsal  aorta  between 
the  third  and  fourth  arches  disappears,  while  the  remainder  persists  to  form 
the  descending  part  of  the  arch  of  the  aorta.  A  constriction,  the  aortic  isthmus,  is 
sometimes  seen  in  the  aorta  between  the  origin  of  the  left  subclavian  and  the 
attachment  of  the  ductus  arteriosus. 

Sometimes  the  right  subclavian  artery  arises  from  the  aortic  arch  distal  to  the 
origin  of  the  left  subclavian  and  passes  upward  and  to  the  right  behind  the  trachea 
and  oesophagus.  This  condition  may  be  explained  by  the  persistence  of  the  right 
dorsal  aorta  and  the  obliteration  of  the  fourth  right  arch. 

In  birds  the  fourth  right  arch  forms  the  arch  of  the  aorta;  in  reptiles  the  fourth 
arch  on  both  sides  persists  and  gives  rise  to  the  double  aortic  arch  in  these  animals. 

The  heart  originally  lies  on  the  ventral  aspect  of  the  pharynx,  immediately 
■behind  the  stomodeum.  With  the  elongations  of  the  neck  and  the  development 
of  the  lungs  it  recedes  within  the  thorax,  and,  as  a  consequence,  the  anterior 
ventral  aortse  are  drawn  out  and  the  original  position  of  the  fourth  and  fifth  arches 
is  greatly  modified.  Thus,  on  the  right  side  the  fourth  recedes  to  the  root  of  the 
neck,  while  on  the  left  side  it  is  withdrawn  within  the  thorax.  The  recurrent 
nerves  originally  pass  to  the  larynx  under  the  sixth  pair  of  arches,  and  are  there- 
fore pulled  backward  with  the  descent  of  these  structures,  so  that  in  the  adult  the 
left  nerve  hooks  around  the  ligamentum  arteriosum;  owing  to  the  disappearance  of 
the  fifth  and  the  sixth  right  arches  the  right  nerve  hooks  around  that  immediately 
above  them,  /.  e.,  the  commencement  of  the  subclavian  artery.  Segmental  arteries 
arise  from  the  primitive  dorsal  aortee  and  course  between  successive  segments. 
The  seventh  segmental  artery  is  of  special  interest,  since  it  forms  the  lower  end  of 
the  vertebral  artery  and,  when  the  forelimb  bud  appears,  sends  a  branch  to  it 
(the  subclavian  artery).  From  the  seventh  segmental  arteries  the  entire  left 
subclavian  and  the  greater  part  of  the  right  subclavian  are  formed.  The  second 
pair  of  segmental  arteries  accompany  the  hypoglossal  nerves  to  the  brain  and  are 
named  the  hypoglossal  arteries.  Each  sends  forward  a  branch  which  forms  the 
cerebral  part  of  the  vertebral  artery  and  anastomoses  with  the  posterior  branch 
of  the  internal  carotid.  The  two  vertebrals  unite  on  the  ventral  surface  of  the 
hind-brain  to  form  the  basilar  artery.  Later  the  hypoglossal  artery  atrophies 
and  the  vertebral  is  connected  with  the  first  segmental  artery.  The  cervical  part 
of  the  vertebral  is  developed  from  a  longitudinal  anastomosis  between  the  first 
seven  segmental  arteries,  so  that  the  seventh  of  these  ultimately  becomes  the  source 
of  the  artery.  As  a  residt  of  the  growth  of  the  upper  limb  the  subclavian  artery 
increases  greatly  in  size  and  the  vertebral  then  appears  to  spring  from  it. 

Recent  observations  show  that  several  segmental  arteries  contribute  branches  to 
the  upper  limb-bud  and  form  in  it  a  free  capillary  anastomosis.  Of  these  branches, 
only  one,  viz.,  that  derived  from  the  seventh  segmental  artery,  persists  to  form 
the  subclavian  artery.  The  subclavian  artery  is  prolonged  into  the  limb  under 
the  names  of  the  axillary  and  brachial  arteries,  and  these  together  constitute  the 
arterial  stem  for  the  upper  arm,  the  direct  continuation  of  this  stem  in  the  forearm 
is  the  volar  interosseous  artery.    A  branch  which  accompanies  the  median  nerve 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM 


155 


soon  increases  in  size  and  forms  the  main  vessel  (median  artery)  of  the  forearm, 
while  the  volar  interosseous  diminishes.  Later  the  radial  and  ulnar  arteries  are 
developed  as  branches  of  the  brachial  part  of  the  stem  and  coincidently  with  their 
enlargement  the  median  artery  recedes;  occasionally  it  persists  as  a  vessel  of  some 
considerable  size  and  then  accompanies  the  median  nerve  into  the  palm  of  the  hand. 
The  primary  arterial  stem  for  the  lower  limb  is  formed  by  the  inferior  gluteal 
(sciatic)  artery,  which  accompanies  the  sciatic  nerve  along  the  posterior  aspect  of 
the  thigh  to  the  back  of  the  knee,  whence  it  is  continued  as  the  peroneal  arter}'. 
This  arrangement  exists  in  reptiles  and  amphibians.  The  femoral  artery  arises 
later  as  a  branch  of  the  common  iliac,  and,  passing  down  the  front  and  medial 
side  of  the  thigh  to  the  bend  of  the  knee,  joins  the  inferior  gluteal  artery.  The 
femoral  quickly  enlarges,  and,  coincidently  with  this,  the  part  of  the  inferior  gluteal 
immediately  above  the  knee  undergoes  atrophy.  The  anterior  and  posterior  tibial 
arteries  are  branches  of  the  main  arterial  stem. 


Anterior  detached  portions 
of  utnbilical  veins 


Venae  revehentes 


Stomach 
Venae  advehentes 
Pancreas 
Bile-duct 


Obliterated  portions 
of  venovjS  rings 

Right  umbilical  vein 


Ductus  venosus 


Liver 


Left  umbilical  vein 


Duodenum 


Portal  vein 
Vitelline 


Fig.   172. — The  liver  and  the  veins  in  connection  with  it,  of  a  human  embrj'^o,  twenty-four  or  twenty-five  days  old; 

as  seen  from  the  ventral  surface.     (After  His.) 


Further  Development  of  the  Veins. — The  formation  of  the  great  veins  of  the 
embryo  may  be  best  considered  by  dividing  them  into  two  groups,  visceral  and 
parietal. 

The  Visceral  Veins. — The  visceral  veins  are  the  two  vitelline  or  omphalomesenteric 
veins  bringing  the  blood  from  the  yolk-sac,  and  the  two  umbilical  veins  returning 
the  blood  from  the  placenta;  these  four  veins  open  close  together  into  the  sinus 
venosus. 

The  Vitelline  Veins  run  upward  at  first  in  front,  and  subsequently  on  either 
side  of  the  intestinal  canal.  They  unite  on  the  ventral  aspect  of  the  canal,  and 
beyond  this  are  connected  to  one  another  by  two  anastomotic  branches,  one  on  the 
dorsal,  and  the  other  on  the  ventral  aspect  of  the  duodenal  portion  of  the  intestine, 
which  is  thus  encircled  by  two  venous  rings  (Fig.  172) ;  into  the  middle  or  dorsal 
anastomosis  the  superior  mesenteric  vein  opens.  The  portions  of  the  veins  above 
the  upper  ring  become  interrupted  by  the  developing  liver  and  broken  up  by  it  into 
a  plexus  of  small  capillary-like  vessels  termed  sinusoids  (Minot).  The  branches 
conveying  the  blood  to  this  plexus  are  named  the  venae  advehentes,  and  become 


156 


EMBRYOLOGY 


the  branches  of  the  portal  vein;  while  the  vessels  draining  the  plexus  into  the 
sinus  venosus  are  termed  the  venae  revehentes,  and  form  the  future  hepatic  veins 
(Figs.  172,  173).  Ultimately  the  left  vena  revehens  no  longer  communicates 
directly  with  the  sinus  venosus,  but  opens  into  the  right  vena  revehens.  The 
persistent  part  of  the  upper  venous  ring,  above  the  opening  of  the  superior  mes- 
enteric vein,  forms  the  trunk  of  the  portal  vein. 


Eight  primitive  jugular  vein 
Eight  cardinal^  lein  ^, 

Eight  duct  of  Cuviei 

Sinus  venosus 
Eight  hepatic  vein 

Portal  vein 
Portal  vein 


Eight  umbilical  vein 


Umbilical  cord- 


Left  primitive 
jugular  vein 

Left  cardinal  vein 


Left  duct  of  Cuvier 

Left  hepatic  vein 
Left  umbilical  vein 


Left  umbilical  vein 


Fio.  173. — Human  embryo  with  heart  and  anterior  body-wall  removed  to  show  the  sinus  venosus  and  its  tributaries. 

(After  His.) 

The  two  Umbilical  Veins  fuse  early  to  form  a  single  trunk  in  the  body-stalk, 
but  remain  separate  within  the  embryo  and  pass  forward  to  the  sinus  venosus 
in  the  side  walls  of  the  body.  Like  the  vitelline  veins,  their  direct  connection 
with  the  sinus  venosus  becomes  interrupted  by  the  developing  liver,  and  thus  at 
this  stage  the  whole  of  the  blood  from  the  yolk-sac  and  placenta  passes  through 
the  substance  of  the  liver  before  it  reaches  the  heart.  The  right  umbilical  and 
right  vitelline  veins  shrivel  and  disappear;  the  left  umbilical,  on  the  other  hand, 
becomes  enlarged  and  opens  into  the  upper  venous  ring  of  the  vitelline  veins;  with 
the  atrophy  of  the  yolk-sac  the  left  vitelline  vein  also  undergoes  atrophy  and 
disappears.  Finally  a  direct  branch  is  established  between  this  ring  and  the  right 
hepatic  vein;  this  branch  is  named  the  ductus  venosus,  and,  enlarging  rapidly, 
it  forms  a  wdde  channel  through  which  most  of  the  blood,  returned  from  the 
placenta,  is  carried  direct  to  the  heart  without  passing  through  the  liver.  A  small 
proportion  of  the  blood  from  the  placenta  is,  how^ever,  conveyed  from  the  left 
umbilical  vein  to  the  liver  through  the  left  vena  advehens.  The  left  umbilical 
vein  and  the  ductus  venosus  undergo  atrophy  and  obliteration  after  birth,  and 
form  respectively  the  ligamentum  teres  and  ligamentum  venosum  of  the  liver. 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM 


157 


The  Parietal  Veins. — The  first  indication  of  a  parietal  system  consists  in  the 
appearance  of  two  short  transverse  veins,  the  ducts  of  Cuvier,  which  open,  one 
on  either  side,  into  the  sinus  venosus.  Each  of  these  ducts  receives  an  ascending 
and  descending  vein.  The  ascending  veins  return  the  blood  from  the  parietes 
of  the  trunk  and  from  the  Wolffian  bodies,  and  are  called  cardinal  veins.  The 
descending  veins  return  the  blood  from  the  head,  and  are  called  primitive  jugular 
veins  (Hg.  174).  The  blood  from  the  lower  limbs  is  collected  by  the  right  and 
left  iliac  and  hypogastric  ^'eins,  which,  in  the  earlier  stages  of  development,  open 
into  the  corresponding  right  and  left  cardinal  veins ;  later,  a  transverse  branch  (the 
left  common  iliac  vein)  is  developed  between  the  lower  parts  of  the  two  cardinal 
veins  (Fig.  176),  and  through  this  the  blood  is  carried  into  the  right  cardinal  vein. 
The  portion  of  the  left  cardinal  vein  below  the  left  renal  vein  atrophies  and  dis- 
appears up  to  the  point  of  entrance  of  the  left  spermatic  vein;  the  portion  above 
the  left  renal  vein  persists  as  the  hemiazygos  and  accessory  hemiazygos  veins 
and  the  lower  portion  of  the  highest  left  intercostal  vein.      The  right  cardinal  vein 


Sinus  venosus 


Primitive  jugtilar 
Subclavian 

Duct  of  Cuvier 
Vitelline 
Umbilical 
Cardinal 

Svbcardinal 
Eenal 


External  iliac 

Hypogastric 

Fig.  174. — Scheme  of  arrangement  of  parietal 
veins. 


Internal  jugular 
External  jugular 
Subclavian 


Duct  of  Cuvier 

Left  cardinal 
Ductus  venosus 


■Renal 
— Subcardinal 


External  iliac 
/\       / Hypogastric 


Fig.   175. — Scheme  showing  early  stages  of 
development  of  the  inferior  vena  cava. 


which  now  receives  the  blood  from  both  lower  extremities,  forms  a  large  venous 
trunk  along  the  posterior  abdominal  wall;  up  to  the  level  of  the  renal  veins  it 
forms  the  lower  part  of  the  inferior  vena  cava.  Above  the  level  of  the  renal  veins 
the  right  cardinal  vein  persists  as  the  azygos  vein  and  receives  the  right  intercostal 
veins,  while  the  hemiazygos  veins  are  brought  into  communication  with  it  by  the 
development  of  transverse  branches  in  front  of  the  vertebral  column  (Figs.  176,  177) 
Inferior  Vena  Cava. — The  development  of  the  inferior  vena  cava  is  associated 
with  the  formation  of  two  veins,  the  subcardinal  veins  (Figs.  174,  175).  These 
lie  parallel  to,  and  on  the  ventral  aspect  of,  the  cardinal  veins,  and  originate  as 
longitudinal  anastomosing  channels  which  link  up  the  tributaries  from  the  mes- 
entery to  the  cardinal  veins ;  they  communicate  with  the  cardinal  veins  above  and 
below,  and  also  b}'  a  series  of  transverse  branches.  The  two  subcardinals  are  for 
a  time  connected  with  each  other  in  front  of  the  aorta  by  cross  branches,  but  these 
disappear  and  are  replaced  by  a  single  transverse  channel  at  the  level  where  the 
renal  veins  join  the  cardinals,  and  at  the  same  level  a  cross  communication  is 


158 


EMBRYOLOGY 


established  on  either  side  between  the  cardinal  and  subcardinal  (Fig.  175).  The 
portion  of  the  right  subcardinal  behind  this  cross  communication  disappears,  while 
that  in  front,  i.  e.,  the  prerenal  part,  forms  a  connection  with  the  ductus  venosus 


Left  inriomlnale 


Might  innominate 
Superior  vena  cava 


Prerenal  part  of 
inferior  vena  cava 


Postrenal  part  of 
inferior  vena  cava 


•Internal  jugular 
■External  jugular 


Duct  of  Cuvier 


Left  carelinal 


Left  suprarenal 
Left  rejial 


Left  common  iliac 
External  iliac 
Hypogastric 


Fig.   176. — Diagram  showing  development  of  main  cross  branches  between  jugulars  and  between  cardinals. 

at  the  point  of  opening  of  the  hepatic  veins,  and,  rapidity  enlarging,  receives  the 
blood  from  the  postrenal  part  of  the  right  cardinal  through  the  cross  communica- 


te/^ innominate 


Right  iymominate 

Superior  vena  cava 
Azygos  vein 


Prerenal  pari  of 
inferior  vena  cava 


Internal  jugular 
External  jugular 
Subclavian 
—  Highest  left  intercostal 

Ligament  of  left  vena  cava 

^- j^ Oblique  vein  of  left  atrium 

^~ — C Coronary  sinus 

Accessory  hemiazygos  vein 


Hemiazygos  vein 
Left  suprarenal 
Left  renal 
Left  internal  spermatic 


Fig.  177. 


—    Left  common  iliac 
External  iliac 
Hypogastric 
-Diagram  showing  completion  of  development  of  the  parietal  veins. 


tion  referred  to.  In  this  manner  a  single  trunk,  the  inferior  vena  cava  (Fig.  177),  is 
formed,  and  consists  of  the  proximal  part  of  the  ductus  venosus,  the  prerenal  part 
of  the  right  subcardinal  vein,  the  postrenal  part  of  the  right  cardinal  vein,  and  the 


bEVELOPMEXT  OF  THE  VASCCLAR  SYSTEM 


159 


cross  branch  which  joins  these  two  veins.  The  left  suhcardinal  (lisai)pears,  except 
the  part  immeiHatcly  in  front  of  the  renal  vein,  which  is  retained  as  the  left  supra- 
renal vein.  The  spermatic  (or  ovarian)  vein  opens  into  the  postrenal  part  of 
the  corresponding  cardinal  vein.  This  portion  of  the  right  cardinal,  as  already 
explained,  forms  the  h)wer  part  of  the  inferior  vena  cava,  so  tliat  the  right  sjiermatic 
opens  directly  into  that  vessel.  The  postrenal  segment  of  the  left  cardinal  dis- 
appears, with  the  exception  of  the  portion  between  the  spermatic  and  renal  vein, 
which  is  retained  as  the  terminal  part  of  the  left  spermatic  vein. 
In  consequence  of  the  atro- 

^-1  uditory  vesicle 


Primitive 
jugular  vein 


Vena  capitis  medialis 
Trigeminal  nerve 

Ophthalmic  vein 


Vena  capitis    _g^ 
lateralis 


Superior  sagittal 
sinus 


Fig.   its. — Diagram  of  veins  of  head  of  an  embrjo  four  weeks  old. 
(After  Mall.) 


phy  of  the  Wolffian  bodies  the 
cardinal  veins  diminish  in  size; 
the  primitive  jugular  veins, 
on  the  other  hand,  become 
enlarged,  owing  to  the  rapid 
development  of  the  head  and 
brain.  They  are  further  aug- 
mented by  recei^'ing  the  veins 
(subclavian)  from  the  upper  ex- 
tremities, and  so  come  to  form 

the  chief  veins  of  the  Cuvierian  ducts;  these  ducts  gradually  assume  an  almost 
vertical  position  in  consequence  of  the  descent  of  the  heart  into  the  thorax.  The 
right  and  left  Cuvierian  ducts  are  originally  of  the  same  diameter,  and  are  frequently 
termed  the  right  and  left  superior  venge  cavae.  By  the  development  of  a  transverse 
branch,  the  left  innominate  vein  between  the  two  primitive  jugular  veins,  the 
blood  is  carried  across  from  the  left  to  the  right  primitive  jugular  (Figs.  176,  177). 
The  portion  of  the  right  primitive  jugular  vein  between  the  left  innominate  and 
the  azygos  vein  forms  the  upper  part  of  the  superior  vena  cava  of  the  adult;  the 
lower  part  of  this  vessel,  i.  e.,  below  the  entrance  of  the  azygos  vein,  is  formed  by 
the  right  Cuvierian  duct.     Below  the  origin  of  the  transverse  branch  the  left 


Posterior 
cerebral  vein' 


Audit 
vesii 

.       1 

ory 
le 

Middle 

cerebral 

vein 

Anterior  cerebral  vein 
\           Torcular  Herophili 

\\  /^                  ^^^^.^^^Superior  sagittal 
\  If                  y     \/      sinus 

Jugular  vein- 


'Trigeminal  nerve 


Vena  capitis  lateralis  Ophthalmic  vein 

Fig.   179. — Diagram  of  veins  of  head  of  an  embryo  five  weeks  old.     (-\fter  Mall.) 


primitive  jugular  vein  and  left  Cuvierian  duct  atrophy,  the  former  constituting 
the  upper  part  of  the  highest  left  intercostal  vein,  while  the  latter  is  represented 
by  the  ligament  of  the  left  vena  cava,  vestigial  fold  of  Marshall,  and  the  oblique 
vein  of  the  left  atrium,  oblique  vein  of  Marshall  (Fig.  177).  Both  right  and  left 
superior  vense  cavse  are  present  in  some  animals,  and  are  occasionally  found  in  the 
adult  human  being.  The  oblique  vein  of  the  left  atrium  passes  downward  across 
the  back  of  the  left  atrium  to  open  into  the  coronary  sinus,  which,  as  already 
indicated,  represents  the  persistent  left  horn  of  the  sinus  venosus. 

The  primitive  jugular  veins  drain  the  blood  from  the  brain,  and  their  proximal 
parts  form  the  internal  jugular  veins.  The  distal  portion  of  each  has  been  named 
the  vena  capitis  medialis  (Fig.  178);  it  runs  on  the  medial  side  of  the  auditory 


160 


EMBRYOLOGY 


vesicle  and  cerebral  nerve  roots,  and  the  portion  of  it  situated  in  the  neighborhood 
of  the  trigeminal  nerve  becomes  the  cavernous  sinus.  The  greater  part  of  the  vena 
capitis  medialis  is  replaced,  however,  by  the  vena  capitis  lateralis  (Fig.  179j,  which 
is  developed  on  the  lateral  aspect  of  the  cerebral  nerves  from  the  trigeminal  to  the 
hypoglossal.  This  vein  receives  three  principal  tributaries,  viz.,  the  anterior 
cerebral  vein  from  the  eye,  fore-brain,  and  mid-brain,  the  middle  cerebral  vein 


Torcular  Hcrophili 


Middle  cerebral  vein 
Posterior  cerebral  vein 


Superior  sagittal  sinus 


Vena  capitis 
lateralis 


Ophthalmic     Anterior 

vein  cerebral  vein 


Auditory     Trigeminal 
vesicle  nerve 

Fig.   180. — Diagram  of  veins  of  head  at  the  beginning  of  the  third  month.     (After  Mall.) 

from  the  cerebellum,  and  the  posterior  cerebral  vein  from  the  lower  part  of  the  hind- 
brain.  At  this  stage,  therefore,  practically  the  whole  of  the  blood  from  the  brain 
is  drained  into  the  vena  capitis  lateralis,  which  leaves  the  skull  in  company  with 
the  facial  nerve  and  opens  into  the  internal  jugular  vein.  The  terminal  branches 
of  the  two  anterior  cerebral  veins  anastomose  in  the  middle  line  and  thus  form  the 


Torcular  Herophili 


Straight  sinus 

Inferior  sagittal  sinus 


Superior  petrosal 
sinus 

Transverse  sinus 


Great  cerebral  vein 

Superior  sagittal  sinus 

Middle  cerebral  vein 
Anterior  cerebral  vein 
Sphenoparietal  sinics 


Auditory  vesicle 
Inferior  petrosal  sinus 

Trigeminal  nerve 

Ophthalmic  vein 
Fig.   181. — Diagram  of  veins  of  head  of  an  older  embryo.     (After  Mall.) 


superior  sagittal  sinus  (Fig.  180).  By  the  backward  growth  of  the  cerebral  hemis- 
pheres this  sinus  comes  to  anastomose  with  the  middle  and  posterior  cerebral  veins, 
the  latter  of  which  leaves  the  skull  through  the  jugular  foramen;  this  last  anastomo- 
sis forms  the  greater  part  of  the  transverse  sinus.  The  vena  capitis  lateralis  under- 
goes atrophy;  the  middle  cerebral  vein  forms  the  superior  petrosal  sinus  (Fig. 
181).    The  inferior  petrosal  sinus  is  a  later  formation.    The  external  jugular  vein 


DEVELOPMEXT  OF  THE  VASCULAR  SYSTEM 


101 


at  first  drains  the  region  behind  the  ear  (posterior  auricuUir)  and  enters  the  primi- 
tive juguhir  as  a  hiteral  tributary.  A  group  of  veins  from  tiie  face  and  lingual  region 
converge  to  form  a  common  vein,  the  linguo-facial/  which  also  terminates  in  the 
primitive  jugular.  Later,  cross  communications  develop  between  the  external 
jugular  antl  the  linguo-facial,  with  the  result  that  the  posterior  group  of  facial 
veins  is  transferred  to  the  external  jugular. 

Peculiarities  of  the  Fetal  Heart. — In  early  fetal  life  the  heart  is  placed  directly 
under  the  head  and  is  relatively  of  large  size.  Later  it  assumes  its  position  in  the 
thorax,  but  lies  at  first  in  the  middle  line;  toward  the  end  of  pregnancy  it  gradu- 
ally becomes  oblique  in  direction.  The  atrial  portion  is  at  first  larger  than  the 
ventricular  part,  and  the  two  atria  communicate  freely  through  the  foramen  ovale. 
In  consequence  of  the  communication  through  the  ductus  arteriosus,  between  the 
pulmonary  artery  and  the  aorta,  the  contents  of  the  right  ventricle  are  mainly 
carried  into  the  latter  vessel  instead  of  to  the  lungs,  and  hence  the  wall  of  the 
right  ventricle  is  as  thick  as  that  of  the  left.  At  the  end  of  fetal  life,  however, 
the  left  ventricle  is  thicker  than  the  right,  a  difference  which  becomes  more  and 
more  emphasized  after  birth. 

The  fetal  circulation  and  the  changes  which  take  place  in  the  circulation  after 
birth  are  described  on  pages  616  to  618. 


Left  innominate 


Jugular  lymph-sac 
Eight  innominate 

S'lperior  vena  cava 


Prereiml  part  of 
inferior  vena  cava 


Postrenal  part  of 
inferior  veiui  cava 

Cisterna  chyli 

Posterior  lymph-sac 


Internal  jugular 
External  jugular 


Duct  of  Cuvier 
Left  cardinal 


Left  suprarenal 
Left  renal 
Eetro-peritoneal 
lymph- sac 


Left  common  iliac 
External  iliac 
Hypogastric 


Fig.   1S2. — Scheme  showing  relative  positions  of  primary  lymph  sacs  based  on  the  description  given  by 

Florence  Sabin. 

The  Lymphatic  Vessels. — The  lymphatic  system  begins  as  a  series  of  sacs-  at 
the  points  of  junction  of  certain  of  the  embryonic  veins.  These  lymph-sacs  are 
developed  by  the  confluence  of  numerous  venous  capillaries,  which  at  first  lose 
their  connections  with  the  venous  system,  but  subsequently,  on  the  formation  of 
the  sacs,  regain  them.  The  lymphatic  system  is  therefore  developmentally  an 
offshoot  of  the  venous  system,  and  the  lining  walls  of  its  vessels  are  always 
endothelial. 

In  the  human  embryo  the  lymph  sacs  from  which  the  lymphatic  vessels  are 
derived  are  six  in  number;  two  paired,  the  jugular  and  the  posterior  lymph-sacs; 
and  two  unpaired,  the  retroperitoneal  and  the  cisterna  chyli.     In  lower  mammals 


'  Le-n-is,  American  Journal  of  Anatomy,  February,  1909,  No.  1,  vol.  is. 
2  Sabin,  ibid. 


11 


162 


EMBRYOLOGY 


an  additional  pair,  subclavian,  is  present,  hut  in  the  human  embryo  these  are 
merel}'  extensions  of  the  jugular  sacs. 

The  position  of  the  sacs  is  as  follows:  (1)  jugular  sac,  the  first  to  appear,  at 
the  junction  of  the  subclavian  vein  with  the  primitive  jugular;  (2)  posterior  sac, 
at  the  junction  of  the  iliac  vein  with  the  cardinal;  (3)  retroperitoneal,  in  the  root 
of  the  mesentery  near  the  suprarenal  glands;  (4)  cisterna  chyli,  opposite  the  third 
and  fourth  lumbar  vertebrae  (Fig.  182).  From  the  lymph-sacs  the  lymphatic 
vessels  bud  out  along  fixed  lines  corresponding  more  or  less  closely  to  the  course 
of  the  embryonic  blood\-essels.  Both  in  the  body-wall  and  in  the  wall  of  the 
intestine,^  the  deeper  plexuses  are  the  first  to  be  developed;  by  continued  growth 
of  these  the  vessels  in  the  superficial  layers  are  gradually  formed.  The  thoracic 
duct  is  probably  formed  from  anastomosing  outgrowths  from  the  jugular  sac  and 
cisterna  chyli.  At  its  connection  with  the  cisterna  chyli  it  is  at  first  double,  but 
the  two  vessels  soon  join. 

All  the  lymph-sacs  except  the  cisterna  chyli  are,  at  a  later  stage,  divided  up  by 
slender  connective  tissue  bridges  and  transformed  into  groups  of  lymph  glands. 
The  lower  portion  of  the  cisterna  chyli  is  similarly  converted,  but  its  upper  portion 
remains'as  the  adult  cisterna. 


A  m  nion 


Allantois 
Hind-gut 


Fig.   183. — Diagram  of  a  sagittal  section  of  a  mammalian  embryo.     Very  early.     (After  Quain.) 


DEVELOPMENT  OF  THE  DIGESTIVE  AND  RESPIRATORY  APPARATUS. 

The  Digestive  Tube.— As  already  indicated  (page  92),  the  primitive  digestive 
tube  consists  of  two  parts,  viz.:  (1)  the  fore-gut,  within  the  cephalic  flexure,  and 
dorsal  to  the  heart;  and  (2)  the  hind-gut,  within  the  caudal  flexure  (Figs.  183,  184). 
Between  these  is  the  wide  opening  of  the  yolk-sac,  which  is  gradually  narrowed 
and  reduced  to  a  small  foramen  leading  into  the  vitelline  duct.  At  first  the  fore- 
gut  and  hind-gut  end  blindly.    The  anterior  end  of  the  fore-gut  is  separated  from 


1  Heuer,  American  Journal  of  Anatomy,  vol.  ix,  No,  1,  February.  1909. 


DEVELOPMEXT  OF  DIGESTIVE  AXD  RESPIRATORY  APPARATUS     163 

the  stomodeum  by  the  biiccopliaryngeal  membrane  (Fig.  184);  the  hind-gut  ends 
in  the  cloaca,  which  is  closed  by  the  cloacal  membrane. 

The  Mouth. — The  mouth  is  developed  partly  from  the  stomodeum,  and  partly 
from  the  floor  of  the  anterior  portion  of  the  fore-gut.  By  the  gro\\i;h  of  the  head ' 
end  of  the  embryo,  and  the  formation  of  the  cephalic  flexure,  the  pericardial  area 
and  the  buccopharyngeal  membrane  come  to  lie  on  the  ventral  surface  of  the 
embryo.  ^Yith  the  further  expansion  of  the  brain,  and  the  forward  bulging  of  the 
pericardium,  the  buccopharyngeal  membrane  is  depressed  between  these  two 
prominences.  This  depression  constitutes  the  stomodeum  (Fig.  184).  It  is  lined 
by  ectoderm,  and  is  separated  from  the  anterior  end  of  the  fore-gut  by  the  bucco- 
pliaryngeal  membrane.  This  membrane  is  devoid  of  mesoderm,  being  formed 
by  the  apposition  of  the  stomodeal  ectoderm  with  the  fore-gut  entoderm;  at  the 
end  of  the  third  week  it  disappears,  and  thus  a  communication  is  established 


Thalamencephalon 


Optic  vesicle 


Mid-hrain 


B  uccopharyngeal 
viemhrane 

Pharynx 
Auditory  pit 

Bulbus  cordis 
Stomach 


Stomodeum 
Ventricle 


Liver 


Cloaca 


Body-stalk 
Uitibilical  vein 


Yolk-sac 


Hind-gut 


Allantois 
Umbilical  artery 


Fig.  184. — Human  embryo  about  fifteen  days  old.   Brain  and  heart  represented  from  right  side.   Digestive  tube  and 

yolk  sac  in  median  section.     (After  His.) 


between  the  mouth  and  the  future  pharynx.  No  trace  of  the  membrane  is  found 
m  the  adult;  and  the  communication  just  mentioned  must  not  be  confused  with  the 
permanent  isthmus  faucium.  The  lips,  teeth,  and  gums  are  formed  from  the  walls 
of  the  stomodeum,  but  the  tongue  is  developed  in  the  floor  of  the  pharynx. 

The  visceral  arches  extend  in  a  ventral  direction  between  the  stomodeum  and 
the  pericardium;  and  with  the  completion  of  the  mandibular  arch  and  the  formation 
of  the  maxillary  processes,  the  mouth  assumes  the  appearance  of  a  pentagonal 
orifi.ce.  The  orifice  is  bounded  in  front  by  the  fronto-nasal  process,  behind  by  the 
mandibular  arch,  and  laterally  by  the  maxillary  processes  (Fig.  185).  With  the 
inward  growth  and  fusion  of  the  palatine  processes  (Figs.  112,  113),  the  stomodeum 
is  divided  into  an  upper  nasal,  and  a  lower  buccal  part.  Along  the  free  margins 
of  the  processes  bounding  the  mouth  cavity  a  shallow  groove  appears;  this  is 
termed  the  primary  labial   groove,  and  from  the  bottom  of  it  a  downgrowth  of 


164 


EMBRYOLOGY 


ectoderm  takes  place  into  the  underlying  mesoderm.  The  central  cells  of  the 
ectodermal  downgrowth  degenerate  and  a  secondary  labial  groove  is  formed;  by 
the  deepening  of  this,  the  lips  and  cheeks  are  separated  from  the  alveolar  processes 
of  the  maxillae  and  mandible. 

The  Salivary  Glands. — The  salivary  glands  arise  as  buds  from  the  epithelial 
lining  of  the  mouth;   the  parotid  appears  during  the  fourth  week  in  the  angle 

between  the  maxillary  process  and  the 
mandibular  arch;  the  submaxillary  ap- 
pears in  the  sixth  week,  and  the  sublin- 
gual during  the  ninth  week  in  the  hollow 
between  the  tongue  and  the  mandibular 
arch. 

The  Tongue  (Figs.  186  to  188).— The 
tongue  is  developed  in  the  floor  of  the 
pharynx,  and  consists  of  an  anterior  or 
buccal  and  a  posterior  or  pharyngeal  part 
which  are  separated  in  the  adult  by  the 
V-shaped  sulcus  terminalis.  During  the 
third  week  there  appears,  immediately 
behind  the  ventral  ends  of  the  two  halves 
of  the  mandibular  arch,  a  rounded 
swelling  named  the  tuberculum  impar, 
which  was  described  by  His  as  un- 
dergoing enlargement  to  form  the 
buccal  part  of  the  tongue.  ]More  re- 
cent researches,  however,  show  that 
this  part  of  the  tongue  is  mainly,  if 
not  entirely,  developed  from  a  pair 
of  lateral  .  swellings  which  rise  from 
the  inner  surface  of  the  mandibular  arch  and  meet  in  the  middle  line.  The  tuber- 
culum impar  is  said  to  form  the  central  part  of  the  tongue  immediately  in  front 
of  the  foramen  cecum,  but  Hammar  insists  that  it  is  purely  a  transitory  structure 
and  forms  no  part  of  the  adult  tongue.    From  the  ventral  ends  of  the  fourth  arch 


Future  a'pex  of  nose 

Medial  nasal  process 

Olfactory  pit 
Lateral  nasal  process 
Glchular  process 
Maxillary  process 
Stomodeum 

Mandibidar  arch 


Fig.   185. — Head  end  of  human  embryo  of  about  thirty 
to  thirty-one  days.     (From  model  by  Peter.) 


Lateral  tongue      Thyroid 
swellings      diverticulum 


Lateral  tongue  swellings 


Entrance  to 
larynx 


Fig.  186. — Floor  of  pharynx  of  human  embryo 
about  twenty-six  days  old.  (From  model  by 
Peter.) 


Entrance  to 

larynx 
Arytenoid 
swellings 


Fig.  187. — Floor  of  pharj'nx  of  human  embryo 
of  about  the  end  of  the  fourth  week.  (From 
model  by  Peter.) 


there  arises  a  second  and  larger  elevation,  in  the  centre  of  which  is  a  median  groove 
or  furrow.  This  elevation  was  named  by  His  the  furcula,  and  is  at  first  separated 
from  the  tuberculum  impar  by  a  depression,  but  later  by  a  ridge,  the  copula, 
formed  by  the  forward  growth  and  fusion  of  the  ventral  ends  of  the  second  and 
third  arches.    The  posterior  or  pharyngeal  part  of  the  tongue  is  developed  from 


DEVELOPMENT  OF  DIGESTIVE  AXD  RESPIRATORY  APPARATUS     165 

the  copula,  which  extends  forward  in  the  form  of  a  V,  so  as  to  embrace  between  its 
two  limbs  the  buccal  part  of  the  tongue.  At  the  apex  of  the  V  a  pit-like  invagination 
occurs,  to  form  the  thyroid  gland,  and  this  depression  is  represented  in  the  adult 
by  the  foramen  cecum  of  the  tongue.  In  the  adult  the  union  of  the  anterior  and 
posterior  parts  of  the  tongue  is  marked  by  the  V-shaped  sulcus  terminalis,  the 
apex  of  which  is  at  the  foramen  cecum,  while  the  two  limbs  run  lateralward  and 
forward.  ])arallel  tt).  l)ut  a  little  behind,  the  vallate  papilUe. 

The  Thyroid  Gland. — The  thyroid  gland  is  developed  from  a  median  diverticulum 
(Fig.  189),  which  appears  about  the  fourth  week  on  the  summit  of  the  tuberculum 
impar,  but  later  is  found  in  the  furrow  immediately  behind  the  tuberculum  (Fig. 
186).  It  grows  downward  and  backward  as  a  tubular  duct,  which  bifurcates  and 
subsequently  subdivides  into  a  series  of  cellular  cords,  from  which  the  isthmus 
and  lateral  lobes  of  the  thyroid  gland  are  developed.  As  already  stated  (page  111), 
the  ultimobranchial  bodies  from  the  fifth  pharyngeal  pouches  are  enveloped  by 
the  lateral  lobes  of  the  thyroid  gland;  they  undergo  atrophy  and  do  not  form  true 
thyroid  tissue.  The  connection  of  the  diverticulum  with  the  pharynx  is  termed 
the  thyroglossal  duct;  its  continuity  is  subsequently  interrupted,  and  it  undergoes 
degeneration,  its  upper  end  being  represented  by  the  foramen  cecum  of  the  tongue, 
and  its  lower  by  the  pyramidal  lobe  of  the  thyroid  gland. 


Arytenoid 
swellings 


Fig.   ISS. — Floor  of  pharynx  of  human  embryo  about  thirty 
days  old.    (From  model  by  Peter.) 


Thyroid  gland 


Parathyroids 


Thymus 


UUimo-hranchial  body 


Fig.  189. — Scheme  showing  development  of  bran- 
chial epithelal  bodies.  (^Modified  from  Kohn.)  /, 
//,  III,  IV.     Branchial  pouches. 


The  Palatine  Tonsils. — The  palatine  tonsils  are  developed  from  the  dorsal  angles 
of  the  second  branchial  pouches.  The  entoderm  which  lines  these  pouches  grows 
in  the  form  of  a  number  of  solid  buds  into  the  surrounding  mesoderm.  These 
buds  become  hollowed  out  by  the  degeneration  and  casting  off  of  their  central  cells, 
and  by  this  means  the  tonsillar  crypts  are  formed.  Lymphoid  cells  accumulate 
around  the  crypts,  and  become  grouped  to  form  the  lymphoid  follicles;  the  latter, 
however,  are  not  well-defined  until  after  birth. 

The  Thymus. — The  thymus  appears  in  the  form  of  two  flask-shaped  entodermal 
diverticula,  which  arise,  one  on  either  side,  from  the  third  branchial  pouch  (Fig. 
189),  and  extend  lateralward  and  backward  into  the  surrounding  mesoderm  in 
front  of  the  ventral  aortse.  Here  they  meet  and  become  joined  to  one  another  by 
connective  tissue,  but  there  is  never  any  fusion  of  the  thymus  tissue  proper.  The 
pharyngeal  opening  of  each  diverticulum  is  soon  obliterated,  but  the  neck  of  the 
flask  persists  for  some  time  as  a  cellular  cord.  By  further  proliferation  of  the  cells 
lining  the  flask,  buds  of  cells  are  formed,  which  become  surrounded  and  isolated 


166 


EMBRYOLOGY 


by  the  invading  mesoderm.  In  the  latter,  numerous  lymphoid  cells  make  their 
appearance,  and  are  aggregated  to  form  lymphoid  foil  ides.  These  lymphoid 
cells  are  probably  derivatives  of  the  entodermal  cells  which  lined  the  original 
diverticula  and  their  subdivisions.  Additional  portions  of  thymus  tissue  are 
sometimes  developed  from  the  fourth  branchial  pouches.  Thymus  continues 
to  grow  until  the  time  of  puberty  and  then  Ijegins  to  atrophy. 

The  Parathyroid  Bodies. — The  parathyroid  bodies  are  developed  as  outgrowths 
from  the  third  and  fourth  branchial  pouches  (P'ig.  189). 

A  pair  of  diverticula  arise 
from  the  fifth  branchial 
pouch  and  form  what  are 
termed  the  ultimobranchial 
bodies  (Fig.  189):  these  fuse 
with  the  thyroid  gland,  but 
probably  contribute  no  true 
thyroid  tissue. 

The  Hypophysis  Cerebri. — 
This  in  the  adult  consists  of 
a  large  anterior,  and  a  small 
posterior,  lobe:  the  former 
is  derived  from  the  ecto- 
derm of  the  stomodeum,  the 
latter  from  the  floor  of  the 
fore-brain.  About  the  fourth 
week  there  appears  a  pouch- 
like diverticulum  of  the  ecto- 
dermal lining  of  the  roof  of 
the  stomodeum.  This  diver- 
ticulum, pouch  of  Rathke 
(Fig.  190),  is  the  rudiment  of 
the  anterior  lobe  of  the  hypo- 
physis; it  extends  upward  in 
front  of  the  cephalic  end  of 
the  notochord  and  the  rem- 
nant of  the  buccopharyngeal 
membrani  and  comes  into 
contact  wnh  the  under  sur- 
face of  the  fore-brain.  It  is 
then  constricted  off  to  form 
a  closed  vesicle,  but  remains 
for  a  time  connected  to  the 
ectoderm  of  the  stomodeum 
by  a  solid  cord  of  cells.  Masses 
of  epithelial  cells  form  on 
either  side  and  in  the  front 
wall  of  the  vesicle,  and  by  the  growth  between  these  of  a  stroma  from  the  mesoderm 
the  development  of  the  anterior  lobe  is  completed.  The  upwardly  directed  hypo- 
physeal involution  becomes  applied  to  the  antero-lateral  aspect  of  a  downwardly 
directed  diverticulum  from  the  base  of  the  fore-brain  (page  128).  This  divertic- 
ulum constitutes  the  future  infundibulum  in  the  floor  of  the  third  ventricle 
while  its  inferior  extremity  becomes  modified  to  form  the  posterior  lobe  of  the 
hj^Dophysis.  In  some  of  the  low^er  animals  the  posterior  lobe  contains  nerve  cells 
and  nerve  fibres,  but  in  man  and  the  higher  vertebrates  these  are  replaced  by 
connective  tissue.     A  canal,  craniopharyngeal  canal,  is  sometimes  found  extending 


Fig.  190. — Vertical  sections  of  the  heads  of  early  embryos  of  the  rab- 
bit. ^Magnified.  (From  Mihalkovics.)  A.  From  an  embryo  5  mm. 
long.  B.  From  an  embryo  6  mm.  long.  C.  Vertical  section  of  the 
anterior  end  of  the  notochord  and  hypophysis,  etc.,  from  an  embrj'O  16 
mm.  long.  In  A  the  buccopharyngeal  membrane  is  still  present.  In  B 
it  is  in  the  process  of  disappearing,  and  the  stomodeum  now  communi- 
cates with  the  primitive  pharynx,  am.  Amnion,  c.  Fore-brain,  ch. 
Notochord.  /.  Anterior  extremity  of  fore-gut,  i.  h.  Heart,  if.  Infun- 
dibulum. m.  Wall  of  brain  cavity,  mc.  Mid-brain.  mo.  Hind-brain. 
p.  Original  position  of  hypophyseal  diverticulum,  py.  ph.  Pharynx. 
sp.e.  Sphenoethmoidal,  be.  Central,  sp.o.  Sphenooccipital  parta  of  basis 
cranii.     tha.  Thalamus. 


DEVELOPMENT  OF  DIGESTIVE  AND  RESPIRATORY  APPARATUS     167 

/        from  the  anterior  part  of  the  fossa  hypophyseos  of  the  sphenoid  bone  to  tlie  under 
I        surface  of  the  skuU,  and  marks  the  original  position  of  Ratiike's  pouch;  while  at 

:t 

•^  NotocJwrd  RathJce\s  pouch 


Li(nrj  diverticulum -- 

Stomach 
Liver -- 


Opening  into 

yolk-sac 


Allantois  I — 


Mandilular 
arch 


—  Postallantoic  part 
of  hind-gut 

Wolffian  duct 


Lung  diverticuhin. 
(Esophagus  ^      ^y^ 


Stomach  -~  -/ 
Pancreas  • 

Bile-duct   i 

Vitelline  duct" 
Allantois  - 


Thyroid  gland 

Mandibular  arch 
I         I    Notochord 


—  Rathhe's  pouch 


Postallantoic  part 
of  hind-gut 


-J- Wolffian  duct 


Fig.   191. — Sketches  in  profile  of  two  stages  in  the  development  of  the  human  digestive  tube.    (His.) 

A  X  30.     B  X  20. 


the  junction  of  the  septum  of  the  nose  with  the  palate  traces  of  the  stomodeal 
end  are  occasionally  present  (Frazer). 


168 


EMBRYOLOGY 


The  Further  Development  of  the  Digestive  Tube.— The  upper  part  of  the  fore-gut 
becomes  dilated  to  form  the  pharynx  (Fig.  184),  in  relation  to  which  the  branchial 
arches  are  developed  (see  page  108) ;  the  succeeding  i)art  remains  tubular,  and  with 
the  descent  of  the  stomach  is  elongated  to  form  the  (vsophagus.  About  the  fourth 
week  a  fusiform  dilatation,  the  future  stomach,  makes  its  appearance,  and  beyond 
this  the  gut  opens  freely  into  the  yolk-sac  (Fig.  191,  A  and  B).  The  opening' is  at 
first  wide,  but  is  gradually  narrowed  into  a  tubular  stalk,  the  yolk-stalk  or  vitelline 
duct.  Between  the  stomach  and  the  mouth  of  the  yolk-sac  the  li\er  diverticulum 
appears.  From  the  stomach  to  the  rectum  the  alimentary  canal  is  attached  to  the 
notochord  by  a  band  of  mesoderm,  from  which  the  common  mesentery  of  the  gut 
is  subsequently  developed.  The  stomach  has  an  additional  attachment,  viz.,  to 
the  ventral  abdominal  wall  as  far  as  the  umbilicus  by  the  septum  transversum. 
The  cephalic  portion  of  the  septum  takes  part  in  the  formation  of  the  Diaphragma, 
while  the  caudal  portion  into  which  the  liver  grows  forms  the  ventral  mesoga:-;trium 
(Fig.  193).  The  stomach  undergoes  a  further  dilatation,  and  its  two  curvatures, 
can  be  recognized  (Figs.  191,  B,  and  192),  the  greater  directed  toward  the  vertebral 


Trachea  — -1 
(Esophagus 

Stomach 

Bile-duct  ■ 


Lung 


-- Trachea 


\f-sha]>ed  loop  of 
small  intestine  - 

Vitelline  duct  - 
Cloaca   • 


>■ —  Pancreas 


Bile-duct- 
Pancreas 


Lung 

(Esophagus 


■Stomach 


Fig.   192. — Front  view  of  two  successive  stages  in  the  development  of  the  digestive  tube.      (His.) 

column  and  the  lesser  toward  the  anterior  wall  of  the  abdomen,  while  its  two 
surfaces  look  to  the  right  and  left  respectively.  Behind  the  stomach  the  gut 
undergoes  great  elongation,  and  forms  a  V-shaped  loop  which  projects  downward 
and  forward;  from  the  bend  or  angle  of  the  loop  the  vitelline  duct  passes  to  the 
umbilicus  (Fig.  193).  For  a  time  a  considerable  part  of  the  loop  extends  beyond 
the  abdominal  cavity  into  the  umbilical  cord,  but  by  the  end  of  the  third  month 
it  is  withdrawn  within  the  cavity.  With  the  lengthening  of  the  tube,  the  mesoderm, 
which  attaches  it  to  the  future  vertebral  column  and  carries  the  bloodvessels  for 
the  supply  of  the  gut,  is  thinned  and  drawn  out  to  form  the  posterior  common 
mesentery.  The  portion  of  this  mesentery  attached  to  the  greater  curvature  of 
the  stomach  is  named  the  dorsal  mesogastrium,  and  the  part  wdiich  suspends  the 
colon  is  termed  the  mesocolon  (Fig.  194).  About  the  sixth  week  a  diverticulum 
of  the  gut  appears  just  behind  the  opening  of  the  vitelline  duct,  and  indicates 
the  future  cecum  and  vermiform  process.  The  part  of  the  loop  on  the  distal  side 
of  the  cecal  diverticulum  increases  in  diameter  and  forms  the  future  ascending 
and  transverse  portions  of  the  large  intestine.  Until  the  fifth  month  the  cecal 
diverticulum  has  a  uniform  calibre,  but  from  this  time  onward  its  distal  part 


DEVELOPMENT  OF  DIGESTIVE  AXD  RESPIRATORY  APPARATUS     169 

remains  rudimentary  and  forms  the  vermiform  process,  while  its  proximal  part 
expands  to  form  the  cecum.  Changes  also  take  place  in  the  shape  and  position 
of  the  stomach.    Its  dorsal  part  or  greater  curvature,  to  which  the  dorsal  meso- 


Septwm  transvcrsum 


Livd 


Falciform  ligament  of  Uvei 
Lesser  omentum 

Umbilical  vein 
Vmbilical  cord 


Aorta 

Dorsal  mesogastrium 

Stomach 


Intestinal  \/-shaped  loop 
Mesentery 


Colon 


Fig.   193. — The  primitive  mesentery  of  a  six  weeks'  human  embryo,  half  schematic.     (Kollraann.) 

gastrium  is  attached,  grows  much  more  rapidly  than  its  ventral  part  or  lesser 
curvature  to  which  the  ventral  mesogastrium  is  fixed.  Further,  the  greater  curva- 
ture is  carried  downward  and  to  the  left,  so  that  the  right  surface  of  the  stomach  is 


Ventral  mesogastrium 


Aorta 


Spleen 

Dorsal 
mesogastrium, 

Coeliac  artery 


Pancreas 


Superior  mesenteric 
artery 


Mesentery 


Inferior  mesenteric  artery 


Hind-gut 


Fig.   194. — Abdominal  part  of  digestive  tube  and  its  attachment  to  the  primitive  or  common  mesentery.     Human 

embryo  of  six  weeks.      (After  Toldt.) 

now  directed  backward  and  the  left  surface  forward  (Fig.  195),  a  change  in  position 
which  explains  why  the  left  vagus  nerve  is  found  on  the  front,  and  the  right  vagus 
on  the  back  of  the  stomach.    The  dorsal  mesogastrium  being  attached  to  the  greater 


170 


EMBRYOLOGY 


curvature  must  necessarily  follow  its  movements,  and  hence  it  becomes  greatly 
elongated  and  drawn  lateralward  and  ventralward  from  the  vertebral  column, 
and,  as  in  the  case  of  the  stomach,  the  rigiit  surfaces  of  both  the  dorsal  and  ventral 
mesogastria  are  now  directed  backward,  and  the  left  forward.  In  this  way  a  pouch, 
the  bursa  omentalis,  is  formed  behind  the  stomach,  and  this  increases  in  size  as 
the  digestive  tube  undergoes  further  development;  the  entrance  to  the  pouch 
constitutes  the  future  foramen  epiplolcum  or  foramen  of  Winslow.  The  duodenum 
is  developed  from  that  part  of  the  tube  which  innnediately  succeeds  the  stomach; 
it  undergoes  little  elongation,  being  more  or  less  fixed  in  position  by  the  liver  and 


Pericardium 


8th  cervical  nerve 

1st  thoracic 
vertebra 


Lung 


Suprarenal 
gland 

Stomach 
12th  thoracic 

nerve 
Mesonephros 


Kidney 


5lh  Imnbar 
nerve 


Small 
intestine 


Ureter 
Wolffian  duct 

Reconstruction  of  a  human  embryo  of  17  mm.     (After  Mall.) 


pancreas,  which  arise  as  diverticula  from  it.  The  duodenum  is  at  first  suspended 
by  a  mesentery,  and  projects  forward  in  the  form  of  a  loop.  The  loop  and  its  mes- 
entery are  subsequently  displaced  by  the  transverse  colon,  so  that  the  jight  surface 
of  the  duodenal  mesentery  is  directed  backward,  and,  adhering  to  the  parietal 
peritoneum,  is  lost.  The  remainder  of  the  digestive  tube  becomes  greatly  elongated, 
and  as  a  consequence  the  tube  is  coiled  on  itself,  and  this  elongation  demands  a 
corresponding  increase  in  the  width  of  the  intestinal  attachment  of  the  mesentery, 
which  becomes  folded. 

At  this  stage  the  small  and  large  intestines  are  attached  to  the  vertebral  column 


DEVELOPMENT  OF  DIGESTIVE  AND  RESPIRATORY  APPARATUS     171 

by  a  common  meseiittTv,  the  coils  of  tlie  small  intestine  falling  to  the  right  of  the 
middle  line,  while  the  large  intestine  lies  on  the  left  side.^ 

The  gut  is  now  rotated  upon  itself,  so  that  the  large  intestine  is  carried  o\'er  in 
front  of  the  small  intestine,  and  the  cecum  is  i)la('ed  inuncdiately  below  the  liver; 
about  the  sixth  month  the  cecum  descends  into  the  right  iliac  fossa,  and  the  large 
intestine  forms  an  arch  consisting  of  the  ascending,  transverse,  and  descending 
portions  of  the  colon — the  transverse  portion  crossing  in  front  of  the  duodenum 
and  lying  just  below  the  greater  curvature  of  the  stomach;  within  this  arch  the 
coils  of  the  small  intestine  are  disposed  (Fig.  197).  Sometimes  the  downward 
progress  of  the  cecum  is  arrested,  so  that  in  the  adult  it  may  be  found  lying  imme- 
diately below  the  liver  instead  of  in  the  right  iliac  region. 


Mesogastnum 


Small 
intestine 


Vitelline  duct 


Greater 
curvature 
of  stomach 


Greater 

omentum 


Point  where 
intestinal 
loops  cross 
each  other 


Meso- 
gastriun, 


Duodenum 


Mesocolon 


Cecum 

Large  Vermiform 

intestine  process 

Mesentery 


Greater  omenttnn 


Rectum, 


Vitelline  duct 


Large  intestine 
Small  intestine 


Rectum 


Fig.  196.- 


-Diagrams  to  illustrate  two  stages  in  the  development  of  the  digestive  tube  and  its  mesentery. 
The  arrow  indicates  the  entrance  to  the  bursa  omentalis. 


Further  changes  take  place  in  the  bursa  omentalis  and  in  the  common  mesenter}^, 
and  give  rise  to  the  peritoneal  relations  seen  in  the  adult.  The  bursa  omentalis, 
which  at  first  reaches  only  as  far  as  the  greater  curvature  of  the  stomach,  grows 
downward  to  form  the  greater  omentum,  and  this  downward  extension  lies  in  front 
of  the  transverse  colon  and  the  coils  of  the  small  intestine  (Fig.  198).  Above,  before 
the  pleuro-peritoneal  opening  is  closed,  the  bursa  omentalis  sends  up  a  diverticulum 
on  either  side  of  the  oesophagus;  the  left  diverticulum  soon  disappears,  but  the  right 
is  constricted  off  and  persists  in  most  adults  as  a  small  sac  lying  within  the  thorax 
on  the  right  side  of  the  lower  end  of  the  oesophagus.  The  anterior  layer  of  the 
transverse  mesocolon  is  at  first  distinct  from  the  posterior  layer  of  the  greater 
omentum,  but  ultimately  the  two  blend,  and  hence  the  greater  omentum  appears 
as  if  attached  to  the  transverse  colon  (Fig.  199).  The  mesenteries  of  the  ascending 
and  descending  parts  of  the  colon  disappear  in  the  majority  of  cases,  while  that  of 
the  small  intestine  assumes  the  oblique  attachment  characteristic  of  its  adult 
condition. 


1  Sometimes  this  condition  persists  throughout  life,  and  it  is  then  found  that  the  duodenum  does  not  cross  from  the 
right  to  the  left  side  of  the  vertebra!  column,  but  lies  entirely  on  the  right  side  of  the  median  plane,  where  it  is  continued 
into  the  jejunum;  the  arteries  to  the  small  intestine  (aa.  intestinales)  also  arise  from  the  right  instead  of  the  left  side 
of  the  superior  mesenteric  artery. 


172 


EMBRYOLOGY 


The  lesser  omentum  is  formed,  as  indicated  above,  by  a  thinning  of  the  meso- 
derm or  ventral  mesogastrium,  which  attaches  the  stomach  and  ckiodenum  to  the 
anterior  abdominal  wall.  By  the  subsequent  growth  of  the  liver  this  leaf  of 
mesoderm  is  divided  into  two  parts,  viz.,  the  lesser  omentum  between  the  stomach 
and  li^•e^,  and  the  falciform  and  coronary  ligaments  between  the  liver  and  the 
abdominal  wall  and  Diaphragma  (Fig.  198). 

The  Rectum  and  Anal  Canal.— The  hind-gut  is  at  first  prolonged  backward  into 
the  body-stalk  as  the  tube  of  the  allantois;  but,  with  the  growth  and  flexure  of  the 
tail-end  of  the  embryo,  the  body-stalk,  with  its  contained  allantoic  tube,  is  carried 
forward  to  the  ventral  aspect  of  the  body,  and  consequently  a  bend  is  formed  at  the 
junction  of  the  hind-gut  and  allantois.  This  bend  becomes  dilated  into  a  pouch, 
which  constitutes  the  entodermal  cloaca;  into  its  dorsal  part  the  hind-gut  opens, 
and  from  its  ventral  part  the  allantois  passes  forward.  At  a  later  stage  the  Wolffian 
and  Miillerian  ducts  open  into  its  ventral  portion.    The  cloaca  is,  for  a  time,  shut 


Fig.  197. — Final  disposition  of  the 
intestines  and  their  vascular  relations. 
(Jonnesco.)  A.  Aorta.  H.  Hepatic 
artery.  M,  Col.  Branches  of  superior 
mesenteric  artery.  m,_  m'.  Branches 
of  inferior  mesenteric  artery.  S. 
Splenic  artery. 


Ventral 
mesogastrium 


Liver 


Umbilical  vein. 

Border  of 

ventral 

mesogastrium 


Stomach 


Bursa 

omentalis 


Pancreas 

Dorsal 
mesogastrium 

Duodenum 


Greater 
omentum 
Tran.sverse 

mesocolon 

Transverse 
colon 


Fig.   198. 


-Schematic  figure  of  the  bursa  omentaUs,  etc. 
embryo  of  eight  weeks.     (Kollmann.) 


Human 


off  from  the  anterior  by  a  membrane,  the  cloacal  membrane,  formed  by  the  apposi- 
tion of  the  ectoderm  and  entoderm,  and  reaching,  at  first,  as  far  forward  as  the 
future  umbilicus.  Behind  the  umbilicus,  however,  the  mesoderm  subsequently 
extends  to  form  the  lower  part  of  the  abdominal  wall  and  symphysis  pubis.  By 
the  growth  of  the  surrounding  tissues  the  cloacal  membrane  comes  to  lie  at  the 
bottom  of  a  depression,  which  is  lined  by  ectoderm  and  named  the  ectodermal 
cloaca  (Fig.  200). 

The  entodermal  cloaca  is  divided  into  a  dorsal  and  a  ventral  part  by  means  of  a 
partition,  the  urorectal  septum  (Fig.  201),  which  grows  downward  from  the  ridge 
separating  the  allantoic  from  the  cloacal  opening  of  the  intestine  and  ultimately 
fuses  with  the  cloacal  membrane  and  divides  it  into  an  anal  and  a  urogenital  part. 
The  dorsal  part  of  the  cloaca  forms  the  rectum,  and  the  anterior  part  of  the  uro- 
genital sinus  and  bladder.  For  a  time  a  communication  named  the  cloacal  duct 
exists  between  the  two  parts  of  the  cloaca  below  the  urorectal  septum;  this  duct 


DEVELOPMENT  OF  DIGESTIVE  AND  RESPIRATORY  APPARATUS     173 

occasionally  persists  as  a  passage  between  the  rectnni  and  urethra.     The  anal 
canal  is  formed  by  an  invagination  of  the  ectoderm  behind  the  urorectal  septum. 

J)taphragi»a 
\        Liner 


Lomer  omentum 

Jiiirna  oitientalit:-- 
StoDiach- 
Pancrea  s 

Greater  omentum  - 

Transverse  mesocolon  - 
Transverse  colon   - 


Lesser  omentum 
--  Bursa  omental  is 
Stoinack 

Pancreas 

Ohlitcnticd  part  of  mesogastrium 
---  Dnoilniuiii 
Transverse  colon 

Mesentery 
Small  intestine 


Small  intcst 


Fig.   199. ^Diagrams  to  illustrate  the  development  of  the  greater  omentum  and  transverse  mesocolon. 


Wolffian  duct 

if 


Ectodermal  cloaca  — f^ij 
Cloacal  membra nc~/    ~7  i  nioicn 


Notochord 


Fig.  200. — Tail  end  of  human  embryo  from  fifteen  to 
eighteen  days  old.     (From  model  by  Keibel.) 


Wolffian  d%ict  ■ 


\   —  Rectum 
Septum 


Fig.  201. — Cloaca  of  human  embryo  from 
twenty-five  to  twenty-seven  days  old.  (From 
model  by  Keibel.) 


Ureter. 
Wolffian  duct 
Mulleiianduct 
Bhddi'i 


Glans  penis 

Urethra 


Vertebral  column 
Fig.  202. — Tail  end  of  human  embryo,  from  eight  and  a  half  to  nine  weeks  old.     (From  model  by  Keibel.) 


174 


EMBRYOLOGY 


This  invagination  is  termed  the  proctodcEum,  and  it  meets  with  the  entoderm  of  the 
hind-gut  and  forms  witli  it  the  anal  membrane.  By  the  absorption  of  this  membrane 
the  anal  canal  becomes  continuous  witli  the  rectum  (Fig.  202).  A  small  part  of  the 
hind-gut  projects  backward  beyond  the  anal  membrane;  it  is  named  the  post-anal 
gut  (Fig.  200),  and  usually  becomes  obliterated  and  disappears.^ 

The  Liver. — The  liver  arises  in  the  form  of  a  diverticulum  or  hollow  outgrowth 
from  the  \'entral  surface  of  that  portion  of  the  gut  which  afterward  becomes  the 
descending  part  of  the  duodenum  (Figs.  191,  203).  This  diverticulum  is  lined  by 
entoderm,  and  grows  upward  and  forward  into  the  septum  transversum,  a  mass 
of  mesoderm  between  the  vitelline  duct  and  the  pericardial  cavity,  and  there  gives 
ofif  two  solid  buds  of  cells  which  represent  the  right  and  the  left  lobes  of  the  liver. 
The  solid  buds  of  cells  grow  into  columns  or  cylinders,  termed  the  hepatic  cylinders, 
which  branch  and  anastomose  to  form  a  close  meshwork.  This  network  invades 
the  vitelline  and  umbilical  veins,  and  breaks  up  these  vessels  into  a  series  of  capil- 
lary-like vessels  termed  sinusoids  (Minot),  which  ramify  in  the  meshes  of  the  cellular 
network  and  ultimately  form  the  venous  capillaries  of  the  liver.    By  the  continued 


Pericardial  cavity 


Anterior  wall  of 
pericardium 


Loiver  wall  of 
pericardium 


Liver 
Bile  duct 


Truncus  arteriosus 

Dorsal  mesocardium 

Atrium 

'^~-  Cuvierian  dud 

Uir)bilical  vein 
Vitelline  vein 

Communication 
between  pericardial 
and  peritoneal  cavities 


Vitelline  duel 

Peritoneal  cavity 

Fig.  203. — Liver  with  the  septum  transversum.     Human  embryo  3  mm.  long.    (After  model  and  figure  by  His.) 


growth  and  ramification  of  the  hepatic  cylinders  the  mass  of  the  liver  is  gradually 
formed.  The  original  diverticulum  from  the  duodenum  forms  the  common  bile- 
duct,  and  from  this  the  cystic  duct  and  gall-bladder  arise  as  a  solid  outgrowth  which 
later  acquires  a  lumen.  The  opening  of  the  common  duct  is  at  first  in  the  ventral 
wall  of  the  duodenum;  later,  owing  to  the  rotation  of  the  gut,  the  opening  is  carried 
to  the  left  and  then  dorsalward  to  the  position  it  occupies  in  the  adult. 

As  the  liver  undergoes  enlargement,  both  it  and  the  ventral  mesogastrium  of 
the  fore-gut  are  gradually  differentiated  from  the  septum  transversum;  and  from 
the  under  surface  of  the  latter  the  liver  projects  downward  into  the  abdominal 
cavity.  By  the  growth  of  the  liver  the  ventral  mesogastrium  is  divided  into  two 
parts,  of  which  the  anterior  forms  the  falciform  and  coronary  ligaments,  and  the 
posterior  the  lesser  omentum.  About  the  third  month  the  liver  almost  fills  the 
abdominal  cavity,  and  its  left  lobe  is  nearly  as  large  as  its  right.    From  this  period 


1  Consult,  in  this  connection,  the  following  article:     "A  Contribution  to  the  Morphology  of  the  Human  Urino- 
genital  Tract,"  by  D.  Berry  Hart,  M.D.,  F.R.C.P.E.,  Journal  of  Anatomy  and  Physiology,  April,  1901,  vol.  xxxv. 


DEVELOPMEXr  OF  DIGESTIVE  AXD  RESPIRATORY  APPARATUS     175 

the  relative  development  of  the  liver  is  less  acti\e,  more  espeeially  that  of  the  left 
lobe,  which  actually  uiulergoes  some  degeneration  and  becomes  smaller  than  the 
right;  but  up  to  the  end  of  fetal  life  the  liver  remains  relatively  larger  than  in 
the  adult. 

The  Pancreas  (Figs.  204,  205). — The  pancreas  is  developed  in  two  parts,  a 
dorsal  and  a  ventral.  The  former  arises  as  a  diverticulum  from  the  dorsal  aspect 
of  the  duodenum  a  short  distance  above  the  hepatic  diverticulum,  and,  growing 
upward  and  backward  into  the  dorsal  mesogastrium,  forms  a  part  of  the  head  and 
uncinate  process  and  the  whole  of  the  body  and  tail  of  the  pancreas.    The  ventral 


Accessory  'pancreatic  duct 
Dorsal  pancreas 


Ventral  pancreas 

Pancreatic  duct 

Bile  duct 

Fig.  204. — Pancreas  of  a  human  embrj-o  of  five 
weeks.     (KoUmann.) 


Accessory  pancreatic  duct 
Dorsal  pancreas 


Bile  duct 


Fig.  205.- 


Ventral  pancreas 
Pancreatic  duct 

-Pancreas  of  a  human  embrj^o  at  end  of 
sixth  week.     (Kollmann.) 


part  appears  in  the  form  of  a  diverticulum  from  the  primitive  bile-duct  and  forms 
the  remainder  of  the  head  and  uncinate  process  of  the  pancreas.  The  duct  of  the 
dorsal  part  (accessory  pancreatic  duct)  therefore  opens  independently  into  the 
duodenum,  while  that  of  the  ventral  part  (pancreatic  duct)  opens  w^th  the  common 
bile-duct.  About  the  sixth  week  the  two  parts  of  the  pancreas  meet  and  fuse 
and  a  communication  is  established  between  their  ducts.  After  this  has  occurred 
the  terminal  part  of  the  accessory  duct,  i.  e.,  the  part  between  the  duodenum  and 
the  point  of  meeting  of  the  two  ducts,  undergoes  little  or  no  enlargement,  while 


Liver 


Lesser 
omentum  Liver 


Left  suprarenal 
gland 


Right  suprarenal 
gland 


Fig. 


206. — Schematic    and    enlarged   cross-section   through   the   body  of 
mesogastrium.     Beginning  of  third  month. 


i    human   embr\-o   in   the   region   of   the 
(Toldt.) 


the  pancreatic  duct  increases,  in  size  and  forms,  the  main  duct  of  the  gland.  The 
opening  of  the  accessory  duct  into  the  duodenum  is  sometimes  obliterated,  and 
even  when  it  remains  patent  it  is  probable  that  the  whole  of  the  pancreatic  secretion 
is  conveyed  through  the  pancreatic  duct. 

At  first  the  pancreas  is  directed  upward  and  backward  between  the  two  layers 
of  the  dorsal  mesogastrium,  which  give  to  it  a  complete  peritoneal  investment, 
and  its  surfaces  look  to  the  right  and  left.  With  the  change  in  the  position  of  the 
stomach  the  dorsal  mesogastrium  is  drawn  downward  and  to  the  left,  and  the  right 
side  of  the  pancreas  is  directed  backward  and  the  left  forward  (Fig.  206).    The 


176 


EMBRYOLOGY 


right  surface  becomes  applied  to  the  posterior  abdominal  wall,  and  the  peritoneum 
which  covered  it  undergoes  absorption  (Fig.  207) ;  and  thus,  in  the  adult,  the  gland 
appears  to  lie  behind  the  peritoneal  cavit}'. 


Lesser 
Stomach    omentum 


Liver 


Liver 


suprarenal  gland 


Left  suprarenal  gland 


Fig.  207. — Section  through  same  region  as  in  Fig.  206,  at  end  of  third  month.     (Toldt.) 

The  Spleen  (Fig.  194). — Although  the  spleen  belongs  to  the  group  of  ductless 
glands,  its  development  may  be  conveniently  referred  to  here.  It  appears  about 
the  fifth  week  as  a  localized  thickening  of  the  mesoderm  in  the  dorsal  mesogastrium 
above  the  tail  of  the  pancreas.  With  the  change  in  position  of  the  stomach  the 
spleen  is  carried  to  the  left,  and  comes  to  lie  behind  the  stomach  and  in  contact 
with  the  left  kidney.  The  part  of  the  dorsal  mesogastrium  which  intervened 
between  the  spleen  and  the  greater  curvature  of  the  stomach  forms  the  gastro- 
splenic  ligament. 


Mouth  of  olfactory  ])it 

Median  fart  of  fronto- 
nasal process 


Processus  globulari 

Hypophysis 
1st  branchial  pouch 

Sinus  cervicalis 
Laryngo-tracheal  tube  '     T, 
Lung 


Maxillary  process 

2Iandibular  arch 

Future  tympanic 
membrane 

Hyoid  arch 

Third  arch 

Fourth  arch 


Fig.  208. — The  head  and  neck  of  a  human  embryo  thirty-two  days  old,  seen  from  the  ventral  sxirface.     The  floor  of 
the  mouth  and  pharynx  have  been  removed.     (His.) 

The  Respiratory  Organs. — The  rudiment  of  the  respiratory  organs  appear 
as  a  median  longitudinal  groove  in  the  ventral  wall  of  the  pharynx.  The  groove 
deepens  and  its  lips  fuse  to  form  a  septum  which  grows  from  below  upward  and 
converts  the  groove  into  a  tube,  the  laryngo-tracheal  tube  (Fig.  208),  the  cephalic 
end  of  which  opens  into  the  pharynx  by  a  slit-like  aperture  formed  by  the  persistent 
anterior  part  of  the  groove.  The  tube  is  lined  by  entoderm  from  which  the  epithe- 
lial lining  of  the  respiratory  tract  is  developed.     The  cephalic  part  of  the  tube 


DEVELOPMENT  OF  DIGESTIVE  AND  RESPIRATORY  APPARATUS     177 

becomes  the  larynx,  and  its  next  succeeding  part  the  trachea,  while  from  its  caudal 
end  two  lateral  outgrowths,  the  right  and  left  lung  buds,  arise,  and  from  them  the 
bronchi  and  lungs  are  developed.  The  first  rudiment  of  the  larynx  consists  of  two 
arytenoid  swellings,  wliich  appear,  one  on  eitlier  side  of  the  cephalic  end  of  the  laryngo- 
tracheal grooN'c,  and  are  continuous  in  front  of  the  groove  with  a  transverse Vidge 
(furcula  of  His)  which  lies  between  the  ventral  ends  of  the  third  branchial  arches 
and  from  which  the  epiglottis  is  subsequently  developed  (Figs.  187,  188).  After 
the  separation  of  the  trachea  from  the  oesophagus,  the  arytenoid  swellings  come 
into  contact  with  one  another  and  with  the  back  of  the  epiglottis,  and  the  entrance 
to  the  larynx  assumes  the  form  of  a  T-shaped  cleft,  the  margins  of  the  cleft  adhere 
to  one  another  and  the  laryngeal  entrance  is  for  a  time  occluded.  The  mesodermal 
wall  of  the  tube  becomes  condensed  to  form  the  cartilages  of  the  larynx  and  trachea. 
The  arytenoid  swellings  are  differentiated  into  the  arytenoid  and  corniculate  car- 
tilages, and  the  folds  joining  them  to  the  epiglottis  form  the  aryepiglottic  folds 
in  which  the  cuneiform  cartilages  are  developed  as  derivatives  of  the  epiglottis. 
The  thyroid  cartilage  appears  as  two  lateral  plates,  each  chondrified  from  two 
centres  and  united  in  the  mid-ventral  line  by  membrane  in  which  an  additional 
centre  of  chondrification  develops.  The  cricoid  cartilage  arises  from  two  cartil- 
aginous centres,  which  soon  unite  ventrally  and  gradually  extend  and  ultimately 
fuse  on  the  dorsal  aspect  of  the  tube. 


J.  Ernest  Frazeri  has  made  an  important  investigation  on  the  development  of  the  larynx, 
and  the  following  are  his  main  conclusions: 

The  opening  of  the  pulmonary  diverticulum  lies  between  the  two  fifth  arch  masses  and  behind 
a  "central  mass"  in  the  middle  hne — the  proximal  end  of  the  diverticulum  is  compressed  between 
the  fifth  arch  masses.  The  fifth  arch  is  joined  by  the  fourth  to  form  a  "lateral  mass"  on  each 
side  of  the  opening,  and  these  "lateral  masses"  grow  forward  and  overlap  the  central  mass  and 
so  form  a  secondary  transverse  cavity,  which  is  really  a  part  of  the  cavity  of  the  pharynx.  The 
two  parts  of  the  cavity  of  the  larynx  are  separated  in  the  adult  by  a  hne  drawn  back  along  the 
vocal  fold  and  then  upward  along  the  border  of  the  arytenoid  eminence  to  the  interarytenoid 
notch.  The  arytenoid  and  cricoid  are  developed  in  the  fifth  arch  mass.  The  thyroid  is  primarily 
a  fourth  arch  derivative,  and  if  it  has  a  fifth  arch  element  this  is  a  later  addition.  The  epiglottis 
is  derived  from  the  "central  mass,"  and  has  a  third  arch  element  in  its  oral  and  upper  aspect; 
the  arch  value  of  the  "central  mass"  is  doubtful. 


Fig.  209. — Lung  buds  from  a  human  embryo  of 
about  four  weeks,  showing  commencing  lobulations. 
(His.) 


Fig 


210  — Lungs  of   a  human   embn  o   more 
advanced  \n  development      (Hia  ) 


The  right  and  left  lung  buds  grow  out  behind  the  ducts  of  Cuvier,  and  are  at 
first  symmetrical,  but  their  ends  soon  become  lobulated,  three  lobules  appearing 
on  the  right,  and  two  on  the  left;  these  subdivisions  are  the  early  indications  of  the 
corresponding  lobes  of  the  lungs  (Figs.  209,  210).  The  buds  undergo  further  sub- 
di-vision  and  ramification,  and  ultimately  end  in  minute  expanded  extremities — 
the  infundibula  of  the  lung.  After  the  sixth  month  the  air-sacs  begin  to  make  their 
appearance  on  the  infundibula  in  the  form  of  minute  pouches.  The  pulmonary 
arteries  are  derived  from  the  sixth  aortic  arches.  During  the  course  of  their 
development  the  lungs  migrate  in  a  caudal  direction,  so  that  by  the  time  of  birth 


1  .lournal  of  Anatomy  and  Physiology,  vol.  xliv. 


12 


178 


EMBRYOLOGY 


the  bifurcation  of  the  trachea  is  opposite  the  fourth  thoracic  vertebra.  As  the 
lungs  grow  they  project  into  that  part  of  the  coelora  which  will  ultimately  form  the 
pleural  cavities,  and  the  superficial  layer  of  the  mesoderm  emcloping  the  lung 
rudiment  expands  on  the  growing  lung  and -is  couNcrtcd  into  the  pulmonary  pleura. 


DEVELOPMENT  OF  THE  BODY  CAVITIES. 

In  the  human  embryo  described  by  Peters  the  mesoderm  outside  the  embryonic 
disk  is  split  into  two  layers  enclosing  an  extra-embryonic  coelom;  there  is  no  trace 
of  an  intra-embryonic  coelom.  At  a  later  stage  four  cavities  are  formed  within  the 
embryo,  ^•iz.,  one  on  either  side  within  the  mesoderm  of  the  pericardial  area,  and 
one  in  either  lateral  mass  of  the  general  mesoderm.  All  these  are  at  first  independent 
of  each  other  and  of  the  extra-embryonic  coelom,  but  later  they  become  continuous. 
The  two  cavities  in  the  general  mesoderm  unite  on  the  ventral  aspect  of  the  gut 
and  form  the  pleuro-peritoneal  cavity,  which  becomes  continuous  with  the  remains 
of  the  extra-embryonic  coelom  around  the  umbilicus;  the  two  cavities  in  the  peri- 
cardial area  rapidly  join  to  form  a  single  pericardial  cavity,  and  from  this  two  lateral 


Mesentery 


Pleuro-  pericardial 
opening 


Pericardium," 


Mesoderm 
surrounding 
I  net  ofCuvier 

'  -Doibal  mesocardium 

I  "1  '-Heart 


Fig.  211. — Figure  obtained  by  combining  several  successive  sections  of  a  human  embryo  of  about  the  fourth  week 
(From  Kollmann.)     The  upper  arrow  is  in  the  pleuroperitoneal  opening,  the  lower  in  the  pleuroperioardial. 


diverticula  extend  caudalward  to  open  into  the  pleuro-peritoneal  cavity  (Fig.  211). 
Between  the  two  latter  diverticula  is  a  mass  of  mesoderm  containing  the  ducts 
of  Cuvier,  and  this  is  continuous  ventrally  with  the  mesoderm  in  which  the  umbili- 
cal veins  are  passing  to  the  sinus  venosus.  A  septum  of  mesoderm  thus  extends 
across  the  body  of  the  embryo.  It  is  attached  in  front  to  the  body-wall  between 
the  pericardium  and  umbilicus;  behind  to  the  body-wall  at  the  level  of  the  second 
cervical  segment;  laterally  it  is  deficient  where  the  pericardial  and  pleuro-peri- 
toneal cavities  communicate,  while  it  is  perforated  in  the  middle  line  by  the  fore- 
gut.  This  partition  is  termed  the  septum  transversum,  and  is  at  first  a  bulky  plate 
of  tissue.  As  development  proceeds  the  dorsal  end  of  the  septum  is  carried  grad- 
ually caudalward,  and  when  it  reaches  the  fifth  cervical  segment  muscular  tissue 
with  the  phrenic  nerve  grow  into  it.  It  continues  to  recede,  however,  until' it 
reaches  the  position  of  the  adult  Diaphragma  on  the  bodies  of  the  upper  lumbar 
vertebrae.  As  already  described  (page  174),  the  liver  buds  grow  into  the  septum 
transversum  and  undergo  development  there. 

The  lung  buds  meantime  have  grown  out  from  the  fore-gut,  and  project  laterally 
into  the  forepart  of  the  pleuro-peritoneal  cavity ;  the  developing  stomach  and  liver 


DEVELOPMEXT  OF  THE  BODY  CAVITIES 


179 


are  iml^edded  in  the  septum  transversum;  caudal  to  this  the  intestines  project  into 
the  back  i)art  of  the  pleuro-peritoneal  cavity  (Fig.  212).  Owing  to  the  descent  of 
the  dorsal  end  of  the  septum  transversum  the  hmg  buds  come  to  He  al)ove  the 

Left  due   of  Cuvier       (Edophayu^     Riyht  duct  of  Cavin- 


Mesoderm 

surrouiidi luj  duct 

Plruw-pericardiril 

opening 
Ridge,  growing  across 

opening 


Onienlal  bursa 


Stomach 


-p^ — Dorsal  mesentery 
~ Peritoneal  recess 


Fig.  212. — Upper  part  of  ccelom  of  human  embryo  of  6.S  mm.,  seen  from  behind.     (From  model  by  Piper.) 

septum  and  thus  pleural  and  peritoneal  portions  of  the  pleuro-peritoneal  cavity 
(still,  however,  in  free  communication  with  one  another)  may  be  recognized;  the 
pericardial  cavity  opens  into  the  pleural  part. 

The  ultimate  separation  of  the  permanent  cavities  from  one  another  is  effected 
by  the  growth  of  a  ridge  of  tissue  on  either  side  from  the  mesoderm  surrounding 


Aorta 

Pleural  cavity 

_^  _  Lung 

(Esopliagus 

Inferior  vena  cava 


Body -wall 
Pericardium 


Fig.  213. — Diagram  of  transverse  section  through  rabbit  embryo.      (After   Keith.) 


the  duct  of  Cuvier  (Figs.  211,  212).  The  front  part  of  this  ridge  grows  across  and 
obliterates  the  pleuro-pericardial  opening;  the  hinder  part  grows  across  the  pleuro- 
peritoneal  opening. 


180 


EMBRYOLOGY 


With  the  continued  growth  of  the  hmgs  the  pleural  cavities  are  pushed  forward 
in  the  body-wall  toward  the  ventral  median  line,  thus  separating  the  pericardium 
from  the  lateral  thoracic  walls  (Fig.  213) .  The  further  development  of  the  peritoneal 
cavity  has  been  described  with  the  development  of  the  digestive  tube  (page  168 
et  seq.). 


Spleen 

Colon 

Suprarenal  gland 

Eleventh  rib 

Twelfth  ri 


Stemo-costal  part  of 
Diaphragina 
Central  tendon  of  Diaphragma 

Inferior  vena  cava 

QP.sophagus 

Vertebral  part  of  Diaphragma 

Posterior  mediastinal  cavity 

Aorta 


Spino-costal  hiatus 


Left  pleura 


Eight  pleura 


Fig.  214. — The  thoracic  aspect  of  the  Diaphragma  of  a  newly  born  child  in  which  the  communication  between  the 
peritoneum  and  pleura  has  not  been  closed  on  the  left  side;  the  position  of  the  opening  is  marked  on  the  right  side  by 
the  spinocostal  hiatus.     (After  Keith.) 


DEVELOPMENT  OF  THE  URINARY  AND  GENERATIVE  ORGANS. 


The  urinary  and  generative  organs  are  developed  from  the  intermediate  cjll- 
mass  which  is  situated  between  the  primitive  segments  and  the  lateral  plates  of 
mesoderm.  The  permanent  organs  of  the  adult  are  preceded  by  a  set  of  structures 
which  are  purely  embryonic,  and  which  with  the  exception  of  the  ducts  disappear 
almost  entirely  before  the  end  of  fetal  life.  These  embryonic  structures  are  on 
either  side;  the  pronephros,  the  mesonephros,  the  metanephros,  and  the  Wolffian  and 
Miillerian  ducts.  The  pronephros  disappears  very  early;  the  structural  elements 
of  the  mesonephros  mostly  degenerate,  but  in  their  place  is  developed  the  genital 
gland  in  association  with  w^hich  the  Wolffian  duct  remains  as  the  duct  of  the  male 
genital  gland,  the  Miillerian  as  that  of  the  female;  some  of  the  tubules  of  the 
metanephros  form  part  of  the  permanent  kidney. 

The  Pronephros  and  Wolffian  Duct. — In  the  outer  part  of  the  intermediate 
cell-mass,  immediately  under  the  ectoderm,  in  the  region  from  the  fifth  cervical  to 
the  third  thoracic  segments,  a  series  of  short  evaginations  from  each  segment  grow 
dorsalward  and  extend  caudalward,  fusing  successively  from  before  backward  to 
form  the  pronephric  duct.  This  continues  to  grow  caudalward  until  it  opens  into 
the  ventral  part  of  the  cloaca;  beyond  the  pronephros  it  is  termed  the  Wolffian  duct. 

The  original  evaginations  form  a  series  of  transverse  tubules  each  of  which  com- 
municates by  means  of  a  funnel-shaped  ciliated  opening  with  the  coelomic  cavity, 
and  in  the  course  of  each  duct  a  glomerulus  also  is  developed.  Secondary  glo- 
meruli are  formed  ventral  to  each  of  the  others,  and  the  complete  group  constitutes 
the  pronephros.    The  pronephros  undergoes  rapid  atrophy  and  disappears. 

The  Mesonephros,  Miillerian  Duct,  and  Genital  Gland. — On  the  medial  side  of 
the  Wolffian  duct,  from  the  sixth  cervical  to  the  third  lumbar  segments,  a  series 
of  tubules,  the  Wolffian  tubules  (Fig.  215),  is  developed;  at  a  later  stage  in  develop- 
ment they  increase  in  number  by  outgrowths  from  the  original  tubules.  These 
tubules  first  appear  as  solid  masses  of  cells,  which  later  become  hollowed  in  the 


DEVELOPMENT  OF  THE  URINARY  AND  GENERATIVE  ORGANS     181 

centre;  one  end  grows  toward  and  finally  opens  into  the  Wolffian  duct,  the  other 
dilates  and  is  invaginated  by  a  tuft  of  capillary  hloodwssels  to  form  a  glomerulus. 
The  tubules  collectively  constitute  the  mesonephros  or  Wolffian  body  (Figs.  195, 
210).  By  the  fifth  or  sixth  week  this  body  forms  an  elongated  spindle-shaped 
structure,  termed  the  urogenital  fold  (Fig.  215),  which  projects  into  the  coelomic 
cavity  at  the  side  of  the  dorsal  mesentery,  reaching  from  the  sei)tum  transversum 


r  Stroma 
Genital  j      of  ovary  — - 
ridge    j  Primitive 
y      ova 


Wolffian  diict 

^.  Mullerian  duct 


---»  Wolffian  tubules 


Body-wall 


Fig.  215. — Section  of  the  urogenital  fold  of  a  chick  embryo  of  the  fourth  day.     (Waldeyer.) 


in  front  to  the  fifth  lumbar  segment  behind ;  in  this  fold  the  reproductive  glands  are 
developed.  The  Wolffian  bodies  persist  and  form  the  permanent  kidneys  in  fishes 
and  amphibians,  but  in  reptiles,  birds,  and  mammals,  they  atrophy  and  for  the 
most  part  disappear  coincidently  with  the  development  of  the  permanent  kidneys. 
The  atrophy  begins  during  the  sixth  or  seventh  week  and  rapidly  proceeds,  so  that 
by  the  beginning  of  the  fifth  month  only  the  ducts  and  a  few  of  the  tubules  remain. 

In  the  male  the  Wolffian  duct  persists, 
and  forms  the  tube  of  the  epididymis,  the 
ductus  deferens  and  the  ejaculatory  duct, 
while  the  seminal  vesicle  arises  during  the 
third  month  as  a  lateral  diverticulum  from 
its  hinder  end.  A  large  part  of  the  head 
end  of  the  mesonephros  atrophies  and  dis- 
appears; of  the  remainder  the  anterior 
tubules  form  the  efferent  ducts  of  the 
testis;  while  the  posterior  tubules  are 
represented  by  the  ductuli  aberrantes, 
and  by  the  paradidymis,  which  is  some- 
times found  in  front  of  the  spermatic 
cord  above  the  head  of  the  epididymis 
(Fig.  219,  C). 

In  the  female  the  Wolffian  bodies  and  ducts  atrophy.  The  remains  of  the 
Wolffian  tubules  are  represented  by  the  epobphoron  or  organ  of  Rosenmiiller,  and 
the  paroophoron,  two  small  collections  of  rudimentary  blind  tubules  wdiich  are 
situated  in  the  mesosalpinx  (Fig.  217).    The  lower  part  of  the  Wolffian  duct 


Fig.  216. — Enlarged  view  from  the  front  of  the 
left  Wolffian  body  before  the  establishment  of  the 
distinction  of  sex.  (From  Farre,  after  Kobelt.)  a, 
a,  b,  c,  d.  Tubular  structure  of  the  Wolffian  body, 
e.  Wolffian  duct.  /.  Its  upper  extremity,  g.  Its 
termination  in  x,  the  urogenital  sinus,  h.  The  duct 
of  Miiller.  i.  Its  upper,  funnel-shaped  extremity. 
k.  Its  lower  end,  terminating  in  the  urogenital  sinus. 
I.  The  genital  gland. 


182 


EMBRYOLOGY 


disappears,  while  the  upper  part  i)ersists  as  tlie  l()Il^■itu(lillal  duct  of  the  epoophoron 
or  duct  of  Gartner^  (Fig.  219,  B). 

The  Miillerian  Ducts. — Shortly  after  the  formation  of  the  Wolffian  ducts  a 
second  pair  of  ducts  is  developed;  these  are  named  the  Miillerian  ducts.  Each 
arises  on  the  lateral  aspect  of  the  correspondino;  Wolffian  duct  as  a  tu})ular  inva- 
gination of  the  cells  lining  the  ccelom  (Fig.  21")).    Th(>  orifice  of  the  invagination 


Fig.  217. — Broad  ligament  of  adult,  showing  epoophoron.  (From  Farre,  after  Kobelt.)  a,  a.  Epodphoron  formed 
from  the  upper  part  of  the  Wolffian  body.  b.  Remains  of  the  uppermost  tubes  sometimes  forming  appendices,  c.  Middle 
set  of  tubes,  d.  Some  lower  atrophied  tubes,  e.  Atrophied  remains  of  the  Wolffian  duct.  /.  The  terminal  bulb  or 
hydatid,    h.  The  uterine  tube,  originally  the  duct  of  Miiller.    i.  Appendix  attached  to  the  extremity.    I.  The  ovary. 


Miillerian  ducts 


remains  patent,  and  undergoes  enlargement  and  modification  to  form  the  abdomi- 
nal ostium  of  the  uterine  tube.  The  ducts  pass  backward  lateral  to  the  Wolffian 
ducts,  but  toward  the  posterior  end  of  the  embryo  they  cross  to  the  medial  side 
of  these  ducts,  and  thus  come  to  lie  side  by  side  between  and  behind  the  latter — 
the  four  ducts  forming  what  is  termed  the  genital  cord  (Fig.  218).  The  Miillerian 
ducts  end  in  an  epithelial  elevation,  the  Miillerian  eminence,  on  the  ventral  part  of 

the  cloaca  between  the  orifices  of  the  Wolflfian 
ducts;  at  a  later  date  they  open  into  the  cloaca 
in  this  situation. 

In  the  male  the  Miillerian  ducts  atrophy, 
but  traces  of  their  anterior  ends  are  repre- 
sented by  the  appendices  testis  {hydatids  of 
Morgagni),  while  their  terminal  fused  portions 
form  the  utriculus  in  the  floor  of  the  prostatic 
portion  of  the  urethra  (Fig.  219,  C). 

In  the  female  the  Miillerian  ducts  persist 
and  undergo  further  development.  The  por- 
tions which  lie  in  the  genital  core  fuse  to  form 
the  uterus  and  vagina;  the  parts  in  front  of 
this  cord  remain  separate,  and  each  forms 
the  corresponding  uterine  tube — the  abdomi- 
nal ostium  of  which  is  developed  from  the 
anterior  extremity  of  the  original  tubular  in- 
vagination from  the  coelom  (Fig.  219,  B).  The 
fusion  of  the  Miillerian  ducts  begins  in  the  third  month,  and  the  septum  formed 
by  their  fused  medial  walls  disappears  from  below  upward,  and  thus  the  cavities 


Fig.  218. — Urogenital  sinus  of  female  human 
embryo  of  eight  and  a  half  to  nine  weeks  old. 
(From  model  by  Keibel) 


'  Berry  Hart  {op.  cit.)  has  described  the  Wolffian  ducts  as  ending  at  the  site  of  the  future  hymen  in  bulbous  enlarge- 
ments, which  he  has  named  the  Wolffian  hilbs;  and  states  that  the  hj'men  is  formed  by  these  bulbs,  "aided  by  a  special 
involution  from  below  of  the  cells  lining  the  urogenital  sinus. "  He  further  believes  that  "the  lower  third  of  the  vagina 
is  due  to  the  coalescence  of  the  upper  portion  of  the  urogenital  sinus  and  the  lower  ends  of  the  Wolffian  ducts,"  and 
that  "the  epithelial  lining  of  the  vagina  is  derived  from  the  Wolffian  bulbs. "  He  also  regards  the  colliculus  seminahs 
of  the  male  urethra  as  being  formed  from  the  lower  part  of  the  Wolffian  ducts. 


DEVELOPMENT  OF  THE  URINARY  AND  GENERATIVE  ORGANS     183 

A 


Fig,  219. — Diagrams  to  show  the  develop- 
ment of  male  and  female  generative  organs 
from  a  common  type.     (Allen  Thomson.) 


A. — Diagram  of  the  primitive  urogenital 
organs  in  the  embryo  previous  to  sexual  dis- 
tinction. 3.  Ureter.  4.  Urinary  bladder.  5. 
I'rachus.  cl.  Cloaca,  cp.  Elevation  which  be- 
comes clitoris  or  penis,  i.  Lower  part  of  the 
intestine.  Is.  Fold  of  integument  from  which 
the  labia  majora  or  scrotum  are  formed. 
m,  m.  Right  and  left  Miillerian  ducts  uniting 
together  and  running  with  the  Wolffian  ducts 
in  gc,  the  genital  cord.  of.  The  genital  ridge 
from  which  either  the  ovary  or  testis  is 
formed,  ug.  Sinus  urogenitalis.  W.  Left 
Wolffian  body,  iv,  lo.  Right  and  left  Wolffian 
duets. 


B. — Diagram  of  the  female  type  of  sexual 
organs.  C.  Greater  vestibular  gland,  and 
immediately  above  it  the  urethra,  cc.  Corpus 
cavernosum  clitoridis.  dG.  Remains  of  the 
left  Wolffian  duct,  such  as  give  rise  to  the 
duct  of  Gartner,  represented  by  dotted  lines; 
that  of  the  right  side  is  marked  w.  f.  The 
abdominal  opening  of  the  left  uterine  tube. 
g.  Round  ligament,  corresponding  to  guber- 
naculum.  h.  Situation  of  the  hymen,  i.  Lower 
part  of  the  intestine.  I.  Labium  major,  n. 
Labium  minus,  o.  The  left  ovary,  po.  Epo- 
ophoron.  sc.  Corpus  cavernosum  urethrae.  u. 
Uterus.  The  uterine  tube  of  the  right  .side 
is  marked  m.  v.  Vulva,  va.  Vagina.  W. 
Scattered  remains  of  Wolffian  tubes  near  it 
(paroophoron  of  Waldeyer). 


C. — Diagram  of  the  male  type  of  sexual 
organs.  C.  Bulbo-urethral  gland  of  one  side. 
cp.  Corpora  cavernosa  penis  cut  short,  e. 
Caput  epididymis,  g.  The  gubernaculum. 
I.  Lower  part  of  the  intestine,  m.  Miillerian 
duct,  the  upper  part  of  which  remains  as 
the  hydatid  of  Morgagni;  the  lower  part, 
represented  bj'  a  dotted  line  descending  to 
the  prostatic  utricle,  constitutes  the  occa- 
sionally existing  cornu  and  tube  of  the  uterus 
masculinus.  pr.  The  prostate,  s.  Scrotum. 
sp.  Corpus  cavernosum  urethrae.  t.  Testis 
in  the  place  of  its  original  formation,  t', 
together  with  the  dotted  lines  above,  indi- 
cates the  direction  in  which  the  testis  and 
epididymis  descend  from  the  abdomen  into 
the  scrotum.  Dd.  Ductus  deferens.  !)/i.  Ductus 
aberrans.  vs.  The  vesicula  seminalis.  W. 
Scattered  remains  of  the  Wolffian  body,  con- 
stituting the  organ  of  Giraldes,  or  the  para- 
didymis of  Waldeyer. 


184 


EMBRYOLOGY 


Wolffian  body 
MulleHan  duct 

Wolffian  duet 


of  the  vagina  and  uterus  are  produced.  About  the  fifth  month  an  annular  con- 
striction marks  the'position  of  the  neck  of  the  uterus,  and  after  the  sixth  month 
the  walls  of  the  uterus  begin  to  thicken.  For  a  time  the  vagina  is  represented  by  a 
solid  rod  of  epithelial  cells,  k  ring-like  outgrowth  of  this  epithelium  occurs  at 
the  lower  end  of  the  uterus  and  marks  the  future  \-aginal  fornices;  about  the  fifth 
or  sixth  month  the  lumen  of  the  vagina  is  produced  by  the  breaking  down  of  the 
central  cells  of  the  epithelium.  The  hymen  represents  the  remains  of  the  Miillerian 
eminence. 

Genital  Glands. — The  first  appearance  of  the  genital  gland  is  essentially  the 
same  in  the  two  sexes,  and  consists  in  a  thickening  of  the  epithelial  layer  which 
lines  the  peritoneal  cavity  on  the  medial  side  of  the  urogenital  fold  (Fig.  215). 
The  thick  plate  of  epithelium  extends  deeply,  pushing  before  it  the  mesoderm  and 
forming  a  distinct  projection.  This  is  termed  the  genital  ridge  (Fig.  215),  and  from 
it  the  testis  in  the  male  and  the  ovary  in  the  female  are  developed.  At  first  the 
mesonephros  and  genital  ridge  are  suspended  by  a  common  mesentery,  but  as  the 
embrj'o  grows  the  genital  ridge  gradually  becomes  pinched  off  from  the  mesone- 
phros, with  which  it  is  at  first  continuous, 
though  it  still  remains  connected  to  the 
remnant  of  this  body  by  a  fold  of  peri- 
toneum, the  mesorchium  or  mesovarium 
(Fig.  220).  About  the  seventh  week  the 
distinction  of  sex  in  the  genital  ridge 
begins  to  be  perceptible. 

The  Ovary. — The  ovary,  thus  formed 
from  the  genital  ridge,  is  at  first  a  mass 
of  cells  derived  from  the  coelomic  epi- 
thelium; later  the  mass  is  differentiated 
into  a  central  part  or  medulla  (Fig.  221) 
covered  by  a  surface  layer,  the  germinal 
epithelium.  Between  the  cells  of  the 
germinal  epithelium  a  number  of  larger 
cells,  the  primitive  ova,  are  found,  and 
these  are  carried  into  the  subjacent 
stroma  by  bud-like  ingrowths  (genital 
cords)  of  the  germinal  epithelium  (Fig. 
222).  The  surface  epithelium  ultimately 
forms  the  permanent  epithelial  covering 
of  this  organ;  it  soon  loses  its  connection 
with  the  central  mass,  and  a  tunica  albuginea  develops  between  them.  The  ova 
are  chiefly  derived  from  the  cells  of  the  central  mass;  these  are  separated  from 
one  another  by  the  growth  of  connective  tissue  in  an  irregular  manner;  each  ovum 
assumes  a  covering  of  connective  tissue  (follicle)  cells,  and  in  this  way  the  rudi- 
ments of  the  ovarian  follicles  are  formed  (Fig.  222).  According  to  Beard  the  primi- 
tive ova  are  early  set  apart  during  the  segmentation  of  the  ovum  and  migrate  into 
the  germinal  ridge. 


t  Medulla  spinalis 
Spinal  ganglion 


Notochord 

Sympathetic  ganglion 
Inferior  vena  cava 
Common  iliac  artery 
Ureter 
Mesovarium 

Intestine 


Bladder 

ITmbilical  artery 


Fig.  220. — Transverse  section  of  human  embryo  eight  and 
a  half  to  nine  weeks  old.     (From  model  by  Keibel.) 


Waldeyer  taught  that  the  primitive  germ  cells  are  derived  from  the  "germinal  epithelium," 
covering  the  genital  ridge.  Beard, i  on  the  other  hand,  maintains  that  in  the  skate  they  are  not 
derived  from  this  epithelium,  but  are  probably  formed  during  the  later  stages  of  cell  cleavage, 
before  there  is  any  trace  of  an  embryo;  and  a  similar  view  was  advanced  by  Nussbaum  as  to  their 
origin  in  amphibia.  Beard  says:  "At  the  close  of  segmentation  many  of  the  future  germ  cells 
lie  in  the  segmentation  cavity  just  beneath  the  site  of  the  future  embryo,  and  there  is  no  doubt 
they  subsequently  wander  into  it."     The  germ  cells,  "after  they  enter  the  resting  phase,  are 


1  Journal  of  Anatomy  and  Physiology,  vol.  xx.wiii. 


DEVELOPMENT  OF  THE  URINARY  AND  GENERATIVE  ORGANS     185 

sharply  marked  off  from  the  cells  of  the  embryo  by  entire  absence  of  mitoses  among  them." 
They  can  be  further  recognized  by  their  irregular  form  and  ama-boid  processes,  and  by  the  fact 


Uterine  tube 


Oerminal  epithelium -, 


Medvlla  — 


i--\-  Epoophoron 


Rf.te 


Mesonephros 


Plica  peritonalis 
tnbce 


Uterine  tube 
Fig   221. — Longitudinal  section  of  ovary  of  cat  embryo  of  9.4  cm.  long.     Schematic.     (After  Ccert.) 


that  their  cytoplasm  has  no  affinity  for  ordinary  stains,  but  assumes  a  brownish  tinge  when  treated 
by  osmic  acid.  The  path  along  which  they  travel  into  the  embryo  is  a  very  definite  one,  viz., 
"from  the  yolk  sac  upward  between  the  splanchnopleure  and  gut  in  the  hinder  portion  of  the 

Genital  cord 


Oerminal 
epithelium, 

Primitive  ova 
Cell-nest 


Blood-vessel  - 
Ovarian  follicle  - 


Fig.  222. — Section  of  the  ovary  of  a  newly  born  child.     (Waldeyer.) 


embryo."    This  pathway,  named  by  Beard  the  germinal  path,  "leads  them  directly  to  the  posi- 
tion which  they  ought  finally  to  take  up  in  the  'germinal  ridge'  or  nidus."    A  considerable  number 


186 


EMBRYOLOGY 


apparently  never  reach  their  proper  destination,  since  "vagrant  germ  cells  are  found  in  all  sorts 
of  places,  but  more  particularly  on  the  mesentery."  Some  of  these  may  possibly  find  their  way 
into  the  germinal  ridge;  some  probably  undergo  atrr)])]iy,  wliilc  others  may  persist  and  become 
the  seat  of  dermoid  tumors. 


Epithelium  ■ 

Tunica 
albuginea 


Supporting 
cell 


-Interstitial 
cell 


,  Genital 
cell 


The  Testis. — The  testis  is  developed  in  much  the  same  way  as  the  ovary.  Like 
the  ovary,  in  its  earhest  stages  it  consists  of  a  central  mass  of  epithelium  covered 
by  a  surface  epithelium.  In  the  central  mass  a  series  of  cords  appear  (Fig.  223), 
and  the  periphery  of  the  mass  is  converted  into  the  tunica  albuginea,  thus  excluding 
the  surface  epithelium  from  any  part  in  the  formation  of  the  tissue  of  the  testis. 
The  cords  of  the  central  mass  run  together  toward  the  future  hilus  and  form  a 
network  which  ultimately  becomes  the  rete  testis.  From  the  cords  the  seminiferous 
tubules  are  developed,  and  between  them  connective  tissue  septa  extend.  The 
seminiferous  tubules  become  connected  with  outgrowths  from  the  Wolffian  body, 
which,  as  before  mentioned,  form  the  efferent  ducts  of  the  testis. 

Descent  of  the  Testes. — The  testes,  at  an  early  period  of  fetal  life,  are  placed 
at  the  back  part  of  the  abdominal  cavity,  behind  the  peritoneum,  and  each  is 

attached  by  a  peritoneal  fold,  the 
mesorchium,  to  the  mesonephros. 
From  the  front  of  the  mesonephros 
a  fold  of  peritoneum  termed  the 
inguinal  fold  grows  forward  to  meet 
and  fuse  with  a  peritoneal  fold, 
the  inguinal  crest,  which  grows 
backward  from  the  antero-lateral 
abdominal  wall.  The  testis  thus  ac- 
quires an  indirect  connection  with 
the  anterior  abdominal  wall;  and  at 
the  same  time  a  portion  of  the  peri- 
toneal cavity  lateral  to  these  fused 
folds  is  marked  off  as  the  future 
saccus  vaginalis.  In  the  inguinal 
crest  a  peculiar  structure,  the  guber- 
naculum  testis,  makes  its  appearance. 
This  is  at  first  a  slender  band,  ex- 
tending from  that  part  of  the  skin 
of  the  groin  which  afterward  forms 
the  scrotum  through  the  inguinal 
canal  to  the  body  and  epididymis  of  the  testis.  As  development  advances,  the 
peritoneum  enclosing  the  gubernaculum  forms  two  folds,  one  above  the  testis 
and  the  other  below  it.  The  one  above  the  testis  is  the  plica  vascularis,  and  con- 
tains ultimately  the  internal  spermatic  vessels;  the  one  below,  the  plica  guber- 
natrix,  contains  the  lower  part  of  the  gubernaculum,  which  has  now  grown  into 
a  thick  cord;  it  ends  below^  at  the  abdominal  inguinal  ring  in  a  tube  of  peritoneum, 
the  saccus  vaginalis,  which  protrudes  itself  down  the  inguinal  canal.  By  the  fifth 
month  the  lower  part  of  the  gubernaculum  has  become  a  thick  cord,  while  the 
upper  part  has  disappeared.  The  lower  part  now  consists  of  a  central  core  of 
unstriped  muscle  fibre,  and  outside  this  of  a  firm  layer  of  striped  elements,  con- 
nected, behind  the  peritoneum,  with  the  abdominal  wall.  As  the  scrotum  develops, 
the  main  portion  of  the  lower  end  of  the  gubernaculum  is  carried,  with  the  skin 
to  which  it  is  attached,  to  the  bottom  of  this  pouch;  other  bands  are  carried  to 
the  medial  side  of  the  thigh  and  to  the  perineum.  The  tube  of  peritoneum  con- 
stituting the  saccus  vaginalis  projects  itself  downward  into  the  inguinal  canal, 
and  emerges  at  the  cutaneous  inguinal  ring,  pushing  before  it  a  part  of  the  Obliquus 
internus  and  the  aponeurosis  of  the  Obliqims  externus,  which  form  respectively 


Fig 


223. — Section  of  a  genital  cord  of  the  testis  of  a  human 
embryo  3.5  cm.  long.     (Felix  and  Buhler.) 


DEVELOPMENT  OF  THE   URIXARY  AXD  GEXERATIVE  ORG  AX  S     187 

the  Cremaster  muscle  and  the  iiitererural  fascia.  It  forms  a  grachiahy  elongating 
poiichj  which  eventually  reaches  the  bottom  of  the  scrotum,  and  behind  this  pouch 
the  testis  is  drawn  by  the  growth  of  the  body  of  the  fetus,  for  the  gubernaculum 
does  not  grow  commensurately  with  the  growth  of  other  parts,  and  therefore 
the  testis,  being  attached  by  the  gubernaculum  to  the  bottom  of  the  scrotum, 
is  prevented  from  rising  as  the  body  grows,  and  is  drawn  first  into  the  inguinal 
canal  and  eventually  into  the  scrotum.  It  seems  certain  also  that  the  guber- 
nacular  cord  becomes  shortened  as  development  proceeds,  and  this  assists  in  caus- 
ing the  testis  to  reach  the  bottom  of  the  scrotum.  By  the  end  of  the  eighth  month 
the  testis  has  reached  the  scrotum,  preceded  by  the  saccus  vaginalis,  which  com- 
municates by  its  upper  extremity  with  the  peritoneal  cavity.  Just  before  birth 
the  upper  part  of  the  saccus  vaginalis  usually  becomes  closed,  and  this  obliteration 
extends  gradually  downward  to  within  a  short  distance  of  the  testis.  The  process 
of  peritoneum  surrounding  the  testis  is  now  entirely  cut  off  from  the  general  peri- 
toneal cavity  and  constitutes  the  tunica  vaginalis. 

Descent  of  the  Ovaries. — In  the  female  there  is  also  a  gubernaculum,  which 
effects  a  considerable  change  in  the  position  of  the  ovary,  though  not  so  extensive 
a  change  as  in  that  of  the  testis.  The  gubernaculum  in  the  female  lies  in  contact 
with  the  fundus  of  the  uterus  and  contracts  adhesions  to  this  organ,  and  thus 
the  ovary  is  prevented  from  descending  below  this  level.  The  part  of  the  guber- 
naculum between  the  ovary  and  the  uterus  becomes  ultimately  the  proper  ligament 
of  the  ovary,  while  the  part  between  the  uterus  and  the  labium  majus  forms  the 
round  ligament  of  the  uterus.  A  pouch  of  peritoneum  analogous  to  the  saccus 
vaginalis  in  the  male  accompanies  it  along  the  inguinal  canal:  it  is  called  the  canal 
of  Nuck.  In  rare  cases  the  gubernaculum  may  fail  to  contract  adhesions  to  the 
uterus,  and  then  the  ovary  descends  through  the  inguinal  canal  into  the  labium 
majus,  and  under  these  circumstances  its  position  resembles  that  of  the  testis. 


Wolffian  duct 
AUantois   \  Kidney  diveiiicidum 
Umbilical  cord    I      |  ]  Rectum 

J 


Umbilical  vessch 
Hiiul-gut 


yofochord 


Fig.  224. — Tail  end    of    human     embryo    twenty- 
five  to  twenty-nine  daj'S  old.    (From  model  by  Keibel.) 


Fig.    225. — Tail   end   of   human   embrj'o   thirty-two 
to  thirty-three  days  old.     (From  model  by  Keibel.) 


The  Metanephros  and  the  Permanent  Kidney. — The  rudiments  of  the  perma- 
nent kidneys  make  their  appearance  about  the  end  of  the  first  or  the  beginning 
of  the  second  month.  Each  kidney  has  a  two-fold  origin,  part  arising  from  the 
metanephros,  and  part  as  a  diverticulum  from  the  hind-end  of  the  Wolffian  duct, 
close  to  where  the  latter  opens  into  the  cloaca  (Figs.  224,  225).  The  metanephros 
arises  in  the  intermediate  cell  mass,  caudal  to  the  mesonephros,  which  it  resembles 
in  structure.  The  diverticulum  from  the  Wolffian  duct  grows  dorsalward  and 
forward  along  the  posterior  abdominal  wall,  where  its  blind  extremity  expands 
and  subsequently  divides  into  several  buds,  which  form  the  rudiments  of  the 
pelvis  and  calices  of  the  kidney;  by  continued  growth  and  subdivision  it  gives 
rise  to  the  collecting  tubules  of  the  kidne}'.  The  proximal  portion  of  the  diver- 
ticulum  becomes  the   ureter.     The   secretory  tubules  are  developed  from  the 


188 


EMBRYOLOGY 


Ureter 
Wolffian  duct  \ 
MhUpi  tan  di 
Bladde-) 
Symphysis  pubis 


metanephros,  which  is  moulded  over  the  growing  end  of  the  diverticuhim  from  the 
Wolffian  duct.  The  tubules  of  the  metanephros,  unlike  those  of  the  pronephros 
and  mesonephros,  do  not  open  into  the  Wolffian  duct.  One  end  expands  to  form 
a  glomerulus,  while  the  rest  of  the  tubule  rapidly  elongates  to  form  the  convoluted 
and  straight  tubules,  the  loops  of  Henle,  and  the  connecting  tubules;  these  last 

join  and  establish  communications 
with,  the  collecting  tubules  derived 
from  the  ultimate  ramifications  of  the 
diverticulum  from  the  Wolffian  duct. 
The  mesoderm  around  the  tubules  be- 
comes condensed  to  form  the  connec- 
tive tissue  of  the  kidney.  The  ureter 
opens  at  first  into  the  hind-end  of  the 
Wolffian  duct;  after  the  sixth  week  it 
separates  from  the  Wolffian  duct,  and 
opens  independently  into  the  part  of 
the  cloaca  which  ultimately  becomes 
the  bladder  (Figs.  226,  227). 

The  secretory  tubules  of  the  kid- 
ney become  arranged  into  pyramidal 
masses  or  lobules,  and  the  lobulated 
condition  of  the  kidneys  exists  for 
some  time  after  birth,  while  traces  of 
it  may  be  found  even  in  the  adult.  The  kidnej^  of  the  ox  and  many  other  animals 
remains  lobulated  throughout  life. 

The  Urinary  Bladder. — The  bladder  is  formed  partly  from  the  entodermal 
cloaca  and  partly  from  the  ends  of  the  Wolffian  ducts;  the  allantois  takes  no  share 
in  its  formation.    After  the  separation  of  the  rectum  from  the  dorsal  part  of  the 


Glans  penis 

Urethra 


Vertebral  column 


Fig.  226. — Tail   end  of  human  embryo;   from  eight  and  a 
half  to  nine  weeks  old.     (From  model  by  Keibel.) 


Wolffian  duct 
Hind-gut 


Bladder 


Outer  zone\ 

>  of  kidney 
Inner  zone) 

Pelvis  of  kidney 


Urogenital 
membrane 


Fig.  227. — Primitive  kidney  and  bladder,  from  a  reconstruction.     (After  Schreiner.) 


cloaca  (p.  172),  the  ventral  part  becomes  subdivided  into  three  portions:  (1)  an 
anterior  vesico-urethral  portion,  continuous  with  the  allantois — into  this  portion  the 
Wolffian  ducts  open;  (2)  an  intermediate  narrow  channel,  the  pelvic  portion;  and 
(3)  a  posterior  phallic  portion,  closed  externally  by  the  urogenital  membrane  (Fig. 
227).     The  second  and  third  parts  together  constitute  the  urogenital  sinus.     The 


DEVELOPMENT  OF  THE  URIXARY  AND  GENERATIVE  ORGANS     189 

vesico-urethral  portion  absorbs  the  ends  of  the  Wolffian  ducts  and  the  associated 
ends  of  the  renal  diverticula,  and  these  give  rise  to  the  trigone  of  the  bladder  and 
part  of  the  prostatic  urethra.  The  remainder  of  the  vesico-urethral  portion  forms 
the  body  of  the  bladder  and  part  of  the  prostatic  urethra;  its  apex  is  prolonged  to 
the  umbilicus  as  a  narrow  canal,  which  later  is  obhterated  and  becomes  the  medial 
umbilical  ligament  (urachus). 


Umbilical  cord 

Genital  tubercle 

Hind-linib 
Cloaca 

Tail 


Genital  tubercle 
— •  habiiun  majus 
— —  Labium  mimm 

Urogenital 

meinbrane 


Glana  penis 

Sci-otal  swelling 

Edge  of  groove  on  phallus' 

Opening  ofurogmital  sin  us 

PeriTietfm 


~  Anus 


Glans  clitoridie 
Labium  majus 
Labium  minus 
Opening  of 
urogenital  sinus 


Peri^iieum 


Glans  penis 


Cavernous  urethra 


Scrotum 


Raphe 


AniLS 


-  Prepuce 

-  Glans  clitoridis 

Labium  majits 
Labium  miiiu-s 


Fig.  228. — Stages  in  the  development  of  the  external  .sexual  organs  in  the  male  and  female.     (Drawn  from  the 

Ecker-Ziegler  models.) 


The  Prostate.— The  prostate  originally  consists  of  two  separate  portions,  each 
of  which  arises  as  a  series  of  diverticular  buds  from  the  epithelial  lining  of  the  uro- 
genital sinus  and  vesico-urethral  part  of  the  cloaca,  between  the  third  and  fourth 
months.  These  buds  become  tubular,  and  form  the  glandular  substance  of  the  two 
lobes,  which  ultimately  meet  and  fuse  behind  the  urethra  and  also  extend  on  to  its 
ventral  aspect.    The  isthmus  or  middle  lobe  is  formed  as  an  extension  of  the  lateral 


190  EMBRYOLOGY 

lobes  between  the  common  ejaculatory  ducts  and  the  })hidder.  Skene's  ducts  in  the 
female  urethra  are  regarded  as  the  homologues  of  the  prostatic  glands. 

The  bulbo-urethral  glands  of  Cowper  in  the  male,  and  greater  vestibular  glands 
of  Bartholin  in  the  female,  also  arise  as  diverticula  from  the  epithelial  lining  of  the 
urogenital  sinus. 

The  External  Organs  of  Generation  (Fig.  22S). — As  already  stated  (page  172), 
the  cloacal  membrane,  composed  of  ectoderm  and  entoderm,  originally  reaches  from 
the  umbilicus  to  the  tail.  The  mesoderm  extends  to  the  midventral  line  for  some 
distance  behind  the  umbilicus,  and  forms  the  lower  part  of  the  abdominal  wall; 
it  ends  below  in  a  prominent  swelling,  the  cloacal  tubercle.  Behind  this  tubercle 
the  urogenital  part  of  the  cloacal  membrane  separates  the  ingrowing  sheets  of 
mesoderm. 

The  first  rudiment  of  the  penis  (or  clitoris)  is  a  structure  termed  the  phallus;  it 
is  derived  from  the  phallic  portion  of  the  cloaca  which  has  extended  on  to  the 
end  and  sides  of  the  under  surface  of  the  cloacal  tubercle.  The  terminal  part  of 
the  phallus  representing  the  future  glans  becomes  solid;  the  remainder,  which 
is  hollow,  is  converted  into  a  longitudinal  groove  by  the  absorption  of  the 
urogenital  membrane. 

In  the  female  a  deep  groove  forms  around  the  phallus  and  separates  it  from  the 
rest  of  the  cloacal  tubercle,  which  is  now  termed  the  genital  tubercle.  The  sides  of 
the  genital  tubercle  grow  backward  as  the  genital  swellings,  which  ultimately  form 
the  labia  majora;  the  tubercle  itself  becomes  the  mons  pubis.  The  labia  minora 
arise  by  the  continued  growth  of  the  lips  of  the  groove  on  the  under  surface  of  the 
phallus;  the  remainder  of  the  phallus  forms  the  clitoris. 

In  the  male  the  early  changes  are  similar,  but  the  pelvic  portion  of  the  cloaca 
undergoes  much  greater  development,  pushing  before  it  the  phallic  portion.  The 
genital  swellings  extend  around  between  the  pelvic  portion  and  the  anus,  and  form  a 
scrotal  area;  during  the  changes  associated  with  the  descent  of  the  testes  this  area 
is  drawn  out  to  form  the  scrotal  sacs.  The  penis  is  developed  from  the  phallus. 
As  in  the  female,  the  urogenital  membrane  undergoes  absorption,  forming  a  channel 
on  the  under  surface  of  the  phallus;  this  channel  extends  only  as  far  forward  as  the 
corona  glandis. 

The  corpora  cavernosa  of  the  penis  (or  clitoris)  and  of  the  urethra  arise  from  the 
mesodermal  tissue  in  the  phallus;  they  are  at  first  dense  structures,  but  later 
vascular  spaces  appear  in  them,  and  they  gradually  become  cavernous. 

The  prepuce  in  both  sexes  is  formed  by  the  growth  of  a  solid  plate  of  ectoderm 
into  the  superficial  part  of  the  phallus;  on  coronal  section  this  plate  presents  the 
shape  of  a  horseshoe.  By  the  breaking  down  of  its  more  centrally  situated  cells 
the  plate  is  split  into  two  lamellae,  and  a  cutaneous  fold,  the  prepuce,  is  liberated 
and  forms  a  hood  over  the  glans.  "Adherent  prepuce  is  not  an  adhesion  really, 
but  a  hindered  central  desquamation"  (Berry  Hart,  oy.  cit.). 

The  Urethra. — As  already  described,  in  both  sexes  the  phallic  portion  of  the 
cloaca  extends  on  to  the  under  surface  of  the  cloacal  tubercle  as  far  forward  as  the 
apex.  At  the  apex  the  walls  of  the  phallic  portion  come  together  and  fuse,  the 
lumen  is  obliterated,  and  a  solid  plate,  the  urethral  plate,  is  formed.  The  remainder 
of  the  phallic  portion  is  for  a  time  tubular,  and  then,  by  the  absorption  of  the 
urogenital  membrane,  it  establishes  a  communication  with  the  exterior;  this  open- 
ing is  the  primitive  urogenital  ostium,  and  it  extends  forward  to  the  corona  glandis. 

In  the  female  this  condition  is  largely  retained;  the  portion  of  the  groove  on  the 
clitoris  broadens  out  while  the  body  of  the  clitoris  enlarges,  and  thus  the  adult 
urethral  opening  is  situated  behind  the  base  of  the  clitoris. 

In  the  male,  by  the  greater  growth  of  the  pelvic  portion  of  the  cloaca  a  longer 
urethra  is  formed,  and  the  primitive  ostium  is  carried  forward  with  the  phallus, 
but  it  still  ends  at  the  corona  glandis.    Later  it  closes  from  behind  forward.    Mean- 


FORM  OF  THE  EMBRYO  AT  DIFFERENT  STAGES  OF  ITS  GROWTH     191 

while  the  urethral  plate  of  the  glaiis  breaks  down  centrally  to  form  a  median 
groove  continuous  with  the  primitive  ostium.  This  groove  also  closes  from  behind 
forward,  so  that  the  external  urethral  opening  is  shifted  forward  to  the  end  of 
the  glans. 


THE  FORM  OF  THE  EMBRYO  AT  DIFFERENT  STAGES  OF  ITS  GROWTH. 

First  Week. — During  this  period  the  ovum  is  in  the  uterine  tube.  Having  been  fertilized  in 
the  upper  part  of  the  tube,  it  slowly  passes  down,  undergoing  segmentation,  and  reaches  the 
uterus.  Peters'  described  a  specimen,  the  age  of  which  he  reckoned  as  from  three  to  four  days. 
It  was  imbedded  in  the  decidua  on  the  posterior  wall  of  the  uterus  and  enveloped  by  a  decidua 
capsularis,  the  central  part  of  which,  however,  consisted  merely  of  a  layer  of  fibrin.  The  ovum 
was  in  the  form  of  a  sac,  the  outer  wall  of  which  consisted  of  a  layer  of  trophoblast;  inside  this 
was  a  thin  layer  of  mesoderm  composed  of  round,  oval,  and  spindle-shaped  cells.  Numerous 
villous  processes — some  consisting  of  trophoblast  only,  others  possessing  a  core  of  mesoderm — 
pi-ojected  from  the  surface  of  the  ovum  into  the  surrounding  decidua.  Inside  this  sac  the  rudi- 
ment of  the  embryo  was  found  in  the  form  of  a  patch  of  ectoderm,  covered  by  a  small  but  com- 
pletely closed  amnion.  It  possessed  a  minute  yolk-sac  and  was  surrounded  by  mesoderm,  which 
was  connected  by  a  band  to  that  Hning  the  trophoblast  (Fig.  88).- 


Heart 


Amnion 


Bochj-stalh 


Chorion 
Fig.  229. — Human  embryo  about  fifteen  day.s  old.      (His.) 

Second  Week. — By  the  end  of  this  week  the  ovum  has  increased  considerably  in  size,  and  the 
majority  of  its  villi  are  vascularized.  The  embryo  has  assumed  a  definite  form,  and  its  cephahc 
and  caudal  extremities  are  easily  distinguished.  The  neural  folds  are  partly  united.  The  embryo 
is  more  completely  separated  from  the  yolk-sac,  and  the  paraxial  mesoderm  is  being  divided  into 
the  primitive  segments  (Fig.  229). 

Third  Week. — By  the  end  of  the  third  week  the  embryo  is  strongly  curved,  and  the  primitive 
segments  number  about  thirty.  The  primary  divisions  of  the  brain  are  visible,  and  the  optic 
and  auditory  vesicles  are  formed.  Four  branchial  grooves  are  present:  the  stomodeum  is  well- 
marked,  and  the  buccopharyngeal  membrane  has  disappeared.  The  rudiments  of  the  limbs 
are  seen  as  short  buds,  and  the  Wolffian  bodies  are  visible  (Fig.  230). 

Fourth  Week. — The  embryo  is  markedly  curved  on  itself,  and  when  viewed  in  profile  is  almost 
circular  in  outfine.  The  cerebral  hemispheres  appear  as  hoUow  buds,  and  the  elevations  which 
form  the  rudiments  of  the  auricula  are  visible.  The  hmbs  now  appear  as  oval  flattened  projec- 
tions (Fig.  231). 

Fifth  Week. — The  embryo  is  less  curved  and  the  head  is  relatively  of  large  size.  Differentiation 
of  the  limbs  into  their  segments  occurs.  The  nose  forms  a  short,  flattened  projection.  The  cloacal 
tubercle  is  evident  (Fig.  232). 


1  Die  Einbettung  des  niensohlichen  Eies,  1899. 

-  Bryce  and  Teacher  (Earbj  Deielopment  and  Imbedding  of  the  Human  Ovum,  190S)  have  described  an  ovum  which 
they  regard  as  thirteen  to  fourteen  days  old.  In  it  the  two  vesicles,  the  amnion  and  yolk-sac,  were  present,  but  there 
was  no  trace  of  a  layer  of  embryonic  ectoderm.  They  are  of  opinion  that  the  age  of  Peters'  ovum  has  been  understated, 
and  estimate  it  as  between  thirteen  and  one-half  and  fourteen  and  one-half  days. 


192 


EMBRYOLOGY 


Sixth  Week. — The  curvature  of  the  embrj'o  is  further  diniini.shed.  The  branchial  grooves — 
except  the  first — have  disappeared,  and  the  rudiments  of  the  fingers  and  toes  can  be  recognized 
(Fig.  233). 


Mid-hrain 

y^ 

V/ 

Hind-hrain 

Fore-hrain  ~~f 

hj 

On 

Auditor ij  vesicle 

Sto7}iodeu7n 

^ 

A, 

%                yJQr-fvqJ 

Mandibular  arch' 

\\       arches 

Heart 

\\ 

.*lJ1 

a 

-Amnion  {cut) 


Body-stalk 
Fig.  230. — Human  embryo  between  eighteen  and  twenty-one  days  old. 


(His.) 


Seventh  and  Eighth  Weeks. — The  flexure  of  the  head  is  gradually  reduced  and  the  neck  is 
somewhat  lengthened.  The  upper  hp  is  completed  and  the  nose  is  more  prominent.  The  nostrils 
are  directed  forward  and  the  palate  is  not  completely  developed.  The  eyehds  are  present  in  the 
shape  of  folds  above  and  below  the  eye,  and  the  different  parts  of  the  auricula  are  distinguish- 
able. By  the  end  of  the  second  month  the  fetus  measures  from  28  to  30  mm.  in  length  (Fig. 
234). 

Heart 


Fore-limb 


Hyoid  arch 

2Iandibular  arch 
Maxillary  process  ^ 

Eye  J' 
Olfactory  pit 


Chorion 


Fig.  231. — Human  embryo,  twenty-seven  to  thirty  days  old.     (His.) 

Third  Month. — The  head  is  extended  and  the  neck  is  lengthened.  The  eyehds  meet  and  fuse, 
remaining  closed  imtil  the  end  of  the  sixth  month.  The  hmbs  are  well-developed  and  nails  appear 
on  the  digits.  The  external  generative  organs  are  so  far  differentiated  that  it  is  possible  to  dis- 
tinguish the  sex.  By  the  end  of  this  month  the  length  of  the  fetus  is  about  7  cm.,  but  if  the  legs 
be  included  it  is  from  9  to  10  cm. 

Fourth  Month. — The  loop  of  gut  which  projected  into  the  umbihcal  cord  is  withdrawn  within 
the  fetus.  The  hairs  begin  to  make  their  appearance.  There  is  a  general  increase  in  size  so  that 
by  the  end  of  the  fourth  month  the  fetus  is  from  12  to  13  cm.  in  length,  but  if  the  legs  be  included 
it  is  from  16  to  20  cm. 


FORM  OF  THE  EMBRYO  AT  DIFFERENT  STAGES  OF  ITS  GROWTH     193 

Fifth  Month. — It  is  during  this  mouth  that  the  first  movements  of  the  fetus  are  usually  ob- 
served. The  erujition  of  hair  on  the  head  commences,  and  the  veniix  caseosa  beguis  to  be  deposited. 
Bj-  the  end  of  tliis  month  the  total  length  of  the  fetus,  including  the  legs,  is  from  25  to  27  cm. 


Heart 


Hyoid  arch 
Mandibular  a'>rJi 

Maxilla)  y  pi  ore 

Ell 


Fore-limb 


Hind-limb 
Fig.  232. — Human  embrj'o,  thirty-one  to  thirtj'-foiir  days  old.     (His.) 

Sixth  Month. — The  body  is  covered  b}'-  fine  hairs  (lanugo)  and  the  deposit  of  vernix  caseosa 
is  considerable.  The  papillae  of  the  skin  are  developed  and  the  free  border  of  the  nail  projects 
from  the  corium  of  the  dermis.  Measured  from  vertex  to  heels,  the  total  length  of  the  fetus 
at  the  end  of  this  month  is  from  30  to  32  cm. 


Auricula 


Fore-limb 


Hind-linib 


Umbilical  cord 


Fig.  23.3. — Human  embrvo  of  about  sis  weeks. 
(His,) 


Fig.  234. — Human  embryo  about  eight  and  a  half 
weeks  old.     (His.) 


Seventh  Month. — The  pupillary  membrane  atrophies  and  the  eyelids  are  open.     The  testis 
descends  with  the  vaginal  sac  of  the  peritoneum.    From  vertex  to  heels  the  total  length  at  the 
end  of  the  seventh  month  is  from  35  to  36  cm.    The  weight  is  a  little  over  thi-ee  pounds. 
13 


194  EMBRYOLOGY 

Eighth  Month. — The  skin  assumes  a  pink  color  and  is  now  entirely  coated  with  vernix  caseosa, 
and  the  lanugo  begins  to  disappear.  Subcutaneous  fat  has  been  developed  to  a  considerable 
extent,  and  the  fetus  presents  a  plump  appearance.  The  total  length,  i.  e.,  from  head  to  heels, 
at  the  end  of  the  eighth  month  is  about  40  cm.,  and  the  weight  varies  between  four  and  one-half 
and  five  and  one-half  pounds. 

Ninth  Month. — The  lanugo  has  largely  disappeared  from  the  trunk.  The  umbilicus  is  almost 
in  the  middle  of  the  body  and  the  testes  are  in  the  scrotum.  At  full  time  the  fetus  weighs  from 
six  and  one-half  to  eight  pounds,  and  measm-es  from  head  to  heels  about  50  cm. 


OSTEOLOGY. 


npHE  general  framework  of  the  body  is  built  up  mainly  of  a  series  of  bones, 
-L  supplemented,  however,  in  certain  regions  by  pieces  of  cartilage;  the  bony 
part  of  the  framework  constitutes  the  skeleton. 

In  comparative  anatomy  the  term  skeleton  has  a  wider  application,  since  in 
some  of  the  lower  animals  hard,  protecting  and  supporting  structures  are  developed 
in  association  with  the  integumentary  system.  In  such  animals  the  skeleton 
is  described  as  consisting  of  an  internal  or  deep  skeleton,  the  endoskeleton,  and 
an  external  or  superficial,  the  exoskeleton.  In  the  human  subject  the  exoskeleton 
is  extremely  rudimentary,  its  only  important  representatives  being  the  nails 
and  the  enamel  of  the  teeth.  The  term  skeleton  is,  therefore,  confined  to  the 
endoskeleton,  and  this  is  divisible  into  an  axial  part,  which  includes  that  of  the 
head  and  trunk,  and  an  appendicular  part,  which  comprises  that  of  the  extremities 
or  limbs. 

In  the  skeleton  of  the  adult  there  are  206  distinct  bones,  as  follows: — 


Axial 

Skeleton 


Vertebral  column      .  .  .  .  .26 

Skull 22 

Hyoid  bone    ...  .  .  .  .1 

Ribs  and  sternum     .  .  .  .  .25 


74 


Appendicular      f  Upper  extremities     .  .  .  .  .64 

Skeleton  \  Lower  extremities     .  .         .  .  .62 

—     126 
Auditory  ossicles         ........  6 

Total 206 

The  patellse  are  included  in  this  enumeration,  but  the  smaller  sesamoid  bones 
are  not  reckoned. 

Bones  are  divisible  into  four  classes:  Long,  Short,  Flat,  and  Irregular. 

Long  Bones. — The  long  bones  are  found  in  the  limbs,  and  each  consists  of  a  body 
or  shaft  and  two  extremities.  The  body,  or  diaphysis  is  cylindrical,  with  a  central 
cavity  termed  the  medullary  canal;  the  wall  consists  of  dense,  compact  tissue 
of  considerable  thickness  in  the  middle  part  of  the  body,  but  becoming  thinner 
toward  the  extremities;  within  the  medullary  canal  is  some  cancellous  tissue, 
scanty  in  the  middle  of  the  body  but  greater  in  amount  toward  the  ends.  The 
extremities  are  generally  expanded,  for  the  purposes  of  articulation  and  to  afford 
broad  surfaces  for  muscular  attachment.  They  are  usually  developed  from  sep- 
arate centres  of  ossification  termed  epiphyses,  and  consist  of  cancellous  tissue 
surrounded  by  thin  compact  bone.  The  medullary  canal  and  the  spaces  in  the 
cancellous  tissue  are  filled  with  marrow.  The  long  bones  are  not  straight,  but 
curved,  the  curve  generally  taking  place  in  two  planes,  thus  affording  greater 
strength  to  the  bone.  The  bones  belonging  to  this  class  are:  the  clavicle,  humerus, 
radius,  ulna,  femur,  tibia,  fibula,  metacarpals,  metatarsals,  and  phalanges. 


196  OSTEOLOGY 

Short  Bones. — Where  a  part  of  the  skeleton  is  intended  for  strength  and  com- 
pactness combined  with  limited  movement,  it  is  constructed  of  a  number  of  short 
bones,  as  in  the  carpus  and  tarsus.  These  consist  of  cancellous  tissue  covered 
by  a  thin  crust  of  compact  substance.  The  patellae,  together  with  the  other 
sesamoid  bones,  are  by  some  regarded  as  short  bones. 

Flat  Bones. — Where  the  principal  requirement  is  either  extensive  protection  or 
the  provision  of  broad  surfaces  for  muscular  attachment,  the  bones  are  expanded 
into  broad,  flat  plates,  as  in  the  skull  and  the  scapula.  These  bones  are  composed 
of  two  thin  layers  of  compact  tissue  enclosing  between  them  a  variable  quantity 
of  cancellous  tissue.  In  the  cranial  bones,  the  layers  of  compact  tissue  are  famili- 
arly known  as  the  tables  of  the  skull;  the  outer  one  is  thick  and  tough;  the  inner 
is  thin,  dense,  and  brittle,  and  hence  is  termed  the  vitreous  table.  The  intervening 
cancellous  tissue  is  called  the  diploe,  and  this,  in  certain  regions  of  the  skull, 
becomes  absorbed  so  as  to  leave  spaces  filled  with  air  {air-sinuses)  between 
the  two  tables.  The  flat  bones  are:  the  occipital,  parietal,  frontal,  nasal,  lacrimal, 
vomer,  scapula,  os  coxae  {hiy  hone),  sternum,  ribs,  and,  according  to  some,  the 
patella. 

Irregular  Bones. — The  irregular  bones  are  such  as,  from  their  peculiar  form, 
cannot  be  grouped  under  the  preceding  heads.  They  consist  of  cancellous  tissue 
enclosed  within  a  thin  layer  of  compact  bone.  The  irregular  bones  are:  the 
vertebrae,  sacrum,  coccyx,  temporal,  sphenoid,  ethmoid,  zygomatic,  maxilla,  mandible, 
palatine,  inferior  nasal  concha,  and  hyoid. 

Surfaces  of  Bones. — If  the  surface  of  a  bone  be  examined,  certain  eminences 
and  depressions  are  seen.  These  eminences  and  depressions  are  of  two  kinds: 
articular  and  non-articular.  Well-marked  examples  of  articular  eminences  are 
found  in  the  heads  of  the  humerus  and  femur;  and  of  articular  depressions  in  the 
glenoid  cavity  of  the  scapula,  and  the  acetabulum  of  the  hip  bone.  Non-articular 
eminences  are  designated  according  to  their  form.  Thus,  a  broad,  rough,  uneven 
elevation  is  called  a  tuberosity,  protuberance,  or  process,  a  small,  rough  prominence, 
a  tubercle ;  a  sharp,  slender  pointed  eminence,  a  spine ;  a  narrow,  rough  elevation, 
running  some  way  along  the  surface,  a  ridge,  crest,  or  line.  Non-articular  depres- 
sions  are  also  of  variable  form,  and  are  described  as  fossae,  pits,  depressions,  grooves, 
furrows,  fissures,  notches,  etc.  These  non-articular  eminences  and  depressions  serve 
to  increase  the  extent  of  surface  for  the  attachment  of  ligaments  and  muscles, 
and  are  usually  well-marked  in  proportion  to  the  muscularity  of  the  subject; 
the  grooves,  fissures,  and  notches  transmit  tendons,  vessels,  or  nerves. 

The  minute  structure,  growth,  and  composition  of  bone  are  described  on 
pages  50  to  59. 

THE  VERTEBRAL  COLUMN  (COLUMNA  VERTEBRALIS ;  SPINAL 

COLUMN). 

The  vertebral  column  is  a  flexuous  and  flexible  column,  formed  of  a  series  of 
bones  called  vertebrae. 

The  vertebrae  are  thirty-three  in  number,  and  are  grouped  under  the  names 
cervical,  thoracic,  lumbar,  sacral,  and  coccygeal,  according  to  the  regions  they 
occupy;  there  are  seven  in  the  cervical  region,  twelve  in  the  thoracic,  five  in  the 
lumbar,  five  in  the  sacral,  and  four  in  the  coccygeal. 

This  number  is  sometimes  increased  by  an  additional  vertebra  in  one  region, 
or  it  may  be  diminished  in  one  region,  the  deficiency  being  supplied  by  an  addi- 
tional vertebra  in  another.  The  number  of  cervical  vertebrae  is,  however,  very 
rarely  increased  or  diminished. 

The  vertebrae  in  the  upper  three  regions  of  the  column  remain  distinct  through- 
out life,  and  are  known  as  true  or  movable  vertebrae;  those  of  the  sacral  and 


GENERAL  CHARACTERISTICS  OF  A   VERTEBRA  197 

coccygeal  regions,  on  the  other  hand,  are  termed  false  or  fixed  vertebrai,  because 
they  are  united  with  one  another  in  the  adult  to  form  two  bones — five  forming 
the  upper  bone  or  sacrum,  and  four  the  terminal  bone  or  coccyx. 

With  the  exception  of  tlio  first  and  second  cervical,  the  true  or  movable  vertebrae 
present  certain  common  characteristics  which  are  best  studied  by  examining  one 
from  the  middle  of  the  thoracic  region. 


GENERAL    CHARACTERISTICS    OF    A    VERTEBRA. 

A  typical  vertebra  consists  of  two  essential  parts — viz.,  an  anterior  segment,  the 
body,  and  a  posterior  part,  the  vertebral  or  neural  arch;  these  enclose  a  foramen, 
the  vertebral  foramen.  The  vertebral  arch  consists  of  a  pair  of  pedicles  and  a  pair 
of  laminae,  and  supports  seven  processes — viz.,  four  articular,  two  transverse,  and 
one  spinous. 

When  the  vertebrae  are  articulated  with  each  other  the  bodies  form  a  strong 
pillar  for  the  support  of  the  head  and  trunk,  and  the  vertebral  foramina  constitute 
a  canal  for  the  protection  of  the  medulla  spinalis  (spinal  cord),  while  between 
every  pair  of  vertebrae  are  two  apertures,  the  intervertebral  foramina,  one  on 
either  side,  for  the  transmission  of  the  spinal  nerves  and  vessels. 

Body  {corpus  vertebrae). — The  body  is  the  largest  part  of  a  vertebra,  and  is 
more  or  less  cylindrical  in  shape.  Its  upper  and  lower  surfaces  are  flattened  and 
rough,  and  give  attachment  to  the  intervertebral  fibrocartilages,  and  each  presents 
a  rim  around  its  circumference.  In  front,  the  body  is  convex  from  side  to  side 
and  concave  from  above  downward.  Behind,  it  is  flat  from  above  downward 
and  slightly  concave  from  side  to  side.  Its  anterior  surface  presents  a  few  small 
apertures,  for  the  passage  of  nutrient  vessels;  on  the  posterior  surface  is  a  single 
large,  irregular  aperture,  or  occasionally  more  than  one,  for  the  exit  of  the  basi- 
vertebral veins  from  the  body  of  the  vertebra. 

Pedicles  (radices  arci  vertebrae) . — The  pedicles  are  two  short,  thick  processes, 
which  project  backward,  one  on  either  side,  from  the  upper  part  of  the  body, 
at  the  junction  of  its  posterior  and  lateral  surfaces.  The  concavities  above  and 
below  the  pedicles  are  named  the  vertebral  notches;  and  when  the  vertebrae  are 
articulated,  the  notches  of  each  contiguous  pair  of  bones  form  the  intervertebral 
foramina,  already  referred  to. 

Laminae. — The  laminae  are  two  broad  plates  directed  backward  and  medialward 
from  the  pedicles.  They  fuse  in  the  middle  line  posteriorly,  and  so  complete  the 
posterior  boundary  of  the  vertebral  foramen.  Their  upper  borders  and  the 
lower  parts  of  their  anterior  surfaces  are  rough  for  the  attachment  of  the 
ligamenta  flava. 

Processes. — Spinous  Process  (processus  spinosus). — The  spinous  process  is 
directed  backward  and  downward  from  the  junction  of  the  laminae,  and  serves 
for  the  attachment  of  muscles  and  ligaments. 

Articular  Processes. — The  articular  processes,  two  superior  and  two  inferior, 
spring  from  the  junctions  of  the  pedicles  and  laminae.  The  superior  project 
upward,  and  their  articular  surfaces  are  directed  more  or  less  back\\^ard;  the 
inferior  project  downward,  and  their  surfaces  look  more  or  less  forward. 

Transverse  Processes  (processus  transmrsi). — ^The  transverse  processes,  two  in 
number,  project  one  at  either  side  from  the  point  where  the  lamina  joins  the 
pedicle,  between  the  superior  and  inferior  articular  processes.  They  serve  for 
the  attachment  of  muscles  and  ligaments. 

Structure  of  a  Vertebra  (Fig.  235). — The  body  is  composed  of  cancellous  tissue,  covered  by 
a  thin  coating  of  compact  bone;  the  lat/ter  is  perforated  by  numerous  orifices,  some  of  large  size 


198 


OSTEOLOGY 


for  the  passage  of  vessels;  the  interior  of  the  bone  is  traversed  by  one  or  two  large  canals,  for  the 
reception  of  veins,  which  converge  toward  a  single  large,  irregular  apertun;,  or  several  small 

apertures,  at  the  posterior  j)art  of  the 
body.     The  arch  and  processes  pro- 
jecting from  it  have  thick  coverings 
.  of  compact  tissue. 


Fig.  23.5. — Sagittal  section  of  a  lumbar  vertebra. 


The  Cervical  Vertebrae  (Verte- 
brae Cervicales). 


The  cervical  vertebrae  (Fig. 
236)  are  the  .smallest  of  the  true 
vertebrae,  and  can  be  readily 
distinguished  from  those  of  the 
thoracic  or  lumbar  regions  by 
the  presence  of  a  foramen  in 
each  transverse  process.  The 
first,  second,  and  seventh  present  exceptional  features  and  must  be  separately 
described;  the  following  characteristics  are  common  to  the  remaining  four. 

The  body  is  small,  and  broader  from  side  to  side  than  from  before  backward 
The  anterior  and  posterior  surfaces  are  flattened  and  of  equal  depth;  the  former 
is  placed  on  a  lower  level  than  the  latter,  and  its  inferior  border  is  prolonged 
downward,  so  as  to  overlap  the  upper  and  forepart  of  the  vertebra  below.  The 
upper  surface  is  concave  transversely,  and  presents  a  projecting  lip  on  either  side; 
the  lower  surface  is  concave  from  before  backward,  convex  from  side  to  side,  and 
presents  laterally  shallow  concavities  which  receive  the  corresponding  projecting 
lips  of  the  subjacent  vertebra.    The  pedicles  are  directed  lateralward  and  backward, 


Aniei'ior  tubercle  of 
transverse  process 
Foramen, 
transversariwtn 
Posterior  tubercle  of 
transverse  process 


j  Spinous ' 
process 

Fig.  236. — A  cervical  vertebra. 


Transverse  process 


Superior  articular 
process 

Inferior  articular 
process 


and  are  attached  to  the  body  midway  between  its  upper  and  lower  borders,  so  that 
the  superior  vertebral  notch  is  as  deep  as  the  inferior,  but  it  is,  at  the  same  time, 
narrower.  The  laminae  are  narrow,  and  thinner  above  than  below;  the  vertebral 
foramen  is  large,  and  of  a  triangular  form.  The  spinous  process  is  short  and  bifid, 
the  two  divisions  being  often  of  unequal  size.  The  superior  and  inferior  articular 
processes  on  either  side  are  fused  to  form  an  articular  pillar,  which  projects  lateral- 
ward  from  the  junction  of  the  pedicle  and  lamina.  The  articular  facets  are  flat 
and  of  an  oval  form:  the  superior  look  backward,  upward,  and  slightly  medial- 
ward:  the  inferior  forward,  downward,  and  slightly  lateralward.  The  transverse 
processes  are  each  pierced  by  the  foramen  trans versarium,  which,  in  the  upper  six 
^'ertebrae,  gives  passage  to  the  vertebral  artery  and  vein  and  a  plexus  of  sympa- 


THE  CERVICAL  VERTEBRA 


199 


thetic  nerves.  Each  process  consists  of  an  anterior  and  a  posterior  part.  The 
anterior  portion  is  the  homologne  of  the  rib  in  the  thoracic  region,  and  is  there- 
fore named  the  costal  process  or  costal  element:  it  arises  from  the  side  of  the  body, 
is  directed  laterahvard  in  front  of  the  foramen,  and  ends  in  a  tubercle,  the  tuber- 
culum  anterius.  TJie  posterior  part,  the  true  transverse  process,  springs  from  the 
vertebral  arch  behind  the  foramen,  and  is  directed  forward  and  lateralward;  it 
ends  in  a  flattened  vertical  tubercle,  the  tuberculum  posterius.  These  two  parts 
are  joined,  outside  the  foramen,  by  a  bar  of  bone  wliieli  exhibits  a  deep  sulcus 
on  its  upper  surface  for  the  passage  of  the  corresponding  spinal  nerve.^ 

Chassaignac  first  pointed  out  that  the  common  carotid  artery  can  be  easily  compressed  against 
the  anterior  tubercle  of  the  transverse  process  of  the  sixth  cervical  vertebra,  and  therefore  this 
tubercle  is  named  the  tuberculum  caroticum  or  Chassaignac' s  tubercle.  It  also  constitutes  an  im- 
portant guide  to  the  vertebral  artery  which  enters  the  foramen  transversarium  of  this  vertebra. 


Anterior  tubercle 


Transverse 
'process 


Outline  of  section  of  odontoid 
process 
Outline  of  section  of  trans- 
verse atlantal  ligament 

Foramen 
transver- 
sarium 


Groove  for  vertebral  artery 
and  first  cervical  nerve 


Posterior  tubercle 

Fig.  237. — First  cervical  vertebra,  or  atlas. 

First  Cervical  Vertebra. — The  first  cervical  vertebra  (Fig.  237)  is  named  the 
atlas  because  it  supports  the  globe  of  the  head.  Its  chief  peculiarity  is  that  it  has 
no  body,  and  this  is  due  to  the  fact  that  the  body  of  the  atlas  has  fused  with  that 
of  the  next  vertebra.  Its  other  peculiarities  are  that  it  has  no  spinous  process, 
is  ring-like,  and  consists  of  an  anterior  and  a  posterior  arch  and  two  lateral  masses. 
The  anterior  arch  forms  about  one-fifth  of  the  ring:  its  anterior  surface  is  convex, 
and  presents  at  its  centre  the  anterior  tubercle  for  the  attachment  of  the  Longus 
colli  muscles;  posteriorly  it  is  concave,  and  marked  by  a  smooth,  oval  or  circular 
facet  (fovea  dentis),  for  articulation  with  the  odontoid  process  {dens)  of  the  axis. 
The  upper  and  lower  borders  respectively  give  attachment  to  the  anterior  atlanto- 
occipital  membrane  and  the  anterior  atlantoaxial  ligament;  the  former  connects 
it  with  the  occipital  bone  above,  and  the  latter  with  the  axis  below.  The  posterior 
arch  forms  about  two-fifths  of  the  circumference  of  the  ring:  it  ends  behind  in  the 
posterior  tubercle,  which  is  the  rudiment  of  a  spinous  process  and  gives  origin  to 
the  Recti  capitis  posteriores  minores.  The  diminutive  size  of  this  process  pre- 
vents any  interference  with  the  movements  between  the  atlas  and  the  skull. 
The  posterior  part  of  the  arch  presents  above  and  behind  a  rounded  edge  for 
the  attachment  of  the  posterior  atlantooccipital  membrane,  while  immediately 
behind  each  superior  articular  process  is  a  groove  (sidciis  arteriae  vertehralis) , 
sometimes  converted  into  a  foramen  by  a  delicate  bony  spiculum  which  arches 
backward  from  the  posterior  end  of  the  superior  articular  process.  This  groove 
represents  the  superior  vertebral  notch,  and  serves  for  the  transmission  of  the 
vertebral  artery,  which,  after  ascending  through  the  foramen  in  the  transverse 


'  The  costal  element  of  a  cervical  vertebra  not  only  includes  the  portion  which  springs  from  the  side  of  the  body,  but 
the  anterior  and  posterior  tubercles  and  the  bar  of  bone  which  connects  them  (Fig.  97) . 


200 


OSTEOLOGY 


process,  winds  around  the  lateral  mass  in  a  direction  backward  and  medialward;  it 
also  transmits  the  suboccipital  (first  spinal)  nerve.  On  the  under  surface  of  the 
posterior  arch,  behind  the  articular  facets,  are  two  shallow  grooves,  the  inferior 
vertebral  notches.  The  lower  border  gives  attachment  to  the  posterior  atlanto- 
axial ligament,  which  connects  it  with  the  axis.  The  lateral  masses  are  the  most 
bulky  and  solid  parts  of  the  atlas,  in  order  to  support  the  weight  of  the  head. 
Each  carries  two  articular  facets,  a  superior  and  an  inferior.  The  superior  facets 
are  of  large  size,  oval,  concave,  and  approach  each  other  in  front,  but  diverge 
behind:  they  are  directed  upward,  medialward,  and  a  little  backward,  each  forming 
a  cup  for  the  corresponding  condyle  of  the  occipital  bone,  and  are  admirably 
adapted  to  the  nodding  movements  of  the  head.  Not  infrequently  they  are 
partially  subdivided  by  indentations  which  encroach  upon  their  margins.  The 
inferior  articular  facets  are  circular  in  form,  flattened  or  slightly  convex  and  directed 
downward  and  medialward,  articulating  with  the  axis,  and  permitting  the  rotatory 
movements  of  the  head.  Just  below  the  medial  margin  of  each  superior  facet  is 
a  small  tubercle,  for  the  attachment  of  the  transverse  atlantal  ligament  w^hich 
stretches  across  the  ring  of  the  atlas  and  divides  the  vertebral  foramen  into  two 
unequal  parts — the  anterior  or  smaller  receiving  the  odontoid  process  of  the  axis, 
the  posterior  transmitting  the  medulla  spinalis  and  its  membranes.  This  part 
of  the  vertebral  canal  is  of  considerable  size,  much  greater  than  is  required  for  the 
accommodation  of  the  medulla  spinalis,  and  hence  lateral  displacement  of  the 
atlas  may  occur  without  compression  of  this  structure.  The  transverse  processes 
are  large;  they  project  lateralward  and  downward  from  the  lateral  masses,  and 
serve  for  the  attachment  of  muscles  which  assist  in  rotating  the  head.  They 
are  long,  and  their  anterior  and  posterior  tubercles  are  fused  into  one  mass;  the 
foramen  transversarium  is  directed  from  below,  upward  and  backward. 


Odontoid  process 


Rough  surface  for  alar  ligament 
Groove  for  transverse  atlantal  ligament 


Spinous  process-^ 


Articular  facet  for 
anterior  arch  of  atlas 


Body 


Transverse  process 
Inferior  articular  process 

Fig.  238. — Second  cervical  vertebra,  epistropheus,  or  axis. 

Second  Cervical  Vertebra. — The  second  cervical  vertebra  (Fig.  2.38)  is  named 
the  epistropheus  or  axis  because  it  forms  the  pivot  upon  which  the  first  vertebra, 
carrying  the  head,  rotates.  The  most  distinctive  characteristic  of  this  bone  is 
the  strong  odontoid  process  which  rises  perpendicularly  from  the  upper  surface 
of  the  body.  The  body  is  deeper  in  front  than  behind,  and  prolonged  downward 
anteriorly  so  as  to  overlap  the  upper  and  fore  part  of  the  third  vertebra.  It  pre- 
sents in  front  a  median  longitudinal  ridge,  separating  two  lateral  depressions  for 
the  attachment  of  the  Longus  colli  muscles.  Its  under  surface  is  concave  from 
before  backw^ard  and  covex  from  side  to  side.  The  dens  or  odontoid  process  exliibits 
a  slight  constriction  or  neck,  w^here  it  joins  the  body.  On  its  anterior  surface 
is  an  oval  or  nearly  circular  facet  for  articulation  with  that  on  the  anterior  arch 


THE  THORACIC  VERTEBRM 


201 


Body. 


of  the  atlas.  On  the  back  of  the  neck,  and  frequently  extending  on  to  its  lateral 
surfaces,  is  a  shallow  groove  for  the  transverse  atlantal  ligament  which  retains 
the  process  in  position.  The  apex  is  pointed,  and  gives  attachment  to  the  middle 
alar  ligament;  below  the  apex  the  process  is  somewhat  enlarged,  and  presents 
on  either  side  a  rough  impression  for  the  attachment  of  the  lateral  alar  ligament; 
these  ligaments  connect  the  process  to  the  occipital  bone.  The  internal  structure 
of  the  odontoid  process  is  more  compact  than  that  of  the  body.  The  pedicles 
are  broad  and  strong,  especially  in  front,  where  they  coalesce  with  the  sides  of 
the  body  and  the  root  of  the  odontoid  process.  They  are  covered  above  by  the 
superior  articular  surfaces.  The  laminae  are  thick  and  strong,  and  the  vertebral 
foramen  large,  but  smaller  than  that  of  the  atlas.  The  transverse  processes  are 
very  small,  and  each  ends  in  a  single  tubercle;  each  is  perforated  by  the  foramen 
transversarium,  which  is  directed  obliquely  upward  and  lateralward.  The  superior 
articular  surfaces  are  round,  slightly  convex,  directed  upward  and  lateralward, 
and  are  supported  on  the  body, 
pedicles,  and  transverse  processes. 
The  inferior  articular  surfaces  have 
the  same  direction  as  those  of  the 
other  cervical  vertebrse.  The  supe- 
rior vertebral  notches  are  very  shal- 
low, and  lie  behind  the  articular 
processes;  the  inferior  lie  in  front 
of  the  articular  processes,  as  in  the 
other  cervical  vertebrae.  The  spinous 
process  is  large,  very  strong,  deeply 
channelled  on  its  under  surface, 
and  presents  a  bifid,  tuberculated 
extremity. 

The  Seventh  Cervical  Vertebra 
(Fig.  239).— The  most  distinctive 
characteristic  of  this  vertebra  is 
the  existence  of  a  long  and  promi- 
nent spinous  process,  hence  the 
name  vertebra  prominens.  This  pro- 
cess is  thick,  nearly  horizontal  in 
direction,  not  bifurcated,  but  ter- 
minating in  a  tubercle  to  which  the  lower  end  of  the  ligamentum  nuchae  is 
attached.  The  transverse  processes  are  of  considerable  size,  their  posterior  roots 
are  large  and  prominent,  while  the  anterior  are  small  and  faintly  marked;  the 
upper  surface  of  each  has  usually  a  shallow  sulcus  for  the  eighth  spinal  nerve, 
and  its  extremity  seldom  presents  more  than  a  trace  of  bifurcation.  The  foramen 
transversarium  may  be  as  large  as  that  in  the  other  cervical  vertebrae,  but  is 
generally  smaller  on  one  or  both  sides;  occasionally  it  is  double,  sometimes  it  is 
absent.  On  the  left  side  it  occasionally  gives  passage  to  the  vertebral  artery; 
more  frequently  the  vertebral  vein  traverses  it  on  both  sides;  but  the  usual 
arrangement  is  for  both  artery  and  vein  to  pass  in  front  of  the  transverse  pro- 
cess, and  not  through  the  foramen.  Sometimes  the  anterior  root  of  the  trans- 
verse process  attains  a  large  size  and  exists  as  a  separate  bone,  which  is  known 
as  a  cervical  rib. 


Spinous  process 
Fig.  239. — Seventh  cervical  vertebra. 


The  Thoracic  Vertebrae  (Vertebrae  Thoracales). 

The  thoracic  vertebrae   (Fig.  240)   are  intermediate    in   size  between  those  of 
the  cervical  and  lumbar  regions;  they  increase  in  size  from  above  downward  the 


202 


OSTEOLOGY 


upper  vertebrse  being  much  smaller  than  those  in  the  lower  part  of  the  region. 
They  are  distinguished  by  the  presence  of  facets  on  the  sides  of  the  bodies  for 
articulation  with  the  heads  of  the  ribs,  and  facets  on  the  transverse  processes  of 
all,  except  the  eleventh  and  twelfth,  for  articulation  with  the  tubercles  of  the  ribs. 
The  bodies  in  the  middle  of  the  thoracic  region  are  heart-shaped,  and  as  broad 
in  the  antero-posterior  as  in  the  transverse  direction.  At  the  ends  of  the  thoracic 
region  they  resemble  respectively  those  of  the  cervical  and  lumbar  vertebrae. 
They  are  slightly  thicker  behind  than  in  front,  flat  above  and  below,  convex  from 
side  to  side  in  front,  deeply  concave  behind,  and  slightly  constricted  laterally 
and  in  front.  They  present,  on  either  side,  two  costal  demi-facets,  one  above, 
near  the  root  of  the  pedicle,  the  other  below,  in  front  of  the  inferior  vertebral 
notch;  these  are  covered  with  cartilage  in  the  recent  state,  and,  when  the  vertebrae 
are  articulated  with  one  another,  form,  with  the  intervening  intervertebral  fibro- 
cartilages,  oval  surfaces  for  the  reception  of  the  heads  of  the  ribs.  The  pedicles 
are  directed  backward  and  slightly  upward,  and  the  inferior  vertebral  notches 
are  of  large  size,  and  deeper  than  in  any  other  region  of  the  vertebral  column. 


Superior  articiilar  process 


Facet  for  articular  part 

of  tubercle  of  rib  ^ 


Demi-facet  for  head  of  rib 


Demi-facet  for  head  of  rib 
Inferior  articular  process 


Fig.  240. — A  thoracic  vertebra. 


The  laminae  are  broad,  thick,  and  imbricated — that  is  to  say,  they  overlap  those 
of  subjacent  vertebrae  like  tiles  on  a  roof.  The  vertebral  foramen  is  small,  and  of 
a  circular  form.  The  spinous  process  is  long,  triangular  on  coronal  section,  directed 
obliquely  downward,  and  ends  in  a  tuberculated  extremity.  These  processes 
overlap  from  the  fifth  to  the  eighth,  but  are  less  obliciue  in  direction  above  and 
below.^  The  superior  articular  processes  are  thin  plates  of  bone  projecting  upward 
from  the  junctions  of  the  pedicles  and  laminae;  their  articular  facets  are  practi- 
cally flat,  and  are  directed  backw^ard  and  a  little  lateralward  and  upward.  The 
inferior  articular  processes  are  fused  to  a  considerable  extent  with  the  laminae, 
and  project  but  slightly  beyond  their  lower  borders;  their  facets  are  directed 
forward  and  a  little  medialward  and  downward.  The  transverse  processes  arise 
from  the  arch  behind  the  superior  articular  processes  and  pedicles;  they  are  thick, 
strong,  and  of  considerable  length,  directed  obliquely  backw-ard  and  lateralward, 

1  In  quadrupeds  the  majority  of  the  spinous  processes  of  the  thoracic  vertebrae  project  upward  and  backward,  while 
those  of  the  lumbar  region  are  directed  upward  and  forward.    The  change  in  inclination  is  effected  in  one  of  the  lower 

thoracic  vertebrae,  the  spine  of  which  points  almost  directly  upward.  This  vertebra  is  known  as  the  anticlinal,  and 
in  man  its  representative  is  the  eleventh  thoracic. 


THE  THORACIC  VERTEBRA 


203 


and  each  ends  in  a  clubbed  extremity,  on  the  front  of  which  is  a  small,  concave 
surface,  for  articulation  with  the  tubercle  of  a  rib. 

The  first,  ninth,  tenth,  eleventh,  and  twelfth   thoracic  vertebrae  present  certain 
peculiarities,  and  must  be  specially  considered  (Fip;.  241). 


An  entire  facet  above, 
a  demi-facct  below 


A  demi-facet  above 


—  One  entire  facet 


One  entire  facet. 
No  facet  on  trans,  proc. 
which  is  rudimentary 


One  entire  facet. 

(No  facet  on  trans- 
I      verse  process. 
-  Infer. artic.j}rocess 
convex  and  turned 
\lateralicards 


Fig.  241. — Peculiar  thoracic  vertebrae. 


The  First  Thoracic  Vertebra  has,  on  either  side  of  the  body,  an  entire  articular 
facet  for  the  head  of  the  first  rib,  and  a  demi-facet  for  tlie  upper  half  of  the  head 
of  the  second  rib.  The  body  is  like  that  of  a  cervical  vertebra,  being  broad  trans- 
versely; its  upper  surface  is  concave,  and  lipped  on  either  side.  The  superior 
articular  surfaces  are  directed  upward  and  backward;  the  spinous  process  is  thick, 
long,  and  almost  horizontal.  The  transverse  processes  are  long,  and  the  upper 
vertebral  notches  are  deeper  than  those  of  the  other  thoracic  vertebrae. 


204 


OSTEOLOGY 


The  Ninth  Thoracic  Vertebra  may  have  no  demi-facets  below.  In  some  sub- 
jects however,  it  has  two  demi-facets  on  either  side;  when  this  occurs  the  tenth 
has  only  demi-facets  at  the  upper  part. 

The  Tenth  Thoracic  Vertebra  has  (except  in  the  cases  just  mentioned;  an  entire 
articular  facet  on  either  side,  which  is  placed  partly  on  the  lateral  surface  of  the 
pedicle. 

In  the  Eleventh  Thoracic  Vertebra  the  body  approaches  in  its  form  and  size 
to  that  of  the  lumbar  vertebrse.  The  articular  facets  for  the  heads  of  the  ribs 
are  of  large  size,  and  placed  chiefly  on  the  pedicles,  which  are  thicker  and  stronger 
in  this  and  the  next  vertebra  than  in  any  other  part  of  the  thoracic  region.  The 
spinous  process  is  short,  and  nearly  horizontal  in  direction.  The  transverse  processes 
are  very  short,  tuberculated  at  their  extremities,  and  have  no  articular  facets. 

The  Twelfth  Thoracic  Vertebra  has  the  same  general  characteristics  as  the 
eleventh,  but  may  be  distinguished  from  it  by  its  inferior  articular  surfaces  being 
convex  and  directed  lateraiward,  like  those  of  the  lumbar  vertebrae;  by  the  general 
form  of  the  body,  laminae,  and  spinous  process,  in  which  it  resembles  the  lumbar 
vertebrae;  and  by  each  transverse  process  being  subdivided  into  three  elevations, 
the  superior,  inferior,  and  lateral  tubercles:  the  superior  and  inferior  correspond 
to  the  mamillary  and  accessory  processes  of  the  lumbar  vertebrae.  Traces  of 
similar  elevations  are  found  on  the  transverse  processes  of  the  tenth  and  eleventh 
thoracic  vertebrae. 


Superior  artiruUu  p/ocf^ 


Fig.  242. — A  lumbar  vertebra  seen  from  the  side. 


The  Lumbar  Vertebrae  (Vertebrae  Lumbalesj. 

The  lumbar  vertebrae  (Figs.  242  and  243)  are  the  largest  segments  of  the  movable 
part  of  the  vertebral  column,  and  can  be  distinguished  by  the  absence  of  a  foramen 
in  the  transverse  process,  and  by  the  absence  of  facets  on  the  sides  of  the  body. 

The  body  is  large,  wider  from  side  to  side  than  from  before  backward,  and  a 
little  thicker  in  front  than  behind.  It  is  flattened  or  slightly  concave  above  and 
below,  concave  behind,  and  deeply  constricted  in  front  and  at  the  sides.  The 
pedicles  are  very  strong,  directed  backward  from  the  upper  part  of  the  body; 
consequently,  the  inferior  vertebral  notches  are  of  considerable  depth.  The 
laminae  are  broad,  short,  and  strong;  the  vertebral  foramen  is  triangular,  larger 
than  in  the  thoracic,  but  smaller  than  in  the  cervical  region.  The  spinous  process 
is  thick,  broad,  and  somewhat  quadrilateral;  it  projects  backward  and  ends  in 
a  rough,  uneven  border,  thickest  below  where  it  is  occasionally  notched.  The 
superior  and  inferior  articular  processes  are  well-defined,  projecting  respectively 
upward  and  downward  from  the  junctions  of  pedicles  and  laminae.      The  facets 


THE  SACRAL  AND  COCCYGEAL  VERTEBRA 


205 


on  the  superior  processes  are  concave,  and  look  backward  and  medialward;  those 
on  the  inferior  are  convex,  and  are  directed  forward  and  lateralward.  The  former 
are  wider  apart  than  the  hitter,  since  in  the  articuhited  cokniin  the  inferior  articular 
processes  are  em])raced  by  the  superior  processes  of  the  subjacent  vertebra.  The 
transverse  processes  are  long,  slender,  and  horizontal  in  the  upper  three  lumbar 
vertebrae;  they  incline  a  little  upward  in  the  lower  two.  In  the  upper  three  verte- 
brae they  arise  from  the  junctions  of  the  pedicles  and  laminae,  but  in  the  lower 
two  they  are  set  farther  forward  and  spring  from  the  jjedicles  and  posterior  parts 
(»f  the  bodies.  They  are  situated  in  front  of  the  articular  processes  instead  of  behind 
them  as  in  the  thoracic  vertebrae,  and  are  homologous  with  the  ribs.  Of  the  three 
tubercles  noticed  in  connection  with  the  transverse  processes  of  the  lower  thoracic 


Transverse  process 


Inferior  articular 
process 


2Iamillary  process 
Accessory  process 


Superior  articular        (—' 
process  f 


Fig.  243  — \  lumbar  -vertebra  viewed  obliquely  from  above. 

vertebrae,  the  superior  one  is  connected  in  the  lumbar  region  with  the  back  part 
of  the  superior  articular  process,  and  is  named  the  mamillary  process;  the  inferior 
is  situated  at  the  back  part  of  the  base  of  the  transverse  process,  and  is  called  the 
accessory  process  (Fig.  243).  Although  in  man  these  are  comparatively  small, 
in  some  animals  they  attain  considerable  size,  and  serve  to  lock  the  vertebrae 
more  closely  together. 

The  Fifth  Lumbar  Vertebra  is  characterized  by  its  body  being  much  deeper 
in  front  than  behind,  which  accords  with  the  prominence  of  the  sacrovertebral 
articulation;  by  the  smaller  size  of  its  spinous  process;  by  the  wide  interval  between 
the  inferior  articular  processes;  and  by  the  thickness  of  its  transverse  processes, 
which  spring  from  the  body  as  well  as  from  the  pedicles. 


The  Sacral  and  Coccygeal  Vertebrae. 

The  sacral  and  coccygeal  vertebrae  consist  at  an  early  period  of  life  of  nine 
separate  segments  which  are  united  in  the  adult,  so  as  to  form  two  bones,  five 
entering  into  the  formation  of  the  sacrum,  four  into  that  of  the  coccyx.  Some- 
times the  coccyx  consists  of  five  bones;  occasionally  the  number  is  reduced  to 
three. 


206 


OSTEOLOGY 


The  Sacrum  (os  sacrum). — The  sacrum  is  a  large,  trianj^nilar  bone,  situated 
in  the  lower  part  of  the  vertebral  column  and  at  the  upper  and  back  part  of  the 
pelvic  cavity,  where  it  is  inserted  like  a  wedge  between  the  two  hip  bones;  its 
upper  part  or  base  articulates  with  the  last  lumbar  vertebra,  its  apex  with  the 
coccyx.  It  is  curved  upon  itself  and  placed  very  obliquely,  its  base  projecting 
forward  and  forming  the  prominent  sacrovertebral  angle  when  articulated  with 
the  last  lumbar  vertebra;  its  central  part  is  projected  backward,  so  as  to  give 
increased  capacity  to  the  pelvic  cavity.  The  sacrum  is  rather  narrower  at  the 
level  of  the  second  segment  than  at  the  level  of  the  third.  It  presents  for  examina- 
tion a  pelvic,  a  dorsal,  and  two  lateral  surfaces,  a  base,  an  apex,  and  a  central 
canal. 


Pronwnforu 


Fig.  244. — Sacrum,  pelvic  surface. 


Pelvic  Surface  (fades  yehina). — The  pelvic  surface  (Fig.  244)  is  concave  from 
above  downward,  and  slightly  so  from  side  to  side.  Its  middle  part  is  crossed 
by  four  transverse  ridges,  the  positions  of  which  correspond  with  the  original 
planes  of  separation  between  the  five  segments  of  the  bone.  The  portions  of  bone 
intervening  between  the  ridges  are  the  bodies  of  the  sacral  vertebrae.  The  body 
of  the  first  segment  is  of  large  size,  and  in  form  resembles  that  of  a  lumbar  vertebra; 
the  succeeding  ones  diminish  from  above  downward,  are  flattened  from  before 
backward,  and  curved  so  as  to  accommodate  themselves  to  the  form  of  the  sacrum, 
being  concave  in  front,  convex  behind.  At  the  ends  of  the  ridges  are  seen  the 
anterior  sacral  foramina,  four  in  number  on  either  side,  somewhat  rounded  in  form 
diminishing  in  size  from  above  downward,  and  directed  lateralward  and  forward; 
they  give  exit  to  the  anterior  divisions  of  the  sacral  nerves  and  entrance  to  the 
lateral  sacral  arteries.  Lateral  to  these  foramina  are  the  lateral  parts  of  the  sacrum, 
each  consisting  of  five  separate  segments  at  an  early  period  of  life;  in  the  adult, 


THE  SACRAL  AXD  COCCYGEAL  VERTEBRAE 


20- 


these  are  blended  with  the  bodies  and  with  each  other.  Each  lateral  part  is  tra- 
versed by  four  broad,  shallow  grooves,  which  lodge  the  anterior  divisions  of  the 
sacral  nerves,  and  are  separated  by  prominent  ridges  of  bone  which  give  origin 
to  the  Piriformis  muscle. 

If  a  sagittal  section  be  made  through  the  centre  of  the  sacrum  (Fig.  240),  the 
bodies  are  seen  to  be  united  at  their  circumferences  by  bone,  wide  intervals  being 
left  centrally,  which,  in  the  recent  state,  are  filled  by  the  inter\-ertebral  fibro- 
cartilages.  In  some  bones  this  union  is  more  complete  between  the  lower  than 
the  upper  segments. 


Sacrospi)ialis 


Lafissimus 
dorsi 


Sacrospinalis 


•r  half  of  fifth 
posterior  sacral  foramen 


Fig.  245. — Sacrum,  dorsal  surface. 


Dorsal  Surface  {fades  dorsalis). — The  dorsal  surface  (Fig.  245)  is  convex  and 
narrower  than  the  pelvic.  In  the  middle  line  it  displays  a  crest,  the  middle  sacral 
crest,  sm^mounted  by  three  or  four  tubercles,  the  rudimentary  spinous  processes 
of  the  upper  three  or  four  sacral  vertebrte.  On  either  side  of  the  middle  sacral 
crest  is  a  shallow  groove,  the  sacral  groove,  which  gives  origin  to  the  Multifidus, 
the  floor  of  the  groove  being  formed  by  the  united  lammse  of  the  corresponding 
vertebrse.  The  laminae  of  the  fifth  sacral  vertebra,  and  sometimes  those  of  the 
fom-th,  fail  to  meet  behind,  and  thus  a  hiatus  or  deficiency  occurs  in  the  posterior 
wall  of  the  sacral  canal.  On  the  lateral  aspect  of  the  sacral  groove  is  a  linear 
series  of  tubercles  produced  by  the  fusion  of  the  articular  processes  which  together 
form  the  indistinct  sacral  articular  crests.  The  articidar  processes  of  the  first 
sacral  vertebra  are  large  and  oval  in  shape;  their  facets  are  concave  from  side  to 
side,  look  backv\"ard  and  medialward,  and  articulate  with  the  facets  on  the  inferior 
processes  of  the  fifth  lumbar  vertebra.  The  tubercles  which  represent  the  inferior 
articular  processes  of  the  fifth  sacral  vertebra  are  prolonged  downward  as  rounded 
processes,  which  are  named  the  sacral  comua,  and  are  coimected  to  the  cornua 


208  OSTEOLOGY 

of  the  coccyx.  Lateral  to  the  articular  processes  are  the  four  posterior  sacral 
foramina;  they  are  smaller  in  size  and  less  regular  in  form  than  the  anterior,  and 
transmit  the  posterior  divisions  of  the  sacral  nerves.  On  the  lateral  side  of  the 
posterior  sacral  foramina  is  a  series  of  tubercles,  which  represent  the  transverse 
processes  of  the  sacral  vertebrae,  and  form  the  lateral  crests  of  the  sacrum.  The 
transverse  tubercles  of  the  first  sacral  vertebra  are  large  and  very  distinct;  they, 
together  with  the  transverse  tubercles  of  the  second  vertebra,  give  attachment 
to  the  horizontal  parts  of  the  posterior  sacroiliac  ligaments;  those  of  the  third 
vertebra  give  attachment  to  the  oblique  fasciculi  of  the  posterior  sacroiliac  liga- 
ments; and  those  of  the  fourth  and  fifth  to  the  sacrotuberous  ligaments. 

Lateral  Surface. — The  lateral  surface  is  broad  above,  but  narrowed  into  a  thin 
edge  below.  The  upper  half  presents  in  front  an  ear-shaped  surface,  the  auricular 
surface  for  articulation  with  the  ilium.  Behind  it  is  a  rough  surface,  the  sacral 
tuberosity,  on  which  are  three  deep  and  uneven  impressions,  for  the  attachment 
of  the  posterior  sacroiliac  ligament.  The  lower  half  is  thin,  and  ends  in  a  pro- 
jection called  the  inferior  lateral  angle;  medial  to  this  angle  is  a  notch,  which  is 
converted  into  a  foramen  by  the  transverse  process  of  the  first  piece  of  the  coccyx, 
and  transmits  the  anterior  division  of  the  fifth  sacral  nerve.  The  thin  lower  half 
of  the  lateral  surface  gives  attachment  to  the  sacrotuberous  and  sacrospinous 
ligaments,  to  some  fibres  of  the  Glutaeus  maximus  behind,  and  to  the  Coccygeus 
in  front. 

Base  {basis  oss.  sacri). — The  base  of  the  sacrum,  which  is  broad  and  expanded, 
is  directed  upward  and  forward.  In  the  middle  is  a  large  oval  articular  surface, 
the  upper  surface  of  the  body  of  the  first  sacral  vertebra,  which  is  connected  with 
the  under  surface  of  the  body  of  the  last  lumbar  vertebra  by  an  intervertebral 
fibrocartilage.  Behind  this  is  the  large  triangular  orifice  of  the  sacral  canal,  which 
is  completed  by  the  laminae  and  spinous  process  of  the  first  sacral  vertebra.  The 
superior  articular  processes  project  from  it  on  either  side;  they  are  oval,  concave, 
directed  backward  and  medialward,  like  the  superior  articular  processes  of  a  lumbar 
vertebra.  They  are  attached  to  the  body  of  the  first  sacral  vertebra  and  to  the 
alse  b}'  short  thick  pedicles;  on  the  upper  surface  of  each  pedicle  is  a  vertebral 
notch,  which  forms  the  lower  part  of  the  foramen  between  the  last  lumbar  and  first 
sacral  vertebrae.  On  either  side  of  the  body  is  a  large  triangular  surface,  which 
supports  the  Psoas  major  and  the  lumbosacral  trunk,  and  in, the  articulated 
pelvis  is  continuous  with  the  iliac  fossa.  This  is  called  the  ala;  it  is  slightly  concave 
from  side  to  side,  convex  from  before  backward,  and  gives  attachment  to  a  few 
of  the  fibres  of  the  Iliacus.  The  posterior  fourth  of  the  ala  represents  the  transverse 
process,  and  its  anterior  three-fourths  the  costal  process  of  the  first  sacral  segment. 

Apex  {ayex  oss.  sacri). — The  apex  is  directed  downward,  and  presents  an  oval 
facet  for  articulation  with  the  coccyx. 

Vertebral  Canal  (canalis  sacralis;  sacral  canal). — The  vertebral  canal  (Fig.  246) 
runs  throughout  the  greater  part  of  the  bone;  above,  it  is  triangular  in  form; 
below,  its  posterior  wall  is  incomplete,  from  the  non-development  of  the  laminae 
and  spinous  processes.  It  lodges  the  sacral  nerves,  and  its  walls  are  perforated  by 
the  anterior  and  posterior  sacral  foramina  through  which  these  nerves  pass  out. 

Structure. — The  sacrum  consists  of  cancellous  tissue  enveloped  by  a  thin  layer  of  compact  bone. 

Articulations. — The  sacrum  articulates  with  four  bones;  the  last  lumbar  vertebra  above,  the 
coccyx  below,  and  the  hip  bone  on  either  side. 

DifEerences  in  the  Sacrum  of  the  Male  and  Female. — In  the  female  the  sacrum  is  shorter  and 
wider  than  in  the  male;  the  lower  half  forms  a  greater  angle  with  the  upper;  the  upper  half  is 
nearly  straight,  the  lower  half  presenting  the  greatest  amount  of  curvature.  The  bone  is  also 
directed  more  obUquely  backward;  this  increases  the  size  of  the  pelvic  cavity  and  renders  the 
sacrovertebral  angle  more  prominent.  In  the  male  the  curvature  is  more  evenly  distributed 
over  the  whole  length  of  the  bone,  and  is  altogether  greater  than  in  the  female. 


THE  SACRAL  AND  COCCYGEAL  VERTEBRAE 


209 


Variations. — The  sacrum,  in  some  cases,  consists  of  six  pieces;  occasionally  the  number  is 
reduced  to  four.  Sometimes  the  uppermost  transverse  tubercles  are  not  joined  to  the  rest  of  the 
ala  on  one  or  both  sides,  or  the  sacral  canal  may  be  open  throughout  a  considerable  part  of  its 
length,  in  consequence  of  the  imperfect  development  of  the  laminae  and  spinous  processes.  The 
sacrum,  also,  varies  considerably  with  respect  to  its  degree  of  curvature. 


Coruua 


Anterior  Surface 


Riidim. 
Trans, 
prac. 


Fig.  246. — Median  sagittal  section  of  the  sacrum. 


Posterior  surface 


Fig.  217. — Coccyx. 


The  Coccyx  (os  coccygis). — The  coccyx  (Fig.  247)  is  usually  formed  of  four 
rudimentary  vertebrse;  the  number  may  however  be  increased  to  five  or  diminished 
to  three.  In  each  of  the  first  three  segments  may  be  traced  a  rudimentary  body 
and  articular  and  transverse  processes;  the  last  piece  (sometimes  the  third)  is  a 
mere  nodule  of  bone.  All  the  segments  are  destitute  of  pedicles,  laminae,  and 
spinous  processes.  The  first  is  the  largest;  it  resembles  the  lowest  sacral  vertebra, 
and  often  exists  as  a  separate  piece;  the  last  three  diminish  in  size  from  above 
downward,  and  are  usually  fused  with  one  another.  Owing  to  the  gradual  diminu- 
tion in  the  size  of  the  segments,  the  coccyx  is  triangular  in  form,  and  presents 
for  examination  an  anterior  and  a  posterior  surface,  two  borders,  a  base,  and  an 
apex. 

Surfaces. — The  anterior  surface  is  slightly  concave,  and  marked  with  three  trans- 
verse grooves  which  indicate  the  junctions  of  the  different  segments.  It  gives 
attachment  to  the  anterior  sacrococc3'geal  ligament  and  the  Levatores  ani,  and 
supports  part  of  the  rectum.  The  posterior  surface  is  convex,  marked  by  transverse 
grooves  similar  to  those  on  the  anterior  surface,  and  presents  on  either  side  a  linear 
row  of  tubercles,  the  rudimentary  articular  processes  of  the  coccygeal  vertebrae. 
Of  these,  the  superior  pair  are  large,  and  are  called  the  coccygeal  comua;  they 
14 


210  OSTEOLOGY 

project  upward,  and  articulate  with  the  cornua  of  the  sacrum,  and  on  either  side 
complete  the  foramen  for  the  transmission  of  the  posterior  division  of  the  fifth 
sacral  nerve. 

Borders. — The  lateral  borders  are  thin,  and  exhibit  a  series  of  small  eminences, 
which  represent  the  transverse  processes  of  the  coccygeal  vertebrae.  Of  these, 
the  first  is  the  largest;  it  is  flattened  from  before  backward,  and  often  ascends 
to  join  the  lower  part  of  the  thin  lateral  edge  of  the  sacrum,  thus  completing  the 
foramen  for  the  transmission  of  the  anterior  division  of  the  fifth  sacral  nerve; 
the  others  diminish  in  size  from  above  downward,  and  are  often  wanting.  The 
borders  of  the  coccyx  are  narrow,  and  give  attachment  on  either  side  to  the  sacro- 
tuberous  and  sacrospinous  ligaments,  to  the  Coccygeus  in  front  of  the  ligaments, 
and  to  the  Glutaeus  maximus  behind  them. 

Base. — The  base  presents  an  oval  surface  for  articulation  with  the  sacrum. 

Apex. — The  apex  is  rounded,  and  has  attached  to  it  the  tendon  of  the  Sphincter 
ani  externus.    It  may  be  bifid,  and  is  sometimes  deflected  to  one  or  other  side. 

Ossification  of  the  Vertebral  Column. — Each  vertebra  is  ossified  from  three  primary  centres 
(Fig.  248),  two  for  the  vertebral  arch  and  one  for  the  body.^  Ossification  of  the  vertebral  arches 
begins  in  the  upper  cervical  vertebrae  about  the  seventh  or  eighth  week  of  fetal  life,  and  gradually 
extends  dovra.  the  column.  The  ossific  granules  first  appear  in  the  situations  where  the  transverse 
processes  afterward  project,  and  spread  backward  to  the  spinous  process  forward  into  the  pedicles, 
and  lateralward  into  the  transverse  and  articular  processes.  Ossification  of  the  bodies  begins 
about  the  eighth  week  in  the  lower  thoracic  region,  and  subsequently  extends  upward  and  down- 
ward along  the  column.  The  centre  for  the  body  does  not  give  rise  to  the  whole  of  the  body  of 
the  adult  vertebra,  the  postero-lateral  portions  of  which  are  ossified  by  extensions  from  the  verte- 
bral arch  centres.  The  body  of  the  vertebra  during  the  first  few  years  of  hfe  shows,  therefore, 
two  sjTichondroses,  neurocentral  synchondroses,  traversing  it  along  the  planes  of  junction  of 
the  three  centres  (Fig.  249).  In  the  thoracic  region,  the  facets  for  the  heads  of  the  ribs  lie  behind 
the  neurocentral  sj'nchondroses  and  are  ossified  from  the  centres  for  the  vertebral  arch.  At 
birth  the  vertebra  consists  of  three  pieces,  the  body  and  the  halves  of  the  vertebral  arch.  During 
the  first  year  the  halves  of  the  arch  unite  behind,  union  taking  place  first  in  the  lumbar  region 
and  then  extending  upward  through  the  thoracic  and  cervical  regions.  About  the  thii'd  year 
the  bodies  of  the  upper  cervical  vertebrae  are  joined  to  the  arches  on  either  side;  in  the  lower 
lumbar  vertebrae  the  union  is  not  completed  until  the  sixth  year.  Before  puberty,  no  other 
changes  occur,  excepting  a  gi-adual  increase  of  these  primary  centres,  the  upper  and  under  sur- 
faces of  the  bodies  and  the  ends  of  the  transverse  and  spinous  processes  being  cartilaginous. 
About  the  sixteenth  year  (Fig.  249),  five  secondary  centres  appear,  one  for  the  tip  of  each  trans- 
verse process,  one  for  the  extremity  of  the  spinous  process,  one  for  the  upper  and  one  for  the 
lower  surface  of  the  body  (Fig.  2.50).  These  fuse  with  the  rest  of  the  bone  about  the  age  of 
twenty-five. 

Exceptions  to  this  mode  of  development  occur  in  the  first,  second,  and  seventh  cervical  verte- 
brae, and  in  the  lumbar  vertebrae. 

Atlas. — The  atlas  is  usually  ossified  from  three  centres  (Fig.  251).  Of  these,  one  appears  in 
each  lateral  mass  about  the  seventh  week  of  fetal  life,  and  extends  backward;  at  birth,  these 
portions  of  bone  are  separated  from  one  another  behind  by  a  narrow  interval  fiUed  witli  cartilage. 
Between  the  third  and  fourth  years  they  unite  either  directly  or  through  the  medium  of  a  separate 
centre  developed  in  the  cartilage.  At  birth,  the  anterior  arch  consists  of  cartilage;  in  this  a 
separate  centre  appears  about  the  end  of  the  first  year  after  birth,  and  joins  the  lateral  masses 
from  the  sixth  to  the  eighth  year — the  lines  of  union  extending  across  the  anterior  portions  of 
the  superior  articular  facets.  Occasionally  there  is  no  separate  centre,  the  anterior  arch  being 
formed  by  the  forward  extension  and  ultimate  junction  of  the  two  lateral  masses;  sometimes 
this  arch  is  ossified  from  two  centres,  one  on  either  side  of  the  middle  fine. 

Epistropheus  or  Axis. — The  axis  is  ossified  from  five  primary  and  two  secondarj^  centres  (Fig. 
252).  The  body  and  vertebral  arch  are  ossified  in  the  same  manner  as  the  corresponding  parts 
in  the  other  vertebrae,  viz.,  one  centre  for  the  body,  and  two  for  the  vertebral  arch.  The  centres 
for  the  arch  appear  about  the  seventh  or  eighth  week  of  fetal  life,  that  for  the  body  about  the 
foin-th  or  fifth  month.  The  dens  or  odontoid  process  consists  originally  of  a  continuation  upward 
of  the  cartilaginous  mass,  in  which  the  lower  part  of  the  body  is  formed.  About  the  sixth  month 
of  fetal  life,  two  centres  make  their  appearance  in  the  base  of  this  process:  thej'  are  placed 
laterally,  and  join  before  birth  to  form  a  conical  bilobed  mass  deeply  cleft  above;  the  interval 

1  A  vertebra  is  occasionally  found  in  which  the  body  consists  of  two  lateral  portions — a  condition  which  proves  that 
the  body  is  sometimes  ossified  from  two  primarj-  centres,  one  on  either  side  of  the  middle  line. 


THE  SACRAL  AND  COCCYGEAL  VERTEBRA 


211 


between  the  sides  of  the  cleft  and  the  summit  of  the  process  is  formed  by  a  wedge-shaped  piece 
of  cartihige.    The  base  of  the  process  is  separated  from  th(>  body  by  a  cartilaginous  disk,  which 

tii'adually  b(!(;oin(!S  ossified    at  its  cir- 
FiG.  248. — Ossification  of  a  vertebra 
By  3  primary  centres 


1  Jor  hody  [Hlh  wck] 


1  for  each  vertebral  arch  [llh  or  8th  week) 

Fig.  249. 
By  3  secondary  centres 


Neurocentral 
synchondrosis 


1  for  each 
trans,  process 
I6th  year 


1  for  spinous  process  {IGth  year) 

Fig.  250. 
By  2  additional  plates 

1  for  upper  surface^ 
of  body 


1  for  under  surface 
of  body 


IQth  year 


Fig.  251— Atlas. 


By  3  centres 


I  for  anter.  arch  (end  of  1st  year) 


1  for  each  \^aweelc 

lateral  mass       J 


Fig.  252.— Axis. 


By  7  centres 

<(P^ 2nd  year 


6th  month 
1  Jor  each  vertebral  arch  (7  th 

or  8th  iceek) 
1  for  body  {4th  month) 
1  for  under  surface  of  body 


Fig.  253. — Lumbar  vertebra. 


2  additional  centres  for  mamillary  processes 


cumference,  Ijut  remains  cartilaginous 
in  its  centre  until  advanced  age.  In 
this  cartilage,  I'udiments  of  the  lower 
epiphysial  lamella  of  the  atlas  and  the 
upper  epiphysial  lamella  of  the  axis 
may  sometimes  be  found.  The  apex 
of  the  odontoid  process  has  a  separate 
centre  which  api^ears  in  the  second  and 
joins  about  the  twelfth  year;  this  is  the 
upper  epiphysial  lamella  of  the  atlas. 
In  addition  to  these  there  is  a  secondary 
centre  for  a  thin  epiphysial  plate  on 
the  under  surface  of  the  body  of  the 
bone. 

Additional  centres 
for  costal  elements  * 


At  birth 


Fig.  254 


At  4J  yrs 


Fig.  255 


Two  epiphysial  plates 
for  each  lateral  surface  * 


At 
25th  year 


Fig.  256. — Ossification  of  the  sacrum. 


The  Seventh  Cervical  Vertebra. — The  anterior  or  costal  part  of  the  transverse  process  of  this 
vertebra  is  sometimes  ossified  from  a  separate  centre  which  appears  about  the  sixth  month  of 


212 


OSTEOLOGY 


fetal  life,  and  joins  the  body  and  posterior  part  of  the  transverse  process  between  the  fifth  and 
sixth  years.  Occasionally  the  costal  part  persists  as  a  separate  piece,  and,  becoming  lengthened 
lateralward  and  forward,  constitutes  what  is  known  as  a  cervical  rib.  Separate  ossific  centres 
have  also  been  found  in  the  costal  processes  of  the  fourth,  fifth,  and  sixth  cervical  vertebrae. 

Lumbar  Vertebrae. — The  lumbar  vertebrae  (Fig.  253)  have  each  two  additional  centres,  for 
the  mamillary  processes.  The  transverse  process  of  the  first  lumbar  is  sometimes  developed  as 
a  separate  piece,  which  may  remain  permanently  ununited  with  the  rest  of  the  bone,  thus  form- 
ing a  lumbar  rib — a  peculiarity,  however,  rarely  met  with. 

Sacrum  (Figs.  254  to  257). — The  body  of  each  sacral  vertebra  is  ossified  from  a  primary  centre 
and  tico  epiphysial  plates,  one  for  its  upper  and  another  for  its  under  surface,  while  each  vertebral 
arch  is  ossified  from  two  centres. 

The  anterior  portions  of  the  lateral  -parts  have  six  additional  centres,  two  for  each  of  the  first 
three  vertebrae;  these  represent  the  costal  elements,  and  make  their  appearance  above  and  lateral 
to  the  anterior  sacral  foramina  (Figs.  254,  255). 

On  each  lateral  surface  two  epiphysial  plates  are  developed  (Figs.  256,  257) :  one  for  the  auric- 
ular surface,  and  another  for  the  remaining  part  of  the  thin  lateral  edge  of  the  bone.^ 

Periods  or  Ossificatiox. — About  the  eighth  or  ninth  week  of  fetal  Ufe,  ossification  of  the 
central  part  of  the  body  of  the  first  sacral  vertebra  commences,  and  is  rapidly  followed  by  deposit 

of  ossific  matter  in  the  second  and  third; 


Centre  for 
neural  arch 


Centre  for 
neural  arch. 


Costal 
element 


Lateral 
epiphysis. 

Fig.  257. 


Centre  for 
hody. 


Lateral 
epiphysis. 


-Base  of  young  sacrum. 


ossification  does  not  commence  in  the 
bodies  of  the  lower  two  segments  until 
between  the  fifth  and  eighth  months  of 
fetal  life.  Between  the  sixth  and  eighth 
months  ossification  of  the  vertebral  arches 
takes  place;  and  about  the  same  time  the 
costal  centres  for  the  lateral  parts  make 
their  appearance.  The  junctions  of  the 
vertebral  arches  with  the  bodies  take  place 
in  the  lower  vertebrae  as  early  as  the 
second  year,  but  are  not  effected  in  the 
uppermost  until  the  fifth  or  sixth  year. 
About  the  sixteenth  year  the  epiphysial 
plates  for  the  upper  and  under  sui-faces  of  the  bodies  are  formed;  and  between  the  eighteenth  and 
twentieth  years,  those  for  the  lateral  surfaces  make  their  appearance.  The  bodies  of  the  sacral 
vertebrae  are,  during  early  life,  separated  from  each  other  by  intervertebral  fibrocartilages,  but 
about  the  eighteenth  year  the  two  lowest  segments  become  imited  by  bone,  and  the  process  of 
bony  union  gradually  extends  upward,  with  the  result  that  between  the  twenty-fifth  and  thirtieth 
years  of  fife  all  the  segments  are  united.  On  examining  a  sagittal  section  of  the  sacrum,  the  situa- 
tions of  the  intervertebral  fibrocartilages  are  indicated  by  a  series  of  oval  cavities  (Fig.  246). 

Coccyx. — The  coccj^  is  ossified  from  four  centres,  one  for  each  segment.  The  ossific  nuclei 
make  their  appearance  in  the  following  order:  in  the  first  segment  between  the  first  and  fourth 
j^ears;  in  the  second  between  the  fifth  and  tenth  j^ears;  in  the  third  between  the  tenth  and  fifteenth 
years;  in  the  fourth  between  the  ourteenth  and  twentieth  years.  As  age  advances,  the  segments 
unite  with  one  another,  the  union  between  the  first  and  second  segments  being  freq  ently  delayed 
until  after  the  age  of  twenty-five  or  thirty.  At  a  late  period  of  life,  especially  in  females,  the  coccyx 
often  fuses  with  the  sacrum. 


THE  VERTEBRAL  COLUMN  AS  A  WHOLE. 

The  vertebral  column  is  situated  in  the  median  line,  as  the  posterior  part  of  the 
trunk;  its  average  length  in  the  male  is  about  71  cm.  Of  this  length  the  cervical 
part  measures  12.5  cm.,  the  thoracic  about  28  cm.,  the  lumbar  18  cm.,  and  the 
sacrum  and  coccyx  12.5  cm.     The  female  column  is  about  61  cm.  in  length. 

Curves. — Viewed  laterally  (Fig.  258),  the  vertebral  column  presents  several 
curves,  which  correspond  to  the  different  regions  of  the  column,  and  are  called 
cervical,  thoracic,  lumbar,  and  pelvic.    The  cervical  curve,  convex  forward,  begins 


'  The  ends  of  the  spinous  processes  of  the  upper  three  sacral  v^ertebrae  are  sometimes  developed  from  separate  epi- 
physes, and  Fawcett  (Anatomischer  Anzeiger,  1907,  Band  xxx)  states  that  a  number  of  epiphysial  nodules  may  be 
seen  in  the  sacrum  at  the  age  of  eighteen  years.  These  are  distributed  as  follows:  One  for  each  of  the  mamillar}'  pro- 
cesses of  the  first  sacral  vertebra;  twelve — six  on  either  side — in  connection  with  the  costal  elements  (two  each  for  the 
first  and  second  and  one  each  for  the  third  and  fourthj  and  eight  for  the  transverse  processes — four  on  either  side — 
one  each  for  the  first,  third,  fourth,  and  fifth.  He  is  further  of  opinion  that  the  lower  part  of  each  lateral  surface  of 
the  sacrum  is  formed  by  the  extension  and  imion  of  the  third  and  fourth  "costal"  and  fourth  and  fifth  "transverse" 
epiphyses. 


THE  VERTEBRAL  COLUMN  AS  A  WHOLE 


213 


at  the  apex  of  the  odontoid  process,  and 
ends  at  the  middle  of  the  second  thoracic 
vertebra;  it  is  the  least  marked  of  all  the 
cn^^'es.  The  thoracic  curve,  concave  for- 
ward, begins  at  the  middle  of  the  second 
and  ends  at  the  middle  of  the  twelfth  tho- 
racic vertebra.  Its  most  prominent  point 
behind  corresponds  to  the  spinous  process 
of  the  seventh  thoracic  vertebra.  The 
lumbar  curve  is  more  marked  in  the  female 
than  in  the  male;  it  begins  at  the  middle  of 
the  last  thoracic  vertebra,  and  ends  at  the 
sacro vertebral  angle.  It  is  convex  ante- 
riorly, the  convexity  of  the  lower  three 
vertebrae  being  much  greater  than  that  of 
the  upper  two.  The  pelvic  curve  begins 
at  the  sacrovertebral  articulation,  and  ends 
at  the  point  of  the  coccyx;  its  concavity 
is  directed  downward  and  forward.  The 
thoracic  and  pelvic  curves  are  termed 
primary  curves,  because  they  alone  are 
present  during  fetal  life.  The  cervical 
and  lumbar  curves  are  compensatory  or 
secondary,  and  are  developed  after  birth, 
the  former  when  the  child  is  able  to  hold 
up  its  head  (at  three  or  four  months),  and 
to  sit  upright  (at  nine  months),  the  latter 
at  twelve  or  eighteen  months,  when  the 
child  begins  to  walk. 

The  vertebral  column  has  also  a  slight 
lateral  curvature,  the  convexity  of  which  is 
directed  toward  the  right  side.  This  may 
be  produced  by  muscular  action,  most 
persons  using  the  right  arm  in  preference 
to  the  left,  especially  in  making  long-con- 
tinued efforts,  when  the  body  is  curved 
to  the  right  side.  In  support  of  this  ex- 
planation it  has  been  found  that  in  one 
or  two  individuals  who  were  left-handed, 
the  convexity  was  to  the  left  side.  By  others 
this  curvature  is  regarded  as  being  produced 
by  the  aortic  arch  and  upper  part  of  the 
descending  thoracic  aorta — a  view  which  is 
supported  by  the  fact  that  in  cases  where 
the  viscera  are  transposed  and  the  aorta  is 
on  the  right  side,  the  convexity  of  the 
curve  is  directed  to  the  left  side. 

Surfaces.  —  Anterior  Surface.  —  When 
viewed  from  in  front,  the  width  of  the  bodies 
of  the  vertebrae  is  seen  to  increase  from  the 
second  cervical  to  the  first  thoracic;  there 
is  then  a  slight  diminution  in  the  next 
three  vertebrae;  below  this  there  is  again 
a  gradual  and  progressive  increase  in  width 


1st  cervical 
or  Atlas 

r ^      ^ 

Sndcervicfil    -l''^^"'^'\ 
or  Axis  \^r,  y^'^-<~^^^ 


1st  thoiacic 


V  -'i' 


4' 


^^. 


><? 


4- 


s-y 


# 


Fig.  238. — Lateral  view  of  the  vertebral  column. 


214  OSTEOLOGY 

as  low  as  the  sacrovertebral  angle.     From  this  point  there  is  a  rapid  fliminution, 
to  the  apex  of  the  eoccyx. 

Posterior  Surface. — The  posterior  surt'aee  of  the  vertebral  eolunin  presents  in 
the  median  line  the  spinous  processes.  In  the  cervical  region  (with  the  exception 
of  the  second  and  seventh  vertebrae)  these  are  short  and  horizontal,  with  bifid 
extremities.  In  the  upper  part  of  the  thoracic  region  they  are  directed  obliquely 
downward;  in  the  middle  they  are  almost  vertical,  and  in  the  lower  part  they  are 
nearly  horizontal.  In  the  lumbar  region  they  are  nearly  horizontal.  The  spinous 
processes  are  separated  by  considerable  intervals  m  the  lumbar  region,  by  narrower 
intervals  in  the  neck,  and  are  closely  approximated  in  the  middle  of  the  thoracic 
region.  Occasionally  one  of  these  proces.ses  deviates  a  little  from  the  median  line 
— a  fact  to  be  remembered  in  practice,  as  irregularities  of  this  sort  are  attendant 
also  on  fractures  or  displacements  of  the  vertebral  column.  On  either  side  of  the 
spinous  processes  is  the  vertebral  groove  formed  by  the  laminae  in  the  cervical  and 
lumbar  regions,  where  it  is  shallow,  and  by  the  laminae  and  transverse  processes 
in  the  thoracic  region,  where  it  is  deep  and  broad;  these  grooves  lodge  the  deep 
muscles  of  the  back.  Lateral  to  the  vertebral  grooves  are  the  articular  processes, 
and  still  more  laterally  the  transverse  processes.  In  the  thoracic  region,  the  trans- 
verse processes  stand  backward,  on  a  plane,  considerably  behind  that  of  the  same 
processes  in  the  cervical  and  lumbar  regions.  In  the  cervical  region,  the  transverse 
processes  are  placed  in  front  of  the  articular  processes,  lateral  to  the  pedicles  and 
between  the  intervertebral  foramina.  In  the  thoracic  region  they  are  posterior 
to  the  pedicles,  intervertebral  foramina,  and  articular  processes.  In  the  lumbar 
region  they  are  in  front  of  the  articular  processes,  but  behind  the  intervertebral 
foramina. 

Lateral  Surfaces. — The  lateral  surfaces  are  separated  from  the  posterior  surface 
by  the  articular  processes  in  the  cervical  and  lumbar  regions,  and  by  the  transverse 
processes  in  the  thoracic  region.  They  present,  in  front,  the  sides  of  the  bodies 
of  the  vertebrae,  marked  in  the  thoracic  region  by  the  facets  for  articulation  with 
the  heads  of  the  ribs.  ]\Iore  posteriorly  are  the  intervertebral  foramina,  formed 
by  the  juxtaposition  of  the  vertebral  notches,  oval  in  shape,  smallest  in  the  cervical 
and  upper  part  of  the  thoracic  regions,  and  gradually  increasing  in  size  to  the  last 
lumbar.  They  transmit  the  spinal  nerves  and  are  situated  between  the  transverse 
processes  in  the  cervical  region,  and  in  front  of  them  in  the  thoracic  and  lumbar 
regions. 

Base.— The  base  of  that  portion  of  the  vertebral  column  which  is  made  up  of ' 
the  twenty-four  movable  vertebrae  is  formed  by  the  under  surface  of  the  body 
of  the  fifth  lumbar  vertebrae;  and  the  summit,  by  the  upper  surface  of  the  atlas. 

Vertebral  Canal. — The  vertebral  canal  follows  the  different  curves  of  the  column; 
it  is  large  and  triangular  in  those  parts  of  the  column  which  enjoy  the  greatest 
freedom  of  movement,  viz.,  the  cervical  and  lumbar  regions;  and  is  small  and 
rounded  in  the  thoracic  region,  where  motion  is  more  limited. 

Applied  Anatomy. — Occasionally  the  coalescence  of  the  laminae  is  not  completed,  and  conse- 
quently a  cleft  is  left  in  the  arches  of  the  vertebrae,  through  which  a  protrusion  of  the  spmal 
membranes  (dura  mater  and  arachnoidj,  and  generally  of  the  medulla  spinahs  itself,  takes  place, 
constituting  the  malformation  known  as  spina  bifida.  This  condition  is  most  common  m  the 
lumbosacral  region,  but  it  may  occur  in  the  thoracic  or  cervical  region,  or  the  arches  throughout 
the  whole  length  of  the  canal  may  remain  incomplete. 

The  construction  of  the  movable  part  of  the  vertebral  column  of  a  number  of  pieces,  securely 
connected  together  and  enjoying  only  a  slight  degree  of  movement  between  any  two  individual 
pieces,  but  permitting  of  a  very  considerable  range  as  a  whole,  allows  a  sufficient  degree  of  mobihty 
without  any  material  diminution  of  strength.  The  many  joints  of  which  the  column  is  composed, 
together  with  the  very  varied  movements  to  which  it  is  subjected,  render  it  hable  to  sprains; 
but,  so  closely  are  the  individual  vertebrae  articulated  that  these  sprains  are  rarely  severe,  and 
an  amount  of  violence  sufficiently  great  to  produce  tearing  of  the  ligaments  would  tend  rather 
to  cause  a  dislocation  or  fracture.     The  further  safety  of  the  column  and  its  slight  liability  to 


THE   VERTEBRAL  CO  LI' MX  AS  A    WHOLE  215 

injury  are  provided  for  by  its  di,si:)Ot;itiou  in  cur\-es  instead  of  in  a  straight  line.  For  it  is  an  elastic 
column,  antl  must  bentl  before  it  breaks;  under  these  circumstances,  being  made  up  of  three  curves, 
it  represents  three  columns,  and  greater  force  is  required  to  produce  bending  of  a  short  column 
than  of  a  longer  one  that  is  equal  to  it  in  breadth  aiul  material.  Again,  the  safety  of  the  column 
is  largely  provided  for  by  the  presence  between  the  bodies  of  the  intervertebraf  fibrocartilages, 
which  act  as  buffers  in  counteracting  the  effects  of  violent  jars  or  shocks. 

Fraclure  dislocation  of  the  vertebral  column  may  be  caused  by  direct  or  indirect  violence. 
Fractures  from  indirect  violence  are  the  more  common,  and  here  the  bodies  of  the  vertebrae  are 
compressed,  while  the  arches  are  torn  asunder;  in  fracture  from  direct  violence,  on  the  other 
hand,  the  arches  are  compressed  and  the  bodies  of  the  vertebrie  separated  from  each  other.  It 
will  therefore  be  seen  that  in  both  classes  of  injury  the  medulla  spinalis  is  the  part  least  hkely  to 
be  injured,  and  may  escape  damage  even  where  there  has  been  considerable  lesion  of  the  bony 
framework.  When  a  fracture  dislocation  is  produced  by  indirect  violence,  the  displacement  is 
almost  alwa^-s  the  same;  the  upper  segment  being  driven  forward  on  the  lower,  so  that  the  medulla 
spinalis  is  compressed  between  the  body  of  the  vertebra  below  and  the  arch  of  the  ^•ertebra  above. 

Diseases  of  the  Vertebral  Column. — Spinal  caries,  or  tuberculous  disease  affecting  the  cancellous 
tissue  of  the  bodies  of  the  vertebrae,  is  a  very  common  condition.  When  the  bodies,  having  been 
destroyed,  begin  to  fall  together,  the  spinous  processes  are  necessarily  thrown  backward  and 
stand  out  prominentl}-,  especially  if  the  disease  affect  the  thoracic  region,  which  is  most  commonly 
the  case.  The  condition  then  goes  by  the  name  of  angular  curvature,  and  great  rigidity  of  the 
muscles  in  the  affected  region  accompanies  it.  Pressure,  by  the  inflammatory  thickenings  of  the 
disease,  is  apt  to  involve  the  spinal  nerves  in  the  affected  region,  giving  rise  to  peripheral  pains, 
and  if  the  disease  be  in  the  lower  thoracic  vertebrse  the  pains  are  referred  to  the  epigastric  or 
umbilical  regions,  and  often  the  chief  thing  complained  of  is  "bell}'  ache."  Chronic  abscess  forma- 
tion in  spinal  caries  is  very  frequent,  and  it  nearty  always  forms  in  front  of  the  vertebral  bodies. 
^Yhen  the  disease  is  in  the  lower  thoracic  region,  the  abscess  usually  tracks  down  behind  the 
Diaphragma  and  enters  the  Psoas  sheath,  forming  the  well-known  psoas  abscess,  which  may  present 
above  the  inguinal  ligament,  or  may  pass  beneath  it  into  the  thigh.  In  other  cases  the  abscess 
takes  a  backward  coiu-se  between  the  transverse  processes  and  presents  as  a  thoracic  or  lumbar 
abscess;  if  the  disease  affect  the  cervical  region  of  the  vertebral  column,  a  post-pharyngeal  abscess 
results. 

Lateral  curvature  of  the  vertebral  column  is  a  common  affection  in  girls  who  are  outgrowing  their 
strength  and  who  sit  or  stand  long  at  lessons,  and  is  due  to  the  uneven  transmission  of  weight 
down  the  column.  In  addition  to  the  lateral  displacement  of  the  spinous  processes  there  is  a 
marked  rotation  of  the  bodies  of  the  vertebrse,  the  displacement  of  which  is  far  in  excess  of  that 
of  the  spinous  processes.  When  the  curve  is  severe  and  the  bones  have  actually  become  distorted, 
the  condition  is  past  cure. 

Kyphosis  is  an  affection  in  which  there  is  an  increase  in  the  normal  thoracic  curve,  and  is  due 
to  bending  forward  of  the  upper  part  of  the  bod}'  carrjdng  the  weight  of  the  head.  It  is  seen 
in  rickety  children,  in  rapidly  growing  adolescents,  in  senile  conditions,  and  in  certain  diseases, 
such  as  osteoarthritis  and  osteitis  deformans.  In  the  senile  kyphosis  often  met  with  in  aged 
laborers,  the  head  is  firmly  fixed  and  bent  forward  and  downward  on  to  the  chest,  and  the  vertebral 
column  is  curved  and  rigid.  The  ribs  are  immobihzed,  the  chest  is  flattened  antero-posteriorly, 
and  breathing  becomes  almost  entirely  abdominal.  Postmortem,  bonj'  ankj'losis  of  the  hgaments 
and  capsules  of  the  intervertebral  joints  is  found,  with  ossification  of  the  ligamenta  flava,  inter- 
spinal and  other  hgaments. 

It  may  be  noted  that  in  marked  cases  of  spinal  deformity  the  trachea  and  aorta  follow  closely 
along  the  line  of  a  spinal  curvature  occurring  in  their  vicinity,  whereas  the  oesophagus  between 
the  tracheal  bifurcation  and  the  stomach  often  passes  like  a  bowstring  across  the  concavity  of 
the  cm-ve. 

Lordosis,  on  the  other  hand,  is  an  exaggeration  of  the  normal  lumbar  cm-ve,  the  trunk  being 
thrown  backward.  This  is  always  a  compensatory  cm-ve,  and  occm-s  when,  from  any  cause  such 
as  pregnane}'  or  tumors,  the  abdomen  is  enlarged.  It  is  more  strongly  marked  in  cases  of  disease 
of  the  hip-joint  where  the  joint  is  permanently  retained  in  a  flexed  position,  so  that  in  order  to 
bring  the  foot  down  to  the  ground  the  pelvis  has  to  be  tilted  forward,  and  this  is  accomplished  bj' 
an  increase  of  the  normal  lumbar  curve. 

Laminectomy. — The  operation  of  laminectomy  is  performed  in  cases  of  pressm-e  on  the  meduUa 
spinahs,  where  the  continuity  of  the  nerve  tracts  has  not  been  completel}'  destroj'ed.  It  consists 
of  cutting  down  on  and  removing  the  laminae  and  spinous  processes  in  the  affected  region,  so  as 
to  reheve  the  meduUa  spinahs  from  pressm-e;  but  it  is  useless  in  cases  of  complete  destruction 
of  this  structm-e.  Laminectomj'  is  chiefl}'  performed  (1)  for  fractm-e  dislocation;  (2)  for  localized 
pressure  in  cases  of  spinal  caries,  the  object  here  being  to  remove  the  laminae  against  which  the 
medulla  spinahs  is  pressed  by  the  inflammatory  mass;  and  (3)  for  the  removal  of  tumors  growing 
inside  the  vertebral  canal  and  compressing  the  medulla  spinahs.  If  such  cases  be  taken  early, 
verj-  satisfactorj-  results  are  obtained. 


216  OSTEOLOGY 


THE   THORAX. 


The  skeleton  of  the  thorax  or  chest  is  an  osseo-cartilaginous  cage,  containing 
and  protecting  the  principal  organs  of  respiration  and  circulation.  It  is  conical 
in  shape,  being  narrow  above  and  broad  below,  flattened  from  before  backward, 
and  longer  behind  than  in  front.  It  is  somewhat  reniform  on  transverse  section 
on  account  of  the  projection  of  the  vertebral  bodies  into  the  cavity. 

Boundaries. — The  posterior  surface  is  formed  by  the  twelve  thoracic  vertebrae 
and  the  posterior  parts  of  the  ribs.  It  is  convex  from  above  downward,  and  pre- 
sents on  either  side  of  the  middle  line  a  deep  groove,  in  consequence  of  the  lateral 
and  backward  direction  which  the  ribs  take  from  their  vertebral  extremities  to 
their  angles.  The  anterior  surface,  formed  by  the  sternum  and  costal  cartilages, 
is  flattened  or  slightly  convex,  and  inclined  from  above  downward  and  forward. 
The  lateral  surfaces  are  convex;  they  are  formed  by  the  ribs,  separated  from 
each  other  by  the  intercostal  spaces,  eleven  in  number,  which  are  occupied  by 
the  Intercostal  muscles  and  membranes. 

The  upper  opening  of  the  thorax  is  reniform  in  shape,  being  broader  from  side 
to  side  than  from  before  backward.  It  is  formed  by  the  first  thoracic  vertebra 
behind,  the  upper  margin  of  the  sternum  in  front,  and  the  first  rib  on  either  side. 
It  slopes  downward  and  forward,  so  that  the  anterior  part  of  the  opening  is  on  a 
low^er  level  than  the  posterior.  Its  antero-posterior  diameter  is  about  5  cm.,  and 
its  transverse  diameter  about  10  cm.  The  lower  opening  is  formed  by  the  twelfth 
thoracic  vertebra  behind,  by  the  eleventh  and  twelfth  ribs  at  the  sides,  and  in  front 
by  the  cartilages  of  the  tenth,  ninth,  eighth,  and  seventh  ribs,  which  ascend  on 
either  side  and  form  an  angle,  the  subcostal  angle,  into  the  apex  of  which  the 
xiphoid  process  projects.  The  lower  opening  is  wider  transversely  than  from 
before  backward,  and  slopes  obliquely  downward  and  backward,  it  is  closed  by 
the  Diaphragma  which  forms  the  floor  of  the  thorax. 

The  thorax  of  the  female  differs  from  that  of  the  male  as  follows:  1.  Its  capacity  is  less.  2. 
The  sternum  is  shorter.  3.  The  upper  margin  of  the  sternum  is  on  a  level  with  the  lower  part 
of  the  body  of  the  third  thoracic  vertebra,  whereas  in  the  male  it  is  on  a  level  with  the  lower 
part  of  the  body  of  the  second.  4.  The  upper  ribs  are  more  movable,  and  so  allow  a  greater 
enlargement  of  the  upper  part  of  the  thorax. 

The  Sternum  (Breast  Bone). 

The  sternum  (Figs.  259  to  261)  is  an  elongated,  flattened  bone,  forming  the 
middle  portion  of  the  anterior  wall  of  the  thorax.  Its  upper  end  supports  the 
clavicles,  and  its  margins  articulate  with  the  cartilages  of  the  first  seven  pairs 
of  ribs.  It  consists  of  three  parts,  named  from  above  downward,  the  manubrium, 
the  body  or  gladiolus,  and  the  xiphoid  process;  in  early  life  the  body  consists  of  four 
segments  or  sternebrcB.  In  its  natural  position  the  inclination  of  the  bone  is  oblique 
from  above,  downward  and  forward.  It  is  slightly  convex  in  front  and  concave 
behind;  broad  above,  becoming  narrowed  at  the  point  where  the  manubrium  joins 
the  body,  after  which  it  again  widens  a  little  to  below  the  middle  of  the  body, 
and  then  narrows  to  its  lower  extremity.  Its  average  length  in  the  adult  is  about 
17  cm.,  and  is  rather  greater  in  the  male  than  in  the  female. 

Manubrium  {manubrium  sterni). — The  manubrium  is  of  a  somewhat  quad- 
rangular form,  broad  and  thick  above,  narrow  below  at  its  junction  with  the  body. 

Surfaces. — Its  anterior  surface,  convex  from  side  to  side,  concave  from  above 
downward,  is  smooth,  and  affords  attachment  on  either  side  to  the  sternal  origins 
of  the  Pectoralis  major  and  Sternocleidomastoideus.  In  well-marked  bones  the 
ridges  limiting  the  attachments  of  these  muscles  are  very  distinct.     Its  posterior 


THE  STERNUM 


217 


surface,  concave  and  smooth,  affords  attachment  on  either  side  to  the  Sterno- 
hvoideus  and  Sternothyreoideus. 

Borders. — The  superior  border  is  the  thickest  and  presents  at  its  centre  the  jugular 
or  prestemal  notch;  on  either  side  of  the  notch  is  an  oval  articnlar  surface,  directed 
upward,  backward,  and  lateralward,  for  articulation  with  the  sternal  end  of  the 


STERNorLEIDOMASTOIDEUS 


Fig.   259. — Anterior  surface  of  sternum  and  costal  cartilages. 


clavicle.  The  inferior  border,  oval  and  rough,  is  covered  in  a  recent  state  with  a 
thin  layer  of  cartilage,  for  articulation  with  the  body.  The  lateral  borders  are  each 
marked  above  by  a  depression  for  the  first  costal  cartilage,  and  below  by  a  small 
facet,  which,  with  a  similar  facet  on  the  upper  angle  of  the  body,  forms  a  notch 
for  the  reception  of  the  costal  cartilage  of  the  second  rib.     Between  the  depression 


218 


OSTEOLOGY 


for  the  first  costal  cartilage  anrl  the  demi-facet  for  the  second  is  a  narrow,  curved 
edcje,  Avhich  slopes  from  a}K:)^•e  downward  and  medialward. 

Body  (corpus  sterni;  gladiolus). — The  body,  considerably  longer,  narrower,  and 
thinner  than  the  manubrium,  attains  its  greatest  breadth  close  to  the  lower  end. 

Surfaces. — Its  anterior  surface  is  nearly  flat,  directed  upward  and  forward, 
and  marked  by  three  transverse  ridges  which  cross  the  bone  opposite  the  third, 
fourth,  and  fifth  articular  depressions.^  It  affords  attachment  on  either  side  to 
the  sternal  origin  of  the  Pectoralis  major.  At  the  junction  of  the  third  and  fourth 
pieces  of  the  body  is  occasionally  seen  an  orifice,  the  sternal  foramen,  of  varying 
size  and  form.  The  posterior  surface,  slightly  concave,  is  also  marked  by  three 
transverse  lines,  less  distinct,  however,  than  those  in  front;  from  its  lower  part, 
on  either  side,  the  Transversus  thoracis  takes  origin. 


For  1st 
'4-  costal 
cartilage 


Xiphoid  process 


Fig.  260. — Posterior  surface  of  sternum. 


Sternal 
arujle 


Articular  surface 
for  clavicle 

Depression  for 

\st  costal  cartilage 

Manubrium 


Der/iifacfis  for  2nd  costal 
cartilage 


[ml —  F'^'f^f  fo'i'  3''<^  costal  cartilage 
Body 


Faat  for  Ath  costal  cartilage 

Facet  fo'r  oth  co-^tal  cartilage 

-Facet  for  Qth  costal  cartilage 
■  Facet  for  7th  costal  cartilage 
Xiphoid  process 


Fig.  261. — Lateral  border  of  sternum. 


Borders. — The  superior  border  is  oval  and  articulates  with  the  manubrium,  the 
junction  of  the  two  forming  the  sternal  angle  (angulus  Ludovici-).  The  inferior 
border  is  narrow,  and  articulates  with  the  xiphoid  process.  Each  lateral  border 
(Fig.  261),  at  its  superior  angle,  has  a  small  facet,  which  with  a  similar  facet  on 
the  manubrium,  forms  a  cavity  for  the  cartilage  of  the  second  rib;  below  this 
are  four  angular  depressions  which  receive  the  cartilages  of  the  third,  fourth, 
fifth,  and  sixth  ribs,  while  the  inferior  angle  has  a  small  facet,  which,  with  a  cor- 
responding one  on  the  xiphoid  process,  forms  a  notch  for  the  cartilage  of  the  seventh 
rib.  These  articular  depressions  are  separated  by  a  series  of  curved  interarticular 
intervals,  which  diminish   in   length  from  above  downward,   and  correspond  to 


1  Paterson  (The  Human  Sternum,  1904;,  who  examined  .524  specimens,  points  out  that  these  ridges  are  altogether 
absent  in  26.7  per  cent  ;  that  in  69  per  cent,  a  ridge  e.usts  opposite  the  third  costal  attachment;  in  .39  per  cent,  opposite 
the  fourth;  and  in  4  per  cent,  only,  opposite  the  fifth. 

-  Named  after  the  French  surgeon  .\ntoine  Louis,  1723-1792.  The  Latin  name  angulus  Ludovici  is  not  infrequently 
mistranslated  into  English  as  "the  angle  of  Ludwig. " 


THE  STERNUM 


219 


Time 

of 

appearance 


Time 

of 
union 


In 

number  of 
centres 


In 

mode  of 
union 


J  far  Ill/Ill uhri III 


f-'j 


/f  for  hddij 


h'l/l  tlMllth 

7th  month 

Ist  ijcdr  after  hirth 


I    >^         /  for  xiphoid    \ 
Fig.  262. — Ossification  of  the  sternum. 


Rarely  unite,  except  in  old  age 
Between  puberty  and  the  25th  year 

Soon  after  puberty 

6  \  Partly  cartilaginous  to  advanced  life 

Fig.  263 

for  first  piece,  two  or  more  centres 

for  second  piece,  itsually  one 
for  third  ^ 


for  fourth  J 
for  fifth 


2,  placed  laterally 


Fig.  264. — Peculiarities. 


Arrest  of  ossification  of  lateral  pieces, 
producing  : 

-Sternal  fissure,  and 
Sternal  foramen 


220  OSTEOLOGY 

the  intercostal  spaces.  ]Most  of  the  cartilages  belonging  to  the  true  ribs,  as  will 
be  seen  from  the  foregoing  description,  articulate  with  the  sternum  at  the  lines 
of  junction  of  its  primitive  component  segments.  This  is  well  seen  in  many  of 
the  lower  animals,  where  the  parts  of  the  bone  remain  ununited  longer  than  in 
man. 

Xiphoid  Process  (jjrocessus  xiphoideiis;  ensiform  or  xi-phoid  appendix). — The 
xiphoid  process  is  the  smallest  of  the  three  pieces:  it  is  thin  and  elongated, 
cartilaginous  in  structure  in  youth,  but  more  or  less  ossified  at  its  upper  part  in 
the  adult. 

Surfaces. — Its  anterior  surface  affords  attachment  on  either  side  to  the  anterior 
costoxiphoid  ligament  and  a  small  part  of  the  Rectus  abdominis;  its  posterior  sur- 
face, to  the  posterior  costoxiphoid  ligament  and  to  some  of  the  fibres  of  the  Dia- 
phragma  and  Transversus  thoracis,  its  lateral  borders,  to  the  aponeuroses  of  the 
abdominal  muscles.  Above,  it  articulates  with  the  lower  end  of  the  body,  and 
on  the  front  of  each  superior  angle  presents  a  facet  for  part  of  the  cartilage  of  the 
seventh  rib;  below,  by  its  pointed  extremity,  it  gives  attachment  to  the  linea 
alba.  The  xiphoid  process  varies  much  in  form;  it  may  be  broad  and  thin,  pointed, 
bifid,  perforated,  curved,  or  deflected  considerably  to  one  or  other  side. 

Structure. — The  sternum  is  composed  of  highly  vascular  cancellous  tissue,  covered  by  a  thin 
layer  of  compact  bone  which  is  thickest  in  the  manubrium  between  the  articular  facets  for  the 
clavicles. 

Ossification. — The  sternum  originally  consists  of  two  cartilaginous  bars,  situated  one  on  either 
side  of  the  median  plane  and  connected  with  the  cartilages  of  the  upper  nine  ribs  of  its  own  side. 
These  two  bars  fuse  with  each  other  along  the  middle  line  to  form  the  cartilaginous  sternum  which 
is  ossified  frotn  six  centres:  one  for  the  manubrium,  four  for  the  body,  and  one  for  the  xiphoid 
process  (Fig.  262).  The  ossific  centres  appear  in  the  intervals  between  the  articular  depressions 
for  the  costal  cartilages,  in  the  following  order:  in  the  manubrium  and  first  piece  of  the  body, 
dm-ing  the  sixth  month;  in  the  second  and  third  pieces  of  the  body,  dm-ing  the  seventh  month  of 
fetal  life;  in  its  fourth  piece,  during  the  first  year  after  birth;  and  in  the  xiphoid  process,  between 
the  fifth  and  eighteenth  years.  The  centres  make  their  appearance  at  the  upper  parts  of  the  seg- 
ments, and  proceed  gradually  downward. "•  To  these  may  be  added  the  occasional  existence  of 
two  smaU  episternal  centres,  which  make  their  appearance  one  on  either  side  of  the  jugular  notch; 
they  are  probably  vestiges  of  the  episternal  bone  of  the  monotremata  and  lizards.  Occasionally 
some  of  the  segments  are  formed  from  more  than  one  centre,  the  number  and  position  of  which 
vary  (Fig.  264).  Thus,  the  first  piece  may  have  two,  three,  or  even  six  centres.  When  two  are 
present,  they  are  generally  situated  one  above  the  other,  the  upper  being  the  larger;  the  second 
piece  has  seldom  more  than  one;  the  third,  fourth,  and  fifth  pieces  are  often  formed  from  two 
centres  placed  laterally,  the  irregular  union  of  which  explains  the  rare  occurrence  of  the  sternal 
foramen  (Fig.  265),  or  of  the  vertical  fissm-e  which  occasionally  intersects  this  part  of  the  bone; 
these  conditions  are  further  explained  by  the  manner  in  which  the  cartilaginous  sternum  is  formed. 
Union  of  the  various  centres  of  the  body  begins  about  puberty,  and  proceeds  from  below  upward 
(Fig.  263) ;  by  the  age  of  twenty-five  they  are  all  united.  The  xiphoid  process  may  become  joined 
to  the  body  before  the  age  of  thirty,  but  this  occurs  more  frequently  after  forty;  on  the  other 
hand,  it  sometimes  remains  unimited  in  old  age.  In  advanced  life  the  manubrium  is  occasionally 
joined  to  the  body  by  bone.  When  this  takes  place,  however,  the  bony  tissue  is  generally  only 
superficial,  the  central  portion  of  the  intervening  cartilage  remaining  imossified. 

Articulations. — The  sternum  articulates  on  either  side  with  the  clavicle  and  upper  seven  costal 
cartilages. 

The  Ribs  (Costae). 

The  ribs  are  elastic  arches  of  bone,  which  form  a  large  part  of  the  thoracic 
skeleton.  They  are  twelve  in  number  on  either  side;  but  this  number  may  be 
increased  by  the  development  of  a  cervical  or  lumbar  rib,  or  may  be  diminished 
to  eleven.  The  first  seven  are  connected  behind  with  the  vertebral  column,  and  in 
front,  through  the  intervention  of  the  costal  cartilages,  with  the  sternum  (Fig. 
259);  they  are  called  true  or  vertebro-sternal  ribs.^     The  remaining  five  are  false 

1  Out  of  141  sterna  between  the  time  of  birth  and  the  age  of  sixteen  years,  Paterson  (op.  cit.)  found  the  fourth  or 
lowest  centre  for  the  body  present  only  in  thirty-eight  cases — i.  e.,  26.9  per  cent. 

2  Sometimes  the  eighth  rib  cartilage  articulates  with  the  sternum;  this  condition  occurs  more  frequently  on  the 
right  than  on  the  left  side. 


THE  RIBS 


221 


ribs;  of  thos{>,  the  first  three  have  their  cartihiges  attached  to  the  cartilage  of  the 
rib  above  (vertebro-chondral) :  the  hist  two  are  free  at  their  anterior  extremities 


Non-articular  pari  of  tubercle 

Articular  part  o,"  tubercle 


Fig.  266. — A  central  rib  of  the  left  side. 
Inferior  aspect. 


and  are  termed  floating  or  vertebral  ribs.  The 
ribs  vary  in  their  direction,  the  ni)per  ones 
being  less  oblique  than  the  lower;  the  obliquity 
reaches  its  maximum  at  the  ninth  rib,  and 
gradually  decreases  from  that  rib  to  the 
twelfth.  The  ribs  are  situated  one  below  the 
other  in  such  a  manner  that  spaces  called 
intercostal  spaces  are  left  between  them.  The 
length  of  each  space  corresponds  to  that  of 
the  adjacent  ribs  and  their  cartilages;  the 
breadth  is  greater  in  front  than  behind,  and 
between  the  upper  than  the  lower  ribs.  The 
ribs  increase  in  length  from  the  first  to  the 
seventh,  below  which  they  diminish  to  the 
twelfth.  In  breadth  they  decrease  from  above 
downward;  in  the  upper  ten  the  greatest 
breadth  is  at  the  sternal  extremity. 

Common  Characteristics  of  the  Ribs  (Figs. 
266,  267).— A  rib  from  the  middle  of  the 
series  should  be  taken  in  order  to  study  the 
common  characteristics  of  these  bones. 

Each  rib  has  two  extremities,  a  posterior  or 
vertebral,  and  an  anterior  or  sternal,  and  an 
intervening  portion — the  body  or  shaft. 

Posterior  Extremity. — The  posterior  or  verte- 
bral extremity  presents  for  examination  a  head, 
neck,  and  tubercle. 

The  head  is  marked  by  a  kidney-shaped 
articular  surface,  divided  by  a  horizontal 
crest  into  two  facets  for  articulation  with 
the  depression  formed  by  the  junction  of 
the  bodies  of  two  contiguous  thoracic  verte- 
brae; the  upper  facet  is  the  smaller;  to  the 
crest  is  attached  the  interarticular  ligament. 
The  neck  is  the  flattened  portion  which 
extends  lateralward  from  the  head;  it  is 
about  2.5  cm.  long,  and  is  placed  in  front  of 
the  transverse  process  of  the  lower  of  the  two 
vertebrae  with  which  the  head  articulates.  Its 
anterior  surface  is  flat  and  smooth,  its  posterior 
rough  for  the  attachment  of  the  ligament  of  the 


222  OSTEOLOGY 

neck,  and  perforated  by  numerous  foramina.  Of  its  two  borders  the  superior  presents 
a  rough  crest  (crista  colli  costae)  for  the  attachment  of  the  antericjr  costotransverse 
Hgament;  its  inferior  border  is  rounded.  On  the  posterior  surface  at  the  junction 
of  the  neck  and  body,  and  nearer  the  lower  than  the  upper  border,  is  an  eminence 
— the  tubercle;  it  consists  of  an  articular  and  a  non-articular  portion.  The  articular 
jjortion,  the  lower  and  more  medial  of  the  two,  presents  a  small,  oval  surface  for 
articulation  with  the  end  of  the  transverse  process  of  the  lower  of  the  two  ^•e^tebrai 
to  which  the  head  is  connected.  The  ncm-articvlar  yrjrtion  is  a  rough  elevation, 
and  affords  attachment  to  the  ligament  of  the  tubercle.  The  tubercle  is  much  more 
prominent  in  the  upper  than  in  the  lower  ribs. 

Body. — The  body  or  shaft  is  thin  and  flat,  with  two  surfaces,  an  external  and  an 
internal ;  and  two  borders,  a  superior  and  an  inferior.  The  external  surface  is  convex, 
smooth,  and  marked,  a  little  in  front  of  the  tubercle,  by  a  prominent  line,  directed 
downward  and  lateralward;  this  gives  attachment  to  a  tendon  of  the  Iliocostalis, 
and  is  called  the  angle.  At  this  point  the  rib  is  bent  in  two  directions,  and  at  the 
same  time  twisted  on  its  long  axis.  If  the  rib  be  laid  upon  its  lower  border,  the 
portion  of  the  body  in  front  of  the  angle  rests  upon  this  border,  while  the  portion 
behind  the  angle  is  bent  medialward  and  at  the  same  time  tilted  upward;  as  the 

Bemifacet  for  vertebra 
-  Interarticular  crest 
DemifrMet  for  vertebra 


Costal  groove 


Fig.  267. — A  central  rib  of  the  left  side,  vie-sved  from  behind. 

result  of  the  twisting,  the  external  surface,  behind  the  angle,  looks  downward, 
and  in  front  of  the  angle,  slightly  upward.  The  distance  between  the  angle  and  the 
tubercle  is  progressively  greater  from  the  second  to  the  tenth  ribs.  The  portion 
between  the  angle  and  the  tubercle  is  rounded,  rough,  and  irregular,  and  serves 
for  the  attachment  of  the  Longissimus  dorsi.  The  external  surface  presents, 
toward  its  sternal  end,  an  oblique  line,  the  anterior  angle.  The  internal  surface 
is  concave,  smooth,  directed  a  little  upward  behind  the  angle,  a  little  downward 
in  front  of  it,  and  is  marked  by  a  ridge  which  commences  at  the  lower  extremity 
of  the  head;  this  ridge  is  strongly  marked  as  far  as  the  angle,  and  gradually  becomes 
lost  at  the  junction  of  the  anterior  and  middle  thirds  of  the  bone.  Between  it 
and  the  inferior  border  is  a  groove,  the  costal  groove,  for  the  intercostal  vessels 
and  nerve.  At  the  back  part  of  the  bone,  this  groove  belongs  to  the  inferior  border, 
but  just  in  front  of  the  angle,  where  it  is  deepest  and  broadest,  it  is  on  the  internal 
surface.  The  superior  edge  of  the  groove  is  rounded  and  serves  for  the  attach- 
ment of  an  Intercostalis  internus;  the  inferior  edge  corresponds  to  the  lower 
margin  of  the  rib,  and  gives  attachment  to  an  Intercostalis  externus.  ^Yithin 
the  groove  are  seen  the  orifices  of  numerous  small  foramina  for  nutrient  vessels 


THE  Rllii^, 


223 


which  traverse  the  shaft  ohHqiiely  from  l)et'()re  backward.  The  superior  border, 
thick  and  rounded,  is  marked  by  an  external  and  an  internal  hp,  more  distinct 
behind  than  in  front,  which  serve  for  the  attachment  of  Interc^ostales  externus 
and  internus.  The  inferior  border  is  thin,  and  has  attached  to  it  an  Intercostahs 
extennis. 

Anterior  Extremity.—  The  anterior  or  sternal  extremity  is  flattened,  and  presents  a 
porous,  o\al,  concave  depression,  into  whicli  tlie  c(jstal  cartilage  is  received. 


Fig.  268 


Fig 


Aiigle- 


FiG.  271 
Single  articular  facet 


Fig.  272 
Single  articular  facet 


Figs.  268  to  272. — Peculiar  ribs. 


Peculiar  Ribs. — The  first,  second,  tenth,  eleventh,  and  twelfth  ribs  present 
certain  variations  from  the  common  characteristics  described  above,  and  require 
special  consideration. 

First  Rib. — The  first  rib  (Fig.  268)  is  the  most  curved  and  usually  the  shortest 
of  all  the  ribs;  it  is  broad  and  flat,  its  surfaces  looking  upward  and  downward, 
and  its  borders  inward  and  outward.     The  head  is  small,  rounded,  and  possesses 


224  OSTEOLOGY 

only  a  single  articular  facet,  for  articulation  with  the  body  of  the  first  thoracic 
vertebra.  The  neck  is  narrow  and  rounded.  The  tubercle,  thick  and  prominent, 
is  placed  on  the  outer  border.  There  is  no  angle,  but  at  the  tubercle  the  rib  is 
slightly  bent,  with  the  convexity  upward,  so  that  the  head  of  the  bone  is  directed 
downward.  The  upper  surface  of  the  body  is  marked  by  two  shallow  grooves, 
separated  from  each  other  by  a  slight  ridge  prolonged  internally  into  a  tubercle, 
the  scalene  tubercle,  for  the  attachment  of  the  Scalenus  anterior;  the  anterior 
groove  transmits  the  subclavian  vein,  the  posterior  the  subclavian  artery  and 
the  lowest  trunk  of  the  brachial  plexus.^  Behind  the  posterior  groove  is  a  rough 
area  for  the  attachment  of  the  Scalenus  medius.  The  under  surface  is  smooth, 
and  destitute  of  a  costal  groove.  The  outer  border  is  convex,  thick,  and  rounded, 
and  at  its  posterior  part  gives  attachment  to  the  first  digitation  of  the  Serratus 
anterior;  the  inner  border  is  concave,  thin,  and  sharp,  and  marked  about  its  centre 
by  the  scalene  tubercle.  The  anterior  extremity  is  larger  and  thicker  than  that 
of  any  of  the  other  ribs. 

Second  Rib. — The  second  rib  (Fig.  269)  is  much  longer  than  the  first,  but  has  a 
very  similar  curvature.  The  non-articular  portion  of  the  tubercle  is  occasionally 
only  feebly  marked.  The  angle  is  slight,  and  situated  close  to  the  tubercle.  The 
body  is  not  twisted,  so  that  both  ends  touch  any  plane  surface  upon  which  it  may 
be  laid;  but  there  is  a  bend,  with  its  convexity  upward,  similar  to,  though  smaller 
than  that  found  in  the  first  rib.  The  body  is  not  flattened  horizontally  like  that 
of  the  first  rib.  Its  external  surface  is  convex,  and  looks  upward  and  a  little  outward ; 
near  the  middle  of  it  is  a  rough  eminence  for  the  origin  of  the  lower  part  of  the 
first  and  the  whole  of  the  second  digitation  of  the  Serratus  anterior;  behind  and 
above  this  is  attached  the  Scalenus  posterior.  The  internal  surface,  smooth,  and 
concave,  is  directed  downward  and  a  little  inward:  on  its  posterior  part  there  is 
a  short  costal  groove. 

Tenth  Rib. — The  tenth  rib  (Fig.  270)  has  only  a  single  articular  facet  on  its  head. 

Eleventh  and  Twelfth  Ribs. — The  eleventh  and  twelfth  ribs  (Figs.  271  and  272) 
have  each  a  single  articular  facet  on  the  head,  which  is  of  rather  large  size;  they 
have  no  necks  or  tubercles,  and  are  pointed  at  their  anterior  ends.  The  eleventh 
has  a  slight  angle  and  a  shallow  costal  groove.  The  twelfth  has  neither;  it  is  much 
shorter  than  the  eleventh,  and  its  head  is  inclined  slightly  downward.  Sometimes 
the  twelfth  rib  is  even  shorter  than  the  first. 

Structure. — The  ribs  consist  of  highly  vascular  cancellous  tissue,  enclosed  in  a  thin  layer  of 
compact    bone. 

Ossification. — ^Each  rib,  with  the  exception  of  the  last  two,  is  ossified  from  four  centres;  a 
primary  centre  for  the  body,  and  three  epiphysial  centres,  one  for  the  head  and  one  each  for  the 
articular  and  non-articular  parts  of  the  tubercle.  The  eleventh  and  twelfth  ribs  have  each  only 
two  centres,  those  for  the  tubercles  being  wanting.  Ossification  begins  near  the  angle  toward  the 
end  of  the  second  month  of  fetal  Ufe,  and  is  seen  first  in  the  sixth  and  seventh  ribs.  The  epiphyses 
for  the  head  and  tubercle  make  their  appearance  between  the  sixteenth  and  twentieth  years,  and 
are  united  to  the  body  about  the  twenty-fifth  year.  Fawcett^  states  that  "in  all  probability  there 
is  usually  no  epiphysis  on  the  non-articular  part  of  the  tuberosity  below  the  sixth  or  seventh  rib. 

The  Costal  Cartilages  (Cartilagines  Costales). 

The  costal  cartilages  (Fig.  259)  are  bars  of  hyaline  cartilage  w^hich  serve  to 
prolong  the  ribs  forward  and  contribute  very  materially  to  the  elasticity  of  the 
walls  of  the  thorax.  The  first  seven  pairs  are  connected  with  the  sternum;  the 
next  three  are  each  articulated  with  the  lower  border  of  the  cartilage  of  the  pre- 
ceding rib;  the  last  two  have  pointed  extremities,  which  end  in  the  wall  of  the 
abdomen.    Like  the  ribs,  the  costal  cartilages  vary  in  their  length,  breadth,  and 

lAnat.  Anzeiger,  1910,  Band  xxxvi.  .  2  Journal  of  Anatomy  and  Physiology,  vol.  xlv. 


THE  COSTAL  CARTILAGES  225 

direction.  They  increase  in  length  from  the  first  to  the  seventh,  then  gradually 
decrease  to  the  twelfth.  Their  breadth,  as  well  as  that  of  the  intervals  between 
them,  diminishes  from  the  first  to  the  last.  They  are  broad  at  their  attachments 
to  the  ribs,  and  taper  toward  their  sternal  extremities,  excepting  the  first  two, 
which  are  of  the  same  breadth  throughout,  and  the  sixth,  seventh,  and  eighth, 
which  are  enlarged  where  their  margins  are  in  contact.  They  also  vary  in  direc- 
tion: the  first  descends  a  little,  the  second  is  horizontal,  the  third  ascends  slightly, 
while  the  others  are  angular,  following  the  course  of  the  ribs  for  a  short  distance, 
and  then  ascending  to  the  sternum  or  preceding  cartilage.  Each  costal  cartilage 
presents  two  surfaces,  two  borders,  and  two  extremities. 

Surfaces. — The  anterior  surface  is  convex,  and  looks  forward  and  upward:  that 
of  the  first  gives  attachment  to  the  costoclavicular  ligament  and  the  Subclavius 
muscle;  those  of  the  first  six  or  seven  at  their  sternal  ends,  to  the  Pectoralis  major. 
The  others  are  covered  by,  and  give  partial  attachment  to,  some  of  the  flat  muscles 
of  the  abdomen.  The  posterior  surface  is  concave,  and  directed  backward  and 
downward;  that  of  the  first  gives  attachment  to  the  Sternothyroideus,  those  of 
the  third  to  the  sixth  inclusive  to  the  Transversus  thoracis,  and  the  six  or  seven 
inferior  ones  to  the  Transversus  abdominis  and  the  Diaphragma. 

Borders. — Of  the  two  borders  the  superior  is  concave,  the  inferior  convex;  they 
afford  attachment  to  the  Intercostales  interni :  the  upper  border  of  the  sixth  gives 
attachment  also  to  the  Pectoralis  major.  The  inferior  borders  of  the  sixth,  seventh, 
eighth,  and  ninth  cartilages  present  heel-like  projections  at  the  points  of  greatest 
convexity.  These  projections  carry  smooth  oblong  facets  which  articulate  respec- 
tively with  facets  on  slight  projections  from  the  upper  borders  of  the  seventh, 
eighth,  ninth,  and  tenth  cartilages. 

Extremities. — The  lateral  end  of  each  cartilage  is  continuous  with  the  osseous 
tissue  of  the  rib  to  which  it  belongs.  The  medial  end  of  the  first  is  continuous 
with  the  sternum;  the  medial  ends  of  the  six  succeeding  ones  are  rounded  and  are 
received  into  shallow  concavities  on  the  lateral  margins  of  the  sternum.  The 
medial  ends  of  the  eighth,  ninth,  and  tenth  costal  cartilages  are  pointed,  and  are 
connected  each  with  the  cartilage  immediately  above.  Those  of  the  eleventh  and 
twelfth  are  pointed  and  free.  In  old  age  the  costal  cartilages  are  prone  to  undergo 
superficial  ossification. 

Applied  Anatomy. — Fracture  of  the  sternum  is  by  no  means  common,  owing,  no  doubt,  to  the 
elasticity  of  the  ribs  and  their  cartilages  which  support  it  like  so  many  springs.  The  fracture 
usually  occurs  in  the  upper  half  of  the  body.  Dislocation  of  the  body  from  the  manubrium  may 
take  place,  and  is  sometimes  described  as  a  fracture. 

The  bone  is  frequently  the  seat  of  gummatous  tumors  and  not  uncommonly  is  affected  with 
caries. 

The  ribs  are  frequently  broken,  though  from  their  connections  and  shape  they  are  able  to 
withstand  great  force,  yielding  under  the  injury  and  recovering  themselves  hke  a  spring.  The 
middle  ribs  are  the  most  hable  to  fracture.  The  first  and  to  a  less  extent  the  second,  being  pro- 
tected by  the  clavicle,  are  rarely  fractured;  and  the  eleventh  and  twelfth  on  account  of  their 
loose  and  floating  condition  enjoy  a  like  immimity.  The  fracture  generally  occiirs  from  indirect 
violence,  from  forcible  compression  of  the  chest  wall,  and  the  bone  then  gives  way  at  its  weakest 
part,  i.  e.,  just  in  front  of  the  angle.  But  the  ribs  may  also  be  broken  by  direct  violence,  in  which 
case  the  bone  is  driven  inward  at  the  point  struck.  Fractm-e  of  the  ribs  is  frequently  comphcated 
with  some  injury  to  the  viscera  contained  within  the  thorax  or  upper  part  of  the  abdominal  caAdty; 
this  is  most  likely  to  occur  in  fractures  from  direct  violence. 

Fracture  of  the  costal  cartilages  or  separation  of  the  cartilages  from  the  ribs,  may  also  take 
place,  though  they  are  comparatively  rare  injuries.  In  workmen  the  pressure  of  tools  may  dis- 
place the  xiphoid  process  inward. 

The  ribs  are  frequently  the  seat  of  tuberculous  disease,  with  the  formation  of  a  chronic  abscess 
in  the  chest  wall.  This  may  not  immediately  overlie  the  carious  portion  of  rib,  as  the  pus  is 
often  directed  a  considerable  distance  along  the.  costal  groove  before  appearing  beneath  the 
integument. 

Resection  of  a  portion  of  a  rib  is  often  required  in  order  to  give  efficient  drainage  to  an  empyema; 
this  is  referred  to  in  the  description  of  the  respiratory  organs. 
15 


226  OSTEOLOGY 

Cervical  ribs  derived  from  the  seventh  cervical  vertebra  (i)age  201)  are  of  not  infrequent  occur- 
rence, and  are  important  clinically  because  they  may  give  rise  to  obscure  nervous  or  vascular 
symptoms.  The  cervical  rib  may  be  a  mere  epiphysis  articulating  only  with  the  transverse  process 
of  the  vertebra,  but  more  commonly  it  consists  of  a  defined  head,  neck,  and  tubercle,  with  or 
without  a  body.  It  extends  lateralward,  or  forward  and  lateralward,  into  the  posterior  triangle 
of  the  neck,  where  it  may  terminate  in  a  free  end  or  may  join  the  first  thoracic  rib,  the  first  costal 
cartilage,  or  the  sternum.^  It  varies  much  in  shape,  size,  direction,  and  mobility.  If  it  reach 
far  enough  forward,  part  of  the  brachial  plexus  and  the  subclavian  artery  and  vein  cross  over 
it,  and  are  apt  to  suffer  compression  in  so  doing.  Pressure  on  the  artery  may  obstruct  the  circula- 
tion so  much  that  arterial  thrombosis  results,  causing  gangrene  of  the  finger  tips.  Pressure  on 
the  nerves  is  commoner,  and  affects  the  eighth  cervical  and  first  thoracic  nerves,  causing  paralysis 
of  the  muscles  they  supply,  and  neuralgic  pains  and  paresthesia  in  the  area  of  skin  to  which  they 
are  distributed :  no  oculopupillary  changes  are  to  be  found.  If  these  symptoms  be  severe,  removal 
of  the  rib  or  as  much  of  it  as  causes  pressure  on  the  vessels  and  nerves  is  called  for.  The  operation 
is  not  free  from  difficulty,  and  has  been  followed  by  paralysis  of  the  muscles  and  by  subclavian 
aneiu'ism,  due  to  injuries  inflicted  in  the  course  of  the  operation. 

The  thorax  is  frequently  found  to  be  altered  in  shape  in  certain  diseases. 

In  rickets,  the  ends  of  the  ribs,  where  they  join  the  costal  cartilages,  become  enlarged,  giving 
rise  to  the  so-called  "rickety  rosary,"  which  in  mild  cases  is  only  found  on  the  internal  surface 
of  the  thorax.  Lateral  to  these  enlargements  the  softened  ribs  sink  in,  so  as  to  present  a  groove 
passing  downward  and  lateralward  on  either  side  of  the  sternum.  This  bone  is  forced  forward 
by  the  bending  of  the  ribs,  and  the  antero-posterior  diameter  of  the  chest  is  increased.  The  ribs 
affected  are  the  second  to  the  eighth,  the  lower  ones  being  prevented  from  falling  in  by  the  pres- 
ence of  the  liver,  stomach,  and  spleen;  and  when  the  abdomen  is  distended,  as  it  often  is  in  rickets, 
the  lower  ribs  may  be  pushed  outward,  causing  a  transverse  groove  (Harrison's  sulcus)  just 
above  the  costal  arch.  This  deformity  or  forward  projection  of  the  sternum,  often  asymmetrical, 
is  known  as  pigeon  breast,  and  may  be  taken  as  evidence  of  active  or  old  rickets  except  in  cases 
of  primary  spinal  curvature.  In  many  instances  it  is  associated  in  children  with  obstruction  in 
the  upper  air  passages,  due  to  enlarged  tonsils  or  adenoid  growths.  In  some  rickety  children  or 
adults,  and  also  in  others  who  give  no  history  or  further  evidence  of  having  had  rickets,  an  opposite 
condition  obtains.  The  lower  part  of  the  sternum  and  often  the  xiphoid  process  as  well  are  deeply 
depressed  backward,  producing  an  oval  hollow  in  the  lower  sternal  and  upper  epigastric  regions. 
This  is  known  as  funnel  breast  (German,  Trichterbrust) ;  it  never  appears  to  produce  the  least 
disturbance  of  any  of  the  vital  functions.  The  phthisical  chest  is  often  long  and  narrow,  and  with 
great  obliquity  of  the  ribs  and  projection  of  the  scapulse  In  pulmonary  empMjsejua  the  chest  is 
enlarged  in  all  its  diameters,  and  presents  on  section  an  almost  circular  outhne.  It  has  received 
the  name  of  the  barrel-shaped  chest.  In  severe  cases  of  lateral  curvature  of  the  vertebral  column 
the  thorax  becomes  much  distorted.  In  consequence  of  the  rotation  of  the  bodies  of  the  vertebrae 
which  takes  place  in  this  disease,  the  ribs  opposite  the  convexity  of  the  dorsal  curve  become 
extremely  convex  behind,  being  thrown  out  and  bulging,  and  at  the  same  time  flattened  in  front, 
so  that  the  two  ends  of  the  same  rib  are  almost  parallel.  Coincidently  with  this  the  ribs  on  the 
opposite  side,  on  the  concavity  of  the  curve,  are  sunk  and  depressed  behind,  and  bulging  and 
convex  in  front. 

It  is  commonly  said  that  in  tuberculosis  of  the  lungs  the  chest  is  characteristically  "flat," 
that  is  to  say,  that  the  ratio  of  its  antero-posterior  to  its  transverse  diameter  is  less  than  the 
normal.  But  by  careful  measurement  in  a  large  number  of  cases.  Woods  Hutchinson  has  shown 
that  this  is  not  so.  Taking  the  transverse  diameter  of  the  chest  at  the  nipple  level  as  =  100,  he 
finds  that  in  the  normal  adult  man  between  the  ages  of  twenty  and  forty-four  the  antero-posterior 
diameter  =71.  In  82  phthisical  subjects  it  was  =79.5,  and  in  30  "flat-chested"  persons  was  = 
80.  He  explains  the  error  as  an  optical  illusion,  due  to  rolUng  forward  of  the  shoulders  in  the 
"fiat  chested;"  the  back  is  seen  to  be  correspondingly  rounded  and  protuberant,  while  the  forward 
position  of  the  shoulders  and  clavicles  lends  an  appearance  of  flattening  to  the  chest. 

More  or  less  shrinkage  of  one  side  of  the  thorax  is  often  seen  as  a  consequence  of  adhesive 
pleurisy,  in  which  the  pulmonary  and  parietal  pleural  adhere  closely  to  one  another  and  the  lung 
becomes  collapsed  and  fibrosed.  If  this  process  be  at  all  complete,  great  deformity  of  the  chest 
results,  the  ribs  on  the  affected  side  faUing  in,  together  with  obliteration  of  the  intercostal  spaces; 
the  contents  of  the  mediastinal  cavity  are  pulled  over  toward  the  affected  side,  the  other  lung 
becomes  emphysematous  compensatorily.  The  vertebral  column  becomes  scoUotic,  with  the 
concavity  of  the  curve  toward  the  affected  side. 

THE   SKULL. 

The  skull  is  supported  on  the  summit  of  the  vertebral  column,  and  is  of  an 
oval  shape,  wider  behind  than  in  front.     It  is  composed  of  a  series  of  flattened 

1  W.  Thorburn,  The  Medical  Chronicle,  Manchester,  1907,  4th  series,  xiv.  No.  3. 


THE  OCCIPITAL  BONE 


00" 


or  irregular  hones  which,  willi  one  exception  (the  mandible),  are  immovably 
jointed  together.  It  is  di\isihle  into  two  ])arts:  (1)  the  cranium,  which  lodges 
and  protects  the  brain,  consists  of  eight  bones,  and  (2)  the  skeleton  of  the  face, 
of  fourteen,  as  follows: 


Skull,  22  bones 


Cranium,  S  bones 


()ccii)ital. 

Two  Parietals. 

Frontal. 

Two  Temporals. 

Sphenoidal. 

Ethmoidal. 


I  Face,  14  bones 


Two  Nasals. 

Two  Maxillae. 

Two  Lacrimals. 

Two  Zygomatics. 

Two  Palatines. 
j  Two  Inferior  Nasal  Conchse. 
I  Vomer. 
l^  Mandible. 

In  the  Basle  nomenclature,  certain  bones  developed  in  association  with  the  nasal 
capsule,  viz.,  the  inferior  nasal  conchse,  the  lacrimals,  the  nasals,  and  the  vomer, 
are  grouped  as  cranial  and  not  as  facial  bones. 

The  hyoid  bone,  situated  at  the  root  of  the  tongue  and  attached  to  the  base 
of  the  skull  by  ligaments,  is  described  in  this  section. 


THE    CRANIAL   BONES    (OSSA    CRANII). 


The  Occipital  Bone  (Os  Occipitale). 

The  occipital  bone  (Figs.  273,  274),  situated  at  the  back  and  lower  part  of  the 
cranium,  is  trapezoid  in  shape  and  curved  on  itself.  It  is  pierced  by  a  large  oval 
aperture,  the  foramen  magnum,  through  which  the  cranial  cavity  communicate 
with  the  vertebral  canal. 

The  curved,  expanded  plate  behind  the  foramen  magnum  is  named  the  squama ; 
the  thick,  somewhat  quadrilateral  piece  in  front  of  the  foramen  is  called  the 
basilar  part,  whilst  on  either  side  of  the  foramen  is  the  lateral  portion. 

The  Squama  {squama  occiijitalis) . — The  squama,  situated  above  and  behind 
the  foramen  magnum,  is  curved  from  above  downward  and  from  side  to  side. 

Surfaces. — The  external  surface  is  convex  and  presents  midway  between  the 
summit  of  the  bone  and  the  foramen  magnum  a  prominence,  the  external  occipital 
protuberance.  Extending  lateralward  from  this  on  either  side  are  two  curved 
lines,  one  a  little  above  the  other.  The  upper,  often  faintly  marked,  is  named 
the  highest  nuchal  line,  and  to  it  the  galea  aponeurotica  is  attached.  The  lower 
is  termed  the  superior  nuchal  line.  That  part  of  the  squama  which  lies  above 
the  highest  nuchal  lines  is  named  the  planum  occipitale,  and  is  covered  by  the 
Occipitalis  muscle;  that  below,  termed  the  planum  nuchale,  is  rough  and  irregular 
for  the  attachment  of  several  muscles.  From  the  external  occipital  protuberance 
a  ridge  or  crest,  the  median  nuchal  line,  often  faintly  marked,  descends  to  the  fora- 
men magnum,  and  affords  attachment  to  the  ligamentum  nuchae;  running  from 
the  middle  of  this  line  across  either  half  of  the  nuchal  plane  is  the  inferior  nuchal 
line.  Several  muscles  are  attached  to  the  outer  surface  of  the  squama,  thus: 
the  superior  nuchal  line  gives  origin  to  the  Occipitalis  and  Trapezius,  and  insertion 


228 


OSTEOLOGY 


to  the  Stemocleidomastoideiis  and  Splenius  capitis:  into  the  surface  between 
the  superior  and  inferior  nuchal  hues  the  Semispinalis  capitis  and  the  Obhquus 
capitis  superior  are  inserted,  while  the  inferior  nuchal  line  and  the  area  below 
it  receive  the  insertions  of  the  Recti  capitis  posteriores  major  and  minor.  The 
posterior  atlantooccipital  membrane  is  attached  around  the  postero-lateral  part 
of  the  foramen  magnum,  just  outside  the  margin  of  the  foramen. 


Highest 
nuchal  line 


Hypoglossal  canal 


Fig.   273. — Occipital  bone.     Outer  surface. 


The  internal  surface  is  deeply  concave  and  divided  into  four  fossae  by  a  cruciate 
eminence.  The  upper  two  fossae  are  triangular  and  lodge  the  occipital  lobes  of 
the  cerebrum;  the  lower  two  are  quadrilateral  and  accommodate  the  hemispheres 
of  the  cerebellum.  At  the  point  of  intersection  of  the  four  divisions  of  the  cruciate 
eminence  is  the  internal  occipital  protuberance.  From  this  protuberance  the  upper 
division  of  the  cruciate  eminence  runs  to  the  superior  angle  of  the  bone,  and  on 
one  side  of  it  (generally  the  right)  is  a  deep  groove,  the  sagittal  sulcus,  which  lodges 
the  hinder  part  of  the  superior  sagittal  sinus;  to  the  margins  of  this  sulcus  the  falx 
cerebri  is  attached.  The  low^er  division  of  the  cruciate  eminence  is  prominent, 
and  is  named  the  internal  occipital  crest;  it  bifurcates  near  the  foramen  magnum 
and  gives  attachment  to  the  falx  cerebelli;  in  the  attached  margin  of  this  falx 
is  the  occipital  sinus,  which  is  sometimes  duplicated.  In  the  upper  part  of  the 
internal  occipital  crest,  a  small  depression  is  sometimes  distinguishable;  it  is 
termed  the  vermian  fossa  since  it  is  occupied  by  part  of  the  vermis  of  the  cerebellum. 
Transverse  grooves,  one  on  either  side,  extend  from  the  internal  occipital  protuber- 
ance to  the  lateral  angles  of  the  bone;  those  grooves  accommodate  the  transverse 
sinuses,  and  their  prominent  margins  give  attachment  to  the  tentorium  cerebelli. 
The  groove  on  the  right  side  is  usually  larger  than  that  on  the  left,  and  is 


THE  OCCIPITAL  BONE 


229 


continuous  with  that  for  the  superior  sagittal  sinus.  Exceptions  to  this  condition 
are,  however,  not  infrequent;  the  left  may  he  larger  than  the  right  or  the  two 
may  be  almost  equal  in  size.  Tlie  angle  of  union  of  the  superior  sagittal  and  trans- 
verse sinuses  is  named  the  confluence  of  the  sinuses  {torcular  Ilerophili^),  and  its 
position  is  indicated  by  a  depression  situated  on  one  or  other  side  of  the 
protuberance. 

Sitlierio  f  A  ng  le  ' 

S  u  //  ej. 


Tnfe.Tiov  Anqlp  \^^ 

Fig.  274. — Occipital  bone.     Inner  surface. 

Lateral  Parts  {pars  lateralis). — The  lateral  parts  are  situated  at  the  sides  of 
the  foramen  magnum;  on  their  under  surfaces  are  the  condyles  for  articulation 
with  the  superior  facets  of  the  atlas.  The  condyles  are  oval  or  reniform  in  shape, 
and  their  anterior  extremities,  directed  forward  and  medialward,  are  closer  together 
than  their  posterior,  and  encroach  on  the  basilar  portion  of  the  bone;  the  posterior 
extremities  extend  back  to  the  level  of  the  middle  of  the  foramen  magnum.  The 
articular  surfaces  of  the  condyles  are  convex  from  before  backward  and  from 
side  to  side,  and  look  downward  and  lateralward.  To  their  margins  are  attached 
the  capsules  of  the  atlantooccipital  articulations,  and  on  the  medial  side  of  each 
is  a  rough  impression  or  tubercle  for  the  alar  ligament.  At  the  base  of  either 
condyle  the  bone  is  tunnelled  by  a  short  canal,  the  hypoglossal  canal  {anterior 
condyloid  foramen) .  This  begins  on  the  cranial  surface  of  the  bone  immediately 
above  the  foramen  magnum,  and  is  directed  lateralward  and  forward  above  the 

1  The  columns  of  blood  coming  in  different  directions  were  suppo.sed  to  be  pressed  together  at  this  point  {torcular, 
a  wine  press). 


230     .  OSTEOLOGY 

condyle.  It  may  be  partially  or  completely  divided  into  two. by  a  spicule  of  bone; 
it  trives  exit  to  the  hypoglossal  or  twelfth  cerebral  nerve,  and  entrance  to  a  meningeal 
brancJi  of  the  ascending  pharyngeal  artery.  Behind  either  condyle  is  a  depression, 
the  condyloid  fossa,  which  receives  the  posterior  margin  of  the  superior  facet  of 
the  atlas  when  the  head  is  bent  backward;  the  floor  of  this  fossa  is  sometimes 
perforated  by  the  condyloid  canal,  through  which  an  emissary'  vein  passes  from  the 
transverse  sinus.  p]xtending  laterahvard  from  the  posterior  half  of  the  condyle 
is  a  quadrilateral  plate  of  bone,  the  jugular  process,  excavated  in  front  by  the  jugular 
notch,  which,  in  the  articulated  skull,  forms  the  posterior  part  of  the  jugular  fora- 
men. The  jugular  notch  may  be  divided  into  two  by  a  bony  spicule,  the  intra- 
jugular  process,  which  projects  lateralward  above  the  hypoglossal  canal.  The 
under  surface  of  the  jugular  process  is  rough,  and  gives  attachment  to  the  Rectus 
capitis  lateralis  muscle  and  the  lateral  atlantooccipital  ligament;  from  this 
surface  an  eminence,  the  paramastoid  process,  sometimes  projects  downward,  and 
may  be  of  sufficient  length  to  reach,  and  articulate  with,  the  transverse  process 
of  the  atlas.  Laterally  the  jugular  process  presents  a  rough  quadrilateral  or  tri- 
angular area  which  is  joined  to  the  jugular  surface  of  the  temporal  bone  by  a  plate 
of  cartilage;  after  the  age  of  twenty-five  this  plate  tends  to  ossify. 

The  upper  surface  of  the  lateral  part  presents  an  oval  eminence,  the  jugular 
tubercle,  which  overlies  the  hypoglossal  canal  and  is  sometimes  crossed  by  an 
oblique  groove  for  the  glossopharyngeal,  vagus,  and  accessory  nerves.  On  the 
upper  surface  of  the  jugular  process  is  a  deep  groove  which  curves  medialward 
and  forward  and  is  continuous  with  the  jugular  notch.  This  groove  lodges  the 
terminal  part  of  the  transverse  sinus,  and  opening  into  it,  close  to  its  medial 
margin,  is  the  orifice  of  the  condyloid  canal. 

Basilar  Part  (/pars  basilaris). — The  basilar  part  extends  forward  and  upward 
from  the  foramen  magnum,  and  presents  in  front  an  area  more  or  less  quadrilateral 
in  outline.  In  the  young  skull  this  area  is  rough  and  uneven,  and  is  joined  to  the 
body  of  the  sphenoid  by  a  plate  of  cartilage.  By  the  twenty-fifth  yesLT  this  cartil- 
aginous plate  is  ossified,  and  the  occipital  and  sphenoid  form  a  continuous  bone. 

Surfaces. — On  its  lower  surface,  about  1  cm.  in  front  of  the  foramen  magnum, 
is  the  pharyngeal  tubercle  which  gives  attachment  to  the  fibrous  raphe  of  the  pharynx. 
On  either  side  of  the  middle  line  the  Longus  capitis  and  Rectus  capitis  anterior 
are  inserted,  and  immediately  in  front  of  the  foramen  magnum  the  anterior 
atlantooccipital  membrane  is  attached. 

The  upper  surface  presents  a  broad,  shallow  groove  which  inclines  upward 
and  forward  from  the  foramen  magnum;  it  supports  the  medulla  oblongata,  and 
near  the  margin  of  the  foramen  magnum  gives  attachment  to  the  membrana 
tectoria.  On  the  lateral  margins  of  this  surface  are  faint  grooves  for  the  inferior 
petrosal  sinuses. 

Foramen  Magnum. — The  foramen  magnum  is  a  large  oval  aperture  with  its  long 
diameter  antero-posterior ;  it  is  wider  behind  than  in  front  where  it  is  encroached 
upon  by  the  condyles.  It  transmits  the  medulla  oblongata  and  its  membranes, 
the  accessory  nerves,  the  vertebral  arteries,  the  anterior  and  posterior  spinal 
arteries,  and  the  membrana  tectoria  and  alar  ligaments. 

Angles. — The  superior  angle  of  the  occipital  bone  articulates  with  the  occipital 
angles  of  the  parietal  bones  and,  in  the  fetal  skull,  corresponds  in  position  with  the 
posterior  fontanelle.  The  inferior  angle  is  fused  with  the  body  of  the  sphenoid. 
The  lateral  angles  are  situated  at  the  extremities  of  the  grooves  for  the  transverse 
sinuses:  each  is  received  into  the  interval  between  the  mastoid  angle  of  the  parietal 
and  the  mastoid  part  of  the  temporal. 

Borders.^ — The  superior  borders  extend  from  the  superior  to  the  lateral  angles: 
they  are  deeply  serrated  for  articulation  with  the  occipital  borders  of  the  parietals, 
and  form  bv  this  union  the  lambdoidal  suture.     The  inferior  borders  extend  from 


THE  PARIETAL  BOXE 


281 


the  lateral  aii.ules  to  the  inferior  aii^le;  the  upper  half  of  each  articulates  with 
the  mastoid  pt)rtion  of  the  corresponding  temporal,  the  lower  half  with  the  petrous 
part  of  the  same  bone.  These  two  portions  of  the  inferior  border  are  separated 
from  one  another  by  the  jugular  i)r()cess,  the  notch  on  the  anterior  surface  of  which 
forms  the  i)osterior  part  of  the  jugular  foramen. 


Planum 
occipitale 


Structure.— Tlu-  occipital,  like  the  otlier  cranial  bones,  consists  of  two  compact  lamellie,  called 
the  fluler  and  inner  tahlcti,  between  which  is  the  cancellous  tissue  or  diploe;  the  bone  is  especially 
thick  at  the  rido;es,  protuberances,  condyles,  and  anterior  part  of  the  basilar  jxirt;  in  the  inferior 
fosste  it  is  thin,  semitransparent,  and  destitute  of  diploe. 

Ossification  (^Fig.  275). — The  planum  occipitale  of  the  squama  is  developed  in  membrane, 
and  may  remain  separate  throughout  life  when  it  constitutes  the  interparietal  bone;  the  rest  of 
the  bone  is  developed  in  cartilage.  The  number 
of  nuclei  for  the  planum  occipitale  is  usually 
given  as  four,  two  appearing  near  the  middle  hne 
about  the  second  month,  and  two  some  little 
distance  from  the  middle  line  about  the  third 
month  of  fetal  life.  The  planum  nuchale  of  the 
squama  is  ossified  from  two  centres,  which  ap- 
pear about  the  seventh  week  of  fetal  life  and  soon 
unite  to  form  a  single  piece.  Union  of  the  upper 
and  lower  portions  of  the  squama  takes  place  in 
the  third  month  of  fetal  life.  An  occasional  centre 
(Kerckring)  appears  in  the  posterior  margin  of  the 
foramen  magnum  during  the  fifth  month;  this 
forms  a  separate  ossicle  (sometimes  double)  which 
unites  with  the  rest  of  the  squama  before  birth. 
Each  of  the  lateral  parts  begins  to  ossify  from  a 
single  centre  during  the  eighth  week  of  fetal  hfe. 
The  basilar  portion  is  ossified  from  two  centres, 
one  in  front  of  the  other;  these  appear  about  the 
sixth  week  of  fetal  Ufe  and  rapidly  coalesce.  MalP 
states  that  the  planum  occipitale  is  ossified  from 
two  centres  and  the  basilar  portion  from  one. 
About  the  fourth  year  the  squama  and  the  two 
lateral  portions  unite,  and  about  the  sixth  year 
the  bone  consists  of  a  single  piece.    Between  the 

eighteenth  and  twenty-fifth  years  the  occipital  and  sphenoid  become  united,  forming  a  single 
bone. 

Articulations. — The  occipital  articulates  with  six  bones:  the  two  parietals,  the  two  temporals, 
the  sphenoid,  and  the  atlas. 


Lateral 
part 


Basila)  part 


Fig.  275. — Occipital  bone  at  birth. 


The  Parietal  Bone  (Os  Parietale). 

The  parietal  bones  form,  by  their  union,  the  sides  and  roof  of  the  cranium.  Each 
bone  is  irregidarly  quadrilateral  in  form,  and  has  two  surfaces,  four  borders, 
and  four  angles. 

Surfaces. — The  external  surface  (Fig.  276)  is  convex,  smooth,  and  marked  near 
the  centre  by  an  eminence,  the  parietal  eminence  (tuber  parietale),  which  indicates 
the  point  where  ossification  commenced.  Crossing  the  middle  of  the  bone  in  an 
arched  direction  are  two  curved  lines,  the  superior  and  inferior  temporal  lines;  the 
former  gives  attacliment  to  the  temporal  fascia,  and  the  latter  indicates  the  upper 
limit  of  the  muscular  origin  of  the  Temporalis.  Above  these  lines  the  bone  is 
covered  by  tlie  galea  aponeurotica;  below  tliem  it  forms  part  of  the  temporal 
fossa,  and  affords  attachment  to  the  Temporalis  muscle.  At  the  back  part  and 
close  to  the  upper  or  sagittal  border  is  tlie  parietal  foramen,  which  transmits  a 
vein  to  the  superior  sagittal  sinus,  and  sometimes  a  small  branch  of  the  occipital 
artery;  it  is  not  constantly  present,  and  its  size  varies  considerably. 


'  American  Journal  of  Anatomy,  1906,  vol.  v. 


232 


OSTEOLOGY 


The  internal  surface  (Fig.  277)  is  concave;  it  presents  depressions  corresponding 
to  the  cerebral  convolutions,  and  numerous  furrows  for  the  ramifications  of  the 
middle  meningeal  vessel;^  the  latter  run  upward  and  backward  from  the  sphenoidal 
angle,  and  from  the  central  and  posterior  part  of  the  squamous  border.  Along 
the  upper  margin  is  a  shallow  groove,  which,  together  with  that  on  the  opposite 
parietal,  forms  a  channel,  the  sagittal  sulcus,  for  the  superior  sagittal  sinus;  the 
edges  of  the  sulcus  afford  attachment  to  the  falx  cerebri.  Near  the  groove  are 
several  depressions,  best  marked  in  the  skulls  of  old  persons,  for  the  arachnoid 
granulations  {Pacchionian  bodies).  In  the  groove  is  the  internal  opening  of  the 
parietal  foramen  when  that  aperture  exists. 


Articulates  ivith  opposite  parietal  bone 
J.. 


Articulates 

with 

frontal 

hone 


<^ '-  v  Pa  rt'e  taJ  r  m  / , 


>nP 


,0^    ?-"/"^"'      ^'^v. 


Articidaies 

with 

occipita 

bo7ie 


With  sphenoid 


Fig.  276. — Left  parietal  bone. 


With  mastoid  portion  of 
temporal  bone 
Outer  surface. 


Borders. — The  sagittal  border,  the  longest  and  thickest,  is  dentated  and  articu- 
lates with  its  fellow  of  the  opposite  side,  forming  the  sagittal  suture.  The  squamous 
border  is  divided  into  three  parts:  of  these,  the  anterior  is  thin  and  pointed,  bevelled 
at  the  expense  of  the  outer  surface,  and  overlapped  by  the  tip  of  the  great  wing 
of  the  sphenoid;  the  middle  portion  is  arched,  bevelled  at  the  expense  of  the  outer 
surface,  and  overlapped  by  the  squama  of  the  temporal;  the  posterior  part  is  thick 
and  serrated  for  articulation  with  the  mastoid  portion  of  the  temporal.  The 
frontal  border  is  deeply  serrated,  and  bevelled  at  the  expense  of  the  outer  surface 
above  and  of  the  inner  below;  it  articulates  with  the  frontal  bone,  forming  one- 
half  of  the  coronal  suture.  The  occipital  border,  deeply  denticulated,  articulates 
with  the  occipital,  forming  one-half  of  the  lambdoidal  suture. 


»  Journal  of  Anatomy  and  Physiology,  1912,  vol.  xlvi. 


THE  FRONTAL  BONE 


233 


Angles. — The  frontal  angle  is  practically  a  right  angle,  and  corresponds  with 
the  point  of  meeting  of  the  sagittal  and  coronal  sutures;  this  point  is  named  the 
bregma;  in  the  fetal  skull  and  for  about  a  year  and  a  half  after  birth  this  region  is 
membranous,  and  is  called  the  anterior  fontanelle.  The  sphenoidal  angle,  thin 
and  acute,  is  received  into  the  interval  between  the  frontal  bone  and  the  great 
wing  of  the  s{)henoid.  Its  inner  surface  is  marked  by  a  deep  groove,  sometimes 
a  canal,  for  the  anterior  divisions  of  the  middle  meningeal  artery.  The  occipital 
angle  is  rounded  and  corresponds  with  the  point  of  meeting  of  the  sagittal  and 
lambdoidal  sutures — a  point  which  is  termed  the  lambda;  in  the  fetus  this  part 
of  the  skull  is  membranous,  and  is  called  the  posterior  fontanelle.  The  mastoid 
angle  is  truncated;  it  articulates  with  the  occipital  bone  and  with  the  mastoid 
portion  of  the  temporal,  and  presents  on  its  inner  surface  a  broad,  shallow  groove 
which  lodges  part  of  the  transverse  sinus.  The  point  of  meeting  of  this  angle 
with  the  occipital  and  the  mastoid  part  of  the  temporal  is  named  the  asterion. 


l,^Uik''^-^— ^-^ 


Occipital 
angle 


Mastoid 
angle 


n     Frontal 
angle 


Sphenoidal  angle 


Fig.  277. — Left  parietal  bone.     Inner  surface. 


Ossification. — The  parietal  bone  is  ossified  in  membrane  from  a  single  centre,  which  appears 
at  the  parietal  eminence  about  the  eighth  week  of  fetal  life.  Ossification  gradually  extends  in 
a  radial  manner  from  the  centre  toward  the  margins  of  the  bone;  the  angles  are  consequently 
the  parts  last  formed,  and  it  is  here  that  the  fontanelles  exist.  Occasionally  the  parietal  bone 
is  divided  into  two  parts,  upper  and  lowei*,  by  an  antero-posterior  suture. 

Articulations. — The  parietal  articulates  with  five  bones:  the  opposite  parietal,  the  occipital, 
frontal,  temporal,  and  sphenoid. 


The  Frontal  Bone  (Os  Frontale). 


The  frontal  bone  resembles  a  cockle-shell  in  form,  and  consists  of  two  portions 
-a  vertical  portion,  the  squama,  corresponding  with  the  region  of  the  forehead; 


234 


OSTEOLOGY 


and  an  orbital  or  horizontal  portion,  Avhich  enters  into  tlie  formation  of  the  roofs 
of  the  orbital  and  nasal  ca\ities. 

Squama  (squama  frontalis). — Surfaces. — The  external  surface  (Fig.  278)  of  this 
portion  is  convex  and  usually  exhibits,  in  the  lower  part  of  the  middle  line,  the 
remains  of  the  frontal  or  metopic  suture;  in  infancy  this  suture  divides  the  bone  into 
two,  a  condition  which  may  persist  throughout  life.  On  either  side  of  this  suture, 
about  3  cm.  above  the  supraorbital  margin,  is  a  rounded  elevation,  the  frontal  emi- 
nence (tuber  frontale).  These  eminences  vary  in  size  in  different  individuals,  are 
occasionally  unsymmetrical,  and  are  especially  prominent  in  young  skulls;  the  sur- 
face of  the  bone  above  them  is  smooth,  and  covered  by  the  galea  aponeurotica. 
Below  the  frontal  eminences,  and  separated  from  them  by  a  shallow  groove,  are 
two  arched  elevations,  the  superciliary  arches;  these  are  prominent  medially,  and 


Zygomatic 
process 


Frontal    U  spine 
Fig.  278. — Frontal  bone.     Outer  surface. 


are  joined  to  one  another  by  a  smooth  elevation  named  the  glabella.  They  are 
larger  in  the  male  than  in  the  female,  and  their  degree  of  prominence  depends 
to  some  extent  on  the  size  of  the  frontal  air  sinuses;^  prominent  ridges  are,  how- 
ever, occasionally  associated  with  small  air  sinuses.  Beneath  each  superciliary 
arch  is  a  curved  and  prominent  margin,  the  supraorbital  margin,  which  forms  the 
upper  boundary  of  the  base  of  the  orbit,  and  separates  the  squama  from  the  orbital 
portion  of  the  bone.  The  lateral  part  of  this  margin  is  sharp  and  prominent, 
affording  to  the  eye,  in  that  situation,  considerable  protection  from  injury;  the 
medial  part  is  rounded.    At  the  junction  of  its  medial  and  intermediate  thirds  is 

'  Some  confusion  is  occasioned  to  students  commencing  the  study  of  anatomy  by  the  name  "sinus"  ha^dng  been 
given  to  two  different  kinds  of  space  connected  with  the  slvuU.  It  may  be  as  well,  therefore,  to  state  here  that  the 
"sinuses"  in  the  interior  of  the  cranium  which  produce  the  grooves  on  the  inner  surfaces  of  the  bones  are  venous 
channels  which  convey  the  blood  from  the  brain,  while  the  "sinuses"  external  to  the  cranial  cavity  (the  frontal, 
sphenoidal,  ethmoidal,  and  maxillary)  are  hollow  spaces  in  the  bones  themselves;  they  communicate  with  the  nasal 
cavities  and  contain  air. 


THE  FROXTAL  BOXE  235 

a  notch,  sometimes  eom-erted  into  a  foramen,  the  supraorbital  notch  or  foramen, 
which  transmits  the  su})ra()rl)ital  vessels  and  nerve.  A  small  aperture  in  the  upper 
part  of  the  notch  transmits  a  vein  from  the  diploe  to  join  the  supraorbital  vein. 
The  supraorbital  margin  ends  laterally  in  the  zygomatic  process,  which  is  strong 
and  j)rominent,  and  articulates  with  the  zygomatic  bone.  Running  upward  and 
backward  from  this  ])r()cess  is  a  well-marked  line,  the  temporal  line,  which  divides 
into  the  upper  and  lower  temporal  lines,  continuous,  in  the  articulated  skull,  with 
the  corresponding  lines  on  the  parietal  bone.  The  area  below  and  behind  the  tem- 
poral line  forms  the  anterior  part  of  the  temporal  fossa,  and  gives  origin  to  the 
Temporalis  muscle.  Between  the  supraorbital  margins  the  squama  projects  down- 
ward to  a  level  below  that  of  the  zygomatic  processes;  this  ])()rtion  is  known  as  the 
nasal  part  and  presents  a  rough,  uneven  inte^^'al,  the  nasal  notch,  which  articulates 
on  either  side  of  the  middle  line  with  the  nasal  bone,  and  laterally  with  the  frontal 
process  of  the  maxilla  and  with  the  lacrimal.  The  term  nasion  is  applied  to  the 
middle  of  the  frontonasal  suture.  From  the  centre  of  the  notch  the  nasal  process 
projects  downward  and  forward  beneath  the  nasal  bones  and  frontal  processes  of 
the  maxillse,  and  supports  the  bridge  of  the  nose.  The  nasal  process  ends  below 
in  a  sharp  spine,  and  on  either  side  of  this  is  a  small  grooved  surface  which  enters 
into  the  formation  of  the  roof  of  the  corresponding  nasal  cavity.  The  spine  forms 
part  of  the  septum  of  the  nose,  articulating  in  front  with  the  crest  of  the  nasal 
bones  and  behind  with  the  perpendicular  plate  of  the  ethmoid. 

The  internal  surface  (Fig.  279)  of  the  squama  is  concave  and  presents  in  the 
upper  part  of  the  middle  line  a  vertical  groove,  the  sagittal  sulcus,  the  edges  of 
which  unite  below  to  form  a  ridge,  the  frontal  crest;  the  sulcus  lodges  the  superior 
sagittal  sinus,  while  its  margins  and  the  crest  afford  attachment  to  the  falx  cerebri. 
The  crest  ends  below  in  a  small  notch  which  is  converted  into  a  foramen,  the  fora- 
men cecum,  by  articulation  with  the  ethmoid.  This  foramen  varies  in  size  in 
dift'erent  subjects,  and  is  frequently  impervious;  when  open,  it  transmits  a  vein 
from  the  nose  to  the  superior  sagittal  sinus.  On  either  side  of  the  middle  line  the 
bone  presents  depressions  for  the  convolutions  of  the  brain,  and  numerous  small 
furrows  for  the  anterior  branches  of  the  middle  meningeal  vessels.  Several  small, 
irregular  fossae  may  also  be  seen  on  either  side  of  the  sagittal  sulcus,  for  the 
reception  of  the  arachnoid  granulations. 

Orbital  or  Horizontal  Part  {pars  orbitalis). — This  portion  consists  of  two  thin 
triangular  plates,  the.  orbital  plates,  which  form  the  vaults  of  the  orbits,  and  are 
separated  from  one  another  by  a  median  gap,  the  ethmoidal  notch. 

Surfaces. — The  inferior  surface  (Fig.  279)  of  each  orbital  plate  is  smooth  and 
concave,  and  presents,  laterally,  under  cover  of  the  zygomatic  process,  a  shallow 
depression,  the  lacrimal  fossa,  for  the  lacrimal  gland ;  near  the  nasal  part  is  a  depres- 
sion, the  fovea  trochlearis,  or  occasionally  a  small  trochlear  spine,  for  the  attach- 
ment of  the  cartilaginous  pulley  of  the  Obliquus  oculi  superior.  The  superior 
surface  is  convex,  and  marked  by  depressions  for  the  convolutions  of  the  frontal 
lobes  of  the  brain,  and  faint  grooves  for  the  meningeal  branches  of  the  ethmoidal 
vessels. 

The  ethmoidal  notch  separates  the  two  orbital  plates;  it  is  quadrilateral,  and 
filled,  in  the  articulated  skull,  by  the  cribriform  plate  of  the  ethmoid.  The  margins 
of  the  notch  present  several  half-cells  which,  when  united  with  corresponding 
half-cells  on  the  upper  surface  of  the  ethmoid,  complete  the  ethmoidal  air  cells. 
Two  grooves  cross  these  edges  transversely;  they  are  converted  into  the  anterior 
and  posterior  ethmoidal  canals  by  the  ethmoid,  and  open  on  the  medial  wall  of  the 
orbit.  The  anterior  canal  transmits  the  nasociliary  nerve  and  anterior  ethmoidal 
vessels,  the  posterior,  the  posterior  ethmoidal  nerve  and  vessels.  In  front  of  the 
ethmoidal  notch,  on  either  side  of  the  frontal  spine,  are  the  openings  of  the  frontal 
air  sinuses.     These  are  two  irregular  cavities,  which  extend  backward,  upward. 


236 


OSTEOLOGY 


and  lateralward  for  a  variable  distance  between  the  two  tables  of  the  skull;  they 
are  separated  from  one  another  by  a  thin  bony  septum,  which  often  deviates  to 
one  or  other  side,  with  the  result  that  the  sinuses  are  rarely  symmetrical.  Absent 
at  birth,  they  are  usually  fairly  well-developed  between  the  seventh  and  eighth 
years,  but  only  reach  their  full  size  after  puberty.  They  vary  in  size  in  different 
persons,  and  are  larger  in  men  than  in  women. ^  They  are  lined  by  mucous  mem- 
brane, and  each  communicates  with  the  corresponding  nasal  cavity  by  means  of  a 
passage  called  the  frontonasal  duct. 


Supraorbital 
foramen 


With  Tnaxdla 

With  nasal 
With  perpendicular  plate  of  ethmoid 


Fiontal  sinus 


Under  surface  of  nasal  process 
forming  part  of  roof  of  nose 


Fig.   279. — Frontal  bone.     Inner  surface. 

Borders. — The  border  of  the  squama  is  thick,  strongly  serrated,  bevelled  at  the 
expense  of  the  inner  table  above,  where  it  rests  upon  the  parietal  bones,  and  at 
the  expense  of  the  outer  table  on  either  side,  where  it  receives  the  lateral  pressure 
of  those  bones;  this  border  is  continued  below  into  a  triangular,  rough  surface, 
which  articulates  with  the  great  wing  of  the  sphenoid.  The  posterior  borders  of 
the  orbital  plates  are  thin  and  serrated,  and  articulate  with  the  small  wings  of  the 
sphenoid. 

Structure. — The  squama  and  the  zygomatic  processes  are  very  thick,  consisting  of  diploic 
tissue  contained  between  two  compact  laminae;  the  diploic  tissue  is  absent  in  the  regions  occupied 
by  the  frontal  air  sinuses.  The  orbital  portion  is  thin,  translucent,  and  composed  entirely  of 
compact  bone;  hence  the  facihty  with  which  instruments  can  penetrate  the  cranium  through 
this  part  of  the  orbit ;  when  the  frontal  sinuses  are  exceptionally  large  they  may  extend  backward 
for  a  considerable  distance  into  the  orbital  portion,  which  in  such  cases  also  consists  of  only  two 
tables. 


1  Aldren  Turner  (The  Accessory  Sinuses  of  the  Nose,  1901)  gives  the  following  measurements  for  a  sinus  of  average 
size:  height,  IM  inches;  breadth,  1  inch;  depth  from  before  backward,  1  inch. 


THE  TEMPORAL  BONE 


237 


Ossification  (Fig.  280).  — The  frontal  bone  is  ossified  in  membrane  from  two  primary 
centres,  one  for  each  half,  which  appear  toward  the  end  of  the  second  month  of  fetal  life,  one 
above  each  supraorbital  margin.  From  each  of  these  centres  ossification  extends  upward  to  form 
the  corresponding  half  of  the  squama,  and  backward  to  form  the  orbital  plate.  The  spine  is 
ossified  from  a  pair  of   secondary  centres, 


on  either  side  of  the  middle  line;  similar 
centres  appear  in  the  nasal  part  and  zygo- 
matic processes.  At  birth  the  bone  consists 
of  two  pieces,  separated  by  the  frontal 
suture,  which  is  usually  obliterated,  except 
at  its  lower  part,  by  the  eighth  year,  but 
occasionally  persists  throughout  life.  It  is 
generally  maintained  that  the  development 
of  the  frontal  sinuses  begins  at  the  end  of 
the  first  or  beginning  of  the  second  year, 
but  Onodi's  recent  researches  indicate  that 
development  begins  at  birth.  The  sinuses 
are  of  considerable  size  by  the  seventh  or 
eighth  year,  but  do  not  attain  their  full 
proportions  until  after  puberty. 

Articulations.  —  The  frontal  articulates 
with  twelve  bones:  the  sphenoid,  the  eth- 
moid, the  two  parietals,  the  two  nasals,  the 
two  maxiUse,  the  two  laci'imals,  and  the 
two  zygomatics. 


Squama 


Nasal  pai't 


Zygomatic  process 


Spine 
Fig.  280.— Frontal  bone  at  birth. 


The  Temporal  Bone  (Os  Temporale). 

The  temporal  bones  are  situated  at  the  sides  and  base  of  the  skull.  Each  consists 
of  five  parts,  viz.,  the  squama,  the  petrous,  mastoid,  and  tympanic  parts,  and  the 
styloid  process. 

The  Squama  (squama  temporalis). — The  squama  forms  the  anterior  and  upper 
part  of  the  bone,  and  is  scale-like,  thin,  and  translucent. 

Surfaces.— Its  outer  surface  (Fig.  281)  is  smooth  and  convex;  it  affords  attach- 
ment to  the  Temporalis  muscle,  and  forms  part  of  the  temporal  fossa;  on  its  hinder 
part  is  a  vertical  groove  for  the  middle  temporal  artery.  A  curved  line,  the  tem- 
poral line,  or  supramastoid  crest,  runs  backward  and  upward  across  its  posterior 
part;  it  serves  for  the  attachment  of  the  temporal  fascia,  and  limits  the  origin 
of  the  Temporalis  muscle.  The  boundary  between  the  squama  and  the  mastoid 
portion  of  the  bone,  as  indicated  by  traces  of  the  original  suture,  lies  about  1  cm. 
below  this  line.  Projecting  from  the  lower  part  of  the  squama  is  a  long,  arched 
process,  the  zygomatic  process.  This  process  is  at  first  directed  lateralward,  its 
two  surfaces  looking  upward  and  downward;  it  then  appears  as  if  twisted  inward 
upon  itself,  and  runs  forward,  its  surfaces  now  looking  medialward  and  lateralward. 
The  superior  border  is  long,  thin,  and  sharp,  and  serves  for  the  attachment  of  the 
temporal  fascia;  the  inferior,  short,  thick,  and  arched,  has  attached  to  it  some 
fibres  of  the  Masseter.  The  lateral  surface  is  convex  and  subcutaneous;  the  medial 
is  concave,  and  affords  attachment  to  the  Masseter.  The  anterior  end  is  deeply 
serrated  and  articulates  with  the  zygomatic  bone.  The  posterior  end  is  connected 
to  the  squama  by  two  roots,  the  anterior  and  posterior  roots.  The  posterior  root,  a 
prolongation  of  the  upper  border,  is  strongly  marked;  it  runs  backward  above  the 
external  acoustic  meatus,  and  is  continuous  with  the  temporal  line.  The  anterior 
root,  continuous  with  the  lower  border,  is  short  but  broad  and  strong;  it  is  directed 
medialward  and  ends  in  a  rounded  eminence,  the  articular  tubercle  {eminentia 
articularis) .  This  tubercle  forms  the  front  boundary  of  the  mandibular  fossa, 
and  in  the  recent  state  is  covered  with  cartilage.  In  front  of  the  articular  tubercle 
is  a  small  triangular  area  which  assists  in  forming  the  infratemporal  fossa;  this 
area  is  separated  from  the  outer  surface  of  the  squama  by  a  ridge  which  is  continu- 
ous behind  with  the  anterior  root  of  the  zygomatic  process,  and  in  front,  in  the 


238 


OSTEOLOGY 


articulated  skull,  with  the  iufrateliiporal  crest  on  the  great  wing  of  the  sphenoid. 
Between  the  posterior  wall  of  the  external  acoustic  meatus  and  the  posterior  root 
of  the  zygomatic  process  is  the  area  called  the  suprameatal  triangle  (JNIacewen), 
or  mastoid  fossa,  through  which  an  instrument  ma}'  be  pushed  into  the  tympanic 
antrum.  At  the  junction  of  the  anterior  root  with  the  zygomatic  process  is  a  pro- 
jection for  the  attachment  of  the  temporomandibular  ligament;  and  behind  the 
anterior  root  is  an  oval  depression,  forming  part  of  the  mandibular  fossa,  for  the 
reception  of  the  condyle  of  the  mandible.  The  mandibular  fossa  {glenoid  fossa) 
is  bounded,  in  front,  by  the  articular  tubercle;  behind,  by  the  tympanic  part  of 
the  bone,  which  separates  it  from  the  external  acoustic  meatus;  it  is  divided  into 
two  parts  by  a  narrow  slit,  the  petrotympanic  fissure  {Glaserian  fissure).     The 


Groove  for  middle 
temporal  artery 


Parietal  notch 

S  iipi  ameatal 
tnangle 

Occipitalis 


Articular  tubercle 
Post- glenoid  process 

Mandibular  fossa 


Petrotympanic  fissure 
Vaginal  process 

Styloglossus 


\    Tympa7iic  part 
Stylohyoidecs 


Styloid  process 
Fig.  281. — Left  temporal  bone.     Outer  surface. 


Occipital  gwove 


anterior  part,  formed  by  the  squama,  is  smooth,  covered  in  the  recent  state  with 
cartilage,  and  articulates  wdth  the  condyle  of  the  mandible.  Behind  this  part 
of  the  fossa  is  a  small  conical  eminence;  this  is  the  representative  of  a  prominent 
tubercle  which,  in  some  mammals,  descends  behind  the  condyle  of  the  mandible, 
and  prevents  its  backward  displacement.  The  posterior  part  of  the  mandibular 
fossa,  formed  by  the  tympanic  part  of  the  bone,  is  non-articular,  and  sometimes 
lodges  a  portion  of  the  parotid  gland.  The  petrotympanic  fissure  leads  into  the 
middle  ear  or  tympanic  cavity;  it  lodges  the  anterior  process  of  the  malleus,  and 
transmits  the  tympanic  branch  of  the  internal  maxillary  artery.  The  chorda 
tympani  nerve  passes  through  a  canal  {ccmal  of  Huguier),  separated  from  the  an- 
terior edge  of  the  petrotympanic  fissure  by  a  thin  scale  of  bone  and  situated  on 
the  lateral  side  of  the  auditory  tube,  in  the  retiring  angle  between  the  squama 
and  the  petrous  portion  of  the  temporal. 


THE  TEMPORAL  BONE 


239 


The  internal  surface  of  the  scjuamn  (Fiji".  2(S2)  is  ccmcave;  it  jjreseiits  clepressions 
correspoiuliiii;'  to  the  eomolutioiis  of  the  temporal  lobe  of  the  brain,  and  grooves 
for  the  branches  of  the  middle  meningeal  vessels. 

Borders, — The  superior  border  is  thin,  and  bevelled  at  the  expense  of  the  internal 
table,  so  as  to  oNcrhip  the  scjnanions  border  of  the  parietal  bone,  forming  with 
it  the  sqnamosal  sntnre.  Posteriorly,  the  superior  border  forms  an  angle,  the 
parietal  notch,  with  the  mastoid  portion  of  the  bone.  The  anteroinferior  border 
is  thick,  serrated,  and  bevelled  at  the  expense  of  the  inner  table  above  and  of 
the  outer  below,  for  articulation  with  the  great  wing  of  the  sphenoid. 

Mastoid  Portion  [yars  mastoidea). — The  mastoid  portion  forms  the  posterior 
part  of  the  bone. 


tctl  h 


^n. 


Par  ieial 
notch 


Emineniia 
arcuala 


Mastoid  foramen  ' 

Aquceductus  vestibuli 

Aqiiceductiis  cochlece 

Internal  acoustic  w^eatus 
Fig.  282. — Left  temporal  bone.     Inner  surface. 


Surfaces. — Its  outer  surface  (Fig.  281)  is  rough,  and  gives  attachment  to  the 
Occipitalis  and  Auricularis  posterior.  It  is  perforated  by  numerous  foramina;  one 
of  these,  of  large  size,  situated  near  the  posterior  border,  is  termed  the  mastoid 
foramen;  it  transmits  a  vein  to  the  transverse  sinus  and  a  small  branch  of  the  occipi- 
tal artery  to  the  dura  mater.  The  position  and  size  of  this  foramen  are  very 
variable;  it  is  not  always  present;  sometimes  it  is  situated  in  the  occipital  bone, 
or  in  the  suture  between  the  temporal  and  the  occipital.  The  mastoid  portion  is 
continued  below  into  a  conical  projection,  the  mastoid  process,  the  size  and  form 
of  which  vary  somewhat;  it  is  larger  in  the  male  than  in  the  female.  This  process 
serves  for  the  attachment  of  the  Sternocleidomastoideus,  Spleniuss  capitis,  and 
Longissimus  capitis.  On  the  medial  side  of  the  process  is  a  deep  groove,  the 
mastoid  notch  (digastric  fossa),  for  the  attachment  of  the  Digastricus;  medial  to 
this  is  a  shallow  fvirrow,  the  occipital  groove,  which  lodges  the  occipital  artery. 


240 


OSTEOLOGY 


The  inner  surface  of  the  mastoid  portion  presents  a  deep,  curved  groove,  the 
sigmoid  sulcus,  which  lodges  part  of  the  transverse  sinus;  in  it  may  be  seen  the 
opening  of  the  mastoid  foramen.  The  groove  for  the  transverse  sinus  is  separated 
from  the  innermost  of  the  mastoid  air  cells  by  a  very  thin  lamina  of  bone,  and  even 
this  may  be  partly  deficient. 

Borders. — The  superior  border  of  the  mastoid  portion  is  broad  and  serrated,  for 
articulation  with  the  mastoid  angle  of  the  parietal.  The  posterior  border,  also 
serrated,  articulates  with  the  inferior  border  of  the  occipital  between  the  lateral 
angle  and  jugular  process.  Anteriorly  the  mastoid  portion  is  fused  with  the 
descending  process  of  the  squama  above;  below  it  enters  into  the  formation  of 
the  external  acoustic  meatus  and  the  tympanic  cavity. 


Ti/m panic  antrum 


Tegmen  tynvpani . 

Prominence  of  lateral  semicircular  canal 
Prominence  of  facial  canal 
Fenestra  vestibuli 
Bristle  in  semicanal  for  Tensor  tympani 
Septum  canalis  musculctubarii 

Bristle  in  hiatus  of  facial  canal 


Carotid  canal 
Bony  part  of  auditory  tube 
Promontory 
Bristle  in  pyramid 
Fenestra  cochleae 

Sulcus  tympanicus 

Mastoid  cells    ^nstle  in  stylomastoid  fora^nen 

Fig.  283. — Coronal  section  of  right  temporal  bone. 

A  section  of  the  mastoid  process  (Fig.  283)  shows  it  to  be  hollowed  out  into  a 
number  of  spaces,  the  mastoid  cells,  which  exhibit  the  greatest  possible  variety 
as  to  their  size  and  number.  At  the  upper  and  front  part  of  the  process  they  are 
large  and  irregular  and  contain  air,  but  toward  the  lower  part  they  diminish  in 
size,  while  those  at  the  apex  of  the  process  are  frequently  quite  small  and  contain 
marrow;  occasionally  they  are  entirely  absent,  and  the  mastoid  is  then  solid 
throughout.  In  addition  to  these  a  large  irregular  cavity  is  situated  at  the  upper 
and  front  part  of  the  bane.  It  is  called  the  tympanic  antrum,  and  must  be  distin- 
guished from  the  mastoid  cells,  though  it  communicates  with  them.  Like  the  mas- 
toid cells  it  is  filled  with  air  and  lined  by  a  prolongation  of  the  mucous  membrane 
of  the  tympanic  cavity,  with  which  it  communicates.  The  tympanic  antrum  is 
bounded  above  by  a  thin  plate  of  bone,  the  tegmen  tympani,  which  separates  it 
from  the  middle  fossa  of  the  base  of  the  skull;  below  by  the  mastoid  process;  later- 
ally by  the  squama  just  below  the  temporal  line,  and  medially  by  the  lateral  semi- 
circular canal  of  the  internal  ear  which  projects  into  its  cavity.  It  opens  in  front 
into  that  portion  of  the  tympanic  cavity  which  is  known  as  the  attic  or  epitympanic 


THE  TEMPO  HAL  BONE 


241 


recess.  The  tympanic  antrum  is  a  cavity  of  some  considerable  size  at  the  time  of 
hirth;  the  mastoid  air  cells  may  he  ref>arded  as  diverticula  from  the  antrum, 
and  begin  to  appear  at  or  before  birth;  by  the  fifth  year  they  are  well-marked, 
but  tiieir  development  is  not  completed  until  toward  puberty. 

Petrous  Portion  {pars  petrosa  [pyramis]). — The  petrous  portion  or  pyramid  is 
pyramidal  and  is  wedged  in  at  the  base  of  the  skull  between  the  sphenoid  and 
occipital.  Directed  medialward,  forward,  and  a  little  upward,  it  presents  for 
examination  a  base,  an  apex,  three  surfaces,  and  three  angles,  and  contains,  in 
its  interior,  the  essential  parts  of  the  organ  of  hearing. 

Base. — The  base  is  fused  with  the  internal  surfaces  of  the  squama  and  mastoid 
portion. 

Apex. — The  apex,  rough  and  uneven,  is  received  into  the  angular  inter\'al  between 
the  posterior  border  of  the  great  wing  of  the  sphenoid  and  the  basilar  part  of  the 
occipital;  it  presents  the  anterior  or  internal 
orifice  of  the   carotid   canal,   and  forms   the 
postero-lateral  boundary  of  the  foramen  lac- 
erum. 

Surfaces. — The  anterior  surface  forms  the 
posterior  part  of  the  middle  fossa  of  the 
base  of  the  skull,  and  is  continuous  with  the 
inner  surface  of  the  squamous  portion,  to  which 
it  is  united  by  the  petrosquamous  suture, 
remains  of  which  are  distinct  even  at  a  late 
period  of  life.  It  is  marked  by  depressions  for 
the  convolutions  of  the  brain,  and  presents 
six  points  for  examination:  (1)  near  the 
centre,  an  eminence  {eminentia  arcuata)  which 
indicates  the  situation  of  the  superior  semi- 
circular canal;  (2)  in  front  of  and  a  little  lateral 
to  this  eminence,  a  depression  indicating  the 
position  of  the  tympanic  cavity:  here  the 
layer  of  bone  which  separates  the  tympanic 
from  the  cranial  cavity  is  extremely  thin, 
and  is  known  as  the  tegmen  tympani;  (3)  a 
shallow  groove,  sometimes  double,  leading 
lateral  ward  and  backward  to  an  oblique  open- 
ing, the  hiatus  of  the  facial  canal,  for  the  passage  of  the  greater  superficial  petrosal 
nerve  and  the  petrosal  branch  of  the  middle  meningeal  artery;  (4)  lateral  to  the 
hiatus,  a  smaller  opening,  occasionally  seen,  for  the  passage  of  the  lesser  superficial 
petrosal  nerve;  (5)  near  the  apex  of  the  bone,  the  termination  of  the  carotid  canal, 
the  w'all  of  w^hich  in  this  situation  is  deficient  in  front;  (6)  above  this  canal  the 
shallow  trigeminal  impression  for  the  reception  of  the  semilunar  ganglion. 

The  posterior  surface  (Fig.  282)  forms  the  front  part  of  the  posterior  fossa  of 
the  base  of  the  skull,  and  is  continuous  with  the  inner  surface  of  the  mastoid 
portion.  Near  the  centre  is  a  large  orifice,  the  internal  acoustic  meatus,  the  size  of 
which  varies  considerably;  its  margins  are  smooth  and  rounded,  and  it  leads  into 
a  short  canal,  about  1  cm.  in  length,  which  runs  lateralward.  It  transmits  the 
facial  and  acoustic  nerves  and  the  internal  auditory  branch  of  the  basilar  artery. 
The  lateral  end  of  the  canal  is  closed  by  a  vertical  plate,  which  is  divided  by  a 
horizontal  crest,  the  crista  falciformis,  into  two  unequal  portions  (Fig.  284).  Each 
portion  is  further  subdivided  by  a  vertical  ridge  into  an  anterior  and  a  posterior 
part.  In  the  portion  beneath  the  crista  falciformis  are  three  sets  of  foramina; 
one  group,  just  below  the  posterior  part  of  the  crest,  situated  in  the  area  cribrosa 
media,  consists  of  several  small  openings  for  the  nerves  to  the  saccule;  below  and 
16 


Fig.  284. — Diagrammatic  view  of  the  fundus 
of  the  right  internal  acoustic  meatus.  (Testut.) 
1.  Crista  falciformis.  2.  Area  facialis,  with  (2') 
internal  opening  of  the  facial  canal.  3.  Ridge 
separating  the  area  facialis  from  the  area  crib- 
rosa superior.  4.  Area  cribrosa  superior,  with 
(4')  openings  for  nerve  filaments.  5.  Anterior 
inferior  cribriform  area,  with  (5')  the  tractus 
spiralis  foraminosus,  and  (5")  the  canaUs  cen- 
tralis of  the  cochlea.  6.  Ridge  separating  the 
tractus  spiralis  foraminosus  from  the  area  crib- 
rosa media.  7.  Area  cribrosa  media,  with  (7') 
orifices  for  nerves  to  saccule.  8.  Foramen 
singulare. 


242 


OSTEOLOGY 


behind  this  area  is  the  foramen  singulare,  or  opening  for  the  nerAe  to  the  posterior 
semieircuhir  duct;  in  front  of  and  below  the  first  is  the  tractus  spiralis  foraminosus, 
consisting  of  a  number  of  small  spirally  arranged  openings,  which  encircle  the  canalis 
centralis  cochleae;  these  openings  together  with  this  central  canal  transmit  the 
nerves  to  the  cochlea.  The  portion  above  the  crista  falciformis  presents  behind, 
the  area  cribrosa  superior,  pierced  by  a  series  of  small  openings,  for  the  passage  of 
the  nerves  to  the  utricle  and  the  superior  and  lateral  semicircular  ducts,  and,  in 
front,  the  area  facialis,  with  one  large  opening,  the  commencement  of  the  canal 
for  the  facial  nerve  (aquaeductus  Fallopii).  Behind  the  internal  acoustic  meatus 
is  a  small  slit  almost  hidden  by  a  thin  plate  of  bone,  leading  to  a  canal,  the  aquae- 
ductus vestibuli,  which  transmits  the  ductus  endolymphaticus  together  with  a 
small  artery  and  vein.  Above  and  between  these  two  openings  is  an  irregular 
depression  which  lodges  a  process  of  the  dura  mater  and  transmits  a  small  vein; 
in  the  infant  this  depression  is  represented  by  a  large  fossa,  the  subarcuate  fossa, 
which  extends  backward  as  a  blind  tunnel  under  the  superior  semicircular  canal. 


Semicanals  for 

•    auditory 

tube  and 

Tensor 

tympa7ii 


Lev.  veli  palatin 

Rmcgh  quadrilateral  surface 

Opening  of  carotid  canal 

Inferior  tympanic  canaliculus 

Aquaeductus  cochleae 

JIastoid  canaliculus 

Jugular  fossa 

Vaginal  process 

Styloid  process 

Stylomastoid  foramen 

Jugular  surface 

Tympanomastoid  fissure 


Stylopharyngeus 


Fig.  285. — Left  temporal  bone.     Inferior  surface. 


The  inferior  surface  (Fig.  285)  is  rough  and  irregular,  and  fornis  part  of  the 
exterior  of  the  base  of  the  skull.  It  presents  eleven  points  for  examination:  (1) 
near  the  apex  is  a  rough  surface,  quadrilateral  in  form,  which  serves  partly  for  the 
attachment  of  the  Levator  veli  palatini  and  the  cartilaginous  portion  of  the  audi- 
tory tube,  and  partly  for  connection  with  the  basilar  part  of  the  occipital  bone 
through  the  intervention  of  some  dense  fibrous  tissue;  (2)  behind  this  is  the  large 
circular  aperture  of  the  carotid  canal,  which  ascends  at  first  vertically,  and  then, 
making  a  bend,  runs  horizontally  forward  and  medialward;  it  transmits  into  the 
cranium  the  internal  carotid  artery,  and  the  carotid  plexus  of  nerves;  (3)  medial 
to  the  opening  for  the  carotid  canal  and  close  to  its  posterior  border,  in  front  of 


THE  TEMPORAL  BOXE  243 

the  juniilar  fossii,  is  a  triangular  depression;  at  the  apex  of  this  is  a  small  oj)ening, 
the  aquaeductus  cochleae,  whieh  lodges  a  tubular  i)r<)l()n^ation  of  the  dura  mater 
and  transmits  a  vein  from  the  cochlea  to  join  the  internal  jujj;ular;  (4)  behind  these 
openings  is  a  deep  depression,  the  jugular  fossa,  of  variabl(>  d(>i)th  and  si/e  in  difl'erent 
skulls;  it  lodges  the  bulb  of  the  internal  jugular  vein;  (5)  in  the  bony  ridge  dividing 
the  carotid  canal  from  the  jugular  fossa  is  the  small  inferior  tympanic  canaliculus 
for  the  passage  of  the  tympanic  branch  of  the  glossoi)liaryngeal  ner\-e;  ((i)  in  the 
lateral  part  of  the  jugular  fossa  is  the  mastoid  canaliculus  for  the  entrance  of  the 
auricular  branch  of  the  vagus  nerve;  (7)  behind  the  jugular  fossa  is  a  quadrilateral 
area,  the  jugular  surface,  covered  with  cartilage  in  the  recent  state,  and  articulating 
Avith  the  jugular  process  of  the  occipital  bone;  (8)  extending  backward  from  the 
carotid  canal  is  the  vaginal  process,  a  sheath-like  plate  of  bone,  which  di\'ides 
behind  into  two  laminae;  the  lateral  lamina  is  continuous  with  the  tympanic  part 
of  the  bone,  the  medial  with  the  lateral  margin  of  the  jugular  surface;  (9)  between 
these  lamina?  is  the  styloid  process,  a  sharp  spine,  about  2.5  cm.  in  length;  (10) 
between  the  styloid  and  mastoid  processes  is  the  stylomastoid  foramen;  it  is  the 
termination  of  the  facial  canal,  and  transmits  the  facial  nerve  and  stylomastoid 
artery;  (11)  situated  between  the  tympanic  portion  and  the  mastoid  process  is  the 
tympanomastoid  fissure,  for  the  exit  of  the  auricular  branch  of  the  vagus  nerve. 

Angles. — The  superior  angle,  the  longest,  is  grooved  for  the  superior  petrosal 
sinus,  and  gives  attachment  to  the  tentorium  cerebelli;  at  its  medial  extremity 
is  a  notch,  in  which  the  trigeminal  nerve  lies.  The  posterior  angle  is  intermediate 
in  length  between  the  superior  and  the  anterior.  Its  medial  half  is  marked  by 
a  sulcus,  w^hich  forms,  with  a  corresponding  sulcus  on  the  occipital  bone,  the 
channel  for  the  inferior  petrosal  sinus.  Its  lateral  half  presents  an  excavation 
— the  jugular  fossa — which,  with  the  jugular  notch  on  the  occipital,  forms  the 
jugular  foramen ;  an  eminence  occasionally  projects  from  the  centre  of  the  fossa, 
and  divides  the  foramen  into  two.  The  anterior  angle  is  divided  into  two  parts 
— a  lateral  joined  to  the  squama  by  a  suture  {petrosquamous) ,  the  remains  of  which 
are  more  or  less  distinct;  a  medial,  free,  which  articulates  with  the  spinous  process 
of  the  sphenoid. 

At  the  angle  of  junction  of  the  petrous  part  and  the  squama  are  two  canals, 
one  above  the  other,  and  separated  by  a  thin  plate  of  bone,  the  septum  canalis 
musculotubarii  {processus  cochleariformis) ;  both  canals  lead  into  the  tympanic 
cavity.  The  upper  one  {semicanalis  m.  tensoris  tympani)  transmits  the  Tensor 
tympani,  the  lower  one  {semicanalis  tuhae  auditivae)  forms  the  bony  part  of  the 
auditory  tube. 

The  tympanic  cavity,  auditory  ossicles,  and  internal  ear,  are  described  with 
the  organ  of  hearing. 

Tympanic  Part  {pars  tympanica). — The  tympanic  part  is  a  curved  plate  of  bone 
lying  below  the  squama  and  in  front  of  the  mastoid  process. 

Surfaces. — Its  postero-superior  surface  is  concave,  and  forms  the  anterior  wall, 
the  floor,  and  part  of  the  posterior  wall  of  the  bony  external  acoustic  meatus. 
Medially,  it  presents  a  narrow  furrow,  the  tympanic  sulcus,  for  the  attachment 
of  the  tympanic  membrane.  Its  antero-inferior  surface  is  quadrilateral  and  slightly 
concave;  it  constitutes  the  posterior  boundary  of  the  mandibular  fossa,  and  is 
in  contact  with  the  retromandibular  part  of  the  parotid  gland. 

Borders. — Its  lateral  border  is  free  and  rough,  and  gives  attachment  to  the  car- 
tilaginous part  of  the  external  acoustic  meatus.  Internally,  the  tympanic  part 
is  fused  wnth  the  petrous  portion,  and  appears  in  the  retreating  angle  between 
it  and  the  squama,  where  it  lies  below  and  lateral  to  the  orifice  of  the  auditory 
tube.  Posteriorly,  it  blends  with  the  squama  and  mastoid  part,  and  forms  the 
anterior  boundary  of  the  tympanomastoid  fissure.  Its  upper  border  fuses  laterally 
with  the  back  of  the  postglenoid  process,  while  medially  it  bounds  the  petro- 


244 


OSTEOLOGY 


tympanic  fissure.  The  medial  part  of  tlie  lower  border  is  thin  and  sharp;  its  lateral 
part  splits  to  enclose  the  root  of  the  styloid  process,  and  is  therefore  named  the 
vaginal  process.  The  central  portion  of  the  tympanic  part  is  thin,  and  in  a  consid- 
erable percentage  of  skulls  is  perforated  by  a  hole,  the  foramen  of  Huschke. 

The  external  acoustic  meatus  is  nearly  2  cm.  long  and  is  directed  inward  and 
slightly  forward:  at  the  same  time  it  forms  a  slight  curve,  so  that  the  floor  of  the 
canal  is  convex  upward.  In  sagittal  section  it  presents  an  oval  or  elliptical  shape 
with  the  long  axis  directed  downward  and  slightly  backward.  Its  anterior  wall 
and  floor  and  the  lower  part  of  its  posterior  wall  are  formed  by  the  tympanic 
part;  the  roof  and  upper  part  of  the  posterior  wall  by  the  squama.  Its  inner 
end  is  closed,  in  the  recent  state,  by  the  tympanic  membrane;  the  upper  limit 
of  its  outer  orifice  is  formed  by  the  posterior  root  of  the  zygomatic  process,  imme- 
diately below  which  there  is  sometimes  seen  a  small  spine,  the  suprameatal  spine, 
situated  at  the  upper  and  posterior  part  of  the  orifice. 

Styloid  Process  {processus  styloideus). — The  styloid  process  is  slender,  pointed, 
and  of  varying  length;  it  projects  downward  and  forw^ard,  from  the  under  surface 
of  the  temporal  bone.  Its  proximal  part  {tymjMnokyal)  is  ensheathed  by  the 
vaginal  process  of  the  tympanic  portion,  while  its  distal  part  {styhhyal)  gives 
attachment  to  the  stylohyoid  and  stylomandibular  ligaments,  and  to  the  Stylo- 
glossus, Stylohyoideus,  and  Stylopharyngeus  muscles.  The  stylohyoid  ligament 
extends  from  the  apex  of  the  process  to  the  lesser  cornu  of  the  hyoid  bone,  and 
in  some  instances  is  partially,  in  others  completely,  ossified. 


Septum  canalis  musculotubarii 

Fenestra  vestibuli 
Tympanic  antrum  ] 


Sulcus  tympanicus 


Bristle  in  facial 
canal 


Lateral  wall  of 
tympanic  antrum 


Fig.  286. — The  three  principal  parts  of  the  temporal  bone  at  birth.     1.  Outer  surface  of  petromastoid  part. 
2.   Outer  surface  of  tjTnpanio  ring.     3.  Inner  surface  of  squama. 

Structure. — The  structure  of  the  squama  is  hke  that  of  the  other  cranial  bones:  the  mastoid 
portion  is  spongy,  and  the  petrous  portion  dense  and  hard. 

Ossification. — The  temporal  bone  is  ossified  from  eight  centres,  exclusive  of  those  for  the  internal 
ear  and  the  tympanic  ossicles,  viz.,  one  for  the  squama  including  the  zygomatic  process,  one  for 
the  tympanic  part,  four  for  the  petrous  and  mastoid  parts,  and  two  for  the  styloid  process.  Just 
before  the  close  of  fetal  hfe  (Fig.  286)  the  temporal  bone  consists  of  three  principal  parts:  1. 
The  squama  is  ossified  in  membrane  from  a  single  nucleus,  which  appears  near  the  root  of  the 
zygomatic  process  about  the  second  month.  2.  The  petromastoid  part  is  developed  from  four 
centres,  which  make  their  appearance  in  the  cartilaginous  ear  capsule  about  the  fifth  or  sixth 
month.  One  (prootic)  appears  in  the  neighborhood  of  the  eminentia  arcuata,  spreads  in  front 
and  above  the  internal  acoustic  meatus  and  extends  to  the  apex  of  the  bone;  it  forms  part  of  the 
cochlea,  vestibule,  superior  semicircular  canal,  and  medial  wall  of  the  tympanic  cavity.  A  second 
{opisthoticy  appears  at  the  promontory  on  the  medial  wall  of  the  tympanic  cavity  and  surrounds 
the  fenestra  cochleae;  it  forms  the  floor  of  the  tympanic  cavity  and  vestibule,  surrounds  the  carotid 
canal,  inve.sts  the  lateral  and  lower  part  of  the  cochlea,  and  spreads  medially  below  the  internal 


THE  SPHENOIDAL  BONE 


245 


acoustic  meatus.  A  third  (plerotic)  roofs  in  the  tympanic  cavity  and  antrum;  while  the  fourth 
(epiotic)  appears  near  the  posterior  semicircular  canal  and  extends  to  form  the  mastoid  process 
(VroUk).  3.  The  lympaidc  ring  is  an  incomplete  circle,  in  the  concavity  of  which  is  a  groove, 
the  tympanic  sulcus,  for  the  attachment  of  the  circumference  of  the  tyrn[)anic  membrane.  This 
ring  expands  to  form  the  tympanic  part,  and  is  ossified  in  membrane  from  a  single  centre  which 
appears  about  the  third  month.  The  styloid  process  is  developed  from  the  proximal  part  of  the 
cartilage  of  the  second  branchial  or  hyoid  arch  by  two  centres:  one  for  the  proximal  part,  the 
tynipanohyal,  appears  before  birth;  the  other,  comprising  the  rest  of  the  process,  is  named  the 
stylohyal,  and  does  not  appear  until  after  birth.  The  tympanic  ring  unites  with  the  squama 
shortly  before  birth;  the  petromastoid  part  and  squama  join  during  the  first  year,  and  the  tym- 
panohVal  portion  of  the  styloid  process  about  the  same  time  (Figs.  287,  288).  The  stylohyal 
does  not  unite  with  the  rest  of  the  bone  until  after  puberty,  and  in  some  skulls  never  at  all. 


Squama 


Squama 


Petrosquamous 
suture 


Petrosquamous  suture 
Emineyitia  arcuata 


Tympanic  ring 


Petromastoid  portion 


Fig.  287. — Temporal  bone  at  birth. 
Outer  aspect. 


Fossa  suharcuata 
Internal  acoustic  meatus 

Fig.  288. — Temporal  bone  at  birth.     Inner 
aspect. 


The  chief  subsequent  changes  in  the  temporal  bone  apart  from  increase  in  size  are:  (1)  The 
tympanic  ring  extends  outward  and  backward  to  form  the  tympanic  part.  This  extension  does 
not,  however,  take  place  at  an  equal  rate  all  around  the  circumference  of  the  ring,  but  occurs  most 
rapidly  on  its  anterior  and  posterior  portions,  and  these  outgrowths  meet  and  blend,  and  thus, 
for  a  time,  there  exists  in  the  floor  of  the  meatus  a  foramen,  the  foramen  of  Huschke;  this  foramen 
is  usually  closed  about  the  fifth  year,  but  may  persist  throughout  fife.  (2)  The  mandibular  fossa 
is  at  first  extremely  shallow,  and  looks  lateralward  as  well  as  downward;  it  becomes  deeper  and 
is  ultimately  directed  downward.  Its  change  in  direction  is  accounted  for  as  follows.  The  part 
of  the  squama  which  forms  the  fossa  Ues  at  first  below  the  level  of  the  zygomatic  process.  As, 
however,  the  base  of  the  skull  increases  in  width,  this  lower  part  of  the  squama  is  directed  hori- 
zontally inward  to  contribute  to  the  middle  fossa  of  the  skull,  and  its  sm-faces  therefore  come 
to  look  upward  and  downward;  the  attached  portion  of  the  zygomatic  process  also  becomes 
everted,  and  projects  like  a  shelf  at  right  angles  to  the  squama.  (3)  The  mastoid  portion  is  at 
first  quite  flat,  and  the  stylomastoid  foramen  and  rudimentary  styloid  process  he  immediately 
behind  the  tympanic  ring.  With  the  development  of  the  air  cells  the  outer  part  of  the  mastoid 
portion  grows  downward  and  forward  to  form  the  mastoid  process,  and  the  styloid  process  and 
stylomastoid  foramen  now  come  to  he  on  the  imder  surface.  The  descent  of  the  foramen  is 
necessarily  accompanied  by  a  corresponding  lengthening  of  the  facial  canal.  (4)  The  dowTiward 
and  forward  growth  of  the  mastoid  process  also  pushes  forward  the  tympanic  part,  so  that  the 
portion  of  it  w-hich  formed  the  original  floor  of  the  meatus  and  contained  the  foramen  of  Huschke 
is  ultimately  found  in  the  anterior  wall.  (5)  The  fossa  subarcuata  becomes  filled  up  and  almost 
obhterated. 

Articulations. — The  temporal  articulates  vfUhfive  bones:  occipital,  parietal,  sphenoid,  mandible, 
and  zygomatic. 


The  Sphenoidal  Bone  (Os  Sphenoidal;  Sphenoid  Bone). 

The  sphenoidal  bone  is  situated  at  the  base  of  the  skull  in  front  of  the  temporals 
and  basilar  part  of  the  occipital.     It  some^Yhat  resembles  a  bat  with  its  wings 


246 


OSTEOLOGY 


extended,  and  is  divided  into  a  median  portion  or  body,  two  great  and  two  small 
wings  extending  outward  from  the  sides  of  the  body,  and  two  pterygoid  processes 
which  project  from  it  below. 

Body  (corpus  syhenoidalis) . — The  body,  more  or  less  cubical  in  shape,  is  hollowed 
out  in  its  interior  to  form  two  large  ca^-ities,  the  sphenoidal  air  sinuses,  which  are 
separated  from  each  other  by  a  septum. 

Surfaces, — The  superior  surface  of  the  body  (Fig.  289)  presents  in  front  a  promi- 
nent spine,  the  ethmoidal  spine,  for  articulation  with  the  cribriform  plate  of  the 
ethmoid;  behind  this  is  a  smooth  surface  slightly  raised  in  the  middle  line,  and 
grooved  on  either  side  for  the  olfactory  lobes  of  the  brain.  This  surface  is  bounded 
behind  by  a  ridge,  which  forms  the  anterior  border  of  a  narrow,  transverse  groove, 
the  chiasmatic  groove  {oytic  groove),  above  and  behind  which  lies  the  optic  chiasma; 
the  groove  ends  on  either  side  in  the  optic  foramen,  which  transmits  the  optic 
nerve  and  opthalmic  artery  into  the  orbital  cavity.  Behind  the  chiasmatic  groove 
is  an  olive-like  elevation,  the  tuberculum  sellae;  and  still  more  posteriorly,  a  deep 
depression,  the  sella  turcica,   the  deepest  part  of  which  lodges  the  hypophysis 


Middle  Clinoid  process 
Posterior  Clinoid  process 


Ethmoidal 
spine 

Groove  for  i        ^.,, 

olfactory         ,Y     . 
I  fg  I    ethmoiC 

/ 


al^-"^' 


Optic  foramen 
Superior  orbital 
fissure 

Foramen  rotundum 

Foramen  Vesalii 

Foramen  ovale 

Foramen  spinosum 


Spina  angularis 


palatine 


Fig.  289. — Sphenoidal  bone.     Upper  surface. 


cerebri  and  is  known  as  the  fossa  hypophyseos.  The  anterior  boundary  of  the 
sella  turcica  is  completed  by  two  small  eminences,  one  on  either  side,  called  the 
middle  clinoid  processes,  while  the  posterior  boundary  is  formed  by  a  square- 
shaped  plate  of  bone,  the  dorsum  sellae,  ending  at  its  superior  angles  in  two  tuber- 
cles, the  posterior  clinoid  processes,  the  size  and  form  of  which  vary  considerably  in 
different  individuals.  The  posterior  clinoid  processes  deepen  the  sella  turcica, 
and  give  attachment  to  the  tentorium  cerebelli.  On  either  side  of  the  dorsum 
sellae  is  a  notch  for  the  passage  of  the  abducent  nerve,  and  below  the  notch  a  sharp 
process,  the  petrosal  process,  which  articulates  with  the  apex  of  the  petrous  portion 
of  the  temporal  bone,  and  forms  the  medial  boundary  of  the  foramen  lacerum. 
Behind  the  dorsum  sellae  is  a  shallow  depression,  the  clivus,  which  slopes  obliquely 
backward,  and  is  continuous  with  the  groove  on  the  basilar  portion  of  the  occipital 
bone;  it  supports  the  upper  part  of  the  pons. 

The  lateral  surfaces  of  the  body  are  united  with  the  great  wings  and  the  medial 
pterygoid  plates.  Above  the  attachment  of  each  great  wing  is  a  broad  groove, 
curved  something  like  the  italic  letter  /;  it  lodges  the  internal  carotid  artery  and 


THE  SPHEXOIDAL  BONE 


247 


the  cavernous  sinus,  and  is  named  the  carotid  groove.  Ak)ng  the  posterior  part 
of  the  lateral  margin  of  this  <iT<)()V(\  in  the  angle  between  the  body  and  great  wing, 
is  a  ridge  of  bone,  called  the  hngula. 

The  posterior  surface,  ([Uiidrilateral  in  form  (Fig.  291),  is  joined,  during  infancy 
and  adoleseenee,  to  the  basilar  part  of  the  ()c('ii)ital  bone  by  a  plate  of  cartilage. 
Between  the  eighteenth  and  twenty-fifth  years  this  becomes  ossified,  ossification 
commencing  above  and  extending  downward. 

The  anterior  surface  of  the  body  (Fig.  290)  presents,  in  the  middle  line,  a  vertical 
crest,  the  sphenoidal  crest,  which  articulates  with  the  perpendicular  plate  of  the 
ethmoid,  and  forms  part  of  the  septum  of  the  nose.  On  either  side  of  the  crest 
is  an  irregular  opening  leading  into  the  corresponding  sphenoidal  air  sinus.  These 
sinuses  are  two  large,  irregular  cavities  hollowed  out  of  the  interior  of  the  body 
of  the  bone,  and  separated  from  one  another  by  a  bony  septum,  which  is  commonly 
bent  to  one  or  the  other  side.  They  vary  considerably  in  form  and  size,^  are 
seldom  symmetrical,  and  are  often  partially  subdivided  by  irregular  bony  laminae. 


Tensor  vel 
palatini 


Medial  pterygoid  plate 
Ilaiindus 


Fig.  290. — Sphenoidal  bone.     Anterior  and  inferior  surfaces. 


Occasionally,  they  extend  into  the  basilar  part  of  the  occipital  nearly  as  far  as  the 
foramen  magnum.  They  begin  to  be  developed  before  birth,  and  are  of  a  consid- 
erable size  by  the  age  of  six.  They  are  partially  closed,  in  front  and  below,  by  two 
thin,  curved  plates  of  bone,  the  sphenoidal  conchae  (see  page  250),  leaving  in  the 
articulated  skull  a  round  opening  at  the  upper  part  of  each  sinus  by  which  it  com- 
municates with  the  upper  and  back  part  of  the  nasal  cavity  and  occasionally  with 
the  posterior  ethmoidal  air  cells.  The  lateral  margin  of  the  anterior  surface  is 
serrated,  and  articulates  with  the  lamina  papyracea  of  the  ethmoid,  completing 
the  posterior  ethmoidal  cells;  the  lower  margin  articulates  with  the  orbital  process 
of  the  palatine  bone,  and  the  upper  with  the  orbital  plate  of  the  frontal  bone. 

The  inferior  surface  presents,  in  the  middle  line,  a  triangular  spine,  the  sphenoidal 
rostrum,  which  is  continuous  with  the  sphenoidal  crest  on  the  anterior  surface, 
and  is  received  in  a  deep  fissure  between  the  alse  of  the  vomer.  On  either  side  of 
the  rostrum  is  a  projecting  lamina,  the  vaginal  process,  directed  medialward  from 
the  base  of  the  medial  pterygoid  plate,  with  which  it  will  be  described. 

1  Aldren  Turner  {op.  cit.)  gives  the  following  as  their  average  measurements:  vertical  height,  V.s  inch;  antero-posterior 
depth,  Vs  inch;  transverse  breadth,  %,  inch. 


248 


OSTEOLOGY 


The  Great  Wings  {aJae  magnae). — The  great  wings,  or  ali-sphenoids,  are  two 
strong  processes  of  bone,  which  arise  from  the  sides  of  the  body,  and  are  curved 
upward,  lateralward,  and  backward;  the  posterior  part  of  each  projects  as  a  tri- 
angular process  which  fits  into  the  angle  between  the  squama  and  the  petrous 
portion  of  the  temporal  and  presents  at  its  apex  a  downwardly  directed  process, 
the  spina  angularis  (sphenoidal  spine). 

Surfaces. — The  superior  or  cerebral  surface  of  each  great  wing  (Fig.  289)  forms 
part  of  the  middle  fossa  of  the  skull;  it  is  deeply  concave,  and  presents  depressions 
for  the  convolutions  of  the  temporal  lobe  of  the  brain.  At  its  anterior  and  medial 
part  is  a  circular  aperture,  the  foramen  rotundum,  for  the  transmission  of  the  maxil- 
lary nerve.  Behind  and  lateral  to  this  is  the  foramen  ovale,  for  the  transmission 
of  the  mandibular  nerve,  the  accessory-  meningeal  artery,  and  sometimes  the 
lesser  superficial  petrosal  nerve. ^  Medial  to  the  foramen  ovale,  a  small  aperture, 
the  foramen  Vesalii,  may  occasionally  be  seen  opposite  the  root  of  the  pterygoid 
process;  it  opens  below  near  the  scaphoid  fossa,  and  transmits  a  small  vein  from 
the  cavernous  sinus.  Lastly,  in  the  posterior  angle,  near  to  and  in  front  of  the  spine, 
is  a  short  canal,  sometimes  double,  the  foramen  spinosum,  which  transmits  the 
middle  meningeal  vessels  and  a  recurrent  branch  from  the  maiidibular  nerve. 


Anterior  clinoid  process 


Foramen  rotundum, 


Spina  angularis 

Pterygoid  canal 

|\^^  tW Lateral  pterygoid  plate 

\  ^"^K Medial  pterygoid  plate 

—Hamulus 


Vaginal  process 

Rostrum 
Fig.  291. — Sphenoidal  bone.     Upper  and  posterior  surfaces. 


The  lateral  surface  (Fig.  290)  is  convex,  and  divided  by  a  transverse  ridge,  the 
infratemporal  crest,  into  two  portions.  The  superior  or  temporal  portion,  convex 
from  above  downw^ard,  concave  from  before  backward,  forms  a  part  of  the  tem- 
poral fossa,  and  gives  attachment  to  the  Temporalis;  the  inferior  or  infratemporal, 
smaller  in  size  and  concave,  enters  into  the  formation  of  the  infratemporal  fossa, 
and,  together  with  the  infratemporal  crest,  affords  attachment  to  the  Pterygoideus 
externus.  It  is  pierced  by  the  foramen  ovale  and  foramen  spinosum,  and  at  its 
posterior  part  is  the  spina  angularis,  w^hich  is  frequently  grooved  on  its  medial 
surface  for  the  chorda  tympani  nerve.  To  the  spina  angularis  are  attached  the 
sphenomandibular  ligament  and  the  Tensor  veli  palatini.  Medial  to  the  anterior 
extremity  of  the  infratemporal  crest  is  a  triangular  process  which  serves  to  increase 


1  The  lesser  superficial  petrosal  nerve  sometimes  passes  through  a  special  canal  {canaliculus  innominalus  of  Arnold) 
situated  medial  to  the  foramen  spinosum. 


THE  SPHENOIDAL  BONE  249 

the  attachment  of  the  Pterygoideus  externus;  extending  downward  and  medialward 
from  this  process  on  to  the  front  part  of  the  Lateral  pterygoid  plate  is  a  ridge  which 
forms  the  anterior  limit  of  the  infratemporal  surface,  and,  in  the  articulated  skull, 
the  posterior  boundary  of  the  pterygomaxillary  fissure. 

The  orbital  surface  of  the  great  wing  (Fig.  290),  smooth,  and  quadrilateral  in 
shape,  is  directed  forward  and  medialward  and  forms  the  posterior  part  of  the 
lateral  wall  of  the  orbit.  Its  upper  serrated  edge  articulates  with  the  orbital  plate 
of  the  frontal.  Its  inferior  rounded  border  forms  the  postero-lateral  boundary  of 
the  inferior  orbital  fissure.  Its  medial  sharp  margin  forms  the  lower  boundary 
of  the  superior  orbital  fissure  and  has  projecting  from  about  its  centre  a  little 
tubercle  which  gives  attachment  to  the  inferior  head  of  the  Rectus  lateralis  oculi; 
at  the  upper  part  of  this  margin  is  a  notch  for  the  transmission  of  a  recurrent 
branch  of  the  lacrimal  artery.  Its  lateral  margin  is  serrated  and  articulates  with 
the  zygomatic  bone.  Below  the  medial  end  of  the  superior  orbital  fissure  is  a 
grooved  surface,  which  forms  the  posterior  wall  of  the  pterygopalatine  fossa, 
and  is  pierced  by  the  foramen  rotundum. 

Margin  (Fig.  289). — Commencing  from  behind,  that  portion  of  the  circum- 
ference of  the  great  wing  which  extends  from  the  body  to  the  spine  is  irregular. 
Its  medial  half  forms  the  anterior  boundary  of  the  foramen  lacerum,  and  presents 
the  posterior  aperture  of  the  pterygoid  canal  for  the  passage  of  the  correspond- 
ing nerve  and  artery.  Its  lateral  half  articulates,  by  means  of  a  synchondrosis, 
with  the  petrous  portion  of  the  temporal,  and  between  the  two  bones  on  the 
under  surface  of  the  skull,  is  a  furrow,  the  sulcus  tubae,  for  the  lodgement  of  the 
cartilaginous  part  of  the  auditory  tube.  In  front  of  the  spine  the  circumference 
presents  a  concave,  serrated  edge,  bevelled  at  the  expense  of  the  inner  table  below, 
and  of  the  outer  table  above,  for  articulation  with  the  temporal  squama.  At 
the  tip  of  the  great  wing  is  a  triangular  portion,  bevelled  at  the  expense  of  the 
internal  surface,  for  articulation  with  the  sphenoidal  angle  of  the  parietal  bone; 
this  region  is  named  the  pterion.  Medial  to  this  is  a  triangular,  serrated  surface, 
for  articulation  with  the  frontal  bone;  this  surface  is  continuous  medially  with 
the  sharp  edge,  which  forms  the  lower  boundary  of  the  superior  orbital  fissure, 
and  laterally  with  the  serrated  margin  for  articulation  wdth  the  zygomatic 
bone. 

The  Small  Wings  (alae  parvae). — The  small  wings  or  orbito-sphenoids  are  tw^o 
thin  triangular  plates,  which  arise  from  the  upper  and  anterior  parts  of  the  body, 
and,  projecting  lateralward,  end  in  sharp  points  (Fig.  289). 

Surfaces. — The  superior  surface  of  each  is  flat,  and  supports  part  of  the  frontal 
lobe  of  the  brain.  The  inferior  surface  forms  the  back  part  of  the  roof  of  the  orbit, 
and  the  upper  boundary  of  the  superior  orbital  fissure.  This  fissure  is  of  a  triangular 
form,  and  leads  from  the  cavity  of  the  cranium  into  that  of  the  orbit:  it  is  bounded 
medially  by  the  body;  above,  by  the  small  wing;  beloic,  by  the  medial  margin  of 
the  orbital  surface  of  the  great  wing;  and  is  completed  laterally  by  the  frontal 
bone.  It  transmits  the  oculomotor,  trochlear,  and  abducent  nerves,  the  three 
branches  of  the  ophthalmic  division  of  the  trigeminal  nerve,  some  filaments  from 
the  cavernous  plexus  of  the  sympathetic,  the  orbital  branch  of  the  middle  menin- 
geal artery,  a  recurrent  branch  from  the  lacrimal  artery  to  the  dura  mater,  and  the 
ophthalmic  vein. 

Borders. — The  anterior  border  is  serrated  for  articulation  with  the  frontal  bone. 
The  posterior  border,  smooth  and  rounded,  is  received  into  the  lateral  fissure  of 
the  brain;  the  medial  end  of  this  border  forms  the  anterior  clinoid  process,  which 
gives  attachment  to  the  tentorium  cerebelli;  it  is  sometimes  joined  to  the  middle 
clinoid  process  by  a  spicule  of  bone,  and  when  this  occurs  the  termination  of  the 
groove  for  the  internal  carotid  artery  is  converted  into  a  foramen  {carotico-clinoid) . 
The  small  wing  is  connected  to  the  body  by  two  roots,  the  upper  thin  and  flat, 


250  OSTEOLOGY 

the  lower  thick  and  triangular;  between  the  two  roots  is  the  optic  foramen,  for  the 
transmission  of  the  optic  nerve  and  ophthalmic  artery. 

Pterygoid  Processes  (processus  pterygoidei) . — The  pter^^goid  processes,  one  on 
either  side,  descend  perpendicularly  from  the  regions  where  the  body  and  great 
wings  unite.  Each  process  consists  of  a  medial  and  a  lateral  plate,  the  upper  parts 
of  which  are  fused  anteriorly;  a  vertical  sulcus,  the  pterygopalatine  groove,  descends 
on  the  front  of  the  line  of  fusion.  The  plates  are  separated  below  by  an  angular 
cleft,  the  pterygoid  fissure,  the  margins  of  which  are  rough  for  articulation  with 
the  pyramidal  process  of  the  palatine  bone.  The  two  plates  diverge  behind  and 
enclose  between  them  a  V-shaped  fossa,  the  pterygoid  fossa,  which  contains  the 
Pterygoideus  internus  and  Tensor  veli  palatini.  Above  this  fossa  is  a  small,  oval, 
shallow  depression,  the  scaphoid  fossa,  which  gives  origin  to  the  Tensor  veli  palatini. 
The  anterior  surface  of  the  pterygoid  process  is  broad  and  triangular  near  its 
root,  where  it  forms  the  posterior  wall  of  the  pterygopalatine  fossa  and  presents 
the  anterior  orifice  of  the  pterygoid  canal. 

Lateral  Pterygoid  Plate. — The  lateral  pterygoid  plate  is  broad,  thin,  and  everted; 
its  lateral  surface  forms  part  of  the  medial  wall  of  the  infratemporal  fossa,  and 
gives  attachment  to  the  Pterygoideus  externus;  its  medial  surface  forms  part  of 
the  pterygoid  fossa,  and  gives  attachment  to  the  Pterygoideus  internus. 

Medial  Pterygoid  Plate. — The  medial  pterygoid  plate  is  narrower  and  longer 
than  the  lateral;  it  curves  lateralward  at  its  lower  extremity  into  a  hook-like  pro- 
cess, the  pterygoid  hamulus,  around  which  the  tendon  of  the  Tensor  veli  palatini 
glides.  The  lateral  surface  of  this  plate  forms  part  of  the  pterygoid  fossa,  the 
medial  surface  constitutes  the  lateral  boundary  of  the  choana  or  posterior  aperture 
of  the  corresponding  nasal  cavity.  Superiorly  the  medial  plate  is  prolonged  on  to 
the  under  surface  of  the  body  as  a  thin  lamina,  named  the  vaginal  process,  which 
articulates  in  front  with  the  sphenoidal  process  of  the  palatine  and  behind  this 
with  the  ala  of  the  vomer.  The  angular  prominence  between  the  posterior  margin 
of  the  vaginal  process  and  the  medial  border  of  the  scaphoid  fossa  is  named  the 
pterygoid  tubercle,  and  immediately  above  this  is  the  posterior  opening  of  the 
pterygoid  canal.  On  the  under  surface  of  the  vaginal  process  is  a  furrow,  which 
is  converted  into  a  canal  by  the  sphenoidal  process  of  the  palatine  bone,  for  the 
transmission  of  the  pharyngeal  branch  of  the  internal  maxillary  artery  and  the 
phar^'ngeal  nerve  from  the  sphenopalatine  ganglion.  The  pharyngeal  aponeurosis 
is  attached  to  the  entire  length  of  the  posterior  edge  of  the  medial  plate,  and  the 
Constrictor  pharyngis  superior  takes  origin  from  its  lower  third.  Projecting 
backward  from  near  the  middle  of  the  posterior  edge  of  this  plate  is  an  angular 
process,  the  processus  tubarius,  w^hich  supports  the  pharyngeal  end  of  the  auditor}^ 
tube.  The  anterior  margin  of  the  plate  articulates  with  the  posterior  border  of 
the  vertical  part  of  the  palatine  bone. 

The  Sphenoidal  Conchae  {conchae  sphenoidales;  sphenoidal  turbinated  processes). 
— The  sphenoidal  conchae  are  two  thin,  curved  plates,  situated  at  the  anterior 
and  lower  part  of  the  body  of  the  sphenoid.  An  aperture  of  variable  size  exists 
in  the  anterior  wall  of  each,  and  through  this  the  sphenoidal  sinus  opens  into  the 
nasal  cavity.  Each  is  irregular  in  form,  and  tapers  to  a  point  behind,  being  broader 
and  thinner  in  front.  Its  upper  surface  is  concave,  and  looks  toward  the  cavity 
of  the  sinus;  its  under  surface  is  convex,  and  forms  part  of  the  roof  of  the  corre- 
sponding nasal  cavity.  Each  bone  articulates  in  front  with  the  ethmoid,  laterally 
with  the  palatine;  its  pointed  posterior  extremity  is  placed  above  the  vomer, 
and  is  received  between  the  root  of  the  pterygoid  process  laterally  and  the  rostrum 
of  the  sphenoid  medially.  A  small  portion  of  the  sphenoidal  concha  sometimes 
enters  into  the  formation  of  the  medial  wall  of  the  orbit,  between  the  lamina 
papyracea  of  the  ethmoid  in  front,  the  orbital  plate  of  the  palatine  below,  and  the 
frontal  bone  above. 


THE  ETIIMOIDM.  BOXE 


251 


Ossification. — Until  the  seventh  or  ei^litli  month  of  fetal  life  the  body  of  the  sphenoid  consists 
of  two  ijarts,  \iz.,  one  in  front  of  the  tuhercnluni  sellae,  the  presphenoid,  with  which  the  small 
wings  are  continuous;  the  other,  comprising  the  sella  turcica  and  dorsum  sellae,  the  poslsphenoid, 
with  which  are  associated  the  great  wings,  and  pterygoid  i)rocesses.  The  greater  part  of  the  bone 
is  ossified  in  cartilage.  There  are  fourteen  centres  in  all,  six  for  the  presphenoid  and  eight  for 
the  postsphenoid. 

Presphenoid. — About  the  ninth  week  of  fetal  life  an  ossific  centre  appears  for  each  of  the  small 
wings  (orbitosphenoids)  just  lateral  to  the  optic  foramen;  shortly  afterward  two  nuclei  appear 
in  the  presphenoid  part  of  the  body.  The  sphenoidal  conchai  are  each  developed  from  a  centre 
which  makes  its  appearance  about  the  fifth  month ;^  at  birth  they  consist  of  small  triangular 
lamina:>,  and  it  is  not  until  the  third  year  that  they  become  hollowed  out  and  cone-shaped;  about 
the  fourth  year  they  fuse  with  the  labyi-inths  of  the  ethmoid,  and  between  the  ninth  and  twelfth 
years  the}^  unite  with  the  sphenoid. 

Postsphenoid, — The  first  ossific  nuclei  are  those  for  the  great  wings  (ali-sphenoids) .  One  makes 
its  appearance  in  each  wing  between  the  foramen  rotundum  and  foramen  ovale  about  the  eighth 
week.  The  orbital  plate  and  that  part  of  the  sphenoid  which  is  found  in  the  temporal  fossa,  as 
well  as  the  lateral  pterygoid  plate,  are  ossified  in  membrane  (Fawcett-).  Soon  after,  the  centres 
for  the  postsphenoid  part  of  the  body  appear,  one  on  either  side  of  the  sella  turcica,  and  become 
blended  together  about  the  middle  of  fetal  life.  Each  medial  pterygoid  plate  (with  the  exception 
of  its  hamulus)  is  ossified  in  membrane,  and  its  centre  probably  appears  about  the  ninth  or  tenth 
w^eek;  the  hamulus  becomes  chondrified  during  the  third  month,  and  almost  at  once  undergoes 
ossification  (Fawcett^).  The  medial  joins  the  lateral  pterygoid  plate  about  the  sixth  month. 
About  the  fourth  month  a  centre  appears  for  each  lingula  and  speedily  joins  the  rest  of  the  bone. 

The  presphenoid  is  united  to  the  postsphenoid  about  the  eighth  month,  and  at  birth  the  bone 
is  in  three  pieces  (Fig.  292) :  a  central,  consisting  of  the  body  and  small  wings,  and  two  lateral, 
each  comprising  a  gi'eat  wing  and  ptery- 
goid process.  In  the  first  year  after 
birth  the  great  wings  and  body  unite, 
and  the  small  wings  extend  inward 
above  the  anterior  part  of  the  body, 
and,  meeting  with  each  other  in  the 
middle  line,  form  an  elevated  smooth 
surface,  termed  the  jugum  sphenoidale. 
By  the  twenty-fifth  year  the  sphenoid 
and  occipital  are  completely  fused.  Be- 
tween the  pre-  and  postsphenoid  there 
are  occasionally  seen  the  remains  of  a 
canal,  the  canalis  craniopharyngeus, 
through  which,  in  early  fetal  life,  the 
hypophyseal  diverticulum  of  the  buccal 
ectoderm  is  transmitted  (see  page  166). 

The  sphenoidal  sinuses  are  present  as  minute  cavities  at  the  time  of  birth  (Onodi),  but  do  not 
attain  their  full  size  until  after  puberty. 

Certain  intrinsic  Ugaments  are  attached  to  the  sphenoid.  The  more  important  of  these  are: 
the  pterygospinous,  stretching  between  the  spina  angularis  and  the  lateral  pterygoid  plate  (see 
cervical  fascia);  the  interclinoid,  a  fibrous  process  joining  the  anterior  to  the  posterior  clinoid 
process;  and  the  caroticoclinoid,  connecting  the  anterior  to  the  middle  clinoid  process.  These 
ligaments  occasionally  ossify. 

Articulations. — The  sphenoid  articulates  with  twelve  bones:  fom-  single,  the  vomer,  ethmoid, 
frontal,  and  occipital;  and  four  paired,  the  parietal,  temporal,  zygomatic,  and  palatine.* 


Fig.   292. — Sphenoidal  bone  at  birth.     Posterior  aspect. 


The  Ethmoidal  Bone  (Os  Ethmoidale;  Ethmoid  Bone). 

The  ethmoidal  bone  is  exceedingly  light  and  spongy,  and  cubical  in  shape;  it 
is  situated  at  the  anterior  part  of  the  base  of  the  cranium,  between  the  two  orbits, 
at  the  roof  of  the  nose,  and  contributes  to  each  of  these  cavities.  It  consists  of 
four  parts:  a  horizontal  or  cribriform  plate,  forming  part  of  the  base  of  the  cranium; 
a  perpendicular  plate,  constituting  part  of  the  nasal  septum;  and  two  lateral  masses 
or  labvrinths. 


1  According  to  Cleland,  each  sphenoidal  concha  is  ossified  from  four  centres. 

2  Journal  of  Anatomy  and  Physiology,  1910,  vol.  xliv. 
2  Anatomischer  Anzeiger,  March,  1905. 

*  It  also  sometimes  articulates  with  the  tuberosity  of  the  maxilla  (see  page  257). 


252 


OSTEOLOGY 


Perpendicular  plate 
Ala 


Crista  gain 


Cribiform  Plate  (lamina  cribrosa;  horizontal  lamina). — The  cribriform  plate 
(Fig.  293)  is  received  into  the  ethmoidal  notch  of  the  frontal  bone  and  roofs  in 
the  nasal  cavities.  Projecting  upward  from  the  middle  line  of  this  plate  is  a  thick, 
smooth,  triangular  process,  the  crista  galli,  so  called  from  its  resemblance  to  a 
cock's  comb.    Its  posterior  border,  long,  thin,  and  slightly  curved,  serves  for  the 

attachment  of  the  falx  cerebri. 
Its  anterior  border,  short  and 
thick,  articulates  with  the  frontal 
bone,  and  presents  two  small  pro- 
jecting alae,  which  are  received 
into  corresponding  depressions  in 
the  frontal  bone  and  complete 
the  foramen  cecum.  Its  sides  are 
smooth,  and  sometimes  bulging 
from  the  presence  of  a  small  air 
sinus  in  the  interior.  On  either 
side  of  the  crista  galli,  the  cribri- 
form plate  is  narrow  and  deeply 
grooved;  it  supports  the  olfactory 
V  , '£     ;-.\  j/ktl  -  Posterior  ethmoidal     bulb   and  is  perforated  by  fora- 

•''^*^»'       -■,--<>'  y^         groove  mina  for  the  passage  of  the  olfac- 

tory nerves.  The  foramina  in  the 
middle  of  the  groove  are  small 
and  transmit  the  nerves  to  the 
roof  of  the  nasal  cavity;  those  at  the  medial  and  lateral  parts  of  the  groove  are 
larger — the  former  transmit  the  nerves  to  the  upper  part  of  the  nasal  septum, 
the  latter  those  to  the  superior  nasal  concha.  At  the  front  part  of  the  cribriform 
plate,  on  either  side  of  the  crista  galli,  is  a  small  fissure  which  is  occupied  by  a 
process  of  dura  mater.  Lateral  to  this  fissure  is  a  notch  or  foramen  which  trans- 
mits the  nasociliary  nerve;  from  this  notch  a  groove  extends  backward  to  the 
anterior  ethmoidal  foramen. 


Cribriform  jdate 

Anterior  ethmoidal 
groove 


Fig.  293. — ^Ethmoidal  bone  from  above. 


^th  EtAmoidtii 


Fig.  29-1. — Perpendicular  plate  of  ethmoid.     Shown  by  removnng  the  right  labyrinth. 


Perpendicular  Plate  {lamina  perpendicular  is;  vertical  plate). — The  perpendicular 
plate  (Figs.  294,  295)  is  a  thin,  fiattened  lamina,  polygonal  in  form,  which  descends 
from  the  under  surface  of  the  cribriform  plate,  and  assists  in  forming  the  septum 
of  the  nose;  it  is  generally  deflected  a  little  to  one  or  other  side.    The  anterior  border 


THE  ETHMOIDAL  BOXE 


253 


articulates  with  the  spine  of  the  frontal  hone  and  the  crest  of  the  nasal  hones. 
The  posterior  border  articulates  hy  its  upper  half  with  the  sphenoidal  crest,  b\'  its 
lower  with  the  vomer.  The  inferior  border  is  thicker  than  the  posterior,  and  serves 
for  the  attachment  of  the  septal  cartilage  of  the  nose.  The  surfaces  of  the  plate 
are  smooth,  except  above,  where  numerous  grooves  and  canals  are  seen;  these 
lead  from  the  medial  foramina  on  the  cribriform  ])late  and  lodge  filaments  of  the 
olfactory  nerves. 

The  Labyrinth  or  Lateral  Mass  Qahyriufhus  ethmoidalis)  consists  of  a  number 
of  thin-walled  cellular  cavities,  the  ethmoidal  cells,  arranged  in  three  groups, 
anterior,  middle,  and  yosterior,  and  inter- 
posed between  two  vertical  plates  of  bone ; 
the  lateral  plate  forms  part  of  the  orbit, 
the  medial,  part  of  the  corresponding 
nasal  cavity.  In  the  disarticulated  bone 
many  of  these  cells  are  opened  into,  but 
when  the  bones  are  articulated,  they  are 
closed  in  at  every  part,  except  where 
they  open  into  the  nasal  cavity. 

Surfaces. — The  upper  surface  of  the  laby- 
rinth (Fig.  293)  presents  a  number  of 
half-broken  cells,  the  walls  of  which  are 
completed,  in  the  articulated  skull,  by 
the  edges  of  the  ethmoidal  notch  of  the 
frontal  bone.  Crossing  this  surface  are 
two  grooves,  converted  into  canals  by  articulation  with  the  frontal;  they  are  the 
anterior  and  posterior  ethmoidal  canals,  and  open  on  the  inner  wall  of  the  orbit. 
The  posterior  surface  presents  large  irregular  cellular  cavities,  which  are  closed  in 
by  articulation  with  the  sphenoidal  concha  and  orbital  process  of  the  palatine. 
The  lateral  surface  (Fig.  296)  is  formed  of  a  thin,  smooth,  oblong  plate,  the  lamina 
papyracea  {os  planum),  which  covers  in  the  middle  and  posterior  ethmoidal  cells 


Fig.  295. 


Crista  fjalU 


Labyrinth 

Superior  nasal 

concha 
Superior  meatus 

Uncinate  process 

Middle  nasal  concha 
Perpendicular  plate 
Ethmoidal  bone  from  behind. 


Ethmoidal 
cells 


Perpendicular 
plate 


Uncinate  process 


Fig.  296. — Ethmoidal  bone  from  the  right  side. 


and  forms  a  large  part  of  the  medial  wall  of  the  orbit;  it  articulates  above  with 
the  orbital  plate  of  the  frontal  bone,  below  with  the  maxilla  and  orbital  process 
of  the  palatine,  in  front  with  the  lacrimal,  and  behind  with  the  sphenoid. 

In  front  of  the  lamina  papyracea  are  some  broken  air  cells  which  are  overlapped 
and  completed  by  the  lacrimal  bone  and  the  frontal  process  of  the  maxilla.  A 
curved  lamina,  the  uncinate  process,  projects  downward  and  backward  from  this 
part  of  the  labyrinth;  it  forms  a  small  part  of  the  medial  wall  of  the  maxillary 
sinus,  and  articulates  with  the  ethmoidal  process  of  the  inferior  nasal  concha. 


254 


OSTEOLOGY 


The  medial  surface  of  the  labyrinth  (Fig.  297)  forms  part  of  the  lateral  wall 
of  the  corresponding  nasal  cavity.  It  consists  of  a  thin  lamella,  which  descends 
from  the  under  surface  of  the  cribriform  plate,  and  ends  below  in  a  free,  convoluted 
margin,  the  middle  nasal  concha.  It  is  rough,  and  marked  above  by  numerous 
grooves,  directed  nearly  vertically  downward  from  the  cribriform  plate;  they 
lodge  branches  of  the  olfactory  nerves,  which  are  distributed  to  the  mucous  mem- 
brane covering  the  superior  nasal  concha.  The  back  part  of  the  surface  is  sub- 
divided by  a  narrow  oblique  fissure,  the  superior  meatus  of  the  nose,  bounded  above 
by  a  thin,  curved  plate,  the  superior  nasal  concha;  the  posterior  ethmoidal  cells 
open  into  this  meatus.    Below,  and  in  front  of  the  superior  meatus,  is  the  convex 


Frontal  sinus 

-Crista  galli 


Sella  turcica 


Uncinate 

process  of 

ethmoid 


Openings  into 
maxillary  sinus 
Medial  pterygoid  plate 
Hamulus 


Fig.  297. — Lateral  wall  of  nasal  cavity,  showing  ethmoidal  bone  in  position. 

surface  of  the  middle  nasal  concha;  it  extends  along  the  wdiole  length  of  the  medial 
surface  of  the  labyrinth,  and  its  lower  margin  is  free  and  thick.  The  lateral  surface 
of  the  middle  concha  is  concave,  and  assists  in  forming  the  middle  meatus  of  the 
nose.  The  middle  ethmoidal  cells  open  into  the  central  part  of  this  meatus,  and  a 
sinuous  passage,  termed  the  infundibulum,  extends  upward  and  forward  through 
the  labyrinth  and  communicates  with  the  anterior  ethmoidal  cells,  and  in  about 
50  per  cent,  of  skulls  is  continued  upward  as  the  frontonasal  duct  into  the  frontal 
sinus. 

Ossification. — The  ethmoid  is  ossified  in  the  cartilage  of  the  nasal  capsule  by  three  centres: 
one  for  the  perpendicular  plate,  and  one  for  each  labyrinth. 

The  labyrinths  are  first  developed,  ossific  granules  making  their  appearance  in  the  region  of 
the  lamina  papyia.cea  between  the  fourth  and  fifth  months  of  fetal  life,  and  extending  into  the 
conchse.  At  birth,  the  bone  consists  of  the  two  labyrinths,  which  are  small  and  ill-developed. 
During  the  first  year  after  birth,  the  perpendicular  plate  and  crista  gaUi  begin  to  ossify  from  a 
single  centre,  and  are  joined  to  the  labyrinths  about  the  beginning  of  the  second  year.  The 
cribriform  plate  is  ossified  partly  from  the  perpendicular  plate  and  partly  from  the  labyrinths. 
The  development  of  the  ethmoidal  cells  begins  during  fetal  life. 


THE  NASAL  BOXES 


255 


Articulations. — The  ethmoid  articulates  with  fifteen  bones:  four  of  the  cranium — the  frontal, 
the  si)heiioi(l,  and  the  two  sphenoidal  concha?;  and  eleven  of  the  face — the  two  nasals,  two  maxilla;, 
two  latrinials.  two  palatines,  two  inferior  nasal  concha?,  and  the  vomer. 

Sutural  or  Wormian'  Bones. — In  addition  to  the  usual  centres  of  o.ssification  of  the  craniinn, 
others  may  occin-  in  the  course  of  the  sutures,  giving  rise  to  irregular,  isolated  bones,  termed 
sutural  or  Wormian  bones.  They  occur  most  frequently  in  the  course  of  the  lambdoidal  suture, 
but  are  occasionally  seen  at  the  fontanelles,  especially  the  ])osterior.  One,  the  plerion  ossicle, 
sometimes  exists  between  the  sphenoidal  angle  of  the  i)arietal  and  the  great  wing  of  the  .sphenoid. 
They  have  a  tendency  to  be  more  or  less  symmetrical  on  the  two  sides  of  the  .skull,  and  vary 
much  in  size.  Their  number  is  generally  limited  to  two  or  three;  but  more  than  a  hundred  have 
been  ftnmd  in  th(>  skull  of  an  adult  hydrocephalic  subject. 

Applied  Anatomy. — An  arrest  in  the  ossifying  process' may  give  rise  to  deficiencies,  gaps,  or 
fissures  in  the  cranium,  which  are  of  importance  from  a  medicolegal  point  of  view,  as  thej^  arc 
liable  to  be  mistaken  for  fractures.  The  fissures  generally  extend  from  the  margins  toward  the 
centre  of  a  bone,  but  the  gaps  may  be  found  in  the  middle  as  well  as  at  the  edges.  In  course  of 
time  they  maj'  become  filled  with  thin  laminae  of  bone.  In  manj^  of  these  cases,  however,  the 
gaps  must  be  regarded  as  due  to  absorption  of  bone  already  formed  rather  than  as  congenital 
deficiencies;  this  is  especially  the  case  when  they  appear  in  the  centre  of  a  bone  such  as  the  parietal, 
the  ossification  of  which  has  already  been  described  as  occurring  in  a  regular  manner  radiating 
from  one  centre.  The  condition  is  most  commonly  seen  in  verj^  badly  nom'ished  children  affected 
with  congenital  syphilis,  and  is  called  cranioiabes. 


THE  FACIAL  BONES   (OSSA  FACIEI). 

The  Nasal  Bones  (Ossa  Nasalia) . 

The  nasal  bones  are  two  small  oblong  bones,  varying  in  size  and  form  in  different 
individuals;  they  are  placed  side  by  side  at  the  middle  and  upper  part  of  the  face, 


FuitVi  Joi  lac)  oiKil  sac 


Infraorhiial 
foramen 


Fig.  298. — Articulation  of  nasal  and  lacrimal  bones  with  maxilla. 

and  form,  by  their  junction,  "the  bridge"  of  the  nose  (Fig.  334).    Each  has  two 
surfaces  and  four  borders. 


'  Ole  Worm,  Professor  of  Anatomy  at  Copenhagen,  1624-1639,  was  erroneously  supposed  to  have  given  the  first 
detailed  description  of  these  bones. 


256 


OSTEOLOGY 


Surfaces. — The  outer  surface  (Fig.  299)  is  concavoconvex  from  above  downward, 
convex  from  side  to  side;  it  is  covered  by  the  Procerus  and  Compressor  naris,  and 
perforated  about  its  centre  by  a  foramen,  for  the  transmission  of  a  small  vein. 
The  inner  surface  (Fig.  300)  is  concave  from  side  to  side,  and  is  traversed  from  above 
downward,  by  a  groove  for  the  passage  of  a  branch  of  the  nasociliary  nerve. 

Borders. — The  superior  border  is  narrow,  thick,  and  serrated  for  articulation  with 
the  nasal  notch  of  the  frontal  bone.  The  inferior  border  is  thin,  and  gives  attach- 
ment to  the  lateral  cartilage  of  the  nose;  near  its  middle  is  a  notch  which  marks 
the  end  of  the  groove  just  referred  to.  The  lateral  border  is  serrated,  bevelled 
at  the  expense  of  the  inner  surface  above,  and  of  the  outer  below,  to  articulate 
with  the  frontal  process  of  the  maxilla.  The  medial  border,  thicker  above  than 
below,  articulates  with  its  fellow  of  the  opposite  side,  and  is  prolonged  behind  into 
a  vertical  crest,  which  forms  part  of  the  nasal  septum :  this  crest  articulates,  from 
above  downward,  with  the  spine  of  the  frontal,  the  perpendicular  plate  of  the 
ethmoid,  and  the  septal  cartilage  of  the  nose. 


nvi'^yi 


Foramen 

fci'  vein 


Fig.  299. — Right  nasal  bone.     Outer  surface. 


Crest 


Groove 
for  nerve 


Fig.  300. — Right  nasal  bone.     Inner  surface. 


Ossification. — Each  bone  is  ossified  from  one  centre,  which  appears  at  the  beginning  of  the 
third  month  of  fetal  life  in  the  membrane  overlying  the  front  part  of  the  cartilaginous  nasal 
capsule. 

Articulations. — The  nasal  articulates  with  four  bones:  two  of  the  cranium,  the  frontal  and 
ethmoid,  and  two  of  the  face,  the  opposite  nasal  and  the  maxilla. 


The  Maxillae  (Upper  Jaw). 

The  maxillae  are  the  largest  bones  of  the  face,  excepting  the  mandible,  and 
form;  by  their  union,  the  whole  of  the  upper  jaw.  Each  assists  in  forming  the 
boundaries  of  three  cavities,  viz.,  the  roof  of  the  mouth,  the  floor  and  lateral 
wall  of  the  nose  and  the  floor  of  the  orbit;  it  also  enters  into  the  formation  of  two 
fossse,  the  infratemporal  and  pterygopalatine,  and  two  fissures,  the  inferior  orbital 
and  pterygomaxillary. 

Each  bone  consists  of  a  body  and  four  processes — zygomatic,  frontal,  alveolar, 
and  palatine. 

The  Body  {corpus  maxillae). — The  body  is  somewhat  pyramidal  in  shape,  and 
contains  a  large  cavity,  the  maxillary  sinus  {antrum  of  Highmore).  It  has  four 
surfaces — an  anterior,  a  posterior  or  infratemporal,  a  superior  or  orbital,  and  a 
medial  or  nasal. 

Surfaces. — The  anterior  surface  (Fig.  301)  is  directed  forward  and  lateralward. 
It  presents  at  its  lower  part  a  series  of  eminences  corresponding  to  the  positions 
of  the  roots  of  the  teeth.  Just  above  those  of  the  incisor  teeth  is  a  depression, 
the  incisive  fossa,  which  gives  origin  to  the  Depressor  alae  nasi;  to  the  alveolar 
border  below  the  fossa  is  attached  a  slip  of  the  Orbicularis  oris;  above  and  a  little 
lateral  to  it,  the  Xasalis  arises.    Lateral  to  the  incisive  fossa  is  another  depression. 


THE  MAXILL.E 


257 


the  canine  fossa;  it  is  larger  and  deeper  than  the  incisive  fossa,  and  is  separated 
from  it  by  a  \ertical  ridge,  the  canine  eminence,  corresponding  to  the  socket  of 
the  canine  tooth;  tiie  canine  fossa  gives  origin  to  the  Caninus.  Above  the  fossa 
is  the  infraorbital  foramen,  the  end  of  the  infraorbital  canal;  it  transmits  the  infra- 
orbital vessels  and  ncr\e.  iVbove  the  foramen  is  the  margin  of  the  orbit,  which 
affords  attachment  to  part  of  the  Quadratus  labii  superioris.  Medially,  the  anterior 
surface  is  limited  by  a  deep  concavity,  the  nasal  notch,  the  margin  of  which  gives 
attachment  to  the  Dilatator  naris  posterior  and  ends  below  in  a  pointed  process, 
whic-h  with  its  fellow  of  the  opposite  side  forms  the  anterior  nasal  spine. 


Med.  palp 


Dilatator  naris  posterior 


tubercle 


Incisive  Jossa 


Alveolar  canals 


Maxillary  tuberosity 


Fig.  301. — Left  maxilla 


Outer  surface. 


The  infratemporal  surface  (Fig.  301)  is  convex,  directed  backw^ard  and  lateral- 
ward,  and  forms  part  of  the  infratemporal  fossa.  It  is  separated  from  the  anterior 
surface  by  the  zygomatic  process  and  by  a  strong  ridge,  extending  upward  from 
the  socket  of  the  first  molar  tooth.  It  is  pierced  about  its  centre  by  the  apertures 
of  the  alveolar  canals,  which  transmit  the  posterior  superior  alveolar  vessels  and 
nerves.  At  the  lower  part  of  this  surface  is  a  rounded  eminence,  the  maxillary 
tuberosity,  especially  prominent  after  the  growth  of  the  wisdom  tooth;  it  is  rough 
on  its  lateral  side  for  articulation  with  the  pyramidal  process  of  the  palatine  bone 
and  in  some  cases  articulates  with  the  lateral  pterygoid  plate  of  the  sphenoid. 
It  gives  origin  to  a  few  fibres  of  the  Pterygoideus  internus.  Immediately  above 
this  is  a  smooth  surface,  which  forms  the  anterior  boundary  of  the  pterygopalatine 
fossa,  and  presents  a  groove,  for  the  maxillary  nerve;  this  groove  is  directed  lateral- 
ward  and  slightly  upward,  and  is  continuous  with  the  infraorbital  groove  on  the 
orbital  surface. 

The  orbital  surface  (Fig.  301)  is  smooth  and  triangular,  and  forms  the  greater 
part  of  the  floor  of  the  orbit.  It  is  bounded  mediaUy  by  an  irregular  margin  which 
in  front  presents  a  notch,  the  lacrimal  notch;  behind  this  notch  the  margin  articu- 
lates with  the  lacrimal,  the  lamina  papyracea  of  the  ethmoid  and  the  orbital  process 
of  the  palatine.  It  is  bounded  hehind  by  a  smooth  rounded  edge  which  forms 
the  anterior  margin  of  the  inferior  orbital  fissure,  and  sometimes  articulates  at 
its  lateral  extremity  with  the  orbital  surface  of  the  great  wing  of  the  sphenoid. 
17 


258 


OSTEOLOGY 


It  is  limited  in  front  by  part  of  the  circumference  of  the  orbit,  which  is  continuous 
medially  with  the  frontal  process,  and  laterally  with  the  zyogmatic  prf)cess.  Near 
the  middle  of  the  posterior  part  of  the  orbital  surface  is  the  infraorbital  groove, 
for  the  passage  of  the  infraorbital  vessels  and  nerve.  The  groove  begins  at  the 
middle  of  the  posterior  border,  where  it  is  continuous  with  that  near  the  upper 
edge  of  the  infratemporal  surface,  and,  passing  forward,  ends  in  a  canal,  which 
subdivides  into  two  branches.  One  of  the  canals,  the  infraorbital  canal,  opens 
just  below  the  margin  of  the  orbit;  the  other,  which  is  smaller,  runs  downward  in 
the  substance  of  the  anterior  wall  of  the  maxillary  sinus,  and  transmits  the  anterior 
superior  alveolar  vessels  and  nerve  to  the  front  teeth  of  the  maxilla.  From  the 
back  part  of  the  infraorbital  canal,  a  second  small  canal  is  sometimes  given  off;  it 
runs  downward  in  the  lateral  wall  of  the  sinus,  and  conveys  the  middle  alveolar 
nerve  to  the  premolar  teeth.  At  the  medial  and  forepart  of  the  orbital  surface, 
just  lateral  to  the  lacrimal  groove,  is  a  depression,  which  gives  origin  to  the  Obliquus 
oculi  inferior. 

With  frontal 


Bones  'partially  closing  orifice  of  sinus 
tnarked  in  red 


Ethmoid — 
Inferior  nasal  concha- 
Palatine 


th  nasal  hone 


Ant.  nasal  spine 


Bristle  passed 
through  incisive 
canal 


Fig.  302. — Left  maxilla.     Nasal  surface. 


The  nasal  surface  (Fig.  302)  presents  a  large,  irregular  opening  leading  into  the 
maxillary  sinus.  At  the  upper  border  of  this  aperture  are  some  broken  air  cells, 
which,  in  the  articulated  skull,  are  closed  in  by  the  ethmoid  and  lacrimal  bones. 
Below  the  aperture  is  a  smooth  concavity  which  forms  part  of  the  inferior  meatus 
of  the  nasal  cavity,  and  behind  it  is  a  rough  surface  for  articulation  with  the  per- 
pendicular part  of  the  palatine  bone;  this  surface  is  traversed  by  a  groove,  com- 
mencing near  the  middle  of  the  posterior  border  and  running  obliquely  downward 
and  forward;  the  groove  is  converted  into  a  canal,  the  pterygopalatine  canal,  by  the 
palatine  bone.  In  front  of  the  opening  of  the  sinus  is  a  deep  groove,  the  lacrimal 
groove,  which  is  converted  into  the  nasolacrimal  canal,  by  the  lacrimal  bone  and 
inferior  nasal  concha;  this  canal  opens  into  the  inferior  meatus  of  the  nose  and 
transmits  the  nasolacrimal  duct.  More  anteriorly  is  an  oblique  ridge,  the  conchal 
crest,  for  articulation  with  the  inferior  nasal  concha.  The  shallow  concavity  above 
this  ridge  forms  part  of  the  atrium  of  the  middle  meatus  of  the  nose,  and  that 
below  it,  part  of  the  inferior  meatus. 


THE  MAXILL.E 


259 


The  Maxillary  Sinus  or  Antrum  of  Highmore  {sinus  maxillaris). — The  maxillary 
sinus  is  a  large  pyramidal  c'a\ity,  within  the  body  of  the  maxilla:  its  apex,  directed 
laterahvard,  is  formed  by  the  zygDmatic  process;  its  base,  directed  mediahvard, 
by  the  lateral  wall  of  the  nose.  Its  walls  are  everywhere  exceedingly  thin,  and 
correspond  to  the  nasal  orbital,  anterior,  and  infratemporal  surfaces  of  the  body 
of  the  bone.  Its  nasal  wall,  or  base,  presents,  in  the  disarticulated  bone,  a  large, 
irregular  aperture,  connnnnicating  with  the  nasal  cavity.  In  the  articulated 
skull  this  aperture  is  much  reduced  in  size  by  the  following  bones:  the  uncinate 
process  of  the  ethmoid  above,  the  ethmoidal  process  of  the  inferior  nasal  concha 
below,  the  vertical  part  of  the  palatine  behind,  and  a  small  part  of  the  lacrimal 
above  and  in  front  (Figs.  302,  303) ;  the  sinus  communicates  with  the  middle  meatus 
of  the  nose,  generally  by  two  small  apertures  left  between  the  above-mentioned 
bones.    In  the  recent  state,  usually  only  one  small  opening  exists,  near  the  upper 


Anterior 
ethmoidal  Joraimn 


Fossa  for 

lacrimal  sac 

Uncinate  process 
of  ethmoid 
Openings  of 
maxillary  sinus 
Inferior  nasal 
concha 


.Posterior  ethmoidal  foramen 
'^Orbital  process  of  palatine 
Gplic  forainen 

Sphenopalatine  foramen 

Sella  turcica 

I   Probe  in  foramen  rot  undum 


-/  -  -  Pi  obe  in  pterygoid  canal 

Piobe  in  pteiygopalatine  canal 

Palatine  hone 

Lateral  pteiygcid  plate 


\'  'j  ^     y^  Pyiamidai  proce--s  of  palatine 

Fig.  303. — Left  maxillary  sinus  opened  from  the  exterior. 


part  of  the  cavity;  the  other  is  closed  by  mucous  membrane.  On  the  posterior 
wall  are  the  alveolar  canals,  transmitting  the  posterior  superior  alveolar  vessels 
and  nerves  to  the  molar  teeth.  The  floor  is  formed  by  the  alveolar  process  of  the 
maxilla,  and,  if  the  sinus  be  of  an  average  size,  is  on  a  level  with  the  floor  of 
the  nose;  if  the  sinus  be  large  it  reaches  below  this  level. 

Projecting  into  the  floor  of  the  antrum  are  several  conical  processes,  correspond- 
ing to  the  roots  of  the  first  and  second  molar  teeth  ;^  in  some  cases  the  floor  is 
perforated  by  the  fangs  of  the  teeth.  The  infraorbital  canal  usually  projects  into 
the  cavity  as  a  well-marked  ridge  extending  from  the  roof  to  the  anterior  wall; 
additional  ridges  are  sometimes  seen  in  the  posterior  wall  of  the  cavity,  and 


1  The  number  of  teeth  whose  roots  are  in  relation  with  the  floor  of  the  antrum  is  variable.    The  sinus  "may  extend 
so  as  to  be  in  relation  to  all  the  teeth  of  the  true  maxilla,  from  the  canine  to  the  dens  sapientiae."     (Salter.) 


260  OSTEOLOGY 

are  caused  by  the  alveolar  canals.    The  size  of  the  cavity  varies  in  different  skulls, 
and  even  on  the  two  sides  of  the  same  skull. ^ 

Applied  Anatomy. — -The  extreme  thinness  of  the  walls  of  this  cavity  affords  an  explanation 
of  the  fact  tliat  a  tumor  growing  from  the  maxillary  sinus  and  encroaching  upon  the  adjacent 
parts  may  push  up  the  floor  of  the  orbit,  and  displace  the  eyeball;  may  project  into  the  nose; 
may  protrude  forward  on  to  the  cheek;  or  may  make  its  way  backward  into  the  infratemporal 
fossa,  or  downward  into  the  mouth. 

The  Zygomatic  Process  (processus  zygomaticus;  malar  lyrocess). — ^The  zygomatic 
process  is  a  rough  triangular  eminence,  situated  at  the  angle  of  separation  of  the 
anterior,  zygomatic,  and  orbital  surfaces.  In  front  it  forms  part  of  the  anterior 
surface;  behind,  it  is  concave,  and  forms  part  of  the  infratemporal  fossa;  above, 
it  is  rough  and  serrated  for  articulation  with  the  zygomatic  bone;  while  below, 
it  presents  the  prominent  arched  border  which  marks  the  division  between  the 
anterior  and  infratemporal  surfaces. 

The  Frontal  Process  {processus  frontalis;  nasal  process). — The  frontal  process 
is  a  strong  plate,  which  projects  upward,  medialward,  and  backward,  by  the  side 
of  the  nose,  forming  part  of  its  lateral  boundary.  Its  lateral  surface  is  smooth, 
continuous  with  the  anterior  surface  of  the  body,  and  gives  attachment  to  the 
Quadratus  labii  superioris,  the  Orbicularis  oculi,  and  the  medial  palpebral  ligament. 
Its  medial  surface  forms  part  of  the  lateral  wall  of  the  nasal  cavity;  at  its  upper 
part  is  a  rough,  uneven  area,  which  articulates  with  the  ethmoid,  closing  in  the 
anterior  ethmoidal  cells;  below  this  is  an  oblique  ridge,  the  ethmoidal  crest,  the 
posterior  end  of  which  articulates  with  the  middle  nasal  concha,  while  the  anterior 
part  is  termed  the  agger  nasi;  the  crest  forms  the  upper  limit  of  the  atrium  of  the 
middle  meatus.  The  upper  border  articulates  with  the  frontal  bone  and  the  anterior 
with  the  nasal;  the  posterior  border  is  thick,  and  hollowed  into  a  groove,  which  is 
continuous  below  with  the  lacrimal  groove  on  the  nasal  surface  of  the  body:  by 
the  articulation  of  the  medial  margin  of  the  groove  with  the  anterior  border  of 
the  lacrimal  a  corresponding  groove  on  the  lacrimal  is  brought  into  continuity, 
and  together  they  form  the  lacrimal  fossa  for  the  lodgement  of  the  lacrimal  sac. 
The  lateral  margin  of  the  groove  is  named  the  anterior  lacrimal  crest,  and  is  con- 
tinuous below^  with  the  orbital  margin;  at  its  junction  with  the  orbital  surface  is 
a  small  tubercle,  the  lacrimal  tubercle,  which  serves  as  a  guide  to  the  position  of 
the  lacrimal  sac. 

The  Alveolar  Process  {processus  alveolaris). — ^The  alveolar  process  is  the  thickest 
and  most  spongy  part  of  the  bone.  It  is  broader  behind  than  in  front,  and  exca- 
vated into  deep  cavities  for  the  reception  of  the  teeth.  These  cavities  are  eight 
in  number,  and  vary  in  size  and  depth  according  to  the  teeth  they  contain.  That 
for  the  canine  tooth  is  the  deepest;  those  for  the  molars  are  the  widest,  and  are 
subdivided  into  minor  cavities  by  septa;  those  for  the  incisors  are  single,  but 
deep  and  narrow.  The  Buccinator  arises  from  the  outer  surface  of  this  process, 
as  far  forward  as  the  first  molar  tooth.  When  the  maxillae  are  articulated  with  each 
other,  their  alveolar  processes  together  form  the  alveolar  arch;  the  centre  of  the 
anterior  margin  of  this  arch  is  named  the  alveolar  point. 

The  Palatine  Process  {processus  palatinus;  palatal  process). — -The  palative 
process,  thick  and  strong,  is  horizontal  and  projects  medialward  from  the  nasal 
surface  of  the  bone.  It  forms  a  considerable  part  of  the  floor  of  the  nose  and  the 
roof  of  the  mouth  and  is  much  thicker  in  front  than  behind.  Its  inferior  surface 
(Fig.  304)  is  concave,  rough  and  uneven,  and  forms,  with  the  palatine  process  of 
the  opposite  bone,  the  anterior  three-fourths  of  the  hard  plate.  It  is  perforated 
by  numerous  foramina  for  the  passage  of  the  nutrient  vessels;  is  channelled  at  the 

1  Aldren  Turner  (op.  cit.)  gives  the  following  measurements  as  those  of  an  average  sized  sinus:  vertical  height 
opposite  first  molar  tooth,  Ijl  inch;  transverse  breadth,  1  inch;  and  antero-posterior  depth,  IJ^  inch. 


THE  MAXILLA 


261 


back  part  of  its  lateral  border  by  a  groove,  sometimes  a  canal,  for  the  transmission 
of  tlie  descending;'  i)alatine  vessels  and  the  anterior  palatine  nerve  from  the  spheno- 
palatine ganglion;  and  presents  little  depressions  for  the  lodgement  of  the  palatine 
glands.  When  the  two  maxiihe  are  articulated,  a  funnel-shaped  opening,  the 
incisive  foramen,  is  seen  in  the  middle  line,  immediately  behind  the  incisor  teeth. 
In  this  opening  the  orifices  of  two  lateral  canals  are  visible;  they  are  named  the 
incisive  canals  or  foramina  of  Stensen;  through  each  of  them  passes  the  terminal 
branch  of  the  descending  palatine  artery  and  the  nasopalatine  nerve.  Occasionally 
two  additional  canals  are  present  in  the  middle  line;  they  are  termed  the  foramina 
of  Scarpa,  and  when  present  transmit  the  nasopalatine  nerves,  the  left  passing 
through  the  anterior,  and  the  right  through  the  posterior  canal.  On  the  under 
surface  of  the  palatine  process,  a  delicate  linear  suture,  well  seen  in  young  skulls, 
mav  sometimes  be  noticed  extending  lateralward  and  forward  on  either  side  from 


Incisive  canals 


Jncisive  foramen 


Foramina  of  Scarpa 


Palatine  process  of  maxilla 
Horizontal  plate  of  palatine  hone 

Fig.  304. — The  bony  palate  and  alveolar  arch. 


Greater  palatine  foramnen 
Lesser  palatine  foramina 


the  incisive  foramen  to  the  interval  between  the  lateral  incisor  and  the  canine  tooth. 
The  small  part  in  front  of  this  suture  constitutes  the  premaxilla  {os  incisimim), 
which  in  most  vertebrates  forms  an  independent  bone;  it  includes  the  whole  thick- 
ness of  the  alveolus,  the  corresponding  part  of  the  floor  of  the  nose  and  the  anterior 
nasal  spine,  and  contains  the  sockets  of  the  incisor  teeth.  The  upper  surface  of 
the  palatine  process  is  concave  from  side  to  side,  smooth,  and  forms  the  greater 
part  of  the  floor  of  the  nasal  cavit3\  It  presents,  close  to  its  medial  margin,  the 
upper  orifice  of  the  incisive  canal.  The  lateral  border  of  the  process  is  incorporated 
with  the  rest  of  the  bone.  The  medial  border  is  thicker  in  front  than  behind,  and 
is  raised  above  into  a  ridge,  the  nasal  crest,  which,  with  the  corresponding  ridge 
of  the  opposite  bone,  forms  a  groove  for  the  reception  of  the  vomer.  The  front 
part  of  this  ridge  rises  to  a  considerable  height,  and  is  named  the  incisor  crest; 
it  is  prolonged  forward  into  a  sharp  process,  which  forms,  together  with  a  similar 


262 


OSTEOLOGY 


process  of  the  opposite  bone,  the  anterior  nasal  spine.    The  posterior  border  is  ser- 
rated for  artieuhition  with  the  horizontal  part  of  the  pahitine  bone. 

Ossification. — The  maxilla  is  ossified  in  membrane.  Mall'  and  P\iwcett-  maintain  that  it  is 
ossified  from  Iwo  centres  only,  one  for  the  maxilla  proi)er  and  one  for  the  ])renuixilla.  These 
centres  appear  during  the  sixth  week  of  fetal  life  and  unite  in  the  beginning  of  the  third  month, 
but  the  suture  between  the  two  portions  persists  on  the  palate  until  nearly  middle  life.  Mall 
states  that  the  frontal  process  is  developed  from  both  centres.  The  maxillary  sinus  appears  as 
a  shallow  groove  on  the  nasal  surface  of  the  bone  about  the  fourth  month  of  fetal  life,  but  does 
not  reach  its  full  size  until  after  the  second  dentition.  The  maxilla  was  formerly  described  as 
ossifying  from  six  centres,  viz.,  one,  the  orhilonasal,  forms  that  portion  of  the  body  of  the  bone 
which  lies  medial  to  the  infraorbital  canal,  including  the  medial  part  of  the  floor  of  the  orbit  and 
the  lateral  wall  of  the  nasal  cavity;  a  second,  the  zygomatic,  gives  origin  to  the  portion  which  lies 
lateral  to  the  infraorbital  canal,  including  the  zygomatic  process;  from  a  third,  the  palatine,  is 
developed  the  palatine  process  posterior  to  the  incisive  canal  together  with  the  adjoining  part 
of  the  nasal  wall;  a  fourth,  the  premaxillary,  forms  the  incisive  bone  which  carries  the  incisor 


Fig.  305. — Anterior  surface  of  maxilla  at  birth. 


Fig.  306. — Inferior  surface  of  maxilla  at  birth. 


Maxillary  sinus 


Fig.  307. 


Palatine  process 
-Nasal  surface  of  maxilla  at  birth. 


teeth  and  corresponds  to  the  premaxilla  of  the  lower  vertebrates;^  a  fifth,  the  nasal,  gives  rise  to 
the  frontal  process  and  the  portion  above  the  canine  tooth;  and  a  sixth,  the  infravonierine,  lies 
between  the  palatine  and  premaxillary  centres  and  beneath  the  vomer;  this  centre,  together  with 
the  corresponding  centre  of  the  opposite  bone,  separates  the  incisive  canals  from  each  other. 

Articulations. — The  maxilla  articulates  with  nine  bones:  two  of  the  cranium,  the  frontal  and 
ethmoid,  and  seven  of  the  face,  viz.,  the  nasal,  zygomatic,  lacrimal,  inferior  nasal  concha,  palatine, 
vomer,  and  its  fellow  of  the  opposite  side.  Sometimes  it  articulates  with  the  orbital  surface, 
and  sometimes  with  the  lateral  pterygoid  plate  of  the  sphenoid. 

CHANGES   PRODUCED   IN   THE    MAXILLA   BY   AGE. 

At  birth  the  transverse  and  antero-posterior  diameters  of  the  bone  are  each  greater  than  the 
vertical.  The  frontal  process  is  well-marked  and  the  body  of  the  bone  consists  of  little  more  than 
the  alveolar  process,  the  teeth  sockets  reaching  almost  to  the  floor  of  the  orbit.  The  maxillary 
sinus  presents  the  appearance  of  a  furrow  on  the  lateral  wall  of  the  nose.  In  the  adult  the  vertical 
diameter  is  the  greatest,  owing  to  the  development  of  the  alveolar  process  and  the  increase  in 
size  of  the  sinus.  In  old  age  the  bone  reverts  in  some  measure  to  the  infantile  condition;  its 
height  is  diminished,  and  after  the  loss  of  the  teeth  the  alveolar  process  is  absorbed,  and  the 
lower  part  of  the  bone  contracted  and  reduced  in  thickness. 


1  American  Journal  of  Anatomy,  1906,  vol.  v. 

2  Journal  of  Anatomy  and  Physiology,  1911,  vol.  xlv. 

'  Some  anatomists  believe  that  the  premaxillary  bone  is  ossified  by  two  centres  (see  page  299). 


THE  ZYGOMATIC  BONE  263 

The  Lacrimal  Bone   (Os  Lacrimale). 

The  lacrimal  bone,  the  sniaUost  and  most  fragile  bone  of  the  face,  is  situated 
at  the  front  i)art  of  the  medial  wall  of  the  orhit  (I'^ig-  309).  It  has  two  surfaces 
and  four  borders. 

Surfaces. — The  lateral  or  orbital  surface  (Fig.  308)  is  divided  hy  a  vertical  ridge, 
the  posterior  lacrimal  crest,  into  two  parts.  In  front  of  this  crest  is  a  longitudinal 
grooN'e,  the  lacrimal  sulcus  {sulcus  lacrimcdls),  the  inner  margin  of  which  unites 
with  the  frontal  process  of  the  maxilla,  and  the  lacrimal  fossa  is  thus  completed. 
The  nj^per  part  of  this  fossa  lodges  the  lacrimal  sac,  the  lower  part,  tlie  naso- 
lacrimal duct.  The  portion  behind  the  crest  is  smootli,  and  forms  part  of  the 
medial  wall  of  the  orbit.  The  crest,  with,  a  part  of  the  orl^ital  surface  imme- 
diately behind  it,  gives  origin  to  the  lacrimal  part  of  the  Orbicularis  oculi  and 
ends  below  in  a  small,  hook-like  projection,  the  lacrimal  hamulus,  which  articu- 
lates with  the  lacrimal  tubercle  of  the  maxilla,  and  completes 
the  upper  orifice  of  the  lacrimal  canal;  it  sometimes  exists  as  witAfrontai 

a  separate  piece,  and  is  then  called  the  lesser  lacrimal  bone.  |     '  J''^'^' 

The  medial  or  nasal  surface  presents  a  longitudinal  furrow, 
corresponding  to  the  crest  on  the  lateral  surface.  The  area  in 
front  of  this  furrow  forms  part  of  the  middle  meatus  of  the 
nose;  that  behind  it  articulates  with  the  ethmoid,  and  completes 
some  of  the  anterior  ethmoidal  cells. 

Borders. — Of  the  jour  borders  the  anterior  articulates  w^th 
the  frontal  process  of  the  maxilla;  the  posterior  with  the  lamina 
papyracea  of  the  ethmoid;  the  superior  with  the  frontal  bone.  infer,  nasai concha 

The  inferior  is  divided  by  the  lower  edge  of  the  posterior  lacri-  fig.  sos.— Left  lacri- 
mal crest  into  tw^o  parts:  the  posterior  part  articulates  with  f^ce.'^E'niarged'*''^  ^"'^" 
the  orbital  plate  of  the  maxilla;  the  anterior  is  prolonged 
downward  as  the  descending  process,  which  articulates  with  the  lacrimal  process 
of  the  inferior  nasal  concha,  and  assists  in  forming  the  canal  for  the  nasolacrimal 
duct. 

Ossification. — The  lacrimal  is  ossified  from  a  single  centre,  which  appears  about  the  twelfth 
week  in  the  membrane  covering  the  cartilaginous  nasal  capsule. 

Articulations. — The  lacrimal  articulates  with  four  bones:  two  of  the  cranium,  the  frontal 
and  ethmoid,  and  two  of  the  face,  the  maxilla  and  the  inferior  nasal  concha. 

The  Zygomatic  Bone  (Os  Zygomaticum;  Malar  Bone). 

The  zygomatic  bone  is  small  and  quadrangular,  and  is  situated  at  the  upper 
and  lateral  part  of  the  face:  it  forms  the  prominence  of  the  cheek,  part  of  the 
lateral  wall  and  floor  of  the  orbit,  and  parts  of  the  temporal  and  infratemporal 
fossse  (Fig.  309).  It  presents  a  malar  and  a  temporal  surface;  four  processes,  the 
frontosphenoidal,  orbital,  maxillary,  and  temporal;  and  four  borders. 

Surfaces. — The  malar  surface  (Fig.  310)  is  convex  and  perforated  near  its  centre 
by  a  small  aperture,  the  zygomaticofacial  foramen,  for  the  passage  of  the  zygomatico- 
facial nerve  and  vessels;  below  this  foramen  is  a  slight  elevation,  w^hich  gives 
origin  to  the  Zygomaticus. 

The  temporal  surface  (Fig.  311),  directed  backward  and  medialward,  is  concave, 
presenting  medially  a  rough,  triangular  area,  for  articulation  with  the  maxilla, 
and  laterally  a  smooth,  concave  surface,  the  upper  part  of  which  forms  the  anterior 
boundary  of  the  temporal  fossa,  the  low^er  a  part  of  the  infratemporal  fossa.  Near 
the  centre  of  this  surface  is  the  zygomaticotemporal  foramen  for  the  transmission 
of  the  zygomaticotemporal  nerve. 


264 


OSTEOLOGY 


Processes. — The  frontosphenoidal  process  is  thick  and  serrated,  and  articulates 
with  the  zygomatic  process  of  the  frontal  bone.  On  its  orbital  surface,  just  within 
the  orbital  margin  and  about  11  mm.  below  the  zygomaticofrontal  suture  is  a 
tubercle  of  varying  size  and  form,  but  present  in  95  per  cent,  of  skulls  (WhitnalP). 


I'  ro  n  tj  u  I  I 


I'  I-Ta  V  ill  n 


Fig.  309. — Left  zygomatic  bone  in  situ. 


The  orbital  process  is  a  thick,  strong  plate,  projecting  backward  and  medialward 
from  the  orbital  margin.  Its  antero-medial  surface  forms,  by  its  junction  with 
the  orbital  surface  of  the  maxilla  and  with  the  great  wing  of  the  sphenoid,  part 
of  the  floor  and  lateral  wall  of  the  orbit.    On  it  are  seen  the  orifices  of  two  canals, 


With  Frontal 


Bristles  passed 
through 
zygomatico- 
orhital  foramina  a}-. 


Fig.  310. — Left  zygomatic  bone.     Malar  surface. 


Fig.  311. — Left  zygomatic  bone.     Temporal  surface. 


the  zygomaticoorbital  foramina;  one  of  these  canals  opens  into  the  temporal  fossa, 
the  other  on  the  malar  surface  of  the  bone;  the  former  transmits  the  zygomatico- 
temporal, the  latter  the  zygomaticofacial  nerve.    Its  postero-Iateral  surface,  smooth 

'  Journal  of  Anatomy  and  Physiology,  vol.  xlv.  The  structures  attached  to  this  tubercle  are:  (1)  the  check 
ligament  of  the  Rectus  lateralis;  (2)  the  lateral  end  of  the  aponeurosis  of  the  Levator  palpebrae  superioris;  (3)  the 
suspensorj'  ligament  of  the  eye  (Lockwood) ;  and  (4)  the  lateral  extremities  of  the  superior  and  inferior  tarsi. 


THE  PALATTXE  BOXE 


265 


and  convex,  forms  parts  of  the  temporal  and  infratemporal  fossae.  Its  anterior 
margin,  smooth  and  rounded,  is  part  of  the  circumference  of  the  orbit.  Its  superior 
margin,  rough,  and  directed  horizontally,  articulates  with  the  frontal  bone  behind 
the  zygomatic  process.  Its  posterior  margin  is  serrated  for  articulation,  with  the 
great  wing  of  the  sphenoid  and  the  orbital  surface  of  the  maxilla.  At  the  angle 
of  junction  of  the  sphenoidal  and  maxillary  portions,  a  short,  concave,  non-articular 
part  is  generally  seen;  this  forms  the  anterior  boundary  of  the  inferior  orbital  fissure: 
occasionally,  this  non-articular  part  is  absent,  the  fissure  then  being  completed  by 
the  junction  of  the  maxilla  and  sphenoid,  or  by  the  interposition  of  a  small  sutural 
bone  in  the  angular  interval  between  them.  The  maxillary  process  presents  a  rough, 
triangular  surface  which  articulates  with  the  maxilla.  The  temporal  process, 
long,  narrow,  and  serrated,  articulates  with  the  zygomatic  process  of  the  temporal. 
Borders. — The  antero-superior  or  orbital  border  is  smooth,  concave,  and  forms 
a  considerable  part  of  the  circumference  of  the  orbit.  The  antero-inferior  or  maxil- 
lary border  is  rough,  and  bevelled  at  the  expense  of  its  inner  table,  to  articulate 
with  the  maxilla;  near  the  orbital  margin  it  gives  origin  to  the  Quadratus  labii 
superioris.  The  postero-superior  or  temporal  border,  curved  like  an  italic  letter  /, 
is  continuous  above  with  the  commencement  of  the  temporal  line,  and  below  with 
the  upper  border  of  the  zygomatic  arch;  the  temporal  fascia  is  attached  to  it. 
The  postero-inferior  or  zygomatic  border  affords  attachment  by  its  rough  edge  to 
the  ^Nlasseter. 


Ossification. — The  z^-gomatic  bone  is  generally  described  as  ossifying  from  three  centres — 
one  for  the  malar  and  two  for  the  orbital  portion;  these  appear  about  the  eighth  week  and  fuse 
about  the  fifth  month  of  fetal  hfe.  ]\Iall  describes  it  as  being  ossified  from  one  centre  which 
appears  just  beneath  and  to  the  lateral  side  of  the  orbit.  After  birth,  the  bone  is  sometimes 
divided  by  a  horizontal  sutm'e  into  an  upper  larger,  and  a  lower  smaller  division.  In  some  quad- 
rumana  the  z5-gomatic  bone  consists  of  two  parts,  an  orbital  and  a  malar. 

Articulations. — ^The  zj-gomatic  articulates  with /our  bones:  the  frontal,  sphenoidal,  temporal, 
and  maxilla. 


Groove  for 
nasolacrimal  duct 


Maxilla) y  sinus 
Orbital  process 


Sphenopalatip 
notch 

Sphenoidal 
Cciichal  crest 


Frontal  process 


—Conchal  crest 


Fig.  312. — Articulation  of  left  palatine  bone  with  maxilla. 

The  Palatine  Bone  (Os  Palatinum;  Palate  Bone). 

The  palatine  bone  is  situated  at  the  back  part  of  the  nasal  cavity  between  the 
maxilla  and  the  pterygoid  process  of  the  sphenoid  (Fig.  312).  It  contributes 
to  the  walls  of  three  cavities:  the  floor  and  lateral  wall  of  the  nasal  cavity,  the 


266 


OSTEOLOGY 


roof  of  the  mouth,  and  the  floor  of  the  orl)it ;  it  enters  into  the  formation  of  two 
fossEe,  the  pterygopalatine  and  pterygoid  fossae;  and  one  fissure,  the  inferior  orbital 
fissure.  The  palatine  bone  somewhat  resem})les  the  letter  L,  and  consists  of  a 
horizontal  and  a  vertical  part  and  three  outstanding  processes — viz.,  the  pyramidal 
process,  ^^hich  is  directed  backward  and  lateralward  from  the  junction  of  the  two 
parts,  and  the  orbital  and  sphenoidal  porcesses,  w^hich  surmount  the  vertical 
part,  and  are  separated  by  a  deep  notch,  the  sphenopalatine  notch. 

The  Horizontal  Part  (pans  horizontalis;  horizontal  plate)  (Figs.  313,  314.). — The 
horizontal  part  is  quadrilateral,  and  has  two  surfaces  and  four  borders. 

Surfaces. — The  superior  surface,  concave  from  side  to  side,  forms  the  back  part 
of  the  floor  of  the  nasal  cavity.  The  inferior  surface,  slightly  concave  and  rough, 
forms,  with  the  corresponding  surface  of  the  opposite  bone,  the  posterior  fourth 
of  the  hard  palate.  Near  its  posterior  margin  may  be  seen  a  more  or  less  marked 
transverse  ridge  for  the  attachment  of  part  of  the  aponeurosis  of  the  Tensor  veli 
palatini. 


^Ital  Fpoc^ 


Maxillary  surface 


Superior  'ineatub 
Sphenopalatine  fora  men 


^1  > 


Maocillary 
']yrocess 


Fig.  31.3. 


HORIZONTAL  PAKT 

-Left  palatine  bone. 
Enlarged. 


to- 


I    A 


<\^         1   S'"^ 

0'        J-  ^        5   -CA 


Sphenopalatine 
forainen 

Sphenoidal  process 
Articular  portion 

Non-artimlar 
portion 


Posterior 
_     nasal 
Musculus  nvulce  spine 


Pyamidal 
process 


HORIZONTAL 
P4.RT 


Nasal  aspect. 


Fig.   314. 


-Left  palatine  bone. 
Enlarged. 


Posterior  aspect. 


Borders. — The  anterior  border  is  serrated,  and  articulates  with  the  palatine  process 
of  the  maxilla.  The  posterior  border  is  concave,  free,  and  serves  for  the  attachment 
of  the  soft  palate.  Its  medial  end  is  sharp  and  pointed,  and,  when  united  with 
that  of  the  opposite  bone,  forms  a  projecting  process,  the  posterior  nasal  spine 
for  the  attachment  of  the  Musculus  uvulae.  The  lateral  border  is  united  with 
the  lower  margin  of  the  perpendicular  part,  and  is  grooved  by  the  lower  end  of 
the  pterygopalatine  canal.  The  medial  border,  the  thickest,  is  serrated  for  articu- 
lation with  its  fellow  of  the  opposite  side;  its  superior  edge  is  raised  into  a  ridge, 
which,  united  with  the  ridge  of  the  opposite  bone,  forms  the  nasal  crest  for  articu- 
lation with  the  posterior  part  of  the  lower  edge  of  the  vomer. 

The  Vertical  Part  {pars  perpendicularis ;  perpendicular  plate)  (Figs.  313,  314). — 
The  vertical  part  is  thin,  of  an  oblong  form,  and  presents  two  surfaces  and  four 
borders. 

Surfaces. — The  nasal  surface  exhibits  at  its  lower  part  a  broad,  shallow  depres- 
sion, which  forms  part  of  the  inferior  meatus  of  the  nose.  Immediately  above  this 
is  a  well-marked  horizontal  ridge,  the  conchal  crest,  for  articulation  with  the 
inferior  nasal  concha;  stih  higher  is  a  second  broad,  shallow  depression,  which 


THE  PALATINE  BONE  267 

forms  part  of  the  middle  meatus,  and  is  limited  above  by  a  horizontal  crest  less 
prominent  than  the  inferior,  the  ethmoidal  crest,  for  articulation  with  the  middle 
nasal  concha.  Above  the  ethmoidal  crest  is  a  narrow,  horizontal  groove,  which 
forms  part  of  the  superior  meatus. 

The  maxillary  surface  is  rough  and  irregular  throughout  the  greater  part  of  its 
extent,  for  articulation  \\'\t\\  the  nasal  surface  of  the  maxilla;  its  upper  and  back 
part  is  smooth  where  it  enters  into  the  formation  of  the  pterygopalatine  fossa; 
it  is  also  smooth  in  front,  wdiere  it  forms  the  posterior  part  of  the  medial  wall  of 
the  maxillary  sinus.  On  the  posterior  part  of  this  surface  is  a  deep  vertical  groove, 
converted  into  the  pterygopalatine  canal,  by  articulation  with  the  maxilla;  this 
canal  transmits  the  descending  palatine  vessels,  and  the  anterior  palatine  nerve. 

Borders. — The  anterior  border  is  thin  and  irregular;  opposite  the  conchal  crest  is  a 
pointed,  projecting  lamina,  the  maxillary  process,  which  is  directed  forw^ard,  and 
closes  in  the  lower  and  back  part  of  the  opening  of  the  maxillary  sinus.  The 
posterior  border  (Fig.  314)  presents  a  deep  groove,  the  edges  of  which  are  serrated 
for  articulation  with  the  medial  pterygoid  plate  of  the  sphenoid.  This  border 
is  continuous  above  with  the  sphenoidal  process;  below  it  expands  into  the 
pyramidal  process.  The  superior  border  supports  the  orbital  process  in  front  and  the 
sphenoidal  process  behind.  These  processes  are  separated  by  the  sphenopalatine 
notch,  which  is  converted  into  the  sphenopalatine  foramen  by  the  under  surface  of 
the  body  of  the  sphenoid.  In  the  articulated  skull  this  foramen  leads  from  the 
pterygopalatine  fossa  into  the  posterior  part  of  the  superior  meatus  of  the  nose, 
and  transmits  the  sphenopalatine  vessels  and  the  superior  nasal  and  nasopalatine 
nerves.  The  inferior  border  is  fused  with  the  lateral  edge  of  the  horizontal  part, 
and  immediately  in  front  of  the  pyramidal  process  is  grooved  by  the  lower  end 
of  the  pterygopalatine  canal. 

The  Pyramidal  Process  or  Tuberosity  (^processus  pyramidalis) . — The  pyramidal 
process  projects  backward  and  lateralw^ard  from  the  junction  of  the  horizontal 
and  vertical  parts,  and  is  received  into  the  angular  interval  between  the  lower 
extremities  of  the  pterygoid  plates.  On  its  posterior  surface  is  a  smooth,  grooved, 
triangular  area,  limited  on  either  side  by  a  rough  articular  furrow.  The  furrows 
articulate  with  the  pterygoid  plates,  while  the  grooved  intermediate  area  completes 
the  lower  part  of  the  pterygoid  fossa  and  gives  origin  to  a  few^  fibres  of  the  Pter}'- 
goideus  internus.  The  anterior  part  of  the  lateral  surface  is  rough,  for  articulation 
with  the  tuberosity  of  the  maxilla;  its  posterior  part  consists  of  a  smooth  triangular 
area  which  appears,  in  the  articulated  skull,  betw^een  the  tuberosity  of  the  maxilla 
and  the  lower  part  of  the  lateral  pterygoid  plate,  and  completes  the  lower  part 
of  the  infratemporal  fossa.  On  the  base  of  the  pyramidal  process,  close  to  its 
union  with  the  horizontal  part,  are  the  lesser  palatine  foramina  for  the  transmis- 
sion of  the  posterior  and  middle  palatine  nerves. 

The  Orbital  Process  {processus  orhitalis). — The  orbital  process  is  placed  on  a 
higher  level  than  the  sphenoidal,  and  is  directed  upward  and  lateralward  from 
the  front  of  the  vertical  part,  to  which  it  is  connected  by  a  constricted  neck.  It 
presents  five  surfaces,  which  enclose  an  air  cell.  Of  these  surfaces,  three  are  articu- 
lar and  two  non-articular.  The  articular  surfaces  are:  (1)  the  anterior  or  maxillary, 
directed  forward,  lateralward,  and  downward,  of  an  oblong  form,  and  rough  for 
articulation  with  the  maxilla;  (2)  the  posterior  or  sphenoidal,  directed  backward, 
upward,  and  medialward;  it  presents  the  opening  of  the  air  cell,  which  usually 
communicates  with  the  sphenoidal  sinus;  the  margins  of  the  opening  are  serrated 
for  articulation  with  the  sphenoidal  concha;  (3)  the  medial  or  ethmoidal,  directed 
forward,  articulates  with  the  labyrinth  of  the  ethmoid.  In  some  cases  the  air 
cell  opens  on  this  surface  of  the  bone  and  then  communicates  with  the  posterior 
ethmoidal  cells.  More  rarely  it  opens  on  both  surfaces,  and  then  communicates 
with  the  posterior  ethmoidal  cells  and  the  sphenoidal  sinus.     The  non-articular 


268  OSTEOLOGY 

surfaces  are:  (1)  the  superior  or  orbital,  directed  upward  and  lateralward;  it  is 
triangular  in  shape,  and  forms  the  back  part  of  the  floor  of  the  orbit;  and  (2)  the 
lateral,  of  an  oblong  form,  directed  toward  the  pterygopalatine  fossa;  it  is  sejjarated 
from  the  orbital  surface  by  a  rounded  border,  which  enters  into  the  formation  of 
the  inferior  orbital  fissure. 

The  Sphenoidal  Process  {processus  sphenoidalis) . — The  sphenoidal  process  is 
a  thin,  compressed  plate,  much  smaller  than  the  orbital,  and  directed  upward 
and  medialward.  It  presents  three  surfaces  and  two  borders.  The  superior  surface 
articulates  with  the  root  of  the  pterygoid  process  and  the  under  surface  of  the 
sphenoidal  concha,  its  medial  border  reaching  as  far  as  the  ala  of  the  vomer;  it 
presents  a  groove  which  contributes  to  the  formation  of  the  pharyngeal  canal. 
The  medial  surface  is  concave,  and  forms  part  of  the  lateral  wall  of  the  nasal  cavity. 
The  lateral  surface  is  divided  into  an  articular  and  a  non-articular  portion:  the 
former  is  rough,  for  articulation  w^ith  the  medial  pterygoid  plate;  the  latter  is 
smooth,  and  forms  part  of  the  pterygopalatine  fossa.  The  anterior  border  forms 
the  posterior  boundary  of  the  sphenopalatine  notch.  The  posterior  border,  serrated 
at  the  expense  of  the  outer  table,  articulates  with  the  medial  pterygoid  plate. 

The  orbital  and  sphenoidal  processes  are  separated  from  one  another  by  the 
sphenopalatine  notch.  Sometimes  the  two  processes  are  united  above,  and  form 
between  them  a  complete  foramen  (Fig.  313),  or  the  notch  may  be  crossed  by  one 
or  more  spicules  of  bone,  giving  rise  to  two  or  more  foramina. 

Ossification. — The  palatine  bone  is  ossified  in  membrane  from  a  single  centre,  which  makes 
its  appearance  about  the  sixth  or  eighth  week  of  fetal  life  at  the  angle  of  junction  of  the  two  parts 
of  the  bone.  From  this  point  ossification  spreads  medialward  to  the  horizontal  part,  downward 
into  the  pyramidal  process,  and  upward  into  the  vertical  part.  Some  authorities  describe  the 
bone  as  ossifying  from  four  centres:  one  for  the  pyramidal  process  and  portion  of  the  vertical 
part  behind  the  pterygopalatine  groove;  a  second  for  the  rest  of  the  vertical  and  the  horizontal 
parts;  a  third  for  the  orbital,  and  a  fourth  for  the  sphenoidal  process.  At  the  time  of  birth  the 
height  of  the  vertical  part  is  about  equal  to  the  transverse  width  of  the  horizontal  part,  whereas 
in  the  adult  the  former  measures  about  twice  as  much  as  the  latter. 

Articulations. — The  palatine  articulates  with  six  bones:  the  sphenoid,  ethmoid,  maxilla, 
inferior  nasal  concha,  vomer,  and  opposite  palatine. 

The  Inferior  Nasal  Concha  (Concha  Nasalis  Inferior ;  Inferior  Turbinated  Bone) . 

The  inferior  nasal  concha  extends  horizontally  along  the  lateral  wall  of  the 
nasal  cavity  (Fig.  315)  and  consists  of  a  lamina  of  spongy  bone,  curled  upon  itself 
like  a  scroll.    It  has  two  surfaces,  two  borders,  and  two  extremities. 

The  medial  surface  (Fig.  316)  is  convex,  perforated  by  numerous  apertures, 
and  traversed  by  longitudinal  grooves  for  the  lodgement  of  vessels.  The  lateral 
surface  is  concave  (Fig.  317),  and  forms  part  of  the  inferior  meatus.  Its  upper 
border  is  thin,  irregular,  and  connected  to  various  bones  along  the  lateral  wall 
of  the  nasal  cavity.  It  may  be  divided  into  three  portions:  of  these,  the  anterior 
articulates  wdth  the  conchal  crest  of  the  maxilla;  the  posterior  wdth  the  conchal 
crest  of  the  palatine;  the  middle  portion  presents  three  well-marked  processes, 
which  vary  much  in  their  size  and  form.  Of  these,  the  anterior  or  lacrimal  process 
is  small  and  pointed  and  is  situated  at  the  junction  of  the  anterior  fourth  with 
the  posterior  three-fourths  of  the  bone :  it  articulates,  by  its  apex,  with  the  descend- 
ing process  of  the  lacrimal  bone,  and,  by  its  margins,  with  the  groove  on  the  back 
of  the  frontal  process  of  the  maxilla,  and  thus  assists  in  forming  the  canal  for  the 
nasolacrimal  duct.  Behind  this  process  a  broad,  thin  plate,  the  ethmoidal  process, 
ascends  to  join  the  uncinate  process  of  the  ethmoid;  from  its  lower  border  a  thin 
lamina,  the  maxillary  process,  curves  downward  and  lateralward;  it  articulates 
Avith  the  maxilla  and  forms  a  part  of  the  medial  wall  of  the  maxillary  sinus.  The 
inferior  border  is  free,  thick,  and  cellular  in  structure,  more  especially  in  the  middle 


THE  VOMER 


209 


of  the  bone.    Both  extremities  are  more  or  less  pouited,  the  posterior  })eing  the 
more  tapering. 


Frontal  sinus 

Griskt  gain 


Sella  turcica 


Uncinate 

process 

oj  ethmoid 


Openings  into 
maxillary  sinus 
Medial  pterygoid  plate 
Pterygoid  hamulus 


Fig.  315. — Lateral  wall  of  right  nasal  cavity  showing  inferior  concha  uj  situ. 


Ossification. — ^The  inferior  nasal  concha  is  ossified  from  a  single  centre,  wliicli  appears  about 
tlie  fifth  month  of  fetal  Ufe  in  the  lateral  wall  of  the  cartilaginous  nasal  capsule. 

Articulations. — The  inferior  nasal  concha  articulates  with  four  bones:  the  ethmoid,  maxilla, 
lacrimal,  and  palatine. 


Fig.  316. — Right  inferior  nasal  concha. 
Medial  surface. 


Fig.  317. — Right  inferior  nasal  concha. 
Lateral  surface. 


The  Vomer. 

The  vomer  is  situated  in  the  median  plane,  but  its  anterior  portion  is  frequently 
bent  to  one  or  other  side.  It  is  thin,  somewhat  quadrilateral  in  shape,  and  forms 
the  hinder  and  lower  part  of  the  nasal  septum  (Fig.  318);  it  has  two  surfaces  and 
four  borders.  The  surfaces  (Fig.  319)  are  marked  by  small  furrows  for  blood- 
vessels, and  on  each  is  the  nasopalatine  groove,  which  runs  obliquely  downward 
and  forward,  and  lodges  the  nasopalatine  nerve  and  vessels.  The  superior  border, 
the  thickest,  presents  a  deep  furrow,  bounded  on  either  side  by  a  horizontal  pro- 
jecting ala  of  bone;  the  furrow  receives  the  rostrum  of  the  sphenoid,  while  the 


270 


OSTEOLOGY 


margins  of  the  ala^  articulate  with  the  vaginal  processes  of  the  medial  pterygoid 
plates  of  the  sphenoid  behind,  and  with  the  sphenoidal  processes  of  the  palatine 
bones  in  front.  The  inferior  border  articulates  with  the  crest  formed  by  the  maxillse 
and  palatine  bones.    The  anterior  border  is  the  longest  and  slopes  downward  and 


Crest  of  nasal  bones 
Frontal  spine 


Space  for  triangular 
cartilage  of  septum 


Fig.  318. — Median  wall  of  left  nasal  cavity  showing  vomer  in  situ. 


forward.  Its  upper  half  is  fused  with  the  perpendicular  plate  of  the  ethmoid; 
its  lower  half  is  grooved  for  the  inferior  margin  of  the  septal  cartilage  of  the  nose. 
The  posterior  border  is  free,  concave,  and  separates  the  choanse.  It  is  thick  and 
bifid  above,  thin  below. 

Ossification. — At  an  early  period 
the  septum  of  the  nose  consists  of  a 
plate  of  cartilage,  the  ethmovomerine 
cartilage.  The  postero-superior  part 
of  this  cartilage  is  ossified  to  form 
the  perpendicular  plate  of  the  eth- 
moid; its  antero-inferior  portion  per- 
sists as  the  septal  cartilage,  while  the 
vomer  is  ossified  in  the  membrane 
covering  its  postero-inferior  part. 
Two  ossific  centres,  one  on  either 
side  of  the  middle  fine,  appear  about 
the  eighth  week  of  fetal  life  in  this 
part  of  the  membrane,  and  hence  the 
vomer  consists  primarily  of  two  lam- 
ellae. About  the  third  month  these 
unite  below,  and  thus  a  deep  groove 
growth  proceeds,  the  union  of  the  lamellae 
the  intervening  plate  of  cartilage  undergoes 
almost  completely  united  to  form  a  median 
bone  is  seen  in  the  everted  alte  of  its  upper 


Uh  Maxilla: 

Fig.  319.— The  vomer. 

is  formed  in  which  the  cartilage  is  lodged.  As 
extends  upward  and  forward,  and  at  the  same  time 
absorption.  By  the  age  of  puberty  the  lamellae  are 
plate,  but  evidence  of  the  bilaminar  origin  of  the 
border  and  the  groove  on  its  anterior  margin. 


THE  MANDIBLE 


271 


Articulations. — The  vomer  articulates  with  six  bones:  two  of  the  cranium,  the  sphenoid  and 
ethmoid;  and  four  of  the  face,  the  two  maxilla;  and  the  two  palatine  bones;  it  also  articulates 
with  I  lie  .scplal  cartilage  of  the  nose. 

Applied  Anatomy. — Tlie  surfaces  of  the  vomer  are  covered  l)y  nuicous  membrane,  which  is 
intimately  connected  with  the  periosteum,  little,  if  any,  subnnu^ous  connective  tissue  intcn-vcning. 
Hence  polypi  are  rarely  found  growing  from  this  surface,  though  they  frecjuently  grow  from  the 
lateral  walls  of  the  nasal  cavities,  where  the  submucous  tissue  is  abundant. 

The  Mandible  (Mandibula ;  Inferior  Maxillary  Bone;  Lower  Jaw). 

The  mandible,  the  hirgest  and  strongest  bone  of  the  face,  serves  for  the  reception 
of  the  lower  teeth.  It  consists  of  a  curved,  horizontal  portion,  the  body,  and  two 
perpendicular  portions,  the  rami,  which  unite  with  the  ends  of  the  body  nearly 
at  right  angles. 

The  Body  (corpus  mandihulae) . — The  body  is  curved  somewhat  like  a  horseshoe, 
and  has  two  surfaces  and  two  borders. 


Coronoid  process 


Condyle 


TEMPORALIS 


Mental 
protuberance 


Groove  for  external 
maxillary  ai'tery 

Fig.  320. — Mandible.     Outer  surface.     Side  view. 


Surfaces. — The  external  surface  (Fig.  .320)  is  marked  in  the  median  line  by  a 
faint  ridge,  indicating  the  symphysis  or  line  of  junction  of  the  two  pieces  of  which 
the  bone  is  composed  at  an  early  period  of  life.  This  ridge  divides  below  and 
encloses  a  triangular  eminence,  the  mental  protuberance,  the  base  of  which  is  de- 
pressed in  the  centre  but  raised  on  either  side  to  form  the  mental  tubercle.  On  either 
side  of  the  symphysis,  just  below  the  incisor  teeth,  is  a  depression,  the  incisive 
fossa,  which  gives  origin  to  the  Mentalis  and  a  small  portion  of  the  Orbicularis 
oris.  Below  the  second  premolar  tooth,  on  either  side,  midway  between  the  upper 
and  lower  borders  of  the  body,  is  the  mental  foramen,  for  the  passage  of  the  mental 
vessels  and  nerve.  Running  backward  and  upward  from  each  mental  tubercle 
is  a  faint  ridge,  the  oblique  line,  which  is  continuous  with  the  anterior  border  of  the 
ramus;  it  affords  attachment  to  the  Quadratus  labii  inferioris  and  Triangularis; 
the  Platysma  is  attached  below  it. 

The  internal  surface  (Fig.  321)  is  concave  from  side  to  side.  Near  the  lower 
part  of  the  symphysis  is  a  pair  of  laterally  placed  spines,  termed  the  mental  spines, 
which  give  origin  to  the  Genioglossi.  Immediately  below  these  is  a  second  pair 
of  spines,  or  more  frequently  a  median  ridge  or  impression,  for  the  origin  of  the 


272 


OSTEOLOGY 


Geniohyoidei.  In  some  cases  the  mental  spines  are  fused  to  form  a  single  eminence, 
in  others  they  are  absent  and  their  position  is  indicated  merely  by  an  irregularity 
of  the  surface.  Above  the  mental  spines  a  median  foramen  and  furrow  are  some- 
times seen;  they  mark  the  line  of  union  of  the  halves  of  the  bone.  Below  the  mental 
spines,  on  either  side  of  the  middle  line,  is  an  oval  depression  for  the  attachment 
of  the  anterior  belly  of  the  Digastricus.  Extending  upward  and  backward  on  either 
side  from  the  lower  part  of  the  s^'mphysis  is  the  mylohyoid  line,  which  gives  origin 
to  the  Mylohyoideus;  the  posterior  part  of  this  line,  near  the  alveolar  margin, 
gives  attachment  to  a  small  part  of  the  Constrictor  pharyngis  superior,  and  to 
the  pterygomandibular  raphe.  Above  the  anterior  part  of  this  line  is  a  smooth 
triangular  area  against  which  the  sublingual  gland  rests,  and  below  the  hinder 
part,  an  oval  fossa  for  the  submaxillary  gland. 


.iti'J'^-i*-., 


Genio- 

glossTis 
Genio- 

hyoideus 


Mylohyoid  line 


BODT 
Fig.  321. — Mandible.     Inner  surface.     Side  view. 


Borders. — The  superior  or  alveolar  border,  wider  behind  than  in  front,  is  holloM^ed 
into  cavities,  for  the  reception  of  the  teeth;  these  cavities  are  sixteen  in  number, 
and  vary  in  depth  and  size  according  to  the  teeth  which  they  contain.  To  the 
outer  lip  of  the  superior  border,  on  either  side,  the  Buccinator  is  attached  as 
far  forward  as  the  first  molar  tooth.  The  inferior  border  is  rounded,  longer  than 
the  superior,  and  thicker  in  front  than  behind;  at  the  point  where  it  joins  the 
lower  border  of  the  ramus  a  shallow  groove;  for  the  external  maxillary  artery, 
may  be  present. 

The  Ramus  {ravms  mandihulae;  'perpendicular  portions). — The  ramus  is  quadri- 
lateral in  shape,  and  has  two  surfaces,  four  borders,  and  two  processes. 

Surfaces. — The  lateral  surface  (Fig.  320)  is  flat  and  marked  by  oblique  ridges 
at  its  lower  part;  it  gives  attachment  throughout  nearly  the  whole  of  its  extent 
to  the  Masseter.  The  medial  surface  (Fig.  321)  presents  about  its  centre  the  oblique 
mandibular  foramen,  for  the  entrance  of  the  inferior  alveolar  vessels  and  nerve. 
The  margin  of  this  opening  is  irregular;  it  presents  in  front  a  prominent  ridge, 
surmounted  by  a  sharp  spine,  the  lingula  mandibulae,  which  gives  attachment  to 
the  sphenomandibular  ligament ;  at  its  lower  and  back  part  is  a  notch  from  which 
the  mylohyoid  groove  runs  obliquely  downward  and  forward,  and  lodges  the  mylo- 
hyoid vessels  and  nerve.    Behind  this  groove  is  a  rough  surface,  for  the  insertion 


THE  MAXDIBLE  273 

of  the  Ptengoideus  internus.  The  mandibular  canal  runs  ohlicjuely  downward 
and  forward  in  the  ramus,  and  then  liori/ontally  forward  in  the  body,  where  it 
is  placed  under  tlie  alveoli  and  communicates  with  them  by  small  openings.  On 
arriving  at  the  incisor  teeth,  it  turns  back  to  communicate  with  the  mental  foramen, 
giving  off  two  small  canals  which  run  to  the  cavities  containing  the  incisor  teeth. 
In  the  })osterior  two-thirds  of  the  bone  the  canal  is  situated  nearer  the  internal 
surface  of  the  mandii)le;  and  in  the  anterior  third,  nearer  its  external  surface.  It 
contains  the  inferior  alveolar  vessels  and  nerve,  from  which  branches  are  dis- 
tributed to  the  teeth.  The  lower  border  of  the  ramus  is  thick,  straight,  and  con- 
tinuous with  the  inferior  Iwrder  of  the  body  of  the  bone.  At  its  junction  with  the 
posterior  border  is  the  angle  of  the  mandible,  which  may  be  either  in\erted  or  everted 
and  is  marked  by  rough,  oblique  ridges  on  each  side,  for  the  attachment  of  the, 
Masseter  laterally,  and  the  Pterygoideus  internus  medially;  the  stylomandibular 
ligament  is  attached  to  the  angle  between  these  muscles.  The  anterior  border  is 
thin  aboA'e,  thicker  below,  and  continuous  with  the  oblique  line.  The  posterior 
border  is  thick,  smooth,  rounded,  and  covered  by  the  parotid  gland.  The  upper 
border  is  thin,  and  is  surmounted  by  two  processes,  the  coronoid  in  front  and  the 
condyloid  behind,  separated  by  a  deep  concavity,  the  mandibular  notch. 

The  Coronoid  Process  (processus  coronoideus)  is  a  thin,  triangular  eminence, 
which  is  flattened  from  side  to  side  and  varies  in  shape  and  size.  Its  anterior 
border  is  convex  and  is  continuous  below  with  the  anterior  border  of  the  ramus; 
its  posterior  border  is  concave  and  forms  the  anterior  boundary  of  the  mandibular 
notch.  Its  lateral  surface  is  smooth,  and  affords  insertion  to  the  Temporalis  and 
Masseter.  Its  medial  surface  gives  insertion  to  the  Temporalis,  and  presents 
a  ridge  which  begins  near  the  apex  of  the  process  and  runs  downward  and  forward 
to  the  inner  side  of  the  last  molar  tooth.  Between  this  ridge  and  the  anterior 
border  is  a  grooved  triangular  area,  the  upper  part  of  which  gives  attachment 
to  the  Temporalis,  the  lower  part  to  some  fibres  of  the  Buccinator. 

The  Condyloid  Process  {pjrocessus  condyloideus)  is  thicker  than  the  coronoid, 
and  consists  of  two  portions :  the  condyle,  and  the  constricted  portion  which  sup- 
ports it,  the  neck.  The  condyle  presents  an  articular  surface  for  articulation  with 
the  articular  disk  of  the  temporomandibular  joint;  it  is  convex  from  before  back- 
ward and  from  side  to  side,  and  extends  farther  on  the  posterior  than  on  the  ante- 
rior surface.  Its  long  axis  is  directed  medialward  and  slightly  backward,  and  if 
prolonged  to  the  middle  line  will  meet  that  of  the  opposite  condyle  near  the  ante- 
rior margin  of  the  foramen  magnum.  At  the  lateral  extremity  of  the  condyle 
is  a  small  tubercle  for  the  attachment  of  the  temporomandibular  ligament.  The 
neck  is  flattened  from  before  backward,  and  strengthened  by  ridges  which  descend 
from  the  forepart  and  sides  of  the  condyle.  Its  posterior  surface  is  convex;  its 
anterior  presents  a  depression  for  the  attachment  of  the  Pterygoideus  externus. 

The  mandibular  notch,  separating  the  two  processes,  is  a  deep  semilunar  depres- 
sion, and  is  crossed  by  the  masseteric  vessels  and  nerve. 

Ossification. — The  mandible  is  ossified  in  the  fibrous  membrane  covering  the  outer  sm-faces 
of  Meckel's  cartilages.  These  cartilages  form  the  cartilaginous  bar  of  the  mandibular  arch  (see 
p.  109),  and  are  two  in  number,  a  right  and  a  left.  Their  proximal  or  cranial  ends  are  connected 
with  the  ear  capsules,  and  theii-  distal  extremities  are  joined  to  one  another  at  the  symphysis 
by  mesodermal  tissue.  They  run  forward  immediately  below  the  condj'les  and  then,  bending 
downward,  he  in  a  groove  near  the  lower  border  of  the  bone;  in  front  of  the  canine  tooth  they 
inchne  upward  to  the  sj^mphj-sis.  From  the  proximal  end  of  each  cartilage  the  malleus  and 
incus,  two  of  the  bones  of  the  middle  ear,  are  developed;  the  next  succeeding  portion,  as  far  as 
the  hngula,  is  replaced  by  fibrous  tissue,  which  persists  to  form  the  sphenomandibular  hgament. 
Between  the  lingula  and  the  canine  tooth  the  cartilage  disappears,  while  the  portion  of  it  below 
and  behind  the  incisor  teeth  becomes  ossified  and  incorporated  with  this  part  of  the  mandible. 

Ossification  takes  place  in  the  membrane  covering  the  outer  surface  of  the  ventral  end  of 
Meckel's  cartilage  (Figs.  322  to  325),  and  each  half  of  the  bone  is  formed  from  a  single  centre 
IS 


274 


OSTEOLOGY 


which  appears,  near  the  mental  foramen,  about  the  sixth  week  of  fetal  Ufe.  By  the  tenth  week 
the  portion  of  Meckel's  cartilage  which  hes  below  and  behind  the  incisor  teeth  is  surrounded  and 
invaded  by  the  membrane  bone.    Somewhat  later,  accessory  nuclei  of  cartilage  make  their  appear- 


Mental  nerve. 


Liur/iud  itcivf 
Iiif  alveola)  n 


Mylohyoid  nerve 


Fig.  322. — Mandible  of   human    embryo  of    24    mm. 
long.     Outer  aspect.     (From  model  by  Low.) 


~  Stajies 
~  1  cicial  nerve 


Mylohyoid  nerve 
Chorda  tympani 


ReicherVs  cartilage 


Fig.   32.3. — Mandible  of  human  embryo  of  24  mm.  long. 
Inner  aspect.     (From  model  by  Low.) 


ance,  viz.,  a  wedge-shaped  nucleus  in  the  condyloid  process  and  extending  downward  through 
the  ramus;  a  small  strip  along  the  anterior  border  of  the  coronoid  process;  and  smaller  nuclei 
in  the  front  part  of  both  alveolar  walls  and  along  the  fi'ont  of  the  lower  border  of  the  bone.  These 
acce.ssory  nuclei  possess  no  separate  ossific  centres,  but  are  invaded  by  the  surrounding  membrane 


Mandibular  loerve 
Meckel's  caitilage 


Jlental  nerve 


Anterior  process  of  )tialleus 


Fig.  324. — Mandible  of  human  embryo  of  9.5  mm.  long.     Outer  aspect. 

(From  model  by  Low.) 


Nuclei  of  cartilage  stippled. 


bone  and  undergo  absorption.  The  inner  alveolar  border,  usually  described  as  arising  from  a 
separate  ossific  centre  {s-plenial  centre),  is  formed  in  the  human  mandible  by  an  ingrowt^h  from 
the  main  mass  of  the  bone.  At  birth  the  bone  consists  of  two  parts,  united  by  a  fibrous  symphysis, 
in  which  ossification  takes  place  during  the  first  year. 


Lingual  nerve 


Auricidotemporal  nerve 


Meckel's 
cartilage 


Ant.  process  of  malleus 
Chorda  tijmpani 


Symphysis  Mylohyoid  nerve 

Fig.  325. — Mandible  of  human  embryo  of  95  mm.  long.     Inner  aspect.     Nuclei  of  cartilage  stippled. 

(From  model  by  Low.) 

The  foregoing  description  of  the  ossification  of  the  mandible  is  based  on  the  researches  of 
Low^  and  Fawcett,-  and  differs  somewhat  from  that  usually  given. 
Articulations. — The  mandible  articulates  with  the  iico  temporal  bones. 

1  Proceedings  of  the  Anatomical  and  Anthropological  Society  of  the  University  of  .\berdeen,  1905,  and  Journal  of 
Anatomy  and  Physiology,  vol.  xliv. 

2  Journal  of  the  American  Medical  Association,  September  2,  1905. 


TJIR  If  VOID  HONK  275 

CHANGES   PRODUCED   IN  THE  MANDIBLE   13Y  AGE. 

At  birth  (Fig.  326),  the  body  of  the  bone  is  a  mere  shell,  containing  the  sockets  of  the  two 
incisor,  the  canine,  and  the  two  deciduous  molar  teeth,  imperfectly  partitioned  off  from  one 
another.  The  mandibular  canal  is  of  large  size,  and  runs  near  the  lower  border  of  the  bone;  the 
mental  foramen  opens  beneath  the  socket  of  the  lirst  deciduous  molar  tooth.  The  angle  is  obtuse 
(175°),  and  the  condyloid  portion  is  nearly  in  line  with  the  body.  The  coronoid  i)rocess  is  of 
comparatively  large  size,  and  projects  above  the  level  of  the  condyle. 

After  birth  (Fig.  327),  the  two  segments  of  the  bone  become  joined  at  the  symphysis,  from 
below  upward,  in  the  first  year;  but  a  trace  of  separation  may  be  visible  in  the  beginning  of  the 
second  year,  near  the  alveolar  margin.  The  body  becomes  elongated  in  its  whole  length,  but 
moi-e  especially  behind  the  mental  foramen,  to  provide  space  for  the  three  additional  teeth  devel- 
oped in  this  part.  The  depth  of  the  body  increases  owing  to  increased  growth  of  the  alveolar 
part,  to  afford  room  for  the  roots  of  the  teeth,  and  by  thickening  of  the  subdental  portion  which 
enables  the  jaw  to  withstand  the  powerful  action  of  the  masticatory  muscles;  but  the  alveolar 
portion  is  the  deeper  of  the  two,  and,  consequently,  the  chief  part  of  the  body  hes  above  the 
oblique  line.  The  mandibular  canal,  after  the  second  dentition,  is  situated  just  above  the  level 
of  the  myloh3'oid  Une;  and  the  mental  foramen  occupies  the  position  usual  to  it  in  the  adult. 
The  angle  becomes  less  obtuse,  owing  to  the  separation  of  the  jaws  by  the  teeth;  about  the  fourth 
year  it  is  140°. 

In  the  adult  (Fig.  328),  the  alveolar  and  subdental  portions  of  the  body  are  usually  of  equa 
depth.  The  mental  foramen  opens  midway  between  the  upper  and  lower  borders  of  the  bone, 
and  the  mandibular  canal  runs  nearly  parallel  with  the  mylohyoid  line.  The  ramus  is  almost 
vertical  in  direction,  the  angle  measuring  from  110°  to  120°. 

In  old  age  (Fig.  329),  the  bone  becomes  greatly  reduced  in  size,  for  with  the  loss  of  the  teeth 
the  alveolar  process  is  absorbed,  and,  consequently,  the  chief  part  of  the  bone  is  below  the  oblique 
line.  The  mandibular  canal,  with  the  mental  foramen  opening  from  it,  is  close  to  the  alveolar 
border.  The  ramus  is  obhque  in  direction,  the  angle  measures  about  140°,  and  the  neck  of  the 
condyle  is  more  or  less  bent  backward. 

The  Hyoid  Bone  (Os  Hyoideum;  Lingual  Bone). 

The  hyoid  bone  is  shaped  like  a  horseshoe,  and  is  suspended  from  the  tips  of  the 
styloid  processes  of  the  temporal  bones  by  the  stylohyoid  ligaments.  It  consists 
of  five  segments,  viz.,  a  body,  two  greater  cornua,  and  two  lesser  cornua. 

The  Body  or  Basihyal  {corpus  oss.  hyoidei). — The  body  or  central  part  is 
of  a  quadrilateral  form.  Its  anterior  surface  (Fig.  330)  is  convex  and  directed 
forward  and  upward.  It  is  crossed  in  its  upper  half  by  a  well-marked  transverse 
ridge  with  a  slight  downward  convexity,  and  in  many  cases  a  vertical  median 
ridge  divides  it  into  two  lateral  halves.  The  portion  of  the  vertical  ridge  above 
the  transverse  line  is  present  in  a  majority  of  specimens,  but  the  lower  portion  is 
evident  only  in  rare  cases.  The  anterior  surface  gives  insertion  to  the  Geniohyoid- 
eus  in  the  greater  part  of  its  extent  both  above  and  below  the  transverse  ridge; 
a  portion  of  the  origin  of  the  Hyoglossus  notches  the  lateral  margin  of  the  Genio- 
hyoideus  attachment.  Below  the  transverse  ridge  the  Mylohyoideus,  Sterno- 
hyoideus,  and  Omohyoideus  are  inserted.  The  posterior  surface  is  smooth, 
concave,  directed  backward  and  downward,  and  separated  from  the  epiglottis  by 
the  hyothyroid  membrane  and  a  quantity  of  loose  areolar  tissue ;  a  bursa  intervenes 
between  it  and  the  hyothyroid  membrane.  The  superior  border  is  rounded,  and 
gives  attachment  to  the  hyothyroid  membrane  and  some  aponeurotic  fibres  of  the 
Genioglossus.  The  inferior  border  affords  insertion  medially  to  the  Sternohyoideus 
and  laterally  to  the  Omohyoideus  and  occasionally  a  portion  of  the  Thyreohyoideus. 
It  also  gives  attachment  to  the  Levator  glandulae  thyreoideae,  when  this  muscle 
is  present.  In  early  life  the  lateral  borders  are  connected  to  the  greater  cornua 
by  synchondroses;  after  middle  life  usually  by  bony  union. 

The  Greater  Cornua  or  Thyrohyals  {cornua  majora) .  —  The  greater  cornua 
project  backward  from  the  lateral  borders  of  the  body;  they  are  flattened  from 
above  downward  and  diminish  in  size  from  before  backward ;  each  ends  in  a  tubercle 
to  which  is  fixed  the  lateral  hyothyroid  ligament.     The  upper  surface  is  rough 


276 


OSTEOLOGY 


Fig.  326.— At  birth. 


Fig.  327. — In  childhood. 


Fig.  32S.— In  the  adult. 


Fig.  329.— In  old  age. 
Side  view  of  the  mandible  at  different  periods  of  life. 


THE  EXTERIOH  OF  THE  SKULL 


'.ii 


DIOASTRICUS  & 
STYUiHYOIDEUS 

T'hyreohyoidecs 
Omohyoideus 


dose  to  its  lateral  border,  for  muscular  attachments:  the  largest  of  these  are  the 
origins  of  the  Hyoglossus  and  Constrictor  pharyngis  medius  which  extend  along 
the  whole  length  of  the  cornu;  the  Digastricus  and  Stylohyoideus  have  small 
insertions    in    front    of  these 

near  the  junction  of  the  l)o(l\'  /^Tk^ ^Greater  coi~nu 

with  the  cornu.  To  the  medial 
border  the  hyothyroid  mem- 
brane is  attached,  while  the 
anterior  half  of  the  lateral 
border  gives  insertion  to  the 
Thyreohyoideus. 

The  Lesser  Cornua  or  Cera- 
tohyals  {cornua  vunora). — The 
lesser  cornu  are  two  small, 
conical  eminences,  attached 
by  their  bases  to  the  angles  of 
junction  between  the  body  and 
greater  cornua.  They  are  con- 
nected to  the  body  of  the  bone 
by  fibrous  tissue,  and  occasionally  to  the  greater  cornua  by  distinct  diarthrodial 
joints,  which  usually  persist  throughout  life,  but  occasionally  become  ankylosed. 

The  lesser  cornua  are  situated  in  the  line  of  the  transverse  ridge  on  the  bod>' 
and  appear  to  be  morphological  continuations  of  it  (Parsons^).  The  apex  of  each 
cornu  gives  attachment  to  the  stylohyoid  ligament  ;2  the  Chondroglossus  rises 
from  the  medial  side  of  the  base. 

Ossification. — -The  hyoid  is  ossified  from  six  centres:  two  for  the  body,  and  one  for  each  cornu. 
Ossification  commences  in  the  greater  cornua  toward  'the  end  of  fetal  hfe,  in  the  body  shortly 
afterward,  and  in  the  lesser  cornua  during  the  first  or  second  year  after  birth. 

Applied  Anatomy. — The  hyoid  bone  is  occasionally  fractured,  generally  from  direct  violence, 
as  in  hanging,  forcible  grasping  of  the  throat  in  garroting  or  throttling,  or  bj'  a  blow.  The  frac- 
ture generally  occurs  about  the  junction  of  the  greater  cornu  with  the  body  of  the  bone,  but 
sometimes  takes  place  through  the  latter;  since  the  muscles  of  the  tongue  have  important  con- 
nections with  this  bone,  there  is  great  pain  upon  any  attempt  being  made  to  move  the  tongue, 
as  in  speaking  or  swallowing. 


Mylohyoibkus     sternohyoidebs 
Geniohyoideus 

Fig.  .3.30. — Hyoid  bone.     Anterior  surface.     Enlarged. 


THE   EXTERIOR   OF   THE    SKULL. 

The  skull  as  a  whole  may  be  viewed  from  different  points,  and  the  views  so 
obtained  are  termed  the  normse  of  the  skull;  thus,  it  may  be  examined  from  above 
(norma  verticalis),  from  below  (norma  basalis),  from  the  side  (norma  lateralis), 
from  behind  (norma  occipitalis),  or  from  the  front  (norma  frontalis). 

Norma  Verticalis. — When  viewed  from  above  the  outline  presented  varies 
greatly  in  different  skulls;  in  some  it  is  more  or  less  oval,  in  others  more  nearly 
circular.  The  surface  is  traversed  by  three  sutures,  viz.:  (1)  the  coronal  sutures, 
nearly  transverse  in  direction,  between  the  frontal  and  parietals;  (2)  the  sagittal 
sutures,  medially  placed,  between  the  parietal  bones,  and  deeply  serrated  in  its 
anterior  two-thirds;  and  (3)  the  upper  part  of  the  lambdoidal  suture,  between  the 
parietals  and  the  occipital.  The  point  of  junction  of  the  sagittal  and  coronal  suture 
is  named  the  bregma,  that  of  the  sagittal  and  lambdoid  sutures,  the  lambda;  they 
indicate  respectively  the  positions  of  the  anterior  and  posterior  fontanelles  in  the 
fetal  skull.  On  either  side  of  the  sagittal  suture  are  the  parietal  eminence  and  parietal 


1  See  article  on  "The  Topography  and  Morphology  of  the  Human  Hyoid  Bone,"  by  F.   G.  Parsons,  Journal  of 
Anatomy  and  Physiology,  vol.  xliii. 

2  These  ligaments  in  many  animals  are  distinct  bones,  and  in  man  maj'  undergo  partial  ossification. 


278  OSTEOLOdY 

foramen — the  latter,  however,  is  freciuently  absent  on  one  or  })oth  sides.  The 
skull  is  often  somewhat  flattened  in  the  neighborhood  of  the  parietal  foramina, 
and  the  term  obelion  is  applied  to  that  point  of  the  sagittal  suture  which  is  on 
a  level  with  the  foramina.  In  front  is  the  glabella,  and  on  its  lateral  aspects  are 
the  superciliary  arches,  and  above  these  the  frontal  eminences.  Immediately  above 
the  glabella  may  be  seen  the  remains  of  the  frontal  suture;  in  a  small  percentage 
of  skulls  this  suture  persists  and  extends  along  the  middle  line  to  the  bregma. 
Passing  backward  and  upward  from  the  zygomatic  processes  of  the  frontal  bone 
are  the  temporal  lines,  which  mark  the  upper  limits  of  the  temporal  fossae.  The 
zygomatic  arches  may  or  may  not  be  seen  projecting  beyond  the  anterior  portions 
of  these  lines. 

Norma  Basalis  (Fig.  331). — The  inferior  surface  of  the  base  of  the  skull,  exclu- 
sive of  the  mandible,  is  bounded  in  front  by  the  incisor  teeth  in  the  maxillae;  behind, 
by  the  superior  nuchal  lines  of  the  occipital;  and  laterally  by  the  alveolar  arch, 
the  lower  border  of  the  zygomatic  bone,  the  zygomatic  arch  and  an  imaginary 
line  extending  from  it  to  the  mastoid  process  and  extremity  of  the  superior  nuchal 
line  of  the  occipital.  It  is  formed  by  the  palatine  processes  of  the  maxillse  and 
palatine  bones,  the  vomer,  the  pterygoid  processes,  the  under  surfaces  of  the 
great  wings,  spinous  processes,  and  part  of  the  body  of  the  sphenoid,  the  under 
surfaces  of  the  squamse  and  mastoid  and  petrous  portions  of  the  temporals,  and 
the  under  surface  of  the  occipital  bone.  The  anterior  part  or  hard  palate  projects 
below  the  level  of  the  rest  of  the  surface,  and  is  bounded  in  front  and  laterally 
by  the  alveolar  arch  containing  the  sixteen  teeth  of  the  maxillse.  Immediately 
behind  the  incisor  teeth  is  the  incisive  foramen.  In  this  foramen  are  two  lateral 
apertures,  the  openings  of  the  incisive  canals  (foramina  of  Stensen)  which  transmit 
the  anterior  branches  of  the  descending  palatine  vessels,  and  the  nasopalatine 
nerves.  Occasionalh'  two  additional  canals  are  present  in  the  incisive  foramen; 
they  are  termed  the  foramina  of  Scarpa  and  are  situated  in  the  middle  line;  when 
present  they  transmit  the  nasopalatine  nerves.  The  vault  of  the  hard  palate 
is  concave,  uneven,  perforated  by  numerous  foramina,  marked  by  depressions  for 
the  palatine  glands,  and  traversed  by  a  crucial  suture  formed  by  the  junction  of  the 
four  bones  of  which  it  is  composed.  In  the  young  skull  a  suture  may  be  seen  ex- 
tending on  either  side  from  the  incisive  foramen  to  the  interval  between  the  lateral 
incisor  and  canine  teeth,  and  marking  oft"  the  os  incisivum  or  premaxillary  bone. 
At  either  posterior  angle  of  the  hard  palate  is  the  greater  palatine  foramen,  for  the 
transmission  of  the  descending  palatine  vessels  and  anterior  palatine  nerve;  and 
running  forward  and  medialward  from  it  a  groove,  for  the  same  vessels  and  nerve. 
Behind  the  posterior  palatine  foramen  is  the  pyramidal  process  of  the  palatine  bone, 
perforated  by  one  or  more  lesser  palatine  foramina,  and  marked  by  the  commence- 
ment of  a  transverse  ridge,  for  the  attachment  of  the  tendinous  expansion  of  the 
Tensor  veli  palatini.  Projecting  backward  from  the  centre  of  the  posterior  border 
of  the  hard  palate  is  the  posterior  nasal  spine,  for  the  attachment  of  the  IMusculus 
uvulae.  Behind  and  above  the  hard  palate  are  the  choanae,  measuring  about 
2.5  cm.  in  their  vertical  and  1.25  cm.  in  their  transverse  diameters.  They  are 
separated  from  one  another  by  the  vomer,  and  each  is  bounded  above  by  the  body 
of  the  sphenoid,  below  by  the  horizontal  part  of  the  palatine  bone,  and  laterally 
by  the  medial  pterygoid  plate  of  the  sphenoid.  At  the  superior  border  of  the 
vomer  may  be  seen  the  expanded  alee  of  this  bone,  receiving  between  them  the  ros- 
trum of  the  sphenoid.  Near  the  lateral  margins  of  the  alse  of  the  vomer,  at  the 
roots  of  the  pterygoid  processes,  are  the  pharyngeal  canals.  The  pterygoid  process 
presents  near  its  base  the  pterygoid  canal,  for  the  transmission  of  a  nerve  and  artery. 
The  medial  pterygoid  plate  is  long  and  narrow^;  on  the  lateral  side  of  its  base  is  the 
scaphoid  fossa,  for  the  origin  of  the  Tensor  veli  palatini,  and  at  its  lower  extremity 
the  hamulus,  around  which  the  tendon  of  this  muscle  turns.    The  lateral  pterygoid 


THE  EXTERIOR  OF  THE  SKULL  279 

plate  is  broad;  its  lateral  surface  forms  the  mc.lial  houiulan  „[  tlie  infratemporal 
tossa,  and  aftords  attaolinicnt  to  tlie  Pterviroidcus  extcrnus. 


Incisors 


Canine 


Incisive  canal 


Trammitu  left  nasopalatine  nerve 
Traiixinits  descendimj  palatine  vemiels 
Transnuts  right  nasupalatine  nei-ve 


Lesser  palatine  foramina 

Posterior  nasal  spine 
Muscuhis  uvulae 
Pteryrjoid  hamulus 


Sphenoidal  process  of  jjalaline 
Pharyrujeal  caiiul 


Tensor  tympani 


Pliaryngeal  tubercle 
Situation   of  auditory   tube  and 
stmicanal  for  Tensor  tympani 

Tenxor  veli  'palatini 
Inferior  li/uipanic  canaliculua 
Aqiiarihidiix  mclilrne 
Jvjiiihir  fiii-Kiiicn 
M,ist,,„l  n,,:„li,-iihis 
TyinpunvJiia-stuid  fissure 


Fig.  331. — Base  of  skull.     Inferior  surface. 


280  OSTEOLOGY 

Behind  the  nasal  ca\-ities  is  the  basihir  portion  of  the  occipital  bone,  presenting 
near  its  centre  the  pharyngeal  tubercle  for  the  attachment  of  the  fibrous  raphe 
of  the  pharynx,  with  depressions  on  either  side  for  the  insertions  of  the  Rectus 
capitis  anterior  and  Longus  capitis.  At  the  base  of  the  lateral  pterygoid  plate 
is  the  foramen  ovale,  for  the  transmission  of  the  mandi})ular  nerve,  the  accessory 
meningeal  artery,  and  sometimes  the  lesser  superficial  petrosal  nerve;  behind  this  are 
the  foramen  spinosum  which  transmits  the  middle  meningeal  vessels,  and  the  promi- 
nent spina  angularis  (sphenoidal  spine),  which  gives  attachment  to  the  spheno- 
mandibular  ligament  and  the  Tensor  veli  palatini.  Lateral  to  the  spina  angularis 
is  the  mandibular  fossa,  divided  into  two  parts  by  the  petrotympanic  fissure;  the 
anterior  portion,  concave,  smooth,  bounded  in  front  by  the  articular  tubercle, 
serves  for  the  articulation  of  the  condyle  of  the  mandible;  the  posterior  portion, 
rough  and  bounded  behind  by  the  tympanic  part  of  the  temporal,  is  sometimes 
occupied  by  a  part  of  the  parotid  gland.  Emerging  from  between  the  laminae 
of  the  vaginal  process  of  the  tympanic  part  is  the  styloid  process;  and  at  the  base 
of  this  process  is  the  stylomastoid  foramen,  for  the  exit  of  the  facial  nerve,  and 
entrance  of  the  stylomastoid  artery.  Lateral  to  the  stylomastoid  foramen,  between 
the  tympanic  part  and  the  mastoid  process,  is  the  tympanomastoid  fissure,  for  the 
auricular  branch  of  the  vagus.  Upon  the  medial  side  of  the  mastoid  process  is 
the  mastoid  notch  for  the  posterior  belly  of  the  Digastricus,  and  medial  to  the  notch, 
the  occipital  groove  for  the  occipital  artery.  At  the  base  of  the  medial  pterygoid 
plate  is  a  large  and  somewhat  triangular  aperture,  the  foramen  lacerum,  bounded 
in  front  by  the  great  wing  of  the  sphenoid,  behind  by  the  apex  of  the  petrous 
portion  of  the  temporal  bone,  and  medially  by  the  body  of  the  sphenoid  and  basilar 
portion  of  the  occipital  bone;  it  presents  in  front  the  posterior  orifice  of  the  ptery- 
goid canal;  behind,  the  aperture  of  the  carotid  canal.  The  lower  part  of  this  opening 
is  filled  up  in  the  recent  state  by  a  fibrocartilaginous  plate,  across  the  upper  or 
cerebral  surface  of  which  the  internal  carotid  artery  passes.  Lateral  to  this  aperture 
is  a  groove,  the  sulcus  tubae  auditivae,  between  the  petrous  part  of  the  temporal  and 
the  great  wing  of  the  sphenoid.  This  sulcus  is  directed  lateralward  and  backward 
from  the  root  of  the  medial  pterygoid  plate  and  lodges  the  cartilaginous  part  of  the 
auditory  tube;  it  is  continuous  behind  with  the  canal  in  the  temporal  bone  which 
forms  the  bony  part  of  the  same  tube.  At  the  bottom  of  this  sulcus  is  a  narrow 
cleft,  the  petrosphenoidal  fissure,  which  is  occupied,  in  the  recent  condition,  by  a 
plate  of  cartilage.  Behind  this  fissure  is  the  under  surface  of  the  petrous  portion 
of  the  temporal  bone,  presenting,  near  its  apex,  the  quadrilateral  rought  surface, 
part  of  which  affords  attachment  to  the  Levator  veli  palatini;  lateral  to  this  surface 
is  the  orifice  of  the  carotid  canal,  and  medial  to  it,  the  depression  leading  to  the 
aquaeductus  cochleae,  the  former  transmitting  the  internal  carotid  artery  and  the 
carotid  plexus  of  the  sympathetic,  the  latter  serving  for  the  passage  of  a  vein  from 
the  cochlea.  Behind  the  carotid  canal  is  the  jugular  foramen,  a  large  aperture, 
formed  in  front  by  the  petrous  portion  of  the  temporal,  and  behind  by  the  occipital; 
it  is  generally  larger  on  the  right  than  on  the  left  side,  and  may  be  subdivided 
into  three  compartments.  The  anterior  compartment  transmits  the  inferior 
petrosal  sinus;  the  intermediate,  the  glossopharyngeal,  vagus,  and  accessory 
nerves;  the  posterior,  the  transverse  sinus  and  some  meningeal  branches  from  the 
occipital  and  ascending  pharyngeal  arteries.  On  the  ridge  of  bone  di^■iding  the 
carotid  canal  from  the  jugular  foramen  is  the  inferior  tympanic  canaliculus  for 
the  transmission  of  the  tympanic  branch  of  the  glossopharyngeal  nerve;  and  on  the 
w^all  of  the  jugular  foramen,  near  the  root  of  the  styloid  process,  is  the  mastoid 
canaliculus  for  the  passage  of  the  auricular  branch  of  the  ^•agus  nerve.  Extending 
forward  from  the  jugular  foramen  to  the  foramen  lacerum  is  the  petrooccipital  fissure 
occupied,  in  the  recent  state,  by  a  plate  of  cartilage.  Behind  the  basilar  portion 
of  the  occipital  bone  is  the  foramen  magnum,  bounded  laterally  by  the  occipital 


THE  EXTERIOR  OF  THE  SKULL 


281 


condyles,  the  medial  sides  of  which  are  rough  for  tlie  attachment  of  the  alar 
ligaments.  Lateral  to  each  condyle  is  the  jugular  process  which  gives  attachment 
to  the  Rectus  capitis  lateralis  muscle  and  the  hitcral  athmtooccipital  ligament. 
The  foramen  magnum  transmits  the  medulla  ol)longata  and  its  membranes,  the 
accessory  nerves,  the  vertebral  arteries,  the  anterior  and  posterior  spinal  arteries, 
and  the  ligaments  connecting  the  occipital  bone  with  the  axis.  The  mid-points 
on  the  anterior  and  posterior  margins  of  the  foramen  magnum  are  respectively 
termed  the  basion  and  the  opisthion.  In  front  of  each  condyle  is  the  canal  for  the 
passage  of  the  hypoglossal  nerve  and  a  meningeal  artery.  Behind  each  condyle 
is  the  condyloid  fossa,  perforated  on  one  or  both  sides  by  the  condyloid  canal,  for 
the  transmission  of  a  vein  from  the  transverse  sinus.  Behind  the  foramen  magnum 
is  the  median  nuchal  line  ending  above  at  the  external  occipital  protuberance,  while 
on  either  side  are  the  superior  and  inferior  nuchal  lines;  these,  as  well  as  the  surfaces 
of  bone  between  them,  are  rough  for  the  attachment  of  the  muscles  which  are 
enumerated  on  pages  227  and  22S. 


Parietal 


Ftontal 


Occipital 


Fig.  332. — Side  view  of  the  skull. 


Norma  Lateralis  (Fig.  332). — When  \iewed  from  the  side  the  skull  is  seen  to 
consist  of  the  cranium  above  and  behind,  and  of  the  face  below  and  in  front.  The 
cranium  is  somewhat  ovoid  in  shape,  but  its  contour  varies  in  different  cases  and 
depends  largely  on  the  length  and  height  of  the  skull  and  on  the  degree  of  promi- 
nence of  the  superciliary  arches  and  frontal  eminences.  Entering  into  its  formation 
are  the  frontal,  the  parietal,  the  occipital,  the  temporal,  and  the  great  wing  of  the 
sphenoid.  These  bones  are  joined  to  one  another  and  to  the  zygomatic  by  the  follow- 


282  OSTEOLOGY 

ing  sutures:  the  zygomaticotemporal  between  the  zNgomatic  })r()cess  of  the  temporal 
and  the  temporal  process  of  the  zygomatic;  the  zygomaticofrontal  uniting  the  zygo- 
matic bone  with  the  zygomatic  process  of  the  frontal ;  the  sutures  surrounding  the 
great  wing  of  the  si)henoid,  viz.,  the  sphenozygomatic  in  front,  the  sphenofrontal 
and  sphenoparietal  above,  and  the  sphenosquamosal  behind.  The  si)lien()})arictal 
suture  varies  in  length  in  different  skulls,  and  is  absent  in  those  cases  where  the 
frontal  articulates  with  the  temporal  squama.  The  point  corresponding  with  the 
posterior  end  of  the  sphenoparietal  suture  is  named  the  pterion;  it  is  situated  about 
3  cm.  behind,  and  a  little  above  the  level  of  the  zygomatic  process  of  the  frontal 
bone. 

The  squamosal  suture  arches  backward  from  the  pterion  and  connects  the  tem- 
poral squama  with  the  lower  border  of  the  parietal:  this  suture  is  continuous 
behind  with  the  short,  nearly  horizontal  parietomastoid  suture,  which  unites  the 
mastoid  process  of  the  temporal  with  the  region  of  the  mastoid  angle  of  the  parietal. 
Extending  from  above  downward  and  forward  across  the  cranium  are  the  coronal 
and  lambdoidal  sutures;  the  former  connects  the  parietals  with  the  frontal,  the  latter, 
the  parietals  with  the  occipital.  The  lambdoidal  suture  is  continuous  below^  with 
the  occipitomastoid  suture  between  the  occipital  and  the  mastoid  portion  of  the 
temporal.  In  or  near  the  last  suture  is  the  mastoid  foramen,  for  the  transmission 
of  an  emissary  vein.  The  point  of  meeting  of  the  parietomastoid,  occipitomastoid, 
and  lambdoidal  sutures  is  known  as  the  asterion.  Immediately  above  the  orbital 
margin  is  the  superciliary  arch,  and,  at  a  higher  level,  the  frontal  eminence.  Near 
the  centre  of  the  parietal  bone  is  the  parietal  eminence.  Posteriorly  is  the  ex- 
ternal occipital  protuberance,  from  which  the  superior  nuchal  line  may  be  followed 
forward  to  the  mastoid  process.  Arching  across  the  side  of  the  cranium  are  the 
temporal  lines,  w^hich  mark  the  upper  limit  of  the  temporal  fossa. 

The  Temporal  Fossa  {fossa  temyoralis). — The  temporal  fossa  is  bounded  above 
and  behind  by  the  temporal  lines,  wdiich  extend  from  the  zygomatic  process  of  the 
frontal  bone  upward  and  backward  across  the  frontal  and  parietal  bones,  and  then 
curve  downward  and  forward  to  become  continuous  with  the  supramastoid  crest 
and  the  posterior  root  of  the  zygomatic  arch.  The  point  w^here  the  upper  temporal 
line  cuts  the  coronal  suture  is  named  the  stephanion.  The  temporal  fossa  is  bounded 
in  front  by  the  frontal  and  zygomatic  bones,  and  opening  on  the  back  of  the  latter 
is  the  zygomaticotemporal  foramen.  Laterally  the  fossa  is  limited  by  the  zygomatic 
arch,  formed  by  the  zygomatic  and  temporal  bones;  helow,  it  is  separated  from  the 
infratemporal  fossa  by  the  infratemporal  crest  on  the  great  wing  of  the  sphenoid, 
and  by  a  ridge,  continuous  wdth  this  crest,  which  is  carried  backward  across  the 
temporal  squama  to  the  anterior  root  of  the  zygomatic  process.  In  front  and 
below%  the  fossa  communicates  with  the  orbital  cavity  through  the  inferior  orbital 
or  sphenomaxillary  fissure.  The  floor  of  the  fossa  is  deeply  concave  in  front  and 
convex  behind,  and  is  formed  by  the  zygomatic,  frontal,  parietal,  sphenoid,  and 
temporal  bones.  It  is  traversed  by  vascular  furrows ;  one,  usually  well-marked,  runs 
upward  above  and  in  front  of  the  external  acoustic  meatus,  and  lodges  the  middle 
temporal  artery.  Two  others,  frequently  indistinct,  may  be  observed  on  the 
anterior  part  of  the  floor,  and  are  for  the  anterior  and  posterior  deep  temporal 
arteries.  The  temporal  fossa  contains  the  Temporalis  muscle  and  its  vessels  and 
nerves,  together  with  the  zygomaticotemporal  nerve. 

The  zygomatic  arch  is  formed  by  the  zygomatic  process  of  the  temporal  and 
the  temporal  process  of  the  zygomatic,  the  two  being  united  by  an  oblique  suture; 
the  tendon  of  the  Temporalis  passes  medial  to  the  arch  to  gain  insertion  into  the 
coronoid  process  of  the  mandible.  The  zygomatic  process  of  the  temporal  arises 
by  two  roots,  an  anterior,  directed  inward  in  front  of  the  mandibular  fossa,  where 
it  expands  to  form  the  articular  tubercle,  and  a  posterior,  which  runs  backward 
above  the  external  acoustic  meatus  and  is  continuous  with  the  supramastoid 


Tiii<:  kxti:rior  of  the  skcll 


283 


crest.     The  iip])(>r  honlcr  of  the  areh  gives  attaclnnent  to  the  teni])oral  fascia; 
the  lower  border  and  medial  surface  gWe  orij;in  to  the  Masseter. 

Below  the  posterior  root  of  the  zygomatic  arch  is  the  elliptical  orifice  of  the 
external  acoustic  meatus,  bounded  in  front,  below,  and  lu'liind  by  tlie  tym])anic 
part  of  the  temporal  bone;  to  its  outer  margin  the  cartilaginous  segment  of  the 
external  acoustic  meatus  is  attached.  The  small  triangular  area  between  the 
posterior  root  of  the  zygomatic  arch  and  the  postero-sui)erior  part  of  the  orifice  is 
termed  the  suprameatal  triangle,  on  the  anterior  border  of  which  a  small  spinous 
process,  the  suprameatal  spine,  is  sometimes  seen.  Between  the  tympanic  part 
and  the  articular  tubercle  is  the  mandibular  fossa,  divided  into  two  i)arts  by  the 
petrotympanic  fissure.  The  anterior  and  larger  part  of  the  fossa  articulates  with 
the  condyle  of  the  mandible  and  is  limited  behind  by  the  external  acoustic  meatus: 
the  posterior  part  sometimes  lodges  a  portion  of  the  parotid  gland.  The  styloid 
process  extends  downward  and  forward  for  a  \^ariable  distance  from  the  lower 
part  of  the  tympanic  part,  and  gives  attachment  to  the  Styloglossus,  StyJohy- 
oideus,  and  Stylopharyngeus,  and  to  the  stylohyoid  and  stylomandibular  ligaments. 
Projecting  downward  behind  the  external  acoustic  meatus  is  the  mastoid  process, 
to  the  outer  surface  of  which  the  Sternocleidomastoideus,  Splenius  capitis,  and 
Longissimus  capitis  are  attached. 


Pa  rictf/I 


Inferim-  orbital  fissure 

Infratemporal  crest 

Pierygomaxillary  fisstire 

Pterygoid  hamulus 

Fig.  333. — Left  infratemporal  fossa 


External  acoustic  meatus 
Tympanic  part  of  temporal 
ijloicl  process 
Mandibular  cavity 
Zygomatic  process  {cut) 
Lateral  pterygoid  plate 


The  Infratemporal  Fossa  (fossa  infratemjjoral is;  zygomatic  fossa)  (Fig.  333). — The 
infratemporal  fossa  is  an  irregularly  shaped  cavity,  situated  below  and  medial  to  the 
zygomatic  arch.  It  is  bounded,  in  front,  by  the  infratemporal  surface  of  the  maxilla 
and  the  ridge  which  descends  from  its  zygomatic  process;  behind,  by  the  articular 
tubercle  of  the  temporal  and  the  spina  angularis  of  the  sphenoid;  above,  by  the  great 
wing  of  the  sphenoid  below  the  infratemporal  crest,  and  by  the  under  surface  of 


284  OSTEOLOGY 

the  temporal  squama;  heloic,  by  the  alveolar  border  of  the  maxilla;  medially,  by 
the  lateral  pterygoid  plate.  It  contains  the  lower  ])art  of  the  Temporalis,  the 
Pterygoidei  internus  and  externus,  the  internal  maxillary  vessels,  and  the  man- 
dibular and  maxillary  nerves.  The  foramen  ovale  and  foramen  spinosum  open  on 
its  roof,  and  the  alveolar  canals  on  its  anterior  wall.  At  its  u])per  and  medial 
part  are  two  fissures,  wliieli  together  form  a  T-shaped  fissure,  the  horizontal  limb 
being  named  the  inferior  orbital,  and  the  vertical  one  the  pterygomaxillary. 

The  inferior  orbital  fissure  {fissura  orbitalis  inferior;  sphenomaxillary  fissure), 
horizontal  in  direction,  opens  into  the  lateral  and  back  part  of  the  orbit.  It  is 
bounded  above  by  the  lower  border  of  the  orbital  surface  of  the  great  wing  of  the 
sphenoid;  hclow,  by  the  lateral  border  of  the  orbital  surface  of  the  maxilla  and  the 
orbital  process  of  the  palatine  bone;  laterally,  by  a  small  part  of  the  zygomatic 
bone:^  medially,  it  joins  at  right  angles  with  the  pterygomaxillary  fissure.  Through 
the  inferior  orbital  fissure  the  orbit  communicates  with  the  temporal,  infratem- 
poral, and  pterygopalatine  fossse;  the  fissure  transmits  the  maxillary  nerve  and 
its  zygomatic  branch,  the  infraorbital  vessels,  the  ascending  branches  from  the 
sphenopalatine  ganglion,  and  a  vein  which  connects  the  inferior  ophthalmic  vein 
with  the  pterygoid  venous  plexus. 

The  pterygomaxillary  fissure  is  vertical,  and  descends  at  right  angles  from  the 
medial  end  of  the  preceding;  it  is  a  triangular  interval,  formed  by  the  diver- 
gence of  the  maxilla  from  the  pterygoid  process  of  the  sphenoid.  It  connects 
the  infratemporal  with  the  pterygopalatine  fossa,  and  transmits  the  terminal  part 
of  the  internal  maxillary  artery. 

The  Pterygopalatine  Fossa  (fossa  pterygoimlatina;  sphenomaxillary  fossa). — The 
pterygopalatine  fossa  is  a  small,  triangular  space  at  the  angle  of  junction  of  the 
inferior  orbital  and  pterygomaxillary  fissures,  and  placed  beneath  the  apex  of 
the  orbit.  It  is  bounded  above  by  the  under  surface  of  the  body  of  the  sphenoid 
and  by  the  orbital  process  of  the  palatine  bone;  in  front,  by  the  infratemporal 
surface  of  the  maxilla;  behind,  by  the  base  of  the  pterygoid  process  and  lower  part 
of  the  anterior  surface  of  the  great  wing  of  the  sphenoid;  medially,  by  the  vertical 
part  of  the  palatine  bone  with  its  orbital  and  sphenoidal  processes.  This  fossa 
communicates  with  the  orbit  by  the  inferior  orbital  fissure,  with  the  nasal  cavity 
by  the  sphenopalatine  foramen,  and  with  the  infratemporal  fossa  by  the  pterygo- 
maxillary fissure.  Five  foramina  open  into  it.  Of  these,  three  are  on  the  posterior 
wall,  viz.,  the  foramen  rotundum,  the  pterygoid  canal,  and  the  pharyngeal  canal, 
in  this  order  downward  and  medial  ward.  On  the  medial  wall  is  the  sphenopalatine 
foramen,  and  below  is  the  superior  orifice  of  the  pterygopalatine  canal.  The  fossa 
contains  the  maxillary  nerve,  the  sphenopalatine  ganglion,  and  the  terminal  part 
of  the  internal  maxillary  artery. 

Norma  Occipitalis. — When  viewed  from  behind  the  cranium  presents  a  more 
or  less  circular  outline.  In  the  middle  line  is  the  posterior  part  of  the  sagittal 
suture  connecting  the  parietal  bones;  extending  downward  and  lateralward  from 
the  hinder  end  of  the  sagittal  suture  is  the  deeply  serrated  lambdoidal  suture  join- 
ing the  parietals  to  the  occipital  and  continuous  below  with  the  parietomastoid  and 
occipitomastoid  sutures;  it  frequentl}-  contains  one  or  more  sutural  bones.  Near 
the  middle  of  the  occipital  squama  is  the  external  occipital  protuberance  or  inion, 
and  extending  lateralward  from  it  on  either  side  is  the  superior  nuchal  line,  and 
above  this  the  faintly  marked  highest  nuchal  line.  The  part  of  the  squama  above 
the  inion  and  highest  lines  is  named  the  planum  occipitale,  and  is  covered  by  the 
Occipitalis  muscle;  the  part  below  is  termed  the  planum  nuchale,  and  is  divided 
by  the  median  nuchal  line  which  runs  downward  and  forward  from  the  inion  to  the 
foramen  magnum;  this  ridge  gives  attachment  to  the  ligamentum  nuchae.     The 

^  Occasionally  the  maxilla  and  the  sphenoid  articulate  with  each  other  at  the  anterior  extremity  of  this  fissure;  the 
zygomatic  is  then  excluded  from  it. 


THE  EXTERIOR  OF  THE  SKULL 


285 


muscles  attached  to  the  phinum  niichale  are  enumerated  on  p.  227.  Below  and  in 
front  are  the  mastoid  processes,  convex  laterally  and  grooved  medially  hy  the 
mastoid  notches.  In  or  near  the  occipitomastoid  suture  is  the  mastoid  foramen  for 
the  passage  of  the  mastoid  emissary  vein. 


F  r  0  n  t  a  I 


Supraorbital  foramen 


Superior  orbital  fissure 

-  Lamina  papyracea  of  ethmoid 

-  Laeritnal 

■  Inferior  orbital  fissure 

■  Zygomaticofacial 'foramen 

Infraorbital  foramen 
Nasal  cavity 
Inferior  nasal  concha 


u ; 


%st  ^Ya  //c' '  i  ' 


Mentcd  foramen 


Fig.   334.— The  skull  from  the  front. 

Norma  Frontalis  (Fig.  334). — When  viewed  from  the  front  the  skull  exhibits  a 
somewhat  oval  outline,  limited  above  by  the  frontal  bone,  heloiv  by  the  body  of  the 
mandible,  and  lateraUy  by  the  zygomatic  bones  and  the  mandibular  rami.  The 
upper  part,  formed  by  the  frontal  squama,  is  smooth  and  convex.  The  lower  part, 
made  up  of  the  bonesvof  the  face,  is  irregular;  it  is  excavated  laterally  by  the  orbital 
cavities,  and  presents. in  the  middle  line  the  anterior  nasal  aperture  leading  to  the 
nasal  cavities,  and  befcw  this  the  transverse  slit  between  the  upper  and  lower 
dental  arcades.  Above,  the  frontal  eminences  stand  out  more  or  less  prominently, 
and  beneath  these  are  the  superciliary  arches,  joined  to  one  another  in  the  middle 
by  the  glabella.  On  and  above  the  glabella  a  trace  of  the  frontal  suture  sometimes 
persists;  beneath  it  is  the  frontonasal  suture,  the  mid-point  of  which  is  termed  the 
nasion.  Behind  and  below  the  frontonasal  suture  the  frontal  articulates  with  the 
frontal  process  of  the  maxilla  and  with  the  lacrimal.    Arching  transversely  below 


286  OSTEOLOGY 

the  superciliary  arches  is  the  ujjper  part  of  tlie  maroin  of  the  orbit,  thin  and  promi- 
nent in  its  lateral  two-thirds,  rounded  in  its  medial  third,  and  presenting,  at  the 
junction  of  these  two  portions,  the  supraorbital  notch  or  foramen  for  the  supra- 
orbital nerve  and  vessels.  The  supraorbital  margin  ends  laterally  in  the  zygomatic 
process  which  articulates  with  the  zygomatic  bone,  and  from  it  the  temporal  line 
extends  upward  and  backward.  Below  the  frontonasal  suture  is  the  bridge  of  the 
nose,  con^'ex  from  side  to  side,  concavo-convex  from  abo\'e  downward,  and  formed 
by  the  two  nasal  bones  supported  in  the  middle  line  by  the  perpendicular  plate 
of  the  ethmoid,  and  laterally  by  the  frontal  jirocesses  of  the  maxillae  w^hich  are 
prolonged  upward  between  the  nasal  and  lacrimal  bones  and  form  the  lower  and 
medial  part  of  the  circumference  of  each  orbit.  Below  the  nasal  bones  and  between 
the  maxillae  is  the  anterior  aperture  of  the  nose,  pyriform  in  shape,  with  the  narrow 
end  directed  upward.  Laterally  this  opening  is  bounded  by  sharp  margins,  to 
which  the  lateral  and  alar  cartilages  of  the  nose  are  attached;  beloic,  the  margins 
are  thicker  and  curve  medialward  and  forward  to  end  in  the  anterior  nasal  spine. 
On  looking  into  the  nasal  cavity,  the  bony  septum  which  separates  the  nasal 
cavities  presents,  in  front,  a  large  triangular  deficiency;  this,  in  the  recent  state, 
is  filled  up  by  the  cartilage  of  the  nasal  septum;  on  the  lateral  wall  of  each  nasal 
cavity  the  anterior  part  of  the  inferior  nasal  concha  is  visible.  Below  and  lateral 
to  the  anterior  nasal  aperture  are  the  anterior  surfaces  of  the  maxillee,  each 
perforated,  near  the  lower  margin  of  the  orbit,  by  the  infraorbital  foramen  for  the 
passage  of  the  infraorbital  nerve  and  vessels.  Below  and  medial  to  this  foramen 
is  the  canine  eminence  separating  the  incisive  from  the  canine  fossa.  Beneath 
these  fossse  are  the  alveolar  processes  of  the  maxillae  containing  the  upper  teeth, 
which  overlap  the  teeth  of  the  mandible  in  front.  The  zygomatic  bone  on  either 
side  forms  the  prominence  of  the  cheek,  the  lower  and  lateral  portion  of  the  orbital 
cavity,  and  the  anterior  part  of  the  zygomatic  arch.  It  articulates  medially  with 
the  maxilla,  behind  with  the  zygomatic  process  of  the  temporal,  and  above  with 
the  great  wing  of  the  sphenoid  and  the  zygomatic  process  of  the  frontal;  it  is  per- 
forated by  the  zygomaticofacial  foramen  for  the  passage  of  the  zygomaticofacial 
nerve.  On  the  body  of  the  mandible  is  a  median  ridge,  indicating  the  position 
of  the  symphysis;  this  ridge  divides  below  to  enclase  the  mental  protuberance,  the 
lateral  angles  of  which  constitute  the  mental  tubercles.  Below  the  incisor  teeth 
is  the  incisive  fossa,  and  beneath  the  second  premolar  tooth  the  mental  foramen 
which  transmits  the  mental  nerve  and  vessels.  The  oblique  line  runs  upward  from 
the  mental  tubercle  and  is  continuous  behind  with  the  anterior  border  of  the  ramus. 
The  posterior  border  of  the  ramus  runs  downward  and  forward  from  the  condyle 
to  the  angle,  which  is  frequently  more  or  less  everted. 

_  The  Orbits  (orbitae)  (Fig.  334). — The  orbits  are  two  quadrilateral  pyramidal  cavi- 
ties, situated  at  the  upper  and  anterior  part  of  the  face,  their  bases  being  directed 
forward  and  lateralward,  and  their  apices  backward  and  medialward,  so  that  their 
long  axes,  if  continued  backward,  would  meet  over  the  body  of  the  sphenoid. 
Each  presents  for  examination  a  roof,  a  floor,  a  medial  and  a  lateral  wall,  a  base, 
and  an  apex. 

The  roof  is  concave,  directed  downward,  and  slightly  forward,  and  formed  in 
front  by  the  orbital  plate  of  the  frontal;  behind  by  the  small  wing  of  the  sphenoid. 
It  presents  medially  the  trochlear  fovea  for  the  attachment  of  the  cartilaginous 
pulley  of  the  Obliquus  oculi  superior;  laterally,  the  lacrimal  fossa  for  the  lacrimal 
gland;  and  posteriorly,  the  suture  between  the  frontal  bone  and  the  small  wing 
of  the  sphenoid. 

The  floor  is  directed  upward  and  lateralward,  and  is  of  less  extent  than  the 
roof;  it  is  formed  chiefl}-  by  the  orbital  surface  of  the  maxilla;  in  front  and  laterally, 
by  the  orbital  process  of  the  zygomatic  bone,  and  behind  and  medially,  to  a  small 
extent,  by  the  orbital  process  of  the  palatine.     At  its  medial  angle  is  the  upper 


THE  EXTKRIOH  OF  THE  SKILL 


2.S'i 


opening  oi  the  nasolacrimal  canal,  immediately  to  the  lateral  side  of  which  is  a 
depression  for  the  origin  of  the  ()l)li(iuus  oculi  inferior.  On  its  lateral  part  is  the 
sntnre  between  the  maxilla  and  zygomatic  hone,  and  at  its  posterior  part  that 
between  the  maxilla  and  the  orbital  i)r()c(\ss  of  the  palatine.  Running  forward 
near  the  middle  of  the  floor  is  the  infraorbital  groove,  ending  in  front  in  the  infra- 
orbital canal  and  transmitting  the  infraorbital  nerve  and  vessels. 

The  medial  wall  (I'ig.  'c>\\b)  is  nearly  vertical,  and  is  formed  from  before  back- 
ward by  the  frontal  process  of  the  maxilla,  the  lacrimal,  the  lamina  papyracea 
of  the  ethmoid,  and  a  small  part  of  the  body  of  the  sphenoid  in  front  of  the  optic 
foramen.  vSometimes  the  sphenoidal  concha  forms  a  i-mall  part  of  this  w^all  (see 
page  250).  It  exhibits  three  vertical  sutures,  viz.,  the  lacrimomaxillary,  lacrimo- 
ethmoidal,  and  sphenoethmoidal.  In  front  is  seen  the  lacrimal  groove,  which  lodges 
the  lacrimal  sac,  and  behind  the  groove  is  the  posterior  lacrimal  crest,  from  wiiich 


Anterior 
ethmoidal  foramen 


Posterior  ethmoidal  foramen 
Orbital  process  of  palatine 
Oiiiic  foramen 

Sphenopalatine  foramen    . 

Se^la  turcica 

I  Piobe  iH  foramen rotundwn 


Fossa  f&>'  . —      , 

lacriinal  sac      \J 

Uncinate  process  . ^^        ""T^IB. 

of  ethmoid  \^-"i^m 

Openings  of    _       -—  \  VmWiPr 

maxillary  sinus 
Inferior  nasal 
cotvcha 


Probe  in  pterygoid  canal 
(  ^Prohe  in  pterygopalatine  canal 

I  ^  Palatine  hone 

Lateral  pterygoid  plate 


Pyramidal  process  of  palatine 


Fig.   335. — Medial  wall  of  left  orbit. 


the  lacrimal  part  of  the  Orbicularis  oculi  arises.  At  the  junction  of  the  medial 
wall  and  the  roof  are  the  frontomaxillary,  frontolacrimal,  frontoethmoidal,  and 
sphenofrontal  sutures.  The  point  of  junction  of  the  anterior  border  of  the  lacrimal 
with  the  frontal  is  named  the  dacryon.  In  the  frontoethmoidal  suture  are  the 
anterior  and  posterior  ethmoidal  foramina,  the  former  transmitting  the  nasociliary 
nerve  and  anterior  ethmoidal  vessels,  the  latter  the  posterior  ethmoidal  nerve  and 
vessels. 

The  lateral  wall,  directed  medialward  and  forw^ard,  is  formed  by  the  orbital 
process  of  the  zygomatic  and  the  orbital  surface  of  the  great  wing  of  the  sphenoid ; 
these  are  united  by  the  sphenozygomatic  suture  which  terminates  below  at  the 
front  end  of  the  inferior  orbital  fissure.  On  the  orbital  process  of  the  zygomatic 
bone  are  the  orbital  tubercle  (Whitnall)  and  the  orifices  of  one  or  two  canals  which 
transmit  the  branches  of  the  zvgomatic  nerve.    Between  the  roof  and  the  lateral 


288  OSTEOLOGY 

wall,  near  the  apex  of  the  orbit,  is  the  superior  orbital  fissure.  Through  this  fissure 
the  oculomotor,  the  trochlear,  the  ophthahnic  division  of  the  trigeminal,  and  the 
abducent  nerves  enter  the  orbital  cavity,  also  some  filaments  from  the  cavernous 
plexus  of  the  sympathetic  and  the  orbital  branches  of  the  middle  meningeal  artery. 
Passing  backward  through  the  fissure  are  the  ophthalmic  vein  and  the  recurrent 
branch  from  the  lacrimal  artery  to  the  dura  mater.  The  lateral  wall  and  the  floor 
are  separated  posteriori^'  by  the  inferior  orbital  fissure  which  transmits  the  maxillary 
nerve  and  its  zygomatic  branch,  the  infraorbital  vessels,  and  the  ascending  branches 
from  the  sphenopalatine  ganglion. 

The  base  of  the  orbit,  quadrilateral  in  shape,  is  formed  above  by  the  supra- 
orbital arch  of  the  frontal  bone,  in  which  is  the  supraorbital  notch  or  foramen  for 
the  passage  of  the  supraorbital  vessels  and  nerve;  beloiv  b>'  the  zygomatic  bone  and 
maxilla,  united  by  the  zygomaticomaxillary  suture;  laterally  by  the  zygomatic 
bone  and  the  zygomatic  process  of  the  frontal  joined  by  the  zygomaticofrontal 
suture;  medially  by  the  frontal  bone  and  the  frontal  process  of  the  maxilla  united 
by  the  frontomaxillary  suture. 

The  apex,  situated  at  the  back  of  the  orbit,  corresponds  to  the  optic  foramen^ 
a  short,  cylindrical  canal,  which  transmits  the  optic  nerve  and  ophthalmic  artery. 

It  will  thus  be  seen  that  there  are  nine  openings  communicating  with  each 
orbit,  viz.,  the  optic  foramen,  superior  and  inferior  orbital  fissures,  supraorbital 
foramen,  infraorbital  canal,  anterior  and  posterior  ethmoidal  foramina,  zygomatic 
foramen,  and  the  canal  for  the  nasolacrimal  duct. 


THE   INTERIOR    OF    THE    SKULL. 

In  order  to  study  the  interior  of  the  skull  the  skull-cap  should  be  removed  by 
a  saw-cut  carried  around  the  cranium  about  the  level  of  the  frontal  eminences 
and  the  upper  limits  of  the  squapaosal  sutures,  cutting  the  occipital  bone  about 
2.5  cm.  above  the  external  protuberance. 

Inner  Surface  of  the  Skull-cap. — The  inner  surface  of  the  skull-cap  is  concaA'e 
and  presents  depressions  for  the  convolutions  of  the  cerebrum,  together  with 
numerous  furrows  for  the  lodgement  of  branches  of  the  meningeal  vessels.  Along 
the  middle  line  is  a  longitudinal  groove,  narrow  in  front,  where  it  commences  at 
the  frontal  crest,  but  broader  behind;  it  lodges  the  superior  sagittal  sinus,  and  its 
margins  afford  attachment  to  the  falx  cerebri.  On  either  side  of  it  are  several 
depressions  for  the  arachnoid  granulations,  and  at  its  back  part,  the  openings  of 
the  parietal  foramina  when  these  are  present.  It  is  crossed,  in  front,  by  the  coronal 
suture,  and  behind  by  the  lambdoidal,  while  the  sagittal  lies  in  the  medial  plane 
between  the  parietal  bones. 

Upper  Surface  of  the  Base  of  the  Skull  (Fig.  336). — The  upper  surface  of  the 
base  of  the  skull  or  floor  of  the  cranial  cavity  presents  three  fossae,  called  the  anterior, 
middle,  and  posterior  cranial  fossae. 

Anterior  Fossa  (Jossa  cranii  anterior) . — The  floor  of  the  anterior-  fossa  is  formed 
by  the  orbital  plates  of  the  frontal,  the  cribriform  plate  of  the  ethmoid,  and  the 
small  wings  and  front  part  of  the  body  of  the  sphenoid ;  it  is  limited  behind  by  the 
posterior  borders  of  the  small  wings  of  the  sphenoid  and  by  the  anterior  margin 
of  the  chiasmatic  groove.  It  is  traversed  by  the  frontoethmoidal,  sphenoethmoidal, 
and  sphenofrontal  sutures.  Its  lateral  portions  roof  in  the  orbital  cavities  and  sup- 
port the  frontal  lobes  of  the  cerebrum;  they  are  convex  and  marked  by  depressions 
for  the  brain  convolutions,  and  grooves  for  branches  of  the  meningeal  vessels. 

1  Some  anatomists  describe  the  apex  of  the  orbit  as  corresponding  with  the  mediaf  end  of  the  superior  orbital  fissure. 
It  seems  better,  however,  to  adopt  the  statement  in  the  text,  since  the  ocular  muScles  take  origin  around  the  optic 
foramen,  and  diverge  from  it  to  the  bulb  of  the  eye. 


THE  INTERIOR  OF  THE  SKULL 


289 


The  central  portion  corresponds  with  the  roof  of  the  nasal  cavity,  and  is  markedly 
depressed  on  either  side  of  the  crista  galli.    It  presents,  in  and  near  the  median 


Groove  for  super,  sagittal  sintis  — 

Grooves  for  anier.  meningeal  vessels 

Foramen  cacum  — 

Cn'nta  galli 

Slit  for  n(isocili(i)-y  nerve 

Groove  fur  iiasociiian/  verve 

Anterior  ethmoidal  foratnen 

Orifices  for  olfactory  nerves 
Posterior  ethmoidal  foramen 

Ethmoidal  spine 


Olfactory  grooves 

Optic  foramen 

Chiasmatic  groove 

T'uberculum  sellae 

Anterior  clinoid  process 

Middle  clinoid  process 

Posterior  clinoid  process 

Groove  for  abducent  nerve 

Foramen  lacerum 

Orifice  of  carotid  canal 

Depression  for  semilunar  ganglion 


Internal  acoustic  meattis 

Slit  for  dura  mater 

Groove  for  supeiior  petrosal  sinus 

Jugular  foramen 

Hypoglossal  canal - 

Aquceductus  vestibuli 

Condyloid  foramen 


Mastoid  foramen 
Posterior  m,eningeal  grooves 


fit'-'- 

Fig.  336. — Base  of  the  skull.     Upper  surface. 


line,  from  before  backward,  the  commencement  of  the  frontal  crest  for  the  attach- 
ment of  the  falx  cerebri;  the  foramen  cecum,  between  the  frontal  bone  and  the  crista 
galli  of  the  ethmoid,  which  usually  transmits  a  small  vein  from  the  nasal  cavity 
19 


290  OSrEOWGY 

to  the  superior  sagittal  sinus;  behind  the  foramen  cecum,  the  crista  galli,  the 
free  margin  of  which  affords  attachment  to  the  falx  cerebri;  on  either  side  of  the 
crista  galli,  the  olfactory  groove  formed  by  the  cribriform  plate,  which  supports 
the  olfactory  bulb  and  presents  foramina  for  the  transmission  of  the  olfactory 
nerves,  and  in  front  a  slit-like  opening  for  the  nasociliary  nerve.  Lateral  to  either 
olfactory  groove  are  the  internal  openings  of  the  anterior  and  posterior  ethmoidal 
foramina;  the  anterior,  situated  about  the  middle  of  the  lateral  margin  of  the  olfac- 
tory groove,  transmits  the  anterior  ethmoidal  vessels  and  the  nasociliary  nerve;  the 
nerve  runs  in  a  groove  along  the  lateral  edge  of  the  cribriform  plate  to  the  slit-like 
opening  above  mentioned;  the  posterior  ethmoidal  foramen  opens  at  the  l)ack  part 
of  this  margin  under  cover  of  the  projecting  lamina  of  the  sphenoid,  and  transmits 
the  posterior  ethmoidal  vessels  and  nerve.  Farther  back  in  the  middle  line  is  the 
ethmoidal  spine,  bounded  behind  by  a  slight  elevation  separating  two  shallow  lon- 
gitudinal grooves  which  support  the  olfactory  lobes.  Behind  this  is  the  anterior 
margin  of  the  chiasmatic  groove,  running  laterahvard  on  either  side  to  the  upper 
margin  of  the  optic  foramen. 

The  Middle  Fossa  {fossa  cranii  media). — The  middle  fossa,  deeper  than  the  pre- 
ceding, is  narrow  in  the  middle,  and  wide  at  the  sides  of  the  skull.  It  is  bounded 
in  front  by  the  posterior  margins  of  the  small  wings  of  the  sphenoid,  the  anterior 
clinoid  processes,  and  the  ridge  forming  the  anterior  margin  of  the  chiasmatic 
groove;  hehincl,  by  the  superior  angles  of  the  petrous  portions  of  the  temporals 
and  the  dorsum  sellae;  laterally  by  the  temporal  squamse,  sphenoidal  angles  of  the 
parietals,  and  great  wings  of  the  sphenoid.  It  is  traversed  by  the  squamosal, 
sphenoparietal,  sphenosquamosal,  and  sphenopetrosal  sutures. 

The  middle  part  of  the  fossa  presents,  in  frojit,  the  chiasmatic  groove  and  tuber- 
culum  sellae ;  the  chiasmatic  groove  ends  on  either  side  at  the  optic  foramen,  which 
transmits  the  optic  nerve  and  ophthalmic  artery  to  the  orbital  cavity.  Behind 
the  optic  foramen  the  anterior  clinoid  process  is  directed  backward  and  medialward 
and  gives  attachment  to  the  tentorium  cerebelli.  Behind  the  tuberculum  sellae 
is  a  deep  depression,  the  sella  turcica,  containing  the  fossa  hypophyseos,  which  lodges 
the  hypophysis,  and  presents  on  its  anterior  wall  the  middle  clinoid  processes. 
The  sella  turcica  is  bounded  posteriorly  by  a  quadrilateral  plate  of  bone,  the  dorsum 
sellae,  the  upper  angles  of  which  are  surmounted  by  the  posterior  clinoid  processes: 
these  afford  attachment  to  the  tentorium  cerebelli,  and  below  each  is  a  notch  for 
the  abducent  nerve.  On  either  side  of  the  sella  turcica  is  the  carotid  groove,  which 
is  broad,  shallow,  and  curved  somewhat  like  the  italic  letter  /.  It  begins  behind 
at  the  foramen  lacerum,  and  ends  on  the  medial  side  of  the  anterior  clinoid  process, 
where  it  is  sometimes  converted  into  a  foramen  (carotico-clinoid)  by  the  union  of 
the  anterior  with  the  middle  clinoid  process;  posteriorly,  it  is  bounded  laterally 
by  the  lingula.  This  groove  lodges  the  cavernous  sinus  and  the  internal  carotid 
artery,  the  latter  being  surrounded  by  a  plexus  of  sympathetic  nerves. 

The  lateral  parts  of  the  middle  fossa  are  of  considerable  depth,  and  support 
the  temporal  lobes  of  the  brain.  They  are  marked  by  depressions  for  the  brain 
convolutions  and  traversed  by  furrows  for  the  anterior  and  posterior  branches 
of  the  middle  meningeal  vessels.  These  furrows  begin  near  the  foramen  spinosum, 
and  the  anterior  runs  forward  and  upward  to  the  sphenoidal  angle  of  the  parietal, 
where  it  is  sometimes  converted  into  a  bony  canal;  the  posterior  runs  laterahvard 
and  backward  across  the  temporal  squama  and  passes  on  to  the  parietal  near 
the  middle  of  its  lower  border.  The  following  apertures  are  also  to  be  seen.  In 
front  is  the  superior  orbital  fissure,  bounded  above  by  the  small  wing,  below,  by  the 
great  wing,  and  medially,  by  the  body  of  the  sphenoid;  it  is  usually  completed 
laterally  by  the  orbital  plate  of  the  frontal  bone.  It  transmits  to  the  orbital 
cavity  the  oculomotor,  the  trochlear,  the  ophthalmic  division  of  the  trigeminal, 
and   the   abducent   nerves,    some  filaments  from   the   cavernous   plexus  of  the 


THE  INTERIOR  OF  THE  SK[ILL  291 

sympathetic,  and  tlic  orbital  hraiich  of  the  iniddle  inciiiii^cal  artery;  and  from  the 
orbital  cavity  a  recurrent  branch  from  the  lacrimal  artery  to  the  dura  mater,  and 
the  ophthalmic  veins.  Behind  the  medial  end  of  the  superior  orbital  fissure  is 
the  foramen  rotundum,  for  the  passage  of  the  maxillary  nerve.  Behind  and  lateral 
to  the  foramen  rotundum  is  the  foramen  ovale,  which  transmits  the  mandibular 
nerve,  the  accessory  meningeal  artery,  and  the  lesser  sujxTficial  jjetrosal  nerve. ^ 
Medial  to  the  foramen  o\'ale  is  the  foramen  Vesalii,  which  varies  in  size  in  different 
individuals,  and  is  often  absent;  when  present,  it  opens  below  at  the  lateral  side 
of  the  scaphoid  fossa,  and  transmits  a  small  vein.  Lateral  to  the  foramen  ovale 
is  the  foramen  spinosum,  for  the  passage  of  the  middle  meningeal  vessels,  and  a 
recurrent  branch  from  the  mandibular  nerve.  Medial  to  the  foramen  ovale  is 
the  foramen  lacerum;  in  the  recent  state  the  lower  part  of  this  aperture  is  filled  up 
b}'  a  layer  of  fibrocartilage,  while  its  upper  and  inner  parts  transmit  the  internal 
carotid  artery  surrounded  by  a  plexus  of  sympathetic  nerves.  The  nerve  of  the 
pterygoid  canal  and  a  meningeal  branch  from  the  ascending  pharyngeal  artery 
pierce  the  layer  of  fibrocartilage.  On  the  anterior  surface  of  the  petrous  portion 
of  the  temporal  bone  are  seen  the  eminence  caused  by  the  projection  of  the  superior 
semicircular  canal;  in  front  of  and  a  little  lateral  to  this  a  depression  corresponding 
to  the  roof  of  the  tympanic  cavity;  the  groove  leading  to  the  hiatus  of  the  facial 
canal,  for  the  transmission  of  the  greater  superficial  petrosal  nerve  and  the  petrosal 
branch  of  the  middle  meningeal  artery;  beneath  it,  the  smaller  groove,  for  the  pas- 
sage of  the  lesser  superficial  petrosal  nerve;  and,  near  the  apex  of  the  bone,  the 
depression  for  the  semilunar  ganglion  and  the  orifice  of  the  carotid  canal. 

The  Posterior  Fossa  (fossa  cranii  posterior). — The  posterior  fossa  is  the  largest 
and  deepest  of  the  three.  It  is  formed  by  the  dorsum  sellae  and  clivus  of  the 
sphenoid,  the  occipital,  the  petrous  and  mastoid  portions  of  the  temporals,  and  the 
mastoid  angles  of  the  parietal  bones;  it  is  crossed  by  the  occipitomastoid  and  the 
parietomastoid  sutures,  and  lodges  the  cerebellum,  pons,  and  medulla  oblongata. 
It  is  separated  from  the  middle  fossa  in  and  near  the  median  line  by  the  dorsum 
sellae  of  the  sphenoid  and  on  either  side  by  the  superior  angle  of  the  petrous  por- 
tion of  the  temporal  bone.  This  angle  gives  attachment  to  the  tentorum  cerebelli, 
is  grooved  for  the  superior  petrosal  sinus,  and  presents  at  its  medial  end  a  notch 
upon  which  the  trigeminal  nerve  rests.  The  fossa  is  limited  behind  by  the  grooves 
for  the  transverse  sinuses.  In  its  centre  is  the  foramen  magnum,  on  either  side  of 
which  is  a  rough  tubercle  for  the  attachment  of  the  alar  ligaments;  a  little  above 
this  tubercle  is  the  canal,  which  transmits  the  hypoglossal  nerve  and  a  meningeal 
branch  from  the  ascending  pharyngeal  artery.  In  front  of  the  foramen  magnum 
the  basilar  portion  of  the  occipital  and  the  posterior  part  of  the  body  of  the  sphenoid 
form  a  grooved  surface  which  supports  the  medulla  oblongata  and  pons;  in  the 
young  skull  these  bones  are  joined  by  a  synchondrosis.  This  grooved  surface  is 
separated  on  either  side  from  the  petrous  portion  of  the  temporal  by  the  petro- 
occipital  fissure,  which  is  occupied  in  the  recent  state  by  a  plate  of  cartilage;  the 
fissure  is  continuous  behind  with  the  jugular  foramen,  and  its  margins  are  grooved 
for  the  inferior  petrosal  sinus.  The  jugular  foramen  is  situated  between  the  lateral 
part  of  the  occipital  and  the  petrous  part  of  the  temporal.  The  anterior  portion 
of  this  foramen  transmits  the  inferior  petrosal  sinus;  the  posterior  portion,  the 
transverse  sinus  and  some  meningeal  branches  from  the  occipital  and  ascending 
pharyngeal  arteries;  and  the  intermediate  portion,  the  glossopharyngeal,  vagus, 
and  accessory  nerves.  Above  the  jugular  foramen  is  the  internal  acoustic  meatus, 
for  the  facial  and  acoustic  nerves  and  internal  auditory  artery;  behind  and  lateral 
to  this  is  the  slit-like  opening  leading  into  the  aquaeductus  vestibuli,  which  lodges 
the  ductus  endolymphaticus;  while  between  these,  and  near  the  superior  angle  of 

1  See  footnote,  page  248. 


292 


OSTEOLOGY 


the  petrous  portion,  is  a  small  triangular  depression,  the  remains  of  the  fossa  sub- 
arcuata,  which  lodges  a  process  of  the  dura  mater  and  occasionally  transmits  a  small 
vein.  Behind  the  foramen  magnum  are  the  inferior  occipital  fossae,  which  support 
the  hemispheres  of  the  cerebellum,  separated  from  one  another  by  the  internal 
occipital  crest,  which  serves  for  the  attachment  of  the  falx  cerebelli,  and  lodges 
the  occipital  sinus.  The  posterior  fossae  are  surmounted  by  the  deep  grooves  for 
the  transverse  sinuses.  Each  of  these  channels,  in  its  passage  to  the  jugular  foramen, 
grooves  the  occipital,  the  mastoid  angle  of  the  parietal,  the  mastoid  portion  of  the 
temporal,  and  the  jugular  process  of  the  occipital,  and  ends  at  the  back  part  of 
the  jugular  foramen.  Where  this  sinus  grooves  the  mastoid  portion  of  the  temporal, 
the  orifice  of  the  mastoid  foramen  may  be  seen;  and,  just  previous  to  its  termina- 
tion, the  condyloid  canal  opens  into  it;  neither  opening  is  constant. 


Crest  of  nasal  bones 
Frontal  spine 


Space  for  triangular 
cartilage  of  septum 


Crest  of  palatines 
Crest  of  maxillce 


Fig.  337. — ^ledial  wall  of  left  nasal  fossa. 


The  Nasal  Cavity  (cavum  nasi;  nasal  fossa). — The  nasal  cavities  are  two  irregular 
spaces,  situated  one  on  either  side  of  the  middle  line  of  the  face,  extending  from  the 
base  of  the  cranium  to  the  roof  of  the  mouth,  and  separated  from  each  other  by  a 
thin  vertical  septum.  They  open  on  the  face  through  the  pear-shaped  anterior  nasal 
aperture,  and  their  posterior  openings  or  choanse  communicate,  in  the  recent 
state,  with  the  nasal  part  of  the  pharynx.  They  are  much  narrower  above  than 
below,  and  in  the  middle  than  at  their  anterior  or  posterior  openings :  their  depth, 
which  is  considerable,  is  greatest  in  the  middle.  They  communicate  with  the 
frontal,  ethmoidal,  sphenoidal,  and  maxillary  sinuses.  Each  cavity  is  bounded 
by  a  roof,  a  floor,  a  medial  and  a  lateral  wall. 

The  roof  (Figs.  337,  338)  is  horizontal  in  its  central  part,  but  slopes  down- 
ward in  front  and  behind ;  it  is  formed  in  front  by  the  nasal  bone  and  the  spine 
of  the  frontal;  in  the  middle,  by  the  cribriform  plate  of  the  ethmoid;  and  behind, 
by  the  body  of  the  sphenoid,  the  sphenoidal  concha,  the  ala  of  the  vomer  and  the 
sphenoidal  process  of  the  palatine  bone.     In  the  cribriform  plate  of  the  ethmoid 


THE  INTERIOR  OF  THE  SKULL 


293 


are  the  foramina  for  the  olfactory  nerves,  and  on  the  posterior  part  of  the  roof 
is  the  openin"'  into  the  sphenoi(hil  sinus. 

The  floor  is  fhittened  from  before  backward  and  concave  from  side  to  side. 
It  is  formed  by  the  pahitine  process  of  the  maxilla  and  the  horizontal  part  of 
the  palatine  bone;  near  its  anterior  end  is  the  opening  of  the  incisive  canal. 

The  medial  wall  (scpfioii  nasi)  (Fig.  337),  is  frequently  deflected  to  one  or  other 
side,  more  often  to  the  left  than  to  the  right.  It  is  formed,  in  front,  by  the  crest 
of  the  nasal  bones  and  frontal  spine;  in  the  middle,  by  the  perpendicular  plate 
of  the  ethmoid;  behind,  by  the  vomer  and  the  rostrum  of  the  sphenoid;  below, 
by  the  crest  of  the  maxillte  and  palatine  bones.  It  presents,  in  front,  a  large, 
triangular  notch,  which  receives  the  cartilage  of  the  septum;  and  behind,  the 
free  edge  of  the  vomer.  Its  surface  is  marked  by  numerous  furrows  for  vessels 
and  nerves  and  by  the  grooves  for  the  nasopalatine  nerve,  and  is  traversed  by 
sutures  connecting  the  bones  of  which  it  is  formed. 


Xasal  bone 
Frontal  spine 


Cribriform  plate  of  ethmoid 
Sphenoid 


Anterior  nasal  spine 

Palatine  proc.  of  maxilla 

Horizontal  part  of  palatine 

Posterior  'nasal  spine 

Incisive  canal 


Probe  passed  through 
nasolacrimal  canal 

Bristle  passed  through 
infundibulum 


-  Frontal  proc.  of  maxilla 
-  Lacrimal 
Ethmoid 

Uncinate  proc.  of  ethmoid 
Inferior  nasal  concha 
Palatine 

Superior  meatus 
Middle  meatus 
Inferior  meatus 


Fig.  338. — Roof,  floor,  and  lateral  wall  of  left  nasal  cavitJ^ 


The  lateral  wall  (Fig.  338)  is  formed,  in  front,  by  the  frontal  process  of  the 
maxilla  and  by  the  lacrimal  bone;  in  the  middle,  by  the  ethmoid,  maxilla,  and 
inferior  nasal  concha;  behind,  by  the  vertical  plate  of  the  palatine  bone,  and  the 
medial  pterygoid  plate  of  the  sphenoid.  On  this  wall  are  three  irregular  antero- 
posterior passages,  termed  the  superior,  middle,  and  inferior  meatuses  of  the  nose. 
The  superior  meatus,  the  smallest  of  the  three,  occupies  the  middle  third  of  the 
lateral  wall.  It  lies  between  the  superior  and  middle  nasal  conchse;  the  spheno- 
palatine foramen  opens  into  it  behind,  and  the  posterior  ethmoidal  cells  in  front. 
The  sphenoidal  sinus  opens  into  a  recess,  the  sphenoethmoidal  recess,  which  is  placed 
above  and  behind  the  superior  concha.  The  middle  meatus  is  situated  between  the 
middle  and  inferior  conchse,  and  extends  from  the  anterior  to  the  posterior  end  of 
the  latter.  The  lateral  wall  of  this  meatus  can  be  satisfactorily  studied  only  after 
the  removal  of  the  middle  concha.    On  it  is  a  curved  fissure,  the  hiatus  semilunaris, 


294 


OSTEOLOGY 


limited  below  by  the  edge  of  the  uncinate  i)r()('ess  of  the  ethmoid  and  above  by 
an  elevation  named  the  bulla  ethmoidalis ;  the  middle  ethmoidal  cells  are  contained 
within  this  bulla  and  open  on  or  near  to  it.  Through  the  hiatus  semilunaris 
the  meatus  communicates  with  a  curved  passage  termed  the  infundibulum,  Avhich 
communicates  in  front  with  the  anterior  ethmoidal  cells  and  in  ratlier  more  than 
fifty  per  cent,  of  skulls  is  continued  upward  as  the  frontonasal  duct  into  the  frontal 
air-sinus;  when  this  continuity  fails,  the  frontonasal  duct  oi)ens  directly  into  the 
anterior  part  of  the  meatus.  Below  the  bulla  ethmoidalis  and  hidden  by  the  unci- 
nate process  of  the  ethmoid  is  the  opening  of  the  maxillary  sinus  (ostium  maxillare) ; 
an  accessory  opening  is  freciuently  present  above  the  posterior  part  of  the  inferior 
nasal  concha.  The  inferior  meatus,  the  largest  of  the  three,  is  the  space  between 
the  inferior  concha  and  the  floor  of  the  nasal  cavity.  It  extends  almost  the  entire 
length  of  the  lateral  wall  of  the  nose,  is  broader  in  front  than  behind,  and  presents 
anteriorly  the  lower  orifice  of  the  nasolacrimal  canal. 

The  Anterior  Nasal  Aperture  (Fig.  334)  is  a  heart-shaped  or  pyriform  opening, 
whose  long  axis  is  vertical,  and  narrow  end  upward;  in  the  recent  state  it  is  much 
contracted  by  the  lateral  and  alar  cartilages  of  the  nose.  It  is  bounded  aboDe  by 
the  inferior  borders  of  the  nasal  bones;  laterally  by  the  thin,  sharp  margins  which 
separate  the  anterior  from  the  nasal  surfaces  of  the  maxillae;  and  heloio  by  the  same 
borders,  where  they  curve  medialward  to  join  each  other  at  the  anterior  nasal 
spine. 

The  choanse  are  each  bounded  above  by  the  under  surface  of  the  body  of  the 
sphenoid  and  ala  of  the  vomer;  below,  by  the  posterior  border  of  the  horizontal 
part  of  the  palatine  bone;  laterally,  by  the  medial  pterygoid  plate;  they  are 
separated  from  each  other  by  the  posterior  border  of  the  vomer. 

DIFFERENCES   IN   THE   SKULL   DUE   TO   AGE. 

At  birth  the  skull  is  large  in  proportion  to  the  other  parts  of  the  skeleton,  but  its  facial  portion 
is  small,  and  equals  only  about  one-eighth  of  the  bulk  of  the  cranium  as  compared  with  one-half 
in  the  adult.  The  frontal  and  parietal  eminences  are  prominent,  and  the  greatest  width  of  the 
skull  is  at  the  level  of  the  latter;  on  the  other  hand,  the  glabella,  superciliary  arches,  and  mastoid 
processes  are  not  developed.  Ossification  of  the  skull  bones  is  not  completed,  and  many  of  them, 
e.  g.,  the  occipital,  temporals,  sphenoid,  frontal,  and  mandible,  consist  of  more  than  one  piece. 
Unossified  membranous  intervals,  termed  fontanelles,  are  seen  at  the  angles  of  the  parietal  bones ; 
these  fontanelles  are  six  in  number:  two,  an  anterior  and  a  posterior,  are  situated  in  the  middle 
line,  and  two,  an  antero-lateral  and  a  postero-lateral,  on  either  side. 


Fig.  339. — Skull  at  birth  showing  anterior  and 
posterior  fontanelles. 


Fig.  340. — The  lateral  fontanelles. 


The  anterior  or  hregmatic  fontanelle  (Fig.  339)  is  the  largest,  and  is  placed  at  the  junction  of 
the  sagittal,  coronal,  and  frontal  sutures;  it  is  lozenge-shaped,  and  measures  about  4  cm.  in  its 
antero-posterior  and  2.5  cm.  in  its  transverse  diameter.     The  posterior  fontanelle  is  triangular 


CRANIOLOGY  295 

in  form  and  is  situated  at  the  junetion  of  the  sagittal  and  lanibdoidal  sutures.  The  lateral  Jonla- 
nclles  (Fig.  340)  are  small,  irregular  in  shape,  and  correspond  resi)ec-tivclj'  with  the  sphenoidal 
and  mastoid  angles  of  the  parietal  bones.  An  additional  fonlanelk;  is  sometimes  seen  in  tlie 
sagittal  suture  at  the  region  of  the  obelion.  The  fontanelles  are  usually  closc'd  by  the  growth 
and  extension  of  the  bones  which  surround  them,  but  sometimes  they  are  the  sites  of  se]iarate 
ossific  centres  which  develop  into  sutural  bones.  The  posterior  and  lateral  fontanelles  are  obliter- 
ated within  a  month  or  two  after  birth,  but  the  anterior  is  not  completely  closed  until  ;ibout  the 
middle  of  the  second  year. 

The  smallness  of  the  face  at  birth  is  mainly  accounted  for  by  the  rudimentaiy  condition  of 
the  maxilhe  and  mandible,  the  non-eruption  of  the  teeth,  and  the  small  size  of  th(!  maxillarj'  air 
sinuses  antl  nasal  cavities.  At  birth  the  nasal  cavities  lie  almost  entirely  between  the  orbits,  and 
the  lower  border  of  the  anterior  nasal  aperture  is  only  a  httle  below  the  level  of  the  orbital  floor. 
With  the  eruption  of  the  deciduous  teeth  there  is  an  enlargement  of  the  face  and  jaws,  and  these 
changes  are  still  more  marked  after  the  second  dentition. 

The  skull  grows  rapidly  from  birth  to  the  seventh  year,  by  which  time  the  foramen  magnum 
and  petrous  parts  of  the  temporals  have  reached  their  full  size  and  the  orbital  cavities  are  only 
a  Httle  smaller  than  those  of  the  adult.  Growth  is  slow  from  the  seventh  year  until  the  approach 
of  puberty,  when  a  second  period  of  activity  occurs :  this  results  in  an  increase  in  all  directions, 
but  it  is  especially  marked  in  the  frontal  and  facial  regions,  where  it  is  associated  with  the  develop- 
ment of  the  air  sinuses. 

ObUteration  of  the  sutures  of  the  vault  of  the  skull  takes  place  as  age  advances.  This  process 
may  commence  between  the  ages  of  thirty  and  forty,  and  is  first  seen  on  the  inner  surface,  and 
some  ten  years  later  on  the  outer  surface  of  the  skull.  The  dates  given  are,  however,  only  approxi- 
mate, as  it  is  impossible  to  state  with  anything  like  accuracy  the  time  at  which  the  sutures  are 
closed.  ObUteration  usually  occurs  first  in  the  posterior  part  of  the  sagittal  suture,  next  in  the 
coronal,  and  then  in  the  lambdoidal. 

In  old  age  the  skull  generally  becomes  thinner  and  lighter,  but  in  a  small  proportion  of  cases 
it  increases  in  thickness  and  weight,  owing  to  an  hypertrophy  of  the  inner  table.  The  most  strik- 
ing featm'e  of  the  old  skull  is  the  diminution  in  the  size  of  the  maxillge  and  mandible  consequent 
on  the  loss  of  the  teeth  and  the  absorption  of  the  alveolar  processes.  This  is  associated  with  a 
marked  reduction  in  the  vertical  measurement  of  the  face  and  with  an  alteration  in  the  angles 
of  the  mandible. 

SEXUAL   DIFFERENCES   IN   THE   SKULL 

Until  the  age  of  puberty  there  is  little  difference  between  the  skull  of  the  female  and  that  of 
the  male.  The  skull  of  an  adult  female  is,  as  a  rule,  lighter  and  smaller,  and  its  cranial  capacity 
about  10  per  cent,  less,  than  that  of  the  male.  Its  walls  are  thinner  and  its  muscular  ridges  less 
strongly  marked;  the  glabella,  superciliary  arches,  and  mastoid  processes  are  less  prominent, 
and  the  corresponding  air  sinuses  are  small  or  rudimentary.  The  upper  margin  of  the  orbit  is 
sharp,  the  forehead  vertical,  the  frontal  and  parietal  eminences  prominent,  and  the  vault  some- 
what flattened.  The  contour  of  the  face  is  more  rounded,  the  facial  bones  are  smoother,  and  the 
maxillae  and  mandible  and  their  contained  teeth  smaller.  From  what  has  been  said  it  will  be  seen 
that  more  of  the  infantile  characteristics  are  retained  in  the  skull  of  the  adult  female  than  in  that 
of  the  adult  male.  A  well-marked  male  or  female  skull  can  easily  be  recognized  as  such,  but  in 
some  cases  the  respective  characteristics  are  so  indistinct  that  the  determination  of  the  sex  may 
be  difficult  or  impossible. 

CRANIOLOGY. 

Skulls  vary  in  size  and  shape,  and  the  term  craniology  is  applied  to  the  study  of  these  varia- 
tions. The  capacity  of  the  cranial  cavity  constitutes  a  good  index  of  the  size  of  the  brain  which 
it  contained,  and  is  most  conveniently  arrived  at  by  filUng  the  cavity  with  shot  and  measuring 
the  contents  in  a  graduated  vessel.  Skulls  may  be  classified  according  to  their  capacities  as 
follows: 

1.  Microcephalic,  with  a  capacity  of  less  than  1350  c.cm. — e.  g.,  those  of  native  Australians 
and  Andaman  Islanders. 

2.  Mesocephalic,  wdth  a  capacity  of  from  1350  c.cm.  to  1450  c.cm. — e.  g.,  those  of  African 
negroes  and  Chinese. 

3  Megacephalic,  with  a  capacity  of  over  1450  c.cm. — e.  g.,  those  of  Em'opeans,  Japanese,  and 
Eskimos. 

In  comparing  the  shape  of  one  skuU  with  that  of  another  it  is  necessary  to  adopt  some  definite 
position  in  which  the  skulls  should  be  placed  during  the  process  of  examination.  They  should 
be  so  placed  that  a  line  carried  through  the  lower  margin  of  the  orbit  and  upper  margin  of  the 
external  acoustic  meatus  is  in  the  horizontal  plane.  The  normse  of  one  skull  can  then  be  com- 
pared with  those  of  another,  and  the  differences  in  contom-  and  surface  form  noted.     Fm-ther, 


296  OSTEOLOGY 

it  is  necessary  that  the  various  linear  measurements  used  to  determine  the  shape  of  the  skull 
should  be  made  between  definite  and  easily  locahzed  points  on  its  surface.  The  principal  points 
may  be  divided  into  two  groups:    (1)  those  in  the  median  plane,  and  (2)  those  on  either  side  of  it. 

The  Points  in  the  Median  Plane  are  the: 

Mental  Point.    The  most  prominent  i)oint  of  the  chin. 

Alveolar  Point  or  Prosthion.  The  central  point  of  the  anterior  margin  of  the  upper  alveolar 
arch. 

Subnasal  Point.  The  middle  of  the  lower  border  of  the  anterior  nasal  aperture,  at  the  base 
of  the  anterior  nasal  spine. 

Nasion.     The  central  point  of  the  frontonasal  suture. 

Glabella.    The  point  in  the  middle  line  at  the  level  of  the  superciliaiy  arches. 

Ophryon.  The  point  in  the  middle  line  of  the  forehead  at  the  level  where  the  temporal  hues 
most  nearly  approach  each  other. 

Bregma.    The  meeting  point  of  the  coronal  and  sagittal  sutures. 

Obelion.    A  point  in  the  sagittal  suture  on  a  level  with  the  parietal  foramina. 

Lambda.    The  point  of  junction  of  the  sagittal  and  lambdoidal  sutures. 

Occipital  Point.    The  point  in  the  middle  line  of  the  occipital  bone  farthest  from  the  glabella. 

Inion.    The  external  occipital  protuberance. 

Opisthion.    The  mid-point  of  the  posterior  margin  of  the  foramen  magnum. 

Basion.    The  mid-point  of  the  anterior  margin  of  the  foramen  magnum. 

The  Points  on  Either  Side  of  the  Median  Plane  are  the: 

Gonion.    The  outer  margin  of  the  angle  of  the  mandible. 

Dacryon.  The  point  of  union  of  the  antero-superior  angle  of  the  lacrimal  with  the  frontal 
bone  and  the  frontal  process  of  the  maxilla. 

Stephanion.    The  point  where  the  temporal  line  intersects  the  coronal  suture. 

Pterion.  The  point  where  the  great  wing  of  the  sphenoid  joins  the  sphenoidal  angle  of  the 
parietal. 

Auricular  Point.    The  centre  of  the  orifice  of  the  external  acoustic  meatus. 

Asterion.    The  point  of  meeting  of  the  lambdoidal,  mastooccipital,  and  mastoparietal  sutures. 

The  horizontal  circumference  of  the  cranium  is  measured  in  a  plane  passing  tkrough  the  glabella 
(Turner)  or  the  ophryon  (Flower)  in  front,  and  the  occipital  point  behind;  it  averages  about 
50  cm.  in  the  female  and  52.5  cm.  in  the  male. 

The  occipitofrontal  or  longitudinal  arc  is  measured  from  the  nasion  over  the  middle  line  of  the 
vertex  to  the  opisthion:  while  the  basinasal  length  is  the  distance  between  the  basion  and  the 
nasion.  These  two  measurements,  plus  the  antero-posterior  diameter  of  the  foramen  magnum, 
represent  the  vertical  circumference  of  the  cranium. 

The  length  is  measured  from  the  glabella  to  the  occipital  point,  while  the  breadth  or  greatest 

transverse  diameter  is  usually  foimd  near  the  external  acoustic  meatus.     The  proportion  of 

u       J  1-       1        ,.  (breadth  X  100) 

breadth  to  length . -r- is  termed  the  cephalic  index  or  index  of  breadth. 

The  height  is  usually  measured  from  the  basion  to  the  bregma,  and  the  proportion  of  height 
,    (height  X  100) 
to  length ,        ..-         constitutes  the  vertical  or  height  index. 

In  studying  the  face  the  principal  points  to  be  noticed  are  the  proportion  of  its  length  and 
breadth,  the  shape  of  the  orbits  and  of  the  anterior  nasal  aperture,  and  the  degree  of  projection 
of  the  jaws. 

The  length  of  the  face  may  be  measured  from  the  ophryon  or  nasion  to  the  chin,  or,  if  the  mandible 
be  wanting,  to  the  alveolar  point;  while  its  width  is  represented  by  the  distance  between  the 
zygomatic  arches.  By  comparing  the  length  with  the  width  of  the  face,  skulls  may  be  divided 
into  two  groups;  dolichofacial  or  leptoprosope  (long  faced)  and  brachyfacial  or  chemoprosope  (short 
faced) . 

The  orbital  index  signifies  the  proportion  which  the  orbital  height  bears  to  the  orbital  width, 
thus : 

orbital  height  X  100 
orbital  width 
The  rwsal  index  expresses  the  proportion  which  the  width  of  the  anterior  nasal  aperture  bears 
to  the  height  of  the  nose,  the  latter  being  measured  from  the  nasion  to  the  lower  margin  of  the 
nasal  aperture,  thus : 

nasal  width  X  100 
nasal  height 
The  degree  of  projection  of  the  jaws  is  determined  by  the  gnathic  or  alveolar  index,  which  repre- 
sents the  proportion  between  the  basialveolar  and  basinasal  lengths,  thus: 

basialveolar  length  X  100 
basinasal  length 


CRANIOLOGY 


297 


The  following  table,  modified  from  that  given  by  Duckwoitli.i  illustrates  how  these  different 
indices  may  be  utilized  in  the  classification  of  skulls: 


Index. 

Classification. 

Below  75 

Between  75  and  SO 
Above  SO 

Nomenclature. 

Examples. 

1.  Cephalic 

Dolichocephalic 

Mesaticephalic 

Brachycephalic 

Kaffirs  and  Native  Australians. 
Europeans  and  Chinese. 
Mongolians  and  Andamans. 

2.  Orbital 

Below  84 

Between  84  and  89 
Above  89 

Below  48 

Between  48  and  53 
Above  53 

Below  98 

Between  98  and  103 

Above  103 

Microseme 

Mesoseme 
Megaseme 

Tasmanians  and  Native  Austra- 
lians. 
Europeans. 
Chinese  and  Polynesians. 

3.  Nasal 

Leptorhine 
Mesorhine 
Platyrhine 

Orthognathous 
Mesognathous 
Prognathous 

Europeans. 

Japanese  and  Chinese. 

Negroes  and  Native  Australians. 

4.  Gnathic 

Europeans. 

Chinese  and  Japanese. 

Native  Australians. 

Applied  Anatomy. — Occasionally  a  protrusion  of  the  brain  or  its  membranes  may  take  place 
through  one  of  the  sutures,  owing  to  non-closure.  When  the  protrusion  consists  of  membranes 
only,  and  is  filled  with  cerebrospinal  fluid,  it  is  called  a  meningocele;  when  it  consists  of  brain  as 
well  as  membranes,  it  is  termed  an  ence'phalocele.  These  malformations  are  usually  found  in  the 
middle  line,  and  most  frequently  at  the  back  of  the  head,  the  protrusion  taking  place  between 
the  centres  of  ossification  of  the  occipital  squama  (see  p.  231).  They  generally  occur  through  the 
upper  part  of  the  vertical  fissure,  which  is  the  last  to  close,  but  not  micommonly  through 
the  lower  part,  when  the  foramen  magnum  may  be  incomplete.  More  rarely  these  protrusions 
are  met  with  in  other  situations,  as  in  the  sagittal,  lambdoidal,  and  other  sutures,  or  through 
abnormal  gaps  at  the  sides  or  base  of  the  skull. 

The  chief  function  of  the  skull  is  to  protect  the  brain,  and  therefore  those  portions  of  the  skull 
which  are  most  exposed  to  external  violence  are  thicker  than  those  which  are  shielded  from  injury 
by  overlying  muscles.  Thus,  the  skull-cap  is  thick  and  dense,  whereas  the  temporal  squamae, 
being  protected  by  the  temporales  muscles,  and  the  inferior  occipital  fossae,  being  shielded  by  the 
muscles  at  the  back  of  the  neck,  are  thin  and  fragile.  Fracture  of  the  skull  is  further  prevented 
by  its  elasticity,  its  roimded  shape,  and  its  construction  of  a  number  of  secondary  elastic  arches, 
each  made  up  of  a  single  bone.  The  manner  in  which  vibrations  are  transmitted  through  the 
bones  of  the  skull  is  also  of  importance  as  regards  its  protective  mechanism,  at  all  events  as  far 
as  the  base  is  concerned.  In  the  vault,  the  bones  being  of  a  fairly  equal  thickness  and  density, 
vibrations  are  transmitted  in  a  uniform  manner  in  all  directions,  but  in  the  base,  owing  to  the 
varying  thickness  and  density  of  the  bones,  this  is  not  so;  and  therefore  in  this  situation  there 
are  special  buttresses  which  serve  to  carry  the  vibrations  in  certain  definite  directions.  At  the 
front  of  the  skull,  on  either  side,  is  the  ridge  which  separates  the  anterior  from  the  middle  fossa 
of  the  base;  and  behind,  the  ridge  or  buttress  which  separates  the  middle  from  the  posterior  fossa; 
and  if  any  violence  is  appUed  to  the  vault,  the  vibrations  would  be  carried  along  these  buttresses 
to  the  sella  turcica,  where  they  meet.  This  part  has  been  termed  the  "centre  of  resistance," 
and  here  there  is  a  special  protective  mechanism  to  guard  the  brain.  The  subarachnoid  cavity 
at  the  base  of  the  brain  is  dilated,  and  the  cerebrospinal  fluid  which  fills  it  acts  as  a  water  cushion 
to  shield  the  brain  from  injury.  In  like  manner,  when  violence  is  applied  to  the  base  of  the  skull, 
as  in  falls  upon  the  feet,  the  vibrations  are  carried  backward  through  the  occipital  crest,  and 
forward  through  the  basilar  part  of  the  occipital  and  body  of  the  sphenoid  to  the  vault  of  the  skull. 

Fractures  of  the  skull  are  best  considered  as  affecting  either  the  vault  or  the  base.  Fractures 
of  the  vault  generally  involve  the  whole  thickness  of  the  bone;  but  sometimes  the  inner  table 
alone  is  fractured,  and  portions  of  it  driven  inward.  As  a  rule,  in  fractures  of  the  skull,  the  inner 
table  is  more  splintered  and  comminuted  than  the  outer,  and  this  is  due  to  several  causes.  It 
is  thinner  and  more  brittle;  the  force  of  the  violence  as  it  passes  inward  becomes  broken  up,  and 
is  more  diffused  by  the  time  it  reaches  the  inner  table;  the  bone  being  in  the  form  of  an  arch  bends 
as  a  whole  and  spreads  out,  and  thus  presses  the  particles  together  on  the  convex  surface  of  the 
arch,  i.  e.,  the  outer  table,  and  forces  them  asunder  on  the  concave  surface  or  inner  table;  and, 
lastly,  there  is  nothing  firm  under  the  inner  table  to  support  it  and  oppose  the  force.  Fractures 
of  the  vault  may  be  either  simple,  or  starred  and  comminuted,  and  the  fragments  may  be  de- 
pressed or  elevated.  Cases  of  fracture  with  elevation  of  the  fractured  portion  are  uncommon, 
and  can  only  be  produced  by  direct  wound.     In  comminuted  fracture,  a  portion  of  the  skuU  is 

1  Morphology  and  Anthropology,  by  W.  L.  H.  Duckworth,  M.A.,  Cambridge  University  Press. 


298  OSTEOLOGY 

broken  into  several  pieces,  the  lines  of  fracture  radiating  from  a  centre  where  the  chief  impact 
of  the  blow  was  felt;  if  the  fracture  is  also  depressed,  a  fissure  circumscribes  the  radiating  lines, 
enclosing  a  portion  of  the  skull.  If  this  area  is  circular  it  is  termed  a  "pond"  fracture,  and  has 
probably  been  caused  by  a  round  instrument,  as  a  life  preserver  or  hammer;  if  elliptical  in  shape 
it  is  termed  a  "gutter"  fracture,  and  owes  its  shape  to  the  instrument  which  has  produced  it, 
as  a  poker.  Fracture  of  the  outer  table  alone  only  occurs  in  the  region  of  the  frontal  sinuses  where 
the  two  tables  are  completely  separated. 

Fractures  of  the  base  of  the  skull  may  be  produced  by  indirect  or  direct  violence.  I.  In  cases 
of  the  former  class  the  violence  is  applied  to  the  vertex  or  some  part  of  the  cranial  convexity, 
as  when  a  person  falls  from  a  height  on  to  his  head  and  a  fracture  of  the  base  results.  The  mechan- 
ism of  this  form  of  fracture  was  formerly  explained  by  the  doctrine  of  conlre-coup,  i.  e.,  that  the 
force  was  transmitted  from  one  side  of  the  skull  to  the  other;  but  this  view  is  no  longer  held, 
and  there  are  at  the  present  day  two  theories  as  to  the  mode  of  causation  of  these  fractures, 
(a)  According  to  Aran's  theory  of  irradiation  all  fractures  of  the  base  are  produced  by  a  fissure, 
which  starts  from  the  point  of  injury  and  radiates  to  the  base.  There  can  be  little  doubt  that 
many  cases  of  fracture  of  the  base,  especially  of  the  middle  fossae,  are  caused  in  this  way,  but  it 
is  insufficient  to  explain  all,  since  instances  have  been  met  with  of  fracture  of  the  base  of  the  skull 
in  which  there  has  been  no  fracture  of  the  vault.  (6)  To  explain  these  cases,  another  theory, 
known  as  the  coni'pression  or  bursting  theory,  has  been  suggested.  If  a  hollow,  elastic  sphere 
is  compressed  from  above  downward,  it  will  bulge  laterally,  and,  if  the  compression  is  sufficient, 
it  will  eventually  burst  in  the  situation  where  it  bulges.  Now,  the  skull  is  an  elastic  sphere,  and 
when  compression  is  applied  to  it,  its  diameter  will  be  reduced  along  the  line  of  greatest  pressure 
and  will  therefore  be  increased  in  other  directions,  and  may  increase  to  such  an  extent  that  burst- 
ing occurs.  In  a  hollow  elastic  sphere  of  uniform  thickness,  the  bulging  and  subsequent  bursting 
take  place  at  the  equatorial  line  midway  between  the  two  points  of  compression;  but  the  skull 
is  not  of  uniform  thickness,  and  therefore  the  bulging  and  subsequent  bursting  take  place  at  the 
weakest  part. 

II.  Direct  violence  may  be  apphed  to  the  base  of  the  skull  in  several  different  ways:  by  the 
impact  of  the  vertebral  column  against  the  condyles  of  the  occipital  bone,  in  falls  on  the  buttocks 
or  feet;  by  the  condyle  of  the  mandible  being  driven  against  the  mandibular  fossa,  in  blows  or  falls 
on  the  chin;  by  the  thrusting  of  a  pointed  instrument  through  the  orbit  or  nose;  by  gunshot 
wounds  through  the  mouth;  and  by  a  fall  or  a  stab  on  the  back  of  the  head. 

In  the  majority  of  cases  the  fracture  is  compound.  The  most  common  place  for  fracture  of 
the  base  to  occur  is  through  the  middle  fossa,  and  here  the  fissure  usually  takes  a  fairly  definite 
course.  Starting  from  the  point  struck,  which  is  generally  somewhere  in  the  neighborhood  of 
the  parietal  eminence,  it  runs  downward  through  the  parietal  and  the  temporal  squama  and 
across  the  petrous  portion,  frequently  traversing  and  implicating  the  internal  acoustic  meatus, 
to  the  foramen  lacerum.  From  this  it  may  pass  across  the  body  of  the  sphenoid,  through  the 
sella  turcica,  to  the  foramen  lacerum  of  the  other  side,  and  may  indeed  travel  around  the  whole 
cranium,  so  as  to  completely  separate  the  anterior  from  the  posterior  part.  The  course  of  the 
fracture  explains  the  symptoms  to  which  fracture  in  this  region  may  give  rise :  thus,  if  the  fissure 
pass  across  the  internal  acoustic  meatus,  injury  to  the  facial  and  acoustic  nerves  may  result, 
with  consequent  facial  paralysis  and  deafness;  or  the  tubular  prolongation  of  the  arachnoid 
around  these  nerves  in  the  meatus  may  be  torn  and  thus  permit  of  the  escape  of  the  cerebro- 
spinal fluid  should  there  be  a  communication  between  the  internal  ear  and  the  tympanic  cavity 
together  with  rupture  of  the  tympanic  membrane,  as  is  frequently  the  case:  again,  if  the  fissure 
pass  across  the  sella  turcica  and  the  mucoperiosteum  covering  the  under  surface  of  the  body  of 
the  sphenoid  is  torn,  blood  will  find  its  way  into  the  pharynx  and  be  swallowed,  and  after  a  time 
vomiting  of  blood  will  result.  Fractures  of  the  anterior  fossa,  involving  the  bones  forming  the 
roof  of  the  orbit  and  nasal  cavity,  are  generally  the  result  of  blows  on  the  forehead;  but  fracture 
of  the  cribriform  plate  of  the  ethmoid  may  be  a  complication  of  fracture  of  the  nasal  bone.  When 
the  fracture  imphcates  the  roof  of  the  orbit,  the  blood  finds  its  way  into  this  cavity,  and,  travelhng 
forward,  appears  as  a  subconjunctival  ecchymosis.  If  the  roof  of  the  nasal  cavity  be  fractured, 
the  blood  escapes  from  the  nose.  In  rare  cases  there  may  be  also  escape  of  cerebrospinal  fluid 
from  the  nose,  should  the  dura  mater  and  arachnoid  have  been  torn.  In  fractures  of  the  posterior 
fossa,  extravasation  of  blood  may  appear  at  the  nape  of  the  neck,  beneath  the  muscles  attached 
to  the  superior  nuchal  line  of  the  occipital  bone. 

Diseases  of  the  Skull. — An  inflammatory  condition  affecting  the  bones  and  the  pericranium 
together  is  generally  caused  by  septic  infection  either  of  a  scalp  wound  exposing  and  bruising 
the  bone,  or  of  a  compound  fracture,  and  is  termed  septic  osteomyelitis.  Occasionally  it  may 
occur  independently  of  injury,  and  then  follows  the  same  course,  and  is  due  to  the  same  causes 
as  acute  infective  osteomyehtis  in  the  long  bones. 

The  most  common  chronic  disease  of  the  skull  is  due  to  syphilis.  In  acquired  syphilis  the 
disease  usually  occurs  as  nodes,  which  arise  most  commonly  in  the  pericranium,  but  may  also 
arise  in  the  diploe,  or  more  rarely  on  the  inner  surface  of  the  skull.  The  formation  of  gummaia 
under  the  periosteum  generally  leads  to  caries,  which  may  be  either  limited,  if   the  gumma  is 


CRANIOLOGY  299 

localized,  or  widespread  if  the  gumma  is  diffuse.  The  caries  is  often  complicated  by  necrosis, 
for  a  condition  of  sclerosis  is  frequently  set  up  in  the  surrounding  bone,  and  the  vessels  in  the 
Haversian  canals  become  compressed  and  the  vitality  of  the  bone  is  interfered  with;  hence  we 
often  find  a  central  necrosing  area  surrounded  by  a  zone  of  caries.  Large  carious  sequestra  may 
be  thrown  off  after  prolonged  suppuration,  leaving  considerable  areas  of  the  dura  mater  exposed. 
A  common  result  of  syi)hilitic  disease  of  the  skull  is  the  production  of  large  hard  masses  of  bone 
on  its  surface,  which  give  it  a  tuberculated  appearance;  in  other  cases,  the  skull  presents  a  curious 
worm-eaten  appearance;  this  is  due  to  the  fact  that  the  osteogenctic  powers  of  the  pericranium 
are  small  and  the  formation  of  bone  on  the  surface  slight.  In  hereditary  sypldlis,  in  addition 
to  the  formation  of  gummata,  which  are  usually  of  the  subperiosteal  varietj^  atrophic  or  hyper- 
trophic changes  may  take  place.  In  the  atrojohic  cases  the  bone  becomes  abnormally  thin,  or 
even  perforated.  In  the  hj'pertro})hic  cases,  a  deposit  of  porous  bone  takes  place  around  the 
anterior  fontanelle;  these  deposits  are  separated  by  the  coronal  and  sagittal  sutures  and  are 
known  as  Parrot's  nodes;  such  a  skull  has  received  the  name  of  naiiform,  from  its  fancied  resem- 
blance to  the  buttocks. 

Hj^pertrophic  changes  also  occur  in  the  skull  in  ostitis  deformans,  acromegaly,  leontiasis  ossea, 
and  in  rickets.  In  rickety  cases  the  skull  becomes  enlarged  from  the  formation  of  periosteal 
outgrowths  of  soft  tissue  on  the  outer  side  of  the  skull.  These  deposits  are  very  rich  in  blood- 
vessels, and  occur  between  the  ridges  of  the  cranial  bones  and  their  centres  of  ossification,  and 
are  symmetrically  arranged — often  about  the  anterior  fontanelle.  The  anterior  fontanelle  itself, 
instead  of  closing  between  the  eighteenth  and  twenty-fourth  months,  as  it  normally  does,  remains 
patent  in  rickets  until  the  third  or  even  the  sixth  year.  The  general  shape  of  the  skull  alters. 
The  forehead  is  high  and  square,  with  prominent  frontal  eminences,  and  the  head  tends  to  be 
cubical  or  box-shaped;  the  enlargement  of  the  head  in  rickets  appears  to  be  greater  than  it  really 
is  because  the  development  of  the  facial  bones  is  retarded.  The  base  of  the  nose  may  appear 
sunken,  from  retarded  development  of  the  basis  cranii.  In  marked  cases  of  rickets  these  changes 
in  the  shape  of  the  skull  are  permanent.  In  congenital  hydrocephalus,  or  enlargement  of  the 
head  due  to  the  presence  of  excess  of  fluid  in  the  ventricles  of  the  brain,  the  cranium  becomes 
globular,  and  its  bones  are  thin  and  atrophic.  They  are  often  widely  separated,  the  intervening 
fontaneUes  being  much  enlarged  and  partially  filled  in  by  numerous  sutural  bones;  the  atrophy 
of  the  cranium  and  brain  may  be  so  extreme  that  the  light  of  a  candle  may  be  plainly  visible 
through  the  whole  thickness  of  the  enlarged  head. 

The  tympanic  antrum,  situated  in  the  mastoid  portion  of  the  temporal  bone,  is  often  the  seat 
of  suppuration  as  a  result  of  infection  extending  backward  from  the  tympanic  cavity.  In  such 
cases,  the  surgeon  has  to  open  the  antrum  in  order  to  give  exit  to  the  pus;  this  he  does  by  intro- 
ducing his  gouge  in  the  suprameatal  triangle  (see  p.  238).  A  line  is  drawn  horizontally  through 
the  upper  border  of  the  bony  external  acoustic  meatus,  and  a  second  vertically  through  the 
posterior  wall  of  the  meatus,  and  the  gouge  is  applied  in  the  angle  where  these  two  hnes  intersect; 
if  the  instriunent  be  introduced  at  a  higher  level  it  will  open  the  middle  fossa  of  the  skull.  It 
is  to  be  carried  in  the  direction  of  the  external  acoustic  meatus — inward,  forward,  and  a  little 
upward — for  the  distance  of  from  1  to  1.5  cm.,  when  the  antrum  will  be  reached.  In  some  cases 
of  middle-ear  trouble,  septic  thrombosis  of  the  transverse  sinus  takes  place,  and  it  becomes  neces- 
sary to  work  backward  and  explore  the  sinus. 

In  cormection  with  the  bones  of  the  face  a  common  malformation  is  cleft  palate.     The  cleft 
usually  starts  posteriorly,  and  its  most  elementary  form  is  a  bifid  uvula;  or  the  cleft  may  extend 
through  the  soft  palate;  or  the  posterior  part  of  the  whole 
of  the  hard  palate  may  be  involved,  the  cleft  extending  as  ,        ih'nn 

far  forward  as  the  incisive  foramen.    In  the  severest  forms, 
the  cleft  extends  through  the  alveolus  and  passes  between        Mesognathion^ 
the  incisive  or  premaxillary  bone  and  the  rest  of  the  max-     Exognathion^ 
ilia;  that  is  to  say,  between  the  lateral  incisor  and  canine 
teeth.    In  some  instances,  the  cleft  runs  between  the  central 
and    lateral    incisor    teeth;    and    this    has    induced   some 
anatomists  to  believe  that  the  premaxillary  bone  is  devel- 
oped from  two  centres  (Fig.  341)  and  not  from  one,  as  was 
stated  on  p.  262.    The  medial  segment,   bearing  a  central     ^'''-  ^""^iftP^^A^hf.?'^ '*''"*^^^^^ 
incisor,  is  called  an  endognathion;  the  lateral  segment,  bear- 
ing the  lateral  incisor,  is  called  a  mesognathion.    The  cleft 

may  affect  one  or  both  sides;  if  the  latter,  the  central  part  is  frequently  displaced  forward  and  re- 
mains miited  to  the  septum  of  the  nose,  the  deficiency  in  the  alveolus  being  complicated  with  a  cleft 
in  the  lip  (hare-hp).  On  examining  a  cleft  palate  in  which  the  alveolus  is  not  implicated,  the  cleft 
will  generally  appear  to  be  in  the  median  line,  but  occasionally  is  unilateral  and  in  some  cases  bilat- 
eral. To  understand  this  it  must  be  borne  in  mind  that  three  processes  are  concerned  in  the  formation 
of  the  palate — the  palatine  processes  of  the  two  maxillae,  w^hich  grow  in  horizontally  and  unite 
in  the  middle  line,  and  the  ethmovomerine  process,  which  grows  dowTiward  from  the  base  of 
the  skull  and  frontonasal  process  to  unite  with  the  palatine  processes  in  the  middle  line."  In 


300  OSTEOLOGY 

those  cases  where  the  palatine  processes  fail  to  unite  with  each  other  and  with  the  medial  process, 
the  cleft  of  the  palate  is  median;  where  one  palatine  process  unites  with  the  medial  septum,  the 
other  faUing  to  do  so,  the  cleft  in  the  palate  is  unilateral.  In  some  cases  where  the  palatine  pro- 
cesses fail  to  meet  in  the  middle,  the  ethmovomerine  process  grows  downward  between  them  and 
thus  produces  a  bilateral  cleft.  Occasionally  there  may  be  a  hole  in  the  middle  line  of  the  hard 
palate,  the  anterior  part  of  the  hard  and  the  soft  palate  being  perfect;  this  is  rare,  because,  as 
a  rule,  the  union  of  the  various  processes  progresses  from  before  backward,  and  therefore  the 
posterior  part  of  the  palate  is  more  frequently  defective  than  the  anterior. 

The  bones  of  the  face  are  sometimes  fractured  as  the  result  of  direct  violence.  Those  most 
commonly  broken  are  the  nasal  bones  and  the  mandible;  the  latter  is  by  far  the  most  frequently 
fractured  of  all  the  facial  bones.  Fracture  of  the  nasal  bone  is  for  the  most  part  transverse,  and 
takes  place  about  1.25  cm.  from  the  free  margin.  The  broken  portion  may  be  displaced  back- 
ward or  more  generallj^  to  one  side  by  the  force  which  produced  the  lesion.  The  zygomatic  bone 
is  probably  never  broken  alone — that  is  to  say,  without  fracture  of  some  of  the  other  bones  of 
the  face.  The  zygomatic  arch  is  occasionally  fractm'ed,  and  when  this  occurs  as  a  result  of  direct 
violence  the  fragments  may  be  displaced  inward.  Fractures  of  the  maxilla  may  vary  much  in 
degree,  from  the  chipping  off  of  a  portion  of  the  alveolar  arch,  to  an  extensive  comminution  of 
the  whole  bone  from  severe  violence,  as  the  kick  of  a  horse.  The  most  common  situation  for  a 
fracture  of  the  mandible  is  in  the  neighborhood  of  the  canine  tooth,  as  at  this  spot  the  bone  is 
weakened  bj"  the  deep  socket  for  the  root  of  this  tooth;  it  is  next  most  frequently  fractured  at 
the  angle;  then  at  the  sj'mphysis;  and  finally  the  neck  of  the  condjde  or  the  coronoid  process 
may  be  broken.  Occasionally  a  double  fractui-e  may  occur,  one  in  either  half  of  the  bone.  The 
fractures  are  usually  compound,  from  laceration  of  the  mucous  membrane  covering  the  gums. 
Displacement  readily  occm-s  and  is  difficult  to  rectify;  it  results  in  inequahty  in  the  line  of  the 
teeth  and  is  commonly  due  to  the  muscles  attached  in  the  region  of  the  symphysis  dragging  this 
portion  doTVTiward. 

The  maxilla  and  the  mandible  are  frequently  the  seat  of  necrosis;  but  the  disease  more  often 
affects  the  lower  than  the  upper  jaw.  It  may  be  the  result  of  periostitis  from  tooth  irritation, 
injury,  or  the  action  of  some  specific  poison,  as  syphihs,  or  from  sahvation  by  mercmy;  it  some- 
times occiirs  in  children  after  attacks  of  the  exanthematous  fevers,  and  a  special  form  occurs 
from  the  action  of  the  fumes  of  phosphorus  in  persons  engaged  in  the  manufacture  of  matches. 
In  the  vast  majority  of  cases,  however,  it  is  of  dental  origin. 

Tumors  originate  in  the  jaw  bones  not  infrequently,  and  may  be  either  innocent  or  malignant. 
In  the  maxilla,  cysts  may  occur  in  the  antrum;  or  in  either  jaw  in  connection  with  the  teeth; 
those  connected  with  the  roots  of  fuUy  developed  teeth  are  known  as  dental  cysts;  those  con- 
nected with  unerupted  teeth,  dentigerous  cysts.  MaUgnant  tumors  show  a  marked  degree  of 
mahgnancy  when  occurring  in  the  maxilla.  The  results  of  distention  of  the  walls  of  the  maxillary 
antrum  are  given  on  page  260. 

The  maxilla  sometimes  requires  removal  for  tumors  or  other  conditions.  In  order  to  remove 
it,  the  patient  should  be  placed  in  the  recumbent  position,  in  a  good  fight,  with  the  head  and 
shoulders  just  raised.  The  central  incisor  tooth  on  the  affected  side  is  then  extracted.  One 
incision  is  begun  just  below  the  medial  canthus  of  the  eye  and  passes  along  the  side  of  the  nose, 
around  the  ala,  and  down  the  middle  fine  of  the  upper  fip  into  the  mouth.  A  second  incision  is 
made  from  the  commencement  of  the  first,  along  the  lower  border  of  the  orbit  as  far  as  the  promi- 
nence of  the  zygomatic  bone.  The  flap  thus  formed  is  reflected,  so  as  to  expose  the  bone.  The 
periosteum  attached  along  the  lower  margin  of  the  orbit  is  now  to  be  incised,  and  -R-ith  the  handle 
of  the  scalpel  the  periostevun  covering  the  floor  of  the  orbit  is  raised  from  the  bone;  for  in  aU 
cases  it  is  essential  that  this  fibrous  layer  should  not  be  removed.  The  mouth  is  now  widely 
opened  with  a  gag,  and  the  mucous  membrane  covering  the  hard  palate  incised  do-mi  to  the 
bone  in  the  middle  fine,  and  the  soft  palate  separated  from  the  hard.  The  surgeon  having  first 
separated  tfie  ala  of  tfie  nose  from  its  bony  attachment,  proceeds  to  divide  the  connections  of 
the  bone  with  the  other  bones  of  the  face.  They  are  (1)  the  jimction  with  the  zygomatic  bone, 
the  line  of  section  being  carried  into  the  inferior  orbital  fissure;  (2)  tfie  frontal  process  of  the 
maxilla;  a  smaU  portion  of  its  upper  extremity,  cormected  with  the  nasal  bone  in  front,  the  lacrimal 
bone  behind,  and  the  frontal  bone  above,  being  left;  (3)  the  connection  with  the  opposite  maxilla 
and  with  the  palatine  bone  in  the  roof  of  the  mouth.  The  bone  is  now  firmly  grasped  with  fion- 
forceps;  and  by  means  of  a  rocking  movement  upward  and  do-miward,  the  remaining  attach- 
ments of  the  orbital  plate  with  the  ethmoid,  and  of  the  back  of  the  bone  with  the  palatine,  are 
broken  through.  OccasionaUy,  in  removing  the  maxiUa,  it  wiU  be  found  that  the  orbital  plate 
can  be  saved,  and  this  should  always  be  done  if  possible.  A  horizontal  saw-cut  should  then  be 
made  just  below  the  infraorbital  foramen. 

THE   EXTREMITIES. 

The  extremities,  or  limbs,  are  long,  jointed  appendages,  each  of  which  is  con- 
nected to  the  trunk  bv  one  end,  and  is  free  in  the  rest  of  its  extent.     Thev  are 


THE  CLAVICLE  301 

four  in  number:  an  upper  pair,  connected  with  the  thorax  and  suhservient  mainly 
to  prehension;  and  a  lower  pair,  connected  with  the  vetrebral  cohimn  and  intended 
for  support  and  locomotion.  Both  pairs  are  constructed  after  one  common  type, 
but  certain  differences  are  observed  between  the  upper  and  lower,  dependent 
on  the  peculiar  offices  they  have  to  perform. 

The  bones  by  which  the  upper  and  lower  limbs  are  attached  to  the  trunk  con- 
stitute respectively  the  shoulder  and  pelvic  girdles.  The  shoulder  girdle  or  girdle 
of  the  superior  extremity  is  formed  by  the  scapulae  and  clavicles,  and  is  imperfect 
in  front  and  behind.  In  front,  however,  it  is  completed  by  the  upper  end  of  the 
sternum,  with  which  the  medial  ends  of  the  clavicles  articulate.  Behind,  it  is 
widely  imperfect,  the  scapulae  being  connected  to  the  trunk  by  muscles  only. 
The  pelvic  girdle  or  girdle  of  the  inferior  extremity  is  formed  by  the  hip  bones, 
which  articulate  with  each  other  in  front,  at  the  symphysis  pubis.  It  is  imperfect 
behind,  but  the  gap  is  filled  in  by  the  upper  part  of  the  sacrum.  The  pelvic  girdle, 
with  the  sacrum,  is  a  complete  ring,  massive  and  comparatively  rigid,  in  marked 
contrast  to  the  lightness  and  mobility  of  the  shoulder  girdle. 


THE  BONES  OF  THE  UPPER  EXTREMITY  (OSS A  EXTREMITATIS  SUPERIORIS). 

The  Clavicle  (Clavicula;  Collar  Bone). 

The  clavicle  (Figs.  342,  343)  forms  the  anterior  portion  of  the  shoulder  girdle. 
It  is  a  long  bone,  curved  somewhat  like  the  italic  letter/,  and  placed  nearly  horizon- 
tally at  the  upper  and  anterior  part  of  the  thorax,  immediately  above  the  first 
rib.  It  articulates  medially  wdth  the  manubrium  sterni,  and  laterally  with  the 
acromion  of  the  scapula.^  It  presents  a  double  curvature,  the  convexity  being 
directed  forward  at  the  sternal  end,  and  the  concavity  at  the  scapular  end.  Its 
lateral  third  is  flattened  from  above  downward,  while  its  medial  two-thirds  is  of 
a  rounded  or  prismatic  form. 

Sternal  extremity  Acromial  extremity 


Fig.  342. — Left  clavicle.      Superior  surface. 

Lateral  Third. — The  lateral  third  has  two  surfaces,  an  upper  and  a  lower;  and 
two  borders,  an  anterior  and  a  posterior. 

Surface. — The  upper  surface  is  flat,  rough,  and  marked  by  impressions  for  the 
attachments  of  the  Deltoideus  in  front,  and  the  Trapezius  behind;  between  these 
impressions  a  small  portion  of  the  bone  is  subcutaneous.  The  under  surface  is 
flat.  At  its  posterior  border,  near  the  point  where  the  prismatic  joins  with  the 
flattened  portion,  is  a  rough  eminence,  the  coracoid  tuberosity  {conoid  tubercle); 
this,  in  the  natural  position  of  the  bone,  surmounts  the  coracoid  process  of  the 

1  The  clavicle  acts  especially  as  a  fulcrum  to  enable  the  muscles  to  give  lateral  motion  to  the  arm.  It  is  accordingly 
absent  in  those  animals  whose  fore-hmbs  are  used  only  for  progression,  but  is  present  for  the  m9st  part  in  animals 
whose  anterior  extremities  are  clawed  and  used  for  prehension,  though  in  some  of  them — as,  for  instance,  in  a  large 
number  of  the  carnivora — it  is  merely  a  rudimentary  bone  suspended  among  the  muscles,  and  not  articulating  with 
either  the  scapula  or  sternum. 


302 


OSTEOLOGY 


scapula,  and  gives  attachment  to  the  conoid  Hgament.  From  tiiis  tuberosity  an 
oblique  ridge,  the  oblique  or  trapezoid  ridge,  runs  forward  and  laterahvard,  and 
afford  attachment  to  the  trapezoid  ligament. 

Borders. — The  anterior  border  is  concave,  thin,  and  rough,  and  gives  attachment 
to  the  Deltoideus;  at  its  medial  part  there  is  frequentl.y  a  tubercle,  the  deltoid 
tubercle.  The  posterior  border  is  convex,  rough,  thicker  than  the  anterior,  and  gives 
attachment  to  the  Trapezius. 

Medial  Two-thirds. — The  medial  two-thirds  constitute  the  prismatic  portion 
of  the  bone,  which  is  curved  so  as  to  be  convex  in  front,  concave  behind,  and  is 
marked  by  three  borders,  separating  three  surfaces. 

Borders. — The  anterior  border  is  continuous  with  the  anterior  margin  of  the  flat 
portion.  Its  lateral  part  is  smooth,  and  corresponds  to  the  interval  between  the 
attachments  of  the  Pectoralis  major  and  Deltoideus;  its  medial  part  forms  the 
lower  boundary  of  an  elliptical  surface  for  the  attachment  of  the  clavicular  portion 
of  the  Pectoralis  major,  and  approaches  the  posterior  border  of  the  bone.  The 
superior  border  is  continuous  with  the  posterior  margin  of  the  flat  portion,  and 
separates  the  anterior  from  the  posterior  surface.  Smooth  and  rounded  laterally, 
it  becomes  rough  toward  the  medial  third  for  the  attachment  of  the  Sternocleido- 
mastoideus,  and  ends  at  the  upper  angle  of  the  sternal  extremity.  The  posterior 
or  subclavian  border  separates  the  posterior  from  the  inferior  surface,  and  extends 
from  the  coracoid  tuberosity  to  the  costal  tuberosity;  it  forms  the  posterior  boun- 
dary of  the  groove  for  the  Subclavius,  and  gives  attachment  to  a  layer  of  cervical 
fascia  w^hich  envelops  the  Omohyoideus. 


Articv^lar  capsule 


Articular  caps7ile 


Fig.   343. — Left  clavicle.     Inferior  surface. 


Surfaces. — The  anterior  surface  is  included  between  the  superior  and  anterior 
borders.  Its  lateral  part  looks  upward,  and  is  continuous  wdth  the  superior  sur- 
face of  the  flattened  portion;  it  is  smooth,  convex,  and  nearly  subcutaneous,  being 
covered  only  by  the  Platysma.  Medially  it  is  divided  by  a  narrow^  subcutaneous 
area  into  two  parts:  a  lower,  elliptical  in  form,  and  directed  forward,  for  the 
attachment  of  the  Pectoralis  major;  and  an  upper  for  the  attachment  of  the 
Sternocleidomastoideus.  The  posterior  or  cervical  surface  is  smooth,  and  looks 
backw^ard  toward  the  root  of  the  neck.  It  is  limited,  above,  by  the  superior 
border;  below,  by  the  subclavian  border;  medially,  by  the  margin  of  the  sternal 
extremity;  and  laterally,  by  the  coracoid  tuberosity.  It  is  concave  medio-laterally, 
and  is  in  relation,  by  its  lower  part,  wdth  the  transverse  scapular  vessels.  This 
surface,  at  the  junction  of  the  curves  of  the  bone,  is  also  in  relation  with  the  brachial 
plexus  of  nerves  and  the  subclavian  vessels.  It  gives  attachment,  near  the  sternal 
extremity,  to  part  of  the  Sternohyoideus ;  and  presents,  near  the  middle,  an  oblique 
foramen  directed  lateralward,  which  transmits  the  chief  nutrient  artery  of  the 
bone.  Sometimes  there  are  two  foramina  on  the  posterior  surface,  or  one  on  the 
posterior  and  another  on  the  inferior  surface.    The  inferior  or  subclavian  surface  is 


THE  CLAVICLE  303 

bounded,  in  front,  by  the  anterior  border;  behind,  l)y  the  subehivian  border. 
It  is  narrowed  medially,  but  gradually  increases  in  width  laterally,  and  is  contin- 
uous with  the  under  surface  of  the  flat  portion.  On  its  medial  part  is  a  broad 
rough  surface,  tlie  costal  tuberosity  {rhoinlnnd  iiiipn'.s.sioii),  ratlier  more  than  2  cm. 
in  length,  for  the  attachment  of  the  costoclavicular  ligament.  The  rest  of  this 
surface  is  occupied  by  a  groove,  which  gives  attachment  to  the  Subclavius;  the 
coracoclavicular  fascia,  which  splits  to  enclose  the  muscle,  is  attached  to  the  margins 
of  the  groove.  Not  infrequently  this  groove  is  subdivided  longitudinally  by  a 
line  whicli  gi\-cs  attachment  to  the  intermuscular  sei)tum  of  the  Subclavius. 

The  Sternal  Extremity  {c.iireinifa.s'  sternal  is;  intenial  extreinify). — The  sternal 
extremity  of  the  clavicle  is  triangular  in  form,  directed  medialward,  and  a  little 
downward  and  forward;  it  presents  an  articular  facet,  concave  from  before  back- 
ward, convex  from  abo\'e  downward,  which  articulates  with  the  manubrium  sterni 
through  the  intervention  of  an  articular  disk.  The  lower  part  of  the  facet  is  con- 
tinued on  to  the  inferior  surface  of  the  bone  as  a  small  semi-oval  area  for  articula- 
tion with  the  cartilage  of  the  first  rib.  The  circumference  of  the  articular  surface 
is  rough,  for  the  attachment  of  numerous  ligaments;  the  upper  angle  gives  attach- 
ment to  the  articular  disk. 

The  Acromial  Extremity  {cxtreniifas  acromialis;  outer  extrcniiti/). — The  acromial 
extremity  presents  a  small,  flattened,  oval  surface  directed  obliquely  downward, 
for  articulation  with  the  acromion  of  the  scapula.  The  circumference  of  the 
articular  facet  is  rough,  especially  above,  for  the  attachment  of  the  acromio- 
clavicular ligaments. 

In  the  female,  the  clavicle  is  generally  shorter,  thinner,  less  curved,  and  smoother  than  in  the 
male.  In  those  persons  who  perform  considerable  manual  labor  it  becomes  thicker  and  more 
curved,  and  its  ridges  for  muscular  attachment  are  prominently  marked. 

Structure. — The  clavicle  consists  of  cancellous  tissue,  enveloped  by  a  compact  layer,  which 
is  much  thicker  in  the  intermediate  part  than  at  the  extremities  of  the  bone. 

Ossification. — The  clavicle  begins  to  ossify  before  any  other  bone  in  the  body;  it  is  ossified 
from  three  centres — viz.,  two  primary  centres,  a  medial  and  a  lateral,  for  the  body,^  which  appear 
during  the  fifth  or  sixth  week  of  fetal  life;  and  a  secondary  centre  for  the  sternal  end,  which 
appears  about  the  eighteenth  or  twentieth  year,  and  unites  with  the  rest  of  the  bone  about  the 
twenty-fifth  year. 

Applied  Anatomy. — The  clavicle  is  very  frequently  fractured,  since  it  is  much  exposed  to  vio- 
lence, and  is  the  only  bony  connection  between  the  upper  hmb  and  the  trunk,  acting  as  a  buttress 
to  keep  the  point  of  the  shoulder  away  from  the  thorax.  It  is,  moreover,  slender,  and  is  very 
superficial.  It  may  be  broken  by  direct  or  indirect  violence.  The  most  common  cause  is,  however, 
indirect  violence,  as  the  result  of  force  apphed  to  the  hand  or  shoulder,  and  the  bone  then  gives 
way  at  the  junction  of  its  lateral  with  its  intermediate  third,  that  is  to  say,  at  the  junction  of 
the  two  curves,  for  tliis  is  its  weakest  part.  The  fracture  is  generally  oblique,  and  the  displace- 
ment of  the  lateral  fragment  is  downward,  forward,  and  medialward.  The  deformitj'  is  mainly 
due  to  the  weight  of  the  arm  acting  upon  the  fragment  when  the  buttress-hke  action  of  the  bone 
is  gone,  assisted  by  the  muscles  which  pass  from  the  thorax  to  the  upper  extremity.  The  medial 
fragment,  as  a  rule,  is  little  displaced.  Beneath  the  bone  the  main  vessels  of  the  upper  Umb  and 
the  great  nerve  cords  of  the  brachial  plexus  Ue  on  the  first  rib  and  are  liable  to  be  woimded,  espe- 
cially in  fracture  from  direct  violence,  when  the  force  of  the  blow  drives  the  broken  ends  inward. 
Fortimately  the  subclavius  intervenes  between  these  structm-es  and  the  clavicle,  and  often  protects 
them  from  injury. 

The  clavicle  is  occasionally  the  seat  of  sarcomatous  tumors,  rendering  the  operation  of  excision 
of  the  entire  bone  necessary.  This  is  an  operation  of  considerable  difficulty  and  danger.  It  is 
best  performed  by  exposing  the  bone  freely,  disarticulating  at  the  acromial  end,  and  tm-ning  it 
forward.  The  removal  of  the  lateral  part  is  comparatively  easy,  but  resection  of  the  medial  part 
is  fraught  with  difficulty,  the  main  danger  being  the  risk  of  wounding  the  great  veins  which  are 
in  relation  with  its  deep  sm-face. 

Great  deformity  of  the  clavicle  maj^  be  met  with  in  rickets,  the  natural  curvatures  of  the  bone 
being  exaggerated  until  it  takes  on  an  S-shape,  and  "green-stick"  fracture  is  not  uncommonly 
seen  associated  therewith. 

1  Mall,  American  Journal  of  Anatomy,  vol.  v;  Fawcett,  Journal  of  Anatomy  and  Physiology,  vol.  xlvii. 


304 


OSTEOLOGY 


The  Scapula  (Shoulder  Blade). 

The  scapula  forms  the  posterior  part  of  the  shoulder  girdle.  It  is  a  flat,  trian- 
gular bone,  with  two  surfaces,  three  borders,  and  three  angles. 

Surfaces. — The  costal  or  ventral  surface  (Fig.  344)  presents  a  broad  concavity, 
the  subscapular  fossa.  The  medial  two-thirds  of  the  fossa  are  marked  by  several 
oblique  ridges,  which  run  lateralward  and  upward.    The  ridges  give  attachment 


Articular  capsule 


Coracoacromial 
ligament 


(^^       Articular 
,     "^^        capsule 


Fig.  344. — Left  scapula.     Costal  surface. 


to  the  tendinous  intersections,  and  the  surfaces  between  them  to  the  fleshy  fibres, 
of  the  Subscapularis.  The  lateral  third  of  the  fossa  is  smooth  and  covered  by  the 
fibres  of  this  muscle.  The  fossa  is  separated  from  the  vertebral  border  by  smooth 
triangular  areas  at  the  medial  and  inferior  angles,  and  in  the  interval  between 
these  by  a  narrow^  ridge  which  is  often  deficient.    These  triangular  areas  and  the 


THE  SCAPULA 


305 


intervening  ridge  afford  attachment  to  the  Serratus  anterior.  At  the  upper  part 
of  the  fossa  is  a  transverse  depression,  where  the  bone  appears  to  be  bent  on  itself 
along  a  line  at  right  angles  to  and  passing  through  the  centre  of  the  glenoid  cavity, 
fornnng  a  considerable  angle,  called  the  subscapular  angle;  this  gives  greater 
strengtli  to  the  body  of  the  bone  by  its  arched  form,  while  the  summit  of  the 
arch  serves  to  support  the  spine  and  acromion. 


Coracohunicnd 
liqametd 


Coraco-acrGinial  ligament 

Trapezoid  ligament 


Fig.  345. — Left  scapula.     Dorsal  surface. 


The  dorsal  surface  (Fig.  345)  is  arched  from  above  downward,  and  is  subdivided 
into  two  unequal  parts  by  the  spine;  the  portion  above  the  spine  is  called  the 
supraspinatous  fossa,  and  that  below  it  the  infraspinatous  fossa. 
20 


306  OSrEOLOGY     . 

The  supraspinatous  fossa,  tlu^  sinalltT  of  the  two,  is  concavo,  smooth,  and  broader 
at  its  vertebral  than  at  its  humeral  end;  its  medial  two-thirds  f2;ive  orig'in  to  the 
Supraspinatus. 

The  infraspinatous  fossa  is  much  larger  than  the  preceding;  toward  its  \'ertebral 
margin  a  shallow  conca^'ity  is  seen  at  its  upper  j^art;  its  centre  presents  a  promi- 
nent con^^exity,  while  near  the  axillary  l)order  is  a  dee])  groove  which  runs  from 
the  upper  toward  the  lower  part.  The  medial  two-thirds  of  the  fossa  give  origin 
to  the  Infraspinatus;  the  lateral  third  is  covered  by  this  muscle. 

The  dorsal  surface  is  marked  near  the  axillary  l)order  by  an  elevated  ridge, 
which  runs  from  the  lower  part  of  the  glenoid  cavity,  downward  and  backward 
to  the  vertebral  border,  about  2.5  cm.  above  the  inferior  angle.  The  ridge  serves 
for  the  attachment  of  a  fibrous  septum,  which  separates  the  Infraspinatus  from 
the  Teres  major  and  Teres  minor.  The  surface  between  the  ridge  and  the  axillary 
border  is  narrow  in  the  upper  two-thirds  of  its  extent,  and  is  crossed  near  its 
centre  by  a  groove  for  the  passage  of  the  scapular  circumflex  vessels;  it  affords 
attachment  to  the  Teres  minor.  Its  lower  third  presents  a  broader,  somewhat 
triangular  surface,  which  gives  origin  to  the  Teres  major,  and  over  which  the  Latis- 
simus  dorsi  glides;  frequently  the  latter  muscle  takes  origin  bj''  a  few  fibres  from 
this  part.  The  broad  and  narrow  portions  above  alluded  to  are  separated  by  an 
oblique  line,  which  runs  from  the  axillary  border,  downward  and  backward,  to 
meet  the  elevated  ridge:  to  it  is  attached  a  fibrous  septum  which  separates  the 
Teres  muscles  from  each  other. 

The  Spine  {syina  scapulae). — The  spine  is  a  prominent  plate  of  bone,  which 
crosses  obliquely  the  medial  four-fifths  of  the  dorsal  surface  of  the  scapula  at  its 
upper  part,  and  separates  the  supra-  from  the  infraspinatous  fossa.  It  begins 
at  the  vertical  border  by  a  smooth,  triangular  area  over  which  the  tendon  of  inser- 
tion of  the  lower  part  of  the  Trapezius  glides,  and,  gradually  becoming  more  ele- 
vated, ends  in  the  acromion,  which  overhangs  the  shoulder-joint.  The  spine  is 
triangular,  and  flattened  from  above  downward,  its  apex  being  directed  toward 
the  vertebral  border.  It  presents  two  surfaces  and  three  borders.  Its  superior 
surface  is  concave;  it  assists  in  forming  the  supraspinatous  fossa,  and  gives  origin 
to  part  of  the  Supraspinatus.  Its  inferior  surface  forms  part  of  the  infraspinatous 
fossa,  gives  origin  to  a  portion  of  the  Infraspinatus,  and  presents  near  its  centre 
the  orifice  of  a  nutrient  canal.  Of  the  three  borders,  the  anterior  is  attached  to  the 
dorsal  surface  of  the  bone;  the  posterior,  or  crest  of  the  spine,  is  broad,  and  presents 
two  lips  and  an  intervening  rough  interval.  The  Trapezius  is  attached  to  the  supe- 
rior lip,  and  a  rough  tubercle  is  generally  seen  on  that  portion  of  the  spine  which 
receives  the  tendon  of  insertion  of  the  lower  part  of  this  muscle.  The  Deltoideus 
is  attached  to  the  w^hole  length  of  the  inferior  lip.  The  interval  between  the  lips 
is  subcutaneous  and  partly  covered  by  the  tendinous  fibres  of  these  muscles.  The 
lateral  border,  or  base,  the  shortest  of  the  three,  is  slightly  concave;  its  edge,  thick 
and  round,  is  continuous  above  with  the  under  surface  of  the  acromion,  below 
with  the  neck  of  the  scapula.  It  forms  the  medial  boundary  of  the  great  scapular 
notch,  which  serves  to  connect  the  supra-  and  infraspinatous  fossae. 

The  Acromion. — The  acromion  forms  the  summit  of  the  shoulder,  and  is  a  large, 
somewhat  triangular  or  oblong  process,  flattened  from  behind  forward,  projecting 
at  first  lateralward,  and  then  curving  forward  and  upward,  so  as  to  overhang  the 
glenoid  cavity.  Its  superior  surface,  directed  upward,  backward,  and  lateralward, 
is  convex,  rough,  and  gives  attachment  to  some  fibres  of  the  Deltoideus,  and  in  the 
rest  of  its  extent  is  subcutaneous.  Its  inferior  surface  is  smooth  and  concaA^e. 
Its  lateral  border  is  thick  and  irregular,  and  presents  three  or  four  tubercles  for  the 
tendinous  origins  of  the  Deltoideus.  Its  medial  border,  shorter  than  the  lateral, 
is  concave,  gives  attachment  to  a  portion  of  the  Trapezius,  and  presents  about 
its  centre  a  small,  oval  surface  for  articulation  with  the  acromial  end  of  the  clavicle. 


THE  SCAPTLA  307 

Its  apex,  which  c'()rrosi)()iuls  to  tlie  point  oi  meeting  of  these  two  borders  in  front, 
is  thin,  and  has  attached  to  it  the  coracoacromial  ligament. 

Borders. — Of  the  three  borders  of  the  scapuhi,  the  superior  is  the  shortest  and 
thinnest;  it  is  concave,  and  extends  from  the  mecHtd  angle  to  the  l)ase  of  the  cora- 
coid  process.  At  its  lateral  part  is  a  deej),  semicircnlar  notch,  the  scapular  notch, 
formed  partly  by  the  base  of  the  coracoid  process.  This  notch  is  converted  into 
a  foramen  by  the  superior  transverse  ligament,  and  serves  for  the  passage  of  the 
suprascapular  nerve;  sometimes  the  ligament  is  ossified.  The  adjacent  part  of 
the  superior  border  affords  attachment  to  the  Omohyoideus.  The  axillary  border 
is  the  thickest  of  the  three.  It  begins  above  at  the  lower  margin  of  the  glenoid 
cavity,  and  inclines  obliquely  downward  and  backward  to  the  inferior  angle. 
Immediately  below  the  glenoid  cavity  is  a  rough  impression,  the  infraglenoid 
tuberosity,  about  2.5  cm.  in  length,  which  gives  origin  to  the  long  head  of  the  Tri- 
ceps brachii;  in  front  of  this  is  a  longitudinal  groove,  which  extends  as  far  as  the 
lower  third  of  this  border,  and  affords  origin  to  part  of  the  Subscapularis.  The 
inferior  third  is  thin  and  sharp,  and  serves  for  the  attachment  of  a  few  fibres  of 
the  Teres  major  behind,  and  of  the  Subscapularis  in  front.  The  vertebral  border 
is  the  longest  of  the  three,  and  extends  from  the  medial  to  the  inferior  angle.  It 
is  arched,  intermediate  in  thickness  between  the  superior  and  the  axillary  borders, 
and  the  portion  of  it  above  the  spine  forms  an  obtuse  angle  with  the  part  below. 
This  border  presents  an  anterior  and  a  posterior  lip,  and  an  intermediate  narrow 
area.  The  anterior  lip  affords  attachment  to  the  Serratus  anterior;  the  posterior 
lip,  to  the  Supraspinatus  above  the  spine,  the  Infraspinatus  below;  the  area 
between  the  two  lips,  to  the  Levator  scapulae  above  the  triangular  surface  at  the 
commencement  of  the  spine,  to  the  Rhomboideus  minor  on  the  edge  of  that  surface, 
and  to  the  Rhomboideus  major  below  it;  this  last  is  attached  by  means  of  a  fibrous 
arch,  connected  above  to  the  lower  part  of  the  triangular  surface  at  the  base  of 
the  spine,  and  below  to  the  lower  part  of  the  border. 

Angles. — Of  the  three  angles,  the  medial,  formed  by  the  junction  of  the  superior 
and  vertebral  borders,  is  thin,  smooth,  rounded,  inclined  somewhat  laterahvard, 
and  gives  attachment  to  a  few^  fibres  of  the  Levator  scapulae.  The  inferior  angle, 
thick  and  rough,  is  formed  by  the  union  of  the  vertebral  and  axillary  borders; 
its  dorsal  surface  aft'ords  attachment  to  the  Teres  major  and  frequently  to  a  few 
fibres  of  the  Latissimus  dorsi.  The  lateral  angle  is  the  thickest  part  of  the  bone, 
and  is  sometimes  called  the  head  of  the  scapula.  On  it  is  a  shallow  pyriform, 
articular  surface,  the  glenoid  cavity,  which  is  directed  laterahvard  and  forward 
and  articulates  with  the  head  of  the  humerus;  it  is  broader  below  than  above 
and  its  vertical  diameter  is  the  longest.  The  surface  is  covered  with  cartilage 
in  the  recent  state;  and  its  margins,  slightly  raised,  give  attachment  to  a  fibro- 
cartilaginous structure,  the  glenoidal  labrum,  which  deepens  the  cavity.  x4t  its 
apex  is  a  slight  elevation,  the  supraglenoid  tuberosity,  to  which  the  long  head  of  the 
Biceps  brachii  is  attached.  The  neck  of  the  scapula  is  the  slightly  constricted  por- 
tion which  surrounds  the  head;  it  is  more  distinct  below  and  behind  than  above 
and  in  front. 

The  Coracoid  Process  (processus  coracoideus) . — The  coracoid  process  is  a  thick 
curved  process  attached  by  a  broad  base  to  the  upper  part  of  the  neck  of  the  scapula ; 
it  runs  at  first  upward  and  medialward;  then,  becoming  smaller,  it  changes  its 
direction,  and  projects  forward  and  lateralward.  The  ascending  portion,  flattened 
from  before  backward,  presents  in  front  a  smooth  concave  surface,  across  which 
the  Subscapularis  passes.  The  horizontal  portion  is  flattened  from  above  down- 
ward; its  upper  surface  is  convex  and  irregular,  and  gives  attachment  to  the  Pec- 
toralis  minor;  its  under  surface  is  smooth;  its  medial  and  lateral  borders  are  rough; 
the  former  gives  attachment  to  the  Pectoralis  minor  and  the  latter  to  the  coraco- 
acromial ligament;  the  apex  is  embraced  by  the  conjoined  tendon  of  origin  of  the 


308 


OSTEOLOGY 


Coracobrachialis  and  short  head  of  the  Biceps  brachii  and  gives  attachment  to 
the  coracoclavicular  fascia.  On  the  medial  part  of  the  root  of  the  coracoid  process 
is  a  rough  impression  for  the  attachment  of  the  conoid  Hgament;  and  running 
from  it  obhquely  forward  and  laterahvard,  on  to  the  upper  surface  of  the  horizontal 
portion,  is  an  elevated  ridge  for  the  attachment  of  the  trapezoid  ligament. 

Structure. — -The  head,  processes,  and  the  thickened  parts  of  the  bone,  contain  cancellous 
tissue;  the  rest  consists  of  a  thin  layer  of  compact  tissue.  The  central  part  of  the  supraspinatous 
fossa  and  the  upper  part  of  the  infraspinatous  fossa,  but  especially  the  former,  are  usually  so  thin 
as  to  be  semitransparent ;  occasionally  the  bone  is  found  wanting  in  this  situation,  and  the  adjacent 
muscles  are  separated  only  by  fibrous  tissue. 

Ossification  (Fig.  346). — ^The  scapula  is  ossified  from  seven  or  more  centres:  one  for  the  body, 
two  for  the  coracoid  process,  two  for  the  acromion,  one  for  the  vertebral  border,  and  one  for  the 
inferior  angle. 


.<^e^. 


Fig.  .346. — Plan  of  ossification  of  the  scapula.     From  seven  centres. 

Ossification  of  the  body  begins  about  the  second  month  of  fetal  life,  by  the  formation  of  an 
irregular  quadrilateral  plate  of  bone,  immediately  behind  the  glenoid  cavity.  This  plate  extends 
so  as  to  form  the  chief  part  of  the  bone,  the  spine  growing  up  from  its  dorsal  surface  about  the 
third  month.  At  birth,  a  large  part  of  the  scapula  is  osseous,  but  the  glenoid  cavity,  the  coracoid 
process,  the  acromion,  the  vertebral  border,  and  the  inferior  angle  are  cartilaginous.  From  the 
fifteenth  to  the  eighteenth  month  after  birth,  ossification  takes  place  in  the  middle  of  the  coracoid 
process,  which  as  a  rule  becomes  joined  with  the  rest  of  the  bone  about  the  fifteenth  year.  Between 
the  fourteenth  and  twentieth  years,  ossification  of  the  remaining  parts  takes  place  in  quick  succes- 
sion, and  usually  in  the  following  order ;  first,  in  the  root  of  the  coracoid  process,  in  the  form  of  a 
broad  scale;  secondly,  near  the  base  of  the  acromion;  thirdly,  in  the  inferior  angle  and  contiguous 
part  of  the  vertebral  border;  foiuthly,  near  the  extremity  of  the  acromion;  fifthly,  in  the  vertebral 
border.  The  base  of  the  acromion  is  formed  by  an  extension  from  the  spine;  the  two  separate 
nuclei  of  the  acromion  unite,  and  then  join  with  the  extension  from  the  spine.  The  upper  third 
of  the  glenoid  cavity  is  ossified  from  a  separate  centre  (subcoracoid),  which  makes  its  appear- 
ance between  the  tenth  and  eleventh  years  and  joins  between  the  sixteenth  and  the  eighteenth. 
Further,  an  epiphysial  plate  appears  for  the  lower  part  of  the  glenoid  cavity,  while  the  tip  of  the 


THE  HUMERUS  309 

coracoid  process  frequently  presents  a  separate  nucleus.  These  various  epiphyses  are  joined 
to  the  bone  by  the  twentj^-fifth  year.  Failure  of  bony  union  between  the  acromion  and  spine 
sometimes  occui-s,  the  junction  being  effected  by  fibrous  tissue,  or  by  an  imperfect  articulation; 
in  some  cases  of  supposed  fracture  of  the  acromion  with  ligamentous  union,  it  is  probable  that 
the  detached  segment  was  never  united  to  the  rest  of  the  bone. 

Articulations. — The  scapula  articulates  with  the  humerus  and  clavicle. 

Applied  Anatomy. — Fractm-es  of  the  body  of  the  scapula  are  rare,  owing  to  the  mobility  of  the 
bone,  the  thick  layers  of  muscles  by  wliich  it  is  encased,  and  the  elasticity  of  the  ribs  on  which 
it  rests.  Fractm-e  of  the  neck  is  also  uncommon.  The  most  frequent  course  of  a  fracture  is  from 
the  scapular  notch  to  the  infraglenoid  tuberosity,  and  it  derives  its  principal  interest  from  its 
simulation  of  a  subglenoid  dislocation  of  the  humerus.  The  diagnosis  can  be  made  by  noting 
the  alteration  in  the  position  of  the  coracoid  process.  The  acromion  is  more  frequently  broken 
than  any  other  part  of  the  bone,  and  fibrous  union  is  very  Uable  to  follow. 

The  presence  of  "winged  scapulae"  {scapulae  alatae)  described  in  thin  persons  of  feeble  muscular 
development  in  whom  the  lower  angles  of  the  blade  bones  project  unduly,  is  due  partly  to  abnormal 
roundness  of  the  thoracic  wall  ("barrel-shaped  chest,"  p.  226),  and  partly  to  weakness  and 
flaccidity  of  the  Latissimus  dorsi  and  Serratus  anterior.  The  shoulders  are  held  low  in  these 
subjects,  and  the  clavicles  slope  downward  and  forward,  carrying  with  them  the  scapula),  which 
fit  iU  to  the  posterior  wall  of  the  chest  and  so  tend  to  project  from  it. 

TuTQors  of  various  kinds  grow  from  the  scapula.  Of  the  innocent  form  probably  the  osteomata 
are  the  most  common.  When  an  osteoma  grows  from  the  venter  of  the  scapula,  as  it  sometimes 
does,  it  is  of  the  compact  variety,  such  as  usually  grows  from  membrane-formed  bones,  as  the 
bones  of  the  skull.  Sarcomatous  tumors  sometimes  grow  from  the  scapula,  and  may  necessitate 
removal  of  the  bone,  with  or  without  amputation  of  the  upper  Umb.  The  bone  may  be  excised 
by  a  T-shaped  incision,  and  the  flaps  being  reflected,  the  removal  is  commenced  from  the  vertebral 
border,  so  that  the  subscapular  vessels  which  he  along  the  axillary  border  are  among  the  last 
structures  divided,  and  can  be  readily  secured. 

The  Humerus  (Arm  Bone). 

The  humerus  (Figs.  347,  348)  is  the  longest  and  largest  bone  of  the  upper 
extremity;  it  is  divisible  into  a  body  and  two  extremities. 

Upper  Extremity. — The  upper  extremity  consists  of  a  large  rounded  head  joined 
to  the  body  by  a  constricted  portion  called  the  neck,  and  two  eminences,  the  greater 
and  lesser  tubercles. 

The  Head  {caput  humeri).- — The  head,  nearly  hemispherical  in  form,^  is  directed 
upward,  medialward,  and  a  little  backward,  and  articulates  with  the  glenoid  cavity 
of  the  scapula.  The  circumference  of  its  articular  surface  is  slightly  constricted, 
and.  is  termed  the  anatomical  neck,  in  contradistinction  to  a  constriction  below  the 
tubercles  called  the  surgical  neck  which  is  frequently  the  seat  of  fracture.  Fracture 
of  the  anatomical  neck  rarely  occurs. 

The  Anatomical  Neck  {collum  anatomicum)  is  obliquely  directed,  forming  an 
obtuse  angle  with  the  body.  It  is  best  marked  in  the  lower  half  of  its  circum- 
ference ;  in  the  upper  half  it  is  represented  by  a  narrow  groove  separating  the  head 
from  the  tubercles.  It  affords  attachment  to  the  articular  capsule  of  the  shoulder- 
joint,  and  is  perforated  by  numerous  vascular  foramina. 

The  Greater  Tubercle  {tuberculum  ma  jus;  greater  tuberosity). — The  greater 
tubercle  is  situated  lateral  to  the  head  and  lesser  tubercle.  Its  upper  surface  is 
rounded  and  marked  by  three  flat  impressions :  the  highest  of  these  gives  insertion 
to  the  Supraspinatus ;  the  middle  to  the  Infraspinatus;  the  lowest  one,  and  the 
body  of  the  bone  for  about  2.5  cm.  below  it,  to  the  Teres  minor.  The  lateral 
surface  of  the  greater  tubercle  is  convex,  rough,  and  continuous  with  the  lateral 
surface  of  the  body. 

The  Lesser  Tubercle  {tuberculum  minus;  lesser  tuberosity). — The  lesser  tubercle, 
although  smaller,  is  more  prominent  than  the  greater:  it  is  situated  in  front,  and 

1  Though  the  head  is  nearly  hemispherical  in  form,  its  margin,  as  Humphrj-  has  shown,  is  by  no  means  a  true  circle. 
Its  greatest  diameter  is,  from  the  top  of  the  intertubercular  groove  in  a  direction  downward,  medialward,  and  back- 
ward. Hence  it  follows  that  the  greatest  elevation  of  the  arm  can  be  obtained  by  rolling  the  articular  surface  in  this 
direction — that  is  to  say,  obliquely  upward,  lateralward,  and  forward. 


310 


OSTEOLOGY 


Articular  capsule 


Common  origin  oj 
Flexor  carpi  radialis 
Palmaris  longus  "^ 

Flexor  digitorum  suhlimis 
Flexor  carpi  ulnaris 


Brachioradialis 


Extensor  carpi  radicdis 
longus 

\]  ^  Articular  capsule 


Common  origin  of 

Extensor  carpi  rad.  hrev. 
,,     digitorum,  communis 
,,     digiti  quinti  prop. 
,,     carpi  ulnaris 

Supinator 


Fig.  347. — Left  humerus.     Anterior  view. 


THE  HUMERUS 


311 


is  directed  mediahvard  and  forward.  Above 
and  in  front  it  presents  an  im])ression  for  the 
insertion  of  the  tendon  of  the  Subscaijuhiris. 

The  tubercles  are  separated  from  each  other 
by  a  deep  groove,  the  intertubercular  groove 
(bicipital  groove),  which  lodges  the  long  tendon 
of  the  Biceps  brachii  and  transmits  a  branch 
of  the  anterior  humeral  circumflex  arter>'  to 
the  shoulder-joint.  It  runs  obliquely  down- 
ward, and  ends  near  the  junction  of  the  upper 
with  the  middle  third  of  the  bone.  In  the 
recent  state  its  upper  part  is  covered  with  a 
thin  layer  of  cartilage,  lined  by  a  prolongation 
of  the  synovial  membrane  of  the  shoulder- 
joint;  its  lower  portion  gives  insertion  to  the 
tendon  of  the  Latissimus  dorsi.  It  is  deep 
and  narrow  above,  and  becomes  shallow  and 
a  little  broader  as  it  descends.  Its  lips  are 
called,  respectively,  the  crests  of  the  greater 
and  lesser  tubercles  (bicipital  ridges),  and  form 
the  upper  parts  of  the  anterior  and  medial 
borders  of  the  body  of  the  bone. 

The  Body  or  Shaft  (corpus  humeri).  —  The 
body  is  almost  cylindrical  in  the  upper  half  of 
its  extent,  prismatic  and  flattened  below,  and 
has  three  borders  and  three  surfaces. 

Borders. — The  anterior  border  runs  from  the 
front  of  the  greater  tubercle  above  to  the  coro- 
noid  fossa  below,  separating  the  antero-medial 
from  the  antero-lateral  surface.  Its  upper  part 
is  a  prominent  ridge,  the  crest  of  the  greater 
tubercle ;  it  serves  for  the  insertion  of  the  tendon 
of  the  Pectoralis  major.  About  its  centre  it 
forms  the  anterior  boundary  of  the  deltoid 
tuberosity;  below,  it  is  smooth  and  rounded, 
affording  attachment  to  the  Brachialis. 

The  lateral  border  runs  from  the  back  part  of 
the  greater  tubercle  to  the  lateral  epicondyle, 
and  separates  the  antero-lateral  from  the  pos- 
terior surface.  Its  upper  half  is  rounded  and 
indistinctly  marked,  serving  for  the  attachment 
of  the  low^er  part  of  the  insertion  of  the  Teres 
minor,  and  below  this  giving  origin  to  the  lateral 
head  of  the  Triceps  brachii;  its  centre  is  tra- 
versed by  a  broad  but  shallow  oblique  depres- 
sion, the  radial  sulcus  (musculospiral  groove). 
Its  lower  part  forms  a  prominent,  rough  margin, 
a  little  curved  from  behind  forward,  the  lateral 
supracondylar  ridge,  which  presents  an  anterior 
lip  for  the  origin  of  the  Brachioradialis  above, 
and  Extensor  carpi  radialis  longus  below%  a 
posterior  lip  for  the  Triceps  brachii,  and  an 
intermediate  ridge  for  the  attachment  of  the 
lateral   intermuscular  septum. 


Articular 
caysuLe 


Articular 
capsule 


Fig.  348. — Left  humerus.     Posterior  view. 


312  OSTEOLOGY 

The  medial  border  extends  from  the  lesser  tii})erck>  to  the  medial  epicondyle. 
Its  upper  third  consists  of  a  prominent  ridge,  the  crest  of  the  lesser  tubercle,  which 
gives  insertion  to  the  tendon  of  the  Teres  major.  About  its  centre  is  a  slight 
impression  for  the  insertion  of  the  Coracobrachialis,  and  just  below  this  is  the 
entrance  of  the  nutrient  canal,  directed  downward;  sometimes  there  is  a  second 
nutrient  canal  at  the  commencement  of  the  radial  sulcus.  The  inferior  third 
of  this  border  is  raised  into  a  slight  ridge,  the  medial  supracondylar  ridge,  which 
becomes  very  prominent  below;  it  presents  an  anterior  lip  for  the  origins  of  the 
Brachialis  and  Pronator  teres,  a  posterior  lip  for  the  medial  head  of  the  Triceps 
brachii,  and  an  intermediate  ridge  for  the  attachment  of  the  medial  intermuscular 
septum. 

Surfaces. — The  antero-lateral  surface  is  directed  lateralward  above,  where  it  is 
smooth,  rounded,  and  covered  by  the  Deltoideus;  forward  and  lateralward  below, 
where  it  is  slightly  concave  from  above  downward,  and  gives  origin  to  part  of 
the  Brachialis.  About  the  middle  of  this  surface  is  a  rough,  triangular  elevation, 
the  deltoid  tuberosity  for  the  insertion  of  the  Deltoideus;  below  this  is  the  radial 
sulcus,  directed  obliquely  from  behind,  forward,  and  downward,  and  transmitting 
the  radial  nerve  and  profunda  artery. 

The  antero-medial  surface,  less  extensive  than  the  antero-lateral,  is  directed 
medialward  above,  forward  and  medialward  below;  its  upper  part  is  narrow,  and 
forms  the  floor  of  the  intertubercular  groove  which  gives  insertion  to  the  tendon  of 
the  Latissimus  dorsi ;  its  middle  part  is  slightly  rough  for  the  attacliment  of  some 
of  the  fibres  of  the  tendon  of  insertion  of  the  Coracobrachialis;  its  lower  part 
is  smooth,  concave  from  above  downward,  and  gives  origin  to  the  Brachialis.^ 

The  posterior  surface  appears  somewhat  twisted,  so  that  its  upper  part  is  directed 
a  little  medialward,  its  lower  part  backward  and  a  little  lateralward.  Nearly 
the  whole  of  this  surface  is  covered  by  the  lateral  and  medial  heads  of  the  Triceps 
brachii,  the  former  arising  above,  the  latter  below  the  radial  sulcus. 

The  Lower  Extremity. — The  lower  extremity  is  flattened  from  before  backward, 
and  curved  slightly  forward;  it  ends  below  in  a  broad,  articular  surface,  which  is 
divided  into  two  parts  by  a  slight  ridge.  Projecting  on  either  side  are  the  lateral 
and  medial  epicondyles.  The  articular  surface  extends  a  little  lower  than  the 
epicondyles,  and  is  curved  slightly  forward;  its  medial  extremity  occupies  a  lower 
level  than  the  lateral.  The  lateral  portion  of  this  surface  consists  of  a  smooth, 
rounded  eminence,  named  the  capitulum  of  the  humerus;  it  articulates  with  the  cup- 
shaped  depression  on  the  head  of  the  radius,  and  is  limited  to  the  front  and  lower 
part  of  the  bone.  On  the  medial  side  of  this  eminence  is  a  shallow  groove,  in  which 
is  received  the  medial  margin  of  the  head  of  the  radius.  Above  the  front  part 
of  the  capitulum  is  a  slight  depression,  the  radial  fossa,  which  receives  the  anterior 
border  of  the  head  of  the  radius,  when  the  forearm  is  flexed.  The  medial  portion 
of  the  articular  surface  is  named  the  trochlea,  and  presents  a  deep  depression  be- 
tween two  well-marked  borders;  it  is  convex  from  before  backward,  concave  from 
side  to  side,  and  occupies  the  anterior,  lower,  and  posterior  parts  of  the  extremity. 
The  lateral  border  separates  it  from  the  groove  which  articulates  with  the  margin 
of  the  head  of  the  radius.  The  medial  border  is  thicker,  of  greater  length,  and 
consequently  more  prominent,  than  the  lateral.  The  grooved  portion  of  the  artic- 
ular surface  fits  accurately  within  the  semilunar  notch  of  the  ulna ;  it  is  broader  and 
deeper  on  the  posterior  than  on  the  anterior  aspect  of  the  bone,  and  is  inclined 

1  A  small,  hook-shaped  process  of  bone,  the  supracondylar  process,  varying  from  2  to  20  mm.  in  length,  is  not  infre- 
quently found  projecting  from  the  antero-medial  surface  of  the  body  of  the  humerus  5  cm.  above  the  medial  epicondyle. 
It  is  curved  downward  and  forward,  and  its  pointed  end  is  connected  to  the  medial  border,  just  above  the  medial 
epicondyle,  by  a  fibrous  band,  which  gives  origin  to  a  portion  of  the  Pronator  teres;  through  the  arch  completed  by 
this  fibrous  band  the  median  nerve  and  brachial  artery  pass,  when  these  structures  de\'iate  from  their  \isual_  course. 
Sometimes  the  ner\'e  alone  is  transmitted  through  it,  or  the  nerv-e  may  be  accompanied  by  the  ulnar  artery,  in  cases 
of  high  division  of  the  brachial.  A  weU-marked  groove  is  usually  found  behind  the  process,  in  which  the  nerve  and 
artery  are  lodged.  This  arch  is  the  homologue  of  the  supracondyloid  foramen  found  in  many  animals,  and  probably 
serves  in  them  to  protect  the  nerve  and  artery  from  compression  during  the  contraction  of  the  muscles  in  this  region. 


THE  HUMERUS 


313 


obliquely  dowmvartl  and  forwartl  toward  the  medial  side.  Above  the  front  part 
of  the  trochlea  is  a  small  depression,  the  coronoid  fossa,  which  receives  the  coronoid 
process  of  the  ulna  during  flexion  of  the  forearm.  Above  the  back  part  of  the  troch- 
lea is  a  deep  triangular  depression,  the  olecranon  fossa,  in  which  the  summit  of  the 
olecranon  is  received  in  extension  of  the  forearm.  These  fossse  are  separated  from 
one  another  by  a  thin,  transparent  lamina  of  bone,  which  is  sometimes  perforated 
by  a  supratrochlear  foramen;  they  are  lined  in  the  recent  state  by  the  synovial 
membrane  of  the  elbow-joint,  and  their  margins  afford  attachment  to  the  anterior 
and  posterior  ligaments  of  this  articulation.  The  lateral  epicondyle  is  a  small, 
tuberculated  eminence,  curved  a  little  forward,  and  giving  attachment  to  the  radial 
collateral  ligament  of  the  elbow-joint,  and  to  a  tendon  common  to  the  origin  of 
the  Supinator  and  some  of  the  Extensor  muscles.  The  medial  epicondyle,  larger 
and  more  prominent  than  the  lateral,  is  directed  a  little  backward;  it  gives  attach- 
ment to  the  ulnar  collateral  ligament  of  the  elbow-joint,  to  the  Pronator  teres, 
and  to  a  common  tendon  of  origin  of  some  of  the  Flexor  muscles  of  the  forearm; 
the  ulnar  nerve  runs  in  a  groove  on  the  back  of  this  epicondyle.  The  epicondjdes 
are  continuous  above  with  the  supracondylar  ridges. 


Structure. ^The  extremities  consist  of  cancellous  tissue,  covered  with  a  thin,  compact  layer 
(Fig.  349) ;  the  body  is  composed  of  a  cyUnder  of  compact  tissue,  thicker  at  the  centre  than  toward 
the  extremities,,  and  contains  a  large  medullary  canal  which  extends  along  its  whole  length. 

Ossification  (Figs.  350,  351). — The  humerus  is  ossi- 
fied from  eight  centres,  one  for  each  of  the  following  Epiphysial  liiie 
parts:  the  body,  the  head,  the  greater  tubercle,  the 
lesser  tubercle,  the  capitulum,  the  trochlea,  and  one 
for  each  epicondyle.  The  centre  for  the  body  appears 
near  the  middle  of  the  bone  in  the  eighth  week  of  fetal 
hfe,  and  soon  extends  toward  the  extremities.  At  birth 
the  humerus  is  ossified  in  nearly  its  whole  length,  only 
the  extremities  remaining  cartilaginous.  Dm'ing  the 
first  year,  sometimes  before  birth,  ossification  commences 
in  the  head  of  the  bone,  and  dui-ing  the  thu'd  year  the 
centre  for  the  greater  tubercle,  and  during  the  fifth  that 
for  the  lesser  tubercle,  make  theii'  appearance.  By  the 
sixth  year  the  centres  for  the  head  and  tubercles  have 
joined,  so  as  to  foi-m  a  single  large  epiphysis,  which  fuses 
with  the  body  about  the  twentieth  year.  The  lower  end 
of  the  humerus  is  ossified  as  foUows.  At  the  end  of 
the  second  year  ossification  begins  in  the  capitulum, 
and  extends  medialward,  to  form  the  chief  part  of  the 
articular  end  of  the  bone;  the  centre  for  the  medial  part 
of  the  trochlea  appears  about  the  age  of  twelve.  Ossifi- 
cation begins  in  the  medial  epicondjde  about  the  fifth 
year,  and  in  the  lateral  about  the  thirteenth  or  four- 
teenth year.  About  the  sixteenth  or  seventeenth  year, 
the  lateral  epicondyle  and  both  portions  of  the  articu- 
lating sm-face,  having  aheady  joined,  unite  with  the  Fig.  349. 
body,  and  at  the  eighteenth  year  the  medial  epicon- 
dyle becomes  joined  to  it. 

Articulations. — The  hmnerus  articulates  with  the  scapula,  ulna,  and  radius. 

Applied  Anatomy. — There  are  several  points  of  surgical  interest  connected  with  the  ossification 
of  the  humerus.  The  upper  end,  though  the  first  to  ossify,  is  the  last  to  join  the  bodj',  and  the 
length  of  the  bone  is  mainly  due  to  growth  from  the  upper  epiphysial  plate.  Hence,  in  cases  of 
amputation  of  the  arm  in  j'oung  subjects,  the  humerus  continues  to  grow  considerably,  and  the 
end  of  the  bone  which  immediately  after  the  operation  was  covered  with  a  thick  cushion  of  soft 
tissue  begins  to  project,  thinning  the  soft  parts  and  rendering  the  stump  conical.  This  may 
necessitate  the  removal  of  about  5  cm.  of  the  bone,  and  even  after  this  operation  a  recurrence 
of  the  conical  stump  may  take  place.  The  region  of  the  upper  epiphysis,  moreover,  is  the  common 
site  for  the  growth  of  tumors,  both  innocent  and  mahgnant 

Fractures  of  the  hmnerus  present  several  points  of  surgical  interest .  The  bone  maj'  be  broken 
by  direct  or  indirect  violence,  like  the  other  long  bones,  but,  in  addition  to  this,  it  is  probably 
more  frequently  fractured  b}'  muscular  action  than  anj^  other  bone  of  this  class.     It  is  usually 


-Longitudinal  section  of  head  of 
left  humerus. 


314 


OSTEOLOGY 


the  body,  just  below  the  insertion  of  the  Deltoideus,  which  is  tlius  broken,  and  the  accident  has 
been  known  to  happen  from  throwing  a  stone.  Fractures  of  the  upp(;r  end  may  take  place  eitlier 
through  the  anatomical  or  surgical  neck,  or  a  separation  of  the  greater  tubercle  may  occur.  Frac- 
ture of  the  anatomical  neck  is  a  very  rare  accident;  in  fact,  it  is  doubted  by  some  whether  it  ever 
occurs.  Fracture  of  the  surgical  neck  of  the  bone  is  not  uncommon,  and  impaction  may  occur; 
on  the  other  hand,  the  upper  end  of  the  lower  fragment  may  be  displaced  into  the  axilla  and  may 
damage  the  vessels  or  nerves.  The  fracture  somewhat  closely  simulates  dislocation  of  the  shoulder- 
joint,  but  can  be  distinguished  by  the  fact  that  the  head  of  the  bone  remains  in  its  normal  jiosi- 
tion  and  the  great  tubercle  still  forms  the  most  prominent  point  of  the  shoulder.  Separation 
of  the  upper  epiphysis  sometimes  occurs  in  the  young  subject,  and  is  marked  by  a  characteristic 
deformity,  consisting  in  the  presence  of  an  abrupt  projection  at  the  front  of  the  joint  some  short 
distance  below  the  coracoid  process,  caused  by  the  upper  end  of  the  diaphy.sis.    In  fractures  of 


Epiphyses  of  head  a)id'\     j^^t 
tuberclesblendatfifthl     j /\ 
year,  and  unite  tvith 
body      at     twentieth 
year 


Unites  with  body\ 
at  eighteenth  year  J  t§* 


Blend  ^f,,^'' 
Body 

Fig.  350. — Plan  of  ossification  of  the  humerus. 


Fig.  351. — Epiphysial  lines  of  humerus  in  a  young 
adult.  Anterior  aspect.  The  lines  of  attachment  of 
the  articular  capsules  are  in  blue. 


the  body  of  the  humerus  the  lesion  may  take  place  at  any  point,  but  appears  to  be  more  common 
in  the  lower  than  the  upper  part  of  the  bone.  The  points  of  interest  in  connection  with  these 
fractures  are:  (1)  that  the  radial  nerve  may  be  injured  as  it  lies  in  the  groove  on  the  bone,  or 
may  become  involved  in  the  callus  which  is  subsequently  thrown  out;  and  (2)  the  frequency 
of  non-union,  which  is  believed  to  be  more  common  in  the  humerus  than  in  any  other  bone. 
An  important  distinction  to  make  in  fractures  of  the  lower  end  is  between  those  that  involve  the 
elbow-joint  and  those  which  do  not;  the  former  are  always  serious,  as  they  may  lead  to  impair- 
ment of  the  utility  of  the  limb;  they  include  the  T-shaped  fracture  and  oblique  fractures  which 
involve  the  articular  surface.  Those  which  do  not  involve  the  joint  are  the  transverse  fracture 
above  the  epicondyles,  and  the  so-called  epitrochlear  fracture,  where  the  tip  of  the  medial  epi- 
condyle  is  broken  off,  generally  from  direct  violence. 


The  Ulna  (Elbow  Bone), 

The  ulna  (Figs.  353,  354)  is  a  long  bone,  prismatic  in  form,  placed  at  the  medial 
side  of  the  forearm,  parallel  with  the  radius.  It  is  divisible  into  a  body  and 
two  extremities.     Its  upper  extremity,   of  great  thickness  and  strength,  forms 


THE  ULNA 


315 


Olecranon 


a  laruv  part  of  the  clhow-joint;  tlie  hone  (liininishcs  in  size  from  above  downward, 
its  lower  extremity  beinjj;  very  small,  and  excluded  from  the  wrist-joint  hy  the 
inter})osition  of  an  articular  disk. 

The  Upper  Extremity  [proxhiml  r.rfrcinifi/)  (Fig.  352). — The  upper  extremity 
presents  two  cur\ed  j)r()cesses,  the  olecranon  and  the  coronoid  process;  and  two 
concave,  articular  cavities,  the  semilunar  and  radial  notches. 

The  Olecranon  {oJccranon  process). — The  olecranon  is  a  large,  thick,  curved 
eminence,  situated  at  the  upper  and  back  part  of  the  ulna.  It  is  bent  forward  at  the 
summit  so  as  to  present  a  prominent  lip  which  is  received  into  the  olecranon  fossa 
of  the  humerus  in  extension  of  the  forearm.  Its  base  is  contracted  where  it  joins  the 
bod>'  and  the  narrowest  part  of  the  upper  end  of  the  ulna.  Its  posterior  surface, 
directed  backward,  is  triangular,  smooth,  subcutaneous,  and  covered  by  a  bursa. 
Its  superior  surface  is  of  quadrilateral  form,  marked  behind  by  a  rough  impression  for 
the  insertion  of  the  Triceps  brachii;  and  in  front,  near  the  margin,  by  a  slight  trans- 
verse groove  for  the  attachment  of  part  of  the  posterior  ligament  of  the  elbow-joint. 
Its  anterior  surface  is  smooth,  concave,  and 
forms  the  upper  part  of  the  semilunar  notch. 
Its  borders  present  continuations  of  the  groove 
on  the  margin  of  the  superior  surface;  they 
serve  for  the  attachment  of  ligaments,  viz., 
the  back  part  of  the  ulnar  collateral  liga- 
ment medially,  and  the  posterior  ligament 
laterally.  From  the  medial  border  a  part 
of  the  Flexor  carpi  ulnaris  arises;  while  to 
the  lateral  border  the  Anconaeus  is  attached. 

The  Coronoid  Process  (processus  coronoideus) . 
— The  coronoid  process  is  a  triangular  emi- 
nence projecting  forward  from  the  upper  and 
front  part  of  the  ulna.  Its  base  is  continuous 
with  the  body  of  the  bone,  and  of  consider- 
able strength.  Its  apex  is  pointed,  slightly 
curved  upward,  and  inflexion  of  the  forearm 
is  received  into  the  coronoid  fossa  of  the 
humerus.  Its  upper  surface  is  smooth,  con- 
cave, and  forms  the  lower  part  of  the  semi- 
lunar notch.  Its  antero-inferior  surface  is 
concave,  and  marked  by  a  rough  impression 
for  the  insertion  of  the  Brachialis.  At  the 
junction  of  this  surface  w4th  the  front  of  the 
body  is  a  rough  eminence,  the  tuberosity  of  the  ulna,  which  gives  insertion  to  a 
part  of  the  Brachialis;  to  the  lateral  border  of  this  tuberosity  the  oblique  cord  is 
attached.  Its  lateral  surface  presents  a  narrow,  oblong,  articular  depression,  the 
radial  notch.  Its  medial  surface,  by  its  prominent,  free  margin,  serves  for  the 
attachment  of  part  of  the  ulnar  collateral  ligament.  At  the  front  part  of  this 
surface  is  a  small  rounded  eminence  for  the  origin  of  one  head  of  the  Flexor 
digitorum  sublimis;  behind  the  eminence  is  a  depression  for  part  of  the  origin 
of  the  Flexor  digitorum  profundus;  descending  from  the  eminence  is  a  ridge  which 
gives  origin  to  one  head  of  the  Pronator  teres.  Frequently,  the  Flexor  pollicis 
longus  arises  from  the  lower  part  of  the  coronoid  process  by  a  rounded  bundle  of 
muscular  fibres. 

The  Semilunar  Notch  (incisura  semilunaris;  greater  sigmoid  cavity). — The  semi- 
lunar notch  is  a  large  depression,  formed  by  the  olecranon  and  the  coronoid  process, 
and  serving  for  articulation  with  the  trochlea  of  the  humerus.  About  the  middle 
of  either  side  of  this  notch  is  an  indentation,  which  contracts  it  somewhat,  and 


Coronoid 
process 


Fig.  352. — Upper  extremity'  of  left  ulna. 
Lateral  aspect. 


316 


OSTEOLOGY 


Articular  capsule 


Flexor  digitorum 
suhlimis 


Occasional  origin 
of  Flexor  poinds  longus 


Articular 
capsule 


Styloid  process 


Radial  origin  of 
Flexor  digitorwrn 
sitblimis 


Brachioradialis 

Groove  for  Abductor 
poinds  longus  and 
Extensor  pollicis  brevis 


Styloid  process 
Fig.  3.53. — Bones  of  left  forearm.     Anterior  aspect. 


THE  ULNA 


3i: 


Arlicidar  cwpsule 

'^  I' if'   <    '^lV\    Flexor  difjiloruiii  suldhnis 


r Abductor  pollicis 

I  Extensor  pollicis 
[^         brevis 


For  Ext.  carpi  radialis  longus 
For  Extensor  carpi  radialis  brevis 

For  Extensor  pollicis  longus 


Articular  capsule 


For  Extensor  carpi  ulnaris 
For  Extensor  digiti  quinti  proprius 


XI     (Extensor  indicis  proprius 
\Extensor  digitorum  comm 


communis 


Fig.  354. — Bones  of  left  forearm.     Posterior  aspect. 


318  OSTEOLOGY 

indicates  the  junction  of  the  olecranon  and  the  coronoid  process.  The  notcli  is 
concave  from  above  downward,  and  diA-ided  into  a  me(Hal  and  a  lateral  portion  by 
a  smooth  ridge  running  from  the  summit  of  the  olecranon  to  the  tip  of  the  coronoid 
process.  The  medial  portion  is  the  larger,  and  is  slightly  concave  transA'crsely; 
the  lateral  is  convex  above,  slightly  concave  below. 

The  Radial  Notch  (iiicisura  radialis;  lesser  sigmoid  cavity). — The  radial  notch 
is  a  narrow,  oblong,  articular  depression  on  the  lateral  side  of  the  coronoid  process; 
it  receives  the  circumferential  articular  surface  of  the  head  of  the  radius.  It  is 
concave  from  before  backward,  and  its  prominent  extremities  serve  for  the  attach- 
ment of  the  annular  ligament. 

The  Body  or  Shaft  {corpus  ulnae). — The  body  at  its  upper  part  is  prismatic 
in  form,  and  curved  so  as  to  be  convex  behind  and  lateralward;  its  central  part 
is  straight;  its  lower  part  is  rounded,  smooth,  and  bent  a  little  lateralward.  It 
tapers  gradually  from  above  downward,  and  has  three  borders  and  three  surfaces. 

Borders. — The  volar  border  {niargo  volaris;  anterior  border)  begins  above  at  the 
prominent  medial  angle  of  the  coronoid  process,  and  ends  below  in  front  of  the 
styloid  process.  Its  upper  part,  well-defined,  and  its  middle  portion,  smooth  and 
rounded,  give  origin  to  the  Flexor  digitorum  profundus;  its  lower  fourth  serves 
for  the  origin  of  the  Pronator  quadratus.  This  border  separates  the  volar  from 
the  medial  surface. 

The  dorsal  border  {margo  dorsalis;  posterior  border)  begins  above  at  the  apex  of 
the  triangular  subcutaneous  surface  at  the  back  part  of  the  olecranon,  and  ends 
below  at  the  back  of  the  styloid  process;  it  is  well-marked  in  the  upper  three- 
fourths,  and  gives  attachment  to  an  aponeurosis  which  affords  a  common  origin  to 
the  Flexor  carpi  ulnaris,  the  Extensor  carpi  ulnaris,  and  the  Flexor  digitorum  pro- 
fundus; its  lower  fourth  is  smooth  and  rounded.  This  border  separates  the  medial 
from  the  dorsal  surface. 

The  interosseous  crest  {crista  inter ossea;  exteri\al  or  interosseous  border)  begins 
above  by  the  union  of  two  lines,  which  converge  from  the  extremities  of  the  radial 
notch  and  enclose  between  them  a  triangular  space  for  the  origin  of  part  of  the 
Supinator;  it  ends  below  at  the  head  of  the  ulna.  Its  upper  part  is  sharp,  its  lower 
fourth  smooth  and  rounded.  This  crest  gives  attachment  to  the  interosseous  mem- 
brane, and  separates  the  volar  from  the  dorsal  surface. 

Surfaces.^ — The  volar  surface  {fades  volaris;  anterior  surface),  much  broader 
above  than  below,  is  concave  in  its  upper  three-fourths,  and  gives  origin  to  the 
Flexor  digitorum  profundus;  its  lower  fourth,  also  concave,  is  covered  by  the 
Pronator  quadratus.  The  lower  fourth  is  separated  from  the  remaining  portion 
by  a  ridge,  directed  obliquely  downward  and  medialward,  which  marks  the  extent 
of  origin  of  the  Pronator  quadratus.  At  the  junction  of  the  upper  with  the 
middle  third  of  the  bone  is  the  nutrient  canal,  directed  obliquely  upward. 

The  dorsal  surface  {fades  dorsalis;  posterior  surface)  directed  backward  and 
lateralward,  is  broad  and  concave  above;  convex  and  somewhat  narrower  in  the 
middle;  narrow,  smooth,  and  rounded  below.  On  its  upper  part  is  an  oblique 
ridge,  which  runs  from  the  dorsal  end  of  the  radial  notch,  downward  to  the  dorsal 
border;  the  triangular  surface  above  this  ridge  receives  the  insertion  of  the 
Anconaeus,  while  the  upper  part  of  the  ridge  affords  attachment  to  the  Supinator. 
Below  this  the  surface  is  subdivided  by  a  longitudinal  ridge,  sometimes  called  the 
perpendicular  line,  into  two  parts:  the  medial  part  is  smooth,  and  covered  by  the 
Extensor  carpi  ulnaris;  the  lateral  portion,  wider  and  rougher,  gives  origin  from 
above  downward  to  the  Supinator,  the  Abductor  pollicis  longus,  the  Extensor  pollicis 
longus,  and  the  Extensor  indicis  proprius. 

The  medial  surface  {fades  medialis;  internal  surface)  is  broad  and  concave 
above,  narrow  and  convex  below.  Its  upper  three-fourths  give  origin  to  the 
Flexor  digitorum  profundus;  its  lower  fourth  is  subcutaneous. 


THE  RADIUS 


319 


The  Lower  Extremity  ((ILsfcil  extremity). — The  lower  extremity  of  the  uhia  is 
small,  and  presents  two  eminences;  the  lateral  and  larger  is  a  rounded,  articular 
eminence,  termed  the  head  of  the  ulna;  the  medial,  narrower  and  more  projecting, 
is  a  non-articular  eminence,  the  styloid  process.  The  head  i)resents  an  articular 
surface,  part  of  which,  of  an  oval  or  semilunar  form,  is  directed  downward,  and 
articulates  with  the  upper  surface  of  the  triangular  articular  disk  which  separates  it 
from  the  Avrist-joint;  the  remaining  portion,  directed  lateralward,  is  narrow,  convex, 
and  received  into  the  ulnar  notch  of  the  radius.  The  styloid  process  projects  from 
the  medial  and  back  part  of  the  bone;  it  descends  a  little  lower  than  the  head, 
and  its  rounded  end  affords  attachment  to  the  ulnar  collateral  ligament  of  the 
wrist-joint.  The  head  is  separated  from  the  styloid  process  by  a  depression  for 
the  attachment  of  the  apex  of  the  triangular  articular  disk,  and  behind,  by  a  shallow 
groove  for  the  tendon  of  the  Extensor  carpi  ulnaris. 


Olecranon 

Appears  at — £^^\— '^°"''*'  ^"'^^^  "^ 
tenth  year       p»;™™«|     sixteenth  year 


Is'i  4 


Appears  at 
fourth  year 


Joins  body  at 
twentieth  year 


Inferior  extremity 


Fig.  355. — Plan  of  ossification  of  the  ulna. 
From  three  centres. 


Fig.  356. — Epiphysial  hnes  of  ulna  in  a  young  adult. 
Lateral  aspect.  The  lines  of  attachment  of  the  articular 
capsules  are  in  blue. 


Structure. — The  structure  of  the  ulna  is  similar  to  that  of  the  other  long  bones. 

Ossification  (Figs.  355,  356) . — The  ulna  is  ossified  from  three  centres :  one  each  for  the  body,  the 
inferior  extremity,  and  the  top  of  the  olecranon.  Ossification  begins  near  the  middle  of  the  body, 
about  the  eighth  week  of  fetal  life,  and  soon  extends  through  the  greater  part  of  the  bone.  At  bii'th 
the  ends  are  cartilaginous.  About  the  fourth  year,  a  centre  appears  in  the  middle  of  the  head, 
and  soon  extends  into  the  styloid  process.  About  the  tenth  year,  a  centre  appears  in  the  olecranon 
near  its  extremity,  the  chief  part  of  this  process  being  formed  by  an  upward  extension  of  the  body. 
The  upper  epiphysis  joins  the  body  about  the  sixteenth,  the  lower  about  the  twentieth  year. 

Articulations. — The  ulna  articulates  with  the  humerus  and  radius. 


The  Radius. 

The  radius  (Figs.  353,  354)  is  situated  on  the  lateral  side  of  the  ulna,  which 
exceeds  it  in  length  and  size.  Its  upper  end  is  small,  and  forms  only  a  small  part 
of  the  elbow-joint;  but  its  lower  end  is  large,  and  forms  the  chief  part  of  the  wrist- 


320  -  OSTEOLOGY 

joint.  It  is  a  long  bone,  prismatic  in  form  and  slightly  curved  longitudinally.  It 
-has  a  body  and  two  extremities. 

The  Upper  Extremity  (pn).vinial  extremity). — The  upper  extremity  presents  a 
head,  neck,  and  tuberosity.  The  head  is  of  a  cylindrical  form,  and  on  its  upper 
surface  is  a  shallow  cup  or  fovea  for  articulation  Avith  the  capitulum  of  the  humerus. 
The  circumference  of  the  head  is  smooth;  it  is  broad  medially  where  it  articulates 
with  the  radial  notch  of  the  ulna,  narrow  in  the  rest  of  its  extent,  which  is  embraced 
by  the  annular  ligament.  The  head  is  supported  on  a  round,  smooth,  and  con- 
stricted portion  called  the  neck,  on  the  back  of  which  is  a  slight  ridge  for  the  inser- 
tion of  part  of  the  Supinator.  Beneath  the  neck,  on  the  medial  side,  is  an  eminence, 
the  radial  tuberosity;  its  surface  is  divided  into  a  posterior,  rough  portion,  for  the 
insertion  of  the  tendon  of  the  Biceps  brachii,  and  an  anterior,  smooth  portion,  on 
which  a  bursa  is  interposed  between  the  tendon  and  the  bone. 

The  Body  or  Shaft  (corpus  radii). — The  body  is  prismoid  in  form,  narrower 
above  than  below,  and  slightly  curved,  so  as  to  be  convex  lateral  ward.  It  presents 
three  borders  and  three  surfaces. 

Borders.^ — The  volar  border  (margo  wlaris;  anterior  border)  extends  from  the  lower 
part  of  the  tuberosity  above  to  the  anterior  part  of  the  base  of  the  styloid  process 
below,  and  separates  the  volar  from  the  lateral  surface.  Its  upper  third  is  promi- 
nent, and  from  its  oblique  direction  has  received  the  name  of  the  oblique  line  of  the 
radius ;  it  gives  origin  to  the  Flexor  digitorum  sublimis  and  Flexor  pollicis  longus ;  the 
surface  above  the  line  gives  insertion  to  part  of  the  Supinator.  The  middle  third  of 
the  volar  border  is  indistinct  and  rounded.  The  lower  fourth  is  prominent,  and  gives 
insertion  to  the  Pronator  quadratus,  and  attachment  to  the  dorsal  carpal  ligament; 
it  ends  in  a  small  tubercle,  into  which  the  tendon  of  the  Brachioradialis  is  inserted. 

The  dorsal  border  (margo  dorsalis;  posterior  border)  begins  above  at  the  back  of 
the  neck,  and  ends  below  at  the  posterior  part  of  the  base  of  the  styloid  process; 
it  separates  the  posterior  from  the  lateral  surface.  It  is  indistinct  above  and  below, 
but  well-marked  in  the  middle  third  of  the  bone. 

The  interosseous  crest  {crista  interossea;  internal  or  interosseous  border)  begins 
above,  at  the  back  part  of  the  tuberosity,  and  its  upper  part  is  rounded  and  indis- 
tinct; it  becomes  sharp  and  prominent  as  it  descends,  and  at  its  lower  part  divides 
into  two  ridges  which  are  continued  to  the  anterior  and  posterior  margins  of  the 
ulnar  notch.  To  the  posterior  of  the  two  ridges  the  lower  part  of  the  interosseous 
membrane  is  attached,  while  the  triangular  surface  between  the  ridges  gives  inser- 
tion to  part  of  the  Pronator  quadratus.  This  crest  separates  the  volar  from  the 
dorsal  surface,  and  gives  attachment  to  the  interosseous  membrane. 

Surface.- — The  volar  surface  {fades  volaris;  anterior  surface)  is  concave  in  its 
upper  three-fourths,  and  gives  origin  to  the  Flexor  pollicis  longus;  it  is  broad  and  flat 
in  its  lower  fourth,  and  affords  insertion  to  the  Pronator  quadratus.  A  prominent 
ridge  limits  the  insertion  of  the  Pronator  quadratus  below,  and  between  this  and 
the  inferior  border  is  a  triangular  rough  surface  for  the  attachment  of  the  volar 
radiocarpal  ligament.  At  the  junction  of  the  upper  and  middle  thirds  of  the 
volar  surface  is  the  nutrient  foramen,  which  is  directed  obliquely  upward. 

The  dorsal  surface  {fades  dorsalis;  posterior  surface)  is  convex,  and  smooth  in 
the  upper  third  of  its  extent,  and  covered  by  the  Supinator.  Its  middle  third  is 
broad,  slightly  concave,  and  gives  origin  to  the  Abductor  pollicis  longus  above, 
and  the  Extensor  pollicis  brevis  below.  Its  lower  third  is  broad,  convex,  and 
covered  by  the  tendons  of  the  muscles  which  subsequently  run  in  the  grooves  on 
the  lower  end  of  the  bone. 

The  lateral  surface  {fades  lateralis;  external  surface)  is  convex  throughout  its 
entire  extent.  Its  upper  third  gives  insertion  to  the  Supinator.  About  its  centre  is 
a  rough  ridge,  for  the  insertion  of  the  Pronator  teres.  Its  lower  part  is  narrow^  and 
covered  by  the  tendons  of  the  Abductor  pollicis  longus  and  Extensor  pollicis  brevis. 


THE  RADIUS  321 

The  Lower  Extremity.— ^The  lower  extremity  is  large,  of  quadrilateral  form, 
and  provided  with  two  articular  surfaces — one  below,  for  the  carpus,  and  another 
at  the  medial  side,  for  the  ulna.  The  carpal  articular  surface  is  triangular,  concave, 
smooth,  and  divided  by  a  slight  antero-posterior  ridge  into  two  parts.  Of  these, 
the  lateral,  triangular,  articulates  with  the  navicular  bone;  the  medial,  quadri- 
lateral, with  the  lunate  bone.  The  articular  surface  for  the  ulna  is  called  the  ulnar 
notch  (sigmoid  cariti/)  of  the  radius;  it  is  narrow,  concave,  smooth,  and  articulates 
with  the  head  of  the  ulna.  These  two  articular  surfaces  are  separated  by  a  promi- 
nent ridge,  to  which  the  base  of  the  triangular  articular  disk  is  attached;  this  disk 
separates  the  wrist-joint  from  the  distal  radioulnar  articulation.  This  end  of  the 
bone  has  three  non-articular  surfaces — volar,  dorsal,  and  lateral.  The  volar  surface, 
rough  and  irregular,  affords  attachment  to  the  volar  radiocarpal  ligament.  The 
dorsal  surface  is  convex,  affords  attachment  to  the  dorsal  radiocarpal  ligament, 
and  is  marked  by  three  grooves.  Enumerated  from  the  lateral  side,  the  first 
groove  is  broad,  but  shallow,  and  subdivided  into  two  by  a  slight  ridge;  the  lateral 
of  these  two  transmits  the  tendon  of  the  Extensor  carpi  radialis  longus,  the  medial 
the  tendon  of  the  Extensor  carpi  radialis  brevis.  The  second  is  deep  but  narrow, 
and  bounded  laterally  by  a  sharply  defined  ridge;  it  is  directed  obliquely  from  above 
downward  and  lateralward,  and  transmits  the  tendon  of  the  Extensor  pollicis 
longus.  The  third  is  broad,  for  the  passage  of  the  tendons  of  the  Extensor  indicis 
proprius  and  Extensor  digitorum  communis.  The  lateral  surface  is  prolonged 
obliquely  downward  into  a  strong,  conical  projection,  the  styloid  process,  which 
gives  attachment  by  its  base  to  the  tendon  of  the  Brachioradialis,  and  by  its  apex 
to  the  radial  collateral  ligament  of  the  wrist-joint.  The  lateral  surface  of  this 
process  is  marked  by  a  flat  groove,  for  the  tendons  of  the  Abductor  pollicis  longus 
and  Extensor  pollicis  brevis. 

Structure. — The  structure  of  the  radius  is  Uke  that  of  the  other  long  bones. 

Ossification  (Figs.  357,  358). — The  radius  is  ossified  from  three  centres:  one  for  the  body, 
and  one  for  either  extremity.  That  for  the  body  malies  its  appearance  near  the  centre  of  the  bone, 
during  the  eighth  week  of  fetal  fife.  About  the  end  of  the  second  year,  ossification  commences 
in  the  lower  end;  and  at  the  fifth  year,  in  the  upper  end.  The  upper  epiphysis  fuses  with  the 
body  at  the  age  of  seventeen  or  eighteen  years,  the  lower  about  the  age  of  twenty.  An  additional 
centre  sometimes  found  in  the  radial  tuberosity,  appears  about  the  fourteenth  or  fifteenth  year. 

Articulations. — The  radius  articulates  with  four  bones:  the  humerus,  ulna,  navicular,  and 
lunate. 

Applied  Anatomy  of  the  Ulna  and  Radius. — The  two  bones  of  the  forearm  are  more  often 
broken  together,  than  is  either  the  radius  or  ulna  separately.  It  is  therefore  convenient  to  con- 
sider in  the  first  instance  the  fractm-es  of  both  bones  and  subsequently  the  principal  fractures 
which  take  place  in  either  bone.  Fractures  of  both  bones  may  be  produced  by  either  direct  or 
indirect  violence,  though  more  commonly  by  direct  violence.  When  indirect  force  is  apphed  to 
the  forearm  the  radius  as  a  rule  gives  way,  though  both  bones  may  suffer.  Fracture  from  indirect 
force  generally  takes  place  somewhere  about  the  middle  of  the  bones,  while  that  from  direct 
violence  may  occur  at  any  part,  but  is  most  frequent  in  the  lower  half  of  the  bones.  The  fracture 
is  usually  transverse,  but  may  be  more  or  less  obhque.  A  point  of  interest  in  connection  with 
these  fractures  is  the  tendency  for  the  two  bones  to  unite  across  the  interosseous  membrane; 
the  limb  should  therefore  be  put  up  in  a  position  midway  between  supination  and  pronation, 
which  is  not  only  the  most  comfortable  position,  but  also  separates  the  bones  most  widely  from 
each  other.  Anterior  and  posterior  splints  are  apphed  in  these  cases,  and  should  be  rather  wider 
than  the  limb,  so  as  to  prevent  any  side  pressure  on  the  bones. 

The  special  fractures  of  the  ulna  are:  (1)  Fractiire  of  the  olecranon,  which  is  usually  caused 
by  direct  violence,  by  falls  on  the  elbow  with  the  forearm  flexed,  but  occasionally  by  muscular 
action  in  sudden  contraction  of  the  Triceps  brachii;  the  most  common  site  of  this  fracture  is  at 
the  constricted  portion  where  the  olecranon  joins  the  body  of  the  bone,  and  the  fracture  is  usually 
transverse;  but  any  part  may  be  broken,  and  even  a  thin  shell  may  be  torn  off.  Fractures  from 
direct  violence  are  occasionally  comminuted.  If  the  fibrous  structures  around  the  process  are 
not  torn  the  displacement  is  slight,  otherwise  the  olecranon  may  be  drawn  up  for  a  very  consider- 
able distance.  (2)  Fracture  of  the  coronoid  process  may  occur  as  a  complication  of  dislocation 
backward  of  the  bones  of  the  forearm,  but  it  is  doubtful  if  it  ever  takes  place  as  an  uncomplicated 
injury.  (3)  Fractm-es  of  the  body  of  the  ulna  may  occur  at  any  part,  but  usuallv  take  place  at 
21 


322 


OSTEOLOGY 


or  a  little  below  the  middle  of  the  bone.  They  are  generally  the  result  of  direct  violence,  but  may 
occur  as  a  complication  of  dislocation  of  the  radius.  (4)  The  styloid  process  may  be  knocked 
ofT  by  direct  violence. 

Fractm'es  of  the  radius  may  consist  of:  (1)  Fracture  of  the  head  of  the  bone;  this  for  the  most 
part  takes  place  in  conjunction  with  some  other  lesion,  but  may  occur  as  an  uncomplicated  injury. 
(2)  Fracture  of  the  neck  also  may  occur,  but  is  usually  complicated  with  other  injury.  (3)  Frac- 
tures of  the  body  of  the  radius  are  very  common,  and  may  take  place  at  any  part  of  the  bone. 
They  may  be  caused  by  direct  or  indirect  violence.  In  fracture  of  the  upper  third  of  the  body — 
that  is  to  say,  above  the  insertion  of  the  Pronator  teres — the  displacement  is  very  great.  The 
upper  fragment  is  strongly  supinated  by  the  biceps  and  supinator  and  flexed  by  the  biceps; 
while  the  lower  fragment  is  pronated  and  drawn  toward  the  ulna  by  the  two  pronators.  If  such 
a  fracture  be  put  up  in  the  ordinary  position,  midway  between  supination  and  pronation,  the 
bone  will  unite  with  the  upper  fragment  in  a  position  of  supination,  and  the  lower  one  in  the  mid- 
position,  and  thus  considerable  impairment  of  the  movement  of  supination  will  result;  the  Umb 
should  therefore  be  put  up  with  the  forearm  supinated.     (4)  The  most  important  fracture  of  the 


Head 


Appears  af_ 
fifth  year 


Unites  with  body 
about  pitberiy 


Appears  at 
secotuL  year 


Unites  with  body 
about  twentieth 


Lower  extremity 


year 


Fig.  357 


-Plan  of  ossification  of  the  radius. 
From  three  centres. 


Fig.  358. — Epiphysial  lines  of  radius  in  a  young 
adult.  Anterior  aspect.  The  line  of  attachment  of  the 
articular  capsule  of  the  wrist-joint  is  in  blue. 


radius  is  that  of  the  lower  end  (Colles'  fracture).  The  fracture  is  transverse,  and  generally  takes 
place  about  2.5  cm.  from  the  lower  extremity.  It  is  caused  by  falls  on  the  palm  of  the  hand,  and 
is  an  injury  of  advanced  life,  occurring  more  frequently  in  the  female  than  in  the  male.  In  conse- 
quence of  the  manner  in  which  the  fracture  is  caused,  the  upper  fragment  is  driven  into  the  lower, 
and  impaction  commonly  is  the  result;  excess  of  violence  may,  however,  disimpact,  the  lower 
fi-agment  being  split  into  two  or  more  pieces,  so  that  no  fixation  occurs.  Separation  of  the  lower 
epiphysis  of  the  radius  may  take  place  in  the  young.  This  injury  and  Colles'  fracture  may  be 
distinguished  from  other  injuries  in  this  neighborhood — especially  dislocation  of  the  wrist,  with 
which  they  are  liable  to  be  confounded — by  observing  the  relative  positions  of  the  styloid  processes 
of  the  ulna  and  radius.  In  the  natural  conditions  of  parts,  with  the  arm  hanging  by  the  side, 
the  styloid  process  of  the  radius  is  on  a  lower  level  than  that  of  the  ulna.  After  fracture  or  separa- 
tion of  the  epiphysis  the  styloid  process  of  the  radius  is  on  the  same  level  as,  or  on  a  higher  level 
than,  that  of  the  ulna,  whereas  it  would  be  imaltered  in  position  in  dislocation.  Reduction  in  the 
case  of  Colles'  fracture  is  usually  easily  effected  by  traction  on  the  hand,  the  limb  being  subse- 
quently splinted  with  the  hand  deflected  toward  the  ulnar  side. 


THE  CARPUS  323 


THE   HAND. 


The  skeleton  of  the  hand  (  Fii^'s.  iJoO,  .')()())  is  suhdh'ided  into  three  se<i,'nients:  the 
carpus  t)r  wrist  bones;  the  metacarpus  or  bones  of  the  palm;  and  the  phalanges  or 
bones  of  the  digits. 

The  Carpus  (Ossa  Carpi). 

The  carpal  bones,  eight  in  number,  are  arranged  in  two  rows.  Those  of  the 
proximal  row,  from  the  radial  to  the  ulnar  side,  are  named  the  navicular,  lunate, 
triangular,  and  pisiform;  those  of  the  distal  row,  in  the  same  order,  are  named  the 
greater  multangular,  lesser  multangular,  capitate,  and  hamate. 

Common  Characteristics  of  the  Carpal  Bones. — Each  bone  (excepting  the  pisi- 
form) presents  six  surfaces.  Of  these  the  volar  or  anterior  and  the  dorsal  or  posterior 
surfaces  are  rough,  for  ligamentous  attachment;  the  dorsal  surfaces  being  the 
broader,  except  in  the  navicular  and  lunate.  The  superior  or  proximal,  and  inferior 
or  distaJ  surfaces  are  articular,  the  superior  generally  convex,  the  inferior  concave; 
the  medial  and  lateral  surfaces  are  also  articular  where  they  are  in  contact  with 
contiguous  bones,  otherwise  they  are  rough  and  tuberculated.  The  structure  'n 
all  is  similar,  viz.,  cancellous  tissue  enclosed  in  a  layer  of  compact  bone. 

Bones  of  the  Proximal  Row  (upper  row). — The  Navicular  Bone  (os  naviculare  manus; 
scaphoid  hone)  (Fig.  3G1). — The  navicular  bone  is  the  largest  bone  of  the  proximal 
row,  and  has  received  its  name  from  its  fancied  resemblance  to  a  boat.  It  is  situated 
at  the  radial  side  of  the  carpus,  its  long  axis  being  from  above  downw^ard,  lateralward, 
and  forward.  The  superior  surface  is  convex,  smooth,  of  triangular  shape,  and  artic- 
ulates with  the  lower  end  of  the  radius.  The  inferior  surface,  directed  downward, 
lateralward,  and  backward,  is  also  smooth,  convex,  and  triangular,  and  is  divided 
by  a  slight  ridge  into  two  parts,  the  lateral  articulating  with  the  greater  multangu- 
lar, the  medial  with  the  lesser  multangular.  On  the  dorsal  surface  is  a  narrow, 
rough  groove,  which  runs  the  entire  length  of  the  bone,  and  serves  for  the  attach- 
ment of  ligaments.  The  volar  surface  is  concave  above,  and  elevated  at  its  lower 
and  lateral  part  into  a  rounded  projection,  the  tubercle,  which  is  directed  forward 
and  gives  attachment  to  the  transverse  carpal  ligament  and  sometimes  origin  to 
a  few  fibres  of  the  Abductor  pollicis  brevis.  The  lateral  surface  is  rough  and  narrow, 
and  gives  attachment  to  the  radial  collateral  ligament  of  the  wrist.  The  medial 
surface  presents  two  articular  facets;  of  these,  the  superior  or  smaller  is  flattened 
of  semilunar  form,  and  articulates  with  the  lunate  bone;  the  inferior  or  larger  is 
concave,  forming  with  the  lunate  a  concavity  for  the  head  of  the  capitate  bone. 

Articulations. — The  navicular  articulates  with  five  bones:  the  radius  proximally,  greater  and 
lesser  multangulars  distally,  and  capitate  and  lunate  medially. 

The  Lunate  Bone  {ps  lunatum;  semilunar  bone)  (Fig.  362). — The  lunate  bone  may 
be  distinguished  by  its  deep  concavity  and  crescentic  outline.  It  is  situated  in 
the  centre  of  the  proximal  row  of  the  carpus,  between  the  navicular  and  triangular. 
The  superior  surface,  convex  and  smooth,  articulates  with  the  radius.  The  inferior 
surface  is  deeply  concave,  and  of  greater  extent  from  before  backward  than  trans- 
versely: it  articulates  w^th  the  head  of  the  capitate,  and,  by  a  long,  narrow  facet 
(separated  by  a  ridge  from  the  general  surface),  with  the  hamate.  The  dorsal 
and  volar  surfaces  are  rough,  for  the  attachment  of  ligaments,  the  former  being 
the  broader,  and  of  a  somewhat  rounded  form.  The  lateral  surface  presents  a 
narrow,  flattened,  semilunar  facet  for  articulation  with  the  navicular.  The  medial 
surface  is  marked  by  a  smooth,  quadrilateral  facet,  for  articulation  with  the 
triangular. 

Articulations. — The  lunate  articulates  with  five  bones:  the  radius  proximally,  capitate  and 
hamate  distally,  navicular  laterally,  and  triangular  medially. 


324 


OSTEOLOGY 


The  Triangular  Bone  {os  triquetum;  cuneiform  hone)  (Fig.  363).- — The  triangular 
bone  may  be  distinguished  by  its  pyramidal  shape,  and  by  an  oval  isolated  facet 
for  articulation  with  the  pisiform  bone.  It  is  situated  at  the  upper  and  ulnar  side 
of  the  carpus.  The  superior  surface  presents  a  medial,  rough,  non-articular  portion, 
and  a  lateral  convex  articular  portion  which  articulates  with  the  triangular  articular 
disk  of  the  wrist.  The  inferior  surface,  directed  lateralward,  is  concave,  sinuously 
curved,  and  smooth  for  articulation  with  the  hamate.    The  dorsal  surface  is  rough 


Carpus 

Flexor  cakpi  ulnabis 

Flkxor  digiti  quinti  bkevis 

Opvonens  digiti  quinti 


Metacarpus 


Groove  for  tendon  of 
Flexor  carpi  eapialis 

Opponens  pollicis 
Flexor  pollicis  brevis 

Abductor  pollicis 

longus 


Flexor  brevts 

AND 

Abductor 
digiti  quinti. 


Flexor  digitorum  suelimis 


Flexor  digitorum  profundus 


Fig.  359. — Bones  of  the  left  hand.     Volar  surface. 


THE  CARPUS 


325 


for  the  attachment  of  ligaments.  The  volar  surface  presents,  on  its  medial  part, 
an  oval  facet,  for  articulation  with  the  pisiform;  its  lateral  part  is  rough  for  liga- 
mentous attachment.  The  lateral  surface,  the  base  of  the  pyramid,  is  marked  by  a 
flat,  quadrilateral  facet,  for  articulation  with  the  lunate.  The  medial  surface, 
the  summit  of  the  pyramid,  is  pointed  and  roughened,  for  the  attachment  of  the 
ulnar  collateral  ligament  of  the  wrist. 


^«n?^- 


Ext.  carpi  radialis 

LONGDS 

Ext.  oarpi  radialis 

BREVIS 


Ext.  carpi  ulnaris 


Metacarpus 


Ext.  digitorum 
communis  and 
Ext.  INDICTS 

PKOPRIUS. 


/  U  Row 


'2.?-'^ Raw 


Fig.  360. — Bones  of  the  left  hand.     Dorsal  surface. 


326 


OSTEOLOGY 


Articulations. — The  triangular  articulates  with  three  bones:  the  lunate  laterally,  the  pisiform 
in  front,  the  hamate  distally;  and  with  the  triangular  ai-ticular  disk  which  separates  it  from  the 
lower  end  of  the  ulna. 

For  radius  Fur   niuito 

Tubercle    'r 


mulSngida r        ^'""  ^^^^^^  multangular 


For  capitate 


Fig.  361. — The  left  navicular  bone. 


The  Pisiform  Bone  (os  jyisiforme)  (Fig.  364).- — The  pisiform  bone  may  be  known 
by  its  small  size,  and  by  its  presenting  a  single  articular  facet.  It  is  situated  on  a 
plane  anterior  to  the  other  carpal  bones  and  is  spheroidal  in  form.     Its  dorsal 


For  triangular 


For  radius 


For  navicular 
For  hamate       For  capitate 

Fig.  362. — The  left  lunate  bone. 

surface  presents  a  smooth,  oval  facet,  for  articulation  with  the  triangular:  this  facet 
approaches  the  superior,  but  not  the  inferior  border  of  the  bone.  The  volar  surface 
is  rounded  and  rough,  and  gives  attachment  to  the  transverse  carpal  ligament, 


For  pisiform  For  lunate 


For  triangular 


For  hamate 
Fig.  363. — The  left  triangular  bone. 


Fig.  364. — The  left  pisiform  bone. 


and  to  the  Flexor  carpi  ulnaris  and  Abductor  digiti  quinti.    The  lateral  and  medial 
surfaces  are  also  rough,  the  former  being  concave,  the  latter  usually  convex. 

Articulation. — The  pisiform  articulates  with  one  bone,  the  triangular. 

Groove  For  navicular 


For  lesser 
multangular 


For  2nd 
metacarpal 


Ridge 


For  \st  metacarpal 

Fig.  365. — The  left  greater  multangular  bone. 


For  lesser 
multangular 


For  2iui  metacarpal 


Bones  of  the  Distal  Row  (loiver  row). — The  Greater  Multangular  Bone  (os  mul- 
tangulum  majus;  trapezium)  (Fig.  365).^ — The  greater  multangular  bone  may  be 
distinguished  by  a  deep  groove  on  its  volar  surface.     It  is  situated  at  the  radial 


THE  CARPUS 


327 


side  (if  the  carpus,  between  the  iia\icuhir  and  the  first  nietaearjial  hone.  The 
superior  surface  is  directed  upward  and  niedialward;  medially  it  is  smooth,  and 
articuhites  with  the  navicuhir;  hiterally  it  is  rough  and  continuous  with  the  lateral 
surface.  The  inferior  surface  is  oval,  concave  from  side  to  side,  convex  from  before 
backward,  so  as  to  form  a  saddle-shaped  surface  for  articulation  with  the  i)ase 
of  the  first  metacarpal  bone.  The  dorsal  surface  is  rough.  The  volar  surface  is 
narrow  and  rough.  At  its  upper  part  is  a  deep  groove,  running  from  above  obliquely 
downward  and  niedialward;  it  transmits  the  tendon  of  the  Flexor  carpi  radialis, 
and  is  bounded  laterally  by  an  oblique  ridge.  This  surface  gives  origin  to  the 
Ojiponens  jiollicis  and  to  the  Abductor  and  Flexor  pollicis  brevis;  it  also  affords 
attachment  to  the  transverse  carpal  ligament.  The  lateral  surface  is  broad  and 
rough,  for  the  attachment  of  ligaments.  The  medial  surface  presents  two  facets; 
the  upper,  large  and  concave,  articulates  with  the  lesser  multangular;  the  lower, 
small  and  oval,  with  the  base  of  the  second  metacarpal. 

Articulations. — The  greater  multangular  articulates  with  four  bones:    the  navicular  proximaily, 
the  first  metacarpal  distally,  and  the  lesser  multangular  and  second  metacarpal  medially. 

The  Lesser  Multangular  Bone  (as  midtangiilum  minus;  trapezoid  hone)  (Fig.  366). 
— The  lesser  multangular  is  the  smallest  bone  in  the  distal  row.  It  may  be  known 
by  its  wedge-shaped  form,  the  broad  end 
of  the  wedge  constituting  the  dorsal,  the 
narrow  end  the  volar  surface;  and  by  its 
having  four  articular  facets  touching  each 
other,  and  separated  by  sharp  edges. 
The  superior  surface,  quadrilateral,  smooth, 
and  slightly  concave,  articulates  with  the 
navicular.  The  inferior  surface  articulates 
with  the  proximal  end  of  the  second 
metacarpal  bone;  it  is  convex  from  side 
to   side,  concave  from  before    backward 

and  subdivided  by  an  elevated  ridge  into  two  unequal  facets.  The  dorsal  and 
volar  surfaces  are  rough  for  the  attachment  of  ligaments,  the  former  being  the 
larger  of  the  two.  The  lateral  surface,  convex  and  smooth,  articulates  with  the 
greater  multangular.  The  medial  surface  is  concave  and  smooth  in  front,  for 
articulation  with  the  capitate;  rough  behind,  for  the  attachment  of  an  inter- 
osseous ligament. 


For  navicular 


Volar 

surface 


For  greater 
multangular 


Dorsal 
surface 


lor 
capitate 


For  2nd 

metacarpal 


Fig.  366. — The  left  lesser  multangular  bone. 


Articulations. — The  lesser  multangular  articulates  with  four  bones:    the  na%'icular  proximaily, 
second  metacarpal  distalh",  greater  multangular  laterally;  and  capitate  mediallj\ 


For  lunate 


For 
navicular 


For  lesser 
multangiilar 


For 
hamate 


For  2nd     metacarpal 
metacarpal 


For  ith  metacarpal  Volar  surface 

Fig.   367. — The  left  capitate  bone. 


The  Capitate  Bone  (os  capitatum;  os  magnum)  (Fig.  367).^ — The  capitate  bone 
is  the  largest  of  the  carpal  bones,  and  occupies  the  centre  of  the  wrist.  It  presents, 
above,  a  rounded  portion  or  head,  which  is  received  into  the  concavity  formed  by 


328  OSTEOLOGY 

the  navicular  and  lunate;  a  constricted  portion  or  neck;  and  below  this,  the  body. 
The  superior  surface  is  round,  smooth,  and  articulates  with  the  lunate.  The  inferior 
surface  is  divided  by  two  ridges  into  three  facets,  for  articulation  with  the  second, 
third,  and  fourth  metacarpal  bones,  that  for  the  third  being  the  largest.  The 
dorsal  surface  is  broad  and  rough.  The  volar  surface  is  narrow,  rounded,  and  rough, 
for  the  attachment  of  ligaments  and  a  part  of  the  Adductor  pollicis  obliquus. 
The  lateral  surface  articulates  with  the  lesser  multangular  by  a  small  facet  at 
its  anterior  inferior  angle,  behind  which  is  a  rough  depression  for  the  attach- 
ment of  an  interosseous  ligament.  Above  this  is  a  deep,  rough  groove,  forming 
part  of  the  neck,  and  serving  for  the  attachment  of  ligaments;  it  is  bounded  supe- 
riorly by  a  smooth,  convex  surface,  for  articulation  with  the  navicular.  The  medial 
surface  articulates  wdth  the  hamate  by  a  smooth,  concave,  oblong  facet,  which 
occupies  its  posterior  and  superior  parts;  it  is  rough  in  front,  for  the  attachment 
of  an  interosseous  ligament. 

Articulations. — The  capitate  articulates  with  seven  bones:  the  navicular  and  lunate  proximally, 
the  second,  third,  and  fourth  metacarpals  distally,  the  lesser  multangular  on  the  radial  side,  and 
the  hamate  on  the  ulnar  side. 

For  lunaie 

For  capitate 
For  triangular 


For  4:ih  tnetacar-pal ..^^^  jj^j 


For  5ih  metacarijul        Hatmdus  '   For  5th  >mtacarpal 

Fig.  368.— The  left  hamate  bone. 

The  Hamate  Bone  (os  liamatum;  unciform  hone)  (Fig.  36S). — The  hamate  bone 
may  be  readily  distinguished  by  its  wedge-shaped  form,  and  the  hook-like  process 
w^hich  projects  from  its  volar  surface.  It  is  situated  at  the  medial  and  lower  angle 
of  the  carpus,  with  its  base  downward,  resting  on  the  fourth  and  fifth  metacarpal 
bones,  and  its  apex  directed  upward  and  lateralward.  The  superior  surface,  the 
apex  of  the  wedge,  is  narrow,  convex,  smooth,  and  articulates  with  the  lunate. 
The  inferior  surface  articulates  with  the  fourth  and  fifth  metacarpal  bones,  by 
concave  facets  which  are  separated  by  a  ridge.  The  dorsal  surface  is  triangular 
and  rough  for  ligamentous  attachment.  The  volar  surface  presents,  at  its  lower 
and  ulnar  side,  a  curved,  hook-like  process,  the  hamulus,  directed  forward  and 
lateralward.  This  process  gives  attachment,  by  its  apex,  to  the  transverse  carpal 
ligament  and  the  Flexor  carpi  ulnaris;  by  its  medial  surface  to  the  Flexor  brevis 
and  Opponens  digiti  quinti;  its  lateral  side  is  grooved  for  the  passage  of  the  Flexor 
tendons  into  the  palm  of  the  hand.  It  is  one  of  the  four  eminences  on  the  front 
of  the  carpus  to  which  the  transverse  carpal  ligament  of  the  wrist  is  attached; 
the  others  being  the  pisiform  medially,  the  oblique  ridge  of  the  greater  multangular, 
and  the  tubercle  of  the  navicular  laterally.  The  medial  surface  articulates  wdth 
the  triangular  bone  by  an  oblong  facet,  cut  obliquely  from  above,  downward 
and  medialward.  The  lateral  surface  articulates  with  the  capitate  by  its  upper 
and  posterior  part,  the  remaining  portion  being  rough,  for  the  attachment  of 
ligaments. 

Articulations.— The  hamate  articulates  with  five  bones:  the  lunate  proximally,  the  fourth 
and  fifth  metacarpals  distally,  the  triangular  medially,  the  capitate  laterally. 


THE  METACARPUS 


329 


The  Metacarpus. 

The  metacarpus  consists  of  five  cylindrical  bones  which  are  numbered  from  the 
lateral  side  (ossct  iitctacarpalia  I-V);  each  consists  of  a  body  and  two  extremities. 

Common  Characteristics  of  the  Metacarpal  Bones. — The  Body  {corpus;  shaft). — 
The  body  is  prismoid  in  form,  and  curved,  so  as  to  be  convex  in  the  longitudinal 
direction  behind,  concave  in  front.  It  presents  three  surfaces:  medial,  lateral, 
and  dorsal.  The  medial  and  lateral  surfaces  are  concave,  for  the  attachment  of 
the  Interossei,  and  separated  from  one  another  by  a  prominent  anterior  ridge. 
The  dorsal  surface  presents  in  its  distal  two-thirds  a  smooth,  triangular,  flattened 
area  which  is  covered  in  the  recent  state,  by  the  tendons  of  the  Extensor  muscles. 
This  surface  is  bounded  by  two  lines,  which  commence  in  small  tubercles  situated 
on  either  side  of  the  digital  extremity,  and,  passing  upward,  converge  and  meet 
some  distance  above  the  centre  of  the  bone  and  form  a  ridge  which  runs  along  the 
rest  of  the  dorsal  surface  to  the  carpal  extremity.  This  ridge  separates  two 
sloping  surfaces  for  the  attachment  of  the  Interossei  dorsales.  To  the  tubercles 
on  the  digital  extremities  are  attached  the  collateral  ligaments  of  the  metacarpo- 
phalangeal joints. 

The  Base  or  Carpal  Extremity  {basis)  is  of  a  cuboidal  form,  and  broader  behind 
than  in  front:  it  articulates  with  the  carpus,  and  with  the  adjoining  metacarpal 
bones;  its  dorsal  and  volar  surfaces  are  rough,  for  the  attachment  of  ligaments. 

The  Head  or  Digital  Extremity  {capitulum)  presents  an  oblong  surface  markedly 
convex  from  before  backw^ard,  less  so  transversely,  and  flattened  from  side  to  side; 
it  articulates  with  the  proximal  phalanx.  It  is  broader,  and  extends  farther  up- 
ward, on  the  volar  than  on  the  dorsal  aspect,  and  is  longer  in  the  antero-posterior 

than  in  the  transverse  diameter.    On  either  side  of  the  head  is  a  tubercle  for  the 

attachment  of  the  collateral  ligament  of  the  metacarpophalangeal  joint.     The 

dorsal  surface,  broad  and  flat,  supports  the  Extensor  tendons;  the  volar  surface 

is  grooved  in  the  middle  line  for  the  passage  of  the  Flexor  tendons,  and  marked 

on  either  side  by  an  articular  eminence  continuous  with  the  terminal  articular 
surface. 
Characteristics  of   the  Individual  Metacarpal  Bones. — The   First   Metacarpal 

Bone  {os  metacarpale  I;  metacarpal  hone  of  the  thiimh)  (Fig.  369)  is  shorter  and 

stouter  than  the  others,  diverges  to  a  greater  degree 

from  the  carpus,  and   its  volar  surface  is  directed 

toward  the  palm.     The  body  is  flattened  and  broad 

on  its  dorsal  surface,  and  does  not  present  the  ridge 

which  is  found  on  the  other  metacarpal  bones;  its 

volar  surface  is  concave  from  above  downward.     On 

its  radial  border  is  inserted  the   Opponens  poUicis; 

its  ulnar  border  gives  origin  to  the  lateral  head  of 

the  first  Interosseus  dorsalis.     The  base  presents  a 

concavo-convex    surface,    for   articulation   with    the 

greater  multangular;  it  has  no  facets  on  its  sides,  but 

on  its  radial  side  is  a  tubercle  for  the  insertion  of  the 

Abductor  pollicis  longus.    The  head  is  less  convex 

than  those  of  the  other  metacarpal  bones,  and  is 

broader  from  side  to  side  than  from  before  backward. 

On  its  volar  surface  are  two  articular  eminences,  of 

which  the  lateral  is  the  larger,  for  the  two  sesamoid 

bones  in  the  tendons  of  the  Flexor  pollicis  brevis. 

The  Second  Metacarpal  Bone  {os  metacarpale  II;    metacarpal  hone  of  the  index 

finger)  (Fig.  370)  is  the  longest,  and  its  base  the  largest,  of  the  four  remaining 

bones.    Its  base  is  prolonged  upward  and  medialward,  forming  a  prominent  ridge. 


For  greater 

multangular 


For  greater 
multangular 


Fig.  369. — -The  first  metacarpal. 
(Left.) 


330 


OSTEOLOGY 


It  presents  four  articular  facets:  three  on  the  upper  surface  and  one  on  the  uhiar 
side.  Of  the  facets  on  the  upper  surface  the  intermediate  is  the  largest  and  is 
concave  from  side  to  side,  convex  from  before  backward  for  articulation  with  the 
lesser  multangular;  the  lateral  is  small,  flat  and  oval  for  articulation  with  the  greater 
multangular;  the  medial,  on  the  summit  of  the  ridge,  is  long  and  narrow  for  articu- 
lation with  the  capitate.  The  facet  on  the  ulnar  side  articulates  with  the  third 
metacarpal.  The  Extensor  carpi  radialis  longus  is  inserted  on  the  dorsal  surface 
and  the  Flexor  carpi  radialis  on  the  volar  surface  of  the  base. 


For  (jreatei- 
For  lesaer  multangular 
multangular 


For  3/ 

metacarpal      For      For  lesser 
ca2ntate      mult- 
angular 


Styloid  For  2nd 
process      meta- 
carpal 


For 
capitate 


For  4Ah 
metacarfal 


Fig.  370. — The  second  metacarpal.     (Left.) 


Fig.  371. — The  third  metacarpal.      (Left.) 


The  Third  Metacarpal  Bone  {os  metacarijale  III;  metacarjjal  bone  of  the  middle 
finger)  (Fig.  371)  is  a  little  smaller  than  the  second.  The  dorsal  aspect  of  its 
base  presents  on  its  radial  side  a  pyramidal  eminence,  the  styloid  process,  which 
extends  upward  behind  the  capitate;  immediately  distal  to  this  is  a  rough  surface 
for  the  attachment  of  the  Extensor  carpi  radialis  brevis.  The  carpal  articular 
facet  is  concave  behind,  flat  in  front,  and  articulates  with  the  capitate.  On  the 
radial  side  is  a  smooth,  concave  facet  for  articulation  with  the  second  metacarpal, 
and  on  the  ulnar  side  two  small  oval  facets  for  the  fourth  metacarpal. 

The  Fourth  Metacarpal  Bone  {os  inetacarjxile  IV;  metacarixd  hone  of  the  ring 
finger)  (Fig.  372)  is  shorter  and  smaller  than  the  third.  The  base  is  small  and 
quadrilateral;  its  superior  surface  presents  two  facets,  a  large  one  medially  for 
articulation  with  the  hamate,  and  a  small  one  laterally  for  the  capitate.  On  the 
radial  side  are  two  oval  facets,  for  articulation  with  the  third  metacarpal ;  and  on 
the  ulnar  side  a  single  concave  facet,  for  the  fifth  metacarpal. 

The  Fifth  Metacarpal  Bone  {os  metacariKile  V;  metacarpal  bone  of  the  little  finger) 
(Fig.  373)  presents  on  its  base  one  facet  on  its  superior  surface,  which  is  concavo- 
convex  and  articulates  with  the  hamate,  and  one  on  its  radial  side,  which  articulates 
with  the  fourth  metacarpal.  On  its  ulnar  side  is  a  prominent  tubercle  for  the  inser- 
tion of  the  tendon  of  the  Extensor  carpi  ulnaris.  The  dorsal  surface  of  the  body 
is  divided  by  an  oblique  ridge,  which  extends  from  near  the  ulnar  side  of  the  base 
to  the  radial  side  of  the  head.    The  lateral  part  of  this  surface  serves  for  the  attach- 


THE  PHALANGES  OF  THE  HAXD 


331 


ment  of  the  fourth  Iiiterosseus  <h)rsa]i.s;  the  medial  i)art  is  smooth,  triaujiuhir,  and 
covered  bv  tlie  Extensor  ten(h)ns  of  the  Httk^  fiimer. 


For 
capitate 


'K'    M'f 


For  bill 

For  3rd  For  meta- 

meiacarpal    hamate        carpal 

Fig.   372. — The  fourth  metacarpal.     (Left.) 


For  Uh 
metacarpal 


For  hamate 


Fig.  373.— The  fifth  metacarpal.      (Left.) 


Articulations. — Besides  their  phalangeal  articulations,  the  metacarpal  bones  articulate  as 
follows:  the  first  with  the  greater  multangular;  the  second  with  the  greater  multangular,  lesser 
multangular,  capitate  and  third  metacarpal;  the  third  with  the  capitate  and  second  and  fourth 
metacarpals;  the  fourth  with  the  capitate,  hamate,  and  third  and  fifth  metacarpals;  and  the 
fifth  with  the  hamate  and  fourth  metacarpal. 


The  Phalanges  of  the  Hand  (Phalanges  Digitorum  Manus). 

The  phalanges  are  fourteen  in  number,  three  for  each  finger,  and  two  for  the 
thumb.  Each  consists  of  a  body  and  two  extremities.  The  body  tapers  from  above 
downward,  is  convex  posteriorly,  concave  in  front  from  above  downward,  flat 
from  side  to  side;  its  sides  are  marked  by  rough  ridges  which  give  attachment 
to  the  fibrous  sheaths  of  the  Flexor  tendons.  The  proximal  extremities  of  the  bones 
of  the  first  row  present  oval,  concave  articular  surfaces,  broader  from  side  to  side 
than  from  before  backward.  The  proximal  extremity  of  each  of  the  bones  of  the 
second  and  third  rows  presents  a  double  concavity  separated  by  a  median  ridge. 
The  distal  extremities  are  smaller  than  the  proximal,  and  each  ends  in  two  condyles 
separated  by  a  shallow  groove;  the  articular  surface  extends  farther  on  the  volar 
than  on  the  dorsal  surface,  a  condition  best  marked  in  the  bones  of  the  first  row. 

The  ungual  phalanges  are  convex  on  their  dorsal  and  flat  on  their  volar  surfaces; 
they  are  recognized  by  their  small  size,  and  by  a  roughened,  elevated  surface  of 
a  horseshoe  form  on  the  volar  surface  of  the  distal  extremity  of  each  which  serves 
to  support  the  sensitive  pulp  of  the  finger. 

Articulations. — In  the  four  fingers  the  phalanges  of  the  first  row  articulate  with  those  of  the 
second  row  and  with  the  metacarpals;  the  phalanges  of  the  second  row  with  those  of  the  first 
and  thii-d  rows,  and  the  ungual  phalanges  with  those  of  the  second  row.  In  the  thumb,  which 
has  only  two  phalanges,  the  first  phalanx  articulates  by  its  proximal  extremity  with  the  meta- 
carpal bone  and  by  its  distal  with  the  ungual  phalanx. 

Ossification  of  the  Bones  of  the  Hand.— The  carpal  bones  are  each  ossified  from  a  single  centre, 
and  ossification  proceeds  in  the  following  order  (Fig.  374) :  in  the  capitate  and  hamate^  during 
the  first  year,  the  former  preceding  the  latter;  in  the  triangular,  during  the  third  year;  in  the 
lunate  and  gi'eater  multangular,  during  the  fifth  year,  the  former  preceding  the  latter;  in  the 
navicular,  during  the  sixth  year;  in  the  lesser  multangular,  during  the  eighth  year;  and  in  the 
pisiform,  about  the  tweKth  year. 


332 


OSTEOLOGY 


Occasionally  an  additional  bone,  the  os  ceittrale,  is  found  on  the  back  of  the  carpus,  lying 
between  the  navicular,  lesser  multangular,  and  capitate.  During  the  second  month  of  fetal  life 
it  is  represented  by  a  small  cartilaginous  nodule,  which  usually  fuses  with  the  cartilaginous  navic- 
ular. Sometimes  the  styloid  process  of  the  third  metacarpal  is  detached  and  forms  an  additional 
ossicle. 

The  metacarpal  bones  are  each  ossified  from  tico  centres:  one  for  the  body  and  one  for  the 
distal  extremity  of  each  of  the  second,  third,  fourth,  and  fifth  bones;  one  for  the  body  and  one 
for  the  base  of  the  first  metacarpal  bone.^  The  first  metacarpal  bone  is  therefore  ossified  in  the 
same  manner  as  the  phalanges,  and  this  has  led  some  anatomists  to  regard  the  thumb  as  being 
made  up  of  three  phalanges,  and  not  of  a  metacarpal  bone  and  two  phalanges.  Ossification  com- 
mences in  the  middle  of  the  body  about  the  eighth  or  ninth  week  of  fetal  life,  the  centres  for  the 
second  and  third  metacarpals  being  the  first,  and  that  for  the  first  metacarpal,  the  last,  to  appear; 
about  the  third  year  the  distal  extremities  of  the  metacarpals  of  the  fingers,  and  the  base  of  the 
metacarpal  of  the  thumb,  begin  to  ossify;  they  unite  with  the  bodies  about  the  twentieth  year. 


CARPUS 

One  centre  for  each  bone  : 
All  cartilaginous  at  birth 


METACARPALS  OF  FINGERS 

Two  centres  for  each  bone  : 
One  for  body 
One  for  head 


PHALANGES 

Two  centres  for  each  bone  : 
One  for  body 
One  for  proximal 
extremity 


ft;|,iSn| ajip.. 


Fig.  374. — Plan  of  ossification  of  the  hand. 


The  phalanges  are  each  ossified  from  two  centres:  one  for  the  body,  and  one  for  the  proximal 
extremity.  Ossification  begins  in  the  body,  about  the  eighth  week  of  fetal  life.  Ossification  of 
the  proximal  extremity  commences  in  the  bones  of  the  first  row  between  the  third  and  fourth 
years,  and  a  year  later  in  those  of  the  second  and  third  rows.  The  two  centres  become  united 
in  each  row  between  the  eighteenth  and  twentieth  years. 

In  the  ungual  phalanges  the  centres  for  the  bodies  appear  at  the  distal  extremities  of  the 
phalanges,  instead  of  at  the  middle  of  the  bodies,  as  in  the  other  phalanges.  Moreover,  of  all 
the  bones  of  the  hand,  the  ungual  phalanges  are  the  first  to  ossify. 

Applied  Anatomy. — The  carpal  bones  are  httle  hable  to  fracture,  except  from  extreme  violence, 
when  the  parts  are  so  comminuted  as  to  necessitate  amputation.     Occasionally  they  are  the 

1  Allen  Thomson  demonstrated  the  fact  that  the  first  metacarpal  bone  is  often  developed  from  three  centres:  that  is 
to  say,  there  is  a  separate  nucleus  for  the  distal  end,  forming  a  distinct  epiphysis  visible  at  the  age  of  seven  or  eight 
years.  He  also  stated  that  there  are  traces  of  a  proximal  epiphysis  in  the  second  metacarpal  bone,  Journal  of  Anatomy 
and  Physiology,  1869. 


THE  HIP  BOXE  333 

seat  of  tuberculous  disease.  The  metacarpal  bones  and  the  phalanges  arc  sometimes  broken 
from  direct  violence.  There  are  two  diseases  of  the  metacarpal  bones  and  phalanges  which  require 
special  mention  on  account  of  their  frequent  occurrence.  One  is  tuberculous  dactjditis,  con- 
sisting in  a  deposit  of  tuberculous  material  in  the  medullary  canal,  expansion  of  the  bone,  with 
subsequent  caseation  and  necrosis.  The  other  is  chondroma,  which  is  perhaps  more  commonly 
found  in  connection  with  the  metacarpal  bones  and  phalanges  than  with  any  other  bones.  The 
tumors  are  usually  multiple,  and  spring  from  beneath  the  periosteum  about  the  epiphysial  plate. 


THE  BONES  OF  THE  LOWER  EXTREMITY  (OSSA  EXTREMITATIS  INFERIORIS). 

The  Hip  Bone  (Os  Coxae;  Innominate  Bone). 

The  hip  bone  is  a  large,  flattened,  irregularly  shaped  bone,  constricted  in  the 
centre  and  expanded  above  and  below.  It  meets  its  fellow  on  the  opposite  side 
in  the  middle  line  in  front,  and  together  they  form  the  sides  and  anterior  wall  of 
the  pelvic  cavity.  It  consists  of  three  parts,  the  ilium,  ischium,  and  pubis,  which 
are  distinct  from  each  other  in  the  young  subject,  but  are  fused  in  the  adult; 
the  union  of  the  three  parts  takes  place  in  and  around  a  large  cup-shaped  articular 
cavity,  the  acetabulum,  which  is  situated  near  the  middle  of  the  outer  surface  of  the 
bone.  The  ilium,  so-called  because  it  supports  the  flank,  is  the  superior  broad  and 
expanded  portion  which  extends  upward  from  the  acetabulum.  The  ischium  is  the 
lowest  and  strongest  portion  of  the  bone ;  it  proceeds  downward  from  the  acetab- 
ulum, expands  into  a  large  tuberosity,  and  then,  curving  forward,  forms,  with 
the  pubis,  a  large  aperture,  the  obturator  foramen.  The  pubis  extends  medialward 
and  downward  from  the  acetabulum  and  articulates  in  the  middle  line  with  the 
bone  of  the  opposite  side :  it  forms  the  front  of  the  pelvis  and  supports  the  external 
organs  of  generation. 

The  Ilium  (os  ilii). — The  ilium  is  divisible  into  two  parts,  the  body  and  the 
ala ;  the  separation  is  indicated  on  the  internal  surface  by  a  curved  line,  the  arcuate 
line,  and  on  the  external  surface  by  the  margin  of  the  acetabulum. 

The  Body  {corpus  oss.  ilii). — The  body  enters  into  the  formation  of  the  acetab- 
ulum, of  which  it  forms  rather  less  than  two-fifths.  Its  external  surface  is  partly 
articular,  partly  non-articular;  the  articular  segment  forms  part  of  the  lunate 
surface  of  the  acetabulum,  the  non-articular  portion  contributes  to  the  acetabular 
fossa.  The  internal  surface  of  the  body  is  part  of  the  wall  of  the  lesser  pelvis  and 
gives  origin  to  some  fibres  of  the  Obturator  internus.  Below,  it  is  continuous  with 
the  pelvic  surfaces  of  the  ischium  and  pubis,  only  a  faint  line  indicating  the  place 
of  union. 

The  Ala  (ala  oss.  ilii). — The  ala  is  the  large  expanded  portion  which  bounds 
the  greater  pelvis  laterally.  It  presents  for  examination  two  surfaces — an  external 
and  an  internal — a  crest,  and  two  borders — an  anterior  and  a  posterior.  The 
external  surface  (Fig.  375),  known  as  the  dorsum  ilii,  is  directed  backward  and  lateral- 
ward  behind,  and  downward  and  lateralward  in  front.  It  is  smooth,  convex  in  front, 
deeply  concave  behind;  bounded  above  by  the  crest,  below  by  the  upper  border 
of  the  acetabulum,  in  front  and  behind  by  the  anterior  and  posterior  borders. 
This  surface  is  crossed  in  an  arched  direction  by  three  lines — the  posterior,  anterior, 
and  inferior  gluteal  lines.  The  posterior  gluteal  line  (superior  curved  line),  the  short- 
est of  the  three,  begins  at  the  crest,  about  5  cm.  in  front  of  its  posterior  extremity; 
it  is  at  first  distinctly  marked,  but  as  it  passes  downward  to  the  upper  part  of  the 
greater  sciatic  notch,  where  it  ends,  it  becomes  less  distinct,  and  is  often  altogether 
lost.  Behind  this  line  is  a  narrow  semilunar  surface,  the  upper  part  of  which 
is  rough  and  gives  origin  to  a  portion  of  the  Glutaeus  maximus ;  the  lower  part  is 
smooth  and  has  no  muscular  fibres  attached  to  it.  The  anterior  gluteal  line  (middle 
curved  line),  the  longest  of  the  three,  begins  at  the  crest,  about  4  cm.  behind  its 


334 


OSTEOLOGY 


anterior  extremity,  and,  taking  a  cnrved  direction  downward  and  backward,  ends 
at  the  upper  part  of  the  greater  sciatic  notch.  Tlie  space  lietween  the  anterior 
and  posterior  gkiteal  lines  and  the  crest  is  concave,  and  gives  origin  to  the  Glutaeus 
medius.  Near  the  middle  of  this  line  a  nutrient  foramen  is  often  seen.  The 
inferior  gluteal  line  {inferior  curved  line),  the  least  distinct  of  the  three,  begins  in 


Ant.  superior 
spine 


Posterior 

superior 

spine 


Posterior 
inferior 
spine 


*"  y^  /'__*^/    .,/  .      .V  I— Anterior  inferior  spine 
Articular  capsule 


Gemellus  superior 
Spine  of  ischium  - 


Gemellus  inferior 


Rectus 
abdomim's 

Pyramidalis 

Adductor 
longus 


Fig.  375. — Right  hip  bone.     External  surface. 

front  at  the  notch  on  the  anterior  border,  and,  curving  backward  and  downward, 
ends  near  the  middle  of  the  greater  sciatic  notch.  The  surface  of  bone  included 
between  the  anterior  and  inferior  gluteal  lines  is  concave  from  above  downward, 
convex  from  before  backward,  and  gives  origin  to  the  Glutaeus  minimus.  Between 
the  inferior  gluteal  line  and  the  upper  part  of  the  acetabulum  is  a  rough,  shallow 
groove,  from  w^hich  the  reflected  tendon  of  the  Rectus  femoris  arises. 


THE  HIP  BOXE 


335 


The  internal  surface  (Fig.  37G)  of  the  ahi  is  Ixjimded  al)ove  by  the  crest,  below, 
by  the  arcuate  line;  in  front  and  behind,  by  the  anterior  and  posterior  borders. 
It  presents  a  hirge,  smooth,  concave  surface,  ^-alled  the  iliac  fossa,  which  gives 
origin  to  the  lliacus  and  is  perforated  at  its  inner  part  by  a  nutrient  canal;  and 
below  this  a  smooth,  rounded  border,  the  arcuate  line,  which  runs  downward,  for- 
ward, and  mcdialward.    Behind  the  iliac  fossa  is  a  rough  surface,  divided  into  two 


Constrictor  iirethrae  /  \    „,  •       •  j? 

Transversus  perinaei  superjic. 

Crus  penis        Ischiocavernosus 
Fig.  376. — Right  hip  bone.     Internal  surface. 


portions,  an  anterior  and  a  posterior.  The  anterior  surface  (auricular  surface), 
so  called  from  its  resemblance  in  shape  to  the  ear,  is  coated  with  cartilage  in  the 
recent  state,  and  articulates  with  a  similar  surface  on  the  side  of  the  sacrum. 
The  posterior  portion,  known  as  the  iliac  tuberosity,  is  elevated  and  rough,  for 
the  attachment  of  the  posterior  sacroiliac  ligaments  and  for  the  origins  of  the 
Sacrospinalis  and  ^^lultifidus.     Below  and  in  front  of  the  auricular  surface  is  the 


336  OSTEOLOGY 

preauricular  sulcus,  more  commonly  present  and  better  marked  in  the  female 
than  in  the  male;  to  it  is  attached  the  pelvic  portion  of  the  anterior  sacroiliac 
ligament. 

The  crest  of  the  ilium  is  convex  in  its  general  outline  but  is  sinuously  curved, 
being  concave  inward  in  front,  concave  outward  behind.  It  is  thinner  at  the  centre 
than  at  the  extremities,  and  ends  in  the  anterior  and  posterior  superior  iliac  spines. 
The  surface  of  the  crest  is  broad,  and  divided  into  external  and  internal  lips, 
and  an  intermediate  line.  About  5  cm.  behind  the  anterior  superior  iliac  spine 
there  is  a  prominent  tubercle  on  the  outer  lip.  To  the  external  lip  are  attached 
the  Tensor  fasciae  latae,  Obliquus  externus  abdominis,  and  Latissimus  dorsi,  and 
along  its  whole  length  the  fascia  lata;  to  the  intermediate  line  the  Obliquus  internus 
abdominis;  to  the  internal  lip,  the  fascia  iliaca,  the  Transversus  abdominis, 
Quadratus  lumborum,  Sacrospinalis,  and  Iliacus. 

The  anterior  border  of  the  ala  is  concave.  It  presents  two  projections,  separated 
by  a  notch.  Of  these,  the  uppermost,  situated  at  the  junction  of  the  crest  and 
anterior  border,  is  called  the  anterior  superior  iliac  spine;  its  outer  border  gives 
attachment  to  the  fascia  lata,  and  the  Tensor  fasciae  latae,  its  inner  border,  to  the 
Iliacus;  while  its  extremity  affords  attachment  to  the  inguinal  ligament  and  gives 
origin  to  the  Sartorius.  Beneath  this  eminence  is  a  notch  from  which  the  Sartorius 
takes  origin  and  across  which  the  lateral  femoral  cutaneous  nerve  passes.  Below 
the  notch  is  the  anterior  inferior  iliac  spine,  which  ends  in  the  upper  lip  of  the 
acetabulum;  it  gives  attachment  to  the  straight  tendon  of  the  Rectus  femoris  and 
to  the  iliofemoral  ligament  of  the  hip-joint.  Medial  to  the  anterior  inferior  spine 
is  a  broad,  shallow  groove,  over  which  the  Iliacus  and  Psoas  major  pass.  This 
groove  is  bounded  medially  by  an  eminence,  the  iliopectineal  eminence,  which 
marks  the  point  of  union  of  the  ilium  and  pubis. 

The  posterior  border  of  the  ala,  shorter  than  the  anterior,  also  presents  two 
projections  separated  by  a  notch,  the  posterior  superior  iliac  spine  and  the  posterior 
inferior  iliac  spine.  The  former  serves  for  the  attachment  of  the  oblique  portion 
of  the  posterior  sacroiliac  ligaments  and  the  Multiiidus;  the  latter  corresponds 
with  the  posterior  extremity  of  the  auricular  surface.  Below  the  posterior  inferior 
spine  is  a  deep  notch,  the  greater  sciatic  notch. 

The  Ischium  {os  ischii). — The  ischium  forms  the  lower  and  back  part  of  the 
hip  bone.    It  is  divisible  into  three  portions — a  body  and  two  rami. 

The  Body  (corpus  oss.  ischii). — The  body  enters  into  and  constitutes  a  little 
more  than  two-fifths  of  the  acetabulum.  Its  external  surface  forms  part  of  the 
lunate  surface  of  the  acetabulum  and  a  portion  of  the  acetabular  fossa.  Its  internal 
surface  is  part  of  the  wall  of  the  lesser  pelvis;  it  gives  origin  to  some  fibres  of  the 
Obturator  internus.  Its  anterior  border  projects  as  the  posterior  obturator  tubercle; 
from  its  posterior  border  there  extends  backw^ard  a  thin  and  pointed  triangular 
eminence,  the  ischial  spine,  more  or  less  elongated  in  different  subjects.  The 
external  surface  of  the  spine  gives  attachment  to  the  Gemellus  superior,  its  internal 
surface  to  the  Coccygeus,  Levator  ani,  and  the  pelvic  fascia;  while  to  the  pointed 
extremity  the  sacrospinous  ligament  is  attached.  Above  the  spine  is  a  large  notch, 
the  greater  sciatic  notch,  converted  into  a  foramen  by  the  sacrospinous  ligament; 
it  transmits  the  Piriformis,  the  superior  and  inferior  gluteal  vessels  and  nerves, 
the  sciatic  and  posterior  femoral  cutaneous  nerves,  the  internal  pudendal  vessels, 
and  nerve,  and  the  nerves  to  the  Obturator  internus  and  Quadratus  femoris.  Of 
these,  the  superior  gluteal  vessels  and  nerve  pass  out  above  the  Piriformis,  the 
other  structures  below  it.  Below  the  spine  is  a  smaller  notch,  the  lesser  sciatic 
notch;  it  is  smooth,  coated  in  the  recent  state  w^ith  cartilage,  the  surface  of  which 
presents  two  or  three  ridges  corresponding  to  the  subdivisions  of  the  tendon  of 
the  Obturator  internus,  which  winds  over  it.  It  is  converted  into  a  foramen  by 
the  sacrotuberous  and  sacrospinous  ligaments,  and  transmits  the  tendon  of  the 


THE  II IP  BONE  337 

Obturator  internus,  the  nerve  which  sui)i)lies  that  muscle,  and  the  internal 
pudendal  ^'essels  and  nerve. 

The  Superior  Ramus  (ravtti^s  superior  oss.  ischii;  descending  ramus). — The 
superior  ramus  projects  downward  and  backward  from  the  body  and  presents 
for  examination  three  surfaces:  external,  internal,  and  posterior.  The  external 
surface  is  quadrilateral  in  shape.  It  is  bounded  above  by  a  groove  which  lodges 
the  tendon  of  the  Obturator  externus;  beloiv,  it  is  continuous  with  the  inferior 
ramus;  in  front  it  is  limited  by  the  posterior  margin  of  the  obturator  foramen; 
behind,  a  prominent  margin  separates  it  from  the  posterior  surface.  In  front  of 
this  margin  the  surface  gives  origin  to  the  Quadratus  femoris,  and  anterior  to  this 
to  some  of  the  fibres  of  origin  of  the  Obturator  externus;  the  lower  part  of  the  sur- 
face gives  origin  to  part  of  the  Adductor  magnus.  The  internal  surface  forms  part 
of  the  bony  wall  of  the  lesser  pelvis.  In  front  it  is  limited  by  the  posterior  margin 
of  the  obturator  foramen.  Below,  it  is  bounded  by  a  sharp  ridge  which  gives 
attachment  to  a  falciform  prolongation  of  the  sacrotuberous  ligament,  and,  more 
anteriorly,  gives  origin  to  the  Transversus  perinaei  and  Ischiocavernosus.  Poste- 
riorly the  ramus  forms  a  large  sw^elling,  the  tuberosity  of  the  ischium,  w^hich  is  divided 
into  two  portions :  a  loW' er,  rough,  somewhat  triangular  part,  and  an  upper,  smooth, 
quadrilateral  portion.  The  lower  portion  is  subdivided  by  a  prominent  longitudinal 
ridge,  passing  from  base  to  apex,  into  two  parts;  the  outer  gives  attachment  to 
the  Adductor  magnus,  the  inner  to  the  sacrotuberous  ligament.  The  upper  portion 
is  subdivided  into  two  areas  by  an  oblique  ridge,  which  runs  dow^nward  and  out- 
ward ;  from  the  upper  and  outer  area  the  Semimembranosus  arises ;  from  the  lower 
and  inner,  the  long  head  of  the  Biceps  femoris  and  the  Semitendinosus. 

The  Inferior  Ramus  {ramus  inferior  oss.  ischii;  ascending  ramus). — The  inferior 
ramus  is  the  thin,  flattened  part  of  the  ischium,  which  ascends  from  the  superior 
ramus,  and  joins  the  inferior  ramus  of  the  pubis — the  junction  being  indicated  in 
the  adult  by  a  raised  line.  The  outer  surface  is  uneven  for  the  origin  of  the  Obturator 
externus  and  some  of  the  fibres  of  the  Adductor  magnus;  its  inner  surface  forms 
part  of  the  anterior  wall  of  the  pelvis.  Its  medial  border  is  thick,  rough,  slightly 
everted,  forms  part  of  the  outlet  of  the  pelvis,  and  presents  two  ridges  and  an 
intervening  space.  The  ridges  are  continuous  with  similar  ones  on  the  inferior 
ramus  of  the  pubis :  to  the  outer  is  attached  the  deep  layer  of  the  superficial  peri- 
neal fascia  {fascia  of  Colles),  and  to  the  inner  the  inferior  fascia  of  the  urogenital 
diaphragm.  If  these  two  ridges  be  traced  downward,  they  will  be  found  to  join 
with  each  other  just  behind  the  point  of  origin  of  the  Transversus  perinaei;  here 
the  two  layers  of  fascia  are  continuous  behind  the  posterior  border  of  the  muscle. 
To  the  intervening  space,  just  in  front  of  the  point  of  junction  of  the  ridges,  the 
Transversus  perinaei  is  attached,  and  in  front  of  this  a  portion  of  the  crus  penis 
vel  clitoridis  and  the  Ischiocavernosus.  Its  lateral  border  is  thin  and  sharp,  and 
forms  part  of  the  medial  margin  of  the  obturator  foramen. 

The  Pubis  {os  2)ubis). — The  pubis,  the  anterior  part  of  the  hip  bone,  is  divisible 
into  a  body,  a  superior  and  an  inferior  ramus. 

The  Body  {corpus  oss.  pubis). — The  body  forms  one-fifth  of  the  acetabulum, 
contributing  by  its  external  surface  both  to  the  lunate  surface  and  the  acetabular 
fossa.  Its  internal  surface  enters  into  the  formation  of  the  wall  of  the  lesser  pelvis 
and  gives  origin  to  a  portion  of  the  Obturator  internus. 

The  Superior  Ramus  {ramus  superior  oss.  jjubis;  ascending  ramus). — The  superior 
ramus  extends  from  the  body  to  the  median  plane  where  it  articulates  with  its 
fellow  of  the  opposite  side.  It  is  conveniently  described  in  two  portions,  viz.,  a 
medial  flattened  part  and  a  narrow  lateral  prismoid  portion. 

The  Medial  Portion  of  the  superior  ramus,  formerly  described  as  the  body  of 
the  pubis,  is  somewhat  quadrilateral  in  shape,  and  presents  for  examination  two 
surfaces  and  three  borders.  The  anterior  surface  is  rough,  directed  downward  and 
22 


338  ^  OSTEOLOGY 

outward,  and  serves  for  the  origin  of  various  muscles.  The  Adductor  longus  arises 
from  the  upper  and  medial  angle,  immediately  below  the  crest;  lower  down,  the 
Obturator  externus,  the  Adductor  brevis,  and  the  upper  part  of  the  Gracilis  take 
origin.  The  posterior  surface,  convex  from  above  downward,  concave  from  side 
to  side,  is  smooth,  and  forms  part  of  the  anterior  wall  of  the  pelvis.  It  gives  origin 
to  the  Levator  ani  and  Obturator  internus,  and  attachment  to  the  puboprostatic 
ligaments  and  to  a  few  muscular  fibres  prolonged  from  the  bladder.  The  upper 
border  presents  a  prominent  tubercle,  the  pubic  tubercle  {puhic  sjnne),  which  j^ro- 
jects  forward;  the  inferior  crus  of  the  subcutaneous  inguinal  ring  (external  abdominal 
ring),  and  the  inguinal  ligament  {Pouparfs  Ugament)  are  attached  to  it.  Passing 
upward  and  lateralward  from  the  pubic  tubercle  is  a  well-defined  ridge,  forming 
a  part  of  the  pectineal  line  which  marks  the  brim  of  the  lesser  pelvis:  to  it  are 
attached  a  portion  of  the  inguinal  falx  (conjoined  tendon  of  Ohliquus  internus 
and  Transversus),  the  lacunar  ligament  (Gimbeniafs  ligament),  and  the  reflected 
inguinal  ligament  (triangular  fascia).  Medial  to  the  pubic  tubercle  is  the  crest, 
which  extends  from  this  process  to  the  medial  end  of  the  bone.  It  affords  attach- 
ment to  the  inguinal  falx,  and  to  the  Rectus  abdominis  and  Pyramidalis.  The 
point  of  junction  of  the  crest  with  the  medial  border  of  the  bone  is  called  the  angle ; 
to  it,  as  well  as  to  the  symphysis,  the  superior  crus  of  the  subcutaneous  inguinal 
ring  is  attached.  The  medial  border  is  articular;  it  is  oval,  and  is  marked  by  eight 
or  nine  transverse  ridges,  or  a  series  of  nipple-like  processes  arranged  in  rows, 
separated  by  grooves;  they  serve  for  the  attachment  of  a  thin  layer  of  cartilage, 
which  intervenes  between  it  and  the  interpubic  fibrocartilaginous  lamina.  The 
lateral  border  presents  a  sharp  margin,  the  obturator  crest,  which  forms  part  of  the 
circumference  of  the  obturator  foramen  and  affords  attachment  to  the  obturator 
membrane. 

The  Lateral  Portion  of  the  ascending  ramus  has  three  surfaces :  superior,  inferior, 
and  posterior.  The  superior  surface  presents  a  continuation  of  the  pectineal  line, 
already  mentioned  as  commencing  at  the  pubic  tubercle.  In  front  of  this  line,  the 
surface  of  bone  is  triangular  in  form,  wider  laterally  than  medially,  and  is  covered 
by  the  Pectineus.  The  surface  is  bounded,  laterally,  by  a  rough  eminence,  the 
iliopectineal  eminence,  which  serves  to  indicate  the  point  of  junction  of  the  ilium 
and  pubis,  and  below  by  a  prominent  ridge  which  extends  from  the  acetabular 
notch  to  the  pubic  tubercle.  The  inferior  surface  forms  the  upper  boundary  of 
the  obturator  foramen,  and  presents,  laterally,  a  broad  and  deep,  oblique  groove, 
for  the  passage  of  the  obturator  vessels  and  nerve;  and  medially,  a  sharp  margin, 
the  obturator  crest,  forming  part  of  the  circumference  of  the  obturator  foramen, 
and  giving  attachment  to  the  obturator  membrane.  The  posterior  surface  consti- 
tutes part  of  the  anterior  boundary  of  the  lesser  pelvis.  It  is  smooth,  convex  from 
above  downward,  and  affords  origin  to  some  fibres  of  the  Obturator  internus. 

The  Inferior  Ramus  (ramus  inferior  oss.  pubis;  descending  ramns) . — The  inferior 
ramus  is  thin  and  flattened.  It  passes  lateralward  and  downward  from  the  medial 
end  of  the  superior  ramus;  it  becomes  narrower  as  it  descends  and  joins  with  the 
inferior  ramus  of  the  ischium  below  the  obturator  foramen.  Its  anterior  surface 
is  rough,  for  the  origin  of  muscles — the  Gracilis  along  its  medial  border,  a  portion 
of  the  Obturator  externus  where  it  enters  into  the  formation  of  the  obturator 
foramen,  and  between  these  two,  the  Adductores  brevis  and  magnus,  the  former 
being  the  more  medial.  The  posterior  surface  is  smooth,  and  gives  origin  to  the 
Obturator  internus,  and,  close  to  the  medial  margin,  to  the  Constrictor  urethrae. 
The  medial  border  is  thick,  rough,  and  everted,  especially  in  females.  It  presents 
two  ridges,  separated  by  an  intervening  space.  The  ridges  extend  dow^nward,  and 
are  continuous  with  similar  ridges  on  the  inferior  ramus  of  the  ischium;  to  the 
external  is  attached  the  fascia  of  Colles,  and  to  the  internal  the  inferior  fascia  of 
the  urogenital  diaphragm.     The  lateral  border  is  thin  and  sharp,  forms  part  of  the 


THE  II I r  BOSK 


339 


circumference  of  the  obturator  forauKMi,  aud  uixcs  attachment  to  the  ol)turator 
nuMnlirauc. 

The  Acetabulum  (cofi/lold  caiutij).-  The  acetabiihuu  is  a  deep,  cup-.shai)e(l,  hemi- 
spherical depression,  directed  downward,  hiteralward,  and  forward.  It  is  formed 
medially  by  the  pubis,  above  by  the  ilium,  laterally  and  below  by  the  ischium; 
a  little  less  than  two-fifths  is  contributed  by  the  ilium,  a  little  more  than  two- 
fifths  by  the  ischium,  and  the  remaininii;  fifth  by  the  pubis.  It  is  bounded  by  a 
prominent  uneven  rim,  which  is  thick  and  stronji;  above,  and  serves  for  the  attach- 
ment of  the  glenoidal  labrum  [cotyluid  ligament) ,  which  contracts  its  orifice,  and 
deepens  the  surface  for  articulation.  It  presents  below  a  deep  notch,  the  acetabular 
notch,  which  is  continuous  with  a  circular  non-articular  depression,  the  acetabular 
fossa,  at  the  bottom  of  the  cavity:  this  depression  is  perforated  by  numerous 
apertures,  and  lodges  a  mass  of  fat.  The  notch  is  converted  into  a  foramen  by 
the  transverse  ligament;  through  the  foramen  nutrient  vessels  and  nerves  enter 
the  joint;  the  margins  of  the  notch  serve  for  the  attachment  of  the  ligamentum 
teres.  The  rest  of  the  acetabulum  is  formed  by  a  curved  articular  surface,  the 
lunate  surface,  for  articulation  with  the  head  of  the  femur. 


j3         7  ,        ,       \  Three  primani  (Ilium,  Ischiwrn,  and  Picbis) 
By  eiqlit  centres      it  ,    -^  ^  ' 

^     ■>  I  i  ive  secondary 


C  >■  (  s  ^ 


Fig.  37/ 


-Plan  of  ossification  of  the  hip  bone.     The  three  primary  centres  unite  through  a  Y-shaped  piece  about 
puberty.     Epiphyses  appear  about  puberty,  and  unite  about  twenty-fifth  year. 


The  Obturator  Foramen  {joramen  obturatum;  thyroid  foramen). — The  obturator 
foramen  is  a  large  aperture,  situated  between  the  ischium  and  pubis.  In  the  male 
it  is  large  and  of  an  oval  form,  its  longest  diameter  slanting  obliquely  from  before 
backward;  in  the  female  it  is  smaller,  and  more  triangular.  It  is  bounded  by  a 
thin,  uneven  margin,  to  which  a  strong  membrane  is  attached,  and  presents, 
superiorly,  a  deep  groove,  the  obturator  groove,  which  runs  from  the  pelvis  obliquely 
medial  ward  and  downward.  This  groove  is  converted  into  a  canal  by  a  ligamentous 
band,  a  specialized  part  of  the  obturator  membrane,  attached  to  tw^o  tubercles: 
one,  the  posterior  obturator  tubercle,  on  the  medial  border  of  the  ischium,  just  in 
front  of  the  acetabular  notch;  the  other,  the  anterior  obturator  tubercle,  on  the 


340  OSTEOLOGY 

obturator  crest   of  the  superior  ramus   of  the   pubis.     Through   the   canal   the 
obturator  vessels  and  nerve  pass  out  of  the  pelvis. 

Structure. — The  thicker  parts  of  the  bone  consist  of  cancellous  tissue,  enclosed  between  two 
layers  of  compact  tissue;  the  thinner  parts,  as  at  the  bottom  of  the  acetabulum  and  centre  of 
the  iliac  fossa,  are  usually  semitransparent,  and  composed  entirely  of  compact  tissue. 

Ossification  (Fig.  377). — The  Mp  bone  is  ossified  from  eight  centres:  three  primaiy — one  each 
for  the  ilium,  ischimn,  and  pubis;  and  five  secondary — one  each  for  the  crest  of  the  ilium,  the 
anterior  inferior  spine  (said  to  occur  more  frequently  in  the  male  than  in  the  female),  the  tuberosity 
of  the  ischium,  the  pubic  symphysis  (more  frequent  in  the  female  than  in  the  male),  and  one  or 
more  for  the  Y-shaped  piece  at  the  bottom  of  the  acetabulum.  The  centres  appear  in  the  follow- 
ing order:  in  the  lower  part  of  the  iUum,  immediately  above  the  greater  sciatic  notch,  about 
the  eighth  or  ninth  week  of  fetal  life;  in  the  superior  ramus  of  the  ischium,  about  the  third  month; 
in  the  superior  ramus  of  the  pubis,  between  the  fom'th  and  fifth  months.  At  birth,  the  three 
primary  centres  are  quite  separate,  the  crest,  the  bottom  of  the  acetabulum,  the  ischial  tuberosity, 
and  the  inferior  rami  of  the  ischium  and  pubis  being  still  cartilaginous.  By  the  seventh  or  eighth 
year,  the  inferior  rami  of  the  pubis  and  ischium  are  almost  completely  united  by  bone.  About 
the  thirteenth  or  fourteenth  year,  the  three  primary  centres  have  extended  their  growth  into  the 
bottom  of  the  acetabulum,  and  are  there  separated  from  each  other  by  a  Y-shaped  portion  of 
cartilage,  which  now  presents  traces  of  ossification,  often  by  two  or  more  centres.  One  of  these, 
the  OS  acetahuU,  appears  about  the  age  of  twelve,  between  the  ihum  and  pubis,  and  fuses  with  them 
about  the  age  of  eighteen;  it  forms  the  pubic  part  of  the  acetabulum.  The  ilium  and  ischium 
then  become  joined,  and  lastly  the  pubis  and  ischium,  through  the  intervention  of  this  Y-shaped 
portion.  At  about  the  age  of  puberty,  ossification  takes  place  in  each  of  the  remaining  portions, 
and  they  join  with  the  rest  of  the  bone  between  the  twentieth  and  twenty-fifth  years.  Separate 
centres  are  frequently  found  for  the  pubic  tubercle  and  the  ischial  spine,  and  for  the  crest  and 
angle  of  the  pubis. 

Articulations. — The  hip  bone  articulates  with  its  fellow  of  the  opposite  side,  and  with  the 
sacrum  and  femur. 

The  Pelvis. 

The  pelvis,  so  called  from  its  resemblance  to  a  basin,  is  a  bony  ring,  interposed 
between  the  movable  vertebrse  of  the  vertebral  column  which  it  supports,  and  the 
lower  limbs  upon  which  it  rests;  it  is  stronger  and  more  massively  constructed 
than  the  wall  of  the  cranial  or  thoracic  cavities,  and  is  composed  of  four  bones: 
the  two  hip  bones  laterally  and  in  front  and  the  sacrum  and  coccyx  behind. 

The  pelvis  is  divided  by  an  oblique  plane  passing  through  the  prominence  of 
the  sacrum,  the  arcuate  and  pectineal  lines,  and  the  upper  margin  of  the  symphysis 
pubis,  into  the  greater  and  the  lesser  pelvis.  The  circumference  of  this  plane  is 
termed  the  linea  terminalis  or  pelvic  brim. 

The  Greater  or  False  Pelvis  {pelvis  major) . — The  greater  pelvis  is  the  expanded 
portion  of  the  cavity  situated  above  and  in  front  of  the  pelvic  brim.  It  is  bounded 
on  either  side  by  the  ilium;  in  front  it  is  incomplete,  presenting  a  wide  interval 
between  the  anterior  borders  of  the  ilia,  which  is  filled  up  in  the  recent  state  by 
the  parietes  of  the  abdomen ;  behind  is  a  deep  notch  on  either  side  between  the  ilium 
and  the  base  of  the  sacrum.  It  supports  the  intestines,  and  transmits  part  of  their 
weight  to  the  anterior  wall  of  the  abdomen. 

The  Lesser  or  True  Pelvis  (-pelvis  minor). — The  lesser  pelvis  is  that  part  of  the 
pelvic  cavity  which  is  situated  below  and  behind  the  pelvic  brim.  Its  bony  walls 
are  more  complete  than  those  of  the  greater  pelvis.  For  convenience  of  descrip- 
tion, it  is  divided  into  an  inlet  bounded  by  the  superior  circumference,  and  outlet 
bounded  by  the  inferior  circumference,  and  a  cavity. 

The  Superior  Circumference. — The  superior  circumference  forms  the  brim  of  the 
pelvis,  the  included  space  being  called  the  superior  aperture  or  inlet  (apertura  pelvis 
[minoris]  superior)  (Fig.  378).  It  is  formed  laterally  by  the  pectineal  and  arcuate 
lines,  in  front  by  the  crests  of  the  pubes,  and  behind  by  the  anterior  margin  of  the 
base  of  the  sacrum  and  sacrovertebral  angle.  The  superior  aperture  is  somewhat 
heart-shaped,  obtusely  pointed  in  front,  diverging  on  either  side,  and  encroached 
upon  behind  by  the  projection  forward  of  the  promontory  of  the  sacrum.    It  has 


THE  PELVIC 


341 


three  principal  diameters:  antero-])osteric)r,  trans\erse,  and  oblique.  The  antero- 
posterior or  conjugate  diameter  extends  from  the  sacrovertebral  angle  to  the  sym- 
physis pubis;  its  average  measurement  is  about  110  mm.  in  the  female.  The 
transverse  diameter  extends  across  the  greatest  width  of  the  superior  aperture, 
from  the  middle  of  the  brim  on  one  side  to  the  same  point  on  the  opposite;  its  aver- 
age measurement  is  about  135  mm.  in  the  female.  The  oblique  diameter  extends 
from  the  iliopectineal  eminence  of  one  side  to  the  sacroiliac  articulation  of  the 
opposite  side;  its  average  measurement  is  about  125  mm.  in  the  female 


Fig.  378. — Diameters  of  superior  aperture  of  lesser  pelvis  (female). 


The  cavity  of  the  lesser  pelvis  is  bounded  in  front  and  below  by  the  pubic  sym- 
physis and  the  superior  rami  of  the  pubes;  above  and  behind,  by  the  pelvic  surfaces 
of  the  sacrum  and  coccjrx,  which,  curving  forward  above  and  below,  contract 
the  superior  and  inferior  apertures  of  the  ca^•ity;  laterally,  by  a  broad,  smooth, 
quadrangular  area  of  bone,  corresponding  to  the  inner  surfaces  of  the  body  and 
superior  ramus  of  the  ischium  and  that  part  of  the  ilium  which  is  below  the  arcuate 
line.  From  this  description  it  will  be  seen  that  the  cavity  of  the  lesser  pelvis 
is  a  short,  curved  canal,  considerably  deeper  on  its  posterior  than  on  its  anterior 
wall.  It  contains,  in  the  recent  subject,  the  pelvic  colon,  rectum,  bladder,  and  some 
of  the  organs  of  generation.  The  rectum  is  placed  at  the  back  of  the  pelvis,  in 
the  curve  of  the  sacrum  and  coccyx;  the  bladder  is  in  front,  behind  the  pubic  sym- 
physis. In  the  female,  the  uterus  and  vagina  occupy  the  interval  between  these 
viscera. 

The  Lower  Circumference. — The  lower  circumference  of  the  pelvis  is  very  irregular; 
the  space  enclosed  by  it  is  named  the  inferior  aperture  or  outlet  {apertura  pelns 
[minoris]  inferior)  (Fig.  379),  and  is  bounded  behind  by  the  point  of  the  coccj'x, 
and  laterally  by  the  ischial  tuberosities.  These  eminences  are  separated  by  three 
notches:  one  in  front,  the  pubic  arch,  formed  by  the  convergence  of  the  inferior 
rami  of  the  ischium  and  pubis  on  either  side.  The  other  notches,  one  on  either 
side,  are  formed  by  the  sacrum  and  coccyx  behind,  the  iscliium  in  front,  and 
the  ilium  above;  they  are  called  the  sciatic  notches;  in  the  natural  state  they  are 
converted  into  foramina  by  the  sacrotuberous  and  sacrospinous  ligaments.  ^Mien 
the  ligaments  are  in  situ,  the  inferior  aperture  of  the  pelvis  is  lozenge-shaped, 
bounded,  in  front,  by  the  pubic  arcuate  ligament  and  the  inferior  rami  of  the 
pubes  and  ischia;  laterally,  by  the  ischial  tuberosities;  and  behind,  by  the  sacro- 
tuberous ligaments  and  the  tip  of  the  coccjtj. 


342 


OSTEOLOGY 


The  diameters  of  tlie  outlet  of  the  pel\-is  are  two,  autero-posterior  and  trans- 
verse. The  antero-posterior  diameter  extends  from  the  tip  of  the  coecyx  to  the 
lower  part  of  the  pubic  symphysis;  its  measurement  is  from  90  to  115  mm.  in  the 
female.  It  varies  with  the  length  of  the  coccyx,  and  is  capable  of  increase  or 
diminution,  on  account  of  the  mobility  of  that  bone.  The  transverse  diameter, 
measured  between  the  posterior  parts  of  the  ischial  tuberosities,  is  about  115  mm. 
in  the  female.^ 


Fig.  379. — Diameters  of  inferior  aperture  of  lesser  pelvis  (female). 


Axes  (Fig.  .380). — A  line  at  right  angles  to  the  plane  of  the  superior  aperture 
at  its  centre  would,  if  prolonged,  pass  through  the  umbilicus  above  and  the  middle 

of  the  coccyx  below;  the  axis  of  the  superior  aperture 
is  therefore  directed  downward  and  backward.  The 
axis  of  the  inferior  aperture,  produced  upward,  would 
touch  the  base  of  the  sacrum,  and  is  also  directed 
downward,  and  slightly  backward.  The  axis  of  the 
cavity — i.  e.,  an  axis  at  right  angles  to  a  series  of 
planes  betweeii  those  of  the  superior  and  inferior 
apertures — is  curved  like  the  cavity  itself:  this  curve 
corresponds  to  the  concavity  of  the  sacrum  and 
coccyx,  the  extremities  being  indicated  by  the  central 
points  of  the  superior  and  inferior  apertures.  A 
knowledge  of  the  direction  of  these  axes  serves  to 
explain  the  course  of  the  fetus  in  its  passage  through 
the  pelvis  during  parturition. 

Position  of  the  Pelvis  (Fig.  380). — In  the  erect 
posture,  the  pelvis  is  placed  obliquely  with  regard 
to  the  trunk:  the  plane  of  the  superior  aperture 
forms  an  angle  of  from  50°  to  60°,  and  that  of  the 
inferior  aperture  one  of  about  15°  with  the  horizontal 
plane.  The  pelvic  surface  of  the  symphysis  pubis 
looks  upward  and  backward,  the  concavity  of  the 
sacrum  and  coccyx  downward  and  forward.  The  position  of  the  pelvis  in  the  erect 
posture  may  be  indicated  by  holding  it  so  that  the  anterior  superior  iliac  spines 
and  the  front  of  the  top  of  the  symphysis  pubis  are  in  the  same  vertical  plane. 


Fig.  380. 


-Median  sagittal  section  of 
pelvis. 


'  The  measurements  of  the  pelvis  given  above  are  fairly  accurate,  but  different  figures  are  given  by  various  authors 
no  doubt  due  mainly  to  differences  in  the  physique  and  stature  of  the  population  from  whom  the  measurements  have 
been  taken. 


THE  r/'JLV/S 


343 


Differences  between  the  Male  and  Female  Pelves.  -Flie  feiualc  pelvis  (Fig. 
382)  is  distinguished  from  that  of  the  male  (Fig.  'ASl)  l)y  its  bones  being  more 
delicate  and  its  <lei)th  less.     The  whole  peKis  is  less  niassi\'e,  and  its  muscular 


Fig.   3S1. — Male  pelvis. 


impressions  are  slightly  marked.  The  ilia  are  less  sloped,  and  the  anterior  iliac 
spines  more  widely  separated;  hence  the  greater  lateral  prominence  of  the  hips. 
The  preauricular  sulcus  is  more  commonly  present  and  better  marked.    The  supe- 


FiG.  382. — Female  pelvis. 


rior  aperture  of  the  lesser  pelvis  is  larger  in  the  female  than  in  the  male;  it  is  more 
nearly  circular,  and  its  obliquity  is  greater.  The  cavity  is  shallower  and  wider; 
the  sacrum  is  shorter,  wider,  and  its  upper  part  is  less  curved;    the  obturator 


344  OSTEOLOGY 

foramina  are  triangular  in  shape  and  smaller  in  size  than  in  the  male.  The  inferior 
aperture  is  larger  and  the  coccyx  more  movable.  The  sciatic  notches  are  wider 
and  shallower,  and  the  spines  of  the  ischia  project  less  inward.  The  acetabula 
are  smaller  and  look  more  distinctly  forward  (Derry^).  The  ischial  tuberosities 
and  the  acetabula  are  wider  apart,  and  the  former  are  more  everted.  The  pubic 
symphysis  is  less  deep,  and  the  pubic  arch  is  wider  and  more  rounded  than  in  the 
male,  where  it  is  an  angle  rather  than  an  arch. 

The  size  of  the  pelvis  varies  not  only  in  the  two  sexes,  but  also  in  different 
members  of  the  same  sex,  and  does  not  appear  to  be  influenced  in  any  way  by  the 
height  of  the  individual.  Women  of  short  stature,  as  a  rule,  have  broad  pelves. 
Occasionally  the  pelvis  is  equally  contracted  in  all  its  dimensions,  so  much  so 
that  all  its  diameters  measure  12.5  mm.  less  than  the  average,  and  this  even  in 
well-formed  women  of  average  height.  The  principal  divergences,  however,  are 
found  at  the  superior  aperture,  and  affect  the  relation  of  the  antero-posterior 
to  the  transverse  diameter.  Thus  the  superior  aperture  may  be  elliptical  either 
in  a  transverse  or  an  antero-posterior  direction,  the  transverse  diameter  in  the 
former,  and  the  antero-posterior  in  the  latter,  greatly  exceeding  the  other  diameters; 
in  other  instances  it  is  almost  circular. 

In  the  foetus,  and  for  several  years  after  birth,  the  pelvis  is  small  in  proportion 
to  that  of  the  adult,  and  the  projection  of  the  sacrovertebral  angle  less  marked. 
The  characteristic  differences  between  the  male  and  female  pelvis  are  distinctly 
indicated  as  early  as  the  fourth  month  of  fetal  life. 

Applied  Anatomy. — There  is  arrest  of  development  in  the  bones  of  the  pelvis  in  cases  of  extro- 
version of  the  bladder;  the  anterior  part  of  the  pelvic  girdle  is  deficient,  the  superior  rami  of 
the  pubes  are  imperfectly  developed,  and  the  symphysis  is  absent.  "The  pubic  bones  are  sepa- 
rated to  the  extent  of  from  two  to  fom-  inches,  the  superior  rami  shortened  and  directed  forward, 
and  the  obturator  foramen  diminished  in  size,  narrowed,  and  turned  outward.  The  iliac  bones 
are  straightened  out  more  than  normal.  The  sacrum  is  xery  pecuhar.  The  lateral  curve,  instead 
of  being  concave,  is  flattened  out  or  even  convex,  with  the  ihosacral  facets  turned  more  outward 
than  normal,  while  the  vertical  curve  is  straightened. "- 

Fractures  of  the  pelvis  are  divided  into  those  of  the  greater  and  those  of  the  lesser  pehis. 
Fractures  of  the  greater  pelvis  vary  in  extent;  a  small  portion  of  the  crest  may  be  broken,  or  one 
of  the  spinous  processes  may  be  torn  off,  or  the  bone  may  be  extensively  comminuted.  This 
latter  accident  is  the  result  of  some  crushing  violence,  and  may  be  complicated  with  fracture 
of  the  lesser  pelvis.  These  cases  may  be  accompanied  by  injury  to  the  intestine  as  it  hes  in  the 
hollow  of  the  bone,  or  to  the  ihac  vessels  as  they  course  along  the  margin  of  the  lesser  pelvis. 
A  fracture  of  the  lesser  pelvis  generally  occurs  through  the  superior  ramus  of  the  pubis  and  the 
inferior  ramus  of  the  ischium,  as  these  are  the  weakest  parts  of  the  bony  ring,  and  may  be  caused 
either  bj'  crushing  violence  apphed  in  an  antero-posterior  direction,  when  the  fracture  occurs 
from  direct  force,  or  by  compression  laterally,  when  the  acetabula  are  pressed  together  and  the 
bone  gives  way  in  the  same  place  from  indirect  violence.  Sometimes  both  sides  of  the  pelvis 
are  fractured,  and  it  is  in  these  cases  that  the  contained  viscera  are  likely  to  be  injured:  the 
urethra,  the  bladder,  the  rectum,  the  small  intestines,  the  vagina,  and  even  the  uterus,  have  all 
been  lacerated  by  displaced  fragments.  Fractures  of  the  acetabulum  are  occasionally  met  with; 
either  a  portion  of  the  rim  may  be  broken  off,  or  a  fracture  may  take  place  through  the  bottom 
of  the  cavity,  and  the  head  of  the  femur  be  driven  into  the  pelvic  cavity.  Separation  of  the 
Y-shaped  cartilage  at  the  bottom  of  the  acetabulum  may  also  occur  in  the  young  subject,  splitting 
the  bone  into  its  three  portions. 

The  coccyx  is  not  infrequently  displaced  forward  to  nearly  a  right  angle  with  the  sacrum  by 
a  kick  or  by  a  fall  backward.  The  condition  is  attended  with  great  pain  in  walking  and  on  mak- 
ing any  expiratory  effort,  such  as  coughing;  defecation,  etc.,  because  the  Coccygei  and  Levatores 
ani  which  form  the  pelvic  diaphragm  are  attached  to  this  bone.  Such  injuries  often  give  rise  to 
severe  persistent  pain,  which  is  exceedinglj^  intractable  and  difficult  of  cure.  The  condition  is 
known  as  coccygodynia  and  for  its  reUef  removal  of  the  coccyx  has  been  practised. 

The  pelvic  bones  often  undergo  important  deformity  in  rickets,  the  effects  of  which  in  the 
adult  woman  may  interfere  seriou.sly  with  child-bearing.  The  deformity  is  due  mainly  to  the 
weight  of  the  trunk,  which  presses  on  the  sacrovertebral  angle  and  greatlj'  increases  it,  so  that 
the  antero-posterior  diameter  of  the  pelvis  is  diminished,  and  may  measm-e  as  httle  as  40  mm., 

1  Journal  of  Anatomy  and  Physiology,  vol.  xliii. 

2  Wood,  Heath's  Dictionary  of  Practical  Surger>%  i,  426. 


THE  FEMUR 


345 


the  entrance  into  the  pelvis  becoming  reniform.  lu  other  cases  all  the  pelvic  bones  give  way, 
so  that  a  general  diminution  in  all  the  diameters  of  the  pelvis  results,  the  pelvic  entrance  becom- 
ing triangular  or  asj^mmetrical.  If  the  i)ubic  symphysis  be  forced  forward,  the  rickety  pelvis 
maj'  even  come  to  resemble  closely  the  deformed  j:)clvis  of  osteomalacia;  in  this  disease  the  weight 
of  the  trunk  causes  an  increase  in  the  sacrovertebral  angle,  and  a  lessening  of  the  antero-posterior 
diameter  of  the  superior  aperture,  and  at  the  same  time  the  pressure  of  the  heads  of  the  femora 
on  the  acetabula  causes  these  cavities,  with  the  adjacent  bone,  to  be  pushed  upward  and  back- 
ward, so  that  the  oblique  diameters  of  the  pelvis  are  also  diminished,  and  the  cavity  of  the  pelvis 
assumes  a  triradiate  shape,  with  the  symphysis  pubis  pushed  forward. 

The  Femur  (Thigh  Bone). 

The  femur  (Figs.  384,  3S5),  the  longest  and  strongest  bone  in  the  skeleton,  is 
almost  perfectly  cylindrical  in  the  greater  part  of  its  extent.  In  the  erect  posture 
it  is  not  vertical,  being  separated  above  from  its  fellow  by  a  considerable  interval, 
which  corresponds  to  the  breadth  of  the  pelvis,  but  inclining  gradualli'  downward 
and  medialward,  so  as  to  approach  its  fellow  toward  its  lower  part,  for  the  purpose 
of  bringing  the  knee-joint  near  the  line  of  gravity  of  the  body.  The  degree  of  this 
inclination  varies  in  different  persons,  and  is  greater  in  the  female  than  in  the  male, 
on  account  of  the  greater  breadth  of  the  pelvis.  The  femur,  like  other  long  bones, 
is  divisible  into  a  body  and  two  extremities. 

Obturator  internus  cuid  Gemelli 

y  J    Pnifoimis 

X^'lj  j         Insertion  of  Obturator 

'~~  exiernus 


Fovea  capitis.  ^ 
for  lig,  teres 


■  Oixater  trochanter 


Lesser  trochanter . 


Fig.  383. — Upper  extremity  of  right  femur  viewed  from  behind  and  above. 


The  Upper  Extremity  {proximal  extremity,  Fig.  383). — The  upper  extremity 
presents  for  examination  a  head,  a  neck,  a  greater  and  a  lesser  trochanter. 

The  Head  (caput  femoris) . — The  head  which  is  globular  and  forms  rather  more 
than  a  hemisphere,  is  directed  upward,  medialward,  and  a  little  forward,  the  greater 
part  of  its  convexity  being  above  and  in  front.  Its  surface  is  smooth,  coated  with 
cartilage  in  the  recent  state,  except  over  an  ovoid  depression,  the  fovea  capitis 
femoris,  which  is  situated  a  little  below  and  behind  the  centre  of  the  head,  and  gives 
attachment  to  the  ligamentum  teres. 

The  Neck  {collum  femoris). — The  neck  is  a  flattened  pyramidal  process  of  bone, 
connecting  the  head  with  the  body,  and  forming  with  the  latter  a  wide  angle  open- 
ing medialward.  The  angle  is  widest  in  infancy,  and  becomes  lessened  during 
growth,  so  that  at  puberty  it  forms  a  gentle  curve  from  the  axis  of  the  body  of  the 
bone.  In  the  adult,  the  neck  forms  an  angle  of  about  125°  with  the  body,  but  this 
varies  in  inverse  proportion  to  the  development  of  the  pelvis  and  the  stature.    In- 


346 


OSTEOLOGY 


Ohluralor  internus 
and  Geiiielli 
Piriformis 


Tubercle 
Articular  capsule 


Medial 
^  ,1]      epicondyle 


Fig.  384. — Right  femur.     Anterior  surface. 


^^'^fe' 


the  female,  in  consequence  of  the 
increased  width  of  the  pelvis,  the 
neck  of  the  femur  forms  more 
nearly  a  right  angle  with  the  body 
than  it  does  in  the  male.  The 
angle  decreases  during  the  period 
of  growth,  but  after  full  growth  has 
been  attained  it  does  not  usually 
undergo  any  change,  even  in  old 
age;  it  varies  considerably  in  differ- 
ent persons  of  the  same  age.  It  is 
smaller  in  short  than  in  long  bones, 
and  when  the  pelvis  is  wide.  In 
addition  to  projecting  upward  and 
medialward  from  the  body  of  the 
femur,  the  neck  also  projects  some- 
what forward;  the  amount  of  this 
forward  projection  is  extremely 
variable,  but  on  an  average  is  from 
12°  to  14°. 

The  neck  is  flattened  from  before 
backward,  contracted  in  the  middle, 
and  broader  laterally  than  medially. 
The  vertical  diameter  of  the  lateral 
Ijalf  is  increased  by  the  obliquity  of 
the  lower  edge,  which  slopes  down- 
ward to  join  the  body  at  the  level 
of  the  lesser  trochanter,  so  that  it 
measures  one-third  more  than  the 
antero-posterior  diameter.  The 
medial  half  is  smaller  and  of  a 
more  circular  shape.  The  anterior 
surface  of  the  neck  is  perforated  by 
numerous  vascular  foramina.  Along 
the  upper  part  of  the  line  of  junc- 
tion of  the  anterior  surface  with 
the  head  is  a  shallow  groove,  best 
marked  in  elderly  subjects;  this 
groove  lodges  the  orbicular  fibres 
of  the  capsule  of  the  hip-joint. 
The  posterior  surface  is  smooth,  and 
is  broader  and  more  concave  than 
the  anterior:  the  posterior  part  of 
the  capsule  of  the  hip-joint  is 
attached  to  it  about  1  cm.  above 
the  intertrochanteric  crest.  The 
superior  border  is  short  and  thick, 
and  ends  laterally  at  the  greater 
trochanter;  its  surface  is  perforated 
by  large  foramina.  The  inferior 
border,  long  and  narrow,  curves  a 
little  backward,  to  end  at  the  lesser 
trochanter. 

The  Trochanters. — The  trochan- 
ters are  prominent  processes  which 


THE  FEMUR 


347 


att'ord  leverage  to  the  muscles 
that  rotate  the  thiuh  on  its  axis. 
They  are  two  in  number,  the 
greater  and  the  lesser. 

The  Greater  Trochanter  {tro- 
chanter DKtjor:  (jrcat  trnvhtutcr)  is 
a  large,  irregular,  (juadrilateral 
eminence,  situated  at  the  junc- 
tion of  the  neck  with  the  upper 
part  of  the  body.  It  is  directed  a 
little  laterahvard  and  backward, 
and,  in  the  adult,  is  about  1  cm. 
lower  than  the  head.  It  has 
two  surfaces  and  four  borders. 
The  lateral  surface,  quadrilateral 
in  form,  is  broad,  rough,  convex, 
and  marked  by  a  diagonal  im- 
pression, which  extends  from 
the  postero-superior  to  the 
antero-inferior  angle,  and  serves 
for  the  insertion  of  the  tendon 
of  the  Glutaeus  mediiis.  Above 
the  impression  is  a  triangular 
surface,  sometimes  rough  for 
part  of  the  tendon  of  the  same 
muscle,  sometimes  smooth  for 
the  interposition  of  a  bursa  be- 
tween the  tendon  and  the  bone. 
Below  and  behind  the  diagonal 
impression  is  a  smooth,  trian- 
gular surface,  over  which  the 
tendon  of  the  Glutaeus  maxi- 
mus  plays,  a  bursa  being  inter- 
posed. The  medial  surface,  of 
much  less  extent  than  the 
lateral,  presents  at  its  base  a 
deep  depression,  the  trochanteric 
fossa  {digital  fossa),  for  the  in- 
sertion of  the  tendon  of  the  Ob- 
turator externus,  and  above  and 
in  front  of  this  an  impression 
for  the  insertion  of  the  Obtura- 
tor internus  and  Gemelli.  The 
superior  border  is  free ;  it  is  thick 
and  irregular,  and  marked  near 
the  centre  by  an  impression  for 
the  insertion  of  the  Piriformis. 
The  inferior  border  corresponds 
to  the  line  of  junction  of  the 
base  of  the  trochanter  with  the 
lateral  surface  of  the  body;  it  is 
marked  by  a  rough,  prominent, 
slightly  curved  ridge,  which  gives 
origin  to  the  upper  part  of  the 
Vastus  lateralis.  The  anterior 
border   is  prominent   and  some- 


FiG.  385 


Articular 
capsule 
Right  femur. 


Posterior  surface. 


348  OSTEOLOGY 

what  irregular;  it  affords  insertion  at  its  lateral  part  to  the  Glutaeus  minimus. 
The  posterior  border  is  very  prominent  and  appears  as  a  free,  rounded  edge,  which 
bounds  the  back  part  of  the  trochanteric  fossa. 

The  Lesser  Trochanter  (trochanter  minor;  small  trochanter)  is  a  conical  eminence, 
which  varies  in  size  in  different  subjects;  it  projects  from  the  lower  and  back  part 
of  the  base  of  the  neck.  From  its  apex  three  well-marked  borders  extend;  two  of 
these  are  above — a  medial  continuous  with  the  lower  border  of  the  neck,  a  lateral 
with  the  intertrochanteric  crest;  the  inferior  border  is  continuous  with  the  middle 
division  of  the  linea  aspera.  The  summit  of  the  trochanter  is  rough,  and  gives 
insertion  to  the  tendon  of  the  Psoas  major. 

A  prominence,  of  variable  size,  occurs  at  the  junction  of  the  upper  part  of  the 
neck  with  the  greater  trochanter,  and  is  called  the  tubercle  of  the  femur;  it  is  the 
point  of  meeting  of  five  muscles:  the  Glutaeus  minimus  laterally,  the  Vastus 
lateralis  below,  and  the  tendon  of  the  Obturator  internus  and  two  Gemelli  above. 
Running  obliquely  downward  and  medialward  from  the  tubercle  is  the  intertro- 
chanteric line  (spiral  line  of  the  femur) ;  it  winds  around  the  medial  side  of  the  body 
of  the  bone,  below  the  lesser  trochanter,  and  ends  about  5  cm.  below  this  eminence 
in  the  linea  aspera.  Its  upper  half  is  rough,  and  affords  attachment  to  the  ilio- 
femoral ligament  of  the  hip-joint;  its  lower  half  is  less  prominent,  and  gives  origin 
to  the  upper  part  of  the  Vastus  medialis.  Running  obliquely  downward  and  medial- 
ward  from  the  summit  of  the  greater  trochanter  on  the  posterior  surface  of  the 
neck  is  a  prominent  ridge,  the  intertrochanteric  crest.  Its  upper  half  forms  the  pos- 
terior border  of  the  greater  trochanter,  and  its  lower  half  runs  downward  and 
medialward  to  the  lesser  trochanter.  A  slight  ridge  is  sometimes  seen  commencing 
about  the  middle  of  the  intertrochanteric  crest,  and  reaching  vertically  downward 
for  about  5  cm.  along  the  back  part  of  the  body:  it  is  called  the  linea  quadrata, 
and  gives  attachment  to  the  Quadratus  femoris  and  a  few  fibres  of  the  Adductor 
magnus.  Generally  there  is  merely  a  slight  thickening  about  the  middle  of 
the  intertrochanteric  crest,  marking  the  attachment  of  the  upper  part  of  the 
Quadratus  femoris. 

The  Body  or  Shaft  (corpus  femoris) . — The  body,  almost  cylindrical  in  form,  is 
a  little  broader  above  than  in  the  centre,  broadest  and  somewhat  flattened  from 
before  backward  below^  It  is  slightly  arched,  so  as  to  be  convex  in  front,  and  con- 
cave behind,  where  it  is  strengthened  by  a  prominent  longitudinal  ridge,  the  linea 
aspera.  It  presents  for  examination  three  borders,  separating  three  surfaces. 
Of  the  three  borders,  one,  the  linea  aspera,  is  posterior,  one  is  medial,  and  the 
other,  lateral. 

The  linea  aspera  (Fig.  385)  is  a  prominent  longitudinal  ridge  or  crest,  on  the 
middle  third  of  the  bone,  presenting  a  medial  and  a  lateral  lip,  and  a  narrow 
rough,  intermediate  line.  Above,  the  linea  aspera  is  prolonged  by  three  ridges. 
The  lateral  ridge  is  very  rough,  and  runs  almost  vertically  upward  to  the  base  of 
the  greater  trochanter.  It  is  termed  the  gluteal  tuberosity,  and  gives  attachment 
to  part  of  the  Glutaeus  maximus:  its  upper  part  is  often  elongated  into  a  roughened 
crest,  on  which  a  more  or  less  well-marked,  rounded  tubercle,  the  third  trochanter, 
is  occasionally  developed.  The  intermediate  ridge  or  pectineal  line  is  continued 
to  the  base  of  the  lesser  trochanter  and  gives  attachment  to  the  Pectineus;  the 
medial  ridge  is  lost  in  the  intertrochanteric  line;  between  these  two  a  portion  of  the 
Iliacus  is  inserted.  Below,  the  linea  aspera  is  prolonged  into  two  ridges,  enclosing 
between  them  a  triangular  area,  the  popliteal  surface,  upon  which  the  popliteal 
artery  rests.  Of  these  two  ridges,  the  lateral  is  the  more  prominent,  and  descends 
to  the  summit  of  the  lateral  condyle.  The  medial  is  less  marked,  especially  at  its 
upper  part,  where  it  is  crossed  by  the  femoral  artery.  It  ends  below  at  the  summit 
of  the  medial  condyle,  in  a  small  tubercle,  the  adductor  tubercle,  which  affords 
insertion  to  the  tendon  of  the  Adductor  magnus. 


THE  FEMUR 


349 


From  the  medial  lip  of  the  linea  aspera  and  its  proh:)ngations  above  and  below, 
the  Vastus  niedialis  arises;  and  from  tlie  lateral  lip  and  its  upward  prokjngation, 
the  Vastus  lateraHs  takes  origin.  The  Ad(kictor  magnus  is  inserted  into  the  hnea 
aspera,  and  to  its  hiteral  prolongation  above,  and  its  medial  prolongation  below. 
Between  the  Vastus  lateralis  and  the  Adductor  magnus  two  muscles  are  attached 
— viz..  the  Glutaeus  maximus  inserted  above,  and  the  short  head  of  the  Biceps 
femoris  arising  below.  Betweeen  the  Adductor  magnus  and  the  Vastus  medialis 
four  muscles  are  inserted:  the  Iliacus  and  Pectineus  above;  the  Adductor  brevis 
and  Adductor  longus  below.  The  linea  aspera  is  perforated  a  little  below  its  centre 
by  the  nutrient  canal,  which  is  directed  obliquely  upward. 

The  other  two  borders  of  the  femur  are  only  slightly  marked:  the  lateral  border 
extends  from  the  antero-inferior  angle  of  the  greater  trochanter  to  the  anterior 
extremity  of  the  lateral  cond}4e;  the  medial  border  from  the  intertrochanteric  line, 
at  a  point  opposite  the  lesser  trochanter,  to  the  anterior  extremity  of  the  medial 
condyle. 

The  anterior  surface  includes  that  portion  of  the  shaft  which  is  situated  between 
the  lateral  and  medial  borders.  It  is  smooth,  convex,  broader  above  and  below 
than  in  the  centre.  From  the  upper  three-fourths  of  this  surface  the  Vastus  inter- 
medins arises;  the  lower  fourth  is  separated  from  the  muscle  by  the  intervention 
of  the  synovial  membrane  of  the  knee-joint  and  a  bursa;  from  the  upper  part  of  it 
the  Articularis  genu  takes  origin.  The  lateral  surface  includes  the  portion  between 
the  lateral  border  and  the  linea  aspera ;  it  is  continuous  above  with  the  correspond- 
ing surface  of  the  greater  trochanter,  below  with  that  of  the  lateral  condyle :  from 
its  upper  three-fourths  the  Vastus  intermedins  takes  origin.  The  medial  surface 
includes  the  portion  between  the  medial  border  and  the  linea  aspera;  it  is  continu- 
ous above  with  the  lower  border  of  the  neck,  below  with  the  medial  side  of  the 
medial  condvle:  it  is  covered  bv  the  Vastus  medialis. 


Lateral  groove  — j 
Lateral  epicondyle 


Media  I  groove 


Medial  epicondyle 
ihHBH!     Semilunar  area 


Fig.  386. — Lower  extremity  of  right  femur  viewed  from  below. 


The  Lower  Extremity  (distal  extremity,  Fig.  386). — The  lower  extremity,  larger 
than  the  upper,  is  somewhat  cuboid  in  form,  but  its  transverse  diameter  is  greater 
than  its  antero-posterior;  it  consists  of  two  oblong  eminences  known  as  the  condyles. 
In  front,  the  condyles  are  but  slightly  prominent,  and  are  separated  from  one  another 
by  a  smooth  shallow  articular  depression  called  the  patellar  surface;  behind,  they 
project  considerably,  and  the  interval  between  them  forms  a  deep  notch,  the 
intercondyloid  fossa.  The  lateral  condyle  is  the  more  prominent  and  is  the  broader 
both  in  its  antero-posterior  and  transverse  diameters,  the  medial  condyle  is  the 
longer  and,  when  the  femur  is  held  with  its  body  perpendicular,  projects  to  a  lo\\'er 
level.  When,  however,  the  femur  is  in  its  natural  oblique  position  the  lower  sur- 
faces of  the  two  condyles  lie  practically  in  the  same  horizontal  plane.  The  condyles 
are  not  quite  parallel  with  one  another;  the  long  axis  of  the  lateral  is  almost 


350  OSTEOLOGY 

directly  aiitero-posterior,  but  that  of  the  medial  runs  backward  and  mediahvard. 
Their  opposed  surfaces  are  small,  rough,  and  concave,  and  form  the  walls  of  the 
intercondyloid  fossa.  This  fossa  is  limited  above  by  a  ridge,  the  intercondyloid 
line,  and  below  by  the  central  ])art  of  the  ])osterior  margin  of  the  patellar  surface. 
The  posterior  cruciate  ligament  of  the  knee-joint  is  attached  to  the  lower  and  front 
part  of  the  medial  wall  of  the  fossa  and  the  anterior  cruciate  ligament  to  an  ini])res- 
sion  on  the  upper  and  back  part  of  its  lateral  wall.  Each  condyle  is  surmounted 
by  an  elevation,  the  epicondyle.  The  medial  epicondyle  is  a  large  convex  eminence 
to  which  the  tibial  collateral  ligament  of  the  knee-joint  is  attached.  At  its  upper 
part  is  the  adductor  tubercle,  already  referred  to,  and  behind  it  is  a  rough  impres- 
sion which  gives  origin  to  the  medial  head  of  the  Gastrocnemius.  The  lateral 
epicondyle,  smaller  and  less  prominent  than  the  medial,  gives  attachment  to  the 
fibular  collateral  ligament  of  the  knee-joint.  Directly  below  it  is  a  small  depression 
from  which  a  smooth  well-marked  groo\e  curves  obliquely  upward  and  backward 
to  the  posterior  extremity  of  the  condyle.  This  groove  is  separated  from  the 
articular  surface  of  the  condyle  by  a  prominent  lip  across  which  a  second,  shallower 
groove  runs  vertically  downward  from  the  depression.  In  the  recent  state  these 
grooves  are  covered  with  cartilage.  The  Popliteus  arises  from  the  depression; 
its  tendon  lies  in  the  oblique  groove  when  the  knee  is  flexed  and  in  the  vertical 
groove  when  the  knee  is  extended.  Above  and  behind  the  lateral  epicondyle  is 
an  area  for  the  origin  of  the  lateral  head  of  the  Gastrocnemius,  above  and  to  the 
medial  side  of  which  the  Plantaris  arises. 

The  articular  surface  of  the  lower  end  of  the  femur  occupies  the  anterior,  inferior, 
and  posterior  surfaces  of  the  condyles.  Its  front  part  is  named  the  patellar  surface 
and  articulates  with  the  patella;  it  presents  a  median  groove  which  extends  down- 
ward to  the  intercondyloid  fossa  and  two  convexities,  the  lateral  of  which  is  broader, 
more  prominent,  and  extends  farther  upward  than  the  medial.  The  lower  and 
posterior  parts  of  the  articular  surface  constitute  the  tibial  surfaces  for  articulation 
with  the  corresponding  condyles  of  the  tibia  and  menisci.  These  surfaces  are 
separated  from  one  another  by  the  intercondyloid  fossa  and  from  the  patellar 
surface  by  faint  grooves  w^hich  extend  obliquely  across  the  condyles.  The  lateral 
groove  is  the  better  marked;  it  runs  lateralward  and  forward  from  the  front  part 
of  the  intercondyloid  fossa,  and  expands  to  form  a  triangular  depression.  When 
the  knee-joint  is  fully  extended,  the  triangular  depression  rests  upon  the  anterior 
portion  of  the  lateral  meniscus,  and  the  medial  part  of  the  groo\'e  comes  into  con- 
tact with  the  medial  margin  of  the  lateral  articular  surface  of  the  tibia  in  front 
of  the  lateral  tubercle  of  the  tibial  intercondyloid  eminence.  The  medial  groove 
is  less  distinct  than  the  lateral.  It  does  not  reach  as  far  as  the  intercondyloid 
fossa  and  therefore  exists  only  on  the  medial  part  of  the  condyle;  it  receives  the 
anterior  edge  of  the  medial  meniscus  when  the  knee-joint  is  extended.  Where  the 
groove  ceases  laterally  the  patellar  surface  is  seen  to  be  continued  backward  as 
a  semilunar  area  close  to  the  anterior  part  of  the  intercondyloid  fossa ;  this  semi- 
lunar area  articulates  with  the  medial  vertical  facet  of  the  patella  in  forced  flexion 
of  the  knee-joint.  The  tibial  surfaces  of  the  condyles  are  convex  from  side  to  side 
and  from  before  backward.  Each  presents  a  double  curve,  its  posterior  segment 
being  an  arc  of  a  circle,  its  anterior,  part  of  a  cycloid.^ 

Structure. — The  body  of  the  femur  is  a  cylinder  of  compact  tissue,  hollowed  by  a  large  medullary 
canal.  The  wall  of  the  cyUnder  is  of  great  thickness  and  density  in  the  middle  third  of  the  body, 
where  the  bone  is  narrowest  and  the  medullary  canal  best  formed;  but  above  and  below  this  the 
wall  becomes  thinner,  while  the  medullary  canal  is  gradually  filled  up  by  cancellous  tissue,  so 
that  the  upper  (Fig.  387j  and  lower  ends  of  the  body,  and  the  articular  extremities  more  especially, 
consist  of  cancellous  tissue,  invested  by  a  thin  compact  layer. 


line 


1  A  cycloid  is  a  cur^^e  traced  by  a  point  in  the  circumference  of  a  wheel  when  the  wheel  is  rolled  along  in  a  straight 


rilE  FEMUR 


351 


The  cancelli  in  the  ends  of  the  femur  are  disposc'd  along  the  Hnes  of  greatest  pressure  and 
tension.  In  the  upper  end  (Fig.  388)  the  chief  hunelhe  are  arranged  in  the  following  manner. 
A  series  of  Ijony  i)lanes  at  right  angles  to  the  articular  smrncc  of  the  head  converge  to  a  central 


fJpipliU-sail  line 


Fig.  387. — Longitudinal  section  of  head  and  neck  of  femur. 


dense  wedge,  which  presents  few  and  dense  cancelli.  The  w^edge  is  supported  by  strong  lamellae, 
which  extend  to  the  sides  of  the  neck  and  are  especially  marked  along  its  upper  and  lower  borders. 
Any  force  therefore  apphed  to  the  head  of  the  femur  is  transmitted  directly  to  the  central  wedge 
and  thence  to  the  junction  of  the  neck  with  the  body.  This 
junction  is  especially  strengthened  by  a  series  of  dense  lamellae 
which  extend  from  the  lesser  trochanter  to  the  lateral  end  of 
the  superior  border  of  the  neck;  this  arrangement  will  ob- 
viously oppose  considerable  resistance  to  either  tensile  or 
shearing  force.  A  smaller  bar  stretching  across  the  junction 
of  the  greater  trochanter  with  the  neck  and  body  resists  the 
shearing  force  of  the  muscles  attached  to  this  prominence. 
These  two  bars,  one  at  the  junction  of  body  and  neck,  the 
other  at  the  junction  of  body  and  greater  trochanter,  form  the 
upper  layers  of  a  series  of  arches  which  extend  across  between 
the  sides  of  the  body  and  transmit  to  the  body  forces  applied 
to  the  upper  end  of  the  bone.  In  the  cancellous  tissue  of  the 
neck  is  a  thin  vertical  plate  of  bone,  the  calcar  femorale,  which 
springs  from  the  compact  wall  of  the  body  in  the  region  of 
the  linea  aspera.  Medially  it  is  attached  to  the  interior  sur- 
face of  the  posterior  wall  of  the  neck  of  the  bone;  laterally  it 
continues  the  plane  of  the  posterior  wall  of  the  neck  into  the 
greater  trochanter  where  it  shades  off  into  the  general  cancel- 
lous tissue.  It  is  thus  situated  in  a  plane  anterior  to  the  inter- 
trochanteric crest  and  to  the  base  of  the  lesser  trochanter 
(Fig.  389). 

In  the  lower  end,  the  cancelli  spring  on  all  sides  from  the  inner  surface  of  the  cylinder,  and 
descend  in  a  perpendicular  direction  to  the  articular  surface,  the  cancelli  being  strongest  and 
having  a  more  accurately  perpendicular  coiu'se  above  the  condyles.    In  addition  to  this,  there 


Fig.  388. — Scheme  showing  disposi- 
tion of  principal  cancellous  lamellse 
in  upper  extremity  of  femur. 


352 


OSTEOLOGY 


are  horizontal  planes  of  cancellous  tissue,  so  that  the  spongy  tissue  in  this  situation  presents 
an  appearance  of  being  mapped  out  into  a  series  of  cubical  areas. 

Articulations. — The  femur  articulates  with  three  bones:    the  hip  bone,  tibia,  and  patella. 

Ossification  (Figs.  390,  391,  392). — The  femur  is  ossified  from  Jive  centres:  one  for  the  body, 
one  for  the  head,  one  for  each  trochanter,  and  one  for  the  lower  extremity.  Of  all  the  long  bones, 
except  the  clavicle,  it  is  the  first  to  show  traces  of  ossification;  this  commences  in  the  middle  of 
the  body,  at  about  the  seventh  week  of  fetal  life,  and  rapidly  extends  upward  and  downward. 
The  centres  in  the  epiphyses  appear  in  the  following  order:  in  the  lower  end  of  the  bone,  at  the 
ninth  month  of  fetal  life  (from  this  centre  the  condyles  and  epicondyles  are  formed) ;  in  the  head, 
at  the  end  of  the  first  year  after  birth;  in  the  greater  trochanter,  during  the  fourth  year;  and 
in  the  lesser  trochanter,  between  the  thirteenth  and  fourteenth  years.  The  order  in  which  the 
epiphyses  are  joined  to  the  body  is  the  reverse  of  that  of  their  appearance;  they  are  not  united 
until  after  puberty,  the  lesser  trochanter  being  first  joined,  then  the  greater,  then  the  head,  and, 
lastly,  the  inferior  extremity,  which  is  not  united  until  the  twentieth  year. 


Appears  at 

4:th  year  ; 

joins  body 

about  ISth  yr 


Caicar 
femorale 


Appears  at 

9th  month  of 

fceial  life 


Appears  at 
end  of  1st  yr.  ; 

joins  body 
about  \%th  yr. 

Appears  IZth^-lUh 
year ;  joins  body 
about  18th  year 


Joins  body  a 
20th  year 


Lower  extremity 


Fig.  389. — Oblique  section  of  upper  extremity  of 
femur  showing  caicar  femorale. 


Fig.  390.- 


-Plan  of  ossification  of  tiie  femur, 
five  centres. 


From 


Applied  Anatomy. — The  lower  end  of  the  femur  is  the  only  epiphysis  in  which  ossification  has 
commenced  at  the  time  of  birth.  The  presence  of  this  ossific  centre  is,  therefore,  a  proof,  in  a 
newly  born  child  found  dead,  that  the  child  has  arrived  at  the  full  period  of  uterogestation,  and 
is  always  reUed  upon  in  medicolegal  investigations.  The  position  of  the  epiphysial  plate  should 
be  carefully  noted.  It  is  on  a  level  with  the  adductor  tubercle,  and  the  epiphysis  does  not,  there- 
fore, form  the  whole  of  the  cartilage-clad  portion  of  the  lower  end  of  the  bone.  It  is  essential  to 
bear  this  point  in  mind  in  performing  excision  of  the  knee,  since  growth  in  length  of  the  femur 
takes  place  chiefly  from  the  lower  epiphysis,  and  any  interference  with  the  epiphysial  cartilage 
in  a  young  child  would  involve  such  ultimate  shortening  of  the  limb,  from  want  of  growth,  as  to 
render  the  limb  almost  useless.    Separation  of  the  lower  epiphysis  may  take  place  up  to  the  age 


THE  FEMUR 


358 


of  twenty,  at  which  time  it  becomes  comi)lctely  joined  to  the  body  of  tlie  bone;  but,  as  a  mattei" 
of  fact,  few  cases  occur  after  the  age  of  sixteen  or  seventeen.  The  epiphysis  of  the  head  of  the 
femur  is  the  seat  of  origin,  in  a  large  number  of  cases,  of  tuberculous  disease  of  the  hip-joint. 
In  the  majority  of  cases  the  disease  begins  in  the  highly  vascular  and  growing  tissue  at  the 
end  of  the  body  in  the  neighborhood  of  the  epiphysial  cartilage,  and  extends  into  the  joint.  The 
epiphysis  for  the  head  is  entirely  intracapsular. 

Fractures  of  the  femur  are  divided,  like  those  of  the  other  long  bones,  into  fractures  of  the 
upper  end;  of  the  body;  and  of  the  lower  end.  The  fractures  of  the  upper  end  may  be  classified 
into  (1)  fracture  of  the  neck;  (2)  fracture  at  the  junction  of  the  neck  with  the  greater  trochanter: 
(3)  fracture  of  the  greater  trochanter;  and  (4)  separation  of  the  epiphysis,  either  of  the  head  or 
of  the  greater  trochanter.  The  first  of  these,  fi'acture  of  the  neck,  is  usually  termed  intracapsular 
fracture,  but  this  is  scarcely  a  correct  designation,  as,  owing  to  the  attachment  of  the  articular 
capsule,  the  fracture  is  partly  within  and  partly  without  the  capsule  when  the  fracture  occurs 
at  the  lower  part  of  the  neck.     It  generally  takes  place  in  old  people,  principally  women,  and 


,  Fig.  391. — Epiphysial  lines  of  femur  in  a  young 
adult.  Anterior  aspect.  The  lines  of  attachment  of 
the  articular  capsules  are  in  blue. 


Fig.  392. — Epiphysial  lines  of  femur  in  a  young' adult. 
Posterior  aspect.  The  hnes  of  attachment  of  the  articular 
capsules  are  in  blue. 


usually  from  a  very  slight  degree  of  indirect  violence.  Probably  the  main  cause  of  its  occurrence 
in  old  people  is  the  senile  degenerative  change  which  takes  place  in  the  bone.  Merkel  believes 
that  it  is  mainly  due  to  the  absorption  of  the  calcar  femorale.  As  a  rule  the  fragments  become 
imited  by  fibrous  tissue,  but  frequently  no  union  takes  place,  and  the  opposed  surfaces  become 
smooth  and  eburnated. 

Fractures  at  the  junction  of  the  neck  with  the  greater  trochanter  are  usually  termed  extra- 
capsular, but  this  designation  is  also  incorrect,  as  the  fracture  is  partly  within  the  capsule,  owing 
to  its  attachment  in  front  to  the  intertrochanteric  line,  which  is  situated  below  the  Line  of  fracture. 
These  fractures  are  produced  by  direct  violence  to  the  greater  trochanter,  as  from  a  fall  laterally 
on  the  hip.  From  the  manner  in  which  the  accident  is  caused  the  neck  of  the  bone  is  driven  into 
the  trochanter,  where  it  may  remain  impacted,  or  the  trochanter  may  be  spHt  into  two  or  more 
fragments,  disimpaction  resulting. 

Fractures  of  the  body  may  occur  at  any  part,  but  the  most  usual  situation  is  at  or  near  .the 
centre  of  the  bone.  They  may  be  caused  by  direct  or  indirect  violence.  Fractures  of  the  upper 
third  of  the  body  ai-e  almost  always  the  result  of  indirect  violence,  while  those  of  the  lower  third 
23 


354 


OSTEOLOGY 


are  the  result,  for  the  most  part,  of  direct  violence.  Fractures  of  the  body  are  generally  oblique, 
but  they  may  be  transverse,  longitudinal,  or  spiral.  The  transverse  fracture  occurs  most  fre- 
quently in  children.  The  fractures  of  the  lower  end  of  the  femur  include  transverse  fracture 
above  the  condyles,  the  most  common;  and  this  may  be  complicated  by  a  vertical  fracture  be- 
tween the  condyles,  constituting  the  T-shaped  fracture.  In  these  cases  the  popliteal  artery  is  in 
danger  of  being  wounded.  Oblique  fracture  separating  either  the  medial  or  lateral  condjde,  and 
a  longitudinal  incomplete  fractm-e  between  the  condyles,  may  also  take  place. 

The  femur  as  well  as  the  other  bones  of  the  leg  is  frequently  the  seat  of  acute  osteomj^elitis 
in  children.  This  is  no  doubt  due  to  their  greater  exposure  to  injmy,  which  is  often  the  exciting 
cause  of  this  disease.  Necrosis  of  portions  of  the  diaphysis  frequently  ensues,  especially  in  the 
region  of  the  pophteal  surface  of  the  femur,  and  the  disease  may  continue  for  years,  great  trouble 
being  experienced  with  discharging  sinuses  which  periodically  close  and  reopen  to  allow  of  the 
exit  of  a  piece  of  dead  bone. 

Tumors  are  not  infrequently  found  growing  from  the  femur:  the  most  common  forms  being 
sarcoma  which  may  grow  either  from  the  periosteum  or  from  the  medullary  tissue  within  the 
interior  of  the  bone,  and  exostosis  which  commonly  originates  in  the  neighborhood  of  the  epiphysial 
cartilage  of  the  lower  end.  The  periosteal  sarcomata  of  the  femur  and  most  of  the  central  growths 
are  usually  of  a  very  high  degree  of  malignancy,  although  the  "myeloid"  growth,  which  is  of  but 
low  malignancy,  may  also  be  found.  The  region  of  the  lower  epiphysial  line  is  by  far  the  com- 
moner seat  for  all  these  tumors,  and  it  should  be  noted  that  the  lower  epiphysis  has  the  longest 
period  of  active  growth,  and  that  these  tumors  usually  appear  toward  the  end  of  the  period  of 
active  growth  of  the  bone. 

Sarcomata  about  the  upper  end  of  the  femur  are  seen  occasionally,  but  very  rarely  in  comparison 
with  those  at  the  lower  end.  Secondary  carcinoma  also  occurs  in  this  bone,  most  commonly  due 
to  a  primary  focus  in  the  breast,  and  spontaneous  fracture  of  the  bone  may  take  place  in  these 
cases. 

The  Patella  (Knee  Cap). 

The  patella  (Figs.  393,  394)  is  a  flat,  triangular  bone,  situated  on  the  front  of 
the  knee-joint.     It  is  usually  regarded  as  a  sesamoid  bone,  developed  in  the 

tendon  of  the  Quadriceps  femoris, 
and  resembles  these  bones  (1)  in 
being  developed  in  a  tendon ;  (2)  in 
its  centre  of  ossification  presenting 
a  knotty  or  tuberculated  outline; 
(3)  in  being  composed  mainly  of 
dense  cancellous  tissue.  It  serves 
to  protect  the  front  of  the  joint, 
and  increases  the  leverage  of  the 
Quadriceps  femoris  by  making  it 
act  at  a  greater  angle.  It  has  an 
anterior  and  a  posterior  surface 
three  borders,  and  an  apex. 
Surfaces.— The  anterior  surface  is  convex,  perforated  by  small  apertures  for  the 
passage  of  nutrient  \'essels,  and  marked  by  numerous  rough,  longitudinal  striae. 
This  surface  is  covered,  in  the  recent  state,  by  an  expansion  from  the  tendon  of 
the  Quadriceps  femoris,  which  is  continuous  below  with  the  superficial  fibres  of 
the  ligamentum  patellae.  It  is  separated  from  the  integument  by  a  bursa.  The 
posterior  surface  presents  above  a  smooth,  oval,  articular  area,  divided  into  two 
facets  by  a  vertical  ridge;  the  ridge  corresponds  to  the  groove  on  the  patellar 
surface  of  the  femur,  and  the  facets  to  the  medial  and  lateral  parts  of  the  same 
surface;  the  lateral  facet  is  the  broader  and  deeper.  Below  the  articular  surface 
is  a  rough,  convex,  non-articular  area,  the  lower  half  of  which  gives  attachment 
to  the  ligamentum  patellae ;  the  upper  half  is  separated  from  the  head  of  the  tibia 
by  adipose  tissue. 

Borders.— The  base  or  superior  border  is  thick,  and  sloped  from  behind,  down- 
ward, and  forward :  it  gives  attachment  to  that  portion  of  the  Quadriceps  femoris 
which  is  derived  from  the  Rectus  femoris  and  Vastus  intermedins.  The  medial  and 
lateral  borders  are  thinner  and  converge  below:  they  give  attachment  to  those 


-'ii^ 


Fig.  393.— Right  patella. 
Anterior  surface. 


Fig.  394. — Right  patella. 
Posterior  surface. 


77/ A'  Tin  I A 


•joo 


})orti()ns  of  the  Qua(lri('e])s  t'einoris  which  arc  (hTi\('(l  from  the  Vasti  hiteraHs  and 
inediaHs. 

Apex. — The  a])ex  is  pointed,  and  <;i\'es  atta<-hnient  to  the  H^ainentnin  patellae. 

Structure. — The  p:itc>lla  consists  of  ;i  nearly  uniform  dense  caneellous  tissue,  covered  by  a 
thin  eonipact  lamina.  The  cancH^lli  immediately  beneath  the  anterior  surface  are  arranged 
parallel  with  it.  In  tlie  rest  of  the  bon(>  tiiey  radiate  from  tlie  articular  surface  toward  the  other 
parts  of  the  bone. 

Ossification. — -Tlie  patella  is  ossified  from  a  single  centre,  which  usually  makes  its  appearance 
in  tlie  second  or  third  year,  but  may  be  delayed  until  the  sixth  year.  More  rarely,  the  bone  is 
developed  by  two  centres,  placed  side  by  side.    Ossification  is  completed  about  the  age  of  ]juberty. 

Articulation. — The  patella  articulates  with  the  femur. 

Applied  Anatomy. — The  main  surgical  interest  about  the  patella  is  in  connection  with  fractures, 
which  are  of  frequent  occurrence.  They  are  most  often  produced  by  muscular  action — that  is 
to  say,  by  violent  contraction  of  the  quadriceps  femoris  while  the  limb  is  in  a  position  of  semi- 
flexion, so  that  the  bone  is  snapped  across  the  condyles  of  the  femur  and  the  fracture  is  transverse. 
Fracture  of  the  patella  is  also  produced  by  direct  violence,  such  as  falls  on  the  knee,  and  here 
the  fracture  is  usually  stellate  and  the  bone  comminuted.  Owing  to  the  displacement  of  the 
fragments,  and  the  difficulty  there  is  in  maintaining  them  in  apposition,  union  takes  place  by 
fibrous  tissue  which  may  subsequently  stretch,  producing  wide  separation  of  the  fragments  and 
permanent  lameness.  Truly  satisfactory  results  after  this  fracture  are  generally  only  to  be 
obtained  by  opening  the  joint  and  wiring  the  fragments  together,  and  this  is  especially  so  when 
there  is  marked  separation  of  the  fragments  owing  to  laceration  of  the  retinacula. 

It  is  an  anatomical  possibiUty,  if  the  fracture  involve  only  the  lower  and  non-articular  part 
of  the  bone,  for  this  to  take  place  without  injury  to  the  synovial  membrane  and  without  involving 
the  cavity  of  the  knee-joint. 


The  Tibia  (Shin  Bone). 

The  tibia  (Figs.  396,  397)  is  situated  at  the  medial  side  of  the  leg,  and, 
excepting  the  femur,  is  the  longest  bone  of  the  skeleton.  It  is  prismoid  in  form, 
expanded  above,  where  it  enters  into  the 

knee-joint,  contracted  in   the   lower  third,  Tuhprosity 

and  again  enlarged  but  to  a  lesser  extent 
below.  In  the  male,  its  direction  is  vertical, 
and  parallel  with  the  bone  of  the  opposite 
side;  but  in  the  female  it  has  a  slightly 
oblique  direction  downward  andlateralward, 
to  compensate  for  the  greater  oblicjuity  of 
the  femur.    It  has  a  body  and  two  extremities. 

The  Upper  Extremity  {proximal  extremity). 
— The  upper  extremity  is  large,  and  expanded 
into  two  eminences,  the  medial  and  lateral 
condyles.  The  superior  articular  surface  pre- 
sents tAVo  smooth  articular  facets  (Fig.  395). 
The  medial  facet,  oval  in  shape,  is  slightly 
concave  from  side  to  side,  and  from  before 
backward.    The   lateral,  nearly  circular,  is 

concave  from  side  to  side,  but  slightly  convex  from  before  backward,  especially 
at  its  posterior  part,  where  it  is  prolonged  on  to  the  posterior  surface  for  a 
short  distance.  The  central  portions  of  these  facets  articulate  with  the  con- 
dyles of  the  femur,  while  their  peripheral  portions  support  the  menisci  of  the 
knee-joint,  which  here  intervene  between  the  two  bones.  Between  the  artic- 
ular facets,  but  nearer  the  posterior  than  the  anterior  aspect  of  the  bone,  is  the 
intercondyloid  eminence  (spine  of  tibia),  surmounted  on  either  side  by  a  prominent 
tubercle,  on  to  the  sides  of  which  the  articular  facets  are  prolonged;  in  front  of 
and  behind  the  intercondyloid  eminence  are  rough  depressions  for  the  attachment 
of  the  anterior  and  posterior  cruciate  ligaments  and  the  menisci.  The  anterior 
surfaces  of  the  condyles  are  continuous  with  one  another,  forming  a  large  somewhat 


Intercondyloid  eminence 

Fig.  39.5. — Upper  surface  of  right  tibia. 


356 


OSTEOLOGY 


Articular  capsule 


Styloid  2)rocess  —y 


Fibular 
collateral 
ligament 


\  el   " 

.    il      ICLLA-/      . 


"s^  v\ 


S 


Articular 
capsule 


Lateral  malleolus 
Fig.  396.— Bones  of  the  right  leg 


Medial  malleolus 


Anterior  surface. 


flattened  area;  this  area  is  trian- 
gular, broad  al)ove,  and  perforated 
by  large  vascular  foramina;  narrow 
below  where  it  ends  in  a  large  ob- 
long elevation,  the  tuberosity  of 
the  tibia,  which  gives  attachment 
to  the  ligamentum  patellae;  a 
bursa  intervenes  between  the  deep 
surface  of  the  ligament  and  the 
part  of  the  bone  immediately 
above  the  tuberosity'.  Posteriorly, 
the  condyles  are  separated  from 
each  other  by  a  shallow  depres- 
sion, the  posterior  intercondyloid 
fossa,  which  gives  attachment  to 
part  of  the  posterior  cruciate  liga- 
ment of  the  knee-joint.  The 
medial  condyle  presents  posteriorly 
a  deep  transverse  groove,  for  the 
insertion  of  the  tendon  of  the 
Semimembranosus.  Its  medial 
surface  is  convex,  rough,  and 
prominent;  it  gives  attachment 
to  the  tibial  collateral  ligament. 
The  lateral  condyle  presents  pos- 
teriorly a  flat  articular  facet,  nearly 
circular  in  form,  directed  down- 
ward, backward,  and  lateralward, 
for  articulation  with  the  head  of 
the  fibula.  Its  lateral  surface  is 
convex,  rough,  and  prominent  in 
front :  on  it  is  an  eminence,  situated 
on  a  level  with  the  upper  border 
of  the  tuberosity  and  at  the  junc- 
tion of  its  anterior  and  lateral 
surfaces,  for  the  attachment  of 
the  iliotibial  band.  Just  below 
this  a  part  of  the  Extensor  digi- 
torum  longus  takes  origin  and  a 
slip  from  the  tendon  of  the  Biceps 
femoris  is  inserted. 

The  Body  or  Shaft  {corims  tibiae). 
— The  body  has  three  borders  and 
three  surfaces. 

Borders. — The  anterior  crest  or 
border,  the  most  prominent  of  the 
three,  commences  above  at  the 
tuberosity,  and  ends  below  at  the 
anterior  margin  of  the  medial 
malleolus.  It  is  sinuous  and 
prominent  in  the  upper  two-thirds 
of  its  extent,  but  smooth  and 
rounded  below;  it  gives  attach- 
ment to  the  deep  fascia  of  the 
les;. 


THE  TJBIA 


357 


The  medial  border  is  smooth  a 
in  the  centre;  it  begins  at  the 
posterior  border  of  the  medial 
malleohis;  its  upper  part  gives 
attachment  to  the  tibial  collat- 
eral ligament  of  the  knee-joint 
to  the  extent  of  about  5  cm., 
and  insertion  to  some  fibres  of 
the  Popliteus;  from  its  middle 
third  some  fibres  of  the  Soleus 
and  Flexor  digitorum  longus 
take  origin. 

The  interosseous  crest  or  lat- 
eral border  is  thin  and  promi- 
nent, especially  its  central  part, 
and  gi\'es  attachment  to  the 
interosseous  membrane;  it  com- 
mences above  in  front  of  the 
fibular  articular  facet,  and 
bifurcates  below,  to  form  the 
boundaries  of  a  triangular  rough 
surface,  for  the  attachment  of 
the  interosseous  ligament  con- 
necting the  tibia  and  fibula. 

Surfaces. — The  medial  surface 
is  smooth,  convex,  and  broader 
above  than  below;  its  upper 
third,  directed  forward  and 
medialward,  is  covered  by  the 
aponeurosis  derived  from  the 
tendon  of  the  Sartorius,  and  by 
the  tendons  of  the  Gracilis  and 
Semitendinosus,  all  of  which 
are  inserted  nearly  as  far  for- 
ward as  the  anterior  crest;  in 
the  rest  of  its  extent  it  is  sub- 
cutaneous. 

The  lateral  surface  is  narrower 
than  the  medial;  its  upper  two- 
thirds  present  a  shallow^  groove 
for  the  origin  of  the  Tibialis 
anterior;  its  lower  third  is 
smooth,  convex,  curves  grad- 
ually forward  to  the  anterior 
aspect  of  the  bone,  and  is 
covered  by  the  tendons  of  the 
Tibialis  anterior.  Extensor  hal- 
lucis  longus,  and  Extensor  digi- 
torum longus,  arranged  in  this 
order  from  the  medial  side. 

The  posterior  surface  (Fig.  397) 
presents,  at  its  upper  part,  a 
prominent  ridge,  the  popliteal 
line,  w^hich  extends  obliquely 
downward  from  the  back  part  of 


nd  rounded  above  and  below,  but  more  prominent 
back  part  of  the  medial  condyle,  and  ends  at  the 


Articular 
capsule  Y"^^ 


Articular 
ws\  capsule 

■^'-■^ Stxjloid 

process 


Articulates  with  tams 


Articular  capsule 
Fig.  397. — Bones  of  the  right  leg.     Posterior  surface. 


358 


OSTEOLOGY 


the  articular  facet  for  the  fibula  to  the  medial  border,  at  the  junction  of  its  upper 
and  middle  thirds;  it  marks  the  lower  limit  of  the  insertion  of  the  Popliteus,  serves 
for  the  attachment  of  the  fascia  covering  this  muscle,  and  gives  origin  to  part  of 
the  Soleus,  Flexor  digitorum  longus,  and  Tibialis  posterior.  The  triangular  area, 
above  this  line,  gives  insertion  to  the  Popliteus.  The  middle  third  of  the  posterior 
surface  is  divided  by  a  vertical  ridge  into  two  parts;  the  ridge  begins  at  the  popliteal 
line  and  is  well-marked  above,  but  indistinct  below;  the  medial  and  broader  por- 
tion gives  origin  to  the  Flexor  digitorum  longus,  the  lateral  and  narrow^er  to  part 
of  the  Tibialis  posterior.  The  remaining  part  of  the  posterior  surface  is  smooth 
and  covered  by  the  Tibialis  posterior,  Flexor  digitorum  longus,  and  Flexor  hallucis 
longus.  Immediately  below  the  popliteal  line  is  the  nutrient  foramen,  which  is 
large  and  directed  obliquely  downward. 

The  Lower  Extremity  {distal  extremity). — The  lower  extremity,  much  smaller 
than  the  upper,  presents  five  surfaces;  it  is  prolonged  downward  on  its  medial 
side  as  a  strong  process,  the  medial  malleolus. 

Surfaces. — The  inferior  articular  surface  is  quadrilateral,  and  smooth  for  articu- 
lation with  the  talus.  It  is  concave  from  before  backward,  broader  in  front  than 
behind,  and  traversed  from  before  backward  by  a  slight  elevation,  separating 
two  depressions.    It  is  continuous  with  that  on  the  medial  malleolus. 


Upper  extremity 


Appears  before  or 
shortly  after  birth 


Appea-'-s  at  2mZ__ 
year 


Joins  body 
'about  20th  year 


Joins  body  about 
\8th  year 


Lower  extremity 


Fig.  398. — Plan  of  ossification  of  the  tibia, 
centres. 


From  three 


Fig.  399. — Epiphysial  lines  of  tibia  and  fibula 
in  a  young  adult.     Anterior  aspect. 


The  anterior  surface  of  the  lower  extremity  is  smooth  and  rounded  above,  and 
covered  by  the  tendons  of  the  Extensor  muscles ;  its  lower  margin  presents  a  rough 
transverse  depression  for  the  attachment  of  the  articular  capsule  of  the  ankle- 
joint. 

The  posterior  surface  is  traversed  by  a  shallow  groove  directed  obliquely  down- 
w-ard  and  medialward,  continuous  wdth  a  similar  groove  on  the  posterior  surface 
of  the  talus  and  serving  for  the  passage  of  the  tendon  of  the  Flexor  hallucis  longus. 

The  lateral  surface  presents  a  triangular  rough  depression  for  the  attachment 
of  the  inferior  interosseous  ligament  connecting  it  with  the  fibula;  the  lower  part 


THE  FI/ULA  859 

of  this  depression  is  siiiot)tli,  coxered  witli  cartilage  in  tiie  recent  state,  and  articu- 
lates with  the  fibula.  The  surface  is  bounded  by  two  prominent  borders,  con- 
tinuous above  with  the  interosseous  crest;  they  afford  attachment  to  the  anterior 
and  posterior  li,u;aments  of  the  lateral  malleolus. 

The  medial  surface  is  jjrolonged  downward  to  form  a  strong  pyramidal  process, 
fiattened  from  without  inward — the  medial  malleolus.  The  medial  surface  of  this 
process  is  convex  and  subcutaneous;  its  lateral  t)r  articular  surface  is  smooth  and 
slightl>'  concave,  and  articulates  with  the  talus;  its  anterior  border  is  rough,  for 
the  attachment  of  the  anterior  fibres  of  the  deltoid  ligament  of  the  ankle-joint; 
its  posterior  border  presents  a  broad  groove,  the  malleolar  sulcus,  directed  obliquely 
downward  and  medialward,  and  occasionally  double;  this  sulcus  lodges  the  tendons 
of  the  Tibialis  posterior  and  Flexor  digitorum  longus.  The  summit  of  the  medial 
malleolus  is  marked  by  a  rough  depression  behind,  for  the  attachment  of  the 
deltoid  ligament. 

Structure. — The  structure  of  the  tibia  is  like  that  of  the  othei-  long  bones.  The  compact  wall 
of  the  body  is  thickest  at  the  junction  of  the  middle  and  lower  thirds  of  the  bone. 

Ossification. — The  tibia  is  ossified  from  three  centres  (Figs.  398,  399) :  one  for  the  bod}'  and 
one  for  either  extremity.  Ossification  begins  in  the  centre  of  the  body,  about  the  seventh  week 
of  fetal  life,  and  gradually  extends  toward  the  extremities.  The  centre  for  the  upper  epiphysis 
appears  before  or  shortly  after  birth;  it  is  flattened  in  form,  and  has  a  thin  tongue-shaped  process 
in  front,  which  forms  the  tuberosity  (Fig.  399) ;  that  for  the  lower  epiphj^sis  appears  in  the  second 
year.  The  lower  epiphysis  joins  the  body  at  about  the  eighteenth,  and  the  upper  one  joins  about 
the  twentieth  year.  Two  additional  centres  occasionally  exist,  one  for  the  tongue-shaped  process 
of  the  upper  epiphysis,  which  forms  the  tuberosity,  and  one  for  the  medial  malleolus. 

Articulations. — The  tibia  articulates  with  three  bones:    the  femur,  fibula,  and  talus. 

The  Fibula  (Calf  Bone). 

The  fibula  (Figs.  396,  397)  is  placed  on  the  lateral  side  of  the  tibia,  with  which 
it  is  connected  above  and  below.  It  is  the  smaller  of  the  two  bones,  and^  in 
proportion  to  its  length,  the  most  slender  of  all  the  long  bones.  Its  upper 
extremity  is  small,  placed  toward  the  back  of  the  head  of  the  tibia,  below  the  level 
of  the  knee-joint,  and  excluded  from  the  formation  of  this  joint.  Its  lower  extremity 
inclines  a  little  forward,  so  as  to  be  on  a  plane  anterior  to  that  of  the  upper  end; 
it  projects  below  the  tibia,  and  forms  the  lateral  part  of  the  ankle-joint.  The 
bone  has  a  body  and  two  extremities. 

The  Upper  Extremity  or  Head  {capitulum  fibulae;  proximal  extremity). — The 
upper  extremity  is  of  an  irregular  quadrate  form,  presenting  above  a  flattened 
articular  surface,  directed  upward,  forward,  and  medialward,  for  articulation  with 
a  corresponding  surface  on  the  lateral  condyle  of  the  tibia.  On  the  lateral  side 
is  a  thick  and  rough  prominence  continued  behind  into  a  pointed  eminence,  the 
apex  (styloid  process),  which  projects  upward  from  the  posterior  part  of  the  head. 
The  prominence,  at  its  upper  and  lateral  part,  gives  attachment  to  the  tendon  of 
the  Biceps  femoris  and  to  the  fibular  collateral  ligament  of  the  knee-joint,  the  liga- 
ment dividing  the  tendon  into  two  parts.  The  remaining  part  of  the  circumference 
of  the  head  is  rough,  for  the  attachment  of  muscles  and  ligaments.  It  presents  in 
front  a  tubercle  for  the  origin  of  the  upper  and  anterior  fibres  of  the  Peronaeus 
longus,  and  a  surface  for  the  attachment  of  the  anterior  ligament  of  the  head; 
and  behind,  another  tubercle,  for  the  attachment  of  the  posterior  ligament  of  the 
head  and  the  origin  of  the  upper  fibres  of  the  Soleus. 

The  Body  or  Shaft  (corpus  fibulae). — The  body  presents  four  borders — the 
antero-lateral,  the  antero-medial,  the  postero-lateral,  and  the  postero-medial ;  and 
four  surfaces — anterior,  posterior,  medial,  and  lateral. 

Borders. — The  antero-lateral  border  begins  above  in  front  of  the  head,  runs  ver- 
tically downward  to  a  little  below  the  middle  of  the  bone,  and  then  curving  some- 
what lateralward,  bifurcates  so  as  to  embrace  a  triangular  subcutaneous  surface 


360  OSTEOLOGY 

immediately  above  the  lateral  malleolus.  This  border  gives  attachment  to  an 
intermuscular  septum,  which  separates  the  Extensor  muscles  on  the  anterior 
surface  of  the  leg  from  the  Peronaei  longus  and  brevis  on  the  lateral  surface. 

The  antero-medial  border,  or  interosseous  crest,  is  situated  close  to  the  medial 
side  of  the  preceding,  and  runs  nearly  parallel  Avith  it  in  the  upper  third  of  its 
extent,  but  diverges  from  it  in  the  lower  two-thirds.  It  begins  above  just  beneath 
the  head  of  the  bone  (sometimes  it  is  quite  indistinct  for  about  2.5  cm.  below  the 
head),  and  ends  at  the  apex  of  a  rough  triangular  surface  immediately  above  the 
articular  facet  of  the  lateral  malleolus.  It  serves  for  the  attachment  of  the  inter- 
osseous membrane,  which  separates  the  Extensor  muscles  in  front  from  the  Flexor 
muscles  behind. 

The  postero-lateral  border  is  prominent;  it  begins  above  at  the  apex,  and  ends 
below  in  the  posterior  border  of  the  lateral  malleolus.  It  is  directed  lateralward 
above,  backward  in  the  middle  of  its  course,  backward,  and  a  little  medialward 
below,  and  gives  attachment  to  an  aponeurosis  which  separates  the  Peronaei  on 
the  lateral  surface  from  the  Flexor  muscles  on  the  posterior  surface. 

The  postero-medial  border,  sometimes  called  the  oblique  line,  begins  above  at  the 
medial  side  of  the  head,  and  ends  by  becoming  continuous  with  the  interosseous 
crest  at  the  lower  fourth  of  the  bone.  It  is  well-marked  and  prominent  at  the  upper 
and  middle  parts  of  the  bone.  It  gives  attachment  to  an  aponeurosis  which  sep- 
arates the  Tibialis  posterior  from  the  Soleus  and  Flexor  hallucis  longus. 

Surfaces. — The  anterior  surface  is  the  interval  between  the  antero-lateral  and 
antero-medial  borders.  It  is  extremely  narrow  and  flat  in  the  upper  third  of  its 
extent:  broader  and  grooved  longitudinallj^  in  its  lower  third;  it  serves  for  the 
origin  of  three  muscles:  the  Extensor  digitorum  longus,  Extensor  hallucis  longus, 
and  Peronaeus  tertius. 

The  posterior  surface  is  the  space  included  between  the  postero-lateral  and  the 
postero-medial  borders;  it  is  continuous  below  with  the  triangular  area  above 
the  articular  surface  of  the  lateral  malleolus;  it  is  directed  back^^ard  above,  back- 
ward and  medialward  at  its  middle,  directly  medialward  below.  Its  upper  third 
is  rough,  for  the  origin  of  the  Soleus;  its  lower  part  presents  a  triangular  surface, 
connected  to  the  tibia  by  a  strong  interosseous  ligament;  the  intervening  part  of 
the  surface  is  covered  by  the  fibres  of  origin  of  the  Flexor  hallucis  longus.  Near 
the  middle  of  this  surface  is  the  nutrient  foramen,  which  is  directed  downward. 

The  medial  surface  is  the  interval  included  between  the  antero-medial  and  the 
postero-medial  borders.     It  is  grooved  for  the  origin  of  the  Tibialis  posterior. 

The  lateral  surface  is  the  space  between  the  antero-lateral  and  postero-lateral 
borders.  It  is  broad,  and  often  deeply  grooved;  it  is  directed  lateralward  in  the 
upper  two-thirds  of  its  course,  backward  in  the  lower  third,  where  it  is  continuous 
with  the  posterior  border  of  the  lateral  malleolus.  This  surface  gives  origin  to 
the  Peronaei  longus  and  brevis. 

The  Lower  Extremity  or  Lateral  Malleolus  {malleolus  lateralis;  distal  extremity; 
external  malleolus) . — The  lower  extremity  is  of  a  pyramidal  form,  and  somewhat 
flattened  from  side  to  side;  it  descends  to  a  lower  level  than  the  medial  malleolus. 
The  lateral  surface  is  convex,  subcutaneous,  and  continuous  with  the  triangular, 
subcutaneous  sm-face  on  the  lateral  side  of  the  body.  The  medial  surface  (Fig. 
400)  presents  in  front  a  smooth  triangul'ar  surface,  convex  from  above  dow^nward, 
which  articulates  with  a  corresponding  surface  on  the  lateral  side  of  the  talus. 
Behind  and  beneath  the  articular  surface  is  a  rough  depression,  which  gives  attach- 
ment to  the  posterior  talofibular  ligament.  The  anterior  border  is  thick  and  rough, 
and  marked  below  by  a  depression  for  the  attachment  of  the  anterior  talofibular 
ligament.  The  posterior  border  is  broad  and  presents  the  shallow  malleolar  sulcus, 
for  the  passage  of  the  tendons  of  the  Peronaei  longus  and  brevis.  The  summit 
is  rounded,  and  give  attachment  to  the  calcaneofibular  ligament. 


THE  FIBULA 


361 


Articulations. — The  fibula  articulates  with  two  bones:    the  tibia  and  talus. 

Ossification. — The  fibula  is  ossified  from  three  centres  (Fig.  401):  one  for  the  body,  and  one 
for  either  entl.  Ossification  begins  in  the  body  about  the  eighth  week  of  fetal  life,  and  extends 
toward  the  extremities.  At  birth  the  ends  are  cartilaginous.  Ossification  commences  in  the 
lower  end  in  the  second  year,  and  in  the  upper  about  the  fourth  year.  The  lower  epiphysis, 
the  first  to  ossify,  unites  with  the  body  about  the  twentieth  year;  the  upper  epiphysis  joins 
about  the  twenty-fifth  year. 

Applied  Anatomy  of  the  Tibia  and  Fibula. — In  fractures  of  the  bones  of  the  leg,  both  bones 
are  generally  involved,  but  cither  bone  may  be  broken  separately,  the  fibula  more  frequently 
than  the  tibia.  Fracture  of  both  bones  may  be  caused  by  either  direct  or  indirect  violence.  When 
it  occiu-s  from  indirect  force,  the  fracture  in  the  tibia  is  at  the  junction  of  the  middle  and  lower 
thirds  of  the  bone.  Many  causes  conduce  to  render  this  the  weakest  part  of  the  bone.  The 
fractm-e  of  the  fibula  is  usually  at  a  rather  higher  level.  These  fractiu'es  present  great  variety, 
both  as  regards  their  direction  and  condition.  Thej^  may  be  oblique,  transverse,  longitudinal, 
or  spiral.  When  oblique,  they  are  for  the  most  part  the  result  of  indirect  violence,  and  the  direc- 
tion of  the  fracture  is  downward,  forward,  and  medialw'ard  in  many  cases,  but  maj'  be  down- 
ward and  lateralward,  or  downward  aiid  backward.  When  transverse,  the  fracture  is  often  at 
the  upper  part  of  the  bone,  and  is  the  result  of  direct  violence.  The  spiral  fracttire  of  the  tibia 
generally  starts  as  a  vertical  fissure,  involving  the  ankle-joint,  and  is  associated  with  fracture  of 
the  fibula  higher  up.    It  is  the  result  of  torsion,  from  twisting  of  the  body  while  the  foot  is  fixed. 


Upper  extremity 


Lntero-sseous 
crest 


Appears  about 
ith  year 


Unites  about 
25th  year 


For  talus 


For  posterior 
talofibular  ligt. 


Appears  at    MS 
2nd  year 


Unites  about 
20th  year 


Fig. 


•iOO. — Lower  extremitj  of  right  fibula. 
INIedial  aspect 


Lower  extremity 

Fig.    4:01. — Plan   of  ossification    of    the 
fibula.     From  three  centres. 

Fractures  of  the  tibia  alone  are  almost  always  the  result  of  direct  violence,  except  where  the 
malleolus  is  broken  off  by  twists  of  the  foot.  Fractures  of  the  fibula  alone  may  arise  from  indirect 
or  direct  force,  those  of  the  low^er  end  being  usually  the  result  of  the  former,  and  those  higher 
up  being  caused  by  a  direct  blow  on  the  part. 

The  tibia  is  the  bone  which  is  most  commonly  and  most  extensively  distorted  in  rickets.  It 
bends  at  the  junction  of  the  middle  and  lower  third,  its  weakest  part,  and  presents  a  curve  forward 
wdth  generally  some  lateral  displacement. 

The  tibia  is  more  often  the  seat  of  acute  infective  necrosis  than  any  other  bone  in  the  body, 
and  with  the  formation  of  the  sequestrum,  a  large  amount  of  new  bony  material  is  thrown  out 
by  the  periosteima.  The  sequence  of  events  in  this  disease  can  be  very  closely  followed  in  the 
case  of  the  tibia,  and  it  is  not  xmcommon  to  find  a  patient  from  whom  the  whole  diaphysis  of  the 
tibia  has  been  removed,  going  about  with  a  new  bone  entirely  of  periosteal  formation.  Chronic 
bone  abscess  is  more  frequently  met  with  in  the  canceUotis  tissue  of  the  head  or  lower  end  -of  the 
tibia  than  in  any  other  bone  in  the  body.  These  abscesses  are  very  chronic,  and  in  most  cases 
the  result  of  tuberculous  osteitis,  although  they  are  sometimes  due  to  the  organisms  of  suppura- 
tion or  even  the  Bacillus  typhosus. 


362 


OSTEOLOaY 


THE    FOOT. 

The  skeleton  of  the  foot  (Figs.  403  and  404)  consists  of  three  parts:  the  tarsus, 
metatarsus,  and  phalanges. 

The  Tarsus  (Ossa  Tarsi). 

The  tarsal  bones  are  se\'en  in  number,  \iz.,  the  calcaneus,  talus,  cuboid,  navicular, 
and  the  first,  second,  and  third  cuneiforms. 


Groovzfor  Ppronceus  hrev 


Trochlear  proca^ 

Groove  for  Peronceus  longus 


tendo  calcaneus 


Lateral  process  of  tuberosity 


B 

For  posterior  facet  of  talus 

For  middle  facet  of  talus 
^^*l^^^  -^°'  ^'  ter-ioi  facet  of  talus 


Medial  process  of  tuberosity      j  '  ^'°''  '^"^"'^^ 

Groove  for  Flexor  Judlucis  longus 

Sustentaculum  tali 

Groove  for  inierosscus  ligament 
Fig.  402.— The  left  calcaneus.     .4.  Postero-lateral  view.     B.  Antero-medial  view. 

The  Calcaneus  {as  calcis)  (Fig.  402).— The  calcaneus  is  the  largest  of  the  tarsal 
bones.  It  is  situated  at  the  lower  and  back  part  of  the  foot,  serving  to  transmit 
the  weight  of  the  body  to  the  ground,  and  forming  a  strong  lever  for  the  muscle? 
of  the  calf.  It  is  irregularly  cuboidal  in  form,  having  its  long  axis  directed  forward 
and  lateralward;  it  presents  for  examination  six  surfaces. 

Surf  aces.— The  superior  surface  extends  behind  on  to  that  part  of  the  bone  which 
projects  backward  to  form  the  heel.    This  varies  in  length  in  different  individuals, 


THE  TARDUS 


363 


Groove  f 01  tendon  of 

PER0NAEI">  LON(TT.b 


(iroovefor  ten  I  >n   if 

PKRONAEIs   }  I  EM'5 


PERONAEUS  TI  I  TILS 
PERONAETS   BRFMb 


Groove  for  tendon  of 

Fr,EXOH   HALLUCIS  LONGUS 


Tarsus 


Metatarsus 


Ext.  digitorum  brevis 


Phcdanges 


Ext.    HALLUCIS  LONGUS 


Fig.  403. — Bones  of  the  right  foot.     Dorsal  surface. 


3G4 


OSTEOLOGY 


j\bductlr  iiallucis 
Medial  iikad  of 


Flexor  hallucis  brevis 


Tubercle  of 
navicular 


Tibialis  anterior 


Two  sesamoid 
hones 


Lateral  wrkd  of  quapratus 

PLANTiE 


f'LEXOR  BREA'IS 

ANi>  Abductor 

DIGITI  QUINTI 


Flexor  digitorum 

BREVIS 


Flexor  digitorum 
longus 


Fig.  404. — Bones  of  the  right  foot.     Plantar  surface. 


THE  TARSUS  365 

is  convex  from  side  to  side,  concave  from  before  backward,  and  supports  a  mass  of 
fat  placed  in  front  of  the  tendo  calcaneus.  Tn  front  of  this  area  is  a  large  usually 
somewhat  oval-shaped  facet,  the  posterior  articular  surface,  which  looks  upward 
and  forward;  it  is  convex  from  behind  forward,  and  articulates  with  the  posterior 
calcaneal  facet  on  the  under  surface  of  the  talus.  It  is  bounded  anteriorly  by  a 
deep  depression  which  is  continued  backward  and  medialward  in  the  form  of  a 
groove,  the  calcaneal  sulcus.  In  the  articulated  foot  this  sulcus  lies  below  a  similar 
one  on  the  under  surface  of  the  talus,  and  the  two  form  a  canal  (sinus  tarsi)  for  the 
lodgement  of  the  interosseous  talocalcaneal  ligament.  In  front  and  to  the  medial 
side  of  this  groove  is  an  elongated  facet,  concave  from  behind  forward,  and  with  its 
long  axis  directed  forward  and  lateralward.  This  facet  is  frequently  divided  into 
two  by  a  notch :  of  the  two,  the  posterior,  and  larger  is  termed  the  middle  articular 
surface;  it  is  supported  on  a  projecting  process  of  bone,  the  sustentaculum  tali, 
and  articulates  with  the  middle  calcaneal  facet  on  the  under  surface  of  the  talus; 
the  anterior  articular  surface  is  placed  on  the  anterior  part  of  the  body,  and  articu- 
lates with  the  anterior  calcaneal  facet  on  the  talus.  The  upper  surface,  anterior 
and  lateral  to  the  facets,  is  rough  for  the  attachment  of  ligaments  and  for  the  origin 
of  the  Extensor  digitorum  brevis. 

The  inferior  or  plantar  surface  is  uneven,  wider  behind  than  in  front,  and  convex 
from  side  to  side;  it  is  bounded  posteriorly  by  a  transverse  elevation,  the  calcaneal 
tuberosity,  which  is  depressed  in  the  middle  and  prolonged  at  either  end  into  a 
process;  the  lateral  process,  small,  prominent,  and  rounded,  gives  origin  to  part 
of  the  Abductor  digiti  quinti ;  the  medial  process,  broader  and  larger,  gives  attach- 
ment, by  its  prominent  medial  margin,  to  the  Abductor  hallucis,  and  in  front 
to  the  Flexor  digitorum  brevis  and  the  plantar  aponeurosis ;  the  depression  between 
the  processes  gives  origin  to  the  Abductor  digiti  quinti.  The  rough  surface  in 
front  of  the  processes  gives  attachment  to  the  long  plantar  ligament,  and  to  the 
lateral  head  of  the  Quadratus  plantae;  while  to  a  prominent  tubercle  nearer  the 
anterior  part  of  this  surface,  as  w^ell  as  to  a  transverse  groove  in  front  of  the  tubercle, 
is  attached  the  plantar  calcaneocuboid  ligament. 

The  lateral  surface  is  broad  behind  and  narrow  in  front,  flat  and  almost  sub- 
cutaneous; near  its  centre  is  a  tubercle,  for  the  attachment  of  the  calcaneofibular 
ligament.  At  its  upper  and  anterior  part,  this  surface  gives  attachment  to  the 
lateral  talocalcaneal  ligament;  and  in  front  of  the  tubercle  it  presents  a  narrow 
surface  marked  by  two  oblique  grooves.  The  grooves  are  separated  by  an  elevated 
ridge,  or  tubercle,  the  trochlear  process  (peroneal  tubercle),,  which  varies  much  in 
size  in  different  bones.  The  superior  groove  transmits  the  tendon  of  the  Peronaeus 
brevis;  the  inferior  groove,  that  of  the  Peronaeus  longus. 

The  medial  surface  is  deeply  concave;  it  is  directed  obliquely  downward  and 
forward,  and  serves  for  the  transmission  of  the  plantar  vessels  and  nerves  into  the 
sole  of  the  foot;  it  affords  origin  to  part  of  the  Quadratus  plantae.  At  its  upper 
and  forepart  is  a  horizontal  eminence,  the  sustentaculum  tali,  which  gives  attach- 
ment to  a  slip  of  the  tendon  of  the  Tibialis  posterior.  This  eminence  is  concave 
above,  and  articulates  with  the  middle  calcaneal  articular  surface  of  the  talus; 
below,  it  is  grooved  for  the  tendon  of  the  Flexor  hallucis  longus ;  its  anterior  margin 
gives  attachment  to  the  plantar  calcaneonavicular  ligament,  and  its  medial, 
to  a  part  of  the  deltoid  ligament  of  the  ankle-joint. 

The  anterior  or  cuboid  articular  surface  is  of  a  somewhat  triangular  form.  It  is 
concave  from  above  downward  and  lateralward,  and  convex  in  a  direction  at  right 
angles  to  this.  Its  medial  border  gives  attachment  to  the  plantar  calcaneonavicular 
ligament. 

The  posterior  surface  is  prominent,  convex,  wider  below  than  above,  and  divisible 
into  three  areas.  The  lowest  of  these  is  rough,  and  covered  by  the  fatty  and  fibrous 
tissue  of  the  heel;  the  middle,  also  rough,  gives  insertion  to  the  tendo  calcaneus 


566 


OSTEOLOGY 


and  Plantaris;  wliile  the  hi.iijliest  is  smooth,  and  is  c()\-ered  by  a  bursa  which  inter- 
venes between  it  and  the  tendo  calcaneus. 

Articulations. — The  calcaneus  articulates  with  two  bones:     the  talus  and  cuboid. 

For  navicular  Neck  A  Trocldra  for  tibia 

^  For  transver>ie  inferior  tihio- 

/       filnilrtr  ligament 


lor  process 


For  lat.  malleolus 


For  med   malleolus 


Trochlea  foi  tibia 


Groove  for  Flexor 
halluris  longus 


For  'plantar  calcaneo- 
navicular ligament 

Middle  calcaneal 
articular  surface 


Posterior  calcaneal 
articular  surface 


Groove  for  Flex, 
halluris  longus 


For  navicular 


For  navicular 

Anterior  calcaneal 
articular  surface 


Groove  for  interosseous 
talocalcaneal  ligament 


Fig.  405. — The  left  talus.     --1.  Supero-lateral  view.     B.  Infero-medial  view.     C.  Inferior  view. 

The  Talus  (astragalus;  ankle  hone)  (Fig.  405).— The  talus  is  the  second  largest 
of  the  tarsal  bones.  It  occupies  the  middle  and  upper  part  of  the  tarsus,  support- 
ing the  tibia  above,  resting  upon  the  calcaneus  below,  articulating  on  either  side 
with  the  malleoli,  and  in  front  with  the  navicular.  It  consists  of  a  body,  a  neck, 
and  a  head. 


77/ A'  TARSUS  367 

The  Body  (rorpii,'i  fali). — The  superior  surface  of  the  body  presents,  l)eliiii(l,  a 
smooth  troehU'ar  surfaee,  tlie  trochlea,  for  artieuhition  with  the  tibia.  The  trochlea 
is  broader  in  front  than  behind,  convex  from  before  backward,  slightly  concave 
from  side  to  side:  in  front  it  is  continnons  with  the  npper  snrface  of  the  neck  of 
the  bone. 

The  inferior  surface  ])resents  two  articular  areas,  the  posterior  and  middle  cal- 
caneal surfaces,  separated  from  one  another  by  a  deep  groo\e,  the  sulcus  tali. 
The  gToove  runs  obliquely  forward  and  lateralward,  becoming  gradually  broader 
and  deei)er  in  front:  in  the  articulated  foot  it  lies  above  a  similar  groove  upon 
the  upper  surface  of  the  calcaneus,  and  forms,  with  it,  a  canal  (sinus  tarsi)  filled 
up  in  the  recent  state  by  the  interosseous  talocalcaneal  ligament.  The  posterior 
calcaneal  articular  surface  is  large  and  of  an  oval  or  oblong  form.  It  articulates 
with  the  corresi)onding  facet  on  the  upper  surface  of  the  calcaneus/  and  is  deeply 
concave  in  the  direction  of  its  long  axis  which  runs  forward  and  lateralward  at 
an  angle  of  about  45°  with  the  median  plane  of  the  body.  The  middle  calcaneal 
articular  surface  is  small,  oval  in  form  and  slightly  convex;  it  articulates  with  the 
upper  surface  of  the  sustentaculum  tali  of  the  calcaneus. 

The  medial  surface  presents  at  its  upper  part  a  pear-shaped  articular  facet  for 
the  medial  malleolus,  continuous  above  with  the  trochlea;  below  the  articular 
surface  is  a  rough  depression  for  the  attachment  of  the  deep  portion  of  the  deltoid 
ligament  of  the  ankle-joint. 

The  lateral  surface  carries  a  large  triangular  facet,  concave  from  above  downward, 
for  articulation  with  the  lateral  malleolus;  its  anterior  half  is  continuous  above  with 
the  trochlea ;  and  in  front  of  it  is  a  rough  depression  for  the  attachment  of  the  ante- 
rior talofibular  ligament.  Between  the  posterior  half  of  the  lateral  border  of  the 
trochlea  and  the  posterior  part  of  the  base  of  the  fibular  articular  surface  is  a  tri- 
angular facet  (Fawcett-)  which  comes  into  contact  with  the  transverse  inferior 
tibiofibular  ligament  during  flexion  of  the  ankle-joint;  below  the  base  of  this  facet 
is  a  groo^-e  which  aft'ords  attachment  to  the  posterior  talofibular  ligament. 

The  posterior  surface  is  narrow,  and  traversed  by  a  groove  running  obliquely 
downward  and  mediahvard,  and  transmitting  the  tendon  of  the  Flexor  hallucis 
longus.  Lateral  to  the  groove  is  a  prominent  tubercle,  the  posterior  process,  to 
which  the  posterior  talofibular  ligament  is  attached;  this  process  is  sometimes 
separated  from  the  rest  of  the  talus,  and  is  then  known  as  the  os  trigonum.  Medial 
to  the  groove  is  a  second  smaller  tubercle. 

The  Neck  {collum  tali). — The  neck  is  directed  forward  and  medialw^ard,  and 
comprises  the  constricted  portion  of  the  bone  between  the  body  and  the  oval  head. 
Its  upper  and  medial  surfaces  are  rough,  for  the  attachment  of  ligaments;  its  lateral 
surface  is  concave  and  is  continuous  below  with  the  deep  groove  for  ,the  inter- 
osseous talocalcaneal  ligament. 

The  Head  {caput  tali). — The  head  looks  forward  and  mediahvard;  its  anterior 
articular  or  navicular  surface  is  large,  oval,  and  convex.  Its  inferior  surface  has  two 
facets,  which  are  best  seen  in  the  recent  condition.  The  medial,  situated  in  front 
of  the  middle  calcaneal  facet,  is  convex,  triangular,  or  semi-oval  in  shape,  and 
rests  on  the  plantar  calcaneonaA'icular  ligament;  the  lateral,  named  the  anterior 
calcaneal  articular  surface,  is  somewhat  flattened,  and  articulates  with  the  facet  on 
the  upper  surface  of  the  anterior  part  of  the  calcaneus. 

Articulations. — The  talus  articulates  with  four  bones:    tibia,  fibula,  calcaneus,  and  navicular. 

The  Cuboid  Bone  {os  ciiboideum)  (Fig.  -106). — The  cuboid  bone  is  placed  on  the 
lateral  side  of  the  foot,  in  front  of  the  calcaneus,  and  behind  the  fourth  and  fifth 
metatarsal  bones.    It  is  of  a  pyramidal  shape,  its  base  being  directed  mediahvard. 

1  Sewell  (Journal  of  Anatomy  and  Physiology,  vol.  xxxviii)  pointed  out  that  in  about  10  per  cent,  of  bones  a  small 
triangular  facet,  continuous  with  the  posterior  calcaneal  facet,  is  present  at  the  junction  of  the  lateral  surface  of  the 
body  with  the  posterior  wall  of  the  sulcus  tali. 

-  Edinburgh  Medical  Journal,  1895. 


368 


OSrEOLOCY 


Surfaces. — The  dorsal  surface,  directed  iijnvard  and  laterahvard,  is  rough,  for  the 
attachment  of  ligaments.  The  plantar  surface  presents  in  front  a  deep  groove, 
the  peroneal  sulcus,  which  runs  obliquely  forward  and  mediahvard;  it  lodges  the 
tendon  of  the  Peronaeus  longiis,  and  is  bounded  })ehind  by  a  prominent  ridge, 
to  which  the  long  plantar  ligament  is  attached.  The  ridge  ends  laterally  in  an 
eminence,  the  tuberosity,  the  surface  of  which  presents  an  oval  facet;  on  this  facet 
glides  the  sesamoid  bone  or  cartilage  frequently  found  in  the  tendon  of  the  Pero- 
naeus longus.  The  surface  of  bone  behind  the  groove  is  rough,  for  the  attachment 
of  the  plantar  calcaneocuboid  ligament,  a  few  fibres  of  the  Flexor  hallucis  brevis, 
and  a  fasciculus  from  the  tendon  of  the  Tibialis  posterior.  The  lateral  surface 
presents  a  deep  notch  formed  by  the  commencement  of  the  peroneal  sulcus.    The 

For  Srd  cuneiform        For  4(h  metatarsal 


Occasional  facet 
for  navicular      r. 


For  5th 
metatarsal 


^^        .,„^™.„.„«.  Pero?icEaZ       Tuhtroady  For  calcaneus 

sulcus 

A  B 

Fig.  406. — The  left  cuboid.     .-1.   Antero-medial  view.     B.  Postero-lateral  view. 


posterior  surface  is  smooth,  triangular,  and  concavo-convex,  for  articulation  with 
the  anterior  surface  of  the  calcaneus;  its  infero-medial  angle  projects  backward 
as  a  process  which  underlies  and  supports  the  anterior  end  of  the  calcaneus.  The 
anterior  surface,  of  smaller  size,  but  also  irregularly  triangular,  is  divided  by  a 
vertical  ridge  into  two  facets:  the  medial,  quadrilateral  in  form,  articulates  with 
the  fourth  metatarsal;  the  lateral,  larger  and  more  triangular,  articulates  with  the 
fifth.  The  medial  surface  is  broad,  irregularly  c[uadrilateral,  and  presents  at 
its  middle  and  upper  part  a  smooth  oval  facet,  for  articulation  with  the  third 
cuneiform;  and  behind  this  (occasionally)  a  smaller  facet,  for  articulation  with 
the  navicular ;  it  is  rough  in  the  rest  of  its  extent,  for  the  attachment  of  strong 
interosseous  ligaments. 

Articulations. — The  cuboid  articulates  with /owr  bones:    the  calcaneus,  third  cuneiform,  and 
fourth  and  fifth  metatarsak;  occasionally  with  a  fifth,  the  navicular. 


For  Ist  cuneiform 


For  2nd  cuneiform 


For  3rd 

cuneiform 


Occasional 
^ facet  for 
cuboid 

Fig.  407. — The  left  navicular.     A.  Antero-lateral  view.     B. 


For  ialas         Tuberosity 
Postero-medial  view. 


The  Navicular  Bone  {os  naviculare  pedis;  scaphoid  bone)  (Fig.  -107). — The 
navicular  bone  is  situated  at  the  medial  side  of  the  tarsus,  between  the  talus 
behind  and  the  cuneiform  bones  in  front. 


THE  TARSUS 


369 


Surfaces. — The  anterior  surface  is  convex  from  side  to  side,  and  subdivided  by  two 
ridges  into  three  facets,  for  articuhition  with  the  three  cuneiform  bones.  The 
posterior  surface  is  oval,  concave,  broader  hiterally  than  medially,  and  articulates 
with  the  rounded  head  of  the  talus.  The  dorsal  surface  is  convex  from  side  to  side, 
and  rough  for  the  attachment  of  ligaments.  The  plantar  surface  is  irregular,  and 
also  rough  for  the  attachment  of  ligaments.  The  medial  surface  presents  a  rounded 
tuberosity,  the  lower  ])art  of  which  gives  attachment  to  part  of  the  tendon  of  the 
Tibialis  posterior.  The  lateral  surface  is  rough  and  irregular  for  the  attachment  of 
ligaments,  and  occasionally  presents  a  small  facet  for  articulation  with  the  cuboid 
bone. 


Articulations. ^The  navicular  articulates  with/o«?-  bones: 
occasionallv  with  a  fifth,  the  cuboid. 


the  talus  and  the  three  cuneiforms; 


The  First  Cuneiform  Bone  (os cuneiform,  primum;  interned  cuneiform)  (Fig.  408). — 
The  first  cuneiform  bone  is  the  largest  of  the  three.cuneiforms.  It  is  situated  at  the 
medial  side  of  the  foot,  between 


For  1st  metatarsal 
-J 


For  2nd 
metatarsal 


For 
2nd  cuneiform 


For  tendon  of 
Tibialis  anterior 


For  navicular 


Fig.  40S.- 


-The  left  first    cuneiform.     A.  Antero-medial    view. 
B.  Postero-lateral  view. 


the  navicular  behind  and  the  base 
of  the  first  metatarsal  in  front. 

Surfaces. — The  medial  surface 
is  subcutaneous,  broad,  and 
quadrilateral;  at  its  anterior 
plantar  angle  is  a  smooth  oval 
impression,  into  which  part  of 
the  tendon  of  the  Tibialis  ante- 
rior is  inserted;  in  the  rest  of  its 
extent  it  is  rough  for  the  attach- 
ment of  ligaments.  The  lateral 
surface  is  concave,  presenting, 
along  its  superior  and  posterior 
borders  a  narrow  L-shaped  sur- 
face, the  vertical  limb  and  pos- 
terior part  of  the  horizontal  limb 

of  which  articulate  with  the  second  cuneiform,  while  the  anterior  part  of  the 
horizontal  limb  articulates  with  the  second  metatarsal  bone:  the  rest  of  this 
surface  is  rough  for  the  attachment  of  ligaments  and  part  of  the  tendon  of  the 
Peronaeus  longus.  The  anterior  surface,  kidney-shaped  and  much  larger  than 
the  posterior,  articulates  with  the  first  metatarsal  bone.  The  posterior  surface 
is  triangular,  concave,  and  articulates  with  the  most  medial  and  largest  of  the 
three  facets  on  the  anterior  surface  of  the  navicular.  The  plantar  surface  is 
rough,  and  forms  the  base  of  the  wedge;  at  its  back  part  is  a  tuberosity  for  the 
insertion  of  part  of  the  tendon  of  the  Tibialis  posterior.  It  also  gives  insertion 
in  front  to  part  of  the  tendon  of  the  Tibialis  anterior.  The  dorsal  surface  is  the 
narrow  end  of  the  wedge,  and  is  directed  upward  and  lateralward;  it  is  rough  for 
the  attachment  of  ligaments. 

Articulations. — -The  first  cuneiform  articulates  with,  four  bones:  the  navicular,  second  cunei- 
form, and  first  and  second  metatarsals. 

The  Second  Cuneiform  Bone  {os  cuneiforme  secundum;  middle  cuneiform)  (Fig. 
409). — The  second  cuneiform  bone,  the  smallest  of  the  three,  is  of  very  regular 
wedge-like  form,  the  thin  end  being  directed  downward.  It  is  situated  between 
the  other  two  cuneiforms,  and  articulates  with  the  navicular  behind,  and  the 
second  metatarsal  in  front. 

Surfaces. — The  anterior  surface,  triangular  in  form,  and  narrower  than  the  pos- 
terior, articulates  with  the  base  of  the  second  metatarsal  bone.  The  posterior  sur- 
face, also  triangular,  articulates  with  the  intermediate  facet  on  the  anterior  surface 
24 


370 


OSTEOLOGY 


of  the  navicular.  The  medial  surface  carries  an  L-shai)e(l  articular  facet,  running 
along  the  superior  and  posterior  borders,  for  articulation  Avitli  the  first  cuneiform, 
and  is  rough  in  the  rest  of  its  extent  for  the  attachment  of  ligaments.    The  lateral 

surface  presents  posteriorly  a  smooth 
For  1st  nmcifonn  For  navicular     facet  for  articulation  with  the  third 

cuneiform  bone.  The  dorsal  surface 
forms  the  base  of  the  wedge;  it  is 
quadrilateral  and  rough  for  the  at- 
tachment of  ligaments.  The  plantar 
surface,  sharp  and  tuberculated,  is 
also  rough  for  the  attachment  of 
ligaments,  and  for  the  insertion  of  a 
slip  from  the  tendon  of  the  Tibialis 
posterior. 


For  2nd  metatarsal  For  3rd  cuneiform 


Fig.  409. — The  left  second  cuneiform.      A.    Antero-medial 
view.     B.  Postero-lateral  view. 


Articulations. — The  second  cuneiform  articulates  with  four  bones:  the  navicular,  first  and 
third  cuneiforms,  and  second  metatarsal. 

The  Third  Cuneiform  Bone  (os  ciineifonne  tertium;  external  cuneiform)  (Fig.  410). 
— The  third  cuneiform  bone,  intermediate  in  size  between  the  two  preceding,  is 
wedge-shaped,  the  base  being  uppermost.  It  occupies  the  centre  of  the  front  row 
of  the  tarsal  bones,  between  the  second  cuneiform  medially,  the  cuboid  laterally, 
the  navicular  behind,  and  the  third  metatarsal  in  front. 

Surfaces.^ — The  anterior  surface,  triangular  in  form,  articulates  with  the  third 
metatarsal  bone.  The  posterior  surface  articulates  with  the  lateral  facet  on  the 
anterior  surface  of  the  navicular,  and  is  rough  below  for  the  attachment  of  liga- 
mentous fibres.  The  medial  surface  presents  an  anterior  and  a  posterior  articular 
facet,  separated  by  a  rough  depression:  the  anterior,  sometimes  divided,  articulates 
with  the  lateral  side  of  the  base  of  the  second  metatarsal  bone;  the  posterior  skirts 


For  navicular     For  2nd  cuneiform 


Fo7-  4th 
metatarsal         For  cuboid 


For  2nd 

metatarsal 

For  3rd 
metatarsal 
Fig.  410. — The  left  third  cuneiform.     .4.  Postero-medial  view.     B.  Antero-lateral  view. 


the  posterior  border,  and  articulates  with  the  second  cuneiform ;  the  rough  depres- 
sion gives  attachment  to  an  interosseous  ligament.  The  lateral  surface  also  pre- 
sents two  articular  facets,  separated  by  a  rough  non-articular  area;  the  anterior 
facet,  situated  at  the  superior  angle  of  the  bone,  is  small  and  semi-oval  in  shape, 
and  articulates  with  the  medial  side  of  the  base  of  the  fourth  metatarsal  bone; 
the  posterior  and  larger  one  is  triangular  or  oval,  and  articulates  with  the  cuboid; 
the  rough,  non-articular  area  serves  for  the  attachment  of  an  interosseous  ligament. 
The  three  facets  for  articulation  with  the  three  metatarsal  bones  are  continuous 
with  one  another;  those  for  articulation  with  the  second  cuneiform  and  navicular 
are  also  continuous,  but  that  for  articulation  with  the  cuboid  is  usually  separate. 
The  dorsal  surface  is  of  an  oblong  form,  its  postero-lateral  angle  being  prolonged 
backward.    The  plantar  surface  is  a  rounded  margin,  and  serves  for  the  attachment 


THE  METATARSUS 


371 


of  i)art  of  tlic  tendon  of  the  "rihialis  ])ost('rior,  i)art  of  the  Flexor  halhieis  brevis, 
and  lioaments. 

Articulations. — Thr  tliiid  cimciform  articulates  with  six  bones:    the  navicular,  second  cunei- 
form, cuboid,  and  second,  (liird,  and  fourth  metatarsals. 


The  Metatarsus. 

The  metatarsus  consists  of  five  bones  which  are  numbered  from  the  medial 
side  (ossa  meiatarsalia  I.-V.);  each  presents  for  examination  a  body  and  two 
extremities. 

Common  Characteristics  of  the  Metatarsal  Bones. — The  body  is  prismoid  in 
form,  tapers  gradually  from  the  tarsal  to  the  phalangeal  extremity,  and  is  curved 
longitudinally,  so  as  to  be  concave  below,  slightly  convex  above.  The  base  or 
posterior  extremity  is  wedge-shaped,  articulating  proximally  with  the  tarsal  bones, 
and  by  its  sides  with  the  contiguous  metatarsal  bones:  its  dorsal  and  plantar 
surfaces  are  rough  for  the  attachment  of  ligaments.  The  head  or  anterior  extremity 
presents  a  convex  articular  surface,  oblong  from  above  downward,  and  extend- 
ing farther  backward  below  than  above.  Its  sides  are  flattened,  and  on  each  is  a 
depression,  surmounted  by  a  tubercle,  for  ligamentous  attachment.  Its  plantar 
surface  is  grooved  antero-posteriorly  for  the  passage  of  the  Flexor  tendons,  and 
marked  on  either  side  by  an  articular  eminence  continuous  with  the  terminal 
articular  surface. 


For  sesamoid  hones 


For  \st  For  Peronoeus 

cuneiform  longus 

Fig.  411. — The  first  metatarsal.      (Left.) 


Foi  lit     "^  \ 
cuneifoim      For  2nd 
cuneiform 

Fig.  412 


For  3rd 

ciLueiforvi 

The  second  metatarsal.     (Left.) 


Characteristics  of  the  Individual  Metatarsal  Bones.  —  The  First  Metatarsal 
Bone  {os  metatarsale  I;  metatarsal  hone  of  the  great  toe)  (Fig.  411). — The  first 
metatarsal  bone  is  remarkable  for  its  great  thickness,  and  is  the  shortest  of 
the  metatarsal  bones.  The  body  is  strong,  and  of  well-marked  prismoid  form. 
The  base  presents,  as  a  rule,  no  articular  facets  on  its  sides,  but  occasionally 
on  the  lateral  side  there  is  an  oval  facet,  by  which  it  articulates  with  the  second 
metatarsal.    Its  proximal  articular  surface  is  of  large  size  and  kidney-shaped;  its 


372 


OSTEOLOGY 


circumference  is  grooved,  for  the  tarsometatarsal  ligaments,  and  mediall}'  gives 
insertion  to  part  of  the  tendon  of  the  Tibialis  anterior;  its  i)lantar  angle  presents 
a  rough  oval  prominence  for  the  insertion  of  the  tendon  of  the  Peronaeus  longus. 
The  head  is  large;  on  its  plantar  surface  are  two  grooved  facets,  on  which  glide 
sesamoid  bones;  the  facets  are  separated  by  a  smooth  elevation. 

The  Second  Metatarsal  Bone  {os  metatarsale  II)  (Fig.  412).- — The  second  meta- 
tarsal bone  is  the  longest  of  the  metatarsal  bones,  being  prolonged  backward 
into  the  recess  formed  by  the  three  cuneiform  bones.  Its  base  is  broad  above, 
narrow  and  rough  below.  It  presents  four  articular  surfaces:  one  behind,  of  a 
triangular  form,  for  articulation  with  the  second  cuneiform ;  one  at  the  upper  part 
of  its  medial  surface,  for  articulation  with  the  first  cuneiform;  and  two  on  its  lateral 
surface,  an  upper  and  lower,  separated  by  a  rough  non-articular  interval.  Each 
of  these  lateral  articular  surfaces  is  divided  into  two  by  a  vertical  ridge;  the  two 
anterior  facets  articulate  with  the  third  metatarsal;  the  two  posterior  (sometimes 
continuous)  with  the  third  cuneiform.  A  fifth  facet  is  occasionally  present  for 
articulation  with  the  first  metatarsal;  it  is  oval  in  shape,  and  is  situated  on  the 
medial  side  of  the  bodv  near  the  base. 


For  2nd 
metatarsal 


For 
Zrd 
cuneiform 

413. — The  third  metatarsal. 


For  Uh 
metatarsal 


(Left.) 


For  37  a 
meiataibul 


Foi  cuboid 

For  3rd  cuneiform  For  5th  metatarsal 

Fig.  414. — The  fourth  metatarsal.     (Left.) 


The  Third  Metatarsal  Bone  (os  metatarsale  III)  (Fig.  413). — The  third  meta- 
tarsal bone  articulates  proximally,  by  means  of  a  triangular  smooth  surface, 
with  the  third  cuneiform;  medially,  by  two  facets,  with  the  second  metatarsal; 
and  laterally,  by  a  single  facet,  with  the  fourth  metatarsal.  This  last  facet  is 
situated  at  the  dorsal  angle  of  the  base. 

The  Fourth  Metatarsal  Bone  (os  metatarsale  IV)  (Fig.  414). — The  fourth  meta- 
tarsal bone  is  smaller  in  size  than  the  preceding;  its  base  presents  an  oblique 
quadrilateral  surface  for  articulation  with  the  cuboid ;  a  smooth  facet  on  the  medial 
side,  divided  by  a  ridge  into  an  anterior  portion  for  articulation  with  the  third 
metatarsal,  and  a  posterior  portion  for  articulation  with  the  third  cuneiform;  on 
the  lateral  side  a  single  facet,  for  articulation  with  the  fifth  metatarsal. 

The  Fifth  Metatarsal  Bone  (os  metatarsale  V)  (Fig.  415). — The  fifth  metatarsal 
bone  is  recognized  by  a  rough  eminence,  the  tuberosity,  on  the  lateral  side  of  its 


THE  PHALANGES  OF  THE  FOOT 


373 


base.  The  base  nrticiilates  behind,  by  a  trianguhir  surt'aee  cut  obHquely  in  a  trans- 
^'e^se  direction,  with  the  cuboid;  and  medially,  with  the  fourth  metatarsal.  On 
the  medial  part  of  its  dorsal  surface  is  inserted  the  tendon  of  the  Peronaeus  tertius 
and  on  the  dorsal  surface  of  the  tuberosity  that  of  the  Peronaeus  brevis.  A  strong 
band  of  the  plantar  aponeurosis  connects  the  i)r()jecting  part  of  the  tuberosity 
with  the  lateral  process  of  the  tuberosity  of  the  calcaneus.  The  plantar  surface 
of  the  base  is  grooved  for  the  tendon  of  the  Abductor  digiti  quinti,  and  gives  origin 
to  the  Flexor  digiti  quinti  brevis. 


For  ith 
metatarsal         For  cuboid         Tuberosity 

Fig.  415. — The  fifth  metatarsal.      (Left.) 

Articulations. — The  base  of  each  metatarsal  bone  articulates  with  one  or  more  of  the  tarsal 
bones,  and  the  head  with  one  of  the  first  row  of  phalanges.  The  first  metatarsal  articulates  with 
the  first  cuneiform,  the  second  with  all  three  cuneiforms,  the  third  with  the  third  cuneiform,  the 
fourth  with  the  third  cuneiform  and  the  cuboid,  and  the  fifth  with  the  cuboid. 


The  Phalanges  of  the  Foot  (Phalanges  Digitorum  Pedis). 

The  phalanges  of  the  foot  correspond,  in  number  and  general  arrangement, 
with  those  of  the  hand;  there  are  two  in  the  great  toe,  and  three  in  each  of  the 
other  toes.  They  differ  from  them,  however,  in  their  size,  the  bodies  being  much 
reduced  in  length,  and,  especially  in  the  first  row,  laterally  compressed. 

First  Row. — The  phalanges  of  the  first  row  closely  resemble  those  of  the  hand. 
The  body  of  each  is  compressed  from  side  to  side,  convex  above,  concave  below. 
The  base  is  concave;  and  the  head  presents  a  trochlear  surface  for  articulation 
with  the  second  phalanx. 

Second  Row. — The  phalanges  of  the  second  row  are  remarkably  small  and  short, 
but  rather  broader  than  those  of  the  first  row. 

The  ungual  phalanges,  in  form,  resemble  those  of  the  fingers;  but  they  are  smaller 
and  are  flattened  from  above  downward ;  each  presents  a  broad  base  for  articula- 
tion with  the  corresponding  bone  of  the  second  row,  and  an  expanded  distal 
extremity  for  the  support  of  the  nail  and  end  of  the  toe. 

Articulations. — In  the  second,  third,  fourth,  and  fifth  toes  the  phalanges  of  the  first  row  articu- 
late behind  with  the  metatarsal  bones,  and  in  froAt  with  the  second  phalanges,  which  in  their 
turn  articulate  with  the  first  and  third:    the  imgual  phalanges  articulate  with  the  second.     In 


374 


OSTEOLOGY 


the  great  toe  the  first  phalanx  articulates  proximally  with  the  metatarsal  bone  and  distaUy  with 
the  ungual  phalanx. 

Ossification  of  the  Bones  of  the  Foot  (Fig.  416).— The  tarsal  bones  are  each  ossified  from  a 
single  centre,  excepting  the  calcaneus,  which  has  an  epiphysis  for  its  posterior  extremity.  The 
centres  make  their  appearance  in  the  following  order:  calcaneus  at  the  sixth  month  of  fetal  life; 
talus,  about  the  seventh  month;  cuboid,  at  the  ninth  month;  third  cuneiform,  during  the  first 
year;  first  cuneiform,  in  the  third  year;  second  cuneiform  and  navicular,  in  the  fourth  year. 
The  epiphysis  for  the  posterior  extremity  of  the  calcaneus  appears  at  the  tenth  year,  and  unites 
with  the  rest  of  the  bone  soon  after  puberty.  The  posterior  process  of  the  talus  is  sometimes 
ossified  from  a  separate  centre,  and  may  remain  distinct  from  the  main  mass  of  the  bone,  when 
it  is  named  the  os  trigonum. 


TARSUS. 

One  centre  for  each  hone, 
except  calcaneus 


OUTER  FOUR  METATARSALS. 

Two  centres  for  each  hone 
One  for  hody 
One  for  head 


PHALANGES. 

Two  centres  for  each  hone  . 
One  for  hody 
One  for  metatarsal 
extremity 


Appears  10th  year  ; 
unites  after  piiberty 


Appears  3rd  year 
)  Unite  18;h-20th  year 


^1  \;^''^ 

"^      %'     P  -'^l^l^ears  1th  week 


Unite  18-20  yr.  I 
Apps.  3rd  yr.  -  ^^^^ 

AjJ2J-  itii  yr. 
Unite  17-lS  yr.  I  ^^^ 

App.  2  4  mo.  —X 


is::^ 


App.  6-7th  yr.  .^         , 
Unite  17-18  yr.  I  ^^^ 

A2>2}-  2-4  mo.  -|\j1:  C~"? 

App.&thyr._  \f 

Unite  17-18  yr.  ?'^  J  ^ 

App.  7th  wk.  -S^S; 

Fig.  416. — Plan  of  ossification  of  the  foot. 

The  metatarsal  bones  are  each  ossified  from  tivo  centres:  one  for  the  body,  and  one  for  the 
head,  of  the  second,  thu-d,  fourth,  and  fifth  metatarsals;  one  for  the  body,  and  one  for  the  base, 
of  the  first  metatarsal.^  Ossification  commences  in  the  centre  of  the  body  about  the  ninth  week, 
and  extends  toward  either  extremity.  The  centre  for  the  base  of  the  first  metatarsal  appears 
about  the  third  year;  the  centres  for  the  heads  of  the  other  bones  between  the  fifth  and  eighth 
years;  they  join  the  bodies  between  the  eighteenth  and  twentieth  years. 

The  phalanges  are  each  ossified  from  tu-o  centres:  one  for  the  body,  and  one  for  the  base. 
The  centre  for  the  body  appears  about  the  tenth  week,  that  for  the  base  between  the  fourth  and 
tenth  years;  it  joins  the  body  about  the  eighteenth  year. 


1  As  was  noted  in  the  first  metacarpal  (see  footnote,  page  332),  so  in  the  first  metatarsal,  there  is  often  a  second 
epiphysis  for  its  head. 


COMPARISON  OF  THE  BOXES  OF  THE  IIAXD  AXD  FOOT  375 


Comparison  of  the  Bones  of  the  Hand  and  Foot. 

The  haiiil  and  foot  are  constructed  on  somewhat  siniihir  i)rinciples,  each  con- 
sisting of  a  proximal  part,  the  carpus  or  the  tarsus,  a  middle  portion,  the  meta- 
carpus, or  the  metatarsus,  and  a  terminal  portion,  the  phalanges.  The  proximal 
part  consists  of  a  series  of  more  or  less  cubical  bones  which  allow  a  slight  amount 
of  gliding  on  one  another  and  are  chiefly  concerned  in  distributing  forces  transmitted 
to  or  from  the  bones  of  the  arm  or  leg.  The  middle  part  is  made  up  of  slightly 
movable  long  bones  which  assist  the  carpus  or  tarsus  in  distributing  forces  and 
also  give  greater  breadth  for  the  reception  of  such  forces.  The  separation  of  the 
indi\idual  bones  from  one  another  allows  of  the  attachments  of  the  Interossei  and 
protects  the  dorsi-palmar  and  dorsi-plantar  vascular  anastomoses.  The  terminal 
portion  is  the  most  movable,  and  its  separate  elements  enjoy  a  varied  range  of 
movements,  the  chief  of  which  are  flexion  and  extension. 

The  function  of  the  hand  and  foot  are,  however,  very  different,  and  the  general 
similarity  between  them  is  greatly  modified  to  meet  these  requirements.  Thus  the 
foot  forms  a  firm  basis  of  support  for  the  body  in  the  erect  posture,  and  is  there- 
fore more  solidly  built  up  and  its  component  parts  are  less  movable  on  each  other 
than  those  of  the  hand.  In  the  case  of  the  phalanges  the  dift'erence  is  readily 
noticeable;  those  of  the  foot  are  smaller  and  their  movements  are  more  limited 
than  those  of  the  hand.  Very  much  more  marked  is  the  difference  between  the 
metacarpal  bone  of  the  thumb  and  the  metatarsal  bone  of  the  great  toe.  The  meta- 
carpal bone  of  the  thumb  is  constructed  to  permit  of  great  mobility,  is  directed  at 
an  acute  angle  from  that  of  the  index  finger,  and  is  capable  of  a  considerable  range 
of  movements  at  its  articulation  w^ith  the  carpus.  The  metatarsal  bone  of  the 
great  toe  assists  in  supporting  the  weight  of  the  body,  is  constructed  with  great 
solidity,  lies  parallel  with  the  other  metatarsals,  and  has  a  very  limited  degree  of 
mobility.  The  carpus  is  small  in  proportion  to  the  rest  of  the  hand,  is  placed 
in  line  with  the  forearm,  and  forms  a  transverse  arch,  the  concavity  of  which 
constitutes  a  bed  for  the  Flexor  tendons  and  the  palmar  vessels  and  nerves.  The 
tarsus  forms  a  considerable  part  of  the  foot,  and  is  placed  at  right  angles  to  the 
leg,  a  position  which  is  almost  peculiar  to  man,  and  has  relation  to  his  erect  pos- 
ture. In  order  to  allow  of  their  supporting  the  weight  of  the  body  with  the  least 
expenditure  of  material  the  tarsus  and  a  part  of  the  metatarsus  are  constructed 
in  a  series  of  arches  (Figs.  417,  418),  the  disposition  of  which  will  be  considered 
after  the  articulations  of  the  foot  have  been  described. 

Applied  Anatomy. — Considering  the  injuries  to  which  the  foot  is  subjected,  it  is  sui-prising 
how  seldom  the  tarsal  bones  are  fractured.  This  is  no  doubt  due  to  the  fact  that  the  tarsus  is 
composed  of  a  number  of  bones,  articulated  by  a  considerable  extent  of  sm-face,  and  joined 
together  by  verj'^  strong  ligaments  which  serve  to  break  the  force  of  violence  appUed  to  this  part 
of  the  body.  TMien  fracture  does  occur,  these  bones  being  composed  for  the  most  part  of  a  soft 
cancellous  structm-e,  covered  only  by  a  thin  shell  of  compact  tissue,  are  often  extensively  com- 
minuted, especially  as  most  of  the  fractm-es  are  produced  by  direct  violence;  and,  as  there  is 
only  a  verj'  scanty  amount  of  soft  parts  over  the  bones,  the  fractures  are  very  often  compound, 
and  amputation  is  often  necessary. 

TMien  fracture  occm-s  in  the  anterior  gi-oup  of  tarsal  bones,  it  is  almost  invariabh'  the  result 
of  direct  violence;  but  fractm-es  of  the  posterior  group — that  is,  of  the  calcaneus  and  talus — are 
usually  produced  by  falls  from  a  height  on  to  the  feet. 

In  club-foot  (talipes),  especially  in  congenital  cases,  the  bones  of  the  tarsus  become  altered  in 
shape  and  size,  and  displaced  from  their  proper  positions.  This  is  principally  the  case  in  con- 
genital tahpes  equinovarus,  in  which  the  head  of  the  talus  becomes  twisted  and  atrophied,  and 
a  similar  condition  maj-  be  present  in  the  other  bones,  more  especially  the  navicular.  The  tarsal 
bones  are  peculiarly  hable  to  become  the  seat  of  tuberculous  caries  following  comparativeh'  trivial 
injuries,  especiallj'  as  thej"  are  not  maintained  in  a  condition  of  rest  to  the  same  extent  as  some 
other  parts  of  the  body  after  similar  injuries.  Caries  of  the  calcaneus  or  talus  maj'  remain  Limited 
to  the  one  bone  for  a  long  period,  but  when  one  of  the  other  bones  is  affected,  the  remainder 


376 


OSTEOLOGY 


frequently  become  involved,  since  the  disease  spreads  througii  the  lurfi;e  and  complicated  synovial 
membrane  which  is  more  or  less  common  to  these  bones. 

Amputation  of  the  foot  is  often  required  either  for  injury  or  disease.    The  principal  amputa- 
tions are  as  follows:     (1)  Syme's:    amputation  at  the  ankle-joint  by  a  heel  flap,  with  removal  of 


Fig.  417. — Skeleton  of  foot.     Medial  aspect. 

the  malleoli  and  sometimes  a  thin  shce  from  the  lower  end  of  the  tibia.  (2)  Pirogoff's:  amputa- 
tion of  the  whole  of  the  tarsal  bones  (except  the  posterior  part  of  the  calcaneus),  and  a^thin  slice 
from  the  tibia  and  fibula,  including  the  two  malleoli.  The  sawn  surface  of  the  calcaneus  is  then 
turned  up  and  united  to  the  cut  surface  of  the  tibia.  (3)  Subastragalar:  amputation  of  the^foot 
below  the  talus  through  the  joint  between  it  and  the  calcaneus. 


Fig.  418. — Skeleton  of  foot.     Lateral  aspect. 

The  bones  of  the  tarsus  occasionally  require  removal  individually.  This  is  especially  the  case 
with  the  talus  for  tuberculous  disease  hmited  to  that  bone;  or  the  talus  may  require  excision  in 
cases  of  subastragalar  dislocation,  or  in  cases  of  inveterate  talipes.  The  cuboid  has  been  removed 
for  the  same  reason. 

Fractures  of  the  metatarsal  bones  and  phalanges  are  nearly  always  the  result  of  direct  violence, 
and  in  the  majority  of  cases  the  injury  is  caused  by  severe  crushing  accidents,  necessitating 
amputation.  The  metatarsal  bones,  and  especially  that  of  the  great  toe,  are  frequently  diseased, 
either  in  tuberculous  subjects  or  in  patients  with  perforating  ulcer  of  the  foot. 

The  Sesamoid  Bones  (Ossa  Sesamoidea). 

Sesamoid  bones  are  small  more  or  less  rounded  masses  embedded  in  certain 
tendons  and  usually  related  to  joint  surfaces.  Their  functions  probably  are  to 
modify  pressure,  to  diminish  friction,  and  occasionally  to  alter  the  direction  of  a 
muscle  pull.  That  they  are  not  developed  to  meet  certain  physical  requirements 
in  the  adult  is  evidenced  by  the  fact  that  they  are  present  as  cartilagionus  nodules 
in  the  fetus,  and  in  greater  numbers  than  in  the  adult.  They  must  be  regarded, 
according  to  Thilenius,  as  integral  parts  of  the  skeleton  phylogenetically  inherited.^ 


Morpholog.  Arbeiten,  1906,  v,  309. 


77//';  Sl<:SAMOlD  BONES  377 

Physical  necessities  probably  come  into  play  in  selecting  and  in  reoulating  the 
degree  of  development  of  the  original  cartilaginons  nodules.  Nevertheless,  irreg- 
ular nodules  of  bone  may  appear  as  the  result  of  intermittent  i)ressure  in  certain 
regions,  c.  g.,  the  "rider's  bone,"  which  is  occasionally  (levek)ped  in  the  Adductor 
muscles  of  the  thigh. 

Sesamoid  bones  are  invested  by  the  fibrous  tissue  of  the  tendons,  except  on  the 
surfaces  in  contact  with  the  i)arts  over  which  they  glide,  where  they  present 
smooth  articular  facets. 

In  the  upper  extremity  the  sesamoid  bones  of  the  joints  are  found  only  on  the 
palmar  surface  of  the  hand.  Two,  of  which  the  medial  is  the  the  larger,  are  constant 
at  the  metacarpophalangeal  joint  of  the  thumb;  one  is  frequently  present  in  the 
corresponding  joint  of  the  little  finger,  and  one  (or  two)  in  the  same  joint  of  the 
index  finger.  Sesamoid  bones  are  also  found  occasionally  at  the  metacarpophal- 
angeal joints  of  the  middle  and  ring  fingers,  at  the  interphalangeal  joint  of  the 
thumb  and  at  the  distal  interphalangeal  joint  of  the  index  finger. 

In  the  lower  extremity  the  largest  sesamoid  bone  of  the  joints  is  the  patella, 
developed  in  the  tendon  of  the  Quadriceps  femoris.  On  the  plantar  aspect  of  the 
foot,  two,  of  which  the  medial  is  the  larger,  are  always  present  at  the  metatar- 
sophalangeal joint  of  the  great  toe;  one  sometimes  at  the  metatarsophalangeal 
joints  of  the  second  and  fifth  toes,  one  occasionally  at  the  corresponding  joint  of 
the  third  and  fourth  toes,  and  one  at  the  interphalangeal  joint  of  the  great  toe. 

Sesamoid  bones  apart  from  joints  are  seldom  found  in  the  tendons  of  the  upper 
limb;  one  is  sometimes  seen  in  the  tendon  of  the  Biceps  brachii  opposite  the  radial 
tuberosity.  They  are,  however,  present  in  several  of  the  tendons  of  the  lower 
limb,  viz.,  one  in  the  tendon  of  the  Peronaeus  longus,  where  it  glides  on  the  cuboid; 
one,  appearing  late  in  life,  in  the  tendon  of  the  Tibialis  anterior,  opposite  the  smooth 
facet  of  the  first  cuneiform  bone;  one  in  the  tendon  of  the  Tibialis  posterior,  oppo- 
site the  medial  side  of  the  head  of  the  talus;  one  in  the  lateral  head  of  the  Gastroc- 
nemius, behind  the  lateral  condyle  of  the  femur;  and  one  in  the  tendon  of  the  Psoas 
major,  where  it  glides  over  the  pubis.  Sesamoid  bones  are  found  occasionally 
in  the  tendon  of  the  Glutaeus  maximus,  as  it  passes  over  the  greater  trochanter, 
and  in  the  tendons  which  wind  around  the  medial  and  lateral  malleoli. 


SYN1)ESM()1.()(JY 


rpHE  bones  of  the  skeleton  are  joined  to  one  another  at  dift'erent  parts  of  their 
J-  surfaces,  and  such  connections  are  termed  Joints  or  Articulations.  Where 
the  joints  are  immovable,  as  in  the  articulations  between  practically  all  the  bones 
of  the  skull,  the  adjacent  margins  of  the  bones  are  almost  in  contact,  being  separated 
merely  by  a  thin  layer  of  fibrous  membrane,  named  the  sutural  ligament.  In  certain 
regions  at  the  base  of  the  skull  this  fibrous  membrane  is  replaced  by  a  layer  of  car- 
tilage. Where  slight  movement  combined  with  great  strength  is  required,  the  osseous 
surfaces  are  united  by  tough  and  elastic  fibrocartilages,  as  in  the  joints  between  the 
vertebral  bodies,  and  in  the  interpubic  articulation.  In  the  freely  movable  joints 
the  surfaces  are  completely  separated;  the  bones  forming  the  articulation  are  ex- 
panded for  greater  convenience  of  mutual  connection,  covered  by  cartilage  and 
enveloped  by  capsules  of  fibrous  tissue.  The  cells  lining  the  interior  of  the  fibrous 
capsule  form  an  imperfect  membrane — the  sjmovial  membrane — which  secretes 
a  lubricating  fluid.  The  joints  are  strengthened  by  strong  fibrous  bands  called 
ligaments,  which  extend  between  the  bones  forming  the  joint. 

Bone. — Bone  constitutes  the  fundamental  element  of  all  the  joints.  In  the 
long  bones,  the  extremities  are  the  parts  which  form  the  articulations;  they  are 
generally  somewhat  enlarged;  and  consist  of  spongy  cancellous  tissue  with  a  thin 
coating  of  compact  substance.  In  the  flat  bones,  the  articulations  usually  take 
place  at  the  edges;  and  in  the  short  bones  at  various  parts  of  their  surfaces.  The 
layer  of  compact  bone  which  forms  the  joint  surface,  and  to  which  the  articular 
cartilage  is  attached,  is  called  the  articular  lamella.  It  differs  from  ordinary 
bone  tissue  in  that  it  contains  no  Haversian  canals,  and  its  lacunee  are  larger 
and  have  no  canaliculi.  The  vessels  of  the  cancellous  tissue,  as  they  approach 
the  articular  lamella,  turn  back  in  loops,  and  do  not  perforate  it;  this  layer  is  con- 
sequently denser  and  firmer  than  ordinary  bone,  and  is  evidently  designed  to  form 
an  unyielding  support  for  the  articular  cartilage. 

Articular  Cartilage. — Articular  cartilage,  which  covers  the  articular  surfaces  of 
bones,  and  fibrocartilages,  which  enters  into  the  structure  of  some  of  the  joints, 
are  described  in  the  section  on  Histology  (pages  47  and  48). 

Ligaments. — Ligaments  are  composed  mainly  of  bundles  of  white  fibrous  tissue 
placed  parallel  with,  or  closely  interlaced  with  one  another,  and  present  a  w^hite, 
shining,  silvery  appearance.  They  are  pliant  and  flexible,  so  as  to  allow  perfect 
freedom  of  movement,  but  strong,  tough,  and  inextensible,  so  as  not  to  yield 
readily  to  applied  force.  Some  ligaments  consist  entirely  of  yellow  elastic  tissue, 
as  the  ligamenta  flava  which  connect  together  the  lamince  of  adjacent  vertebrae, 
and  the  ligamentum  nuchae  in  the  lower  animals.  In  these  cases  the  elasticity  of 
the  ligament  is  intended  to  act  as  a  substitute  for  muscular  power. 

The  Articular  Capsules. — The  articular  capsules  form  complete  envelopes  for  the 
freely  movable  joints.  Each  capsule  consists  of  two  strata — an  external  {stratum 
fibrosum)  composed  of  white  fibrous  tissue,  and  an  internal  (stratum  synoviale) 
which  is  a  secreting  layer,  and  is  usually  described  separately  as  the  synovial 
membrane. 

The  fibrous  capsule  is  attached  to  the  whole  circumference  of  the  articular  end 
of  each  bone  entering  into  the  joint,  and  thus  entirely  surrounds  the  articulation. 


380  SYNDESMOLOGY 

The  synovial  membrane  imests  the  inner  surface  of  the  fibrous  capsule,  and  is 
reflected  over  any  tendons  i)assing  through  the  joint  cavity,  as  the  tendon  of  the 
Popliteus  in  the  knee,  and  the  tendon  of  the  Biceps  brachii  in  the  shoulder.  It  is 
composed  of  a  thin,  delicate,  connective  tissue,  with  branched  connective-tissue 
corpuscles  Its  secretion  is  thick,  viscid,  and  glairy,  like  the  white  of  an  egg,  and 
is  hence  termed  synovia.  In  the  fetus  this  membrane  is  said,  by  Toynbee,  to  be 
continued  over  the  surfaces  of  the  cartilages;  but  in  the  adult  such  a  continuation 
is  wanting,  excepting  at  the  circumference  of  the  cartilage,  upon  which  it  encroaches 
for  a  short  distance  and  to  which  it  is  firmly  attached.  In  some  of  the  joints  the 
synovial  membrane  is  thrown  into  folds  which  pass  across  the  cavity;  they  are 
especially  distinct  in  the  knee.  In  other  joints  there  are  flattened  folds,  subdivided 
at  their  margins  into  fringe-like  processes  which  contain  convoluted  vessels. 
These  folds  generally  project  from  the  synovial  membrane  near  the  margin  of  the 
cartilage,  and  lie  flat  upon  its  surface.  They  consist  of  connective  tissue,  covered 
with  endothelium,  and  contain  fat  cells  in  variable  quantities,  and,  more  rarely, 
isolated  cartilage  cells;  the  larger  folds  often  contain  considerable  quantities  of 
fat. 

Closely  associated  with  synovial  membrane,  and  therefore  conveniently  described 
in  this  section,  are  the  mucous  sheaths  of  tendons  and  the  mucous  bursse. 

Mucous  sheaths  (vaginae  mucosae)  serve  to  facilitate  the  gliding  of  tendons  in 
fibroosseous  canals.  Each  sheath  is  arranged  in  the  form  of  an  elongated  closed 
sac,  one  layer  of  w^hich  adheres  to  the  wall  of  the  canal,  and  the  other  is  reflected 
upon  the  surface  of  the  enclosed  tendon.  These  sheaths  are  chiefly  found  surround- 
ing the  tendons  of  the  Flexor  and  Extensor  muscles  of  the  fingers  and  toes  as  they 
pass  through  fibroosseous  canals  in  or  near  the  hand  and  foot. 

Bursae  mucosae  are  interposed  between  surfaces  which  glide  upon  each  other. 
They  consist  of  closed  sacs  containing  a  minute  quantity  of  clear  viscid  fluid,  and 
may  be  grouped,  according  to  their  situations,  under  the  headings  subcutaneous, 
submuscular,  subfacial,  and  subtendinous. 

CLASSIFICATION    OF   JOINTS. 

The  articulations  are  divided  into  three  classes:  synarthroses  or  immovable, 
amphiarthroses  or  slightly  movable,  and  diarthroses  or  freely  movable,  joints. 

Synarthroses  (immovable  articulations). — Synarthroses  include  all  those  articu- 
lations in  which  the  surfaces  of  the  bones  are  in  almost  direct  contact,  fastened 
together  by  intervening  connective  tissue  or  hyaline  cartilage,  and  in  which  there 
is  no  appreciable  motion,  as  in  the  joints  between  the  bones  of  the  skull,  excepting 
those  of  the  mandible.  There  are  four  varieties  of  synarthrosis:  sutura,  schindylesis, 
gomphosis,  and  synchondrosis. 

Suturalligament  .^^^\  /  Cartilage 

Periosteum  '.•■•■- -^rn  w  / 


Pericliondrii 

Periosteum 

Fig.  419. — Section  across  the  sagittal  suture.  Fig.  420. — Section  through  occipitosphenoid  synchon- 

drosis of  an  infant. 

Sutura. — Sutura  is  that  form  of  articulation  where  the  contiguous  margins  of  the 
bones  are  united  by  a  thin  layer  of  fibrous  tissue;  it  is  met  with  only  in  the  skull 
(Fig.  419).  When  the  margins  of  the  bones  are  connected  by  a  series  of  processes, 
and  indentations  interlocked  together,  the  articulation  is  termed  a  true  suture 


CLASS! FIC AT JOX  OF  JOIXTS  381 

(sntiira  irra);  aiul  of  this  there  are  three  \urieties:  sutura  dentata,  serrata,  and 
limbosa.  The  margins  of  the  bones  are  not  in  direct  contact,  being  separated  by  a 
thin  hiyer  of  fibrous  tissue,  continuous  externally  with  the  pericranium,  internally 
with  the  dura  mater.  The  sutura  dentata  is  so  called  from  the  tooth-like  form  of 
the  projecting  processes,  as  in  the  suture  between  the  parietal  bones.  In  the 
sutura  serrata  the  edges  of  the  bones  are  serrated  like  the  teeth  of  a  fine  saw,  as 
between  the  two  portions  of  the  frontal  bone.  In  the  sutura  limbosa,  there  is  besides 
the  interlocking,  a  certain  degree  of  bevelling  of  the  articular  surfaces,  so  that  the 
bones  overlap  one  another,  as  in  the  suture  between  the  parietal  and  frontal  bones. 
When  the  articulation  is  formed  by  roughened  surfaces  placed  in  apposition  with 
one  another,  it  is  termed  a  false  suture  {siititm  notlia),  of  which  there  are  two  kinds: 
the  sutura  squamosa,  formed  by  the  overlapping  of  contiguous  bones  by  broad 
bevelled  margins,  as  in  the  squamosal  suture  between  the  temporal  and  parietal, 
and  the  sutura  harmonia,  where  there  is  simple  apposition  of  contiguous  rough 
surfaces,  as  in  the  articulation  between  the  maxilla?,  or  between  the  horizontal 
parts  of  the  palatine  bones. 

Schindylesis. — Schindylesis  is  that  form  or  articulation  in  which  a  thin  plate 
of  bone  is  received  into  a  cleft  or  fissure  formed  by  the  separation  of  two  lamina?  in 
another  bone,  as  in  the  articulation  of  the  rostrum  of  the  sphenoid  and  perpendicular 
plate  of  the  ethmoid  with  the  vomer,  or  in  the  reception  of  the  latter  in  the  fissure 
between  the  maxillte  and  between  the  palatine  bones. 

Gomphosis. — Gomphosis  is  articulation  by  the  insertion  of  a  conical  process  into 
a  socket;  this  is  not  illustrated  by  any  articulation  between  bones,  properly  so 
called,  but  is  seen  in  the  articulations  of  the  roots  of  the  teeth  with  the  alveoli 
of  the  mandible  and  maxillse. 

Synchondrosis. — Where  the  connecting  medium  is  cartilage  the  joint  is  termed 
a  synchondrosis  (Fig.  420).  This  is  a  temporary  form  of  joint,  for  the  cartilage 
is  converted  into  bone  before  adult  life.  Such  joints  are  found  between  the 
epiphyses  and  bodies  of  long  bones,  between  the  occipital  and  the  sphenoid  at, 
and  for  some  years  after,  birth,  and  between  the  petrous  portion  of  the  temporal 
and  the  jugular  process  of  the  occipital. 

Amphiarthroses    [slightly    movable    articulations). — In    these    articulations    the 
contiguous  bony  surfaces  are  either  connected  by  broad  flattened  disks  of  fibro- 
cartilage,  of  a  more  or  less  complex  struc- 
ture, as   in  the   articulations  between  the 
bodies  of  the  vertebrae;  or  are  united  by  an  Ligamenu 

interosseous  ligament,    as    in    the    inferior  '^'.''^  '^^  7     ' 

tibiofibular  articulation.     The  first  form  is      a.,-    1°^^'^' !^r 

1  ,.,„.,-,,,      ^1  1       Articular  cartilage. 

termed  a  symphysis  (hig.  421),  the  second 
a  syndesmosis. 

DiarthrOSeS  (freely    movable    articulations).         Fig.  421.— Diagrammatic  section  of  a  symphysis. 

— This  class   includes   the   greater  number 

of  the  joints  in  the  body.  In  a  diarthrodial  joint  the  contiguous  bony  surfaces 
are  covered  with  articular  cartilage,  and  connected  by  ligaments  lined  by  synovial 
membrane  (Fig.  422).  The  joint  may  be  divided,  completely  or  incompletely, 
by  an  articular  disk  or  meniscus,  the  periphery  of  which  is  continuous  with 
the  fibrous  capsule  while  its  free  surfaces  are  covered  by  synovial  membrane 
(Fig.  423). 

The  varieties  of  joints  in  this  class  have  been  determined  by  the  kind  of  motion 
permitted  in  each.  There  are  two  varieties  in  which  the  movement  is  uniaxial,  that 
is  to  say,  all  movements  take  place  around  one  axis.  In  one  form,  the  ginglymus, 
this  axis  is,  practically  speaking,  transverse;  in  the  other,  the  trochoid  or  pivot- 
joint,  it  is  longitudinal.  There  are  two  varieties  where  the  movement  is  biaxial, 
or  around  two  horizontal  axes  at  right  angles  to  each  other,  or  at  any  intervening 


382 


SYNDESMOLOGY 


axis  between  the  two.  These  are  the  condyloid  and  X\\v  saddle-joint.  There  is 
one  form  where  the  movement  is  polyaxial,  the  enarthrosis  or  ball-and-socket  joint; 
and  finally  there  are  the  arthrodia  or  gliding  joints. 


Articular  cartilage 
Synovial  memhrane 
Fibrous  capsule 


Fig.  422. — Diagrammatic  section  of  a  diarthrodial  joint. 


Synovial  memhrane 

Articular  cartilage 
Articular  disc 


Fibrous  capsule 


Fig.  423. — Diagrammatic  section  of  a  diarthrodial 
joint,  with  an  articular  disk. 


Ginglymus  or  Hinge-joint.- — In  this  form  the  articular  surfaces  are  moulded 
to  each  other  in  such  a  manner  as  to  permit  motion  only  in  one  plane,  forward 
and  backward,  the  extent  of  motion  at  the  same  time  being  considerable.  The 
direction  wdiich  the  distal  bone  takes  in  this  motion  is  seldom  in  the  same  plane 
as  that  of  the  axis  of  the  proximal  bone;  there  is  usually  a  certain  amount  of  devia- 
tion from  the  straight  line  during  flexion.  The  articular  surfaces  are  connected 
together  by  strong  collateral  ligaments,  which  form  their  chief  bond  of  union. 
The  best  examples  of  ginglymus  are  the  interphalangeal  joints  and  the  joint  between 
the  humerus  and  ulna;  the  knee-  and  ankle-joints  are  less  typical,  as  they  allow 
a  slight  degree  of  rotation  or  of  side-to-side  movement  in  certain  positions  of  the 
limb. 

Trochoid  or  Pivot-joint  (articulatio  trochoidea;  rotary  joint). — Where  the  movement 
is  limited  to  rotation,  the  joint  is  formed  by  a  pivot-like  process  turning  within 
a  ring,  or  a  ring  on  a  pivot,  the  ring  being  formed  partly  of  bone,  partly  of  ligament. 
In  the  proximal  radioulnar  articulation,  the  ring  is  formed  by  the  radial  notch 
of  the  ulna  and  the  annular  ligament;  here,  the  head  of  the  radius  rotates  w^ithin 
the  ring.  In  the  articulation  of  the  odontoid  process  of  the  axis  with  the  atlas 
the  ring  is  formed  in  front  by  the  anterior  arch,  and  behind  b}^  the  transverse 
ligament  of  the  atlas;  here,  the  ring  rotates  around  the  odontoid  process. 

Condyloid  Articulation  {articulatio  ellipsoidea). — In  this  form  of  joint,  an  ovoid 
articular  surface,  or  condyle,  is  received  into  an  elliptical  cavity  in  such  a  manner 
as  to  permit  of  flexion,  extension,  adduction,  abduction,  and  circumduction,  but 
no  axial  rotation.    The  wrist-joint  is  an  example  of  this  form  of  articulation. 

Articulation  by  Reciprocal  Reception  {articidatio  sellaris;  saddle-joint). — In  this 
variety  the  opposing  surfaces  are  reciprocally  concavo-convex.  The  movements 
are  the  same  as  in  the  preceding  form ;  that  is  to  say,  flexion,  extension,  adduction, 
abduction,  and  circumduction  are  allowed;  but  no  axial  rotation.  The  best  example 
of  this  form  is  the  carpometacarpal  joint  of  the  thumb. 

Enarthrosis  (ball-and-socket  joints) . — Enarthrosis  is  a  joint  in  which  the  distal 
bone  is  capable  of  motion  around  an  indefinite  number  of  axes,  which  have  one 
common  centre.  It  is  formed  by  the  reception  of  a  globular  head  into  a  cup-like 
cavity,  hence  the  name  "ball-and-socket."  Examples  of  this  form  of  articulation 
are  found  in  the  hip  and  shoulder. 

Arthrodia  {gliding  joints)  is  a  joint  which  admits  of  only  gliding  movement;  it 
is  formed  by  the  apposition  of  plane  surfaces,  or  one  slightly  concave,  the  other 
slightly  convex,  the  amount  of  motion  between  them  being  limited  by  the  ligaments 


THE  KIXDS  OF  MOVEMENT  ADMITTED  IX  ,101  XT S  383 

or  osseous  processes  surroiiiiding  the  articulation.  It  is  the  form  present  in  the 
joints  between  the  articuUir  processes  of  the  \'ertebr8e,  the  car])al  joints,  except 
that  of  the  capitate  with  the  navicular  and  lunate,  and  the  tarsal  joints  with  the 
exception  of  that  between  the  talus  and  the  navicular. 


THE  KINDS  OF  MOVEMENT   ADMITTED  IN  JOINTS. 

The  movements  admissible  in  joints  may  be  divided  into  four  kinds:  gliding 
and  angular  movements,  circumduction,  and  rotation.  These  movements  are  often, 
however,  more  or  less  combined  in  the  various  joints,  so  as  to  produce  an  infinite 
variety,  and  it  is  seldom  that  onh'  one  kind  of  motion  is  found  in  any  particular 
joint. 

Gliding  Movement. — Gliding  movement  is  the  simplest  kind  of  motion  that  can 
take  place  in  a  joint,  one  surface  gliding  or  moving  over  another  without  any 
angular  or  rotatory  movement.  It  is  common  to  all  movable  joints;  but  in  some, 
as  in  most  of  the  articulations  of  the  carpus  and  tarsus,  it  is  the  only  motion  per- 
mitted. This  movement  is  not  confined  to  plane  surfaces,  but  may  exist  between 
any  two  contiguous  surfaces,  of  whatever  form. 

Angular  Movement. — Angular  movement  occurs  only  between  the  long  bones, 
and  by  it  the  angle  between  the  two  bones  is  increased  or  diminished.  It  may 
take  place:  (1)  forward  and  backward,  constituting  flexion  and  extension;  or  (2) 
toward  and  from  the  median  plane  of  the  body,  or,  in  the  case  of  the  fingers  or 
toes,  from  the  middle  line  of  the  hand  or  foot,  constituting  adduction  and  abduction. 
The  strictly  ginglymoid  or  hinge-joints  admit  of  flexion  and  extension  only.  Abduc- 
tion and  adduction,  combined  with  flexion  and  extension,  are  met  with  in  the  more 
movable  joints;  as  in  the  hip,  the  shoulder,  the  wrist,  and  the  carpometacarpal 
joint  of  the  thumb. 

Circumduction.^ — Circumduction  is  that  form  of  motion  which  takes  place  between 
the  head  of  a  bone  and  its  articular  cavity,  when  the  bone  is  made  to  circumscribe 
a  conical  space;  the  base  of  the  cone  is  described  by  the  distal  end  of  the  bone, 
the  apex  is  in  the  articular  cavity ;  this  kind  of  motion  is  best  seen  in  the  shoulder- 
and  hip-joints. 

Rotation.- — Rotation  is  a  form  of  movement  in  which  a  bone  moves  around  a 
central  axis  without  undergoing  any  displacement  from  this  axis ;  the  axis  of  rota- 
tion may  lie  in  a  separate  bone,  as  in  the  case  of  the  pivot  formed  by  the  odontoid 
process  of  the  axis  vertebrae  around  which  the  atlas  turns;  or  a  bone  may  rotate 
around  its  ownTongitudinal  axis,  as  in  the  rotation  of  the  humerus  at  the  shoulder- 
joint;  or  the  axis  of  rotation  may  not  be  quite  parallel  to  the  long  axis  of  the 
bone,  as  in  the  movement  of  the  radius  on  the  ulna  during  pronation  and  supina- 
tion of  the  hand,  where  it  is  represented  by  a  line  connecting  the  centre  of  the 
head  of  the  radius  above  with  the  centre  of  the  head  of  the  ulna  below. 

Ligamentous  Action  of  Muscles. — The  movements  of  the  different  joints  of  a  hmb  are  combined 
by  means  of  the  long  muscles  passing  over  more  than  one  joint.  These,  when  relaxed  and  stretched 
to  their  greatest  extent,  act  as  elastic  hgaments  in  restraining  certain  movements  of  one  joint, 
except  when  combined  with  corresponding  movements  of  the  other — the  latter  movements  being 
usually  in  the  opposite  direction.  Thus  the  shortness  of  the  hamstring  muscles  prevents  com- 
plete flexion  of  the  hip,  unless  the  knee-joint  is  also  flexed  so  as  to  bring  their  attachments  nearer 
together.  The  uses  of  this  arrangement  are  threefold:  (1)  It  coordinates  the  kinds  of  move- 
ments which  are  the  most  habitual  and  necessary,  and  enables  them  to  be  performed  with  the 
least  expenditure  of  power.  (2)  It  enables  the  short  muscles  which  pass  over  only  one  joint  to 
act  upon  more  than  one.  (3)  It  provides  the  joints  with  ligaments  which,  while  they  are  of  very 
great  power  in  resisting  movements  to  an  extent  incompatible  with  the  mechanism  of  the  joint, 
at  the  same  time  spontaneously  yield  when  necessary. 

Applied  Anatomy. — W.  W.  Keen  points  out  how  important  it  is  "that  the  svn-geon  should 
remember  this  ligamentous  action  of  muscles  in  making  passive  motion — for  instance,  at  the  wrist 


384  SYXDESMOLOGY 

after  Colles'  fracture.  If  the  fingers  be  extended,  the  wrist  can  be  flexed  to  a  right  angle.  If, 
however,  they  be  first  flexed  as  in  'making  a  fist,'  flexion  at  the  wrist  is  quickty  Umited  to  from 
fort}'  to  fifty  degrees  in  different  persons,  and  is  very  painful  Vjeyond  that  point.  Hence  passive 
motion  here  should  be  made  with  the  fingers  extended.  In  the  leg,  when  flexing  the  hip,  the  knee 
should  be  flexed." 

The  articulations  ma>'  be  grou})e(l  into  those  of  the  trunk,  and  those  of  the  upper 
and  hnver  extremities. 


ARTICULATIONS   OF   THE   TRUNK. 

These  may  be  divided  into  the  following  groups,  viz.: 

I.  Of  the  Vertebral  Column.  ^T.  Of  the  Cartilages  of  the  Ribs  with  the 

II.  Of  the  Atlas  with  the  Axis.  Sternum,  and  with  Each  Other. 

III.  Of  the  Vertebral  Column  with       VII.  Of  the  Sternum. 

the  Cranium.  ^TII.  Of   the   vertebral    Column   with   the 

IV.  Of  the  Mandible.  Pelvis. 
V.  Of  the  Ribs  with  the  Vertebrse.       IX.  Of  the  Pelvis. 

I.     Articulations  of  the  Vertebral  Column. 

The  articulations  of  the  vertebral  column  consist  of  (1)  a  series  of  amphi- 
arthrodial  joints  between  the  vertebral  bodies,  and  (2)  a  series  of  diathrodial 
joints  between  the  vertebral  arches. 

1.  Articulations  of  Vertebral  Bodies  (intercentral  ligaments). — The  articulations 
between  the  bodies  of  the  vertebrse  are  amphiarthrodial  joints,  and  the  individual 
vertebrae  move  only  slightly  on  each  other.  When,  however,  this  slight  degree 
of  movement  between  the  pairs  of  bones  takes  place  in  all  the  joints  of  the  vertebral 
column,  the  total  range  of  movement  is  very  considerable.  The  ligaments  of  these 
articulations  are  the  following: 

The  Anterior  Longitudinal.  The  Posterior  Longitudinal. 

The  Intervertebral  Fibrocartilages. 

The  Anterior  Longitudinal  Ligament  (ligamentum  longitudinale  anterius;  anterior 
common  ligament)  (Figs.  424,  435). — The  anterior  longitudinal  ligament  is  a  broad 
and  strong  band  of  fibres,  which  extends  along  the  anterior  surfaces  of  the  bodies 
of  the  vertebrae,  from  the  axis  to  the  sacrum.  It  is  broader  below  than  above, 
thicker  in  the  thoracic  than  in  the  cervical  and  lumbar  regions,  and  somewhat 
thicker  opposite  the  bodies  of  the  vertebrse  than  opposite  the  intervertebral  fibro- 
cartilages. It  is  attached,  above,  to  the  body  of  the  axis,  where  it  is  continuous 
with  the  anterior  atlantoaxial  ligament,  and  extends  down  as  far  as  the  upper 
part  of  the  front  of  the  sacrum.  It  consists  of  dense  .longitudinal  fibres,  which 
are  intimately  adherent  to  the  intervertebral  fibrocartilages  and  the  prominent 
margins  of  the  vertebrae,  but  not  to  the  middle  parts  of  the  bodies.  In  the  latter 
situation  the  ligament  is  thick  and  serves  to  fill  up  the  concavities  on  the  anterior 
surfaces,  and  to  make  the  front  of  the  vertebral  column  more  even.  It  is  composed 
of  several  layers  of  fibres,  which  vary  in  length,  but  are  closely  interlaced  with 
each  other.  The  most  superficial  fibres  are  the  longest  and  extend  between  four 
or  five  vertebrse.  A  second,  subjacent  set  extends  between  two  or  three  vertebrae; 
while  a  third  set,  the  shortest  and  deepest,  reaches  from  one  vertebra  to  the  next. 
At  the  sides  of  the  bodies  the  ligament  consists  of  a  few  short  fibres  which  pass 
from  one  vertebra  to  the  next,  separated  from  the  concavities  of  the  vertebral 
bodies  by  oval  apertures  for  the  passage  of  vessels. 


Afx'TlCLLATIOXS  OF  THE   VERTEBRAL  COLUMX 


385 


The  Posterior  Longitudinal  Ligament  (li(/a)n('itfuni  lougiiudhidJc  posierius;  posterior 
collision  lu/atiif')ii)  (Figs.  424,  4'2r)). — The  posterior  longitudinal  ligament  is  situated 
within  the  vertebral  canal,  and  extends  along  the  posterior  surfaces  of  the  bodies 


Fig.  424. — Median  sagittal  section  of  two  lumbar  vertebrae  and  their  ligaments. 


Pedicle  (cut) 


Intervertebral 
fibrocariilage 


of  the  vertebra?,  from  the  body  of  the  axis,  where  it  is  continuous  with  the  membrana 
tectoria,  to  the  sacrum.  It  is  broader  above  than  below,  and  thicker  in  the  thoracic 
than  in  the  cervical  and  lumbar  regions.  In  the  situation  of  the  intervertebral 
fibrocartilages  and  contiguous  margins  of  the  vertebrae,  where  the  ligament  is  more 
intimately  adherent,  it  is  broad,  and  in  the 
thoracic  and  lumbar  regions  presents  a  series 
of  dentations  with  intervening  concave  margins ; 
but  it  is  narrow  and  thick  over  the  centres  of 
the  bodies,  from  which  it  is  separated  by  the 
basivertebral  veins.  This  ligament  is  com- 
posed of  smooth,  shining,  longitudinal  fibres, 
denser  and  more  compact  than  those  of  the 
anterior  ligament,  and  consists  of  superficial 
layers  occupying  the  interval  between  three 
or  four  vertebrae,  and  deeper  layers  which  ex- 
tend between  adjacent  vertebrae. 

The  Intervertebral  Fibrocartilages  (fibrocariil- 
agines  intervertebrales;  intervertebral  disks)  (Figs. 
424,  436). — The  intervertebral  fibrocartilages 
are  interposed  between  the  adjacent  surfaces  of 
the  bodies  of  the  vertebra?,  from  the  axis  to  the 
sacrum,  and  form  the  chief  bonds  of  connection 
between  the  vertebrae.  They  vary  in  shape,  size, 
and  thickness,  in  different  parts  of  the  verte- 
bral column.  In  shape  and  size  they  correspond  with  the  surfaces  of  the  bodies 
between  which  they  are  placed,  except  in  the  cervical  region,  where  they  are  slightly 
smaller  from  side  to  side  than  the  corresponding  bodies.     In  thickness  they  vary 


Fig.  425.- 


-Posterior  longitudinal  ligament,  in 
the  thoracic  region. 


386  SYNDESMOLOGY 

not  only  in  the  different  regions  of  the  cokimn,  but  in  different  parts  of  the  same 
fibrocartilage ;  they  are  thicker  in  front  than  behind  in  the  cervical  and  lumbar 
regions,  and  thus  contribute  to  the  anterior  convexities  of  these  parts  of  the  column; 
while  they  are  of  nearly  uniform  thickness  in  the  thoracic  region,  the  anterior  con- 
cavity of  this  part  of  the  column  being  almost  entirely  owing  to  the  shape  of 
the  vertebral  bodies.  The  intervertebral  fibrocartilages  constitute  about  one-fourth 
of  the  length  of  the  vertebral  column,  exclusive  of  the  first  two  vertebrae;  but  this 
amount  is  not  equally  distributed  between  the  various  bones,  the  cervical  and 
lumbar  portions  having,  in  proportion  to  their  length,  a  much  greater  amount  than 
the  thoracic  region,  with  the  result  that  these  parts  possess  greater  pliancy  and 
freedom  of  movement.  The  intervertebral  fibrocartilages  are  adherent,  by  their 
surfaces,  to  thin  layers  of  hyaline  cartilage  which  cover  the  upper  and  under 
surfaces  of  the  bodies  of  the  vertebrae;  in  the  lower  cervical  vertebrse,  however, 
small  joints  lined  by  synovial  membrane  are  occasionally  present  between  the 
upper  surfaces  of  the  bodies  and  the  margins  of  the  fibrocartilages  on  either 
side.  By  their  circumferences  the  intervertebral  fibrocartilages  are  closely  con- 
nected in  front  to  the  anterior,  and  behind  to  the  posterior,  longitudinal  liga- 
ments. In  the  thoracic  region  they  are  joined  laterally,  by  means  of  the  inter- 
articular  ligaments,  to  the  heads  of  those  ribs  which  articulate  with  two  vertebrse. 

Structure  of  the  Intervertebral  Fibrocartilages. — Each  is  composed,  at  its  circumference,  of 
laminse  of  fibrous  tissue  and  fibrocartilage,  forming  the  annulus  fibrosus;  and,  at  its  centre,  of 
a  soft,  pulp 5^,  highly  elastic  substance,  of  a  yellowish  color,  which  projects  considerably  above 
the  surrounding  level  when  the  disk  is  divided  horizontally.  This  pulpy  substance  {nucleus 
pulposus),  especially  well-developed  in  the  lumbar  region,  is  the  remains  of  the  notochord.  The 
laminse  are  arranged  concentrically;  the  outermost  consist  of  ordinary  fibrous  tissue,  the  others 
of  white  fibrocartilage.  The  laminse  are  not  quite  vertical  in  their  direction,  those  near  the  cir- 
cimxference  being  curved  outward  and  closely  approximated;  while  those  nearest  the  centre 
curve  in  the  opposite  direction,  and  are  somewhat  more  widely  separated.  The  fibres  of  which 
each  lamina  is  composed  are  directed,  for  the  most  part,  obhquely  from  above  downward,  the 
fibres  of  adjacent  laminse  passing  in  opposite  directions  and  varying  in  every  layer;  so  that  the 
fibres  of  one  layer  are  directed  across  those  of  another,  like  the  Umbs  of  the  letter  X.  This  laminar 
arrangement  belongs  to  about  the  outer  half  of  each  fibrocartilage.  The  pulpy  substance  presents 
no  such  arrangement,  and  consists  of  a  fine  fibrous  matrix,  containing  angular  cells  united  to 
form  a  reticular  structure. 

Applied  Anatomy. — When  an  aneurism  presses  on  the  vertebral  column,  the  vertebral  bodies 
are  often  deeply  eroded  by  the  tumor,  while  the  intervertebral  fibrocartilages  remain  intact. 
The  fibrocartilages  are  the  first  to  be  destroyed,  however,  in  tuberculosis  of  the  vertebral  coliunn, 
where,  as  not  infrequently  happens,  the  disease  begins  in  the  fibrocartilages,  and  spreads  thence 
to  the  bodies  of  the  two  adjoining  vertebrse  simultaneously. 

2.  Articulations  of  Vertebral  Arches. — The  joints  between  the  articular  pro- 
cesses of  the  vertebrse  belong  to  the  arthrodial  variety  and  are  enveloped  by 
capsules  lined  by  synovial  membranes;  while  the  laminae  spinous  and  transverse 
processes  are  connected  by  the  following  ligaments: 

The  Ligamenta  Flava.  The  Ligamentum  Nuchae. 

The  Supraspinal.  The  Interspinal. 

The  Intertransverse. 

The  Articular  Capsules  (capsulae  articulares;  capsular  ligaments)  (Fig.  424). — 
The  articular  capsules  are  thin  and  loose,  and  are  attached  to  the  margins  of  the 
articular  processes  of  adjacent  vertebrae.  They  are  longer  and  looser  in  the  cervical 
than  in  the  thoracic  and  lumbar  regions. 

The  Ligamenta  Flava  {ligmenta  subflava  (Fig.  426). — The  ligamenta  flava  connect 
the  laminae  of  adjacent  vertebrae,  from  the  axis  to  the  first  segment  of  the  sacrum. 
They  are  best  seen  from  the  interior  of  the  vertebral  canal ;  when  looked  at  from  the 
outer  surface  they  appear  short,  being  overlapped  by  the  laminse.    Each  ligament 


ARTICULATIONS  OF  THE  VERTEBRAL  COLUMN 


387 


Pedicle  {cut) 


Lamina 


Fig.  426. — Vertebral  arches  of  three  thoracic  vertebrae 
^'iewed  from  the  front. 


consists  of  two  lateral  portions  which  commence  one  on  either  side  of  the  roots 
of  the  articular  processes,  and  extend  backA\ard  to  the  point  where  the  laminae 
meet  to  form  the  spinous  process ;  the  posterior  margins  of  the  two  portions  are  in 
contact  and  to  a  certain  extent  united,  slight  intervals  being  left  for  the  passage 
of  small  vessels.  Each  consists  of  yellow  elastic  tissue,  the  fibres  of  which,  almost 
perpendicular  in  direction,  are  at- 
tached to  the  anterior  surface  of 
the  lamina  above,  some  distance 
from  its  inferior  margin,  and  to  the 
posterior  surface  and  upper  margin 
of  the  lamina  below.  In  the  cervical 
region  the  ligaments  are  thin,  but 
broad  and  long;  they  are  thicker  in 
the  thoracic  region,  and  thickest  in 
the  lumbar  region.  Their  marked 
elasticity  serves  to  preserve  the  up- 
right posture,  and  to  assist  the 
vertebral  column  in  resuming  it 
after  flexion. 

The  Supraspinal  Ligament  (liga- 
mentum  supraspinale;  supraspinous 
ligament)  (Fig.  424). — The  supra- 
spinal ligament  is  a  strong  fibrous 
cord,  which  connects  together  the 
apices  of  the  spinous  processes  from 

the  seventh  cervical  vertebra  to  the  sacrum;  at  the  points  of  attachment  to  the 
tips  of  the  spinous  processes  fibrocartilage  is  developed  in  the  ligament.  It  is 
thicker  and  broader  in  the  lumbar  than  in  the  thoracic  region,  and  intimately 
blended,  in  both  situations,  with  the  neighboring  fascia.  The  most  superficial 
fibres  of  this  ligament  extend  over  three  or  four  vertebrae;  those  more  deeply 
seated  pass  between  two  or  three  vertebrae ;  w^hile  the  deepest  connect  the  spinous 
processes  of  neighboring  vertebrae.  Between  the  spinous  processes  it  is  continuous 
with  the  interspinal  ligaments.  It  is  continued  upward  to  the  external  occipital 
protuberance  and  median  nuchal  line,  as  the  ligamentum  nuchae. 

The  Ligamentum  Nuchae.^ — The  ligamentum  nuchae  is  a  fibrous  membrane,  which, 
in  the  neck,  represents  the  supraspinal  ligaments  of  the  lower  vertebrae.  It  extends 
from  the  external  occipital  protuberance  and  median  nuchal  line  to  the  spinous 
process  of  the  seventh  cervical  vertebra.  From  its  anterior  border  a  fibrous  lamina 
is  given  oft',  which  is  attached  to  the  posterior  tubercle  of  the  atlas,  and  to  the 
spinous  processes  of  the  cervical  vertebrae,  and  forms  a  septum  between  the  muscles 
on  either  side  of  the  neck.  In  man  it  is  merely  the  rudiment  of  an  important  elastic 
ligament,  which,  in  some  of  the  lower  animals,  serves  to  sustain  the  weight  of  the 
head. 

The  Interspinal  Ligaments  (ligamenta  inter spinalia;  interspinous  ligaments) 
(Fig.  424). — The  interspinal  ligaments  thin  and  membranous,  connect  adjoining 
spinous  processes  and  extend  from  the  root  to  the  apex  of  each  process.  They 
meet  the  ligamenta  flava  in  front  and  the  supraspinal  ligament  behind.  They 
are  narrow  and  elongated  in  the  thoracic  region;  broader,  thicker,  and  quadrilateral 
in  form  in  the  lumbar  region;  and  only  slightly  developed  in  the  neck. 

The  Intertransverse  Ligaments  (ligamenta  intertransversaria) . — The  intertransverse 
ligaments  are  interposed  between  the  transverse  processes.  In  the  cervical  region 
they  consist  of  a  few  irregular,  scattered  fibres;  in  the  thoracic  region  they  are 
rounded  cords  intimately  connected  with  the  deep  muscles  of  the  back;  in  the 
lumbar  region  they  are  thin  and  membranous. 


388  SYNDESMOLOGY 

Movements. — The  movements  permitted  in  the  vertebral  cohunn  are:  flexion,  extension, 
lateral  moroneiU,  circumduction,  and  rotation. 

In  flexion,  or  movement  forward,  the  anterior  longitudinal  ligament  is  relaxed,  and  the  inter- 
vertebral fibrocartilages  are  cornpressed  in  front;  while  the  posterior  longitudinal  ligament,  the 
Ugamenta  flava,  and  the  inter-  and  supraspinal  ligaments  are  stretched,  as  well  as  the  posterior 
fibres  of  the  intervertebral  fibrocartilages.  The  interspaces  between  the  lamina;  are  widened, 
and  the  inferior  articular  processes  glide  upward,  upon  the  superior  articular  processes  of  the 
subjacent  vertebrae.  Flexion  is  the  most  extensive  of  all  the  movements  of  the  vertebral  column, 
and  is  freest  in  the  lumbar  region. 

In  extension,  or  movement  backward,  an  exactly  opposite  disposition  of  the  parts  takes  place. 
This  movement  is  Umited  by  the  anterior  longitudinal  ligament,  and  by  the  approximation  of 
the  spinous  processes.    It  is  freest  in  the  cervical  region. 

In  lateral  movement,  the  sides  of  the  intervertebral  fibrocartilages  are  compressed,  the  extent 
of  motion  being  limited  by  the  resistance  offered  by  the  surrounding  ligaments.  This  movement 
may  take  place  in  any  part  of  the  column,  but  is  freest  in  the  cervical  and  lumbar  regions. 

Circumduction  is  verj^  limited,  and  is  merely  a  succession  of  the  preceding  movements. 

Rotation  is  produced  by  the  twisting  of  the  intervertebral  fibrocartilages;  this,  although  only 
shght  between  any  two  vertebra;,  allows  of  a  considerable  extent  of  movement  when  it  takes  place 
in  the  whole  length  of  the  column,  the  front  of  the  upper  part  of  the  column  being  turned  to  one 
or  other  side.  This  movement  occurs  to  a  shght  extent  in  the  cervical  region,  is  freer  in  the  upper 
part  of  the  thoracic  region,  and  absent  in  the  lumbar  region. 

The  extent  and  variety  of  the  movements  are  influenced  by  the  shape  and  direction  of  the 
articular  surfaces.  In  the  cervical  region  the  upward  incUnation  of  the  superior  articular  surfaces 
allows  of  free  flexion  and  extension.  Extension  can  be  carried  farther  than  flexion;  at  the  upper 
end  of  the  region  it  is  checked  by  the  locking  of  the  posterior  edges  of  the  superior  atlantal  facets 
in  the  condyloid  fossae  of  the  occipital  bone;  at  the  lower  end  it  is  limited  bj^  a  mechanism  whereby 
the  inferior  articular  processes  of  the  seventh  cervical  vertebra  slip  into  grooves  behind  and 
below  the  superior  articular  processes  of  the  first  thoracic.  Flexion  is  arrested  just  beyond  the 
point  where  the  cervical  convexity  is  straightened;  the  movement  is  checked  by  the  apposition 
of  the  projecting  lower  Lips  of  the  bodies  of  the  vertebrae  with  the  shelving  surfaces  on  the  bodies 
of  the  subjacent  vertebrae.  Lateral  flexion  and  rotation  are  free  in  the  cervical  region;  they  are, 
however,  always  combined.  The  upward  and  medial  inclinations  of  the  superior  articular  surfaces 
impart  a  rotator}^  movement  during  lateral  flexion,  while  pure  rotation  is  prevented  by  the  slight 
medial  slope  of  these  surfaces. 

In  the  thoracic  region,  notably  in  its  upper  part,  all  the  movements  are  limited  in  order  to 
reduce  interference  with  respiration  to  a  minimum.  The  ahnost  complete  absence  of  an  upward 
incUnation  of  the  superior  articular  surfaces  prohibits  any  marked  flexion,  while  extension  is 
checked  by  the  contact  of  the  inferior  articular  margins  with  the  laminae,  and  the  contact  of  the 
spinous  processes  with  one  another.  The  mechanism  between  the  seventh  cervical  and  the  first 
thoracic  vertebrae,  which  limits  extension  of  the  cervical  region,  will  also  serve  to  limit  flexion  of 
the  thoracic  region  when  the  neck  is  extended.  Rotation  is  free  in  the  thoracic  region:  the 
superior  articular  processes  are  segments  of  a  cyUnder  whose  axis  is  in  the  mid-ventral  line  of  the 
vertebral  bodies.  The  direction  of  the  articular  facets  would  allow  of  free  lateral  flexion,  but 
this  movement  is  considerably  limited  in  the  upper  part  of  the  region  by  the  resistance  of  the 
ribs  and  sternum. 

In  the  lumbar  region  flexion  and  extension  are  free.  Flexion  can  be  carried  farther  than  exten- 
sion, and  is  possible  to  just  beyond  the  straightening  of  the  lumbar  curve;  it  is,  therefore,  greatest 
at  the  lowest  part  where  the  curve  is  sharpest.  The  inferior  articular  facets  are  not  in  close  appo- 
sition with  the  superior  facets  of  the  subjacent  vertebrae,  and  on  this  account  a  considerable 
amoimt  of  lateral  flexion  is  permitted.  For  the  same  reason  a  slight  amount  of  rotation  can  be 
carried  out,  but  this  is  so  soon  checked  by  the  interlocking  of  the  articular  surfaces  that  it  is 
negligible. 

The  principal  muscles  which  produce  flexion  are  the  Sternocleidomastoideus,  Longus  capitis, 
and  Longus  coUi;  the  Scaleni;  the  abdominal  muscles  and  the  Psoas  major.  Extension  is  produced 
by  the  intrinsic  muscles  of  the  back,  assisted  in  the  neck  by  the  Splenius,  Semispinales  dorsi  and 
cervicis,  and  the  Mtdtifidus.  Lateral  motion  is  produced  by  the  intrinsic  muscles  of  the  back 
by  the  Splenius,  the  Scaleni,  the  Quadratus  lumborum,  and  the  Psoas  major,  the  muscles  of  one 
side  only  acting;  and  rotation  by  the  action  of  the  following  muscles  of  one  side  only,  viz.,  the 
Sternocleidomastoideus,  the  Longus  capitis,  the  Scaleni,  the  IMultifidus,  the  Semispinalis  capitis, 
and  the  abdominal  muscles. 

n.    Articulation  of  the  Atlas  with  the  Epistropheus  or  Axis  (Articulatio 

Atlantoepistrophica) . 

The  articulation  of  the  atlas  with  the  axis  is  of  a  complicated  nature,  com- 
prising no  fewer  than  four  distinct  joints.    There  is  a  pivot  articulation  between 


ARTICULATIOX  OF  THE  ATLAS  WITH  THE  EPISTROPHEUS  OR  AXIS     389 


the  odontoid  process  of  the  axis  and  the  rin^-  formed  by  the  anterior  arch  and 
the  tranversc  hgament  of  the  athis  (see  Fig.  429);  here  there  are  two  joints:  one 
between  the  posterior  surface  of  the  anterior  arch  of  the  atlas  and  the  front  of 
the  odontoid  process;  the  other  between  the  anterior  surface  of  the  ligament  and 
the  back  of  the  process.  Between  the  articular  processes  of  the  two  bones  there 
is  on  either  side  an  arthrodial  or  gliding  joint.  The  ligaments  connecting  these 
bones  are: 


Two  Articular  Capsules. 
The  Anterior  Atlantoaxial. 


The  Posterior  Atlantoaxial. 
The  Transverse. 


The  Articular  Capsules  {capsidae  articulares;  cajjsular  ligaments) . — The  articular 
capsules  are  thin  and  loose,  and  connect  the  margins  of  the  lateral  masses  of  the 
atlas  with  those  of  the  posterior  articular  surfaces  of  the  axis.  Each  is  strength- 
ened at  its  posterior  and  medial  part  by  an  accessory  ligament,  which  is  attached 
below  to  the  body  of  the  axis  near  the  base  of  the  odontoid  process,  and  above 
to  the  lateral  mass  of  the  atlas  near  the  transverse  ligament. 


Atlanto- 

ocoipital      f  Articular  capsule 

-[  and 

[^synovial  membrane 


tlanto- 

al  f  Articular  capsule 

and 
ysynovial  membrane 


Fig.  427. — Anterior  atlantoocoipital  membrane  and  atlantoaxial  ligament. 

The  Anterior  Atlantoaxial  Ligament  (Fig.  427). — This  ligament  is  a  strong  mem- 
brane, fixed,  above,  to  the  lower  border  of  the  anterior  arch  of  the  atlas;  below, 
to  the  front  of  the  body  of  the  axis.  It  is  strengthened  in  the  middle  line  by  a 
rounded  cord,  which  connects  the  tubercle  on  the  anterior  arch  of  the  atlas  to  the 
body  of  the  axis,  and  is  a  continuation  upward  of  the  anterior  longitudinal  liga- 
ment.   The  ligament  is  in  relation,  in  front,  with  the  Longi  capitis. 

The  Posterior  Atlantoaxial  Ligament  (Fig.  428). — This  ligament  is  a  broad,  thin 
membrane  attached,  above,  to  the  lower  border  of  the  posterior  arch  of  the  atlas; 
below,  to  the  upper  edges  of  the  laminae  of  the  axis.  It  supplies  the  place  of 
the  ligamenta  flava,  and  is  in  relation,  behind,  with  the  Obliqui  capitis  inferiores. 

The  Transverse  Ligament  of  the  Atlas  (ligamentum  transversum  atlantis)  (Figs. 
429,  430,  431).- — The  transverse  ligament  of  the  atlas  is  a  thick,  strong  band,  which 
arches  across  the  ring  of  the  atlas,  and  retains  the  odontoid  process  in  contact  with 
the  anterior  arch.    It  is  concave  in  front,  convex  behind,  broader  and  thicker  in 


390 


SYNBESMOLOGY 


the  middle  than  at  the  ends,  and  firml}'  attached  on  either  side  to  a  small  tubercle 
on  the  medial  surface  of  the  lateral  mass  of  the  atlas.  As  it  crosses  the  odontoid 
process,  a  small  fasciculus  {cms  superius)  is  prolonged  upward,  and  another  {cms 
inferius)  downward,  from  the  superficial  or  posterior  fibres  of  the  ligament.    The 


Arch  for  passage  of 
vertebral  artery 
and  first  cervical 
nerve 


Fig.  428. — Posterior  atlantooccipital  membrane  and  atlantoaxial  ligament. 

former  is  attached  to  the  basilar  part  of  the  occipital  bone,  in  close  relation  with 
the  membrana  tectoria;  the  latter  is  fixed  to  the  posterior  surface  of  the  body 
of  the  axis;  hence,  the  whole  ligament  is  named  the  cruciate  ligament  of  the  atlas. 
The  transverse  ligament  divides  the  ring  of  the  atlas  into  two  unequal  parts: 
of  these,  the  posterior  and  larger  serves  for  the  transmission  of  the  medulla  spinalis 


Fig.  429. — Articulation  between  odontoid  process  and  atlas. 

and  its  membranes  and  the  accessory  nerves;  the  anterior  and  smaller  contains 
the  odontoid  process.  The  neck  of  the  odontoid  process  is  constricted  where  it  is 
embraced  posteriorly  by  the  transverse  ligament,  so  that  this  ligament  suffices 
to  retain  the  odontoid  process  in  position  after  all  the  other  ligaments  have  been 
divided. 


ARTICULATIOX  OF  THE  ATLAS  WITH  THE  EPISTROPHEUS  OR  AXIS     391 


1 


'— Anneal  odontoid 
liijainent 


Atlanta,  f  Articular  capsule 

_,.,-    -f  7-!  and 

ipitai.  \^,^,pi„„i(i,i  membrane 


C  Articular  capside 
Atlanto-j  ^,,^,,   ^ 

axi  a  i    y  synovial  membrane 


Fig.  430. — Membrana  tectoria,  transverse,  and  alar  ligaments. 


Anterior  atlanto- 
occipital  membrane 

Membrana  tectoria 

Crus  superius  of 

transverse  ligament 

Apical  odont.  lig. 

Ant.  arch  of  atlas 

Odontoid  process 
of  axis 
Articular  cavity 

Transverse  ligament 

Anterior  atlanto- 
axial ligament 


Intervertebral 
fhrocartilage 


Anterior  longitudinal 
ligament 


S II  pel  fie  ml  layer  of  membrana  tectoria 


Ganalis  hypoglossi 


Posterior  ailanto- 
cccipital  membrane 


'gVJ*\  Posterior  arch 
^""•^  '         of  atlas 


Suboccipital  nerve 


Posterior  longitudinal  ligament 
Fig.  431.— Median  sagittal  section  through  the  occipital  bone  and  first  three  cervical  vertebra.     (Spalteholz.) 


392  SYNDESMOLOGY 

Synovial  Membranes. — There  is  a  synovial  membrane  for  each  of  the  torn-  joints;  the  joint 
cavity  bet^Yeen  the  odontoid  process  and  the  transverse  ligament  is  often  continuous  with  those 
of  the  atlantooccipital  articulations. 

The  opposed  articular  surfaces  of  the  atlas  and  axis  are  not  reciprocally  curved;  both  surfaces 
are  convex  in  their  long  axes.    When,  therefore,  the  upper  facet  glides  forward  on  the  lower  it 

Movements.— This  joint  allows  the  rotation  of  the  atlas  (and,  with  it,  the  skull)  upon  the 
axis,  the  extent  of  rotation  being  hmited  by  the  alar  hgaments. 

also  descends;  the  fibres  of  the  articular  capsule  are  relaxed  in  a  vertical  direction,  and  will  then 
permit  of  movement  in  an  antero-posterior  direction.  By  this  means  a  shorter  capsule  suffices 
and  the  strength  of  the  joint  is  materially  increased.^ 

The  principal  muscles  by  w^hich  these  movements  are  produced  are  the  Sternocleidomastoideus 
and  Semispinalis  capitis  of  one  side,  acting  with  the  Longus  capitis,  Splenius,  Longissimus  capitis, 
Rectus  capitis  posterior  major,  and  Obliqui  capitis  superior  and  inferior  of  the  other  side. 

III.    Articulations  of  the  Vertebral  Column  with  the  Cranium. 

The  ligaments  connecting  the  vertebral  column  with  the  cranium  may  be 
divided  into  two  sets:  those  uniting  the  atlas  with  the  occipital  bone,  and  those 
connecting  the  axis  with  the  occipital  bone. 

•  Articulation  of  the  Atlas  with  the  Occipital  Bone  {articulatio  atlantooccipitalis) . 
—The  articulation  between  the  atlas  and  the  occipital  bone  consists  of  a  pair  of 
condyloid  joints.    The  ligaments  connecting  the  bones  are : 

Two  Articular  Capsules.  The  Posterior  Atlantooccipital 

The  Anterior  Atlantooccipital  membrane. 

membrane.  Two  Lateral  Atlantooccipital, 

The  Articular  Capsules  {capsulae  articulares;  capsular  ligaments). — The  articular 
capsules  surround  the  condyles  of  the  occipital  bone,  and  connect  them  with  the 
articular  processes  of  the  atlas:  they  are  thin  and  loose. 

The  Anterior  Atlantooccipital  Membrane  {memhrana  atlantooccipitalis  anterior; 
,  anterior  atlantodccipital  ligament)  (Fig.  427).— The  anterior  atlantooccipital  mem- 
brane is  broad  and  composed  of  densely  woven  fibres,  which  pass  between  the 
anterior  margin  of  the  foramen  magnum  above,  and  the  upper  border  of  the 
anterior  arch  of  the  atlas  below;  laterally,  it  is  continuous  with  the  articular 
capsules;  in  front,  it  is  strengthened  in  the  middle  line  by  a  strong,  rounded 
cord,  which  connects  the  basilar  part  of  the  occipital  bone  to  the  tubercle  on  the 
anterior  arch  of  the  atlas.  This  membrane  is  in  relation  in  front  with  the  Recti 
capitis  anteriores,  behind  with  the  alar  ligaments. 

The  Posterior  Atlantooccipital  Membrane  {memhrana  atlantooccipitalis  posterior; 
posterior  atlantooccipital  ligament)  (Fig.  428).— The  posterior  atlantooccipital  mem- 
brane, broad  but  thin,  is  connected  above,  to  the  posterior  margin  of  the  foramen 
magnum;  below,  to  the  upper  border  of  the  posterior  arch  of  the  atlas.  On  either 
side  this  membrane  is  defective  below,  over  the  groove  for  the  vertebral  artery, 
and  forms  with  this  groove  an  opening  for  the  entrance  of  the  artery  and  the 
exit  of  the  suboccipital  nerve.  The  free  border  of  the  membrane,  arching  over 
the  artery  and  nerve,  is  sometimes  ossified.  The  membrane  is  in  vdoXiow,  behind, 
with  the  Recti  capitis  posteriores  minores  and  Obliqui  capitis  superiores;  \\\  front, 
with  the  dura  mater  of  the  vertebral  canal,  to  which  it  is  intimately  adherent. 

The  Lateral  Ligaments.— The  lateral  ligaments  are  thickened  portions  of  the 
articular  capsules,  reinforced  by  bundles  of  fibrous  tissue,  and  are  directed  obliquely 
upward  and  medialward;  they  are  attached  above  to  the  jugular  processes  of  the 
occipital  bone,  and  below,  to  the  bases  of  the  transverse  processes  of  the  atlas. 

1  Corner  ("The  Phj^siology  of  the  Atlanto-axial  Joints,"  Journal  of  Anatomy  and  Physiology,  vol.  xli)  states  that 
the  movements  which  take  place  at  these  articulations  are  of  a  complex  nature.  The  first  part  of  the  movement  is 
an  eccentric  or  asymmetrical  one;  the  atlanto-axial  joint  of  the  side  to  which  the  head  is  mpved  is  fixed,  or  practically 
fixed  by  the  muscles  of  the  neck,  and  forms  the  centre  of  the  movement,  while  the  opposite  atlantal  facet  is  carried 
downward  and  forward  on  the  corresponding  axial  facet.  The  second  part  of  the  movement  is  centric  and  symmetrical, 
the  odontoid  process  forming  the  axis  of  the  movement. 


ARTICULATION  OF  THE  MANDIBLE  393 

Synovial  Membranes. — There  are  two  synovial  inenibranes:  one  lining  each  of  the  articular 
capsules.  The  joints  frequently  communicate  with  that  between  the  posterior  surface  of  the 
odontoid  process  and  the  transverse  hgament  of  the  atlas. 

Movements. — The  movements  permitted  in  this  joint  are  (a)  flexion  and  extension,  which 
give  rise  to  the  ordinary  forward  and  backward  nodding  of  the  head,  and  (b)  slight  lateral  motion 
to  one  or  other  side.  Flexion  is  produced  mainly  by  the  action  of  the  Longi  capitis  and  Recti 
capitis  anteriores;  extension  by  the  Recti  capitis  posteriores  major  and  minor,  the  Obliquus  su- 
perior, the  Semispinalis  capitis,  Splenius  capitis,  Sternocleidomastoideus,  and  upper  fibres  of  the 
Trapezius.  The  Recti  laterales  are  concerned  in  the  lateral  movement,  assisted  by  the  Trapezius, 
Splenius  capitis,  Semispinalis  capitis,  and  the  Sternocleidomastoideus  of  the  same  side,  all  acting 
together. 

Ligaments  Connecting  the  Axis  with  the  Occipital  Bone. — 

The  Membrana  Tectoria.  Two  Alar.  The  Apical  Odontoid. 

The  Membrana  Tectoria  {occipitoaxial  ligament)  (Figs.  430,  431).^ — The  mem- 
brana tectoria  is  situated  within  the  vertebral  canal.  It  is  a  broad,  strong  band, 
which  covers  the  odontoid  process  and  its  ligaments,  and  appears  to  be  a  prolon- 
gation upward  of  the  posterior  longitudinal  ligament  of  the  vertebral  column.  It 
is  fixed,  below,  to  the  posterior  surface  of  the  body  of  the  axis,  and,  expanding  as 
it  ascends,  is  attached  to  the  basilar  groove  of  the  occipital  bone,  in  front  of  the 
foramen  magnum,  where  it  blends  with  the  cranial  dura  mater.  Its  anterior  sur- 
face is  in  relation  with  the  transverse  ligament  of  the  atlas,  and  its  posterior 
surface  with  the  dura  mater. 

The  Alar  Ligaments  (ligamenta  alaria;  odontoid  ligaments)  (Fig.  430). — The  alar 
ligaments  are  strong,  rounded  cords,  which  arise  one  on  either  side  of  the  upper 
part  of  the  odontoid  process,  and,  passing  obliquely  upward  and  lateralward,  are 
inserted  into  the  rough  depressions  on  the  medial  sides  of  the  condyles  of  the  occipi- 
tal bone.  In  the  triangular  interval  between  these  ligaments  is  another  fibrous 
cord,  the  apical  odontoid  ligament  (Fig.  431),  which  extends  from  the  tip  of  the  odon- 
toid process  to  the  anterior  margin  of  the  foramen  magnum,  being  intimately 
blended  with  the  deep  portion  of  the  anterior  atlantooccipital  membrane  and 
superior  crus  of  the  transverse  ligament  of  the  atlas.  It  is  regarded  as  a  rudimentary 
intervertebral  fibrocartilage,  and  in  it  traces  of  the  notochord  may  persist.  The 
alar  ligaments  limit  rotation  of  the  cranium  and  therefore  receive  the  name  of 
check  ligaments. 

In  addition  to  the  ligaments  which  unite  the  atlas  and  axis  to  the  skull, 
the  ligamentum  nuchae  (page  387)  must  be  regarded  as  one  of  the  ligaments 
connecting  the  vertebral  column  with  the  cranium. 

Applied  Anatomy. — The  ligaments  which  unite  the  component  parts  of  the  vertebral  column, 
together  are  so  strong,  and  the  bones  are  so  interlocked  by  the  arrangement  of  their  articulating 
processes,  that  dislocation  is  very  uncommon,  and,  indeed,  except  in  the  upper  part  of  the  neck, 
rarely  occurs  unless  accompanied  by  fracture.  Dislocation  of  the  occipital  bone  from  the  atlas 
has  been  recorded  only  in  one  or  two  cases;  but  dislocation  of  the  atlas  from  the  axis,  with  rupture 
of  the  transverse  hgament,  is  much  more  common;  it  is  the  mode  in  which  death  is  produced  in 
many  cases  of  execution  by  hanging.  In  the  lower  part  of  the  neck — that  is,  below  the  third 
cervical  vertebra — dislocation  unattended  by  fracture  occasionally  takes  place. 

IV.     Articulation  of  the  Mandible  (Articulatio  Mandibularis ;  Temporo- 
mandibular Articulation). 

This  is  a  ginglymo-arthrodial  joint;  the  parts  entering  into  its  formation  on 
either  side  are:  the  anterior  part  of  the  mandibular  fossa  of  the  temporal  bone 
and  the  articular  tubercle  above;  and  the  condyle  of  the  mandible  below.  The 
ligaments  of  the  joint  are  the  following: 

The  Articular  Capsule.  The  Sphenomandibular. 

The  Temporomandibular.  The  Articular  Disk. 

The  Stylomandibular. 


394 


SYNDESMOLOGY 


The  Articular  Capsule  (capsida  articularis;  capsular  ligament). — The  articular 
capsule  is  a  thin,  loose  envelope,  attached  above  to  the  circumference  of  the 
mandibular  fossa  and  the  articular  tubercle  immediately  in  front;  below,  to  the 
neck  of  the  condvle  of  the  mandible. 


Fig.'  432. — -Articulation  of  the  mandible.     Lateral  aspect. 


The    Temporomandibular    Ligament    (ligamentum    temporomandibulare;    external 
lateral  ligament)   (Fig.  432). — The  temporomandibular  ligament  consists  of  two 


Fig.  433. — Articulation  of  the  mandible.     Medial  aspect.  Fig.  434.— Sagittal  section  of  the  articulation  of  the 

mandible. 

short,  narrow  fasciculi,  one  in  front  of  the  other,  attached,  above,  to  the  lateral 
surface  of  the  zygomatic  arch  and  to  the  tubercle  on  its  lower  border;  below, 


ARTICULATION  OF  THE  MANDIBLE  395 

to  the  lateral  surface  and  posterior  border  of  the  neck  of  the  mandible.  It  is  broader 
above  than  below,  and  its  fibres  are  directed  obliquely  downward  and  backward. 
It  is  covered  by  the  ])ari)ti<l  gland,  and  by  the  integument. 

The  Sphenomandibular  Ligament  {llgamentiim  sphenomandibidare;  internal  lateral 
ligament)  (Fig.  433). — The  sphenomandibular  ligament  is  a  flat,  thin  band  which  is 
attached  above  to  the  spina  angularis  of  the  sphenoid  bone,  and,  becoming  broader 
as  it  descends,  is  fixed  to  the  lingula  of  the  mandibular  foramen.  Its  lateral  surface 
is  in  relation,  above,  with  the  Pterygoideus  externus;  lower  down,  it  is  separated 
from  the  neck  of  the  cond^de  by  the  internal  maxillary  vessels;  still  low'er,  the 
inferior  alveolar  vessels  and  nerve  and  a  lobule  of  the  parotid  gland  lie  between 
it  and  the  ramus  of  the  mandible.  Its  medial  surface  is  in  relation  with  the  Ptery- 
goideus internus. 

The  Articular  Disk  (discus  articularis;  inter  articular  fibrocartilage;  articular  menis- 
cus) (Fig.  434). — The  articular  disk  is  a  thin,  oval  plate,  placed  between  the 
condyle  of  the  mandible  and  the  mandibular  fossa.  Its  upper  surface  is  concavo- 
convex  from  before  backward,  to  accommodate  itself  to  the  form  of  the  man- 
dibular fossa  and  the  articular  tubercle.  Its  under  surface,  in  contact  with  the 
condyle,  is  concave.  Its  circumference  is  connected  to  the  articular  capsule;  and  in 
front  to  the  tendon  of  the  Pterygoideus  externus.  It  is  thicker  at  its  periphery, 
especially  behind,  than  at  its  centre.  The  fibres  of  w^hich  it  is  composed  have  a 
concentric  arrangement,  more  apparent  at  the  circumference  than  at  the  centre. 
It  divides  the  joint  into  two  cavities,  each  of  which  is  furnished  with  a  synovial 
membrane. 

The  Synovial  Membranes. — The  synovial  membranes,  two  in  number,  are  placed  one  above, 
and  the  other  below,  the  articular  disk.  The  upper  one,  the  larger  and  looser  of  the  two,  is 
continued  from  the  margin  of  the  cartilage  covering  the  mandibular  fossa  and  articular  tubercle 
on  to  the  upper  surface  of  the  disk.  The  lower  one  passes  from  the  under  surface  of  the  disk 
to  the  neck  of  the  condyle,  being  prolonged  a  little  farther  downward  behind  than  in  front.  The 
articular  disk  is  sometimes  perforated  in  its  centre,  and  the  two  cavities  then  communicate  with 
each  other. 

The  Stylomandibular  Ligament  {ligamentum  stylomandibulare) ;  stylomaxillary 
ligament  (Fig.  433) . — The  stylomandibular  ligament  is  a  specialized  band  of  the 
cervical  fascia,  which  extends  from  near  the  apex  of  the  stjdoid  process  of  the 
temporal  bone  to  the  angle  and  posterior  border  of  the  ramus  of  the  mandible, 
between  the  JNIasseter  and  Pterygoideus  internus.  This  ligament  separates  the 
parotid  from  the  submaxillary  gland,  and  from  its  deep  surface  some  fibres  of  the 
Styloglossus  take  origin.  Although  classed  among  the  ligaments  of  the  temporo- 
mandibular joint,  it  can  only  be  considered  as  accessory  to  it. 

The  nerves  of  the  temporomandibular  joint  are  derived  from  the  auriculotemporal  and  masse- 
teric branches  of  the  mandibular  nerve,  the  arteries  from  the  superficial  temporal  branch  of  the 
external  carotid. 

Movements. — The  movements  permitted  in  this  articulation  are  extensive.  Thus,  the  mandible 
may  be  depressed  or  elevated,  or  carried  forward  or  backward;  a  slight  amount  of  side-to-side 
movement  is  also  permitted.  It  must  be  borne  in  mind  that  there  are  two  distinct  joints  in  this 
articulation — one  between  the  condyle  and  the  articular  disk,  and  another  between  the  disk  and 
the  mandibular  fossa.  When  the  mouth  is  but  shghtly  opened,  as  during  ordinary  conversation, 
the  movement  is  confined  to  the  lower  of  the  two  joints.  On  the  other  hand,  when  the  mouth 
is  opened  more  widely,  both  joints  are  concerned  in  the  movement;  in  the  lower  joint  the  move- 
ment is  of  a  hinge-hke  character,  the  condyle  moving  around  a  transverse  axis  on  the  disk,  while 
in  the  upper  joint  the  movement  is  of  a  gUding  character,  the  disk,  together  with  the  condyle, 
ghding  forward  on  to  the  articular  tubercle,  aromid  an  axis  which  passes  thi'ough  the  mandibular 
foramina.  These  two  movements  take  place  simultaneously,  the  condyle  and  disk  move  for- 
ward on  the  eminence,  and  at  the  same  time  the  condyle  revolves  on  the  disk.  In  shutting  the 
mouth  the  reverse  action  takes  place;  the  disk  glides  back,  carrying  the  condyle  with  it,  and  this 
at  the  same  time  moves  back  to  its  former  position.  When  the  mandible  is  carried  horizontally 
forward,  as  in  protruding  the  lower  incisor  teeth  in  front  of  the  upper,  the  movement  takes  place 
principally  in  the  upper  joint,  the  disk  and  the  condyle  ghding  forward  on  the  mandibular  fossa 


396  SYNDESMOLOGY 

and  articular  tubercle.  The  grinclins  or  chewing  moA-ement  is  produced  by  one  condyle,  with 
its  disk,  gliding  alternately  forward  and  backward,  while  the  other  condyle  moves  simultaneously 
in  the  opposite  direction;  at  the  same  time  the  condyle  undergoes  a  vertical  rotation  on  the  disk. 
One  condyle  advances  and  rotates,  the  other  condyle  recedes  and  rotates,  in  alternate  succession. 

The  mandible  is  depressed  by  its  own  weight,  assisted  by  the  Platysma,  the  Digastricus,  the 
Mylohyoideus,  and  the  Geniohyoideus.  It  is  elevated  by  the  Masseter,  Pterygoideus  internus, 
and  the  anterior  part  of  the  Temporalis.  It  is  drawn  forward  by  the  simultaneous  action  of  the 
Pterygoidei  internus  and  externus,  the  superficial  fibres  of  the  Masseter  and  the  anterior  fibres 
of  the  Temporalis;  and  backward  by  the  deep  fibres  of  the  Masseter  and  the  posterior  fibres  of  the 
Temporahs.  The  grinding  movement  is  caused  by  the  alternate  action  of  the  Pterygoidei  of 
either  side. 

Applied  Anatomy. — The  mandible  is  dislocated  only  in  one  direction,  viz.,  forward.  The 
accident  is  caused  by  violence  or  by  muscular  action.  When  the  mouth  is  open,  the  condyle  is 
situated  on  the  articular  tubercle,  and  any  sudden  violence,  or  even  a  sudden  muscular  spasm, 
as  during  a  convulsive  yawn,  may  displace  the  condyle  forward  into  the  infratemporal  fossa. 
The  displacement  may  be  unilateral  or  bilateral.  Reduction  is  accomphshed  by  depressing  the 
jaw  with  the  thumbs  placed  on  the  last  molar  teeth,  and  at  the  same  time  elevating  the  chin. 
The  downward  pressure  overcomes  the  spasm  of  the  Masseter,  Temporalis,  and  Pterygoideus 
internus,  and  elevation  of  the  chin  throws  the  condyle  backward;  the  above-mentioned  muscles 
then  draw  the  condyle  back  into  its  normal  position. 

In  close  relation  to  the  condyle  of  the  mandible  are  the  external  acoustic  meatus  and  the  tym- 
panic cavity;  any  force,  therefore,  applied  to  the  bone  is  hable  to  be  attended  with  damage  to 
these  parts,  or  inflammation  in  the  joint  may  extend  to  them;  or  on  the  other  hand  inflammation 
of  the  tympanic  cavity  may  involve  the  articulation  and  cause  its  destruction,  thus  leading  to 
ankylosis  of  the  joint.  The  joint  is  also  occasionally  the  seat  of  osteoarthritis,  causing  great 
suffering  during  efforts  of  mastication.  A  peculiar  affection  sometimes  attacks  the  neck  and 
condyle  of  the  mandible,  consisting  in  hypertrophy  and  elongation  of  these  parts  and  consequent 
protrusion  of  the  chin  to  the  opposite  side. 

V.     Costovertebral  Articulations  (Articulationes  Costovertebrales). 

The  articulations  of  the  ribs  with  the  vertebral  column  may  be  divided  into  two 
sets,  one  connecting  the  heads  of  the  ribs  with  the  bodies  of  the  vertebree,  another 
uniting  the  necks  and  tubercles  of  the  ribs  with  the  transverse  processes. 

1 .  Articulations  of  the  Heads  of  the  Ribs  {articulationes  capitulorum;  costocentral 
articidations)  (Fig.  435). — These  constitute  a  series  of  gliding  or  arthrodial  joints, 
and  are  formed  by  the  articulation  of  the  heads  of  the  typical  ribs  with  the  facets 
on  the  contiguous  margins  of  the  bodies  of  the  thoracic  vertebrae  and  with  the 
intervertebral  fibrocartiiages  between  them;  the  first,  tenth,  eleventh,  and  twelfth 
ribs  each  articulate  with  a  single  vertebra.    The  ligaments  of  the  joints  are: 

The  Articular  Capsule.  The  Radiate. 

The  Interarticular. 

The  Articular  Capsule  {capsula  articularis;  capsular  ligament).- — The  articular 
capsule  surrounds  the  joint,  being  composed  of  short,  strong  fibres,  connecting 
the  head  of  the  rib  with  the  circumference  of  the  articular  cavity  formed  by  the 
intervertebral  fibrocartilage  and  the  adjacent  vertebrae.  It  is  most  distinct  at 
the  upper  and  lower  parts  of  the  articulation;  some  of  its  upper  fibres  pass  through 
the  intervertebral  foramen  to  the  back  of  the  intervertebral  fibrocartilage,  while 
its  posterior  fibres  are  continuous  with  the  ligament  of  the  neck  of  the  rib. 

The  Radiate  Ligament  {ligamentum  capituli  costae  radiatum;  anterior  costoverte- 
bral or  stellate  ligament). — The  radiate  ligament  connects  the  anterior  part' of  the 
head  of  each  rib  wdth  the  side  of  the  bodies  of  two  vertebrae,  and  the  interverte- 
bral fibrocartilage  between  them.  It  consists  of  three  flat  fasciculi,  which  are 
attached  to  the  anterior  part  of  the  head  of  the  rib,  just  beyond  the  articular  sur- 
face. The  superior  fasciculus  ascends  and  is  connected  with  the  body  of  the  verte- 
bra above;  the  inferior  one  descends  to  the  body  of  the  vertebra  below;  the  middle 
one,  the  smallest  and  least  distinct,  is  horizontal  and  is  attached  to  the  interver- 
tebral fibrocartilage.    The  radiate  ligament  is  in  relation,  \\\  front,  with  the  thoracic 


COSTOVERTEBRAL  ARTICULATJOXS 


397 


ganglia  of  the  sympathetic  trunk,  the  i)h'ura,  and,  on  the  right  side,  with  the  azygos 
vein;  behind,  with  the  interarticuhir  ligament  and  synovial  membranes. 

In  the  case  of  the  first  rib,  this  ligament  is  not  divided  into  three  fasciculi,  but 
its  fibres  are  attached  to  the  lx)dy  of  the  last  cer\'ical  vertebra,  as  well  as  to  that 
of  the  first  thoracic.  In  the  articulations  of  the  heads  of  the  tenth,  eleventh,  and 
twelfth  ribs,  each  of  which  articulates  with  a  single  vertebra,  the  triradiate  arrange- 
ment does  not  exist;  but  the  fibres  of  the  ligament  in  each  case  are  connected  to 
the  vertebra  above,  as  well  as  to  that  with  which  the  rib  articulates. 


Upper  synovial  camty  / 

Interarticular  ligament     / 

Lower  synovial  cavity 

Fig.  435. — Costovertebral  articulations.     Anterior  view. 


The  Interarticular  Ligament  (ligamentum  capituli  costae  inter  articular  e;  inter- 
articular ligament). — The  interarticular  ligament  is  situated  in  the  interior  of  the 
joint.  It  consists  of  a  short  band  of  fibres,  flattened  from  above  downward,  attached 
by  one  extremity  to  the  crest  separating  the  two  articular  facets  on  the  head  of 
the  rib,  and  by  the  other  to  the  intervertebral  fibrocartilage;  it  divides  the  joint 
into  two  cavities.  In  the  joints  of  the  first,  tenth,  eleventh,  and  twelfth  ribs,  the 
interarticular  ligament  does  not  exist;  consequently,  there  is  but  one  cavity  in 
each  of  these  articulations.  This  ligament  is  the  homologue  of  the  ligamentum 
conjugale  present  in  some  mammals,  and  uniting  the  heads  of  opposite  ribs,  across 
the  back  of  the  intervertebral  fibrocartilage. 

Synovial  Membranes. — There  are  two  synovial  membranes  in  each  of  the  articulations  where 
an  interarticular  hgament  exists,  one  above  and  one  below  this  structure;  but  only  one  in  those 
joints  where  there  are  single  cavities. 

2.  Costotransverse  Articulations  {articidationes  costotramrersariae)  (Fig.  436). — 
The  articular  portion  of  the  tubercle  of  the  rib  forms  with  the  articular  surface 
on  the  adjacent  transverse  process  an  arthrodial  joint. 

In  the  eleventh  and  twelfth  ribs  this  articulation  is  wanting. 

The  ligaments  of  the  joint  are: 

The  Articular  Capsule.  The  Posterior  Costotransverse. 

The  Anterior  Costotransverse.  The  Ligament  of  the  Neck  of  the  Rib. 

The  Ligament  of  the  Tubercle  of  the  Rib. 


398 


SYNDESMOLOGY 


The  Articular  Capsule  {capsula  articidaris ;  capsuJur  li(jmnent). — The  articular  cap- 
sule is  a  thin  membrane  attached  to  the  circumferences  of  the  articular  surfaces, 
and  lined  bv  a  synovial  membrane. 


Anterior  costotraiisverse 
ligament  divided 

Ligament  of  the  necJc 


Ligament  of  the 

tubercle 


'^^  \         Synovial  cavity 


Fig.  436. — Costotransverse  articulation.     Seen  from  above. 


Fig.  437. — Section  of  the  costotransverse 
joints  from  the  third  to  the  ninth  inclusive. 
Contrast  the  concave  facets  on  the  upper  with 
the  flattened  facets  on  the  lower  transverse 
processes. 


The  Anterior  Costotransverse  Ligament  {liga- 
mentum  costotranstersarium  anterius;  anterior 
superior  ligament).- — The  anterior  costotrans- 
verse ligament  is  attached  below  to  the  sharp 
crest  on  the  upper  border  of  the  neck  of  the 
rib,  and  passes  obliquely  upward  and  lateral- 
ward  to  the  lower  border  of  the  transverse 
process  immediately  above.  It  is  in  relation, 
in  front,  with  the  intercostal  vessels  and 
nerves;  its  medial  border  is  thickened  and 
free,  and  bounds  an  aperture  which  transmits 
the  posterior  branches  of  the  intercostal  vessels 
and  nerves;  its  lateral  border  is  continuous 
with  a  thin  aponeurosis,  which  covers  the 
Intercostalis  externus. 

The  first  rib  has  no  anterior  costotransverse 
ligament.  A  band  of  fibres,  the  lumbocostal 
ligament,  in  series  with  the  anterior  costotrans- 
verse ligaments,  connects  the  neck  of  the 
twelfth  rib  to  the  base  of  the  transverse  pro- 
cess of  the  first  lumbar  vertebra ;  it  is  merely 
a  thickened  portion  of  the  posterior  layer  of 
the  lumbodorsal  fascia. 

The  Posterior  Costotransverse  Ligament  {liga- 
mentuin  costotransversarinm  ijosterius).  —  The 
posterior  costotransverse  ligament  is  a  feeble 
band  which  is  attached  below  to  the  neck  of 


STERNOCOSTAL  ARTICULATIONS  399 

the  rib  and  passes  upward  and  mediahvard  to  the  base  of  the  transverse  process 
and  lateral  border  of  the  inferior  articular  process  of  the  vertebra  above. 

The  Ligament  of  the  Neck  of  the  Rib  Qigavieuium  colli  cnstae;  middle  costotransverse 
or  interosseous  ligament).-  -The  ligament  of  the  neck  of  the  rib  consists  of  short 
but  strong  fibres,  connecting  the  rough  surface  on  the  back  of  the  neck  of  the  rib 
with  the  anterior  surface  of  the  adjacent  transverse  process.  A  rudimentary 
ligament  may  be  present  in  the  case  of  the  eleventh  and  twelfth  ribs. 

The  Ligament  of  the  Tubercle  of  the  Rib  {ligamentum  tubercuU  costae;  posterior 
costotransverse  ligament). — The  ligament  of  the  tubercle  of  the  rib  is  a  short  but 
thick  and  strong  fasciculus,  which  passes  obliquely  from  the  apex  of  the  transverse 
process  to  the  rough  non-articular  portion  of  the  tubercle  of  the  rib.  The  ligaments 
attached  to  the  upper  ribs  ascend  from  the  transverse  processes;  they  are  shorter 
and  more  oblique  than  those  attached  to  the  inferior  ribs,  which  descend  slightly. 

Movements. — The  heads  of  the  ribs  are  so  closely  connected  to  the  bodies  of  the  vertebrae 
by  the  radiate  and  interarticular  Ugaments  that  only  slight  gUding  movements  of  the  articular 
surfaces  on  one  another  can  take  place.  Similarly,  the  strong  hgaments  binding  the  necks  and 
tubercles  of  the  ribs  to  the  transverse  processes  limit  the  movements  of  the  costotransverse 
joints  to  shght  gliding,  the  natm-e  of  which  is  determined  by  the  shape  and  direction  of  the  articular 
surfaces  (Fig.  437).  In  the  upper  six  ribs  the  articular  surfaces  on  the  tubercles  are  oval  in  shape 
and  convex  from  above  downward;  they  fit  into  corresponding  concavities  on  the  anterior  sur- 
faces of  the  transverse  processes,  so  that  upward  and  downward  movements  of  the  tubercles  are 
associated  with  rotation  of  the  rib  neck  on  its  long  axis.  In  the  seventh,  eighth,  ninth,  and  tenth 
ribs  the  articular  surfaces  on  the  tubercles  are  flat,  and  are  directed  obhquely  downward,  medial- 
ward,  and  backward.  The  surfaces  with  which  they  articulate  are  placed  on  the  upper  margins 
of  the  transverse  processes;  when,  therefore,  the  tubercles  are  drawn  up  they  are  at  the  same 
time  carried  backward  and  medialward.  The  two  joints,  costocentral  and  costotransverse,  move 
simultaneously  and  in  the  same  directions,  the  total  effect  being  that  the  neck  of  the  rib  moves 
as  if  on  a  single  joint,  of  which  the  costocentral  and  costotransverse  articulations  form  the  ends. 
In  the  upper  six  ribs  the  neck  of  the  rib  moves  but  slightly  upward  and  downward;  its  chief 
movement  is  one  of  rotation  around  its  own  long  axis,  rotation  backward  being  associated  with 
depression,  rotation  forward  with  elevation.  In  the  seventh,  eighth,  ninth,  and  tenth  ribs  the 
neck  of  the  rib  moves  upward,  backward,  and  medialward,  or  downward,  forward,  and  lateral- 
ward;  very  shght  rotation  accompanies  these  movements. 

VI.     Sternocostal  Articulations  (Articulationes  Sternocostales ;  Costosternal 

Articulations)  (Fig.  438) 

The  articulations  of  the  cartilages  of  the  true  ribs  with  the  sternum  are 
arthrodial  joints,  with  the  exception  of  the  first,  in  which  the  cartilage  is  directly 
united  with  the  sternum,  and  which  is,  therefore,  a  synarthrodia!  articulation. 
The  ligaments  connecting  them  are: 

The  Articular  Capsules.  The  Interarticular  Sternocostal. 

The  Radiate  Sternocostal.  The  Costoxiphoid. 

The  Articular  Capsules  (capsulae  articulares;  capsular  ligaments). — The  articular 
capsules  surround  the  joints  between  the  cartilages  of  the  true  ribs  and  the 
sternum.  They  are  very  thin,  intimately  blended  with  the  radiate  sternocostal 
ligaments,  and  strengthened  at  the  upper  and  lower  parts  of  the  articulations  by  a 
few  fibres,  which  connect  the  cartilages  to  the  side  of  the  sternum. 

The  Radiate  Sternocostal  Ligaments  (ligamenta  sternocostalia  radiata;  chondro- 
sternal  or  sternocostal  ligaments). — These  ligaments  consist  of  broad  and  thin  mem- 
branous bands  that  radiate  from  the  front  and  back  of  the  sternal  ends  of  the 
cartilages  of  the  true  ribs  to  the  anterior  and  posterior  surfaces  of  the  sternum. 
They  are  composed  of  fasciculi  which  pass  in  different  directions.  The  superior 
fasciculi  ascend  obliquely,  the  inferior  fasciculi  descend  obliquely,  and  the  middle 
fasciculi  run  horizontally.  The  superficial  fibres  are  the  longest;  they  intermingle 
with  the  fibres  of  the  ligaments  above  and  below  them,  with  those  of  the  opposite 


400 


SYNDESMOLOGY 


side,  and  in  front  with  the  tendinous  fibres  of  orit^nn  of  the  Pectoralis  major,  form- 
ing a  thick  fibrous  membrane  (membrana  sternij  which  envelopes  the  sternum. 
This  is  more  distinct  at  the  lower  than  at  the  upper  part  of  the  bone. 

The  Interarticular  Sternocostal  Ligament  {licfamentum  sternocostale  inter  articular  e; 
interarticular  chondrosteriial  rigament).— This  ligament  is  found  constantly  only 
between  the  second  costal  cartilages  and  the  sternum.    The  cartilage  of  the  second 


The  synovial  cavities  are  exposed  by 
a  coronal  section  of  the  sternum  and  cartilages 


Cartilage  continuous  with 
sternum 


Interarticular  ligament  and 
two  synovial  membranes 


Single  synovial 
membrane 


Fig.  438. — Sternocostal  and  interchondral  articulations.     Anterior  view. 

rib  is  connected  with  the  sternum  by  means  of  an  interarticular  ligament,  attached 
by  one  end  to  the  cartilage  of  the  rib,  and  by  the  other  to  the  fibrocartilage  which 
unites  the  manubrium  and  body  of  the  sternum.  This  articulation  is  provided 
with  two  synovial  membranes.  Occasionally  the  cartilage  of  the  third  rib  is  con- 
nected with  the  first  and  second  pieces  of  the  body  of  the  sternum  by  an  interartic- 
ular ligament.     Still  more  rarely,  similar  ligaments  are  found  in  the  other  four 


ARTICULATION  OF  THE  MANUBRIUM  AND  BODY  OF  STERNUM     401 

joints  of  the  series.    In  the  lower  two  the  li,i>;anient  sometimes  completely  obliterates 
the  cavity,  so  as  to  convert  the  articulation  into  an  amphiarthrosis. 

The  Costoxiphoid  Ligaments  {ligamenta  costoxiphoidea;  chondroxiphoid  ligaments) . 
— These  ligaments  connect  the  anterior  and  posterior  surfaces  of  the  seventh 
costal  cartilage,  and  sometimes  those  of  the  sixth,  to  the  front  and  back  of  the 
xiphoid  process.  They  vary  in  length  and  breadth  in  different  subjects;  those  on 
the  back  of  the  joint  are  less  distinct  than  those  in  front. 

Synovial  Membranes. — There  is  no  synovial  membrane  between  the  first  costal  cartilage  and 
the  sternum,  as  this  cartilage  is  directly  continuous  with  the  manubrium.  There  are  two  in  the 
articulation  of  the  second  costal  cartilage  and  generally  one  in  each  of  the  other  joints;  but  those 
of  the  sixth  and  seventh  sternocostal  joints  are  sometimes  absent;  where  an  interarticular  liga- 
ment is  present,  there  are  two  synovial  cavities.  After  middle  life  the  articular  surfaces  lose  their 
polish,  become  roughened,  and  the  synovial  membranes  apparently  disappear.  In  old  age,  the 
cartilages  of  most  of  the  ribs  become  continuous  with  the  sternum,  and  the  joint  cavities  are 
consequently  obhterated. 

Movements. — Shght  gliding  movements  are  permitted  in  the  sternocostal  articulations. 

Interchondral  Articulations  {articulationes  interchondrales;  articulations  of  the 
cartilages  of  the  ribs  with  each  other)  (Fig.  438). — The  contiguous  borders  of  the  sixth, 
seventh,  and  eighth,  and  sometimes  those  of  the  ninth  and  tenth,  costal  cartilages 
articulate  with  each  other  by  small,  smooth,  oblong  facets.  Each  articulation 
is  enclosed  in  a  thin  articular  capsule,  lined  by  synovial  membrane  and  strengthened 
laterally  and  medially  by  ligamentous  fibres  (interchondral  ligaments)  which  pass 
from  one  cartilage  to  the  other.  Sometimes  the  fifth  costal  cartilages,  more  rarely 
the  ninth  and  tenth,  articulate  by  their  low^er  borders  with  the  adjoining  cartilages 
by  small  oval  facets;  more  frequentl}^  the  connection  is  by  a  few  ligamentous  fibres. 

Costochondral  Articulations. — The  lateral  end  of  each  costal  cartilage  is  received 
into  a  depression  in  the  sternal  end  of  the  rib,  and  the  two  are  held  together  by  the 
periosteum. 

VII.    Articulation  of  the  Manubrium  and  Body  of  the  Sternum. 

The  manubrium  is  united  to  the  body  of  the  sternum  either  by  an  amphiarthrodial 
joint^ — a  piece  of  fibrocartilage  connecting  the  segments — or  by  a  diarthrodial 
joint,  in  which  the  articular  surface  of  each  bone  is  clothed  with  a  lamina  of  car- 
tilage. In  the  latter  case,  the  cartilage  covering  the  body  is  continued  without 
interruption  on  to  the  cartilages  of  the  facets  for  the  second  ribs.  Rivington 
found  the  diarthrodial  form  of  joint  in  about  one-third  of  the  specimens  examined 
by  him,  Maisonneuve  more  frequently.  It  appears  to  be  rare  in  childhood,  and 
is  formed,  in  Rivington's  opinion,  from  the  amphiarthrodial  form,  by  absorption. 
The  diarthrodial  joint  seems  to  have  no  tendency  to  ossify,  while  the  amphiar- 
throdial is  more  liable  to  do  so,  and  has  been  found  ossified  as  early  as  thirty-four 
years  of  age.  The  two  segments  are  further  connected  by  anterior  and  posterior 
intersternal  ligaments  consisting  of  longitudinal  fibres. 

Mechanism  of  the  Thorax. — Each  rib  possesses  its  own  range  and  variety  of  movements,  but 
the  movements  of  all  are  combined  in  the  respiratory  excm'sions  of  the  thorax.  Each  rib  may 
be  regarded  as  a  lever  the  fulcrum  of  which  is  situated  immediately  outside  the  costotransverse 
articulation,  so  that  when  the  body  of  the  rib  is  elevated  the  neck  is  depressed  and  vice  versa; 
from  the  disproportion  in  length  of  the  arms  of  the  lever  a  sUght  movement  at  the  vertebral  end 
of  the  rib  is  greatly  magnified  at  the  anterior  extremity. 

The  anterior  ends  of  the  ribs  lie  on  a  lower  plane  than  the  posterior;  when  therefore  the  body 
of  the  rib  is  elevated  the  anterior  extremity  is  thrust  also  forward.  Again,  the  middle  of  the  body 
of  the  rib  hes  in  a  plane  below  that  passing  through  the  two  extremities,  so  that  when  the  body 
is  elevated  relatively  to  its  ends  it  is  at  the  same  time  carried  outward  from  the  median  plane 
of  the  thorax.  Finther,  each  rib  forms  the  segment  of  a  ciu've  which  is  greater  than  that  of  the 
rib  immediately  above,  and  therefore  the  elevation  of  a  rib  increases  the  transverse  diameter 
of  the  thorax  in  the  plane  to  which  it  is  raised.  The  modifications  of  the  rib  movements  at  their 
vertebral  ends  have  akeady  been  described  (page  399).  Fui'ther  modifications  result  from  the 
26 


402 


SYNDESMOLOGY 


attachments  of  their  anterior  extremities,  and  it  is  convenient  therefore  to  consider  separately 
the  movements  of  the  ribs  of  the  three  groups — vertebrosternal,  vertebrochondral,  and  vertebral. 

V erkhrosternal  Ribs  (P'igs.  439, 
440).— The  first  rib  differs  from  the 
others  of  this  group  in  that  its  at- 
tachment to  the  sternum  is  a  rigid 
one;  this  is  counterbalanced  to  some 
extent  by  the  fact  that  its  head 
possesses  no  interarticular  ligament, 
and  is  therefore  more  movable.  The 
first  pair  of  ribs  with  the  manu- 
brium sterni  move  as  a  single  piece, 
the  anterior  portion  being  elevated 
by  rotatory  movements  at  the 
vertebral  extremities.  In  normal 
quiet  respiration  the  movement  of 
this  arc  is  practically  7iil;  when  it 
does  occur  the  anterior  part  is 
raised  and  carried  forward,  increas- 
ing the  antero-posterior  and  trans- 
verse diameters  of  this  region  of  the 
chest.  The  movement  of  the  second 
rib  is  also  slight  in  normal  respira- 
tion, as  its  anterior  extremity  is 
fixed  to  the  manubrium,  and  pre- 
vented therefore  from  moving  up- 
ward. The  sternocostal  articulation, 
however,  allows  the  middle  of  the 
body  of  the  rib  to  be  drawn  up,  and 
in  this  way  the  transverse  thoracic  diameter  is  increased.  Elevation  of  the  third,  fourth,  fifth, 
and  sixth  ribs  raises  and  thrusts  forward  their  anterior  extremities,  the  greater  part  of  the  move- 
ment being  effected  by  the  rotation  of  the  rib  neck  backward.  The  thrust  of  the  anterior 
extremities  carries  forward  and  upward  the  body  of  the  sternum,   which  moves  on  the  joint 


Fig.  439. — Lateral  view  of  first  and  seventh  ribs  in  position,  sliow- 
ing  the  movements  of  the  sternum  and  ribs  in  A ,  ordinary  expiration ; 
B,  quiet  inspiration;  C,  deep  inspiration. 


Fig.  440. — Diagram  showing  the  axes  of  movement 
(A  B  and  C  D)  oi  a  vertebrosternal  rib.  The  inter- 
rupted lines  indicate  the  position  of  the  rib  in 
inspiration. 


Fig.  441. — Diagram  showing  the  axis  of  movement 
(*4  B)  of  a  vertebrochondral  rib.  The  interrupted  lines 
indicate  the  position  of  the  rib  in  inspiration. 


between  it  and  the  manubrium,  and  thus  the  antero-posterior  thoracic  diameter  is  increased. 
This  movement  is,  however,  soon  arrested,  and  the  elevating  force  is  then  expended  in  raising 
the  middle  part  of  the  body  of  the  rib   and    everting   its   lower  border;  at   the  same  time  the 


ARTIVLLATIOS  OF  THE  VERTEBRAL  COLUMX  WITH  THE  PELVIS     403 

costochondnil  unfile  is  opened  out.  By  these  latter  movements  a  considerable  inca-ease  in  the 
transverse  diameter  of  the  thorax  is  efTeeted. 

Vcrlebrochondral  Ribs  (Fig.  441). — The  seventh  rib  is  included  with  this  group,  as  it  conforms 
more  closelj-  to  their  type.  While  the  movements  of  these  ribs  assist  in  enlarging  the  thorax 
for  respiratory  purposes,  they  are  also  concerned  in  increasing  the  upper  abdominal  space  for 
viscera  displaced  by  the  action  of  the  Diaphragma.  The  costal  cartilages  articulate  with  one 
another,  so  that  (>ach  pushes  up  that  above  it,  the  final  thrust  being  directed  to  pushing  forward 
and  upward  the  lower  end  of  the  body  of  the  sternum.  The  amount  of  elevation  of  the  anterior 
extremities  is  limited  on  account  of  the  very  slight  rotation  of  the  rib  neck.  Elevation  of  the 
shaft  is  accompanied  b}'  an  outward  and  backward  movement;  the  outward  movement  everts 
the  anterior  end  of  the  rib  and  opens  up  the  subcostal  angle,  while  the  backward  movement 
pulls  back  the  anterior  extremity  and  counteracts  the  forward  thrust  due  to  its  elevation;  this 
latter  is  most  noticeable  in  the  lower  ribs,  which  are  the  shortest.  The  total  result  is  a  con.sider- 
able  inci'ease  in  the  transverse  and  a  diminution  in  the  median  antero-posterior  diameter  of  the 
upper  part  of  the  abdomen;  at  the  same  time,  however,  the  lateral  antero-posterior  diameters  of 
the  abdomen  are  increased. 

Vertebral  Ribs. — Since  these  ribs  have  free  anterior  extremities  and  only  costocentral  articula- 
"tions  with  no  interarticular  ligaments,  they  are  capable  of  slight  movements  in  all  directions. 
WTien  the  other  ribs  are  elevated  these  are  depressed  and  fixed  to  form  points  of  action  for  the 
Diaphragma. 


Aferture  of  communication 

with 
bursa  under  Psoas  and 
Iliacus 


Fejtiur'm 
Fig.  442. — Articulations  of  pelvis  and  hip.     Anterior  view. 


VIII,    Articulation  of  the  Vertebral  Column  with  the  Pelvis. 


The  ligaments  connecting  the  fifth  himbar  vertebra  witli  the  sacrum  are  similar 
to  those  which  join  the  movable  segments  of  the  vertebral  column  with  each  other 
— viz.:  1.  The  continuation  downward  of  the  anterior  and  posterior  longitudinal 
ligaments.  2.  The  intervertebral  fibrocartilage,  connecting  the  body  of  the  fifth 
lumbar  to  that  of  the  first  sacral  vertebra  and  forming  an  amphiarthrodial  joint. 
3.  Ligamenta  flava,  uniting  the  laminae  of  the  fifth  lumbar  vertebra  with  those 
of  the  first  sacral.  4.  Capsules  connecting  the  articular  processes  and  forming 
a  double  arthrodia.    5.  Inter-  and  supraspinal  ligaments. 


404  SYNDESMOLOGY 

On  either  side  an  additional  ligament,  the  iliolumbar,  connects  the  pelvis  with 
the  A'ertebral  column. 

The  Iliolumbar  Ligament  (ligamentum  iliolumbale)  (Fig.  442). — The  iliolumbar 
ligament  is  attached  above  to  the  lower  and  front  part  of  the  transverse  process 
of  the  fifth  lumbar  vertebra.  It  radiates  as  it  passes  lateralward  and  is  attached 
by  two  main  bands  to  the  pelvis.  The  lower  bands  run  to  the  base  of  the  sacrum, 
blending  with  the  anterior  sacroiliac  ligament;  the  upper  is  attached  to  the  crest 
of  the  ilium  immediately  in  front  of  the  sacroiliac  articulation,  and  is  continuous 
above  with  the  lumbodorsal  fascia.  In  front,  it  is  in  relation  with  the  Psoas  major; 
behind,  with  the  muscles  occupying  the  vertebral  groove;  above,  with  the  Quadratus 
lumborum. 

IX.    Articulations  of  the  Pelvis. 

The  ligaments  connecting  the  bones  of  the  pelvis  with  each  other  may  be  divided 
into  four  groups:  1.  Those  connecting  the  sacrum  and  ilium.  2.  Those  passing 
between  the  sacrum  and  ischium.  3.  Those  uniting  the  sacrum  and  coccyx.  4. 
Those  between  the  two  pubic  bones. 

1.  Sacroiliac  Articulation  (articulatio  sacroiliaca). — The  sacroiliac  articulation 
is  an  amphiarthrodial  joint,  formed  between  the  auricular  surfaces  of  the  sacrum 
and  the  ilium.  The  articular  surface  of  each  bone  is  covered  with  a  thin  plate 
of  cartilage,  thicker  on  the  sacrum  than  on  the  ilium.  These  cartilaginous  plates 
are  in  close  contact  with  each  other,  and  to  a  certain  extent  are  united  together 
by  irregular  patches  of  softer  fibrocartilage,  and  at  their  upper  and  posterior  part 
by  fine  interosseous  fibres.  In  a  considerable  part  of  their  extent,  especially  in 
advanced  life,  they  are  separated  by  a  space  containing  a  synovia-like  fluid,  and 
hence  the  joint  presents  the  characteristics  of  a  diarthrosis.  The  ligaments  of  the 
joint  are: 

The  Anterior  Sacroiliac.  The  Posterior  Sacroiliac. 

The  Interosseous. 

The  Anterior  Sacroiliac  Ligament  {ligamentum  sacroiliacum  anterius)  (Fig.  442)  .■ — 
The  anterior  sacroiliac  ligament  consists  of  numerous  thin  bands,  which  connect 
the  anterior  surface  of  the  lateral  part  of  the  sacrum  to  the  margin  of  the  auricular 
surface  of  the  ilium  and  to  the  preauricular  sulcus. 

The  Posterior  Sacroiliac  Ligament  (ligamentum  sacroiliacum  posterius)  (Fig.  443). 
— The  posterior  sacroiliac  ligament  is  situated  in  a  deep  depression  between  the 
sacrum  and  ilium  behind;  it  is  strong  and  forms  the  chief  bond  of  union  between 
the  bones.  It  consists  of  numerous  fasciculi,  which  pass  between  the  bones  in 
various  directions.  The  upper  part  (short  posterior  sacroiliac  ligament)  is  nearly 
horizontal  in  direction,  and  passes  from  the  first  and  second  transverse  tubercles 
on  the  back  of  the  sacrum  to  the  tuberosity  of  the  ilium.  The  lower  part  (long 
posterior  sacroiliac  ligament)  is  oblique  in  direction;  it  is  attached  by  one  extremity 
to  the  third  transverse  tubercle  of  the  back  of  the  sacrum,  and  by  the  other  to  the 
posterior  superior  spine  of  the  ilium. 

The  Interosseous  Sacroiliac  Ligament  (ligamentum  sacroiliacum  inter os s eum) . — 
This  ligament  lies  deep  to  the  posterior  ligament,  and  consists  of  a  series  of  short, 
strong  fibres  connecting  the  tuberosities  of  the  sacrum  and  ilium. 

2.  Ligaments  Connecting  the  Sacrum  and  Ischium  (Fig.  443). 

The  Sacrotuberous.  The  Sacrospinous. 

The    Sacrotuberous    Ligament    (ligamentum    sacrotuberosum;    great    or    posterior 

sacrosciatic  ligament). — The  sacrotuberous  ligament  is  situated  at  the  lower  and 

back  part  of  the  pelvis.    It  is  flat,  and  triangular  in  form;  narrower  in  the  middle 

than  at  the  ends;  attached  by  its  broad  base  to  the  posterior  inferior  spine  of  the 


ARTICULATIONS  OF  THE  PELVIS 


405 


ilium,  to  the  fourth  and  fifth  transverse  tuherek's  of  the  sacrum,  and  to  the  lower 
part  of  the  lateral  margin  of  that  bone  and  the  coccyx.  Passing  obliquely  downward, 
forward,  and  lateralward,  it  becomes  narrow  and  thick,  but  at  its  insertion  into 
the  inner  margin  of  the  tuberosity  of  the  ischium,  it  increases  in  breadth,  and  is 
prolonged  forward  along  the  inner  margin  of  the  ramus,  as  the  falciform  process, 
the  free  concave  edge  of  which  gives  attachment  to  the  obturator  fascia;  one  of  its 
surfaces  is  turned  toward  the  perineum,  the  other  toward  the  Obturator  internus. 
The  lower  border  of  the  ligament  is  directly  continuous  with  the  tendon  of  origin 
of  the  long  head  of  the  Biceps  femoris,  and  b}'  many  is  believed  to  be  the  proximal 
end  of  this  tendon,  cut  off  by  the  projection  of  the  tuberosity  of  the  ischium. 


Fig.  443. — Articulations  of  pelvis  and  hip.     Posterior  view. 


Relations. — The  posterior  surface  of  this  hgament  gives  origin,  by  its  whole  extent,  to  the 
Glutaeus  maximus.  Its  anterior  surface  is  in  part  united  to  the  sacrospinous  Ugament.  Its  upper 
harder  forms,  above,  the  posterior  boundary  of  the  greater  sciatic  foramen,  and,  below,  the  pos- 
terior boundary  of  the  lesser  sciatic  foramen.  Its  lower  border  forms  part  of  the  boundary  of  the 
perineum.  It  is  pierced  by  the  coccygeal  nerve  and  the  coccygeal  branch  of  the  inferior  gluteal 
artery. 

The  Sacrospinous  Ligament  {ligamentum  sacrospinosum;  small  or  anterior  sacro- 
sciatic  ligament). — The  sacrospinous  ligament  is  thin,  and  triangular  in  form; 
it  is  attached  by  its  apex  to  the  spine  of  the  ischium,  and  medially,  by  its  broad 
base,  to  the  lateral  margins  of  the  sacrum  and  coccyx,  in  front  of  the  sacrotuberous 
ligament  with  wdiich  its  fibres  are  intermingled. 

Relations. — ^It  is  in  relation,  anteriorly,  with  the  Coccygeus  muscle,  to  which  it  is  closely  con- 
nected; posteriorly,  it  is  covered  by  the  sacrotuberous  ligament,  and  crossed  by  the  internal 
pudendal  vessels  and  nerve.  Its  upper  border  forms  the  lower  boundary  of  the  greater  sciatic 
foramen;  its  lower  border,  part  of  the  margin  of  the  lesser  sciatic  foramen. 


406  SYNDES}fr)LOGY 

These  two  ligaments  convert  the  sciatic  notches  into  foramina.  The  greater  sciatic  foramen 
is  bounded,  in  front  and  above,  by  the  posterior  border  of  the  hip  bone;  hcliind,  \)\  the  sacrotuberous 
Ugament;  and  below,  by  the  sacrospinous  hgament.  It  is  partially  filled  up,  in  the  recent  state, 
by  the  Piriformis  which  leaves  the  pelvis  through  it.  Above  this  muscle,  the  superior  gluteal 
vessels  and  nerve  emerge  from  the  pelvis;  and  below  it,  the  inferior  gluteal  vessels  and  nerve, 
the  internal  pudendal  vessels  and  nerve,  the  sciatic  and  posterior  femoral  cutaneous  nerves,  and 
the  nerves  to  the  Obturator  internus  and  Quadratus  femoris  make  their  exit  from  the  pelvis. 
The  lesser  sciatic  foramen  is  bounded,  in  front,  by  the  tuberosity  of  the  ischium;  above,  by  the 
spine  of  the  ischium  and  sacrospinous  ligament;  behind,  by  the  sacrotuberous  ligament.  It  trans- 
mits the  tendon  of  the  Obturator  internus,  its  nerve,  and  the  internal  pudendal  vessels  and  nerve 

3.  Sacrococcygeal  Symphysis  {.siimphysis  sacrococcygea;  articulation  of  the  sacrvin 
and  coccyx). — This  articulation  is  an  amphiarthroclial  joint,  formed  between  the 
oval  surface  at  the  apex  of  the  sacrum,  and  the  base  of  the  coccyx.  It  is  homol- 
ogous with  the  joints  between  the  bodies  of  the  vertebrte,  and  is  connected  by 
similar  ligaments.    They  are: 

The  Anterior  Sacrococcygeal.  The  Lateral  Sacrococcygeal. 

The  Posterior  Sacrococcygeal.  The  Interposed  Fibrocartilage. 

The  Interarticular. 

The  Anterior  Sacrococcygeal  Ligament  (ligamentum  sacrococcygeum  anterius). — 
This  consists  of  a  few  irregular  fibres,  which  descend  from  the  anterior  surface 
of  the  sacrum  to  the  front  of  the  coccyx,  blending  with  the  periosteum. 

The  Posterior  Sacrococcygeal  Ligament  (ligamentum  sacrococcygeum  posterius). — 
This  is  a  flat  band,  which  arises  from  the  margin  of  the  lower  orifice  of  the  sacral 
canal,  and  descends  to  be  inserted  into  the  posterior  surface  of  the  coccyx.  This 
ligament  completes  the  lower  and  back  part  of  the  sacral  canal,  and  is  divisible 
into  a  short  deep  portion  and  a  longer  superficial  part.  It  is  in  relation,  behind, 
with  the  Glutaeus  maximus. 

The  Lateral  Sacrococcygeal  Ligament  {ligamentum  sacrococcygeum  laterale;  inter- 
transverse ligament). — The  lateral  sacrococcygeal  ligament  exists  on  either  side 
and  connects  the  transverse  process  of  the  coccyx  to  the  lower  lateral  angle  of  the 
sacrum;  it  completes  the  foramen  for  the  fifth  sacral  nerve. 

A  disk  of  fibrocartilage  is  interposed  between  the  contiguous  surfaces  of  the 
sacrum  and  coccyx;  it  differs  from  those  between  the  bodies  of  the  vertebrae  in 
that  it  is  thinner,  and  its  central  part  is  firmer  in  texture.  It  is  somewhat  thicker 
in  front  and  behind  than  at  the  sides.  Occasionally  the  coccyx  is  freely  movable 
on  the  sacrum,  most  notably  during  pregnancy ;  in  such  cases  a  synovial  membrane 
is  present. 

The  Interarticular  Ligaments  are  thin  bands,  which  unite  the  cornua  of  the  two 
bones. 

The  different  segments  of  the  coccyx  are  connected  together  by  the  extension 
downw^ard  of  the  anterior  and  posterior  sacrococcygeal  ligaments,  thin  annular 
disks  of  fibrocartilage  being  interposed  between  the  segments.  In  the  adult  male, 
all  the  pieces  become  ossified  together  at  a  comparatively  early  period;  but  in  the 
female,  this  does  not  commonly  occur  until  a  later  period  of  life.  At  more  advanced 
age  the  joint  between  the  sacrum  and  coccyx  is  obliterated. 

Movements. — The  movements  which  take  place  between  the  sacrum  and  coccyx,  and  between 
the  different  pieces  of  the  latter  bone,  are  forward  and  backward;  they  are  very  limited.  Their 
extent  increases  during  pregnancy. 

4.  The  Pubic  Symphysis  {symphysis  ossium  yuhis;  articulation  of  the  imbic 
hones)  (Fig.  444). — The  articulation  between  the  pubic  bones  is  an  amphiarthro- 
dial  joint,  formed  between  the  two  oval  articular  surfaces  of  the  bones.  The 
ligaments  of  this  articulation  are: 

The  Anterior  Pubic.  The  Superior  Pubic. 

The  Posterior  Pubic.  The  Arcuate  Pubic. 

The  Interpubic  Fibrocartilaginous  Lamina. 


ARTIClLAriONS  OF  TJII'J  J'KLVIS 


407 


The  Anterior  Pubic  Ligament  (Fiji;.  442). — The  anterior  pubic  lioament  consists 
of  several  sui)erinii)ose(l  layers,  which  pass  across  the  front  of  the  articulation. 
The  superficial  fibres  pass  obliciuely  from  one  bone  to  the  other,  decussating  and 
forming  an  interlacement  with  the  fibres  of  the  aj'joneuroses  of  the  Obliqui  externi 
and  the  medial  tendons  of  origin  of  the  Recti  abdominis.  The  deep  fibres  pass 
transversely  across  the  symphysis,  and  arc  blended  with  the  fibrocartilaginous 
lamina. 

The  Posterior  Pubic  Ligament. — The  posterior  pubic  ligament  consists  of  a  few 
thin,  scattered  fibres,  which  unite  the  two  pubic  bones  posteriorly. 

The  Superior  Pubic  Ligament  {Ugamentuin  puhicum  superius). — The  superior 
pubic  ligament  connects  together  the  two  pubic  bones  superiorly,  extending  later- 
ally as  far  as  the  pubic  tubercles. 


A)it.  sup.  iliac  spine- ^: 


Inierpuhic 
fibro- 
cartilaginous 
lamina 


Transverse  acetabular 
ligament 


Fig.  444. — Symphysis  pubis  expo-sed  by  a  coronal  section. 

The  Arcuate  Pubic  Ligament  {Ugamentuin  arcuatum  pubis;  inferior  pubic  or 
subpubic  ligament). — The  arcuate  pubic  ligament  is  a  thick,  triangular  arch  of 
ligamentous  fibres,  connecting  together  the  two  pubic  bones  below,  and  forming 
the  upper  boundary  of  the  pubic  arch.  Above,  it  is  blended  with  the  interpubic 
fibrocartilaginous  lamina;  laterally,  it  is  attached  to  the  inferior  rami  of  the 
pubic  bones;  below,  it  is  free,  and  is  separated  from  the  fascia  of  the  urogenital 
diaphragm  by  an  opening  through  which  the  deep  dorsal  vein  of  the  penis  passes 
into  the  pelvis. 

The  Interpubic  Fibrocartilaginous  Lamina  {lamina  fibrocartilaginea  interpiibica; 
interpubic  disk). — The  interpubic  fibrocartilaginous  lamina  connects  the  opposed 
surfaces  of  the  pubic  bones.  Each  of  these  surfaces  is  covered  by  a  thin  layer  of 
hyaline  cartilage  firmly  joined  to  the  bone  by  a  series  of  nipple-like  processes  which 
accurately  fit  into  corresponding  depressions  on  the  osseous  surfaces.  These 
opposed  cartilaginous  surfaces  are  connected  together  by  an  intermediate  lamina 
of  fibrocartilage  which  varies  in  thickness  in  dift'erent  subjects.  It  often  contains 
a  cavity  in  its  interior,  probably  formed  by  the  softening  and  absorption  of  the 
fibrocartilage,  since  it  rarely  appears  before  the  tenth  year  of  life  and  is  not  lined 


408 


SYNDESMOLOGY 


by  synovial  membrane.  This  cavity  is  larger  in  the  female  than  in  the  male,  but 
it  is  very  doubtful  whether  it  enlarges,  as  was  formerly  supposed,  during  pregnancy. 
It  is  most  frequently  limited  to  the  upper  and  back  part  of  the  joint;  it  occasion- 
ally reaches  to  the  front,  and  may  extend  the  entire  length  of  the  cartilage.  It  may 
be  easily  demonstrated  when  present  by  making  a  coronal  section  of  the  symphysis 
pubis  near  its  posterior  surface  (Fig.  444). 


Fig.  445. — Coronal  section  of  anterior  sacral  segment. 

Mechanism  of  the  Pelvis. — The  pelvic  girdle  supports  and  protects  the  contained  viscera  and 
affords  surfaces  for  the  attachments  of  the  trunk  and  lower  limb  muscles.  Its  most  important 
mechanical  function,  however,  is  to  transmit  the  weight  of  the  trunk  and  upper  limbs  to  the 
lower  extremities. 

It  may  be  divided  into  two  arches  by  a  vertical  plane  passing  through  the  acetabular  cavities; 
the  posterior  of  these  arches  is  the  one  chiefly  concerned  in  the  function  of  transmitting  the 
weight.  Its  essential  parts  are  the  upper  three  sacral  vertebrae  and  two  strong  piUars  of  bone 
running  from  the  sacroihac  articulations  to  the  acetabular  cavities.  For  the  reception  and  diffu- 
sion of  the  weight  each  acetabular  cavity  is  strengthened  by  two  additional  bars  rxmning  toward 


Fig.  446. — Coronal  section  of  middle  sacral  segment. 


the  pubis  and  ischium.  In  order  to  lessen  concussion  in  rapid  changes  of  distribution  of  the 
weight,  joints  (sacroihac  articulations)  are  interposed  between  the  sacrum  and  the  iliac  bones; 
an  accessory  joint  (pubic  symphysis)  exists  in  the  middle  of  the  anterior  arch.  The  sacrum  forms 
the  summit  of  the  posterior  arch;  the  weight  transmitted  falls  on  it  at  the  lumbosacral  articula- 
tion and,  theoretically,  has  a  component  in  each  of  two  directions.  One  component  of  the  force 
is  expended  in  driving  the  sacrum  downward  and  backward  between  the  ihac  bones,  while  the 
other  thrusts  the  upper  end  of  the  sacrum  downward  and  forward  toward  the  pelvic  cavity. 

The  movements  of  the  sacrum  are  regulated  by  its  form.  Viewed  as  a  whole,  it  presents  the 
shape  of  a  wedge  with  its  base  upward  and  forward.  The  first  component  of  the  force  is  there- 
fore acting  against  the  resistance  of  the  wedge,  and  its  tendency  to  separate  the  ihac  bones  is 
resisted  by  the  sacroiliac  and  iholumbar  hgaments  and  by  the  Ugaments  of  the  pubic  symphysis. 

If  a  series  of  coronal  sections  of  the  sacroiliac  joints  be  made,  it  will  be  foimd  possible  to  divide 


STERNOCLAVICULAR  ARTICULATION  409 

the  articular  portion  of  the  sacrum  into  three  segments:  anterior,  middle,  and  posterior.  In 
the  anterior  segment  (Fig.  445),  which  involves  the  first  sacral  vertebra,  the  articular  surfaces 
show  sUght  sinuosities  and  are  almost  parallel 
to  one  another;  the  distance  between  their 
dorsal  nuu-gins  is,  however,  slightly  greater 
than  that  between  their  ventral  margins. 
This  segment  therefore  presents  a  shght 
wedge  shape  with  the  truncated  apex  down- 
ward. The  middle  segment  (Fig.  446)  is  a 
narrowband  across  the  centres  of  the  articu- 
lations. Its  dorsal  width  is  distinctly 
greater  than  its  ventral,  so  that  the  segment 
is  more  definitely  wedge-shaped,  the  trun- 
cated apex  being  again  directed  downward. 
Each  articular  sm-face  presents  in  the  centre  Fig.  447.— Coronal  section  of  posterior  sacral  segment. 

a  marked  concavity  from  above  downward, 

and  into  this  a  corresponding  convexity  of  the  iliac  articular  surface  fits,  forming  an  interlocking 
mechanism.  In  the  posterior  segment  (Fig.  447)  the  ventral  width  is  greater  than  the  dorsal, 
so  that  the  wedge  form  is  the  reverse  of  those  of  the  other  segments — i.  e.,  the  truncated  apex 
is  directed  upward.      The  articular  surfaces  are  only  slightly  concave. 

Dislocation  downward  and  forward  of  the  sacrum  by  the  second  component  of  the  force  applied 
to  it  is  prevented  therefore  by  the  middle  segment,  which  interposes  the  resistance  of  its  wedge 
shape  and  that  of  the  interlocking  mechanism  on  its  surfaces;  a  rotatory  movement,  however, 
is  produced  by  which  the  anterior  segment  is  tilted  downward  and  the  posterior  upward ;  the  axis 
of  this  rotation  passes  through  the  dorsal  part  of  the  middle  segment.  The  movement  of  the 
anterior  segment  is  slightly  limited  by  its  wedge  form,  but  chiefly  by  the  posterior  and  inter- 
osseous sacroihac  ligaments;  that  of  the  posterior  segment  is  checked  to  a  sUght  extent  by  its 
wedge  form,  but  the  chief  limiting  factors  are  the  sacrotuberous  and  sacrospinous  hgaments. 
In  all  these  movements  the  effect  of  the  sacroihac  and  iUolumbar  hgaments  and  the  hgaments 
of  the  symphysis  pubis  in  resisting  the  separation  of  the  ihac  bones  must  be  recognized. 

During  pregnancy  the  pelvic  joints  and  ligaments  are  relaxed,  and  capable  therefore  of  more 
extensive  movements.  When  the  fetus  is  being  expelled  the  force  is  apphed  to  the  front  of  the 
sacrmn.  Upward  dislocation  is  again  prevented  by  the  interlocking  mechanism  of  the  middle 
segment.  As  the  fetal  head  passes  the  anterior  segment  the  latter  is  carried  upward,  enlarging 
the  antero-posterior  diameter  of  the  pelvic  inlet;  when  the  head  reaches  the  posterior  segment 
this  also  is  pressed  upward  against  the  resistance  of  its  wedge,  the  movement  only  being  possible 
by  the  laxity  of  the  joints  and  the  stretching  of  the  sacrotuberous  and  sacrospinous  ligaments. 

ARTICULATIONS   OF   THE  UPPER   EXTREMITY. 

The  articulations  of  the  Upper  Extremity  may  be  arranged  as  follows: 

I.  Sternoclavicular.  VI.  Wrist. 

II.  Acromioclavicular.  VII.  Intercarpal. 

III.  Shoulder.  VIII.  Carpometacarpal. 

IV.  Elbow.  IX.  Intermetacarpal. 

V.  Radioulnar.  X.  Metacarpophalangeal. 

XL  Articulations  of  the  Digits. 

I.     Sternoclavicular  Articulation  (Articulatio  Sternoclavicularis)  (Fig.  448). 

The  sternoclavicular  articulation  is  a  double  arthrodial  joint.  The  parts  entering 
into  its  formation  are  the  sternal  end  of  the  clavicle,  the  upper  and  lateral  part 
of  the  manubrium  sterni,  and  the  cartilage  of  the  first  rib.  The  articular  surface 
of  the  clavicle  is  much  larger  than  that  of  the  sternum,  and  is  invested  with  a  layer 
of  cartilage,^  which  is  considerably  thicker  than  that  on  the  latter  bone.  The 
ligaments  of  this  joint  are: 

The  Articular  Capsule.  The  Interclavicidar. 

The  Anterior  Sternoclavicular.  The  Costoclavicular. 

The  Posterior  Sternoclavicular.  The  Articular  Disk. 

1  According  to  Bruch,  the  sternal  end  of  the  clavicle  is  covered  by  a  tissue  which  is  fibrous  rather  than  cartilaginous 
in  structure. 


410 


SYNDESMOLOGY 


The  Articular  Capsule  {cap.siila  arilcuJaris;  cap.syJar  ligament). — The  articular 
capsule  surrounds  the  articulation  and  varies  in  thickness  and  strength.  In  front 
and  behind  it  is  of  considerable  thickness,  and  forms  the  anterior  and  posterior 
sternoclavicular  ligaments;  but  above,  and  especially  below,  it  is  thin  and  par- 
takes more  of  the  character  of  areolar  than  of  true  fibrous  tissue. 

The  Anterior  Sternoclavicular  Ligament  (ligamentum  sternoclaviculare  anterior).- — 
The  anterior  sternoclavicular  ligament  is  a  broad  band  of  fibres,  covering  the 
anterior  surface  of  the  articulation ;  it  is  attached  above  to  the  upper  and  front  part 
of  thesternal  end  of  the  clavicle,  and,  passing  obliquely  downward  and  medialward, 
is  attached  below  to  the  front  of  the  upper  part  of  the  manubrium  sterni.  This 
ligament  is  covered  by  the  sternal  portion  of  the  Sternocleidomastoideus  and  the 
integument;  behind,  it  is  in  relation  with  the  capsule,  the  articular  disk,  and  the 
two  synovial  membranes. 


Fig.  448. — Sternoclavicular  articulation.     Anterior  view. 


The  Posterior  Sternoclavicular  Ligament  (ligamentum  sternoclaviculare  posteriiis). — 
The  posterior  sternoclavicular  ligament  is  a  similar  band  of  fibres,  covering  the 
posterior  surface  of  the  articulation;  it  is  attached  above  to  the  upper  and  back 
part  of  the  sternal  end  of  the  clavicle,  and,  passing  obliquely  downward  and 
medialward,  is  fixed  below  to  the  back  of  the  upper  part  of  the  manubrium  sterni. 
It  is  in  relation,  in  front,  with  the  articular  disk  and  synovial  membranes;  behind, 
with  the  Sternohyoideus  and  Sternothyreoideus. 

The  Interclavicular  Ligament  (ligamentum  interclaviculare) . — This  ligament  is  a 
flattened  band,  which  varies  considerably  in  form  and  size  in  difterent  individuals, 
it  passes  in  a  curved  direction  from  the  upper  part  of  the  sternal  end  of  one  clavicle 
to  that  of  the  other,  and  is  also  attached  to  the  upper  margin  of  the  sternum.  It 
is  in  relation,  in  front,  with  the  integument  and  Sternocleidomastoidei ;  behind, 
with  the  Sternothyreoidei. 

The  Costoclavicular  Ligament  (ligamentum  costoclavicular e;  rhomboid  ligament). — 
This  ligament  is  short,  flat,  strong,  and  rhomboid  in  form.  Attached  below  to 
the  upper  and  medial  part  of  the  cartilage  of  the  first  rib,  it  ascends  obliquely 
backward  and  lateralward,  and  is  fixed  above  to  the  costal  tuberosity  on  the  under 
surface  of  the  clavicle.  It  is  in  relation,  in  front,  with  the  tendon  of  origin  of  the 
Subclavius;  behind,  with  the  subclavian  vein. 

The  Articular  Disk  (discus  articular  is) . — The  articular  disk  is  flat  and  nearly 
circular,  interposed  between  the  articulating  surfaces  of  the  sternum  and  clavicle. 
It  is  attached,  above,  to  the  upper  and  posterior  border  of  the  articular  surface  of 
the  clavicle;  below,  to  the  cartilage  of  the  first  rib,  near  its  junction  with  the  sternum; 
and  bv  its  circumference  to  the  interclavicular  and  anterior  and  posterior  sterno- 


.  I C  ROM  IOC  LA  1  ICi  LA  H  ART  ICC  LA  TIOX  41 1 

clavicular  lis;aments.  It  is  thicker  at  the  circumference,  especially  its  upper  and 
back  i)art.  than  at  its  centre.  It  divides  the  joint  into  two  cavities,  each  of  which 
is  furnished  with  a  syno\'ial  nienihrane. 

Synovial  Membranes. — Of  the  two  synovial  membranes  found  in  this  articulation,  the  lateral 
is  rellorlcd  from  the  sternal  end  of  the  clavicle,  over  the  adjacent  surface  of  the  articular  disk, 
and  arountl  the  nuu-fiin  of  the  facet  on  the  cartilage  of  the  first  rib;  the  medial  is  attached  to  the 
margin  of  the  articular  surface  of  the  sternum  and  clothes  the  adjacent  surface  of  the  articular 
disk;  the  latter  is  the  larger  of  the  two. 

Movements. — -This  articulation  admits  of  a  limited  amount  of  motion  in  nearly  every  direc- 
tion— upward,  downward,  backward,  forwaixl,  as  well  as  circumduction.  When  these  move- 
ments take  place  in  the  joint,  the  clavicle  iia  its  motion  carries  the  scapula  with  it,  this  bone 
gliding  on  the  outer  surface  of  the  chest.  This  joint  therefore  forms  the  centre  from  which  all 
movements  of  the  supporting  arch  of  the  shoulder  originate,  and  is  the  only  point  of  articulation 
of  the  shoulder  girdle  with  the  trunk.  The  movements  attendant  on  elevation  and  depression  of 
the  shoulder  take  place  between  the  clavicle  and  the  articular  disk,  the  bone  rotating  upon  the 
ligament  on  an  axis  drawn  from  before  backward  through  its  own  articular  facet;  when  the  shoulder 
is  moA'ed  forward  and  backward,  the  clavicle,  with  the  articular  disk  rolls  to  and  fro  on  the 
articular  surface  of  the  sternum,  revolving,  with  a  sUding  movement,  around  an  axis  drawn  nearly 
vertically  through  the  sternum;  in  the  circumduction  of  the  shoulder,  which  is  compounded  of 
these  two  movements,  the  clavicle  revolves  upon  the  articular  disk  and  the  latter,  with  the  clavicle, 
rolls  upon  the  sternum.^  Elevation  of  the  shoulder  is  limited  principally  by  the  costoclavicular 
ligament;  depression,  by  the  interclavicular  ligament  and  articular  disk.  The  muscles  which 
raise  the  shoulder  are  the  upper  fibres  of  the  Trapezius,  the  Levator  scapulae,  and  the  clavicular 
head  of  the  Sternocleidomastoideus,  assisted  to  a  certain  extent  by  the  Rhomboidei,  which  pull 
the  vertebral  border  of  the  scapula  backward  and  upward  and  so  raise  the  shoulder.  The  depres- 
sion of  the  shoulder  is  principally  effected  by  gravity  assisted  by  the  Subclavius,  Pectoralis  minor 
and  lower  fibres  of  the  Trapezius.  The  shoulder  is  drawn  backward  by  the  Rhomboidei  and  the 
middle  and  lower  fibres  of  the  Trapezius,  and  forward  by  the  Serratus  anterior  and  PectoraUs 
minor. 

Applied  Anatomy. — The  strength  of  this  joint  mainly  depends  upon  its  ligaments,  and  it  is 
owing  to  these,  and  to  the  fact  that  the  force  of  the  blow  is  usually  transmitted  along  the  long 
axis  of  the  clavicle,  that  dislocation  rarely  occurs,  and  that  the  bone  is  broken  rather  than  dis- 
placed. When  dislocation  does  occur,  the  course  which  the  displaced  bone  takes  depends  more 
upon  the  direction  in  which  the  violence  is  applied  than  upon  the  anatomical  construction  of 
the  joint;  it  may  be  either  forward,  backward,  or  upward.  Should  it  be  displaced  backward  it 
may  cause  pressure  on  the  trachea.  The  chief  point  worthy  of  note,  as  regards  the  construction 
of  the  joint,  in  connection  with  dislocation,  is  the  fact  that,  owing  to  the  shape  of  the  articular 
surfaces,  and  the  strength  of  the  joint  mainly  depending  upon  the  ligaments,  the  displacement 
when  reduced  is  very  liable  to  recur,  and  hence  it  is  extremely  difficult  to  keep  the  end  of  the  bone 
in  its  proper  place. 

II.    Acromioclavicular  Articulation  (Articulatio  Acromioclavicularis ;  Scapulo- 
clavicular Articulation)  (Fig.  449). 

The  acromioclavicular  articulation  is  an  arthrodial  joint  between  the  acromial 
end  of  the  clavicle  and  the  medial  margin  of  the  acromion  of  the  scapula.  Its 
ligaments  are: 

The  Articular  Capsule.  The  Articular  Disk. 

The  Superior  Acromioclavicular.       rpi     p  i     "     i       [Trapezoid  and 

The  Inferior  Acromioclavicular.  I       Conoid. 

The  Articular  Capsule  (capsida  articularis;  capsular  ligament). — The  articular 
capsule  completely  surrounds  the  articular  margins,  and  is  strengthened  above 
and  below  by  the  superior  and  inferior  acromioclavicular  ligaments. 

The  Superior  Acromioclavicular  Ligament  {ligamentum  acromioclaviculare) . — 
This  ligament  is  a  quadrilateral  band,  covering  the  superior  part  of  the  articula- 
tion, and  extending  between  the  upper  part  of  the  acromial  end  of  the  clavicle 
and  the  adjoining  part  of  the  upper  surface  of  the  acromion.  It  is  composed 
of  parallel  fibres,  which  interlace  with  the  aponeuroses  of  the  Trapezius  and 
Deltoideus;  below,  it  is  in  contact  with  the  articular  disk  when  this  is  present. 

1  Humphrj',  On  the  Human  Skeleton,  page  402. 


412 


SYNDESMOLOGY 


The  Inferior  Acromioclavicular  Ligament. — This  ligament  is  somewhat  thinner 
than  the  preceding;  it  covers  the  untler  part  of  the  articulation,  and  is  attached  to 
the  adjoining  surfaces  of  the  two  bones.  It  is  in  relation,  above,  in  rare  cases  with 
the  articular  disk;  helow,  with  the  tendon  of  the  Supraspinatus. 

The  Articular  Disk  (discus  articular  is) . — The  articular  disk  is  frequently  absent 
in  this  articulation.  When  present,  it  generally  only  partially  separates  the  artic- 
ular surfaces,  and  occupies  the  upper  part  of  the  articulation.  More  rarely,  it 
completely  divides  the  joint  into  two  cavities. 

The  Synovial  Membrane. — There  is  usually  only  one  synovial  membrane  in  this  articulation, 
but  when  a  complete  articular  disk  is  present,  there  are  two. 


Fig.  449. — -The  left  shoulder  and  acromioclavicular  joints,  and  the  proper  ligaments  of  the  scapula. 

The  Coracoclavicular  Ligament  {licjamentum  coracoclaviculare)  (Fig.  449).^ — This 
ligament  serves  to  connect  the  clavicle  with  the  coracoid  process  of  the  scapula. 
It  does  not  properly  belong  to  this  articulation,  but  is  usually  described  with  it, 
since  it  forms  a  most  efficient  means  of  retaining  the  clavicle  in  contact  with  the 
acromion.    It  consists  of  two  fasciculi,  called  the  trapezoid  and  conoid  ligaments. 

The  Trapezoid  Ligament  {ligamentum  trapezoideum) ,  the  anterior  and  lateral  fas- 
ciculus, is  broad,  thin,  and  quadrilateral :  it  is  placed  obliquely  between  the  cora- 
coid process  and  the  clavicle.  It  is  attached,  below,  to  the  upper  surface  of  the 
coracoid  process;  above,  to  the  oblique  ridge  on  the  under  surface  of  the  clavicle. 
Its  anterior  border  is  free;  its  posterior  border  is  joined  with  the  conoid  ligament, 
the  two  forming,  by  their  junction,  an  angle  projecting  backward. 

The  Conoid  Ligament  (ligamentum  conoideum),  the  posterior  and  medial  fa&ciculus, 
is  a  dense  band  of  fibres,  conical  in  form,  with  its  base  directed  upward.  It  is 
attached  by  its  apex  to  a  rough  impression  at  the  base  of  the  coracoid  process, 
medial  to  the  trapezoid  ligament;  above,  by  its  expanded  base,  to  the  coracoid 


THE  LIGAMENTS  OF  THE  SCAPULA  413 

tuberosity  on  the  under  surface  of  the  c-hivicle,  and  to  a  Hue  proceeding  medial- 
ward  from  it  for  1.25  cm.  These  ligaments  are  in  rehition,  in  front,  with  the 
Subclavius  and  Deltoideus;  behind,  with  the  Trapezius. 

Movements. — The  movements  of  this  articulation  are  of  two  kinds:  (1)  a  gliding  motion  of 
the  articular  entl  of  the  clavicle  on  the  acromion;  (2)  rotation  of  the  scapula  forward  and  back- 
ward upon  the  clavicle.  The  extent  of  this  rotation  is  limited  by  the  two  portions  of  the  coraco- 
clavicular  ligament,  the  trapezoid  limiting  rotation  forward,  and  the  conoid  backward. 

The  acromioclavicular  joint  has  important  functions  in  the  movements  of  the  upper  extremity. 
It  has  been  well  pointed  out  by  Humphry,  that  if  there  had  been  no  joint  between  the  clavicle 
and  scapula,  the  circular  movement  of  the  scapula  on  the  ribs  (as  in  throwing  the  shoulders  back- 
ward or  forward)  would  have  been  attended  with  a  greater  alteration  in  the  direction  of  the 
shoulder  than  is  consistent  with  the  free  use  of  the  arm  in  such  positions,  and  it  would  have  been 
impossible  to  give  a  blow  straight  foi'ward  with  the  full  force  of  the  arm;  that  is  to  say,  with  the 
combined  force  of  the  scapula,  arm,  and  forearm.  "This  joint,"  as  he  happily  says,  "is  so  adjusted 
as  to  enable  either  bone  to  turn  in  a  hiiage-like  manner  upon  a  vertical  axis  drawn  through  the 
other,  and  it  permits  the  surfaces  of  the  scapula,  like  the  baskets  in  a  roundabout  swing,  to  look 
the  same  way  in  every  position,  or  nearly  so."  Again,  when  the  whole  arch  formed  by  the  clavicle 
and  scapula  rises  and  falls  (in  elevation  or  depression  of  the  shoulder),  the  joint  between  these 
two  bones  enables  the  scapula  still  to  maintain  its  lower  part  in  contact  with  the  ribs. 

Applied  Anatomy. — The  acromioclavicular  joint  owes  its  security  mainly  to  the  coracoclavicular 
ligament,  which  limits  the  amount  of  movement  of  the  acromial  end  of  the  clavicle  either  upward, 
backward,  or  forward.  Owing  to  the  slanting  shape  of  the  articular  surfaces  of  this  joint,  dis- 
location generally  occurs  upward;  that  is  to  say,  the  acromial  end  of  the  clavicle  is  displaced  above 
the  acromion  of  the  scapula.  The  displacement  is  often  incomplete,  on  account  of  the  strong 
coracoclavicular  ligaments,  which  remain  untorn.  The  same  difficulty  exists,  as  in  the  sterno- 
clavicular dislocation,  in  maintaining  the  ends  of  the  bone  in  position  after  reduction. 


THE  LIGAMENTS   OF   THE   SCAPULA. 

The  ligaments  of  the  scapula  (Fig.  449)  are : 

Coracoacromial,  Superior  and  Inferior  Transverse. 

The  Coracoacromial  Ligament  {ligamentum  coracoacromiale) . — This  ligament  is  a 
strong  triangular  band,  extending  between  the  coracoid  process  and  the  acromion. 
It  is  attached,  by  its  apex,  to  the  summit  of  the  acromion  just  in  front  of  the 
articular  surface  for  the  clavicle ;  and  by  its  broad  base  to  the  w^hole  length  of  the 
lateral  border  of  the  coracoid  process.  This  ligament,  together  with  the  coracoid 
process  and  the  acromion,  forms  a  vault  for  the  protection  of  the  head  of  the 
humerus.  It  is  in  relation,  above,  with  the  clavicle  and  under  surface  of  the  Del- 
toideus; beloio,  with  the  tendon  of  the  Supraspinatus,  a  bursa  being  interposed. 
Its  lateral  border  is  continuous  with  a  dense  lamina  that  passes  beneath  the  Del- 
toideus upon  the  tendons  of  the  Supraspinatus  and  Infraspinatus.  The  ligament 
is  sometimes  described  as  consisting  of  two  marginal  bands  and  a  thinner  inter- 
vening portion,  the  two  bands  being  attached  respectively  to  the  apex  and  the 
base  of  the  coracoid  process,  and  joining  together  at  the  acromion.  When  the 
Pectoralis  minor  is  inserted,  as  occasionally  is  the  case,  into  the  capsule  of  the 
shoulder-joint  instead  of  into  the  coracoid  process,  it  passes  between  these  two 
bands,  and  the  intervening  portion  of  the  ligament  is  then  deficient. 

The  Superior  Transverse  Ligament  {ligamentum  transversum  scapulae  superius; 
transverse  or  suprascapular  ligament). — This  ligament  converts  the  scapular  notch 
into  a  foramen.  It  is  a  thin  and  flat  fasciculus,  narrower  at  the  middle  than  at  the 
extremities,  attached  by  one  end  to  the  base  of  the  coracoid  process,  and  by  the 
other  to  the  medial  end  of  the  scapular  notch.  The  suprascapular  nerve  runs 
through  the  foramen;  the  transverse  scapular  vessels  cross  over  the  ligament. 
The  ligament  is  sometimes  ossified. 

The  Liferior  Transverse  Ligament  {ligamentum  transversum  scapulae  inferius; 
spinoglenoid  ligament). — This  ligament  is  a  weak  membranous  band,   situated 


414 


SYNDESMOLOGY 


behind  the  neck  of  the  scapuhx  and  stretching  from  the  hiteral  border  of  the  spine 
to  the  margin  of  the  glenoid  cavity.  It  forms  an  arch  inider  which  the  transverse 
scapular  vessels  and  suprascapular  nerve  enter  the  infraspinatous  fossa. 

III.    Humeral  Articulation  or  Shoulder-joint  (Articulatio  Humeri)  (Fig.  449). 

The  shoulder-joint  is  an  enarthrodial  or  ball-and-socket  joint.  The  bones 
entering  into  its  formation  are  the  hemispherical  head  of  the  humerus  and  the 
shallow  glenoid  cavity  of  the  scapula,  an  arrangement  Avhich  permits  of  very 
considerable  movement,  while  the  joint  itself  is  protected  against  displacement 
by  the  tendons  which  surround  it.  The  ligaments  do  not  maintain  the  joint  sur- 
faces in  apposition,  because  when  they  alone  remain  the  humerus  can  be  separated 
to  a  considerable  extent  from  the  glenoid  cavity;  their  use,  therefore,  is  to  limit 

Suiter lor  transverse  ligament 


Transverse 
humeral 
ligament 

Prolongation  of 
synovial  m,etn- 
brane  on  tendon 
of  Biceps  hrachii 


Bursa 

under 
Subscapularis 


Fig.  450. — Capsule  of  shoulder-joint  (distended).     Anterior  aspect. 


the  amount  of  movement.  The  joint  is  protected  above  by  an  arch,  formed  by 
the  coracoid  process,  the  acromion,  and  the  coracoacromial  ligament.  The  artic- 
ular cartilage  on  the  head  of  the  humerus  is  thicker  at  the  centre  than  at  the  cir- 
cumference, the  reverse  being  the  case  with  the  articular  cartilage  of  the  glenoid 
cavity.    The  ligaments  of  the  shoulder  are: 


The  Articular  Capsule. 
The  Coracohumeral. 


The  Glenohumeral. 

The  Transverse  Humeral. 


The  Glenoidal  Labrum.^ 

The  Articular  Capsule  {capsida  articidaris;  capsular  ligament)  (Fig.  450). — The 
articular  capsule  completely  encircles  the  joint,  being  attached,  above,  to  the 
circumference  of  the  glenoid  cavity  beyond  the  glenoidal  labrum;  below,  to  the 
anatomical  neck  of  the  humerus,  approaching  nearer  to  the  articular  cartilage 
above  than  in  the  rest  of  its  extent.    It  is  thicker  above  and  below  than  elsewhere, 


1  The  long  tendon  of  origin  of  the  biceps  brachii  also  acts  as  one  of  the  ligaments  of  this  joint.    See  the  observations 
on  page  383,  on  the  function  of  the  muscles  passing  over  more  than  one  joint. 


HUMERAL  ARTICULATIOX  OR  SHOULDER-JOLVf  415 

and  is  so  remarkably  loose  and  lax,  that  it  has  no  action  in  keeping  the  bones  in 
contact,  but  allows  them  to  be  separated  from  each  other  more  than  2.5  cm.,  an 
evident  j^nnision  for  that  extreme  freedom  of  mox-ement  which  is  peculiar  to  this 
articulation.  It  is  strengthened,  above,  by  the  Sui)raspinatus;  beloiv,  by  the  long 
head  of  the  Triceps  brachii;  behind,  by  the  tendons  of  the  Infraspinatus  and  Teres 
minor;  and  in  front,  by  the  tendon  of  the  Subscapularis.  There  are  usually  three 
openings  in  the  capsule.  One  anteriorly,  below  the  coracoid  process,  establishes 
a  communication  between  the  joint  and  a  bursa  l)eneath  the  tendon  of  the  Sub- 
scapularis.-  The  second,  which  is  not  constant,  is  at  the  posterior  part,  where  an 
opening  sometimes  exists  between  the  joint  and  a  bursal  sac  under  the  tendon 
of  the  Infraspinatus.  The  third  is  between  the  tubercles  of  the  humerus,  for  the 
passage  of  the  long  tendon  of  the  Biceps  brachii. 

The  Coracohumeral  Ligament  {Ugamentum  coracohumerale) . — This  ligament  is 
a  broad  band  which  strengthens  the  upper  part  of  the  capsule.  It  arises  from 
the  lateral  border  of  the  coracoid  process,  and  passes  obliciuely  downward  and 
lateral  ward  to  the  front  of  the  greater  tubercle  of  the  humerus,  blending  with  the 
tendon  of  the  Supraspinatus.  This  ligament  is  intimately  united  to  the  capsule 
by  its  hinder  and  lower  border;  but  its  anterior  and  upper  border  presents  a  free 
edge,  which  overlaps  the  capsule. 

Glenohumeral  Ligaments. — In  addition  to  the  coracohumeral  ligament,  three 
supplemental  bands,  which  are  named  the  glenohumeral  ligaments,  strengthen 
the  capsule.  These  may  be  best  seen  by  opening  the  capsule  at  the  back  of  the 
joint  and  removing  the  head  of  the  humerus.  One  on  the  medial  side  of  the  joint 
passes  from  the  medial  edge  of  the  glenoid  cavity  to  the  lower  part  of  the  lesser 
tubercle  of  the  humerus.  A  second  at  the  lower  part  of  the  joint  extends  from 
the  under  edge  of  the  glenoid  cavity  to  the  under  part  of  the  anatomical  neck  of 
the  humerus.  A  third  at  the  upper  part  of  the  joint  is  fixed  above  to  the  apex 
of  the  glenoid  cavity  close  to  the  root  of  the  coracoid  process,  and  passing  down- 
ward along  the  medial  edge  of  the  tendon  of  the  Biceps  brachii,  is  attached  below 
to  a  small  depression  above  the  lesser  tubercle  of  the  humerus.  In  addition  to 
these,  the  capsule  is  strengthened  in  front  by  two  bands  derived  from  the  tendons 
of  the  Pectoralis  major  and  Teres  major  respectively. 

The  Transverse  Humeral  Ligament  (Fig.  450)  is  a  broad  band  passing  from  the 
lesser  to  the  greater  tubercle  of  the  humerus,  and  always  limited  to  that  portion 
of  the  bone  which  lies  above  the  epiphysial  line.  It  converts  the  intertubercular 
groove  into  a  canal,  and  is  the  homologue  of  the  strong  process  of  bone  which 
connects  the  summits  of  the  two  tubercles  in  the  musk  ox. 

The  Glenoidal  Labrum  {labrium  glenoidale;  glenoid  ligament)  is  a  fibrocartilaginous 
rim  attached  around  the  margin  of  the  glenoid  cavity.  It  is  triangular  on  section, 
the  base  being  fixed  to  the  circumference  of  the  cavity,  while  the  free  edge  is  thin 
and  sharp.  It  is  continuous  above  with  the  tendon  of  the  long  head  of  the  Biceps 
brachii,  which  gives  off  two  fasciculi  to  blend  with  the  fibrous  tissue  of  the  labrum. 
It  deepens  the  articular  cavity,  and  protects  the  edges  of  the  bone. 

Synovial  Membrane. — The  synovial  membrane  is  reflected  from  the  margin  of  the  glenoid 
cavity  over  the  labrum;  it  is  then  reflected  over  the  inner  surface  of  the  capsule,  and  covers 
the  lower  part  and  sides  of  the  anatomical  neck  of  the  humerus  as  far  as  the  articular  cartilage 
on  the  head  of  the  bone.  The  tendon  of  the  long  head  of  the  Biceps  brachii  passes  through  the 
capsule  and  is  enclosed  in  a  tubular  sheath  of  synovial  membrane,  which  is  reflected  upon  it 
from  the  summit  of  the  glenoid  cavity  and  is  continued  around  the  tendon  into  the  intertubercular 
groove  as  far  as  the  surgical  neck  of  the  humerus  (Fig.  450).  The  tendon  thus  traverses  the  articu- 
lation, but  it  is  not  contained  within  the  sjmovial  cavity. 

Bursae. — The  bursse  in  the  neighborhood  of  the  shoulder-joint  are  the  following:  (1)  A  constant 
bm'sa  is  situated  between  the  tendon  of  the  Subscapularis  muscle  and  the  capsule;  it  communi- 
cates with  the  synovial  cavity  tln-ough  an  opening  in  the  front  of  the  capsule;  (2)  a  bursa  which 
occasionally  communicates  with  the  joint  is  sometimes  found  between  the  tendon  of  the  Infra- 
spinatus and  the  capsule;  (3)  a  large  bm'sa  exists  between  the  under  surface  of  the  Deltoideus 


416  .        SYNDESMOLOGY 

and  the  capsule,  but  does  not  communicate  with  the  joint;  this  bursa  is  prolonged  under  the 
acromion  and  coracoacromial  ligament,  and  intervenes  between  these  structures  and  the  capsule; 
(■i)  a  large  bursa  is  situated  on  the  summit  of  the  acromion;  (5)  a  bursa  is  frequently  found 
between  the  coracoid  process  and  the  capsule;  (6)  a  bursa  exists  beneath  the  Coracobrachiahs; 
(7)  one  lies  between  the  Teres  major  and  the  long  head  of  the  Triceps  brachii;  (8)  one  is  placed 
in  front  of,  and  another  behind,  the  tendon  of  the  Latissimus  dorsi. 

The  muscles  in  relation  with  the  joint  are,  above,  the  Supraspinatus;  below,  the  long  head  of 
the  Triceps  bracliii;  in  front,  the  Subscapularis;  behind,  the  Infraspinatus  and  Teres  minor;  within, 
the  tendon  of  the  long  head  of  the  Biceps  brachii.  The  Deltoideus  covers  the  articulation  in 
front,  behind,  and  laterally. 

The  arteries  supplying  the  joint  are  articular  branches  of  the  anterior  and  posterior  humeral 
circumflex,  and  transverse  scapular. 

The  nerves  are  derived  from  the  axillary  and  suprascapular. 

Movements. — The  shoulder-joint  is  capable  of  every  variety  of  movement,  flexion,  extension, 
abduction,  adduction,  circumduction,  and  rotation.  The  humerus  is  flexed  (drawn  forward) 
by  the  Pectorahs  major,  anterior  fibres  of  the  Deltoideus,  Coracobrachiahs,  and  when  the  fore- 
arm is  flexed,  by  the  Biceps  brachii;  extended  (drawn  backward)  by  the  Latissimus  dorsi.  Teres 
major,  posterior  fibres  of  the  Deltoideus,  and,  when  the  forearm  is  extended,  by  the  Triceps 
brachii;  it  is  abducted  by  the  Deltoideus  and  Supraspinatus;  it  is  adducted  by  the  Subscapularis, 
Pectorahs  major,  Latissimus  dorsi,  and  Teres  major,  and  by  the  weight  of  the  hmb;  it  is  rotated 
outward  by  the  Infraspinatus  and  Teres  minor;  and  it  is  rotated  inward  by  the  Subscapularis, 
Latissimus  dorsi.  Teres  major,  Pectorahs  major,  and  the  anterior  fibres  of  the  Deltoideus. 

The  most  striking  peculiarities  in  this  joint  are:  (1)  The  large  size  of  the  head  of  the  humerus 
in  comparison  mth  the  depth  of  the  glenoid  cavity,  even  when  this  latter  is  supplemented  by  the 
glenoidal  labrum.  (2)  The  looseness  of  the  capsule  of  the  joint.  (3)  The  intimate  connection  of 
the  capsule  with  the  muscles  attached  to  the  head  of  the  humerus.  (4)  The  pecuhar  relation  of 
the  tendon  of  the  long  head  of  the  Biceps  brachii  to  the  joint. 

It  is  in  consequence  of  the  relative  sizes  of  the  two  articular  surfaces,  and  the  looseness  of 
the  articular  capsule,  that  the  joint  enjoys  such  free  movement  in  all  directions.  When  these 
movements  of  the  arm  are  arrested  in  the  shoulder- joint  by  the  contact  of  the  bony  surfaces, 
and  by  the  tension  of  the  fibres  of  the  capsule,  together  with  that  of  the  muscles  acting  as  accessor}' 
ligaments,  the  arm  can  be  carried  considerably  farther  by  the  movements  of  the  scapula,  involv- 
ing, of  course,  motion  at  the  acromio-  and  sternoclavicular  joints.  These  joints  are  therefore 
to  be  regarded  as  accessory  structm-es  to  the  shoulder-joint  (see  pages  411  and  413).  The  extent 
of  the  scapular  movements  is  very  considerable,  especially  in  extreme  elevation  of  the  arm,  a 
movement  best  accompHshed  when  the  arm  is  thrown  somewhat  forward  and  outward,  because 
the  margin  of  the  head  of  the  humerus  is  by  no  means  a  true  circle;  its  greatest  diameter  is  from 
the  intertubercular  groove,  downward,  medialward,  and  backward,  and  the  greatest  elevation 
of  the  arm  can  be  obtained  by  rolhng  its  articular  surface  in  the  direction  of  this  measurement. 
The  great  width  of  the  central  portion  of  the  humeral  head  also  allows  of  very  free  horizontal 
movement  when  the  arm  is  raised  to  a  right  angle,  in  which  movement  the  arch  formed  by  the 
acromion,  the  coracoid  process  and  the  coracoacromial  hgament,  constitutes  a  sort  of  supple- 
mental articular  cavity  for  the  head  of  the  bone. 

The  looseness  of  the  capsule  is  so  great  that  the  arm  will  fall  about  2.5  cm.  from  the  scapula 
when  the  muscles  are  dissected  from  the  capsule,  and  an  opening  made  in  it  to  counteract  the 
atmospheric  pressiire.  The  movements  of  the  joint,  therefore,  are  not  regulated  by  the  capsult 
so  much  as  by  the  surroimding  muscles  and  by  the  pressure  of  the  atmosphere,  an  arrangemene 
which  "renders  the  movements  of  the  joint  much  more  easy  than  they  would  otherwise  haA'e 
been,  and  permits  a  swinging,  pendulum-hke  vibration  of  the  Umb  when  the  muscles  are  at  rest" 
(Hiunphry).  The  fact,  also,  that  in  all  ordinary  positions  of  the  joint  the  capsule  is  not  put  on 
the  stretch,  enables  the  arm  to  move  freely  in  all  directions.  Extreme  movements  are  checked 
by  the  tension  of  appropriate  portions  of  the  capsule,  as  well  as  by  the  interlocking  of  the  bones. 
Thus  it  is  said  that  "abduction  is  checked  by  the  contact  of  the  great  tuberosity  with  the  upper 
edge  of  the  glenoid  cavity;  adduction  by  the  tension  of  the  coracohimaeral  hgament"  (Beaimis 
et  Bouchard).  Cleland^  maintains  that  the  limitations  of  movement  at  the  shoulder-joint  are 
due  to  the  structure  of  the  joint  itself,  the  glenoidal  labrum  fitting,  in  different  positions  of  the 
elevated  arm,  into  the  anatomical  neck  of  the  humerus. 

The  scapula  is  capable  of  being  moved  upward  and  downward,  forward  and  backward,  or,  bj- 
a  combination  of  these  movements,  circumducted  on  the  wall  of  the  chest.  The  muscles  which 
raise  the  scapula  are  the  upper  fibres  of  the  Trapezius,  the  Levator  scapulae,  and  the  Rhomboidei ; 
those  which  depress  it  are  the  lower  fibres  of  the  Trapezius,  the  Pectorahs  minor,  and,  through 
the  clavicle,  the  Subclavius.  The  scapula  is  drawn  backward  by  the  Rhomboidei  and  the  middle 
and  lower  fibres  of  the  Trapezius,  and  forward  by  the  Serratus  anterior  and  Pectorahs  minor, 
assisted,  when  the  arm  is  fixed,  by  the  Pectorahs  major.     The  mobihty  of  the  scapula  is  very 

'  Journal  of  Anatomy  and  Physiologj',  1867,  i,  8.5. 


HLMERAL  ARTICULATIOX  OR  SHOi'LDER-JOINT  417 

considerable,  and  greatly  assists  the  movements  of  the  arm  at  the  shoulder-joint.  Thus,  in 
raising  the  arm  from  the  side,  the  Deltoideus  and  Supraspinatus  can  only  lift  it  to  a  right  angle 
with  the  trunk,  the  further  elevation  of  the  limb  being  effected  by  the  Trapezius  and  Serratus 
anterior  moving  the  scapula  on  the  wall  of  the  chest.  This  mobihty  is  of  special  importance  in 
ankjdosis  of  the  shoulder-joint,  the  movements  of  this  bone  compensating  to  a  veiy  great  extent 
for  the  immobility  of  the  joint. 

Cathcart^  has  pointed  out  that  in  abducting  the  arm  and  raising  it  above  the  head,  the  scapula 
rotates  throughout  the  whole  movement  with  the  exception  of  a  short  space  at  the  beginning 
and  at  the  end;  that  the  humerus  moves  on  the  scapula  not  only  while  passing  from  the  hanging 
to  the  horizontal  position,  but  also  in  travelling  upward  as  it  approaches  the  vertical  above; 
that  the  clavicle  moves  not  only  during  the  second  half  of  the  movement  but  in  the  first  as  well, 
though  to  a  less  extent — i.  e.,  the  scapula  and  clavicle  are  concerned  in  the  first  stage  as  well 
as  in  the  second;  and  that  the  humerus  is  partly  involved  in  the  second  as  well  as  chiefly  in  the 
first. 

The  intimate  union  of  the  tendons  of  the  Supraspinatus,  Infraspinatus,  Teres  minor  and 
Subscapularis  with  the  capsule,  converts  these  muscles  into  elastic  and  spontaneously  acting 
ligaments  of  the  joint. 

The  peculiar  relations  of  the  tendon  of  the  long  head  of  the  Biceps  brachii  to  the  shoulder- 
joint  appear  to  subserve  various  purposes.  In  the  first  place,  by  its  connection  with  both  the 
shoulder  and  elbow  the  muscle  harmonizes  the  action  of  the  two  joints,  and  acts  as  an  elastic 
ligament  in  all  positions,  in  the  manner  previously  discussed  (see  page  383).  It  strengthens  the 
upper  part  of  the  articular  cavity,  and  prevents  the  head  of  the  humerus  from  being  pressed  up 
against  the  acromion,  when  the  Deltoideus  contracts;  it  thus  fixes  the  head  of  the  humerus  as 
the  centre  of  motion  in  the  glenoid  cavity.  By  its  passage  along  the  intertubercular  groove  it 
assists  in  steadying  the  head  of  the  humerus  in  the  various  movements  of  the  arm.  When  the 
arm  is  raised  from  the  side  it  assists  the  Supraspinatus  and  Infraspinatus  in  rotating  the  head 
of  the  humerus  in  the  glenoid  cavity.  It  also  holds  the  head  of  the  bone  firmly  in  contact  wnth 
the  glenoid  cavity,  and  prevents  its  slipping  over  its  lower  edge,  or  being  displaced  by  the  action 
of  the  Latissimus  dorsi  and  Pectoralis  major,  as  in  climbing  and  many  other  movements. 

Applied  Anatomy. — Owing  to  the  construction  of  the  shoulder-joint  and  the  freedom  of  move- 
ment which  it  enjoys,  as  well  as  in  consequence  of  its  exposed  situation,  it  is  more  frequently 
dislocated  than  any  other  joint.  Dislocation  occurs  when  the  arm  is  abducted,  and  when,  there- 
fore, the  head  of  the  humerus  presses  against  the  lower  and  front  part  of  the  capsule,  which  is  the 
thinnest  and  least  supported  part  of  the  hgament.  The  rent  in  the  capsule  almost  invariably 
takes  place  in  this  situation,  and  through  it  the  head  of  the  bone  escapes,  so  that  the  dislocation 
in  most  instances  is  primarily  subglenoid.  The  head  of  the  bone  does  not  usually  remain  in  this 
situation,  between  the  tendons  of  the  Subscapularis  and  the  Triceps  brachii,  but  generally  assumes 
some  other  position,  which  varies  according  to  the  direction  and  amount  of  force  producing  the 
dislocation  and  the  relative  strength  of  the  muscles  in  front  of  and  behind  the  joint.  As  the 
muscles  at  the  back  are  stronger  than  those  in  front,  and  especially  since  the  long  head  of  the 
Triceps  brachii  prevents  the  bone  from  passing  backward,  dislocation  forward  is  much  the  more 
common.  The  most  frequent  position  which  the  head  of  the  humerus  ultimately  assumes  is  on 
the  front  of  the  neck  of  the  scapula,  beneath  the  coracoid  process,  and  hence  named  subcoracoid. 
Occasionally,  in  consequence  of  a  greater  amoimt  of  force  being  brought  to  bear  on  the  limb, 
the  head  is  driven  farther  medialward,  and  rests  on  the  upper  part  of  the  front  of  the  chest,  be- 
neath the  clavicle  (subclavicular) .  Sometimes  it  remains  in  the  position  in  which  it  was  primarily 
displaced,  resting  on  the  axillary  border  of  the  scapula  (subglenoid),  and  rarely  it  passes  back- 
ward and  remains  in  the  infraspinatous  fossa,  beneath  the  spine  (subspinous). 

The  shoulder- joint  may  be  the  seat  of  any  of  those  inflammatory  affections,  either  acute  or 
chronic,  which  attack  joints,  though  perhaps  less  frequently  than  some  other  articulations  of 
equal  size  and  importance.  Acute  synovitis  may  result  from  injury,  rheumatism,  or  pyemia, 
or  may  follow  secondarily  on  acute  epiphysitis  in  infants.  It  is  attended  with  effusion  into  the 
joint,  and  when  this  occurs  the  capsule  is  evenly  distended,  and  the  contour  of  the  joint  rounded. 
Special  projections  may  occur  at  the  sites  of  the  openings  in  the  capsule.  Thus  a  swelling  may 
appear  just  medial  to  the  lesser  tubercle,  from  effusion  into  the  bxu-sa  beneath  the  Subscapularis; 
or,  again,  a  swelUng  which  is  sometimes  bilobed  may  be  seen  in  the  interval  between  the  Deltoideus 
and  PectoraUs  major,  from  effusion  into  the  diverticulum  which  runs  down  the  intertubercular 
groove  with  the  tendon  of  the  Biceps  brachii.  The  effusion  into  the  joint  cavity  can  be  best 
ascertained  by  examination  from  the  axilla,  where  a  soft,  elastic,  fluctuating  swelling  can  usually 
be  felt.  In  cases  of  septic  synovitis,  where  incision  is  required,  the  opening  should  be  made  in 
front,  over  the  most  prominent  point  of  the  sweUing.  After  the  pus  has  been  evacuated  a  counter- 
opening  should  be  made  behind,  so  as  to  ensure  efficient  di-ainage. 

Tuberculous  arthritis  not  infrequently  attacks  the  shoulder-joint,  and  may  lead  to  total  destruc- 
tion of  the  articulation,  when  ankylosis  may  result,  or  long-protracted  suppuration  may  necessitate 

1  Journal  of  Anatomy  and  Physiology,  1884,  vol.  xviii. 

27 


418  SYXDESMOLOGY 

excision.  This  joint  is  also  one  of  those  which  is  most  liable  to  be  the  seat  of  osteoarthritis,  and 
may  also  be  affected  in  gout  and  rheumatism;  or  in  locomotor  ataxia,  when  it  becomes  the  seat 
of  Charcot's  disease. 

Ankylosis  is  occasionally  met  with  in  the  shoulder-joint  as  the  result  of  destructive  changes. 
The  ankylosis  usually  takes  place  with  the  arm  in  a  dependent  position,  and  any  attempt  to 
raise  the  arm  is  attended  by  a  rotation  of  the  scapula  on  the  wall  of  the  chest. 

Excision  of  the  shoulder-joint  may  be  required  in  cases  of  arthritis  (especially  the  tuberculous 
form)  which  have  gone  on  to  destruction  of  the  articulation;  in  compound  dislocations  and  frac- 
tures, particularly  those  arising  from  gunshot  injuries,  in  which  there  has  been  extensive  injury 
to  the  head  of  the  bone;  in  some  cases  of  old  unreduced  dislocation,  where  there  is  much  pain. 
The  operation  is  best  performed  by  making  an  incision  from  the  middle  of  the  coracoacromial 
ligament  do-mi  the  arm  for  about  7  or  8  cm.;  this  will  expose  the  intertubercular  groove  contain- 
ing the  tendon  of  the  Biceps  brachii,  which  should  be  hooked  out  of  the  way.  The  capsule  is 
freely  opened,  and  the  muscles  attached  to  the  greater  and  lesser  tubercles  of  the  humerus  are 
stripped  off  mth  the  capsiile,  without  dividing  their  attachments  to  the  latter.  The  head  of 
the  bone  can  then  be  thriist  out  of  the  wound  and  sawn  off;  or  divided  with  a  narrow  saw  in  situ 
and  subsequently  removed.  The  section  should  be  made,  if  possible,  just  below  the  articular 
surface,  so  as  to  leave  the  bone  as  long  as  possible. 

IV.     Elbow-joint    Articulatio  Cubiti;   (Tigs.  451,  452). 

The  elbow-joint  is  a  ginglymus  or  hinge-joint.  The  trochlea  of  the  humerus  is 
received  into  the  semilunar  notch  of  the  ulna,  and  the  capitulum  of  the  humerus 
articulates  ^\dth  the  fovea  on  the  head  of  the  radius.  The  articular  surfaces  are 
connected  together  by  a  capsule,  which  is  thickened  medially  and  laterally,  and, 
to  a  less  extent,  in  front  and  behind.  These  thickened  portions  are  usually  described 
as  distinct  ligaments  under  the  following  names : 

The  Anterior.  The  Ulnar  Collateral. 

The  Posterior.  The  Radial  Collateral. 

The  Anterior  Ligament  (Fig.  451). — ^The  anterior  ligament  is  a  broad  and  thin 
fibrous  layer  covering  the  anterior  surface  of  the  joint.  It  is  attached  to  the  front 
of  the  medial  epicondyle  and  to  the  front  of  the  humerus  immediately  above  the 
coronoid  and  radial  fossEe;  heloic,  to  the  anterior  surface  of  the  coronoid  process 
of  the  ulna  and  to  the  annular  ligament  I'page  422j,  being  continuous  on  either 
side  with  the  collateral  ligaments.  Its  superficial  fibres  pass  obliquely  from  the 
medial  epicondyle  of  the  humerus  to  the  annular  ligament.  The  middle  fibres, 
vertical  in  direction,  pass  from  the  upper  part  of  the  coronoid  depression  and 
become  partly  blended  with  the  preceding,  but  are  inserted  mainly  into  the  anterior 
surface  of  the  coronoid  process.  The  deep  or  transA'erse  set  intersects  these  at 
right  angles.  This  ligament  is  in  relation,  in  front,  with  the  Brachialis,  except 
at  its  most  lateral  part. 

The  Posterior  Ligament  'Fig.  452 j. — This  posterior  ligament  is  thin  and  mem- 
branous, and  consists  of  transverse  and  oblique  fibres.  Above,  it  is  attached  to 
the  humerus  immediately  behind  the  capitulum  and  clo.se  to  the  medial  margin 
of  tihe  trochlea,  to  the  margins  of  the  olecranon  fossa,  and  to  the  back  of  the  lateral 
epicondyle  some  little  distance  from  the  trochlea.  Below,  it  is  fixed  to  the  upper 
and  lateral  margins  of  the  olecranon,  to  the  posterior  part  of  the  annular  ligament, 
and  to  the  ulna  behind  the  radial  notch.  The  transverse  fibres  form  a  strong  band 
which  bridges  across  the  olecranon  fossa ;  under  cover  of  this  band  a  pouch  of 
synovial  membrane  and  a  pad  of  fat  project  into  the  upper  part  of  the  fossa  when 
the  joint  is  extended.  In  the  fat  are  a  few  scattered  fibrous  bundles,  which  pass 
from  the  deep  surface  of  the  transverse  band  to  the  upper  part  of  the  fossa.  This 
ligament  is  in  relation,  heJiind,  with  the  tendon  of  the  Triceps  brachii  and  the 
Anconaeus. 

The  Ulnar  Collateral  Ligament  (Ugamentum  collaterale  ulnare;  internal  lateral 
ligament)  (Fig.  451  j. — This  ligament  is  a  thick  triangular  band  consisting  of  two 


ELBOW-JOINT 


419 


portions,  an  aiit(>ri()r  and  i)osterior  nnitcd  hy  a  thinner  intermediate  portion.  The 
anterior  portion,  directed  ol)li(iuel\-  forward,  is  attached,  ahow,  h\  its  apex,  to  the 
front  part  of  the  medial  epicondyle  of  the  humerus;  and,  below,  hy  its  broad  base 
to  the  me(Hal  margin  of  the  coronoid  process.  The  posterior  portion,  also  of  trian- 
gular form,  is  attached,  above,  by  its  apex,  to  the  lower  and  Inick  jjart  of  the  medial 
epicondyle;  below,  to  the  medial  margin  of  the  olecranon.  Ik^tween  these  two 
bands  a  few  intermediate  fibres  descend  from  the  medial  epicondyle  to  blend  with 
a  transverse  band  which  bridges  across  the  notch  between  the  olecranon  and  the 
coronoid  process.  This  ligament  is  in  relation  with  the  Triceps  brachii  and  Flexor 
carpi  ulnaris  and  the  ulnar  nerve,  and  gives  origin  to  part  of  the  Flexor  digitorum 
sublimis. 


Fig.  451. — Left  elbow-joint,  showing  anterior  and 
ulnar  collateral  ligaments. 


Fig.  452. — ^Left  elbow-joint,  showing  posterior  and 
radial  collateral  ligaments. 


The  Radial  Collateral  Ligament  {ligamentum  collaterale  radiale;  external  lateral 
ligament)  (Fig.  452). — This  ligament  is  a  short  and  narrow  fibrous  band,  less  dis- 
tinct than  the  ulnar  collateral,  attached,  above,  to  a  depression  below  the  lateral 
epicondyle  of  the  humerus;  below,  to  the  annular  ligament,  some  of  its  most  pos- 
terior fibres  passing  over  that  ligament,  to  be  inserted  into  the  lateral  margin  of 
the  ulna.    It  is  intimately  blended  with  the  tendon  of  origin  of  the  Supinator. 

Sjrnovial  Membrane  (Figs.  453,  454). — The  synovial  membrane  is  very  extensive.  It  extends 
from  the  margin  of  the  articular  sm-face  of  the  humerus,  and  lines  the  coronoid,  radial  and  olec- 
ranon fossae  on  that  bone;  it  is  reflected  over  the  deep  surface  of  the  capsule  and  forms  a  pouch 
between  the  radial  notch,  the  deep  surface  of  the  annular  ligament,  and  the  circumference  of  the 
head  of  the  radius.    Projecting  between  the  radius  and  ulna  into  the  cavity  is  a  cresceiitic  fold  of 


420 


SYNDESMOLOGY 


synovial  membrane,  suggesting  the  division  of  the  joint  into  two;  one  the  humeroradial,  the 
other  the  humeroulnar. 

Between  the  capsule  and  the  synovial  membrane  are  three  masses  of  fat:  the  largest,  over 
the  olecranon  fossa,  is  pressed  into  the  fossa  by  the  Triceps  brachii  during  the  flexion;  the  second, 
over  the  coronoid  fossa,  and  the  third,  over  the  radial  fossa,  are  pressed  by  the  Brachialis  into 
their  respective  fossae  during  extension. 

The  muscles  in  relation  with  the  joint  are,  in  front,  the  Brachialis;  behind,  the  Triceps  brachii 
and  Anconaeus;  laterally,  the  Supinator,  and  the  common  tendon  of  origin  of  the  Extensor  muscles; 
medially,  the  common  tendon  of  origin  of  the  Flexor  muscles,  and  the  Flexor  carpi  ulnaris. 

The  arteries  supplying  the  joint  are  derived  from  the  anastomosis  between  the  profunda  and 
the  superior  and  inferior  iiLnar  collateral  branches  of  the  brachial,  with  the  anterior,  posterior, 
and  interosseous  recm-rent  branches  of  the  ulnar,  and  the  recurrent  branch  of  the  radial.  These 
vessels  form  a  complete  anastomotic  network  around  the  joint. 


Fig.  453. — Capsule  of  elbow-joint  (distended). 
Anterior  aspect. 


Fig.  454. — Capsule  of  elbow-joint  (distended). 
Posterior  aspect. 


The  nerves  of  the  joint  are  a  twig  from  the  ulnar,  as  it  passes  between  the  medial  condyle  and 
the  olecranon;  a  filament  from  the  musculocutaneous,  and  two  from  the  median. 

Movements. — The  elbow-joint  comprises  three  different  portions — viz.,  the  joint  between 
the  ulna  and  humerus,  that  between  the  head  of  the  radius  and  the  humerus,  and  the  proximal 
radioulnar  articulation,  described  below.  All  these  articular  surfaces  are  enveloped  by  a  common 
synovial  membrane,  and  the  movements  of  the  whole  joint  should  be  studied  together.  The  com- 
bination of  the  movements  of  flexion  and  extension  of  the  forearm  with  those  of  pronation  and 
supination  of  the  hand,  which  is  ensured  by  the  two  being  performed  at  the  same  joint,  is  essential 
to  the  accuracy  of  the  various  minute  movements  of  the  hand. 

The  portion  of  the  joint  between  the  ulna  and  humerus  is  a  simple  hinge-joint,  and  allows  of 
movements  of  flexion  and  extension  only.  Owing  to  the  obUquity  of  the  trochlea  of  the  humerus, 
this  movement  does  not  take  place  in  the  antero-posterior  plane  of  the  body  of  the  humerus. 


ELBOW-JOINT  421 

When  the  forearm  is  extended  and  supinated,  the  axes  of  the  arm  and  forearm  are  not  in  the  same 
line;  the  arm  forms  an  obtuse  angle  with  the  forearm,  the  hand  and  forearm  being  directed  lateral- 
ward.  During  flexion,  however,  the  forearm  and  the  hand  tend  to  approach  the  middle  hne  of 
the  body,  and  thus  enable  the  hand  to  be  easily  carried  to  the  face.  The  accurate  adaptation 
of  the  trochlea  of  the  humerus,  with  its  prominences  and  depressions,  to  the  semilunar  notch  of 
the  ulna,  prevents  any  lateral  movement.  Flexion  is  produced  by  the  action  of  the  Biceps  brachii 
and  Brachialis,  assisted  by  the  Brachioradiahs  and  the  muscles  arising  from  the  medial  condyle 
of  the  humerus;  cxleusion,  by  the  Triceps  brachii  and  Anconaeus,  assisted  by  the  Extensors  of 
the  wrist,  the  Extensor  digitoruni  comnmnis,  and  the  Extensor  digiti  quinti  proprius. 

The  joint  between  the  head  of  the  radius  and  the  capitulum  of  the  humerus  is  an  arthrodial 
joint.  The  bony  surfaces  would  of  themselves  constitute  an  enarthrosis  and  allow  of  movement 
in  all  directions,  were  it  not  for  the  annular  Ugament,  by  which  the  head  of  the  radius  is  bound 
to  the  radial  notch  of  the  ulna,  and  which  prevents  any  separation  of  the  two  bones  laterally. 
It  is  to  the  same  ligament  that  the  head  of  the  radius  owes  its  security  from  dislocation,  which 
would  otherwise  tend  to  occur,  from  the  shallowness  of  the  cup-like  surface  on  the  head  of  the 
radius.  In  fact,  but  for  this  hgament,  the  tendon  of  the  Biceps  brachii  would  be  hable  to  pull 
the  head  of  the  radius  out  of  the  joint.  The  head  of  the  radius  is  not  in  complete  contact  with 
the  capitulum  of  the  humerus  in  all  positions  of  the  joint.  The  capitulum  occupies  only  the 
anterior  and  inferior  surfaces  of  the  lower  end  of  the  humerus,  so  that  in  complete  extension  a 
part  of  the  radial  head  can  be  plainly  felt  projecting  at  the  back  of  the  articulation.  In  full 
flexion  the  movement  of  the  radial  head  is  hampered  by  the  compression  of  the  surrounding  soft 
parts,  so  that  the  freest  rotatory  movement  of  the  radius  on  the  humerus  (pronation  and  supina- 
tion) takes  place  in  semiflexion,  in  which  position  the  two  articular  surfaces  are  in  most  intimate 
contact.  Flexion  and  extension  of  the  elbow-joint  are  limited  by  the  tension  of  the  structures 
on  the  front  and  back  of  the  joint;  the  limitation  of  flexion  is  also  aided  by  the  soft  structm-es  of 
the  arm  and  forearm  coming  into  contact. 

In  any  position  of  flexion  or  extension,  the  radius,  carrying  the  hand  with  it,  can  be  rotated  in 
the  proximal  radioulnar  joint.  The  hand  is  directly  articulated  to  the  lower  surface  of  the  radius 
only,  and  the  ulnar  notch  on  the  lower  end  of  the  radius  travels  aroimd  the  lower  end  of  the  ulna. 
The  latter  bone  is  excluded  from  the  wrist-joint  by  the  articular  disk.  Thus,  rotation  of  the  head 
of  the  radius  around  an  axis  passing  through  the  centre  of  the  radial  head  of  the  humerus  imparts 
circular  movement  to  the  hand  through  a  very  considerable  arc. 

Applied  Anatomy. — From  the  great  breadth  of  the  joint,  and  the  manner  in  which  the  articular 
surfaces  are  interlocked,  and  also  on  account  of  the  strong  collateral  ligaments  and  the  support 
which  the  joint  derives  from  the  mass  of  muscles  attached  to  each  epicondyle  of  the  humerus, 
lateral  displacement  of  the  bones  is  very  uncommon;  whereas  antero-posterior  dislocation,  on 
account  of  the  shortness  of  the  antero-posterior  diameter,  the  weakness  of  the  anterior  and 
posterior  hgaments,  and  the  want  of  support  of  muscles,  occurs  much  more  frequently.  Dislo- 
cation backward  takes  place  when  the  forearm  is  in  a  position  of  extension,  and  forward  when  in 
a  position  of  flexion.  For,  in  the  extended  position,  the  coronoid  process  is  not  locked  into  the 
coronoid  fossa,  and  loses  its  grip  to  a  certain  extent,  whereas  the  olecranon  is  in  the  olecranon 
fossa,  and  entirely  prevents  displacement  forward.  On  the  other  hand,  during  flexion,  the  coronoid 
process  is  in  the  coronoid  fossa,  and  prevents  dislocation  backward,  while  the  olecranon,  having 
left  the  olecranon  fossa,  is  not  so  efficient  in  preventing  a  forward  displacement.  When  lateral 
dislocation  does  take  place  it  is  generally  incomplete.  Dislocation  of  the  elbow-joint  is  of  common 
occm'rence  in  children,  far  more  common  than  dislocation  of  any  other  articiUation.  As  a  rule, 
in  yoimg  persons,  the  appUcation  of  any  severe  violence  to  a  joint  is  more  likely  to  produce  a 
fracture  of  bone  than  dislocation.  In  lesions  of  this  joint  there  is  often  very  great  difficulty  in 
ascertaining  the  exact  natm-e  of  the  injury. 

The  elbow-joint  is  occasionally  the  seat  of  acute  synovitis.  The  joint-cavity  then  becomes 
distended  witla  fluid,  the  bulging  showing  itself  principally  around  the  olecranon,  in  consequence 
of  the  laxness  of  the  posterior  hgament.  Again,  there  is  often  some  swelling  just  above  the  head 
of  the  radius,  in  the  Ime  of  the  radiohumeral  joint,  or  the  whole  elbow  may  assume  a  fusiform 
appearance.  There  is  not  generally  much  swelhng  at  the  front  of  the  joint,  though  sometimes 
deep-seated  fulness  beneath  the  Brachiahs  may  be  noted.  W^hen  suppm'ation  occurs  the  abscess 
usually  points  at  one  or  other  border  of  the  Triceps  brachii;  occasionaUy  the  pus  discharges  itself 
in  front,  near  the  insertion  of  the  Brachiahs.  In  cases  of  suppm-ative  sjTiovitis,  incisions  should 
be  made  into  the  joint  on  either  side  of  the  olecranon,  care  being  taken  to  avoid  woimding  the 
uhiar  nerve  on  the  medial  side.  Chronic  synovitis,  usually  of  tuberculous  origin,  is  of  common 
occm-rence  in  the  elbow-joint;  in  such  cases  the  forearm  tends  to  assume  the  position  of  semi- 
flexion, which  is  that  of  greatest  ease  and  relaxation  of  hgaments.  It  should  be  borne  in  mind 
that  if  ankylosis  occm*  in  this  or  the  extended  position,  the  limb  will  not  be  nearlj-  so  useful  as 
if  ankylosed  in  a  position  of  rather  less  than  a  right  angle.  The  elbow-joint  is  also  sometimes 
affected  with  osteoarthi'itis,  but  less  commonly  than  some  of  the  larger  joints. 

Excision  of  the  elbow  is  principally  requii-ed  for  one  of  three  conditions — viz.,  tuberculous 
arthritis,  injurj'  and  its  results,  or  faultj^  ankylosis — but  maj^  be  necessary  for  some  other  rarer 


422 


SYNDESMOLOGY 


conditions,  such  as  disorganizing  arthritis  after  pyemia  and  unreduced  dislocations.  The  results 
of  the  operation  are,  as  a  rule,  more  favorable  than  those  of  excision  of  any  other  joint,  especially 
in  any  of  the  first  three  conditions  mentioned  above.  The  operation  is  best  performed  by  a 
vertical  incision  down  the  back  of  the  joint;  a  straight  incision  is  made  about  10  cm.  long,  the 
mid-point  of  which  is  on  a  level  with  and  a  little  to  the  medial  side  of  the  tip  of  the  olecranon. 
This  incision  is  made  down  to  the  bone,  through  the  substance  of  the  Triceps  brachii.  The 
operator,  guarding  the  soft  parts  with  his  thumb-nail,  separates  them  from  the  bone  with  the 
point  of  his  knife.  In  doing  this  there  are  two  structures  which  he  should  carefully  avoid:  the 
ulnar  nerve,  which  as  it  courses  down  between  the  medial  epicondyle  and  the  olecranon  lies 
parallel  but  a  little  medial  to  his  incision;  and  the  prolongation  of  the  Triceps  brachii  into  the 
deep  fascia  of  the  forearm  over  the  Anconaeus.  Having  cleared  the  bones  and  divided  the  col- 
lateral and  posterior  ligaments,  the  forearm  is  strongly  flexed  and  the  ends  of  the  bones  turned 
out  and  sawn  off.  The  turning  out  of  the  ends  of  the  bones  is  rendered  easier  by  first  cutting 
off  the  olecranon  with  a  pair  of  cutting  bone  forceps.  The  section  of  the  humerus  should  be 
through  the  base  of  the  epicondyles,  that  of  the  ulna  and  radius  should  be  just  below  the  level 
of  the  radial  notch  of  the  ulna  and  the  neck  of  the  radius.  In  this  operation  the  object  is  to  obtain 
such  imion  as  shall  allow  free  motion  of  the  bones  of  the  forearm;  and,  therefore,  passive  move- 
ments must  be  commenced  early — that  is  to  say,  about  the  tenth  day.  It  is  most  important  to 
maintain  the  continuity  of  the  Triceps  brachii  with  the  deep  fascia  of  the  forearm,  so  as  to  obtain 
good  power  of  extension  in  the  new  joint. 


V.    Radioulnar  Articulations  (Articulatio  Radioulnaris) . 

The  articulation  of  the  radius  with  the  ulna  is  effected  by  ligaments  which  con- 
nect together  the  extremities  as  well  as  the  bodies  of  these  bones.  The  ligaments 
may,  consequently,  be  subdivided  into  three  sets :  1 ,  those  of  the  proximal  radio- 
ulnar articulation;  2,  the  middle  radioulnar  ligaments;  3,  those  of  the  distal  radio- 
ulnar articulation. 

Proximal  Radioulnar  Articulation  (articulatio  radioulnaris  proximalis;  superior 
radioulnar  joint). — This  articulation  is  a  trochoid  or  pivot-joint  between  the 
circumference  of  the  head  of  the  radius  and  the  ring  formed  by  the  radial  notch 
of  the  ulna  and  the  annular  ligament. 


Head  of  radius    Quadrate 
{cut)  ligament 


Semilunar 
notch 


Annular  ligament 

Radial  notch    ' 


Olecranon  [cut) 

Fig.  455. — Annular  ligament  of  radius,  from  above.     The  head  of  the  radius  has  been  sawn  ofi  and  the  bone 

dislodged  from  the  ligament. 

The  Annular  Ligament  (ligamentum  annulare  radii;  orbicular  ligament)  (Fig.  455). 
— This  ligament  is  a  strong  band  of  fibres,  which  encircles  the  head  of  the  radius, 
and  retains  it  in  contact  with  the  radial  notch  of  the  ulna.  It  forms  about  four- 
fifths  of  the  osseo-fibrous  ring,  and  is  attached  to  the  anterior  and  posterior  margins 
of  the  radial  notch ;  a  few  of  its  lower  fibres  are  continued  around  below  the  cavity 
and  form  at  this  level  a  complete  fibrous  ring.  Its  upper  border  blends  with  the 
anterior  and  posterior  ligaments  of  the  elbow,  while  from  its  lower  border  a  thin 


RADIOULNAR  ARTICULATIONS  423 

loose  membrane  passes  to  be  attached  to  the  neck  of  the  radius;  a  thickened  band 
"which  extends  from  the  inferior  border  of  the  annular  li<i;ament  below  the  radial 
notch  to  the  neck  of  the  radius  is  known  as  the  quadrate  ligament.  The  superficial 
surface  of  the  annular  ligament  is  strengthened  by  the  radial  collateral  ligament 
of  the  elbow,  and  all'ords  origin  to  part  of  the  Supinator.  Its  deep  surface  is  smooth, 
and  lined  by  syno^'ial  membrane,  which  is  continuous  with  that  of  the  elbow-joint. 

Movements. — The  movements  allowed  in  this  articulation  are  limited  to  rotatory  movements 
of  the  head  of  the  radius  within  the  ring  formed  by  the  annular  ligament  and  the  radial  notch 
of  the  ulna;  rotation  forward  being  called  pronation;  rotation  backward,  supination.  Supination 
is  performed  by  the  Biceps  brachii  and  Supinator,  assisted  to  a  shght  extent  by  the  Extensor 
muscles  of  the  thumb.     Pronation  is  performed  by  the  Pronator  teres  and  Pronator  quadratus. 

Applied  Anatomy. — Dislocation  of  the  head  of  the  radius  alone  is  a  not  uncommon  accident, 
and  occurs  most  frequently  in  young  persons  from  falls  on  the  hand  when  the  forearm  is  extended 
and  supinated,  the  head  of  the  bone  being  displaced  forward.  It  is  attended  by  rupture  of  the 
annular  ligament.  Occasionally  a  peculiar  injury,  which  is  supposed  to  be  a  subluxation,  occurs 
in  young  children  in  lifting  them  from,  the  ground  by  the  hand  or  forearm.  It  is  believed  that 
the  head  of  the  radius  is  displaced  downward  in  the  annular  ligament,  the  upper  border  of  which 
becomes  folded  over  the  head  of  the  radius,  between  it  and  the  capitulum  of  the  humerus.  The 
forearm  becomes  fixed  in  a  position  of  semiflexion,  midway  between  supination  and  pronation, 
and  great  pain  is  complained  of  upon  any  attempt  to  move  the  joint.  The  synovial  membrane 
of  the  proximal  radioulnar  joint  is  directly  continuous  with  that  of  the  elbow-joint,  and,  therefore, 
any  septic  or  tuberculous  disease  which  affects  the  latter  also  involves  the  former  joint.  The 
proximal  radioulnar  joint  is  always  removed  in  an  excision  of  the  elbow  (see  p.  422). 

Middle  Radioulnar  Union. — The  shafts  of  the  radius  and  ulna  are  connected 
b}'  the  Oblique  Cord  and  the  Interosseous  Membrane. 

The  Oblique  Cord  {chorda  obliqua;  oblique  ligament)  (Fig.  451). — -The  oblique 
cord  is  a  small,  flattened  band,  extending  downward  and  lateralward,  from  the 
lateral  side  of  the  tubercle  of  the  ulna  at  the  base  of  the  coronoid  process  to  the 
radius  a  little  below  the  radial  tuberosity.  Its  fibres  run  in  the  opposite  direction 
to  those  of  the  interosseous  membrane.    It  is  sometimes  wanting. 

The  Interosseous  Membrane  (mevibrana  interossea  antebrachii). — The  interosseous 
membrane  is  a  broad  and  thin  plane  of  fibrous  tissue  descending  obliquely  down- 
ward and  medialward,  from  the  interosseous  crest  of  the  radius  to  that  of  the  ulna; 
the  lower  part  of  the  membrane  is  attached  to  the  posterior  of  the  two  lines  into 
which  the  interosseous  crest  of  the  radius  divides.  It  is  deficient  above,  commencing 
about  2.5  cm.  beneath  the  tuberosity  of  the  radius;  is  broader  in  the  middle  than 
at  either  end ;  and  presents  an  oval  aperture  a  little  above  its  lower  margin  for  the 
passage  of  the  volar  interosseous  vessels  to  the  back  of  the  forearm.  This  mem- 
brane serves  to  connect  the  bones,  and  to  increase  the  extent  of  surface  for  the 
attachment  of  the  deep  muscles.  Between  its  upper  border  and  the  oblique  cord 
is  a  gap,  through  which  the  dorsal  interosseous  vessels  pass.  Two  or  three  fibrous 
bands  are  occasionally  found  on  the  dorsal  surface  of  this  membrane ;  they  descend 
obliquely  from  the  ulna  toward  the  radius,  and  have  consequently  a  direction 
contrary  to  that  of  the  other  fibres.  The  membrane  is  in  relation,  in  front,  by 
its  upper  three-fourths,  with  the  Flexor  pollicis  longus  on  the  radial  side,  and  with 
the  Flexor  digitorum  profundus  on  the  ulnar,  lying  in  the  interval  between  which 
are  the  volar  interosseous  vessels  and  nerve;  by  its  lower  fourth  with  the  Pronator 
quadratus;  behind,  with  the  Supinator,  Abductor  pollicis  longus.  Extensor  pollicis 
brevis.  Extensor  pollicis  longus.  Extensor  indicis  proprius;  and,  near  the  wrist, 
with  the  volar  interosseous  artery  and  dorsal  interosseous  nerve. 

Distal  Radioulnar  Articulation  {articidatio  radioulnaris  distalis;  inferior  radio- 
ulnar joint). — This  is  a  pivot-joint  formed  between  the  head  of  the  ulna  and  the 
ulnar  notch  on  the  lower  end  of  the  radius.  The  articular  surfaces  are  connected 
together  by  the  following  ligaments : 

The  Volar  Radioulnar.  The  Dorsal  Radioulnar. 

The  Articular  Disk. 


424 


SYNDESMOLOGY 


The  Volar  Radioulnar  Ligament  {anterior  radiouhuir  ligament)  (Fig.  456). — This 
ligament  is  a  narrow  band  of  fibres  extending  from  the  anterior  margin  of  the  ulnar 
notch  of  the  radius  to  the  front  of  the  head  of  the  ulna. 


^  1  "(si 


^^'^<r,    iVrist-ioint 


Distal  radio-id'^ur 
articulation 


' I  '.Y%ti  Intercarpal  articulations 

i     \  P 

—PisoJiamate  ligament 
Ptsometacarpal  ligament 

Ca  rpometacarpal 
articulations 


Fig.  456. — Ligaments  of  wrist.     Anterior  view 


The  Dorsal  Radioulnar  Ligament  {posterior  radioulnar  ligament)  (Fig.  457). — 
This  ligament  extends  between  corresponding  surfaces  on  the  dorsal  aspect  of  the 
articulation. 


Distal  radio-ulnar^ 

articulation       /^j«  tJ*",^ 


Intercarpal  articulations  y  ^ 


Fig.  4.57. — Ligaments  of  wrist.     Posterior  view. 


The  Articular  Disk  {discus  articularis;  triangular  fihrocartilage)  (Fig.  458). — The 
articular  disk  is  triangular  in  shape,  and  is  placed  transversely  beneath  the  head 
of  the  ulna,  binding  the  lower  ends  of  the  ulna  and  radius  firmly  together.     Its 


RADIOCARPAL  ARTICULATION  OR  WRIST-JOIXT 


425 


periphery  is  thicker  than  its  centre,  which  is  occasionally  perforated.  It  is  attached 
by  its  apex  to  a  depression  between  the  styloid  process  and  the  head  of  the  ulna; 
and  by  its  base,  which  is  thin,  to  the  prominent  edge  of  the  radius,  which  separates 
the  ulnar  notch  from  the  carpal  articular  surface.  Its  margins  are  united  to  the 
ligaments  of  the  wrist-joint.  Its  upper  surface,  smooth  and  concave,  articulates 
wath  the  head  of  the  ulna,  forming  an  arthrodial  joint;  its  under  surface,  also  con- 
cave and  smooth,  forms  part  of  the  wrist-joint  and  articulates  with  the  triangular 
bone  and  medial  part  of  the  lunate.  Both  surfaces  are  clothed  by  synovial  mem- 
brane; the  upper,  by  that  of  the  distal  radioulnar  articulation,  the  under,  by  that 
of  the  wrist. 


Wrist-joint  ■ 

Radial  collateral 
ligament 


Distal  radioulnar 
articulation 

Articular  disc 

Ulnar  collateral  ligament 


Pisiform 


Fig.  458. — Vertical  section  through  the  articulations  at  the  wrist,  showing  the  synovial  cavities. 

Synovial  Membrane  (Fig.  458). — The  synovial  membrane  of  this  articulation  is  extremely 
loose,  and  extends  upward  as  a  recess  (recessus  sacciformis)  between  the  radius  and  the  ulna. 

Movements.- — The  movements  in  the  distal  radioulnar  articulation  consist  of  rotation  of  the 
lower  end  of  the  radius  around  an  axis  which  passes  through  the  centre  of  the  head  of  the  ulna. 
When  the  radius  rotates  forward,  pronation  of  the  forearm  and  hand  is  the  result ;  and  when  back- 
ward, supination.  It  will  thus  be  seen  that  in  pronation  and  supination  the  radius  describes  the 
segment  of  a  cone,  the  axis  of  which  extends  from  the  centre  of  the  head  of  the  radius  to  the 
middle  of  the  head  of  the  ulna.  In  this  movement  the  head  of  the  ulna  is  not  stationary,  but 
describes  a  curve  in  a  direction  opposite  to  that  taken  by  the  head  of  the  radius.  This,  however, 
is  not  to  be  regarded  as  a  rotation  of  the  ulna — the  cm-ve  which  the  head  of  this  bone  describes 
is  due  to  a  combined  antero-posterior  and  rotatory  movement,  the  former  taking  place  ahnost 
entirely  at  the  elbow-joint,  the  latter  at  the  shoulder-joint. 


VI.    Radiocarpal  Articulation  or  Wrist-joint  (Articulatio  Radiocarpea) 

(Figs.  456,  457). 

The  wrist-joint  is  a  condyloid  articulation.  The  parts  forming  it  are  the  lower 
end  of  the  radius  and  under  surface  of  the  articular  disk  above;  and  the  navicular, 
lunate,  and  triangular  bones  below.  The  articular  surface  of  the  radius  and  the 
under  surface  of  the  articular  disk  form  together  a  transversely  elliptical  concave 
surface,  the  receiving  cavity.  The  superior  articular  surfaces  of  the  navicular, 
lunate,  and  triangular  form  a  smooth  convex  surface,  the  condyle,  which  is  received 


426  SYNDESMOLOGY 

into  the  concavity.     The  joint  is  surrounded  by  a  capsule,  strengthened  })y  the 
following  ligaments: 

The  Volar  Radiocarpal.  The  Ulnar  Collateral. 

The  Dorsal  Radiocarpal.  The  Radial  Collateral. 

The  Volar  Radiocarpal  Ligament  {ligaiiientuni  radiocarijeum  volare;  anteriur  liga- 
ment) (Fig.  456). — This  ligament  is  a  broad  membranous  band,  attached  above 
to  the  anterior  margin  of  the  lower  end  of  the  radius,  to  its  styloid  process,  and  to 
the  front  of  the  lower  end  of  the  ulna;  its  fibres  pass  downward  and  medialward 
to  be  inserted  into  the  volar  surfaces  of  the  navicular,  lunate,  and  triangular 
bones,  some  being  continued  to  the  capitate.  In  addition  to  this  broad  mem- 
brane, there  is  rounded  fasciculus,  superficial  to  the  rest,  which  reaches  from  the 
base  of  the  styloid  process  of  the  ulna  to  the  lunate  and  triangular  bones.  The 
ligament  is  perforated  by  apertures  for  the  passage  of  vessels,  and  is  in  relation, 
m  front,  with  the  tendons  of  the  Flexor  digitorum  profundus  and  Flexor  pollicis 
longus;  behind,  it  is  closely  adherent  to  the  anterior  border  of  the  articular  disk 
of  the  distal  radioulnar  articulation. 

The  Dorsal  Radiocarpal  Ligament  (ligamentum  radiocarpeuni  dorsale;  'posterior 
ligament)  (Fig.  457). — The  dorsal  radiocarpal  ligament  less  thick  and  strong  than 
the  volar,  is  attached,  above,  to  the  posterior  border  of  the  lower  end  of  the  radius; 
its  fibres  are  directed  obliquely  downward  and  medialw^ard,  and  are  fixed,  below, 
to  the  dorsal  surfaces  of  the  navicular,  lunate,  and  triangular,  being  continuous 
with  those  of  the  dorsal  intercarpal  ligaments.  It  is  in  relation,  behind,  with  the 
Extensor  tendons  of  the  fingers;  in  front,  it  is  blended  with  the  articular  disk. 

The  Ulnar  Collateral  Ligament  {ligamentum  collaterale  carpi  ulnare;  internal 
lateral  ligament)  (Fig.  456). — The  ulnar  collateral  ligament  is  a  rounded  cord, 
attached  above  to  the  end  of  the  styloid  process  of  the  ulna,  and  dividing  below 
into  two  fasciculi,  one  of  which  is  attached  to  the  medial  side  of  the  triangular 
bone,  the  other  to  the  pisiform  and  transverse  carpal  ligament. 

The  Radial  Collateral  Ligament  (ligamentum  collaterale  carpi  radiate;  external 
lateral  ligament)  (Fig.  456). — The  radial  collateral  ligament  extends  from  the  tip 
of  the  styloid  process  of  the  radius  to  the  radial  side  of  the  navicular,  some  of  its 
fibres  being  prolonged  to  the  greater  multangular  bone  and  the  transverse  carpal 
ligament.  It  is  in  relation  with  the  radial  artery,  which  separates  the  ligament 
from  the  tendons  of  the  Abductor  pollicis  longus  and  Extensor  pollicis  brevis. 

Synovial  Membrane  (Fig.  458). — The  synovial  membrane  lines  the  deep  surfaces  of  the  liga- 
ments above  described,  extending  from  the  margin  of  the  lower  end  of  the  radius  and  articular 
disk  above  to  the  margins  of  the  articular  surfaces  of  the  carpal  bones  below.  It  is  loose  and 
lax,  and  presents  numerous  folds,  especially  behind. 

The  wrist-joint  is  covered  in  front  by  the  Flexor,  and  behind  by  the  Extensor  tendons. 

The  arteries  supplying  the  joint  are  the  volar  and  dorsal  carpal  branches  of  the  radial  and 
ulnar,  the  volar  and  dorsal  metacarpals,  and  some  ascending  branches  from  the  deep  volar  arch. 

The  nerves  are  derived  from  the  ulnar  and  dorsal  interosseous. 

Movements. — The  movements  permitted  in  this  joint  are  flexion,  extension,  abduction,  adduc- 
tion, and  circumduction.  They  will  be  studied  with  those  of  the  carpus,  with  which  they  are 
combined. 

Applied  Anatomy. — The  wrist-joint  is  rarely  dislocated,  its  strength  depending  mainly  upon 
the  numerous  strong  tendons  which  surround  the  articulation.  Its  security  is  further  provided 
for  by  the  number  of  small  bones  of  which  the  carpus  is  made  up,  and  which  are  united  by  very 
strong  ligaments.  The  slight  movements  which  take  place  between  the  several  bones  serve  to 
break  the  jars  that  result  from  falls  or  blows  on  the  hand.  Dislocation  backward,  wliich  is  the 
more  common,  simulates  to  a  considerable  extent  CoUes'  fracture  of  the  radius,  and  is  liable 
to  be  mistaken  for  it.  The  differential  diagnosis  can  be  easily  made  bj-  observing  the  relative 
positions  of  the  styloid  processes  of  the  radius  and  the  ulna.  In  the  natural  condition  the  styloid 
process  of  the  radius  is  on  a  lower  level,  i.  e.,  nearer  the  ground,  when  the  arm  hangs  by  the  side 
than  that  of  the  ulna,  and  this  relationship  is  not  disturbed  in  dislocation.  In  CoUes'  fracture 
the  styloid  process  of  the  radius  is  on  the  same  level  as,  or  even  a  higher  level  than,  that  of  the 
ulna. 


INTERCARPAL  ARTICULATIONS  427 

The  wrist-joint  is  occasionally  the  seat  of  acute  synovitis.  When  the  joint  cavity  is  distended 
with  fluid,  the  swelling  is  greatest  on  the  dorsal  aspect  of  the  wrist,  showing  a  general  fulness, 
with  some  bulging  between  the  tendons.  The  inflammation  is  prone  to  extend  to  the  intercarpal 
joints  and  to  attack  also  the  sheaths  of  the  tendons  in  the  neighborhood.  Chronic  inflamnuition 
of  the  wrist  is  generally  tuberculous,  and  often  leads  to  similar  disease  in  the  mucous  slieaths 
of  adjacent  tendons  and  the  intercarpal  joints,  with  resulting  ankylosis. 

VII.     Intercarpal  Articulations  (Articulationes  Intercarpeae ;  Articulations 

of  the  Carpus). 

These  articulations  may  be  subdivided  into  three  sets : 

1.  The  Articulations  of  the  Proximal  Row  of  Carpal  Bones. 

2.  The  Articulations  of  the  Distal  Row  of  Carpal  Bones. 

3.  The  Articulations  of  the  Two  Rows  with  each  Other. 

Articulations  of  the  Proximal  Row  of  Carpal  Bones. — These  are  arthrodial 
joints.  The  navicular,  lunate,  and  triangular  are  connected  by  dorsal,  volar,  and 
interosseous  ligaments. 

The  Dorsal  Ligaments  (ligamenta  intercarpea  dorsalia). — The  dorsal  ligaments, 
two  in  number,  are  placed  transversely  behind  the  bones  of  the  first  row;  they 
connect  the  navicular  and  lunate,  and  the  lunate  and  triangular. 

The  Volar  ligaments  {ligamenta  intercarpea  volaria;  palmar  ligaments). — The  volar 
ligaments,  also  two,  connect  the  navicular  and  lunate,  and  the  lunate  and  trian- 
gular; they  are  less  strong  than  the  dorsal,  and  placed  very  deeply  behind  the 
Flexor  tendons  and  the  volar  radiocarpal  ligament. 

The  Interosseous  Ligaments  {ligamenta  intercarpea  interossea)  (Fig.  458). — The 
interosseous  ligaments  are  two  narrow  bundles,  one  connecting  the  lunate  with 
the  navicular,  the  other  joining  it  to  the  triangular.  They  are  on  a  level  with  the 
superior  surfaces  of  these  bones,  and  their  upper  surfaces  are  smooth,  and  form 
part  of  the  convex  articular  surface  of  the  wrist-joint. 

The  ligaments  connecting  the  pisiform  bone  are  the  articular  capsule  and  the. 
two  volar  ligaments. 

The  articular  capsule  is  a  thin  membrane  which  connects  the  pisiform  to  the 
triangular;  it  is  lined  by  synovial  membrane. 

The  two  volar  ligaments  are  strong  fibrous  bands;  one,  the  pisohamate  ligament, 
connects  the  pisiform  to  the  hamate,  the  other,  the  pisometacarpal  ligament,  joins 
the  pisiform  to  the  base  of  the  fifth  metacarpal  bone  (Fig.  456).  These  ligaments 
are,  in  reality,  prolongations  of  the  tendon  of  the  Flexor  carpi  ulnaris. 

Articulations  of  the  Distal  Row  of  Carpal  Bones. — These  also  are  arthrodial 
joints;  the  bones  are  connected  by  dorsal,  volar,  and  interosseous  ligaments. 

The  Dorsal  Ligaments  {ligamenta  intercarpea  dorsalia). — The  dorsal  ligaments, 
three  in  number,  extend  transversely  from  one  bone  to  another  on  the  dorsal 
surface,  connecting  the  greater  with  the  lesser  multangular,  the  lesser  multangular 
with  the  capitate,  and  the  capitate  with  the  hamate. 

The  Volar  Ligaments  {ligamenta  intercarpea  volaria;  palmar  ligaments). — The 
volar  ligaments,  also  three,  have  a  similar  arrangement  on  the  volar  surface. 

The  Interosseous  Ligaments  {ligamenta  intercarpea  interossea) .—The  three  inter- 
osseous ligaments  are  much  thicker  than  those  of  the  first  row;  one  is  placed  be- 
tween the  capitate  and  the  hamate,  a  second  between  the  capitate  and  the  lesser 
multangular,  and  a  third  between  the  greater  and  lesser  multangular s.  The  first 
is  much  the  strongest,  and  the  third  is  sometimes  wanting. 

Articulations  of  the  Two  Rows  of  Carpal  Bones  with  Each  Other.— The  joint 
between  the  navicular,  lunate,  and  triangular  on  the  one  hand,  and  the  second 
row  of  carpal  bones  on  the  other,  is  named  the  midcarpal  joint,  and  is  made  up  of 
three  distinct  portions:  in  the  centre  the  head  of  the  capitate  and  the  superior 


428  SYNDESMOLOGY 

surface  of  the  hamate  articulate  with  the  deep  cup-shaped  cavity  formed  by  the 
navicular  and  lunate,  and  constitute  a  sort  of  ball-and-socket  joint.  On  the 
radial  side  the  greater  and  lesser  multangulars  articulate  with  the  navicular, 
and  on  the  ulnar  side  the  hamate  articulates  with  the  triangular,  forming  gliding 
joints. 

The  ligaments  are:  volar,  dorsal,  ulnar  and  radial  collateral. 

The  Volar  Ligaments  (ligamenta  intercarpea  volaria;  anterior  or  palmar  ligaments). 
— The  volar  ligaments  consist  of  short  fibres,  which  pass,  for  the  most  part,  from 
the  volar  surfaces  of  the  bones  of  the  first  row  to  the  front  of  the  capitate. 

The  Dorsal  Ligaments  (ligamenta  intercarpea  dorsalia;  posterior  ligaments). — 
The  dorsal  ligaments  consist  of  short,  irregular  bundles  passing  between  the  dorsal 
surfaces  of  the  bones  of  the  first  and  second  rows. 

The  Collateral  Ligaments  {lateral  ligaments). — The  collateral  ligaments  are  very 
short;  one  is  placed  on  the  radial,  the  other  on  the  ulnar  side  of  the  carpus;  the 
former,  the  stronger  and  more  distinct,  connects  the  navicular  and  greater  mul- 
tangular, the  latter  the  triangular  and  hamate;  they  are  continuous  with  the 
collateral  ligaments  of  the  wrist-joint.  In  addition  to  these  ligaments,  a  slender 
interosseous  band  sometimes  connects  the  capitate  and  the  navicular. 

Synovial  Membrane. — The  synovial  membrane  of  the  carpus  is  very  extensive  (Fig.  458)  t 
and  bounds  a  synovial  cavity  of  very  irregular  shape.  The  upper  portion  of  the  cavity  inter- 
venes between  the  under  surfaces  of  the  navicular,  limate,  and  triangular  bones  and  the  upper 
smrfaces  of  the  bones  of  the  second  row.  It  sends  two  prolongations  upward — ^between  the  navic- 
ular and  lunate,  and  the  lunate  and  triangular — and  three  prolongations  downward  between 
the  four  bones  of  the  second  row.  The  prolongation  between  the  greater  and  lesser  multangulars, 
or  that  between  the  lesser  multangular  and  capitate,  is,  owing  to  the  absence  of  the  interosseous 
ligament,  often  continuous  with  the  cavity  of  the  carpometacarpal  joints,  sometimes  of  the 
second,  third,  fourth,  and  fifth  metacarpal  bones,  sometimes  of  the  second  and  third  only.  In 
the  latter  condition  the  joint  between  the  hamate  and  the  fourth  and  fifth  metacarpal  bones 
has  a  separate  synovial  membrane.  The  synovial  cavities  of  these  joints  are  prolonged  for  a 
short  distance  between  the  bases  of  the  metacarpal  bones.  There  is  a  separate  synovial  mem- 
brane between  the  pisiform  and  triangular. 

Movements. — The  articulation  of  the  hand  and  wrist  considered  as  a  whole  involves  foiu- 
articular  surfaces:  (o)  the  inferior  surfaces  of  the  radius  and  articular  disk;  (fe)  the  superior 
surfaces  of  the  navicular,  lunate,  and  triangular,  the  pisiform  having  no  essential  part  in  the 
movement  of  the  hand;  (c)  the  S-shaped  surface  formed  by  the  inferior  surfaces  of  the  navicular, 
limate,  and  triangular;  (d)  the  reciprocal  surface  formed  by  the  upper  surfaces  of  the  bones  of 
the  second  row.  These  four  surfaces  form  two  jokits:  (1)  a  proximal,  the  wrist-joint  proper; 
and  (2)  a  distal,  the  mid-carpal  joint. 

1.  The  wrist-joint  proper  is  a  true  condyloid  articulation,  and  therefore  all  movements  but 
rotation  are  permitted.  Flexion  and  extension  are  the  most  free,  and  of  these  a  greater  amoimt 
of  extension  than  of  flexion  is  permitted,  since  the  articulating  surfaces  extend  farther  on  the  dorsal 
than  on  the  volar  surfaces  of  the  carpal  bones.  In  this  movement  the  carpal  bones  rotate  on  a 
transverse  axis  drawn  between  the  tips  of  the  styloid  processes  of  the  radius  and  ulna.  A  certain 
amount  of  adduction  (or  ulnar  flexion)  and  abduction  (or  radial  flexion)  is  also  permitted.  The 
former  is  considerably  greater  in  extent  than  the  latter  on  account  of  the  shortness  of  the  styloid 
process  of  the  ulna,  abduction  being  soon  limited  by  the  contact  of  the  styloid  process  of  the 
radius  with  the  greater  multangular.  In  this  movement  the  carpus  revolves  upon  an  antero- 
posterior axis  drawn  through  the  centre  of  the  wrist. ^  Finally,  circumduction  is  permitted  by 
the  combined  and  consecutive  movements  of  adduction,  extension,  abduction,  and  flexion.  No 
rotation  is  possible,  but  the  effect  of  rotation  is  obtained  by  the  pronation  and  supination  of  the 
radius  on  the  ulna.  The  movement  of  flexion  is  performed  by  the  Flexor  carpi  radiahs,  the  Flexor 
carpi  ulnaris,  and  the  Palmaris  longus;  extension  by  the  Extensores  carpi  radiales  longus  and 
brevis  and  the  Extensor  carpi  ulnaris;  adduction  (ulnar  flexion)  by  the  Flexor  carpi  ulnaris  and 
the  Extensor  carpi  uhiaris;  and  abduction  (radial  flexion)  by  the  Abductor  pollicis  longus,  the 
Extensors  of  the  thumb,  and  the  Extensores  carpi  radiales  longus  and  brevis  and  the  Flexor  carpi 
radialis.  When  the  fingers  are  extended,  flexion  of  the  wrist  is  performed  by  the  Flexores  carpi 
radialis  and  uLnaris  and  extension  by  the  Extensor  digitorum  communis.  When  the  fingers  are 
flexed,  flexion  of  the  ua-ist  is  performed  by  the  Flexores  digitorum  sublimis  and  profimdus,  and 
extension  by  the  Extensores  carpi  radiales  and  ulnaris. 

1  H.  M.  Johnston  (Journal  of  Anatomy  and  Physiology,  vol.  xli)  maintains  that  in  ulnar  and  radial  flexion  only 
slight  lateral  movement  occurs  at  the  radiocarpal  joint,  and  that  in  complete  flexion  and  extension  of  the  hand  there 
is  a  small  degree  of  ulnar  flexion  at  the  radiocarpal  joint. 


CARPOMETACARPAL  ARTICULATIONS  429 

2.  The  chief  movements  permitted  in  the  mid-curpal  joint  are  flexion  and  extension  and  a 
slight  amount  of  rotation.  In  flexion  and  extension,  wiiieh  are  the  movements  most  freely  enjoyed, 
the  greater  and  lesser  multaugulars  on  the  radial  side  and  the  hamate  on  the  ulnar  side  glide 
forward  and  backward  on  the  navicular  and  triangular  respectively,  while  the  head  of  the  capitate 
and  the  superior  smiace  of  the  hamate  rotate  in  the  cup-shaped  cavity  of  the  navicular  and 
lunate.  Flexion  at  this  joint  is  freer  than  extension.  A  very  trifling  amount  of  rotation  is  also 
permitted,  the  head  of  the  capitate  rotating  around  a  vertical  axis  drawn  through  its  own  centre; 
while  at  the  same  time  a  slight  gUding  movement  takes  place  in  the  lateral  and  medial  portions 
of  the  joint. 

Vni.     Carpometacarpal  Articulations  ( Articulations s  Carpometacarpeae) . 

Carpometacarpal  Articulation  of  the  Thumb  {articulatlo  carpometacarpea  pollicis). 
— This  is  a  joint  of  reciprocal  reception  between  the  first  metacarpal  and  the 
greater  multangular;  it  enjoys  great  freedom  of  movement  on  account  of  the 
configuration  of  its  articular  surfaces,  which  are  saddle-shaped.  The  joint  is  sur- 
rounded by  a  capsule,  which  is  thick  but  loose,  and  passes  from  the  circumference 
of  the  base  of  the  metacarpal  bone  to  the  rough  edge  bounding  the  articular  surface 
of  the  greater  multangular;  it  is  thickest  laterally  and  dorsally,  and  is  lined  b}' 
synovial  membrane. 

Movements. — In  this  articulation  the  movements  permitted  are  flexion  and  extension  in  the 
plane  of  the  pahn  of  the  hand,  abduction  and  adduction  in  a  plane  at  right  angles  to  the  palm, 
circumduction,  and  opposition.  It  is  by  the  movement  of  opposition  that  the  tip  of  the  thumb 
is  brought  into  contact  with  the  volar  sm'faces  of  the  shghtly  flexed  fingers.  This  movement  is 
effected  through  the  mediima  of  a  smaU  sloping  facet  on  the  anterior  hp  of  the  saddle-shaped 
articular  surface  of  the  greater  multangular.  The  Flexor  muscles  pull  the  corresponding  part 
of  the  articular  surface  of  the  metacarpal  bone  on  to  this  facet,  and  the  movement  of  opposition 
is  then  carried  out  by  the  Adductors. 

Flexion  of  this  joint  is  produced  by  the  Flexores  poUicis  longus  and  brevis,  assisted  by  the 
Opponens  poUicis  and  the  Adductor  poUicis.  Extension  is  effected  mainly  by  the  abductor 
pollicis  longus,  assisted  by  the  Extensores  pollicis  longus  and  brevis.  Adduction  is  carried  out 
by  the  Adductor;  abduction  mainly  by  the  Abductores  poUicis  longus  and  brevis,  assisted  by  the 
Extensors. 

Articulations  of  the  Other  Four  Metacarpal  Bones  with  the  Carpus  (articulationes 
carpometacarpeae). — The  joints  between  the  carpus  and  the  second,  third,  fourth, 
and  fifth  metacarpal  bones  are  arthrodial.  The  bones  are  united  by  dorsal,  volar, 
and  interosseous  ligaments. 

The  Dorsal  Ligaments  {ligamenta  carpometacarpea  dorsalia) . — The  dorsal  ligaments, 
the  strongest  and  most  distinct,  connect  the  carpal  and  metacarpal  bones  on  their 
dorsal  surfaces.  The  second  metacarpal  bone  receives  two  fasciculi,  one  from  the 
greater,  the  other  from  the  lesser  multangular;  the  third  metacarpal  receives  two, 
one  each  from  the  lesser  multangular  and  capitate;  the  fourth  two,  one  each  from 
the  capitate  and  hamate;  the  fifth  receives  a  single  fasciculus  from  the  hamate, 
and  this  is  continuous  with  a  similar  ligament  on  the  volar  surface,  forming  an 
incomplete  capsule. 

The  Volar  Ligaments  {ligamenta  carpometacarpea  volaria;  palmar  ligaments). — 
The  volar  ligaments  have  a  somewhat  similar  arrangement,  with  the  exception 
of  those  of  the  third  metacarpal,  which  are  three  in  number :  a  lateral  one  from  the 
greater  multangular,  situated  superficial  to  the  sheath  of  the  tendon  of  the  Flexor 
carpi  radialis;  and  intermediate  one  from  the  capitate;  and  a  medial  one  from 
the  hamate. 

The  Interosseous  Ligaments.- — The  interosseous  ligaments  consist  of  short,  thick 
fibres,  and  are  limited  to  one  part  of  the  carpometacarpal  articulation;  they  con- 
nect the  contiguous  inferior  angles  of  the  capitate  and  hamate  with  the  adjacent 
surfaces  of  the  third  and  fourth  metacarpal  bones. 

Synovial  Membrane. — The  synovial  membrane  is  a  continuation  of  that  of  the  intercarpal 
joints.  Occasionally,  the  joint  between  the  hamate  and  the  foiurth  and  fifth  metacarpal  bones 
has  a  separate  synovial  membrane. 


430  SYNDESMOLOGY 

The  synovial  membranes  of  the  wrist  and  carpus  (Fig.  458)  are  thus  seen  to  be  five  in  number. 
The  first  passes  from  the  lower  end  of  the  ulnar  to  the  ulnar  notch  of  the  radius,  and  hues  the  upper 
surface  of  the  articular  disk.  The  second  passes  from  the  articular  disk  and  the  lower  end  of  the 
radius  above,  to  the  bones  of  the  first  row  below.  The  third,  the  most  extensive,  passes  between 
the  contiguous  margins  of  the  two  rows  of  carpal  bones,  and  sometimes,  in  the  event  of  one  of 
the  interosseous  ligaments  being  absent,  between  the  bones  of  the  second  row  to  the  carpal  extremi- 
ties of  the  second,  third,  fourth,  and  fifth  metacarpal  bones.  The  fourth  extends  from  the  margin 
of  the  greater  multangular  to  the  metacarpal  bone  of  the  thumb.  The  fifth  runs  between  the 
adjacent  margins  of  the  triangular  and  pisiform  bones.  Occasionally  the  fourth  and  fifth  carpo- 
metacarpal joints  have  a  separate  synovial  membrane. 

Movements. — The  movements  permitted  in  the  carpometacarpal  articulations  of  the  fingers 
are  hmited  to  slight  gliding  of  the  articular  surfaces  upon  each  other,  the  extent  of  which  varies 
in  the  different  joints.  The  metacarpal  bone  of  the  little  finger  is  most  movable,  then  that  of 
the  ring  finger;  the  metacarpal  bones  of  the  index  and  middle  fingers  are  almost  immovable. 

IX.  Intermetacarpal  Articulations  (Articulationes  Intermetacarpeae ;  Articulations 
of  the  Metacarpal  Bones  with  Each  Other) . 

The  bases  of  the  second,  third,  fourth  and  fifth  metacarpal  bones  articulate 
with  one  another  by  small  surfaces  covered  with  cartilage,  and  are  connected 
together  by  dorsal,  volar,  and  interosseous  ligaments. 

The  dorsal  (ligamenta  hasium  oss.  metacarp.  dorsalia)  and  volar  ligaments  [liga- 
menta  hasium  oss.  metacarp.  volaria;  palmar  ligaments)  pass  transversely  from 
one  bone  to  another  on  the  dorsal  and  volar  surfaces.  The  interosseous  ligaments 
{ligamenta  hasium  oss.  metacarp.  interossea)  connect  their  contiguous  surfaces, 
just  distal  to  their  collateral  articular  facets. 

The  synovial  membrane  for  these  joints  is  continuous  with  that  of  the  carpometacarpal 
articulations. 

The  Transverse  Metacarpal  Ligament  {ligamentum  capitulorum  [oss.  metacarpalium] 
transversum)  (Fig.  459).^ — This  ligament  is  a  narrow  fibrous  band,  which  runs  across 
the  volar  surfaces  of  the  heads  of  the  second,  third,  fourth  and  fifth  meta- 
carpal bones,  connecting  them  together.  It  is  blended  with  the  volar  (glenoid) 
ligaments  of  the  metacarpophalangeal  articulations.  Its  volar  surface  is  concave 
where  the  Flexor  tendons  pass  over  it;  behind  it  the  tendons  of  the  Interossei  pass 
to  their  insertions. 

X.    Metacarpophalangeal  Articulations  (Articulationes  Metacarpophalangeae ; 
Metacarpophalangeal  Joints)   (Figs.  459,  460). 

These  articulations  are  of  the  condyloid  kind,  formed  by  the  reception  of  the 
rounded  heads  of  the  metacarpal  bones  into  shallow  cavities  on  the  proximal  ends 
of  the  first  phalanges,  with  the  exception  of  that  of  the  thumb,  which  presents 
more  of  the  characters  of  a  ginglymoid  joint.  Each  joint  has  a  volar  and  two 
collateral  ligaments. 

The  Volar  Ligaments  {glenoid  ligaments  of  Cruveilhier;  palmar  or  vaginal  ligaments). 
— The  volar  ligaments  are  thick,  dense,  fibrocartilaginous  structures,  placed  upon 
the  volar  surfaces  of  the  joints  in  the  intervals  between  the  collateral  ligaments,  to 
which  they  are  connected ;  they  are  loosely  united  to  the  metacarpal  bones,  but  are 
very  firmly  attached  to  the  bases  of  the  first  phalanges.  Their  volar  surfaces  are 
intimately  blended  with  the  transverse  metacarpal  ligament,  and  present  grooves 
for  the  passage  of  the  Flexor  tendons,  the  sheaths  surrounding  which  are  connected 
to  the  sides  of  the  grooves.  Their  deep  surfaces  form  parts  of  the  articular  facets 
for  the  heads  of  the  metacarpal  bones,  and  are  lined  by  synovial  membranes. 

The  Collateral  Ligaments  {ligameiita  collateralia;  lateral  ligaments). — The  col- 
lateral ligaments  are  strong,  rounded  cords,  placed  on  the  sides  of  the  joints; 
each  is  attached  by  one  extremity  to  the  posterior  tubercle  and  adjacent  depres- 


ARTICULATIONS  OF  THE  DIGITS 


431 


sion  on  the  side  of  the  head  of  the  metacarpul  bone,  and  by  the  other  to  the 
contiguous  extremity  of  the  phalanx. 

The  dorsal  surfaces  of  these  joints  are  covered  by  the  expansions  of  the  Extensor 
tendons,  together  with  some  loose  areolar  tissue  which  connects  the  deep  surfaces 
of  the  tendons  to  tlie  bones. 


Metacarpal  bone 


Transverse 

metacarpal 

ligament 


Groove  for 
Flexor  tendons 


1st  phalanx 


Volar  ligament 


Volar  ligament 


Metacarpa  I 
bone 


Srd  phalanx 


Collateral 
ligament 


Collateral 

'ligament 


Collateral 
ligament 


Fig.  459. — ^Metacarpophalangeal  articulation  and 
articulations  of  digit.     Volar  aspect. 


Fig.    460. — Metacarpophalangeal   articulation   and 
articulations  of  digit.     Ulnar  aspect. 


Movements. — The  movements  which  occur  in  these  jouits  are  flexion,  extension,  adduction, 
abduction,  and  circumduction;  the  movements  of  abduction  and  adduction  are  very  hmited, 
and  cannot  be  performed  when  the  fingers  are  flexed. 


XI.    Articulations  of  the  Digits  (Articulationes  Digitorum  Manus ;  Interphalangeal 

Joints)  (Figs.  459,  460). 

The  interphalangeal  articulations  are  hinge-joints;  each  has  a  volar  and  two 
collateral  ligaments.  The  arrangement  of  these  ligaments  is  similar  to  those  in 
the  metacarpophalangeal  articulations.  The  Extensor  tendons  supply  the  place 
of  posterior  ligaments. 

Movements. — The  only  movements  permitted  in  the  interphalangeal  joints  are  flexion  and 
extension;  these  movements  are  more  extensive  between  the  first  and  second  phalanges  than 
between  the  second  and  third.  The  amount  of  flexion  is  very  considerable,  but  extension  is 
hmited  by  the  volar  and  coUateral  ligaments. 

Muscles  Acting  on  the  Joints  of  the  Digits. — Flexion  of  the  metacarpophalangeal  joints  of  the 
fingers  is  effected  by  the  Flexores  digitorum  subhmis  and  profundus,  Lumbricales,  and  Interossei, 
assisted  in  the  case  of  the  httle  finger  by  the  Flexor  digiti  quinti  brevis.    Extension  is  produced 


432  SYNDESMOLOGY 

by  the  Extensor  digitorum  communis,  Extensor  indicis  proprius,  and  Extensor  digiti  quinti  pro- 
prius. 

Flexion  of  the  interphalangeal  joints  of  the  fingers  is  accompUshed  by  the  Flexor  digitorum 
profundus  acting  on  the  proximal  and  distal  joints  and  by  the  Flexor  digitorum  sublimis  acting 
on  the  proximal  joints.  Extension  is  effected  mainly  by  the  Lumbricales  and  Interossei,  the 
long  Extensors  having  httle  or  no  action  upon  these  joints. 

Flexion  of  the  metacarpophalangeal  joint  of  the  thumb  is  effected  by  the  Flexores  pollicis 
longus  and  brevis;  extension  by  the  Extensores  pollicis  longus  and  brevis.  Flexion  of  the  inter- 
phalangeal joint  is  accompUshed  by  the  Flexor  pollicis  longus,  and  extension  by  the  Extensor 
pollicis  longus. 

ARTICULATIONS   OF   THE   LOWER   EXTREMITY. 

The  articulations  of  the  Lower  Extremity  comprise  the  following: 

I.  Hip.  V.  Intertarsal. 

II.  Knee.  VI.  Tarsometatarsal. 

III.  Tibiofibular.  VII.  Intermetatarsal. 

IV.  Ankle.  VIII.  Metatarsophalangeal. 

IX.  Articulations  of  the  Digits. 

I.     Coxal  Articulation  or  Hip-joint  (Articulatio  Coxae). 

This  articulation  is  an  enarthrodial  or  ball-and-socket  joint,  formed  b}""  the 
reception  of  the  head  of  the  femur  into  the  cup-shaped  cavity  of  the  acetabulum. 
The  articular  cartilage  on  the  head  of  the  femur,  thicker  at  the  centre  than  at  the 
circumference,  covers  the  entire  surface  with  the  exception  of  the  fovea  capitis 
f emoris,  tO  w' hich  the  ligamentum  teres  is  attached ;  that  on  the  acetabulum  forms 
an  incomplete  marginal  ring,  the  lunate  surface.  Within  the  lunate  surface  there 
is  a  circular  depression  devoid  of  cartilage,  occupied  in  the  recent  state  by  a  mass 
of  fat,  covered  by  synovial  membrane.    The  ligaments  of  the  joint  are: 

The  Articular  Capsule.  The  Pubocapsular. 

The  Iliofemoral.  The  Ligamentum  Teres  Femoris. 

The  Ischiocapsular.  The  Glenoidal  Labrum. 

The  Transverse  Acetabular 

The  Articular  Capsule  {capsula  articularis;  capsular  ligament)  (Figs.  442,  443). — 
The  articular  capsule  is  strong  and  dense.  Above,  it  is  attached  to  the  margin 
of  the  acetabulum  5  to  6  mm.  beyond  the  glenoidal  labrum  behind;  but  in  front, 
it  is  attached  to  the  outer  margin  of  the  labrum,  and,  opposite  to  the  notch  where 
the  margin  of  the  cavity  is  deficient,  it  is  connected  to  the  transverse  ligament, 
and  by  a  few  fibres  to  the  edge  of  the  obturator  foramen.  It  surrounds  the  nedk 
of  the  femur,  and  is  attached,  in  front,  to  the  intertrochanteric  line;  above,  to  the 
base  of  the  neck;  behind,  to  the  neck,  about  L25  cm.  above  the  intertrochanteric 
crest;  below,  to  the  lower  part  of  the  neck,  close  to  the  lesser  trochanter.  From 
its  femoral  attachment  some  of  the  fibres  are  reflected  upward  along  the  neck 
as  longitudinal  bands,  termed  retinacula.  The  capsule  is  much  thicker  at  the  upper 
and  forepart  of  the  joint,  where  the  greatest  amount  of  resistance  is  required; 
behind  and  below,  it  is  thin  and  loose.  It  consists  of  two  sets  of  fibres,  circular 
and  longitudinal.  The  circular  fibres,  zona  orbicularis,  are  most  abundant  at  the 
lower  and  back  part  of  the  capsule  (Fig.  463),  and  form  a  sling  or  collar  around  the 
neck  of  the  femur.  Anteriorly  they  blend  with  the  deep  surface  of  the  iliofemoral 
ligament,  and  gain  an  attachment  to  the  anterior  inferior  iliac  spine.  The  longi- 
tudinal fibres  are  greatest  in  amount  at  the  upper  and  front  part  of  the  capsule, 
where  they  are  reinforced  by  distinct  bands,  or  accessory  ligaments,  of  which  the 
most  important  is  the  iliofemoral  ligament.    The  other  accessory  bands  are  knowm 


COXAl.  ARTICILATIOS   Oh'   II IP  JOIST 


433 


as  tlie  pubocapsular  and  tlie  ischiocapsular  ligaments.  "Tlic  external  surface  of  the 
capsule  is  rough,  eo\ere(l  by  numerous  muscles,  and  separated  in  front  from  the 
Psoas  major  and  lliacus  by  a  bursa,  which  not  infrequently  communicates  by  a 
circular  aperture  (Fia;.  442)  with  the  cavity  of  the  joint. 

The  Iliofemoral  Ligament  {llgamenUim  Uiofciiioralc;  Y-llgainriit;  ligdiiieid  of 
B'kjcIow)  (Fig.  4()1).: — The  iliofemoral  ligament  is  a  baud  of  great  strength  which 
lies  in  front  of  the  joint;  it  is  intimately  connected  with  the  capsule,  and  serves 
to  strengthen  it  in  this  situation.  It  is  attached,  above,  to  the  lower  part  of  the 
anterior  inferior  iliac  spine;  below,  it  divides  into  two  bands,  one  of  M'hich  passes 
downward  and  is  fixed  to  the  lower  part  of  the  intertrochanteric  line;  the  other 
is  directed  downward  and  lateralward  and  is  attached  to  the  upper  part  of  the 


Ani.  rnf.  iliac  '<pine~ 


Intertrochanteric 

line  \\         ^  ^A' 


Fig.  461. — Right  hip-joint  from  the  front.      (Spalteholz.) 


same  line.  Between  the  two  bands  is  a  thinner  part  of  the  capsule.  In  some 
cases  there  is  no  division,  and  the  ligament  spreads  out  into  a  flat  triangular  band 
w^hich  is  attached  to  the  w^hole  length  of  the  intertrochanteric  line.  This  ligament 
is  frequently  called  the  Y-shaped  ligament  of  Bigelow;  and  its  upper  band  is  some- 
times named  the  iliotrochanteric  ligament. 

The  Pubocapsular  Ligament  (ligamentum  imhocaysidare;  pubofemoral  ligament). — 
This  ligament  is  attached,  above,  to  the  obturator  crest  and  the  superior  ramus 
of  the  pubis;  below,  it  blends  with  the  capsule  and  with  the  deep  surface  of  the 
vertical  band  of  the  iliofemoral  ligament. 

The  Ischiocapsular  Ligament  (ligamentum   ischioca'psulare;    ischiocapsular   band; 
ligament  of  Berlin) . — The  ischiocapsular  ligament  consists  of  a  triangular  band  of 
strong  fibres,  which  spring  from  the  ischium  below  and  behind  the  acetabulum, 
and  blend  with  the  circular  fibres  of  the  capsule. 
28 


434 


SYNDESMOLOGY 


The  Ligamentum  Teres  Ferhoris  (Fig.  4G2). — The  ligamentum  teres  femoris  is  a 
triangular,  somewhat  flattened  band  implanted  by  its  apex  into  the  antero-superior 
part  of  the  fovea  capitis  femoris;  its  base  is  attached  by  two  bands,  one  into  either 
side  of  the  acetabular  notch,  and  between  these  bony  attachments  it  blends  with  the 
transverse  ligament.  It  is  ensheathed  Ijy  the  synovial  membrane,  and  varies  greatly 
in  strength  in  dift'erent  subjects;  occasionally  only  the  synovial  fold  exists,  and  in 
rare  cases  even  this  is  absent.  The  ligament  is  made  tense  when  the  thigh  is 
semiflexed  and  the  limb  then  adducted  or  rotated  outward;  it  is,  on  the  other 
hand,  relaxed  when  the  limb  is  abducted.  It  has,  however,  but  little  influence  as  a 
ligament. 


Spine  of 
ischiutu 


i  ovea  capitis 


Lesser  trochanter %r:    \,  , 


Fig.  462. — Left  hip-joint,  opened  b3'  removing  the  floor  of  the  acetabulum  from  within  the  pelvis. 


The  Glenoidal  Labium  (labrum  glenoidale;  cotyloid  ligament). — The  glenoidal 
labrum  is  a  fibrocartilaginous  rim  attached  to  the  margin  of  the  acetabulum,  the 
cavity  of  which  it  deepens ;  at  the  same  time  it  protects  the  edge  of  the  bone,  and 
fills  up  the  inequalities  of  its  surface.  It  bridges  over  the  notch  as  the  transverse 
ligament,  and  thus  forms  a  complete  circle,  which  closely  surrounds  the  head  of  the 
femur  and  assists  in  holding  it  in  its  place.  It  is  triangular  on  section,  its  base  being 
attached  to  the  margin  of  the  acetabulum,  while  its  opposite  edge  is  free  and 
sharp.  Its  two  surfaces  are  invested  by  synovial  membrane,  the  external  one 
being  in  contact  with  the  capsule,  the  internal  one  being  inclined  inward  so  as 
to  narroAv  the  acetabulum,  and  embrace  the  cartilaginous  surface  of  the  head  of 
the  femur.  It  is  much  thicker  above  and  behind  than  below  and  in  front,  and 
consists  of  compact  fibres. 

The  Transverse  Acetabular  Ligament  {ligamentum  transver sum  acetahuli;  transverse 
ligament). — This  ligament  is  in  reality  a  portion  of  the  glenoidal  labrum,  though 
differing  from  it  in  having  no  cartilage  cells  among  its  fibres.    It  consists  of  strong, 


coxAL  AirncrLATiox  or  IUP-.IOIXT 


435 


flattened  fibres,  which  cross  the  acetabuhir  notch,  and  convert  it  into  a  foramen 
through  wliich  the  nutrient  vessels  enter  the  joint. 

Synovial  Membrane  (Fig.  463). — The  synovial  nioinhianc  is  very  extensive.  Commencing 
at  the  margin  of  the  cartilaginous  surface  of  the  head  of  the  femur,  it  covers  the  portion  of  the 
neck  which  is  contained  within  the  joint;  from  the  neck  it  is  reflected  on  the  internal  surface  of 
the  capsule,  covers  both  surfaces  of  the  glenoidal  labrum  and  the  mass  of  fat  contained  in  the 
depression  at  the  bottom  of  the  acetabulum,  and  ensheathes  the  ligamentum  teres  as  far  as  the 
head  of  the  femiu".  The  joint  cavity  sometimes  communicates  through  a  hole  in  the  capsule 
between  the  vertical  band  of  the  iliofemoral  ligament  and  the  pubocapsular  ligament  with  a  bur.sa 
situated  on  the  deep  surfaces  of  the  Psoas  major  and  lliacus. 


Spine  of 
ischium 


Capsule 

Greater  irochonier 


Fig.  463. — Capsule  of  hip-joint  (distended).     Posterior  aspect. 

The  muscles  in  relation  with  the  joint  are,  in  front,  the  Psoas  major  and  Ihacus,  separated 
from  the  capsule  by  a  bursa;  above,  the  reflected  head  of  the  Rectus  femoris  and  Glutaeus  minimus, 
the  latter  being  closely  adherent  to  the  capsule;  medially,  the  Obturator  externus  and  Pectineus; 
behind,  the  Piriformis,  Gemellus  superior,  Obtui-ator  internus,  Gemellus  inferior,  Obturator 
externus,  and  Quadratus  femoris  (Fig.  464). 

The  arteries  supphdng  the  joint  are  derived  from  the  obturator,  medial  femoral  circumflex, 
and  superior  and  inferior  gluteals. 

The  nerves  are  articular  branches  from  the  sacral  plexus,  sciatic,  obturator,  accessory  obturator, 
and  a  filament  from  the  branch  of  the  femoral  supplying  the  Rectus  femoris. 

Movements. — The  movements  of  the  hip  are  very  extensive,  and  consist  of  flexion,  extension, 
adduction,  abduction,  circvmiduction,  and  rotation. 

The  length  of  the  neck  of  the  femm-  and  its  inclinations  to  the  body  of  the  bone  have  the 
effect  of  converting  the  angular  movements  of  flexion,  extension,  adduction,  and  abduction  par- 
tially into  rotatory  movements  in  the  joint.  Thus  when  the  thigh  is  flexed  or  extended,  the 
head  of  the  femur,  on  accoimt  of  the  medial  incUnation  of  the  neck,  rotates  within  the  acetabidum 
with  only  a  slight  amomit  of  gliding  to  and  fro.  The  forward  slope  of  the  neck  similar Ij'  affects 
the  movements  of  adduction  and  abduction.  Conversely  rotation  of  the  thigh  which  is  permitted 
by  the  upward  inchnation  of  the  neck,  is  not  a  simple  rotation  of  the  head  of  the  femm"  in  the 
acetabulum,  but  is  accompanied  by  a  certain  amount  of  gliding. 


436 


SYNDESMOLOGY 


The  hip-joint  presents  a  very  striking  contrast  to  the  shoukler-joint  in  the  much  more  com- 
plete mechanical  arrangements  for  its  secm-ity  and  for  the  limitation  of  its  movements.  In  the 
shoulder,  as  has  been  seen,  the  head  of  the  humerus  is  not  adapted  at  all  in  size  to  the  glenoid 
cavity,  and  is  hardly  restrained  in  any  of  its  ordinary  movements  by  the  capsule.  In  the  hip- 
joint,  on  the  contrary,  the  head  of  the  femur  is  closely  fitted  to  the  acetabulum  for  an  area  extend- 
ing over  nearly  half  a  sphere,  and  at  the  margin  of  the  bony  cup  it  is  still  more  closely  embraced 
by  the  glenoidal  labrum,  so  that  the  head  of  the  femur  is  held  in  its  place  by  that  ligament  even 
when  the  fibres  of  the  capsule  have  been  quite  divided.  The  iliofemoral  ligament  is  the  strongest 
of  all  the  ligaments  in  the  body,  and  is  put  on  the  stretch  by  any  attempt  to  extend  the  femur 
beyond  a  straight  line  with  the  trunk.  That  is  to  say,  this  ligament  is  the  chief  agent  in  main- 
taining the  erect  position  without  muscular  fatigue;  for  a  vertical  line  passing  through  the  centre 
of  gravity  of  the  trunk  falls  behind  the  centres  of  rotation  in  the  hip-joints,  and  therefore  the 
pelvis  tends  to  fall  backward,  but  is  prevented  by  the  tension  of  the  iliofemoral  ligaments.  The 
security  of  the  joint  may  be  provided  for  also  by  the  two  bones  being  directly  united  through  the 
ligamentum  teres;  but  it  is  doubtful  whether  this  ligament  has  much  influence  upon  the  mechanism 


Femoral  artery 


Fevioral  nerve 
Iliofemoral  ligament 
Rectus  fcmoris 


Femoral  vein 

Ligam,enitim  teres 


Piriformis 


Sciatic  nerve 

Obturator  interiius 
Fig.  464. — Structures  surrounding  right  hip-joint. 


of  the  joint.  When  the  knee  is  flexed,  flexion  of  the  hip-joint  is  arrested  by  the  soft  parts  of  the 
thigh  and  abdomen  being  brought  into  contact,  and  when  the  knee  is  extended,  by  the  action  of 
the  hamstring  muscles;  extension  is  checked  by  the  tension  of  the  iliofemoral  ligament;  adduc- 
tion by  the  thighs  coming  into  contact;  adduction  with  flexion  by  the  lateral  band  of  the  ilio- 
femoral ligament  and  the  lateral  part  of  the  capsule;  abduction  by  the  medial  band  of  the 
iliofemoral  Ugament  and  the  pubocapsular  Ugament ;  rotation  outward  by  the  lateral  band  of  the 
iliofemoral  ligament;  and  rotation  inward  by  the  ischiocapsular  ligament  and  the  hinder  part  of 
the  capsule.  The  muscles  which  flex  the  femur  on  the  pelvis  are  the  Psoas  major,  Iliacus,  Rectus 
femoris,  Sartorius,  Pectineus,  Adductores  longus  and  brevis,  and  the  anterior  fibres  of  the  Glutaei 
medius  and  minimus.  Extension  is  mainly  performed  by  the  Glutaeus  maximus,  assisted  by  the 
hamstring  muscles  and  the  ischial  head  of  the  Adductor  magnus.  The  thigh  is  adducted  by  the 
Adductores  magnus,  longus,  and  brevis,  the  Pectineus,  the  Gracilis,  and  lower  part  of  the  Glutaeus 
maximus,  and  abducted  by  the  Glutaei  medius  and  minimus,  and  the  upper  part  of  the  Glutaeus 
maximus.  The  muscles  which  rotate  the  thigh  inward  are  the  Glutaeus  minimus  and  the  anterior 
fibres  of  the  Glutaeus  medius,  the  Tensor  fasciae  latae  and  the  Iliacus  and  Psoas  major;  while 


COXAL  AHTK'i'LATIOS  OR  Jill'  Ji)L\T 


487 


those  which  rotate  it  oulinird  arc  tlic  po.sti'ritjr  libros  of  the  (Jlutaeus  medius,  the  Piriiormis, 
Obturatores  externus  aiui  interims,  Gemelh  superior  and  inferior,  Quadratus  femoris,  (Uutaeus 
maximus,  the  Adductores  longus,  brevis,  and  niagnus,  the  Pectineus,  and  the  Sartorius. 

Applied  Anatomy.— In  dislocation  of  the  hip,  "the  head  of  the  tliigh  bone  may  rest  at  any 
point  around  its  socket"  (liryant);  but  whatever  position  it  ultimately  assumes,  the  i)rimary 
displacement  is  generally  downward  and  medialward,  th(^  capsule  giving  way  at  its  weakest — 
that  is,  its  lower  and  medial — i)art.  The  situation  that  the  head  of  the  bone  subsequently  assumes 
is  determined  by  the  degree  of  flexion  or  extension,  and  of  outward  or  inward  rotation  of  the 
thigh  at  the  moment  of  luxation,  influenced,  no  doubt,  by  the  iliofemoral  ligament,  which  is  not 
easily  ruptured.  When,  for  instance,  the  head  of  the  bone  is  forced  backward,  this  ligament 
forms  a  fixed  axis,  around  which  the  head  of  the  bone  rotates,  and  is  thus  driven  on  to  the  dorsum 
of  the  ilium.  The  iliofemoral  ligament  also  influences  the  position  of  the  thigh  in  the  various 
dislocations;  in  the  dislocations  backward  it  is  tense,  and  produces  inversion  of  the  limb;  in  the 
dislocation  on  to  the  pubis,  it  is  relaxed,  and  therefore  allows  the  external  rotators  to  evert  the 
thigh;  while  in  dislocation  into  the  obturator  foramen  it  is  tense,  and  produces  flexion.  The 
muscles  inserted  into  the  upper  part  of  the  femur,  with  the  exception  of  the  Obturator  internus, 
have  very  little  direct  influence  in  determining  the  position  of  the  head  of  the  bone.  Bigelow, 
however,  has  endeavored  to  show  that  the  Obturator  internus  is  the  principal  agent  in  deciding 
whether,  in  the  backward  dislocations,  the  head  of  the  bone  shall  be  ultimately  lodged  on  the 
dorsum  of  the  ilium,  or  in  or   near  the  greater  sciatic 

notch;  in  both  dislocations  the  head  passes,  in  the  first  --— ' 

instance,  in  the  same  direction;  but,  as  Bigelow  asserts, 
in  the  displacement  on  to  the  dorsum  the  head  of  the 
bone  travels  up  behind  the  acetabulum,  in  front  of  the 
muscle;  while  in  the  dislocation  into  the  greater  sciatic 
notch  the  head  passes  behind  the  muscle,  and  is  pre- 
vented from  reaching  the  dorsum,  in  consequence  of  the 
tendon  of  the  muscle  arching  over  the  neck  of  the  bone, 
and  it  therefore  remains  in  the  neighborhood  of  the 
notch.  Bigelow  distinguishes  these  two  forms  of  dis- 
location by  describing  them  as  dislocations  backward, 
"above  and  below"  the  Obturator  internus. 

The  iliofemoral  ligament  is  rarely  torn  in  dislocations 
of  the  hip,  and  this  fact  is  taken  advantage  of  by  the 
surgeon  in  reducing  these  dislocations  by  manipulation. 
It  is  made  to  act  as  the  fulcrum  to  a  lever,  of  which 
the  long  arm  is  the  body  of  the  femur,  and  the  short 
arm  the  neck  of  the  bone  (Fig.  465). 

The  hip-joint  is  rarely  the  seat  of  acute  synovitis 
from  injury,  on  account  of  its  deep  position  and  its 
thick  covering  of  soft  parts.  Acute  inflammation  may, 
and  does,  frequently  occur  as  the  result  of  bacterial 
infections,  as  in  rheumatism,  pyemia,  etc.  When,  in 
these  cases,  effusion  takes  place,  and  the  joint  is  dis- 
tended with  fluid,  the  swelling  is  not  very  easy  to  detect 
on  account  of  the  thickness  of  the  capsule  and  the  depth 
of  the  articulation.  It  is  principally  to  be  found  on  the 
front  of  the  joint,  just  medial  to  the  iliofemoral  liga- 
ment; or  behind,  at  the  lower  and  back  part.  In  these 
two  places  the  capsule  is  thinner  than  elsewhere.  Dis- 
ease of  the  hip-joint  is  much  oftenerof  a  chronic  char- 
acter, and  is  usually  of  tuberculous  origin.  It  begins  usually  in  the  bone,  and,  in  most  cases, 
in  the  growing,  highly  vascular  tissue  in  the  neighborhood  of  the  epiphysial  cartilage  of  the 
femoral  head.  In  this  respect  it  differs  very  materially  from  tuberculous  arthritis  of  the  knee, 
where  the  disease  usually  commences  in  the  synovial  membrane. 

In  chronic  hip  disease  the  affected  limb  assumes  an  altered  position,  the  cause  of  which  it  is 
important  to  understand.  In  the  early  stage  of  a  typical  case,  the  limb  is  flexed,  abducted,  and 
rotated  outward.  In  this  position  all  the  ligaments  of  the  joint  are  relaxed;  the  front  of  the 
capsule  by  flexion;  the  lateral  band  of  the  iliofemoral  ligament  by  abduction;  and  the  medial 
band  of  this  ligament  and  the  back  of  the  capsule  by  rotation  outward.  It  is,  therefore,  the 
position  of  greatest  ease.  The  condition  is  not  quite  obvious  at  first,  upon  examining  a  patient. 
If  the  patient  be  laid  in  the  supine  position,  the  affected  limb  will  be  found  to  be  extended  and 
parallel  with  the  other.  But  it  will  be  seen  that  the  pelvis  is  tilted  downward  on  the  diseased 
side  and  the  limb  apparently  longer  than  its  fellow,  and  that  the  lumbar  portion  of  the  vertebral 
column  is  arched  forward  (lordosis).  The  condition  is  thus  explained:  a  limb  which  is  flexed 
and  abducted  is  obviously  useless  for  progression,  and  in  order  to  overcome  the  difficulty  the 


Fig. 


465. — Hip-joint,  showing  the   iHofemoral 
ligament.     (After  Bigelow.) 


438  SYNDESMOLOGY 

patient  depresses  the  affected  side  of  liis  pelvis,  thus  producing  parallehsni  of  his  hmbs,  and  at 
the  same  time  rotates  his  pelvis  on  its  transverse  horizontal  axis,  so  as  to  direct  the  limb  down- 
ward, instead  of  forward.  In  the  later  stages  of  the  disease  the  limb  becomes  flexed  and  adducted 
and  inverted.  This  position  probably  depends  upon  muscular  action,  at  all  events  as  regards 
the  adduction.  The  Adductor  muscles  are  supplied  by  the  obturator  nerve,  which  also  largely 
supplies  the  joint.  These  muscles  are  therefore  thrown  into  reflex  spasm  by  the  irritation  of 
the  peripheral  terminations  of  this  nerve  in  the  inflamed  articulation. 

Osteoarthritis  is  common  in  the  hip-joint,  and  more  so  in  the  male  than  in  the  female,  in  whom 
the  knee-joint  is  more  frequently  affected.  It  is  a  disease  of  middle  age  or  advanced  life.  When 
much  deformity  is  associated  with  chronic  osteoarthritis  the  condition  is  spoken  of  as  arthritis 
deformans  of  the  hip,  or  morbus  coxae  senilis.  The  head  of  the  femur  is  worn  away,  and  after  it 
often  the  neck  too,  until  a  new  irregular  articular  surface  is  produced,  around  which  a  new  forma- 
tion of  bone  occurs,  and  also  about  the  edges  of  the  acetabulum,  which  is  widened  and  eroded 
by  a  similar  chronic  process.  Pain  in  the  joint,  shortening  of  the  limb,  and  great  limitation  of 
movement  result,  with  much  creaking  and  grating  when  the  joint  is  moved. 

Congenital  dislocation  is  more  commonly  met  with  in  the  hip-joint  than  in  any  other  articula- 
tion. The  displacement  usually  takes  place  on  to  the  dorsum  ilii.  It  gives  rise  to  extreme  lordosis 
and  a  waddling  gait  is  noticed  as  soon  as  the  child  commences  to  walk. 

Excision  of  the  hip  may  be  required  for  disease  or  for  injury,  especially  gunshot.  It  may  be 
performed  either  by  an  anterior  or  a  posterior  incision.  The  former  entails  less  interference  with 
important  structures,  especially  muscles,  than  the  latter,  but  permits  of  less  efficient  drainage. 
In  the  operation  from  the  front,  an  incision  is  made  8  to  10  cm.  in  length,  starting  immediately 
below  and  lateral  to  the  anterior  superior  iliac  spine,  downward  between  the  Sartorius  and  Tensor 
fasciae  latae,  to  the  neck  of  the  bone,  dividing  the  capsule  at  its  upper  part.  The  neck  of  the 
femur  is  then  divided,  and  the  head  of  the  bone  extracted.  All  diseased  tissue  is  carefully  removed 
with  a  sharp  spoon  or  scissors,  and  the  cavity  thoroughly  flushed  out  with  a  hot  antiseptic  or 
sterile  fluid.  The  posterior  method  consists  in  making  an  incision  8  to  10  cm.  long  commencing 
midway  between  the  top  of  the  greater  trochanter  and  the  iliac  crest,  and  extending  down  the 
posterior  border  of  the  trochanter.  The  muscles  are  detached  from  the  greater  trochanter,  and 
the  capsule  opened  freely.  The  head  and  neck  are  freed  from  the  soft  parts  and  as  much  affected 
bone  removed  as  is  thought  necessary.    The  head  of  the  bone  is  then  levered  out  of  the  acetabulum. 

11.     The  Knee-joint  (Articulatio  Genu). 

The  knee-joint  was  formerly  described  as  a  ginglymus  or  hinge-joint,  but  is 
really  of  a  much  more  complicated  character.  It  must  be  regarded  as  consisting 
of  three  articulations  in  one:  two  condyloid  joints,  one  between  each  condyle 
of  the  femur  and  the  corresponding  meniscus  and  condyle  of  the  tibia;  and  a  third 
between  the  patella  and  the  femur,  partly  arthrodial,  but  not  completely  so, 
since  the  articular  surfaces  are  not  mutually  adapted  to  each  other,  so  that  the 
movement  is  not  a  simple  gliding  one.  This  view  of  the  construction  of  the  knee- 
joint  receives  confirmation  from  the  study  of  the  articulation  in  some  of  the  lower 
mammals,  where,  corresponding  to  these  three  subdivisions,  three  synovial  cavities 
are  sometimes  found,  either  entirely  distinct  or  only  connected  together  by  small 
communications.  This  view  is  further  rendered  probable  by  the  existence  in  the 
middle  of  the  joint  of  the  two  cruciate  ligaments,  which  must  be  regarded  as 
the  collateral  ligaments  of  the  medial  and  lateral  joints.  The  existence  of  the 
patellar  fold  of  synovial  membrane  would  further  indicate  a  tendency  to  separa- 
tion of  the  synovial  cavity  into  two  minor  sacs,  one  corresponding  to  the  lateral 
and  the  other  to  the  medial  joint. 

The  bones  are  connected  together  by  the  following  ligaments: 

The  Articular  Capsule.  The  Anterior  Cruciate. 

The  Ligamentum  Patellae.  The  Posterior  Cruciate. 

The  Oblique  Popliteal.  The  Medial  and  Lateral  Menisci. 

The  Tibial  Collateral.  The  Transverse. 

The  Fibular  Collateral.  The  Coronary. 

The  Articular  Capsule  {capsula  articularis;  capsular  ligament)  (Fig.  466). — The 
articular  capsule  consists  of  a  thin,  but  strong,  fibrous  membrane  which  is  strength- 
ened in  almost  its  entire  extent  by  bands  inseparably  connected  with  it.    Above 


THE  KNEE-JOINT 


439 


and  in  front,  beneath  the  tendon  of  the  Quadriceios  femoris,  it  is  represented  only 
by  the  synovial  membrane.  Its  chief  strengthening  bands  are  derived  from  the 
fascia  hita  and  from  the  tendons  siirrounchng  the  joint.  In  front,  expansions 
from  the  Vasti  and  from  the  fascia  hita  and  its  ihotibial  band  fill  in  the  intervals 
between  the  anterior  and  collateral  ligaments,  constituting  the  medial  and  lateral 
patellar  retinacula.  Behind  the  capsule  consists  of  vertical  fibres  which  arise 
from  the  condyles  and  from  the  sides  of  the  intercondyloid  fossa  of  the  femur; 
the  posterior  part  of  the  capsule  is  therefore 
situated  on  the  sides  of  ancl  in  front  of  the 
cruciate  ligaments,  which  are  thus  excluded  from 
the  joint  cavity.  Behind  the  cruciate  ligaments 
is  the  oblique  popliteal  ligament  which  is  aug- 
mented by  fibres  derived  from  the  tendon  of  the 
Semimembranosus.  Laterally,  a  prolongation 
from  the  iliotibial  band  fills  in  the  interval  be- 
tween the  oblique  popliteal  and  the  fibular  collat- 
eral ligaments,  and  partly  covers  the  latter. 
Medially,  expansions  from  the  Sartorius  and 
Semimembranosus  pass  upward  to  the  tibial 
collateral  ligament  and  strengthen  the  capsule. 

The  Ligamentum  Patellae  {anterior  ligament) 
(Fig.  466) . — The  ligamentum  patellae  is  the  cen- 
tral portion  of  the  common  tendon  of  the  Quad- 
riceps femoris,  which  is  continued  from  the 
patella  to  the  tuberosity  of  the  tibia.  It  is  a 
strong,  flat,  ligamentous  band,  about  8  cm.  in 
length,  attached,  above,  to  the  apex  and  adjoin- 
ing margins  of  the  patella  and  the  rough  depres- 
sion on  its  posterior  surface ;  below,  to  the 
tuberosity  of  the  tibia;  its  superficial  fibres  are 
continuous  over  the  front  of  the  patella  with 
those  of  the  tendon  of  the  Quadriceps  femoris. 
The  medial  and  lateral  portions  of  the  tendon 
of  the  Quadriceps  pass  down  on  either  side  of 
the  patella,  to  be  inserted  into  the  upper  extremity 
of  the  tibia  on  either  side  of  the  tuberosity;  these 
portions  merge  into  the  capsule,  as  stated  above, 

forming  the  medial  and  lateral  patellar  retinacula.  The  posterior  surface  of  the 
ligamentum  patellae  is  separated  from  the  synovial  membrane  of  the  joint  by  a 
large  infrapatellar  pad  of  fat,  and  from  the  tibia  by  a  bursa. 

The  Oblique  Popliteal  Ligament  {ligamentum  popliteum  obliquum;  posterior  liga- 
ment) (Fig.  467). — This  ligament  is  a  broad,  flat,  fibrous  band,  formed  of  fasciculi 
separated  from  one  another  by  apertures  for  the  passage  of  vessels  and  nerves. 
It  is  attached  above  to  the  upper  margin  of  the  intercondyloid  fossa  and  posterior 
surface  of  the  femur  close  to  the  articular  margins  of  the  condyles,  and  below  to 
the  posterior  margin  of  the  head  of  the  tibia.  Superficial  to  the  main  part  of  the 
ligament  is  a  strong  fasciculus,  derived  from  the  tendon  of  the  Semimembranosus 
and  passing  from  the  back  part  of  the  medial  condyle  of  the  tibia  obliquely  upward 
and  lateralward  to  the  back  part  of  the  lateral  condyle  of  the  femur.  The  oblique 
popliteal  ligament  forms  part  of  the  floor  of  the  popliteal  fossa,  and  the  popliteal 
artery  rests  upon  it. 

The  Tibial  Collateral  Ligament  {ligamentum  collaterale  tibiale;  internal  lateral  liga- 
ment) (Fig.  466). — The  tibial  collateral  is  a  broad,  flat,  membranous  band,  situated 
nearer  to  the  back  than  to  the  front  of  the  joint.    It  is  attached,  above,  to  the  medial 


Fig. 


466. — Right  knee-joint, 
view. 


440 


SYNDESMOLOGY 


condyle  of  the  femur  immediately  below  the  adductor  tubercle;  below,  to  the  medial 
condyle  and  medial  surface  of  the  body  of  the  tibia.  The  fibres  of  the  posterior 
part  of  the  ligament  are  short  and  incline  backward  as  they  descend;  they  are 
inserted  into  the  tibia  above  the  groove  for  the  Semimembranosus.  The  anterior 
part  of  the  ligament  is  a  flattened  band,  about  10  cm.  long,  which  inclines  forward 
as  it  descends.  It  is  inserted  into  the  medial  surface  of  the  body  of  the  tibia  about 
2.5  cm.  below  the  level  of  the  condyle.  It  is  crossed,  at  its  lower  part,  by  the 
tendons  of  the  Sartorius,  Gracilis,  and  Semitendinosus,  a  bursa  being  interposed. 
Its  deep  surface  covers  the  inferior  medial  genicular  A'^essels  and  nerve  and  the 
anterior  portion  of  the  tendon  of  the  Semimembranosus,  w^ith  which  it  is  connected 
by  a  few  fibres;  it  is  intimately  adherent  to  the  medial  meniscus. 


Fig.  46/. — Right  knee-joint.     Posterior  view. 


Fig.  468. — Right  knee-joint,  from  the  front, 
showing  interior  ligaments. 


The  Fibular  Collateral  Ligament  {ligamentuin  coUaterale  fibidare;  external  lateral  or 
long  external  lateral  ligament)  (Fig.  469). — The  fibular  collateral  is  a  strong,  rounded, 
fibrous  cord,  attached,  above,  to  the  back  part  of  the  lateral  condyle  of  the  femur, 
immediately  above  the  groove  for  the  tendon  of  the  Popliteus;  below,  to  the  lateral 
side  of  the  head  of  the  fibula,  in  front  of  the  styloid  process.  The  greater  part  of 
its  lateral  surface  is  covered  by  the  tendon  of  the  Biceps  femoris;  the  tendon, 
however,  divides  at  its  insertion  into  two  parts,  which  are  separated  by  the  liga- 
ment. Deep  to  the  ligament  are  the  tendon  of  the  Popliteus,  and  the  inferior 
lateral  genicular  vessels  and  nerve.  The  ligament  has  no  attachment  to  the  lateral 
meniscus. 

An  incon.stant  bundle  of  fibres,  the  short  fibular  collateral  ligament,  is  placed  behind  and 
parallel  with  the  preceding,  attached,  above,  to  the  lower  and  back  part  of  the  lateral  condyle 
of  the  femur;  beloit,  to  the  summit  of  the  styloid  process  of  the  fibula.  Passing  deep  to  it  are 
the  tendon  of  the  Popliteus,  and  the  inferior  lateral  genicular  vessels  and  nerve. 


77/A'  KSEE-JOIST 


441 


The  Cruciate  Ligaments  {ligdinciita  cruciata  genu;  crucial  lu/ainenh-). — The  cru- 
ciate ligaments  are  t)f  considerable  streiifj;th,  situated  in  the  middle  of  the  joint, 
nearer  to  its  posterior  than  to  its  anterior  surface.  They  are  called  cruciate  because 
they  cross  each  other  somewhat  like  the  lines  of  the  letter  X;  and  have  received 
the  names  anterior  and  posterior,  from  the  i)osition  of  their  attachments  to  the 
tibia. 

The  Anterior  Cruciate  Ligament  [ligantcithnii  cniciatuiii  anfcria-s-;  e.vfcnial  crucial 
ligament)  (Fig.  408)  is  attached  to  the  depression  in  front  of  the  intercondyloid 
eminence  of  the  tibia,  being  blended  with  the  anterior  extremity  of  the  lateral 
meniscus;  it  passes  upward,  backward,  and  lateralward,  and  is  fixed  into  the  medial 
and  back  part  of  the  lateral  condyle  of  the  femur. 


Ant.  cruc iateligament 
Te>ulo7i  of  Popliteu-s 

Lateral  meniscus 

Fibular  collateral 
ligament 


Ligament  of 
Wrisherg 

Medial  meniscu^i 

Tibial  collateral 
ligament 


Fig.  469. — Left  knee-joint  from  behind,  phoning  inteiior  ligaments. 

The  Posterior  Cruciate  Ligament  (ligamentum  cruciatum  posterius;  internal  crucial 
ligament)  (Fig.  469)  is  stronger,  but  shorter  and  less  oblique  in  its  direction,  than 
the  anterior.  It  is  attached  to  the  posterior  intercondyloid  fossa  of  the  tibia,  and 
to  the  posterior  extremity  of  the  lateral  meniscus;  and  passes  upward,  forAvard, 
and  medialward,  to  be  fixed  into  the  lateral  and  front  part  of  the  medial  condyle 
of  the  femur. 

The  Menisci  [semilunar  fihrocartilages)  (Fig.  470). — The  menisci  are  two  crescentic 
lamella?,  which  serve  to  deepen  the  surfaces  of  the  head  of  the  tibia  for  articulation 
with  the  condyles  of  the  femur.  The  peripheral  border  of  each  meniscus  is  thick, 
convex,  and  attached  to  the  inside  of  the  capsule  of  the  joint;  the  opposite  border 
is  thin,  concave,  and  free.  The  upper  surfaces  of  the  menisci  are  concave,  and 
in  contact  with  the  condyles  of  the  femur;  their  lower  surfaces  are  flat,  and  rest 
upon  the  head  of  the  tibia;  both  surfaces  are  smooth,  and  invested  by  synovial 
membrane.  Each  meniscus  covers  approximately  the  peripheral  two-thirds  of 
the  corresponding  articular  surface  of  the  tibia. 


442 


SYNDESMOLOGY 


The  medial  meniscus  (meniscus  medialis;  internal  semilunar  fibrocartilage)  is 
nearly  semicircular  in  form,  a  little  elongated  from  before  backward,  and  broader 
behind  than  in  front;  its  anterior  end,  thin  and  pointed,  is  attached  to  the  anterior 
intercondyloid  fossa  of  the  tibia,  in  front  of  the  anterior  cruciate  ligament;  its 
posterior  end  is  fixed  to  the  posterior  intercondyloid  fossa  of  the  tibia,  between 
the  attachments  of  the  lateral  meniscus  and  the  posterior  cruciate  ligament. 


Anterior  cruciate  ligament 


Transverse  ligament 


I   Ligament  of  Wrishcrg 
Posterior  cruciate  ligament 

Fig.  470. — Head  of  right  tibia  seen  from  above,  showing  menisci  and  attachments  of  ligaments. 


The  lateral  meniscus  (meniscus  lateralis;  external  semilunar  fibrocartilage)  is  nearly 
circular  and  covers  a  larger  portion  of  the  articular  surface  than  the  medial  one. 
It  i&  grooved  laterally  for  the  tendon  of  the  Popliteus,  which  separates  it  from  the 
fibular  collateral  ligament.  Its  anterior  end  is  attached  in  front  of  the  intercon- 
dyloid eminence  of  the  tibia,  lateral  to,  and  behind,  the  anterior  cruciate  ligament, 
with  which  it  blends;  the  posterior  end  is  attached  behind  the  intercondyloid 
eminence  of  the  tibia  and  in  front  of  the  posterior  end  of  the  medial  meniscus. 
The  anterior  attachment  of  the  lateral  meniscus  is  twisted  on  itself  so  that  its 
free  margin  looks  backward  and  upward,  its  anterior  end  resting  on  a  sloping 
shelf  of  bone  on  the  front  of  the  lateral  process  of  the  intercondyloid  eminence. 
Close  to  its  posterior  attachment  it  sends  off  a  strong  fasciculus,  the  ligament  of 
Wrisberg  (Figs.  469,  470),  w^hich  passes  upward  and  medialward,  to  be  inserted 
into  the  medial  condyle  of  the  femur,  immediately  behind  the  attachment  of  the 
posterior  cruciate  ligament.  Occasionally  a  small  fasciculus  passes  forward  to 
be  inserted  into  the  lateral  part  of  the  anterior  cruciate  ligament.  The  lateral 
meniscus  gives  off  from  its  anterior  convex  margin  a  fasciculus  which  forms  the 
transverse  ligament. 

The  Transverse  Ligament  (ligamentum  transversuvi  genu).- — The  transverse  liga- 
ment connects  the  anterior  convex  margin  of  the  lateral  meniscus  to  the  anterior 
end  of  the  medial  meniscus;  its  thickness  varies  considerably  in  different  subjects, 
and  it  is  sometimes  absent. 

The  coronary  ligaments  are  merely  portions  of  the  capsule,  which  connect  the 
periphery  of  each  meniscus  with  the  margin  of  the  head  of  the  tibia. 

Synovial  Membrane. — The  synovial  membrane  of  the  knee-joint  is  the  largest  and  most  exten- 
sive in  the  body.  Commencing  at  the  upper  border  of  the  patella,  it  forms  a  large  cul-de-sac 
beneath  the  Quadriceps  femoris  (Figs.  471,  472)  on  the  lower  part  of  the  front  of  the  femur, 
and  frequently  communicates  with  a  bursa  interposed  between  the  tendon  and  the  front  of  the 
femur.  The  pouch  of  synovial  membrane  between  the  Quadriceps  and  front  of  the  femur  is 
supported,  during  the  movements  of  the  knee,  by  a  small  muscle,  the  Articularis  genu,  which 


THE  KXEE-JOIXT 


443 


is  inserted  into  it.  On  either  side  of  the  patella,  the  synovial  membrane  extends  beneath  the 
aponem-oses  of  the  \'asti,  and  more  especially  beneath  that  of  the  Va-stus  medialLs.  Below  the 
patella  it  is  separated  from  the  ligamentum  patellae  by  a  considerable  quantity  of  fat.  known  as 
the  infrapatellar  pad.  From  the  medial  and  lateral  borders  of  the  articular  surface  of  the  patella, 
reduplications  of  the  synovial  momljrane  project  into  the  interior  of  the  joint.  These  form  two 
fringe-hke  folds  termed  the  alar  folds;  below,  these  folds  converge  and  are  continued  as  a  single 
band,  the  patellar  fold  (ligamcnluin  mucosum),  to  the  front  of  the  intercondyloid  fossa  of  the  femur. 
On  either  side  of  the  joint,  the  s\'novial  membrane  passes  downward  from  the  femur,  lining  the 
capsule  to  its  point  of  attachment  to  the  menisci;  it  may  then  be  traced  over  the  upper  surfaces 
of  these  to  their  free  borders,  and  thence  along  their  under  surfaces  to  the  tibia  (Figs.  472,  473). 


Oblique  poplitt 
ligament 


Medial  meniscus 


k — Adipose  tissue 


Bursa  under  Quadriceps 
fevioris 


Medial  meniscus 


^j^  Ligament  urn  paiellce 


Bursa  between  tibia  and 
ligamentum  patellae 


Fig.  471. — ^Sagittal  section  of  right  knee-joint. 


At  the  back  part  of  the  lateral  meniscus  it  forms  a  cul-de-sac  between  the  gi'oove  on  its  surface 
and  the  tendon  of  the  Popliteus;  it  is  reflected  across  the  front  of  the  cruciate  ligaments,  which 
are  therefore  situated  outside  the  SATiovial  cavity. 

Bursae. — The  bursae  near  the  knee-joint  are  the  following:  In  front  there  are  four  bm-sae:  a 
large  one  is  interposed  between  the  patella  and  the  skin,  a  small  one  between  the  upper  part  of 
the  tibia  and  the  ligamentum  patellae,  a  thii-d  between  the  lower  part  of  the  tuberosity  of  the 
tibia  and  the  skin,  and  a  fourth  between  the  anterior  sm-face  of  the  lower  part  of  the  femur  and 
the  deep  siirface  of  the  Quadiiceps  femoris,  usually  commimicating  with  the  knee-joint.  LateraUj- 
there  are  four  bursae:  (1)  one  (which  sometimes  coimaiunicates  with  the  joint)  between  the 
lateral  head  of  the  Gastrocnemius  and  the  capsule;  (2)  one  between  the  fibular  collateral  ligament 


444 


SYNDESMOLOGY 


and  the  tendon  of  the  Biceps;  (3)  one  between  the  fil)ul:ir  collaUTul  Uganient  and  the  tendon  of 
the  Pophteus  (this  is  sometimes  only  an  expansion  from  the  next  bursa);  (4)  one  between  the 
tendon  of  the  Pophteus  and  the  lateral  condyle  of  the  femur,  usually  an  extension  from  the 
synovial  membrane  of  the  joint.  Medially,  there  are  five  burste:  (1)  one  between  the  medial 
head  of  the  Gastrocnemius  and  the  (;apsule;  this  sends  a  prolongation  between  the  tendon  of  the 
medial  head  of  the  Gastrocnemius  and  the  tendon  of  the  Semimembranosus  and  often  communi- 
cates with  the  joint;  (2)  one  superficial  to  the  tibial  collateral  ligament,  between  it  and  the  tendons 
of  the  Sartorius,  Gracilis,  and  Semitendinosus;  (3)  one  deep  to  the  tibial  collateral  ligament, 
between  it  and  the  tendon  of  the  Semimembranosus  (this  is  sometimes  only  an  expansion 
from  the  next  bursa) ;  (4)  one  between  the  tendon  of  the  Semimembranosus  and  the  head  of 
the  tibia;  (5)  occasionally  there  is  a  bursa  between  the  tendons  of  the  Semimembranosus  and 
Semitendinosus. 


Ouadi  iccfs 
jemons 


Fibular  collateral 
ligament 
Tendon  of  Popllteus 

Lateral  meniscus 


n    L'gamcntum 
I J         patellae 


Fig.  472. — Capsule  of  right  knee-joint  (di.stended) .     Lateral  aspect. 


Structures  Around  the  Joint. — In  front,  and  at  the  sides,  is  the  Quadriceps  femoris;  laterally 
the  tendons  of  the  Biceps  femoris  and  Pophteus  and  the  common  peroneal  nerve;  medially, 
the  Sartorius,  Gracihs,  Semitendinosus,  and  Semimembranosus;  behind,  the  pophteal  vessels, 
and  the  tibial  nerve,  Pophteus,  Plant  aris,  and  medial  and  lateral  heads  of  the  Gastrocnemius, 
some  lymph  glands,  and  fat. 

The  arteries  supplying  the  joint  are  the  highest  genicular  (anastomotica  magna),  a  branch 
of  the  femoral,  the  genicular  branches  of  the  popliteal,  the  recurrent  branches  of  the  anterior 
tibial,  and  the  descending  branch  from  the  lateral  femoral  circumflex  of  the  profunda  femoris. 

The  nerves  are  derived  from  the  obturator,  femoral,  tibial,  and  common  peroneal. 

Movements. — The  movements  which  take  place  at  the  knee-joint  are  flexion  and  extension, 
and,  in  certain  positions  of  the  joint,  internal  and  external  rotation.  The  movements  of  flexion 
and  extension  at  this  joint  differ  from  those  in  a  typical  hinge-joint,  such  as  the  elbow,  in  that 
(a)  the  axis  around  which  motion  takes  place  is  not  a  fixed  one,  but  shifts  forward  during  extension 
and  backward  during  flexion;  (5)  the  commencement  of  flexion  and  the  end  of  extension  are 
accompanied  by  rotatory  movements  associated  with  the  fixation  of  the  limb  in  a  position  of 


THE  KNKK-JOIJ^T 


445 


Icxion   Id  lull  cxicMision  may  lIuTol'ore  bo  (Inscribed 


posterior  parts  ol    I  lu 
surfaces,  and   in   tlii^ 


leinora.i  condyle,^ 
position  a  slif^ht- 


I'cst   on  tlio  corre 
amount,  of  sim])l( 


great  stability.     The  movement    from 
in  throe  phases: 

1.  In  the  fully  flexed  condition  I  he 
spondiiAf;-  portions  of  the  meniscol  il)ial 
rolling  movement  is  allowed. 

2.  During  the  passage  of  the  limb  from  the  flexed  to  the  extended  jjosition  a  gliding  movement 
is  superposeil  on  the  rolling,  so  that  the  axis,  which  at  the  commencement  is  re])rcseiited  by  a 
line  through  the  inner  and  outer  condyles  of  the  femur,  gradually  shifts  forward.  In  this  part 
of  the  movement,  the  posterior  two-tliirds  of  the  tibial  arti(adar  surfaces  of  the  two  femoral 
condyles  are  involved,  and  as  these  have  similar  curvatures  and  are  parallel  to  one  another,  they 
move  forward  equally. 


Posterior  cruciate 
ligcmieni 

Medial  meniscus 


Tibial  collateral 
lifjanieni 


Anterior  cruciate 
ligctment 

Lateral  meniscus 

fibular  collateral 
ligament 


Fig.  473. — Capsule  of  riglit  knee-joint  (distended).     Posterior  aspect. 

3.  The  lateral  condyle  of  the  femur  is  brought  almost  to  rest  by  the  tightening  of  the  anterior 
cruciate  Ugament;  it  moves,  however,  shghtly  forward  and  medialward,  pvishing  before  it  the 
anterior  part  of  the  lateral  meniscus.  The  tibial  surface  on  the  medial  condyle  is  prolonged 
farther  forward  than  that  on  the  lateral,  and  this  prolongation  is  directed  lateralward.  When, 
therefore,  the  movement  forward  of  the  condyles  is  checked  by  the  anterior  cruciate  ligament, 
continued  muscular  action  causes  the  medial  condyle,  dragging  with  it  the  meniscus,  to  travel 
backward  and  medialward,  thus  producing  an  internal  rotation  of  the  thigh  on  the  leg.  When 
the  position  of  full  extension  is  reached  the  lateral  part  of  the  groove  on  the  lateral  condyle  is 
pressed  against  the  anterior  part  of  the  corresponding  meniscus,  while  the  medial  part  of  the 
groove  rests  on  the  articular  margin  in  front  of  the  lateral  process  of  the  tibial  intercondyloid 
eminence.  Into  the  groove  on  the  medial  condyle  is  fitted  the  anterior  part  of  the  medial  meniscus, 
while  the  anterior  cruciate  ligament  and  the  articular  margin  in  front  of  the  medial  process  of 
the  tibial  intercondyloid  eminence  are  received  into  the  forepart  of  the  intercondyloid  fossa  of 
the  femur.  This  third  phase  by  which  all  these  parts  are  brought  into  accurate  apposition  is 
known  as  the  "screwing  home,"  or  locking  movement  of  the  joint. 

The  complete  movement  of  flexion  is  the  converse  of  that  described  above,  and  is  therefore 
preceded  by  an  external  rotation  of  the  femur  which  unlocks  the  extended  joint. 

The  axes  around  which  the  movements  of  flexion  and  extension  take  place  are  not  preciselj- 
at  right  angles  to  either  bone;  in  flexion,  the  femur  and  tibia  are  in  the  same  plane,  but  in  exten- 
sion the  one  bone  forms  an  angle,  opening  lateralward  with  the  other. 


446  SYNDESMOLOGY 

In  addition  to  the  rotatory  movements  associated  with  the  comijlctioii  of  extension  and  the 
initiation  of  flexion,  rotation  inward  or  outward  can  be  effected  when  the  joint  is  partially  flexed; 
these  movements  take  place  mainty  between  the  tibia  and  the  menisci,  and  are  freest  when  the 
leg  is  bent  at  right  angles  with  the  thigh. 

Movements  of  Patella. — The  articular  surface  of  the  patella  is  indistinctly  divided  into  seven 
facets — upper,  middle,  and  lower  horizontal  pairs,  and  a  medial  perpendicular  facet  (Fig.  474). 

When  the  knee  is  forcibly  flexed,  the  medial  perpendicular 
facet  is  in  contact  with  the  semilunar  surface  on  the  lateral 
part  of  the  medial  condyle;  this  semilunar  surface  is  a  pro- 
longation backward  of  the  medial  part  of  the  patellar  surface. 
As  the  leg  is  carried  from  the  flexed  to  the  extended  position, 
first  the  highest  pair,  then  the  middle  pair,  and  lastly  the 
lowest  pair  of  horizontal  facets  is  successively  brought  into 
contact  with  the  patellar  sm'face  of  the  femur.  In  the  ex- 
tended position,  when  the  Quadriceps  femoris  is  relaxed,  the 
patella  Ues  loosely  on  the  front  of  the  lower  end  of  the  femur. 
During  flexion,  the  ligamentum  patellae  is  put  upon 
the  stretch,  and  in  extreme  flexion  the  posterior  cruciate 
„        .  .  .    ,       ligament,  the    oblique    popliteal,   and   collateral   Ugaments, 

Fig.  474. — Posterior   surface    of    the  i,  \-    t  ^  l     ^    \^  j.      ■  ■    j.       i-  j. 

right  patella,  showing  diagrammatically  and,  to  a  shght  extent,  the  anterior  cruciate  hgament, 
the  areas  of  contact  with  the  femur  in  are  relaxed.  Flexion  is  checked  during  life  by  the  contact 
posi  ions  o      e  -nee.  ^^  ^-^^   ^^^   ^.^j^   the   thigh.     When   the   knee-joint  is  fully 

extended  the  oblique  pophteal  and  collateral  ligaments, 
the  anterior  cruciate  ligament,  and  the  posterior  cruciate  ligament,  are  rendered  tense; 
in  the  act  of  extending  the  knee,  the  ligamentum  patellae  is  tightened  by  the  Quadriceps 
femoris,  but  in  full  extension  with  the  heel  supported  it  is  relaxed.  Rotation  inward  is  checked 
by  the  anterior  cruciate  ligament;  rotation  outward  tends  to  xmcross  and  relax  the  cruciate  liga- 
ments, but  is  checked  by  the  tibial  collateral  ligament.  The  main  function  of  the  cruciate  liga- 
ment is  to  act  as  a  direct  bond  between  the  tibia  and  femur  and  to  prevent  the  former  bone  from 
being  carried  too  far  backward  or  forward.  They  also  assist  the  collateral  Ugaments  in  resisting 
any  bending  of  the  joint  to  either  side.  The  menisci  are  intended,  as  it  seems,  to  adapt  the  surfaces 
of  the  tibia  to  the  shape  of  the  femoral  condyles  to  a  certain  extent,  so  as  to  fill  up  the  intervals 
which  would  otherwise  be  left  in  the  varying  positions  of  the  joint,  and  to  obviate  the  jars  which 
would  be  so  frequently  transmitted  up  the  hmb  in  jumping  or  by  falls  on  the  feet;  also  to  permit 
of  the  two  varieties  of  motion,  flexion  and  extension,  and  rotation,  as  explained  above.  The 
patella  is  a  great  defence  to  the  front  of  the  knee-joint,  and  distributes  upon  a  large  and  tolerably 
even  surface,  during  kneeling,  the  pressure  which  would  otherwise  fall  upon  the  prominent  ridges 
of  the  condyles;  it  also  affords  leverage  to  the  Quadriceps  femoris. 

When  standing  erect  in  the  attitude  of  "attention,"  the  weight  of  the  body  falls  in  front  of 
a  line  carried  across  the  centres  of  the  knee-joints,  and  therefore  tends  to  produce  overextension 
of  the  articulations;  this,  however,  is  prevented  by  the  tension  of  the  anterior  cruciate,  oblique 
popUteal,  and  collateral  ligaments. 

Extension  of  the  leg  on  the  thigh  is  performed  by  the  Quadriceps  femoris;  flexion  by  the  Biceps 
femoris,  Semitendinosus,  and  Semimembranosus,  assisted  by  the  GraciUs,  Sartorius,  Gastroc- 
nemius, Popliteus,  and  Plantaris.  Rotation  outward  is  effected  by  the  Biceps  femoris,  and  rota- 
tion inward  by  the  Popliteus,  Semitendinosus,  and,  to  a  shght  extent,  the  Semimembranosus,  the 
Sartorius,  and  the  Gracihs.  The  Pophteus  comes  into  action  especially  at  the  commencement 
of  the  movement  of  flexion  of  the  knee;  by  its  contraction  the  leg  is  rotated  inward,  or,  if  the 
tibia  be  fixed,  the  thigh  is  rotated  outward,  and  the  knee-joint  is  unlocked. 

Applied  Anatomy. — From  a  consideration  of  the  construction  of  the  knee-joint,  it  would  at 
first  sight  appear  to  be  one  of  the  least  secure  joints  in  the  body.  It  is  formed  between  the  two 
longest  bones,  and  therefore  the  amount  of  leverage  which  can  be  brought  to  bear  upon  it  is  con- 
siderable; the  articular  surfaces  are  but  ill-adapted  to  each  other,  and  the  range  of  motion  which 
it  enjoys  is  great.  All  these  circumstances  tend  to  render  the  articulation  insecure;  never- 
theless on  account  of  the  powerful  hgaments  which  bind  the  bones  together,  the  joint  is  one  of 
the  strongest  in  the  body,  and  dislocation  from  traumatism  is  a  rare  occurrence.  When,  on  the 
other  hand,  the  hgaments  have  been  softened  or  destroyed  by  disease,  partial  displacement  is 
Uable  to  occur,  and  is  frequently  brought  about  by  the  action  of  the  muscles. 

One  or  other  of  the  menisci  may  become  displaced  and  nipped  between  the  femur  and  tibia. 
The  accident  is  produced  by  a  twist  of  the  leg  when  the  knee  is  flexed,  and  is  accompanied  by  a 
sudden  pain  and  fixation  of  the  knee  in  a  flexed  position.  The  meniscus  may  be  displaced  either 
medialward  or  lateralward;  that  is  to  say,  either  toward  the  tibial  intercondyloid  eminence,  so 
that  the  cartilage  becomes  lodged  in  the  intercondyloid  fossa;  or  to  one  side,  so  that  the  cartilage 
projects  beyond  the  margin  of  the  two  articular  surfaces.  The  medial  meniscus  is  much  more 
commonly  affected  than  the  lateral. 

Acute  synovitis,  the  result  of  traumatism,  is  of  frequent  occurrence  in  the  knee,  on  account  of 


ARTICULATIONS  BKTWEEX  THE  TIBIA   AXD  FIBULA  447 

the  superficial  position  of  the  joint.  When  the  cavity  is  distended  with  fluid,  the  swelling  shows 
itself  above  and  at  the  sides  of  the  patella,  reacihing  about  2.5  cm.,  occasionally  5  cm.  or  more, 
above  the  patellar  surface  of  the  fenun-,  and  extending  a  little  higher  under  the  Vastus  medialis 
than  under  the  Vastus  lateralis.  The  lower  level  of  the  synovial  membrane  is  just  at  the  level 
of  the  head  of  the  tibia.  Chronic  synovitis  shows  itself  principally  in  the  form  of  pulpy  degenera- 
tion of  the  sj'novial  membrane,  the  result  of  tuberculous  infection.  Syphilitic  disease  with  gum- 
matous infiltration  of  the  synovial  membrane  may  take  place.  The  knee  is  one  of  the  joints 
most  commonly  afTccted  with  osteoarthritis,  and  is  more  frequently  the  seat  of  this  disease  in 
women  than  in  men.  The  occurrence  of  the  so-called  loose  cartilages  is  almost  confined  to  the 
knee,  though  thej'  are  occasionally  met  with  in  other  joints.  Many  of  them  occur  in  cases  of 
osteoarthritis,  in  which  calcareous  or  cartilaginous  material  is  formed  in  one  of  the  synovial 
fringes  and  constitutes  the  foreign  body,  and  may  or  may  not  become  detached,  only  in  the 
former  case  meriting  the  usual  term,  "loose"  cartilage.  In  other  cases  they  have  their  origin  in 
the  exudation  of  inflammatory  lymph,  and  possibly,  in  some  rare  instances,  a  portion  of  the 
articular  cartilage  or  one  of  the  menisci  becomes  detached  and  constitutes  the  foreign  body. 

In  inflammatory  affections  of  the  knee-joint,  the  position  of  greatest  ease,  and  therefore  the 
one  which  is  always  assumed,  is  that  of  slight  flexion.  In  this  position  there  is  the  most  complete 
relaxation  of  ligamentous  structures,  and,  therefore,  the  greatest  diminution  in  the  tension  caused 
bj'  the  effusion.  If  this  flexed  position  be  maintained  for  any  length  of  time,  it  becomes  perma- 
nent from  fibrous  adhesions  taking  place,  and  the  utility  of  the  limb  is  materially  impaired. 
Attention  should  therefore  be  paid  by  the  surgeon  to  the  position  of  the  limb;  and  by  carefully 
appUed  spUnts,  with  the  leg  in  an  extended  position,  this  untoward  result  should  be  prevented. 
In  cases  of  septic  synovitis,  incisions  to  evacuate  the  pus  should  be  made  vertically  on  either  side 
of  the  patella,  between  it  and  the  condyles  of  the  femur. 

Genu  valgum,  or  knock-knee,  is  a  common  deformity  of  childhood.  In  this  condition,  as  the 
patient  stands,  the  medial  condyles  of  the  two  femora  are  in  contact,  but  the  two  medial  malleoli 
are  more  or  less  widely  separated  from  each  other.  When,  however,  the  knees  are  flexed  to  a  right 
angle,  the  two  legs  are  practically  parallel  with  each  other.  At  the  commencement  of  the  disease 
there  is  a  yielding  of  the  tibial  collateral  ligament  and  other  fibrous  structures  on  the  medial  side 
of  the  joint;  as  a  result  of  this  there  is  a  constant  undue  pressure  of  the  lateral  condyle  of  the 
tibia  against  the  lateral  condyle  of  the  femur.  This  pressure  causes  arrest  of  growth,  and,  possibly, 
wasting  of  the  lateral  condyle,  and  a  consequent  tendency  for  the  tibia  to  become  separated  from 
the  medial  condyle  of  the  femur.  Irregular  overgrowth  from  the  medial  portion  of  the  epiphysial 
line  takes  place,  giving  rise  to  apparent  enlargement  of  the  medial  condyle  of  the  femur,  the  line 
of  the  epiphysis  becoming  oblique,  with  a  direction  downward  and  medialward,  instead  of  at 
right  angles  to  the  axis  of  the  bone.  If  the  deformity  be  marked,  an  osteotomy  of  the  femur  is 
required  to  correct  it. 

Excision  of  the  knee-joint  is  most  frequently  required  for  tuberculous  disease  of  this  articula- 
tion, but  is  also  practised  in  cases  of  disorganization  of  the  knee  from  other  causes.  It  is  also 
occasionally  called  for  in  cases  of  injury,  gmishot  or  otherwise.  The  operation  is  best  performed 
by  a  horseshoe-shaped  incision,  starting  from  one  femoral  condyle,  descending  as  low  as  the 
tuberosity  of  the  tibia,  and  then  carried  upward  to  the  other  femoral  condyle.  The  bone  ends 
having  been  cleared,  and  in  those  cases  where  the  operation  is  performed  for  tuberculous  disease 
all  pulpy  tissue  having  been  carefuUy  removed,  the  section  of  the  femur  is  first  made.  This 
should  never  include,  in  children,  more  than,  at  the  most,  two-thirds  of  the  articular  surface, 
otherwise  the  epiphysial  cartilage  will  be  involved,  with  disastrous  results  as  regards  the  growth 
of  the  limb.  Afterward  a  thin  slice,  not  more  than  1.25  cm.,  should  be  removed  from  the  upper 
end  of  the  tibia.  If  any  diseased  tissue  still  appears  to  be  left  in  the  bones,  it  should  be  removed 
with  the  gouge,  rather  than  by  a  f mother  section. 

The  bursse  about  the  knee-joint  are  sometimes  the  seat  of  enlargement.  The  bursa  between 
the  front  of  the  patella  and  the  skin  is  frequently  affected  in  individuals  who  are  in  the  habit  of 
constantly  kneeling,  and  the  condition  is  then  known  as  "housemaid's  knee."  The  bm-sa  be- 
neath the  Semimembranosus  tendon  also  occasionally  becomes  enlarged,  and  forms  a  fluctuating 
swelling  at  the  back  of  the  knee.  During  extension,  the  swelling  is  firm  and  tense;  but  during 
flexion  it  becomes  soft,  and,  as  the  bursa  often  communicates  with  the  sjiiovial  cavity  of  the 
joint,  the  fluid  it  contains  can  be  made  to  disappear  by  pressure  when  the  knee  is  flexed.  Exten- 
sion of  septic  processes  within  the  joint  is  apt  to  occur  along  the  tendon  sheath  of  the  PopUteus, 
and  this  may  lead  to  deep-seated  suppuration  in  the  popliteal  fossa,  often  associated  with  septic 
thrombosis  of  the  popUteal  vein;  when  this  occurs  amputation  of  the  limb  is  necessary. 


III.    Articulations  between  the  Tibia  and  Fibula. 

The  articulations  between  the  tibia  and  fibula  are  effected  by  ligaments  which 
connect  the  extremities  and  bodies  of  the  bones.    The  ligaments  may  consequently 


448  SYNDESMOLOGY 

be  suhdividefl  into  three  sets:  (1)  those  of  the  Tihi(jfibiilar  articuhition;  (2)  the 
interosseous  membrane;  (3)  those  of  the  Tibiofibular  syndesmosis. 

Tibiofibular  Articulation  (ariicidatio  iihiofibrihiris;  superior  tibiofibular  articula- 
tion).— This  articulation  is  an  arthrodial  joint  between  the  lateral  condyle  of  the 
tibia  and  the  head  of  the  fibula.  The  contiguous  surfaces  of  the  bones  present 
flat,  oval  facets  covered  with  cartilage  and  connected  together  by  an  articular 
capsule  and  by  anterior  and  posterior  ligaments. 

The  Articular  Capsule  (capsula  articularis;  capsular  ligament). — The  articular 
capsule  surrounds  the  articulation,  being  attached  around  the  margins  of  the 
articular  facets  on  the  tibia  and  fibula;  it  is  much  thicker  in  front  than 
behind. 

The  Anterior  Ligament  (anterior  superior  ligament). — The  anterior  ligament  of 
the  head  of  the  fibula  (Fig.  468)  consists  of  two  or  three  broad  and  fiat  bands, 
which  pass  obliquely  upward  from  the  front  of  the  head  of  the  fibula  to  the  front 
of  the  lateral  condyle  of  the  tibia. 

The  Posterior  Ligament  (posterior  superior  ligament). — The  posterior  ligament  of 
the  head  of  the  fibula  (Fig.  469)  is  a  single  thick  and  broad  band,  which  pas.ses 
obliquely  upward  from  the  back  of  the  head  of  the  fibula  to  the  back  of  the  lateral 
condyle  of  the  tibia.    It  is  covered  by  the  tendon  of  the  Popliteus. 

Synovial  Membrane. — A  synovial  membrane  lines  the  capsule;  it  is  continuous  with  that  of 
the  knee-joint  in  occasional  cases  when  the  two  joints  communicate. 

Interosseous  Membrane  (membrana  interossea  cruris;  middle  tibiofibular  liga- 
ment).— An  interosseous  membrane  extends  between  the  interosseous  crests  of  the 
tibia  and  fibula,  and  separates  the  muscles  on  the  front  from  those  on  the  back 
of  the  leg.  It  consists  of  a  thin,  aponeurotic  lamina  composed  of  oblique  fibres, 
which  for  the  most  part  run  downward  and  lateralward;  some  few  fibres,  however, 
pass  in  the  opposite  direction.  It  is  broader  above  than  below.  Its  upper  margin 
does  not  quite  reach  the  tibiofibular  joint,  but  presents  a  free  concave  border, 
above  which  is  a  large,  oval  aperture  for  the  passage  of  the  anterior  tibial  vessels 
to  the  front  of  the  leg.  In  its  lower  part  is  an  opening  for  the  passage  of  the  anterior 
peroneal  vessels.  It  is  continuous  below  with  the  interosseous  ligament  of  the  tibio- 
fibular syndesmosis,  and  presents  numerous  perforations  for  the  passage  of  small 
vessels.  It  is  in  relation,  in  front,  with  the  Tibialis  anterior.  Extensor  digitorum 
longus,  Extensor  hallucis  proprius,  Peronaeus  tertius,  and  the  anterior  tibial 
vessels  and  deep  peroneal  nerve;  behind,  with  the  Tibialis  posterior  and  Flexor 
hallucis  longus. 

Tibiofibular  Syndesmosis  (syndesmosis  tibiofibidaris;  inferior  tibiofibular  articu- 
lation).— This  syndesmosis  is  formed  by  the  rough,  convex  surface  of  the  medial 
side  of  the  lower  end  of  the  fibula,  and  a  rough  concave  surface  on  the  lateral  side 
of  the  tibia.  Below,  to  the  extent  of  about  4  mm.  these  surfaces  are  smooth,  and 
covered  with  cartilage,  which  is  continuous  with  that  of  the  ankle-joint.  The 
ligaments  are:  anterior,  posterior,  inferior  transverse,  and  interosseous. 

The  Anterior  Ligament  (ligamentum  malleoli  lateralis  anterius;  anterior  inferior 
ligament). — ^The  anterior  ligament  of  the  lateral  malleolus  (Fig.  476)  is  a  flat, 
triangular  band  of  fibres,  broader  below  than  above,  which  extends  obliquely 
downward  and  lateralward  betvxeen  the  adjacent  margins  of  the  tibia  and  fibula, 
on  the  front  aspect  of  the  syndesmosis.  It  is  in  relation,  m  front,  with  the  Peronaeus 
tertius,  the  aponeurosis  of  the  leg,  and  the  integument;  behind,  with  the  interosseous 
ligament;  and  lies  in  contact  with  the  cartilage  covering  the  talus. 

The  Posterior  Ligament  (ligamentum  malleoli  lateralis  posterius;  po.sterior  inferior 
ligament).- — The  posterior  ligament  of  the  lateral  malleolus  (Fig."  476),  smaller 
than  the  preceding,  is  disposed  in  a  similar  manner  on  the  posterior  surface  of 
the  syndesmosis. 


TALOCRURAL  ARTICULATION  OR  ANKLE-JOINT 


449 


The  Inferior  Transverse  Ligament. — The  inferior  transverse  ligament  lies  in  front 
of  the  posterior  ligament,  and  is  a  strong,  thick  band,  of  yellowish  fibres  which 
passes  transversely  across  the  back  of  the  joint,  from  the  lateral  malleolus  to  the 
posterior  border  of  the  articular  surface  of  the  tibia,  almost  as  far  as  its  malleolar 
process.  This  ligament  projects  below  the  margin  of  the  bones,  and  forms  part 
of  the  articulating  surface  for  the  talus. 

The  Interosseous  Ligament. — The  interosseous  ligament  consists  of  numerous 
short,  strong,  fibrous  bands,  which  pass  between  the  contiguous  rough  surfaces  of 
the  tibia  and  fibula,  and  constitute  the  chief  bond  of  union  between  the  bones. 
It  is  continuous,  above,  with  the  interosseous  membrane. 

Synovial  Membrane. — The  synovial  membrane  associated  with  the  small  arthrodial  part  of 
this  joint  is  continuous  with  that  of  the  ankle-joint. 


IV.  Talocrural  Articulation  or  Ankle-joint  (Articulatio  Talocruralis ;  Tibiotarsal 

Articulation) . 

The  ankle-joint  is  a  ginglymus,  or  hinge-joint.  The  structures  entering  into  its 
formation  are  the  lower  end  of  the  tibia  and  its  malleolus,  the  malleolus  of  the 
fibula,  and  the  transverse  ligament,  which  together  form  a  mortise  for  the  recep- 
tion of  the  upper  convex  surface  of  the  talus  and  its  medial  and  lateral  facets. 
The  bones  are  connected  by  the  following  ligaments: 


The  Articular  Capsule. 
The  Deltoid. 


The  Anterior  Talofibular. 
The  Posterior  Talofibular. 
The  Calcaneofibular. 


The  Articular  Capsule  {cajjsida  articularis;  capsular  ligament). — The  articular  cap- 
sule surrounds  the  joints,  and  is  attached,  above,  to  the  borders  of  the  articular 
surfaces  of  the  tibia  and  malleoli ;  and  below,  to  the  talus  around  its  upper  articular 
surface. 


Tarsometatarsal 
articulations 


Intertarsal 


Fig.  475. — Right  talocrural  intertarsal  and  tarsometatarsal  articulations.     Medial  aspect. 

The  anterior  part  of  the  capsule  (anterior  ligament)  (Fig.  475)  is  a  broad,  thin, 
membranous  layer,  attached,  above,  to  the  anterior  margin  of  the  lower  end  of 
29 


450 


SYNDESMOLOGY 


the  tibia;  below,  to  the  takis,  in  front  of  its  superior  articular  surface.  It  is  in 
relation,  in  front,  with  the  Extensor  tendons  of  the  toes,  the  tendons  of  the  Tibialis 
anterior  and  Peronaeus  tertius,  and  the  anterior  tibial  vessels  and  deep  peroneal 
nerve. 

The  posterior  part  of  the  capsule  {yosterior  ligament)  is  very  thin,  and  consists 
principally  of  transverse  fibres.  It  is  attached,  above,  to  the  margin  of  the  articular 
surface  of  the  tibia,  blending  Avith  the  transverse  ligament;  helou\  to  the  talus 
behind  its  superior  articular  facet.  Laterally,  it  is  somewhat  thickened,  and  is 
attached  to  the  hollow  on  the  medial  surface  of  the  lateral  malleolus. 

The  Deltoid  Ligament  (ligamentum  deltoideiim;  internal  lateral  ligament) 
(Fig.  475). — The  deltoid  ligament  is  a  strong,  flat,  triangular  band,  attached, 
above,  to  the  apex  and  anterior  and  posterior  borders  of  the  medial  malleolus. 
It  consists  of  two  sets  of  fibres,  superficial  and  deep.  Of  the  superficial  fibres  the 
most  anterior  (tibionavicular)  pass  forward  to  be  inserted  into  the  tuberosity  of 
the  navicular  bone,  and  immediately  behind  this  they  blend  with  the  medial  margin 
of  the  plantar  calcaneonavicular  ligament;  the  middle  (calcaneotibial)  descend 
almost  perpendicularly  to  be  inserted  into  the  whole  length  of  the  sustentaculum 
tali  of  the  calcaneus;  the  posterior  fibres  (2)osterior  talotibial)  pass  backward  and 
lateralward  to  be  attached  to  the  inner  side  of  the  talus,  and  to  the  prominent 
tubercle  on  its  posterior  surface,  medial  to  the  groove  for  the  tendon  of  the  Flexor 
hallucis  longus.  The  deep  fibres  (anterior  talotibial)  are  attached,  above,  to  the 
tip  of  the  medial  malleolus,  and,  below,  to  the  medial  surface  of  the  talus.  The 
deltoid  ligament  is  covered  by  the  tendons  of  the  Tibialis  posterior  and  Flexor 
digitorum  longus. 

The  anterior  and  posterior  talofibular  and  the  calcaneofibular  ligaments  were 
formerly  described  as  the  three  fasciculi  of  the  external  lateral  ligament  of  the 
ankle-joint. 


Fig.  476. — Right  talocrural  intertarsal  and  tarsometatarsal  articulations.     Lateral  aspect. 


The  Anterior  Talofibular  Ligament  (ligamentum  talofibular e  anterius)  (Fig.  476). 
— The  anterior  taliofibular  ligament,  the  shortest  of  the  three,  passes  from  the 
anterior  margin  of  the  fibular  malleolus,  forward  and  medially,  to  the  talus,  in 
front  of  its  lateral  articular  facet. 


TALOCRURAL  ARTICULATION  OR  ANKLE-JOINT 


451 


The  Posterior  Talofibular  Ligament  {lU/uiitcidum  talujibulare  poaterius)  (Fig.  476). 
— The  posterior  talofibular  ligament,  the  strongest  and  most  deeply  seated,  runs 
almost  horizontally'  from  the  depression  at  the  medial  and  back  part  of  the  fibular 
malleolus  to  a  prominent  tubercle  on  the  posterior  surface  of  the  talus  immediately 
lateral  to  the  groove  for  the  tendon  of  the  Flexor  hallucis  longus. 

The  Calcaneofibular  Ligament  (ligamentum  calccmeofibulare)  (Fig.  470).- — ^The 
calcaneofibular  ligament,  the  longest  of  the  three,  is  a  narrow,  rounded  cord,  run- 
ning from  the  apex  of  the  fibular  malleolus  downward  and  slightly  backward' to  a 
tubercle  on  the  lateral  surface  of  the  calcaneus.  It  is  covered  by  the  tendons  of 
the  Peronaei  longus  and  brevis. 


\  1  Wm^)^ Anterior  talofibular  ligament 


rm^^^^  P^^^^'''"^'''  talofibular  ligament 
'Illl^Sm      Calvaneofihular  ligament 
,^  Lateral  talocalcaneal  ligament 


Anterior 

talocalcaneal 

ligament 


Fig.  477. — Capsule  of  left  talocrural  articulation  (distended).     Lateral  aspect. 


Synovial  Membrane  (Fig.  477). — The  synovial  membrane  invests  the  deep  surfaces  of  the 
ligaments,  and  sends  a  small  process  upward  between  the  lower  ends  of  the  tibia  and  fibula. 

Relations. — -The  tendons,  vessels,  and  nerves  in  connection  with  the  joint  are,  in  front,  from  the 
medial  side,  the  TibiaUs  anterior,  Extensor  haUucis  proprius,  anterior  tibial  vessels,  deep  peroneal 
nerve.  Extensor  digitorum  longus,  and  Peronaeus  tertius;  behind,  from  the  medial  side,  the  TibiaUs 
posterior.  Flexor  digitorum  longus,  posterior  tibial  vessels,  tibial  nerve.  Flexor  hallucis  longus; 
and,  in  the  groove  behind  the  fibular  malleolus,  the  tendons  of  the  Peronaei  longus  and  brevis. 

The  arteries  supplying  the  joint  are  derived  from  the  malleolar  branches  of  the  anterior  tibial 
and  the  peroneal. 

The  nerves  are  derived  from  the  deep  peroneal  and  tibial. 

Movements. — When  the  body  is  in  the  erect  position,  the  foot  is  at  right  angles  to  the  leg. 
The  movements  of  the  joint  are  those  of  dorsiflexion  and  extension;  dorsiflexion  consists  in  the 
approximation  of  the  dorsum  of  the  foot  to  the  front  of  the  leg,  while  in  extension  the  heel  is 
drawn  up  and  the  toes  pointed  downward.  The  malleoh  tightly  embrace  the  talus  in  aU  positions 
of  the  joint,  so  that  any  slight  degree  of  side-to-side  movement  which  may  exist  is  simply  due  to 
stretching  of  the  Ugaments  of  the  talofibular  syndesmosis,  and  slight  bending  of  the  body  of  the 
fibula.  The  superior  articular  surface  of  the  talus  is  broader  in  front  than  behind.  In  dorsi- 
flexion, therefore,  greater  space  is  required  between  the  two  malleoU.  This  is  obtained  by  a  slight 
outward  rotatory  movement  of  the  lower  end  of  the  fibula  and  a  stretching  of  the  ligaments  of 
the  syndesmosis ;  this  lateral  movement  is  facilitated  by  a  slight  gliding  at  the  tibiofibular  articula- 
tion, and  possibly  also  by  the  bending  of  the  body  of  the  fibula.  Of  the  Ugaments,  the  deltoid 
is  of  very  great  power — so  much  so,  that  it  usually  resists  a  force  which  fractures  the  process  of 
bone  to  which  it  is  attached.  Its  middle  portion,  together  with  the  calcaneofibular  Ugament, 
binds  the  bones  of  the  leg  firmly  to  the  foot,  and  resists  displacement  in  every  direction.  Its 
anterior  and  posterior  fibres  limit  extension  and  flexion  of  the  foot  respectively,  and  the  anterior 
fibres  also  Umit  abduction.    The  posterior  talofibular  ligament  assists  the  calcaneofibular  in 


452  SYNDESMOLOGY 

resisting  the  displacement  of  the  foot  backward,  and  deepens  the  cavity  for  the  reception  of  the 
talus.  The  anterior  talofibular  is  a  security  against  the  displacement  of  the  foot  forward,,  and 
limits  extension  of  the  joint. 

The  movements  of  inversion  and  eversion  of  the  foot,  together  with  the  minute  changes  in 
form  by  which  it  is  apphed  to  the  ground  or  takes  hold  of  an  object  in  chmbing,  etc.,  are  mainly 
eflfected  in  the  tarsal  joints;  the  joint  which  enjoys  the  greatest  amount  of  motion  being  that  be- 
tween the  talus  and  calcaneus  behind  and  the  navicular  and  cuboid  in  front.  This  is  often  called 
the  transverse  tarsal  joint,  and  it  can,  with  the  subordinate  joints  of  the  tarsus,  replace  the  ankle- 
joint  in  a  great  measure  when  the  latter  has  become  ankylosed. 

Extension  of  the  foot  upon  the  tibia  and  fibula  is  produced  by  the  Gastrocnemius,  Soleus, 
Plantai'is,  Tibialis  posterior,  Peronaei  longus  and  brevis,  Flexor  digitorum  longus,  and  Flexor 
haUucis  longus;  dorsifiexion,  by  the  Tibialis  anterior,  Peronaeus  tertius.  Extensor  digitorum  longus, 
and  Extensor  hallucis  proprius.^ 

Applied  Anatomy. — As  the  ankle-joint  is  a  very  strong  and  powerful  articulation,  displace- 
ment of  the  talus  from  the  tibiofibular  mortise  is  a  rare  accident,  and  great  force  is  required  to 
produce  it.  Nevertheless,  dislocation  does  occasionally  occur,  either  antero-posteriorly  or  to 
one  or  other  side.  In  the  latter,  which  is  th?  more  common,  fracture  is  a  necessary  accompani- 
ment of  the  injury.  The  dislocation  in  these  cases  is  somewhat  peculiar,  and  is  not  a  displace- 
ment in  a  horizontal  direction,  such  as  usually  occurs  in  dislocations  of  ginglymoid  joints,  but 
the  talus  undergoes  a  partial  rotation  around  an  antero-posterior  axis  drawn  through  its  own 
centre,  so  that  the  superior  surface,  instead  of  being  directed  upward,  is  incUned  more  or  less 
medialward  or  lateralward  according  to  the  variety  of  the  displacement. 

The  ankle-joint  is  more  frequently  sprained  than  any  joint  in  the  body,  and  this  may  lead  to 
acute  synovitis.  In  these  cases,  when  the  synovial  sac  is  distended  with  fluid,  the  bulging  appears 
principally  in  the  front  of  the  joint,  beneath  the  anterior  tendons,  and  on  either  side,  between 
the  Tibiahs  anterior  and  the  deltoid  ligament  on  the  medial  side,  and  between  the  Peronaeus 
tertius  and  the  anterior  talofibular  ligament  laterally.  In  addition  to  this,  bulging  often  occurs 
posteriorly,  and  a  fluctuating  swelling  may  be  detected  on  either  side  of  the  tendo  calcaneus. 
A  large  proportion  of  so-caUed  "sprains"  of  the  ankle  have  been  proved  by  a;-ray  examination 
to  be  some  variety  of  fracture  about  the  malleoli,  with  or  without  displacement. 

Chronic  synovitis  may  result  from  frequent  sprains,  and  when  once  this  joint  has  been  .sprained 
it  is  Liable  to  a  recurrence  of  the  injury;  or  the  synovitis  may  be  tuberculous  in  its  origin,  the 
disease  usually  beginning  in  the  talus  and  extending  to  the  joint,  though  it  may  commence  in 
the  synovial  membrane,  the  result  probably  of  some  slight  strain  in  a  tuberculous  subject. 

Excision  of  the  ankle-joint  is  not  often  performed,  since  the  foot  after  excision  is  often  of  very 
little  use;  far  less  useful,  in  fact,  than  it  is  after  Syme's  amputation,  which  is,  therefore,  a  prefer- 
able operation  in  these  cases.  Further,  disease  of  the  ankle-joint  is  frequently  associated  with 
disease  of  the  tarsal  bones. 

V.     Intertarsal  Articulations  (Articulationes  Intertarseae ;  Articulations 

of  the  Tarsus). 

Talocalcaneal  Articulation  (articulatio  talocalcanea;  articulation  of  the  calcaneus 
and  astragalus;  calcaneo-astragaloid  articulation). — The  articulations  between  the 
calcaneus  and  talus  are  two  in  number — anterior  and  posterior.  Of  these,  the 
anterior  forms  part  of  the  talocalcaneonavicular  joint,  and  will  be  described  with 
that  articulation.  The  posterior  or  talocalcaneal  articulation  is  formed  between 
the  posterior  calcaneal  facet  on  the  inferior  surface  of  the  talus,  and  the  posterior 
facet  on  the  superior  surface  of  the  calcaneus.  It  is  an  arthrodial  joint,  and  the 
two  bones  are  connected  by  an  articular  capsule  and  by  anterior,  posterior,  lateral, 
medial,  and  interosseous  talocalcaneal  ligaments. 

The  Articular  Capsule  (capsula  articularis) . — The  articular  capsule  envelops 
the  joint,  and  consists  for  the  most  part  of  short  fibres,  which  are  split  up  into 
distinct  slips;  between  these  there  is  only  a  weak  fibrous  investment. 

The  Anterior  Talocalcaneal  Ligament  {ligamentum  talocalcaneum  anterius;  anterior 
calcaneo-astragaloid  ligament)  (Figs.  477,  480). — The  anterior  talocalcaneal  liga- 
ment extends  from  the  front  and  lateral  surface  of  the  neck  of  the  talus  to 
the  superior  surface  of  the  calcaneus.     It  forms  the  posterior  boundary  of  the 

1  The  student  must  bear  in  mind  that  the  Extensor  digitorum  longus  and  Extensor  hallucis  proprius  are  extensors 
of  the  toes,  but  flexors  of  the  ankle;  and  that  the  Flexor  digitorum  longus  and  Flexor  hallucis  longus  are  flexors  of  the 
toes,  but  extensors  of  the  ankle. 


IXTERTARSAL  ARTICULATIONS 


453 


talocalcaneonavicular  joint,  and  is  sometimes  described  as  the  anterior  interosseous 
ligament. 

The  Posterior  Talocalcaneal  Ligament  (Jigainoifuni  talocalcaneum  posterius; 
posicrior  calcaitco-aMragdIoid  ligaiiicnt)  (Fig.  475). — The  posterior  talocalcaneal 
ligament  connects  the  lateral  tubercle  of  the  talus  with  the  upper  and  medial  part 
of  the  calcaneus;  it  is  a  short  band,  and  its  fibres  radiate  from  their  narrow  attach- 
ment to  the  talus. 

The  Lateral  Talocalcaneal  Ligament  iligamoifiim.  talocalcaneum  laterale;  external 
calcanco-astragaluid  ligament)  (Figs.  477,  480). — The  lateral  talocalcaneal  ligament 
is  a  short,  strong  fasciculus,  passing  from  the  lateral  surface  of  the  talus,  imme- 
diately beneath  its  fibular  facet  to  the  lateral  surface  of  the  calcaneus.  It  is  placed 
in  front  of,  but  on  a  deeper  plane  than,  the  calcaneofibular  ligament,  with  the  fibres 
of  which  it  is  parallel. 

The  Medial  Talocalcaneal  Ligament  (ligamentum  talocalcaneum  mediale;  internal 
calcaneo-astragaloid  ligament). — The  medial  talocalcaneal  ligament  connects  the 
medial  tubercle  of  the  back  of  the  talus  with  the  back  of  the  sustentaculum  tali. 
Its  fibres  blend  with  those  of  the  plantar  calcaneonavicular  ligament. 


Jledial  malleolus 
Deltoid  ligament 
Tibialis  posterior- 


Flexor  digitorum  longus 

Flexor  halliicis  longus 

Med.  plantar  nerve  and  vessels 

Quadratus  planice 

Abductor  hallucis 

Lat.  plantar  nerve  and  vessels 
Flexor  digitorum  brevis 


Interosseous  ligament  of  tibio- 
fibular syndesmosis 


Lateral  malleolus 

rof,^^ —  Calcaneofibular  ligament 

^^^, Interosseous  talocalcaneal 

ligament 

Peronceus  hrevis' 


PerojicBUS  longus 
Abductor  digiti  quinii 


Fig.  478. — Coronal  section  through  right  talocrural  and  talocalcaneal  joints. 

The  Interosseous  Talcocalcaneal  Ligament  (ligamentmn  talocalcaneum  interosseum) 
(Figs.  47S,  480). — The  interosseous  talocalcaneal  ligament  forms  the  chief  bond 
of  union  between  the  bones.  It  is,  in  fact,  a  portion  of  the  united  capsules  of  the 
talocalcaneonavicular  and  the  talocalcaneal  joints,  and  consists  of  two  partially 
united  layers  of  fibres,  one  belonging  to  the  former  and  the  other  to  the  latter  joint. 
It  is  attached,  above,  to  the  groove  between  the  articular  facets  of  the  under  surface 
of  the  talus;  below,  to  a  corresponding  depression  on  the  upper  surface  of  the  cal- 
caneus. It  is  very  thick  and  strong,  being  at  least  2.5  cm.  in  breadth  from -side 
to  side,  and  serves  to  bind  the  calcaneus  and  talus  firmly  together. 


454  SYNDESMOLOGY 

Synovial  Membrane  (Fig.  481). — The  synovial  membrane  lines  the  capsule  of  the  joint,  and 
is  distinct  from  the  other  synovial  membranes  of  the  tarsus. 

Movements. — The  movements  permitted  between  the  talus  and  calcaneus  are  hmited  to  glid- 
ing of  the  one  bone  on  the  other  backward  and  forward  and  from  side  to  side. 

Talocalcaneonavicular  Articulation  {articulaiio  talocalcaneonancularis) . — This 
articulation  is  an  arthrodial  joint:  the  rounded  head  of  the  tahis  being  received 
into  the  concavity  formed  by  the  posterior  surface  of  the  navicular,  the  anterior 
articular  surface  of  the  calcaneus,  and  the  upper  surface  of  the  plantar  calcaneo- 
navicular ligament.  There  are  two  ligaments  in  this  joint:  the  articular  capsule 
and  the  dorsal  talonavicular. 

The  Articular  Capsule  (capsida  articular  is) . — The  articular  capsule  is  imperfectly 
developed  except  posteriorly,  where  it  is  considerably  thickened  and  forms,  with 
a  part  of  the  capsule  of  the  talocalcaneal  joint,  the  strong  interosseous  ligament 
which  fills  in  the  canal  formed  by  the  opposing  grooves  on  the  calcaneus  and  talus, 
as  above  mentioned. 

The  Dorsal  Talonavicular  Ligament  (ligamentum  talonavicular e  dorsale;  superior 
astragalonamcular  ligament)  (Fig.  475). — This  ligament  is  a  broad,  thin  band,  which 
connects  the  neck  of  the  talus  to  the  dorsal  surface  of  the  navicular  bone;  it  is 
covered  by  the  Extensor  tendons.  The  plantar  calcaneonavicular  supplies  the 
place  of  a  plantar  ligament  for  this  joint. 

Synovial  Membrane. — The  synovial  membrane  Unes  aU  parts  of  the  capsule  of  the  joint. 
Movements. — This  articulation  permits  of  a  considerable  range  of  gliding  movements;  its 
feeble  construction  allows  occasionally  of  dislocation  of  the  other  bones  of  the  tarsus  from  the  talus. 

Calcaneocuboid  Articulation  (articulaiio  calcaneocuboidea;  articulation  of  the 
calcaneus  ivith  the  cuboid). — The  ligaments  connecting  the  calcaneus  with  the 
cuboid  are  five  in  number,  viz.,  the  articular  capsule,  the  dorsal  calcaneocuboid, 
part  of  the  bifurcated,  the  long  plantar,  and  the  plantar  calcaneocuboid. 

The  Articular  Capsule  {capsula  articular  is) . — The  articular  capsule  is  an  imper- 
fectly developed  investment,  containing  certain  strengthened  bands,  which  form 
the  other  ligaments  of  the  joint. 

The  Dorsal  Calcaneocuboid  Ligament  (ligamentum  calcaneocuboideum  dorsale;  supe- 
rior calcaneocuboid  ligament)  (Fig.  476).— The  dorsal  calcaneocuboid  ligament  is 
a  thin  but  broad  fasciculus,  which  passes  between  the  contiguous  surfaces  of  the 
calcaneus  and  cuboid,  on  the  dorsal  surface  of  the  joint. 

The  Bifurcated  Ligament  (ligamentum  bifurcatum;  internal  calcaneocuboid;  inter- 
osseous ligament)  (Fig.  476,  480).— The  bifurcated  ligament  is  a  strong  band, 
attached  behind  to  the  deep  hollow  on  the  upper  surface  of  the  calcaneus  and  divid- 
ing in  front  in  a  Y-shaped  manner  into  a  calcaneocuboid  and  a  calcaneonavicular 
part.  The  calcaneocuboid  part  is  fixed  to  the  medial  side  of  the  cuboid  and  forms 
one  of  the  principal  bonds  between  the  first  and  second  rows  of  the  tarsal  bones. 
The  calcaneonavicular  part  is  attached  to  the  lateral  side  of  the  navicular. 

The  Long  Plantar  Ligament  {ligamentum  plantare  longum;  long  calcaneocuboid 
ligament;  superficial  long  plantar  ligament)  (Fig.  479).— The  long  plantar  ligament 
is  the  longest  of  all  the  ligaments  of  the  tarsus:  it  is  attached  behind  to  the  plantar 
surface  of  the  calcaneus  in  front  of  the  tuberosity,  and  in  front  to  the  tuberosity 
on  the  plantar  surface  of  the  cuboid  bone,  the  more  superficial  fibres  being  con- 
tinued forward  to  the  bases  of  the  second,  third,  and  fourth  metatarsal  bones. 
This  ligament  converts  the  groove  on  the  plantar  surface  of  the  cuboid  into  a 
canal  for  the  tendon  of  the  Peronaeus  longus. 

The  Plantar  Calcaneocuboid  Ligament  {ligamentum  calcaneocuboideum  plantare; 
short  calcaneocuboid  ligament;  short  plantar  ligament)  (Fig.  479).— The  plantar 
calcaneocuboid  ligament  lies  nearer  to  the  bones  than  the  preceding,  from  which 
it  is  separated  by  a  little  areolar  tissue.  It  is  a  short  but  wide  band  of  great  strength, 
and  extends  from  the  tubercle  and  the  depression  in  front  of  it,  on  the  forepart 


INTERTARSAL  ARTICULATIONS 


455 


of  the  plantar  surface  of  the  calcaneus,  to  the  i)lantar  surface  of  the  cu})oid  behind 
the  peroneal  groove. 

Synovial  Membrane.— The  synovial  membrane  lines  the  inner  surface  of  the  cajisule  and  is 
distinct  from  that  of  the  other  tarsal  articulations  (Fig.  481). 

Movements.— The  movements  permitted  between  the  calcaneus  and  cuboid  are  limited  to 
slight  glidhig  movements  of  the  bones  upon  each  other. 

The  tnmst'erse  tarsal  joint  is  formed  by  the  articulation  of  the  calcaneus  with  the  cuboid,  and 
the  articulation  of  the  talus  with  the  navicular.  The  movement  which  takes  place  in  this  Joint 
is  more  extensive  than  that  in  the  other  tarsal  joints,  and  consists  of  a  sort  of  rotation  by  means 
of  which  the  foot  may  be  sUghtly  flexed  or  extended,  the  sole  being  at  the  same  time  carried 
medially  (inverted)  or  laterally  (everted). 

The  Ligaments  Connecting  the  Calcaneus  and  Navicular.— Though  the  calcaneus 

and  navicular  do  not  directly  articulate,  they  are  connected  by  two  ligaments: 

the  calcaneonavicular  part  of  the  bifurcated,  and  the  plantar  calcaneonavicular. 

The  calcaneonavicular  part  of  the  bifurcated  ligament  is  described  on  page  454. 

The  Plantar  Calcaneonavicular  Ligament  (liga- 
mentum  calcaneonavicular  e  plant  are;  inferior  or 
internal  calcaneonavicular  ligament;  calcaneona- 
vicular ligament)  (Fig.  480). — The  plantar  cal- 
caneonavicular ligament  is  a  broad  and  thick 
band  of  fibres,  which  connects  the  anterior 
margin  of  the  sustentaculum  tali  of  the  calca- 


Lateral 
talocalcaneal 

ligament 

Anterior 
talocalcaneal 

ligatnent 


Tibialis 
posterior 


Interosseous 

talocalcaneal 

ligairbent 


Fig.  479.- 


-Ligaments  of  plantar  surface  of  the 
right  foot. 


Fig.  480. — Talocalcaneal  and  talocalcaneonavicular  articula- 
tions exposed  from  above  by  removing  the  talus. 


neus  to  the  plantar  surface  of  the  navicular.  This  ligament  not  only  serves  to 
connect  the  calcaneus  and  navicular,  but  supports  the  head  of  the  talus,  forming 
part  of  the  articular  cavity  in  which  it  is  received.  The  dorsal  surface  of  the 
ligament  presents  a  fibrocartilaginous  facet,  lined  by  the  synovial  membrane, 
and  upon  this  a  portion  of  the  head  of  the  talus  rests.  Its  plantar  surface  is 
supported  by  the  tendon  of  the  Tibialis  posterior ;  its  medial  border  is  blended  with 
the  forepart  of  the  deltoid  ligament  of  the  ankle-joint. 


456 


SYNDESMOLOGY 


Applied  Anatomy. — The  plantar  calcaneonavicular  ligament,  by  supporting  the  head  of  the 
talus,  is  principally  concerned  in  maintaining  the  arch  of  the  foot.  When  it  yields,  the  head  of 
the  talus  is  pressed  downward,  medialward,  and  forward  by  the  weight  of  the  body,  and  the 
foot  becomes  flattened,  expanded,  and  turned  lateralward,  and  exhibits  the  condition  known  as 
flat-foot.  This  ligament  contains  a  considerable  amount  of  elastic  fibres,  so  as  to  give  elasticity 
to  the  arch  and  spring  to  the  foot;  hence  it  is  sometimes  called  the  "spring"  ligament.  It  is 
supported,  on  its  plantar  surface,  by  the  tendon  of  the  Tibialis  posterior,  which  spreads  out  at 
its  insertion  into  a  number  of  fasciculi,  to  be  attached  to  most  of  the  tarsal  and  metatarsal 
bones.  This  prevents  undue  stretching  of  the  ligament,  and  is  a  protection  against  the  occur- 
rence of  flat-foot;  hence  muscular  weakness  is,  in  most  cases,  the  primary  cause  of  the 
deformity. 

Cuneonavicular  Articulation  (articidatio  cuneonamcularis ;  articulation  of  the 
navicular  with  the  cuneiform  hones). — The  navicular  is  connected  to  the  three 
cuneiform  bones  by  dorsal  and  plantar  ligaments. 

The  Dorsal  Ligaments  (ligamenta  navicular icuneif or mia  dorsalia).- — The  dorsal 
ligaments  are  three  small  bundles,  one  attached  to  each  of  the  cuneiform  bones. 
The  bundle  connecting  the  navicular  with  the  first  cuneiform  is  continuous  around 
the  medial  side  of  the  articulation  with  the  plantar  ligament  which  unites  these 
two  bones. 

The  Plantar  Ligaments  (ligamenta  navicular  icuneif  or  mia  ylantaria). — The  plantar 
ligaments  have  a  similar  arrangement  to  the  dorsal,  and  are  strengthened  by  slips 
from  the  tendon  of  the  Tibialis  posterior. 


Deltoid 
ligament 


■Ankle-joint 


Talofibular 
ligame^it 


Interosseous 

alocalcaneal 

ligament 


Mctata)  sals. 
Fig.  481. — Oblique  section  of  left  intertarsal  and  tarsometatarsal  articulations,  showing  the  synovial  cavities 


Synovial  Membrane. — The  synovial  membrane  of  these  joints  is  part  of  the  great  tarsal  synovial 
membrane  (Fig.  481). 

Movements. — Mere  gliding  movements  are  permitted  between  the  navicular  and  cuneiform 
bones. 


TARSOMETATARSAL  ARTICULATIONS  457 

Cuboideonavicular  Articulation. — The  navicular  bone  is  connected  with  the 
cuboid  by  dorsal,  phnitar,  and  interosseous  ligaments. 

The  Dorsal  Ligament  [Ii(/a)iienfn))i  ciiboideonavicvlare  dorsale)  .■ — The  dorsal  ligament 
extends  obliciueiy  forward  and  lateralward  from  the  navicular  to  the  cuboid  bone. 

The  Plantar  Ligament  {ligameiitum  cuboideonauiculare  ylantare). — The  plantar 
ligament  passes  nearly  transversely  between  these  two  bones. 

The  Interosseous  Ligament. — The  interosseous  ligament  consists  of  strong  trans- 
verse fibres,  and  connects  the  rough  non-articular  portions  of  the  adjacent  surfaces 
of  the  two  bones. 

Synovial  Membrane. — The  synovial  membrane  of  this  joint  is  part  of  the  great  tarsal  synovial 
membrane  (Fig.  -481). 

Movements. — The  movements  permitted  between  the  navicular  and  cuboid  bones  are  limited 
to  a  slight  ghding  upon  each  other. 

Intercuneiform  and  Cuneocuboid  Articulations. — The  three  cuneiform  bones  and 
the  cuboid  are  connected  together  by  dorsal,  plantar,  and  interosseous  ligaments. 

The  Dorsal  Ligaments  {ligamenta  interciineiformia  dorsalia). — The  dorsal  liga- 
ments consist  of  three  transverse  bands:  one  connects  the  first  with  the  second 
cuneiform,  another  the  second  with  the  third  cuneiform,  and  another  the  third 
cuneiform  with  the  cuboid. 

The  Plantar  Ligaments  {ligamenta  intercuneiformia  plantaria). — The  plantar  liga- 
ments have  a  similar  arrangement  to  the  dorsal,  and  are  strengthened  by  slips 
from  the  tendon  of  the  Tibialis  posterior. 

The  Interosseous  Ligaments  (ligamenta  intercuneiformia  interossea). — The  inter- 
osseous ligaments  consist  of  strong  transverse  fibres  which  pass  between  the  rough 
non-articular  portions  of  the  adjacent  surfaces  of  the  bones. 

Synovial  Membrane. — The  synovial  membrane  of  these  joints  is  part  of  the  great  tarsal  synovial 
membrane  (Fig.  481). 

Movements. — The  movements  permitted  between  these  bones  are  limited  to  a  slight  gliding 
upon  each  other. 

Applied  Anatomy. — In  spite  of  the  great  strength  of  the  ligaments  which  connect  the  tarsal 
bones  together,  dislocation  at  some  of  the  tarsal  joints  does  occasionally  occur.  When  this 
takes  place,  it  is  most  commonly  in  connection  with  the  talus;  for  not  only  may  this  bone  be 
dislocated  from  the  tibia  and  fibula  at  the  ankle-joint,  but  the  other  bones  may  be  dislocated 
from  it,  the  bone  remaining  in  situ  in  the  tibiofibular  mortise.  This  constitutes  what  is  known  as . 
the  subtalar  dislocation.  Or,  agaih,  the  talus  may  be  dislocated  from  all  its  connections — from  the 
tibia  and  fibula  above,  the  calcaneous  below,  and  the  navicular  in  front — and  may  even  undergo 
a  rotation,  on  either  a  vertical  or  a  horizontal  axis.  In  the  former  case  the  long  axis  of  the  bone 
is  directed  across  the  joint,  so  that  the  head  faces  the  articular  surface  on  one  or  other  malleolus; 
in  the  latter,  the  collateral  sm-faces  are  directed  upward  and  downward,  so  that  the  superior 
surface  faces  to  one  or  the  other  side.  Reduction  in  these  cases  is  often  very  difficult  or  impossible, 
and  the  displaced  talus  may  require  removal  by  open  operation.  Dislocation  may  also  occur 
at  the  transverse  tarsal  joint,  the  anterior  tarsal  bones  being  luxated  from  the  talus  and  calcaneus. 
The  other  tarsal  bones  are  occasionally,  though  rarely,  dislocated  from  their  connections. 

VI.     Tarsometatarsal  Articulations  (Articulationes  Tarsometatarseae) . 

These  are  arthrodial  joints.  The  bones  entering  into  their  formation  are  the 
first,  second,  and  third  cuneiforms,  and  the  cuboid,  which  articulate  w^ith  the  bases 
of  the  metatarsal  bones.  The  first  metatarsal  bone  articulates  with  the  first  cunei- 
form; the  second  is  deeply  wedged  in  between  the  first  and  third  cuneiforms 
articulating  by  its  base  with  the  second  cuneiform;  the  third  articulates  with  the 
third  cuneiform;  the  fourth,  with  the  cuboid  and  third  cuneiform;  and  the  fifth, 
with  the  cuboid.  The  bones  are  connected  by  dorsal,  plantar,  and  interosseous 
ligaments. 

The  Dorsal  Ligaments  {ligamenta  tarsometatarsea  dorsalia) . — The  dorsal  ligaments 
are  strong,  flat  bands.  The  first  metatarsal  is  joined  to  the  first  cuneiform  by  a 
broad,  thin  band;  the  second  has  three,  one  from  each  cuneiform  bone;  the  third 


458  SYNDESMOLOGY 

has  one  from  the  third  cuneiform;  tlie  fourtli  has  one  from  the  third  cuneiform 
and  one  from  the  cuboid;  and  the  fifth,  one  from  the  cuboid. 

The  Plantar  Ligaments  iUgamenta  tarsometatarsea  ylantaria). — The  plantar  Hga- 
ments  consist  of  k)ngitudinal  and  ohhque  hands,  (Hsposed  with  less  regularity 
than  the  dorsal  ligaments.  Those  for  the  first  and  second  metatarsals  are  the 
strongest;  the  second  and  third  metatarsals  are  joined  by  oblique  bands  to  the 
first  cuneiform;  the  fourth  and  fifth  metatarsals  are  connected  by  a  few  fibres 
to  the  cuboid. 

The  Interosseous  Ligaments  {ligamenta  cimeometatarsea  interussia). — The  inter- 
osseous ligaments  are  three  in  number.  The  first  is  the  strongest,  and  passes  from 
the  lateral  surface  of  the  first  cuneiform  to  the  adjacent  angle  of  the  second  meta- 
tarsal. The  second  connects  the  third  cuneiform  with  the  adjacent  angle  of  the 
second  metatarsal.  The  third  connects  the  lateral  angle  of  the  third  cuneiform 
with  the  adjacent  side  of  the  base  of  the  third  metatarsal. 

Sjmovial  Membrane  (Fig.  481). — -The  synovial  membrane  between  the  first  cuneiform  and 
the  first  metatarsal  forms  a  distinct  sac.  The  synovial  membrane  between  the  second  and  third 
cuneiforms  behind,  and  the  second  and  thud  metatarsal  bones  in  front,  is  part  of  the  great  tarsal 
synovial  membrane.  Two  prolongations  are  sent  forward  from  it,  one  between  the  adjacent  sides 
of  the  second  and  third,  and  another  between  those  of  the  third  and  fourth  metatarsal  bones. 
The  synovial  membrane  between  the  cuboid  and  the  fourth  and  fifth  metatarsal  bones  forms  a 
distinct  sac.    From  it  a  prolongation  is  sent  forward  between  the  fourth  and  fifth  metatarsal  bones. 

Movements. — The  movements  permitted  between  the  tarsal  and  metatarsal  bones  are  limited 
to  shght  ghding  of  the  bones  upon  each  other. 

Nerve  Supply. — The  intertarsal  and  tarsometatarsal  joints  are  supplied  by  the  deep  peroneal 
nerve. 

VII.     Intermetatarsal  Articulations  (Articulationes  Intermetatarseae) . 

The  base  of  the  first  metatarsal  is  not  connected  with  that  of  the  second  by  any 
ligaments;  in  this  respect  the  great  toe  resembles  the  thumb. 

The  bases  of  the  other  four  metatarsals  are  connected  by  the  dorsal,  plantar, 
and  interosseous  ligaments. 

The  Dorsal  Ligaments  {ligamenta  basiwn  [oss.  metatars.]  dorsalia)  pass  transversely 
between  the  dorsal  surfaces  of  the  bases  of  the  adjacent  metatarsal  bones. 

The  Plantar  Ligaments  (ligamenta  hasiiim  [oss.  metatars]  plantaria). — The  plantar 
ligaments  have  a  similar  arrangement  to  the  dorsal. 

The  Interosseous  Ligaments  {ligamenta  hasium  [oss.  metatars.]  interossea). — The 
interosseous  ligaments  consist  of  strong  transverse  fibres  which  connect  the  rough 
non-articular  portions  of  the  adjacent  surfaces. 

Synovial  Membranes  (Fig.  481). — The  synovial  membranes  between  the  second  and  third, 
and  the  third  and  fourth  metatarsal  bones  are  part  of  the  great  tarsal  synovial  membrane;  that 
between  the  fourth  and  fifth  is  a  prolongation  of  the  synovial  membrane  of  the  cuboideometatarsal 
joint. 

Movements. — The  movement  permitted  between  the  tarsal  ends  of  the  metatarsal  bones 
is  limited  to  a  slight  gUding  of  the  articular  surfaces  upon  one  another. 

The  heads  of  all  the  metatarsal  bones  are  connected  together  by  the  transverse 
metatarsal  ligament. 

The  Transverse  Metatarsal  Ligament. — The  transverse  metatarsal  ligament  is  a 
narrow  band  wdiich  runs  across  and  connects  together  the  heads  of  all  the  meta- 
tarsal bones;  it  is  blended  anteriorly  with  the  plantar  (glenoid)  ligaments  of  the 
metatarsophalangeal  articulations.  Its  plantar  surface  is  concave  where  the 
Flexor  tendons  run  below  it;  above  it  the  tendons  of  the  Interossei  pass  to  their 
insertions.  It  diflfers  from  the  transverse  metacarpal  ligament  in  that  it  connects 
the  metatarsal  to  the  others. 

The  Synovial  Membranes  in  the  Tarsal  and  Tarsometatarsal  Joints  (Fig.  481). — The  synovial 
membranes  found  in  the  articulations  of  the  tarsus  and  metatarsus  are  six  in  number:    one  for 


ARCHES  OF  Tflh:  FOOT  459 

the  talocalcaueal  articulation;  a  sccoiul  i'or  the  talocalcanoonavicidar  articulation;  a  third  for 
the  calcaneocuboid  articulation;  and  a  fourth  for  the  cuneonavicnilar,  intercuneiform,  and  cuneo- 
cuboid  articulations,  the  articulations  of  the  second  and  third  cuneiforms  with  the  bases  of  the 
second  and  third  metatarsal  bones,  and  the  adjatient  surfaces  of  the  bases  of  the  second,  third, 
and  fourth  metatarsal  bones;  a  fifth  for  the  first  cuneiform  with  the  metatarsal  bone  of  the  great 
toe;  and  a  sixth  for  the  articulation  of  the  cuboid  with  the  fourth  and  fifth  metatarsal  bones. 
A  small  synovial  cavity  is  sometimes  found  between  the  contiguous  surfaces  of  the  navicular 
and  cuboid  bones. 

VIII.  Metatarsophalangeal  Articulations  (Articulationes  Metatarsophalangeae) . 

The  metatarsophalangeal  articulations  are  of  the  condyloid  kind,  formed  by 
the  reception  of  the  rounded  heads  of  the  metatarsal  bones  in  shallow  cavities 
on  the  ends  of  the  first  phalanges. 

The  ligaments  are  the  plantar  and  two  collateral. 

The  Plantar  Ligaments  {ligamenta  accessoria  j)lantaria;  glenoid  ligaments  of  Cru- 
veilhier). — The  plantar  ligaments  are  thick,  dense,  fibrous  structures.  They  are 
placed  on  the  plantar  surfaces  of  the  joints  in  the  intervals  between  the  collateral 
ligaments,  to  which  they  are  connected;  they  are  loosely  united  to  the  metatarsal 
bones,  but  very  firmh'  to  the  bases  of  the  first  phalanges.  Their  plantar  surfaces 
are  intimately  blended  with  the  transverse  metatarsal  ligament,  and  grooved  for 
the  passage  of  the  Flexor  tendons,  the  sheaths  surrounding  which  are  connected 
to  the  sides  of  the  grooves.  Their  deep  surfaces  form  part  of  the  articular  facets 
for  the  heads  of  the  metatarsal  bones,  and  are  lined  by  synovial  membrane. 

The  Collateral  Ligaments  {ligamenta  collateralia;  lateral  ligaments). — The  collat- 
eral ligaments  are  strong,  rounded  cords,  placed  one  on  either  side  of  each  joint, 
and  attached,  by  one  end,  to  the  posterior  tubercle  on  the  side  of  the  head  of  the 
metatarsal  bone,  and,  by  the  other,  to  the  contiguous  extremity  of  the  phalanx. 

The  place  of  dorsal  ligaments  is  supplied  by  the  Extensor  tendons  on  the  dorsal 
surfaces  of  the  joints. 

Movements. — ^The  movements  permitted  in  the  metatarsophalangeal  articulations  are  flexion, 
extension,  abduction,  and  adduction. 

IX.  Articulations  of  the  Digits  (Articulationes  Digitorum  Pedis;  Articulations  of 

the  Phalanges). 

The  interphalangeal  articulations  are  ginglymoid  joints,  and  each  has  a  plantar 
and  two  collateral  ligaments. 

The  arrangement  of  these  ligaments  is  similar  to  that  in  the  metatarsophalangeal 
articulations:  the  Extensor  tendons  supply  the  places  of  dorsal  ligaments. 

Movements. — ^The  only  movements  permitted  in  the  joints  of  the  digits  are  flexion  and  exten- 
sion; these  movements  are  more  extensive  between  the  first  and  second  phalanges  than  between 
the  second  and  third.  The  amount  of  flexion  is  very  considerable,  but  extension  is  limited  by  the 
plantar  and  collateral  ligaments. 

Applied  Anatomy. — Gout  peculiarly  affects  the  metatarsophalangeal  joint  of  the  big  toe,  be- 
ginning with  the  deposit  of  sodium  and  calcium  urates  in  the  articular  cartilages,  and  slow  necrosis 
of  the  surrounding  tissue.  Later  the  circumarticular  fibrous  tissue  becomes  the  seat  of  these 
gouty  deposits,  and  considerable  thickening  and  deformity  may  result.  The  other  chief  joint 
affections,  such  as  rheumatism,  gonorrhoeal  arthritis,  tuberculosis,  or  syphilis,  seldom  attack 
the  big  toe-joint;  but  septic  arthritis  associated  with  perforating  ulcer  of  the  foot  is  not  uncommon. 

Arches  of  the  Foot. 

In  order  to  allow  it  to  support  the  weight  of  the  body  in  the  erect  posture  with 
the  least  expenditure  of  material,  the  foot  is  constructed  of  a  series  of  arches 
formed  by  the  tarsal  and  metatarsal  bones,  and  strengthened  by  the  ligaments 
and   tendons  of  the  foot. 


460  SYNDESMOLOGY 

The  main  arches  are  the  antero-posterior  arches,  which  may,  for  descriptive 
purposes,  be  regarded  as  divisible  into  two  types — a  medial  and  a  lateral.  The 
medial  arch  (see  Fig.  417,  page  376)  is  made  up  by  the  calcaneus,  the  talus,  the 
navicular,  the  three  cuneiforms,  and  the  first,  second,  and  third  metatarsals.  Its 
summit  is  at  the  superior  articular  surface  of  the  talus,  and  its  two  extremities  or 
piers,  on  which  it  rests  in  standing,  are  the  tuberosity  on  the  plantar  surface  of 
the  calcaneus  posteriorly  and  the  heads  of  the  first,  second,  and  third  metatarsal 
bones  anteriorly.  The  chief  characteristic  of  this  arch  is  its  elasticity,  due  to  its 
height  and  to  the  number  of  small  joints  between  its  component  parts.  Its  weakest 
part,  i.  e.,  the  part  most  liable  to  yield  from  overpressure,  is  the  joint  between 
the  talus  and  navicular,  but  this  portion  is  braced  by  the  plantar  calcaneonavicular 
ligament,  which  is  elastic  and  is  thus  able  to  quickly  restore  the  arch  to  its  pristine 
condition  when  the  disturbing  force  is  removed.  The  ligament  is  strengthened 
medially  by  blending  with  the  deltoid  ligament  of  the  ankle-joint,  and  is  supported 
inferiorly  by  the  tendon  of  the  Tibialis  posterior,  which  is  spread  out  in  a  fan- 
shaped  insertion  and  prevents  undue  tension  of  the  ligament  or  such  an  amount 
of  stretching  as  would  permanently  elongate  it.  The  arch  is  further  supported  by 
the  plantar  aponeurosis,  by  the  small  muscles  in  the  sole  of  the  foot,  by  the  tendons 
of  the  Tibialis  anterior  and  posterior  and  Peronaeus  longus,  and  by  the  ligaments 
of  all  the  articulations  involved.  The  lateral  arch  (see  Fig.  418,  page  376)  is  com- 
posed of  the  calcaneus,  the  cuboid,  and  the  fourth  and  fifth  metatarsals.  Its 
summit  is  at  the  talocalcaneal  articulation,  and  its  chief  joint  is  the  calcaneocuboid, 
which  possesses  a  special  mechanism  for  locking,  and  allows  only  a  limited  move- 
ment. The  most  marked  features  of  this  arch  are  its  solidity  and  its  slight  eleva- 
tion; two  strong  ligaments,  the  long  plantar  and  the  plantar  calcaneocuboid, 
together  with  the  Extensor  tendons  and  the  short  muscles  of  the  little  toe,  preserve 
its  integrity. 

While  these  medial  and  lateral  arches  may  be  readily  demonstrated  as  the 
component  antero-posterior  arches  of  the  foot,  yet  the  fundamental  longitudinal 
arch  is  contributed  to  by  both,  and  consists  of  the  calcaneus,  cuboid,  third  cunei- 
form, and  third  metatarsal :  all  the  other  bones  of  the  foot  may  be  removed  without 
destroying  this  arch. 

In  addition  to  the  longitudinal  arches  the  foot  presents  a  series  of  transverse 
arches.  At  the  posterior  part  of  the  metatarsus  and  the  anterior  part  of  the  tarsus 
the  arches  are  complete,  but  in  the  middle  of  the  tarsus  they  present  more  the 
characters  of  half-domes  the  concavities  of  which  are  directed  downward  and 
medialward,  so  that  when  the  medial  borders  of  the  feet  are  placed  in  apposition 
a  complete  tarsal  dome  is  formed.  The  transverse  arches  are  strengthened  by  the 
interosseous,  plantar,  and  dorsal  ligaments,  by  the  short  muscles  of  the  first  and 
fifth  toes  (especially  the  transverse  head  of  the  Adductor  hallucis),  and  by  the 
Peronaeus  longus,  whose  tendon  stretches  across  between  the  piers  of  the  arches. 


MYOLOGY; 


rPHE  Muscles  are  connected  Avith  the  bones,  cartilages,  ligaments,  and  skin, 
-*-  either  directly,  or  through  the  intervention  of  fibrous  structures  called  tendons 
or  aponeuroses,  ^yhe^e  a  muscle  is  attached  to  bone  or  cartilage,  the  fibres  end 
in  blunt  extremities  upon  the  periosteum  or  perichondrium,  and  do  not  come  into 
direct  relation  with  the  osseous  or  cartilaginous  tissue.  Where  muscles  are  con- 
nected with  its  skin,  they  lie  as  a  flattened  layer  beneath  it,  and  are  connected 
with  its  areolar  tissue  by  larger  or  smaller  bundles  of  fibres,  as  in  the  muscles  of 
the  face. 

The  muscles  vary  extremely  in  their  form.  In  the  limbs,  they  are  of  considerable 
length,  especially  the  more  superficial  ones;  they  surround  the  bones,  and  constitute 
an  important  protection  to  the  various  joints.  In  the  trunk,  they  are  broad, 
flattened,  and  expanded,  and  assist  in  forming  the  walls  of  the  trunk  cavities. 
Hence  the  reason  of  the  terms,  long,  broad,  short,  etc.,  used  in  the  description  of  a 
muscle. 

There  is  considerable  variation  in  the  arrangement  of  the  flbres  of  certain  muscles 
with  reference  to  the  tendons  to  which  they  are  attached.  In  some  muscles  the 
fibres  are  parallel  and  run  directly  from  their  origin  to  their  insertion;  these  are 
quadrilateral  muscles,  such  as  the  Thyreohyoideus.  A  modification  of  these  is 
found  in  the  fusiform  muscles,  in  which  the  fibres  are  not  quite  parallel,  but  slightly 
curved,  so  that  the  muscle  tapers  at  either  end;  in  their  actions,  however,  they 
resemble  the  quadrilateral  muscles.  Secondly,  in  other  muscles  the  fibres  are 
convergent;  arising  by  a  broad  origin,  they  converge  to  a  narrow  or  pointed  inser- 
tion. This  arrangement  of  fibres  is  found  in  the  triangular  muscles — e.  g.,  the 
Temporalis.  In  some  muscles,  which  otherwise  would  belong  to  the  quadrilateral 
or  triangular  type,  the  origin  and  insertion  are  not  in  the  same  plane,  but  the  plane 
of  the  line  of  origin  intersects  that  of  the  line  of  insertion;  such  is  the  case  in  the 
Pectineus.  Thirdly,  in  some  muscles  {e.  g.,  the  Peronei)  the  fibres  are  oblique  and 
converge,  like  the  plumes  of  a  quill  pen,  to  one  side  of  a  tendon  which  runs  the  entire 
length  of  the  muscle;  such  muscles  are  termed  unipennate.  K  modification  of  this 
condition  is  found  where  oblique  fibres  converge  to  both  sides  of  a  central  tendon; 
these  are  called  bipennate,  and  an  example  is  afforded  in  the  Rectus  femoris. 
Finally,  there  are  muscles  in  which  the  fibres  are  arranged  in  curved  bundles  in 
one  or  more  planes,  as  in  the  Sphincters.  The  arrangement  of  the  fibres  is  of  con- 
siderable importance  in  respect  to  the  relative  strength  and  range  of  movement 
of  the  muscle.  Those  muscles  where  the  fibres  are  long  and  few  in  number  have 
great  range,  but  diminished  strength;  where,  on  the  other  hand,  the  fibres  are 
short  and  more  numerous,  there  is  great  power,  but  lessened  range. 

The  names  applied  to  the  various  muscles  have  been  derived:  (1)  from  their 
situation,  as  the  Tibialis,  Radialis,  Ulnaris,  Peronaeus;  (2)  from  their  direction,  as 
the  Rectus  abdominis,  Obliqui  capitis,  Transversus  abdominis;  (3)  from  their  uses, 
as  Flexors,  Extensors,  Abductors,  etc.;  (4)  from  their  shape,  as  the  Deltoideus, 

1  The  muscles  and  fasciae  are  described  conjointly,  in  order  that  the  student  may  consider  the  arrangement  of  the 
latter  in  his  dissection  of  the  former.  It  is  rare  for  the  student  of  anatomy  in  this  country  t9  have  the  opportunity 
of  dissecting  the  fasciae  separately;  and  it  is  for  this  reason,  as  well  as  from  the  close  connection  that  exists  between 
the  muscles  and  their  investing  sheaths,  that  they  are  considered  together.  Some  general  observations  are  first  made 
on  the  anatomy  of  the  muscles  and  fasciae,  the  special  descriptions  being  given  in  connection  with  the  different  regions. 


462  MYOLOGY 

Rhomboideus;  (5)  from  the  number  of  their  divisions,  as  the  Biceps  and  Triceps; 
(6)  from  their  points  of  attachment,  as  the  Sternocleidomastoideus,  Sternohyoideus, 
Sternothyreoideus. 

In  the  description  of  a  muscle,  the  term  origin  is  meant  to  imply  its  more  fixed 
or  central  attachment;  and  the  term  insertion  the  movable  point  on  which  the  force 
of  the  muscle  is  applied;  but  the  origin  is  absolutely  fixed  in  only  a  small  number 
of  muscles,  such  as  those  of  the  face  which  are  attached  by  one  extremity  to  immov- 
able bones,  and  by  the  other  to  the  movable  integument;  in  the  greater  number, 
the  muscle  can  be  made  to  act  from  either  extremity. 

In  the  dissection  of  the  muscles,  attention  should  be  directed  to  the  exact  origin, 
insertion,  and  actions  of  each,  and  to  its  more  important  relations  with  surrounding 
parts.  While  accurate  knowledge  of  the  points  of  attachment  of  the  muscles  is 
of  great  importance  in  the  determination  of  their  actions,  it  is  not  to  be  regarded 
as  conclusive.  The  action  of  the  muscle  deduced  from  its  attachments,  or  even 
by  pulling  on  it  in  the  dead  subject,  is  not  necessarily  its  action  in  the  living.  By 
pulling,  for  example,  on  the  Brachioradialis  in  the  cadaver  the  hand  may  be  slightly 
supinated  when  in  the  prone  position  and  slightly  pronated  when  in  the  supine 
position,  but  there  is  no  evidence  that  these  actions  are  performed  by  the  muscle 
during  life.  It  is  impossible  for  an  individual  to  throw  into  action  any  one  muscle; 
in  other  words,  movements,  not  muscles,  are  represented  in  the  central  nervous 
system.  To  carry  out  a  movement  a  definite  combination  of  muscles  is  called  into 
play,  and  the  individual  has  no  power  either  to  leave  out  a  muscle  from  this  com- 
bination or  to  add  one  to  it.  One  (or  more)  muscle  of  the  combination  is  the  chief 
moving  force;  when  this  muscle  passes  over  more  than  one  joint  other  muscles 
(syngeric  muscles)  come  into  play  to  inhibit  the  movements  not  required;  a  third 
set  of  muscles  (fixation  muscles)  fix  the  limb — i.  e.,  in  the  case  of  the  limb-movements 
— and  also  prevent  disturbances  of  the  equilibrium  of  the  body  generally.  As  an 
example,  the  movement  of  the  closing  of  the  fist  may  be  considered:  (1)  the  prime 
movers  are  the  Flexores  digitorum.  Flexor  pollicis  longus,  and  the  small  muscles 
of  the  thumb;  (2)  the  synergic  muscles  are  the  Extensores  carpi,  which  prevent 
flexion  of  the  wrist;  while  (3)  the  fixation  muscles  are  the  Biceps  and  Triceps 
brachii,  which  steady  the  elbow^  and  shoulder.  A  further  point  which  must  be 
borne  in  mind  in  considering  the  actions  of  muscles  is  that  in  certain  positions 
a  movement  can  be  effected  by  gravity,  and  in  such  a  case  the  muscles  acting  are 
the  antagonists  of  those  which  might  be  supposed  to  be  in  action.  Thus  in  flexing 
the  trunk  when  no  resistance  is  interposed  the  Sacrospinales  contract  to  regulate 
the  action  of  gravity,  and  the  Recti  abdominis  are  relaxed.^ 

By  a  consideration  of  the  action  of  the  muscles,  the  surgeon  is  able  to  explain 
the  causes  of  displacement  in  various  forms  of  fracture,  and  the  causes  which  pro- 
duce distortion  in  various  deformities,  and,  consequently,  to  adopt  appropriate 
treatment  in  each  case.  The  relations,  also,  of  some  of  the  muscles,  especially 
those  in  immediate  apposition  with  the  larger  bloodvessels,  and  the  surface  mark- 
ings they  produce,  should  be  remembered,  as  they  form  useful  guides  in  the 
application  of  ligatures  to  those  vessels. 

The  minute  anatomy  of  muscular  tissue  is  described  on  pages  64  to  69. 

Applied  Anatomy. — Degeneration  of  muscular  tissue  is  important  clinically,  and  is  met  with 
in  two  main  conditions.  In  one,  the  degeneration  is  myopathic,  or  primary  in  the  muscles  them- 
selves; in  the  other  it  is  neuropathic,  or  secondary  to  some  lesion  of  the  nervous  system — a  hemor- 
rhage into  the  brain,  for  example,  or  injury  or  inflammation  of  some  part  of  the  medulla  spinalis 
or  peripheral  nerves.  In  either  case  more  or  less  paralysis  and  atrophy  of  the  affected  muscles 
result.  When  the  degeneration  begins  primarily  in  the  muscles,  however,  it  often  happens  that 
though  the  muscle  fibres  waste  away,  their  place  is  taken  by  fibrous  and  fatty  tissue  to  such 
an  extent  that  the  affected  muscles  increase  in  volmne,  and  actually  appear  to  hypertrophy. 

1  Consult  in  this  connection  the  Croonian  Lectures  (190.3)  on  "Muscular  Movements  and  Their  Representation  in 
the  Central  Nervous  System,"  by  Charles  E.  Beevor,  M.D. 


TENDONS,  APONEUROSPJS,  AND  FASCIA  463 

Ossification  of  muscular  tissue  as  a  result  of  repeated  strain  or  injury  is  not  infrequent.  It 
is  oftenest  found  about  the  tendon  of  the  Adductor  longus  and  \'astus  medialis  in  horsemen, 
or  in  the  Pectoralis  major  and  Deltoideus  of  soldiers.  It  may  take  the  form  of  exostoses  firmly 
fixed  to  the  bone — e.  g.,  "rider's  bone"  on  the  femur — or  of  layers  or  spicules  of  bone  lying  in 
the  muscles  or  their  fascias  and  tendons.  Busse  states  tliat  these  bony  deposits  are  preceded 
by  a  hemorrhagic  myositis  due  to  injury,  the  effused  blood  organizing  and  being  finally  converted 
into  bone.  In  the  rarer  disease,  progressive  myositis  ossificans,  there  is  an  unexplained  tendency 
for  practically  any  of  the  voluntary  muscles  to  become  converted  into  solid  and  brittle  bony 
masses  which  are  eompletelj^  rigid. 

TENDONS,   APONEUROSES,  AND  FASCIA. 

Tendons  are  white,  glistening,  fibrous  cords,  varying  in  length  and  thickness, 
sometimes  round,  sometimes  flattened,  and  devoid  of  elasticity.  They  consist 
almost  entirely  of  white  fibrous  tissue,  the  fibrils  of  which  have  an  undulating 
course  parallel  with  each  other  and  are  firmly  united  together.  They  are  ver}^ 
sparingly  supplied  with  bloodvessels,  the  smaller  tendons  presenting  in  their 
interior  no  trace  of  them.  Nerves  supplying  tendons  have  special  modifications 
of  their  terminal  fibres,  named  organs  of  Golgi. 

Aponeuroses  are  flattened  or  ribbon-shaped  tendons,  of  a  pearly  white  color, 
iridescent,  glistening,  and  similar  in  structure  to  the  tendons.  They  are  only 
sparingly  supplied  with  bloodvessels. 

The  tendons  and  aponeuroses  are  connected,  on  the  one  hand,  with  the  muscles, 
and,  on  the  other  hand,  with  the  movable  structures,  as  the  bones,  cartilages  liga- 
ments, and  fibrous  membranes  (for  instance,  the  sclera) .  Where  the  muscular  fibres 
are  in  a  direct  line  with  those  of  the  tendon  or  aponeurosis,  the  two  are  directly 
continuous.  But  where  the  muscular  fibres  join  the  tendon  or  aponeurosis  at  an 
oblique  angk,  they  end,  according  to  Kolliker,  in  rounded  extremities  which  are 
received  into  corresponding  depressions  on  the  surface  of  the  latter,  the  connective 
tissue  between  the  muscular  fibres  being  continuous  wdth  that  of  the  tendon.  The 
latter  mode  of  attachment  occurs  in  all  the  penniform  and  bipenniform  muscles, 
and  in  those  muscles  the  tendons  of  which  commence  in  a  membranous  form, 
as  the  Gastrocnemius  and  Soleus. 

The  fasciae  are  fibroareolar  or  aponeurotic  laminae,  of  variable  thickness  and 
strength,  found  in  all  regions  of  the  body,  investing  the  softer  and  more  delicate 
organs.  During  the  process  of  development  many  of  the  cells  of  the  mesoderm 
are  difl'erentiated  into  bones,  muscles,  vessels,  etc.;  the  cells  of  the  mesoderm  which 
are  not  so  utilized  form  an  investment  for  these  structures  and  are  differentiated 
into  the  true  skin  and  the  fasciee  of  the  body.  They  have  been  subdivided,  from 
the  situations  in  which  they  occur,  into  superficial  and  deep. 

The  superficial  fascia  is  found  immediately  beneath  the  integument  over  almost  the 
entire  surface  of  the  body.  It  connects  the  skin  with  the  deep  fascia,  and  consists 
of  fibroareolar  tissue,  containing  in  its  meshes  pellicles  of  fat  in  varying  quantity. 
It  varies  in  thickness  in  different  parts  of  the  body;  in  the  groin  it  is  so  thick  that 
it  may  be  subdivided  into  several  laminae.  Beneath  the  fatty  layer  there  is  generally 
another  layer  of  superficial  fascia,  comparatively  devoid  of  adipose  tissue,  in  which 
the  trunks  of  the  subcutaneous  vessels  and  nerves  are  found,  as  the  superficial 
epigastric  vessels  in  the  abdominal  region,  the  superficial  veins  in  the  forearm, 
the  saphenous  veins  in  the  leg  and  thigh,  and  the  superficial  lymph  glands.  Certain 
cutaneous  muscles  also  are  situated  in  the  superficial  fascia,  as  the  Platysma  in 
the  neck,  and  the  Orbicularis  oculi  around  the  eyelids.  This  fascia  is  most  dis- 
tinct at  the  lower  part  of  the  abdomen,  perineum,  and  extremities;  it  is  very  thin 
in  those  regions  where  muscular  fibres  are  inserted  into  the  integument,  as  on  the 
side  of  the  neck,  the  face,  and  around  the  margin  of  the  anus.  It  is  very  dense  in 
the  scalp,  in  the  palms  of  the  hands,  and  soles  of  the  feet,  forming  a  fibro-fatty 
layer,  which  binds  the  integument  firmly  to  the  underlying  structures. 


464 


MYOLOGY 


The  superficial  fascia  connects  the  skin  to  the  subjacent  parts,  facilitates  the 
movement  of  the  skin,  serves  as  a  soft  nidus  for  the  passage  of  vessels  and  nerves 
to  the  integument,  and  retains  the  warmth  of  the  body,  since  the  fat  contained  in 
its  areolae  is  a  bad  conductor  of  heat. 

The  deep  fascia  is  a  dense,  inelastic,  fibrous  membrane,  forming  sheaths  for  the 
muscles,  and  in  some  cases  affording  them  broad  surfaces  for  attachment.  It 
consists  of  shining  tendinous  fibres,  placed  parallel  with  one  another,  and  connected 
together  by  other  fibres  disposed  in  a  rectilinear  manner.  It  forms  a  strong  invest- 
ment which  not  only  binds  down  collectively  the  muscles  in  each  region,  but  gives  a 
separate  sheath  to  each,  as  well  as  to  the  vessels  and  nerves.  The  fasciae  are  thick 
in  unprotected  situations,  as  on  the  lateral  side  of  a  limb,  and  thinner  on  the  medial 
side.  The  deep  fasciae  assist  the  muscles  in  their  actions,  by  the  degree  of  tension 
and  pressure  they  make  upon  their  surfaces;  and,  in  certain  situations,  where  they 
are  strengthened  by  the  presence  in  them  of  degenerated  muscular  fibres  which 
have  become  converted  into  fibrous  sheets,  the  degree  of  tension  and  pressure 
is  regulated  by  the  associated  muscles,  as,  for  instance,  by  the  Tensor  fasciae  latae 
and  Glutaeus  maximus  in  the  thigh,  by  the  Biceps  in  the  upper  and  lower  extremi- 
ties, and  Palmaris  longus  in  the  hand.  In  the  limbs,  the  fasciae  not  only  invest 
the  entire  limb,  but  give  off  septa  which  separate  the  various  muscles,  and  are 
attached  to  the  periosteum:  these  prolongations  of  fasciae  are  usually  spoken  of  as 
intermuscular  septa. 

The  Fasciae  and  Muscles  may  be  arranged,  according  to  the  general  division 
of  the  body,  into  those  of  the  head  and  neck;  of  the  trunk;  of  the  upper  extremity; 
and  of  the  lower  extremity. 


THE  FASCIiE  AND  MUSCLES   OF   THE   HEAD. 

I.   THE   MUSCLE    OF    THE    SCALP. 

Epicranius. 

Dissection  (Fig.  482). — The  head  being  shaved,  and  a  block  placed  beneath  the  back  of  the 
neck,  make  a  vertical  incision  through  the  skin,  commencing  at  the  root  of  the  nose  in  front, 


1.  Dissection  of  scalp. 

2,  3,  of  auricular  region. 
4,  5,  6,  of  face. 

7,  8,  of  neck. 


Fig.  482. — Dissection  of  the  head,  face,  and  neck. 


and  terminating  behind  at  the  occipital  protuberance;  make  a  second  incision  in  a  horizontal 
direction  along  the  forehead  and  around  the  side  of  the  head,  from  the  anterior  to  the  posterior 


THE  MUSCLE  OF  THE  SCALP 


465 


extremity  of  the  preceding.  Raise  the  skin  in  front,  from  the  subjacent  muscle,  from  below 
upward;  this  must  be  done  with  extreme  care,  removing  the  integument  from  the  outer  surface 
of  the  vessels  and  the  nerves  which  lie  immediately  beneath  the  skin. 

The  Skin  of  the  Scalp. — This  is  thicker  than  in  any  other  part  of  the  body.  It  is  intimately 
ailherent  to  the  superhcial  fascia,  which  attaches  it  firmly  to  the  imderlying  aponeurosis  and 
muscle.  Movements  of  the  muscle  move  the  skin.  The  hair  follitdes  are  very  closely  set  together, 
and  extend  throughout  the  whole  thickness  of  the  skin.  It  also  (iontains  a  number  of  sebaceous 
glands. 


Corrugatot 


Dilatator  naiis  ant. 
Dilatator  naris  jMst 
Nasalis 
Depressor  septi '" 


Mentalia 


Fig.  483. — Muscles  of  the  head,  face,  and  neck. 


The  superficial  fascia  in  the  cranial  region  is  a  firm,  dense,  fibro-fatty  layer, 
intimately  adherent  to  the  integument,  and  to  the  Epicraniiis  and  its  tendinous 
aponeurosis;  it  is  continuous,  behind,  with  the  superficial  fascia  at  the  back  of  the 
neck;  and,  laterally,  is  continued  over  the  temporal  fascia.  It  contains  between 
its  layers  the  superficial  vessels  and  nerves  and  much  granular  fat. 

The  Epicranius  (Occipitofrontalis)  (Fig.  483)  is  a  broad,  musculofibrous  layer, 
which  covers  the  whole  of  one,  side  of  the  vertex  of  the  skull,  from  the  occipital 
30 


466  MYOLOGY 

bone  to  the  eyebrow.  It  consists  of  two  parts,  the  OccipitaHs  and  the  Frontalis, 
connected  by  an  intervening  tendinous  aponeurosis,  the  galea  aponeurotica. 

The  Occipitalis,  thin  and  quadrilateral  in  form,  arises  by  tendinous  fibres  from 
the  lateral  two-thirds  of  the  superior  nuchal  line  of  the  occipital  bone,  and  from 
the  mastoid  part  of  the  temporal.    It  ends  in  the  galea  aponeurotica. 

The  Frontalis  is  thin,  of  a  ciuadrilateral  form,  and  intimately  adherent  to  the 
superficial  fascia.  It  is  broader  than  the  Occipitalis  and  its  fibres  are  longer  and 
paler  in  color.  It  has  no  bony  attachments.  Its  medial  fibres  are  continuous  with 
those  of  the  Procerus;  its  immediate  fibres  blend  with  the  Corrugator  and  Orbicu- 
laris oculi;  and  its  lateral  fibres  are  also  blended  with  the  latter  muscle  over 
the  zygomatic  process  of  the  frontal  bone.  From  these  attachments  the  fibres 
are  directed  upward,  and  join  the  galea  aponeurotica  below  the  coronal  suture. 
The  medial  margins  of  the  Frontales  are  joined  together  for  some  distance  above 
the  root  of  the  nose;  but  between  the  Occipitales  there  is  a  considerable,  though 
variable,  interval,  occupied  by  the  galea  aponeurotica. 

The  galea  aponeurotica  (epicranial  aponeurosis)  covers  the  upper  part  of  the 
cranium;  behind,  it  is  attached,  in  the  interval  between  the  Occipitales,  to  the 
external  occipital  protuberance  and  highest  nuchal  lines  of  the  occipital  bone; 
in  front,  it  forms  a  short  and  narrow  prolongation  between  the  Frontales.  On 
either  side  it  gives  origin  to  the  Auriculares  anterior  and  superior ;  in  this  situation 
it  loses  its  aponeurotic  character,  and  is  continued  over  the  temporal  fascia  to  the 
zygomatic  arch  as  a  layer  of  laminated  areolar  tissue.  It  is  closely  connected  to 
the  integument  by  the  firm,  dense,  fibro-fatty  layer  which  forms  the  superficial 
fascia  of  the  scalp :  it  is  attached  to  the  pericranium  by  loose  cellular  tissue,  which 
allows  the  aponeurosis,  carrying  with  it  the  integument  to  move  tlirough  a  consid- 
erable distance. 

Nerves. — The  Frontalis  is  supplied  by  the  temporal  branches  of  the  facial  nerve,  and  the 
Occipitalis  by  the  posterior  auricular  branch  of  the  same  nerve. 

Actions. — The  Frontales  raise  the  eyebrows  and  the  skin  over  the  root  of  the  nose,  and  at  the 
same  time  draw  the  scalp  forward,  throwing  the  integument  of  the  forehead  into  transverse 
wrinkles.  The  Occipitales  draw  the  scalp  backward.  By  bringing  alternately  into  action  the 
Frontales  and  Occipitales  the  entire  scalp  may  be  moved  forward  and  backward.  In  the  ordinary 
action  of  the  muscles,  the  eyebrows  are  elevated,  and  at  the  same  time  the  aponeurosis  is  fixed 
by  the  Occipitales,  thus  giving  to  the  face  the  expression  of  surprise;  if  the  action  be  exaggerated, 
the  eyebrows  are  still  further  raised,  and  the  skin  of  the  forehead  thrown  into  transverse  wrinkles, 
as  in  the  expression  of  fright  or  horror. 

A  thin  muscular  slip,  the  Transversus  nuchae,  is  present  in  a  considerable  pro- 
portion (25  per  cent.)  of  cases;  it  arises  from  the  external  occipital  protuberance 
or  from  the  superior  nuchal  line,  either  superficial  or  deep  to  the  Trapezius;  it 
is  frequently  inserted  with  the  Auricularis  posterior,  but  may  join  the  posterior 
edge  of  the  Sternocleidomastoideus. 

Applied  Anatomy. — From  an  anatomical  point  of  view,  the  scalp  consists  of  five  layers,  viz., 
the  skin,  subcutaneous  tissue,  Epicranius  and  its  aponeurosis,  subaponeurotic  connective  tissue, 
and  pericranium.  But  from  a  surgical  standpoint  it  is  better  to  regard  the  first  three  of  these 
structures  as  a  single  layer,  since  they  are  all  intimately  fused  together,  and  when  torn  off  in  an 
accident,  or  turned  down  as  a  flap  in  a  surgical  operation,  remain  firmly  connected  to  each  other. 
In  consequence  of  the  dense  character  of  the  subcutaneous  tissue,  the  amount  of  sweUing  which 
occurs  as  the  result  of  inflammation  is  shght;  and  the  edges  of  a  wound  which  does  not  involve 
the  Epicranius  or  its  aponeurosis  do  not  gape.  The  bloodvessels,  also,  which  lie  in  this  tissue, 
when  wounded,  do  not  contract  and  retract  freely;  and  therefore  the  hemorrhage  from  scalp 
wounds  is  often  very  considerable,  but  can  always  be  arrested  by  pressm-e — ^a  matter  of  great 
importance,  as  it  is  often  very  difficult  or  impossible  to  pick  up  with  forceps  a  wounded  vessel 
in  the  scaljj. 

The  subaponeurotic  connective  tissue  is,  from  a  surgical  point  of  view,  of  considerable  impor- 
tance. It  is  loose  and  lax,  and  is  easily  torn  through;  and  hence,  when  the  scalp  is  wounded,  this 
is  the  tissue  which  is  torn  when  the  flap  is  separated  from  the  parts  beneath.  The  vessels  are 
contained  in  the  flap,  and  there  is  Httle  risk  of  sloughing,  unless  the  vitality  of  the  part  has  been 


THE  MUSCLES  OE  THE  EYELIDS 


467 


uctuiiUy  tlestroyed  by  the  injury.  In  couyequencc  of  the  loose  nature  of  the  sul)tii)oneurotic 
tissue,  any  septic  infhiinniation  is  ai)t  to  assume  a  very  dilTuse  form  and  spread  over  the  skull, 
and,  unless  relieved  by  timely  incisions,  may  lead  to  serious  c()m{)hcations.  Owing  to  the  attach- 
ments of  the  aponeiu-osis  to  the  zj^gomatic  arch  and  highest  nuchal  line,  subaponeurot  ic  etTusions 
sag  down  in  these  situations,  but  do  not  extend  bej'^ond  to  the  infratemporal  fossa  or  into  the  neck; 
anteriorly,  however,  where  there  is  no  definite  attachment  to  bone,  the  effusion  will  pass  down 
over  the  nose,  and  into  the  eyelids.  When  making  incisions  into  the  scalp,  care  should  be  taken 
to  avoid  the  course  of  the  main  arteri(>s. 

The  skin  of  the  scalp  is  abimdantly  sui)iilied  with  sebaceous  and  sudori])ar()us  glands.  The 
former  are  sometimes  the  seat  of  cystic  enlargement,  constituting  the  so-called  sebaceous  cysts 
or  wens. 

II.     THE  MUSCLES  OF  THE  EYELIDS. 


The  muscles  of  the  eyelids  are: 
Levator  palpebrae  superioris. 


Orbicularis  oculi. 


Corrugator. 


Dissection  (Fig.  482). — ^In  order  to  expose  the  muscles  of  the  face,  continue  the  longitudinal 
incision  made  in  the  dissection  of  the  Epicranius  down  the  median  line  of  the  face  to  the  tip 
of  the  nose,  and  from  this  point  onward  to  the  upper  lip;  and  carry  another  incision  along  the 
margin  of  the  lip  to  the  angle  of  the  mouth,  and  transversely  across  the  face  to  the  angle  of  the 
mandible.  Then  make  an  incision  in  front  of  the  external  ear,  from  the  angle  of  the  mandible 
upward  to  join  the  transverse  incision  made  in  exposing  the  Epicranius.  These  incisions  include 
a  square-shaped  flap,  which  should  be  removed  in  the  direction  marked  in  the  figure,  with  care, 
as  the  muscles  at  some  points  are  intimately  adherent  to  the  integument. 

The  Levator  palpebrae  superioris  is  described  with  the  Anatomy  of  the  Eye. 


Probe  in  frontal  sinus 


Probe  in  ant.  eth- 
moidal cells 


Crista  galli 


^. —  Lacrimal  part  of 
Orbicularis  oculi 

Probe  in  lacrimal  sac 


—  f  Probes  from  frontal 
\sinus  and  ant.  eth- 
moidal cells 

Middle  meatus 


Septum  of  nose 


Probe  in  nasolacrimal 
duct 


Infraorbital  no  ve  and  a) toy 


Fig.  4S4. — Left  orbicularis  oculi,  seen  from  behind. 


The  Orbicularis  oculi  (Orbicularis  jxdpebrarum)  (Fig.  484)  arises  from  the  nasal 
part  of  the  frontal  bone,  from  the  frontal  process  of  the  maxilla  in  front  of  the 
lacrimal  groove,  and  from  the  anterior  surface  and  borders  of  a  short  fibrous  band. 


468  MYOLOGY 

the  medial  palpebral  ligament.  From  this  origin,  the  fibres  are  directed  lateral- 
ward,  forming  a  broad  and  thin  layer,  which  occupies  the  eyelids  or  palpebrae, 
surrounds  the  circumference  of  the  orbit,  and  spreads  over  the  temple,  and  down- 
ward on  the  cheek.  The  palpebral  portion  of  the  muscle  is  thin  and  pale;  it  arises 
from  the  bifurcation  of  the  medial  palpebral  ligament,  forms  a  series  of  concentric 
curves,  and  is  inserted  into  the  lateral  palpebral  raphe.  The  orbital  portion  is  thicker 
and  of  a  reddish  color;  its  fibres  form  a  complete  ellipse  without  interruption  at 
the  lateral  palpebral  commissure;  the  upper  fibres  of  this  portion  blend  with  the 
Frontalis  and  Corrugator.  The  lacrimal  part  (Tensor  tarsi)  is  a  small,  thin  muscle, 
about  6  mm.  in  breadth  and  12  mm.  in  length,  situated  behind  the  medial  palpebral 
ligament  and  lacrimal  sac  (Fig.  484).  It  arises  from  the  posterior  crest  and  adjacent 
part  of  the  orbital  surface  of  the  lacrimal  bone,  and  passing  behind  the  lacrimal 
sac,  divides  into  two  slips,  upper  and  lower,  which  are  inserted  into  the  superior 
and  inferior  tarsi  medial  to  the  puncta  lacrimalia;  occasionally  it  is  very  indistinct. 

The  medial  palpebral  ligament  (tendo  oculi),  about  4  mm.  in  length  and  2  mm. 
in  breadth,  is  attached  to  the  frontal  process  of  the  maxilla  in  front  of  the  lacrimal 
groove.  Crossing  the  lacrimal  sac,  it  divides  into  two  parts,  upper  and  lower, 
each  attached  to  the  medial  end  of  the  corresponding  tarsus.  As  the  ligament 
crosses  the  lacrimal  sac,  a  strong  aponeurotic  lamina  is  given  off  from  its  posterior 
surface;  this  expands  over  the  sac,  and  is  attached  to  the  posterior  lacrimal  crest. 

The  lateral  palpebral  raphe  is  a  much  weaker  structure  than  the  medial  palpebral 
ligament.  It  is  attached  to  the  margin  of  the  frontosphenoidal  process  of  the 
zygomatic  bone,  and  passes  medialward  to  the  lateral  commissure  of  the  eyelids, 
where  it  divides  into  two  slips,  which  are  attached  to  the  margins  of  the  respective 
tarsi. 

The  Corrugator^  (Corrugator  swpercilii)  is  a  small,  narrow,  pyramidal  muscle, 
placed  at  the  medial  end  of  tlie  eyebrow,  beneath  the  Frontalis  and  Obricularis 
oculi.  It  arises  from  the  medial  end  of  the  superciliary  arch;  and  its  fibres  pass 
upward  and  lateralward,  between  the  palpebral  and  orbital  portions  of  the  Orbicu- 
laris oculi,  and  are  inserted  into  the  deep  surface  of  the  skin,  above  the  middle  of 
the  orbital  arch. 

Nerves. — The  Orbicularis  oculi  and  Corrugator  are  supplied  by  the  facial  nerve. 

Actions. — The  Orbicularis  oculi  is  the  sphincter  muscle  of  the  eyeUds.  The  palpebral  portion 
acts  involuntarily,  closing  the  hds  gently,  as  in  sleep  or  in  blinking;  the  orbital  portion  is  subject 
to  the  will.  When  the  entire  muscle  is  brought  into  action,  the  skin  of  the  forehead,  temple, 
and  cheek  is  drawn  toward  the  medial  angle  of  the  orbit,  and  the  eyehds  are  firmly  closed,  as  in 
photophobia.  The  skin  thus  drawn  upon  is  thrown  into  folds,  especially  radiating  from  the 
lateral  angle  of  the  eyelids;  these  folds  become  permanent  in  old  age,  and  form  the  so-called 
"crows'  feet."  The  Levator  palpebrae  superioris  is  the  direct  antagonist  of  this  muscle;  it  raises 
the  upper  eyelid  and  exposes  the  front  of  the  bulb  of  the  eye.  Each  time  the  eyeUds  are  closed 
through  the  action  of  the  Orbicularis,  the  medial  palpebral  hgament  is  tightened,  the  wall  of 
the  lacrimal  sac  is  thus  drawn  lateralward  and  forward,  so  that  a  vacuum  is  made  in  it,  and  the 
tears  are  sucked  along  the  lacrimal  canals  into  it.  The  lacrimal  part  of  the  Orbicularis  oculi 
draws  the  eyehds  and  the  ends  of  the  lacrimal  canals  medialward  and  compresses  them  against 
the  surface  of  the  globe  of  the  eye,  thus  placing  them  in  the  most  favorable  situation  for  receiving 
the  tears;  it  also  compresses  the  lacrimal  sac.  The  Corrugator  draws  the  ej'ebrow  downward 
and  medialward,  producing  the  vertical  wrinkles  of  the  forehead.  It  is  the  "frowning"  muscle, 
and  may  be  regarded  as  the  principal  muscle  in  the  expression  of  suffering. 

m.     THE  MUSCLES  OF  THE  NOSE   (Fig.   483). 

The  muscles  of  the  nose  comprise: 

Procerus.  Depressor  septi. 

Nasalis.  Dilatator  naris  posterior. 

Dilatator  naris  anterior. 

'  The  corrugator  is  not  recognized  as  a  separate  muscle  in  the  Basle  Nomenclature. 


THE  MUSCLES  OF  THE  MOUTH  469 

The  Procerus  [Pyraniidalis  nasi)  is  a  small  pyramidal  slip  ar.ising  by  tendinous 
fibres  from  the  fascia  covering  the  lower  part  of  the  nasal  bone  and  upper  part 
of  the  lateral  nasal  cartilage;  it  is  inserted  into  the  skin  over  the  lower  part  of 
the  forehead  between  the  two  eyebrows,  its  fibres  decussating  with  those  of  the 
F'routalis. 

The  Nasalis  {('oni pressor  naris)  consists  of  two  parts,  transverse  and  alar.  The 
transverse  part  arises  from  the  maxilla,  above  and  lateral  to  the  incisive  fossa; 
its  fibres  proceed  upward  and  medialward,  expanding  into  a  thin  aponeurosis 
which  is  continuous  on  the  bridge  of  the  nose  with  that  of  the  muscle  of  the  oppo- 
site side,  and  with  the  aponeurosis  of  the  Procerus.  The  alar  part  is  attached  by 
one  end  to  the  greater  alar  cartilage,  and  by  the  other  to  the  integument  at  the 
point  of  the  nose. 

The  Depressor  septi  (Depressor  alae  nasi)  arises  from  the  incisive  fossa  of  the 
maxilla ;  its  fibres  ascend  to  be  inserted  into  the  septum  and  back  part  of  the  ala 
of  the  nose.  It  lies  between  the  mucous  membrane  and  muscular  structure  of 
the  lip. 

The  Dilatator  naris  posterior  is  placed  partly  beneath  the  Quadratus  labii 
superioris.  It  arises  from  the  margin  of  the  nasal  notch  of  the  maxilla,  and  from 
the  lesser  alar  cartilages,  and  is  inserted  into  the  skin  near  the  margin  of  the 
nostril. 

The  Dilatator  naris  anterior  is  a  delicate  fasciculus,  passing  from  the  greater 
alar  cartilage  to  the  integument  near  the  margin  of  the  nostril;  it  is  situated  in 
front  of  the  preceding. 

Nerves. — All  the  muscles  of  this  group  are  supplied  by  the  facial  nerve. 

Actions. — The  Procerus  draws  down  the  medial  angle  of  the  eyebrows  and  produces  transverse 
wrinkles  over  the  bridge  of  the  nose.  The  two  Dilatatores  enlarge  the  aperture  of  the  nares. 
Their  action  in  ordinary  breathing  is  to  resist  the  tendencj^  of  the  nostrils  to  close  from  atmos- 
pheric pressure,  but  in  difficult  breathing,  as  well  as  in  some  emotions,  such  as  anger,  they  con- 
tract strongly.  The  Depressor  septi  is  a  direct  antagonist  of  the  other  muscles  of  the  nose,  drawing 
the  ala  of  the  nose  do-miward,  and  thereby  constricting  the  aperture  of  the  nares.  The  Xasalis 
depresses  the  cartilaginous  part  of  the  nose  and  draws  the  ala  toward  the  septum. 


IV.     THE  MUSCLES  OF  THE  MOUTH. 

The  muscles  of  the  mouth  are : 

Quadratus  labii  superioris.  Quadratus  labii  inferioris. 

Caninus.  Triangularis. 

Zygomaticus.  Buccinator. 

Mentalis.  Orbicularis  oris. 

Risorius. 

Dissection. — The  dissection  of  these  muscles  may  be  considerably  facihtated  bj'  filling  the 
cavit}-  of  the  mouth  with  tow,  so  as  to  distend  the  cheeks  and  Hps;  the  mouth  should  then  be 
closed  by  a  few  stitches  and  the  integument  carefulty  removed  from  the  surface. 

The  Quadratus  labii  superioris  is  a  broad  sheet,  the  origin  of  which  extends 
from  the  side  of  the  nose  to  the  zygomatic  bone.  Its  medial  fibres  form  the  angular 
head,  which  arises  by  a  pointed  extremity  from  the  upper  part  of  the  frontal  process 
of  the  maxilla  and  passing  obliquely  downward  and  lateralward  divides  into  two 
slips.  One  of  these  is  inserted  into  the  greater  alar  cartilage  and  skin  of  the  nose; 
the  other  is  prolonged  into  the  lateral  part  of  the  upper  lip,  blending  with  the 
infraorbital  head  and  with  the  Orbicularis  oris.  The  intermediate  portion  or 
infraorbital  head  arises  from  the  lower  margin  of  the  orbit  immediately  above  the 
infraorbital  foramen,  some  of  its  fibres  being  attached  to  the  maxilla,  others  to  the 
zygomatic  bone.     Its  fibres  converge,  to  be  inserted  into  the  muscular  substance 


470  MYOLOGY 

of  the  upper  lip  between  the  anguhir  head  and  the  Caninus.  The  lateral  fibres, 
forming  the  zygomatic  head,  arise  from  the  malar  surface  of  the  zygomatic  bone 
immediately  behind  the  zygomaticomaxillary  suture  and  pass  downward  and 
medialward  to  the  upper  lip. 

The  Caninus  [Lcmfor  anguli  oris)  arises  from  the  canine  fossa,  immediately 
below  the  infraorbital  foramen;  its  fibres  are  inserted  into  the  angle  of  the  mouth, 
intermingling  with  those  of  the  Zygomaticus,  Triangularis,  and  Orbicularis  oris. 

The  Zygomaticus  {Zygomaticus  major)  arises  from  the  zygomatic  bone,  in  front 
of  the  zygomaticotemporal  suture,  and  descending  obliquely  with  a  medial  inclina- 
tion, is  inserted  into  the  angle  of  the  mouth,  wdiere  it  blends  with  the  fibres  of  the 
Caninus,  Orbicularis  oris,  and  Triangularis. 

Nerves. — This  group  of  muscles  is  supplied  by  the  facial  nerve. 

Actions. — The  Quadratus  labii  superioris  is  the  proper  elevator  of  the  upper  lip,  carrying  it 
at  the  same  time  a  httle  forward.  Its  angular  head  acts  as  a  dilator  of  the  naris;  the  infraorbital 
and  zygomatic  heads  assist  in  forming  the  nasolabial  furrow,  which  passes  from  the  side  of  the 
nose  to  the  upper  hp  and  gives  to  the  face  an  expression  of  sadness.  When  the  whole  muscle 
is  in  action  it  gives  to  the  countenance  an  expression  of  contempt  and  disdain.  The  Quadratus 
labii  superioris  raises  the  angle  of  the  mouth  and  assists  the  Caninus  in  producing  the  nasolabial 
furrow.     The  zygomaticus  draws  the  angle  of  the  mouth  backward  and  upward,  as  in  laughing. 

The  Mentalis  (Levator  menti)  is  a  small  conical  fasciculus,  situated  at  the  side 
of  the  frenulum  of  the  lower  lip.  It  arises  from  the  incisive  fossa  of  the  mandible, 
and  descends  to  be  inserted  into  the  integument  of  the  chin. 

The  Quadratus  labii  inferioris  {Depressor  labii  injerioris;  Quadratus  menti)  is 
a  small  quadrilateral  muscle.  It  arises  from  the  oblique  line  of  the  mandible, 
between  the  symphysis  and  the  mental  foramen,  and  passes  upward  and  medial- 
ward,  to  be  inserted  into  the  integument  of  the  low^er  lip,  its  fibres  blending  with 
the  Orbicularis  oris,  and  with  those  of  its  fellow  of  the  opposite  side.  At  its  origin 
it  is  continuous  with  the  fibres  of  the  Platysma.  Much  yellow  fat  is  intermingled 
with  the  fibres  of  this  muscle. 

The  Triangularis  {Depressor  anguli  oris)  arises  from  the  oblique  line  of  the 
mandible,  wdience  its  fibres  converge,  to  be  inserted,  by  a  narrow  fasciculus,  into 
the  angle  of  the  mouth.  At  its  origin  it  is  continuous  with  the  Platysma,  and  at 
its  insertion  with  the  Orbicularis  oris  and  Risorius;  some  of  its  fibres  are  directly 
continuous  with  those  of  the  Caninus,  and  others  are  occasionally  found  crossing 
from  the  muscle  of  one  side  to  that  of  the  other;  these  latter  fibres  constitute 
the  Transversus  menti. 

Nerves. — This  group  of  muscles  is  supplied  by  the  facial  nerve. 

Actions. — The  Mentahs  raises  and  protrudes  the  lower  hp,  and  at  the  same  time  wrinkles  the 
skin  of  the  chin,  expressing  doubt  or  disdain.  The  Quadratus  labii  inferioris  draws  the  lower 
lip  directly  downward  and  a  httle  lateralward,  as  in  the  expression  of  irony.  The  Triangularis 
depresses  the  angle  of  the  mouth,  being  the  antagonist  of  the  Caninus  and  Zygomaticus;  acting 
with  the  Caninus,  it  will  draw  the  angle  of  the  mouth  medialward. 

The  Buccinator  (Fig.  485)  is  a  thin  quadrilateral  muscle,  occupying  the  interval 
between  the  maxilla  and  the  mandible  at  the  side  of  the  face.  It  arises  from  the 
outer  surfaces  of  the  alveolar  processes  of  the  maxilla  and  mandible,  corresponding 
to  the  three  molar  teeth;  and  behind,  from  the  anterior  border  of  the  pterygoman- 
dibular raphe  which  separates  it  from  the  Constrictor  pharyngis  superior.  The 
fibres  converge  toward  the  angle  of  the  mouth,  where  the  central  fibres  intersect 
each  other,  those  from  below  being  continuous  with  the  upper  segment  of  the 
Orbicularis  oris,  and  those  from  above  with  the  lower  segment;  the  upper  and  lower 
fibres  are  continued  forward  into  the  corresponding  lip  without  decussation. 

Relations. — The  Buccinator  is  covered  by  the  buccopharyngeal  fascia,  and  is  in  relation  by 
its  superficial  surface,  behind,  with  a  large  mass  of  fat,  which  separates  it  from  the  ramus  of  the 
mandible,  the  Masseter,  and  a  small  portion  of  the  Temporalis;  this  fat  has  been  named  the 


THE  MUSCLES  OF  THE  MOUTH 


471 


suctorial  pad,  because  it  is  sui)i)osed  to  assist  in  the  act  of  sucking.  In  front  the  superficial  surface 
of  the  Buccinator  is  in  relation  with  the  Zygoniaticus,  Risorius,  Caninus,  Triangularis,  and  the 
parotid  duct  which  pierces  it  opposite  the  second  molar  tooth  of  the  maxilla;  the  external  maxillary 
artery  antl  anterior  facial  vein  cross  it  from  below  upward;  it  is  also  crossed  by  the  branches  of 
the  facial  and  buccinator  nerves.  The  deep  surjace  is  in  relation  with  the  buccal  glands  and 
mucous  membrane  of  the  mouth. 

The  pterygomandibular  raphe  {pterycjomandibular  ligament)  is  a  tendinous  band 
of  the  buccopharyngeal  fascia,  attached  by  one  extremity  to  the  hamulus  of  the 
medial  pterygoid  plate,  and  by  the  other  to  the  posterior  end  of  the  mylohyoid 
line  of  the  mandible.  Its  medial  surjace  is  covered  by  the  mucous  membrane  of 
the  mouth.  Its  laferal  surface  is  separated  from  the  ramus  of  the  mandible  by  a 
quantity  of  adipose  tissue.  Its  posterior  border  gives  attachment  to  the  Constrictor 
pharyngis  superior;  its  anterior  border,  to  part  of  the  Buccinator  (Fig.  485). 

The  Orbicularis  oris  (Fig.  486)  is  not  a  simple  sphincter  muscle  like  the  Orbic- 
ularis oculi;  it  consists  of   numerous  strata  of  muscular  fibres  surrounding  the 

orifice  of  the  mouth  but  having  dift'erent 
direction.  It  consists  partly  of  fibres  de- 
rived from  the  other  facial  muscles  which 
are  inserted  into  the  lips,  and  partly  of 
fibres  proper  to  the  lips.  Of  the  former, 
a  considerable  number  are  derived  from 
the  Buccinator  and  form  the  deeper 
stratum  of  the  Orbicularis.  Some  of  the 
Buccinator  fibres — namely,  those  near 
the  middle  of  the  muscle^ — decussate  at 
the  angle  of  the  mouth,  those  arising 
from  the  maxilla  passing  to  the  lower  lip, 


BUCCINATOR 


Fig.  485. — Muscles  of  the  pharynx  and  cheek. 


Fig.  486.- 


TRIANGULAFUS 

-Scheme  showing  arrangement  of  fibres  of 
Orbicularis  oris. 


and  those  from  the  mandible  to  the  upper  lip.  The  uppermost  and  lowermost 
fibres  of  the  Buccinator  pass  across  the  lips  from  side  to  side  without  decussation. 
Superficial  to  this  stratum  is  a  second,  formed  on  either  side  by  the  Caninus  and 
Triangularis,  which  cross  each  other  at  the  angle  of  the  mouth;  those  from  the 
Caninus  passing  to  the  lower  lip,  and  those  from  the  Triangularis  to  the  upper  lip, 
along  which  they  run,  to  be  inserted  into  the  skin  near  the  median  line.  In  addi- 
tion to  these  there  are  fibres  from  the  Quadratus  labii  superioris,  the  Zygomaticus, 
and  the  Quadratus  labii  inferioris;  these  intermingle  with  the  transverse  fibres 
aboA'e  described,  and  have  principally  an  oblique  direction.  The  proper  fibres 
of  the  lips  are  oblique,  and  pass  from  the  under  surface  of  the  skin  to  the  mucous 
membrane,  through  the  thickness  of  the  lip.  Finally  there  are  fibres  by  whicli  the 
muscle  is  connected  with  the  maxillse  and  the  septum  of  the  nose  above  and  with 


472  MYOLOGY 

the  mandible  below.  In  the  upper  lip  these  consist  of  two  hands,  lateral  and  mecHal, 
on  either  side  of  the  middle  line;  the  lateral  band  {m.  incisivus  labii  superioris) 
arises  from  the  alveolar  border  of  the  maxilla,  opposite  the  lateral  incisor  tooth, 
and  arching  laterahvard  is  continuous  with  tKe  other  muscles  at  the  angle  of  the 
mouth;  the  medial  band  (m.  na.wJahiaUfi)  connects  the  upper  lip  to  the  back  of  the 
septum  of  the  nose.  The  interval  between  the  two  medial  bands  corresponds 
with  the  depression,  called  the  philtrum,  seen  on  the  lip  beneath  the  septum  of  the 
nose.  The  additional  fibres  for  the  lower  lip  constitute  a  slip  (???.  incisivus  labii 
inferioris)  on  either  side  of  the  middle  line;  this  arises  from  the  mandible,  lateral 
to  the  Mentalis,  and  intermingles  with  the  other  muscles  at  the  angle  of  the 
mouth. 

The  Risorius  arises  in  the  fascia  over  the  Masseter  and,  passing  horizontally 
forward,  superficial  to  the  Platysma,  is  inserted  into  the  skin  at  the  angle  of  the 
mouth  (Fig.  483).  It  is  a  narrow  bundle  of  fibres,  broadest  at  its  origin,  but  varies 
much  in  its  size  and  form. 

Nerves. — The  muscles  in  this  group  are  all  supplied  by  the  facial  nerve. 

Actions. — The  Orbicularis  oris  in  its  ordinary  action  effects  the  direct  closure  of  the  lips;  by 
its  deep  fibres,  assisted  by  the  obhque  ones,  it  closely  apphes  the  hps  to  the  alveolar  arch.  The 
superficial  part,  consisting  principally  of  the  decussating  fibres,  brings  the  lips  together  and  also 
protrudes  them  forward.  The  Buccinators  compress  the  cheeks,  so  that,  during  the  process  of 
mastication,  the  food  is  kept  under  the  immediate  pressure  of  the  teeth.  When  the  cheeks  have 
been  previously  distended  with  air,  the  Buccinator  muscles  expel  it  from  between  the  lips,  as  in 
blowing  a  trumpet;  hence  the  name  (buccina,  a  trumpet).  The  Risorius  retracts  the  angle  of 
the  mouth,  and  produces  an  unpleasant  grinning  expression. 

IV.     THE  MUSCLES  OF  MASTICATION. 

The  chief  muscles  of  mastication  are: 

Masseter.  Pterygoideus  externus. 

Temporalis.  Pterygoideus  internus. 

Parotideomasseteric  Fascia  {masseteric  fascia) . — Covering  the  Masseter,  and  firmly 
connected  with  it,  is  a  strong  layer  of  fascia  derived  from  the  deep  cervical  fascia. 
Above,  this  fascia  is  attached  to  the  lower  border  of  the  zygomatic  arch,  and  behind, 
it  invests  the  parotid  gland. 

The  Masseter  (Fig.  483)  is  a  thick,  somewhat  quadrilateral  muscle,  consisting 
of  two  portions,  superficial  and  deep.  The  superficial  portion,  the  larger,  arises 
by  a  thick,  tendinous  aponeurosis  from  the  zygomatic  process  of  the  maxilla,  and 
from  the  anterior  two-thirds  of  the  lower  border  of  the  zygomatic  arch :  its  fibres 
pass  downward  and  backward,  to  be  inserted  into  the  angle  and  lower  half  of  the 
lateral  surface  of  the  ramus  of  the  mandible.  The  deep  portion  is  much  smaller, 
and  more  muscular  in  texture;  it  arises  from  the  posterior  third  of  the  lower  border 
and  from  the  whole  of  the  medial  surface  of  the  zygomatic  arch;  its  fibres  pass 
downward  and  forward,  to  be  inserted  into  the  upper  half  of  the  ramus  and  the 
lateral  surface  of  the  coronoid  process  of  the  mandible.  The  deep  portion  of  the 
muscle  is  partly  concealed,  in  front,  by  the  superficial  portion;  behind,  it  is  covered 
by  the  parotid  gland.  The  fibres  of  the  two  portions  are  continuous  at  their 
insertion. 

Relations. — The  Masseter  is  in  relation  by  its  superficial  surface  with  the  integument,  Platysma, 
Risorius,  Zygomaticus,  the  parotid  gland  and  its  accessory  portion;  the  parotid  duct,  the  branches 
of  the  facial  nerve  and  the  transverse  facial  vessels  cross  it.  By  its  deep  surface,  it  is  in  relation 
with  the  insertion  of  the  TemporaUs  and  the  ramus  of  the  mandible;  a  mass  of  fat  separates  it 
from  the  Buccinator  and  the  buccinator  nerve.  The  masseteric  nerve  and  artery  enter  the  muscle 
on  its  deep  surface.  Its  posterior  ■margin  is  overlapped  by  the  parotid  gland.  Its  anterior  margin 
projects  over  the  Buccinator  and  is  crossed  below  bj'  the  anterior  facial  vein. 


THE  MUSCLES  OF  MASTICATION 


473 


Temporal  Fascia. — The  temporal  faseia  covers  the  Temjioralis  muscle,  It  is  a 
stront;-,  fibrous  in\estmeut,  covered,  laterally,  by  the  Auricularis  anterior  and  supe- 
rior, by  the  galea  aponeurotica,  and  by  ])art  of  the  Orbicularis  oculi.  The  super- 
ficial temi)oral  \essels  and  the  auriculotemporal  nerve  cross  it  from  below  upward. 
Above,  it  is  a  single  layer,  attached  to  the  entire  extent  of  the  superior  temporal 
line;  but  bcloic,  where  it  is  fixed  to  the  zygomatic  arch,  it  consists  of  two  layers,  one 
of  which  is  inserted  into  the  lateral,  and  the  other  into  the  medial  border  of  the 
arch.  A  small  cpiantity  of  fat,  the  orbital  branch  of  the  superficial  temporal  artery, 
and  a  filament  from  the  zygomatic  branch  of  the  maxillary  nerve,  are  contained 
between  these  two  layers.  It  affords  attachment  b>'  its  deep  surface  to  the  super- 
ficial fibres  of  the  Temporalis. 

Dissection. — In  order  to  expose  the  Temporalis,  remove  the  temporal  fascia,  which  may  be 
eiTccted  by  separating  it  at  its  attachment  along  the  upper  border  of  the  zygoma  and  dissecting 
it  upward  from  the  surface  of  the  muscle.  The  zj^gomatic  arch  should  then  be  divided  in  front 
at  its  junction  with  the  zygomatic  bone,  and  behind  near  the  external  auditor}^  meatus,  and 
drawii  downward  with  the  Masseter,  which  should  be  detached  from  its  insertion  into  the  ramus 
and  angle  of  the  mandible.    The  whole  extent  of  the  Temporalis  is  then  exposed. 


Fig.  4S7. — The  Temporalis;  the  zygomatic  arch  and  Masseter  have  been  removed. 


The  Temporalis  {Temporal  muscle)  (Fig.  487)  is  a  broad,  radiating  muscle, 
situated  at  the  side  of  the  head.  It  arises  from  the  whole  of  the  temporal  fossa 
(except  that  portion  of  it  which  is  formed  by  the  zygomatic  bone)  and  from  the 
deep  surface  of  the  temporal  fascia.  Its  fibres  converge  as  they  descend,  and  end 
in  a  tendon,  which  passes  deep  to  the  zygomatic  arch  and  is  inserted  into  the  medial 
surface,  apex,  and  anterior  border  of  the  coronoid  process,  and  the  anterior  border 
of  the  ramus  of  the  mandible  nearly  as  far  forward  as  the  last  molar  tooth. 

Relations. — The  Temporalis  is  in  relation  by  its  superficial  surface  with  the  integument,  the 
Auriculares  anterior  and  superior,  the  temporal  fascia,  the  superficial  temporal  vessels,  the 
auriculotemporal  nerve,  the  temporal  branches  of  the  facial  and  zygomatic  nerves,  the  galea 
aponeurotica,  the  zygomatic  arch,  and  the  Masseter.  By  its  deep  surface,  it  is  in  relation  with 
the  temporal  fossa,  the  Pterygoideus  externus  and  part  of  the  Buccinator,  the  internal  maxillary 
artery,  and  its  deep  temporal  branches,  the  deep  temporal  nerves,  and  the  buccinator  vessels 
and  nerve.  Behind  the  tendon  are  the  massetei'ic  vessels  and  nerve.  Its  anterior  border  is  sepa- 
rated from  the  zygomatic  bone  by  a  mass  of  fat. 


474 


MYOLOGY 


Dissection. — The  Temporalis  having  been  examined,  saw  through  the  base  of  the  coronoid 
process  and  draw  it  upward,  together  with  the  TemporaUs,  which  should  be  detached  from  the 
surface  of  the  temporal  fossa.  Divide  the  ramus  of  the  mandible  just  below  the  condyle,  and 
also,  by  a  ti'ansverse  incision  extending  across  the  middle,  ju.^t  above  the  dental  foramen;  remove 
the  fragment,  and  the  Pterygoidci  will  be  exposed. 

The  Pterygoideus  externus  {External  pterygoid  muscle)  (Fig.  488)  is  a  short,  thick 
muscle,  somewhat  conical  in  form,  which  extends  almost  horizontally  between  the 
infratemporal  fossa  and  the  condyle  of  the  mandible.  It  arises  by  two  heads; 
an  upper  from  the  lower  part  of  the  lateral  surface  of  the  great  wing  of  the  sphenoid 
and  from  the  infratemporal  crest;  a  lower  from  the  lateral  surface  of  the  lateral 
pterygoid  plate.  Its  fibres  pass  horizontally  backward  and  lateralward,  to  be 
inserted  into  a  depression  in  front  of  the  neck  of  the  condyle  of  the  mandible,  and 
into  the  front  margin  of  the  articular  disk  of  the  temporomandibular  articulation. 


Fig.  488. — The  Pterygoidei ;  the  zygomatic  arch  and  a  portion  of  the  ramus  of  the  mandible  have  been  removed. 

Relations. — Its  superficial  surface  is  in  relation  with  the  ramus  of  the  mandible,  the  internal 
maxillary  artery,  which  crosses  it,i  the  tendon  of  the  Temporahs,  and  the  Masseter.  Its  deep 
surface  rests  against  the  upper  part  of  the  Pterygoideus  internus,  the  sphenomandibular  ligament, 
the  middle  meningeal  artery,  and  the  mandibular  nerve;  its  upper  border  is  in  relation  with  the 
temporal  and  masseteric  branches  of  the  mandibular  nerve;  its  lower  border  with  the  lingual 
and  inferior  alveolar  nerves.  The  buccal  nerve  and  the  internal  maxillary  artery  pass  between 
the  two  portions  of  the  muscle  (Fig.  488) . 

The  Pterygoideus  internus  (Internal  pterygoid  muscle)  (Fig.  488)  is  a  thick,  quad- 
rilateral muscle.  It  arises  from  the  medial  surface  of  the  lateral  pterygoid  plate 
and  the  grooved  surface  of  the  pyramidal  process  of  the  palatine  bone;  it  has  a 
second  slip  of  origin  from  the  lateral  surfaces  of  the  pyramidal  process  of  the  pala- 
tine and  tuberosity  of  the  maxilla.  Its  fibres  pass  downward,  lateralward,  and 
backward,  and  are  inserted,  by  a  strong  tendinous  lamina,  into  the  lower  and  back 
part  of  the  medial  surface  of  the  ramus  and  angle  of  the  mandible,  as  high  as  the 
mandibular  foramen. 

Relations. — Its  lateral  surface  is  in  relation  with  the  ramus  of  the  mandible,  from  wliich  it  is 
separated,  at  its  upper  part,  by  the  Pterygoideus  externus,  the  sphenomandibular  Mgament,  the 
internal  maxillary  artery,  the  inferior  alveolar  vessels  and  nerve,  the  hngual  nerve,  and  a  process 
of  the  parotid  gland.  Its  medial  surface  is  in  relation  with  the  Tensor  veli  palatini,  being  separated 
from  the  Constrictor  pharyngis  superior  by  some  areolar  tissue. 

1  In  many  cases  the  artery  will  be  found  under  cover  of  the  muscle. 


THE  LATERAL  CERVICAL  MUSCLES  475 

Nerves. — The  muscles  of  mastication  are  supplied  by  the  iiuuulibular  nerve. 

Actions. — The  Tempoi-alis,  Masseter,  and  Pterygoideus  internus  raise  the  mandible  against 
the  maxilku  with  great  force.  The  Pterygoideus  cxtornus  assists  in  opening  the  mouth,  but  its 
main  action  is  to  draw  forward  the  condyle  and  articular  disk  so  that  the  mandible  is  protruded 
and  the  inferior  incisors  projected  in  front  of  the  u{)per;  in  this  action  it  is  assisted  by  the  Ptery- 
goideus internus.  The  mandible  is  retracted  by  the  posterior  fibres  of  the  Temporalis.  If  the 
Pterygoidei  internus  and  externus  of  one  side  act,  the  corresponding  side  of  the  mandible  is 
drawn  forward  while  the  opposite  condyle  remains  comparatively  fixed,  and  side-to-side  move- 
ments, such  as  occur  during  the  tritui-ation  of  food,  take  place. 


THE  FASCI-ai  AND  MUSCLES  OF  THE   ANTERO-LATERAL  REGION 

OF  THE  NECK. 

The  antero-lateral  muscles  of  the  neck  may  be  arranged  into  the  following 
groups : 

I.  Superficial  Cervical.  III.  Supra-  and  Infra-hyoid. 

II.  Lateral  Cervical.  IV.  Anterior  Vertebral. 

V.  Lateral  Vertebral. 

I.     THE  SUPERFICIAL  CERVICAL  MUSCLE. 
Platysma. 

Dissection — A  block  having  been  placed  at  the  back  of  the  neck,  and  the  face  turned  to  the 
side  opposite  that  to  be  dissected,  so  as  to  place  the  parts  upon  the  stretch,  make  two  trans- 
verse incisions,  one  from  the  chin,  along  the  margin  of  the  mandible,  to  the  mastoid  process, 
and  the  other  along  the  upper  border  of  the  clavicle.  Connect  these  by  an  oblique  incision  made 
in  the  com'se  of  the  Sternocleidomastoideus,  from  the  mastoid  process  to  the  sternum;  the  two 
flaps  of  integument  having  been  removed  in  the  direction  shown  in  Fig.  482,  the  superficial 
fascia  will  be  exposed. 

The  Superficial  Fascia  of  the  neck  is  a  thin  lamina  investing  the  Platysma, 
and  is  hardly  demonstrable  as  a  separate  membrane. 

The  Platysma  (Fig.  483)  is  a  broad  sheet  arising  from  the  fascia  covering  the 
upper  parts  of  the  Pectoralis  major  and  Deltoideus;  its  fibres  cross  the  clavicle, 
and  proceed  obliquely  upward  and  medial  ward  along  the  side  of  the  neck.  The 
anterior  fibres  interlace,  below  and  behind  the  symphysis  menti,  with  the  fibres 
of  the  muscle  of  the  opposite  side;  the  posterior  fibres  cross  the  mandible,  some 
being  inserted  into  the  bone  below  the  oblique  line,  others  into  the  skin  and  sub- 
cutaneous tissue  of  the  lower  part  of  the  face,  many  of  these  fibres  blending  with 
the  muscles  about  the  angle  and  lower  part  of  the  mouth.  Sometimes  fibres  can 
be  traced  to  the  zygomaticus,  or  to  the  margin  of  the  Orbicularis  oculi.  Beneath 
the  Platysma,  the  external  jugular  vein  descends  from  the  angle  of  the  mandible 
to  the  clavicle. 

Actions. — When  the  entire  Platysma  is  in  action  it  produces  a  slight  wi-inkling  of  the  surface 
of  the  skin  of  the  neck  in  an  oblique  direction.  Its  anterior  portion,  the  thickest  part  of  the 
muscle,  depresses  the  low^er  jaw;  it  also  serves  to  draw  down  the  lower  lip  and  angle  of  the  mouth 
in  the  expression  of  melancholy. 

Nerve. — The  Platysma  is  supplied  by  the  cervical  branch  of  the  facial  nerve. 

n.     THE  LATERAL  CERVICAL  MUSCLES. 

The  lateral  muscles  are : 

Trapezius  and  Sternocleidomastoideus. 

The  Trapezius  is  described  on  page  522. 


476 


MYOLOGY 


The  Fascia  Colli  {deep  cervical  fascia)  (Fig.  4S9). — The  fascia  colli  lies  under  cover 
of  the  Platysma,  and  invests  the  neck;  it  also  forms  sheaths  for  the  carotid  vessels, 
and  for  the  structures  situated  in  front  of  the  vertebral  column. 


OmoTiyoideus 
Tlnj)  Old  gland 
Common  carotid  anay 
Int.  jugular  vein      \  y 

Sternccle  idoinasto  ideus 


Vagus  nerve^~~ , 

Ext.  jugular  vein 
Scalenus  anterior 

Scalenus  mcdius' 

Sflenius  colli 
Levator  scapulae 


Trapeziub 


Ant.  jugular  vein 

~-  SternoJiyoidctis 
'  Sternoihyreoideus 

Trachea 


((  ^^^fe-      Oeso2:)h 


agus 


~~ '  oth  cervical  vertebra 
—  Vertebral  vessels 


Semisjnnalis  colli 


Sem,is}:iinalis  capitis 
Splenius  capitis 


Fig.  489. — Section  of  the  neck  at  about  the  level  of  the  sixth  cervical  vertebra.     Showing  the  arrangement  of  the 

fascia  coli. 

The  investing  portion  of  the  fascia  is  attached  behind  to  the  ligamentum  nuchae 
and  to  the  spinous  process  of  the  seventh  cervical  vertebra.  It  forms  a  thin  in- 
vestment to  the  Trapezius,  and  at  the  anterior  border  of  this  muscle  is  continued 
forward  as  a  rather  loose  areolar  layer,  covering  the  posterior  triangle  of  the  neck, 
to  the  posterior  border  of  the  Sternocleidomastoideus,  where  it  begins  to  assume 
the  appearance  of  a  fascial  membrane.  Along  the  hinder  edge  of  the  Sterno- 
cleidomastoideus it  divides  to  enclose  the  muscle,  and  at  the  anterior  margin  again 
forms  a  single  lamella,  which  covers  the  anterior  triangle  of  the  neck,  and  reaches 
forward  to  the  middle  line,  where  it  is  continuous  with  the  corresponding  part  from 
the  opposite  side  of  the  neck.  In  the  middle  line  of  the  neck  it  is  attached  to  the 
symphysis  menti  and  the  body  of  the  hyoid  bone. 


THE  LATERAL  CERVICAL  MUSCLES  477 

Above,  the  fascia  is  attached  to  the  sujierior  nuchal  Hne  of  the  occipital,  to  the 
mastoid  process  of  the  temporal,  and  to  the  whole  length  of  the  inferior  border 
of  the  l)0(ly  of  the  mandible.  ()i)])osite  the  angle  of  the  mandible  the  fascia  is  very 
strong,  and  binds  the  anterior  edge  of  the  Sternoclcidomastoideus  firmly  to  that 
bone.  Between  the  mandible  and  the  mastoid  process  it  ensheathes  the  parotid 
gland — the  layer  which  covers  the  gland  extends  upward  under  the  name  of  the 
parotideomasseteric  fascia  and  is  fixed  to  the  zygomatic  arch.  From  the  part  which 
passes  under  the  parotid  gland  a  strong  band  extends  upward  to  the  styloid  process, 
forming  the  stylomandibular  ligament.  Two  other  l)ands  may  be  defined:  the 
sphenomandibular  (page  395)  and  the  pterygospinous  ligaments.  The  pterygospinous 
ligament  stretches  from  the  upper  part  of  the  posterior  border  of  the  lateral  ptery- 
goid plate  to  the  spinous  process  of  the  sphenoid.  It  occasionally  ossifies,  and  in 
such  cases,  between  its  upper  border  and  the  base  of  the  skull,  a  foramen  is  formed 
which  transmits  the  branches  of  the  mandibular  nerve  to  the  muscles  of  mastication. 

Below,  the  fascia  is  attached  to  the  acromion,  the  clavicle,  and  the  manubrium 
sterni.  Some  little  distance  above  the  last  it  splits  into  two  layers,  superficial 
and  deep.  The  former  is  attached  to  the  anterior  border  of  the  manubrium,  the 
latter  to  its  posterior  border  and  to  the  interclavicular  ligament.  Between  these 
two  layers  is  a  slit-like  interval,  the  suprasternal  space  {space  of  Burns) ;  it  contains 
a  small  quantity  of  areolar  tissue,  the  lower  portions  of  the  anterior  jugular  veins 
and  their  transverse  connecting  branch,  the  sternal  heads  of  the  Sternocleido- 
mastoidei,  and  sometimes  a  lymph  gland. 

The  fascia  which  lines  the  deep  surface  of  the  Sternocleidomastoideus  gives  off 
the  following  processes:  (1)  A  process  envelops  the  tendon  at  the  Omohyoideus, 
and  binds  it  down  to  the  sternum  and  first  costal  cartilage.  (2)  A  strong  sheath, 
the  carotid  sheath,  encloses  the  carotid  artery,  internal  jugular  vein,  and  vagus 
nerve.  (3)  The  prevertebral  fascia  extends  medialward  behind  the  carotid  vessels, 
where  it  assists  in  forming  their  sheath,  and  passes  in  front  of  the  prevertebral 
muscles.  It  forms  the  posterior  limit  of  a  fibrous  compartment,  which  contains 
the  larynx  and  trachea,  the  thyroid  gland,  and  the  pharynx  and  oesophagus.  The 
prevertebral  fascia  is  fixed  above  to  the  base  of  the  skull,  and  below  is  continued 
into  the  thorax  in  front  of  the  Longus  colli  muscles.  Parallel  to  the  carotid  sheath 
and  along  its  medial  aspect  the  prevertebral  fascia  gives  off  a  thin  lamina,  the 
buccopharyngeal  fascia,  which  closely  invests  the  Constrictor  muscles  of  the  pharynx, 
and  is  continued  forward  from  the  Constrictor  pharyngis  superior  on  to  the  Buc- 
cinator. It  is  attached  to  the  prevertebral  layer  by  loose  connective  tissue  only, 
and  thus  an  easily  distended  space,  the  retropharyngeal  space,  is  found  between 
them.  .  This  space  is  limited  above  by  the  base  of  the  skull,  while  below  it  extends 
behind  the  oesophagus  into  the  posterior  mediastinal  cavity  of  the  thorax.  The  pre- 
vertebral fascia  is  prolonged  downward  and  lateralward  behind  the  carotid  vessels 
and  in  front  of  the  Scaleni,  and  forms  a  sheath  for  the  brachial  nerves  and  sub- 
clavian vessels  in  the  posterior  triangle  of  the  neck;  it  is  continued  under  the  clavicle 
as  the  axillary  sheath  and  is  attached  to  the  deep  surface  of  the  coracoclavicular 
fascia.  Immediately  above  and  behind  the  clavicle  an  areolar  space  exists  between 
the  investing  layer  and  the  sheath  of  the  subclavian  vessels,  and  in  this  space  are 
found  the  low^er  part  of  the  external  jugular  vein,  the  descending  clavicular  nerves, 
the  transverse  scapular  and  transverse  cervical  vessels,  and  the  inferior  belly  of  the 
Omohyoideus  muscle.  This  space  is  limited  below  by  the  fusion  of  the  coraco- 
clavicular fascia  with  the  anterior  wall  of  the  axillary  sheath.  (4)  The  pretrachial 
fascia  extends  medially  in  front  of  the  carotid  vessels,  and  assists  in  forming  the 
carotid  sheath.  It  is  continued  behind  the  depressor  muscles  of  the  hyoid  bone, 
and,  after  enveloping  the  thyroid  gland,  is  prolonged  in  front  of  the  trachea  to 
meet  the  corresponding  layer  of  the  opposite  side.  Above,  it  is  fixed  to  the  liyoid 
bone,  while  below  it  is  carried  downward  in  front  of  the  trachea  and  large  vessels 


478  MYOLOGY 

at  the  root  of  the  neck,  and  ultimately  blends  with  the  fibrous  pericardium.  Tliis 
layer  is  fused  on  either  side  with  the  prevertebral  fascia,  and  with  it  completes  the 
compartment  containing  the  larynx  and  trachea,  the  thyroid  gland,  and  the  pharynx 
and  oesophagus.^ 

Applied  Anatomy. — The  deep  cervical  fascia  is  of  considerable  importance  from  a  surgical  point 
of  view.  The  investing  layer  opposes  the  extension  of  abscesses  toward  the  surface,  and  pus  forming 
beneath  it  has  a  tendency  to  extend  laterally.  If  the  pus  be  contained  in  the  anterior  triangle, 
it  may  find  its  way  into  the  anterior  mediastinal  cavity,  in  front  of  the  layer  of  fascia  which 
passes  down  into  the  thorax  to  blend  with  the  pericardium;  but  owing  to  the  less  density  and 
thickness  of  the  fascia  in  this  situation  it  more  frequently  finds  its  way  to  the  surface  and  points 
above  the  sternum.  Pus  forming  beneath  the  pretracheal  layer  would  in  all  probability  find 
its  way  into  the  posterior  mediastinal  cavity.  Pus  forming  behind  the  prevertebral  layer,  in 
cases,  for  instance,  of  caries  of  the  bodies  of  the  cervical  vertebrae,  may  extend  toward  the  lateral 
part  of  the  neck  and  point  in  the  posterior  triangle,  or  may  perforate  this  layer  of  fascia  and 
the  buccopharyngeal  fascia  and  point  into  the  pharynx  {retropharyngeal  abscess). 

In  cases  of  cut  throat,  when  the  wound  involves  only  the  investing  layer  the  injury  is  usually 
trivial,  the  special  danger  being  injury  to  the  external  jugular  vein,  and  the  special  complication, 
diffuse  cellulitis.  But  where  the  second  of  the  two  layers  is  opened  up,  important  structures 
may  be  injured,  and  serious  results  follow. 

The  sternal  head  of  origin  of  the  Sternocleidomastoideus  is  contained  in  the  suprasternal 
space,  so  that  this  space  is  opened  in  division  of  this  tendon.  The  lower  part  of  the  anterior 
jugular  vein  is  also  contained  in  the  same  space. 

The  Sternocleidomastoideus  {Sternomastoid  muscle)  (Fig.  490)  passes  obliquely 
across  the  side  of  the  neck.  It  is  thick  and  narrow  at  its  central  part,  but  broader 
and  thinner  at  either  end.  It  arises  from  the  sternum  and  clavicle  by  two  heads. 
The  medial  or  sternal  head  is  a  rounded  fasciculus,  tendinous  in  front,  fleshy  behind, 
which  arises  from  the  upper  part  of  the  anterior  surface  of  the  manubrium  sterni, 
and  is  directed  upward,  lateralward,  and  backward.  The  lateral  or  clavicular  head, 
composed  of  fleshy  and  aponeurotic  fibres,  arises  from  the  superior  border  and 
anterior  surface  of  the  medial  third  of  the  clavicle;  it  is  directed  almost  vertically 
upward.  The  two  heads  are  separated  from  one  another  at  their  origins  by  a 
triangular  interval,  but  gradually  blend,  below  the  middle  of  the  neck,  into  a  thick, 
rounded  muscle  which  is  inserted,  by  a  strong  tendon,  into  the  lateral  surface  of 
the  mastoid  process,  from  its  apex  to  its  superior  border,  and  by  a  thin  aponeurosis 
into  the  lateral  half  of  the  superior  nuchal  line  of  the  occipital  bone. 

The  Sternocleidomastoideus  varies  much  in  its  extent  of  origin  from  the  clavicle : 
in  some  cases  the  clavicular  may  be  as  narrow  as  the  sternal  head;  in  others,  as 
much  as  7.5  cm.  in  breadth.  When  the  clavicular  origin' is  broad,  it  is  occasionally 
subdivided  into  several  slips,  separated  by  narrow  intervals.  More  rarely,  the 
adjoining  margins  of  the  Sternocleidomastoideus  and  Trapezius  have  been  found 
in  contact. 

Triangles  of  the  Neck. — This  muscle  divides  the  quadrilateral  area  of  the  side  of  the  neck 
into  two  triangles,  an  anterior  and  a  posterior.  The  boundaries  of  the  anterior  triangle  are,  in 
front,  the  median  line  of  the  neck;  above,  the  lower  border  of  the  body  of  the  mandible,  and  an 
imaginary  line  drawn  from  the  angle  of  the  mandible  to  the  Sternocleidomastoideus;  behind, 
the  anterior  border  of  the  Sternocleidomastoideus.  The  apex  of  the  triangle  is  at  the  upper 
border  of  the  sternum.  The  boundaries  of  the  posterior  triangle  are,  in  fro7it,  the  posterior  border 
of  the  Sternocleidomastoideus;  below,  the  middle  third  of  the  clavicle;  behind,  the  anterior  margin 
of  the  Trapezius.  The  apex  corresponds  with  the  meeting  of  the  Sternocleidomastoideus  and 
Trapezius  on  the  occipital  bone.  The  anatomy  of  these  triangles  will  be  more  fully  described 
with  that  of  the  vessels  of  the  neck  (p.  642). 

Relations. — The  superficial  surface  of  the  Sternocleidomastoideus  is  in  relation  with  the  integu- 
ment and  Platysma,  from  which  it  is  separated  by  the  external  jugular  vein,  several  of  the 
superficial  branches  of  the  cervical  plexus,  and  the  investing  layer  of  the  deep  cervical  fascia. 
The  deep  surface  of  the  muscle  is  in  relation  with  the  sternoclavicular  articulation,  the  pro- 
cess of  the  deep  cervical  fascia  which  binds  the  inferior  belly  of  the  Omohyoideus  to  the 
sternum  and  clavicle,  the  Sternohyoideus,  Sternothyreoideus,  Omohyoideus,  posterior  belly  of 

1  F.  G.  Parsons  (Journal  of  Anatomy  and  Physiology,  vol.  xliv)  regards  the  carotid  sheath  and  the  fascial  planes 
in  the  neck  as  structures  which  are  artificially  produced  by  dissection. 


THE  LATERAL  CERVICAL  MUSCLES 


479 


the  Digastricus,  Levator  scapulae,  Spleuius  and  Scaleni  muscles,  the  common  carotid  artery,  the 
internal  and  anterior  jugular  veins,  the  origins  of  the  internal  and  external  carotid  arteries,  the 
occipital,  subclaviaii,  transverse  cervical,  and  transverse  scapular  arteries  and  veins,  the  phrenic, 
vagus,  hypoglossal,  descendens  and  communicantes  hypoglossi  nerves,  the  accessory  nerve 
which  pierces  its  upper  third,  the  cervical  plexus,  the  upper  part  of  the  brachial  plexus,  parts 
of  the  thyroid  and  parotid  glands  and  their  vessels,  and  the  deep  cervical  lymi)h  glands. 

Actions. — -When  only  one  Sternocleidomastoideus  acts,  it  draws  the  head  toward  the  shoulder 
of  the  same  side,  assisted  by  the  Splenius  and  the  Obliquus  capitis  inferior  of  the  opposite  side. 
At  the  same  time  it  rotates  the  head  so  as  to  carry  the  face  toward  the  opposite  side.  Acting 
together  from  their  sternoclavicular  attachments  the  muscles  will  flex  the  cervical  part  of  the 
vertebral  column.  If  the  head  be  fixed,  the  two  muscles  assist  in  elevating  the  thorax  in  forced 
inspiration. 


Fig.  490. — Muscles  of  the  neck.     Lateral  view. 


Nerves. — The  Sternocleidomastoideus  is  supplied  by  the  accessory  nerve  and  branches  from 
the  anterior  divisions  of  the  second  and  third  cervical  nerves. 

Applied  Anatomy. — The  surgical  anatomy  of  the  Sternocleidomastoideus  is  of  importance  in 
connection  with  the  deformity  known  as  wry-neck,  which  is  due  to  a  contracted  condition  of  this 
muscle.  The  wry-neck  may  be  -temporary,  as  the  result  of  direct  irritation  of  the  muscle  or  of 
the  nerves  supplying  it,  and  may  occur  in  acute  glandular  enlargement,  cellulitis  of  the  neck, 
myositis  of  the  muscle,  or  cervical  caries.  It  may,  however,  be  permanent,  and  is  then  most 
often  due  to  injm-y  to  the  muscle  during  birth,  especially  in  breech  presentations,  rupture  of 
the  fibres  and  subsequent  cicatricial  contraction  taking  place.  In  these  cases,  division  of  the 
muscle  is  often  necessary  to  effect  a  cure,  and  this  may  be  done  either  subcutaneously  or  through 
an  open  wound.  The  subcutaneous  method  is  thus  performed;  the  external  jugular  and  anterior 
jugular  veins  having  been,  if  possible,  defined,  a  tenotomy  knife  is  introduced  close  to  the  margin 
of  one  tendon  of  origin  of  the  muscle,  about  1.25  cm.  above  the  clavicle,  and  the  tenotome  passed 
flat  behind  the  tendon  and  then  turned  forward,  and  the  tendon  divided  from  behind  forward 
while  the  muscle  is  put  well  upon  the  stretch  by  an  assistant.  The  other  tendon  is  then  divided 
in  a  similar  manner.  In  dividing  the  clavicular  origin,  it  is  always  desirable  to  introduce  the 
tenotome  along  the  posterior  border,  in  order  to  avoid  the  external  jugular  vein.  The  open  method 
is,  however,  much  to  be  preferred,  as  being  the  more  effectual  and  the  less  dangerous,  if  precau- 
tions are  taken  to  keep  the  wound  aseptic.  The  tendons  of  origin  are  freely  exposed  by  a. hori- 
zontal incision  across  the  root  of  the  neck  and  carefully  divided;  any  tense  bands  of  fascia  which 


480 


MYOLOGY 


exist  should  also  be  divided.    The  wound  is  now  sutured  and  dressed,  and  the  head  fixed  in  as 
straight  a  position  as  possible. 

There  is  also  a  condition  coming  on  in  adult  life  (spasinodic  torlicollis)  which  is  a  very  distress- 
ing form  of  functional  nervous  disease.  It  begins  with  tonic  or  clonic  spasm  of  one  of  the  Sterno- 
cleidomastoidei,  which  is  soon  followed  by  spasm  of  the  Trapezius,  particularly  its  clavicular 
portion.  The  Splenius  of  the  opposite  side,  the  Scaleni,  Semispinales  capitis,  and  Longissimi 
capitis  may  all  become  involved  in  turn,  with  secondary  contracture  of  the  deep  cervical  fascia. 
Operation  in  these  cases  often  fails  to  give  satisfactory  results.  Tenotomy  of  the  affected  muscles 
or  section  of  the  nerves  supplying  them  may  afford  temporary  relief,  but  the  .spasm  often  returns 
when  the  cut  nerves  or  muscles  rejoin. 


III.     THE  SUPRA-  AND  INFRAHYOID  MUSCLES   (Figs.  490,  491). 
The  suprahyoid  muscles  are : 

Digastricus.  Mylohyoideus. 


Stylohyoideus. 


Geniohyoideus. 


Dissection. — To  dissect  these  muscles  a  block  should  be  placed  beneath  the  back  of  the  neck, 
and  the  head  drawn  backward  and  retained  in  that  position.  On  the  removal  of  the  deep  fascia 
the  muscles  are  at  once  exposed. 


Sternum 

Fig.  491. — Muscles  of  the  neck.     Anterior  view. 

The  Digastricus  (Digastric  muscle)  consists  of  two  fleshy  belhes  united  by  an 
intermediate  rounded  tendon.  It  lies  below  the  body  of  the  mandible,  and  extends, 
in  a  curved  form,  from  the  mastoid  process  to  the  symphysis  menti.  The  posterior 
belly,  longer  than  the  anterior;  arises  from  the  mastoid  notch  of  the  temporal 
bone  and  passes  downward  and  forward.  The  anterior  belly  arises  from  a  depression 
on  the  inner  side  of  the  lower  border  of  the  mandible,  close  to  the  symphysis,  and 
passes  downward  and  backward.  The  two  bellies  end  in  an  intermediate  tendon 
which  perforates  the  Stylohyoideus  muscle,  and  is  held  in  connection  with  the  side 
of  the  body  and  the  greater  cornu  of  the  hyoid  bone  by  a  fibrous  loop,  which  is 
sometimes  lined  bv  a  mucous  sheath.     A  broad  aponeurotic  layer  is  given  off 


THE  SUPRA-  AND  INFRAHYOID  MUSCLES  481 

from  the  tendon  of  the  Digastricus  on  either  side,  to  he  attached  to  the  hody 
and  greater  cornu  of  the  hyoid  bone;  this  is  termed  the  suprahyoid  aponeurosis. 

The  Digastricus  divides  the  anterior  triangle  of  the  neck  into  three  smaller  triangle  (1)  the 
submaxillary  triangle,  bounded  above  by  the  lower  border  of  the  body  of  the  mandible,  and 
a  line  drawn  from  its  angle  to  the  Sternocleidomastoideus,  below  by  the  posterior  belly  of  the 
Digastricus  and  the  Stylohyoideus,  in  front  by  the  anterior  belly  of  the  Digastricus;  (2)  the 
carotid  triangle,  bounded  above  by  the  posterior  belly  of  the  Digastricus  and  Stylohyoideus, 
behind  by  the  Sternocleidomastoideus,  below  by  the  Omohyoideus;  (3)  the  suprahyoid  or  sub- 
mental triangle,  boiftidcd  laterally  by  the  anterior  belly  of  the  Digastricus,  medially  by  the 
middle  line  of  the  neck  from  the  hyoid  bone  to  the  symphysis  menti,  and  interiorly  by  the  body 
of  the  hyoid  bone. 

Relations. — The  Digastricus  is  in  relation  by  its  superficial  surface  with  the  Platysma,  Sterno- 
cleidomastoideus, part  of  the  Splenius,  Longissimus  capitis,  mastoid  process,  Stylohyoideus,  and 
the  parotid  gland.  The  deep  surface  of  the  anterior  belly  lies  on  the  Mylohyoideus;  that  of  the 
posterior  bellj'^  on  the  Styloglossus,  Stylopharyiigeus,  and  Hyoglossus  muscles,  the  external 
carotid  artery  and  its  occipital,  lingual,  external  maxillary,  and  ascending  pharyngeal  branches, 
the  internal  carotid  artery,  internal  jugular  -s^ein,  and  hypoglossal  nerve. 

The  stylohyoideus  (Stylohyoid  muscle)  is  a  slender  muscle,  lying  in  front  of,  and 
above,  the  posterior  belly  of  the  Digastricus.  It  arises  from  the  back  and  lateral 
surface  of  the  styloid  process,  near  the  base;  and,  passing  downward  and  forward, 
is  inserted  into  the  body  of  the  hyoid  bone,  at  its  junction  with  the  greater  cornu, 
and  just  above  the  Omohyoideus.  It  is  perforated,  near  its  insertion,  by  the  tendon 
of  the  Digastricus. 

The  Stylohyoid  Ligament  (ligavientum  stylohyoideus). — In  connection  with  the 
Stylohyoideus  muscle  a  ligamentous  band,  the  stylohyoid  ligament,  may  be 
described.  It  is  a  fibrous  cord,  which  is  attached  to  the  tip  of  the  styloid  process 
of  the  temporal  and  the  lesser  cornu  of  the  hyoid  bone.  It  frequently  contains  a 
little  cartilage  in  its  centre,  is  often  partially  ossified,  and  in  many  animals  forms 
a  distinct  bone,  the  epihyal. 

The  Mylohyoideus  (Mylohyoid  muscle),  flat  and  triangular,  is  situated  imme- 
diately above  the  anterior  belly  of  the  Digastricus,  and  forms,  with  its  fellow  of  the 
opposite  side,  a  muscular  floor  for  the  cavity  of  the  mouth.  It  arises  from  the  whole 
length  of  the  mylohyoid  line  of  the  mandible,  extending  from  the  symphysis  in 
front  to  the  last  molar  tooth  behind.  The  posterior  fibres  pass  medialward  and 
slightly  downward,  to  be  inserted  into  the  body  of  the  hyoid  bone.  The  middle  and 
anterior  fibres  are  inserted  into  a  median  fibrous  raphe  extending  from  the  sym- 
physis menti  to  the  hyoid  bone,  where  they  join  at  an  angle  with  the  fibres  of  the 
opposite  muscle.  This  median  raphe  is  sometimes  wanting;  the  fibres  of  the  two 
muscles  are  then  continuous. 

Relations. — The  Mylohyoideus  is  in  relation  by  its  superficial  or  under  surface  with  the  Platys- 
ma, the  anterior  belly  of  the  Digastricus,  the  suprahyoid  aponeurosis,  the  superficial  part  of  the 
submaxillary  gland,  the  external  maxillary  and  submental  vessels,  and  the  mylohyoid  vessels 
and  nerve.  By  its  deep  or  superior  surface  it  is  in  relation  with  the  Geniohyoideus,  part  of  the 
Hyoglossus,  and  the  Styloglossus  muscles,  the  hypoglossal  and  Ungual  nerves,  the  submaxillary 
ganglion,  the  subUngual  gland,  the  deep  portion  of  the  submaxillary  gland  and  the  submaxillary 
duct,  the  lingual  and  subUngual  vessels,  and  the  buccal  mucous  membrane. 

Dissection. — The  Mylohyoideus  should  now  be  removed,  in  order  to  expose  the  muscles  which 
lie  beneath;  this  is  effected  by  reflecting  it  from  its  atta^ments  to  the  hyoid  bone  and  mandible, 
and  separating  it  by  a  vertical  incision  from  its  fellow  of  the  opposite  side. 

The  Geniohyoideus  (Geniohyoid  muscle)  is  a  narrow  muscle,  situated  above  the 
medial  border  of  the  Mylohyoideus.  It  arises  from  the  inferior  mental  spine  on 
the  back  of  the  symphysis  menti,  and  runs  backward  and  slightly  downward,  to 
be  inserted  into  the  anterior  surface  of  the  body  of  the  hyoid  bone;  it  lies  in  con- 
tact with  its  fellow  of  the  opposite  side.        * 

Nerves. — -The  Mylohyoideus  and  anterior  belly  of  the  Digastricus  are  suppUed  by  the  mylo- 
hyoid branch  of  the  inferior  alveolar;  the  Stylohyoideus  and  posterior  belly  of  the  Digastricus, 
by  the  facial;  the  Geniohyoideus,  by  the  hypoglossal. 
31 


482  MYOLOGY 

Actions. — ^These  muscles  perform  two  very  important  actions.     During  the  act  of  deglutition 

they  raise  the  hyoid  bone,  and  with  it  the  base  of  the  tongue;  when  the  hyoid  bone  is  fixed  by  its 
depressors  and  those  of  the  larynx,  they  depress  the  mandible.  During  the  first  act  of  degluti- 
tion, when  the  mass  of  food  is  being  driven  from  the  mouth  into  the  pharynx,  the  hyoid  bone 
and  with  it  the  tongue,  is  carried  upward  and  forward  by  the  anterior  bellies  of  the  Digastrici, 
the  Mylohyoidei,  and  Geniohyoidei.  In  the  second  act,  when  the  mass  is  passing  through  the 
pharynx,  the  direct  elevation  of  the  hyoid  bone  takes  place  by  the  combined  action  of  all  the 
muscles;  and  after  the  food  has  passed,  the  hyoid  bone  is  carried  upward  and  backward  by  the 
posterior  bellies  of  the  Digastrici  and  the  Stylohyoidei,  which  assist  in  preventing  the  return 
of  the  food  into  the  mouth. 

The  infrahyoid  muscles  are : 

Sternohyoideiis.  Thyreohyoideus. 

Sternothyreoideiis.  Omohyoideus. 

Dissection. — The  muscles  in  this  region  may  be  exposed  by  removing  the  deep  fascia  from 
the  front  of  the  neck.  In  order  to  see  the  entire  extent  of  the  Omohyoideus  it  is  necessary  to 
divide  the  Sternocleidomastoideus  at  its  centre,  and  turn  its  ends  aside,  and  to  detach  the  Trape- 
zius from  the  clavicle  and  scapula.  This,  however,  should  not  be  done  until  the  Trapezius  has 
been  dissected. 

The  Sternohyoideus  {Sternohyoid  muscle)  is  a  thin,  narrow  muscle,  which  arises 
from  the  posterior  surface  of  the  medial  end  of  the  clavicle,  the  posterior  sterno- 
clavicular ligament,  and  the  upper  and  posterior  part  of  the  manubrium  sterni. 
Passing  upward  and  medialward,  it  is  inserted,  by  short,  tendinous  fibres,  into  the 
lower  border  of  the  body  of  the  hyoid  bone.  Below,  this  muscle  is  separated 
from  its  fellow  by  a  considerable  interval;  but  the  two  muscles  come  into  contact 
with  one  another  in  the  middle  of  their  course,  and  from  this  upward,  lie  side  by 
side.  It  sometimes  presents,  immediately  above  its  origin,  a  transverse  tendinous 
inscription. 

The  Sternothyreoideus  (Sternothyroid  muscle)  is  shorter  and  wider  than  the 
preceding  muscle,  beneath  which  it  is  situated.  It  arises  from  the  posterior  surface 
of  the  manubrium  sterni,  below  the  origin  of  the  Sternohyoideus,  and  from  the  edge 
of  the  cartilage  of  the  first  rib,  and  sometimes  that  of  the  second  rib,  it  is  inserted 
into  the  oblique  line  on  the  lamina  of  the  thyroid  cartilage.  This  muscle  is  in 
close  contact  with  its  fellow  at  the  lower  part  of  the  neck,  but  diverges  somewhat 
as  it  ascends;  it  is  occasionally  traversed  by  a  transverse  or  oblique  tendinous 
inscription. 

The  Thyreohyoideus  {Thyrohyoid  muscle)  is  a  small,  quadrilateral  muscle 
appearing  like  an  upward  continuation  of  the  Sternothyreoideus.  It  arises  from 
the  oblique  line  on  the  lamina  of  the  thyroid  cartilage,  and  is  inserted  into  the 
lower  border  of  the  greater  cornu  of  the  hyoid  bone. 

The  Omohyoideus  {Omohyoid  muscle)  consists  of  two  fleshy  bellies  united  by 
a  central  tendon.  It  arises  from  the  upper  border  of  the  scapula,  and  occasionally 
from  the  superior  transverse  ligament  which  crosses  the  scapular  notch,  its  extent 
of  attachment  to  the  scapula  varying  from  a  few  millimetres  to  2.5  cm.  From 
this  origin,  the  inferior  belly  forms  a  flat,  narrow  fasciculus,  which  inclines  forward 
and  slightly  upward  across  the  lower  part  of  the  neck,  being  bound  down  to  the 
clavicle  by  a  fibrous  expansion;  it  then  passes  behind  the  Sternocleidomastoideus, 
becomes  tendinous  and  changes  its  direction,  forming  an  obtuse  angle.  It  ends 
in  the  superior  belly,  which  passes  almost  vertically  upward,  close  to  the  lateral 
border  of  the  Sternohyoideus,  to  be  inserted  into  the  lower  border  of  the  body 
of  the  hyoid  bone,  lateral  to  the  insertion  of  the  Sternohyoideus.  The  central 
tendon  of  this  muscle  varies  much  iif  length  and  form,  and  is  held  in  position  by 
a  process  of  the  deep  cervical  fascia,  which  sheaths  it,  and  is  prolonged  down  to 
be  attached  to  the  clavicle  and  first  rib;  it  is  by  this  means  that  the  angular  form 
of  the  muscle  is  maintained. 


THE  ANTERIOR  VERTEBRAL  MUSCLES 


483 


Th(>  iut'crit)!-  hcUy  of  tlic  OinoliyoicUai.s  tlividcs  the  poslcrior  triniitilc  of  the  neck  into  an  upper 
or  occipital  triangle  aiul  ;i  lown-  or  subclavian  triangle,  w liilc  its  suix'iior  })elly  divides  the  anterior 
triangk'  into  an  uj)])or  or  carotid  triangle  aiul  a  lower  or  muscular  triangle. 

Nerves. — The  'riiyreohyoidcus  is  .supi)lied  by  a  branch  from  t  he  hypoglossal  nerve;  the  superior 
belly  of  the  Omohyoideus  by  the  tleseendens  hypoglossi;  the  Btcrnohyoidcus,  Sternothyreoideus, 
ami  inferior  lielly  of  the  Omohyoideus  are  sui:)phed  by  branches  from  the  loop  between  the  des- 
cendeiis  hyj^oglossi  and  descendens  eervicalis. 

Actions. — These  muscles  depress  the  larynx  and  hyoid  bone,  after  they  have  been  drawn  up 
with  the  pharynx  in  the  act  of  deglutition.  The  Omohyoidei  not  only  depress  the  hyoid  bone, 
but  carry  it  backward  and  to  one  or  the  other  side.  They  are  concerned  especially  in  prolonged 
inspiratory  efforts;  for  by  rendering  the  lower  part  of  the  cervical  fascia  tense  they  lessen  the 
inward  suction  of  the  soft  parts,  which  would  otherwise  compress  the  great  vessels  and  the 
apices  of  the  lungs.  The  Thyreohyoideus  may  act  as  an  elevator  of  the  thyroid  cartilage,  when 
the  hyoid  bone  ascends,  drawing  the  thyroid  cartilage  up  behind  the  hyoid  bone.  The  Sterno- 
thyreoideus acts  as  a  depressor  of  the  thyroid  cartilage. 


IV.     THE  ANTERIOR  VERTEBRAL  MUSCLES   (Fig.  492). 
The  anterior  vertebral  muscles  are: 


Longiis  colli. 
Longus  capitis. 


Rectus  capitis  anterior. 
Rectus  capitis  lateralis. 


Fig.  492. — The  anterior  vertebral  muscles. 


The  Longus  colli  is  situated  on  the  anterior  surface  of  the  vertebral  column, 
between  the  atlas  and  the  third  thoracic  vertebra.  It  is  broad  in  the  middle, 
narrow  and  pointed  at  either  end,  and  consists  of  three  portions,  a  superior  oblique. 


484  MYOLOGY 

an  inferior  oblique,  and  a  vertical.  The  superior  oblique  portion  arises  from  the 
anterior  tubercles  of  the  transverse  processes  of  the  third,  fourth,  and  fifth  cervical 
vertebrte;  and,  ascending  obliquely  with  a  medial  inclination,  is  inserted  by  a  narrow 
tendon  into  the  tubercle  on  the  anterior  arch  of  the  atlas.  The  inferior  oblique 
portion,  the  smallest  part  of  the  muscle,  arises  from  the  front  of  the  bodies  of  the 
first  two  or  three  thoracic  vertebrse;  and,  ascending  obliquely  in  a  lateral  direction, 
is  inserted  into  the  anterior  tubercles  of  the  transverse  processes  of  the  fifth  and 
sixth  cervical  vertebrse.  The  vertical  portion  arises,  below,  from  the  front  of  the 
bodies  of  the  upper  three  thoracic  and  lower  three  cervical  vertebrse,  and  is  in- 
serted into  the  front  of  the  bodies  of  the  second,  third,  and  fourth  cervical  vertebrae. 

The  Longus  capitis  (Rectus  capitis  anticus  major),  broad  and  thick  above, 
narrow  below,  arises  by  four  tendinous  slips,  from  the  anterior  tubercles  of  the 
transverse  processes  of  the  third,  fourth,  fifth,  and  sixth  cervical  vertebrse,  and 
ascends,  converging  toward  its  fellow  of  the  opposite  side,  to  be  inserted  into  the 
inferior  surface  of  the  basilar  part  of  the  occipital  bone. 

The  Rectus  capitis  anterior  (Rectus  capitis  anticus  minor)  is  a  short,  flat  muscle, 
situated  immediately  behind  the  upper  part  of  the  Longus  capitis.  It  arises  from 
the  anterior  surface  of  the  lateral  mass  of  the  atlas,  and  from  the  root  of  its 
transverse  process,  and  passing  obliquely  upward  and  medialward,  is  inserted  into 
the  inferior  surface  of  the  basilar  part  of  the  occipital  bone  immediately  in  front 
of  the  foramen  magnum. 

The  Rectus  capitis  lateralis,  a  short,  flat  muscle,  arises  from  the  upper  surface 
of  the  transverse  process  of  the  atlas,  and  is  inserted  into  the  under  surface  of  the 
jugular  process  of  the  occipital  bone. 

Nerves. — -The  Rectus  capitis  anterior  and  the  Rectus  capitis  lateralis  are  supplied  from  the 
loop  between  the  first  and  second  cervical  nerves;  the  Longus  capitis,  by  branches  from  the 
first,  second,  and  third  cervical;  the  Longus  colh,  by  branches  from  the  second  to  the  seventh 
cervical  nerves. 

Actions. — The  Longus  capitis  and  Rectus  capitis  anterior  are  the  direct  antagonists  of  the 
muscles  at  the  back  of  the  neck,  serving  to  restore  the  head  to  its  natural  position  after  it  has 
been  di-awn  backward.  These  muscles  also  flex  the  head,  and  from  their  obhquity,  rotate  it, 
so  as  to  turn  the  face  to  one  or  the  other  side.  The  Rectus  lateraUs,  acting  on  one  side,  bends 
the  head  laterally.  The  Longus  colli  flexes  and  shghtly  rotates  the  cervical  portion  of  the  vertebral 
column. 

V.     THE  LATERAL  VERTEBRAL  MUSCLES   (Fig.  492). 

The  lateral  vertebral  muscles  are : 

Scalenus  anterior.  Scalenus  medius. 

Scalenus  posterior. 

The  Scalenus  anterior  (Scalenus  anticus)  lies  deeply  at  the  side  of  the  neck, 
behind  the  Sternocleidomastoideus.  It  arises  from  the  anterior  tubercles  of  the 
transverse  processes  of  the  third,  fourth,  fifth,  and  sixth  cervical  vertebrse,  and 
descending,  almost  vertically,  is  inserted  by  a  narrow,  flat  tendon  into  the  scalene 
tubercle  on  the  inner  border  of  the  first  rib,  and  into  the  ridge  on  the  upper  surface 
of  the  rib  in  front  of  the  subclavian  groove. 

Relations. — In  front  of  the  Scalenus  anterior  are  the  clavicle,  the  Subclavius,  Sternocleido- 
mastoideus, and  Omohyoideus  muscles,  the  transverse  cervical,  the  transverse  scapular,  and 
ascending  cervical  arteries,  the  subclavian  vein,  and  the  plu-enic  nerve.  By  its  posterior  surface, 
it  is  in  relation  with  the  cords  of  the  brachial  plexus,  the  subclavian  artery,  and  the  pleura,  which 
separate  it  from  the  Scalenus  medius.  Below,  it  is  separated  from  the  Longus  colh  by  the  vertebral 
artery,  and  above,  from  the  Longus  capitis,  by  the  ascending  cervical  branch  of  the  inferior 
thjToid  arterj^ 

The  Scalenus  medius,  the  largest  and  longest  of  the  three  Scaleni,  arises 
from  the  posterior  tubercles  of  the  transverse  processes  of  the  lower  six  cervical 


THE  DEEP  MUSCLES  OF  THE  BACK  485 

vertebra',  and  descending  along  the  side  of  the  vertebral  column,  is  inserted  by  a 
broad  attachment  into  the  upper  surface  of  the  first  ril),  between  the  tubercle 
and  the  subclavian  groove. 

Relations. — The  Scalenus  niedius  is  in  relation  by  its  anterior  surface  with  the  Sternocleido- 
mastoidcus;  it  is  crossed  by  the  clavicle  and  the  Omohyoidcus;  the  subclavian  artery  and  the 
cervical  nerves  separate  it  from  the  Scalenus  anterior.  Lateral  to  it  are  the  Levator  scapulae 
and  the  Scalenus  jiostcrior.  The  long  thoracic  nerve  is  formed  in  the  substance  of  the  Scalenus 
medius  and  emerges  from  it;  the  dorsal  scapular  nerve  also  pierces  it. 

The  Scalenus  posterior  {Scalenus  posticus),  the  smallest  and  most  deeply  seated 
of  the  three  Scaleni,  arises,  by  two  or  three  separate  tendons,  from  the  posterior 
tubercles  of  the  transverse  processes  of  the  lower  two  or  three  cervical  vertebrae, 
and  is  inserted  by  a  thin  tendon  into  the  outer  surface  of  the  second  rib,  behind 
the  attachment  of  the  Serratus  anterior.  It  is  occasionally  blended  Avith  the 
Scalenus  medius. 

Nerves. — The  Scaleni  are  supplied  by  branches  from  the  second  to  the  seventh  cervical  nei'ves. 

Actions. — When  the  Scaleni  act  from  above,  they  elevate  the  first  and  second  ribs,  and  are, 
therefore,  inspiratory  muscles.  Acting  from  below,  they  bend  the  vertebral  column  to  one  or 
other  side;  if  the  muscles  of  both  sides  act,  the  vertebral  column  is  shghtly  flexed. 


THE  FASCI.ZE  AND  MUSCLES  OF  THE  TRUNK. 

The  muscles  of  the  trunk  may  be  arranged  in  six  groups: 

I.  Deep  Muscles  of  the  Back.  IV.  Muscles  of  the  Abdomen. 

II.  Suboccipital  Muscles.  V.  Muscles  of  the  Pelvis. 

III.  Muscles  of  the  Thorax.  VI.  Muscles  of  the  Perineum. 


I.  THE  DEEP  MUSCLES  OF  THE  BACK  (Fig.  494). 

The  deep  or  intrinsic  muscles  of  the  back  consist  of  a  complex  group  of  muscles 
extending  from  the  pelvis  to  the  skull.    They  are: 

Splenius  capitis.  Multifidus. 

Splenius  cervicis.  Rotatores. 

Sacrospinalis.  Interspinales. 

Semispinalis.  Intertransversarii. 

Dissection  of  the  Muscles  of  the  Back  by  Layers  (Fig.  493). — Fiist  Layer. — Place  the  body 
in  a  prone  position,  with  the  arms  extended  over  the  sides  of  the  table,  and  the  thorax  and 
abdomen  supported  by  several  blocks,  so  as  to  render  the  muscles  tense.  Then  make  an  inci- 
sion along  the  middle  line  of  the  back  from  the  occipital  protuberance  to  the  coccyx.  Make  a 
transverse  incision  from  the  upper  end  of  this  to  the  mastoid  process,  and  a  third  incision  from 
its  lower  end,  along  the  crest  of  the  ilium  to  about  its  middle.  This  large  intervening  space 
should,  for  convenience  of  dissection,  be  subdivided  by  a  fom-th  incision,  extending  obUquely 
from  the  spinous  process  of  the  last  thoracic  vertebra,  upward  and  outward  to  the  acromion 
process.  This  incision  corresponds  with  the  lower  border  of  the  Trapezius  muscle.  The  flaps 
of  integument  are  then  to  be  removed  in  the  direction  shown  in  the  figure. 

Second  Layer. — The  Trapezius  must  be  removed,  in  order  to  expose  the  second  layer;  to  effect 
this,  detach  the  muscle  from  its  attachment  to  the  clavicle  and  spine  of  the  scapula,  and  tm-n 
it  back  toward  the  vertebral  coliman. 

Third  Layer. — To  bring  into  view  the  third  layer  of  muscles,  remove  the  whole  of  the  second, 
together  with  the  Latissimus  dorsi,  by  cutting  through  the  Levator  scapulae  and  Rhomboidei 
muscles  near  their  origin,  and  reflecting  them  downward,  and  by  dividing  the  Latissimus  dorsi 
in  the  middle  by  a  vertical  incision  carried  from  its  upper  to  its  lower  part,  and  reflecting  the 
two  halves  of  the  muscle. 

Fourth  Layer. — To  expose  the  muscles  of  the  fourth  layer,  remove  entirely  the  Serrati  and 
the  vertebral  and  lumbar  fasciae.  Then  detach  the  Splenius  by  separating  its  attachment  to  the 
spinous  processes  and  reflecting  it  outward. 


486 


MYOLOGY 


Fifth  Layer. — Remove  the  muscles  of  the  preceding  layer  by  dividing  and  turning  aside  the 
Semispinalis  capitis;  then  detach  the  Spinalis  and  Longissimus  dorsi  from  their  attachments, 
divide  the  Sacrospinalis  at  its  connection  below  to  the  sacral  lumbar  vertebrae  and  turn  it  out- 
ward. The  muscles  filling  up  the  interval  between  the  spinous  and  transverse  processes  are  then 
exposed. 

The  Lumbodorsal  Fascia  (fasciti  hni/hodorsalis;  linnbar  (ijxmeiirosi.s  and  vertebral 
fascia). — The  lumbodorsal  fascia  is  a  deep  investing  membrane  which  co\-ers  the 

deep  muscles  of  the  back  of  the  trunk.  Above,  it 
passes  in  front  of  the  Serratus  posterior  superior 
and  is  continuous  with  a  similar  investing  layer 
on  the  back  of  the  neck — the  nuchal  fascia. 

In  the  thoracic  region  the  lumbodorsal  fascia 
is  a  thin  fibrous  lamina  which  serves  to  bind 
down  the  Extensor  muscles  of  the  vertebral 
column  and  to  separate  them  from  the  muscles 
connecting  the  vertebral  column  to  the  upper 
extremity.  It  contains  both  longitudinal  and 
transverse  fibres,  and  is  attached,  medially,  to 
the  spinous  processes  of  the  thoracic  vertebrae; 
laterally  to  the  angles  of  the  ribs. 

In  the  lumbar  region  the  fascia  (lumbar  apon- 
eurosis) is  in  two  layers,  anterior  and  posterior 
(Fig.  494).  The  posterior  layer  is  attached  to 
the  spinous  processes  of  the  lumbar  and  sacral 
vertebrae  and  to  the  supraspinal  ligament;  the 
anterior  is  attached,  medially,  to  the  tips  of  the 
transverse  processes  of  the  lumbar  vertebrae  and 
to  the  intertransverse  ligaments,  below,  to  the 
iliolumbar  ligament,  and  above,  to  the  lumbo- 
costal ligament.  The  tw^o  layers  unite  at  the 
lateral  margin  of  the  Sacrospinalis,  to  form  the 
tendon  of  origin  of  the  Transversus  abdominis. 
The  Splenius  capitis  (Fig.  516)  arises  from 
the  lower  half  of  the  ligamentum  nuchae,  from 
the  spinous  process  of  the  seventh  cervical 
vertebra,  and  from  the  spinous  processes  of  the  upper  three  or  four  thoracic 
vertebrae.    The  fibres  of  the  muscle  are  directed  upw^ard  and  lateralward  and 

Ohliquus  externus 


Fig.  493. — Dissection  of  the  muscles  of  the 
back. 


Lumbodorsal   \ 


fascia 


Fasciaon 
Quad.  Luwb. 


Anterior  layer 


\        Posterior  layer 


Fig.  494. — Diagram  of  a  transverse  .section  of  the  posterior  abdominal  wall,  to  show  the  disposition  of  the  lumbodorsal 

fascia. 


are  inserted,  under  cover  of  the  Sternocleidomastoideus,  into  the  mastoid  process 
of  the  temporal  bone,  and  into  the  rough  surface  on  the  occipital  bone  just 
below  the  lateral  third  of  the  superior  nuchal  line. 


THE  DEEP  MUSCLES  OF  THE  BACK 


487 


The  Splenius  cervicis  {Spleniu,  colli)  (Fig.  rAC,)  arises  by  a  narrow  tendinous 
l)an(l  In.ni  tin-  spinous  processes  of  the  third  to  the  sixth  thoracic  vertebrje;  it  is 

Occipital  bone 


Multindus 


First  thoracic  vertebra 


First  lumbar  vertebra Vv-> 


First  sacral  vertebra 


Fig.  495. — Deep  muscles  of  the  back. 


488  MYOLOGY 

inserted,  by  tendinous  fasciculi,   into  the  posterior  tubercles  of  the  transverse 
processes  of  the  upper  two  or  three  cervical  vertebrae. 

Sl  Nerves. — The  Splenii  are  supplied  by  the  lateral  branches  of  the  posterior  divisions  of  the 
middle  and  lower  cervical  nerves. 

Actions. — The  Splenii  of  the  two  sides,  acting  together,  draw  the  head  directly  backward, 
assisting  the  Trapezius  and  Semispinahs  capitis;  acting  separately,  they  draw  the  head  to  one 
side,  and  slightly  rotate  it,  turning  the  face  to  the  same  side.  They  also  assist  in  supporting  the 
head  in  the  erect  position. 

The  Sacrospinalis  {Erector  spinae)  (Fig.  495),  and  its  prolongations  in  the 
thoracic  and  cervical  regions,  lie  in  the  groove  on  the  side  of  the  vertebral  column. 
They  are  covered  in  the  lumbar  and  thoracic  regions  by  the  lumbodorsal  fascia, 
and  in  the  cervical  region  by  the  nuchal  fascia.  This  large  muscular  and  tendinous 
mass  varies  in  size  and  structure  at  different  parts  of  the  vertebral  column.  In 
the  sacral  region  it  is  narrow  and  pointed,  and  at  its  origin  chiefly  tendinous  in 
structure.  In  the  lumbar  region  it  is  larger,  and  forms  a  thick  fleshy  mass  which, 
on  being  followed  upward,  is  subdivided  into  three  columns;  these  gradually 
diminish  in  size  as  they  ascend  to  be  inserted  into  the  vertebrae  and  ribs. 

The  Sacrospinalis  arises  from  the  anterior  surface  of  a  broad  and  thick  tendon, 
which  is  attached  to  the  medial  crest  of  the  sacrum,  to  the  spinous  processes  of 
the  lumbar  and  the  eleventh  and  twelfth  thoracic  vertebrae,  and  the  supraspinal 
ligament,  to  the  back  part  of  the  inner  lip  of  the  iliac  crests  and  to  the  lateral 
crests  of  the  sacrum,  where  it  blends  with  the  sacrotuberous  and  posterior  sacro- 
iliac ligaments.  Some  of  its  fibres  are  continuous  with  the  fibres  of  origin  of  the 
Glutaeus  maximus.  The  muscular  fibres  form  a  large  fieshy  mass  which  splits, 
in  the  upper  lumbar  region  into  three  columns,  viz.,  a  lateral,  the  Iliocostalis,  an 
intermediate,  the  Longissimus,  and  a  medial,  the  Spinalis.  Each  of  these  consists 
from  below  upward,  of  three  parts,  as  follows: 

Lateral  Colwiui.  Intermediate  Column.  Medial  Column. 

Iliocostalis.  Longissimus.  Spinalis. 

(a)  I.  lumborum.  (a)  L.  dorsi.  {a)  S.  dorsi. 

(h)  I.  dorsi.  (6)  L.  cervicis.  (6)  S.  cervicis. 

(c)  I.  cervicis.  (c)  L.  capitis.  (c)  S.  capitis. 

The  Iliocostalis  lumborum  (Iliocostalis  muscle;  Sacrolumhalis  muscle)  is  inserted, 
by  six  or  seven  flattened  tendons,  into  the  inferior  borders  of  the  angles  of  the  lower 
six  or  seven  ribs. 

The  Iliocostalis  dorsi  (Musculus  accessorius)  arises  by  flattened  tendons  from 
the  upper  borders  of  the  angles  of  the  lower  six  ribs  medial  to  the  tendons  of 
insertion  of  the  Iliocostalis  lumborum;  these  become  muscular,  and  are  inserted 
into  the  upper  borders  of  the  angles  of  the  upper  six  ribs  and  into  the  back  of  the 
transverse  process  of  the  seventh  cervical  vertebra. 

The  Iliocostalis  cervicis  {Cervicalis  ascendens)  arises  from  the  angles  of  the  third, 
fourth,  fifth,  and  sixth  ribs,  and  is  inserted  into  the  posterior  tubercles  of  the  trans- 
verse processes  of  the  fourth,  fifth,  and  sixth  cervical  vertebrae. 

The  Longissimus  dorsi  is  the  intermediate  and  largest  of  the  continuations  of 
the  Sacrospinalis.  In  the  lumbar  region,  where  it  is  as  yet  blended  with  the  Ilio- 
costalis lumborum,  some  of  its  fibres  are  attached  to  the  whole  length  of  the  pos- 
terior surfaces  of  the  transverse  processes  and  the  accessory  processes  of  the  lumbar 
vertebrae,  and  to  the  anterior  layer  of  the  lumbodorsal  fascia.  In  the  thoracic 
region  it  is  inserted,  by  rounded  tendons,  into  the  tips  of  the  transverse  processes 
of  all  the  thoracic  vertebrae,  and  by  fleshy  processes  into  the  lower  nine  or  ten  ribs 
between  their  tubercles  and  angles. 

The  Longissimus  cervicis  (TransversaUs  cervicis),  situated  medial  to  the  Longis- 
simus dorsi,  arises  by  long  thin  tendons  from  the  summits  of  the  transverse  pro- 
cesses of  the  upper  four  or  five  thoracic  vertebrae,  and  is  inserted  by  similar  tendons 


THE  DEEP  MUSCLES  OF  THE  BACK  489 

into  the  posterior  tubercles  of  the  transverse  processes  of  the  cervical  vertebree 
from  the  second  to  the  sixth  inclusive. 

The  Longissimus  capitis  (Trachelomastoid  muscle)  lies  medial  to  the  Longissimus 
cervicis,  between  it  and  the  Semispinalis  capitis.  It  arises  by  tendons  from  the 
the  transverse  processes  of  the  upper  four  or  five  thoracic  vertebrae,  and  the  artic- 
ular processes  of  the  lower  three  or  four  cervical  vertebrae,  and  is  inserted  into  the 
posterior  margin  of  the  mastoid  process,  beneath  the  Splenius  capitis  and  Sterno- 
cleidomastoideus.  It  is  almost  always  crossed  by  a  tendinous  intersection  near 
its  insertion. 

The  Spinalis  dorsi,  the  medial  continuation  of  the  Sacrospinalis,  is  scarcely 
separable  as  a  distinct  muscle.  It  is  situated  at  the  medial  side  of  the  Longissimus 
dorsi,  and  is  intimately  blended  with  it;  it  arises  by  three  or  four  tendons  from  the 
spinous  processes  of  the  first  two  lumbar  and  the  last  two  thoracic  vertebrae :  these, 
uniting,  form  a  small  muscle  w^hich  is  inserted  by  separate  tendons  into  the  spinous 
processes  of  the  upper  thoracic  vertebra?,  the  number  varying  from  four  to  eight. 
It  is  intimately  united  with  the  Semispinalis  dorsi,  situated  beneath  it. 

The  Spinalis  cervicis  (Spinalis  colli)  is  an  inconstant  muscle,  which  arises  from 
the  lower  part  of  the  ligamentum  nuchae,  the  spinous  process  of  the  seventh  cer- 
vical, and  sometimes  from  the  spinous  processes  of  the  first  and  second  thoracic 
vertebrae,  and  is  inserted  into  the  spinous  process  of  the  axis,  and  occasionally  into 
the  spinous  processes  of  the  two  vertebrae  below  it. 

The  Spinalis  capitis  (Biventer  cervicis)  is  usually  inseparably  connected  with  the 
Semispinalis  capitis  (see  below) . 

The  Semispinalis  dorsi  consists  of  thin,  narrow,  fleshy  fasciculi,  interposed 
between  tendons  of  considerable  length.  It  arises  by  a  series  of  small  tendons 
from  the  transverse  processes  of  the  sixth  to  the  tenth  thoracic  vertebrae,  and  is 
inserted,  by  tendons,  into  the  spinous  processes  of  the  upper  four  thoracic  and  lower 
two  cervical  vertebrae. 

The  Semispinalis  cervicis  {Semispinalis  colli),  thicker  than  the  preceding, 
arises  by  a  series  of  tendinous  and  fleshy  fibres  from  the  transverse  processes  of 
the  upper  five  or  six  thoracic  vertebrae,  and  is  inserted  into  the  cervical  spinous 
processes,  from  the  axis  to  the  fifth  inclusive.  The  fasciculus  connected  with  the 
axis  is  the  largest,  and  is  chiefly  muscular  in  structure. 

The  Semispinalis  capitis  {Complexus)  is  situated  at  the  upper  and  back  part' 
of  the  neck,  beneath  the  Splenius,  and  medial  to  the  Longissimus  cervicis  and 
capitis.  It  arises  by  a  series  of  tendons  from  the  tips  of  the  transverse  processes 
of  the  upper  six  or  seven  thoracic  and  the  seventh  cervical  vertebrae,  and  from  the 
articular  processes  of  the  three  cervical  above  this.  The  tendons,  uniting,  form 
a  broad  muscle,  which  passes  upward,  and  is  inserted  between  the  superior  and 
inferior  nuchal  lines  of  the  occipital  bone.  The  medial  part,  usually  more  or  less 
distinct  from  the  remainder  of  the  muscle,  is  frequently  termed  the  Spinalis  capitis ; 
it  is  also  named  the  Biventer  cervicis  since  it  is  traversed  by  an  imperfect  tendinous 
inscription. 

The  Multifidus  (Midtifidiis  spinae)  consists  of  a  number  of  fleshy  and  tendinous 
fasciculi,  which  fill  up  the  groove  on  either  side  of  the  spinous  processes  of  the  ver- 
tebrae, from  the  sacrum  to  the  axis.  In  the  sacral  region,  these  fasciculi  arise  from 
the  back  of  the  sacrum,  as  low^  as  the  fourth  sacral  foramen,  from  the  aponeu- 
rosis of  origin  of  the  Sacrospinalis,  from  the  medial  surface  of  the  posterior  superior 
iliac  spine,  and  from  the  posterior  sacroiliac  ligaments;  in  the  lumbar  region, 
from  all  the  mamillary  processes;  in  the  thoracic  region,  from  all  the  transverse 
processes;  and  in  the  cervical  region,  from  the  articular  processes  of  the  lower 
four  vertebrae.  Each  fasciculus,  passing  obliquely  upward  and  medialward,  is 
inserted  into  the  whole  length  of  the  spinous  process  of  one  of  the  vertebrae  above. 
These  fasciculi  vary  in  length:  the  most  superficial,  the  longest,  pass  from  one 


490  MYOLOGY 

vertebra  to  the  third  or  fourth  above;  those  next  in  order  run  from  one  vertebra 
to  the  second  or  third  above;  while  the  deepest  connect  two  contif^uous  vertebra?. 

The  Rotatores  (Roiatores  spinae)  he  beneath  the  jNIultifidus  and  are  found  only 
in  the  thoracic  region;  they  are  eleven  in  number  on  either  side.  Each  muscle  is 
small  and  somewhat  quadrilateral  in  form;  it  arises  from  the  upper  and  back  part  of 
the  transverse  process,  and  is  inserted  into  the  lower  border  and  lateral  surface  of 
the  lamina  of  the  vertebra  above,  the  fibres  extending  as  far  as  the  root  of  the  spinous 
process.  The  first  is  found  between  the  first  and  second  thoracic  vertebrae;  the 
last,  between  the  eleventh  and  twelfth.  Sometimes  the  number  of  these  muscles 
is  diminished  by  the  absence  of  one  or  more  from  the  upper  or  lower  end. 

The  Interspinales  are  short  muscular  fasciculi,  placed  in  pairs  between  the 
spinous  processes  of  the  contiguous  vertebrae,  one  on  either  side  of  the  interspinal 
ligament.  In  the  cervical  region  they  are  most  distinct,  and  consist  of  six  pairs, 
the  first  being  situated  between  the  axis  and  third  vertebra,  and  the  last  between 
the  seventh  cervical  and  the  first  thoracic.  They  are  small  narrow  bundles, 
attached,  above  and  below,  to  the  apices  of  the  spinous  processes.  In  the  thoracic 
region,  they  are  found  between  the  first  and  second  vertebrae,  and  sometimes  be- 
tween the  second  and  third,  and  between  the  eleventh  and  twelfth.  In  the  lumbar 
region  there  are  four  pairs  in  the  intervals  between  the  five  lumbar  vertebrae. 
There  is  also  occasionally  one  between  the  last  thoracic  and  first  lumbar,  and  one 
between  the  fifth  lumbar  and  the  sacrum. 

The  Extensor  coccygis  is  a  slender  muscular  fasciculus,  which  is  not  always  present;  it  extends 
over  the  lower  part  of  the  posterior  surface  of  the  sacrum  and  coccyx.  It  arises  by  tendinous 
fibres  from  the  last  segment  of  the  sacrum,  or  first  piece  of  the  coccyx,  and  passes  downward  to 
be  inserted  into  the  lower  part  of  the  coccyx.  It  is  a  rudiment  of  the  Extensor  muscle  of  the 
caudal  vertebrae  of  the  lower  animals. 

The  Intertransversarii  {Intertransversales)  are  small  muscles  placed  between 
the  transverse  processes  of  the  vertebrae.  In  the  cervical  region  they  are  best 
developed,  consisting  of  rounded  muscular  and  tendinous  fasciculi,  and  are  placed 
in  pairs,  passing  between  the  anterior  and  the  posterior  tubercles  respectively  of 
the  transverse  processes  of  two  contiguous  vertebrae,  and  separated  from  one 
another  by  an  anterior  primary  division  of  the  cervical  nerve,  which  lies  in  the 
groove  between  them.  The  muscles  connecting  the  anterior  tubercles  are  termed 
the  Intertransversarii  anteriores;  those  between  the  posterior  tubercles,  the  Inter- 
transversarii posteriores;  both  sets  are  supplied  by  the  anterior  divisions  of  the 
spinal  nerves  (Lickley^).  There  are  seven  pairs  of  these  muscles,  the  first  pair 
being  between  the  atlas  and  axis,  and  the  last  pair  between  the  seventh  cervical 
and  first  thoracic  vertebrae.  In  the  thoracic  region  they  are  present  between  the 
transverse  processes  of  the  lower  three  thoracic  vertebrae,  and  between  the  trans- 
verse processes  of  the  last  thoracic  and  the  first  lumbar.  In  the  lumbar  region 
they  are  arranged  in  pairs,  on  either  side  of  the  vertebral  column,  one  set  occupy- 
ing the  entire  interspace  between  the  transverse  processes  of  the  lumbar  vertebrae, 
the  Intertransversarii  laterales;  the  other  set,  Intertransversarii  mediales,  passing 
from  the  accessory  process  of  one  vertebra  to  the  mamillary  of  the  vertebra  below. 
The  Intertransversarii  laterales  are  supplied  by  the  anterior  divisions,  and  the 
Intertransversarii  mediales  by  the  posterior  divisions  of  the  spinal  nerves  (Lichley, 
oy.  cit.). 

II.     THE  SUBOCCIPITAL  MUSCLES   (Fig.  495). 

The  suboccipital  group  comprises: 

Rectus  capitis  posterior  major.  Obliquus  capitis  inferior. 

Rectus  capitis  posterior  minor.  Obliquus  capitis  superior. 

I  Journal  of  Anatomy  and  Physiology,  1904,  vol.  xxxix. 


THE  SIBOCCIPITAL  MUSCLES  491 

The  Rectus  capitis  posterior  major  {Rectus  capitib-  ijo.s-ticus-  major)  aris-es  b}-  a 
pointed  tendon  from  the  spinous  process  of  the  axis,  and,  becoming  broader  as 
it  ascends,  is  inserted  into  the  lateral  part  of  the  inferior  nuchal  line  of  the  occipital 
bone  and  the  surface  of  the  bone  immediately  below  the  line.  Aii  the  muscles  of 
the  two  sides  pass  upward  and  lateralward,  they  leave  between  them  a  triangular 
space,  in  which  the  Recti  cai)itis  ])osteriores  minores  are  seen. 

The  Rectus  capitis  posterior  minor  (Rectus  capitis  posticus  minor)  arises  by  a 
narrow  pointed  tendon  from  the  tubercle  on  the  posterior  arch  of  the  atlas,  and, 
widenino-  as  it  ascends,  is  inserted  into  the  medial  part  of  the  inferior  nuchal  line 
of  the  occipital  !)()ne  and  the  surface  between  it  and  the  foramen  magnum. 

The  Obliquus  capitis  inferior  (Obliq^ms  inferior),  the  larger  of  the  two  Oblique 
muscles,  arises  from  the  apex  of  the  spinous  process  of  the  axis,  and  passes  lateral- 
ward  and  slightly  upward,  to  be  inserted  into  the  lower  and  back  part  of  the 
transverse  process  of  the  atlas. 

The  Obliquus  capitis  superior  (Obliquus  superior),  narrow  below,  wide  and 
expanded  above,  arises  by  tendinous  fibres  from  the  upper  surface  of  the  transverse 
process  of  the  atlas,  joining  with  the  insertion  of  the  preceding.  It  passes  upward 
and  medialward,  and  is  inserted  into  the  occipital  bone,  between  the  superior  and 
inferior  nuchal  lines,  lateral  to  the  Semispinalis  capitis. 

The  Suboccipital  Triangle. — Between  the  Obliqui  and  the  Rectus  capitis  posterior  major  is 
the  suboccipital  triangle.  It  is  bounded,  above  and  medially,  by  the  Rectus  capitis  posterior 
major;  aboDe  and  laterally,  by  the  Obliquus  capitis  superior;  below  and  laterally,  by  the  Obliquus 
capitis  inferior.  It  is  covered  by  a  layer  of  dense  fibro-fatty  tissue,  situated  beneath  the  Semi- 
spinalis capitis.  The  floor  is  formed  by  the  posterior  occipitoatlantal  membrane,  and  the  posterior 
arch  of  the  atlas.  In  the  deep  groove  on  the  upper  surface  of  the  posterior  arch  of  the  atlas  are 
the  vertebral  artery  and  the  first  cervical  or  suboccipital  nerve. 

Nerves. — The  deep  muscles  of  the  back  and  the  suboccipital  muscles  are  supplied  by  the 
posterior  primary  divisions  of  the  spinal  nerves. 

Actions. — The  Sacrospinalis  and  its  upward  continuations  and  the  Spinales  serve  to  main- 
tain the  vertebral  column  in  the  erect  posture;  they  also  serve  to  bend  the  trunk  backward  when 
it  is  required  to  counterbalance  the  influence  of  any  weight  at  the  front  of  the  body — as,  for 
instance,  when  a  heavy  weight  is  suspended  from  the  neck,  or  when  there  is  any  great  abdominal 
distension,  as  in  pregnancy  or  dropsy;  the  peculiar  gait  under  such  circumstances  depends  upon 
the  vertebral  column  being  drawn  backward,  by  the  counterbalancing  action  of  the  Sacrospinales. 
The  muscles  which  form  the  continuation  of  the  Sacrospinales  on  to  the  head  and  neck  steady 
those  parts  and  fix  them  in  the  upright  position.  If  the  Iliocostalis  lumborum  and  Longissimus 
dorsi  of  one  side  act,  they  serve  to  draw  down  the  chest  and  vertebral  column  to  the  correspond- 
ing side.  The  IHocostales  cervicis,  taking  their  fixed  points  from  the  cervical  vertebrae,  elevate 
those  ribs  to  which  they  are  attached;  taking  their  fixed  points  from  the  ribs,  both  muscles  help 
to  extend  the  neck;  while  one  muscle  bends  the  neck  to  its  own  side.  When  both  Longissimi 
cervicis  act  from  below,  they  bend  the  neck  backward.  When  both  Longissimi  capitis  act  from 
below,  they  bend  the  head  backward;  while,  if  only  one  muscle  acts,  the  face  is  turned  to  the 
side  on  which  the  muscle  is  acting,  and  then  the  head  is  bent  to  the  shoulder.  The  two  Recti 
draw  the  head  backward.  The  Rectus  capitis  posterior  major,  owing  to  its  obliquity,  rotates 
the  skull,  with  the  atlas,  around  the  odontoid  process,  turning  the  face  to  the  same  side.  The 
Multifidus  acts  successively  upon  the  different  parts  of  the  column;  thus,  the  sacrum  furnishes 
a  fixed  point  from  which  the  fasciculi  of  this  muscle  acts  upon  the  lumbar  region;  which  in  turn 
becomes  the  fixed  point  for  the  fascicuU  moving  the  thoracic  region,  and  so  on  throughout  the 
entire  length  of  the  column.  The  Multifidus  also  serves  to  rotate  the  column,  so  that  the  front 
of  the  trunk  is  turned  to  the  side  opposite  to  that  from  which  the  muscle  acts,  this  muscle  being 
assisted  in  its  action  by  the  Obliquus  externus  abdominis.  The  Obliquus  capitis  superior  draws 
the  head  backward  and  to  its  own  side.  The  Obliquus  inferior  rotates  the  atlas,  and  with  it  the 
skull,  around  the  odontoid  process,  turning  the  face  to  the  same  side.  When  the  Semispinals  of 
the  two  sides  act  together,  they  help  to  extend  the  vertebral  column;  when  the  muscles  of  only 
one  side  act,  they  rotate  the  thoracic  and  cervical  parts  of  the  column,  turning  the  body  to  the 
opposite  side.  The  Semispinales  capitis  draw  the  head  directly  backward;  if  one  muscle  acts, 
it  draws  the  head  to  one  side,  and  rotates  it  so  that  the  face  is  turned  to  the  opposite  side.  The 
Interspinales  by  approximating  the  spinous  processes  help  to  extend  the  column.  The  Inter- 
transversarii  approximate  the  transverse  processes,  and  help  to  bend  the  column  to  one  side. 
The  Rotatores  assist  the  Multifidus  to  rotate  the  vertebral  column,  so  that  the  front  of  the  trunk 
is  turned  to  the  side  opposite  to  that  from  which  the  muscles  act. 


492  MYOLOGY 

Applied  Anatomy. — In  cases  of  tuberculous  caries  of  the  vertebral  bodies,  and  in  other  diseases 
affecting  the  vertebral  column,  rigidity  of  the  spinal  muscles  is  one  of  the  earliest  and  most  con- ' 
stant  sj^mptoms.  A  child  with  commencing  spinal  disease  always  maintains  the  affected  portion 
of  the  column  in  a  state  of  absolute  rigidity,  to  prevent  the  inflamed  structures  from  being  moved 
against  each  other;  this  is  one  of  the  best  examples  of  nature's  method  of  producing  rest  of  the 
affected  part. 

III.    THE   MUSCLES    OF    THE    THORAX. 

The  muscles  belonging  to  this  group  are  the 

Intereostales  externi.  Levatores  costarum. 

Intercostales  interni.  Serratus  posterior  superior. 

Subcostales.  Serratus  posterior  inferior. 

Transversus  thoracis.  Diaphragma. 

Intercostal  Fascias. — In  each  intercostal  space  thin  but  firm  layers  of  fascia 
cover  the  outer  surface  of  the  Intercostalis  externus  and  the  inner  surface  of  the 
Intercostalis  internus;  and  a  third,  more  delicate  layer,  is  interposed  between  the 
two  planes  of  muscular  fibres.  They  are  best  marked  in  those  situations  where 
the  muscular  fibres  are  deficient,  as  between  the  Intercostales  externi  and  sternum 
in  front,  and  between  the  Intercostales  interni  and  vertebral  column  behind. 

The  Intercostales  (Intercostal  muscles)  (Fig.  520)  are  two  thin  planes  of  muscular 
and  tendinous  fibres  occupying  each  of  the  intercostal  spaces.  They  are  named 
external  and  internal  from  their  surface  relations — the  external  being  superficial 
to  the  internal. 

The  Intercostales  externi  (External  intercostals)  are  eleven  in  number  on  either 
side.  They  extend  from  the  tubercles  of  the  ribs  behind,  to  the  cartilages  of  the 
ribs  in  front,  where  they  end  in  thin  membranes,  the  anterior  intercostal  membranes, 
which  are  continued  forward  to  the  sternum.  Each  arises  from  the  lower  border 
of  a  rib,  and  is  inserted  into  the  upper  border  of  the  rib  below.  In  the  two  lower 
spaces  they  extend  to  the  ends  of  the  cartilages,  and  in  the  upper  two  or  three 
spaces  they  do  not  quite  reach  the  ends  of  the  ribs.  They  are  thicker  than  the 
Intercostales  interni,  and  their  fibres  are  directed  obliquely  downward  and  lateral- 
ward  on  the  back  of  the  thorax,  and  downward,  forward,  and  medialward  on  the 
front. 

The  Intercostales  interni  (Internal  intercostals)  are  also  eleven  in  number  on 
either  side.  They  commence  anteriorly  at  the  sternum,  in  the  interspaces  between 
the  cartilages  of  the  true  ribs,  and  at  the  anterior  extremities  of  the  cartilages  of 
the  false  ribs,  and  extend  backward  as  far  as  the  angles  of  the  ribs,  whence  they 
are  continued  to  the  vertebral  column  by  thin  aponeuroses,  the  posterior  intercostal 
membranes.  Each  arises  from  the  ridge  on  the  inner  surface  of  a  rib,  as  well  as 
from  the  corresponding  costal  cartilage,  and  is  inserted  into  the  upper  border 
of  the  rib  below.  Their  fibres  are  also  directed  obliquely,  but  pass  in  a  direction 
opposite  to  those  of  the  Intercostales  externi. 

The  Subcostales  (Infracostales)  consist  of  muscular  and  aponeurotic  fasciculi, 
which  are  usually  well-developed  only  in  the  lower  part  of  the  thorax;  each  a,rises 
from  the  inner  surface  of  one  rib  near  its  angle,  and  is  inserted  into  the  inner 
surface  of  the  second  or  third  rib  below.  Their  fibres  run  in  the  same  direction 
as  those  of  the  Intercostales  interni. 

The  Transversus  thoracis  (Triangularis  sterni)  is  a  thin  plane  of  muscular  and 
tendinous  fibres,  situated  upon  the  inner  surface  of  the  front  wall  of  the  chest 
(Fig.  496).  It  arises  on  either  side  from  the  lower  third  of  the  posterior  surface 
of  the  body  of  the  sternum,  from  the  posterior  surface  of  the  xiphoid  process, 
and  from  the  sternal  ends  of  the  costal  cartilages  of  the  lower  three  or  four  true 
ribs.    Its  fibres  diverge  upward  and  lateralward,'  to  be  inserted  by  slips  into  the 


THE  MUSCLES  OF  THE  THORAX 


493 


lower  borders  and  inner  surfaces  of  the  costal  cartilages  of  the  second,  third,  fourth, 
fifth,  and  sixth  ribs.  The  lowest  fibres  of  this  muscle  are  horizontal  in  their  direc- 
tion, and  are  continuous  with  those  of  the  Transversus  abdominis;  the  intermediate 
fibres  are  oblique,  while  the  highest  arc  almost  vertical.  This  muscle  varies  in  its 
attachments,  not  only  in  different  sub- 
jects, but  on  opposite  sides  of  the  same 
subject. 

The  Levatores  costarum  (Fig.  495), 
twelve  in  number  on  either  side,  are  small 
tendinous  and  fleshy  bundles,  which 
arise  from  the  ends  of  the  transverse 
processes  of  the  seventh  cervical  and 
upper  eleven  thoracic  vertebrae;  they 
pass  obliquely  downward  and  lateral- 
ward,  like  the  fibres  of  the  Intercostales 
externi,  and  each  is  inserted  into  the 
outer  surface  of  the  rib  immediately 
below  the  vertebra  from  which  it  takes 
origin,  between  the  tubercle  and  the 
angle  (Levatores  costarum  breves) .  Each 
of  the  four  lower  muscles  divides  into 
two  fasciculi,  one  of  which  is  inserted 
as  above  described;  the  other  passes 
down  to  the  second  rib  below  its  origin 
(Levatores  costarum  longi) . 

The  Serratus  posterior  superior  (Ser- 
ratus  ijosticns  suiJerior)  is  a  thin,  quad- 
rilateral muscle,  situated  at  the  upper 
and  back  part  of  the  thorax.  It  arises 
by  a  thin  and  broad  aponeurosis  from 
the  lower  part  of  the  ligamentum  nu- 
ehae,  from  the  spinous  processes  of  the 
seventh  cervical  and  upper  two  or  three 
thoracic  vertebrae  and  from  the  supra- 
spinal ligament.  Inclining  downward  and  lateralward  it  becomes  muscular,  and 
is  inserted,  by  four  fleshy  digitations,  into  the  upper  borders  of  the  second,  third, 
fourth,  and  fifth  ribs,  a  little  beyond  their  angles. 

The  Serratus  posterior  inferior  (Serratus  posticus  inferior)  (Fig.  516)  is  situated 
at  the  junction  of  the  thoracic  and  lumbar  regions:  it  is  of  an  irregularly  quadri- 
lateral form,  broader  than  the  preceding,  and  separated  from  it  by  a  wide  interval. 
It  arises  by  a  thin  aponeurosis  from  the  spinous  processes  of  the  lower  two  thoracic 
and  upper  two  or  three  lumbar  vertebra?,  and  from  the  supraspinal  ligament. 
Passing  obliquely  upward  and  lateralward,  it  becomes  fleshy,  and  divides  into 
four  flat  digitations,  which  are  inserted  into  the  inferior  borders  of  the  lower  four 
ribs,  a  little  beyond  their  angles.  The  thin  aponeurosis  of  origin  is  intimately 
blended  with  the  lumbodorsal  fascia. 

Nerves. — The  muscles  of  this  group  are  supplied  by  the  intercostal  nerves. 

The  Diaphragma  (Diaphragm)  (Figs.  497,  498)  is  a  dome-shaped  musculo- 
fibrous  septum  which  separates  the  thoracic  from  the  abdominal  cavity,  its  convex 
upper  surface  forming  the  floor  of  the  former,  and  its  concave  under  surface  the 
roof  of  the  latter.  Its  peripheral  part  consists  of  muscular  fibres  which  take  origin 
from  the  circumference  of  the  thoracic  outlet  and  converge  to  be  inserted  into  a 
central  tendon. 


Stetnal 
o>  igin  of 
Diaphragma 


Fig.  496. — Posterior  surface  of  sternum  and  costal 
cartilages,  showing  Transversus  thoracis. 


494 


MYOLOGY 


The  muscular  fibres  may  be  grouped  according  to  their  origins  into  three  parts 
-sternal,  costal,  and  lumbar.     The  sternal  part  r/n'.vf.s-  b\-  two  fleshy  slips  from 

Vena  caved  foramen 

(Esophageal 


Aortic  hiatus 
Fig.  497. — Posterior  half  of  Diaphragma.     (Modified  from  model  by  His.) 


Xiphoid  process 


Opening  for  Lesser  Splanchnic  Nerve 


Fig.  498. — The  Diaphragma.     Under  surface 


THE  MUSCLES  OF  THE  THORAX  495 

the  back  of  the  xiphoid  process;  the  costal  part  from  the  inner  surfaces  of  the  car- 
tilages and  adjacent  portions  of  the  lower  six  ribs  on  either  side,  interdigitating 
with  the  Transversus  abdominis;  and  the  lumbar  part  from  aponeurotic  arches, 
named  the  lumbocostal  arches,  and  from  the  lumbar  \'ertebra?  by  two  pillars  or 
crura.    There  are  two  lumbocostal  arches,  a  medial  and  a  lateral,  on  either  side. 

The  Medial  Lumbocostal  Arch  (circus  lumhocostalis  mediaUs  [Ilalleri];  internal 
arcuate  llgiuncitt)  is  a  tendinous  arch  in  the  fascia  covering  the  upper  part  of  the 
Psoas  major;  medially,  it  is  continuous  with  the  lateral  tendinous  margin  of  the 
corresponding  crus,  and  is  attached  to  the  side  of  the  body  of  the  first  or  second 
lumbar  vertebra ;  laterally,  it  is  fixed  to  the  front  of  the  transverse  process  of  the 
first  and,  sometimes  also,  to  that  of  the  second  lumbar  vertebra. 

The  Lateral  Lumbocostal  Arch  (arcus  lumhocostalis  lateralis  [Halleri];  external 
arcuate  ligament)  arches  across  the  upper  part  of  the  Quadratus  lumborum,  and 
is  attached,  medially,  to  the  front  of  the  transverse  process  of  the  first  lumbar 
vertebra,  and,  laterally,  to  the  tip  and  lower  margin  of  the  twelfth  rib. 

The  Crura. — At  their  origins  the  crura  are  tendinous  in  structure,  and  blend 
with  the  anterior  longitudinal  ligament  of  the  vertebral  column.  The  right  crus, 
larger  and  longer  than  the  left,  arises  from  the  anterior  surfaces  of  the  bodies  and 
intervertebral  fibrocartilages  of  the  upper  three  lumbar  vertebrae,  while  the  left 
crus  arises  from  the  corresponding  parts  of  the  upper  two  only.  The  medial  ten- 
dinous margins  of  the  crura  pass  forward  and  medialward,  and  meet  in  the  middle 
line  to  form  an  arch  across  the  front  of  the  aorta;  this  arch  is  often  poorly  defined. 

From  this  series  of  origins  the  fibres  of  the  Diaphragma  converge  to  be  inserted 
into  the  central  tendon.  The  fibres  arising  from  the  xiphoid  process  are  very  short, 
and  occasionally  aponeurotic;  those  from  the  medial  and  lateral  lumbocostal 
arches,  and  more  especially  those  from  the  ribs  and  their  cartilages,  are  longer, 
and  describe  marked  curves  as  they  ascend  and  converge  to  their  insertion.  The 
fibres  of  the  crura  diverge  as  they  ascend,  the  most  lateral  being  directed  upward 
and  lateralward  to  the  central  tendon.  The  medial  fibres  of  the  right  crus  ascend 
on  the  left  side  of  the  oesophageal  hiatus,  and  occasionally  a  fasciculus  of  the  left 
crus  crosses  the  aorta  and  runs  obliquely  through  the  fibres  of  the  right  crus  tow^ard 
the  vena  caval  foramen  (Low^). 

The  Central  Tendon. — The  central  tendon  of  the  Diaphragma  is  a  thin  but  strong 
aponeurosis  situated  near  the  centre  of  the  vault  formed  by  the  muscle,  but  some- 
what closer  to  the  front  than  to  the  back  of  the  thorax,  so  that  the  posterior  muscu- 
lar fibres  are  the  longer.  It  is  situated  immediately  below  the  pericardium,  with 
which  it  is  partially  blended.  It  is  shaped  somewhat  like  a  trefoil  leaf,  consisting 
of  three  divisions  or  leaflets  separated  from  one  another  by  slight  indentations. 
The  right  leaflet  is  the  largest,  the  middle,  directed  toward  the  xiphoid  process, 
the  next  in  size,  and  the  left  the  smallest.  In  structure  the  tendon  is  composed 
of  several  planes  of  fibres,  which  intersect  one  another  at  various  angles  and  unite 
into  straight  or  curved  bundles — an  arrangement  which  gives  it  additional  strength. 

Openings  in  the  Diaphragma. — The  Diaphragma  is  pierced  by  a  series  of  apertures 
to  permit  of  the  passage  of  structures  between  the  thorax  and  abdomen.  Three 
large  openings — the  aortic,  the  oesophageal,  and  the  vena  caval — and  a  series  of 
smaller  ones  are  described. 

The  aortic  hiatus  is  the  lowest  and  most  posterior  of  the  large  apertures;  it  lies 
at  the  level  of  the  twelfth  thoracic  vertebra.  Strictly  speaking,  it  is  not  an  aperture 
in  the  Diaphragma  but  an  osseoaponeurotic  opening  between  it  and  the  vertebral 
column,  and  therefore  behind  the  Diaphragma;  occasionally  some  tendinous  fibres 
prolonged  across  the  bodies  of  the  vertebrae  from  the  medial  parts  of  the  lower  ends 
of  the  crura  pass  behind  the  aorta,  and  thus  convert  the  hiatus  into  a  fibrous  ring. 

1  Journal  of  Anatomj'  and  Physiology,  vol.  xlii. 


496  MYOLOGY 

The  hiatus  is  situated  slightly  to  the  left  of  the  middle  line,  and  is  bounded  in  front 
by  the  crura,  and  behind  by  the  body  of  the  first  lumbar  vertebra.  Through  it 
pass  the  aorta,  the  azygos  vein,  and  the  thoracic  duct;  occasionally  the  azygos 
vein  is  transmitted  through  the  right  crus. 

The  oesophageal  hiatus  is  situated  in  the  muscular  part  of  the  Diaphragma  at 
the  level  of  the  tenth  thoracic  vertebra,  and  is  elliptical  in  shape.  It  is  placed 
above,  in  front,  and  a  little  to  the  left  of  the  aortic  hiatus,  and  transmits  the 
oesophagus,  the  vagus  nerves,  and  some  small  oesophageal  arteries. 

Thr  vena  caval  foramen  is  the  highest  of  the  three,  and  is  situated  about  the  level 
of  the  fibrocartilage  between  the  eighth  and  ninth  thoracic  vertebrae.  It  is  quad- 
rilateral in  form,  and  is  placed  at  the  junction  of  the  right  and  middle  leaflets 
of  the  central  tendon,  so  that  its  margins  are  tendinous.  It  transmits  the  inferior 
vena  cava,  the  wall  of  which  is  adherent  to  the  margins  of  the  opening,  and  some 
branches  of  the  right  phrenic  nerve. 

Of  the  lesser  apertures,  two  in  the  right  crus  transmit  the  greater  and  lesser 
right  splanchnic  nerves ;  three  in  the  left  crus  give  passage  to  the  greater  and  lesser 
left  splanchnic  nerves  and  the  hemiazygos  vein.  The  gangliated  trunks  of  the 
sympathetic  usually  enter  the  abdominal  cavity  behind  the  Diaphragma,  under 
the  medial  lumbocostal  arches.  The  structures  piercing  the  crura  are  sometimes 
utilized  to  divide  each  crus  into  three  parts — medial,  intermediate,  and  lateral. 
Between  the  medial  and  intermediate  crura  pass  the  hemiazygos  vein  and  the 
splanchnic  nerves;  between  the  intermediate  crus  and  the  lateral  crus  (which 
consists  of  the  fibres  rising  from  the  medial  lumbocostal  arch)  the  gangliated  trunks 
pass. 

On  either  side  two  small  intervals  exist  at  which  the  muscular  fibres  of  the 
Diaphragma  are  deficient  and  are  replaced  by  areolar  tissue.  One  between  the 
sternal  and  costal  parts  transmits  the  superior  epigastric  branch  of  the  internal 
mammary  artery  and  some  lymphatics  from  the  abdominal  wall  and  convex 
surface  of  the  liver.  The  other,  between  the  fibres  springing  from  the  medial  and 
lateral  lumbocostal  arches,  is  less  constant;  when  this  interval  exists,  the  upper 
and  back  part  of  the  kidney  is  separated  from  the  pleura  by  areolar  tissue  only. 

Relations. — The  upper  surface  of  the  Diaphragma  is  in  relation  with  three  serous  membranes, 
viz.,  on  either  side  the  pleura,  which  separates  it  from  the  base  of  the  corresponding  lung,  and 
on  the  middle  leaflet  of  the  central  tendon  the  pericardium,  which  intervenes  between  it  and  the 
heart.  The  central  portion  hes  on  a  shghtly  lower  level  than  the  summits  of  the  lateral  portions. 
The  greater  part  of  the  under  sm-face  is  covered  by  the  peritoneum.  The  right  side  is  accurately 
moulded  over  the  convex  surface  of  the  right  lobe  of  the  Uver,  the  right  kidney,  and  right  supra- 
renal gland;  the  left  over  the  left  lobe  of  the  hver,  the  fundus  of  the  stomach,  the  spleen,  the  left 
kidnej^,  and  left  suprarenal  gland. 

Nerves. — The  Diaphragma  is  supphed  by  the  phrenic  and  lower  intercostal  nerves. 

Actions.^The  Diaphragma  is  the  principal  muscle  of  inspiration,  and  presents  the  form  of 
a  dome  concave  toward  the  abdomen.  The  central  part  of  the  dome  is  tendinous,  and  the  peri- 
cardium is  attached  to  its  upper  surface;  the  circumference  is  muscular.  Dm-ing  inspuation  the 
lowest  ribs  are  fixed,  and  from  these  and  the  crura  the  muscular  fibres  contract  and  draw  do^m- 
ward  and  forward  the  central  tendon  with  the  attached  pericardium.  In  this  movement  the 
curvature  of  the  Diaphragma  is  scarcely  altered,  the  dome  moving  downward  nearly  parallel 
to  its  original  position  and  pushing  before  it  the  abdominal  viscera.  The  descent  of  the  abdominal 
viscera  is  permitted  by  the  elasticity  of  the  abdominal  wall,  but  the  Umit  of  this  is  soon  reached. 
The  central  tendon  apphed  to  the  abdominal  viscera  then  becomes  a  fixed  point  for  the  action 
of  the  Diaphragma,  the  effect  of  which  is  to  elevate  the  lower  ribs  and  through  them  to  push 
forward  the  body  of  the  stermun  and  the  upper  ribs.  The  right  cupola  of  the  Diaphragma, 
lying  on  the  hver,  has  a  greater  resistance  to  overcome  than  the  left,  which  lies  over  the  stomach, 
but  to  compensate  for  this  the  right  crus  and  the  fibres  of  the  right  side  generally  are  stronger 
than  those  of  the  left. 

In  all  expulsive  acts  the  Diaphragma  is  called  into  action  to  give  additional  power  to  each 
expulsive  effort.  Thus,  before  sneezing,  coughing,  laughing,  crying,  or  vomitmg,  and  previous 
to  the  expulsion  of  m-ine  or  feces,  or  of  the  fetus  from  the  uterus,  a  deep  inspiration  takes  place. 
The  height  of  the  Diaphragma  is  constantly  varying  dm-ing  respiration;  it  also  varies  with  the 


THE  MUSCLES  OF  THE  THORAX  497 

degree  of  distcMision  of  the  stonuicli  aiul  intoslincs  ;iml  with  the  size  of  the  hver.  After  a  forced 
expu'ation  the  right  cupohi  is  on  a  level  in  front  with  th(>  fourth  costal  cartilage,  at  the  side  with 
the  fifth,  sixth,  and  seventh  ribs,  and  behind  with  the  eighth  rib;  the  left  cupola  is  a  little  lower 
than  the  right.  Halls  Dally'  stat(\s  that  the  absolute  range  of  movement  between  deep  inspira- 
tion and  deep  expiration  averages  in  the  male  and  female  30  mm.  on  the  right  side  and  28  mm. 
on  tlie  left;  in  quiet  respiration  the  average  movement  is  1^.5  mm.  on  the  right  side  and  12  mm. 
on  the  left. 

Skiagraphy  shows  that  the  height  of  the  Diaphragma  in  the  thorax  varies  considerably  with 
the  position  of  the  body.  It  stands  highest  when  the  body  is  horizontal  and  the  patient  on  his 
back,  and  in  this  jiosition  it  performs  the  largest  respiratory  excursions  with  normal  breathing. 
When  the  body  is  erect  the  dome  of  the  Diaphragma  falls,  and  its  respiratory  movements  become 
smaller.  The  dome  falls  still  lower  when  the  sitting  posture  is  assumed,  and  in  this  position  its 
respiratory  excursions  are  sm.allest.  These  facts  may,  perhaps,  explain  why  it  is  that  patients 
suffering  from  severe  dyspncea  are  most  comfortable  and  least  short  of  breath  when  they  sit  up. 
When  the  body  is  horizontal  and  the  patient  on  his  side,  the  two  halves  of  the  Diaphragma  do 
not  behave  alike.  The  uppermost  half  sinks  to  a  level  lower  even  than  when  the  patient  sits, 
and  moves  little  with  respiration;  the  lower  half  rises  higher  in  the  thorax  than  it  does  when  the 
patient  is  supine,  and  its  respiratory  excursions  are  much  increased.  In  vmilateral  disease  of  the 
plem'a  or  lungs  analogous  interference  with  the  position  or  movement  of  the  diaphragma  can 
generally  be  observed  skiagraphically. 

It  appears  that  the  position  of  the  Diaphragma  in  the  thorax  depends  upon  three  main  factors, 
viz.:  (1)  the  elastic  retraction  of  the  lung  tissue,  tending  to  pull  it  upward;  (2)  the  pressure 
exerted  on  its  under  surface  by  the  viscera;  this  naturally  tends  to  be  a  negative  pressure,  or  down- 
ward suction,  when  the  patient  sits  or  stands,  and  positive,  or  an  upward  pressure,  when  he  lies 
(3)  the  intra-abdominal  tension  due  to  the  abdominal  muscles.  These  are  in  a  state  of  contrac- 
tion in  the  standing  position  and  not  in  the  sitting;  hence  the  Diaphragma,  when  the  patient 
stands,  is  pushed  up  higher  than  when  he  sits. 

The  Intercostales  interni  and  externi  have  probably  no  action  in  moving  the  ribs.  They  con- 
tract simultaneously  and  form  strong  elastic  supports  which  prevent  the  intercostal  spaces  being 
pushed  out  or  drawn  in  dming  respiration.  The  anterior  portions  of  the  Intercostales  interni 
probably  have  an  additional  function  in  keeping  the  sternocostal  and  interchondral  joint  sur- 
faces in  apposition,  the  posterior  parts  of  the  Intercostales  externi  performing  a  similar  function 
for  the  costovertebral  articulations.  The  Levatores  costarum  being  inserted  near  the  fulcra  of 
the  ribs  can  have  little  action  on  the  ribs;  they  act  as  rotators  and  lateral  flexors  of  the  vertebral 
column.  The  Transversus  thoracis  draws  down  the  costal  cartilages,  and  is  therefore  a  muscle 
of  expiration. 

The  Serrati  are  respiratory  muscles.  The  Serratus  posterior  superior  elevates  the  ribs  and 
is  therefore  an  inspiratory  muscle.  The  Serratus  posterior  inferior  draws  the  lower  ribs  dowoi- 
ward  and  backward,  and  thus  elongates  the  thorax;  it  also  fixes  the  lower  ribs,  thus  assisting 
the  inspiratory  action  of  the  Diaphragma  and  resisting  the  tendency  it  has  to  draw  the  lower 
ribs  upw^ard  and  forward.    It  must  therefore  be  regarded  as  a  muscle  of  inspiration. 

Mechanism  of  Respiration. — ^The  respiratory  movements  must  be  examined  during  (a)  quiet 
respiration,  and  (5)  deep  respiration. 

Quiet  Respiration. — The  first  and  second  pairs  of  ribs  are  fixed  by  the  resistance  of  the  cervical 
structm-es;  the  last  pair,  and  through  it  the  eleventh,  by  the  Quadratus  lumborum.  The  other 
ribs  are  elevated,  so  that  the  first  two  intercostal  spaces  are  diminished  while  the  others  are 
increased  in  width.  It  has  aheady  been  shown  (p.  401)  that  elevation  of  the  third,  fourth,  fifth, 
and  sixth  ribs  leads  to  an  increase  in  the  antero-posterior  and  transverse  diameters  of  the  thorax; 
the  vertical  diameter  is  increased  by  the  descent  of  the  diaphragmatic  dome  so  that  the  lungs 
are  expanded  in  all  directions  except  backward  and  upward.  Elevation  of  the  eighth,  ninth, 
and  tenth  ribs  is  accompanied  by  a  lateral  and  backward  movement,  leading  to  an  increase  in 
the  transverse  diameter  of  the  upper  part  of  the  abdomen;  the  elasticity  of  the  anterior  abdominal 
wall  allows  a  slight  increase  in  the  antero-posterior  diameter  of  this  part,  and  in  this  way  the 
decrease  in  the  vertical  diameter  of  the  abdomen  is  compensated  and  space  provided  for  its 
displaced  viscera.  Exphation  is  effected  by  the  elastic  recoil  of  its  walls  and  by  the  action  of 
the  abdominal  muscles,  which  push  back  the  viscera  displaced  downward  by  the  Diaphragma. 

Deep  Respiration. — All  the  movements  of  quiet  respiration  are  here  carried  out,  but  to  a 
greater  extent.  In  deep  inspiration  the  shoulders  and  the  vertebral  borders  of  the  scapulae  are 
fixed  and  the  limb  muscles.  Trapezius,  Serratus  anterior,  Pectorales,  and  Latissimus  dorsi,  are 
called  into  play.  The  Scaleni  are  in  strong  action,  and  the  Sternocleidomastoidei  also  assist 
when  the  head  is  fixed  by  drawing  up  the  sternum  and  by  fixing  the  clavicles.  The  first  rib  is 
therefore  no  longer  stationary,  but,  with  the  sternum,  is  raised;  with  it  all  the  other  ribs  except 
the  last  are  raised  to  a  higher  level.  In  conjunction  wdth  the  increased  descent  of  the  Diaphragma 
this  provides  for  a  considerable  augmentation  of  all  the  thoracic  diameters.    The  anterior  abdomi- 

1  Journal  of  Anatomy  and  Physiology,  1908,  vol.  xliii. 

32 


498 


MYOLOGY 


nal  muscles  come  into  action  so  that  the  umbihcus  is  drawn  upward  and  backward,  but  this 
allows  the  Diaphragma  to  exert  a  more  powerful  influence  on  the  lower  ribs;  the  transverse  diam- 
eter of  the  upper  part  of  the  abdomen  is  greatly  increased  and  the  subcostal  angle  opened  out. 
The  deeper  muscles  of  the  back,  e.  g.,  the  Serrati  posteriores  superiores  and  the  Sacrospinales 
and  their  continuations,  are  also  brought  into  action;  the  thoracic  curve  of  the  vertebral  column 
is  partially  straightened,  and  the  whole  column,  above  the  lower  lumbar  vertebrae,  drawn  back- 
ward. This  increases  the  antero-posterior  diameters  of  the  thorax  and  upper  part  of  the  abdomen 
and  ^\adens  the  intercostal  spaces.  Deep  expiration  is  effected  by  the  recoil  of  the  walls  and  by 
the  contraction  of  the  antero-lateral  muscles  of  the  abdominal  wall,  and  the  Serrati  posteriores 
inferiores  and  Transversus  thoracis. 

Halls  Dally  {op.  cit.)  gives  the  following  figures  as  representing  the  average  changes  which 
occur  during  deepest  possible  respiration.  The  manubrium  stemi  moves  30  mm.  in  an  upward 
and  14  mm.  in  a  forward  direction;  the  width  of  the  subcostal  angle,  at  a  level  of  30  mm.  below 
the  articulation  between,  the  body  of  the  sternmn  and  the  xiphoid  process,  is  increased  by  26 
mm.;  the  umbihcus  is  retracted  and  drawn  upward  for  a  distance  of  13  mm. 

IV.    THE   MUSCLES    AND  FASCI.ffi   OF    THE    ABDOMEN. 

The  miisclcs  of  the  abdomen  may  be  divided  into  two  groups:  (1)  the  antero- 
lateral muscles;  (2)  the  posterior  muscles. 


1.  The  Antero-lateral  Muscles  of  the  Abdomen. 


The  muscles  of  this  group  are: 

Obliquus  externus. 
Obliquus  internus. 


Transversus. 
Rectus. 


Pyramidalis. 


Dissection  (Fig.  499). — To  dissect  the  abdominal  muscles,  make  a  vertical  incision  from  the 
ensiform  cartilage  to  the  symphysis  pubis;  a  second  incision  from  the  umbilicus  obliquely  upward 
and  outward  to  the  outer  surface  of  the  thorax,  as  high  as  the  lower  border  of  the  fifth  or  sixth 

rib;  and  a  third,  commencing  midway  between  the  umbihcus 
and  pubes,  transversely  outward  to  the  anterior  superior 
iliac  spine,  and  along  the  crest  of  the  ihxmi  as  far  as  its 
posterior  third.  Then  reflect  the  three  flaps  included  be- 
tween these  incisions  from  within  outward,  in  the  lines  of 
direction  of  the  muscle  fibres.  If  necessary,  the  abdomi- 
nal muscles  may  be  made  tense  by  inflating  the  peritoneal 
cavity  through  the  umbihcus. 

The  Superficial  Fascia. — The  superficial  fascia  of 
the  abdomen  consists,  over  the  greater  part  of  the 
abdominal  wall,  of  a  single  layer  containing  a 
variable  amount  of  fat;  but  near  the  groin  it  is 
easily  divisible  into  two  layers,  between  which  are 
found  the  superficial  vessels  and  nerves  and  the 
superficial  inguinal  lymph  glands. 

The  superficial  layer  (jascia  of  Camjjer)  is  thick, 
areolar  in  texture,  and  contains  in  its  meshes  a 
varying   quantity  of   adipose  tissue.     Below,   it 
passes  over  the  inguinal  ligament,  and  is  continu- 
ous with  the  superficial  fascia  of  the  thigh.    In  the 
male,  Camper's  fascia  is  continued  over  the  penis 
and  outer   surface  of  the   spermatic  cord  to  the 
scrotum,  where  it  helps  to  form  the  dartos.    As  it 
passes  to  the  scrotum  it  changes  its  characteristics, 
becoming  thin,  destitute  of  adipose  tissue,  and  of   a  pale  reddish  color,  and  in 
the  scrotum  it  acquires  some  involuntary  muscular  fibres.     From  the  scrotum 
it  may  be  traced  backward   into  continuity   with   the   superficial   fascia  of  the 


Fig.  499. — Dissection  of  abdomen. 


THE  AXTERO-LATERAL  MUSCLES  OF  THE  ABDOMEX  499 

perineum.     In  the  female,  Camper's  fascia  is  continued  from  the  abdomen  into 
the  hibia  majora. 

The  deep  layer  (fascici  of  Scarpa)  is  tliimier  and  more  memhranous  in  character 
than  tlie  superficial,  and  contains  a  considerable  quantity  of  yellow  elastic  fibres. 
It  is  loosely  connected  by  areolar  tissue  to  the  aponeurosis  of  the  Obliquus  externus 
abdominis,  but  in  the  middle  line  it  is  more  intimately  adherent  to  the  linea  alba 
and  to  the  symphysis  pubis,  and  is  prolonjied  on  to  the  dorsum  of  the  penis,  form- 
ing the  fundiform  lio-ament;  above,  it  is  continuous  with  the  superficial  fascia 
over  the  rest  of  the  trunk;  below  and  laterally,  it  blends  with  the  fascia  lata  of 
the  thigh  a  little  below  the  inguinal  ligament;  medially  and  below,  it  is  continued 
over  the  penis  and  spermatic  cord  to  the  scrotum,  where  it  helps  to  form  the  dartos. 
From  the  scrotum  it  may  be  traced  backward  into  continuity  with  the  deep  layer 
of  the  superficial  fascia  of  the  perineum  (fascia  of  CoUes).  In  the  female,  it  is  con- 
tinued into  the  labia  majora  and  thence  to  the  fascia  of  Colles. 

The  Obliquus  externus  abdominis  {External  or  descending  oblique  muscle)  (Fig. 
500),  situated  on  the  lateral  and  anterior  parts  of  the  abdomen,  is  the  largest  and 
the  most  superficial  of  the  three  flat  muscles  in  this  region.  It  is  broad,  thin,  and 
irregularly  quadrilateral,  its  muscular  portion  occupying  the  side,  its  aponeurosis 
the  anterior  wall  of  the  abdomen.  It  arises,  by  eight  fleshy  digitations,  from  the 
external  surfaces  and  inferior  borders  of  the  lower  eight  ribs;  these  digitations 
are  arranged  in  an  oblique  line  which  runs  downward  and  backward,  the  upper 
ones  being  attaclied  close  to  the  cartilages  of  the  corresponding  ribs,  the  lowest 
to  the  apex  of  the  cartilage  of  the  last  rib,  the  intermediate  ones  to  the  ribs  at 
some  distance  from  their  cartilages.  The  five  superior  serrations  increase  in  size 
from  above  downward,  and  are  received  between  corresponding  processes  of  the 
Serratus  anterior;  the  three  lower  ones  diminish  in  size  from  above  downward 
and  receive  between  them  corresponding  processes  from  the  Latissimus  dorsi. 
From  tliese  attachments  the  fleshy  fibres  proceed  in  various  directions.  Those 
from  the  lowest  ribs  pass  nearly  vertically  downward,  and  are  inserted  into  the 
anterior  half  of  the  outer  lip  of  the  iliac  crest;  the  middle  and  upper  fibres,  directed 
downward  and  forward,  end  in  an  aponeurosis,  opposite  a  line  drawn  from  the 
prominence  of  the  ninth  costal  cartilage  to  the  anterior  superior  iliac  spine. 

The  aponeurosis  of  the  Obliquus  externus  abdominis  is  a  thin  but  strong  mem- 
branous structure,  the  fibres  of  which  are  directed  downward  and  medialward. 
It  is  joined  with  that  of  the  opposite  muscle  along  the  middle  line,  and  covers 
the  whole  of  the  front  of  the  abdomen;  above,  it  is  covered  by  and  gives  origin 
to  the  lower  fibres  of  the  Pectoralis  major;  heloic,  its  fibres  are  closely  aggregated 
together,  and  extend  obliquely  across  from  the  anterior  superior  iliac  spine  to 
the  pubic  tubercle  and  the  pectineal  line.  In  the  middle  line,  it  interlaces  with 
the  aponeurosis  of  the  opposite  muscle,  forming  the  linea  alba,  which  extends  from 
the  xiphoid  process  to  the  symphysis  pubis. 

That  portion  of  the  aponeurosis  which  extends  between  the  anterior  superior 
iliac  spine  and  the  pubic  tubercle  is  a  thick  band,  folded  inward,  and  continuous 
below  witli  the  fascia  lata;  it  is  called  the  inguinal  ligament.  The  portion  which 
is  reflected  from  the  inguinal  ligament  at  the  pubic  tubercle  is  attached  to  the 
pectineal  line  and  is  called  the  lacunar  ligament.  From  the  point  of  attachment 
of  the  latter  to  the  pectineal  line,  a  few  fibres  pass  upward  and  medialward,  behind 
the  medial  crus  of  the  subcutaneous  inguinal  ring,  to  the  linea  alba;  they  diverge 
as  they  ascend,  and  form  a  thin  triangular  fibrous  band  wliicli  is  called  the  reflected 
inguinal  ligament. 

In  the  aponeurosis  of  the  Obliquus  externus,  immediately  above  the  crest  of 
the  pubis,  is  a  triangular  opening,  the  subcutaneous  inguinal  ring,  formed  by  a 
separation  of  the  fibres  of  the  aponeurosis  in  this  situation. 

The  following   structures   require   further   description,   viz.,  the  subcutaneous 


500 


MYOLOGY 


inguinal  ring,  the  intercrural  fibres  and  fascia,  and  the  inguinal,  lacunar,  and  reflected 
inguinal  ligaments. 

The  Subcutaneous  Inguinal  Ring  {annuluii  InguinuiL';  subcutancus;  external 
abdominal  ring)  (Fig.  501). — The  subcutaneous  inguinal  ring  is  an  interval  in  the 
aponeurosis  of  the  Obhquus  externus,  just  above  and  hiteral  to  the  crest  of  the 
pubis.  The  aperture  is  obHque  in  direction,  somewhat  trianguhir  in  form,  and 
corresponds  with  the  course  of  the  fibres  of  the  aponeurosis.    It  usually  measures 


Fig.   500. — The  Obliquus  externus  abdominis. 

from  base  to  apex  about  2.5  cm.,  and  transversely  about  1.25  cm.  It  is  bounded 
helow  by  the  crest  of  the  pubis;  on  either  side  by  the  margins  of  the  opening  in  the 
aponeurosis,  which  are  called  the  crura  of  the  ring;  and  above,  by  a  series  of  curved 
intercrural  fibres.  The  inferior  crus  {external  lyillar)  is  the  stronger  and  is  formed  by 
that  portion  of  the  inguinal  ligament  which  is  inserted  into  the  pubic  tubercle; 
it  is  curved  so  as  to  form  a  kind  of  groove,  upon  which,  in  the  male,  the  spermatic 
cord  rests.  The  superior  crus  {iriternal  pillar)  is  a  broad,  thin,  flat  band,  attached  to 
the  front  of  the  symphysis  pubis  and  interlacing  with  its  fellow  of  the  opposite  side. 


THE  AXTERO-LATERAL  MLSCLES  OF  THE  ABDOMEN 


501 


The  subcutaneous  in«uinal  ring  gives  passage  to  the  spermatic  cord  and  iho- 
inguinal  nerve  in  the  male,  and  to  the  round  Hgament  of  the  uterus  and  the 
ilioinguinal  nerve  in  the  female;  it  is  much  larger  in  men  than  in  women,  on 
account  of  the  large  size  of  the  spermatic  cord. 

The  Intercrural  Fibres  ( fibrae  intercrurales;  intercolunmar  fibres).— The  mtercrural 
fibres  are  a  series  of  curved  tendinous  fibres,  which  arch  across  the  lower  part  of 
the  aponeurosis  of  the  Obliquus  externus,  describing  curves  with  the  convexities 
downward.  The\-  have  received  their  name  from  stretching  across  between  the 
two  crura  of  the  subcutaneous  inguinal  ring,  and  they  are  much  thicker  and  stronger 


Superficial  iliac 
circumflex  vein 


r  11  Subcutaneous  inguinal 
ring 


'  Fig.  -501. — The  subcutaneous  inguinal  ring. 

at  the  inferior  crus,  where  they  are  connected  to  the  inguinal  ligament,  than  supe- 
riorly, where  they  are  inserted  into  the  linea  alba.  The  intercrural  fibres  increase 
the  strength  of  the  lower  part  of  the  aponeurosis,  and  prevent  the  divergence  of 
the  crura  from  one  another;  they  are  more  strongly  developed  in  the  male  than  m 
the  female. 

As  they  pass  across  the  subcutaneous  inguinal  ring,  the\'  are  connected  together 
by  delicate  fibrous  tissue,  forming  a  fascia,  called  the  intercrural  fascia.  This  inter- 
crural fascia  is  continued  down  as  a  tubular  prolongation  around  tke  spermatic 
cord  and  testis,  and  encloses  them  in  a  sheath;  hence  it  is  also  called  the  external 
spermatic  fascia.  The  subcutaneous  inguinal  ring  is  seen  as  a  distinct  aperture 
only  after  the  intercrural  fascia  has  been  removed. 

The  Inguinal  Ligament  (ligamentum  inguinale  [Pouparti]  ;  Pouparfs  ligament) 
(Fig.  502).— The  inguinal  ligament  is  the  lower  border  of  the  aponeurosis  of  the 


502 


MYOLOGY 


Obliquus  externus,  and  extends  from  the  anterior  superior  iliae  spine  to  the  pubic 
tubercle.  From  this  latter  point  it  is  reflected  backward  and  lateralward  to  be 
attached  to  the  pectineal  line  for  about  1.25  cm.,  forming  the  lacunar  ligament. 
Its  general  direction  is  convex  downward  toward  the  thigh,  where  it  is  continuous 
with  the  fascia  lata.  Its  lateral  half  is  rounded,  and  oblique  in  direction;  its 
medial  half  gradually  widens  at  its  attachment  to  the  pubis,  is  more  horizontal 
in  direction,  and  lies  beneath  the  spermatic  cord. 

The  Lacunar  Ligament  (ligamentum  lacunar e  [Gimbernati]  ;  Gimbernat's  ligament) 
(Fig.  502). — The  lacunar  ligament  is  that  part  of  the  aponeurosis  of  the  Obliquus 
externus  w^hich  is  reflected  backward  and  lateralward,  and  is  attached  to  the  pecti- 
neal line.  It  is  about  1.25  cm.  long,  larger  in  the  male  than  in  the  female,  almost 
horizontal  in  direction  in  the  erect  posture,  and  of  a  triangular  form  with  the  base 


Symphysis 
pubis 


TransvPTse  acetabular 
ligament 


Fig.  502. — The  inguinal  and  lacunar  ligaments. 


directed  lateralward.  Its  base  is  concave,  thin,  and  sharp,  and  forms  the  medial 
boundary  of  the  femoral  ring.  Its  apex  corresponds  to  the  pubic  tubercle.  Its 
posterior  margin  is  attached  to  the  pectineal  line,  and  is  continuous  with  the 
pectineal  fascia.  Its  anterior  margin  is  attached  to  the  inguinal  ligament.  Its 
surfaces  are  directed  upward  and  downward. 

The  Reflected  Inguinal  Ligament  {ligamentum  inguinale  refiexum  [Collesi]  ;  trian- 
gular fascia) . — The  reflected  inguinal  ligament  is  a  layer  of  tendinous  fibres  of  a 
triangular  shape,  formed  by  an  expansion  from  the  lacunar  ligament  and  the  inferior 
crus  of  the  subcutaneous  inguinal  ring.  It  passes  medialward  behind  the  spermatic 
cord,  and  expands  into  a  somewhat  fan-shaped  band,  lying  behind  the  superior 
crus  of  the  subcutaneous  inguinal  ring,  and  in  front  of  the  inguinal  aponeurotic 
falx,  and  interlaces  with  the  ligament  of  the  other  side  of  the  linea  alba. 

Ligament  of  Cooper. — ^This  is  a  strong  fibrous  band,  which  was  first  described  by  Sir  Astley 
Cooper.  It  extends  lateralward  from  the  base  of  the  lacunar  ligament  (Fig.  502)  along  the 
pectineal  Une.  to  which  it  is  attached.  It  is  strengthened  by  the  pectineal  fascia,  and  by  a 
lateral  expansion  from  the  lower  attachment  of  the  hnea  alba  {adminiculum  lineae  albae). 


THE  ANTERO-LATKliAL  MUSCLES  OF  THE  ABDOMEN 


503 


Dissection.— Detach  the  Obhquus  cxternus  abdominis  by  dividing  it  across,  just  in  front  of 
its  attachment  to  the  ribs,  as  far  as  its  posterior  border,  and  separate  it  below  from  the  crest 
of  the  ihum  as  far  as  the  anterior  superior  spine;  then  separate  the  muscle  carefully  from  the 
Obhquus  internus  abdominis,  which  lies  beneath,  and  turn  it  toward  the  opposite  side. 

The  Obliquus  internus  abdominis  {Intertial  or  ascending  oblique  muscle)  (Fig. 
503),  thinner  and  smaller  than  the  Obliquus  externus,  beneath  which  it  lies,  is  of 
an  irregularly  quadrilateral  form,  and  situated  at  the  lateral  and  anterior  parts 
of  the  abdomen.  It  arises,  by  fleshy  fibres,  from  the  lateral  half  of  the  grooved 
upper  surface  of  the  inguinal  ligament,  from  the  anterior  two-thirds  of  the  middle 
lip  of  the  iliac  crest,  and  from  the  posterior  lamella  of  the  lumbodorsal  fascia. 
From  this  origin  the  fibres  diverge;  those  from  the  inguinal  ligament,  few  in  number 


Inguinal  apon- 
eurotic falx 

Cremaster 


Fig.  503. — The  Obliquus  internus  abdominis. 

and  paler  in  color  than  the  rest,  arch  downward  and  medialward  across  the  sper- 
matic cord  in  the  male  and  the  round  ligament  of  the  uterus  in  the  female,  and, 
becoming  tendinous,  are  inserted,  conjointly  with  those  of  the  Transversus,  into 
the  crest  of  the  pubis  and  medial  part  of  the  pectineal  line  behind  the  lacunar 
ligament,  forming  what  is  known  as  the  inguinal  aponeurotic  falx.  Those  from  the 
anterior  third  of  the  iliac  origin  are  horizontal  in  their  direction,  and,  becoming 
tendinous  along  the  lower  fourth  of  the  linea  semilunaris,  pass  in  front  of  the  Rectus 
abdominis  to  be  inserted  into  the  linea  alba.  Those  arising  from  the  middle  third 
of  the  iliac  origin  run  obliquely  upward  and  medialward,  and  end  in  an  aponeurosis; 
this  divides  at  the  lateral  border  of  the  Rectus  into  two  lamellae,  which  are  con- 
tinued forward,  one  in  front  of  and  the  other  behind  this  muscle,  to  the  linea  alba: 


504 


MYOLOGY 


the  posterior  lamella  has  an  attachment  to  the  cartilages  of  the  seventh,  eighth, 
and  ninth  ribs.  The  most  posterior  fibres  pass  almost  vertically  upward,  to  be 
inserted  into  the  inferior  borders  of  the  cartilages  of  the  three  lower  ribs,  being 
continuous  with  the  Intercostales  interni. 

The  Cremaster  (Fig.  504)  is  a  thin  muscular  layer,  composed  of  a  number  of 
fasciculi  which  arise  from  the  middle  of  the  inguinal  ligament  where  its  fibres 

are  continuous  with  those  of  the 
Obliquus  internus  and  also  occasion- 
ally with  the  Transversus.  It  passes 
along  the  lateral  side  of  the  spermatic 
cord,  descends  with  it  through  the  sub- 
cutaneous inguinal  ring  upon  the  front 
and  sides  of  the  cord,  and  forms  a  series 
of  loops  which  dift'er  in  thickness  and 
length  in  different  subjects.  x\t  the 
upper  part  of  the  cord  the  loops  are 
short,  but  they  become  in  succession 
longer  and  longer,  the  longest  reaching 
down  as  low  as  the  testis,  where  a  few- 
are  inserted  into  the  tunica  vaginalis. 
These  loops  are  united  together  by 
areolar  tissue,  and  form  a  thin  cover- 
ing over  the  cord  and  testis,  the  cremas- 
teric fascia.  The  fibres  ascend  along 
the  medial  side  of  the  cord,  and  are 
inserted  by  a  small  pointed  tendon 
into  the  tubercle  and  crest  of  the 
pubis  and  into  the  front  of  the  sheath 
of  the  Rectus  abdominis. 


>^^ 


Fig.  504. — The  Cremaster. 


Dissection. — Detach  the  Obhquus  internus 
abdominis  in  order  to  expose  the  Transversus 
abdominis  beneath.  This  may  be  effected  by 
dividing  the  muscle,  above,  at  its  attachment 
to  the  ribs;  below,  at  its  connection  with  the 
inguinal  ligament  and  the  crest  of  the  iUum; 
and  behind,  by  a  vertical  incision  extending  from  the  last  rib  to  the  crest  of  the  ihum.  The 
muscle  should  previously  be  made  tense  by  drawing  upon  it  with  the  fingers  of  the  left  hand, 
and  if  its  division  be  carefully  effected,  the  cellular  interval  between  it  and  the  Transversus 
abdominis,  as  well  as  the  direction  of  the  fibres  of  the  latter  muscle,  will  afford  a  clear  guide 
to  their  separation;  along  the  crest  of  the  ilium  the  circumflex  ihac  vessels  are  interposed  be- 
tween them,  and  form  an  important  guide  in  separating  them.  The  muscle  should  then  be 
thrown  inward  toward  the  hnea  alba. 

The  Transversus  abdominis  {Transversals  muscle)  (Fig.  505),  so  called  from 
the  direction  of  its  fibres,  is  the  most  internal  of  the  flat  muscles  of  the  abdomen, 
being  placed  immediately  beneath  the  Obliquus  internus.  It  arises,  by  fleshy 
fibres,  from  the  lateral  third  of  the  inguinal  ligament,  from  the  anterior  three-fourths 
of  the  inner  lip  of  the  iliac  crest,  from  the  inner  surfaces  of  the  cartilages  of  the 
lower  six  ribs,  interdigitating  with  the  Diaphragma,  and  from  the  lumbodorsal 
fascia.  The  muscle  ends  in  front  in  a  broad  aponeurosis,  the  lower  fibres  of  which 
curve  downward  and  medialward,  and  are  inserted,  together  with  those  of  the 
Obliquus  internus,  into  the  crest  of  the  pubis  and  pectineal  line,  forming  the  ingui- 
nal aponeurotic  falx.  Throughout  the  rest  of  its  extent  the  aponeurosis  passes 
horizontally  to  the  middle  line,  and  is  inserted  into  the  linea  alba;  its  upper  three 
fourths  lie  behind  the  Rectus  and  blend  with  the  posterior  lamella  of  the  aponeur- 
osis of  the  Obliquus  internus;  its  lower  fourth  is  in  front  of  the  Rectus. 


THE  AXTERO-LATERAL  MUSCLES  OF  THE  ABDOMEN 


505 


The  inguinal  aponeurotic  falx  (fair  aponeurotica  mcjuinaUs;  conjoined  tendon  of 
Internal  oblique  a)td  Trausirrscdils  muscle)  of  the  ObHqims  interims  and  Trans- 
versus  is  mainlv  formed  by  the  lower  part  of  the  tendon  of  the  Transversiis  and 
is  inserted  into  the  crest  of  the  pubis  and  pectineal  line  immediately  behind 
the  subcutaneous  inguinal  ring,  serving  to  protect  what  would  otherwise  be  a 
weak  point  in  tlic  abdominal  wall.    Lateral  to  the  falx  is  a  ligamentous  band  con- 


Linea  alba  


PiQ    505.— The  Transversus  abdominis,  Rectus  abdominis,  and  Pyramidalis. 


nected  with  the  lower  margin  of  the  Transversus  and  extending  down  behind  the 
inferior  epigastric  arterv  to  the  superior  ramus  of  the  pubis;  it  is  termed  the  inter- 
foveolar  ligament  of  Hesselbach  (Fig.  506)  and  sometimes  contains  a  few  muscular 
fibres. 

Dissection.— To  expose  the  Rectus  abdominis  muscle,  open  its  sheath  by  a  vertical  incision 
extending  from  the  costal  arch  to  the  pubis,  and  then  reflect  the  two  portions  from  the  sur- 
face of  the  muscle,  which  is  easily  done,  excepting  at  the  lineae  transversae,  where  so  dose  an 
adhesion  exists  that  the  greatest  care  is  requisite  in  separating  them.    Now  raise  the  outer  edge 


506 


MYOLOGY 


of  the  muscle,  in  order  to  examine  the  posterior  layer  of  the  sheath.  By  dividing  the  muscle 
in  the  centre,  and  turning  its  lower  part  downward,  the  point  where  the  posterior  wall  of  the 
sheath  terminates  in  a  thin  curved  margin  will  be  seen. 

The  Rectus  abdominis  (Fig.  505)  is  a  long  flat  muscle,  which  extends  along 
the  whole  length  of  the  front  of  the  abdomen,  and  is  separated  from  its  fellow 
of  the  opposite  side  by  the  linea  alba.  It  is  much  broader,  but  thinner,  above  than 
below,  and  arises  by  two  tendons;  the  lateral  or  larger  is  attached  to  the  crest 
of  the  pubis,  the  medial  interlaces  with  its  fellow  of  the  opposite  side,  and  is  con- 
nected w^ith  the  ligaments  covering  the  front  of  the  symphysis  pubis.  The  muscle 
is  inserted  by  three  portions  of  unequal  size  into  the  cartilages  of  the  fifth,  sixth, 
and  seventh  ribs.  The  upper  portion,  attached  principally  to  the  cartilage  of  the 
fifth  rib,  usually  has  some  fibres  of  insertion  into  the  anterior  extremity  of  the  rib 
itself.  Some  fibres  are  occasionally  connected  with  the  costoxiphoid  ligaments, 
and  the  side  of  the  xiphoid  process. 


Linea 
semicircularis 


Transversus 


Rectus      L 

abdomijiis      \   \    \   \'  \i\ 


Inferior  epigastric 
artery  ami  vein 


Obliquus 
internus 


Inguinal  aponeuiotic  falx        Inieijoveolar  ligament 
Fig.  506. — The  interfoveolar  ligament,  seen  from  in  front.      (Modified  from  Braune. 

The  Rectus  is  crossed  by  .fibrous  bands,  three  in  number,  which  are  named  the 
tendinous  inscriptions;  one  is  usually  situated  opposite  the  umbilicus,  one  at  the 
extremity  of  the  xiphoid  process,  and  the  third  about  midway  between  the  xiphoid 
process  and  the  umbilicus.  These  inscriptions  pass  transversely  or  obliquely 
across  the  muscle  in  a  zigzag  course;  they  rarely  extend  completely  through  its 
substance  and  may  pass  only  halfway  across  it;  they  are  intimately  adherent  in 
front  to  the  sheath  of  the  muscle.  Sometimes  one  or  two  additional  inscriptions, 
generally  incomplete,  are  present  below  the  umbilicus. 

The  Rectus  is  enclosed  in  a  sheath  (Fig.  507)  formed  by  the  aponeuroses  of  the 
Obliqui  and  Transversus,  which  are  arranged  in  the  following  manner.  At  the  lateral 
margin  of  the  Rectus,  the  aponeurosis  of  the  Obliquus  internus  divides  into  two 
lamellae,  one  of  which  passes  in  front  of  the  Rectus,  blending  with  the  aponeurosis 
of  the  Obliquus  externus,  the  other,  behind  it,  blending  with  the  aponeurosis  of 
the  Transversus,  and  these,  joining  again  at  the  medial  border  of  the  Rectus, 
are  inserted  into  the  linea  alba.  This  arrangement  of  the  aponeurosis  exists  from 
the  costal  margin  to  midway  between  the  umbilicus  and  symphysis  pubis,  where 


THE  ANTERO-LATERAL  MUSCLES  OF  THE  ABDOMEN 


507 


the  posterior  wall  of  the  sheath  ends  in  a  thin  curved  margin,  the  linea  semicircu- 
laris,  the  concavity  of  which  is  directed  downward :  below  this  level  the  aponeuroses 
of  all  three  muscles  pass  in  front  of  the  Rectus.  The  Rectus,  in  the  situation  where 
its  sheath  is  deficient  below,  is  separated  from  the  peritoneum  by  the  transversalis 
fascia  (Fig.  508).  Since  the  tendons  of  the  Obliquus  internus  and  Transversus 
only  reach  as  high  as  the  costal  margin,  it  follows  that  above  this  level  the  sheath 
of  the  Rectus  is  deficient  behind,  the  muscle  resting  directly  on  the  cartilages  of 
the  ribs,  and  being  covered  merely  by  the  tendon  of  the  Obliquus  externus. 


Linea  alba 


Obliquus  internus  / 
Transversus 
Fig.  507. — Diagram  of  sheath  of  Rectus. 


The  Pyramidalis  (Fig.  505)  is  a  small  triangular  muscle,  placed  at  the  lower 
part  of  the  abdomen,  in  front  of  the  Rectus,  and  contained  in  the  sheath  of  that 
muscle.  It  arises  by  tendinous  fibres  from  the  front  of  the  pubis  and  the  anterior 
pubic  ligament;  the  fleshy  portion  of  the  muscle  passes  upward,  diminishing 
in  size  as  it  ascends,  and  ends  by  a  pointed  extremity  which  is  inserted  into  the 
linea  alba,  midway  between  the  umbilicus  and  pubis.  This  muscle  may  be  wanting 
on  one  or  both  sides;  the  lower  end  of  the  Rectus  then  becomes  proportionately 
increased  in  size.  Occasionally  it  is  double  on  one  side,  and  the  muscles  of  the  two 
sides  are  sometimes  of  unequal  size.    It  may  extend  higher  than  the  level  stated. 


Obliquus  internus  - 

Transversus^ 
Fig.  508. — Diagram  of  a  transverse  section  through  the  anterior  abdominal  wall,  below  the  linea  semicircularis. 

Besides  the  Rectus  and  Pyramidalis,  the  sheath  of  the  Rectus  contains  the  superior  and  inferior 
epigastric  arteries,  and  the  lower  intercostal  nerves. 

Nerves. — The  abdominal  muscles  are  supphed  by  the  lower  intercostal  nerves.  The  Obhquus 
internus  and  Transversus  also  receive  filaments  from  the  anterior  branch  of  the  iliohypogastric 
and  sometimes  from  the  ilioinguinal.  The  Cremaster  is  supphed  by  the  external  spermatic  branch 
of  the  genitofemoral  and  the  Pyramidahs  usually  by  the  tweKth  thoracic. 

The  Linea  Alba. — ^The  hnea  alba  is  a  tendinous  raphe  in  the  middle  line  of  the  abdomen, 
stretching  between  the  xiphoid  process  and  the  symphysis  pubis.  It  is  placed  between  the  medial 
borders  of  the  Recti,  and  is  formed  by  the  blending  of  the  aponem-oses  of  the  ObUqui  and  Trans- 
versa It  is  narrow  below,  corresponding  to  the  hnear  interval  existing  between  the  Recti;  but 
broader  above,  where  these  muscles  diverge  from  one  another.  At  its  lower  end  the  hnea  alba 
has  a  double  attachment — its  superficial  fibres  passing  in  front  of  the  medial  heads  of  the  Recti 
to  the  symphysis  pubis,  while  its  deeper  fibres  form  a  triangular  lamella,  attached  behind  the 
Recti  to  the  posterior  lip  of  the  crest  of  the  pubis,  and  named  the  adminiculum  Uneae  albae. 
It  presents  apertures  for  the  passage  of  vessels  and  nerves;  the  vunbihcus,  which  in  the  fetus 
exists  as  an  aperture  and  transmits  the  umbihcal  vessels,  is  closed  in  the  adult. 

The  Lineae  Semilunares. — The  lineae  semilunares  are  two  curved  tendinous  hues  placed  one 
on  either  side  of  the  linea  alba.  Each  corresponds  with  the  lateral  border  of  the  Rectus,  extends 
from  the  cartilage  of  the  ninth  rib  to  the  pubic  tubercle,  and  is  formed  by  the  aponeurosis  of  the 
Obhquus  internus  at  its  line  of  division  to  enclose  the  Rectus,  reinforced  in  front  by  that  of  the 
Obliquus  externus,  and  behind  by  that  of  the  Transversus. 


508  MYOLOGY 

Actions. — When  the  pelvis  and  thorax  are  fixed,  the  abdominal  muscles  compress  the  abdominal 
viscera  by  constricting  the  cavity  of  the  abdomen,  in  which  action  they  are  materially  assisted 
by  the  descent  of  the  Diaphragma.  By  these  means  assistance  is  given  in  expelling  the  feces 
from  the  rectum,  the  m-ine  from  the  bladder,  the  fetus  from  the  uterus,  and  the  contents  of  the 
stomach  in  vomiting. 

If  the  pelvis  and  vertebral  column  be  fixed,  these  muscles  compress  the  lower  part  of  the  thorax, 
materially  assisting  expiration.  If  the  pelvis  alone  be  fixed,  the  thorax  is  bent  directly  forward, 
when  the  muscles  of  both  sides  act;  when  the  muscles  of  only  one  side  contract,  the  trunk  is  bent 
toward  that  side  and  rotated  toward  the  opposite  side. 

If  the  thorax  be  fixed,  the  muscles,  acting  together,  draw  the  pelvis  upward,  as  in  climbing; 
or,  acting  singly,  they  draw^  the  pelvis  upward,  and  bend  the  vertebral  column  to  one  side  or  the 
other.  The  Recti,  acting  from  below,  depress  the  thorax,  and  consequently  flex  the  vertebral 
column ;  when  acting  from  above,  they  flex  the  pelvis  upon  the  vertebral  column.  The  PjTamidales 
are  tensors  of  the  linea  alba. 

The  Transversalis  Fascia. — The  transversalis  fascia  is  a  thin  aponeurotic  membrane 
which  Hes  between  the  inner  surface  of  the  Transversus  and  the  extraperitoneal 
fat.  It  forms  part  of  the  general  layer  of  fascia  lining  the  abdominal  parietes,  and 
is  directly  continuous  with  the  iliac  and  pelvic  fasciae.  In  the  inguinal  region, 
the  transversalis  fascia  is  thick  and  dense  in  structure  and  is  joined  by  fibres  from 
the  aponeurosis  of  the  Transversus,  but  it  becomes  thin  as  it  ascends  to  the  Dia- 
phragma, and  blends  with  the  fascia  covering  the  under  surface  of  this  muscle. 
Behind,  it  is  lost  in  the  fat  which  covers  the  posterior  surfaces  of  the  kidneys. 
Below,  it  has  the  following  attachments :  posteriorly,  to  the  whole  length  of  the  iliac 
crest,  between  the  attachments  of  the  Transversus  and  Iliacus;  between  the  ante- 
rior superior  iliac  spine  and  the  femoral  vessels  it  is  connected  to  the  posterior 
margin  of  the  inguinal  ligament,  and  is  there  continuous  with  the  iliac  fascia. 
Medial  to  the  femoral  vessels  it  is  thin  and  attached  to  the  pubis  and  pectineal 
line,  behind  the  inguinal  aponeurotic  falx,  with  which  it  is  united;  it  descends  in 
front  of  the  femoral  vessels  to  form  the  anterior  wall  of  the  femoral  sheath.  Beneath 
the  inguinal  ligament  it  is  strengthened  by  a  band  of  fibrous  tissue,  which  is  only 
loosely  connected  to  the  ligament,  and  is  specialized  as  the  deep  crural  arch.  The 
spermatic  cord  in  the  male  and  the  round  ligament  of  the  uterus  in  the  female 
pass  through  the  transversalis  fascia  at  a  spot  called  the  abdominal  inguinal  ring. 
This  opening  is  not  visible  externally,  since  the  transversalis  fascia  is  prolonged  on 
these  structures  as  the  infundibuliform  fascia. 

The  Abdominal  Inguinal  Ring  {annulus  inguinalis  abdominis;  internal  or  deep 
abdominal  ring).— The  abdominal  inguinal  ring  is  situated  in  the  transversalis 
fascia,  midway  between  the  anterior  superior  iliac  spine  and  the  symphysis  pubis, 
and  about  1.25  cm.  above  the  inguinal  ligament  (Fig.  509).  It  is  of  an  oval  form, 
the  long  axis  of  the  oval  being  vertical;  it  varies  in  size  in  different  subjects,  and 
is  much  larger  in  the  male  than  in  the  female.  It  is  bounded,  above  and  laterally, 
by  the  arched  lower  margin  of  the  Transversus;  below  and  medially,  by  the  inferior 
epigastric  vessels.  It  transmits  the  spermatic  cord  in  the  male  and  the  round 
ligament  of  the  uterus  in  the  female.  From  its  circumference  a  thin  funnel-shaped 
membrane,  the  infundibuliform  fascia,  is  continued  around  the  cord  and  testis, 
enclosing  them  in  a  distinct  covering. 

The  Inguinal  Canal  {canalis  inguinalis;  spermatic  canal). — The  inguinal  canal 
contains  the  spermatic  cord  and  the  ilioinguinal  nerve  in  the  male,  and  the  round 
ligament  of  the  uterus  and  the  ilioinguinal  nerve  in  the  female.  It  is  an  oblique 
canal  about  4  cm.  long,  slanting  downward  and  medialward,  and  placed  parallel 
with  and  a  little  above  the  inguinal  ligament;  it  extends  from  the  abdominal 
inguinal  ring  to  the  subcutaneous  inguinal  ring.  It  is  bounded,  in  front,  by  the 
integument  and  superficial  fascia,  by  the  aponeurosis  of  the  Obliquus  externus 
throughout  its  whole  length,  and  by  the  Obliquus  internus  in  its  lateral  third; 
behind,  by  the  reflected  inguinal  ligament,  the  inguinal  aponeurotic  falx,  the  trans- 
versalis fascia,  the  extraperitoneal  connective  tissue  and  the  peritoneum;  above, 


THE  ANTERO-LATERAL  MUSCLES  OF  THE  ABDOMEN 


509 


by  the  arched  fibres  of  Oblic^uus  interims  and  Transversus  abdominis;  beloiv,  by 
the  union  of  the  transversalis  fascia  witii  the  ini^ninal  Hgament,  and  at  its  medial 
end  by  the  Lacunar  ligament. 

Extraperitoneal  Connective  Tissue. — Between  the  inner  surface  of  the  general 
layer  of  the  fascia  which  lines  the  interior  of  the  abdominal  and  pelvic  cavities, 
and  the  peritoneum,  there  is  a  considerable  amount  of  connective  tissue,  termed 
the  extraperitoneal  or  subperitoneal  connective  tissue. 

The  parietal  portion  lines  the  cavity  in  varying  quantities  in  difl'erent  situations. 
It  is  especially  abundant  on  the  posterior  wall  of  the  abdomen,  and,  particularly 
around  the  kidneys,  where  it  contains  much  fat.  On  the  anterior  wall  of  the  abdo- 
men, except  in  the  pubic  region,  and  on  the  lateral  wall  above  the  iliac  crest, 
it  is  scanty,  and  here  the  transversalis  fascia  is  more  closely  connected  with  the 
peritoneum.  There  is  a  considerable  amount  of  extraperitoneal  connective  tissue 
in  the  pelvis. 


Abdominal  inguinal 
ring 

Inf.  epigastric  arter 


Fig.  509. — The  abdominal  inguinal  ring. 


The  visceral  portion  follows  the  course  of  the  branches  of  the  abdominal  aorta 
between  the  layers  of  the  mesenteries  and  other  folds  of  peritoneum  which  connect 
the  various  viscera  to  the  abdominal  wall.  The  two  portions  are  directly  con- 
tinuous with  each  other. 

The  Deep  Crural  Arch. — Curving  over  the  external  iliac  vessels,  at  the  spot  where 
they  become  femoral,  on  the  abdominal  side  of  the  inguinal  ligaments  and  loosely 
connected  with  it,  is  a  thickened  band  of  fibres  called  the  deep  crural  arch.  It 
is  apparently  a  thickening  of  the  transversalis  fascia  joined  laterally  to  the  centre 
of  the  lower  margin  of  the  inguinal  ligament,  and  arching  across  the  front  of 
the  femoral  sheath  to  be  inserted  by  a  broad  attachment  into  the  pubic  tubercle 
and  pectineal  line,  behind  the  inguinal  aponeurotic  falx.  In  some  subjects  this 
structure  is  not  very  prominently  marked,  and  not  infrequently  it  is  altogether 
wanting. 


510  MYOLOGY 

2.  The  Posterior  Muscles  of  the  Abdomen. 

Psoas  major.  Iliacus. 

Psoas  minor.  Quadratus  lumborum. 

The  Psoas  major,  the  Psoas  minor,  and  the  Iliacus,  with  the  fascite  covering 
them,  will  be  described  with  the  muscles  of  the  lower  extremity  (see  page  559). 

The  Fascia  Covering  the  Quadratus  Lumborum. — This  is  a  thin  layer  attached, 
medially,  to  the  bases  of  the  transverse  processes  of  the  lumbar  vertebra;  beloiv, 
to  the  iliolumbar  ligament;  above,  to  the  apex  and  lower  border  of  the  last  rib. 
The  upper  margin  of  this  fascia,  which  extends  from  the  transverse  process  of  the 
first  lumbar  vertebra  to  the  apex  and  lower  border  of  the  last  rib,  constitutes  the 
lateral  lumbocostal  arch  (page  495).  Laterally,  it  blends  with  the  lumbodorsal 
fascia,  the  anterior  layer  of  which  intervenes  between  the  Quadratus  lumborum 
and  the  Sacrospinalis. 

The  Quadratus  lumborum  (Fig.  495,  page  487)  is  irregularly  quadrilateral  in 
shape,  and  broader  below  than  above.  It  arises  by  aponeurotic  fibres  from  the 
iliolumbar  ligament  and  the  adjacent  portion  of  the  iliac  crest  for  about  5  cm., 
and  is  inserted  into  the  lower  border  of  the  last  rib  for  about  half  its  length,  and 
by  four  small  tendons  into  the  apices  of  the  transverse  processes  of  the  upper  four 
lumbar  vertebrae.  Occasionally  a  second  portion  of  this  muscle  is  found  in  front 
of  the  preceding.  It  arises  from  the  upper  borders  of  the  transverse  processes  of 
the  lower  three  or  four  lumbar  vertebrae,  and  is  inserted  into  the  lower  margin  of 
the  last  rib.  In  front  of  the  Qaudratus  lumborum  are  the  colon,  the  kidney,  the 
Psoas  major  and  minor,  and  the  Diaphragma;  between  the  fascia  and  the  muscle 
are  the  twelfth  thoracic,  ilioinguinal,  and  iliohypogastric  nerves. 

Nerve  Supply. — The  tweKth  thoracic  and  first  and  second  lumbar  nerves  supplj^  this  muscle. 

Actions. — The  Quadratus  lumborum  draws  down  the  last  rib,  and  acts  as  a  muscle  of  inspira- 
tion by  helping  to  fix  the  origin  of  the  Diaphragma.  If  the  thorax  and  vertebral  column  are 
fixed,  it  may  act  upon  the  pelvis,  raising  it  toward  its  own  side  when  only  one  muscle  is  put  in 
action;  and  when  both  muscles  act  together,  either  from  below  or  above,  they  flex  the  trunk. 

V.     THE  MUSCLES  AND  FASCLffi  OF  THE  PELVIS. 

Obturator  internus.  Levator  ani. 

Piriformis.  Coccygeus. 

The  muscles  within  the  pelvis  may  be  divided  into  two  groups :  (1)  the  Obturator 
internus  and  the  Piriformis,  which  are  muscles  of  the  lower  extremity,  and  will  be 
described  with  these  (pages  571  and  572) ;  (2)  the  Levator  ani  and  the  Coccygeus, 
which  together  form  the  pelvic  diaphragm  and  are  associated  with  the  pelvic  viscera. 
The  classification  of  the  two  groups  under  a  common  heading  is  convenient  in 
connection  with  the  fasciae  investing  the  muscles.  These  fasciae  are  closely  related 
to  one  another  and  to  the  deep  fascia  of  the  perineum,  and  in  addition  have  special 
connections  with  the  fibrous  coverings  of  the  pelvic  viscera ;  it  is  customary  there- 
fore to  describe  them  together  under  the  term  pelvic  fascia. 

Pelvic  Fascia. — ^The  fascia  of  the  pelvis  may  be  resolved  into:  (a)  the  facial 
sheaths  of  the  Obturator  internus.  Piriformis,  and  pelvic  diaphragm;  (6)  the 
fascia  associated  with  the  pelvic  viscera. 

The  fascia  of  the  Obturator  internus  covers  the  pelvic  surface  of,  and  is  attached 
around  the  margin  of  the  origin  of,  the  muscle.  Above,  it  is  loosely  connected  to 
the  back  part  of  the  arcuate  line,  and  here  it  is  continuous  with  the  iliac  fascia. 
In  front  of  this,  as  it  follows  the  line  of  origin  of  the  Obturator  internus,  it  gradually 
separates  from  the  iliac  fascia  and  the  continuity  between  the  two  is  retained  only 
through  the  periosteum.  It  arches  beneath  the  obturator  vessels  and  nerve,  com- 
pleting the  obturator  canal,  and  at  the  front  of  the  pelvis  is  attached  to  the  back 


THE  }fUSCLES  AXD  FASCLE  OF  THE  PELVIS 


511 


of  the  superior  ramus  of  the  pubis.  Below,  the  obturator  fascia  is  attached  to  the 
falciform  process  of  the  sacrotuberous  ligament  and  to  the  pubic  arch,  where  it 
becomes  continuous  with  the  superior  fascia  of  the  urogenital  diaphragm.  Behind, 
it  is  prolonged  into  the  gluteal  region. 

The  internal  pudendal  vessels  and  pudendal  nerve  cross  the  pelvic  surface  of 
the  Obturator  internus  and  are  enclosed  in  a  special  canal — Alcock's  canal — 
formed  by  the  obturator  fascia. 

The  fascia  of  the  Piriformis  is  very  thin  and  is  attached  to  the  front  of  the  sacrum 
and  the  sides  of  the  greater  sciatic  foramen;  it  is  prolonged  on  the  muscle  into 
the  gluteal  region.  At  its  sacral  attachment  around  the  margins  of  the  anterior 
sacral  foramina  it  comes  into  intimate  association  with  and  ensheathes  the 
nerves  emerging  from  these  foramina.  Hence  the  sacral  nerves  are  frequently 
described  as  lying  behind  the  fascia.  The  internal  iliac  vessels  and  their  branches, 
on  the  other  hand,  lie  in  the  subperitoneal  tissue  in  front  of  the  fascia,  and  the 
branches  to  the  gluteal  region  emerge  in  special  sheaths  of  this  tissue,  above  and 
below  the  Piriformis  muscle. 


[  Svperior 
Diaphragmatw       layer 
part  of  pelvic  J 

fascia  Inferior 

\    layer 

Tendinous  arch 


Fascia  endopelvina 
Vesicula  seminalis 

Dtictus  deferens 
Rectovesical  layer 

Fig.  510. — Coronal  section  of  pelvis,  showing  arrangement  of  fasciae.     Viewed  from  behind.     (Diagrrfinmatic.) 

The  diaphragmatic  part  of  the  pelvic  fascia  (Fig.  510)  covers  both  surfaces  of  the 
Levatores  ani.  The  inferior  layer  is  known  as  the  anal  fascia;  it  is  attached  above 
to  the  obturator  fascia  along  the  line  of  origin  of  the  Levator  ani,  while  below  it 
is  continuous  with  the  superior  fascia  of  the  urogenital  diaphragm,  and  with  the 
fascia  on  the  Sphincter  ani  internus.  The  layer  covering  the  upper  surface  of  the 
pelvic  diaphragm  follows,  above,  the  line  of  origin  of  the  Levator  ani  and  is  there- 
fore somewhat  variable.  In  front  it  is  attached  to  the  back  of  the  symphysis 
pubis  about  2  cm.  above  its  lower  border.  It  can  then  be  traced  laterally  across 
the  back  of  the  superior  ramus  of  the  pubis  for  a  distance  of  about  1.25  cm.,  when 
it  reaches  the  obturator  fascia.  It  is  attached  to  this  fascia  along  a  line  which 
pursues  a  somewhat  irregular  course  to  the  spine  of  the  ischium.  The  irregularity 
of  this  line  is  due  to  the  fact  that  the  origin  of  the  Levator  ani,  which  in  lower 
forms  is  from  the  pelvic  brim,  is  in  man  lower  down,  on  the  obturator  fascia. 
Tendinous  fibres  of  origin  of  the  muscle  are  therefore  often  found  extending  up 
toward,  and  in  some  cases  reaching,  the  pelvic  brim,  and  on  these  the  fascia  is 
carried. 


512 


MYOLOGY 


It  will  be  evident  that  the  fascia  covering  that  part  of  the  Obturator  internus 
which  Hes  above  the  origin  of  the  Levator  ani  is  a  composite  fascia  and  includes 
the  following:  (a)  the  obturator  fascia;  (6)  the  fascia  of  the  Levator  ani;  (c) 
degenerated  fibres  of  origin  of  the  Levator  ani. 

The  lower  margin  of  the  fascia  covering  the  upper  surface  of  the  pelvic  diaphragm 
is  attached  along  the  line  of  insertion  of  the  Levator  ani. 

At  the  level  of  a  line  extending  from  the  lower  part  of  the  symphysis  pubis 
to  the  spine  of  the  ischium  is  a  thickened  whitish  band  in  this  upper  la>er  of  the 
diaphragmatic  part  of  the  pelvic  fascia.  It  is  termed  the  tendinous  arch  or  white 
line  of  the  pelvic  fascia,  and  marks  the  line  of  attachment  of  the  special  fascia 
(^pars  endopch'ina  fasciae  pelvis)  which  is  associated  with  the  pelvic  viscera. 


Peritoncuin 

Veaical  laye 

urogemtal-   jj^^..^^ 
diaphragm  y    ^^^^^ 


Rectovesical  layer 
CajJsnle  of 
prostate 


Rectal  layer 

Transversus  perinoei  sujierfieialis 
Colles'  fascia 
Urogenital  diaphragm 
Fig.  5H. — Median  sagittal  section  of  pelvis,  showing  arrangement  of  fasciae. 

The  endopelvic  part  of  the  pelvic  fascia  is  continued  over  the  various  pelvic 
viscera  (Fig.  511)  to  form  for  them  fibrous  coverings  which  will  be  described  later 
(see  section  on  Splanchnology).  It  is  attached  to  the  diaphragmatic  part  of  the 
pelvic  fascia  along  the  tendinous  arch,  and  has  been  subdivided  in  accordance 
with  the  viscera  to  which  it  is  related.  Thus  its  anterior  part,  known  as  the  vesical 
layer,  forms  the  anterior  and  lateral  ligaments  of  the  bladder.  Its  middle  part 
crosses  the  floor  of  the  pelvis  between  the  rectum  and  vesiculae  seminales  as  the 
rectovesical  layer;   in  the  female  this  is  perforated  by  the  vagina.     Its  posterior 


THE  MUSCLES  AXD  FASCLE  OF  THE  PELVIS 


513 


portion  passes  to  the  side  of  the  rectum;  it  forms  a  loose  sheath  for  the  rectum, 
but  is  firmly  attached  around  the  anal  canal;  this  i)ortion  is  known  as  the  rectal 
layer. 

The  Levator  ani  i^Fig.  512)  is  a  broad,  thin  muscle,  situated  on  the  side  of  the 
pelvis.  It  is  attached  to  the  inner  surface  of  the  side  of  the  lesser  pelvis,  and  unites 
with  its  fellow  of  the  opposite  side  to  form  the  greater  part  of  the  floor  of  the  pelvic 
cavity.  It  supports  the  viscera  in  this  cavity,  and  surrounds  the  various  structures 
which  pass  through  it.  It  arises,  in  front,  from  the  posterior  surface  of  the  superior 
ramus  of  the  pubis  lateral  to  the  symphysis;  behind,  from  the  inner  surface  of  the 
spine  of  the  ischium;  and  between  these  two  points,  from  the  obturator  fascia. 


/A-vV'. 


Superior  glutoeal  vessels 


Obturator  nerve 

and  vessels 


Left  lobe  of  prostate  (cut) 


Anococcygeal  raphe 


Fig.  512. — Left  Levator  ani  from  -witliin. 


Posteriorly,  this  fascial  origin  corresponds,  more  or  less  closely,  with  the  tendinous 
arch  of  the  pelvic  fascia,  but  in  front,  the  muscle  arises  from  the  fascia  at  a  vary- 
ing distance  above  the  arch,  in  some  cases  reaching  nearly  as  high  as  the  canal 
for  the  obturator  vessels  and  nerve.  The  fibres  pass  downward  and  backw^ard 
to  the  middle  line  of  the  floor  of  the  pelvis;  the  most  posterior  are  inserted  into  the 
side  of  the  last  two  segments  of  the  cocc^'x;  those  placed  more  anteriorly  unite 
with  the  muscle  of  the  opposite  side,  in  a  median  fibrous  raphe  (anococcygeal 
33 


514  MYOLOGY 

raphe),  which  extends  between  the  coccyx  and  the  margin  of  the  anus.  The  middle 
fibres  are  inserted  into  the  side  of  the  rectum,  blciuUng  with  the  fibres  of  the 
Sphincter  muscles;  lastly,  the  anterior  fibres  descend  upon  the  side  of  the  prostate 
to  unite  beneath  it  with  the  muscle  of  the  opposite  side,  joining  with  the  fibres  of 
the  Spliincter  ani  externus  and  Transversus  perinaei,  at  the  central  tendinous  point 
of  the  perineum. 

The  anterior  portion  is  occasionally  separated  from  the  rest  of  the  muscle  by 
connective  tissue.  From  this  circumstance,  as  well  as  from  its  peculiar  relation 
with  the  prostate,  which  it  supports  as  in  a  sling,  it  has  been  described  as  a  distinct 
muscle,  under  the  name  of  Levator  prostatas.  In  the  female  the  anterior  fibres  of 
the  Levator  ani  descend  upon  the  side  of  the  vagina. 

Relations. — By  its  upper  or  pelvic  surface,  with  the  diaphragmatic  part  of  the  pelvic  fascia 
which  separates  it  from  tfie  bladder,  prostate,  rectum,  and  peritoneum.  By  its  lower  or  perineal 
surface,  it  forms  the  medial  boundary  of  the  ischiorectal  fossa,  and  is  covered  by  the  inferior  layer 
of  the  diaphi'agmatic  part  of  the  pelvic  fascia  (anal  fascia) .  Its  posterior  border  is  free  and  sepa- 
rated from  the  Coccygeus  by  areolar  tissue.  Its  anterior  border  is  separated  from  the  muscle  of 
the  opposite  side  by  a  triangular  space,  through  which  the  urethra,  and  in  the  female  the  vagina, 
pass  from  the  pelvis. 

The  Levator  ani  may  be  divided  into  ihococcygeal  and  pubococcygeal  parts. 

The  Iliococcygeus  arises  from  the  ischial  spine  and  from  the  posterior  part  of  the  tendinous 
arch  of  the  pelvic  fascia,  and  is  attached  to  the  coccyx  and  anococcygeal  raph^;  it  is  usually  thin, 
and  may  fail  entirely,  or  be  largely  replaced  by  fibrous  tissue.  An  accessory  slip  at  its  posterior 
part  is  sometimes  named  the  Iliosacralis.  The  Pubococcygeus  arises  from  the  back  of  the  pubis 
and  from  the  anterior  part  of  the  obturator  fascia,  and  "is  directed  backward  almost  horizontally 
along  the  side  of  the  anal  canal  toward  the  coccyx  and  sacrum,  to  which  it  finds  attachment. 
Between  the  termination  of  the  vertebral  column  and  the  anus,  the  two  Pubococcygei  muscles 
come  together  and  form  a  thick,  fibromuscular  layer  lying  on  the  raphe  formed  by  the  lUococcygei" 
(Peter  Thompson).  The  greater  part  of  this  muscle  is  inserted  into  the  coccyx  and  into  the  last 
one  or  two  pieces  of  the  sacrum.  This  insertion  into  the  vertebral  column  is,  however,  not- 
admitted  by  all  observers.  The  fibres  which  form  a  sling  for  the  rectum  are  named  the  Pubo- 
rectalis  or  Sphincter  recti.  They  arise  from  the  lower  part  of  the  symphysis  pubis,  and  from  the 
superior  fascia  of  the  urogenital  diaphragm.  They  meet  with  the  corresponding  fibres  of  the 
opposite  side  around  the  lower  part  of  the  rectum,  and  form  for  it  a  strong  sHng. 

Nerve  Supply. — The  Levator  ani  is  suppUed  by  a  branch  from  the  fourth  sacral  nerve  and 
by  a  branch  which  is  sometimes  derived  from  the  perineal,  sometimes  from  the  inferior  hemor- 
rhoidal division  of  the  pudendal  nerve. 

The  Coccygeus  (Fig.  512)  is  situated  behind  the  preceding.  It  is  a  triangular 
plane  of  muscular  and  tendinous  fibres,  arising  by  its  apex  from  the  spine  of  the 
ischium  and  sacrospinous  ligament,  and  inserted  by  its  base  into  the  margin  of  the 
coccyx  and  into  the  side  of  the  lowest  piece  of  the  sacrum.  It  assists  the  Levator 
ani  and  Piriformis  in  closing  in  the  back  part  of  the  outlet  of  the  pelvis. 

Nerve  Supply. — The  Coccygeus  is  supphed  by  a  branch  from  the  fourth  and  fifth  sacral  nerves. 

Actions. — The  Levatores  ani  constrict  the  lower  end  of  the  rectum  and  vagina.  They  elevate 
and  invert  the  lower  end  of  the  rectum  after  it  has  been  protruded  and  everted  during  the  expul- 
sion of  the  feces.  They  are  also  muscles  of  forced  expiration.  The  Coccygei  puU  forward  and 
support  the  coccyx,  after  it  has  been  pressed  backward  during  defecation  or  parturition.  The 
Levatores  ani  and  Coccygei  together  form  a  muscular  diaphragm  which  supports  the  pelvic 
viscera. 

VI.    THE   MUSCLES    AND    FASCIA    OF    THE    PERINEUM. 

The  perineum  corresponds  to  the  outlet  of  the  pelvis.  Its  deep  boundaries 
are — in  front,  the  pubic  arch  and  the  arcuate  ligament  of  the  pubis ;  behind,  the  tip 
of  the  coccyx;  and  on  either  side  the  inferior  rami  of  the  pubis  and  ischium,  and  the 
sacrotuberous  ligament.  The  space  is  somewhat  lozenge-shaped  and  is  limited 
on  the  surface  of  the  body  by  the  scrotum  in  front,  by  the  buttocks  behind,  and 
laterally  by  the  medial  side  of  the  thigh.  A  line  drawn  transversely  across  in 
front  of  the  ischial  tuberosities  divides  the  space  into  two  portions.  The  pos- 
terior contains  the  termination  of  the  anal  canal  and  is  known  as  the  anal  region; 


THE  MUSCLES  OF  THE  AXAL  REGION 


515 


the  anterior,  which  contjiins  the  external  urogenital  organs,  is  termed  the  urogenital 

region. 

The  muscles  of  the  perineum  may  therefore  be  divided  into  two  groups: 

1.  Those  of  the  anal  region. 

2.  Those  of  the  urogenital  region:  a,  In  the  male;  b,  In  the  female. 

1.  The  Muscles  of  the  Anal  Region. 

Corrugator  cutis  ani.  Sphincter  ani  externus.         Sphincter  ani  internus. 

The  Superficial  Fascia.— The  superficial  fascia  is  very  thick,  areolar  in  texture, 
and  contains  much  fat  in  its  meshes.  On  either  side  a  pad  of  fatty  tissue  extends 
deeply  between  the  Levator  ani  and  Obturator  internus  into  a  space  known  as  the 

iscluorectal  fossa.  .  „ 

The  Deep  Fascia.— The  deep  fascia  forms  the  limng  of  the  ischiorectal  fossa; 
it  comprises  the  anal  fascia,  and  the  portion  of  obturator  fascia  below  the  origin 
of]Levator  ani. 


Fig.  513. — The  perineum. 


The  integument  and  superficial  layer  of  superficial  fascia  reflected. 


Ischiorectal  Fossa  (fossa  isckioredalis)  (Fig.  513).— The  fossa  is  somew'hat  pris- 
matic in  shape,  with  its  base  directed  to  the  surface  of  the  perineum,  and  its  apex 
at  the  line  of  meeting  of  the  obturator  and  anal  fascife.  It  is  bounded  medially 
by  the  Sphincter  ani  externus  and  the  anal  fascia;  lateraUij,  by  the  tuberosity_  of 
the  ischium  and  the  obturator  fascia;  anteriorly,  by  the  fascia  of  Colles  covering 
the  Transversus  perinaei  superficialis,  and  by  the  inferior  fascia  of  the  urogenital 
diaphragm;  posteriorly,  bv  the  Glutaeus  maximus  and  the  sacrotuberous  ligament. 
Crossing  the  space  transversely  are  the  inferior  hemorrhoidal  vessels  and  nerves; 
at  the  back  part  are  the  perineal  and  perforating  cutaneous  branches  of  the 
pudendal  plexus;  while  from  the  forepart  the  posterior  scrotal  (or  labial)  vessels 
and   nerves   emerge.     The  internal  pudendal  vessels  and  pudendal  nerve  lie  m 


516  MYOLOGY 

Alcock's  canal  on  the  lateral  wall.     The  fossa  is  filled  with  fatty  tissue  across 
which  numerous  fibrous  bands  extend  from  side  to  side. 

Applied  Anatomy. — Abscess  in  the  ischiorectal  fossa  commonly  occurs;  it  is  most  often  the 
result  of  infection  from  the  bowel,  and  is  especially  prone  to  occur  in  tuberculous  subjects;  occa- 
sionally it  follows  perforation  by  a  foreign  body  which  has  been  swallowed,  such  as  a  fish  bone. 
The  abscess  may  bulge  at  the  side  of  the  anus,  at  the  border  of  Glutaeus  maximus,  or  against 
the  rectal  wall.  There  is  great  pain  on  defecation.  On  examining  the  bowel,  fulness  on  the  side 
of  the  abscess  may  be  detected.  If  left  to  itself  the  pus  will  find  exit  through  the  skin,  or  into 
the  rectum  between  the  two  Sphincters;  and  the  condition  will  degenerate  into  one  of  the  varieties 
of  fistula,  owing  to  the  constant  pull  of  the  Sphincter  ani  externus  preventing  closure  of  the 
walls  of  the  cavity.  These  abscesses  should  be  opened  at  the  earliest  possible  moment,  as  they 
tend  to  track  and  burrow  widely  into  the  soft  fat  in  the  fossa,  and  also  in  the  subcutaneous  tissues. 
An  incision  should  be  made  tangential  to  the  anus  over  the  region  of  the  ischiorectal  fossa,  and 
should  then  be  converted  into  a  T,  by  making  a  second  incision  laterally  at  right  angles  to  it, 
so  that  the  wound  may  be  kept  open  and  may  heal  up  from  the  bottom.  Frequently,  however, 
in  spite  of  care,  a  fistula  ensues  which  requires  division  of  the  Sphincter  ani  externus  for  its  cure. 

The  Corrugator  Cutis  Ani. — Around  the  anus  is  a  thin  stratum  of  involuntary- 
muscular  fibre,  which  radiates  from  the  orifice.  Medially  the  fibres  fade  off  into 
the  submucous  tissue,  while  laterally  they  blend  with  the  true  skin.  By  its  contrac- 
tion it  raises  the  skin  into  ridges  around  the  margin  of  the  anus. 

The  Sphincter  ani  externus  {External  spJwicter  ani)  (Fig  513)  is  a  flat  plane 
of  muscular  fibres,  elliptical  in  shape  and  intimately  adherent  to  the  integument 
surrounding  the  margin  of  the  anus.  It  measures  about  8  to  10  cm.  in  length,  from 
its  anterior  to  its  posterior  extremity,  and  is  about  2.5  cm.  broad  opposite  the 
anus.  It  consists  of  two  strata,  superficial  and  deep.  The  superficial,  constituting 
the  main  portion  of  the  muscle,  arises  from  a  narrow  tendinous  band,  the  anococcy- 
geal raphe,  which  stretches  from  the  tip  of  the  coccyx  to  the  posterior  margin  of 
the  anus;  it  forms  two  flattened  planes  of  muscular  tissue,  which  encircle  the  anus 
and  meet  in  front  to  be  inserted  into  the  central  tendinous  point  of  the  perineum, 
joining  with  the  Transversus  perinaei  superficialis,  the  Levator  ani,  and  the  Bul- 
bocavernosus.  The  deeper  portion  forms  a  complete  sphincter  to  the  anal  canal. 
Its  fibres  surround  the  canal,  closely  applied  to  the  Sphincter  ani  internus,  and  in 
front  blend  with  the  other  muscles  at  the  central  point  of  the  perineum.  In  a 
considerable  proportion  of  cases  the  fibres  decussate  in  front  of  the  anus,  and  are 
continuous  with  the  Transversi  perinaei  superficiales.  Posteriorly,  they  are  not 
attached  to  the  coccj-x,  but  are  continuous  with  those  of  the  opposite  side  behind 
the  anal  canal.  The  upper  edge  of  the  muscle  is  ill-defined,  since  fibres  are  given 
off  from  it  to  join  the  Levator  ani. 

Nerve  Supply. — A  branch  from  the  fourth  sacral  and  twigs  from  the  inferior  hemorrhoidal 
branch  of  the  pudendal  supply  the  muscle. 

Actions. — The  action  of  this  muscle  is  peculiar.  (1)  It  is,  like  other  muscles,  always  in  a  state 
of  tonic  contraction,  and  having  no  antagonistic  muscle  it  keeps  the  anal  canal  and  orifice  closed. 

(2)  It  can  be  put  into  a  condition  of  greater  contraction  under  the  influence  of  the  wiU,  so  as 
more  firmly  to  occlude  the  anal  aperture,  in  expiratory  efforts  unconnected  with  defecation. 

(3)  Taking  its  fixed  point  at  the  coccyx,  it  helps  to  fix  the  central  point  of  the  perineum,  so  that 
the  Bulbocavernosus  may  act  from  this  fixed  point. 

The  Sphincter  ani  internus  {Internal  sphincter  ani)  is  a  muscular  ring  which 
surrounds  about  2.5  cm.  of  the  anal  canal;  its  inferior  border  is  in  contact  with, 
but  quite  separate  from,  the  Sphincter  ani  externus.  It  is  about  5  mm.  thick,  and 
is  formed  by  an  aggregation  of  the  involuntary  circular  fibres  of  the  intestine. 
Its  lower  border  is  about  6  mm.  from  the  orifice  of  the  anus. 

Actions. — Its  action  is  entirely  involuntary.  It  helps  the  Sphincter  ani  externus  to  occlude 
the  anal  aperture  and  aids  in  the  expulsion  of  the  feces. 


THE  MUSCLES  OF  THE  UROGEXITAL  REGIOX  IN  THE  MALE       517 

2.  A.   The  Muscles  of  the  Urogenital  Region  in  the  Male  (Fig.  514). 

Transversus  perinaei  superficialis.  Ischiocaveriiosus. 

Biilbocavernosus.  Transversus  perinaei  protundus. 

Si)luncter  urethrae  membranaceae. 

Superficial  Fascia.^The  superficial  fascia  of  this  region  consists  of  two  layers, 
superficial  and  deep. 


Fig.  514. — Muscles  of  male  perineum. 

The  superficial  layer  is  thick,  loose,  areolar  in  texture,  and  contains  in  its  meshes 
much  adipose  tissue,  the  amount  of  which  varies  m  different  subjects.  In  frmt, 
i?is  continuous  with  the  dartos  tunic  of  the  scrotum;  feeAmd,  w-.th  the  subcuta- 
neous areolar  tissue  surrounding  the  anus;  and,  on  either  srde^jith  the  same  fascia 
«n  the  inner  sides  of  the  thighs.  In  the  middle  Km,  it  is  adherent  to  the  skm  on 
the  raph^  and  to  the  deep  layer  of  the  superficial  fascia. 

The  deep  layer  ot  superficial  fascia  (fascia  of  Colle.,)  (Fig.  513)  is  thin,  aponeurot^ 
in  structure,  and  of  considerable  strength,  serving  to  bind  down  the  muscles  of 
the  root  of  the  penis.  It  is  continuous,  in  front,  with  the  dartos  tunic  the  deep 
fascia  of  the  penis,  the  fascia  of  the  spermatic  cord,  and  Scarpa  s  fascia  upon  the 


518  MYOLOGY 

anterior  -wall  of  the  abdomen;  on  either  side  it  is  firmly  attached  to  the  margins 
of  the  rami  of  the  pubis  and  ischium,  hiteral  to  the  crus  penis  and  as  far  back  as 
the  tuberosity  of  the  ischium;  posteriorly,  it  curves  around  the  Transversi  perinaei 
superficiales  to  join  the  lower  margin  of  the  inferior  fascia  of  the'  urogenital  dia- 
phragm. In  the  middle  line,  it  is  connected  with  the  superficial  fascia  and  with  the 
median  septum  of  the  Bulbocavernosus.  This  fascia  not  only  co^•ers  the  muscles 
in  this  region,  but  at  its  back  part  sends  upward  a  vertical  septum  from  its  deep 
surface,  Avhich  separates  the  posterior  portion  of  the  subjacent  space  into  two. 

The  Central  Tendinous  Point  of  the  Perineum. — ^This  is  a  fibrous  point  in  the  middle 
line  of  the  perineum,  between  the  urethra  and  anus,  and  about  1.25  cm.  in  front 
of  the  latter.  At  this  point  six  muscles  converge  and  are  attached:  viz.,  the 
Sphincter  ani  externus,  the  Bulbocavernosus,  the  two  Transversi  perinaei  super- 
ficiales, and  the  anterior  fibres  of  the  Levatores  ani. 

The  Transversus  perinaei  superficialis  {Transversus  perinaei;  Superficial  transverse 
perineal  muscle)  is  a  narrow  muscular  slip,  which  passes  more  or  less  transversely 
across  the  perineal  space  in  front  of  the  anus.  It  arises  by  tendinous  fibres  from 
the  inner  and  forepart  of  the  tuberosity  of  the  ischium,  and,  running  medialward, 
is  inserted  into  the  central  tendinous  point  of  the  perineum,  joining  in  this  situa- 
tion with  the  muscle  of  the  opposite  side,  with  the  Sphincter  ani  externus  behind, 
and  with  the  Bulbocavernosus  in  front.  In  some  cases,  the  fibres  of  the  deeper 
layer  of  the  Sphincter  ani  externus  decussate  in  front  of  the  anus  and  are  con- 
tinued into  this  muscle.  Occasionally  it  gives  off  fibres,  which  join  with  the 
Bulbocavernosus  of  the  same  side. 

Actions. — The  simultaneous  contraction  of  the  two  muscles  serves  to  fix  the  central  tendinous 
point  of  the  perineum. 

The  Bulbocavernosus  {Ejaculator  urinae;  Accelerator  urinae)  is  placed  in  the 
middle  line  of  the  perineum,  in  front  of  the  anus.  It  consists  of  tAvo  symmetrical 
parts,  united  along  the  median  line  by  a  tendinous  raphe.  It  arises  from  the  cen- 
tral tendinous  point  of  the  perineum  and  from  the  median  raphe  in  front.  Its 
fibres  diverge  like  the  barbs  of  a  quill-pen;  the  most  posterior  form  a  thin  layer, 
which  is  lost  on  the  inferior  fascia  of  the  urogenital  diaphragm;  the  middle  fibres 
encircle  the  bulb  and  adjacent  parts,  of  the  corpus  cavernosum  urethrae,  and  join 
with  the  fibres  of  the  opposite  side,  on  the  upper  part  of  the  corpus  cavernosum 
urethrae,  in  a  strong  aponeurosis;  the  anterior  fibres,  spread  out  over  the  side 
of  the  corpus  cavernosum  penis,  to  be  inserted  partly  into  that  body,  anterior  to 
the  Ischiocavernosus,  occasionally  extending  to  the  pubis,  and  partly  ending  in  a 
tendinous  expansion  which  covers  the  dorsal  vessels  of  the  penis.  The  latter 
fibres  are  best  seen  by  dividing  the  muscle  longitudinally,  and  reflecting  it  from 
the  surface  of  the  corpus  cavernosum  urethrae. 

Actions. — This  muscle  serves  to  empty  the  canal  of  the  urethra,  after  the  bladder  has  expelled 
its  contents;  during  the  greater  part  of  the  act  of  micturition  its  fibres  are  relaxed,  and  it  only 
comes  into  action  at  the  end  of  the  process.  The  middle  fibres  are  supposed  by  Ivrause  to  assist 
in  the  erection  of  the  corpus  cavernosum  urethi'ae,  by  compressing  the  erectile  tissue  of  the  bulb. 
The  anterior  fibres,  according  to  T;yTrel,  also  contribute  to  the  erection  of  the  penis  by  compressing 
the  deep  dorsal  vein  of  the  penis  as  they  are  inserted  into,  and  continuous  with,  the  fascia  of  the 
penis. 

The  Ischiocavernosus  (Erector  penis)  covers  the  crus  penis.  It  is  an  elongated 
muscle,  broader  in  the  middle  than  at  either  end,  and  situated  on  the  lateral  bound- 
ary of  the  perineum.  It  arises  by  tendinous  and  fleshy  fibres  from  the  inner  sur- 
face of  the  tuberosity  of  the  ischium,  behind  the  crus  penis;  and  from  the  rami  of 
the  pubis  and  ischium  on  either  side  of  the  crus.  From  these  points  fleshy  fibres 
succeed,  and  end  in  an  aponeurosis  which  is  inserted  into  the  sides  and  under 
surface  of  the  crus  penis. 


THE  MUSCLES  OF  THE  UROGENITAL  REGION  IN  THE  MALE       519 

Action. — Tlie  Ischiocavernosus  compresses  the  cms  penis,  and  retards  the  return  of  tlie  blood 
through  the  veins,  and  thus  serves  to  maintain  the  organ  erect. 

Between  the  muscles  just  examined  a  triangular  space  exists,  bounded  medially  by  the  Bulbo- 
cavernosus,  laterally  by  the  Ischiocavernosus,  and  behinrl  by  the  Transversus  perinaei  super- 
ficialis;  the  floor  is  formed  by  the  inferior  fascia  of  the  urogenital  diaphragm.  Running  from 
behind  forward  in  the  space  are  the  posterior  scrotal  vessels  and  nerves,  and  the  perineal  branch 
of  the  posterior  femoral  cutaneous  nerve;  the  transverse  perineal  artery  courses  along  its  posterior 
boundary  on  the  Transversus  perinaei  superficialis. 

The  Deep  Fascia. — The  deep  fascia  of  the  urogenital  region  forms  an  investment 
for  the  Transversus  perinaei  profundus  and  the  Sphincter  urethrae  membranaceae, 
but  within  it  lie  also  the  deep  vessels  and  nerves  of  this  part,  the  whole  forming  a 
transverse  septum  which  is  known  as  the  urogenital  diaphragm.  From  its  shape 
it  is  usually  termed  the  triangular  ligament,  and  is  stretched  almost  horizontally 
across  the  pubic  arch,  so  as  to  close  in  the  front  part  of  the  outlet  of  the  pelvis. 
It  consists  of  two  dense  membranous  laminae  (Fig.  515),  which  are  united  along 
their  posterior  borders,  but  are  separated  in  front  by  intervening  structures.  The 
superficial  of  these  two  layers,  the  inferior  fascia  of  the  urogenital  diaphragm,  is  tri- 
angular in  shape,  and  about  4  cm.  in  depth.    Its  apex  is  directed  forward,  and  is 


urogenital-,    j  f^ 
diaphragm  I     ,- 


ferior 


Bulbocavernosus 


Fig.    515. — Coronal  section  of  anterior  part  of  pelvis,  through  the  pubio  arch.     Seen  from  in  front.     (Diagrammatic.) 


separated  from  the  arcuate  pubic  ligament  by  an  oval  opening  for  the  transmission 
of  the  deep  dorsal  vein  of  the  penis.  Its  lateral  margins  are  attached  on  either  side 
to  the  inferior  rami  of  the  pubis  and  ischium,  above  the  crus  penis.  Its  base  is 
directed  toward  the  rectum,  and  connected  to  the  central  tendinous  point  of  the 
perineum.  It  is  continuous  with  the  deep  layer  of  the  superficial  fascia  behind  the 
Transversus  perinaei  superficialis,  and  with  the  inferior  layer  of  the  diaphragmatic 
part  of  the  pelvic  fascia.  It  is  perforated,  about  2.5  cm.  below  the  symphysis 
pubis,  by  the  urethra,  the  aperture  for  which  is  circular  and  about  6  mm.  in  diameter 
by  the  arteries  to  the  bulb  and  the  ducts  of  the  bulbourethral  glands  close  to  the 
urethral  orifice;  by  the  deep  arteries  of  the  penis,  one  on  either  side  close  to  the 
pubic  arch  and  about  halfway  along  the  attached  margin  of  the  fascia ;  by  the  dorsal 
arteries  and  nerves  of  the  penis  near  the  apex  of  the  fascia.  Its  base  is  also  perfor- 
ated by  the  perineal  vessels  and  nerves,  while  between  its  apex  and  the  arcuate 
pubic  ligament  the  deep  dorsal  vein  of  the  penis  passes  upward  into  the  pelvis. 


520  MYOLOGY 

If  the  inferior  fascia  of  the  urogenital  diaphragm  be  detached  on  either  side, 
the  following  structures  will  be  seen  between  it  and  the  superior  fascia:  the  deep 
dorsal  vein  of  the  penis;  the  membranous  portion  of  the  urethra;  the  Transversus 
perinaei  profundus  and  Sphincter  urethrae  membranaceae  muscles;  the  bulbo- 
urethral glands  and  their  ducts;  the  pudendal  vessels  and  dorsal  nerves  of  the  penis; 
the  arteries  and  nerves  of  the  urethral  bulb,  and  a  plexus  of  veins. 

The  superior  fascia  of  the  urogenital  diaphragm  is  continuous  with  the  obturator 
fascia  and  stretches  across  the  pubic  arch.  If  the  obturator  fascia  be  traced  medially 
after  leaving  the  Obturator  internus  muscle,  it  will  be  found  attached  by  some  of 
its  deeper  or  anterior  fibres  to  the  inner  margin  of  the  pubic  arch,  while  its  super- 
ficial or  posterior  fibres  pass  over  this  attachment  to  become  continuous  with  the 
superior  fascia  of  the  urogenital  diaphragm.  Behind,  this  layer  of  the  fascia  is 
continuous  with  the  inferior  fascia  and  .with  the  fascia  of  Colles ;  in  front  it  is  con- 
tinuous with  the  fascial  sheath  of  the  prostate,  and  is  fused  with  the  inferior  fascia 
to  form  the  transverse  ligament  of  the  pelvis. 

The  Transversus  perinaei  profundus  arises  from  the  inferior  rami  of  the  ischium 
and  runs  to  the  median  line,  where  it  interlaces  in  a  tendinous  raphe  with  its  fellow 
of  the  opposite  side.  It  lies  in  the  same  plane  as  the  Sphincter  urethrae  membran- 
aceae; formerly  the  two  muscles  were  described  together  as  the  Constrictor  urethrae. 

The  Sphincter  urethrae  membranaceae  surrounds  the  whole  length  of  the  mem- 
branous portion  of  the  urethra,  and  is  enclosed  in  the  fasciae  of  the  urogenital  dia- 
phragm. Its  external  fibres  arise  from  the  junction  of  the  inferior  rami  of  the  pubis 
and  ischium  to  the  extent  of  1.25  to  2  cm.,  and  from  the  neighboring  fasciae. 
They  arch  across  the  front  of  the  urethra  and  bulbourethral  glands,  pass  around 
the  urethra,  and  behind  it  unite  with  the  muscle  of  the  opposite  side,  by  means 
of  a  tendinous  raphe.  Its  innermost  fibres  form  a  continuous  circular  investment 
for  the  membranous  urethra. 

Actions. — The  muscles  of  both  sides  act  together  as  a  sphincter,  compressing  the  membranous 
portion  of  the  urethra.  During  the  transmission  of  fluids  they,  like  the  Bulbocavernosus,  are 
relaxed,  and  only  come  into  action  at  the  end  of  the  process  to  eject  the  last  drops  of  the  fluid. 

Nerve  Supply. — The  perineal  branch  of  the  pudendal  nerve  supplies  this  group  of  muscles. 

2.  B.   The  Muscles  of  the  Urogenital  Region  in  the  Female  (Fig.  515). 

Transversus  perinaei  superficialis.  Ischiocavernosus. 

Bulbocavernosus.  Transversus  perinaei  profundus. 

Sphincter  urethrae  membranaceae. 

The  Transversus  perinaei  superficialis  {Transversus  yerinaei;  Superficial  trans- 
verse perineal  muscle)  in  the  female  is  a  narrow  muscular  slip,  M'hich  arises  by  a 
small  tendon  from  the  inner  and  forepart  of  the  tuberosity  of  the  ischium,  and 
is  inserted  into  the  central  tendinous  point  of  the  perineum,  joining  in  this  situa- 
tion with  the  muscle  of  the  opposite  side,  the  Sphincter  ani  externus  behind,  and 
the  Bulbocavernosus  in  front. 

Action. — The  simultaneous  contraction  of  the  two  muscles  serves  to  fix  the  central  tendinous 
point  of  the  perineum. 

The  Bulbocavernosus  (Sphincter  vaginae)  surrounds  the  orifice  of  the  vagina. 
It  covers  the  lateral  parts  of  the  vestibular  bulbs,  and  is  attached  posteriorly 
to  the  central  tendinous  point  of  the  perineum,  where  it  blends  with  the  Sphincter 
ani  externus.  Its  fibres  pass  forward  on  either  side  of  the  vagina  to  be  inserted 
into  the  corpora  cavernosa  clitoridis,  a  fasciculus  crossing  over  the  body  of  the 
organ  so  as  to  compress  the  deep  dorsal  vein. 

Actions. — The  Bulbocavernosus  diminishes  the  orifice  of  the  vagina.  The  anterior  fibres 
contribute  to  the  erection  of  the  clitoris,  as  they  are  inserted  into  and  are  continuous  with  the 
fascia  of  the  clitoris,  compressing  the  deep  dorsal  vein  during  the  contraction  of  the  muscle. 


THE  MUSCLES  OF  THE  UROGENITAL  REGION  IN  THE  FEMALE     521 

The  Ischiocavernosus  {Erector  clltoridis)  is  smaller  than  the  corresponding 
muscle  in  the  male.  It  covers  the  unattached  surface  of  the  crus  clitoridis.  It  is 
an  elongated  muscle,  broader  at  the  middle  than  at  either  end,  and  situated  on 
the  side  of  the  lateral  boundary  of  the  perineum.  It  arises  by  tendinous  and  fleshy 
fibres  from  the  inner  surface  of  the  tuberosity  of  the  ischium,  behind  the  crus 
clitoridis;  from  the  surface  of  the  crus;  and  from  the  adjacent  portion  of  the  ramus 
of  the  ischium.  From  these  points  fleshy  fibres  succeed,  and  end  in  an  aponeurosis, 
which  is  inserted  into  the  sides  and  under  surface  of  the  crus  clitoridis. 


Clitoris 


Urethra 
Vagina 


Sphincter  ani  externus 
Fig.  516. — -Muscles  of  the  female  perineum.     (Modified  from  a  drawing  by  Peter  Thompson.) 

Actions.— The  Ischiocavernosus  compresses  the  crus  cKtoridis  and  retards  the  return  of  blood 
through  the  veins,  and  thus  serves  to  maintain  the  organ  erect. 

The  fascia  of  the  urogenital  diaphragm  in  the  female  is  not  so  strong  as  in  the 
male.  It  is  attached  to  the  pubic  arch,  its  apex  being  connected  with  the  arcuate 
pubic  ligament.  It  is  divided  in  the  middle  line  by  the  aperture  of  the  vagina, 
with  the  external  coat  of  which  it  becomes  blended,  and  in  front  of  this  is  perfor- 
ated by  the  urethra.  Its  posterior  border  is  continuous,  as  in  the  male,  with  the 
deep  layer  of  the  superficial  fascia  around  the  Transversus  perinaei  superficialis. 

Like  the  corresponding  fascia  in  the  male,  it  consists  of  two  layers,  between 
which  are  to  be  found  the  following  structures:  the  deep  dorsal  vein  of  the  clitoris, 
a  portion  of  the  urethra  and  the  Constrictor  urethra  muscle,  the  larger  vestibular 
glands  and  their  ducts;  the  internal  pudendal  vessels  and  the  dorsal  nerves  of  the 
clitoris;  the  arteries  and  nerves  of  the  bulbi  vestibuli,  and  a  plexus  of  veins. 

The  Transversus  perinaei  profundus  arises  from  the  inferior  rami  of  the  ischium 
and  runs  across  to  the  side  of  the  vagina.  The  Sphincter  urethrae  membranaceae 
{Constrictor  urethrae),  like  the  corresponding  muscle  on  the  male,  consists  of  external 
and  internal  fibres.     The  external  fibres  arise  on  either  side  from  the  margin  of  the 


522  MYOLOGY 

inferior  ramus  of  the  pubis.  They  are  directed  across  the  public  arch  in  front  of 
the  urethra,  and  pass  around  it  to  blend  with  the  muscular  fil)res  of  the  opposite 
side,  between  the  urethra  and  vagina.  The  irmervwst  fibres  encircle  the  lower  end 
of  the  urethra. 

Nerve  Supply. — The  muscles  of  this  group  are  supplied  by  the  perineal  branch  of  the  pudendal- 


THE  MUSCLES   AND  FASCI-ffl   OF   THE  UPPER  EXTREMITY. 

The  muscles  of  the  upper  extremity  are  divisible  into  groups,  corresponding 
with  the  different  regions  of  the  limb. 

I.  Muscles  Connecting  the  Upper  Extremity  to  the  Vertebral  Column. 
II.  Muscles  Connecting  the  Upper  Extremity  to  the  Anterior  and  Lateral 
Thoracic  Walls. 

III.  Muscles  of  the  Shoulder.  V.  Muscles  of  the  Forearm. 

IV.  Muscles  of  the  Arm.  VI.  Muscles  of  the  Hand. 


I.     THE  MUSCLES  CONNECTING  THE  UPPER  EXTREMITY  TO  THE 
VERTEBRAL  COLUMN. 

The  muscles  of  this  group  are : 

Trapezius.  Rhomboideus  major. 

Latissimus  dorsi.  '     Rhomboideus  minor. 

Levator  scapulae. 

Superficial  Fascia.^ — The  superficial  "fascia  of  the  back  forms  a  layer  of  con- 
siderable thickness  and  strength,  and  contains  a  quantity  of  granular  fat.  It  is 
continuous  with  the  general  superficial  fascia. 

Deep  Fascia. — The  deep  fascia  is  a  dense  fibrous  layer,  attached  above  to  the 
superior  nuchal  line  of  the  occipital  bone;  in  the  middle  line  it  is  attached  to  the 
ligamentum  nuchae  and  supraspinal  ligament,  and  to  the  spinous  processes  of  all 
the  vertebrae  below  the  seventh  cervical ;  laterally,  in  the  neck  it  is  continuous  with 
the  deep  cervical  fascia;  over  the  shoulder  it  is  attached  to  the  spine  of  the  scapula 
and  to  the  acromion,  and  is  continued  downward  over  the  Deltoideus  to  the  arm; 
on  the  thorax  it  is  continuous  with  the  deep  fascia  of  the  axilla  and  chest,  and  on 
the  abdomen  with  that  covering  the  abdominal  muscles;  below,  it  is  attached  to 
the  crest  of  the  ilium. 

The  Trapezius  (Fig.  517)  is.  a  flat,  triangular  muscle,  covering  the  upper  and 
back  part  of  the  neck  and  shoulders.  It  arises  from  the  external  occipital  protu- 
berance and  the  medial  third  of  the  superior  nuchal  line  of  the  occipital  bone,  from 
the  ligamentum  nuchae,  the  spinous  process  of  the  seventh  cervical,  and  the  spinous 
processes  of  all  the  thoracic  vertebrae,  and  from  the  corresponding  portion  of  the 
supraspinal  ligament.  From  this  origin,  the  superior  fibres  proceed  downward 
and  lateralward,  the  inferior  upward  and  lateralward,  and  the  middle  horizontally; 
the  superior  fibres  are  inserted  into  the  posterior  border  of  the  lateral  third  of  the 
clavicle;  the  middle  fibres  into  the  medial  margin  of  the  acromion,  and  into  the  supe- 
rior lip  of  the  posterior  border  of  the  spine  of  the  scapula;  the  inferior  fibres  con- 
verge near  the  scapula,  and  end  in  an  aponeurosis,  which  glides  over  the  smooth 
triangular  surface  on  the  medial  end  of  the  spine,  to  be  inserted  into  a  tubercle 
at  the  apex  of  this  smooth  triangular  surface.  At  its  occipital  origin,  the  Trapezius 
is  connected  to  the  bone  by  a  thin  fibrous  lamina,  firmly  adherent  to  the  skin. 
At  the  middle  it  is  connected  to  the  spinous  processes  by  a  broad  semi-elliptical 
aponeurosis,  which  reaches  from  the  sixth  cervical  to  the  third  thoracic  vertebrae, 
and  forms,  w^ith  that  of  the  opposite  muscle,  a  tendinous  ellipse.    The  rest  of  the 


MUSCLES  OF  THE  UPPER  EXTREMITY 


523 


Lumbar  triangle 


Fig.  517.— Muscles  connecting  the  upper  extremity  to  the  vertebral  column. 


524  MYOLOGY 

muscle  arises  by  numerous  short  tendinous  fibres.  The  two  Trapezius  muscles 
together  resemble  a  trapezium,  or  diamond-shaped  quadrangle:  two  angles  corre- 
sponding to  the  shoulders;  a  third  to  the  occipital  protuberance;  and  the  fourth 
to  the  spinous  process  of  the  twelfth  thoracic  vertebra. 

The  clavicular  insertion  of  this  muscle  varies  in  extent;  it  sometimes  reaches 
as  far  as  the  middle  of  the  clavicle,  and  occasionally  may  blend  with  the  posterior 
edge  of  the  Sternocleidomastoideus,  or  overlap  it. 

The  Latissimus  dorsi  (Fig.  517)  is  a  triangular,  flat  muscle,  which  covers  the 
lumbar  region  and  the  lower  half  of  the  thoracic  region,  and  is  gradually  con- 
tracted into  a  narrow  fasciculus  at  its  insertion  into  the  humerus.  It  arises  by 
tendinous  fibres  from  the  spinous  processes  of  the  lower  six  thoracic  vertebrae 
and  from  the  posterior  layer  of  the  lumbodorsal  fascia  (see  page  486),  by  which 
it  is  attached  to  the  spines  of  the  lumbar  and  sacral  vertebrae,  to  the  supraspinal 
ligament,  and  to  the  posterior  part  of  the  crest  of  the  ilium.  It  also  arises  by 
muscular  fibres  from  the  external  lip  of  the  crest  of  the  ilium  lateral  to  the  margin 
of  the  Sacrospinalis,  and  from  the  three  or  four  lower  ribs  by  fleshy  digitations, 
which  are  interposed  between  similar  processes  of  the  Obliquus  abdominis  externus 
(Fig.  500,  page  500).  From  this  extensive  origin  the  fibres  pass  in  dift'erent  direc- 
tions, the  upper  ones  horizontally,  the  middle  obliquely  upward,  and  the  lower 
vertically  upward,  so  as  to  converge  and  form  a  thick  fasciculus,  which  crosses  the 
inferior  angle  of  the  scapula,  and  usually  receives  a  few  fibres  from  it.  The  muscle 
curves  around  the  lower  border  of  the  Teres  major,  and  is  twisted  upon  itself,  so 
that  the  superior  fibres  become  at  first  posterior  and  then  inferior,  and  the  vertical 
fibres  at  first  anterior  and  then  superior.  It  ends  in  a  quadrilateral  tendon,  about 
7  cm.  long,  which  passes  in  front  of  the  tendon  of  the  Teres  major,  and  is  inserted 
into  the  bottom  of  the  intertubercular  groove  of  the  humerus ;  its  insertion  extends 
higher  on  the  humerus  than  that  of  the  tendon  of  the  Pectoralis  major.  The  lower 
border  of  its  tendon  is  united  with  that  of  the  Teres  major,  the  surfaces  of  the  two 
being  separated  near  their  insertions  by  a  bursa ;  another  bursa  is  sometimes  inter- 
posed between  the  muscle  and  the  inferior  angle  of  the  scapula.  The  tendon  of 
the  muscle  gives  off  an  expansion  to  the  deep  fascia  of  the  arm. 

A  muscular  slip,  the  axillary  arch,  varjdng  from  7  to  10  cm.  in  length,  and  from  5  to  15  mm. 
in  breadth,  occasionally  springs  from  the  upper  edge  of  the  Latissimus  dorsi  about  the  middle 
of  the  posterior  fold  of  the  axilla,  and  crosses  the  axilla  in  front  of  the  axillary  vessels  and  nerves, 
to  join  the  under  surface  of  the  tendon  of  the  Pectorahs  major,  the  Coracobrachiahs,  or  the  fascia 
over  the  Biceps  brachii.  This  axillary  arch  crosses  the  axillary  artery,  just  above  the  spot  usually 
selected  for  the  application  of  a  hgature,  and  may  mislead  the  surgeon  duriag  the  operation.  It 
is  present  in  about  7  per  cent,  of  subjects  and  may  be  easily  recognized  by  the  transverse  direction 
of  its  fibres. 

A  fibrous  sHp  usually  passes  from  the  lower  border  of  the  tendon  of  the  Latissimus  dorsi,  near 
its  insertion,  to  the  long  head  of  the  Triceps  brachii.  This  is  occasionally  muscular,  and  is  the 
representative  of  the  Dorsoepitrochlearis  brachii  of  apes. 

The  lateral  margin  of  the  Latissimus  dorsi  is  separated  below  from  the  Obliquus 
externus  abdominis  by  a  small  triangular  interval,  the  lumbar  triangle  of  Petit, 
the  base  of  which  is  formed  by  the  iliac  crest,  and  its  floor  by  the  Obliquus  internus 
abdominis.  Another  triangle  is  situated  behind  the  scapula.  It  is  bounded  above 
by  the  Trapezius,  below  by  the  Latissimus  dorsi,  and  laterally  by  the  vertebral 
border  of  the  scapula;  the  floor  is  partly  formed  by  the  Rhomboideus  major. 
If  the  scapula  be  drawn  forward  by  folding  the  arms  across  the  chest,  and  the 
trunk  bent  forward,  parts  of  the  sixth  and  seventh  ribs  and  the  interspace  between 
them  become  subcutaneous  and  available  for  auscultation.  The  space  is  there- 
fore known  as  the  triangle  of  auscultation. 

Nerves. — The  Trapezius  is  supplied  by  the  accessory  nerve,  and  by  branches  from  the  third 
and  fourth  cervical  nerves;  the  Latissimus  dorsi  by  the  sixth,  seventh,  and  eighth  cervical  nerves 
through  the  thoracodorsal  (long  subscapular)  nerve. 


MUSCLES  OF  THE  UPPER  EXTREMITY  525 

The  Rhomboideus  major  (Fig.  517)  arises  by  tendinous  fibres  from  the  spinous 
processes  of  the  second,  third,  fourth,  and  fifth  thoracic  vertebrae  and  the  supra- 
spinal Hgament,  and  is  inserted  into  a  narrow  tendinous  arch,  attached  above  to 
the  lower  part  of  the  triangular  surface  at  the  root  of  the  spine  of  the  scapula; 
below  to  the  inferior  angle,  the  arch  being  connected  to  the  vertebral  border  by  a 
thin  membrane.  When  the  arch  extends,  as  it  occasionally  does,  only  a  short 
distance,  the  muscular  fibres  are  inserted  directly  into  the  scapula. 

The  Rhomboideus  minor  (Fig.  517)  arises  from  the  lower  part  of  the  ligamentum 
nucliae  and  from  the  spinous  processes  of  the  seventh  cervical  and  first  thoracic 
vertebrae.  It  is  inserted  into  the  base  of  the  triangular  smooth  surface  at  the  root 
of  the  spine  of  the  scapula,  and  is  usually  separated  from  the  Rhomboideus  major 
by  a  slight  interval,  but  the  adjacent  margins  of  the  two  muscles  are  occasionally 
united. 

The  Levator  scapulae  {Levator  anguli  scapulae)  (Fig.  517)  is  situated  at  the 
back  and  side  of  the  neck.  It  arises  by  tendinous  slips  from  the  transverse  pro- 
cesses of  the  atlas  and  axis  and  from  the  posterior  tubercles  of  the  transverse 
processes  of  the  third  and  fourth  cervical  vertebrae.  It  is  inserted  into  the  verte- 
bral border  of  the  scapula,  between  the  medial  angle  and  the  triangular  smooth 
surface  at  the  root  of  the  spine. 

Nerves. — The  Rhomboidei  are  supplied  by  the  dorsal  scapular  nen-e  from  the  fifth  cervical; 
the  Levator  scapulae  by  the  third  and  fourth  cervical  nerves,  and  frequently  by  a  branch  from 
the  dorsal  scapular. 

Actions. — The  movements  effected  by  the  preceding  muscles  are  nimaerous,  as  may  be  con- 
ceived from  their  extensive  attachments.  "Wlien  the  whole  Trapezius  is  in  action  it  retracts  the 
scapula  and  braces  back  the  shoulder;  If  the  head  be  fixed,  the  upper  part  of  the  muscle  wiU  elevate 
the  point  of  the  shoulder,  as  in  supporting  weights;  when  the  lower  fibres  contract  they  assist 
in  depressing  the  scapula.  The  middle  and  lower  fibres  of  the  muscle  rotate  the  scapula,  causing 
elevation  of  the  acromion.  If  the  shoulders  be  fixed,  the  Trapezii,  acting  together,  will  draw 
the  head  dii-ectly  backward;  or  if  only  one  act,  the  head  is  drawn  to  the  corresponding  side. 

When  the  Latissimus  dorsi  acts  upon  the  humerus,  it  depresses  and  di-aws  it  backward,  and 
at  the  same  time  rotates  it  inward.  It  is  the  muscle  which  is  principal!}-  employed  in  giving  a 
downward  blow,  as  iu  felling  a  tree  or  in  sabre  practice.  If  the  arm  be  fixed,  the  muscle  may 
act  in  various  ways  upon  the  trunk;  thus,  it  may  raise  the  lower  ribs  and  assist  in  forcible  inspira- 
tion; or,  if  both  arms  be  fixed,  the  two  muscles  may  assist  the  abdominal  muscles  and  Pectorales 
in  suspending  and  drawing  the  trunk  forward,  as  in  climbing. 

If  the  head  be  fixed,  the  Levator  scapulae  raises  the  medial  angle  of  the  scapula;  if  the  shoulder 
be  fixed,  the  muscle  inclines  the  neck  to  the  corresponding  side  and  rotates  it  in  the  same  direc- 
tion. The  Rhomboidei  carry  the  inferior  angle  backward  and  upward,  thus  producing  a  shght 
rotation  of  the  scapvda  upon  the  side  of  the  chest,  the  Rhomboideus  major  acting  especially  on 
the  inferior  angle  of  the  scapula,  through  the  tendinous  arch  bj"  which  it  is  inserted.  The  Rhom- 
boidei, acting  together  with  the  middle  and  inferior  fibres  of  the  Trapezius,  will  retract  the 
scapula. 


n.     THE   MUSCLES    CONNECTING    THE   UPPER   EXTREMITY   TO    THE 
ANTERIOR    AND   LATERAL    THORACIC   WALLS. 

The  muscles  of  the  anterior  and  lateral  thoracic  regions  are: 

Pectoralis  major.  Subclavius. 

Pectoralis  minor.  Serratus  anterior. 

Dissection  of  Pectoral  Region  and  Axilla  (Fig.  518). — The  arm  being  drawTi  away  from  the 
side  nearly  at  right  angles  with  the  trunk  and  rotated  outward,  make  a  vertical  incision  through 
the  integument  in  the  median  fine  of  the  thorax,  from  the  upper  to  the  lower  part  of  the  sternum; 
a  second  incision  along  the  lower  border  of  the  Pectorahs  major  muscle,  from  the  ensiform  cartilage 
to  the  inner  side  of  the  axiUa;  a  third,  from  the  sternum  along  the  clavicle,  as  far  as  its  centre; 
and  a  fourth,  from  the  middle  of  the  clavicle  obliquely  downward,  along  the  interspace  between 
the  Pectorahs  major  and  Deltoideus  muscles,  as  low  as  the  fold  of  the  axilla.  The  flap  of  integu- 
ment is  then  to  be  dissected  off  in  the  direction  indicated  in  the  figm-e.  but  not  entire!}-  removed, 


526 


MYOLOGY 


Dissection  of 
idder  and  Arm. 


Bend  0/  Elbow. 


as  it  should  be  replaced  on  completing  the  dissection.  If  a  transverse  incision  is  now  made  from 
the  lower  end  of  the  sternum  to  the  side  of  the  thorax,  as  far  as  the  posterior  fold  of  the  axilla, 
and  the  integument  reflected  outward,  the  axillarj'  space  will  be  more  completely  exposed. 

Superficial  Fascia. — The  superficial  fascia  of  the  anterior  thoracic  region  is  con- 
tinuous with  that  of  the  neck  and  upper  extremity  above,  and  of  the  abflomen 

below.  It  encloses  the  mamma  and 
gives  off  numerous  septa  which  pass 
into  the  gland,  supporting  its  various 
lobes.  From  the  fascia  over  the  front 
of  the  mamma,  fibrous  processes 
pass  forward  to  the  integument  and 
papilla;  these  were  called  by  Sir  A. 
Cooper  the  ligamenta  suspensoria. 

Pectoral  Fascia.  —  The  pectoral 
fascia  is  a  thin  lamina,  covering  the 
surface  of  the  Pectoralis  major,  and 
sending  numerous  prolongations  be- 
tween its  fasciculi:  it  is  attached, 
in  the  middle  line,  to  the  front  of 
the  sternum;  above,  to  the  clavicle; 
laterally  and  below  it  is  contintious 
with  the  fascia  of  the  shoulder,  axilla, 
and  thorax.  It  is  very  thin  over  the 
upper  part  of  the  Pectoralis  major, 
but  thicker  in  the  interval  between 
it  and  the  Latissimus  dorsi,  w^here 
it  closes  in  the  axillary  space  and 
forms  the  axillary  fascia;  it  divides 
at  the  lateral  margin  of  the  Latis- 
simus dorsi  into  two  layers,  one  of 
which  passes  in  front  of,  and  the 
other  behind  it;  these  proceed  as 
far  as  the  spinous  processes  of  the 
thoracic  vertebrae,  to  which  they  are 
attached.  As  the  fascia  leaves  the  lower  edge  of  the  Pectoralis  major  to  cross 
the  floor  of  the  axilla  it  sends  a  layer  upward  under  cover  of  the  muscle;  this  lamina 
splits  to  envelop  the  Pectoralis  minor,  at  the  upper  edge  of  which  it  is  continuous 
with  the  coracoclavicular  fascia.  The  hollow  of  the  armpit,  seen  when  the  arm 
is  abducted,  is  produced  mainly  by  the  traction  of  this  fascia  on  the  axillary  floor, 
and  hence  the  lamina  is  sometimes  named  the  suspensory  ligament  of  the  axilla. 
At  the  lower  part  of  the  thoracic  region  the  deep  fascia  is  well-developed,  and  is 
continuous  with  the  fibrous  sheaths  of  the  Recti  abdominis. 

Applied  Anatomy. — In  cases  of  suppuration  in  the  axilla,  the  axillary  fascia  prevents  the  exten- 
sion of  the  pus  in  a  downward  direction,  and  so  it  has  a  tendency  to  spread  upward,  beneath 
the  Pectoral  muscles,  toward  the  root  of  the  neck.  Early  evacuation  is  therefore  necessary. 
The  incision  should  be  made  midway  between  the  anterior  and  posterior  axillary  folds,  so  as  to 
avoid  the  lateral  thoracic  and  subscapular  vessels,  and  the  edge  of  the  knife  should  be  directed 
away  from  the  axillary  vessels. 

The  Pectoralis  major  (Fig.  519)  is  a  thick,  triangular  muscle,  situated  at  the 
upper  and  forepart  of  the  chest.  It  arises  from  the  anterior  surface  of  the  sternal 
half  of  the  clavicle;  from  half  the  breadth  of  the  anterior  surface  of  the  sternum, 
as  low  down  as  the  attachment  of  the  cartilage  of  the  sixth  or  seventh  rib ;  from  the 
cartilages  of  all  the  true  ribs,  with  the  exception,  frequently,  of  the  first  or  seventh, 
or  both,  and  from  the  aponeurosis  of  the  Obliquus  exiternus  abdominis.    From  this 


Palm  of  Hand. 


Fig.  518. — Dissection  of  the  upper  extremity. 


MUSCLES  OF  THE  UPPER  EXTREMITY 


527 


extensive  origin  the  filires  converge  toward  their  insertion;  those  arising  from  the 
clavicle  pass  ol)lit|uely  downward  and  hiterahvard,  and  are  usually  separated  from 
the  rest  by  a  slight  interval;  those  from  the  lower  part  of  the  sternum,  and  the 
cartilages  of  the  lower  true  ribs,  run  upward  and  lateralward;  while  the  middle 
fibres  pass  horizontally.  They  all  end  in  a  flat  tendon,  about  5  cm.  broad,  which 
is  inserted  into  the  crest  of  the  greater  tubercle  of  the  humerus.  This  tendon  con- 
sists of  two  laminte,  placed  one  in  front  of  the  other,  and  usually  blended  together 
below.    The  anterior  lamina,  the  thicker,  receives  the  clavicular  and  the  uppermost 


Fig.  519. — Superficial  muscles  of  the  chest  and  front  of  the  arm. 

Sternal  fibres;  they  are  inserted  in  the  same  order  as  that  in  which  they  arise: 
that  is  to  say,  the  most  lateral  of  the  clavicular  fibres  are  inserted  at  the  upper 
part  of  the  anterior  lamina;  the  uppermost  sternal  fibres  pass  down  to  the  lower 
part  of  the  lamina  which  extends  as  low  as  the  tendon  of  the  Deltoideus  and  joms 
with  it.  The  posterior  lamina  of  the  tendon  receives  the  attachment  of  the  greater 
part  of  the  sternal  portion  and  the  deep  fibres,  i.  e.,  those  from  the  costal  cartilages. 
These  deep  fibres,  and  particularly  those  from  the  lower  costal  cartilages,  ascend 
the  higher,  turning  backward  successively  behind  the  superficial  and  upper  ones, 


528  MYOLOGY 

so  that  the  tendon  appears  to  be  twisted.  The  posterior  lamina  reaches  higher 
on  the  humerus  than  the  anterior  one,  and  from  it  an  expansion  is  given  oft"  which 
covers  the  intertubercular  groove  and  blends  with  the  capsule  of  the  shoulder- 
joint.  From  the  deepest  fibres  of  this  lamina  at  its  insertion  an  expansion  is  given 
off  which  lines  the  intertubercular  groove,  while  from  the  lower  border  of  the  tendon 
a  third  expansion  passes  downward  to  the  fascia  of  the  arm. 

Relations. — The  Pectoralis  major  is  in  relation  by  its  anterior  surface  with  the  integument,  the 
superficial  fascia,  the  Platysma,  the  anterior  and  middle  supraclavicular  nerves,  the  mamma, 
and  the  deep  fascia;  by  its  posterior  surface,  with  the  sternum,  the  ribs  and  costal  cartilages,  the 
coracoclavicular  fascia,  the  Subclavius,  PectoraUs  minor,  Serratus  anterior,  and  the  Intercostales; 
it  forms  the  anterior  wall  of  the  axillary  space,  and  covers  the  axillary  vessels  and  nerv^es  and 
the  Biceps  brachii  and  Coracobrachialis.  Its  upper  border  hes  parallel  with  the  Deltoideus,  from 
which  it  is  separated  by  a  sKght  interspace  in  which  he  the  cephaUc  vein  and  deltoid  branch  of 
the  thoracoacromial  artery.  Its  lower  border  forms  the  anterior  fold  of  the  axilla,  being  separated 
medially  from  the  Latissimus  dorsi  by  a  considerable  interval;  but  the  two  muscles  gradually 
converge  toward  the  lateral  part  of  the  space. 

Dissection. — Detach  the  Pectoralis  major  by  dividing  the  muscle  along  its  attachment  to  the 
clavicle,  and  by  making  a  vertical  incision  through  its  substance  a  httle  external  to  its  line  of 
attachment  to  the  sternum  and  costal  cartilages.  The  muscle  should  then  be  reflected  outward, 
and  its  tendon  carefully  examined.  The  Pectorahs  minor  is  now  exposed,  and  immediately 
above  it,  in  the  interval  between  its  upper  border  and  the  clavicle,  a  strong  fascia,  the  coraco- 
clavicular fascia. 

Coracoclavicular  Fascia  {fascia  coracociavicularis;  costocoracoid  membrane;  clavi- 
yectoral  fascia).- — The  coracoclavicular  fascia  is  a  strong  fascia  situated  under 
cover  of  the  clavicular  portion  of  the  Pectoralis  major.  It  occupies  the  interval 
between  the  Pectoralis  minor  and  Subclavius,  and  protects  the  axillary  vessels 
and  nerves.  Traced  upward,  it  splits  to  enclose  the  Subclavius,  and  its  two  layers 
are  attached  to  the  clavicle,  one  in  front  of  and  the  other  behind  the  muscle;  the 
latter  layer  fuses  with  the  deep  cervical  fascia  and  wdth  the  sheath  of  the  axillary 
vessels.  Medially,  it  blends  with  the  fascia  covering  the  first  two  intercostal 
spaces,  and  is  attached  also  to  the  first  rib  medial  to  the  origin  of  the  Subclavius. 
Laterally,  it  is  very  thick  and  dense,  and  is  attached  to  the  coracoid  process. 
The  portion  extending  from  the  first  rib  to  the  coracoid  process  is  often  whiter  and 
denser  than  the  rest,  and  is  sometimes  called  the  costocoracoid  ligament.  Below 
this  it  is  thin,  and  at  the  upper  border  of  the  Pectoralis  minor  it  splits  into  two 
layers  to  invest  the  muscle;  from  the  lower  border  of  the  Pectoralis  minor  it  is 
continued  downward  to  join  the  axillary  fascia,  and  lateralward  to  join  the  fascia 
over  the  short  head  of  the  Biceps  brachii.  The  coracoclavicular  fascia  is  pierced 
by  the  cephalic  vein,  thoracoacromial  artery  and  vein,  and  external  anterior 
thoracic  nerve. 

The  Pectoralis  minor  (Fig.  520)  is  a  thin,  triangular  muscle,  situated  at  the 
upper  part  of  the  thorax,  beneath  the  Pectoralis  major.  It  arises  from  the  upper 
margins  and  outer  surfaces  of  the  third,  fourth,  and  fifth  ribs,  near  their  cartilage 
and  from  the  aponeuroses  covering  the  Intercostalis;  the  fibres  pass  upward  and 
lateralward  and  converge  to  form  a  flat  tendon,  which  is  inserted  into  the  medial 
border  and  upper  surface  of  the  coracoid  process  of  the  scapula. 

Relations. — By  its  anterior  surface  it  is  in  relation  with  the  Pectoralis  major,  the  lateral 
anterior  thoracic  ner^'e,  and  the  pectoral  branch  of  the  thoracoacromial  artery;  by  its  posterior 
surface,  with  the  ribs,  Intercostales,  Serratus  anterior,  the  axillary  space,  and  the  axillary  vessels 
and  brachial  plexus  of  nerves.  Its  upper  border  is  separated  from  the  clavicle  by  a  narrow  tri- 
angular interval  occupied  by  the  coracoclavicular  fascia,  behind  which  are  the  axillary  vessels 
and  nerves.  Running  parallel  to  the  lower  border  of  the  muscle  is  the  lateral  thoracic  artery, 
and  piercing  the  muscle  is  the  medial  anterior  thoracic  nerve. 

The  Subclavius  (Fig.  520)  is  a  small  triangular  muscle,  placed  between  the 
clavicle  and  the  first  rib.  It  arises  by  a  short,  thick  tendon  from  the  first  rib  and 
its  cartilage  at  their  junction,  in  front  of  the  costoclavicular  ligament;  the  fleshy 


MrSCLES  OF  THE   CPPEIi  EXTREMITY 


529 


fibres  proceed  obliquely  ii])war(l  and  laterahvard,  to  be  inserted  into  the  groove 
on  the  under  surface  of  the  clavicle  between  the  costoclavicular  and  conoid 
ligaments. 

Relations. — Its  deep  surface  is  separated  from  the  first  rib  by  the  subclavian  vessels  and  brachial 
plexus  of  nerves.  Its  anterior  surface  is  separated  from  the  Pectoralis  major  by  the  coraco- 
clavicular  fascia,  which,  with  the  clavicle,  forms  an  osseofibrous  sheath  for  the  muscle. 

The  Serratus  anterior  {Serratus  magnus)  (Fig.  520)  is  a  thin  muscular  sheet, 
situated  between  the  ribs  and  the  scapula  at  the  upper  and  lateral  part  of 
the  chest.  It  arises  by  fleshy  digitations  from  the  outer  surfaces  and  superior 
borders  of  the  upper  eight  or  nine  ribs,  and  from  the  aponeuroses  covering  the 
intervening   Intercostales.     Each  digitation   (except  the   first)   arises    from  the 


Radius 


Fig.  520. — Deep  muscles  of  the  chest  and  front  of  the  arm,  with  the  boundaries  of  the  axilla. 

corresponding  rib ;  the  first  springs  from  the  first  and  second  ribs ;  and  from  the  fascia 
covering  the  first  intercostal  space.  From  this  extensive  attachment  the  fibres 
pass  backward,  closely  applied  to  the  chest-wall,  and  reach  the  vertebral  border 
of  the  scapula,  and  are  inserted  into  its  ventral  surface  in  the  following  manner. 
The  first  digitation  is  inserted  into  a  triangular  area  on  the  ventral  surface  of  the 
medial  angle.  The  next  two  digitations  spread  out  to  form  a  thin,  triangular 
sheet,  the  base  of  which  is  directed  backward  and  is  inserted  into  nearly  the  whole 
length  of  the  ventral  surface  of  the  vertebral  border.  The  lower  five  or  six  digita- 
tions converge  to  form  a  fan-shaped  mass,  the  apex  of  which  is  inserted,  by  muscular 
and  tendinous  fibres,  into  a  triangular  impression  on  the  ventral  surface  of  the 
inferior  angle.  The  lower  four  slips  interdigitate  at  their  origins  with  the  upper 
five  slips  of  the  Obliquus  externus  abdominis. 
34 


530  MYOLOGY 

Relations.— This  muscle  is  partly  covered,  in  front,  by  the  Pectorales  and  by  the  mamma; 
behind,  by  the  Subscapularis.  The  axillary  vessels  and  nerves  he  upon  its  upper  part,  while  its 
deep  surface  rests  upon  the  ribs  and  Intercostales. 

Nerves. — The  PectoraUs  major  is  supplied  by  the  medial  and  lateral  anterior  thoracic  nerves; 
through  these  ners-es  the  muscle  receives  filaments  from  all  the  spinal  nerves  entering  into  the 
formation  of  the  brachial  plexus;  the  Pectorahs  minor  receives  its  fibres  from  the  eighth  cervical 
and  first  thoracic  nerves  through  the  medial  anterior  thoracic  nerve.  The  Subclavius  is  supUed 
by  a  filament  from  the  fifth  and  sixth  cervical  nerves;  the  Serratus  anterior  is  supplied  by  the 
long  thoracic,  which  is  derived  from  the  fifth,  sixth,  and  seventh  cervical  nerves. 

Actions. — If  the  arm  has  been  raised  by  the  Deltoideus,  the  Pectorahs  major  will,  conjointly 
with  the  Latissimus  dorsi  and  Teres  major,  depress  it  to  the  side  of  the  chest.  If  acting  alone, 
it  adducts  and  draws  forward  the  arm,  bringing  it  across  the  front  of  the  chest,  and  at  the  same 
time  rotates  it  inward.  The  Pectoralis  minor  depresses  the  point  of  the  shoulder,  dra\\Tng  the 
scapula  downward  and  medialward  toward  the  thorax,  and  throwng  the  inferior  angle  back- 
ward. The  Subclavius  depresses  the  shoulder,  carrj^mg  it  downward  and  fom^ard.  When  the 
arms  are  fixed,  all  three  of  these  muscles  act  upon  the  ribs;  drawing  them  upward  and  expand- 
ing the  chest,  and  thus  becoming  very  important  agents  in  forced  inspiration.  The  Serratus 
anterior,  as  a  whole,  carries  the  scapula  forward,  and  at  the  same  time  raises  the  vertebral  border 
of  the  bone.  It  is  therefore  concerned  in  the  action  of  pushing.  Its  lower  and  stronger  fibres 
move  forward  the  lower  angle  and  assist  the  Trapezius  in  rotating  the  bone  at  the  sternoclavicular 
joint,  and  thus  assist  this  muscle  in  raising  the  acromion  and  supporting  weights  upon  the  shoulder. 
It  is  also  an  assistant  to  the  Deltoideus  in  raising  the  arm,  inasmuch  as  during  the  action  of  this 
latter  muscle  it  fixes  the  scapula  and  so  steadies  the  glenoid  cavity  on  which  the  head  of  the 
humerus  rotates.  After  the  Deltoideus  has  raised  the  arm  to  a  right  angle  with  the  trunk,  the 
Serratus  anterior  and  the  Trapezius,  by  rotating  the  scapula,  raise  the  arm  into  an  almost  vertical 
position.  It  is  possible  that  when  the  shoulders  are  fixed  the  lower  fibres  of  the  Serratus  anterior 
may  assist  in  raising  and  everting  the  ribs;  but  it  is  not  the  important  inspiratory  muscle  it  was 
formerly  believed  to  be. 

Applied  Anatomy. — When  the  Serratus  anterior  is  paralyzed,  the  vertebral  border,  and  especially 
the  lower  angle  of  the  scapula,  leave  the  ribs  and  stand  out  prominently  on  the  surface,  giving 
a  pecuhar  "winged"  appearance  to  the  back  (p.  309).  The  patient  is  unable  to  raise  the  arm, 
and  an  attempt  to  do  so  is  followed  by  a  further  projection  of  the  lower  angle  of  the  scapula 
from  the  back  of  the  thorax. 


m.     THE    MUSCLES    AND    FASCLffi    OF    THE    SHOULDER. 

In  this  group  are  included: 

Deltoideus.  Infraspinatus. 

Subscapularis.  Teres  minor. 

Supraspinatus.  Teres  major. 

Dissection. — ^After  completing  the  dissection  of  the  axilla,  if  the  muscles  of  the  back  have 
been  dissected,  the  upper  extremity  should  be  separated  from  the  trunk.  Saw  through  the 
clavicle  at  its  centre,  and  then  cut  through  the  muscles  which  connect  the  scapula  and  arm  with 
the  trunk — viz.,  the  Pectoralis  minor  in  front,  Serratus  anterior  at  the  side,  and  the  Levator 
anguli,  the  Pvhomboideus,  Trapezius,  and  Latissimus  dorsi  behind.  These  muscles  should  be 
cleaned  and  traced  to  their  respective  insertions.  Then  make  an  incision  through  the  integu- 
ment, commencing  at  the  outer  third  of  the  clavicle,  and  extending  along  the  margin  of  that  bone, 
the  acromion  process,  and  spine  of  the  scapula;  the  integument  should  be  dissected  from  above 
downward  and  outward,  when  the  fascia  covering  the  Deltoideus  will  be  exposed  (Fig.  518, 
No.  3). 

Deep  Fascia. — The  deep  fascia  covering  the  Deltoideus  invests  the  muscle,  and 
sends  numerous  septa  between  its  fasciculi.  In  front  it  is  continuous  with  the  fascia 
covering  the  Pectoralis  major;  behind,  where  it  is  thick  and  strong,  with  that 
covering  the  Infraspinatus;  above,  it  is  attached  to  the  clavicle,  the  acromion, 
and  the  spine  of  the  scapula;  below,  it  is  continuous  with  the  deep  fascia  of  the 
arm. 

The  Deltoideus  {Deltoid  muscle)  (Fig.  519)  is  a  large,  thick,  triangular  muscle,  which 
covers  the  shoulder- joint  in  front,  behind,  and  laterally.  It  arises  from  the  anterior 
border  and  upper  surface  of  the  lateral  third  of  the  clavicle;  from  the  lateral  margin 


THE  MUSCLES  AXD  FASCLE  OF  THE  SHOULDER  531 

and  upper  surface  of  the  acromion,  and  from  the  knver  lip  of  the  posterior  border 
of  the  spine  of  the  scapula,  as  far  back  as  the  triangular  surface  at  its  medial  end. 
From  this  extensive  origin  the  fibres  converge  toward  their  insertion,  the  middle 
passing  vertically,  the  anterior  obliquely  backward  and  lateralward,  the  posterior 
obliquely  forward  and  lateralward;  they  unite  in  a  thick  tendon,  which  is  inserted 
into  the  deltoid  prominence  on  the  middle  of  the  lateral  side  of  the  body  of  the 
humerus.  At  its  insertion  the  muscle  gives  off  an  expansion  to  the  deep  fascia  of 
the  arm.  This  muscle  is  remarkably  coarse  in  texture,  and  the  arrangement  of 
its  fibres  is  somewhat  peculiar;  the  central  portion  of  the  muscle— that  is  to  say, 
the  part  arising  from  the  acromion — consists  of  oblique  fibres;  these  arise  in  a 
bipenniform  manner  from  the  sides  of  the  tendinous  intersections,  generally  four 
in  number,  which  are  attached  above  to  the  acromion  and  pass  downward  parallel 
to  one  another  in  the  substance  of  the  muscle.  The  oblique  fibres  thus  formed  are 
inserted  into  similar  tendinous  intersections,  generally  three  in  number,  which 
pass  upward  from  the  insertion  of  the  muscle  and  alternate  with  the  descending 
septa.  The  portions  of  the  muscle  arising  from  the  clavicle  and  spine  of  the  scapula 
are  not  arranged  in  this  manner,  but  are  inserted  into  the  margins  of  the  inferior 
tendon. 

Relations. — The  Deltoideus  is  in  relation  by  its  superficial  surface  with  the  integument,  the 
superficial  and  deep  fasciae,  Platysma,  and  posterior  supraclavicular  nerves.  Its  deep  surface 
is  separated  from  the  capsule  of  the  shoulder-joint  by  a  large  bursa,  and  covers  the  coracoid 
process,  coracoacromial  hgament,  Pectoralis  minor,  Coracobrachialis,  both  heads  of  the  Biceps 
brachii,  the  tendon  of  the  Pectorahs  major,  the  insertions  of  the  Supraspinatus,  Infraspmatus, 
and  Teres  minor,  the  long  and  lateral  heads  of  the  Triceps  brachii,  the  humeral  circvunflex  vessels, 
the  axillary  nerve,  and  the  upper  part  of  the  body  of  the  hmnerus.  Its  anterior  border  is  separated 
at  its  upper  part  from  the  Pectorahs  major  by  a  narrow  interval,  which  lodges  the  cephahc  vein 
and  deltoid  branch  of  the  thoracoacromial  artery;  lower  down  the  two  muscles  are  in  close  contact. 
Its  posterior  border  rests  on  the  Infraspinatus  and  Triceps. 

Nerves. — The  Deltoideus  is  supphed  by  the  fifth  and  sixth  cervical  through  the  axiUary  nerve. 

Actions. — The  Deltoideus  raises  the  arm  from  the  side,  so  as  to  bring  it  at  right  angles  with 
the  trunk.  Its  anterior  fibres,  assisted  by  the  Pectorahs  major,  draw  the  arm  forward;  and  its 
posterior  fibres,  aided  by  the  Teres  major  and  Latissimus  dorsi,  draw  it  backward. 

Applied  Anatomy.^The  Deltoideus  is  very  hable  to  atroph}-,  and  ua  this  condition  dislocation 
of  the  shoulder-joints  is  simulated,  as  there  is  flattening  of  the  shoulder  and  apparent  prominence 
of  the  acromion;  the  distance  also  between  the  acromion  and  the  head  of  the  bone  is  mcreased, 
and  the  tips  of  the  fingers  can  be  mserted  between  them.  Atrophy  of  the  Deltoideus  may  be 
due  to  disuse,  such  as  follows  chronic  arthritis  or  permanent  injm-y  of  the  shoulder-jomt.  It 
also  frequently  results  from  degenerations  occurring  in  the  medulla  spmahs,  or  injury  to  the 
axiUary  nerve  ("crutch  palsy").  The  Deltoideus,  Supraspinatus,  and  Infraspinatus  often  escape 
in  myopathic  atrophies  affectmg  the  other  muscles  of  the  upper  arm  or  shoulder  in  yoimg  persons. 

Dissection. — Divide  the  Deltoideus  across,  near  its  upper  part,  by  an  incision  carried  along  the 
margin  of  the  clavicle,  the  acromion  process  and  spine  of  the  scapula,  and  reflect  it  do^Tiward, 
when  the  structm-es  under  cover  of  it  will  be  seen. 

Subscapular  Fascia  (fascia  subscapularis) . — The  subscapular  fascia  is  a  thin 
membrane  attached  to  the  entire  circumference  of  the  subscapular  fossa,  ^and 
affording  attachment  by  its  deep  surface  to  some  of  the  fibres  of  the  Sub- 
scapularis. 

The  Subscapularis  (Fig.  520)  is  a  large  triangular  muscle  which  fills  the  sub- 
scapular fossa,  and  arises  from  its  medial  two-thirds  and  from  the  lower  two- 
thirds  of  the  groove  on  the  axillary  border  of  the  bone.  Some  fibres  arise  from 
tendinous  laminae  which  intersect  the  muscle  and  are  attached  to  ridges  on  the 
bone;  others  from  an  aponeurosis,  which  separates  the  muscle  from  the  Teres 
major  and  the  long  head  of  the  Triceps  brachii.  The  fibres  pass  lateralward, 
and,  gradually  converging,  end  in  a  tendon  which  is  inserted  into  the  lesser  tubercle 
of  the  humerus  and  the  front  of  the  capsule  of  the  shoulder-joint.  The  tendon 
of  the  muscle  is  separated  from  the  neck  of  the  scapula  by  a  large  bursa,  which 
communicates  with  the  cavity  of  the  shoulder-joint  through  an  aperture  in  the 
capsule. 


532 


MYOLOGY 


Relations. — The  milerlor  surface  of  this  inusclu  forms  a  considerable  part  of  the  posterior  wall 
of  the  axilla,  and  is  in  relation  with  the  Serratus  anterior,  Coracobrachialis,  and  Biceps  brachii, 
the  axillary  vessels  and  brachial  plexus  of  nerves,  and  the  subscapular  vessels  and  nerves.  Its 
posterior  surface  is  in  relation  with  the  scapula  and  the  capsule  of  the  shoulder-joint.  Its  lower 
border  is  in  contact  with  the  Teres  major  and  Latissimus  dorsi. 

Nerves. — The  Subscapularis  is  supplied  by  the  fifth  and  sixth  cervical  nerves  througli  the 
upper  and  lower  subscapular  nerves. 

Actions. — The  Subscapularis  rotates  the  head  of  the  humerus  inward;  when  the  arm  is  raised, 
it  draws  the  humerus  forward  and  downward.  It  is  a  powerful  defence  to  the  front  of  the  shoulder- 
joint,  preventing  displacement  of  the  head  of  the  humerus. 

Dissection. — To  expose  these  muscles,  and  to  examine  their  insertion  into  the  humerus,  detach 
the  Deltoideus  and  Trapezius  from  their  attachment  to  the  spine  of  the  scapula  and  acromion 
process.  Remove  the  clavicle  by  dividing  the  ligaments  connecting  it  with  the  coracoid  process, 
and  separate  it  at  its  articulation  with  the  scapula;  divide  the  acromion  process  near  its  root 
with  a  saw.  The  fragments  being  removed,  the  tendons  of  the  posterior  Scapular  muscles  will 
be  fully  exposed.  A  block  should  be  placed  beneath  the  shoulder-joint,  so  as  to  make  the  muscles 
tense. 


Fig.  521. — Muscles  on  the  dorsum  of  the  scapula,  and  the  Triceps  brachii. 


Supraspinatous  Fascia  (fascia  supraspinata) . — The  supraspinatous  fascia  com- 
pletes the  osseofibrous  case  in  which  the  Supraspinatus  muscle  is  contained;  it 
affords  attachment,  by  its  deep  surface,  to  some  of  the  fibres  of  the  muscle.  It  is 
thick  medially,  but  thinner  laterally  under  the  coracoacromial  ligament. 
]]3The  Supraspinatus  (Fig.  521)  occupies  the  whole  of  the  supraspinatous  fossa, 
arising  from  its  medial  two-thirds,  and  from  the  strong  supraspinatous  fascia. 
The  muscular  fibres  converge  to  a  tendon,  which  crosses  the  upper  part  of  the 
shoulder-joint,  and  is  inserted  into  the  highest  of  the  three  impressions  on  the 
greater  tubercle  of  the  humerus ;  the  tendon  is  intimately  adherent  to  the  capsule 
of  the  shoulder-joint. 


THE  MUSCLES  AND  FASCI.E  OF  THE  ARM  533 

Infraspinatous  Fascia  { fascia,  'nifrasphiaia). — The  int'raspinatous  fascia  is  a  dense 
fibrous  iiu'inhraiu',  coNering  the  Infraspinatous  niuscU'  and  fixed  to  the  circumfer- 
ence of  the  infras])inatous  fossa;  it  affords  attachment,  by  its  deep  surface,  to  some 
fibres  of  that  muscle.  It  is  intimately  attached  to  the  deltoid  fascia  along  the  over- 
lapping border  of  the  Deltoideus. 

The  Infraspinatus  (Fig.  021)  is  a  thick  triangular  muscle,  which  occupies  the 
chief  part  of  the  infraspinatous  fossa;  it  arises  by  fleshy  fibres  from  its  medial  two- 
thirds,  and  by  tendinous  fibres  from  the  ridges  on  its  surface;  it  also  arises  from 
the  infraspinatous  fascia  which  covers  it,  and  separates  it  from  the  Teretes  major 
and  minor.  The  fibres  converge  to  a  tendon,  which  glides  over  the  lateral  border 
of  the  spine  of  the  scapula,  and,  passing  across  the  posterior  part  of  the  capsule  of 
the  shoulder-joint,  is  inserted  into  the  middle  impression  on  the  greater  tubercle 
of  the  humerus.  The  tendon  of  this  muscle  is  sometimes  separated  from  the 
capsule  of  the  shoulder-joint  by  a  bursa,  which  may  communicate  with  the  joint 
cavity. 

The  Teres  minor  (Fig.  521)  is  a  narrow,  elongated  muscle,  which  arises  from 
the  dorsal  surface  of  the  axillary  border  of  the  scapula  for  the  upper  two-thirds  of 
its  extent,  and  from  two  aponeurotic  laminae,  one  of  which  separates  it  from  the 
Infraspinatus,  the  other  from  the  Teres  major.  Its  fibres  run  obliquely  upward 
and  lateralward;  the  upper  ones  end  in  a  tendon  which  is  inserted  into  the  lowest 
of  the  three  impressions  on  the  greater  tubercle  of  the  humerus;  the  lowest  fibres 
are  inserted  directly  into  the  humerus  immediately  below  this  impression.  The 
tendon  of  this  muscle  passes  across,  and  is  united  with,  the  posterior  part  of  the 
capsule  of  the  shoulder-joint. 

The  Teres  major  (Fig.  521)  is  a  thick  but  somewhat  flattened  muscle,  which 
arises  from  the  oval  area  on  the  dorsal  surface  of  the  inferior  angle  of  the  scapula, 
and  from  the  fibrous  septa  interposed  between  the  muscle  and  the  Teres  minor 
and  Infraspinatus;  the  fibres  are  directed  upward  and  lateralward,  and  end  in  a 
flat  tendon,  about  5  cm.  long,  which  is  inserted  into  the  crest  of  the  lesser  tubercle 
of  the  humerus.  The  tendon,  at  its  insertion,  lies  behind  that  of  the  Latissimus 
dorsi,  from  which  it  is  separated  by  a  bursa,  the  two  tendons  being,  however, 
united  along  their  lower  borders  for  a  short  distance. 

Nerves. — The  Supraspinatus  and  Infraspinatus  are  supplied  by  the  fifth  and  sixth  cervical 
nerves  through  the  suprascapular  nerve;  the  Tei'es  minor,  by  the  fifth  cervical,  through  the 
axillary;  and  the  Teres  major,  by  the  fifth  and  sixth  cervical,  through  the  lowest  subscapular. 

Actions. — The  Supraspinatus  assists  the  Deltoideus  in  raising  the  arm  from  the  side  of  the 
trunk  and  fixes  the  head  of  the  humerus  in  the  glenoid  cavity.  The  Infraspinatus  and  Teres 
minor  rotate  the  head  of  the  humerus  outward;  they  also  assist  in  carrying  the  arm  backward. 
One  of  the  most  important  uses  of  these  three  muscles  is  to  protect  the  shoulder-joint,  the  Supra- 
spinatus supporting  it  above,  and  the  Infraspinatus  and  Teres  minor  behind.  The  Teres  major 
assists  the  Latissimus  dorsi  in  drawing  the  previously  raised  humerus  downward  and  backward, 
and  in  rotating  it  inward ;  when  the  arm  is  fixed  it  may  assist  the  Pectorales  and  the  Latissimus 
dorsi  in  drawing  the  trunk  forward. 


IV.    THE   MUSCLES    AND    FASCIA    OF    THE    ARM. 

The  muscles  of  the  arm  are : 

Coracobrachialis.  Brachialis. 

Biceps  brachii.  Triceps  brachii. 

Dissection. — The  arm  being  placed  on  the  table,  with  the  front  surface  uppermost,  make 
a  vertical  incision  through  the  integument  along  the  middle  hue,  from  the  clavicle  to  about 
two  inches  below  the  elbow-joint,  where  it  should  be  joined  bj^  a  transverse  incision,  extending 
from  the  inner  to  the  outer  side  of  the  forearm;  the  two  flaps  being  reflected  on  either  side,  the 
fascia  should  be  examined  (Fig.  518). 


534  MYOLOGY 

Brachial  Fascia  (fascia  brachil;  deep  fascia  of  the  arm). — The  brachial  fascia  is 
continuous  with  that  covering  the  Deltoideus  and  the  Pectoralis  major,  by  means 
of  which  it  is  attached,  above,  to  the  clavicle,  acromion,  and  spine  of  the  scapula; 
it  forms  a  thin,  loose,  membranous  sheath  for  the  muscles  of  the  arm,  and  sends 
septa  between  them;  it  is  composed  of  fibres  disposed  in  a. circular  or  spiral  direc- 
tion, and  connected  together  by  vertical  and  oblique  fibres.  It  differs  in  thickness 
at  different  parts,  being  thin  over  the  Biceps  brachii,  but  thicker  where  it  covers 
the  Triceps  brachii,  and  over  the  epicondyles  of  the  humerus:  it  is  strengthened 
by  fibrous  aponeuroses,  derived  from  the  Pectoralis  major  and  Latissimus  dorsi 
medially,  and  from  the  Deltoideus  laterally.  On  either  side  it  gives  oif  a  strong 
intermuscular  septum,  which  is  attached  to  the  corresponding  supracondylar 
ridge  and  epicondyle  of  the  humerus.  The  lateral  intermuscular  septum  extends 
from  the  lower  part  of  the  crest  of  the  greater  tubercle,  along  the  lateral  supra- 
condylar ridge,  to  the  lateral  epicondyle;  it  is  blended  with  the  tendon  of  the  Del- 
toideus, gives  attachment  to  the  Triceps  brachii  behind,  to  the  Brachialis,  Brachio- 
radialis,  and  Extensor  carpi  radialis  longus  in  front,  and  is  perforated  by  the  radial 
nerve  and  profunda  branch  of  the  brachial  artery.  The  medial  intermuscular 
septum,  thicker  than  the  preceding,  extends  from  the  lower  part  of  the  crest  of 
the  lesser  tubercle  of  the  humerus  below  the  Teres  major,  along  the  medial  supra- 
condylar ridge  to  the  medial  epicondyle;  it  is  blended  with  the  tendon  of  the 
Coracobrachialis,  and  affords  attachment  to  the  Triceps  brachii  behind  and  the 
Brachialis  in  front.  It  is  perforated  by  the  ulnar  nerve,  the  superior  ulnar 
collateral  artery,  and  the  posterior  branch  of  the  inferior  ulnar  collateral  artery. 
At  the  elbow,  the  deep  fascia  is  attached  to  the  epicondyles  of  the  humerus  and 
the  olecranon  of  the  ulna,  and  is  continuous  with  the  deep  fascia  of  the  forearm. 
Just  below  the  middle  of  the  arm,  on  its  medial  side,  is  an  oval  opening  in  the  deep 
fascia,  which  transmits  the  basilic  vein  and  some  lymphatic  vessels. 

The  Coracobrachialis  (Fig.  520),  the  smallest  of  the  three  muscles  in  this  region, 
is  situated  at  the  upper  and  medial  part  of  the  arm.  It  arises  from  the  apex  of 
the  coracoid  process,  in  common  with  the  short  head  of  the  Biceps  brachii,  and  from 
the  intermuscular  septum  between  the  two  muscles;  it  is  inserted  by  means  of  a  flat 
tendon  into  an  impression  at  the  middle  of  the  medial  surface  and  border  of  the 
body  of  the  humerus  between  the  origins  of  the  Triceps  brachii  and  Brachialis. 
It  is  perforated  by  the  musculocutaneous  nerve. 

Relations. — The  Coracobrachialis  is  in  relation,  in  front,  with  the  Pectoralis  major  above, 
and  at  its  insertion  with  the  brachial  vessels  and  median  nerve  which  cross  it;  behind,  with  the 
tendons  of  the  Subscapularis,  Latissimus  dorsi,  and  Teres  major,  the  medial  head  of  the  Triceps 
brachii,  the  hmnerus,  and  the  anterior  humeral  circumflex  vessels;  by  its  medial  border,  with  the 
third  part  of  the  axillary  and  upper  part  of  the  brachial  artery  and  the  median  and  musculo- 
cutaneous nerves;  by  its  lateral  border,  with  the  short  head  of  the  Biceps  brachii  and  Brachialis. 

The  Biceps  brachii  (Biceps;  Biceps  flexor  cuhiti)  (Fig.  520)  is  a  long  fusiform 
muscle,  placed  on  the  front  of  the  arm,  and  arising  by  two  heads,  from  which 
circumstance  it  has  received  its  name.  The  short  head  arises  by  a  thick  flattened 
tendon  from  the  apex  of  the  coracoid  process,  in  common  with  the  Coracobrachialis. 
The  long  head  arises  from  the  supraglenoid  tuberosity  at  the  upper  margin  of  the 
glenoid  cavity,  and  is  continuous  with  the  glenoidal  labrum.  This  tendon,  enclosed 
in  a  special  sheath  of  the  synovial  membrane  of  the  shoulder-joint,  arches  over 
the  head  of  the  humerus;  it  emerges  from  the  capsule  through  an  opening  close 
to  the  humeral  attachment  of  the  ligament,  and  descends  in  the  intertubercular 
groove;  it  is  retained  in  the  groove  by  the  transverse  humeral  ligament  and  by  a 
fibrous  prolongation  from  the  tendon  of  the  Pectoralis  major.  Each  tendon  is 
succeeded  by  an  elongated  muscular  belly,  and  the  two  bellies,  although  closelj'' 
applied  to  each  other,  can  readily  be  separated  until  within  about  7.5  cm,  of  the 
elbow-joint.    Here  they  end  in  a  flattened  tendon,  which  is  inserted  into  the  rough 


THE  MUSCLES  AXD  FASCLE  OF  THE  ARM  535 

posterior  portion  of  the  tuberosity  of  the  radius,  a  bursa  being  interposed  between 
the  tendon  and  the  front  part  of  the  tuberosity.  As  the  tendon  of  the  muscle 
approaches  the  radius  it  is  twisted  upon  itself,  so  that  its  anterior  surface  becomes 
lateral  and  is  applied  to  the  tuberosity  of  the  radius  at  its  insertion.  Opposite 
the  bend  of  the  elbow  the  tendon  gives  off,  from  its  medial  side,  a  broad  aponeu- 
rosis, the  lacertus  fibrosus  (bicipital  fascia)  which  passes  obliquely  downward  and 
medialward  across  the  brachial  artery,  and  is  continuous  with  the  deep  fascia 
covering  the  origins  of  the  Flexor  muscles  of  the  forearm  (Fig.  519). 

A  third  head  to  the  Biceps  brachii  is  occasionally  found,  arising  at  the  upper  and  medial  part 
of  the  Brachialis,  with  the  fibres  of  which  it  is  continuous,  and  inserted  into  the  lacertus  fibrosus 
and  medial  side  of  the  tendon  of  the  muscle.  In  most  cases  this  additional  slip  hes  behind  the 
brachial  arterj"-  in  its  course  down  the  arm.  In  some  instances  the  third  head  consists  of  two 
slips,  which  pass  down,  one  in  front  of  and  the  other  behind  the  arterj^  concealing  the  vessel  in  the 
lower  half  of  the  arm. 

Relations. — The  Biceps  brachii  is  overlapped  above  bj'  the  Pectorahs  major  and  Deltoideus; 
in  the  rest  of  its  extent  it  is  covered  by  the  superficial  and  deep  fasciae  and  the  integument.  It 
rests  above  on  the  shoulder-joint  and  upper  part  of  the  humei'us;  below,  it  lies  on  the  Brachiahs, 
the  musculocutaneous  nerve,  and  the  Supinator.  Its  medial  border  is  in  relation  with  the  Coraco- 
brachialis,  and  overlaps  the  brachial  vessels  and  median  nerve;  its  lateral  border,  with  the  Del- 
toideus and  Brachioradialis. 

The  Brachialis  (Brachialis  anficus)  (Fig.  520)  covers  the  front  of  the  elbow-joint 
and  the  lower  half  of  the  humerus.  It  arises  from  the  lower  half  of  the  front 
of  the  humerus,  commencing  above  at  the  insertion  of  the  Deltoideus,  which  it 
embraces  by  two  angular  processes.  Its  origin  extends  below  to  within  2.5  cm. 
of  the  margin  of  the  articular  surface.  It  also  arises  from  the  intermuscular  septa, 
but  more  extensively  from  the  medial  than  the  lateral;  it  is  separated  from  the 
lateral  below  by  the  Brachioradialis  and  Extensor  carpi  radialis  longus.  Its  fibres 
converge  to  a  thick  tendon,  which  is  inserted  into  the  tuberosity  of  the  ulna  and 
the  rough  depression  on  the  anterior  surface  of  the  coronoid  process. 

Relations. — The  Brachiahs  is  in  relation,  in  front,  with  the  Biceps  brachii,  the  brachial  vessels, 
musculocutaneous  and  median  nerves;  behind,  with  the  humerus  and  front  of  the  elbow-joint; 
by  its  medial  border,  with  the  Triceps  brachii,  ulnar  nerve,  and  Pronator' teres,  from  which  it  is 
separated  by  the  intermuscular  septum:  by  its  lateral  border,  with  the  radial  nerve,  radial  recurrent 
artery,  the  Brachioradialis  and  Extensor  carpi  radiahs  longus. 

Nerves. — -The  Coracobrachiahs,  Biceps  brachii  and  Brachiahs  are  supphed  by  the  musculo- 
cutaneous nerve;  the  Brachiahs  usually  receives  an  additional  filament  from  the  radial.  The 
Coracobrachiahs  receives  its  supply  primarily  from  the  seventh  cervical,  the  Biceps  brachii  and 
Brachialis  from  the  fifth  and  sixth  cervical  nerves. 

Actions. — The  Coracobrachiahs  draws  the  himierus  forward  and  medialward,  and  at  the 
same  time  assists  in  retaining  the  head  of  the  bone  in  contact-  with  the  glenoid  ca^^ty.  The 
Biceps  brachii  is  a  flexor  of  the  elbow  and,  to  a  less  extent,  of  the  shoulder;  it  is  also  a  powerful 
supinator,  and  serves  to  render  tense  the  deep  fascia  of  the  forearm  by  means  of  the  lacertus 
fibrosus  given  off  from  its  tendon.  The  Brachialis  is  a  flexor  of  the  forearm,  and  forms  an  impor- 
tant defence  to  the  elbow-joint.  T\Tien  the  forearm  is  fixed,  the  Biceps  brachii  and  Brachiahs 
flex  the  arm  upon  the  forearm,  as  in  efforts  of  climbing. 

Applied  Anatomy. — The  long  tendon  of  the  Biceps  brachii  is  sometimes  dislocated  from  the 
intertubercular  groove.  ^Tien  this  has  taken  place,  the  arm  is  fixed  in  a  position  of  abduction, 
but  the  head  of  the  humerus  can  be  felt  in  its  proper  position.  It  can  general!}'  be  replaced  by 
flexing  the  forearm  on  the  arm  and  rotatiag  the  hmb.  Rupture  of  the  long  tendon  of  the  Biceps 
brachii  may  also  take  place. 

The  Triceps  brachii  (Triceps;  Triceps  extensor  cubiti)  (Fig.  521)  is  situated  on 
the  back  of  the  arm,  extending  the  entire  length  of  the  dorsal  surface  of  the  humerus. 
It  is  of  large  size,  and  arises  by  three  heads  (long,  lateral,  and  medial),  hence  its 
name. 

The  long  head  arises  by  a  flattened  tendon  from  the  infraglenoid  tuberosity 
of  the  scapula,  being  blended  at  its  upper  part  with  the  capsule  of  the  shoulder- 
joint;  the  muscular  fibres  pass  downward  between  the  two  other  heads  of  the 
muscle,  and  join  with  them  in  the  tendon  of  insertion. 


536  MYOLOGY 

The  lateral  head  arhes  from  the  posterior  surface  of  the  body  of  the  humerus, 
between  the  insertion  of  the  Teres  minor  and  the  upper  part  of  the  groove  for  the 
radial  nerve,  and  from  the  lateral  border  of  the  humerus  and  the  lateral  intermus- 
cular septum;  the  fibres  from  this  origin  converge  toward  the  tendon  of  insertion. 

The  medial  head  arises  from  the  posterior  surface  of  the  body  of  the  humerus, 
below  the  groove  for  the  radial  nerve;  it  is  narrow  and  pointed  above,  and  extends 
from  the  insertion  of  the  Teres  major  to  within  2.5  em.  of  the  trochlea:  it  also 
arises  from  the  medial  border  of  the  humerus  and  from  the  back  of  the  whole 
length  of  the  medial  intermuscular  septum.  Some  of  the  fibres  are  directed 
downward  to  the  olecranon,  while  others  converge  to  the  tendon  of  insertion. 

The  tendon  of  the  Triceps  brachii  begins  about  the  middle  of  the  muscle:  it  con- 
sists of  two  aponeurotic  laminae,  one  of  which  is  subcutaneous  and  covers  the  back 
of  the  lower  half  of  the  muscle;  the  other  is  more  deeply  seated  in  the  substance 
of  the  muscle.  After  receiving  the  attachment  of  the  muscular  fibres,  the  two 
lamellae  join  together  above  the  elbow,  and  are  inserted,  for  the  most  part,  into 
the  posterior  portion  of  the  upper  surface  of  the  olecranon;  a  band  of  fibres  is, 
however,  continued  downward,  on  the  lateral  side,  over  the  Anconaeus,  to  blend 
with  the  deep  fascia  of  the  forearm. 

The  long  head  of  the  Triceps  brachii  descends  between  the  Teres  minor  and  Teres  major, 
dividing  the  triangular  space  between  these  two  muscles  and  the  humerus  into  two  smaller  spaces, 
one  triangular,  the  other  quadrangular  (Fig.  521).  The  triangular  space  contains  the  scapular 
circumflex  vessels;  it  is  bounded  by  the  Teres  minor  above,  the  Teres  major  below,  and  the 
scapular  head  of  the  Triceps  laterally.  The  quadrangular  space  transmits  the  posterior  humeral 
circumflex  vessels  and  the  axillary  nerve;  it  is  bounded  by  the  Teres  minor  and  capsule  of  the 
shoulder-joint  above,  the  Teres  major  below,  the  long  head  of  the  Triceps  brachii  medially,  and 
the  humerus  laterally. 

The  Subanconaeus  is  the  name  given  to  a  few  fibres  which  spring  from  the  deep  surface  of 
the  lower  part  of  the  Triceps  brachii,  and  are  inserted  into  the  posterior  ligament  and  synovial 
membrane  of  the  elbow-joint. 

Nerves. — The  Triceps  brachii  is  supplied  by  the  seventh  and  eighth  cervical  nerves  through 
the  radial  nerve. 

Actions. — The  Triceps  brachii  is  the  great  extensor  muscle  of  the  forearm,  and  is  the  direct 
antagonist  of  the  Biceps  brachii  and  Brachiahs.  When  the  arm  is  extended,  the  long  head  of 
the  muscle  may  assist  the  Teres  major  and  Latissimus  dorsi  in  drawing  the  humerus  backward 
and  in  adducting  it  to  the  thorax.  The  long  head  supports  the  under  part  of  the  shoulder-joint. 
The  Subanconaeus  draws  up  the  synovial  membrane  of  the  elbow-joint  during  extension  of  the 
forearm. 

Applied  Anatomy. — The  continuity  of  the  insertion  of  the  Triceps  brachii  with  the  deep  fascia 
of  the  forearm  is  of  importance  in  the  operation  of  excision  of  the  elbow;  it  should  always  be 
carefuUy  preserved  from  injury.  By  means  of  these  fibres  the  patient  is  enabled  to  extend  the 
forearm,  a  movement  which  would  otherwise  be  accomphshed  mainly  by  gravity — that  is  to 
say,  by  allowing  the  forearm  to  drop  by  its  own  weight. 

V.    THE   MUSCLES    AND    FASCI.ffi    OF    THE    FOREARM. 

Dissection. — To  dissect  the  forearm,  place  the  hmb  in  the  position  indicated  in  Fig.  518,  make 
a  vertical  incision  along  the  middle  line  from  the  elbow  to  the  wrist,  and  a  transverse  incision 
at  the  extremity  of  this;  the  superficial  structures  being  removed,  the  deep  fascia  of  the  forearm 
is  exposed. 

Antibrachial  Fascia  {fascia  antibrachii;  deep  fascia  of  the  forearm). — The  anti- 
brachial  fascia  continuous  above  with  the  brachial  fascia,  is  a  dense,  membranous 
investment,  which  forms  a  general  sheath  for  the  muscles  in  this  region;  it  is  at- 
tached, behind,  to  the  olecranon  and  dorsal  border  of  the  ulna,  and  gives  off  from  its 
deep  surface  numerous  intermuscular  septa,  which  enclose  each  muscle  separately. 
Over  the  Flexor  tendons  as  they  approach  the  wrist  it  is  especially  thickened,  and 
forms  the  volar  carpal  ligament.  This  is  continuous  with  the  transverse  carpal  liga- 
ment, and  forms  a  sheath  for  the  tendon  of  the  Palmaris  longus  which  passes  over 
the  transverse  carpal  ligament  to  be  inserted  into  the  palmar  aponeurosis.    Behind, 


THE  VOLAR  AST  I  BRACHIAL  MUSCLES  537 

near  the  wrist-joint,  it  is  thickened  by  the  addition  of  many  transverse  fibres,  and 
forms  the  dorsal  carpal  ligament.  It  is  mnch  thicker  on  the  dorsal  than  on  the  volar 
snrface,  and  at  the  lower  than  at  the  nj)per  i)art  of  the  forearm,  and  is  strengthened 
above  by  tendinons  hbres  derived  from  the  Biceps  brachii  in  front,  and  from  the 
Triceps  brachii  behind.  It  gives  origin  to  muscular  fibres,  especially  at  the  upper 
part  of  the  medial  and  lateral  sides  of  the  forearm,  and  forms  the  boundaries  of 
a  series  of  cone-shaped  cavities,  in  which  the  muscles  are  contained.  Besides  the 
vertical  septa  separating  the  indi\idiial  muscles,  transverse  septa  are  given  off 
both  on  the  volar  and  dorsal  surfaces  of  the  forearm,  separating  the  deep  from  the 
superficial  layers  of  muscles.  Apertures  exist  in  the  fascia  for  the  passage  of 
vessels  and  nerves;  one  of  these  apertures  of  large  size,  situated  at  the  front  of  the 
elbow,  serves  for  the  passage  of  a  communicating  branch  between  the  superficial 
and  deep  veins. 

The  antibrachial  or  forearm  muscles  may  be  divided  into  a  volar  and  a  dorsal 
group. 

1.  The  Volar  Antibrachial  Muscles. 

These  muscles  are  divided  for  convenience  of  description  into  two  groups, 
superficial  and  deep. 

The  Superficial  Group  (Fig.  522). 

Pronator  teres.  Palmaris  longus. 

Flexor  carpi  radialis.  Flexor  carpi  ulnaris. 

Flexor  digitorum  sublimis. 

The  muscles  of  this  group  take  origin  from  the  medial  epicondyle  of  the  humerus 
by  a  common  tendon;  they  receive  additional  fibres  from  the  deep  fascia  of  the  fore- 
arm near  the  elbow,  and  from  the  septa  which  pass  from  this  fascia  between  the 
individual  muscles. 

The  Pronator  teres  has  two  heads  of  origin — humeral  and  ulnar.  The  humeral 
head,  the  larger  and  more  superficial,  arises  immediately  above  the  medial  epi- 
condyle, and  from  the  tendon  common  to  the  origin  of  the  other  muscles;  also 
from  the  intermuscular  septum  between  it  and  the  Flexor  carpi  radialis  and  from 
the  antibrachial  fascia.  The  ulnar  head  is  a  thin  fasciculus,  w^hich  arises  from  the 
medial  side  of  the  coronoid  process  of  the  ulna,  and  joins  the  preceding  at  an  acute 
angle.  The  median  nerve  enters  the  forearm  between  the  two  heads  of  the  muscle, 
and  is  separated  from  the  ulnar  artery  by  the  ulnar  head.  The  muscle  passes  ob- 
liquely across  the  forearm,  and  ends  in  a  flat  tendon,  which  is  inserted  into  a  rough 
impression  at  the  middle  of  the  lateral  surface  of  the  body  of  the  radius.  The 
lateral  border  of  the  muscle  forms  the  medial  boundary  of  a  triangular  hollow 
situated  in  front  of  the  elbow-joint  and  containing  the  brachial  artery,  median 
nerve,  and  tendon  of  the  Biceps  brachii. 

Applied  Anatomy. — This  muscle,  when  suddenly  brought  into  active  use,  as  in  the  game  of 
lawn  tennis,  is  apt  to  be  strained,  producing  shght  swelling,  tenderness,  and  pain  on  putting  the 
muscle,  into  action.    This  is  known  as  "lawn-tennis  arm." 

The  Flexor  carpi  radialis  lies  on  the  medial  side  of  the  preceding  muscle.  It 
arises  from  the  medial  epicondyle  by  the  common  tendon;  from  the  fascia  of  the 
forearm;  and  from  the  intermuscular  septa  between  it  and  the  Pronator  teres 
laterally,  the  Palmaris  longus  medially,  and  the  Flexor  digitorum  sublimis  beneath. 
Slender  and  aponeurotic  in  structure  at  its  commencement,  it  increases  in  size, 
and  ends  in  a  tendon  which  forms  rather  more  than  the  lower  half  of  its  length. 
This  tendon  passes  through  a  canal  in  the  lateral  part  of  the  transverse  carpal 
ligament  and  runs  through  a  groove  on  the  greater  multangular  bone;  the  groove 
is  converted  into  a  canal  by  fibrous  tissue,  and  lined  by  a  mucous  sheath.  The  ten- 
don is  inserted  into  the  base  of  the  second  metacarpal  bone,  and  sends,  a  slip  to 


538 


MYOLOGY 


the  base  of  the  third  metacarpal  bone. 
The  radial  artery,  in  the  lower  part  of 
the  forearm,  lies  between  the  tendon 
of  this  muscle  and  the  Brachioradialis. 
The  Palmaris  longus  is  a  slender, 
fusiform  muscle,  lying  on  the  medial 
side  of  the  preceding.  It  arises  from 
the  medial  epicondyle  of  the  humerus 
by  the  common  tendon,  from  the  inter- 
muscular septa  between  it  and  the 
adjacent  muscles,  and  from  the  anti- 
brachial  fascia.     It  ends  in  a  slender, 


Fig.  522. — Front  of  the  left  forearm, 
muscles. 


Superficial 


Fig.  523.— Front  of  the  left  forearm.     Deep 
muscles. 


THE  VOLAR  AXTIBRACHIAL  MUSCLES  539 

flattened  tendon,  which  passes  over  the  upper  part  of  the  transverse  carpal  liga- 
ment, and  is  iri'^oied  into  the  central  part  of  the  transverse  carpal  ligament  and 
lower  part  of  the  palmar  aponeurosis,  frequently  sending  a  tendinous  slip  to  the 
short  muscles  of  the  thmnb. 

This  muscle  is  often  absent,  and  is  subject  to  very  considerable  variations;  it  may  be  tendinous 
above  and  muscular  below;  or  it  may  be  muscular  in  the  centre  with  a  tendon  above  and  below; 
or  it  may  present  two  muscular  bundles  with  a  central  tendon;  or  finally  it  may  consist  solely 
of  a  tendinous  band.  Just  above  the  wrist,  the  median  nerve  lies  close  to  the  tendon,  on  its  lateral 
and  dorsal  aspects. 

The  Flexor  carpi  ulnaris  lies  along  the  ulnar  side  of  the  forearm.  It  arises 
by  two  heads,  humeral  and  ulnar,  connected  by  a  tendinous  arch,  beneath  which 
the  ulnar  nerve  and  posterior  ulnar  recurrent  artery  pass.  The  humeral  head  arises 
from  the  medial  epicondyle  of  the  humerus  by  the  common  tendon;  the  ulnar 
head  arises  from  the  medial  margin  of  the  olecranon  and  from  the  upper  two-thirds 
of  the  dorsal  border  of  the  ulna  by  an  aponeurosis,  common  to  it  and  the  Extensor 
carpi  ulnaris  and  Flexor  digitorum  profundus ;  and  from  the  intermuscular  septum 
between  it  and  the  Flexor  digitorum  sublimis.  The  fibres  end  in  a  tendon,  which 
occupies  the  anterior  part  of  the  lower  half  of  the  muscle  and  is  inserted  into  the 
pisiform  bone,  and  is  prolonged  from  this  to  the  hamate  and  fifth  metacarpal 
bones  by  the  pisohamate  and  pisometacarpal  ligaments;  it  is  also  attached  by  a 
few  fibres  to  the  transverse  carpal  ligament.  The  ulnar  vessels  and  nerve  lie  on 
the  lateral  side  of  the  tendon  of  this  muscle,  in  the  lower  two-thirds  of  the  forearm. 

The  Flexor  digitorum  sublimis  is  placed  beneath  the  previous  muscle;  it  is 
the  largest  of  the  muscles  of  the  superficial  group,  and  arises  by  three  heads — • 
humeral,  ulnar,  and  radial.  The  humeral  head  arises  from  the  medial  epicondyle 
of  the  humerus  by  the  common  tendon,  from  the  ulnar  collateral  ligament  of  the 
elbow-joint,  and  from  the  intermuscular  septa  between  it  and  the  preceding 
muscles.  The  ulnar  head  arises  from  the  medial  side  of  the  coronoid  process, 
above  the  ulnar  origin  of  the  Pronator  teres  (see  Fig.  353,  page  316).  The  radial 
head  arises  from  the  oblique  line  of  the  radius,  extending  from  the  radial  tuberosity 
to  the  insertion  of  the  Pronator  teres.  The  muscle  speedily  separates  into  two 
planes  of  muscular  fibres,  superficial  and  deep:  the  superficial  plane  divides  into 
two  parts  which  end  in  tendons  for  the  middle  and  ring  fingers;  the  deep  plane 
gives  off  a  muscular  slip  to  join  the  portion  of  the  superficial  plane  which  is  asso- 
ciated with  the  tendon  of  the  ring  finger,  and  then  divides  into  two  parts,  which 
end  in  tendons  for  the  index  and  little  fingers.  As  the  four  tendons  thus  formed 
pass  beneath  the  transverse  carpal  ligament  into  the  palm  of  the  hand,  they  are 
arranged  in  pairs,  the  superficial  pair  going  to  the  middle  and  ring  fingers,  the  deep 
pair  to  the  index  and  little  fingers.  The  tendons  diverge  from  one  another  in  the 
palm  and  form  dorsal  relations  to  the  superficial  volar  arch  and  digital  branches 
of  the  median  and  ulnar  nerves.  Opposite  the  bases  of  the  first  phalanges  each 
tendon  divides  into  two  slips  to  allow  of  the  passage  of  the  corresponding  tendon 
of  the  Flexor  digitorum  profundus ;  the  two  slips  then  reunite  and  form  a  grooved 
channel  for  the  reception  of  the  accompanying  tendon  of  the  Flexor  digitorum 
profundus.  Finally  the  tendon  divides  and  is  inserted  into  the  sides  of  the  second 
phalanx  about  its  middle. 

The  Deep  Group  (Fig.  523). 

Flexor  digitorum  profundus.  Flexor  pollicis  longus. 

Pronator  quadratus. 

Dissection. — Divide  each  of  the  superficial  muscles  at  its  centre,  and  turn  either  end  aside; 
the  deep  layer  of  muscles,  together  with  the  median  nerve  and  ulnar  vessels,  will  then  be  exposed. 


540  MYOLOGY 

The  Flexor  digitorum  profundus  is  situated  on  the  uhiar  side  of  the  forearm, 
immediately  beneath  the  superficial  Flexors.  It  arises  from  the  upper  three- 
fourths  of  the  volar  and  medial  surfaces  of  the  body  of  the  ulna,  embracing  the 
insertion  of  the  Brachialis  above,  and  extending  below  to  within  a  short  distance 
of  the  Pronator  quadratus.  It  also  arises  from  a  depression  on  the  medial  side  of 
the  coronoid  process;  by  an  aponeurosis  from  the  upper  three-fourths  of  the  dorsal 
border  of  the  ulna,  in  common  with  the  Flexor  and  Extensor  carpi  ulnaris;  and 
from  the  ulnar  half  of  the  interosseous  membrane.  The  muscle  ends  in  four  tendons 
which  run  under  the  transverse  carpal  ligament  dorsal  to  the  tendons  of  the  Flexor 
digitorum  sublimis.  Opposite  the  first  phalanges  the  tendons  pass  through  the 
openings  in  the  tendons  of  the  Flexor  digitorum  sublimis,  and  are  finally  inserted 
into  the  bases  of  the  last  phalanges.  The  portion  of  the  muscle  for  the  index  finger 
is  usually  distinct  throughout,  but  the  tendons  for  the  middle,  ring,  and  little 
fingers  are  connected  together  by  areolar  tissue  and  tendinous  slips,  as  far  as  the 
palm  of  the  hand. 

Fibrous  Sheaths  of  the  Flexor  Tendons. — After  leaving  the  palm,  the  tendons 
of  the  Flexores  digitorum  sublimis  and  profundus  lie  in  osseo-aponeurotic  canals 
(Fig.  534),  formed  behind  by  the  phalanges  and  in  front  by  strong  fibrous  bands, 
which  arch  across  the  tendons,  and  are  attached  on  either  side  to  the  margins  of 
the  phalanges.  Opposite  the  middle  of  the  proximal  and  second  phalanges  the 
bands  (digital  vaginal  ligaments)  are  very  strong,  and  the  fibres  are  transverse; 
but  opposite  the  joints  they  are  much  thinner,  and  consist  of  annular  and  cruciate 
ligamentous  fibres.  Each  canal  contains  a  mucous  sheath,  which  is  reflected  on 
the  contained  tendons. 

Within  each  canal  the  tendons  of  the  Flexores  digitorum  sublimis  and  profundus 
are  connected  to  each  other,  and  to  the  phalanges,  by  slender,  tendinous  bands, 
called  vincula  tendina  (Fig.  524).  There  are  two  sets  of  these;  {a)  the  vincula 
brevia,  which  are  two  in  number  in  each  finger,  and  consist  of  triangular  bands 
of  fibres,  one  connecting  the  tendon  of  the  Flexor  digitorum  sublimis  to  the  front 
of  the  first  interphalangeal  joint  and  head  of  the  first  phalanx,  and  the  other  the 
tendon  of  the  Flexor  digitorum  profundus  to  the  front  of  the  second  interphalan- 
geal joint  and  head  of  the  second  phalanx;  (6)  the  vincula  longa,  which  connect 
the  under  surfaces  of  the  tendons  of  the  Flexor  digitorum  profundus  to  those  of  the 
subjacent  Flexor  sublimis  after  the  tendons  of  the  former  have  passed  through 
the  latter. 

Four  small  muscles,  the  Lumbricales,  are  connected  with  the  tendons  of  the 
Flexor  profundus  in  the  palm.  They  will  be  described  with  the  muscles  of  the 
hand  (page  555). 

The  Flexor  poUicis  longus  is  situated  on  the  radial  side  of  the  forearm,  lying 
in  the  same  plane  as  the  preceding.  It  arises  from  the  grooved  volar  surface  of 
the  body  of  the  radius,  extending  from  immediately  below  the  tuberosity  and 
oblique  line  to  within  a  short  distance  of  the  Pronator  quadratus.  It  arises  also 
from  the  adjacent  part  of  the  interosseous  membrane,  and  generally  by  a  fleshy 
slip  from  the  medial  border  of  the  coronoid  process,  or  from  the  medial  epicondyle 
of  the  humerus.  The  fibres  end  in  a  fiattened  tendon,  which  passes  beneath  the 
transverse  carpal  ligament,  is  then  lodged  between  the  lateral  head  of  the  Flexor 
pollicis  brevis  and  the  oblique  part  of  the  Adductor  pollicis,  and,  entering  an  osseo- 
aponeurotic  canal  similar  to  those  for  the  Flexor  tendons  of  the  fingers,  is  inserted 
into  the  base  of  the  distal  phalanx  of  the  thumb.  The  volar  interosseous  nerve 
and  vessels  pass  downward  on  the  front  of  the  interosseous  membrane  between 
the  Flexor  pollicis  longus  and  Flexor  digitorum  profundus. 

The  Pronator  quadratus  is  a  small,  flat,  quadrilateral  muscle,  extending  across 
the  front  of  the  lower  parts  of  the  radius  and  ulna.  It  arises  from  the  pronator 
ridge  on  the  lower  part  of  the  volar  surface  of  the  body  of  the  ulna;  from  the  medial 


THE  VOLAR  AXTIBRACIIIAL  MUSCLES 


541 


part  of  the  volar  surface  of  the  h)\ver  fourtli  of  the  ulna;  and  from  a  strong  apon- 
eurosis which  covers  the  medial  third  of  the  muscle.  The  fibres  pass  laterahvard 
and  slightly  downward,  to  be  inserted  into  the  lower  fourth  of  the  lateral  border 
and  the  volar  surface  of  the  body  of  the  radius.  The  deeper  fibres  of  the  muscle 
are  inserted  into  the  triangular  area  above  the  ulnar  notch  of  the  radius — an 
attachment  comparable  with  the  origin  of  the  Supinator  from  the  triangular  area 
below  the  radial  notch  of  the  ulna. 


Tendon  of  Exi. 
carpi  nid.  longus 


Tendon  of  Ext. 
digitormn  communis 


Tendon  of  Extensor  indici 
pro  prills 


First  Lumbrical 


Tendon  of  Abditctor 

poll  ids  longus 
Greater  midtetngideir  hone 


Radial  artery 


1 Tendon  of  Ext.  pollicis  hrevis 


,     W4       I 

t  /////    Li      I      i,\ -H — Tendon  of  Ext.  pollicis  longus 


'/// 


Vincula  brevia 


/  V    \  ^        1 

[p.  -%  /J~r~\  \  Flexor  d, 


digitorum  sublimis 
Flexor  digitorum  profundus 


Vincula  longa 


Fig.  524. — Tendons  of  forefinger  and  vincula  tendina 


Nerves. — All  the  muscles  of  the  superficial  layer  are  suppHed  by  the  median  nerve,  excepting 
the  Flexor  carpi  ulnaris,  which  is  supphed  by  the  ulnar.  The  Pronator  teres,  the  Flexor  carpi 
radiahs,  and  the  Palmaris  longus  derive  their  supply  primarily  from  the  sixth  cervical  nerve; 
the  Flexor  digitorum  sublimis  from  the  seventh  and  eighth  cervical  and  first  thoracic  nerves, 
and  the  Flexor  carpi  ulnaris  from  the  eighth  cervical  and  first  thoracic.  Of  the  deep  layer,  the 
Flexor  digitorum  profundus  is  supplied  by  the  eighth  cervical  and  first  thoracic  through  the 
ulnar,  and  the  volar  interosseous  branch  of  the  median.  The  Flexor  pollicis  longus  and  Pronator 
quadratus  are  supplied  by  the  eighth  cervical  and  first  thoracic  through  the  volar  interosseous 
branch  of  the  median. 

Actions. — These  muscles  act  upon  the  forearm,  the  wi'ist,  and  hand.  The  Pronator  teres 
rotates  the  radius  upon  the  ulna,  rendering  the  hand  prone;  when  the  radius  is  fixed,  it  assists 
in  flexing  the  forearm.  The  Flexor  carpi  radiahs  is  a  flexor  and  abductor  of  the  wrist;  it  also 
assists  in  pronating  the  hand,  and  in  bending  the  elbow.  The  Flexor  carpi  ulnaris  is  a  flexor  and 
adductor  of  the  wrist;  it  also  assists  in  bending  the  elbow.  The  Palmaris  longus  is  a  flexor  of  the 
wrist-joint;  it  also  assists  in  flexing  the  elbow.  The  Flexor  digitorum  subhmis  flexes  first  the 
middle  and  then  the  proximal  phalanges;  it  also  assists  in  flexing  the  wrist  and  elbow.  The 
Flexor  digitorum  profundus  is  one  of  the  flexors  of  the  phalanges.  After  the  Flexor  sublimis 
has  bent  the  second  phalanx,  the  Flexor  profundus  flexes  the  terminal  one;  but  it  cannot  do  so 
until  after  the  contraction  of  the  superficial  muscle.     It  also  assists  in  flexing  the  wrist.     The 


542  MYOLOGY 

Flexor  pollicis  longus  is  a  flexor  of  the  phalanges  of  the  thumb;  when  the  thumb  is  fixed,  it  assists 
in  flexing  the  wrist.  The  Pronator  quadratus  rotates  the  radius  upon  the  ulna,  rendering  the 
hand  prone. 

2.  The  Dorsal  Antibrachial  Muscles. 

These  muscles  are  divided  for  convenience  of  description  into  two  groups, 
superficial  and  deep. 

The  Superficial  Group  (Fig.  525). 

Brachioradialis.  Extensor  digitorum  communis. 

Extensor  carpi  radialis  longus.  Extensor  digiti  quinti  proprius. 

Extensor  carpi  radialis  brevis.  Extensor  carpi  ulnaris. 

Anconaeus. 

Dissection. — Divide  the  integument  in  the  same  manner  as  in  the  dissection  of  the  volar  anti- 
brachial region,  and,  after  having  examined  the  cutaneous  vessels  and  nerves  and  deep  fascia, 
remove  all  those  structures.  The  muscles  will  then  be  exposed.  The  removal  of  the  fascia  will 
be  considerably  facilitated  by  detaching  it  from  below  upward.  Great  care  should  be  taken 
to  avoid  cutting  across  the  tendons  of  the  muscles  of  the  thumb,  which  cross  obhquely  the  larger 
tendons  running  down  the  back  of  the  radius. 

The  Brachioradialis  {Supinator  longus)  is  the  most  superficial  muscle  on  the 
radial  side  of  the  forearm.  It  arises  from  the  upper  two-thirds  of  the  lateral 
supracondylar  ridge  of  the  humerus,  and  from  the  lateral  intermuscular  septum, 
being  limited  above  by  the  groove  for  the  radial  neri^e.  Interposed  between  it 
and  the  Brachialis  are  the  radial  nerve  and  the  anastomosis  between  the  anterior 
branch  of  the  profunda  artery  and  the  radial  recurrent.  The  fibres  end  above 
the  middle  of  the  forearm  in  a  flat  tendon,  which  is  inserted  into  the  lateral  side 
of  the  base  of  the  styloid  process  of  the  radius.  The  tendon  is  crossed  near  its 
insertion  by  the  tendons  of  the  Abductor  pollicis  longus  and  Extensor  pollicis 
brevis;  on  its  ulnar  side  is  the  radial  artery. 

The  Extensor  carpi  radialis  longus  {Extensor  carpi  radialis  longior)  is  placed  partlj- 
beneath  the  Brachioradialis.  It  arises  from  the  lower  third  of  the  lateral  supracon- 
dylar ridge  of  the  humerus,  from  the  lateral  intermuscular  septum,  and  by  a  few 
filDres  from  the  common  tendon  of  origin  of  the  Extensor  muscles  of  the  forearm. 
The  fibres  end  at  the  upper  third  of  the  forearm  in  a  fiat  tendon,  which  runs  along 
the  lateral  border  of  the  radius,  beneath  the  Abductor  pollicis  longus  and  Extensor 
pollicis  brevis;  it  then  passes  beneath  the  dorsal  carpal  ligament,  where  it  lies  in  a 
groove  on  the  back  of  the  radius  common  to  it  and  the  Extensor  carpi  radialis  brevis, 
immediately  behind  the  styloid  process.  It  is  inserted  into  the  dorsal  surface  of 
the  base  of  the  second  metacarpal  bone,  on  its  radial  side. 

The  Extensor  carpi  radialis  brevis  {Extensor  carpi  radialis  brevior)  is  shorter  and 
thicker  than  the  preceding  muscle,  beneath  which  it  is  placed.  It  arises  from  the 
lateral  epicondyle  of  the  humerus,  by  a  tendon  common  to  it  and  the  three  following 
muscles;  from  the  radial  collateral  ligament  of  the  elbow-joint;  from  a  strong 
aponeurosis  which  covers  its  surface;  and  from  the  intermuscular  septa  between  it 
and  the  adjacent  muscles.  The  fibres  end  about  the  middle  of  the  forearm  in  a 
flat  tendon,  which  is  closely  connected  with  that  of  the  preceding  muscle,  and 
accompanies  it  to  the  wrist;  it  passes  beneath  the  Abductor  pollicis  longus  and 
Extensor  pollicis  brevis,  then  beneath  the  dorsal  carpal  ligament,  and  is  inserted 
into  the  dorsal  surface  of  the  base  of  the  third  metacarpal  bone  on  its  radial  side. 
Under  the  dorsal  carpal  ligament  the  tendon  lies  on  the  back  of  the  radius  in 
a  shallow  groove,  to  the  ulnar  side  of  that  which  lodges  the  tendon  of  the  Extensor 
carpi  radialis,  longus,  and  separated  from  it  by  a  faint  ridge. 

The  tendons  of  the  two  preceding  muscles  pass  through  the  same  compartment 
of  the  dorsal  carpal  ligament  in  a  single  mucous  sheath. 


THE  DORSAL  ANT  I  BRACHIAL  MUSCLES 


543 


Abductor 
pollicis 
longus 
Ext.  poinds 
brevis 

Ext.  poinds 

loiKJllS 


Fig.  525. — Posterior  surface  of  the  forearm. 
Superficial  muscles. 


Fig.   526. — Posterior  surface  of  the  forearm.     Deep 
muscles. 


544  MYOLOGY 

The  Extensor  digitorum  communis  uriscs  from  the  hiteral  epieoiid^le  of  the 
humerus,  by  the  common  tendon;  from  the  intermuscular  septa  between  it  and  the 
adjacent  muscles,  and  from  the  antibrachial  fascia.  It  divides  below  into  four 
tendons,  which  pass,  together  with  that  of  the  Extensor  indicis  proprius,  through 
a  separate  compartment  of  the  dorsal  carpal  ligament,  within  a  mucous  sheath. 
The  tendons  then  diverge  on  the  back  of  the  hand,  and  are  inserted  into  the  second 
and  third  phalanges  of  the  fingers  in  the  following  manner.  Opposite  the  meta- 
carpophalangeal articulation  each  tendon  is  bound  by  fasciculi  to  the  collateral 
ligaments  and  serves  as  the  dorsal  ligament  of  this  joint;  after  having  crossed  the 
joint,  it  spreads  out  into  a  broad  aponeurosis,  which  covers  the  dorsal  surface  of 
the  first  phalanx  and  is  reinforced,  in  this  situation,  by  the  tendons  of  the  Inter- 
ossei  and  Lumbricalis.  Opposite  the  first  interphalangeal  joint  this  aponeurosis 
divides  into  three  slips;  an  intermediate  and  two  collateral:  the  former  is  inserted 
into  the  base  of  the  second  phalanx;  and  the  two  collateral,  which  are  continued 
onward  along  the  sides  of  the  second  phalanx,  unite  by  their  contiguous  margins, 
and  are  inserted  into  the  dorsal  surface  of  the  last  phalanx.  As  the  tendons  cross 
the  interphalangeal  joints,  they  furnish  them  with  dorsal  ligaments.  The  tendon 
to  the  index  finger  is  accompanied  by  the  Extensor  indicis  proprius,  which  lies 
on  its  ulnar  side.  On  the  back  of  the  hand,  the  tendons  to  the  middle,  ring,  and 
little  fingers  are  connected  by  two  obliquely  placed  bands,  one  from  the  third 
tendon  passing  downward  and  lateralward  to  the  second  tendon,  and  the  other 
passing  from  the  same  tendon  downward  and  medialward  to  the  fourth.  Occa- 
sionally the  first  tendon  is  connected  to  the  second  by  a  thin  transverse  band. 

The  Extensor  digit!  quinti  proprius  (Extensor  minimi  digiti)  is  a  slender  muscle 
placed  on  the  medial  side  of  the  Extensor  digitorum  communis,  wdth  which  it  is 
generally  connected.  It  arises  from  the  common  Extensor  tendon  by  a  thin 
tendinous  slip,  from  the  intermuscular  septa  between' it  and  the  adjacent  muscles. 
Its  tendon  runs  through  a  compartment  of  the  dorsal  carpal  ligament  behind  the 
distal  radio-ulnar  joint,  then  divides  into  two  as  it  crosses  the  hand,  and  finally 
joins  the  expansion  of  the  Extensor  digitorum  communis  tendon  on  the  dorsum 
of  the  first  phalanx  of  the  little  finger. 

The  Extensor  carpi  ulnaris  lies  on  the  ulnar  side  of  the  forearm.  It  arises 
from  the  lateral  epicondyle  of  the  humerus,  by  the  common  tendon;  by  an  aponeu- 
rosis from  the  dorsal  border  of  the  ulna  in  common  with  the  Flexor  carpi  ulnaris 
and  the  Flexor  digitorum  profundus;  and  from  the  deep  fascia  of  the  forearm. 
It  ends  in  a  tendon,  which  runs  in  a  groove  between  the  head  and  the  styloid 
process  of  the  ulna,  passing  through  a  separate  compartment  of  the  dorsal  carpal 
ligament,  and  is  inserted  into  the  prominent  tubercle  on  the  ulnar  side  of  the  base 
of  the  fifth  metacarpal  bone. 

The  Anconaeus  is  a  small  triangular  muscle  which  is  placed  on  the  back  of  the 
elbow-joint,  and  appears  to  be  a  continuation  of  the  Triceps  brachii.  It  arises 
by  a  separate  tendon  from  the  back  part  of  the  lateral  epicondyle  of  the  humerus ; 
its  fibres  diverge  and  are  inserted  into  the  side  of  the  olecranon,  and  upper  fourth 
of  the  dorsal  surface  of  the  body  of  the  ulna. 

The  Deep  Group  (Fig.  526). 

Supinator.  Extensor  pollicis  brevis. 

Abductor  pollicis  longus.  Extensor  pollicis  longus. 

Extensor  indicis  proprius. 

The  Supinator  {Supinator  brevis)  (Fig.  527)  is  a  broad  muscle,  curved  around 
the  upper  third  of  the  radius.  It  consists  of  two  planes  of  fibres,  between  which 
the  deep  branch  of  the  radial  nerve  lies.  The  two  planes  arise  in  common^the 
superficial  one  by  tendinous  and  the  deeper  by  muscular  fibres — from  the  lateral 


THE  DORSAL  AST  1  BRACHIAL  MLSCLES 


545 


epicoiidyle  of  tlic  Iuuiktus;  from  tlie  radial  collateral  ligament  of  the  elbow-joint, 
and  the  annular  liuanient;  from  the  ridge  on  the  ulna,  whieh  runs  obliquely  down- 
ward from  the  dorsal  end  of  the  radial  notch;  from  the  triangular  depression  })elow 
the  notch;  and  from  a  tendinous  expansion  which  covers  the  surface  of  the  muscle. 
The  superficial  fibres  surround  the  upper  part  of  the  radius,  and  are  inserted  into 
the  lateral  edge  of  the  radial  tuberosity  and  the  oblique  line  of  the  radius,  as  low 
down  as  the  insertion  of  the  Pronator  teres.  The  upper  fibres  of  the  deeper  plane 
form  a  sling-like  fasciculus,  which  encircles  the  neck  of  the  radius  above  the  tuber- 
osity and  is  attached  to  the  back  part  of  its  medial  surface;  the  greater  part  of 
this  portion  of  the  muscle  is  inserted 
into  the  dorsal  and  lateral  surfaces 
of  the  body  of  the  radius,  midway 
between  the  oblique  line  and  the  head 
of  the  bone. 

The  Abductor  pollicis  longus  (Ex- 
tensor OSS.  nietacarpi  poUicis)  lies  im- 
mediately below  the  Supinator  and 
is  sometimes  united  with  it.  Is 
arises  from  the  lateral  part  of  the 
dorsal  surface  of  the  body  of  the  ulna 
below  the  insertion  of  the  Anco- 
naeus,  from  the  interosseous  mem- 
brane, and  from  the  middle  third  of 
the  dorsal  surface  of  the  body  of  the 
radius.  Passing  obliquely  downward 
and  lateralward,  it  ends  in  a  tendon, 
which  runs  through  a  groove  on  the 
lateral  side  of  the  lower  end  of  the 
radius,  accompanied  by  the  tendon 
of  the  Extensor  pollicis  brevis,  and 
is  inserted  into  the  radial  side  of  the 
base  of  the  first  metacarpal  bone. 
It  occasionally  gives  ofi^  two  slips 
near  its  insertion:  one  to  the  greater 
multangular  bone  and  the  other  to  . 
blend  with  the  origin  of  the  Abduc- 
tor pollicis  brevis. 

The  Extensor  pollicis  brevis  (Ex- 
tensor primi  internodii  pollicis)  lies 
on  the  medial  side  of,  and  is-  closely 
connected  with,  the  Abductor  pollicis 
longus.  It  arises  from  the  dorsal  surface  of  the  body  of  the  radius  below  that 
muscle,  and  from  the  interosseous  membrane.  Its  direction  is  similar  to  that  of 
the  Abductor  pollicis  longus,  its  tendon  passing  through  the  same  groove  on  the 
lateral  side  of  the  lower  end  of  the  radius,  to  be  inserted  into  the  base  of  the  first 
phalanx  of  the  thumb. 

The  Extensor  pollicis  longus  {Extensor  secundi  internodii  pjollicis)  is  much  larger 
than  the  preceding  muscle,  the  origin  of  which  it  partly  covers.  It  arises  from 
the  lateral  part  of  the  middle  third  of'  the  dorsal  surface  of  the  body  of  the  ulna 
below  the  origin  of  the  Abductor  pollicis  longus,  and  from  the  interosseous  mem- 
brane. It  ends  in  a  tendon,  which  passes  through  a  separate  compartment  in  the 
dorsal  carpal  ligament,  lying  in  a  narrow,  oblique  groove  on  the  back  of  the  lower 
end  of  the  radius.  It  then  crosses  obliquely  the  tendons  of  the  Extensores  carpi 
radialis  longus  and  brevis,  and  is  separated  from  the  Extensor  brevis  pollicis  by  a 
35 


Lateral  epicondyle 

Radial  collateral  Itg. 

Annular  ligament 

Deep  branch  of  radial 
nerve 


Intewsseous  recurrent 
art. 


Deep  branch  of  radial 

nerve 
Dorsal  interosseous 

art. 


Fig.  527. — The  Supinator. 


546  MYOLOGY 

triangular  interval,  in  which  the  radial  artery  is  found;  and  is  finally  inserted  into 
the  base  of  the  last  phalanx  of  the  thumb.  The  radial  artery  is  crossed  by  the 
tendons  of  the  Abductor  pollicis  longus  and  of  the  Extensores  pollicis  longus  and 
brevis. 

The  Extensor  indicis  proprius  (Extensor  hidicls)  is  a  narrow,  elongated  muscle, 
placed  medial  to,  and  parallel  with,  the  preceding.  It  arises,  from  the  dorsal  sur- 
face of  the  body  of  the  ulna  below  the  origin  of  the  Extensor  pollicis  longus,  and 
from  the  interosseous  membrane.  Its  tendon  passes  under  the  dorsal  carpal 
ligament  in  the  same  compartment  as  that  which  transmits  the  tendons  of  the 
Extensor  digitorum  communis,  and  opposite  the  head  of  the  second  metacarpal 
bone,  joins  the  ulnar  side  of  the  tendon  of  the  Extensor  digitorum  communis 
which  belongs  to  the  index  finger. 

Nerves. — The  Brachioradialis  is  supplied  by  the  fifth  and  sixth,  the  Extensores  carpi  radialis 
longus  and  brevis  by  the  sixth  and  seventh,  and  the  Aijconaeus  by  the  seventh  and  eighth  cervical 
nerves,  through  the  radial  nerve;  the  remaining  muscles  are  innervated  through  the  deep  radial 
nerve,  the  Supinator  being  supplied  by  the  sixth,  and  aU  the  other  muscles  by  the  seventh  cervical. 

Actions. — The  muscles  of  the  lateral  and  dorsal  aspects  of  the  forearm,  which  comprise  all 
the  Extensor  muscles  and  the  Supinator,  act  upon  the  forearm,  wrist,  and  hand;  they  are  the 
du'ect  antagonists  of  the  Pronator  and  Flexor  muscles.  The  Anconaeus  assists  the  Triceps  in 
extending  the  forearm.  The  Brachioradiahs  is  a  flexor  of  the  elbow-joint,  but  only  acts  as  such 
when  the  movement  of  flexion  has  been  initiated  by  the  Biceps  brachii  and  Brachiahs.  The 
action  of  the  Supinator  is  suggested  by  its  name;  it  assists  the  Biceps  in  bringing  the  hand  into 
the  supine  position.  The  Extensor  carpi  radialis  longus  extends  the  wrist  and  abducts  the  hand. 
It  may  also  assist  in  bending  the  elbow-joint;  at  all  events  it  serves  to  fix  or  steady  this  articula- 
tion. The  Extensor  carpi  radialis  brevis  extends,  the  wrist,  and  may  also  act  sHghtly  as  an  abductor 
of  the  hand.  The  Extensor  carpi  ulnaris  extends  the  wrist,  but  when  acting  alone  inclines  the 
hand  toward  the  ulnar  side;  by  its  continued  action  it  extends  the  elbow-joint.  The  Extensor 
digitorima  communis  extends  the  phalanges,  then  the  wrist,  and  finally  the  elbow.  It  acts  prin- 
cipally on  the  proximal  phalanges,  the  middle  and  terminal  phalanges  being  extended  mainly 
by  the  Interossei  and  Lumbricales.  It  tends  to  separate  the  fingers  as  it  extends  them.  The 
Extensor  digiti  quinti  proprius  extends  the  Little  finger,  and  by  its  continued  action  assists  in 
extending  the  wrist.  It  is  owing  to  this  muscle  that  the  little  finger  can  be  extended  or  pointed 
while  the  others  are  flexed.  The  chief  action  of  the  Abductor  poUicis  longus  is  to  carry  the  thumb 
laterally  from  the  palm  of  the  hand.  By  its  continued  action  it  helps  to  extend  and  abduct  the 
wrist.  The  Extensor  poUicis  brevis  extends  the  proximal  phalanx,  and  the  Extensor  poUicis 
longus  the  terminal  phalanx  of  the  thumb;  by  their  continued  action  they  help  to  extend  and 
abduct  the  wrist.  The  Extensor  indicis  proprius  extends  the  index  finger,  and  by  its  continued 
action  assists  in  extending  the  wrist. 

Applied  Anatomy. — The  tendons  of  the  Abductor  longus  and  Extensors  of  the  thxmib  are  hable 
to  become  strained,  and  their  sheaths  inflamed  {tenosynovitis)  after  excessive  exercise,  producing 
a  sausage-shaped  swelling  along  the  course  of  the  tendons  and  giving  a  pecuhar  grating  sensation 
to  the  touch  when  the  muscles  are  put  in  action. 

Paralysis  of  the  Extensor  muscles  of  the  wrists  and  fingers,  with  its  resulting  "wrist  drop," 
is  common  in  acute  or  chronic  lead  poisoning.  The  Brachioradiahs  usually  escapes  in  these 
cases,  unless  the  muscles  of  the  upper  arm  are  paralyzed  also.  Usually  the  different  Extensor 
muscles  are  unequally  affected;  thus  the  thumb,  or  index  or  httle  finger,  may  be  but  slightly 
impUcated,  and  may  recover  rapidly  while  the  Extensors  of  the  other  fingers  or  the  wrist  remain 
powerless.  Some  paresis  is  often  shown  by  the  Flexors  of  the  fingers  also,  these  muscles  being 
thrown  into  a  state  of  tremor  whenever  extension  of  the  fingers  is  attempted.  Atrophy  often 
foUows  paralysis  in  lead  poisoning. 

VI.     THE   MUSCLES    AND    FASCIA    OF   THE    HAND. 

The  muscles  of  the  hand  are  subdivided  into  three  groups:  (1)  those  of  the 
thumb,  which  occupy  the  radial  side  and  produce  the  thenar  eminence ;  (2)  those 
of  the  little  finger,  which  occupy  the  ulnar  side  and  give  rise  to  the  hypothenar 
eminence;  (3)  those  in  the  middle  of  the  palm  and  between  the  metacarpal  bones. 

Dissection  (Fig.  518). — Make  a  transverse  incision  across  the  front  of  the  wrist,  and  a  second 
across  the  heads  of  the  metacarpal  bones;  connect  the  two  by  a  vertical  incision  in  the  middle 
Mne,  and  continue  it  through  the  centre  of  the  middle  finger.  The  volar,  transverse,  and  dorsal 
carpal  hgaments  and  the  palmar  aponeurosis  should  then  be  dissected. 


THE  MUSCLES  AND  FASCI/E  OF  THE  HAND 


547 


Volar  Carpal  Ligament  (Ugamcntinu  carpi  volare). — The  volar  carpal  ligament 
is  the  thickeiu'd  hand  of  antihraehial  fascia  which  extends  from  the  radius  to  the 
ulna  over  the  Flexor  tendons  as  thev  enter  the  wrist. 


Median  nerve 
Palmaris  longus 
Flex.  foil.  long. 
Flex.  carp.  rod. 
Radial  artery 


Ahd.  jmU.  long. 
Ext.  poll  brev. 

Ext.  carp.  rnd.  long. 


Flexor  dig.  sublimit 

Ulnar  artery 
I     Ulnar  nerve 


Fle.T.  carp.  idn. 


Flex.  dig.  profundus 


E.vt.  carp.  rad.  hiev  ~       j 1 1 "V        \  ^^^-  ca»'P-  uln. 

Ext  poll  long  \        \  \        Distal  ladio-ulnar  artic. 

E.vt.  indicia,  prop.       1  Ext.  dig.  quinti  prop. 

Ext.  dig.  commun. 
Fig.  528. — Transverse  section  across  distal  ends  of  radius  and  ulna. 


Transverse  Carpal  Ligament  {ligamentum  carpi  transversum;  anterior  annular 
ligament)  (Figs.  528,  529). — The  transverse  carpal  ligament  is  a  strong,  fibrous 
band,  which  arches  over  the  carpus,  converting  the  deep  groove  on  the  front  of 
the  carpal  bones  into  a  tunnel,  through  which  the  Flexor  tendons  of  the  digits 
and  the  median  nerve  pass.     It  is  attached,  medially,  to  the  pisiform  and  the 

Median  nerve    Transverse  carpal  ligament 
Flex.  poll.  long.    \     \   Palmaris  longus 
Flex,  carpi  rad.      \     \    \  Flex.  dig.  sublimis 

Muscles  of  tliuml       \      \\\\  //  Ulnar  art.  a7id  nerve 

_^^^_ ^       ^     ^     11--     ^ ,t Muscles  of  little  finger 

Abd.  poll.  long.  ^         *       \     \     i    i  z^-i         /-» 

Ext.  poll.  brev. 


Flex.  dig.  profundus 


Ext.  carp.  rad.  long.  ^  \, 
Radial  artery 


Ext.  carp.  rad.  brev. 

Ext.  poll.  long. 


Ext.  carp.  uln. 
Ext.  dig.  quinti  prop. 


Ext.  dig.  communis 
Ext.  indicis  prop. 

Fig.  529. — Transverse  section  across  the  wrist  and  digits. 


hamulus  of  the  hamate  bone;  laterally,  to  the  tuberosity  of  the  navicular,  and  to 
the  medial  part  of  the  volar  surface  and  the  ridge  of  the  greater  multangular.  It 
is  continuous,  above,  with  the  volar  carpal  ligament;  and  below,  with  the  palmar 
aponeurosis.  It  is  crossed  by  the  ulnar  vessels  and  nerve,  and  the  cutaneous 
branches  of  the  median  and  ulnar  nerves.    At  its  lateral  end  is  the  tendon  of  the 


548 


MYOLOGY 


Flexor  carpi  radialis,  which  Hcs  in  the  groove  on  the  greater  multangular  between 
the  attachments  of  the  ligament  to  the  bone.  On  its  volar  surface  the  tendons  of 
the  Palmaris  longus  and  Flexor  carpi  ulnaris  are.  partly  inserted:  below,  it  gives 
origin  to  the  short  muscles  of  the  thumb  and  little  finger 


Sheaths  of  terminal 
parts  of  Flexores 
digitorum 


Muscles  of  the 
eminence 


Sheath  of  Flexor 
poUicis  longus 

Sheath  of  Flexor  carpi 
radialis 


JIuscles  of  hypo- 
ihenar  erainence 


Coiiunon  sheath  of 
/     Flexo)  es  digitorum 
subli/iiis  and 
piofuiidus 


Uxor  carpi  ulnaris 


Fig.  530. — The  mucous  sheaths  of  the  tendons  on  the  front  of  the  wrist  and  digits. 


The  Mucous  Sheaths  of  the  Tendons  on  the  Front  of  the  Wrist. — Two  sheaths  envelop 
the  tendons  as  they  pass  beneath  the  transverse  carpal  ligament,  one  for  the 
Flexores  digitorum  sublimis  and  profundus,  the  other  for  the  Flexor  pollicis 
longus  (Fig.  530).  They  extend  into  the  forearm  for  about  2.5  cm.  above  the 
transverse  carpal  ligament,  and  occasionally  communicate  with  each  other  under 


THE  MUSCLES  AXD  EASCLE  OF  THE  HAXD 


549 


the  ligament.  The  sheath  which  surrounds  the  Flexores  digitorum  extends  down- 
ward about  half-way  along  the  metacarpal  bones,  where  it  ends  in  blind  diverticula 
around  the  tendons  to  the  index,  middle,  and  ring  fingers.  It  is  prolonged  on 
the  tendons  to  the  little  finger   and  usually  communicates   with   the  mucous 


7 AM.  poll.  long. 


J. —  Ext.  carp.  rod.  long. 

T Ejrt.  carp.  rad.  brev. 


Fig.  531. — The  mucous  sheaths  of  the  tendons  on  the  back  of  the  wriii. 

sheath  of  these  tendons.  The  sheath  of  the  tendon  of  the  Flexor  pollicis  longus 
is  continued  along  the  thumb  as  far  as  the  insertion  of  the  tendon.  The  mucous 
sheaths  enveloping  the  terminal  parts  of  the  tendons  of  the  Flexores  digitorum 
have  been  described  on  page  oAi). 


550  MYOLOGY 

Dorsal  Carpal  Ligament  {ligamentum  carpi  dorsale;  posterior  annular  ligament) 
(Figs.  528,  529).— The  dorsal  carpal  ligament  is  a  strong,  fibrous  band,  extending 
obliquely  downward  and  medialward  across  the  back  of  the  wrist,  and  consisting 
of  part  of  the  deep  fascia  of  the  back  of  the  forearm,  strengthened  by  the  addition 
of  some  transverse  fibres.  It  is  attached,  medially,  to  the  styloid  process  of  the  ulna 
and  to  the  triangular  and  pisiform  bones;  laterally,  to  the  lateral  margin  of  the 
radius;  and,  in  its  passage  across  the  wrist,  to  the  ridges  on  the  dorsal  surface  of 
the  radius. 

The  Mucous  Sheaths  of  the  Tendons  on  the  Back  of  the  Wrist. — Between  the  dorsal 
carpal  ligament  and  the  bones  six  compartments  are  formed  for  the  passage  of 
tendons,  each  compartment  having  a  separate  mucous  sheath.  One  is  found  in 
each  of  the  following  positions  (Fig.  531) :  (1)  on  the  lateral  side  of  the  styloid  pro- 
cess, for  the  tendons  of  the  Abductor  pollicis  longus  and  Extensor  pollicis  brevis; 
(2)  behind  the  styloid  process,  for  the  tendons  of  the  Extensores  carpi  radialis 
longus  and  brevis;  (3)  about  the  middle  of  the  dorsal  surface  of  the  radius,  for  the 
tendon  of  the  Extensor  pollicis  longus;  (4)  to  the  medial  side  of  the  latter,  for  the 
tendons  of  the  Extensor  digitorum  communis  and  Extensor  indicis  proprius;  (5) 
opposite  the  interval  between  the  radius  and  ulna,  for  the  Extensor  digiti  quinti 
proprius;  (6)  between  the  head  and  styloid  process  of  the  ulna,  for  the  tendon  of 
the  Extensor  carpi  idnaris.  The  sheaths  lining  these  compartments  extend  from 
above  the  dorsal  carpal  ligament ;  those  for  the  tendons  of  Abductor  pollicis  longus, 
Extensor  brevis  pollicis,  Extensores  carpi  radialis,  and  Extensor  carpi  ulnaris 
stop  immediately  proximal  to  the  bases  of  the  metacarpal  bones,  while  the  sheaths 
for  Extensor  communis  digitorum,  Extensor  indicis  proprius,  and  Extensor  digiti 
quinti  proprius  are  prolonged  to  the  junction  of  the  proximal  and  intermediate 
thirds  of  the  metacarpus. 

Palmar  Aponeurosis  {aponeurosis  palmaris;  palmar  fascia)  (Fig.  532).^ — The 
palmar  aponeurosis  invests  the  muscles  of  the  palm,  and  consists  of  central,  lateral, 
and  medial  portions. 

The  central  portion  occupies  the  middle  of  the  palm,  is  triangular  in  shape,  and 
of  great  strength  and  thickness.  Its  apex  is  continuous  with  the  lower  margin 
of  the  transverse  carpal  ligament,  and  receives  the  expanded  tendon  of  the  Pal- 
maris longus.  Its  base  divides  below  into  four  slips,  one  for  each  finger.  Each 
slip  gives  off  superficial  fibres  to  the  skin  of  the  palm  and  finger,  those  to  the  palm 
joining  the  skin  at  the  furrow  corresponding  to  the  metacarpophalangeal  articula- 
tions, and  those  to  the  fingers  passing  into  the  skin  at  the  transverse  fold  at  the 
bases  of  the  fingers.  The  deeper  part  of  each  slip  subdivides  into  two  processes, 
which  are  inserted  into  the  fibrous  sheaths  of  the  Flexor  tendons.  From  the  sides 
of  these  processes  offsets  are  attached  to  the  transverse  metacarpal  ligament. 
By  this  arrangement  short  channels  are  formed  on  the  front  of  the  heads  of  the 
metacarpal  bones;  through  these  the  Flexor  tendons  pass.  The  intervals  between 
the  four  slips  transmit  the  digital  vessels  and  nerves,  and  the  tendons  of  the  Lum- 
bricales.  At  the  points  of  division  into  the  slips  mentioned,  numerous  strong, 
transverse  fasciculi  bind  the  separate  processes  together.  The  central  part  of  the 
palmar  aponeurosis  is  intimately  bound  to  the  integument  by  detise  fibroareolar 
tissue  forming  the  superficial  palmar  fascia,  and  gives  origin  by  its  medial  margin 
to  the  Palmaris  brevis.  It  covers  the  superficial  volar  arch,  the  tendons  of  the 
Flexor  muscles,  and  the  branches  of  the  median  and  ulnar  nerves;  and  on  either 
side  it  gives  off  a  septum,  which  is  continuous  with  the  interosseous  aponeurosis, 
and  separates  the  intermediate  from  the  collateral  groups  of  muscles. 

The  lateral  and  medial  portions  of  the  palmar  aponeurosis  are  thin,  fibrous  layers, 
which  cover,  on  the  radial  side,  the  muscles  of  the  ball  of  the  thumb,  and,  on  the 
ulnar  side,  the  muscles  of  the  little  finger;  they  are  continuous  with  the  central 
portion  and  with  the  fascia  on  the  dorsum  of  the  hand. 


THE  MUSCLES  AND  FA  SOLE  OF  THE  HAND 


551 


The  Superficial  Transverse  Ligament  of  the  Fingers  is  a  thin  bund  of  transverse 
fascicuH  (Fig.  5;)2) ;  it  stretches  across  the  roots  of  the  four  fingers,  and  is  closely 
attached  to  the  skin  of  the  ck>fts,  and  mechally  to  the  fifth  metacarpal  bone, 
forming  a  sort  of  rudimentary  web.  Beneath  it  the  (hgital  vessels  and  nerves 
pass  to  their  destinations. 


Proper  digital  artery  and  nerve 


Uhmr  artery  and  nerve 


Fig.  532. — The  palmar  aponeurosis. 

Applied  Anatomy.— The  palmar  aponeurosis  is  liable  to  undergo  contraction,  producmg  a 
very  inconvenient  deformity,  known  as  Duptiytren's  contraction.  The  ring  and  little  fingers 
are  most  frequently  imphcated,  but  the  others  may  also  be  involved.  The  proximal  phalanx  is 
flexed  and  cannot  be  straightened,  and  the  two  distal  phalanges  become  similarly  flexed  as  the 

Owing  to  their  constant  exposure  to  injury  and  septic  influences,  the  fingers  are  very  hable 
to  become  the  seat  of  serious  inflammatory  mischief.  To  this  inflammation  the  term  -paronychia 
or  whitloiu  is  given,  and  the  affection  may  assume  various  degrees  of  seventy.  In  the  mildest 
cases  the  disease  is  confined  to  the  superficial  layer  of  the  skin,  and  suppm-ation  takes  place 
beneath  it.  This  is  known  as  subcuticular  paronychia,  and  is  a  comparatively  simple  condition, 
for  an  incision  through  the  epidermis  wiU  at  once  reheve  it.  The  only  comphcation  is  that  the 
pus  may  burrow  under  the  nail,  causing  increased  pain.  A  more  severe  condition  is  the  paronychia 
cellulosa,  in  which  the  pulp  of  the  end  of  the  finger  is  involved.  This  is  attended  with  intense 
thi'obbing  pain,  owing  to  the  fact  that  the  inflamed  area  is  covered  by  thick  and  often  horny 
epitheUum,  especially  when  the  disease  occurs  in  the  laboring  classes,  as  it  so  frequently  does. 
In  these  cases,  unless  a  timely  incision  is  made,  the  inflammation  is  hable  to  involve  the. perios- 
teum coA-ering  the  phalanx,  and  subperiosteal  paronychia  is  set  up,  which  is  followed  by  necrosis 


552 


MYOLOGY 


of  a  part  or  the  whole  of  the  ungual  phalanx.  In  other  cases,  the  inflammation  maj'  involve 
the  theca  of  the  Flexor  tendons,  and  a  thecal  paronychia  may  result.  The  inflammation  then 
rapidly  spreads  up  the  sheath;  but  the  extent  will  depend  upon  the  particular  digit  involved. 
From  the  description  of  the  Flexor  sheaths  given  above,  it  will  be  evident  that  inflammation 
of  the  mucous  sheaths  of  the  thumb  and  little  finger  may  prove  a  far  more  formidable  affection 
than  that  of  the  other  three  digits,  because  the  sheaths  of  these  two  digits  communicate  with  the 
large  mucous  sheath  which  surrounds  the  Flexor  tendons  (p.  548),  and  the  inflammation  may 
extend  into  the  palm  of  the  hand  and  beneath  the  transverse  carpal  ligament  into  the  forearm. 

In  order  to  relieve  these  conditions,  free  and  early  incisions  are  necessary,  and  must  be  made 
with  discrimination,  in  order  to  avoid  wounding  important  structures.  In  the  pulp  of  the  finger — 
i.  e.,  over  the  distal  phalanx — the  incision  should  be  made  in  the  middle  hne  and  down  to  the  bone. 
In  the  rest  of  the  finger,  the  incision  should  be  made  in  the  middle  line  over  the  phalanges,  and 
not  over  the  interphalangeal  joints.  In  the  palm  of  the  hand,  incisions  may  be  made  either  on 
the  distal  or  proximal  side  of  the  superficial  volar  arch.  On  the  distal  side  the  incisions  should 
be  made  over  the  metacarpal  bones,  preferably  those  of  the  index  and  middle  finger.  On  the 
proximal  side,  the  safest  line  of  incision  is  along  the  radial  side  of  the  hypothenar  eminence, 
between  the  ulnar  artery  and  nerve  medially,  and  the  median  nerve  laterally.  When  suppura- 
tion has  extended  under  the  transverse  carpal  ligament,  and  incisions  are  required  in  the  fore- 
arm, the  positions  in  which  they  should  be  made  are  over  the  tendons  of  the  Flexor  digitorum 
sublimis,  between  the  median  nerve  and  the  ulnar  artery,  and  over  the  tendon  of  the  Flexor 
poUicis  longus,  between  the  radial  artery  and  the  tendon  of  the  Flexor  carpi  radiahs. 

Chronic  inflammation  of  the  common  flexor  sheath  is  occasionally  met  with,  constituting  a 
disease  known  as  compound  palmar  ganglion;  it  presents  an  hour-glass  outline,  with  a  swelling 
in  front  of  the  wrist  and  another  in  the  palm  of  the  hand,  and  a  constriction,  corresponding  to 
the  transverse  carpal  Ugament,  between  the  two.  The  fluid  can  be  forced  from  the  one  swelling 
to  the  other  under  the  ligament,  and  when  this  is  done,  a  creaking  sensation  is  sometimes  per- 
ceived, from  the  presence  of  "melon-seed"  bodies  in  the  interior  of  the  gangUon. 

1.  The  Lateral  Volar  Muscles  (Figs.  533,  534). 

Abductor  pollicis  brevis.  Flexor  pollicis  brevis. 

Opponens  pollicis.  Adductor  pollicis  (obliquus) . 

Adductor  pollicis  (transversus). 


Pisomefacarpal  liq. 


Fig.  533. — The  muscles  of  the  thumb. 


The  Abductor  pollicis  brevis  {Abductor  pollicis)  is  a  thin,  flat  muscle,  placed 
immediately  beneath  the  integument.  It  arises  from  the  transverse  carpal  liga- 
ment, the  tuberosity  of  the  navicular,  and  the  ridge  of  the  greater  multangular, 


THE  LATERAL  VOLAR  MUSCLES  553 

frequently  by  two  distinct  slips.  Runnino-  laterahvard  and  downward,  it  is 
inserted  by  a  thin,  flat  tendon  into  the  racHal  side  of  the  base  of  the  first  phalanx 
of  the  thumb  and  the  capsule  of  the  metacari)ophalanf2;eal  articulation. 

The  Opponens  pollicis  is  a  small,  triangular  muscle,  placed  beneath  the  pre- 
ceding. It  arises  from  the  ridge  on  the  greater  multangular  and  from  the  trans- 
verse carpal  ligament,  passes  downward  and  laterahvard,  and  is  inserted  into  the 
whole  length  of  the  metacarpal  bone  of  the  thumb  on  its  radial  side. 


Fig.  534. — The  muscles  of  the  left  hand.     Palmar  surface. 

The  Flexor  pollicis  brevis  consists  of  two  portions,  lateral  and  medial.    The 
lateral  and  more  superficial  portion  arises  from  the  lower  border  of  the  transverse 


554  MYOLOGY 

carpal  ligament  and  the  lower  part  of  the  ridge  on  the  greater  multangular  bone; 
it  passes  along  the  radial  side  of  the  tendon  of  the  Flexor  pollicis  longus,  and, 
becoming  tendinous,  is  inserted  into  the  radial  side  of  the  base  of  the  first  phalanx 
of  the  thumb;  in  its  tendon  of  insertion  there  is  a  sesamoid  bone.  The  medial 
and  deeper  portion  of  the  muscle  is  very  small,  and  arises  from  the  Ulnar  side  of  the 
first  metacarpal  bone  between  the  Adductor  pollicis  (obliquus)  and  the  lateral 
head  of  the  first  Interosseous  dorsalis,  and  is  inserted  into  the  ulnar  side  of  the  base 
of  the  first  phalanx  with  the  Adductor  pollicis  (obliquus).  The  medial  part  of 
the  Flexor  brevis  pollicis  is  sometimes  described  as  the  first  Interosseous  volaris. 

The  Adductor  pollicis  (obliquus)  {Adductor  obliquus  iJolUcis)  arises  by  several 
slips  from  the  capitate  bone,  the  bases  of  the  second  and  third  metacarpals,  the 
intercarpal  ligaments,  and  the  sheath  of  the  tendon  of  the  Flexor  carpi  radialis. 
From  this  origin  the  greater  number  of  fibres  pass  obliquely  downward  and  con- 
verge to  a  tendon,  which,  uniting  with  the  tendons  of  the  medial  portion  of  the 
Flexor  pollicis  brevis  and  the  transverse  part  of  the  Adductor,  is  inserted  into 
the  ulnar  side  of  the  base  of  the  first  phalanx  of  the  thumb,  a  sesamoid  bone 
being  present  in  the  tendon.  A  considerable  fasciculus,  however,  passes  more 
obliquely  beneath  the  tendon  of  the  Flexor  pollicis  longus  to  join  the  lateral  portion 
of  the  Flexor  brevis  and  the  Abductor  pollicis  brevis. 

The  Adductor  pollicis  (transversus)  {Adductor  transversus  jjollicis)  (Fig.  533) 
is  the  most  deeply  seated  of  this  group  of  muscles.  It  is  of  a  triangular  form 
arising  by  a  broad  base  from  the  lower  two-thirds  of  the  volar  surface  of  the 
third  metacarpal  bone;  the  fibres  converge,  to  be  inserted  with  the  medial  part  of 
the  Flexor  pollicis  brevis  and  the  Adductor  pollicis  (obliquus)  into  the  ulnar  side 
of  the  base  of  the  first  phalanx  of  the  thumb. 

Nerves. — The  Abductor  brevis,  Opponens,  and  lateral  head  of  the  Flexor  poUicis  brevis  are 
supphed  by  the  sixth  and  seventh  cervical  nerves  through  the  median  nerve;  the  medial  head 
of  the  Flexor  brevis,  and  the  Adductor,  by  the  eighth  cervical  through  the  ulnar  nerve. 

Actions. — The  Abductor  poUicis  brevis  draws  the  thumb  forward  in  a  plane  at  right  angles 
to  that  of  the  pahn  of  the  hand.  The  Abductor  poUicis  is  the  opponent  of  this  muscle,  and  approxi- 
mates the  thumb  to  the  palm.  The  Opponens  poUicis  flexes  the  metacarpal  bone,  i.  e.,  draws 
it  medialward  over  the  palm;  the  Flexor  poUicis  brevis  flexes  and  adducts  the  proximal  phalanx. 

2.  The  Medial  Volar  Muscles  (Figs.  533,  534). 

Palmaris  brevis.  Flexor  digiti  quinti  brevis. 

Abductor  digiti  quinti.  Opponens  digiti  quinti. 

The  Palmaris  brevis  is  a  thin,  quadrilateral  muscle,  placed  beneath  the  integu- 
ment of  the  ulnar  side  of  the  hand.  It  arises  by  tendinous  fasciculi  from  the 
transverse  carpal  ligament  and  palmar  aponeurosis;  the  fleshy  fibres  are  inserted 
into  the  skin  on  the  ulnar  border  of  the  palm  of  the  hand. 

The  Abductor  digiti  quinti  {Abductor  minimi  digiti)  is  situated  on  the  ulnar 
border  of  the  palm  of  the  hand.  It  arises  from  the  pisiform  bone  and  from  the 
tendon  of  the  Flexor  carpi  ulnaris,  and  ends  in  a  flat  tendon,  which  divides  into  two 
slips;  one  is  inserted  into  the  ulnar  side  of  the  base  of  the  first  phalanx  of  the  little 
finger;  the  other  into  the  ulnar  border  of  the  aponeurosis  of  the  Extensor  digiti 
quinti  proprius.  » 

The  Flexor  digiti  quinti  brevis  {Flexor  brevis  minimi  digiti)  lies  on  the  same 
plane  as  the  preceding  muscle,  on  its  radial  side.  It  arises  from  the  convex  surface 
of  the  hamulus  of  the  hamate  bone,  and  the  volar  surface  of  the  transverse  carpal 
ligament,  and  is  inserted  into  the  ulnar  side  of  the  base  of  the  first  phalanx  of  the 
little  finger.  It  is  separated  from  the  Abductor,  at  its  origin,  by  the  deep  branches 
of  the,  ulnar  artery  and  nerve.  This  muscle  is  sometimes  wanting;  the  Abductor 
is  then,  usually,  of  large  size. 


THE  IXTEUMEDIATE  MUSCLES 


555 


Tlie  Opponens  digiti  quinti  (Opponens  minimi  digiti)  (Fig.  533)  is  of  a  tri- 
angular t'orin,  aiul  i)lace(l  iinmediately  beneath  the  preceding  muscles.  It  arises 
from  the  convexity  of  the  hamulus  of  the  hamate  bone,  and  contiguous  portion 
of  the  transverse  carpal  ligament;  it  is  inserted  into  the  whole  length  of  the  meta- 
carpal bone  of  the  little  finger,  along  its  ulnar  margin. 

Nerves. — All  the  muscles  of  this  group  are  supplied  by  the  eighth  cervical  nerve  through  the 
ulnar  nerve. 

Actions. — The  Abductor  and  Flexor  digiti  quinti  brevis  abduct  the  little  finger  from  the  ring 
finger  and  assist  in  flexing  the  proximal  phalanx.  The  Opponens  digiti  quinti  draws  forward 
the  fifth  metacarpal  bone,  so  as  to  deepen  the  hollow  of  the  palm.  The  Palmaris  brevis  corrugates 
the  skin  on  the  ulnar  side  of  the  palm. 


3.  The  Intermediate  Muscles. 


Lumbricales. 


Interossei. 


The  Lumbricales  (Fig.  534)  are  four  small  fleshy  fasciculi,  associated  with  the 
tendons  of  the  Flexor  digitorum  profundus.  The  first  and  second  arise  from  the 
radial  sides  and  volar  surfaces  of  the  tendons  of  the  index  and  middle  fingers 
respectively;  the  third,  from  the  contiguous  sides  of  the  tendons  of  the  middle  and 
ring  fingers;  and  the  fourth,  from  the  contiguous  sides  of  the  tendons  of  the  ring 
and  little  fingers.  Each  passes  to  the  radial  side  of  the  corresponding  finger,  and 
opposite  the  metacarpophalangeal  articulation  is  inserted  into  the  tendinous 
expansion  of  the  Extensor  digitorum  communis  covering  the  dorsal  aspect  of  the 
finger. 


Fig.  535. — The  Interossei  dorsales  of  left  hand. 


Fig.  536. — The  Interossei  volares  of  left  hand 


The  Interossei  (Figs.  535,  536)  are  so  named  from  occupying  the  intervals 
between  the  metacarpal  bones,  and  are  divided  into  two  sets,  a  dorsal  and  a  volar. 

The  Interossei  dorsales  (Dorsal  interossei)  are  four  in  number,  and  occupy  the 
intervals  between  the  metacarpal  bones.  They  are  bipenniform  muscles,  each  arising 
by  two  heads  from  the  adjacent  sides  of  the  metacarpal  bones,  but  more  exten- 
sively from  the  metacarpal  bone  of  the  finger  into  which  the  muscle  is  inserted. 
They  are  inserted  into  the  bases  of  the  first  phalanges  and  into  the  aponeuroses 


556  MYOLOGY 

of  the  tendons  of  the  Extensor  digitonim  comnuinis.  Between  the  double  origin 
of  each  of  these  muscles  is  a  narrow  triangular  interval;  through  the  first  of  these 
the  radial  artery  passes;  through  each  of  the  other  three  a  i)erf()rating  branch  from 
the  deep  volar  arch  is  transmitted. 

The  first  or  Abductor  indicis  is  larger  than  the  others.  It  is  flat,  triangular  in 
form,  and  arises  by  two  heads,  separated  by  a  fibrous  arch  for  the  passage  of  the 
radial  artery  from  the  dorsum  to  the  palm  of  the  hand.  The  lateral  head  arises 
from  the  proximal  half  of  the  ulnar  border  of  the  first  metacarpal  bone;  the  medial 
head,  from  almost  the  entire  length  of  the  radial  border  of  the  second  metacarpal 
bone;  the  tendon  is  inserted  into  the  radial  side  of  the  index  finger.  The  second 
and  third  are  inserted  into  the  middle  finger,  the  former  into  its  radial,  the  latter 
into  its  ulnar  side.    The  fourth  is  inserted  into  the  ulnar  side  of  the  ring  finger. 

The  Interossei  volares  (Palmar  inter ossei),  three  in  number,  are  smaller  than  the 
Interossei  dorsales,  and  placed  upon  the  volar  surfaces  of  the  metacarpal  bones, 
rather  than  betw^een  them.  Each  arises  from  the  entire  length  of  the  metacarpal 
bone  of  one  finger,  and  is  inserted  into  the  side  of  the  base  of  the  first  phalanx  and 
aponeurotic  expansion  of  the  Extensor  communis  tendon  to  the  same  finger. 

The  first  arises  from  the  ulnar  side  of  the  second  metacarpal  bone,  and  is  inserted 
into  the  same  side  of  the  first  phalanx  of  the  index  finger.  The  second  arises  from 
the  radial  side  of  the  fourth  metacarpal  bone,  and  is  inserted  into  the  same  side 
of  the  ring  finger.  The  third  arises  from  the  radial  side  of  the  fifth  metacarpal 
bone,  and  is  inserted  into  the  same  side  of  the  little  finger.  From  this  account 
it  may  be  seen  that  each  finger  is  provided  with  two  Interossei,  with  the  exception 
of  the  little  finger,  in  which  the  Abductor  takes  the  place  of  one  of  the  pair. 

As  already  mentioned  (p.  554),  the  medial  head  of  the  Flexor  pollicis  brevis  is 
sometimes  described  as  the  Interosseus  volaris  primus. 

Nerves. — The  two  lateral  Lumbricales  are  supplied  by  the  sixth  and  seventh  cervical  nerves, 
through  the  third  and  fourth  digital  branches  of  the  median  nerve;  the  two  medial  Lumbricales 
and  all  the  Interossei  are  suppUed  by  the  eighth  cervical  nerve,  through  the  deep  palmar  branch 
of  the  ulnar  nerve.    The  third  Lumbricahs  frequently  receives  a  twig  from  the  median. 

Actions. — The  Interossei  volares  adduct  the  fingers  to  an  imaginary  line  drawn  longitudinally 
through  the  centre  of  the  middle  finger;  and  the  Interossei  dorsales  abduct  the  fingers  from  that 
line.  In  addition  to  this  the  Interossei,  in  conjunction  with  the  Lumbricales,  flex  the  first 
phalanges  at  the  metacarpophalangeal  joints,  and  extend  the  second  and  third  phalanges  in 
consequence  of  their  insertions  into  the  expansions  of  the  Extensor  tendons.  The  Extensor 
digitorum  communis  is  beheved  to  act  almost  entirely  on  the  first  phalanges. 

Applied  Anatomy. — In  considering  the  actions  of  the  various  muscles  upon  fractures  of  the 
upper  extremity,  the  most  common  forms  of  injury  have  been  selected  both  for  illustration  and 
description. 

Fracture  of  the  middle  of  the  clavicle  (Fig.  537)  is  usually  attended  with  considerable  displace- 
ment of  the  lateral  fragment,  which  is  drawn  downward  and  medialward,  and  at  the  same  time 
rotated,  so  that  its  lateral  end  is  carried  forward  and  its  medial  end  backward. 

The  displacement  is  produced  as  follows:  the  lateral  fragment  is  drawn  downward  by  the 
weight  of  the  arm,  the  Trapezius  not  being  able  to  support  this.  It  is  drawn  medialioard  by  the 
Subclavius  and  Pectoralis  minor,  possibly  assisted  by  the  Pectoralis  major  and  Latissimus  dorsi; 
and  is  rotated  on  an  axis  drawn  through  its  own  centre  by  the  Serratus  anterior,  which  causes 
the  scapula  to  rotate  on  the  wall  of  the  chest,  and  carries  the  acromion  and  the  end  of  the  lateral 
fragment  of  the  clavicle  forward,  and  so  carries  the  medial  end  of  the  lateral  portion  backward. 
The  causes  of  displacement  having  been  ascertained,  it  is  easy  to  apply  the  appropriate  treat- 
ment. The  lateral  fragment  is  to  be  drawn  lateralward,  and,  together  with  the  scapula,  raised 
to  a  level  with  the  medial  fragment,  and  retained  in  that  position. 

In  fracture  of  the  acromial  end  of  the  clavicle,  between  the  conoid  and  trapezoid  hgaments, 
only  slight  displacement  occurs,  as  these  ligaments,  from  their  oblique  insertion,  serve  to  hold 
both  portions  of  the  bone  in  apposition.  Fracture,  also,  of  the  sternal  end,  medial  to  the  costo- 
clavicular hgament,  is  attended  with  only  slight  displacement,  this  hgament  serving  to  retain 
the  fragments  in  close  apposition. 

Fracture  of  the  acromion  is  usually  caused  by  violence  appUed  to  the  upper  and  lateral  part 
of  the  shoulder.  There  is  great  displacement;  the  lateral  fragment  being  drawn  downward  by 
the  weight  of  the  arm,  and  rotated  forward  and  medialward,  so  that  it  forms  a  right  angle  with  the 
rest  of  the  bone. 


THE  INTERMEDIATE  ^MUSCLES 


557 


Fracture  of  the  surgical  neck  of  the  humerus  (Fig.  538)  is  very  common.  It  is  attended  with 
considerable  displacement,  and  its  ai)poarances  correspond  somewhat  with  those  of  dislocation 
of  the  head  of  the  humerus  into  the  axilla.  The  upper  fragment  remains  in  its  place  under  the 
coracoacromial  ligament;  the  lower  is  drawn  medialward  by  the  Pectoralis  major,  Latissimus 
dorsi,  and  Teres  major;  and  the  humerus  is  thrown  obliquely  from  the  side  of  the  chest  by  the 
Deltoideus,  and  occasionally  elevated  so  as  to  cause  the  upper  end  of  the  lower  fragment  to 
project  beneath  and  in  front  of  the  coracoid  process.  The  deformity  is  reduced  by  fixing  the 
shoulder,  and  drawing  the  arm  lateralward  and  downward.  To  counteract  the  opposing  muscles, 
and  to  keep  the  fragments  in  position,  a  cone-shaped  pad  should  be  placed  in  the  axilla,  and  the 
arm  bandaged  to  the  side  bj^  a  broad  roller  passed  around  the  chest  in  such  a  manner  that  the 
elbow  is  carried  slightly  forward,  so  as  to  throw  the  upper  end  of  the  lower  fragment  backward 
and  lateralward  toward  the  head  of  the  bone.  The  whole  is  then  covered  with  a  carefully  moulded 
gutta-percha  or  poroplastic  shoulder  cap. 


Fig.  5.37. — Fracture  of  the  middle  of  the  clavicle. 


Fig.  538.- 


-Fracture  of  the  surgical  neck  of  the 
humerus. 


In  fracture  of  the  body  of  the  humerus  below  the  insertion  of  the  Pectoralis  major,  Latissimus 
dorsi,  and  Teres  major,  and  above  the  insertion  of  the  Deltoideus,  there  is  also  considerable 
deformity,  the  upper  fragment  being  drawn  medialward  by  the  first-mentioned  muscles,  and  the 
lower  fragment  upward  and  lateralward  by  the  Deltoideus.  Shortening  of  the  Umb  results,  with 
a  considerable  prominence  at  the  seat  of  fracture,  from  the  fractured  ends  of  the  bone  riding  over 
one  another,  especially  if  the  fracture  take  place  in  an  oblique  direction.  The  fragments  may  be 
brought  into  apposition  by  extension  from  the  elbow,  and  retained  in  that  position  by  adopting 
the  same  means  as  in  the  preceding  injury. 

In  fracture  of  the  body  of  the  kmnerus  immediately  below  the  insertion  of  the  Deltoideus  the 
amount  of  deformity  depends  greatly  upon  the  direction  of  the  fracture.  If  it  occur  in  a  trans- 
verse direction,  only  shght  displacement  takes  place,  the  upper  fragment  being  drawn  a  httle 
forward;  but  in  obUque  fracture,  the  combined  actions  of  the  Biceps  brachii  and  BrachiaUs  in 
front  and  the  Triceps  brachii  behind  draw  upward  the  lower  fragment,  causing  it  to  ghde  over 
the  upper,  either  backward  or  forward,  according  to  the  direction  of  the  fracture.  Simple  exten- 
sion reduces  the  deformity,  and  the  apphcation  of  a  shoulder  cap  and  splints  to  the  arm  wiU 
retain  the  fragments  in  apposition. 

Fracture  of  the  humerus  (Fig.  539)  immediately  above  the  condyles  deserves  very  attentive 
consideration,  as  the  general  appearances  correspond  somewhat  with  those  produced  by  separa- 
tion of  the  epiphysis  of  the  humerus,  and  with  those  of  dislocation  of  the  radius  and  ulna  back- 
ward. If  the  direction  of  the  fracture  is  obhque,  from  above,  downward  and  forward,  the  lower 
fragment  is  drawn  upward  by  the  BrachiaUs  and  Biceps  brachii  in  front,  and  the  Triceps  brachii 
behind;  and  at  the  same  time  is  drawn  backward  behind  the  upper  fragment  by  the  Triceps  brachii. 
This  fracture  may  be  diagnosticated  from  dislocation,  by  the  increased  mobility,  the  existence 
of  crepitus,  and  the  fact  that  the  deformity  is  remedied  by  extension,  but  is  reproduced  on  the 


558 


MYOLOGY 


discontinuance  of  it.  The  age  of  the  patient  is  of  importance  in  distinguishing  this  form  of  injurj' 
from  separation  of  the  epiphysis.  In  some  cases  where  the  injury  has  been  produced  by  falls  on 
the  elbow,  the  lower  fragment  is  drawTi  upward  and  forward,  causing  a  considerable  prominence 
in  front,  the  upper  fragment  projecting  backward  beneath  the  tendon  of  the  Triceps  brachii. 

In  fracture  of  the  olecranon  (Fig.  540)  the  detached  fragment  is  displaced  upward,  by  the 
action  of  the  Triceps  brachii,  from  1  to  5  cm.;  the  prominence  of  the  elbow  is  consecjuently  lost, 
and  a  deep  hollow  is  felt  at  the  back  part  of  the  joint,  which  is  much  increased  on  flexing  the 
limb.  The  patient  at  the  same  time  loses,  more  or  less,  the  power  of  extending  the  forearm. 
The  treatment  consists  in  wiring  the  fragments  together;  but  if  for  some  reason  this  operation 
is  not  desirable,  they  should  be  approximated  by  strapping  or  a  figure-of-eight  bandage,  and  the 
arm  put  up  in  an  extended  position  in  order  to  relax  the  Triceps  brachii.  Massage  and  passive 
movements  must  be  employed  early,  for  fear  of  ankylosis.  Union,  when  wiring  is  not  resorted 
to,  is  usually  fibrous. 


Fig.  539. — Fracture  of  the  humerus  above  the  condyles. 


Fig.  540. — Fracture  of  the  olecranon. 


In  fracture  of  the  radius  below  the  insertion  of  the  Biceps  brachii,  but  above  the  insertion 
of  the  Pronator  teres,  the  upper  fragment  is  strongly  supinated  by  the  Biceps  brachii  and  Supi- 
nator, and  at  the  same  time  drawn  forward  and  flexed  by  the  Biceps  brachii;  the  lower  fragment 
is  pronated  and  drawn  toward  the  ulna  by  both  Pronators.  Thus  there  is  extreme  displacement 
with  very  little  deformity.  In  treating  such  a  fracture  the  arm  must  be  put  up  in  a  position  of 
supination,  otherwise  union  will  take  place  with  great  impairment  of  the  movements  of  the 
hand.    In  fractm-es  of  the  radius  below  the  insertion  of  the  Pronator  teres  (Fig.  541),  the  upper 

fragment  is  drawn  upward  by  the  Biceps  brachii 
and  medialward  by  the  Pronator  teres,  into  a 
position  midway  between  pronation  and  supina- 
tion, and  a  degree  of  fulness  in  the  upper  half 
of  the  forearm  is  thus  produced.  The  lower 
fragment  is  drawn  downward  toward  the  ulna 
and  pronated  by  the  Pronator  quadratus;  at 
the  same  time,  the  Brachioradialis,  by  elevating 
the  styloid  process,  into  which  it  is  inserted,  wiU 
serve  to  depress  the  upper  end  of  the  lower  frag- 
ment still  more  toward  the  ulna.  In  order  to 
relax  the  opposing  muscles  the  forearm  should  be 
bent,  and  the  hmb  placed  in  a  position  midway 
between  pronation  and  supination;  the  fractiire  is  then  easily  reduced  by  extension  from  the 
wrist  and  elbow.  WeU-padded  splints  should  be  applied  on  both  sides  of  the  forearm  from  the 
elbow  to  the  wrist. 

In  fracture  of  the  body  of  the  ulna  the  upper  fragment  retains  its  usual  position,  but  the  lower 
is  drawn  toward  the  radius  by  the  Pronator  quadratus,  producing  a  well-marked  depression  at 
the  seat  of  fracture,  and  some  fulness  on  the  dorsal  and  volar  smiaces  of  the  forearm.  The  frac- 
ture is  easily  reduced  by  extension  from  the  wrist  and  elbow.  The  forearm  should  be  flexed, 
and  placed  in  a  position  midway  between  pronation  and  supination,  and  well-padded  sphnts 
apphed  from  the  elbow  to  the  ends  of  the  fingers. 


Fig.  541. — Fracture  of  the  body  of  the  radius. 


THE  MUSCLES  AND  FASCLE  OF  THE  ILIAC  REGION 


559 


In  fracture  of  tlie  bodies  of  the  racUtis  and  ulna  loqelher,  the  lower  fragments  are  drawn  upward, 
sometimes  forward,  sometimes  backward,  according  to  the  direction  of  the  fracture,  by  the 
combined  actions  of  the  Flexor  and  Extensor  muscles,  producing  a  degree  of  fulness  on  either  the 
dorsal  or  volar  surface  of  the  forearm.  At  the  same  time  the  lower  fragments  are  drawn  into 
contact  by  the  Pronator  quadratus,  the  radius  being  in  a  state  of  pronation.  The  upper  frag- 
ment of  the  radius  is  drawn  upward  and  medialward  by  the  Biceps  brachii  and  Pronator  teres 
to  a  higher  level  than  the  ulna;  the  upper  portion  of  the  ulna  is  slightly  elevated  by  the  Brachialis. 
The  fracture  may  be  reduced  by  extension  from  the  wrist  and  elbow,  and  the  forearm  should 
be  placed  in  the  same  jiosition  as  in  fracture  of  the  ulna. 


Fig.  542. — Fracture  of  the  lower  end  of  the  radius. 

In  fracture  of  the  lower  end  of  the  radius  (Fig.  542)  the  displacement  produced  is  very  con- 
siderable, and  bears  some  resemblance  to  dislocation  of  the  carpus  backward,  from  which  it 
should  be  carefully  distinguished.  The  lower  fragment  is  displaced  backward  and  upward, 
but  this  displacement  is  due  to  the  force  of  the  blow  driving  the  portion  of  the  bone  into  this 
position,  and  not  to  any  muscular  influence.  The  upper  fragment  projects  forward,  often  lacerat- 
ing the  substance  of  the  Pronator  quadratus,  and  is  drawn  by  this  muscle  into  close  contact  with 
the  lower  end  of  the  ulna,  causing  a  projection  on  the  volar  surface  of  the  forearm,  immediately 
above  the  carpus,  from  the  Flexor  tendons  being  thrust  forward.  This  fracture  may  be  distin- 
guished from  dislocation  by  the  relative  positions  of  the  styloid  processes  of  the  radius  and  ulna 
(the  former  of  which  is  displaced  upward  in  fracture)  and  by  the  deformity  being  removed  on 
making  sufficient  extension,  when  crepitus  may  be  occasionally  detected.  The  age  of  the  patient 
will  assist  in  determining  whether  the  injury  is  fracture  or  separation  of  the  epiphysis.  The 
treatment  consists  in  flexing  the  forearm,  and  making  powerful  extension  from  the  wrist  and 
elbow,  depressing  at  the  same  time  the  radial  side  of  the  hand,  and  retaining  the  parts  in  a  posi- 
tion of  adduction  toward  the  ulnar  side. 


THE  MUSCLES  AND  FASCIA  OF  THE  LOWER  EXTREMITY. 


The  muscles  of  the  lower  extremity  are  subdivided  into  groups  corresponding 
with  the  different  re2;ions  of  the  limb. 


I.  Muscles  of  the  Iliac  Region. 
II.  Muscles  of  the  Thigh. 


III.  Muscles  of  the  Leg. 

IV.  Muscles  of  the  Foot. 


I.     THE  MUSCLES  AND  FASCIA  OF  THE  ILIAC  REGION  (Fig.  543). 


Psoas  major. 


Psoas  minor. 


Iliacus. 


Dissection. — No  detailed  description  is  required  for  the  dissection  of  these  muscles.  On  the 
removal  of  the  viscera  from  the  abdomen  they  are  exposed,  covered  by  the  peritoneum  and  a 
thin  layer  of  fascia,  the  iliac  fascia. 

The  Fascia  Covering  the  Psoas  and  Iliacus  is  thin  above,  and  becomes  gradually 
thicker  below  as  it  approaches  the  inguinal  ligament. 

The  portion  covering  the  Psoas  is  thickened  above  to  form  the  medial  lumbo- 
costal arch,  which  stretches  from  the  transverse  process  of  the  first  lumbar  vertebra 
to  the  body  of  the  second.    Medially,  it  is  attached  by  a  series  of  arched  processes 


560 


MYOLOGY 


t  ^  ^SisJ.?' 


uw^^ 


W'li ' , 


I  3,2^1 


^ 


VI 


'f//^ 


rrou 


Fig.  543. 


'  / 


-Muscles  of  the  iliac  and  anterior 
femoral  regions. 


to  the  intervertebral  fihrocartilages,  and  promi- 
nent margins  of  the  bodies  of  the  vertebrae, 
and  to  the  ui)])or  i)art  of  the  sacrum;  the  inter- 
vals left,  oi)})osite  the  constricted  portions  of 
the  bodies,  transmit  the  lumbar  arteries  and 
veins  and  filaments  of  the  sympathetic  trunk. 
Laterally,  above  the  crest  of  the  ilium,  it  is 
continuous  with  the  fascia  co\'ering  the  front 
of  the  Quadratus  lumborum  (see  page  510), 
while  below  the  crest  of  the  ilium  it  is  con- 
tinuous with  the  fascia  covering  the  Iliacus, 

The  portions  investing  the  Iliacus  {fascia  iliaca; 
iliac  fascia)  is  connected,  laterally  to  the  M'hole 
length  of  the  inner  lip  of  the  iliac  crest;  and 
medially,  to  the  linea  terminalis  of  the  lesser 
pelvis,  where  it  is  continuous  with  the  peri- 
osteum. At  the  iliopectineal  eminence  it  re- 
ceives the  tendon  of  insertion  of  the  Psoas 
minor,  when  that  muscle  exists.  Lateral  to  the 
femoral  vessels  it  is  intimately  connected  to 
the  posterior  margin  of  the  inguinal  ligament, 
and  is  continuous  with  the  transversalis  fascia. 
Immediately  lateral  to  the  femoral  vessels  the 
iliac  fascia  is  prolonged  backward  and  medial- 
ward  from  the  inguinal  ligament  as  a  band, 
the  iliopectineal  fascia,  which  is  attached  to 
the  iliopectineal  eminence.  This  fascia  divides 
the  space  between  the  inguinal  ligament  and 
the  hip  bone  into  two  lacunae  or  compart- 
ments, the  medial  of  which  transmits  the 
femoral  vessels,  the  lateral  the  Psoas  major 
and  Iliacus  and  the  femoral  nerve.  Medial 
to  the  vessels  the  iliac  fascia  is  attached  to 
the  pectineal  line  behind  the  inguinal  apon- 
eurotic falx,  where  it  is  again  continuous  with 
the  transversalis  fascia.  On  the  thigh  the 
fascise  of  the  Iliacus  and  Psoas  form  a  single 
sheet  termed  the  iliopectineal  fascia.  Where 
the  external  iliac  vessels  pass  into  the  thigh,  the 
fascia  descends  behind  them,  forming  the  pos- 
terior wall  of  the  femoral  sheath.  The  portion 
of  the  iliopectineal  fascia  which  passes  behind 
the  femoral  vessels  is  also  attached  to  the 
pectineal  line  beyond  the  limits  of  the  attach- 
ment of  the  inguinal  aponeurotic  falx;  at  this 
part  it  is  continuous  with  the  pectineal  fascia. 
The  external  iliac  vessels  lie  in  front  of  the 
iliac  fascia,  but  all  the  branches  of  the  lumbar 
plexus  are  behind  it;  it  is  separated  from  the 
peritoneum  by  a  quantity  of  loose  areolar 
tissue. 

The  Psoas  major  (Psoas  viagnus)  (Fig.  543) 
is  a  long  fusiform  muscle  placed  on  the  side 
of  the  lumbar  region  of  the  vertebral  column 
and   brim  of  the  lesser  pelvis.    It  arises   (1) 


THE  MUSCLES  AND  FASCIA  OF  THE  ILIAC  REGION  561 

from  the  anterior  surfaces  of  the  liases  and  lower  liorders  of  the  transverse  processes 
of  all  the  lumbar  vertebrae;  (2)  from  the  sides  of  the  bodies  and  the  corresponding 
intervertebral  fibrocartilages  of  the  last  thoracic  and  all  the  lumbar  vertebrse 
by  five  slips,  each  of  which  is  attached  to  the  adjacent  upper  and  lower  margins 
of  two  vertebne,  and  to  the  intervertebral  fibrocartilage;  (3)  from  a  series  of 
tendinous  arches  which  extend  across  the  constricted  parts  of  the  bodies  of  the 
lumbar  vertebne  between  the  previous  slips;  the  lumbar  arteries  and  veins,  and 
filaments  from  the  sympathetic  trunk  pass  beneath  these  tendinous  arches.  The 
muscle  proceeds  downward  across  the  brim  of  the  lesser  pelvis,  and  diminishing 
gradually  in  size,  passes  beneath  the  inguinal  ligament  and  in  front  of  the  capsule 
of  the  hip-joint  and  ends  in  a  tendon;  the  tendon  receives  nearly  the  whole  of 
the  fibres  of  the  Iliacus  and  is  inserted  into  the  lesser  trochanter  of  the  femur. 
A  large  bursa  Mdiich  may  communicate  with  the  cavity  of  the  hip-joint,  separates 
the  tendon  from  the  pubis  and  the  capsule  of  the  joint. 

Relations. — In  the  abdomen  the  Psoas  major  is  in  relation  by  its  anterior  surface  with  the 
medial  lumbocostal  arch,  the  fascia  covering  the  muscle,  the  extraperitoneal  fat  and  peritoneum, 
the  kidney,  Psoas  minor,  renal  vessels,  ureter,  spermatic  vessels,  and  genitofemoral  nerve.  In 
front  of  the  right  Psoas  is  the  inferior  vena  cava  and  the  terminal  portion  of  the  ileum,  and  in 
front  of  the  left  the  iUac  colon.  By  its  posterior  surface  it  is  in  relation  with  the  transverse 
processes  of  the  lumbar  vertebrae,  and  the  Quadratus  lumborum.  The  lumbar  plexus  is  situated 
in  the  posterior  part  of  the  substance  of  the  muscle.  By  its  medial  side,  the  muscle  is  in  relation 
with  the  bodies  of  the  lumbar  vertebraj,  the  lumbar  arteries,  the  ganghated  trunk  of  the  sympa- 
thetic, and  the  lumbar  lymph  glands;  with  the  inferior  vena  cava  on  the  right,  and  the  aorta  on  , 
the  left  side,  and  along  the  brim  of  the  pelvis  with  the  external  iliac  artery. 

In  the  thigh  it  is  in  relation,  in  front,  with  the  fascia  lata;  behind,  with  the  capsule  of  the  hip- 
joint,  from  which  it  is  separated  by  a  bursa;  by  its  medial  border,  with  the  Pectineus  and  medial 
circumflex  femoral  artery,  and  also  with  the  femoral  artery,  which  sUghtly  overlaps  it;  by  its 
lateral  border,  with  the  femoral  nerve  and  Iliacus. 

The  Psoas  minor  (Psoas  parvus)  is  a  long  slender  muscle,  placed  in  front  of  the 
Psoas  major.  It  arises  from  the  sides  of  the  bodies  of  the  tw^elfth  thoracic  and  first 
lumbar  vertebrae  and  from  the  fibrocartilage  between  them.  It  ends  in  a  long 
flat  tendon  which  is  inserted  into  the  pectineal  line  and  iliopectineal  eminence, 
and,  by  its  lateral  border,  into  the  iliac  fascia.    This  muscle  is  often  absent. 

The  Iliacus  is  a  flat,  triangular  muscle,  w^hich  fills  the  iliac  fossa.  It  arises  from 
the  upper  two-thirds  of  this  fossa,  and  from  the  inner  lip  of  the  iliac  crest;  behind, 
from  the  anterior  sacroiliac  and  the  iliolumbar  ligaments,  and  base  of  the  sacrum; 
in  front,  it  reaches  as  far  as  the  anterior  superior  and  anterior  inferior  iliac  spines, 
and  the  notch  between  them.  The  fibres  converge  to  be  inserted  into  the  lateral 
side  of  the  tendon  of  the  Psoas  major,  some  of  them  being  prolonged  on  to  the  body 
of  the  femur  for  about  2.5  cm.  below  and  in  front  of  the  lesser  trochanter.^ 

Relations. — Within  the  abdomen  the  lUacus  is  in  relation  by  its  anterior  surface  with  the  ihac 
fascia,  which  separates  the  muscle  from  the  extraperitoneal  fat  and  peritoneum,  and  with  the 
lateral  femoral  cutaneous  nerve;  on  the  right  side,  with  the  cecimi;  on  the  left  side,  with  the  ihac 
colon;  by  its  posterior  surface,  with  the  iliac  fossa;  by  its  medial  border,  with  the  Psoas  major  and 
femoral  nerve. 

In  the  thigh,  it  is  in  relation,  by  its  anterior  surface,  with  the  fascia  lata.  Rectus  femoris,  Sar- 
torius,  and  profunda  femoris  artery;  behind,  with  the  capsule  of  the  hip-joint,  a  bursa  common 
to  it  and  the  Psoas  major  being  interposed. 

Nerves. — The  Psoas  major  is  suppUed  by  branches  of  the  second  and  third  lumbar  nerve; 
the  Psoas  minor  by  a  branch  of  the  first  lumbar  nerve;  and  the  Ihacus  by  branches  of  the  second 
and  third  lumbar  nerves  through  the  femoral  nerve. 

Actions. — The  Psoas  major,  acting  from  above,  flexes  the  thigh  upon  the  pelvis,  being  assisted 
by  the  Iliacus;  acting  from  below,  with  the  femur  fixed,  it  bends  the  lumbar  portion  of  the  verte- 
bral column  forward  and  to  its  own  side,  and  then,  in  conjunction  with  the  Iliacus,  tilts  the  pelvis 
forward.     When  the  muscles  of  both  sides  are  acting  from  below,  they  serve  to  maintain  the 

1  The  Psoas  major  and  iliacus  are  sometimes  regarded  as  a  single  muscle  named  the  Iliopsoas. 

36 


562  MYOLOGY 

erect  posture  by  supporting  the  vertebral  column  and  pelvis  upon  the  femora,  or  in  continued 
action  bend  the  trunk  and  pelvis  forward,  as  in  raising  the  trunk  from  the  recumbent  posture. 

The  Psoas  minor  is  a  tensor  of  the  iliac  fascia. 

Applied  Anatomy. — There  is  no  definite  septum  between  the  portions  of  fascia  covering  the 
Psoas  and  Iliacus  respectively,  and  the  fascia  is  only  connected  to  the  subjacent  muscles  by  a 
quantity  of  loose  connective  tissue.  When  an  abscess  forms  beneath  this  fascia,  as  it  is  very 
apt  to  do,  the  matter  is  contained  in  an  osseofibrous  cavity  which  is  closed  on  all  sides  within  the 
abdomen,  and  is  open  only  at  its  lower  part,  where  the  fascia  is  prolonged  over  the  muscles  into 
the  thigh. 

Abscess  within  the  sheath  of  the  Psoas  major  (psoas  abscess)  is  generally  due  to  tuberculous 
caries  of  the  bodies  of  the  lower  thoracic  or  the  lumbar  vertebraj.  When  the  disease  is  in  the 
thoracic  region,  the  matter  tracks  down  the  posterior  mediastinal  cavity  in  front  of  the  bodies 
of  the  vertebrte,  and,  passing  beneath  the  medial  lumbocostal  arch,  enters  the  sheath  of  the  Psoas, 
down  which  it  travels  as  far  as  the  pelvic  brim;  it  then  gets  beneath  the  iliac  portion  of  the  fascia, 
and  fills  up  the  iliac  fossa.  In  consequence  of  the  attachment  of  the  fascia  to  the  arcuate  Une, 
it  rarely  finds  its  way  into  the  lesser  pelvis,  but  passes  by  a  narrow  opening  under  the  inguinal 
hgament  into  the  thigh,  lateral  to  the  femoral  vessels.  It  thus  follows  that  a  psoas  abscess  may 
be  described  as  consisting  of  four  parts:  (1)  a  somewhat  narrow  channel  at  its  upper  part,  in 
the  psoas  sheath;  (2)  a  dilated  sac  in  the  iliac  fossa;  (3)  a  constricted  neck  under  the  inguinal 
ligament,  and  (4)  a  dilated  sac  in  the  upper  part  of  the  thigh.  When  the  lumbar  vertebraj  are 
the  seat  of  the  disease,  the  matter  finds  its  w^ay  directly  into  the  substance  of  the  Psoas.  The 
muscular  fibres  are  destroyed,  and  the  nerves  contained  in  the  abscess  are  isolated  and  exposed 
in  its  interior;  the  iliac  vessels  which  he  in  front  of  the  fascia  remain  intact,  and  the  peritoneum 
seldom  becomes  imphcated.  All  psoas  abscesses  do  not,  however,  pursue  this  course;  the  matter 
may  leave  the  sheath  of  the  muscle  above  the  crest  of  the  ilium,  and  tracking  backward  may  point 
in  the  loin  {lumbar  abscess);  or  it  may  point  above  the  inguinal  hgament  in  the  inguinal  region; 
or  it  may  foUow  the  course  of  the  branches  of  the  hypogastric  vessels  into  the  lesser  pelvis,  and, 
passing  through  the  greater  sciatic  foramen,  discharge  itself  on  the  back  of  the  thigh. 


n.     THE  MUSCLES  AND  FASCIA  OF  THE  THIGH. 


1.  The  Anterior  Femoral  Muscles  (Fig.  543). 


Tensor  fasciae  latae.  Quadriceps 

Sartorius.  femoris. 

Articularis  genu. 


Rectus  femoris. 
Vastus  lateralis. 
Vastus  medialis. 
Vastus  intermedins. 


Dissection. — To  expose  the  muscles  and  fasciae  in  this  region,  make  an  incision  along  the  inguinal 
ligament,  from  the  anterior  superior  spine  of  the  ilium  to  the  spine  of  the  pubis;  a  vertical  incision 
from  the  centre  of  this,  along  the  middle  of  the  thigh  to  below  the  knee-joint;  and  a  transverse 
incision  from  the  inner  to  the  outer  side  of  the  leg,  at  the  lower  end  of  the  vertical  incision.  The 
flaps  of  integument  having  been  removed,  the  superficial  and  deep  fasciae  should  be  examined. 
The  more  advanced  student  should  commence  the  study  of  this  region  by  an  examination  of  the 
anatomy  of  femoral  hernia  and  femoral  triangle,  the  incisions  for  the  dissection  of  which  are 
marked  out  in  Fig.  544. 

Superficial  Fascia. — The  superficial  fascia  forms  a  continuous  layer  over  the  whole 
of  the  thigh;  it  consists  of  areolar  tissue  containing  in  its  meshes  much  fat,  and  may 
be  separated  into  two  or  more  layers,  between  which  are  found  the  superficial 
vessels  and  nerves.  It  varies  in  thickness  in  different  parts  of  the  limb;  in  the  groin 
it  is  thick,  and  the  two  layers  are  separated  from  one  another  by  the  superficial 
inguinal  lymph  glands,  the  great  saphenous  vein,  and  several  smaller  vessels. 
The  superficial  layer  is  continuous  above  with  the  superficial  fascia  of  the  abdomen. 
The  deep  layer  of  the  superficial  fascia  is  a  very  thin,  fibrous  stratum,  best  marked 
on  the  medial  side  of  the  great  saphenous  vein  and  below  the  inguinal  ligament. 
It  is  placed  beneath  the  subcutaneous  vessels  and  nerves  and  upon  the  surface  of  the 
fascia  lata.  It  is  intimately  adherent  to  the  fascia  lata  a  little  below  the  inguinal 
ligament.  It  covers  the  fossa  ovalis  (saphenous  opening),  being  closely  united  to 
its  circumference,  and  is  connected  to  the  sheath  of  the  femoral  vessels.     The 


THE  ANTERIOR  FEMORAL  MUSCLES 


563 


/.  Dissection  of 
femoral  hernia, 

I  and  femoral  or 
Scarpa's  tri- 
angle. 


^  \3.  Front  of  thigh. 


portion  of  fascia  {'o^■erino•  this  fossa  is  perforated  by  the  great  saphenous  vein  and 
hy  numerous  blood  and  lyin])hati('  ^•essels,  lience  it  has  been  termed  the  fascia 
cribrosa,  the  oi)enini>;s  for  these  \'essels  ha\ini;-  been  Hkened  to  the  lioles  in  a  sieve. 
A  hirge  subcutaneous  bursa  is  found  in  the  sui)erficial  fascia  over  the  patella. 

Deep  Fascia. — The  deep  fascia  of  the  thigh  is  named,  from  its  great  extent, 
the  fascia  lata;  it  constitutes  an  investment  for  the  whole  of  this  region  of  the  limb, 
but  \  aries  in  thic-kness  in  diti'erent  j)arts.  Thus,  it  is  thicker  in  the  ui)i)er  and  lateral 
part  of  the  thigh,  where  it  receives  a  fibrous  exi)ansion  from  the  Glutaeus  maximus, 
and  where  the  Tensor  fasciae  latae  is  inserted  between  its  layers.;  it  is  very  thin 
behind  and  at  the  upper  and  medial  part,  where  it  covers  the  Adductor  muscles, 
antl  again  becomes  stronger  around  the  knee, 
receiving  fibrous  expansions  from  the  tendon 
of  the  Biceps  femoris  laterally,  from  the  Sarto- 
rius  medially,  and  from  the  Quadriceps  femoris 
in  front.  The  fascia  lata  is  attached,  above  and 
behind,  to  the  back  of  the  sacrum  and  coccyx; 
laterally,  to  the  iliac  crest;  in  front,  to  the 
inguinal  ligament,  and  to  the  superior  ramus  of 
the  pubis ;  and  medially,  to  the  inferior  ramus  of 
the  pubis,  to  the  inferior  ramus  and  tuberosity 
of  the  ischium,  and  to  the  lower  border  of  the 
sacrotuberous  ligament.  From  its  attachment 
to  the  iliac  crest  it  passes  down  over  the  Glu- 
taeus medius  to  the  upper  border  of  the  Glutaeus 
maximus,  where  it  splits  into  two  layers,  one 
passing  superficial  to  and  the  other  beneath  this 
muscle ;  at  the  lower  border  of  the  muscle  the 
two  layers  reunite.  Laterally,  the  fascia  lata 
receives  the  greater  part  of  the  tendon  of  inser- 
tion of  the  Glutaeus  maximus,  and  becomes 
proportionately  thickened.  The  portion  of  the 
fascia  lata  attached  to  the  front  part  of  the  iliac 
crest,  and  corresponding  to  the  origin  of  the 
Tensor  fasciae  latae,  extends  down  the  lateral 
side  of  the  thigh  as  two  layers,  one  superficial  to 
and  the  other  beneath  this  muscle;  at  the  lower 
end  of  the  muscle  these  two  layers  unite  and 
form  a  strong  band,  having  first  received  the 
insertion  of  the  muscle.  This  band  is  continued 
downward,  under  the  name  of  the  iliotibial  band 
{tractus  iliotibialis)  and  is  attached  to  the  lateral 
condyle  of  the  tibia.  The  part  of  the  iliotibial 
band  which  lies  beneath  the  Tensor  fasciae  latae 
is  prolonged  upward  to  join  the  lateral  part  of 

the  capsule  of  the  hip-joint.  Below,  the  fasciae  lata  is  attached  to  all  the  promi- 
nent points  around  the  knee-joint,  viz.,  the  condyles  of  the  femur  and  tibia,  and 
the  head  of  the  fibula.  On  either  side  of  the  patella  it  is  strengthened  by  transverse 
fibres  from  the  lower  parts  of  the  Vasti,  which  are  attached  to  and  support  this 
bone.  Of  these  the  lateral  are  the  stronger,  and  are  continuous  with  the  iliotibial 
band.  The  deep  surface  of  the  fascia  lata  gives  off  two  strong  intermuscular 
septa,  which  are  attached  to  the  whole  length  of  the  linea  aspera  and  its  prolon- 
gations above  and  below;  the  lateral  and  stronger  one,  which  extends  from  the 
insertion  of  the  Glutaeus  maximus  to  the  lateral  condyle,  separates  the  Vastus 
lateralis  in  front  from  the  short  head  of  the  Biceps  femoris  behind,  and  gives 


3.  Front  of  leg. 


4-  Dorsum  of  foot. 


Fig.   544. — Dissection  of  lower  extremity. 
Front  view. 


564 


MYOLOGY 


partial  origin  to  these  muscles;  the  medial  and  thinner  one  separates  the  Vastus 
medialis  from  the  Adductores  and  Pectineus.  Besides  these  there  are  numerous 
smaller  septa,  separating  the  individual  muscles,  and  enclosing  each  in  a  distinct 
sheath. 

The  Fossa  Ovalis  (saphenous  opening)  (Fig.  545). — At  the  upper  and  medial 
part  of  the  thigh,  a  little  below  the  medial  end  of  the  inguinal  ligament,  is  a  large 
oval-shaped  aperture  in  the  fascia  lata;  it  transmits  the  great  saphenous  vein, 
and  other,  smaller  vessels,  and  is  termed  the  fossa  ovalis.  The  fascia  cribrosa, 
which  is  pierced  by  the  structures  passing  through  the  opening,  closes  the  aperture 
and  must  be  removed  to  expose  it.  The  fascia  lata  in  this  part  of  the  thigh  is 
described  as  consisting  of  a  superficial  and  a  deep  portion. 


Fig.   545. — The  fossa  ovalis. 


The  superficial  portion  of  the  fascia  lata  is  the  part  on  the  lateral  side  of  the  fossa 
ovalis.  It  is  attached,  laterally,  to  the  crest  and  anterior  superior  spine  of  the  ilium, 
to  the  whole  length  of  the  inguinal  ligament,  and  to  the  pectineal  line  in  con- 
junction with  the  lacunar  ligament.  From  the  tubercle  of  the  pubis  it  is  reflected 
downward  and  lateralward,  as  an  arched  margin,  the  falciform  margin,  forming 
the  lateral  boundary  of  the  fossa  ovalis;  this  margin  overlies  and  is  adherent  to  the 
anterior  layer  of  the  sheath  of  the  femoral  vessels:  to  its  edge  is  attached  the  fascia 
cribrosa.  The  upward  and  medial  prolongation  of  the  falciform  margin  is  named 
the  superior  cornu;  its  downward  and  medial  prolongation,  the  inferior  cornu.  The 
latter  is  well-defined,  and  is  continuous  behind  the  great  saphenous  vein  with  the 
pectineal  fascia. 


THE  ANTEIilOR  FK MORAL  MUSCLES  565 

The  deep  portion  is  situated  on  the  medial  side  of  the  fossa  ovalis,  and  at  the 
lower  margin  of  the  fossa  is  eontinuous  with  the  su])erfieial  portion;  traeed  upward, 
it  covers  the  Fectineus,  Ad(hictor  longus,  and  Gracilis,  and,  passing  behind  the 
sheath  of  the  femoral  vessels,  to  which  it  is  closely  united,  is  continuous  with  the 
iliopectineal  fascia,  and  is  attached  to  the  pectineal  line. 

From  this  descrij)tion  it  may  be  observed  that  the  superficial  portion  of  the 
fascia  lata  lies  in  front  of  the  femoral  vessels,  and  the  deep  portion  behind  them, 
so  that  an  apparent  aperture  exists  between  the  two,  through  which  the  great 
saphenous  passes  to  join  the  femoral  vein. 

The  Tensor  fasciae  latae  (Tensor  fasciae  femoris)  arises  from  the  anterior  part 
of  the  outer  lip  of  the  iliac  crest;  from  the  outer  surface  of  the  anterior  superior 
iliac  spine,  and  part  of  the  outer  border  of  the  notch  below  it,  between  the  Glutaeus 
medius  and  Sartorius;  and  from  the  deep  surface  of  the  fascia  lata.  It  is  inserted 
between  the  two  layers  of  the  iliotibial  band  of  the  fascia  lata  about  the  junction 
of  the  middle  and  upper  thirds  of  the  thigh. 

The  Sartorius,  the  longest  muscle  in  the  body,  is  narrow  and  ribbon-like;  it 
arises  by  tendinous  fibres  from  the  anterior  superior  iliac  spine  and  the  upper  half 
of  the  notch  below  it.  It  passes  obliquely  across  the  upper  and  anterior  part  of 
the  thigh,  from  the  lateral  to  the  medial  side  of  the  limb,  then  descends  vertically, 
as  far  as  the  medial  side  of  the  knee,  passing  behind  the  medial  condyle  of  the  femur 
to  end  in  a  tendon.  This  curves  obliquely  forward  and  expands  into  a  broad  apon- 
eurosis, which  is  inserted,  in  front  of  the  Gracilis  and  Semitendinous,  into  the  upper 
part  of  the  medial  surface  of  the  body  of  the  tibia,  nearly  as  far  forward  as  the 
anterior  crest.  The  upper  part  of  the  aponeurosis  is  curved  backward  over  the 
upper  edge  of  the  tendon  of  the  Gracilis  so  as  to  be  inserted  behind  it.  An  offset, 
from  its  upper  margin,  blends  with  the  capsule  of  the  knee-joint,  and  another 
from  its  lower  border,  with  the  fascia  on  the  medial  side  of  the  leg. 

Relations. — The  relations  of  this  muscle  to  the  femoral  artery  are  important,  as  it  constitutes 
the  chief  guide  in  tying  the  vessel.  In  the  upper  third  of  the  thigh  it  forms  the  lateral  side  of  a 
triangular  space,  the  femoral  (Scarpa's)  triangle,  the  medial  side  of  which  is  formed  by  the  medial 
border  of  the  Adductor  longus,  and  the  base,  directed  upward,  by  the  inguinal  hgament;  the 
femoral  artery  passes  perpendicularly  through  the  middle  of  this  space  from  its  base  to  its  apex. 
In  the  middle  third  of  the  thigh  the  femoral  artery  is  contained  in  the  adductor  ( Hunter's)  canal, 
on  the  roof  of  which  the  Sartorius  lies. 

The  Quadriceps  femoris  (Quadriceps  extensor)  includes  the  four  remaining 
muscles  on  the  front  of  the  thigh.  It  is  the  great  extensor  muscle  of  the  leg,  forming 
a  large  flesh}^  mass  which  covers  the  front  and  sides  of  the  femur.  It  is  subdi^•ided 
into  separate  portions,  which  have  received  distinctive  names.  One  occupying 
the  middle  of  the  thigh,  and  connected  above  w^ith  the  ilium,  is  called  from  its 
straight  course  the  Rectus  femoris.  The  other  three  lie  in  immediate  connection 
with  the  body  of  the  femur,  which  they  cover  from  the  trochanters  to  the  condyles. 
The  portion  on  the  lateral  side  of  the  femur  is  termed  the  Vastus  lateralis;  that 
covering  the  medial  side,  the  Vastus  medialis ;  and  that  in  front,  the  Vastus 
intermedius. 

The  Rectus  femoris  is  situated  in  the  middle  of  the  front  of  the  thigh ;  it  is  fusi- 
form in  shape,  and  its  superficial  fibres  are  arranged  in  a  bipenniform  manner, 
the  deep  fibres  running  straight  down  to  the  deep  aponeurosis.  It  arises  by  two 
tendons:  one,  the  anterior  or  straight,  from  the  anterior  inferior  iliac  spine;  the 
other,  the  posterior  or  reflected,  from  a  groove  above  the  brim  of  the  acetabulum. 
The  two  unite  at  an  acute  angle,  and  spread  into  an  aponeurosis  which  is  prolonged 
downward  on  the  anterior  surface  of  the  muscle,  and  from  this  the  muscular  fibres 
arise.  The  muscle  ends  in  a  broad  and  thick  aponeurosis  which  occupies  the  lower 
two-thirds  of  its  posterior  surface,  and,  gradually  becoming  narrowed  into  a  flat- 
tened tendon,  is  inserted  into  the  base  of  the  patella. 


566  MYOLOdY 

The  Vastus  lateralis  (yastus  externus)  is  the  largest  part  of  the  Quadriceps 
femoris.  It  arises  by  a  broad  aponeurosis,  which  is  attached  to  the  upper  part  of 
the  intertrochanteric  line,  to  the  anterior  and  inferior  borders  of  the  greater  tro- 
chanter, to  the  lateral  lip  of  the  gluteal  tuberosity,  and  to  the  upper  half  of  the 
lateral  lip  of  the  linea  aspera;  this  aponeurosis  covers  the  upper  three-fourths  of 
the  muscle,  and  from  its  deep  surface  many  fibres  take  origin.  A  few  additional 
fibres  arise  from  the  tendon  of  the  Glutaeus  maximus,  and  from  the  lateral  inter- 
muscular septum  between  the  Vastus  lateralis  and  short  head  of  the  Biceps  femoris. 
The  fibres  form  a  large  fleshy  mass,  which  is  attached  to  a  strong  aponeurosis, 
placed  on  the  deep  surface  of  the  lowTr  part  of  the  muscle :  this  aponeurosis  becomes 
contracted  and  thickened  into  a  flat  tendon  inserted  into  the  lateral  border  of  the 
patella,  blending  with  the  Quadriceps  femoris  tendon,  and  giving  an  expansion  to 
the  capsule  of  the  knee-joint. 

The  Vastus  medialis  and  Vastus  intermedius  appear  to  be  inseparably  united, 
but  when  the  Rectus  femoris  has  been  reflected  a  narrow  interval  will  be  observed 
extending  upward  from  the  medial  border  of  the  patella  between  the  two  muscles, 
and  the  separation  may  be  continued  as  far  as  the  lower  part  of  the  intertrochan- 
teric line,  where,  however,  the  two  muscles  are  frequently  continuous. 

The  Vastus  medialis  {Vastus  internus)  arises  from  the  lower  half  of  the  inter- 
trochanteric line,  the  medial  lip  of  the  linea  aspera,  the  upper  part  of  the  medial 
supracondylar  line,  the  tendons  of  the  Adductor  longus  and  the  Adductor  magnus 
and  the  medial  intermuscular  septum.  Its  fibres  are  directed  downward  and  for- 
ward, and  are  chiefly  attached  to  an  aponeurosis  which  lies  on  the  deep  surface 
of  the  muscle  and  is  inserted  into  the  medial  border  of  the  patella  and  the  Quad- 
riceps femoris  tendon,  an  expansion  being  sent  to  the  capsule  of  the  knee-joint. 

The  Vastus  intermedius  (Crureus)  arises  from  the  front  and  lateral  surfaces  of  the 
body  of  the  femur  in  its  upper  two-thirds  and  from  the  lower  part  of  the  lateral 
intermuscular  septum.  Its  fibres  end  in  a  superficial  aponeurosis,  which  forms 
the  deep  part  of  the  Quadriceps  femoris  tendon. 

The  tendons  of  the  different  portions  of  the  Quadriceps  unite  at  the  lower  part  of  the  thigh, 
so  as  to  form  a  single  strong  tendon,  which  is  inserted  into  the  base  of  the  patella,  some  few  fibres 
passing  over  it  to  blend  with  the  Ugamentum  patelte.  More  properly,  the  patella  may  be  regarded 
as  a  sesamoid  bone,  developed  in  the  tendon  of  the  Quadriceps;  and  the  ligamentum  patellae, 
which  is  continued  from  the  apex  of  the  patella  to  the  tuberosity  of  the  tibia,  as  the  proper  tendon 
of  insertion  of  the  muscle,  the  medial  and  lateral  patellar  retinacula  (see  p.  439)  being  expan- 
sions from  its  borders.  A  bursa,  which  usually  communicates  with  the  cavity  of  the  knee-joint, 
is  situated  between  the  femur  and  the  portion  of  the  Quadriceps  tendon  above  the  patella;  another 
is  interposed  between  the  tendon  and  the  upper  part  of  the  front  of  the  tibia;  and  a  third,  the 
prepatellar  bursa,  is  placed  over  the  patella  itself. 

The  Articularis  genu  (Suhcrureus)  is  a  small  muscle,  usually  distinct  from  the 
Vastus  intermedius,  but  occasionally  blended  with  it;  it  arises  from  the  anterior 
surface  of  the  lower  part  of  the  body  of  the  femur,  and  is  inserted  into  the  upper 
part  of  the  synovial  membrane  of  the  knee-joint.  It  sometimes  consists  of  several 
separate  muscular  bundles. 

Nerves. — The  Tensor  fasciae  latae  is  supphed  by  the  fourth  and  fifth  lumbar  and  first  sacral 
nerves  through  the  superior  gluteal  nerve;  the  other  muscles  of  this  region,  by  the  second,  third, 
and  fourth  lumbar  nerves,  through  the  femoral  nerve. 

Actions. — The  Tensor  fasciae  latae  is  a  tensor  of  the  fascia  lata;  continuing  its  action,  the 
obhque  direction  of  its  fibres  enables  it  to  abduct  the  thigh  and  to  rotate  it  inward.  In  the  erect 
posture,  acting  from  below,  it  will  serve  to  steady  the  pelvis  upon  the  head  of  the  femur;  and 
by  means  of  the  ihotibial  band  it  steadies  the  condyles  of  the  femur  on  the  articular  surfaces  of 
the  tibia,  and  assists  the  Glutaeus  maximus  in  supporting  the  knee  in  the  extended  position. 
The  Sartorius  flexes  the  leg  upon  the  thigh,  and,  continuing  to  act,  flexes  the  thigh  upon  the, 
pelvis;  it  next  abducts  and  rotates  the  thigh  outward.  When  the  knee  is  bent,  the  Sartorius 
assists  the  Semitendinosus,  Semimembranosus,  and  PopUteus  in  rotating  the  tibia  inward.  Tak- 
ing its  fixed  point  from  the  leg,  it  flexes  the  pelvis  upon  the  thigh,  and,  if  one  muscle  acts,  assists 


THE  MKniAL  FliMORAL  MiSCLES  5()7 

in  rotating  the  pelvis.  The  Quach-iceps  fenioris  extends  the  leg  upon  the  thigh.  The  Rectus 
femoris  assists  the  Psoas  major  and  Iliacus  in  supporting  the  pelvis  and  trunk  upon  the  femur. 
It  also  assists  in  flexing  the  thigh  on  the  i)elvis,  or  if  the  thigh  be  fixed  it  will  flex  the  pelvis.  The 
Vastus  nu'dialis  draws  the  patella  medialward  as  well  as  upward. 

Applied  Anatomy. — A  few  fibres  of  the  Rectus  femoris  are  occasionally  ruptured  from  severe 
strain.  This  accident  is  especially  hable  to  occur  daring  the  games  of  football  and  baseball. 
The  patient  exi)eriences  a  sudden  i)ain  in  the  pai"t,  as  if  he  had  been  struck,  and  the  Rectus  stands 
out  as  is  felt  to  be  tense  and  rigid.  The  accident  is  often  followed  by  considerable  swelling  from, 
inflammatory  effusion.  Occasionally  the  Quadriceps  femoris  may  be  torn  away  from  its  inser- 
tion into  the  patella;  or  the  hgamentu^^  i)atellae  may  be  ruptured  about  2.5  cm.  above  the  bone. 
This  accident  is  caused  in  the  .same  manner  as  fracture  of  the  patella  by  muscular  action,  viz., 
by  a  violent  muscular  effort  to  prevent  falling  while  the  knee  is  in  a  position  of  semiflexion.  A 
distinct  gap  can  be  felt  above  the  patella,  and,  owing  to  the  retraction  of  the  muscular  fibres, 
imion  may  fail  to  take  place. 

2.  The  Medial  Femoral  Muscles. 

Gracilis.  Adductor  longus.  Adductor  magnus. 

Pectineus.  Adductor  brevis. 

Dissection. — These  muscles  are  at  once  exposed  by  removing  the  fascia  from  the  forepart 
and  inner  side  of  the  thigh.  The  Hmb  should  be  abducted,  so  as  to  render  the  muscles  tense  and 
easier  of  dissection. 

The  Gracilis  (Fig.  543)  is  the  most  superficial  muscle  on  the  medial  side  of  the 
thigh.  It  is  thin  and  flattened,  broad  above,  narrow  and  tapering  below.  It 
arises  by  a  thin  aponeurosis  from  the  anterior  margins  of  the  lower  half  of  the 
symphysis  pubis  and  the  upper  half  of  the  pubic  arch.  The  fibres  run  vertically 
downward,  and  end  in  a  rounded  tendon,  which  passes  behind  the  medial  condyle 
of  the  femur,  curves  around  the  medial  condyle  of  the  tibia,  where  it  becomes  flat- 
tened, and  is  inserted  into  the  upper  part  of  the  medial  surface  of  the  body  of  the 
tibia,  below  the  condyle.  A  few  of  the  fibres  of  the  lower  part  of  the  tendon  are 
prolonged  into  the  deep  fascia  of  the  leg.  At  its  insertion  the  tendon  is  situated 
immediately  above  that  of  the  Semitendinosus,  and  its  upper  edge  is  overlapped 
by  the  tendon  of  the  Sartorius,  with  which  it  is  in  part  blended.  It  is  separated 
from  the  tibial  collateral  ligament  of  the  knee-joint,  by  a  bursa  common  to  it  and 
the  tendon  of  the  Semitendinosus. 

The  Pectineus  (Fig.  543)  is  a  flat,  quadrangular  muscle,  situated  at  the  anterior 
part  of  the  upper  and  medial  aspect  of  the  thigh.  It  arises  from  the  pectineal  line, 
and  to  a  slight  extent  from  the  surface  of  bone  in  front  of  it,  between  the 
iliopectineal  eminence  and  tubercle  of  the  pubis,  and  from  the  fascia  covering  the 
anterior  surface  of  the  muscle;  the  fibres  pass  downward,  backward,  and  lateral- 
ward,  to  be  inserted  into  a  rough  line  leading  from  the  lesser  trochanter  to  the 
linea  aspera. 

Relations. — It  is  in  relation  by  its  anterior  surface  with  the  fascia  lata,  which  separates  it  from 
the  femoral  vessels  and  great  saphenous  vein;  by  its  posterior  surface,  with  the  capsule  of  the 
hip-joint,  the  Adductor  brevis,  Obtm-ator  externus,  and  the  anterior  branch  of  the  obturator 
nerve;  by  its  lateral  border,  with  the  Psoas  major  and  the  medial  femoral  circumflex  vessels;  by 
its  medial  border,  with  the  margin  of  the  Adductor  longus. 

The  Adductor  longus  (Fig.  546),  the  most  superficial  of  the  three  Adductores, 
is  a  triangular  muscle,  lying  in  the  same  plane  as  the  Pectineus.  It  arises  by  a 
flat,  narrow  tendon,  from  the  front  of  the  pubis,  at  the  angle  of  junction  of  the  crest 
with  the  symphysis;  and  soon  expands  into  a  broad  fleshy  belly.  This  passes 
downward,  backward,  and  lateralward,  and  is  inserted,  by  an  aponeurosis,  into  the 
linea  aspera,  between  the  Vastus  medialis  and  the  Adductor  magnus,  with  both 
of  which  it  is  usually  blended. 

Relations. — It  is  in  relation  by  its  anterior  surface  with  the  fascia  lata,  the  Sartorius, 
and,  near  its  insertion,  with  the  femoral  artery  and  vein;  by  its  posterior  surface,   with  the 


568 


MYOLOGY 


Adductores  brevis  and  magnus,  the  anterior  branch  of  the  obturator  nerve,  and  near  its 
insertion  with  the  profunda  femoris  artery  and  vein;  by  its  lateral  border,  with  the  Pectineus; 
by   its   medial   border,   with  the  Gracihs. 

The  Adductor  brevis  (Fig.  540)  is  situ- 
ated immediately  l)ehiiid  the  two  precethng 
muscles.  It  is  somewhat  triangular  in  form, 
and  arises  by  a  narrow  origin  from  the 
outer  surfaces  of  the  superior  and  inferior 
rami  of  the  pubis,  between  the  Gracilis 
and  Obturator  externus.  Its  fibres,  passing 
backward,  lateralward,  and  downward,  are 
inserted,  by  an  aponeurosis,  into  the  line 
leading  from  the  lesser  trochanter  to  the 
linea  aspera  and  into  the  upper  part  of  the 
linea  aspera,  immediately  behind  the  Pectin- 
eus and  upper  part  of  the  Adductor  longus. 

Relations. — It  is  in  relation  by  its  anterior  surface 
with  the  Pectineus,  Adductor  longus,  profunda 
femoris  artery,  and  anterior  branch  of  the  obturator 
nerve;  by  its  posterior  surface,  with  the  Adductor 
magnus,  and  posterior  branch  of  the  obturator  nerve; 
by  its  lateral  border,  with  the  medial  femoral  circum- 
flex artery,  the  Obturator  externus,  and  conjoined 
teiidon  of  the  Psoas  major  and  Iliacus;  by  its  medial 
border,  with  the  Gracilis  and  Adductor  magnus.  It 
is  pierced  near  its  insertion  by  the  second,  or  first 
and  second,  perforating  branches  of  the  profunda 
femoris  artery. 


The  Adductor  magnus  (Tig.  546)  is  a  large 
triangular  muscle,  situated  on  the  medial  side 
of  the  thigh.  It  arises  from  a  small  part 
of  the  inferior  ramus  of  the  pubis,  from  the 
inferior  ramus  of  the  ischium,  and  from  the 
outer  margin  of  the  inferior  part  of  the 
tuberosity  of  the  ischium.  Those  fibres 
which  arise  from  the  ramus  of  the  pubis  are 
short,  horizontal  in  direction,  and  are  inserted 
into  the  rough  line  leading  from  the  greater 
trochanter  to  the  linea  aspera,  medial  to  the 
Glutaeus  maximus;^  those  from  the  ramus  of 
the  ischium  are  directed  downward  and  lat- 
eralward with  different  degrees  of  obliquity, 
to  be  iiiserted,  by  means  of  a  broad  aponeu- 
rosis, into  the  linea  aspera  and  the  upper 
part  of  its  medial  prolongation  below.  The 
medial  portion  of  the  muscle,  composed 
principally  of  the  fibres  arising  from  the 
tuberosity  of  the  ischium,  forms  a  thick 
fleshy  mass  consisting  of  coarse  bundles 
which  descend  almost  vertically,  and  end 
about  the  lower  third  of  the  thigh  in  a 
rounded  tendon  which  is  inserted  into  the 
adductor  tubercle  on  the  medial  condyle  of 


Fig.  546.- 


-Deep  muscles  of  the  medial  femoral 
region. 


1  These  uppermost  fibres  are  sometimes  described  as  a  separate  muscle — the  Adductor  minimus — Trhich  is  situated 
somewhat  anterior  to  the  other  parts  of  the  muscle. 


THE  MUSCLES  OF  THE  GLUTEAL  REGION  569 

the  femur,  aiul  is  connected  by  a  fibrous  expansion  to  the  line  leading  upward 
frt)ni  tile  tubercle  to  the  linea  asi)era.  At  the  insertion  of  the  muscle,  there  is  a 
series  of  osseoa])oneurotic  ojieninos,  formed  by  tendinous  arches  attached  to  the 
bone.  The  upper  four  openings  are  small,  and  give  passage  to  the  perforating 
branches  of  the  profunda  femoris  artery.  The  lowest  is  of  large  size,  and  transmits 
the  femoral  vessels  to  the  popliteal  fossa.  *  su 

Relations. — It  is  in  relation  by  its  anterior  surface  with  the  Pectineus,  Adductores  brevis  and 
longus,  llio  femoral  and  profunda  vessels,  and  the  posterior  branch  of  the  obturator  nerve;  by 
its  posterior  surface,  with  the  sciatic  nerve,  the  Glutaeus  maximus.  Biceps  femoris,  Semitendinosus, 
and  Semimembranosus.  Its  superior  border  lies  parallel  with  the  Quadratus  femoris,  the  medial 
femoral  circumflex  artery  passing  between  them.  Its  medial  border  is  in  relation  with  the  Gracilis, 
Sartorius,  and  fascia  lata. 

Nerves. — The  three  Adductores  and  the  Gracilis  are  supplied  by  the  third  and  fourth  lumbar 
nerves  through  the  obturator  nerve;  the  Adductor  magnus  receiving  an  additional  branch  from 
the  sacral  plexus  through  the  sciatic.  The  Pectineus  is  supplied  by  the  second,  third,  and  fourth 
lumbar  nerves  through  the  femoral  nerve,  and  by  the  third  lumbar  through  the  accessory  obturator 
when  this  latter  exists.    Occasionally  it  receives  a  branch  from  the  obturator  nerve. ^ 

Actions. — -The  Pectineus  and  three  Adductores  adduct  the  thigh  powerfully;  they  are  especially 
used  in  horse  exercise,  the  sides  of  the  saddle  being  grasped  between  the  knees  by  the  contraction 
of  these  muscles.  In  consequence  of  the  obliquity  of  their  insertions  into  the  linea  aspera,  they 
rotate  the  thigh  outward,  assisting  the  external  Rotators,  and  when  the  limb  has  been  abducted, 
they  draw  it  medialward,  carrying  the  thigh  across  that  of  the  opposite  side.  The  Pectineus 
and  Adductores  brevis  and  longus  assist  the  Psoas  major  and  Ihacus  in  flexing  the  thigh  upon 
the  pelvis.  In  progression,  all  these  muscles  assist  in  drawing  forward  the  lower  limb.  The 
Gracilis  assists  the  Sartorius  in  flexing  the  leg  and  rotating  it  inward ;  it  is  also  an  adductor  of  the 
thigh.  If  the  lower  extremities  be  fixed,  these  muscles,  taking  their  fixed  points  below,  may  act 
upon  the  pelvis,  serving  to  maintain  the  body  in  an  erect  posture;  or,  if  their  action  be  continued, 
flex  the  pelvis  forward  upon  the  femur. 

Applied  Anatomy. — The  Adductor  longus  is  hable  to  be  severely  strained  in  those  who  ride 
much  on  horseback,  or  its  tendon  may  be  ruptured  by  suddenly  gripping  the  saddle.  Occasionally, 
especially  in  cavalry  soldiers,  the  tendon  becomes  ossifled,  constituting  the  rider's  hone. 

3.  The  Muscles  of  the  Gluteal  Region  (Fig.  548). 

Glutaeus  maximus.  Obturator  internus. 

Glutaeus  medius.  Gemellus  superior. 

Glutaeus  minimus.  Gemellus  inferior. 

Piriformis.  Quadratus  femoris. 
Obturator  externus. 

Dissection  (Fig.  547). — The  subject  should  be  turned  on  its  face,  a  block  placed  beneath  the 
pelvis  to  make  the  buttocks  tense,  and  the  limbs  allowed  to  hang  over  the  end  of  the  table,  with 
the  foot  inverted  and  the  thigh  abducted.  Make  an  incision  through  the  integument  along  the 
crest  of  the  ihum  to  the  middle  of  the  sacrum,  and  thence  downward  to  the  tip  of  the  coccyx, 
and  carry  a  second  incision  from  that  point  obliquely  downward  and  outward  to  the  outer  side 
of  the  thigh,  four  inches  below  the  great  trochanter.  The  portion  of  integument  included  between 
these  incisions  is  to  be  removed  in  the  direction  shown  in  the  figure. 

The  Glutaeus  maximus,  the  most  superficial  muscle  in  the  gluteal  region,  is  a 
broad  and  thick  fleshy  mass  of  a  quadrilateral  shape,  and  forms  the  prominence 
of  the  nates.  Its  large  size  is  one  of  the  most  characteristic  features  of  the  muscular 
system  in  man,  connected  as  it  is  with  the  power  he  has  of  maintaining  the  trunk 
in  the  erect  posture.  The  muscle  is  remarkably  coarse  in  structure,  being  made 
up  of  fasciculi  lying  parallel  with  one  another  and  collected  together  into  large 
bundles  separated  by  fibrous  septa.  It  arises  from  the  posterior  gluteal  line  of 
the  ilium,  and  the  rough  portion  of  bone  including  the  crest,  immediately  above 
and  behind  it ;  from  the  posterior  surface  of  the  lower  part  of  the  sacrum  and  the  ■ 

'  The  Pectineus  may  consist  of  two  incompletely  separated  strata;  the  lateral  or  dorsal  stratum,  which  is  constant, 
is  supplied  bj'  a  branch  from  the  femoral  nerve,  or  in  the  absence  of  this  branch  by  the  accessory  obturator  nerve, 
the  medial  or  ventral  stratum,  when  present,  is  supplied  by  the  obturator  nerve. — A.  M.  Paterson,  Journal  of  Anatomy 
and  Physiology,  xxvi,  43. 


570 


MYOLOGY 


side  of  the  coccyx;  from  the  aponeurosis  of  tlie  Sacrospinalis,  the  sacrotuberous 
ligament,  and  the  fascia  (gluteal  aponeurosis)  covering  the  Glutaeus  medius. 
The  fibres  are  directed  obliquely  down^vard  and  laterahvard;  those  forming  the 
upper  and  larger  portion  of  the  muscle,  together  Avith  the  superficial  fibres  of  the 
lower  portion,  end  in  a  thick  tendinous  lamina,  which  passes  across  the  greater 
trochanter,  and  is  inserted  into  the  iliotibial  band  of  the  fascia  lata;  the  deeper 
fibres  of  the  lower  portion  of  the  muscle  are  inserted  into  the  gluteal  tuberosity 
between  the  Vastus  lateralis  and  Adductor  magnus. 


Bursse. 

of  these, 


1 


1.  Dmection  of 
gluteal  region. 


S 


— Three  bursas  ai'e  usually  found  in  relation  with  the  deep  surface  of  this  muscle.    One 
of  large  size,  and  generally  multilocular,  separates  it  from  the  greater  trochanter;  a 

second,  often  wanting,  is  situated  on  the  tuberosity  of 
the  ischium;  a  third  is  found  between  the  tendon  of  the 
muscle  and  that  of  the  Vastus  laterahs. 

Relations. — The  Glutaeus  maximus  is  in  relation  by 
its  superficial  surface  with  a  thin  fascia  which  separates 
it  from  the  subcutaneous  tissue;  by  its  deep  surface,  from 
above  downward,  with  the  iUum,  sacrum,  coccy^x,  and 
sacrotuberous  hgament,  part  of  the  Glutaeus  medius, 
Piriformis,  Gemelli,  Obturator  internus,  Quadratus 
femoris,  the  tuberosity  of  the  ischium,  greater  trochanter, 
the  origins  of  the  Biceps  femoris,  Semitendinosus,  Semi- 
membranosus, and  the  Adductor  magnus.  The  super- 
ficial part  of  the  superior  gluteal  artery  reaches  the  deep 
sm-face  of  the  muscle  by  passing  between  the  Piriformis 
and  the  Glutaeus  medius;  the  inferior  gluteal  and  in- 
ternal pudendal  vessels  and  the  sciatic,  pudendal,  and 
lateral  femoral  cutaneous  nerves,  and  muscular  branches 
from  the  sacral  plexus,  issue  from  the  pelvis  below  the 
Piriformis.  The  first  perforating  artery  and  the  ter- 
minal branches  of  the  medial  circumflex  femoral  artery 
are  also  found  under  cover  of  the  lower  part  of  the 
muscle.  Its  upper  border  is  thin,  and  connected  with  the 
Glutaeus  medius  by  the  gluteal  aponeurosis.  Its  lower 
border  is  free  and  prominent,  and  is  crossed  by  the  fold 
of  the  nates. 

Dissection. — Divide  the  Glutaeus  maximus  near  its 
origin  by  a  vertical  incision  carried  from  its  upper  to 
its  lower  border;  a  cellular  interval  wiU  be  exposed, 
separating  it  from  the  Glutaeus  medius  and  Rotator 
muscles  beneath.  The  upper  portion  of  the  muscle  is 
to  be  altogether  detached,  and  the  lower  portion  tm-ned 
outward;  the  loose  areolar  tissue  filling  up  the  inter- 
space between  the  trochanter  major  and  tuberosity  of 
the  ischium  being  removed,  the  parts  already  enumer- 
ated as  exposed  by  the  removal  of  this  muscle  will  be 


3.  Back  of  thigh. 


[3  \  2.  Popliteal  space. 


4/4-  Back  of  leg. 


g   \  5.  Sole  of  foot. 


Fig.   547. — Dissection  of  lower  extremity. 
Posterior  view. 


The  Glutaeus  medius  is  a  broad,  thick,  radi- 
ating muscle,  situated  on  the  outer  surface  of 
the  pelvis.  Its  posterior  third  is  covered  by 
the  Glutaeus  maximus,  its  anterior  two-thirds 
by  the  gluteal  aponeurosis,  which  separates  it  from  the  superficial  fascia  and  in- 
tegument. It  arises  from  the  outer  surface  of  the  ilium  between  the  iliac  crest 
and  posterior  gluteal  line  above,  and  the  anterior  gluteal  line  below;  it  also  arises 
from  the  gluteal  aponeurosis  covering  its  outer  surface.  The  fibres  converge  to 
a  strong  flattened  tendon,  which  is  inserted  into  the  oblique  ridge  which  runs  down- 
ward and  forward  on  the  lateral  surface  of  the  greater  trochanter.  A  bursa 
separates  the  tendon  of  the  muscle  from  the  surface  of  the  trochanter  over  which 
it  glides. 

The  Glutaeus  minimus,  the  smallest  of  the  three  Glutaei,  is  placed  immediately 
beneath  the  preceding.    It  is  fan-shaped,  arising  from  the  outer  surface  of  the  ilium. 


THE  MUSCLES  OF  THE  (i Li  TEAL  REGION 


571 


between  the  anterior  and  inferior 
ghiteal  lines,  and  l)ehind,  from 
the  margin  of  the  greater  sciatic 
notch.  The  fibres  converge  to 
the  deep  surface  of  a  radiated 
aponeurosis,  and  this  ends  in  a 
tension  which  is  inserted  into  an 
impression  on  the  anterior  border 
of  the  greater  trochanter,  and 
gives  an  expansion  to  the  capsule 
of  the  hip-joint.  A  bursa  is 
interposed  between  the  tendon 
and  the  greater  trochanter.  Be- 
tween the  Glutaeus  medius  and 
Glutaeus  minimus  are  the  deep 
branches  of  the  superior  gluteal 
vessels  and  the  superior  gluteal 
nerve.  The  deep  surface  of  the 
Glutaeus  minimus  is  in  relation 
with  the  reflected  tendon  of  the 
Rectus  femoris  and  the  capsule 
of  the  hip-joint. 

The  Piriformis  is  a  flat  muscle, 
pyramidal  in  shape,  lying  almost 
parallel  with  the  posterior  margin 
of  the  Glutaeus  medius.  It  is 
situated  partly  within  the  pelvis 
against  its  posterior  wall,  and 
partly  at  the  back  of  the  hip- 
joint.  It  arises  from  the  front  of 
the  sacrum  by  three  fleshy  digi- 
tations,  attached  to  the  portions 
of  bone  between  the  first,  second, 
third,  and  fourth  anterior  sacral 
foramina,  and  to  the  grooves 
leading  from  the  foramina :  a  few 
fibres  also  arise  from  the  margin 
of  the  greater  sciatic  foramen, 
and  from  the  anterior  surface  of 
the  sacrotuberous  ligament.  The 
muscle  passes  out  of  the  pelvis 
through  the  greater  sciatic  fora- 
men, the  upper  part  of  which  it 
fills,  and  is  inserted  by  a  rounded 
tendon  into  the  upper  border  of 
the  greater  trochanter  behind, 
but  often  partly  blended  with, 
the  common  tendon  of  the  Ob- 
turator internus  and  Gemelli. 

Relations.  —  Within  the  ■pelvis  the 
Piriformis  is  in  relation  by  its  anterior 
surface  with  the  rectum  (especially  on 
the  left  side),  the  sacral  plexus  of 
nerves,  and  branches  of  the  hjrpogastric 
vessels;   and    by  its    posterior    surface 


Medial 

hamstring 

tendojis 

Sartor  ins 

Gracilis 

Semitendinosus 
Serni- 
membranosus 


Lateral 

liamsiring 

tendon 

Biceps 
femoris 


FiQ.  548. — Muscles  of  the  gluteal  and  posterior  femoral  regions. 


572 


MYOLOGY 


with  the  sacrum.  Outside  the  pelvis,  its  anterior  surface  is  in  contact  with  the  posterior  surface 
of  the  ischium  and  capsule  of  the  hip-joint;  and  its  posterior  surface,  with  the  Glutaeus  maxi- 
mus;  its  upper  border  is  in  relation  with  the  Glutaeus  medius,  and  the  superior  gluteal  vessels 
and  nerve;  its  lower  border,  with  the  Gemellus  superior  and  Coccygeus,  the  inferior  gluteal 
and  internal  pudendal  vessels,  and  the  sciatic,  posterior  femoral  cutaneous,  and  pudendal 
nerves,  and  muscular  branches  from  the  sacral  plexus,  passing  from  the  pelvis  in  the  interval 
between  the  two  muscles.     The  muscle  is  frequently  pierced  by  the  common  peroneal  nerve. 

Obturator  Membrane  (Fig.  549) . — The  obturator  membrane  is  a  thin  fibrous  sheet, 
which  almost  completely  closes  the  obturator  foramen.  Its  fibres  are  arranged 
in  interlacing  bundles  mainly  transverse  in  direction;  the  uppermost  bundle  is 
attached  to  the  obturator  tubercles  and  completes  the  obturator  canal  for  the  pas- 
sage of  the  obturator  vessels  and  nerve.  The  membrane  is  attached  to  the  sharp 
margin  of  the  obturator  foramen  except  at  its  lower  lateral  angle,  where  it  is  fixed 
to  the  pelvic  surface  of  the  inferior  ramus  of  the  ischium,  i.  e.,  within  the  margin. 
Both  obturator  muscles  are  connected  with  this  membrane. 


Ant,  sup.  iliac  spi'it- 


Obturator  canal 
Lacunar  ligament 
Pubic  tubercle 


Symphysis 
pubis 


Tiansverse  acetabular 
ligament 


Fig.   549. — The  obturator  membrane. 


Dissection. — The  next  muscle,  as  well  as  the  origin  of  the  Piriformis,  can  only  be  seen  when 
the  pelvis  is  divided  and  the  viscera  removed. 

The  Obturator  internus  is  situated  partly  within  the  lesser  pelvis,  and  partly 
at  the  back  of  the  hip-joint.  It  arises  from  the  inner  surface  of  the  antero-lateral 
wall  of  the  pelvis,  where  it  surrounds  the  greater  part  of  the  obturator  foramen, 
being  attached  to  the  inferior  rami  of  the  pubis  and  ischium,  and  at  the  side  to  the 
inner  surface  of  the  hip  bone  below  and  behind  the  pelvic  brim,  reaching  from  the 
upper  part  of  the  greater  sciatic  foramen  above  and  behind  to  the  obturator  fora- 
men below  and  in  front.  It  also  arises  from  the  pelvic  surface  of  the  obturator 
membrane  except  in  the  posterior  part,  from  the  tendinous  arch  which  completes  the 
canal  for  the  passage  of  the  obturator  vessels  and  nerve,  and  to  a  slight  extent  from 
the  obturator  fascia,  which  covers  the  muscle.  The  fibres  converge  rapidly  toward 
the  lesser  sciatic  foramen,  and  end  in  four  or  five  tendinous  bands,  which  are  found 


THE  MUSCLES  OF  THE  GLUTEAL  REGIOX  573 

on  the  deep  surface  of  the  muscle;  these  bands  are  reflected  at  a  right  angle  over 
the  grooved  surface  of  the  ischium  between  its  spine  and  tuberosity.  This  bony 
surface  is  covered  by  smooth  cartihige,  which  is  separated  from  the  tendon  by  a 
bursa,  and  presents  one  or  more  ridges  corresponding  with  the  furrows  between 
the  tendinous  bands.  These  bands  leave  the  pelvis  through  the  lesser  sciatic  fora- 
men and  unite  into  a  single  flattened  tendon,  which  passes  horizontally  across  the 
capsule  of  the  hiji-joint,  and,  after  receiving  the  attachments  of  the  Gemelli,  is 
inserted  into  the  forepart  of  the  medial  surface  of  the  greater  trochanter  above 
the  trochanteric  fossa.  A  bursa,  narrow  and  elongated  in  form,  is  usually  found 
between  the  tendon  and  the  capsule  of  the  hip-joint;  it  occasionally  communicates 
with  the  bursa  between  the  tendon  and  the  ischium. 

Relations. — Within  the  pelvis,  this  muscle  is  in  relation,  bj'  its  antero-lateral  surface,  with  the 
obturator  membrane  and  inner  sm'face  of  the  anterior  waU  of  the  pelvis;  by  its  pelvic  surface, 
with  the  obturator  fascia,  and  the  origin  of  the  Levator  ani,  and  with  the  internal  pudendal  vessels 
and  pudendal  nerve  which  cross  it.  This  surface  forms  the  lateral  boundary  of  the  ischiorectal 
fossa.  Outside  the  pelvis,  the  muscle  is  covered  by  the  Glutaeus  maximus,  crossed  by  the  sciatic 
nerve,  and  rests  on  the  back  part  of  the  hip-joint.  When  the  tendon  of  the  Obturator  internus 
emerges  from  the  lesser  sciatic  foramen  it  is  overlapped  both  in  front  and  behind  by  the  two 
Gemelh  which  form  a  muscular  canal  for  it;  near  its. insertion  the  GemelU  pass  in  front  of  the 
tendon  and  form  a  groove  in  which  it  hes. 

The  Gemelli  are  two  small  muscular  fasciculi,  accessories  to  the  tendon  of  the 
Obturator  internus  which  is  received  into  a  groove  between  them. 

The  Gemellus  superior,  the  smaller  of  the  two,  arises  from  the  outer  surface  of 
the  spine  of  the  ischium,  blends  with  the  upper  part  of  the  tendon  of  the  Obturator 
internus,  and  is  inserted  with  it  into  the  medial  surface  of  the  greater  trochanter. 
It  is  sometimes  wanting. 

The  Gemellus  inferior  arises  from  the  upper  part  of  the  tuberosity  of  the  ischium, 
immediately  below  the  groove  for  the  Obturator  internus  tendon.  It  blends  with 
the  lower  part  of  the  tendon  of  the  Obturator  internus,  and  is  inserted  with  it 
it  into  the  medial  surface  of  the  greater  trochanter. 

The  Quadratus  femoris  is  a  flat,  quadrilateral  muscle,  between  the  Gemellus 
inferior  and  the  upper  margin  of  the  Adductor  magnus;  it  is  separated  from  the 
latter  by  the  terminal  branches  of  the  medial  femoral  circumflex  vessels.  It  arises 
from  the  upper  part  of  the  external  border  of  the  tuberosity  of  the  ischium,  and  is 
inserted  into  the  upper  part  of  the  linea  quadrata — that  is,  the  line  which  extends 
vertically  downward  from  the  intertrochanteric  crest.  A  bursa  is  often  found 
between  the  front  of  this  muscle  and  the  lesser  trochanter. 

The  Obturator  externus  (Fig.  550)  is  a  flat,  triangular  muscle,  which  covers 
the  outer  surface  of  the  anterior  wall  of  the  pelvis.  It  arises  from  the  margin 
of  bone  immediately  around  the  medial  side  of  the  obturator  foramen,  viz.,  from 
the  rami  of  the  pubis,  and  the  inferior  ramus  of  the  ischium;  it  also  arises  from  the 
medial  two-thirds  of  the  outer  surface  of  the  obturator  membrane,  and  from  the 
tendinous  arch  which  completes  the  canal  for  the  passage  of  the  obturator  vessels 
and  nerves.  The  fibres  springing  from  the  pubic  arch  extend  on  to  the  inner  sur- 
face of  the  bone,  where  they  obtain  a  narrow  origin  between  the  margin  of  the 
foramen  and  the  attachment  of  the  obturator  membrane.  The  fibres  converge 
and  pass  backward,  lateralward,  and  upward,  and  end  in  a  tendon  which  runs 
across  the  back  of  the  neck  of  the  femur  and  lower  part  of  the  capsule  of  the  hip- 
joint  and  is  inserted  into  the  trochanteric  fossa  of  the  femur.  The  obturator  vessels 
lie  between  the  muscle  and  the  obturator  membrane;  the  anterior  branch  of  the 
obturator  nerve  reaches  the  thigh  by  passing  in  front  of  the  muscle,  and  the 
posterior  branch  by  piercing  it. 

Nerves. — The  Glutaeus  maximus  is  supphed  by  the  fifth  lumbar  and  first  and  second  sacral 
nerves  through  the  inferior  gluteal  nerve;  the  Glutaei  medius  and  minimus  by  the  fourth  and 


574 


MYOLOGY 


fifth  lumbar  and  first  sacral  nerves  through  the  superior  gluteal;  the  Piriformis  is  supplied  by  the 
first  and  second  sacral  nerves;  the  Gemellus  inferior  and  Quadratus  femoris  by  the  last  lumbar 
and  first  sacral  nerves;  the  Gemellus  superior  and  Obturator  internus  by  the  first,  second,  and 
third  sacral  nerves,  and  the  Obturator  externus  by  the  third  and  fourth  lumbar  nerves  through 
the  obturator. 


Head  of  femur 


Obturator  nerve 


A)tl.  inf.  iliac  spine 


Fig.   .5.50. — The  Obturator  externus. 

Actions. — When  the  Glutaeus  maximus  takes  its  fixed  point  from  the  pelvis,  it  extends  the 
femur  and  brings  the  bent  thigh  into  a  line  with  the  body.  Taking  its  fixed  point  from  below, 
it  acts  upon  the  pelvis,  supporting  it  and  the  trunk  upon  the  head  of  the  femur;  this  is  especially 
obvious  in  standing  on  one  leg.  Its  most  powerful  action  is  to  cause  the  bod}'  to  regain  the  erect 
position  after  stooping,  by  drawing  the  pelvis  backward,  being  assisted  in  this  action  by  the 
Biceps  femoris,  Semitendinosus,  and  Semimembranosus.  The  Glutaeus  maximus  is  a  tensor  of 
the  fascia  lata,  and  by  its  connection  with  the  ihotibial  band  steadies  the  femiu:  on  the  articular 
surfaces  of  the  tibia  diu-ing  standing,  when  the  Extensor  muscles  are  relaxed.  The  lower  part 
of  the  muscle  also  acts  as  an  adductor  and  external  rotator  of  the  limb.  The  Glutaei  medius  and 
minimus  abduct  the  thigh,  when  the  limb  is  extended,  and  are  principally  called  into  action  in 
supporting  the  body  on  one  Umb,  in  conjunction  with  the  Tensor  fasciae  latae.  Their  anterior 
fibres,  by  drawing  the  greater  trochanter  forward,  rotate  the  thigh  inward,  in  which  action  the}' 
are  also  assisted  by  the  Tensor  fasciae  latae.  The  remaining  muscles  are  powerful  external 
rotators  of  the  thigh.  In  the  sitting  posture,  when  the  thigh  is  flexed  upon  the  pelvis,  their  action 
as  rotators  ceases,  and  they  become  abductors,  with  the  exception  of  the  Obturator  externus, 
which  still  rotates  the  femur  outward. 


4.  The  Posterior  Femoral  Muscles  fHamstring  Muscles)  (Fig.  548). 


Biceps  femoris. 


Semitendinosus. 


Semimembrano.sus. 


Dissection  (Fig.  547j. — Make  a  vertical  incision  along  the  middle  of  the  back  of  the  thigh, 
from  the  lower  fold  of  the  buttock  to  about  three  inches  below  the  back  of  the  knee-joint,  and 
there  connect  it  with  a  transverse  incision,  carried  from  the  inner  to  the  outer  side  of  the  leg. 
Make  a  third  incision  transversely  at  the  junction  of  the  middle  with  the  lower  third  of  the  thigh. 
The  integimient  having  been  removed  from  the  back  of  the  knee,  and  the  boundaries  of  the 
popliteal  fossa  having  been  examined,  the  removal  of  the  integument  from  the  remaining  part 
of  the  thigh  .should  be  continued,  when  the  fascia  and  muscles  of  this  region  will  be  exjjosed. 

The  Biceps  femoris  (Biceps)  is  situated  on  the  posterior  and  lateral  aspect  of  the 
thigh.  It  has  two  heads  of  origin;  one,  the  long  head,  arises  from  the  lower  and  inner 
impression  on  the  back  part  of  the  tuberosity  of  the  ischium,  by  a  tendon  common 
to  it  and  the  Semitendinosus,  and  from  the  lower  part  of  the  sacrotuberous  liga- 
ment; the  other,  the  short  head,  arises  from  the  lateral  lip  of  the  linea  aspera, 


THE  POSTERIOR  FEMORAL  MUSCLES  r^T^) 

between  the  Adductor  maf2;nus  and  Vastus  lateralis,  extending  up  almost  as  hi<ili 
as  the  insertion  of  the  Glutaeus  maximus;  from  the  lateral  prolongation  of  the 
linea  aspera  to  withing  5  cm.  of  the  lateral  condyle;  and  from  the  lateral  inter- 
muscular septmn.  The  fibres  of  the  long  head  form  a  fusiform  belly,  which  passes 
obliciuely  doAvnward  and  lateralward  across  the  sciatic  nerve  to  end  in  an  aponeu- 
rosis which  covers  the  posterior  surface  of  the  muscle,  and  receives  the  fibres  of 
the  short  head;  this  aponeurosis  becomes  gradually  contracted  into  a  tendon, 
which  is  inserted  into  the  lateral  side  of  the  head  of  the  fibula,  and  by  a  small 
slip  into  the  lateral  condyle  of  the  tibia.  At  its  insertion  the  tendon  divides  into 
two  portions,  which  embrace  the  fibular  collateral  ligament  of  the  knee-joint. 
From  the  posterior  border  of  the  tendon  a  thin  expansion  is  given  off  to  the  fascia 
of  the  leg.  The  tendon  of  insertion  of  this  muscle  forms  the  lateral  hamstring; 
the  common  peroneal  nerve  descends  along  its  medial  border. 

The  Semitendinosus,  remarkable  for  the  great  length  of  its  tendon  of  insertion, 
is  situated  at  the  posterior  and  medial  aspect  of  the  thigh.  It  arises  from  the  lower 
and  medial  impression  on  the  tuberosity  of  the  ischium,  by  a  tendon  common 
to  it  and  the  long  head  of  the  Biceps  femoris;  it  also  arises  from  an  aponeurosis 
which  connects  the  adjacent  surfaces  of  the  two  muscles  to  the  extent  of  about 
7.5  cm.  from  their  origin.  The  muscle  is  fusiform  and  ends  a  little  below  the  middle 
of  the  thigh  in  a  long  round  tendon  which  lies  along  the  medial  side  of  the  popliteal 
fossa;  it  then  curves  around  the  medial  condyle  of  the  tibia  and  passes  over  the 
tibial  collateral  ligament  of  the  knee-joint,  from  which  it  is  separated  by  a  bursa, 
and  is  inserted  into  the  upper  part  of  the  medial  surface  of  the  body  of  the  tibia, 
nearly  as  far  forward  as  its  anterior  crest.  At  its  insertion  it  gives  off  from  its 
lower  border  a  prolongation  to  the  deep  fascia  of  the  leg  and  lies  behind  the  tendon 
of  the  Sartorius,  and  below  that  of  the  Gracilis,  to  which  it  is  united.  A  tendinous 
intersection  is  usually  observed  about  the  middle  of  the  muscle. 

The  Semimembranosus,  so  called  from  its  membranous  tendon  of  origin,  is  situ- 
ated at  the  back  and  medial  side  of  the  thigh.  It  arises  by  a  thick  tendon  from 
the  upper  and  outer  impression  on  the  tuberosity  of  the  ischium,  above  and  lateral 
to  the  Biceps  femoris  and  Semitendinosus,  and  is  inserted  into  the  groove  on  the 
back  of  the  medial  condyle  of  the  tibia.  The  tendon  of  origin  expands  into  an  apon- 
eurosis, which  covers  the  upper  part  of  the  anterior  surface  of  the  muscle;  from 
this  aponeurosis  muscular  fibres  arise,  and  converge  to  another  aponeurosis  which 
covers  the  lower  part  of  the  posterior  surface  of  the  muscle  and  contracts  into  the 
tendon  of  insertion.  The  tendon  of  insertion  gives  off  certain  fibrous  expansions: 
one,  of  considerable  size,  passes  upw^ard  and  lateralward  to  be  inserted  into  the  back 
part  of  the  lateral  condyle  of  the  femur,  forming  part  of  the  oblique  popliteal 
ligament  of  the  knee-joint;  a  second  is  continued  downward  to  the  fascia  which 
covers  the  Popliteus  muscle;  while  a  few  fibres  join  the  tibial  collateral  ligament 
of  the  joint  and  the  fascia  of  the  leg.  The  muscle  overlaps  the  upper  part  of  the 
popliteal  vessels. 

The  tendons  of  insertion  of  the  two  preceding  muscles  form  the  medial  hamstrings. 

Nerves. — The  muscles  of  this  region  are  suppUed  by  the  fourth  and  fifth  lumbar  and  the  first, 
second,  and  third  sacral  nerves;  the  nerve  to  the  short  head  of  the  Biceps  femoris  is  derived  from 
the  common  peroneal,  the  other  muscles  are  supplied  through  the  tibial  nerve. 

Actions. — The  hamstring  muscles  flex  the  leg  upon  the  thigh.  When  the  knee  is  semiflexed, 
the  Biceps  femoris  in  consequence  of  its  obhque  direction  rotates  the  leg  slightly  outward;  and 
the  Semitendinosus,  and  to  a  shght  extent  the  Semimembranosus,  rotate  the  leg  inward,  assist- 
ing the  Pophteus.  Taking  their  fixed  point  from  below,  these  muscles  serve  to  support  the  pelvis 
upon  the  head  of  the  femur,  and  to  draw  the  trunk  directly  backward,  as  in  raising  it  from  the 
stooping  position  or  in  feats  of  strength,  when  the  body  is  thrown  backward  in  the  form  of  an 
arch.  As  already  indicated  on  page  383,  complete  flexion  of  the  hip  cannot  be  effected  unless 
the  knee-joint  is  also  flexed,  on  account  of  the  shortness  of  the  hamstring  muscles. 

Applied  Anatomy. — In  disease  of  the  knee-joint,  contraction  of  the  hamstring  tendons  is  a 
frequent  comphcation;  this  causes  flexion  of  the  leg,  and  a  partial  dislocation  of  the  tibia  back- 


576  MYOLOGY 

ward,  with  a  slight  degree  of  rotation  outward,  probably  due  to  the  action  of  the  Biceps  femoris. 
The  hamstring  tendons  occasionally  require  subcutaneous  division  in  some  forms  of  sjjurious 
ankylosis  of  the  knee-joint  dependent  upon  permanent  contraction  and  rigidity  of  the  muscles, 
or  from  contracture  of  the  ligamentous  and  other  tissues  surrounding  the  joint,  the  result  of 
disease.  The  relation  of  the  common  peroneal  nerve,  which  Ues  in  close  apposition  to  the  medial 
border  of  the  tendon  of  the  Biceps  femoris,  must  always  be  borne  in  mind  in  dividing  this  tendon, 
and  a  free  incision  with  exposure  of  the  tendon,  before  division,  is  the  safer  proceeding. 


III.    THE  MUSCLES  AND  FASCIA  OF  THE  LEG. 

The  muscles  of  the  leg  may  be  divided  into  three  groups:  anterior,  posterior, 
and  lateral. 

1.  The  Anterior  Crural  Muscles  (Fig.  551). 

Tibialis  anterior.  Extensor  digitorum  longus. 

Extensor  hallucis  longus.  Peronaeus  tertius. 

Dissection  (Fig.  543). — The  knee  should  be  bent,  a  block  placed  beneath  it,  and  the  foot  kept 
in  an  extended  position;  then  make  an  incision 'through  the  integument  in  the  middle  Hne  of  the 
leg  to  the  ankle,  and  contmue  it  along  the  dorsum  of  the  foot  to  the  toes.  Make  a  second  incision 
transversely  across  the  ankle,  and  a  third  in  the  same  direction  across  the  bases  of  the  toes;  remove 
the  flaps  of  integument  included  between  these  incisions  in  order  to  examine  the  deep  fascia  of 
the  leg. 

Deep  Fascia  {fascia  cruris) . — The  deep  fascia  of  the  leg  forms  a  complete  invest- 
ment to  the  muscles,  and  is  fused  with  the  periosteum  over  the  subcutaneous 
surfaces  of  the  bones.  It  is  continuous  above  with  the  fascia  lata,  and  is  attached 
around  the  knee  to  the  patella,  the  ligamentum  patellae,  the  tuberosity  and  con- 
dyles of  the  tibia,  and  the  head  of  the  fibula.  Behind,  it  forms  the  popliteal  fascia, 
covering  in  the  popliteal  fossa;  here  it  is  strengthened  by  transverse  fibres,  and 
perforated  by  the  small  saphenous  vein.  It  receives  an  expansion  from  the  tendon 
of  the  Biceps  femoris  laterally,  and  from  the  tendons  of  the  Sartorius,  Gracilis, 
Semitendinosus,  and  Semimembranosus  medially;  in  front,  it  blends  with  the  peri- 
osteum covering  the  subcutaneous  surface  of  the  tibia,  and  with  that  covering 
the  head  and  malleolus  of  the  fibula;  below,  it  is  continuous  with  the  transverse 
crural  and  laciniate  ligaments.  It  is  thick  and  dense  in  the  upper  and  anterior 
part  of  the  leg,  and  gives  attachment,  by  its  deep  surface,  to  the  Tibialis  anterior 
and  Extensor  digitorum  longus;  but  thinner  behind,  w^here  it  covers  the  Gastroc- 
nemius and  Soleus.  It  gives  off  from  its  deep  surface,  on  the  lateral  side  of  the  leg, 
two  strong  intermuscular  septa,  the  anterior  and  posterior  peroneal  septa,  which 
enclose  the  Peronaei  longus  and  brevis,  and  separate  them  from  the  muscles  of 
the  anterior  and  posterior  crural  regions,  and  several  more  slender  processes  which 
enclose  the  individual  muscles  in  each  region.  A  broad  transverse  intermuscular 
septum,  called  the  deep  transverse  fascia  of  the  leg,  intervenes  between  the  super- 
ficial and  deep  posterior  crural  muscles. 

Dissection. — Remove  the  fascia  by  dividing  it  in  the  same  dii'ection  as  the  integument,  except- 
ing opposite  the  ankle,  where  it  should  be  left  entire.  Commence  the  removal  of  the  fascia  from 
below,  opposite  the  tendons,  and  detach  it  in  the  line  of  direction  of  the  muscle  fibres. 

The  Tibialis  anterior  ( Tibialis  anticus)  is  situated  on  the  lateral  side  of  the  tibia ; 
it  is  thick  and  fleshy  above,  tendinous  below.  It  arises  from  the  lateral  condyle 
and  upper  half  or  two-thirds  of  the  lateral  surface  of  the  body  of  the  tibia;  from 
the  adjoining  part  of  the  interosseous  membrane;  from  the  deep  surface  of  the 
fascia;  and  from  the  intermuscular  septum  between  it  and  the  Extensor  digitorum 
longus.  The  fibres  run  vertically  downward,  and  end  in  a  tendon,  which  is  apparent 
on  the  anterior  surface  of  the  muscle  at  the  lower  third  of  the  leg.  After  passing 
through  the  most  medial  compartments  of  the  transverse  and  cruciate  crural 


THE  ANTERIOR  CRURAL  MUSCLES 


on 


ligaments,  it  is  inserted  into  the  medial  and  under 
surface  of  the  first  cuneiform  bone,  and  the  base 
of  the  first  metatarsal  bone.  This  muscle  o^•erlaps 
the  anterior  tibial  vessels  and  deep  peroneal  nerve 
in  the  upper  i)art  of  the  leg. 

The  Extensor hallucis  longus  {Extensor  proprius 
halliicis)  is  a  thin  nniscle,  situated  between  the 
Tibialis  anterior  and  the  Extensor  digitorum 
longus.  It  arises  from  the  anterior  surface  of  the 
fibula  for  about  the  middle  two-fourths  of  its 
extent,  medial  to  the  origin  of  the  Extensor  digi- 
torum longus;  it  also  arises  from  the  interosseous 
membrane  to  a  similar  extent.  The  anterior 
tibial  vessels  and  deep  peroneal  nerve  lie  between 
it  and  the  Tibialis  anterior.  The  fibres  pass 
downward,  and  end  in  a  tendon,  which  occupies 
the  anterior  border  of  the  muscle,  passes  through 
a  distinct  compartment  in  the  cruciate  crural 
ligament,  crosses  from  the  lateral  to  the  medial 
side  of  the  anterior  tibial  vessels  near  the  bend  of 
the  ankle,  and  is  inserted  into  the  base  of  the  distal 
phalanx  of  the  great  toe.  Opposite  the  metatarso- 
phalangeal articulation,  the  tendon  gives  off  a  thin 
prolongation  on  either  side,  to  cover  the  surface 
of  the  joint.  An  expansion  from  the  medi&l  side 
of  the  tendon  is  usually  inserted  into  the  base  of 
the  proximal  phalanx. 

The  Extensor  digitorum  longus  is  a  penniform 
muscle,  situated  at  the  lateral  part  of  the  front 
of  the  leg.  It  arises  from  the  lateral  condyle  of 
the  tibia;  from  the  upper  three-fourths  of  the 
anterior  surface  of  the  body  of  the  fibula;  from 
the  upper  part  of  the  interosseous  membrane; 
from  the  deep  surface  of  the  fascia;  and  from  the 
intermuscular  septa  between  it  and  the  Tibialis 
anterior  on  the  medial,  and  the  Peronaei  on  the 
lateral  side.  Between  it  and  the  Tibialis  anterior 
are  the  upper  portions  of  the  anterior  tibial  vessels 
and  deep  peroneal  nerve.  The  tendon  passes  under 
the  transverse  and  cruciate  crural  ligaments  in 
company  with  the  Peronaeus  tertius,  and  divides 
into  four  slips,  which  run  forward  on  the  dorsum 
of  the  foot,  and  are  inserted  into  the  second  and 
third  phalanges  of  the  four  lesser  toes.  The  ten- 
dons to  the  second,  third,  and  fourth  toes  are 
each  joined,  opposite  the  metatarsophalangeal 
articulation,  on  the  lateral  side  by  a  tendon  of 
the  Extensor  digitorum  brevis.  The  tendons  are 
inserted  in  the  following  manner:  each  receives  a 
fibrous  expansion  from  the  Interossei  and  Lum- 
bricalis,  and  then  spreads  out  into  a  broad  apon- 
eurosis, which  covers  the  dorsal  surface  of  the 
first  phalanx:  this  aponeurosis,  at  the  articulation 
of  the  first  with  the  second  phalanx,  divides  into 
37 


m 


A 


1'  ''g^'^^i^ 


Fig.  551. — Muscles  of  the  front  of 
the  leg. 


578  MYOLOGY 

three  slips — an  intermediate,  which  is  inserted  into  the  base  of  the  second  phalanx; 
and  two  collateral  slips,  which,  after  uniting  on  the  dorsal  surface  of  the  second 
phalanx,  are  continued  onward,  to  be  inserted  into  the  base  of  the  third  phalanx. 
The  Peronaeus  tertius  is  a  part  of  the  Extensor  digitorum  longus,  and  might 
be  described  as  its  fifth  tendon.  The  fibres  belonging  to  this  tendon  arise  from 
the  lower  third  or  more  of  the  anterior  surface  of  the  fibula;  from  the  lower  part 
of  the  interosseous  membrane;  and  from  an  intermuscular  septum  between  it 
and  the  Peronaeus  brevis.  The  tendon,  after  passing  under  the  transverse  and 
cruciate  crural  ligaments  in  the  same  canal  as  the  Extensor  digitorum  longus, 
is  inserted  into  the  dorsal  surface  of  the  base  of  the  metatarsal  bone  of  the  little 
toe.    This  muscle  is  sometimes  wanting. 

Nerves. — These  muscles  are  supplied  by  the  fourth  and  fifth  lumbar  and  first  sacral  nerves 
through  the  deep  peroneal  nerve. 

Actions. — The  Tibialis  anterior  and  Peronaeus  tertius  are  the  direct  flexors  of  the  foot  at  the 
ankle-joint;  the  former  muscle,  when  acting  in  conjunction  with  the  Tibiahs  posterior,  raises  the 
medial  border  of  the  foot,  i.  e.,  inverts  the  foot;  and  the  latter,  acting  with  the  Peronaei  brevis 
and  longus,  raises  the  lateral  border  of  the  foot,  i.  e.,  everts  the  foot.  The  Extensor  digitorum 
longus  and  Extensor  hallucis  longus  extend  the  phalanges  of  the  toes,  and,  continuing  their 
action,  flex  the  foot  upon  the  leg.  Taking  their  fixed  points  from  below,  in  the  erect  posture, 
all  these  muscles  serve  to  fix  the  bones  of  the  leg  in  the  perpendicular  position,  and  give  increased 
strength  to  the  ankle-joint. 

2.  The  Posterior  Crural  Muscles. 

Dissection  (Fig.  547). — Make  a  vertical  incision  along  the  middle  Une  of  the  back  of  the  leg, 
from  the  lower  part  of  the  pophteal  fossa  to  the  heel,  connecting  it  below  by  a  transverse  incision 
extending  between  the  two  malleoh;  the  flaps  of  integument  being  removed,  the  fascia  and  muscles 
should  be  examined. 

The  muscles  of  the  back  of  the  leg  are  subdivided  into  two  groups — superficial 
and  deep.  Those  of  the  superficial  group  constitute  a  powerful  muscular  mass, 
forming  the  calf  of  the  leg.  Their  large  size  is  one  of  the  most  characteristic 
features  of  the  muscular  apparatus  in  man,  and  bears  a  direct  relation  to  his  erect 
attitude  and  his  mode  of  progression. 

The  Superficial  Group  (Fig.  552). 

Gastrocnemius.  Soleus.  Plantaris. 

The  Gastrocnemius  is  the  most  superficial  muscle,  and  forms  the  greater  part 
of  the  calf.  It  arises  by  two  heads,  which  are  connected  to  the  condyles  of  the 
femur  by  strong,  flat  tendons.  The  medial  and  larger  head  takes  its  origin  from  a 
depression  at  the  upper  and  back  part  of  the  medial  condyle  and  from  the  adjacent 
part  of  the  femur.  The  lateral  head  arises  from  an  impression  on  the  side  of  the 
lateral  condyle  and  from  the  posterior  surface  of  the  femur  immediately  above 
the  lateral  part  of  the  condyle.  Both  heads,  also,  arise  from  the  subjacent  part 
of  the  capsule  of  the  knee.  Each  tendon  spreads  out  into  an  aponeurosis,  which 
covers  the  posterior  surface  of  that  portion  of  the  muscle  to  which  it  belongs. 
From  the  anterior  surfaces  of  these  tendinous  expansions,  muscular  fibres  are 
given  off;  those  of  the  medial  head  being  thicker  and  extending  lower  than  those 
of  the  lateral.  The  fibres  unite  at  an  angle  in  the  middle  line  of  the  muscle  in  a 
tendinous  raphe,  w^hich  expands  into  a  broad  aponeurosis  on  the  anterior  surface 
of  the  muscle,  and  into  this  the  remaining  fibres  are  inserted.  The  aponeurosis, 
gradually  contracting,  unites  with  the  tenon  of  the  Soleus,  and  forms  with  it 
the  tendo  calcaneus. 

Relations. — The  Gastrocnemius  is  in  relation  by  its  superficial  surface  with  the  fascia  of  the 
leg,  which  separates  it  from  the  small  saphenous  vein  and  the  peroneal  anastomotic,  medial  sural 
cutaneous,  and  sural  nerves;  the  common  peroneal  nerve  crosses  the  lateral  head,  lying  partly 
under  cover  of  the  Biceps  femoris.  Its  deep  surface  is  in  relation  with  the  obhque  pophteal  liga- 
ment of  the  knee-joint,  the  Pophteus,  Soleus,  Plantaris,  popliteal  vessels,  and  tibial  nerve.    In 


THE  POSTERIOR  CRURAL  MUSCLES  579 

front  of  the  tendon  of  the  medial  head  is  a  bursa,  which,  in  some  cases,  communicates  with  the 
cavity  of  the  knee-joint.  The  tendon  of  the  lateral  head  sometimes  contains  a  sesamoid  fibro- 
cartilage  or  bone,  where  it  plays  ov(>r  the  (•()rr(\siionding  condyle;  and  one  is  occasionally  found 
in  the  tendon  of  the  medial  head. 

The  Soleus  is  a  broad  flat  muscle  situated  iininediately  in  front  of  the  Gastroc- 
nemius. It  arises  by  tendhious  fibres  from  the  back  of  the  head  of  the  fibula, 
and  from  the  upper  third  of  the  posterior  surface  of  the  body  of  the  bone;  from  the 
popliteal  line,  and  the  middle  third  of  the  medial  border  of  the  tibia;  some  fibres 
also  arise  from  a  tendinous  arch  placed  between  the  tibial  and  fibular  origins 
of  the  muscle,  in  front  of  which  the  popliteal  vessels  and  tibial  nerve  run.  The 
fibres  end  in  an  aponeurosis  which  covers  the  posterior  surface  of  the  muscle,  and, 
gradually  becoming  thicker  and  narrower,  joins  with  the  tendon  of  the  Gastroc- 
nemius, and  forms  with  it  the  tendo  calcaneus. 

Relations. — By  its  superficial  surface  it  is  in  relation  with  the  Gastrocnemius  and  Plantaris; 
by  its  deep  surface,  with  the  Flexor  digitorum  longus,  Flexor  hallucis  longus,  Tibialis  posterior, 
and  posterior  tibial  vessels  and  nerve,  from  which  it  is  separated  by  the  deep  transverse  fascia 
of  the  leg. 

The  Gastrocnemius  and  Soleus  together  form  a  muscular  mass  which  is  occa- 
sionally described  as  the  Triceps  surae;  its  tendon  of  insertion  is  the  tendo  calcaneus. 

Tendo  Calcaneus  (tendo  AchiUis). — The  tendo  calcaneus,  the  common  tendon  of  the 
Gastrocnemius  and  Soleus,  is  the  thickest  and  strongest  in  the  body.  It  is  about 
15  cm.  long,  and  begins  near  the  middle  of  the  leg,  but  receives  fleshy  fibres  on  its 
anterior  surface,  almost  to  its  lower  end.  Gradually  becoming  contracted  below, 
it  is  inserted  into  the  middle  part  of  the  posterior  surface  of  the  calcaneus,  a  bursa 
being  interposed  between  the  tendon  and  the  upper  part  of  this  surface.  The  ten- 
don spreads  out  somewhat  at  its  lower  end,  so  that  its  narrowest  part  is  about 
4  cm.  above  its  insertion.  It  is  covered  by  the  fascia  and  the  integument,  and  is 
separated  from  the  deep  muscles  and  vessels  by  a  considerable  interval  filled  up 
with  areolar  and  adipose  tissue.  Along  its  lateral  side,  but  superficial  to  it,  is  the 
small  saphenous  vein. 

The  Plantaris  is  placed  between  the  Gastrocnemius  and  Soleus.  It  arises  from 
the  lower  part  of  the  lateral  prolongation  of  the  linea  aspera,  and  from  the  oblique 
popliteal  ligament  of  the  knee-joint.  It  forms  a  small  fusiform  belly,  from  7  to 
10  cm.  long,  ending  in  a  long  slender  tendon  which  crosses  obliquely  between  the 
two  muscles  of  the  calf,  and  runs  along  the  medial  border  of  the  tendo  calcaneus, 
to  be  inserted  with  it  into  the  posterior  part  of  the  calcaneus.  This  muscle  is  some- 
times double,  and  at  other  times  wanting.  Occasionally,  its  tendon  is  lost  in  the 
laciniate  ligament,  or  in  the  fascia  of  the  leg. 

Nerves. — The  Gastrocnemius  and  Soleus  are  supplied  by  the  first  and  second  sacral  nerves, 
and  the  Plantaris  by  the  fourth  and  fifth  lumbar  and  first  sacral  nerves,  through  the  tibial  nerve. 

Actions. — The  muscles  of  the  calf  are  the  chief  extensors  of  the  foot  at  the  ankle-joint.  They 
possess  considerable  power,  and  are  constantly  called  into  use  in  standing,  walking,  dancing, 
and  leaping;  hence  the  large  size  they  usuallj^  present.  In  walking,  these  muscles  raise  the  heel 
from  the  ground;  the  body  being  thus  supported  on  the  raised  foot,  the  opposite  limb  can  be 
carried  forward.  In  standing,  the  Soleus,  taking  its  fixed  point  from  below,  steadies  the  leg  upon 
the  foot  and  prevents  the  body  from  falling  forward.  The  Gastrocnemius,  acting  from  below, 
serves  to  flex  the  femur  upon  the  tibia,  assisted  by  the  PopUteus.  The  Plantaris  is  the  rudiment 
of  a  large  muscle  which  in  some  of  the  lower  animals  is  continued  over  the,  calcaneus  to  be  inserted 
into  the  plantar  aponeurosis.  In  man  it  is  an  accessory  to  the  Gastrocnemius,  extending  the 
ankle  if  the  foot  be  free,  or  bending  the  knee  if  the  foot  be  fixed. 

The  Deep  Group  (Fig.  553). 

Popliteus.  Flexor  digitorum  longus. 

Flexor  hallucis  longus.  Tibialis  posterior. 

Dissection. — Detach  the  Soleus  from  its  attachment  to  the  fibula  and  tibia,  and  turn  it  down- 
ward, when  the  deep  layer  of  muscles  is  exposed,  covered  by  the  deep  transverse  fascia  of  the  leg. 


580 


MYOLOGY 


Deep  Transverse  Fascia.— The  deep  transverse  fascia  of  the  leg  is  a  transversely 
placed,  intermuscular  septum,  between  the  superficial  and  deep  muscles  of  the 


S^5  =>< 


}  Jt  hal  W/Iahml ,; 


/   '' 


f     I  il 

ICALCPKEUSI 


m 


I'iH 


Tendons  of 

~  Peronae  longus 

et  brevis 


FemuA 


\       > 


-^ 


.i~ 


y/, 


Fig.   552. — Aluscles  of  the  back  of  the 
Superficial  layer. 


Fig.  553. — Muscles  of  the  back  of  the  leg. 
Deep  layer. 


back  of  the  leg.  At  the  sides  it  is  connected  to  the  margms  of  the  tibia  and 
fibula.  Above,  where  it  covers  the  Popliteus,  it  is  thick  and  dense,  and  receives 
an  expansion  from  the  tendon  of  the  Semimembranosus;  it  is  thinner  m  the  middle 


THE  POSTERIOR  CRURAL  MUSCLES  581 

of  the  leg;  but  below,  where  it  covers  the  tendons  passhig  behind  the  malleoli, 
it  is  thickened  and  continuous  with  the  laciniate  ligament. 

Dissection. — This  fascia  should  now  be  removed,  commencing  from  bcdow  opposite  the  tendons, 
and  detaching  it  from  the  muscles  in  the  direction  of  their  fibres. 

The  Popliteus  is  a  thin,  flat,  triangular  muscle,  which  forms  the  lower  part  of 
the  floor  of  the  popliteal  fossa.  It  arises  by  a  strong  tendon  about  2.5  cm.  long, 
from  a  depression  at  the  anterior  part  of  the  groove  on  the  lateral' condyle  of  the 
femur,  and  to  a  small  extent  from  the  oblique  popliteal  ligament  of  the  knee-joint; 
and  is  inserted  into  the  medial  two-thirds  of  the  triangular  surface  above  the  pop- 
liteal line  on  the  posterior  surface  of  the  body  of  the  tibia,  and  into  the  tendinous 
expansion  covering  the  surface  of  the  muscle. 

Relations. — The  tendon  of  the  muscle  is  covered  by  that  of  the  Biceps  femoris  and  by  the 
fibular  collateral  ligament  of  the  knee-joint;  it  grooves  the  posterior  border  of  the  lateral  meniscus, 
and  is  invested  by  the  synovial  membrane  of  the  knee-joint.  The  fascia  covering  the  muscle 
separates  it  from  the  Gastrocnemius,  Plantaris,  popliteal  vessels,  and  tibial  nerve.  The  deep 
sm-face  of  the  muscle  is  in  contact  with  the  obhque  popliteal  Ugament  of  the  knee-joint  and  the 
back  of  the  tibia. 

The  Flexor  hallucis  longus  is  situated  on  the  fibular  side  of  the  leg.  It  arises 
from  the  inferior  two-thirds  of  the  posterior  surface  of  the  body  of  the  fibula,  with 
the  exception  of  2.5  cm.  at  its  lowest  part;  from  the  lower  part  of  the  interosseous 
membrane;  from  an  intermuscular  septum  between  it  and  the  Peronaei,  laterally, 
and  from  the  fascia  covering  the  Tibialis  posterior,  medially.  The  fibres  pass 
obliquely  downward  and  backward,  and  end  in  a  tendon  which  occupies  nearly 
the  whole  length  of  the  posterior  surface  of  the  muscle.  This  tendon  lies  in  a  groove 
which  crosses  the  posterior  surface  of  the  lower  end  of  the  tibia,  the  posterior 
surface  of  the  talus,  and  the  under  surface  of  the  sustentaculum  tali  of  the  calca- 
neus ;  in  the  sole  of  the  foot  it  runs  forward  between  the  two  heads  of  the  Flexor 
hallucis  brevis,  and  is  inserted  into  the  base  of  the  last  phalanx  of  the  great  toe. 
The  grooves  on  the  talus  and  calcaneus,  which  contain  the  tendon  of  the  muscle, 
are  converted  by  tendinous  fibres  into  distinct  canals,  lined  by  a  mucous  sheath. 
As  the  tendon  passes  forward  in  the  sole  of  the  foot,  it  is  situated  above,  and 
crosses  from  the  lateral  to  the  medial  side  of  the  tendon  of  the  Flexor  digitorum 
longus,  to  which  it  is  connected  by  a  fibrous  slip. 

Relations. — The  Flexor  hallucis  longus  is  in  relation  by  its  superficial  surface  with  the  Soleus 
and  tendo  calcaneus,  from  which  it  is  separated  by  the  deep  transverse  fascia;  by  its  deep  surface, 
with  the  fibula,  Tibialis  posterior,  the  peroneal  vessels,  the  lower  part  of  the  interosseous  mem- 
brane, and  the  ankle-joint;  by  its  lateral  border,  with  the  Peronaei;  by  its  medial  border,  with  the 
Tibialis  posterior  and  posterior  tibial  vessels  and  tibial  nerve. 

The  Flexor  digitorum  longus  is  situated  on  the  tibial  side  of  the  leg.  At  its 
origin  it  is  thin  and  pointed,  but  it  gradually  increases  in  size  as  it  descends.  It 
arises  from  the  posterior  surface  of  the  body  of  the  tibia,  from  immediately  below 
the  popliteal  line  to  within  7  or  8  cm.  of  its  lower  extremity,  medial  to  the  tibial 
origin  of  the  Tibialis  posterior;  it  also  arises  from  the  fascia  covering  the  Tibialis 
posterior.  The  fibres  end  in  a  tendon,  which  runs  nearly  the  whole  length  of  the 
posterior  surface  of  the  muscle.  This  tendon  passes  behind  the  medial  malleolus, 
in  a  groove,  common  to  it  and  the  Tibialis  posterior,  but  separated  from  the  latter 
by  a  fibrous  septum,  each  tendon  being  contained  in  a  special  compartment  lined 
by  a  separate  mucous  sheath.  It  passes  obliquely  forward  and  lateralward,  super- 
ficial to  the  deltoid  ligament  of  the  ankle-joint,  into  the  sole  of  the  foot  (Fig.  557), 
where  it  crosses  below  the  tendon  of  the  Flexor  hallucis  longus,  and  receives  from  it 
a 'strong  tendinous  slip.  It  then  expands  and  is  joined  by  the  Quadratus  plantae, 
and  finally  divides  into  four  tendons,  which  are  inserted  into  the  bases  of  the  last 
phalanges  of  the  second,  third,  fourth,  and  fifth  toes,  each  tendon  passing  through 


582  MYOLOGY 

an  opening  in  the  corresponding  tendon  of  the  Flexor  digitorum  brevis  opposite 
the  base  of  the  first  phalanx. 

Relations. — In  the  leg  this  muscle  is  in  relation  by  its  superficial  surface  with  the  posterior 
tibial  vessels  and  tibial  nerve,  and  the  deep  transverse  fascia  which  separates  it  from  the  Soleus; 
by  its  deep  surface,  with  the  tibia  and  TibiaUs  posterior.  In  the  foot,  it  is  covered  by  the  Abductor 
hallucis  and  Flexor  digitorum  brevis,  and  crosses  superficial  to  the  Flexor  hallucis  longus. 

The  Tibialis  posterior  ( Tibialis  posticus)  lies  between  the  two  preceding  muscles, 
and  is  the  most  deeply  seated  of  the  muscles  on  the  back  of  the  leg.  It  begins 
above  by  two  pointed  processes,  separated  by  an  angular  interval  through  which 
the  anterior  tibial  vessels  pass  forward  to  the  front  of  the  leg.  It  arises  from  the 
whole  of  the  posterior  surface  of  the  interosseous  membrane,  excepting  its  lowest 
part;  from  the  lateral  portion  of  the  posterior  surface  of  the  body  of  the  tibia, 
between  the  commencement  of  the  popliteal  line  above  and  the  junction  of  the 
middle  and  lower  thirds  of  the  body  below;  and  from  the  upper  two-thirds  of  the 
medial  surface  of  the  fibula;  some  fibres  also  arise  from  the  deep  transverse  fascia, 
and  from  the  intermuscular  septa  separating  it  from  the  adjacent  muscles.  In 
the  lower  fourth  of  the  leg  its  tendon  passes  in  front  of  that  of  the  Flexor  digitorum 
longus  and  lies  with  it  in  a  groove  behind  the  medial  malleolus,  but  enclosed  in  a 
separate  sheath;  it  next  passes  under  the  laciniate  and  over  the  deltoid  ligament 
into  the  foot,  and  then  beneath  the  plantar  calcaneonavicular  ligament.  The 
tendon  contains  a  sesamoid  fibrocartilage,  as  it  runs  under  the  plantar  calcaneo- 
navicular ligament.  It  is  inserted  into  the  tuberosity  of  the  navicular  bone,  and 
gives  off  fibrous  expansions,  one  of  which  passes  backward  to  the  sustentaculum  tali 
of  the  calcaneus,  others  forward  and  lateralward  to  the  three  cuneiforms,  the 
cuboid,  and  the  bases  of  the  second,  third,  and  fourth  metatarsal  bones. 

Relations. — The  Tibiahs  posterior  is  in  relation  by  its  superficial  surface  with  the  Soleus,  from 
which  it  is  separated  by  the  deep  transverse  fascia,  the  Flexor  digitorum  longus,  the  posterior 
tibial  vessels  and  tibial  nerve,  and  the  peroneal  vessels;  by  its  deep  surface,  with  the  interosseous 
membrane,  the  tibia,  fibula,  and  ankle-joint. 

Nerves. — The  Popliteus  is  supplied  by  the  fourth  and  fifth  lumbar  and  first  sacral  nerves, 
the  Flexor  digitorum  longus  and  Tibialis  posterior  by  the  fifth  lumbar  and  first  sacral,  and  the 
Flexor  hallucis  longus  by  the  fifth  lumbar  and  the  first  and  second  sacral  nerves,  through  the 
tibial  nerve. 

Actions. — The  Popliteus  assists  in  flexing  the  leg  upon  the  thigh;  when  the  leg  is  flexed,  it  will 
rotate  the  tibia  inward.  It  is  especially  called  into  action  at  the  beginning  of  the  act  of  bending 
the  knee,  inasmuch  as  it  produces  the  slight  inward  rotation  of  the  tibia  which  is  essential  in  the 
early  stage  of  this  movement.  The  Tibiahs  posterior  is  a  direct  extensor  of  the  foot  at  the  ankle- 
joint;  acting  in  conjunction  with  the  Tibiahs  anterior,  it  turns  the  sole  of  the  foot  upward  and 
medialward,  i.  e.,  inverts  the  foot,  antagonizing  the  Peronaei,  which  turn  it  upward  and  lateral- 
ward  (evert  it).  In  the  sole  of  the  foot  the  tendon  of  the  Tibiahs  posterior  hes  directly  below  the 
plantar  calcaneonavicular  hgament,  and  is  therefore  an  important  factor  in  maintaining  the 
arch  of  the  foot.  The  Flexor  digitorum  longus  and  Flexor  hallucis  longus  are  the  direct  flexors  of 
the  phalanges,  and,  continuing  their  action,  extend  the  foot  upon  the  leg;  they  assist  the  Gastroc- 
nemius and  Soleus  in  extending  the  foot,  as  in  the  act  of  walking,  or  in  standing  on  tiptoe.  In 
consequence  of  the  obhque  direction  of  its  tendons  the  Flexor  digitorum  longus  would  draw  the 
toes  medialward,  were  it  not  for  the  Quadratus  plantae,  which  is  inserted  into  the  lateral  side 
of  the  tendon,  and  draws  it  to  the  middle  line  of  the  foot.  Taking  their  fixed  point  from  the 
foot,  these  muscles  serve  to  maintain  the  upright  posture  by  steadying  the  tibia  and  fibula 
perpendicularly  upon  the  talus. 

3.  The  Lateral  Crural  Muscles  (Fig.  553). 
Peronaeus  longus.  Peronaeus  brevis. 

Dissection. — The  muscles  are  readily  exposed  by  removing  the  fascia  covering  their  surface, 
from  below  upward,  in  the  fine  of  direction  of  their  fibres. 

The  Peronaeus  longus  is  situated  at  the  upper  part  of  the  lateral  side  of  the 
leg,  and  is  the  more  superficial  of  the  two  muscles.    It  arises  from  the  head  and 


THE  LATERAL  CRURAL  MUSCLES  583 

ui)l)er  two-thirds  of  the  hitcral  surface  of  thi-  Ixxly  of  the  fihiila,  from  the  deep 
surfaee  of  the  fascia,  and  from  tlie  intermuscuhir  septa  l)et\veeii  it  and  the  muscles 
on  the  front  and  back  of  the  k'j;-;  occasionally  also  by  a  few  fibres  from  the  lateral 
condyle  of  the  tibia.  Between  its  attachments  to  the  head  and  to  the  body  of  the 
fibula  there  is  a  fi;ap  through  which  the  common  peroneal  nerve  passes  to  the  front 
of  the  leg.  It  ends  in  a  long  tendon,  which  runs  behind  the  lateral  malleolus,  in 
a  groove  common  to  it  and  the  tendon  of  the  Peronaeus  brevis,  behind  which  it 
lies;  the  groove  is  converted  into  a  canal  by  the  superior  peroneal  retinaculum,  and 
the  tendons  in  it  are  contained  in  a  common  mucous  sheath.  The  tendon  then 
extends  obliquely  forward  across  the  lateral  side  of  the  calcaneus,  beloAv  the  troch- 
lear process,  and  the  tendon  of  the  Peronaeus  brevis,  and  under  cover  of  the  inferior 
peroneal  retinaculum.  It  crosses  the  lateral  side  of  the  cuboid,  and  then  runs  on  the 
under  surface  of  that  bone  in  a  groove  which  is  converted  into  a  canal  by  the  long 
plantar  ligament;  the  tendon  then  crosses  the  sole  of  the  foot  obliquely,  and.  is 
inserted  into  the  lateral  side  of  the  base  of  the  first  metatarsal  bone  and  the  lateral 
side  of  the  first  cuneiform.  Occasionally  it  sends  a  slip  to  the  base  of  the  second 
metatarsal  bone.  The  tendon  changes  its  direction  at  two  points:  first,  behind  the 
lateral  malleolus;  secondly,  on  the  cuboid  bone;  in  both  of  these  situations  the  ten- 
don is  thickened,  and,  in  the  latter,  a  sesamoid  fibrocartilage  (sometimes  a  bone), 
is  usually  developed  in  its  substance. 

The  Peronaeus  brevis  lies  under  cover  of  the  Peronaeus  longus,  and  is  a  shorter 
and  smaller  muscle.  It  arises  from  the  low^r  tw^o-thirds  of  the  lateral  surface  of 
the  body  of  the  fibula;  medial  to  the  Peronaeus  longus;  and  from  the  intermuscular 
septa  separating  it  from  the  adjacent  muscles  on  the  front  and  back  of  the  leg. 
The  fibres  pass  vertically  downw^ard,  and  end  in  a  tendon  w^hich  runs  behind  the 
lateral  malleolus  along  w-ith  but  in  front  of  that  of  the  preceding  muscle,  the  two 
tendons  being  enclosed  in  the  same  compartment,  and  lubricated  by  a  common 
mucous  sheath.  It  then  runs  forw^ard  on  the  lateral  side  of  the  calcaneus,  above 
the  trochlear  process  and  the  tendon  of  the  Peronaeus  longus,  and  is  inserted  into 
the  tuberosity  at  the  base  of  the  fifth  metatarsal  bone,  on  its  lateral  side. 

On  the  lateral  surface  of  the  calcaneus  the  tendons  of  the  Peronaei  longus  and 
brevis  occupy  separate  osseoaponeurotic  canals  formed  by  the  calcaneus  and  the 
perineal  retinacula;  each  tendon  is  enveloped  by  a  forw^ard  prolongation  of  the 
common  mucous  sheath. 

Nerves. — The  Peronaei  longus  and  brevis  are  supplied  by  the  fourth  and  fifth  lumbar  and 
first  sacral  nerves  through  the  superficial  peroneal  nerve. 

Actions. — The  Peronaei  longus  and  brevis  extend  the  foot  upon  the  leg,  in  conjunction  with 
the  Tibiahs  posterior,  antagonizing  the  Tibiahs  anterior  and  Peronaeus  tertius,  which  are  flexors 
of  the  foot.  The  Peronaeus  longus  also  everts  the  sole  of  the  foot,  and  from  the  oblique  direction 
of  the  tendon  across  the  sole  of  the  foot  is  an  important  agent  in  the  maintenance  of  the  trans- 
verse arch.  Taking  their  fixed  points  below,  the  Peronaei  serve  to  steady  the  leg  upon  the  foot. 
This  is  especially  the  case  in  standing  upon  one  leg,  when  the  tendency  of  the  superincumbent 
weight  is  to  thi'ow  the  leg  medialward;  the  Peronaeus  longus  overcomes  this  tendenc}^  by  drawing 
on  the  lateral  side  of  the  leg. 

Applied  Anatomy. — The  student  should  now  consider  the  positions  of  the  tendons  of  the  various 
muscles  of  the  leg,  their  relation  with  the  ankle-joint  and  surroimding  bloodvessels,  and  especially 
theu-  actions  upon  the  foot,  as  their  rigidity  and  contraction  give  rise  to  one  or  other  of  the  kinds 
of  deformity  known  as  club-foot.  The  most  simple  and  common  deformity,  and  one  that  is  rarely, 
if  ever,  congenital,  is  talipes  equinus,  the  heel  being  raised  by  the  rigidity  and  contraction  of  the 
Gastrocnemius  so  that  the  patient  walks  upon  the  ball  of  the  foot.  In  talipes  varus  the  foot  is 
forcibly  adducted  and  the  medial  side  of  the  sole  raised,  sometimes  to  a  right  angle  with  the 
ground,  by  the  action  of  the  Tibiales  anterior  and  posterior.  In  talipes  valgus  the  lateral  edge 
of  the  foot  is  raised  by  the  Peronaei,  and  the  patient  walks  on  the  medial  side  of  the  foot.  In 
talipes  calcaneus  the  toes  are  raised  by  the  Extensor  muscles,  the  heel  is  depressed  and  the  patient 
walks  upon  it.  Other  varieties  of  deformity  are  met  with,  as  talipes  equinovarus,  equinovalgus, 
and  calcaneovalgiis,  whose  names  sufficiently  indicate  their  natm-e.  Of  these,  tahpes  equinovarus 
is  the  most  common  congenital  form;  the  heel  is  raised  bj^  the  tendo  calcaneus,  the  medial  border 
of  the  foot  dra^m  upward  by  the  Tibiahs  anterior,  the  anterior  two-thirds  twisted  medialward 


584 


MYOLOGY 


by  the  Tibialis  posterior,  and  the  arch  increased  by  the  contraction  of  the  plantar  aponeurosis, 
so  that  the  patient  walks  on  the  middle  of  the  lateral  border  of  the  foot.  Each  of  these  deformities 
may  sometimes  be  successfully  relieved  by  division  of  the  opposing  tendons  and  fascia;  by  this 
means  the  foot  regains  its  proper  position,  and  the  tendons  heal  by  the  organization  of  lymph 
thrown  out  between  the  divided  ends.  The  operation  is  easily  performed  by  putting  the  con- 
tracted tendon  upon  the  stretch,  and  dividing  it  by  means  of  a  narrow,  shaip-pointed  knife 
inserted  beneath  it. 

Rupture  of  a  few  of  the  fibres  of  the  Gastrocneraius,  or  rupture  of  the  Plantaris  tendon,  not 
uncommonl}'  occurs,  especially  in  men  somewhat  advanced  in  life,  from  some  sudden  exertion, 
and  frequently  occurs  during  the  game  of  lawn  tennis,  and  is  hence  known  as  lawn-tennis  leg. 
The  accident  is  accompanied  by  a  sudden  pain,  and  produces  a  sensation  as  if  the  individual 
had  been  struck  a  violent  blow  on  the  part.  The  tendo  calcaneus  is  also  sometimes  ruptured. 
It  is  stated  that  John  Hunter  ruptured  his  tendo  calcaneus  while  dancing,  at  the  age  of  forty. 
The  bursa  between  the  tendo  calcaneus  and  the  posterior  surface  of  the  calcaneus  sometimes 
becomes  inflamed,  especially  in  pedestrians  and  "long-distance"  walkers.  It  causes  great  and 
disabling  pain,  and  entirely  prevents  the  sufferer  from  continuing  his  walk. 


THE    FASCIA   AROUND    THE    ANKLE. 

Fibrous  bands,  or  thickened  portions  of  the  fascia,  bind  down  the  tendons  in 
front  of  and  behind  the  ankle  in  their  passage  to  the  foot.  They  comprise  three 
ligaments,  viz.,  the  transverse  crural,  the  cruciate  crural,  and  the  laciniate;  and 
the  superior  and  inferior  peroneal  retinacula. 


Tibialis  anterior 

Extensor  dig.  longus 


Ext.  hall.  long. 

Ext.  dig.  hrevis 


Tendo  calcaneus 

Peronaeus  longus 


Pp.ronaeus  hrevis  Peronaeus  tertius 

Fig.  554. — The  mucous  sheaths  of  the  tendons  around  the  ankle. 


Lateral  aspect. 


Transverse  Crural  Ligament  (ligamentum  transversum  cruris;  upper  part  of  anterior 
annular  ligament)  (Fig.  554). — The  transverse  crural  ligament  binds  down  the 
tendons  of  Extensor  digitorum  longus.  Extensor  hallucis  longus,  Peronaeus  tertius, 
and  Tibialis  anterior  as  they  descend  on  the  front  of  the  tibia  and  fibula;  under 
it  are  found  also  the  anterior  tibial  vessels  and  deep  peroneal  nerve.  It  is  attached 
laterally  to  the  lower  end  of  the  fibula,  and  medially  to  the  tibia;  above  it  is  con- 
tinuous with  the  fascia  of  the  leg. 

Cruciate  Crural  Ligament  (ligamentum  cruciatum  cruris;  lower  part  of  anterior 
annular  ligament)  (Figs.  554,  555). — The  cruciate  crural  ligament  is  a  Y-shaped 
band  placed  in  front  of  the  ankle-joint,  the  stem  of  the  Y  being  attached  laterally 


THE  FASCIA   AROUND  THE  AXKLE 


58;! 


to  the  upper  surface  of  the  calcaneus,  in  front  of  the  depression  for  the  interosseous 
talocalcancan  ligament;  it  is  directed  mediahvard  as  a  double  layer,  one  lamina 
passing  in  front  of,  and  the  other  behind,  the  tendons  of  the  Peronaeus  tertius 
and  Extensor  digitorum  longus.  At  the  medial  l)order  of  the  latter  tendon  these 
two  layers  join  together,  forming  a  compartment  in  which  the  tendons  are 
enclosed.  From  the  medial  extremity  of  this  sheath  the  two  limbs  of  the  Y  diverge : 
one  is  directed  upward  and  mediahvard,  to  be  attached  to  the  tibial  malleolus, 
passing  over  the  Extensor  hallucis  longus  and  the  vessels  and  nerves,  but  enclosing 
the  Tibialis  anterior  by  a  splitting  of  its  fibres.  The  other  limb  extends  downward 
and  mediahvard,  to  be  attached  to  the  border  of  the  plantar  aponeurosis,  and  passes 
over  the  tendons  of  the  Extensor  hallucis  longus  and  Tibialis  anterior  and  also 
the  vessels  and  ner^•es. 


Tibialis  anterior         J'ii: 


Tibialis  posterior 


Ext.  hall.  lonq. 


Flexor  Jiallucis  longus 

B 

T  endocalcaneus 

Fig.  555. — The  mucous  sheaths  of  the  tendons  around  the  ankle.     Medial  aspect. 


Laciniate  Ligament  (ligamentum  lancinatinn;  internal  annular  ligament). — The 
laciniate  ligament  is  a  strong  fibrous  band,  extending  from  the  tibial  malleolus 
above  to  the  margin  of  the  calcaneus  below,  converting  a  series  of  bony  grooves 
in  this  situation  into  canals  for  the  passage  of  the  tendons  of  the  Flexor  muscles 
and  the  posterior  tibial  vessels  and  tibial  nerve  into  the  sole  of  the  foot.  It  is 
continuous  by  its  upper  border  with  the  deep  fascia  of  the  leg,  and  by  its  lower 
border  with  the  plantar  aponeurosis  and  the  fibres  of  origin  of  the  Abductor 
hallucis  muscle,  Enumerated  from  the  medial  side,  the  four  canals  which  it  forms 
transmit  the  tendon  of  the  Tibialis  posterior;  the  tendon  of  the  Flexor  digitorum 
longus;  the  posterior  tibial  vessels  and  tibial  nerve,  which  run  through  a  broad 
space  beneath  the  ligament;  and  lastly,  in  a  canal  formed  partly  by  the  talus,  the 
tendon  of  the  Flexor  hallucis  longus. 

Peroneal  Retinacula. —  The  peroneal  retinacula  are  fibrous  bands  which  bind 
down  the  tendons  of  the  Peronaei  longus  and  brevis  as  they  run  across  the  lateral 
side  of  the  ankle.  The  fibres  of  the  superior  retinaculum  {external  annular  ligament) 
are  attached  ahoxe  to  the  lateral  malleolus  and  below  to  the  lateral  surface  of  the 
calcaneus.  The  fibres  of  the  inferior  retinaculum  are  continuous  in  front  with  those 
of  the  cruciate  crural  ligament;  behind  they  are  attached  to  the  lateral  surface  of 
the  calcaneus;  some  of  the  fibres  are  fixed  to  the  peroneal  trochlea,  forming  a  septum 
between  the  tendons  of  the  Peronaei  longus  and  brevis. 


586  MYOLOGY 

The  Mucous  Sheaths  of  the  Tendons  Around  the  Ankle.^ — All  the  tendons  crossing 
the  ankle-joint  are  enclosed  for  part  of  their  lengtii  in  mucous  sheaths  which  have 
an  almost  uniform  length  of  about  8  cm.  each.  On  the  fro7it  of  the  ankle  (Fig.  554) 
the  sheath  for  the  Tibialis  anterior  extends  from  the  upper  margin  of  the  trans- 
verse crural  ligament  to  the  interval  between  the  diverging  limbs  of  the  cruciate 
ligament;  those  for  the  Extensor  digitorum  longus  and  Extensor  hallucis  longus 
reach  upward  to  just  above  the  level  of  the  tips  of  the  malleoli,  the  former  being 
the  higher.  The  sheath  of  the  Extensor  hallucis  longus  is  prolonged  on  to  the  base 
of  the  first  metatarsal  bone,  while  that  of  the  Extensor  digitorum  longus  reaches 
only  to  the  level  of  the  base  of  the  fifth  metatarsal.  On  the  medial  side  of  the  ankle 
(Fig.  555)  the  sheath  for  the  Tibialis  posterior  extends  highest  up — to  about 
4  cm.  above  the  tip  of  the  malleolus — while  below  it  stops  just  short  of  the  tuber- 
osity of  the  navicular.  The  sheath  for  Flexor  hallucis  longus  reaches  up  to  the  level 
of  the  tip  of  the  malleolus,  while  that  for  the  Flexor  digitorum  longus  is  slightly 
higher;  the  former  is  continued  to  the  base  of  the  first  metatarsal,  but  the  latter 
stops  opposite  the  first  cuneiform  bone. 

On  the  lateral  side  of  the  ankle  (Fig.  554)  a  sheath  which  is  single  for  the  greater 
part  of  its  extent  encloses  the  Peronaei  longus  and  brevis.  It  extends  upw^ard 
for  about  4  cm.  above  the  tip  of  the  malleolus  and  downward  and  forward  for 
about   the    same   distance. 

IV.    THE   MUSCLES    AND    FASCIA   OF   THE    FOOT. 

1.  The  Dorsal  Muscle  of  the  Foot. 

Extensor  digitorum  brevis. 

The  fascia  on  the  dorsum  of  the  foot  is  a  thin  membranous  layer,  continuous 
above  with  the  transverse  and  cruciate  crural  ligaments;  on  either  side  it  blends 
with  the  plantar  aponeurosis;  anteriorly  it  forms  a  sheath  for  the  tendons  on  the 
dorsum  of  the  foot. 

The  Extensor  digitorum  brevis  (Fig.  554)  is  a  broad,  thin  muscle,  which  arises 
from  the  forepart  of  the  upper  and  lateral  surfaces  of  the  calcaneus,  in  front  of 
the  groove  for  the  Peronaeus  brevis;  from  the  lateral  talocalcanean  ligament; 
and  from  the  common  limb  of  the  cruciate  crural  ligament.  It  passes  obliquely 
across  the  dorsum  of  the  foot,  and  ends  in  four  tendons.  The  most  medial,  which 
is  the  largest,  is  inserted  into  the  dorsal  surface  of  the  base  of  the  first  phalanx  of 
the  great  toe,  crossing  the  dorsalis  pedis  artery;  it  is  frequently  described  as  a 
separate  muscle — the  Extensor  hallucis  brevis.  The  other  three  are  inserted  into 
the  lateral  sides  of  the  tendons  of  the  Extensor  digitorum  longus  of  the  second, 
third,  and  fourth  toes. 

Nerves. — It  is  supplied  by  the  deep  peroneal  nerve. 

Actions. — The  Extensor  digitorum  brevis  extends  the  phalanges  of  the  four  toes  into  which 
it  is  inserted,  but  in  the  great  toe  acts  only  on  the  first  phalanx.  The  obliquity  of  its  direction 
counteracts  the  oblique  movement  given  to  the  toes  by  the  long  Extensor,  so  that  when  both 
muscles  act,  the  toes  are  evenly  extended. 

2.  The  Plantar  Muscles  of  the  Foot. 

Plantar  Aponeurosis  {aijoneurosis  p  lantaris;  plantar  fascia) . — The  plantar  apon- 
eurosis is  of  great  strength,  and  consists  of  pearly  white  glistening  fibres,  disposed, 
for  the  most  part,  longitudinally:  it  is  divided  into  central,  lateral,  and  medial 
portions. 

The  central  portion,  the  thickest,  is  narrow  behind  and  attached  to  the  medial 
process  of  the  tuberosity  of  the  calcaneus,  posterior  to  the  origin  of  the  Flexor 


rJlE  PLANTAR  MUSCLES  OF  THE  FOOT  587 

digitoriim  brevis;  and  becoming  broader  and  thinner  in  front,  divides  near  the 
heads  of  the  metatarsal  bones  into  five  processes,  one  for  each  of  the  toes.  Each 
of  these  processes  divides  opposite  the  metatarsoi)hahingeal  articulation  into  two 
strata,  su])erficial  and  dccj).  The  superficial  stratum  is  inserted  into  the  skin  of 
the  transverse  sulcus  which  separates  the  toes  from  the  sole.  The  deeper  stratum 
divides  into  two  slips  which  embrace  the  side  of  the  Flexor  tendons  of  the  toes, 
and  blend  with  the  sheaths  of  the  tendons,  and  with  the  transverse  metatarsal 
ligament,  thus  forming  a  series  of  arches  through  which  the  tendons  of  the  short 
and  long  Fh^xors  pass  to  the  toes.  The  intervals  left  between  the  five  processes 
allow  the  digital  vessels  and  nerves  and  the  tendons  of  the  Lumbricales  to  become 
superficial.  At  the  point  of  division  of  the  aponeurosis,  numerous  transverse 
fasciculi  are  superadded;  these  serve  to  increase  the  strength  of  the  aponeurosis 
at  this  part  by  binding  the  processes  together,  and  connecting  them  with  the  integu- 
ment. The  central  portion  of  the  plantar  aponeurosis  is  continuous  with  the  lateral 
and  medial  portions  and  sends  upward  into  the  foot,  at  the  lines  of  junction,  two 
strong  vertical  intermuscular  septa,  broader  in  front  than  behind,  which  separate 
the  intermediate  from  the  lateral  and  medial  plantar  groups  of  muscles;  from  these 
again  are  derived  thinner  transverse  septa  which  separate  the  various  layers  of 
muscles  in  this  region.  The  upper  surface  of  this  aponeurosis  gives  origin  behind 
to  the  Flexor  digitorum  brevis. 

The  lateral  and  medial  portions  of  the  plantar  aponeurosis  are  thinner  than 
the  central  piece,  and  cover  the  sides  of  the  sole  of  the  foot. 

The  lateral  portion  covers  the  under  surface  of  the  Abductor  digiti  quinti;  it  is 
thin  in  front  and  thick  behind,  where  it  forms  a  strong  band  between  the  lateral 
process  of  the  tuberosity  of  the  calcaneus  and  the  base  of  the  fifth  metatarsal  bone; 
it  is  continuous  medially  with  the  central  portion  of  the  plantar  aponeurosis,  and 
laterally  with  the  dorsal  fascia. 

The  medial  portion  is  thin,  and  covers  the  under  surface  of  the  Abductor  hallucis ; 
it  is  attached  behind  to  the  laciniate  ligament,  and  is  continuous  around  the  side 
of  the  foot  with  the  dorsal  fascia,  and  laterally  wdth  the  central  portion  of  the  plantar 
aponeurosis. 

The  muscles  in  the  plantar  region  of  the  foot  may  be  divided  into  three  groups, 
in  a  similar  manner  to  those  in  the  hand.  Those  of  the  medial  plantar  region 
are  connected  with  the  great  toe,  and  corrrespond  with  those  of  the  thumb;  those 
of  the  lateral  plantar  region  are  connected  with  the  little  toe,  and  correspond  with 
those  of  the  little  finger;  and  those  of  the  intermediate  plantar  region  are  connected 
with  the  tendons  intervening  between  the  two  former  groups.  But  in  order  to 
facilitate  the  description  of  these  muscles,  it  is  more  convenient  to  divide  them  into 
four  layers,  in  the  order  in  which  they  are  successively  exposed. 

The  First  Layer  (Fig.  556). 

x\bductor  hallucis.  Flexor  digitorum  brevis. 

Abductor  digiti  quinti. 

Dissection. — Remove  the  fascia  on  the  inner  and  outer  sides  of  the  foot,  commencing  in  front 
over  the  tendons  and  proceeding  backward.  The  central  portion  should  be  divided  transversely 
in  the  middle  of  the  foot,  and  the  two  flaps  dissected  forward  and  backward. 

The  Abductor  hallucis  lies  along  the  medial  border  of  the  foot  and  covers  the 
origins  of  the  plantar  vessels  and  nerves.  It  arises  from  the  medial  process  of  the 
tuberosity  of  the  calcaneus,  from  the  laciniate  ligament,  from  the  plantar  aponeu- 
rosis, and  from  the  intermuscular  septum  between  it  and  the  Flexor  digitorum 
brevis.  The  fibres  end  in  a  tendon,  which  is  inserted,  together  with  the  medial 
tendon  of  the  Flexor  hallucis  brevis,  into  the  tibial  side  of  the  base  of  the  first 
phalanx  of  the  great  toe. 


588 


MYOLOGY 


The  Flexor  digitorum  brevis  lies  in  the  middle  of  the  sole  of  the  foot,  imme- 
diately above  the  central  part  of  the  plantar  aponeurosis,  with  which  it  is  firmly 
united.  Its  deep  surface  is  separated  from  the  lateral  plantar  vessels  and  nerves 
by  a  thin  layer  of  fascia.  It  arises  by  a  narrow  tendon,  from  the  medial  process 
of  the  tuberosity  of  the  calcaneus,  from  the  central  part  of  the  plantar  aponeurosis, 
and  from  the  intermuscular  septa  between  it  and  the  adjacent  muscles.  It  passes 
forward,  and  divides  into  four  tendons,  one  for  each  of  the  four  lesser  toes.  Oppo- 
site the  bases  of  the  first  phalanges,  each  tendon 
divides  into  two  slips,  to  allow  of  the  passage 
of  the  corresponding  tendon  of  the  Flexor  digi- 
torum longus;  the  two  portions  of  the  tendon 
then  unite  and  form  a  grooved  channel  for  the 
reception  of  the  accompanying  long  Flexor 
tendon.  Finally,  it  divides  a  second  time,  and 
is  inserted  into  the  sides  of  the  second  phalanx 
about  its  middle.  The  mode  of  division  of  the 
tendons  of  the  Flexor  digitorum  brevis,  and  of 
their  insertion  into  the  phalanges,  is  analogous 
to  that  of  the  tendons  of  the  Flexor  digitorum 
sublimis  in  the  hand. 

Fibrous  Sheaths  of  the  Flexor  Tendons. — The 
terminal  portions  of  the  tendons  of  the  long 
and  short  Flexor  muscles  are  contained  in 
osseoaponeurotic  canals  similar  in  their  ar- 
rangement to  those  in  the  fingers.  These 
canals  are  formed  above  by  the  phalanges 
and  below  by  fibrous  bands,  which  arch  across 
the  tendons,  and  are  attached  on  either  side 
to  the  margins  of  the  phalanges.  Opposite 
the  bodies  of  the  proximal  and  second  pha- 
langes the  fibrous  bands  are  strong,  and  the 
fibres  are  transverse;  but  opposite  the  joints 
they  are  much  thinner,  and  the  fibres  are 
directed  obliquely.  Each  canal  contains  a 
mucous  sheath,  which  is  reflected  on  the  con- 
tained tendons. 

The  Abductor  digiti  quinti  (Abductor  minimi 
digiti)  lies  along  the  lateral  border  of  the  foot, 
and  is  in  relation  by  its  medial  margin  with 
the  lateral  plantar  vessels  and  nerves.  It  arises, 
by  a  broad  origin,  from  the  lateral  process  of 
the  tuberosity  of  the  calcaneus,  from  the  under 
surface  of  the  calcaneus  between  the  two  pro- 
cesses of  the  tuberosity,  from  the  forepart  of 
the  medial  process,  from  the  plantar  aponeu- 
rosis, and  from  the  intermuscular  septum 
between  it  and  the  Flexor  digitorum  brevis.  Its  tendon,  after  gliding  over  a  smooth 
facet  on  the  under  surface  of  the  base  of  the  fifth  metatarsal  bone,  is  inserted, 
with  the  Flexor  digiti  quinti  brevis,  into  the  fibular  side  of  the  base  of  the  first 
phalanx  of  the  fifth  toe. 

Dissection. — The  muscles  of  the  superficial  layer  should  be  divided  at  their  origin  by  inserting 
the  knife  beneath  each,  and  cutting  obliquely  backward,  so  as  to  detach  them  from  the  bone; 
they  should  then  be  drawn  forward,  in  order  to  expose  the  second  layer,  but  not  cut  away  at 
their  insertion.  The  two  layers  are  separated  by  a  thin  membrane,  the  deep  plantar  aponeurosis, 
on  the  removal  of  which  is  seen  the  tendon  of  the  Flexor  digitorum  longus,  the  Quadratus  plantae. 


Fig.  556.- 


-Muscles  of  the  sole  of  the  foot. 
First  layer. 


THE  PLAXTAR  .}[USrLES  OF  THE  FOOT  589 

the  tendon  of  the  Flexor  halkicis  longus,  and  the  Lumbricales.  The  long  Flexor  tendons  diverge 
from  each  other  at  an  acute  an^le;  the  Flexor  liallucis  longus  runs  along  the  inner  side  of  the 
foot,  on  a  plane  superior  to  that  of  the  Flexor  digitoruin  longus,  the  dirciction  of  the  latter  being 
obliquely  outward. 

The  Second  Layer  (Fig.  557). 
Qiiadratiis  plantae.  Lumbricales. 

The  Quadratus  plantae  (Flexor  accessorius)  is  separated  from  the  muscles  of 
the  first  layer  by  the  lateral  plantar  vessels  and  nerve.  It  arises  by  two  heads, 
which  are  separated  from  each  other  by  the  long  plantar  ligament:  the  medial 
or  larger  head  is  muscular,  and  is  attached  to  the  medial  concave  surface  of  the 
calcaneus,  below  the  groove  which  lodges  the  tendon  of  the  Flexor  hallucis  longus ; 
the  lateral  head,  flat  and  tendinous,  arises  from  the  lateral  border  of  the  inferior 
surface  of  the  calcaneus,  in  front  of  the  lateral  process  of  its  tuberosity,  and  from 
the  long  plantar  ligament.  The  two  portions  join  at  an  acute  angle,  and  end  in  a 
flattened  band  which  is  inserted  into  the  lateral  margin  and  upper  and  under  sur- 
faces of  the  tendon  of  the  Flexor  digitorum  longus,  forming  a  kind  of  groove,  in 
which  the  tendon  is  lodged.  It  usually  sends  slips  to  those  tendons  of  the  Flexor 
digitorum  longus  which  pass  to  the  second,  third,  and  fourth  toes. 

The  Lumbricales  are  four  small  muscles,  accessory  to  the  tendons  of  the  Flexor 
digitorum  longus  and  numbered  from  the  medial  side  of  the  foot;  they  arise  from 
these  tendons,  as  far  back  as  their  angles  of  division,  each  springing  from  two 
tendons,  except  the  first.  The  muscles  end  in  tendons,  which  pass  forward  on 
the  medial  sides  of  the  four  lesser  toes,  and  are  inserted  into  the  expansions  of 
the  tendons  of  the  Extensor  digitorum  longus  on  the  dorsal  surfaces  of  the  first 
phalanges. 

Dissection. — The  Flexor  tendons  should  be  divided  at  the  back  part  of  the  foot,  and  the 
Quadratus  plantae  at  its  origin,  and  drawn  forward,  in  order  to  expose  the  third  layer. 

The  Third  Layer  (Fig.  558). 

Flexor  hallucis  brevis.  Adductor  hallucis. 

Flexor  digiti  qiiinti  brevis. 

The  Flexor  hallucis  brevis  arises,  by  a  pointed  tendinous  process,  from  the  medial 
part  of  the  under  surface  of  the  cuboid  bone,  from  the  contiguous  portion  of  the 
third  cuneiform,  and  from  the  prolongation  of  the  tendon  of  the  Tibialis  posterior 
w^hich  is  attached  to  that  bone.  It  divides  in  front  into  tw^o  portions,  which  are 
inserted  into  the  medial  and  lateral  sides  of  the  base  of  the  first  phalanx  of  the 
great  toe,  a  sesamoid  bone  being  present  in  each  tendon  at  its  insertion.  The  medial 
portion  is  blended  with  the  Abductor  hallucis  previous  to  its  insertion;  the  lateral 
portion  with  the  Adductor  hallucis;  the  tendon  of  the  Flexor  hallucis  longus  lies 
in  a  groove  between  them;  the  lateral  portion  is  sometimes  described  as  the  first 
Interosseous  plantaris. 

The  Adductor  hallucis  {Adductor  obliquus  hallucis)  arises  by  two  heads — oblique 
and  transverse.  The  oblique  head  is  a  large,  thick,  fleshy  mass,  crossing  the  foot 
obliquely  and  occupying  the  hollow  space  inider  the  first,  second,  third,  and  fourth 
metatarsal  bones.  It  arises  from  the  bases  of  the  second,  third,  and  fourth  meta- 
tarsal bones,  and  from  the  sheath  of  the  tendon  of  the  Peronaeus  longus,  and  is 
inserted,  together  with  the  lateral  portion  of  the  Flexor  hallucis  brevis,  into  the 
lateral  side  of  the  base  of  the  first  phalanx  of  the  great  toe.  The  transverse  head 
( Transversus  pedis)  is  a  narrow,  flat  fasciculus  which  arises  from  the  plantar  meta- 
tarsophalangeal ligaments  of  the  third,  fourth,  and  fifth  toes  (sometimes  only 
from  the  third  and  fourth),  and  from  the  transverse  ligament  of  the  metatarsus. 
It  is  inserted  into  the  lateral  side  of  the  base  of  the  first  phalanx  of  the  great  toe, 
its  fibres  blending  with  the  tendon  of  insertion  of  the  oblique  head. 


590 


MYOLOGY 


The  Abductor,  Flexor  brevis,  and  iVdductor  of  the  ureat  toe,  hke  the  similar 
muscles  of  the  thumb,  give  off,  at  their  insertions,  fibrous  expansions  to  blend 
with  the  tendons  of  the  Extensor  digitorum  longus. 


Fig.  557. — Muscles  of  the  sole  of  the  foot. 
Second  layer. 


Fig.  558. — Muscles  of  the  sole  of  the  foot. 
Third  layer. 


The  Flexor  digiti  quinti  brevis  {Flexor  brevis  minimi  digiii)  lies  under  the 
metatarsal  bone  of  the  little  toe,  and  resembles  one  of  the  Interossei.  It  arises 
from  the  base  of  the  fifth  metatarsal  bone,  and  from  the  sheath  of  the  Peronaeus 
longus;  its  tendon  is  inserted  into  the  lateral  side  of  the  base  of  the  first  phalanx 
of  the  fifth  toe.  Occasionally  a  few  of  the  deeper  fibres  are  inserted  into  the 
lateral  part  of  the  distal  half  of  the  fifth  metatarsal  bone;  these  are  described  by 
some  as  a  distinct  muscle,  the  Opponens  digiti  quinti. 


The  Fourth  Layer. 

Interossei. 

The  Interossei  in  the  foot  are  similar  to  those  in  the  hand,  with  this  exception, 
that  they  are  grouped  arovnid  the  middle  line  of  the  second  digit,  instead  of  that 


THE  PLAXTAli  MUSCLES  OF  THE  FOOT 


591 


of  the  //;//•(/.     Thoy  are  seven  in  lumiber,  and  consist  of  two  ^ronps,  dorsal  and 
plantar. 

The  Interossei  dorsales  {Dorsal  inti'rossci)  (Fig.  559),/o(//- in  nnmber,  are  situated 
between  the  metatarsal  l)ones.  They  are  bipenniform  muscles,  each  arising  by 
two  heads  from  the  adjacent  sides  of  the  metatarsal  bones  between  which  it  is 
placed;  their  tendons  are  iuscried  into  the  bases  of  the  first  phalanges,  and  into  the 
aponeurosis  of  the  tendons  of  the  Extensor  digitorum  longus.  In  the  angular 
interval  left  between  the  heads  of  each  of  the  three  lateral  muscles,  one  of  the 
perforating  arteries  passes  to  the  dorsum  of  the  foot;  through  the  space  between 
the  heads  of  the  first  muscle  the  deep  plantar  branch  of  the  dorsalis  pedis  artery 
enters  the  sole  of  the  foot.  The  first  is  inserted  into  the  medial  side  of  the  second 
toe;  the  other  three  are  inserted  into  the  lateral  sides  of  the  second,  third,  and 
fourth  toes. 


Fig.  559. — The  Interossei  dorsales.     Left  foot. 


Fig.  560. — The  Interossei  plantares.     Left  foot. 


The  Interossei  plantares  {Plantar  interossei)  (Fig.  560),  three  in  number,  lie 
beneath  rather  than  between  the  metatarsal  bones,  and  each  is  connected  with 
but  one  metatarsal  bone.  They  arise  from  the  bases  and  medial  sides  of  the  bodies 
of  the  third,  fourth,  and  fifth  metatarsal  bones,  and  are  inserted  into  the  medial 
sides  of  the  bases  of  the  first  phalanges  of  the  same  toes,  and  into  the  aponeuroses 
of  the  tendons  of  the  Extensor  digitorum  longus. 

Nerves. — The  Flexor  digitorum  brevis,  the  Flexor  haUucis  brevis,  the  Abductor  hallucis, 
and  the  first  Lumbricahs  are  supphed  by  the  medial  plantar  nerve;  all  the  other  muscles  in  the 
sole  of  the  foot  by  the  lateral  plantar.  The  first  Interosseous  dorsalis  frequently  receives  an 
extra  filament  from  the  medial  branch  of  the  deep  peroneal  nerve  on  the  dorsum  of  the  foot, 
and  the  second  Interosseous  dorsalis  a  twig  from  the  lateral  branch  of  the  same  nerve. 

Actions. — All  the  muscles  of  the  foot  act  upon  the  toes,  and  may  be  grouped  as  abductors, 
adductors,  flexors,  or  extensors.  The  abductors  are  the  Interossei  dorsales,  the  Abductor  hallucis, 
and  the  Abductor  digiti  quinti.  The  Interossei  dorsales  are  abductors  from  an  imaginary  line 
passing  through  the  axis  of  the  second  toe,  so  that  the  first  muscle  draws  the  second  toe  medial- 
ward,  toward  the  great  toe,  the  second  muscle  draws  the  same  toe  lateralward,  and  the  third 
and  fourth  di'aw  the  third  and  fourth  toes  in  the  same  direction.  Like  the  Interossei  in  the  hand, 
each  assists  in  flexing  the  first  phalanx  and  extending  the  second  and  third  phalanges.  The 
Abductor  haUucis  abducts  the  great  toe  from  the  second,  and  also  flexes  its  proximal  phalanx. 


592 


MYOLOGY 


In  the  same  way  the  action  of  the  Abductor  digiti  fjuinli  is  twofold,  as  an  abductor  of  this  toe 
from  the  fourth,  and  also  as  a  flexor  of  its  proximal  phalanx.  The  adductors  are  the  Interossei 
plantares  and  the  Adductor  hallucis.  The  Interossei  plantares  adduct  the  third,  fourth,  and 
fifth  toes  toward  the  imaginary  hne  passing  through  the  second  toe,  and  by  means  of  their  inser- 
tions into  the  aponeuroses  of  the  Extensor  tendons  they  assist  in  flexing  the  proximal  phalanges 
and  extending  the  middle  and  terminal  phalanges.  The  obhque  head  of  the  Adductor  hallucis 
is  chiefly  concerned  in  adducting  the  great  toe  toward  the  second  one,  but  also  assists  in  flexing 
this  toe;  the  transverse  head  approximates  all  the  toes  and  thus  increases  the  cm-ve  of  the  trans- 
verse arch  of  the  metatarsus.  The  flexors  are  the  Flexor  digitorum  brevis,  the  Quadratus  plantae, 
the  Flexor  hallucis  brevis,  the  Flexor  digiti  quinti  brevis,  and  the  Lumbricales.  The  Flexor 
digitorum  brevis  flexes  the  second  phalanges  upon  the  first,  and,  continuing  its  action,  flexes  the 
first  phalanges  also,  and  brings  the  toes  together.  The  Quadratus  plantae  assists  the  Flexor  digi- 
torum longus  and  converts  the  obhque  pull  of  the  tendons  of  that  muscle  into  a  direct  backward 
puU  upon  the  toes.  The  Flexor  digiti  quinti  brevis  flexes  the  httle  toe  and  draws  its  metatarsal 
bone  downward  and  medialward.  The  Lumbricales,  like  the  corresponding  muscles  in  the  hand, 
assist  in  flexing  the  proximal  phalanges,  and  by  their  insertions  into  the  tendons  of  the  Extensor 
digitorum  longus  aid  that  muscle  in  straightening  the  middle  and  terminal  phalanges.  The 
Extensor  digitorum  brevis  extends  the  first  phalanx  of  the  great  toe  and  assists  the  long  Extensor 
in  extending  the  next  three  toes,  and  at  the  same  time  gives  to  the  toes  a. lateral  direction  when 
they  are  extended. 


Piriformis 
Gemellus  superior 
Obturator  internum 
Gemellus  inferior 
Obturator  externns 
Quadratus  femoris 


Fig.  561. — Fracture  of  the  neck  of  the  femur  within  the  articular  capsule. 


Applied  Anatomy. — The  student  should  now  consider  the  effects  produced  by  the  action  of 
the  various  muscles  in  fractures  of  the  bones  of  the  lower  extremity.  The  more  common  forms 
of  fracture  are  selected  for  illustration  and  description. 

In  fracture  of  the  neck  of  the  femur  inside  the  articular  capsule  (Fig.  561),  the  characteristic 
signs  are  shght  shortening  of  the  limb,  and  eversion  of  the  foot,  neither  of  which  may  appear 
until  some  time  after  the  injury.  The  eversion  is  caused  by  the  w^eight  of  the  hmb  rotating  it 
outward.    The  shortening  is  produced  by  the  contractions  of  all  the  muscles  about  the  joint. 

In  fracture  of  the  femur  just  below  the  trochanters  (Fig.  562),  the  upper  fragment  is  tilted  forward 
almost  at  right  angles  with  the  pelvis,  by  the  Psoas  major  and  Ihacus;  and,  at  the  same  time, 
everted  and  drawn  laterally  by  the  external  rotator  muscles  and  Glutaei,  causing  a  marked 
prominence  at  the  upper  and  lateral  side  of  the  thigh,  and  much  pain  from  the  bruising  and  lacera- 
tion of  the  muscles.  The  hmb  is  shortened,  because  the  lower  fragment  is  drawn  upward  by  the 
Rectus  femoris  in  front,  and  the  Biceps"femoris,  Semimembranosus,  and  Semitendinosus  behind; 
it  is,  at  the  same  time,  everted.  This  fractm-e  may  be  reduced  by  relaxation  of  all  the  muscles 
involved,  to  effect  which  the  hmb  should  be  put  up  with  the  thigh  flexed  on  the  pelvis  and  the 
leg  on  the  thigh. 


THE  PLANTAR  MUSCLES  OF  THE  FOOT 


593 


Oblique  fracture  of  the  femur  immediately  above  the  condyles  (Fis-  563)  is  a  formidable  injury, 
and  attended  with  consitlerable  displacement.  On  examination  of  the  limb,  the  lower  fragment 
may  be  felt  deep  in  the  popliteal  fossa,  being  drawn  backward  by  the  Gastrocnemius,  and  upward 
by  the  Hamstrings  and  li(>ctus  femoris.  The  pointed  end  of  the  upper  fragment  is  drawn  medial- 
ward  by  the  Pectineus  and  Adductores,  and  tilted  forward  by  the  Psoas  major  and  Iliacus,  piercing 
the  Rectus,  and  occasionally  the  integument.  Relaxation  of  these  muscles,  and  direct  approxima- 
tion of  the  broken  fragments,  are  effected  by  traction  with  the  limb  fully  flexed.  The  greatest 
care  is  requisite  in  keei)ing  the  pointed  extremity  of  the  upper  fragment  in  proper  position; 
otherwise,  after  union  of  the  fracture,  the  power  of  extension  of  the  limb  is  partially  destroyed, 
the  Rectus  femoris  being  held  down  by  the  fractured  end  of  the  bone. 


j  -''..'  ■  ■'-  Semimeinhranosus 
' ' '  'i  .  Semitendinosus 


Fig.  562. 


-Fracture  of  the  femur  below  the 
trochanters. 


Fig. 


563. — Fracture  of  the  femur  above  the 
condyles. 


In  transverse  fracture  of  the  patella  (Fig.  564)  the  fragments  are  separated  by  the  action  of 
the  Quadriceps  femoris  and  by  the  effusion  which  takes  place  into  the  joint;  the  extent  of  separa- 
tion of  the  two  fragments  depending  upon  the  degree  of  laceration  of  the  hgamentous  structures 
around  the  bone. 

In  obHque  fracture  of  the  body  of  the  tibia  (Fig.  565),  if  the  fractm-e  has  taken  place  obhquely 
from  above,  downward  and  forward,  the  fragments  ride  over  one  another,  the  lower  fragment 
being  drawn  backward  and  upward  by  the  powerful  action  of  the  muscles  of  the  calf;  the  pointed 
extremity  of  the  upper  fragment  projects  forward  immediately  beneath  the  integument,  often 
protruding  through  it,  and  rendering  the  fracture  compound.  If  the  direction  of  the  fractui'e 
is  the  reverse  of  that  shown  in  the  figm-e,  the  pointed  extremity  of  the  lower  fragment  projects 
forward,  rising  up  on  the  lower  end  of  the  upper  one.  By  bending  the  knee,  which  relaxes  the 
opposing  muscles,  and  making  extension  from  the  ankle  and  counter-extension  at  the  knee,  the 
fragments  may  be  brought  into  apposition.  It  is  sometimes  necessary,  however,  in  compound 
fractm'e  to  remove  a  portion  of  the  projecting  bone  with  the  saw  before  complete  adaptation 
can  be  effected. 

Fracture  of  the  fibula  with  dislocation  of  the  foot  lateralivard,  commonly  known  as  Pott's  fracture, 

is  one  of  the  most  frequent  injuries  in  the  region  of  the  ankle-joint.    The  fibula  is  fractured  about 

7  or  8  cm.  above  the  ankle;  in  addition  to  this  the  medial  malleolus  is  broken  off,  or  the  deltoid 

ligament  torn  through,  and  the  talus  displaced  from  the  corresponding  smiace  of  the  tibia.    The 

38 


594 


MYOLOGY 


foot  is  markedly  everted,  and  the  sharp  edge  of  the  upper  end  of  the  fractured  malleolus  presses 
strongly  against  the  skin;  at  the  same  time,  the  heel  is  drawn  up  by  the  muscles  of  the  calf.  This 
injury  can  generally  be  reduced  by  flexing  the  leg  at  right  angles  with  the  thigh,  which  relaxes 


Fig.  564. — Fracture  of  the  patella. 


Fig.   565. — Oblique  fracture  of  the  body  of  the  tibia. 


all  the  opposing  muscles,  and  by  making  extension  from  the  ankle  and  coimter-extension  at  the 
knee.  There  is  later  a  great  tendency  for  the  foot  to  fall  backward  at  the  ankle-joint,  and  constant 
supervision  is  required  to  counteract  this. 


ANGlOLUaY. 


rpPIE  vascular  system  is  divided  for  descriptive  purposes  into  (a)  the  blood 
-*-  vascular  system,  which  comprises  the  heart  and  bloodvessels  for  the  circula- 
tion of  the  blood;  and  (6)  the  lymph  vascular  system,  consisting  of  lymph  glands 
and  lymphatic  vessels,  through  which  a  colorless  fluid,  the  lymph,  circulates.  It 
must  be  noted,  however,  that  the  two  systems  communicate  with  each  other  and 
are  intimately  associated  developmentally. 

The  heart  is  the  central  organ  of  the  blood  vascular  system,  and  consists  of  a 
hollow  muscle;  by  its  contraction  the  blood  is  pumped  to  all  parts  of  the  body 
through  a  complicated  series  of  tubes,  termed  arteries.  The  arteries  undergo 
enormous  ramification  in  their  course  throughout  the  body,  and  end  in  minute 
vessels,  called  arterioles,  which  in  their  turn  open  into  a  close-meshed  network 
of  microscopic  vessels,  termed  capillaries.  After  the  blood  has  passed  through  the 
capillaries  it  is  collected  into  a  series  of  larger  vessels,  called  veins,  by  which  it  is 
returned  to  the  heart.  The  passage  of  the  blood  through  the  heart  and  blood- 
vessels constitutes  what  is  termed  the  circulation  of  the  blood,  of  which  the  following 
is  an  outline.^ 

The  human  heart  is  divided  by  septa  into  right  and  left  halves,  and  each  half 
is  further  divided  into  two  cavities,  an  upper  termed  the  atrium  and  a  lower  the 
ventricle.  The  heart  therefore  consists  of  four  chambers,  two,  the  right  atrium 
and  right  ventricle,  forming  the  right  half,  and  two,  the  left  atrium  and  left  ventricle 
the  left  half.  The  right  half  of  the  heart  contains  venous  or  impure  blood;  the  left, 
arterial  or  pure  blood.  The  atria  are  receiving  chambers,  and  the  ventricles  dis- 
tributing ones.  From  the  cavity  of  the  left  ventricle  the  pure  blood  is  carried  into 
a  large  artery,  the  aorta,  through  the  numerous  branches  of  which  it  is  distributed 
to  all  parts  of  the  body,  with  the  exception  of  the  lungs.  In  its  passage  through 
the  capillaries  of  the  body  the  blood  gives  up  to  the  tissues  the  materials  necessary 
for  their  growth  and  nourishment,  and  at  the  same  time  receives  from  the  tissues 
the  waste  products  resulting  from  their  metabolism.  In  doing  so  it  is  changed 
from  arterial  into  venous  blood,  which  is  collected  by  the  veins  and  through  them 
returned  to  the  right  atrium  of  the  heart.  From  this  cavity  the  impure  blood 
passes  into  the  right  ventricle,  and  is  thence  conveyed  through  the  pulmonary 
arteries  to  the  lungs.  In  the  capillaries  of  the  lungs  it  again  becomes  arterialized, 
and  is  then  carried  to  the  left  atrium  by  the  pulmonary  veins.  From  the  left  atrium " 
it  passes  into  the  left  ventricle,  from  which  the  cycle  once  more  begins. 

The  course  of  the  blood  from  the  left  ventricle  through  the  body  generally  to 
the  right  side  of  the  heart  constitutes  the  greater  or  systemic  circulation,  while  its 
passage  from  the  right  ventricle  through  the  lungs  to  the  left  side  of  the  heart  is 
termed  the  lesser  or  pulmonary  circulation. 

It  is  necessary,  however,  to  state  that  the  blood  which  circulates  through  the 
spleen,  pancreas,  stomach,  small  intestine,  and  the  greater  part  of  the  large  intes- 
tine is  not  returned  directly  from  these  organs  to  the  heart,  but  is  conveyed  by  the 
portal  vein  to  the  liver.  In  the  liver  this  vein  divides,  like  an  artery,  and  ultimately 
ends  in  capillary-like  vessels  (sinusoids),  from  which  the  rootlets  of  a  series  of  veins, 
called  the  hepatic  veins,  arise;  these  carry  the  blood  into  the  inferior  vena  cava, 

1  The  composition  of  the  blood  is  described  on  pp.  61  to  64. 


596 


ANGIOLOGY 


whence  it  is  conveyed  to  the  right  atrium.  From  this  it  will  be  seen  that  the 
blood  contained  in  the  portal  vein  passes  through  two  sets  of  vessels:  (1)  the 
capillaries  in  the  spleen,  pancreas,  stomach,  etc.,  and  (2)  the  sinusoids  in  the  liver. 
Speaking  generally,  the  arteries  may  be  said  to  contain  pure  and  the  veins 
impure  blood.  This  is  true  of  the  systemic,  but  not  of  the  pulmonary  vessels, 
since  it  has  been  seen  that  the  impure  blood  is  conveyed  from  the  heart  to  the  lungs 
by  the  pulmonary  arteries,  and  the  pure  blood  returned  from  the  lungs  to  the  heart 
by  the  pulmonary  veins.  Arteries,  therefore,  must  be  defined  as  vessels  which 
convey  blood  from  the  heart,  and  veins  as  vessels  which  return  blood  to  the  heart. 

Structure  of  Arteries  (Fig.  566). — The  arteries  are  composed  of  three  coats:  an  internal  or 
endotheUal  coat  {tunica  intima  of  Kolliker);  a  middle  or  muscular  coat  {tunica  media);  and  an 

external  or  connective-tissue  coat  {tunica  adventitia). 
The  two  inner  coats  together  are  very  easily  separated 
from  the  external,  as  by  the  ordinary  operation  of 
tying  a  Ugatm-e  around  an  artery.  If  a  fine  string  be 
tied  forcibly  upon  an  artery  and  then  taken  off,  the 
external  coat  will  be  found  undivided,  but  the  two 
inner  coats  are  divided  in  the  track  of  the  hgature 
and  can  easily  be  further  dissected  from  the  outer 
coat. 

The  inner  coat  {tunica  intima)  can  be  separated 
from  the  middle  by  a  httle  maceration,  or  it  maj'^  be 
stripped  off  in  small  pieces;  but,  on  account  of  its 
friabiUty,  it  cannot  be  separated  as  a  complete  mem- 
brane. It  is  a  fine,  transparent,  colorless  structure 
which  is  highly  elastic,  and,  after  death,  is  commonly 
corrugated  into  longitudinal  wrinkles.  The  inner  coat 
consists  of:  (1)  A  layer  of  pavement  endothehum, 
the  cells  of  which  are  polygonal,  oval,  or  fusiform, 
and  have  very  distinct  round  or  oval  nuclei.  This 
endothelium  is  brought  into  view  most  distinctly  by 
staining  with  nitrate  of  silver.  (2)  A  subendotheUal 
layer,  consisting  of  delicate  connective  tissue  with 
branched  cells  lying  in  the  interspaces  of  the  tissue; 
in  arteries  of  less  than  2  mm.  in  diameter  the  sub- 
endothehal  layer  consists  of  a  single  stratum  of  stel- 
late cells,  and  the  connective  tissue  is  only  largely 
developed  in  vessels  of  a  considerable  size.  (3)  An 
elastic  or  fenestrated  layer,  which  consists  of  a  mem- 
brane containing  a  net-work  of  elastic  fibres,  having 
principally  a  longitudinal  direction,  and  in  which, 
under  the  microscope,  smaU  elongated  apertures  or 
perforations  may  be  seen,  giving  it  a  fenestrated  ap- 
pearance. It  was  therefore  called  by  Henle  the  fenes- 
trated membrane.  This  membrane  forms  the  chief 
thickness  of  the  inner  coat,  and  can  be  separated  into 
several  layers,  some  of  which  present  the  appearance 
of  a  net-work  of  longitudinal  elastic  fibres,  and  others 
a  more  membranous  character,  marked  by  pale  fines 
having  a  longitudinal  direction.  In  minute  arteries 
the  fenestrated  membrane  is  a  very  thin  layer;  but  in  the  larger  arteries,  and  especially  in  the 
aorta,  it  has  a  very  considerable  thickness. 

The  middle  coat  {tunica  media)  is  distinguished  from  the  inner  by  its  color  and  by  the  trans- 
verse arrangement  of  its  fibres.  In  the  smaller  arteries  it  consists  principally  of  plain  muscle 
fibres  in  fine  bundles,  arranged  in  lamellae  and  disposed  circularly  around  the  vessel.  These 
lamellae  vary  in  number  according  to  the  size  of  the  vessel;  the  smallest  arteries  having  only  a 
single  layer  (Fig.  567),  and  those  sHghtly  larger  three  or  four  layers.  It  is  to  this  coat  that  the 
thickness  of  the  wafi  of  the  artery  is  mainly  due  (Fig.  566A,  m).  In  the  larger  arteries,  as  the 
iliac,  femoral,  and  carotid,  elastic  fibres  unite  to  form  lamellae  which  alternate  with  the  layers 
of  muscular  fibres;  these  lamellae  are  united  to  one  another  by  elastic  fibres  which  pass  between 
the  muscular  bundles,  and  are  connected  with  the  fenestrated  membrane  of  the  inner  coat  (Fig. 
568).  In  the  largest  arteries,  as  the  aorta  and  innominate,  the  amount  of  elastic  tissue  is  very 
considerable;  in  these  vessels  a  few  bundles  of  white  connective  tissue  also  have  been  found  in 


Fig.  566. — Transverse  section  through  a  small 
artery  and  vein  of  the  mucous  membrane  of  the 
epiglottis  of  a  child.  X  350.  (Klein  and  Noble 
Smith.)  A.  Artery,  showing  the  nucleated  endo- 
thelium, e,  which  lines  it;  the  vessel  being  con- 
tracted, the  endothelial  cells  appear  very  thick. 
Underneath  the  endothelium  is  the  wavy  elastic 
lamina.  The  chief  part  of  the  wall  of  the  vessel 
is  occupied  by  the  circular  muscle  coat  m;  the 
rod-shaped  nuclei  of  the  muscle  cells  are  well  seen. 
Outside  this  is  a,  part  of  the  adventitia.  This  is 
composed  of  bundles  of  connective  tissue  fibres, 
shown  in  section,  with  the  nuclei  of  the  connec- 
tive tissue  corpuscles.  The  adventitia  gradually 
merges  into  the  surrounding  connective  tissue. 
V.  Vein  showing  a  thin  endothelial  membrane, 
e,  raised  accidentally  from  the  intima,  which  on 
account  of  its  delicacy  is  seen  as  a  mere  line  on  the 
media  m.  This  latter  is  composed  of  a  few  circular 
unstriped  muscle  cells  a.  The  adventitia,  similar 
in  structure  to  that  of  an  artery. 


STRUCTURE  OF  ARTERIES 


597 


the  middle  coat.      The  muscle  fibre  cells  are  about  50;u  in  length  and  contain  well-marked,  rod- 
shaped  nuclei,  which  are  often  sUghtly  curved. 

The  external  coat  (tunica  adventitia)  consists  mainly  of  fine  and  closely  felted  bundles  of  white 
connective  tissue,  but  also  contains  clastic  fibres  in  all  but  the  smallest  arteries.  The  elastic 
tissue  is  much  more  abundant  next  the  tunica  media, 
and  it  is  sometimes  described  as  forming  here,  between 
the  adventitia  and  media,  a  special  layer,  the  tunica 
elastica  externa  of  Henle.  This  layer  is  most  marked 
in  arteries  of  medium  size.  In  the  largest  vessels  the 
external  coat  is  relatively  thin;  but  in  small  arteries 
it  is  of  greater  proportionate  thickness.  In  the  smaller 
arteries  it  consists  of  a  single  layer  of  white  connec- 
tive tissue  and  elastic  fibres;  while  in  the  smallest 
arteries,  just  above  the  capillaries,  the  elastic  fibres 
are  wanting,  and  the  connective  tissue  of  which  the 
coat  is  composed  becomes  more  nearly  homogeneous 
the  nearer  it  approaches  the  capillaries,  and  is  grad- 
ually reduced  to  a  thin  membranous  envelope,  which 
finally  disappears. 

Some  arteries  have  extremely  thin  walls  in  propor- 
tion to  their  size;  this  is  especially  the  case  in  those 
situated  in  the  cavity  of  the  cranium  and  vertebral 
canal,  the  difference  depending  on  the  thinness  of  the 
external  and  middle  coats. 

The  arteries,  in  their  distribution  throughout  the 
body,  are  included  in  thin  fibro-areolar  investments, 
which  form  their  sheaths.  The  vessel  is  loosely  con- 
nected with  its  sheath  by  delicate  areolar  tissue;  and 
the  sheath  usually  encloses  the  accompanying  veins, 
and  sometimes  a  nerve.      Some  arteries,  as  those  in  the  cranium,  are  not  included  in  sheaths. 

All  the  larger  arteries,  like  the  other  organs  of  the  body,  are  supphed  with  bloodvessels.    These 

Endothelial  and  suh- 
endothelial  layer  of 
inner  coat 
—  Elastic  layer 

Innermost  layers  of 
middle  coat 


Fig.  567. — Small  artery  and  vein,  pia  mater  of 
sheep.  X  250.  Surface  view  above  the  inter- 
rupted line;  longitudinal  section  below.  Artery 
in  red;  vein  in  blue. 


Outermost  layers  of 
—       middle  coat 

Innermost  fart  of 
Older  coat 


Outermost  part  of 
outer  coat 


Fig.  56S. — Section  of  a  medium-sized  artery.     (After  Griinstein.) 


nutrient  vessels,  called  the  vasa  vasorum,  arise  from  a  branch  of  the  artery,  or  from  a  neighbor- 
ing vessel,  at  some  considerable  distance  from  the  point  at  which  they  are  distributed;  they 


598  ANGIOLOGY 

ramify  in  the  loose  areolar  tissue  connecting  the  artery  with  its  sheath,  and  are  distributed  to 
the  external  coat,  but  do  not,  in  man,  penetrate  the  other  coats;  in  some  of  the  larger  mammals 
a  few  vessels  have  been  traced  into  the  middle  coat.  Minute  veins  return  the  blood  from  these 
vessels;  they  empty  themselves  into  the  vein  or  veins  accompanying  the  artery.  Lymphatic 
vessels  are  also  present  in  the  outer  coat. 

Arteries  are  also  supplied  with  nerves,  which  are  derived  from  the  sympathetic,  but  may  pass 
through  the  cerebrospinal  nerves.  They  form  intricate  plexuses  upon  the  surfacics  of  the  larger 
trunks,  and  run  along  the  smaller  arteries  as  single  filaments,  or  bundles  of  filaments  which  twist 
around  the  vessel  and  unite  with  each  other  in  a  plexiform  manner.  The  branches  derived  from 
these  plexuses  penetrate  the  external  coat  and  are  distributed  principally  to  the  muscular  tissue 
of  the  middle  coat,  and  thus  regulate,  by  causing  the  contraction  and  relaxation  of  this  tissue 
the  amount  of  blood  sent  to  any  part. 

The  Capillaries. — The  smaller  arterial  branches  (excepting  those  of  the  cavernous  structure 
of  the  sexual  organs,  of  the  splenic  puliD,  and  of  the  placenta)  terminate  in  net-works  of  vessels 
which  pervade  nearly  every  tissue  of  the  body.  These  vessels,  from  their  minute  size,  are  termed 
capillaries.  They  are  interposed  between  the  smallest  branches  of  the  arteries  and  the  commenc- 
ing veins,  constituting  a  net -work,  the  branches  of  which  maintain  the  same  diameter  throughout; 
the  meshes  of  the  net-work  are  more  uniform  in  shape  and  size  than  those  formed  by  the  anasto- 
moses of  the  small  arteries  and  veins. 

The  diameters  of  the  capillaries  vary  in  the  different  tissues  of  the  body,  the  usual  size  being 
about  8ju.  The  smallest  are  those  of  the  brain  and  the  mucous  membrane  of  the  intestines; 
and  the  largest  those  of  the  skin  and  the  marrow  of  bone,  where  they  are  stated  to  be  as  large 
as  20^  in  diameter.  The  form  of  the  capillary  net  varies  in  the  different  tissues,  the  meshes  being 
generally  roimded  or  elongated. 

The  rounded  form  of  mesh  is  most  common,  and  prevails  where  there  is  a  dense  network,  as  in 
the  lungs,  in  most  glands  and  mucous  membranes,  and  in  the  cutis;  the  meshes  are  not  of  an 
absolutely  circular  outUne,  but  more  or  less  angular,  sometimes  nearly  quadrangular,  or  polygonal, 
or  more  often  irregular. 

Elongated  meshes  are  observed  in  the  muscles  and  nerves,  the  meshes  resembhng  parallelograms 
in  form,  the  long  axis  of  the  mesh  running  parallel  with  the  long  axis  of  the  nerve  or  muscle. 
Sometimes  the  capillaries  have  a  looped  arrangement;  a  single  vessel  projecting  from  the  common 
net-work  and  returning  after  forming  one  or  more  loops,  as  in  the  papillse  of  the  tongue  and 
skin. 

The  number  of  the  capillaries  and  the  size  of  the  meshes  determine  the  degree  of  vascularity 
of  a  part.  The  closest  network  and  the  smallest  interspaces  are  found  in  the  lungs  and  in  the 
choroid  coat  of  the  eye.  In  these  situations  the  interspaces  are  smaller  than  the  capillary  vessels 
themselves.  In  the  intertubular  plexus  of  the  kidney,  in  the  conjunctiva,  and  in  the  cutis,  the 
interspaces  are  from  three  to  four  times  as  large  as  the  capillaries  which  form  them;  and  in  the 
brain  from  eight  to  ten  times  as  large  as  the  capillaries  in  their  long  diameters,  and  from  four 
to  six  times  as  large  in  their  transverse  diameters.  In  the  adventitia  of  arteries  the  width  of  the 
meshes  is  ten  times  that  of  the  capillary  vessels.  As  a  general  rule,  the  more  active  the  func- 
tion of  the  organ,  the  closer  is  its  capillary  net  and  the  larger  its  supply  of  blood;  the  meshes  of 
the  network  are  very  narrow  in  all  growing  parts,  in  the  glands,  and  in  the  mucous  membranes, 
wider  in  bones  and  Ugaments  which  are  comparatively  inactive;  bloodvessels  are  nearly  alto- 
gether absent  in  tendons,  in  which  very  httle  organic  change  occurs  after  their  formation.  In 
the  liver  the  capillaries  take  a  more  or  less  radial  course  toward  the  intralobular  vein,  and  their 
walls  are  incomplete,  so  that  the  blood  comes  into  direct  contact  with  the  hver  cells.  These 
vessels  in  the  liver  are  not  true  capillaries  but  "sinusoids;"  they  are  developed  by  the  growth 
of  columns  of  hver  cells  into  the  blood  spaces  of  the  embryonic  organ. 

Structure. — The  wall  of  a  capillary  consists  of  a  fine  transparent  endothehal  layer,  composed 
of  cells  joined  edge  to  edge  by  an  interstitial  cement  substance,  and  continuous  with  the  endo- 
thelial cells  which  line  the  arteries  and  veins.  When  stained  with  nitrate  of  silver  the  edges  which 
bound  the  epithehal  cells  are  brought  into  view  (Fig.  569).  These  cells  are  of  large  size  and  of 
an  irregular  polygonal  or  lanceolate  shape,  each  containing  an  oval  nucleus  which  may  be  dis- 
played by  carmine  or  hematoxyUn.  Between  their  edges,  at  various  points  of  their  meeting, 
roundish  dark  spots  are  sometimes  seen,  which  have  been  described  as  stomata,  though  they  are 
closed  by  intercellular  substance.  They  have  been  beheved  to  be  the  situations  through  which 
the  colorless  corpuscles  of  the  blood,  when  migrating  from  the  bloodvessels,  emerge;  but  this 
view,  though  probable,  is  not  universally  accepted. 

Kolossow  describes  these  cells  as  having  a  rather  more  complex  structure.  He  states  that 
each  consists  of  two  parts:  of  hyaline  groxmd  plates,  and  of  a  protoplasmic  granular  part,  in 
which  is  imbedded  the  nucleus,  on  the  outside  of  the  ground  plates.  The  hyahne  internal  coat 
of  the  capillaries  does  not  form  a  complete  membrane,  but  consists  of  "plates"  which  are  inelastic, 
and  though  in  contact  with  each  other  are  not  continuous;  when  therefore  the  capillaries  are  sub- 
jected to  intravascular  pressure,  the  plates  become  separated  from  each  other;  the  protoplasmic 
portions  of  the  cells,  on  the  other  hand,  are  united  together.    In  some  organs,  e.  g.,  the  glomeruli 


STRUCTURE  OF  VEINS 


599 


Fig.  569. — Capillaries  from  the  mesen- 
tery of  a  guinea-pig,  after  treatment  with 
solution  of  nitrate  of  silver,  a.  Cells. 
b.  Their  nuclei. 


of  the  kidneys,  intercellular  cement  (iaiuiol   l)c  dcnionstrated  in  the  capillary  wall  and  the  cells 
are  believed  to  form  a  syncytium. 

In  many  situations  a  delicate  sheath  or  envelope  of  branched  nucleated  connective  tissue  cells 
is  found  around  the  simple  capillary  tube,  particularly  in  the  larger  ones;  and  in  other  places, 
especially  in  the  glands,  the  cajiillarics  are  invested  with  retiform  connective  tissue. 

Sinusoids. — In  certain  organs,  viz.,  the  heart,  the  liver,  the  suprarenal  and  parathyroid 
glands,  the  glomus  caroti(uun  and  glomus  coccygeum,  the  smallest  bloodvessels  present  various 
differences  from  true  capillaries.  They  are  wider,  with  an 
irregular  lumen,  and  have  no  connective  tissue  covering, 
their  endothelial  cells  being  in  direct  contact  with  the  cells  of 
the  organ.  Moreover,  they  are  either  arterial  or  venous  and 
not  intermediate  as  are  the  true  capillaries.  These  vessels 
have  been  called  sinusoids  by  Minot.  They  are  formed 
by  coluums  of  cells  or  trabecular  pushing  their  way  into  a 
large  bloodvessel  or  blood  space  and  carrying  its  endothe- 
lium before  them;  at  the  same  time  the  wall  of  the  vessel 
or  space  grows  out  between  the  cell  columns. 

Structure  of  Veins. — ^The  veins,  like  the  arteries,  are  com- 
posed of  three  coats:  internal,  middle,  and  external;  and 
these  coats  are,  with  the  necessary  modifications,  analogous 
to  the  coats  of  the  arteries;  the  internal  being  the  endo- 
thelial, the  middle  the  muscular,  and  the  external  the 
connective  tissue  or  areolar  (Fig.  570).  The  main  differ- 
ence between  the  veins  and  the  arteries  is  in  the  compara- 
tive weakness  of  the  middle  coat  in  the  former. 

In  the  smallest  veins  the  three  coats  are  hardly  to  be  dis- 
tinguished (Fig.  567).  The  endothelium  is  supported  on  a 
membrane  separable  into  two  layers,  the  outer  of  which 
is  the  thicker,  and  consists  of  a  delicate,  nucleated  mem- 
brane {adventitia) ,  while  the  inner  is  composed  of  a  network 
of  longitudinal  elastic  fibres  {media).  In  the  veins  next 
above  these  in  size  (0.4  mm.  in  diameter),  according  to 
KoUiker,  a  connective  tissue  layer  containing  numerous 
muscle  fibres  circular^  disposed  can  be  traced,  forming  the 
middle  coat,  while  the  elastic  and  connective  tissue  elements  of  the  outer  coat  become 
more  distinctly  perceptible.  In  the  middle-sized  veins  the  typical  structure  of  these  vessels 
becomes  clear.  The  endothelium  is  of  the  same  character  as  in  the  arteries,  but  its  cells 
are  more  oval  and  less  fusiform.  It  is  supported  by  a  connective  tissue  layer,  consisting  of 
a  delicate  net-work  of  branched  cells,  and  external  to  this  is  a  layer  of  elastic  fibres  disposed 
in  the  form  of  a  net-work  in  place  of  the  definite  fenestrated  membrane  seen  in  the  arteries. 
This  constitutes  the  internal  coat.  The  middle  coat  is  composed  of  a  thick  layer  of  con- 
nective tissue  with  elastic  fibres,  intermixed,  in  some  veins,  with  a  transverse  layer  of  muscular 
tissue.  The  white  fibrous  element  is  in  considerable  excess,  and  the  elastic  fibres  are  in  much 
smaller  proportion  in  the  veins  than  in  the  arteries.  The  outer  coat  consists,  as  in  the  arteries, 
o^  areolar  tissue,  with  longitudinal  elastic  fibres.  In  the  largest  veins  the  outer  coat  is  from 
two  to  five  times  thicker  than  the  middle  coat,  and  contains  a  large  number  of  longitudinal 
muscular  fibres.  These  are  most  distinct  in  the  inferior  vena  cava,  especially  at  the  termination 
of  this  vein  in  the  heart,  in  the  trunks  of  the  hepatic  veins,  in  all  the  large  trunks  of  the  portal 
vein,  and  in  the  external  ihac,  renal,  and  azygos  veins.  In  the  renal  and  portal  veins  they  extend 
through  the  whole  thickness  of  the  outer  coat,  but  in  the  other  veins  mentioned  a  layer  of  con- 
nective and  elastic  tissue  is  found  external  to  the  muscular  fibres.  All  the  large  veins  which  open 
into  the  heart  are  covered  for  a  short  distance  with  a  layer  of  striped  muscular  tissue  continued 
on  to  them  from  the  heart.  Muscular  tissue  is  wanting:  (1)  in  the  veins  of  the  maternal  part 
of  the  placenta;  (2)  in  the  venous  sinuses  of  the  dura  mater  and  the  veins  of  the  pia  mater  of 
the  brain  and  meduUa  spinaUs;  (3)  in  the  veins  of  the  retina;  (4)  in  the  veins  of  the  cancellous 
tissue  of  bones;  (5)  in  the  venous  spaces  of  the  corpora  cavernosa.  The  veins  of  the  above-men- 
tioned parts  consist  of  an  internal  endotheUal  lining  supported  on  one  or  more  layers  of  areolar 
tissue. 

Most  veins  are  provided  with  valves  which  serve  to  prevent  the  reflux  of  the  blood.  Each 
valve  is  formed  by  a  reduphcation  of  the  inner  coat,  strengthened  by  connective  tissue  and  elastic 
fibres,  and  is  covered  on  both  surfaces  with  endothehum,  the  arrangement  of  which  differs  on 
the  two  surfaces.  On  the  surface  of  the  valve  next  the  wall  of  the  vein  the  cells  are  arranged 
transversely;  while  on  the  other  surface,  over  which  the  current  of  blood  flows,  the  cells  are 
arranged  longitudinally  in  the  direction  of  the  current.  Most  commonly  two  such  valves  are 
found  placed  opposite  one  another,  more  especially  in  the  smaller  veins  or  in  the  larger  trunks 
at  the  point  where  they  are  joined  by  smaller  branches;  occasionally  there  are  three  and  some- 


600 


ANGIOLOGY 


times  only  one.  The  valves  are  semilunar.  They  are  attached  by  their  convex  edges  to  the 
wall  of  the  vein;  the  concave  margins  are  free,  directed  in  the  course  of  the  venous  current,  and 
lie  in  close  apposition  with  the  wall  of  the  vein  as  long  as  the  current  of  blood  takes  its  natural 
course;  if,  however,  any  regurgitation  takes  place,  the  valves  become  distended,  their  opposed 
edges  are  brought  into  contact,  and  the  current  is  interrupted.  The  wall  of  the  vein  on  the 
cardiac  side  of  the  point  of  attachment  of  each  valve  is  expanded  into  a  pouch  or  sinus,  which 
gives  to  the  vessel,  when  injected  or  distended  with  blood,  a  knotted  appearance.  The  valves 
are  very  numerous  in  the  veins  of  the  extremities,  especially  of  the  lower  extremities,  these  vessels 

Endothelium  •■  ~ . 
Elastic  layer  y-^' 


Middle  coat ; — ■ 


Outer  coat . 


Fig.  570. — Section  of  a  medium-sized  vein. 


having  to  conduct  the  blood  against  the  force  of  gravity.  They  are  absent  in  the  very  small 
veins,  i.  e.,  those  less  than  2  mm.  in  diameter,  also  in  the  venae  cavse,  hepatic,  renal,  uterine,  and 
ovarian  veins.  A  few  valves  are  found  in  each  spermatic  vein,  and  one  also  at  its  point  of  jxmc- 
tion  with  the  renal  vein  or  inferior  vena  cava  respectively.  The  cerebral  and  spinal  veins,  the 
veins  of  the  cancellated  tissue  of  bone,  the  pulmonary  veins,  and  the  umbilical  vein  and  its 
branches,  are  also  destitute  of  valves.  A  few  valves  are  occasionally  found  in  the  azygos  and 
intercostal  veins.  Rudimentary  valves  are  found  in  the  tributaries  of  the  portal  venous  system. 
The  veins,  like  the  arteries,  are  supphed  with  nutrient  vessels,  vasa  vasorum.  Nerves  also 
are  distributed  to  them  in  the  same  manner  as  to  the  arteries,  but  in  much  less  abundance. 


THE  THORACIC  CAVITY. 


The  heart  and  lungs  are  situated  in  the  thorax,  the  walls  of  which  afford  them 
protection.  The  heart  lies  between  the  two  lungs,  and  is  enclosed  within  a  fibrous 
bag,  the  pericardium,  while  each  lung  is  invested  by  a  serous  membrane,  the  pleura. 
The  skeleton  of  the  thorax,  and  the  shape  and  boundaries  of  the  cavity,  have  already 
been  described  (page  216). 

The  Cavity  of  the  Thorax. — The  capacity  of  the  cavity  of  the  thorax  does  not 
correspond  with  its  apparent  size  externally,  because  (1)  the  space  enclosed  by 
the  lower  ribs  is  occupied  by  some  of  the  abdominal  viscera;  and  (2)  the  cavity 


THE  PERICARDIUM  601 

extends  above  the  anterior  parts  of  the  first  ribs  into  the  neck.  The  size  of  the 
thoracic  cavity  is  constantly  varying  during  life  with  the  movements  of  the  ribs 
and  Diai^hragma,  and  ^^•itll  the  degree  of  distention  of  the  abdominal  viscera. 
From  the  collapsed  state  of  the  lungs  as  seen  when  the  thorax  is  opened  in  the  dead 
body,  it  would  appear  as  if  the  viscera  only  partly  filled  the  cavity,  but  during 
life  there  is  no  vacant  space,  that  which  is  seen  after  death  being  filled  up  by  the 
ex])anded  lungs. 

The  Upper  Opening  of  the  Thorax. — The  parts  which  pass  through  the  upper 
opening  of  the  thorax  are,  from  before  backward,  in  or  near  the  middle  line,  the 
Sternohyoideus  and  Sternothyreoideus  muscles,  the  remains-  of  the  thymus,  the 
inferior  thyroid  veins,  the  trachea,  oesophagus,  thoracic  duct,  and  the  Longus 
colli  muscles;  at  the  sides,  the  innominate  artery,  the  left  common  carotid,  left 
subclavian  and  internal  mammary  arteries  and  the  costocervical  trunks,  the 
innominate  veins,  the  vagus,  cardiac,  phrenic,  and  sympathetic  nerves,  the  greater 
parts  of  the  anterior  divisions  of  the  first  thoracic  nerves,  and  the  recurrent  nerve 
of  the  left  side.  The  apex  of  each  lung,  covered  by  the  pleura,  also  projects 
through  this  aperture,  a  little  above  the  level  of  the  sternal  end  of  the  first  rib. 

The  Lower  Opening  of  the  Thorax.T— The  lower  opening  of  the  thorax  is  wider 
transversely  than  from  before  backward.  It  §lopes  obliquely  downward  and  back- 
ward, so  that  the  thoracic  cavity  is  much  deeper  behind  than  in  front.  The  Dia- 
phragma  (see  page  493)  closes  the  opening  and  forms  the  floor  of  the  thorax.  The 
floor  is  flatter  at  the  centre  than  at  the  sides,  and  higher  on  the  right  side  than  on 
the  left;  in  the  dead  body  the  right  side  reaches  the  level  of  the  upper  border  of 
the  fifth  costal  cartilage,  while  the  left  extends  only  to  the  corresponding  part 
of  the  sixth  costal  cartilage.  From  the  highest  point  on  each  side  the  floor  slopes 
suddenly  downward  to  the  costal  and  vertebral  attachments  of  the  Diaphragma; 
this  slope  is  more  marked  behind  than  in  front,  so  that  only  a  narrow  space  is  left 
between  the  Diaphragma  and  the  posterior  wall  of  the  thorax. 


THE   PERICARDIUM. 

The  pericardium  (Fig.  571)  is  a  conical  fibro-serous  sac,  in  which  the  heart  and 
the  roots  of  the  great  vessels  are  contained.  It  is  placed  behind  the  sternum  and 
the  cartilages  of  the  third,  fourth,  fifth,  sixth,  and  seventh  ribs  of  the  left  side, 
in  the  mediastinal  cavity. 

In  front,  it  is  separated  from  the  anterior  wall  of  the  thorax,  in  the  greater  part 
of  its  extent,  by  the  lungs  and  pleurae ;  but  a  small  area,  somewhat  variable  in  size, 
and  usually  corresponding  with  the  left  half  of  the  lower  portion  of  the  body  of 
the  sternum  and  the  medial  ends  of  the  cartilages  of  the  fourth  and  fifth  ribs  of 
the  left  side,  comes  into  direct  relationship  with  the  chest  wall.  The  lower  extrem- 
ity^ of  the  thymus,  in  the  child,  is  in  contact  with  the  front  of  the  upper  part  of 
the  pericardium.  Behind,  it  rests  upon  the  bronchi,  the  oesophagus,  the  descending 
thoracic  aorta,  and  the  posterior  part  of  the  mediastinal  surface  of  each  lung. 
Laterally,  it  is  covered  by  the  pleurae,  and  is  in  relation  with  the  mediastinal  sur- 
faces of  the  lungs;  the  phrenic  nerve,  with  its  accompanying  vessels,  descends 
between  the  pericardium  and  pleura  on  either  side. 

Structure  of  the  Pericardium. — Although  the  pericardium  is  usually  described  as  a  single  sac, 
an  examination  of  its  structm-e  shows  that  it  consists  essentially  of  two  sacs  intimately  connected 
with  one  another,  but  totally  different  m  structm'e.  The  outer  sac,  kno^Ti  as  the  fibrous  peri- 
cardium, consists  of  fibrous  tissue.  The  inner  sac,  or  serous  pericardium,  is  a  dehcate  mem- 
brane which  hes  within  the  fibrous  sac  and  lines  its  walls;  it  is  composed  of  a  single  layer  of 
flattened  cells  resting  on  loose  connective  tissue.  The  heart  invaginates  the  wall  of  the  serous 
sac  from  above  and  behind,  and  practically  obliterates  its  cavity,  the  space  being  a  potential 
one,  except  in  front,  where  a  small  interspace  exists  below  the  apex  of  the  heart. 


602 


AN  GIG  LOGY 


The  fibrous  pericardium  forms  a  flask-shaped  baK,  the  neck  of  which  is  closed  by  its  fusion 
with  the  external  coats  of  the  si'cat  vessels,  while  its  base  is  attached  to  the  central  tendon  and 
to  the  muscular  fibres  of  the  left  side  of  the  Diaphragma.  In  some  of  the  lower  mammals  the 
base  is  either  completely  separated  from  the  Diapln-agma  or  joined  to  it  by  some  loose  areolar 
tissue;  in  man  much  of  its  diaphragmatic  attachment  consists  of  loose  fibrous  tissue  which  can 
be  readily  broken  down,  but  over  a  small  area  the  central  tendon  of  the  Diaphragma  and  the 
pericardium  are  completely  fused.  Above,  the  fibrous  pericardium  not  only  blends  with  the 
external  coats  of  the  great  vessels,  but  is  continuous  with  the  pretracheal  layer  of  the  deep  cervical 
fascia.  By  means  of  these  upper  and  lower  connections  it  is  securely  anchored  within  the  thoracic 
cavity.  It  is  also  attached  to  the  posterior  surface  of  the  sternum  by  the  superior  and  inferior 
stemopericardiac  ligaments ;  the  upper  passing  to  the  manubrium,  and  the  lower  to  the  xiphoid 
process.     On  either  side , of  the  ascending  aorta  it  sends  upward  a  diverticulum;  that  on  the  left 


R.  common  carotid  a. 
R.  subclavian  a       ^-—r^/  L.  coinmon  carotid  a. 


L.  subclavian  a. 


Sup.  vena  cava 


R.  'pulmonary 

veiiib 


Cut  edges  of  serous 
pericardium, 


':ix-p^  ^-  pulmomtry  veins 


Fig.  .571. 


-Posterior  wall  of  the  pericardial  sac,  showing  the  lines  of  reflection  of  the  serous  pericardium  on  the 

great  vessels. 


side,  somewhat  conical  in  shape,  passes  between  the  arch  of  the  aorta  and  the  pulmonary  artery, 
toward  the  ligamentum  arteriosum,  where  it  ends  in  a  cecal  extremity  which  is  attached  by  loose 
connective  tissue  to  the  hgament ;  that  on  the  right  side  passes  between  the  ascending  aorta  and 
superior  vena  cava,  and  also  ends  in  a  blind  extremity. 

The  vessels  receiving  fibrous  prolongations  from  this  membrane  are:  the  aorta,  the  superior 
vena  cava,  the  right  and  left  pulmonary  arteries,  and  the  four  pulmonary  veins.  The  mferior 
vena  cava  enters  the  pericardium  through  the  central  tendon  of  the  Diaphragma,  and  receives 
no  covering  from  the  fibrous  layer. 


THE  PERICARDIUM  603 

The  serous  pericardium  is,  as  already  stated,  a  closed  sac  which  linos  the  fil)rous  pericardium 
and  is  invaginated  l)y  the  heart;  it  therefore  consists  of  a  visceral  and  a  parietal  portion.  The 
visceral  portion,  or  epicardium,  covers  the  heart  and  the  great  vessels,  and  from  the  latter  is 
continuous  with  the  i)arietal  layer  which  lines  the  fibrous  pericardium.  The  portion  which 
covers  the  vessels  is  arranged  in  tlie  form  of  two  tubes.  The  aorta  and  pulmonary  artery  are 
enclosed  in  one  tube,  the  arterial  mesocardium.  The  superior  and  inferior  venaj  cava?  and  the 
four  pulmonar\'  veins  are  enclosed  in  a  second  tube,  the  venous  mesocardium,  the  attachment 
of  wliich  to  the  parietal  layer  j^resents  the  shape  of  an  inverted  U.  The  cid-iJe-sdc  enclosed  between 
the  limbs  of  the  H  lies  behind  the  left  atrium  and  is  known  as  the  oblique  sinus,  while  the  passage 
between  the  venous  and  arterial  mesocardia — i.  e.,  between  the  aorta  and  pubiionary  artery  in 
front  and  the  atria  behind — is  termed  the  transverse  sinus. 

The  Ligament  of  the  Left  Vena  Cava. — Between  the  left  pulmonary  artery  and  subjacent 
pidmonary  \ein  is  a  triangular  fold  of  the  serous  pericardium;  it  is  knowoi  as  the  ligament  of  the 
left  vena  cava  {rcsligial  fold  of  Marshall).  It  is  formed  by  the  dupUcature  of  the  serous  layer 
over  the  remnant  of  the  lower  part  of  the  left  superior  vena  cava  {dud  ofCuvier),  which  becomes 
obliterated  during  fetal  life,  and  remains  as  a  fibrous  band  stretching  from  the  highest  left  inter- 
costal vein  to  the  left  atrium,  where  it  is  continuous  with  a  small  vein,  the  vein  of  the  left  atrium 
(oblique  rein  of  Marshall),  which  opens  into  the  coronary  sinus. 

The  arteries  of  the  pericardium  are  derived  from  the  internal  mammarj^  and  its  musculo- 
phrenic branch,  and  from  the  descending  thoracic  aorta. 

The  nerves  of  the  percardium  are  derived  from  the  vagus  and  phrenic  nerves,  and  the  sj^mpa- 
thetic  trunks. 

Apphed  Anatomy. — Effusion  of  fluid  into  the  pericardial  sac  often  occurs  in  acute  rheumatism 
or  pneumonia,  or  in  patients  with  chronic  vascular  and  renal  disease,  embarrassing  the  heart's 
action  and  giving  rise  to  signs  of  cardiac  distress,  such  as  pallor,  a  rapid  and  feeble  pulse,  dyspnoea, 
and  restlessness.  On  examination,  the  apical  cardiac  impulse  is  absent,  or  replaced  by  a  more 
extensive  indefinite  and  wavering  pulsation;  it  may  appear  to  be  in  the  second,  third,  or  fourth 
left  space,  and  is  then  not  an  apex  impulse,  as  Potain  has  stated,  but  due  to  the  impact  of  some 
portion  of  the  heart  wall  nearer  its  base.  In  cliildren  the  precordial  intercostal  spaces  may  bulge 
outward.  The  most  striking  sign,  however,  is  the  great  increase  in  all  directions  of  the  precordial 
dulness  on  percussion.  This  becomes  pear-shaped,  the  stalk  of  the  pear  reaching  up  to  about  the 
left  sternoclavicular  articulation;  the  dulness  also  extends  some  distance  to  the  right  of  the 
sternum,  particular^  in  the  fifth  interspace  (Rotch).  The  fluid  collects  mainly  on  either  side 
of  the  heart,  and  below  it,  especially  on  the  left  side,  where  the  Diaphi-agma  can  yield  more 
readilj'  to  pressiu-e  than  it  can  on  the  right.  Ewart  has  drawn  attention  to  the  presence  of  a 
square  patch  of  dulness  over  the  base  of  the  left  lung  behind,  reaching  up  to  the  level  of  the 
ninth  or  tenth  rib,  and  extending  laterally  as  far  as  the  inferior  angle  of  the  scapula;  the  imder- 
IjTug  lung  tissue  gives  the  physical  signs  of  compression  or  collapse. 

Paracentesis  of  the  pericardium  is  often  required  to  reheve  the  m'gent  cardiac  or  respiratorj^ 
distress  in  these  cases,  and  should  be  performed  -ndthout  hesitation  and  before  the  patient  is 
in  extremis.  It  may  also  be  required  when  the  pericardium  is  filled  with  blood  or  pus,  and  as  it 
is  advisable  to  perform  this  operation  without  transfixing  the  pleura,  the  puncture  should  be  made 
either  in  the  fifth  or  sixth  intercostal  space  on  the  left  side  and  close  to  the  sternum,  sO  as  to 
avoid  wounding  the  internal  mammary  artery,  which  descends  about  1.25  cm.  from  the  sternal 
margin;  or  the  needle  may  be  entered  at  the  left  costoxiphoid  angle  and  made  to  pass  upward 
and  backward  behind  the  lower  end  of  the  body  of  the  sternum  into  the  pericardial  sac.  Cursch- 
mann,^  however,  argues  that  the  heart  itself  necessarih*  hes  almost  in  contact  with  the  anterior 
wall  of  the  thorax  even  in  cases  of  the  largest  pericardial  effusion,  so  that  there  is  risk  of  piercing 
it  if  the  puncture  is  made  in  the  fourth  or  fifth  left  intercostal  space  within  even  so  much  as  5 
to  8  cm.  of  the  sternal  margin.  He  therefore  advises  that  in  moderately  large  pericardial  effusions 
the  trocar  should  be  inserted  in  the  left  mamillary  hne,  or  lateral  to  it  if  the  effusion  is  very  large, 
in  the  fifth  or  sixth  interspace.  In  consequence  of  the  uncertain  and  varying  position  of  the 
anterior  reflexion  of  the  pleura,  transfixion  of  the  plem-al  sac  cannot  always  be  a^'oided.  Peri- 
cardiotomy is  required  when  the  effusion  is  of  a  pm-ulent  nature.  In  this  operation  a  portion  of 
the  fifth  or  sixth  costal  cartilage  is  excised.  An  incision  is  made  along  the  left  border  of  the 
sternum  from  the  upper  border  of  the  fomih  cartilage  to  the  seventh.  The  fifth  costal  cartilage 
is  now  separated  from  the  sternima  by  means  of  a  gouge,  great  care  being  taken  not  to  let  the 
instrmnent  shp  and  penetrate  too  deeph'.  The  cartilage  is  then  seized  with  Hon  forceps  and 
raised,  the  tissues  beneath  it  being  peeled  off,  so  as  to  avoid  wounding  the  internal  mammarj' 
artery  or  the  pleura.  The  Transversus  thoracis  is  now  scratched  through,  with  a  director  or  the 
nail  of  the  index  finger,  close  to  the  sternum,  and  the  pericardium  felt  for  and  opened,  the  finger 
guarding  the  pleura  and  left  internal  mammarj-  artery. 

'  Therapie  der  Gegenwart,  1905. 


604 


AXaiOLOGY 


THE  HEART   (COR). 

The  heart  is  a  hollow  muscular  organ  of  a  somewhat  conical  form;  it  lies  between 
the  hmgs  in  the  middle  mediastinum  and  is  enclosed  in  the  pericardium  (Fig.  572). 
It  is  placed  obliquely  in  the  chest  behind  the  body  of  the  sternum  and  adjoining 
parts  of  the  rib  castilages,  and  projects  farther  into  the  left  than  into  the  right 
half  of  the  thoracic  cavity,  so  that  about  one-third  of  it  is  situated  on  the  right 
and  two-thirds  on  the  left  of  the  median  plane. 

Size. — The  heart,  in  the  adult,  measures  about  12  cm.  in  length,  8  to  9  cm.  in 
breadth  at  the  broadest  part,  and  6  cm.  in  thickness.  Its  weight,  in  the  male, 
varies  from  280  to  340  grams;  in  the  female,  from  230  to  280  grams.  The  heart 
continues  to  increase  in  weight  and  size  up  to  an  advanced  period  of  life;  this 
increase  is  more  marked  in  men  than  in  women. 


Cut  edge  of  pa  icardium 


Fig.  572. — Front  view  of  heart  and  lungs. 


Component  Parts. — As  has  already  been  stated  (page  595),  the  heart  is  sub- 
divided by  septa  into  right  and  left  halves,  and  a  constriction  subdivides  each 
half  of  the  organ  into  two  cavities,  the  upper  cavity  being  called  the  atrium,  the 
lower  the  ventricle.  The  heart  therefore  consists  of  four  chambers,  viz.,  right  and 
left  atria,  and  right  and  left  ventricles. 

The  division  of  the  heart  into  four  cavities  is  indicated  on  its  surface  by  grooves. 
The  atria  are  separated  from  the  ventricles  by  the  coronary  sulcus  {auriculo- 
ventricular  groove);  this  contains  the  trunks  of  the  nutrient  vessels  of  the  heart, 
and  is  deficient  in  front,  where  it  is  crossed  by  the  root  of  the  pulmonary  artery. 
The  interatrial  groove,  separating  the  two  atria,  is  scarcely  marked  on  the  posterior 


THE  HEART 


005 


surface,  while  anteriorly  it  is  hidden  by  the  pulmonary  artery  and  aorta.  The 
ventricles  are  separated  by  two  grooves,  one  of  which,  the  anterior  longitudinal 
sulcus,  is  situated  on  the  sternocostal  surface  of  the  heart,  dose  to  its  left  margin, 
the  other  posterior  longitudinal  sulcus,  on  the  diaphragmatic  surface  near  the  right 
margin;  these  grooxcs  extend  from  the  base  of  the  \-entricular  i)ortion  to  a  notch, 
the  incisura  apicis  cordis,  on  the  acute  margin  of  the  heart  just  to  the  right  of  the 
apex. 

The  base  {basis  cordis)  (Fig.  578),  directed  upward,  backward,  and  to  the  right, 
is  separated  from  the  fifth,  sixtli,  seventh,  and  eighth  thoracic  vertebra  by  the 
oesophagus,  aorta,  and  thoracic  duct.  It  is  formed  mainly  by  the  left  atrium, 
and,  to  a  small  extent,  by  the  back  part  of  the  right  atrium.  Somewhat  quadri- 
lateral in  form,  it  is  in  relation  above  with  the  bifurcation  of  the  pulmonary  artery, 


Azijgos  vein 


Left  jyulmonary  vehis 

Ohlique  vein  of  left  atrium 
Great  cardiac  vein 
Left  marginal  vein 


Rigid  ptdm-onary 
veins 


^^^  Small  cardiac  vein 

Posterior  vein  of  left  ventricle 

Middle  cardiac  vein 
Fig.   573. — Base  and  diaphragmatic  surface  of  heart. 


and  is  bounded  below  by  the  posterior  part  of  the  coronary  sulcus,  containing  the 
coronary  sinus.  On  the  right  it  is  limited  by  the  sulcus  terminalis  of  the  right 
atrium,  and  on  the  left  by  the  ligament  of  the  left  vena  cava  and  the  oblique  vein 
of  the  left  atrium.  The  four  pulmonary  veins,  two  on  either  side,  open  into  the 
left  atrium,  while  the  superior  vena  cava  opens  into  the  upper,  and  the  anterior 
vena  cava  into  the  lower,  part  of  the  right  atrium. 

The  Apex  {apex  cordis). — The  apex  is  directed  downward,  forward,  and  to  the 
left,  and  is  overlapped  by  the  left  lung  and  pleura:  it  lies  behind  the  fifth  left 
intercostal  space,  8  to  9  cm.  from  the  mid-sternal  line,  or  about  4  cm.  below  and 
2  mm.  to  the  medial  side  of  the  left  mammary  papilla. 

The  sternocostal  surface  (Fig.  574)  is  directed  forward,  upward,  and  to  the  left. 
Its  lower  part  is  convex,  formed  chiefly  by  the  right  ventricle,  and  traversed  near 
its  left  margin  by  the  anterior  longitudinal  sulcus.    Its  upper  part  is  separated  from 


606 


ANGIOLOGY 


the  lower  by  the  coronary  sulcus,  and  is  formed  by  the  atria;  it  presents  a  deep 
concavity  (Fig.  576),  occupied  by  the  ascending  aorta  and  the  pulmonary  artery. 

The  diaphragmatic  surface  (Fig.  573),  directed  downward  and  slightly  backward, 
is  formed  hx  the  ventricles,  and  rests  upon  the  central  tendon  and  a  small  part  of 
the  left  muscular  portion  of  the  Diaphragma.  It  is  separated  from  the  base  by 
the  posterior  part  of  the  coronary  sulcus,  and  is  traversed  obliquely  by  the  posterior 
longitudinal  sulcus. 

The  right  margin  of  the  heart  is  long,  and  is  formed  by  the  right  atrium  above 
and  the  right  ventricle  below.  The  atrial  portion  is  rounded  and  almost  vertical; 
it  is  situated  behind  the  third,  fourth,  and  fifth  right  costal  cartilages  about  1.25 
cm.  from  the  margin  of  the  sternum.  The  ventricular  portion,  thin  and  sharp, 
is  named  the  acute  margin;  it  is  nearly  horizontal,  and  extends  from  the  sternal 
end  of  the  sixth  right  costal  cartilage  to  the  apex  of  the  heart. 

The  left  or  obtuse  margin  is  shorter,  full,  and  rounded:  it  is  formed  mainly  by 
the  left  ventricle,  but  to  a  slight  extent,  above,  by  the  left  atrium.  It  extends 
from  a  point  in  the  second  left  intercostal  space,  about  2.5  mm.  from  the  sternal 
margin,  obliquely  downward,  with  a  convexity  to  the  left,  to  the  apex  of  the  heart. 


Ant.  desc.  branch  of  left 
coronary  artery 


RigJit  corona' 


Fig.  574. — Sternocostal  surface  of  heart. 

Right  Atrium  {atrium  dextrum;  right  auricle). — The  right  atrium  is  larger  than 
the  left,  but  its  walls  are  somewhat  thinner,  measuring  about  2  mm.;  its  cavity 
is  capable  of  containing  about  57  c.c.  It  consists  of  two  parts:  a  principal  cavity, 
or  sinus  venarum,  situated  posteriorly,  and  an  anterior,  smaller  portion,  the  auricula. 

Sinus  Venarum  {siiius  venosus). — The  sinus  venarum  is  the  large  quadrangular 
cavity  placed  between  the  two  vense  cavse.  Its  walls,  which  are  extremely  thin, 
are  connected  below  with  the  right  ventricle,  and  medially  with  the  left  atrium, 
but  are  free  in  the  rest  of  their  extent. 

Auricula  {auricula  dextra;  right  auricidar  appendix). — The  auricula  is  a  small 
conical  muscular  pouch,  the  margins  of  which  present  a  dentated  edge.  It  projects 
from  the  upper  and  front  part  of  the  sinus  forward  and  toward  the  left  side,  over- 
lapping the  root  of  the  aorta. 


THE  HEART 


607 


The  separation  of  the  aiiriciihi  from  the  sinus  venarum  is  indieated  externally 
by  a  groove,  the  terminal  sulcus,  whieh  extends  from  the  front  of  the  superior  vena 
cava  to  the  front  of  the  inferior  vena  cava,  and  represents  the  line  of  union  of  the 
sinus  venosus  of  the  embryo  with  the  primitive  atrium.  On  the  inner  wall  of  the 
atrium  the  separation  is  marked  by  a  vertical,  smooth,  muscular  ridge,  the  terminal 
crest.  Behind  the  crest  the  internal  surface  of  the  atrium  is  smooth,  while  in  front 
of  it  the  muscular  fibres  of  the  wall  are  raised  into  parallel  ridges  resembling  the 
teeth  of  a  comb,  and  hence  named  the  musculi  pectinati. 

Dissection. — To  examine  the  interior  of  the  auricula,  an  incision  should  be  made  along  its  right 
border  from  the  entrance  of  the  superior  vena  cava  to  that  of  the  inferior  vena  cava.  A  second 
cut  is  to  be  made  fi-om  the  centre  of  the  first  incision  to  the  tip  of  the  auricula  dextra,  and  the 
flap  raised. 

Pulmonary  valve 


Opening  of  sup.  vena 

cava 
Crista  tertninalis 
Atrial  septum 

Limbiis  fossce  ovalis 


Opening  of  coronary 
sinus 


Opening  of  inf.  vena 
cava 


Ant.  cusp  of  triciispid 
lulve 

Chordce  taidinece 

Papillary 

'^Vi  A*  W^  "^   muscles 


Valve  of  inf.  vena  cava 

Valve  of  coronal y  sinus 


Fig    575  — Interior  of  right  side  ol  heart 


Its  interior  (Fig.  575)  presents  the  following  parts  for  examination; 
Superior  vena  cava. 


Openings 


Inferior  vena  cava. 
Coronary  sinus. 
Foramina  venarum 

minimarum. 
_  Atrioventricular. 


Valves 


f  Valve  of  the  inferior  vena  cava. 
I  Valve  of  the  coronary  sinus. 


Fossa  ovalis. 
Limbus  fossae  ovalis. 
Intervenous  tubercle. 
JNIusculi  pectinati. 
Crista  terminalis. 

The  superior  vena  cava  returns  the  blood  from  the  upper  half  of  the  body,  and 
opens  into  the  upper  and  back  part  of  the  atrium,  the  direction  of  its  orifice  being 
downward  and  forward.    Its  opening  has  no  valve. 

The  inferior  vena  cava,  larger  than  the  superior,  returns  the  blood  from  the 
lower  half  of  the  body,  and  opens  into  the  lowest  part  of  the  atrium,  near  the 
atrial  septum,  its  orifice  being  directed  upward  and  backward,  and  guarded  by 


608  ANGIOLOGY 

a  rudimentary  valve,  the  valve  of  the  inferior  vena  cava  {Eustachian  valve).  The 
blood  entering  the  atrium  through  the  superior  vena  cava  is  directed  downward 
and  forward,  i.  e.,  toward  the  atrioventricular  orifice,  while  that  entering  through 
the  inferior  vena  cava  is  directed  upward  and  backward,  toward  tiie  atrial  septum. 
This  is  the  normal  direction  of  the  two  currents  in  fetal  life. 

The  coronary  sinus  opens  into  the  atrium,  between  the  orifice  of  the  inferior 
vena  cava  and  the  atrioventricular  opening.  It  returns  blood  from  the  substance 
of  the  heart  and  is  protected  by  a  semicircular  valve,  the  valve  of  the  coronary 
sinus  {valve  of  Thebesius). 

The  foramina  venarum  minimarum  {foramina  Thebesii)  are  the  orifices  of  minute 
veins  {venae  cordis  minimae),  which  return  blood  directly  from  the  muscular  sub- 
stance of  the  heart. 

The  atrioventricular  opening  {tricuspid  orifice)  is  the  large  oval  aperture  of  com- 
munication between  the  atrium  and  the  ventricle;  it  will  be  described  with  the 
right  ventricle. 

The  valve  of  the  inferior  vena  cava  {valvula  venae  cavae  infer ioris  [Eustachii]; 
Eustachian  valve)  is  situated  in  front  of  the  orifice  of  the  inferior  vena  cava.  It 
is  semilunar  in  form,  its  convex  margin  being  attached  to  the  anterior  margin 
of  the  orifice;  its  concave  margin,  which  is  free,  ends  in  two  cornua,  of  which 
the  left  is  continuous  with  the  anterior  edge  of  the  limbus  fossae  ovalis  while 
the  right  is  lost  on  the  wall  of  the  atrium.  The  valve  is  formed  by  a  duplicature 
of  the  lining  membrane  of  the  atrium,  containing  a  few  muscular  fibres.  In  the 
fetus  this  valve  is  of  large  size,  and  serves  to  direct  the  blood  from  the  inferior 
vena  cava,  through  the  foramen  ovale,  into  the  left  atrium.  In  the  adult  it  occa- 
sionally persists,  and  may  assist  in  preventing  the  reflux  of  blood  into  the  inferior 
vena  cava ;  more  commonly  it  is  small,  and  may  present  a  cribriform  or  filamentous 
appearance;  sometimes  it  is  altogether  wanting. 

The  valve  of  the  coronary  sinus  {valvula  sinus  coronarii  [Thebesii];  Thebesian 
valve)  is  a  semicircular  fold  of  the  lining  membrane  of  the  atrium,  at  the  orifice  of 
the  coronary  sinus.  It  prevents  the  regurgitation  of  blood  into  the  sinus  during  the 
contraction  of  the  atrium.     This  valve  may  be  double  or  it  may  be  cribriform. 

The  fossa  ovalis  is  an  oval  depression  on  the  septal  wall  of  the  atrium,  and  corre- 
sponds to  the  situation  of  the  foramen  ovale  in  the  fetus.  It  is  situated  at  the  lower 
part  of  the  septum,  above  and  to  the  left  of  the  orifice  of  the  inferior  vena  cava. 

The  limbus  fossae  ovalis  {annulus  ovalis)  is  the  prominent  oval  margin  of  the  fossa 
ovalis.  It  is  most  distinct  above  and  at  the  sides  of  the  fossa;  below,  it  is  deficient. 
A  small  slit-like  valvular  opening  is  occasionally  found,  at  the  upper  margin  of 
the  fossa,  leading  upward  beneath  the  limbus,  into  the  left  atrium;  it  is  the  remains 
of  the  fetal  aperture  between  the  two  atria. 

The  intervenous  tubercle  {tuberculum  intervenosum;  tubercle  of  Loiver)  is  a  small 
projection  on  the  posterior  wall  of  the  atrium,  above  the  fossa  ovalis.  It  is  distinct 
in  the  hearts  of  quadrupeds,  but  in  man  is  scarcely  visible.  It  was  supposed  by 
Lower  to  direct  the  blood  from  the  superior  vena  cava  toward  the  atrio- 
ventricular opening. 

Right  Ventricle  {veniriculus  dexter). — The  right  ventricle  is  triangular  in  form, 
and  extends  from  the  right  atrium  to  near  the  apex  of  the  heart.  Its  antero- 
superior  surface  is  rounded  and  convex,  and  forms  the  larger  part  of  the  sterno- 
costal surface  of  the  heart.  Its  under  surface  is  flattened,  rests  upon  the  Dia- 
phragma,  and  forms  a  small  part  of  the  diaphragmatic  surface  of  the  heart.  Its 
posterior  wall  is  formed  by  the  ventricular  septum,  which  bulges  into  the  right 
ventricle,  so  that  a  transverse  section  of  the  cavity  presents  a  semilunar  outline. 
Its  upper  and  left  angle  forms  a  conical  pouch,  the  conus  arteriosus,  from  which 
the  pulmonary  artery  arises.  A  tendinous  band,  which  may  be  named  the  tendon 
of  the  conns  arteriosus,  extends  upward  from  the  right  atrioventricular  fibrous 


THE  HEART 


609 


ring  and  connects  tlie  posterior  surface  of  the  conus  arteriosus  to  the  aorta.  The 
wall  of  the  right  ventricle  is  thinner  than  that  of  the  left,  the  proportion  between 
them  being  as  1  to  3;  it  is  thickest  at  the  base,  and  gradually  becomes  thinner 
toward  the  apex.  The  cavity  equals  in  size  that  of  the  left  ventricle,  and  is 
capable  of  containing  about  85  c.c. 

Dissection. — To  examine  the  interior  of  the  right  ventricle,  its  anterior  wall  should  be  turned 
downward  and  to  the  right  in  the  form  of  a  triangular  flap.  This  is  accomplished  by  making  two 
incisions:  (1)  From  the  pulmonary  artery  to  the  apex  of  the  ventricle  parallel  to,  but  a  little 
to  the  right  of,  the  anterior  interatrial  groove;  (2)  another,  starting  from  the  upper  extremity, 
of  the  first  and  carried  outward  parallel  to,  but  a  little  below,  the  atrioventricular  groove,  care 
being  taken  not  to  injure  the  atrioventricular  opening. 


Its  interior  (Fig.  575)  presents  the  following  parts  for  examination 

^       .  J Right  atrioventricular.  ,.  ,         (Tricuspid. 

Upenmgs    1  t^  ,  ,  v'alves  i  tj  i 

^        ^      ^rulmonary  artery.  Irulmonary 

Trabeculae  carneae.  Chordae  tendineae. 


The  right  atrioventricular  orifice  is  the  large  oval  aperture  of  communication 
between  the  right  atrium  and  ventricle.  Situated  at  the  base  of  the  ventricle, 
it  measures  about  4  cm.  in  diameter  and  is  surrounded  by  a  fibrous  ring,  covered 
by  the  lining  membrane  of  the  heart ;  it  is  considerably  larger  than  the  correspond- 
ing aperture  on  the  left  side,  being  sufficient  to  admit  the  ends  of  four  fingers 
It  is  guarded  by  the  tricuspid  valve. 


Right  uuncula 


i  light 
atrium 


Left 
auricula 


Left  'pidinonary  veins 

Fig.  576. — Heart  seen  from  above. 


Rigid  'pulmonary 
veins 


Fig.  577. — Base  of  ventricles  exposed  by  removal 
of  the  atria. 


The  opening  of  the  pulmonary  artery  is  circular  in  form,  and  situated  at  the 
summit  of  the  conus  arteriosus,  close  to  the  ventricular  septum.  It  is  placed  above 
and  to  the  left  of  the  atrioventricular  opening,  and  is  guarded  by  the  pulmonary 
semilunar  valves. 

The  tricuspid  valve  {valvula  tricuspidalis)  (Figs.  575,  577)  consists  of  three  some- 
what triangular  cusps  or  segments.  The  largest  cusp  is  interposed  between  the 
atrioventricular  orifice  and  the  conus  arteriosus  and  is  termed  the  anterior  or  infundib- 
ular cusp.  A  second,  the  posterior  or  marginal  cusp,  is  in  relation  to  the  right  margin 
of  the  ventricle,  and  a  third,  the  medial  or  septal  cusp,  to  the  ventricular  septum. 
They  are  formed  by  duplicatures  of  the  lining  membrane  of  the  heart,  strengthened 
39 


610  ANGIOLOGY 

by  intervening  layers  of  fibrous  tissue:  their  central  parts  are  thick  and  strong, 
their  marginal  portions  thin  and  translucent,  and  in  the  angles  between  the  latter 
small  intermediate  segments  are  sometimes  seen.  Their  bases  are  attached  to  a 
fibrous  ring  surrounding  the  atrioventricular  orifice  and  are  also  joined  to  each  other 
so  as  to  form  a  continuous  annular  membrane,  while  their  apices  project  into  the 
ventricular  cavity.  Their  atrial  surfaces,  directed  toward  the  blood  current  from 
the  atrium,  are  smooth;  their  ventricular  surfaces,  directed  toward  the  wall  of  the 
ventricle,  are  rough  and  irregular,  and,  together  with  the  apices  and  margii^.s  of 
the  cusps,  give  attachment  to  a  number  of  delicate  tendinous  cords,  the  chordae 
tendineae. 

The  trabeculae  carneae  {columnae  carneae)  are  rounded  or  irregular  muscular 
columns  which  project  from  the  whole  of  the  inner  surface  of  the  ventricle,  with 
the  exception  of  the  conus  arteriosus.  They  are  of  three  kinds :  some  are  attached 
along  their  entire  length  on  one  side  and  merely  form  prominent  ridges,  others 
are  fixed  at  their  extremities  but  free  in  the  middle,  while  a  third  set  (musculi 
papillares)  are  continuous  by  their  bases  with  the  wall  of  the  ventricle,  while  their 
apices  give  origin  to  the  chordae  tendineae  w^hich  pass  to  be  attached  to  the  seg- 
ments of  the  tricuspid  valve.  There  are  two  papillary  muscles,  anterior  and  pos- 
terior :  of  these,  the  anterior  is  the  larger,  and  its  chordae  tendineae  are  connected 
with  the  anterior  and  posterior  cusps  of  the  valve:  the  posterior  papillary  muscle 
sometimes  consists  of  two  or  three  parts;  its  chordae  tendineae  are  connected 
wdth  the  posterior  and  medial  cusps.  In  addition  to  these,  some  chordae  tendineae 
spring  directly  from  the  ventricular  septum,  or  from  small  papillary  eminences  on  it, 
and  pass  to  the  anterior  and  medial  cusps.  A  muscular  band,  well-marked  in  sheep 
and  some  other  animals,  frequently  extends  from  the  base  of  the  anterior  papillary 
muscle  to  the  ventricular  septum.  From  its  attachments  it  may  assist  in  preventing 
overdistension  of  the  ventricle,  and  so  has  been  named  the  moderator  band. 

The  pulmonary  semilunar  valves  (Fig.  576)  are  three  in  number,  two  in  front 
and  one  behind,  formed  by  duplicatures  of  the  lining  membrane,  strengthened 
by  fibrous  tissue.  They  are  attached,  by  their  convex  margins,  to  the  wall  of  the 
artery,  at  its  junction  wdth  the  ventricle,  their  free  borders  being  directed  upward 
into  the  lumen  of  the  vessel.  The  free  and  attached  margins  of  each  are  strength- 
ened by  tendinous  fibres,  and  the  former  presents,  at  its  middle,  a  thickened  nodule 
{corpus  Arantii).  From  this  nodule  tendinous  fibres  radiate  through  the  segment 
to  its  attached  margin,  but  are  absent  from  two  narrow  crescentic  portions,  the 
lunulae,  placed  one  on  either  side  of  the  nodule  immediately  adjoining  the  free 
margin.  Between  the  semilunar  valves  and  the  wall  of  the  pulmonary  artery  are 
three  pouches  or  sinuses  {sinuses  of  Valsalva). 

Dissection. — In  order  to  examine  the  interior  of  the  left  atrium,  make  an  incision  on  the  pos- 
terior surface  of  the  atrium  from  the  puhnonary  veins  on  one  side  to  those  on  the  other,  the 
incision  being  carried  a  Uttle  way  into  the  vessels.  Make  another  incision  from  the  middle  of 
the  horizontal  one  to  the  auricula  sinistra. 

Left  Atrium  {atrium  sinistum;  left  auricle). — The  left  atrium  is  rather  smaller 
than  the  right,  but  its  walls  are  thicker,  measuring  about  3  mm. ;  it  consists,  like 
the  right,  of  two  parts,  a  principal  cavity  and  an  auricula. 

The  principal  cavity  is  cuboidal  in  form,  and  concealed,  in  front,  by  the  pul- 
monary artery  and  aorta;  in  front  and  to  the  right  it  is  separated  from  the  right 
atrium  by  the  atrial  septum;  opening  into  it  on  either  side  are  the  two  pulmonary 
veins. 

Auricula  {auricula  sinistra;  left  auricular  appendix). — The  auricula  is  somewhat 
constricted  at  its  junction  with  the  principal  cavity;  it  is  longer,  narrower,  and  more 
curved  than  that  of  the  right  side,  and  its  margins  are  more  deeply  indented.  It 
is  directed  forward  and  toward  the  right  and  overlaps  the  root  of  the  pulmonary 
artery. 


rilE  HEART 


611 


The  interior  of  the  left  atriiiin  (Fig.  578)  presents  the  following  parts  for 
examination: 

Openings  of  the  fonr  pulmonary  veins. 
Left  atrioventricular  opening. 
Musculi  pectinati. 

The  pulmonary  veins,  four  in  number,  open  into  the  uj)per  part  of  the  posterior 
surface  of  the  left  atrium — two  on  either  side  of  its  middle  line:  they  are  not 
provided  Avith  valves.    The  two  left  veins  frequently  end  by  a  common  opening. 

The  left  atrioventricular  opening  is  the  aperture  between  the  left  atrium  and 
ventricle,  and  is  rather  smaller  than  the  corresponding  opening  on  the  right  side. 

The  musculi  pectinati,  fe\ver  and  smaller  than  in  the  right  auricula,  are  confined 
to  the  inner  surface  of  the  auricula. 

On  the  atrial  septum  may  be  seen  a  lunated  impression,  bounded  below  by  a 
crescentic  ridge,  the  concavity  of  which  is  turned  upward.  The  depression  is 
just  above  the  fossa  ovalis  of  the  right  atrium. 


Fig.   578. — Interior  of  left  side  of  heart. 


Dissection. — To  examine  the  interior  of  the  left  ventricle,  make  an  incision  a  little  to  thejleft 
of  the  anterior  interatrial  groove  from  the  base  to  the  apex  of  the  heart,  and  carry  it  up  from 
thence,  a  little  to  the  left  of  the  posterior  interatrial  groove,  nearly  as  far  as  the  atrioventricular 
groove. 

Left  Ventricle  {ventriculus  sinister) . — The  left  ventricle  is  longer  and  more  conical 
in  shape  than  the  right,  and  on  transverse  section  its  concavity  presents  an  oval 
or  nearly  circular  outline.  It  forms  a  small  part  of  the  sternocostal  surface  and  a 
considerable  part  of  the  diaphragmatic  surface  of  the  heart;  it  also  forms  the  apex 
of  the  heart.    Its  walls  are  about  three  times  as  thick  as  those  of  the  right  ventricle. 

Its  interior  (Fig.  578)  presents  the  following  parts  for  examination: 


r\       •  [Left  atrioventricular. 

Openmgs  |^^^^^.^  ^ 

Trabeculae  carneae. 


XT  T         (Bicuspid  or  Mitral, 
valves  |^Qj.^j^ 

Chordae  tendineae. 


612 


AXGIOWGY 


The  left  atrioventricular  opening  {mitral  orifice)  is  placed  below  and  to  the  left 
of  the  aortic  orifice.  It  is  a  little  smaller  than  the  corresponding  aperture  of  the 
opposite  side,  admitting  only  two  fingers.  It  is  surrounded  by  a  dense  fibrous  ring, 
covered  by  the  lining  membrane  of  the  heart,  and  is  guarded  by  the  bicuspid  or 
mitral  valve. 

The  aortic  opening  is  a  circular  aperture,  in  front  and  to  the  right  of  the  atrio- 
ventricular, from  which  it  is  separated  by  the  anterior  cusp  of  the  bicuspid  valve. 
Its  orifice  is  guarded  by  the  aortic  semilunar  valves.  The  portion  of  the  ventricle 
immediately  below  the  aortic  orifice  is  termed  the  aortic  vestibule,  and  possesses 
fibrous  instead  of  muscular  walls. 

The  bicuspid  or  mitral  valve  (valvula  hicusjAdalis  [metralis])  (Figs.  577,  578)  is 
attached  to  the  circumference  of  the  left  atrioventricular  orifice  in  the  same  way 
that  the  tricuspid  valve  is  on  the  opposite  side.  It  consists  of  two  triangular  cusps, 
formed  by  duplicatures  of  the  lining  membrane,  strengthened  by  fibrous  tissue, 
and  containing  a  few  muscular  fibres.  The  cusps  are  of  unequal  size,  and  are  larger, 
thicker,  and  stronger  than  those  of  the  tricuspid  valve.  The  larger  cusp  is  placed 
in  front  and  to  the  right  between  the  atrioventricular  and  aortic  orifices,  and  is 
known  as  the  anterior  or  aortic  cusp;  the  smaller  or  posterior  cusp  is  placed  behind 
and  to  the  left  of  the  opening.  Two  smaller  cusps  are  usually  found  at  the  angles 
of  junction  of  the  larger.  The  cusps  of  the  bicuspid  valve  are  furnished  with  chordae 
tendineae,  which  are  attached  in  a  manner  similar  to  those  on  the  right  side;  they 
are,  however,  thicker,  stronger,  and  less  numerous. 


Aortic  sinus    Left  post. 
Noduhcs  ^-^^^^ 


Lunula 


Oriains  of  coronary  arteries 


Uiglit  fast,  valve 


Ant.  valve 


Fig.   579. — Aorta  laid  open  to  show  the  semilunar  valves. 


The  aortic  semilunar  valves  (Figs.  576,  579)  are  three  in  number,  and  surround 
the  orifice  of  the  aorta;  two  are  posterior  (right  and  left)  and  one  anterior.  They 
are  similar  in  structure,  and  in  their  mode  of  attachment,  to  the  pulmonary  semi- 
lunar valves,  but  are  larger,  thicker,  and  stronger;  the  lunulae  are  more  distinct, 
and  the  noduli  or  corpora  Arantii  thicker  and  more  prominent.  Opposite  the  valves 
the  aorta  presents  slight  dilatations,  the  aortic  sinuses  {sinuses  of  Valsalva),  which 
are  larger  than  those  at  the  origin  of  the  pulmonary  artery. 

The  trabeculae  cameae  are  of  three  kinds,  like  those  upon  the  right  side,  but 
they  are  more  numerous,  and  present  a  dense  interlacement,  especially  at  the 
apex,  and  upon  the  posterior  wall  of  the  ventricle.  The  musculi  papillares  are  two 
in  number,  one  being  connected  to  the  anterior,  the  other  to  the  posterior  wall; 
they  are  of  large  size,  and  end  in  rounded  extremities  from  which  the  chordae 
tendineae  arise.  The  chordae  tendineae  from  each  papillary  muscle  are  connected 
to  both  cusps  of  the  bicuspid  valve. 


THE  HEART 


013 


Ventricular  Septum  [scpimn  rciitriciilnniin :  infcrrriifricuhd' .s-rjduui)  (Fi^".  580). — 
The  ventricular  septum  is  directed  ()l)li(iucly  backward  and  to  the  right,  and  is 
curved  with  the  convexity  toward  the  right  ventricle:  its  margins  correspond 
with  the  anterior  and  posterior  longitudinal  sulci.  The  greater  portion  of  it  is 
thick  and  muscular  and  constitutes  the  muscular  ventricular  septum,  but  its  upper 
and  posterior  part,  which  separates  the  aortic  vestibule  from  the  lower  part  of 
the  right  atrium  and  ui)per  i)art  of  the  right  ventricle,  is  thin  and  fibrous,  and  is 
termed  the  membranous  ventricular  septum.  An  abnormal  communication  may 
exist  between  the  ventricles  at  this  part  owing  to  defective  de\-elopment  of  the 
membranous  septum. 

Structure. — The  heart  consists  of  muscular  fibres,  and  of  fibrous  rings  which  serve  for  their 
attachment.  It  is  covered  by  the  visceral  layer  of  the  serous  pericardium  (epicardiumj ,  and 
lined  by  the  endocardium.    Between  these  two  membranes  is  the  muscular  wall  or  myocardium. 

The  endocardium  is  a  thin,  smooth  membrane  which  lines  and  gives  the  glistening  appear- 
ance to  the  inner  surface  of  the  heart;  it  assists  in  forming  the  valves  by  its  reduplications,  and 
is  continuous  with  the  lining  membrane  of  the  large  bloodvessels.  It  consists  of  connective 
tissue  and  elastic  fibres,  and  is  attached  to  the  muscular  structure  by  loose  elastic  tissue  which 
contains  bloodvessels  and  nerves;  its  free  surface  is  covered  by  endothelial  cells. 


Left  auunda 


Inferior 
vena  cava 

Membranoub 
sephwi 
Muscuh 
pectinati 


Aortic  valve 


^_^^^_^  Papillai  y 
TI)3^V'    -muscles 


Anterior  papillary  muscle 
Fig.  580. — Section  of  the  heart  showing  the  ventricular  septum. 


The  fibrous  rings  surround  the  atrioventricular  and  arterial  orifices,  and  are  stronger  upon 
the  l6ft  than  on  the  right  side  of  the  heart.  The  atrioA'entricular  rings  serve  for  the  attachment 
of  the  muscular  fibres  of  the  atria  and  ventricles,  and  for  the  attachment  of  the  bicuspid  and 
tricuspid  valves.  The  left  atrioventricular  ring  is  closely  connected,  by  its  right  margin,  with 
the  aortic  arterial  ring;  between  these  and  the  right  atrioventricular  ring  is  a  triangular  mass  of 
fibrous  tissue,  the  trigonum  fibrosum,  which  represents  the  as  cordis  seen  in  the  heart  of  some  of 
the  larger  animals,  as  the  ox  and  elephant.  Lastly,  there  is  the  tendinous  band,  already  referred 
to  (p.  608),  on  the  posterior  surface  of  the  conus  arteriosus. 

The  fibrous  rings  surrounding  the  arterial  orifices  serve  for  the  attachment  of  the  great  vessels 
and  semilunar  valves.  Each  ring  receives,  by  its  ventricular  margin,  the  attachment  of  some 
of  the  muscular  fibres  of  the  ventricles;  its  opposite  margin  presents  three  deep  semicircular 
notches,  to  which  the  middle  coat  of  the  artery  is  firmly  fixed.  The  attachment  of  the  artery 
to  its  fibrous  ring  is  strengthened  by  the  extei'nal  coat  and  serous  membrane  externally,  and 


614  ANGIOLOGY 

by  the  endocardium  internally.  From  the  margins  of  the  semicircular  notches  the  fibrous  structure 
of  the  ring  is  continued  into  the  segments  of  the  valves.  The  middle  coat  of  the  artery  in  this 
situation  is  thin,  and  the  vessel  is  filiated  to  form  the  sinuses  of  the  aorta  and  pulmonary  artery. 

The  muscular  structure  of  the  heart  consists  of  bands  of  fibres,  which  present  an  exceedingly 
intricate  interlacement.  They  comprise  (a)  the  fibres  of  the  atria,  (6)  the  fibres  of  the  ventricles, 
and  (c)  the  atrioventricular  bundle  of  His. 

The  fibres  of  the  atria  are  arranged  in  two  laj^ers — a  superficial,  common  to  both  cavities,  and 
a  deep,  proper  to  each.  The  superficial  fibres  are  most  distinct  on  the  front  of  the  atria,  across 
the  bases  of  which  they  run  in  a  transverse  dire(!tion,  forming  a  thin  and  incomplete  layer.  Some 
of  these  fibres  run  into  the  atrial  septum.  The  deep  fibres  consist  of  looped  and  annular  fibres. 
The  looped  fibres  pass  upward  over  each  atrium,  being  attached  by  their  two  extremities  to  the 
corresponding  atrioventricular  ring,  in  front  and  behind.  The  annular  fibres  sm-round  the  auricula;, 
and  form  annular  bands  around  the  terminations  of  the  veins  and  around  the  fossa  ovahs. 

The  fibres  of  the  ventricles  are  arranged  in  a  complex  manner,  and  various  accounts  have 
been  given  of  their  course  and  connections;  the  following  description  is  based  on  the  work  of 
McCallum.i  They  consist  of  superficial  and  deep  layers,  all  of  which,  with  the  exception  of 
two,  are  inserted  into  the  papillary  muscles  of  the  ventricles.  The  superficial  layers  consist  of 
the  following:  (a)  Fibres  which  spring  from  the  tendon  of  the  conus  arteriosus  and  sweep  down- 
ward and  toward  the  left  across  the  anterior  longitudinal  sulcus  and  around  the  apex  of  the 
heart,  where  they  pass  upward  and  inward  to  terminate  in  the  papillary  muscles  of  the  left 
ventricle;  those  arising  from  the  upper  half  of  the  tendon  of  the  conus  arteriosus  pass  to  the 
anterior  papillary  muscle,  those  from  the  lower  half  to  the  posterior  papillary  muscle  and  the 
papillary  muscles  of  the  septum.  (6)  Fibres  which  arise  from  the  right  atrioventricular  ring  and 
run  diagonally  across  the  diaphragmatic  surface  of  the  right  ventricle  and  around  its  right  border 
on  to  its  costosternal  surface,  where  they  dip  beneath  the  fibres  just  described,  and,  crossing  the 
anterior  longitudinal  sulcus,  wdnd  around  the  apex  of  the  heart  and  end  in  the  posterior  papillary 
muscle  of  the  left  ventricle,  (c)  Fibres  which  spring  from  the  left  atrioventricular  ring,  and, 
crossing  the  posterior  longitudinal  sulcus,  pass  successively  into  the  right  ventricle  and  end  in 
its  papillary  muscles.  The  deep  layers  are  three  in  number;  they  arise  in  the  papillary  muscles 
of  one  ventricle  and,  curving  in  an  S-shaped  manner,  turn  in  at  the  longitudinal  sulcus  and  end 
in  the  papillary  muscles  of  the  other  ventricle.  The  layer  w^hich  is  most  superficial  in  the  right 
ventricle  lies  next  the  lumen  of  the  left,  and  vice  versa.  Those  of  the  first  layer  almost  encircle 
the  right  ventricle  and,  crossing  in  the  septum  to  the  left,  unite  with  the  superficial  fibres  from 
the  right  atrioventricular  ring  to  form  the  posterior  papillary  muscle.  Those  of  the  second 
layer  have  a  less  extensive  com-se  in  the  wall  of  the  right  ventricle,  and  a  correspondingly  greater 
course  in  the  left,  where  they  join  with  the  superficial  fibres  from  the  anterior  half  of  the  tendon 
of  the  conus  arteriosus  to  form  the  papillary  muscles  of  the  septum.  Those  of  the  third  layer 
pass  almost  entirely  around  the  left  ventricle  and  unite  with  the  superficial  fibres  from  the  lower 
half  of  the  tendon  of  the  conus  arteriosus  to  form  the  anterior  papillary  muscle.  Besides  the 
layers  just  described  there  are  two  bands  which  do  not  end  in  papillary  muscles.  One  springs 
from  the  right  atrioventricular  ring  and  crosses  in  the  atrioventricular  septum;  it  then  encircles 
the  deep  layers  of  the  left  ventricle  and  ends  in  the  left  atrioventricular  ring.  The  second  band 
is  apparently  confined  to  the  left  ventricle;  it  is  attached  to  the  left  atrioventricular  ring,  and 
encircles  the  portion  of  the  ventricle  adjacent  to  the  aortic  orifice. 

The  atrioventricular  bundle  of  His  is  the  only  direct  muscular  connection  known  to  exist 
between  the  atria  and  the  ventricles.  It  arises  in  connection  with  two  small  collections  of  spindle- 
shaped  cells,  the  sinoatrial  and  atrioventricular  nodes.  The  sinoatrial  node  is  situated  on  the 
anterior  border  of  the  opening  of  the  superior  vena  cava;  from  it  strands  of  fusiform  fibres  run 
imder  the  endocardium  of  the  wall  of  the  atrium  to  the  atrioventricular  node.  The  atrioventricular 
node  Hes  near  the  orifice  of  the  coronary  sinus  in  the  annular  and  septal  fibres  of  the  right  atrium; 
from  it  the  atrioventricular  bundle  passes  forward  in  the  lower  part  of  the  membranous  septum, 
and  divides  into  right  and  left  fascicuh.  These  rim  down  in  the  right  and  left  ventricles,  one  on 
either  side  of  the  ventricular  septum,  covered  by  endocardiiun.  In  the  lower  parts  of  the  ventricles 
they  break  up  into  numerous  strands  which  end  in  the  papillary  muscles  and  in  the  ventricular 
muscle  generally.  The  greater  portion  of  the  atrioventricular  bundle  consists  of  narrow,  somewhat 
fusiform  fibres,  but  its  terminal  strands  are  composed  of  Purkinje  fibres. 

Dr.  A.  Morison^  has  showm  that  in  the  sheep  and  pig  the  atrioventricular  bundle  "is  a  great 
avenue  for  the  transmission  of  nerves  from  the  auricular  to  the  ventricular  heart;  large  and 
numerous  nerve  trunks  entering  the  bundle  and  com-sing  with  it."  From  these,  branches  pass 
off  and  form  plexuses  around  groups  of  Purkinje  cells,  and  from  these  plexuses  fine  fibrils  go  to 
innervate  individual  cells. 

Applied  Anatomy. — Chnical  and  experimental  evidence  go  to  prove  that  this  bundle  conveys 
the  impulse  to  systohc  contraction  from  the  atrial  septum  to  the  ventricles,  and  much  attention 
has  recently  been  paid  to  it,   because  it  appears  to  become  fibrosed  and  to  lose  much  of  its 

^  Johns  Hopkins  Hospital  Reports,  vol.  ix. 

2  Journal  of  Anatomy  and  Physiology,  vol.  xWi. 


THE  HEART  615 

conducting  power  (lieart-block)  in  many  cases  of  Stokes-Adams'  disease.  This  condition  is 
characterized  by  a  slow  pulse,  a  tendency  to  syncopal  or  epileptiform  seizures,  and  the  fact 
that  while  th(>  cardiac  atria  heal  at  a  normal  rate,  the  ventricles  contract  much  less  frequently. 

Vessels  and  Nerves. — The  arteries  sup])lying  the  heart  are  the  right  and  left  coronarj^  from 
the  aoria:  tlic  veins  end  in  the  right  airium. 

The  lymphatics  end  in  the  thoracic  and  right  lymphatic  ducts. 

The  nerves  arc  derived  from  the  cardiac  jilexus,  which  are  formed  partly  from  the  vagi,  and 
parti}'  from  the  sympathetic  trunks.  They  are  freely  distributed  both  on  the  surface  and  in  the 
substance  of  the  heart,  the  separate  nerve  filaments  being  furnished  with  small  gangha. 

The  Cardiac  Cycle  and  the  Actions  of  the  Valves. — By  the  contractions  of  the 
heart  the  blood  is  pumped  through  the  arteries  to  all  parts  of  the  body.  These 
contractions  occur  regularly  and  at  the  rate  of  about  seventy  per  minute.  Each 
wave  of  contraction  or  yeriod  of  activity  is  followed  by  a  yeriod  of  rest,  the  two 
periods  constituting  what  is  known  as  a  cardiac  cycle. 

Each  cardiac  cycle  consists  of  three  phases,  which  succeed  each  other  as  follows: 
(1)  a  short  simultaneous  contraction  of  both  atria,  termed  the  atrial  systole,  fol- 
lowed, after  a  slight  pause,  by  (2)  a  simultaneous,  but  more  prolonged,  contraction 
of  both  ventricles,  named  the  ventricular  systole,  and  (3)  a  period  of  rest,  during  which 
the  whole  heart  is  relaxed.  The  atrial  contraction  commences  around  the  venous 
openings,  and  sweeping  over  the  atria  forces  their  contents  through  the  atrio- 
ventricular openings  into  the  ventricles,  regurgitation  into  the  veins  being  pre- 
vented by  the  contraction  of  their  muscular  coats.  When  the  ventricles  contract, 
the  tricuspid  and  bicuspid  valves  are  closed,  and  prevent  the  passage  of  the  blood 
back  into  the  atria;  the  musculi  papillares  at  the  same  time  are  shortened,  and, 
pulling  on  the  chordae  tendineae,  prevent  the  inversion  of  the  valves  into  the  atria. 
As  soon  as  the  pressure  in  the  ventricles  exceeds  that  in  the  pulmonary  artery  and 
aorta,  the  valves  guarding  the  orifices  of  these  vessels  are  opened  and  the  blood  is 
driven  from  the  right  ventricle  into  the  pulmonary  artery  and  from  the  left  into 
the  aorta.  The  moment  the  systole  of  the  ventricles  ceases,  the  pressure  of  the 
blood  in  the  pulmonary  artery  and  aorta  closes  the  pulmonary  and  aortic  semilunar 
valves  to  prevent  regurgitation  of  blood  into  the  ventricles,  the  valves  remaining 
shut  until  reopened  by  the  next  ventricular  systole.  During  the  period  of  rest  the 
tension  of  the  tricuspid  and  bicuspid  valves  is  relaxed,  and  blood  is  flowing  from 
the  veins  into  the  atria,  being  aspirated  by  negative  intrathoracic  pressure,  and 
slightly  also  from  the  atria  into  the  ventricles.  The  average  duration  of  a  cardiac 
cycle  is  about  j-^  of  a  second,  made  up  as  follows : 

Atrial  systole,  yV-  Atrial  diastole,  -jo- 

Ventricular  systole,  3%.  Ventricular  diastole,  y^. 

Total  systole,  y\-.  Complete  diastole,  ^. 

The  rhythmical  action  of  the  heart  is  muscular  in  origin — that  is  to  say,  the 
heart  muscle  itself  possesses  the  inherent  property  of  contraction  apart  from  any 
nervous  stimulation.  The  more  embryonic  the  muscle  the  better  is  it  able  to  initiate 
and  propagate  the  contraction  wave;  this  explains  why  the  normal  systole  of  the 
heart  starts  at  the  entrance  of  the  veins,  for  there  the  muscle  is  most  embryonic 
in  nature.  At  the  atrioventricular  junction  there  is  a  slight  pause  in  the  wave  of 
muscular  contraction.  To  obviate  this  as  far  as  possible  a  peculiar  band  of  marked 
embryonic  type  passes  across  the  junction  and  so  carries  on  the  contraction  wave 
to  the  ventricles.  This  band,  composed  of  special  fibres,  is  the  atrioventricular 
bundle  of  His  (p.  614).  The  nerves,  although  not  concerned  in  originating  the 
contractions  of  the  heart  muscle,  play  an  important  role  in  regidating  their  force 
and  frequency  in  order  to  subserve  the  physiological  needs  of  the  organism. 

Applied  Anatomy. — Wounds  of  the  heart  are  often  immediately  fatal,  but  not  necessarily  so. 
They  may  be  non-penetrating,  when  death  may  occur  from  hemorrhage  if  one  of  the  coronary 
vessels  has  been  wounded,  or  subsequently  from  pericarditis.  Even  a  penetrating  wound  is  not 
necessarity  fatal,  as  a  considerable  mmiber  of  cases  have  been  recorded  in  which  the  wound  has 
been  sutured  successfully. 


616      ■  ANGIOLOGY 


PECULIARITIES    IN    THE    VASCULAR    SYSTEM    OF    THE    FETUS. 

The  development  of  the  heart  and  vascular  system  is  described  on  pages  141 
to  162.  ■  .     ' 

The  chief  peculiarities  of  the  fetal  heart  are  the  direct  communication  between 
the  atria  through  the  foramen  ovale,  and  the  large  size  of  the  ^'alve  of  the  inferior 
vena  cava.  Among  other  peculiarities  the  following  may  be  noted.  (1)  In  early 
fetal  life  the  heart  lies  immediately  below  the  mandibular  arch,  and  as  develop- 
ment proceeds  it  is  gradually  drawn  within  the  thorax.  (2)  For  a  time  the  atrial 
portion  exceeds  the  ventricular  in  size,  and  the  walls  of  the  ventricles  are  of  equal 
thickness:  toward  the  end  of  fetal  life  the  ventricular  portion  becomes  the  larger 
and  the  wall  of  the  left  ventricle  exceeds  that  of  the  right  in  thickness.  (3)  Its 
size  is  large  as  compared  with  that  of  the  rest  of  the  body,  the  proportion  at  the 
second  month  being  1  to  50,  and  at  birth,  1  to  120,  while  in  the  adult  the  average 
is  about  1  to  160. 

The  foramen  ovale,  situated  at  the  lower  part'  of  the  atrial  septum,  forms  a  free 
communication  between  the  atria  until  the  end  of  fetal  life.  A  septum  (septum 
secunduvi)  grows  down  from  the  upper  wall  of  the  atrium  to  the  right  of  the  primary 
septum  in  which  the  foramen  ovale  is  situated;  shortly  after  birth  it  fuses  with 
the  primary  septum  and  the  foramen  ovale  is  obliterated. 

The  valve  of  the  inferior  vena  cava  serves  to  direct  the  blood  from  that  vessel 
through  the  foramen  ovale  into  the  left  atrium. 

The  peculiarities  in  the  arterial  system  of  the  fetus  are  the  communication 
between  the  pulmonary  artery  and  the  aorta  by  means  of  the  ductus  arteriosus, 
and  the  continuation  of  the  hypogastric  arteries  as  the  umbilical  arteries  to  the 
placenta. 

The  ductus  arteriosus  is  a  short  tube,  about  1.25  cm.  in  length  at  birth,  and 
of  the  diameter  of  a  goose-quill.  In  the  early  condition  it  forms  the  continuation 
of  the  pulmonary  artery,  and  opens  into  the  aorta,  just  beyond  the  origin  of  the 
left  subclavian  artery;  and  so  conducts  the  greater  amount  of  the  blood  from  the 
right  ventricle  into  the  aorta.  When  the  branches  of  the  pulmonary  artery  have 
become  larger  relatively  to  the  ductus  arteriosus,  the  latter  is  chieflj^  connected 
to  the  left  pulmonary  artery. 

The  hypogastric  arteries  run  along  the  sides  of  the  bladder  and  thence  upward 
on  the  back  of  the  anterior  abdominal  wall  to  the  umbilicus;  here  they  pass  out 
of  the  abdomen  and  are  continued  as  the  umbilical  arteries  in  the  umbilical  cord 
to  the  placenta.    They  convey  the  fetal  blood  to  the  placenta. 

The  peculiarities  in  the  venous  system  of  the  fetus  are  the  communications 
established  between  the  placenta  and  the  liver  and  portal  vein,  through  the  umbil- 
ical vein;  and  between  the  umbilical  vein  and  the  inferior  vena  cava  through  the 
ductus  venosus. 

Fetal  Circulation  (Fig.  581). — The  fetal  blood  is  returned  from  the  placenta  to 
the  fetus  by  the  umbilical  vein.  This  vein  enters  the  abdomen  at  the  umbilicus, 
and  passes  upward  along  the  free  margin  of  the  falciform  ligament  of  the  liver  to 
the  under  surface  of  that  organ,  where  it  gives  off  two  or  three  branches,  one  of 
large  size  to  the  left  lobe,  and  others  to  the  lobus  quadratus  and  lobus  caudatus. 
At  the  porta  hepatis  (transverse  fissure  of  the  liver)  it  divides  into  two  branches : 
of  these,  the  larger  is  joined  by  the  portal  vein,  and  enters  the  right  lobe;  the 
smaller  is  continued  upward,  under  the  name  of  the  ductus  venosus,  and  joins 
the  inferior  vena  cava.  The  blood,  therefore,  which  traverses  the  umbilical  vein, 
passes  to  the  inferior  vena  cava  in  three  different  ways.  A  considerable  quantity 
circulates  through  the  liver  with  the  portal  venous  blood,  before  entering  the 
inferior  vena  cava  by  the  hepatic  veins;  some  enters  the  liver  directly,  and  is 


PECULIARITIES  IX  THE  VASCULAR  SYSTEM  OF  THE  FETUS      017 

carried  to  the  inferior  cava  by  the  hepatic  veins;  the  remainder  passes  directly 
into  the  inferior  vena  cava  through  the  ductus  venosus. 

In  the  inferior  vena  cava,  the  blood  carried  by  the  ductus  venosus  and  hepatic 
veins  becomes  mixed  with  that  returning  from  the  lower  extremities  and  abdominal 


Fig.  581.— Plan  of  the  fetal  circulation.     In  this  plan  the  figured  arrows  represent  the  kind  of  blood,  as  well  as  the 

direction  which  it  takes  in  the  vessles.     Thus— arterial  blood  is  figured   > >;  venous  blood,   > >;   misea 

(arterial  and  venous)  blood,  >• ■^. 

wall.  It  enters  the  right  atrium,  and,  guided  by  the  valve  of  the  inferior  vena 
cava,  passes  through  the  foramen  ovale  into  the  left  atrium,  where  it  mixes  w-ith 
a  small  quantity  of  blood  returned  from  the  lungs  by  the  pulmonary  veins.  From 
the  left  atrium  "it  passes  into  the  left  ventricle;  and  from  the  left  ventricle  mto  the 
aorta,  by  means  of  which  it  is  distributed  almost  entirely  to  the  head  and  upper 


618  ANGIOLOGY 

extremities,  a  small  quantity  being  probably  carried  into  the  descending  aorta. 
From  the  head  and  upper  extremities  the  blood  is  returned  by  the  superior  vena 
cava  to  the  right  atrium,  where  it  mixes  with  a  small  portion  of  the  blood  from  the 
inferior  vena  cava.  From  the  right  atrium  it  descends  into  the  right  ventricle, 
and  thence  passes  into  the  pulmonary  artery.  The  lungs  of  the  fetus  being  inactive, 
only  a  small  quantity  of  the  blood  of  the  pulmonary  artery  is  distributed  to  them 
by  the  right  and  left  pulmonary  arteries,  and  returned  b\^  the  pulmonary  veins 
to  the  left  atrium:  the  greater  part  passes  through  the  ductus  arteriosus  into  the 
aorta,  where  it  mixes  with  a  small  quantity  of  the  blood  transmitted  b}^  the  left 
ventricle  into  the  aorta.  Through  this  vessel  it  descends,  and  is  in  part  distributed 
to  the  lower  extremities  and  the  viscera  of  the  abdomen  and  pelvis,  but  the  greater 
amount  is  conveyed  by  the  umbilical  arteries  to  the  placenta. 

From  the  preceding  account  of  the  circulation  of  the  blood  in  the  fetus  the  fol- 
lowing facts  will  be  evident:  (1)  The  placenta  serves  the  purposes  of  nutrition 
and  excretion,  receiving  the  impure  blood  from  the  fetus,  and  returning  it  purified 
and  charged  with  additional  nutritive  material.  (2)  Nearly  the  whole  of  the  blood 
of  the  umbilical  vein  traverses  the  liver  before  entering  the  inferior  vena  cava; 
hence  the  large  size  of  the  liver,  especially  at  an  early  period  of  fetal  life.  (3)  The 
right  atrium  is  the  point  of  meeting  of  a  double  current,  the  blood  in  the  inferior 
vena  cava  being  guided  by  the  valve  of  this  vessel  into  the  left  atrium,  while  that 
in  the  superior  vena  cava  descends  into  the  right  ventricle.  At  an  early  period 
of  fetal  life  it  is  highly  probable  that  the  two  streams  are  quite  distinct;  for  the 
inferior  vena  cava  opens  almost  directly  into  the  left  atrium,  and  the  valve  of  the 
inferior  vena  cava  would  exclude  the  current  from  the  right  ventricle.  At  a  later 
period,  as  the  separation  between  the  two  atria  becomes  more  distinct,  it  seems 
probable  that  some  mixture  of  the  two  streams  must  take  place.  (4)  The  pure 
blood  carried  from  the  placenta  to  the  fetus  by  the  umbilical  vein,  mixed  with  the 
blood  from  the  portal  vein  and  inferior  vena  cava,  passes  almost  directly  to  the 
arch  of  the  aorta,  and  is  distributed  by  the  branches  of  that  vessel  to  the  head 
and  upper  extremities.  (5)  The  blood  contained  in  the  descending  aorta,  chiefly 
derived  from  that  which  has  already  circulated  through  the  head  and  limbs, 
together  with  a  small  quantity  from  the  left  ventricle,  is  distributed  to  the 
abdomen  and  lower  extremities. 

Changes  in  the  Vascular  System  at  Birth. — At  birth,  when  respiration  is  estab- 
lished, an  increased  amount  of  blood  from  the  pulmonary  artery  passes  through  the 
lungs,  and  the  placental  circulation  is  cut  off.  The  foramen  ovale  is  closed  by  about 
the  tenth  day  after  birth :  the  valvular  fold  above  mentioned  adheres  to  the  margin 
of  the  foramen  for  the  greater  part  of  its  circumference,  but  a  slit-like  opening  is 
left  between  the  two  atria  above,  and  this  sometimes  persists. 

The  ductus  arteriosus  begins  to  contract  immediately  after  respiration  is  estab- 
lished, and  is  completely  closed  from  the  fourth  to  the  tenth  day;  it  ultimately 
degenerates  into  an  impervious  cord,  the  ligamentum  arteriosum,  which  connects 
the  left  pulmonary  artery  to  the  arch  of  the  aorta. 

Of  the  hypogastric  arteries,  the  parts  extending  from  the  sides  of  the  bladder 
to  the  umbilicus  become  obliterated  between  the  second  and  fifth  days  after  birth, 
and  project  as  fibrous  cords,  the  lateral  umbilical  ligaments,  toward  the  abdominal 
cavity,  carrying  on  them  folds  of  peritoneum. 

The  umbilical  vein  and  ductus  venosus  are  completely  obliterated  between  the 
second  and  fifth  days  after  birth;  the  former  becomes  the  ligamentum  teres,  the 
latter  the  ligamentum  venosum,  of  the  liver. 


TIIK  AKTFJIIRS. 


T^HE  tlistrihution  of  the  systematic  arteries  is  like  a  highly  ramified  tree,  the 
-^  common  trunk  of  which,  formed  by  the  aorta,  commences  at  the  left  ventricle, 
while  the  smallest  ramifications  extend  to  the  peripheral  parts  of  the  body  and  the 
contained  organs.  Arteries  are  found  in  all  parts  of  the  body,  except  in  the  hairs, 
nails,  epidermis,  cartilages,  and  cornea ;  the  larger  trunks  usually  occupy  the  most 
protected  situations,  running,  in  the  limbs,  along  the  flexor  surface,  where  they 
are  less  exposed  to  injury. 

There  is  considerable  variation  in  the  mode  of  division  of  the  arteries:  occasion- 
ally a  short  trunk  subdivides  into  several  branches  at  the  same  point,  as  may  be 
observed  in  the  cceliac  artery  and  the  thyrocervical  trunk:  the  vessel  may  give  off 
several  branches  in  succession,  and  still  continue  as  the  main  trunk,  as  is  seen  in 
the  arteries  of  the  limbs;  or  the  division  may  be  dichotomous,  as,  for  instance,  when 
the  aorta  divides  into  the  two  common  iliacs. 

A  branch  of  an  artery  is  smaller  than  the  trunk  from  which  it  arises;  but  if  an 
artery  divides  into  two  branches,  the  combined  sectional  area  of  the  two  vessels 
is,  in  nearly  every  instance,  somewhat  greater  than  that  of  the  trunk;  and  the 
combined  sectional  area  of  all  the  arterial  branches  greatly  exceeds  that  of  the 
aorta;  so  that  the  arteries  collectively  may  be  regarded  as  a  cone,  the  apex  of 
which  corresponds  to  the  aorta,  and  the  base  to  the  capillary  system. 

The  arteries,  in  their  distribution,  communicate  with  one  another,  forming 
what  are  called  anastomoses,  and  these  communications  are  very  free  between 
the  large  as  well  as  between  the  smaller  branches.  The  anastomosis  between  trunks 
of  equal  size  is  found  where  great  activity  of  the  circulation  is  requisite,  as  in  the 
brain;  here  the  two  vertebral  arteries  unite  to  form  the  basilar,  and  the  two  ante- 
rior cerebral  arteries  are  connected  by  a  short  communicating  trunk;  it  is  also 
found  in  the  abdomen,  where  the  intestinal  arteries  have  very  ample  anastomoses 
between  their  larger  branches.  In  the  limbs  the  anastomoses  are  most  numerous 
and  of  largest  size  around  the  joints,  the  branches  of  an  artery  above  uniting 
with  branches  from  the  vessels  below.  These  anastomoses  are  of  considerable  in- 
terest to  the  surgeon,  as  it  is  by  their  enlargement  that  a  collateral  circulation  is 
established  after  the  application  of  a  ligature  to  an  artery.  The  smaller  branches 
of  arteries  anastomose  more  frequently  than  the  larger;  and  between  the  smallest 
twigs  these  anastomoses  become  so  numerous  as  to  constitute  a  close  network 
that  pervades  nearly  every  tissue  of  the  body. 

Throughout  the  body  generally  the  larger  arterial  branches  pursue  a  fairly 
straight  course,  but  in  certain  situations  they  are  tortuous.  Thus  the  external 
maxillary  artery  in  its  course  over  the  face,  and  the  arteries  of  the  lips,  are  extremely 
tortuous  to  accommodate  themselves  to  the  movements  of  the  parts.  The  uterine 
arteries  are  also  tortuous,  to  accommodate  themselves  to  the  increase  of  size  which 
the  uterus  undergoes  during  pregnancy. 

Applied  Anatomy. — All  the  arteries,  and  most  of  all  the  aorta,  are  Uable  to  a  degenerative 
process  known  as  atheroma,  arteriosclerosis,  or,  more  recentlj",  atherosclerosis  (Alarchand), 
that  is  of  the  greatest  clinical  importance.  It  is  essentially  a  senile  change,  although  it  ma}-  begin 
at  any  age  and  is  predisposed  to  by  renal  disease,  gout,  diabetes  meUitus,  lead  poisonilig,  and 
a  number  of  other  morbid  states,  and  results  in  the  replacement  of  the  arterial  elastic  tissue  by 


620 


ANGIOLOGY 


fibrous  tissue.  Its  chief  ill  effects  are  two.  In  the  first  place,  it  is  associated  with  a  permanent 
and  often  considerable  rise  in  the  arterial  blood  pressure,  entailing  a  corresponding  liyjiertrophy 
of  the  heart;  in  the  second,  it  weakens  tke  ve.ssel  walls,  rendering  them  more  liable  to  rupture, 
while  at  the  same  time  it  is  apt  to  lessen  the  calibre  of  the  affected  vessels. 

The  arteries  are  also  frequently  attacked  by  syphihs,  which  gives  rise  to  inflammation  and 
degeneration  of  their  middle  coats.  Recent  researches'  go  to  prove  that  arterial  aneurisms, 
other  than  those  due  to  direct  injury,  occur  almost  solely  in  syphihtic  patients. 

1  'ransnersus  thoracis 
Internal  mnmman/  vennel 


Left  phrenic 
nerve 


Fuhnojuiry  pleura 
eura 


Sympathetic  trunk  /  \J  \  -^-V^o-^  ^'e"*' 

Thoracic  duct  Vagus  nerves 

Fig.  582. — Transverse  section  of  thorax,  showing  relations  of  pulmonary  artery. 


The  Pulmonary  Artery  (A.  Pulmonalis)  (Fig.  582). 

The  pulmonary  artery  conveys  the  venous  blood  from  the  right  ventricle  of  the 
heart  to  the  lungs.  It  is  a  short,  wide  vessel,  about  5  cm.  in  length  and  3  cm.  in 
diameter,  arising  from  the  conus  arteriosus  of  the  right  ventricle.  It  extends 
obliquely  upward  and  backward,  passing  at  first  in  front  and  then  to  the  left 
of  the  ascending  aorta,  as  far  as  the  under  surface  of  the  aortic  arch,  where  it 
divides,  about  the  level  of  the  fibrocartilage  between  the  fifth  and  sixth  thoracic 
vertebra?,  into  right  and  left  branches  of  nearly  equal  size. 

Relations. — The  whole  of  this  vessel  is  contained  within  the  pericardium.  It  is  enclosed  with 
the  ascending  aorta  in  a  single  tube  of  the  visceral  layer  of  the  serous  pericardium,  which  is  con- 
tinued upward  upon  them  from  the  base  of  the  heart.  The  fibrous  layer  of  the  pericardium  is 
gradually  lost  upon  the  external  coats  of  the  two  branches  of  the  artery.  In  front,  the  pulmonary 
artery  is  separated  from  the  anterior  end  of  the  second  left  intercostal  space  by  the  pleura  and 
left  lung,  in  addition  to  the  pericardium;  it  rests  at  first  upon  the  ascending  aorta,  and  higher 
up  lies  in  front  of  the  left  atrium  on  a  plane  posterior  to  the  ascending  aorta.  On  either  side  of 
its  origin  is  the  auricula  of  the  corresponding  atrium  and  a  coronary  artery,  the  left  coronary 
artery  passing,  in  the  first  part  of  its  course,  behind  the  vessel.  The  superficial  part  of  the  cardiac 
plexus  hes  above  its  bifm-cation,  between  it  and  the  arch  of  the  aorta. 

The  right  branch  of  the  pulmonary  artery  {ramus  dexter  a.  pulmonalis),  longer 
and  larger  than  the  left,  runs  horizontally  to  the  right,  behind  the  ascending  aorta 
and  superior  vena  cava  and  in  front  of  the  right  bronchus,  to  the  root  of  the  right 


1  C.  U.  Aitchison,  Archives  of  the  Pathological  Institute  of  the  London  Hospital,  190S,  ii,  1. 


THE  ASCENDING  AORTA  621 

lung,  where  it  divides  into  two  branches.  The  lower  and  larger  of  these  goes  to 
the  middle  and  lower  lobes  of  the  lung;  the  upper  and  smaller  is  distributed  to  the 
upper  lobe. 

The  left  branch  of  the  pulmonary  artery  (raniiis-  dninter  a.  pidiiionalis),  shorter 
and  somewhat  smaller  than  the  right,  passes  horizontally  in  front  of  the  descending 
aorta  and  left  bronchus  to  the  root  of  the  left  lung,  where  it  divides  into  two 
branches,  one  for  each  lobe  of  the  lung. 

Above,  it  is  connected  to  the  concavity  of  the  aortic  arch  by  the  ligamentum 
arteriosum,  on  the  left  of  which  is  the  left  recurrent  nerve,  and  on  the  right  the 
superficial  part  of  the  cardiac  plexus.  Below,  it  is  joined  to  the  upper  left  pul- 
monary vein  by  the  ligament  of  the  left  vena  cava  (page  159). 

The  terminal  branches  of  the  pulmonary  arteries  will  be  described  with  the 
anatomy  of  the  lungs. 

Applied  Anatomy. — Stenosis  of  the  pulmonary  artery,  either  with,  or,  more  rarely,  without 
defective  formation  of  the  ventricular  septum,  is  one  of  the  commonest  congenital  defects  of  the 
heart.  It  may  be  due  either  to  fetal  endocarditis,  or  to  maldevelopment  of  the  bulbus  cordis 
(p.  149). 1  As  in  most  forms  of  congenital  heart  disease,  the  child  is  cyanosed  (morbus  caeruleus), 
especially  when  excited  or  on  exertion,  and  rarely  Hves  to  grow  up,  commonly  dying  of  heart 
failure  in  infancy,  or  of  pulmonary  tuberculosis  or  intercm-rent  disease  in  childhood.  The  chief 
signs  of  the  condition  are  the  loud,  harsh  systoUc  cardiac  miu'mur  best  heard  over  the  second 
left  costal  cartilage,  cyanosis,  clubbing  of  the  finger  tips,  and  the  presence  of  an  excess  of  red 
corpuscles  in  the  blood. 

EmboUsm  of  the  pulmonary  artery  by  a  clot  of  blood  coming  from  the  right  side  of  the  heart 
in  patients  with  heart  disease,  or  from  a  thrombosed  vein  in  cases,  for  example,  of  influenza, 
enteric  fever,  puerperal  sepsis,  or  fractured  hmbs,  is  a  common  cause  of  sudden  or  rapid  death. 
The  patient  may  cry  out  with  sudden  excruciating  pain  in  the  precordia  when  the  detached 
embolus  lodges,  and  after  a  brief  period  of  intense  dyspnoea,  pallor,  and  anguish,  die. 


THE  AORTA. 

The  aorta  is  the  main  trunk  of  a  series  of  vessels  which  convey  the  oxygenated 
blood  to  the  tissues  of  the  body  for  their  nutrition.  It  commences  at  the  upper 
part  of  the  left  ventricle,  where  it  is  about  3  cm.  in  diameter,  and  after  ascending 
for  a  short  distance,  arches  backward  and  to  the  left  side,  over  the  root  of  the  left 
lung;  it  then  descends  within  the  thorax  on  the  left  side  of  the  vertebral  column, 
passes  into  the  abdominal  cavity  through  the  aortic  hiatus  in  the  Diaphragma, 
and  ends,  considerably  diminished  in  size  (about  1.75  cm.  in  diameter),  opposite 
the  lower  border  of  the  fourth  lumbar  vertebra,  by  dividing  into  the  right  and  left 
common  iliac  arteries.  Hence  it  is  described  in  several  portions,  viz.,  the  ascending 
aorta,  the  arch  of  the  aorta,  and  the  descending  aorta,  which  last  is  again  divided  into 
the  thoracic  and  abdominal  aortse. 


THE  ASCENDING  AORTA  (AORTA  ASCENDENS)   (Fig.  583). 

The  ascending  aorta  is  about  5  cm.  in  length.  It  commences  at  the  upper  part 
of  the  base  of  the  left  ventricle,  on  a  level  with  the  lower  border  of  the  third  costal 
cartilage  behind  the  left  half  of  the  sternum;  it  passes  obliquely  upward,  forward, 
and  to  the  right,  in  the  direction  of  the  heart's  axis,  as  high  as  the  upper  border 
of  the  second  right  costal  cartilage,  describing  a  slight  curve  in  its  course,  and  being 
situated,  about  6  cm.  behind  the  posterior  surface  of  the  sternum.  At  its  origin 
it  presents,  opposite  the  segments  of  the  aortic  valve,  three  small  dilatations 
called  the  aortic  sinuses.    At  the  union  of  the  ascending  aorta  with  the  aortic  arch 

1  Keith  (Studies  in  Pathologj-,  Aberdeen  University,  1906)  believes  that  the  great  majority  of  cases  which  are  classified 
as  congenital  stenosis  of  the  pulmonary  or  of  the  aortic  orifices  are,  in  reality,  due  to  an  arrest  of  development  or  mal- 
formation of  the  bulbus  cordis. 


622 


ANGIOLOGY 


the  calibre  of  the  vessel  is  increased,  owing  to  a  bulging  of  its  right  wall.  This 
dilatation  is  termed  the  bulb  of  the  aorta,  and  on  transverse  section  presents  a  some- 
what oval  figure.  The  ascending  aorta  is  contained  within  the  pericardium,  and 
is  enclosed  in  a  tube  of  the  serous  pericardium,  common  to  it  and  the  pulmonary 
artery. 

Relations. — The  ascending  aorta  is  covered  at  its  commencement  by  the  trunk  of  the  pul- 
monary artery  and  the  right  auricula,  and,  higher  up,  is  separated  from  the  sternum  by  the 
pericardium,  the  right  pleura,  the  anterior  margin  of  the  right  lung,  some  loose  areolar  tissue, 
and  the  remains  of  the  thymus;  posteriorhj,  it  rests  upon  the  left  atrium  and  right  pulmonary 
artery.  On  the  right  side,  it  is  in  relation  with  the  superior  vena  cava  and  right  atrium,  the 
former  lying  partly  behind  it;  on  the  left  side,  with  the  pulmonary  artery. 

Left  vagus 
Left  phrenic 
—  Thoracic  duct 


Fig.  583. — The  arch  of  the  aorta,  and  its  branches. 

Branches.— The  only  branches  of  the  ascending  aorta  are  the  two  coronary 
arteries  which  supply  the  heart;  they  arise  near  the  commencement  of  the  aorta 
immediately  above  the  attached  margins  of  the  semilunar  valves. 

The  Coronary  Arteries.— The  Right  Coronary  Artery  (a.  coronaria  [cordis] 
dextra)  arises  from  the  anterior  aortic  sinus.  It  passes  at  first  between  the  conus 
arteriosus  and  the  right  auricula  and  then  runs  in  the  right  portion  of  the  coronary 
sulcus,  coursing  at  first  from  the  left  to  right  and  then  on  the  diaphragmatic  surface 


THE  ARCH  OF  THE  AORTA  623 

of  the  heart  from  right  to  left  as  far  as  the  posterior  longitudinal  sulcus,  down 
which  it  is  continued  to  the  apex  of  the  heart  as  the  posterior  descending  branch. 
It  gives  off  a  large  marginal  branch  which  follows  the  acute  margin  of  the  heart 
and  supplies  branches  to  both  surfaces  of  the  right  ventricle.  It  also  gives  twigs 
to  the  right  atrium  and  to  the  part  of  the  left  ventricle  which  adjoins  the 
posterior  longitudinal  sulcus. 

The  Left  Coronary  Artery  (a.  coronaria  [cordis]  sinistra),  larger  than  the  right, 
arises  from  the  left  posterior  aortic  sinus  and  divides  into  an  anterior  descending 
and  a  circumflex  branch.  The  anterior  descending  branch  passes  at  first  behind  the 
pulmonary  artery  and  then  comes  forward  between  that  vessel  and  the  left  auricula 
to  reach  the  anterior  longitudinal  sulcus,  along  which  it  descends  to  the  incisura 
apicis  cordis;  it  gives  branches  to  both  ventricles.  The  circumflex  branch  follows 
the  left  part  of  the  coronary  sulcus,  running  first  to  the  left  and  then  to  the  right, 
reaching  nearly  as  far  as  the  posterior  longitudinal  sulcus;  it  gives  branches  to  the 
left  atrium  and  ventricle.  There  is  a  free  anastomosis  between  the  minute 
branches  of  the  two  coronar}"  arteries  in  the  substance  of  the  heart. 

Peculiarities. — These  vessels  occasionally  arise  bj^  a  common  trunk,  or  their  number  may  be 
increased  to  three,  the  additional  branch  being  of  small  size.  ]More  rarely,  there  are  two  addi- 
tional branches. 

Applied  Anatomy. — The  sudden  blocking  of  a  coronary  arterj^  by  an  embolus,  or  its  more 
gradual  obstruction  by  arterial  disease  or  thrombosis,  is  a  common  cause  of  sudden  death  in 
persons  past  middle  age.  If  the  obstruction  to  the  passage  of  blood  is  incomplete,  true  angina 
pectoris  maj^  occiu".  In  this  condition  the  patient  is  suddenly  seized  with  a  spasm  of  agonizing 
pain  in  the  precordial  region  and  down  the  left  arm,  together  with  an  indescribable  sense  of 
anguish.  He  may  die  in  such  an  attack,  or  succmnb  a  few  hom's  or  days  later  from  heart  failure, 
or  sm'vive  a  number  of  attacks. 

THE  ARCH  OF  THE  AORTA  (ARCUS  AORTAE;  TRANSVERSE 
AORTA)   (Fig.  5S3). 

The  arch  of  the  aorta  begins  at  the  level  of  the  upper  border  of  the  second  sterno- 
costal articulation  of  the  right  side,  and  runs  at  first  upward,  backward,  and  to  the 
left  in  front  of  the  trachea ;  it  is  then  directed  backward  on  the  left  side  of  the  trachea 
and  finally  passes  downward  on  the  left  side  of  the  body  of  the  fourth  thoracic 
vertebra,  at  the  lower  border  of  which  it  becomes  continuous  with  the  descending 
aorta.  It  thus  forms  two  curvatures:  one  wath  its  convexity  upward,  the  other 
with  its  convexity  forward  and  to  the  left.  Its  upper  border  is  usually  about  2.5 
em.  below  the  superior  border  to  the  manubrium  sterni. 

Relations. — The  arch  of  the  aorta  is  covered  anteriorly  by  the  pleurse  and  anterior  margins 
of  the  lungs,  and  b}^  the  remains  of  the  thj^mus.  As  the  vessel  runs  backward  its  left  side  is  in 
contact  with  the  left  lung  and  pleura.  Passing  do^miward  on  the  left  side  of  this  part  of  the  arch 
are  four  nerves;  in  order  from  before  backward  these  are,  the  left  phrenic,  the  lower  of  the  superior 
cardiac  branches  of  the  left  vagus,  the  superior  cardiac  branch  of  the  left  sjTiipathetic,  and  the 
trunk  of  the  left  vagus.  As  the  last  nerve  crosses  the  arch  it  gives  off  its  recurrent  branch,  which 
hooks  around  below  the  vessel  and  then  passes  upward  on  its  right  side.  The  highest  left  inter- 
costal vein  runs  obliquely  upward  and  forward  on  the  left  side  of  the  arch,  between  the  pkrenic 
and  vagus  nerves.  On  the  right  are  the  deep  part  of  the  cardiac  plexus,  the  left  recm'rent  nerve, 
the  oesophagus,  and  the  thoracic  duct;  the  trachea  hes  behind  and  to  the  right  of  the  vessel. 
Above  are  the  innominate,  left  common  carotid,  and  left  subclavian  arteries,  which  arise  from 
the  convexitj'  of  the  arch  and  are  crossed  close  to  their  origins  by  the  left  innominate  vein.  Below 
are  the  bifm-cation  of  the  pulmonary  arterj^,  the  left  bronchus,  the  ligamentum  arteriosum,  the 
superficial  part  of  the  cardiac  plexus,  and  the  left  recm-rent  nerve.  As  ah'eady  stated,  the  hga- 
mentum  arteriosum  connects  the  commencement  of  the  left  pulmonary  artery  to  the  aortic  arch. 

Between  the  origin  of  the  left  subclavian  artery  and  the  attachment  of  the  ductus 
arteriosus  the  lumen  of  the  fetal  aorta  is  considerably  narrowed,  forming  what  is 
termed  the  aortic  isthmus,  while  immediately  beyond  the  ductus  arteriosus  the 
vessel  presents  a  fusiform  dilation  which  His  has  named  the  aortic  spindle — the 


624  AXGIOLOGY 

point  of  junction  of  the  two  parts  being  marked  in  the  concavity  of  the  arch  by  an 
indentation  or  angle.  These  conditions  persist,  to  some  extent,  in  the  adult,  where 
His  found  that  the  average  diameter  of  the  spindle  exceeded  that  of  the  isthmus 
by  3  mm. 

Distinct  from  this  diffuse  and  moderate  stenosis  at  the  isthmus  is  the  condition  known  as 
coarctation  of  the  aorta,  or  marked  stenosis  often  amounting  to  complete  obUteration  of  its  lumen, 
seen  in  adults  and  occurring  at  or  near,  oftenest  a  little  below,  the  insertion  of  the  ligamentum 
arteriosum  into  the  aorta.  According  to  Bonnet^  this  coarctation  is  never  found  in  the  fetus  or 
at  birth,  and  is  due  to  an  abnormal  extension  of  the  peculiar  tissue  of  the  ductus  into  the  aortic 
wall,  which  gives  rise  to  a  simultaneous  stenosis  of  both  vessels  as  it  contracts  after  birth — the 
ductus  is  usually  obhterated  in  these  cases.  An  extensive  collateral  circulation  is  set  up,  by  the 
costocervicals,  internal  mammaries,  and  the  descending  branches  of  the  transverse  cervical 
above  the  stenosis,  and  below  it  by  the  first  four  aortic  intercostals,  the  pericardiaco-phrenics, 
and  the  superior  and  inferior  epigastrics. 

Peculiarities. — The  height  to  which  the  aorta  rises  in  the  thorax  is  usually  about  2.5  cm. 
below  the  upper  border  of  the  sternum;  but  it  may  ascend  nearly  to  the  top  of  the  bone.  Occa- 
sionally it  is  found  4  cm.,  more  rarely  from  5  to  8  cm.  below  this  point.  Sometimes  the  aorta 
arches  over  the  root  of  the  right  lung  (right  aortic  arch)  instead  of  over  that  of  the  left,  and  passes 
down  on  the  right  side  of  the  vertebral  column,  a  condition  which  is  found  in  birds.  In  such  cases 
all  the  thoracic  and  abdominal  viscera  are  transposed.  Less  frequently  the  aorta,  after  arching 
over  the  root  of  the  right  lung,  is  directed  to  its  usual  position  on  the  left  side  of  the  vertebral 
column;  this  peculiarity  is  not  accompanied  by  transposition  of  the  viscera.  The  aorta  occa- 
sionally divides,  as  in  some  quadrupeds,  into  an  ascending  and  a  descending  trunk,  the  former 
of  which  is  directed  vertically  upward,  and  subdivides  into  three  branches,  to  supply  the  head 
and  upper  extremities.  Sometimes  the  aorta  subdivides  near  its  origin  into  two  branches,  which 
soon  reimite.  In  one  of  these  cases  the  oesophagus  and  trachea  were  found  to  pass  through  the 
interval  between  the  two  branches;  this  is  the  normal  condition  of  the  vessel  in  the  reptiUa. 

Applied  Anatomy. — Of  all  the  vessels  of  the  arterial  system,  the  aorta,  and  more  especially 
its  arch,  is  most  frequently  the  seat  of  disease;  hence  it  is  important  to  consider  some  of  the 
consequences  that  may  ensue  from  aneurism  of  this  part. 

Aneurism  of  the  ascending  aorta,  in  the  situation  of  the  aortic  sinuses,  in  the  great  majority 
of  cases,  affects  the  anterior  sinus;  this  is  mainly  owing  to  the  fact  that  the  regurgitation  of 
blood  upon  the  sinuses  takes  place  chiefly  on  the  anterior  aspect  of  the  vessel.  As  the  aneurismal 
sac  enlarges,  it  may  compress  any  or  all  of  the  structm'es  in  immediate  proximity  with  it,  but 
chiefly  projects  toward  the  right  anterior  side;  and,  consequently,  interferes  mainly  with  those 
structm-es  that  have  a  corresponding  relation  with  the  vessel.  If  it  project  forward,  it  may 
destroy  the  sternum  and  the  cartilages  of  the  ribs,  usually  on  the  right  side,  and  appear  as  a 
pulsating  tumor  on  the  front  of  the  chest,  just  below  the  manubrium;  or  it  may  burst  into  the 
pericardium,  or  may  compress,  or  open  into  the  right  lung,  the  trachea,  bronchi,  or  oesophagus. 
In  the  majority  of  cases  it  bursts  into  the  cavity  of  the  pericardium,  the  patient  suddenly  drops 
down  dead,  and,  upon  a  postmortem  examination,  the  pericardial  sac  is  found  full  of  blood; 
or  it  may  compress  the  right  atrium,  or  the  pulmonary  artery,  and  adjoining  part  of  the  right 
ventricle,  and  open  into  one  or  the  other  of  these  parts.  It  may  press  upon  the  .superior  vena 
cava  or  the  innominate  veins,  causing  great  venous  engorgement.  The  face  becomes  livid  and 
swollen,  the  right  arm  and  anterior  thoracic  wall  oedematous,  and  the  congestion  of  the  brain 
gives  rise  to  headache  and  vertigo.  An  aneurism  has  occasionally  perforated  into  the  superior 
vena  cava,  setting  up  an  arteriovenous  aneurism.  When  this  happens  the  patient  suddenly 
becomes  very  short  of  breath,  intensely  congested  and  oedematous  in  the  face  and  upper  part 
of  the  body,  and  develops  a  palpable  thrill  and  a  continuous  humming  murmur,  loudest  during 
systole,  over  the  sternum.  Death  follows  a  few  days  or  weeks  after  such  a  perforation;  and 
somewhat  similar  symptoms  are  occasioned  when  an  aortic  anem'ism  erodes  and  bm'sts  into 
the  pulmonary  artery. 

Regarding  the  arch  of  the  aorta,  the  student  is  reminded  that  the  vessel  lies  against  the  trachea, 
oesophagus,  and  thoracic  duct;  that  the  recmTent  nerve  winds  around  it;  and  that  from  its  upper 
part  are  given  off  three  large  trunks,  which  supply  the  head,  neck,  and  upper  extremities.  An 
aneui'ismal  tumor  taking  origin  from  the  posterior  part  of  the  vessel,  its  most  usual  site,  may 
press  upon  the  trachea  and  give  rise  to  the  sign  known  as  tracheal  tugging,  impede  the  breathing, 
or  produce  cough,  dyspnoea,  bronchiectasis,  hemoptysis,  or  stridulous  breathing,  or  it  may  ulti- 
mately burst  into  that  tube,  producing  fatal  hemorrhage.  Again,  its  pressure  on  the  left  recm-rent 
nerve  may  give  rise  to  symptoms  of  laryngeal  paralysis;  or  it  may  press  upon  the  thoracic  duct 
and  destroy  life  by  inanition;  or  it  may  involve  the  oesophagus,  producing  dysphagia,  and  has 
not  infrequently  been  mistaken  for  oesophageal  stricture;  or  it  may  burst  into  the  oesophagus, 
when  fatal  hemorrhage  will  occur.     Compression  or  stretching  of  the  sympathetic  filaments 

1  Rev.  de  Med.,  Paris,  1903. 


THE  INNOM-INATE  ARTERY  625 

may,  in  the  former  ease,  produce  dilatation  of  tlic  pupil;  in  the  latter,  contraction,  if  the  con- 
ducting jiower  is  abolisheil,  on  the  affected  side.  This  has  proved  to  be  an  important  diagnostic 
sign  in  this  disease.  Again,  the  innominate  artery,  or  the  subclavian,  or  left  carotid,  may  be  so 
obstructed  by  clots  as  to  produce  a  weakness,  or  even  a  disappearance,  of  the  pulse  in  one  or  the 
other  wrist,  or  in  the  left  superficial  temporal  artery;  or  the  tumor  may  present  itself  at  or  above 
the  manul)rium,  generallj'  cither  in  the  median  line,  or  to  the  right  of  the  sternum,  and  may  sim- 
ulate an  aneurism  of  one  of  the  arteries  of  the  neck. 

Many  of  the  physical  signs  of  an  aortic  aneurism  may  be  simulated  with  extraordinary  fidelity 
by  the  preternatural  pulsation  or  throbbing  of  a  distended  and  elastic  aorta,  when  no  true  aneu- 
rismal  dilatation  exists.  This  condition  may  be  met  with  in  young  persons  with  aortic  reflux 
and  greatlj'  hypertrophied  hearts,  in  patients  who  are  of  a  neurotic  or  hysterical  temperament, 
and  in  cases  of  Graves'  disease  or  of  marked  anemia.  The  condition  is  known  as  dynamic  dilata- 
tion of  the  aorta,  and  in  no  way  threatens  life. 

Branches  (Figs.  583,  584). — The  branches  given  off  from  the  arch  of  the  aorta 
are  three  in  number:  the  innominate,  the  left  common  carotid,  and  the  left  subclavian. 

Peculiarities. — Position  of  the  Branches. — The  branches,  instead  of  arising  from  the  highest 
part  of  the  arch,  may  spring  from  the  commencement  of  the  arch  or  upper  part  of  the  ascending 
aorta;  or  the  distance  between  them  at  their  origins  may  be  increased  or  diminished,  the  most 
frequent  change  in  this  respect  being  the  approximation  of  the  left  carotid  toward  the  innominate 
artery. 

The  number  of  the  primary  branches  may  be  reduced  to  one,  or  more  commonly  two;  the  left 
carotid  arising  from  the  innominate  artery;  or  (more  rarely)  the  carotid  and  subclavian  arteries 
of  the  left  side  arising  from  a  left  innominate  artery.  But  the  number  may  be  increased  to  four, 
from  the  right  carotid  and  subclavian  arteries  arising  directly  from  the  aorta,  the  innominate 
being  absent.  In  most  of  these  latter  cases  the  right  subclavian  has  been  found  to  arise  from  the 
left  end  of  the  arch;  in  other  cases  it  is  the  second  or  third  branch  given  off,  instead  of  the  first. 
Another  common  form  in  which  there  are  four  primary  branches  is  that  in  which  the  left  vertebral 
arterj''  arises  from  the  arch  of  the  aorta  between  the  left  carotid  and  subclavian  arteries.  Lastly, 
the  number  of  trunks  from  the  arch  may  be  increased  to  five  or  six;  in  these  instances,  the  external 
and  internal  carotids  arise  separately  from  the  arch,  the  common  carotid  being  absent  on  one  or 
both  sides.  In  some  few  cases  six  branches  have  been  found,  and  this  condition  is  associated 
with  the  origin  of  both  vertebral  arteries  from  the  arch. 

Number  Usual,  Arrangement  Different. — When  the  aorta  arches  over  to  the  right  side,  the 
three  branches  have  an  arrangement  the  reverse  of  what  is  usual;  the  innominate  artery  is  a  left 
one,  and  the  right  carotid  and  subclavian  arise  separately.  In  other  cases,  where  the  aorta  takes 
its  usual  course,  the  two  carotids  may  be  joined  in  a  common  trunk,  and  the  subclavians  arise 
separatel}^  from  the  arch,  the  right  subclavian  generally  arising  from  the  left  end  of  the  arch. 

In  some  instances  other  arteries  spring  from  .the  arch  of  the  aorta.  Of  these  the  most  common 
are  the  bronchial,  one  or  both,  and  the  thyreoidea  ima;  but  the  internal  mammary  and  the  inferior 
thyroid  have  been  seen  to  arise  from  this  vessel. 

The  Innominate  Artery  (A.  Anonyma;  Brachiocephalic  Artery)  (Fig.  583). 

The  innominate  artery  is  the  largest  branch  of  the  arch  of  the  aorta,  and  is  from 
4  to  5  cm.  in  length.  It  arises,  on  a  level  with  the  upper  border  of  the  second 
right  costal  cartilage,  from  the  commencement  of  the  arch  of  the  aorta,  on  a  plane 
anterior  to  the  origin  of  the  left  carotid;  it  ascends  obliquely  upward,  backward, 
and  to  the  right  to  the  level  of  the  upper  border  of  the  right  sternoclavicular 
articulation,  where  it  divides  into  the  right  common  carotid  and  right  subclavian 
arteries. 

Relations. — Anteriorly,  it  is  separated  from  the  manubrium  sterni  by  the  Sternohyoideus  and 
Sternothjreoideus,  the  remains  of  the  thymus,  the  left  innominate  and  right  inferior  thyroid  veins 
which  cross  its  root,  and  sometimes  the  superior  cardiac  branches  of  the  right  vagus.  Posterior 
to  it  is  the  trachea,  which  it  crosses  obhquely.  On  the  right  side  are  the  right  innominate  vein, 
the  superior  vena  cava,  the  right  phrenic  nerve,  and  the  pleura;  and  on  the  left  side,  the  remains 
of  the  thjTnus,  the  origin  of  the  left  common  carotid  artery,  the  inferior  thyroid  veins,  and  the 
trachea. 

Branches. — The  innominate  artery  usually  gives  off  no  branches;  but  occasion- 
ally a  small  branch,  the  thyreoidea  ima,  arises  from  it.     Sometimes  it  gives  oft'  a 
thymic  or  bronchial  branch. 
40 


626  ANGIOLOGY 

The  thyreoidea  ima  (a.  fhijreoidea  ima)  ascends  in  front  of  the  trachea  to  the 
lower  part  of  the  thyroid  gland,  which  it  supplies.  It  varies  greatly  in  size,  and 
appears  to  compensate  for  deficiency  or  absence  of  one  of  the  other  thyroid 
vessels.  It  occasionally  arises  from  the  aorta,  the  right  common  carotid,  the 
subclavian  or  the  internal  mammary. 

Point  of  Division. — The  innominate  artery  sometimes  divides  above  the  level  of  the  sterno- 
clavicular joint,  less  frequently  below  it. 

Position. — When  the  aortic  arch  is  on  the  right  side,  the  innominate  is  directed  to  the  left  side 

of  the  neck. 

Collateral  Circulation. — Allan  Burns  demonstrated,  on  the  dead  subject,  the  possibihtj'  of  the 
establishment  of  the  collateral  circulation  after  hgature  of  the  innominate  artery,  bj-  tying  and 
dividing  that  artery.  He  then  found  that  "Even  coar.se  injection,  impelled  into  the  aorta,  pas.sed 
freeh'  by  the  anastomosing  branches  into  the  arteries  of  the  right  arm,  filling  them  and  all  the 
vessels  of  the  head  completely."^  The  branches  bj'  which  this  circulation  would  be  carried  on 
are  very  numerous;  thus,  all  the  communications  across  the- middle  line  between  the  branches 
of  the  carotid  arteries  of  opposite  sides  would  be  available  for  the  supplj'  of  blood  to  the  right 
side  of  the  head  and  neck;  while  the  anastomosis  between  the  costocervical  of  the  subclavian  and 
the  first  aortic  intercostal  fsee  infra  on  the  collateral  circulation  after  obhteration  of  the  thoracic 
aorta)  would  bring  the  blood,  by  a  free  and  direct  course,  into  the  right  subclavian.  The  numerous 
connections,  also,  between  the  intercostal  arteries  and  the  branches  of  the  axillary  and  internal 
mammary  arteries  would,  doubtless,  assist  in  the  supply  of  blood  to  the  right  arm,  while  the 
inferior  epigastric  from  the  external  ihac  would,  bj'  means  of  its  anastomo.sis  with  the  internal 
mammarj^,  compensate  for  any  deficiency  in  the  vascularity  of  the  wall  of  the  chest. 

Applied  Anatomy. — Aneurism  of  the  innominate  artery  not  infrequently  occurs  as  an  accom- 
paniment to  aneurism  of  the  arch  of  the  aorta.  It  caases  bulging  of  the  right  sternoclavicular 
articulation,  pushing  forward  the  Sternocleidomastoideus  muscle  and  filling  up  the  jugular 
notch.  It  produces  serious  pressure  symptoms;  from  pressure  on  the  innominate  veins  it  may 
cause  oedema  of  the  upper  extremities,  and  of  the  head  and  neck;  from  pressure  on  the  trachea 
it  produces  dyspnoea;  and  from  pressure  on  the  right  recurrent  nerve,  hoarseness  and  larjmgeal 
cough. 

Although  the  operation  of  tying  the  innominate  arterj-  has  been  performed  by  several  surgeons, 
not  many  successes  have  been  recorded.  The  chief  danger  of  the  operation  appears  to  be  the 
frequency  of  secondary  hemorrhage;  but  in  the  present  day,  with  the  practice  of  aseptic  surgery 
and  our  greater  knowledge  of  the  use  of  the  ligature,  more  favorable  results  may  be  anticipated. 
The  main  obstacles  to  the  operation  are,  the  deep  situation  of  the  artery  behind  the  sternum, 
and  the  number  of  important  structures  which  surround  it. 

In  order  to  apply  a  hgature  to  this  vessel,  the  patient  is  to  be  placed  upon  his  back  ^dth  the 
thorax  slightly  raised,  the  head  bent  a  little  backward,  and  the  right  shoulder  strongly  depressed, 
so  as  to  draw  out  the  artery  from  behind  the  sternum  into  the  neck.  An  incision  7  cm.  or  more 
in  length  is  then  made  along  the  anterior  border  of  the  Sternocleidomastoideus,  terminating  at 
the  sternal  end  of  the  cla\acle.  From  this  point,  a  second  incision  is  carried  about  the  same 
length  along  the  upper  border  of  the  clavicle.  The  skin  is  then  dissected  back,  and  the  Platysma 
divided;  the  sternal  end  of  the  Sternocleidomastoideus  is  now  brought  into  view,  and  a  director 
being  passed  beneath  it,  and  close  to  its  deep  surface  so  as  to  avoid  any  small  vessels,  it  is  to  be 
divided;  in  like  manner  the  cla\acular  origin  is  to  be  divided  throughout  the  whole  or  greater 
part  of  its  attachment.  By  pressing  aside  any  loose  cellular  tissue  or  vessels  "that  may  now  appear, 
the  Stemohyoideus  and  StemothjTeoideus  muscles  wiU  be  exposed,  and  must  be  divided.  The 
inferior  thjToid  veins  may  come  into  view,  and  must  be  carefuUj"  drawn  either  upward  or  down- 
ward, by  means  of  a  blunt  hook,  or  tied  with  double  hgatures  and  divided.  After  tearing  through 
a  strong  fibrocellular  lamina,  the  right  common  carotid  is  brought  into  view,  and  being  traced 
do^Tiward,  the  innominate  artery  is  reached.  The  left  innominate  vein  should  now  be  depressed; 
the  right  innominate  vein,  the  internal  jugular  vein,  and  the  vagus  nerve  drawn  to  the  right 
side;  and  a  curved  aneurysm  needle  maj'  then  be  passed  around  the  vessel,  close  to  its  surface, 
and  in  a  direction  from  below  upward  and  medially;  care  being  taken  to  avoid  the  right  pleural 
sac,  the  trachea,  and  cardiac  nerA'es.  The  hgature  should  be  appUed  to  the  artery  as  high  as 
possible,  in  order  to  allow  room  between  it  and  the  aorta  for  the  formation  of  the  coagulum. 
The  importance  of  avoiding  the  th3Toid  plexus  of  veins  during  the  primary  steps  of  the  operation, 
and  the  pleural  sac  while  including  the  vessel  in  the  ligature,  should  be  most  carefullj'  borne  in 
mind. 

'  Surgical  Anatomy  of  the  Head  and  Neck,  p.  62. 


THE  COMMOX  CAROTID  ARTERY  627 

THE   ARTERIES    OF   THE   HEAD   AND   NECK. 

The  principal  arteries  of  supply  to  the  head  and  neck  are  the  two  common 
carotids;  thoy  ascend  in  the  neck  and  each  divides  into  two  branches,  viz.,  (1)  the 
external  carotid,  sujjplying  the  exterior  of  the  head,  the  face,  and  the  greater  part 
of  the  neck;  (2)  the  internal  carotid,  supplying  to  a  great  extent  the  parts  within 
the  cranial  and  orbital  cavities. 

THE  COMMON  CAROTID  ARTERY  (A.  CAROTIS  COMMUNIS). 

The  common  carotid  arteries  differ  in  length  and  in  their  mode  of  origin.  The 
right  begins  at  the  bifurcation  of  the  innominate  artery  behind  the  sternoclavicular 
joint  and  is  confined  to  the  neck.  The  left  springs  from  the  highest  part  of  the 
arch  of  the  aorta  to  the  left  of,  and  on  a  plane  posterior  to  the  innominate  artery, 
and  therefore  consists  of  a  thoracic  and  a  cervical  portion. 

The  thoracic  portion  of  the  left  common  carotid  artery  ascends  from  the  arch  of 
the  aorta  through  the  superior  mediastinal  cavity  to  the  level  of  the  left  sterno- 
clavicular joint,  where  it  is  continuous  with  the  cervical  portion. 

Relations. — In  front,  it  is  separated  from  the  manubrium  sterni  by  the  Sternoh3^oideus  and 
SternothjTeoideus,  the  anterior  portions  of  the  left  pleura  and  lung,  the  left  innominate  vein, 
and  the  remains  of  the  thj'mus;  behind,  it  lies  on  the  trachea,  oesophagus,  left  recurrent  nerve, 
and  thoracic  duct.  To  its  right  side  below  is  the  innominate  artery,  and  above,  the  trachea,  the 
inferior  thjToid  veins,  and  the  remains  of  the  thymus;  to  its  left  side  are  the  left  vagus  and  phrenic 
nerves,  left  plem-a,  and  lung.     The  left  subclavian  arterj^  is  posterior  and  slightly  lateral  to  it. 

The  cervical  portions  of  the  common  carotids  resemble  each  other  so  closely 
that  one  description  will  apply  to  both  (Fig.  585).  Each  vessel  passes  obliquely 
upward,  from  behind  the  sternoclavicular  articulation,  to  the  level  of  the  upper 
border  of  the  thyroid  cartilage,  where  it  divides  into  the  external  and  internal 
carotid  arteries. 

At  the  lower  part  of  the  neck  the  two  common  carotid  arteries  are  separated 
from  each  other  by  a  very  narrow  interval  which  contains  the  trachea;  but  at  the 
upper  part,  the  thyroid  gland,  the  larynx  and  pharynx  project  forward  between 
the  two  vessels.  The  common  carotid  artery  is  contained  in  a  sheath,  which  is 
derived  from  the  deep  cervical  fascia  and  encloses  also  the  internal  jugular  vein 
and  vagus  nerve,  the  vein  lying  lateral  to  the  artery,  and  the  nerve  between  the 
artery  and  vein,  on  a  plane  posterior  to  both.  On  opening  the  sheath,  each  of 
these  three  structures  is  seen  to  have  a  separate  fibrous  investment. 

Relations. — At  the  lower  part  of  the  neck  the  common  carotid  artery  is  very  deeply  seated, 
being  covered  by  the  integument,  superficial  fascia,  Platj'sma,  and  deep  cervical  fascia,  the  Sterno- 
cleidomastoideus,  Sternohyoideus,  SternothjTeoideus,  and  Omohyoideus;  in  the  upper  part  of 
its  course  it  is  more  superficial,  being  covered  merely  by  the  integument,  the  superficial  fascia, 
Platysma,  deep  cervical  fascia,  and  medial  margin  of  the  Sternocleidomastoideus.  When  the 
latter  muscle  is  drawn  backward,  the  artery  is  seen  to  be  contained  in  a  triangular  space,  the 
carotid  triangle,  bounded  behind  by  the  Sternocleidomastoideus,  above  by  the  Stylohj'oideus 
and  posterior  belly  of  the  Digastricus,  and  below  by  the  superior  belly  of  the  Omohyoideus. 
This  part  of  the  artery  is  crossed  obhquely,  from  its  medial  to  its  lateral  side,  by  the  sterno- 
cleidomastoid branch  of  the  superior  thjToid  artery;  it  is  also  crossed  bj^  the  superior  and  middle 
thjToid  veins  which  end  in  the  internal  jugular;  descending  in  front  of  its  sheath  is  the  descending 
branch  of  the  hj'poglossal  nerve,  this  filament  being  joined  by  one  or  two  branches  from  the 
cervical  nerves,  which  cross  the  vessel  obUquel3^  Sometimes  the  descending  branch  of  the  hj-po- 
glossal  nerve  is  contained  within  the  sheath.  The  superior  thjToid  vein  crosses  the  arterj-  near 
its  termination,  and  the  middle  thyroid  vein  a  httle  below  the  level  of  the  cricoid  cartilage;  the 
anterior  jugular  vein  crosses  the  artery  just  above  the  clavicle,  but  is  separated  from  it  by  the 
Sternohyoideus  and  SternothjTeoideus.  Behind,  the  artery  is  separated  from  the  transverse 
processes  of  the  cervical  vertebr£e  by  the  Longus  coUi  and  Longus  capitis,  the  sj^mpathetic  trunk 
being  interposed  between  it  and  the  muscles.  The  inferior  thjToid  artery  crosses  behind  the 
lower  part  of  the  vessel.  Medially,  it  is  in  relation  with  the  oesophagus,  trachea,  and  thjToid 
gland  (which  overlaps  it),  the  inferior  thjT-'oid  arterj-  and  recm-rent  nerve  being  interposed;  higher 


628 


A  NG 10  LOGY 


up,  with  the  larynx  and  pharynx.  Lateral  to  the  artery  are  tlie  internal  jugular  vein  and  vagus 
nerve. 

At  the  lower  part  of  the  neck,  the  right  recurrent  nerve  crosses  obliquely  behind  the  artery; 
the  right  internal  jugular  vein  diverges  from  the  artery,  but  the  left  approaches  and  often  over- 
laps the  lower  part  of  the  artery. 

Behind  the  angle  of  bifurcation  of  the  common  carotid  artery  is  a  reddish-brown  o\'al  body, 
known  as  the  glomus  caroticum  (carotid  bodij) .  It  is  similar  in  structure  to  the  glomus  coccygeum 
{coccygeal  body)  which  is  situated  on  the  middle  sacral  artery. 


Fig.  585. — Superficial  dissection  of  the  right  side  of  the  neck,  showing  the  carotid  and  subclavian  arteries. 

Peculiarities  as  to  Origin. — The  right  common  carotid  may  arise  above  the  level  of  the  upper 
border  of  the  sternoclavicular  articulation;  this  variation  occurs  in  about  12  per  cent,  of  cases. 
In  other  cases  the  artery  may  arise  as  a  separate  branch  from  the  arch  of  the  aorta,  or  in  con- 
junction with  the  left  carotid.  The  left  common  carotid  varies  in  its  origin  more  than  the  right. 
In  the  majority  of  abnormal  cases  it  arises  with  the  innominate  artery;  if  that  artery  is  absent, 
the  two  carotids  arise  usually  by  a  single  trunk.  It  is  rarely  joined  with  the  left  subclavian, 
except  in  cases  of  transposition  of  the  aortic  arch. 

Peculiarities  as  to  Point  of  Division. — In  the  majority  of  abnormal  cases  this  occurs  higher 
than  usual,  the  artery  dividing  opposite  or  even  above  the  hyoid  bone;  more  rarely,  it  occurs 


THE  COMMON  CAROTID  ARTERY  ()29 

below,  opposite  the  middle  of  the  larynx,  or  the  lower  border  of  the  cricoid  cartilage;  one  case 
is  related  by  Morgagni,  where  the  artery  was  only  4  cm.  in  length  and  divided  at  the  root  of  the 
neck.  Veiy  rarely,  the  conmion  carotid  ascends  in  the  neck  without  any  subdivision,  either  the 
external  or  the  internal  carotid  being  wanting;  and  in  a  few  cases  the  common  carotid  has  been 
found  to  be  absent,  the  external  and  internal  carotids  arising  directly  from  the  arch  of  the  aorta. 
This  peculiarity  existed  on  both  sides  in  some  instances,  on  one  side  in  others. 

Occasional  Branches. — The  common  carotid  usually  gives  off  no  branch  previous  to  its  bifurca- 
tion, but  it  occasionally  gives  origin  to  the  superior  thyroid  or  its  laryngeal  branch,  the  ascend- 
ing pharyngeal,  the  inferior  thyroid,  or,  more  rarely,  the  vertebral  artery. 

Applied  Anatomy. — Aneurisms  are  not  commonly  met  with  on  the  common  carotid;  when  they 
do  occm-  thej^  are  usually  situated  low  dowii  at  the  root  of  the  neck,  or  just  below  the  point  of 
bifurcation  of  the  vessel.  They  do  not  frequently  assume  a  large  size,  and  are  more  commonly 
found  on  the  right  side.  As  they  increase  in  size  they  displace  the  trachea  and  larynx,  and  there- 
fore dyspnoea  becomes  a  prominent  symptom.  Dysphagia  also  may  be  present  from  pressure 
on  the  a^sophagus,  especially  if  the  aneurism  is  on  the  left  side;  and  pressure  on  the  recurrent 
nerve  may  produce  hoarseness  and  laryngeal  cough.  Pressure  on  the  sympathetic  will  cause 
pupillary  changes — dilatation  of  the  pupil  when  the  sympathetic  is  irritated,  contraction  when 
it  has  become  pai'al3'zed — and  may  also  give  rise  to  unilateral  sweating.  Pressure  on  the  super- 
ficial branches  of  the  cervical  plexus  may  give  rise  to  pain  in  the  head,  face,  and  neck;  pressure 
on  the  vagus  to  iri-egular  action  of  the  heart  and  to  asthmatic  attacks.  It  is  important  to  bear 
in  mind  that  an  enlarged  lymph  gland  in  the  superior  carotid  triangle,  receiving  a  transmitted 
pulsation  from  the  carotid  artery,  may  simulate  aneurism  of  that  vessel,  but  may  be  distinguished 
from  it  by  the  character  of  the  pulsation,  which  is  not  distensile. 

EmboUsm  of  the  left  common  carotid  has  been  known  to  produce  aphasia  by  interference 
with  the  blood  supply  of  the  brain. 

Digital  compression  of  the  common  carotid  is  sometimes  required,  and  is  best  effected  by 
compressing  the  vessel  with  the  thumb  against  the  anterior  tubercle  of  the  transverse  process 
of  the  sixth  cervical  vertebra  (see  p.  199). 

Ligature  of  the  common  carotid  artery  may  be  necessary  in  a  case  of  woimd  of  that  vessel 
or  its  branches,  in  aneurism,  or  in  a  case  of  pulsating  tumor  of  the  orbit  or  skuU.  If  the  wound 
involves  the  trunk  of  the  common  carotid,  it  will  be  necessary  to  tie  the  artery  above  and  below 
the  wounded  part.  In  cases  of  aneurism,  the  whole  of  the  artery  is  accessible,  and  any  part  of 
it  may  be  tied.  When  the  case  is  such  as  to  allow  of  a  choice  being  made,  the  upper  part  of  the 
carotid  should  be  selected  as  the  spot  upon  which  to  place  a  hgature,  for  the  lower  part  of  the 
vessel  is  placed  very  deeply  in  the  neck,  and  is  covered  by  three  layers  of  muscles;  moreover, 
on  the  left  side,  the  internal  jugular  vein,  in  the  great  majority  of  cases,  passes  obhquely  in  front 
of  it.  The  part  of  the  vessel  which  is-most  favorable  for  the  operation  is  that  opposite  the  level 
of  the  cricoid  cartilage.  It  occasionally  happens  that  the  carotid  artery  bifurcates  below  its 
usual  position;  if  the  artery  be  exposed  at  its  point  of  bifurcation,  both  divisions  of  the  vessel 
should  be  tied  near  their  origin,  in  preference  to  tying  the  trunk  of  the  artery  near  its  termina- 
tion; and  if,  in  consequence  of  the  entire  absence  of  the  common  carotid,  or  from  its  early  divi- 
sion, two  arteries,  the  external  and  internal  carotids,  are  met  with,  the  Hgature  should  be  placed 
on  that  vessel  which  is  found  on  compression  to  be  connected  with  the  diseased  area. 

In  this  operation,  the  direction  of  the  vessel  and  the  anterior  margin  of  the  Sternocleido- 
mastoideus  are  the  chief  guides  to  its  performance.  The  patient,  should  be  placed  on  his  back 
with  the  head  extended  and  turned  slightly  to  the  opposite  side;  an  incision  is  to  be  made,  7  or 
8  cm.  long,  in  the  direction  of  the  anterior  border  of  the  Sternocleidomastoideus,  so  that  the 
centre  corresponds  to  the  level  of  the  cricoid  cartilage.  After  dividing  the  integument,  super- 
ficial fascia,  Platysma,  and  deep  fascia,  the  margins  of  the  wound  are  held  asunder  by  retractors, 
and  the  ramus  descendens  hypoglossi  is  now  exposed,  and  must  be  avoided.  The  sheath  of  the 
vessel  is  to  be  raised  by  forceps,  and  opened  to  a  small  extent  over  the  artery  at  its  medial  side. 
The  internal  jugular  vein  may  present  itself  alternately  distended  and  relaxed,  and  must  be 
carefully  avoided.  The  aneurism  needle  is  passed  from  the  lateral  aspect,  care  being  taken  to 
keep  the  needle  in  close  contact  with  the  artery,  and  thus  avoid  the  risk  of  injuring  the  internal 
jugular  vein,  or  including  the  vagus  nerve.  Before  the  ligature  is  tied,  it  should  be  ascertained 
that  nothing  but  the  artery  is  included  in  it. 

Ligature  of  the  common  carotid  near  the  root  of  the  neck  is  sometimes  required  in  cases  of 
aneurism  of  the  upper  part  of  the  carotid,  especially  if  the  sac  is  of  large  size.  It  is  best  performed 
by  dividing  the  sternal  origin  of  the  Sternocleidomastoideus,  but  may  be  done  in  some  cases, 
if  the  anem'ism  is  not  of  very  large  size,  by  an  incision  along  the  anterior  border  of  the  muscle, 
extending  down  to  the  sternoclavicular  articulation,  and  by  then  retracting  the  muscle.  The 
easiest  and  best  plan,  however,  is  to  make  an  incision  5  to  7  cm.  long  down  the  lower  part  of  the 
anterior  border  of  the  Sternocleidomastoideus  to  the  sternoclavicular  joint,  and  a  second  inci- 
sion, starting  from  the  termination  of  the  first,  along  the  upper  border  of  the  clavicle  for  about 
5  cm.  This  incision  is  made  through  the  superficial  and  deep  fasciae  and  the  sternal  origin  of  the 
muscle  is  exposed.    This  is  to  be  divided  on  a  director  and  turned  up,  with  the  superficial  struc- 


630  A  NG 10  LOGY 

tures,  as  a  triangular  flap.  Some  loose  connective  tissue  is  to  be  divided  or  torn  through,  and 
the  lateral  border  of  the  Sternohyoideus  exposed.  In  doing  this,  care  must  be  taken  not  to  wound 
the  anterior  jugular  vein,  which  crosses  this  muscle  to  reach  the  external  jugular  or  subclavian 
vein.  The  8ternohyoidcus  and  Sternothyrcoideus  are  to  be  drawn  mediahvard  by  means  of  a 
retractor,  and  the  sheath  of  the  vessel  exposed.  This  must  be  opened  on  its  medial  or  tracheal 
side,  so  as  to  avoid  the  internal  jugular  vein.  Special  care  is  necessary  on  the  left  side,  where 
the  artery  is  commonly  overlapped  by  the  vein;  on  the  right  side  there  is  usually  an  interval 
between  the  artery  and  the  vein,  and  the  risk  of  wounding  tlie  latter  is  less. 

The  common  carotid  artery,  being  a  long  vessel  without  any  branches,  is  particularly  suit- 
able for  the  performance  of  Brasdor's  operation  for  the  cure  of  an  aneurism  of  the  lower  part 
of  the  vessel.  Brasdor's  procedure  consists  in  ligaturing  the  artery  on  the  distal  side  of  the  aneu- 
rism, and  in  the  case  of  the  common  carotid  there  are  no  branches  given  off  from  the  vessel  between 
the  aneurism  and  the  site  of  the  Ugature;  hence  the  flow  of  blood  through  the  sac  of  the  aneurism 
is  diminished,  and  cure  takes  place  in  the  usual  way  by  the  deposit  of  laminated  fibrin. 

Collateral  Circulation. — After  hgature  of  the  common  carotid,  the  collateral  circulation  can 
be  perfectly  established,  by  the  free  communication  which  exists  between  the  carotid  arteries 
of  opposite  sides,  both  withdut  and  within  the  cranium,  and  by  enlargement  of  the  branches  of 
the  subclavian  artery  on  the  side  corresponding  to  that  on  which  the  vessel  has  been  tied.  The 
chief  communications  outside  the  skull  take  place  between  the  superior  and  inferior  thyroid 
arteries,  and  the  profunda  cervicis  and  ramus  descendens  of  the  occipital;  the  vertebral  takes 
the  place  of  the  internal  carotid  within  the  cranium. 

The  External  Carotid  Artery  (A.  Carotis  Externa)  (Fig.  585). 

The  external  carotid  artery  begins  opposite  the  upper  border  of  the  thyroid 
cartilage,  and,  taking  a  slightly  curved  course,  passes  upward  and  forward,  and 
then  inclines  backward  to  the  space  behind  the  neck  of  the  mandible,  where  it 
divides  into  the  superficial  temporal  and  internal  maxillary  arteries.  It  rapidly 
diminishes  in  size  in  its  course  up  the  neck,  owing  to  the  number  and  large  size 
of  the  branches  given  off  from  it.  In  the  child,  it  is  somewhat  smaller  than  the 
internal  carotid;  but  in  the  adult,  the  two  vessels  are  of  nearly  equal  size.  At  its 
origin,  this  artery  is  more  superficial,  and  placed  nearer  the  middle  line  than  the 
internal  carotid,  and  is  contained  within  the  carotid  triangle. 

Relations. — The  external  carotid  artery  is  covered  by  the  skin,  superficial  fascia,  Platysma, 
deep  fascia,  and  anterior  margin  of  the  Sternocleidomastoideus;  it  is  crossed  by  the  hypoglossal 
nerve,  by  the  lingual,  ranine,  common  facial,  and  superior  thyroid  veins;  and  by  the  Digastricus 
and  Stylohyoideus;  higher  up  it  passes  deeply  into  the  substance  of  the  parotid  gland,  where 
it  hes  deep  to  the  facial  nerve  and  the  junction  of  the  temporal  and  internal  maxillary  veins. 
Medial  to  it  are  the  hyoid  bone,  the  wall  of  the  pharynx,  the  superior  laryngeal  nerve,  and  a 
portion  of  the  parotid  gland.  Lateral  to  it,  in  the  lower  part  of  its  course,  is  the  internal  carotid 
artery.  Posterior  to  it,  near  its  origin,  is  the  superior  laryngeal  nerve;  and  higher  up,  it  is  sepa- 
rated from  the  internal  carotid  by  the  Styloglossus  and  Stylopharyngeus,  the  glossopharyngeal 
nerve,  the  pharyngeal  branch  t)f  the  vagus,  and  part  of  the  parotid  gland. 

Applied  Anatomy, — Ligature  of  the  external  carotid  may  be  required  in  cases  of  wound  of  this 
vessel  or  of  its  branches  when  these  cannot  be  tied,  and  in  some  cases  of  pulsating  tumors  of  the 
scalp  or  face.  It  is  also  done  as  a  preliminary  measure  to  excision  of  the  maxilla.  The  seat  of 
election  for  Ugature  is  between  the  origins  of  its  superior  thyroid  and  lingual  branches,  about  a 
finger's  breadth  below  the  tip  of  the  greater  cornu  of  the  hyoid  bone.  To  tie  the  vessel,  an  inci- 
sion is  made  from  the  angle  of  the  mandible  to  the  upper  border  of  the  thjroid  cartilage,  and 
the  superficial  tissues  and  the  deep  fascia  divided.  The  anterior  border  of  the  Sternocleido- 
mastoideus must  be  retracted  and  the  lower  border  of  the  parotid  gland  raised,  so  as  to  expose 
the  tendon  of  the  Digastricus  and  the  hypoglossal  nerve,  which  cross  the  artery.  The  great 
difficulty  in  doing  this  is  due  to  the  plexus  of  veins  derived  from  the  superior  thwoid  and  Ungual 
veins,  which  overlie  the  artery.  If  necessary,  these  must  be  ligatured  and  divided.  Care  must 
be  taken  not  to  mistake  the  hngual  and  external  maxillary,  when  they  arise  by  a  common  trunk, 
as  they  sometimes  do,  for  the  external  carotid.  The -needle  is  to  be  passed  from  the  lateral  to 
the  medial  side  of  the  vessel,  carefully  avoiding  the  superior  laryngeal  nerve,  which  lies  in  close 
proximity  to  the  artery.  The  circulation  is  at  once  reestablished  by  the  free  communication 
between  most  of  the  large  branches  of  the  artery  (external  maxillary,  hngual,  superior  thjToid, 
occipital)  and  the  corresponding  arteries  of  the  opposite  side,  and  by  the  anastomosis  of  its 
branches  with  those  of  the  internal  carotid,  and  of  the  occipital  with  branches  of  the  subclavian,  etc. 

Branches. — The  branches  of  the  external  carotid  artery  may  be  divided  into  four 
sets. 


rilE  EXTERNAL  CAROTID  ARTERY  631 

Auferior.  Posterior.  Ascending.  Terminal. 

Superior  Thyroid.  Occipital.  Ascendin<ij  Superficial  Temporal. 

Lingual.  Posterior  Auricular.  Pharyngeal.  Internal  Maxillary. 
External  Maxillary. 

1.  The  superior  thyroid  artery  (a.  thi/reoidea  superior)  (Fig.  585)  arises  from 
the  external  carotid  artery  just  below  the  level  of  the  greater  cornu  of  the  hyoid 
bone  and  ends  in  the  thyroid  gland. 

Relations. — From  its  origin  under  the  anterior  border  of  the  Sternocleidomastoideus  it  runs 
upward  and  forward  for  a  short  distance  in  the  carotid  triangle,  where  it  is  covered  by  the  skin, 
Platysma,  and  fascia;  it  then  arches  downward  beneath  the  Omohyoideus,  Sternohyoideus,  and 
Sternothyreoideus.  To  its  medial  side  are  the  Constrictor  pharyngis  inferior  and  the  external 
branch  of  the  superior  laryngeal  nerve. 

Branches. — It  distributes  twigs  to  the  adjacent  muscles,  and  numerous  branches 
to  the  thyroid  gland,  anastomosing  with  its  fellow  of  the  opposite  side,  and  with 
the  inferior  thyroid  arteries.  The  branches  to  the  gland  are  generally  two  in 
number;  one,  the  larger,  supplies  principally  the  anterior  surface;  on  the  isthmus 
of  the  gland  it  anastomoses  with  the  corresponding  artery  of  the  opposite  side: 
a  second  branch  descends  on  the  posterior  surface  of  the  gland  and  anastomoses 
with  the  inferior  thyroid  artery. 

Besides  the  arteries  distributed  to  the  muscles  and  to  the  thyroid  gland,  the 
branches  of  the  superior  thyroid  are: 

Hyoid.  Superior  Laryngeal. 

Sternocleidomastoid.  Cricothyroid. 

The  Hyoid  Branch  {ramus  hyoideus;  infrahyoid  branch)  is  small  and  runs  along 
the  lower  border  of  the  hyoid  bone  beneath  the  Thyreohyoideus  and  anastomoses 
with  the  vessel  of  the  opposite  side. 

The  Sternocleidomastoid  Branch  (ramus  sternocleidomastoideus;  sternomastoid 
hranch)  runs  downward  and  lateralward  across  the  sheath  of  the  common  carotid 
artery,  and  supplies  the  Sternocleidomastoideus  and  neighboring  muscles  and 
integument;  it  frequently'  arises  as  a  separate  branch  from  the  external  carotid. 

The  Superior  Laryngeal  Artery  (a.  laryngea  superior),  larger  than  either  of  the 
preceding,  accompanies  the  internal  laryngeal  branch  of  the  superior  laryngeal 
nerve,  beneath  the  Thj^eohyoideus;  it  pierces  the  hyothyroid  membrane,  and 
supplies  the  muscles,  mucous  membrane,  and  glands  of  the  larynx,  anastomosing 
with  the  branch  from  the  opposite  side. 

The  Cricothyroid  Branch  {ramus  cricothyreoideus)  is  small  and  runs  transversely 
across  the  cricothyroid  membrane,  communicating  with  the  artery  of  the  opposite 
side. 

Applied  Anatomy. — The  superior  thyroid,  or  one  of  its  branches,  is  often  divided  in  cases  of 
cut  thi'oat,  giving  rise  to  considerable  hemorrhage.  In  such  cases,  the  artery  should  be  secured, 
the  wound  being  enlarged  for  that  purpose,  if  necessary.  The  operation  may  be  easily  performed, 
the  artery  being  very  superficial,  and  the  only  structures  of  impoi-tance  covei'ing  it  being  a  few 
small  veins.  The  operation  of  tying  the  superior  thyroid  artery  in  bronchocele  has  been  per- 
formed, but  the  collateral  circulation  between  this  vessel  and  the  artery  of  the  opposite  side,  and 
the  inferior  thyroid,  is  so  free  that  the  operation  has  been  given  up,  especially  as  better  results 
are  obtained  by  other  means. 

The  position  of  the  sternocleidomastoid  branch  is  of  importance  in  connection  with  the  opera- 
tion of  ligature  of  the  common  carotid  artery.  It  crosses  and  lies  on  the  sheath  of  this  vessel  and 
may  chance  to  be  wounded  in  opening  the  sheath.  The  position  of  the  cricothyroid  branch  should 
be  remembered,  as  it  may  prove  the  source  of  troublesome  hemorrhage  dm-ing  the  operation  of 
laryngotomy. 

2.  The  lingual  artery  (a.  lingualis)  (Fig.  590)  arises  from  the  external  carotid 
between  the  superior  thyroid  and  external  maxillary ;  it  first  runs  obliquelj^  upward 
and  medialward  to  the  greater  cornu  of  the  hyoid  bone;  it  then  curves  downward 


632  ANGIOLOGY 

and  forward,  forming  a  loop  whicli  is  crossed  by  the  hypoglossal  nerve,  and  passing 
beneath  the  Digastriciis  and  Styloliyoidens  it  runs  horizontally  forward,  beneath 
the  Hyoglossus,  and  finally,  ascending  almost  perpendicularly  to  the  tongue,  turns 
forward  on  its  lower  surface  as  far  as  the  tip,  under  the  name  of  the  profunda 
linguae. 

Relations. — Its  first,  or  oblique,  portion  is  superficial,  and  is  contained  within  the  carotid 
triangle;  it  rests  upon  the  Constrictor  pharyngis  medius,  and  is  covered  by  the  Platysma  and 
the  fascia  of  the  neck.  Its  second,  or  curved,  portion  also  lies  upon  the  Constrictor  pharyngis 
medius,  being  covered  at  first  by  the  tendon  of  the  Digastricus  and  by  the  Stylohyoideus,  and 
afterward  by  the  Hyoglossus.  Its  third,  or  horizontal,  portion  lies  between  the  Hyoglossus  and 
Genioglossus.  The  foui'th,  or  terminal  part,  under  the  name  of  the  profunda  linguae  (ranine 
artery)  runs  along  the  under  sm-face  of  the  tongue  to  its  tip;  here  it  is  superficial,  being  covered 
only  by  the  mucous  membrane;  above  it  is  the  LongitudinaHs  inferior,  and  on  the  medial  side 
the  Genioglossus.  The  hypoglossal  nerve  crosses  the  first  part  of  the  Hngual  artery,  but  is  sepa- 
rated from  the  second  part  by  the  Hyoglossus. 

Branches. — The  branches  of  the  lingual  artery  are: 

Hyoid.  Sublingual. 

Dorsales  linguae.  Profunda  linguae. 

The  Hyoid  Branch  {ramus  hyoideus;  suprahyoid  branch)  runs  along  the  upper 
border  of  the  hyoid  bone,  supplying  the  muscles  attached  to  it  and  anastomosing 
with  its  fellow  of  the  opposite  side. 

The  Arteriae  Dorsales  Linguae  {rami  dorsales  linguae)  consist  usually  of  two  or 
three  small  branches  which  arise  beneath  the  Hyoglossus;  they  ascend  to  the  back 
part  of  the  dorsum  of  the  tongue,  and  supply  the  mucous  membrane  in  this  situa- 
tion, the  glossopalatine  arch,  the  tonsil,  soft  palate,  and  epiglottis;  anastomosing 
with  the  vessels  of  the  opposite  side. 

The  Sublingual  Artery  {a.  sublingualis)  arises  at  the  anterior  margin  of  the  Hyo- 
glossus, and  runs  forward  between  the  Genioglossus  and  Mylohyoideus  to  the  sub- 
lingual gland.  It  supplies  the  gland  and  gives  branches  to  the  Mylohyoideus  and 
neighboring  muscles,  and  to  the  mucous  membrane  of  the  mouth  and  gums.  One 
branch  runs  behind  the  alveolar  process  of  the  mandible  in  the  substance  of  the 
gum  to  anastomose  with  a  similar  artery  from  the  other  side;  another  pierces 
the  Mylohyoideus  and  anastomoses  with  the  submental  branch  of  the  external 
maxillary  artery. 

The  Arteria  Profunda  Linguae  {ranine  artery;  deep  lingual  artery)  is  the  terminal 
portion  of  the  lingual  artery;  it  pursues  a  tortuous  course  and  runs  along  the  under 
surface  of  the  tongue,  below  the  LongitudinaHs  inferior,  and  above  the  mucous 
membrane;  it  lies  on  the  lateral  side  of  the  Genioglossus,  accompanied  by  the 
lingual  nerve.  At  the  tip  of  the  tongue,  it  is  said  to  anastomose  with  the  artery 
of  the  opposite  side,  but  this  is  denied  by  Hyrtl.  In  the  mouth,  these  vessels  are 
placed  one  on  either  side  of  the  frenulum  linguae. 

Applied  Anatomy. — The  Ungual  artery  is  not  infrequently  divided  near  its  origin  in  cases  of 
cut  throat;  while  severe  hemorrhage,  which  cannot  be  restrained  by  ordinary  means,  may  ensue 
from  a  wound,  or  deep  ulcer,  of  the  tongue.  In  the  former  case,  the  primary  wound  may  be 
enlarged  if  necessary,  and  the  bleeding  vessel  secured;  in  the  latter,  it  has  been  suggested  that 
the  lingual  artery  should  be  tied  near  its  origin.  Ligature  of  the  lingual  artery  has  been  also 
occasionally  practised,  as  a  prehminary  measure  to  removal  of  the  tongue.  The  operation  is  a 
difficult  one  on  account  of  the  depth  of  the  artery,  the  number  of  important  parts  by  which  it 
is  surrounded,  and  its  occasional  irregularity  of  origin.  An  incision  is  to  be  made  in  a  curved 
direction  from  a  finger's  breadth  behind  the  symphysis  menti  downward  to  the  cornu  of  the 
hyoid  bone,  and  then  upward  to  near  the  angle  of  the  mandible.  Care  must  be  taken  not  to  carry 
this  incision  too  far  backward,  for  fear  of  endangering  the  anterior  facial  vein.  In  the  first  inci- 
sion the  skin,  superficial  fascia,  and  Platysma  will  be  divided,  and  the  deep  fascia  displayed. 
This  is  then  to  be  incised  and  the  submaxillary  gland  exposed  and  pulled  upward  by  retractors. 
A  triangular  space  is  now  seen,  bounded  in  front  by  the  posterior  border  of  the  Mylohyoideus; 
below  and  behind,  by  the  tendon  of  the  Digastricus;  and  above,  by  the  hypoglossal  nerve.  The 
floor  of  the  space  is  formed  by  the  Hyoglossus,  beneath  which  the  artery  Ues.    The  parts  are  to 


THE  EXTERNAL  CAROTID  ARTERY 


633 


be  drawn  forward  by  a  bhuil  hook  inycrtt'd  beneath  the  tendon  of  tlie  Difrastri(;u8,  and  the  fibres 
of  the  Hj'oglossiis  cut  throufj;h  horizontally  ju.st  above  the  Digastricus.  The  artery  will  then 
be  exposed;  and  in  passing  the  aneurism  needle,  care  must  be  taken  not  to  open  the  pharynx. 
The  hypoglossal  nerve  must  also  be  avoided. 

Troublesome  hemorrhage  may  occur  in  the  division  of  the  frenulum  linguae  in  children,  if  the 
aa.  profundae  linguae,  which  lie  one  on  either  side  of  it,  be  wounded.  The  operation  should 
always  be  performed  with  a  pair  of  blunt-pointed  scissors,  and  the  mucous  membrane  alone 
divided  by  a  very  superficial  cut,  which  cannot  endanger  any  vessel.  Any  further  liberation 
of  the  tongue  which  may  be  necessary  can  be  effected  by  tearing. 


Angular 


Lateral 
nasal 


Septal 
Superior  labial 

Inferior  labial 


Fig.  586. — The  arteries  of  the  tace  and  scalp. 


3.  The  external  maxillary  artery  (a.  maxillaris  externa;  facial  artery)  (Fig.  586), 
arises  in  the  carotid  triangle  a  little  above  the  lingual  artery  and,  sheltered  by  the 
ramus  of  the  mandible,  passes  obliquely  up  beneath  the  Digastricus  and  Stylo- 
hyoideus,  over  which  it  arches  to  enter  a  groove  on  the  posterior  surface  of  the 
submaxillary  gland.  It  then  curves  upward  over  the  body  of  the  mandible  at  the 
antero-inferior  angle  of  the  Masseter;  passes  forward  and  upward  across  the  cheek 
to  the  angle  of  the  mouth,  then  ascends  along  the  side  of  the  nose,  and  ends  at 
the  medial  commissure  of  the  eye,  under  the  name  of  the  angular  artery.  This 
vessel,  both  in  the  neck  and  on  the  face,  is  remarkably  tortuous:  in  the  former 
situation,  to  accommodate  itself  to  the  movements  of  the  pharynx  in  deglutition; 
and  in  the  latter,  to  the  movements  of  the  mandible,  lips,  and  cheeks. 

Relations. — In  the  neck,  its  origin  is  superficial,  being  covered  by  the  integument,  Platysma, 
and  fascia;  it  then  passes  beneath  the  Digastricus  and  Stylohyoideus  muscles  and  part  of  the 

1  The  muscular  tissue  of  the  lips  must  be  supposed  to  have  been  cut  away,  in  order  to  show  the  course  of  Ihe  labial 
arteries. 


634  ANGIOLOGY 

submaxillary  gland,  and  frequently  beneath  the  hypoglossal  nerve.  It  lies  upon  the  Constrictores 
pharyngis  medius  and  superior,  the  latter  of  which  separates  it,  at  the  summit  of  its  arch,  from 
the  lower  and  back  part  of  the  tonsil.  On  the  face,  where  it  passes  over  the  body  of  the  mandible, 
it  is  comparatively  superficial,  lying  immediately  beneath  the  Platysma.  In  its  course  over  the 
face,  it  is  covered  by  the  integument,  the  fat  of  the  cheek,  and,  near  the  angle  of  the  mouth, 
by  the  Platysma,  Risorius,  and  Zygomaticus.  It  rests  on  the  Buccinator  and  Caninus,  and 
passes  either  over  or  under  the  infraorbital  head  of  the  Quadratus  labii  superioris.  The  anterior 
facial  vein  lies  lateral  to  the  artery,  and  takes  a  more  direct  course  across  the  face,  where  it  is 
separated  from  the  artery  by  a  considerable  interval.  In  the  neck  it  lies  superficial  to  the  artery. 
The  branches  of  the  facial  nerve  cross  the  artery  from  behind  forward. 

Branches. — The  branches  of  the  artery  may  be  divided  into  two  sets:  those 

given  oft'  in  the  neck  (cervical),  and  those  on  the  face  (facial). 

Cervical  Branches.  Facial  Branches. 

Ascending  Palatine.  Inferior  Labial. 

Tonsillar.  Superior  Labial. 

Glandular.  Lateral  Nasal. 

Submental.  Angular. 

Muscular.  Muscular, 

The  Ascending  Palatine  Artery  (a.  yalatina  ascendens)  (Fig.  590)  arises  close  to 
the  origin  of  the  external  maxillary  artery  and  passes  up  between  the  Styloglossus 
and  Stylopharyngeus  to  the  side  of  the  pharynx,  along  which  it  is  continued  between 
the  Constrictor  pharyngis  superior  and  the  Pterygoideus  internus  to  near  the  base 
of  the  skull.  It  divides  near  the  Levator  veli  palatini  into  two  branches:  one  fol- 
lows the  course  of  this  muscle,  and,  winding  over  the  upper  border  of  the  Constrictor 
pharyngis  superior,  supplies  the  soft  palate  and  the  palatine  glands,  anastomosing 
with  its  fellow  of  the  opposite  side  and  with  the  descending  palatine  branch  of  the 
internal  maxillary  artery;  the  other  pierces  the  Constrictor  pharyngis  superior 
and  supplies  the  palatine  tonsil  and  auditory  tube,  anastomosing  with  the  tonsillar 
and  ascending  pharyngeal  arteries. 

The  Tonsillar  Branch  (ramus  tonsillaris)  (Fig.  590)  ascends  between  the  Ptery- 
goideus internus  and  Styloglossus,  and  then  along  the  side  of  the  pharynx, 
perforating  the  Constrictor  pharyngis  superior,  to  ramify  in  the  substance  of  the 
palatine  tonsil  and  root  of  the  tongue. 

The  Glandular  Branches  (rami  glandulares;  submaxillary  branches)  consist  of  three 
or  four  large  vessels,  which  supply  the  submaxillary  gland,  some  being  prolonged 
to  the  neighboring  muscles,  lymph  glands,  and  integument. 

The  Submental  Artery  (a.  submentalis)  the  largest  of  the  cervical  branches,  is 
given  off  from  the  facial  artery  just  as  that  vessel  quits  the  submaxillar}'  gland: 
it  runs  forward  upon  the  Mylohyoideus,  just  below  the  body  of  the  mandible, 
and  beneath  the  Digastricus.  It  supplies  the  surrounding  muscles,  and  anastomoses 
with  the  sublingual  artery  and  with  the  mylohyoid  branch  of  the  inferior  alveolar; 
at  the  symphysis  menti  it  turns  upward  over  the  border  of  the  mandible  and 
divides  into  a  superficial  and  a  deep  branch.  The  superficial  branch  passes  between 
the  integument  and  Quadratus  labii  inferioris,  and  anastomoses  with  the  inferior 
labial  artery;  the  deep  branch  runs  between  the  muscle  and  the  bone,  supplies 
the  lip,  and  anastomoses  w^th  the  inferior  labial  and  mental  arteries. 

The  Inferior  Labial  Artery  (a.  labialis  inferior;  inferior  coronary  artery)  arises  near 
the  angle  of  the  mouth;  it  passes  upward  and  forward  beneath  the  Triangularis 
and,  penetrating  the  Orbicularis  oris,  runs  in  a  tortuous  course  along  the  edge  of 
the  lower  lip  between  this  muscle  and  the  mucous  membrane.  It  supplies  the 
labial  glands,  the  mucous  membrane,  and  the  muscles  of  the  lower  lip;  and  anas- 
tomoses with  the  artery  of  the  opposite  side,  and  with  the  mental  branch  of  the 
inferior  alveolar  artery. 

The  Superior  Labial  Artery  (a.  labialis  superior;  superior  coronary  artery)  is  larger 
and  more  tortuous  than  the  inferior.    It  follows  a  similar  course  along  the  edge 


THE  EXTERNAL  CAROTID  ARTERY  635 

of  the  upper  lip,  lying  })et\veen  the  mucous  membrane  and  the  Orbicularis  oris, 
and  anastomoses  with  the  artery  of  the  opposite  side.  It  supplies  the  upper  lip, 
and  gives  off  in  its  course  two  or  three  vessels  which  ascend  to  the  nose;  a  septal 
branch  ramifies  on  the  nasal  septum  as  far  as  the  point  of  the  nose,  and  an  alar 
branch  sn])j)lics  the  ala  of  the  nose. 

The  Lateral  Nasal  branch  is  derived  from  the  external  maxillary  as  that  vessel 
ascends  along  the  side  of  the  nose.  It  supplies  the  ala  and  dorsum  of  the  nose,  anas- 
tomosing with  its  fellow,  with  the  septal  and  alar  branches,  with  the  dorsal  nasal 
branch  of  the  ophthalmic,  and  with  the  infraorbital  branch  of  the  internal  maxillary. 

The  Angular  Artery  {a.  amiularis)  is  the  terminal  part  of  the  external  maxillary; 
it  ascends  to  the  medial  angle  of  the  orbit,  imbedded  in  the  fibres  of  the  angular 
head  of  the  Quadratus  labii  superioris,  and  accompanied  by  the  angular  vein. 
On  the  cheek  it  distributes  branches  which  anastomose  with  the  infraorbital; 
after  supplying  the  lacrimal  sac  and  Orbicularis  oculi,  it  ends  by  anastomosing 
with  the  dorsal  nasal  branch  of  the  ophthalmic  artery. 

The  Muscular  Branches  in  the  neck  are  distributed  to  the  Pterygoideus  internus  and 
Stylohyoideus,  and  on  the  face  to  the  Masseter  and  Buccinator.  The  anastomoses 
of  the  external  maxillary  artery  are  very  numerous,  not  only  with  the  vessel  of 
the  opposite  side,  but,  in  the  neck,  with  the  sublingual  branch  of  the  lingual,  with 
the  ascending  pharyngeal,  and  by  its  ascending  palatine  and  tonsillar  branches 
with  the  palatine  branch  of  the  internal  maxillary;  on  the  face,  with  the  mental 
branch  of  the  inferior  alveolar  as  it  emerges  from  the  mental  foramen,  with  the 
transverse  facial  branch  of  the  superficial  temporal,  with  the  infraorbital  branch 
of  the  internal  maxillary,  and,  with  the  dorsal  nasal  branch  of  the  ophthalmic. 

Peculiarities. — The  external  maxillary  artery  not  infrequently  arises  in  common  with  the 
Ungual.  It  varies  in  its  size  and  in  the  extent  to  which  it  supphes  the  face;  it  occasionally  ends 
as  the  submental,  and  not  infrequently  extends  only  as  high  as  the  angle  of  the  mouth  or  nose. 
The  deficiency  is  then  compensated  for  by  enlargement  of  one  of  the  neighboring  arteries. 

Applied  Anatomy. — The  passage  of  the  external  maxiUary  artery  over  the  bodj^  of  the  mandible 
would  appear  to  afford  a  favorable  position  for  the  application  of  pressm-e  in  cases  of  hemor- 
rhage from  the  hps,  the  result  either  of  an  accidental  wound  or  during  an  operation;  but  its  apph- 
cation  is  useless,  except  for  a  very  short  time,  on  account  of  the  free  communication  of  this  vessel 
with  its  feUow,  and  with  numerous  branches  from  different  sources.  In  a  wound  involving  the 
hp,  it  is  better  to  seize  the  part  between  the  fingers,  and  evert  it,  when  the  bleeding  vessel  may 
be  at  once  secured  -n-ith  pressure  forceps.  In  order  to  prevent  hemorrhage  in  cases  of  removal 
of  gro^\'ths  from  the  Up,  the  latter  should  be  compressed  on  either  side  between  the  fingers  and 
thumb,  or  by  a  pair  of  specially  devised  clamp  forceps,  while  the  surgeon  excises  the  diseased 
part.  In  order  to  stop  hemorrhage  when  the  Up  has  been  divided  in  an  operation,  it  is  necessary, 
when  closing  the  wound,  to  pass  the  sutm-es  through  the  cut  edges,  almost  as  deep  as  its  mucous 
surface;  by  these  means,  not  onlj^  are  the  cut  surfaces  more  neatly  and  securely  adapted  to  each 
other,  but  the  possibiUty  of  hemorrhage  is  prevented  by  including  the  divided  artery  in  the 
suture.  If,  on  the  contrary,  the  suture  be  passed  through  merely  the  cutaneous  portion  of  the 
wound,  hemorrhage  occurs  into  the  cavity  of  the  mouth.  The  student  should  observe  the  rela- 
tion of  the  angular  artery  to  the  lacrimal  sac;  as  the  vessel  passes  up  along  the  medial  margin 
of  the  orbit,  it  ascends  on  the  nasal  side  of  the  sac.  In  operating  for  fistula  lacrimaUs,  the  sac 
should  always  be  opened  on  its  lateral  side  in  order  that  this  vessel  may  be  avoided. 

4.  The  occipital  artery  (a.  occipitalis)  (Fig.  586)  arises  from  the  posterior  part 
of  the  external  carotid,  opposite  the  external  maxillary,  near  the  lower  margin 
of  the  posterior  belly  of  the  Digastricus,  and  ends  in  the  posterior  part  of  the  scalp. 

Course  and  Relations. — At  its  origin,  it  is  covered  bj^  the  posterior  beUy  of  the  Digastricus 
and  the  Stylohj^oideus,  and  the  hypoglossal  nerve  winds  around  it  from  behind  forward;  higher 
up,  it  crosses  the  internal  carotid  artery,  the  internal  jugular  vein,  and  the  vagus  and  accessor}^ 
nerves.  It  next  ascends  to  the  interval  between  the  transverse  process  of  the  atlas  and  the  mastoid 
process  of  the  temporal  bone,  and  passes  horizontaUy  backward,  grooving  the  surface  of  the 
latter  bone,  being  covered  by  the  Sternocleidomastoideus,  Splenius  capitis,  Longissimus  capitis, 
and  Digastricus,  and  resting  upon  the  Rectus  capitis  lateraUs,  the  ObUquus  superior,  and  Semi- 
spinalis  capitis.  It  then  changes  its  coiu:se  and  runs  verticaUy  upward,  pierces  the  fascia  con- 
necting the  cranial  attachment  of  the  Trapezius  with  the  Sternocleidomastoideus,  and  ascends 


636  ANGIOLOGY 

in  a  tortuous  course  in  the  superficial  fascia  of  the  scalp,  where  it  divides  into  numerous  branches, 
which  reach  as  high  as  the  vertex  of  the  skull  and  anastomose  with  the  posterior  auricular  and 
superficial  temporal  arteries.    Its  terminal  portion  is  accompanied  by  the  greater  occipital  nerve. 

Branches. — The  branches  of  the  occipital  artery  are: 

Muscular.  Sternocleidomastoid.  Auricular. 

Meningeal.  Descending. 

The  Muscular  Branches  {rami  musculares)  supply  the  Digastricus,  Stylohyoideus, 
Splenius,  and  Longissimus  capitis. 

The  Sternocleidomastoid  Artery  (a.  sternocleidomastoidea;  sternomastoid  artery) 
generally  arises  from  the  occipital  close  to  its  commencement,  but  sometimes 
springs  directly  from  the  external  carotid.  It  passes  downward  and  backward 
over  the  hypoglassal  nerve,  and  enters  the  substance  of  the  muscle,  in  company 
with  the  accessory  nerve. 

The  Auricular  Branch  (ramus  auricularis)  supplies  the  back  of  the  concha  and 
frequently  gives  off  a  branch,  which  enters  the  skull  through  the  mastoid  foramen 
and  supplies  the  dura  mater,  the  diploe,  and  the  mastoid  cells;  this  latter  branch 
sometimes  arises  from  the  occipital  artery,  and  is  then  known  as  the  mastoid  branch. 

The  Meningeal  Branch  (ramus  meningeus;  dural  branch)  ascends  with  the  internal 
jugular  vein,  and  enters  the  skull  through  the  jugular  foramen  and  condyloid 
canal,  to  supply  the  dura  mater  in  the  posterior  fossa. 

The  Descending  Branch  (ramus  descendens;  arteria  princeps  cervicis)  (Fig.  590), 
the  largest  branch  of  the  occipital,  descends  on  the  back  of  the  neck,  and  divides 
into  a  superficial  and  deep  portion.  The  superficial  portion  runs  beneath  the 
Splenius,  giving  off  branches  which  pierce  that  muscle  to  supply  the  Trapezius  and 
anastomose  with  the  ascending  branch  of  the  transverse  cervical :  the  deep  portion 
runs  down  between  the  Semispinales  capitis  and  colli,  and  anastomoses  with  the 
vertebral  and  with  the  a.  profunda  cervicalis,  a  branch  of  the  costocervical  trunk. 
The  anastomosis  between  these  vessels  assists  in  establishing  the  collateral  circu- 
lation after  ligature  of  the  common  carotid  or  subclavian  artery. 

The  terminal  branches  of  the  occipital  artery  are  distributed  to  the  back  of  the 
head:  they  are  very  tortuous,  and  lie  between  the  integument  and  Occipitalis, 
anastomosing  with  the  artery  of  the  opposite  side  and  with  the  posterior  auricular 
and  temporal  arteries,  and  supplying  the  Occipitalis,  the  integument,  and  peri- 
cranium. One  of  the  terminal  branches  may  give  off  a  meningeal  twig  which  passes 
through  the  parietal  foramen. 

5.  The  posterior  auricular  artery  (a.  auricularis  posterior)  (Fig.  586)  is  small 
and  arises  from  the  external  carotid,  above  the  Digastricus  and  Stylohj^oideus, 
opposite  the  apex  of  the  styloid  process.  It  ascends,  under  cover  of  the  parotid 
gland,  on  the  styloid  process  of  the  temporal  bone,  to  the  groove  between  the 
cartilage  of  the  ear  and  the  mastoid  process,  immediately  above  which  it  divides 
into  its  auricular  and  occipital  branches. 

Branches. — Besides  several  small  branches  to  the  Digastricus,  Stylohyoideus, 
and  Sternocleidomastoideus,  and  to  the  parotid  gland,  this  vessel  gives  off  three 
branches: 

Stylomastoid.  Auricular.  Occipital. 

The  Stylomastoid  Artery  (a.  stylomastoidea)  enters  the  stylomastoid  foramen  and 
supplies  the  tj'^mpanic  cavity,  the  tympanic  antrum  and  mastoid  cells,  and  the 
semicircular  canals.  In  the  young  subject  a  branch  from  this  vessel  forms,  with 
the  anterior  tympanic  artery  from  the  internal  maxillary,  a  vascular  circle,  which 
surrounds  the  tympanic  membrane,  and  from  which  delicate  vessels  ramify  on  that 
membrane.  It  anastomoses  with  the  superficial  petrosal  branch  of  the  middle 
meningeal  artery  by  a  twig  which  enters  the  hiatus  canalis  facialis. 


THE  EXTERNAL  CAROTID  ARTERY  637 

The  Auricular  Branch  (ramus  auricularis)  ascends  behind  the  ear,  beneath  the 
Auricularis  ])osterior,  and  is  distributed  to  the  back  of  the  auricula,  upon  which 
it  ramifies  minutely,  some  branches  curving  around  the  margin  of  the  cartilage, 
others  perforating  it,  to  supply  the  anterior  surface.  It  anastomoses  with  the 
parietal  and  anterior  auricular  branches  of  the  superficial  temporal. 

The  Occipital  Branch  {ramus  occipitalis)  passes  backward,  over  the  Sternocleido- 
mastoideus,  to  the  scalp  above  and  behind  the  ear.  It  supplies  the  Occipitalis 
and  the  scalp  in  this  situation  and  anastomoses  with  the  occipital  artery. 

6.  The  ascending  pharyngeal  artery  (a.  pharyngea  ascendens)  (Fig.  590),  the 
smallest  branch  of  the  external  carotid,  is  a  long,  slender  vessel,  deeply  seated  in 
the  neck,  beneath  the  other  branches  of  the  external  carotid  and  under  the  Stylo- 
pharyngeus.  It  arises  from  the  back  part  of  the  external  carotid,  near  the  com- 
mencement of  that  vessel,  and  ascends  vertically  between  the  internal  carotid 
and  the  side  of  the  pharynx,  to  the  under  surface  of  the  base  of  the  skull,  lying 
on  the  Longus  capitis. 

Branches. — Its  branches  are: 

Pharyngeal.  Prevertebral. 

Palatine.  Inferior  Tympanic. 

Posterior  Meningeal. 

The  Pharyngeal  Branches  (rami  pharyngei)  are  three  or  four  in  number.  Two 
of  these  descend  to  supply  the  Constrictores  pharyngis  medius  and  inferior  and 
the  Stylopharyngeus,  ramifying  in  their  substance  and  in  the  mucous  membrane 
lining  them. 

The  Palatine  Branch  varies  in  size,  and  may  take  the  place  of  the  ascending 
palatine  branch  of  the  facial  artery,  when  that  vessel  is  small.  It  passes  inward 
upon  the  Constrictor  pharyngis  superior,  sends  ramifications  to  the  soft  palate 
and  tonsil,  and  supplies  a  branch  to  the  auditory  tube. 

The  Prevertebral  Branches  are  numerous  small  vessels,  which  supply  the  Longi 
capitis  and  colli,  the  sympathetic  trunk,  the  hypoglossal  and  vagus  nerves,  and  the 
lymph  glands;  they  anastomose  with  the  ascending  cervical  artery. 

The  Inferior  Tympanic  Artery  (a.  tympanica  inferior)  is  a  small  branch  which 
passes  through  a  minute  foramen  in  the  petrous  portion  of  the  temporal  bone,  in 
company  with  the  tympanic  branch  of  the  glossopharyngeal  nerve,  to  supply  the 
medial  wall  of  the  tympanic  cavity  and  anastomose  with  the  other  tympanic  arteries. 

The  Meningeal  Branches  are  several  small  vessels,  which  supply  the  dura  mater. 
One,  the  posterior  meningeal,  enters  the  cranium  through  the  jugular  foramen; 
a  second  passes  through  the  foramen  lacerum;  and  occasionally  a  third  through 
the  canal  for  the  hypoglassal  nerve. 

Applied  Anatomy. — The  ascending  pharyngeal  artery  has  been  wounded  from  the  throat;  as  in 
the  case  in  which  the  stem  of  a  tobacco  pipe  was  driven  into  the  vessel,  causing  fatal  hemorrhage. 

7.  The  superficial  temporal  artery  (a.  temporalis  superficialis)  (Fig.  586),  the 
smaller  of  the  two  terminal  branches  of  the  external  carotid,  appears,  from  its 
direction,  to  be  the  continuation  of  that  vessel.  It  begins  in  the  substance  of  the 
parotid  gland,  behind  the  neck  of  the  mandible,  and  crosses  over  the  posterior  root 
of  the  zygomatic  process  of  the  temporal  bone;  about  5  cm.  above  this  process 
it  divides  into  two  branches,  a  frontal  and  a  parietal. 

Relations. — As  it  crosses  the  zygomatic  process,  it  is  covered  by  the  Auricularis  anterior  muscle, 
and  by  a  dense  fascia;  it  is  crossed  by  the  temporal  and  zygomatic  branches  of  the  facial  nerve 
and  one  or  two  veins,  and  is  accompanied  by  the  auriculotemporal  nerve,  which  Ues  immediately 
behind  it. 

Branches. — Besides  some  twigs  to  the  parotid  gland,  to  the  temporomandibular 
joint,  and  to  the  Masseter  muscle,  its  branches  are: 


638  ANGIOLOGY 

Transverse  Facial.  Anterior  Auricular. 

Middle  Temporal.  Frontal. 

Parietal. 

The  Transverse  Facial  Artery  (a.  transversa  faciei)  is  given  oft'  from  the  superficial 
temporal  before  that  vessel  quits  the  parotid  gland ;  running  forward  through  the 
substance  of  the  gland,  it  passes  transversely  across  the  side  of  the  face,  between 
the  parotid  duct  and  the  lower  border  of  the  zygomatic  arch,  and  divides  into  numer- 
ous branches,  which  supply  the  parotid  gland  and  duct,  the  Masseter,  and  the 
integument,  and  anastomose  with  the  external  maxillary,  masseteric,  buccinator, 
and  infraorbital  arteries.  This  vessel  rests  on  the  Masseter,  and  is  accompanied 
by  one  or  two  branches  of  the  facial  nerve. 

The  Middle  Temporal  Artery  (a.  temiJoralis  media)  arises  immediately  above  the 
zj^gomatic  arch,  and,  perforating  the  temporal  fascia,  gives  branches  to  the  Tem- 
poralis, anastomosing  with  the  deep  temporal  branches  of  the  internal  maxillary. 
It  occasionally  gives  off  a  zygomaticoorbital  branch,  which  runs  along  the  upper 
border  of  the  zygomatic  arch,  between  the  two  layers  of  the  temporal  fascia,  to 
the  lateral  angle  of  the  orbit.  This  branch,  which  may  arise  directly  from  the 
superficial  temporal  artery,  supplies  the  Orbicularis  oculi,  and  anastomoses  with 
the  lacrimal  and  palpebral  branches  of  the  ophthalmic  artery. 

The  Anterior  Am^icular  Branches  {rami  auriculares  anieriores)  are  distributed  to 
the  anterior  portion  of  the  auricula,  the  lobule,  and  part  of  the  external  meatus, 
anastomosing  with  the  posterior  auricular. 

The  Frontal  Branch  {ramus  frontalis;  anterior  temporal)  runs  tortuously  upward 
and  forward  to  the  forehead,  supplying  the  muscles,  integument,  and  pericranium 
in  this  region,  and  anastomosing  with  the  supraorbital  and  frontal  arteries. 

The  Parietal  Branch  {ramus  pai'ietalis;  posterior  temporal)  larger  than  the  frontal, 
curves  upward  and  backward  on  the  side  of  the  head,  lying  superficial  to  the  tem- 
poral fascia,  and  anastomosing  with  its  fellow  of  the  opposite  side,  and  with  the 
posterior  auricular  and  occipital  arteries. 

Applied  Anatomy. — The  temporal  artery,  as  it  crosses  the  zygomatic  process,  hes  immediately 
beneath  the  skin,  and  its  pulsations  may  be  readily  felt  during  the  administration  of  an  anesthetic, 
or  vmder  circumstances  where  the  radial  pulse  is  not  available;  it  may  be  easily  compressed  against 
the  bone  in  order  to  check  bleeding  from  the  temporal  region  of  the  scalp.  When  a  flap  is  raised 
from  this  part  of  the  head,  for  trephining,  the  incision  should  be  shaped  hke  a  horseshoe,  with 
its  convexity  upward,  so  that  the  flap  shall  contain  the  temporal  artery,  which  ensures  a  sufficient 
supply  of  blood.  The  same  principle  is  appUed,  as  far  as  possible,  in  making  incisions  to  raise 
flaps  in  other  parts  of  the  scalp.  Formerly  the  operation  of  arteriotomy  was  performed  upon 
this  vessel  in  cases  of  inflammation  of  the  eye  or  brain,  but  this  operation  is  now  obsolete. 

8.  The  internal  maxillary  artery  (a.  maxillaris  interna)  (Fig.  587),  the  larger 
of  the  two  terminal  branches  of  the  external  carotid,  arises  behind  the  neck  of  the 
mandible,  and  is  at  first  imbedded  in  the  substance  of  the  parotid  gland ;  it  passes 
forward  between  the  ramus  of  the  mandible  and  the  sphenomandibular  ligament, 
and  then  runs,  either  superficial  or  deep  to  the  Pterygoideus  externus,  to  the 
pterygopalatine  fossa.  It  supplies  the  deep  structures  of  the  face,  and  may  be 
divided  into  mandibular,  pterygoid,  and  pterygopalatine  portions. 

The  first  or  mandibular  portion  passes  horizontally  forward,  between  the  ramus 
of  the  mandible  and  the  sphenomandibular  ligament,  where  it  lies  parallel  to  and 
a  little  below  the  auriculotemporal  nerve;  it  crosses  the  inferior  alveolar  nerve, 
and  runs  along  the  lower  border  of  the  Pterygoideus  externus. 

The  second  or  pterygoid  portion  runs  obliquely  forward  and  upward  under  cover 
of  the  ramus  of  the  mandible  and  insertion  of  the  Temporalis,  on  the  superficial 
(very  frequently  on  the  deep)  surface  of  the  Pterygoideus  externus;  it  then  passes 
between  the  two  heads  of  origin  of  this  muscle  and  enters  the  fossa. 

The  third  or  pterygopalatine  portion  lies  in  the  pterygopalatine  fossa  in  relation 
with  the  sphenopalatine  ganglion. 


THE  EXTERNAL  CAROTID  ARTERY 


639 


The  branches  of  this  vessel  may  be  divided  into  three  groups  (Fig.  588),  corre- 
sponding with  its  three  divisions. 


-    Inciscr  branch 


Fig.   587. — The  internal  maxillary  artery. 


Sphenopalatine 
orbital 


Post.  sup.  alveolar 


Mylohyoid 


Fig.  588. — Plan  of  branches  of  internal  maxillary  artery. 

Branches  of  the  First  or  Mandibular  Portions.— 

Anterior  Tvmpanic.  Middle  Meningeal. 

Deep  Auricular.  Accessory  Meningeal. 

Inferior  Alveolar. 


640  ANGIOLOGY 

The  Anterior  Tympanic  Artery  (a.  tyvipanica  anterior;  tympanic  artery)  passes 
upward  behind  the  temporomandibular  articulation,  enters  the  tympanic  cavity 
through  the  petrot^^mpanic  fissure,  and  ramifies  upon  the  tympanic  membrane, 
forming  a  vascular  circle  around  the  membrane  with  the  stylomastoid  branch  of 
the  posterior  auricular,  and  anastomosing  with  the  artery  of  the  pterygoid  canal 
and  with  the  caroticotympanic  branch  from  the  internal  carotid. 

The  Deep  Auricular  Artery  (a.  auricularis  profunda)  often  arises  in  common  with 
the  preceding.  It  ascends  in  the  substance  of  the  parotid  gland,  behind  the  tem- 
poromandibular articulation,  pierces  the  cartilaginous  or  bony  wall  of  the  external 
acoustic  meatus,  and  supplies  its  cuticular  lining  and  the  outer  surface  of  the 
tympanic  membrane.    It  gives  a  branch  to  the  temporomandibular  joint. 

The  Middle  Meningeal  Artery  (a.  meningea  media;  medidural  artery)  is  the  largest 
of  the  arteries  which  supply  the  dura  mater.  It  ascends  between  the  spheno- 
mandibular  ligament  and  the  Pterygoideus  externus,  and  between  the  two  roots 
of  the  auriculotemporal  nerve  to  the  foramen  spinosum  of  the  sphenoid  bone, 
through  which  it  enters  the  cranium;  it  then  runs  forward  in  a  groove  on  the  great 
wing  of  the  sphenoid  bone,  and  divides  into  two  branches,  anterior  and  posterior. 
The  anterior  branch,  the  larger,  crosses  the  great  wing  of  the  sphenoid,  reaches  the 
groove,  or  canal,  in  the  sphenoidal  angle  of  the  parietal  bone,  and  then  divides 
into  branches  which  spread  out  between  the  dura  mater  and  internal  surface  of 
the  cranium,  some  passing  upward  as  far  as  the  vertex,  and  others  backward  to 
the  occipital  region.  The  posterior  branch  curves  backward  on  the  squama  of  the 
temporal  bone,  and,  reaching  the  parietal  some  distance  in  front  of  its  mastoid 
angle,  divides  into  branches  which  supply  the  posterior  part  of  the  dura  mater  and 
cranium.  The  branches  of  the  middle  meningeal  artery  are  distributed  partly 
to  the  dura  mater,  but  chiefly  to  the  bones;  they  anastomose  with  the  arteries  of 
the  opposite  side,  and  with  the  anterior  and  posterior  meningeal. 

The  middle  meningeal  on  entering  the  cranium  gives  off  the  following  branches:  (1)  Numerous 
small  vessels  supply  the  semilunar  ganghon  and  the  dura  mater  in  this  situation.  (2)  A  superficial 
petrosal  branch  enters  the  hiatus  of  the  facial  canal,  suppMes  the  facial  nerve,  and  anastomoses 
with  the  stylomastoid  branch  of  the  posterior  auricular  artery.  (3)  A  superior  tsrmpanic  artery 
runs  in  the  canal  for  the  Tensor  tympani,  and  suppUes  this  muscle  and  the  lining  membrane  of 
the  canal.  (4)  Orbital  branches  pass  tlirough  the  superior  orbital  fissure  or  through  separate 
canals  in  the  great  wing  of  the  sphenoid,  to  anastomose  with  the  lacrimal  or  other  branches  of 
the  ophthalmic  artery.  (5)  Temporal  branches  pass  through  foramina  in  the  great  wing  of  the 
sphenoid,  and  anastomose  in  the  temporal  fossa  with  the  deep  temporal  arteries. 

Applied  Anatomy. — The  middle  meningeal  is  an  artery  of  considerable  surgical  importance, 
as  it  may  be  torn  in  fractures  of  the  temporal  region  of  the  skull,  or,  indeed,  by  injuries  causing 
separation  of  the  dura  mater  from  the  bone,  without  fracture.  The  injury  may  be  followed  by 
considerable  hemorrhage  between  the  bone  and  dura  mater,  which  produces  symptoms  of  com- 
pression of  the  brain,  and  requires  trephining  for  its  relief.  As  the  compression  imphcates  the 
motor  region  of  the  cortex,  paralysis  on  the  opposite  side  of  the  body  forms  the  prominent  symp- 
tom of  the  lesion.  The  anterior  branch  of  this  artery  crosses  the  sphenoidal  angle  of  the  parietal 
bone  at  a  point  4  cm.  behind  the  zygomatic  pi'ocess  of  the  frontal  bone,  and  4.5  cm.  above 
the  zygomatic  arch.  From  this  point  it  passes  upward  and  shghtly  backward  to  the  sagittal 
suture,  lying  about  1.25  to  2  cm.  behind  the  coronal  suture.  The  posterior  branch  runs  back- 
ward over  the  squama  of  the  temporal  bone.  In  order  to  expose  the  anterior  branch  of  the  artery, 
a  point  is  taken  4  cm.  above  the  zygomatic  arch  and  the  same  distance  behind  the  zygomatic 
process  of  the  frontal  bone.  Here  the  pin  of  the  trephine  is  to  be  applied.  A  horseshoe-shaped 
flap,  measm-ing  8  cm.  in  length  and  transversely,  and  consisting  of  all  the  structures  of  the  scalp 
down  to  and  including  the  pericranium,  is  first  made,  with  its  base  just  above  the  zj^gomatic 
arch.  This  flap  is  reflected  and  a  2.5  cm.  trephine  apphed.  After  the  crown  of  bone  has  been 
removed,  the  blood  clot  is  exposed,  and  gently  got  rid  of,  and  if  possible  the  bleeding-point  must 
be  found  and  controlled. 

The  Accessory  Meningeal  Branch  (ramus  menimjeus  accessorivs;  small  meningeal 
or  parvidnral  branch)  is  sometimes  derived  from  the  preceding.  It  enters  the 
skull  through  the  foramen  ovale,  and  supplies  the  semilunar  ganglion  and  dura 
mater. 


THE  EXTERNAL  CAROTID  ARTERY  G41 

The  Inferior  Alveolar  Artery  (a.  aheolaris  inferior;  inferior  dental  artery)  descends 
with  the  inferior  alveohir  nerve  to  the  mancHbular  foramen  on  the  medial  surface 
of  the  ramus  of  the  mandible.  It  runs  along  the  mandibular  canal  in  the  substance 
of  the  bone,  accompanied  by  the  nerve,  and  opposite  the  first  premolar  tooth  divides 
into  two  branches,  incisor  and  mental.  The  incisor  branch  is  continued  forward 
beneath  the  incisor  teeth  as  far  as  the  middle  line,  where  it  anastomoses  with  the 
artery  of  the  opposite  side;  the  mental  branch  escapes  with  the  nerve  at  the  mental 
foramen,  supplies  the  chin,  and  anastomoses  with  the  submental  and  inferior 
labial  arteries.  Near  its  origin  the  inferior  alveolar  artery  gives  off  a  lingual  branch 
which  descends  with  the  lingual  nerve  and  supplies  the  mucous  membrane  of  the 
mouth.  x\s  the  inferior  alveolar  artery  enters  the  foramen,  it  gives  off  a  mylohyoid 
branch  which  runs  in  the  mylohyoid  groove,  and  ramifies  on  the  under  surface  of 
the  Mylohyoideus.  The  inferior  alveolar  artery  and  its  incisor  branch  during 
their  course  through  the  substance  of  the  bone  give  off  a  few  twigs  which  are  lost 
in  the  cancellous  tissue,  and  a  series  of  branches  which  correspond  in  number  to 
the  roots  of  the  teeth :  these  enter  the  minute  apertures  at  the  extremities  of  the 
roots,  and  supply  the  pulp  of  the  teeth. 

Branches  of  the  Second  or  Pterygoid  Portion. — 

Deep  Temporal.  Masseteric. 

Pterygoid.  Buccinator. 

The  Deep  Temporal  Branches,  two  in  number,  anterior  and  posterior,  ascend 
between  the  Temporalis  and  the  pericranium;  they  supply  the  muscle,  and  anasto- 
mose with  the  middle  temporal  artery;  the  anterior  communicates  with  the  lacrimal 
artery  by  means  of  small  branches  which  perforate  the  zygomatic  bone  and  great 
wing  of  the  sphenoid. 

The  Pterygoid  Branches  {rami  pterygoidei) ,  irregular  in  their  number  and  origin, 
supply  the  Pterygoidei. 

The  Masseteric  Artery  (a.  masseterica)  is  small  and  passes  lateralward  through 
the  mandibular  notch  to  the  deep  surface  of  the  Masseter.  It  supplies  the  muscle, 
and  anastomoses  with  the  masseteric  branches  of  the  external  maxillary  and  with 
the  transverse  facial  artery. 

The  Buccinator  Artery  {a.  huccinatoria;  buccal  artery)  is  small  and  runs  obliquely 
forward,  between  the  Pterygoideus  internus  and  the  insertion  of  the  Temporalis, 
to  the  outer  surface  of  the  Buccinator,  to  which  it  is  distributed,  anastomosing 
with  branches  of  the  external  maxillary  and  with  the  infraorbital. 

Branches  of  the  Third  or  Pterygopalatine  Portion. — 

Posterior  Superior  Alveolar.  Artery  of  the  Pterygoid  Canal. 

Infraorbital.  Pharyngeal. 

Descending  Palatine.  Sphenopalatine. 

The  Posterior  Superior  Alveolar  Artery  (a.  aheolaris  superior  posterior;  alveolar  or 
posterior  dental  artery)  is  given  off  from  the  internal  maxillary,  frequently  in  con- 
junction with  the  infraorbital  just  as  the  trunk  of  the  vessel  is  passing  into  the 
pterygopalatine  fossa.  Descending  upon  the  tuberosity  of  the  maxilla,  it  divides 
into  numerous  branches,  some  of  which  enter  the  alveolar  canals,  to  supply  the 
molar  and  premolar  teeth  and  the  lining  of  the  maxillary  sinus,  while  others  are 
continued  forward  on  the  alveolar  process  to  supply  the  gums. 

The  Infraorbital  Artery  (a.  infraorhitalis)  appears,  from  its  direction,  to  be  the 
continuation  of  the  trunk  of  the  internal  maxillary,  but  often  arises  in  conjunction 
with  the  posterior  superior  alveolar.  It  runs  along  the  infraorbital  groove  and 
canal  with  the  infraorbital  nerve,  and  emerges  on  the  face  through  the  infraorbital 
foramen,  beneath  the  infraorbital  head  of  the  Quadratus  labii  superioris.  While 
in  the  canal,  it  gives  off  (a)  orbital  branches  which  assist  in  supplying  the  Rectus 
inferior  and  Obliquus  inferior  and  the  lacrimal  sac,  and  {h)  anterior  superior  alveolar 
41 


642  ANGIOLOGY 

branches  which  descend  through  the  anterior  alvcohir  canals  to  sui)ply  the  iipi)er 
incisor  and  canine  teeth  and  the  mucous  membrane  of  the  maxillary  sinus.  On 
the  face,  some  branches  pass  upward  to  the  medial  angle  of  the  orbit  and  the 
lacrimal  sac,  anastomosing  with  the  angular  branch  of  the  external  maxillary 
artery;  others  run  toward  the  nose,  anastomosing  with  the  dorsal  nasal  branch  of 
the  ophthalmic;  and  others  descend  between  the  Quadratus  labii  superioris  and 
the  Caninus,  and  anastomose  with  the  external  maxillary,  transverse  facial,  and 
buccinator  arteries.  The  four  remaining  branches  arise  from  that  portion  of  the 
internal  maxillary  which  is  contained  in  the  pterygopalatine  fossa. 

The  Descending  Palatine  Artery  (a.  ixdatina  descendens)  descends  through  the 
pterygopalatine  canal  with  the  anterior  palatine  branch  of  the  sphenopalatine 
ganglion,  and,  emerging  from  the  greater  palatine  foramen,  runs  forward  in  a  groove 
on  the  medial  side  of  the  alveolar  border  of  the  hard  palate  to  the  incisive  canal; 
the  terminal  branch  of  the  artery  passes  upward  through  this  canal  to  anastomose 
with  the  sphenopalatine  artery.  Branches  are  distributed  to  the  gums,  the  palatine 
glands,  and  the  mucous  membrane  of  the  roof  of  the  mouth;  while  in  the  pterygo- 
palatine canal  it  gives  off  twigs  which  descend  in  the  lesser  palatine  canals  to  supply 
the  soft  palate  and  palatine  tonsil,  anastomosing  with  the  ascending  palatine  artery. 

Applied  Anatomy. — The  position  of  the  descending  palatine  artery  on  the  hard  palate  should 
be  borne  in  mind  in  performing  an  operation  for  the  closure  of  a  cleft  in  the  hard  palate,  as  it  is 
in  danger  of  being  wounded,  and  may  give  rise  to  formidable  hemorrhage;  it  has  even  been  found 
necessary  to  plug  the  pterygopalatine  canal  in  order  to  arrest  the  bleeding. 

The  Artery  of  the  Pterygoid  Canal  {a.  canalis  ijterygoidei;  Vidian  artery)  passes 
backward  along  the  pterygoid  canal  with  the  corresponding  nerve.  It  is  distributed 
to  the  upper  part  of  the  pharynx  and  to  the  auditory  tube,  sending  into  the  tympanic 
cavity  a  small  branch  which  anastomoses  with  the  other  tympanic  arteries. 

The  Pharyngeal  Branch  is  very  small;  it  runs  backward  through  the  pharyngeal 
canal  with  the  pharyngeal  nerve,  and  is  distributed  to  the  upper  part  of  the  pharynx 
and  to  the  auditory  tube. 

The  Sphenopalatine  Artery  (a.  sphenofolatina;  nasopalatine  artery)  passes  through 
the  sphenopalatine  foramen  into  the  cavity  of  the  nose,  at  the  back  part  of  the 
superior  meatus.  Here  it  gives  off  its  posterior  lateral  nasal  branches  which  spread 
forward  over  the  conchse  and  meatuses,  anastomose  with  the  ethmoidal  arteries 
and  the  nasal  branches  of  the  descending  palatine,  and  assist  in  supplying  the 
frontal,  maxillary,  ethmoidal,  and  sphenoidal  sinuses.  Crossing  the  under  surface  of 
the  sphenoid  the  sphenopalatine  artery  ends  on  the  nasal  septum  as  the  posterior 
septal  branches;  these  anastomose  with  the  ethmoidal  arteries  and  the  septal 
branch  of  the  superior  labial;  one  branch  descends  in  a  groove  on  the  vomer  to 
the  incisive  canal  and  anastomoses  with  the  descending  palatine  artery. 

THE  TRIANGLES  OF  THE  NECK   (Fig.  589). 

The  side  of  the  neck  presents  a  somewhat  quadrilateral' outline,  limited,  above> 
by  the  lower  border  of  the  body  of  the  mandible,  and  an  imaginary  line  extending 
from  the  angle  of  the  mandible  to  the  mastoid  process;  helow,  by  the  upper  border 
of  the  clavicle;  in  front,  by  the  middle  line  of  the  neck;  behind,  by  the  anterior 
margin  of  the  Trapezius.  This  space  is  subdivided  into  two  large  triangles  by  the 
Sternocleidomastoideus,  which  passes  obliquely  across  the  neck,  from  the  sternum 
and  clavicle  below,  to  the  mastoid  process  and  occipital  bone  above.  The  triangular 
space  in  front  of  this  muscle  is  called  the  anterior  triangle ;  and  that  behind  it,  the 
posterior  triangle. 

Anterior  Triangle. — The  anterior  triangle  is  bounded,  in  front,  by  the  middle  line 
of  the  neck;  behind,  by  the  anterior  margin  of  the  Sternocleidomastoideus;  its 
base,  directed  upward,  is  formed  by  the  lower  border  of  the  body  of  the  mandible. 


THE  TRIANGLES  OF  TIIE  NECK 


643 


and  a  line  extending  from  the  angle  of  the  mandible  to  the  mastoid  process;  its 
apex  is  below,  at  the  sternum.  This  space  is  subdivided  into  four  smaller  triangles 
by  the  Digastricus  above,  and  the  superior  belly  of  the  Omohyoideus  below. 
These  smaller  triangles  are  named  the  inferior  carotid,  the  superior  carotid,  the 
submaxillary,  and  the  suprahyoid. 


Suprahyoid  triangle 
Submaxillarij  triangle 

Superior  carotid  triangle 


Inferior  carotid  triangle 


Occipital  triangle 


Subclavian  triangle 
Fig.  5S9. — The  triangles  of  the  neck. 


The  Inferior  Carotid,  or  Muscular  Triangle,  is  bounded,  in  front,  by  the  median 
line  of  the  neck  from  the  hyoid  bone  to  the  sternum;  behind,  by  the  anterior  margin 
of  the  Sternocleidomastoideus;  above,  by  the  superior  belly  of  the  Omohyoideus. 
It  is  covered  by  the  integument,  superficial  fascia,  Platysma,  and  deep  fascia, 
ramifying  in  which  are  some  of  the  branches  of  the  supraclavicular  nerves.  Be- 
neath these  superficial  structures  are  the  Sternohyoideus  and  Sternothyreoideus, 
which,  together  with  the  anterior  margin  of  the  Sternocleidomastoideus,  conceal 
the  lower  part  of  the  common  carotid  artery.^  This  vessel  is  enclosed  within  its 
sheath,  together  with  the  internal  jugular  vein  and  vagus  nerve;  the  vein  lies 
lateral  to  the  artery  on  the  right  side  of  the  neck,  but  overlaps  it  below  on  the  left 
side;  the  nerve  lies  betw^een  the  artery  and  vein,  on  a  plane  posterior  to  both. 
In  front  of  the  sheath  are  a  few  descending  filaments  from  the  ansa  hypoglossi; 
behind  the  sheath  are  the  inferior  thyroid  artery,  the  recurrent  nerve,  and  the  sym- 
pathetic trunk;  and  on  its  medial  side,  the  oesophagus,  the  trachea,  the  thyroid 
gland,  and  the  lower  part  of  the  larynx.  By  cutting  into  the  upper  part  of  this 
space,  and  slightly  displacing  the  Sternocleidomastoideus,  the  common  carotid 
artery  may  be  tied  below  the  Omohyoideus. 

The  Superior  Carotid,  or  Carotid  Triangle,  is  bounded,  hehind  by  the  Sternocleido- 
mastoideus; below,  by  the  superior  belly  of  the  Omohyoideus;  and  above,  by  the 
Stylohyoideus  and  the  posterior  belly  of  the  Digastricus.  It  is  covered  by  the  integu- 
ment, superficial  fascia,  Platysma  and  deep  fascia;  ramifying  in  which  are  branches 
of  the  facial  and  cutaneous  cervical  nerves.  Its  floor  is  formed  by  parts  of  the  Thyro- 
hyoideus,  Hyoglossus,  and  the  Constrictores  pharyngis  medius  and  inferior.    This 

1  Therefore  the  common  carotid  artery  and  internal  jugular  vein  are  not,  strictly  speaking,  contained  in  this  tri- 
angle, since  they  are  covered  by  the  Sternocleidomastoideus;  that  is  to  say,  they  lie  under  that  muscle,  which  forms 
the  posterior  border  of  the  triangle.  But  as  thej'  he  very  close  to  the  structures  which  are  really  contained  in  the 
triangle,  and  whose  position  it  is  essential  to  remember  in  operating  on  this  part  of  the  artery,  it  is  expedient  to  study 
the  relations  of  all  these  parts  together. 


644  ANGIOLOGY 

space  when  dissected  is  seen  to  contain  the  upper  part  of  the  common  carotid 
artery,  which  bifurcates  opposite  the  upper  border  of  the  thyroid  cartilage  into  the 
external  and  internal  carotid.  These  vessels  are  somewhat  concealed  from  veiw 
by  the  anterior  margin  of  the  Sternocleidomastoideus,  which  overlaps  them. 
The  external  and  internal  carotids  lie  side  by  side,  the  external  being  the  more 
anterior  of  the  two.  The  following  branches  of  the  external  carotid  are  also  met 
with  in  this  space:  the  superior  thyroid,  running  forward  and  downward;  the 
lingual,  directly  forward;  the  external  maxillary,  forward  and  upward;  the  occipital, 
backward;  and  the  ascending  pharyngeal,  directly  upward  on  the  medial  side  of  the 
internal  carotid.  The  veins  met  with  are:  the  internal  jugular,  which  lies  on 'the 
lateral  side  of  the  common  and  internal  carotid  arteries;  and  veins  corresponding 
to  the  above-mentioned  branches  of  the  external  carotid — viz.,  the  superior  thyroid, 
the  lingual,  common  facial,  ascending  pharyngeal,  and  sometimes  the  occipital- 
all  of  which  end  in  the  internal  jugular.  The  nerves  in  this  space  are  the  following. 
In  front  of  the  sheath  of  the  common  carotid  is  the  ramus  descendens  hypoglossi. 
The  hypoglossal  nerve  crosses  both  the  internal  and  external  carotids  above, 
curving  around  the  origin  of  the  occipital  artery.  Within  the  sheath,  between  the 
artery  and  vein,  and  behind  both,  is  the  vagus  nerve;  behind  the  sheath,  the  sym- 
pathetic trunk.  On  the  lateral  side  of  the  vessels,  the  accessory  nerve  runs  for  a 
short  distance  before  it  pierces  the  Sternocleidomastoideus;  and  on  the  medial 
side  of  the  external  carotid,  just  below  the  hyoid  bone,  may  be  seen  the  internal 
branch  of  the  superior  laryngeal  nerve;  and,  still  more  inferiorly,  the  external 
branch  of  the  same  nerve.  The  upper  portion  of  the  larynx  and  lower  portion  of 
the  pharynx  are  also  found  in  the  front  part  of  this  space. 

The  Submaxillary  or  Digastric  Triangle  corresponds  to  the  region  of  the  neck 
immediately  beneath  the  body  of  the  mandible.  It  is  bounded,  above,  by  the  lower 
border  of  the  body  of  the  mandible,  and  a  line  drawn  from  its  angle  to  the  mastoid 
process;  heloiv,  by  the  posterior  belly  of  the  Digastricus  and  the  Stylohyoideus; 
in  front,  by  the  anterior  belly  of  the  Digastricus.  It  is  covered  by  the  integument, 
superficial  fascia,  Platysma,  and  deep  fascia,  ramifying  in  which  are  branches 
of  the  facial  nerve  and  ascending  filaments  of  the  cutaneous  cervical  nerve.  Its 
floor  is  formed  by  the  Mylohyoideus,  Hyoglossus,  and  Constrictor  pharyngis 
superior.  It  is  divided  into  an  anterior  and  a  posterior  part  by  the  stylomandibular 
ligament.  The  anterior  part  contains  the  submaxillary  gland,  superficial  to  which 
is  the  anterior  facial  vein,  while  imbedded  in  the  gland  is  the  external  maxillary 
artery  and  its  glandular  branches;  beneath  the  gland,  on  the  surface  of  the  Mylo- 
hyoideus, are  the  submental  artery  and  the  mylohyoid  artery  and  nerve.  The 
posterior  part  of  this  triangle  contains  the  external  carotid  artery,  ascending  deeply 
in  the  substance  of  the  parotid  gland;  this  vessel  lies  here  in  front  of,  and  super- 
ficial to,  the  internal  carotid,  being  crossed  by  the  facial  nerve,  and  gives  off  in 
its  course  the  posterior  auricular,  superficial  temporal,  and  internal  maxillary 
branches:  more  deeply  are  the  internal  carotid,  the  internal  jugular  vein,  and  the 
vagus  nerve,  separated  from  the  external  carotid  by  the  Styloglossus  and  Stylo- 
pharyngeus,  and  the  glossopharyngeal  nerve.^ 

The  Suprahyoid  Triangle  is  limited  hehind  by  the  anterior  belly  of  the  Digastricus, 
in  front  by  the  middle  line  of  the  neck  between  the  mandible  and  the  hyoid  bone ; 
below,  by  the  body  of  the  hyoid  bone;  its  floor  is  formed  by  the  Mylohyoideus. 
It  contains  one  or  two  lymph  glands  and  some  small  veins;  the  latter  unite  to  form 
the  anterior  jugular  vein. 

Posterior  Triangle.— The  posterior  triangle  is  bounded,  in  front,  by  the  Sterno- 
cleidomastoideus; behind,  by  the  anterior  margin  of  the  Trapezius;  its  base  is  formed 

1  The  remark  made  about  the  inferior  carotid  triangle  applies  also  to  this  one.  The  structures  enumerated  as  con- 
tained in  its  posterior  part  Ue,  strictly  speaking,  beneath  the  muscles  wjiich  form  the  posterior  boundary  of  the  tri- 
angle; but  as  it  is  very  important  to  bear  in  mind  .their  close  relation  to  the  parotid  gland,  all  these  parts  are  spoken 
of  together. 


THE  IXTERXAL  CAROTID  ARTERY  645 

by  the  middle  third  of  the  clavicle;  its  a))ex,  by  the  occipital  bone.  The  space 
is  crossed,  about  2.5  cm.  above  the  clavicle,  by  the  inferior  belly  of  the  Omo- 
hyoideus,  which  divides  it  into  two  triangles,  an  upper  or  occipital,  and  a  lower  or 
subclavian. 

The  Occipital  Triangle,  the  larger  division  of  the  posterior  triangle,  is  bounded, 
in  front,  by  the  Sternocleidomastoideiis;  heJiind,  by  the  Trapezius;  below,  by  the 
Omohyoideus.  Its  fioor  is  formed  from  abo^'e  downward  b\'  the  Splenius  capitis, 
Levator  scapulae,  and  the  Scaleni  medius  and  posterior.  It  is  covered  by  the  skin, 
the  superficial  and  deep  fasciae,  and  by  the  Platysma  below.  The  accessory  nerve 
is  directed  obliquely  across  the  space  from  the  Sternocleidomastoideus,  which  it 
pierces,  to  the  under  surface  of  the  Trapezius;  below,  the  supraclavicular  nerves 
and  the  transverse  cervical  vessels  and  the  upper  part  of  the  brachial  plexus  cross 
thcLspace.  A  chain  of  lymph  glands  is  also  found  running  along  the  posterior  border 
of  the  Sternocleidomastoideus,  from  the  mastoid  process  to  the  root  of  the  neck. 

The  Subclavian  Triangle,  the  smaller  division  of  the  posterior  triangle,  is  bouixled, 
above,  by  the  inferior  bellv  of  the  Omohyoideus;  below,  by  the  clavicle;  its  base  is 
formed  by  the  posterior  border  of  the  Sternocleidomastoideus.  Its  floor  is  formed 
by  the  first  rib  with  the  first  digitation  of  the  Serratus  anterior.  The  size  of  the 
subclavian  triangle  varies  with  the  extent  of  attachment  of  the  clavicular  portions 
of  the  Sternocleidomastoideus  and  Trapezius,  and  also  with  the  height  at  which 
the  Omohyoideus  crosses  the  neck.  Its  height  also  varies  according  to  the  position 
of  the  arm,  being  diminished  by  raising  the  limb,  on  account  of  the  ascent  of  the 
clavicle,  and  increased  by  drawing  the  arm  donwward,  when  that  bone  is  depressed. 
This  space  is  covered  by  the  integument,  the  superficial  and  deep  fascise  and  the 
Platysma,  and  crossed  by  the  supraclavicular  nerves.  Just  above  the  level  of  the 
clavicle,  the  third  portion  of  the  subclavian  artery  curves  lateralward  and  downward 
from  the  lateral  margin  of  the  Scalenus  anterior,  across  the  first  rib,  to  the  axilla, 
and  this  is  the  situation  most  commonly  chosen  for  ligaturing  the  vessel.  Some- 
times this  vessel  rises  as  high  as  4  cm.  above  the  clavicle;  occasionally,  it  passes 
in  front  of  the  Scalenus  anterior,  or  pierces  the  fibres  of  that  muscle.  The  sub- 
clavian vein  lies  behind  the  clavicle,  and  is  not  usually  seen  in  this  space;  but  in 
some  cases  it  rises  as  high  as  the  artery,  and  has  even  been  seen  to  pass  with  that 
vessel  behind  the  Scalenus  anterior.  The  brachial  plexus  of  nerves  lies  above 
the  artery,  and  in  close  contact  with  it.  Passing  transversely  behind  the  clavicle 
are  the  transverse  scapular  vessels;  and  traversing  its  upper  angle  in  the  same 
direction,  the  transverse  cervical  artery  and  vein.  The  external  jugular  vein  runs 
vertically  downward  behind  the  posterior  border  of  the  Sternocleidomastoideus, 
to  terminate  in  the  subclavian  vein;  it  receives  the  transverse  cervical  and  trans- 
verse scapular  veins,  which  form  a  plexus  in  front  of  the  artery,  and  occasionally 
a  small  vein  which  crosses  the  clavicle  from  the  cephalic.  The  small  nerve  to  the 
Subclavius  also  crosses  this  triangle  about  its  middle,  and  some  lymph  glands  are 
usually  found  in  the  space. 

The  Internal  Carotid  Artery  (A.  Carotis  Interna)  (Fig.  590). 

The  internal  carotid  artery  supplies  the  anterior  part  of  the  brain,  the  eye  and  its 
appendages,  and  sends  branches  to  the  forehead  and  nose.  Its  size,  in  the  adult, 
is  equal  to  that  of  the  external  carotid,  though,  in  the  child,  it  is  larger  than  that 
vessel.  It  is  remarkable  for  the  number  of  curvatures  that  it  presents  in  different 
parts  of  its  course.  It  occasionally  has  one  or  two  flexures  near  the  base  of  the  skull, 
while  in  its  passage  through  the  carotid  canal  and  along  the  side  of  the  body  of 
the  sphenoid  bone  it  describes  a  double  curvature  and  resembles  the  italic  letter  S. 

Course  and  Relations. — In  considering  the  course  and  relations  of  this  vessel 
it  may  be  divided  into  four  portions:  cervical,  petrous,  cavernous,  and  cerebral. 


()4(3 


ANGIOLOGY 


Cervical  Portion.— This  portion  of  the  internal  carotid  beo;ins  at  the  bifurca- 
tion of  the  common  carotid,  opposite  the  ui)per  border  of  the  thyroid  cartilage, 
and  runs  perijendicularly  upward,  in  front  of  the  transverse  processes  of  the  upper 
three  cervical  vertebroe,  to  the  carotid  canal  in  the  petrous  portion  of  the  temporal 
bone.    It  is  comparatively  superficial  at  its  commencement,  where  it  is  contained 


First  aortic  intercostal 

Fig.  590. — The  internal  carotid  and  vertebral  arteries.     Right  side. 

in  the  carotid  triangle,  and  lies  behind  and  lateral  to  the  external  carotid,  over- 
lapped by  the  Sternocleidomastoideus,  and  covered  by  the  deep  fascia,  Platysma, 
and  integument:  it  then  passes  beneath  the  parotid  gland,  being  crossed  by  the 
hypoglossal  nerve,  the  Digastricus  and  Stylohyoideus,  and  the  occipital  and  pos- 
terior auricular  arteries.  Higher  up,  it  is  separated  from  the  external  carotid  by 
the  Styloglossus  and  Stylopharyngeus,  the  tip  of  the  styloid  process  and  the  stylo- 


THE  INTERNAL  CAROTID  ARTERY  647 

liyoid  ligament,  the  glossopharyngeal  nerve  and  the  pharyngeal  branch  of  the  \'agus. 
It  is  in  relation,  behind,  with  the  Longus  capitis,  tlie  superior  cer\ical  ganglion  of 
the  sympathetic  trunk,  and  the  superior  laryngeal  nerve;  laterally,  with  the  internal 
jugular  vein  and  vagus  nerve,  the  nerve  lying  on  a  plane  posterior  to  the  artery; 
medially,  with  the  pharynx,  superior  laryngeal  nerve,  and  ascending  pharyngeal 
artery.  At  the  base  of  the  skull  the  glossopharyngeal,  vagus,  accessory,  and  hypo- 
glossal nerves  lie  between  the  artery  and  the  internal  jugular  vein. 

Petrous  Portion. — When  the  internal  carotid  artery  enters  the  canal  in  the 
petrous  portion  of  the  temporal  bone,  it  first  ascends  a  short  distance,  then  curves 
forward  and  medialw^ard,  and  again  ascends  as  it  leaves  the  canal  to  enter  the 
cavity  of  the  skull  between  the  lingula  and  petrosal  process  of  the  sphenoid.  The 
artery  lies  at  first  in  front  of  the  cochlea  and  tympanic  cavity;  from  the  latter 
cavity  it  is  separated  by  a  thin,  bony  lamella,  which  is  cribriform  in  the  young 
subject,  and  often  partly  absorbed  in  old  age,  Farther  forward  it  is  separated 
from  the  semilunar  ganglion  by  a  thin  plate  of  bone,  which  forms  the  floor  of  the 
fossa  for  the  ganglion  and  the  roof  of  the  horizontal  portion  of  the  canal.  Fre- 
quently this  bony  plate  is  more  or  less  deficient,  and  then  the  ganglion  is  separated 
from  the  artery  by  fibrous  membrane.  The  artery  is  separated  from  the  bony  wall 
of  the  carotid  canal  by  a  prolongation  of  dura  mater,  and  is  surrounded  by  a  number 
of  small  veins  and  by  filaments  of  the  carotid  plexus,  derived  from  the  ascending 
branch  of  the  superior  cervical  ganglion  of  the  sympathetic  trunk. 

Cavernous  Portion. — In  this  part  of  its  course,  the  artery  is  situated  between 
the  layers  of  the  dura  mater  forming  the  cavernous  sinus,  but  covered  by  the  lining 
membrane  of  the  sinus.  It  at  first  ascends  toward  the  posterior  clinoid  process, 
then  passes  forward  by  the  side  of  the  body  of  the  sphenoid  bone,  and  again  curves 
upward  on  the  medial  side  of  the  anterior  clinoid  process,  and  perforates  the  dura 
mater  forming  the  roof  of  the  sinus.  This  portion  of  the  artery  is  surrounded  by 
filaments  of  the  sympathetic  nerve,  and  on  its  lateral  side  is  the  abducent  nerve. 

Cerebral  Portion. — Having  perforated  the  dura  mater  on  the  medial  side  of 
the  anterior  clinoid  process,  the  internal  carotid  passes  between  the  optic  and  oculo- 
motor nerves  to  the  anterior  perforated  substance  at  the  medial  extremity  of  the 
lateral  cerebral  fissure,  where  it  gives  ofi'  its  terminal  or  cerebral  branches. 

Peculiarities. — The  length  of  the  internal  carotid  varies  according  to  the  length  of  the  neck, 
and  also  according  to  the  point  of  bifurcation  of  the  common  carotid.  It  arises  sometimes  from 
the  arch  of  the  aorta;  in  such  rare  instances,  this  vessel  has  been  found  to  be  placed  nearer  the 
middle  line  of  the  neck  than  the  external  carotid,  as  far  upward  as  the  larynx,  when  the  latter 
vessel  crossed  the  internal  carotid.  The  course  of  the  artery,  instead  of  being  straight,  may  be 
very  tortuous.  A  few  instances  are  recorded  in  which  this  vessel  was  altogether  absent;  in  one 
of  these  the  common  carotid  passed  up  the  neck,  and  gave  off  the  usual  branches  of  the  external 
carotid;  the  cranial  portion  of  the  internal  carotid  was  replaced  by  two  branches  of  the  internal 
maxillary,  which  entered  the  skull  through  the  foramen  rotundum  and  foramen  ovale,  and  joined 
to  form  a  single  vessel. 

Applied  Anatomy. — The  cervical  part  of  the  internal  carotid  is  very  rarely  wounded.  It  is, 
however,  sometimes  injured  by  a  stab  or  gunshot  wound  in  the  neck,  or  even  occasionally  by  a 
stab  from  within  the  mouth,  as  when  a  person  receives  a  thrust  from  the  end  of  a  parasol,  or  falls 
down  with  a  tobacco  pipe  in  his  mouth.  Although  the  internal  carotid  lies  about  2  cm.  behind 
and  lateral  to  the  tonsil,  instances  have  occurred  in  which  the  artery  has  been  wounded  during 
the  operation  of  excision  of  the  tonsil,  and  fatal  hemorrhage  has  supervened.  The  incision  for 
ligature  of  the  cervical  portion  of  the  internal  carotid  should  be  made  along  the  anterior  border 
of  the  Sternocleidomastoideus,  from  the  angle  of  the  mandible  to  the  upper  border  of  the  thyroid 
cartilage.  The  superficial  structures  being  divided,  and  the  Sternocleidomastoideus  defined 
and  drawn  lateralward,  the  areolar  tissue  must  be  carefully  separated  and  the  posterior  belly 
of  the  Digastricus  and  the  hypoglossal  nerve  sought  for  as  guides  to  the  vessel.  When  the  artery 
is  found,  the  external  carotid  should  be  drawn  medialward  and  the  Digastricus  upward,  and  the 
anem-ism  needle  passed  from  the  lateral  to  the  medial  side. 

Obstruction  of  the  internal  carotid  by  embolism  or  thrombosis  may  give  rise  to  symptoms  of 
cerebral  anemia  and  softening  if  the  collateral  circulation  is  ill-developed.  The  patient  suffers 
from  giddiness,  with  failure  of  the  mental  powers;  and  convulsions,  coma,  or  hemiplegia  on  the 
opposite  side  of  the  body,  may  be  observed. 


648  ANGIOLOGY 

Branches.-^The  cervical  portion  of  the  internal  carotid  gives  off  no  branches. 
Those  from  the  other  portions  are: 

,     _,  „    ^.  (Caroticotympanic. 

From  the  Petrous  Portion        ^^^^^^^  ^^  ^^^  Pterygoid  Canal. 


From  the  Cavernous  Portion 


From  the  Cerebral  Portion 


Cavernous. 
Hypophyseal. 
Semilunar. 
Anterior  Meningeal. 
Ophthalmic. 

Anterior  Cerebral. 
Middle  Cerebral. 
Posterior  Communicating. 
Choroidal. 


1.  The  caroticotympanic  branch  {ramus  caroticotymyanicus;  tympanic  branch) 
is  small;  it  enters  the  tympanic  cavity  through  a  minute  foramen  in  the  carotid 
canal,  and  anastomoses  with  the  anterior  tympanic  branch  of  the  internal  maxillary, 
and  with  the  stylomastoid  artery. 

2.  The  artery  of  the  pterygoid  canal  (a.  canilis  pterygoidei  [Vidii];  Vidian  artery) 
is  a  small,  inconstant  branch  which  passes  into  the  pterygoid  canal  and  anas- 
tomoses with  a  branch  of  the  internal  maxillary  artery. 

3.  The  cavernous  branches  are  numerous  small  vessels  which  supply  the  hypo- 
physis, the  semilunar  ganglion,  and  the  walls  of  the  cavernous  and  inferior  petrosal 
sinuses.    Some  of  them  anastomose  with  branches  of  the  middle  meningeal. 

4.  The  hypophyseal  branches  are  one  or  two  minute  vessels  supplying  the 
hypophysis. 

5.  The  semilunar  branches  are  small  vessels  to  the  semilunar  ganglion. 

6.  The  anterior  meningeal  branch  (a.  meningea  anterior)  is  a  small  branch  which 
passes  over  the  small  wing  of  the  sphenoid  to  supply  the  dura  mater  of  the  anterior 
cranial  fossa;  it  anastomoses  with  the  meningeal  branch  from  the  posterior  eth- 
moidal artery. 

7.  The  ophthalmic  artery  (a.  ophthalmica)  (Fig.  591)  arises  from  the  interrial 
carotid,  just  as  that  vessel  is  emerging  from  the  cavernous  sinus,  on  the  medial 
side  of  the  anterior  clinoid  process,  and  enters  the  orbital  cavity  through  the  optic 
foramen,  below  and  lateral  to  the  optic  nerve.  It  then  passes  over  the  nerve  to 
reach  the  medial  wall  of  the  orbit,  and  thence  horizontally  forward,  beneath  the 
lower  border  of  the  Obliquus  superior,  and  divides  it  into  two  terminal  branches, 
the  frontal  and  dorsal  nasal.  As  the  artery  crosses  the  optic  nerve  it  is  accompanied 
by  the  nasociliary  nerve,  and  is  separated  from  the  frontal  nerve  by  the  Rectus 
superior  and  Levator  palpebrae  superioris. 

Branches.— The  branches  of  the  ophthalmic  artery  may  be  divided  into  an  orbital 
group,  distributed  to  the  orbit  and  surrounding  parts;  and  an  ocular  group,  to  the 
muscles  and  bulb  of  the  eye. 

Orbital  Group.  Ocular  Group. 

Lacrimal.  Central  Artery  of  the  Retina. 

Supraorbital.  Short  Posterior  Ciliary. 

Posterior  Ethmoidal.  Long  Posterior  Ciliary. 

Anterior  Ethmoidal.  Anterior  Ciliary. 

Medial  Palpebral.  Muscular. 
Frontal. 
Dorsal  Nasal. 


THE  INTERNAL  CAROTID  ARTERY 


649 


The  Lacrimal  Artery  {a.  lacriinulLs)  arises  close  to  the  optic  foramen,  and  is  one 
of  the  largest  branches  derived  from  the  ophthalmic:  not  infrequently  it  is  given 
off  before  the  artery  enters  the  orbit.  It  accompanies  the  lacrimal  nerve  along 
the  upper  border  of  the  Rectus  lateralis,  and  supplies  the  lacrimal  gland.  Its 
terminal  branches,  escaping  from  the  gland,  are  distributed  to  the  eyelids  and  con- 
junctiva: of  those  supplying  the  eyelids,  two  are  of  considerable  size  and  are  named 
the  lateral  palpebral  arteries;  they  run  medialward  in  the  upper  and  lower  lids 
respectively  and  anastomose  with  the  medial  palpebral  arteries,  forming  an  arterial 
circle  in  this  situation.  The  lacrimal  artery  give  off  one  or  two  zygomatic  branches, 
one  of  which  passes  through  the  zygomatico-temporal  foramen,  to  reach  the  tem- 
poral fossa,  and  anastomoses  with  the  deep  temporal  arteries;  another  appears 
on  the  cheek  through  the  zygomatico-facial  foramen,  and  anastomoses  with  the 
transverse  facial.  A  recurrent  branch  passes  backward  through  the  lateral  part  of 
the  superior  orbital  fissure  to  the  dura  mater,  and  anastomoses  with  a  branch  of 
the  middle  meningeal  artery.  The  lacrimal  artery  is  sometimes  derived  from  one 
of  the  anterior  branches  of  the  middle  meningeal  artery. 

Dorsal  nasal        Medial  palpebral 

H.i     Frontal     .        Supraorbital 


Anterior  ethmoidal 


Posterior  ethmoidal  _ 


Muscular 


I  Zygomntic  branches 
J^  of  lacrimal 

Arteria 
centralis  retince 

Lacrimal 


Ophthalmic 


Internal  carotid 


Fig.   591. — The  ophthalmic  artery  and  its  branches. 


The  Supraorbital  Artery  (a.  swpraorhitalis)  springs  from  the  ophthalmic  as  that 
vessel  is  crossing  over  the  optic  nerve.  It  passes  upward  on  the  medial  borders 
of  the  Rectus  superior  and  Levator  palpebrae,  and  meeting  the  supraorbital  nerve 
accompanies  it  between  the  periosteum  and  Levator  palpebrae  to  the  supraorbital 
foramen;  passing  through  this  it  divides  into  a  superficial  and  a  deep  branch, 
which  supply  the  integument,  the  muscles,  and  the  pericranium  of  the  forehead, 
anastomosing  with  the  frontal,  the  frontal  branch  of  the  superficial  temporal,  and 
the  artery  of  the  opposite  side.  This  artery  in  the  orbit  supplies  the  Rectus  superior 
and  the  Levator  palpebrae,  and  sends  a  branch  across  the  pulley  of  the  Obliquus 
superior,  to  supply  the  parts  at  the  medial  palpebral  commissure.  At  the  supra- 
orbital foramen  it  frequently  transmits  a  branch  to  the  diploe. 


650  AXGIOLOGY 

The  Ethmoidal  Arteries  are  two  in  number:  posterior  and  anterior.  The  posterior 
ethmoidal  artery,  the  smaller,  passes  through  the  postericjr  ethmoidal  canal,  supplies 
the  posterior  ethmoidal  cells,  and,  entering  the  cranium,  gives  off  a  meningeal 
branch  to  the  dura  mater,  and  nasal  branches  which  descend  into  the  nasal  cavity 
through  apertures  in  the  cribriform  plate,  anastomosing  with  branches  of  the 
sphenopalatine.  The  anterior  ethmoidal  artery  accompanies  the  nasociliary  nerve 
through  the  anterior  ethmoidal  canal,  supplies  the  anterior  and  middle  ethmoidal 
cells  and  frontal  sinus,  and,  entering  the  cranium,  gives  off  a  meningeal  branch 
to  the  dura  mater,  and  nasal  branches;  these  latter  descend  into  the  nasal  cavity 
through  the  slit  by  the  side  of  the  crista  galli,  and,  running  along  the  groove  on 
the  inner  surface  of  the  nasal  bone,  supply  branches  to  the  lateral  wall  and  septum 
of  the  nose,  and  a  terminal  branch  which  appears  on  the  dorsum  of  the  nose  between 
the  nasal  bone  and  the  lateral  cartilage. 

The  Medial  Palpebral  Arteries  iaa.  palpebrales  mediales;  internal  imlpehral 
arteries),  two  in  number,  superior  and  inferior,  arise  from  the  ophthalmic,  opposite 
the  pulley  of  the  Obliquus  superior;  they  leave  the  orbit  to  encircle  the  eyelids 
near  their  free  margins,  forming  a  superior  and  an  inferior  arch,  which  lie  between 
the  Orbicularis  oculi  and  the  tarsi.  The  superior  palpebral  anastomoses,  at  the 
lateral  angle  of  the  orbit,  with  the  zygomaticoorbital  branch  of  the  temporal  artery 
and  with  the  upper  of  the  two  lateral  palpebral  branches  from  the  lacrimal  arterj-; 
the  inferior  palpebral  anastomoses,  at  the  lateral  angle  of  the  orbit,  with  the  lower 
of  the  two  lateral  palpebral  branches  from  the  lacrimal  and  with  the  transverse 
facial  artery,  and,  at  the  medial  part  of  the  lid,  with  a  branch  from  the  angular 
artery.  From  this  last  anastomoses  a  branch  passes  to  the  nasolacrimal  duct, 
ramifying  in  its  mucous  membrane,  as  far  as  the  inferior  meatus  of  the  nasal 
cavity. 

The  Frontal  Artery  (a.  frontalis),  one  of  the  terminal  branches  of  the  ophthalmic, 
leaves  the  orbit  at  its  medial  angle  with  the  supratrochlear  nerve,  and,  ascending 
on  the  forehead,  supplies  the  integument,  muscles,  and  pericranium,  anastomosing 
with  the  supraorbital  artery,  and  with  the  artery  of  the  opposite  side. 

The  Dorsal  Nasal  Artery  (a.  dorsalis  nasi;  nasal  artery),  the  other  terminal  branch 
of  the  ophthalmic,  emerges  from  the  orbit  above  the  medial  palpebral  ligament, 
and,  after  giving  a  twig  to  the  upper  part  of  the  lacrimal  sac,  divides  into  two 
branches,  one  of  which  crosses  the  root  of  the  nose,  and  anastomoses  with  the 
angular  artery,  the  other  runs  along  the  dorsum  of  the  nose,  supplies  its  outer 
surface;  and  anastomoses  with  the  artery  of  the  opposite  side,  and  with  the  lateral 
nasal  branch  of  the  external  maxillary. 

The  Central  Artery  of  the  Retina  (a.  centralis  retinae)  is  the  first  and  one  of  the 
smallest  branches  of  the  ophthalmic  artery.  It  runs  for  a  short  distance  within 
the  dural  sheath  of  the  optic  nerve,  but  about  1.25  cm.  behind  the  eyeball  it  pierces 
the  nerve  obliquely,  and  runs  forward  in  the  centre  of  its  substance  to  the  retina. 
Its  mode  of  distribution  will  be  described  with  the  anatomy  of  the  eye. 

The  Ciliary  Arteries  (aa.  ciliares)  are  divisible  into  three  groups,  the  long  and  short, 
posterior,  and  the  anterior.  The  short  posterior  ciliary  arteries  from  six  to  twelve 
in  number,  arise  from  the  ophthalmic,  or  its  branches;  they  pass  forward  around  the 
optic  nerve  to  the  posterior  part  of  the  eyeball,  pierce  the  sclera  around  the  entrance 
of  the  nerve,  and  supply  the  choroid  and  ciliary  processes.  The  long  posterior 
ciliary  arteries,  two  in  number,  pierce  the  posterior  part  of  the  sclera  at  some  little 
distance  from  the  optic  nerve,  and  run  forward,  along  either  side  of  the  eyeball, 
between  the  sclera  and  choroid,  to  the  ciliary  muscle,  where  they  divide  into  two 
branches;  these  form  an  arterial  circle,  the  circulus  arteriosus  major,  around  the 
circumference  of  the  iris,  from  which  numerous  converging  branches  run,  in  the 
substance  of  the  iris,  to  its  pupillary  margin,  where  they  form  a  second  arterial 
circle,  the  circulus  arteriosus  minor.     The  anterior  ciliary  arteries  are  derived  from 


THE  INTERNAL  CAROTID  ARTERY 


651 


the  muscular  hraufhes;  they  ruu  to  the  front  of  the  eyeball  in  company  with  the 
tendons  of  the  Recti,  form  a  vascular  zone  beneath  the  conjunctiva,  and  then 
pierce  the  sclera  a  short  distance  from  the  cornea  and  end  in  the  circulus  arteriosus 
major. 

The  Muscular  Branches,  {rami  muscularcs) ,  two  in  number,  superior  and  inferior, 
frequently  s})ring  from  a  common  trunk.  The  superior,  often  wanting,  supplies 
the  Levator  palpebrae  superioris,  Rectus  superior,  and  Obliquus  superior.  The 
inferior,  more  constantly  present,  passes  forward  between  the  optic  nerve  and  Rectus 
inferior,  and  is  distributed  to  the  Recti  lateralis,  medialis,  and  inferior,  and  the 
Obliquus  inferior.  This  vessel  gives  off  most  of  the  anterior  ciliary  arteries.  Addi- 
tional muscular  branches  are  given  off  from  the  lacrimal  and  supraorbital  arteries, 
or  from  the  trunk  of  the  ophthalmic. 


Fig.  592. — The  arteries  of  the  base  of  the  brain.    The  temporal  pole  of  the  cerebrum  and  a  portion  of  the  cerebellar 
hemisphere  have  been  removed  on  the  right  side. 

8..  The  anterior  cerebral  artery  (a.  cerebri  anterior)  (Figs.  592,  593,  594)  arises 
from  the  internal  carotid,  at  the  medial  extremity  of  the  lateral  cerebral  fissure. 
It  passes  forward  and  medialw^ard  across  the  anterior  perforated  substance,  above 
the  optic  nerve,  to  the  commencement  of  the  longitudinal  fissure.  Here  it  comes 
into  close  relationship  with  the  opposite  artery,  to  which  it  is  connected  by  a  short 
trunk,  the  anterior  communicating  artery.  From  this  point  the  two  vessels  run  side 
by  side  in  the  longitudinal  fissure,  curve  around  the  genu  of  the  corpus  callosum, 
and  turning  backward  continue  along  the  upper  surface  of  the  corpus  callosum 
to  its  posterior  part,  where  they  end  by  anastomosing  with  the  posterior  cerebral 
arteries. 


G52 

Branches, 

branches : 


ANGIOLOGY 
-In  its  course  the  anterior  cerebral  artery  gives  off  tlie  following 


Antero-medial  Ganglionic. 
Inferior. 


Anterior. 
Middle. 


Posterior. 


The  Antero-medial  Ganglionic  Branches  are  a  group  of  small  arteries  which  arise 
at  the  commencement  of  the  anterior  cerebral  artery;  they  pierce  the  anterior 
perforated  substance  and  lamina  terminalis,  and  supply  the  rostrum  of  the  corpus 


Fig.  593. — Outer  surface  of  cerebral  hemisphere,  showing  areas  supplied  by  cerebral  arteries. 


callosum,  the  septum  pellucidum,  and  the  head  of  the  caudate  nucleus.  The 
inferior  branches,  two  or  three  in  number,  are  distributed  to  the  orbital  surface  of 
the  frontal  lobe,  wdiere  they  supply  the  olfactory  lobe,  gyrus  rectus,  and  internal 
orbital  gyrus.  The  anterior  branches  supply  a  part  of  the  superior  frontal  gyrus, 
and  send  twigs  over  the  edge  of  the  hemisphere  to  the  superior  and  middle  frontal 
gyri  and  upper  part  of  the  anterior  central  gyrus.  The  middle  branches  supply 
the  corpus  callosum,  the  cingulate  gyrus,  the  medial  surface  of  the  superior  frontal 
gyrus,  and  the  upper  part  of  the  anterior  central  gyrus.  The  posterior  branches 
supply  the  precuneus  and  adjacent  lateral  surface  of  the  hemisphere. 


Fig.  594. — Medial  surface  of  cerebral  hemisphere,  showing  areas  supplied  by  cerebral  arteries. 

The  Anterior  Communicating  Artery  (a.  coiiwiunicans  anterior)  connects  the  two 
anterior  cerebral  arteries  across  the  commencement  of  the  longitudinal  fissure. 
Sometimes  this  vessel  is  wanting,  the  two  arteries  joining  together  to  form  a 
single  trunk,  which  afterward  divides;  or  it  may  be  wholly,  or  partially,  divided 
into  two.  Its  length  averages  about  4  mm.,  but  varies  greatly.  It  gives  off  some 
of  the  antero-medial  ganglionic  vessels,  but  these  are  principally  derived  from  the 
anterior  cerebral. 

9.  The  middle  cerebral  artery  {a.  cerebri  media)  (Figs.  592,  593),  the  largest 
branch  of  the  internal  carotid,  runs  at  first  lateralward  in  the  lateral  cerebral  or 


THE  ARTERIES  OF  THE  BRAIN  653 

Sylvian  fissure  and  then  backward  and  upward  on  the  surface  of  the  insula,  where 
it  divides  into  a  number  of  branches  which  are  distributed  to  the  lateral  surface 
of  the  cerebral  hemisphere. 
Branches. — The  branches  of  this  vessel  are  the: 

Antero-lateral  Ganglionic.  Ascending  Parietal. 

Inferior  Lateral  Frontal.  Parietotemporal. 

Ascending  Frontal.  Temporal. 

The  Antero-lateral  Ganglionic  Branches,  a  group  of  small  arteries  which  arise  at 
the  commencement  of  the  middle  cerebral  artery,  are  arranged  in  two  sets:  one, 
the  internal  striate,  passes  upward  through  the  inner  segments  of  the  lentiform 
nucleus,  and  supplies  it,  the  caudate  nucleus,  and  the  internal  capsule;  the  other, 
the  external  striate,  ascends  through  the  outer  segment  of  the  lentiform  nucleus, 
and  supplies  the  caudate  nucleus  and  the  thalamus.  One  artery  of  this  group 
is  of  larger  size  than  the  rest^  and  is  of  special  importance,  as  being  the  artery  in 
the  brain  most  frequently  ruptured;  it  has  been  termed  by  Charcot  the  artery 
of  cerebral  hemorrhage.  It  ascends  between  the  lentiform  nucleus  and  the  external 
capsule,  and  ends  in  the  caudate  nucleus.  The  inferior  lateral  frontal  supplies 
the  inferior  frontal  gyrus  (Brocas  convolution)  and  the  lateral  part  of  the  orbital 
surface  of  the  frontal  lobe.  The  ascending  frontal  supplies  the  anterior  central 
gyrus.  The  ascending  parietal  is  distributed  to  the  posterior  central  gyrus  and  the 
lower  part  of  the  superior  parietal  lobule.  The  parietotemporal  supplies  the  supra- 
marginal  and  angular  gyri,  and  the  posterior  parts  of  the  superior  and  middle 
temporal  gyri.  The  temporal  branches,  two  or  three  in  number,  are  distributed 
to  the  lateral  surface  of  the  temporal  lobe. 

10.  The  posterior  communicating  artery  (a.  communicans  iMsterior)  (Fig.  592) 
runs  backward  from  the  internal  carotid,  and  anastomoses  with  the  posterior 
cerebral,  a  branch  of  the  basilar.  It  varies  in  size,  being  sometimes  small,  and  occa- 
sionally so  large  that  the  posterior  cerebral  may  be  considered  as  arising  from  the 
internal  carotid  rather  than  from  the  basilar.  It  is  frequently  larger  on  one  side 
than  on  the  other.  From  its  posterior  half  are  given  off  a  number  of  small  branches, 
the  postero-medial  ganglionic  branches,  which,  with  similar  vessels  from  the  posterior 
cerebral,  pierce  the  posterior  perforated  substance  and  supply  the  medial  surface 
of  the  thalami  and  the  walls  of  the  third  ventricle. 

11.  The  anterior  choroidal  (a.  chorioidea;  choroid  artery)  is  a  small  but  constant 
branch,  which  arises  from  the  internal  carotid,  near  the  posterior  communicating 
artery.  Passing  backward  and  lateralward  between  the  temporal  lobe  and  the 
cerebral  peduncle,  it  enters  the  inferior  horn  of  the  lateral  ventricle  through  the 
choroidal  fissure  and  ends  in  the  choroid  plexus.  It  is  distributed  to  the  hippo- 
campus, fimbria,  tela  chorioidea  of  the  third  ventricle,  and  choroid  plexus. 


THE    ARTERIES    OF   THE   BRAIN. 

Since  the  mode  of  distribution  of  the  vessels  of  the  brain  has  an  important 
bearing  upon  a  considerable  number  of  the  pathological  lesions  which  may  occur 
in  this  part  of  the  nervous  system,  it  is  important  to  consider  a  little  more  in  detail 
the  manner  in  which  the  vessels  are  distributed. 

The  cerebral  arteries  are  derived  from  the  internal  carotid  and  vertebral,  which 
at  the  base  of  the  brain  form  a  remarkable  anastomosis  known  as  the  arterial  circle 
of  Willis.  It  is  formed  in  front  by  the  anterior  cerebral  arteries,  branches  of  the 
internal  carotid,  which  are  connected  together  by  the  anterior  communicating; 
behind  by  the  two  posterior  cerebral  arteries;  branches  of  the  basilar,  which  are 
connected  on  either  side  w^ith  the  internal  carotid  by  the  posterior  communicating 


654 


ANGIOLOGY 


4.7it.  communicating 
Ant.  cerebral 


Post  com- 
municating 


(Figs.  592,  595).  The  parts  of  the  brain  induded  within  this  arterial  circle  are 
the  lamina  terminalis,  the  optic  chiasma,  the  infundil^ulum,  the  tuber  cinereum, 
the  corpora  mamillaria,  and  the  posterior  perforated  su})stance. 

The  three  trunks  which  together  supply  each  cerebral  hemisphere  arise  from  the 
arterial  circle  of  Willis.  From  its  anterior  part  proceed  the  two  anterior  cerebrals, 
from  its  antero-lateral  parts  the  middle  cerebrals,  and  from  its  posterior  part  the 
posterior  cerebrals.  Each  of  these  principal  arteries  gives  origin  to  two  difi'erent 
systems  of  secondary  vessels.  One  of  these  is  named  the  ganglionic  system,  and  the 
vessels  belonging  to  it  supply  the  thalami  and  corpora  striata;  the  other  is  the  cortical 
system,  and  its  vessels  ramify  in  the  pia  mater  and  supply  the  cortex  and  subjacent 
brain  substance.  These  two  systems  do  not  communicate  at  any  point  of  their 
peripheral  distribution,  but  are  entirely  independent  of  each  other,  and  there  is 

between  the  parts  supplied  by  the  two  sys- 
tems a  borderland  of  diminished  nutritive 
activity,  where,  it  is  said,  softening  is  especi- 
ally liable  to  occur  in  the  brains  of  old  people. 
The  Ganglionic  System. — All  the  vessels 
of  this  system  are  given  off  from  the  arterial 
circle  of  Willis,  or  from  the  vessels  close  to 
it.  They  form  six  principal  groups:  (I)  the 
antero-medial  group,  derived  from  the  anterior 
cerebrals  and  anterior  communicating;  (II) 
the  postero-medial  group,  from  the  posterior 
cerebrals  and  posterior  communicating;  (III 
and  IV)  the  right  and  left  antero-lateral 
groups,  from  the  middle  cerebrals;  and  (V 
and  VI)  the  right  and  left  postero-lateral 
groups,  from  the  posterior  cerebrals,  after 
they  have  wound  around  the  cerebral  pedun- 
cles. The  vessels  of  this  system  are  larger 
than  those  of  the  cortical  system,  and  are 
what  Cohnheim  designated  terminal  arteries 
— that  is  to  say,  vessels  which  from  their 
origin  to  their  termination  neither  supply 
nor  receive  any  anastomotic  branch,  so  that, 
through  any  one  of  the  vessels  only  a  limited 
area  of  the  thalamus  or  corpus  striatum  can 
be  injected,  and  the  injection  cannot  be  driven 
beyond  the  area  of  the  part  supplied  by  the 
particular  vessel  which  is  the  subject  of  the 
experiment. 
The  Cortical  Arterial  System. — The  vessels  forming  this  system  are  the  terminal 
branches  of  the  anterior,  middle,  and  posterior  cerebral  arteries.  They  divide 
and  ramify  in  the  substance  of  the  pia  mater,  and  give  off  branches  which  penetrate 
the  brain  cortex,  perpendicularly.  These  branches  are  divisible  into  two  classes, 
long  and  short.  The  long,  or  medullary  arteries,  pass  through  the  gray  substance 
and  penetrate  the  subjacent  white  substance  to  the  depth  of  3  or  4  cm.,  without 
intercommunicating  otherwise  than  by  very  fine  capillaries,  and  thus  constitute 
so  many  independent  small  systems.  The  short  vessels  are  confined  to  the  cortex, 
where  they  form  with  the  long  vessels  a  compact  net-work  in  the  middle  zone 
of  the  gray  substance,  the  outer  and  inner  zones  being  sparingly  supplied  with 
blood.  The  vessels  of  the  cortical  arterial  system  are  not  so  strictly  "terminal" 
as  those  of  the  ganglionic  system, 'but  they  approach  this  type  very  closely,  so 
that  injection  of  one  area  "from  the  vessel  of  another  area,  though  possible,  is 


Posterior 
inferior 
cerebellar 


Fig.  595. — Diagram  of  the  arterial  circulation  at 
the  base  of  the  brain.  A.L.  Antero-lateral.  A.M. 
Antero-medial.  P.L.  Postero-lateral.  P.M.  Postero- 
medial ganglionic  branches. 


THE  SUBCLAVIAN  ARTERY  655 

freciuently  very  difficult,  and  is  only  effected  through  vessels  of  small  calibre.  As 
a  result  of  this,  obstruction  of  one  of  the  main  branches,  or  its  divisions,  may  have 
the  effect  of  ])roducing'  softening  in  a  limited  area  of  the  cortex. 

THE  ARTERIES  OF  THE  UPPER  EXTREMITY. 

The  artery  which  supplies  the  upper  extremity  continues  as  a  single  trunk 
from  its  commencement  down  to  the  elbow;  but  different  portions  of  it  have  received 
different  names,  according  to  the  regions  through  which  they  pass.  That  part 
of  the  vessel  which  extends  from  its  origin  to  the  outer  border  of  the  first  rib  is 
termed  the  subclavian;  beyond  this  point  to  the  lower  border  of  the  axilla  it  is 
named  the  axillary;  and  from  the  lower  margin  of  the  axillary  space  to  the  bend 
of  the  elbow  it  is  termed  brachial;  here  the  trunk  ends  by  dividing  into  two  branches 
the  radial  and  ulnar. 

THE  SUBCLAVIAN  ARTERY  (A.  SUBCLAVIA)  (Fig.  596). 

On  the  right  side  the  subclavian  artery  arises  from  the  innominate  artery  behind 
the  right  sternoclavicular  articulation;  on  the  left  side  it  springs  from  the  arch 
of  the  aorta.  The  two  vessels,  therefore,  in  the  first  part  of  their  course,  differ 
in  length,  direction,  and  relation  with  neighboring  structures. 

In  order  to  facilitate  the  description,  each  subclavian  artery  is  divided  into 
three  parts.  The  first  portion  extends  from  the  origin  of  the  vessel  to  the  medial 
border  of  the  Scalenus  anterior;  the  second  lies  behind  this  muscle;  and  the  third 
extends  from  the  lateral  margin  of  the  muscle  to  the  outer  border  of  the  first  rib, 
where  it  becomes  the  axillary  artery.  The  first  portions  of  the  two  vessels  require 
separate  descriptions;  the  second  and  third  parts  of  the  two  arteries  are  practically 
alike. 

First  Part  of  the  Right  Subclavian  Artery  (Figs.  583,  596). — The  first  part  of 
the  right  subclavian  artery  arises  from  the  innominate  artery,  behind  the  upper 
part  of  the  right  sternoclavicular  articulation,  and  passes  upward  and  lateralward 
to  the  medial  margin  of  the  Scalenus  anterior.  It  ascends  a  little  above  the  clavicle, 
the  extent  to  which  it  does  so  varying  in  dift'erent  cases. 

Relations. — It  is  covered,  in  Jront,  by  the  integument,  superficial  fascia,  Platysma,  deep  fascia, 
the  clavicular  origin  of  the  Sternocleidomastoideus,  the  Sternohyoideus,  and  Sternothyreoideus, 
and  another  layer  of  the  deep  fascia.  It  is  crossed  by  the  internal  jugular  and  vertebral  veins, 
by  the  vagus  nerve  and  the  cardiac  branches  of  the  vagus  and  sympathetic,  and  by  the  sub- 
clavian loop  of  the  sympathetic  trunk  which  forms  a  ring  around  the  vessel.  The  anterior  jugular 
vein  is  directed  lateralward  in  front  of  the  artery,  but  is  separated  from  it  by  the  Sternohj-oideus 
and  Sternothyreoideus.  Below  and  behind  the  artery  is  the  pleura,  which  separates  it  from  the 
apex  of  the  lung;  behind  is  the  sympathetic  trunk,  the  Longus  coUi  and  the  first  thoracic  vertebra. 
The  right  recurrent  nerve  winds  around  the  lower  and  back  part  of  the  vessel. 

First  Part  of  the  Left  Subclavian  Artery  (Fig.  583).— The  first  part  of  the  left 
subclavian  artery  arises  from  the  arch  of  the  aorta,  behind  the  left  common  carotid, 
and  at  the  level  of  the  fourth  thoracic  vertebra;  it  ascends  in  the  superior  medias- 
tinal cavity  to  the  root  of  the  neck  and  then  arches  lateralward  to  the  medial 
border  of  the  Scalenus  anterior. 

Relations. — It  is  in  relation,  in  front,  with  the  vagus,  cardiac,  and  phrenic  nerves,  which  he 
parallel  with  it,  the  left  common  carotid  artery,  left  internal  jugular  and  vertebral  veins,  and 
the  commencement  of  the  left  innominate  vein,  and  is  covered  by  the  Sternothj-reoideus,  Sterno- 
hj^oideus,  and  Sternocleidomastoideus;  behind,  it  is  in  relation  with  the  oesophagus,  thoracic 
duct,  left  recurrent  nerve,  inferior  cervical  ganglion  of  the  sympathetic  trunk,  and  Longus  colli; 
higher  up,  however,  the  oesophagus  and  thoracic  duct  he  to  its  right  side;  the  latter  ultimately 
arching  over  the  vessel  to  join  the  angle  of  union  between  the  subclavian  and  internal  jugular 
veins.  Medial  to  it  are  the  oesophagus,  trachea,  thoracic  duct,  and  left  recurrent  nerve;  lateral 
to  it,  the  left  pleura  and  lung. 


/ 


650 


A  XG 10  LOGY 


Second  and  Third  Parts  of  the  Subclavian  Artery  (Fig.  590). — The  second 
portion  of  the  subclavian  artery  lies  behind  the  Scalenus  anterior;  it  is  very  short, 
anrl  forms  the  highest  part  of  the  arch  described  by  the  vessel. 


Fig.  596. — Superficial  dissection  of  the  right  side  of  the  neck,  showing  the  carotid  and  subcla-vian  arteries. 

Relations. — It  is  covered,  in  front,  by  the  skin,  superficial  fascia,  Platysma,  deep  cervical 
fascia,  Stemocleidomastoideus,  and  Scalenus  anterior.  On  the  right  side  of  the  neck  the 
phrenic  nerv'e  is  separated  from  the  second  part  of  the  artery  by  the  Scalenus  anterior,  while 
on  the  left  side  it  crosses  the  first  part  cf  the  arterj'  close  to  the  medial  edge  of  the  muscle. 
Behind  the  vessel  are  the  pleura  and  the  Scalenus  medius;  above,  the  brachial  plexus  of  nerves; 
below,  the  pleura.  The  subclavian  vein  hes  below  and  in  front  of  the  artery,  separated  from  it 
by  the  Scalenus  anterior. 

The  third  portion  of  the  subclavian  artery  runs  downward  and  lateralward  from 
the  lateral  margin  of  the  Scalenus  anterior  to  the  outer  border  of  the  first  rib, 
where  it  becomes  the  axillary  artery.  This  is  the  most  superficial  portion  of  the 
vessel,  and  is  contained  in  the  subclavian  triangle  (see  page  645). 


THE  SL'BCLAVIAX  ARTERY  657 

Relations. — It  i.s  covered,  in  front,  by  the  skin,  the  sujjerficial  fascia,  the  Platysma,  the  supra- 
clavicular nerves,  and  the  deep  cervical  fascia.  The  external  jugular  vein  crosses  its  medial 
part  and  receives  the  transverse  scapular,  transverse  cervical,  and  anterior  jugular  veins,  which 
frequently  form  a  i>lexus  in  front  of  the  arter}^  Behind  the  veins,  the  nerve  to  the  Bubclavius 
descends  in  front  of  the  artery.  The  terminal  part  of  the  artery  lies  behind  the  clavicle  and  the 
Subclavius  and  is  crossed  by  the  transverse  scapular  vessels.  The  subclavian  vein  is  in  front 
of  and  at  a  slight Ij'  lower  level  than  the  arter3\  Behind,  it  lies  on  the  lowest  trunk  of  the  brachial 
plexus,  which  intervenes  between  it  and  the  Scalenus  medius.  Above  and  to  its  lateral  side  are 
the  upper  trunks  of  the  brachial  plexus  and  the  Omohyoideus.  Below,  it  rests  on  the  upper 
surface  of  tli(>  first  rib. 

Peculiarities. — The  subclavian  arteries  vary  in  their  origin,  their  course,  and  the  height  to 
which  they  rise  in  the  neck. 

The  origin  of  the  right  subclavian  from  the  innominate  takes  place,  in  some  cases,  above  the 
sternoclavicular  articulation,  and  occasionally,  but  less  frequently,  below  that  joint.  The  artery 
may  arise  as  a  separate  trunk  from  the  arch  of  the  aorta,  and  in  such  cases  it  may  be  either  the 
first,  second,  third,  or  even  the  last  branch  derived  from  that  vessel;  in  the  majority,  however, 
it  is  the  first  or  last,  rarety  the  second  or  third.  When  it  is  the  first  branch,  it  occupies  the  ordinary 
position  of  the  innominate  artery;  when  the  second  or  third,  it  gains  its  usual  position  by  passing 
behind  the  right  carotid;  and  when  the  last  branch,  it  arises  from  the  left  extremity  of  the  arch, 
and  passes  obhquely  toward  the  right  side,  usually  behind  the  trachea,  oesophagus,  and  right 
carotid,  sometimes  between  the  oesophagus  and  trachea,  to  the  upper  border  of  the  first  rib, 
whence  it  follows  its  ordinary  course.  In  very  rare  instances,  this  ves.sel  arises  from  the  thoracic 
aorta,  as  low  dowm  as  the  fourth  thoracic  vertebra.  Occasionally,  it  perforates  the  Scalenus 
anterior;  more  rarety  it  passes  in  front  of  that  muscle.  Sometimes  the  subclavian  vein  passes 
with  the  arterj^  behind  the  Scalenus  anterior.  The  artery  may  ascend  as  high  as  4  cm.  above 
the  clavicle,  or  any  intermediate  point  between  this  and  the  upper  border  of  the  bone,  the  right 
subclavian  usually  ascending  higher  than  the  left. 

The  left  subclavian  is  occasionally  joined  at  its  origin  with  the  left  carotid. 

The  left  subclavian  artery  is  more  deeplj^  placed  than  the  right  in  the  first  part  of  its  course, 
and,  as  a  rule,  does  not  reach  quite  as  high  a  level  in  the  neck.  The  posterior  border  of  the  Sterno- 
cleidomastoideus  corresponds  pretty  closely  to  the  lateral  border  of  the  Scalenus  anterior,  so 
that  the  thii-d  portion  of  the  artery,  the  part  most  accessible  for  operation,  lies  immediately 
lateral  to  the  posterior  border  of  the  Sternocleidomastoideus. 

Applied  Anatomy. — An  aneurism  may  form  on  any  part  of  the  subclavian  artery,  except  the 
intrathoracic  portion  of  the  left  vessel,  which  is  said  never  to  be  the  seat  of  anemism.  The  most 
common  site  is,  however,  the  third  portion,  especially  on  the  right  side,  on  account  of  the  greater 
exposm-e  to  injmy  and  the  greater  amovmt  of  use  of  the  right  upper  extremity.  In  this  situation 
it  may  cause  pressure  on  the  brachial  plexus,  producing  pain  and  numbness  in  the  arm  and  fingers, 
with  loss  of  power  or  paralysis  of  the  muscles  of  these  parts.  (Edema  of  the  arm  may  result 
from  pressure  on  the  subclavian  vein.  The  external  jugular  vein  may  become  distended  and 
varicose.  The  treatment  is  unsatisfactory,  since  proximal  ligature  cannot  be  undertaken  with 
much  chance  of  success.  If  constitutional  treatment  and  direct  pressm-e  on  the  aneurismal  sac 
fail,  the  best  treatment  is  excision  of  the  sac,  if  it  be  small.  In  aneurisms  of  the  first  portion  of 
this  artery  there  is  oedema  of  the  head  and  face,  with  lividity,  congestion  of  the  brain,  and  semi- 
consciousness from  pressure  on  the  internal  jugular  vein;  and  spasmodic  action  of  the  Diaphragma 
from  pressure  on  the  phrenic  nerve.  The  collateral  circulation  is  so  good  that  blocking  of  the 
subclavian  artery  by  embohsm  or  thi-ombosis  often  fails  to  give  rise  to  any  striking  signs  or 
sjTnptoms,  beyond  occasional  pains  in  the  neck  and  shoulder  and  some  degree  of  weakness  and 
wasting  in  the  muscles  of  the  arm. 

Compression  of  the  subclavian  artery  may  be  requii'ed  to  control  hemorrhage,  and  there  is  only 
one  situation  in  which  it  can  be  effectually  apphed,  viz.,  where  the  artery  passes  across  the  upper 
sm-face  of  the  first  rib.  In  order  to  compress  the  vessel  in  this  situation,  the  shoulder  should  be 
depressed,  and  the  surgeon  grasping  the  side  of  the  neck  should  press  with  his  thumb  in  the 
angle  formed  by  the  posterior  border  of  the  Sternocleidomastoideus  with  the  upper  border  of 
the  clavicle,  downward,  backward,  and  inward  against  the  rib;  if  from  any  cause  the  shoulder 
cannot  be  sufficiently  depressed,  pressure  may  be  made  from  before  backward,  so  as  to  compress 
the  artery  against  the  Scalenus  medius  and  transverse  process  of  the  seventh  cervical  vertebra. 
In  appropriate  cases,  a  preliminary  incision  may  be"  made  thi'ough  the  cervical  fascia,  and  the 
finger  may  be  pressed  do^-n  directly  upon  the  artery. 

Ligature  of  the  subclavian,  artery  may  be  required  in  cases  of  wounds,  or  of  aneurism  in  the 
axilla,  or  in  cases  of  anem-ism  on  the  cardiac  side  of  the  point  of  hgatm-e;  and  the  third  part  of 
the  arterj'  is  that  which  is  most  favorable  for  an  operation,  on  account  of  its  being  comparatively 
superficial,  and  most  remote  from  the  origin  of  the  large  branches.  In  those  cases  where  the 
clavicle  is  not  displaced,  this  operation  may  be  performed  with  comparative  facihty;  but  where 
the  clavicle  is  pushed  up  by  a  large  anemismal  tumor  in  the  axilla,  the  artery  lies  at  a  great  depth 
from  the  surface,  and  this  materialh'  increases  the  difficulty  of  the  operation.  Under  these 
42 


658  ANGIOLOGY 

circumstances,  it  becomes  a  matter  of  importance  to  consider  the  height  to  which  this  vessel  reaches 
above  the  bone.  In  ordinary  cases,  its  arch  is  about  1.25  cm.  above  the  clavicle,  occasionally 
as  high  as  4  cm.,  and  sometimes  so  low  as  to  be  on  a  level  with  its  upper  border.  If  the  clavicle 
be  displaced,  these  variations  wiU  necessarily  make  the  operation  more  or  less  difficult,  accord- 
ing as  the  vessel  is  less  or  more  accessible.  The  vessel  is  also  hgatured  as  a  preUminary  measure 
to  the  complete  interscapulothoracic  amputation  of  the  upper  extremity,  in  which  case  the 
transverse  scapular  and  transverse  cervical  arteries  may,  if  found,  be  ligatured  at  the  same  time, 
making  the  "fore-quarter"  amputation  an  almost  bloodless  procedure. 

The  procedure  in  the  operation  of  tying  the  third  portion  of  the  subclavian  artery  is  as  follows: 
The  patient  being  placed  on  a  table  in  the  supine  position,  with  the  head  drawn  over  to  the  oppo- 
site side,  and  the  shoulder  depressed  as  much  as  possible,  the  integument  should  be  pulled  down- 
ward over  the  clavicle,  and  an  incision  made  through  it,  upon  that  bone,  from  the  anterior  border 
of  the  Trapezius  to  the  posterior  border  of  the  Sternocleidomastoideus.  The  object  in  drawing 
the  skin  downward  is  to  avoid  any  risk  of  wounding  the  external  jugular  vein,  for  as  it  perforates 
the  deep  fascia  above  the  clavicle,  it  cannot  be  drawn  downward  with  the  skin.  The  soft  parts 
should  now  be  allowed  to  ghde  up,  and  the  cervical  fascia  divided  upon  a  director,  and  if  the 
interval  between  the  Trapezius  and  Sternocleidomastoideus  be  insufficient  for  the  performance 
of  the  operation,  a  portion  of  one  or  both  may  be  divided.  The  external  jugular  vein  will  now 
be  seen  toward  the  medial  side  of  the  wound;  this  and  the  transverse  scapular  and  transverse 
cervical  veins  which  end  in  it  should  be  held  aside.  If  the  external  jugular  vein  be  at  all  in  the 
way  and  exposed  to  injxiry,  it  should  be  tied  in  two  places  and  divided.  The  transverse  scapular 
artery  should  be  avoided,  and  the  Omohyoideus  held  aside  if  necessary.  In  the  space  beneath 
this  muscle,  careful  search  must  be  made  for  the  vessel;  a  deep  layer  of  fascia  and  some  connec- 
tive tissue  having  been  divided  carefully,  the  lateral  margin  of  the  Scalenus  anterior  muscle 
must  be  felt  for,  and  the  finger  being  guided  by  it  to  the  first  rib,  the  pulsation  of  the  subclavian 
artery  will  be  felt  as  it  passes  over  the  rib.  The  sheath  of  the  vessels  having  been  opened,  the 
aneurism  needle  may  then  be  passed  around  the  artery  from  above  downward  and  medialward 
so  as  to  avoid  including  any  of  the  branches  of  the  brachial  plexus.  If  the  clavicle  be  so  raised 
by  the  tumor  that  the  application  of  the  ligature  cannot  be  effected  in  this  situation,  the  artery 
may  be  tied  above  the  first  rib,  or  even  behind  the  Scalenus  anterior;  the  difficulties  of  the  opera- 
tion in  such  a  case  will  be  materially  increased,  on  account  of  the  greater  depth  of  the  artery, 
and  the  alteration  in  position  of  the  surrounding  parts. 

The  second  part  of  the  subclavian  artery,  the  portion  which  rises  highest  in  the  neck,  has  been 
considered  favorable  for  the  apphcation  of  the  hgature  when  it  is  difficult  to  tie  the  artery  in  the 
third  part  of  its  course.  There  are,  however,  many  objections  to  the  operation  in  this  situation. 
It  is  necessary  to  divide  the  Scalenus  anterior,  upon  which  hes  the  phrenic  nerve,  and  at  the 
medial  side  of  which  is  situated  the  internal  jugular  vein;  and  a  wound  of  either  of  these  struc- 
tures might  lead  to  the  most  dangerous  consequences.  Again,  the  artery  is  in  contact,  below, 
with  the  plem-a,  which  must  also  be  avoided;  and,  lastly,  the  proximity  of  so  many  of  its  large 
branches  arising  medially  to  this  point  must  be  a  stiU  further  objection  to  the  operation.  In 
cases,  however,  where  the  sac  of  an  axillary  aneurism  encroaches  on  the  neck,  it  may  be  necessary 
to  divide  the  lateral  half  or  two-thirds  of  the  Scalenus  anterior,  so  as  to  place  the  ligature  on  the 
vessel  at  a  greater  distance  from  the  sac.  The  operation  is  performed  exactly  in  the  same  way 
as  ligature  of  the  third  portion,  until  the  Scalenus  anterior  is  exposed,  when  it  is  to  be  divided 
on  a  director  (never  to  a  greater  extent  than  its  lateral  two-thirds),  and  it  immediately  retracts. 
The  operation  is  therefore  merely  an  extension  of  the  operation  for  hgature  of  the  third  portion 
of  the  vessel. 

In  those  cases  of  aneurism  of  the  axillary  or  subclavian  artery  which  encroach  upon  the 
lateral  portion  of  the  Scalenus  anterior  to  such  an  extent  that  a  hgature  cannot  be  appHed  in 
that  situation,  it  may  be  deemed  advisable,  as  a  last  resource,  to  tie  the  first  portion  of  the  sub- 
clavian artery.  On  the  left  side,  this  operation  is  almost  impracticable;  the  great  depth  of  the 
artery  from  the  surface,  its  intimate  relation  with  the  pleura,  and  its  close  proximity  to  the 
thoracic  duct  and  to  so  many  important  veins  and  nerves,  present  a  series  of  difficidties  which 
it  is  next  to  impossible  to  overcome. ^  On  the  right  side,  the  operation  is  practicable,  and  has 
been  performed  on  several  occasions.  The  main  objection  to  the  operation  in  this  situation  is 
the  smaUness  of  the  interval  which  usually  exists  between  the  commencement  of  the  vessel  and 
the  origin  of  the  nearest  branch.  The  operation  may  be  performed  in  the  following  manner: 
The  patient  being  placed  on  the  table  in  the  supine  position,  with  the  neck  extended,  an  incision 
should  be  made  along  the  upper  border  of  the  medial  part  of  the  clavicle,  and  a  second  along 
the  medial  border  of  the  Sternocleidomastoideus,  meeting  the  former  at  an  angle.  The  attach- 
ments of  both  heads  of  the  Sternocleidomastoideus  must  be  divided  on  a  director,  and  turned 
lateralward;  a  few  small  arteries  and  veins,  and  occasionally  the  anterior  jugular,  must  be  avoided, 
or,  if  necessary,  hgatured  in  two  places  and  divided,  and  the  Sternohyoideus  and  Sternothyreoideus 
divided  in  the  same  manner  as  the  preceding  muscle.    After  tearing  through  the  deep  fascia,  the 

'  The  operation  has,  however,  been  performed  by  J.  K.  Rodgers,  by  Halsted,  and  by  Schumpert. 


THE  SUBCLAVIAN  ARTERY  659 

internal  jugular  vein  will  be  seen  crossing  the  subclavian  artery;  this  should  be  pressed  aside, 
and  the  artery  secured  by  passing  the  needle  from  below  upward,  by  which  the  pleura  is  more 
effectually  avoided.  The  exact  position  of  the  vagus,  recurrent,  and  phrenic  nerves  and  the 
sympathetic  trunk  should  be  borne  in  mind,  and  the  ligature  should  be  appUed  near  the  origin 
of  the  vertebral,  in  order  to  afford  as  much  room  as  possible  for  the  formation  of  a  coagulum 
between  the  ligature  and  the  origin  of  the  vessel.  It  should  be  remembered  that  the  right  sub- 
clavian artery  is  occasionally  deeply  placed  in  the  first  part  of  its  course,  when  it  arises  from  the 
left  side  of  the  aortic  arch,  and  passes  in  such  cases  behind  the  oesophagus,  or  between  it  and  the 
trachea. 

Collateral  Circulation. — After  ligature  of  the  third  part  of  the  subclavian  artery,  the  collateral 
circulation  is  established  mainly  by  three  sets  of  vessels,  thus  described  in  a  dissection : 

1.  A  posterior  set,  consisting  of  the  transverse  scapular  and  the  descending  ramus  of  the  trans- 
verse cervical  branches  of  the  subclavian,  anastomosing  with  the  subscapular  from  the  axillary. 

2.  A  medial  set,  produced  by  the  connection  of  the  internal  mammary  on  the  one  hand,  with 
the  highest  intercostal  and  lateral  thoracic  arteries,  and  the  branches  from  the  subscapular  on 
the  other. 

3.  A  middle  or  axillary  set,  consisting  of  a  number  of  small  vessels  derived  from  branches  of 
the  subclavian,  above,  and,  passing  through  the  axilla,  terminating  either  in  the  main  trunk, 
or  some  of  the  branches  of  the  axillary  below.  This  last  set  presented  most  con.spicuously  the 
pecuhar  character  of  newly  formed  or,  rather,  dilated  arteries,  being  excessively  tortuous,  and 
forming  a  complete  plexus. 

The  chief  agent  in  the  restoration  of  the  axillary  artery  below  the  tumor  was  the  subscapular 
artery,  which  communicated  most  freely  with  the  internal  mammary,  transverse  scapular  and 
descending  ramus  of  the  transverse  cervical  branches  of  the  subclavian,  from  all  of  which  it 
received  so  great  an  influx  of  blood  as  to  dilate  it  to  three  times  its  natural  size.^ 

When  a  hgature  is  applied  to  the  first  part  of  the  subclavian  artery,  the  collateral  circulation  is 
carried  on  by :  (1)  the  anastomosis  between  the  superior  and  inferior  thyroids;  (2)  the  anastomosis 
of  the  two  vertebrals;  (3)  the  anastomosis  of  the  internal  mammary  with  the  inferior  epigastric 
and  the  aortic  intercostals;  (4)  the  costocervical  anastomosing  with  the  aortic  intercostals;  (5) 
the  profunda  cervicis  anastomosing  with  the  descending  branch  of  the  occipital;  (6)  the  scapular 
branches  of  the  thjTocervical  trunk  anastomosing  with  the  branches  of  the  axillary,  and  (7)  the 
thoracic  branches  of  the  axillary  anastomosing  with  the  aortic  intercostals. 

Branches. — The  branches  of  the  subclavian  artery  are: 

Vertebral.  Internal  mammary. 

Thyrocervical.  Costocervical. 

On  the  left  side  all  four  branches  generally  arise  from  the  first  portion  of  the 
vessel;  but  on  the  right  side  (Fig.  596)  the  costocervical  trunk  usually  springs 
from  the  second  portion  of  the  vessel.  On  both  sides  of  the  neck,  the  first  three 
branches  arise  close  together  at  the  medial  border  of  the  Scalenus  anterior;  in 
the  majority  of  cases,  a  free  interval  of  from  1.25  to  2,5  cm.  exists  between  the 
commencement  of  the  artery  and  the  origin  of  the  nearest  branch. 

1.  The  vertebral  artery  (a.  mrtebralis)  (Fig.  590),  is  the  first  branch  of  the  sub- 
clavian, and  arises  from  the  upper  and  back  part  of  the  first  portion  of  the  vessel. 
It  is  surrounded  by  a  plexus  of  nerve  fibres  derived  from  the  inferior  cervical 
ganglion  of  the  sympathetic  trunk,  and  ascends  through  the  foramina  in  the 
transverse  processes  of  the  upper  six  cervical  vertebrae  ;2  it  then  winds  behind  the 
superior  articular  process  of  the  atlas  and,  entering  the  skull  through  the  foramen 
magnum,  unites,  at  the  lower  border  of  the  pons,  with  the  vessel  of  the  opposite 
side  to  form  the  basilar  artery. 

Relations. — The  vertebral  artery  may  be  divided  into  four  parts:  The  first  part  rmis  upward 
and  backward  between  the  Longus  colli  and  the  Scalenus  anterior.  In  front  of  it  are  the  internal 
jugular  and  vertebral  veins,  and  it  is  crossed  by  the  inferior  thyroid  artery;  the  left  vertebral 
is  crossed  by  the  thoracic  duct  also.  Behind  it  are  the  transverse  process  of  the  seventh  cervical 
vertebra,  the  sympathetic  trimk  and  its  inferior  cervical  ganghon.  The  second  part  runs  upward 
through  the  foramina  in  the  transverse  processes  of  the  upper  six  cervical  vertebrae,  and  is  sur- 
rounded by  branches  from  the  inferior  cervical  sympathetic  ganghon  and  by  a  plexus  of  veins 

1  Guy's  Hospital  Reports,  vol.  i,  1S36.  Case  of  axillary  aneurism,  in  which  Aston  Key  had  tied  the  subclavian 
artery  on  the  lateral  edge  of  the  Scalenus  anterior,  twelve  years  previously. 

-  The  vertebral  artery  sometimes  enters  the  foramen  in  the  transverse  process  of  the  fifth  vertebra,  and  has  been 
seen  entering  that  of  the  seventh  vertebra. 


660  ANGIOLOGY 

which  unite  to  form  the  vertebral  w'm  at  the  lower  part  of  the  neck.  It  is  situated  in  front  of 
the  trunks  of  the  cervical  nerves,  and  pursues  an  almost  vertical  course  as  far  as  the  transverse 
process  of  the  atlas,  above  which  it  runs  upward  and  lateralward  to  the  foramen  in  the  trans- 
verse process  of  the  atlas.  The  third  part  issues  from  the  latter  foramen  on  the  medial  side  of 
the  Rectus  capitis  lateralis,  and  cur^'cs  backward  behind  the  superior  articular  process  of  the 
atlas,  the  anterior  ramus  of  the  first  cervical  nerve  being  on  its  medial  side;  it  then  lies  in  the 
groove  on  the  upper  surface  of  the  posterior  arch  of  the  atlas,  and  enters  the  vertebral  canal 
by  passing  beneath  the  posterior  atlantooccipital  membrane.  This  j)art  of  the  artery  is  covered 
by  the  Semispinalis  capitis  and  is  contained  in  the  suboccipital  triangle — a  triangular  space 
bounded  by  the  Rectus  capitis  posterior  major,  the  Obhquus  superior,  and  the  Obliquus  inferior. 
The  first  cervical  or  suboccipital  nerve  lies  between  the  artery  and  the  posterior  arch  of  the  atlas. 
The  fourth  part  pierces  the  dura  mater  and  inchnes  medialward  to  the  front  of  the  medulla 
oblongata;  it  is  placed  between  the  hypoglossal  nerve  and  the  anterior  root  of  the  first  cervical 
nerve  and  beneath  the  first  digitation  of  the  ligamentum  denticulatum.  At  the  lower  border 
of  the  pons  it  unites  with  the  vessel  of  the  opposite  side  to  form  the  basilar  artery. 

Branches. — The  branches  of  the  vertebral  artery  may  be  divided  into  two  sets: 
those  given  off  in  the  neck,  and  those  within  the  cranium. 

Cervical  Branches.  '  Cranial  Branches. 

SpinaL  Meningeal. 

Muscular.  Posterior  Spinal. 

Anterior  Spinal. 

Posterior  Inferior  Cerebellar. 

Medullary. 

Spinal  Branches  {rami  spinales)  enter  the  vertebral  canal  through  the  interverte- 
bral foramina,  and  each  divides  into  two  branches.  Of  these,  one  passes  along 
the  roots  of  the  nerves  to  supply  the  medulla  spinalis  and  its  membranes,  anasto- 
mosing with  the  other  arteries  of  the  medulla  spinalis;  the  other  divides  into  an 
ascending  and  a  descending  branch,  which  unite  with  similar  branches  from  the 
arteries  above  and  below,  so  that  two  lateral  anastomotic  chains  are  formed  on  the 
posterior  surfaces  of  the  bodies  of  the  vertebrae,  near  the  attachment  of  the  pedicles. 
From  these  anastomotic  chains  branches  are  supplied  to  the  periosteum  and  the 
bodies  of  the  vertebrae,  and  others  form  communications  with  similar  branches  from 
the  opposite  side;  from  these  communications  small  twigs  arise  which  join  similar 
branches  above  and  below,  to  form  a  central  anastomotic  chain  on  the  posterior 
surface  of  the  bodies  of  the  vertebrae. 

Muscular  Branches  are  given  off  to  the  deep  muscles  of  the  neck,  where  the 
vertebral  artery  curves  around  the  articular  process  of  the  atlas.  They  anastomose 
with  the  occipital,  and  with  the  ascending  and  deep  cervical  arteries. 

The  Meningeal  Branch  (ramus  meningeus;  posterior  meningeal  branch)  springs 
from  the  vertebral  opposite  the  foramen  magnum,  ramifies  between  the  bone 
and  dura  mater  in  the  cerebellar  fossa,  and  supplies  the  falx  cerebelli.  It  is  fre- 
quently represented  by  one  or  two  small  branches. 

The  Posterior  Spinal  Artery  {a.  spinalis  posterior;  dorsal  spinal  artery)  arises 
from  the  vertebral,  at  the  side  of  the  medulla  oblongata;  passing  backward,  it 
descends  on  this  structure,  lying  in  front  of  the  posterior  roots  of  the  spinal  nerves, 
and  is  reinforced  by  a  succession  of  small  branches,  which  enter  the  vertebral 
canal  through  the  intervertebral  foramina;  by  means  of  these  it  is  continued  to 
the  lower  part  of  the  medulla  spinalis,  and  to  the  cauda  equina.  Branches  from 
the  posterior  spinal  arteries  form  a  free  anastomosis  around  the  posterior  roots 
of  the  spinal  nerves,  and  communicate,  by  means  of  very  tortuous  transverse 
branches,  with  the  vessels  of  the  opposite  side.  Close  to  its  origin  each  gives  off 
an  ascending  branch,  which  ends  at  the  side  of  the  fourth  ventricle. 

The  Anterior  Spinal  Artery  (a.  spinalis  anterior;  ventral  spinal  artery)  is  a  small 
branch,  which  arises  near  the  termination  of  the  vertebral,  and,  descending  in 
front  of  the  medulla  oblongata,  unites  with  its  fellow  of  the  opposite  side  at  the 


THE  Si'BCL.WIAX  ARTERY  G61 

level  of  the  foramen  magnuni.  One  of  these  vessels  is  usually  larger  than  the  other, 
but  oeeasionally  they  are  about  equal  in  size.  The  siii<i;le  trunk,  thus  formed, 
descends  on  the  front  of  the  medulla  spinalis,  and  is  reinforced  by  a  succession 
of  small  branches  which  enter  the  vertebral  canal  through  the  intervertebral 
foramina;  these  branches  are  derived  from  the  vertebral  and  the  ascending  cervical 
of  the  inferior  thyroid  in  the  neck;  from  the  intercostals  in  the  thorax;  and  from 
the  lumbar,  iliolumbar,  and  lateral  sacral  arteries  in  the  abdomen  and  pelvis. 
They  unite,  by  means  of  ascending  and  descending  branches,  to  form  a  single 
anterior  median  artery,  which  extend  as  far  as  the  lower  part  of  the  medulla  spinalis, 
and  is  continued  as  a  slender  twig  on  the  filum  terminale.  This  vessel  is  placed 
in  the  pia  mater  along  the  anterior  median  fissure;  it  supplies  that  membrane,  and 
the  substance  of  the  medulla  spinalis,  and  sends  off  branches  at  its  lower  part  to 
be  distributed  to  the  cauda  equina. 

Applied  Anatomy. — Bleeding  into  the  membranes  or  into  the  substance  of  the  medulla  spinalis 
itself  is  not  common,  but  may  occur  from  injuries  received  at  birth  when  labor  is  unduly  pro- 
longed or  instruments  are  used.  It  is  also  met  with  in  chronic  insanity,  and  in  tetanus  or  strych- 
nine poisoning. 

The  Posterior  Inferior  Cerebellar  Artery  {a.  cerebeUi  inferior  posterior)  (Fig.  592), 
the  largest  branch  of  the  vertebral,  winds  backward  around  the  upper  part  of  the 
medulla  oblongata,  passing  between  the  origins  of  the  vagus  and  accessory  nerves, 
over  the  restiform  body  to  the  imder  surface  of  the  cerebellum,  w^here  it  divides 
into  two  branches.  The  medial  branch  is  continued  backward  to  the  notch  between 
the  two  hemispheres  of  the  cerebellum;  while  the  lateral  supplies  the  under  surface 
of  the  cerebellum,  as  far  as  its  lateral  border,  where  it  anastomoses  with  the  anterior 
inferior  cerebellar  and  the  superior  cerebellar  branches  of  the  basilar  artery. 
Branches  from  this  artery  supply  the  choroid  plexus  of  the  fourth  ventricle. 

The  Medullary  Arteries  (bulbar  arteries)  are  several  minute  vessels  which  spring 
from  the  vertebral  and  its  branches  and  are  distributed  to  the  medulla  oblongata. 

The  Basilar  Artery  (a.  basilaris)  (Fig.  592),  so  named  from  its  position  at  the 
base  of  the  skull,  is  a  single  trunk  formed  by  the  junction  of  the  two  vertebral 
arteries:  it  extends  from  the  lower  to  the  upper  border  of  the  pons,  lying  in  its 
median  groove,  under  cover  of  the  arachnoid.  It  ends  by  dividing  into  the  two 
posterior  cerebral  arteries. 

Its  branches,  on  either  side,  are  the  following: 

Pontine.  Anterior  Inferior  Cerebellar. 

Internal  Auditory.  Superior  Cerebellar. 

Posterior  Cerebral. 

The  pontine  branches  {rami  ad  pontem;  transverse  branches)  are  a  number  of  small 
vessels  which  come  off  at  right  angles  from  either  side  of  the  basilar  artery  and 
supply  the  pons  and  adjacent  parts  of  the  brain. 

The  internal  auditory  artery  (a.  auditiva  interna;  auditory  artery),  a  long  slender 
branch,  arises  from  near  the  middle  of  the  artery;  it  accompanies  the  acoustic  nerve 
through  the  internal  acoustic  meatus,  and  is  distributed  to  the  internal  ear. 

The  anterior  inferior  cerebellar  artery  (a.  cerebeUi  inferior  anterior)  passes  back- 
ward to  be  distributed  to  the  anterior  part  of  the  under  surface  of  the  cerebellum, 
anastomosing  with  the  posterior  inferior  cerebellar  branch  of  the  vertebral. 

The  superior  cerebellar  artery  («.  cerebeUi  superior)  arises  near  the  termination 
of  the  basilar.  It  passes  lateralward,  immediately  below  the  oculomotor  nerve, 
which  separates  it  from  the  posterior  cerebral  artery,  winds  around  the  cerebral 
peduncle,  close  to  the  trochlear  nerve,  and,  arriving  at  the  upper  surface  of  the 
cerebellum,  divides  into  branches  which  ramify  in  the  pia  mater  and  anastomose 
with  those  of  the  inferior  cerebellar  arteries.    Several  branches  are  given  to  the 


662  ANGIOLOGY 

pineal  body,  the  anterior  medullary  velum,  and  the  tela  chorioidea  of  the  third 
ventricle. 

The  posterior  cerebral  artery  {a.  cerebri  posterior)  (Figs.  592,  593,  594)  is  larger 
than  the  preceding,  from  which  it  is  separated  near  its  origin  by  the  oculomotor 
nerve.  Passing  lateralward,  parallel  to  the  superior  cerebellar  artery,  and  receiving 
the  posterior  communicating  from  the  internal  carotid,  it  winds  around  the  cerebral 
peduncle,  and  reaches  the  tentorial  surface  of  the  occipital  lobe  of  the  cerebrum, 
where  it  breaks  up  into  branches  for  the  supply  of  the  temporal  and  occipital 
lobes. 

The  branches  of  the  posterior  cerebral  artery  are  divided  into  two  sets,  ganglionic 
and  cortical: 

r  Posterior-medial . 


Ganglionic   ]  Posterior  Choroidal.       r    +•     i 
T-.     ,        1x1  ^  orticai 

IPostero-lateral. 


Anterior  Temporal. 
Posterior  Temporal. 
Calcarine. 
Parietooccipital. 

Ganglionic. — The  postero-medial  ganglionic  branches  (Fig.  595)  are  a  group  of 
small  arteries  which  arise  at  the  commencement  of  the  posterior  cerebral  artery; 
these,  with  similar  branches  from  the  posterior  communicating,  pierce  the  pos- 
terior perforated  substance,  and  supply  the  medial  surfaces  of  the  thalami  and  the 
walls  of  the  third  ventricle.  The  posterior  choroidal  branches  run  forward  beneath 
the  splenium  of  the  corpus  callosum,  and  supply  the  tela  chorioidea  of  the  third 
ventricle  and  the  choroid  plexus.  The  postero-lateral  ganglionic  branches  are  small 
arteries  which  arise  from  the  posterior  cerebral  artery  after  it  has  turned  around  the 
cerebral  peduncle;  they  supply  a  considerable  portion  of  the  thalamus. 

Cortical. — The  cortical  branches  are:  the  anterior  temporal,  distributed  to  the 
uncus  and  the  anterior  part  of  the  fusiform  gyrus;  the  posterior  temporal,  to  the 
fusiform  and  the  inferior  temporal  gyri;  the  calcarine,  to  the  cuneus  and  gyrus 
lingualis  and  the  back  part  of  the  convex  surface  of  the  occipital  lobe;  and  the 
parietooccipital,  to  the  cuneus  and  the  precuneus. 

2.  The  thyrocervical  trunk  {truncus  thyreocermcalis ;  thyroid  axis)  (Fig.  596)  is 
a  short  thick  trunk,  which  arises  from  the  front  of  the  first  portion  of  the  subclavian 
artery,  close  to  the  medial  border  of  the  Scalenus  anterior,  and  divides  almost 
immediately  into  three  branches,  the  inferior  thyroid,  transverse  scapular,  and  trans- 
verse cervical. 

The  Inferior  Thyroid  Artery  {a.  thyreoidea  inferior)  passes  upward,  in  front  of  the 
vertebral  artery  and  Longus  colli;  then  turns  medialward  behind  the  carotid  sheath 
and  its  contents,  and  also  behind  the  sympathetic  trunk,  the  middle  cervical 
ganglion  resting  upon  the  vessel.  Reaching  the  lower  border  of  the  thyroid  gland 
it  divides  into  two  branches,  which  supply  the  postero-inferior  parts  of  the  gland, 
and  anastomose  wdth  the  superior  thyroid,  and  with  the  corresponding  artery  of 
the  opposite  side.  The  recurrent  nerve  passes  upw^ard  generally  behind,  but  occa- 
sionally in  front,  of  the  artery. 

The  branches  of  the  inferior  thyroid  are : 

Inferior  Laryngeal . .  GEsophageal . 

Tracheal.  Ascending  Cervical. 

Muscular. 

The  inferior  laryngeal  artery  (a.  laryngea  inferior)  ascends  upon  the  trachea  to 
the  back  part  of  the  larynx  under  cover  of  the  Constrictor  pharyngis  inferior,  in 
company  w^ith  the  recurrent  nerve,  and  supplies  the  muscles  and  mucous  mem- 
brane of  this  part,  anastomosing  with  the  branch  from  the  opposite  side,  and  with 
the  superior  laryngeal  branch  of  the  superior  thyroid  artery. 

The  tracheal  branches  (rami  tracheales)  are  distributed  upon  the  trachea,  and 
anastomose  below  with  the  bronchial  arteries. 


THE  SUBCLAVIAN  ARTERY 


663 


Desc.  br.  of 
transverse  cervical 


Trati'fver'te  scapular 


Acromial  branch 
it  tlioiacoaooinial 


The  oesophageal  branches  {rami  ucsophagel)  supply  the  oesophagus,  and  anasto- 
mose with  the  (esophageal  branches  of  the  aorta. 

The  ascending  cervical  artery  {a.  cervicalis  ascendens)  is  a  small  branch  which 
arises  from  the  inferior  thyroid  as  that  vessel  is  passing  behind  the  carotid  sheath; 
it  runs  up  on  the  anterior  tubercles  of  the  transverse  processes  of  the  cervical 
vertebra  in  the  interval  between  the  Scalenus  anterior  and  Longus  capitis.  To 
the  muscles  of  the  neck  it  gives  .twigs  which  anastomose  with  branches  of  the  ver- 
tebral, and  it  sends  one  or  two  spinal  branches  into  the  vertebral  canal  through 
the  intervertebral  foramina  to  be  distributed  to  the  medulla  spinalis  and  its  mem- 
branes, and  to  the  bodies  of  the  vertebrae,  in  the  same  manner  as  the  spinal  branches 
from  the  vertebral.  It  anastomoses  with  the  ascending  pharyngeal  and  occipital 
arteries. 

The  muscular  branches  supply  the  depressors  of  the  hyoid  bone,  and  the  Longus 
colli.  Scalenus  anterior,  and  Constrictor  pharyngis  inferior. 

The  Transverse  Scapular  Artery  (a.  transversa  scapulae;  suprascapular  artery)  passes 
at  first  downward  and  lateralward  across  the  Scalenus  anterior  and  phrenic 
nerve,  being  covered  by  the 
Sternocleidomastoideus ;  it  then 
crosses  the  subclavian  artery 
and  the  brachial  plexus,  and 
runs  behind  and  parallel  with 
the  clavicle  and  Subclavius, 
and  beneath  the  inferior  belly 
of  the  Omohyoideus,  to  the 
superior  border  of  the  scapula; 
it  passes  over  the  superior 
transverse  ligament  of  the 
scapula  which  separates  it  from 
the  suprascapular  nerve,  and 
enters  the  supraspinatous  fossa 
(Fig.  597).  In  this  situation  it 
lies  close  to  the  bone,  and  rami- 
fies between  it  and  the  Supra- 
spinatus,  to  which  it  supplies 
branches.  It  then  descends  be- 
hind the  neck  of  the  scapula, 
through  the  great  scapular 
notch  and  under  cover  of  the 
inferior  transverse  ligament,  to 
reach  the  infraspinatous  fossa,  where  it  anastomoses  with  the  scapular  circumflex 
and  the  descending  branch  of  the  transverse  cervical.  Besides  distributing  branches 
to  the  Sternocleidomastoideus,  Subclavius,  and  neighboring  muscles,  it  gives  off  a 
suprasternal  branch,  which  crosses  over  the  sternal  end  of  the  clavicle  to  the  skin  of 
the  upper  part  of  the  chest;  and  an  acromial  branch,  which  pierces  the  Trapezius 
and  supplies  the  skin  over  the  acromion,  anastomosing  with  the  thoracoacromial 
artery.  As  the  artery  passes  over  the  superior  transverse  ligament  of  the  scapula, 
it  sends  a  branch  into  the  subscapular  fossa,  w^here  it  ramifies  beneath  the  Sub- 
scapularis,  and  anastomoses  with  the  subscapular  artery  and  with  the  descending 
branch  of  the  transverse  cervical.  It  also  sends  articular  branches  to  the  acro- 
mioclavicular and  shoulder-joints,  and  a  nutrient  artery  to  the  clavicle. 

The  Transverse  Cervical  Artery  (a.  transversa  colli;  transversalis  colli  artery)  lies 
at  a  higher  level  than  the  transverse  scapular;  it  passes  transversely  above  the 
inferior  belly  of  the  Omohyoideus  to  the  anterior  margin  of  the  Trapezius,  beneath 
which  it  divides  into  an  ascending  and  a  descending  branch.     It  crosses  in  front  of 


Fig.  597. — The  scapular  and  circumflex  arteries. 


664  AXGIOLOGY 

the  phrenic  nerve  and  the  Scaleni,  and  in  front  of  or  between  the  divisions  of  the 
brachial  plexus,  and  is  covered  by  the  Platysma  and  Sternocleidomastoideus,  and 
crossed  by  the  Omohyoideus  and  Trapezius. 

The  ascending  branch  (ramus  ascendens;  superficial  cervical  artery)  ascends  be- 
neath the  anterior  margin  of  the  Trapezius,  distributing  branches  to  it,  and  to  the 
neighboring  muscles  and  lymph  glands  in  the  neck,  and  anastomosing  with  the 
superficial  branch  of  the  descending  ramus  of  the  occipital  artery. 

The  descending  branch  {ramus  descendens;  posterior  scapular  artery)  (Fig.  597) 
passes  beneath  the  Levator  scapulae  to  the  medial  angle  of  the  scapula,  and  then 
descends  under  the  Rhomboidei  along  the  vertebral  border  of  that  bone  as  far  as 
the  inferior  angle.  It  supplies  the  Rhomboidei,  Latissimus  dorsi  and  Trapezius, 
and  anastomoses  with  the  transverse  scapular  and  subscapular  arteries,  and  with 
the  posterior  branches  of  some  of  the  intercostal  arteries. 

Peculiarities. — The  ascending  branch  of  the  transverse  cer^-ical  frequently  arises  direeth^ 
from  the  th\TocerA'ical  trunk;  and  the  descending  branch  from  the  third,  more  rarely  from  the 
second,  part  of  the  subclavian. 

3.  The  internal  mammary  artery  (a.  viammaria  interna)  (Fig.  59S)  arises  from 
the  under  surface  of  the  first  portion  of  the  subclavian,  opposite  the  thyro- 
cervical trunk.  It  descends  behind  the  cartilages  of  the  upper  six  ribs  at  a  distance 
of  about  1.25  cm.  from  the  margin  of  the  sternum,  and  at  the  level  of  the  sixth 
intercostal  space  divides  into  the  musculophrenic  and  superior  epigastric  arteries. 

Relations. — It  is  directed  at  first  downward,  forward,  and  medialward  behind  the  sternal 
end  of  the  clavicle,  the  subclavian  and  internal  jugular  veins,  and  the  first  costal  cartilage,  and 
passes  forward  close  to  the  lateral  side  of  the  innominate  vein.  As  it  enters  the  thorax  the  phrenic 
nerve  crosses  from  its  lateral  to  its  medial  side.  Below  the  first  costal  cartilage  it  descends  almost 
vertically  to  its  point  of  bifurcation.  It  is  covered  in  front  by  the  cartilages  of  the  upper  six 
ribs  and  the  intervening  Intercostales  interni  and  anterior  intercostal  membranes,  and  is  crossed 
by  the  terminal  portions  of  the  upper  six  intercostal  nerv-es.  It  rests  on  the  pleura,  as  far  as  the 
third  costal  cartilage;  below  this  level,  upon  the  Transversus  thoracis.  It  is  accompanied  by  a 
pair  of  veins;  these  tmite  above  to  form  a  single  vessel,  which  runs  medial  to  the  arterj'  and  ends 
in  the  corresponding  innominate  vein. 

Branches.- — The  branches  of  the  internal  mammary  are: 

Pericardiacophrenic.  Intercostal. 

Anterior  Mediastinal.  Perforating. 

Pericardial.  .  Musculophrenic. 
Sternal.  Superior  Epigastric. 

The  Pericardiacophrenic  Artery  (a.  pericardiacophrenica;  a.  comes  nervi  phrenici) 
is  a  long  slender  branch,  which  accompanies  the  phrenic  nerve,  between  the  pleura 
and  pericardium,  to  the  Diaphragma,  to  which  it  is  distributed;  it  anastomoses 
with  the  musculophrenic  and  inferior  phrenic  arteries. 

The  Anterior  Mediastinal  Arteries  (aa.  mediastinales  anteriores;  mediastinal  arte- 
ries) are  small  vessels,  distributed  to  the  areolar  tissue  and  lymph  glands  in  the 
anterior  mediastinal  cavity,  and  to  the  remains  of  the  thymus. 

The  Pericardial  Branches  supply  the  upper  part  of  the  anterior  surface  of  the 
pericardium;  the  lower  part  receives  branches  from  the  musculophrenic  artery. 

The  Sternal  Branches  (rami  sternales)  are  distributed  to  the  Transversus  thoracis, 
and  to  the  posterior  surface  of  the  sternum. 

The  anterior  mediastinal,  pericardial,  and  sternal  branches,  together  with  some 
twigs  from  the  pericardiacophrenic,  anastomose  with  branches  from  the  intercostal 
and  bronchial  arteries,  and  form  a  subpleural  mediastinal  plexus. 

The  Intercostal  Branches  (rami  intercostales;  anterior  intercostal  arteries)  supply 
the  upper  five  or  six  intercostal  spaces.  Two  in  number  in  each  space,  these  small 
vessels  pass  lateralward,  one  lying  near  the  lower  margin  of  the  rib  above,  and  the 


THE  SUBCLAVIAN  ARTERY 


665 


other  near  the  upper  marohi  of  the  rib  below,  and  anastomose  with  the  intercostal 
arteries  from  the  aorta.    They  are  at  first  situated  between  the  pleura  and  the 


Scalenus  anterior  — 


Musculophrenic  artery 


Thoraco-acrcmial  artery 

R —  / 


Common  carotid  artery 

nnominate  artery 
Internal  mammary  artery 


Perforating  branches 


Superior  epigastric  artery 


^^= — •  Inferior  epigastric  artery 


-s= —  External  iliac  artery 


Fig.  598. — The  internal  mammarj  arterj  and  its  branches. 

Intercostales  interni,  and  then  between  the  Intercostales  interni  and  externi. 
They  supply  the  Intercostales  and,  by  branches  which  perforate  the  Intercostales 
externi,  the  Pectorales  and  the  mamma. 


666  ANGIOLOGY 

The  Perforating  Branches  (rami  'perforcnites)  correspond  to  the  five  or  six  inter- 
costal spaces.  They  pass  forward  through  the  intercostal  spaces,  and,  curving 
lateralward,  supply  the  Pectoralis  major  and  the  integument.  Those  which  corre- 
spond to  the  second,  third,  and  fourth  spaces  give  branches  to  the  mamma,  and 
during  lactation  are  of  large  size. 

The  Musculophrenic  Artery  (a.  musculophrenica)  is  directed  obliquely  downward 
and  lateralward,  behind  the  cartilages  of  the  false  ribs;  it  perforates  the  Dia- 
phragma  at  the  eighth  or  ninth  costal  cartilage,  and  ends,  considerably  reduced 
in  size,  opposite  the  last  intercostal  space.  It  gives  off  intercostal  branches 
to  the  seventh,  eighth,  and  ninth  intercostal  spaces;  these  diminish  in  size  as  the 
spaces  decrease  in  length,  and  are  distributed  in  a  manner  precisely  similar  to  the 
intercostals  from  the  internal  mammary.  The  musculophrenic  also  gives  branches 
to  the  lower  part  of  the  pericardium,  and  others  which  run  backward  to  the  Dia- 
phragma,  and  downward  to  the  abdominal  muscles. 

The  Superior  Epigastric  Artery  (a.  epigastrica  superior)  continues  in  the  original 
direction  of  the  internal  mammary;  it  descends  through  the  interval  between  the 
costal  and  sternal  attachments  of  the  Diaphragma,  and  enters  the  sheath  of  the 
Rectus  abdominis,  at  first  lying  behind  the  muscle,  and  then  perforating  and  sup- 
plying it,  and  anastomosing  with  the  inferior  epigastric  artery  from  the  external 
iliac.  Branches  perforate  the  anterior  wall  of  the  sheath  of  the  Rectus,  and  supply 
the  muscles  of  the  abdomen  and  the  integument,  and  a  small  branch  passes  in 
front  of  the  xiphoid  process  and  anastornoses  with  the  artery  of  the  opposite  side. 
It  also  gives  some  twigs  to  the  Diaphragma,  w^hile  from  the  artery  of  the  right 
side  small  branches  extend  into  the  falciform  ligament  of  the  liver  and  anastomose 
with  the  hepatic  artery. 

Applied  Anatomy. — The  internal  mammary  artery  is  liable  to  be  wounded  in  stabs  of  the 
chest  wall  and  in  the  operation  of  paracentesis  pericardii  (p.  603).  It  is  most  easily  reached 
by  a  transverse  incision  in  the  second  intercostal  space. 

4.  The  costocervical  trunk  {truncus  costocervicalis ;  superior  intercostal  artery) 
(Fig.  590)  arises  from  the  upper  and  back  part  of  the  subclavian  artery,  behind 
the  Scalenus  anterior  on  the  right  side,  and  medial  to  that  muscle  on  the  left  side. 
Passing  backward,  it  gives  off  the  profunda  cervicalis,  and,  continuing  as  the  highest 
intercostal  artery,  descends  behind  the  pleura  in  front  of  the  necks  of  the  first  and 
second  ribs,  and  anastomoses  with  the  first  aortic  intercostal.  As  it  crosses  the 
neck  of  the  first  rib  it  lies  medial  to  the  anterior  division  of  the  first  thoracic  nerve, 
and  lateral  to  the  first  thoracic  ganglion  of  the  sympathetic  trunk. 

In  the  first  intercostal  space,  it  gives  off  a  branch  which  is  distributed  in  a 
manner  similar  to  the  distribution  of  the  aortic  intercostals.  The  branch  for  the 
second  intercostal  space  usually  joins  with  one  from  the  highest  aortic  intercostal 
artery.  This  branch  is  not  constant,  but  is  more  commonly  found  on  the  right 
side;  when  absent,  its  place  is  supplied  by  an  intercostal  branch  from  the  aorta. 
Each  intercostal  gives  oft'  a  posterior  branch  which  goes  to  the  posterior  vertebral 
muscles,  and  sends  a  small  spinal  branch  through  the  corresponding  intervertebral 
foramen  to  the  medulla  spinalis  and  its  membranes. 

The  Profunda  Cervicalis  {a.  cervicalis  profunda;  deep  cervical  branch)  arises,  in 
most  cases,  from  the  costocervical  trunk,  and  is  analogous  to  the  posterior  branch 
of  an  aortic  intercostal  artery:  occasionally  it  is  a  separate  branch  from  the  sub- 
clavian artery.  Passing  backward,  above  the  eighth  cervical  nerve  and  between 
the  transverse  process  of  the  seventh  cervical  vertebra  and  the  neck  of  the  first  rib, 
it  runs  up  the  back  of  the  neck,  between  the  Semispinales  capitis  and  colli,  as  high 
as  the  axis  vertebra,  supplying  these  and  adjacent  muscles,  and  anastomosing  with 
the  deep  division  of  the  descending  branch  of  the  occipital,  and  with  branches  of 
the  vertebral.  It  gives  off  a  spinal  twig  which  enters  the  canal  through  the  inter- 
vertebral foramen  between  the  seventh  cervical  and  first  thoracic  vertebrae. 


THE  AXILLA  ()67 


THE    AXILLA. 


The  axilla  is  a  p}Tamidal  space,  situated  between  the  upper  lateral  part  of  the 
chest  and  the  medial  side  of  the  arm. 

Boundaries. — The  apex,  which  is  directed  upward  toward  the  root  of  the  neck, 
corresponds  to  the  interval  between  the  outer  border  of  the  first  rib,  the  superior 
border  of  the  scapula,  and  the  posterior  surface  of  the  clavicle,  and  through  it 
the  axillary  vessels  and  nerves  pass.  The  base,  directed  downward,  is  broad  at 
the  chest  but  narrow  and  pointed  at  the  arm;  it  is  formed  by  the  integument  and  a 
thick  layer  of  fascia,  the  axillary  fascia,  extending  between  the  lower  border  of  the 
Pectoralis  major  in  front,  and  the  lower  border  of  the  Latissimus  dorsi  behind. 
.  The  anterior  wall  is  formed  by  the  Pectorales  major  and  minor,  the  former  covering 
the  whole  of  this  wall,  the  latter  only  its  central  part.  The  space  between  the  upper 
border  of  the  Pectoralis  minor  and  the  clavicle  is  occupied  by  the  coracoclavicular 
fascia.  The  posterior  wall,  which  extends  somewhat  lower  than  the  anterior,  is 
formed  by  the  Subscapularis  above,  the  Teres  major  and  Latissimus  dorsi  below. 
On  the  medial  side  are  the  first  four  ribs  with  their  corresponding  Intercostales, 
and  part  of  the  Serratus  anterior.  On  the  lateral  side,  where  the  anterior  and 
posterior  walls  converge,  the  space  is  narrow,  and  bounded  by  the  humerus,  the 
Coracobrachialis,  and  the  Biceps  brachii. 

Contents. — It  contains  the  axillary  vessels,  and  the  brachial  plexus  of  nerves, 
with  their  branches,  some  branches  of  the  intercostal  nerves,  and  a  large  number 
of  lymph  glands,  together  with  a  quantity  of  fat  and  loose  areolar  tissue.  The 
axillary  artery  and  vein,  with  the  brachial  plexus  of  nerves,  extend  obliquely  along 
the  lateral  boundary  of  the  axilla,  from  its  apex  to  its  base,  and  are  placed  much 
nearer  to  the  anterior  than  to  the  posterior  wall,  the  vein  lying  to  the  thoracic  side 
of  the  artery  and  partially  concealing  it.  At  the  forepart  of  the  axilla,  in  contact 
with  the  Pectorales,  are  the  thoracic  branches  of  the  axillary  artery,  and  along 
the  lower  margin  of  the  Pectoralis  minor  the  lateral  thoracic  artery  extends  to  the 
side  of  the  chest.  At  the  back  part,  in  contact  with  the  lower  margin  of  the  Sub- 
scapularis, are  the  subscapular  vessels  and  nerves;  winding  around  the  lateral 
border  of  this  muscle  are  the  scapular  circumflex  vessels;  and,  close  to  the  neck 
of  the  humerus,  the  posterior  humeral  circumflex  vessels  and  the  axillary  nerve 
curve  backward  to  the  shoulder.  Along  the  medial  or  thoracic  side  no  vessel  of 
any  importance  exists,  the  upper  part  of  the  space  being  crossed  merely  by  a  few 
small  branches  from  the  highest  thoracic  artery.  There  are  some  important  nerves, 
however,  in  this  situation,  viz.,  the  long  thoracic  nerve,  descending  on  the  surface 
of  the  Serratus  anterior,  to  which  it  is  distributed;  and  the  intercostobrachial 
nerve,  perforating  the  upper  and  anterior  part  of  this  wall,  and  passing  across  the 
axilla  to  the  medial  side  of  the  arm. 

The  position  and  arrangement  of  the  lymph  glands  are  described  on  pages  780 
arid  781. 

Applied  Anatomy. — The  axilla  is  a  space  of  considerable  surgical  importance.  It  transmits 
the  large  vessels  and  nerves  to  the  upper  extremity,  and  these  may  be  the  seat  of  injury  or  disease; 
it  contains  numerous  lymph  glands  which  may  require  removal;  in  it  is  a  quantity  of  loose  con- 
nective and  adipose  tissue  which  may  be  readily  infiltrated  with  blood  or  inflammatory  exuda- 
tion; and  it  may  be  the  seat  of  rapidly  growing  tumors.  Moreover,  it  is  covered  at  its  base  by 
thin  skin,  which  is  largely  supphed  with  sebaceous  and  sweat  glands,  and  is  frequently  the  seat 
of  small  cutaneous  abscesses  and  boils. 

Penetrating  wounds  in  the  axilla  are  sometimes  accompanied  by  extensive  hemorrhage,  either 
from  wounds  of  the  main  vessels,  or  of  one  of  the  large  branches  of  the  axillary  artery,  e.  g.,  the 
lateral  thoracic  or  the  subscapular.  Where  the  blood  cannot  find  an  easy  exit  externally,  it 
collects  in  the  axillary  space  and  forms  a  large  swelling  which  projects  in  the  floor  of  the  axilla 
and  also  bulges  forward  the  PectoraHs  major.  The  treatment  consists  in  freely  opening  up  the 
cavity  and  searching  for  and  securing  the  bleeding  vessel. 


668  AKGIOLOGY 

When  suppuration  occurs  in  the  axilla,  the  arrangement  of  the  fascia?  plays  a  very  important 
part  in  the  direction  which  the  pus  takes.  As  described  on  page  528,  the  coracoclavicular  fascia, 
after  covering  in  the  space  between  the  clavicle  and  the  upper  border  of  the  PectoraUs  minor 
splits  to  enclose  this  muscle,  and,  reblending  at  its  lower  border,  becomes  incorporated  with 
the  axillarj'  fascia  at  the  anterior  fold  of  the  axilla.  Suppuration  may  take  place  either  superficial 
to  or  beneath  this  layer  of  fascia;  that  is,  either  between  the  Pectorales  or  behind  the  PectoraUs 
minor;  in  the  former  case,  the  abscess  would  point  either  at  the  anterior  border  of  the  axillary 
fold,  or  in  the  groove  between  the  Deltoideus  and  the  Pectoralis  major;  in  the  latter,  the  pus 
would  have  a  tendency  to  surround  the  vessels  and  nerves,  and  ascend  into  the  neck,  that  being 
the  direction  in  which  there  is  lea.st  resistance.  Its  progress  toward  the  surface  is  prevented  by 
the  axillarj^  fascia;  its  progress  backward,  by  the  insertion  of  the  Serratus  anterior;  forward, 
by  the  coracoclavicular  fascia;  medialward,  by  the  wall  of  the  thorax;  and  lateralward,  by  the 
upper  limb.  The  pus  in  these  cases,  after  extending  into  the  neck,  has  been  known  to  spread 
through  the  superior  opening  of  the  thorax  into  the  mediastinal  cavity.  Instances  have  been 
recorded  where  the  pus  found  its  way  along  the  course  of  the  vessels  into  the  upper  arm. 

When  opening  an  axillary  abscess,  the  knife  should  be  entered  in  the  floor  of  the  axilla,  midwaj' 
between  the  anterior  and  posterior  margins  and  near  the  thoracic  side  of  the  space.  After  an 
incision  has  been  made  through  the  skin  and  fascia  it  is  well  to  use  a  director  and  dressing  forceps 
in  the  manner  directed  by  Hilton. 

The  relations  of  the  vessels  and  nerves  in  the  several  parts  of  the  axilla  are  important,  for  it 
is  the  almost  universal  plan,  in  the  present  day,  to  remove  the  glands  from  the  axilla  in  operating 
for  cancer  of  the  breast.  In  performing  such  an  operation,  it  is  necessary  to  proceed  with  much 
caution  in  the  direction  of  the  lateral  wall  and  apex  of  the  space,  as  here  the  axillary  vessels 
are  in  danger  of  being  wounded.  The  subscapular,  scapular  circumflex,  and  posterior  humeral 
circumflex  vessels  on  the  posterior  wall  and  the  thoracic  branches  along  the  anterior  wall  must 
be  avoided.  In  clearing  out  the  axilla,  the  axillary  vein  should  be  first  defined  and  traced  up 
to  the  apex  of  the  space  by  means  of  a  director.  The  Pectoralis  major  is  retracted  by  an  assistant ; 
or,  as  is  more  commonly  the  practice  in  the  present  day,  the  sternocostal  origin  of  this  muscle 
is  first  removed.  This  proceeding  not  only  lessens  the  chance  of  recurrence  of  the  disease,  but 
also  enables  the  surgeon  to  clear  out  the  axillary  cavity  more  thoroughly.  TMien  the  apex  of 
the  space  is  reached  all  fat  and  glands  must  be  carefully  removed  and  the  whole  axilla  cleared 
by  separating  the  tissues  along  the  medial  and  posterior  walls,  so  that  when  the  proceeding  is 
completed  the  axilla  is  emptied  of  all  its  contents  except  the  main  vessels  and  nerves. 

The  Axillary  Artery  (A.  Axillaris)  (Fig.  599). 

The  axillary  artery,  the  continuation  of  the  subclavian,  commences  at  the  outer 
border  of  the  first  rib,  and  ends  at  the  lower  border  of  the  tendon  of  the  Teres 
major,  where  it  takes  the  name  of  brachial.  Its  direction  varies  with  the  position 
of  the  limb;  thus  the  vessel  is  nearly  straight  when  the  arm  is  directed  at  right 
angles  with  the  trunk,  concave  upward  when  the  arm  is  elevated  above  this,  and 
convex  upward  and  lateralward  when  the  arm  lies  by  the  side.  At  its  origin  the 
artery  is  very  deeply  situated,  but  near  its  termination  is  superficial,  being  covered 
only  b}^  the  skin  and  fascia.  To  facilitate  the  description  of  the  vessel  it  is  divided 
into  three  portions;  the  first  part  lies  above,  the  second  behind,  and  the  third 
below  the  Pectoralis  minor. 

Relations. — The  first  portion  of  the  axillary  artery  is  covered  anteriorly  by  the  clavicular 
portion  of  the  PectoraHs  major  and  the  coracocla\'icular  fasca,  and  is  crossed  by  the  lateral 
anterior  thoracic  nerve,  and  the  thoracoacromial  and  cephahc  veins;  posterior  to  it  are  the  first 
intercostal  space,  the  corresponding  Inter costalis  externus,  the  first  and  second  digitations  of 
the  Serratus  anterior,  and  the  long  thoracic  and  medial  anterior  thoracic  nerves,  and  the  medial 
cord  of  the  brachial  plexus;  on  its  lateral  side  is  the  brachial  plexus,  from  which  it  is  separated 
by  a  little  areolar  tissue;  on  its  medial,  or  thoracic  side,  is  the  axillary  vein  which  overlaps  the 
artery.  It  is  enclosed,  together  wath  the  axillary  vein  and  the  brachial  plexus,  in  a  fibrous  sheath 
— the  axillary  sheath — continuous  above  with  the  deep  cervical  fascia. 

The  second  portion  of  the  axillary  artery  is  covered,  anteriorly,  by  the  Pectorales  major  and 
minor;  posterior  to  it  are  the  posterior  cord  of  the  brachial  plexus,  and  some  areolar  tissue  which 
intervenes  between  it  and  the  Subscapularis;  on  the  medial  side  is  the  axillary  vein,  separated 
from  the  artery  by  the  medial  cord  of  the  brachial  plexus  and  the  medial  anterior  thoracic  nerve; 
on  the  lateral  side  is  the  lateral  cord  of  the  brachial  plexus.  The  brachial  plexnis  thus  smrounds 
the  artery  on  three  sides,  and  separates  it  from  direct  contact  with  the  vein  and  adjacent  muscles. 

The  tldrd  portion  of  the  axillary  artery  extends  from  the  lower  border  of  the  PectoraUs  minor 
to  the  lower  border  of  the  tendon  of  the  Teres  major.    In  front,  it  is  covered  by  the  lower  part 


THE  AXILLARY  ARTERY 


669 


of  the  Pectoralis  major  above,  but  only  b\-  the  integument  and  fascia  below;  behind,  it  is  in  rela- 
tion with  the  lower  part  of  the  Subscapularis,  and  the  tendons  of  the  Latissimus  dorsi  and  Teres 
major;  on  its  lateral  side  is  the  Coracobrachialis,  and  on  its  medial  or  thoracic  side,  the  axillarj- 
vein.  The  nerves  of  the  brachial  plexus  bear  the  following  relations  to  this  part  of  the  artery: 
on  the  lateral  side  are  the  lateral  head  and  the  trunk  of  the  median,  and  the  musculocutaneous 
for  a  short  distance;  on  the  /nedial  side  the  ulnar  (between  the  vein  and  artery)  and  medial  brachial 
cutaneous  (to  the  medial  side  of  the  vein);  in  front  are  the  medial  head  of  the  median  and  the 
medial  antibrachial  cutaneous,  and  behind,  the  radial  and  axiUary,  the  latter  onh-  as  far  as  the 
lower  border  of  the  Subscapularis. 


Anterior 
humeral 
circuvijUx      I 


Fig.  599. — The  axillan-  artery  and  its  branches. 


Applied  Anatomy. — Compression  of  the  vessel  may  be  required  in  the  removal  of  tumors,  or 
in  amputation  of  the  upper  part  of  the  arm;  and  the  only  situation  in  which  this  can  be  effectuallj' 
made  is  in  the  lower  part  of  its  course;  by  pressing  it  against  the  humerus  in  this  situation,  the 
circulation  may  be  effectually  arrested. 

With  the  exception  of  the  pophteal,  the  axillary  artery  is  perhaps  more  frequently  lacerated 
than  any  other  arterj'  in  the  body  by  ^-iolent  movements,  especiallj'  in  those  cases  where  its 
coats  are  diseased.  It  has  occasionally  been  ruptured  in  attempts  to  reduce  old  dislocations 
of  the  shoulder-joint.  This  lesion  is  most  likely  to  occur  diu-ing  the  preliminary  breaking  down 
of  adhesions,  in  cases  where  the  ai'ten,-  has  become  fixed  to  the  capsule  of  the  joint.  Aneurism 
of  the  axillary  artery  sometimes  occurs;  a  large  number  of  the  cases  are  traumatic  in  their  origin, 
due  to  the  injmies  to  which  the  artery  is  exposed  in  the  varied,  extensive,  and  often  violent 
movements  of  the  limb. 

The  application  of  a  ligature  to  the  axillary  artery  may  be  requii-ed  in  cases  of  aneurism  of  the 
upper  part  of  the  brachial,  or  as  a  distal  operation  for  anem-ism  of  the  subclavian;  and  there  are 
only  two  situations  in  which  it  can  be  secured,  ■sdz.,  in  the  first  and  in  the  thii'd  parts  of  its  coiu*se; 
for  the  second  part  of  the  artery  is  so  deeph"  seated,  and  so  closely  surroimded  with  large  nerve 
trimks,  that  the  application  of  a  hgatm-e  to  it  there  would  be  almost  impracticable. 

In  the  third  part  of  its  course  the  operation  is  simple,  and  maj-  be  performed  in  the  following 
manner.  The  arm  is  separated  from  the  side,  with  the  hand  supiaated,  and  an  incision  about 
5  cm.  in  length  is  made  through  the  integimient  forming  the  floor  of  the  axilla,  a  Little  nearer  to 
the  anterior  than  to  the  posterior  fold  of  the  axilla.  After  carefully  dissecting  thi'ough  the  areolar 
tissue  and  fascia,  the  median  nerve  and  axillary  vein  are  exposed:  the  nerve  is  displaced  to  the 


670  A  NG 10  LOGY 

lateral,  and  the  vein  to  the  medial  side  of  the  arm,  the  elbow  being  at  the  same  time  bent  so  as  to 
relax  the  structm-es  and  facilitate  their  separation;  the  hgature  may  be  passed  around  the  artery 
from  the  ulnar  to  the  radial  side.  This  portion  of  the  artery  is  occasionally  crossed  by  a  muscular 
slip,  the  axillary  arch  (p.  524),  derived  from  the  Latissimus  dorsi. 

The  first  porlion  of  the  axillary  artery  may  be  tied  in  cases  of  aneurism  encroaching  so  far 
upward  that  a  ligatiu-e  cannot  be  apphed  to  the  lower  part  of  the  artery.  Notwithstanding  that 
this  operation  has  been  performed  in  some  few  patients  with  success,  its  performance  is  attended 
with  much  difficulty  and  danger.  The  student  will  remark  that,  in  this  situation,  it  would  be 
necessary  to  divide  a  thick  muscle,  and,  after  incising  the  coracoclavicular  fascia,  the  artery  would 
be  exposed  at  the  bottom  of  a  more  or  less  deep  space,  with  the  cephaUc  and  axillary  veins  in  such 
relation  with  it  as  must  render  the  appUcation  of  a  Mgature  to  it  particularly  hazardous.  Under 
such  circumstances,  it  is  an  easier  and,  at  the  same  time,  more  advisable  operation,  to  tie  the 
third  part  of  the  subclavian  artery.  The  first  part  of  the  axillary  can  be  best  secured  by  a  curved 
incision  with  the  convexity  downward  from  a  point  1.25  cm.  lateral  to  the  sternoclavicular  joint 
to  a  point  1.25  cm.  on  the  medial  side  of  the  coracoid  process.  The  limb  is  to  be  well  abducted 
and  the  head  inclined  to  the  opposite  side,  and  the  incision  carried  through  the  superficial  struc- 
tures, care  being  taken  of  the  cephahc  vein  at  the  lateral  angle  of  the  incision.  The  clavicular 
origin  of  the  PectoraUs  major  is  then  divided  in  the  whole  extent  of  the  wound.  The  arm  is  now 
brought  to  the  side,  and  the  upper  edge  of  the  Pectoralis  minor  defined  and  drawn  downward. 
The  coracoclavicular  fascia  is  carefully  divided  on  a  director,  close  to  the  coracoid  process,  and 
the  axillary  sheath  exposed;  this  is  to  be  opened  with  special  care  on  account  of  the  vein  over- 
lapping the  artery.    The  needle  should  be  passed  from  below,  so  as  to  avoid  wounding  the  vein.' 

Collateral  Circulation  after  Ligature  of  the  Axillary  Artery, — If  the  artery  be  tied  above  the 
origin  of  the  thoracoacromial,  the  collateral  circulation  will  be  carried  on  by  the  same  branches 
as  after  the  ligature  of  the  third  part  of  the  subclavian  (p.  658);  if  at  a  lower  point,  between  the 
thoracoacromial  and  the  subscapular,  the  latter  vessel,  by  its  free  anastomosis  with  the  trans- 
verse scapular  and  transverse  cervical  branches  of  the  subclavian,  will  become  the  chief  agent 
in  carrying  on  the  circulation;  the  lateral  thoracic,  if  it  be  below  the  hgatm-e,  will  materially  contrib- 
ute by  its  anastomoses  with  the  intercostal  and  internal  mammary  arteries.  If  the  point  included 
in  the  ligature  is  below  the  origin  of  the  subscapular  artery,  it  wiU  most  probably  also  be  below 
the  origins  of  the  two  humeral  circumflex  arteries.  The  chief  agents  in  restoring  the  circulation 
wiU  then  be  the  subscapular  and  the  two  humeral  circumflex  arteries  anastomosing  with  the 
a.  profunda  brachii. 

Branches.- — The  branches  of  the  axillary  are : 

From  first  part,  Highest  Thoracic.  From  second  part  \  t  „j-„_„i  Thoracic' 

[Subscapular. 
From  third  part    s  Posterior  Humeral  Circumflex. 
[Anterior  Humeral  Circumflex. 

1.  The  highest  thoracic  artery  (a.  thoracalis  suprema;  superior  thoracic  artery) 
is  a  small  vessel,  which  may  arise  from  the  thoracoacromial.  Running  forward 
and  medialward  along  the  upper  border  of  the  Pectoralis  minor,  it  passes  between 
it  and  the  Pectoralis  major  to  the  side  of  the  chest.  It  supplies  branches  to  these 
muscles,  and  to  the  parietes  of  the  thorax,  and  anastomoses  with  the  internal  mam- 
mary and  intercostal  arteries. 

2.  The  thoracoacromial  artery  (a.  thoracoacromialis;  acromiothoracic  artery;  tho- 
racic axis)  is  a  short  trunk,  which  arises  from  the  forepart  of  the  axillary  artery, 
its  origin  being  generally  overlapped  by  the  upper  edge  of  the  Pectoralis  minor 
Projecting  forward  to  the  upper  border  of  this  muscle,  it  pierces  the  coracoclavicular 
fascia  and  divides  into  four  branches — pectoral,  acromial,  clavicular,  and  deltoid. 
The  pectoral  branch  descends  between  the  two  Pectorales,  and  is  distributed  to 
them  and  to  the  mamma,  anastomosing  with  the  intercostal  branches  of  the  internal 
mammary  and  with  the  lateral  thoracic.  The  acromial  branch  runs  lateralward 
over  the  coracoid  process  and  under  the  Deltoideus,  to  which  it  gives  branches; 
it  then  pierces  that  muscle  and  ends  on  the  acromion  in  an  arterial  network  formed 
by  branches  from  the  transverse  scapular,  thoracoacromial,  and  posterior  humeral 
circumflex  arteries.  The  clavicular  branch  runs  upward  and  medialward  to  the 
sternoclavicular   joint,  supplying  this   articulation,    and   the   Subclavius.     The 


THE  AXILLARY  ARTERY 


671 


Besc.  ir.  of 
transverse  cervical 


Transverse  scapular 


yicromial  branch 
[LO-atiuinial 


deltoid  {hiiincral)  branch,  often  arising  with  the  acromial,  crosses  over  the  PectoraUs 
minor  and  passes  in  the  same  groove  as  the  cephalic  vein,  between  the  Pectoralis 
major  and  Deltoideiis,  and  gives  branches  to  both  muscles. 

3.  The  lateral  thoracic  artery  (a.  ihoracalis  lateralis;  long  thoracic  artery;  external 
mammari/  artery)  follows  the  lower  border  of  the  Pectoralis  minor  to  the  side  of 
the  chest,  sui)plying  the  Serratus  anterior  and  the  Pectoralis,  and  sending  branches 
across  the  axilla  to  the  axillary  glands  and  Subscapularis;  it  anastomoses  with  the 
internal  mammary,  subscapular,  and  intercostal  arteries,  and  with  the  pectoral 
branch  of  the  thoracoacromial.  In  the  female  it  supplies  an  external  mammary 
branch  which  turns  round  the  free  edge  of  the  Pectoralis  major  and  supplies  the 
mamma. 

4.  The  subscapular  artery  (a.  subscapularis)  the  largest  branch  of  the  axillary 
artery,  arh'es  at  the  lower  border  of  the  Subscapularis,  which  it  follows  to  the  in- 
ferior angle  of  the  scapula,  where  it  anastomoses  wdth  the  lateral  thoracic  and  inter- 
costal arteries  and  with  the  descending  branch  of  the  transverse  cervical,  and  ends 
in  the  neighboring  muscles.  About  4  cm.  from  its  origin  it  gives  off  a  branch,  the 
scapular  circumflex  artery. 

The  Scapular  Circumflex  Artery  (a.  circumflexa  scapulae;  dorsalis  scajJidae  artery) 
is  general!}'  larger  than  the  continuation  of  the  subscapular.  It  curves  around  the 
axillary  border  of  the  scapula, 
traversing  the  space  between 
the  Subscapularis  above,  the 
Teres  major  below,  and  the  long 
head  of  the  Triceps  laterally 
(Fig.  600);  it  enters  the  infra- 
spinatous  fossa  under  cover  of 
the  Teres  minor,  and  anasto- 
moses with  the  transverse  scap- 
ular artery  and  the  descending 
branch  of  the  transverse  cervical. 
In  its  course  it  gives  off  two 
branches:  one  {infrascapular) 
enters  the  subscapular  fossa  be- 
neath the  Subscapularis,  which 
it  supplies,  anastomosing  with 
the  transverse  scapular  artery 
and  the  descending  branch  of 
the  transverse  cervical;  the  other 
is  continued  along  the  axillary 
border  of  the  scapula,  between 
the  Teretes  major  and  minor, 
and  at  the  dorsal  surface  of  the 
inferior  angle  anastomoses  with  the  descending  branch  of  the  transverse  cervical. 
In  addition  to  these,  small  branches  are  distributed  to  the  back  part  of  the  Del- 
toideus  and  the  long  head  of  the  Triceps  brachii,  anastomosing  with  an  ascend- 
ing branch  of  the  a.  profunda  brachii. 

5.  The  posterior  humeral  circumflex  artery  (a.  circumflexa  humeri  posterior;  pos- 
terior circumflex  artery)  (Fig.  600)  arises  from  the  axillary  arter}'  at  the  low^er  border 
of  the  Subscapularis,  and  runs  backward  with  the  axillary  nerve  through  the  quad- 
rangular space  bounded  by  the  Subscapularis  and  Teres  minor  above,  the  Teres 
major  below,  the  long  head  of  the  Triceps  brachii  medially,  and  the  surgical  neck 
of  the  humerus  laterally.  It  winds  around  the  neck  of  the  humerus  and  is  dis- 
tributed to  the  Deltoideus  and  shoulder-joint,  anastomosing  with  the  anterior 
humeral  circumflex  and  profunda  brachii. 


Fig.  600. — The  scapular  and  circumflex  arteries. 


672  AXGIOLOGY 

6.  The  anterior  humeral  circumflex  artery  (a.  circurujlexa  huineri  anterior;  anterior 
circumflex  artery)  (Fig.  000),  consi(kTabl.\-  smaller  than  the  posterior,  om^.?  nearly 
opposite  it,  from  the  lateral  side  of  the  axillary  artery  It  runs  horizontally,  })eneath 
the  Coracobrachialis  and  short  head  of  the  Biceps  brachii,  in  front  of  the  neck  of 
the  humerus.  On  reaching  the  intertubercular  sulcus,  it  gives  off  a  branch  which 
ascends  in  the  sulcus  to  supply  the  head  of  the  humerus  and  the  shoulder-joint. 
The  trunk  of  the  vessel  is  then  continued  onward  beneath  the  long  head  of  the 
Biceps  brachii  and  the  Deltoideus,  and  anastomoses  with  the  posterior  humeral 
circumflex  artery. 

Peculiarities. — The  branches  of  the  axillary  artery  vary  considerably  in  different  subjects. 
Occasionally  the  subscapular,  humeral  circumflex,  and  profunda  arteries  arise  from  a  common 
trunk,  and  when  this  occurs  the  branches  of  the  brachial  plexus  surround  this  trunk  instead  of 
the  main  vessel.  Sometimes  the  axillary  artery  divides  into  the  radial  and  ulnar  arteries,  and 
occasionally  it  gives  origin  to  the  volar  interosseous  artery  of  the  forearm. 

The  Brachial  Artery  (A.  Brachialis)  (Fig.  601). 

The  brachial  artery  commences  at  the  lower  margin  of  the  tendon  of  the  Teres 
major,  and,  passing  down  the  arm,  ends  about  1  cm.  below  the  bend  of  the  elbow, 
where  it  divides  into  the  radial  and  ulnar  arteries.  At  first  the  brachial  artery  lies 
medial  to  the  humerus;  but  as  it  runs  down  the  arm  it  gradually  gets  in  front  of 
the  bone,  and  at  the  bend  of  the  elbow^  it  lies  midway  between  its  two  epicondyles. 

Relations. — The  artery  is  superficial  throughout  its  entire  extent,  being  covered,  in  front, 
by  the  integument  and  the  superficial  and  deep  fasciae;  the  lacertus  fibrosus  (bicipital  fascia) 
lies  in  front  of  it  opposite  the  elbow  and  separates  it  from  the  vena  mediana  cubiti;  the  median 
nerve  crosses  from  its  lateral  to  its  medial  side  opposite  the  insertion  of  the  CoracobrachiaUs. 
Behind,  it  is  separated  from  the  long  head  of  the  Triceps  brachii  by  the  radial  nerve  and  a.  pro- 
funda brachii.  It  then  lies  upon  the  medial  head  of  the  Triceps  brachii,  next  upon  the  insertion 
of  the  Coracobrachialis,  and  lastly  on  the  Brachialis.  Laterally,  it  is  in  relation  above  with  the 
median  nerve  and  the  Coracobrachialis,  below  with  the  Biceps  brachii,  the  two  muscles  over- 
lapping the  artery  to  a  considerable  extent.  Medially,  its  upper  half  is  in  relation  with  the  medial 
antibrachial  cutaneous  and  ulnar  nerves,  its  lower  half  with  the  median  nerve.  The  basilic  vein 
lies  on  its  medial  side,  but  is  separated  from  it  in  the  lower  part  of  the  arm  by  the  deep  fascia. 
The  artery  is  accompanied  by  two  vense  comitantes,  which  lie  in  close  contact  with  it,  and  are 
connected  together  at  intervals  by  short  transverse  branches. 

The  Anticubital  Fossa. — iVt  the  bend  of  the  elbow  the  brachial  artery  sinks 
deeply  into  a  triangular  interval,  the  anticubital  fossa.  The  base  of  the  triangle 
is  directed  upward,  and  is  represented  by  a  line  connecting  the  two  epicondyles 
of  the  humerus;  the  sides  are  formed  by  the  medial  edge  of  the  Brachioradialis 
and  the  lateral  margin  of  the  Pronator  teres;  the  floor  is  formed  by  the  Brachialis 
and  Supinator.  This  space  contains  the  brachial  artery,  with  its  accompanying 
veins;  the  radial  and  ulnar  arteries;  the  median  and  radial  nerves;  and  the  tendon 
of  the  Biceps  brachii.  The  brachial  artery  occupies  the  middle  of  the  space,  and 
divides  opposite  the  neck  of  the  radius  into  the  radial  and  ulnar  arteries ;  it  is  covered, 
in  front,  by  the  integument,  the  superficial  fascia,  and  the  vena  mediana  cubiti, 
the  last  being  separated  from  the  artery  by  the  lacertus  fibrosus.  Behind  it  is 
the  Brachialis  which  separates  it  from  the  elbow-joint.  The  median  nerve  lies 
close  to  the  medial  side  of  the  artery,  above,  but  is  separated  from  it  below  by  the 
ulnar  head  of  the  Pronator  teres.  The  tendon  of  the  Biceps  brachii  lies  to  the  lateral 
side  of  the  artery;  the  radial  nerve  is  situated  upon  the  Supinator,  and  concealed 
by  the  Brachioradialis. 

Peculiarities  of  the  Brachial  Artery  as  Regards  its  Course. — The  brachial  artery,  accompanied 
by  the  median  nerve,  may  leave  the  medial  border  of  the  Biceps  brachii,  and  descend  toward 
the  medial  epicondyle  of  the  humerus;  in  such  cases  it  usually  passes  behind  the  supracondylar 
process  of  the  humerus,  from  which  a  fibrous  arch  is  in  most  cases  thrown  over  the  artery;  it 
then  runs  beneath  or  through  the  substance  of  the  Pronator  teres,  to  the  bend  of  the  elbow. 


77//';  BRACHIAL  ARTERY 


673 


.  antihracli, 
cuian.  nerve 

ial  nerve 


profunda 
brachii 


Tliis  variation  hears  coiusiilcraljlc  analog;}'  willi  tiic  uoi'uiai  condiliou  of  the  artery  in  some  of 
the  (•arni\ora;  it  lias  h(>eii  referred  to  in  the  description  of  the  humerus  (p.  312). 

As  Regards  its  Division. — Occasionally,  the  artery  is  divided  for  a  short  distance  at  its  upper 
l)art  into  two  trunks,  which  are  united  below.  Frequently  the  artery  divides  at  a  higher  level 
than  usual,  and  the  vessels  con(!erned  in  this  high  division  are  three,  viz.,  radial,  ulnar,  and 
interosseous.  Most  frequently  the  radial  is  giv(;n  off  high  up,  the  other  limb  of  the  bifurcation 
consisting  of  the  ulnar  and  interosseous;  in  some  instances  the  ulnar  arises  above  the  ordinary 
level,  and  the  radial  antl  interosseous 
form  the  other  limb  of  the  division;  occa- 
sionally the  interosseous  arises  high  up. 

Sometimes,  long  slender  vessels,  vasa 
abcrranlia,  connect  the  brachial  or  the 
axillary  artery  with  one  of  the  arteries 
of  the  forearm,  or  branches  from  them. 
These  vessels  usually  join  the  radial. 

Varieties  in  Muscular  Relations. — The 
brachial  artery  is  occasionally  concealed, 
in  some  part  of  its  course,  by  muscular 
or  tendinous  slips  derived  from  the  Cora- 
cobrachialis.  Biceps  brachii,  Brachialis, 
or  Pronator  teres. 

Applied  Anatomy. — In  spite  of  the  fact 
that  the  brachial  artery  is  very  superficial 
and  but  little  protected  by  surrounding 
tissues,  it  is  seldom  wounded.  This,  no 
doubt,  is  due  to  its  situation  on  the  medial 
side  of  the  arm,  which  is  little  exposed  to 
injury.  Compression  of  the  brachial  artery 
is  required  in  cases  of  amputation  and 
some  other  operations  in  the  arm  and 
forearm,  and  may  be  effected  in  almost 
any  part  of  the  course  of  the  artery.  If 
pressure  be  made  in  the  upper  part  of 
the  limb,  it  should  be  directed  lateral- 
ward;  if  in  the  lower  part,  backward,  as 
the  artery  lies  on  the  medial  side  of  the 
humerus  above,  and  in  front  of  it  below. 
The  most  favorable  situation  is  about 
the  middle  of  the  arm,  where  the  artery 
lies  on  the  tendon  of  the  Coracobrachialis 
on  the  medial  surface  of  the  humerus. 

The  application  of  a  ligature  to  the 
brachial  artery  may  be  required  in  cases 
of  wound  of  the  vessel,  and  in  some 
cases  of  wound  of  the  volar  arch.  It  is 
also  sometimes  necessary  in  cases  of 
aneurism  of  the  brachial,  radial,  ulnar, 
or  interosseous  arteries.  The  artery  may 
be  secured  in  any  part  of  its  course. 
The  chief  guides  in  determining  its  posi- 
tion are  the  surface  markings  produced 
by  the  medial  margins  of  the  Coraco- 
brachiahs  and  Biceps  brachii,  and  the 
known  course  of  the  vessel;  its  pulsation 
should   be  carefully  felt  for  before  any 

operation  is  performed,  as  the  vessel  occasionally  deviates  from  its  usual  position.  It  is  essential 
in  applying  a  ligature  to  this  vessel  that  the  arm  should  be  held  away  from  the  side,  and  supported 
only  from  the  elbow,  for  if  the  arm  be  allowed  to  rest  on  any  firm  structure  the  Triceps  brachii  is 
pressed  forward  and  overlaps  the  vessel,  thus  making  the  operation  much  more  difficult. 

In  the  upper  third  of  the  arm  the  artery  may  be  exposed  in  the  following  manner.  The  patient 
being  placed  supine  upon  a  table,  the  affected  hmb  should  be  raised  from  the  side,  and  the  hand 
supinated.  An  incision  about  5  cm.  in  length  is  made  on  the  medial  side  of  the  Coracobrachialis, 
and  the  subjacent  fascia  cautiously  divided,  so  as  to  avoid  wounding  the  medial  antibrachial 
cutaneous  nerve  or  basihc  vein,  as  the  latter  sometimes  runs  on  the  surface  of  the  artery  as  high 
as  the  axilla.  The  fascia  having  been  divided,  it  should  be  remembered  that  the  ulnar  nerve 
and  the  medial  antibrachial  cutaneous  nerve  lie  on  the  medial  side  of  the  artery,  the  median  nerve 
43 


ulnar  collateral 
artery 


ulnar  collateral 
artery 


Fig.  601.— The  brachial  artery, 


674  AXGIOLOGY 

on  the  lateral  side  but  occasionally  superficial  to  the  artery  in  this  situation,  and  that  the  venae 
eomitantes  are  also  in  relation  with  the  vessel,  one  on  either  side.  These  being  carefully  sepa- 
rated, the  aneurism  needle  should  be  passed  around  the  artery  from  the  medial  side. 

In  the  case  of  a  high  division,  the  two  arteries  are  usually  placed  side  by  side;  and  if  they  are 
exposed  in  an  operation,  the  surgeon  should  endeavor  to  ascertain,  by  alternately  pressing  on 
each  vessel,  which  is  connected  with  the  wound  or  aneurism,  when  a  hgature  may  be  applied 
accordingly;  if  pulsation  or  hemorrhage  ceases  only  when  both  vessels  are  compressed,  both  must 
be  tied. 

In  the  middle  of  the  arm  the  brachial  artery  may  be  exposed  by  making  an  incision  along  the 
medial  margin  of  the  Biceps  brachii.  The  forearm  being  bent  so  as  to  relax  the  muscle,  it  should 
be  drawn  sHghtly  aside,  and  the  fascia  carefully  divided,  when  the  median  nerve  will  be  exposed 
lying  upon  (sometimes  behind)  the  artery;  the  nerve  being  drawn  medialward  and  the  muscle 
lateralward,  the  artery  should  be  separated  from  its  accompanying  veins  and  secured.  In  this 
situation  the  superior  ulnar  collateral  {inferior  profunda^)  may  be  mistaken  for  the  main  trunk, 
especially  if  enlarged  from  the  collateral  circulation  having  become  estabh.shed;  this  may  be 
avoided  by  directing  the  incision  toward  the  Biceps  brachii,  rather  than  toward  the  Triceps 
brachii. 

The  loirer  part  of  the  brachial  artery  is  of  interest  from  a  surgical  point  of  view,  on  account  of 
the  relation  which  it  bears  to  the  veins  most  commonly  opened  in  venesection.  Of  these  vessels, 
the  vena  mediana  cubiti  (median  ba.silic  vein)  is  the  largest  and  most  prominent,  and,  conse- 
quently, the  one  usually  selected  for  the  operation.  This  vein  runs  parallel  with  the  brachial 
artery,  from  which  it  is  separated  by  the  lacertus  fibrosus  (bicipital  fascia),  and  care  should  be 
taken,  in  opening  the  vein,  not  to  carry  the  incision  too  deep,  so  as  to  endanger  the  artery. 

Collateral  Circulation. — After  the  apphcation  of  a  ligature  to  the  brachial  artery  in  the  upper 
third  of  the  arm,  the  circulation  is  carried  on  by  branches  from  the  humeral  circumflex  and  sub- 
scapular arteries  anastomosing  with  ascending  branches  from  the  profunda  brachii.  If  the 
artery  be  tied  belovj  the  origin  of  the  profunda  brachii  and  superior  ulnar  collateral,  the  circula- 
tion is  maintained  by  the  branches  of  these  two  arteries  anastomosing  with  the  inferior  ulnar 
collateral,  the  radial  and  ulnar  recurrents,  and  the  dorsal  interosseous. 

Branches. — The  branches  of  the  brachial  artery  are: 

Profunda  Brachii.  Superior  Ulnar  Collateral. 

Nutrient.  Inferior  Ulnar  Collateral. 

Muscular. 

1 .  The  arteria  profunda  brachii  (superior  profunda  artery)  is  sl  large  vessel  which 
arises  from  the  medial  and  back  part  of  the  brachial,  just  below  the  lower  border 
of  the  Teres  major.  It  follows  closely  the  radial  nerve,  running  at  first  backward 
between  the  medial  and  lateral  heads  of  the  Triceps  brachii,  then  along  the  groove 
for  the  radial  nerve,  where  it  is  covered  by  the  lateral  head  of  the  Triceps  brachii, 
to  the  lateral  side  of  the  arm;  there  it  pierces  the  lateral  intermuscular  septum, 
and,  descending  between  the  Brachioradialis  and  the  Brachialis  to  the  front  of 
the  lateral  epicondyle  of  the  humerus,  ends  by  anastomosing  with  the  radial  recur- 
rent artery.  It  gives  branches  to  the  Deltoideus  and  to  the  muscles  between  which 
it  lies;  it  supplies  an  occasional  nutrient  artery  which  enters  the  humerus  behind  the 
deltoid  tuberosity.  A  branch  ascends  between  the  long  and  lateral  heads  of  the 
Triceps  brachii  to  anastomose  with  the  posterior  humeral  circumflex  artery;  a 
middle  collateral  branch  descends  in  the  middle  head  of  the  Triceps  brachii  and 
assists  in  forming  the  anastomosis  above  the  olecranon;  and,  lastly,  a  radial  collateral 
branch  runs  down  behind  the  lateral  intermuscular  septum  to  the  back  of  the  lateral 
epicondyle  of  the  humerus,  where  it  anastomoses  with  the  interosseous  recurrent 
and  the  inferior  ulnar  collateral  arteries. 

2.  The  nutrient  artery  (a.  mdricia  humeri)  of  the  body  of  the  humerus  ari.ses 
about  the  middle  of  the  arm  and  enters  the  nutrient  canal  near  the  insertion  of  the 
Cora  cobra  chialis. 

3.  The  superior  ulnar  collateral  artery  (a.  collateralis  uhiaris  superior;  inferior 
profunda  artery),  of  small  size,  arises  from  the  brachial  a  little  below  the  middle 
of  the  arm;  it  frequently  springs  from  the  upper  part  of  the  a.  profunda  brachii. 
It  pierces  the  medial  intermuscular  septum,  and  descends  on  the  surface  of  the  medial 
head  of  the  Triceps  brachii  to  the  space  between  the  medial  epicondyle  and 


THE  BRACHIAL  ARTERY 


6' 


olecranon,  accompanied  by  the  ulnar  nerve,  and  ends  under  the  Flexor  carpi  ulnaris 
by  anastomosing  with  the  posterior  ulnar  recurrent,  and  inferior  ulnar  collateral. 
It  sometimes  sends  a  branch  in  front  of  the  medial  epicondyle,  to  anastomose 
with  the  anterior  ulnar  recurrent. 

4.  The  inferior  ulnar  collateral  artery  {a.  coUateralis  ulnaris  inferior;  anastomotica 
magna  artery)  arises  about  5  cm.  abo\'e  the  elbow.  It  passes  medialward  upon  the 
Brachialis,  and  piercing  the  medial  intermuscular  septum,  winds  around  the  back  of 
the  humerus  between  the  Triceps  brachii  and  the  bone,  forming,  by  its  junction  with 
the  profunda  brachii,  an  arch  above  the  olecranon  fossa.  As  the  vessel  lies  on  the 
Brachialis,  it  gives  off  branches  which  ascend  to  join  the  superior  ulnar  collateral: 
others  descend  in  front  of  the  medial  epicondyle,  to  anastomose  with  the  anterior 
ulnar  recurrent.  Behind  the  medial  epicondyle  a  branch  anastomoses  with  the 
superior  ulnar  collateral  and  posterior  ulnar  recurrent  arteries. 

5.  The  muscular  branches  {rami  muscidares)  three  or  four  in  number,  are  dis- 
tributed to  the  Coracobrachialis,  Biceps  brachii,  and  Brachialis. 


Anterior  branch  of  'profunda 


Radial  collateral  branch 
of  profunda 


Radial  recurrent 


Interosseous  recurrent 
Radial 


A.  profunda  brachii 

Sup.  ulnar  collateral 
Brachial 

Inf.  ulnar  collateral 


Anterior  idnar  recurrent 
Posterior  ulnar  recurrent 


Interosseous 
Dorsal  interosseous 

Ulnar 

Volar  interosseous 


Fig.  602. — Diagram  of  the  anastomosis  around  the  elbow-joint. 

The  Anastomosis  Around  the  Elbow-joint  (Fig.  602). — The  vessels  engaged  in 
this  anastomosis  may  be  conveniently  divided  into  those  situated  in  front  of  and 
those  behind  the  medial  and  lateral  epicondyles  of  the  humerus.  The  branches 
anastomosing  in  front  of  the  medial  epicondyle  are :  the  anterior  branch  of  the 
inferior  ulnar  collateral,  the  anterior  ulnar  recurrent,  and  the  anterior  branch  of 
the  superior  ulnar  collateral.  Those  behind  the  medial  epicondyle  are:  the  inferior 
ulnar  collateral,  the  posterior  ulnar  recurrent,  and  the  posterior  branch  of  the  supe- 
rior ulnar  collateral.  The  branches  anastomosing  in  front  of  the  lateral  epicondyle 
are:  the  radial  recurrent  and  the  terminal  part  of  the  profunda  brachii.  Those 
behind  the  lateral  epicondyle  (perhaps  more  properly  described  as  being  situated 


676  AXGIOLOGY 

between  the  lateral  epicondyle  and  the  olecranon)  are:  the  inferior  ulnar  collateral, 
the  interosseous  recurrent,  and  the  radial  collateral  branch  of  the  profunda  brachii. 
There  is  also  an  arch  of  anastomosis  above  the  olecranon,  formed  by  the  interosseous 
recurrent  joining  with  the  inferior  ulnar  collateral  and  posterior  ulnar  recurrent 
(Fig.  605). 

The  Radial  Artery  (A.  Radialis)  (Fig.  603). 

The  radial  artery  appears,  from  its  direction,  to  be  the  continuation  of  the  brachial, 
but  it  is  smaller  in  calibre  than  the  ulnar.  It  commences  at  the  bifurcation  of  the 
brachial,  just  below  the  bend  of  the  elbow,  and  passes  along  the  radial  side  of  the 
forearm  to  the  wrist.  It  then  winds  backward,  around  the  lateral  side  of  the  carpus, 
beneath  the  tendons  of  the  Abductor  pollicis  longus  and  Extensores  pollicis  longus 
and  brevis  to  the  upper  end  of  the  space  between  the  metacarpal  bones  of  the  thumb 
and  index  finger.  Finally  it  passes  forward  between  the  two  heads  of  the  first 
Interosseous  dorsalis,  into  the  palm  of  the  hand,  where  it  crosses  the  metacarpal 
bones  and  at  the  ulnar  side  of  the  hand  unites  with  the  deep  volar  branch  of  the 
ulnar  artery  to  form  the  deep  volar  arch.  The  radial  artery  therefore  consists 
of  three  portions,  one  in  the  forearm,  a  second  at  the  back  of  the  wrist,  and  a  third 
in  the  hand. 

Relations. — (a)  In  the  forearm  the  artery  extends  from  the  neck  of  the  radius  to  the  forepart 
of  the  styloid  process,  being  placed  to  the  medial  side  of  the  body  of  the  bone  above,  and  in  front 
of  it  below.  Its  upper  part  is  overlapped  by  the  fleshy  beUy  of  the  Brachioradiahs;  the  rest  of 
the  artery  is  superficial,  being  covered  by  the  integument  and  the  superficial  and  deep  fasciae. 
In  its  course  downward,  it  hes  upon  the  tendon  of  the  Biceps  brachii,  the  Supinator,  the  Pronator 
teres,  the  radial  origin  of  the  Flexor  digitorum  subhmis,  the  Flexor  poUicis  longus,  the  Pronator 
quadratus,  and  the  lower  end  of  the  radius.  In  the  upper  third  of  its  course  it  hes  between  the 
Brachioradiahs  and  the  Pronator  teres;  in  the  lower  two-thirds,  between  the  tendons  of  the 
Brachioradiahs  and  Flexor  carpi  radiahs.  The  superficial  branch  of  the  radial  nerve  is  close  to 
the  lateral  side  of  the  artery  in  the  middle  third  of  its  course;  and  some  filaments  of  the  lateral 
antibrachial  cutaneous  nerve  run  along  the  lower  part  of  the  artery  as  it  winds  around  the  wrist. 
The  vessel  is  accompanied  by  a  pair  of  venae  comitantes  throughout  its  whole  course. 

(6)  At  the  wrist  the  artery  reaches  the  back  of  the  carpus  by  passing  between  the  radial  collateral 
hgament  of  the  wrist  and  the  tendons  of  the  Abductor  polhcis  longus  and  Extensor  poUicis  brevis. 
It  then  descends  on  the  navicular  and  greater  multangular  bones,  and  before  disappearing  be- 
tween the  heads  of  the  first  Interosseus  dorsalis  is  crossed  by  the  tendon  of  the  Extensor  pollicis 
longus.  In  the  interval  between  the  two  Extensores  polhcis  it  is  crossed  by  the  digital  rami  of 
the  superficial  branch  of  the  radial  nerve  which  go  to  the  thumb  and  index  finger. 

(c)  In  the  hand,  it  passes  from  the  upper  end  of  the  first  interosseous  space,  between  the  heads 
of  the  first  Interosseus  dorsahs,  transversely  across  the  pahn  between  the  Adductor  polhcis 
obhquus  and  Adductor  polhcis  transversus,  but  sometimes  piercing  the  latter  muscle,  to  the 
base  of  the  metacarpal  bone  of  the  httle  finger,  where  it  anastomoses  with  the  deep  volar  branch 
from  the  uhiar  artery,  completing  the  deep  volar  arch  (Fig.  604). 

Peculiarities. — The  origin  of  the  radial  artery  is,  ua  nearly  one  case  in  eight,  higher  than  usual; 
more  often  it  arises  from  the  axillary  or  upper  part  of  the  brachial  than  from  the  lower  part  of 
the  latter  vessel.  In  the  forearm  it  deviates  less  frequently  from  its  normal  position  than  the 
ulnar.  It  has  been  found  lying  on  the  deep  fascia  instead  of  beneath  it.  It  has  also  been  observed 
on  the  surface  of  the  Brachioradiahs,  instead  of  under  its  medial  border;  and  in  turning  around 
the  wrist,  it  has  been  seen  lying  on,  instead  of  beneath,  the  Exten.sor  tendons  of  the  thumb. 

Applied  Anatomy. — The  radial  artery  is  much  exposed  to  injury  in  its  lower  third,  and  is  fre- 
quently wounded  by  the  hand  being  driven  through  a  pane  of  glass,  by  the  shpping  of  a  knife 
or  chisel  held  in  the  other  hand,  etc.  The  injury  may  be  followed  by  a  traumatic  aneurism,  for 
which  the  operation  of  laying  open  the  sac  and  secm-ing  the  vessel  above  and  below  is  necessary. 

The  operation  of  tying  the  radial  artery  is  required  in  cases  of  wounds  either  of  its  trimk,  or 
of  some  of  its  branches,  or  for  anemism;  and  the  vessel  may  be  exposed  in  any  part  of  its  course 
through  the  forearm  without  the  division  of  any  muscular  fibres.  The  operation  in  the  middle 
or  distal  third  of  the  forearm  is  easily  performed;  but  in  the  proximal  thu-d,  near  the  elbow,  it 
is  attended  with  some  diflSculty,  from  the  greater  depth  of  the  vessel,  and  from  its  being  over- 
lapped by  the  Brachioradiahs. 

To  tie  the  artery  in  the  proximal  third,  an  incision  7  or  8  cm.  in  length  should  be  made  through 
the  integmnent,  in  a  fine  drawm  from  the  centre  of  the  bend  of  the  elbow  to  the  front  of  the  styloid 
process  of  the  radius,  avoiding  the  branches  of  the  median  vein;  the  fascia  of  the  arm  being  divided. 


THE  RADIAL  ARTERY 


677 


and  the  lirarhioradialis  drawn  aside,  the  artery  will  be  exposed.    The  venae  comitantes  should 
be  carefully  separated  from  the  vessel  and  the  ligature  passed  from  the  radial  to  the  ulnar  side. 


Badial 
recurrent 


Badial 
recurrent 


Dorsal 
interosseous 


Muscular 


Deep  volar   Volar  radial  carpa 
branch  Superficial  volar 

of  ulnar 


Inferior  ulnar 
collateral 


Anterior  ulnar 

recurrent 
Posterior  ulnar 

recurrent 


Muscular 


r  uhuir  carpal 


Deep  volar  hrancli 
of  ulnar 


Fig.  603. — The  radial  and  ulnar  arteries. 


Fig.  604. — Ulnar  and  radial  arteries.     Deep  view. 


In  the  middle  third  of  the  forearm  the  artery  may  be  exposed  by  making  an  incision  of  similar 
length  on  the  medial  border  of  the  BrachioradiaKs.    In  this  situation,  the  superficial  part  of  the 


678  ANGIOLOGY 

radial  nerve  lies  in  close  relation  with  the  lateral  side  of  the  artery,  and  should,  as  well  as  the 
veins,  be  carefull}'  avoided. 

In  the  distal  third,  the  arterj^  is  easily  secured  by  dividing  the  integument  and  fascia  in  the 
interval  between  the  tendons  of  the  Brachioradialis  and  Flexor  carpi  radialis. 

Branches. — The  branches  of  the  radial  artery  may  be  divided  into  three  groups, 
corresponding  with  the  three  regions  in  which  the  vessel  is  situated. 

Ill  the  Forearm.  At  the  Wrist.  In  the  Hand. 

Radial  Recurrent.         Dorsal  Carpal.  Princeps  Pollicis. 

^Muscular.  First  Dorsal  Metacarpal.         Volaris  Indicis  Radialis. 

Volar  Carpal.  \'olar  Metacarpal. 

Superficial  Volar.  Perforating. 

Recurrent. 

The  radial  recurrent  artery  (a.  recur  reus  radialis)  arises  immediately  below  the 
elbow.  It  ascends  between  the  branches  of  the  radial  nerve,  lying  on  the  Supinator 
and  then  between  the  Brachioradialis  and  Brachialis,  supplying  these  muscles 
and  the  elbow-joint,  and  anastomosing  with  the  terminal  part  of  the  profunda 
brachii. 

The  muscular  branches  (rami  muscidares)  are  distributed  to  the  muscles  on  the 
radial  side  of  the  forearm. 

The  volar  carpal  branch  (ramus  carpeus  volaris;  anterior  radial  carpal  artery) 
is  a  small  vessel  which  arises  near  the  lower  border  of  the  Pronator  quadratus, 
and,  running  across  the  front  of  the  carpus,  anastomoses  with  the  volar  carpal 
branch  of  the  ulnar  artery.  This  anastomosis  is  joined  by  a  branch  from  the  volar 
interosseous  above,  and  by  recurrent  branches  from  the  deep  volar  arch  below, 
thus  forming  a  volar  carpal  net-work  which  supplies  the  articulations  of  the  wrist 
and  carpus. 

The  superficial  volar  branch  (ramus  volaris  superficialis ;  supjerficialis  volae  artery) 
arises  from  the  radial  artery,  just  where  this  vessel  is  about  to  wind  around  the 
lateral  side  of  the  wrist.  Running  forward,  it  passes  through,  occasionally  over, 
the  muscles  of  the  ball  of  the  thumb,  which  it  supplies,  and  sometimes  anastomoses 
with  the  terminal  portion  of  the  ulnar  artery,  completing  the  superficial  volar  arch. 
This  vessel  varies  considerably  in  size:  usually  it  is  very  small,  and  ends  in  the 
muscles  of  the  thumb;  sometimes  it  is  as  large  as  the  continuation  of  the  radial. 

The  dorsal  carpal  branch  (ramus  carpeus  dorsalis;  posterior  radial  carpal  artery) 
is  a  small  vessel  which  arises  beneath  the  Extensor  tendons  of  the  thumb;  crossing 
the  carpus  transversely  toward  the  medial  border  of  the  hand,  it  anastomoses  with 
the  dorsal  carpal  branch  of  the  ulnar  and  wdth  the  volar  and  dorsal  interosseous 
arteries  to  form  a  dorsal  carpal  network.  From  this  network  are  given  off  three 
slender  dorsal  metacarpal  arteries,  which  run  downward  on  the  second,  third,  and 
fourth  Interossei  dorsales  and  bifurcate  into  the  dorsal  digital  branches  for  the 
supply  of  the  adjacent  sides  of  the  middle,  ring,  and  little  fingers  respectively, 
communicating  wdth  the  proper  volar  digital  branches  of  the  superficial  volar 
arch.  Near  their  origins  they  anastomose  with  the  deep  volar  arch  by  the  superior 
perforating  arteries,  and  near  their  points  of  bifurcation  with  the  common  volar 
digital  vessels  of  the  superficial  volar  arch  by  the  inferior  perforating  arteries. 

The  first  dorsal  metacarpal  arises  just  before  the  radial  arter\'  passes  between 
the  two  heads  of  the  first  Interosseous  dorsalis  and  divides  almost  immediately 
into  two  branches  which  supply  the  adjacent  sides  of  the  thumb  and  index  finger; 
the  radial  side  of  the  thumb  receives  a  branch  directly  from  the  radial  artery. 

The  arteria  princeps  pollicis  arises  from  the  radial  just  as  it  turns  medialward 
to  the  deep  part  of  the  hand;  it  descends  between  the  first  Interosseus  dorsalis  and 
Adductor  pollicis  obliquus,  along  the  ulnar  side  of  the  metacarpal  bone  of  the 
thumb  to  the  base  of  the  first  phalanx,  where  it  lies  beneath  the  tendon  of  the 


THE  ULNAR  ARTERY  679 

Flexor  })()llicis  loiigus  and  (li\"idcs  into  two  branches.  These  make  their  appear- 
ance between  the  medial  and  lateral  insertions  of  the  Adductor  pollicis  obliquus, 
and  run  along  the  sides  of  the  thumb,  forming  on  the  volar  surface  of  the  last 
phalanx  an  arch,  from  which  branches  are  distril^uted  to  the  integument  and 
subcutaneous  tissue  of  the  thumb. 

The  arteria  volaris  indicis  radialis  {mdialis  indicis  artery)  arises  close  to  the  pre- 
cetling,  descends  between  the  first  Interosseus  dorsalis  and  Adductor  pollicis  trans- 
versus,  and  runs  along  the  radial  side  of  the  index  finger  to  its  extremity,  where  it 
anastomoses  with  the  proper  digital  artery,  supplying  the  ulnar  side  of  the  finger.  At 
the  lower  border  of  the  Adductor  pollicis  transversus  this  vessel  anastomoses  with 
the  princeps  pollicis,  and  gives  a  communicating  branch  to  the  superficial  volar  arch. 
The  a.  princeps  pollicis  and  a.  volaris  indicis  radialis  may  spring  from  a  common 
trunk  termed  the  first  volar  metacarpal  artery. 

The  deep  volar  arch  {arcus  rolaris  profundus;  deep  palmar  arch)  (Fig.  604)  is 
formed  by  the  anastomosis  of  the  terminal  part  of  the  radial  artery  with  the  deep 
volar  branch  of  the  ulnar.  It  lies  upon  the  carpal  extremities  of  the  metacarpal 
bones  and  on  the  Interossei,  being  covered  by  the  Adductor  pollicis  obliquus,  the 
Flexor  tendons  of  the  fingers,  and  the  Lumbricales.  Alongside  of  it,  but  running 
in  the  opposite  direction — that  is  to  say,  toward  the  radial  side  of  the  hand — is 
the  deep  branch  of  the  ulnar  nerve. 

The  volar  metacarpal  arteries  {aa.  metacarpeae  volares;  palmar  interosseous 
arteries),  three  or  four  in  number,  arise  from  the  convexity  of  the  deep  volar  arch; 
they  run  distally  upon  the  Interossei,  and  anastomose  at  the  clefts  of  the  fingers 
with  the  common  digital  branches  of  the  superficial  volar  arch. 

The  perforating  branches  {rami  perforantes) ,  three  in  number,  pass  backward 
from  the  deep  volar  arch,  through  the  second,  third,  and  fourth  interosseous  spaces 
and  between  the  heads  of  the  corresponding  Interossei  dorsalis,  to  anastomose 
with  the  dorsal  metacarpal  arteries. 

The  recurrent  branches  arise  from  the  concavity  of  the  deep  volar  arch.  They 
ascend  in  front  of  the  wrist,  supply  the  intercarpal  articulations,  and  end  in  the 
volar  carpal  network. 

The  Ulnar  Artery  (A.  Ulnaris)  (Fig.  604). 

The  ulnar  artery,  the  larger  of  the  two  terminal  branches  of  the  brachial,  begins 
a  little  below  the  bend  of  the  elbow,  and,  passing  obliquely  dow^nward,  reaches 
the  ulnar  side  of  the  forearm  at  a  point  about  midway  between  the  elbo^\'  and  the 
wrist.  It  then  runs  along  the  ulnar  border  to  the  wrist,  crosses  the  transverse 
carpal  ligament  on  the  radial  side  of  the  pisiform  bone,  and  immediately  beyond 
this  bone  divides  into  two  branches,  which  enter  into  the  formation  of  the  superficial 
and  deep  volar  arches. 

Relations. — (a)  In  the  forearm. — In  its  xipper  half,  it  is  deeply  seated,  being  covered  by  the 
Pronator  teres,  Flexor  carpi  radialis,  PaLmaris  longus,  and  Flexor  digitorum  sublimis;  it  lies 
upon  the  Brachialis  and  Flexor  digitorum  profundus.  The  median  nerve  is  in  relation  with  the 
medial  side  of  the  arterj'  for  about  2.5  cm.  and  then  crosses  the  vessel,  being  separated  from  it 
bj^  the  ulnar  head  of  the  Pronator  teres.  In  the  lower  half  of  the  forearm  it  lies  upon  the  Flexor 
digitorum  profundus,  being  covered  by  the  integument  and  the  superficial  and  deep  fasciae, 
and  placed  between  the  Flexor  carpi  uhiaris  and  Flexor  digitorum  subhmis.  It  is  accompanied 
by  two  venae  comit antes,  and  is  overlapped  in  its  middle  third  by  the  Flexor  carpi  uhiaris;  the 
uhiar  nerve  Ues  on  the  medial  side  of  the  lower  two-thuds  of  the  artery,  and  the  palmar  cutaneous 
branch  of  the  nerve  descends  on  the  lower  part  of  the  vessel  to  the  pahn  of  the  hand. 

(6)  At  the  ivrist  (Fig.  603)  the  ulnar  artery  is  covered  bj^  the  iategument  and  the  volar  carpal 
ligament,  and  hes  upon  the  transverse  carpal  ligament.  On  its  medial  side  is  the  pisiform  bone, 
and,  somewhat  behind  the  artery,  the  uhiar  nerve. 

Peculiarities. — The  uhiar  arteiy  varies  in  its  origin  in  the  proportion  of  about  one  in  thuteen 
cases;  it  may  arise  about  5  to  7  cm.  below  the  elbow,  but  more  frequently  higher,  the  brachial 


In  the  Forearm 


680  AXGIOLOGY 

being  more  often  the  source  of  origin  than  the  axillary.  Variations  in  the  position  of  this  \-essel 
are  more  common  than  in  the  radial.  When  its  origin  is  normal,  the  course  of  the  vessel  is  rarely 
changed.  When  it  arises  high  up,  it  is  almost  invariably  superficial  to  the  Flexor  muscles  in  the 
forearm,  lying  commonly  beneath  the  fascia,  more  rarely  between  the  fascia  and  integument. 
In  a  few  cases,  its  position  was  subcutaneous  in  the  upper  part  of  the  forearm,  and  subaponeurotic 
in  the  lower  part. 

Applied  Anatomy. — The  application  of  a  ligature  to  this  vessel  is  required  in  cases  of  wound 
of  the  arterj^,  or  of  its  branches,  or  in  consequence  of  aneurism.  In  the  upper  half  of  the  forearm 
the  artery  is  deeply  seated  beneath  the  superficial  Flexor  muscles,  and  the  application  of  a  liga- 
ture in  this  situation  is  attended  with  some  difficulty.  An  incision  is  to  be  made  in  the  course 
of  a  Une  drawn  from  the  front  of  the  medial  epicondyle  of  the  humerus  to  the  lateral  side  of  the 
pisiform  bone,  so  that  the  centre  of  the  incision  is  three  fingers'  breadth  below  the  medial  epi- 
condyle. The  skin  and  superficial  fascia  having  been  divided,  and  the  deep  fascia  exposed,  the 
white  line  which  separates  the  Flexor  carpi  ulnaris  from  the  other  Flexor  muscles  is  to  be  sought 
for,  and  the  fascia  incised  in  this  Une.  The  Flexor  carpi  ulnaris  is  now  to  be  carefully  separated 
from  the  other  muscles,  when  the  ulnar  nerve  will  be  exposed  lying  on  the  Flexor  digitorum 
profundus,  and  must  be  drawn  aside.  The  artery  will  be  found  accompanied  by  its  venae  comi- 
tantes,  and  may  be  ligatured  as  it  lies  to  the  lateral  side  of  the  nerve.  In  the  middle  and  lower 
thirds  of  the  forearm,  this  vessel  may  be  easily  secured  by  making  an  incision  on  the  radial  side 
of  the  tendon  of  the  Flexor  carpi  ulnaris;  when  the  deep  fascia  is  divided,  and  the  tendon  sepa- 
rated from  the  Flexor  subUmis,  the  vessel  will  be  exposed,  accompanied  by  its  venae  comitantes, 
the  ulnar  nerve  lying  on  its  medial  side. 

Branches. — The  branches  of  the  uhiar  artery  may  be  arranged  in  the  following 
groups : 

Anterior  Recurrent.  4///,    w  'f    /  ^olar  Carpal. 

Posterior  Recurrent.         "  [  Dorsal  Carpal. 

Common  Interosseous,     j^  ^j^^  Hand    ^  ^^^P  Volar. 
Muscular.  i  Superficial  Volar  Arch. 

The  anterior  ulnar  recurrent  artery  (a.  recurrentes  ulnaris  anterior)  arises  imme- 
diately below  the  elbow-joint,  runs  upward  between  the  Brachialis  and  Pronator 
teres,  supplies  twigs  to  those  muscles,  and,  in  front  of  the  medial  epicondyle,  anasto- 
moses with  the  superior  and  inferior  ulnar  collateral  arteries. 

The  posterior  ulnar  recurrent  artery  (a.  recurrentes  ulnaris  posterior)  is  much 
larger,  and  arises  somewhat  lower  than  the  preceding.  It  passes  backward  and 
medialward  on  the  Flexor  digitorum  profundus,  behind  the  Flexor  digitorum  sub- 
limis,  and  ascends  behind  the  medial  epicondyle  of  the  humerus.  In  the  interval 
between  this  process  and  the  olecranon,  it  lies  beneath  the  Flexor  carpi  ulnaris, 
and  ascending  between  the  heads  of  that  muscle,  in  relation  with  the  ulnar  nerve, 
it  supplies  the  neighboring  muscles  and  the  elbow-joint,  and  anastomoses  with 
the  superior  and  inferior  ulnar  collateral  and  the  interosseous  recurrent  arteries 
(Fig.  605). 

The  common  interosseous  artery  {a.  interossea  communis)  (Fig.  604),  about  1  cm. 
in  length,  arises  immediately  below  the  tuberosity  of  the  radius,  and,  passing 
backward  to  the  upper  border  of  the  interosseous  membrane,  divides  into  two 
branches,  the  volar  and  dorsal  interosseous  arteries. 

The  Volar  Interosseous  Artery  {a.  interossea  volaris;  anterior  interosseous  artery) 
(Fig.  604) ,  passes  down  the  forearm  on  the  volar  surface  of  the  interosseous  mem- 
brane. It  is  accompanied  by  the  volar  interosseous  branch  of  the  median  nerve, 
and  overlapped  by  the  contiguous  margins  of  the  Flexor  digitorum  profundus  and 
Flexor  poUicis  longus,  giving  off  in  this  situation  muscular  branches,  and  the  nutrient 
arteries  of  the  radius  and  ulna.  At  the  upper  border  of  the  Pronator  quadratus  it 
pierces  the  interosseous  membrane  and  reaches  the  back  of  the  forearm,  where  it 
anastomoses  with  the  dorsal  interosseous  artery  (Fig.  605).  It  then  descends,  in 
company  with  the  terminal  portion  of  the  dorsal  interosseous  nerve,  to  the  back 
of  the  wrist  to  join  the  dorsal  carpal  net-work.  The  volar  interosseous  artery  gives 
off  a  slender  branch,  the  arteria  mediana,  which  accompanies  the  median  nerve,  and 
gives  offsets  to  its  substance;  this  artery  is  sometimes  much  enlarged,  and  runs 


THE  ULNAR  ARTERY 


681 


with  the  nerve  into  the  palm  of  the  hand.  Before  it  pierces  the  interosseous 
membrane  the  volar  interosseous  sends  a  branch  downward  behind  the  Pronator 
qundratns  to  join  the  volar  carpal  network. 


profunda  brachii 


Inf.  ulnar  collateral 


Posterior  ulnar  recurrent 


Dorsal  interosseous 


Dorsal  ulnar  carpal 


Termination  of  volar 
interosseous 


Dorsal  radial  carpal 


Fig.  605. — Arteries  of  the  back  of  the  forearm  and  hand. 


The  Dorsal  Interosseous^ Artery  (a.  interossea  dorsalis;  "posterior  interosseous  artery) 
(Fig.  605)  passes  backward  between  the  oblique  cord  and  the  upper  border  of  the 
interosseous  membrane.  ^  It  appears  between  the  contiguous  borders  of  the  Supinator 
and  the  Abductor  pollicis  longus,  and  runs  down  the  back  of  the  forearm  between 


682  ANGIOLOGY 

the  superficial  and  deep  layers  of  muscles,  to  both  of  which  it  distributes  branches. 
Where  it  lies  upon  the  Abductor  pollicis  longus  and  the  Extensor  pollicis  brevis, 
it  is  accompanied  by  the  dorsal  interosseous  nerve.  At  the  lower  part  of  the  fore- 
arm it  anastomoses  with  the  termination  of  the  volar  interosseous  artery,  and  Avith 
the  dorsal  carpal  network.  It  gives  off,  near  its  origin,  the  interosseous  recurrent 
artery,  which  ascends  to  the  interval  between  the  lateral  epicondyle  and  olecranon, 
on  or  through  the  fibres  of  the  Supinator,  but  beneath  the  Anconaeus,  and  anasto- 
moses with  the  radial  collateral  branch  of  the  profunda  brachii,  the  posterior 
ulnar  recurrent  and  the  inferior  ulnar  collateral. 

The  muscular  branches  (rami  muscular es)  are  distributed  to  the  muscles  along 
the  ulnar  side  of  the  forearm. 

The  volar  carpal  branch  [ramus  carpeus  volares;  anterior  ulnar  carpal  artery)  is  a 
small  vessel  which  crosses  the  front  of  the  carpus  beneath  the  tendons  of  the  Flexor 
digitorum  profundus,  and  anastomoses  with  the  corresponding  branch  of  the  radial 
arte^3^ 

The  dorsal  carpal  branch  (ramifs  carpeus  clorsalis;  posterior  ulnar  carpal  artery) 
arises  immediately  above  the  pisiform  bone,  and  winds  backward  beneath  the 
tendon  of  the  Flexor  carpi  ulnaris;  it  passes  across  the  dorsal  surface  of  the  carpus 
beneath  the  Extensor  tendons,  to  anastomose  wath  a  corresponding  branch  of  the 
radial  artery.  Immediately  after  its  origin,  it  gives  off  a  small  branch,  which  runs 
along  the  ulnar  side  of  the  fifth  metacarpal  bone,  and  supplies  the  ulnar  side  of  the 
dorsal  surface  of  the  little  finger. 

The  deep  volar  branch  (ramus  wlaris  profundus;  profunda  branch)  (Fig.  604) 
passes  between  the  Abductor  digiti  quinti  and  Flexor  digiti  quinti  brevis  and 
through  the  origin  of  the  Opponens  digiti  quinti;  it  anastomoses  with  the  radial 
artery,  and  completes  the  deep  volar  arch. 

The  superficial  volar  arch  (arcus  volar  is  siqyerficialis;  superficial  pjalmar  arch) 
(Fig.  603)  is  formed  by  the  ulnar  artery,  and  is  usually  completed  by  a  branch 
from  the  a.  volaris  indicis  radialis,  but  sometimes  by  the  superficial  volar  or  by 
a  branch  from  the  a.  princeps  pollicis  of  the  radial  artery.  The  arch  passes  across 
the  palm,  describing  a  curve,  wdth  its  convexity  downward. 

Relations.— The  superficial  volar  arch  is  covered  by  the  skin,  the  Palmaris  brevis,  and  the 
pahnar  aponem'osis.  It  Ues  upon  the  transverse  carpal  hgament,  the  Flexor  digiti  quinti  brevis 
and  Opponens  digiti  quinti,  the  tendons  of  the  Flexor  digitorum  subhmis,  the  Lumbricales,  and 
the  divisions  of  the  median  and  ulnar  nerves. 

Three  Common  Volar  Digital  Arteries  (cm.  digitales  volares  communes;  palmar  digital 
arteries)  (Fig.  603)  arise  from  the  convexity  of  the  arch  and  proceed  downward 
on  the  second,  third,  and  fourth  Lumbricales.  Each  receives  the  corresponding 
volar  metacarpal  artery  and  then  divides  into  a  pair  of  proper  volar  digital  arteries 
(aa.  digitales  volares  propriae;  collatercd  digital  arteries)  which  run  along  the  con- 
tiguous sides  of  the  index,  middle,  ring,  and  little  fingers,  behind  the  corresponding 
digital  nerves ;  they  anastomose  freely  in  the  subcutaneous  tissue  of  the  finger  tips 
and  by  smaller  branches  near  the  interphalangeal  joints.  Each  gives  off  a  couple 
of  dorsal  branches  which  anastomose  with  the  dorsal  digital  arteries,  and  supply 
the  soft  parts  on  the  back  of  the  second  and  third  phalanges,  including  the  matrix 
of  the  finger-nail.  The  proper  volar  digital  artery  for  medial  side  of  the  little 
finger  springs  from  the  ulnar  artery  under  cover  of  the  Palmaris  brevis. 

Applied  Anatomy. — Wounds  of  the  volar  arches  are  of  special  interest,  and  are  always  difficult 
to  deal  with.  When  the  superficial  arch  is  involved  it  is  generally  possible  (enlarging  the  wound 
when  necessary)  to  secure  the  vessel  and  tie  it  on  both  sides  of  the  bleeding  point;  or  in  cases 
where  it  is  found  impossible  to  encircle  the  vessel  with  a  hgature,  a  pair  of  hemostatic  forceps 
may  be  apphed  and  left  on  for  twenty-four  or  forty-eight  hours.  FaiUng  this,  the  wound  may 
be  plugged  with  gauze  and  an  outside  dressing  carefully  bandaged  on.  The  plug  should  be  allowed 
to  remain  untouched  for  three  or  four  days.  It  is  useless  in  these  cases  to  ligature  one  of  the 
arteries  of  the  forearm  alone,  and  indeed  simultaneous  ligature  of  both  radial  and  uhiar  arteries 


THE  THORACIC  AORTA  683 

above  the  wrist  is  often  unsuccessful,  on  account  of  the  anastomosis  carried  on  by  the  carpal 
arches.  Therefore,  upon  the  failure  of  jiressure  to  arrest  hemorrhage,  it  is  expedient  to  apply 
a  ligature  to  the  brachial  artery.  When  an  incision  for  deep-seated  suppuration  in  the  tendon 
sheath  is  required,  the  situation  of  the  superficial  arch  must  always  be  borne  in  mind,  and  the 
incisions  placed  either  above  or  below  it.  The  position  of  the  common  digital  branches  of  the 
artery  must  also  be  remembered,  and  incisions  must  be  made  opposite  the  heads  of  the  meta- 
carpal bones  and  not  between  them. 


THE   ARTERIES    OF   THE   TRUNK. 

THE    DESCENDING    AORTA. 

The  descending  aorta  is  (ii\'ided  into  two  portions,  the  thoracic  and  abdominal, 
in  correspondence  Avith  the  t^vo  great  cavities  of  the  trunk  in  which  it  is  situated. 

The  Thoracic  Aorta  (Aorta  Thoracalis)   (Fig.  606). 

The  thoracic  aorta  is  contained  in  the  posterior  mediastinal  cavity.  It  begins 
at  the  lower  border  of  the  fourth  thoracic  vertebra  where  it  is  continuous  with 
the  aortic  arch,  and  ends  in  front  of  the  lower  border  of  the  twelfth  at  the  aortic 
hiatus  in  the  Diaphragma.  At  its  commencement,  it  is  situated  on  the  left  of  the 
vertebral  column;  it  approaches  the  median  line  as  it  descends;  and,  at  its  termina- 
tion, lies  directly  in  front  of  the  column.  The  vessel  describes  a  curve  which  is 
concave  forward,  and  as  the  branches  given  off  from  it  are  small,  its  diminution 
in  size  is  inconsiderable. 

Relations. — It  is  in  relation,  anteriorly,  from  above  downward,  with  the  root  of  the  left  lung, 
the  pericardium,  the  oesophagus,  and  the  Diaphragma;  'posteriorly,  with  the  vertebral  column 
and  the  hemiazygos  veins;  on  the  right  side,  with  the  azygos  vein  and  thoracic  duct;  on  the  lejt 
side,  with  the  left  pleura  and  limg.  The  oesophagus,  with  its  accompanying  plexus  of  nerves, 
lies  on  the  right  side  of  the  aorta  above;  but  at  the  lower  part  of  the  thorax  it  is  placed  in  front 
of  the  aorta,  and,  close  to  the  Diaphragma,  is  situated  on  its  left  side. 

Peculiarities. — The  aorta  is  occasionally  found  to  be  obhterated  at  the  junction  of  the  arch 
with  the  thoracic  aorta,  just  below  the  ductus  arteriosus.  Whether  this  is  the  result  of  disease, 
or  of  congenital  malformation,  is  immaterial  to  oiu-  present  pm'pose;  it  affords  an  interesting 
opportunity  of  observing  the  resources  of  the  collateral  circulation.  The  course  of  the  anastomos- 
ing vessels,  by  which  the  blood  is  brought  from  the  upper  to  the  lower  part  of  the  artery,  will  be 
found  well  described  in  an  account  of  two  cases  in  the  Pathological  Transactions,  vols,  viii  and  x. 
In  the  former,  Sydney  Jones  thus  sums  up  the  detailed  description  of  the  anastomosing  A^essels: 
The  principal  communications  by  which  the  circulation  was  carried  on  were:  (1)  The  internal 
mammary,  anastomosing  with  the  intercostal  arteries,  with  the  inferior  phrenic  of  the  abdominal 
aorta  by  means  of  the  musculophrenic  and  pericardiacophrenic,  and  largely  with  the  inferior 
epigastric.  (2)  The  costocervical  trunk,  anastomosing  anteriorly  by  means  of  a  large  branch 
with  the  first  aortic  intercostal,  and  posteriorly  with  the  posterior  branch  of  the  same  artery. 
(3)  The  inferior  thja-oid,  by  means  of  a  branch  about  the  size  of  an  ordinary  radial,  forming  a 
communication  with  the  first  aortic  intercostal.  (4)  The  transverse  cervical,  by  means  of  very 
large  communications  with  the  posterior  branches  of  the  intercostals.  (5)  The  branches  (of 
the  subclavian  and  axillary)  going  to  the  side  of  the  chest  were  large,  and  anastomosed  freel}^ 
with  the  lateral  branches  of  the  intercostals.  In  the  second  case  Wood  describes  the  anastomoses 
in  a  somewhat  similar  manner,  adding  the  remark  that  "the  blood  which  was  brought  into  the 
aorta  through  the  anastomosis  of  the  intercostal  arteries  appeared  to  be  expended  principally 
in  supplying  the  abdomen  and  pelvis;  while  the  supply  to  the  lower  extremities  had  passed  through 
the  internal  mammary  and  epigastrics." 

In  a  few  cases  an  apparently  double  descending  thoracic  aorta  has  been  found,  the  two  vessels 
lying  side  bj'  side,  and  eventually  fusing  to  form  a  single  tube  in  the  lower  part  of  the  thorax  or 
in  the  abdomen.  One  of  them  is  the  aorta,  the  other  represents  a  dissecting  aortic  aneurism 
which  has  become  canalized;  opening  above  and  below  into  the  true  aorta,  and  at  first  sight 
presenting  the  appearances  of  a  proper  bloodvessel. 

Applied  Anatomy. — The  effects  likelj'  to  be  produced  by  aneurism  of  the  thoracic  aorta,  a 
disease  of  common  occurrence,  must  now  be  considered.  When  the  great  depth  of  the  vessel 
from  the  sm'face  and  the  number  of  important  structures  which  sm-round  it  are  remembered, 
it  may  easily  be  conceived  what  a  variety  of  obscure  sj^mptoms  are  likely  to  arise  from  disease 


684 


AXGIOLOCjY 


of  this  part  of  the  arterial  system,  and  how  they  may  be  mistaken  for  tliose  of  other  affections. 
Aneurism  of  the  thoracic  aorta  most  usually  extends  backward,  along  the  left  side  of  the  vertebral 
column,  producing  absorption  of  the  bodies  of  the  vertebrae,  with  curvature  of  the  column;  while 
the  irritation  or  pressure  on  the  medulla  spinalis  will  give  rise  to  pain,  either  in  the  chest,  back, 
or  loins,  with  radiating  pain  in  the  left  upper  intercostal  spaces,  from  pressure  on  the  intercostal 
nerves;  at  the  same  time  the  tumor  may  project  backward  on  either  side  of  the  vertebral  column, 
beneath  the  integument,  as  a  pulsating  swelling,  simulating  abscess  connected  with  diseased 


Highest  intercostal  artery 


Highest  intercostal  vein 
/ 

Rami  communicantes 


Lig.  arterwsum 


bone;  or  it  may  displace  the  oesophagus  and  compress  the  lungs  on  one  or  the  other  side.  If 
the  tumor  extend  forward,  it  may  press  upon  and  displace  the  heart,  giving  rise  to  palpitation 
and  other  symptoms  of  disease  of  that  organ;  it  may  displace  or  compress  the  a?sophagus,  caus- 
ing pain  and  difficulty  of  swallowing;  and  ultimately  even  open  into  it  by  ulceration,  producing 
fatal  hemorrhage.  If  the  disease  extend  to  the  right  side,  it  may  press  upon  the  thoracic  duct; 
or  it  may  burst  into  the  pleural  cavity,  or  into  the  trachea  or  lung;  and  lastly,  it  may  open  into 
the  posterior  mediastinal  cavity.  Pressure  on  one  of  the  bronchi,  usually  the  left,  will  cause 
cough,  and  in  time  set  up  bronchiectasis;  pressure  on  the  left  pulmonary  plexus  has  been  said 


THE  THORACIC  AORTA  685 

to  give  rise  to  asthmatic  attacks.  Of  late  years,  the  diagnosis  of  thoracic  aneurism  has  been 
much  facihtated  by  the  cmj)loyment  of  the  x-rays,  by  means  of  which  the  outhne  of  the  sac  may 
be  demonstrated. 

Branches  of  the  Thoracic  Aorta.^ — 


Visceral 


Pericardial.  (  Intcrrostal. 

Bronchial.  Parietal.      Subcostal. 
Oesophageal.  (  Superior  Phrenic. 

Mediastinal. 


The  pericardial  branches  {rami  pericardiaci)  consist  of  a  few  small  \'essels  which 
are  distributed  to  the  posterior  surface  of  the  pericardium. 

The  bronchial  arteries  (aa.  bronchioles)  vary  in  number,  size,  and  origin.  There 
is  as  a  rule  only  one  right  bronchial  artery,  which  arises  from  the  first  aortic  inter- 
costal, or  from  the  upper  left  bronchial  artery.  The  left  bronchial  arteries  are  usually 
two  in  number,  and  arise  from  the  thoracic  aorta.  The  upper  left  bronchial  arises 
opposite  the  fifth  thoracic  vertebra,  the  lower  just  below  the  level  of  the  left  bron- 
chus. Each  vessel  runs  on  the  back  part  of  its  bronchus,  dividing  and  subdividing 
along  the  bronchial  tubes,  supplying  them,  the  areolar  tissue  of  the  lungs,  the 
bronchial  lymph  glands,  and  the  oesophagus. 

The  (esophageal  arteries  (aa.  oesophageae)  four  or  five  in  number,  arise  from 
the  front  of  the  aorta,  and  pass  obliquely  downward  to  the  oesophagus,  forming 
a  chain  of  anastomoses  along  that  tube,  anastomosing  with  the  oesophageal  branches 
of  the  inferior  thyroid  arteries  above,  and  with  ascending  branches  from  the  left 
inferior  phrenic  and  left  gastric  arteries  below. 

The  mediastinal  branches  (rami  mediastinales)  are  numerous  small  vessels 
which  supply  the  lymph  glands  and  loose  areolar  tissue  in  the  posterior  mediastinal 
cavity. 

Intercostal  Arteries  (aa.  intercostal e s) . — There  are  usually  nine  pairs  of  aortic 
intercostal  arteries.  They  arise  from  the  back  of  the  aorta,  and  a  redistributed 
to  the  lower  nine  intercostal  spaces,  the  first  two  spaces  being  supplied  by  the  highest 
intercostal  artery,  a  branch  of  the  costocervical  trunk  of  the  subclavian.  The 
right  aortic  intercostals  are  longer  than  the  left,  on  account  of  the  position  of  the 
aorta  on  the  left  side  of  the  vertebral  column;  they  pass  across  the  bodies  of  the 
vertebrae  behind  the  oesophagus,  thoracic  duct,  and  vena  azygos,  and  are  covered 
by  the  right  lung  and  pleura.  The  left  aortic  intercostals  run  backward  on  the 
sides  of  the  vertebrae  and  are  covered  by  the  left  lung  and  pleura;  the  upper  two 
vessels  are  crossed  by  the  highest  left  intercostal  vein,  the  lower  vessels  by  the 
hemiazygos  veins.  The  further  course  of  the  intercostal  arteries  is  practically 
the  same  on  both  sides.  Opposite  the  heads  of  the  ribs  the  sympathetic  trunk 
passes  downward  in  front  of  them,  and  the  splanchnic  nerves  also  descend  in  front 
by  the  lower  arteries.  Each  artery  then  divides  into  an  anterior  and  a  posterior 
ramus. 

The  Anterior  Ramus  crosses  the  corresponding  intercostal  space  obliquely  toward 
the  angle  of  the  upper  rib,  and  thence  is  continued  forward  in  the  costal  groove.  It 
is  placed  at  first  between  the  pleura  and  the  posterior  intercostal  membrane,  then 
it  pierces  this  membrane,  and  lies  between  it  and  the  Intercostalis  externus  as  far  as 
the  angle  of  the  rib;  from  this  onward  it  runs  between  the  Intercostales  externus 
and  internus,  and  anastomoses  in  front  with  the  intercostal  branch  of  the  internal 
mammary  or  musculophrenic.  Each  artery  is  accompanied  by  a  vein  and  a  nerve, 
the  former  being  above  and  the  latter  below  the  artery,  except  in  the  upper  spaces, 
where  the  nerve  is  at  first  above  the  artery.  The  first  aortic  intercostal  artery 
anastomoses  with  the  intercostal  branch  of  the  costocervical  trunk,  and  may  form 
the  chief  supply  of  the  second  intercostal  space.     The  lower  two  intercostal  arteries 


6S6  AXGIOLOGY 

are  continued  anteriorly  from  the  intercostal  spaces  into  the  abdominal  wall,  and 
anastomose  with  the  subcostal,  superior  epigastric,  and  lumbar  arteries. 

Branches. — The  anterior  rami  give  off  the  following  branches: 

Collateral  Intercostal.  Lateral  Cutaneous. 

Muscular.  ]\Iammary. 

The  collateral  intercostal  branch  comes  off  from  the  intercostal  artery  near  the 
angle  of  the  rib,  and  descends  to  the  upper  border  of  the  rib  below,  along  which  it 
courses  to  anastomose  with  the  intercostal  branch  of  the  internal  mammary. 

Muscular  branches  are  given  to  the  Intercostales  and  Pectorales  and  to  the 
Serratus  anterior;  they  anastomose  with  the  highest  and  lateral  thoracic  branches 
of  the  axillary  artery. 

The  lateral  cutaneous  branches  accompany  the  lateral  cutaneous  branches  of  the 
thoracic  nerves. 

Mammary  branches  are  given  off  by  the  vessels  in  the  third,  fourth,  and  fifth 
spaces.  They  supply  the  mamma,  and  increase  considerably  in  size  during  the 
period  of  lactation. 

The  Posterior  Ramus  runs  backward  through  a  space  which  is  bounded  above 
and  below  by  the  necks  of  the  ribs,  medially  by  the  body  of  a  vertebra,  and  laterally 
by  an  anterior  costotransverse  ligament.  It  gives  off  a  spinal  branch  which  enters 
the  vertebral  canal  through  the  intervertebral  foramen  and  is  distributed  to  the 
medulla  spinalis  and  its  membranes  and  the  A^ertebrse.  It  then  courses  over 
the  transverse  process  with  the  posterior  division  of  the  thoracic  nerve,  supplies 
branches  to  the  muscles  of  the  back  and  cutaneous  branches  which  accompany 
the  corresponding  cutaneous  branches  of  the  posterior  division  of  the  nerve. 

Applied  Anatomy. — The  position  of  the  anterior  rami  of  the  intercostal  vessels  should  be 
borne  in  mind  in  performing  the  operation  of  paracentesis  thoracis.  The  puncture  should  never 
be  made  nearer  the  middle  line  posteriorly  than  the  angle  of  the  rib,  as  the  artery  crosses  the 
space  medial  to  this  point.  In  the  lateral  portion  of  the  chest,  where  the  puncture  is  usually 
made,  the  artery  hes  at  the  upper  part  of  the  intercostal  space,  and  therefore  the  punctm-e  should 
be  made  just  above  the  upper  border  of  the  rib  forming  the  lower  boundary  of  the  space. 

The  subcostal  arteries,  so  named  because  they  lie  below  the  last  ribs,  constitute 
the  lowest  pair  of  branches  derived  from  the  thoracic  aorta,  and  are  in  series  with 
the  intercostal  arteries.  Each  passes  along  the  lower  border  of  the  twelfth  rib 
behind  the  kidney  and  in  front  of  the  Quadratus  lumborum  muscle,  and  is  accom- 
panied by  the  twelfth  thoracic  nerve.  It  then  pierces  the  posterior  aponeurosis 
of  the  Transversus  abdominis,  and,  passing  forward  between  this  muscle  and  the 
Obliquus  internus,  anastomoses  with  the  superior  epigastric,  lower  intercostal,  and 
lumbar  arteries.  Each  subcostal  artery  gives  off  a  posterior  branch  which  has  a 
similar  distribution  to  the  posterior  ramus  of  an  intercostal  artery. 

The  superior  phrenic  branches  are  small  and  arise  from  the  lower  part  of  the 
thoracic  aorta;  they  are  distributed  to  the  posterior  part  of  the  upper  surface  of 
the  Diaphragma,  and  anastomose  with  the  musculophrenic  and  pericardiacophrenic 
arteries. 

A  small  aberrant  artery  is  sometimes  found  arising  from  the  right  side  of  the  thor- 
acic aorta  near  the  origin  of  the  right  bronchial.  It  passes  upward  and  to  the  right 
behind  the  trachea  and  the  oesophagus,  and  may  anastomose  with  the  highest 
right  intercostal  artery.  It  represents  the  remains  of  the  right  dorsal  aorta,  and  in  a 
small  proportion  of  cases  is  enlarged  to  form  the  first  part  of  the  right  subclavian 
artery. 

The  Abdominal  Aorta  (Aorta  Abdominalis)  (Fig.  607). 

The  abdominal  aorta  begins  at  the  aortic  hiatus  of  the  Diaphragma,  in  front 
of  the  lower  border  of  the  body  of  the  last  thoracic  vertebra,  and,  descending  in 


THE  ABDOMIXAL  AORTA 


68- 


front  of  the  vertebral  column,  ends  on  the  body  of  the  fourth  lumbar  vertebra, 
commonlv  a  little  to  the  left  of  the  middle  line,^  by  dividing;  into  the  two  common 
iliac  arteries.  It  diminishes  rapidly  in  size,  in  consequence  of  the  many  large 
branches  which  it  gives  off.  As  it  lies  upon  the  bodies  of  the  vertebne,  the  curve 
which  it  describes  is  convex  forward,  the  summit  of  the  convexity  correspondmg 
to  the  third  lumbar  vertebra. 


\  A  P  H   R  A 


Inferior  phrenic  arteries 


Internal 

sperjnatic 

vessels 


Fig    607  — The  abdominal  aurta  ind  its  branches 


Relations.— The  abdominal  aorta  is  covered,  anteriorly,  by  the  lesser  omentum  and  stomach, 
behind  which  are  the  branches  of  the  coehac  artery  and  the  cceUac  plexus;  below  these,  by  the 
Henal  vein,  the  pancreas,  the  left  renal  vein,  the  inferior  part  of  the  duodenum,  the  mesentery, 
and  aortic  plexus.  Posteriorly,  it  is  separated  from  the  lumbar  vertebra?  and  mtervertebral 
fibrocartilages  by  the  anterior  longitudinal  Ugament  and  left  lumbar  vems.  On  the  right  side 
it  is  in  relation  above  with  the  azygos  vein,  cisterna  chyh,  thoracic  duct,  and  the  right  mis  ot 
the  Diaphragma— the  last  separating  it  from  the  upper  part  of  the  inferior  vena  cava,  and  from 
the  right  coehac  ganghon;  the  inferior  vena  cava  is  in  contact  with  the  aorta  below.  On  the 
left  side  are  the  left  crus  of  the  Diaphragma,  the  left  coehac  ganghon,  the  ascending  part  of  the 
duodenum,  and  some  coils  of  the  small  intestine. 

Applied  Anatomy.— The  abdommal  aorta  may  be  the  seat  of  an  aneurism  either  at  its  upper 
part,  close  to  and  often  involving  the  coehac  artery,  or  at  its  lower  part,  near  the  bifurcation. 

1  Lord  Lister,  having  accuratelv  examined  30  bodies  in  order  to  ascertain  the  exact  point  of  termination  of  this 
vessel,  found  it  "either  absolutely,  or  almost  absolutely,  mesial  m  1.5  while  in  13  it  de^nated  more  or  le==  to  the  left, 
and  in  2  was  slightly  to  the  right. "     System  of  Surgery,  edited  by  T.  Holmes,  2d  ed.,  v,  boJ. 


688  ANGIOLOGY 

Occasionally  aneurisms  are  met  with  on  some  of  the  branches  of  the  aorta,  the  mesenteric  or 
lienal,  quite  independent  of  the  main  trunk. 

When  an  aneurismal  sac  is  connected  with  the  posterior  part  of  the  abdominal  aorta,  it  usually 
produces  absorption  of  the  bodies  of  the  vertebra?.  Pain  is  invariably  present,  and  is  usually  of 
two  kinds — a  fixed  and  constant  pain  in  the  back,  caused  by  the  tumor  pressing  on  or  displacing 
the  branches  of  the  ca?liac  plexus  and  splanchnic  nerves;  and  a  sharp  lancinating  pain,  radiating 
along  those  branches  of  the  lumbar  nerves  which  are  pressed  on  by  the  tumor;  hence  the  pain 
in  the  loins,  the  testes,  the  hypogastrium,  and  in  the  lower  hmb  (generally  of  the  left  side).  This 
form  of  aneurism  usually  bursts  into  or  behind  the  peritoneal  cavity. 

When  an  aneurismal  sac  is  connected  with  the  front  of  the  aorta  near  the  coeliac  artery,  it 
forms  a  pulsating  tumor  in  the  left  hypochondriac  or  epigastric  regions,  usually  attended  with 
symptoms  of  disturbance  of  the  digestive  tube,  as  sickness,  dyspepsia,  or  constipation,  and 
accompanied  bj^  pain,  which  is  constant,  but  nearly  always  fixed,  in  the  loins,  epigastrium,  or 
some  part  of  the  abdomen;  the  radiating  pain  being  rare,  as  the  lumbar  nerves  are  seldom  impli- 
cated. This  form  of  aneurism  may  burst  into  the  peritoneal  cavity,  behind  the  peritoneum, 
between  the  layers  of  the  mesentery,  or,  more  rarely,  into  the  duodenum;  it  rarely  extends  back- 
ward so  as  to  affect  the  vertebral  column. 

Occlusion  of  the  abdominal  aorta  by  thrombosis  or  embohsm  is  rare,  but  produces  very  severe 
symptoms  when  it  does  occur.  The  patient  complains  of  intense  pain  in  the  legs;  pallor  of  the 
legs,  followed  by  coldness,  lividity,  paresis,  paralysis,  and  finally  gangrene,  are  likely  to  succeed, 
death  usually  supervening  within  a  fortnight. 

The  abdominal  aorta  has  been  tied  in  several  cases,  and  although  none  of  the  patients  perma- 
nently recovered,  still,  as  one  case  lived  forty-eight  days,  the  possibiUty  of  the  reestablishment 
of  the  circulation  may  be  considered  to  be  proved. 

Collateral  Circulation. — The  collateral  circulation  would  be  carried  on  by  the  anastomoses 
between  the  internal  mammary  and  the  inferior  epigastric;  by  the  free  communication  between 
the  superior  and  inferior  mesenteries,  if  the  Ugature  were  placed  between  these  vessels;  or  by  the 
anastomosis  between  the  inferior  mesenteric  and  the  internal  pudendal,  when  (as  is  more  common) 
the  point  of  Hgature  is  below  the  origin  of  the  inferior  mesenteric;  and  possibly  by  the  anastomoses 
of  the  lumbar  arteries  with  the  branches  of  the  hypogastric. 

Branches. — The  branches  of  the  abdominal  aorta  may  be  divided  into  three 
sets:  visceral,  parietal,  and  terminal. 

Visceral  Branches.  Parietal  Branches.     ■ 

Coeliac.  Inferior  Phrenics. 

Superior  Mesenteric.        '  Lumbars. 

Inferior  Mesenteric.  Middle  Sacral. 
Middle  Suprarenals. 
Renals. 

Internal  Spermatics.  Terminal  .Branches. 

Ovarian  (in  the  female).  Common  Iliacs. 

Of  the  visceral  branches,  the  coeliac  artery  and  the  superior  and  inferior  mes- 
enteric arteries  are  unpaired,  while  the  suprarenals,  renals,  internal  spermatics, 
and  ovarian  are  paired.  Of  the  parietal  branches  the  inferior  phrenics  and  lumbars 
are  paired;  the  middle  sacral  is  unpaired.    The  terminal  branches  are  paired. 

The  coeliac  artery  (a.  coeliaca;  coeliac  axis)  (Figs.  608,  609)  is  a  short  thick  trunk, 
about  1.25  cm.  in  length,  which  arises  from  the  front  of  the  aorta,  just  below 
the  aortic  hiatus  of  the  Diaphragma,  and,  passing  nearly  horizontally  forward, 
divides  into  three  large  branches,  the  left  gastric,  the  hepatic,  and  the  splenic;  it 
occasionally  gives  off  one  of  the  inferior  phrenic  arteries. 

Relations. — The  coehac  artery  is  covered  by  the  lesser  omentum.  On  the  right  side  it  is  in 
relation  with  the  right  coehac  ganglion  and  the  caudate  process  of  the  hver;  on  the  left  side,  with 
the  left  coehac  ganghon'and  the  cardiac  end  of  the  stomach.  Below,  it  is  in  relation  to  the  upper 
border  of  the  pancreas,  and  the  henal  vein. 

1.  The  Left  Gastric  Artery  (a.  gastrica  sinistra;  gastric  or  coronary  artery),  the 
smallest  of  the  three  branches  of  the  coeliac  artery,  passes  upward  and  to  the  left, 
posterior  to  the  omental  bursa,  to  the  cardiac  orifice  of  the  stomach.  Here  it  dis- 
tributes branches  to  the  oesophagus,  which  anastomose  with  the  aortic  oesophageal 


THE  ABDOMINAL  AORTA 


689 


arteries;  others  supply  the  cardiac  part  of  the  stomach,  anastomosing  with  branches 
of  the  lienal  artery.  It  then  runs  from  left  to  right,  along  the  lesser  curvature  of  the 
stomach  to  the  pylorus,  between  the  layers  of  the  lesser  omentum ;  it  gives  branches 
to  both  surfaces  of  the  stomach  and  anastomoses  with  the  right  gastric  artery. 

2.  The  Hepatic  Artery  (a.  hepatica)  in  the  adult  is  intermediate  in  size  between 
the  left  gastric  and  lienal;  in  the  fetus,  it  is  the  largest  of  the  three  branches  of 
the  coeliac  artery.  It  is  first  directed  forward  and  to  the  right,  to  the  upper  margin 
of  the  superior  part  of  the  duodenum,  forming  the  lower  boundary  of  the  epiploic 
foramen  {foramen  of  JVinslow).  It  then  crosses  the  portal  vein  anteriorly  and 
ascends  between  the  layers  of  the  lesser  omentum,  and  in  front  of  the  epiploic  fora- 
men, to  the  porta  hepatis,  where  it  divides  into  two  branches,  right  and  left,  which 


Cystic  artery 


Fig.  60S. — The  coeliac  artery  and  its  branches;  the  liver  has  been  raised,  and  the  lesser  omentum  and  anterior 

layer  of  the  greater  omentum  removed. 

supply  the  corresponding  lobes  of  the  liver,  accompanying  the  ramifications  of  the 
portal  vein  and  hepatic  ducts.    The  hepatic  artery,  in  its  course  along  the  right 
border  of  the  lesser  omentum,  is  in  relation  with  the  common  bile-duct  and  portal 
vein,  the  duct  lying  to  the  right  of  the  artery,  and  the  vein  behind. 
Its  branches  are: 

Right  Gastric. 

Gastroduodenal  l^^sK^^^t^o^P^Pl^i^-         '     , 
{  bupenor  rancreaticoduodenal. 

Cystic. 

The  right  gastric  artery  {a.  gastrica  dextra;  'pyloric  artery)  arises  from  the  hepatic, 
above  the  pylorus,  descends  to  the  pjdoric  end  of  the  stomach,  and  passes  from 
44 


690 


ANGIOLOGY 


right  to  left  along  its  lesser  curvature,  supplying  it  with  branches,  and  anastomosing 
with  the  left  gastric  artery. 

The  gastroduodenal  artery  (a.  gastroduodenalis)  (Fig.  609)  is  a  short  but  large 
branch,  which  descends,  near  the  pylorus,  between  the  superior  part  of  the  duo- 
denum and  the  neck  of  the  pancreas,  and  divides  at  the  lower  border  of  the  duodenum 
into  two  branches,  the  right  gastroepiploic  and  the  superior  pancreaticoduodenal. 
Previous  to  its  division  it  gives  off  two  or  three  small  branches  to  the  pyloric  end 
of  the  stomach  and  to  the  pancreas. 

Branches  to  greater  omentum 


Fig.  609. — The  coeliac  artery  and  its  branches;  the  stomach  has  been  raised  and  the  peritoneum  removed. 


The  right  gastroepiploic  artery  (a.  gastroepiploica  dextra)  runs  from  right  to  left 
along  the  greater  curvature  of  the  stomach,  between  the  layers  of  the  greater 
omentum,  anastomosing  with  the  left  gastroepiploic  branch  of  the  lienal  artery. 
Except  at  the  pylorus,  where  it  is  in  contact  with  the  stomach,  it  lies  about  a  finger's 
breadth  from  the  greater  curvature.  This  vessel  gives  off  numerous  branches, 
some  of  which  ascend  to  supply  both  surfaces  of  the  stomach,  while  others  descend 
to  supply  the  greater  omentum  and  anastomose  with  branches  of  the  middle  colic. 

The  superior  pancreaticoduodenal  artery  (a.  yancreaticoduodenalis  superior) 
descends  between  the  contiguous  margins  of  the  duodenum  and  pancreas.  It 
supplies  both  these  organs,  and  anastomoses  with  the  inferior  pancreaticoduodenal 
branch  of  the  superior  mesenteric  artery,  and  with  the  pancreatic  branches  of  the 
lienal  artery. 


THE  ABDOMINAL  AORTA  691 

The  cystic  artery  {a.  ci/stim)  (Fig.  ()()S),  usually  a  branch  of  the  right  hepatic, 
passes  downward  and  forward  along  the  neck  of  the  gall-bladder,  and  divides  into 
two  branches,  one  of  which  ramifies  on  the  free  surface,  the  other  on  the  attached 
surface  of  the  gall-bladder. 

3.  The  Lienal  or  Splenic  Artery  (a.  lienaUs),  the  largest  branch  of  the  coeliac 
artery,  is  remarkable  for  the  tortuosity  of  its  course.  It  passes  horizontally  to 
the  left  side,  behind  the  stomach  and  the  omental  bursa  of  the  peritoneum,  and 
along  the  upper  border  of  the  pancreas,  accompanied  by  the  lienal  vein,  which 
lies  below  it;  it  crosses  in  front  of  the  upper  part  of  the  left  kidney,  and,  on  arriving 
near  the  spleen,  divides  into  branches,  some  of  which  enter  the  hilus  of  that  organ 
between  the  two  layers  of  the  phrenicolienal  ligament  to  be  distributed  to  the  tissues 
of  the  spleen;  some  are  given  to  the  pancreas,  while  others  pass  to  the  greater  curva- 
ture of  the  stomach  between  the  laj'ers  of  the  gastrolienal  ligament.  Its  branches 
are: 

Pancreatic.  Short  Gastric. 

Left  Gastroepiploic. 

The  pancreatic  branches  {rami  pancreatici)  are  numerous  small  vessels  derived 
from  the  lienal  as  it  runs  behind  the  upper  border  of  the  pancreas,  supplying  its 
body  and  tail.  One  of  these,  larger  than  the  rest,  is  sometimes  given  oflF  near  the 
tail  of  the  pancreas;  it  runs  from  left  to  right  near  the  posterior  surface  of  the  gland, 
following  the  course  of  the  pancreatic  duct,  and  is  called  the  arteria  pancreatica 
magna.  These  vessels  anastomose  with  the  pancreatic  branches  of  the  pancreatico- 
duodenal and  superior  mesenteric  arteries. 

The  short  gastric  arteries  {aa.  gastricae  breves;  vasa  hrevia)  consist  of  from  five  to 
seven  small  branches,  which  arise  from  the  end  of  the  lienal  artery,  and  from  its 
terminal  divisions.  They  pass  from  left  to  right,  between  the  layers  of  the  gastro- 
lienal ligament,  and  are  distributed  to  the  greater  curvature  of  the  stomach,  anasto- 
mosing with  branches  of  the  left  gastric  and  left  gastroepiploic  arteries. 

The  left  gastroepiploic  artery  (a.  gastroepvploica  sinistra)  the  largest  branch  of  the 
lienal,  runs  from  left  to  right  about  a  finger's  breadth  or  more  from  the  greater 
curvature  of  the  stomach,  between  the  layers  of  the  greater  omentum,  and  anasto- 
moses with  the  right  gastroepiploic.  In  its  course  it  distributes  several  ascending 
branches  to  both  surfaces  of  the  stomach;  others  descend  to  supply  the  greater 
omentum  and  anastomose  with  branches  of  the  middle  colic. 

Applied  Anatomy. — Embolism  of  branches  of  the  henal  artery  is  tolerably  common  in  heart 
disease,  the  embolus  coming  from  the  left  side  of  the  heart.  It  is  characterized  by  the  occurrence 
of  a  sudden  sharp  pain  or  "stitch"  in  the  splenic  region,  with  subsequent  local  enlargement  of 
the  spleen  from  the  formation  of  an  infarct  in  its  substance. 

The  superior  mesenteric  artery  (a.  mesenterica  superior)  (Fig.  610)  is  a  large 
vessel  which  supplies  the  wdiole  length  of  the  small  intestine,  except  the  superior 
part  of  the  duodenum ;  it  also  supplies  the  cecum  and  the  ascending  part  of  the  colon 
and  about  one-half  of  the  transverse  part  of  the  colon.  It  arises  from  the  front 
of  the  aorta,  about  1.25  cm.  below  the  coeliac  artery,  and  is  crossed  at  its  origin  by 
the  lienal  vein  and  the  neck  of  the  pancreas.  It  passes  downward  and  forward, 
anterior  to  the  processus  uncinatus  of  the  head  of  the  pancreas  and  inferior  part 
of  the  duodenum,  and  descends  between  the  layers  of  the  mesentery  to  the  right 
iliac  fossa,  where,  considerably  diminished  in  size,  it  anastomoses  with  one  of 
its  own  branches,  viz.,  the  ileocolic.  In  its  course  it  crosses  in  front  of  the  inferior 
vena  cava,  the  right  ureter  and  Psoas  major,  and  forms  an  arch,  the  convexity  of 
which  is  directed  forward  and  dow^nward  to  the  left  side,  the  concavity  backward 
and  upward  to  the  right.  It  is  accompanied  by  the  superior  mesenteric  vein, 
which  lies  to  its  right  side,  and  it  is  surrounded  by  the  superior  mesenteric  plexus 
of  nerves. 


692 


ANGIOLOGY 


Dissection. — In  order  to  expose  the  superior  mesenteric  artery  raise  the  great  omentum  and 
transverse  colon,  draw  down  the  small  intestines,  and  cut  through  the  peritoneum  where  the 
transverse  mesocolon  and  mesentery  join;  the  artery  will  then  be  exposed  just  as  it  issues  from 
over  the  processus  uncinatus  of  the  head  of  the  pancreas. 


Fig.  610.— The  superior  mesenteric  artery  and  its  branches. 

Branches. — Its  branches  are: 

Inferior  Pancreaticoduodenal.  Ileocolic. 

Intestinal.  Right  Colic. 

Middle  Colic. 

The  Inferior  Pancreaticoduodenal  Artery  (a.  yancreaticoduodenalis  inferior)  is  given 
off  from  the  superior  mesenteric  or  from  its  first  intestinal  branch,  opposite  the 
upper  border  of  the  inferior  part  of  the  duodenum.  It  courses  to  the  right 
between  the  head  of  the  pancreas  and  duodenum,  and  then  ascends  to  anastomose 
with  the  superior  pancreaticoduodenal  artery.  It  distributes  branches  to  the  head 
of  the  pancreas  and  to  the  descending  and  inferior  parts  of  the  duodenum. 

The  Intestinal  Arteries  {aa.  intestinales;  xasa  intestini  tenuis)  arise  from  the  convex 
side  of  the  superior  mesenteric  artery.  They  are  usually  from  twelve  to  fifteen 
in  number,  and  are  distributed  to  the  jejunum  and  ileum.  They  run  nearly  parallel 
with  one  another  between  the  layers  of  the  mesentery,  each  vessel  dividing  into 
two  branches,  which  unite  with  adjacent  branches,  forming  a  series  of  arches,  the 


THE  ABDOMINAL  AORTA 


693 


convexities  of  which  are  directeil  toward  the  intestine  (Fig.  Gil).  From  this  first 
set  of  arches  branches  arise,  which  nnite  with  similar  ])ranches  from  above  and  below 
and  thus  a  second  series  of  arches  is  formed;  from  the  lower  l)ranches  of  the  artery, 
a  third,  a  fourth,  or  even  a  fifth  series  of  arches  may  be  formed,  diminishing  in 
size  the  nearer  they  approach  the  intestine.  In  the  short,  upper  part  of  the  mesen- 
tery only  one  set  of  arches  exists,  but  as  the  depth  of  the  mesentery  increases, 
second,  third,  fourth,  or  even  fifth  groups  are  developed.  From  the  terminal 
arches  numerous  small  straight  vessels  arise  which  encircle  the  intestine,  upon 
which  they  are  distributed,  ramifying  between  its  coats.  From  the  intestinal 
arteries  small  branches  are  given  off  to  the  lymph  glands  and  other  structures 
between  the  layers  of  the  mesentery. 


Fig.  611. — Loop  of  small  intestine  showing  distribution  of  intestinal  arteries.  (From  a  preparation  by  Mr.  Hamilton 
Drummond.)  The  vessels  were  injected  while  the  gut  was  in  situ;  the  gut  was  then  removed,  and  an  a;-ray  photograph 
taken. 


The  Ileocolic  Artery  (a.  ileocolica)  is  the  lowest  branch  arising  from  the  concavity 
of  the  superior  mesenteric  artery.  It  passes  downward  and  to  the  right  behind  the 
peritoneum  toward  the  right  iliac  fossa,  where  it  divides  into  a  superior  and  an 
inferior  branch;  the  inferior  anastomoses  with  the  end  of  the  superior  mesenteric 
artery,  the  superior  with  the  right  colic  artery. 

The  inferior  branch  of  the  ileocolic  runs  toward  the  upper  border  of  the  ileo- 
colic junction  and  supplies  the  following  branches  (Fig.  612) : 

(a)  colic,  which  pass  upward  on  the  ascending  colon;  (b)  anterior  and  posterior 
cecal,  which  are  distributed  to  the  front  and  back  of  the  cecum;  (c)  an  appendicular 
artery,  which  descends  behind  the  termination  of  the  ileum  and  enters  the  mesen- 
teriole  of  the  vermiform  process;  it  runs  near  the  free  margin  of  this  mesenteriole 
and  ends  in  branches  which  supply  the  vermiform  process;  and  (d)  ileal,  which  run 


694 


AXGIOLOGY 


upward  and  to  the  left  on  the  lower  part  of  the  ileum,  and  anastomose  with  the 
termination  of  the  superior  mesenteric. 

The  Right  Colic  Artery  (a.  colica  dextra)  arises  from  about  the  middle  of  the  con- 
cavity of  the  superior  mesenteric  artery,  or  from  a  stem  common  to  it  and  the  ileo- 
colic. It  passes  to  the  right  behind  the  peritoneum,  and  in  front  of  the  right 
internal  spermatic  or  ovarian  vessels,  the  right  ureter  and  the  Psoas  major,  toward 
the  middle  of  the  ascending  colon;  sometimes  the  vessel  lies  at  a  higher  level, 
and  crosses  the  descending  part  of  the  duodenum  and  the  lower  end  of  the  right 
kidney.  x\t  the  colon  it  divides  into  a  descending  branch,  which  anastomoses  with 
the  ileocolic,  and  an  ascending  branch,  which  anastomoses  with  the  middle  colic. 
These  branches  form  arches,  from  the  convexity  of  which  vessels  are  distributed 
to  the  ascending  colon. 


Termiiud  fart  of  ileocolic 

CcBcal  branches 

Ileal  branches 


Appendicular 
artery 


'^•form  process 

Fig.  612. — Arteries  of  cecum  and  vermiform  process. 


The  Middle  Colic  Artery  (a.  colica  media)  arises  from  the  superior  mesenteric 
just  below  the  pancreas  and,  passing  downward  and  forward  between  the  layers  of 
the  transverse  mesocolon,  divides  into  two  branches,  right  and  left;  the  former 
anastomoses  with  the  right  colic;  the  latter  with  the  left  colic,  a  branch  of  the  in- 
ferior mesenteric.  The  arches  thus  formed  are  placed  about  two  fingers'  breadth 
from  the  transverse  colon,  to  which  they  distribute  branches. 

The  inferior  mesenteric  artery  (a.  mesenterica  inferior)  (Fig.  613)  supplies  the 
left  half  of  the  transverse  part  of  the  colon,  the  whole  of  the  descending  and  iliac 
parts  of  the  colon,  the  sigmoid  colon,  and  the  greater  part  of  the  rectum.  It  is 
smaller  than  the  superior  mesenteric,  and  arises  from  the  aorta,  about  3  or  4  cm. 
above  its  division  into  the  common  iliacs  and  close  to  the  lower  border  of  the 
inferior  part  of  the  duodenum.  It  passes  downward  posterior  to  the  peritoneum, 
lying  at  first  anterior  to  and  then  on  the  left  side  of  the  aorta.  It  crosses  the 
left  common  iliac  artery  and  is  continued  into  the  lesser  pelvis  under  the  name  of 
the  superior  hemorrhoidal  artery,  which  descends  between  the  two  layers  of  the 
sigmoid  mesocolon  and  ends  on  the  upper  part  of  the  rectum. 


THE  ABDOMJXAL  AORTA 


695 


Dissection. — In  order  to  expose  the  inferior  mesenteric  artery  draw  the  small  intestines  and 
mesentery  over  to  the  right  side  of  the  abdomen,  raise  the  transverse  colon  toward  the  thorax, 
and  divide  the  peritoneum  covering  the  front  of  the  aorta. 


Middle  Hemorrhoidal 
Inferior  Hemorrhoidal 


Fig.  613. — The  inferior  mesenteric  artery  and  its  branches. 


Branches. — Its  branches  are: 
Left  Colic. 


Sigmoid. 


Superior  Hemorrhoidal. 


The  Left  Colic  Artery  (a.  coUca  sinistra)  runs  to  the  left  behind  the  peritoneum 
and  in  front  of  the  Psoas  major,  and  after  a  short,  but  variable,  course  divides 
into  an  ascending  and  a  descending  branch;  the  stem  of  the  artery  or  its  branches 
cross  the  left  ureter  and  left  internal  spermatic  vessels.  The  ascending  branch 
crosses  in  front  of  the  left  kidney  and  ends,  between  the  two  layers  of  the  transverse 
mesocolon,  by  anastomosing  with  the  middle  colic  artery;  the  descending  branch 
anastomoses  with  the  highest  sigmoid  artery.  From  the  arches  formed  by  these 
anastomoses  branches  are  distributed  to  the  descending  colon  and  the  left  part 
of  the  transverse  colon. 

The  Sigmoid  Arteries  (oo.  sigmoideae)  (Fig.  614),  two  or  three  in  number,  run 
obliciuely  downward  and  to  the  left  behind  the  peritoneum  and  in  front  of  the 
Psoas  major,  ureter,  and  internal  spermatic  vessels.  Their  branches  supply  the  lower 
part  of  the  descending  colon,  the  iliac  colon,  and  the  sigmoid  or  pelvic  colon;  anasto- 
mosing above  with  the  left  colic,  and  below  with  the  superior  hemorrhoidal  artery. 


696 


ANGIOLOGY 


The  Superior  Hemorrhoidal  Artery  (a.  haemorrhoidalis  superior)  (Fig.  614),  the 
continuation  of  the  inferior  mesenteric,  descends  into  the  pelvis  between  the  la\'ers 
of  the  mesentery  of  the  sigmoid  colon,  crossing,  in  its  course,  the  left  common 
iliac  vessels.  It  divides,  opposite  the  third  sacral  vertebra,  into  two  branches, 
which  descend  one  on  either  side  of  the  rectum,  and  about  10  or  12  cm.  from  the 
anus  break  up  into  several  small  branches.  These  pierce  the  muscular  coat  of  the 
bowel  and  run  downward,  as  straight  vessels,  placed  at  regular  intervals  from  each 
other  in  the  wall  of  the  gut  between  its  muscular  and  mucous  coats,  to  the  level 
of  the  Sphincter  ani  internus;  here  they  form  a  series  of  loops  around  the  lower  end 
of  the  rectum,  and  communicate  with  the  middle  hemorrhoidal  branches  of  the 
hypogastric,  and  with  the  inferior  hemorrhoidal  branches  of  the  internal  pudendal. 


J   Q.'H'Uta. 


) 


Fig.  614. — Sigmoid  colon  and   rectum,   showing    distribution  of   branches  of   inferior   mesenteric  artery  and  their 
anastomoses.     (From  a  preparation  by  Mr.  Hamilton  Drummond.)     Prepared  in  same  manner  as  Fig.  611. 


Applied  Anatomy. — ^EmboHsm  of  the  mesenteric  arteries  produces  acute  and  severe  symp- 
toms, of  which  the  chief  are  abdominal  pain  and  tenderness,  nausea  and  vomiting,  diarrhoea 
or  constipation;  blood  is  foimd  in  the  stools  of  nearly  half  the  patients.  In  many  cases  the  symp- 
toms closely  resemble  those  of  intestinal  obstruction. 

The  middle  suprarenal  arteries  (aa.  swprarenales  media;  middle  capsular  arteries; 
suprarenal  arteries)  are  two  small  vessels  which  arise,  one  from  either  side  of  the 
aorta,  opposite  the  superior  mesenteric  artery.  They  pass  lateralward  and  slightly 
upward,  over  the  crura  of  the  Diaphragma,  to  the  suprarenal  glands,  where  they 
anastomose  with  suprarenal  branches  of  the  inferior  phrenic  and  renal  arteries.  In 
the  fetus  these  arteries  are  of  large  size. 

The  renal  arteries  {aa.  renales)  (Fig.  607),  are  two  large  trunks,  which  arise 
from  the  side  of  the  aorta,  immediately  below  the  superior  mesenteric  artery. 


THE  ABDOMINAL  AORTA  097 

Each  is  directed  across  the  cms  of  the  Diaphragma,  so  as  to  form  nearly  a  right 
angle  with  the  aorta.  The  right  is  longer  than  the  left,  on  account  of  the  position 
of  the  aorta;  it  passes  behind  the  inferior  vena  cava,  the  right  renal  vein,  the  head 
of  the  pancreas,  and  the  descending  part  of  the  duodenum.  The  left  is  somewhat 
higher  than  the  right;  it  lies  behind  the  left  renal  vein,  the  body  of  the  pancreas 
and  the  lienal  vein,  and  is  crossed  by  the  inferior  mesenteric  vein.  Before  reaching 
the  hilus  of  the  kidney,  each  artery  divides  into  four  or  five  branches;  the  greater 
number  of  these  lie  between  the  renal  vein  and  ureter,  the  vein  being  in  front, 
the  ureter  behind,  but  one  or  more  branches  are  usually  situated  behind  the  ureter. 
Each  vessel  gives  off  some  small  inferior  suprarenal  branches  to  the  suprarenal 
gland,  the  ureter,  and  the  surrounding  cellular  tissue  and  muscles.  One  or  two 
accessory  renal  arteries  are  frequently  found,  more  especially  on  the  left  side 
they  usually  arise  from  the  aorta,  and  may  come  off  above  or  below  the  main  artery, 
the  former  being  the  more  common  position.  Instead  of  entering  the  kidney  at  the 
hilus,  they  usually  pierce  the  upper  or  lower  part  of  the  gland. 

The  internal  spermatic  arteries  {aa.  spermaticae  internae;  spermatic  arteries) 
(Fig.  607)  are  distributed  to  the  testes.  They  are  two  slender  vessels  of  consid- 
erable length,  and  arise  from  the  front  of  the  aorta  a  little  below  the  renal  arteries. 
Each  passes  obliquely  downward  and  lateralward  behind  the  peritoneum,  resting 
on  the  Psoas  major,  the  right  spermatic  lying  in  front  of  the  inferior  vena  cava 
and  behind  the  middle  colic  and  ileocolic  arteries  and  the  terminal  part  of  the 
ileum,  the  left  behind  the  left  colic  and  sigmoid  arteries  and  the  iliac  colon.  Each 
crosses  obliquely  over  the  ureter  and  the  lower  part  of  the  external  iliac  artery 
to  reach  the  abdominal  inguinal  ring,  through  which  it  passes,  and  accompanies 
the  other  constituents  of  the  spermatic  cord  along  the  inguinal  canal  to  the 
scrotum,  where  it  becomes  tortuous,  and  divides  into  several  branches.  Two  or 
three  of  these  accompany  the  ductus  deferens,  and  supply  the  epididymis,  anasto- 
mosing with  the  artery  of  the  ductus  deferens;  others  pierce  the  back  part  of  the 
tunica  albuginea,  and  supply  the  substance  of  the  testis.  The  internal  spermatic 
artery  supplies  one  or  two  small  branches  to  the  ureter,  and  in  the  inguinal  canal 
gives  one  or  two  twigs  to  the  Cremaster. 

The  ovarian  arteries  {aa.  ovaricae)  are  the  corresponding  arteries  in  the  female 
to  the  internal  spermatic  in  the  male.  They  supply  the  ovaries,  are  shorter  than  the 
internal  spermatics,  and  do  not  pass  out  of  the  abdominal  cavity.  The  origin 
and  course  of  the  first  part  of  each  artery  are  the  same  as  those  of  the  internal 
spermatic,  but  on  arriving  at  the  upper  opening  of  the  lesser  pelvis  the  ovarian 
artery  passes  inward,  between  the  two  layers  of  the  ovariopelvic  ligament  and  of 
the  broad  ligament  of  the  uterus,  to  be  distributed  to  the  ovary.  Small  branches 
are  given  to  the  ureter  and  the  uterine  tube,  and  one  passes  on  to  the  side  of  the 
uterus,  and  unites  with  the  uterine  arter3%  Other  offsets  are  continued  on  the  round 
ligament  of  the  uterus,  through  the  inguinal  canal,  to  the  integument  of  the  labium 
majus  and  groin. 

At  an  early  period  of  fetal  life,  when  the  testes  or  ovaries  lie  by  the  side  of  the 
vertebral  column,  below  the  kidneys,  the  internal  spermatic  or  ovarian  arteries 
are  short;  but  with  the  descent  of  these  organs  into  the  scrotum  or  lesser  pelvis, 
the  arteries  are  gradually  lengthened. 

The  inferior  phrenic  arteries  {aa.  phrenicae  inferiores)  (Fig,  607)  are  two  small 
vessels,  which  supply  the  Diaphragma  but  present  much  variety  in  their  origin. 
They  may  arise  separately  from  the  front  of  the  aorta,  immediately  above  the  coeliac 
artery,  or  by  a  common  trunk,  which  may  spring  either  from  the  aorta  or  from  the 
cceliac  artery.  Sometimes  one  is  derived  from  the  aorta,  and  the  other  from  one  of 
the  renal  arteries;  they  rarely  arise  as  separate  vessels  from  the  aorta.  They 
diverge  from  one  another  across  the  crura  of  the  Diaphragma,  and  then  run  ob- 
liquely upward  and  lateralward  upon  its  under  surface.    The  left  phrenic  passes 


698  ANGIOLOGY 

behind  the  oesophagus,  and  runs  forward  on  the  left  side  of  the  oesophageal  hiatus. 
The  right  phrenic  passes  behind  the  inferior  vena  cava,  and  along  the  right  side 
of  the  foramen  which  transmits  that  vein.  Near  the  back  part  of  the  central 
tendon  each  vessel  divides  into  a  medial  and  a  lateral  branch.  The  medial  branch 
curves  forward,  and  anastomoses  with  its  fellow  of  the  opposite  side,  and  with 
the  musculophrenic  and  pericardiacophrenic  arteries.  The  lateral  branch  passes 
toward  the  side  of  the  thorax,  and  anastomoses  with  the  lower  intercostal  arteries, 
and  with  the  musculophrenic.  The  lateral  branch  of  the  right  phrenic  gives  off 
a  few  vessels  to  the  inferior  vena  cava;  and  the  left  one,  some  branches  to  the 
oesophagus.  Each  vessel  gives  off  superior  suprarenal  branches  to  the  suprarenal 
gland  of  its  own  side.  The  spleen  and  the  liver  also  receive  a  few  twigs  from  the 
left  and  right  vessels  respectively. 

The  lumbar  arteries  iaa.  liimhahs)  are  in  series  with  the  intercostals.  They 
are  usually  four  in  number  on  either  side,  and  arise  from  the  back  of  the  aorta, 
opposite  the  bodies  of  the  upper  four  lumbar  vertebrse.  A  fifth  pair,  small  in  size, 
is  occasionally  present:  they  arise  from  the  middle  sacral  artery.  They  run  lateral- 
ward  and  backward  on  the  bodies  of  the  lumbar  vertebrae,  behind  the  sympathetic 
trunk,  to  the  intervals  between  the  adjacent  transverse  processes,  and  are  then 
continued  into  the  abdominal  wall.  The  arteries  of  the  right  side  pass  behind  the 
inferior  vena  cava,  and  the  upper  two  on  each  side  run  behind  the  corresponding 
crus  of  the  Diaphragma.  The  arteries  of  both  sides  pass  beneath  the  tendinous 
arches  which  give  origin  to  the  Psoas  major,  and  are  then  continued  behind  this 
muscle  and  the  lumbar  plexus.  They  now  cross  the  Quadratus  lumborum,  the  upper 
three  arteries  running  behind,  the  last  usually  in  front  of  the  muscle.  At  the  lateral 
border  of  the  Quadratus  lumborum  they  pierce  the  posterior  aponeurosis  of  the 
Transversus  abdominis  and  are  carried  forward  between  this  muscle  and  the 
Obliquus  internus.  They  anastomose  with  the  lower  intercostal,  the  subcostal, 
the  iliolumbar,  the  deep  iliac  circumflex,  and  the  inferior  epigastric  arteries. 

Branches. — In  the  interval  between  the  adjacent  transverse  processes  each  lumbar 
artery  gives  off  a  posterior  ramus  which  is  continued  backward  between  the  trans- 
verse processes  and  is  distributed  to  the  muscles  and  skin  of  the  back;  it  furnishes 
a  spinal  branch  which  enters  the  vertebral  canal  and  is  distributed  in  a  manner 
similar  to  the  spinal  branches  of  the  posterior  rami  of  the  intercostal  arteries 
(page  686).  Muscular  branches  are  supplied  from  each  lumbar  artery  and  from  its 
posterior  ramus  to  the  neighboring  muscles. 

The  middle  sacral  artery  {a.  sacralis  media)  (Fig.  607)  is  a  small  vessel,  which 
arises  from  the  back  of  the  aorta,  a  little  above  its  bifurcation.  It  descends  in 
the  middle  line  in  front  of  the  fourth  and  fifth  lumbar  vertebrae,  the  sacrum  and 
coccyx,  and  ends  in  the  glomus  coccygeum  {coccygeal  gland).  From  it,  minute 
branches  are  said  to  pass  to  the  posterior  surface  of  the  rectum.  On  the  last 
lumbar  vertebra  it  anastomoses  with  the  lumbar  branch  of  the  iliolumbar  artery; 
in  front  of  the  sacrum  it  anastomoses  with  the  lateral  sacral  arteries,  and  sends 
offsets  into  the  anterior  sacral  foramina.  It  is  crossed  by  the  left  common  iliac 
vein,  and  is  accompanied  by  a  pair  of  venae  comitantes;  these  unite  to  form  a  single 
vessel,  which  opens  into  the  left  common  iliac  vein. 


THE  COMMON  ILIAC  ARTERIES  (AA.  lUACAE  COMMUNES)  (Figs.  607,  615). 

The  abdominal  aorta  divides,  on  the  left  side  of  the  body  of  the  fourth  lumbar 
vertebra,  into  the  two  common  iliac  arteries.  Each  is  about  5  cm.  in  length.  They 
diverge  from  the  termination  of  the  aorta,  pass  downward  and  lateralward,  and 
divide,  opposite  the  intervertebral  fibrocartilage  between  the  last  lumbar  vertebra 
and  the  sacrum,  into  two  branches,  the  external  iliac  and  hypogastric  arteries; 


THE  COMMON  ILIAC  ARTERIES 


699 


the  former  su])i)lies  tlie  lower  extremity;  the  hitter,  the  viscera  and  parietes  of  the 
pelvis. 

The  right  common  iliac  artery  (Fig.  (ilo)  is  somewhat  loiif^^T  than  the  left,  and 
passes  more  ol)li(iuely  across  the  body  of  the  last  lumbar  vertebra.  In  fro7it  of 
it  are  the  peritoneuni,  the  small  intestines,  branches  of  the  sympathetic  nerves, 
and,  at  its  point  of  division,  the  ureter.  Behind,  it  is  separated  from  the  bodies  of 
the  fourth  and  fifth  lumbar  vertebne,  and  the  intervening  fibrocartilage,  by  the 
terminations  of  the  two  common  iliac  veins  and  the  commencement  of  the  inferior 
vena  cava.  Latr rally,  it  is  in  relation,  above,  with  the  inferior  vena  cava  and  the 
right  common  iliac  vein;  and,  below,  with  the  Psoas  major.  Medial  to  it,  above, 
is  the  left  common  iliac  vein. 


Middle  saaal 


Sup   hemoi  rhoidcd 


Fig.   615. — The  arteries  of  the  pelvis. 

The  left  common  iliac  artery  is  in  relation,  in  front,  with  the  peritoneum,  the 
small  intestines,  branches  of  the  sympathetic  nerves,  and  the  superior  hemorrhoidal 
artery;  and  is  crossed  at  its  point  of  bifurcation  by  the  ureter.  It  rests  on  the 
bodies  of  the  fourth  and  fifth  lumbar  vertebrae,  and  the  intervening  fibrocartilage. 
The  left  common  iliac  vein  lies  partly  medial  to,  and  partly  behind  the  artery; 
laterally,  the  artery  is  in  relation  with  the  Psoas  major. 

Branches. — The  common  iliac  arteries  give  off  small  branches  to  the  peritoneum. 
Psoas  major,  ureters,  and  the  surrounding  areolar  tissue,  and  occasionally  give 
origin  to  the  iliolumbar,  or  accessory  renal  arteries. 


700  AXGIOWGY 

Peculiarities. — The  point  of  origin  varies  according  to  the  bifurcation  of  the  aorta.  In  three- 
fourths  of  a  large  number  of  cases,  the  aorta  bifurcated  either  upon  the  fourth  lumbar  vertebra, 
or  upon  the  fibrocartilage  between  it  and  the  fifth;  the  bifurcation  being,  in  one  case  out  of  nine, 
below,  and  in  one  out  of  eleven,  above  this  point.  In  about  SO  per  cent,  of  the  cases  the  aorta 
bifurcated  within  1.25  cm.  above  or  below  the  level  of  the  crest  of  the  ilium;  more  frequently 
below  than  above. 

The  point  of  division  is  subject  to  great  variety.  In  two-thirds  of  a  large  number  of  cases  it 
was  between  the  last  lumbar  vertebra  and  the  upper  border  of  the  sacrum;  being  above  that  point 
in  one  case  out  of  eight,  and  below  it  in  one  case  out  of  six.  The  left  common  iliac  artery  divides 
lower  down  more  frequently  than  the  right. 

The  relative  lengths,  also,  of  the  two  common  iliac  arteries  vary.  The  right  common  iliac  was 
the  longer  in  sixty-three  cases;  the  left  in  fifty-two;  while  they  were  equal  in  fifty-three.  The 
length  of  the  arteries  varied,  in  five-sevenths  of  the  cases  examined,  from  3.5  to  7.5  cm.;  in  about 
half  of  the  remaining  cases  the  artery  was  longer,  and  in  the  other  half,  shorter;  the  minimum 
length  being  less  than  1.25  cm.,  the  maximum,  11  cm.  In  rare  instances,  the  right  common 
ihac  has  been  found  wanting,  the  external  iliac  and  hypogastric  arising  directly  from  the  aorta. 

Applied  Anatomy. — The  application  of  a  ligature  to  the  common  iliac  artery  may  be  required 
on  account  of  aneurism  or  hemorrhage,  implicating  the  external  iliac  or  hypogastric.  The  easiest 
and  best  method  of  tying  the  artery  is  by  a  transperitoneal  route.  The  abdomen  is  opened,  the 
intestines  are  drawn  aside  and  the  peritoneum  covering  the  artery  divided;  the  sheath  is  then 
opened  and  the  needle  passed  from  the  medial  to  the  lateral  side.  On  the  right  side  great  care 
must  be  exercised  in  passing  the  needle,  since  both  the  common  ihac  veins  lie  behind  the  artery. 
After  the  vessel  has  been  tied,  the  incision  in  the  peritoneum  over  the  artery  should  be  sutured. 
Formerly  there  were  different  methods  by  which  the  common  ihac  artery  was  tied,  without  open- 
ing the  peritoneal  cavity,  but  these  have  now  been  discarded. 

Collateral  Circulation. — The  principal  agents  in  carrying  on  the  collateral  circulation  after  the 
application  of  a  hgature  to  the  common  iliac  are:  the  anastomoses  of  the  hemorrhoidal  branches 
of  the  hypogastric  with  the  superior  hemorrhoidal  from  the  inferior  mesenteric;  of  the  uterine, 
ovarian,  and  vesical  arteries  of  the  opposite  sides;  of  the  lateral  sacral  with  the  middle  sacral 
artery;  of  the  inferior  epigastric  with  the  internal  mammary,  inferior  intercostal,  and  lumbar 
arteries;  of  the  deep  iliac  circumflex  with  the  lumbar  arteries;  of  the  iliolumbar  with  the  last 
lumbar  artery;  of  the  obturator  artery,  by  means  of  its  pubic  branch,  with  the  vessel  of  the 
opposite  side  and  with  the  inferior  epigastric. 

The  Hypogastric  Artery  (A.  Hypogastrica ;  Internal  Iliac  Artery)  (Fig.  615). 

The  hypogastric  artery  supplies  the  walls  and  viscera  of  the  pelvis,  the  buttock, 
the  generative  organs^  and  the  medial  side  of  the  thigh.  It  is  a  short,  thick  vessel, 
smaller  than  the  external  iliac,  and  about  4  cm.  in  length.  It  arises  at  the  bifur- 
cation of  the  common  iliac,  opposite  the  lumbosacral  articulation,  and,  passing 
downward  to  the  upper  margin  of  the  greater  sciatic  foramen,  divides  into  two 
large  trunks,  an  anterior  and  a  posterior. 

Relations. — It  is  in  relation  in  front  with  the  ureter;  behind,  with  the  internal  iliac  vein,  the 
lumbosacral  trunk,  and  the  Piriformis  muscle;  laterally,  near  its  origin,  with  the  external  iliac 
vein,  which  lies  between  it  and  the  Psoas  major  muscle;  lower  down,  with  the  obturator  nerve. 

In  the  fetus,  the  hypogastric  artery  is  twice  as  large  as  the  external  iliac,  and  is 
the  direct  continuation  of  the  common  iliac.  It  ascends  along  the  side  of  the 
bladder,  and  runs  upward  on  the  back  of  the  anterior  wall  of  the  abdomen  to  the 
umbilicus,  converging  toward  its  fellow  of  the  opposite  side.  Having  passed  through 
the  umbilical  opening,  the  two  arteries,  now  termed  umbilical,  enter  the  umbilical 
cord,  where  they  are  coiled  around  the  umbilical  vein,  and  ultimately  ramify  in 
the  placenta. 

At  birth,  when  the  placental  circulation  ceases,  the  pelvic  portion  only  of  the 
artery  remains  patent  and  constitutes  the  hypogastric  and  the  first  part  of  the 
superior  vesical  artery  of  the  adult;  the  remainder  of  the  vessel  is  converted  into 
a  solid  fibrous  cord,  the  lateral  umbilical  ligament  (obliterated  hypogastric  artery) 
which  extends  from  the  pelvis  to  the  umbilicus. 

Peculiarities  as  Regards  Length. — In  two-thirds  of  a  large  number  of  cases,  the  length  of  the 
hypogastric  varied  between  2.25  and  3.4  cm.;  in  the  remaining  third  it  was  more  frequently 
longer  than  shorter,  the  maximum  length  being  about  7  cm.  the  minimum  about  1  cm. 


THE  HYPOGASTRIC  ARTERY  701 

Tho  lengths  of  Llic  coininon  iliac  and  hypogastric  arteries  bear  an  inverse  proportion  to  each 
other,  the  hypogastric  artery  being  long  when  the  common  iliac  is  short,  and  vice  versa. 

As  Regards  its  Place  of  Division. — -The  place  of  division  of  the  hypogastric  varies  between 
tlie  upper  margin  of  the  sacrum  and  the  upper  border  of  the  greater  sciatic  foramen. 

Tlie  right  and  left  hyi)ogastric  arteries  in  a  series  of  cases  often  differed  in  length,  but  neither 
seemed  constantly  to  exceed  the  other. 

Applied  Anatomy. — -The  application  of  a  ligature  to  the  hypogastric  artery  may  be  required 
in  cases  of  aneurism  or  hemorrhage  affecting  one  of  its  branches.  The  vessel  may  be  best  secured 
by  an  abdominal  section  in  the  median  line,  and  reaching  the  vessel  through  the  peritoneal  cavity. 
It  should  be  remembered  that  the  vein  lies  behind,  and,  on  the  right  side,  a  little  lateral  to  the 
artery,  and  in  close  contact  with  it;  the  ureter,  which  lies  in  front,  must  also  be  avoided.  The 
degree  of  facility  in  applying  a  Hgature  to  this  vessel  will  mainly  depend  upon  its  length.  It  has 
been  seen  that,  in  the  great  majority  of  the  cases  examined,  the  artery  was  short,  varying  from 
2  to  4  cm.;  in  these  cases,  the  artery  is  deeply  seated  in  the  pelvis;  when,  on  the  contrary,  the 
vessel  is  longer,  it  is  found  partly  above  that  cavity.  If  the  artery  be  very  short,  as  occasionally 
happens,  it  would  be  preferable  to  apply  a  ligature  to  the  common  iliac. 

Collateral  Circulation. — The  circulation  after  ligature  of  the  hypogastric  artery  is  carried  on 
by  the  anastomoses  of  the  uterine  and  ovarian  arteries;  of  the  vesical  arteries  of  the  two  sides; 
of  the  hemorrhoidal  branches  of  the  hypogastric  with  those  from  the  inferior  mesenteric;  of  the 
obturator  artery,  by  means  of  its  pubic  branch,  with  the  vessel  of  the  opposite  side,  and  with"  the 
inferior  epigastric  and  medial  femoral  circumflex;  of  the  circumflex  and  perforating  branches  of 
the  profunda  femoris  with  the  infei'ior  gluteal;  of  the  superior  gluteal  with  the  posterior  branches 
of  the  lateral  sacral  arteries;  of  the  iUolumbar  with  the  last  lumbar;  of  the  lateral  sacral  with  the 
middle  sacral;  and  of  the  iliac  circumflex  with  the  iliolumbar  and  superior  gluteal.^ 

Branches. — The  branches  of  the  hypogastric  artery  are: 

From  the  Anterior  Trunk.  From  the  Posterior  Trunk. 

Superior  Vesical.  Iliolumbar. 

Middle  Vesical.  Lateral  Sacral. 

Inferior  Vesical.  Superior  Gluteal. 

Middle  Hemorrhoidal. 
Obturator. 
Internal  Pudendal. 
Inferior  Gluteal. 

■VT     •     1    \ln  the  Female. 
Vagmal    j 

The  superior  vesical  artery  (a.  vesicalis  superior)  supplies  numerous  branches 
to  the  upper  part  of  the  bladder.  From  one  of  these  a  slender  vessel,  the  artery 
to  the  ductus  deferens,  takes  origin  and  accompanies  the  duct  in  its  course  to  the 
testis,  where  it  anastomoses  with  the  internal  spermatic  artery.  Other  branches 
supply  the  ureter.  The  first  part  of  the  superior  vesical  artery  represents  the 
terminal  section  of  the  pervious  portion  of  the  fetal  hypogastric  artery. 

The  middle  vesical  artery  {a.  vesicalis  medialis),  usually  a  branch  of  the  superior, 
is  distributed  to  the  fundus  of  the  bladder  and  the  vesiculae  seminales. 

The  inferior  vesical  artery  (a.  vesicalis  inferior)  frequently  arises  in  common 
with  the  middle  hemorrhoidal,  and  is  distributed  to  the  fundus  of  the  bladder,  the 
prostate,  and  the  vesiculae  seminales.  The  branches  to  the  prostate  communicate 
with  the  corresponding  vessels  of  the  opposite  side. 

The  middle  hemorrhoidal  artery  (a.  haemorrhoidalis  media)  usually  arises  with 
the  preceding  vessel.  It  is  distributed  to  the  rectum,  anastomosing  with  the 
inferior  vesical  and  with  the  superior  and  inferior  hemorrhoidal  arteries.  It  gives 
offsets  to  the  vesiculae  seminales  and  prostate. 

The  uterine  artery  (a.  uterina)  (Fig.  616)  springs  from  the  anterior  division  of 
the  hypogastric  and  runs  medialward  on  the  Levator  ani  and  toward  the  cervix 
uteri;  about  2  cm.  from  the  cervix  it  crosses  above  and  in  front  of  the  ureter,  to 
which  it  supplies  a  small  branch.  Reaching  the  side  of  the  uterus  it  ascends  in  a 
tortuous  manner  between  the  two  layers  of  the  broad  ligament  to  the  junction 

1  For  a  description  of  a  case  in  which  Owen  made  a  dissection  ten  years  after  ligature  of  the  hypogastric  arterj-, 
see  Med.-Chir.  Trans.,  vol.  xvi. 


702 


AXGIOLOGY 


of  the  uterine  tube  and  uterus.  It  then  runs  laterahvard  toward  the  hihis  of  the 
ovary,  and  ends  by  joining  with  the  ovarian  artery.  It  supphes  l)ranches  to  the 
cervix  uteri  and  others  which  descend  on  the  vagina;  the  latter  anastomose  with 
branches  of  the  ^•aginal  arteries  and  form  with  them  two  median  longitudinal 
vessels — the  azygos  arteries  of  the  vagina — one  of  which  runs  down  one  in  front  of 
and  the  other  behind  the  vagina.  It  supplies  numerous  branches  to  the  body  of  the 
uterus,  and  from  its  terminal  portion  twigs  are  distributed  to  the  uterine  tube  anfl 
the  round  ligament  of  the  uterus. 

The  vaginal  artery  (a.  vaginalis)  usually  corresponds  to  the  inferior  vesical  in 
the  male;  it  descends  upon  the  vagina,  supplying  its  mucous  membrane,  and  sends 
branches  to  the  bulb  of  the  vestibule,  the  fundus  of  the  bladder,  and  the  contiguous 
part  of  the  rectum.  It  assists  in  forming  the  azygos  arteries  of  the  vagina,  and 
is  frequently  represented  by  two  or  three  branches. 

Branches  to  tube 

Brandies  to  fuiulus 


Fig.  616. — The  arteries  of  the  internal  organs  of  generation  of  the  female,  seen  from  behind.     (After  Hyrtl.) 

The  obturator  artery  (a.  ohtundoria)  passes  forward  and  downward  on  the  lateral 
wall  of  the  pelvis,  to  the  upper  part  of  the  obturator  foramen,  and,  escaping  from 
the  pelvic  cavity  through  the  obturator  canal,  it  divides  into  an  anterior  and  a 
posterior  branch.  In  the  pelvic  cavity  this  vessel  is  in  relation,  laterally,  with  the 
obturator  fascia;  medially,  with  the  ureter,  ductus  deferens,  and  peritoneum; 
while  a  little  below  it  is  the  obturator  nerve. 

Branches. — Inside  the  pelvis  the  obturator  artery  gives  off  iliac  branches  to  the 
iliac  fossa,  which  suppl}'  the  bone  and  the  Iliacus,  and  anastomose  with  the  ilio- 
lumbar artery;  a  vesical  branch,  which  runs  backward  to  supply  the  bladder;  and 
a  pubic  branch,  which  is  given  off  from  the  ves.sel  just  before  it  leaves  the  pelvic 
cavity.  The  pubic  branch  ascends  upon  the  back  of  the  pubis,  communicating 
vi-'iih  the  corresponding  vessel  of  the  opposite  side,  and  with  the  inferior  epigastric 
artery. 

Outside  the  pelvis,  the  obturator  artery  divides  at  the  upper  margin  of  the  obtur- 
ator foramen,  into  an  anterior  and  a  posterior  branch  which  encircle  the  foramen 
under  cover  of  the  Obturator  externus. 


THE  HYPOGASTRIC  ARTERY  703 

The  anterior  branch  runs  forward  on  tlie  outer  surface  of  the  obturator  mem- 
brane i\ud  then  curxes  dowmvard  along  the  anterior  margin  of  the  foramen.  It 
distributes  branches  to  the  01)turator  externus,  Pectineus,  Adductores,  and  GraciHs, 
antl  anastomoses  with  the  posterior  branch  and  with  the  medial  femoral  circum- 
flex artery. 

The  posterior  branch  follows  the  posterior  margin  of  the  foramen  and  turns  for- 
ward on  the  inferior  ramus  of  the  ischium,  where  it  anastomoses  with  the  anterior 
branch.  It  gives  twigs  to  the  muscles  attached  to  the  ischial  tuberosity  and  anas- 
tomoses with  the  inferior  gluteal.  It  also  supplies  an  articular  branch  which 
enters  the  hip-joint  through  the  acetabular  notch,  ramifies  in  the  fat  at  the  bottom 
of  the  acetabulum  and  sends  a  twdg  along  the  ligamentum  teres  to  the  head  of  the 
femur. 

Peculiarities. — The  obturator  artery  sometimes  arises  from  the  main  stem  or  from  the  posterior 
trunk  of  the  hypogastric,  or  it  may  spring  from  the  superior  gluteal  artery;  occasionally  it  arises 
from  the  external  iliac.  In  about  two  out  of  every  seven  cases  it  springs  fi'om  the  inferior  epi- 
gastric and  descends  almost  vertically  to  the  upper  part  of  the  obtm-ator  foramen.  The  artery 
in  this  course  usually  lies  in  contact  with  the  external  iUac  vein,  and  on  the  lateral  side  of  the 
femoral  ring  (Fig.  617^1) ;  in  such  cases  it  would  not  be  endangered  in  the  operation  for  strangulated 
femoral  hernia.  Occasionally,  however,  it  curves  along  the  free  margin  of  the  lacunar  hgament 
(Fig.  617 -B),  and  if  in  such  circumstances  a  femoral  hernia  occurred,  the  vessel  would  almost 
completely  encircle  the  neck  of  the  hernial  sac,  and  would  be  in  gi'eat  danger  of  being  wounded 
if  an  operation  were  performed  for  strangulation. 

J?        I 


Fig.  617. — Variations  in  origin  and  courses  of  obturator  artery. 

The  internal  pudendal  artery  (a.  pudenda  interna;  internal  inidic  artery)  is  the 
smaller  of  the  two  terminal  branches  of  the  anterior  trunk  of  the  hypogastric,  and 
supplies  the  external  organs  of  generation.  Though  the  course  of  the  artery  is 
the  same  in  the  two  sexes,  the  vessel  is  smaller  in  the  female  than  in  the  male,  and 
the  distribution  of  its  branches  somew^hat  different.  The  description  of  its  arrange- 
ment in  the  male  will  first  be  given,  and  subsequently  the  differences  which  it 
presents  in  the  female  will  be  mentioned. 

The  internal  pudendal  artery  in  the  male  passes  downw^ard  and  outward  to  the 
lower  border  of  the  greater  sciatic  foramen,  and  emerges  from  the  pelvis  between 
the  Piriformis  and  Coccygeus ;  it  then  crosses  the  ischial  spine,  and  enters  the  peri- 
neum through  the  lesser  sciatic  foramen.  The  artery  now  crosses  the  Obturator 
internus,  along  the  lateral  wall  of  the  ischiorectal  fossa,  being  situated  about  4  cm. 
above  the  lower  margin  of  the  ischial  tuberosity.  It  gradually  approaches  the 
margin  of  the  inferior  ramus  of  the  ischium  and  passes  forw^ard  between  the  two 
layers  of  the  fascia  of  the  urogenital  diaphragm;  it  then  runs  forw^ard  along  the 
medial  margin  of  the  inferior  ramus  of  the  pubis,  and  about  1.25  cm.  behind  the 
pubic  arcuate  ligament  it  pierces  the  inferior  fascia  of  the  urogenital  diaphragm 
and  divides  into  the  dorsal  and  deep  arteries  of  the  penis. 

Relations. — Within  the  pelvis,  it  hes  in  front  of  the  Piriformis  muscle,  the  sacral  plexus  of 
nerves,  and  the  inferior  gluteal  artery.  As  it  crosses  the  ischial  spine,  it  is  covered  by  the  Glutaeus 
maximus  and  overlapped  by  the  sacrotuberous  ligament.  Here  the  pudendal  nerve  hes  to  the 
medial  side  and  the  nerve  to  the  Obtm-ator  internus  to  the  lateral  side  of  the  vessel.  In  the  peri- 
neum it  lies  on  the  lateral  wall  of  the  ischiorectal  fossa,  in  a  canal  (Alcock's  canal)  formed  by  the 


ro4 


ANGIOLOGY 


splitting  of  the  obturator  fascia.    It  is  accompanied  by  a  pair  of  venae  comitantes  and  the  pudendal 
nerve. 

Peculiarities. — The  internal  pudendal  artery  is  sometimes  smaller  than  usual,  or  fails  to  give 
off  one  or  two  of  its  usual  branches;  in  such  cases  the  deficienc}^  is  supphed  by  branches  derived 
from  an  additional  vessel,  the  accessory  pudendal,  which  generally  arises  from  the  internal 
pudendal  artery  before  its  exit  from  the  greater  sciatic  foramen.  It  passes  forw^ard  along  the 
lower  part  of  the  bladder  and  across  the  side  of  the  prostate  to  the  root  of  the  penis,  where  it 
perforates  the  urogenital  diaphragm,  and  gives  off  the  branches  usually  derived  from  the  internal 
pudendal  artery.  The  deficiency  most  frequently  met  with  is  that  in  which  the  internal  pudendal 
ends  as  the  artery  of  the  urethral  bulb,  the  dorsal  and  deep  arteries  of  the  penis  being  derived 
from  the  accessory  pudendal.  The  internal  pudendal  artery  may  also  end  as  the  perineal,  the 
artery  of  the  urethral  bulb  being  derived,  with  the  other  two  branches,  from  the  accessory  vessel. 
Occasionally  the  accessory  pudendal  artery  is  derived  from  one  of  the  other  branches  of  the 
hypogastric  artery,  most  frequently  the  inferior  vesical  or  the  obturator. 

Branches. — The  branches  of  the  internal  pudendal  artery  (Figs.  618,  619)  are: 

Muscular.  Artery  of  the  Urethral  Bulb. 

Inferior  Hemorrhoidal.  Urethral. 

Perineal.  Deep  Artery  of  the  Penis. 

Dorsal  Arterv  of  the  Penis. 


Posterior  scrotal  arteries 
Posterior  scrotal  nerves 

Pudendal  nerve 
Internal  pudendal  artery 


Fig.  618. — The  superficial  branches  of  the  internal  pudendal  artecy. 


The  Muscular  Branches  consist  of  two  sets:  one  given  off  in  the  pelvis;  the  other, 
as  the  vessel  crosses  the  ischial  spine.  The  former  consists  of  several  small  offsets 
which  supply  the  Levator  ani,  the  Obturator  internus,  the  Piriformis,  and  the 
Coccygeus.  The  branches  given  off  outside  the  pelvis  are  distributed  to  the 
adjacent  parts  of  the  Glutaeus  maximus  and  external  rotator  muscles.  They 
anastomose  with  branches  of  the  inferior  gluteal  artery. 

The  Inferior  Hemorrhoidal  Artery  (a.  haemorrJwidalis  injerior)  arises  from  the 
internal  pudendal  as  it  passes  above  the  ischial  tuberosity.  Piercing  the  wall 
of  Alcock's  canal  it  divides  into  two  or  three  branches  which  cross  the  ischiorectal 
fossa,  and  are  distributed  to  the  muscles  and  integument  of  the  anal  region,  and 


THE  HYPOGASTRIC  ARTERY 


705 


send  offshoots  around  the  lower  edge  of  tlie  (dutaeus  maximus  to  the  skhi  of  the 
buttock.  They  anastomose  with  the  corresponding  vessels  of  the  opposite  side,  with 
the  suj)eri()r  and  middle  hemorrhoidal,  and  with  the  perineal  artery. 

The  Perineal  Artery  {a.  pcrinci;  superficial  ju'rliical  artery)  arises  from  the  internal 
pudendal,  in  front  of  the  preceding  branches,  and  turns  upward,  crossing  either 
over  or  under  the  Transversus  perinaei  superficialis,  and  runs  forward,  parallel 
to  the  pubic  arch,  in  the  interspace  between  the  Bulbocavernous  and  Ischiocaver- 
nosus.  both  of  which  it  supplies,  and  finally  diNides  into  several  posterior  scrotal 
branches  which  are  distributed  to  the  skin  and  dartos  tunic  of  the  scrotum.  As 
it  crosses  the  Transversus  perinaei  superficialis  it  gives  off  the  transverse  perineal 
artery  which  runs  transversely  on  the  cutaneous  surface  of  the  muscle,  and  anasto- 
moses with  the  corresponding  vessel  of  the  opposite  side  and  with  the  perineal 
and  inferior  hemorrhoidal  arteries.  It  supplies  the  Transversus  perinaei  super- 
ficialis and  the  structures  between  the  anus  and  the  urethral  bulb. 


Deep  artcnj  of  penis 
Dorsal  artery  of  penis 


Artery  of  urethral  bulb 
Internal  pudendal  artery     — ^ 
Bulbo-urethral  gland 


Fig.  619. — The  deeper  branches  of  the  internal  pudendal  artery. 

The  Artery  of  the  Urethral  Bulb  (o.  bidbi  urethrae)  is  a  short  vessel  of  large  calibre 
which  arises  from  the  internal  pudendal  between  the  two  layers  of  fascia  of  the  uro- 
genital diaphragm;  it  passes  medialward,  pierces  the  inferior  fascia  of  the  urogenital 
diaphragm,  and  gives  oft'  branches  which  ramify  in  the  bulb  of  the  urethra  and  in 
the  posterior  part  of  the  corpus  cavernosum  urethrae.  It  gives  off  a  small  branch 
to  the  bulbo-urethral  gland. 

The  Urethral  Artery  (a.  urethralis)  arises  a  short  distance  in  front  of  the  artery 
of  the  urethral  bulb.  It  runs  forward  and  medialward,  pierces  the  inferior  fascia 
of  the  urogenital  diaphragm  and  enters  the  corpus  cavernosum  urethrae,  in  which 
it  is  continued  forward  to  the  glans  penis. 

The  Deep  Artery  of  the  Penis  (a.  profunda  penis;  artery  to  the  corpus  cavernosum), 
one  of  the  terminal  branches  of  the  internal  pudendal,  arises  from  that  vessel 
while  it  is  situated  between  the  two  fascise  of  the  urogenital  diaphragm;  it 
pierces  the  inferior  fascia,  and,  entering  the  crus  penis  obliquely,  runs  forward 
in  the  centre  of  the  corpus  cavernosum  penis,  to  which  its  branches  are  distributed. 
45 


706  ANGIOLOGY 

The  Dorsal  Artery  of  the  Penis  (a.  dorsalis  penis)  ascends  between  the  cms  penis 
and  the  pubic  symphysis,  and,  piercing  the  inferior  fascia  of  the  urogenital  dia- 
phragm, passes  between  the  two  layers  of  the  suspensory  ligament  of  the  penis, 
and  runs  forward  on  the  dorsum  of  the  penis  to  the  glans,  w'here  it  divides  into  two 
branches,  which  supply  the  glans  and  prepuce.  On  the  penis,  it  lies  between  the 
dorsal  nerve  and  deep  dorsal  vein,  the  former  being  on  its  lateral  side.  It  supplies 
the  integument  and  fibrous  sheath  of  the  corpus  cavernosum  penis,  sending  branches 
through  the  sheath  to  anastomose  with  the  preceding  vessel. 

The  internal  pudendal  artery  in  the  female  is  smaller  than  in  the  male.  Its  origin 
and  course  are  similar,  and  there  is  considerable  analogy  in  the  distribution  of  its 
branches.  The  perineal  artery  supplies  the  labia  pudendi;  the  SiTtery  of  the  bulb 
supplies  the  bulbus  vestibuli  and  the  erectile  tissue  of  the  vagina;  the  deep  artery 
of  the  clitoris  supplies  the  corpus  cavernosum  clitoridis;  and  the  dorsal  artery  of 
the  clitoris  supplies  the  dorsum  of  that  organ,  and  ends  in  the  glans  and  prepuce 
of  the  clitoris. 

The  inferior  gluteal  artery  (a.  glutaea  inferior;  sciatic  artery)  (Fig.  620),  the 
larger  of  the  two  terminal  branches  of  the  anterior  trunk  of  the  hypogastric,  is 
distributed  chiefly  to  the  buttock  and  back  of  the  thigh.  It  passes  down  on  the 
sacral  plexus  of  nerves  and  the  Piriformis,  behind  the  internal  pudendal  artery, 
to  the  lower  part  of  the  greater  sciatic  foramen,  through  which  it  escapes  from  the 
pelvis  between  the  Piriformis  and  Coccygeus.  It  then  descends  in  the  interval 
betw^een  the  greater  trochanter  of  the  femur  and  tuberosity  of  the  ischium,  accom- 
panied by  the  sciatic  and  posterior  femoral  cutaneous  nerves,  and  covered  by  the 
Glutaeus  maximus,  and  is  continued  down  the  back  of  the  thigh,  supplying  the 
skin,  and  anastomosing  with  branches  of  the  perforating  arteries. 

Inside  the  pelvis  it  distributes  branches  to  the  Piriformis,  Coccygeus,  and  Levator 
ani;  some  branches  w^hich  supply  the  fat  around  the  rectum,  and  occasionally 
take  the  place  of  the  middle  hemorrhoidal  artery;  and  vesical  branches  to  the 
fundus  of  the  bladder,  vesiculae  seminales,  and  prostate.  Outside  the  pekis  it  gives 
off  the  following  branches : 

Muscular.  Anastomotic. 

Coccygeal.  Articular. 

Comitans  Nervi  Ischiadici.  Cutaneous. 

The  Muscular  Branches  supply  the  Glutaeus  maximus,  anastomosing  with  the 
superior  gluteal  artery  in  the  substance  of  the  muscle;  the  external  rotators, 
anastomosing  with  the  internal  pudendal  artery;  and  the  muscles  attached  to 
the  tuberosity  of  the  ischium,  anastomosing  with  the  posterior  branch  of  the 
obturator  and  the  medial  femoral  circumflex  arteries. 

The  Coccygeal  Branches  run  medialward,  pierce  the  sacrotuberous  ligament,  and 
supply  the  Glutaeus  maximus,  the  integument,  and  other  structures  on  the  back 
of  the  coccyx. 

The  Arteria  Comitans  Nervi  Ischiadici  is  a  long,  slender  vessel,  which  accom- 
panies the  sciatic  nerve  for  a  short  distance ;  it  then  penetrates  it,  and  runs  in  its 
substance  to  the  lower  part  of  the  thigh. 

The  Anastomotic  is  directed  downward  across  the  external  rotators,  and  assists 
in  forming  the  so-called  crucial  anastomosis  by  joining  with  the  first  perforating 
and  medial  and  lateral  femoral  circumflex  arteries. 

The  Articular  Branch,  generally  derived  from  the  anastomotic,  is  distributed  to 
the  capsule  of  the  hip-joint. 

The  Cutaneous  Branches  are  distributed  to  the  skin  of  the  buttock  and  back  of 
the  thigh. 

The  iliolumbar  artery  (a.  iliolumbalis)  a  branch  of  the  posterior  trunk  of  the 
hypogastric,  turns  upward  behind  the  obturator  nerve  and  the  external  iliac  vessels, 


THE  HYPOGASTRIC  ARTERY 


707 


to  the  mctlial  border  of  the  Psoas  major,  behind  which  it  divides  into  a  lumbar  and 
an  ihac  branch. 

The  Lumbar  Branch  (ramus  lumhalis)  supphes  the  Psoas  major  and  Quadratus 
hniiboruni,  anastomoses  with  the  last  lumbar  artery,  and  sends  a  small  spinal 
branch  through  the  intervertebral 
foramen  between  the  last  lumbar 
vertebra  and  the  sacrum,  into  the 
vertebral  canal,  to  supply  the 
Cauda  equina. 

The  Iliac  Branch  {ramus  iliaciis) 
descends  to  supply  the  Iliacus; 
some  offsets,  running  between  the 
muscle  and  the  bone,  anastomose 
with  the  iliac  branches  of  the  ob- 
turator; one  of  these  enters  an 
oblique  canal  to  supply  the  bone, 
w'hile  others  run  along  the  crest  of 
the  ilium,  distributing  branches  to 
the  gluteal  and  abdominal  muscles, 
and  anastomosing  in  their  course 
with  the  superior  gluteal,  iliac 
circumflex,  and  lateral  femoral 
circumflex  arteries. 

The  lateral  sacral  arteries  iaa. 
sacrales  laterales)  (Fig.  615)  arise 
from  the  posterior  division  of  the 
hypogastric;  there  are  usually  two, 
a  superior  and  an  inferior. 

The  superior,  of  large  size,  passes 
medialward,  and,  after  anastomos- 
ing with  branches  from  the  middle 
sacral,  enters  the  first  or  second 
anterior  sacral  foramen,  supplies 
branches  to  the  contents  of  the 
sacral  canal,  and,  escaping  by  the 
corresponding  posterior  sacral  fora- 
men, is  distributed  to  the  skin  and 
muscles  on  the  dorsum  of  the 
sacrum,  anastomosing  with  the 
superior  gluteal. 

The  inferior  runs  obliquely  across 
the  front  of  the  Piriformis  and  the 
sacral  nerves  to  the  medial  side  of 
the  anterior  sacral  foramina,  de- 
scends on  the  front  of  the  sacrum, 
and  anastomoses  over  the  coccyx 
wdth  the  middle  sacral  and  opposite 

lateral  sacral  arterj'.  In  its  course  it  gives  off  branches,  which  enter  the  anterior 
sacral  foramina;  these,  after  supplying  the  contents  of  the  sacral  canal,  escapes 
by  the  posterior  sacral  foramina,  and  are  distributed  to  the  muscles  and  skin  on 
the  dorsal  surface  of  the  sacrum,  anastomosing  with  the  gluteal  arteries. 

The  superior  gluteal  artery  (a.  ghdaea  superior;  gluteal  artery)  (Fig.  620)  is  the 
largest  branch  of  the  hypogastric,  and  appears  to  be  the  continuation  of  the  pos- 
terior division  of  that  vessel.    It  is  a  short  artery  which  runs  backward  between 


Termination  cj 

medial  femoral 

circumfiex 


First 

perforating 


Second 

perforating 

Third 

perforating 


Termination 
of  profunda 


Superior  muscular 


Lateral 
superior 
geniciclar 


— Medial  superior  genicular 


—  Sural 


Fig.  620. — The  arteries  of  the  ghiteal  and  posterior 
femoral  regions. 


708  ANGIOLOGY 

the  lumbosacral  trunk  and  the  first  sacral  nerve,  and,  passing  out  of  the  pelvis 
above  the  upper  border  of  the  Piriformis,  immediately  divides  into  a  superficial 
and  a  deep  branch.  Within  the  pelvis  it  gives  off  a  few  branches  to  the  Iliacus, 
Piriformis,  and  Obturator  internus,  and  just  previous  to  quitting  that  cavity,  a 
nutrient  artery  which  enters  the  ilium. 

The  superficial  branch  enters  the  deep  surface  of  the  Glutaeus  maximus,  and 
divides  into  numerous  branches,  some  of  which  supply  the  muscle  and  anastomose 
with  the  inferior  gluteal,  while  others  perforate  its  tendinous  origin,  and  supply 
the  integument  covering  the  posterior  surface  of  the  sacrum,  anastomosing  with 
the  posterior  branches  of  the  lateral  sacral  arteries. 

The  deep  branch  lies  under  the  Glutaeus  medius  and  almost  immediately  sub- 
divides into  two.  Of  these,  the  superior  division,  continuing  the  original  course 
of  the  vessel,  passes  along  the  upper  border  of  the  Glutaeus  minimus  to  the  anterior 
superior  spine  of  the  ilium,  anastomosing  with  the  deep  iliac  circumflex  artery  and 
the  ascending  branch  of  the  lateral  femoral  circumflex  artery.  The  inferior  division 
crosses  the  Glutaeus  minimus  obliquely  to  the  greater  trochanter,  distributing 
branches  to  the  Glutaei  and  anastomoses  with  the  lateral  femoral  circumflex  artery. 
Some  branches  pierce  the  Glutaeus  minimus  and  supply  the  hip-joint. 

Applied  Anatomy. — Any  of  these  three  vessels  may  require  to  be  ligatured  for  a  wound,  or 
for  aneurism  which  is  generally  traumatic.  The  superior  gluteal  artery  is  hgatured  by  turning 
the  patient  two-thirds  over  on  to  his  face  and  making  an  incision  from  the  posterior  superior 
spine  of  the  ilium  to  the  upper  and  posterior  angle  of  the  greater  trochanter.  This  must  expose 
the  Glutaeus  maximus,  and  its  fibres  are  to  be  separated  through  the  whole  thickness  of  the 
muscle  and  pulled  apart  with  retractors.  The  contiguous  margins  of  the  Glutaeus  medius  and' 
Piriformis  are  now  to  be  separated  from  each  other,  and  the  artery  will  be  exposed  emerging 
from  the  greater  sciatic  foramen.  In  ligature  of  the  inferior  gluteal  artery,  the  incision  should 
be  made  parallel  with  that  for  ligature  of  the  superior  gluteal  but  4  cm.  lower  down.  After  the 
fibres  of  the  Glutaeus  maximus  have  been  separated,  the  vessel  is  to  be  sought  for  at  the  lower 
border  of  the  Piriformis;  the  sciatic  nerve,  which  lies  just  above  it,  forms  the  chief  guide  to  the 
artery. 

The  External  Iliac  Artery  (A.  Iliaca  Externa)  (Fig.  615). 

The  external  iliac  artery  is  larger  than  the  hypogastric,  and  passes  obliquely 
downward  and  lateralward  along  the  medial  border  of  the  Psoas  major,  from  the 
bifurcation  of  the  common  iliac  to  a  point  beneath  the  inguinal  ligament,  midway 
between  the  anterior  superior  spine  of  the  ilium  and  the  symphysis  pubis,  where 
it  enters  the  thigh  and  becomes  the  femoral  artery. 

Relations. — In  front  and  medially,  the  artery  is  in  relation  with  the  peritoneum,  subperitoneal 
areolar  tissue,  the  termination  of  the  ileum  and  frequently  the  vermiform  process  on  the  right 
side,  and  the  sigmoid  colon  on  the  left,  and  a  thin  layer  of  fascia,  derived  from  the  iliac  fascia, 
which  surrounds  the  artery  and  vein.  At  its  origin  it  is  crossed  by  the  ovarian  vessels  in  the 
female,  and  occasionally  by  the  ureter.  The  internal  spermatic  vessels  lie  for  some  distance 
upon  it  near  its  termination,  and  it  is  crossed  in  this  situation  by  the  external  spermatic  branch 
of  the  genitofemoral  nerve  and  the  deep  iliac  circumflex  vein;  the  ductus  deferens  in  the  male, 
and  the  round  ligament  of  the  uterus  in  the  female,  curve  down  across  its  medial  side.  Behind, 
it  is  in  relation  with  the  medial  border  of  the  Psoas  major,  from  which  it  is  separated  by  the 
ihac  fascia.  At  the  upper  part  of  its  course,  the  external  iliac  vein  lies  partly  behind  it,  but  lower 
down  lies  entirely  to  its  medial  side.  Laterally,  it  rests  against  the  Psoas  major,  from  which  it 
is  separated  by  the  iliac  fascia.  Numerous  lymphatic  vessels  and  lymph  glands  he  on  the  front 
and  on  the  medial  side  of  the  vessel. 

Applied  Anatomy. — The  application  of  a  ligature  to  the  external  ihac  may  be  required  in 
cases  of  aneurism  of  the  femoral  artery,  iliofemoral  aneurism,  or  for  a  wound  of  the  artery.  The 
vessel  may  be  secured  in  any  part  of  its  com-se,  excepting  near  its  upper  end,  which  is  to  be  avoided 
on  account  of  the  proximity  of  the  hypogastric,  and  near  its  lower  end,  which  should  also  be 
avoided  on  account  of  the  proximity  of  the  inferior  epigastric  and  deep  iliac  circumflex  vessels. 
The  operation  may  be  performed  by  opening  the  abdomen  and  incising  the  peritoneum  over  the 
artery  (transperitoneal) ;  or  by  an  incision  in  the  ihac  region,  dividing  all  the  structures  down  to 
the  peritoneum,  which  is  then  reflected  medialwai'd  unopened  from  the  iliac  fossa  until  the  artery 
is  reached  (retroperitoneal). 


THE  EXTERNAL  ILIAC  ARTERY  709 

The  transperitoneal  ligature  requires  an  incision  through  the  abdominal  wall  into  the  peritoneal 
cavity.  The  intestines  are  then  pushed  upward  and  held  out  of  the  way  bj^  a  broad  abdominal 
retractor,  and  an  incision  matle  through  the  peritoneum  at  the  margin  of  the  pelvis  in  the  course 
of  the  artery;  the  vessel  is  secured  in  any  part  of  its  course  which  may  seem  desirable  to  the 
operator.  The  advantages  of  this  operation  appear  to  be,  that  if  it  is  found  necessary,  the  common 
iliac  arterj-  can  be  ligatured  instead  of  the  external  iliac  without  extension  or  modification  of 
the  incision;  and  secondly,  that  the  vessel  can  be  ligatured  without  in  any  way  interfering  with 
the  sac  of  an  aneurism. 

The  retroperitoneal  ligature  may  be  performed  by  an  incision  above  and  parallel  to  the  lateral 
half  of  the  inguinal  ligament.  The  abdominal  muscles  and  transversalis  fascia  having  been 
cautiously  divided,  the  peritoneum  should  be  separated  from  the  iliac  fossa  and  raised  toward 
the  pelvis;  and  on  introducing  the  finger  to  the  bottom  of  the  wound,  the  arterj-  may  be  felt 
pulsating  along  the  medial  border  of  the  Psoas  major.  The  external  iliac  vein  is  generally  found 
on  the  medial  side  of  the  arterj^,  and  must  be  cautiously  separated  from  it,  and  the  aneurism 
needle  should  be  introduced  on  the  medial  side,  between  the  artery  and  vein. 

Collateral  Circulation. — ^The  principal  anastomoses  in  carrying  on  the  collateral  circulation, 
after  the  application  of  a  ligature  to  the  external  ihac,  are:  the  iholumbar  with  the  iliac  circum- 
flex; the  superior  gluteal  with  the  lateral  femoral  circumflex;  the  obturator  with  the  medial  femoral 
circumflex;  the  inferior  gluteal  with  the  first  perforating  and  circumflex  branches  of  the  profunda 
artery;  and  the  internal  pudendal  with  the  external  pudendal.  When  the  obturator  arises  from 
the  inferior  epigastric,  it  is  supplied  with  blood  by  branches,  from  either  the  hj-pogastric,  the 
lateral  sacral,  or  the  internal  pudendal.  The  inferior  epigastric  receives  its  supph-  from  the 
internal  mammary  and  lower  intercostal  arteries,  and  from  the  hypogastric  by  the  anastomoses 
of  its  branches  with  the  obturator. ^ 

Branches. — Besides  several  small  branches  to  the  Psoas  major  and  the  neighbor- 
ing lymph  glands,  the  external  iliac  gives  off  two  branches  of  considerable  size: 

Inferior  Epigastric.  Deep  Iliac  Circumflex. 

The  inferior  epigastric  artery  («.  epigastrica  inferior;  deep  epigastric  artery) 
(Fig.  623)  arises  from  the  external  iliac,  immediately  above  the  inguinal  ligament. 
It  curves  forward  in  the  subperitoneal  tissue,  and  then  ascends  obliquely  along 
the  medial  margin  of  the  abdominal  inguinal  ring;  continuing  its  course  upward, 
it  pierces  the  transversalis  fascia,  and,  passing  in  front  of  the  linea  semicircularis, 
ascends  between  the  Rectus  abdominis  and  the  posterior  lamella  of  its  sheath. 
It  finally  divides  into  numerous  branches,  which  anastomose,  above  the  umbilicus, 
with  the  superior  epigastric  branch  of  the  internal  mammary  and  with  the  lower 
intercostal  arteries  (Fig.  598).  As  the  inferior  epigastric  artery  passes  obliquely 
upward  from  its  origin  it  lies  along  the  lower  and  medial  margins  of  the  abdominal 
inguinal  ring,  and  behind  the  commencement  of  the  spermatic  cord.  The  ductus 
deferens,  as  it  leaves  the  spermatic  cord  in  the  male,  and  the  round  ligament  of  the 
uterus  in  the  female,  winds  around  the  lateral  and  posterior  aspects  of  the  artery. 

Branches. — The  branches  of  the  vessel  are :  the  external  spermatic  artery  (cremasteric 
artery),  which  accompanies  the  spermatic  cord,  and  supplies  the  Cremaster  and 
other  coverings  of  the  cord,  anastomosing  with  the  internal  spermatic  artery  (in 
the  female  it  is  very  small  and  accompanies  the  round  ligament) ;  a  pubic  branch 
which  runs  along  the  inguinal  ligament,  and  then  descends  along  the  medial  margin 
of  the  femoral  ring  to  the  back  of  the  pubis,  and  there  anastomoses  with  the  pubic 
branch  of  the  obturator  artery;  muscular  branches,  some  of  which  are  distributed  to 
the  abdominal  muscles  and  peritoneum,  anastomosing  with  the  iliac  circumflex 
and  lumbar  arteries;  branches  which  perforate  the  tendon  of  the  Obliquus 
externus,  and  supply  the  integument,  anastomosing  with  branches  of  the  super- 
ficial epigastric. 

Peculiarities. — The  origin  of  the  inferior  epigastric  maj'  take  place  from  anj"  part  of  the  external 
iliac  between  the  inguinal  ligament  and  a  point  6  cm.  above  it;  or  it  may  arise  below  this  ligament, 
from  the  femoral.  It  frequently'  springs  from  the  external  ihac,  by  a  common  trunk  with  the 
obtm-ator.     Sometimes  it  arises  from  the  obtm-ator,  the  latter  vessel  being  furnished  bj'  the 

1  Sir  Astley  Cooper  describes  in  Guy's  Hospital  Reports,  vol.  i,  the  dissection  of  a  limb  eighteen  years  after  successful 
ligature  of  the  external  iliac  artery. 


710  ANGIOLOGY 

hypogastric,  or  it  may  be  formed  of  two  branches,  one  derived  from  the  external  ihac,  the  other 
from  the  hypogastric. 

Applied  Anatomy. — The  inferior  epigastric  artery  has  impoi'tant  surgical  relations,  and  is  one 
of  the  principal  means,  through  its  anastomosis  with  the  internal  mammary,  of  establishing  the 
collateral  circulation  after  ligature  of  either  the  common  or  external  iliac  arteries.  It  lies  close 
to  the  abdominal  inguinal  ring,  and  is  therefore  medial  to  an  oblique  inguinal  hernia,  but  lateral 
to  a  direct  inguinal  hernia,  as  these  emerge  from  the  abdomen.  It  forms  the  lateral  boundary 
of  Hesselbach's  triangle,  and  is  in  close  relationship  with  the  spermatic  cord,  which  hes  in  front 
of  it  in  the  inguinal  canal,  separated  only  by  the  transvei'sahs  fascia.  The  ductus  deferens  hooks 
around  its  lateral  side. 

The  deep  iliac  circumflex  artery  (a.  circumflexa  ilium  profunda)  arises  from  the 
lateral  aspect  of  the  external  iliac  nearly  opposite  the  inferior  epigastric  artery. 
It  ascends  obliquely  lateralward  behind  the  inguinal  ligament,  contained  in  a 
fibrous  sheath  formed  by  the  junction  of  the  transversalis  fascia  and  iliac  fascia, 
to  the  anterior  superior  iliac  spine,  where  it  anastomoses  with  the  ascending  branch 
of  the  lateral  femoral  circumflex  artery.  It  then  pierces  the  transversalis  fascia 
and  passes  along  the  inner  lip  of  the  crest  of  the  ilium  to  about  its  middle,  where 
it  perforates  the  Transversus,  and  runs  backward  between  that  muscle  and  the 
Obliquus  internus,  to  anastomose  with  the  iliolumbar  and  superior  gluteal  arteries. 
Opposite  the  anterior  superior  spine  of  the  ilium  it  gives  off  a  large  branch,  which 
ascends  between  the  Obliquus  internus  and  Transversus  muscles,  supplying  them, 
and  anastomosing  with  the  lumbar  and  inferior  epigastric  arteries. 


THE  ARTERIES   OF  THE  LOWER  EXTREMITY. 

The  artery  which  supplies  the  greater  part  of  the  lower  extremity  is  the  direct 
continuation  of  the  external  iliac.  It  runs  as  a  single  trunk  from  the  inguinal 
ligament  to  the  lower  border  of  the  Popliteus,  where  it  divides  into  two  branches, 
the  anterior  and  posterior  tibial.  The  upper  part  of  the  main  trunk  is  named  the 
femoral,  the  lower  part  the  popliteal. 

THE  FEMORAL  ARTERY  (A.   FEMORALIS)   (Figs.  624,  625). 

The  femoral  artery  begins  immediately  behind  the  inguinal  ligament,  midway 
between  the  anterior  superior  spine  of  the  ilium  and  the  symphysis  pubis,  and 
passes  down  the  front  and  medial  side  of  the  thigh.  It  ends  at  the  junction  of  the 
middle  with  the  lower  third  of  the  thigh,  where  it  passes  through  an  opening  in 
the  Adductor  magnus  to  become  the  popliteal  artery.  The  vessel,  at  the  upper  part 
of  the  thigh,  lies  in  front  of  the  hip-joint;  in  the  lower  part  of  its  course  it  lies  to 
the  medial  side  of  the  body  of  the  femur,  and  between  these  two  parts,  where  it 
crosses  the  angle  between  the  head  and  body,  the  vessel  is  some  distance  from  the 
bone.  The  first  4  cm.  of  the  vessel  is  enclosed,  together  with  the  femoral  vein, 
in  a  fibrous  sheath — the  femoral  sheath.  In  the  upper  third  of  the  thigh  the  femoral 
artery  is  contained  in  the  femoral  triangle  {Scarpa's  triangle),  and  in  the  middle 
third  of  the  thigh,  in  the  adductor  canal  {Hunter's  canal). 

The  femoral  sheath  {crural  sheath)  (Figs.  621,  622)  is  formed  by  a  prolongation 
downward,  behind  the  inguinal  ligament,  of  the  fasciae  which  line  the  abdomen, 
the  transversalis  fascia  being  continued  down  in  front  of  the  femoral  vessels  and 
the  iliac  fascia  behind  them.  The  sheath  assumes  the  form  of  a  short  funnel,  the 
wide  end  of  which  is  directed  upward,  while  the  lower,  narrow  end  fuses  with  the 
fascial  investment  of  the  vessels,  about  4  cm.  below  the  inguinal  ligament.  It  is 
strengthened  in  front  by  a  band  termed  the  deep  crural  arch  (page  509) .  The  lateral 
wall  of  the  sheath  is  vertical  and  is  perforated  by  the  lumboinguinal  nerve;  the 
medial  wall  is  directed  obliquely  downward  and  lateralward,  and  is  pierced  by  the 


THE  FEMORAL  ARTERY 


711 


Fig.  621. — Femoral  sheath  laid  open  to  show  its  three  compartments. 


Lai.  fern,  cutan.  nerve 
/ 


Femoral  nerve 

Lumbo-inguinal  ticrve 
Femoral  artery 
Femoral  sheath 
Femoral  vein 
Femoral  ring 

Lacunar  ligament 


Fig.  622. — Structures  passing  behind  the  inguinal  hgament. 


712 


AXGIOLOGY 


great  saphenous  vein  and  by  some  lymphatic  vessels.  The  sheath  is  divided  by 
two  vertical  partitions  which  stretch  between  its  anterior  and  posterior  walls. 
The  lateral  compartment  contains  the  femoral  artery,  and  the  intermerliate  the 
femoral  vein,  while  the  medial  and  smallest  compartment  is  named  the  femoral 
canal,  and  contains  some  lymphatic  vessels  and  a  lymph  gland  imbedded  in  a  small 
amount  of  areolar  tissue.  "The  femoral  canal  is  conical  and  measures  about  1.25 
cm.  in  length.  Its  base,  directed  upward  and  named  the  femoral  ring,  is  oval  in 
form,  its  long  diameter  being  directed  transversely  and  measuring  about  1.25  cm. 
The  femoral  ring  (Figs.  622,  G23)  is  bounded  in  front  by  the  inguinal  ligament, 
hehmd  by  the  Pectineus  covered  by  the  pectineal  fascia,  medially  by  the  crescentic 
base  of  the  lacunar  ligament,  and  laterally  by  the  fibrous  septum  on  the  medial 
side  of  the  femoral  vein.  The  spermatic  cord  in  the  male  and  the  round  ligament 
of  the  uterus  in  the  female  lie  immediately  above  the  anterior  margin  of  the  ring, 
while  the  inferior  epigastric  vessels  are  close  to  its  upper  and  lateral  angle.  The 
femoral  ring  is  closed  by  a  somewhat  condensed  portion  of  the  extraperitoneal 
fatty  tissue,  named  the  septum  femorale  (crural  seidum),  the  abdominal  surface 


Fig.   623. — The  relations  of  the  femoral  and  abdominal  inguinal  rings,  seen  from  within  the  abdomen.     Right  side. 

of  which  supports  a  small  lymph  gland  and  is  covered  by  the  parietal  layer  of  the 
peritoneum.  The  .septum  femorale  is  pierced  by  numerous  lymphatic  vessels 
passing  from  the  deep  inguinal  to  the  external  iliac  lymph  glands,  and  the  parietal 
peritoneum  immediately  above  it  presents  a  slight  depression  named  the  femoral 
fossa. 

The  femoral  triangle  (trigonum  femorale;  Scarpa's  triangle)  (Fig.  (324)  corre- 
sponds to  the  depression  seen  immediately  below  the  fold  of  the  groin.  Its  apex 
is  directed  downward,  and  the  sides  are  formed  laterally  by  the  medial  margin 
of  the  Sartorius,  medially  by  the  medial  margin  of  the  Adductor  longus,  and  above 
by  the  inguinal  ligament.  The  floor  of  the  space  is  formed  from  its  lateral  to  its 
medial  side  by  the  Iliacus,  Psoas  major,  Pectineus,  in  some  cases  a  small  part  of 
the  Adductor  brevis,  and  the  Adductor  longus;  and  it  is  divided  into  two  nearly 
equal  parts  by  the  femoral  vessels,  which  extend  from  near  the  middle  of  its  base 
to  its  apex:  the  artery  giving  off  in  this  situation  its  superficial  and  profunda 
branches,  the  vein  receiving  the  deep  femoral  and  great  saphenous  tributaries. 
On  the  lateral  side  of  the  femoral  artery  is  the  femoral  nerve  dividing  into  its 


THE  FEMORAL  ARTERY 


■13 


branches.     Besides    the    vessels   and  nerves,  this  space  contains  some  fat  and 
lymphatics. 

The  adductor  canal  (caiKtlift  adducforius;  Hunter's  canaJ)  is  an  aponeurotic 
tunnel  in  the  middle  third  of  the  thigh,  extending;  from  the  apex  of  the  femoral 
triangle  to  the  opening  in  the  Adductor  magnus.  It  is  bounded,  in  front  and  later- 
ally, by  the  Vastus  medialis;  behind  by  the  i\.dductores  longus  and  magnus;  and 
is  covered  in  by  a  strong  aponeurosis  which  extends  from  the  Vastus  medialis, 
across  the  femoral  vessels  to  the  Adductores  longus  and  magnus;  lying  on  the 
aponeurosis  is  the  Sartorius  muscle.  The  canal  contains  the  femoral  artery  and 
vein,  the  saphenous  nerve,  and  the  nerve  to  the  Vastus  mediahs. 

Superficial  iliac  cu cumflex  vessels 
Femoral  nerve 
Superficial  epiga^tiic  vessels 

Superficial  external  pude^idal  vessels 
Deep  external  pudendal  vessels 


Great  saphenous  vein 

Fig.  624. — The  left  femoral  triangle. 


Relations  of  the  Femoral  Artery. — In  the  femoral  triangle  (Fig.  624)  the  artery  is  superficial. 
In  front  of  it  are  the  skin  and  superficial  fascia,  the  superficial  subinguinal  lymph  glands,  the 
superficial  iliac  circumflex  vein,  the  superficial  layer  of  the  fascia  lata  and  the  anterior  part  of 
the  femoral  sheath.  The  lumboinguinal  nerve  courses  for  a  short  distance  within  the  lateral 
compartment  of  the  femoral  sheath,  and  lies  at  first  in  front  and  then  lateral  to  the  artery.  Near 
the  apex  of  the  femoral  triangle  the  medial  branch  of  the  anterior  femoral  cutaneous  nerve 
crosses  the  artery  from  its  lateral  to  its  medial  side. 

Behind  the  artery  are  the  posterior  part  of  the  femoral  sheath,  the  pectineal  fascia,  the  medial 
part  of  the  tendon  of  the  Psoas  major,  the  Pectineus  and  the  Adductor  longus.  The  artery  is 
separated  from  the  capsule  of  the  hip-joint  by  the  tendon  of  the  Psoas  major,  from  the  Pectineus 
by  the  femoral  vein  and  profimda  vessels,  and  from  the  Adductor  longus  by  the  femoral  vein. 
The  nerve  to  the  Pectineus  passes  medialward  behind  the  artery.  On  the  lateral  side  of  the 
artery,  but  separated  from  it  by  some  fibres  of  the  Psoas  major,  is  the  femoral  nerve.    The  femora 


714 


ANGIOWGY 


vein  is  on  the  medial  side  of  the  upper  part  of  the  artery,  but  is  behind  the  vessel  in  the  lower 
part  of  the  femoral  triangle. 

In  the  adductor  canal  (Fig.  625)  the  femoral  artery  is  more  deeply  situated,  being  covered  by 
the  integument,  the  superficial  and  deep  fasciae,  the  Sartorius  and  the  fibrous  roof  of  the  canal; 
the  saphenous  nerve  crosses  from  its  lateral  to  its  medial  side.  Behind  the  artery  are  the  Adduc- 
tores  longus  and  magnus;  in  front  and  lateral  to  it  is  the  Vastus  medialis.  The  femoral  vein 
lies  posterior  to  the  upper  part,  and  lateral  to  the  lower  part  of  the  artery 


Scrolmn 


-  Saphenous  nerve  - 
^ —  Highest  genicular 


Lateral  sup. 


Lateral  inf.  genicular ~ 


Musculo-articular  hr.  of 

highest  genicxdar 
Medial  sup.  genicular 


Medial  inf.  genicular 


Anterior  tibial  recurrent— jj;j-\-'^^i_    i .  i . ,  ,  v/i  j 

Fig.   625. — The  femoral  artery. 


Peculiarities. — Several  cases  are  recorded  in  which  the  femoral  artery  divided  into  two  trunks 
below  the  origin  of  the  profunda,  and  became  reunited  near  the  opening  in  the  Adductor  magnus, 
so  as  to  form  a  single  pophteal  artery.  One  occm-red  in  a  patient  who  was  operated  upon  for 
popliteal  anemrism.  A  few  cases  have  been  recorded  in  which  the  femoral  artery  was  absent, 
its  place  being  suppUed  by  the  inferior  gluteal  artery  which  accompanied  the  sciatic  nerve  to  the 


THE  FEMORAL  ARTERY  715 

popliteal  fossa.  The  external  iliac  in  these  cases  was  small,  and  terminated  in  the  profunda. 
The  femoral  vein  is  occasional^'  placed  along  the  medial  side  of  the  artery  throughout  the  entire 
extent  of  the  femoral  trangle;  or  it  may  be  split  so  that  a  large  vein  is  placed  on  either  side  of 
the  artery  for  a  greater  or  lesser  distance. 

Applied  Anatomy. — Compression  of  the  femoral  artery,  which  is  constantly  requisite  in  ampu- 
tations and  other  operations  on  the  lower  Umb,  is  most  effectually  made  immediatelj^  below 
the  inguinal  ligament.  In  this  situation  the  artery  is  very  superficial,  and  is  merely  separated 
from  the  superior  ramus  of  the  pubis  by  the  Psoas  major;  here  digital  compression  will  effectually 
control  the  circulation  through  it.  The  vessel  may  also  be  controlled  in  the  middle  third  of  the 
thigh  by  a  tourniquet,  which  presses  the  vessel  against  the  medial  side  of  the  body  of  the  female. 

The  superficial  position  of  the  femoral  artery  in  the  femoral  triangle  renders  it  particularly 
liable  to  be  injured  in  wounds,  stabs,  or  gunshot  injuries  in  the  groin.  On  account  of  the  close 
relationship  between  the  artery  and  vein,  the  latter  vessel  is  also  liable  to  be  wounded  in  these 
injuries.  In  such  cases,  the  artery  being  compressed  as  it  crosses  the  ramus  of  the  pubis,  the  skin 
wound  should  be  enlarged  and  the  wound  in  the  vessel  sought  for,  and  a  ligature  applied  above 
and  below  the  bleeding  point. 

The  application  of  a  ligature  to  the  femoral  artery  may  be  required  in  cases  of  wound  or  aneu- 
rism of  the  popHteal,  femoral,  or  arteries  of  the  leg;  and  the  vessel  may  be  exposed  and  tied  in 
any  part  of  its  course.  The  most  favorable  situation  for  the  application  of  a  ligature  to  the  femoral 
is  at  the  apex  of  the  femoral  triangle.  In  order  to  reach  the  artery  in  this  situation,  an  incision 
7  cm.  long  should  be  made  in  the  course  of  the  vessel,  the  patient  lying  in  the  recumbent  posi- 
tion, with  the  limb  slightly  flexed  and  abducted,  and  rotated  outward.  A  large  vein  is  frequently 
met  with,  passing  in  the  course  of  the  artery  to  join  the  great  saphenous  vein;  this  must  be  avoided, 
and  the  fascia  lata  having  been  cautiously  divided,  and  the  Sartorius  displayed,  that  muscle 
must  be  drawn  lateralward,  in  order  to  expose  fully  the  sheath  of  the  vessels.  The  finger  having 
been  introduced  into  the  wound,  and  the  pulsation  of  the  artery  felt,  the  sheath  is  opened  on 
the  lateral  side  of  the  vessel  to  a  sufficient  extent  to  allow  of  the  introduction  of  the  aneurism 
needle.  In  this  part  of  the  operation  the  saphenous  nerve  and  the  nerve  to  the  Vastus  medialis, 
which  are  in  close  relation  with  the  sheath,  should  be  avoided.  The  aneurism  needle  must  be 
carefully  introduced  and  kept  close  to  the  artery,  to  avoid  the  femoral  vein,  which  lies  behind  the 
vessel  in  this  part  of  its  course,  and  is  very  closely  bound  up  with  it. 

To  exjoose  the  artery  in  the  adductor  canal,  an  incision  7  cm.  in  length  should  be  made  through 
the  integument,  a  finger's  breadth  medial  to  the  line  of  the  artery,  the  centre  of  the  incision  being 
in  the  middle  of  the  thigh — i.  e.,  midway  between  the  groin  and  the  knee.  The  fascia  lata  having 
been  divided,  and  the  lateral  border  of  the  Sartorius  exposed,  this  muscle  should  be  drawn  medial- 
ward,  when  the  strong  fascia  which  is  stretched  across  from  the  Adductors  to  the  Vastus  medialis 
will  be  observed,  and  must  be  freely  divided;  the  sheath  of  the  vessels  is  now  seen,  and  must  be 
opened,  and  the  artery  secured  by  passing  the  anem-ism  needle  between  it  and  the  vein,  from 
the  lateral  to  the  medial  side  of  the  artery.  In  this  situation  the  femoral  vein  lies  lateral  to, 
and  the  saphenous  nerve  in  front  of  the  artery. 

Collateral  Circulation. — After  Ugature  of  the  femoral  artery,  the  main  channels  for  carrying 
on  the  circulation  are  the  anastomoses  between — (1)  the  superior  and  inferior  gluteal  branches 
of  the  hypogastric  with  the  medial  and  lateral  femoral  circumflex  and  first  perforating  branches 
of  the  profunda  femoris;  (2)  the  obturator  branch  of  the  hypogastric  with  the  medial  femoral 
cu-cumflex  of  the  profunda;  (3)  the  internal  pudendal  of  the  hypogastric  with  the  superficial 
and  deep  external  pudendal  of  the  femoral;  (4)  the  deep  iUac  circumflex  of  the  external  ihac  with 
the  lateral  femoral  circumflex  of  the  profunda  and  the  superficial  ihac  circumflex  of  the  femoral, 
and  (5)  the  inferior  gluteal  of  the  hypogastric  with  the  perforating  branches  of  the  profunda. 

Branches. — The  branches  of  the  femoral  artery  are; 

Superficial  Epigastric.  Deep  External  Pudendal. 

Superficial  Iliac  Circumflex.  Muscular. 

Superficial  External  Pudendal.  Profunda  Femoris. 

Highest  Genicular. 

The  superficial  epigastric  artery  (a.  epigastrica  superficialis)  arises  from  the 
front  of  the  femoral  artery  about  1  cm.  below  the  inguinal  ligament,  and,  passing 
through  the  femoral  sheath  and  the  fascia  cribrosa,  turns  upward  in  front  of  the 
inguinal  ligament,  and  ascends  between  the  two  layers  of  the  superficial  fascia  of 
the  abdominal  wall  nearly  as  far  as  the  umbilicus.  It  distributes  branches  to  the 
superficial  subinguinal  lymph  glands,  the  superficial  fascia,  and  the  integument; 
it  anastomoses  with  branches  of  the  inferior  epigastric,  and  with  its  fellow  of  the 
opposite  side. 


716  AXGIOLOGY 

The  superficial  iliac  circumflex  artery  (a.  circumflexa  iliinu  .s'upcrficialis),  the 
smallest  of  the  cutaneous  branches,  arises  close  to  the  preceding,  and,  piercing 
the  fascia  lata,  runs  laterahvard,  parallel  with  the  inguinal  ligament,  as  far  as  the 
crest  of  the  ilium;  it  di\-ides  into  branches  which  supply  the  integument  of  the 
groin,  the  superficial  fascia,  and  the  superficial  subinguinal  lymph  glands,  anas- 
tomosing with  the  deep  iliac  circumflex,  the  superior  gluteal  and  lateral  femoral 
circumflex  arteries. 

The  superficial  external  pudendal  artery  (a.  pudenda  externa  superficialis; 
superficial  external  pudic  artery)  arises  from  the  medial  side  of  the  femoral  artery, 
close  to  the  preceding  vessels,  and,  after  piercing  the  femoral  sheath  and  fascia 
cribrosa,  courses  medialward,  across  the  spermatic  cord  (or  round  ligament  in  the 
female),  to  be  distributed  to  the  integument  on  the  lower  part  of  the  abdomen, 
the  penis  and  scrotum  in  the  male,  and  the  labium  majus  in  the  female,  anasto- 
mosing with  branches  of  the  internal  pudendal. 

The  deep  external  pudendal  artery  (a.  pudenda  externa  profunda;  deep  external 
pudic  artery),  more  deeply  seated  than  the  preceding,  passes  medialward  across 
the  Pectineus  and  the  Adductor  longus  muscles;  it  is  covered  by  the  fascia  lata, 
which  it  pierces  at  the  medial  side  of  the  thigh,  and  is  distributed,  in  the  male, 
to  the  integument  of  the  scrotum  and  perineum,  in  the  female  to  the  labium  majus; 
its  branches  anastomose  with  the  scrotal  (or  labial)  branches  of  the  perineal  artery. 

Muscular  branches  {rami  musculares)  are  supplied  by  the  femoral  artery  to  the 
Sartorius,  Vastus  medialis,  and  Adductores. 

The  profunda  femoris  artery  (a.  profunda  femoris;  deep  femoral  artery)  (Fig. 
(325)  is  a  large  vessel  arising  from  the  lateral  and  back  part  of  the  femoral  artery, 
from  2  to  5  cm.  below  the  inguinal  ligament.  At  first  it  lies  lateral  to  the  femoral 
artery ;  it  then  runs  behind  it  and  the  femoral  vein  to  the  medial  side  of  the  femur, 
and,  passing  downward  behind  the  Adductor  longus,  ends  at  the  lower  third  of  the 
thigh  in  a  small  branch,  which  pierces  the  Adductor  magnus,  and  is  distributed 
on  the  back  of  the  thigh  to  the  hamstring  muscles.  The  terminal'  part  of  the  pro- 
funda is  sometimes  named  the  fourth  perforating  artery. 

Relations. — Behind  it,  from  above  downward,  are  the  Iliacus,  Pectineus,  Adductor  brevis, 
and  Adductor  magnus.  In  front  it  is  separated  from  the  femoral  artery  by  the  femoral  and  pro- 
funda veins  above  and  by  the  Adductor  longus  below.  Laterally,  the  origin  of  the  Vastus  medialis 
intervenes  between  it  and  the  femur. 

Peculiarities. — This  vessel  sometimes  arises  from  the  medial  side,  and,  more  rarely,  from  the 
back  of  the  femoral  artery;  but  a  more  important  pecuharity,  from  a  surgical  point  of  view,  is 
that  relating  to  the  height  at  which  the  vessel  arises.  In  three-fourths  of  a  large  number  of  cases 
it  arose  from  2.25  to  5  cm.  below  the  inguinal  ligament;  in  a  few  cases  the  distance  was  less  than 
2.2.5  cm.;  more  rarely,  oppo.site  the  ligament;  and  in  one  case  above  the  inguinal  ligament,  from 
the  external  ihac.  Occasionally  the  distance  between  the  origin  of  the  vessel  and  the  inguinal 
ligament  exceeds  5  cm. 

Branches. — The  profunda  gives  off  the  following  branches: 

Lateral  Femoral  Circumflex.  Perforating. 

Medial  Femoral  Circumflex.  ]\Iuscular. 

The  Lateral  Femoral  Circumflex  Artery  (a.  circumflexa  femoris  lateralis;  external 
circumflex  artery)  arises  from  the  lateral  side  of  the  profunda,  passes  horizontally 
between  the  divisions  of  the  femoral  nerve,  and  behind  the  Sartorius  and  Rectus 
femoris,  and  divides  into  ascending,  transverse,  and  descending  branches. 

The  ascending  branch  passes  upward,  beneath  the  Tensor  fasciae  latae,  to  the 
lateral  aspect  of  the  hip,  and  anastomoses  with  the  terminal  branches  of  the  superior 
gluteal  and  deep  iliac  circumflex  arteries. 

The  descending  branch  runs  downward,  behind  the  Rectus  femoris,  upon  the 
Vastus  lateralis,  to  which  it  gives  offsets;  one  long  branch  descends  in  the  muscle 
as  far  as  the  knee,  and  anastomoses  Avith  the  superior  lateral  genicular  branch  of 


THE  FEMORAL  ARTERY  717 

the  popliteal  artery.  It  is  accompanied  by  the  branch  of  the  femoral  nerve  to  the 
Vastus  lateralis. 

The  transverse  branch,  the  smallest,  passes  lateralward  over  the  Vastus  inter- 
medins, pierces  the  \'astus  lateralis,  and  winds  around  the  femur,  just  below  the 
greater  trochanter,  anastomosing  on  the  back  of  the  thigh  with  the  medial  femoral 
circumflex,  inferior  gluteal,  and  first  perforating  arteries. 

The  Medial  Femoral  Circumflex  Artery  (a.  circiimflexa  feinoris  medialis;  internal 
circumflex  arteri/)  arises  from  the  medial  and  posterior  aspect  of  the  profunda, 
and  winds  around  the  medial  side  of  the  femur,  passing  first  between  the  Pectineus 
and  Psoas  major,  and  then  between  the  Obturator  externus  and  the  Adductor 
brevis.  At  the  upper  border  of  the  Adductor  brevis  it  gives  off  two  branches: 
one  is  distributed  to  the  Adductores,  the  Gracilis,  and  Obturator  externus,  and 
anastomoses  with  the  obturator  artery;  the  other  descends  beneath  the  Adductor 
brevis,  to  supply  it  and  the  iVdductor  magnus;  the  contmuation  of  the  vessel 
passes  backward  and  divides  into  superficial,  deep,  and  acetabular  branches.  The 
superficial  branch  appears  between  the  Quadratus  femoris  and  upper  border  of  the 
Adductor  magnus,  and  anastomoses  with  the  inferior  gluteal,  lateral  femoral 
circumflex,  and  first  perforating  arteries  (crucial  anastomosis).  The  deep  branch 
runs  obliquely  upward  upon  the  tendon  of  the  Obturator  externus  and  in  front 
of  the  Quadratus  femoris  toward  the  trochanteric  fossa,  where  it  anastomoses 
with  twigs  from  the  gluteal  arteries.  The  acetabular  branch  arises  opposite  the 
acetabular  notch  and  enters  the  hip-joint  beneath  the  transverse  ligament  in  com- 
pany wdth  an  articular  branch  from  the  obturator  artery;  it  supplies  the  fat  in  the 
bottom  of  the  acetabulum,  and  is  continued  along  the  round  ligament  to  the  head 
of  the  femur. 

The  Perforating  Arteries  (Fig.  620),  usually  three  in  number,  are  so  named  because 
they  perforate  the  tendon  of  the  Adductor  magnus  to  reach  the  back  of  the  thigh. 
They  pass  backward  close  to  the  linea  aspera  of  the  femur  under  cover  of  small 
tendinous  arches  in  the  muscle.  The  first  is  given  oflF  above  the  Adductor  brevis, 
the  second  in  front  of  that  muscle,  and  the  third  immediately  below  it. 

The  first  perforating  artery  (a.  perjorans  prima)  passes  backward  between  the  Pec- 
tineus and  Adductor  brevis  (sometimes  it  perforates  the  latter) ;  it  then  pierces 
the  Adductor  magnus  close  to  the  linea  aspera.  It  gives  branches  to  the  Adductores 
brevis  and  magnus.  Biceps  femoris,  and  Glutaeus  maximus,  and  anastomoses  with 
the  inferior  gluteal,  medial  and  lateral  femoral  circumfiex  and  second  perforating 
arteries. 

The  second  perforating  artery  (a.  perforans  secunda),  larger  than  the  first,  pierces 
the  tendons  of  the  Adductores  brevis  and  magnus,  and  divides  into  ascending 
and  descending  branches,  which  supply  the  posterior  femoral  muscles,  anasto- 
mosing with  the  first  and  third  perforating.  The  second  artery  frequently  arises 
in  common  with  the  first.  The  nutrient  artery  of  the  femur  is  usually  given  oft' 
from  the  second  perforating  artery;  when  two  nutrient  arteries  exist,  they  usually 
spring  from  the  first  and  third  perforating  vessels. 

The  third  perforating  artery  (a.  perforans  tertia)  is  given  off  below  the  Adductor 
brevis;  it  pierces  the  Adductor  magnus,  and  divides  into  brandies  wliich  supply 
the  posterior  femoral  muscles;  anastomosing  above  witli  the  higher  perforating 
arteries,  and  below  with  the  terminal  branches  of  the  profunda  and  the  muscular 
branches  of  the  popliteal.  The  nutrient  artery  of  the  femur  may  arise  from  this 
branch.  The  termination  of  the  profunda  artery,  already  described,  is  sometimes 
termed  the  fourth  perforating  artery. 

Numerous  muscular  branches  arise  from  the  profunda;  some  of  these  end  in  the 
Adductores,  others  pierce  the  Adductor  magnus,  give  branches  to  the  hamstrings, 
and  anastomose  with  the  medial  femoral  circumflex  artery  and  with  the  superior 
muscular  branches  of  the  popliteal. 


718  ANGIOLOGY 

The  highest  genicular  artery  {a.  genu  suprema;  cmasfomofica  mar/na  artery)  (Fig. 
625)  arises  from  the  femoral  just  before  it  passes  through  the  opening  in  the 
tendon  of  the  Adductor  magnus,  and  immediately  divides  into  a  saphenous  and  a 
musculo-articular  branch. 

The  saphenous  branch  pierces  the  aponeurotic  covering  of  the  adductor  canal, 
and  accompanies  the  saphenous  nerve  to  the  medial  side  of  the  knee.  It  passes 
betAveen  the  Sartorius  and  Gracilis,  and,  piercing  the  fascia  lata,  is  distributed  to 
the  integument  of  the  upper  and  medial  part  of  the  leg,  anastomosing  with  the 
medial  inferior  genicular  artery. 

The  musculoarticular  branch  descends  in  the  substance  of  the  Vastus  medialis, 
and  in  front  of  the  tendon  of  the  Adductor  magnus,  to  the  medial  side  of  the  knee, 
where  it  anastomoses  with  the  medial  superior  genicular  artery  and  anterior  recur- 
rent tibial  artery.  A  branch  from  this  vessel  crosses  above  the  patellar  surface 
of  the  femur,  forming  an  anastomotic  arch  with  the  lateral  superior  genicular 
artery,  and  supplying  branches  to  the  knee-joint. 

THE  POPLITEAL   FOSSA   (Fig.   626). 

Dissection. — A  vertical  incision  about  eight  inches  in  length  should  be  made  along  the  back 
part  of  the  knee-joint,  connected  above  and  below  by  a  transverse  incision  from  the  inner  to  the 
outer  side  of  the  hmb.  The  flaps  of  integument  included  between  these  incisions  should  be 
reflected  in  the  direction  shown  in  Fig.  570. 

Boundaries. — The  popliteal  fossa  or  space  is  a  lozenge-shaped  space,  at  the 
back  of  the  knee-joint.  Laterally  it  is  bounded  by  the  Biceps  femoris  above, 
and  by  the  Plantaris  and  the  lateral  head  of  the  Gastrocnemius  below;  medially 
it  is  limited  by  the  Semitendinous  and  Semimembranosus  above,  and  by  the  medial 
head  of  the  Gastrocnemius  below.  The  floor  is  formed  by  the  popliteal  surface 
of  the  femur,  the  oblique  popliteal  ligament  of  the  knee-joint,  the  upper  end  of  the 
tibia,  and  the  fascia  covering  the  Popliteus;  the  fossa  is  covered  in  by  the  fascia  lata. 

Contents. — The  popliteal  fossa  contains  the  popliteal  vessels,  the  tibial  and  the 
common  peroneal  nerves,  the  termination  of  the  small  saphenous  vein,  the  lower 
part  of  the  posterior  femoral  cutaneous  nerve,  the  articular  branch  from  the  obtur- 
ator nerve,  a  few  small  lymph  glands,  and  a  considerable  quantity  of  fat.  The 
tibial  nerve  descends  through  the  middle  of  the  fossa,  lying  under  the  deep  fascia 
and  crossing  the  vessels  posteriorly  from  the  lateral  to  the  medial  side.  The  com- 
mon peroneal  nerve  descends  on  the  lateral  side  of  the  upper  part  of  the  fossa,  close 
to  the  tendon  of  the  Biceps  femoris.  On  the  floor  of  the  fossa  are  the  popliteal 
vessels,  the  vein  being  superficial  to  the  artery  and  united  to  it  by  dense  areolar 
tissue;  the  vein  is  a  thick-walled  vessel,  and  lies  at  first  lateral  to  the  artery,  and 
then  crosses  it  posteriorly  to  gain  its  medial  side  below;  sometimes  it  is  double, 
the  artery  lying  between  the  two  veins,  which  are  usually  connected  by  short  trans- 
verse branches.  The  articular  branch  from  the  obturator  nerve  descends  upon  the 
artery  to  the  knee-joint.  The  popliteal  lymph  glands,  six  or  seven  in  number, 
are  imbedded  in  the  fat;  one  lies  beneath  the  popliteal  fascia  near  the  termination 
of  the  external  saphenous  vein,  another  between  the  popliteal  artery  and  the  back 
of  the  knee-joint,  while  the  others  are  placed  at  the  sides  of  the  popliteal  vessel. 
Arising  from  the  artery,  and  passing  off  from  it  at  right  angles,  are  its  genicular 
branches. 

The  Popliteal  Artery  (A.  Poplitea)  (Fig.  626). 

The  popliteal  artery  is  the  continuation  of  the  femoral,  and  courses  through  the 
popliteal  fossa.  It  extends  from  the  opening  in  the  Adductor  magnus,  at  the  junc- 
tion of  the  middle  and  lower  thirds  of  the  thigh,  downward  and  lateralward  to  the 
intercondyloid  fossa  of  the  femur,  and  then  vertically  downward  to  the  lower 
border  of  the  Popliteus,  where  it  divides  into  anterior  and  posterior  tibial  arteries. 


THE  POPLITEAL  ARTERY 


719 


Relations. — In  froni  of  the  artery  from  above  downward  are  the  popHteal  surface  of  the  femur 
(which  is  separated  from  the  vessel  by  some  fat),  the  back  of  the  knee-joint,  and  the  fascia  cover- 
ing the  Poplitous.  Behind,  it  is  overlapped  by  the 
Semimembranosus  above,  and  is  covered  by  the 
Gastrocnemius  and  Plantaris  below.  In  the  middle 
part  of  its  course  the  artery  is  separated  from  the 
integument  and  fascia?  by  a  quantity  of  fat,  and  is 
crossed  from  the  lateral  to  the  medial  side  by  the 
tibial  nerve  and  the  popliteal  vein,  the  vein  being 
between  the  nerve  and  the  artery  and  closely  ad- 
herent to  the  latter.  On  its  lateral  side,  above,  are 
the  Biceps  femoris,  the  tibial  nerve,  the  popliteal 
vein,  and  the  lateral  condyle  of  the  femur;  below, 
the  Plantaris  and  the  lateral  head  of  the  Gastroc- 
nemius. On  its  medial  side,  above,  are  the  Semi- 
membranosus and  the  medial  condyle  of  the  femur; 
below,  the  tibial  nerve,  the  popUteal  vein,  and  the 
medial  head  of  the  Gastrocnemius.  The  relations 
of  the  popliteal  lymph  glands  to  the  arteiy  are 
described  above. 

Peculiarities  in  Point  of  Division. — Occasionally 
the  popliteal  artery  divides  into  its  terminal 
branches  opposite  the  knee-joint.  The  anterior 
tibial  under  these  circumstances  usually  passes  in 
front  of  the  Popliteus. 

Unusual  Branches.  —  The  artery  sometimes 
divides  into  the  anterior  tibial  and  peroneal,  the 
posterior  tibial  being  wanting,  or  very  small.  Oc- 
casionally it  divides  into  three  branches,  the  ante- 
rior and  posterior  tibial,  and  peroneal. 

Applied  Anatomy. — The  popHteal  artery  is  not 
infrequently  the  seat  of  injury.  It  may  be  torn 
by  direct  violence,  as  by  the  passage  of  a  cart  wheel 
over  the  knee,  or  by  hyperextension  of  the  knee. 
It  may  also  be  lacerated  by  fracture  of  the  lower 
part  of  the  body  of  the  femur,  or  by  antero-posterior 
dislocation  of  the  knee-joint.  It  has  been  torn  in 
breaking  down  adhesions  in  cases  of  fibrous  anky- 
losis of  the  knee,  and  is  in  danger  of  being  wounded, 
and  in  fact  has  been  wounded,  in  performing  Mac- 
ewen's  operation  of  osteotomy  of  the  lower  end  of 
the  femur  for  genu  valgum.  The  popliteal  artery 
is  more  frequently  the  seat  of  aneurism  than  any 
other  artery  in  the  body,  with  the  exception  of  the 
thoracic  aorta.  No  doubt  this  is  due  in  a  great 
measure  to  the  amoimt  of  movement  to  which  it 
is  subjected,  and  to  the  fact  that  it  is  supported 
by  loose  and  lax  tissue  only,  and  not  by  muscles  as 
is  the  case  with  most  arteries.  When  the  knee  is 
acutely  flexed  the  popHteal  artery  becomes  bent  on 
itself  to  such  an  extent  as  to  entirely  arrest  the  cir- 
culation through  it. 

Ligature  of  the  popliteal  artery  is  reqiured  in 
cases  of  wound  of  the  vessel,  but  for  aneitrism  it  is 
preferable  to  tie  the  femoral.  The  popliteal  may 
be  tied  in  the  upper  or  lower  part  of  its  course; 
but  in  the  middle  of  the  fossa  the  operation  is  at- 
tended with  considerable  difficulty,  from  the  great 
depth  of  the  vessel,  and  from  the  extreme  degree 
of  tension  of  the  lateral  and  medial  boundaries  of 
the  fossa. 

In  order  to  expose  the  upper  part  of  the  vessel, 
the  patient  should  be  placed  in  the  supine  posi- 
tion, with  the  knee  flexed  and  the  thigh  abducted 
and  rotated  outward,  so  that  it  rests  on  its  lateral  surface;  an  incision  7  or  8  cm.  in  length, 
beginning  at  the  junction  of  the  middle  and  lower  thirds  of  the  thigh,  is  to  be  made  paraUel 


Perf.  branch 
of  peroneal 


Fig. 


626. — The  popliteal,  posterior  tibial,  and 
peroneal  arteries. 


720  A  NG 10  LOGY 

to  and  immediately  behind  the  tendon  of  the  adductor  magnus,  and  the  skin,  superficial  and 
deep  fasciiE  divided.  The  tendon  of  the  muscle  is  thus  exposed,  and  is  to  be  drawn  forward, 
and  the  hamstring  tendons  backward.  A  quantity  of  fatty  tissue  will  now  be  opened  up,  in 
which  the  artery  will  be  felt  pulsating.  This  is  to  be  separated  with  the  point  of  a  director 
until  the  arterj^  is  exposed.  The  vein  and  nerve  will  not  be  seen,  as  they  lie  to  the  lateral  side 
of  the  artery.  The  sheath  is  to  be  opened  and  the  aneurism  needle  passed  from  before  backward, 
keeping  its  point  close  to  the  artery  for  fear  of  injuring  the  vein.  The  only  structure  to  avoid 
in  the  superficial  incision  is  the  great  saphenous  vein. 

To  expose  the  vessel  in  the  lower  part  of  its  course,  where  the  artery  lies  between  the  two 
heads  of  the  Gastrocnemius,  the  patient  should  be  placed  in  the  prone  position  with  the  limb 
extended.  An  incision  should  then  be  made  through  the  integument  in  the  middle  line,  commenc- 
ing opposite  the  bend  of  the  knee-joint,  care  being  taken  to  avoid  the  small  saphenous  vein  and 
the  medial  sural  cutaneous  nerve.  After  dividing  the  deep  fascia,  and  separating  some  dense 
cellular  tissue,  the  artery,  vein,  and  nerve  will  be  exposed,  between  the  two  heads  of  the  Gastroc- 
nemius. Some  muscular  branches  of  the  popliteal  should  be  avoided  if  possible,  or,  if  divided, 
tied  immediately.  The  leg  being  now  flexed,  in  order  the  more  effectually  to  separate  the  two 
heads  of  the  Gastrocnemius,  the  nerve  should  be  drawn  medialward  and  the  vein  lateralward, 
and  the  aneurism  needle  passed  between  the  artery  and  vein  from  the  lateral  to  the  medial  side. 

Branches. — The  branches  of  the  popliteal  artery  are: 

- ,         ,        f  Superior  Lateral  Superior  Genicular. 

Muscular  ^^  g^^^j  ^.^^^^  Genicular. 

Cutaneous.  Medial  Inferior  Genicular, 

Medial  Superior  Genicular  Lateral  Inferior  Genicular. 

The  superior  muscular  branches,  two  or  three  in  number,  arise  from  the  upper 
part  of  the  artery,  and  are  distributed  to  the  lower  parts  of  the  Adductor  magnus 
and  hamstring  muscles,  anastomosing  with  the  terminal  part  of  the  profunda 
femoris. 

The  sural  arteries  (aa.  swales;  inferior  viuscular  arteries)  are  two  large  branches, 
which  are  distributed  to  the  Gastrocnemius,  Soleus,  and  Plantaris.  They  arise 
from  the  popliteal  artery  opposite  the  knee-joint. 

The  cutaneous  branches  arise  either  from  the  popliteal  artery  or  from  some  of 
its  branches;  they  descend  between  the  two  heads  of  the  Gastrocnemius,  and, 
piercing  the  deep  fascia,  are  distributed  to  the  skin  of  the  back  of  the  leg.  One 
branch  usually  accompanies  the  small  saphenous  vein. 

The  superior  genicular  arteries  {aa.  genu  superior es;  superior  articular  arteries) 
(Figs.  625,  626),  two  in  number,  arise  one  on  either  side  of  the  popliteal,  and  wind 
around  the  femur  immediately  above  its  condyles  to  the  front  of  the  knee-joint.  The 
medial  superior  genicular  runs  in  front  of  the  Semimembranosus  and  Semitendinosus, 
above  the  medial  head  of  the  Gastrocnemius,  and  passes  beneath  the  tendon  of  the 
Adductor  magnus.  It  divides  into  two  branches,  one  of  which  supplies  the  Vastus 
medialis,  anastomosing  with  the  highest  genicular  and  medial  inferior  genicular 
arteries ;  the  other  ramifies  close  to  the  surface  of  the  femur,  supplying  it  and  the 
knee-joint,  and  anastomosing  with  the  lateral  superior  genicular  artery.  The  medial 
superior  genicular  artery  is  frequently  of  small  size,  a  condition,  which  is  associated 
with  an  increase  in  the  size  of  the  highest  genicular.  The  lateral  superior  genicular 
passes  above  the  lateral  condyle  of  the  femur,  beneath  the  tendon  of  the  Biceps 
femoris,  and  divides  into  a  superficial  and  a  deep  branch;  the  superficial  branch 
supplies  the  Vastus  lateralis,  and  anastomoses  with  the  descending  branch  of  the 
lateral  femoral  circumflex  and  the  lateral  inferior  genicular  arteries;  the  deep 
branch  supplies  the  lower  part  of  the  femur  and  knee-joint,  and  forms  an  anasto- 
motic arch  across  the  front  of  the  bone  with  the  highest  genicular  and  the  medial 
inferior  genicular  arteries. 

The  middle  genicular  artery  (a.  getiu  media;  azygos  articular  artery)  is  a  small 
branch,  arising  opposite  the  back  of  the  knee-joint.  It  pierces  the  oblique  popliteal 
ligament,  and  supplies  the  ligaments  and  synovial  membrane  in  the  interior  of 
the  articulation. 


THE  POPLITEAL  ARTERY 


'21 


The  inferior  genicular  arteries  (rtrt.  gcim  inferiores;  inferior  articular  arteries)  (Figs. 
625,  62()),  two  in  number,  arise  from  the  popliteal  beneath  the  Gastrocnemius.  The 
medial  inferior  genicular  first  descends  along  the  upper  margin  of  the  Popliteus,  to 
which  it  gives  I)ranches;  it  then  passes  below  the  medial  condyle  of  the  tibia,  beneath 
the  tibial  collateral  ligament,  at  the  anterior  border  of  which  it  ascends  to  the  front 
and  medial  side  of  the  joint,  to  supply  the  upper  end  of  the  tibia  and  the  articula- 
tion of  the  knee,  anastomosing  with  the  lateral  inferior  and  medial  superior  genic- 
ular arteries.  The  lateral  inferior  genicular  runs  laterahvard  above  the  head  of  the 
fibula  to  the  front  of  the  knee-joint,  passing  in  its  course  beneath  the  lateral  head 
of  the  Gastrocnemius,  the  fibular  collateral  ligament,  and  the  tendon  of  the  Biceps 
femoris.  It  ends  by  dividing  into  branches,  which  anastomose  with  the  medial 
inferior  and  lateral  superior  genicular  arteries,  and  with  the  anterior  recurrent 
tibial  artery. 


Descending  hranch  of 
lateral  femoral  circwmflex 


Lateral  superic^r  genicular 


Lateral  inferior  genicular 


Fibular  -^-^ 
Anterior  recurrent  tibial 


Anterior  tibial 


Highest  genicular 


Musculo-articular  branch  of 
highest  genicular 

Saphenoxis  branch  of  highest 
genicular 

Medial  superior  genicular 


Medial  inferior  genicular 


Fig.  627. — Circumpatellar  anastomosis. 


The  Anastomosis  Around  the  Knee-joint  (Fig.  627). — Around  and  above  the  patella, 
and  on  the  contiguous  ends  of  the  femur  and  tibia,  is  an  intricate  net-work  of  vessels 
forming  a  superficial  and  a  deep  plexus.  The  superficial  plexus  is  situated  between 
the  fascia  and  skin  around  about  the  patella,  and  forms  three  well-defined  arches : 
one,  above  the  upper  border  of  the  patella,  in  the  loose  connective  tissue  over  the 
Quadriceps  femoris;  the  other  two,  below  the  level  of  the  patella,  are  situated  in 
the  fat  behind  the  ligamentum  patellae.  The  deep  plexus,  which  forms  a  close 
net-work  of  vessels,  lies  on  the  lower  end  of  the  femur  and  upper  end  of  the  tibia 
around  their  articular  surfaces,  and  sends  numerous  offsets  into  the  interior  of  the 
joint.  The  arteries  which  form  this  plexus  are  the  two  medial  and  the  two  lateral 
genicular  branches  of  the  popliteal,  the  highest  genicular,  the  descending  branch 
af  the  lateral  femoral  circumflex,  and  the  anterior  recurrent  tibial. 
46 


722  ANGIOLOGY 

The  Anterior  Tibial  Artery  (A.  Tibialis  Anterior)  (Fig.  62S). 

The  anterior  tibial  artery  commences  at  the  bifurcation  of  the  popHteal,  at  the 
lower  border  of  the  Popliteus,  passes  forward  between  the  two  heads  of  the  Tibialis 
posterior,  and  through  the  aperture  above  the  upper  border  of  the  interosseous 
membrane,  to  the  deep  part  of  the  front  of  the  leg :  it  here  lies  close  to  the  medial 
side  of  the  neck  of  the  fibula.  It  then  descends  on  the  anterior  surface  of  the  inter- 
osseous membrane,  gradually  approaching  the  tibia;  at  the  lower  part  of  the  leg 
it  lies  on  this  bone,  and  then  on  the  front  of  the  ankle-joint,  where  it  is  more 
superficial,  and  becomes  the  dorsalis  pedis. 

Relations. — In  the  upper  two-thirds  of  its  extent,  the  anterior  tibial  artery  rests  upon  the  inter- 
osseous membrane;  in  the  lower  third,  upon  the  front  of  the  tibia,  and  the  anterior  hgament  of 
the  ankle-joint.  In  the  upper  third  of  its  course,  it  lies  between  the  TibiaHs  anterior  and  Extensor 
digitorum  longus;  in  the  middle  third  between  the  Tibialis  anterior  and  Extensor  hallucis  longus. 
At  the  ankle  it  is  crossed  from  the  lateral  to  the  medial  side  by  the  tendon  of  the  Extensor  hallucis 
longus,  and  hes  between  it  and  the  first  tendon  of  the  Extensor  digitorum  longus.  It  is  covered 
in  the  upper  two-thirds  of  its  course,  by  the  muscles  which  he  on  either  side  of  it,  and  by  the  deep 
fascia;  in  the  lower  third,  by  the  integument  and  fascia,  and  the  transverse  and  cruciate  crural 
ligaments. 

The  anterior  tibial  artery  is  accompanied  by  a  pair  of  venae  comitantes  which  he  one  on  either 
side  of  the  artery;  the  deep  peroneal  nerve,  coursing  around  the  lateral  side  of  the  neck  of  the 
fibula,  comes  into  relation  with  the  lateral  side  of  the  artery  shortly  after  it  has  reached  the 
front  of  the  leg;  about  the  middle  of  the  leg  the  nerve  is  in  front  of  the  artery;  at  the  lower  part 
it  is  generally  again  on  the  lateral  side. 

Peculiarities  in  Size. — This  vessel  may  be  diminished  in  size,  may  be  deficient  to  a  greater 
or  less  extent,  or  may  be  entirely  wanting,  its  place  being  supplied  by  perforating  branches  from 
the  posterior  tibial,  or  by  the  perforating  branch  of  the  peroneal  artery. 

Course. — The  artery  occasionally  deviates  toward  the  fibular  side  of  the  leg,  regaining  its 
usual  position  at  the  front  of  the  ankle.  In  rare  instances  the  vessel  has  been  found  to  approach 
the  surface  in  the  middle  of  the  leg,  being  covered  merely  by  the  integument  and  fascia  below 
that  point. 

Applied  Anatomy. — The  anterior  tibial  artery  is  liable  to  be  injin-ed  in  fractures  of  the  lower 
third  of  the  tibia,  on  account  of  its  close  proximity  to  the  bone.  The  apphcation  of  a  hgature 
to  the  vessel  is  rarely  required,  except  in  cases  of  wound  or  for  traumatic  aneurism.  The  opera- 
tion in  the  upper  third  of  the  leg  is  attended  with  great  difficulty  on  accoimt  of  the  depth  of  the 
vessel  from  the  smface.  An  incision  about  10  cm.  in  length  is  made  in  the  line  of  the  artery  to 
about  a  hand's  breadth  below  the  level  of  the  knee-joint.  The  skin  and  superficial  structures 
having  been  divided  and  the  deep  fascia  exposed,  the  wound  must  be  carefully  dried,  its  edges 
retracted,  and  the  white  Line  separating  the  Tibiahs  anterior  from  the  Extensor  digitorum  longus 
sought  for.  When  this  has  been  clearly  defined,  the  deep  fascia  is  to  be  divided  in  this  Une,  and 
the  Tibiahs  anterior  separated  from  adjacent  muscles  imtil  the  interosseous  membrane  is  reached. 
The  foot  is  to  be  flexed  in  order  to  relax  the  muscles,  and  upon  drawing  them  apart  the  artery 
will  be  found  lying  on  the  interosseous  membrane  with  the  nerve  lateral  or  superficial  to  it.  The 
nerve  should  be  drawn  lateralward,  the  venae  comitantes  separated  from  the  artery  and  the 
needle  passed  around  it. 

To  tie  the  vessel  in  the  lower  third  of  the  leg  above  the  ankle-joint,  an  incision  about  7  cm. 
in  length  should  be  made  through  the  integument  between  the  tendons  of  the  Tibiahs  anterior 
and  Extensor  hallucis  longus,  the  deep  fascia  being  divided  to  the  same  extent.  The  tendon  on 
either  side  should  be  retracted,  when  the  vessel,  accompanied  by  the  venae  comitantes,  wiU  be 
seen  lying  upon  the  tibia,  with  the  nerve  on  the  lateral  side. 

Branches.^ — The  branches  of  the  anterior  tibial  artery  are: 

Posterior  Tibial  Recurrent.  Muscular. 

Fibular.  Anterior  Medial  Malleolar. 

Anterior  Tibial  Recurrent.  Anterior  Lateral  Malleolar. 

The  posterior  tibial  recurrent  artery  {a.  recurrens  tibialis  posterior)  an  inconstant 
branch,  is  given  off  from  the  anterior  tibial  before  that  vessel  passes  through  the 
interosseous  space.  It  ascends  in  front  of  the  Popliteus,  which  it  supplies,  and 
anastomoses  with  the  inferior  genicular  branches  of  the  popliteal  artery,  giving 
an  offset  to  the  tibiofibular  joint. 


THE  ANTERIOR  TIBIAL  ARTERY 


723 


Lateral 
infeiior 
genicular 


Medial 
inferior 
genicular 


The  fibular  artery  is  sometimes  derived  from  the  anterior  tibial,  sometimes  from 
the  posterior  tibial.  It  jxisses  laterahvard,  around  the  neck  of  the  fibula,  through 
the  Soleus,  which  it  suppHes,  and  ends  in  the  substance  of  the  Peroneus  longus. 

The  anterior  tibial  recurrent  artery 
(a.  recurrcns  tibialis  anterior)  arises 
from  the  anterior  tibial,  as  soon  as 
that  vessel  has  passed  through  the 
interosseous  space;  it  ascends  in  the 
Tibialis  anterior,  ramifies  on  the  front 
and  sides  of  the  knee-joint,  and  assists 
in  the  formation  of  the  patellar  plexus 
by  anastomosing  with  the  genicular 
branches  of  the  popliteal,  and  with  the 
highest  genicular  artery. 

The  muscular  branches  (ravii  muscu- 
lares)  are  numerous;  they  are  distrib- 
uted to  the  muscles  w-hich  lie  on  either 
side  of  the  vessel,  some  piercing  the 
deep  fascia  to  supply  the  integument, 
others  passing  through  the  interosseous 
membrane,  and  anastomosing  with 
branches  of  the  posterior  tibial  and 
peroneal  arteries. 

The  anterior  medial  malleolar  artery 
(a.  maUeolaris  anterior  mediaUs;  inter- 
nal malleolar  artery)  arises  about  5  cm. 
above  the  ankle-joint,  and  passes  be- 
hind the  tendons  of  the  Extensor 
hallucis  longus  and  Tibialis  anterior,  to 
the  medial  side  of  the  ankle,  upon  which 
it  ramifies,  anastomosing  with  branches 
of  the  posterior  tibial  and  medial  plantar 
arteries  and  with  the  medial  calcaneal 
from  the  posterior  tibial. 

The  anterior  lateral  malleolar  artery 
(a.  maUeolaris  anterior  lateralis;  external 
malleolar  artery)  passes  beneath  the 
tendons  of  the  Extensor  digitorum 
longus  and  Peronaeus  tertius  and  sup- 
plies the  lateral  side  of  the  ankle, 
anastomosing  wdth  the  perforating 
branch  of  the  peroneal  artery,  and  with 
ascending  twigs  from  the  lateral  tarsal 
artery. 

The  arteries  around  the  ankle-joint 
anastomose  freely  with  one  another 
and  form  net-works  below^  the  corre- 
sponding malleoli.  The  medial  malleolar 
net-work  is  formed  by  the  anterior 
medial  malleolar  branch  of  the  anterior 
tibial,  the  medial  tarsal  branches  of 
the  dorsalis  pedis,  the  posterior  medial 
malleolar  and  medial  calcaneal  branches 

of    the     posterior     tibial     and     branches  Yig.  628.— Anterior  tibial  and  dcrsaUs  pedis  arteries. 


Perf.  hr.  of 
-peroneal 

Ant.  lot. 
malleolar 


Ant.  med. 
malleolar 


Deep 
plantar 


724  AmiOLOGY 

from  the  medial  plantar  artery.  The  lateral  malleolar  net-work  is  formed  by  the 
anterior  lateral  malleolar  branch  of  the  anterior  tibial,  the  lateral  tarsal  branch 
of  the  dorsalis  pedis,  the  perforating  and  the  lateral  calcaneal  branches  of  the 
peroneal,  and  twigs  from  the  lateral  plantar  artery. 

The  Arteria  Dorsalis  Pedis  (Dorsalis  Pedis  Artery)  (Fig.  628). 

The  arteria  dorsalis  pedis,  the  continuation  of  the  anterior  tibial,  passes  forward 
from  the  ankle-joint  along  the  tibial  side  of  the  dorsum  of  the  foot  to  the  proximal 
part  of  the  first  intermetatarsal  space,  where  it  divides  into  two  branches,  the  first 
dorsal  metatarsal  and  the  deep  plantar. 

Relations. — This  vessel,  in  its  course  forward,  rests  upon  the  front  of  the  articular  capsule 
of  the  ankle-joint,  the  talus,  navicular,  and  second  cuneiform  bones,  and  the  ligaments  connect- 
ing them,  being  covered  by  the  integument,  fascia  and  cruciate  hgament,  and  crossed  near  its 
termination  by  the  first  tendon  of  the  Extensor  digitorum  brevis.  On  its  tibial  side  is  the  tendon 
of  the  Extensor  hallucis  longus;  on  its  fibular  side,  the  first  tendon  of  the  Extensor  digitorum 
longus,  and  the  termination  of  the  deep  peroneal  nerve.    It  is  accompanied  by  two  veins. 

Peculiarities  in  Size. — The  dorsal  artery  of  the  foot  may  be  larger  than  usual,  to  compensate 
for  a  deficient  plantar  artery;  or  its  terminal  branches  to  the  toes  may  be  absent,  the  toes  then 
being  supphed  by  the  medial  plantar;  or  its  place  may  be  taken  altogether  by  a  large  perforating 
branch  of  the  peroneal  artery. 

Position. — This  artery  frequently  curves  lateralward,  lying  lateral  to  the  Une  between  the 
middle  of  the  ankle  and  the  back  part  of  the  first  interosseous  space. 

Applied  Anatomy. — This  artery  may  be  tied,  by  making  an  incision  5  cm.  in  length,  through 
the  integument,  on  the  fibular  side  of  the  tendon  of  the  Extensor  hallucis  longus,  in  the  interval 
between  it  and  the  medial  border  of  the  Extensor  digitorum  brevis.  The  incision  should  not 
extend  farther  forward  than  the  proximal  part  of  the  first  intermetatarsal  space,  as  the  artery 
divides  m  that  situation.  The  deep  fascia  being  divided  to  the  same  extent,  the  artery  will  be 
exposed,  the  deep  peroneal  nerve  lying  lateral  to  it. 

Branches. — The  branches  of  the  arteria  dorsalis  pedis  are: 

Lateral  Tarsal.  iVrcuate. 

Medial  Tarsal.  First  Dorsal  Metatarsal. 

Deep  Plantar. 

The  lateral  tarsal  artery  (a.  tar  sea  lateralis;  tarsal  artery)  arises  from  the  dorsalis 
pedis,  as  that  vessel  crosses  the  navicular  bone;  it  passes  in  an  arched  direction 
lateralward,  lying  upon  the  tarsal  bones,  and  covered  by  the  Extensor  digitorum 
brevis;  it  supplies  this  muscle  and  the  articulations  of  the  tarsus,  and  anastomoses 
with  branches  of  the  arcuate,  anterior  lateral  malleolar  and  lateral  plantar  arteries, 
and  with  the  perforating  branch  of  the  peroneal  artery. 

The  medial  tarsal  arteries  {aa.  tarseae  mediales)  are  two  or  three  small  branches 
which  ramify  on -the  medial  border  of  the  foot  and  join  the  medial  malleolar  net-work. 

The  arcuate  artery  (a.  arcuata;  metatarsal  artery)  arises  a  little  anterior  to  the 
'  lateral  tarsal  artery;  it  passes  lateralward,  over  the  bases  of  the  metatarsal  bones, 
beneath  the  tendons  of  the  Extensor  digitorum  brevis,  its  direction  being  influenced 
by  its  point  of  origin;  and  it  anastomoses  with  the  lateral  tarsal  and  lateral  plantar 
arteries.  This  vessel  gives  off  the  second,  third,  and  fourth  dorsal  metatarsal  arteries, 
which  run  forward  upon  the  corresponding  Interossei  dorsales;  in  the  clefts  between 
the  toes,  each  divides  into  two  dorsal  digital  branches  for  the  adjoining  toes.  At 
the  proximal  parts  of  the  interosseous  spaces  these  vessels  receive  the  posterior 
perforating  branches  from  the  plantar  arch,  and  at  the  distal  parts  of  the  spaces 
they  are  joined  by  the  anterior  perforating  branches,  from  the  plantar  metatarsal 
arteries.  The  fourth  dorsal  metatarsal  artery  gives  off  a  branch  which  supplies 
the  lateral  side  of  the  fifth  toe. 

The  first  dorsal  metatarsal  artery  (o.  dorsalis  hallucis)  runs  forward  on  the  first 
Interosseous  dorsalis,  and  at  the  cleft  between  the  first  and  second  toes  divides 


THE  POSTERIOR  TIBIAL  ARTERY  725 

into  two  branches,  one  of  which  passes  beneath  the  tendon  of  the  Extensor  hallucis 
longns,  and  is  distributed  to  the  me(Hal  border  of  the  great  toe;  the  other  bifurcates 
to  supply  the  adjoinino'  sides  of  the  great  and  second  toes. 

The  deep  plantar  artery  {ramus  plantaris  profundus;  communicating  artery) 
descends  into  the  sole  of  the  foot,  between  the  two  heads  of  the  first  Interosseous 
dorsalis,  and  unites  with  the  termination  of  the  lateral  plantar  artery,  to  complete 
the  plantar  arch.  It  sends  a  branch  along  the  medial  side  of  the  great  toe,  and  is 
continued  forward  along  the  first  interosseous  space  as  the  first  plantar  metatarsal 
artery,  which  bifurcates  for  the  supply  of  the  adjacent  sides  of  the  great  and  second 
toes. 

The  Posterior  Tibial  Artery  (A.  Tibialis  Posterior)  (Fig.  626). 

The  posterior  tibial  artery  begins  at  the  lower  border  of  the  Popliteus,  opposite 
the  interval  between  the  tibia  and  fibula;  it  extends  obliquely  downward,  and,  as 
it  descends,  it  approaches  the  tibial  side  of  the  leg,  lying  behind  the  tibia,  and  in 
the  lower  part  of  its  course  is  situated  midway  between  the  medial  malleolus  and 
the  medial  process  of  the  calcaneal  tuberosity.  Here  it  divides  beneath  the  origin 
of  the  Adductor  hallucis  into  the  medial  and  lateral  plantar  arteries. 

Relations. — The  posterior  tibial  artery  lies  successively  upon  the  Tibialis  posterior,  the  Flexor 
digitorum  longus,  the  tibia,  and  the  back  of  the  ankle-joint.  It  is  covered  by  the  deep  trans- 
verse fascia  of  the  leg,  which  separates  it  above  from  the  Gastrocnemius  and  Soleus ;  at  its  termi- 
nation it  is  covered  by  the  Abductor  hallucis.  In  the  lower  third  of  the  leg,  where  it  is  more 
superficial,  it  is  covered  only  by  the  integument  and  fascia,  and  runs  parallel  with  the  medial 
border  of  the  tendo  calcaneus.  It  is  accompanied  by  two  veins,  and  by  the  tibial  nerve,  which 
lies  at  first  to  the  medial  side  of  the  artery,  but  soon  crosses  it  posteriorly,  and  is  in  the  greater 
part  of  its  com'se  on  its  lateral  side. 

Behind  the  medial  malleolus,  the  tendons,  bloodvessels,  and  nerve  are  arranged,  under  cover 
of  the  laciniate  ligament,  in  the  following  order  from  the  medial  to  the  lateral  side:  (1)  the 
tendons  of  the  Tibialis  posterior  and  Flexor_  digitorum  longus,  lying  in  the  same  groove,  behind 
the  malleolus,  the  former  being  the  more  medial.  Next  is  the  posterior  tibial  artery,  with  a  vein 
on  either  side  of  it;  and  lateral  to  the  vessels  is  the  tibial  nerve;  about  1.25  cm.  nearer  the  heel 
is  the  tendon  of  the  Flexor  hallucis  longus. 

Peculiarities  in  Size. — -The  posterior  tibial  is  not  infrequently  smaller  than  usual,  or  absent, 
its  place  being  supplied  by  a  large  peroneal  artery,  which  either  joins  the  small  posterior  tibial 
artery,  or  continues  alone  to  the  sole  of  the  foot. 

Applied  Anatomy. — The  apphcation  of  a  Ugature  to  the  posterior  tibial  may  be  required  in 
cases  of  wound  of  the  sole  of  the  foot,  attended  with  great  hemorrhage,  when  the  vessel  should 
be  tied  at  the  ankle.  In  cases  of  wound  of  the  posterior  tibial,  it  will  be  necessary  to  enlarge  the 
opening  so  as  to  expose  the  vessel  at  the  wounded  point,  excepting  where  the  vessel  is  injured 
by  a  punctm-ed  woimd  from  the  front  of  the  leg.  In  cases  of  aneurism  from  wound  of  the  artery 
low  down,  the  vessel  should  be  tied  in  the  middle  of  the  leg. 

To  tie  the  posterior  tibial  artery  at  the  ankle,  a  semilunar  incision,  about  6  cm.  in  length, 
convex  backward,  should  be  made  through  the  integument,  midway  between  the  heel  and  the 
medial  malleolus,  or  a  Uttle  nearer  the  latter.  The  subcutaneous  tissue  having  been  divided, 
a  strong  and  dense  fascia,  the  laciniate  (internal  annular)  Ugament,  is  exposed.  This  ligament 
is  continuous  above  with  the  deep  fascia  of  the  leg,  covers  the  vessels  and  nerves,  and  is  intimately 
adherent  to  the  sheaths  of  the  tendons.  This  having  been  cautiously  divided  upon  a  director, 
the  sheath  of  the  vessels  is  exposed,  and,  being  opened,  the  artery  is  seen  with  one  of  the  venae 
comitantes  on  either  side.  The  aneurism  needle  should  be  passed  around  the  vessel  from  the 
heel  toward  the  ankle,  in  order  to  avoid  the  tibial  nerve,  care  at  the  same  time  being  taken  not 
to  include  the  venae  comitantes. 

The  vessel  may  also  be  tied  in  the  lower  thu'd  of  the  leg  by  making  an  incision  about  8  cm. 
in  length,  parallel  with  the  medial  border  of  the  tendo  calcaneus.  The  great  saphenous  vein 
being  carefully  avoided,  the  two  layers  of  fascia  must  be  divided  upon  a  director,  when  the 
artery  is  exposed  along  the  lateral  margin  of  the  Flexor  digitorum  longus,  with  one  of  its  venae 
comitantes  on  either  side,  and  the  nerve  lying  lateral  to  it. 

Ligature  of  the  posterior  tibial  in  the  middle  of  the  leg  is  a  very  difficult  operation,  on  account 
of  the  great  depth  of  the  vessel  from  the  surface.  The  patient  being  placed  in  the  recumbent 
position,  the  injm-ed  hmb  should  rest  on  its  fibular  side,  the  knee  being  partially  bent,  and  the 
foot  extended,  so  as  to  relax  the  muscles  of  the  calf.  An  incision  about  10  cm.  in  length  should 
then  be  made  through  the  integument,  a  finger's  breadth  behind  the  medial  margin  of  the  tibia, 
care  being  taken  to  avoid  the  great  saphenous  vein.    The  deep  fascia  having  been  divided,  the 


726  ANGIOLOGY 

margin  of  the  Gastrocnemius  is  exposed,  and  must  be  drawn  aside,  and  the  tibial  attachment 
of  the  Soleus  divided.  The  artery  may  now  be  felt  pulsating  beneath  the  deep  transverse  fascia, 
about  2.5  cm.  from  the  margin  of  the  tibia.  This  fascia  having  been  divided,  and  the  limb  placed 
in  such  a  position  as  to  relax  the  muscles  of  the  calf  as  much  as  possible,  the  veins  should  be  sepa- 
rated from  the  artery  and  the  aneurism  needle  passed  around  the  vessel  from  the  lateral  to  the 
medial  side,  so  as  to  avoid  wounding  the  tibial  nerve. 

Branches. — The  branches  of  the  posterior  tibial  artery  are : 

Peroneal.  Posterior  Medial  Malleolar. 

Nutrient.  Communicating. 

Muscular.  Medial  Calcaneal. 

The  peroneal  artery  (a.  peronaea)  is  deeply  seated  on  the  back  of  the  fibular 
side  of  the  leg.  It  arises  from  the  posterior  tibial,  about  2.5  cm.  below  the  lower 
border  of  the  Popliteus,  passes  obliquely  toward  the  fibula,  and  then  descends 
along  the  medial  side  of  that  bone,  contained  in  a  fibrous  canal  between  the  Tibialis 
posterior  and  the  Flexor  hallucis  longus,  or  in  the  substance  of  the  latter  muscle. 
It  then  runs  behind  the  tibiofibular  syndesmosis  and  divides  into  lateral  calcaneal 
branches  which  ramify  on  the  lateral  and  posterior  surfaces  of  the  calcaneus. 

It  is  covered,  in  the  upper  part  of  its  course,  by  the  Soleus  and  deep  transverse 
fascia  of  the  leg;  below,  by  the  Flexor  hallucis  longus. 

Peculiarities  in  Origin. — The  peroneal  artery  may  arise  7  or  8  cm.  below  the  Popliteus,  or  from 
the  posterior  tibial  high  up,  or  even  from  the  popliteal. 

Its  size  is  more  frequently  increased  than  diminished;  and  then  it  either  reinforces  the  posterior 
tibial  by  its  junction  with  it,  or  altogether  takes  the  place  of  the  posterior  tibial  in  the  lower 
part  of  the  leg  and  foot,  the  latter  vessel  onlj^  existing  as  a  short  muscular  branch.  In  those 
rare  cases  where  the  peroneal  artery  is  smaller  than  usual,  a  branch  from  the  posterior  tibial 
supplies  its  place;  and  a  branch  from  the  anterior  tibial  compensates  for  the  diminished  anterio!" 
peroneal  artery.    In  one  case  the  peroneal  artery  was  entirely  wanting. 

Branches. — The  branches  of  the  peroneal  are: 

Muscular.  Perforating. 

Nutrient.  Communicating. 

Lateral  Calcaneal. 

Muscular  Branches. — The  peroneal  artery,  in  its  course,  gives  off  branches  to 
the  Soleus,  Tibialis  posterior.  Flexor  hallucis  longus,  and  Peronei. 

The  Nutrient  Artery  (a.  nutricia  fibulae)  supplies  the  fibula,  and  is  directed 
downward. 

The  Perforating  Branch  {ramus  perforans;  anterior  peroneal  artery)  pierces  the 
interosseous  membrane,  about  5  cm.  above  the  lateral  malleolus,  to  reach  the  front 
of  the  leg,  where  it  anastomoses  with  the  anterior  lateral  malleolar;  it  then  passes 
down  in  front  of  the  tibiofibular  syndesmosis,  gives  branches  to  the  tarsus,  and 
anastomoses  with  the  lateral  tarsal.  The  perforating  branch  is  sometimes  enlarged, 
and  takes  the  place  of  the  dorsalis  pedis  artery. 

The  Communicating  Branch  {ramus  communicans)  is  given  off  from  the  peroneal 
about  2.5  cm.  from  its  lower  end,  and  joins  the  communicating  branch  of  the 
posterior  tibial. 

The  Lateral  Calcaneal  {ramus  calcaneus  lateralis;  external  calcaneal)  are  the  ter- 
minal branches  of  the  peroneal  artery;  they  pass  to  the  lateral  side  of  the  heel, 
and  communicate  with  the  lateral  malleolar  and,  on  the  back  of  the  heel,  with  the 
medial  calcaneal  arteries. 

The  nutrient  artery  (a.  nutricia  tibiae)  of  the  tibia  arises  from  the  posterior 
tibial,  near  its  origin,  and  after  supplying  a  few  muscular  branches  enters  the 
nutrient  canal  of  the  bone,  which  it  traverses  obliquely  from  above  downward. 
This  is  the  largest  nutrient  artery  of  bone  in  the  body. 


THE  POSTERIOR  TIBIAL  ARTERY 


727 


The  muscular  branches  of  the  posterior  til)ial  arc  distributed  to  the  Soleus  and 
deep  muscles  along  the  back  of  the  leg. 

The  posterior  medial  malleolar  artery  (a.  nudleolaris  posterior  inedUdis;  internal 
malleolar  artery)  is  a  small  branch  which  winds  around  the  tibial  malleolus  and 
ends  in  the  medial  malleolar  net-work. 

The  communicating  branch  (ravivs  communicans)  runs  transversely  across  the 
back  of  the  tibia,  about  5  cm.  above  its  lower  end,  beneath  the  Flexor  hallucis 
longus,  and  joins  the  communicating  branch  of  the  peroneal. 

The  medial  calcaneal  {rami  calcanei  mediales;  internal  calcaneal)  are  several 
large  arteries  which  arise  from  the  posterior  tibial  just  before  its  division;  they 
pierce  the  laciniate  ligament  and  are  distributed  to  the  fat  and  integument  behind 
the  tendo  calcaneus  and  about  the  heel,  and  to  the  muscles  on  the  tibial  side  of 
the  sole,  anastomosing  with  the  peroneal  and  medial  malleolar  and,  on  the  back 
of  the  heel,  with  the  lateral  calcaneal  arteries. 


Deep  plantar 

1st  plantar 
metatarsal  \ 


Fig.  629. — The  plantar  arteries.      Superficial  view. 


Fig.  630. — The  plantar  arteries.     Deep  view. 


The  medial  plantar  artery  (a.  plantaris  medialis;  internal  plantar  artery)  (Figs. 
629  and  630),  much  smaller  than  the  lateral,  passes  forw^ard  along  the  medial  side 
of  the  foot.  It  is  at  first  situated  above  the  Abductor  hallucis,  and  then  between 
it  and  the  Flexor  digitorum  brevis,  both  of  which  it  supplies.  At  the  base  of  the 
first  metatarsal  bone,  wdiere  it  is  much  diminished  in  size,  it  passes  along  the  medial 
border  of  the  first  toe,  anastomosing  with  the  first  dorsal  metatarsal  artery.  Small 
superficial  digital  branches  accompany  the  digital  branches  of  the  medial  plantar 
nerve  and  join  the  plantar  metatarsal  arteries  of  the  first  three  spaces. 

The  lateral  plantar  artery  {a.  plantaris  lateralis;  external  plantar  artery),  much 
larger  than  the  medial,  passes  obliquely  lateralward  and  forward  to  the  base  of 
the  fifth  metatarsal  bone.  It  then  turns  medialw^ard  to  the  interval  between  the 
bases  of  the  first  and  second  metatarsal  bones,  w^here  it  unites  with  the  deep  plantar 
branch  of  the  dorsalis  pedis  artery,  thus  completing  the  plantar  arch.  As  this  artery 
passes  lateralward,  it  is  first  placed  between  the  calcaneus  and  Abductor  hallucis. 


728  ANGIOLOGY 

and  then  between  the  Flexor  digitorum  brevis  and  Quadratus  plantae;  as  it  runs 
fonvard  to  the  base  of  the  little  toe  it  lies  more  superficially  between  the  Flexor 
digitorum  brevis  and  Abductor  digiti  quinti,  covered  by  the  plantar  aponeurosis 
and  integument.  The  remaining  portion  of  the  vessel  is  deeply  situated;  it  extends 
from  the  base  of  the  fifth  metatarsal  bone  to  the  proximal  part  of  the  first  inter- 
osseous space,  and  forms  the  plantar  arch;  it  is  convex  forward,  lies  below  the  bases 
of  the  second,  third,  and  fourth  metatarsal  bones  and  the  corresponding  Interossei, 
and  upon  the  oblique  part  of  the  Adductor  hallucis. 

Applied  Anatomy. — Wounds  of  the  plantar  arch  are  always  serious,  on  account  of  the  depth 
of  the  vessel  and  the  important  structures  which  must  be  interfered  with  in  an  attempt  to  liga- 
ture it.  They  must  be  treated  on  similar  lines  to  those  of  wounds  of  the  volar  arches  (see  p.  682). 
Pressure  locally,  combined  -^vith  elevation  of  the  limb,  may  in  some  cases  be  sufficient  to  arrest 
the  bleeding,  but  this  faiUng,  an  attempt  should  be  made  to  find  the  bleeding  point  and  ligature 
it.  Should  this  prove  unsuccessful,  it  may  be  necessary  to  Ugature  the  femoral  below  the  origin* 
of  the  profunda  femoris,  as  ligature  of  the  anterior  and  posterior  tibial  arteries  may  not  be 
sufiicient  to  control  the  hemorrhage,  and  it  is  safer  and  quicker  to  tie  the  femoral  under  the 
circumstances. 

Branches. — The  plantar  arch,  besides  distributing  numerous  branches  to  the 
muscles,  integument,  and  fasciae  in  the  sole,  gives  off  the  following  branches: 

Perforating.  Plantar  Metatarsal. 

The  Perforating  Branches  {rami  jjerforantes)  are  three  in  number;  they  ascend 
through  the  proximal  parts  of  the  second,  third,  and  fourth  interosseous  spaces, 
between  the  heads  of  the  Interossei  dorsales,  and  anastomose  with  the  dorsal 
metatarsal  arteries. 

The  Plantar  Metatarsal  Arteries  (aa.  metatarseae  plantares;  digital  branches)  are 
four  in  number,  and  run  forward  between  the  metatarsal  bones  and  in  contact 
^dth  the  Interossei.  Each  divides  into  a  pair  of  plantar  digital  arteries  which  sup- 
ply the  adjacent  sides  of  the  toes.  Near  their  points  of  division  each  sends  upward 
an  anterior  perforating  branch  to  join  the  corresponding  dorsal  metatarsal  artery. 
The  first  plantar  metatarsal  artery  {arteria-  'princefjs  hallucis)  springs  from  the  junc- 
tion between  the  lateral  plantar  and  deep  plantar  arteries  and  sends  a  digital 
branch  to  the  medial  side  of  the  first  toe.  The  digital  branch  for  the  lateral  side 
of  the  fifth  toe  arise  from  the  lateral  plantar  artery  near  the  base  of  the  fifth 
metatarsal  bone. 


THE  VEINS. 


nnilE  Veins  convey  the  blood  from  the  capillaries  of  the  different  parts  of  the 
-*-  body  to  the  heart.  They  consist  of  two  distinct  sets  of  vessels,  the  pulmonary 
and  systemic. 

The  Pulmonary  Veins,  unlike  other  veins,  contain  arterial  blood,  which  they  return 
from  the  lungs  to  the  left  atrium  of  the  heart. 

The  Systemic  Veins  return  the  venous  blood  from  the  body  generally  to  the 
right  atrium  of  the  heart. 

The  Portal  Vein,  an  appendage  to  the  systemic  venous  system,  is  confined  to 
the  abdominal  cavity,  and  returns  the  venous  blood  from  the  spleen  and  the  viscera 
of  digestion  to  the  liver.  This  vessel  ramifies  in  the  substance  of  the  liver  and  there 
breaks  up  into  a  minute  network  of  capillary-like  vessels,  from  which  the  blood 
is  conveyed  by  the  hepatic  veins  to  the  inferior  vena  cava. 

The  veins  commence  by  minute  plexuses  w^hich  receive  the  blood  from  the  capil- 
laries. The  branches  arising  from  these  plexuses  unite  together  into  trunks,  and 
these,  in  their  passage  toward  the  heart,  constantly  increase  in  size  as  they  receive 
tributaries,  or  join  other  veins.  The  veins  are  larger  and  altogether  more  numerous 
than  the  arteries;  hence,  the  entire  capacity  of  the  venous  system  is  much  greater 
than  that  of  the  arterial;  the  capacity  of  the  pulmonary  veins,  however,  only 
slightly  exceeds  that  of  the  pulmonary  arteries.  The  veins  are  cylindrical  like  the 
arteries;  their  walls,  however,  are  thin  and  they  collapse  when  the  vessels  are 
empty,  and  the  uniformity  of  their  surfaces  is  interrupted  at  intervals  by  slight 
constrictions,  which  indicate  the  existence  of  valves  in  their  interior.  They  com- 
municate very  freely  with  one  another,  especially  in  certain  regions  of  the  body; 
and  these  communications  exist  between  the  larger  trunks  as  well  as  between  the 
smaller  branches.  Thus,  between  the  venous  sinuses  of  the  cranium,  and  between 
the  veins  of  the  neck,  where  obstruction  would  be  attended  with  imminent  danger 
to  the  cerebral  venous  system,  large  and  frequent  anastomoses  are  found.  The 
same  free  communication  exists  between  the  veins  throughout  the  whole  extent 
of  the  vertebral  canal,  and  between  the  veins  composing  the  various  venous  plexuses 
in  the  abdomen  and  pelvis,  e.  g.,  the  spermatic,  uterine,  vesical,  and  pudendal. 

The  systemic  venous  channels  are  subdivided  into  three  sets,  viz.,  superficial 
and  deep  veins,  and  venous  sinuses. 

The  Superficial  Veins  {cutaneous  veins)  are  found  between  the  layers  of  the 
superficial  fascia  immediately  beneath  the  skin;  they  return  the  blood  from  these 
structures,  and  communicate  with  the  deep  veins  by  perforating  the  deep  fascia. 

The  Deep  Veins  accompany  the  arteries,  and  are  usually  enclosed  in  the  same 
sheaths  with  those  vessels.  With  the  smaller  arteries — as  the  radial,  ulnar,  brachial, 
tibial,  peroneal — they  exist  generally  in  pairs,  one  lying  on  each  side  of  the  vessel, 
and  are  called  venae  comitantes.  The  larger  arteries — such  as  the  axillary,  sub- 
clavian, popliteal,  and  femoral — have  usually  only  one  accompanying  vein.  In 
certain  organs  of  the  body,  however,  the  deep  veins  do  not  accompany  the  arteries; 
for  instance,  the  veins  in  the  skull  and  vertebral  canal,  the  hepatic  veins  in  the  liver, 
and  the  larger  veins  returning  blood  from  the  bones. 

Venous  Sinuses  are  found  only  in  the  interior  of  the  skull,  and  consist  of  canals 
formed  by  a  separation  of  the  two  layers  of  the  dura  mater;  their  outer  coat  con- 
sists of  fibrous  tissue,  their  inner  of  an  endothelial  layer  continuous  with  the  lining 
membrane  of  the  veins. 


730  ANGIOLOGY 


THE   PULMONARY  VEINS   (VENAE   PULMONALES). 

The  pulmonary  veins  return  the  arteriahzed  blood  from  the  kings  to  the  left 
atrium  of  the  heart.  They  are  four  in  number,  two  from  each  lung,  and  are  desti- 
tute of  valves.  The  commence  in  a  capillary  net-work  upon  the  walls  of  the  air  sacs, 
where  they  are  continuous  with  the  capillary  ramifications  of  the  pulmonary  artery, 
and,  joining  together,  form  one  vessel  for  each  lobule.  These  vessels  uniting 
successively,  form  a  single  trunk  for  each  lobe,  three  for  the  right,  and  two  for 
the  left  lung.  The  vein  from  the  middle  lobe  of  the  right  lung  generally  unites 
with  that  from  the  upper  lobe,  so  that  ultimately  two  trunks  from  each  lung  are 
formed;  they  perforate  the  fibrous  layer  of  the  pericardium  and  open  separately 
into  the  upper  and  back  part  of  the  left  atrium.  Occasionally  the  three  veins 
on  the  right  side  remain  separate.  Not  infrequently  the  two  left  pulmonary 
veins  end  by  a  common  opening. 

At  the  root  of  the  hing,  the  superior  pulmonary  vein  lies  in  front  of  and  a  little 
below  the  pulmonary  artery;  the  inferior  is  situated  at  the  lowest  part  of  the  hilus 
of  the  lung  and  on  a  plane  posterior  to  the  upper  vein.  Behind  the  pulmonary 
artery  is  the  bronchus. 

Within  the  pericardium,  their  anterior  surfaces  are  invested  by  the  serous  layer 
of  this  membrane. 

The  right  pulmonary  veins  pass  behind  the  right  atrium  and  superior  vena  cava; 
the  left  in  front  of  the  descending  thoracic  aorta. 


THE  SYSTEMIC  VEINS. 

The  systemic  veins  may  be  arranged  into  three  groups :  (1)  The  veins  of  the  heart. 
(2)  The  veins  of  the  upper  extremities,  head,  neck,  and  thorax,  which  end  in  the 
superior  vena  cava.  (3)  The  veins  of  the  lower  extremities,  abdomen,  and  pelvis, 
which  end  in  the  inferior  vena  cava. 

THE  VEINS   OF  THE  HEART   (VV.   Cordis)    (Fig.   631). 

Coronary  Sinus  {sinus  coronarius). — Most  of  the  veins  of  the  heart  open  into 
the  coronary  sinus.  This  is  a  wide  venous  channel  about  2.25  cm.  in  length 
situated  in  the  posterior  part  of  the  coronary  sulcus,  and  covered  by  muscular 
fibres  from  the  left  atrium.  It  ends  in  the  right  atrium  between  the  opening  of 
the  inferior  vena  cava  and  the  atrioventricular  aperture,  its  orifice  being  guarded 
by  a  semilunar  valve,  the  valve  of  the  coronary  sinus  {vahe  of  Thehesius). 

Tributaries. — Its  tributaries  are  the  great,  small,  and  middle  cardiac  veins,  the 
posterior  vein  of  the  left  ventricle,  and  the  oblique  vein  of  the  left  atrium,  all  of 
which,  except  the  last,  are  provided  with  valves  at  their  orifices. 

1.  The  Great  Cardiac  Vein  (v.  cordis  magna;  left  coronary  vein)  begins  at  the  apex 
of  the  heart  and  ascends  along  the  anterior  longitudinal  sulcus  to  the  base  of  the 
ventricles.  It  then  curves  to  the  left  in  the  coronary  sulcus,  and  reaching  the 
back  of  the  heart,  opens  into  the  left  extremity  of  the  coronary  sinus.  It  receives 
tributaries  from  the  left  atrium  and  from  both  ventricles:  one,  the  left  marginal 
vein,  is  of  considerable  size,  and  ascends  along  the  left  margin  of  the  heart. 

2.  The  Small  Cardiac  Vein  {v.  cordis  ixirm;  right  coronary  vein)  runs  in  the  coronary 
sulcus  between  the  right  atrium  and  ventricle,  and  opens  into  the  right  extremity 
of  the  coronary  sinus.  It  receives  blood  from  the  back  of  the  right  atrium  and 
ventricle;  the  right  marginal  vein  ascends  along  the  right  margin  of  the  heart  and 
joins  it  in  the  coronary  sulcus,  or  opens  directly  into  the  right  atrium. 


THE  VEINS  OF  THE  HEAD  AND  NECK 


731 


3.  The  Middle  Cardiac  Vein  (r.  cordis-  iiicdUi)  coinniciices  at  the  apex  of  the  heart, 
ascends  in  the  posterior  longitudinal  sulcus,  and  ends  in  the  coronary  sinus  near 
its  right  cxtrrniity. 

4.  The  Posterior  Vein  of  the  Left  Ventricle  ( i\  po^'terior  ventriculi  sinistri)  runs  on 
the  diaphragmatic  surface  of  the  left  ventricle  to  the  coronary  sinus,  hut  may  end 
in  the  great  cardiac  vein. 

5.  The  Oblique  Vein  of  the  Left  Atrium  («.  ohliqua  atrii  sinistri  [Marshalli] ;  oblique 
vein  of  Marshall)  is  a  small  vessel  which  descends  obliquely  on  the  back  of  the  left 
atrium  and  ends  in  the  coronary  sinus  near  its  left  extremity;  it  is  continuous  above 
with  the  ligament  of  the  left  vena  cava  {lig.  venae  cav'ae  sinistrae;  vestigial  fold  of 
Marshall),  and  the  two  structures  form  the  remnant  of  the  left  Cuverian  duct. 

Azygos  vein 


Left  'pulmonary  veins 

Oblique  vein  of  left  atrium 
Great  cardiac  vein 


Left  marginal  vein 


Rigid  pulmonary 
veins 


Small  cardiac  vein 


Posterior  vein  of  left  ventricle 

Middle  cardiac  vein, 
Fig.  631. — Base  and  diaphragmatic  surface  of  heart. 


The  following  cardiac  veins  do  not  end  in  the  coronary  sinus:  (1)  the  anterior 
cardiac  veins,  comprising  three  or  four  small  vessels  which  collect  blood  from  the 
front  of  the  right  ventricle  and  open  into  the  right  atrium ;  the  right  marginal  vein 
frequently  opens  into  the  right  atrium,  and  is  therefore  sometimes  regarded  as 
belonging  to  this  group;  (2)  the  smallest  cardiac  veins  {veins  of  Thehesius),  con- 
sisting of  a  number  of  minute  veins  wdiich  arise  in  the  muscular  wall  of  the  heart; 
the  majority  open  into  the  atria,  but  a  few  end  in  the  ventricles. 


THE  VEINS  OF  THE  HEAD  AND  NECK. 

The  veins  of  the  head  and  neck  may  be  subdivided  into  three  groups:  (1)  The 
veins  of  the  exterior  of  the  head  and  face.  (2)  The  veins  of  the  neck.  (3)  The  diploic 
veins,  the  veins  of  the  brain,  and  the  venous  sinuses  of  the  dura  mater. 


732 


ANGIOLOGY 


The  Veins  of  the  Exterior  of  the  Head  and  Face  (Fig.  G32). 
The  veins  of  the  exterior  of  the  head  and  face  are: 


Frontal. 
Supraorbital. 
Angular. 
Anterior  Facial. 


Occipital. 


Superficial  Temporal 
Internal  Maxillary. 
Posterior  Facial. 
Posterior  Auricular. 


Frmfal 

Coiinininicating  branch 
uith  ophthalmic  vein 

Angular 


Lingval 
PhatyngeaZ 


Superior  thyroid 


Fig.  632. — Veins  of  the  head  and  neck. 


The  frontal  vein  (y.  frontalis)  hegins  on  the  forehead  in  a  venous  plexus  which 
communicates  with  the  frontal  branches  of  the  superficial  temporal  vein.  The 
veins  converge  to  form  a  single  trunk,  which  runs  downward  near  the  middle  line 
of  the  forehead  parallel  with  the  vein  of  the  opposite  side.  The  two  veins  are  joined, 
at  the  root  of  the  nose,  by  a  transverse  branch,  called  the  nasal  arch,  which  receives 
some  small  veins  from  the  dorsum  of  the  nose.  At  the  root  of  the  nose  the  veins 
diverge,  and,  each  at  the  medial  angle  of  the  orbit,  joins  the  supraorbital  vein,  to 


THE  VEINS  OF  THE  EXTERIOR  OF  THE  HEAD  AND  FACE         733 

form  the  angular  vein.  Occasionally  the  frontal  veins  join  to  form  a  single  trunk, 
Avhich  bifurcates  at  the  root  of  the  nose  into  the  two  angular  veins. 

The  supraorbital  vein  {i\  siiprctorhitaJis)  begins  on  the  forehead  where  it  com- 
municates with  the  frontal  branch  of  the  superficial  temporal  vein.  It  runs  down- 
ward superficial  to  the  Frontalis  muscle,  and  joins  the  frontal  vein  at  the  medial 
angle  of  the  orbit  to  form  the  angular  vein.  Prexious  to  its  junction  with  the  frontal 
vein,  it  sends  through  the  supraorbital  notch  into  the  orbit  a  branch  which  com- 
municates with  the  ophthalmic  vein;  as  this  vessel  passes  through  the  notch,  it 
receives  the  frontal  diploic  vein  through  a  foramen  at  the  bottom  of  the  notch. 

The  angular  vein  (v.  angularis)  formed  by  the  junction  of  the  frontal  and  supra- 
orbital veins,  runs  obliquely  downward,  on  the  side  of  the  root  of  the  nose,  to  the 
level  of  the  lower  margin  of  the  orbit,  where  it  becomes  the  anterior  facial  vein. 
It  receives  the  veins  of  the  ala  nasi,  and  communicates  with  the  superior  ophthalmic 
vein  through  the  nasofrontal  vein,  thus  establishing  an  important  anastomosis 
between  the  anterior  facial  vein  and  the  cavernous  sinus. 

The  anterior  facial  vein  {t.  facialis  anterior;  facial  rein)  commences  at  the  side 
of  the  root  of  the  nose,  and  is  a  direct  continuation  of  the  angular  vein.  It  lies 
behind  the  external  maxillary  (facial)  artery  and  follows  a  less  tortuous  course. 
It  runs  obliquely  dow'nward  and  backward,  beneath  the  zygomaticus  and  zygo- 
matic head  of  the  Quadratus  labii  superioris,  descends  along  the  anterior  border 
and  then  on  the  superficial  surface  of  the  Masseter,  crosses  over  the  body  of  the 
mandible,  and  passes  obliquely  backward,  beneath  the  Platysma  and  cervical 
fascia,  superficial  to  the  submaxillary  gland,  the  Digastricus  and  Stylohyoideus. 
It  unites  with  the  posterior  facial  vein  to  form  the  common  facial  vein,  which 
crosses  the  external  carotid  artery  and  enters  the  internal  jugular  xeva.  at  a  vari- 
able point  below  the  hyoid  bone.  From  near  its  termination  a  communicating 
branch  often  runs  down  the  anterior  border  of  the  Sternocleidomastoideus  to  join 
the  lower  part  of  the  anterior  jugular  vein. 

Tributaries. — The  anterior  facial  vein  receives  a  branch  of  considerable  size, 
the  deep  facial  vein,  from  the  pter3^goid  venous  plexus.  It  is  also  joined  by  the 
superior  and  inferior  palpebral,  the  superior  and  inferior  labial,  the  buccinator 
and  the  masseteric  veins.  Below  the  mandible  it  receives  the  submental,  palatine, 
and  submaxillary  veins,  and,  generally,  the  vena  comitans  of  the  hypoglossal  nerve. 

Applied  Anatomy. — There  are  some  points  about  the  anterior  facial  vein  which  render  it  of 
great  importance  in  surgery.  It  is  not  so  flaccid  as  are  most  superficial  veins,  and,  in  consequence 
of  this,  remains  more  patent  when  divided.  It  has,  moreover,  no  valves.  It  communicates 
freely  with  the  intracranial  circulation,  not  only  at  its  commencement  by  the  angular  and  supra- 
orbital veins  which  commimicate  with  the  ophthalmic  vein,  a  tributary  of  the  cavernous  sinus, 
but  also  by  the  deep  facial  vein,  which  communicates  through  the  pterygoid  plexus  with  the 
cavernous  sinus  by  branches  which  pass  through  the  foramen  ovale  and  foramen  lacerum  (see 
p.  746).  These  facts  have  an  important  bearing  upon  the  surgery  of  some  diseases;  any  phlegmo- 
nous inflammation  of  the  face  following  a  poisoned  wound  is  hable  to  set  up  thrombosis  in  the 
anterior  facial  vein,  and  detached  portions  of  the  clot  may  give  rise  to  purulent  foci  in  other 
parts  of  the  body.  On  account  of  its  communications  with  the  cerebral  sinuses,  these  thrombi 
are  apt  to  extend  upward  into  them,  and  so  induce  a  fatal  issue;  this  has  been  known  to  follow  in 
cases  of  ordinary  carbuncle  of  the  face.  The  position  of  the  vein  should  always  be  borne  in  mind 
when  incisions  are  made  for  the  rehef  of  suppm-ation  about  the  mandible. 

The  superficial  temporal  vein  {v.  temporalis  siiperficialis)  begins  on  the  side  and 
vertex  of  the  skull  in  a  plexus  which  communicates  with  the  frontal  and  supra- 
orbital veins,  with  the  corresponding  vein  of  the  opposite  side,  and  with  the  pos- 
terior auricular  and  occipital  veins.  From  this  net-work  frontal  and  parietal  branches 
arise,  and  unite  above  the  zygomatic  arch  to  form  the  trunk  of  the  vein,  which  is 
joined  in  this  situation  by  the  middle  temporal  vein,  from  the  substance  of  the  Tem- 
poralis. It  then  crosses  the  posterior  root  of  the  zygomatic  arch,  enters  the  sub- 
stance of  the  parotid  gland,  and  unites  with  the  internal  maxillary  vein  to  form  the 
posterior  facial  vein. 


734  ANGIOLOGY 

Tributaries.— The  superficial  temporal  vein  receives  in  its  course  some  parotid 
veins,  articular  veins  from  the  temporomandibular  joint,  anterior  auricular  veins 
from  the  auricula,  and  the  transverse  facial  from  the  side  of  the  face.  The  middle 
temporal  vein  receives  the  orbital  vein,  which  is  formed  by  some  lateral  palpebral 
branches,  and  passes  backward  between  the  layers  of  the  temporal  fascia  to  join 
the  superficial  temporal  vein. 

The  pterygoid  plexus  (plexus  pterygoideus)  is  of  considerable  size,  and  is  situated 
between  the  Temporalis  and  Pterygoideus  externus,  and  partly  between  the  two 
Pterygoidei.  It  receives  tributaries  corresponding  with  the  branches  of  the  internal 
maxillary  artery.  Thus  it  receives  the  sphenopalatine,  the  middle  meningeal,  the 
deep  temporal,  the  pterygoid,  masseteric,  buccinator,  alveolar,  and  some  palatine 
veins,  and  a  branch  which  communicates  with  the  ophthalmic  vein  through  the 
inferior  orbital  fissure.  This  plexus  communicates  freely  with  the  anterior  facial 
vein;  it  also  communicates  with  the  cavernous  sinus,  by  branches  through  the 
foramen  Vesalii,  foramen  ovale,  and  foramen  lacerum. 

The  internal  maxillary  vein  {v.  maxillaris  interna)  is  a  short  trunk  which  accom- 
panies the  first  part  of  the  internal  maxillary  artery.  It  is  formed  by  a  confluence 
of  the  veins  of  the  pterygoid  plexus,  and  passes  backward  between  the  spheno- 
mandibular  ligament  and  the  neck  of  the  mandible,  and  unites  with  the  temporal 
vein  to  form  the  posterior  facial  vein. 

The  posterior  facial  vein  («.  facialis  posterior;  temporomaxillary  vein),  formed 
by  the  union  of  the  superficial  temporal  and  internal  maxillary  veins,  descends  in 
the  substance  of  the  parotid  gland,  superficial  to  the  external  carotid  artery  but 
beneath  the  facial  nerve,  between  the  ramus  of  the  mandible  and  the  Sternocleido- 
mastoideus  muscle.  It  divides  into  two  branches,  an  anterior,  which  passes  forward 
and  unites  with  the  anterior  facial  vein  to  form  the  common  facial  vein  and  a  pos- 
terior, which  is  joined  by  the  posterior  auricular  vein  and  becomes  the  external 
jugular  vein. 

The  posterior  auricular  vein  (y.  auricularis  posterior)  begins  upon  the  side  of 
the  head,  in  a  plexus  which  communicates  with  the  tributaries  of  the  occipital, 
and  superficial  temporal  veins.  It  descends  behind  the  auricula,  and  joins  the 
posterior  division  of  the  posterior  facial  vein  to  form  the  external  jugular.  It 
receive  the  stylomastoid  vein,  and  some  tributaries  from  the  cranial  surface  of  the 
auricula. 

The  occipital  vein  iv.  occipitalis)  begins  in  a  plexus  at  the  back  part  of  the  vertex 
of  the  skull.  From  the  plexus  emerges  a  single  vessel,  which  pierces  the  cranial 
attachment  of  the  Trapezius  and,  dipping  into  the  suboccipital  triangle,  joins  the 
deep  cervical  and  vertebral  veins.  Occasionally  it  follows  the  course  of  the  occipital 
artery  and  ends  in  the  internal  jugular;  in  other  instances,  it  joins  the  posterior 
auricular  and  through  it  opens  into  the  external  jugular.  The  parietal  emissary 
vein  connects  it  with  the  superior  sagittal  sinus;  and  as  it  passes  across  the  mastoid 
portion  of  the  temporal  bone,  it  receives  the  mastoid  emissary  vein  which  connects 
it  with  the  transverse  sinus.    The  occipital  diploic  vein  sometimes  joins  it. 

The  Veins  of  the  Neck  (Fig.  633). 

The  veins  of  the  neck,  which  return  the  blood  from  the  head  and  face,  are : 

External  Jugular.  Anterior  Jugular. 

Posterior  External  Jugular.  Internal  Jugular. 

Vertebral. 

The  external  jugular  vein  («.  jugularis  externa)  receives  the  greater  part  of  the 
blood  from  the  exterior  of  the  cranium  and  the  deep  parts  of  the  face,  being  formed 
by  the  junction  of  the  posterior  division  of  the  posterior  facial  with  the  posterior 


THE  VEINS  OF  THE  XECK 


735 


auricular  vein.  It  commences  in  the  substance  of  the  parotid  gland,  on  a  level 
with  the  angle  of  the  mandible,  and  runs  perpendicularly  down  the  neck,  in  the 
direction  of  a  line  drawn  from  the  angle  of  the  mandil)le  to  the  middle  of  the  clavicle 
at  the  posterior  border  of  the  Sternocleidomastoideus.  In  its  course  it  crosses 
the  Sternocleidomastoideus  obliquely,  and  in  the  subclavian  triangle  perforates 
the  deep  fascia,  and  ends  in  the  subclavian  vein,  lateral  to  or  in  front  of  the  Scalenus 
anterior.  It  is  separated  from  the  Sternocleidomastoideus  by  the  investing  layer 
of  the  deep  cer^'ical  fascia,  and  is  covered  by  the  Platysma,  the  superficial  fascia, 
and  the  integument;  it  crosses  the  cutaneous  cervical  nerve,  and  its  upper  half 
runs  parallel  with  the  great  auricular  nerve.     The  external  jugular  vein  varies  in 


Exl.  carotid 


Subclavian  vein 
Fig.  633. — The  veins  of  the  neck,  viewed  from  in  front.     (After  Spalteholz.) 

size,  bearing  an  inverse  proportion  to  the  other  veins  of  the  neck,  it  is  occasionally 
double.  It  is  provided  with  two  pairs  of  valves,  the  lower  pair  being  placed  at 
its  entrance  into  the  subclavian  vein,  the  upper  in  most  cases  about  4  cm.  above  the 
clavicle.  The  portion  of  vein  between  the  two  sets  of  valves  is  often  dilated,  and 
is  termed  the  sinus.  These  valves  do  not  prevent  the  regurgitation  of  the  blood, 
or  the  passage  of  injection  from  below  upward. 

Tributaries. — ^This  vein  receives  the  occipital  occasionally,  the  posterior  external 
jugular,  and,  near  its  termination,  the  transverse  cervical,  transverse  scapular,  and 
anterior  jugular  veins;  in  the  substance  of  the  parotid,  a  large  branch  of  commu- 
nication from  the  internal  jugular  joins  it. 


736  AXGIOLOGY 

Applied  Anatomy. — Venesection  used  formerly  to  be  performed  on  the  external  jugular  vein, 
but  is  now  probably  never  resorted  to.  The  anatomical  point  to  be  remembered  in  performing 
this  operation  is  to  cut  across  the  fibres  of  the  Platysma  in  opening  the  vein,  so  that  by  their 
contraction  they  will  expose  the  orifice  in  the  vein  and  so  allow  the  flow  of  blood. 

The  posterior  external  jugular  vein  («.  jngvlaris  jxjsterior)  begins  in  the  occipital 
region  and  returns  the  blood  from  the  skin  and  superficial  muscles  in  the  upper  and 
back  part  of  the  neck,  lying  between  the  Splenius  and  Trapezius.  It  runs  down 
the  back  part  of  the  neck,  and  opens  into  the  external  jugular  vein  just  below  the 
middle  of  its  course. 

The  anterior  jugular  vein  (v.  jngvlaris  anterior)  begins  near  the  hyoid  bone  by 
the  confluence  of  several  superficial  veins  from  the  submaxillary  region.  It  descends 
between  the  median  line  and  the  anterior  border  of  the  Sternocleidomastoideus, 
and,  at  the  lower  part  of  the  neck,  passes  beneath  that  muscle  to  open  into  the  ter- 
mination of  the  external  jugular,  or,  in  some  instances,  into  the  subclavian  vein 
(Figs.  632,  633).  It  varies  considerably  in  size,  bearing  usually  an  inverse  propor- 
tion to  the  external  jugular;  most  frequently  there  are  two  anterior  jugulars,  a 
right  and  left;  but  sometimes  only  one.  Its  tributaries  are  some  laryngeal  veins, 
and  occasionally  a  small  thyroid  vein.  Just  above  the  sternum  the  two  anterior 
jugular  veins  communicate  by  a  transverse  trunk,  the  venous  jugular  arch,  which 
receive  tributaries  from  the  inferior  thyroid  veins;  each  also  communicates  with  the 
internal  jugular.    There  are  no  valves  in  this  vein. 

The  internal  jugular  vein  {v.  jugularis  interna)  collects  the  blood  from  the  brain, 
from  the  superficial  parts  of  the  face,  and  from  the  neck.  It  is  directly  continuous 
with  the  transverse  sinus,  and  begins  in  the  posterior  compartment  of  the  jugular 
foramen,  at  the  base  of  the  skull.  At  its  origin  it  is  somewhat  dilated,  and  this 
dilatation  is  called  the  superior  bulb.  It  runs  down  the  side  of  the  neck  in  a  vertical 
direction,  lying  at  first  lateral  to  the  internal  carotid  artery,  and  then  lateral 
to  the  common  carotid,  and  at  the  root  of  the  neck  unites  with  the  subclavian  vein 
to  form  the  innominate  vein;  a  little  above  its  termination  is  a  second  dilatation, 
the  inferior  bulb.  Above,  it  lies  upon  the  Rectus  capitis  lateralis,  behind  the  internal 
carotid  artery  and  the  nerves  passing  through  the  jugular  foramen;  lower  down, 
the  vein  and  artery  lie  upon  the  same  plane,  the  glossopharyngeal  and  hypoglossal 
nerves  passing  forward  between  them;  the  vagus  descends  between  and  behind 
the  vein  and  the  artery  in  the  same  sheath,  and  the  accessory  riins  obliquely 
backward,  superficial  or  deep  to  the  vein.  At  the  root  of  the  neck  the  right  internal 
jugular  vein  is  placed  at  a  little  distance  from  the  common  carotid  arterj-,  and 
crosses  the  first  part  of  the  subclavian  artery,  while  the  left  internal  jugular  vein 
usually  overlaps  the  common  carotid  artery.  The  left  vein  is  generally  smaller 
than  the  right,  and  each  contains  a  pair  of  valves,  which  are  placed  about  2.5  cm. 
above  the  termination  of  the  vessel. 

Tributaries. — This  vein  receives  in  its  course  the  inferior  petrosal  sinus,  the 
common  facial,  lingual,  pharyngeal,  superior  and  middle  thyroid  veins,  and  some- 
times the  occipital.  The  thoracic  duct  on  the  left  side  and  the  right  lymphatic 
duct  on  the  right  side  open  into  the  angle  of  union  of  the  internal  jugular  and 
subclavian  veins. 

The  Inferior  Petrosal  Sinus  (sinus  petrosus  inferior)  leaves  the  skull  through  the 
anterior  part  of  the  jugular  foramen,  and  joins  the  superior  bulb  of  the  internal 
jugular  vein. 

The  Lingual  Veins  (vv.  linguales)  begin  on  the  dorsum,  sides,  and  under  surface 
of  the  tongue,  and,  passing  backward  along  the  course  of  the  lingual  artery,  end 
in  the  internal  jugular  vein.  The  vena  comitans  of  the  hypoglassal  nerve  (ranine 
vein),  a  branch  of  considerable  size,  begins  below  the  tip  of  the  tongue,  and  may 
join  the  lingual;  generally,  however,  it  passes  backw^ard  on  the  Hyoglossus,  and 
joins  the  common  facial. 


THE  VEINS  OF  THE  NECK 


737 


The  Pharyngeal  Veins  {in\  pliari/iigcac)  begin  in  the  pharyngeal  plexus  on  the  outer 
surface  of  the  pharynx,  and,  after  receiving  some  posterior  meningeal  veins  and  the 
vein  of  the  pterygoid  canal,  end  in  the  internal  jugular.  They  occasionally  open 
into  the  facial,  lingual,  or  superior  thyroid  \'ein. 

The  Superior  Thyroid  Vein  (c.  fin/reuidea  siqjerioris)  (Fig.  ()34)  begins  in  the  sub- 
stance and  on  the  surface  of  the  thyroid  gland,  by  tributaries  corresponding  with 
the  branches  of  the  superior  thyroid  artery,  and  ends  in  the  upper  part  of  the 
internal  jugular  vein.    It  receives  the  superior  laryngeal  and  cricothyroid  veins. 

The  Middle  Thyroid  Vein  (Fig.  ()34)  collects  the  blood  from  the  lower  part  of  the 
thyroid  gland,  and  after  being  joined  by  some  veins  from  the  larynx  and  trachea, 
ends  in  the  lower  part  of  the  internal  jugular  vein. 

The  common  facial  and  occipital  veins  have  been  described. 


External  carotid  artery 
Superior  thyroid  artery 


Vagus  nerve ^j 


Superior  thyroid  vein 


—  Middle  thyroid  vein 


Fig.  634. — The  veins  of  the  thyroid  gland. 


Applied  Anatomy. — The  internal  jugular  vein  requires  ligature  in  cases  of  septic  thrombosis 
of  the  transverse  sinus,  in  order  to  prevent  septic  emboli  being  carried  into  the  general  circula- 
tion. This  operation  has  been  performed  in  many  cases,  with  the  most  satisfactory  results. 
The  cases  are  generaUy  those  of  chronic  disease  of  the  middle  ear,  with  discharge  of  pus  which 
perhaps  has  existed  for  many  years.  The  patient  is  seized  with  acute  septic  inflammation,  spread- 
ing to  the  mastoid  cells,  and  setting  up  septic  thrombosis  of  the  transverse  sinus  and  extending 
downward  into  the  internal  jugular  vein.  Such  cases  are  always  extremely  grave,  for  there  is 
danger  of  portions  of  the  septic  clot  being  detached  and  causing  septic  embohsm  in  the  lungs, 
the  portions  of  clot  having  passed  through  the  right  side  of  the  heart.  If  the  condition  be  sus- 
pected, the  diseased  bone  should  be  removed  at  once  from  the  mastoid  process.  The  sinus  is 
then  investigated,  and  if  it  be  found  thrombosed,  the  surgeon  should  proceed  to  ligature  the 
internal  jugular  vein,  by  an  incision  along  the  anterior  border  of  the  Sternocleidomastoideus, 
the  centre  of  which  is  on  a  level  with  the  greater  cornu  of  the  hyoid  bone.  The  vein  should  be 
hgatured  in  two  places  and  divided  between.  After  the  vessel  has  been  seciu-ed  and  divided, 
the  transverse  sinus  is  to  be  thoroughly  cleared  out,  and,  by  removing  the  ligature  from  the 
upper  end  of  the  divided  vein,  all  septic  clots  removed  by  syringing  from  the  sinus  through  the 
vein.  If  hemorrhage  occur  from  the  distal  end  of  the  sinus,  it  can  be  arrested  by  careful  plugging 
with  antiseptic  gauze. 
47 


738  AXGIOLOGY 

The  internal  jugular  vein  is  also  surgically  important,  because  it  is  surrounded  by  a  large 
number  of  deep  cervical  lymph  glands;  and  when  these  are  enlarged  in  tuberculous  or  malignant 
disease,  they  are  apt  to  become  adherent  to  the  vessel,  rendering  their  removal  difficult  and  often 
dangerous.  The  proper  course  to  pm-sue  in  these  cases  is  to  ligatm-e  the  vessel  above  and  below 
the  glandular  mass,  and  resect  the  included  portion  together  with  the  glands. 

Cardiac  pulsation  is  often  demonstrable  in  the  internal  jugular  vein  at  the  root  of  the  neck. 
There  are  no  valves  in  the  innominate  veins  or  superior  vena  cava;  in  consequence,  the  systole 
of  the  right  atrium  causes  a  wave  to  pass  up  these  vessels,  and  when  the  conditions  are  favorable 
this  wave  appears  as  a  somewhat  feeble  flicker  over  the  internal  jugular  vein  at  the  root  of  the 
neck,  quite  distinct  from,  and  just  preceding,  the  more  forcible  impulse  transmitted  from  the 
underlying  common  carotid  artery  and  due  to  the  ventricular  systole.  This  atrial  systolic  venous 
impulse  is  much  increased  in  conditions  in  which  the  right  atrium  is  abnormally  distended  with 
blood  or  is  hjTsertrophied,  as  is  often  the  case  in  disease  of  the  bicuspid  valve.  In  Stokes-Adams 
disease  (p.  614)  it  is  this  pulsation  which  gives  evidence  of  the  fact  that  the  atria  are  beating 
faster — often  two  or  three  times  faster — than  the  ventricles. 

The  vertebral  vein  {a.  Tertebralis)  is  formed  in  the  suboccipital  triangle,  from 
numerous  small  tributaries  which  spring  from  the  internal  vertebral  venous  plexuses 
and  issue  from  the  vertebral  canal  above  the  posterior  arch  of  the  atlas.  They 
unite  with  small  veins  from  the  deep  muscles  at  the  upper  part  of  the  back  of 
the  neck,  and  form  a  vessel  which  enters  the  foramen  in  the  transverse  process 
of  the  atlas,  and  descends,  forming  a  dense  plexus  around  the  vertebral  artery, 
in  the  canal  formed  by  the  foramina  transversaria  of  the  cervical  vertebrae.  This 
plexus  ends  in  a  single  trunk,  which  emerges  from  the  foramen  transversarium  of 
the  sixth  cervical  vertebra,  and  opens  at  the  root  of  the  neck  into  the  back  part 
of  the  innominate  vein  near  its  origin,  its  mouth  being  guarded  by  a  pair  of  valves. 
On  the  right  side,  it  crosses  the  first  part  of  the  subclavian  artery. 

Tributaries. — The  vertebral  vein  communicates  with  the  transverse  sinus  by 
a  vein  which  passes  through  the  condyloid  canal,  when  that  canal  exists.  It 
receives  branches  from  the  occipital  vein  and  from  the  prevertebral  muscles,  from 
the  internal  and  external  vertebral  venous  plexuses,  from  the  anterior  vertebral 
and  the  deep  cervical  veins;  close  to  its  termination  it  is  sometimes  joined  by  the 
first  intercostal  vein. 

The  Anterior  Vertebral  Vein  commences  in  a  plexus  around  the  transverse  pro- 
cesses of  the  upper  cervical  vertebrae,  descends  in  company  wdth  the  ascending 
cervical  artery  between  the  Scalenus  anterior  and  Longus  capitis  muscles,  and 
opens  into  the  terminal  part  of  the  vertebral  vein. 

The  Deep  Cervical  Vein  (v.  cervicalis  iirofunda;  posterior  vertebral  or  yosterior 
deep  cervical  vein)  accompanies  its  artery  between  the  Semispinales  capitis  and 
colli.  It  begins  in  the  suboccipital  region  by  communicating  branches  from  the 
occipital  vein  and  by  small  veins  from  the  deep  muscles  at  the  back  of  the  neck. 
It  receives  tributaries  from  the  plexuses  around  the  spinous  processes  of  the  cer- 
vical vertebrse,  and  terminates  in  the  lower  part  of  the  vertebral  vein. 

The  Diploic  Veins  (Venae  Diploicae)  (Fig.  635). 

The  diploic  veins  occupy  channels  in  the  diploe  of  the  cranial  bones.  They  are 
large  and  exhibit  at  irregular  intervals  pouch-like  dilatations;  their  walls  are  thin, 
and  formed  of  endothelium  resting  upon  a  layer  of  elastic  tissue. 

So  long  as  the  cranial  bones  are  separable  from  one  another,  these  veins  are 
confined  to  the  particular  bones;  but  when  the  sutures  are  obliterated,  they  unite 
with  each  other,  and  increase  in  size.  They  communicate  with  the  meningeal 
veins  and  the  sinuses  of  the  dura  mater,  and  with  the  veins  of  the  pericranium. 
They  consist  of  (1)  the  frontal,  which  opens  into  the  supraorbital  vein  and  the 
superior  sagittal  sinus;  (2)  the  anterior  temporal,  which  is  confined  chiefly  to  the 
frontal  bone,  and  opens  into  the  sphenoparietal  sinus  and  into  one  of  the  deep 
temporal  veins,  through  an  aperture  in  the  great  wing  of  the  sphenoid;  (3)  the 


THE  VEIXS  OF  THE  BRAiy  739 

posterior  temporal,  which  is  situated  in  the  parietal  hone,  and  ends  in  the  transverse 
sinus,  through  an  aperture  at  the  mastoid  ang'le  of  the  parietal  bone  or  through  the 
mastoid  foramen;  and  (4)  the  occipital,  the  largest  of  the  four,  which  is  confined 
to  the  occipital  hone,  and  opens  either  externally  into  the  occipital  vein,  or  inter- 
nally into  the  transverse  sinus  or  into  the  confluence  of  the  sinuses  {torcular 
IlcrophUi). 


Fig.  635. — Veins  of  the  diploe  as  displayed  by  the  removal  of  the  outer  table  of  the  skull. 

The  Veins  of  the  Brain. 

The  veins  of  the  brain  possess  no  valves,  and  their  walls,  owing  to  the  absence 
of  muscular  tissue,  are  extremely  thin.  They  pierce  the  arachnoid  membrane  and 
the  inner  or  meningeal  layer  of  the  dura  mater,  and  open  into  the  cranial  venous 
sinuses.    They  may  be  divided  into  tw^o  sets,  cerebral  and  cerebellar. 

The  cerebral  veins  {vv.  cerebri)  are  divisible  into  external  and  internal  groups 
according  as  they  drain  the  outer  surfaces  or  the  inner  parts  of  the  hemispheres. 

The  external  veins  are  the  superior,  inferior,  and  middle  cerebral. 

The  Superior  Cerebral  Veins  {vv.  cerebri  swperiores) ,  eight  to  twelve  in  number, 
drain  the  superior,  lateral,  and  medial  surfaces  of  the  hemispheres,  and  are  mainly 
lodged  in  the  sulci  between  the  gyri,  but  some  run  across  the  gyri.  They  open  into 
the  superior  sagittal  sinus;  the  anterior  veins  runs  nearly  at  right  angles  to  the 
sinus ;  the  posterior  and  larger  veins  are  directed  obliquely  forward  and  open  into 
the  sinus  in  a  direction  more  or  less  opposed  to  the  current  of  the  blood  contained 
within  it. 

The  Middle  Cerebral  Vein  {v.  cerebri  media;  superficial  Sylvian  vein)  begins  on  the 
lateral  surface  of  the  hemisphere,  and,  running  along  the  lateral  cerebral  fissure, 
ends  in  the  cavernous  or  the  sphenoparietal  sinus.  It  is  connected  (a)  w-ith  the 
superior  sagittal  sinus  by  the  great  anastomotic  vein  of  Trolard,  which  opens  into  one 
of  the  superior  cerebral  veins;  (b)  wdth  the  transverse  sinus  by  the  posterior  anasto- 
motic vein  of  Labbe,  wdiich  courses  over  the  temporal  lobe. 

The  Inferior  Cerebral  Veins  (vv.  cerebri  inferiores),  of  small  size,  drain  the  under 
surfaces  of  the  hemispheres.  Those  on  the  orbital  surface  of  the  frontal  lobe  join 
the  superior  cerebral  veins,  and  through  these  open  into  the  superior  sagittal 
sinus;  those  of  the  temporal  lobe  anastomose  with  the  middle  cerebral  and  basal 
veins,  and  join  the  cavernous,  sphenoparietal,  and  superior  petrosal  sinuses. 


740  ANGIOLOGY 

The  basal  vein  is  formed  at  the  anterior  perforated  substance  by  the  union  of  {a) 
a  small  anterior  cerebral  vein  which  accompanies  the  anterior  cerebral  artery,  (6) 
the  deep  middle  cerebral  vein  {deep  Sylvian  vein),  which  receives  tributaries  from 
the  insula  and  neighboring  gyri,  and  runs  in  the  lower  part  of  the  lateral  cerebral 
fissure,  and  (c)  the  inferior  striate  veins,  which  leave  the  corpus  striatum  through 
the  anterior  perforated  substance.  The  basal  vein  passes  backward  around  the 
cerebral  peduncle,  and  ends  in  the  internal  cerebral  vein  (vein  of  Galen) ;  it  receives 
tributaries  from  the  interpeduncular  fossa,  the  inferior  horn  of  the  lateral  ventricle, 
the  hippocampal  gyrus,  and  the  mid-brain. 

The  Internal  Cerebral  Veins  {m.  cerebri  internae;  veins  of  Galen;  deep  cerebral 
veins)  drain  the  deep  parts  of  the  hemisphere  and  are  two  in  number;  each  is  formed 
near  the  interventricular  foramen  by  the  union  of  the  terminal  and  choroid  veins. 
They  ran  backward  parallel  with  one  another,  between  the  layers  of  the  tela 
chorioidea  of  the  third  ventricle,  and  beneath  the  splenium  of  the  corpus  callosum, 
where  they  unite  to  form  a  short  trunk,  the  great  cerebral  vein;  just  before  their 
union  each  receives  the  corresponding  basal  vein. 

The  terminal  vein  (v.  terminalis;  vena  corporis  striati)  commences  in  the  groove 
between  the  corpus  striatum  and  thalamus,  receives  numerous  veins  from  both 
of  these  parts,  and  unites  behind  the  crus  fornicis  with  the  choroid  vein,  to  form 
one  of  the  internal  cerebral  veins.  The  choroid  vein  runs  along  the  whole  length  of 
the  choroid  plexus,  and  receives  veins  from  the  hippocampus,  the  fornix,  and  the 
corpus  callosum. 

The  Great  Cerebral  Vein  (v.  cerebri  magna  [Galeni];  great  vein  of  Galen),  formed  by 
the  union  of  the  two  internal  cerebral  veins,  is  a  short  median  trunk  which  curves 
backward  and  upward  around  the  splenium  of  the  corpus  callosum  and  ends  in  the 
anterior  extremity  of  the  straight  sinus. 

The  cerebellar  veins  are  placed  on  the  surface  of  the  cerebellum,  and  are  dis- 
posed in  two  sets,  superior  and  inferior.  The  superior  cerebellar  veins  (vv.  cerebelli 
superiores)  pass  partly  forward  and  medialward,  across  the  superior  vermis,  to  end 
in  the  straight  sinus  and  the  internal  cerebral  veins,  partly  lateralward  to  the  trans- 
verse and  superior  petrosal  sinuses.  The  inferior  cerebellar  veins  {vv.  cerebelli  infe- 
riores)  of  large  size,  end  in  the  transverse,  superior  petrosal,  and  occipital  sinuses. 

The  Sinuses  of  the  Dura  Mater  (Sinus  Durae  Matris).    Ophthalmic  Veins  and 

Emissary  Veins. 

The  sinuses  of  the  dura  mater  are  venous  channels  which  drain  the  blood  from  the 
brain;  they  are  devoid  of  valves,  and  are  situated  between  the  two  layers  of  the 
dura  mater  and  lined  by  endothelium  continuous  with  that  which  lines  the  veins. 
They  may  be  divided  into  two  groups:  (1)  a  postero-superior,  at  the  upper  and  back 
part  of  the  skull,  and  (2)  an  antero-inferior,  at  the  base  of  the  skull. 

The  postero-superior  group  comprises  the 

Superior  Sagittal.  Straight. 

Inferior  Sagittal.  Two  Transverse. 

Occipital. 

The  superior  sagittal  sinus  {sinus  sagittalis  superior;  superior  longitudinal  sinvs) 
(Figs.  636,  637)  occupies  the  attached  or  convex  margin  of  the  falx  cerebri.  Com- 
mencing at  the  foramen  cecum,  through  which  it  receives  a  vein  from  the  nasal 
cavity,  it  runs  from  before  backward,  grooving  the  inner  surface  of  the  frontal, 
the  adjacent  margins  of  the  two  parietals,  and  the  superior  division  of  the  cruciate 
eminence' of  the  occipital;  near  the  internal  occipital  protuberance  it  deviates  to 
one  or  other  side  (usually  the  right),  and  is  continued  as  the  corresponding  trans- 
verse sinus.    It  is  triangular  in  section,  narrow  in  front,  and  gradually  increases  in 


THE  SINUSES  OF  THE  DURA  MATER 


741 


size  as  it  passes  backward.  Its  inner  surface  presents  the  openings  of  the  superior 
cerebral  veins,  which  run,  for  the  most  part,  obhquely  forward,  and  open  chiefly 
at  the  back  part  of  tlie  sinus,  their  orifices  being  concealed  by  fibrous  folds ;  numerous 
fibrous  bands  (chordae  IVillLstl)  extend  transversely  across  the  inferior  angle  of 
the  sinus;  and,  lastly,  small  openings  communicate  with  irregularly  shaped  venous 
spaces  {venous  lacunoe)  in  the  dura  mater  near  the  sinus.  There  are  usually  three 
lacuntie  on  either  side  of  the  sinus:  a  small  frontal,  a  large  parietal,  and  an  occipital, 
intermediate  in  size  between  the  other  two  (Sargent^-  Most  of  the  cerebral 
veins  from  the  outej  surface  of  the  hemisphere  open  into  these  lacunar,  and  numer- 
ous arachnoid  granulations  {Pacchionian  bodies)  project  into  them  from  below. 
The  superior  sagittal  sinus  receives  the  superior  cerebral  veins,  veins  from  the  diploe 
and  dura  mater,  and,  near  the  posterior  extremity  of  the  sagittal  suture,  veins  from 
the  pericranium,  which  pass  through  the  parietal  foramina. 


Dural  vein 


Superior  sagittal 
sinus 


|i;,.       Venous 
lacuna 


Venous  lacun 


Fig.  636. — Superior  sagittal  sinus  laid  open  after  removal  of  the  skull  cap.  The  chordae  Willisii  are  clearly  seen. 
The  venous  lacunae  are  also  well  shown;  from  two  of  them  probes  are  passed  into  the  superior  sagittal  sinus. 
(Poirier  and  Charpy.) 


Applied  Anatomy. — The  numerous  communications  which  take  place  between  this  sinus  and 
the  veins  of  the  nose,  scalp,  and  diploe,  cause  it  to  be  at  times  the  seat  of  infective  thrombosis 
from  suppurative  processes  in  these  parts. 

The  inferior  sagittal  sinus  (sinus  sagittalis  inferior;  inferior  longitudinal  sinus) 
(Fig.  637)  is  contained  in  the  posterior  half  or  two-thirds  of  the  free  margin  of  the 
falx  cerebri.  It  is  of  a  cylindrical  form,  increases  in  size  as  it  passes  backward,  and 
ends  in  the  straight  sinus.  It  receives  several  veins  from  the  falx  cerebri,  and 
occasionally  a  few  from  the  medial  surfaces  of  the  hemispheres. 

The  straight  sinus  (siiiiis  rectus;  tentorial  sinus)  (Figs.  637,  638)  is  situated  at 
the  line  of  junction  of  the  falx  cerebri  with  the  tentorium  cerebelli.    It  is  triangular 

1  Journal  of  Anatomy  and  Physiology,  vol.  xlv. 


742 


AXGIOLOGY 


in  section,  increases  in  size  as  it  proceeds  backward,  and  runs  downward  and  back- 
ward from  the  end  of  the  inferior  sagittal  sinus  to  the  transverse  sinus  of  the  oppo- 
site side  to  that  into  which  the  superior  sagittal  sinus  is  prolonged.  Its  terminal 
part  communicates  by  a  cross  branch  with  the  confluence  of  the  sinuses.  Besides 
the  inferior  sagittal  sinus,  it  receives  the  great  cerebral  vein  (great  vein  of  Galen) 
and  the  superior  cerebellar  veins.    A  few^  transverse  bands  cross  its  interior. 


Great  cerebral  vein 

Glossophai-yngeal  nerve 

Vagus  nerce 
Accessory  nerve 

Acoustic  nerve 

Facial  nerve 
Abducent  nerve    Trigeminal  nerve 
Fig.  637. — Dura  mater  and  its  processes  exposed  By  removing  part  of  the  right  half  of  the  skull,  and 


the  brain. 


The  transverse  sinuses  {sinus  transversns;  lateral  sinuses)  (Figs.  638,  639)  are 
of  large  size  and  begin  at  the  internal  occipital  protuberance;  one,  generally  the 
right,  being  the  direct  continuation  of  the  superior  sagittal  sinus,  the  other  of  the 
straight  sinus.  Each  transverse  sinus  passes  lateralward  and  forward,  describing 
a  slight  curve  with  its  convexity  upward,  to  the  base  of  the  petrous  portion  of 
the  temporal  bone,  and  lies,  in  this  part  of  its  course,  in  the  attached  margin  of 
the  tentorium  cerebelli;  it  then  leaves  the  tentorium  and  curves  downw^ard  and 
medialward  to  reach  the  jugular  foramen,  where  it  ends  in  the  internal  jugular 
vein.  In  its  course  it  rests  upon  the  squama  of  the  occipital,  the  mastoid  angle 
of  the  parietal,  the  mastoid  part  of  the  temporal,  and,  just  before  its  termination, 
the  jugular  process  of  the  occipital;  the  portion  which  occupies  the  groove  on  the 
mastoid  part  of  the  temporal  is  sometimes  termed  the  sigmoid  sinus.  The  trans- 
verse sinuses  are  frequently  of  unequal  size,  that  formed  by  the  superior  sagittal 
sinus  being  the  larger;  they  increase  in  size  as  they  proceed  from  behind  forward. 
On  transverse  section  the   horizontal  portion  exhibits  a  prismatic,  the  curved 


THE  SINUSES  OF  THE  DURA   MATER 


743 


portion  a  semicyliiidrical  I'orm.  They  receive  the  blood  from  the  superior  petrosal 
sinuses  at  the  base  of  the  petrous  portion  of  the  temporal  bone;  they  communicate 
with  the  veins  of  the  pericranium  by  means  of  the  mastoid  and  condyloid  emissary 
veins;  and  they  receive  some  of  the  inferior  cerebral  and  inferior  cerebellar  veins, 
and  some  veins  from  the  diploe.  The  petrosquamous  sinus,  when  present,  runs 
backward  along  the  junction  of  the  squama  and  petrous  portion  of  the  temporal, 
and  opens  into  the  transverse  sinus. 


optic  lien 
Biaphragma  sellcti 
Free  margin  of  tentorixtm 


Internal  carotid  artery 
Oculoinofor  nerve 

Attached  margin  of  tentorium 


Conjluence  of  the  hunises 
Fig.  63S. — Tentorium  cerebelli  from  above. 

The  occipital  sinus  {sinus  occipitalis)  (Fig.  639)  is  the  smallest  of  the  cranial 
sinuses.  It  is  situated  in  the  attached  margin  of  the  falx  cerebelli,  and  is  generally 
single,  but  occasionally  there  are  two.  It  commences  around  the  margin  of  the  for- 
amen magnum  by  several  small  venous  channels,  one  of  which  joins  the  terminal 
part  of  the  transverse  sinus;  it  communicates  with  the  posterior  internal  vertebral 
venous  plexuses  and  ends  in  the  confluence  of  the  sinuses. 

The  Confluence  of  the  Sinuses  {confluens  siniium;  torcidar  Herophili)  is  the  term 
applied  to  the  dilated  extremity  of  the  superior  sagittal  sinus.  It  is  of  irregular 
form,  and  is  lodged  on  one  side  (generally  the  right)  of  the  internal  occipital  pro- 
tuberance. From  it  the  transverse  sinus  of  the  same  side  is  derived.  It  receives 
also  the  blood  from  the  occipital  sinus,  and  is  connected  across  the  middle  hne  with 
the  commencement  of  the  transverse  sinus  of  the  opposite  side. 

The  antero-inferior  group  of  sinuses  comprises  the 

Two  Cavernous.  Two  Superior  Petrosal. 

Two  Intercavernous.  Tw^o  Inferior  Petrosal. 

Basilar  Plexus. 


744 


ANGIOLOGY 


The  cavernous  sinuses  (sim(s  cavernosus)  (Fig.  639)  are  so  named  because  they 
present  a  reticidated  structure,  due  to  their  being  traversed  by  numerous  inter- 
lacing fihiments.  They  are  of  irreguhir  form,  hirger  behind  than  in  front,  and  are 
placed  one  on  either  side  of  the  body  of  the  sphenoid  bone,  extending  from  the 
superior  orbital  fissure  to  the  apex  of  the  petrous  portion  of  the  temporal  bone. 
Each  opens  behind  into  the  petrosal  sinuses.  On  the  medial  wall  of  each  sinus  is 
the  internal  carotid  artery,  accompanied  by  filaments  of  the  carotid  plexus;  near 
the  artery  is  the  abducent  ner^'e;  on  the  lateral  wall  are  the  oculomotor  and  troch- 
lear nerves,  and  the  ophthalmic  and  maxillary  divisions  of  the  trigeminal  nerve 


Levator  p^ilpebrce 

Rectus  superior, 


Sup.  oph- 
ihalmic  vein 


Sphenoparietal 
s'nus 


End  of  straight  sinus 


Vertebral  artery 
Superior  sagittal  sinus 
Fig.  639. — The  sinuses  at  the  base  of  the  skull. 


(Fig.  640).  These  structures  are  separated  from  the  blood  flowing  along  the  sinus 
by  the  lining  membrane  of  the  sinus.  The  cavernous  sinus  receives  the  superior 
ophthalmic  vein  through  the  superior  orbital  fissure,  some  of  the  cerebral  veins, 
and  also  the  small  sphenoparietal  sinus,  which  courses  along  the  under  surface  of  the 
small  wing  of  the  sphenoid.  It  communicates  with  the  transverse  sinus  by  means 
of  the  superior  petrosal  sinus;  with  the  internal  jugular  vein  through  the  inferior 
petrosal  sinus  and  a  plexus  of  veins  on  the  internal  carotid  artery;  with  the  ptery- 
goid venous  plexus  through  the  foramen  Vesalii,  foramen  ovale,  and  foramen 
lacerum,  and  with  the  angular  vein  through  the  ophthalmic  vein.   The  two  sinuses 


THE  SINUSES  OF  THE  DURA  MATER 


745 


also  communicate  with  each  other  hy  means  of  the  anterior  and  posterior  inter- 
cavernous sinuses. 

Applied  Anatomy. — An  arteriovenous  communication  may  be  established  between  the  cavernous 
sinus  and  the  internal  carotid  artery,  giving  rise  to  a  pulsating  tumor  in  the  orbit.  Ilicse  com- 
munications may  be  the  result  of  injury,  such  as  a  bullet  wound,  a  stab,  or  a  blow,  or  fall  suffi- 
ciently severe  to  cause  a  fracture  of  the  base  of  the  skull  in  this  situation.  The  syini)toms  are 
sudden  noise  and  pain  in  the  head,  followed  by  exophthalmos,  swelling  and  congestion  of  the 
lids  and  conjunctiva?,    and  dovelo])ment  of 


Internal  carotid  artery 

Cavernous  shms 


Oculoinotor  nerve 
Trochlear  nerve 

Ophthalmic  nerve- 
Abducent  nerve 


Maxillary  nerve  — ife  W  '''■^ 


a  pulsating  tumor  at  the  margin  of  the  orbit, 
with  thrill  and  the  characteristic  bruit; 
accompanying  these  symptoms  there  may 
be  impairment  of  sight,  paralysis  of  the 
iris  and  orbital  muscles,  and  pain  of  varying 
intensity.  In  some  cases  the  opposite  orbit 
becomes  affected  by  the  passage  of  the 
arterial  blood  into  the  opposite  sinus  by 
means  of  the  intercavernous  sinuses;  or  the 
arterial  blood  may  find  its  way  through  the 
emissary  veins  (see  p.  747)  into  the  ptery- 
goid plexus,  and  thence  into  the  veins  of 
the  face.  Pulsating  tumors  of  the .  orbit 
may  also  be  due  to  traumatic  aneurism  of 
one  of  the  orbital  arteries,  and  symptoms 
resembhng  those  of  pulsating  tumor  may  be 
produced    by   pressure  on    the   ophthalmic 

vein,  as  it  enters  the  sinus,  by  an  aneurism  of  the  internal  carotid  artery.    Ligature  of  the  internal 
or  common  carotid  artery  has  been  performed  in  these  cases  with  considerable  success. 

Of  recent  years  more  attention  has  been  paid  to  thrombosis  of  the  cavernous  sinus  than  formerly, 
and  it  is  now  well  established  that  caries  in  the  upper  parts  of  the  nasal  cavities  and  suppuration 
in  certain  of  the  accessory  sinuses  of  the  nose  are  frequently  responsible  for  septic  thrombosis 
of  the  cavernous  sinuses,  in  exactly  the  same  way  as  transverse  sinus  thrombosis  is  due  to  septic 
disease  in  the  mastoid  process.  Many  deaths  from  meningitis,  hitherto  unaccounted  for,  are  in 
reality  due  to  the  spread  of  an  infection  from  an  ethmoidal  or  sphenoidal  air  cell  to  the  cavernous 
sinus,  and  thence  to  the  meninges.  It  is  obvious,  therefore,  that  no  case  of  chronic  nasal  suppura- 
tion should  be  left  untieated 


Fig.  640. — Oblique  section  through  tlie  cavernous  sinus. 


Cavernous  _^ 
sinus 

Inferior 
ophthalmic 


Fig.  641. — Veins  of  orbit.     (Poirier  and  Charpy.) 


The  ophthalmic  veins  (Fig.  641),  two  in  number,  superior  and  inferior,  are 
devoid  of  valves. 

The  Superior  Ophthalmic  Vein  (v.  ophthalmica  suiJerior)  begins  at  the  inner  angle 
of  the  orbit  in  a  vein  named  the  nasofrontal  which  communicates  anteriorly  with  the 
angular  vein;  it  pursues  the  same  course  as  the  ophthalmic  artery,  and  receives 


746  ANGIOLOGY 

tributaries  corresponding  to  the  branches  of  that  vessel.  Forming  a  short  single 
trunk,  it  passes  between  the  two  heads  of  the  Rectus  lateralis  and  through  the  medial 
part  of  the  superior  orbital  fissure,  and  ends  in  the  cavernous  sinus. 

The  Inferior  Ophthalmic  Vein  («.  ophihalmica  inferior)  begins  in  a  venous  net-work 
at  the  forepart  of  the  floor  and  medial  wall  of  the  orbit;  it  receives  some  veins  from 
the  Rectus  inferior,  Obliquus  inferior,  lacrimal  sac  and  eyelids,  runs  backward  in 
the  lower  part  of  the  orbit  and  divides  into  two  branches.  One  of  these  passes 
through  the  inferior  orbital  fissure  and  joins  the  pterygoid  venous  plexus,  while 
the  other  enters  the  cranium  through  the  superior  orbital  fissure  and  ends  in  the 
cavernous  sinus,  either  by  a  separate  opening,  or  more  frequently  in  common  with 
the  superior  ophthalmic  vein. 

The  intercavernous  sinuses  {sini  intercavernosi)  (Fig.  639)  are  two  in  number,  an 
anterior  and  a  posterior,  and  connect  the  two  cavernous  sinuses  across  the  middle 
line.  The  anterior  passes  in  front  of  the  hypophysis  cerebri,  the  posterior  behind  it, 
and  they  form  with  the  cavernous  sinuses  a  venous  circle  (circular  sinus)  around  the 
hypophysis.  The  anterior  one  is  usually  the  larger  of  the  two,  and  one  or  other  is 
occasionally  absent. 

The  superior  petrosal  sinus  (sinus  petrosus  superior)  (Fig.  639)  small  and  narrow, 
connects  the  cavernous  with  the  transverse  sinus.  It  runs  lateralward  and  back- 
ward, from  the  posterior  end  of  the  cavernous  sinus,  over  the  trigeminal  nerve, 
and  lies  in  the  attached  margin  of  the  tentorium  cerebelli  and  in  the  superior 
petrosal  sulcus  of  the  temporal  bone;  it  joins  the  transverse  sinus  where  the  latter 
curves  downward  on  the  inner  surface  of  the  mastoid  part  of  the  temporal.  It 
receives  some  cerebellar  and  inferior  cerebral  veins,  and  veins  from  the  tympanic 
cavity. 

The  inferior  petrosal  sinus  (siiius  petrosus  inferior)  (Fig.  639)  is  situated  in  the 
inferior  petrosal  sulcus  formed  by  the  junction  of  the  petrous  part  of  the  temporal 
with  the  basilar  part  of  the  occipital.  It  begins  in  the  postero-inferior  part  of  the 
cavernous  sinus,  and,  passing  through  the  anterior  part  of  the  jugular  foramen, 
ends  in  the  superior  bulb  of  the  internal  jugular  vein.  The  inferior  petrosal  sinus 
receives  the  internal  auditory  veins  and  also  veins  from  the  medulla  oblongata, 
pons,  and  under  surface  of  the  cerebellum. 

The  exact  relation  of  the  parts  to  one  another  in  the  jugular  foramen  is  as  follows: 
the  inferior  petrosal  sinus  lies  medially  and  anteriorly  with  the  meningeal  branch 
of  the  ascending  pharyngeal  artery,  and  is  directed  obliquely  downward  and  back- 
ward; the  transverse  sinus  is  situated  at  the  lateral  and  back  part  of  the  foramen 
with  a  meningeal  branch  of  the  occipital  artery,  and  between  the  two  sinuses  are 
the  glossopharyngeal,  vagus,  and  accessory  nerves.  These  three  sets  of  structures 
are  divided  from  each  other  by  two  processes  of  fibrous  tissue.  The  junction  of  the 
inferior  petrosal  sinus  with  the  internal  jugular  vein  takes  place  on  the  lateral 
aspect  of  the  nerves. 

The  basilar  plexus  (plexus  hasilaris;  transverse  or  basilar  sinus)  (Fig.  640)  con- 
sists of  several  interlacing  venous  channels  between  the  layers  of  the  dura  mater 
over  the  basilar  part  of  the  occipital  bone,  and  serves  to  connect  the  two  inferior 
petrosal  sinuses.    It  communicates  with  the  anterior  vertebral  venous  plexus. 

Emissary  Veins  (emissaria). — The  emissary  veins  pass  through  apertures  in  the 
cranial  wall  and  establish  communication  between  the  sinuses  inside  the  skull  and 
the  veins  external  to  it.  Some  are  always  present,  others  only  occasionally  so. 
The  principal  emissary  veins  are  the  following:  (1)  A  mastoid  emissary  vein, 
usually  present,  runs  through  the  mastoid  foramen  and  unites  the  transverse  sinus 
with  the  posterior  auricular  or  with  the  occipital  vein.  (2)  A  parietal  emissary 
vein  passes  through  the  parietal  foramen  and  connects  the  superior  sagittal  sinus 
with  the  veins  of  the  scalp.  (3)  A  net-work  of  minute  veins  (rete  canalis  hypoglossi) 
traverses  the  hypoglossal  canal  and  joins  the  transverse  sinus  with  the  vertebral 


THE  SUPERFICIAL  VEINS  OF  THE  UPPER  EXTREMITY  747 

vein  and  deep  veins  of  the  neck.  (4)  An  inconstant  condyloid  emissary  vein  passes 
through  the  condyloid  canal  and  connects  the  transverse  sinus  with  the  deep  veins 
of  the  neck.  (5)  A  net-work  of  ^'eins  (rete  Joraminis  qvalis)  unites  the  cavernous 
sinus  with  the  i)terygoid  plexus  through  the  foramen  ovale.  (6)  Two  or  three  small 
veins  run  through  the  foramen  lacerum  and  connect  the  cavernous  sinus  with  the 
pterygoid  plexus.  (7)  The  emissary  vein  of  the  foramen  of  Vesalius  connects  the 
same  parts.  (S)  An  internal  carotid  })lexus  of  veins  traverses  the  carotid  canal  and 
unites  the  cavernous  sinus  with  the  internal  jugular  vein.  (9)  A  vein  is  trans- 
mitted through  the  foramen  caecum  and  connects  the  superior  sagittal  sinus  with 
the  veins  of  the  nasal  cavity. 

Applied  Anatomy. — These  emissary  veins  together  with  the  other  communications  between 
the  intra-  and  extracranial  circulation  are  of  great  importance  in  surgery.  Inflammatory  processes 
commencing  on  the  outside  of  the  skull  may  travel  inward  through  them,  and  lead  to  osteo- 
phlebitis of  the  diploe  and  inflammation  of  the  membranes  of  the  brain.  To  this  in  former  days 
was  to  be  attributed  one  of  the  principal  dangers  of  wounds  of  the  scalp. 

By  means  of  these  emissary  veins  blood  may  be  abstracted  from  the  intracranial  circulation — 
e.  g.,  leeches  applied  behind  the  ear  drain  blood  almost  directly  from  the  transverse  sinus",  through 
the  mastoid  vein.  Again,  epistaxis  in  children  will  frequently  relieve  severe  headache,  the  blood 
which  flows  from  the  nose  being  partly  derived  from  the  superior  sagittal  sinus  by  means  of  the 
vein  passing  through  the  foramen  caecum. 

THE    VEINS    OF    THE   UPPER   EXTREMITY    AND    THORAX. 

The  veins  of  the  upper  extremity  are  divided  into  two  sets,  superficial  and  deep ; 
the  two  sets  anastomose  frequently  with  each  other.  The  superficial  veins  are 
placed  immediately  beneath  the  integument  between  the  two  layers  of  superficial 
fascia.  The  deep  veins  accompany  the  arteries,  and  constitute  the  venae  comi- 
tantes  of  those  vessels.  Both  sets  are  provided  with  valves,  which  are  more 
numerous  in  the  deep  than  in  the  superficial  veins. 

The  Superficial  Veins  of  the  Upper  Extremity. 

The  superficial  veins  of  the  upper  extremity  are  the  digital,  metacarpal,  cephalic, 
basilic,  median. 

Digital  Veins. — The  dorsal  digital  veins  pass  along  the  sides  of  the  fingers  and 
are  joined  to  one  another  by  oblique  communicating  branches.  Those  from  the 
adjacent  sides  of  the  fingers  unite  to  form  three  dorsal  metacarpal  veins  (Fig. 
642),  which  end  in  a  dorsal  venous  net-work  opposite  the  middle  of  the  meta- 
carpus. The  radial  part  of  the  net-work  is  joined  hy  the  dorsal  digital  vein  from  the 
radial  side  of  the  index  finger  and  by  the  dorsal  digital  veins  of  the  thumb,  and 
is  prolonged  upward  as  the  cephalic  vein.  The  ulnar  part  of  the  net-work  receives 
the  dorsal  digital  vein  of  the  ulnar  side  of  the  little  finger  and  is  continued  upward 
as  the  basilic  vein.  A  communicating  branch  frequently  connects  the  dorsal 
venous  network  with  the  cephalic  vein  about  the  middle  of  the  forearm. 

The  volar  digital  veins  on  each  finger  are  connected  to  the  dorsal  digital  veins 
by  oblique  intercapitular  veins.  They  drain  into  a  venous  plexus  which  is  situated 
over  the  thenar  and  hypothenar  eminences  and  across  the  front  of  the  wrist. 

The  cephalic  vein  (Fig.  643)  begins  in  the  radial  part  of  the  dorsal  venous  net- 
work and  winds  upward  around  the  radial  border  of  the  forearm,  receiving  tribu- 
taries from  both  surfaces.  Below  the  front  of  the  elbow  it  gives  off  the  vena  mediana 
cubiti  {median  basilic  win),  which  receives  a  communicating  branch  from  the  deep 
veins  of  the  forearm  and  passes  across  to  join  the  basilic  vein.  The  cephalic  vein 
then  ascends  in  front  of  the  elbow  in  the  groove  between  the  Brachioradialis  and 
the  Biceps  brachii.  It  crosses  superficial  to  the  musculocutaneous  nerve  and  ascends 
in  the  groove  along  the  lateral  border  of  the  Biceps  brachii.    In  the  upper  third 


748 


ANGIOLOGY 


of  the  arm  it  passes  between  the  Pectorahs  major  and  Deltoideus,  where  it  is  accom- 
panied hx  the  deltoid  branch  of  the  thoracoacromial  artery.  It  pierces  the  coraco- 
clavicular  fascia  and,  crossing  the  axillary  artery,  ends  in  the  axillary  vein  just 
below  the  clavicle.  Sometimes  it  communicates  with  the  external  jugular  vein  by 
a  branch  which  ascends  in  front  of  the  clavicle. 


Dorsal  venous 
neiworJ: 


Fig.  612. — The  veins  on  the  dorsum  of  the  hand.     (Bourgery.) 

The  accessory  cephalic  vein  (v.  cephalica  accessoria)  arises  either  from  a  small 
tributory  plexus  on  the  back  of  the  forearm  or  from  the  ulnar  side  of  the  dorsal 
venous  net-work;  it  joins  the  cephalic  below  the  elbow.  In  some  cases  the  accessory 
cephalic  springs  from  the  cephalic  above  the  wrist  and  joins  it  again  higher  up.  A 
large  oblique  branch  frequently  connects  the  basilic  and  cephalic  veins  on  the  back 
of  the  forearm. 

The  basilic  vein  (v.  basilica)  (Fig.  643)  hegiiis  in  the  ulnar  part  of  the  dorsal 
venous  network.  It  runs  up  the  posterior  surface  of  the  ulnar  side  of  the  forearm 
and  inclines  forward  to  the  anterior  surface  below  the  elbow,  where  it  is  joined  by 
the  vena  mediana  cubiti.  It  ascends  obliquely  in  the  groove  between  the  Biceps 
brachii  and  Pronator  teres  and  crosses  the  brachial  artery,  from  which  it  is  separated 


THE  SUPERFICIAL  VEINS  OF  THE  UPPER  EXTREMITY 


749 


by  the  lacertus  fihrosus;  filaments  of   the  medial   antibrachial  cutaneous  nerve 


pass  both  in  front  of  and  l)ehind 
ward  along  the  medial  border  of 
a  little  below  the  middle  of  the  arm, 
and,  ascending  on  the  medial  side 
of  the  brachial  artery  to  the  lower 
border  of  the  Teres  major,  is  con- 
tinued onward  as  the  axillary  vein. 
The  median  antibrachial  vein 
{v.  mediana  antibrachii)  drains  the 
venous  plexus  on  the  volar  surface 
of  the  hand.  It  ascends  on  the 
ulnar  side  of  the  front  of  the  fore- 
arm and  ends  in  the  basilic  vein  or 
in  the  vena  mediana  cubiti;  in  a 
small  proportion  of  cases  it  divides 
into  two  branches,  one  of  which 
joins  the  basilic,  the  other  the 
cephalic,   below  the  elbow. 

Applied  Anatomy. — Venesection  is  gen- 
erally performed  at  the  bend  of  the 
elbow,  and  as  a  matter  of  practice  the 
largest  vein  in  this  situation  is  com- 
monly selected.  This  is  usually  the 
vena  mediana  cubiti  {median  basilic), 
and  there  are  anatomical  advantages 
and  disadvantages  in  selecting  this  vein. 
The  advantages  are,  that  in  addition  to 
its  being  the  largest  vessel,  and  therefore 
yielding  a  greater  supply  of  blood,  it  is 
the  least  movable  and  can  be  easily 
steadied  on  the  lacertus  fibrosus  (bicipital 
fascia),  on  which  it  rests.  The  disad- 
vantages are,  that  it  is  in  close  relation- 
ship with  the  brachial  artery,  separated 
only  by  the  lacertus  fibrosus;  and  for- 
merly, when  venesection  was  frequently 
practised,  arteriovenous  aneurism  was 
no  uncommon  result  of  this  practice. 

Intravenous  infusion  of  normal  saline 
solution  is  very  frequently  required  in 
modern  surgery  for  all  conditions  of 
severe  shock  and  after  profuse  hemor- 
rhages, the  older  method  of  transfusion 
of  blood  having  quite  sunk  into  oblivion. 
The  patient's  arm  is  surrounded  by  a 
tight  bandage  so  as  to  impede  the 
venous  return,  and  a  small  incision  is 
made  over  the  largest  vein  visible  in 
front  of  the  elbow;  a  double  ligature  is 
now  passed  around  the  vein,  and  the 
lower  one  is  tied;  the  vein  is  then  opened 
and  a  cannula  connected  with  a  funnel 
by  tubing  and  filled  with  hot  saUne 
solution  is  inserted  The  bandage  is 
next  removed  from  the  arm,  and  two, 
three,  or  more  pints  of  fluid  are  allowed 
to  flow  into  the  vein;  when  a  sufficient 
quantity  has  gone  in,  the  upper  ligature 
around  the  vein  is  tied  and  a  stitch  put 
in  the  skin  wound. 


this   portion  of   the  vein.     It   then   runs   up- 
the   Biceps  brachii,  perforates  the  deep  fascia 


Cephalic  vein 


Basilic  vein 


Vena  mediana 
cubiti 


Basilic  vein 


Medial  anti- 
brachial cutane- 
ous nerve 
Median  anti- 
brachial vein 


Fig.  643. — The  superficial  veins  of  the  upper  extremity. 


750  AXGIOLOGY 

The  Deep  Veins  of  the  Upper  Extremity. 

The  deep  veins  follow  the  course  of  the  arteries,  forming  their  venae  comitantes. 
They  are  generall}'  arranged  in  pairs,  and  are  situated  one  on  either  side  of  the 
corresponding  artery,  and  connected  at  intervals  by  short  transverse  branches. 

Deep  Veins  of  the  Hand. — The  superficial  and  deep  volar  arterial  arches  are 
each  accompanied  by  a  pair  of  venae  comitantes  which  constitute  respectively 
the  superficial  and  deep  volar  venous  arches,  and  receive  the  veins  corresponding 
to  the  branches  of  the  arterial  arches;  thus  the  common  volar  digital  veins,  formed  by 
the  union  of  the  proper  volar  digital  veins,  open  into  the  superficial,  and  the  volar 
metacarpal  veins  into  the  deep  volar  venous  arches.  The  dorsal  metacarpal  veins 
receive  perforating  branches  from  the  volar  metacarpal  veins  and  end  in  the  rarlial 
veins  and  in  the  superficial  veins  on  the  dorsum  of  the  wrist. 

The  deep  veins  of  the  forearm  are  the  venae  comitantes  of  the  radial  and  ulnar 
veins  and  constitute  respectively  the  upward  continuations  of  the  deep  and  super- 
ficial volar  venous  arches;  they  unite  in  front  of  the  elbow  to  form  the  brachial 
veins.  The  radial  veins  are  smaller  than  the  ulnar  and  receive  the  dorsal  meta- 
carpal veins.  The  ulnar  veins  receive  tributaries  from  the  deep  volar  venous 
arches  and  communicate  wdth  the  superficial  veins  at  the  wrist;  near  the  elbow 
they  receive  the  volar  and  dorsal  interosseous  veins  and  send  a  large  communicating 
branch  (profunda  vein)  to  the  vena  mediana  cubiti. 

The  brachial  veins  {vv.  hrachiales)  are  placed  one  on  either  side  of  the  brachial 
artery,  receiving  tributaries  corresponding  with  the  branches  given  off  from  that 
vessel;  near  the  lower  margin  of  the  Subscapularis,  they  join  the  axillary  vein;  the 
medial  one  frequently  joins  the  basilic  vein. 

These  deep  veins  have  numerous  anastomoses,  not  only  with  each  other,  but 
also  with  the  superficial  veins. 

The  axillary  vein  (v.  axillaris)  begins  at  the  lower  border  of  the  Teres  major, 
as  the  continuation  of  the  basilic  vein,  increases  in  size  as  it  ascends,  and  ends  at  the 
outer  border  of  the  first  rib  as  the  subclavian  vein.  Near  the  lower  border  of 
the  Subscapularis  it  receives  the  brachial  veins  and,  close  to  its  termination,  the 
cephalic  vein;  its  other  tributaries  correspond  with  the  branches  of  the  axillary 
artery.  It  lies  on  the  medial  side  of  the  artery,  w^hich  it  partly  overlaps;  between 
the  two  vessels  are  the  medial  cord  of  the  brachial  plexus,  the  median,  the  ulnar, 
and  the  medial  anterior  thoracic  nerves.  It  is  provided  with  a  pair  of  valves  oppo- 
site the  lower  border  of  the  Subscapularis;  valves  are  also  found  at  the  ends  of  the 
cephalic  and  subscapular  A^eins. 

Applied  Anatomy. — Since  the  axillary  vein  is  superficial  to  and  larger  than  the  axillary  artery, 
which  it  overlaps,  it  is  more  hable  to  be  wounded  than  the  artery  in  the  operation  of  extirpation 
of  the  axillary  glands,  especially  as  these  glands,  when  diseased,  are  apt  to  become  adherent  to 
it.  When  it  is  wounded,  tTiere  is  always  a  danger  of  air  being  drawn  into  it,  and  death  resulting. 
To  avoid  wounding  the  axillary  vein  in  the  extirpation  of  glands  from  the  axilla,  it  is  advisable  to 
expose  the  vein  as  soon  as  possible;  no  sharp  cutting  instruments  should  be  used  after  the  axiUary 
cavity  has  been  freely  exposed;  and  care  should  be  taken  to  use  no  undue  force  in  isolating  the 
glands  (see  p.  781).  Should  the  vein  be  so  imbedded  in  a  maUgnant  deposit  that  the  latter  cannot 
be  removed  without  taking  away  a  part  of  the  vein,  this  must  be  done  after  the  vessel  has  been 
ligatured  above  and  below. 

The  subclavian  vein  (v.  subclavia),  the  continuation  of  the  axillary,  extends 
from  the  outer  border  of  the  first  rib  to  the  sternal  end  of  the  clavicle,  where  it 
unites  wdth  the  internal  jugular  to  form  the  innominate  vein.  It  is  in  relation,  in 
front,  with  the  clavicle  and  Subclavius;  hehind  and  above,  with  the  subclavian 
artery,  from  which  it  is  separated  medially  by  the  Scalenus  anterior  and  the  phrenic 
nerve.  Beloic,  it  rests  in  a  depression  on  the  first  rib  and  upon  the  pleura.  It  is 
usually  provided  with  a  pair  of  valves,  which  are  situated  about  2.5  cm.  from  its 
termination. 


THE  VEINS  OF  THE  THORAX  751 

The  subclavian  vein  occasionally  rises  in  the  neck  to  a  level  with  the  third  part 
of  the  subclavian  artery,  and  occasionally  j^asses  with  this  vessel  behind  the  Scalenus 
anterior. 

Tributaries. — This  vein  receives  the  external  ju^mlar  vein,  sometimes  the  anterior 
jugular  vein,  and  occasionally  a  small  branch,  which  ascends  in  front  of  the  clavicle, 
from  the  cejihalic.  At  its  angle  of  junction  with  the  internal  jugular,  the  left 
subcla^•ian  \eu\  receives  the  thoracic  duct,  and  the  right  subclavian  \'ein  the  right 
lymphatic  duct. 

The  Veins  of  the  Thorax  (Fig.  644) 

The  innominate  veins  i^vv.  anonymae;  bmchiucephalic  veins)  are  tw^o  large  trunks, 
placed  one  on  either  side  of  the  root  of  the  neck,  and  formed  by  the  union  of  the 
internal  jugular  and  subclavian  veins  of  the  corresponding  side;  they  are  devoid 
of  valves. 

The  Right  Innominate  Vein  (v.  anonyma  dextra)  is  a  short  vessel,  about  2.5  cm. 
in  length,  which  begins  behind  the  sternal  end  of  the  clavicle,  and,  passing  almost 
vertically  downward,  joins  w-ith  the  left  innominate  vein  just  below  the  cartilage 
of  the  first  rib,  close  to  the  right  border  of  the  sternum,  to  form  the  superior  vena 
cava.  It  lies  in  front  and  to  the  right  of  the  innominate  artery;  on  its  right  side 
are  the  phrenic  nerve  and  the  pleura,  w^hich  are  interposed  between  it  and  the  apex 
of  the  lung.  This  vein,  at  its  commencemnt,  receives  the  right  vertebral  vein;  and, 
lower  down,  the  right  internal  mammary  and  right  inferior  thyroid  veins,  and  some- 
times the  vein  from  the  first  intercostal  space. 

The  Left  Innominate  Vein  {v.  anonyma  sinistra),  about  6  cm.  in  length,  begins 
behind  the  sternal  end  of  the  clavicle  and  runs  obliquely  downw-ard  and  to  the 
right  behind  the  upper  half  of  the  manubrium  sterni  to  the  sternal  end  of  the  first 
right  costal  cartilage,  where  it  unites  with  the  right  innominate  vein  to  form  the 
superior  vena  cava.  It  is  separated  from  the  manubrium  sterni  by  the  Sterno- 
hyoideus  and  Sternothyreoideus,  the  thymus  or  its  remains,  and  some  loose  areolar 
tissue.  Behind  it  are  the  three  large  arteries,  innominate,  left  common  carotid,  and 
left  subclavian,  arising  from  the  aortic  arch,  together  wdth  the  vagus  and  phrenic 
nerves.  The  left  innominate  vein  may  occupy  a  higher  level,  crossing  the  jugular 
notch  and  lying  directly  in  front  of  the  trachea. 

Tributaries. — Its  tributaries  are  the  left  vertebral,  left  internal  mammary,  left 
inferior  thyroid,  and  the  left  highest  intercostal  veins,  and  occasionally  some 
thymic  and  pericardiac  veins. 

Peculiarities. — Sometimes  the  innominate  veins  open  separately  into  the  right  atrium;  in 
such  cases  the  right  vein  takes  the  ordinary  course  of  the  superior  vena  cava;  the  left  vein — 
left  superior  vena  cava,  as  it  is  then  termed — which  may  commimicate  by  a  small  branch  with 
the  right  one,  passes  in  front  of  the  root  of  the  left  lung,  and,  turning  to  the  back  of  the  heart, 
ends  in  the  right  atrium.  This  occasional  condition  in  the  adult  is  due  to  the  persistence  of  the 
early  fetal  condition,  and  is  the  normal  state  of  things  in  birds  and  some  mammaha. 

The  internal  mammary  veins  {vv.  mammariae  internae)  are  venae  comitantes 
to  the  lower  half  of  the  internal  mammary  artery,  and  receive  tributaries  corre- 
sponding to  the  branches  of  the  artery.  They  then  unite  to  form  a  single  trunk, 
which  runs  up  on  the  medial  side  of  the  artery  and  ends  in  the  corresponding 
innominate  vein.  The  superior  phrenic  vein,  i.  e.,  the  vein  accompanying  the  peri- 
cardiacophrenic artery,  usually  opens  into  the  internal  mammary  vein. 

The  inferior  thyroid  veins  (vv.  thyreoideae  inferiores)  two,  frequently  three  or 
four,  in  number,  arise  in  the  venous  plexus  on  the  thyroid  gland,  communicating 
with  the  middle  and  superior  thyroid  veins.  They  form  a  plexus  in  front  of  the 
trachea,  behind  the  Sternothyreoidei.  From  this  plexus,  a  left  vein  descends  and 
joins  the  left  innominate  trunk,  and  a  right  vein  passes  obliquely  downward  and  to 
the  right  across  the  innominate  artery  to  open  into  the  right  innominate  vein. 


752 


ANGIOLOGY 


just  at  its  junction  with  the  superior  vena  cava;  sometimes  the  right  and  left  veins 
open  by  a  common  trunk  in  the  latter  situation.    These  veins  receive  oesophageal, 


Anterior  jugxdar 


Superior  thyroid 


Middle 
thyroi 


External  jugular 


Internal 
mammal  1/ 


Suprarenal 


Suprar 


Fig.  644. — The  venae  cavae  and  azygos  veins,  with  their  tributaries. 

tracheal,  and  inferior  laryngeal    veins,  and    are   provided  with  valves  at  their 
terminations  in  the  innominate  veins. 


THE  VEINS  OF  THE  THORAX  ■  753 

The  highest  intercostal  vein  (r.  intcrcosiaUs  suyrema;  superior  intercostal  veins) 
(right  and  left)  drain  the  blood  from  the  upper  three  or  four  intercostal  spaces. 
The  right  vein  {v.  intcrcostaJis  suprema  dextra)  passes  downward  and  opens  into  the 
vena  azy^os;  the  left  vein  (r.  intercostalis  suprema  sinistra)  runs  across  the  arch 
of  the  aorta  and  the  origins  of  the  left  subclavian  and  left  common  carotid 
arteries  antl  opens  into  the  left  innominate  xem.  It  usually  receives  the  left 
bronchial  vein,  and  sometimes  the  left  superior  phrenic  vein,  and  communicates 
below  witli  the  accessory  hemiazygos  vein. 

The  superior  vena  cava  (('.  cava  superior)  drains  the  l)lood  from  the  upper  half 
of  the  body.  It  measures  about  7  cm.  in  length,  and  is  formed  by  the  junction  of 
the  two  innominate  veins.  It  begins  immediately  below  the  cartilage  of  the  right 
first  rib  close  to  the  sternum,  and,  descending  vertically  behind  the  first  and  second 
intercostal  spaces,  ends  in  the  upper  part  of  the  right  atrium  opposite  the  upper 
border  of  the  third  right  costal  cartilage :  the  lower  half  of  the  vessel  is  within  the 
pericardium.  In  its  course  it  describes  a  slight  curve,  the  convexity  of  which  is 
to  the  right  side. 

Relations. — In  front  are  the  anterior  margins  of  the  right  kmg  and  pleura  with  the  pericardium 
intervening  below;  these  separate  it  from  the  first  and  second  intercostal  spaces  and  from  the 
second  and  third  right  costal  cartilages;  behind  it  are  the  root  of  the  right  lung  and  the  right 
vagus  nerve.  On  its  right  side  are  the  phrenic  nerve  and  right  pleura;  on  its  left  side,  the  com- 
mencement of  the  innominate  artery  and  the  ascending  aorta,  the  latter  overlapping  it.  Just 
before  it  pierces  the  pericardium,  it  receives  the  azygos  vein  and  several  small  veins  from  the 
pericardium  and  other  contents  of  the  mediastinal  cavity.  The  portion  contained  within  the 
pericardium  is  covered,  in  front  and  laterally,  by  the  serous  layer  of  the  membrane.  The  superior 
vena  cava  has  no  valves. 

The  azygos  vein  {v.  azygos;  vena  azygos  major)  begins  opposite  the  first  or  second 
lumbar  vertebra,  by  a  branch,  the  ascending  lumbar  vein  (page  763) ;  sometimes  by 
a  branch  from  the  right  renal  vein,  or  from  the  inferior  vena  cava.  It  enters  the 
thorax  through  the  aortic  hiatus  in  the  Diaphragma,  and  passes  along  the  right  side 
of  the  vertebral  column  to  the  fourth  thoracic  vertebra,  where  it  arches  forward 
over  the  root  of  the  right  lung,  and  ends  in  the  superior  vena  cava,  just  before 
that  vessel  pierces  the  pericardium.  In  the  aortic  hia*lus,  it  lies  with  the  thoracic 
duct  on  the  right  side  of  the  aorta;  in  the  thorax  it  lies  upon  the  intercostal  arteries, 
on  the  right  side  of  the  aorta  and  thoracic  duct,  and  is  partly  covered  by  pleura. 

Tributaries. — It  receives  the  right  subcostal  and  intercostal  veins,  the  upper  three 
or  four  of  these  latter  opening  by  a  common  stem,  the  highest  superior  intercostal 
vein.  It  receives  the  hemiazygos  veins,  several  oesophageal,  mediastinal,  and  peri- 
cardial veins,  and,  near  its  termination,  the  right  bronchial  vein.  A  few  imperfect 
valves  are  found  in  the  azygos  vein;  but  its  tributaries  are  provided  with  complete 
valves. 

The  intercostal  veins  on  the  left  side,  below  the  upper  three  intercostal  spaces, 
usually  form  two  trunks,  named  the  hemiazygos  and  accessory  hemiazygos  veins. 

The  Hemiazygos  Veins  {v.  hemiazygos;  vena  azygos  minor  inferior)  begins  in  the 
left  ascending  lumbar  or  renal  vein,  Tt  enters  the  thorax,  through  the  left  crus 
of  the  Diaphragma,  and,  ascending  on  the  left  side  of  the  vertebral  column,  as  high 
as  the  ninth  thoracic  vertebra,  passes  across  the  column,  behind  the  aorta,  oeso- 
phagus, and  thoracic  duct,  to  end  in  the  azygos  vein.  It  receives  the  low^er  four 
or  five  intercostal  veins  and  the  subcostal  vein  of  the  left  side,  and  some  oesophageal 
and  mediastinal  veins. 

The  Accessory  Hemiazygos  Vein  {v.  hemiazygos  accessoria;  vena  azygos  minor  supe- 
rior) descends  on  the  left  side  of  the  vertebral  column,  and  varies  inversely  in  size 
with  the  highest  left  intercostal  vein.  It  receives  veins  from  the  three  or  four 
intercostal  spaces  between  the  highest  left  intercostal  vein  and  highest  tributary 
of  the  hemiazygos;  the  left  bronchial  vein  sometimes  opens  into  it.  It  either  crosses 
48 


754 


ANGIOLOGY 


the  body  of  the  eighth  thoracic  vertebra  to  join  the  azygos  vein  or  ends  in  the 
hemiazygos.  When  this  vein  is  small,  or  altogether  wanting,  the  left  highest 
intercostal  vein  may  extend  as  low  as  the  fifth  or  sixth  intercostal  space. 

Applied  Anatomy. — In  obstruction  of  the  superior  vena  cava,  the  azygos  and  hemiazygos 
veins  are  one  of  the  principal  means  by  which  the  venous  circulation  is  carried  on,  connecting 
as  thej^  do  the  superior  and  inferior  venae  cavae,  and  communicating  with  the  common  ihac  veins 
by  the  ascending  lumbar  veins  and  with  many  of  the  tributaries  of  the  inferior  vena  cava. 

Thrombosis  of  the  superior  vena  cava  is  oftenest  due  to  pressure  exerted  on  the  vessel  by  an 
aneurism  or  a  tumor;  it  may  also  occur  by  propagation  of  clotting  from  a  tributary  peripheral 
vein.  If  occlusion  of  the  vessel  take  place  slowly,  a  collateral  venous  circulation  may  be  estab- 
lished; the  patient  will  have  some  oedema  with  dilatation  and  congestion  of  the  veins  about  the 
head  and  neck,  and  may  also  suffer  from  attacks  of  dyspnoea  and  recurrent  pleural  effusion. 
In  most  cases,  however,  the  blockage  of  the  superior  cava  takes  place  rapidly,  and  is  rapidly  fatal . 

The  Bronchial  Veins  (vv.  bronchiales)  return  the  blood  from  the  larger  bronchi,  and 
from  the  structures  at  the  roots  of  the  lungs;  that  of  the  right  side  opens  into  the 
azygos  vein,  near  its  termination;  that  of  the  left  side,  into  the  highest  left  inter- 
costal or  the  accessory  hemiazygos  vein.  A  considerable  quantity  of  the  blood  which 
is  carried  to  the  lungs  through  the  bronchial  arteries  is  returned  to  the  left  side  of 
the  heart  through  the  pulmonary  veins. 


Posterior  external  plexuses 


Fig.  645. — Transverse  section  of  a  thoracic  vertebra, 
showing  the  vertebral  venous  plexuses. 


Fig.  6i6. — Median  sagittal  section  of  two  thoracic  verte- 
brae, showing  the  vertebral  venous  plexuses. 


The  Veins  of  the  Vertebral  Column  (Figs.  645,  646). 

The  veins  which  drain  the  blood  from  the  vertebral  column,  the  neighboring 
muscles,  and  the  meninges  of  the  medulla  spinalis  form  intricate  plexuses  extending 
along  the  entire  length  of  the  column;  these  plexuses  may  be  divided  into  two 
groups,  external  and  internal,  according  to  their  positions  inside  or  outside  the 
vertebral  canal.  The  plexuses  of  the  two  groups  anastomose  freely  with  each  other 
and  end  in  the  intervertebral  veins. 

The  external  vertebral  venous  plexuses  (plexus  venosi  vertehrales  externi;  extra- 
sinnal  veins)  best  marked  in  the  cervical  region,  consist  of  anterior  and  posterior 
plexuses  which  anastomose  freely  with  each  other.  The  anterior  external  plexuses 
lie  in  front  of  the  bodies  of  the  vertebrae,  communicate  with  the  basivertebral  and 
intervertebral  veins,  and  receive  tributaries  from  the  vertebral  bodies.  The  pos- 
terior external  plexuses  are  placed  partly  on  the  posterior  surfaces  of  the  vertebral 


THE  VEINS  OF   THE  LOWER   EXTREMITY,  ABDOMEN,  AND  PELVIS     755 

arches  and  tlieir  processes,  and  partly  between  the  deep  dorsal  muscles. '  They  are 
best  developed  in  the  cervical  region,  and  there  anastomose  with  the  vertebral, 
occipital,  and  deep  c(>r\ical  \('iiis. 

The  internal  vertebral  venous  plexuses  {plc.vu.s-  venosl  vertebrales  inierni;  intra- 
syinal  veins)  lie  within  the  vertebral  canal  between  the  dura  mater  and  the  verte- 
brae, and  receive  tributaries  from  the  bones  and  from  the  medulla  spinalis.  They 
form  a  closer  net-work  than  the  external  plexuses,  and,  running  mainly  in  a  vertical 
direction,  form  four  longitudinal  veins,  two  in  front  and  two  behind;  they  therefore 
may  be  divided  into  anterior  and  posterior  groups.  The  anterior  internal  plexuses 
consist  of  large  veins  which  lie  on  the  posterior  surfaces  of  the  vertebral  bodies  and 
intervertebral  fibrocartilages  on  either  side  of  the  posterior  longitudinal  ligament; 
under  cover  of  this  ligament  they  are  connected  by  transverse  branches  into  which 
the  basivertebral  veins  open.  The  posterior  internal  plexuses  are  placed,  one  on 
either  side  of  the  middle  line  in  front  of  the  vertebral  arches  and  ligamenta  flava, 
and  anastomose  by  veins  passing  through  those  ligaments  with  the  posterior  exter- 
nal plexuses.  The  anterior  and  posterior  plexuses  communicate  freely  with  one 
another  by  a  series  of  venous  rings  {retia  venosa  vertebrarum) ,  one  opposite  each 
vertebra.  Around  the  foramen  magnum  they  form  an  intricate  net-W'Ork  which 
opens  into  the  vertebral  veins  and  is  connected  above  with  the  occipital  sinus, 
the  basilar  plexus,  the  condyloid  emissary  vein,  and  the  rete  canalis  hypoglossi. 

The  basivertebral  veins  (vv.  basivertebrales)  emerge  from  the  foramina  on  the 
posterior  surfaces  of  the  vertebral  bodies.  They  are  contained  in  large,  tortuous 
channels  in  the  substance  of  the  bones,  similar  in  every  respect  to  those  found  in 
the  diploe  of  the  cranial  bones.  They  communicate  through  small  openings  on  the 
front  and  sides  of  the  bodies  of  the  vertebrae  with  the  anterior  external  vertebral 
plexuses,  and  converge  behind  to  the  principal  canal,  which  is  sometimes  double 
toward  its  posterior  part,  and  open  by  valved  orifices  into  the  transverse  branches 
which  unite  the  anterior  internal  vertebral  plexuses.  They  become  greatly  enlarged 
in  advanced  age. 

The  intervertebral  veins  (vv.  intervertebrales)  accompany  the  spinal  nerves 
through  the  intervertebral  foramina;  they  receive  the  veins  from  the  medulla 
spinalis,  drain  the  internal  and  external  vertebral  plexuses  and  end  in  the  vertebral, 
intercostal,  lumbar,  and  lateral  sacral  veins,  their  orifices  being  provided  wdth 
valves. 

The  veins  of  the  medulla  spinalis  {vv.  spinales;  veins  of  the  spinal  cord)  are 
situated  in  the  pia  mater  and  form  a  minute,  tortuous,  venous  plexus.  They 
emerge  chiefly  from  the  median  fissures  of  the  medulla  spinalis  and  are  largest  in 
the  lumbar  region.  In  this  plexus  there  are  (1)  two  median  longitudinal  veins, 
one  in  front  of  the  anterior  fissure,  and  the  other  behind  the  posterior  sulcus  of  the 
cord,  and  (2)  four  lateral  longitudinal  veins  which  run  behind  the  nerve  roots. 
They  end  in  the  intervertebral  veins.  Near  the  base  of  the  skull  they  unite,  and 
form  two  or  three  small  trunks,  which  communicate  with  the  vertebral  veins, 
and  then  end  in  the  inferior  cerebellar  veins,  or  in  the  inferior  petrosal  sinuses. 


THE  VEINS  OF  THE  LOWER  EXTREMITY,  ABDOMEN,  AND  PELVIS. 

The  veins  of  the  lower  extremity  are  subdivided,  like  those  of  the  upper,  into 
two  sets,  superficial  and  deep ;  the  superficial  veins  are  placed  beneath  the  integument 
between  the  tw^o  layers  of  superficial  fascia;  the  deep  veins  accompany  the  arteries. 
Both  sets  of  veins  are  provided  with  valves,  which  are  more  numerous  in  the  deep 
than  in  the  superficial  set.  Valves  are  also  more  numerous  in  the  veins  of  the 
lower  than  in  those  of  the  upper  limb. 


756 


AXGIOLOGY 


The  Superficial  Veins  of  the  Lower  Extremity. 

The  superficial  veins  of  the  lower  extremity  are  the  great  and  small  saphenous 

veins  and  their  tributaries. 

On  the  dorsum  of  the  foot  the  dorsal  digital  veins  receive,  in  the  clefts  between  the 

toes,  the  intercapitular  veins  from  the  plantar  cutaneous  venous  arch  and  join  to 

form  short  common  digital  veins  which  unite  across 
the  distal  ends  of  the  metatarsal  bones  in  a  dorsal 
venous  arch.  Proximal  to  this  arch  is  an  irregular 
venous  net-work  which  receives  tributariesf  rom  the 
i%l  deep  veins  and  is  joined  at  the  sides  of  the  foot  by 

a  medial  and  a  lateral  marginal  vein,  formed  mainly 
by  the  union  of  branches  from  the  superficial 
parts  of  the  sole  of  the  foot. 

On  the  sole  of  the  foot  the  superficial  veins  form 
a  plantar  cutaneous  venous  arch  which  extends 
across  the  roots  of  the  toes  and  opens  at  the  sides 
of  the  foot  into  the  medial  and  lateral  marginal 
veins.  Proximal  to  this  arch  is  a  plantar  cutaneous 
venous  net-work  which  is  especially  dense  in  the  fat 
beneath  the  heel;  this  net-work  communicates  with 
the  cutaneous  venous  arch  and  with  the  deep 
veins,  but  is  chiefly  drained  into  the  medial  and 
lateral  marginal  veins. 

The  great  saphenous  vein  {v.  saphena  magna; 
internal  or  long  sa'phenons  win)  (Fig.  647),  the 
longest  vein  in  the  body,  begins  in  the  medial 
marginal  vein  of  the  dorsum  of  the  foot  and  ends 
in  the  femoral  vein  about  3  cm.  below  the  inguinal 
ligament.  It  ascends  in  front  of  the  tibial  malle- 
olus and  along  the  medial  side  of  the  leg  in  rela- 
tion with  the  saphenous  nerve.  It  runs  upward 
behind  the  medial  condyles  of  the  tibia  and  femur 
and  along  the  medial  side  of  the  thigh  and,  passing 
through  the  fossa  ovalis,  ends  in  the  femoral  vein. 
8^   I  'fM^'\  Tributaries. — At  the  ankle  it  receives  branches 

from  the  sole  of  the  foot  through  the  medial 
marginal  vein;  in  the  leg  it  anastomoses  freely 
with  the  small  saphenous  vein,  communicates  with 
the  anterior  and  posterior  tibial  veins  and  receives 
many  cutaneous  veins;  in  the  thigh  it  communi- 
cates with  the  femoral  vein  and  receives  numerous 
tributaries;  those  from  the  medial  and  posterior 
parts  of  the  thigh  frequently  unite  to  form  a 
large  accessory  saphenous  vein  which  joins  the 
main  vein  at  a  variable  level.  Near  the  fossa 
ovalis  (Fig.  648)  it  is  joined  by  the  superficial  epi- 
gastric, superficial  iliac  circumflex,  and  superficial 
external  pudendal  veins.  A  vein,  named  the 
thoracoepigastric,  runs  along  the  lateral  aspect  of 
the  trunk  between  the  superficial  epigastric  vein 
below^  and  the  lateral  thoracic  vein  above  and 
establishes  an  important  communication  betw^een 

647.-The^  greot^^sapheoous  vein  and       ^j^^  femoral    and    axilkxy   VciuS. 


J 


m 


Fig. 


THE  SUPERFICIAL  VEIXS  OF  THE  LOWER  EXTREMITY 


/ot 


The  valves  in  the  great  saphenous  vein  \ary  from  ten  to  twenty  in  number; 
the.y  are  more  numerous  in  the  leg-  than  in  the  thigh. 

The  small  saphenous  vein  (/'.  sajjlwim  parra;  external  or  short  saphenous  vein) 
(Fig.  649)  hcyln.s-  heliind  the  hiteral  malk'ohis  as  a  eontinuation  of  the  lateral 
marginal  vein;  it  first  ascends  along  the  lateral  margin  of  the  tendocalcaneus, 
and  then  crosses  it  to  reach  the  middle  of  the  back  of  the  leg.  Running  directly 
upward,  it  perforates  the  deep  fascia  in  the  lower  part  of  the  popliteal  fossa,  and 
ends  in  the  popliteal  vein,  between  the  heads  of  the  Gastrocnemius.  It  communi- 
cates with  the  deep  veins  on  the  dorsum  of  the  foot,  and  receives  numerous  large 
tributaries  from  the  back  of  the  leg.  Before  it  pierces  the  deep  fascia,  it  gives  off 
a  branch  which  runs  upward  and  forward  to  join  the  great  saphenous  vein.  The 
small  saphenous  \'ein  possesses  from  nine  to  tweh'e  valves,  one  of  which  is  always 
found  near  its  termination  in  the  popliteal  vein.  In  the  lower  third  of  the  leg  the 
small  saphenous  vein  is  in  close  relation  with  the  sural  nerve,  in  the  upper  two- 
thirds  wath  the  medial  sural  cutaneous  nerve. 


Fig.  648. — The  great  saphenous  vein  and  its  tributaries  at  the  fossa  ovalis. 


Applied  Anatomy. — A  varicose  condition  of  the  saphenous  veins  is  more  frequently  met  with 
than  in  the  other  veins  of  the  body,  except  perhaps  the  spermatic  and  hemorrhoidal  veins.  The 
main  cause  of  this  is  the  high  blood  pressure,  determined  chiefly  by  the  erect  position,  and  the 
length  of  the  column  of  blood,  which  has  to  be  propelled  in  an  uphill  direction.  In  normal  vessels 
there  is  only  just  sufficient  force  to  perform  this  task;  and  in  those  cases  where  there  is  diminished 
resistance  of  the  walls  of  the  veins,  these  vessels  are  liable  to  dilate  and  a  varicose  condition  is 
set  up.  This  diminished  resistance  may  be  due  to  heredity,  the  vein  walls  being  congenitally 
weak,  or  it  may  follow  inflammatory  conditions  of  the  vessels.  Increased  blood  pressure  in  the 
veins,  caused  by  any  obstacle  to  the  return  of  the  venous  blood,  such  as  the  pressm-e  of  a  tumor, 


'58 


ANGIOLOGY 


or  the  gravid  uterus,  or  tight  gartering,  may  also  produce  varix.  In  the  normal  condition  of  the 
veins,  the  valves  in  their  interior  break  up  the  column  of  blood  into  a  number  of  smaller  columns, 
and  so  to  a  considerable  extent  mitigate  the  ill  effects  of  the  erect  position;  but  when  the  dilata- 
tion of  the  veins  has  reached  a  certain  limit,  the  valves  become  incapable  of  supporting  the  over- 
lying column  of  blood,  and  the  pressure  is  increased,  tending  to  em- 
phasize also  the  varicose  condition.  Both  the  saphenous  veins  in 
the  leg  are  accompanied  by  nerves,  the  great  saphenous  being 
joined  by  its  companion  nerve  just  below  the  level  of  the  knee- 
joint.  No  doubt  much  of  the  pain  of  varicose  veins  in  the  leg  is 
due  to  this  fact. 

Operations  for  the  rehef  of  varicose  veins  are  frequently  re- 
quired, portions  of  the  veins  being  removed  after  having  been 
ligatured  above  and  below.  It  is  important  to  note  whether  the 
main  varicose  area  drains  into  the  great  or  the  small  saphenous 
vein — the  former  condition  being  much  the  more  common — and 
to  control  the  venous  retiun  by  removing  a  small  portion  of  the 
main  trunk  just  before  it  opens  into  the  deep  vein  by  passing 
through  the  deep  fascia;  thus  in  most  cases  a  piece  should  be  re- 
moved from  the  great  saphenous  just  before  it  passes  through 
the  fossa  ovalis  {saphenous  o-pening),  and  in  addition  the  affected 
veins  should  be  excised  just  above  and  just  below  the  level  of  the 
knee-joint.  In  other  cases  the  small  saphenous  will  have  to  be 
dealt  with  immediately  below  the  point  where  it  pierces  the  fascial 
roof  of  the  popliteal  fossa. 

The  Deep  Veins  of  the  Lower  Extremity. 

The  deep  veins  of  the  lower  extremity  accompany  the 
arteries  and  their  branches;  they  possess  numerous  valves. 
The  plantar  digital  veins  {m.  digitales  plantares)  arise 
from  plexuses  on  the  plantar  surfaces  of  the  digits, 
and,  after  sending  intercapitular  veins  to  join  the  dorsal 
digital  veins,  unite  to  form  four  metatarsal  veins;  these 
run  backward  in  the  metatarsal  spaces,  communicate, 
by  means  of  perforating  veins,  with  the  veins  on  the 
dorsum  of  the  foot,  and  unite  to  form  the  deep  plantar 
venous  arch  which  lies  alongside  the  plantar  arterial  arch. 
From  the  deep  plantar  venous  arch  the  medial  and 
lateral  plantar  veins  run  backward  close  to  the  corre- 
sponding arteries  and,  after  communicating  with  the 
great  and  small  saphenous  veins,  unite  behind  the  medial 
malleolus  to  form  the  posterior  tibial  veins. 
The  posterior  tibial  veins  (vv.  tibiales  posteriores)  accompany  the  posterior 
tibial  artery,  and  are  joined  by  the  peroneal  veins. 

The  anterior  tibial  veins  {vv.  tibiales  anteriores)  are  the  upward  continuation 
of  the  venae  comitantes  of  the  dorsalis  pedis  artery.  They  leave  the  front  of -the 
leg  by  passing  between  the  tibia  and  fibula,  over  the  interosseous  membrane,  and 
unite  with  the  posterior  tibial,  to  form  the  popliteal  vein. 

The  Popliteal  Vein  (v.  poplitea)  is  formed  by  the  junction  of  the  anterior  and 
posterior  tibial  veins  at  the  lower  border  of  the  Popliteus;  it  ascends  through  the 
popliteal  fossa  to  the  aperture  in  the  Adductor  magnus,  where  it  becomes  the  femoral 
vein.  In  the  lower  part  of  its  course  it  is  placed  medial  to  the  artery;  between 
the  heads  of  the  Gastrocnemius  it  is  superficial  to  that  vessel;  but  above  the  knee- 
joint,  it  is  close  to  its  lateral  side.  It  receives  tributaries  corresponding  to  the 
branches  of  the  popliteal  artery,  and  it  also  receives  the  small  saphenous  vein. 
The  valves  in  the  popliteal  vein  are  usually  four  in  number. 

The  femoral  vein  {v.  femoralis)  accompanies  the  femoral  artery  through  the 
upper  two-thirds  of  the  thigh.    In  the  lower  part  of  its  course  it  lies  lateral  to  the 


Fig.  649. — The  small  saphenous 
vein. 


THE  VEINS  OF  THE  ABDOMEN  AND  PELVIS 


759 


artery;  higher  up,  it  is  behind  it;  and  at  the  inguinal  hgament,  it  Hes  on  its  medial 
side,  and  on  the  same  plane.  It  receives  numerous  muscular  tributaries,  and 
about  4  cm.  below  the  inguinal  ligament  is  joined  by  the  v.  profunda  femoris; 
near  its  termination  it  is  joined  by  the  great  saphenous  vein.  The  valves  in  the 
femoral  vein  are  three  in  number. 

The  Deep  Femoral  Vein  {v.  profunda  femoris)  receives  tributaries  corresponding 
to  the  perforating  branches  of  the  profunda  artery,  and  through  these  establishes 
communications  with  the  popliteal  vein  below  and  the  inferior  gluteal  vein  above. 
It  also  receives  the  medial  and  lateral  femoral  circumflex  veins. 


Third  hnnhar 


Deep 
circuinjiex 


Obturator  — 


Prostatic  plexus 


Deep  dorsal  vetii, 
of  penis 


Scrotal 


Vesical  plexus  Internal  pudendal 

Fig.  650. — The  veins  of  the  right  half  of  the  male  pelvis.     (Spalteholz.) 

The  Veins  of  the  Abdomen  and  Pelvis  (Fig.  650). 

The  external  iliac  vein  (v.  iliaca  externa),  the  upw^ard  continuation  of  the  femoral 
vein,  begins  behind  the  inguinal  ligament,  and,  passing  upward  along  the  brim 
of  the  lesser  pelvis,  ends  opposite  the  sacroiliac  articulation,  by_  uniting  with  the 
hypogastric  vein  to  form  the  common  iliac  vein.  On  the  right  side,  it  lies  at  first 
medial  to  the  artery:  but,  as  it  passes  upward,  gradually  inclines  behind  it.    On 


760  '  ANGIOLOGY 

the  left  side,  it  lies  altogether  on  the  medial  side  of  the  artery.  It  frequently 
contains  one,  sometimes  two,  valves. 

Tributaries, — The  external  iliac  vein  receives  the  inferior  epigastric,  deep  iHac 
circumflex,  and  pubic  veins. 

The  Inferior  Epigastric  Vein  {v.  epigastrica  inferior;  deep  epigastric  vein)  is  formed 
by  the  union  of  the  venae  comitantes  of  the  inferior  epigastric  artery,  which  com- 
municate above  with  the  superior  epigastric  vein;  it  joins  the  external  iliac  about 
1.25  cm.  above  the  inguinal  ligament. 

The  Deep  Iliac  Circumflex  Vein  (v.  circumfiexa  ilium  profunda)  is  formed  by  the 
union  of  the  venae  comitantes  of  the  deep  iliac  circumflex  artery,  and  joins  the 
external  iliac  vein  about  2  cm.  above  the  inguinal  ligament. 

The  Pubic  Vein  communicates  with  the  obturator  vein  in  the  obturator  foramen, 
and  ascends  on  the  back  of  the  pubis  to  the  external  iliac  vein. 

The  hypogastric  vein  {v.  hypogastrica;  internal  iliac  vein)  begins  near  the  upper 
part  of  the  greater  sciatic  foramen,  passes  upward  behind  and  slightly  medial  to 
the  hypogastric  artery  and,  at  the  brim  of  the  pelvis,  joins  with  the  external  iliac 
to  form  the  common  iliac  vein. 

Tributaries, — With  the  exception  of  the  fetal  umbilical  vein  which  passes  upward 
and  backward  from  the  umbilicus  to  the  liver,  and  the  iliolumbar  vein  which  usually 
joins  the  common  iliac  vein,  the  tributaries  of  the  hypogastric  vein  correspond 
with  the  branches  of  the  hypogastric  artery.  It  receives  (a)  the  gluteal,  internal 
pudendal,  and  obturator  veins,  which  have  their  origins  outside  the  pelvis;  (b)  the 
lateral  sacral  veins,  which  lie  in  front  of  the  sacrum;  and  (c)  the  middle  hemorrhoidal, 
vesical,  uterine,  and  vaginal  veins,  which  originate  in  venous  plexuses  connected 
with  the  pelvic  viscera. 

1.  The  Superior  Gluteal  Veins  (vv.  glutaeae  superiores;  gluteal  veins)  are  venae 
comitantes  of  the  superior  gluteal  artery ;  they  receive  tributaries  from  the  buttock 
corresponding  with  the  branches  of  the  artery,  and  enter  the  pelvis  through  the 
greater  sciatic  foramen,  above  the  Piriformis,  and  frequently  unite  before  ending 
in  the  hypogastric  vein. 

2.  The  Inferior  Gluteal  Veins  {vv.  glutaeae  infer  lores;  sciatic  veins) ,  or  venae  comi- 
tantes of  the  inferior  gluteal  artery,  begin  on  the  upper  part  of  the  back  of  the 
thigh,  where  they  anastomose  with  the  medial  femoral  circumflex  and  first  perfor- 
ating veins.  They  enter  the  pelvis  through  the  lower  part  of  the  greater  sciatic 
foramen  and  join  to  form  a  single  stem  wdiich  opens  into  the  lower  part  of  the  hypo- 
gastric vein. 

3.  The  Internal  Pudendal  Veins  {internal  pudic  veins)  are  the  venae  comitantes 
of  the  internal  pudendal  artery.  They  begin  in  the  deep  veins  of  the  penis  which 
issue  from  the  corpus  cavernosum  penis,  accompany  the  internal  pudendal  artery, 
and  unite  to  form  a  single  vessel,  wdiich  ends  in  the  hypogastric  vein.  They  receive 
the  veins  from  the  urethral  bulb,  and  the  perineal  and  inferior  hemorrhoidal  veins. 
The  deep  dorsal  vein  of  the  penis  communicates  with  the  internal  pudendal  veins, 
but  ends  mainly  in  the  pudendal  plexus, 

4.  The  Obturator  Vein  {v.  ohturatoria)  begins  in  the  upper  portion  of  the  adductor 
region  of  the  thigh  and  enters  the  pelvis  through  the  upper  part  of  the  obturator 
foramen.  It  runs  backward  and  upward  on  the  lateral  wall  of  the  pelvis  below  the 
obturator  artery,  and  then  passes  between  the  ureter  and  the  hypogastric  artery, 
to  end  in  the  hypogastric  vein. 

5.  The  Lateral  Sacral  Veins  (vv.  sacrales  laterales)  accompany  the  lateral  sacral 
arteries  on  the  anterior  surface  of  the  sacrum  and  end  in  the  hypogastric  vein. 

6.  The  Middle  Hemorrhoidal  Vein  {v.  haemorrhoidalis  media)  takes  origin  in  the 
hemorrhoidal  plexus  and  receives  tributaries  from  the  bladder,  prostate,  and 
seminal  vesicle;  it  runs  lateralward  on  the  pelvic  surface  of  the  Levator  ani  to 
end  in  the  hypogastric  vein. 


THE  VEINS  OF  THE  ABDOMEN  AND  PELVIS  761 

The  hemorrhoidal  plexus  (plexus  haemorrhoidaUs)  surrounds  the  rectum,  and 
communicates  in  front  with  the  vesical  plexus  in  the  male,  and  the  uterovaginal 
plexns  in  the  female.  It  consists  of  two  parts,  an  internal  in  the  submucosa,  and  an 
external  outside  the  muscular  coat.  The  internal  plexus  presents  a  series  of  dilated 
pouches  which  are  arranged  in  a  circle  around  the  tube,  immediately  above  the 
anal  orifice,  and  are  connected  by  transverse  branches. 

The  lower  part  of  the  external  plexus  is  drained  by  the  inferior  hemorrhoidal 
veins  into  the  internal  pudendal  vein;  the  middle  part  by  the  middle  hemorrhoidal 
vein  which  joins  the  hypogastric  vein;  and  the  upper  part  by  the  superior  hemor- 
rhoidal XGXW  which  forms  the  commencement  of  the  inferior  mesenteric  vein, 
a  tributary  of  the  portal  vein.  A  free  communication  between  the  portal  and  sys- 
temic venous  systems  is  established  through  the  hemorrhoidal  plexus. 

The  pudendal  plexus  {plexus  pudendalis;  vesicoprostatic  plexus)  lies  behind  the 
arcuate  pubic  ligament  and  the  lower  part  of  the  symphysis  pubis,  and  in  front  of 
the  bladder  and  prostate.  Its  chief  tributary  is  the  deep  dorsal  vein  of  the  penis, 
but  it  also  receives  branches  from  the  front  of  the  bladder  and  prostate.  It  com- 
municates w'ith  the  vesical  plexus  and  with  the  internal  pudendal  vein  and  drains 
into  the  vesical  and  hypogastric  veins.  The  prostatic  veins  form  a  well-marked 
prostatic  plexus  which  lies  partly  in  the  fascial  sheath  of  the  prostate  and  partly 
between  the  sheath  and  the  prostatic  capsule.  It  communicates  with  the  pudendal 
and  vesical  plexuses. 

The  vesical  plexus  (plexus  ■vesicalis)  envelops  the  lower  part  of  the  bladder  and 
the  base  of  the  prostate  and  communicates  wdth  the  pudendal  and  prostatic  plexuses 
It  is  drained,  by  means  of  several  vesical  veins,  into  the  hypogastric  veins. 

Applied  Anatomy. — The  veins  of  the  hemorrhoidal  plexus  are  apt  to  become  dilated  and  vari- 
cose, and  form  piles.  This  is  due  to  several  anatomical  reasons:  the  vessels  are  contained  in 
very  loose,  connective  tissue,  so  that  they  get  less  support  from  surrounding  structures  than 
most  other  veins,  and  are  less  capable  of  resisting  increased  blood  pressm'e;  the  condition  is 
favored  by  gravitation,  being  influenced  by  the  erect  posture,  either  sitting  or  standing,  and  by 
the  fact  that  the  superior  hemorrhoidal  and  portal  veins  have  no  valves;  the  veins  pass  through 
muscular  tissue  and  are  liable  to  be  compressed  by  its  contraction,  especially  during  the  act  of 
defecation;  they  are  affected  by  every  form  of  portal  obstruction. 

The  prostatic  plexus  of  veins  is  apt  to  become  congested  in  many  inflammatory  conditions 
in  the  neighborhood,  such  as  acute  gonorrheal  prostatitis.  It  is  owing  to  the  free  communication 
which  exists  between  this  and  the  middle  hemorrhoidal  plexus  that  great  relief  can  be  given  by 
free  saline  purgation. 

Hemorrhage  may  be  very  free  from  the  prostatic  plexus  after  operations  on  that  gland,  but 
can  usually  be  checked  by  hot  fluid  irrigation.  Septic  thrombosis  sometimes  occurs  after  opera- 
tions, and  infected  emboli  may  find  their  way  into  the  general  circulation. 

The  Dorsal  Veins  of  the  Penis  (vv.  dorsales  penis)  are  tw'o  in  number,  a  superficial 
and  a  deep.  The  superficial  vein  drains  the  prepuce  and  skin  of  the  penis,  and, 
running  backward  in  the  subcutaneous  tissue,  inclines  to  the  right  or  left,  and  opens 
into  the  corresponding  superficial  external  pudendal  vein,  a  tributary  of  the  great 
saphenous  vein.  The  deep  vein  lies  beneath  the  deep  fascia  of  the  penis;  it  receives 
the  blood  from  the  glans  penis  and  corpora  cavernosa  penis  and  courses  backw^ard 
in  the  middle  line  between  the  dorsal  arteries;  near  the  root  of  the  penis  it  passes 
between  the  two  parts  of  the  suspensory  ligament  and  then  through  an  aperture 
between  the  arcuate  pubic  ligament  and  the  transverse  ligament  of  the  pelvis, 
and  divides  into  two  branches,  which  enter  the  pudendal  plexus.  The  deep  vein 
also  communicates  below^  the  symphysis  pubis  with  the  internal  pudendal  vein. 

The  uterine  plexuses  lie  along  the  sides  and  superior  angles  of  the  uterus  between 
the  two  layers  of  the  broad  ligament,  and  communicate  with  the  ovarian  and 
vaginal  plexuses.  They  are  drained  by  a  pair  of  uterine  veins  on  either  side:  these 
arise  from  the  lower  part  of  the  plexuses,  opposite  the  external  orifice  of  the  uterus, 
and  open  into  the  corresponding  hypogastric  vein. 


762  AXGIOLOGY 

The  vaginal  plexuses  are  placed  at  the  sides  of  the  vagina;  they  communicate 
with  the  uterine,  vesical,  and  hemorrhoidal  plexuses,  and  are  drained  by  the 
vaginal  veins,  one  on  either  side,  into  the  hypogastric  veins. 

The  common  iliac  veins  (vv.  iliacae  communes)  are  formed  by  the  union  of  the 
external  iliac  and  hypogastric  veins,  in  front  of  the  sacroiliac  articulation;  passing 
obliquely  upward  toward  the  right  side,  they  end  upon  the  fifth  lumbar  vertebra, 
by  uniting  with  each  other  at  an  acute  angle  to  form  the  inferior  vena  cava.  The 
right  common  iliac  is  shorter  than  the  left,  nearly  vertical  in  its  direction,  and 
ascends  behind  and  then  lateral  to  its  corresponding  artery.  The  left  common 
iliac,  longer  than  the  right  and  more  oblique  in  its  course,  is  at  first  situated  on  the 
medial  side  of  the  corresponding  artery,  and  then  behind  the  right  common  iliac. 
Each  common  iliac  receives  the  iliolumbar,  and  sometimes  the  lateral  sacral  veins. 
The  left  receives,  in  addition,  the  middle  sacral  vein.  No  valves  are  found  in  these 
veins. 

The  Middle  Sacral  Veins  {w.  sacrales  mediales)  accompany  the  corresponding 
artery  along  the  front  of  the  sacrum,  and  join  to  form  a  single  vein,  which  ends  in 
the  left  common  iliac  vein;  sometimes  in  the  angle  of  junction  of  the  two  iliac  veins. 

Peculiarities. — The  left  common  iliac  vein,  instead  of  joining  with  the  right  in  its  usual  posi- 
tion, occasionally  ascends  on  the  left  side  of  the  aorta  as  high  as  the  kidney,  where,  after  receiving 
the  left  renal  vein,  it  crosses  over  the  aorta,  and  then  joins  with  the  right  vein  to  form  the  vena 
cava.  In  these  cases,  the  two  common  iliacs  are  connected  by  a  small  communicating  branch 
at  the  spot  where  they  are  usually  united. 

The  inferior  vena  cava  {v.  cava  inferior)  (Fig.  644),  returns  to  the  heart  the  blood 
from  the  parts  below  the  Diaphragma.  It  is  formed  by  the  junction  of  the  two 
common  iliac  veins,  on  the  right  side- of  the  fifth  lumbar  vertebra.  It  ascends  along 
the  front  of  the  vertebral  column,  on  the  right  side  of  the  aorta,  and,  having  reached 
the  liver,  is  continued  in  a  groove  on  its  posterior  surface.  It  then  perforates 
the  Diaphragma  between  the  median  and  right  portions  of  its  central  tendon; 
it  subsequently  inclines  forward  and  medialward  for  about  2.5  cm.,  and,  piercing 
the  fij^rous  pericardium,  passes  behind  the  serous  pericardium  to  open  into  the 
lower  and  back  part  of  the  right  atrium.  In  front  of  its  atrial  orifice  is  a  semilunar 
valve,  termed  the  valve  of  the  inferior  vena  cava:  this  is  rudimentary  in  the  adult 
but  is  of  large  size  and  exercises  an  important  function  in  the  fetus  (see  page  618). 

Relations. — The  abdominal  portion  of  the  inferior  vena  cava  is  in  relation  in  front,  from  below 
upward,  with  the  right  common  iliac  artery,  the  mesentery,  the  right  internal  spermatic  artery, 
the  inferior  part  of  the  duodenum,  the  pancreas,  the  common  bile  duct,  the  portal  vein,  and  the 
posterior  surface  of  the  hver;  the  last  partly  overlaps  and  occasionally  completely  surroimds  it; 
behind,  with  the  vertebral  column,  the  right  Psoas  major,  the  right  crus  of  the  Diaphragma,  the 
right  inferior  phrenic,  suprarenal,  renal  and  lumbar  arteries,  right  sympathetic  trunk  and  right 
coeliac  ganglion,  and  the  medial  part  of  the  right  suprarenal  gland;  on  the  right  side,  with  the 
right  kidney  and  ureter;  on  the  left  side,  with  the  aorta,  right  crus  of  the  Diaphragma,  and  the 
caudate  lobe  of  the  liver. 

The  thoracic  portion  is  only  about  2.5  cm.  in  length,  and  is  situated  partly  inside  and  partly 
outside  the  pericardial  sac.  The  extrapericardial  part  is  separated  from  the  right  pleura  and 
lung  by  a  fibrous  band,  named  the  right  phrenicopericardiac  ligament.  This  hgament,  often 
feebly  marked,  is  attached  below  to  the  margin  of  the  vena-caval  opening  in  the  Diaphragma,  and 
above  to  the  pericardium  in  front  of  and  behind  the  root  of  the  right  lung.  The  infrapericardiac 
part  is  very  short,  and  is  covered  antero-laterally  by  the  serous  layer  of  the  pericardium. 

Peculiarities. — In  Position. — This  vessel  is  sometimes  placed  on  the  left  side  of  the  aorta, 
as  high  as  the  left  renal  vein,  and,  after  receiving  this  vein,  crosses  over  to  its  usual  position  on 
the  right  side;  or  it  may  be  placed  altogether  on  the  left  side  of  the  aorta,  and  in  such  a  case  the 
abdominal  and  thoracic  viscera,  together  with  the  great  vessels,  are  all  transposed. 

Point  of  Termination. — Occasionally  the  inferior  vena  cava  joins  the  azygos  vein,  which  is 
then  of  large  size.  In  such  cases,  the  superior  vena  cava  receives  the  whole  of  the  blood  from 
the  body  before  transmitting  it  to  the  right  atrium,  except  the  blood  from  the  hepatic  veins, 
which  passes  directly  into  the  right  atrium. 

Applied  Anatomy. — Thrombosis  of  the  inferior  vena  cava  is  due  to  much  the  same  causes  as 
that  of  the  superior  (see  p.  754).    It  usually  causes  oedema  of  the  legs  and  back,  without  ascites; 


THE  VEINS  OF  THE  ABDOMEN  AND  PELVIS  763 

if  the  renal  veins  are  involved,  blood  and  albumin  will  often  ai)pear  in  the  urine.  An  extensive 
collateral  venous  circulation  is  soon  established  by  onlargemcnt  either  of  the  superficial  or  of  the 
deep  veins,  or  of  both.  In  the  first  case  the  epigastric,  the  iliac  circumflex,  the  lateral  thoracic, 
the  internal  mammary,  the  intercostals,  the  external  pudendal,  and  the  lumbovertebral  anasto- 
matic  veins  of  Braune  effect  the  communication  with  the  superior  cava;  in  the  second,  the  deep 
anastomosis  is  made  by  the  azygos  and  hemiazygos  and  the  lumbar  veins. ^ 

Tributaries. — The  inferior  vena  cava  receives  the  following  veins: 

Lumbar.  Renal.  Inferior  Phrenic. 

Right  Spermatic  or  Ovarian.  Suprarenal.    .  Hepatic, 

The  Lumbar  Veins  (vv.  lumbales)  four  in  number  on  each  side,  collect  the  blood 
by  dorsal  tributaries  from  the  muscles  and  integument  of  the  loins,  and  by  abdomi- 
nal tributaries  from  the  walls  of  the  abdomen,  where  they  communicate  with  the 
epigastric  veins.  At  the  vertebral  column,  they  receive  veins  from  the  vertebral 
plexuses,  and  then  pass  forward,  around  the  sides  of  the  bodies  of  the  vertebrae, 
beneath  the  Psoas  major,  and  end  in  the  back  part  of  the  inferior  cava.  The  left 
lumbar  veins  are  longer  than  the  right,  and  pass  behind  the  aorta.  The  lumbar 
veins  are  connected  together  by  a  longitudinal  vein  which  passes  in  front  of  the 
transverse  processes  of  the  lumbar  vertebrae,  and  is  called  the  ascending  lumbar; 
it  forms  the  most  frequent  origin  of  the  corresponding  azygos  or  hemiazygos  vein, 
and  serves  to  connect  the  common  iliac,  iliolumbar,  and  azygos  or  hemiazygos 
veins  of  its  own  side  of  the  body. 

The  Spermatic  Veins  (vv.  spermaticae)  emerge  from  the  back  of  the  testis,  and 
receive  tributaries  from  the  epididymis;  they  unite  and  form  a  convoluted  plexus, 
called  the  pampiniform  plexus,  which  constitutes  the  greater  mass  of  the  spermatic 
cord;  the  vessels  composing  this  plexus  are  very  numerous,  and  ascend  along  the 
cord,  in  front  of  the  ductus  deferens.  Below  the  subcutaneous  inguinal  ring  they 
unite  to  form  three  or  four  veins,  which  pass  along  the  inguinal  canal,  and,  entering 
the  abdomen  through  the  abdominal  inguinal  ring,  coalesce  to  form  two  veins, 
which  ascend  on  the  Psoas  major,  behind  the  peritoneum,  lying  one  on  either  side 
of  the  internal  spermatic  artery.  These  unite  to  form  a  single  vein,  which  opens 
on  the  right  side  into  the  inferior  vena  cava,  at  an  acute  angle;  on  the  left  side 
into  the  left  renal  vein,  at  a  right  angle.  The  spermatic  veins  are  provided  with 
valves.-  The  left  spermatic  vein  passes  behind  the  iliac  colon,  and  is  thus  exposed 
to  pressure  from  the  contents  of  that  part  of  the  bowel. 

Applied  Anatomy. — The  spermatic  veins  are  very  frequently  varicose,  constituting  the  condi- 
tion known  as  varicocele.  Though  it  is  quite  possible  that  the  originating  cause  of  this  affection 
may  be  a  congenital  weakness  of  the  walls  of  the  veins  of  the  pampiniform  plexus,  still  it  must 
be  admitted  that  there  are  many  anatomical  reasons  why  these  veins  should  become  varicose, 
viz. :  the  imperfect  support  afforded  to  them  by  the  loose  tissue  of  the  scrotum;  their  great  length; 
their  vertical  course;  their  dependent  position;  their  plexiform  arrangement  in  the  scrotum, 
with  their  termination  in  one  small  vein  in  the  abdomen;  their  few  and  imperfect  valves;  and 
the  fact  that  they  may  be  subjected  to  pressure  in  their  passage  through  the  abdominal  wall. 
Varicocele  almost  invariably  occurs  on  the  left  side,  and  this  has  been  accoimted  for  by  the  facts 
that  the  left  spermatic  vein  joins  the  left  renal  at  a  right  angle;  that  it  is  overlaid  by  the  iliac  colon, 
and  that  when  this  portion  of  the  gut  is  full  of  fecal  matter,  in  cases  of  constipation,  its  weight 
impedes  the  retiu-n  of  the  venous  blood;  and  that  the  left  spermatic  veins  are  somewhat  longer 
than  the  right. 

The  operation  for  the  removal  of  a  varicocele  consists  in  making  a  small  incision  just  over  the 
subcutaneous  inguinal  ring  and  passing  an  aneurism  needle  around  the  mass  of  veins,  taking  care 
that  the  ductus  deferens  is  not  included.  The  veins  are  isolated  from  the  ductus  and  hgatured 
above  and  below,  as  high  and  as  low  as  possible,  and  the  intermediate  portion  cut  away;  the 
divided  ends  are  fixed  together  with  a  suture,  and  the  skin  woimd  closed. 

1  G.  Blumer,  in  Osier  and  McCrae's  Modern  Medicine,  Philadelphia,  1908,  vol.  iv. 

2  Ri\'ington  has  pointed  out  that  valves  are  usually  found  at  the  orifices  of  both  the  right  and  left  spermatic  veins. 
When  no  valves  exist  at  the  opening  of  the  left  spermatic  vein  into  the  left  renal  vein,  valves  are  generally  present  in 
the  left  renal  vein  -ndthin  6  mm.  from  the  orifice  of  the  spermatic  vein. — Journal  of  Anatomy  and  Physiologj-,  vn,  163. 


764  ANGIOLOGY 

The  Ovarian  Veins  {m.  ovaricae)  correspond  with  the  spermatic  in  the  male;  they 
form  a  plexus  in  the  broad  lio-ament  near  the  oA'ar}-  and  uterine  tube,  and  communi- 
cate with  the  uterine  plexus.  They  end  in  the  same  way  as  the  spermatic  veins 
in  the  male.  Valves  are  occasionally  found  in  these  veins.  Like  the  uterine  veins, 
they  become  much  enlarged  during  pregnancy. 

The  Renal  Veins  (vv.  renales)  are  of  large  size,  and  placed  in  front  of  the  renal 
arteries.  The  left  is  longer  than-  the  right,  and  passes  in  front  of  the  aorta,  just 
below  the  origin  of  the  superior  mesenteric  artery.  It  receives  the  left  spermatic 
and  left  inferior  phrenic  veins,  and,  generally,  the  left  suprarenal  vein.  It  opens 
into  the  inferior  vena  cava  at  a  slightly  higher  level  than  the  right. 

The  Suprarenal  Veins  {vv.  supraremdes)  are  two  in  number:  the  right  ends  in  the 
inferior  vena  cava;  the  left,  in  the  left  renal  or  left  inferior  phrenic  vein. 

The  Inferior  Phrenic  Veins  {vv.  yhrenicae  iiiferiores)  follow  the  course  of  the  inferior 
phrenic  arteries;  the  right  ends  in  the  inferior  vena  cava;  the  left  is  often  repre- 
sented by  two  branches,  one  of  which  ends  in  the  left  renal  or  suprarenal  vein, 
while  the  other  passes  in  front  of  the  oesophageal  hiatus  in  the  Diaphragma  and 
opens  into  the  inferior  vena  cava. 

The  Hepatic  "Veins  {vv.  hepaticae)  commence  in  the  substance  of  the  liver,  in  the 
terminations  of  the  portal  vein  and  hepatic  artery,  and  are  arranged  in  two  groups, 
upper  and  lower.  The  upper  group  usually  consists  of  three  large  veins,  which 
converge  toward  the  posterior  surface  of  the  liver,  and  open  into  the  inferior 
vena  cava,  while  that  vessel  is  situated  in  the  groove  on  the  back  part  of  the  liver. 
The  veins  of  the  lower  group  vary  in  number,  and  are  of  small  size;  they  come 
from  the  right  and  caudate  lobes.  The  hepatic  veins  run  singly,  and  are  in  direct 
contact  with  the  hepatic  tissue.     They  are  destitute  of  valves. 


THE   PORTAL   SYSTEM    OF   VEINS    (Fig.    651). 

The  portal  system  includes  all  the  veins  which  drain  the  blood  from  the  abdominal 
part  of  the  digestive  tube  (with  the  exception  of  the  lower  part  of  the  rectum) 
and  from  the  spleen,  pancreas,  and  gall-bladder.  From  these  viscera  the  blood 
is  conveyed  to  the  liver  by  the  portal  vein.  In  the  liver  this  vein  ramifies  like  an 
artery  and  ends  in  capillary-like  vessels  termed  sinusoids,  from  which  the  blood  is 
conveyed  to  the  inferior  vena  cava  by  the  hepatic  veins.  From  this  it  wdll  be  seen 
that  the  blood  of  the  portal  system  passes  through  two  sets  of  minute  vessels, 
viz.,  (a)  the  capillaries  of  the  digestive  tube,  spleen,  pancreas,  and  gall-bladder; 
and  (b)  the  sinusoids  of  the  liver.  In  the  adult  the  portal  vein  and  its  tributaries 
are  destitute  of  valves;  in  the  fetus  and  for  a  short  time  after  birth  valves  can  be 
demonstrated  in  the  tributaries  of  the  portal  vein;  as  a  rule  thej'^  soon  atrophy 
and  disappear,  but  in  some  subjects  they  persist  in  a  degenerate  form. 

The  portal  vein  {vena  portae)  is  about  8  cm.  in  length,  and  is  formed  at  the  level 
of  the  second  lumbar  vertebra  by  the  junction  of  the  superior  mesenteric  and  lienal 
veins,  the  union  of  these  veins  taking  place  in  front  of  the  inferior  vena  cava  and 
behind  the  neck  of  the  pancreas.  It  passes  upward  behind  the  superior  part  of 
the  duodenum  and  then  ascends  in  the  right  border  of  the  lesser  omentum  to  the 
right  extremity  of  the  porta  hepatis,  where  it  divides  into  a  right  and  a  left  branch, 
which  accompany  the  corresponding  branches  of  the  hepatic  artery  into  the  sub- 
stance of  the  liver.  In  the  lesser  omentum  it  is  placed  behind  and  between  the 
common  bile  duct  and  the  hepatic  artery,  the  former  lying  to  the  right  of  the  latter. 
It  is  surrounded  by  the  hepatic  plexus  of  nerves,  and  is  accompanied  by  numerous 
lymphatic  vessels  and  some  lymph  glands.  The  right  branch  of  the  portal  vein 
enters  the  right  lobe  of  the  liver,  but  before  doing  so  generally  receives  the  cystic 
vein.    The  left  branch,  longer  but  of  smaller  calibre  than  the  right,  crosses  the  left 


THE  PORTAL  SYSTEM  OF  VEINS 


705 


sagittal  fossa,  gives  branches  to  the  caiuhite  lobe,  and  then  enters  the  left  lobe  of 
the  liver.  As  it  crosses  the  left  sagittal  fossa  it  is  joined  in  front  by  a  fibrous  cord, 
the  ligamentum  teres  (nhJUcvdied  innhiltnil  iriii),  and  is  united  to  the  inferior  vena 
cava  by  a  second  fibrous  cord,  the  ligamentum  venosum  (obliterated  ductus  venosus). 


Fig.  651. — The  portal  vein  and  its  tributaries. 


Tributaries.— The  tributaries  of  the  portal  vein  are: 

Lienal.  •  Pyloric. 

Superior  Mesenteric.  Cystic. 

Coronary.  Parumbilical. 

The  Lienal  Vein  {v.  lienalis;  splenic  vein)  commences  by  five  or  six  large  branches 
which  return  the  blood  from  the  spleen.  These  unite  to  form  a  single  vessel,  which 
passes  from  left  to  right,  grooving  the  upper  and  back  part  of  the  pancreas,  below 
the  lineal  artery,  and  ends  behind  the  neck  of  the  pancreas  by  uniting  at  a  right 
angle  with  the^uperior  mesenteric  to  form  the  portal  vein.  The  lienal  vein  is 
of  large  size,  but  is  not  tortuous  like  the  artery. 


766  ANGIOLOGY 

Tributaries. — The  lineal  vein  receives  the  short  gastric  veins,  the  left  gastro- 
epiploic vein,  the  pancreatic  veins,  and  the  inferior  mesenteric  veins. 

The  short  gastric  veins  (vv.  gastricae  breves)  Joutot  five  in  number,  drain  the  fundus 
and  left  part  of  the  greater  curvature  of  the  stomach,  and  pass  between  the  two 
layers  of  the  gastrolienal  ligament  to  end  in  the  lienal  vein  or  in  one  of  its  large 
tributaries. 

The  left  gastroepiploic  vein  {v.  gastroepiploica  sinistra)  receives  branches  from 
the  antero-superior  and  postero-inf erior  surfaces  of  the  stomach  and  from  the  greater 
omentum;  it  runs  from  right  to  left  along  the  greater  curvature  of  the  stomach 
and  ends  in  the  commencement  of  the  lienal  vein. 

The  pancreatic  veins  {w.  yancreaticae)  consist  of  several  small  vessels  which  drain 
the  body  and  tail  of  the  pancreas,  and  open  into  the  trunk  of  the  lienal  vein. 

The  inferior  mesenteric  vein  {v.  mesenterica  inferior)  returns  blood  from  the  rectum 
and  the  sigmoid,  and  descending  parts  of  the  colon.  It  begins  in  the  rectum  as 
the  superior  hemorrhoidal  vein,  which  has  its  origin  in  the  hemorrhoidal  plexus, 
and  through  this  plexus  communicates  with  the  middle  and  inferior  hemor- 
rhoidal veins.  The  superior  Hemorrhoidal  vein  leaves  the  lesser  pelvis  and  crosses 
the  left  common  iliac  vessels  with  the  superior  hemorrhoidal  artery,  and  is  con- 
tinued upward  as  the  inferior  mesenteric  vein.  This  vein  lies  to  the  left  of  its 
artery,  and  ascends  behind  the  peritoneum  and  in  front  of  the  left  Psoas  major; 
it  then  passes  behind  the  body  of  the  pancreas  and  opens  into  the  lienal  vein; 
sometimes  it  ends  in  the  angle  of  union  of  the  lienal  and  superior  mesenteric  veins. 

Tributaries. — The  inferior  mesenteric  vein  receives  the  sigmoid  veins  from  the 
sigmoid  colon  and  iliac  colon,  and  the  left  colic  vein  from  the  descending  colon  and 
left  colic  flexure. 

The  Superior  Mesenteric  Vein  {v.  mesenterica  superior)  returns  the  blood  from  the 
small  intestine,  from  the  cecum,  and  from  the  ascending  and  transverse  portions 
of  the  colon.  It  begins  in  the  right  iliac  fossa  by  the  union  of  the  veins  which  drain 
the  terminal  part  of  the  ileum,  the  cecum,  and  vermiform  process,  and  ascends 
between  the  two  layers  of  the  mesentery  on  the  right  side  of  the  superior  mes- 
enteric artery.  In  its  upward  course  it  passes  in  front  of  the  right  ureter,  the 
inferior  vena  cava,  the  inferior  part  of  the  duodenum,  and  the  lower  portion  of 
the  head  of  the  pancreas.  Behind  the  neck  of  the  pancreas  it  unites  with  the  lienal 
vein  to  form  the  portal  vein. 

Tributaries. — Besides  the  tributaries  which  correspond  with  the  branches  of  the 
superior  mesenteric  artery,  viz.,  the  intestinal,  ileocolic,  right  colic,  and  middle  colic 
veins,  the  superior  mesenteric  vein  is  joined  by  the  right  gastroepiploic  and  pan- 
creaticoduodenal veins. 

The  right  gastroepiploic  vein  {v.  gastroepiyloica  dextra)  receives  branches  from  the 
greater  omentum  and  from  the  lower  parts  of  the  antero-superior  and  postero- 
inf  erior  surfaces  of  the  stomach;  it  runs  from  left  to  right  along  the  greater  curva- 
ture of  the  stomach  between  the  two  layers  of  the  greater  omentum. 

The  pancreaticoduodenal  veins  {m.  pancreaticoduodenales)  accompany  their  corre- 
sponding arteries;  the  lower  of  the  two  frequently  joins  the  right  gastroepiploic 
vein. 

The  Coronary  Vein  {v.  coronaria  ventriculi;  gastric  vein)  derives  tributaries  from 
both  surfaces  of  the  stomach;  it  runs  from  right  to  left  along  the  lesser  curvature 
of  the  stomach,  between  the  two  layers  of  the  lesser  omentum,  to  the  oesophageal 
opening  of  the  stomach,  where  it  receives  some  oesophageal  veins.  It  then  turns 
backward  and  passes  from  left  to  right  behind  the  omental  bursa  and  ends  in  the 
portal  vein. 

The  Pyloric  Vein  is  of  small  size,  and  runs  from  left  to  right  along  the  pyloric 
portion  of  the  lesser  curvature  of  the  stomach,  between  the  two  layers  of  the  lesser 
omentum,  to  end  in  the  portal  vein. 


THE  PORTAL  SYSTEM  OF  VEINS  767 

The  Cystic  Vein  (/'.  ci/.sfica)  drains  the  blood  from  the  gall-bladder,  and,  accom- 
panying the  cystic  duct,  usually  ends  in  the  right  branch  of  the  portal  vein. 

Parumbilical  Veins(rr.  parumbilicales). — In  the  course  of  the  ligamentum  teres 
of  the  liver  and  of  the  middle  umbilical  ligament,  small  veins  (parumbilical)  are 
found  which  establish  an  anastomosis  between  the  veins  of  the  anterior  abdominal 
wall  and  the  portal,  hypogastric,  and  iliac  veins.  The  best  marked  of  these  small 
veins  is  one  which  commences  at  the  umbilicus  and  runs  backward  and  upward 
in,  or  on  the  surface  of,  the  ligamentum  teres  between  the  layers  of  the  falciform 
ligament  to  end  in  the  left  portal  vein. 

Applied  Anatomy. — Obstruction  to  the  portal  vein  may  produce  ascites,  and  this  may  arise 
from  many  causes:  as  (1)  the  pressure  of  a  tumor  on  the  portal  vein,  such  as  cancer  or  hydatid 
cyst  in  the  liver,  enlarged  lymph  glands  in  the  lesser  omentum,  or  cancer  of  the  head  of  the 
pancreas;  (2)  from  cirrhosis  of  the  liver,  when  the  radicles  of  the  portal  vein  are  pressed  upon 
by  the  contracting  fibrous  tissue  in  the  portal  canals;  (3)  from  valvular  disease  of  the  heart,  and 
back  pressure  on  the  hepatic  veins,  and  so  on  the  whole  of  the  circulation  through  the  liver.  In 
this  condition  the  prognosis  as  regards  life  and  freedom  from  ascites  may  be  much  improved  by 
the  establishment  of  a  good  collateral  venous  circulation  to  relieve  the  portal  obstruction  in  the 
liver.  This  is  effected  by  communications  between  (a)  the  gastric  veins  and  the  oesophageal 
veins  which  often  project  as  a  varicose  bunch  into  the  stomach,  emptying  themselves  into  the 
hemiazygos  vein;  (b)  the  veins  of  the  colon  and  duodenum  and  the  left  renal  vein;  (c)  the  accessory 
portal  system  of  Sappey,  branches  of  which  pass  in  the  round  and  falciform  ligaments  (particu- 
larly the  latter)  to  unite  with  the  epigastric  and  internal  mammary  veins,  and  through  the  dia- 
phragmatic veins  with  the  azygos;  a  single  large  vein,  shown  to  be  a  parumbilical  vein,  may  pass 
from  the  hilus  of  the  liver  by  the  round  ligament  to  the  umbilicus,  producing  there  a  bunch  of 
prominent  varicose  veins  known  as  the  caput  medusae;  (d)  the  veins  of  Retzius,  which  connect 
the  intestinal  veins  with  the  inferior  vena  cava  and  its  retroperitoneal  branches;  (e)  the  inferior 
mesenteric  veins,  and  the  hemorrhoidal  veins  that  open  into  the  hypogastrics;  (/)  very  rarely 
the  ductus  venosus  remains  patent,  affording  a  direct  connection  between  the  portal  vein  and 
the  inferior  vena  cava. 

An  operation  for  the  relief  of  portal  obstruction  on  these  lines  has  been  advocated  by  Ruther- 
ford Morison  and  by  Talma.  It  consists  in  curetting  the  opposed  surfaces  of  the  hver  and  Dia- 
phragma  and  stitching  them  together,  so  as  to  secure  vascular  inflammatory  adhesions  between 
the  two.  The  greater  omentum  may  with  advantage  be  interposed  between  them,  so  as  to  increase 
the  amount  of  the  adhesions,  and  the  spleen  has  been  similarly  scraped  and  sutured  to  or  into 
the  abdominal  wall.    The  operation  should  not  be  deferred  imtil  the  patient  is  moribund. 

Thi'ombosis  of  the  portal  vein,  or  pylethrombosis,  is  a  very  serious  event,  and  is  oftenest  due 
to  pathological  processes  causing  compression  of  the  vessel  or  injury  to  its  wall,  such  as  tumors 
or  inflammation  about  the  pylorus,  head  of  the  pancreas,  or  vermiform  process,  or  to  gall-stones, 
or  cirrhosis  of  the  liver.  If  the  thrombus  is  infected  with  bacteria,  as  is  often  the  case  when  it 
is  due  to  appendicitis,  septic  or  suppurative  pylephlebitis  results;  this  condition  is  known  also 
as  portal  pyemia.  Fragments  of  the  infected  clot  break  off  and  are  carried  away  to  lodge  in  the 
smaller  veins  in  the  liver,  with  the  development  of  multiple  abscesses  in  its  substance  and  a 
rapidly  fatal  result.  When  the  thrombus  is  sterile,  the  chief  signs  produced  are  enlargement 
of  the  spleen,  recurrent  ascites,  and  the  establishment  of  a  collateral  venous  circulation,  the 
case  clinically  resembling  one  of  atrophic  cirrhosis  of  the  liver. 

The  symptoms  of  thrombosis  of  the  mesenteric  veins  are  very  much  the  same  as  those  of 
embolism  of  the  mesenteric  arteries  (see  p.  696). 


THE  LYMPHATIC  SYSTEM. 


HTHE  lymphatic  system  includes  the  lymphatic  vessels  and  lymph  glands.  The  lym- 
-^  phatic  vessels  of  the  small  intestine  receive  the  special  designation  of  lacteals 
or  chyliferous  vessels ;  they  differ  in  no  respect  from  the  lymphatic  vessels  generally 
excepting  that  during  the  process  of  digestion  they  contain  a  milk-white  fluid, 
the  chyle. 

The  lymphatic  vessels  are  exceedingly  delicate,  and  their  coats  are  so  transparent 
that  the  fluid  they  contain  is  readily  seen  through  them.  They  are  interrupted 
at  intervals  by  constrictions,  which  give  them  a  knotted  or  beaded  appearance; 
these  constrictions  correspond  to  the  situations  of  valves  in  their  interior.  Lym- 
phatic vessels  have  been  found  in  nearly  every  texture  and  organ  of  the  body 
which  contains  bloodvessels.  Such  non-vascular  structures  as  cartilage,  the  nails, 
cuticle,  and  hair  have  none,  but  these  with  exceptions  it  is  probable  that  eventually 
all  parts  will  be  found  to  be  permeated  by  these  vessels. 

Structure  of  Lymphatic  Vessels. — The  larger  lymphatic  vessels  are  each  composed  of  three 
coats.  The  internal  coat  is  thin,  transparent,  sUghtly  elastic,  and  consists  of  a  layer  of  elongated 
endothelial  cells  with  wavy  margins  by  which  the  contiguous  cells  are  dovetailed  into  one  another; 
the  cells  are  supported  on  an  elastic  membrane.  The  middle  coat  is  composed  of  smooth  muscular 
and  fine  elastic  fibres,  disposed  in  a  transverse  direction.  The  external  coat  consists  of  connective 
tissue,  intermixed  with  smooth  muscular  fibres  longitudinally  or  obhquely  disposed;  it  forms 
a  protective  covering  to  the  other  coats,  and  serves  to  connect  the  vessel  with  the  neighboring 
structures.  In  the  smaUer  vessels  there  are  no  muscular  or  elastic  fibres,  and  the  waU  consists 
only  of  a  connective-tissue  coat,  hned  by  endothehum.  The  thoracic  duct  has  a  more  complex 
structure  than  the  other  lymphatic  vessels;  it  presents  a  distinct  subendothehal  layer  of  branched 
corpuscles,  similar  to  that  found  ia  the  arteries;  ia  the  middle  coat  there  is,  in  addition  to  the 
muscular  and  elastic  fibres,  a  layer  of  connective  tissue  with  its  fibres  arranged  longitudinally. 
The  lymphatic  vessels  are  supphed  by  nutrient  vessels,  which  are  distributed  to  their  outer 
and  middle  coats;  and  here  also  have  been  traced  many  non-meduUated  nerves  in  the  form  of 
a  fine  plexus  of  fibrils. 

The  valves  of  the  lymphatic  vessels  are  formed  of  thin  layers  of  fibrous  tissue  covered  on  both 
surfaces  by  endothelium  which  presents  the  same  arrangement  as  on  the  valves  of  veins  (p.  599). 
In  form  the  valves  are  semilunar;  they  are  attached  by  their  convex  edges  to  the  wall  of  the 
vessel,  the  concave  edges  being  free  and  directed  along  the  course  of  the  contained  current. 
Usually  two  such  valves,  of  equal  size,  are  found  opposite  one  another;  but  occasionally  excep- 
tions occur,  especiaUy  at  or  near  the  anastomoses  of  lymphatic  vessels.  Thus,  one  valve  may 
be  of  small  size  and  the  other  increased  in  proportion. 

In  the  lymphatic  vessels  the  valves  are  placed  at  much  shorter  intervals  than  in  the  veins. 
They  are  most  numerous  near  the  lymph  glands,  and  are  found  more  frequently  in  the  lymphatic 
vessels  of  the  neck  and  upper  extremity  than  in  those  of  the  lower  extremity.  The  waU  of 
the  lymphatic  vessel  immediately  above  the  point  of  attachment  of  each  segment  of  a  valve  is 
expanded  into  a  pouch  or  sinus  which  gives  to  these  vessels,  when  distended,  the  knotted  or 
beaded  appearance  aheady  referred  to.  Valves  are  wanting  in  the  vessels  composing  the  plexi- 
form  net -work  in  which  the  lymphatic  vessels  usually  originate  on  the  surface  of  the  body. 

The  lymph  glands  ilymiolioglandulae)  are  small  oval  or  bean-shaped  bodies,  situ- 
ated in  the  course  of  lymphatic  and  lacteal  vessels  so  that  the  lymph  and  chyle 
pass  through  them  on  their  way  to  the  blood.  Each  generally  presents  on  one  side 
a  slight  depression — the  hilus — through  which  the  bloodvessels  enter  and  leave  the 
interior.  The  efferent  lymphatic  vessel  also  emerges  from  the  gland  at  this  spot, 
while  the  aff'erent  vessels  enter  the  organ  at  different  parts  of  the  periphery.  On 
section  (Fig.  652)  a  lymph  gland  displays  two  different  structures:  an  external, 


STRCCTCRE  OF  LYMJ'JI  GLANDS 


"09 


of  lighter  color — the  cortical;  and  an  internal,  darker — the  medullary.  The  cortical 
structure  does  not  form  a  complete  investment,  but  is  deficient  at  the  hilum, 
where  the  medullary  portion  reaches  the  surface  of  the  gland;  so  that  the  efl'erent 
vessel  is  derived  directly  from  the  medullary  structures,  while  the  afferent  vessels 
empty  themselves  into  the  cortical  substance. 


Lymphoid 

tissue  in 

cortex 


Svbcaps^dar 
hjmph-path 


Lymjyh-path 
in  medulla 


Fig.  652. — Section  of  small  lymph  gland  of  rabbit.      X  100. 

Structure  of  Lymph  Glands. — A  lymph  gland  consists  of  (1)  a  fibrous  envelope,  or  capsule, 
from  wliicli  a  frame-work  of  processes  (trabeculce)  proceeds  inward,  imperfectly  dividing  the 
gland  into  open  spaces  freely  communicating  with  each  other;  (2)  a  quantity  of  lymphoid  tissue 
occupying  these  spaces  without  completely  filUng  them;  (3)  a  free  supply  of  bloodvessels,  which 


Fig.  6-53. — Lymph  gland  tissue.     Highly  magnified,     a,  Trabeculae.     6.  Small  artery  in  substance  of  same, 
c.  Lymph  paths,     d.  Lymph  corpuscles,     e.  Capillary  plexus. 

are  supported  in  the  trabecule;  and  (4)  the  afferent  and  efferent  vessels  communicating  through 
the  Ij-mph  paths  in  the  substance  of  the  gland.  The  nerves  passmg  into  the  hilus  are  few  in 
number  and  are  chiefly  distributed  to  the  bloodvessels  supplying  the  gland. 

The  capsule  is  composed  of  connective  tissue  with  some  plain  muscle  fibres,  and  from  its  internal 

surface  are  given  off  a  number  of  membranous  processes  or  trabeculse,  consisting,  in  man,  of 

connective  tissue,  with  a  smaU  admixture  of  plain  muscle  fibres;  but  in  many  of  the  lower  animals 

composed  almost  entirely  of  involuntary  muscle.    Thej-  pass  inward,  radiating  toward  the  centre 

49 


770  ANGIOLOGY 

of  the  gland,  for  a  certain  distance — that  is  to  say,  for  about  one-third  or  one-fourth  of  the  space 
between  the  circumference  and  the  centre  of  the  gland.  In  some  animals  they  are  sufficiently 
well-marked  to  divide  the  peripheral  or  cortical  portion  of  the  gland  into  a  number  of  compart- 
ments (so-called  follicles),  but  in  man  this  arrangement  is  not  obvious.  The  larger  trabeculse 
springing  from  the  capsule  break  up  into  finer  bands,  and  these  interlace  to  form  a  mesh-work 
in  the  central  or  medullary  portion  of  the  gland.  In  these  spaces  formed  by  the  interlacing 
trabeculse  is  contained  the  proper  gland  substance  or  lymphoid  tissue.  The  gland  pulp  does 
not,  however,  completely  fill  the  spaces,  but  leaves,  between  its  outer  margin  and  the  enclosing 
trabecultp,  a  channel  or  space  of  uniform  width  throughout.  This  is  termed  the  lymph  path 
or  l3rmph  sinus  (Fig.  652).  Running  across  it  are  a  number  of  finer  trabecule  of  retiform  con- 
nective tissue,  the  fibres  of  which  are,  for  the  most  part,  covered  by  ramifying  cells. 

On  account  of  the  peculiar  arrangement  of  the  frame-work  of  the  organ,  the  gland  pulp  in  the 
cortical  portion  is  disposed  in  the  form  of  nodules,  and  in  the  medullary  part  in  the  form  of  rounded 
cords.  It  consists  of  ordinary  lymphoid  tissue  (Fig.  653),  being  made  up  of  a  delicate  net-work 
of  retiform  tissue,  which  is  continuous  with  that  in  the  lymph  paths,  but  marked  off  from  it 
by  a  closer  reticulation;  it  is  probable,  moreover,  that  the  reticular  tissue  of  the  gland  pulp  and 
the  lymph  paths  is  continuous  with  that  of  the  trabeculse,  and  ultimately  with  that  of  the  capsule 
of  the  gland.  In  its  meshes,  in  the  nodules  and  cords  of  lymphoid  tissue,  are  closely  packed 
lymph  corpuscles.  The  gland  pulp  is  traversed  by  a  dense  plexus  of  capillary  bloodvessels. 
The  nodules  or  follicles  in  the  cortical  portion  of  the  gland  frequently  show,  in  their  centres, 
areas  where  karyokinetic  figures  indicate  a  division  of  the  lymph  corpuscles.  These  areas  are 
termed  germ  centres.  The  ceUs  composing  them  have  more  abundant  protoplasm  than  the 
peripheral  cells. 

The  afferent  vessels,  as  stated  above,  enter  at  aU  parts  of  the  periphery  of  the  gland,  and  after 
branching  and  forming  a  dense  plexus  in  the  substance  of  the  capsule,  open  into  the  lymph  sinuses 
of  the  cortical  part.  In  doing  this  they  lose  aU  their  coats  except  their  endothelial  lining,  which 
is  continuous  with  a  layer  of  similar  cells  Uning  the  lymph  paths.  In  like  manner  the  efferent 
vessel  commences  from  the  lymph  sinuses  of  the  medidlary  portion.  The  stream  of  lymph  carried 
to  the  gland  by  the  afferent  vessels  thus  passes  through  the  plexus  in  the  capsule  to  the  lymph 
paths  of  the  cortical  portion,  where  it  is  exposed  to  the  action  of  the  gland  pulp ;  flowing  through 
these  it  enters  the  paths  or  sinuses  of  the  medullary  portion,  and  finally  emerges  from  the  hilus 
by  means  of  the  efferent  vessel.  The  stream  of  lymph  in  its  passage  through  the  lymph  sinuses 
is  much  retarded  by  the  presence  of  the  reticulum,  hence  morphological  elements,  either  normal 
or  morbid,  are  easily  arrested  and  deposited  in  the  sinuses.  Many  lymph  corpuscles  pass  with 
the  efferent  lymph  stream  to  join  the  general  blood  stream.  The  arteries  of  the  gland  enter 
at  the  hilus,  and  either  go  at  once  to  the  gland  pulp,  to  break  up  into  a  capillary  plexus,  or  else 
run  along  the  trabeculse,  partly  to  supply  them  and  partly  running  across  the  lymph  paths, 
to  assist  in  forming  the  capillary  plexus  of  the  gland  pulp.  This  plexus  traverses  the  lymphoid 
tissue,  but  does  not  enter  into  the  lymph  sinuses.  From  it  the  veins  commence  and  emerge 
from  the  organ  at  the  same  place  as  that  at  which  the  arteries  enter. 

The  lymphatic  vessels  are  arranged  into  a  superficial  and  a  deep  set.  On  the 
surface  of  the  body  the  superficial  lymphatic  vessels  are  placed  immediately 
beneath  the  integument,  accompanying  the  superficial  veins;  they  join  the  deep 
lymphatic  vessels  in  certain  situations  by  perforating  the  deep  fascia.  In  the 
interior  of  the  body  they  lie  in  the  submucous  areolar  tissue,  throughout  the  whole 
length  of  the  digestive,  respiratory,  and  genito-urinary  tracts;  and  in  the  subserous 
tissue  of  the  thoracic  and  abdominal  walls.  Plexiform  networks  of  minute  lym- 
phatic vessels  are  found  interspersed  among  the  proper  elements  and  bloodvessels 
of  the  several  tissues;  the  vessels  composing  the  net-work,  as  well  as  the  meshes 
between  them,  are  much  larger  than  those  of  the  capillary  plexus.  From  these 
net-works  small  vessels  emerge,  which  pass,  either  to  a  neighboring  gland,  or  to 
join  some  larger  lymphatic  trunk.  The  deep  lymphatic  vessels,  fewer  in  number, 
but  larger  than  the  superficial,  accompany  the  deep  bloodvessels.  Their  mode  of 
origin  is  probably  similar  to  that  of  the  superficial  vessels.  The  lymphatic  vessels 
of  any  part  or  organ  exceed  the  veins  in  number,  but  in  size  they  are  much  smaller. 
Their  anastomoses  also,  especially  those  of  the  large  trunks,  are  more  frequent, 
and  are  effected  by  vessels  equal  in  diameter  to  those  which  they  connect,  the  con- 
tinuous trunks  retaining  the  same  diameter. 

Applied  Anatomy. — The  lymphatic  chaimels  and  lymph  glands  draining  any  infected  area 
of  the  body  are  very  liable  to  become  infected,  resulting  in  acute  or  chronic  lymphangitis  and 
lymphadenitis.     In  acute  cases  the  paths  of  the  superficial  lymphatic  vessels  are  often  marked 


THE  THORACIC  DUCT  771 

out  on  the  skin  by  pain,  redness,  heat,  and  swelling,  while  the  glands  swell  and  may  suppurate. 
Chronic  inflammation  leads  to  growth  and  fibrosis  of  the  lymphatic  vessels  and  the  connective 
tissue  around  them;  obstruction  to  the  passage  of  the  lymph  results,  as  the  fibrous  tissue  contracts 
and  causes  stenosis  or  obliteration  of  the  lymphatic  channels,  and  hard  oedema  of  the  involved 
skin  and  subcutaneous  tissues  follows  {pachijdennia  hjnphancjiectalica) .  Chronic  lymphangitis, 
together  with  the  blocking  of  numerous  lymiihatic  vessels  by  the  escaped  ova  of  the  minute 
parasitic  worm  Microfilaria  nocturna,  is  the  cause  of  elephantiasis,  a  condition  common  in  the 
tropics  and  subtropics,  and  characterized  by  enormous  enlargement  and  thickening  of  the  integu- 
ments of  some  part  of  the  body,  most  frequently  of  the  leg.  Tubercular  and  syi)hihtic  enlarge- 
ments of  the  lymphatic  vessels  and  glands  are  both  very  commonly  met  with.  Primary  tumors 
of  the  lymphatic  vessels  are  lymphangioma  and  endothelioma;  the  so-called  "congenital  cystic 
hj'groma"  of  the  neck,  arm,  trunk,  or  thigh,  is  a  cystic  lymphangioma.  Primary  tumors  of  the 
lymph  glands  may  be  innocent  (lymphadenoma,  myxoma,  chondroma)  or  maUgnant  (lympho- 
sarcoma") ;  cancer  is  never  met  with  as  a  primary  affection,  but  is  extremely  common  secondarily 
to  cancer  of  some  other  part  of  the  body. 

The  appearance  of  secondary  mahgnant  deposits  or  of  secondary  infection  in  parts  of  the 
body  that  seem  not  to  be  directly  associated  by  any  lymphatic  connection  with  the  seat  of  the 
primary  growth  or  infection  has  often  been  observed,  and  explained  as  due  to  "retrograde  trans- 
port" of  cancer  cells  or  bacteria  by  a  reversed  flow  of  lymph.  Weleminsky,^  however,  believes 
that  the  explanation  is  to  be  found  in  the  fact  that  when  the  infected  glands  have  grown  to  a 
certain  size  they  no  longer  permit  the  normal  flow  of  lymph  through  them,  and  that  under  these 
circumstances  very  dehcate  lymphatic  connections,  whose  existence  normally  remains  imsus- 
pected,  develop  to  a  surprising  extent  between  groups  of  lymph  glands  that  at  first  sight  appear 
to  be  unconnected  with  one  another. 

THE   THORACIC   DUCT. 

The  thoracic  duct  {ductus  thoracicus)  (Fig.  654)  conveys  the  greater  part  of  the 
lymph  and  chyle  into  the  blood.  It  is  the  common  trunk  of  all  the  lymphatic 
vessels  of  the  body,  excepting  those  on  the  right  side  of  the  head,  neck,  and  thorax, 
and  right  upper  extremity,  the  right  lung,  right  side  of  the  heart,  and  the  convex 
surface  of  the  liver.  In  the  adult  it  varies  in  length  from  38  to  45  cm.  and  extends 
from  the  second  lumbar  vertebra  to  the  root  of  the  neck.  It  begins  in  the  abdomen 
by  a  triangular  dilatation,  the  cisterna  chyli,  which  is  situated  on  the  front  of  the 
body  of  the  second  lumbar  vertebra,  to  the  right  side  of  and  behind  the  aorta, 
by  the  side  of  the  right  crus  of  the  Diaphragma.  It  enters  the  thorax  through  the 
aortic  hiatus  of  the  Diaphragma,  and  ascends  through  the  posterior  mediastinal 
cavity  between  the  aorta  and  azygos  vein.  Behind  it  in  this  region  are  the  vertebral 
column,  the  right  intercostal  arteries,  and  the  hemiazygos  veins  as  they  cross  to 
open  into  the  azygos  vein;  in  front  of  it  are  the  Diaphragma,  oesophagus,  and  peri- 
cardium, the  last  being  separated  from  it  by  a  recess  of  the  right  pleural  cavity. 
Opposite  the  fifth  thoracic  vertebra,  it  inclines  toward  the  left  side,  enters  the  supe- 
rior mediastinal  cavity,  and  ascends  behind  the  aortic  arch  and  the  thoracic  part 
of  the  left  subclavian  artery  and  between  the  left  side  of  the  oesophagus  and  the 
left  pleura,  to  the  upper  orifice  of  the  thorax.  Passing  into  the  neck  it  forms  an 
arch  which  rises  about  3  or  4  cm.  above  the  clavicle  and  crosses  anterior  to  the 
subclavian  artery,  the  vertebral  artery  and  vein,  and  the  thyrocervical  trunk  or 
its  branches.  It  also  passes  in  front  of  the  phrenic  nerve  and  the  medial  border 
of  the  Scalenus  anterior,  but  is  separated  from  these  two  structures  by  the  pre- 
vertebral fascia.  In  front  of  it  are  the  left  common  carotid  artery,  vagus  nerve, 
and  internal  jugular  vein;  it  ends  by  opening  into  the  angle  of  junction  of  the  left 
subclavian  vein  with  the  left  internal  jugular  vein.  The  thoracic  duct,  at  its  com- 
mencement, is  about  equal  in  diameter  to  a  goose-quill,  but  it  diminishes  consid- 
erably in  calibre  in  the  middle  of  the  thorax,  and  is  again  dilated  just  before  its 
termination.  It  is  generally  flexuous,  and  constricted  at  intervals  so  as  to  present 
a  varicose  appearance.  Not  infrequently  it  divides  in  the  middle  of  its  course  into 
two  vessels  of  unequal  size  which  soon  reunite,  or  into  several  branches  which  form 

1  Berliner  klin.  Woch.,  1905,  No.  24,  p.  743. 


772 


ANGIOLOGY 


a  plexiform  interlacement.     It  occasionally  divides  at  its  upper  part  into  two 
branches,  right  and  left;  the  left  ending  in  the  usual  manner,  while  the  right  opens 

into  the  right   subclavian  vein,   in 
t^  connection  wdth  the  right  lymphatic 

duct.  The  thoracic  duct  has  several 
valves;  at  its  termination  it  is  pro- 
vided with  a  pair,  the  free  borders 
of  which  are  turned  toward  the  vein, 
so  as  to  prevent  the  passage  of 
venous  blood  into  the  duct. 

The  cisterna  chyli  (receptacvlum 
chyli)  (Fig.  655)  receives  the  two 
lumbar  lymphatic  trunks,  right  and 
left,  and  the  intestinal  lymphatic 
trunk.  The  lumbar  trunks  are  formed 
by  the  union  of  the  efferent  vessels 
from  the  lateral  aortic  lymph  glands. 
They  receive  the  lymph  from  the 
lower  limbs,  from  the  walls  and 
viscera  of  the  pelvis,  from  the  kid- 
neys and  suprarenal  glands  and  the 
deep  lymphatics  of  the  greater  part 
of  the  abdominal  wall.  The  intes- 
tinal trunk  receives  the  lymph  from 
the  stomach  and  intestine,  from  the 
pancreas  and  spleen,  and  from  the 
lower  and  front  part  of  the  liver. 

Tributaries.  —  Opening  into  the 
commencement  of  the  thoracic  duct, 
on  either  side,  is  a  descending  trunk 
from  the  posterior  intercostal  lymph 
glands  of  the  lower  six  or  seven  in- 
tercostal spaces.  In  the  thorax  the 
duct  is  joined,  on  either  side,  by  a 
trunk  which  drains  the  upper  lumbar 
lymph  glands  and  pierces  the  crus  of 
the  Diaphragma.  It  also  receives 
the  efferents  from  the  posterior 
mediastinal  lymph  glands  and  from 
the  posterior  intercostal  lymph 
glands  of  the  upper  six  left  spaces. 
In  the  neck  it  is  joined  by  the  left 
jugular  and  left  subclavian  trunks, 
and  sometimes  by  the  left  broncho- 
mediastinal trunk;  the  last-named, 
however,  usually  opens  indepen- 
dently into  the  junction  of  the  left 
subclavian  and  internal  jugular 
veins. 

The  right  lymphatic  duct  (ductus  lymyhaticus  dexter)  (Fig.  656),  about  1.25  cm. 
in  length,  courses  along  the  medial  border  of  the  Scalenus  anterior  at  the  root  of 
the  neck  and  ends  in  the  right  subclavian  vein,  at  its  angle  of  junction  with  the  right 
internal  jugular  vein.  Its  orifice  is  guarded  by  two  semilunar  valves,  which  pre^'ent 
the  passage  of  venous  blood  into  the  duct. 


Fig.  654. — The  thoricic  and  right  lymphatic  ducts. 


THE  THORACIC  DUCT 


773 


Tributaries. — The  right  ]yin])liatic'  diut  receives  the  lymph  from  the  right  side 
of  the  liead  and  neek  through  tlie  right  jugular  trunk;  from  the  riglit  upper  extremity 
through  the  right  subclavian  trunk;  from  the  right  side  of  the  thorax,  right  lung, 
right  side  of  the  heart,  and  part  of  the  convex  surface  of  the  liver,  through  the 
right  bronchomediastinal  trunk.  These  three  collecting  trunks  frequently  open 
separately  in  the  angle  of  union  of  the  two  veins. 


Fig.  655. — Modes  of  origin  of  thoracic  duct.  (Poirier  and  Charpy.)  a.  Thoracic  duct.  a'.  Cisterna  chyH.  6,  c. 
Efferent  trunks  from  lateral  aortic  glands,  d.  An  efferent  vessel  which  pierces  the  left  crus  of  the  diaphragm,  e,  f. 
Lateral  aortic  glands,    h.  Retroaortic  glands,   i.  Intestinal  trunk,    j.  Descending  branch  from  intercostal  lymphatics. 

Applied  Anatomy. — Blockage  of  the  thoracic  duct  by  mature  specimens  of  the  minute  parasitic 
worm  Microfilaria  nocturna  gives  rise  to  stasis  of  the  chyle,  and  to  its  passage  in  various  abnormal 
directions  on  its  course  past  the  obstruction.  The  neighboring  abdominal,  renal,  and  pelvic 
Ijanphatics  become  enlarged,  varicose,  and  tortuous,  and  chyle  may  make  its  way  into  the  urine 
(chyluria),  the  tunica  vaginalis  (chylocele),  the  abdominal  cavity  {chylous  ascites),  or  the  plem-al 
cavity  (chylous  pleural  effusion),  in  consequence  of  rupture  of  some  of  these  distended  lymphatic 
vessels. 


Fig.  656. — Terminal  collecting  trunks  of  right  side.      (Poirier  and  Charpy.)     a.  Jugular  trunk,     b. 
trunk,     c.  Bronchomediastinal  trunk,     d.  Right  lymphatic  trunk,     e.  Gland  of  internal  mammary  chain, 
of  deep  cervical  chain. 


The  thoracic  duct  may  be  secondarily  infected  in  intestinal  or  pulmonary  tuberculosis,  and 
may  contain  either  miliary  tubercles,  caseating  tuberculous  masses,  or  even  tuberculous  ulcers. 
It  is  often  the  seat  of  secondary  carcinomatous  deposits  in  cases  of  cancer  of  some  abdominal 
viscus,  becoming  infiltrated  throughout  imtil  it  becomes  a  stiff  moniliform  rod  as  thick  as  a  pencil, 
with  multiple  stenoses  and  dilatations  of  its  kunen;  in  such  cases  the  left  supraclavicidar  glands 
often  become  infected  and  enlarged,  while  the  lungs  remain  entirely  free  from  secondary  growths. 


774 


ANGIOLOGY 


THE  LYMPHATICS  OF  THE  HEAD,  FACE,  AND  NECK. 


The  Lymph  Glands  of  the  Head  (Fig.  657). 
The  lymph  glands  of  the  head  are  arranged  in  the  following  groups: 
Occipital.  Facial. 

Deep  Facial. 

Lingual. 

Retropharyngeal. 


Posterior  Auricular. 
Anterior  Auricular. 
Parotid. 


Posterior 

auricular r^ 

glands  \\ 

Occipital \\ 

glands 


^^  Maxillary  glaiids 


Parotid  glands 
Buccinator  glaiids 


Supramandihular 
glands 

Submaxillary 
glands 

Submental  glands 


'erior  dec-p 
cervical  glands 


Fig.  657.— Superficial  lymph  gland.s  and  lymphatic  vessels  of  head  and  neck. 

The  occipital  glands  (lymphoglandulae  occipitales),  one  to  three  in  number,  are 
placed  on  the  back  of  the  head  close  to  the  margin  of  the  Trapezius  and  resting 
on  the  insertion  of  the  Semispinalis  capitis.  Their  afferent  vessels  drain  the  occipi- 
tal region  of  the  scalp,  while  their  efferents  pass  to  the  superior  deep  cervical 
glands. 

The  posterior  auricular  glands  (lymphoglandulae  auriculares;  mastoid  glands), 
usually  two  m  number,  are  situated  on  the  mastoid  insertion  of  the  Sternocleido- 
mastoideus,  beneath  the  Auricularis  posterior.  Their  afferent  vessels  drain  the 
posterior  part  of  the  temporoparietal  region,  the  upper  part  of  the  cranial  surface 


THE  LYMPH  GLANDS  OF  THE  HEAD 


75 


of  the  auricula  or  pinna,  and  the  back  of  the  external  acoustic  meatus;  their 
eflerents  pass  to  the  superior  deep  cervical  glands. 

The  anterior  auricular  glands  (lymphoghutdulae  auricidares  anteriores;  suiwrficial 
parotid  or  prctniriciihtr  glands),  from  one  to  three  in  number,  lie  immediately  in 
front  of  the  tragus.  Their  ali'erents  drain  the  lateral  surface  of  the  auricula  and  the 
skin  of  the  adjacent  part  of  the  temporal  region;  their  efi'erents  pass  to  the  superior 
deep  cervical  glands. 

The  parotid  glands  (lymphoglandidae  parotidcae),  form  two  groups  in  relation 
with  the  parotid  salivary  gland,  viz.,  a  group  imbedded  in  the  substance  of  the  gland, 
and  a  group  of  subparotid  glands  lying  on  the  lateral  wall  of  the  pharynx.  Occa- 
sionally small  glands  are  found  in  the  subcutaneous  tissue  over  the  parotid  gland. 
Their  afferent  vessels  drain  the  root  of  the  nose,  the  eyelids,  the  frontotemporal 
region,  the  external  acoustic  meatus  and  the  tympanic  cavity,  possibly  also  the 
posterior  parts  of  the  palate  and  the  floor  of  the  nasal  cavity.  The  efferents  of 
these  glands  pass  to  the  superior  deep  cervical  glands.  The  afferents  of  the  sub- 
parotid  glands  drain  the  nasal  part  of  the  pharynx  and  the  posterior  parts  of  the 
nasal  cavities;  their  efferents  pass  to  the  superior  deep  cervical  glands.  ' 


Afferent  vessel  to  deep 
cervical  glands 


Glandular  nodule 

Gland  of  deep  cervical 

chain 
Efferent  vessels  of  retro- 
pharyngeal glands 


Fig.  658. — Lymphatics  of  pharj^nx.     (Poirier  and  Charpy.) 


The  facial  glands  comprise  three  groups :  (a)  infraorbital  or  maxillary,  scattered 
over  the  infraorbital  region  from  the  groove  between  the  nose  and  cheek  to  the 
zygomatic  arch;  (b)  buccinator,  one  or  more  placed  on  the  Buccinator  opposite  the 
angle  of  the  mouth;  (c)  supramandibular,  on  the  outer  surface  of  the  mandible, 
in  front  of  the  JNIasseter  and  in  contact  with  the  external  maxillary  artery  and 
anterior  facial  vein.  Their  efferent  vessels  drain  the  eyelids,  the  conjunctiva, 
and  the  skin  and  mucous  membrane  of  the  nose  and  cheek;  their  efferents  pass  to 
the  submaxillary  glands. 

The  deep  facial  glands  (lymphoglandulae  faciales  profunda;  internal  maxillary 
glands)  are  placed  beneath  the  ramus  of  the  mandible,  on  the  outer  surface  of  the 
Pterygoideus  externus,  in  relation  to  the  internal  maxillary  artery.  Their  afferent 
vessels  drain  the  temporal  and  infratemporal  fossae  and  the  nasal  part  of  the  pharynx 
their  efferents  pass  to  the  superior  deep  cervical  glands. 

The  lingual  glands  {lymplioglandulae  linguales)  are  two  or  three  small  nodules 
lying  on  the  Hyoglossus  and  under  the  Genioglossus.  They  form  merely  glandular 
substations  in  the  course  of  the  lymphatic  vessels  of  the  tongue. 


776 


ANGIOLOGY 


The  retropharyngeal  glands  (Fig.  658),  from  one  to  three  in  number,  lie  in  the 
buccopharyngeal  fascia,  behind  the  upper  part  of  the  pharynx  and  in  front  of  the 
arch  of  the  atlas,  being  separated,  however,  from  the  latter  by  the  Longus  capitis. 
Their  aft'erents  drain  the  nasal  cavities,  the  nasal  part  of  the  pharynx,  and  the 
auditory  tubes;  their  efferents  pass  to  the  superior  deep  cervical  glands. 

The  lymphatic  vessels  of  the  scalp  are  divisible  into  (a)  those  of  the  frontal  region, 
which  terminate  in  the  anterior  auricular  and  parotid  glands;  (b)  those  of  the 
temporoparietal  region,  which  end  in  the  parotid  and  posterior  auricular  glands; 
and  (c)  those  of  the  occipital  region,  which  terminate  partly  in  the  occipital 
glands  and  partly  in  a  trunk  w^hich  runs  down  along  the  posterior  border  of  the 
Sternocleidomastoideus  to  end  in  the  inferior  deep  cervical  glands. 

The  lymphatic  vessels  of  the  auricula  and  external  acoustic  meatus  are  also  divisible 
into  three  groups:  (a)  an  anterior,  from  the  lateral  surface  of  the  auricula  and 
anterior  wall  of  the  meatus  to  the  anterior  auricular  glands;  (b)  a  posterior,  from 
the  margin  of  the  auricula,  the  upper  part  of  its  cranial  surface,  the  internal  surface 
and  posterior  wall  of  the  meatus  to  the  posterior  auricular  and  superior  deep  cervical 
glands;  (c)  an  inferior,  from  the  floor  of  the  meatus  and  from  the  lobule  of  the  auric- 
ula to  the  superficial  and  superior  deep  cervical  glands. 


Parotid  glaiids 


Superficial  cervi- 
cal glands 


Facial  glands 


Submaxillary  glands 


Deep  cervical  glands 


Fig.  659. — The  lymphatics  of  the  face.     (After  Kiittner.) 

The  lymphatic  vessels  of  the  face  (Fig.  659)  are  more  numerous  than  those  of  the 
scalp.  Those  from  the  eyelids  and  conjunctiva  terminate  partly  in  the  submaxillary 
but  mainly  in  the  parotid  glands.  The  vessels  from  the  posterior  part  of  the  cheek 
also  pass  to  the  parotid  glands,  w^hile  those  from  the  anterior  portion  of  the  cheek, 
the  side  of  the  nose,  the  upper  lip,  and  the  lateral  portions  of  the  lower  lip  end  in 
the  submaxillary  glands.  The  deeper  vessels  from  the  temporal  and  infratemporal 
fosste  pass  to  the  deep  facial  and  superior  deep  cervical  glands.  The  deeper  vessels 
of  the  cheek  and  lips  end,  like  the  superficial,  in  the  submaxillary  glands.  Both 
superficial  and  deep  vessels  of  the  central  part  of  the  lower  lip  run  to  the  submental 
glands. 

The  lymphatic  vessels  of  the  nasal  cavities  can  be  injected  from  the  subdural 
and  subarachnoid  cavities.     Those  from  the  anterior  parts  of  the  nasal  cavities 


THE  LYMPH  GLANDS  OF  THE  HEAD 


communicate  with  the  \es.scls  of  the  integument  of  the  nose  and  end  in  the  sub- 
maxillary glands;  those  from  the  posterior  two-thirds  of  the  nasal  cavities  and 
from  the  accessory  air  sinuses  pass  partly  to  the  retropharyngeal  and  partly  to 
the  sui)erior  deej)  cervical  glands. 

Lymphatic  Vessels  of  the  Mouth. — The  vessels  of  the  gums  pass  to  the  submaxillary 
glands;  those  of  the  hard  plate  are  continuous  in  front  with  those  of  the  upper 
gum,  but  pass  backward  to  pierce  the  Constrictor  pharyngis  superior  and  end  in 
the  superior  deep  cervical  and  subparotid  glands;  those  of  the  soft  palate  pass 
backward  anil  lateralward  and  end  partly  in  the  retropharyngeal  and  subparotid, 
and  partly  in  the  superior  deep  cervical  glands.  The  vessels  of  the  anterior  part 
of  the  floor  of  the  mouth  pass  either  directly  to  the  inferior  glands  of  the  superior 
deep  cervical  group,  or  indirectly  through  the  submental  glands;  from  the  rest 
of  the  floor  of  the  mouth  the  vessels  pass  to  the  submaxillary  and  superior  deep 
cervical  glands. 


Vessels  from 
root  of  tongue 


Vessels  from 
margin  of 

tongue 


Principal 
gland  of 
tongue 


\  V  essels  from 
-'       apex 


Submental 
gland 

}  Trunks  from 
margin  of 
tongue 


—  Interrupting  nodule 


Supra  -  omoli  yo  id 
gland 


Fig.  660. — Lymphatics  of  the  tongue.      (Poirier.) 


The  lymphatic  vessels  of  the  palatine  tonsil,  usually  three  to  five  in  number, 
pierce  the  buccopharyngeal  fascia  and  constrictor  pharyngis  superior  and  pass 
between  the  Stylohyoideus  and  internal  jugular  vein  to  the  uppermost  of  the 
superior  deep  cervical  glands.  They  end  in  a  gland  which  lies  at  the  side  of  the 
posterior  belly  of  the  Digastricus,  on  the  internal  jugular  vein;  occasionally  one 
or  two  additional  vessels  run  to  small  glands  on  the  lateral  .side  of  the  vein  under 
cover  of  the  Sternocleidomastoideus. 


778  ANGIOLOGY 

The  lymphatic  vessels  of  the  tongue  (Fig.  660)  are  drained  chiefly  into  the  deep 
cervical  glands  lying  between  the  posterior  belly  of  the  Digastricus  and  the  superior 
belly  of  the  Omohyoideus;  one  gland  situated  at  the  bifurcation  of  the  common 
carotid  artery  is  so  intimately  associated  with  these  vessels  that  it  is  known  as  the 
principal  gland  of  the  tongue.  The  lymphatic  vessels  of  the  tongue  may  be  divided 
into  four  groups:  (1)  apical,  from  the  tip  of  the  tongue  to  the  suprahyoid  glands 
and  principal  gland  of  the  tongue;  (2)  lateral,  from  the  margin  of  the  tongue — 
some  of  these  pierce  the  Mylohyoideus  to  end  in  the  submaxillary  glands,  others 
pass  down  on  the  Hyoglossus  to  the  superior  deep  cervical  glands;  (3)  basal,  from 
the  region  of  the  papillae  A'allatae  to  the  superior  deep  cervical  glands;  and  (4) 
■  median,  a  few  of  which  perforate  the  Mylohyoideus  to  reach  the  submaxillary 
glands,  -while  the  majority  turn  around  the  posterior  border  of  the  muscle  to 
enter  the  superior  deep  cervical  glands. 

The  Lymph  Glands  of  the  Neck. 

The  lymph  glands  of  the  neck  include  the  following  groups: 

Submaxillary.  Superficial  Cervical. 

Submental.  Anterior  Cer\dcal. 

Deep  Cervical. 

The  submaxillary  glands  (lymphoglandulae  submaxillares)  (Fig.  659),  three  to 
six  in  number,  are  placed  beneath  the  body  of  the  mandible  in  the  submaxillary 
triangle,  and  rest  on  the  superficial  surface  of  the  submaxillary  salivary  gland. 
One  gland,  the  middle  gland  of  Stahr,  which  lies  on  the  external  maxillary  artery 
as  it  turns  over  the  mandible,  is  the  most  constant  of  the  series;  small  lymph  glands 
are  sometimes  found  on  the  deep  surface  of  the  submaxillary  salivary  glands.  The 
afferents  of  the  submaxillary  glands  drain  the  medial  palpebral  commissure, 
the  cheek,  the  side  of  the  nose,  the  upper  lip,  the  lateral  part  of  the  lower  lip, 
the  gums,  and  the  anterior  part  of  the  margin  of  the  tongue;  efferent  vessels 
from  the  facial  and  submental  glands  also  enter  the  submaxillary  glands.  Their 
efferent  vessels  pass  to  the  superior  deep  cervical  glands. 

The  submental  or  suprahyoid  glands  are  situated  between  the  anterior  bellies 
of  the  Digastrici.  Their  af!'erents  drain  the  central  portions  of  the  lower  lip  and 
floor  of  the  mouth  and  the  apex  of  the  tongue;  their  efferents  pass  partly  to  the 
submaxillary  glands  and  partly  to  a  gland  of  the  deep  cervical  group  situated  on 
the  internal  jugular  vein  at  the  level  of  the  cricoid  cartilage. 

The  superficial  cervical  glands  (lymphoglandulae  cervicales  superficiahs)  lie  in 
close  relationship  with  the  external  jugular  vein  as  it  emerges  from  the  parotid 
gland,  and,  therefore,  superficial  to  the  Sternocleidomastoideus.  Their  afferents 
drain  the  lower  parts  of  the  auricula  and  parotid  region,  while  their  efferents  pass 
around  the  anterior  margin  of  the  Sternocleidomastoideus  to  join  the  superior  deep 
cervical  glands. 

The  anterior  cervical  glands  form  an  irregular  and  inconstant  group  on  the  front 
of  the  larynx  and  trachea.  They  may  be  divided  into  (a)  a  superficial  set,  placed 
on  the  anterior  jugular  vein;  (b)  a  deeper  set,  which  is  further  subdivided  into 
prelarATigeal,  on  the  middle  cricothyroid  ligament,  and  pretracheal,  on  the  front 
of  the  trachea.  This  deeper  set  drains  the  lower  part  of  the  larynx,  the  thyroid 
gland,  and  the  upper  part  of  the  trachea;  its  efferents  pass  to  the  lowest  of  the 
superior  deep  cervical  glands. 

The  deep  cervical  glands  (lymphoglandidae  cervicales  profundae)  (Figs.  657, 
660)  are  numerous  and  of  large  size :  they  form  a  chain  along  the  carotid  sheath, 
lying  by  the  side  of  the  pharynx,  oesophagus,  and  trachea,  and  extending  from  the 
base  of  the  skull  to  the  root  of  the  neck.    They  are  usually  described  in  two  groups: 


THE  LYMPH  GLANDS  OF  THE  UPPER  EXTREMITY  779 

d)  the  superior  deep  cervical  glands  lying  under  the  Sternocleidomastoideus  in 
close  rehition  with  the  accessory  nerve  and  the  internal  iugular  vein,  some  of  the 
glands  lying  in  front  of  and  others  behind  the  vessel;  (2)  the  inferior  deep  cervical 
glands  extentling  i)eyond  the  posterior  margin  of  the  Sternocleidomastoideus 
into  the  supraclavicular  triangle,  where  they  are  closely  related  to  the  brachial 
plexus  and  subclavian  vein.  A  few  minute  paratracheal  glands  are  situated  along- 
side the  recurrent  nerves  on  the  lateral  aspects  of  the  trachea  and  oesophagus. 
The  superior  deep  cervical  glands  drain  the  occipital  portion  of  the  scalp,  the 
auricula,  the  back  of  the  neck,  a  considerable  part  of  the  tongue,  the  larynx,  thyroid 
gland,  trachea,  nasal  part  of  the  pharynx,  nasal  cavities,  palate,  and  oesophagus. 
They  receive  also  the  efferent  vessels  from  all  the  other  glands  of  the  head  and 
neck,  except  those  from  the  inferior  deep  cervical  glands.  The  inferior  deep  cervical 
glands  drain  the  back  of  the  scalp  and  neck,  the  superficial  pectoral  region,  part 
of  the  arm  (see  page  782),  and,  occasionally,  part  of  the  superior  surface  of  the 
liver.  In  addition,  the}'  receive  vessels  from  the  superior  deep  cervical  glands. 
The  efferents  of  the  superior  deep  cervical  glands  pass  partly  to  the  inferior  deep 
cervical  glands  and  partly  to  a  trunk  which  unites  with  the  efferent  vessel  of  the 
inferior  deep  cervical  glands  and  forms  the  jugular  trunk.  On  the  right  side,  this 
trunk  ends  in  the  junction  of  the  internal  jugular  and  subclavian  veins;  on  the  left 
side  it  joins  the  thoracic  duct. 

The  lymphatic  vessels  of  the  skin  and  muscles  of  the  neck  pass  to  the  deep  cervical 
glands.  From  the  upper  part  of  the  pharynx  the  lymphatic  vessels  pass  to  the  retro- 
pharyngeal, from  the  lower  part  to  the  deep  cervical  glands.  From  the  larynx 
two  sets  of  vessels  arise,  an  upper  and  a  lower.  The  vessels  of  the  upper  set  pierce 
the  hyothyroid  membrane  and  join  the  superior  deep  cer\acal  glands.  Of  the 
lower  set,  some  pierce  the  conus  elasticus  and  join  the  pretracheal  and  pre- 
laryngeal glands;  others  run  between  the  cricoid  and  first  tracheal  ring  and  enter 
the  inferior  deep  cervical  glands.  The  h-mphatic  vessels  of  the  thyroid  gland  con- 
sist of  two  sets,  an  upper,  which  accompanies  the  superior  th^Toid  artery  and  enters 
the  superior  deep  cervical  glands,  and  a  lower,  which  runs  partly  to  the  pretracheal 
glands  and  partly  to  the  small  paratracheal  glands  which  accompany  the  recurrent 
nerves.  These  latter  glands  receive  also  the  lymphatic  vessels  from  the  cervical 
portion  of  the  trachea. 

Applied  Anatomy. — The  cerWcal  glands  are  very  frequently  the  seat  of  tuberculous  disease. 
This  condition  is  most  usually  set  up  by  some  lesion  in  those  parts  from  which  they  receive  their 
lymph.  It  is  very  desirable  therefore  for  the  sm-geon,  ia  deahng  with  these  cases,  to  possess  a 
knowledge  of  the  relation  of  the  respective  groups  of  glands  to  the  peripher3%  while  in  order  to 
eradicate  them  by  operation  a  long  and  difficult  dissection  maj-  be  required. 

THE   LYMPHATICS   OF   THE  UPPER   EXTREMITY. 

The  Lymph  Glands  of  the  Upper  Extremity  (Fig.  661). 

The  lymph  glands  of  the  upper  extremity  are  divided  into  two  sets,  superficial 
and  deep. 

The  superficial  lymph  glands  are  few  and  of  small  size.  One  or  two  supra- 
trochlear glands  are  placed  above  the  medial  epicondyle  of  the  humerus,  medial 
to  the  basilic  vein.  Their  afferents  drain  the  middle,  ring,  and  little  fingers,  the 
medial  portion  of  the  hand,  and  the  superficial  area  over  the  ulnar  side  of  the  fore- 
arm; these  vessels  are,  however,  in  free  communication  with  the  other  lymphatic 
vessels  of  the  forearm.  Their  efferents  accompany  the  basilic  vein  and  join  the 
deeper  vessels.  One  or  two  deltoideopectoral  glands  are  found  beside  the  cephalic 
vein,  between  the  Pectoralis  major  and  Deltoideus,  immediately  below  the  clavicle. 
They  are  situated  in  the  course  of  the  external  collecting  trunks  of  the  arm. 


780 


ANGIOLOGY 


The  deep  lymph  glands  are  chiefly  grouped  in  the  axilla,  although  a  few  may 
be  found  in  the  forearm,  in  the  course  of  the  radial,  ulnar,  and  interosseous  vessels, 
and  in  the  arm  along  the  medial  side  of  the  brachial  artery. 


Deltoideo- 
pectoral 
glayids 


Axillary  glands 


Fig.  661. — The  superficial  lymph  glands  and  lymphatic  vessels  of  the  upper  extremity. 


The  Axillary  Glands  {lymphoglandulae  axillares)  (Fig.  662)  are  of  large  size,  vary 
from  twent}^  to  thirty  in  number,  and  may  be  arranged  in  the  following  groups: 

1.  A  lateral' group  of  from  four  to  six  glands  lies  in  relation  to  the  medial  and 
posterior  aspects  of  the  axillary  vein;  the  afferents  of  these  glands  drain  the  whole 
arm  with  the  exception  of  that  portion  whose  vessels  accompany  the  cephalic 
vein.  The  efferent  vessels  pass  partly  to  the  central  and  subclavicular  groups  of 
axillary  glands  and  partly  to  the  inferior  deep  cervical  glands. 

2.  An  anterior  or  pectoral  group  consists  of  four  or  five  glands  along  the  lower 
border  of  the  Pectoralis  minor,  in  relation  with  the  lateral  thoracic  artery.  Their 
afferents  drain  the  skin  and  muscles  of  the  anterior  and  lateral  thoracic  walls, 
and  the  central  and  lateral  parts  of  the  mamma;  their  efferents  pass  partly  to  the 
central  and  partly  to  the  subclavicular  groups  of  axillary  glands. 


THE  LYMPHATIC  VESSELS  OF  THE  UPPER  EXTREMITY 


781 


3.  A  posterior  or  subscapular  group  of  six  or  seven  glands  is  placed  along  the  lower 
margin  of  the  posterior  wall  of  the  axilla  in  the  course  of  the  subscapular  artery. 
The  atferents  of  this  group  drain  the  skin  and  muscles  of  the  lower  part  of  the  back 
of  the  neck  and  of  the  posterior  thoracic  wall;  their  efferents  pass  to  the  central 
group  of  axillary  glands. 

4.  A  central  or  intermediate  group  of  three  or  four  large  glands  is  imbedded  in 
the  adipose  tissue  near  the  base  of  the  axilla.  Its  aft'erents  are  the  efl'erent  vessels 
of  all  the  preceding  groups  of  axillary  glands;  its  eft'erents  pass  to  the  subclavicular 
group. 

Lateral  group 
Deltoideopcctoral  glands    ,— 


^l  a  I  lunar  y  hjmphaiic 

ending  in 
svbclavicular  glands 


Pectoral  group 
Matnmary  collecting 
trunks 


Subareolar  plexus 


Cidaneous  collecting  trunk 
from  the  thorccic  icall 


Cutaneous  collecting 
flunks 


Collecting  trunks 
passing  to  internal 
mammary  glands 

Fig.  662. — Lymphatics  of  the  mamma,  and  the  axillary  glands  (semidiagrammatic) .     (Poirier  and  Charpj-.) 


5.  A  medial  or  subclavicular  group  of  six  to  twelve  glands  is  situated  partly 
posterior  to  the  upper  portion  of  the  Pectoralis  minor  and  partly  above  the  upper 
border  of  this  muscle.  Its  only  direct  territorial  aff  erents  are  those  which  accompany 
the  cephalic  vein  and  one  which  drains  the  upper  peripheral  part  of  the  mamma, 
but  it  receives  the  efferents  of  all  the  other  axillary  glands.  The  efferent  vessels 
of  the  subclavicular  group  unite  to  form  the  subclavian  trunk,  which  opens  either 
directly  into  the  junction  of  the  internal  jugular  and  subclavian  veins  or  into  the 
jugular  lymphatic  trunk;  on  the  left  side  it  may  end  in  the  thoracic  duct.  A  few 
efferents  from  the  subclavicular  glands  usually  pass  to  the  inferior  deep  cervical 
glands. 

Applied  Anatomy. — In  malignant  disease  or  infectious  processes  implicating  the  upper  part 
of  the  back  and  shoulder,  the  front  of  the  chest  and  mamma,  the  upper  part  of  the  front  and  side 
of  the  abdomen,  or  the  hand,  forearm,  and  arm,  enlargement  of  the  axillary  glands  is  very  often 
found. 

The  Lymphatic  Vessels  of  the  Upper  Extremity. 

The  lymphatic  vessels  of  the  upper  extremity  are  divided  into  two  sets,  super- 
ficial and  deep. 

The  superficial  lymphatic  vessels  commence  (Fig.  663)  in  the  lymphatic  plexus 
which  everj-where  pervades  the  skin;  the  meshes  of  the  plexus  are  much  finer  in  the 


782 


ANGIOLOGY 


palm  and  on  the  flexor  aspect  of  the  digits  than  elsewhere.    The  digital  plexuses 
are  drained  by  a  pair  of  vessels  which  run  on  the  sides  of  each  digit,  and  incline 

backward  to  reach  the  dorsum  of  the 
hand.  From  the  dense  plexus  of  the 
palm,  vessels  pass  in  different  direc- 
tions, viz.,  upward  toward  the  wrist, 
downward  to  join  the  digital  vessels, 
medialward  to  join  the  vessels  on  the 
ulnar  border  of  the  hand,  and  lateral- 
ward  to  those  on  the  thumb.  Sev- 
eral vessels  from  the  central  part  of 
the  plexus  unite  to  form  a  trunk, 
which  passes  around  the  metacarpal 
bone  of  the  index  finger  to  join  the 
vessels  on  the  back  of  that  digit  and 
on  the  back  of  the  thumb.  Running 
upward  in  front  of  and  behind  the 
wrist,  the  lymphatic  vessels  are  col- 
lected into  radial,  median,  and  ulnar 
groups,  which  accompany'  respectively 
the  cephalic,  median,  and  basilic  veins 
in  the  forearm.  A  few  of  the  ulnar 
lymphatics  end  in  the  supratrochlear 
glands,  but  the  majority  pass  directly 
to  the  lateral  group  of  axillary 
glands.  Some  of  the  radial  vessels 
are  collected  into  a  trunk  which 
ascends  wdth  the  cephalic  vein  to  the 
deltoideopectoral  glands;  the  efferents 
from  this  group  pass  either  to  the 
subclavicular  axillary  glands  or  to 
the  inferior  cervical  glands. 
The  deep  lymphatic  vessels  accompany  the  deep  bloodvessels.  In  the  fore- 
arm, they  consist  of  four  sets,  corresponding  with  the  radial,  ulnar,  volar,  and 
dorsal  interosseous  arteries;  they  communicate  at  intervals  with  the  superficial 
lymphatics,  and  some  of  them  end  in  the  glands  which  are  occasionally  found  beside 
the  arteries.  In  their  course  upward,  a  few  end  in  the  glands  which  lie  upon  the 
brachial  artery;  but  most  of  them  pass  to  the  lateral  group  of  axillary  glands. 


FlG. 


663. — Lymphatic  vessels  of   the  dorsal   surface  of  the 
hand.     (Sappey.) 


THE  LYMPHATICS   OF  THE  LOWER  EXTREMITY. 


The  Lymph  Glands  of  the  Lower  Extremity. 

The  lymph  glands  of  the  lower  extremity  consist  of  the  anterior  tibial  gland 
and  the  popliteal  and  inguinal  glands. 

The  anterior  tibial  gland  (lymphoglandula  tibialis  anterior)  is  small  and  incon- 
stant. It  lies  on  the  interosseous  membrane  in  relation  to  the  upper  part  of  the 
anterior  tibial  vessels,  and  constitutes  a  substation  in  the  course  of  the  anterior 
tibial  lymphatic  trunks. 

The  popliteal  glands  (lymphoglandulae  popliteae)  (Fig.  664),  small  in  size  and 
some  six  or  seven  in  number,  are  imbedded  in  the  fat  contained  in  the  popliteal 
fossa.  One  lies  immediately  beneath  the  popliteal  fascia,  near  the  terminal  part 
of  the  small  saphenous  vein,  and  drains  the  region  from  which  this  vein  derives 


THE  LYMPH  GLANDS  OF  THE  LOWER  EXTREMITY 


783 


its  tributaries.  Another  is  placed  between  the  popliteal  artery  and  the  posterior 
surface  of  the  knee-joint;  it  receives  the  lymphatic  vessels  from  the  knee-joint 
together  with  those  which  accompany  the  genicular  arteries.  The  others  lie  at 
the  sides  of  the  popliteal  vessels,  and  receive  as  efl'erents  the  trunks  which  accom- 
pany the  anterior  and  posterior  tibial  vessels.  The  efferents  of  the  popliteal  glands 
pass  almost  entirely  alongside  the  femoral  vessels  to  the  deep  inguinal  glands,  but 
a  few  may  accompany  the  great  saphenous  vein,  and  end  in  the  glands  of  the 
superficial  subinguinal  group. 

The  inguinal  glands  {hjmphoglandulae  mguinales)  (Fig.  665),  from  twelve  to 
twenty  in  number,  are  situated  at  the  upper  part  of  the  femoral  triangle.  They 
may  be  divided  into  two  groups  by  a  horizontal  line  at  the  level  of  the  termination 
of  the  great  saphenous  vein;  those  lying  above  this  line  are  termed  the  superficial 
inguinal  glands,  and  those  below  it  the  subinguinal  glands,  the  latter  group  consisting 
of  a  superficial  and  a  deep  set. 


^  —  Tibial  nerve 
—  Popliteal  vein 

Popliteal  artery 
Common  peronceal  nerve 

Gland  at  side  of  popliteal 
vessels 


Gland  on   back  of  knee 

joint 

Gland  at  termination  of 

small  saph.  vein 


Fig.  664. — Lymph  glands  of  popliteal  fossa.     (Poirier  and  Charpy.) 

The  Superficial  Inguinal  Glands  form  a  chain  immediately  below  the  inguinal 
ligament.  They  receive  as  afferents  lymphatic  vessels  from  the  integument  of 
the  penis,  scrotum,  perineum,  buttock,  and  abdominal  wall  below  the  level  of  the 
umbilicus. 

The  Superficial  Subinguinal  Glands  (lymphoglandulae  suhinguinales  superficiales) 
are  placed  on  either  side  of  the  upper  part  of  the  great  saphenous  vein;  their 
efferents  consist  chiefly  of  the  superficial  lymphatic  vessels  of  the  lower  extremity; 
but  they  also  receive  some  of  the  vessels  which  drain  the  integument  of  the  penis, 
scrotum,  perineum,  and  buttock. 

The  Deep  Subinguinal  Glands  (lyviphoglandulae  suhinguinales  profundae)  vary 
from  one  to  three  in  number,  and  are  placed  under  the  fascia  lata,  on  the  medial 
side  of  the  femoral  vein.  When  three  are  present,  the  lowest  is  situated  just  below 
the  junction  of  the  great  saphenous  and  femoral  veins,  the  middle  in  the  femoral 
canal,  and  the  highest  in  the  lateral  part  of  the  femoral  ring.  The  middle  one  is 
the  most  inconstant  of  the  three,  but  the  highest,  the  gland  of  Cloquet  or  Rosenmiiller, 


784 


ANGIOLOGY 


.Ouperficial 
ingmnal  ■ 
glands 


Sicperficial 

suhinguinal- 

glands 


\-i=^ 


is  also  frequently  absent.  They  receive 
as  afferents  the  deep  lymphatic  trunks 
which  accompany  the  femoral  vessels, 
the  h'mphatics  from  the  glans  penis  vel 
clitoridis,  and  also  some  of  the  efferents 
from  the  superficial  subinguinal  glands. 

Applied  Anatomy. — Inflammation  and  sup- 
puration of  the  popliteal  glands  are  most  com- 
monly due  to  a  sore  on  the  lateral  side  of  the 
heel. 

The  inguinal  and  subinguinal  glands  fre- 
quently become  enlarged  in  diseases  implicat- 
ing the  parts  from  which  their  lymphatic 
vessels  originate.  Thus  in  mahgnant  or  syphi- 
litic affections  of  the  prepuce  and  penis,  or 
labia  majora,  in  cancer  of  the  scrotum,  in 
abscess  in  the  perineum,  or  in  similar  diseases 
affecting  the  integument  and  superficial  struc- 
tures in  those  parts,  or  the  subumbilical  part 
of  the  abdominal  wall,  or  the  gluteal  region,  the 
upper  group  of  glands  is  almost  invariably  en- 
larged, the  lower  groups  being  implicated  in 
diseases  affecting  the  lower  limb. 


'<)        ^ 


Fig.  665- 


-The  superficial  lymph  glands  and  lymphatic 
vessels  of  the  lower  extremity. 


The  Lymphatic  Vessels  of  the  Lower 
Extremity. 

The  lymphatic  vessels  of  the  lower 
extremity  consist  of  two  sets,  superficial 
and  deep,  and  in  their  distribution  corre- 
spond closely  with  the  veins. 

The  superficial  lymphatic  vessels  lie 
in  the  superficial  fascia,  and  are  divi- 
sible into  two  groups:  a  medial,  which 
follows  the  course  of  the  great  saphenous 
vein,  and  a  lateral,  which  accompanies 
the  small  saphenous  vein.  The  vessels 
of  the  medial  group  (Fig.  665)  are  larger 
and  more  numerous  than  those  of  the 
lateral  group,  and  commence  on  the 
tibial  side  and  dorsum  of  the  foot ;  they 
ascend  both  in  front  of  and  behind  the 
medial  malleolus,  run  up  the  leg  with  the 
great  saphenous  vein,  pass  with  it  behind 
the  medial  condyle  of  the  femur,  and 
accompany  it  to  the  groin,  where  they 
end  in  the  subinguinal  group  of  super- 
ficial glands.  The  vessels  of  the  lateral 
group  arise  from  the  fibular  side  of  the 
foot;  some  ascend  in  front  of  the  leg, 
and,  just  below  the  knee,  cross  the  tibia 
to  join  the  lymphatics  on  the  medial  side 
of  the  thigh;  others  pass  behind  the 
lateral  malleolus,  and,  accompanying  the 
small  saphenous  vein,  enter  the  popliteal 
glands. 


THE  LYMPH  GLANDS  OF  THE  ABDOMEN  AND  PELVIS 


785 


The  deep  lymphatic  vessels  arc  few  in  number,  and  accompany  the  deep  blood- 
vessels. In  the  leg,  they  consist  of  three  sets,  the  anterior  tibial,  posterior  tibial, 
and  peroneal,  which  accompany  the  corresponding  bloodvessels,  two  or  three  with 
each  artery;  they  enter  the  popliteal  lymi)h  glands. 

The  deep  lymphatic  vessels  of  the  gluteal  and  ischial  regions  follow  the  course 
of  the  corresponding  bloodvessels.  Those  accompanying  the  superior  gluteal 
vessels  end  in  a  gland  which  lies  on  the  intrapelvic  portion  of  the  superior  gluteal 
artery  near  the  upper  border  of  the  greater  sciatic  foramen.  Those  following 
the  inferior  gluteal  vessels  traverse  one  or  two  small  glands  which  lie  below  the 
Piriformis  muscle,  and  end  in  the  hypogastric  glands. 


Rigid  lateral  aoitic 


Lift  latual  ao)tic 

C'Gmmoii  lUac 


Gland  m 

front  of  iucnd 

promonto)  y 

Coimnon  iliac  ■ 


External  iliac 


Common 
iliac 


External  iliac 


p—  External  iliac 


Obturator  atiti 


Obturator  gland 


Fig.  666. — The  parietal  lymph  glands  of  the  pelvis.     (Cun^o  and  Marcille.) 


THE   LYMPHATICS   OF   THE   ABDOMEN   AND   PELVIS. 


The  Lymph  Glands  of  the  Abdomen  and  Pelvis. 

The  lymph  glands  of  the  abdomen  and  pelvis  may  be  divided,  from  their  situa- 
tions, into  {a)  parietal,  lying  behind  the  peritoneum  and  in  close  association  with 
the  larger  bloodvessels;  and  (h)  visceral,  which  are  found  in  relation  to  the  visceral 
arteries. 
50 


786 


ANGIOLOGY 


The  parietal  glands  (Figs.  666,  667)  include  the  following  groups: 


Iliac  Circumflex. 

Hypogastric. 

Sacral. 


[Lateral  Aortic. 
Lumbar  -  Preaortic. 

iRetroaortic. 


External  IHac. 
Common  Iliac. 
Epigastric. 

The  External  Iliac  Glands,  from  eight  to  ten  in  number,  lie  along  the  external 
iUac  vessels.  They  are  arranged  in  three  groups,  one  on  the  lateral,  another 
on  the  medial,  and  a  third  on  the  anterior  aspect  of  the  vessels;  the  third  group  is, 
however,  sometimes  absent.  Their  principal  afferents  are  derived  from  the  inguinal 
and  subinguinal  glands,  the  deep  lymphatics  of  the  abdominal  wall  below  the  umbili- 
cus and  of  the  adductor  region  of  the  thigh,  and  the  lymphatics  from  the  glans 
penis  vel  clitoridis,  the  membranous  urethra,  the  prostate,  the  fundus  of  the  bladder, 
the  cervix  uteri,  and  upper  part  of  the  vagina. 


Hypogastric 


Qland  in  front  of 
sacral  promontory  / 


Lateral  sacral 


External  iliac 
glands 


Internal  lymphatic>>  of 

bladder 

Lyynphatic  from  glans 

penis 


Lymphatics  ofhladdei 


Hypogastric 

Satellite  trunk  of 
internal  puden- 


i       dal  vessels. 


Trunk  of  middle 
hcemorrhoidal 
vessels. 


Pioitatic  collecting  trunk 
Uiethial  collecting  ttunks 

Glandular  nodule  mfiont  of  symphysis  Piostatic  collectinq  trunk 

Fig.  667. — Uiopelvic  glands  (lateral  view) .     (Cun6o  and  Marcille.) 

The  Common  Iliac  Glands,  four  to  six  in  number,  are  grouped  behind  and  on  the 
sides  of  the  common  iliac  artery,  one  or  two  being  placed  below  the  bifurcation 
of  the  aorta,  in  front  of  the  fifth  lumbar  vertebra.  They  drain  chiefly  the  hypo- 
gastric and  external  iliac  glands,  and  their  efferents  pass  to  the  lateral  aortic  glands. 

The  Epigastric  Glands  {lymphoglandulae  eingastricae) ,  three  or  four  in  number, 
are  placed  alongside  the  lower  portion  of  the  inferior  epigastric  vessels. 

The  Iliac  Circumflex  Glands,  two  to  four  in  number,  are  situated  along  the  course 
of  the  deep  iliac  circumflex  vessels;  they  are  sometimes  absent. 

The  Hypogastric  Glands  (lymphoglandulae  hypogastricae;  internal  iliac  gland) 
(Fig.  667)  surround  the  hypogastric  vessels,  and  receive  the  lymphatics  corre- 
sponding to  the  distribution  of  the  branches  of  the  hypogastric  artery,  i.  e.,  they 
receive  lymphatics  from  all  the  pelvic  viscera,  from  the  deeper  parts  of  the  perineum, 


THE  LYMPHATIC  VESSELS  OF  THE  ABDOMEN  AND  PELVIS      787 

including-  the  nu'nihranoiis  and  ca^•crn()ll.s  portions  of  the  urethra,  and  from  the 
l)uttock  and  back  of  the  thigh.  An  obturator  gland  is  sometimes  seen  in  the  upper 
part  of  the  obturator  foramen. 

The  Sacral  Glands  are  phiced  in  the  concavity  of  the  sacrum,  in  relation  to  the 
middle  and  lateral  sacral  arteries;  they  receive  lymphatics  from  the  rectum  and 
posterior  wall  of  the  pelvis. 

The  etferents  of  the  hypogastric  group  end  in  the  common  iliac  glands. 

The  Lumbar  Glands  (lymphoglandulae  lumbales)  are  very  numerous,  and  consist 
of  right  and  left  lateral  aortic,  preaortic,  and  retroaortic  groups. 

The  right  lateral  aortic  glands  are  situated  partly  in  front  of  the  inferior  vena 
cava,  near  the  termination  of  the  renal  vein,  and  partly  behind  it  on  the  origin  of  the 
Psoas  major,  and  on  the  right  crus  of  the  Diaphragma.  The  left  lateral  aortic 
glands  form  a  chain  on  the  left  side  of  the  abdominal  aorta  in  front  of  the  origin 
of  the  Psoas  major  and  left  crus  of  the  Diaphragma.  The  glands  on  either  side 
receive  (a)  the  efferents  of  the  common  iliac  glands,  (b)  the  lymphatics  from  the 
testis  in  the  male  and  from  the  ovary,  uterine  tube,  and  body  of  the  uterus  in  the 
female;  (c)  the  lymphatics  from  the  kidney  and  suprarenal  gland;  and  {d)  the 
lymphatics  draining  the  lateral  abdominal  muscles  and  accompanjdng  the  lumbar 
veins.  Most  of  the  efferent  vessels  of  the  lateral  aortic  glands  converge  to  form 
the  right  and  left  lumbar  trunks  which  join  the  cisterna  chyli,  but  some  enter  the 
pre-  and  retroaortic  glands,  and  others  pierce  the  crura  of  the  Diaphragma  to  join 
the  lower  end  of  the  thoracic  duct.  The  preaortic  glands  lie  in  front  of  the  aorta, 
and  may  be  divided  into  coeliac,  superior  mesenteric,  and  inferior  mesenteric  groups, 
arranged  around  the  origins  of  the  corresponding  arteries.  They  receive  a  few 
vessels  from  the  lateral  aortic  glands,  but  their  principal  afferents  are  derived  from 
the  viscera  supplied  by  the  three  arteries  with  which  they  are  associated.  Some 
of  their  efferents  pass  to  the  retroaortic  glands,  but  the  majority  unite  to  form 
the  intestinal  trunk,  which  enters  the  cisterna  chyli.  The  retroaortic  glands  are  placed 
below  the  cisterna  chyli,  on  the  bodies  of  the  third  and  fourth  lumbar  vertebrse. 
They  receive  lymphatic  trunks  from  the  lateral  and  preaortic  glands,  while  their 
efferents  end  in  the  cisterna  chyli. 


The  Lymphatic  Vessels  of  the  Abdomen  and  Pelvis. 

The  lymphatic  vessels  of  the  walls  of  the  abdomen  and  pelvis  may  be  divided 
into  two  sets,  superficial  and  deep. 

The  superficial  vessels  follow^  the  course  of  the  superficial  bloodvessels  and 
converge  to  the  superficial  inguinal  glands;  those  derived  from  the  integument 
of  the  front  of  the  abdomen  below  the  umbilicus  follow^  the  course  of  the  superficial 
epigastric  vessels,  and  those  from  the  sides  of  the  lumbar  part  of  the  abdominal 
wall  pass  along  the  crest  of  the  ilium,  wdth  the  superficial  iliac  circumflex  vessels. 
The  superficial  lymphatic  vessels  of  the  gluteal  region  turn  horizontally  around  the 
buttock,  and  join  the  superficial  inguinal  and  subinguinal  glands. 

The  deep  vessels  run  alongside  the  principal  bloodvessels.  Those  of  the  parietes 
of  the  pelvis,  which  accompany  the  superior  and  inferior  gluteal,  and  obturator 
vessels,  follow  the  course  of  the  hypogastric  artery,  and  ultimately  join  the  lateral 
aortic  glands. 

Lymphatic  Vessels  of  the  Perineum  and  External  Genitals. — The  lymphatic  vessels 
of  the  perineum,  of  the  integument  of  the  penis,  and  of  the  scrotum  (or  vulva), 
follow  the  course  of  the  external  pudendal  vessels,  and  end  in  the  superficial  ingui- 
nal and  subinguinal  glands.  Those  of  the  glans  penis  vel  clitoridis  terminate 
partly  in  the  deep  subinguinal  glands  and  partly  in  the  external  iliac  glands. 

The  visceral  glands  are  associated  with  the  branches  of  the  coeliac,  superior 


788 


ANGIOLOGY 


and  inferior  mesenteric  arteries.  Those  related  to  the  branches  of  the  coeliac 
artery  form  three  sets,  gastric,  hepatic,  and  pancreaticoHenal. 

The  Gastric  Glands  fFigs.  (j(>*^,  OOO)   consist  of   two   sets,  superior  and  inferior. 

The  Superior  Gastric  Glands  {lymphoglandulae  gastricae  siiperiores)  acc(jmpany 
the  left  gastric  artery  and  are  divisible  into  three  groups,  viz.:  (a)  upper,  on  the 
stem  of  the  artery;  (b)  lower,  accompanying  the  descending  branches  of  the  artery 
along  the  cardiac  half  of  the  lesser  curA-atiire  of  the  stomach,  })et\veen  the  two  layers 
of  the  lesser  omentum;  and  (c)  paracardial  outlying  members  of  the  gastric  glands, 
disposed  in  a  manner  comparable  to  a  chain  of  beads  around  the  neck  of  the  stomach 
(Jamieson  and  Dobson^).  They  receive  their  afferents  from  the  stomach;  their 
efferents  pass  to  the  coeliac  group  of  preaortic  glands. 


Paracardial  glands 


Superior  gastric  gland- 
Eepaiic  glands 


Svbpyioric 
glands 


1       Pa/icreaticolienal  glands 


Inferior  gastric  glands 
Fig.  668. — Lymphatics  of  stomach,  etc.     (.Jamieson  and  Dobson.) 


The  Inferior  Gastric  Glands  (lymphoglandulae  gastricae  inferiores;  right  gastro- 
epipjloic  gland),  four  to  seven  in  number,  lie  between  the  two  layers  of  the  greater 
omentum  along  the  pyloric  half  of  the  greater  curvature  of  the  stomach,  and  may 
be  regarded  as  an  outlying  group  of  the  hepatic  glands. 

The  Hepatic  Glands  (lymphoglandidae  hepaticae)  (Fig.  668),  consist  of  the  follow- 
ing groups:  ici)  hepatic,  on  the  stem  of  the  hepatic  artery,  and  extending  upward 
along  the  common  bile  duct,  between  the  two  layers  of  the  lesser  omentum,  as 
far  as  the  porta  hepatis;  the  cystic  gland,  a  member  of  this  group,  is  placed  near 
the  neck  of  the  gall-bladder;  ih)  subpyloric,  four  or  five  in  number,  in  close  relation 
to  the  bifurcation  of  the  gastroduodenal  artery,  in  the  angle  between  the  superior 
and  descending  parts  of  the  duodenum;  an  outlying  member  of  this  group  is  some- 
times found  above  the  duodenum  on  the  right  gastric  (pyloric)  artery.  The  glands 
of  the  hepatic  chain  receive  afferents  from  the  stomach,  duodenum,  liver,  gall- 
bladder, and  pancreas;  their  efferents  join  the  coeliac  group  of  preaortic  glands. 

The  PancreaticoHenal  Glands  (lymphoglandidae  pancreaticolienales;  splenic 
glands)  (Fig.  669)  accompany  the  lienal  (splenic)  artery,  and  are  situated  in  rela- 
tion to  the  posterior  surface  and  upper  border  of  the  pancreas;  one  or  two  members 


1  Lancet.  April  20  and  27,  1907. 


THE  LYMPHATIC  VESSELS  OF  THE  ABDOMEX  AXD  PELVIS       7 


89 


of  this  o-roup  are  found  in  the  gastrolienal  ligament  (Jamieson  and  Dobson,  op.  cit.). 
Their  ali'erents  are  derived  from  the  stomaeh,  spleen,  and  pancreas,  their  efferents 
join  the  ccvliac  groui)  of  preaortic  glands.  _ 

The  superior  mesenteric  glands  may  be  divided  into  three  pruicipal  groups: 
mesenteric,  ileocolic,  and  mesocolic. 

The  Mesenteric  Glands  (h/wplio(ihimIuJae  mesentericae)  lie  between  the  layers  ot 
the  mesentery.  Tlic\  \ary  from  one  hundred  to  one  hundred  and  fifty  in  number, 
and  mav  be  grouped  into  three  sets,  viz. :  one  lying  close  to  the  wall  of  the  small 
intestine,  among  the  terminal  twigs  of  the  superior  mesenteric  artery;  a  second, 
in  relation  to  the  loops  and  primary  branches  of  the  vessels;  and  a  third  along 
the  trunk  of  the  artery. 


Svbpylonc 
glands 


Fig.  669. — Lymphatics  of  stomach,  etc.     The  stomach  has  been  turned  upward.     (Jamieson  and  Dobson.) 


Applied  Anatomy. — Enlargement  of  the  mesenteric  Ij-mphatic  glands  is  seen  in  most  diseased 
conditions  of  the  intestinal  tract,  and  is  well-marked  in  enteric  fever,  tuberculous  ulceration  or 
malignant  growths  of  the  bowel.  The  enlarged  glands  can  often  be  palpated  through  the  wall 
of  the  abdomen. 

The  Ileocolic  glands  (Figs.  670,  671),  from  ten  to  twenty  in  number,  form  a  chain 
around  the  ileocolic  artery,  but  show  a  tendency  to  subdivision  into  two  groups, 
one  near  the  duodenum  and  another  on  the  lower  part  of  the  trunk  of  the  artery. 
Where  the  vessel  divides  into  its  terminal  branches  the  chain  is  broken  up  into  sev- 
eral groups,  viz.:  (a)  ileal,  in  relation  to  the  ileal  branch  of  the  artery;  (6)  anterior 
ileocolic,  usually  of  three  glands,  in  the  ileocolic  fold,  near  the  wall  of  the  cecum; 
(c)  posterior  ileocolic,  mostly  placed  in  the  angle  between  the  ileum  and  the  colon, 
but  partly  lying  behind  the  cecum  at  its  junction  with  the  ascending  colon;  {d) 


■90 


ANGIOLOGY 


a  single  gland,  between  the  layers  of  the  mesenteriole  of  the  vermiform  process; 
(e)  right  colic,  along  the  medial  side  of  the  ascending  colon. 


Duodenum 


Upper  group  of 
ileocolic  glands 


Lower  group  of 
ileocolic  glands 


Cecum  Vermiform  process 

Fig.  670. — The  lymphatics  of  cecum  and  vermiform  process  from  the  front.     (Jamieson  and  Dobson.) 


Upper  group  of 
ileocolic  glands 


Lower  group  of 
ileocolic  glands 


Vermiform  process  Cecum 

Fig.  671. — The  lymphatics  of  cecum  and  vermiform  process  from  behind.     (Jamieson  and  Dobson.) 


THE  LYMPHATIC  VESSELS  OF  ABDOMINAL  AND  PELVIC   VISCERA     791 

The  Mesocolic  Glands  (It/niphoglandulae  mesocolicae)  are  numerous,  and  lie  between 
the  layers  of  the  transverse  niesocok)n,  in  chxse  relation  to  the  transverse  colon; 
they  are  best  developed  in  the  neighborhood  of  the  right  and  left  colic  flexures. 
One  or  two  small  glands  are  occasionally  seen  along  the  trunk  of  the  right  colic 
artery  and  others  are  found  in  relation  to  the  trunk  and  branches  of  the  middle 
colic  artery. 

The  superior  mesenteric  glands  receive  afferents  from  the  jejunum,  ileum,  cecum, 
vermiform  process,  and  the  ascending  and  transverse  parts  of  the  colon;  their 
efferents  pass  to  the  preaortic  glands. 


Inferior  mesenteric  glands 


Fig.  672. — Lymphatics  of  colon.      (Jamieson  and  Dobson  ) 

The  inferior  mesenteric  glands  (Fig.  672)  consist  of:  (a)  small  glands  on  the 
branches  of  the  left  colic  and  sigmoid  arteries;  (6)  a  group  in  the  sigmoid  mesocolon, 
around  the  superior  hemorrhoidal  artery;  and  (c)  a  pararectal  group  in  contact  with 
the  muscular  coat  of  the»  rectum.  They  drain  the  descending  iliac  and  sigmoid 
parts  of  the  colon  and  the  upper  part  of  the  rectum;  their  efferents  pass  to  the 
preaortic  glands. 

The  Lymphatic  Vessels  of  the  Abdominal  and  Pelvic  Viscera. 

The  lymphatic  vessels  of  the  abdominal  and  pelvic  viscera  consist  of  (1)  those 
of  the  subdiaphragmatic  portion  of  the  digestive  tube  and  its  associated  glands, 
the  liver  and  pancreas;  (2)  those  of  the  spleen  and  suprarenal  glands;  (3)  those  of 
the  urinary  organs;  (4)  those  of  the  reproductive  organs. 

^  1.  The  lymphatic  vessels  of  the  subdiaphragmatic  portion  of  the  digestive  tube 
are  situated  partly  in  the  mucous  membrane  and  partly  in  the  seromuscular  coats, 
but  as  the  former  system  drains  into  the  latter,  the  two  may  be  considered  as  one. 


792  ANGIOLOGY 

The  Lymphatic  Vessels  of  the  Stomach  (Figs.  6GS,  669)  are  continuous  at  the 
cardiac  orifice  with  those  of  the  oesophagus,  and  at  the  pylorus  with  those  of  the 
duodenum.  They  mainly  follow  the  bloodvessels,  and  may  be  arranged  in  four 
sets.  Those  of  the  first  set  accompany  the  branches  of  the  left  gastric  artery, 
receiving  tributaries  from  a  large  area  on  either  surface  of  the  stomach,  and  ter- 
minate in  the  superior  gastric  glands.  Those  of  the  second  set  drain  the  fundus 
and  body  of  the  stomach  on  the  left  of  a  line  drawn  vertically  from  the  oesophagus; 
they  accompany,  more  or  less  closely,  the  short  gastric  and  left  gastroepiploic 
arteries,  and  end  in  the  pancreaticolienal  glands.  The  vessels  of  the  third  set  drain 
the  right  portion  of  the  greater  curvature  as  far  as  the  pyloric  portion,  and  end  in 
the  inferior  gastric  glands,  the  efferents  of  which  pass  to  the  subpyloric  group. 
Those  of  the  fourth  set  drain  the  pyloric  portion  and  pass  to  the  hepatic  and 
subpyloric  glands,  and  to  the  superior  gastric  glands. 

The  Lymphatic  Vessels  of  the  Duodenum  consist  of  an  anterior  and  a  posterior 
set,  which  open  into  a  series  of  small  pancreaticoduodenal  glands  on  the  anterior 
and  posterior  aspects  of  the  groove  between  the  head  of  the  pancreas  and  the  duo- 
denum. The  efferents  of  these  glands  run  in  two  directions,  upward  to  the  hepatic 
glands  and  downward  to  the  preaortic  glands  around  the  origin  of  the  superior 
mesenteric  artery. 

The  Lymphatic  Vessels  of  the  Jejunum  and  Ileum  are  termed  lacteals,  from  the 
milk-white  fluid  they  contain  during  intestinal  digestion.  They  run  between  the 
layers  of  the  mesentery  and  enter  the  mesenteric  glands,  the  efferents  of  which 
end  in  the  preaortic  glands. 

The  Lymphatic  Vessels  of  the  Vermiform  Process  and  Cecum  (Figs.  670,  671)  are 
numerous,  since  in  the  wall  of  this  process  there  is  a  large  amount  of  adenoid  tissue. 
From  the  body  and  tail  of  the  vermiform  process  eight  to  fifteen  vessels  ascend 
between  the  layers  of  the  mesenteriole,  one  or  two  being  interrupted  in  the  gland 
which  lies  between  the  layers  of  this  peritoneal  fold.  They  unite  to  form  three 
or  four  vessels,  which  end  partly  in  the  lower  and  partly  in  the  upper  glands  of  the 
ileocolic  chain.  The  vessels  from  the  root  of  the  vermiform  process  and  from  the 
cecum  consist  of  an  anterior  and  a  posterior  group.  The  anterior  vessels  pass  in 
front  of  the  cecum,  and  end  in  the  anterior  ileocolic  glands  and  in  the  upper  and 
lower  glands  of  the  ileocolic  chain;  the  posterior  vessels  ascend  over  the  back  of  the 
cecum  and  terminate  in  the  posterior  ileocolic  glands  and  in  the  lower  glands  of  the 
ileocolic  chain. 

Lymphatic  Vessels  of  the  Colon  (Fig.  672). — The  lymphatic  vessels  of  the  ascend- 
ing and  transverse  parts  of  the  colon  finally  end  in  the  mesenteric  glands,  after 
traversing  the  right  colic  and  mesocolic  glands.  Those  of  the  descending  and  iliac 
sigmoid  parts  of  the  colon  are  interrupted  by  the  small  glands  on  the  branches 
of  the  left  colic  and  sigmoid  arteries,  and  ultimately  end  in  the  preaortic  glands 
around  the  origin  of  the  inferior  mesenteric  artery. 

Lymphatic  Vessels  of  the  Anus,  Anal  Canal,  and  Rectum. — The  lymphatics  from 
the  anus  pass  forward  and  end  with  those  of  the  integument  of  the  perineum  and 
scrotum  in  the  superficial  inguinal  glands;  those  from  the  anal  canal  accompany 
•the  middle  and  inferior  hemorrhoidal  arteries,  and  end  in  the  hypogastric  glands; 
while  the  vessels  from  the  rectum  traverse  the  pararectal  glands  and  pass  to  those 
in  the  sigmoid  mesocolon;  the  eft'erents  of  the  latter  terminate  in  the  preaortic 
glands  around  the  origin  of  the  inferior  mesenteric  artery. 

The  Lymphatic  Vessels  of  the  Liver  are  divisible  into  two  sets,  superficial  and  deep. 
The  former  arise  in  the  subperitoneal  areolar  tissue  over  the  entire  surface  of  the 
organ,  and  may  be  grouped  into  (a)  those  on  the  convex  surface,  (b)  those  on  the 
inferior  surface. 

(a)  On  the  convex  surface:  The  vessels  from  the  back  part  of  this  surface  reach 


THE  LYMPHATIC  VESSELS  OF  ABDOMINAL  AND  PELVIC   VISCERA     793 

their  terminal  glands  by  three  different  routes;  the  vessels  of  the  middle  set,  five 
or  six  in  number,  pass  through  the  vena-caval  foramen  in  the  Diaphragma  and  end 
in  one  or  two  glands  which  are  situated  around  the  terminal  part  of  the  inferior 
vena  ca^'a;  a  few  vessels  from  the  left  side  pass  backward  toward  the  oesophageal 
hiatus,  and  terminate  in  the  paracardial  group  of  superior  gastric  glands;  the  vessels 
from  the  right  side,  one  or  two  in  number,  run  on  the  abdominal  surface  of  the 
Diaphragma,  and,  after  crossing  its  right  crus,  end  in  the  preaortic  glands  which 
surround  the  origin  of  the  coeliac  artery.  From  the  portions  of  the  right  and  left 
lobes  adjacent  to  the  falciform  ligament,  the  lymphatic  vessels  converge  to  form 
two  trunks,  one  of  which  accompanies  the  inferior  vena  cava  through  the  Dia- 
phragma, and  ends  in  the  glands  around  the  terminal  part  of  this  vessel;  the  other 
runs  downward  and  forward,  and,  turning  around  the  anterior  sharp  margin  of  the 
liver,  accompanies  the  upper  part  of  the  ligamentum  teres,  and  ends  in  the  upper 
hepatic  glands.  From  the  anterior  surface  a  few  additional  vessels  turn  around  the 
anterior  sharp  margin  to  reach  the  upper  hepatic  glands. 

(6)  On  the  inferior  surface:  The  vessels  from  this  surface  mostly  converge 
to  the  porta  hepatis,  and  accompany  the  deep  lymphatics,  emerging  from  the 
porta  to  the  hepatic  glands;  one  or  two  from  the  posterior  parts  of  the  right  and 
caudate  lobes  accompany  the  inferior  vena  cava  through  the  Diaphragma,  and 
end  in  the  glands  around  the  terminal  part  of  this  vein. 

The  deep  lymphatics  converge  to  ascending  and  descending  trunks.  The  ascend- 
ing trunks  accompany  the  hepatic  veins  and  pass  through  the  Diaphragma  to  end 
in  the  glands  around  the  terminal  part  of  the  inferior  vena  cava.  The  descending 
trunks  emerge  from  the  porta  hepatis,  and  end  in  the  hepatic  glands. 

The  Lymphatic  Vessels  of  the  Gall-bladder  pass  to  the  hepatic  glands  in  the  porta 
hepatis;  those  of  the  common  bile  duct  to  the  hepatic  glands  alongside  the  duct 
and  to  the  upper  pancreaticoduodenal  glands. 

The  Lymphatic  Vessels  of  the  Pancreas  follow  the  course  of  its  bloodvessels. 
Most  of  them  enter  the  pancreaticolienal  glands,  but  some  end  in  the  pancreatico- 
duodenal glands,  and  others  in  the  preaortic  glands  near  the  origin  of  the  superior 
mesenteric  artery. 

2.  The  lymphatic  vessels  of  the  spleen  and  suprarenal  glands. 

The  Lymphatic  Vessels  of  the  Spleen,  both  superficial  and  deep,  pass  to  the  pan- 
creaticolienal glands. 

The  Lymphatic  Vessels  of  the  Suprarenal  Glands  usually  accompany  the  suprarenal 
veins,  and  end  in  the  lateral  aortic  glands;  occasionally  some  of  them  pierce  the 
crura  of  the  Diaphragma  and  end  in  the  glands  of  the  posterior  mediastinal  cavity. 

3.  The  lymphatic  vessels  of  the  urinary  organs. 

The  Lymphatic  Vessels  of  the  Kidney  form  three  plexuses:  one  in  the  substance 
of  the  kidney,  a  second  beneath  its  fibrous  capsule,  and  a  third  in  the  perinephric 
fat;  the  second  and  third  communicate  freely  with  each  other.  The  vessels  from 
the  plexus  in  the  kidney  substance  converge  to  form  four  or  five  trunks  which 
issue  at  the  hiius.  Here  they  are  joined  by  vessels  from  the  plexus  under  the 
capsule,  and,  following  the  course  of  the  renal  vein,  end  in  the  lateral  aortic  glands. 
The  perinephric  plexus  is  drained  directly  into  the  upper  lateral  aortic  glands. 

The  Lymphatic  Vessels  of  the  Ureter  run  in  different  directions.  Those  from 
its  upper  portion  end  partly  in  the  efferent  vessels  of  the  kidney  and  partly  in  the 
lateral  aortic  glands;  those  from  the  portion  immediately  above  the  brim  of  the 
lesser  pelvis  are  drained  into  the  common  iliac  glands;  while  the  vessels  from  the 
intrapelvic  portion  of  the  tube  either  join  the  efferents  from  the  bladder,  or  end 
in  the  hypogastric  glands. 

The  Lymphatic  Vessels  of  the  Bladder  (Fig.  673)  originate  in  two  plexuses,  an 
intra-  and  an  extramuscular,  it  being  generally  admitted  that  the  mucous  mem- 


794 


ANGIOLOGY 


brane  is  devoid  of  lymphatic.^  The  efferent  vessels  are  arranged  in  two  groups, 
one  from  the  anterior  and  another  from  the  posterior  surface  of  the  bladder.  The 
vessels  from  the  anterior  surface  pass  to  the  external  iliac  glands,  but  in  their  course 
minute  glands  are  situated.  These  minute  glands  are  arranged  in  two  groups, 
an  anterior  vesical,  in  front  of  the  bladder,  and  a  lateral  vesical,  in  relation  to  the 
lateral  umbilical  ligament.  The  vessels  from  the  posterior  surface  pass  to  the  hypo- 
gastric, external,  and  common  iliac  glands;  those  draining  the  upper  part  of  this 
surface  traverse  the  lateral  vesical  glands. 

The  Lymphatic  Vessels  of  the  Prostate  (Fig.  674)  terminate  chiefly  in  the  hypo- 
gastric and  sacral  glands,  but  one  trunk  from  the  posterior  surface  ends  in  the  exter- 
nal iliac  glands,  and  another  from  the  anterior  surface  joins  the  vessels  which  drain 
the  membranous  part  of  the  urethra. 


Common  iliac 
artery 


External  iliac \\L\\lii 

glands 

Lyrn'phntics  C 
irom,  bladder   \ 


Gland  in  front  of 
sacral  promontory 


Hypogastric 
glands 

Ureter 

I  J       il Lymph'xiics  from 

bladder 


Fig.  673. — Lymphatics  of  the  bladder.      (Cun6o  and  Marcille.) 

Lymphatic  Vessels  of  the  Urethra. — The  lymphatics  of  the  cavernous  portion  of 
the  urethra  accompany  those  of  the  glans  penis,  and  terminate  with  them  in  the  deep 
subinguinal  and  external  iliac  glands.  Those  of  the  membranous  and  prostatic 
portions,  and  those  of  the  whole  urethra  in  the  female,  pass  to  the  hypogastric  glands. 

(4)  The  lymphatic  vessels  of  the  reproductive  organs. 

The  Lymphatic  Vessels  of  the  Testes  consist  of  two  sets,  superficial  and  deep, 
the  former  commencing  on  the  surface  of  the  tunica  vaginalis,  the  latter  in  the 
epididymis  and  body  of  the  testis.  They  form  from  four  to  eight  collecting  trunks 
which  ascend  with  the  spermatic  veins  in  the  spermatic  cord  and  along  the  front 
of  the  Psoas  major  to  the  level  where  the  spermatic  vessels  cross  the  ureter  and  end 
in  the  lateral  and  preaortic  groups  of  lumbar  glands.^ 

The  Lymphatic  Vessels  of  the  Ductus  Deferens  pass  to  the  external  iliac  glands; 
those  of  the  vesiculae  seminales  partly  to  the  hypogastric  and  partly  to  the  external 
glands. 

1  Some  authorities  maintain  that  a  plexus  of  lymphatic  vessels  does  exist  in  the  mucous  membrane  of  the  bladder 
(consult  M6decine  op6ratoire  des  Voies  urinaires,  par  J.  Albarran,  Paris,  1909). 

-  "The  Lymphatics  of  the  Testicle,"  by  Jamieson  and  Dobson,  Lancet,  February  19,  1900. 


THE  LYMPHATIC  VE.'SSELS  OF   ABDOMIXAL  AND  PELVIC   VISCERA     795 

The  Lymphatic  Vessels  of  the  Ovary  are  similar  to  those  of  the  testis,  and  ascend 
with  the  ovarian  artery  to  the  lateral  and  preaortic  glands. 

The  Lymphatic  Vessels  of  the  Uterine  Tube  pass  partly  with  those  of  the  ovary 
and  partly  w  ith  those  of  the  uterus. 


Fig.  674. — Lymphatics  of  the  prostate.  (Cuneo  and  Marcille.)  a,  b.  Externa.1  iliac  glands,  c.  Vessel  draining 
into  external  iliac  glands,  d.  Retroprostatic  lymph  nodes,  e.  Vessels  draining  into  gland  on  sacral  promontory. 
/.  Gland  in  front  of  sacral  p^omontorJ^  g.  Lateral  sacral  glands,  h.  Middle  hemorrhoidal  gland,  i.  Middle  hemor- 
rhoidal lymphatic  vessels. 


The  Lymphatic  Vessels  of  the  Uterus  (Fig.  675)  consist  of  two  sets,  superficial 
and  deep,  the  former  being  placed  beneath  the  peritoneum,  the  latter  in  the  sub- 
stance of  the  organ.  The  lymphatics  of  the  cervix  uteri  run  in  three  directions: 
transversely  to  the  external  iliac  glands,  postero-laterally  to  the  hypogastric  glands, 
and  posteriorly  to  the  common  iliac  glands.  The  majority  of  the  vessels  of  the  body 
and  fundus  of  the  uterus  pass  lateralward  in  the  broad  ligaments,  and  are  continued 
up  wdth  the  ovarian  vessels  to  the  lateral  and  preaortic  glands;  a  few^,  however, 
run  to  the  external  iliac  glands,  and  one  or  tw^o  to  the  superficial  inguinal  glands. 
In  the  unimpregnated  uterus  the  lymphatic  vessels  are  very  small,  but  during 
gestation  they  are  greatly  enlarged. 

The  Lymphatic  Vessels  of  the  Vagina  are  carried  in  three  directions:  those  of 
the  upper  part  of  the  vagina  to  the  external  iliac  glands,  those  of  the  middle  part 
to  the  hypogastric  glands,  and  those  of  the  low^er  part  to  the  common  iliac  glands. 


796 


ANGIOLOGY 


On  the  course  of  the  vessels  from  the  middle  and  lower  i)arts  small  glands  are 
situated.  Some  lymphatic  vessels  from  the  lower  part  of  the  vagina  join  those 
of  the  vulva  and  pass  to  the  superficial  inguinal  glands.  The  lymphatics  of  the 
vagina  anastomose  with  those  of  the  cervix  uteri,  vulva,  and  rectum,  but  not  with 
those  of  the  bladder. 


Fig  675. — Lymphatics  of  the  uterus.  (Cuneo  and  Marnille.)  a.  Efierents  to  lateral  aortic  glands.  6,  c,  d.  Efferents 
to  external  iliac  glands,  e.  Net-work  on  lateral  asoect  of  cervix  uteri.  /.  Glands  in  front  of  sacral  promontory.  _  g. 
Efferents  to  galnds  in  front  of  sacral  promontorj-.  h.  HjTJOgastric  glands,  i.  Lateral  sacral  glands,  j.  Vessels  drain- 
ing into  bj-pogastric  glands,     k.  Vessels  passing  to  lateral  sacral  glands. 


THE  LYMPHATICS  OF  THE  THORAX. 


The  lymph  glands  of  the  thorax  may  be  divided  into  parietal  and  visceral — the 
former  being  situated  in  the  thoracic  wall,  the  latter  in  relation  to  the  viscera. 

The  parietal  lymph  glands  include  the  sternal,  intercostal,  and  diaphragmatic 
glands. 

1.  The  Sternal  Glands  (lymphoglanchdae  sternales;  internal  mammary  glands)  are 
placed  at  the  anterior  ends  of  the  intercostal  spaces,  by  the  side  of  the  internal 
mammary  artery.  They  derive  afferents  from  the  mamma,  from  the  deeper  struc- 
tures of  the  anterior  abdominal  wall  above  the  level  of  the  umbilicus,  from  the 
upper  surface  of  the  liver  through  a  small  group  of  glands  which  lie  behind  the 
xiphoid  process,  and  from  the  deeper  parts  of  the  anterior  portion  of  the  thoracic 
wall.  Their  efferents  usually  unite  to  form  a  single  trunk  on  either  side;  this  may 
open  directly  into  the  junction  of  the  internal  jugular  and  subclavian  veins,  or 


THE  LYMPHATICS  OF  THE  THORAX  797 

that  of  the  right  side  may  join  the  right  subcUivian  trunk,  and  that  of  the  left 
the  thoracie  duct. 

2.  The  Intercostal  Glands  {liimyhocjlandidae  inter cosialcs)  occupy  the  posterior 
parts  of  the  intercostal  spaces,  in  relation  to  the  intercostal  vessels.  They  receive 
the  deep  lymphatics  from  the  postero- lateral  aspect  of  the  chest;  some  of  these 
vessels  are  interrupted  by  small  lateral  intercostal  glands.  The  efferents  of  the 
glands  in  the  lower  four  or  five  spaces  unite  to  form  a  trunk,  which  descends  and 
opens  either  into  the  cisterna  chyli  or  into  the  commencement  of  the  thoracic  duct. 
The  efferents  of  the  glands  in  the  upper  spaces  of  the  left  side  end  in  the  thoracic 
duct;  those  of  the  corresponding  right  spaces,  in  the  right  lymphatic  duct. 

3.  The  Diaphragmatic  Glands  lie  on  the  thoracic  aspect  of  the  Diaphragma, 
and  consist  of  three  sets,  anterior,  middle,  and  posterior. 

The  anterior  set  comprises  (a)  two  or  three  small  glands  behind  the  base  of  the 
xiphoid  process,  which  receive  afferents  from  the  convex  surface  of  the  liver,  and 
(6)  one  or  two  glands  on  either  side  near  the  junction  of  the  seventh  rib  with  its 
cartilage,  which  receive  lymphatic  vessels  from  the  front  part  of  the  Diaphragma. 
The  efferent  vessels  of  the  anterior  set  pass  to  the  sternal  glands. 

The  middle  set  consists  of  two  or  three  glands  on  either  side  close  to  where  the 
phrenic  nerves  enter  the  Diaphragma.  On  the  right  side  some  of  the  glands  of  this 
group  lie  within  the  fibrous  sac  of  the  pericardium,  on  the  front  of  the  termination 
of  the  inferior  vena  cava.  The  afferents  of  this  set  are  derived  from  the  middle 
part  of  the  Diaphragma,  those  on  the  right  side  also  receiving  afferents  from  the 
convex  surface  of  the  liver.    Their  efferents  pass  to  the  posterior  mediastinal  glands. 

The  posterior  set  consists  of  a  few  glands  situated  on  the  back  of  the  crura  of 
the  Diaphragma,  and  connected  on  the  one  hand  with  the  lumbar  glands  and  on 
the  other  with  the  posterior  mediastinal  glands. 

The  superficial  lymphatic  vessels  of  the  thoracic  wall  ramify  beneath  the  skin 
and  converge  to  the  axillary  glands.  Those  over  the  Trapezius  and  Latissimus 
dorsi  run  forward  and  unite  to  form  about  ten  or  twelve  trunks  which  end  in  the 
subscapular  group.  Those  over  the  pectoral  region,  including  the  vessels  from  the 
skin  covering  the  peripheral  part  of  the  mamma,  run  backward,  and  those  over 
the  Serratus  anterior  upward,  to  the  pectoral  group.  Others  near  the  lateral  margin 
of  the  sternum  pass  inward  between  the  rib  cartilages  and  end  in  the  sternal  glands, 
while  the  vessels  of  opposite  sides  anastomose  across  the  front  of  the  sternum.  A 
few  vessels  from  the  upper  part  of  the  pectoral  region  ascend  over  the  clavicle  to 
the  supraclavicular  group  of  cervical  glands. 

The  Lymphatic  Vessels  of  the  Mamma  originate  in  a  plexus  in  the  interlobular 
spaces  and  on  the  walls  of  the  galactophorous  ducts.  Those  from  the  central  part 
of  the  gland  pass  to  an  intricate  plexus  situated  beneath  the  areola,  a  plexus  which 
receives  also  the  lymphatics  from  the  skin  over  the  central  part  of  the  gland  and 
those  from  the  areola  and  nipple.  Its  efferents  are  collected  into  two  trunks  which 
pass  to  the  pectoral  group  of  axillary  glands.  The  vessels  which  drain  the  medial 
part  of  the  mamma  pierce  the  thoracic  wall  and  end  in  the  sternal  glands,  while 
a  vessel  has  occasionally  been  seen  to  emerge  from  the  upper  part  of  the  mamma 
and,  piercing  the  Pectoralis  major,  terminate  in  the  subclavicular  glands  (Fig.  662). 

The  deep  lymphatic  vessels  of  the  thoracic  wall  consist  of: 

1.  The  lymphatics  of  the  muscles  which  lie  on  the  ribs:  most  of  these  end  in 
the  axillary  glands,  but  some  from  the  Pectoralis  major  pass  to  the  sternal  glands. 
2.  The  intercostal  vessels  which  drain  the  Intercostales  and  parietal  pleura.  Those 
draining  the  Intercostales  externi  run  backward  and,  after  receiving  the  vessels 
which  accompany  the  posterior  branches  of  the  intercostal  arteries,  end  in  the 
intercostal  glands.  Those  of  the  Intercostales  interni  and  parietal  pleura  consist 
of  a  single  trunk  in  each  space.  These  trunks  run  forward  in  the  subpleural  tissue 
and  the  upper  six  open  separately  into  the  sternal  glands  or  into  the  vessels  which 


798  ANGIOLOGY 

unite  them;  those  of  the  lower  spaces  unite  to  forni  a  single  trunk  which  terminates 
in  the  lowest  of  the  sternal  glands.  3.  The  lymphatic  vessels  of  the  Diaphragma, 
which  form  two  plexuses,  one  on  its  thoracic  and  another  on  its  abdominal  surface. 
These  plexuses  anastomose  freely  with  each  other,  and  are  best  marked  on  the 
parts  covered  respectively  by  the  pleurae  and  peritoneum.  That  on  the  thoracic 
surface  communicates  with  the  lymphatics  of  the  costal  and  mediastinal  parts  of 
the  pleura,  and  its  efferents  consist  of  three  groups :  (a)  anterior,  passing  to  the  gland 
which  lie  near  the  junction  of  the  seventh  rib  with  its  cartilage;  (b)  middle,  to  the 
glands  on  the  oesophagus  and  to  those  around  the  termination  of  the  inferior  vena 
cava;  and  (c)  posterior,  to  the  glands  which  surround  the  aorta  at  the  point  where 
this  vessel  leaves  the  thoracic  cavity. 

The  plexus  on  the  abdominal  surface  is  composed  of  fine  vessels,  and  anasto- 
moses with  the  lymphatics  of  the  liver  and,  at  the  periphery  of  the  Diaphragma, 
with  those  of  the  subperitoneal  tissue.  The  efferents  from  the  right  half  of  this 
plexus  terminate  partly  in  a  group  of  glands  on  the  trunk  of  the  corresponding 
inferior  phrenic  artery,  while  others  end  in  the  right  lateral  aortic  glands.  Those 
from  the  left  half  of  the  plexus  pass  to  the  pre-  and  lateral  aortic  glands  and  to  the 
glands  on  the  terminal  portion  of  the  oesophagus. 

The  visceral  lymph  glands  consist  of  three  groups,  viz.:  anterior  mediastinal, 
posterior  mediastinal,  and  tracheobronchial. 

The  Anterior  Mediastinal  Glands  {lymylioglandulae  mediastinales  anteriores)  are 
placed  in  the  anterior  part  of  the  superior  mediastinal  cavity,  in  front  of  the  aortic 
arch  and  in  relation  to  the  innominate  veins  and  the  large  arterial  trunks  which 
arise  from  the  aortic  arch.  They  receive  afferents  from  the  thymus  and  pericar- 
dium, and  from  the  sternal  glands;  their  efferents  unite  with  those  of  the  tracheo- 
bronchial glands,  to  form  the  right  and  left  bronchomediastinal  trunks. 

The  Posterior  Mediastinal  Glands  {lymyhoglandulae  mediastinales  posteriores) 
lie  behind  the  pericardium  in  relation  to  the  oesophagus  and  descending  thoracic 
aorta.  Their  afferents  are  derived  from  the  oesophagus,'  the  posterior  part  of  the 
pericardium,  the  Diaphragma,  and  the  convex  surface  of  the  liver.  Their  efferents 
mostly  end  in  the  thoracic  duct,  but  some  join  the  tracheobronchial  glands. 

The  Tracheobronchial  Glands  (Fig.  676)  form  four  main  groups:  (a)  tracheal, 
on  either  side  of  the  trachea;  (b)  bronchial,  in  the  angles  between  the  lower  part 
of  the  trachea  and  bronchi  and  in  the  angle  between  the  two  bronchi ;  (c)  broncho- 
pulmonary, in  the  hilus  of  each  lung;  and  (d)  pulmonary,  in  the  lung  substance,  on 
the  larger  branches  of  the  bronchi.  The  afferents  of  the  tracheobronchial  glands 
drain  the  lungs  and  bronchi,  the  thoracic  part  of  the  trachea  and  the  heart;  some 
of  the  efferents  of  the  posterior  mediastinal  glands  also  end  in  this  group.  Their 
efferent  vessels  ascend  upon  the  trachea  and  unite  with  efferents  of  the  internal 
mammary  and  anterior  mediastinal  glands  to  form  the  right  and  left  broncho- 
mediastinal trunks.  The  right  bronchomediastinal  trunk  may  join  the  right 
lymphatic  duct,  and  the  left  the  thoracic  duct,  but  more  frequently  they  open 
independently  of  these  ducts  into  the  junction  of  the  internal  jugular  and 
subclavian  veins  of  their  own  side. 

Applied  Anatomy. — In  all  town  dwellers  there  are  continually  being  swept  into  these  glands 
from  the  bronchi  and  alveoli  large  quantities  of  the  dust  and  black  carbonaceous  pigment  that 
are  so  freely  inhaled  in  cities.  At  first  the  glands  are  moderately  enlarged,  firm,  inky  black,  and 
gritty  on  section;  later  they  enlarge  still  further,  often  becoming  fibrous  from  the  irritation  set 
up  by  the  minute  foreign  bodies  with  which  they  are  crammed,  and  may  break  down  into  a  soft 
slimy  mass  or  may  calcify.  In  tuberculosis  of  the  lungs  these  glands  are  practically  always 
infected;  they  enlarge,  being  filled  with  tuberculous  deposits  that  may  soften,  or  become  fibrous, 
or  calcify.  Not  infrequently  an  enlarged  tuberculous  gland  perforates  into  a  bronchus,  discharg- 
ing its  contents  into  the  tube.  When  this  happens  there  is  great  danger  of  acute  pulmonary 
tuberculosis,  the  infecting  gland  substance  being  rapidly  spread  throughout  the  bronchial  system 
by  the  coughing  its  presence  in  the  air  passages  excites. 


THE  LYMPHATICS  OF  THE  THORAX 


799 


The  lymphatic  vessels  of  the  thoracic  viscera  comprise  those  of  the  heart  and 
pericardium,  lungs  and  pleura,  thymus,  and  oesophagus. 

The  Lymphatic  Vessels  of  the  Heart  consist  of  two  plexuses:  (a)  deep,  immediately 
under  the  endocardium;  and  (6)  superficial,  subjacent  to  the  visceral  pericardium. 
The  deep  plexus  opens  into  the  superficial,  the  efferents  of  which  form  right  and 
left  collecting  trunks.  The  left  trunks,  two  or  three  in  number,  ascend  in  the  anterior 
longitudinal  sulcus,  receiving,  in  their  course,  vessels  from  both  ventricles.  On 
reaching  the  coronary  sulcus  they  are  joined  b\'  a  large  trunk  from  the  diaphragmatic 
surface  of  the  heart,  and  then  unite  to  form  a  single  vessel  which  ascends  between 
the  pulmonary  artery  and  the  left  atrium  and  ends  in  one  of  the  tracheobronchial 

R.  recurrent  nerve 

Paratracheal  glands 
Innominate  artery 


L.  iracheobronchial 
glands 


L.  ironcJiopulmo- 
nary  glands 


R.  tracheobronchial 
glands 


%£^^^CJ — 'ZP"^'  b'^onchoptdmon- 
r^/^^/  ary  glands 


Fig.  676. — The  tracheobronchial  lymph  glands.      (From  a  figure  designed  by  M.  Hall6.) 


glands.  The  right  trunk  receives  its  afferents  from  the  right  atrium  and  from  the 
right  border  and  diaphragmatic  surface  of  the  right  ventricle.  It  ascends  in  the 
posterior  longitudinal  sulcus  and  then  runs  forward  in  the  coronary  sulcus,  and 
passes  up  behind  the  pulmonary  artery,  to  end  in  one  of  the  tracheobronchial 
glands. 

The  Lymphatic  Vessels  of  the  Lungs  originate  in  two  plexuses,  a  superficial  and  a 
deep.  The  superficial  plexus  is  placed  beneath  the  pulmonary  pleura.  The  deep 
accompanies  the  branches  of  the  pulmonary  vessels  and  the  ramifications  of  the 
bronchi.  In  the  case  of  the  larger  bronchi  the  deep  plexus  consists  of  two  net-works 
— one,  submucous,  beneath  the  mucous  membrane,  and  another,  peribronchial, 
outside  the  walls  of  the  bronchi.  In  the  smaller  bronchi  there  is  but  a  single  plexus, 
which  extends  as  far  as  the  bronchioles,  but  fails  to  reach  the  alveoli,  in  the  walls 


800  ANGIOLOGY 

of  which  there  are  no  traces  of  lymphatic  vessels.  The  superficial  efferents  turn 
around  the  borders  of  the  lungs  and  the  margins  of  their  fissures,  and  converge  to 
end  in  some  glands  situated  at  the  hilus;  the  deep  efferents  are  conducted  to  the 
hilus  along  the  pulmonary  vessels  and  bronchi,  and  end  in  the  tracheobronchial 
glands.  Little  or  no  anastomosis  occurs  between  the  superficial  and  deep  lymph- 
atics of  the  lungs,  except  in  the  region  of  the  hilus. 

The  Lymphatic  Vessels  of  the  Pleura  consist  of  two  sets — one  in  the  visceral 
and  another  in  the  parietal  part  of  the  membrane.  Those  of  the  visceral  pleura 
drain  into  the  superficial  eft'erents  of  the  lung,  while  the  lymphatics  of  the  parietal 
pleura  have  three  modes  of  ending,  viz.:  (a)  those  of  the  costal  portion  join  the 
lymphatics  of  the  Intercostales  interni  and  so  reach  the  sternal  glands;  (b)  those 
of  the  diaphragmatic  part  are  drained  by  the  efferents  of  the  Diaphragma;  while 
(c)  those  of  the  mediastinal  portion  terminate  in  the  posterior  mediastinal  glands. 

The  Lymphatic  Vessels  of  the  Thymus  end  in  the  anterior  mediastinal,  tracheo- 
bronchial, and  sternal  glands. 

The  Lymphatic  Vessels  of  the  (Esophagus  form  a  plexus  around  that  tube,  and  the 
collecting  vessels  from  the  plexus  drain  into  the  posterior  mediastinal  glands. 


NEUROLOGY. 


T^HE  Nervous  System  is  the  most  complicated  and  highly  organized  of  the  various 
systems  which  make  up  the  human  body.  It  may  be  divided  into  two  parts, 
central  and  peripheral. 

The  central  nervous  system  consists  of  (a)  an  upper  expanded  portion,  the  enceph- 
alon  or  brain,  contained  within  the  cranium,  and  (b)  a  lower,  elongated,  nearly 
cylindrical  portion,  the  medulla  spinalis  or  spinal  cord,  lodged  in  the  vertebral 
canal;  the  two  portions  are  continuous  with  one  another  at  the  level  of  the  upper 
border  of  the  atlas  vertebra. 

The  peripheral  nervous  system  consists  of  a  series  of  nerves  by  which  the  central 
nervous  system  is  connected  with  the  various  tissues  of  the  body.  For  descriptive 
purposes  these  nerves  may  be  arranged  in  two  groups,  cerebrospinal  and  sympathetic, 
the  arrangement,  however,  being  an  arbitrary  one,  since  the  two  groups  are  inti- 
mateh^  connected  and  closely  intermingled.  The  cerebrospinal  nerves  are  forty- 
three  in  number  on  either  side — twelve  cerebral,  attached  to  the  brain,  and  thirty- 
one  spinal,  to  the  medulla  spinalis.  They  are  associated  with  the  functions  of  the 
special  and  general  senses  and  with  the  voluntary  movements  of  the  body.  The 
sympathetic  nerves  transmit  the  impulses  which  regulate  the  movements  of  the 
viscera,  determine  the  calibre  of  the  bloodvessels,  and  control  the  phenomena  of 
secretion.  In  relation  with  them  are  two  rows  of  central  ganglia,  situated  one  on 
either  side  of  the  middle  line  in  front  of  the  vertebral  column;  these  ganglia  are 
intimately  connected  with  the  medulla  spinalis  and  the  spinal  nerves,  and  are  also 
joined  to  each  other  by  vertical  strands  of  nerve  fibres  so. as  to  constitute  a  pair 
of  knotted  cords,  the  sympathetic  trunks,  which  reach  from  the  base  of  the  skull 
to  the  coccyx.  The  sympathetic  nerves  issuing  from  the  ganglia  form  three  great 
prevertebral  plexuses  which  supply  the  thoracic,  abdominal,  and  pelvic  viscera; 
in  relation  to  the  walls  of  these  viscera  intricate  nerve  plexuses  and  numerous 
peripheral  ganglia  are  found. 

The  nervous  system  is  built  up  of  nervous  and  non-nervous  tissues — the  former 
consisting  of  nerve  cells  and  nerve  fibres;  the  latter,  of  neuroglia  and  bloodvessels, 
together  with  certain  enveloping  membranes. 

The  minute  structure  of  the  nervous  elements,  and  of  the  neuroglia,  has  been 
described  in  the  chapter  on  Histology  (pp.  69  to  76) ;  and  an  outline  of  the  devel- 
opment of  the  nervous  system  furnished  in  that  on  Embryology  (pp.  117  to  133). 
The  structure  of  the  individual  parts  of  the  brain  is  given  under  their  specific 
descriptions. 

Structure  of  the  Peripheral  Nerves  and  GangUa. — The  cerebrospinal  nerves  consist  of  numerous 
nerve  fibres  collected  together  and  enclosed  in  membranous  sheaths  (Fig.  677).  A  small  bundle 
of  fibres,  enclosed  in  a  tubular  sheath,  is  called  a  funiculus ;  if  the  nerve  is  of  small  size,  it  may 
consist  only  of  a  single  funiculus;  but  if  large,  the  funiculi  are  collected  together  into  larger  bundles 
or  fasciculi,  which  are  boimd  together  in  a  common  membranous  investment.  In  structure,  the 
common  membranous  investment,  or  sheath  of  the  whole  nerve  (epineurium) ,  as  well  as  the  septa 
given  off  from  it  to  separate  the  fasciculi,  consist  of  connective  tissue,  composed  of  white  and 
yellow  elastic  fibres,  the  latter  existing  in  great  abundance.  The  tubular  sheath  of  the  funiculi 
(perineurium)  is  a  fine,  smooth,  transparent  membrane,  which  may  be  easily  separated,  in  the 
form  of  a  tube,  from  the  fibres  it  encloses;  in  structure  it  is  made  up  of  connective  tissue,  which 
has  a  distinctly  lamellar  arrangement.  The  nerve  fibres  are  held  together  and  supported  within 
51 


802  NEUROLOGY 

the  funiculus  by  delicate  connective  tissue,  called  the  endoneurium.  It  is  continuous  with  septa 
which  pass  inward  from  the  innermost  layer  of  the  perineurium,  and  shows  a  ground  substance 
in  which  are  imbedded  fine  bundles  of  fibrous  connective  tissue  running  for  the  most  part 
longitudinally.  It  serves  to  support  capillary  vessels,  arranged  so  as  to  form  a  net-work  with 
elongated  meshes.  The  cerebrospinal  nerves  consist  almost  exclusively  of  medullated  nerve 
fibres,  only  a  very  small  proportion  of  non-meduUated  being  present. 

The  bloodvessels  supplying  a  nerve  end  in  a  minute  capillary  plexus,  the  vessels  composing 
which  pierce  the  perineurium,  and  run,  for  the  most  part,  parallel  with  the  fibres;  they  are  con- 
nected together  by  short,  transverse  vessels,  forming  narrow,  oblong  meshes,  similar  to  the 
capillary  system  of  muscle.  Fine  non-meduUated  nerve  fibres,  vasomotor  fibres,  accompany  these 
capillary  vessels,  and  break  up  into  elementary  fibrils,  which  form  a  network  around  the  vessels. 
Horsley  has  demonstrated  certain  medullated  fibres  running  in  the  epineurium  and  terminating 
in  small  spheroidal  tactile  corpuscles  or  end  bulbs  of  Krause.  These  nerve  fibres,  which  Marshall 
beheves  to  be  sensory,  and  which  he  has  termed  nervi  nervorum,  are  considered  by  him^to  have 
an  important  bearing  upon  certain  neuralgic  pains. 


Cpincurium 


4'^<'»S»»JS".  /     set 


/  -  / 


y 


r 


Fig.  677. — Transverse  section  of  human  tibial  nen^e. 

The  nerve  fibres,  so  far  as  is  at  present  knowm,  do  not  coalesce,  but  pursue  an  uninterrupted 
course  from  the  centre  to  the  periphery.  In  separating  a  nerve,  however,  into  its  component 
funicuh,  it  may  be  seen  that  these  do  not  pursue  a  perfectly  insulated  course,  but  occasionally 
join  at  a  very  acute  angle  with  other  funiculi  proceeding  in  the  same  dii'ection;  from  this,  branches 
are  given  off,  to  join  again  in  Like  manner  with  other  funiculi.  It  must  be  distinctly  understood, 
however,  that  in  these  communications  the  individual  nerve  fibres  do  not  coalesce,  but  merely 
pass  into  the  sheath  of  the  adjacent  nerve,  become  intermixed  with  its  nerve  fibres,  and  again 
pass  on  to  intermingle  with  the  nerve  fibres  in  some  adjoining  funiculus. 

Nerves,  in  their  com-se,  subdivide  into  branches,  and  these  frequently  communicate  with 
branches  of  a  neighboring  nerve.  The  communications  which  thus  take  place  form  what  is  called 
a  plexus.  Sometimes  a  plexus  is  formed  by  the  primary  branches  of  the  trunks  of  the  nerves — 
as  the  cervical,  brachial,  lumbar,  and  sacral  plexuses — and  occasionally  by  the  terminal  funiculi, 
as  in  the  plexuses  formed  at  the  periphery  of  the  body  In  the  formation  of  a  plexus,  the  compo- 
nent nerves  divide,  then  join,  and  again  subdivide  in  such  a  complex  manner  that  the  indiA'idual 
funiculi  become  interlaced  most  intricately;  so  that  each  branch  leaving  a  plexus  may  contain 
filaments  from  all  the  primary  nervous  trunks  which  form  the  plexus.  In  the  formation  also  *of 
smaller  plexuses  at  the  periphery  of  the  body  there  is  a  free  interchange  of  the  funiculi  and 
primitive  fibres.    In  each  case,  however,  the  individual  fibres  remain  separate  and  distinct. 

It  is  probable  that  through  this  interchange  of  fibres,  every  branch  passing  off  from  a  plexus 
has  a  more  extensive  connection  with  the  spinal  cord  than  if  it  had  proceeded  to  its  distribution 
without  forming  connections  with  other  nerves.  Consequently  the  parts  supphed  by  these  nerves 
have  more  extended  relations  -nath  the  nervous  centres;  by  this  means,  also,  groups  of  muscles 
may  be  associated  for  combined  action. 


PERIPHERAL  TERMIXATIOXS  OF  NERVES  803 

The  sympathetic  nerves  are  constructed  in  the  same  manner  as  the  cerebrospinal  nerves,  but 
consist  mainly  of  nou-medullated  fibres,  collected  in  funiculi  and  enclosed  in  sheaths  of  connective 
tissue.  There  is,  however,  in  these  nerves  a  certain  admixture  of  meduUated  fibres.  The  number 
of  the  latter  varies  in  different  nerves,  and  may  be  estimated  by  the  color  of  the  nerve.  Those 
branches  of  the  sympathetic  which  present  a  well-marked  gray  color  are  composed  chiefly  of 
non-meduUated  nerve  fibres,  intermixed  with  a  few  medullated  fibres;  while  those  of  a  white 
color  contain  manj'  of  the  latter  fibres,  and  few  of  the  former. 

The  cerebrospinal  and  sympathetic  nerve  fibres  convey  various  impressions.  The  sensory 
nerves,  called  also  centripetal  or  afferent  nerves,  transmit  to  the  nervous  centres  impressions 
maile  upon  the  peripheral  extremities  of  the  nerves,  and  in  this  wa}^  the  mind,  tlirough  the  medium 
of  the  brain,  becomes  conscious  of  external  objects.  The  centrifugal  or  efferent  nerves  transmit 
impressions  from  the  nervous  centres  to  the  parts  to  which  the  nerves  are  distributed,  these 
impressions  either  exciting  muscular  contraction,  or  influencing  the  processes  of  nutrition,  growth, 
and  secretion. 

Origins  and  Terminations  of  Nerves. — By  the  expression  "the  terminations  of  nerve  fibres" 
is  signifietl  their  connections  with  the  nerve  centres  and  with  the  parts  thej^  suppty.  The  former 
are  sometimes  called  theu-  origins  or  central  terminations ;  the  latter  their  peripheral  terminations. 

Origins  of  Nerves. — ^The  origin  in  some  cases  is  single — that  is  to  say,  the  whole  nerve  emerges 
from  the  nervous  centre  by  a  single  root;  in  other  instances  the  nerve  arises  by  two  or  more  roots 
which  come  off  from  different  parts  of  the  nerve  centre,  sometimes  widely  apart  from  each  other, 
and  it  often  happens,  when  a  nerve  arises  in  this  way  by  two  roots,  that  the  functions  of  these 
two  roots  are  different;  as,  for  example,  in  the  spinal  nerves,  each  of  which  arises  by  two  roots, 
the  anterior  of  which  is  motor,  and  the  posterior  sensory.  The  point  where  the  nerve  root  or 
roots  emerge  from  the  surface  of  the  nervous  centre  is  named  the  superficial  or  apparent  origin, 
but  the  fibres  of  the  nerve  can  be  traced  for  a  certain  distance  into  the  substance  of  the  nervous 
centre  to  some  portion  of  the  gi'ay  matter,  which  constitutes  the  deep  or  real  origin  of  the  nerve. 
The  centrifugal  or  efferent  nerve  fibres  originate  in  the  nerve  cells  of  the  gray  substance,  the 
axis-cj^linder  processes  of  these  cells  being  prolonged  to  form  the  fibres.  In  the  case  of  the  centrip- 
etal or  afferent  nerves  the  fibres  grow"  inward  either  from  nerve  cells  in  the  organs  of  special 
sense,  e.  g.,  the  retina,  or  from  nerve  cells  in  the  gangha.  Having  entered  the  nerve  centre  they 
branch  and  send  their  ultimate  twigs  among  the  cells,  without,  however,  uniting  with  them. 

Peripheral  Terminations  of  Nerves. — Nerve  fibres  terminate  peripherally  in  various  ways, 
and  these  may  be  conveniently  studied  in  the  sensory  and  motor  nerves  respectively.  The 
terminations  of  the  sensory  nerves  are  dealt  with  in  the  section  on  Sense  Organs. 

Motor  nerves  can  be  traced  into  either  unstriped  or  striped  muscular  fibres.  In  the  unstriped 
or  involuntary  77iuscles  the  nerves  are  derived  from  the  sympathetic,  and  are  composed  mainly 
of  non-medullated  fibres.  Near  their  terminations  they  di\dde  into  nimierous  branches,  which 
commimicate  and  form  intimate  plexuses.  At  the  junctions  of  the  branches  small  triangular 
nuclear  bodies  (ganghon  cells)  are  situated.  From  these  plexuses  minute  branches  are  given  off 
which  divide  and  break  up  into  the  ultimate  fibrillae  of  w^hich  the  nerves  are  composed.  These 
fibrillse  coui-se  between  the  involuntary  muscle  cells,  and,  according  to  EHscher,  terminate  on 
the  surfaces  of  the  ceUs,  opposite  the  nuclei,  in  minute  swellings. 

In  the  striped  or  voluntary  muscle,  the  nerves  supplying  the  muscular  fibres  are  derived  from 
the  cerebrospinal  nerves,  and  are  composed  mainly  of  medullated  fibres.  The  nerve,  after  enter- 
ing the  sheath  of  the  muscle,  breaks  up  into  fibres  or  bundles  of  fibres,  w^hich  form  plexuses, 
and  gi-aduallj^  divide  untU,  as  a  rule,  a  single  nerve  fibre  enters  a  single  muscular  fibre.  Some- 
times, however,  if  the  muscular  fibre  be  long,  more  than  one  nerve  fibre  enters  it.  Within  the 
muscular  fibre  the  nerve  terminates  in  a  special  expansion,  called  by  Klihne,  who  first  accurately 
described  it,  a  motor  end  plate  (Fig.  678) .  The  nerve  fibre,  on  approaching  the  muscular  fibre, 
suddenly  loses  its  medullary  sheath,  the  neiu-olemma  becomes  continuous  with  the  sarcolemma 
of  the  muscle,  and  only  the  axis-cylinder  enters  the  muscular  fibre.  There  it  at  once  spreads 
out,  ramifying  like  the  roots  of  a  tree,  immediately  beneath  the  sarcolemma,  and  becomes 
imbedded  in  a  layer  of  gi-anular  matter,  containing  a  number  of  clear,  oblong  nuclei,  the  w^hole 
constituting  an  end-plate  from  which  the  contractile  wave  of  the  muscular  fibre  is  said  to  start. 

Ganglia  are  small  aggregations  of  nerve  cells.  They  are  found  on  the  posterior  roots  of  the 
spinal  nerves ;  on  the  sensory  roots  of  the  trigeminal,  facial,  glossopharyngeal,  and  vagus  nerves, 
and  on  the  acoustic  nerves.  They  are  also  found  in  connection  with  the  sympathetic  nerves. 
On  section  they  are  seen  to  consist  of  a  reddish-graj^  substance,  traversed  by  numerous  white 
nerve  fibres;  they  vary  considerably  in  form  and  size;  the  largest  are  found  in  the  cavitj^  of  the 
abdomen;  the  smallest,  not  visible  to  the  naked  eye,  exist  in  considerable  numbers  upon  the 
nerves  distributed  to  the  different  viscera.  Each  ganghon  is  invested  bj^  a  smooth  and  firm, 
closely  adhering,  membranous  envelope,  consisting  of  dense  areolar  tissue;  this  sheath  is  con- 
tinuous with  the  perinemium  of  the  nerves,  and  sends  numerous  processes  into  the  interior  to 
support  the  bloodvessels  supplying  the  substance  of  the  ganghon. 

In  structure  aU  gangha  are  essentially  similar,  consisting  of  the  same  structirral  elements — 
viz.,  nerve  cells  and  nerve  fibres.    Each  nerve  cell  has  a  nucleated  sheath  which  is  continuous 


804 


NEUROLOGY 


with  the  neurolemma  of  the  nerve  fibre  with  which  the  cell  is  connected.  The  nerve  cells  in  the 
gangUa  of  the  spinal  nerves  (Fig.  679)  are  pjTiform  in  shape,  and  have  each  a  single  process. 
A  short  distance  from  the  cell  and  while  stiU  within  the  ganglion  this  process  divides  in  a  T-shaped 
manner,  one  limb  of  the  cross-bar  turning  into  the  medulla  spinalis,  the  other  limb  passing  out- 
ward to  the  periphery.  In  the  sympathetic  gangha  (Fig.  680)  the  nerve  cells  are  multipolar 
and  each  has  one  axis-cyUnder  process  and  several  dendrons;  the  axon  emerges  from  the  ganglion 


Fig.  678. — Muscular  fibres  of  Lacerta  viridis  with  the  terminations  of  nerves,  a.  Seen  in  profile.  P  P.  The  nerve 
end-plates.  S  S.  The  base  of  the  plate,  consisting  of  a  granular  mass  with  nuclei.  6.  The  same  as  seen  in  looking  at 
a  perfectly  fresh  fibre,  the  nervous  ends  being  probably  stiU  excitable.  (The  forms  of  the  variously  divided  plate  can 
hardly  be  represented  in  a  woodcut  by  sufficiently  delicate  and  pale  contours  to  reproduce  correctly  what  is  seen  in 
nature.)    c.  The  same  as  seen  two  hours  after  death  frorii  poisoning  by  curare. 

as  a  non-medullated  nerve  fibre.  Similar  cells  are  found  in  the  ganglia  connected  with  the  tri- 
geminal nerve,  and  these  gangha  are  therefore  regarded  as  the  cerebral  portions  of  the  "autonomic" 
system.  The  autonomic  nervous  system  includes  those  portions  of  the  nervous  mechanism  in 
which  a  meduUated  nerve  fibre  from  the  central  system  passes  to  a  ganghon,  sympathetic  or 
peripheral,  from  which  fibres,  usually  non-medullated,  are  distributed  to  such  structures,  e.  g., 
bloodvessels,  as  are  not  under  voluntary  control.  The  spinal  and  sympathetic  gangha  differ 
somewhat  in  the  size  and  disposition  of  the  cells  and  in  the  number  of  nerve  fibres  entering  and 


Fig.  679. — Transverse  section  of  spinal  ganglion  of  rabbit.  A.  Ganglion.  X  30.  a.  Large  clear  nerve  cell.  6. 
Small  deeply  staining  nerve  cell.  c.  Nuclei  of  capsule.  X  250.  The  lines  in  the  centre  point  to  the  corresponding 
cells  in  the  ganglion. 


leaving  them.  In  the  spinal  gangha  (Fig.  679)  the  nerve  cells  are  much  larger  and  for  the  most 
part  collected  in  groups  near  the  periphery,  while  the  fibres,  which  are  mostly  meduUated,  traverse 
the  central  portion  of  the  ganghon;  whereas  in  the  sympathetic  ganglia  (Fig.  680)  the  cells  are 
smaller  and  distributed  in  irregular  groups  throughout  the  whole  ganglion;  the  fibres  also  are 
irregulary  scattered;  some  of  the  entering  ones  are  meduUated,  while  many  of  those  leaving  the 
ganghon  are  non-meduUated. 


THE  MEDULLA  SPLXALIS  OR  SPINAL  CORD 


805 


Neuron  Theory. — The  nerve  cell  and  its  processes  collectively  constitute  what  is  termed  a 
neuron,  and  AA'aldeycr  formulated  the  theory  that  the  nervous  system  is  built  up  of  numerous 
neurons,  "anatomically  and  genetically  independent 
of  one  another."  According  to  this  theory  {neuron 
theory)  the  processes  of  one  neuron  only  come  into 
contact,  and  are  never  in  direct  continuity,  with 
thoseof  other  neurons;  while  impulses  are  transmitted 
from  one  nerve  cell  to  another  through  these  points 
of  contact.  This  theory  is  based  on  the  following 
facts,  viz.:  (1)  embryonic  nerve  cells  or  neuroblasts 
are  entirely  distinct  from  one  another;  (2)  when 
nervous  tissues  are  stained  by  the  Golgi  method  no 
continuity  is  seen  even  between  neighboring  neurons; 
and  (3)  when  degenerative  changes  occur  in  nervous 
tissue,  either  as  the  result  of  disease  or  experiment, 
they  never  spread  from  one  nem-on  to  another,  but 
are  limited  to  the  individual  nem-ons,  or  gi'oups  of 
neurons,  primarily  affected.    It  must,  however,  be 


Nerve-cells  of  ganglion 


i: 


K'^:h^^-? 


Fig.  680. — Transverse  section  of  sympathetic  ganglion  of  cat. 
A.  Ganglion.     X  50.    a.  A  nerve  cell.     X  250. 


Fig.  681. — Sagittal  section  of  vertebral  canal 
to  show  the  lower  end  of  the  meduUa  spinalis 
and  the  filum  terminale.  (Testut.)  Li,  Lv.  First 
and  fifth  lumbar  vertebrse.  Sii.  Second  sacral 
vertebra.  1.  I3ura  mater.  2.  Lower  part  of 
tube  of  dura  mater.  3.  Lower  extremity  of 
medulla  spinalis.  4.  Intradural,  and  5,  Extra- 
dural portions  of  filum  terminale.  6.  Attach- 
ment of  filum  terminale  to  first  segment  of 
coccyx. 


added  that  within  the  past  few  years  the  validity  of  the  neuron  theory  has  been  called  in 
question  bj^  certain  eminent  histologists,  who  maintain  that  by  the  emplojrment  of  more  deU- 
cate  histological  methods,  minute  fibrils  can  be  followed  from  one  nerve  cell  into  another. 


THE  MEDULLA   SPINALIS   OR   SPINAL  CORD. 

Dissection. — To  dissect  the  medulla  spinaUs  and  its  membranes  it  will  be  necessary  to  lay 
open  the  whole  length  of  the  vertebral  canal.  For  this  purpose  the  muscles  must  be  separated 
from  the  vertebral  grooves,  so  as  to  expose  the  spinous  processes  and  laminae  of  the  vertebrae; 
and  the  latter  must  be  sawn  through  on  each  side,  close  to  the  roots  of  the  transverse  processes, 
from  the  third  or  fom-th  cervical  vertebra  above  to  the  sacrum  below.  The  vertebral  arches 
ha^'ing  been  displaced  by  means  of  a  chisel  and  the  separate  fragment^  removed,  the  dura  will 
be  exposed,  covered  by  a  plexus  of  veins  and  a  quantity  of  loose  areolar  tissue,  often  infiltrated 
with  serous  fluid.  The  arches  of  the  upper  vertebrae  are  best  divided  by  means  of  a  strong  pair 
of  cutting  bone  forceps  or  by  a  rachitome. 

The  medulla  spinalis  or  spinal  cord  forms  the  elongated,  nearly  cylindrical,  part 
of  the  central  nervous  system  which  occupies  the  upper  two-thirds  of  the  vertebral 
canal.  Its  average  length  in  the  male  is  about  45  cm.,  in  the  female  from  -42  to  43 
cm.,  while  its  weight  amounts  to  about  30  gms.  It  extends  from  the  level  of  the 
upper  border  of  the  atlas  to  that  of  the  lower  border  of  the  first,  or  upper  border 


806  NEUROLOGY 

of  the  second,  lumbar  vertebra.  Above,  it  is  continuous  with  the  brain;  below,  it 
ends  in  a  conical  extremity,  the  conus  medullaris,  from  the  apex  of  which  a  delicate 
filament,  the  filum  terminale,  descends  as  far  as  the  first  segment  of  the  coccyx 
(Fig.  681). 

The  position  of  the  medulla  spinalis  varies  wdth  the  movements  of  the  vertebral 
column,  its  lower  extremity  being  drawn  slightly  upward  when  the  column  is 
flexed.  It  also  varies  at  different  periods  of  life;  up  to  the  third  month  of  fetal 
life  the  medulla  spinalis  is  as  long  as  the  vertebral  canal,  but  from  this  stage  onward 
the  vertebral  column  elongates  more  rapidly  than  the  medulla  spinalis,  so  that  by 
the  end  of  the  fifth  month  the  medulla  spinahs  terminates  at  the  base  of  the  sacrum, 
and  at  birth  about  the  third  lumbar  vertebra. 

The  medulla  spinalis  does  not  fill  the  part  of  the  vertebral  canal  in  which  it  lies; 
it  is  ensheathed  by  three  protective  membranes,  separated  from  each  other  by  two 
concentric  spaces.  The  three  membranes  are  named  from  without  inward,  the 
dura  mater,  the  arachnoid,  and  the  pia  mater.  The  dura  mater  is  a  strong,  fibrous 
membrane  which  forms  a  wide,  tubular  sheath;  this  sheath  extends  below  the  ter- 
mination of  the  medulla  spinalis  and  ends  in  a  pointed  cul-de-sac  at  the  level  of  the 
lower  border  of  the  second  sacral  vertebra.  The  dura  mater  is  separated  from  the 
wall  of  the  vertebral  canal  by  the  epidural  cavity,  which  contains  a  quantity  of  loose 
areolar  tissue  and  a  plexus  of  veins;  between  the  dura  mater  and  the  subjacent 
arachnoid  is  a  capillary  interval,  the  subdural  cavity,  which  contains  a  small  quan- 
tity of  fluid,  probably  of  the  nature  of  lymph.  The  arachnoid  is  a  thin,  transparent 
sheath,  separated  from  the  pia  mater  by  a  comparatively  wide  interval,  the  sub- 
arachnoid cavity,  w^hich  is  filled  with  cerebrospinal  fluid.  The  pia  mater  closely 
invests  the  medulla  spinalis  and  sends  delicate  septa  into  its  substance;  a  narrow 
band,  the  ligamentum  denticulatum,  extends  along  each  of  its  lateral  surfaces 
and  is  attached  by  a  series  of  pointed  processes  to  the  inner  surface  of  the  dura 
mater. 

Thirty-one  pairs  of  spinal  nerves  spring  from  the  medulla  spinahs,  each  nerve 
having  an  anterior  or  ventral,  and  a  posterior  or  dorsal  root,  the  latter  being  dis- 
tinguished by  the  presence  of  an  oval  swelling,  the  spinal  ganglion,  which  contains 
numerous  nerve  cells.  Each  root  consists  of  several  bundles  of  nerve  fibres,  and 
at  its  attachment  extends  for  some  distance  along  the  side  of  the  medulla  spinalis. 
The  pairs  of  spinal  nerves  are  grouped  as  follows:  cervical  8,  thoracic  12,  lumbar 
5,  sacral  5,  coccygeal  1,  and,  for  convenience  of  description,  the  medulla  spinalis 
is  divided  into  cervical,  thoracic,  lumbar  and  sacral  regions,  corresponding  with 
the  attachments  of  the  different  groups  of  nerves. 

Although  no  trace  of  transverse  segmentation  is  visible  on  the  surface  of  the 
medulla  spinalis,  it  is  convenient  to  regard  it  as  being  built  up  of  a  series  of  super- 
imposed spinal  segments  or  neuromeres,  each  of  which  has  a  length  equivalent 
to  the  extent  of  attachment  of  a  pair  of  spinal  nerves.  Since  the  extent  of  attach- 
ment of  the  successive  pairs  of  nerves  varies  in  different  parts,  it  follows  that  the 
spinal  segments  are  of  varying  lengths;  thus,  in  the  cervical  region  they  average 
about  13  mm.,  in  the  mid-thoracic  region  about  26  mm.,  while  in  the  lumbar  and 
sacral  regions  they  diminish  rapidly  from  about  15  mm.  at  the  level  of  the  first  pair 
of  lumbar  nerves  to  about  4  mm.  opposite  the  attachments  of  the  lower  sacral 
nerves. 

As  a  consequence  of  the  relative  inequality  in  the  rates  of  growth  of  the  medulla 
spinalis  and  vertebral  column,  the  nerve  roots,  which  in  the  early  embryo  passed 
transversely  outward  to  reach  their  respective  intervertebral  foramina,  become 
more  and  more  oblique  in  direction  from  above  downward,  so  that  the  lumbar 
and  sacral  nerves  descend  almost  vertically  to  reach  their  points  of  exit.  From  the 
appearance  these  nerves  present  at  their  attachment  to  the  medulla  spinalis  and 
from  their  great  length  they  are  collectively  termed  the  cauda  equina  (Fig.  682). 


THE  MEDULLA  SPINALIS  OR  SPINAL  CORD 


807 


The  filum  terminale  is  a  delicate  filament,  about  20  cm.  in  length,  prolonged 
downAvard  from  the  apex  of  the  conns  medullaris.  It  consists  of  two  parts,  an  upper 
and  a  l()\\er.  The  upper  ])art,  or  filum 
terminale  internum,  measures  about  15 
cm.  in  length  and  reaches  as  far  as  the 
lower  border  of  the  second  sacral  verte- 
bra. It  is  contained  within  the  tubular 
sheath  of  dura  mater,  and  is  surrounded 
by  the  nerves  forming  the  cauda  equina, 
from  which  it  can  be  readily  recognized 
by  its  bluish-white  color.  The  lower 
part,  or  filum  terminale  externum,  is 
closely  invested  by,  and  is  adherent  to, 
the  dura  mater;  it  extends  downward 
from   the  apex  of  the  tubular  sheath 


Decussation  nf 
the  'pyramids 


Anterior  median 
fissure 


Dura  mater 

Conus  medullaris 
Posterior  nerveroots 


Filum  terminale 


Postero- 

■  intermediate 

sulcus 


Cervical 
enlargement 


Posterior 
median  sulcus 

Postero- 
lateral sulcus 


—  Filum 


Lumbar 
enlargement 


■  Comis 


Fig.  682. — Cauda  equina  and  filum  terminale  seen 
from  behind.  The  dura  mater  has  been  opened  and 
spread  out,  and  the  arachnoid  has  been  removed. 


Ventral  aspect        Dorsal  aspect 
Fig.  6S3. — Diagrams  of  the  medulla  spinalis. 


808  NEUROLOGY 

and  is  attached  to  the  back  of  the  first  segment  of  the  coccyx.  The  filum  ter- 
minale  consists  mainly  of  fibrous  tissue,  continuous  above  with  that  of  the  pia 
mater.  Adhering  to  its  outer  surface,  however,  are  a  few  strands  of  nerve  fibres 
which  probably  represent  rudimentary  second  and  third  coccygeal  nerves;  further, 
the  central  canal  of  the  medulla  spinalis  extends  downward  into  it  for  5  or  6  cm. 

Enlargements. — The  medulla  spinalis  is  not  quite  cylindrical,  being  slightly 
flattened  from  before  backward;  it  also  presents  two  swellings  or  enlargements, 
an  upper  or  cervical,  and  a  lower  or  lumbar  (Fig.  683). 

The  cervical  enlargement  is  the  more  pronounced,  and  corresponds  with  the  attach- 
ments of  the  large  nerves  which  supply  the  upper  limbs.  It  extends  from  about 
the  third  cervical  to  the  second  thoracic  vertebra,  its  maximum  circumference 
(about  38  mm.)  being  on  a  level  with  the  attachment  of  the  sixth  pair  of  cervical 
nerves. 

The  lumbar  enlargement  gives  attachment  to  the  nerves  which  supply  the  lower 
limbs.  It  commences  about  the  level  of  the  ninth  thoracic  vertebra,  and  reaches 
its  maximum  circumference,  of  about  33  mm.,  opposite  the  last  thoracic  vertebra, 
below  which  it  tapers  rapidly  into  the  conus  medullaris. 

Fissures  and  Sulci  (Fig.  684). — An  anterior  median  fissure  and  a  posterior 
median  sulcus  incompletely  divide  the  medulla  spinalis  into  two  symmetrical 
parts,  which  are  joined  across  the  middle  line  by  a  commissural  band  of  nervous 
matter. 

The  Anterior  Median  Fissure  {fissura  viediana  anterior)  has  an  average  depth  of 
about  3  mm.,  but  this  is  increased  in  the  lower  part  of  the  medulla  spinalis.  It 
contains  a  double  fold  of  pia  mater,  and  its  floor  is  formed  by  a  transverse  band 
of  white  substance,  the  anterior  white  commissure,  which  is  perforated  by  blood- 
vessels on  their  way  to  or  from  the  central  part  of  the  medulla  spinalis. 

The  Posterior  Median  Sulcus  (sulcus  medianus  posterior)  is  very  shallow;  from  it 
a  septum  of  neuroglia  reaches  rather  more  than  half-way  into  the  substance  of  the 
medulla  spinalis;  this  septum  varies  in  depth  from  4  to  6  mm.,  but  diminishes 
considerably  in  the  lower  part  of  the  medulla  spinalis. 

On  either  side  of  the  posterior  median  sulcus,  and  at  a  short  distance  from  it, 
the  posterior  nerve  roots  are  attached  along  a  vertical  furrow  named  the  postero- 
lateral sulcus.  The  portion  of  the  medulla  spinalis  which  lies  between  this  and  the 
posterior  median  sulcus  is  named  the  posterior  funiculus.  In  the  cervical  and  upper 
thoracic  regions  this  funiculus  presents  a  longitudinal  furrow,  the  postero-inter- 
mediate  sulcus;  this  marks  the  position  of  a  septum  which  extends  into  the  posterior 
funiculus  and  subdivides  it  into  two  fasciculi — a  medial,  named  the  fasciculus 
gracilis  (tract  of  Goll);  and  a  lateral,  the  fasciculus  cuneatus  (tract  of  Burdach) 
(Fig.  690).  The  portion  of  the  medulla  spinalis  which  lies  in  front  of  the  postero- 
lateral sulcus  is  termed  the  antero-lateral  region.  The  anterior  nerve  roots,  unlike 
the  posterior,  are  not  attached  in  linear  series,  and  their  position  of  exit  is  not 
marked  by  a  sulcus.  They  arise  by  separate  bundles  wdiich  spring  from  the  anterior 
column  of  gray  substance  and,  passing  forw^ard  through  the  white  substance, 
emerge  over  an  area  of  some  slight  wndth.  The  most  lateral  of  these  bundles  is 
generally  taken  as  a  dividing  line  which. separates  the  antero-lateral  region  into 
two  parts,  viz.,  an  anterior  funiculus,  between  the  anterior  median  fissure  and  the 
most  lateral  of  the  anterior  nerve  roots;  and  a  lateral  funiculus,  between  the  exit 
of  these  roots  and  the  postero-lateral  sulcus.  In  the  upper  part  of  the  cervical 
region  a  series  of  nerve  roots  passes  outward  through  the  lateral  funiculus  of  the 
medulla  spinalis;  these  unite  to  form  the  spinal  portion  of  the  accessory  nerve, 
which  runs  upward  and  enters  the  cranial  cavity  through  the  foramen  magnum. 

The  Internal  Structure  of  the  Medulla  Spinalis. — On  examining  a  transverse 
section  of  the  medulla  spinalis  (Fig.  684)  it  is  seen  to  consist  of  gray  and  white 
nervous  substance,  the  former  being  enclosed  within  the  latter. 


THE  MEDULLA  SPINALIS  OR  SPINAL  CORD 


809 


Gray  Substance  {suhstaidla  (/risea  centralis). — The  gray  substance  consists  of 
two  symmetrical  portions,  one  in  each  half  of  the  medulla  spinalis:  these  are 
joined  across  the  middle  line  by  a  transverse  commissure  of  gray  substance,  through 
which  runs  a  minute  canal,  the  central  canal,  just  \'isible  to  the  naked  eye.  In  a 
transverse  section  each  half  of  the  gray  substance  is  shaped  like  a  comma  or 
crescent,  the  concavity  of  which  is  directed  laterally;  and  these,  together  with 
the  intervening  gray  commissure,  present  the  appearance  of  the  letter  H.  An 
imaginary  coronal  plane  through  the  central  canal  serves  to  divide  each  crescent 
into  an  anterior  or  ventral,  and  a  posterior  or  dorsal  column. 

The  Anterior  Column  {columna  anterior;  anterior'  cornu),  directed  forward,  is 
broad  and  of  a  rounded  or  quadrangular  shape.  Its  posterior  part  is  termed  the 
base,  and  its  anterior  part  the  head,  but  these  are  not  differentiated  from  each  other 
by  any  well-defined  constriction.  It  is  separated  from  the  surface  of  the  medulla 
spinalis  by  a  layer  of  white  substance  which  is  traversed  by  the  bundles  of  the 
anterior  nerve  roots.  In  the  thoracic  region,  the  postero-lateral  part  of  the  anterior 
column  projects  lateralward  as  a  triangular  field,  which  is  named  the  lateral  column 
(columna  lateralis;  lateral  cornu). 


Posterior  median  sulcus 


Posterior  median  septum 

Postero-lateral  sulcus 


Posterior 
column 


Formatio 
reticularis 
Lateral 
column 


Anterior 
column 


Anterior  nerve  roots        Anterior  median  fissure 
Fig.  684. — Transverse  section  of  the  medulla  spinalis  in  the  mid-thoracic  region. 

The  Posterior  Column  {columna  yosterior;  posterior  cornu)  is  long  and  slender, 
and  is  directed  backward  and  lateralward :  it  reaches  almost  as  far  as  the  postero- 
lateral sulcus,  from  which  it  is  separated  by  a  thin  layer  of  white  substance,  the 
tract  of  Lissauer.  It  consists  of  a  base,  directly  continuous  with  the  base  of  the 
anterior  horn,  and  a  neck  or  slightly  constricted  portion,  which  is  succeeded  by 
an  oval  or  fusiform  area,  termed  the  head,  of  which  the  apex  approaches  the  postero- 
lateral sulcus.  The  apex  is  capped  by  a  V-shaped  or  crescentic  mass  of  trans- 
lucent, gelatinous  neuroglia,  termed  the  substantia  gelatinosa  of  Rolando,  which 
contains  both  neuroglia  cells,  and  small  nerve  cells.  Between  the  anterior  and 
posterior  columns  the  gray  substance  extends  as  a  series  of  processes  into  the 
lateral  funiculus,  to  form  a  net-work  called  the  formatio  reticularis. 

The  quantity  of  gray  substance,  as  well  as  the  form  which  it  presents  on  trans- 
verse section,  varies  markedly  at  different  levels.  In  the  thoracic  region  it  is  small, 
not  only  in  amount  but  relatively  to  the  surrounding  w^hite  substance.     In  the 


810 


NEUROLOGY 


CI 


C2, 


as. 


cervical  and  lumbar  enlargements  it  is  greatly  increased :  in  the  latter,  and  especially 
in  the  conns  mediillaris,  its  proportion  to  the  white  substance  is  greatest  (Fig. 

685).  In  the  cervical  region  its  posterior  column  is 
comparatively  narrow,  while  its  anterior  is  broad 
and  expanded;  in  the  thoracic  region,  both  columns 
are  attenuated,  and  the  lateral  column  is  evident; 
in  the  lumbar  enlargement,  both  are  expanded;  while 
in  the  conus  medullaris  the  gray  substance  assumes 
the  form  of  two  oval  masses,  one  in  each  half  of  the 
cord,  connected  together  by  a  broad  gray  commissure. 

The  Central  Canal  (canalis  ceniraJis)  runs  through- 
out the  entire  length  of  the  medulla  spinalis.  The 
portion  of  gray  substance  in  front  of  the  canal  is 
named  the  anterior  gray  commissure ;  that  behind  it, 
the  posterior  gray  commissure.  The  former  is  thin, 
and  is  in  contact  anteriorly  with  the  anterior  white 
commissure:  it  contains  a  couple  of  longitudinal 
veins,  one  on  either  side  of  the  middle  line.  The 
posterior  gray  commissure  reaches  from  the  central 
canal  to  the  posterior  median  septum,  and  is  thin- 
nest in  the  thoracic  region,  and  thickest  in  the  conus 
medullaris.  The  central  canal  is  continued  upward 
through  the  lower  part  of  the  medulla  oblongata,  and 
opens  into  the  fourth  ventricle  of  the  brain;  below, 
it  reaches  for  a  short  distance  into  the  filum  termi- 
nale.  In  the  lower  part  of  the  conus  medullaris  it 
exhibits  a  fusiform  dilatation,  the  terminal  ventricle; 
this  has  a  vertical  measurement  of  from  8  to  10 
mm.,  is  triangular  on  cross-section  with  its  base 
directed  forward,  and  tends  to  undergo  obliteration 
after  the  age  of  forty  years. 

Throughout  the  cervical  and  thoracic  regions  the 
central  canal  is  situated  in  the  anterior  third  of  the 
medulla  spinalis;  in  the  lumbar  enlargement  it  is 
near  the  middle,  and  in  the  conus  medullaris  it 
approaches  the  posterior  surface.  It  is  filled  with 
cerebrospinal  fluid,  and  lined  by  ciliated,  columnar 
epithelium,  outside  of  which  is  an  encircling  band 
of  gelatinous  substance,  the  substantia  gelatinosa 
centralis.  This  gelatinous  substance  consists  mainly 
of  neuroglia,  but  contains  a  few  nerve  cells  and 
fibres;  it  is  traversed  by  processes  from  the  deep  ends 
of  the  columnar  ciliated  cells  which  line  the  central 
canal  'Fig.  686). 

Structure  of  the  Gray  Substance. — The  gray  sub- 
stance consists  of  numerous  nerve  cells  and  nerve 
fibres  held  together  by  neuroglia.  Throughout  the 
greater  part  of  the  gray  substance  the  neuroglia 
presents  the  appearance  of  a  sponge-like  net-work, 
but  around  the  central  canal  and  on  the  apices  of 
the  posterior  columns  it  consists  of  the  gelatinous 
substance  already  referred  to.  The  nerve  cells  are 
multipolar,  and  vary  greatly  in  size  and  shape.  They 
consist  of  (1)   motor  cells  of  large  size,  which  are 


C.8. 


Th2. 


ThS, 


Th12 


L.3. 


S.2. 


Coa 


Fio.  685. — Trans\'erse  sections  of  the 
medulla  spinalis  at  different  levels. 


THE  MEDULLA  SPINALIS  OR  SPIXAL  CORD 


811 


situated  in  the  anterior  horn,  and  are  especially  numerous  in  the  cervical  and 
lumbar  enlargements;  the  axons  of  most  of  these  cells  pass  out  to  form  the  anterior 
nerve  roots,  but  before  leaving  the  white  substance  they  frequently  give  off 
collaterals,  which  reenter  and  ramify  in  the  gray  substance.^  (2)  Cells  of  small 
OF  medium  size,  whose  axons  pass  into  the  white  matter,  where  some  pursue  an 
ascending,  and  others  a  descending  course,  but  most  of  them  divide  in  a  T-shape 
manner  into  descending  and  ascending  processes.  They  give  off  collaterals  which 
enter  and  ramify  in  the  gray  substance,  and  the  terminations  of  the  axons  behave 
in  a  similar  manner.  The  lengths  of  these  axons  vary  greatly :  some  are  short  and 
pass  only  between  adjoining  spinal  segments,  while  others  are  longer  and  connect 
more  distant  segments.  These  cells 
and  their  processes  constitute  a 
series  of  association  or  interseg- 
mental neurons  (Fig.  687),  which 
link  together  the  different  parts  of 
the  medulla  spinalis.  The  axons 
of  most  of  these  cells  are  confined 
to  that  side  of  the  medulla  spinalis 
in  which  the  nerve  cells  are  situ- 
ated, but  some  cross  to  the  oppo- 
site side  through  the  anterior  com- 
missure, and  are  termed  crossed 
commissural  fibres.  Some  of  these 
latter  end  directly  in  the  gray  sub- 
stance, while  others  enter  the  wdiite 


Neuroglial  cells 

Ejiendymal  cells 

Fig.  686. — Section  of  central  canal  of  medulla 
spinalis,  showing  ependymal  and  neuroglial  cells, 
(v.  Lenhossek.) 


;  ^^^-'^ 


Collateral 


—  Ascending 


\-- Descending 


"Arborisation 


Fig.  687. — Cells  of  medulla  spinalis.  (Poirier.)  Diagram 
showing  in  longitudinal  section  the  intersegmental  neurons 
of  the  medulla  spinalis.  The  gray  and  white  parts  corre- 
spond respectively  to  the  gray  and  white  substance  of  the 
medulla  spinalis. 


substance,  and  ascend  or  descend  in  it  for  varying  distances,  before  finally  termi- 
nating in  the  gray  substance.  (3)  Cells  of  the  type  II  of  Golgi,  limited  to  the 
posterior  column,  are  found  in  the  substantia  gelatinosa  of  Rolando;  their  axons 
are  short  and  entirely  confined  to  the  gray  substance,  in  w^hich  they  break  up 
into  numerous  fine  filaments.  Most  of  the  nerve  cells  are  arranged  in  longitu- 
dinal column,  and  appear  as  groups  on  transverse  section  (Figs.  688,  689). 

Nerve  Cells  in  the  Anterior  Column. — The  nerve  cells  in  the  anterior  column  are 
arranged  in  columns  of  varying  length.    The  longest  occupies  the  medial  part  of 


1  Lenhossek  and  Cajal  found  that  in  the  chick  embrj'o  the  axons  of  a  few  of  these  nerve  cells  passed  backward  through 
the  posterior  column,  and  emerged  as  the  motor  fibres  of  the  posterior  nerve  roots.  These  fibres  are  said  to  control  the 
peristaltic  movements  of  the  intestine.     Their  presence,  in  man,  has  not  j'et  been  determined. 


812 


NEUROLOGY 


the  anterior  column,  and  is  named  the  antero-medial  column:  it  is  absent  only  in 
the  fifth  lumbar,  the  first  sacral  and  the  upper  part  of  the  second  sacral  segments 
(Bruce). ^  Behind  it  is  a  dorso-medial  column  of  small  cells,  which  extends  from  the 
second  thoracic  to  the  first  lumbar  segment,  and  is  also  present  in  the  first,  sixth, 
and  seventh  cervical  segments. 


-11 


Fig.  688. — Mode  of  distribution  of  the  nerve  cells  in  the  gray  substance.  (Schematic.)  (Testut.)  1,  2.  Medial 
and  lateral  groups  of  nerve  cells  in  anterior  column.  3.  Nerve  cells  in  lateral  column.  4,4.  Dorsal  nucleus.  5.  Group 
of  nerve  cells  in  substantia  gelatinosa  of  Rolando.  6.  Nerve  cell  of  anterior  column,  the  axon  of  which  is  passing  into 
the  posterior  nerve  root.  7.  Cells  of  substantia  gelatinosa  centralis.  8,  S'.  Solitary  cells.  9.  Cells  of  Golgi.  10. 
Cells  of  origin  of  the  superficial  antero-lateral  fasciculus.     11.  Anterior  root.     12.   Posterior  root.     13.   Spinal  ganglion. 


In  the  cervical  and  lumbar  enlargements,  where  the  anterior  column  is  expanded 
in  a  lateral  direction,  the  following  additional  columns  are  present,  viz. :  (a)  antero- 
lateral, in  the  fourth,  fifth,  and  sixth  cervical  and  the  second  thoracic  segments, 
and  in  the  lower  four  lumbar  and  upper  two  sacral  segments;  (6)  postero-lateral, 
in  the  lower  five  cervical,  lower  four  lumbar,  and  upper  three  sacral  segments; 
(c)  post-postero-lateral,  in  the  last  cervical,  first  thoracic,  and  upper  three  sacral 
segments;  and  {d)  a  central,  in  the  lower  four  lumbar  and  upper  two  sacral  segments. 
Throughout  the  base  of  the  anterior  column  are  scattered  solitary  cells,  the  axons 
of  some  of  which  form  crossed  commissural  fibres,  while  others  constitute  the  motor 
fibres  of  the  posterior  nerve  roots.     (See  footnote,  page  811.) 

Nerve  Cells  in  the  Lateral  Column. — These  form  a  column  which  is  best  marked 
where  the  lateral  gray  column  is  differentiated,  viz.,  in  the  thoracic  region;-  but 
it  can  be  traced  throughout  the  entire  length  of  the  medulla  spinalis  in  the  form 
of  groups  of  small  cells  wdiich  are  situated  in  the  anterior  part  of  the  formatio 
reticularis.  The  cells  of  this  column  are  fusiform  or  star-shaped,  and  of  a  medium 
size :  the  axons  of  some  of  them  pass  into  the  anterior  nerve  roots,  by  w' hich  they 
are  carried  to  the  sympathetic  nerves;  while  the  axons  of  others  pass  into  the 
anterior  and  lateral  funiculi,  where  they  become  longitudinal. 

1  Topographical  Atlas  of  the  Spinal  Cord,  1901. 

2  According  to  Bruce  and  Pirie  (B.  M.  J.,  November  17,  1906)  this  column  extends  from  the  middle  of  the  eighth 
cervical  segment  to  the  lower  part  of  the  second  lumbar  or  the  upper  part  of  the  third  lumbar  segment. 


THE  MEDULLA  SLLXALLS  OR  SPINAL  CORD 


813 


Lateral 
column' 

Postero- 
lateral 

column 


Dorso-medial 
column 

Antero-medial 
column 


Nerve  Cells  in  the  Posterior  Column. — 1.  The  dorsal  nucleus  (nucleus-  don-ali.'i;  col- 
umn of  Clarke)  occupies  the  medial  j)art  of  the  base  of  the  posterior  cohiinu,  and 
appears  on  the  transverse  section  as  a  well-defined  oval  area.  It  begins  below 
at  the  level  of  the  second  or  third  lumbar  nerve,  and  reaches  its  maximum  size 
opposite  the  twelfth  thoracic  nerve. 
Above  the  level  of  the  ninth  thoracic 
nerve  its  size  diminishes,  and  the 
column  ends  opposite  the  last  cer- 
vical or  first  thoracic  nerve.  It  is 
represented,  however,  in  the  other 
regions  by  scattered  cells,  which 
become  aggregated  to  form  a  cer- 
vical nucleus  opposite  the  third 
cervical  nerve,  and  a  sacral  nucleus 
in  the  middle  and  lower  part  of 
the  sacral  region.  Its  cells  are  of 
medium  size,  and  of  an  oval  or 
pyriform  shape;  their  axons  pass 
into  the  peripheral  part  of  the 
lateral  funiculus  of  the  same  side, 
and  there  ascend,  under  the  name  of 
the  cerebellospinal  {direct  cerebellar) 
fasciculus.  2.  The  nerve  cells  in  the 
substantia  gelatinosa  of  Rolando  are 
arranged  in  three  zones:  a  posterior 
or  marginal,  of  large  angular  or  fusi- 
form cells;  an  intermediate,  of  small 
fusiform  cells;  and  an  anterior,  of 
star-shaped  cells.  The  axons  of 
these  cells  pass  into  the  lateral  and 
posterior  funiculi,  and  there  assume 
a  vertical  course.  In  the  anterior 
zone  some  Golgi  cells  are  found 
whose  short  axons  ramify  in  the 
gray  substance.  3.  Solitary  cells 
of  varying  form  and  size  are  scat- 
tered throughout  the  posterior 
column.  Some  of  these  are  grouped 
to  form  the  posterior  basal  column 
in  the  base  of  the  posterior  column, 
lateral  to  the  dorsal  nucleus;  the 
posterior  basal  column  is  wellr 
marked  in  the  gorilla  (Waldeyer), 
but  is  ill-defined  in  man.  The  axons 
of  its  cells  pass  partly  to  the  pos- 
terior and  lateral  funiculi  of  the 
same  side,  and  partly  through  the 
anterior  white  commissure  to  the 
lateral  funiculus  of  the  opposite  side. 
Before  leaving  the  gray  substance,' 
a  considerable  number  run  longitu- 
dinally for  a  varying  distance  in  the 
head  of  the  posterior  column,  form- 
ing what  is  termed  the  longitudinal 
fasciculus  of  the  posterior  column. 


Antero-medial 
column 


Antero-laieral, 
columyi 


Postero-lateral 
colmnn 


Central  t 
column 


Fig. 


689. — Transverse  sections  of  the  medulla  spinalis  at 
different  levels  to  show  the  arrangement  of  the  principal  cell 
columns.     • 


814 


NEUROLOGY 


A  few  star-shaped  or  fusiform  nerve  cells  of  varying  size  are  found  in  the  sub- 
stantia gelatinosa  centraHs.  Their  axons  pass  into  the  hxteral  funicuhis  of  the 
same,  or  of  the  opposite  side. 

The  nerve  fibres  in  the  gray  substance  form  a  dense  interlacement  of  minute 
fibrils  among  the  nerve  cells.  This  interlacement  is  formed  partly  of  axons  which 
pass  from  the  cells  in  the  gray  substance  to  enter  the  white  funiculi  or  nerve  roots; 
partly  of  the  axons  of  Golgi's  cells  which  ramify  only  in  the  gray  substance;  and 
partly  of  collaterals  from  the  nerve  fibres  in  the  white  funiculi  which,  as  already 
stated,  enter  the  gray  substance  and  ramify  within  it. 

Posterior  median  iulcus 
Cornucmnmissural  fasciculus 
Fasciculus  gracilis 
Com  in  a  fasciculus 
Fasciculus  cuneatus 


Lissaucr's 
fasciculus 


Lateral  cerebro- 
spinal fasciculus 

Cerebellospinal 
fasciculus 

Rubrospinal 
fasciculus 

Lateral  proper 
fasciculus 


Superficial  anterolateral 
fasciculus 

Olivospinal  fasciculus 

A  nterior  propter  fasciculus 
Anterior  cerebrospinal  fasciculus 

A  nterior  median  fissure 

Fig.  690. — Diagram  of  the  principal  fasciculi  in  the  medulla  spinalis. 

White  Substance  {substantia  alba). — The  white  substance  of  the  medulla  spinalis 
consists  of  medullated  nerve  fibres  imbedded  in  a  sponge-like  net-work  of  neuroglia, 
and  is  arranged  in  three  funiculi:  anterior,  lateral,  and  posterior.  The  anterior 
funiculus  lies  between  the  anterior  median  fissure  and  the  most  lateral  of  the  ante- 
rior nerve  roots:  the  lateral  funiculus  between  these  nerve  roots  and  the  postero- 
lateral sulcus;  and  the  posterior  funiculus  between  the  postero-lateral  and  the  pos- 
terior median  sulci  (Fig.  690).  The  fibres  vary  greatly  in  thickness,  the  smallest 
being  found  in  the  fasciculus  gracilis,  the  tract  of  Lissauer,  and  inner  part  of  the 
lateral  funiculus ;  while  the  largest  are  situated  in  the  anterior  funiculus,  and  in  the 
peripheral  part  of  the  lateral  funiculus.  Some  of  the  nerve  fibres  assume  a  more 
or  less  transverse  direction,  as  for  example  those  which  cross  from  side  to  side 
in  the  anterior  white  commissure,  but  the  majority  pursue  a  longitudinal  course 
and  are  divisible  into  (1)  those  connecting  the  medulla  spinalis  with  the  brain  and 
conveying  impulses  to  or  from  the  latter,  and  (2)  those  which  are  confined  to  the 
medulla  spinalis  and  link  together  its  different  segments,  i.  e.,  intersegmental  or 
association  fibres. 

Nerve  Fasciculi. — The  longitudinal  fibres  are  grouped  into  more  or  less  definite 
bundles  or  fasciculi.    These  are  not  recognizable  from  each  other  in  the  normal 


A  nterior 
nerve  roots 


THE  MEDULLA  SPINALLH  OR  SPINAL  CORD  815 

state,  and  their  existence  has  been  determined  by  the  following  methods:  (1) 
A.  Waller  discovered  that  if  a  bundle  of  nerve  fibres  be  cut,  the  portions  of  the 
fibres  which  are  separated  from  their  cells  rapidly  degenerate  and  become  atrophied, 
Avhile  the  cells  and  the  parts  of  the  fibres  connected  with  them  undergo  little  alter- 
ation.^ This  is  known  as  Wallerian  degeneration.  Similarly,  if  a  group  of  nerve 
cells  be  destroyed,  the  fibres  arising  from  them  undergo  degeneration.  Thus, 
if  the  motor  cells  of  the  cerebral  cortex  be  destroyed,  or  if  the  fibres  arising  from 
these  cells  be  severed,  a  descending  degeneration  from  the  seat  of  injury  ta,kes 
place  in  the  fibres.  In  the  same  manner,  if  a  spinal  ganglion  be  destroyed,  or  the 
fibres  which  ])ass  from  it  into  the  medulla  spinalis  be  cut,  an  ascending  degenera- 
tion will  extend  along  these  fibres.  (2)  By  tracing  the  development  of  the  nervous 
system,  it  has  been  observed  that  at  first  the  nerve  fibres  are  merely  naked  axis- 
cjdinders,  and  that  they  do  not  all  acquire  their  medullary  sheaths  at  the  same 
time;  hence  the  fibres  can  be  grouped  into  difl'erent  bundles  according  to  the  dates 
at  which  the}^  receive  their  medullary  sheaths.  (3)  Various  methods  of  staining 
nervous  tissue  are  of  great  value  in  tracing  the  course  and  mode  of  termination  of 
the  axis-cylinder  processes. 

Fasciculi  in  the  Anterior  Funiculus. — The  principal  fasciculus  is  the  anterior  cerebro- 
spinal (fasciculus  cerehrospinalis  anterior;  direct  'pyramidal  tract),  which  is  usually 
small,  but  varies  inversely  in  size  with  the  lateral  cerebrospinal  fasciculus.  It 
lies  close  to  the  anterior  median  fissure,  and  is  present  only  in  the  upper  part 
of  the  medulla  spinalis;  gradually  diminishing  in  size  as  it  descends,  it  ends  about 
the  middle  of  the  thoracic  region.  It  consists  of  descending  fibres  which  arise 
from  cells  in  the  motor  area  of  the  cerebral  hemisphere  of  the  same  side,  and 
which,  as  they  run  downward  in  the  medulla  spinalis,  cross  in  succession  through 
the  anterior  white  commissure  to  the  opposite  side,  where  they  end  by  arborizing 
around  the  motor  cells  in  the  anterior  column. 

In  addition  to  the  anterior  cerebrospinal  fasciculus  there  are  strands  of  fibres 
in  the  anterior  funiculus  connecting  certain  ganglia  in  the  brain  with  the  gray  sub- 
stance of  the  medulla  spinalis.  The  most  important  of  these  is  the  vestibulospinal, 
situated  chiefly  in  the  marginal  part  of  the  funiculus  and  mainly  derived  from  the 
cells  of  Deiters'  nucleus,  i.  e.,  the  chief  terminal  nucleus  of  the  vestibular  division 
of  the  acoustic  nerve.  Of  the  other  descending  fibres  some  pass  downward  from 
the  corpora  quadrigemina  (tectospinal)  and  others  are  continuous  with  the  medial 
longitudinal  fasciculus. 

The  remaining  fibres  of  the  anterior  funiculus  constitute  what  is  termed  the 
anterior  proper  fasciculus  {fasciculus  anterior  proprius;  anterior  basis  bundle).  It 
consists  of  (a)  longitudinal  intersegmental  fibres  which  arise  from  cells  in  the  gray 
substance,  more  especially  from  those  of  the  medial  group  of  the  anterior  column, 
and,  after  a  longer  or  shorter  course,  reenter  the  gray  substance;  (6)  fibres  which 
cross  in  the  anterior  white  commissure  from  the  gray  substance  of  the  opposite 
side;  (c)  fibres  arising  from  cells  of  the  cerebellum  and  extending  down  the 
medulla  spinalis  to  end  around  the  cells  of  the  anterior  column — these  fibres 
constitute  an  irregular  tract,  cerebellospinal  tract  of  Lowenthal,  disposed  in  the 
peripheral  portions  of  the  anterior  and  lateral  proper  fasciculi;  and  {d)  fibres  of 
the  anterior  nerve  roots,  which  run  obliquely  forward  to  reach  the  surface  of  the 
medulla  spinalis. 

Fasciculi  in  the  Lateral  Funiculus.  —  1.  Descending  Fasciculi.  —  (a)  The  lateral 
cerebrospinal  fasciculus  (fasciculus  cerebrospinalis  lateralis;  crossed  pyramidal 
tract)  extends  throughout  the  entire  length  of  the  medulla  spinalis,  and  on  trans- 
verse section  appears  as  an  oval  area  in  front  of  the  posterior  column  and  medial 

1  Somewhat  later  a  change,  termed  chromalolysis,  takes  place  in  the  nerve  cells,  and  consists  of  a  breaking  down  and 
an  ultimate  disappearance  of  the  Nissl  bodies.  Further,  the  body  of  the  cell  is  swollen,  the  nucleus  displaced  toward 
the  periphery,  and  the  part  of  the  axon  still  attached  to  the  altered  cell  is  diminished  in  size  and  somewhat  atrophied. 
Under  favorable  conditions  the  cell  is  capable  of  reassuming  its  normal  appearance,  and  its  axon  may  grow  again. 


816  NEUROLOGY 

to  the  cerebellospinal.  Its  fibres  arise  from  cells  in  the  motor  area  of  the  cerebral 
hemisphere  of  the  opposite  side.  They  pass  downward  in  company  with  those 
of  the  anterior  cerebrospinal  fasciculus  through  the  same  side  of  the  brain  as  that 
from  which  they  originate,  but  they  cross  to  the  opposite  side  in  the  medulla  oblon- 
gata and  descend  in  the  lateral  funiculus  of  the  medulla  spinalis;  they  end  by 
arborizing  around  the  motor  cells  in  the  anterior  column.^ 

The  anterior  and  lateral  cerebrospinal  fasciculi  constitute  the  motor  fasciculi 
of  the  medulla  spinalis  and  have  their  origins  in  the  motor  cells  of  the  cerebral 
cortex.  They  descend  through  the  internal  capsule  of  the  cerebrum,  traverse  the 
cerebral  peduncles  and  pons  and  enter  the  pyramid  of  the  medulla  oblongata. 
In  the  lower  part  of  the  latter  about  two-thirds  of  them  cross  the  middle  line  and 
run  downward  in  the  lateral  funiculus  as  the  lateral  cerebrospinal  fasciculus,  while 
the  remaining  fibres  do  not  cross  the  middle  line,  but  are  continued  into  the  same 
side  of  the  medulla  spinalis,  where  they  form  the  anterior  cerebrospinal  fasciculus. 
The  fibres  of  the  latter,  however,  cross  the  middle  line  in  the  anterior  white  com- 
missure, and  thus  all  the  motor  fibres  from  one  side  of  the  brain  ultimately  reach 
the  opposite  side  of  the  medulla  spinalis.  The  proportion  of  fibres  which  cross 
in  the  medulla  oblongata  is  not  a  constant  one,  and  thus  the  anterior  and  lateral 
cerebrospinal  fasciculi  ^-ary  inversely  in  size.  Sometimes  the  former  is  absent, 
and  in  such  cases  it  may  be  presumed  that  the  decussation  of  the  motor  fibres  in 
the  medulla  oblongata  has  been  complete.  The  fibres  of  these  two  fasciculi  do 
not  acquire  their  medullary  sheaths  until  after  birth.  In  some  animals  the  motor 
fibres  are  situated  in  the  posterior  funiculus. 

(6)  The  rubrospinal  fasciculus  (Monakow)  {prepyr amidol  tract),  lies  on  the  ventral 
aspect  of  the  lateral  cerebrospinal  fasciculus  and  on  transverse  section  appears 
as  a  somewhat  triangular  area.  Its  fibres  descend  from  the  mid-brain,  where  they 
have  their  origin  in  the  red  nucleus  of  the  tegmentum  of  the  opposite  side. 

(c)  The  tectospinal  fasciculus  originates  in  the  superior  colliculus  (upper  quad- 
rigeminal  body)  of  the  opposite  side,  and  its  fibres  are  partly  intermingled  with 
those  of  the  rubrospinal  fasciculus,  and  are  partly  contained  in  the  anterior 
funiculus. 

{d)  The  olivospinal  fasciculus  (Helweg)  arises  in  the  vicinity  of  the  inferior 
olivary  nucleus  in  the  medulla  oblongata,  and  is  seen  only  in  the  cervical  region 
of  the  medulla  spinalis,  where  it  forms  a  small  triangular  area  at  the  periphery, 
close  to  the  most  lateral  of  the  anterior  nerve  roots.  Its  exact  origin  and  its  mode 
of  ending  have  not  yet  been  definitely  made  out. 

2.  Ascending  Fasciculi. — (a)  The  cerebellospinal  fasciculus  {fasciculus  cerehello- 
spinalis;  direct  cerebellar  tract  of  Flechsig)  is  situated  at  the  periphery  of  the  pos- 
terior part  of  the  lateral  funiculus,  and  on  transverse  section  appears  as  a  flattened 
band  reaching  as  far  forward  as  a  line  drawn  transversely  through  the  central 
canal.  Medially,  it  is  in  contact  with  the  lateral  cerebrospinal  fasciculus,  behind, 
with  the  fasciculus  of  Lissauer.  It  begins  about  the  level  of  the  second  or  third 
lumbar  nerve  and,  increasing  in  size  as  it  ascends,  passes  to  the  cerebellum  through 
tlie  restiform  body.  Its  fibres  are  generally  regarded  as  being  formed  b}'  the  axons 
of  the  cells  of  the  dorsal  nucleus  (Clarke's  column);  the}'  receive  their  medullary 
sheaths  about  the  sixth  or  seventh  month  of  fetal  life. 

(b)  The  superficial  antero-lateral  fasciculus  (fasciculus  anterolateralis  superficialis; 
tract  of  Gowers)  skirts  the  periphery  of  the  lateral  funiculus  in  front  of  the  cerebello- 
spinal fasciculus.  In  transverse  section  it  is  shaped  somewhat  like  a  comma,  the 
expanded  end  of  which  lies  in  front  of  the  lateral  cerebrospinal  fasciculus  while 
the  tail  reaches  forward  into  the  anterior  funiculus.    Its  fibres  come  from  the  oppo- 

1  It  is  probable  (Sohafer,  Proc.  Physiolog.  Soc,  1899)  that  the  fibres  of  the  anterior  and  lateral  cerebrospinal  fasciculi 
are  not  related  in  this  direct  manner  -nith  the  cells  of  the  anterior  column,  but  terminate  by  arborizing  around  the  cells 
at  the  base  of  the  posterior  column  and  the  cells  of  Clarke's  column,  which  in  turn  link  them  to  the  motor  cells  in  the 
anterior  column,  usually  of  several  segments  of  the  cord.  In  consequence  of  these  interposed  neurons  the  fibres  of  the 
cerebrospinal  fasciculi  correspond  not  to  individual  muscles,  but  to  associated  groups  of  "muscles. 


THE  MEDULLA  SPINALIS  OR  SPINAL  CORD  817 

site  side  of  the  medulla  spiiuilis  and  cross  in  the  anterior  white  commissure;  they 
are  derived  from  the  cells  of  the  dorsal  nucleus  and  from  other  cells  of  the  posterior 
column.  The  superficial  antero-lateral  fasciculus  begins  about  the  level  of  the  third 
pair  of  lumbar  nerves,  and,  increasing  in  size  as  it  ascends,  can  l)e  followed  into  the 
me(hiUa  oblongata  and  pons.  It  consists  of  three  fasciculi:  (1)  the  ventral  spino- 
cerebellar, the  largest  of  the  three,  passes  to  the  cerebellum  by  way  of  the  brachia 
conjunctiva;  (2)  the  spinothalamic  ends  in  the  thalamus,  and  is  sometimes  termed 
the  secondary  sensory  fasciculus;  and  (3)  the  spinotectal  passes  to  the  corpora 
quadrigemina. 

(c)  The  fasciculus  of  Lissauer  is  a  small  strand  situated  in  relation  to  the  tip 
of  the  posterior  column  close  to  the  entrance  of  the  posterior  nerve  roots.  It 
consists  of  fine  fibres  which  do  not  receive  their  medullary  sheaths  until  toward 
the  close  of  fetal  life.  It  is  usually  regarded  as  being  formed  by  some  of  the  fibres 
of  the  posterior  nerve  roots,  which  ascend  for  a  short  distance  in  the  tract  and  then 
enter  the  posterior  column,  but  since  its  fibres  are  myelinated  later  than  those  of 
the  posterior  nerve  roots,  and  do  not  undergo  degeneration  in  locomotor  ataxia, 
they  are  probably  intersegmental  in  character. 

(d)  The  lateral  proper  fasciculus  (fasciculus  lateralis  i^roprius;  lateral  basis  bundle) 
constitutes  the  remainder  of  the  lateral  column,  and  is  continuous  in  front  with  the 
anterior  proper  fasciculus.  It  consists  chiefly  of  intersegmental  fibres  which  arise 
from  cells  in  the  gray  substance,  and,  after  a  longer  or  shorter  course,  reenter  the 
gray  substance  and  ramify  in  it.  Some  of  its  fibres  are,  however,  continued  upward 
into  the  brain  under  the  name  of  the  medial  longitudinal  fasciculus. 

Fasciculi  in  the  Posterior  Funiculus. — This  funiculus  comprises  two  main  fasciculi, 
viz.,  the  fasciculus  gracilis,  and  the  fasciculus  cuneatus.  These  are  separated  from 
each  other  in  the  cervical  and  upper  thoracic  regions  by  the  postero-intermediate 
septum,  and  consist  mainly  of  ascending  fibres  derived  from  the  posterior  nerve 
roots. 

The  fasciculus  gracilis  (tract  of  Goll)  is  wedge-shaped  on  transverse  section,  and 
lies  next  the  posterior  median  septum,  its  base  being  at  the  surface  of  the  medulla 
spinalis,  and  its  apex  directed  toward  the  posterior  gray  commissure.  It  increases 
in  size  from  below^  upward,  and  consists  of  long  thin  fibres  which  are  derived  from 
the  posterior  nerve  roots,  and  ascend  as  far  as  the  medulla  oblongata,  w^here  they 
end  in  the  nucleus  gracilis. 

The  fasciculus  cuneatus  {tract  of  Burdach)  is  triangular  on  transverse  section, 
and  lies  between  the  fasciculus  gracilis  and  the  posterior  column,  its  base  corre- 
sponding wdth  the  surface  of  the  medulla  spinalis.  Its  fibres,  larger  than  those  of 
the  fasciculus  gracilis,  are  mostly  derived  from  the  same  source,  viz.,  the  posterior 
nerve  roots.  Some  ascend  for  only  a  short  distance  in  the  tract,  and,  entering 
the  gray  matter,  come  into  close  relationship  with  the  cells  of  the  dorsal  nucleus; 
while  others  can  be  traced  as  far  as  the  medulla  oblongata,  where  they  end  in  the 
gracile  and  cuneate  nuclei. 

Occupying  the  ventral  part  of  the  posterior  funiculus  is  a  strand  of  fibres  termed 
the  cornu-commissural  fasciculus.  It  is  somewhat  triangular  on  transverse  section, 
and  occupies  the  angle  between  the  posterior  gray  commissure  and  the  posterior 
column.  It  is  best  marked  in  the  lumbar  region,  but  can  be  traced  into  the  thoracic 
and  cervical  regions.  Its  fibres,  derived  from  the  cells  of  the  posterior  column, 
divide  into  ascending  and  descending  branches  which  reenter  and  ramify  in  the 
gray  substance.  It  has  been  found  to  preserve  its  integrity  in  certain  cases  of 
locomotor  ataxia. 

Descending  Fibres  in  the  Posterior  Funiculus  (Fig.  692) . — The  posterior  funiculus 

contains  some  descending  fibres  which  occupy  different  parts  at  different  levels. 

In  the  cervical  and  upper  thoracic  regions,  they  appear  as  a  comma-shaped  fasciculus 

in  the  lateral  part  of  the  fasciculus  cuneatus,  the  blunt  end  of  the  comma  being 

52 


818 


NEUROLOGY 


directed  toward  the  posterior  gray  commissure;  in  the  lower  thoracic  region  they 
form  a  dorsal  peripheral  band  on  the  posterior  surface  of  the  funiculus;  in  the  lumbar 
region,  they  are  situated  by  the  side  of  the  posterior  median  septum,  and  appear 
on  section  as  a  semi-elliptical  bundle,  which,  together  with  the  corresponding 
bundle  of  the  opposite  side,  forms  the  oval  area  of  Flechsig;  while  in  the  conus 
medullaris  they  assume  the  form  of   a  triangular  strand  in  the  postero-medial  part 


First 

thoracic 

7ierve 


Descending  comma  fasciculus 


\\  Sacral 

A'l  '  nerves 


I N        Posterior 

column 


\ Posterior 

column 


Oval  area  of  FlecJisig. 


Posterior 
/  /  /      ■  ;:fy       column 


Fig.  691. — Formation  of  the  fasciculus  gracilis.  (Poirier.) 
IMedulla  spinalis  viewed  from  behind.  To  the  left,  the 
fasciculus  gracilis  is  shaded.  To  the  right,  the  drawing 
shows  that  the  fasciculus  gracihs  is  formed  by  the  long 
fibres  of  the  posterior  roots,  and  that  in  this  tract  the 
sacral  nerves  lie  next  the  median  plane,  the  lumbar  to 
their  lateral  side,  and  the  thoracic  stiU  more  laterally. 


^i, Posterior 

column 


Fig.  692. — Descending  fibres  in  the  posterior 
funiculi,  shown  at  different  levels.  (After  Testut.) 
A.  In  the  conus  medullaris.  _  B.  In  the  lumbar 
region.  C.  In  the  lower  thoracic  region.  D.  In  the 
upper  thoracic  region. 


of  the  fasciculus  gracilis.  These  descending  fibres  are  mainly  intersegmental 
in  character  and  derived  from  cells  in  the  posterior  column,  but  some  consist 
of  the  descending  branches  of  the  posterior  nerve  roots.  The  comma-shaped 
fasciculus  was  supposed  to  belong  to  the  second  category,  but  against  this  view 
is  the  fact  that  it  does  not  undergo  descending  degeneration  when  the  posterior 
nerve  roots  are  destroyed. 

Roots  of  the  Spinal  Nerves. — As  already  stated,  each  spinal  nerve  possesses 
two  roots,  an  anterior  and  a  posterior,  which  are  attached  to  the  surface  of  the 


THE  MEDULLA  SPINALIS  OR  SPINAL  CORD 


819 


medulla  si)inalis  oppDsite  the  corresponding-  eoliunn  of  gray  substance  (Fig.  093); 
their  fibres  become  medullated  about  the  fifth  month  of  fetal  life. 

The  Anterior  Nerve  Root  (radix  anterior)  consists  of  efferent  fibres,  which  are 
the  axons  of  the  ner\e  cells  in  the  ventral  part  of  the  anterior  column.  A  short 
distance  from  their  origins,  these  axons  are  invested  by  medullary  sheaths  and, 
passing  forward,  emerge  in  two  or  three  irregular  rows  ov^er  an  area  which  measures 
about  3  mm.  in  width. 

The  Posterior  Root  (radix  posterior)  comprises  some  six  or  eight  fasciculi,  attached 
in  linear  series  along  the  postero-lateral  sulcus.  It  consists  of  afferent  fibres  which 
arise  from  the  nerve  cells  in  a  spinal  ganglion.  Each  ganglion  cell  gives  oft'  a  single 
fibre  which  divides  in  a  T-shaped  manner  into  two  processes,  medial  and  lateral. 
The  medial  processes  of  the  ganglion  cells  grow  into  the  medulla  spinalis  as  the 
posterior  roots  of  the  spinal  nerves,  while  the  lateral  are  directed  toward  the 
periphery. 


Fig.  693. — A  spinal  nerve  with  its  an- 
terior and  posterior  roots.  (Testut.)  1 
A  portion  of  the  medulla  spinali,  viewed 
from  the  left  side.  2.  Anterior  median  fis- 
sure. 3.  Anterior  column.  4.  Posterior 
column.  5.  Lateral  columns.  6.  Formatio 
reticularis.  7.  Anterior  root.  S.  Posterior 
root,  with  8',  its  ganglion.  9.  Spinal  nerve; 
9',  its  posterior  division. 


Fig.  694. — Posterior  roots  entering  medulla  spinalis  and  dividing 
into  ascending  and  descending  branches.  (Van  Gehuchten.)  o. 
Stem  fibre.  6,  6.  Ascending  and  descending  limbs  of  bifurcation, 
c.  Collateral  arising  from  stem  fibre. 


The  posterior  nerve  root  enters  the  medulla  spinalis  in  three  chief  bundles, 
medial,  intermediate,  and  lateral.  The  medial  strand  passes  directly  into  the  fas- 
ciculus cuneatus :  it  consists  of  coarse  fibres,  which  acquire  their  medullary  sheaths 
about  the  fifth  month  of  intrauterine  life ;  the  intermediate  strand  consists  of  coarse 
fibres,  which  enter  the  gelatinous  substance  of  Rolando;  the  lateral  is  composed 
of  fine  fibres,  which  assume  a  longitudinal  direction  in  the  tract  of  Lissauer,  and 
do  not  acquire  their  medullary  sheaths  until  after  birth. 

Having  entered  the  medulla  spinalis,  all  the  fibres  of  the  posterior  nerve  roots 
divide  into  ascending  and  descending  branches,  and  these  in  their  turn  give  off 
collaterals  which  enter  the  gray  substance  (Fig.  694).  The  descending  fibres  are 
short,  and  soon  enter  the  gray  substance.  The  ascending  fibres  are  grouped  into 
long,  short,  and  intermediate:  the  long  fibres  ascend  in  the  fasciculus  cuneatus 
and  fasciculus  gracilis  as  far  as  the  medulla  oblongata,  where  they  end  by  arbori- 
zing around  the  cells  of  the  cuneate  and  gracile  nuclei;  the  short  fibres  run  upward 
for  a  distance  of  only  5  or  6  mm.  and  enter  the  gray  substance;  while  the  inter- 


820  NEUROLOGY 

mediate  fibres,  after  a  somewhat  longer  course,  have  a  similar  destination.  All 
fibres  entering  the  gray  substance  end  b}'  arborizing  around  its  nerve  cells,  those 
of  intermediate  length  being  especially  associated  with  the  cells  of  the  dorsal 
nucleus. 

The  fibres  of  the  posterior  nerve  roots  pursue  an  oblique  course  upward,  being 
situated  at  first  in  the  lateral  part  of  the  fasciculus  cuneatus:  higher  up,  they  occupy 
the  middle  of  this  fasciculus,  having  been  displaced  by  the  accession  of  other 
entering  fibres;  while  still  higher,  they  ascend  in  the  fasciculus  gracilis.  The  upper 
cervical  fibres  do  not  reach  this  fasciculus,  but  are  entirely  confined  to  the  fascic- 
ulus cuneatus.  The  localization  of  these  fibres  is  very  precise:  the  sacral  nerves 
lie  in  the  medial  part  of  the  fasciculus  gracilis  and  near  its  periphery,  the  lumbar 
nerves  lateral  to  them,  the  thoracic  nerves  still  more  laterally;  while  the  cervical 
nerves  are  confined  to  the  fasciculus  cuneatus  (Fig.  691). 

The  development  of  the  medulla  spinalis  is  described  in  the  section  on  Embry- 
ology (pages  117  to  120). 

Applied  Anatomy. — Several  cases  have  been  recorded^  in  which  a  local  doubling  of  the  medulla 
spinalis  has  taken  place.  The  condition  is  probably  due  to  some  interference  with  the  develop- 
ment of  the  neural  tube  in  the  embryo;  in  a  few  it  was  associated  with  spina  bifida,  while  in  one 
recent  case^  the  two  parts  were  separated  by  a  dermoid  tumor.  Other  congenital  abnormalities 
of  the  medulla  spinalis  occur  in  connection  with  spina  bifida  (see  p.  214),  and  also  in  syringo- 
myelia. In  this  latter  chronic  condition  an  abnormal  prohferation  of  the  neurogUa  takes  place, 
generally  near  the  central  canal  and  in  the  cervical  enlargement,  and  later  this  mass  becomes 
absorbed,  leaving  an  irregular  cavity  in  its  place.  This  gives  rise  to  a  number  of  interesting 
signs  and  symptoms,  such  as  analgesia  (or  insensitiveness  to  pain),  inability  to  distinguish  between 
cold  and  heat,  progressive  atrophy  in  the  muscles  of  the  hands  and  arms,  trophic  changes  in  the 
bones  and  joints,  and  painless  whitlows.  Severe  injuries  to  the  medulla  spinahs  may  occur  in 
fra.ctures  or  fracture-dislocations  of  the  vertebral  column  anywhere  above  the  second  lumbar 
vertebra.  If  the  meduUa  spinalis  is  completely  crushed  or  torn  across,  total  paralysis  and  anes- 
thesia of  all  parts  of  the  body  drawing  their  nerve  supply  from  below  the  injured  spot  will  follow, 
with  loss  of  control  over  the  actions  of  the  bladder  and  rectum.  The  higher  up  such  a  lesion 
occurs,  the  worse  the  prognosis.  Thus,  when  the  medulla  spinaUs  is  crushed  by  fracture  of  the 
atlas  or  axis,  the  vital  centres  in  the  meduUa  oblongata  are  injured,  and  death  occurs  at  once. 
If  the  origin  of  the  phrenic  nerve — mainly  the  fourth  cervical — just  escape  in  a  case  where  the 
neck  is  broken,  respiration  will  have  to  be  carried  on  by  the  Diaphragma  alone,  and  death  is 
likely  to  ensue  before  long  from  pulmonary  complications.  When  the  back  is  broken  in  the 
lower  thoracic  region,  hfe  is  not  immediately  threatened;  but  unless  the  patient  is  carefully 
nursed,  death  may  foUow  at  any  time  from  the  development  of  bed-sores  in  the  anesthetic  area, 
or  from  septic  infection  spreading  up  the  ureters  into  the  kidneys  and  secondary  to  the  cystitis 
that  is  so  prone  to  occur  in  patients  who  have  no  control  over  the  bladder.  Inflammation  of  the 
medulla  spinalis,  or  spinal  myelitis,  sometimes  foUows  influenza  or  one  of  the  acute  specific  fevers. 
A  transverse  patch  of  such  myeUtis  extending  completely  across  the  medulla  spinahs  produces 
more  or  less  complete  interruption  of  the  passage  of  nervous  impulses  through  it.  Hence  it  will 
occasion  more  or  less  complete  paralysis  and  anesthesia  of  the  parts  of  the  body  obtaining  their 
nerve  supply  from  below  it,  and,  in  addition,  a  zone  of  cutaneous  hyperesthesia  at  its  level,  in 
consequence  of  the  irritation  of  the  sensory  fibres  entering  the  inflamed  region  of  the  meduUa 
spinalis.  The  disease  mainly  attacking  children,  and  known  as  infantile  spinal  paralysis,  or 
acute  anterior  poliomyelitis,  is  a  bacterial  infection  of  the  pia  mater  that  spreads  into  the  medulla 
spinalis  along  the  bloodvessels,  and  destroys  groups  of  the  motor  neurons  aggregated  in  the 
anterior  column.  Destruction  of  the  cells  causes  rapid  and  permanent  paralysis  of  the  muscles 
innervated,  and  groups  of  muscles  in  one  or  more  of  the  hmbs  are  commonly  picked  out  for 
attack.  The  affected  limbs  are  thus  partially  paralyzed,  and  their  subsequent  growth  and  nutri- 
tion both  suffer.  Further,  the  muscles  that  normally  antagonize  the  affected  groups  of  muscles, 
finding  their  actions  unopposed,  tend  to  assume  a  state  of  spastic  contraction.  In  consequence, 
much  dwarfing  and  deformity  follow  later,  and  may  demand  for  their  reUef  such  operations  as 
tenotomy,  the  transplantation  of  tendons,  or  even  amputation. 

Inflammation  of  the  gangha  on  one  or  more  of  any  of  the  posterior  nerve  roots  is  the  cause 
of  shingles^  or  herpes  zoster,  in  which  there  is  a  painful  eruption  of  groups  of  cutaneous  vesicles 
corresponding  to  the  distribution  of  the  nerves  derived  from  the  affected  ganglia.     It  is  com- 

'  For  an  analysis  of  these  cases  consult  paper  by  Bruce,  Stuart  !McDonald,  and  Pirie,  Review  of  Neurology  and 
Psychiatry,  January,  1906. 

2  Harriehausen,  D.  Ztschrft.  f.  Nervenheilk.,  Band  xxxvi,  Heft  3  and  4,  S.  268. 
^  From  Lat.  cingulum,  a  belt. 


THE  RHOMBENCEPHALON  OR  HIND-BRAIN 


821 


monest  along  the  course  of  the  intercostal  nerves;  the  eruption  is  often  preceded  and  followed, 
as  well  as  accompanied,  by  girdle  pains,  and  in  old  people  these  may  be  prolonged  and  serious 
in  character.  Herpes  is  the  analogue  on  the  sensory  side  to  anterior  poUomyelitis  on  the  motor 
side  of  the  nervous  system. 

THE   ENCEPHALON   OR  BRAIN. 

Dissection. — To  examine  the  brain  with  its  membranes,  the  skull-cap  must  be  removed.  In 
order  to  effect  this,  saw  through  the  external  table,  the  section  commencing,  in  front,  about 
2  cm.  (*  inch)  above  the  margin  of  the  orbits,  and  extending,  behind,  to  a  little  above  the  level 
of  the  occipital  protuberance.  Then  break  the  internal  table  with  the  chisel  and  hammer,  to 
avoid  injuring  the  investing  membranes  or  brain;  loosen  and  forcibly  detach  the  skull-cap,  and  the 
dm-a  will  be  exposed.  The  adhesion  between  the  bone  and  the  dura  often  is  very  intimate,  par- 
ticularly along  the  sutures. 

General  Considerations  and  Divisions.— The  encephalon,  or  brain,  is  contained 
within  the  cranium,  and  constitutes  the  upper,  greatly  expanded  part  of  the  central 
nervous  system.  In  its  early  em- 
bryonic condition  it  consists  of  three 
hollow  vesicles,  termed  the  rhomb- 
encephalon or  hind-brain,  the  mesen- 
cephalon or  mid-brain,  and  the 
prosencephalon  or  fore-brain;  and 
the  parts  derived  from  each  of 
these  can  be  recognized  in  the 
adult  (Fig.  695).  Thus  in  the  pro- 
cess of  development  the  wall  of  the 
rhombencephalon  undergoes  modi- 
fication to  form  the  medulla  ob- 
longata, the  pons,  and  cerebellum, 
while  its  cavity  is  expanded  to 
form  the  fourth  ventricle.  The 
mesencephalon  forms  only  a  small 
part  of  the  adult  brain;  its  cavity 
becomes  the  cerebral  aqueduct 
(aqueduct  of  Sylvius),  which  serves 
as  a  tubular  communication  be- 
tween the  third  and  fourth  ventricles;  while  its  walls  are  thickened  to  form  the 
corpora  quadrigemina  and  cerebral  peduncles.  The  prosencephalon  undergoes 
great  modification:  its  anterior  part  or  telencephalon  expands  laterally  in  the 
form  of  tw^o  hollow  vesicles,  the  cavities  of  which  become  the  lateral  ventricles, 
while  the  surrounding  walls  form  the  cerebral  hemispheres  and  their  commissures; 
the  cavity  of  the  posterior  part  or  diencephalon  forms  the  greater  part  of  the  third 
ventricle,  and  from  its  walls  are  developed  most  of  the  structures  wdiich  bound 
that  cavity.  Further  details  regarding  these  important  changes  are  given  in  the 
section  on  Embryology  (pages  120  to  132). 


Cerebral  peduncle 
Brcpchium  conjunctivum 

Brachium  pontis 
Bestiform  body 

Medulla  oblongata 


Fig.  695. — Scheme  showing  the  connections  of  the  several 
parts  of  the  brain.     (After  Schwalbe.) 


THE   RHOMBENCEPHALON    OR   HIND-BRAIN. 


The  rhombencephalon  or  hind-brain  occupies  the  posterior  fossa  of  the  cranial 
cavity  and  lies  below  a  fold  of  dura  mater,  the  tentorium  cerebelli.  It  consists 
of  {a)  the  myelencephalon,  comprising  the  medulla  oblongata  and  the  lower  part 
of  the  fourth  ventricle;  {h)  the  metencephalon,  consisting  of  the  pons,  cerebellum, 
and  the  intermediate  part  of  the  fourth  ventricle;  and  (c)  the  isthmus  rhomben- 
cephali,  a  constricted  portion  immediately  adjoining  the  mesencephalon  and  includ- 


822  NEUROLOGY 

ing  the  brachia,  conjunctiva  of  the  cerebellum,  the  anterior  medullary  velum, 
and  the  upper  part  of  the  fourth  ventricle. 

The  Medulla  Oblongata  (spinal  bulb). — The  medulla  oblongata  is  the  lowest  and 
smallest  division  of  the  brain;  its  structure,  however,  is  extremeh'  complex,  since  it 
gives  attachment  to  many  of  the  cerebral  nerves,  and  forms  the  connecting  link 
between  the  medulla  spinalis  below  and  the  cerebrum  and  cerebellum  above. 

It  extends  from  the  lower  margin  of  the  pons  to  a  plane  passing  transversely 
below  the  pyramidal  decussation  and  above  the  first  pair  of  cervical  nerves;  this 
plane  corresponds  with  the  upper  border  of  the  atlas  behind,  and  the  middle  of  the 
odontoid  process  of  the  epistropheus  or  axis  in  front;  at  this  level  the  medulla 
oblongata  is  continuous  with  the  medulla  spinalis.  Its  anterior  surface  is  separated 
from  the  basilar  part  of  the  occipital  bone  and  the  upper  part  of  the  odontoid 
process  by  the  membranes  of  the  brain  and  the  occipitoaxial  ligaments.  Its  pos- 
terior surface  is  received  into  the  fossa  between  the  hemispheres  of  the  cerebellum, 
and  the  upper  portion  of  it  forms  the  lower  part  of  the  floor  of  the  fourth  ventricle. 
The  vertebral  arteries  pass  upward  and  forward  in  relation  to  its  lateral  surfaces; 
they  then  curve  forward  on  to  its  anterior  surface  and  unite  at  the  lower  border 
of  the  pons  to  form  the  basilar  artery. 

The  medulla  oblongata  is  pyramidal  in  shape,  its  broad  extremity  being  directed 
upward  toward  the  pons,  while  its  narrow,  lower  end  is  continuous  with  the  medulla 
spinalis.  It  measures  about  3  cm.  in  length,  about  2  cm.  in  breadth  at  its  widest 
part,  and  about  1.25  cm.  in  thickness.  The  central  canal  of  the  medulla  spinalis 
is  prolonged  into  its  lower  half,  and  then  opens  into  the  cavity  of  the  fourth  ven- 
tricle; the  medulla  oblongata  may  therefore  be  divided  into  a  lower  closed  part 
containing  the  central  canal,  and  an  upper  open  part  corresponding  with  the  lower 
portion  of  the  fourth  ventricle.  Its  anterior  and  posterior  surfaces  are  marked  by 
median  fissures. 

The  Anterior  Median  Fissure  (fissura  mediana  anterior;  ventral  or  xeniromedian 
fissure)  contains  a  fold  of  pia  mater,  and  extends  along  the  entire  length  of  the 
medulla  oblongata:  it  ends  at  the  lower  border  of  the  pons  in  a  small  triangular 
expansion,  termed  the  foramen  caecum.  Its  lower  part  is  interrupted  by  bundles 
of  fibres  which  cross  obliquely  from  one  side  to  the  other,  and  constitute  the  pyra- 
midal decussation.  Some  fibres,  termed  the  anterior  external  arcuate  fibres,  emerge 
from  the  fissure  above  this  decussation  and  curve  lateralward  and  upward  over 
the  surface  of  the  medulla  oblongata. 

The  Posterior  Median  Fissure  (fissura  mediana  posterior;  dorsal  or  dorsomedian 
fissure)  is  a  narrow  groove;  and  exists  only  in  the  closed  part  of  the  medulla  oblon- 
gata; it  becomes  gradually  shallower  from  below  upward,  and  finally  ends  about 
the  middle  of  the  medulla  oblongata,  where  the  central  canal  expands  into  the 
cavity  of  the  fourth  ventricle. 

These  two  fissures  divide  the  closed  part  of  the  medulla  oblongata  into  sym- 
metrical halves,  each  presenting  elongated  eminences  which,  on  surface  view, 
are  continuous  with  the  funiculi  of  the  medulla  spinalis.  In  the  open  part  the 
halves  are  separated  by  the  anterior  median  fissure,  and  by  a  median  raphe  which 
extends  from  the  bottom  of  the  fissure  to  the  floor  of  the  fourth  ventricle.  Further, 
certain  of  the  cerebral  nerves  pass  through  the  substance  of  the  medulla  oblongata, 
and  are  attached  to  its  surface  in  series  with  the  roots  of  the  spinal  nerves;  thus, 
the  fibres  of  the  hjqjoglossal  nerve  represent  the  upward  continuation  of  the 
anterior  nerve  roots,  and  emerge  in  linear  series  from  a  furrow  termed  the 
antero-lateral  sulcus.  Similarly,  the  accessory,  vagus,  and  glossopharyngeal  nerves 
correspond  with  the  posterior  nerve  roots,  and  are  attached  to  the  bottom  of  a  sulcus 
named  the  postero-lateral  sulcus.  Advantage  is  taken  of  this  arrangement  to  sub- 
divide each  half  of  the  medulla  oblongata  into  three  districts,  anterior,  middle, 
and  posterior.     Although  these  three  districts  appear  to  be  directly  continuous 


THE  RHOMBENCEPHALON  OR  HIND-BRAIN 


823 


with  the  corresponding  funiculi  of  the  medulla  spinalis,  they  do  not  necessarily 
contain  the  same  fibres,  since  some  of  the  fasciculi  of  the  medulla  spinalis  end  in 
the  medulla  oblongata,  while  others  alter  their  course  in  passing  through  it. 

The  anterior  district  {Fig.  09(3)  is  named  the  pyramid  (pyramis  meduUae  ohlongatae) 
and  lies  between  the  anterior  median  fissure  and  the  antero-lateral  sulcus.  Its 
upper  end  is  slightly  constricted, 

and    between    it    and    the    pons  "' 

the  fibres  of  the  abducent  nerve 
emerge;  a  little  below  the  pons  it 
becomes  enlarged  and  prominent, 
and  finally  tapers  into  the  anterior 
funiculus  of  the  medulla  spinalis, 
with  which,  at  first  sight,  it  ap- 
pears to  be  directly  continuous. 

The  two  pyramids  contain  the 
motor  fibres  which  pass  from  the 
brain  to  the  medulla  spinalis. 
When  these  pyramidal  fibres  are 
traced  downward  it  is  found  that 
some  two-thirds  or  more  of  them 


Bracliium 

pout  is 
cerebelli 


Fig.  696. — Medulla  oblongata  and  pons. 
Anterior  surface. 


Fig.  697. — Decussation  of  pyramids.  Scheme  showing  pas- 
sage of  various  fasciculi  from  medulla  spinalis  to  medulla  ob- 
longata. (Testut.)  a.  Pons.  b.  Medulla  oblongata,  c. 
Decussation  of  the  pj-ramids.  d.  Section  of  cer^-ical  part  of 
medulla  spinalis.  1.  Anterior  cerebrospinal  fasciculus  (in 
red).  2.  Lateral  cerebrospinal  fasciculus  (in  red).  3.  Sensory- 
tract  (fasciculi  gracilis  et  cuneatus)  (in  blue).  3'.  Gracile 
and  cuneate  nuclei.  4.  Antero-lateral  proper  fasciculus  (in 
dotted  line).  5.  Pyramid.  6.^  Lemniscus.  7.  Medial  longi- 
tudinal fasciculus.  8.  Superficial  antero-lateral  fasciculus  (in 
blue).     9.   Cerebellospinal  fasciculus  (in  j'ellow). 


leave  the  pyramids  in  successive  bundles,  and  decussate  in  the  anterior  median 
fissure,  forming  what  is  termed  the  pyramidal  decussation.  Having  crossed  the 
middle  line,  they  pass  down  in  the  posterior  part  of  the  lateral  funiculus  as  the 
lateral  cerebrospinal  fasciculus.  The  remaining  fibres — i.  e.,  those  which  occupy' 
the  lateral  part  of  the  pyramid — do  not  cross  the  middle  line,  but  are  carried 
downw^ard  as  the  anterior  cerebrospinal  fasciculus  (Fig.  697)  into  the  anterior 
funiculus  of  the  same  side. 

The  greater  part  of  the  anterior  proper  fasciculus  of  the  medulla  spinalis  is  con- 
tinued upward  through  the  medulla  oblongata  under  the  name  of  the  medial 
longitudinal  fasciculus. 

The  lateral  district  (Fig.  698)  is  limited  in  front  by  the  antero-lateral  sulcus 
and  the  roots  of  the  hj-poglossal  nerve,  and  behind  by  the  postero-lateral  sulcus 
and  the  roots  of  the  accessory,  vagus,  and  glossopharyngeal  nerves.  Its  upper  part 
consists  of  a  prominent  oval  mass  which  is  named  the  olive,  while  its  lower  part 


824 


NEUROLOGY 


is  of  the  same  width  as  the  lateral  funiculus  of  the  medulla  spinalis,  and  appears 
on  the  surface  to  be  a  direct  continuation  of  it.  As  a  matter  of  fact,  only  a  portion 
of  the  lateral  funiculus  is  continued  upward  into  this  district,  for  the  lateral  cerebro- 
spinal fasciculus  passes  into  the  pyramid  of  the  opposite  side,  and  the  cerebello- 
spinal fasciculus  is  carried  into  the  restiform  body  in  the  posterior  district.  The 
remainder  of  the  lateral  funiculus,  which  consists  chiefly  of  the  lateral  proper 
fasciculus  and  the  superficial  antero-lateral  fasciculus  can  be  traced  into  the 
lateral  district.  Most  of  these  fibres  dip  beneath  the  olive  and  disappear  from 
the  surface;  but  a  small  strand  remains  superficial,  and  ascends  between  the  olive 
and  the  postero-lateral  sulcus.  In  a  depression  at  the  upper  end  of  this  strand  is 
the  acoustic  nerve. 

Superior  hraclihmi      Lateral  geniculate  body 
Inferior  brachium   \      I    ^ledial  geniculate  body 

1/      /    / 

Optic  tract 


Pulvinar 
Pineatbody 


Superior  collicidi 
Inferior  collicidi 

Frenulum  veli 

Trochlear  nerve 

Lateral  lemniscus 

Brachium  conjunctivum 

Brachium  pontis 
Hhomboid  fossa 


Clava  — 
Glossopharyngeal  and  vagus  nerve. 


Optic  commissure 


Oculomotor  nerve 


Trigeminal  nerve 


Acoustic  nerve 
Facial  nerce 


Abducent  nerve 
Hypoglossal  nerve 


Accessory  verve  ^ 

Fig.  698. — Hind-  and  mid-brains;  postero-lateral  view. 

The  olive  {olim;  olivary  body)  is  situated  lateral  to  the  pyramid,  from  which  it 
is  separated  by  the  antero-lateral  sulcus,  and  the  fibres  of  the  hypoglossal  nerve. 
Behind,  it  is  separated  from  the  postero-lateral  sulcus  by  the  small  superficial 
strand  of  the  lateral  funiculus  already  referred  to.  It  measures  about  1.25  cm.  in 
length,  and  between  its  upper  end  and  the  pons  there  is  a  slight  depression  to  which 
the  roots  of  the  facial  nerve  are  attached.  The  external  arcuate  fibres  wind  across 
the  lower  part  of  the  pyramid  and  olive  and  enter  the  restiform  body. 

The  posterior  district  (Fig.  699)  lies  behind  the  postero-lateral  sulcus  and  the 
roots  of  the  accessory,  vagus,  and  the  glossopharyngeal  nerves,  and,  like  the  lateral 
district,  is  divisible  into  a  lower  and  an  upper  portion. 

The  lower  part  is  limited  behind  by  the  posterior  median  fissure,  and  consists 
of  the  fasciculus  gracilis  and  the  fasciculus  cuneatus.  The  fasciculus  gracilis  is 
placed  parallel  to  and  along  the  side  of  the  posterior  median  fissure,  and  separated 
from  the  fasciculus  cuneatus  by  the  postero-intermediate  sulcus  and  septum. 
The  gracile  and  cuneate  fasciculi  are  at  first  vertical  in  direction;  but  at  the  lower 
part  of  the  rhomboid  fossa  they  diverge  from  the  middle  line  in  a  V-shaped  manner, 
and  each  presents  an  elongated  swelling.  That  on  the  fasciculus  gracilis  is  named 
the  clava,  and  is  produced  by  a  subjacent  nucelus  of  gray  matter,  the  nucleus 


THE  RHOMBENCEPHALOS  OR  UIXD-BRAIX 


825 


gracilis;  that  on  the  fascicukis  cuneatus  is  termed  the  cuneate  tubercle,  and  is  Uke- 
wise  caused  by  a  gray  nucleus,  named  the  nucleus  cuneatus.  The  fibres  of  these 
fasciculi  terminate  by  arborizing  around  the  cells  in  their  respective  nuclei.  A 
third  elevation,  produced  by  the  substantia  gelatinosa  of  Rolando,  is  present  in 
the  lower  part  of  the  posterior  district  of  the  medulla  o})longata.  It  lies  on  the 
lateral  aspect  of  the  fasciculus  cuneatus,  and  is  sei)aratcd  from  the  surface  of  the 
medulla  oblongata  by  a  band  of  nerve  fibres  which  form  the  spinal  tract  (spinal 
root)  of  the  trigeminal  nerve.  Narrow  below,  this  elevation  gradually  expands 
above,  and  ends,  about  1.25  cm.  below  the  pons,  in  a  tubercle,  the  tubercle  of 
Rolando  (iuhcr  cinercum). 


—    Cerebral  peduncle 


Trochlear  nerve 

Trigeminal  nerve 
Facial  nerve 
Acoustic  nerve 


achiiun  conj^(,nctivum 
Brachium  pontis 

Hcati/orm  body 


Glossopharyngeal 
nerve 

Vagus  nerve 
Accessory  nerve 
(cerebral  part) 
Hypoglossal  nerve 

Accessory  nerve 
(spinal  part) 


fertebral  artery 
Clava 
Fasciculus  ciineatus 

Fasciculus  gracilis 


Dura  mater 
(laid  open) 


Fig.  699. — Upper  part  of  medulla  spinalis  and  hind-  and  mid-brains;  posterior  aspect,  exposed  in  situ. 

The  upper  part  of  the  posterior  district  of  the  medulla  oblongata  is  occupied 
by  the  restiform  body,  a  thick  rope-like  strand  situated  between  the  lower  part 
of  the  fourth  ventricle  and  the  roots  of  the  glossopharyngeal  and  A^agus  nerves. 
The  restiform  bodies  connect  the  medulla  spinalis  and  medulla  oblongata  with 
the  cerebellum,  and  are  sometimes  named  the  inferior  peduncles  of  the  cerebellum. 
As  they  pass  upward,  they  diverge  from  each  other,  and  assist  in  forming  the  lower 
part  of  the  lateral  boundaries  of  the  fourth  ventricle;  higher  up,  they  are  directed 
backward,  each  passing  to  the  corresponding  cerebellar  hemisphere.  Near  their 
entrance  into  the  cerebellum  they  are  crossed  by  several  strands  of  fibres,  which 
run  to  the  median  sulcus  of  the  rhomboid  fossa,  and  are  named  the  striae  medullares. 


826 


NEUROLOGY 


The  restiform  body  appears  to  be  the  upward  continuation  of  the  fasciculus  gracilis 
and  fasciculus  cuneatus;  this,  however,  is  not  so,  as  the  fibres  of  these  fasciculi  end 
in  the  gracile  and  cuneate  nuclei.  The  constitution  of  the  restiform  body  will  be 
subsequently  discussed. 

Internal  Structure  of  the  Medulla  Oblongata. — Although  the  external  form  of  the 
medulla  oblongata  bears  a  certain  resemblance  to  that  of  the  upper  part  of  the 
medulla  spinalis,  its  internal  structure  differs  widely  from  that  of  the  latter,  and 
this  for  the  following  principal  reasons:  (1)  certain  fasciculi  which  extend  from  the 
medulla  spinalis  to  the  brain,  and  vice  versa,  undergo  a  rearrangement  in  their 
passage  through  the  medulla  oblongata;  (2)  others  which  exist  in  the  medulla  spin- 
alis end  in  the  medulla  oblongata;  (3)  new  fasciculi  originate  in  the  gray  substance 
of  the  medulla  oblongata  and  pass  to  different  parts  of  the  brain;  (4)  the  gray  sub- 
stance, which  in  the  medulla  spinalis  forms  a  continuous  H-shaped  column,  becomes 
greatly  modified  and  subdivided  in  the  medulla  oblongata,  where  also  new  masses 
of  gray  substance  are  added ;  (o)  on  account  of  the  opening  out  of  the  central  canal 


Fig.  700. — Section  of  the  medulla  oblongata  through 
the  lower  part  of  the  decussation  of  the  pjTamids.  (Tes- 
tut.)  1.  Anterior  median  fissure.  2.  Posterior  median 
sulcus.  3.  Anterior  column  (in  red),  with  3',  anterior 
root.  4.  Posterior  column  (in  blue),  with  4',  posterior 
roots.  .5.  Lateral  cerebrospinal  fasciculus.  6.  Posterior 
funiculus.  The  red  arrow,  a,  a',  indicates  the  course  the 
lateral  cerebrospinal  fasciculus  takes  at  the  level  of  the 
decussation  of  the  pyramids;  the  blue  arrow,  6,  h',  indi- 
cates the  course  which  the  sensorj^  fibres  take. 


Fig.  701. — Section  of  the  medulla  oblongata  at  the 
level  of  the  decussation  of  the  pyramids.  (Testut.)  1 
Anterior  median  fissure.  2.  Posterior  median  sulcus. 
3.  Motor  roots.  4.  Sensory  roots.  .5.  Base  of  the 
anterior  column,  from  which  the  head  (.5')  has  been 
detached  by  the  lateral  cerebrospinal  fasciculus.  6. 
Decussation  of  the  lateral  cerebrospinal  fasciculus.  7. 
Posterior  columns  (in  blue;.    8.  Gracile  nucleus. 


of  the  medulla  spinalis,  certain  parts  of  the  gray  substance,  which  in  the  medulla 
spinalis  were  more  or  less  centrally  situated,  are  displayed  in  the  rhomboid  fossa; 
(6)  the  medulla  oblongata  is  intimately  associated  with  many  of  the  cerebral 
nerves,  some  arising  from,  and  others  ending  in,  nuclei  within  its  substance. 

The  internal  structure  of  the  medulla  oblongata  is  best  studied  in  series  of 
transverse  (Figs.  704,  705)  and  of  longitudinal  sections.  A  short  description 
of  the  course  taken  by  the  principal  fasciculi,  and  of  the  arrangement  of  the 
gray  substance,  will  now  be  given. 

The  Cerebrospinal  Fasciculi. — The  downward  course  of  these  fasciculi  from  the 
pyramids  of  the  medulla  oblongata  and  their  partial  decussation  have  already 
been  described  (page  816).  In  crossing  to  reach  the  lateral  funiculus  of  the  oppo- 
site side,  the  fibres  of  the  lateral  cerebrospinal  fasciculi  extend  backward  through 
the  anterior  columns,  and  separates  the  head  of  each  of  these  columns  from  its 
base  (Figs.  700,  701).  The  base  retains  its  position  in  relation  to  the  ventral 
aspect  of  the  central  canal,  and,  when  the  latter  opens  into  the  fourth  ventricle, 
appears  in  the  rhomboid  fossa  close  to  the  middle  line,  where  it  forms  the  nuclei 
of  the  hypoglossal  and  abducent  nerves;  while  above  the  level  of  the  ventricle  it 
exi.sts  as  the  nuclei  of  the  trochlear  and  oculomotor  nerves  in  relation  to  the  floor 
of  the  cerebral  aqueduct.  The  head  of  the  column  is  pushed  lateralward  and  forms 
the  nucleus  ambiguus,  which  gives  origin  from  below  upward  to  the  cerebral  part 


THE  RHOMBENCEPHALON  OR  HIND-BRAIN 


827 


of  the  accessory  and  the  motor  fibres  of  the  va^us  and  glossopharyngeal,  and  still, 
higher  to  the  motor  fibres  of  the  facial  and  trigeminal  nerves. 

The  fasciculus  gracilis  and  fasciculus  cuneatus  constitute  the  posterior  sensory 
fasciculi  of  the  medulla  spinalis;  they  are  prolonged  upward  into  the  lower  part 
of  the  medulla  oblongata,  where  they  end  respectively  in  the  nucleus  gracilis  and 
nucleus  cuneatus.  These  two  nuclei  are  continuous  with  the  central  gray  substance 
of  the  medulla  spinalis,  and  may  be  regarded  as  dorsal  projections  of  this,  each 
being  covered  superficially  by  the  fibres  of  the  corresponding  fasciculus.     On 

transverse  section  (Fig.  704)  the  nucleus 
gracilis  appears  as  a  single,  more  or  less 
quadrangular  mass,  while  the  nucleus 
cuneatus  consists  of  two  parts:  a  larger, 
somewhat  triangular,  medial  nucleus, 
composed  of  small  or  medium-sized  cells, 
and  a  smaller  lateral  nucleus  containing 
large  cells. 

The   fibres   of  the,  fasciculus   gracilis 
and  fasciculus  cuneatus  end  by  arborizing 

7       6    2 


Fig.  702. — Superior  terminations  of  the  posterior  fas- 
ciculi of  the  medulla  spinaUs.  (Testut.)  1.  Posterior 
median  sulcus.  2.  Fasciculus  gracilis.  3.  Fasciculus 
cuneatus.  4.  Gracile  nucleus.  5.  Cuneate  nucleus.  6, 
6',  6".  Sensory  fibres  forming  the  lemniscus.  7.  Sen- 
sory decussation.  8.  Cerebellar  fibres  uncrossed  (in 
black).    9.  Cerebellar  fibres  crossed  (in  black). 


Fig.  703. — Transverse  section  passing  through  the 
sensory  decussation.  (Schematic.)  (Testut.)  1.  Ante- 
rior median  fissure.  2.  Posterior  median  sulcus.  3,  3. 
Head  and  base  of  anterior  column  (in  red) .  4.  Hypo- 
glossal nerve.  5.  Bases  of  posterior  columns.  6.  Gracile 
nucleus.  7.  Cuneate  nucleus.  8,  8.  Lemniscus.  9. 
Sensory  decussation.      10.  Cerebrospinal  fasciculus. 


around  the  cells  of  these  nuclei  (Fig.  702).  From  the  cells  of  the  nuclei  new  fibres 
arise ;  some  of  these  are  continued  as  the  posterior  external  arcuate  fibres  into  the 
restiform  body,  and  through  it  to  the  cerebellum,  but  most  of  them  pass  forward 
through  the  neck  of  the  posterior  column,  thus  cutting  off  its  head  from  its  base 
(Fig.  703) .  Curving  forward,  they  decussate  in  the  middle  line  with  the  correspond- 
ing fibres  of  the  opposite  side,  and  run  upward  immediately  behind  the  cerebro- 
spinal fibres,  as  a  flattened  band,  named  the  lemniscus  or  fillet.  The  decussation 
of  these  sensory  fibres  is  situated  above  that  of  the  motor  fibres,  and  is  named 
the  decussation  of  the  lemniscus  or  sensory  decussation.  The  lemniscus  is  joined  by 
the  spinothalamic  fasciculus  (page  817),  the  fibres  of  w^hich  are  derived  from  the 
cells  of  the  gray  substance  of  the  opposite  side  of  the  medulla  spinalis. 

The  base  of  the  posterior  column  at  first  lies  on  the  dorsal  aspect  of  the  central 
canal,  but  when  the  latter  opens  into  the  fourth  ventricle,  it  appears  in  the  lateral 
part  of  the  rhomboid  fossa.  It  forms  the  terminal  nuclei  of  the  sensory  fibres  of 
the  vagus  and  glossopharyngeal  nerves,  and  is  associated  with  the  vestibular  part 
of  the  acoustic  nerve  and  the  sensory  root  of  the  facial  nerve.  Still  higher,  it  forms  a 
mass  of  pigmented  cells — the  locus  coeruleus — in  which  some  of  the  sensory  fibres 


828 


NEUROLOGY 


of  the  trigeminal  nerve  appear  to  end.  The  head  of  the  posterior  column  forms  a 
long  nucleus,  in  which  the  fibres  of  the  spinal  tract  of  the  trigeminal  nerve  largely 
end. 


glossal 
Nticleus  of  medial  eminence   nucleus 


Hypo-       ^'T?     ^''^''^" 


nuclei 


Raphe  ~ 
Formatio  reticularis  grisea  — 

Formatio  reticularis  alba ^" 


Accessory  olivary  nuclei   _^_-, 


Nucleus  gracilis 

Nucleus  cuneatus 

Restiform  hody 


Spinal  tract  of 
Yi    trigeminal  nerve 


Vagus  nerve 
Arcuate  fibres 


Infaior  olivary  nucleus 

Hypoglossal  nerve 
Anterior  median  fissure 
Fig.  704. — Section  of  the  medulla  oblongata  at  about  the  middle  of  the  olive.     (Schwalbe.) 

Nucleus  of  vagus 
Ligula        I      Medial  longitudinal  fasciculus 
Nucleus  intercalatus 


Eypoglossal  'nucleus 
Fourth  ventricle 


Fasciculus  solitarius 

Descending  root  of  vestibular  nerve 
Restiform  body 

Nucleus  lateralis 


Spinal  tract  of  tri- 
geminal nerve 


Vagus  nerve 

Nucleus  amhiguus 
Dorsal  accessory 
olivary  nucleus 


Inferior  olivary  nucleus 
Hypoglossal  ne7-ve 


Cerebrospinal  fasciculus  /  \         Medial  accessory  olivary  nucleus 

Lemniscus  Nucleus  arcuatus 

Fig.  705. — Transverse  section  of  medulla  oblongata  below  the  middle  of  the  olive. 

The  cerebellospinal  fasciculus  {fasciculus  cerebellospiJialis;  direct  cerebellar  tract) 
leaves  the  lateral  district  of  the  medulla  oblongata;  most  of  its  fibres  are  carried 
backward  into  the  restiform  body  of  the  same  side,  and  through  it  are  conveyed 


THE  RHOMBENCEPHALOX  OR  HIND-BRAIN 


829 


to  tlie  cerebelliiin ;  but  some  run  ui)\varcl  with  the  fil)res  of  the  lemniscus,  and, 
reaching  the  inferior  colHcuhis,  undergo  decussation,  and  are  carried  to  the 
cerebehum  through  tlie  brachium  conjunctivum. 

The  proper  fasciculi  (baffi^-  bundles)  of  the  anterior  and  lateral  funiculi  largely 
consist  of  intersegmental  fibres,  which  link  together  the  difl'erent  segments  of  the 
medulla  spinalis;  they  assist  in 
the  production  of  the  formatio 
reticularis  of  the  medulla  oblon- 
gata, and  many  of  them  are  ac- 
cumulated into  a  fasciculus  which 
runs  up  close  to  the  median  raphe 
between  the  lemniscus  and  the 
rhomboid  fossa;  this  strand  is 
named  the  medial  longitudinal 
fasciculus,  and  will  be  again  re- 
ferred to. 

Gray  Substance  of  the  Medulla 
Oblongata  (Figs.  704,  705).— In 
addition  to  the  gracile  and  cun- 
eate  nuclei,  there  are  several 
other  nuclei  to  be  considered. 
Some  of  these  are  traceable  from 
the  gray  substance  of  the  medulla 
spinalis,  while  others  are  unrepre- 
sented in  it. 

1.  The  hypoglossal  nucleus  is 
derived  from  the  base  of  the 
anterior  column;  in  the  lower 
closed  part  of  the  medulla  ob- 
longata it  is  situated  on  the  ven- 
trolateral aspect  of  the  central 
canal;  but  in  the  upper  part  it 
approaches  the  rhomboid  fossa, 
where  it  lies  close  to  the  middle 
line,  under  an  eminence  named 
the  trigonum  hypoglossi  (Fig.  719). 
The  nucleus  measures  about 
2  cm.  in  length,  and  consists 
of  large  multipolar  nerve  cells, 
whose  axons  constitute  the  roots 
of  the  hypoglossal  nerve.  These 
nerve  roots  pass  forward  between 
the  anterior  and  lateral  districts  of  the  medulla  oblongata,  and  emerge  from  the 
antero-lateral  sulcus. 

2.  The  motor  nucleus  (Figs.  706,  707),  common  to  the  glossopharyngeal,  vagus, 
and  cerebral  part  of  the  accessory  nerves,  is  named  the  nucleus  ambiguus.  It  rep- 
resents the  head  of  the  anterior  column,  lies  deeply  in  the  formatio  reticularis 
grisea,  and  extends  throughout  nearly  the  whole  length  of  the  medulla  oblongata. 

3.  The  sensory  nucleus  (Figs.  706,  708),  or  terminal  nucleus  of  the  sensory  fibres 
of  the  glossopharyngeal  and  vagus,  represents  the  base  of  the  posterior  column. 
It  measures  about  2  cm.  in  length,  and  in  the  lower,  closed  part  of  the  medulla 
oblongata  is  situated  behind  the  hypoglossal  nucleus;  whereas  in  the  upper,  open 
part  it  lies  lateral  to  that  nucleus,  and  corresponds  to  an  eminence,  named  the 
ala  cinerea  {trigonum  vagi),  in  the  rhomboid  fossa. 


Nucleus 
(IX  i 


Fig.  706. — The  cerebral  nerve  nuclei  schematically  represented; 
dorsal  -vaew.  Motor  nuclei  in  red;  sensory  in  blue.  (The  olfactory 
and  optic  centres  are  not  represented.) 


830 


NEUROLOGY 


4.  The  nuclei  of  the  acoustic  nerve  are  described  on  page  830. 

5.  The  olivary  nuclei  (Fig.  704)  are  three  in  number  on  either  side  of  the  middle 
line,  viz.,  the  inferior  ohvary  nucleus,  and  the  medial  and  dorsal  accessory  olivary 
nuclei;  they  consist  of  small,  round,  yellowish  cells  and  numerous  fine  nerve  fibres. 
(a)  The  inferior  olivary  nucleus  is  the  largest,  and  is  situated  within  the  olive. 
It  consists  of  a  gray  folded  lamina  arranged  in  the  form  of  an  incomplete  capsule, 
opening  medially  by  an  aperture  called  the  hilus ;  emerging  from  the  hilus  are  numer- 
ous fibres  which  collectively  constitute  the  peduncle  of  the  olive,  ih)  The  medial 
accessory  olivary  nucleus  lies  between  the  inferior  olivary  nucleus  and  the  pyramid, 
and  forms  a  curved  lamina,  the  concavity  of  which  is  directed  laterally.  The 
fibres  of  the  hypoglossal  nerve,  as  they  traverse  the  medulla,  pass  between  the 
medial  accessory  and  the  inferior  olivary  nuclei,  (c)  The  dorsal  accessory  olivary 
nucleus  is  the  smallest,  and  appears  on  transverse  section  as  a  curved  lamina 
behind  the  inferior  olivarv  nucleus. 


Cervical  nerves 


Fig.  707. — Nuclei  of  origin  of  cerebral  motor  nerves  schematically  represented;  lateral  view. 


The  inferior  olivary  nucleus  is  connected  (1)  with  that  of  the  opposite  side 
by  fibres  which  cross  through  the  raphe ;  (2)  with  the  anterior  column  of  the  same 
side  of  the  medulla  spinalis  by  the  spinoblivary  fasciculus;  (3)  with  the  thalamus 
of  the  cerebrum  by  the  cerebroolivary  fasciculus  which  passes  through  the  pons 
and  tegmentum;  (4)  with  the  opposite  cerebellar  hemisphere  b}^  the  cerebello- 
oiivary  fasciculus,  the  fibres  of  w^hich  cross  the  raphe  and  turn  backward  to  enter 
the  deep  part  of  the  restiform  body.  Removal  of  one  cerebellar  hemisphere  is 
followed  by  atrophy  of  the  opposite  olivary  nucleus. 

6.  The  nucleus  arcuatus  is  described  below  with  the  anterior  external  arcuate 
fibres. 

Restiform  Bodies  (corpus  restiformes) . — ^The  position  of  the  restiform  bodies  has 
already  been  described   (page  825).     Each  comprises:     (1)   the  cerebellospinal 


THE  RHOMBENCEPHALON  OR  HIND-BRAIN 


831 


fasciculus,  ^vhicll  ascends  from  the  lateral  funiculus  of  the  medulla  spinalis;  (2) 
descending  cerebellar  fibres,  many  of  which  are  disseminated  throughout  the  per- 
ipheral part  of  the  anterior  and  lateral  funiculi  of  the  medulla  spinalis,  while  others 
are  conducted  to  the  motor  nuclei  of  the  cerebral  nerves;  and  (3)  the  arcuate  fibres, 
which  are  arranged  in  three  sets,  viz.,  internal,  and  anterior  and  posterior  external. 
The  internal  arcuate  fibres  form  the  deeper  and  larger  part  of  the  restiform 
body.  They  decussate  in  the  middle  line  of  the  medulla  oblongata,  and  having 
reached  the  ()i)posite  side,  terminate  partly  in  the  gracile  and  cuneate  nuclei, 
while  many  of  them  enter  the  hilus  of  the  inferior  olivar}^  nucleus,  and  constitute 
the  cerebelloolivary  tract  already  described  (Fig.  7G9). 


Fig.  708. — Primary  terminal  nuclei    of    the    afferent   (sensory)    cerebral    nerves    schematically  represented;    lateral 
view.     The  olfactory  and  optic  centres  are  not  represented. 


The  anterior  external  arcuate  fibres  vary  as  to  their  prominence  in  diflFerent  cases : 
in  some  they  form  an  almost  continuous  layer  covering  the  pyramid  and  olive, 
w^hile  in  others  they  are  barely  visible  on  the  surface.  They  arise  from  the  cells 
of  the  gracile  and  cuneate  nuclei,  and  passing  forward  through  the  formatio  reticu- 
laris, decussate  in  the  middle  line.  Most  of  them  reach  the  surface  by  way  of  the 
anterior  median  fissure,  and  arch  backward  over  the  pyramid.  Reinforced  by 
others  which  emerge  between  the  pyramid  and  olive,  they  pass  backward  over 
the  olive  and  lateral  district  of  the  medulla  oblongata,  and  enter  the  restiform 
body.  They  thus  connect  the  cerebellum  with  the  gracile  and  cuneate  nuclei  of 
the  opposite  side.  As  the  fibres  arch  across  the  pyramid,  they  enclose  a  small 
nucleus  which  lies  in  front  of  and  medial  to  the  pyramid.  This  is  named  the  nucleus 
arcuatus,  and  is  serially  continuous  above  with  the  nuclei  pontis  in  the  pons;  it 
contains  small  fusiform  cells,  around  which  some  of  the  arcuate  fibres  end,  and 
from  which  others  arise. 


i.'^o 


NEUROLOGY 


The  posterior  external  arcuate  fibres  also  take  origin  in  the  gracile  and  cuneate 
nuclei;  they  pass  to  the  restiform  body  of  the  same  side. 


Fig.  709. — Diagram  showing  the  course  of  the  arcuate  fibres.  (Testut.)  1.  Medulla  oblongata  anterior  surface. 
2.  Anterior  median  fissure.  3.  Fourth  ventricle.  4.  Inferior  olivary  nucleus,  with  the  accessory  olivary  nuclei.  5. 
Gracile  nucleus.  6.  Cuneate  nucleus.  7.  Trigeminal.  8.  Restiform  bodies,  seen  from  in  front.  9.  Posterior  external 
arcuate  fibres.  10.  Anterior  external  arcuate  fibres.  11.  Internal  arcuate  fibres.  12.  Peduncle  of  inferior  olivary 
nucleus.    13.  Nucleus  arcuatus.     14.  Vagus.    15.  Hypoglossal. 


Fig.  710. — The  formatio  reticularis  of  the  medulla  oblongata,  shown  by  a  transverse  section  passing  through  the 
middle  of  the  olive.  (Testut.)  1.  Anterior  median  fissure.  2.  Fourth  ventricle.  3.  Formatio  reticularis,  with  3', 
its  internal  part  (reticularis  alba),  and  3",  its  external  part  (reticularis  grisea).  4.  Raph6.  5.  Pyramid.  6.  Lemniscus. 
7.  Inferior  oUvary  nucleus  with  the  two  accessory  ohvary  nuclei.  8.  Hypoglossal  nerve,  with  S',  its  nucleus  of  origm. 
9.  Vagus  nerve,  with  9',  its  nucleus  of  termination.  10.  Lateral  dorsal  acoustic  nucleus.  11.  Nucleus  ambiguus 
(nucleus  of  origin  of  motor  fibres  of  glossopharyngeal,  vagus,  and  cerebral  portion  of  spinal  accessory).  12.  Gracile 
nucleus.  13.  Cuneate  nucleus.  14.  Head  of  posterior  column,  with  14',  the  lower  sensory  root' of  trigeminal  nerve. 
15.  Fasciculus  soUtarius.  16.  Anterior  external  arcuate  fibres,  with  16',  the  nucleus  arcuatus.  17.  Nucleus  laterahs 
18.  Nucleus  of  fasciculus  teres.     19.  Ligula. 

Formatio  Reticularis  (Fig.  710). — This  term  is  applied  to  the  coarse  reticulum 
which  occupies  the  anterior  and  lateral  districts  of  the  medulla  oblongata.     It 


TIIK  lillOMHESCEI'IIALOX  OR  HIXD-HRMX  833 

is  situated  behiiul  the  jnraniid  and  olJN'e,  extending-  laterally  as  far  as  the  restifurm 
bodies,  and  dorsally  to  within  a  short  distance  of  the  rhomboid  fossa.  The  reticulum 
is  caused  by  the  intersection  of  bundles  of  fibres  running  at  right  angles  to  each 
other,  some  being  longitudinal,  others  more  or  less  transverse  in  direction.  The 
formatio  reticularis  presents  a  ditt'erent  appearance  in  the  anterior  district  from 
what  it  does  in  the  lateral;  in  the  former,  there  is  an  almost  entire  absence  of  nerve 
cells,  and  hence  this  part  is  known  as  the  reticularis  alba;  whereas  in  the  lateral 
district  nerve  cells  are  numerous,  and  as  a  consequence  it  presents  a  gray  appear- 
ance, and  is  termed  the  reticularis  grisea. 

In  the  substance  of  the  formatio  reticularis  are  two  small  nuclei  of  gray  matter: 
one,  the  inferior  central  nucleus  {luicleus  of  Roller),  near  the  dorsal  aspect  of  the  hilus 
of  the  inferior  olivary  nucleus;  the  other,  the  nucleus  lateralis,  between  the  olive 
and  the  spinal  tract  of  the  trigeminal  nerve. 

In  the  reticularis  alba  the  longitudinal  fibres  form  two  well-defined  fasciculi, 
viz.:  (1)  the  lemniscus,  which  lies  close  to  the  raphe,  immediately  behind  the 
fibres  of  the  pyramid ;  and  (2)  the  medial  longitudinal  fasciculus,  which  is  continued 
upward  from  the  anterior  and  lateral  proper  fasciculi  of  the  medulla  spinalis,  and, 
in  the  upper  part  of  the  medulla  oblongata,  lies  between  the  lemniscus  and  the  gray 
substance  of  the  rhomboid  fossa.  The  longitudinal  fibres  in  the  reticularis  grisea 
are  derived  from  the  lateral  funiculus  of  the  medulla  spinalis  after  the  lateral 
cerebrospinal  fasciculus  has  passed  over  to  the  opposite  side,  and  the  cerebello- 
spinal fasciculus  has  entered  the  restiform  body.  They  form  indeterminate  fibres, 
with  the  exception  of  a  bundle  named  the  fasciculus  solitarius,  which  is  made 
up  of  descending  fibres  of  the  vagus  and  glossopharyngeal  nerves.  The  trans- 
verse fibres  of  the  formatio  reticularis  are  the  arcuate  fibres  already  described 
(page  831). 

Applied  Anatomy. — In  bulbar  paralysis,  i.  e.,  paralysis  of  the  medulla  oblongata,  which  is 
realty  a  special  form  of  a  progressive  degeneration  affecting  the  whole  efferent  or  motor  tract, 
the  disease  begins  with  impairment  of  the  movements  of  the  lips,  tongue,  pharynx,  and  larynx, 
due  to  degeneration  of  the  motor  cells  in  the  nuclei  of  the  medulla  oblongata.  Speech  and  swallow- 
ing become  difficult,  and  the  saliva  dribbles  from  the  open  mouth.  Other  groups  of  muscles 
soon  become  involved,  and  death  often  occm-s  from  "aspiration  pneumonia/'  set  up  by  food 
that  has  accidentally  passed  down  the  trachea. 

The  Pons  (j^ons  Varoli).  —  The  pons  or  forepart  of  the  rhombencephalon  is 
situated  in  front  of  the  cerebellum.  From  its  superior  surface  the  cerebral  peduncles 
emerge,  one  on  either  side  of  the  middle  line.  Curving  around  each  peduncle,  close 
to  the  upper  surface  of  the  pons,  a  thin  white  band,  the  taenia  pontis,  is  frequently 
seen ;  it  enters  the  cerebellum  between  the  brachium  pontis  and  brachium  conjunc- 
tivum.  Behind  and  below,  the  pons  is  continuous  with  the  medulla  oblongata, 
but  is  separated  from  it  in  front  by  a  furrow  in  which  the  abducent,  facial,  and 
acoustic  nerves  appear. 

Its  ventral  or  anterior  surface  (pars  hasilaris  pontis)  is  very  prominent,  markedly 
convex  from  side  to  side,  less  so  from  above  downward.  It  consists  of  transverse 
fibres  arched  like  a  bridge  across  the  middle  line,  and  gathered  on  either  side  into 
a  compact  mass  which  forms  the  brachium  pontis.  It  rests  upon  the  clivus  of  the 
sphenoidal  bone,  and  is  limited  above  and  below  by  well-defined  borders.  In  the 
middle  line  is  the  sulcus  basilaris  for  the  lodgement  of  the  basilar  artery;  this  sulcus 
is  bounded  on  either  side  by  an  eminence  caused  by  the  descent  of  the  cerebrospinal 
fibres  through  the  substance  of  the  pons.  Outside  these  eminences,  near  the  upper 
border  of  the  pons,  the  trigeminal  nerves  make  their  exit,  each  consisting  of  a 
smaller,  medial,  motor  root,  and  a  larger,  lateral,  sensory  root;  vertical  lines 
drawn  immediately  beyond  the  trigeminal  nerves,  may  be  taken  as  the  boundaries 
betw^een  the  ventral  surface  of  the  pons  and  the  brachia  pontis. 
53 


834 


NEUROLOGY 


Its  dorsal  or  posterior  surface  ipar-s  dorsalis  pontis),  triangular  in  shape,  is  liidden 
by  the  cerebellum,  and  is  bounded  laterally  by  the  brachia  conjunctiva ;  it  forms 
the  upper  part  of  the  rhomboid  fossa,  with  which  it  will  be  described. 

Structure  (Fig.  711). — ^Transverse  sections  of  the  pons  show  it  to  be  composed 
of  two  parts  which  differ  in  appearance  and  structure:  thus,  the  basilar  or  ventral 
portion  consists  for  the  most  part  of  fibres  arranged  in  transverse  and  longitudinal 
bundles,  together  with  a  small  amount  of  gray  substance;  while  the  dorsal  tegmental 
portion  is  a  continuation  of  the  reticular  formation  of  the  medulla  oblongata, 
and  most  of  its  constituents  are  continued  into  the  tegmenta  of  the  cerebral 
peduncles. 


Fig.  711. — Coronal  section  of  the  pons,  at  its  upper  part.  (Testut.)  1.  Fourth  ventricle;  its  ependyma  in  yellow. 
2.  Anterior  mediillary  velum,  with  2',  its  white  stratum,  and  2",  its  gray  stratum.  3.  MesencephaUc  root  of  trigeminal. 
4.  Nerve  cells  associated  with  this  root.  5.  Medial  longitudinal  fasciculus.  6.  Formatio  reticularis.  7.  Lateral 
sulcus.  8.  Section  of  brachium  conjunotivum.  9.  Medial  lemniscus.  9'.  Lateral  lemniscus.  10,  10.  Transverse 
fibres  of  pons.     11,  11.  Cerebrospinal  fasciculi.     12.  Raph6.     V.  Trigeminal. 

The  basilar  part  of  the  pons  consists  of — {a)  superficial  and  deep  transverse 
fibres,  (h)  longitudinal  fasciculi,  and  (c)  some  small  nuclei  of  gray  substance, 
termed  the  nuclei  pontis. 

The  superficial  transverse  fibres  [fihrae  pontis  superficiales)  constitute  a  rather 
thick  layer  on  the  ventral  surface  of  the  pons,  and  are  collected  into  a  large 
rounded  bundle  on  either  side  of  the  middle  line.  This  bundle,  with  the  addition 
of  some  transverse  fibres  from  the  deeper  part  of  the  pons,  forms  the  greater  part 
of  the  brachium  pontis. 

The  deep  transverse  fibres  {fihrae  pontis  profundae)  partly  intersect  and  partly 
lie  on  the  dorsal  aspect  of  the  cerebrospinal  fibres.  They  course  to  the  lateral 
border  of  the  pons,  and  form  part  of  the  brachium  pontis;  the  further  connections 
of  this  brachium  will  be  discussed  with  the  anatomy  of  the  cerebellum. 

The  longitudinal  fasciculi  (fasciculi  longitudinales)  are  derived  from  the  cerebral 
peduncles,  and  enter  the  upper  surface  of  the  pons.  They  stream  downward  on 
either  side  of  the  middle  line  in  larger  or  smaller  bundles,  separated  from  each 
other  by  the  deep  transverse  fibres;  these  longitudinal  bundles  cause  a  forward 
projection  of  the  superficial  transverse  fibres,  and  thus  give  rise  to  the  eminences 
on  the  anterior  surface.    Some  of  these  fibres  end  in  the  nuclei  pontis,  and  others, 


THE  RHOMBENCEPHALON  OR  IIIND-BRAIN  835 

after  decussating,  in  the  motor  nuclei  of  the  trigeminal,  abducent,  facial,  and  hypo- 
glossal nerves ;  but  most  of  them  are  carried  through  the  pons,  and  at  its  lower  surface 
are  collected  into  the  pyramids  of  the  medulla.  The  fibres  which  end  in  the  motor 
nuclei  of  the  cerebral  nerves  are  derived  from  the  cells  of  the  cerebral  cortex,  and 
bear  the  siune  relation  to  the  motor  cells  of  the  cerebral  nerves  that  the  cerebro- 
spinal fibres  bear  to  the  motor  cells  in  the  anterior  column  of  the  medulla  spinalis. 

The  nuclei  pontis  are  serially  continuous  with  the  arcuate  nuclei  in  the  medulla, 
and  consist  of  small  groups  of  multipolar  nerve  cells  which  are  scattered  between 
the  bundles  of  transverse  fibres. 

The  dorsal  or  tegmental  part  of  the  pons  is  chiefly  composed  of  an  upward  con- 
tinuation of  the  reticular  formation  and  gray  substance  of  the  medulla  oblongata. 
It  consists  of  transverse  and  longitudinal  fibres  and  also  contains  important  gray 
nuclei,  and  is  subdivided  by  a  median  raphe,  which,  however,  does  not  extend  into 
the  basilar  part,  being  obliterated  by  the  transverse  fibres.  The  transverse  fibres 
in  the  lower  part  of  the  pons  are  collected  into  a  distinct  strand,  named  the 
trapezoid  body.  This  consists  of  fibres  which  arise  from  the  cells  of  the  ventral  or 
accessory  acoustic  nucleus,  and  will  be  referred  to  in  connection  with  the  cochlear 
division  of  the  acoustic  nerve.  In  the  substance  of  the  trapezoid  body  is  a  collec- 
tion of  nerve  cells,  which  constitutes  the  trapezoid  nucleus.  The  longitudinal  fibres, 
which  are  continuous  with  those  of  the  medulla  oblongata,  are  mostly  collected 
into  two  fasciculi  on  either  side.  One  of  these  lies  between  the  trapezoid  body 
and  the  reticular,  formation,  and  forms  the  upward  prolongation  of  the  lemniscus; 
the  second  is  situated  near  the  floor  of  the  fourth  ventricle,  and  is  the  medial 
longitudinal  fasciculus.  Other  longitudinal  fibres,  more  diffusely  distributed,  arise 
from  the  cells  of  the  gray  substance  of  the  pons. 

The  rest  of  the  dorsal  part  of  the  pons  is  a  continuation  upward  of  the  formatio 
reticularis  of  the  medulla  oblongata,  and,  like  it,  presents  the  appearance  of  a  net- 
work, in  the  meshes  of  which  are  numerous  nerve  cells.  Besides  these  scattered 
nerve  cells,  there  are  some  larger  masses  of  gray  substance,  viz.,  the  superior 
olivary  nucleus  and  the  nuclei  of  the  trigeminal,  abducent,  facial,  and  acoustic 
nerves  (Fig.  706). 

1.  The  superior  olivary  nucleus  {nucleus  olivaris  sujjerior)  is  a  small  mass  of  gray 
substance  situated  on  the  dorsal  surface  of  the  lateral  part  of  the  trapezoid  body. 
Rudimentary  in  man,  but  well  developed  in  certain  animals,  it  exhibits  the  same 
structure  as  the  inferior  olivary  nucleus,  and  is  situated  immediately  above  it. 
Some  of  the  fibres  of  the  trapezoid  body  end  by  arborizing  around  the  cells  of 
this  nucleus,  while  others  arise  from  these  cells. 

2.  The  nuclei  of  the  trigeminal  nerve  (nuclei  n.  trigemini)  in  the  pons  are  two  in 
number:  a  motor  and  a  sensory.  The  motor  nucleus  is  situated  in  the  upper  part  of 
the  pons,  close  to  its  posterior  surface  and  along  the  line  of  the  lateral  margin  of  the 
fourth  ventricle.  The  axis-cylinder  processes  of  its  cells  form  a  portion  of  the  motor 
root  of  the  trigeminal  nerve :  the  remaining  fibres  of  the  motor  root  of  this  nerve  con- 
sist of  a  fasciculus  which  arises  from  the  gray  substance  of  the  floor  of  the  cerebral 
aqueduct,  and  hence  is  named  the  mesencephalic  root.  The  sensory  nucleus  is  lateral 
to  the  motor  one,  and  beneath  the  brachium  conjunctivum.  Some  of  the  sensory 
fibres  of  the  trigeminal  nerve  end  in  this  nucleus;  but  the  greater  number  descend, 
under  the  name  of  the  spinal  tract  of  the  trigeminal  nerve,  to  end  in  the  substantia 
gelatinosa  of  Rolando.  The  roots,  motor  and  sensory,  of  the  trigeminal  nerve 
pass  through  the  substance  of  the  pons  and  emerge  near  the  upper  margin  of  its 
anterior  surface. 

3.  The  nucleus  of  the  abducent  nerve  {nucleus  n.  ahducentis)  is  a  circular  mass  of 
gray  substance  situated  close  to  the  fioor  of  the  fourth  ventricle,  above  the  striae 
medullares  and  subjacent  to  the  medial  eminence:  it  lies  a  little  lateral  to  the 
ascending  part  of  the  facial  nerve.    The  fibres  of  the  abducent  nerve  pass  forward 


836  NEUROLOGY 

through  the  entire  thickness  of  the  pons  on  the  medial  side  of  the  superior  ohvary 
nucleus,  and  between  the  lateral  fasciculi  of  the  cerebrospinal  fibres,  and  emerge 
in  the  furrow  between  the  lower  border  of  the  pons  and  the  pyramid  of  the 
medulla  oblongata. 

4.  The  nucleus  of  the  facial  nerve  (nucleus  n.  fascial i.s-)  is  situated  deeply  in  the 
reticular  formation  of  the  pons,  on  the  dorsal  aspect  of  the  superior  oli^-ary  nucleus, 
and  the  roots  of  the  nerve  derived  from  it  pursue  a  remarkably  tortuous  course  in 
the  substance  of  the  pons.  At  first  they  pass  backward  and  medial  ward  until  they 
reach  the  rhomboid  fossa,  close  to  the  median  sulcus,  where  they  are  collected  into 
a  round  bundle;  this  passes  upward  and  forward,  producing  an  elevation,  the 
colliculus  facialis,  in  the  rhomboid  fossa,  and  then  takes  a  sharp  bend,  and  arches 
lateralward  through  the  substance  of  the  pons  to  emerge  at  its  lower  border  in 
the  interval  between  the  olive  and  the  restiform  body  of  the  medulla  oblongata. 

5.  The  nuclei  of  the  acoustic  nerve  {nuclei  n.  acustici)  consists  of  a  cochlear  and  a 
vestibular  division.  The  fibres  of  the  cochlear  division  end  in  two  nuclei:  (a)  the 
lateral  cochlear  nucleus,  corresponding  to  the  tuberculum  acusticum  on  the  dorso- 
lateral surface  of  the  restiform  body;  and  (6)  the  ventral  or  accessory  cochlear 
nucleus,  placed  between  the  two  divisions  of  the  nerve,  on  the  ventral  aspect  of 
the  restiform  body.  The  nuclei  in  which  the  vestibular  division  ends  are  (a)  the 
dorsal  or  chief  vestibular  nucleus,  corresponding  to  the  low^er  part  of  the  area 
acustica  in  the  rhomboid  fossa;  the  caudal  end  of  this  nucleus  is  sometimes 
termed  the  descending  or  spinal  vestibular  nucleus;  (6)  the  nucleus  of  Deiters,  con- 
sisting of  large  cells  and  situated  in  the  lateral  angle  of  the  rhomboid  fossa;  the 
dorso-lateral  part  of  this  nucleus  is  sometimes  termed  the  nucleus  of  Bechterew. 

Applied  Anatomy. — Injury  to  the  pons,  such  as  may  occur  on  the  occlusion  or  rupture  of  one 
of  its  bloodvessels,  often  gives  rise  to  a  special  train  of  symptoms  that  is  almost  diagnostic.  Pon- 
tine lesions  are  characterized  mainly  by  "alternate  paralyses;"  that  is  to  say,  by  paralysis  of 
one  of  the  motor  cerebral  nerves  on  one  side,  and  of  the  limbs  on  the  other  side  of  the  body.  Thus 
a  hemorrhage  into  the  lower  part  of  the  pons  might  cause  paralysis  of  the  face,  Imuer  segment 
paralysis,  on  the  same  side,  from  destruction  of  the  facial  nucleus  or  nerve  root,  and  paralysis 
of  the  arm  and  leg  on  the  opposite  side  from  injury  to  the  adjacent  cerebrospinal  tract.  In  the 
same  way,  paralysis  of  the  Rectus  lateralis  of  one  eye  and  of  the  Rectus  mediahs  of  the  other, 
conjugate  paralysis,  of  the  muscles  turning  the  two  eyes  in  one  direction,  and  often  paralysis  of 
one  side  of  the  face  as  well,  together  with  palsy  of  the  hmbs  on  the  opposite  side  of  the  body, 
may  be  found  when  the  lesion  occurs  about  the  nucleus  of  the  abducent  nerve.  Hearing  is  often 
unaffected  in  pontine  lesions,  possibly  because  the  central  acoustic  tract  occupies  a  ventral  and 
lateral  position  in  the  pons. 

The  Cerebellum. — The  cerebellum  constitutes  the  largest  part  of  the  hind- 
brain.  It  lies  behind  the  pons  and  medulla  oblongata;  between  its  central  portion 
and  these  structures  is  the  cavity  of  the  fourth  ventricle.  It  rests  on  the  inferior 
occipital  fossse,  while  above  it  is  the  tentorium  cerebelli,  a  fold  of  dura  mater 
which  separates  it  from  the  tentorial  surface  of  the  cerebrum.  It  is  somewhat 
oval  in  form,  but  constricted  medially  and  flattened  from  abo^-e  downward,  its 
greatest  diameter  being  from  side  to  side.  Its  surface  is  not  convoluted  like  that 
of  the  cerebrum,  but  is  traversed  by  numerous  curved  furrows  or  sulci,  which 
vary  in  depth  at  different  parts,  and  separate  the  laminae  of  which  it  is  composed. 
Its  average  weight  in  the  male  is  about  150  gms.  In  the  adult  the  proportion 
between  the  cerebellum  and  cerebrum  is  about  1  to  8,  in  the  infant  about  1  to  20. 

Lobes  of  the  Cerebellum. — The  cerebellum  consists  of  three  parts,  a  median  and 
two  lateral,  which  are  continuous  with  each  other,  and  are  substantially  the  same 
in  structure.  The  median  portion  is  constricted,  and  is  called  the  vermis,  from  its 
annulated  appearance  which  it  owes  to  the  transverse  ridges  and  furrows  upon  it; 
the  lateral  expanded  portions  are  named  the  hemispheres.  On  the  upper  surface 
of  the  cerebellum  the  vermis  is  elevated  above  the  level  of  the  hemispheres,  but 
on  the  under  surface  it  is  sunk  almost  out  of  sight  in  the  bottom  of  a  deep  depres- 


THE  RHOMBENCEPHALON  OR  HIND-BRAIN 


837 


sion  between  tliein;  this  depression  is  ealled  the  vallecula  cerebelli,  and  lodges  the 
posterior  part  of  the  medulla  oblongata.  The  part  of  the  vermis  on  the  upper 
surface  of  the  cerebellum  is  named  the  superior  vermis;  that  on  the  lower  surface, 
the  inferior  vermis.  The  hemispheres  are  separated  below  and  behind  by  a  deep 
notch,  the  posterior  cerebellar  notch,  and  in  front  by  a  broader  shallower  notch, 
the  anterior  cerebellar  notch.  The  anterior  notch  lies  close  to  the  pons  and  upper 
part  of  the  medulla,  and  its  superior  edge  encircles  the  inferior  colliculi  and  the 
brachia  conjunctiva  cerebelli.  The  posterior  notch  contains  the  upper  part  of  the 
falx  cerebelli,  a  fold  of  dura  mater. 

The  cerebellum  is  characterized  by  its  laminated  or  foliated  appearance;  it  is 
marked  by  deep,  somewhat  curved  fissures,  which  extend  for  a  considerable  dis- 
tance into  its  substance,  and  divide  it  into  a  series  of  layers  or  leaves.  The  largest 
and  deepest  fissure  is  named  the  horizontal  sulcus.  It  commences  in  front  of  the 
pons,  and  passes  horizontally  around  the  free  margin  of  the  hemisphere  to  the 
middle  line  behind,  and  divides  the  cerebellum  into  an  upper  and  a  lower  portion. 
Several  secondary  but  deep  fissures  separate  the  cerebellum  into  lobes,  and  these 
are  further  subdivided  by  shallower  sulci,  which  separate  the  individual  folia  or 
lamina?  from  each  other.  Sections  across  the  laminae  show  that  the  folia,  though 
differing  in  appearance  from  the  convolutions  of  the  cerebrum,  are  analogous 
to  them,  inasmuch  as  they  consist  of  central  white  substance  covered  by  gray 
substance. 

Ala  lobuli  centralis  Prceclival  fissure 

Lohulus  centralis       \  ^°:*Z'!i"'^     ..^^        I         Postclival 

fissure 

Horizontal 
sulcus 


Fig.   712. — Upper  surface  of  the  cerebellum.      (Schafer.) 


The  cerebellum  is  connected  to  the  cerebrum,  pons,  and  medulla  oblongata; 
to  the  cerebrum  by  the  brachia  conjunctiva,  to  the  pons  by  the  brachia  pontis, 
and  to  the  medulla  oblongata  by  the  restiform  bodies. 

The  upper  surface  of  the  cerebellum  (Fig.  712)  is  elevated  in  the  middle  and  sloped 
toward  the  circumference^  the  hemispheres  being  connected  together  by  the  supe- 
rior vermis,  which  assumes  the  form  of  a  raised  median  ridge,  most  prominent 
in  front,  but  not  sharply  defined  from  the  hemispheres.  The  superior  vermis  is 
subdivided  from  before  backward  into  the  lingula,  the  lobulus  centralis,  the  mon- 
ticulus  and  the  folium  vermis,  and  each  of  these,  with  the  exception  of  the  lingula, 
is  continuous  with  the  corresponding  parts  of  the  hemispheres — the  lobulus 
centralis  with  the  alae,  the  monticulus  with  the  quadrangular  lobules,  and  the 
folium  vermis  with  the  superior  semilunar  lobules. 

The  lingula  (lingula  cerebelli)  is  a  small  tongue-shaped  process,  consisting  of 
four  or  five  folia;  it  lies  in  front  of  the  lobulus  centralis,  and  is  concealed  by  it. 
Anteriorly,  it  rests  on  the  dorsal  surface  of  the  anterior  medullary  velum,  and  its 
w^hite  substance  is  continuous  w-ith  that  of  the  velum. 


838 


NEUROLOGY 


The  Lobulus  Centralis  and  Alae. — The  lobulus  centralis  is  a  small  square  lobule, 
situated  in  the  anterior  cerebellar  notch.  It  overlaps  the  lingula,  from  which  it 
is  separated  b}^  the  precentral  fissure;  laterally,  it  extends  along  the  upper  and 
anterior  part  of  each  hemisphere,  where  it  forms  a  wing-like  prolongation,  the  ala 
lobuli  centralis. 

The  Monticulus  and  Quadrangular  Lobules. — The  monticulus  is  the  largest  part 
of  the  superior  vermis.  Anteriorly,  it  overlaps  the  lobulus  centralis,  from  which 
it  is  separated  by  the  postcentral  fissure;  laterally,  it  is  continuous  with  the  quad- 
rangular lobule  in  the  hemispheres.  It  is  divided  by  the  preclival  fissure  into  an 
anterior,  raised  part,  the  culmen  or  summit,  and  a  posterior  sloped  part,  the  clivus; 
the  quadrangular  lobule  is  similarly  divided.  The  culmen  and  the  anterior  parts 
of  the  quadrangular  lobules  form  the  lobus  culminis;  the  clivus  and  the  posterior 
parts,  the  lobus  clivi. 

The  Folium  Vermis  and  Superior  Semilunar  Lobule. — The  folium  vermis  {folium 
cacuminis;  cacuminal  lobe)  is  a  short,  narrow,  concealed  band  at  the  posterior 
extremity  of  the  vermis,  consisting  apparently  of  a  single  folium,  but  in  reality 
marked  on  its  upper  and  under  surfaces  by  secondary  fissures.  Laterally,  it 
expands  in  either  hemisphere  into  a  considerable  lobule,  the  superior  semilunar 
lobule  {lobulus  semilunaris  superior;  postero-superior  lobules),  which  occupies  the 
posterior  third  of  the  upper  surface  of  the  hemisphere,  and  is  bounded  below  by 
the  horizontal  sulcus.  The  superior  semilunar  lobules  and  the  folium  vermis  form 
the  lobus  semilunaris. 


Ala  lohuli  centralis       Flocculus 


Postnodular  fissure 


Ant.  medullary  velwm 
Lobulus  centralis 


Horizontal  sulcus 


Tuber  vermis 
Fig.  713. — Under  surface  of  the  cerebellum.      (Schafer.) 


The  under  surface  of  the  cerebellum  (Fig.  713)  presents,  in  the  middle  line,  the 
inferior  vermis,  buried  in  the  vallecula,  and  separated  from  the  hemisphere  on  either 
side  by  a  deep  groove,  the  sulcus  valleculas.  Here,  as  on  the  upper  surface,  there 
are  deep  fissures,  dividing  it  into  separate  segments  or  lobules ;  but  the  arrangement 
is  more  complicated,  and  the  relation  of  the  segments  of  the  vermis  to  those  of  the 
hemispheres  is  less  clearly  marked.  The  inferior  vermis  is  subdivided  from  before 
backward,  into  (1)  the  nodule,  (2)  the  uvula,  (3)  the  pyramid,  and  (4)  the  tuber 
vermis;  the  corresponding  parts  on  the  hemispheres  are  (1)  the  flocculus,  (2)  the 
tonsilla  cerebelli,  (3)  the  biventral  lobule,  and  (4)  the  inferior  semilunar  lobule.  The 
three  main  fissures  are  (1)  the  postnodular  fissure,  which  runs  transversely  across 
the  vermis,  between  the  nodule  and  the  uvula.  In  the  hemispheres  this  fissure 
passes  in  front  of  the  tonsil,  crosses  between  the  flocculus  in  front  and  the  biventral 
lobule  behind,  and  joins  the  anterior  end  of  the  horizontal  sulcus.     (2)  The  pre- 


THE  RHOMBENCEPHALON  OR  HIND-BRAIN  839 

pyramidal  fissure  crosses  the  vermis  between  the  uvuhi  in  front  and  the  pyramid 
behind,  then  curves  forward  between  the  tonsil  and  the  biventral  lobe,  to  join 
the  postnodular  fissure.  (3)  The  postpyramidal  fissure  passes  across  the  vermis 
between  the  ])yrami(l  and  the  tuber  \ermis,  and,  in  the  hemispheres,  courses 
behind  the  tonsil  and  biventral  lobules,  and  then  along  the  lateral  border  of  the 
biventral  lobule  to  the  postnodular  sulcus;  in  the  hemisphere  it  forms  the  anterior 
boundary  of  the  inferior  semilunar  lobule. 

The  Nodule  and  Flocculus. — The  nodule  {nodulus  vermis;  nochiJar  lohe) ,  or  anterior 
end  of  the  inferior  vermis,  abuts  against  the  roof  of  the  fourth  ventricle,  and  can 
only  be  distinctlj^  seen  after  the  cerebellum  has  been  separated  from  the  medulla 
oblongata  and  pons.  On  either  side  of  the  nodule  is  a  thin  layer  of  white  sub- 
stance, named  the  posterior  medullary  velum.  It  is  semilunar  in  form,  its  convex 
border  being  continuous  with  the  white  substance  of  the  cerebellum;  it  extends 
on  either  side  as  far  as  the  flocculus.  The  flocculus  is  a  prominent,  irregular 
lobule,  situated  in  front  of  the  biventral  lobule,  between  it  and  the  brachium 
pontis  cerebelli.  It  is  subdivided  into  a  few  small  laminae,  and  is  connected  to 
the  inferior  medullary  velum  by  its  central  white  core.  The  flocculi,  together 
with  the  posterior  medullary  velum  and  nodule,  constitute  the  lobus  noduli. 

The  Uvula  and  Tonsilla. — The  uvula  {uvula  vermis;  uvular  lobe)  forms  a  consid- 
erable portion  of  the  inferior  vermis;  it  is  separated  on  either  side  from  the  tonsil 
by  the  sulcus  valleculse,  at  the  bottom  of  which  it  is  connected  to  the  tonsil  by  a 
ridge  of  gray  matter,  indented  on  its  surface  by  shallow  furrows,  and  hence  called 
the  furrowed  band.  The  tonsilla  (tonsilla  cerebelli;  amygdaline  nucleus)  is  a  rounded 
mass,  situated  in  the  hemispheres.  Each  lies  in  a  deep  fossa,  termed  the  bird's 
nest  {nidus  avis),  between  the  uvula  and  the  biventral  lobule.  The  uvula  and  ton- 
sillse  form  the  lobus  uvulae. 

The  Pyramid  and  Biventral  lobules  constitute  the  lobus  pyramidis.  The  pyramid 
is  a  conical  projection,  forming  the  largest  prominence  of  the  inferior  vermis. 
It  is  separated  from  the  hemispheres  by  the  sulcus  valleculae,  across  which  it  is 
connected  to  the  biventral  lobule  by  an  indistinct  gray  band,  analogous  to  the 
furrowed  band  already  described.  The  biventral  lobule  is  triangular  in  shape; 
its  apex  points  backward,  and  is  joined  by  the  gray  band  to  the  pyramid.  The 
lateral  border  is  separated  from  the  inferior  semilunar  lobule  by  the  postpyramidal 
fissure.  The  base  is  directed  forward,  and  is  on  a  line  with  the  anterior  border  of 
the  tonsil,  and  is  separated  from  the  flocculus  by  the  postnodular  fissure. 

The  Tuber  Vermis  (tuber  valvulae)  and  the  Inferior  Semilunar  Lobule  (lobulus  semi- 
lunaris inferior;  postero-superior  lobule)  collectively  form  the  lobus  tuberus  (tuberae 
lobe).  The  tuber  vermis,  the  most  posterior  division  of  the  inferior  vermis,  is  of 
small  size,  and  laterally  spreads  out  into  the  large  inferior  semilunar  lobules, 
which  comprise  at  least  two-thirds  of  the  inferior  surface  of  the  hemisphere. 

Internal  Structure  of  the  Cerebellum. — The  cerebellum  consists  of  white  and  gray 
substance. 

White  Substance. — If  a  sagittal  section  (Fig.  714)  be  made  through  either  hem- 
isphere, the  interior  will  be  found  to  consist  of  a  central  stem  of  white  substance, 
in  the  middle  of  which  is  a  gray  mass,  the  dentate  nucleus.  From  the  surface  of  this 
central  white  stem  a  series  of  plates  are  prolonged;  these  are  covered  with  gray 
substance  and  form  the  laminae.  In  consequence  of  the  main  branches  from  the 
central  stem  dividing  and  subdividing,  a  characteristic  appearance,  named  the 
arbor  vitae,  is  presented.  If  the  sagittal  section  be  made  through  the  middle  of 
the  vermis,  it  will  be  found  that  the  central  stem  divides  into  a  vertical  and  a  hor- 
izontal branch.  The  vertical  branch  passes  upward  to  the  culmen  monticuli, 
where  it  subdivides  freely,  one  of  its  ramifications  passing  forward  and  upward 
to  the  central  lobule.  The  horizontal  branch  passes  backward  to  the  folium  vermis, 
greath'  diminished  in  size  in  consequence  of  having  given  oft'  large  secondary 


840 


NEUROLOGY 


branches;  one,  from  its  upper  surface,  ascends  to  the  chvus  monticuh;  the  others 
descend,  and  enter  the  lobes  in  the  inferior  vermis,  viz.,  the  tuber  vermis,  the 
pyramid,  the  uvula,  and  the  nodule. 


Ala  lohidi  CdtUalis 
L/ingula 


\V    Brachiuin  coniunctivum 


Horizontal 
sulcus 


TONSll- 

Nodule         Fourth  ventricle 
Fig.   714. — Sagittal  section  of  the  cerebellum,  near  the  junction  of  the  vermis  with  the  hemisphere.    (Schafer  ) 

Brachium  conjunctivwin 

I         Bestiform  body 


Biathnim  pontes 


Trigeminal 

nerve 


Acoustic  nerve 

Pyramid 

Olive 


Eestiform  body 
Fig.   715. — Dissection  showing  the  projection  fibres  of  the  cerebellum.      (After  E.  B.  Jamieson.) 

The  white  substance  of  the  cerebellum  includes  two  sets  of  nerve  fibres:  (1) 
projection  fibres,  (2)  fibrae  propriae. 

Projection  Fibres. — The  cerebellum  is  connected  to  the  other  parts  of  the  brain 
by  three  large  bundles  of  projection  fibres,  viz.,  to  the  cerebrum  by  the  brachia 
conjunctiva,  to  the  pons  by  the  brachia  pontis,  and  to  the  medulla  oblongata 
by  the  rcstiform  bodies  (Fig.  715). 


THE  RHOMBENCEPHALON  OH  HIND-BRAIN  841 

The  brachia  conjunctiva  (superior  cerebellar  peduncles),  two  in  number,  emerge 
from  the  upper  and  medial  part  of  the  white  substance  of  the  hemispheres  and 
are  placed  under  cover  of  the  upper  part  of  the  cerebellum.  They  are  joined  to  each 
other  across  the  middle  line  by  the  anterior  medullary  velum,  and  can  be  followed 
upward  as  far  as  the  inferior  colliculi,  under  which  they  disappear.  Below,  they 
form  the  upper  lateral  boundaries  of  the  fourth  ventricle,  but  as  they  ascend  they 
converge  on  the  dorsal  aspect  of  the  ventricle  and  thus  assist  in  roofing  it  in. 

The  fibres  of  the  brachium  conjunctivum  are  mainly  derived  from  the  cells 
of  the  dentate  nucleus  of  the  cerebellum  and  emerge  from  the  hilus  of  this  nucleus; 
a  few  arise  from  the  cells  of  the  smaller  gray  nuclei  in  the  cerebellar  white  sub- 
stance, and  others  from  the  cells  of  the  cerebellar  cortex.  They  are  continued 
upward  beneath  the  corpora  quadrigemina,  and  the  fibres  of  the  two  brachia  under- 
go a  complete  decussation  ventral  to  the  Sylvian  aqueduct.  Having  crossed  the 
middle  line  they  divide  into  ascending  and  descending  groups  of  fibres,  the  former 
ending  in  the  red  nucleus,  the  thalamus,  and  the  nucleus  of  the  oculomotor  nerve, 
while  the  descending  fibres  can  be  traced  as  far  as  the  dorsal  part  of  the  pons; 
Cajal  believes  them  to  be  continued  into  the  anterior  funiculus  of  the  medulla 
spinalis. 

As  already  stated  (page  816),  the  majority  of  the  fibres  of  the  superficial  antero- 
lateral fasciculi  of  the  medulla  spinalis  pass  to  the  cerebellum,  which  they  reach 
b}^  way  of  the  brachia  conjunctiva. 

The  brachia  pontis  {middle  cerebellar  peduncles)  (Fig.  715)  are  composed  entirely  of 
centripetal  fibres,  which  arise  from  the  cells  of  the  nuclei  pontis  of  the  opposite  side 
and  end  in  the  cerebellar  cortex;  the  fibres  are  arranged  in  three  fasciculi,  superior, 
inferior,  and  deep.  The  superior  fasciculus,  the  most  superficial,  is  derived  from 
the  upper  transverse  fibres  of  the  pons;  it  is  directed  backward  and  lateralward 
superficial  to  the  other  two  fasciculi,  and  is  distributed  mainly  to  the  lobules  on 
the  inferior  surface  of  the  cerebellar  hemisphere  and  to  the  parts  of  the  superior 
surface  adjoining  the  posterior  and  lateral  margins.  The  inferior  fasciculus  is 
formed  by  the  lowest  transverse  fibres  of  the  pons ;  it  passes  under  cover  of  the 
superior  fasciculus  and  is  continued  downward  and  backward  more  or  less  parallel 
with  it,  to  be  distributed  to  the  folia  on  the  under  surface  close  to  the  vermis. 

The  deep  fasciculus  comprises  most  of  the  deep  transverse  fibres  of  the  pons. 
It  is  at  first  covered  by  the  superior  and  inferior  fasciculi,  but  crosses  obliquely 
and  appears  on  the  medial  side  of  the  superior,  from  which  it  receives  a  bundle; 
its  fibres  spread  out  and  pass  to  the  upper  anterior  cerebellar  folia.  The  fibres 
of  this  fasciculus  cover  those  of  the  restiform  body.^ 

The  restiform  bodies  {corpus  restiformes ;  inferior  cerebellar  peduncles)  pass  at  first 
upward  and  lateralward,  forming  part  of  the  lateral  walls  of  the  fourth  ventricle, 
and  then  bend  abruptly  backward  to  enter  the  cerebellum  between  the  brachia 
conjunctiva  and  brachia  pontis.  Each  contains  the  following  fasciculi:  (1)  the 
cerebellospinal  fasciculus  of  the  medulla  spinalis,  which  ends  mainly  in  the  superior 
vermis;  (2)  fibres  from  the  gracile  and  cuneate  nuclei  of  the  same  and  of  the  opposite 
sides;  (3)  fibres  from  the  opposite  olivary  nuclei;  (4)  crossed  and  uncrossed  fibres 
from  the  reticular  formation  of  the  medulla  oblongata;  (5)  vestibular  fibres,  derived 
partly  from  the  vestibular  division  of  the  acoustic  nerve  and  partly  from  the  nuclei 
in  which  this  division  ends — these  fibres  occupy  the  medial  segment  of  the  restiform 
body  and  divide  into  ascending  and  descending  groups  of  fibres;  the  ascending 
fibres  partly  end  in  the  roof  nucleus  of  the  opposite  side  of  the  cerebellum;  (6) 
cerebellobulbar  fibres  which  come  from  the  opposite  roof  nucleus  and  probably 
from  the  dentate  nucleus,  and  are  said  to  end  in  the  nucleus  of  Deiters  and  in  the 
formatio  reticularis  of  the  medulla  oblongata. 

^  See  article  by  E.  B.  Jamieson,  Journal  of  Anatomy  and  Physiology,  vol.  xliv. 


842  NEUROLOGY 

The  anterior  medullary  velum  {velum  medullar e  anterius;  valve  of  Vieussens;  superior 
medullary  velum)  is  a  thin,  transparent  lamina  of  white  substance,  which  stretches 
between  the  brachial  conjunctiva;  on  the  dorsal  surface  of  its  lower  half  the  folia 
and  lingula  are  prolonged.  It  forms,  together  with  the  brachia  conjunctiva,  the 
roof  of  the  upper  part  of  the  fourth  ventricle;  it  is  narrow  above,  where  it  passes 
beneath  the  inferior  colliculi,  and  broader  below,  where  it  is  continuous  with  the 
white  substance  of  the  superior  vermis.  A  slightl}^  elevated  ridge,  the  fraenulum 
veli,  descends  upon  its  upper  part  from  betw^een  the  inferior  colliculi,  and  on  either 
side  of  this  the  trochlear  nerve  emerges. 

The  posterior  medullary  velum  {velum  medullare  yosterius;  inferior  medullary  velum) 
is  a  thin  layer  of  white  substance,  prolonged  from  the  white  centre  of  the  cerebellum, 
above  and  on  either  side  of  the  nodule;  it  forms  a  part  of  the  roof  of  the  fourth 
ventricle.  Somewhat  semilunar  in  shape,  its  convex  edge  is  continuous  with  the 
white  substance  of  the  cerebellum,  while  its  thin  concave  margin  is  apparently 
free;  in  reality,  however,  it  is  continuous  with  the  epithehum  of  the  ventricle, 
which  is  prolonged  downward  from  the  posterior  medullary  velum  to  the  ligulse. 

The  two  medullary  vela  are  in  contact  with  each  other  along  their  line  of  emer- 
gence from  the  white  substance  of  the  cerebellum;  and  this  line  of  contact  forms 
the  summit  of  the  roof  of  the  fourth  ventricle,  which,  in  a  vertical  section  through 
the  cavity,  appears  as  a  pointed  angle. 

The  Fibrae  Propriae  of  the  cerebellum  are  of  two  kinds:  (1)  commissural  fibres, 
which  cross  the  middle  line  at  the  anterior  and  posterior  parts  of  the  vermis  and 
connect  the  opposite  halves  of  the  cerebellum;  (2)  arcuate  or  association  fibres, 
which  connect  adjacent  laminae  wdth  each  other. 

Gray  Substance. — The  gray  substance  of  the  cerebellum  is  found  in  two  situations : 
(1)  on  the  surface,  forming  the  cortex;  (2)  as  independent  masses  in  the  anterior. 

(1)  The  gray  substance  of  the  cortex  presents  a  characteristic  foliated  appearance, 
due  to  the  series  of  laminae  which  are  given  off  from  the  central  white  substance; 
these  in  their  turn  give  off  secondary  laminae,  which  are  covered  by  gray  substance. 
Externally,  the  cortex  is  covered  by  pia  mater;  internally  is  the  medullary  centre, 
consisting  mainly  of  nerve  fibres. 

Microscopic  Appearance  of  the  Cortex  (Fig.  716). — The  cortex  consists  of  two 
layers,  viz.,  an  external  gray  molecular  layer,  and  an  internal  rust-colored  nuclear 
layer;  between  these  is  an  incomplete  stratum  of  cells  which  are  characteristic  of 
the  cerebellum,  viz.,  the  cells  of  Purkinje. 

The  external  gray  or  molecular  layer  consists  of  fibres  and  cells.  The  nerve  fibres 
are  delicate  fibrillse,  and  are  derived  from  the  following  sources:  (a)  the  dendrites 
and  axon  collaterals  of  Purkinje's  cells;  (6)  fibres  from  cells  in  the  nuclear  layer; 
(c)  fibres  from  the  central  white  substance  of  the  cerebellum;  {d)  fibres  derived 
from  cells  in  the  molecular  layer  itself.  In  addition  to  these  are  other  fibres,  which 
have  a  vertical  direction,  and  are  the  processes  of  large  neuroglia  cells,  situated 
in  the  nuclear  layer.  They  pass  outward  to  the  periphery  of  the  gray  matter, 
where  they  expand  into  little  conical  enlargements  which  form  a  sort  of  limiting 
membrane  beneath  the  pia  mater,  analogous  to  the  membrana  limitans  interna 
in  the  retina,  formed  by  the  sustentacular  fibres  of  Miiller. 

The  cells  of  the  molecular  layer  are  small,  and  are  arranged  in  two  strata,  an 
outer  and  an  inner.  They  all  possess  branched  axons;  those  of  the  inner  layer 
are  termed  basket  cells ;  they  run  for  some  distance  parallel  with  the  surface  of  the 
folium — giving  off  collaterals  which  pass  in  a  vertical  direction  toward  the  bodies 
of  Purkinje's  cells,  around  which  they  become  enlarged,  and  form  basket-like 
net-works. 

The  cells  of  Purkinje  form  a  single  stratum  of  large,  flask-shaped  cells  at  the 
junction  of  the  molecular  and  nuclear  layers,  their  bases  resting  against  the  latter; 
in  fishes  and  reptiles  they  are  arranged  in  several  layers.    The  cells  are  flattened 


THE  RHOMBENCEPHALON  OR  HIND-BRAIN 


843 


in  a  direction  transverse  to  the  long  axis  of  the  foHum,  and  thus  appear  broad 
in  sections  carried  across  the  fohum,  and  fusiform  in  sections  parallel  to  the  long 
axis  of  the  folium.  From  the  neck  of  the  flask  one  or  more  dendrites  arise  and  pass 
into  the  molecular  layer,  where  they  subdivide  and  form  an  extremely  rich  arbores- 
cence,  the  various  subdivisions  of  the  dendrites  being  covered  by  lateral  spine- 
like processes.  This  arborescence  is  not  circular,  but,  like  the  cell,  is  flattened  at 
right  angles  to  the  long  axis  of  the  folium;  in  other  words,  it  does  not  resemble 
a  round  bush,  but  has  been  aptly  compared  by  Obersteiner  to  the  branches  of  a 
fruit  tree  trained  against  a  trellis  or  a  wall.  Hence,  in  sections  carried  across 
the  folium  the  arborescence  is  broad  and  expanded;  whereas  in  those  which  are 
parallel  to  the  long  axis  of  the  folium,  the  arborescence,  like  the  cell  itself,  is 
seen  in  profile,  and  is  limited  to  a  narrow  area. 


Cell  of  Purkinje 


Axons  of 
granule  cells 
cut  trans- 
versely 


Small  cell 

of  molecular 

layer 


Basket  cell. 


\  Molecular 
layer 


'^ i  Golgi  cell 


VNv^lear 
layer 


Neuroglia  cell 


i      I  Axon  of  cell  of  Purhinje 


•  Tendril  fibre 
Moss  fibre 
Fig.  716. — Transverse  section  of  a  cerebellar  folium.      (Diagrammatic,  after  Cajal  and  KoUiker.) 

From  the  bottom  of  the  flask-shaped  cell  the  axon  arises;  this  passes  through 
the  nuclear  layer,  and,  becoming  medullated,  is  continued  as  a  nerve  fibre  in  the 
subjacent  white  substance.  As  this  axon  traverses  the  granular  layer  it  gives  off 
fine  collaterals,  some  of  which  run  back  into  the  molecular  layer. 

The  internal  rust-colored  or  nuclear  layer  (Fig.  716)  is  characterized  by  containing 
numerous  small  nerve  cells  of  a  reddish-brown  color,  together  with  many  nerve 


844 


NEUROLOGY 


fibrils.  Most  of  the  cells  are  nearly  spherical  and  provided  with  short  dendrites 
which  spread  out  in  a  spider-like  manner  in  the  nuclear  layer.  Their  axons  pass 
outward  into  the  molecular  layer,  and,  bifurcating  at  right  angles,  run  for  some 
distance  parallel  with  the  surface.  In  the  outer  part  of  the  nuclear  la^-er  are  some 
larger  cells,  of  the  type  II  of  Golgi.  Their  axons  undergo  frequent  division  as  soon 
as  the}^  leave  the  nerve  cells,  and  pass  into  the  nuclear  la\^er;  while  their  dendrites 
ramify  chiefly  in  the  molecular  layer. 

Finally,  in  the  gray  substance  of  the  cerebellar  cortex  there  are  fibres  which 
come  from  the  white  centre  and  penetrate  the  cortex.  The  cell-origin  of  these 
fibres  is  unknown,  though  it  is  believed  that  it  is  probably  in  the  gray  substance 
of  the  medulla  spinalis.  Some  of  these  fibres  end  in  the  nuclear  layer  by  dividing 
into  numerous  branches,  on  which  are  to  be  seen  peculiar  moss-like  appendages; 
hence  they  have  been  termed  b}'  Ramon  y  Cajal  the  moss  fibres;  they  form  an 
arborescence  around  the  cells  of  the  nuclear  layer.  Other  fibres,  the  clinging  or 
tendril  fibres,  derived  from  the  medullary  centre  can  be  traced  into  the  molecular 
layer,  where  their  branches  cling  around  the  dendrites  of  Purkinje's  cells. 

(2)  The  independent  centres  of  gray  substance  in  the  cerebellum  are  four  in 
number  on  either  side:  one  is  of  large  size,  and  is  known  as  the  nucleus  dentatus; 
the  other  three,  much  smaller,  are  situated  near  the  middle  of  the  cerebellum,  and 
are  known  as  the  nucleus  emboliformis,  nucleus  globosus,  and  nucleus  fastigii. 


Nucleus  dentaius         Braduum  conjundivum 

Corpora  quadrigemina 


hiferior  olivary  nucleus 
Fig.  717. — Sagittal  section  through  right  cerebellar  hemi-sphere.     The  right  olive  has  also  been  cut  sagitally. 


The  nucleus  dentatus  (Fig.  717)  is  situated  a  little  to  the  medial  side  of  the  centre 
of  the  stem  of  the  white  substance  of  the  hemisphere.  It  consists  of  an  irregularly 
folded  lamina,  of  a  grayish-yellow  color,  containing  white  fibres,  and  presenting 
on  its  antero-medial  aspect  an  opening,  the  hilus,  from  which  most  of  the  fibres  of 
the  brachium  conjunctiva  emerge  (page  841). 

The  nucleus  emboliformis  lies  immediately  to  the  medial  side  of  the  nucleus 
dentatus,  and  partly  covering  its  hilus.  The  nucleus  globosus  is  an  elongated 
mass,  directed  antero-posteriorly,  and  placed  medial  to  preceding.  The  nucleus 
fastigii  is  somewhat  larger  than  the  other  two,  and  is  situated  close  to  the  middle 
line  at  the  anterior  end  of  the  superior  vermis,  and  immediately  over  the  roof 
of  the  fourth  ventricle,  from  which  it  is  separated  by  a  thin  layer  of  white  substance. 

Applied  Anatomy. — The  general  functions  of  the  cerebellum  in  the  human  economy  appear 
to  be  the  coordination  of  movements  and  equilibration.  The  exact  functions  of  its  different 
parts  are  still  quite  uncertain,  owing  to  the  contradictory  nature  of  the  evidence  furnished  by 


THE  RHOMBENCEPHALON  OR  HIND-BRAIN  845 

(1)  abhitioii  ex])ci'imcnts  upon  animals,  and  (2)  clinical  observations  in  man  of  the  effects  pro- 
duced by  abscesses  or  tumors  affecting  tlifferent  portions  of  the  organ.  According  to  W.  Aldren 
Turner,  "The  following  localizing  sj'^nijitoms  would  therefore  indicate  the  presence  of  a  tumor 
implicating  the  right  cerebellar  hemisphere  and  middle  peduncle;  deafness  in  the  right  ear,  un- 
associated  with  middle-ear  complications;  an  imsteadj'^  and  imcertain  gait,  with  a  tendency  to 
fall  more  particular!}'  to  the  right  side;  coarse  nystagmoid  oscillations  on  looking  to  the  right; 
movements  resembling  those  of  disseminated  sclerosis  on  volitional  effort  of  the  right  arm;  an 
awkward  uncertain  action  of  the  right  leg;  a  slight  increase  of  the  right  knee-jei-k;  and,  perhaps, 
slight  blunting  of  sensibility  over  the  right  cornea  and  side  of  the  face." 

The  Fourth  Ventricle  {ventricuhis  quarius). — The  fourth  ventricle,  or  cavity 
of  the  rhombencephalon,  i.s  situated  in  front  of  the  cereheUum  and  behind  the  pons 
and  upper  half  of  the  medulla  oblongata.  Developmentally  considered,  the  fourth 
ventricle  consists  of  three  parts:  a  superior  belonging  to  the  isthmus  rhombencephali, 
an  intermediate,  to  the  metencephalon,  and  an  inferior,  to  the  myelencephalon. 
It  is  lined  by  ciliated  epitheliiuii,  and  is  continuous  bek)W  with  the  central  canal 
of  the  medulla  oblongata;^  above,  it  communicates,  by  means  of  a  passage  termed 
the  cerebral  aqueduct,  with  the  cavity  of  the  third  ^•entricle.  It  presents  four 
angles,  and  possesses  a  roof  or  dorsal  wall,  a  floor  or^  ventral  wall,  and  lateral 
boundaries. 

Angles. — The  superior  angle  is  on  a  level  wath  the  upper  border  of  the  pons, 
and  is  continuous  with  the  lower  end  of  the  cerebral  aqueduct.  The  inferior  angle 
is  on  a  level  with  the  lower  end  of  the  olive,  and  opens  into  the  central  canal  of  the 
medulla  oblongata.  Each  lateral  angle  corresponds  with  the  point  of  meeting 
of  the  brachia  and  restiform  body.  A  little  below  the  lateral  angles,  on  a  level 
with  the  striae  medullares,  the  ventricular  cavity  is  prolonged  outward  in  the  form 
of  two  narroM"  lateral  recesses,  one  on  either  side;  these  are  situated  between  the 
restiform  bodies  and  the  flocculi,  and  reach  as  far  as  the  attachments  of  the  glosso- 
pharyngeal and  vagus  nerves. 

Lateral  Boundaries. — The  lower  part  of  each  lateral  boundary  is  constituted 
by  the  clava,  the  fasciculus  cuneatus,  and  the  restiform  body;  the  upper  part  by 
the  brachium  pontis  and  the  brachium  conjunctivum. 

Roof  or  Dorsal  Wall  (Fig.  718). — The  upper  portion  of  the  roof  is  formed  by 
the  brachia  conjunctiva  and  the  anterior  medullary  velum;  the  lower  portion, 
by  the  posterior  medullary  velum,  the  epithelial  lining  of  the  ventricle  covered 
by  the  tela  chorioidea  inferior,  the  taeniae  of  the  fourth  ventricle,  and  the  obex. 

The  brachia  conjunctiva  (page  841),  on  emerging  from  the  central  w-hite  sub- 
stance of  the  cerebellum,  pass  upward  and  forward,  forming  at  first  the  lateral 
boundaries  of  the  upper  part  of  the  cavity;  on  approaching  the  inferior  colliculi, 
they  converge,  and  their  medial  portions  overlap  the  cavity  and  form  part  of  its 
roof. 

The  anterior  medullary  velum  (page  842)  fills  in  the  angular  interval  between 
the  brachia  conjunctiva,  and  is  continuous  behind  with  the  central  white  sub- 
stance of  the  cerebellum;  it  is  covered  on  its  dorsal  surface  by  the  lingula  of  the 
superior  vermis. 

The  posterior  medullary  velum  (page  842)  is  continued  downward  and  forward 
from  the  central  white  substance  of  the  cerebellum  in  front  of  the  nodule  and 
tonsils,  and  ends  inferiorly  in  a  thin,  concave,  somewhat  ragged  margin.  Below 
this  margin  the  roof  is  devoid  of  nervous  matter  except  in  the  immediate  vicinity 
of  the  lower  lateral  boundaries  of  the  ventricle,  where  two  narrow  white  bands,  the 
taeniae  of  the  fourth  ventricle  (ligulae),  appear;  these  bands  meet  over  the  inferior 
angle  of  the  ventricle  in  a  thin  triangular  lamina,  the  obex.  The  non-nervous  part 
of  the  roof  is  formed  by  the  epithelial  lining  of  the  ventricle,  which  is  prolonged 
downward  as  a  thin  membrane,  from  the  deep  surface  of  the  posterior  medullary 

1  J.  T.  Wilson  (Journal  of  Anatomy  and  Physiology,  vol.  xl)  has  pointed  out  that  the  central  canal  of  the  medulla 
oblongata,  immediately  below  its  entrance  into  the  fourth  ventricle,  retains  the  cleft-like  form  presented  by  the  fetal 
medulla  spinalis,  and  that  it  is  marked  by  dorso-  and  ventro-lateral  sulci. 


846 


NEUROLOGY 


velum  to  the  corresponding  surface  of  the  obex  and  taeniae,  and  thence  on  to  the 
floor  of  the  ventricular  cavity;  it  is  covered  and  strengthened  by  a  portion  of  the 
pia  mater,  which  is  named  the  tela  chorioidea  of  the  fourth  ventricle. 

The  taeniae  of  the  fourth  ventricle  {taenia  ventriculi  qnartl;  ligula)  are  two  narrow 
bands  of  white  matter,  one  on  either  side,  which  complete  the  lower  part  of  the  roof 
of  the  cavity.  Each  consists  of  a  vertical  and  a  horizontal  part.  The  vertical  part 
is  continuous  below  the  obex  with  the  clava,  to  which  it  is  adherent  by  its  lateral 
border.  The  horizontal  portion  extends  transversely  across  the  restiform  body, 
below  the  striae  medullares,  and  roofs  in  the  lower  and  posterior  part  of  the  lateral 
recess;  it  is  attached  by  its  lower  margin  to  the  restiform  body,  and  partly  encloses 
the  choroid  plexus,  which,  however,  projects  beyond  it  like  a  cluster  of  grapes;  and 
hence  this  part  of  the  taenia  has  been  termed  the  cornucopia  (Bochdalek).  The  obex 
is  a  thin,  triangular,  gray  lamina,  which  roofs  in  the  lower  angle  of  the  ventricle  and 
is  attached  by  its  lateral  margins  to  the  clavae.^  The  tela  chorioidea  of  the  fourth 
ventricle  is  the  name  applied  to  the  triangular  fold  of  pia  mater  w^hich  is  carried 
upward  between  the  cerebellum  and  the  medulla  oblongata.     It  consists  of  two 


Corpora 
quadrigemina 
Cerebral 
pedu7icle 
A  nterior 
medullary 
velum 
Ependymal 
lining  of 
ventricle 


Posterior 
medullary  velum 

Chorioid  plexus 

Cisterna  cerKbollmnedidlaris  of 
subarachnoid  cavity 

Central  canal        ^ ,  /^  ., .  ,  ,  •      <• 

Cisterna  pontis  oj 

subarachnoid  cavity 
Fig.  718. — Scheme  of  roof  of  fourth  ventricle.     The  arrow  is  in  the  foramen  of  Majendie. 


layers,  which  are  continuous  with  each  other  in  front,  and  are  more  or  less  adherent 
throughout.  The  posterior  layer  covers  the  antero-inferior  surface  of  the  cere- 
bellum, while  the  anterior  is  applied  to  the  structures  wdiich  form  the  lower  part 
of  the  roof  of  the  ventricle,  and  is  continuous  inferiorly  with  the  pia  mater  on  the 
restiform  bodies  and  closed  part  of  the  medulla. 

Choroid  Plexuses. — These  consist  of  two  highly  vascular  inflexions  of  the  tela 
chorioidea,  which  invaginate  the  lower  part  of  the  roof  of  the  ventricle  and  are 
everywhere  covered  by  the  epithelial  lining  of  the  cavity.  Each  consists  of  a  ver- 
tical and  a  horizontal  portion :  the  former  lies  close  to  the  middle  line,  and  the  latter 
passes  into  the  lateral  recess  and  projects  beyond  its  apex.  The  vertical  parts  of 
the  plexuses  are  distinct  from  each  other,  but  the  horizontal  portions  are  joined 
in  the  middle  line;  and  hence  the  entire  structure  presents  the  form  of  the  letter  T, 
the  vertical  limb  of  which,  however,  is  double. 

1  J.  T.  Wilson,  op.  cit.,  recognizes  two  forms  of  obex:  (o)  the  true  obex,  constituted  by  a  medullary  thickening  of 
the  roof  plate,  and  (6)  a  false  or  membranous  obex,  where  the  medullary  thickening  fails  to  take  place,  and  where  the 
roof  plate  is  represented  only  by  the  ependymal  layer  clothing  the  ventral  surface  of  a  pial  reduplication  which  forms 
the  main  substance  of  the  membranous  fold  in  question. 


THE  RHOMBENCEPHALON  OR  HIND-BRAIN 


847 


Openings  in  the  Roof. — In  the  roof  of  the  fourth  ventricle  there  are  three  openings, 
a  medial  and  two  lateral:  the  medial  aperture  (foramen  Majendii),  is  situated  imme- 
diately above  the  inferior  angle  of  the  ventricle;  the  lateral  apertures  are  found 
at  the  extremities  of  the  lateral  recesses.  By  means  of  these  three  openings  the 
ventricle  communicates  with  the  subarachnoid  cavity,  and  the  cerebrospinal 
fluid  can  circulate  from  the  one  to  the  other. 

Rhomboid  Fossa  (fossa  rhomboidea;  "floor'"  of  the  fourth  ventricle)  (Fig.  719). — 
The  anterior  part  of  the  fourth  ventricle  is  named,  from  its  shape,  the  rhomboid 
fossa,  and  its  anterior  wall,  formed  b}'  the  back  of  the  pons  and  medulla  oblongata, 
constitutes  the  floor  of  the  fourth  ventricle.  It  is  covered  by  a  thin  layer  of  gray 
substance  continuous  with  that  of  the  medulla  spinalis;  superficial  to  this  is  a  thin 
lamina  of  neuroglia  which  constitutes  the  ependyma  of  the  ventricle  and  supports 
a  layer  of  ciliated  epithelium.    The  fossa  consists  of  three  parts,  superior,  inter- 


Tcenia  pont 


Frenulum  veil 

Trochlear  nerve 
Ant.  medullary  velum 
Bi  a chiu m  conjunct ivum 
Nucleus  deniatus 


Superior  fovea 
Collicidus  facialis 

Striae  medulla/ Si, ^\^ 
Area  acustica^ 
Trigonum  hypoglossi  / 
Ala,  cineieii 
Tcenia  of  fourth  ventrid 


Fig.  719. 


'Funiculus  separans 
Aiea  postrema 
Obex 
Clava 
-Rhomboid  fossa. 


mediate,  and  inferior.  The  superior  part  is  triangular  in  shape  and  limited  laterally 
by  the  brachia  conjunctiva  cerebelli;  its  apex,  directed  upward,  is  continuous  with 
the  cerebral  aqueduct;  its  base  it  represented  by  an  imaginary  line  at  the  level  of  the 
upper  ends  of  the  superior  fovese.  The  intermediate  part  extends  from  this  level 
to  that  of  the  horizontal  portions  of  the  taeniae  of  the  ventricle ;  it  is  narrow  above 
where  it  is  limited  laterally  by  the  brachia  pontis,  but  widens  below  and  is  pro- 
longed into  the  lateral  recesses  of  the  ventricle.  The  inferior  part  is  triangular, 
and  its  downwardly  directed  apex,  named  the  calamus  scriptorius,  is  continuous 
with  the  central  canal  of  the  closed  part  of  the  medulla  oblongata. 

The  rhomboid  fossa  is  divided  into  symmetrical  halves  by  a  median  sulcus 
which  reaches  from  the  upper  to  the  lower  angles  of  the  fossa  and  is  deeper  below 
than  above.  On  either  side  of  this  sulcus  is  an  elevation,  the  medial  eminence, 
bounded  laterally  by  a  sulcus,  the  sulcus  limitans.  In  the  superior  part  of  the  fossa 
the  medial  eminence  has  a  width  equal  to  that  of  the  corresponding  half  of  the 


848  NEUROLOGY 

fossa,  but  opposite  the  superior  fovea  it  forms  an  elongated  swelling,  the  colliculus 
facialis,  which  overlies  the  nucleus  of  the  abducent  nerve,  and  is,  in  part  at  least, 
produced  by  the  ascending  portion  of  the  root  of  the  facial  nerve.  In  the  inferior 
part  of  the  fossa  the  medial  eminence  assumes  the  form  of  a  triangular  area,  the 
trigonum  hypoglossi.  When  examined  under  water  with  a  lens  this  trigone  is  seen 
to  consist  of  a  medial  and  a  lateral  area  separated  by  a  series  of  oblique  furrows; 
the  medial  area  corresponds  with  the  upper  part  of  the  nucleus  of  the  hypoglossal 
nerve,  the  lateral  with  a  small  nucleus,  the  nucleus  intercalatus. 

The  sulcus  limitans  forms  the  lateral  boundary  of  the  medial  eminence.  In 
the  superior  part  of  the  rhomboid  fossa  it  corresponds  with  the  lateral  limit  of  the 
fossa  and  presents  a  bluish-gray  area,  the  locus  coeruleus,  which  owes  its  color 
to  an  underlying  patch  of  deeply  pigmented  nerve  cells,  termed  the  substantia 
ferruginea.  At  the  level  of  the  colliculus  facialis  the  sulcus  limitans  widens  into 
a  flattened  depression,  the  superior  fovea,  and  in  the  inferior  part  of  the  fossa  appears 
as  a  distinct  dimple,  the  inferior  fovea.  Lateral  to  the  fovese  is  a  rounded  elevation 
named  the  area  acustica,  which  extends  into  the  lateral  recess  and  there  forms  a 
feebly  marked  swelling,  the  tuberculum  acusticum.  Winding  around  the  restiform 
body  and  crossing  the  area  acustica  and  the  medial  eminence  are  a  number  of  white 
strands,  the  striae  medullares,  which  form  a  portion  of  the  cochlear  division  of  the 
acoustic  nerve  and  disappear  into  the  median  sulcus.  Below  the  inferior  fovea, 
and  betw^een  the  trigonum  hypoglossi  and  the  lower  part  of  the  area  acustica  is  a 
triangular  dark  field,  the  ala  cinerea,  w^hich  corresponds  to  the  sensory  nucleus 
of  the  vagus  and  glossopharyngeal  nerves.  The  lower  end  of  the  ala  cinerea  is 
crossed  by  a  narrow  translucent  ridge,  the  funiculus  separans,  and  between  this 
funiculus  and  the  clava,  is  a  small  tongue-shaped  area,  the  area  postrema.  On 
section  it  is  seen  that  the  funiculus  separans  is  formed  by  a  strip  of  thickened 
ependyma,  and  the  area  postrema  by  loose,  highly  vascular,  neuroglial  tissue  con- 
taining nerve  cells  of  moderate  size. 


THE   MESENCEPHALON    OR   MID-BRAIN. 

The  mesencephalon  or  mid-brain  (Fig.  725)  is  the  short,  constricted  portion  which 
connects  the  pons  and  cerebellum  with  the  thalamencephalon  and  cerebral  hemi- 
spheres. It  is  directed  upward  and  forward,  and  consists  of  (1)  a  ventro-lateral 
portion,  composed  of  a  pair  of  cylindrical  bodies,  named  the  cerebral  peduncles; 
(2)  a  dorsal  portion,  consisting  of  four  rounded  eminences,  named  the  corpora 
quadrigemina;  and  (3)  an  intervening  passage  or  tunnel,  the  cerebral  aqueduct, 
which  represents  the  original  cavity  of  the  mid-brain  and  connects  the  third  with 
the  fourth  ventricle  (Fig.  720). 

The  cerebral  peduncles  (pechmculvs  cerebri;  cms  cerebri)  are  two  cylindrical 
masses  situated  at  the  base  of  the  brain,  and  largely  hidden  by  the  temporal  lobes 
of  the  cerebrum,  which  must  be  drawn  aside  or  removed  in  order  to  expose  them. 
They  emerge  from  the  upper  surface  of  the  pons,  one  on  either  side  of  the  middle 
line,  and,  diverging  as  they  pass  upward  and  forward,  disappear  into  the  substance 
of  the  cerebral  hemispheres.  The  depressed  area  between  the  crura  is  termed  the 
interpeduncular  fossa,  and  consists  of  a  layer  of  grayish  substance,  the  posterior 
perforated  substance,  which  is  pierced  by  small  apertures  for  the  transmission  of 
bloodvessels;  its  lower  part  lies  on  the  ventral  aspect  of  the  medial  portions  of  the 
tegmenta,  and  contains  a  nucleus  named  the  interpeduncular  ganglion  (page  850) ; 
its  upper  part  assists  in  forming  the  floor  of  the  third  ventricle.  The  ventral  sur- 
face of  each  peduncle  is  crossed  from  the  medial  to  the  lateral  side  by  the  superior 
cerebellar  and  posterior  cerebral  arteries;  its  lateral  surface  is  in  relation  to  the 
gyrus  hippocampi  of  the  cerebral  hemisphere  and  is  crossed  from  behind  forward 


THE  MESENCEPHALON  OR  MID-BRAIN 


849 


by  the  trochlear  nerve.  Close  to  the  point  of  disappearance  of  the  peduncle  into 
the  cerebral  hemipshere,  the  optic  tract  winds  forward  around  its  ventro-lateral 
surface.  The  medial  surface  of  the  "  peduncle  forms  the  lateral  boundary 
of  the  interpeduncular  fossa,  and  is 
marked  by  a  longitudinal  furrow,  the 
oculomotor  sulcus,  from  which  the  roots 
of  the  oculomotor  nerve  emerge.  On 
the  lateral  surface  of  each  peduncle 
there  is  a  second  longitudinal  furrow, 
termed  the  lateral  sulcus ;  the  fibres  of 
the  lateral  lemniscus  come  to  the  sur- 
face in  this  sulcus,  and  pass  backward 
and  upward,  to  disappear  under  the 
inferior  colliculus. 

Structure  of  the  Cerebral  Peduncles 
(Figs.  721,  722). — On  transverse  sec- 
tion, each  peduncle  is  seen  to  consist 
of  a  dorsal  and  a  ventral  part,  separ- 
ated by  a  deeply  pigmented  lamina  of 
gray  substance,  termed  the  substantia 
nigra.  The  dorsal  part  is  named  the 
tegmentum;  the  ventral,  the  base  or 
cnista;  the  two  bases  are  separated 
from  each  other,  but  the  tegmenta  are 
joined  in  the  median  plane  by  a  for- 


d.. 

6..J 


Fig.  720. — Coronal  section  through  mid-brain.  (Sche- 
matic.) (Testut.)  1.  Corpora  quadrigemina.  2.  Cere- 
bral aqueduct.  3.  Central  gray  stratum.  4.  Interpedun- 
cular space.  5.  Sulcus  lateralis.  6.  Substantia  nigra.  7. 
Red  nucleus  of  tegmentum.  8.  Oculomotor  nerve,  with  8', 
1  1  .  PI  lypi  '^^  nucleus  of  origin,    a.  Lemniscus   (in  blue)   with  a'  the 

ward  prolongation    or    the    raphe  or  the       medial    lemniscus    and     a"     the     lateral     lemniscus.     6. 
T      ,  -11        ,1        ,  ,  n  Medial  longitudinal  fasciculus,     c.   Raph6.     d.  Temporo- 

pons.      Laterally,  the  tegmenta  are  tree;       pontine  fibres,    e.  Portlonof  medial  lemniscus,  which  runs 
dorsally,    they  blend    with    the    corpora       ll,£"    ^'-''°'""    -^?l'^-«--^d  insula.    /.  Cerebrospinal 


quadrigemina. 


g.  Frontopontine  fibres. 


Inferior  coUiculi 


Cerebral  aqueduct 

Nucleus  of  oczdomotor 

nerve  ■ 


Laterallemniscus 

Medial  longitudinal 
fasciculus 

Medial  lemniscus 


Fig.  721. 


Eaphe 
-Transverse  section  of  mid-brain  at  level  of  inferior  colHculi. 


The  base  (basis  peduncidi;  cnista  or  pes)  is  semilunar  on  transverse  section,  and 

consists  almost  entirely  of  longitudinal  bundles  of  efferent  fibres,  which  arise  from 

the  cells  of  the  cerebral  cortex  and  are  grouped  into  three  principal  sets,  viz., 

cerebrospinal,  frontopontine,  and  temporopontine  (Fig.  720).    The  cerebrospinal 

54 


850 


NEUROLOGY 


fibres,  (leri\e(l  from  the  cells  of  the  motor  area  of  the  cerebral  cortex,  occupy 
the  middle  three-fifths  of  the  base;  they  are  continued  partly  to  the  nuclei  of  the 
motor  cerebral  nerves,  but  mainly  into  the  pyramids  of  the  medulla  oblongata. 
The  frontopontine  fibres  are  situated  in  the  medial  fifth  of  the  base;  they  arise  from 
the  cells  of  the  frontal  lobe  and  end  in  the  nuclei  of  the  pons.  The  temporopontine 
fibres  are  lateral  to  the  cerebrospinal  fibres;  they  originate  in  the  tempcjral  lobe 
and  end  in  the  nuclei  pontis.^ 


Su2)enor  colliciili 


I  aijuc'iho-t 


ucleus  of  oculomotor  nerve 
Medial  longitudinal 
fasciculus 


Fig.  722. — Transverse  .section  of  mid-brain  at  level  of  superior  colliculi. 


The  substantia  nigra  ( inter calatum)  is  a  layer  of  gray  substance  containing 
numerous  deeply  pigmented,  multipolar  nerve  cells.  It  is  semilunar  on  transverse 
section,  its  concavitj-  being  directed  toward  the  tegmentum;  from  its  convexity, 
prolongations  extend  between  the  fibres  of  the  base  of  the  peduncle.  Thicker 
medially  than  laterally,  it  reaches  from  the  oculomotor  sulcus  to  the  lateral  sulcus, 
and  extends  from  the  upper  surface  of  the  pons  to  the  subthalamic  region;  its 
medial  part  is  traversed  by  the  fibres  of  the  oculomotor  nerve  as  these  stream  for- 
ward to  reach  the  oculomotor  sulcus.  The  connections  of  the  cells  of  the  substantia 
nigra  have  not  been  definitely  established. 

The  tegmentum  is  continuous  below  with  the  reticular  formation  of  the  pons, 
and,  like  it,  consists  of  longitudinal  and  transverse  fibres,  together  with  a  consider- 
able amount  of  gray  substance.  The  principal  gray  masses  of  the  tegmentum 
are  the  red  nucleus  and  the  interpeduncular  ganglion;  of  its  fibres  the  chief  longi- 
tudinal tracts  are  the  brachiurn  conjunctivum,  the  medial  longitudinal  fasciculus, 
and  the  lemniscus. 

Gray  Substance. — ^The  red  nucleus  is  situated  in  the  anterior  part  of  the  teg- 
mentum, and  is  continued  upward  into  the  posterior  part  of  the  subthalamic  region. 
In  sections  at  the  level  of  the  superior  colliculus  it  appears  as  a  circular  mass 
which  is  traversed  by  the  fibres  of  the  oculomotor  nerve.  Most  of  the  fibres  of  the 
brachium  conjunctivum  end  in  it  (page  847).  The  axons  of  its  larger  cells  cross 
the  middle  line  and  are  continued  downward  into  the  lateral  funiculus  of  the 
medulla  spinalis  as  the  rubrospinal  tract  (page  816);  those  of  its  smaller  cells  end 
mainly  in  the  thalamus. 

■  The  interpeduncular  ganglion  is  a  median  collection  of  nerve  cells  situated  in 
the  ventral  part  of  the  tegmentum.     The  fibres  of  the  fasciculus  retroflexus  of 

1 A  band  of  fibres,  the  Iraclus  peduncularis  transversus,  is  sometimes  seen  emerging  from  in  front  of  the  superior  collic- 
ulus; it  passes  around  the  ventral  aspect  of  the  peduncle  about  midway  between  the  pon.s  and  the  optic  tract,  and 
dips  into  the  oculomotor  sulcus.  This  band  is  a  constant  structure  in  many  mammals,  but  is  only  present  in  about 
30  per  cent,  of  human  brains.  Since  it  undergoes  atrophj'  after  enucleation  of  the  eyeballs,  it  may  be  considered  as 
forming  a  path  for  visual  sensations. 


THE  MESENCEPHALOX  OH  MID-BRAIX 


851 


Meyncrt,  which  have  their  origin  in  the  cells  of  the  ganglion  habenuhe  (page  859), 
end  in  it. 

Besides  the  two  nuclei  mentioned,  there  are  small  collections  of  cells  which 
form  the  dorsal  and  ventral  nuclei  and  the  central  nucleus  or  nucleus  of  the  raphe. 

White  Substance. — (1)  The  origin  and  course  of  the  brachium  conjunctivum 
have  already  been  described  (page  841). 

(2)  The  medial  (posterior)  longitudinal  fasciculus  (Fig.  723)  is  continuous  below 
with  the  proper  fasciculi  of  the  anterior  and  lateral  funiculi  of  the  medulla  spinalis, 
and  has  been  traced  by  Edinger  as  far  as  a  nucleus,  the  nucleus  of  the  medial  longi- 
tudinal fasciculus,  situated  in  the  hypothalamus,  immediately  in  front  of  the  cerebral 
aqueduct.  In  the  medulla  oblongata  and  pons  it  runs  close  to  the  middle  line, 
near  the  floor  of  the  fourth  ventricle;  in  the  mesencephalon  it  is  situated  on  the 


Xudeus  of  medial 
longitudinal  jaxcicidus 


Superior  cullicidug 

Xuclcia  of  oculoinotor 
nerve 


Xiicleus  of  trigeminal 

nerve 
Xiicleiis  of  abducent 

nerve 

Xucleiis  of  facial  nerve 


Xudeus  of  glossopharyn 
geal  and  vagus  nerves 
Xudeus  of  hypoglossal 
nerve 


Xi>clei(s  of  accessor)/ 
nerve 


Fig.  723. — Scheme  of  the  medial  longitudinal  fasciculus;  motor  fibres  in  red,  sensory  in  blue. 


ventral  aspect  of  the  cerebral  aqueduct,  below  the  nuclei  of  the  oculomotor  and 
trochlear  nerves.  Its  connections  are  imperfectly  known,  but  it  consists  largely 
of  ascending  and  descending  intersegmental  or  association  fibres,  which  connect 
the  nuclei  of  the  rhombencephalon  and  mesencephalon  to  each  other.  Many  of 
the  descending  fibres  arise  in  the  superior  coUiculus,  and,  after  decussating  in  the 
middle  line,  end  in  the  motor  nuclei  of  the  pons  and  medulla  oblongata.  The 
ascending  fibres  arise  from  the  cells  of  the  gray  substance  of  the  upper  part  of  the 
medulla  spinalis,  and  from  the  nuclei  in  the  medulla  oblongata  and  pons,  and  pass 


852  NEUROLOGY 

without  undergoing  decussation  to  the  higher  nuclei.  Fibres  are  also  carried  through 
the  medial  longitudinal  fasciculus  from  the  nucleus  of  the  abducent  nerve  into  the 
oculomotor  nerve  of  the  opposite  side,  and  through  this  nerve  to  the.  Rectus 
medialis  oculi.  Again,  fibres  are  said  to  be  prolonged  through  this  fasciculus 
from  the  nucleus  of  the  oculomotor  nerve  into  the  facial  nerve,  and  are  distributed 
to  the  Orbicularis  oculi,  the  Corrugator,  and  the  Frontalis.^ 


Corpora 
quadn'gemina 


Superior  olivary 
nucleus 


Cochlear  nucleus 
Sensory  cerebral  nuclei 

Nucleus  gracilis 
Nucleus  cuneatus 


Fig.  724. — Scheme  showing  the  course  of  the  fibres  of  the  lemniscus;  medial  lemniscus  in  blue,  lateral  in  red. 

(3)  The  lemniscus  or  fillet  (Fig.  724). — The  fibres  of  the  lemniscus  take  origin 
in  the  gracile  and  cuneate  nuclei  of  the  medulla  oblongata,  and  cross  to  the  oppo- 
site side  in  the  sensory  decussation  (page  827).  They  then  pass  upward  through 
the  medulla  oblongata,  in  which  they  are  situated  behind  the  cerebrospinal  fibres 
and  between  the  olives.  Here  they  are  joined  by  the  fibres  of  the  superficial  antero- 
lateral fasciculus,  these  having  already  undergone  decussation  in  the  medulla 
spinalis.  As  the  lemniscus  ascends,  it  receives  additional  fibres  from  the  terminal 
nuclei  of  the  sensory  cerebral  nerves  of  the  opposite  side.  In  the  pons,  it  assumes 
a  flattened,  ribbon-like  appearance,  and  is  placed  dorsal  to  the  trapezium.     In 

1  A.  Bruce  and  J.  H.  Harvey  Pirrie,  "On  the  Origin  of  the  Facial  Nerve,"  Review  of  Neurology  and  Psychiatry, 
December,  1908,  No.  12,  vol.  vi,  produce  weighty  evidence  against  the  view  that  the  facial  nerve  derives  fibres  from 
the  nucleus  of  the  oculomotor  nerve. 


THE  MESENCEPHALON  OR  MID-BRAIN 


853 


6    2 


:..  ,„.o- 


the  mesencephalon,  its  lateral  part  is  folded  backward  and  forms  nearly  a  right 
angle  with  its  medial  portion;  and  hence  it  is  customary  to  speak  of  the  lemniscus 
as  consisting  of  lateral  and  medial  parts. 

The  lateral  lemniscus  (Icm)ii6-cus  lateralis)  comes  to  the  surface  of  the  mes- 
encephalon along  its  lateral  sulcus,  and  disappears  under  the  inferior  colliculus. 
It  consists  of  fibres  from  the  terminal  nuclei  of  the  cochlear  division  of  the  acoustic 
nerve,  together  with  others  from  the  superior  olivary  and  trapezoid  nuclei.  Most 
of  these  fibres  are  crossed,  but  some  are  uncrossed.  Many  of  them  pass  to  the 
inferior  colliculus  of  the  same  or  opposite  side,  but  others  are  prolonged  to 
the  thalamus,  and  thence  through  the  occipital  part  of  the  internal  capsule  to 
the  middle  and  superior  temporal  gyri. 

The  medial  lemniscus  (lemniscus  medialis)  begins  in  the  gracile  and  cuneate  nuclei 
of  the  opposite  side,  and  is  joined  by  the  superficial  antero-lateral  fasciculus  of  the 
medulla  spinalis  and  by  fibres  from  the  terminal  nuclei  of  the  sensory  cerebral  nerves 
of  the  opposite  side,  excepting  the  cochlear 
division  of  the  acoustic.  In  the  cerebral  pe- 
duncle, a  few  of  its  fibres  pass  upward  in  the 
lateral  part  of  the  base  of  the  peduncle,  on  the 
dorsal  aspect  of  the  temporopontine  fibres, 
and  reach  the  lentiform  nucleus  and  the  insula. 
The  greater  part  of  the  medial  lemniscus,  on 
the  other  hand,  is  prolonged  through  the  teg- 
mentum, and  most  of  its  fibres  end  in  the 
thalamus ;  probably  some  are  continued  directly 
through  the  occipital  part  of  the  internal  capsule 
to  the  cerebral  cortex.  From  the  cells  of  the 
thalamus  a  relay  of  fibres  is  prolonged  to  the 
cerebral  cortex. 

In  the  tegmentum  there  are,  besides  these 
three  tracts,  the  tectospinal  fasciculus  from  the 
superior  colliculus  and  the  rubrospinal  fascic- 
ulus from  the  red  nucleus;  these  cross  the 
middle  line  and  are  continued  downward  into 
the  medulla  spinalis. 

The  corpora  quadrigemina  (Fig.  729)  are  four  rounded  eminences  which  form 
the  dorsal  part  of  the  mesencephalon.  They  are  situated  above  and  in  front  of 
the  anterior  medullary  velum  and  brachia  conjunctiva,  and  below  and  behind  the 
third  ventricle  and  posterior  commissure.  They  are  covered  by  the  splenium  of  the 
corpus  callosum,  and  are  partly  overlapped  on  either  side  by  the  medial  angle, 
or  pulvlnar,  of  the  posterior  end  of  the  thalamus;  on  the  lateral  aspect,  under 
cover  of  the  pulvinar,  is  an  oval  eminence,  named  the  medial  geniculate  body. 
The  corpora  quadrigemina  are  arranged  in  pairs  (superior  and  inferior  colliculi), 
and  are  separated  from  one  another  by  a  crucial  sulcus.  The  longitudinal  part 
of  this  sulcus  expands  superiorly  to  form  a  slight  depression  which  supports  the 
pineal  body,  a  cone-like  structure  which  projects  backward  from  the  thalam- 
encephalon  and  partly  obscures  the  superior  colliculi.  From  the  inferior  end  of 
the  longitudinal  sulcus,  a  white  band,  termed  the  frinulum  veli,  is  prolonged  down- 
ward to  the  anterior  medullary  velum;  on  either  side  of  this  band  the  trochlear 
nerve  emerges,  and  passes  forward  on  the  lateral  aspect  of  the  cerebral  peduncle 
to  reach  the  base  of  the  brain.  The  superior  colliculi  are  larger  and  darker  in  color 
than  the  inferior,  and  are  oval  in  shape.  The  inferior  colliculi  are  hemispherical, 
and  somewhat  more  prominent  than  the  superior.  The  superior  colliculi  are 
associated  with  the  sense  of  sight,  the  inferior  with  that  of  hearing. 

From  the  lateral  aspect  of  each  colliculus  a  w^hite  band,  termed  the  brachium, 


Fig.  725. — Transverse  section  passing  through 
the  sensory  decussation.  Schematic.  (Testut.) 
1.  Anterior  median  fissure.  2.  Posterior  median 
sulcus.  3,  3'.  Head  and  base  of  anterior  column 
(in  red).  4.  Hypoglossal  nerve.  5.  Bases  of 
posterior  column.  6.  Gracile  nucleus.  7.  Cune- 
ate nucleus.  8,  8.  Lemniscus.  9.  Sensory 
decussation.     10.  Cerebrospinal  fasciculus. 


854  NEUROLOGY 

is  prolonged  upward  and  forward.  The  superior  brachium  extends  laterahvard 
from  the  superior  colhculus,  and,  passing  between  the  pulvinar  and  medial  genicu- 
late body,  is  partly  continued  into  an  eminence  called  the  lateral  geniculate  body, 
and  partly  into  the  optic  tract.  The  inferior  brachium  passes  forward  and  upward 
from  the  inferior  colliculus  and  disappears  under  cover  of  the  medial  geniculate  body. 

In  close  relationship  with  the  corpora  quadrigemina  are  the  brachia  conjunctiva, 
which  emerge  from  the  upper  and  medial  parts  of  the  cerebellar  hemispheres. 
They  run  upward  and  forward,  and,  passing  under  the  inferior  colliculi,  enter  the 
tegmenta  as  already  described  (page  841). 

Structure  of  the  Corpora  Quadrigemina. — The  inferior  colliculus  (coUiculvs  inferior; 
inferior  quadrigeminal  body;  postgeinina)  consists  of  a  compact  nucleus  of  gray 
substance  containing  large  and  small  multipolar  nerve  cells,  and  more  or  less 
completely  surrounded  by  white  fibres  derived  from  the  lateral  lemniscus. 
Most  of  these  fibres  end  in  the  gray  nucleus  of  the  same  side,  but  some  cross  the 
middle  line  and  end  in  that  of  the  opposite  side.  From  the  cells  of  the  gray 
nucleus,  fibres  are  prolonged  through  the  inferior  brachium  into,  the  tegmentum 
of  the  cerebral  peduncle,  and  are  carried  to  the  thalamus  and  the  cortex  of  the 
temporal  lobe;  other  fibres  cross  the  middle  fine  and  end  in  the  opposite  colliculus. 

The  superior  colliculus  {colliculus  superior;  sujjerior  quadrigeminal  body; 
pregemina)  is  covered  by  a  thin  stratum  (stratum  zonale)  of  white  fibres, 
the  majority  of  which  are  derived  from  the  optic  tract.  Beneath  this  is  the 
stratum  cinereum,  a  cap-like  layer  of  gray  substance,  thicker  in  the  centre  than 
at  the  circumference,  and  consisting  of  numerous  small  multipolar  nerve  cells, 
imbedded  in  a  fine  netw^ork  of  nerve  fibres.  Still  deeper  is  the  stratum  opticum, 
containing  large  multipolar  nerve  cells,  separated  by  numerous  fine  nerve  fibres. 
Finally,  there  is  the  stratum  lemnisci,  consisting  of  fibres  derived  partly  from  the 
lemniscus  and  partly  from  the  cells  of  the  stratum  opticum;  interspersed  among 
these  fibres  are  many  large  multipolar  nerve  cells.  The  two  last-named  strata 
are  sometimes  termed  the  gray-white  layers,  from  the  fact  that  they  consist  of  both 
gray  and  white  substance.  Of  the  afterent  fibres  which  reach  the  superior  colliculus, 
some  are  derived  from  the  lemniscus,  but  the  majority  have  their  origins  in  the 
retina  and  are  conveyed  to  it  through  the  superior  brachium;  all  of  them  end  by 
arborizing  around  the  cells  of  the  gray  substance.  Of  the  efferent  fibres,  some 
cross  the  middle  line  to  the  opposite  colliculus;  many  ascend  through  the  superior 
brachium,  and  finally  reach  the  cortex  of  the  occipital  lobe  of  the  cerebrum;  while 
others,  after  undergoing  decussation  (fountain  decussation  of  Meynert)  form  the 
tectospinal  fasciculus  which  descends  through  the  formatio  reticularis  of  the  mesen- 
cephalon, pons,  and  medulla  oblongata  into  the  medulla  spinalis,  where  it  is  found 
partly  in  the  anterior  funiculus  and  partly  intermingled  w^ith  the  fibres  of  the 
rubrospinal  tract. 

The  corpora  quadrigemina  are  larger  in  the  lower  animals  than  in  man.  In 
fishes,  reptiles,  and  birds  they  are  hollow,  and  only  two  in  number  (corpora 
bigemina);  they  represent  the  superior  colliculi  of  mammals,  and  are  frequently 
termed  the  optic  lobes,  because  of  their  intimate  connection  with  the  optic 
tracts. 

The  cerebral  aqueduct  {aqueductus  cerebri;  aqueduct  of  Sylvius)  is  a  narrow- 
canal,  about  15  mm.  long,  situated  between  the  corpora  quadrigemina  and  teg- 
menta, and  connecting  the  third  with  the  fourth  ventricle.  Its  shape,  as  seen  in 
transverse  section,  varies  at  different  levels,  being  T-shaped,  triangular  above, 
and  oval  in  the  middle;  the  central  part  is  slightly  dilated,  and  was  named  by 
Retzius  the  ventricle  of  the  mid-brain.  It  is  lined  by  ciliated  columnar  epithelium, 
and  is  surrounded  by  a  layer  of  gray  substance  named  the  central  gray  stratum: 
this  is  continuous  below  with  the  gray  substance  in  the  rhomboid  fossa,  and  above 
with  that  of  the  thhd  ventricle.     Dorsally,  it  is  partly  separated  from  the  gray 


THE  PROSENCEPMALOX  OR  FORE-BRAIN  855 

substance  of  the  ([iiadrigeminal  bodies  by  the  fibres  of  the  lemniscus;  ventral  to 
it  are  the  medial  longitudinal  fasciculus,  and  the  formatio  reticularis  of  the  teg- 
mentum. Scattered  throughout  the  central  gray  stratum  are  immerous  nerve 
cells  of  various  sizes,  interlaced,  by  a  net-work  of  fine  fibres.  Besides  these  scattered 
cells  it  contains  three  groups  which  constitute  the  nuclei  of  the  oculomotor  and 
trochlear  ner\es,  and  the  nucleus  of  the  mesencephalic  root  of  the  trigeminal  nerve. 
The  nucleus  of  the  trigeminal  nerve  extends  along  the  entire  length  of  the  aqueduct, 
and  occupies  the  lateral  part  of  the  gray  stratum,  while  the  nuclei  of  the  oculo- 
motor and  trochlear  nerves  are  situated  in  its  ventral  part.  The  nucleus  of  the 
oculomotor  nerve  is  about  10  cm.  long,  and  lies  under  the  superior  colliculus,  beyond 
which,  lu)we^■er,  it  extends  for  a  short  distance  into  the  gray  substance  of  the  third 
ventricle.  The  nucleus  of  the  trochlear  nerve  is  small  and  nearly  circular,  and  is  on 
a  level  with  a  plane  carried  transversely  through  the  upper  part  of  the  inferior 
colliculus. 

THE    PROSENCEPHALON    OR    FORE-BRAIN. 

The  prosencephalon  or  fore-brain  consists  of:  (1)  the  diencephalon,  corresponding 
in  a  large  measure  to  the  third  ventricle  and  the  structures  which  bound  it;  and 
(2)  the  telencephalon,  comprising  the  largest  part  of  the  brain,  viz.,  the  cerebral 
hemispheres;  these  hemispheres  are  intimately  connected  with  each  other  across 
the  middle  line,  and  each  contains  a  large  ca^dty,  named  the  lateral  ventricle. 
The  lateral  ventricles  communicate  through  the  interventricular  foramen  with  the 
third  ventricle,  but  are  separated  from  each  other  by  a  medial  septum,  the  septum 
pellucidum;  this  contains  a  slit- like  cavity,  which  does  not  communicate  with  the 
ventricles. 

The  Diencephalon. — The  diencephalon  is  connected  above  and  in  front  with 
the  cerebral  hemispheres;  behind  with  the  mesencephalon.  Its  upper  surface  is 
concealed  by  the  corpus  callosum,  and  is  covered  by  a  fold  of  pia  mater,  named  the 
tela  chorioidea  of  the  third  ventricle;  inferiorlv  it  reaches  to  the  base  of  the  brain. 

The  diencephalon  comprises:  (1)  the  thalamencephalon ;  (2)  the  pars  mamillaria 
hypothalami;  and  (3)  the  posterior  part  of  the  third  ventricle.  For  descriptive  purposes, 
however,  it  is  more  convenient  to  consider  the  whole  of  the  third  ventricle  and  its 
boundaries  together;  this  necessitates  the  inclusion,  under  this  heading,  of  the  pars 
optica  h^t'pothalami  and  the  corresponding  part  of  the  third  ventricle — structures 
which  properly  belong  to  the  telencephalon. 

The  Thalamencephalon. — The  thalamencephalon  comprises:  (1)  the  thalamus; 
(2)  the  metathalamus  or  corpora  geniculata;  and  (3)  the  epithalamus,  consisting  of 
the  trigonum  habenulae,  the  pineal  body,  and  the  posterior  commissure. 

The  Thalami  {optic  thalamus)  (Figs.  726,  727)  are  two  large  ovoid  masses,  situated 
one  on  either  side  of  the  third  ventricle  and  reaching  for  some  distance  behind  that 
cavity.  Each  measures  about  4  cm.  in  length,  and  presents  two  extremities,  an 
anterior  and  a  posterior,  and  four  surfaces,  superior,  inferior,  medial,  and  lateral. 

The  anterior  extremity  is  narrow;  it  lies  close  to  the  middle  line  and  forms  the 
posterior  boundary  of  the  interventricular  foramen. 

The  posterior  extremity  is  expanded,  directed  backward  and  lateralward,  and 
overlaps  the  superior  colliculus.  Medially  it  presents  an  angular  prominence, 
the  pulvinar,  which  is  continued  laterally  into  an  oval  swelling,  the  lateral  geniculate 
body,  while  beneath  the  pulvinar,  but  separated  from  it  by  the  superior  brachium, 
is  a  second  oval  swelling,  the  medial  geniculate  body. 

The  superior  surface  is  free,  slightly  convex,  and  covered  by  a  layer  of  white 
substance,  termed  the  stratum  zonale.  It  is  separated  laterally  from  the  caudate 
nucleus  by  a  white  band,  the  stria  terminalis,  and  by  the  terminal  vein.  It  is  divided 
into  a  medial  and  a  lateral  portion  by  an  oblique  shallow  furrow  which  runs  from 


856 


NEUROLOGY 


behind  forward  and  medialward  and  corresponds  with  the  lateral  margin  of  the 
fornix;  the  lateral  part  forms  a  portion  of  the  floor  of  the  lateral  ventricle,  and  is 
.covered  by  the  epithelial  lining  of  this  cavity;  the  medial  part  is  covered  by  the 
tela  chorioidea  of  the  third  ventricle,  and  is  destitute  of  an  epithelial  covering. 
In  front,  the  superior  is  separated  from  the  medial  surface  by  a  salient  margin, 
the  taenia  thalami,  along  which  the  epithelial  lining  of  the  third  ventricle  is  reflected 
on  to  the  under  surface  of  the  tela  chorioidea.  Behind,  it  is  limited  medially  by 
a  groove,  the  sulcus  habenulae,  which  intervenes  between  it  and  a  small  triangular 
area,  termed  the  trigonum  habenulae. 

The  inferior  surface  rests  upon  and  is  continuous  with  the  upward  prolongation 
of  the  tegmentum  (subthalamic  tegmental  region),  in  front  of  which  it  is  related  to 
the  substantia  innominata  of  Meynsrt. 


Fig.  726. — Dissection  showing  the  ventricles  of  the  brain. 


The  medial  surface  constitutes  the  upper  part  of  the  lateral  wall  of  the  third 
ventricle,  and  is  connected  to  the  corresponding  surface  of  the  opposite  thalamus 
by  a  flattened  gray  band,  the  massa  intermedia  {jniddle  or  gray  commissure) .  This 
mass  averages  about  1  cm.  in  its  antero-posterior  diameter:  it  sometimes  consists 
of  two  parts  and  occasionally  is  absent.  It  contains  nerve  cells  and  nerve  fibres; 
a  few  of  the  latter  may  cross  the  middle  line,  but  most  of  them  pass  toward  the 
middle  line  and  then  curve  lateralward  on  the  same  side. 

The  lateral  surface  is  in  contact  with  a  thick  band  of  white  substance  which 
forms  the  occipital  part  of  the  internal  capsule  and  separates  the  thalamus  from 
the  lentiform  nucleus  of  the  corpus  striatum. 

Structure. — The  thalamus  consists  chiefly  of  gray  substance,  but  its  upper  sur- 
face is  covered  by  a  layer  of  white  substance,  named  the  stratum  zonale,  and  its 
lateral  surface  by  a  similar  layer  termed  the  lateral  medullary  lamina.     Its  gray 


THE  PROSENCEPHALON  OR  FORE-BRAIN 


857 


substance  is  incompletely  sul)(li\i(le(l  into  three  parts — anterior,  medial,  and  lateral 
— by  a  white  layer,  the  medial  medullary  lamina.  The  anterior  part  comprises  the 
anterior  tubercle,  the  medial  part  lies  next  the  lateral  wall  of  the  third  ventricle 
while  the  lateral  and  largest  part  is  interposed  between  the  medullary  laminae 
and  includes  the  pulvinar.  The  lateral  part  is  traversed  by  numerous  fibres  which 
radiate  from  the  thalamus  into  the  internal  capsule,  and  i^ass  through  the  latter 
to  the  cerebral  cortex.  These  three  parts  are  built  up  of  numerous  nuclei,  the 
connections  of  many  of  which  are  imperfectly  known. 


Thalamus 

Lateral  ventricle 
Caudate  nucleus 
Internal  capsule 

Lcntiforni  nucleus 

Claustrum 
Insula 


Corpus  callosutn 
Choroid  plexu.t  of 
lateral  ventricle 
'  Fornix 

Choroid  plexus  of 
third  ventricle 

Third  ventricle 


Red  nucleus 

Substantia  nigra 
Post.  perf.  substance 


Base  of  peduncle 
Nucleus  of  Luys 
Toenia  hippocampi 


Inferior  cornu  of  lateral  ventricle 
Hippocampus 


Gyrus  dentatus    Caudate  nucleus 
Fig.  727. — Coronal  section  of  brain  immediately  in  front  of  pons. 

Comiections.— The  thalamus  may  be  regarded  as  a  large  ganglionic  mass  in  which 
the  ascending  tracts  of  the  tegmentum  and  a  considerable  proportion  of  the  fibres 
of  the  optic  tract  end,  and  from  the  cells  of  which  numerous  fibres  (thalamocortical) 
take  origin,  and  radiate  to  almost  every  part  of  the  cerebral  cortex.  The  lemniscus, 
together  with  the  other  longitudinal  strands  of  the  tegmentum,  enters  its  ventral 
part:  the  thalamomamillary  fasciculus  {bundle  of  Vicq  d'Azyr),  from  the  corpus 
mamillare,  enters  in  its  anterior  tubercle,  while  many  of  the  fibres  of  the  optic 
tract  terminate  in  its  posterior  end.  The  thalamus  also  receives  numerous  fibres 
(corticothalamic)  from  the  cells  of  the  cerebral  cortex.  The  fibres  that  arise  from 
the  cells  of  the  thalamus  form  four  principal  groups  or  stalks:  (a)  those  of  the  ante- 
rior stalk  pass  through  the  frontal  part  of  the  internal  capsule  to  the  frontal  lobe; 
(6)  the  fibres  of  the  posterior  stalk  {optic  radiations)  arise  in  the  pulvinar  and  are 


858 


NEUROLOGY 


conveyed  through  the  occipital  part  of  the  internal  capsule  to  the  occipital  lobe;  (c) 
the  fibres  of  the  inferior  stalk  leave  the  under  and  medial  surfaces  of  the  thalamus, 
and  pass  beneath  the  lentiform  nucleus  to  the  temporal  lobe  and  insula;  {d)  those 
of  the  parietal  stalk  pass  from  the  lateral  nucleus  of  the  thalamus  to  the  parietal 
lobe.  Fibres  also  extend  from  the  thalamus  into  the  corpus  striatum — those 
destined  for  the  caudate  nucleus  leave  the  lateral  surface,  and  those  for  the  lenti- 
form nucleus,  the  inferior  surface  of  the  thalamus. 

Thalamus 

Caudate  nucleun 

Internal  capxule 
Globus  pallidiis 
Putame.n 
Claustrum 
■>^l  J»!-ula 


Corpus  callosuin 

Lateral  ventricle 

Choroid  plexus 

Fornix 

Third  ventricle 
Medial  inedullary  lamina 

I ntermediate  mass 

Third  ventricle 

Ojitic  tract 


Amygdaloid  nucleus 
Fig.  728. — Coronal  section  of  brain  through  intermediate  mass  of  third  ventricle. 


The  Metathalamus  (Fig.  729)  comprises  the  geniculate  bodies,  which  are  two  in 
number — a  medial  and  a  lateral — on  each  side. 

The  medial  geniculate  body  {corpus  geniculatum  mediale;  internal  geniculate  body; 
yostgeniculatum)  lies  under  cover  of  the  pulvinar  of  the  thalamus  and  on  the  lateral 
aspect  of  the  corpora  quadrigemina.  Oval  in  shape,  with  its  long  axis  directed 
forward  and  lateralward,  it  is  lighter  in  color  and  smaller  in  size  than  the  lateral. 
The  inferior  brachium  from  the  inferior  colliculus  disappears  under  cover  of  it 
while  from  its  lateral  extremity  a  strand  of  fibres  passes  to  join  the  optic  tract. 
Entering  it  are  many  acoustic  fibres  from  the  lateral  lemniscus.  The  medial 
geniculate  bodies  are  connected  with  one  another  by  the  commissure  of  Gudden, 
which  passes  through  the  posterior  part  of  the  optic  chiasma. 

The  lateral  geniculate  body  (corpus  geniculatum  laterale;  external  geniculate  body; 
pregenicidatum)  is  an  oval  elevation  on  the  lateral  part  of  the  posterior  end  of  the 


77//-;  PROSENCEPHALON  OP  FORE-BRAIN 


859 


thalanuis,  aiul  is  connected  with  the  sni)cri()r  collicnlus  by  the  superior  brachium. 
It  is  of  a  dark  color,  and  presents  a  himinated  arrangement  consisting  of  alternate 
layers  of  gray  and  white  substance.  It  receives  numerous  fibres  from  the  optic 
tract,  while  other  fibres  of  tliis  tract  pass  over  or  through  it  into  tlie  pulvinar. 
Its  cells  are  large  and  ])ignuMite{l;  their  axons  i)ass  to  tiie  visual  area  in  the  occipital 
part  of  the  cerebral  cortex. 

The  superior  colliculus,  the  ])ul\inar,  and  the  lateral  geniculate  body  receive 
many  fibres  from  the  optic  tracts,  and  are  therefore  Intimately  connected  with 
sight,  constituting  what  are  termed  the  lower  visual  centres.  Extirpation  of  the 
eyes  in  a  newly  born  animal  entails  an  arrest  of  the  development  of  these  centres, 
but  has  no  effect  on  the  medial  geniculate  bodies  or  on  the  inferior  colliculi.  More- 
over, the  latter  are  well-developed  in  the  mole,  an  animal  in  which  the  superior 
colliculi  are  rudimentary. 

Superior  brachiuia     Lateral  geniculate  hmly 


Inferior  brachium 
Pulvinar 
Pineal  body 


Medial  geniculate  body 

I 

Opt  10  t/ait 


Superior  colliculi 
Inferior  colliculi 

Frenulum  veil 

Trochlear  nerve 

Lateral  lemniscus 

Brachiuyn  conjunctivum 

Brachium  pontis 
Rhomboid  fossa 


Glossopharyngeal  and  vagus  nerves 


Optic  cuinntissure 


Oculom,otor  nei-ve 


Trigeminal  nerve 


Arowitic  nerve 
I<'acial  nei  i^e 


Abducent  nerve 


Hypoglossal  nerve 


Accessory  nerve 

Fig.  729. — Hind-  and  mid-brains;  postero-lateral  view. 

The  Epithalamus  comprises  the  trigonum  habenulae,  the  pineal  body,  and  the 
posterior  commissure. 

The  trigonum  habenulae  is  a  small  depressed  triangular  area  situated  in  front 
of  the  superior  colliculus  and  on  the  lateral  aspect  of  the  posterior  part  of  the  taenia 
thalami.  It  contains  a  group  of  nerve  cells  termed  the  ganglion  habenulae.  Fibres 
enter  it  from  the  stalk  of  the  pineal  body,  and  others,  forming  what  is  termed  the 
habenular  commissure,  pass  across  the  middle  line  to  the  corresponding  ganglion 
of  the  opposite  side.  Most  of  its  fibres  are,  how^ever,  directed  downward  and  form 
a  bundle,  the  fasciculus  retroflexus  of  Meynert,  which  passes  medial  to  the  red 
nucleus,  and,  after  decussating  wdth  the  corresponding  fasciculus  of  the  opposite 
side,  ends  in  the  interpeduncular  ganglion. 

The  pineal  body  {corpus  ijineale;  ejn'physis)  is  a  small,  conical,  reddish-gray  body 
which  lies  in  the  depression  betw^een  the  superior  colliculi.  It  is  placed  beneath  the 
splenium  of  the  corpus  callosum,  but  is  separated  from  this  by  the  tela  chorioidea 
of  the  third  ventricle,  the  lowTr  layer  of  which  envelops  it.  It  measures  about 
8  cm.  in  length,  and  its  base,  directed  forward,  is  attached  by  a  stalk  or  peduncle 


860  NEUROLOGY 

of  white  substance.  The  stalk  of  the  pineal  body  divides  anteriorly  into  two 
laminse,  a  dorsal  and  a  ventral,  separated  from  one  another  by  the  pineal  recess 
of  the  third  ventricle.  The  ventral  lamina  is  continuous  with  the  posterior  com- 
missure; the  dorsal  lamina  is  continuous  with  the  habenular  commissure  and 
divides  into  two  strands  the  medullary  striee,  which  run  forward,  one  on  either 
side,  along  the  junction  of  the  medial  and  upper  surfaces  of  the  thalamus  to  blend 
in  front  with  the  columns  of  the  fornix. 

Structure. — The  pineal  body  is  destitute  of  nervous  substance,  and  consists  of  follicles  Lined 
by  epithelium  and  enveloped  by  connective  tissue.  These  follicles  contain  a  variable  quantity 
of  gritty  material,  composed  of  phosphate  and  carbonate  of  calcium,  phosphate  of  magnesium 
and  ammonia,  and  a  little  animal  matter. 

The  pineal  body  is  generally  believed  to  be  the  homologue  of  the  pineal  eye  of  lizards.  In 
these  animals  it  is  attached  by  an  elongated  stalk  and  projects  through  an  aperture  in  the  roof 
of  the  cranium.  Its  extremity  hes  immediately  under  the  epidermis,  and,  on  microscopic  exami- 
nation, presents  in  a  rudimentary  fashion  structures  similar  to  those  found  in  the  eyeball.  Recent 
observations  tend  to  the  conclusion  that  the  pineal  body  arises  as  a  paired  structure,  probably 
serially  homologous  with  the  paired  eyes. 

The  posterior  commissure  is  a  rounded  band  of  white  fibres  crossing  the  middle 
line  on  the  dorsal  aspect  of  the  upper  end  of  the  cerebral  aqueduct.  Its  fibres 
acquire  their  medullary  sheaths  early,  but  their  connections  have  not  been  definitely 
determined.  Most  of  them  have  their  origin  in  a  nucleus,  the  nucleus  of  the  poste- 
rior commissure  {nucleus  of  Darkschewitsch) ,  which  lies  in  the  central  gray  substance 
of  the  upper  end  of  the  cerebral  aqueduct,  in  front  of  the  nucleus  of  the  oculomotor 
nerve.  Some  are  probably  derived  from  the  posterior  part  of  the  thalamus  and  from 
the  superior  colliculus,  while  others  are  believed  to  be  continued  downward  into 
the  medial  longitudinal  fasciculus. 

The  Hypothalamus  (Fig.  730)  includes  the  subthalamic  tegmental  region  and 
the  structures  forming  the  greater  part  of  the  floor  of  the  third  ventricle,  viz.,  the 
corpora  mamillaria,  tuber  cinereum,  infundibulum,  hypophysis,  and  optic  chiasma. 

The  subthalamic  tegmental  region  consists  of  the  upward  continuation  of  the 
tegmentum;  it  lies  on  the  ventro-lateral  aspect  of  the  thalamus  and  separates 
it  from  the  fibres  of  the  internal  capsule.  The  red  nucleus  and  the  substantia 
nigra  are  prolonged  into  its  lower  part;  in  front  it  is  continuous  with  the  substantia 
innominate  of  Meynert,  medially  with  the  gray  substance  of  the  floor  of  the  third 
ventricle. 

It  consists  from  above  downward  of  three  strata:  (1)  stratum  dorsale,  directly 
applied  to  the  under  surface  of  the  thalamus  and  consisting  of  fine  longitudinal 
fibres;  (2)  zona  incerta,  a  continuation  forward  of  the  formatio  reticularis  of  the 
tegmentum;  and  (3)  the  corpus  subthalamicum  (nucleus  of  Luys),  a  brownish  mass 
presenting  a  lenticular  .shape  on  transverse  section,  and  situated  on  the  dorsal 
aspect  of  the  fibres  of  the  base  of  the  cerebral  peduncle;  it  is  encapsuled  by  a  lamina 
of  nerve  fibres  and  contains  numerous  medium-sized  nerve  cells,  the  connections 
of  which  are  as  yet  not  fully  determined. 

The  corpora  mamillaria  {corjnis  alhicantia)  are  two  round  white  masses,  each 
about  the  size  of  a  small  pea,  placed  side  by  side  below  the  gray  substance  of  the 
floor  of  the  third  ventricle  in  front  of  the  posterior  perforated  substance.  They 
consist  of  white  substance  externally  and  of  gray  substance  internally,  the  cells  of 
the  latter  forming  two  nuclei,  a  medial  of  smaller  and  a  lateral  of  larger  cells.  The 
white  substance  is  mainly  formed  by  the  fibres  of  the  columns  of  the  fornix,  which 
descend  to  the  base  of  the  brain  and  end  partly  in  the  corpora  mamillaria.  From 
the  cells  of  the  gray  substance  of  each  mamillary  body  two  fasciculi  arise:  one, 
the  thalamomamillary  fasciculus  {bundle  of  Vicq  d'Azyr),  passes  upward  into  the 
anterior  nucleus  of  the  thalamus;  the  other  is  directed  downward  into  the  tegmen- 
tum. Afferent  fibres  are  believed  to  reach  the  corpus  mamillare  from  the  medial 
lemniscus  and  from  the  tegmentum. 


THE  PROSENCEPHALON  OR  FORE-BRAIN 


861 


The  tuber  cinereum  is  a  hollow  cmineiice  of  ^rji>'  substance  situated  between 
the  corpora  niainillaria  behind,  and  the  oi)tic  chiasma  in  front.     Laterally  it  is 


Corpora  fixiadrigem  ina 


Tela  chorioidea  of  third  ventricle.      Posterior  commissure 
Intermediate  mass 
Interventricular  foramen       , 

/      Pineal  body 

\     -^      /  'iplemnm 

N  ^4 


P'ft  mater 


Genu  /  /  ^ 

Rostnun      /    /  ^ 
Anteno)    commissure  ^  / 
Lamina  teiminalis 
Optxe  recas 
Optic  chiasma 
Injundibul 


Coipits  onamilla) 
Oculomotor 
•     Cerebral  aqueduct 


Chorioid  plexus 


Fourth  ventricle 
Fig.  730. — Median  sagittal  section  of  brain.     The  relations  of  the  pia  mater  are  indicated  by  the  red  color. 

continuous  with  the  anterior  per-' 
forated  substances  and  anteriorly 
with  a  thin  lamina,  the  lamina 
terminalis.  From  the  under  surface 
of  the  tuber  cinereum  a  hollow 
conical  process,  the  infundibulum, 
projects  downward  and  forward 
and  is  attached  to  the  posterior 
lobe  of  the  hypophysis. 

In  the  lateral  part  of  the  tuber  eine- 
reum  is  a  nucleus  of  nerve  ceils,  the  basal 
optic  nucleus  of  Meynert,  while  close  to 
the  ca\ity  of  the  third  ventricle  are  three 
additional  nuclei.  Between  the  tuber 
cineremn  and  the  corpora  mamiUaria  a 
small  elevation,  with  a  corresponding 
depression  in  the  third  ventricle,  is  some- 
times seen.  Retzius  has  named  it  the 
eminentia  saccularis,  and  regards  it  as  a 
representative  of  the  saccus  vasculosus 
found  in  this  situation  in  some  of  the 
lower  vertebrates. 

The  hypophysis    (pituitary  body)   (Fig.  731)  is  a  reddish-gray,  somewhat  oval 
mass,  measuring  about  1.25  cm.  in  its  transverse,  and  about  8  cm.  in  its  antero- 


FiG.  731. — The  hypophysis  cerebri,  in  position.  Shown  in 
sagittal  section.  (Testut.)  1,  1'.  Anterior  and  posterior  lobes 
of  hj-pophysis.  2.  Infundibulum.  3.  Optic  chiasma.  4. 
Lamina  terminalis.  5.  Optic  recess.  6.  Anterior  commissure. 
7,  7'.  Circular  sinus.  8.  Anterior  cerebral  artery.  9.  Basilar 
artery.  10.  Posterior  cerebral  artery.  11.  Corpus  mamillare. 
12.  Cerebral  peduncle.     13.  Pons. 


862  NEUROLOGY 

posterior  diameter.  It  is  attached  to  the  end  of  the  iiifundibiikiin,  and  is  sitnated 
in  the  fossa  hypophyseos  of  the  sphenoidal  bone,  where  it  is  retained  by  a  circular 
fold  of  dura  mater,  the  diaphragma  sella;  this  fold  almost  completely  roofs  in  the 
fossa,  leaving  only  a  small  central  aperture  through  which  the  infundibulum  passes. 
The  hypophysis  consists  of  an  anterior  and  a  posterior  lobe,  which  differ  from 
one  another  in  their  mode  of  development  and  in  their  structure  (Fig.  732).  The 
anterior  lobe  is  the  larger,  and  is  somewhat  kidney-shaped,  the  concavity  being 
directed  backward  and  embracing  the  posterior  lobe.  It  is  developed  from  a  diver- 
ticulum of  the  ectoderm  of  the  primitive  buccal  cavity  or  stomodeum  (see  page 
166)  and  consists  of  a  pars  anterior  and  a  pars  intermedia,  separated  from  each 
other  by  a  narrow  cleft,  the  remnant  of  the  pouch  or  diverticulum.  The  pars 
anterior  is  extremely  vascular  and  consists  of  epithelial  cells  of  varying  size  and 
shape,  arranged  in  cord-like  trabeculse  or  alveoli  and  separated  by  large,  thin- 
walled  bloodvessels.  The  pars  intermedia  is  a  thin  lamina  closely  applied  to  the 
body  and  neck  of  the  posterior  lobe  and  extending  on  to  the  neighboring  parts  of 
the  brain ;  it  contains  few  bloodvessels  and  consists  of  finely  granular  cells  between 
which  are  small  masses  of  colloid  material.  The  posterior  lobe  is  developed  as  a 
downgrowth  from  the  floor  of  the  embryonic  brain,  and  during  early  fetal  life  con- 
tains a  cavity  continuous  with  that  of  the  third  ventricle.    In  some  animals,  e.  g., 


OpUc  cliiasma    I 
Zrd  ventricle 
Extension  of  pars  intermedia 
into  brain  substance 

Process  of  pars  intermedia     ,  "v  ^''S^^^S^^^et^J ''     ^-rt-    -i^\ 

Anterior  lobe    ^  '"^^^^^^^^^^^^^    Posterior  lobe 

Intraglandular  cleft 

Pars  intermedia 
Fig.   732. — Median  sagittal  section  through  the  hypophysis  of  an  adult  monkey.     Semidiagrammatic.      (Herring.) 

cat,  this  cavity  persists  throughout  life.  Although  of  nervous  origin  the  posterior 
lobe  contains  no  nerve  cells  or  fibres.  It  consists  of  neuroglia  cells  and  fibres  and 
is  invaded  by  columns  which  grow  into  it  from  the  pars  intermedia;  imbedded 
in  it  are  large  quantities  of  a  colloid  substance  histologically  similar  to  that  found 
in  the  thyroid  gland.  In  certain  of  the  lower  vertebrates,  e.  g.,  fishes,  nervous 
structures  are  present,  and  the  lobe  is  of  large  size. 

Applied  Anatomy. — Prof.  Schafer  has  isolated  from  the  pars  intermedia  a  substance,  no  doubt 
an  internal  secretion,  that  causes  constriction  of  the  bloodvessels,  rise  of  arterial  blood  pressure, 
and  increased  secretion  of  urine,  when  injected  subcutaneously.  Enlargement  of  the  hypo- 
physis and  of  the  cavity  of  the  sella  turcica  are  found  in  the  rare  disease  acromegaly,  which  is 
characterized  by  gradual  enlargement  of  the  face,  hands,  and  feet,  with  headache  and  often  a 
pecuhar  type  of  bhndness.  This  blindness  is  due  to  the  pressure  of  the  enlarging  hypophysis 
on  the  optic  chiasma  (Fig.  731).  The  pressure  causes  atrophy,  for  the  most  part  of  the  nerve 
fibres  coming  from  the  nasal  sides  of  the  retinse;  with  the  result  that  the  patient  loses  his  two 
temporal  fields  of  vision  while  retaining  his  nasal  fields  (bitemporal  hemianopsy). 

Optic  Chiasma  {chiasma  oyticum;  optic  commissure). — The  optic  chiasma  is  a 
flattened,  somewhat  quadrilateral  band  of  fibres,  situated  at  the  junction  of  the 
floor  and  anterior  wall  of  the  third  ventricle.    Most  of  its  fibres  have  their  origins 


THE  PROSENCEPHALON  OR  FORE-BRAIN 


sm 


in  the  retina,  and  reacli  the  chiasnia  tlirough  tlie  ()i)tic-  nerves,  which  are  continuous 
with  its  antero-hiteral  angles.  In  the  chiasma,  they  undergo  a  partial  decussation 
(Fig.  733) ;  the  fibres  from  the  nasal  half  of  the  retina  decussate  and  enter  the  optic 
tract  of  the  opposite  side,  while  the  fibres  from  the  temporal  half  of  the  retina  do 
not  undergo  decussation,  but  pass  back  into  the  (^ptic  tract  of  the  same  side. 
Occup^-ing  the  posterior  part  of  the  commissure,  however,  is  a  strand  of  fibres, 
the  commisure  of  Gudden,  which  is  not  derived  from  the  optic  nerves;  it  forms  a 
connecting  link  between  the  medial  geniculate  bodies. 


7 Optic  nerve 

7 Crossed  fibres 

Uncrossed  fibres 
Optic  chiasnia 


Commissure  of  Gudden 


Pidvinar 

Lateral  genicidate  body 
Superior  colliculus 
Medial  genicidate  body 

Nucleus  of  oculomotor  nerve 
Nucleus  of  trochlear  nerve 
Nucleus  of  abducent  nerve 


Cortex  of  occipital  lobes 
Fig.  733.— Scheme  showing  central  connections  of  the  optic  nerves  and  optic  tracts. 

Optic  Tracts.— The  optic  tracts  are  continued  backward  and  lateralward  from 
the  postero-lateral  angles  of  the  optic  chiasma.  Each  passes  between  the  anterior 
perforated  substance  and  the  tuber  cinereum,  and,  winding  around  the  ventro- 
lateral aspect  of  the  cerebral  peduncle,  divides  into  a  medial  and  a  lateral  root. 
The  former  comprises  the  fibres  of  Gudden's  commissure.  The  lateral  root  consists 
mainly  of  afferent  fibres  which  arise  in  the  retina  and  undergo  partial  decussation 
in  the  optic  chiasma,  as  described;  but  it  also  contains  a  few  fine  efferent  fibres 
which  have  their  origins  in  the  brain  and  their  terminations  m  the  retina,  \\hen 
traced  backward,  the  afferent  fibres  of  the  lateral  root  are  found  to  end  m  the  lateral 
geniculate  bodv  and  pulvinar  of  the  thalamus,  and  in  the  superior  colliculus;  and 


864 


NEUROLOGY 


these  three  structures  constitute  the  lower  visual  centres.  Fibres  arise  from  the 
nerve  cells  in  these  centres  and  pass  through  the  occipital  part  of  the  internal 
capsule,  under  the  name  of  the  optic  radiations,  to  the  cortex  of  the  occipital  lobe 
of  the  cerebrum,  where  the  higher  or  cortical  visual  centre  is  situated.  Some  of  the 
fibres  of  the  optic  radiations  take  an  opposite  course,  arising  from  the  cells  of  the 
occipital  cortex  and  passing  to  the  lower  visual  centres.  Some  fibres  are  detached 
from  the  optic  tract,  and  pass  through  the  cerebral  peduncle  to  the  nucleus  of 
the  oculomotor  nerve.  These  may  be  regarded  as  the  afferent  branches  for  the 
Sphincter  pupillae  and  Ciliaris  muscles.  Other  fibres  have  been  described  as 
reaching  the  cerebellum  through  the  brachia  conjunctiva;  while  others,  again, 
are  lost  in  the  pons. 

The  Third  Ventricle  {ventriculus  tertius)  (Figs.  726,  730). — The  third  ventricle  is 
a  median  cleft  between  the  two  thalami.  Behind,  it  communicates  with  the  fourth 
ventricle  through  the  cerebral  aqueduct,  and  in  front  with  the  lateral  ventricles 
through  the  interventricular  foramen.  Somewhat  triangular  in  shape,  with  the 
apex  directed  backward,  it  has  a  roof,  a  floor,  an  anterior  and  a  posterior  boundary 
and  a  pair  of  lateral  walls. 


Lateral 
ventricle 


Tela  chorioidea 
Internal  cerebral  veins 
Epithelial  lining  of  ventricle 


Epithelial  lining 

of  ventricle 
Termiiud  vein 
Choroid  plexus  of 
lateral  ventricle 


Choroid  plexuses  of  third  ventricle 
Third  ventricle 


Fig.  734. — Coronal  section  of  lateral  and  third  ventricles.      (Diagrammatic.) 

The  roof  (Fig.  7.34)  is  formed  by  a  layer  of  epithelium,  which  stretches  between 
the  upper  edges  of  the  lateral  walls  of  the  cavity  and  is  continuous  with  the  epithe- 
lial lining  of  the  ventricle.  It  is  covered  by  and  adherent  to  a  fold  of  pia  mater, 
named  the  tela  chorioidea  of  the  third  ventricle,  from  the  under  surface  of  which 
a  pair  of  vascular  fringed  processes,  the  choroid  plexuses  of  the  third  ventricle, 
project  downward,  one  on  either  side  of  the  middle  line,  and  invaginate  the 
epithelial  roof  into  the  ventricular  cavity. 

The  floor  slopes  downward  and  forward  and  is  formed  mainly  b}^  the  structures 
w'hich  constitute  the  hypothalamus:  from  before  backward  these  are:  the  optic 
chiasma,  the  tuber  cinereum  and  infundibulum,  and  the  corpora  mamillaria. 
Behind  the  last,  the  floor  is  formed  by  the  interpeduncular  fossa  and  the  tegmenta 
of  the  cerebral  peduncles.  The  ventricle  is  prolonged  downward  as  a  funnel- 
shaped  recess,  the  recessus  infundibuli,  into  the  infundibulum,  and  to  the  apex  of 
the  latter  the  hj-pophysis  is  attached. 

The  anterior  boundary  is  constituted  below  by  the  lamina  terminalis,  a  thin  layer 
of  gray  substance  stretching  from  the  upper  surface  of  the  optic  chiasma  to  the 
rostrum  of  the  corpus  callosum;  above  by  the  columns  of  the  fornix  and  the  anterior 
commissure.  At  the  junction  of  the  floor  and  anterior  wall,  immediately  above 
the  optic  chiasma,  the  ventricle  presents  a  small  angular  recess  or  diverticulum, 


THE  PROSENCEPHALON  OR  FORE-BRAIN  865 

the  optic  recess.  Between  the  cukimns  of  the  fornix,  and  above  the  anterior 
commissure,  is  a  second  recess  termed  the  vulva.  At  the  junction  of  the  roof  and 
anterior  wall  of  the  ventricle,  and  situated  between  the  thalami  behind  and  the 
columns  of  the  fornix  in  front,  is  the  interventricular  foramen  (foramen  of  Monro) 
through  which  the  third  communicates  with  the  lateral  ventricles. 

The  posterior  boundary  is  constituted  by  the  pineal  body,  the  posterior  commissure 
and  the  cerebral  aqueduct.  A  small  recess,  the  recessus  pinealis,  projects  into  the 
stalk  of  the  pineal  body,  while  in  front  of  and  above  the  pineal  body  is  a  second 
recess,  the  recessus  suprapinealis,  consisting  of  a  diverticulum  of  the  epithelium 
which  forms  the  ventricular  roof. 

Each  lateral  wall  consists  of  an  upper  portion  formed  by  the  medial  surface  of 
the  anterior  two-thirds  of  the  thalamus,  and  a  lower  consisting  of  an  upward 
continuation  of  the  gray  substance  of  the  ventricular  floor.  These  two  parts 
correspond  to  the  alar  and  basal  laminse  respectively  of  the  lateral  w'all  of  the 
fore-brain  vesicle  and  are  separated  from  each  other  by  a  furrow,  the  sulcus  of 
Monro,  wdiich  extends  from  the  interventricular  foramen  to  the  cerebral  aqueduct 
(pages  125  and  126).  The  lateral  w^all  is  limited  above  by  the  taenia  thalami.  The 
columns  of  the  fornix  curve  downward  in  front  of  the  interventricular  foramen,  and 
then  run  in  the  lateral  walls  of  the  ventricle,  where,  at  first,  they  form  distinct 
prominences,  but  subsequently  are  lost  to  sight.  The  lateral  w^alls  are  joined  to 
each  other  across  the  cavity  of  the  ventricle  by  a  band  of  gray  matter,  the  massa 
intermedia  (page  856). 

Interpeduncular  Fossa  (Fig.  735). — This  is  a  somewhat  lozenge-shaped  area  of  the 
base  of  the  brain,  limited  in  front  by  the  optic  chiasma,  behind  by  the  antero- 
superior  surface  of  the  pons,  antero-laterally  by  the  converging  optic  tracts, 
and  postero-laterally  by  the  diverging  cerebral  peduncles.  The  structures  con- 
tained in  it  have  already  been  described;  from  behind  forward,  they  are  the  pos- 
terior perforated  substance,  corpora  mamillaria,  tuber  cinereum,  infundibulum, 
and  hypophysis. 

The  Telencephalon. — The  telencephalon  includes:  (1)  the  cerebral  hemispheres 
with  their  cavities,  the  lateral  ventricles;  and  (2)  the  pars  optica  hypothalami  and 
the  anterior  portion  of  the  third  ventricle  (already  described  under  the  dienceph- 
alon).  As  stated  in  the  chapter  on  Embryology  (page  128),  each  cerebral  hemi- 
sphere may  be  divided  into  three  fundamental  parts,  viz.,  the  rhinencephalon, 
the  corpus  striatum,  and  the  neopallium.  The  rhinencephalon,  associated  with 
the  sense  of  smell,  is  the  oldest  part  of  the  telencephalon,  and  forms  almost  the 
whole  of  the  hemisphere  in  some  of  the  lower  animals,  e.  g.,  fishes,  amphibians, 
and  reptiles.  In  man  it  is  rudimentary,  whereas  the  neopallium  undergoes  great 
development  and  forms  the  chief  part  of  the  hemisphere. 

The  Cerebral  Hemispheres. — The  cerebral  hemispheres  constitute  the  largest 
part  of  the  encephalon,  and,  when  viewed  together  from  above,  assume  the  form 
of  an  ovoid  mass  broader  behind  than  in  front,  the  greatest  transverse  diameter 
corresponding  with  a  line  connecting  the  tw^o  parietal  eminences.  The  hemispheres 
are  separated  medially  by  a  deep  cleft,  named  the  longitudinal  cerebral  fissure, 
and  each  possesses  a  central  cavity,  the  lateral  ventricle. 

The  Longitudinal  Cerebral  Fissure  (fissiira  cerebri  longitudinalis;  great  longitudinal 
fissure)  contains  a  sickle-shaped  process  of  dura  mater,  the  falx  cerebri.  It  front 
and  behind,  the  fissure  extends  from  the  upper  to  the  under  surfaces  of  the  hemi- 
spheres and  completely  separates  them,  but  its  middle  portion  only  separates  them 
for  about  one-half  of  their  vertical  extent;  for  at  this  part  they  are  connected  across 
the  middle  line  by  a  great  central  white  commissure,  the  corpus  callosum. 

In  a  median  sagittal  section  (Fig.  730)  the  cut  corpus  callosum  presents  the 
appearance  of  a  broad,  arched  band.  Its  thick  posterior  end,  termed  the  splehium, 
overlaps  the  mid-brain,  but  is  separated  from  it  by  the  tela  chorioidea  of  the  third 


866 


NEUROLOGY 


ventricle  and  the  pineal  body.  Its  anterior  curved  end,  termed  the  genu,  gradually 
tapers  into  a  thinner  portion,  the  rostrum,  which  is  continued  downward  and  back- 
ward in  front  of  the  anterior  commissure  to  join  the  lamina  terminalis.  Arching 
backward  from  immediately  behind  the  anterior  commissure  to  the  under  surface 
of  the  splenium  is  a  second  white  band  named  the  fornix:  between  this  and  the 
corpus  callosum  are  the  laminae  and  cavity  of  the  septum  pellucidum. 


Frontal  lobe 


Temporal 
lobe 


Occipital  lobe 


Fig.  735. — Base  of  brain. 


Surfaces  of  the  Cerebral  Hemispheres. — Each  hemisphere  presents  three  surfaces: 
lateral,  medial,  and  inferior. 

The  lateral  surface  is  convex  in  adaptation  to  the  concavity  of  the  corresponding 
half  of  the  vault  of  the  cranium.  The  medial  surface  is  flat  and  vertical,  and  is 
separated  from  that  of  the  opposite  hemipshere  by  the  great  longitudinal  fissure 
and  the  falx  cerebri.  The  inferior  surface  is  of  an  irregular  form,  and  may  be  divided 
into  three  areas:  anterior,  middle,  and  posterior.  The  anterior  area,  formed  by 
the  orbital  surface  of  the  frontal  lobe,  is  concave,  and  rests  on  the  roof  of  the  orbit 
and  nose;  the  middle  area  is  convex,  and  consists  of  the  under  surface  of  the  tem- 
poral lobe:  it  is  adapted  to  the  corresponding  half  of  the  middle  cranial  fossa.  The 
posterior  area  is  concave,  directed  medialward  as  well  as  downward,  and  is  named 
the  tentorial  surface,  since  it  rests  upon  the  tentorium  cerebelli,  which  intervenes 
between  it  and  the  upper  surface  of  the  cerebellum. 

These  three  surfaces  are  separated  from  each  other  by  the  following  borders: 


THE  PROSENCEPHALON  OR  FORE-BRAIN 


867 


(a)  supero-medial,  hetwocn  the  lateral  and  medial  surfaces;  (b)  infero-lateral,  between 

the  lateral  and  inferior  surfaces;  the  anterior  part  of  this  border  separating  the 

lateral  from  the  orbital  surface,  is  known  as  the  superciliary  border;  (c)  medial 

occipital,   separatin"'  the  medial  and  tentorial  surfaces;  and   (d)   medial  orbital, 

separating  the  orbital  from  the  medial  surface. 

The  anterior  end  of  the  hemisphere  is  named 

the  frontal  pole;  the  posterior,  the  occipital  pole; 

and  the  anterior  end  of  the  temporal  lobe,  the 

temporal    pole.    About   5   cm.   in  front  of   the 

occipital    pole   on  the  infero-lateral  border  is 

an  indentation  or  notch,  named  the  preoccipital 

notch. 

The  surfaces  of  the  hemispheres  are  moulded 
into  a  number  of  irregular  eminences,  named 
gyri  or  convolutions,  and  separated  by  furrows 
termed  fissures  and  sulci.  The  furrows  are  of 
two  kinds,  complete  and  incomplete.  The  former 
appear  early  in  fetal  life,  are  few  in  number, 
and  are  produced  by  infoldings  of  the  entire 
thickness  of  the  brain  wall,  and  give  rise  to 
corresponding  elevations  in  the  interior  of  the 
ventricle.  They  comprise  the  hippocampal  fis- 
sure, and  parts  of  the  calcarine  and  collateral 
fissures.  The  incomplete  furroW'S  are  very 
numerous,  and  only  indent  the  subjacent  wdiite 
substance,  without  producing  any  corresponding 
elevations  in  the  ventricular  cavity. 

The  gyri  and  their  intervening  fissures  and 
the  sulci  are  fairly  constant  in  their  arrange- 
ment ;  at  the  same  time  they  vary  within  certain 
limits,  not  only  in  different  individuals,  but  on 
the  two  hemispheres  of  the  same  brain.  The 
convoluted  condition  of  the  surface  permits  of 
a  great  increase  of  the  gray  matter  without  the 
sacrifice  of  much  additional  space.  The  num- 
ber and  extent  of  the  gyri,  as  well  as  the  depth 
of  the  intervening  furrows,  appear  to  bear  a 
direct  relation  to  the  intellectual  powers  of 
the  individual. 

Certain  of  the  fissures  and  sulci  are  utilized  for  the  purpose  of  dividing  the  hemi- 
sphere into  lobes,  and  are  therefore  termed  interlobular;  included  under  this  category 
are  the  lateral  cerebral,  parietooccipital,  calcarine,  and  collateral  fissures,  the 
central  and  cingulate  sulci,  and  the  sulcus  circularis. 

The  Lateral  Cerebral  Fissure  {fissura  cerebri  lateralis  [Sykii] ;  fissure  of  Sylvius)  (Fig. 
737)  is  a  well-marked  cleft  on  the  inferior  and  lateral  surfaces  of  the  hemisphere, 
and  consists  of  a  short  stem  w^hich  divides  into  three  rami.  The  stem  is  situated 
on  the  base  of  the  brain,  and  commences  in  a  depression  at  the  lateral  angle  of  the 
anterior  perforated  substance.  From  this  point  it  extends  between  the  anterior 
part  of  the  temporal  lobe  and  the  orbital  surface  of  the  frontal  lobe,  and  reaches 
the  lateral  surface  of  the  hemisphere.  Here  it  divides  into  three  rami:  an  anterior 
horizontal,  an  anterior  ascending,  and  a  posterior.  The  anterior  horizontal  ramus 
passes  forward  for  about  2.5  cm.  into  the  inferior  frontal  gyrus,  while  the  anterior 
ascending  ramus  extends  upward  into  the  same  convolution  for  about  an  equal 
distance.  The  posterior  ramus  is  the  longest;  it  runs  backward  and  slightly  upward 
for  about  7  cm.,  and  ends  by  an  upward  inflexion  in  the  parietal  lobe. 


Fig.  736. — Lateral  surface  of  left  cerebral 
hemisphere,  viewed  from  above. 


868 


NEUROLOGY 


The  Central  Sulcus  {sulcus  centralis  [Rolaiidi] ;  fissure  of  li^daudo;  central  fissure) 
(Figs.  736,  737)  is  situated  about  the  middle  of  the  lateral  surface  of  the  hemisphere, 
and  begins  in  or  near  the  longitudinal  cerebral  fissure,  a  little  behind  its  mid-point. 
It  runs  sinuously  downward  and  forward,  and  ends  a  little  above  the  posterior 


Fig.  737. — Lateral  surface  of  left  cerebral  hemisphere,  viewed  from  the  side. 

ramus  of  the  lateral  fissure,  and  about  2.5  cm.  behind  the  anterior  ascending  ramus 
of  the  same  fissure.  It  described  two  chief  curves:  a  superior  genu  with  its  con- 
cavity directed  forward,  and  an  inferior  genu  with  its  concavity  directed  backward. 
The  central  sulcus  forms  an  angle  opening  forward  of  about  70°  with  the  median 
plane. 


Fig.  738. — Medial  surface  of  left  cerebral  hemisphere. 


The  Parietooccipital  Fissure  (fissura  parietooccipitalis). — Only  a  small  part  of  this 
fissure  is  seen  on  the  lateral  surface  of  the  hemisphere,  its  chief  part  being  on  the 
medial  surface. 


THE  PROSENCEPHALOX  OR  FORE-BRAIN  869 

The  lateral  part  of  tlie  parietooccipital  fissure  (Fig.  737)  is  situated  aliout  5  cm. 
in  front  of  the  occipital  pole  of  the  hemisphere,  and  measures  about  1.25  cm.  in 
length. 

The  medial  part  of  the  parietooccipital  fissure  (Fig.  738)  runs  downward  and  for- 
ward as  a  deep  cleft  on  the  medial  surface  of  the  hemisphere,  and  joins  the  calcarine 
fissure  below  and  behind  the  posterior  end  of  the  corpus  callosum.  In  most  cases 
it  contains  a  submerged  gyrus. 

The  Calcarine  Fissure  (fissiira  ccdcarina)  (Fig.  738)  is  on  the  medial  surface  of 
the  hemisphere.  It  begins  near  the  occipital  pole  in  two  converging  rami,  and  runs 
forward  to  a  point  a  little  below  the  splenium  of  the  corpus  callosum,  where  it  is 
joined  at  an  acute  angle  by  the  medial  part  of  the  parietooccipital  fissure.  The 
anterior  part  of  this  fissure  gives  rise  to  the  prominence  of  the  calcar  avis  in  the 
posterior  cornu  of  the  lateral  ventricle. 

The  Cingulate  Sulcus  {sulcus  cinguli;  caUosomarginal  fissure)  (Fig.  738)  is  on  the 
medial  surface  of  the  hemisphere;  it  begins  below  the  anterior  end  of  the  corpus 
callosum  and  runs  upward  and  forward  nearly  parallel  to  the  rostrum  of  this  body 
and,  curving  in  front  of  the  genu,  is  continued  backward  above  the  corpus  callosum, 
and  finally  ascends  to  the  supero-medial  border  of  the  hemisphere  a  short  distance 
behind  the  upper  end  of  the  central  sulcus.  It  separates  the  superior  frontal  from 
the  cingulate  gyrus. 

The  Collateral  Fissure  {fissura  collaieralis)  (Fig.  738)  is  on  the  tentorial  surface 
of  the  hemisphere  and  extends  from  near  the  occipital  pole  to  within  a  short  dis- 
tance of  the  temporal  pole.  Behind,  it  lies  below  and  lateral  to  the  calcarine  fissure, 
from  which  it  is  separated  by  the  lingual  gyrus;  in  front,  it  is  situated  between  the 
hippocampal  gyrus  and  the  anterior  part  of  the  fusiform  gjTus. 

The  Sulcus  Circularis  {circuminsular  fissure)  (Fig.  741)  is  on  the  lower  and  lateral 
surfaces  of  the  hemisphere:  it  surrounds  the  insula  and  separates  it  from  the 
frontal,  parietal,  and  temporal  lobes. 

Lobes  of  the  Hemispheres.^ — By  means  of  these  fissures  and  sulci,  assisted  by 
certain  arbitrary  lines,  each  hemisphere  is  divided  into  the  following  lobes:  the 
frontal,  the  parietal,  the  temporal,  the  occipital,  the  limbic,  and  the  insula. 

Frontal  Lobe  ilobus  frontalis) . — On  the  lateral  surface  of  the  hemisphere  this  lobe 
extends  from  the  frontal  pole  to  the  central  sulcus,  the  latter  separating  it  from 
the  parietal  lobe.  Below,  it  is  limited  by  the  posterior  ramus  of  the  lateral 
fissure,  which  intervenes  between  it  and  the  central  lobe.  On  the  medial  sur- 
face, it  is  separated  from  the  cingulate  gyrus  by  the  cingulate  sulcus;  and  on  the 
inferior  smface,  it  is  bounded  behind  by  the  stem  of  the  lateral  fissure. 

The  lateral  surface  of  the  frontal  lobe  (Fig.  737)  is  traversed  by  three  sulci  which 
divide  it  into  four  gyri:  the  sulci  are  named  the  precentral,  and  the  superior  and 
inferior  frontal;  the  gyri  are  the  anterior  central,  and  the  superior,  middle,  and 
inferior  frontal.  The  precentral  sulcus  runs  parallel  to  the  central  sulcus,  and  is 
usually  divided  into  an  upper  and  a  lower  part;  between  it  and  the  central  sulcus  is 
the  anterior  central  gyms.  From  the  precentral  sulcus,  the  superior  and  inferior 
frontal  sulci  run  forward  and  downward,  and  divide  the  remainder  of  the  lateral 
surface  of  the  lobe  into  three  parallel  gyri,  named,  respectively  the  superior,  middle, 
and  inferior  frontal  gyri. 

The  anterior  central  gyrus  {gyrus  centralis  anterior;  ascending  frontal  convolution; 
precentral  gyre)  is  bounded  in  front  by  the  precentral  sulcus,  behind  by  the  central 
sulcus;  it  extends  from  the  supero-medial  border  of  the  hemisphere  to  the  posterior 
ramus  of  the  lateral  fissure. 

The  superior  frontal  gyrus  {gyrus  frontalis  superior;  superfrontal  gyre)  is  situated 
above  the  superior  frontal  sulcus  and  is  continued  on  to  the  medial  surface  of  the 
hemisphere.  The  portion  on  the  lateral  surface  of  the  hemisphere  is  usually  more 
or  less  completely  subdivided  into  an  upper  and   a   lower  part   by  an  antero- 


870 


NEUROLOGY 


posterior  sulcus,  the  paramedial  sulcus,  which,  ho\ve\Tr,  is  frequently  interrupted 
by  bridging  gyri. 

The  middle  frontal  gyrus  (gyrus  frontalis  medius;  inedifrontal  gyre),  between  the 
superior  and  inferior  frontal  sulci,  is  continuous  with  the  anterior  orbital  gyrus  on 
the  inferior  surface  of  the  hemisphere;  it  is  frequently  subdivided  into  two  by  a 
horizontal  sulcus,  the  medial  frontal  sulcus  of  Eberstaller,  which  ends  anteriorly  in 
a  wide  bifurcation. 

The  inferior  frontal  gyrus  {gyrus  frontalis  inferior;  subfrontal  gyre)  lies  below  the 
inferior  frontal  sulcus,  and  extends  forward  from  the  lower  part  of  the  precentral 
sulcus;  it  is  continuous  with  the  lateral  and  posterior  orbital  gyri  on  the  under 
surface  of  the  lobe.  It  is  subdivided  by  the  anterior  horizontal  and  ascending  rami 
of  the  lateral  fissure  into  three  parts,  viz.,  (1)  the  orbital  part,  below^  the  anterior 
horizontal  ramus  of  the  fissure;  (2)  the  triangular  part  (cap  of  Broca),  between 
the  ascending  and  horizontal  rami;  and  (3)  the  basilar  part,  behind  the  anterior 
ascending  ramus.  The  left  inferior  frontal  gyrus  is,  as  a  rule,  more  highly 
developed  than  the  right,  and  is  named  the  gyrus  of  Broca,  from  the  fact  that 
Broca  described  it  as  the  centre  for  articulate  speech. 

The  inferior  or  orbital  surface  of  the  frontal  lobe  is  concave,  and  rests  on  the  orbital 
plate  of  the  frontal  bone  (Fig.  739).  It  is  divided  into  four  orbital  gyri  by  a  well- 
marked  H-shaped  orbital  sulcus.  These  are 
named,  from  their  position,  the  medial,  anterior, 
lateral,  and  posterior  orbital  gyri.  The  medial 
orbital  gyrus  presents  a  well-marked  antero- 
posterior sulcus,  the  olfactory  sulcus,  for  the 
olfactory  tract;  the  portion  medial  to  this  is 
named  the  straight  gyrus,  and  is  continuous  with 
the  superior  frontal  gyrus  on  the  medial  surface. 
The  medial  surface  of  the  frontal  lobe  is  occu- 
pied by  the  medial  part  of  the  superior  frontal 
gyrus  (marginal  gyrus)  (Fig.  738).  It  lies  be- 
tween the  cingulate  sulcus  and  the  supero-medial 
margin  of  the  hemisphere.  The  posterior  part 
of  this  gyrus  is  sometimes  marked  off  by  a  ver- 
tical sulcus,  and  is  distinguished  as  the  paracen- 
tral lobule,  because  it  is  continuous  with  the 
anterior  and  posterior  central  gyri. 

Parietal  Lobe  (lohus  parietalis). — The  parietal 
lobe  is  separated  from  the  frontal  lobe  by  the 
central  sulcus,  but  its  boundaries  below  and 
behind  are  not  so  definite.  Posteriorly,  it  is  limited  by  the  parietooccipital  fissure, 
and  by  a  line  carried  across  the  hemisphere  from  the  end  of  this  fissure  toward 
the  preoccipital  notch.  Below,  it  is  separated  from  the  temporal  lobe  by  the 
posterior  ramus  of  the  lateral  fissure,  and  by  a  line  carried  backward  from  it  to 
meet  the  line  passing  downward  to  the  preoccipital  notch. 

The  lateral  surface  of  the  parietal  lobe  (Fig.  737)  is  cleft  by  a  well-marked  furrow, 
the  intraparietal  sulcus  of  Turner,  which  consists  of  an  oblique  and  a  horizontal 
portion.  The  oblique  part  is  named  the  postcentral  sulcus,  and  commences  beloAV, 
about  midway  between  the  lower  end  of  the  central  sulcus  and  the  upturned  end 
of  the  lateral  fissure.  It  runs  upward  and  backward,  parallel  to  the  central  sulcus, 
and  is  sometimes  divided  into  an  upper  and  a  lower  ramus.  It  forms  the  hinder 
limit  of  the  posterior  central  gyrus. 

From  about  the  middle  of  the  postcentral  sulcus,  or  from  the  upper  end  of  its 
inferior  ramus,  the  horizontal  portion  of  the  intraparietal  sulcus  is  carried  backward 
and  slightly  upward  on  the  parietal  lobe,  and  is  prolonged,  under  the  name  of  the 


Fig.  739. — Orbital  surface  of  left  frontal  lobe. 


THE  PROSENCEPHALON  OR  FORE-BRAIN  871 

occipital  ramus,  on  to  the  occipital  Iol)r,  where  it  divides  into  two  parts,  which  form 
nearly  a  right  angle  with  the  main  stem  and  constitute  the  transverse  occipital  sulcus. 
The  part  of  the  parietal  lobe  above  the  horizontal  portion  of  the  iiitraparietal 
sulcus  is  named  the  superior  parietal  lobule ;  the  part  l)elow,  the  inferior  parietal  lobule. 

The  posterior  central  gyrus  {gyrus  centralis  posterior;  ascending  imrietal  conrolution; 
'postcentral  gyre)  extends  from  the  longitudinal  fissure  above  to  the  posterior  ramus 
of  the  lateral  fissure  below.  It  lies  parallel  with  the  anterior  central  gyrus,  with 
which  it  is  connected  below,  and  also,  sometimes,  above,  the  central  sulcus. 

The  superior  parietal  lobule  {lobulus  parietalis  superior)  is  bounded  in  front  by 
the  upper  part  of  the  postcentral  sulcus,  but  is  usually  connected  with  the  pos- 
terior central  gyrus  above  the  end  of  the  sulcus;  behind  it  is  the  lateral  part  of 
the  parietooccipital  fissure,  around  the  end  of  which  it  is  joined  to  the  occipital 
lobe  by  a  curved  gyrus,  the  arcus  parietobccipitalis ;  below,  it  is  separated  from  the 
inferior  parietal  lobule  by  the  horizontal  portion  of  the  intraparietal  sulcus. 

The  inferior  parietal  lobule  {lobulus  parietalis  inferior;  suhparietal  district  or  lobule) 
lies  below^  the  horizontal  portion  of  the  intraparietal  sulcus,  and  behind  the  lower 
part  of  the  postcentral  sulcus.  It  is  divided  from  before  backward  into  two  gyri. 
One,  the  supramarginal,  arches  over  the  upturned  end  of  the  lateral  fissure;  it  is 
continuous  in  front  with  the  postcentral  gyrus,  and  behind  with  the  superior  tem- 
poral gyrus.  The  second,  the  angular,  arches  over  the  posterior  end  of  the  superior 
temporal  sulcus,  behind  which  it  is  continuous  with  the  middle  temporal  gyrus. 

The  medial  surface  of  the  parietal  lobe  (Fig.  738)  is  bounded  behind  by  the 
medial  part  of  the  parietooccipital  fissure;  in  front,  by  the  posterior  end  of  the  cin- 
gulate  sulcus;  and  below,  it  is  separated  from  the  cingulate  gyrus  by  the  subparietal 
sulcus.  It  is  of  small  size,  and  consists  of  a  square-shaped  convolution,  which  is 
termed  the  precuneus  or  quadrate  lobe. 

Occipital  Lobe  {lobus  occipitalis). — The  occipital  lobe  is  small  and  pyramidal 
in  shape;  it  presents  three  surfaces:  lateral,  medial,  and  tentorial. 

The  lateral  surface  is  limited  in  front  by  the  lateral  part  of  the  parietooccipital 
fissure,  and  by  a  line  carried  from  the  end  of  this  fissure  to  the  preoccipital  notch; 
it  is  traversed  by  the  transverse  occipital  and  the  lateral  occipital  sulci.  The 
transverse  occipital  sulcus  is  continuous  with  the  posterior  end  of  the  occipital 
ramus  of  the  intraparietal  sulcus,  and  runs  across  the  upper  part  of  the  lobe,  a 
short  distance  behind  the  parietooccipital  fissure.  The  lateral  occipital  sulcus 
extends  from  behind  forward,  and  divides  the  lateral  surface  of  the  occipital  lobe 
into  a  superior  and  an  inferior  gyrus,  which  are  continuous  in  front  with  the  parietal 
and  temporal  lobes. ^ 

The  medial  surface  of  the  occipital  lobe  is  bounded  in  front  by  the  medial  part 
of  the  parietooccipital  fissure,  and  is  traversed  by  the  calcarine  fissure,  which 
subdivides  it  into  the  cuneus  and  the  lingual  gyrus.  The  cuneus  is  a  wedge-shaped 
area  between  the  calcarine  fissure  and  the  medial  part  of  the  parietooccipital 
fissure.  The  lingual  gyrus  lies  between  the  calcarine  fissure  and  the  posterior  part 
of  the  collateral  fissure;  behind,  it  reaches  the  occipital  pole;  in  front,  it  is  con- 
tinued on  to  the  tentorial  surface  of  the  temporal  lobe,  and  joins  the  hippocampal 
gyrus. 

The  tentorial  surface  of  the  occipital  lobe  is  limited  in  front  by  an  imaginary 
transverse  line  through  the  preoccipital  notch,  and  consists  of  the  posterior  part 
of  the  fusiform  gyrus  (occipitotemporal  convolution)  and  the  lower  part  of  the  lingual 
gyrus,  which  are  separated  from  each  other  by  the  posterior  segment  of  the 
collateral  fissure. 

Temporal  Lobe  {lobus  temporalis). — The  temporal  lobe  presents  superior,  lateral, 
and  inferior  surfaces. 

1  Elliot  Smith  has  named  the  lateral  occipital  sulcus  the  sulcus  lunatus;  he  regards  it  as  the  representative,  in  the 
human  brain,  of  the  "  Affenspalte  "  of  the  brain  of  the  ape. 


872 


NEUROLOGY 


The  superior  surface  forms  the  lower  Hmit  of  the  lateral  fissure  and  overlaps 
the  insula.  On  opening  out  the  lateral  fissure,  three  or  four  gyri  will  be  seen  spring- 
ing from  the  depth  of  the  hinder  end  of  the  fissure,  and  running  obliquely  forward 
and  outward  on  the  posterior  part  of  the  upper  surface  of  the  superior  temporal 
gyrus;  these  are  named  the  transverse  temporal  gyri  (Heschl)  (Fig.  740). 

The  lateral  surface  (Fig.  737)  is  bounded  above  by  the  posterior  ramus  of  the 
lateral  fissure,  and  by  the  imaginary  line  continued  backward  from  it;  below, 
it  is  limited  by  the  infero-lateral  border  of  the  hemisphere.  It  is  divided  into 
superior,  middle,  and  inferior  gyi'i  by  the  superior  and  middle  temporal  sulci. 
The  superior  temporal  sulcus  runs  from  before  backward  across  the  temporal  lobe, 
some  little  distance  below,  but  parallel  with,  the  posterior  ramus  of  the  lateral 
fissure;  and  hence  it  is  often  termed  the  parallel  sulcus.  The  middle  temporal  sulcus 
takes  the  same  direction  as  the  superior,  but  is  situated  at  a  lower  level,  and  is 
usually  subdivided  into  two  or  more  parts.    The  superior  temporal  gyrus  lies  between 


Clauslrum 
Insula 


Transverse  tem2')oral  gyri 


Optic  tract 

Lentijorm  nucleus 
Internal  capsule 

Thalamus 

Fimbria 

»7 -J —  Tail  of  caudate  nucleus 

— ^^j — Inferior  cornu  of  lateral 
ventricle 


Fig.   740. — Section  of  brain  showing  upper  surface  of  temporal  lobe. 


the  posterior  ramus  of  the  lateral  fissure  and  the  superior  temporal  sulcus,  and  is 
continuous  behind  with  the  supramarginal  and  angular  gyri.  The  middle  temporal 
gyrus  is  placed  between  the  superior  and  middle  temporal  sulci,  and  is  joined  pos- 
teriorly with  the  angular  gyrus.  The  inferior  temporal  gyrus  is  placed  below  the 
middle  temporal  sulcus,  and  is  connected  behind  with  the  inferior  occipital  gj^rus; 
it  also  extends  around  the  infero-lateral  border  on  to  the  inferior  surface  of  the 
temporal  lobe,  where  it  is  limited  by  the  inferior  sulcus. 

The  inferior  surface  is  concave,  and  is  continuous  posteriorly  with  the  tentorial 
surface  of  the  occipital  lobe.  It  is  traversed  by  the  inferior  temporal  sulcus,  which 
extends  from  near  the  occipital  pole  behind,  to  within  a  short  distance  of  the  tem- 
poral pole  in  front,  but  is  frequently  subdivided  b}'^  bridging  gyri.  Lateral  to  this 
fissure  is  the  narrow  tentorial  part  of  the  inferior  temporal  gyrus,  and  medial  to 
it  the  fusiform  gyrus,  which  extends  from  the  occipital  to  the  temporal  pole;  this 
gyrus  is  limited  medially  by  the  collateral  fissure,  which  separates  it  from  the 
lingual  gyrus  behind  and  from  the  hippocampal  gyrus  in  front. 


Till':  I'h'OSENCEPHALOA   Oh'  FORK  BRAIN 


873 


The  Insula  {isUutd  of  Rcll;  veidrnl  lohc)  {Vii;.  741)  lies  deeply  in  the  lateral  or 
Sylvian  fissure,  and  can  only  be  seen  when  the  lips  of  that  fissure  are  widely  sep- 
arated, since  it  is  overlapped  and  hidden  l)y  the  gyri  which  bound  the  fissure. 
These  gyri  are  termed  the  opercula  of  the  insula;  they  are  separated  from  each  other 
by  the  three  rami  of  the  lateral  fissure,  and  arc  named  the  orl)ital,  frontal,  fronto- 
parietal, and  temj)oral  opercula.  The  orbital  operculum  lies  l)el()vv  the  anterior 
horizontal  ramus  of  the  fissure,  the  frontal  between  this  and  the  anterior  ascending 
ramus,  the  parietal  between  the  anterior  ascending  ramus  and  the  upturned  end 
of  the  i)osterior  ramus,  and  the  temporal  below  the  posterior  ramus.  The  frontal 
operculum  is  of  small  size  in  those  cases  where  the  anterior  horizontal  and  ascending 
rami  of  the  lateral  fissure  arise  from  a  common  stem.  The  insula  is  surrounded 
by  a  deep  circular  sulcus  which  separates  it  from  the  frontal,  parietal,  and  temporal 
lobes.  When  the  opercula  have  been  removed,  the  insula  is  seen  as  a  triangular 
eminence,  the  apex  of  which  is  directed  tow^ard  the  anterior  perforated  substance. 
It  is  divided  into  a  larger  anterior  and  a  smaller  posterior  part  by  a  deep  sulcus, 
which  runs  backward  and  upward  from  the  apex  of  the  insula.  The  anterior 
part  is  subdivided  by  shallow  sulci  into  three  or  four  short  gyri,  while  the  posterior 
part  is  formed  by  one  long  gyrus,  which  is  often  bifurcated  at  its  upper  end.  The 
cortical  gray  substance  of  the  insula  is  continuous  Avith  that  of  the  different  opercula, 
w^hile  its  deep  surface  corresponds  with  the  lentiform  nucleus  of  the  corpus  striatum. 


Fig.  741. — The  insula  of  the  left  side,  exposed  by  removing  the  opercula. 

Limbic  Lobe  (Fig.  738). — The  term  limbic  lobe  was  introduced  by  Broca,  and 
under  it  he  included  the  cingulate  and  hippocampal  gyri,  which  together  arch 
around  the  corpus  callosum  and  the  hippocampal  fissure.  These  he  separated  on 
the  morphological  ground  that  they  are  well-developed  in  animals  possessing  a 
keen  sense  of  smell  (osmatic  animals),  such  as  the  dog  and  fox.  They  were  thus 
regarded  as  a  part  of  the  rhinencephalon,  but  it  is  now  recognized  that  the}^  belong 
to  the  neopallium;  the  cingulate  gyrus  is  therefore  sometimes  described  as  a  part 
of  the  frontal  lobe,  and  the  hippocampal  as  a  part  of  the  temporal  lobe. 

The  cingulate  gyrus  {gyrus  cinguli;  caUosal  convolution)  is  an  arch-shaped  convo- 
lution, lying  in  close  relation  to  the  superficial  surface  of  the  corpus  callosum, 
from  which  it  is  separated  by  a  slit-like  fissure,  the  cailosal  fissure.  It  commences 
below^  the  rostrum  of  the  corpus  callosum,  curves  around  in  front  of  the  genu, 
extends  along  the  upper  surface  of  the  body,  and  finally  turns  downward  behind 
the  splenium,  where  it  is  connected  by  a  narrow^  isthmus  wdth  the  hippocampal 


874 


NEUROLOGY 


gyrus.  It  is  separated  from  the  medial  part  of  the  superior  frontal  gyrus  by  the 
cingulate  sulcus,  and  from  the  precuneus  by  the  subparietal  sulcus. 

The  hippocampal  gyrus  {gyrus  hippocampi)  is  bounded  above  by  the  hippocampal 
fissure,  and  below  by  the  anterior  part  of  the  collateral  fissure.  Behind,  it  is  con- 
tinuous superiorly,  through  the  isthmus,  with  the  cingulate  gyrus  and  inferiorly 
with  the  lingual  gyrus.  Running  in  the  substance  of  the  cingulate  and  hippocampal 
gyri,  and  connecting  them  together,  is  a  tract  of  arched  fibres,  named  the  cingulum 
(page  890).  The  anterior  extremity  of  the  hippocampal  gyrus  is  recurved  in  the 
form  of  a  hook  (uncus),  which  is  separated  from  the  apex  of  the  temporal  lobe  by 
a  slight  fissure,  the  incisura  temporalis.  Although  superficially  continuous  with  the 
hippocampal  gyrus,  the  uncus  forms  morphologically  a  part  of  the  rhinencephalon. 

The  Hippocampal  Fissure  {fissura  hippocampi;  dentate  fissure)  begins  immediately 
behind  the  splenium  of  the  corpus  callosum,  and  runs  forward  between  the  hippo- 
campal and  dentate  gyri  to  end  in  the  uncus.  It  is  a  complete  fissure  (page  867), 
and  gives  rise  to  the  prominence  of  the  hippocampus  in  the  inferior  cornu  of  the 
lateral  ventricle. 

Gyrus  supracallosus 

4- 


Fascia  dentata 
hippocampi 


Uncus 


Anterior  perforated  substance     /  Band  of  Giacomini 

Fig.  742. — Scheme  of  rhinencephalon. 


Rhinencephalon  (Fig.  742). — The  rhinencephalon  comprises  the  olfactory  lobe, 
the  uncus,  the  subcallosal  and  supracallosal  gyri,  the  fascia  dentata  hippocampi, 
the  septum  pellucidum,  the  fornix,  and  the  hippocampus. 

1.  The  Olfactory  Lobe  (lohtis  olfactorius)  is  situated  under  the  inferior  or  orbital 
surface  of  the  frontal  lobe.  In  many  vertebrates  it  constitutes  a  well-marked 
portion  of  the  hemisphere  and  contains  an  extension  of  the  lateral  ventricle;  but 
in  man  and  some  other  mammals  it  is  rudimentary.  It  consists  of  the  olfactory 
bulb  and  tract,  the  olfactory  trigone,  the  parolfactory  area  of  Broca,  and  the  anterior 
perforated  substance. 

(a)  The  olfactory  bulb  (bulbus  olfactorius)  is  an  oval,  reddish-gray  mass  which 
rests  on  the  cribriform  plate  of  the  ethmoid  and  forms  the  anterior  expanded 
extremity  of  the  olfactory  tract.  Its  under  surface  receives  the  olfactory  nerves, 
which  pass  upward  through  the  cribriform  plate  from  the  olfactory  region  of  the 
nasal  cavity.    Its  minute  structure  is  described  on  page  893. 

(b)  The  olfactory  tract  (tractus  olfactorius)  is  a  narroM'  white  band,  triangular 
on  coronal  section,  the  apex  being  directed  upward.  It  lies  in  the  olfactory  sulcus 
on  the  inferior  surface  of  the  frontal  lobe,  and  divides  posteriorly  into  two  striae, 
a  medial  and  a  lateral.    The  lateral  stria  is  directed  across  the  lateral  part  of  the 


THE  PROSENCEPHALON  OR  FORE-BRAIN  875 

anterior  perforated  substance  and  then  bends  abruptly  medialward  toward  the 
uncus  of  the  hippocampal  gyrus.  The  medial  stria  turns  medialward  behind 
the  parolfactory  area  and  ends  in  the  subcallosal  gyrus;  in  some  cases  a  small 
intermediate  stria  is  seen  running  backward  to  the  anterior  perforated  substance. 

(c)  The  olfactory  trigone  {tn'gomnn  ol f actor imn)  is  a  small  triangular  area  in  front 
of  the  anterior  perforated  substance.  Its  apex,  directed  forward,  occupies  the 
posterior  part  of  the  olfactory  sulcus,  and  is  brought  into  view  by  throwing  back 
the  olfactory  tract. 

(d)  The  parolfactory  area  of  Broca  (area  par olf actor ia)  is  a  small  triangular  field 
on  the  medial  surface  of  the  hemisphere  in  front  of  the  subcallosal  gyrus,  from  which 
it  is  separated  by  the  posterior  parolfactory  sulcus;  it  is.  continuous  below  with 
the  olfactory  trigone,  and  above  and  in  front  with  the  cingulate  gyrus;  it  is  limited 
anteriorly  by  the  anterior  parolfactory  sulcus. 

(e)  The  anterior  perforated  substance  {substantia  perforata  anterior)  is  an  irregularly 
quadrilateral  area  in  front  of  the  optic  tract  and  behind  the  olfactory  trigone, 
from  which  it  is  separated  by  the  fissure  prima ;  medially  and  in  front  it  is  continuous 
with  the  subcallosal  gyrus;  laterally  it  is  bounded  by  the' lateral  stria  of  the  olfactory 
tract  and  is  continued  into  the  uncus.  Its  gray  substance  is  confluent  above 
with  that  of  the  corpus  striatum,  and  is  perforated  anteriorly  by  numerous  small 
bloodvessels. 

2.  The  Uncus  has  already  been  described  (page  874)  as  the  recurved,  hook-like 
portion  of  the  hippocampal  gyrus. 

3.  The  Subcallosal,  Supracallosal,  and  Dentate  Gyri  form  a  rudimentary  arch- 
shaped  lamina  of  gray  substance  extending  over  the  corpus  callosum  and  above 
the  hippocampal  gyrus  from  the  anterior  perforated  substance  to  the  uncus. 

(a)  The  subcallosal  gyrus  (gyrus  suhcallosus;  peduncle  of  the  corpus  callosum)  is 
a  narrow  lamina  on  the  medial  surface  of  the  hemisphere  in  front  of  the  lamina 
terminalis,  behind  the  parolfactory  area,  and  below  the  rostrum  of  the  corpus 
callosum.  It  is  continuous  around  the  genu  of  the  corpus  callosum  with  the  supra- 
callosal gyrus. 

(b)  The  supracallosal  gyrus  (indusiuin  griseum;  gyrus  epicallosus)  consists  of  a 
thin  layer  of  gray  substance  in  contact  with  the  upper  surface  of  the  corpus 
callosum  and  continuous  laterally  with  the  gray  substance  of  the  cingulate  gyrus. 
It  contains  two  longitudinally  directed  strands  of  fibres  termed  respectively  the 
medial  and  lateral  longitudinal  striae.  The  supracallosal  gyrus  is  prolonged  around 
the  splenium  of  the  corpus  callosum  as  a  delicate  lamina,  the  fasciola  cinerea, 
which  is  continuous  below  with  the  fascia  dentata  hippocampi. 

(c)  The  fascia  dentata  hippocampi  (gyrus  dentatus)  is  a  narrow  band  extending 
downward  and  forward  above  the  hippocampal  gyrus  but  separated  from  it  by 
the  hippocampal  fissure;  its  free  margin  is  notched  and  overlapped  by  the  fimbria 
— the  fimbriodentate  fissure  intervening.  Anteriorly  it  is  continued  into  the  notch 
of  the  uncus,  where  it  forms  a  sharp  bend  and  is  then  prolonged  as  a  delicate  band, 
the  band  of  Giacomini,  over  the  incus,  on  the  lateral  surface  of  which  it  is  lost. 

The  remaining  parts  of  the  rhinencephalon,  viz.,  the  septum  pellucidum,  fornix, 
and  hippocampus,  will  be  described  in  connection  with  the  lateral  ventricle. 

Interior  of  the  Cerebral  Hemispheres. — If  the  upper  part  of  either  hemisphere  be 
removed,  at  a  level  about  1.25  cm.  above  the  corpus  callosum,  the  central  white  sub- 
stance will  be  exposed  as  an  oval-shaped  area,  the  centrum  ovale  minus,  surrounded 
by  a  narrow  convoluted  margin  of  gray  substance,  and  studded  with  numerous 
minute  red  dots  (puncta  vasculosa),  produced  by  the  escape  of  blood  from  divided 
bloodvessels.  If  the  remaining  portions  of  the  hemispheres  be  slightly  drawn  apart 
a  broad  band  of  white  substance,  the  corpus  callosum,  will  be  observed,  connecting 
them  at  the  bottom  of  the  longitudinal  fissure;  the  margins  of  the  hemispheres 
which  overlap  the  corpus  callosum  are  called  the  labia  cerebri.     Each  labrium  is 


876 


NEUROLOGY 


part  of  the  cingulate  gyrus  already  described;  and  the  sHt-hke  interval  between 
it  and  the  upper  surface  of  the  corpus  callosum  is  termed  the  callosal  fissure  (Fig. 
738) .  If  the  hemispheres  be  sliced  off  to  a  level  with  the  upper  surface  of  the  corpus 
callosum,  the  white  substance  of  that  structure  will  be  seen  connecting  the  two 
hemispheres.  The  large  expanse  of  medullary  matter  now  exposed,  surrounded  by 
the  convoluted  margin  of  gray  substance,  is  called  the  centrum  ovale  majus. 

The  Corpus  Callosum  (Fig.  743)  is  the  great  transverse  commissure  which  unites 
the  cerebral  hemispheres  and  roofs  in  the  lateral  ventricles.  A  good  conception 
of  its  position  and  size  is  obtained  by  examining  a  median  sagittal  section  of  the 
brain  (Fig.  730),  when  it  is  seen  to  form  an  arched  structure  about  10  cm.  long. 
Its  anterior  end  is  about  4  cm.  from  the  frontal  pole,  and  its  posterior  end  about 
6  cm.  from  the  occipital  pole  of  the  hemisphere. 


Fig.   743. — Corpus  callosum  from  above. 


The  anterior  end  is  named  the  genu,  and  is  bent  downward  and  backward  in  front 
of  the  septum  pellucidum;  diminishing  rapidly  in  thickness,  it  is  prolonged  backward 
under  the  name  of  the  rostrum,  which  is  connected  below  with  the  lamina  terminalis. 
The  anterior  cerebral  arteries  are  in  contact  with  the  under  surface  of  the  rostrum; 
they  then  arch  over  the  front  of  the  genu,  and  are  carried  backward  above  the  body 
of  the  corpus  callosum. 

The  posterior  end  is  termed  the  splenium  and  constitutes  the  thickest  part  of  the 
corpus  callosum.  It  overlaps  the  tela  chorioidea  of  the  third  ventricle  and  the 
mesencephalon,  and  ends  in  a  thick,  convex,  free  border.    A  sagittal  section  of 


THE  PROSENCEPHALON  OR  FORE-BRAIN 


877 


the  spleniiim  shows  that  the  posterior  end  of  the  corpus  callosum  is  acutely  bent 
forward,  the  upper  and  lower  parts  being  appHed  to  each  other. 

The  superior  surface  is  convex  from  before  backward,  and  is  about  2.5  cm.  wide. 
Its  medial  i)art  forms  the  bottom  of  the  k)ngitudinal  fissure,  and  is  in  contact 
posteriori}^  with  the  lower  border  of  the  falx  cerebri.  Laterally  it  is  overlapped  by 
the  cingulate  gyrus,  but  is  separated  from  it  by  the  slit-like  callosal  fissure.  It  is 
traversed  by  numerous  transverse  ridges  and  furrows,  and  is  covered  by  a  thin 
layer  of  gray  matter,  the  supracallosal  gyrus,  which  exhibits  on  either  side  of  the 
middle  line  the  medial  and  lateral  longitudinal  striae,  already  described  (page  875) . 

The  inferior  surface  is  concave,  and  forms  on  either  side  of  the  middle  line  the 
roof  of  the  lateral  ventricle.  Medially,  this  surface  is  attached  in  front  to  the 
septum  pellucidum;  behind  this  it  is  fused  with  the  upper  surface  of  the  body 
of  the  fornix,  while  the  splenium  is  in  contact  with  the  tela  chorioidea. 

On  either  side,  the  fibres  of  the  corpus  callosum  radiate  in  the  white  substance 
and  pass  to  the  various  parts  of  the  cerebral  cortex;  those  curving  forward  from  the 
genu  into  the  frontal  lobe  constitute  the  forceps  anterior,  and  those  curving  backward 
into  the  occipital  lobe,  the  forceps  posterior.  Between'these  two  parts  is  the  main 
body  of  the  fibres  which  constitute  the  tapetum  and  extend  laterally  on  either  side 
into  the  temporal  lobe,  and  cover  in  the  central  part  of  the  lateral  ventricle. 


Cerebral  aqueduct 

Fourth  ventricle 
Fig.   744. — Scheme  showing  relations  of  the  ventricles  to  the  surface  of  the  brain. 

The  Lateral  Ventricles  {tentriculus  lateralis)  (Fig.  744). — The  two  lateral  ventricles 
are  irregular  cavities  situated  in  the  lower  and  medial  parts  of  the  cerebral  hemi- 
spheres, one  on  either  side  of  the  middle  line.  They  are  separated  from  each  other 
by  a  median  vertical  partition,  the  septum  pellucidum,  but  communicate  with  the 
third  ventricle  and  indirectly  with  each  other  through  the  interventricular  foramen. 
They  are  lined  by  a  thin,  diaphanous  membrane,  the  ependyma,  covered  by  ciliated 
epithelium,  and  contain  cerebrospinal  fluid,  which,  even  in  health,  may  be  secreted 
in  considerable  amount.  Each  lateral  ventricle  consists  of  a  central  part  or  body, 
and  three  prolongations  from  it,  termed  cornua  (Figs.  745,  746) . 

The  central  part  {jjars  centralis  ventriculi  lateralis;  cello)  (Fig.  747)  of  the  lateral 
ventricle  extends  from  the  interventricular  foramen  to  the  splenium  of  the  corpus 


NEUROLOGY 


callosum.  It  is  an  irregularly  curved  cavity,  triangular  on  transverse  section, 
with  a  roof,  a  floor,  and  a  medial  wall.  The  roof  is  formed  by  the  under  surface  of 
the  corpus  callosum;  the  floor  by  the  following  parts,  enumerated  in  their  order  of 
position,  from  before  backward:  the  caudate  nucleus  of  the  corpus  striatum,  the 


Third  ventricle 


Suprapineal  recess 


Fig.   745. — Drawing  of  a  cast  of  the  ventricular  cavities,  viewed  from  above.      (Retzius.) 

stria  terminalis  and  the  terminal  vein,  the  lateral  portion  of  the  upper  surface  of 
the  thalamus,  the  choroid  plexus,  and  the  lateral  part  of  the  fornix;  the  medial 
wall  is  the  posterior  part  of  the  septum  pellucidum,  which  separates  it  from  the 
opposite  ventricle. 

Interventricular  foramen 


commissure 


Suprapineal  recess 
Cerebral  aqueduct 


Optic  recess 
Infundihuium 


Lateral  recess 
Fig.  746. — Drawing  of  a  cast  of  the  ventricular  cavities,  -viewed  from  the  side.      (Retzius. J 

The  anterior  cornu  (cornu  anterius;  anterior  horn;  'precornu)  (Fig.  746)  passes 
forward  and  lateralward,  with  a  slight  inclination  downward,  from  the  interventric- 
ular foramen  into  the  frontal  lobe,  curving  around  the  anterior  end  of  the  caudate 
nucleus.    Its  floor  is  formed  by  the  upper  surface  of  the  reflected  portion  of  the 


THE  PROSENCEPHALOX  OP  FORE-BRAIX 


879 


corpus  callosum,  the  rostrum.  It  is  bounded  medially  by  the  anterior  portion 
of  the  septum  pellucidum,  and  laterally  by  the  head  of  the  caudate  nucleus.  Its 
apex  reaches  the  posterior  surface  of  the  genu  of  the  corpus  callosum. 

The  posterior  cornu  {cornu  posterins;  yostcornu)  (Figs.  747,  748)  passes  into  the 
occipital  lobe,  its  direction  being  backward  and  lateralward,  and  then  medialward. 
Its  roof  is  formed  by  the  fibres  of  the  corpus  callosum  passing  to  the  temporal  and 
occipital  lobes.  On  its  medial  wall  is  a  longitudinal  eminence,  the  calcar  avis 
{Mppocampiis  minor) ,  which  is  an  involution  of  the  ventricular  wall  produced  by 
the  calcarine  fissure.  Above  this  the  forceps  posterior  of  the  corpus  callosum, 
sweeping  around  to  enter  the  occipital  lobe,. causes  another  projection,  termed  the 
bulb  of  the  posterior  cornu.  The  calcar  avis  and  bulb  of  the  posterior  cornu  are 
extremely  variable  in  their  degree  of  development;  in  some  cases  they  are  ill- 
defined,  in  others  prominent. 


Fig.   747. — Central  part  and  anterior  and  posterior  cornua  of  lateral  ventricles  exposed  from  above. 


The  inferior  cornu  (cornu  inferior;  descending  horn;  middle  horn;  medicornu)  (Fig. 
749),  the  largest  of  the  three,  traverses  the  temporal  lobe  of  the  brain,  forming 
in  its  course  a  curve  around  the  posterior  end  of  the  thalamus.  It  passes  at  first 
backward,  lateralward,  and  downward,  and  then  curves  forward  to  within  2.5  cm. 
of  the  apex  of  the  temporal  lobe,  its  direction  being  fairly  well  indicated  on  the 
surface  of  the  brain  by  that  of  the  superior  temporal  sulcus.  Its  roof  is  formed 
chiefly  by  the  inferior  surface  of  the  tapetum  of  the  corpus  callosum,  but  the  tail 
of  the  caudate  nucleus  and  the  stria  terminalis  also  extend  forward  in  the  roof  of 
the  inferior  cornu  to  its  extremity,  where  they  end  in  a  mass  of  gray  substance, 


880 


NEUROLOGY 


the  nucleus  amygdalae.    Its  floor  presents  the  following  parts:  the  hippocampus,  the 
fimbria  hippocampi,  the  collateral  eminence,  and  the  choroirl  plexus.     When  the 


Bulb  of  posterior  cormi 

Posterior  cornu—r 
Calcar  avis—^ 
Collateral  eminence 

Calcarine  fissure 


Collateral  fissure  - 


Fig.   748. — Coronal  section  through  posterior  cornu    of  lateral  ventricle. 

choroid  plexus  is  removed,  a  cleft-like  opening  is  left  along  the  medial  wall  of 
the  inferior  cornu;  this  cleft  constitutes  the  lower  part  of  the  choroidal  fissure. 

Clioroid  plexus 

Riilb  of  posterior  cornu 
Calcar  avis 


Latetal 
cerebral 
fissuie 

Collateral  eminei 
\  Fimbria  hippoannpi 
Hippocampus 
Fig.   749. — Posterior  and  inferior  cornua  of  left  lateral  ventricle  exposed  from  the  side. 

The  hippocampus  (hippocampus  major)  (Figs.  749,  750)  is  a  curved  eminence, 
about  5  cm.  long,  which  extends  throughout  the  entire  length  of  the  floor  of  the 


THE  PROSENCEPHALON  OR  FORE-BRAIN 


881 


inferior  cornu.  Its  lower  end  is  enlarged,  and  presents  two  or  tiiree  rounded  eleva- 
tions or  digitations  which  give  it  a  paw-like  appearance,  and  hence  it  is  named 
the  pes  hippocampi.  If  a  transverse  section  be  made  through  the  hippocampus, 
it  will  be  seen  that  this  eminence  is  produced  by  the  folding  of  the  wall  of  the 
hemisphere  to  form  the  hippocampal  fissure.  The  main  mass  of  the  hippocampus 
consists  of  gray  substance,  but  on  its  ventricular  surface  is  a  thin  white  layer, 
the  alveus,  which  is  continuous  with  the  fimbria  hippocampi. 

The  collateral  eminence  {eminentia  collaieralis)  (Fig.  750)  is  an  elongated 
swelling  lying  lateral  to  and  parallel  with  the  hippocampus.  It  corresponds  with 
the  middle  part  of  the  collateral  fissure,  and  its  size 
depends  on  the  depth  and  direction  of  this  fissure. 
It  is  continuous  behind  with  a  flattened  triangular 
area,  the  trigonum  collaterale,  situated  between  the 
posterior  and  inferior  cornua. 

The  fimbria  hippocampi  is  a  continuation  of  the 
crus  of  the  fornix,  and  will  be  discussed  with  that 
body;  a  description  of  the  choroid  plexus  will  be 
found  on  page  887. 

The  corpus  striatum  has  received  its  name  from 
the  striped  appearance  which  a  section  of  its  ante- 
rior part  presents,  in  consequence  of  diverging  white 
fibres  being  mixed  with  the  gray  substance  which 
forms  its  chief  mass.  A  part  of  the  corpus  striatum 
is  imbedded  in  the  white  substance  of  the  hemi- 
sphere, and  is  therefore  external  to  the  ventricle; 
it  is  termed  the  extraventricular  portion,  or  the  lenti- 
form  nucleus ;  the  remainder,  however,  projects  into 
the  ventricle,  and  is  named  the  intraventricular  por- 
tion, or  the  caudate  nucleus  (Fig.  747). 

The  caudate  nucleus  (nucleus  caudatus:  candaium) 
(Fig.  751)  is  a  pear-shaped,  highly  arched  gray 
mass;  its  broad  extremity,  or  head,  is  directed 
forward  into  the  anterior  cornu  of  the  lateral  ven- 
tricle, and  is  continuous  with  the  anterior  perforated 

substance  and  with  the  anterior  end  of  the  lentiform  nucleus;  its  narrow  end, 
or  tail,  is  directed  backward  on  the  lateral  side  of  the  thalamus,  from  which  it  is 
separated  by  the  stria  terminalis  and  the  terminal  vein.  It  is  then  continued  down- 
ward into  the  roof  of  the  inferior  cornu,  and  ends  in  the  nucleus  amygdalae,  at  the 
apex  of  the  temporal  lobe.  It  is  covered  by  the  lining  of  the  ventricle,  and  crossed 
by  some  veins  of  considerable  size.  It  is  separated  from  the  lentiform  nucleus, 
in  the  greater  part  of  its  extent,  by  a  thick  lamina  of  white  substance,  called  the 
internal  capsule,  but  the  two  portions  of  the  corpus  striatum  are  united  in  front 
(Figs.  752,  753). 

The  lentiform  nucleus  {nucleus  lentiformis;  lenticular  nucleus;  lenticula)  is  lateral 
to  the  caudate  nucleus  and  thalamus,  and  is  seen  only  in  sections  of  the  hemisphere. 
When  divided  horizontally,  it  exhibits,  to  some  extent,  the  appearance  of  a  biconvex 
lens  (Fig.  751),  while  a  coronal  section  of  its  central  part  presents  a  somewhat 
triangular  outline.  It  is  shorter  than  the  caudate  nucleus  and  does  not  extend  as 
far  forward.  It  is  bounded  laterally  by  a  lamina  of  white  substance  called  the 
external  capsule,  and  lateral  to  this  is  a  thin  layer  of  gray  substance  termed  the 
claustrum.  Its  anterior  end  is  continuous  with  the  lower  part  of  the  head  of 
the  caudate  nucleus  and  with  the  anterior  perforated  substance. 

In  a  coronal  section  through  the  middle  of  the  lentiform  nucleus,  two  medullary 
laminae  are  seen  dividing  it  into  three  parts.    The  lateral  and  largest  part  is  of  a 
56 


750. — Inferior  and  posterior  cornua, 
-s-iewed  from  above. 


52 


NEUROLOGY 


reddish  color,  and  is  known  as  the  putamen,  while  the  medial  and  intermediate 
are  of  a  yellowish  tint,  and  together  constitute  the  globus  pallidus;  all  three  are 
marked  bv  fine  radiating  white  fibres,  which  are  most  distinct  in  the  putamen 
(Fig.  753): 

The  gray  substance  of  the  corpus  striatum  is  traversed  by  nerve  fibres,  some 
of  which  originate  in  it.  The  cells  are  multipolar,  both  large  and  small;  those  of 
the  lentiform  nucleus  contain  yellow  pigment.  The  caudate  and  lentiform  nuclei 
are  not  only  directly  continuous  with  each  other  anteriorly,  but  are  connected  to 
each  other  by  numerous  fibres.    The  corpus  striatum  is  also  connected:  (1)  to  the 


Gemi,  of  corpus  callosum 
Anterior  cornu  of  lateral  ventricle 

Caudate  nucleus 
•lituni'  pellucidiim. 
Internal  capsule  (Jrontal  part) 

Column  of  fornix  —!^ 
Genu  of  internal  capsule  __ 

Putamen . 

Globus  pallidus Wv'// 

Internal  capsule  {occipital part ) 


Postenor  cornu  of  lateral  ventricl 


External  capsule, 
Claustrum 
Insula 


Tail  of  caudate  nude 

Hippocampus  — -y 


Inferior  cornu  of  lateral  ventricle 


Optic  radiation 


Fig.  751. — Horizontal  section  of  right  cerebral  hemisphere. 

cerebral  cortex,  by  what  are  termed  the  corticostriate  fibres;  (2)  to  the  thalamus, 
by  fibres  which  pass  through  the  internal  capsule,  and  by  a  strand  named  the 
ansa  lentif ormis ;  (3)  to  the  cerebral  peduncle,  by  fibres  which  leave  the  lower 
aspect  of  the  caudate  and  lentiform  nuclei. 

The  claustrum  (Figs.  751,  753)  is  a  thin  layer  of  gray  substance,  situated  on  the 
lateral  surface  of  the  external  capsule.  Its  transverse  section  is  triangular,  with 
the  apex  directed  upward.  Its  medial  surface,  contiguous  to  the  external  capsule, 
is  smooth,  but  its  lateral  surface  presents  ridges  and  furrows  corresponding  with 
the  gyri  and  sulci  of  the  insula,  with  which  it  is  in  close  relationship.  The  claustrum 
is.  regarded  as  a  detached  portion  of  the  gray  substance  of  the  insula,  from  w^hich 


THE  PROSEXCEPHALOX  OR  FORE-BRAIX 


883 


it  is  separated  by  a  layer  of  white  fibres,  the  capsula  extrema  {band  of  Baillarger). 
Its  cells  are  small  and  spindle-shaped,  and  contain  yellow  pigment;  they  are  similar 
to  those  of  the  deepest  layer  of  the  cortex. 

The  nucleus  amygdalae  {avu/gdala)  is  an  ovoid  gray  mass,  situated  at  the  lower 
end  of  the  roof  of  the  inferior  cornii.  It  is  merely  a  localized  thickening  of  the 
gray  cortex,  continuous  with  that  of  the  uncus;  in  front  it  is  continuous  with  the 
putamen,  behind  with  the  stria  terminalis  and  the  tail  of  the  caudate  nucleus. 


Superior  frontal  gyrus 


Middle  frontal 


Corpus  callosum 

Anterior  eormi 

SeptiLm  pellucidum 

Caudate  nucleus 

Internal  capsule 

Lentiform  nucleus 


Sulcus  clfactonus 


Insula    I 
Temporal  lobt 
Inferior  frontal  gyru8 

Fig.   752. — Coronal  section  through  anterior  cornua  of  lateral  ventricles. 


The  internal  capsule  (capsula  interna)  (Fig.  754)  is  a  flattened  band  of  white 
fibres,  between  the  lentiform  nucleus  on  the  lateral  side  and  the  caudate  nucleus 
and  thalamus  on  the  medial  side.  In  horizontal  section  (Figs.  751)  it  is  seen  to  be 
somewhat  abruptly  curved,  with  its  convexity  inward;  the  prominence  of  the  curve 
is  called  the  genu,  and  projects  between  the  caudate  nucleus  and  the  thalamus. 
The  portion  in  front  of  the  genu  is  termed  the  frontal  part,  and  separates  the  len- 
tiform from  the  caudate  nucleus;  the  portion  behind  the  genu  is  the  occipital  part, 
and  separates  the  lentiform  nucleus  from  the  thalamus. 

The  frontal  part  of  the  internal  capsule  contains:  (1)  fibres  running  from  the 
thalamus  to  the  frontal  lobe;  (2)  fibres  connecting  the  lentiform  and  caudate 
nuclei;  (3)  fibres  connecting  the  cortex  with  the  corpus  striatum;  and  (4)  fibres 
passing  from  the  frontal  lobe  through  the  medial  fifth  of  the  base  of  the  cerebral 
peduncle  to  the  nuclei  pontis.  The  fibres  in  the  region  of  the  genu  are  named 
the  geniculate  fibres ;  they  originate  in  the  motor  part  of  the  cerebral  cortex,  and, 
after  passing  downward  through  the  base  of  the  cerebral  peduncle  with  the  cerebro- 


884 


NEUROLOGY 


spinal  fibres,  undergo  decussation  and  end  in  the  motor  nuclei  of  the  cerebral 
nerves  of  the  opposite  side.  The  anterior  two-thirds  of  the  occipital  part  of  the 
internal  capsule  contains  the  cerebrospinal  fibres,  which  arise  in  the  motor  area 
of  the  cerebral  cortex  and,  passing  downward  through  the  middle  three-fifths  of 
the  base  of  the  cerebral  peduncle,  are  continued  into  the  pyramids  of  the  medulla 
oblongata.  The  posterior  third  of  the  occipital  part  contains:  (1)  sensory  fibres, 
largely  derived  from  the  thalamus,  though  some  may  be  continued  upward  from 
the  medial  lemniscus;  (2)  the  fibres  of  optic  radiation,  from  the  lower  visual  centres 
to  the  cortex  of  the  occipital  lobe;  (3)  acoustic  fibres,  from  the  lateral  lemniscus  to 
the  temporal  lobe ;  and  (4)  fibres  which  pass  from  the  occipital  and  temporal  lobes 
to  the  nuclei  pontis. 


Corpus  callosum^ 


Anterior  corniju^ 

Cavity  of  septum 

pellucidum 

Columns  of 
fornix 

Anterior 
commissure 

Third  ventricle 

Optic 
chiasma 


^Caudate  nucleus 
Internal  capsule 

Putamen 


Globus  pallidus 
' —  Claustrum 


In.sida 


Fig.  753. — Coronal  section  of  brain  through  anterior  comniissure. 


The  fibres  of  the  internal  capsule  radiate  widely  as  they  pass  to  and  from  the 
various  parts  of  the  cerebral  cortex,  forming  the  corona  radiata  (Fig.  754)  and 
intermingling  with  the  fibres  of  the  corpus  callosum. 

The  external  capsule  (capsula  externa)  (Fig.  751)  is  a  lamina  of  white  substance, 
situated  lateral  to  the  lentiform  nucleus,  between  it  and  the  claustrum,  and  con- 
tinuous with  the  internal  capsule  below  and  behind  the  lentiform  nucleus.  It 
probably  contains  fibres  derived  from  the  thalamus,  the  anterior  commissure,  and 
the  subthalamic  region. 

The  substantia  innominata  of  Meynert  is  a  stratum  consisting  partly  of  gray  and 
partly  of  white  substance,  which  lies  below  the  anterior  part  of  the  thalamus 
and  lentiform  nucleus.  It  consists  of  three  layers,  superior,  middle,  and  inferior. 
The  superior  layer  is  named  the  ansa  lentiformis,  and  its  fibres,  derived  from  the 
medullary  lamina  of  the  lentiform  nucleus,  pass  medially  to  end  in  the  thalamus 


THE  PROSENCEPHALON  OR  FORE-BRAIN 


885 


and  subthalamic  region,  while  others  are  said  to  end  in  the  tegmentum  and  red 
nucleus.  The  middle  layer  consists  of  nerve  cells  and  nerve  fibres;  fibres  enter  it 
from  the  parietal  lobe  through  the  external  capsule,  while  others  are  said  to  con- 
nect it  with  the  medial  longitudinal  fasciculus.  The  inferior  layer  forms  the  main 
part  of  the  inferior  stalk  of  the  thalamus,  and  connects  this  body  with  the  temporal 
lobe  and  the  insula. 

The  stria  terminalis  (taenia  semicircular  is)  is  a  narrow  band  of  white  substance 
situated  in  the  depression  between  the  caudate  nucleus  and  the  thalamus.  Ante- 
riorly, its  fibres  are  partly  continued  into  the  column  of  the  fornix ;  some,  however, 
pass  over  the  anterior  commissure  to  the  gray  substance  between  the  caudate 
nucleus  and  septum  pellucidum,  while  others  are  said  to  enter  the  caudate  nucleus. 
Posteriorly,  it  is  continued  into  the  roof  of  the  inferior  cornu  of  the  lateral  ventricle, 
at  the  extremity  of  which  it  enters  the  nucleus  amygdalse.     Superficial  to  it  is  a 


R.  oculomotor  nerve 

L.  oculomotor  nerve 

Brachium  conjunciivum 

Pijramid 

Olive 
Fig.   754. — Dissection  sho-nang  the  course  of  the  cerebrospinal  fibres.      (E.  B.  Jamieson.) 


Restifotm  body 


large  vein,  the  terminal  vein  (wem  of  the  corpus  striatum),  which  receives  numerous 
tributaries  from  the  corpus  striatum  and  thalamus;  it  runs  forward  to  the  inter- 
ventricular foramen  and  there  joins  with  the  vein  of  the  choroid  plexus  to  form 
the  corresponding  internal  cerebral  vein.  On  the  surface  of  the  terminal  vein  is 
a  narrow  white  band,  named  the  lamina  affixa. 

The  Fornix  (Figs.  730,  755)  is  a  longitudinal,  arch-shaped  lamella  of  w^hite 
substance,  situated  below  the  corpus  callosum,  and  continuous  with  it  behind, 
but  separated  from  it  in  front  by  the  septum  pellucidum.  It  may  be  described 
as  consisting  of  two  symmetrical  bands,  one  for  either  hemisphere.  The  two 
portions  are  not  united  to  each  other  in  front  and  behind,  but  their  central  parts 
are  joined  together  in  the  middle  line.  The  anterior  parts  are  called  the  columns 
of  the  fornix;  the  intermediate  united  portions,  the  body;  and  the  posterior  parts, 
the  crura. 


886 


NEUROLOGY 


The  body  (corpus  fornicis)  of  the  fornix  is  triangular,  narrow  in  front,  and  broad 
behind.  The  medial  part  of  its  upper  surface  is  connected  to  the  septum  pellucidum 
in  front  and  to  the  corpus  callosum  behind.  The  lateral  portion  of  this  surface 
forms  part  of  the  floor  of  the  lateral  ventricle,  and  is  covered  by  the  ventricular 
epithelium.  Its  lateral  edge  overlaps  the  choroid  plexus,  and  is  continuous  with 
the  epithelial  covering  of  this  structure.  The  under  surface  rests  upon  the  tela 
chorioidea  of  the  third  ventricle,  which  separates  it  from  the  epithelial  roof  of  that 
cavity,  and  from  the  medial  portions  of  the  upper  surfaces  of  the  thalami.  Below, 
the  lateral  portions  of  the  body  of  the  fornix  are  joined  by  a  thin  triangular  lamina, 
named  the  psalterium  (lyra).  This  lamina  contains  some  transverse  fibres  which 
connect  the  two  hippocampi  across  the  middle  line  and  constitute  the  hippocampal 
commissure.  Between  the  psalterium  and  the  corpus  callosum  a  horizontal  cleft, 
the  so-called  ventricle  of  the  fornix  {ventricle  of  Verga),  is  sometimes  found. 


Cavity  of  septum  2}ellucidum 
ic  chiasma 

ic  nerve 
T^iber  cinerexim 

Optic  trad 


Corpora 
mamUlaria 


Corpus 

callosum 

(under  mirface) 

Fimbria 
hippocampi 


Fig. 


755. — The  fornix  and  corpus  callosum  from  below.     (From  a  specimen  in  the  Department  of  Human 
Anatomy  of  the  University  of  Oxford.) 


The  columns  (columna  fornicis;  anterior  pillars;  fornicolumns)  of  the  fornix  arch 
downward  in  front  of  the  interventricular  foramen  and  behind  the  anterior  commis- 
sure, and  each  descends  through  the  gray  substance  in  the  lateral  wall  of  the  third 
ventricle  to  the  base  of  the  brain,  where  it  ends  in  the  corpus  mamillare.  From 
the  cells  of  the  corpus  mamillare  the  thalamomamillary  fasciculus  (bundle  of  Vicq 
d'Azyr)  takes  origin  and  is  prolonged  into  the  anterior  nucleus  of  the  thalamus. 
The  column  of  the  fornix  and  the  thalamomamillary  fasciculus  together  form  a  loop 
resembling  the  figure  8,  but  the  continuity  of  the  loop  is  broken  in  the  corpus 


THE  PROSENCEPHALON  OR  FORE-BRAIN  887 

mamillare.  The  column  of  the  fornix  is  joined  by  the  stria  medullaris  of  the  pineal 
body  and  by  the  superficial  fibres  of  the  stria  terminalis,  and  is  said  to  receive 
also  fibres  from  the  septum  pellncidum.  Zuekerkandl  describes  an  olfactory  fascic- 
ulus which  becomes  detached  from  the  main  portion  of  the  column  of  the  fornix, 
and  passes  downward  in  front  of  the  anterior  commissure  to  the  base  of  the  brain, 
where  it  divides  into  two  bundles,  one  joining  the  medial  stria  of  the  olfactory 
tract;  the  other  joins  the  subcallosal  gyrus,  and  through  it  reaches  the  hippocampal 
gyrus. 

The  crura  {crus  fornicis;  posterior  pillars)  of  the  fornix  are  prolonged  backward 
from  the  body.  They  are  flattened  bands,,  and  at  their  commencement  are  inti- 
matel}''  connected  with  the  under  surface  of  the  corpus  callosum.  Diverging  from 
one  another,  each  curves  around  the  posterior  end  of  the  thalamus,  and  passes 
downward  and  forward  into  the  inferior  cornu  of  the  lateral  ventricle  (Fig.  757). 
Here  it  lies  along  the  concavity  of  the  hippocampus,  on  the  surface  of  which  some 
of  its  fibres  are  spread  out  to  form  the  alveus,  while  the  remainder  are  continued 
as  a  narrow  white  band,  the  fimbria  hippocampi,  which  is  prolonged  into  the  uncus 
of  the  hippocampal  gyrus.  The  inner  edge  of  the  fitnbria  overlaps  the  fascia 
dentata  hippocampi  {dentate  gyrus)  (page  875),  from  which  it  is  separated  by  the 
fimbriodentate  fissure ;  from  its  lateral  margin,  which  is  thin  and  ragged,  the  ventric- 
ular epithelium  is  reflected  over  the  choroid  plexus  as  the  latter  projects  into  the 
chorioidal  fissure. 

Interventricular  Foramen  {foramen  of  Monro). — Between  the  columns  of  the  fornix 
and  the  anterior  ends  of  the  thalami,  an  oval  aperture  is  present  on  either  side: 
this  is  the  interventricular  foramen,  and  through  it  the  lateral  ventricles  communi- 
cate Avith  the  third  ventricle.  Behind  the  epithelial  lining  of  the  foramen  the  choroid 
plexuses  of  the  lateral  ventricles  are  joined  across  the  middle  line. 

The  Anterior  Commissure  {precommissure)  is  a  bundle  of  white  fibres,  connecting 
the  two  cerebral  hemispheres  across  the  middle  line,  and  placed  in  front  of  the 
columns  of  the  fornix.  On  sagittal  section  it  is  oval  in  shape,  its  long  diameter 
being  vertical  and  measuring  about  5  mm.  Its  fibres  can  be  traced  lateralward 
and  backward  on  either  side  beneath  the  corpus  striatum  into  the  substance  of 
the  temporal  lobe.  It  serves  in  this  way  to  connect  the  two  temporal  lobes,  but 
it  also  contains  decussating  fibres  from  the  olfactory  tracts. 

The  Septum  Pellucidum  {septum  lucidum)  (Fig.  730)  is  a  thin,  verticallj'  placed 
partition  consisting  of  two  laminae,  separated  in  the  greater  part  of  their  extent 
by  a  narrow  chink  or  interval,  the  cavity  of  the  septum  pellucidum.  It  is  attached, 
above,  to  the  under  surface  of  the  corpus  callosum;  below,  to  the  anterior  part  of 
the  fornix  behind,  and  the  reflected  portion  of  the  corpus  callosum  in  front.  It  is 
triangular  in  form,  broad  in  front  and  narrow  behind;  its  inferior  angle  corre- 
sponds with  the  upper  part  of  the  anterior  commissure.  The  lateral  surface  of  each 
lamina  is  directed  toward  the  body  and  anterior  cornu  of  the  lateral  ventricle, 
and  is  covered  by  the  ependyma  of  that  cavity. 

The  cavity  of  the  septum  pellucidum  {cavum  septi  pellucidi;  pseudocele;  fifth 
ventricle)  is  generally  regarded  as  part  of  the  longitudinal  cerebral  fissure,  which 
has  become  shut  off  by  the  union  of  the  hemispheres  in  the  formation  of  the  corpus 
callosum  above  and  the  fornix  below.  Each  half  of  the  septum  therefore  forms 
part  of  the  medial  wall  of  the  hemisphere,  and  consists  of  a  medial  layer  of  gray 
substance,  derived  from  that  of  the  cortex,  and  a  lateral  layer  of  white  substance 
continuous  with  that  of  the  cerebral  hemispheres.  This  cavity  is  not  developed 
from  the  cavity  of  the  cerebral  vesicles,  and  never  communicates  with  the  ventricles 
of  the  brain. 

The  Choroid  Plexus  of  the  Lateral  Ventricle  {plexus  chorioideiis  ventricidus  later- 
alis; paraplexus)  (Fig.  757)  is  a  highly  vascular,  fringe-like  process  of  pia  mater, 
which  projects  into  the  ventricular  cavity.     The  plexus,  however,  is  everj^where 


NEUROLOGY 


covered  by  a  layer  'of  epithelium  continuous  with  the  epithelial  lining  of  the 
ventricle.  It  extends  from  the  interventricular  foramen,  where  it  is  joined 
with  the  plexus  of  the  opposite  ventricle,  to  the  end  of  the  inferior  cornu.  The 
part  in  relation  to  the  body  of  the  ventricle  forms  the  vascular  fringed  margin 
of  a  triangular  process  of  pia  mater,  named  the  tela  chorioidea  of  the  third 
ventricle,  and  projects  from  under  cover  of  the  lateral  edge  of  the  fornix.  It 
lies  upon  the  upper  surface  of  the  thalamus,  from  which  the  epithelium  is  reflected 
over  the  plexus  on  to  the  edge  of  the  fornix  (Fig.  734).  The  portion  in  relation 
to  the  inferior  cornu  lies  in  the  concavity  of  the  hippocampus  and  overlaps  the 
fimbria  hippocampi:  from  the  lateral  edge  of  the  fimbria  the  epithelium  is  reflected 
over  the  plexus  on  to  the  roof  of  the  cornu  (Fig.  756).  It  consists  of  minute  and 
highly  vascular  villous  processes,  each  with  an  afferent  and  an  efferent  vessel.  The 
arteries  of  the  plexus  are:  (a)  the  anterior  choroidal,  a  branch  of  the  internal  carotid, 
which  enters  the  plexus  at  the  end  of  the  inferior  cornu;  and  (6)  the  posterior 
choroidal,  one  or  two  small  branches  of  the  posterior  cerebral,  which  pass  forward 
under  the  splenium.  The  veins  of  the  choroid  plexus  unite  to  form  a  tortuous  vein, 
which  courses  from  behind  forward  to  the  interventricular  foramen  and  there  joins 
with  the  terminal  vein  to  form  the  corresponding  internal  cerebral  vein. 


Tail  of  caudate  nucleus 


Choroid  plexu-s 

Epithelial  lifting  of  ventricle 


Pia  mater 

Fimbria 
Fimbriodentate 
fissure 

Alveus 

Fascia  den  lata 
hippocampi 

Dentate  fissure' 

Fig.  756. — Coronal  section  of  inferior  horn  of  lateral  ventricle. 


(Diagrammatic.) 


When  the  choroid  plexus  is  pulled  away,  the  continuity  between  its  epithelial 
covering  and  the  epithelial  lining  of  the  ventricle  is  severed,  and  a  cleft-like  space 
is  produced.  This  is  named  the  choroidal  fissure;  like  the  plexus,  it  extends  from 
the  interventricular  foramen  to  the  end  of  the  inferior  cornu.  The  upper  part  of 
the  fissure,  i.  e.,  the  part  nearest  the  interventricular  foramen  is  situated  between 
the  lateral  edge  of  the  fornix  and  the  upper  surface  of  the  thalamus;  farther  back 
at  the  beginning  of  the  inferior  cornu  it  is  between  the  commencement  of  the  fim- 
bria hippocampi  and  the  posterior  end  of  the  thalamus,  while  in  the  inferior  cornu  it 
lies  between  the  fimbria  in  the  floor  and  the  stria  terminalis  in  the  roof  of  the  cornu. 

The  tela  chorioidea  of  the  third  ventricle  (iela  chorioidea  rentriculi  tertii;  velum 
interpositum)  (Fig.  757)  is  a  double  fold  of  pia  mater,  triangular  in  shape,  which 
lies  beneath  the  fornix.  The  lateral  portions  of  its  lower  surface  rest  upon  the 
thalami,  while  its  medial  portion  is  in  contact  with  the  epithelial  roof  of  the  third 
ventricle.  Its  apex  is  situated  at  the  interventricular  foramen;  its  base  corresponds 
with  the  splenium  of  the  corpus  callosum,  and  occupies  the  interval  between  that 
structure  above  and  the  corpora  quadrigemina  and  pineal  body  below.     This 


THE  PROSENCEPHALOX  OR  FORE-BRAIX 


889 


interval^  together  with  the  h)\ver  portions  of  the  ehoroiiUil  fissures,  is  sometimes 
spoken  of  as  the  transverse  fissure  of  the  brain.  At  its  base  the  two  laj-ers  of  the 
vekim  separate  from  each  other,  and  are  continuous  with  the  pia  mater  investing 
the  brain  in  this  region.  Its  lateral  margins  are  modified  to  form  the  highly  vas- 
cular choroid  plexuses  of  the  lateral  ventricles.  It  is  supplied  by  the  anterior  and 
posterior  choroidal  arteries  already  described.  The  veins  of  the  tela  chorioidea  are 
named  the  internal  cerebral  veins  {venae  Galeni) ;  they  are  two  in  number,  and  run 
backward  between  its  layers,  each  being  formed  at  the  interventricular  foramen  by 
the  union  of  the  terminal  vein  with  the  choroidal  \em.  The  internal  cerebral 
veins  unite  posteriorly  in  a  single  trunk,  the  great  cerebral  vein  {vena  magna  Galeni), 
which  passes  backward  beneath  the  splenium  and  ends  in  the  straight  sinus. 


Fig. 


-Tela  chorioidea  of  the  third  ventricle,  and  the  choroid  plexus  of  the  left  lateral  ventricle,  exposed 

from  above. 


Structure  of  the  Cerebral  Hemispheres. — The  cerebral  hemispheres  are  composed 
of  gray  and  white  substance:  the  former  covers  their  surface,  and  is  termed  the 
cortex;  the  latter  occupies  the  interior  of  the  hemispheres. 

The  white  substance  consists  of  medullated  fibres,  varying  in  size,  and  arranged 
in  bundles  separated  by  neuroglia.  They  may  be  divided,  according  to  their 
course  and  connections,  into  three  distinct  systems.  (1)  Projection  fibres  connect 
the  hemisphere  with  the  lower  parts  of  the  brain  and  with  the  medulla  spinalis. 
(2)  Transverse  or  commissural  fibres  unite  the  two  hemispheres.  (3)  Association 
fibres  connect  different  structures  in  the  same  hemisphere;  these  are,  in  many 


890 


NEUROLOGY 


instances,  collateral  branches  of  the  i)rojection  fibres,  but  others  are  the  axons 
of  independent  cells. 

1.  The  projection  fibres  consist  of  eft'erent  and  afferent  fibres  uniting  the  cortex 
with  the  lower  parts  of  the  brain  and  with  the  medulla  spinalis.  The  principal 
efferent  strands  are:  (1)  the  motor  tract,  occupying  the  genu  and  anterior  two-thirds 
of  the  occipital  part  of  the  internal  capsule,  and  consisting  of  (a)  the  geniculate 
fibres,  which  decussate  and  end  in  the  motor  nuclei  of  the  cerebral  nerves  of  the 
opposite  side;  and  (6)  the  cerebrospinal  fibres,  which  are  prolonged  through  the 
pyramid  of  the  medulla  oblongata  into  the  medulla  spinalis:  (2)  the  corticopontine 
fibres,  ending  in  the  nuclei  pontis.  The  chief  afferent  fibres  are:  (1)  those  of  the 
lemniscus  which  are  not  interrupted  in  the  thalamus;  (2)  those  of  the  brachia 
conjunctiva  cerebelli  which  are  not  interrupted  in  the  red  nucleus  and  thalamus; 
(3)  numerous  fibres  arising  within  the  thalamus,  and  passing  through  its  stalks 
to  the  difterent  parts  of  the  cortex  (page  857);  (4)  optic  and  acoustic  fibres,  the 
former  passing  to  the  occipital,  the  latter  to  the  temporal  lobe. 

2.  The  transverse  or  commissural  fibres  connect  the  two  hemispheres.  They 
include:  (a)  the  transverse  fibres  of  the  corpus  callosum,  (b)  the  anterior  commissure, 
(c)  the  posterior  commissure,  and  (d)  the  lyra  or  hippocampal  commissure;  they 
have  alreadv  been  described. 


Fig.   758. — Diagram  showing  principal  systems  of  association  fibres  in  the  cerebrum. 

3.  The  association  fibres  (Fig.  758)  unite  different  parts  of  the  same  hemi- 
sphere, and  are  of  two  kinds:  (1)  those  connecting  adjacent  gyri,  short  association 
fibres ;  (2)  those  passing  between  more  distant  parts,  long  association  fibres. 

The  short  association  fibres  lie  immediately  beneath  the  gra}"  substance  of  the 
cortex  of  the  hemispheres,  and  connect  together  adjacent  gyri. 

The  lojig  association  fibres  include  the  following:  (a)  the  uncinate  fasciculus; 
(6)  the  cingulum;  (c)  the  superior  longitudinal  fasciculus;  (d)  the  inferior  longi- 
tudinal fasciculus;  (e)  the  perpendicular  fasciculus;  (/)  the  occipitofrontal 
fasciculus;  and  (g)  the  fornix. 

(a)  The  uncinate  fascicidvs  passes  across  the  bottom  of  the  lateral  fissure,  and 
unites  the  gyri  of  the  frontal  lobe  with  the  anterior  end  of  the  temporal  lobe. 

(b)  The  cingulum  is  a  band  of  white  matter  contained  within  the  cingulate 
gyrus.  Beginning  in  front  at  the  anterior  perforated  substance,  it  passes  forward 
and  upward  parallel  with  the  rostrum,  winds  around  the  genu,  runs  backward  above 
the  corpus  callosum,  turns  around  the  splenium,  and  ends  in  the  hippocampal  gyrus. 


THE  PROSENCEPHALOX  OR  FORE-BRAIN  891 

(c)  The  fiupcriur  luiigitiidinal  fasciculus  passes  backward  from  the  frontal  lobe 
above  the  lentiform  nucleus  and  insula;  some  of  its  fibres  end  in  the  occipital 
lobe,  and  others  curve  d()\Ainvar(l  and  forward  into  the  temporal  lobe. 

(d)  The  inferior  longiiudinal  fasciculus  connects  the  temporal  and  occipital 
lobes,  running  along-  the  lateral  walls  of  the  inferior  and  posterior  cornua  of  the 
lateral  ventricle. 

{e)  The  'peryendiculur  fasciculvs  runs  vertically  through  the  front  part  of  the 
occipital  lobe,  and  connects  the  inferior  parietal  lobule  with  the  fusiform  gyrus. 

(/)  The  occipiUfrovtal  fasciculus  passes  backward  from  the  frontal  lobe,  along 
the  lateral  border  of  the  caudate  nucleus,  and  on  the  mesial  aspect  of  the  corona 
radiata;  its  fibres  radiate  in  a  fan-like  manner  and  pass  into  the  occipital  and  tem- 
poral lobes  lateral  to  the  posterior  and  inferior  cornua.  Dejerine  regards  the  fibres 
of  the  tapetum  as  being  derived  from  this  fasciculus,  and  not  from  the  corpus 
callosum. 

(g)  The  fornix  connects  the  hippocampal  gyrus  with  the  corpus  mamillare 
and,  by  means  of  the  thalamomamillary  fasciculus,  with  the  thalamus  (see  page 
SS()).  Through  the  fibres  of  the  hippocampal  commissure  it  probably  also  unites 
the  opposite  hippocampal  gyri. 

The  gray  substance  of  the  hemisphere  is  divided  into:  (1)  that  of  the  cerebral 
cortex,  and  (2)  that  of  the  caudate  nucleus,  the  lentiform  nucleus,  the  claustrum, 
and  the  nucleus  amygdala?. 

Structure  of  the  Cerebral  Cortex  (Fig.  759). — The  cerebral  cortex  differs  in  thickness  and 
structure  in  different  parts  of  the  hemisphere.  It  is  thinner  in  the  occipital  region  than  in  the 
anterior  and  posterior  central  gyi'i,  and  it  is  also  much  thinner  at  the  bottom  of  the  sulci  than 
on  the  top  of  the  gyri.  Again,  the  minute  structure  of  the  anterior  central  differs  from  that  of 
the  posterior  central  gyrus,  and  areas  possessing  a  speciahzed  type  of  cortex  can  be  mapped  out 
in  the  occipital  lobe. 

On  examining  a  section  of  the  cortex  with  a  lens,  it  is  seen  to  consist  of  alternating  white  and 
gray  layers  thus  disposed  from  the  sm-face  inwai'd:  (1)  a  thin  layer  of  white  substance;  (2)  a 
layer  of  gray  substance;  (3)  a  second  white  layer  (outer  band  of  Baillarger  or  hand  of  Gennari); 
(4)  a  second  gray  layer;  (5)  a  third  white  layer  {inner  hand  of  Baillarger) ;  (6)  a  third  gray  layer, 
which  rests  on  the  meduUary  substance  of  the  gyrus. 

The  cortex  is  made  up  of  nerve  cells  of  varying  size  and  shape,  and  of  nerve  fibres  which  are 
either  meduUated  or  naked  axis-cylinders,  imbedded  in  a  matrix  of  neuroglia. 

Nerve  Cells. — According  to  Cajal,  the  nerve  cells  are  arranged  in  four  layers,  named  from  the 
sm-face  inward  as  follows:  (1)  the  molecular  layer,  (2)  the  layer  of  small  pyramidal  cells,  (3) 
the  layer  of  large  pyramidal  ceUs,  (4)  the  layer  of  polymorphous  cells. 

The  Molecular  Layer. — In  this  layer  the  cells  are  polygonal,  triangular,  or  fusiform  in  shape. 
Each  polygonal  cell  gives  off  some  four  or  five  dendrites,  while  its  axon  may  arise  directly  from 
the  cell  or  from  one  of  its  dendrites.  Each  triangular  cell  gives  off  two  or  three  dendrites,  from 
one  of  which  the  axon  arises.  The  fusiform  cells  are  placed  with  their  long  axes  parallel  to  the 
surface  and  are  mostly  bipolar,  each  pole  being  prolonged  into  a  dendrite,  which  runs  horizontally 
for  some  distance  and  furnishes  ascending  branches.  Their  axons,  two  or  three  in  number,  arise 
from  the  dendrites,  and,  like  them,  take  a  horizontal  course,  giving  off  numerous  ascending 
collaterals.  The  distribution  of  the  axons  and  dendrites  of  all  three  sets  of  cells  is  hmited  to  the 
molecular  layer. 

The  Layer  of  Small  and  the  Layer  of  Large  Pyramidal  Cells. — The  cells  in  these  two  layers 
may  be  studied  together,  since,  with  the  exception  of  the  difference  in  size  and  the  more  super- 
ficial position  of  the  smaller  cells,  they  resemble  each  other.  The  average  length  of  the  small 
cells  is  from  10  to  15m;  that  of  the  large  cells  from  20  to  30m.  The  body  of  each  cell  is  pyramidal 
in  shape,  its  base  being  directed  to  the  deeper  parts  and  its  apex  toward  the  sm-face.  It  contains 
granular  pigment,  and  stains  deeply  with  ordinary  reagents.  The  nucleus  is  of  large  size,  and 
round  or  oval  in  shape.  The  base  of  the  cell  gives  off  the  axis  cyhnder,  and  this  runs  into  the 
central  white  substance,  giving  off  collaterals  in  its  course,  and  is  distributed  as  a  projection, 
commissural,  or  association  fibre.  The  apical  and  basal  parts  of  the  cell  give  off  dendrites;  the 
apical  dendrite  is  directed  toward  the  surface,  and  ends  in  the  molecular  layer  by  dividing  into 
niunerous  branches,  all  of  which  may  be  seen,  when  prepared  by  the  silver  or  methylene-blue 
method,  to  be  studded  with  projecting  bristle-hke  processes.  The  largest  pyramidal  cells  are 
found  in  the  upper  part  of  the  anterior  central  gyrus  and  in  the  paracentral  lobule;  they  are 
often  arranged  in  groups  or  nests  of  from  three  to  five,  and  are  named  the  gia7it  cells  of  Betz. 


892 


NEUROLOGY 


In  the  former  situation  they  may  exceed  50m  in  length  and  40m  in  breadth,  while  in  the  para- 
central lobule  they  may  attain  a  length  of  65m. 

Layer  of  Polymor-phous  Cells. — The  cells  in  this  layer,  as  their  name  imphes,  are  very  irregular 
in  contour;  they  may  be  fusiform,  oval,  triangular,  or  star-shaped.  Their  dendrites  are  directed 
outward,  but  do  not  reach  so  far  as  the  molecular  layer;  their  axons  pass  into  the  subjacent  white 
matter. 


Molecular 
■   layer 


Layer  of 

small 

'pyramidal 

cells 


Layer  of 

large 

pyramidal 

cells 


Layer  of 

polymorphou  s 

cells 


Plexzis  of  Exner 


Q^^^  ~  Band  of  Beckterew 


Outer  band  of  Bail- 
larger,  or  band  of 
Gennari 


Vertical  fibres 


Internal  band  of 
Baillarger 


2 Deep  tangential 

fibres 


\  "        White  medullary 

^  ~^  substance 


jTjQ    759. —Cerebral  cortex.     (Poirier.)     To  the  left,  the  groups  of  cells;  to  the  right,  the  systems  of  fibres.    Quite 
to  the  left  of  the  figure  a  sensory  nerve  fibre  is  shown. 

There  are  two  other  kinds  of  cells  in  the  cerebral  cortex.  They  are:  (a)  the  cells  of  Golgi, 
the  axons  of  which  divide  immediately  after  their  origins  into  a  large  number  of  branches,  which 
are  directed  toward  the  surface  of  the  cortex;  (6)  the  cells  of  MartinoUi,  which  are  chiefly  foiind 
in  the  polymorphous  layer;  theh-  dendrites  are  short,  and  may  have  an  ascending  or  descendmg 
course,  while  their  axons  pass  out  into  the  molecular  layer  and  form  an  extensive  horizontal 
arborization.  ,         „  ,  u         j  i 

Nerve  Fibres.— These  fill  up  a  large  part  of  the  intervals  between  the  cells,  and  may  be  medul- 
lated  or  non-meduliated— the  latter  comprising  the  axons  of  the  smallest  pjTamidal  cells  and 
the  cells  of  Golgi.  In  their  direction  the  fibres  may  be  either  tangential  or  radial.  The  tangential 
fibres  run  parallel  to  the  surface  of  the  hemisphere,  intersecting  the  radial  fibres  at  a  right  angle. 


THE  PROSENCEPHALON  OR  FORE-BRAIN  893 

They  constitute  sevcnil  stnilii,  t)f  wliich  the  following  tire  the  more  inijjortant:  (1)  a  stratum 
of  white  fibres  covering  the  Kuperfioial  aspect  of  the  molecular  layer  (plexus  of  Exner) ;  (2)  the 
band  of  Bechterew,  in  the  outer  part  of  the  layer  of  small  i)yramidal  cells;  (3)  the  band  of  Gennari 
or  external  band  of  Baillarger,  running  through  the  layer  of  large  pyramidal  cells;  (4)  the  internal 
band  of  Baillarger,  between  the  layer  of  large  pyramidal  cells  and  the  polymorphous  layer;  (5) 
the  deep  tangential  fibres,  in  the  lower  part  of  the  polymorphous  layer.  The  tangential  fibres 
consist  of  (o)  the  collaterals  of  the  pyramidal  and  polymorphous  cells  and  of  the  cells  of  Martinotti; 
(b)  the  branching  axons  of  Golgi's  cells;  (c)  the  collaterals  and  terminal  arborizations  of  the 
projection,  commissural,  or  association  fibres.  The  radial  fibres. — Some  of  these,  viz.,  the  axons 
of  the  pyramidal  and  polymorphous  cells,  descend  into  the  central  white  matter,  while  others, 
the  terminations  of  the  projection,  commissural,  or  association  fibres,  ascend  to  end  in  the  cortex. 
The  axons  of  the  cells  of  Martinotti  are  also  ascending  fibres. 

Special  Types  of  Cerebral  Cortex. — It  has  been  already  pointed  out  that  the  minute  structure 
of  the  cortex  differs  in  different  regions  of  the  hemisphere;  and  A.  W.  CampbelP  has  endeavored 
to  pi'ove,  as  the  result  of  an  exhaustive  examination  of  a  series  of  human  and  anthropoid  brains, 
"that  there  exists  a  direct  correlation  between  physiological  function  and  histological  structure." 
The  principal  regions  where  the  "typical"  structure  is  departed  from  will  now  be  referred  to. 

1.  In  the  calcarine  fissure  and  the  gyri  bounding  it,  the  internal  band  of  Baillarger  is  absent, 
while  the  band  of  Gennari  is  of  considerable  thickness,  and  forms  a  characteristic  featm-e  of  this 
region  of  the  cortex.  If  a  section  be  examined  microscopically,  an  additional  layer  of  ceUs  is 
seen  to  be  interpolated  between  the  molecular  layer  and  the  lay^r  of  small  pyramidal  cells.  This 
extra  layer  consists  of  two  or  three  strata  of  fusiform  cells,  the  long  axes  of  which  are  at  right 
angles  to  the  surface;  each  cell  gives  off  two  dendrites,  external  and  internal,  from  the  latter  of 
wliich  the  axon  arises  and  passes  into  the  white  central  substance.  In  the  layer  of  small  pyi'amidal 
ceUs,  fusiform  cells,  identical  with  the  above,  are  seen,  as  well  as  ovoid  or  star-like  cells  with 
ascending  axons  {cells  of  Martinotti) .  This  is  the  visual  area  of  the  cortex,  and  it  has  been  shown 
by  J.  S.  Bolton^  that  in  old-standing  cases  of  optic  atrophy  the  thickness  of  Gennari's  band  is 
reduced  by  nearly  50  per  cent. 

A.  W.  Campbell  says:  "Histologically,  two  distinct  types  of  cortex  can  be  made  out  in  the 
occipital  lobe.  The  first  of  these  coats  the  walls  and  boimding  convolutions  of  the  calcarine 
fissure,  and  is  distinguished  by  the  well-known  line  of  Gennari  or  Vicq  d'Azyr;  the  second  area 
forms  an  investing  zone  a  centimetre  or  more  broad  around  the  first,  and  is  characterized  by  a 
remarkable  wealth  of  fibres,  as  well  as  by  curious  pyriform  cells  of  large  size  richly  stocked  with 
chromophihc  elements — cells  which  seem  to  have  escaped  the  observation  of  Ramon  y  Cajal, 
Bolton,  and  others  who  have  worked  at  this  region.  As  to  the  functions  of  these  two  regions 
there  is  abundant  evidence,  anatomical,  embryological,  and  pathological,  to  show  that  the  first 
or  calcarine  area  is  that  to  which  visual  sensations  primarily  pass,  and  we  are  gradually  obtain- 
ing proof  to  the  effect  that  the  second  investing  area  is  constituted  for  the  interpretation  and 
further  elaboration  of  these  sensations.  These  areas  therefore  deserve  the  names  visuo-sensory 
and  visuo-psychic." 

2.  The  anterior  central  gyrus  is  characterized  by  the  presence  of  the  giant  cells  of  Betz  and 
by  "a  wealth  of  nerve  fibres  immeasurably  superior  to  that  of  any  other  part"  (Campbell),  and 
in  these  respects  differs  from  the  posterior  central  gyrus.  These  two  gyri,  together  with  the 
paracentral  lobide,  were  long  regarded  as  constituting  the  "motor  areas"  of  the  hemisphere; 
but  Sherrington  and  Grunbaum  have  shown^  that  in  the  chimpanzee  the  motor  area  never  extends 
on  to  the  free  face  of  the  posterior  central  gyrus,  but  occupies  the  entire  length  of  the  anterior 
central  gyrus,  and  in  most  cases  the  greater  part  or  the  whole  of  its  width.  It  extends  into  the 
depth  of  the  central  sulcus,  occupying  the  anterior  wall,  and  in  some  places  the  floor,  and  in 
some  extending  even  into  the  deeper  part  of  the  posterior  wall  of  the  sulcus. 

3.  In  the  hippocampus  the  molecular  layer  is  very  thick  and  contains  a  large  number  of  Golgi 
cells.  It  has  been  divided  into  three  strata:  (a)  s.  convolutum  or  s.  granulosum,  containing 
many  tangential  fibres;  (6)  s.  lacunosum,  presenting  niunerous  vascular  spaces;  (c)  s.  radiatum, 
exhibiting  a  rich  plexus  of  fibrils.  The  two  layers  of  pyramidal  cells  are  condensed  into  one, 
and  the  cells  are  mostly  of  large  size.  The  axons  of  the  cells  in  the  polymorphous  layer  may 
rim  in  an  ascending,  a  descending,  or  a  horizontal  direction.  Between  the  polymorphous  layer 
and  the  ventricular  ependyma  is  the  white  substance  of  the  alveus. 

4.  In  the  fascia  dentata  hippocampi  or  dentate  gyrus  the  molecular  layer  contains  some  pyrami- 
dal cells,  while  the  layer  of  pyramidal  cells  is  almost  entirely  represented  by  small  ovoid  cells. 

5.  The  Olfactory  Bidb. — In  many  of  the  lower  animals  this  contains  a  cavity  which  communi- 
cates through  the  olfactory  tract  with  the  lateral  ventricle.  In  man  the  original  cavity  is  fiUed 
up  by  neurogUa  and  its  wall  becomes  thickened,  but  much  more  so  on  its  ventral  than  on  its 
dorsal  aspect.  Its  dorsal  part  contains  a  small  amount  of  gray  and  white  substance,  but  it  is 
scanty  and  ill-defined.  A  section  through  the  ventral  part  (Fig.  760)  shows  it  to  consist  of  the 
following  layers  from  without  inward: 

1  Histological  Studies  on  the  Localization  of  Cerebral  Function,  Cambridge  University  Press 

2  Philosophical  Transactions  of  Royal  Society,  Series  B,  cxciii,  165. 
'  Transactions  of  the  Pathological  Society  of  London,  vol.  liii. 


894 


NEUROLOGY 


1.  A  layer  of  olfactoiy  nerve  fibres,  which  are  fhe  non-medullated  axons  prolonged  from  the 
olfactory  cells  of  the  nasal  cavity,  and  reach  the  bulb  by  passing  through  the  cribriform  plate 
of  the  ethmoid  bone.  At  first  they  cover  the  bulb,  and  then  penetrate  it  to  end  by  forming 
synapses  with  the  dendrites  of  the  mitral  cells,  presently  to  be  described. 

2.  Glomerular  Layer.— This  contains  numerous  spheroidal  reticulated  enlargements,  termed 
glomeruli,  produced  by  the  branching  and  arborization  of  the  processes  of  the  olfactory  nerve 
fibres  with  the  descending  dendrites  of  the  mitral  cells. 

3.  Molecular  Layer. — This  is  formed  of  a  matrix  of  neuroglia,  imbedded  in  which  are  the  mitral 
cells.  These  cells  are  pyramidal  in  shape,  and  the  basal  part  of  each  gives  off  a  thick  dendrite 
which  descends  into  the  glomerular  layer,  where  it  arborizes  as  indicated  above,  and  others  which 
interlace  with  similar  dendrites  of  neighboring  mitral  cells.  The  axons  pass  through  the  next 
layer  into  the  white  matter  of  the  bulb,  and  after  becoming  bent  on  themselves  at  a  right  angle, 
are  continued  into  the  olfactory  tract. 

4.  Nerve  Fibre  Layer.— This  hes  next  the  central  core  of  neuroglia,  and  its  fibres  consist  of 
the  axons  or  afferent  processes  of  the  mitral  cells  passing  to  the  brain;  some  efferent  fibres  are, 
however,  also  present,  and  end  in  the  molecular  layer,  but  nothing  is  known  as  to  their  exact 
origin. 


White  suhstnnce   dorsnl  part) 


.Neuroglia 


TI  hUe  substance  {ventral 
part) 

Medullary  layer 

-  Mitral  cells 

2Iolecular 
''     layer 


Glomerular  layer 


Layer  of  olfactoJ  y  nerve  fibres 
Fig.   760. — Coronal  section  of  olfactory  bulb.     (Schwalbe.) 


Weight  of  the  Encephalon. — The  average  weight  of  the  brain,  in  the  adult  male,  is  about  1380 
gms.;  that  of  the  female,  about  1250  gms.  In  the  male,  the  maximum  weight  out  of  278  cases 
was  1840  gms.  and  the  minimum  weight  964  gms.  The  maximum  weight  of  the  adult  female 
brain,  out  of  191  cases,  was  1585  gms.  and  the  minimum  weight  879  gms.  The  brain  increases 
rapidly  during  the  first  four  years  of  life,  and  reaches  its  maximum  weight  by  about  the  twentieth 
year.  As  age  advances,  the  brain  decreases  slowly  in  weight;  in  old  age  the  decrease  takes  place 
more  rapidly,  to  the  extent  of  about  28  gms. 

The  human  brain  is  heavier  than  that  of  any  of  the  lower  animals,  except  the  elephant  and 
whale.  The  brain  of  the  former  weighs  from  3.5  to  4.5  kilogm.,  and  that  of  a  whale,  in  a  speci- 
men 22.8  metres  long,  weighed  rather  more  than  225  kilogm. 

Cerebral  Localization. — Physiological  and  pathological  research  have  now  gone  far  to  prove 
that  a  considerable  part  of  the  surface  of  the  brain  may  be  mapped  out  into  a  series  of  more 
or  less  definite  areas,  each  of  which  is  intimately  connected  with  some  well-defined  function. 

The  chief  areas  are  indicated  in  Figs.  761  and  762. 

Motor  Areas. — The  motor  area  occupies  the  anterior  central  and  frontal  gyri  and  the  para- 
central lobule.  The  centres  for  the  lower  limb  are  located  on  the  uppermost  part  of  the  anterior 
central  gyrus  and  its  continuation  on  to  the  paracentral  lobule;  those  for  the  trunk  are  on  the 
upper  portion,  and  those  for  the  upper  hmb  on  the  middle  portion  of  the  anterior  central  gyrus. 
The  facial  centres  are  situated  on  the  lower  part  of  the  anterior  central  gyrus,  those  for  the  tongue, 
larynx,  muscles  of  mastication,  and  pharynx  on  the  frontal  operculum,  while  those  for  the  head 
and  neck  occupy  the  posterior  end  of  the  middle  frontal  gyrus. 

Sensory  Areas. — Tactile  and  temperature  senses  are  located  on  the  posterior  central  gyrus, 
while  the  sense  of  form  and  sohdity  is  on  the  superior  parietal  lobule  and  precuneus.  With 
regard  to  the  special  senses,  the  area  for  the  sense  of  taste  is  probably  related  to  the  imcus  and 


THE  PROSENCEPJIAWX  OR  FORE-BUAIN 


895 


hippocampal  gyrus.  The  auditory  area  occujiies  the  middle  third  of  the  superior  temporal  gyrus 
and  the  adjacent  gyri  in  the  lateral  fissure;  the  visual  area,  the  calcarine  fissure  and  cuncus;  the 
olfactory  area,  the  rhineneephalon.  As  special  centres  of  much  importance  may  be  noted:  the 
emissive  centre  for  speech  on  the  left  inferior  frontal  and  anterior  central  gyri  (Broca) ;  the  auditory 
receptive  centre  on  the  transverse  and  sujierior  tenijioral  gyri,  and  the  visual  receptive  centre 
on  the  lingual  gyrus  and  cuneus. 


Fig.   761. — Areas  of  localization  on  lateral  surface  of  hemisphere.     Motor  area  in  red.     Area  of  general  sensations 
in  blue.     Auditory  area  in  green.     Visual  area  in  yellow.     The  psj-chic  portions  are  in  lighter  tints. 

Applied  Anatomy. — The  internal  capsule  is  of  great  interest  to  the  clinician  because  it  is  so  often 
the  seat  of  hemorrhage  (from  the  lenticulo-striate  and  lenticulo-optic  arteries,  Charcot's  "arteries 
of  cerebral  hemorrhage"),  oi'  of  thrombosis,  in  patients  whose  vessels  are  weakened  by  old  age 


Fig.  762. — Areas  of  localization  on  medial  surface  of  hemisphere.     Motor  area  in  red.     Area  of  general  sensations 
in  blue.     'S'isual  area  in  yellow.     Olfactory  area  in  purple.     The  psychic  portions  are  in  lighter  tints. 


or  disease.  A  stroke  or  apoplexy  is  the  result;  blood  is  effused  from  the  ruptm-ed  vessel  and  tears 
up  the  surroimding  brain  tissue,  and  also  interferes  with  the  neighboring  fibres  by  the  compres- 
sion set  up  by  its  mass.  If  the  hemorrhage  is  sudden  and  at  all  large,  rapid  and  complete  loss 
of  consciousness  follows,  with  paralj'sis  of  the  opposite  side  of  the  body  and  loss  of  control  over 


896  NE I  HO  LOGY 

the  sphincters.  If  it  is  the  occipital  part  of  the  internal  capsule  tliat  is  involved,  tlie  paralysis 
will  be  more  marked  in  the  leg  than  in  the  arm,  and  will  be  associated  with  hemianesthesia,  and 
also  with  homonymous  hemianopsia  or  blindness  of  the  corresponding  halves  of  the  two  retinae, 
the  patient  being  unable  to  see  objects  on  the  opposite  side  of  the  body.  If  the  hemorrhage  is 
very  extensive  blood  often  makes  its  way  into  the  ventricles,  and  death  may  follow  in  a  few  hours 
or  days  without  recovery  of  consciousness,  and  with  hyperpyrexia.  If  the  hemorrhage  is  small, 
consciousness  is  soon  regained,  and  a  fair  degree  of  recovery  from  the  paralysis  follows,  particu- 
larly in  the  leg.  If  the  hemorrhage  takes  place  very  slowly,  the  hemiplegia  sets  in  gradually 
{ingravescent  apoplexy),  with  headache  and  gradual  clouding  of  the  faculties.  It  is  the  upper 
motor  neuron  (see  below)  that  is  injured  in  cerebral  hemorrhage;  hence  the  muscles  on  the  affected 
side  of  the  body  become  spastic,  with  increased  reflexes,  while  such  muscular  atrophy  as  follows 
is  mainly  due  to  disuse. 


THE   MOTOR    AND    SENSORY    TRACTS. 

The  anatomy  of  the  various  parts  of  the  central  nervous  system  having  been 
described,  a  short  account  will  now  be  given  of  the  motor  and  sensory  nerve  tracts 
connecting  the  brain  and  the  medulla  spinalis.  The  methods  employed  in  elucidat- 
ing this  complex  subject  have  already  been  referred  to  (page  815). 

The  Motor  Tract  (Fig.  763). — The  constituent  fibres  of  this  tract  are  the  axis- 
cylinder  processes  of  cells  situated  in  the  motor  area  of  the  cortex.  The  fibres 
are  at  first  somewhat  widely  diffused,  but  as  they  descend  through  the  corona 
radiata  they  gradually  approach  each  other,  and  pass  between  the  lentiform  nucleus 
and  thalamus,  in  the  genu  and  anterior  two-thirds  of  the  occipital  part  of  the  inter- 
nal capsule ;  those  in  the  genu  are  named  the  geniculate  fibres,  while  the  remainder 
constitute  the  cerebrospinal  fibres;  proceeding  downward  they  enter  the  middle 
three-fifths  of  the  base  of  the  cerebral  peduncle.  The  geniculate  fibres  cross  the 
middle  line,  and  end  by  arborizing  around  the  cells  of  the  motor  nuclei  of  the  cere- 
bral nerves.  The  cerebrospinal  fibres  are  continued  downward  into  the  pyramids 
of  the  medulla  oblongata,  and  the  transit  of  the  fibres  from  the  medulla  oblongata 
is  effected  by  two  paths.  The  fibres  nearest  to  the  anterior  median  fissure  cross 
the  middle  line,  forming  the  decussation  of  the  pyramids,  and  descend  in  the 
opposite  side  of  the  medulla  spinalis,  as  the  lateral  cerebrospinal  fasciculus  {crossed 
pyramidal  tract) .  Throughout  the  length  of  the  medulla  spinalis  fibres  from  this 
column  pass  into  the  gray  substance,  to  terminate  by  ramifying  around  the  motor 
cells  of  the  anterior  column.  The  more  laterally  placed  portion  of  the  tract  does 
not  decussate  in  the  medulla  oblongata,  but  descends  as  the  anterior  cerebrospinal 
fasciculus  {direct  pyramidal  tract) ;  these  fibres,  however,  end  in  the  anterior  gray 
column  of  the  opposite  side  of  the  medulla  spinalis  by  passing  across  in  the  anterior 
white  commissure.  There  is  considerable  variation  in  the  extent  to  which  decus- 
sation takes  place  in  the  medulla  oblongata;  about  two-thirds  or  three-fourths  of 
the  fibres  usu-ally  decussate  in  the  medulla  oblongata  and  the  remainder  in  the 
medulla  spinalis. 

The  axons  of  the  motor  cells  in  the  anterior  column  pass  out  as  the  fibres  of  the 
anterior  roots  of  the  spinal  nerves,  along  which  the  impulses  are  conducted  to  the 
muscles  of  the  trunk  and  limbs. 

From  this  it  will  be  seen  that  all  the  fibres  of  the  motor  tract  pass  to  the  nuclei 
of  the  motor  nerves  on  the  opposite  side  of  the  brain  or  medulla  spinaHs,  a  fact 
which  explains  why  a  lesion  involving  the  motor  area  of  one  side  causes  paralysis 
of  the  muscles  of  the  opposite  side  of  the  body.  Further,  it  will  be  seen  that  there 
is  a  break  in  the  continuity  of  the  motor  chain;  in  the  case  of  the  cerebral  nerves 
this  break  occurs  in  the  nuclei  of  these  nerves;  and  in  the  case  of  the  spinal  nerves, 
in  the  anterior  gray  column  of  the  medulla  spinalis.  For  clinical  purposes  it  is 
convenient  to  emphasize  this  break  and  divide  the  motor  tract  into  two  portions : 
(1)  a  series  of  upper  motor  neurons  which  comprises  the  motor  cells  in  the  cortex 


THE  MOTOR  AND  SENSORY  TRACTS 


897 


and  their  descending  fibres  down  to  the  nuclei  of  the  motor  nerves;  (2)  a  series 
of  lower  motor  neurons  a\  hich  inchides  the  cells  of  the  nuclei  of  the  motor  cerebral 
nerves  or  the  cells  of  the  anterior  columns  of  the  medulla  spinalis  and  their  axis- 
cylinder  processes  to  the  periphery.^ 


Jeniculate  fibres 


Motor  area  of 
cortex 


Internal 
capsule 


Decussation  of  pyramids 

Anterior  cerebrospinal  fasciculus 
Lateral  cerebrospinal  fasciculus 


Anterior  nerve  roots 


Fig.  763. — The  motor  tract.      (Modified  from  Poirier.) 


The  Sensory  Tract  (Fig.  764)  .—Sensory  impulses  are  conveyed  to  the  medulla 
spinalis  through  the  posterior  roots  of  the  spinal  nerves.  On  entering  the  medulla 
spinalis  these  root  fibres  divide  into  descending  and  ascending  branches;  the  former 
soon  enter  the  gray  substance :  some  of  the  latter  end  in  the  gray  substance  after  a 
longer  or  shorter  course,  while  others  are  continued  directly  into  the  posterior 

1  As  already  mentioned  (footnote,  p.  816),  a  neuron  in  the  posterior  column  of  the  medulla  spinalis  is  probably  inter- 
posed between  each  upper  and  lower  motor  neuron. 

57 


898  NEUROLOGY 

funiculi,  where  they  form  the  fascicukis  gracihs  and  fasciculus  cuneatus.  From 
the  cells  of  the  posterior  column,  fibres  arise  which  cross  the  middle  line  and  ascend 
in  the  superficial  antero-lateral  fasciculus.  The  fibres  of  the  fasciculus  gracilis 
and  fasciculus  cuneatus  end  by  arborizing  around  the  cells  of  the  gracile  and  cuneate 
nuclei  in  the  medulla  oblongata,  and  from  these  cells  the  fibres  of  the  medial 


Medial  lemniscus 


Sensory  decussation 


Fasciculus  cuneatus 
Fasciculus  gracilis 


Nucleus  cuneaius 
Nucleus  gracilis 


—  ■  Posterior  nerve  roots 


Fig.  764. — The  sensory  tract.     (Modified  from  Poirier.) 

lemniscus  take  origin  and  cross  to  the  opposite  side  in  the  sensory  decussation. 
The  medial  lemniscus  is  then  joined  by  the  fibres  of  the  superficial  antero-lateral 
fasciculus,  which  have  already  crossed  in  the  medulla  spinalis,  and  in  its  further 
course  receives  fibres  from  the  cerebral  sensory  nuclei  of  the  opposite  side,  with 
the  exception  of  the  cochlear  division  of  the  acoustic  nerve.  Ascending  through 
the  cerebral  peduncle,  the  lemniscus  gives  off  some  fibres  to  the  lentiform  nucleus 


THE  MOTOR  AND  SEXSORY  TRACTS  899 

and  insula,  but  the  greater  part  of  it  is  carried  into  the  thalamus,  where  most 
of  its  fibres  end — only  a  small  proportion  being  continued  directly  into  the  cerebral 
cortex.  From  the  gray  substance  of  the  thalamus  the  fibres  of  the  third  link  in 
the  chain  arise  and  pass  to  the  cerebral  cortex.  The  fibres  from  the  terminal  nuclei 
of  the  cochlear  nerve  pass  upward  in  the  lateral  lemniscus,  and  are  carried  through 
the  occipital  part  of  the  internal  capsule  to  the  temporal  lobe.  Further,  the  super- 
ficial antero-lateral  fasciculus  gives  off  fibres  which  reach  the  cerebellum  through 
the  brachia  conjunctiva.  It  will  be  evident,  therefore,  that  in  most  cases  there 
are  three  cell-stations  interposed  in  the  course  of  the  sensory  impulses.  For  clinical 
purposes,  therefore,  three  neurons  are  described:  (1)  the  lowest  sensory  neurons 
comprise  the  cells  of  the  posterior  root  ganglia  and  their  peripheral  and  central 
processes;  (2)  the  intermediate  sensory  neurons  are  the  cells  of  the  nuclei  cuneati 
and  gracilis  and  their  processes,  while  (3)  the  highest  sensory  neurons  are  the  cells 
of  the  thalami  and  the  fibres  passing  from  these  to  the  cerebral  cortex. 

Applied  Anatomy. — The  chief  sjTnptoms  of  diseases  of  the  brain  and  medulla  spinaUs  depend 
upon  the  particular  systems  of  neurons  picked  out  for  attack,  a^d  some  of  them  may  be  briefly 
summarized  as  foUows:  Motor  paralysis  of  the  spastic  type,  with  rigidity  of  the  muscles  and 
increased  reflexes,  follows  destruction  of  the  upper  motor  neurons;  flaccid  paralysis,  with  loss  of 
the  reflexes  and  rapid  muscular  atrophy,  foUows  destruction  of  the  lower  motor  neurons.  Sensory 
paralysis  foUows  injury  to  any  part  of  the  sensory  path;  in  tabes  it  is  due  to  injury  of  the  lowest 
sensory  neurons,  in  hemiplegia  to  destruction  of  the  highest  sensory  axon  as  it  traverses  the 
occipital  part  of  the  internal  capsule.  Dissociation  of  sensations,  or  the  loss  of  some  forms  of 
sensation  while  others  remain  imimpaired,  is  seen  in  a  number  of  conditions  such  as  tabes  or 
syringomyelia;  it  shows  that  the  paths  through  which  various  forms  of  sensation  travel  to  the 
brain  are  different.  Abnormalities  of  reflex  actions  are  of  very  great  help  in  the  diagnosis  of  nervous 
complaints.  The  numerous  superficial  or  skin  reflexes,  e.  g.,  the  scapular,  irritation  of  the  skin 
over  the  scapula  produces  contraction  of  the  scapular  muscles;  the  abdominal,  stroking  the 
abdomen  causes  its  retraction;  the  cremasteric,  stroking  the  inner  side  of  the  thigh  causes  retrac- 
tion of  the  testis  on  that  side;  the  plantar,  tickling  the  sole  of  the  foot  brings  on  plantar  flexion 
of  the  toes,  if  present,  show  that  the  reflex  arcs  on  whose  integrity  their  existence  depends  are 
intact;  but  they  are  often  absent  in  health,  and  so  cannot  be  trusted  to  indicate  disease.  The 
deep  reflexes  or  tendon  reactions,  such  as  the  knee-jerk  or  the  tendo-calcaneus  jerk,  are  increased 
in  chronic  degeneration  of,  or  gradually  increasing  pressure  on,  the  cerebrospinal  fibres  (upper 
motor  neuron),  in  nervous  or  hysterical  patients,  and  when  the  irritabihty  of  the  cells  of  the 
anterior  column  (lower  motor  neuron)  is  increased,  as  happens  in  tetanus  or  in  poisoning  by 
strychnine.  They  are  lost  when  the  lower  motor  or  lower  sensory  neurons  are  diseased,  and  in 
a  few  other  conditions;  absence  of  the  knee-jerk  is  very  rare  in  health,  and  suggests  disease  in 
some  part  of  its  reflex  arc,  in  the  third  and  fourth  Imnbar  segments  of  the  cord,  or  else,  more 
rarely,  grave  intracranial  or  spinal  disease  cutting  off  the  lower  from  the  higher  nervous  centres. 
The  organic  reflexes  of  the  pupil,  bladder,  and  rectum  are  of  the  greatest  practical  importance. 
The  commonest  defect  in  the  reflexes  of  the  pupil  is  reflex  iridoplegia,  or  failm'e  to  contract  on 
exposm-e  to  hght,  without  failure  to  contract  on  convergence  or  accommodation  (Argyll-Robert- 
son pupil).  The  pupil  is  also  contracted  (miosis),  and  may  or  may  not  dilate  when  the  skui  of 
the  neck  is  pinched  (the  cihospinal  reflex) .  Micturition  is  a  spinal  reflex  much  under  the  control 
of  the  brain;  if  the  centre  for  mictm'ition  in  the  second  sacral  segment  is  destroyed  the  sphincter 
and  the  walls  of  the  bladder  are  paralyzed,  the  bladder  becomes  distended  with  m-ine,  and  incon- 
tinence from  overflow  results.  If  this  centre  escapes  injury  but  is  cut  off  more  or  less  completely 
from  impulses  descending  to  it  from  above,  there  will  be  more  or  less  interference  with  micturition. 
This  varies  in  degi'ee  from  the  "precipitate  mictm-ition"  of  tabetic  patients,  who  must  perforce 
hurry  to  pass  water  the  moment  the  impulse  seizes  them,  to  the  state  of  "reflex  incontinence," 
when  the  bladder  automatically  empties  itseK  from  time  to  time,  almost  without  the  patient's 
knowledge.  Defecation  is  a  very  similar  spinal  reflex,  and  is  hable  to  very  similar  disorders  of 
function. 

The  upper  motor  neuron  (p.  896)  is  affected  in  hemiplegia,  the  lower  motor  neuron  (p.  897)  in 
infantile  spinal  paralysis;  both  these  systems  of  nem'ons  are  diseased  together  in  the  somewhat 
rare  disorders  known  as  amyotrophic  lateral  sclerosis  and  progressive  muscidar  atrophy.  The 
chief  symptom  here  is  wasting  and  weakness  in  certain  groups  of  muscles;  the  palsy  wiU  be  flaccid, 
with  loss  of  the  reflexes,  or  spastic,  with  increased  reflexes,  according  as  the  degeneration  mainly 
involves  the  lower  or  the  upper  motor  neuron.  The  sphincters  are  affected  only  in  the  later 
stages  of  these  diseases. 

Pathological  changes  in  the  lowest  sensory  neuron  are  the  cause  of  tabes  dorsalis  or  locomotor 
ataxy,  which  occurs  almost  entirely  in  adults  who  have  had  syphihs.    In  the  early  or  preataxic 


900  NEUROLOGY 

stage  the  patient  may  exhibit  tlic  Argyll-Rol)(>rt.son  pupil  (page  SOU),  and  loss  of  the  knee-jerks, 
and  complain  of  sharp,  stabbing  pains  ("lightning  pains")  in  the  limbs,  difficult  or  precipitate 
micturition,  and  sometimes  of  severe  and  painful  attacks  of  indigestion  (gastric  crises).  In  the 
second  or  ataxic  stage,  coming  on  perhaps  years  later,  he  will  complain,  in  addition,  of  inter- 
ference with  his  powers  of  getting  about  and  turning,  although  his  muscular  strength  is  well 
preserved.  He  is  unable  to  stand  steady  with  his  eyes  shut  or  in  the  dark,  his  gait  becomes 
exaggerated  and  stamping  in  character,  he  has  to  use  a  stout  stick  to  walk  with,  and  he  may 
suffer  from  painful  crises  in  various  parts  of  the  body.  Control  over  the  sphincters  is  further 
weakened,  and  on  examination  there  will  be  found  marked  incoordination  of  the  limbs,  zones 
of  anesthesia  about  the  trunk  or  down  the  limbs,  and  marked  analgesia  (or  insensitiveness  to 
pain)  when  pressure  is  applied  to  the  bones,  tendons,  trachea,  tongue,  eyeballs,  mammae,  and 
testes.^  The  ataxy  progresses  until  the  third  or  bedridden  stage  is  reached;  control  over  the 
sphincters  is  still  further  lost,  and  the  patient  is  likely  to  die  of  intercurrent  disease  or  of  general 
paralysis  of  the  insane. 

No  nervous  disease  is  recognized  as  dependent  upon  degeneration  of  either  the  intermediate 
or  highest  sensory  neuron. 

MENINGES    OF   THE   BRAIN    AND   MEDULLA   SPINALIS. 

The  brain  and  medulla  spinalis  are  enclosed  within  three  membranes.  These 
are  named  from  without  inward :  the  dura  mater,  the  arachnoid,  and  the  pia  mater. 

The  Dura  Mater. 

The  dura  mater  is  a  thick  and  dense  inelastic  membrane.  The  portion  which 
encloses  the  brain  differs  in  several  essential  particulars  from  that  which  surrounds 
the  medulla  spinalis,  and  therefore  it  is  necessary  to  describe  them  separately; 
but  at  the  same  time  it  must  be  distinctly  understood  that  the  two  form  one  com- 
plete membrane,  and  are  continuous  with  each  other  at  the  foramen  magnum. 

The  cerebral  dura  mater  {dura  mater  encephali;  dura  of  the  brain)  lines  the 
interior  of  the  skull,  and  serves  the  two-fold  purpose  of  an  internal  periosteum 
to  the  bones,  and  a  membrane  for  the  protection  of  the  brain.  It  is  composed  of 
two  layers,  an  inner  or  meningeal  and  an  outer  or  endosteal,  closely  connected 
together,  except  in  certain  situations,  where,  as  already  described  (page  729), 
they  separate  to  form  sinuses  for  the  passage  of  venous  blood.  Its  outer  surface 
is  rough  and  fibrillated,  and  adheres  closely  to  the  inner  surfaces  of  the  bones, 
the  adhesions  being  most  marked  opposite  the  sutures  and  at  the  base  of  the  skull 
its  inner  surface  is  smooth  and  lined  by  a  layer  of  endothelium.  It  sends  inward 
four  processes  which  divide  the  cavity  of  the  skull  into  a  series  of  freely  communica- 
ting compartments,  for  the  lodgement  and  protection  of  the  different  parts  of  the 
brain;  and  it  is  prolonged  to  the  outer  surface  of  the  skull,  through  the  various 
foramina  which  exist  at  the  base,  and  thus  becomes  continuous  with  the  peri- 
cranium; its  fibrous  layer  forms  sheaths  for  the  nerves  which  pass  through  these 
apertures.  Around  the  margin  of  the  foramen  magnum  it  is  closely  adherent  to 
the  bone,  and  is  continuous  with  the  spinal  dura  mater. 

Processes. — The  processes  of  the  cerebral  dura  mater,  which  projects  into  the 
cavity  of  the  skull,  are  formed  by  reduplications  of  the  inner  or  meningeal  layer 
of  the  membrane,  and  are  four  in  number:  the  falx  cerebri,  the  tentorium  cerebelli, 
the  falx  cerebelli,  and  the  diaphragma  sellse. 

The  falx  cerebri  (Fig.  765),  so  named  from  its  sickle-like  form,  is  a  strong,  arched 
process  which  descends  vertically  in  the  longitudinal  fissure  between  the  cerebral 
hemispheres.  It  is  narrow  in  front,  where  it  is  attached  to  the  crista  galli  of  the 
ethmoid;  and  broad  behind,  where  it  is  connected  with  the  upper  surface  of  the 
tentorium  cerebelli.  Its  upper  margin  is  convex,  and  attached  to  the  inner  surface 
of  the  skull  in  the  middle  line,  as  far  back  as  the  internal  occipital  protuberance; 
it  contains  the  superior  sagittal  sinus.  Its  lower  margin  is  free  and  concave,  and 
contains  the  inferior  sagittal  sinus. 

1  J.  Grasset,  Le  Tabes,  Maladie  de  la  Sensibilite  profonde,  Montpellier,  1909. 


THK  DURA  MATKR 


901 


The  tentorium  cerebelli  (Fig.  766)  is  an  arched  lamina,  elevated  in  the  middle, 
and  inciinini:;  downward  toward  the  circumference.  It  covers  the  superior  surface 
of  the  cerebellum,  and  supports  the  occij)ital  lobes  of  the  brain.  Its  anterior  border 
is  free  and  conca^'e,  and  bounds  a  large  oval  opening,  the  incisura  tentorii,  for  the 
transmission  of  the  cerebral  peduncles.  It  is  attached,  behind,  by  its  convex  border, 
to  the  transverse  ridges  upon  the  inner  surface  of  the  occipital  bone,  and  there 
encloses  the  transverse  sinuses;  in  front,  to  the  superior  angle  of  the  petrous  part 
of  the  temporal  bone  on  either  side,  enclosing  the  superior  petrosal  sinuses.  At 
the  apex  of  the  petrous  part  of  the  temporal  bone  the  free  and  attached  borders 
meet,  and,  crossing  one  another,  are  continued  forward  to  be  fixed  to  the  anterior 
and  posterior  clinoid  processes  respectively.  To  the  middle  line  of  its  upper  surface 
the  posterior  border  of  the  falx  cerebri  is  attached,  the  straight  sinus  being  placed 
at  their  line  of  junction. 


Great  cerebral  vein 

GlonsopharyiLijeal  nerve 

Vagus  nerve 
Accessory  nerve 

Acoustic  nerve 

Facial  nerve 

Abducent  nerve    Trigeminal  nerve 
Fig.  765. — Dura  mater  and  its  processes  exposed  by  removing  part  of  the  right  half  of  the  skull  and  the  brain. 


The  falx  cerebelli  is  a  small  triangular  process  of  dura  mater,  received  into  the 
posterior  cerebellar  notch.  Its  base  is  attached,  above,  to  the  under  and  back  part 
of  the  tentorium;  its  posterior  margin,  to  the  lower  division  of  the  vertical  crest 
on  the  inner  surface  of  the  occipital  bone.  As  it  descends,  it  sometimes  divides 
into  two  smaller  folds,  which  are  lost  on  the  sides  of  the  foramen  magnum. 

The  diaphragma  sellae  is  a  small  circular  horizontal  fold,  which  roofs  in  the  sella 
turcica  and  afmost  completely  covers  the  hypophysis;  a  small  central  opening 
transmits  the  infundibulum. 


902 


NEUROLOGY 


Structure. — The  cranial  dura  mater  consists  of  white  fibrous  tissue  and  clastic  fibres  arranged 
in  flattened  lamina;  which  are  imperfectly  separated  by  lacunar  spaces  and  bloodvessels  into 
two  layers,  endosteal  and  meningeal.  The  endosteal  layer  is  the  internal  periosteum  for  the 
cranial  bones,  and  contains  the  bloodvessels  for  their  supply.  At  the  margin  of  the  foramen 
magnum  it  is  continuous  with  the  periosteum  lining  the  vertebral  canal.  The  meningeal  or 
supporting  layer  is  lined  on  its  inner  surface  by  a  layer  of  nucleated  endothehum,  similar  to  that 
found  on  serous  membranes. 

Optic  nei-ve  Internal  carotid  artery 

Oculomotor  nerve 

Attached  margin  of  tentorium 
Free  margin  of  tentouum 


niaphragma  sellce 
\ 


E7id  of  superior  sagittal  sinus 
Fig.  766. — Tentorium  cerebelli  seen  from  above. 


The  arteries  of  the  dura  mater  are  very  numerous.  Those  in  the  anterior  fossa  are  the  anterior 
meningeal  branches  of  the  anterior  and  posterior  ethmoidal  and  internal  carotid,  and  a  branch 
from  the  middle  meningeal.  Those  in  the  middle  fossa  are  the  middle  and  accessory  meningeal 
of  the  internal  maxillary;  a  branch  from  the  ascending  pharyngeal,  which  enters  the  skull  through 
the  foramen  lacerum;  branches  from  the  internal  carotid,  and  a  recurrent  branch  from  the  lacrimal. 
Those  in  the  posterior  fossa  are  meningeal  branches  from  the  occipital,  one  entering  the  skull 
through  the  jugular  foramen,  and  another  through  the  mastoid  foramen;  the  posterior  meningeal 
from  the  vertebral;  occasional  meningeal  branches  from  the  ascending  pharyngeal,  entering  the 
skull  through  the  jugular  foramen  and  hypoglossal  canal;  and  a  branch  from  the  middle  meningeal. 

The  veins  returning  the  blood  from  the  cranial  dura  mater  anastomose  with  the  diploic  veins 
and  end  in  the  various  sinuses.  Many  of  the  meningeal  veins  do  not  open  directly  into  the  sinuses, 
but  indirectly  through  a  series  of  ampullae,  termed  venous  lacunae.  These  are  found  on  either 
side  of  the  superior  sagittal  sinus,  especially  near  its  middle  portion,  and  are  often  invaginated 
by  arachnoid  granulations;  they  also  exist  near  the  transverse  and  straight  sinuses.  They 
communicate  with  the  underlying  cerebral  veins,  and  also  with  the  diploic  and  emissary  veins. 

The  nerves  of  the  cerebral  dm-a  mater  are  filaments  from  the  semilunar  ganglion,  from  the 
ophthalmic,  maxillary,  mandibular,  vagus,  and  hypoglossal  nerves,  and  from  the  sympathetic. 

The  spinal  dura  mater  (dura  mater  spinalis;  spinal  dura)  (Fig.  767)  forms  a 
loose  sheath  around  the  medulla  spinalis,  and  represents^  onl}'  the  inner  or  meningeal 
layer  of  the  cerebral  dura  mater;  the  outer  or  endosteal  layer  ceases  at  the  foramen 
magnum,  its  place  being  taken  by  the  periosteum  lining  the  vertebral  canal.    The 


THE  ARACHNOID 


903 


spinal  dura  mater  is  separated  from  the  arachnoid  by  a  potential  cavity,  the  sub- 
dural cavity;  the  two  membranes  are,  in  fact,  in  contact  with  each  other,  except 
where  they  are  separated  by  a  minute  quantity  of 
fluid,  which  serves  to  moisten  the  apposed  surfaces. 
It  is  separated  from  the  wall  of  the  vertebral  canal 
by  a  space,  the  epidural  space,  which  contains  a  quan- 
tity of  loose  areolar  tissue  and  a  plexus  of  veins;  the 
situation  of  these  veins  between  the  dura  mater  and 
the  periosteum  of  the  vertebrae  corresponds  therefore 
to  that  of  the  cranial  sinuses  between  the  meningeal 
and  endosteal  layers  of  the  cerebral  dura  mater.  The 
spinal  dura  mater  is  attached  to  the  circumference  of 
the  foramen  magnum,  and  to  the  second  and  third 
cervical  vertebrae;  it  is  also  connected  to  the  pos- 
terior longitudinal  ligament,  especially  near  the  low^er 
end  of  the  vertebral  canal,  by  fibrous  slips.  The 
subdural  cavity  ends  at  the  lower  border  of  the  second 
sacral  vertebra ;  below  this  le-s^el  the  dura  mater  closely 
invests  the  filum  terminale  and  descends  to  the  back  of 
the  coccyx,  where  it  blends  with  the  periosteum.  The 
sheath  of  dura  mater  is  much  larger  than  is  necessary 
for  the  accommodation  of  its  contents,  and  its  size  is 
greater  in  the  cervical  and  lumbar  regions  than  in 
the  thoracic.  On  each  side  may  be  seen  the  double 
openings  which  transmit  the  two  roots  of  the  corre- 
sponding spinal  nerve,  the  dura  mater  being  continued 

in  the  form  of  tubular  prolongations  on  them  as  they  pass  through  the  interverte- 
bral foramina.  These  prolongations  are  short  in  the  upper  part  of  the  vertebral 
column,  but  gradually  become  longer  below,  forming  a  number  of  tubes  of  fibrous 
membrane,  which  enclose  the  lower  spinal  nerves  and  are  contained  in  the  verte- 
bral canal. 

Structure. — The  spinal  dvira  mater  resembles  in  structure  the  meningeal  or  supporting  layer 
of  the  cranial  dm-a  mater,  consisting  of  white  fibrous  and  elastic  tissue  arranged  in  bands  or 
lamellae  which,  for  the  most  part,  are  parallel  with  one  another  and  have  a  longitudinal  arrange- 
ment. Its  internal  surface  is  smooth  and  covered  by  a  layer  of  endothehum.  It  is  sparingly 
supplied  with  bloodvessels,  and  a  few  nerves  have  been  traced  into  it. 


Fig. 


767. — The  medulla  spinalis  and 
its  membranes. 


The  Arachnoid. 

The  arachnoid  is  a  delicate  membrane  enveloping  the  brain  and  medulla  spinalis 
and  lying  between  the  pia  mater  internally  and  the  dura  mater  externally;  it  is 
separated  from  the  pia  mater  by  the  subarachnoid  cavity,  which  is  filled  with 
cerebrospinal  fluid. 

The  cerebral  part  (arachnoidea  encepJiali)  of  the  arachnoid  invests  the  brain 
loosely,  and  does  not  dip  into  the  sulci  between  the  gyri,  nor  into  the  fissures,  with 
the  exception  of  the  longitudinal.  On  the  upper  surface  of  the  brain  the  arachnoid 
is  thin  and  transparent;  at  the  base  it  is  thicker,  and  slightly  opaque  toward  the 
central  part,  w^here  it  extends  across  between  the  two  temporal  lobes  in  front 
of  the  pons,  so  as  to  leave  a  considerable  interval  between  it  and  the  brain. 

The  spinal  part  (arachnoidea  spinalis)  of  the  arachnoid  is  a  thin,  delicate,  tubular 
membrane  loosely  investing  the  medulla  spinalis.  Above,  it  is  continuous  with 
the  cerebral  arachnoid;  beloiv,  it  widens  out  and  invests  the  cauda  equina  and  the 
nerves  proceeding  from  it.  It  is  separated  from  the  dura  mater  by  the  subdural 
space,  but  here  and  there  this  space  is  traversed  by  isolated  connective-tissue 
trabeculse,  w^hich  are  most  numerous  on  the  posterior  surface  of  the  medulla  spinalis. 


904 


NEUROLOGY 


The  arachnoid  surrounds  the  cerebral  and  spinal  nerves,  and  encloses  them 
in  loose  sheaths  as  far  as  their  points  of  exit  from  the  skull  and  vertebral  canal; 

Structure. — The  arachnoid  consists  of  bundles  of  white  fibrous  and  elastic  tissue  intimately- 
blended  together.  Its  outer  surface  is  covered  with  a  layer  of  endothelium.  Vessels  of  consider- 
able size,  but  few  in  number,  and,  according  to  Bochdalek,  a  rich  plexus  of  nerves  derived  from 
the  motor  root  of  the  trigeminal,  the  facial,  and  the  accessory  nerves,  are  found  in  the  arachnoid 

The  subarachnoid  cavity  {cavum  suharachnoideale;  subarachnoid  space)  is  the 
interval  between  the  arachnoid  and  pia  mater.  It  is  occupied  by  a  spongy  tissue 
consisting  of  trabeculse  of  delicate  connective  tissue,  and  intercommunicating 
channels  in  which  the  subarachnoid  fluid  is  contained.  This  cavity  is  small  on  the 
surface  of  the  hemispheres  of  the  brain;  on  the  summit  of  each  gyrus  the  pia  mater 
and  the  arachnoid  are  in  close  contact ;  but  in  the  sulci  between  the  gyri,  triangular 
spaces  are  left,  in  which  the  subarachnoid  trabecular  tissue  is  found,  for  the  pia 
mater  dips  into  the  sulci,  whereas  the  arachnoid  bridges  across  them  from  gyrus  to 
gyrus.  At  certain  parts  of  the  base  of  the  brain,  the  arachnoid  is  separated  from  the 
pia  mater  by  wide  intervals,  which  communicate  freely  with  each  other  and  are 
named  subarachnoid  cisternse;  in  these  the  subarachnoid  tissue  is  less  abundant. 


Otitic  chiasma 


Oisterna  interpeduncu  laris 

Fourth  ventricle 
Cisterna  poniia 


Cisterna 
cerebellomcchdlaris 
Fig.  768. — Diagram  showing  the  positions  of  the  three  principal  subarachnoid  cisternse. 

Subarachnoid  Cisternse  (cistemae  subarachnoidales)  (Fig.  768). — The  cisterna 
cerebellomedullaris  (cisterna  magna)  is  triangular  on"  sagittal  section,  and  results 
from  the  arachnoid  bridging  over  the  interval  between  the  medulla  oblongata 
and  the  under  surfaces  of  the  hemispheres  of  the  cerebellum;  it  is  continuous 
with  the  subarachnoid  cavity  of  the  medulla  spinalis  at  the  level  of  the  foramen 
magnum.  The  cisterna  pontis  is  a  considerable  space  on  the  ventral  aspect  of  the 
pons.  It  contains  the  basilar  artery,  and  is  continuous  behind  with  the  subarach- 
noid cavity  of  the  medulla  spinalis,  and  with  the  cisterna  cerebellomedullaris;  and 
in  front  of  the  pons  with  the  cisterna  interpeduncularis.  The  cisterna  interpeduncu- 
laris  (cisterna  basalis)  is  a  wide  cavity  where  the  arachnoid  extends  across  between 
the  two  temporal  lobes.  It  encloses  the  cerebral  peduncles  and  the  structures 
contained  in  the  interpeduncular  fossa,  and  contains  the  arterial  circle  of  Willis. 
In  front,  the  cisterna  interpeduncularis  extends  forward  across  the  optic  chiasma, 
forming  the  cisterna  chiasmatis,  and  on  to  the  upper  surface  of  the  corpus  callosum, 
for  the  arachnoid  stretches  across  from  one  cerebral  hemisphere  to  the  other  immedi- 
ately beneath  the  free  border  of  the  falx  cerebri,  and  thus  leaves  a  space  in  which 


THE  ARACHNOID 


905 


the  anterior  cerebral  arteries  are  contained.  The  cisterna  fossae  cerebri  lateralis  is 
formed  in  front  of  either  temporal  lobe  by  the  arachnoid  bridging  across  the  lateral 
fissure.  This  cavity  contains  the  middle  cerebral  artery.  The  cisterna  venae 
magnae  cerebri  occupies  the  interval  between  the  splenium  of  the  corpus  callosum 
and  the  superior  surface  of  the  cerebellum;  it  extends  between  the  layers  of  the  tela 
chorioidea  of  the  third  ventricle  and  contains  the  great  cerebral  vein. 

The  subarachnoid  cavity  communicates  with  the  general  ventricular  cavity 
of  the  brain  by  three  openings;  one,  the  foramen  of  Majendie,  is  in  the  middle  line 
at  the  inferior  part  of  the  roof  of  the  fourth  ventricle;  the  other  two  are  at  the 
extremities  of  the  lateral  recesses  of  that  ventricle,  behind  the  upper  roots  of  the 
glossopharyngeal  nerves.  It  is  stated  by  Meckel  that  the  lateral  ventricles  also 
communicate  with  the  subarachnoid  cavity  at  the  apices  of  their  inferior  cornua. 
There  is  no  direct  communication  between  the  subdural  and  subarachnoid  cavities. 


Emissary  tiein 
Venous  lacuna 

\        \        Cerebral  vei 
Diploic  vein         \ 


Sup.  sagittal  sinus 

Arachnoid  granulation 


Meningeal  vein 


Subdural  cavity 
Subarachnoid  cavity 


Dura  mater 
Arachnoid 

Cerebral  cortex 


Pia  mater 


Fig.  769. — Diagrammatic  representation  of  a  section  across  the  top  of  the  skull,  showing  the  membranes  of  the 

brain,  etc.     (Modified  from  Testut.) 

The  spinal  part  of  the  subarachnoid  cavity  is  a  very  wide  interval,  and  is  the 
largest  at  the  lower  part  of  the  vertebral  canal,  where  the  arachnoid  encloses 
the  nerves  which  form  the  cauda  equina.  Above,  it  is  continuous  with  the  cranial 
subarachnoid  cavity;  below,  it  ends  at  the  level  of  the  lower  border  of  the  second 
sacral  vertebra.  It  is  partially  divided  by  a  longitudinal  septum,  the  subarachnoid 
septum,  which  connects  the  arachnoid  with  the  pia  mater  opposite  the  posterior 
median  sulcus  of  the  medulla  spinalis,  and  forms  a  partition,  incomplete  and  cribri- 
form above,  but  more  perfect  in  the  thoracic  region.  The  spinal  subarachnoid 
cavity  is  further  subdivided  by  the  ligamentum  denticulatum,  which  wall  be  described 
with  the  pia  mater. 

The  cerebrospinal  fluid  is  a  clear  limpid  fluid,  having  a  saltish  taste,  and  a  sUghtly  alkaline 
reaction.  According  to  Lassaigne,  it  consists  of  98.5  parts  of  water,  the  remaining  1.5  per  cent, 
being  solid  matters,  animal  and  saUne.  It  varies  in  quantity,  being  most  abundant  in  old  persons, 
and  is  quickly  secreted. 

The  arachnoid  granulations  {granulationes  arachnoideales;  glandulae  Pacchioni; 
arachnoid  villi;  Pacchionian  bodies)    (Fig.  769)  are  small,  fleshy-looking  eleva- 


906 


NEUROLOGY 


tions,  usually  collected  into  clusters  of  variable  size,  which  are  present  upon  the 
outer  surface  of  the  dura  mater,  in  the  vicinity  of  the  superior  sagittal  sinus,  and 
in  some  other  situations.  Upon  laying  open  the  sagittal  sinus  and  the  venous 
lacunse  on  either  side  of  it  granulations  will  be  found  protruding  into  its  interior. 
They  are  not  seen  in  infancy,  and  very  rarely  until  the  third  year.  They  are 
usually  found  after  the  seventh  year;  and  from  this  period  they  increase  in 
number  and  size  as  age  advances.  They  are  not  glandular  in  structure,  but  are 
enlarged  normal  villi  of  the  arachnoid.  As  they  grow  they  push  the  thinned 
dura  mater  before  them,  and  cause  absorption  of  the  bone  from  pressure,  and 
so  produce  the  pits  or  depressions  on  the  inner  wall  of  the  calvarium. 

Structure. — An  arachnoidal  granulation  consists  of  the  following  parts:  (1)  In  the  interior 
is  a  core  of  subarachnoid  tissue,  continuous  with  the  mesh-work  of  the  general  subarachnoid 
tissue  through  a  narrow  pedicle,  by  which  the  granulation  is  attached  to  the  arachnoid.  (2) 
Around  this  tissue  is  a  layer  of  arachnoid  membrane,  limiting  and  enclosing  the  subaraclxnoid 
tissue.  (3)  Outside  this  is  the  thinned  wall  of  the  lacuna,  which  is  separated  from  the  arachnoid 
by  a  space  which  corresponds  to  and  is  continuous  with  the  subdural  cavity.  (4)  And  finally, 
if  the  granulation  projects  into  the  sagittal  sinus,  it  will  be  covered  by  the  greatly  thinned  upper 
waUs  of  the  sinus.  It  will  be  seen,  therefore,  that  fluid  injected  into  the  subarachnoid  cavity  will 
find  its  way  into  these  granulations,  and  it  has  been  found  experimentally  that  it  passes  by  osmosis 
from  the  granulations  into  the  venous  sinuses  into  which  they  project. 


The  Pia  Mater. 

The  pia  mater  is  a  vascular  membrane,  consisting  of  a  minute  plexus  of  blood- 
vessels, held  together  by  an  extremely  fine  areolar  tissue. 

The  cerebral  pia  mater  {yia  mater  enceyhali;  pia  of  the  brain)  invests  the  entire 
surface  of  the  brain,  dips  between  the  cerebral  gyri  and  cerebellar  laminae,  and  is 
invaginated  to  form  the  tela  chorioidea  of  the  third  ventricle,  and  the  choroid 
plexuses  of  the  lateral  and  third  ventricles  (pages  887  and  888) ;  as  it  passes  over 
the  roof  of  the  fourth  ventricle,  it  forms  the  tela  chorioidea  and  the  choroid 
plexuses  of  this  ventricle.  Upon  the  surfaces  of  the  hemispheres,  where  it  covers 
the  gray  substance,  it  gives  oflf  from  its  deep  surface  a  multitude  of  sheaths,  around 
the  minute  vessels,  that  extend  perpendicularly  for  some  distance  into  the  cerebral 
substance.  On  the  cerebellum  the  membrane  is  more  delicate;  the  vessels  from  its 
deep  surface  are  shorter,  and  its  relations  to  the  cortex  are  not  so  intimate. 


Subdural  cavity 


Pia  mater 
Arachnoid 
Dura  mater 


Subdural  cavity 


Fig.  770. — Diagrammatic  transverse  section  of  the  medulla  spinalis  and  its  membranes. 

The  spinal  pia  mater  (pia  mater  spinalis;  pia  of  the  cord)  (Figs.  767,  770)  is 
thicker,  firmer,  and  less  vascular  than  the  cerebral  pia  mater :  this  is  due  to  the  fact 
that  it  consists  of  two  layers,  the  outer  or  additional  one  being  composed  of  bundles 
of  connective-tissue  fibres,  arranged  for  the  most  part  longitudinally.  Between 
the  layers  are  cleft-like  spaces  which  communicate  with  the  subarachnoid  cavity, 
and  a  number  of  bloodvessels  which  are  enclosed  in  perivascular  Ij^mphatic  sheaths. 


THE  CEREBRAL  NERVES  907 

The  spinal  pia  mater  covers  the  entire  surface  of  the  me(killa  spinaHs,  and  is  very 
intimately  adherent  to  it;  in  front  it  sends  a  process  backward  into  the  anterior 
fissure.  A  longitudinal  fibrous  band,  called  the  linea  splendens,  extends  along  the 
middle  line  of  the  anterior  surface;  and  a  somewhat  similar  band,  the  ligamentum 
denticulatum,  is  situated  on  either  side.  Below  the  conus  medullaris,  the  pia  mater 
is  continued  as  a  long,  slender  filament  (filum  terminale),  which  descends  through 
the  centre  of  the  mass  of  nerves  forming  the  cauda  equina.  It  blends  with  the 
dura  mater  at  the  level  of  the  lower  border  of  the  second  sacral  vertebra,  and  extends 
downward  as  far  as  the  base  of  the  coccyx,  where  it  fuses  with  the  periosteum.  It 
assists  in  maintaining  the  medulla  spinalis  in  its  position  during  the  movements 
of  the  trunk,  and  is,  from  this  circumstance,  called  the  central  ligament  of  the 
medulla  spinalis. 

The  pia  mater  forms  sheaths  for  the  cerebral  and  spinal  nerves;  these  sheaths 
are  closely  connected  with  the  nerves,  and  blend  with  their  common  membranous 
investments. 

The  ligamentum  denticulatum  {defitate  ligament)  (Fig.  767)  is  a  narrow  fibrous 
band  situated  on  either  side  of  the  medulla  spinalis  throughout  its  entire  length, 
and  separating  the  anterior  from  the  posterior  nerve  roots.  Its  medial  border  is 
continuous  with  the  pia  mater  at  the  side  of  the  medulla  spinalis.  Its  lateral 
border  presents  a  series  of  triangular  tooth-like  processes,  the  points  of  w^hich  are 
fixed  at  intervals  to  the  dura  mater.  These  processes  are  twenty-one  in  number, 
on  either  side,  the  first  being  attached  to  the  dura  mater,  opposite  the  margin 
of  the  foramen  magnum,  between  the  vertebral  artery  and  the  hypoglossal  nerve; 
and  the  last  near  the  lower  end  of  the  medulla  spinalis. 

Applied  Anatomy. — -Evidence  of  great  value  in  the  diagnosis  of  meningitis  may  sometimes 
be  obtained  by  puncturing  the  spinal  membranes  and  withdrawing  some  of  the  cerebrospinal 
fluid;  moreover,  the  operation  of  lumbar  puncture  is  in  many  cases  curative,  under  the  suppo- 
sition that  the  draining  of  some  of  the  cerebrospinal  fluid  reUeves  the  patient  by  diminishing 
the  intracranial  pressure.  The  operation  is  performed  by  inserting  a  trocar,  of  the  smallest 
size,  between  the  laminae  of  the  third  and  fourth,  or  of  the  fourth  and  fifth  lumbar  vertebrae, 
through  the  ligamentum  flavum.  The  medulla  spinaUs,  even  of  a  child  at  birth,  does  not  reach 
below  the  third  lumbar  vertebra,  and  therefore  the  canal  may  be  punctured  between  the  third 
and  fourth  lumbar  vertebrae  without  any  risk  of  injuring  this  structure.  The  point  of  puncture 
is  indicated  by  laying  the  patient  on  the  side  and  dropping  a  perpendicular  line  from  the  highest 
point  of  the  iliac  crest ;  this  will  cross  the  upper  border  of  the  spinous  process  of  the  f om-th  lumbar 
vertebra,  and  wiU  indicate  the  level  at  which  the  trocar  should  be  inserted  a  little  to  one  side 
of  the  middle  line.  The  punctiire  may  require  to  be  repeated  more  than  once,  and  the  greatest 
precaution  must  be  taken  not  to  allow  septic  infection  of  the  meninges.  If  there  be  any  appre- 
ciable increase  of  pressure,  the  fluid  will  flow  through  the  trocar  with  the  greatest  freedom. 

In  addition  to  the  constitutional  signs  and  symptoms  of  fever,  acute  spinal  meningitis  exhibits 
certain  characteristic  features.  Pain  and  tenderness  to  pressure  along  the  vertebral  column  are 
common,  and  so  are  pains  in  the  hmbs  or  around  the  trunk  from  irritation  of  the  posterior  nerve 
roots  by  the  inflammatory  products.  Irritation  of  the  anterior  nerve  roots  is  shown  by  the 
increased  tone  of  the  muscles,  which  may  go  on  to  the  point  where  they  pass  into  a  state  of  spasm 
with  much  increased  reflexes;  this  is  often  seen  in  the  retraction  of  the  head  and  neck.  Later 
in  the  disease  the  reflexes  are  often  lost,  when,  also,  the  urine  and  feces  may  be  passed  involuntarily. 

THE  CEREBRAL  NERVES  (NERVI  CEREBRALES;  CRANIAL  NERVES). 

There  are  twelve  pairs  of  cerebral  nerves;  they  are  attached  to  the  brain  and 
are  transmitted  through  foramina  in  the  base  of  the  cranium.  The  different  pairs 
are  named  from  before  backward  as  follows : 

1st.    Olfactory.  7th.  Facial. 

2d.     Optic.  8th.  Acoustic. 

3rd.   Oculomotor.  9th.  Glossopharyngeal. 

4th.   Trochlear.  10th.  Vagus. 

5th.   Trigeminal.  11th.  Accessory. 

6th.   Abducent.  12th.  Hypoglossal. 


908 


NEUROLOGY 


The  area  of  attachment  of  a  cerebral  nerve  to  the  surface  of  the  brain  is  termed 
its  superficial  or  apparent  origin.  The  fibres  of  the  nerve  can  be  traced  into  the  sub- 
stance of  the  brain  to  a  special  nucleus  of  gray  substance.  The  motor  or  efferent 
cerebral  nerves  arise  within  the  brain  from  groups  of  nerve  cells  which  constitute 
their  nuclei  of  origin.  The  sensory  or  afferent  cerebral  nerves  arise  from  groups 
of  nerve  cells  outside  the  brain;  these  nerve  cells  may  be  grouped  to  form  ganglia 
on  the  trunks  of  the  nerves  or  may  be  situated  in  peripheral  sensory  organs  such 
as  the  nose  and  eye.  The  central  processes  of  these  cells  run  into  the  brain,  and 
there  end  by  arborizing  around  nerve  cells,  which  are  grouped  to  form  nuclei  of 
termination.  The  nuclei  of  origin  of  the  motor  nerves  and  the  nuclei  of  termination 
of  the  sensory  nerves  are  brought  into  relationship  with  the  cerebral  cortex,  the 
former  through  the  geniculate  fibres  of  the  internal  capsule,  the  latter  through 
the  lemniscus.  The  geniculate  fibres  arise  from  the  cells  of  the  motor  area  of  the 
cortex,  and,  after  crossing  the  middle  line,  end  by  arborizing  around  the  cells  of  the 
nuclei  of  origin  of  the  motor  cerebral  nerves.  On  the  other  hand,  fibres  arise  from 
the  cells  of  the  nuclei  of  termination  of  the  sensory  nerves,  and  after  crossing  to 
the  opposite  side,  join  the  lemniscus,  and  thus  connect  these  nuclei,  directly  or 
indirectly,  with  the  cerebral  cortex. 

THE  OLFACTORY  NERVES   (NN.  OLFACT^RII;  FIRST  NERVE)   (Fig.  771). 

The  olfactory  nerves  or  nerves  of  smell  are  distributed  to  the  mucous  membrane 
of  the  olfactory  region  of  the  nasal  cavity :  this  region  comprises  the  superior  nasal 
concha,  and  the  corresponding  part  of  the  nasal  septum.  The  nerves  originate 
from  the  central  or  deep  processes  of  the  olfactory  cells  of  the  nasal  mucous  mem- 
brane. They  form  a  plexiform  net-work  in  the  mucous  membrane,  and  are  then 
collected  into  about  twenty  branches,  which  pierce  the  cribriform  plate  of  the  eth- 
moid bone  in  two  groups,  a  lateral  and  a  medial  group,  and  end  in  the  glomeruli 


Fibres  of  olfactory 
tract 

Mitral  cells 


1 — .  Glomeruli 


Olfactory  cell 

Olfactory 

epithelium 


mil-.  Olfactory 
\AxUJ    enaiih 


Fig.  771.^Nerves  of  septum  of  nose.     Right  side. 


Fig.  772. — Plan  of  olfactory  neurons 


of  the  olfactor}^  bulb  (Fig.  772).  Each  branch  receives  tubular  sheaths  from  the 
dura  mater  and  pia  mater,  the  former  being  lost  in  the  periosteum  of  the  nose, 
the  latter  in  the  neurolemma  of  the  nerve. 

The  olfactory  nerves  are  non-medullated,  and  consist  of  axis-cylinders  surrounded 
by  nucleated  sheaths,  in  which,  however,  there  are  fewer  nuclei  than  are  found  in 
the  sheaths  of  ordinary  non-medullated  nerve  fibres. 

The  olfactory  centre  in  the  cortex  is  generally  associated  with  the  rhinencephalon 
(page  874). 


THE  OPTIC  NERVE 


909 


Applied  Anatomy. — In  severe  injuries  to  the  head  involving  the  anterior  fossa  of  the  base  of 
the  skull,  tlie  olfactory  bulb  may  become  separated  from  the  olfactory  nerves,  or  the  nerves 
may  be  torn,  thus  producing  loss  of  smell  {anostiiia),  and  with  this  there  is  a  considerable  loss 
in  the  sense  of  taste,  since  much  of  the  perfection  of  the  sense  of  taste  is  due  to  the  substances 
being  also  odorous,  and  simultaneously  exciting  the  sense  of  smell. 

Anosmia  often  occurs  after  influenza  or  other  acute  infection  of  the  nose.  Parosmia,  or  a  per- 
version of  the  sense  of  smell,  may  occur  in  lesions  of  the  cortical  olfactory  centres,  or  in  insanity. 


THE  OPTIC  NERVE  (N.  OPTICUS;  SECOND  NERVE)  (Fig.  773). 


Fig. 


773. — The  left  optic  nerve  and  the 
optic  tracts. 


The  optic  nerve,  or  nerve  of  sight,  is  distributed  exclusively  to  the  bulb  of  the 
eye.    The  nerves  of  opposite  sides  are  connected  together  at  the  optic  chiasma, 
and  from  the  back  of  the  chiasma  the  nerve 
fibres  may  be  traced  to  the  brain,  in  the  optic 
tracts. 

The  optic  tract,  at  its  connection  with  the 
brain,  is  divided  into  two  bands,  lateral  and 
medial.  The  lateral  band  is  larger;  it  is  con- 
nected with  the  lateral  geniculate  body,  the 
pulvinar  of  the  thalamus  and  the  superior  collic- 
ulus.  The  medial  band  ends  in  the  medial  genic- 
ulate body;  its  fibres  are  merely  commissural, 
forming  Gudden's  commissure.  From  these 
attachments  the  tract  winds  obliquely  across 
the  under  surface  of  the  cerebral  peduncle  in 
the  form  of  a  flattened  band,  and  is  attached 
to  the  peduncle  by  its  anterior  margin.  It  then 
assumes  a  cylindrical  form,  and,  as  it  passes  for- 
ward, is  connected  with  the  tuber  cinereum  and 
lamina  terminalis.  It  finally  joins  with  the  tract 
of  the  opposite  side  to  form  the  optic  chiasma. 

The  optic  chiasma  {chiasma  oyticum),  somewhat  quadrilateral  in  form,  rests 
upon  the  tuberculum  sellae  and  on  the  anterior  part  of  the  diaphragma  sellae. 
It  is  in  relation,  above,  with  the  lamina  terminalis;  behind ,  with  the  tuber  cinereum; 
on  either  side,  with  the  anterior  perforated  substance.  Within  the  chiasma,  the 
optic  nerves  undergo  a  partial  decussation.  The  fibres  forming  the  medial  part  of 
each  tract  and  posterior  part  of  the  chiasma  have  no  connection  with  the  optic 
nerves.  They  simply  cross  in  the  chiasma,  and  connect  the  medial  geniculate 
bodies  of  the  two  sides;  they  form  the  commissure  of  Gudden.  The  remaining  and 
principal  part  of  the  chiasma  consists  of  two  sets  of  fibres,  crossed  and  uncrossed. 
The  crossed  fibres  which  are  the  more  numerous,  occupy  the  central  part  of  the 
chiasma,  and  pass  from  the  optic  nerve  of  one  side  to  the  optic  tract  of  the  other, 
decussating  in  the  chiasma  with  similar  fibres  of  the  opposite  optic  nerve.  The 
uncrossed  fibres  occupy  the  lateral  part  of  the  chiasma,  and  pass  from  the  nerve 
of  one  side  into  the  tract  of  the  same  side.^ 

The  great  majority  of  the  fibres  of  the  optic  nerve  (Fig.  774)  consist  of  the 
afferent  fibres  of  nerve  cells  in  the  retina;  a  few,  however,  are  efferent  fibres,  and 
grow  out  from  cells  in  the  brain.  They  become  medullated  about  the  tenth  week 
after  birth.  The  afterent  fibres  end  in  arborizations  around  the  cells  in  the  lateral 
geniculate  body,  pulvinar,  and  superior  colliculus,  which  constitute  the  lower 
visual  centres.  From  the  cells  of  these  centres  fibres  are  prolonged  to  the  cortical 
visual  centre,  situated  in  the  cuneus  and  in  the  neighborhood  of  the  calcarine 
fissure. 


1  A  specimen  of  congenital  absence  of  the  optic  chiasma  is  to  be  found  in  the  Museum  of  the  Westminister  Hospital. 
See  also  Henle,  Nervenlehre,  p.  393,  ed.  2. 


910 


NEUROLOGY 


Some  fibres  are  detached  from  the  optic  tract,  and  pass  through  the  cerebral 
peduncle  to  the  nucleus  of  the  oculomotor  nerve.  These  fibres  are  small,  and 
may  be  regarded  as  afferent  branches  for  the  Sphincter  pupil lae  and  Ciliaris  muscles. 
Other  fibres  pass  to  the  cerebellum  through  the  brachia  conjunctiva,  while  others 
end  in  the  nuclei  in  the  pons. 

The  optic  nerves  arise  from  the  forepart  of  the  chiasma,  and,  diverging  from 
one  another,  each  becomes  rounded  in  form  and  firm  in  texture,  and  is  enclosed  in 
a  sheath  derived  from  the  pia  mater  and  arachnoid.  The  nerve  passes  beneath 
the  anterior  cerebral  artery,  and  enters  the  optic  foramen,  receiving  as  it  does  so 


Optic  nerve 
Crossed  fibres 
Uncrossed  fibres 

Optic  chiasma 

Optic  tract 
Commissure  of  Gudden 


Pidvinar 

Lateral  geniculate  body 
,  Superior  colliculus 
Medial  genicidate  body 

Nucleus  of  Qculomotor  nerve 
Nucleus  of  trochlear  nerve 

Niicleus  of  abducent  nerve 


Fig.  774.- 


Cortex  of  occipital  lobes 
-Scheme  showing  central  connections  of  the  optic  nerves  and  optic  tracts. 


a  sheath  from  the  dura  mater.  When  the  nerve  reaches  the  orbit  this  sheath  divides 
into  two  layers,  one  of  which  becomes  continuous  with  the  periosteum  of  the  orbit ; 
the  other  forms  the  proper  sheath  of  the  nerve,  and  surrounds  it  as  far  as  the  bulb 
of  the  eye.  The  nerve  runs  forward  and  lateralward  through  the  cavity  of  the  orbit, 
pierces  the  sclera  and  choroid  at  the  back  part  of  the  bulb  of  the  eye,  about  3  to  4 
mm.  to  the  nasal  side  of  its  centre,  and  expands  to  form  the  stratum  opticum  of  the 
retina.  A  little  behind  the  bulb  of  the  eye  the  arteria  centralis  retinae  perforates 
the  optic  nerve,  and  runs  along  its  interior  in  a  tubular  canal  of  fibrous  tissue. 
It  supplies  the  retina,  and  is  accompanied  by  corresponding  veins.  The  retina  is 
described  with  the  anatomy  of  the  eyeball. 


THE  OCULOMOTOR  NERVE  911 

Applied  Anatomy. — The  optic  nerve  is  peculiarly  liable  to  become  the  seat  of  neuritis  or  undergo 
atrophy  iu  affection  of  the  central  nervous  system,  and  as  a  rule  the  pathological  relationship 
between  the  two  affections  is  exceedingly  difficult  to  trace.  There  are,  however,  certain  points 
in  connection  with  the  anatomy  of  this  nerve  which  tend  to  throw  light  upon  the  frequent  asso- 
ciation of  these  affections  with  intracranial  disease.  (1)  From  its  mode  of  development,  and  from 
its  structure,  the  optic  nerve  must  be  regarded  as  a  prolongation  of  the  brain  substance,  rather 
than  as  an  ordinary  cerebrospinal  nerve.  (2)  As  it  passes  from  the  brain  it  receives  sheaths 
from  the  three  cerebral  membranes,  a  perineural  sheath  from  the  ])ia  mater,  an  intermediate 
sheath  from  the  arachnoid,  and  an  outer  sheath  from  the  dura  mater,  which  is  also  connected 
with  the  periosteum  as  it  passes  through  the  optic  foramen.  These  sheaths  are  separated  from 
each  other  bj^  cavities  which  communicate  with  the  subdural  and  subarachnoid  cavities  respec- 
tively. The  innermost  or  perinem-al  sheath  sends  a  process  around  the  arteria  centralis  retinae 
into  the  interior  of  the  nerve,  and  enters  intimately  into  its  structm-e.  Thus  inflammatory 
affections  of  the  meninges  or  of  the  brain  may  readily  extend  along  these  spaces,  or  along  the 
interstitial  connective  tissue  in  the  nerve. 

The  com-se  of  the  fibres  in  the  optic  chiasma  has  an  important  pathological  bearing,  and  has 
been  the  subject  of  much  controversy.  Microscopic  examination,  experiments,  and  pathology 
aU  seem  to  point  to  the  fact  that  there  is  a  partial  decussation  of  the  fibres,  each  optic  tract  supply- 
ing the  corresponding  haK  of  each  eye,  so  that  the  right  tract  suppUes  the  right  half  of  each  eye, 
and  the  left  tract  the  left  half  of  each  eye.  At  the  same  time  Charcot  believes,  and  his  \i%w  has 
met  with  general  acceptation,  that  the  fibres  which  do  not  decussate  at  the  optic  chiasma  undergo 
decussation  in  the  corpora  quadrigemina,  so  that  the  lesion  of  the  cerebral  centre  of  one  side 
causes  complete  blindness  of  the  opposite  eye,  because  both  sets  of  decussating  fibres  are  destroyed; 
whereas  if  one  tract,  say  the  right,  be  destroyed  by  disease,  there  will  be  blindness  of  the  right 
half  of  both  retinae. 

An  antero-posterior  section  through  the  chiasma  would  divide  the  decussating  fibres,  and 
would  therefore  produce  blindness  of  the  medial  half  of  each  eye;  while  a  section  at  the  margin 
of  the  side  of  the  optic  chiasma  would  produce  blindness  of  the  lateral  half  of  the  retina  of  the 
same  side.     An  earlj^  symptom  of  tumor  growth  in  the  hypophysis  is  pressure  on  the  chiasma. 

The  optic  nerve  may  also  be  affected  in  injuries  or  diseases  involving  the  orbit;  in  fractures 
of  the  anterior  fossa  of  the  base  of  the  skuU;  in  tumors  of  the  orbit  itself,  or  those  invading  this 
cavity  from  neighboring  parts. 

THE  OCULOMOTOR  NERVE  (N.  OCULOMOTORIUS ;  THIRD  NERVE) 

(Figs.  776,  777,  778). 

The  oculomotor  nerve  supplies  all  the  ocular  muscles,  except  the  Obliquus 
superior  and  Rectus  lateralis;  it  also  supplies  through  its  connections  with  the 
ciliary  ganglion,  the  Sphincter  pupillae  and  the  Ciliaris  muscles. 

The  fibres  of  the  oculomotor  nerve  arise  from  a  nucleus  which  lies  in  the  gray 
substance  of  the  floor  of  the  cerebral  aqueduct  and  extends  in  front  of  the  aqueduct 
for  a  short  distance  into  the  floor  of  the  third  ventricle.  From  this  nucleus  the 
fibres  pass  forward  through  the  tegmentum,  the  red  nucleus,  and  the  medial  part 
of  the  substantia  nigra,  forming  a  series  of  curves  with  a  lateral  convexity,  and 
emerge  from  the  oculomotor  sulcus  on  the  medial  side  of  the  cerebral  peduncle. 

The  nucleus  of  the  oculomotor  nerve  does  not  consist  of  a  continuous  column 
of  cells,  but  is  broken  up  into  a  number  of  smaller  nuclei,  which  are  arranged  in 
two  groups,  anterior  and  posterior.  Those  of  the  posterior  group  are  six  in  number, 
five  of  which  are  symmetrical  on  the  two. sides  of  the  middle  line,  while  the  sixth 
is  centrally  placed  and  is  common  to  the  nerves  of  both  sides.  The  anterior  group 
consists  of  two  nuclei,  an  antero-medial  and  an  antero-lateral  (Fig.  775). 

The  nucleus  of  the  third  nerve  is  said  to  give  fibres  to  the  facial  nerve,  which 
probably  supply  the  Orbicularis  oculi,  Corrugator,  and  Frontalis  muscles.^  It 
is  also  connected  with  the  nuclei  of  the  trochlear  and  abducent  nerves,  with  the 
cerebellum,  the  superior  colliculus,  and  the  cortex  of  the  occipital  lobe  of  the 
cerebrum. 

The  nucleus  of  the  oculomotor  nerve,  considered  from  a  physiological  standpoint, 
can  be  subdivided  into  several  smaller  groups  of  cells,  each  group  controlling  a 

1  See  footnote,  p.  S52. 


912 


NEUROLOGY 


6.- 


5- 


4'_ 


.r  _ 


/' 


^' 


.>^ 


1-;  X 


particular  muscle.  The  nerves  to  the  different  muscles  appear  to  take  their  origin 
from  behind  forward,  as  follows:  Obliquus  inferior,  Rectus  inferior,  Rectus  superior. 
Levator  palpebrae  superioris,  and  Rectus  medialis;  while  from  the  anterior  end  of 
the  nucleus  the  fibres  for  the  Ciliaris  and  the  Sphincter  pupillse  take  their  origin. 

On  emerging  from  the  brain,  the  nerve  is 
invested  with  a  sheath  of  pia  mater,  and 
enclosed  in  a  prolongation  from  the  arachnoid. 
It  passes  between  the  superior  cerebellar  and 
posterior  cerebral  arteries,  and  then  pierces 
the  dura  mater  in  front  of  and  lateral  to  the 
posterior  clinoid  process,  passing  between  the 
free  and  attached  borders  of  the  tentorium 
cerebelli.  It  runs  along  the  lateral  wall  of  the 
cavernous  sinus,  above  the  other  orbital 
nerves,  receiving  in  its  course  one  or  two 
filaments  from  the  cavernous  plexus  of  the 
sympathetic,  and  a  communicating  branch 
from  the  ophthalmic  division  of  the  trigemi- 
nal. It  then  divides  into  two  branches, 
which  enter  the  orbit  through  the  superior 
orbital  fissure,  betw-een  the  two  heads  of  the 
Rectus  lateralis.  Here  the  nerve  is  placed 
below  the  trochlear  nerve  and  the  frontal  and 
lacrimal  branches  of  the  ophthalmic  nerve, 
while  the  nasociliary  nerve  is  placed  between 
its  two  rami. 

The  superior  ramus,  the  smaller,  passes 
medialward  over  the  optic  nerve,  and  sup- 
plies the  Rectus  superior  and  Levator  palpe- 
brae superioris.  The  inferior  ramus,  the  larger, 
divides  into  three  branches.  One  passes  be- 
neath the  optic  nerve  to  the  Rectus  medialis; 
another,  to  the  Rectus  inferior;  the  third  and 
longest  runs  forward  between  the  Recti  inferior  and  lateralis  to  the  Obliquus 
inferior.    From  the  last  a  short  thick  branch  is  given  off  to  the  lower  part  of  the 


e 

-f-: 

l— - 

..r 

mw       ^  9 

[) 

Fig.  775. — Figure  showing  the  different  groups 
of  cells,  which  constitute,  according  to  Perlia, 
the  nucleus  of  origin  of  the  oculomotor  nerve. 
(Testut.)  1.  Posterior  dorsal  nucleus.  1'.  Pos- 
terior ventral  nucleus.  2.  Anterior  dorsal  nucleus. 
2'.  Anterior  ventral  nucleus.  3.  Central  nucleus. 
4.  Nucleus  of  Edinger  and  Westphal.  5.  Antero- 
internal  nucleus.  6.  Antero-external  nucleus.  8. 
Crossed  fibres.  9.  Trochlear  nerve,  with  9',  its 
nucleus  of  origin,  and  9",  its  decussation.  10. 
Third  ventricle.     M,  M.  Median  line. 


LEVATOR  PALPEBR/E 


RECTUS  SUPERIOR 


Short  ciliary 

RECTUS  MEDIALIS 
RECTUS  INFERIOR 
OBLIQUUS  INFERIOR 


Fig.   776 — Plan  of  oculomotor  nerve. 


ciliary  ganglion,  and  forms  its  short  root.  All  these  branches  enter  the  muscles  on 
their  ocular  surfaces,  with  the  exception  of  the  nerve  to  the  Obliquus  inferior 
which  enters  the  muscle  at  its  posterior  border. 


THE  TROCHLEAR  NERVE 


913 


Applied  Anatomy. — -Paralysis  of  the  oculomotor  nerve  may  be  the  result  of  many  causes, 
such  as  cerebral  disease;  or  conditions  causing  pressure  on  the  cavernous  sinus;  or  periostitis  of 
the  bones  entering  into  the  formation  of  the  superior  orbital  fissure.  It  results,  when  complete, 
in  (1)  ptosis,  or  drooping  of  the  upper  eyelid,  in  consequence  of  the  Levator  palpebrae  superioris 
being  paralyzed;  (2)  external  strabismus,  on  account  of  the  unopposed  action  of  the  Rectus 
lateralis  and  Obliquus  superior,  which  are  not  supplied  by  the  oculomotor  nerve  and  are  there- 
fore not  paralyzed;  (3)  dilatation  of  the  pupil,  because  the  Sphincter  pupillae  is  paralyzed;  (4) 
loss  of  power  of  acconnnodation  and  of  contraction  on  exposm-e  to  light,  as  the  Sphincter  pupillae 
and  the  Ciliaris  are  paralyzed;  (5)  shght  prominence  of  the  eyeball,  owing  to  most  of  its  muscles 
being  relaxed;  and  (6)  the  patient  will  complain  of  the  resulting  diplopia,  or  double  vision,  the 
false  image  being  higher  than  the  true,  and  the  separation  of  the  two  images  increasing  with 
medial  movements.  Occasionally  paralysis  may  affect  only  a  part  of  the  nerve — that  is  to  say, 
there  may  be,  for  example,  a  dilated  and  fixed  pupil,  with  ptosis,  but  no  other  signs.  Irritation 
of  the  nerve  causes  spasm  of  one  or  other  of  the  muscles  supplied  by  it;  thus,  there  may  be  internal 
strabismus  from  spasm  of  the  Rectus  medialis;  accommodation  for  near  objects  only,  from  spasm 
of  the  Ciharis;  or  miosis  (contraction  of  the  pupil)  from  irritation  of  the  Sphincter  pupillae. 

The  oculomotor  nerve  is  particularly  liable  to  become  involved  in  a  syphilitic  periarteritis 
as  it  leaves  the  base  of  the  brain,  when  passing  between  the  posterior  cerebral  and  superior  cere- 
bellar arteries;  associated  with  locomotor  ataxia  various  partial  or  complete  paralyses  of  the 
nerve  are  often  seen. 


THE  TROCHLEAR  NERVE  (N.  TROCHLEARIS;  FOURTH  NERVE)  (Fig.  777). 

The  trochlear  nerve,  the  smallest  of  the  cerebral  nerves,  supplies  the  Obhquus 
superior  oculi. 

It  arises  from  a  nucleus  situated  in  the 
floor  of  the  cerebral  aqueduct,  opposite 
the  upper  part  of  the  inferior  coUiculus. 
From  its  origin  it  runs  downward  through 
the  tegmentum,  and  then  turns  backward 
into  the  upper  part  of  the  anterior  medul- 
lary velum.  Here  it  decussates  with  its 
fellow  of  the  opposite  side  and  emerges 
from  the  surface  of  the  velum  at  the  side 
of  the  frenulum  veli,  immediately  behind 
the  inferior  colliculus. 

The  nerve  is  directed  across  the  brach- 
ium  conjunctiva  cerebelli,  and  then  winds 
forward  around  the  cerebral  peduncle, 
immediately  above  the  pons,  pierces  the 
dura  mater  in  the  free  border  of  the  ten- 
torium cerebelli,  just  behind,  and  lateral 
to,  the  posterior  clinoid  process,  and 
passes  forward  in  the  lateral  wall  of  the 
cavernous  sinus,  between  the  oculomotor 
nerve  and  the  ophthalmic  division  of  the 
trigeminal.  It  crosses  the  oculomotor 
nerve,  and  enters  the  orbit  through  the 
superior  orbital  fissure.  It  now  becomes 
the  highest  of  all  the  nerves,  and  lies 
medial  to  the  frontal  nerve.  In  the  orbit 
it  passes  medialward,  above  the  origin  of 
the  Levator  palpebrae  superioris,  and 
finally  enters  the  orbital  surface  of  the 
Obliquus  superior. 

In  the  lateral  wall  of  the  cavernous  sinus  the  trochlear  nerve  forms  communica- 
tions with  the  ophthalmic  division  of  the  trigeminal  and  with  the  cavernous  plexus 
58 


Motor  root 
Sensory  root' 


Recurrent 
filament  to 
dura  mater 


Fig.  777. — Nerves  of  the  orbit.     Seen  from  above. 


914  NEUROLOGY 

of  the  sympathetic.  In  the  superior  orbital  fissure  it  occasionally  gives  off  a 
branch  to  the  lacrimal  nerve.  It  gives  off  a  recurrent  branch  which  passes  back- 
ward between  the  layers  of  the  tentorium  cerebelli  and  divides  into  two  or  three 
filaments  which  may  be  traced  as  far  as  the  wall  of  the  transverse  sinus. 

Applied  Anatomy. — When  the  trochlear  nerve  is  paralyzed  there  is  loss  of  function  in  the 
Obhquus  superior,  so  that  the  patient  is  unable  to  turn  his  eye  downward  and  outward.  Should 
the  patient  attempt  to  do  this,  the  eye  of  the  affected  side  is  rotated  inward,  producing  diplopia 
or  double  vision.  Single  vision  exists  in  the  whole  of  the  field  so  long  as  the  eyes  look  above  the 
horizontal  plane,  but  diplopia  occurs  on  looking  downward.  To  counteract  this  the  patient  holds 
his  head  forward,  and  also  inchnes  it  to  the  sound  side. 

THE  TRIGEMINAL  NERVE   (N.  TRIGEMINUS;  FIFTH  OR  TRIFACIAL 

NERVE). 

The  trigeminal  nerve  is  the  largest  cerebral  nerve  and  is  the  great  sensory  nerve 
of  the  head  and  face,  and  the  motor  nerve  of  the  muscles  of  mastication. 

It  emerges  from  the  side  of  the  pons,  near  its  upper  border,  by  a  small  motor 
and  a  large  sensory  root — the  former  being  situated  in  front  of  and  medial  to  the 
latter. 

Motor  Root. — The  fibres  of  the  motor  root  arise  from  two  nuclei,  a  superior  and 
an  inferior.  The  superior  nucleus  consists  of  a  strand  of  cells  occupying  the  whole 
length  of  the  lateral  portion  of  the  gray  substance  of  the  cerebral  aqueduct.  The 
inferior  or  chief  nucleus  is  situated  in  the  upper  part  of  the  pons,  close  to  its  dorsal 
surface,  and  along  the  line  of  the  lateral  margin  of  the  rhomboid  fossa.  The  fibres 
from  the  superior  nucleus  constitute  the  mesencephalic  root :  they  descend  through 
the  mesencephalon,  and,  entering  the  pons,  join  with  the  fibres  from  the  lower 
nucleus,  and  the  motor  root,  thus  formed,  passes  forward  through  the  pons  to  its 
point  of  emergence. 

Sensory  Root. — The  fibres  of  the  sensory  root  arise  from  the  cells  of  the  semilunar 
ganglion  which  lies  in  a  cavity  of  the  dura  mater  near  the  apex  of  the  petrous  part 
of  the  temporal  bone.  They  pass  backward  below  the  superior  petrosal  sinus 
and  tentorium  cerebelli,  and,  entering  the  pons,  divide  into  upper  and  lower  roots. 
The  upper  root  ends  partly  in  a  nucleus  which  is  situated  in  the  pons  lateral  to  the 
lower  motor  nucleus,  and  partly  in  the  locus  caeruleus;  the  lower  root  descends 
through  the  pons  and  medulla  oblongata,  and  ends  in  the  upper  part  of  the  sub- 
stantia gelatinosa  of  Rolando.  This  lower  root  is  sometimes  named  the  spinal 
root  of  the  nerve.  Medullation  of  the  fibres  of  the  sensory  root  begins  about  the 
fifth  month  of  fetal  life,  but  the  whole  of  its  fibres  are  not  medullated  until  the 
third  month  after  birth. 

The  semilunar  ganglion  (ganglion semilunare  [Gasseri];  Gasserian  ganglion)  occu- 
pies a  cavity  (cavum  Meckelii)  in  the  dura  mater  covering  the  trigeminal  impression 
near  the  apex  of  the  petrous  part  of  the  temporal  bone.  It  is  somewhat  crescentic  in 
shape,  with  its  convexity  directed  forward :  medially,  it  is  in  relation  with  the  inter- 
nal carotid  artery  and  the  posterior  part  of  the  cavernous  sinus.  The  motor  root 
runs  in  front  of  and  medial  to  the  sensory  root,  and  passes  beneath  the  ganglion; 
it  leaves  the  skull  through  the  foramen  ovale,  and,  immediately  below  this 
foramen,  joins  the  mandibular  nerve.  The  greater  superficial  petrosal  nerve  lies 
also  underneath  the  ganglion. 

The  ganglion  receives,  on  its  medial  side,  filaments  from  the  carotid  plexus 
of  the  sympathetic.  It  give  oft'  minute  branches  to  the  tentorium  cerebelli,  and  to 
the  dura  mater  in  the  middle  fossa  of  the  cranium.  From  its  convex  border,  which 
is  directed  forward  and  lateralward,  three  large  nerves  proceed,  viz.,  the  ophthalmic, 
maxillary,  and  mandibular.  The  ophthalmic  and  maxillary  consist  exclusively 
of  sensory  fibres;  the  mandibular  is  joined  outside  the  cranium  by  the  motor  root. 


77/A'  TRIGEMINAL  NERVE 


915 


Associated  with  the  three  (Ii\isioiis  of  the  tri<;'eniiiuil  nerve  are  four  small  ganglia. 
The  ciliary  ganglion  is  connected  with  the  o])htlialmic  nerve;  the  sphenopalatine 
ganglion  with  the  maxillary  nerve;  and  the  otic  and  submaxillary  ganglia  with  the 
mandibular  nerve.  All  four  receive  sensory  filaments  from  the  trigeminal,  and 
motor  and  sym])athetic  filaments  from  various  sources;  these  filaments  are  called 
the  roots  of  the  ganglia. 

The  ophthalmic  nerve  (?;.  ophthalmicAis)  (Figs.  777,  778),  or  first  division  of  the 
trigeminal,  is  a  sensory  nerve.  It  supplies  branches  to  the  cornea,  ciliary  body, 
and  iris;  to  the  lacrimal  gland  and  conjunctiva;  to  the  part  of  the  mucous  membrane 
of  the  nasal  cavity;  and  to  the  skin  of  the  eyelids,  eyebrow,  forehead,  and  nose. 
It  is  the  smallest  of  the  three  divisions  of  the  trigeminal,  and  arises  from  the  upper 
part  of  the  semilunar  ganglion  as  a  short,  flattened  band,  about  2.5  cm.  long, 
which  passes  forward  along  the  lateral  wall  of  the  cavernous  sinus,  below  the 
oculomotor  and  trochlear  nerves;  just  before  entering  the  orbit,  through  the  supe- 
rior orbital  fissure,  it  divides  into  three  branches,  lacrimal,  frontal,  and  nasociliary. 


Internal  carotid  artery     Upper  division  of 
and  carotid  plexus         oculomotor  nerve 


Fig.  778. — Nerves  of  the  orbit,   and  the  ciliary  ganghon.     Side  view. 


The  ophthalmic  nerve  is  joined  by  filaments  from  the  cavernous  plexus  of  the 
sympathetic,  and  communicates  with  the  oculomotor,  trochlear,  and  abducent 
nerves;  it  gives  off  a  recurrent  filament  which  passes  between  the  layers  of  the 
tentorium. 

The  Lacrimal  Nerve  {n.  lacrimalis)  is  the  smallest  of  the  three  branches  of  the 
ophthalmic.  It  sometimes  receives  a  filament  from  the  trochlear  nerve,  but  this 
is  possibly  derived  from  the  branch  which  goes  from  the  ophthalmic  to  the  troch- 
lear nerve.  It  passes  forward  in  a  separate  tube  of  dura  mater,  and  enters  the  orbit 
through  the  narrowest  part  of  the  superior  orbital  fissure.  In  the  orbit  it  runs 
along  the  upper  border  of  the  Rectus  lateralis,  with  the  lacrimal  artery,  and  com- 
municates with  the  zygomatic  branch  of  the  maxillary  nerve.  It  enters  the  lacrimal 
gland  and  gives  oflF  several  filaments,  which  supply  the  gland  and  the  conjunctiva. 
Finally  it  pierces  the  orbital  septum,  and  ends  in  the  skin  of  the  upper  eyelid, 
joining  with  filaments  of  the  facial  nerve.  The  lacrimal  nerve  is  occasionally 
absent,  and  its  place  is  then  taken  by  the  zygomaticotemporal  branch  of  the  max- 
illary. Sometimes  the  latter  branch  is  absent,  and  a  continuation  of  the  lacrimal 
is  substituted  for  it. 


916  NEUROLOGY 

The  Frontal  Nerve  {n.  frontalis)  is  the  largest  branch  of  the  ophthalmic,  and  may 
be  regarded,  both  from  its  size  and  direction,  as  the  continuation  of  the  nerve. 
It  enters  the  orbit  through  the  superior  orbital  fissure,  and  runs  forward  between 
the  Levator  palpebrae  superioris  and  the  periosteum.  Midway  between  the  apex 
and  base  of  the  orbit  it  divides  into  two  branches,  supratrochlear  and  supraorbital. 

The  supratrochlear  nerve  {n.  supratrochharis) ,  the  smaller  of  the  two,  passes 
above  the  pullej^  of  the  Obliquus  superior,  and  gives  off  a  descending  filament,  to 
join  the  infratrochlear  branch  of  the  nasociliarj^  nerve.  It  then  escapes  from  the 
orbit  between  the  pulley  of  the  Obliquus  superior  and  the  supraorbital  foramen, 
curves  up  on  to  the  forehead  close  to  the  bone,  ascends  beneath  the  Corrugator 
and  Frontalis,  and  dividing  into  branches  which  pierce  these  muscles,  it  supplies 
the  skin  of  the  lower  part  of  the  forehead  close  to  the  middle  line  and  sends 
filaments  to  the  conjunctiva  and  skin  of  the  upper  eyelid. 

The  supraorbital  nerve  (n.  supraorhitalis)  passes  through  the  supraorbital  foramen, 
and  gives  off,  in  this  situation,  palpebral  filaments  to  the  upper  eyelid.  It  then 
ascends  upon  the  forehead,  and  ends  in  two  branches,  a  medial  and  a  lateral, 
which  supply  the  integument  of  the  scalp,  reaching  nearly  as  far  back  as  the  lamb- 
doidal  suture;  they  are  at  first  situated  beneath  the  Frontalis,  the  medial  branch 
perforating  the  muscle,  the  lateral  branch  the  galea  aponeurotica.  Both  branches 
supply  small  twigs  to  the  pericranium. 

The  Nasociliary  Nerve  {n.  nasociliaris;  nasal  nerve)  is  intermediate  in  size  between 
the  frontal  and  lacrimal,  and  is  more  deeply  placed.  It  enters  the  orbit  between 
the  two  heads  of  the  Rectus  lateralis,  and  betw^een  the  superior  and  inferior  rami 
of  the  oculomotor  nerve.  It  passes  across  the  optic  nerve  and  runs  obliquely 
beneath  the  Rectus  superior  and  Obliquus  superior,  to  the  medial  wall  of  the  orbital 
cavity.  Here  it  passes  through  the  anterior  ethmoidal  foramen,  and,  entering 
the  cavity  of  the  cranium,  traverses  a  shallow  groove  on  the  lateral  margin  of  the 
front  part  of  the  cribriform  plate  of  the  ethmoid  bone,  and  runs  down,  through 
a  slit  at  the  side  of  the  crista  galli,  into  the  nasal  cavity.  It  supplies  internal 
nasal  branches  to  the  mucous  membrane  of  the  front  part  of  the  septum  and  lateral 
w^all  of  the  nasal  cavity.  Finally,  it  emerges,  as  the  external  nasal  branch,  between 
the  lower  border  of  the  nasal  bone  and  the  lateral  nasal  cartilage,  and,  passing 
down  beneath  the  Nasalis  muscle,  supplies  the  skin  of  the  ala  and  apex  of  the  nose. 

The  nasociliary  nerve  gives  off  the  following  branches,  viz. :  the  long  root  of  the 
ciliary  ganglion,  the  long  ciliary,  and  the  ethmoidal  nerves. 

The  long  root  of  the  ciliary  ganglion  {radix  longa  ganglii  ciliaris)  usually  arises 
from  the  nasociliary  between  the  two  heads  of  the  Rectus  lateralis.  It  passes 
forward  on  the  lateral  side  of  the  optic  nerve,  and  enters  the  postero-superior  angle 
of  the  ciliary  ganglion;  it  is  sometimes  joined  by  a  filament  from  the  cavernous 
plexus  of  the  sympathetic,  or  from  the  superior  ramus  of  the  trochlear  nerve. 

The  long  ciliary  nerves  (nn.  ciliares  longi),  two  or  three  in  number,  are  given  off 
from  the  nasociliary,  as  it  crosses  the  optic  nerve.  They  accompany  the  short 
ciliary  nerves  from  the  ciliary  ganglion,  pierce  the  posterior  part  of  the  sclera, 
and  running  forward  between  it  and  the  choroid,  are  distributed  to  the  Ciliaris 
muscle,  iris,  and  cornea. 

The  infratrochlear  nerve  (n.  infratrocJilearis)  is  given  off  from  the  nasociliary 
just  before  it  enters  the  anterior  ethmoidal  foramen.  It  runs  forward  along  the 
upper  border  of  the  Rectus  medialis,  and  is  joined,  near  the  pulley  of  the  Obliquus 
superior,  by  a  filament  from  the  supratrochlear  nerve.  It  then  passes  to  the 
medial  angle  of  the  eye,  and  supplies  the  skin  of  the  eyelids  and  side  of  the  nose, 
the  conjunctiva,  lacrimal  sac,  and  caruncula  lacrimalis. 

The  ethmoidal  branches  {nn.  ethmoidales)  supply  the  ethmoidal  cells;  the  posterior 
branch  leaves  the  orbital  cavity  through  the  posterior  ethmoidal  foramen  and  gives 
some  filaments  to  the  sphenoidal  sinus. 


THE  TRIGEMINAL  NERVE  917 

The  Ciliary  Ganglion  (gdiu/lion  cillare;  ojihtluthtilc  or  lenticular  gamjlion)  (Figs. 
776,  77S). — The  ciliary  ganglion  is  a  small,  quadrangular,  flattened  ganglion,  of  a 
reddish-gray  color,  and  about  the  size  of  a  pin's  head;  it  is  situated  at  the  back 
part  of  the  orbit,  in  some  loose  fat  between  the  optic  nerve  and  the  Rectus  lateralis 
muscle,  lying  generall}'  on  the  lateral  side  of  the  ophthalmic  artery. 

Its  roots  are  three  in  number,  and  enter  its  posterior  border.  One,  the  long 
or  sensory  root,  is  derived  from  the  nasociliary  nerve,  and  joins  its  postero-superior 
angle.  The  second,  the  short  or  motor  root,  is  a  thick  nerve  (occasionally  divided 
into  two  parts)  derived  from  the  branch  of  the  oculomotor  nerve  to  the  Obliquus 
inferior,  and  connected  with  the  postero-inferior  angle  of  the  ganglion.  The  third, 
the  sympathetic  root,  is  a  slender  filament  from  the  cavernous  plexus  of  the  sym- 
pathetic; it  is  frequently  blended  with  the  long  root.  According  to  Tiedemann, 
the  ciliary  ganglion  receives  a  twig  of  communication  from  the  sphenopalatine 
ganglion. 

Its  branches  are  the  short  ciliary  nerves.  These  are  delicate  jfilaments,  from  six 
to  ten  in  number,  which  arise  from  the  forepart  of  the  ganglion  in  two  bundles 
connected  with  its  superior  and  inferior  angles;  the  Tower  bundle  is  the  larger. 
They  run  forward  with  the  ciliary  arteries  in  a  wavy  course,  one  set  above  and  the 
other  below  the  optic  nerve,  and  are  accompanied  by  the  long  ciliary  nerves  from 
the  nasociliary.  They  pierce  the  sclera  at  the  back  part  of  the  bulb  of  the  eye,  pass 
forward  in  delicate  grooves  on  the  inner  surface  of  the  sclera,  and  are  distributed 
to  the  Ciliaris  muscle,  iris,  and  cornea.  Tiedemann  has  described  a  small  branch 
as  penetrating  the  optic  nerve  with  the  arteria  centralis  retinae. 

The  maxillary  nerve  {n.  maxillaris;  superior  maxillary  nerve)  (Fig.  779),  or 
second  division  of  the  trigeminal,  is  a  sensory  nerve.  It  is  intermediate,  both  in 
position  and  size,  between  the  ophthalmic  and  mandibular.  It  begins  at  the  middle 
of  the  semilunar  ganglion  as  a  flattened  plexiform  band,  and,  passing  horizontally 
forward,  it  leaves  the  skull  through  the  foramen  rotundum,  where  it  becomes  more 
cylindrical  in  form,  and  firmer  in  texture.  It  then  crosses  the  pterygopalatine 
fossa,  inclines  lateralward  on  the  back  of  the  maxilla,  and  enters  the  orbit  through 
the  inferior  orbital  fissure;  it  traverses  the  infraorbital  groove  and  canal  in  the 
floor  of  the  orbit,  and  appears  upon  the  face  at  the  infraorbital  foramen. '^  At 
its  termination,  the  nerve  lies  beneath  the  Quadratus  labii  superioris,  and  divides 
into  a  leash  of  branches  which  spread  out  upon  the  side  of  the  nose,  the  lower 
eyelid,  and  the  upper  lip,  joining  with  filaments  of  the  facial  nerve. 

Branches. — Its  branches  may  be  divided  into  four  groups,  according  as  they  are 
given  off  in  the  cranium,  in  the  pterygopalatine  fossa,  in  the  infraorbital  canal,  or 
on  the  face. 

In  the  Cranium Middle  meningeal. 

[  Zygomatic. 
In  the  Pterygopalatine  Fossa      .      <  Sphenopalatine. 

{ Posterior  superior  alveolar. 

T    ^1     T  J        1  •.   1  /-(       1  ( Anterior  superior  alveolar. 

In  the  Intraorbital  Canal     .        .     i  tv/t-jji  •       ^       i 

I  Middle  superior  alveolar. 

f  Inferior  palpebral. 

On  the  Face <^  External  nasal. 

[  Superior  labial. 

The  Middle  Meningeal  Nerve  (w.  menijigeus  medius;  meningeal  or  dural  branch)  is 
given  off  from  the  maxillary  nerve  directly  after  its  origin  from  the  semilunar 
ganglion;  it  accompanies  the  middle  meningeal  artery  and  supplies  the  dura  mater. 

The  Zygomatic  Nerve  {n.  zygomaticus;  temporomalar  nerve;  orbital  nerve)  arises 
in  the  pterygopalatine  fossa,   enters  the  orbit  by  the  inferior  orbital  fissure, 

*  After  it  enters  the  infraorbital  canal,  the  nerve  is  frequently  called  the  infraorbital. 


918 


NEUROLOGY 


and  divides  at  the  back  of  that  cavity  into  two  branches,  zygomaticotemporal  and 
zygomaticofacial. 

The  zygomaticotemporal  branch  (raiNVs  zygoviaticotemyorcdw;  temyoral  branch) 
runs  along  the  lateral  wall  of  the  orbit  in  a  groove  in  the  zygomatic  bone,  receives 
a  branch  of  comm.unication  from  the  lacrimal,  and,  passing  through  a  foramen 
in  the  zygomatic  bone,  enters  the  temporal  fossa.  It  ascends  between  the  bone, 
and  substance  of  the  Temporalis  muscle,  pierces  the  temporal  fascia  about  2.5  cm. 
above  the  zygomatic  arch,  and  is  distributed  to  the  skin  of  the  side  of  the  fore- 
head, and  communicates  with  the  facial  nerve  and  with. the  auriculotemporal 
branch  of  the  mandibular  nerve.  As  it  pierces  the  temporal  fascia,  it  gives  off  a 
slender  twig,  which  runs  between  the  two  laj^ers  of  the  fascia  to  the  lateral  angle 
of  the  orbit. 


Sensory  root 
Motor  root 


A  uriculotemporcd 
nerve 


Fig.  779. — Distribution  of  the  maxillary  and  mandibular  nerves,  and  the  submaxillary  ganghon. 

The  zygomaticofacial  branch  (ramus  zycjomaiicofacialis;  malar  branch)  passes 
along  the  infero-lateral  angle  of  the  orbit,  emerges  upon  the  face  through  a  foramen 
in  the  zygomatic  bone,  and,  perforating  the  Orbicularis  oculi,  supplies  the  skin  on 
the  prominence  of  the  cheek.  It  joins  with  the  facial  nerve  and  wdth  the  inferior 
palpebral  branches  of  the  maxillary. 

The  Sphenopalatine  Branches  {nn.  sphenopalatini) ,  two  in  number,  descend  to  the 
sphenopalatine  ganglion. 

The  Posterior  Superior  Alveolar  Branches  {rami  alveolares  superiores  posteriores; 
-posterior  sup)erior  dental  branches)  arise  from  the  trunk  of  the  nerve  just  before 
it  enters  the  infraorbital  groove;  they  are  generally  two  in  number,  but  sometimes 
arise  by  a  single  trunk.    They  descend  on  the  tuberosity  of  the  maxilla  and  give  off 


THE  TRIGEMINAL  NERVE  919 

several  twigs  to  the  gums  and  neighboring  parts  of  the  mucous  membrane  of  the 
cheek.  They  then  enter  the  posterior  alveolar  canals  on  the  infratemporal  surface 
of  the  maxilla,  and,  passing  from  behind  forward  in  the  substance  of  the  bone, 
communicate  with  the  middle  superior  alveolar  nerve,  and  give  ofi'  branches  to  the 
lining  membrane  of  the  maxillary  sinus  and  three  twigs  to  each  molar  tooth;  these 
twigs  enter  the  foramina  at  the  apices  of  the  roots  of  the  teeth. 

The  Middle  Superior  Alveolar  Branch  (ramus  aheolaris  superior  medius;  middle 
superior  dental  branch),  is  given  off  from  the  nerve  in  the  posterior  part  of  the  infra- 
orbital canal,  and  runs  downward  and  forward  in  a  canal  in  the  lateral  wall  of  the 
maxillary  sinus  to  supply  the  two  premolar  teeth.  It  forms  a  superior  dental  plexus 
with  the  anterior  and  posterior  superior  alveolar  branches. 

The  Anterior  Superior  Alveolar  Branch  (ramus  aheolaris  superior  anteriores;  ante- 
rior superior  dental  branch),  of  considerable  size,  is  given  off  from  the  nerve  just 
before  its  exit  from  the  infraorbital  foramen;  it  descends  in  a  canal  in  the  anterior 
wall  of  the  maxillary  sinus,  and  divides  into  branches  which  supply  the  incisor 
and  canine  teeth.  It  communicates  with  the  middle  superior  alveolar  branch, 
and  gives  off  a  nasal  branch,  which  passes  through  a  minute  canal  in  the  lateral  wall 
of  the  inferior  meatus,  and  supplies  the  mucous  membrane  of  the  anterior  part  of 
the  inferior  meatus  and  the  floor  of  the  nasal  cavity,  communicating  with  the  nasal 
branches  from  the  sphenopalatine  ganglion. 

The  Inferior  Palpebral  Branches  (rami  palpebrales;  inferiores  palpebral  branches) 
ascend  behind  the  Orbicularis  oculi.  They  supply  the  skin  and  conjunctiva  of  the 
lower  eyelid,  joining  at  the  lateral  angle  of  the  orbit  with  the  facial  and  zygomatico- 
facial nerves. 

The  External  Nasal  Branches  (rami  nasales  externi)  supply  the  skin  of  the  side 
of  the  nose  and  of  the  septum  mobile  nasi,  and  join  with  the  terminal  twigs  of  the 
nasociliary  nerve. 

The  Superior  Labial  Branches  (rami  labiales superior es;  labial  branches) ,  ihelargest 
and  most  numerous,  descend  behind  the  Quadratus  labii  superioris,  and  are  dis- 
tributed to  the  skin  of  the  upper  lip,  the  mucous  membrane  of  the  mouth,  and  labial 
glands.  They  are  joined,  immediately  beneath  the  orbit,  by  filaments  from  the 
facial  nerve,  forming  with  them  the  infraorbital  plexus. 

Sphenopalatine  Ganglion  (ganglion  sphenopalatinum;  ganglion  of  Meckel)  (Fig. 
780). — ^The  sphenopalatine  ganglion,  the  largest  of  the  ganglia  associated  with 
the  branches  of  the  trigeminal  nerve,  is  deeply  placed  in  the  pterygopalatine  fossa, 
close  to  the  sphenopalatine  foramen.  It  is  triangular  or  heart-shaped,  of  a  reddish- 
gray  color,  and  is  situated  just  below  the  maxillary  nerve  as  it  crosses  the  fossa. 
It  receives  a  sensory,  a  motor,  and  a  sympathetic  root. 

Its  sensory  root  is  derived  from  two  sphenopalatine  branches  of  the  maxillary 
nerve;  their  fibres,  for  the  most  part,  pass  directly  into  the  palatine  nerves;  a  few, 
however,  enter  the  ganglion,  constituting  its  sensory  root.  Its  motor  root  is  probably 
derived  from  the  facial  nerve  through  the  greater  superficial  petrosal  nerve  and 
its  sympathetic  root  from  the  carotid  plexus  through  the  deep  petrosal  nerve. 
These  two  nerves  join  to  form  the  nerve  of  the  pterygoid  canal,  before  their 
entrance  into  the  ganglion. 

The  greater  superficial  petrosal  nerve  (n.  petrosus  superficialis  major;  large  super- 
ficial petrosal  nerve)  is  given  oft'  from  the  genicular  ganglion  of  the  facial  nerve;  it 
passes  through  the  hiatus  of  the  facial  canal,  enters  the  cranial  cavity,  and  runs 
forward  beneath  the  dura  mater  in  a  groove  on  the  anterior  surface  of  the  petrous 
portion  of  the  temporal  bone.  It  then  enters  the  cartilaginous  substance  which 
fills  the  foramen  lacerum,  and  joining  with  the  deep  petrosal  branch  forms  the 
nerve  of  the  pterygoid  canal. 

The  deep  petrosal  nerve  (n.  petrosus  profundus;  large  deep  petrosal  nerve)  is  given 
off  from  the  carotid  plexus,  and  runs  through  the  carotid  canal  lateral  to  the  internal 


920 


NEUROLOGY 


carotid  artery.  It  then  enters  the  cartilaginous  substance  which  fills  the  foramen 
lacerum,  and  joins  with  the  greater  superficial  petrosal  nerve  to  form  the  nerve 
of  the  pterygoid  canal. 

The  nerve  of  the  pterygoid  canal  (?i.  ccmalis  pterygoidei  [Vidii];  Vidian  nerve), 
formed  by  the  junction  of  the  two  preceding  nerves  in  the  cartilaginous  substance 
which  fills  the  foramen  lacerum,  passes  forward,  through  the  pterygoid  canal,  with 
the  corresponding  artery,  and  is  joined  by  a  small  ascending  sphenoidal  branch 
from  the  otic  ganglion.  Finally,  it  enters  the  pterygopalatine  fossa,  and  joins 
the  posterior  angle  of  the  pterygopalatine  ganglion. 


Termination  of       \    -ff, 
nasopalatine 
nerve 


Fig.  780. — The  sphenopalatine  ganglion  and  its  branches. 


Branches  of  Distribution. — These  are  divisible  into  four  groups,  viz.,  orbital, 
palatine,  posterior,  superior  nasal,  and  pharyngeal. 

The  orbital  branches  (rcuni  orbitales;  ascending  branches)  are  two  or  three  delicate 
filaments,  wdiich  enter  the  orbit  by  the  inferior  orbital  fissure,  and  supply  the  peri- 
osteum. According  to  Luschka,  some  filaments  pass  through  foramina  in  the  fronto- 
ethmoidal  suture  to  supply  the  mucous  membrane  of  the  posterior  ethmoidal  and 
sphenoidal  sinuses. 

The  palatine  nerves  {nn.  jjalatini;  descending  branches)  are  distributed  to  the  roof 
of  the  mouth,  soft  palate,  tonsil,  and  lining  membrane  of  the  nasal  cavity.  Most 
of  their  fibres  are  derived  from  the  sphenopalatine  branches  of  the  maxillary  nerve. 
They  are  three  in  number:  anterior,  middle,  and  posterior. 

The  anterior  palatine  nerve  {n.  palatinus  anterior)  descends  through  the  pterygo- 
palatine canal,  emerges  upon  the  hard  palate  through  the  greater  palatine  foramen, 
and  passes  forward  in  a  groove  in  the  hard  palate,  nearly  as  far  as  the  incisor  teeth. 
It  supplies  the  gums,  the  mucous  membrane  and  glands  of  the  hard  palate,  and 
communicates  in  front  with  the  terminal  filaments  of  the  nasopalatine  nerve. 
While  in  the  pterygopalatine  canal,  it  gives  off  posterior  inferior  nasal  branches, 
which  enter  the  nasal  cavitj^  through  openings  in  the  palatine  bone,  and  ramify 


THE  TRIGEMINAL  NERVE  921 

over  the  inferior  nasal  concha  and  niichlle  and  inferior  meatuses;  at  its  exit  from 
the  canal,  a  palatine  branch  is  distributed  to  both  surfaces  of  the  soft  palate. 

The  middle  palatine  nerve  {n.  palatinus  medium)  emerges  thrf)ugh  one  of  the  minor 
palatine  canals  and  distributes  branches  to  the  uvula,  tonsil,  and  soft  palate.  It  is 
occasionally  wanting. 

The  posterior  palatine  nerve  (/i.  palatinus  posterior)  descends  through  the  pterygo- 
palatine canal,  and  emerges  by  a  separate  opening  behind  the  greater  palatine 
foramen;  it  supplies  the  soft  palate,  tonsil,  and  uvula.  The  middle  and  posterior 
palatine  join  with  the  tonsillar  branches  of  the  glossopharyngeal  to  form  a  plexus 
(circulus  tonsillaris)  around  the  tonsil. 

The  posterior  superior  nasal  branches  (rami  nasales  posteriores  superiores)  are  dis- 
tributed to  the  septum  and  lateral  wall  of  the  nasal  fossa.  They  enter  the  posterior 
part  of  the  nasal  cavity  by  the  sphenopalatine  foramen  and  supply  the  mucous 
membrane  covering  the  superior  and  middle  nasal  conchse,  the  lining  of  the  poste- 
rior ethmoidal  cells,  and  the  posterior  part  of  the  septum.  One  branch,  longer 
and  larger  than  the  others,  is  named  the  nasopalatine  nerve.  It  enters  the  nasal 
cavity  through  the  sphenopalatine  foramen,  passes  across  the  roof  of  the  nasal 
cavity  below  the  orifice  of  the  sphenoidal  sinus  to  reach  the  septum,  and  then  runs 
obliquely  downward  and  forward  between  the  periosteum  and  mucous  membrane 
of  the  low^er  part  of  the  septum.  It  descends  to  the  roof  of  the  mouth  through  the 
incisive  canal  and  communicates  with  the  corresponding  nerve  of  the  opposite 
side  and  with  the  anterior  palatine  nerve.  It  furnishes  a  few  filaments  to  the 
mucous  membrane  of  the  nasal  septum. 

The  pharyngeal  nerve  {pterygopalatine  7ierve)  is  a  small  branch  arising  from  the 
posterior  part  of  the  ganglion.  It  passes  through  the  pharyngeal  canal  with  the 
pharyngeal  branch  of  the  internal  maxillary  artery,  and  is  distributed  to  the  mucous 
membrane  of  the  nasal  part  of  the  pharynx,  behind  the  auditory  tube. 

The  mandibular  nerve  {n.  mandibularis;  inferior  maxillary  nerve)  (Figs.  779, 
781)  supplies  the  teeth  and  gums  of  the  mandible,  the  skin  of  the  temporal  region, 
the  auricula,  the  lower  lip,  the  lower  part  of  the  face,  and  the  muscles  of  mastica- 
tion; it  also  supplies  the  mucous  membrane  of  the  anterior  two-thirds  of  the  tongue. 
It  is  the  largest  of  the  three  divisions  of  the  fifth,  and  is  made  up  of  two  roots :  a 
large,  sensory  root  proceeding  from  the  inferior  angle  of  the  semilunar  ganglion, 
and  a  small  motor  root  (the  motor  part  of  the  trigeminal),  which  passes  beneath  the 
ganglion,  and  unites  with  the  sensory  root,  just  after  its  exit  through  the  foramen 
ovale.  Immediately  beneath  the  base  of  the  skull,  the  nerve  gives  off  from  its 
medial  side  a  recurrent  branch  (nervus  spinosus)  and  the  nerve  to  the  Pterygoideus 
internus,  and  then  divides  into  two  trunks,  an  anterior  and  a  posterior. 

The  Nervus  Spinous  (recurrent  or  meningeal  branch)  enters  the  skull  through  the 
foramen  spinosum  with  the  middle  meningeal  artery.  It  divides  into  two  branches, 
anterior  and  posterior,  which  accompany  the  main  divisions  of  the  artery  and 
supply  the  dura  mater;  the  posterior  branch  also  supplies  the  mucous  lining  of 
the  mastoid  cells;  the  anterior  communicates  with  the  meningeal  branch  of  the 
maxillary  nerve. 

The  Internal  Pterygoid  Nerve  (n.  pterygoideus  internus) . — The  nerve  to  the  Ptery- 
goideus internus  is  a  slender  branch,  which  enters  the  deep  surface  of  the  muscle; 
it  gives  off  one  or  two  filaments  to  the  otic  ganglion. 

The  anterior  and  smaller  division  of  the  mandibular  nerve  receives  nearly  the 
whole  of  the  fibres  of  the  motor  root  of  the  nerve,  and  supplies  the  muscles  of 
mastication  and  the  skin  and  mucous  membrane  of  the  cheek.  Its  branches  are 
the  masseteric,  deep  temporal,  buccinator,  and  external  pterygoid. 

The  Masseteric  Nerve  (/i.  massetericus)  passes  lateralward,  above  the  Pterygoideus 
externus,  in  front  of  the  temporomandibular  articulation,  and  behind  the  tendon 
of  the  Temporalis;  it  crosses  the  mandibular  notch  with  the  masseteric  artery. 


922 


NEUROLOGY 


to  the  deep  surface  of  the  Masseter,  in  which  it  ramifies  nearly  as  far  as  its  anterior 
border.    It  gives  a  filament  to  the  temporomandibular  joint. 

The  Deep  Temporal  Nerves  {nn.  temporales  frofundi)  are  two  in  number,  anterior 
and  posterior.  They  pass  above  the  upper  border  of  the  Pterygoideus  externus 
and  enter  the  deep  surface  of  the  Temporalis.  The  posterior  branch,  of  small  size, 
is  placed  at  the  back  of  the  temporal  fossa,  and  sometimes  arises  in  common  with 
the  masseteric  nerve.  The  anterior  branch  is  frequently  given  off  from  the  buccina- 
tor nerve,  and  then  turns  upward  over  the  upper  head  of  the  Pterygoideus  externus. 
Frequently  a  third  or  intermediate  branch  is  present. 


A  uriculotemporal 


Deep  temporal 


Masseteric 
Splienomandibvlar 
ligament 
Inferior  alveolar 
Mylohyoid 

Lingual 
Ramus  of  man- 
dible (cut) 


Fig.   781. — The  Pterj'goideus  externus  and  the  branches  of  the  mandibular  nerve  in  relation  to  it. 

The  Buccinator  Nerve  (??.  buccinatorus;  long  buccal  nerve)  passes  forward  between 
the  two  heads  of  the  Pterygoideus  externus,  and  downward  beneath  or  through 
the  lower  part  of  the  Temporalis ;  it  emerges  from  under  the  anterior  border  of  the 
Masseter,  ramifies  on  the  surface  of  the  Buccinator,  and  unites  wdth  the  buccal 
branches  of  the  facial  nerve.  It  supplies  a  branch  to  the  Pterygoideus  externus 
during  its  passage  through  that  muscle,  and  may  give  off  the  anterior  deep  temporal 
nerve.  The  buccinator  nerve  supplies  the  skin  over  the  Buccinator,  and  the  mucous 
membrane  lining  its  inner  surface. 

External  Pterygoid  Nerve  {n.  yterygoideus  externus). — ^The  nerve  to  the  Ptery- 
goideus externus  frequently  arises  in  conjunction  wdth  the  buccinator  nerve, 
but  it  may  be  given  off  separately  from  the  anterior  division  of  the  mandibular 
nerve.    It  enters  the  deep  surface  of  the  muscle. 

The  posterior  and  larger  division  of  the  mandibular  nerve  is  for  the  most  part 
sensory,  but  receives  a  few  filaments  from  the  motor  root.  It  divides  into  auriculo- 
temporal, lingual,  and  inferior  alveolar  nerves. 


THE  TRIGEMINAL  NERVE  923 

The  Auriculotemporal  Nerve  (ii.  auriculotemjjoralis)  generally  arises  by  two  roots, 
between  which  the  middle  meningeal  artery  ascends.  It  runs  backward  beneath 
the  Pterygoideiis  externus  to  the  medial  side  of  the  neck  of  the  mandible.  It  then 
turns  upward  with  the  superficial  temporal  artery,  between  the  auricula  and  con- 
dyle of  the  mandible,  under  cover  of  the  parotid  gland;  escaping  from  beneath 
the  gland,  it  ascends  over  the  zygomatic  arch,  and  divides  into  superficial  temporal 
branches. 

The  branches  of  communication  of  the  auriculotemporal  nerve  are  with  the  facial 
nerve  and  with  the  otic  ganglion.  The  branches  to  the  facial,  usually  two  in  number, 
pass  forward  from  behind  the  neck  of  the  mandible  and  join  the  facial  nerve  at 
the  posterior  border  of  the  Masseter.  The  filaments  to  the  otic  ganglion  are  derived 
from  the  roots  of  the  auriculotemporal  nerve  close  to  their  origin. 

Its  branches  of  distribution  are: 

Anterior  auricular.  Articular. 

Branches  to  the  external  acoustic  meatus.  Parotid. 

Superficial  temporal. 

The  anterior  auricular  branches  {nn.  auriculares  anteriores)  are  usually  two  in 
number;  they  supply  the  front  of  the  upper  part  of  the  auricula,  being  distributed 
principally  to  the  skin  covering  the  front  of  the  helix  and  tragus. 

The  branches  to  the  external  acoustic  meatus  {n.  meatus  auditorii  externi),  two  in 
number,  enter  the  meatus  between  its  bony  and  cartilaginous  portions  and  supply 
the  skin  lining  it;  the  upper  one  sends  a  filament  to  the  tympanic  membrane. 

The  articular  branches  consist  of  one  or  two  twigs  which  enter  the  posterior  part 
of  the  temporomandibular  joint. 

The  parotid  branches  {rami  iiarotidei)  supply  the  parotid  gland. 

The  superficial  temporal  branches  {rami  temporales  swperficiales)  accompany  the 
superficial  temporal  artery  to  the  vertex  of  the  skull;  they  supply  the  skin  of  the 
temporal  region  and  communicate  with  the  facial  and  zygomaticotemporal  nerves. 

The  Lingual  Nerve  {n.  lingualis)  supplies  the  mucous  membrane  of  the  anterior 
two-thirds  of  the  tongue.  It  lies  at  first  beneath  the  Pterygoideus  externus,  medial 
to  and  in  front  of  the  inferior  alveolar  nerve,  and  is  occasionally  joined  to  this 
nerve,  by  a  branch  which  may  cross  the  internal  maxillary  artery.  The  chorda 
tympani  also  joins  it  at  an  acute  angle  in  this  situation.  The  nerve  then  passes 
between  the  Pterygoideus  internus  and  the  ramus  of  the  mandible,  and  crosses 
obliquely  to  the  side  of  the  tongue  over  the  Constrictor  pharyngis  superior  and 
Styloglossus,  and  then  between  the  Hj^oglossus  and  deep  part  of  the  submaxillary 
gland ;  it  finally  runs  across  the  duct  of  the  submaxillary  gland,  and  along  the  tongue 
to  its  tip,  lying  immediately  beneath  the  mucous  membrane. 

Its  branches  of  communication  are  with  the  facial  (through  the  chorda  tympani), 
the  inferior  alveolar  and  hypoglossal  nerves,  and  the  submaxillary  ganglion.  The 
branches  to  the  submaxillary  ganglion  are  two  or  three  in  number;  those  connected 
with  the  hypoglossal  nerve  form  a  plexus  at  the  anterior  margin  of  the  Hyoglossus. 

Its  branches  of  distribution  supply  the  sublingual  gland,  the  mucous  membrane 
of  the  mouth,  the  gums,  and  the  mucous  membrane  of  the  anterior  two-thirds  of 
the  tongue;  the  terminal  filaments  communicate,  at  the  tip  of  the  tongue,  with 
the  hypoglossal  nerve. 

The  Inferior  Alveolar  Nerve  {n.  aheolaris  inferior;  inferior  dental  nerve)  is  the  largest 
branch  of  the  mandibular  nerve.  It  descends  with  the  inferior  alveolar  artery,  at 
first  beneath  the  Pterygoideus  externus,  and  then  between  the  sphenomandibular 
ligament  and  the  ramus  of  the  mandible  to  the  mandibular  foramen.  It  then 
passes  forward  in  the  mandibular  canal,  beneath  the  teeth,  as  far  as  the  mental 
foramen,  where  it  divides  into  two  terminal  branches,  incisive  and  mental. 


924 


NEUROLOGY 


The  braiielR's  of  the  inferior  alveohir  nerve  are  the  mylohyoid,  dental,  incisive, 
and  mental. 

The  mylohyoid  nerve  (/z.  mi/lohyoideus)  is  derived  from  the  inferior  alveolar  just 
before  it  enters  the  mandibular  foramen.  It  descends  in  a  groove  on  the  deep 
surface  of  the  ramus  of  the  mandible,  and  reaching  the  under  surface  of  the 
Mylohyoideus  supplies  this  muscle  and  the  anterior  belly  of  the  Digastricus. 

The  dental  branches  supply  the  molar  and  premolar  teeth.  They  correspond 
in  number  to  the  roots  of  those  teeth;  each  nerve  entering  the  orifice  at  the  point 
of  the  root,  and  supplying  the  pulp  of  the  tooth;  above  the  alveolar  nerve  they  form 
an  inferior  dental  plexus. 

The  incisive  branch  is  continued  onward  within  the  bone,  and  supplies  the  canine 
and  incisor  teeth. 

The  mental  nerve  {n.  mentalis)  emerges  at  the  mental  foramen,  and  divides 
beneath  the  Triangularis  muscle  into  three  branches;  one  descends  to  the  skin  of 
the  chin,  and  two  ascend  to  the  skin  and  mucous  membrane  of  the  lower  lip;  these 
branches  communicate  freely  with  the  facial  nerve. 

Two  small  ganglia,  the  otic  and  the  submaxillary,  are  connected  with  the  man- 
dibular nerve. 


Fig.  .782. — The  otic  ganglion  and  its  branches. 


Otic  Ganglion  {ganglion  oticum)  (Fig.  782). — The  otic  ganglion  is  a  small,  oval- 
shaped,  flattened  ganglion  of  a  reddish-gray  color,  situated  immediately  below 
the  foramen  ovale;  it  lies  on  the  medial  surface  of  the  mandibular  nerve,  and 
surrounds  the  origin  of  the  nerve  to  the  Pterygoideus  internus.  It  is  in  relation, 
laterally,  with  the  trunk  of  the  mandibular  nerve  at  the  point  where  the  motor  and 
sensory  roots  join;  medially,  with  the  cartilaginous  part  of  the  auditory  tube, 
and  the  origin  of  the  Tensor  veli  palatini;  ^posteriorly ,  with  the  middle  meningeal 
artery. 

Branches  of  Communication. — It  is  connected  by  two  or  three  short  filaments 
with  the  nerve  to  the  Pterygoideus  internus,  from  which  it  may  obtain  a  motor, 
and  possibly  a  sensory  root.  It  communicates  with  the  glossopharyngeal  and  facial 
nerves,  through  the  lesser,  superficial  petrosal  nerve  continued  from  the  tympanic 
plexus,  and  through  this  nerve  it  probably  receives  a  sensory  root  from  the  glosso- 
pharyngeal and  a  motor  root  from  the  facial;  its  sympathetic  root  consists  of  a 
filament  from  the  plexus  surrounding  the  middle  meningeal  artery.    The  ganglion 


THE  TRIGEMINAL  NERVE  925 

also  communicates  with  the  auriculotemporal  nerve  by  a  branch  which  is  prob- 
ably derived  from  the  glossopharyngeal,  and  wJiich  passes  to  the  ganglion,  and  then 
through  it  and  auriculotemporal  nerve  to  the  i)arotid  gland.  A  slender  filament 
(sphenoidal)  ascends  from  it  to  the  nerve  of  the  Pterygoid  canal,  and  a  small  branch 
connects  it  with  the  chorda  tympani. 

Its  branches  of  distribution  are:  a  filament  to  the  Tensor  tympani,  and  one  to 
the  Tensor  veli  palatini.  The  former  passes  backward,  lateral  to  the  auditory 
tube;  the  latter  arises  from  the  ganglion,  near  the  origin  of  the  nerve  to  the  Ptery- 
goideus  internus,  and  is  directed  forward.  The  fibres  of  these  nerves  are,  however, 
mainly  derived  from  the  nerve  to  the  Pterygoideus  internus. 

Submaxillary  Ganglion  (ganglion  submaxillare)  (Fig.  779). — The  submaxillary 
ganglion  is  of  small  size  and  is  fusiform  in  shape.  It  is  situated  above  the  deep 
portion  of  the  submaxillary  gland,  on  the  hyoglossus,  near  the  posterior  border 
of  the  Mylohyoideus,  and  is  connected  by  filaments  with  the  lower  border  of  the 
lingual  nerve.  It  is  suspended  from  the  lingual  nerve  by  two  filaments  which  join 
the  anterior  and  posterior  parts  of  the  ganglion.  Through  the  posterior  of  these 
it  receives  a  branch  from  the  chorda  tympani  nerve  which  runs  in  the  sheath  of 
the  lingual;  it  communicates  with  the  sympathetic  by  filaments  from  the 
sympathetic  plexus  around  the  external  maxillary  artery. 

Its  branches  of  distribution  are  five  or  six  in  number;  they  arise  from  the  lower 
part  of  the  ganglion,  and  supply  the  mucous  membrane  of  the  mouth  and  the  duct 
of  the  submaxillary  gland,  some  being  lost  in  the  submaxillary  gland.  The  branch 
of  communication  from  the  lingual  to  the  forepart  of  the  ganglion  is  by  some 
regarded  as  a  branch  of  distribution,  through  which  filaments  pass  from  the  gan- 
glion to  the  lingual  nerve,  and  by  it  are  conveyed  to  the  sublingual  gland  and  the 
tongue. 

Applied  Anatomy. — Paralysis  of  the  trigeminal  nerve  causes  anesthesia  of  the  corresponding 
anterior  half  of  the  scalp,  and  of  the  face,  excepting  over  a  small  area  near  the  angle  of  the  man- 
dible supplied  by  the  cervical  nerves,  and  of  the  cornea  and  conjunctiva,  and  of  the  mucous 
membrane  of  the  nose,  mouth,  and  tongue.  Taste  is  lost  (ageusia)  on  the  affected  side.  Paralysis 
and  atrophy  follow  in  the  Temporalis,  Masseter,  and  Pterygoidei,  possibly  also  in  the  Tensor 
tympani;  when  the  mouth  is  opened  the  mandible  is  thrust  over  toward  the  paralyzed  side.  Inter- 
ference with  the  secretion  of  the  tears,  the  nasal  mucus,  and  the  sahva,  causes  dryness  of  the 
corresponding  mucous  membranes.  The  sense  of  smell  is  gradually  lost  on  the  affected  side 
from  the  trophic  changes  that  follow  in  the  nasal  mucous  membrane.  Inflammation  of  the  eye- 
ball, under  these  circumstances  known  as  neuroparalytic  ophthalmia,  is  not  rare,  and  is  due  to 
the  dryness  and  insensitiveness  of  the  conjimctiva;  it  is  not  a  "trophic"  phenomenon,  but  depends 
on  the  occurrence  and  neglect  of  traumatic  inflammation  in  the  anesthetic  eye. 

Trigeminal  Nerve  Reflexes. — Pains  referred  to  various  branches  of  the  trigeminal  nerve  are  of 
very  frequent  occurrence,  and  should  always  lead  to  a  careful  examination  in  order  to  discover 
a  local  cause.  As  a  general  rule  the  diffusion  of  pain  over  the  various  branches  of  the  nerve  is 
at  first  confined  to  one  only  of  the  main  divisions,  and  the  search  for  the  causative  lesion  should 
always  commence  with  a  thorough  examination  of  all  those  parts  which  are  supplied  by  that 
division;  although  in  severe  cases  pain  may  radiate  over  the  branches  of  the  other  main  divisions. 
The  commonest  example  of  this  condition  is  the  neuralgia  which  is  so  often  associated  with 
dental  caries — here,  although  the  tooth  itself  may  not  appear  to  be  painful,  the  most  distressing 
referred  pains  may  be  experienced,  and  these  are  at  once  reUeved  by  treatment  directed  to  the 
affected  tooth. 

Many  other  examples  of  trigeminal  reflexes  could  be  quoted,  but  it  will  be  sufficient  to  mention 
the  more  common  ones.  Dealing  with  the  ophthalmic  nerve,  severe  supraorbital  pain  is  com- 
monly associated  with  acute  glaucoma  or  with  disease  of  the  frontal  or  ethmoidal  air  cells.  Malig- 
nant growths  or  empyema  of  the  maxillary  antrum,  or  unhealthy  conditions  about  the  inferior 
conchae  or  the  septum  of  the  nose,  are  often  found  giving  rise  to  "second  division"  neuralgia, 
and  should  be  always  looked  for  in  the  absence  of  dental  disease  in  the  maxilla. 

It  is  on  the  mandibular  nerve,  however,  that  some  of  the  most  striking  reflexes  are  seen.  It 
is  quite  common  to  meet  with  patients  who  complain  of  pain  in  the  ear,  in  whom  there  is  no  sign 
of  aural  disease,  and  the  cause  is  usually  to  be  found  in  a  carious  tooth  in  the  mandible.  More- 
over, with  an  ulcer  or  cancer  of  the  tongue,  often  the  first  pain  to  be  experienced  is  one  which 
radiates  to  the  ear  and  temporal  fossa,  over  the  distribution  of  the  auriculotemporal  nerve. 


926 


NEUROLOGY 


The  trigeminal  nerve  is  often  the  seat  of  severe  neuralgia  for  which  no  local  cause  can  be  dis- 
covered; each  of  the  three  divisions  has  been  divided,  or  a  portion  of  the  nerve  excised,  for  this 
affection,  usually,  however,  with  only  temporary  relief.  The  supraorbital  nerve  may  be  exposed 
by  making  an  incision  4  cm.  in  length  along  the  supraorbital  margin,  below  the  eyebrow  which 
is  to  be  drawn  upward,  the  centre  of  the  incision  corresponding  to  the  supraorbital  notch.  The 
skin  and  Orbicularis  oculi  having  been  divided,  the  nerve  can  be  easily  found  emerging  from  the 
notch,  and  lying  in  some  loose  cellular  tissue.  It  should  be  drawn  up  by  a  blunt  hook  and  1.25 
cm.  of  it  resected,  or  the  nerve  can  be  injected  with  absolute  alcohol. 

The  infraorbital  nerve  has  been  divided  at  its  exit  by  an  incision  on  the  cheek;  or  the  floor 
of  the  orbit  has  been  exposed,  the  infraorbital  canal  opened  up,  and  the  anterior  part  of  the  nerve 
resected;  or  the  whole  nerve,  together  with  sphenopalatine  ganglion  as  far  back  as  the  foramen 
rotundum  may  be  removed,  but  even  then  a  return  of  the  neuralgia  in  some  other  branches  of 
the  trigeminal  nerve  is  the  rule  rather  than  the  exception.  The  operation  is  performed  as  follows: 
the  maxilla  is  first  exposed  by  a  T-shaped  incision,  one  hmb  passing  along  the  lower  margin  of 
the  orbit,  the  other  from  the  centre  of  this  vertically  down  the  cheek  to  the  angle  of  the  mouth. 
The  nerve  is  to  be  found,  divided,  and  a  piece  of  silk  tied  to  it  as  a  guide.  A  smaU  trephine  (half- 
inch)  is  applied  to  the  bone,  below,  but  including  the  infraorbital  foramen,  and  the  maxiUary 
sinus  opened.  The  trephine  is  then  applied  to  the  posterior  wall  of  the  sinus,  and  the  pterygo- 
palatine fossa  exposed.  The  infraorbital  canal  is  opened  up  from  below,  and  the  nerve  drawn 
down  into  the  trephine  hole,  and  held  on  the  stretch  by  means  of  the  piece  of  silk;  it  is  severed 
with  fine  curved  scissors  as  near  the  foramen  rotundum  as  possible,  any  branches  coming  off 
from  the  ganglion  being  also  divided. 


Fig.  783. — Diagram  showing  cutaneous  areas  of  face  and  scalp. 

The  inferior  alveolar  nerve  can  be  reached  by  a  transverse  incision  over  the  ramus  of  the  man- 
dible placed  so  as  to  avoid  injury  to  the  facial  nerve;  the  Masseter  having  been  divided,  a  small 
trephine  is  apphed  to  the  ramus  immediately  beneath  the  mandibular  notch,  and,  when  the 
bone  has  been  removed,  the  nerve  is  found  lying  on  the  Pterygoideus  internus  just  as  it  enters 
the  mandibular  foramen,  and  it  can  here  be  resected.  The  lingual  nerve  is  occasionally  divided 
with  the  view  of  reheving  the  pain  in  cancerous  disease  of  the  tongue.  This  may  be  done  in  that 
part  of  its  course  where  it  hes  below  and  behind  the  last  molar  tooth.  If  a  line  be  drawn  from 
the  middle  of  the  crown  of  the  last  molar  tooth  to  the  angle  of  the  mandible  it  will  cross  the  nerve, 
which  hes  about  1.25  cm.  behind  the  tooth,  parallel  to  the  bulging  alveolar  ridge  on  the  inner 
side  of  the  body  of  the  bone.  The  tongue  should  be  pulled  forward  and  over  to  the  opposite  side, 
when  the  nerve  can  be  seen  standing  out  as  a  firm  cord  under  the  mucous  membrane  by  the  side 
of  the  tongue,  and  after  division  of  the  mucous  membrane  can  be  easily  seized  with  a  hook  and 
a  portion  excised.  This  is  a  simple  enough  operation  on  the  cadaver,  but  when  the  disease  is 
extensive  and  has  extended  to  the  floor  of  the  mouth,  as  is  generally  the  case  when  the  division  is 
required,  the  operation  is  not  practicable. 


THE  ABDUCENT  NERVE 


927 


In  severe  cases  of  neuralgia  of  the  trigeminal  nerve,  the  semilunar  ganglion  has  been  removed 
in  whole  or  in  part  with  a  considerable  measure  of  success.  Rose  was  the  first  to  perform  this 
operation;  and  he  reached  the  ganglion  by  trcjihining  the  base  of  the  skull  in  the  position  of  the 
foramen  ovale,  after  dividing  the  zygomatic  arch,  in  front  and  behind,  and  turning  it  and  the 
Massetcr  downward,  and  cutting  through  the  coronoid  process  of  the  mandible,  and  turning  it 
and  the  Temporalis  upward.  A  more  efficient  method  appears  to  be  that  known  as  the  Krause- 
Hartley  method.  The  bone  forming  the  temporal  fossa  having  been  removed  to  a  sufficient 
extent,  the  dura  mater  beneath  the  temporal  lobe  of  the  brain  is  gradually  raised  from  the  middle 
fossa,  until  the  foramen  spinosum,  with  the  middle  meningeal  artery  passing  through  it,  is  exposed. 
This  vessel  is  to  be  ligatured  in  two  places,  and  divided  between  the  ligatures;  and  then  by  further 
raising  the  diu-a  mater,  the  foramina  ovale  and  rotundum  will  be  exposed,  with  the  mandibular 
and  maxillary  nerves  passing  through  them.  These  nerves  are  to  be  clearly  defined  and  divided. 
The  dura  mater  is  then  to  be  raised  from  the  ganglion,  when  the  ophthalmic  nerve  will  be  exposed 
and  must  be  divided,  and  the  gangfion,  by  means  of  a  little  careful  dissection,  raised  from  its 
bed  and  removed.  In  some  cases  where  the  neuralgia  has  been  limited  to  the  maxillary  nerve 
an  intracranial  resection  of  that  nerve  alone  has  been  performed  with  gi-eat  success.  In  other 
cases  where  the  disease  has  not  affected  the  ophthalmic  division,  resection  of  the  lateral  half 
of  the  ganglion  only,  with  the  maxillary  and  mandibular  nerves,  has  been  performed,  thus  leaving 
the  sensory  nerve  supply  to  the  cornea  intact.  The  motor  root  is  usually  resected  with  the  man- 
dibular nerve,  leading  to  complete  paralysis  of  the  muscles  of  mastication  on  that  side. 

THE  ABDUCENT  NERVE  (N.  ABDUCENS;  SIXTH  NERVE)  (Fig.  778). 


The  abducent  nerve  supplies  the  Rectus  lateraHs  oculi. 

Its  fibres  arise  from  a  small  nucleus  situated  in  the  upper  part  of  the  rhomboid 
fossa,  close  to  the  middle  line  and  beneath  the  colliculus  facialis.  They  pass  down- 
ward and  forward  through  the  pons,  and 
emerge  in  the  furrow  between  the  lower 
border  of  the  pons  and  the  upper  end  of  the 
pyramid  of  the  medulla  oblongata. 

From  the  nucleus  of  the  sixth  nerve,  fibres 
pass  through  the  medial  longitudinal  fascic- 
ulus to  the  oculomotor  nerve  of  the  opposite 
side,  along  which  they  are  carried  to  the 
Rectus  medialis.  The  Rectus  lateralis  of  one 
eye  and  the  Rectus  medialis  of  the  other  may 
therefore  be  said  to  receive  their  nerves  from 
the  same  nucleus  (Fig.  784). 

The  nerve  pierces  the  dura  mater  on  the 
dorsum  sellae  of  the  sphenoid,  runs  through 
a  notch  in  the  bone  below  the  posterior  clinoid 
process,  and  passes  forward  through  the 
cavernous  sinus,  on  the  lateral  side  of  the 
internal  carotid  artery.  It  enters  the  orbit 
through  the  superior  orbital  fissure,  above 
the  ophthalmic  vein,  from  which  it  is  sepa- 
rated by  a  lamina  of  dura  mater.  It  then 
passes  between  the  two  heads  of  the  Rectus 
lateralis,  and  enters  the  ocular  surface  of  that 
muscle.  The  abducent  nerve  is  joined  by  sev- 
eral filaments  from  the  carotid  and  cavernous 
plexuses,  and  by  one  from  the  ophthalmic 
nerve.  The  oculomotor,  trochlear,  ophthalmic, 
and  abducent  nerves  bear  certain  relations  to 
each  other  in  the  cavernous  sinus,-  at  the 
superior  orbital  fissure,  and  in  the  cavity  of 
the  orbit,  as  follows: 


Fig.   784.- 


Figure  showing  the  mode  of  inner- 
vation of  the  Recti  medialis  and  laterahs  of  the 
eye  (after  Duval  and  Laborde).  (Testut.)  a. 
Left  eyeball,  b.  Right  eyeball.  1.  Rectus  late- 
ralis. 2.  Rectus  medialis.  3.  Rhomboid  fossa. 
4.  Nucleus  of  abducent  nerve.  5.  Nucleus  of 
oculomotor  nerve.  6.  Abducent  nerve.  7.  Nerve 
to  Rectus  medialis  arising  from  the  nucleus  of  the 
oculomotor  of  the  same  side.  7'.  Nerve  to  Rectus 
medialis  arising  from  the  nucleus  of  the  abducent 
of  the  opposite  side.  8.  Decussation  of  the  fibres 
of  the  abducent  nerve  to  the  Rectus  medialis. 


928 


NEUROLOGY 


In  the  cavernous  sinus  (Fig.  785),  the  oculomotor,  trochlear,  and  ophthalmic 
nerves  are  placed  in  the  lateral  wall  of  the  sinus,  in  the  order  given,  from  above 
downward.     The  abducent  nerve  lies  at  the  lateral  side  of  the  internal  carotid 
artery.     As  these  nerves  pass  forward  to  the  superior  orbital  fissure,  the  oculo- 
motor   and    ophthalmic    divide   into 
Internal  carotui  artery       branches,   and    the    abduccut   nerve 

Cavernous  sinus  '  ^  i     .     .  i     • 

approaches  the  others;  so  that  their 
relative  positions  are  considerably- 
changed. 

In  the  superior  orbital  fissure  (Fig. 
786),    the   trochlear   nerve   and    the 
frontal  and  lacrimal  divisions  of  the 
ophthalmic    lie    in   this   order    from 
the  medial  to  the  lateral  side   upon 
the  same  plane;  they  enter  the  cavity 
of  the  orbit  above  the  muscles.    The 
remaining  nerves  enter  the  orbit  be- 
tween the  two  heads  of  the  Rectus 
lateralis.     The   superior    division    of 
the  oculomotor  is  the  highest  of   these;  beneath  this  lies  the  nasociliary  branch 
of  the  ophthalmic;  then  the  inferior  division  of  the  oculomotor;  and  the  abducent 
lowest  of  all. 


Oculomotor  iv 
Trochlear  nerve 

O'phtlialiidc  nerve 
Abducent  nerve 

Maxillary  nerve 


Fia.  785. 


-Oblique  section  through  the  right  cavernous 
sinus. 


Frontal  nerve 


Sup. 


ruTnus  of  oculomotor  nerve 
Suj}.  orbital  fissure 
Lacrimal  nerve     \ 


Levator  palpebrce 
I      Nasociliary  nerve 
I     Trochlear  nerve 
Trochlea 


Abducent  neri'i 

Inf.  ramus  of  oculomotor     Inf.  orbital         Optic  foramen 
nerve  fissure 

Fig.  786. — Dissection  showing  origins  of  right  ocular  muscles,  and  nerves  entering  by  the  superior  orbital  fissure. 

In  the  orbit,  the  trochlear,  frontal,  and  lacrimal  nerves  lie  immediately  beneath 
the  periosteum,  the  trochlear  nerve  resting  on  the  Obliquus  superior,  the  frontal 
on  the  Levator  palpebrae  superioris,  and  the  lacrimal  on  the  Rectus  lateralis. 
The  superior  division  of  the  oculomotor  nerve  lies  unmediately  beneath  the  Rectus 
superior,  while  the  nasociliary  nerve  crosses  the  optic  nerve  to  reach  the  medial 
wall  of  the  orbit.  Beneath  these  is  the  optic  nerve,  surrounded  in  front  by  the 
ciliary  nerves,  and  having  the  ciliary  ganglion  on  its  lateral  side,  between  it  and  the 
Rectus  lateralis.  Below  the  optic  nerve  are  the  inferior  division  of  the  oculomotor, 
and  the  abducent,  the  latter  lying  on  the  medial  surface  of  the  Rectus  lateralis. 


THE  FACIAL  NERVE 


929 


Applied  Anatomy. — The  abducent  nerve  is  frequently  involved  in  fractures  of  the  base  of  the 
skull.  The  result  of  paralysis  of  this  nerve  is  medial  or  convergent  squint.  Diplopia  is  also 
present.  When  injured  so  that  its  function  is  destroyed  there  is,  in  addition  to  the  paralysis  of 
the  Rectus  lateralis  oculi,  often  a  certain  amount  of  contraction  of  the  pupil,  because  some  of 
the  sympathetic  fibres  to  the  Dilatator  pupillae  muscle  are  conveyed  through  this  nerve. 


THE   FACIAL  NERVE    (N.  FACIALIS;  SEVENTH  NERVE)  (Figs.  787,  789). 

The  facial  nerve  consists  of  a  motor  and  a  sensory  part,  the  latter  being  frequently 
described  under  the  name  of  the  nemis  intermedins  {yars  intermedii  of  Wrisberg) 
(Fig.  787).  The  two  parts  emerge  at  the  lower  border  of  the  pons  in  the  recess 
between  the  olive  and  the  restiform  body,  the  motor  part  being  the  more  medial; 
immediately  to  the  lateral  side  of  the  sensory  part  is  the  acoustic  nerve. 


To  Acoustic 


Com.  with 

auric,  branch 

of  vagus 


Genicular  oanglion 

Greaterjuperficial  Petrpsgi 


er_supeiyic/^^^        'Deep  petrosal 


Nerve  of 
"pteryg.  canal 


Otic  ganglion 


Lingual, 


To  posterior 
belli/  of 

DIGASTRICUS 


TO  STYLOHYOiDEUS 


Mccndibular 
I  Cervical 
Fig.  787. — Plan  of  the  facial  nerve.     The  course  of  the  sensory  fibres  is  represented  by  the  blue  Unes. 


The  motor  part  supplies  the  muscles  of  the  face,  scalp,  and  auricular,  the  Buc- 
cinator and  Platysma,  the  Stapedius,  the  Stylohyoideus,  and  posterior  belly  of  the 
Digastricus;  it  also  contains  some  fibres  which  constitute  the  vasodilator  nerves 
of  the  submaxillary  and  sublingual  glands,  and  are  conve^^ed  to  these  glands  through 
the  chorda  tympani  nerve.  The  sensory  part  contains  the  fibres  of  taste  for  the 
anterior  two-thirds  of  the  tongue. 

The  motor  root  arises  from  a  nucleus  which  lies  deeply  in  the  reticular  formation 
of  the  lower  part  of  the  pons.  This  nucleus  is  situated  above  the  nucleus  ambiguus, 
behind  the  superior  olivary  nucleus,  and  medial  to  the  spinal  tract  of  the  trige- 
minal nerve.  From  this  origin  the  fibres  pursue  a  curved  course  in  the  substance 
59 


930  NEUROLOGY 

of  the  pons.  The}'  first  pass  backward  and  medialward  toward  the  rhomboid 
fossa,  and,  reaching  the  posterior  end  of  the  nucleus  of  the  abducent  nerve,  run 
upward  close  to  the  middle  line  beneath  the  colliculus  fascialis.  At  the  anterior 
end  of  the  nucleus  of  the  abducent  nerve  they  make  a  second  bend,  and  run  down- 
ward and  forward  through  the  pons  to  their  point  of  emergence  between  the  olive 
and  the  restiform  body. 

Some  fibres  from  the  nucleus  of  the  oculomotor  nerve  are  said  to  descend  in  the 
medial  longitudinal  fasciculus  and  join  the  motor  root  of  the  facial  nerve  before  it 
leaves  the  pons.  These  fibres  are  believed  to  supply  the  Orbicularis  oculi,  Cor- 
rugator,  and  Frontalis,  since  these  muscles  have  been  observed  to  escape  paralysis 
in  lesions  of  the  motor  nucleus  of  the  facial  nerve. ^ 

The  sensory  root  arises  from  the  genicular  ganglion,  which  is  situated  on  the  genic- 
ulum  of  the  facial  nerve  in  the  facial  canal,  behind  the  hiatus  of  the  canal.  The  cells 
of  this  ganglion  are  unipolar,  and  the  single  process  divides  in  a  T-shaped  manner 
into  central  and  peripheral  branches.  The  central  branches  leave  the  trunk  of 
the  facial  nerve  in  the  internal  acoustic  meatus,  and  form  the  sensory  root;  the 
peripheral  branches  are  continued  into  the  chorda  tympani  and  greater  super- 
ficial petrosal  nerves.  Entering  the  brain  at  the  lower  border  of  the  pons  between 
the  motor  root  and  the  acoustic  nerve,  the  fibres  of  the  sensory  root  pass  into  the 
substance  of  the  medulla  oblongata  and  end  in  the  upper  part  of  the  terminal 
nucleus  of  the  glossopharyngeal  nerve  and  in  the  fasciculus  solitarius. 

From  their  superficial  attachments  to  the  brain,  the  two  roots  of  the  facial  nerve 
pass  lateralward  and  forward  with  the  acoustic  nerve  to  the  internal  acoustic 
meatus.  In  the  meatus  the  motor  root  lies  in  a  groove  on  the  upper  and  anterior 
surface  of  the  acoustic  nerve,  the  sensory  root  being  placed  between  them. 

At  the  bottom  of  the  meatus,  the  facial  nerve  enters  the  facial  canal,  which  it 
traverses  to  its  termination  at  the  stylomastoid  foramen.  It  is  at  first  directed 
lateralward  between  the  cochlea  and  vestibule  toward  the  medial  wall  of  the 
tympanic  cavity;  it  then  bends  suddenly  backw^ard  and  arches  downward  behind 
the  tympanic  cavity  to  the  stylomastoid  foramen.  The  point  w^here  it  changes 
its  direction  is  named  the  geniculum ;  it  presents  a  reddish  ganglif orm  swelling,  the 
genicular  ganglion  {ganglion  geniculi;  geniculate  ganglion;  nucleus  of  the  sensory  root 


External  superficial  petrosal 

Branch  to  join  lesser  superficial  petrosal 

Greater  superficial  petrosal 

Genicular  ganglimi 

Facial 

Acoustic 

Fig.  788. — The  course  and  connections  of  the  facial  nerve  in  the  temporal  bone. 

oj  the  nerve)  (Fig.  788).  On  emerging  from  the  stylomastoid  foramen,  the  facial 
nerve  runs  forw^ard  in  the  substance  of  the  parotid  gland,  crosses  the  external 
carotid  artery,  and  divides  behind  the  ramus  of  the  mandible  into  branches,  from 
which  numerous  offsets  are  distributed  over  the  side  of  the  head,  face,  and  upper 
part  of  the  neck,  supplying  the  superficial  muscles  in  these  regions.  The  branches 
and  their  offsets  unite  to  form  the  parotid  plexus. 

Branches  of  Communication. — The  branches  of  communication  of  the  facial  nerve 
may  be  arranged  as  follows: 

1  See  footnote,  p.  852. 


THE  FACIAL  NERVE 


931 


In  the  internal  acoustic 
meatus   . 


At  the  genicular  ganglion 


In  the  facial  canal    . 

At  its  exit  from  the  stylo- 
mastoid foramen  . 

Behind  the  ear 
On  the  face 
In  the  neck 


With  the  acoustic  nerve. 

With  the  sphenopalatine  ganglion  by  the  greater 
superficial  petrosal  nerve. 

With  the  otic  ganglion  by  a  branch  which  joins 
the  lesser  superficial  petrosal  nerve. 

With  the  sympathetic  on  the  middle  meningeal 
artery. 

With  the  auricular  branch  of  the  vagus. 

With  the  glossopharyngeal. 

With  the  vagus. 
I  With  the  great  auricular, 
[with  the  auriculotemporal. 

With  the  lesser  occipital. 

With  the  trigeminal. 

With  the  cutaneous  cervical. 


In  the  internal  acoustic  meatus  some  minute  filaments  pass  from  the  facial  to 
the  acoustic  nerve. 

The  greater  superficial  petrosal  nerve  {large  superficial  petrosal  nerve)  arises  from 
the  genicular  ganglion,  and  consists  chiefly  of  sensory  branches  which  are  dis- 
tributed to  the  mucous  membrane  of  the  soft  palate;  but  it  probably  contains  a  few 
motor  fibres  which  form  the  motor  root  of  the  sphenopalatine  ganglion.  It  passes 
forward  through  the  hiatus  of  the  facial  canal,  and  runs  in  a  sulcus  on  the  anterior 
surface  of  the  petrous  portion  of  the  temporal  bone  beneath  the  semilunar  ganglion, 
to  the  foramen  lacerum.  It  receives  a  twig  from  the  tympanic  plexus,  and  in  the 
foramen  is  joined  by  the  deep  petrosal,  from  the  sympathetic  plexus  on  the  internal 
carotid  artery,  to  form  the  nerve  of  the  pterygoid  canal  which  passes  forward 
through  the  pterygoid  canal  and  ends  in  the  sphenopalatine  ganglion.  The  genicular 
ganglion  is  connected  with  the  otic  ganglion  by  a  branch  which  joins  the  lesser 
superficial  petrosal  nerve,  and  also  with  the  sympathetic  filaments  accompanying 
the  middle  meningeal  artery.  According  to  Arnold,  a  twig  passes  back  from  the 
ganglion  to  the  acoustic  nerve.  Just  before  the  facial  nerve  emerges  from  the 
stylomastoid  foramen,  it  generally  receives  a  twig  from  the  auricular  branch  of 
the  vagus. 

After  its  exit  from  the  stylomastoid  foramen,  the  facial  nerve  sends  a  twig  to 
the  glossopharyngeal,  and  communicates  with  the  auricular  branch  of  the  vagus, 
with  the  great  auricular  nerve  of  the  cervical  plexus,  with  the  auriculotemporal 
nerve  in  the  parotid  gland,  and  with  the  lesser  occipital  behind  the  ear;  on  the  face 
with  the  terminal  branches  of  the  trigeminal,  and  in  the  neck  with  the  cutaneous 
cervical  nerve. 

Branches  of  Distribution. — The  branches  of  distribution  (Fig.  787)  of  the  facial 
nerve  may  be  thus  arranged: 


With  the  facial  canal 

At  its  exit  from  the  stylo- 
mastoid foramen 


On  the  face 


f  Nerve  to  the  Stapedius  muscle. 
\  Chorda  tympani. 
(  Posterior  auricular. 
■I  Digastric, 
t  Stylohyoid. 

Temporal. 

Zygomatic. 

Buccal. 

Mandibular. 

Cervical. 


932 


NEUROLOGY 


The  Nerve  to  the  Stapedius  in.  stapedius:  tympanic  branch)  arises  opposite  the 
pyramidal  eminence  (page  1052);  it  passes  through  a  small  canal  in  this  eminence 
to  reach  the  muscle. 

The  Chorda  Tympani  Nerve  is  gi\'en  off  from  the  facial  as  it  passes  downward 
behind  the  tympanic  cavity,  about  6  mm.  from  the  stylomastoid  foramen.  It 
runs  upward  and  forward  in  a  canal,  and  enters  the  tympanic  cavity,  through  an 
aperture  (iter  chordae  posterius)  on  its  posterior  wall,  close  to  the  medial  surface 
of  the  posterior  border  of  the  tympanic  membrane  and  on  a  level  M-ith  the  upper 


Termination 
of  supratrochlear 
of  infratrochlear 
of  nasociliary 


Fig.  789. — The  nerves  of  the  scalp,  face,  and  side  of  neck. 


end  of  the  manubrium  of  the  malleus.  It  traverses  the  tympanic  cavity,  between 
the  fibrous  and  mucous  layers  of  the  tympanic  membrane,  crosses  the  manubrium 
of  the  malleus,  and  emerges  from  the  cavity  through  a  foramen  situated  at  the  inner 
end  of  the  petrotympanic  fissure,  and  named  the  iter  chordae  anterius  {canal  of 
Huguier).  It  then  descends  between  the  Pterygoid eus  externus  and  internus  on 
the  medial  surface  of  the  spina  angularis  of  the  sphenoid,  which  it  sometimes 
grooves,  and  joins,  at  an  acute  angle,  the  posterior  border  of  the  lingual  nerve. 
It  receives  a  few  efferent  fibres  from  the  motor  root;  these  enter  the  submaxillary 
ganglion,  and  through  it  are  distributed  to  the  submaxillary  and  sublingual  glands; 


THE  FACIAL  NERVE  933 

the  majority  of  its  fibres  are  efferent,  and  are  eontinued  onward  through  the  mus- 
cular substance  of  the  tongue  to  the  mucous  membrane  covering  its  anterior 
two-thirds;  tliey  constitute  the  ner\'e  of  taste  for  tliis  portion  of  the  tongue.  Before 
uniting  witli  tlie  Ungual  nerve  the  chorda  tympani  is  joined  by  a  small  branch  from 
the  otic  ganglion. 

The  Posterior  Auricular  Nerve  (??.  aiiricularis  ■posterior)  arises  close  to  the  stylo- 
mastoid foramen,  and  runs  upward  in  front  of  the  mastoid  process;  here  it  is  joined 
by  a  filament  from  the  auricular  branch  of  the  vagus,  and  communicates  with  the 
posterior  branch  of  the  great  auricular,  and  with  the  lesser  occipital.  As  it  ascends 
between  the  external  acoustic  meatus  and  mastoid  process  it  divides  into  auricular 
and  occipital  branches.  The  auricular  branch  supplies  the  Auricularis  posterior 
and  the  intrinsic  muscles  on  the  cranial  surface  of  the  auricula.  The  occipital 
branch,  the  larger,  passes  backward  along  the  superior  nuchal  line  of  the  occipital 
bone,  and  supplies  the  Occipitalis. 

The  Digastric  Branch  {ramus  digasfricus)  arises  close  to  the  stylomastoid  foramen, 
and  divides  into  several  filaments,  which  supply  the  posterior  belly  of  the  Digas- 
tricus;  one  of  these  filaments  joins  the  glossopharyngeall  nerve. 

The  Stylohyoid  Branch  (ramus  stylohyoideus)  frequently  arises  in  conjunction 
with  the  digastric  branch ;  it  is  long  and  slender,  and  enters  the  Stylohyoideus  about 
its  middle. 

The  Temporal  Branches  {rami  temporales)  cross  the  zygomatic  arch  to  the  temporal 
region,  supplying  the  Auriculares  anterior  and  superior,  and  joining  with  the  zygo- 
maticotemporal branch  of  the  maxillary,  and  with  the  auriculotemporal  branch 
of  the  mandibular.  The  more  anterior  branches  supply  the  Frontalis,  the  Orbicu- 
laris oculi,  and  the  Corrugator,  and  join  the  supraorbital  and  lacrimal  branches 
of  the  ophthalmic. 

The  Zygomatic  Branches  {rami  zygomatici;  malar  branches)  run  across  the  zygo- 
matic bone  to  the  lateral  angle  of  the  orbit,  where  they  supply  the  Orbicularis  oculi, 
and  join  with  filaments  from  the  lacrimal  nerve  and  the  zygomaticofacial  branch 
of  the  maxillary  nerve. 

The  Buccal  Branches  {rami  buccales;  infraorbital  branches),  of  larger  size  than  the 
rest,  pass  horizontally  forw^ard  to  be  distributed  below  the  orbit  and  around  the 
mouth.  The  superficial  branches  run  beneath  the  skin  and  above  the  superficial 
muscles  of  the  face,  which  they  supply:  some  are  distributed  to  the  Procerus, 
joining  at  the  medial  angle  of  the  orbit  with  the  infratrochlear  and  nasociliary 
branches  of  the  ophthalmic.  The  deep  branches  pass  beneath  the  Zygomaticus  and 
the  Quadratus  labii  superioris,  supplying  them  and  forming  an  infraorbital  plexus  w^ith 
the  infraorbital  branch  of  the  maxillary  nerve.  These  branches  also  supply  the 
small  muscles  of  the  nose.  The  lower  deep  branches  supply  the  Buccinator  and 
Orbicularis  oris,  and  join  with  filaments  of  the  buccinator  branch  of  the  mandibular 
nerve. 

The  Mandibular  Branch  {ramus  marginalis  mandibulae)  passes  forward  beneath 
the  Platysma  and  Triangularis,  supplying  the  muscles  of  the  lower  lip  and  chin, 
and  communicating  with  the  mental  branch  of  the  inferior  alveolar  nerve. 

The  Cervical  Branch  {ramus  colli)  runs  forward  beneath  the  Platysma,  and  forms 
a  series  of  arches  across  the  side  of  the  neck  over  the  suprahyoid  region.  One 
branch  descends  to  join  the  cervical  cutaneous  nerve  from  the  cervical  plexus; 
others  supply  the  Platysma. 

Applied  Anatomy. — Facial  palsy  is  commonly  miilateral,  and  may  be  either:  (1)  peripheral, 
from  lesion  of  the  facial  nerve;  (2)  nuclear,  from  destruction  of  the  facial  nucleus;  or  (3)  central, 
cerebral,  or  supranuclear,  from  injury  in  the  brain  to  the  fibres  passing  from  the  cortex  through 
the  internal  capsule  to  the  facial  nucleus,  or  from  injury  to  the  face  area  of  the  motor  cortex 
itself.  In  supranuclear  facial  paralysis,  which  is  usually  part  of  a  hemiplegia,  it  is  the  lower  part 
of  the  face  that  is  chiefly  affected,  while  the  forehead  can  be  freely  wrinkled  on  the  palsied  side, 
the  eye  can  be  closed  fairly  well,  and  the  eyeball  is  not  rolled  up  under  the  upper  Ud;  emotional 


934  NEUROLOGY 

movements  of  the  face  are  much  better  executed  than  voluntary;  and  the  electrical  reactions 
of  the  muscles  on  the  affected  side  are  not  altered.  If  the  paralysis  is  due  to  lesion  of  the  facial 
nucleus,  the  Orbicularis  oris  escapes,  as  the  nuclear  origin  of  the  nerve  to  this  muscle  seems  to 
be  connected  with  that  of  the  tongue  nerves;  otherwise  the  symptoms  arc  identical  with  those 
of  the  common  peripheral  facial  palsy,  of  which  several  types  may  be  distinguished  according 
to  the  point  in  its  course  at  which  the  facial  nerve  is  injured.  If  the  lesion  occurs  (a)  in  the  pons, 
facial  paralysis  is  produced  as  in  (d)  below;  taste  and  hearing  are  not  affected,  but  the  abducent 
nerve  also  will  be  paralyzed  because  the  fibres  of  the  facial  nerve  loop  aiound  its  nucleus  in  the 
pons.  When  the  nerve  is  paralyzed  (6)  in  the  petrous  bone,  in  addition  to  the  paralysis  of  the 
muscles  of  expression,  there  is  loss  of  taste  in  the  anterior  part  of  the  tongue,  and  the  patient  is 
unable  to  recognize  the  difference  between  bitters  and  sweets,  acids  and  salines,  from  involvement 
of  the  chorda  tympani.  The  mouth  is  dry,  because  the  salivary  glands  are  not  secreting;  and 
the  sense  of  hearing  is  affected  from  paralysis  of  the  Stapedius.  When  the  cause  of  the  paralysis 
is  (c)  fracture  of  the  base  of  the  skull,  the  acoustic  and  petrosal  nerves  are  usually  involved. 
But  by  far  the  commonest  cause  of  facial  palsy  is  (d)  exposure  of  the  nerve  to  cold  or  injury  at 
or  after  its  exit  from  the  stylomastoid  foramen  {Bell's  paralysis).  In  these  cases  the  face  looks 
asymmetrical  even  when  at  rest,  and  more  so  in  the  old  than  in  the  yoxmg.  The  affected  side 
of  the  face  and  forehead  remains  motionless  when  voluntary  or  emotional  movement  is  attempted. 
The  lines  on  the  forehead  are  smoothed  out,  the  eye  can  be  shut  only  by  hand,  tears  fail  to  enter 
the  lacrimal  puncta  because  they  are  no  longer  in  contact  with  the  conjimctiva,  the  conjimctival 
reflex  is  absent,  and  efforts  to  close  the  eye  merely  cause  the  eyeball  to  roll  upward  until  the 
cornea  hes  under  the  upper  hd.  The  tip  of  the  nose  is  drawn  over  toward  the  soxind  side;  the 
nasolabial  fold  is  partially  obliterated  on  the  affected  side,  and  the  ala  nasi  does  not  move  properly 
on  respiration.  The  Ups  remain  in  contact  on  the  paralyzed  side,,  and  cannot  be  put  together 
for  whistUng;  when  a  smile  is  attempted  the  angle  of  the  mouth  is  drawn  up  on  the  unaffected 
side;  on  the  affected  side  the  Ups  remain  nearly  closed,  and  the  mouth  assumes  a  characteristic 
triangular  form.  During  mastication  food  accumulates  in  the  cheek,  from  paralysis  of  the  Bucci- 
nator, and  dribbles  or  is  pushed  out  from  between  the  paralyzed  lips.  On  protrusion  the  tongue 
seems  to  be  thrust  over  toward  the  palsied  side,  but  verification  of  its  position  by  reference  to 
the  incisor  teeth  will  show  that  this  is  not  really  so.  The  Platysma  and  the  muscles  of  the 
auricula  are  paralyzed;  in  severe  cases  the  articulation  of  labials  is  impaired  The  electrical 
reactions  of  the  affected  muscles  are  altered  (reaction  of  degeneration),  and  the  degree  to  which 
this  alteration  has  taken  place  after  a  week  or  ten  days  gives  a  valuable  guide  to  the  prognosis. 
Most  cases  of  Bell's  palsy  recover  completely. 

The  facial  nerve  is  at  fault  in  cases  of  so-called  histrionic  spasm,  which  consists  in  an  almost 
constant  and  uncontrollable  twitching  of  some  or  all  of  the  muscles  of  the  face.  This  twitching 
is  sometimes  so  severe  as  to  cause  great  discomfort  and  annoyance  to  the  patient,  and  to  interfere 
with  sleep,  and  for  its  relief  the  facial  nerve  has  been  stretched.  The  operation  is  performed  by 
making  an  incision  behind  the  ear,  from  the  root  of  the  mastoid  process  to  the  angle  of  the  man- 
dible. The  parotid  is  turned  forward  and  the  dissection  carried  along  the  anterior  border  of  the 
Stemocleidomastoideus  and  mastoid  process,  imtil  the  upper  border  of  the  posterior  belly  of  the 
Digastricus  is  found.  The  nerve  is  parallel  to  this  on  about  the  level  of  the  middle  of  the  mastoid 
process.  When  found,  the  nerve  must  be  stretched  by  passing  a  blimt  hook  beneath  it  and  pulling 
it  forward  and  outward.  Too  great  force  must  not  be  used,  for  fear  of  permanent  injury  to  the 
nerve. 


THE  ACOUSTIC  NERVE   (N.   ACUSTICUS;  EIGHTH  OR  AUDITORY  NERVE). 

The  acoustic  nerve,  or  nerve  of  hearing,  is  distributed  exclusively  to  the  internal 
ear.  It  consists  of  two  sets  of  fibres,  which,  although  differing  in  their  central 
connections,  are  both  concerned  in  the  transmission  of  afferent  impulses  from  the 
internal  ear  to  the  medulla  oblongata  and  pons,  and  from  there,  by  means  of  fibres 
which  arise  from  collections  of  gray  substance  in  these  structures,  to  the  cerebrum 
and  cerebellum.  One  set  of  fibres  forms  the  vestibular  root  of  the  nerve,  and  arises 
from  the  cells  in  the  vestibular  ganglion  situated  in  the  internal  acoustic  meatus; 
the  other  set  constitutes  the  cochlear  root,  and  takes  origin  from  the  cells  in  the 
ganglion  spirale,  which  occupies  the  spiral  canal  of  the  cochlea.  Both  of  these 
gangha  consist  of  bipolar  nerve  cells;  from  each  of  the  cells  a  central  fibre  passes 
to  the  brain,  a  peripheral  fibre  to  the  internal  ear.  At  its  connection  with  the  brain 
the  eighth  nerve  occupies  the  groove  between  the  pons  and  medulla,  lying  behind 
the  facial  nerve  and  in  front  of  the  restiform  body. 


THE  ACOUSTIC  NERVE 


935 


Vestibular  Root  (radix  vestibularis;  vestibular  nerve)  (Fig.  790). — The  fibres  of 
this  root  enter  the  iiieckilla  oblongata  on  the  medial  side  of  those  of  the  cochlear 
root,  and  pass  between  the  restifonn  body  and  the  spinal  tract  of  the  trigeminal. 
They  then  divide  into  ascentling  and  descending  fibres.  The  latter  end  by  arbor- 
izing around  the  cells  of  the  medial  nucleus,  which  is  situated  in  the  area  acustica 
of  the  rhomboid  fossa.  The  ascending  fibres  either  end  in  the  same  manner  or  in 
the  lateral  nucleus,  which  is  situated  lateral  to  the  area  acustica  and  farther  from 
the  ventricular  floor;  the  lateral  nucleus  consists  of  two  parts,  a  medial,  the  nucleus 
of  Deiters,  and  a  lateral,  the  nucleus  of  Bechterew.  Some  of  the  axons  of  the  cells 
of  the  lateral  nucleus,  and  possibly  also  of  the  medial  nucleus,  are  continued  upward 
through  the  restiform  body  to  the  roof  nuclei  of  the  opposite  side  of  the  cerebellum, 
to  which  also  other  fibres  of  the 
vestibular  root  are  prolonged  with- 
out interruption  in  the  nuclei  of 
the  medulla  oblongata.  A  second 
set  of  fibres  from  the  medial  and 
lateral  nuclei  end  partly  in  the 
tegmentum,  while  the  remainder 
ascend  in  the  medial  longitudinal 
fasciculus  to  arborize  around  the 
cells  of  the  nuclei  of  the  oculo- 
motor nerve. 

Cochlear  Root  (radix  cochlearis; 
cochlear  nerve)  (Fig.  791). — The 
cochlear  root  is  placed  lateral  to 
the  vestibular  root.  Its  fibres  end 
in  two  nuclei:  one,  the  accessory 
nucleus,  lies  immediately  in  front 
of  the  restiform  body;  the  other, 
the  tuberculum  acusticum,  some- 
what lateral  to  it. 

The  striae  medullares  (striae 
acusticae)  are  the  axons  of  the  cells 
of  the  tuberculum  gicusticum. 
They    pass    over    the     restiform 

bpdy,  and  across  the  rhomboid  fossa  to  the  median  sulcus.  Here  they  dip  into 
the  substance  of  the  pons,  to  end  around  the  cells  of  the  superior  olivary  nuclei 
of  both  sides.  There  are,  however,  other  fibres,  and  these  are  both  direct  and 
crossed,  which  pass  into  the  lateral  lemniscus.  The  cells  of  the  accessory  nucleus 
give  origin  to  fibres  which  run  transversely  in  the  pons  and  constitute  the  trapezium. 
Of  the  trapezoid  fibres  some  end  around  the  cells  of  the  superior  olivary  nucleus 
or  of  the  trapezoid  nucleus  of  the  same  or  opposite  side,  while  others,  crossed  or 
uncrossed,  pass  directly  into  the  lateral  lemniscus. 

If  the  further  connections  of  the  cochlear  nerve  of  one  side,  say  the  left,  be  con- 
sidered, it  is  found  that  they  lie  lateral  to  the  main  sensory  tract,  the  lemniscus, 
and  are  therefore  termed  the  lateral  lemniscus.  The  fibres  comprising  the  left 
lateral  lemniscus  arise  in  the  superior  olivary  and  trapezoid  nuclei  of  the  same  or 
opposite  side,  while  others  are  the  uninterrupted  fibres  already  alluded  to,  and  these 
are  either  crossed  or  uncrossed,  the  former  being  the  axons  of  the  cells  of  the  right 
accessory  nucleus  or  of  the  cells  of  the  right  tuberculum  acusticum,  while  the 
latter  are  derived  from  the  cells  of  the  left  nuclei.  In  the  upper  part  of  the  lateral 
lemniscus  there  is  a  collection  of  nerve  cells,  the  nucleus  of  the  lateral  lemniscus, 
around  the  cells  of  which  some  of  the  fibres  arborize  and  from  the  cells  of  which 
axons  originate  to  continue  upward  the  tract  of  the  lateral  lemniscus.    The  ultimate 


Fig.  790. — Terminal  nuclei  of  the  vestibular  root  of  the  acous- 
tic nerve,  with  their  upper  connections.  (Schematic.)  (Testut.) 
1.  Posterior  or  cochlear  root,  with  its  two  nuclei.  2.  Accessory- 
nucleus.  3.  Tuberculum  acusticum.  4.  Anterior  or  vestibular 
root.  5.  Internal  nucleus.  6 .  Nucleus  of  Deiters.  7.  Nucleus  of 
Bechterew.  8.  Inferior  or  descending  root  of  acoustic.  9.  As- 
cending cerebellar  fibres.  10.  Fibres  going  to  raph6.  11.  Fibres 
taking  an  oblique  course.  12.  Lemniscus.  13.  Inferior  sensory- 
root  of  trigeminal.  14.  Cerebrospinal  fasciculus.  15.  Raph6.  16. 
Fourth  ventricle.  17.  Restiform  body.  18.  Origin  of  striae 
medullares. 


936 


NEUROLOGY 


ending  of  the  left  lateral  lemniscus  is  parth'  in  tlie  opposite  medial  geniculate 
body,  and  partly  in  the  inferior  colliculi.  From  the  cells  of  these  bodies  new  fibres 
arise  and  ascend  in  the  occipital  part  of  the  internal  capsule  to  reach  the  posterior 
three-fifths  of  the  left  superior  temporal  gyrus  and  the  transverse  temporal  gyri. 

The  acoustic  nerve  contains  a  few  efferent  fibres  which  arise  in  the  quadrigeminal 
bodies,  the  nucleus  of  the  lateral  lemniscus,  the  superior  olivary  and  trapezoid 
nuclei. 


6     14 


Fig.  791. — Terminal  nuclei  of  the  cochlear  root  of  the  acoustic  nerve,  with  their  upper  connections.  (Schematic.) 
(Testut.)  The  vestibular  root  with  its  terminal  nuclei  and  their  efferent  fibres  have  been  suppressed.  On  the  other 
hand,  in  order  not  to  obscure  the  trapezoid  body,  the  efferent  fibres  of  the  terminal  nuclei  on  the  right  side  have  been 
resected  in  a  considerable  portion  of  their  extent.  The  trapezoid  body,  therefore,  shows  only  one-half  of  its  fibres, 
viz.,  those  which  come  from  the  left.  1.  Vestibular  root  of  the  acoustic,  divided  at  its  entrance  into  the  meduUa 
oblongata.  2.  Cochlear  root.  3.  Accessory  nucleus  of  acoustic  nerve.  4.  Tuberculum  acusticum.  5.  Efferent 
fibres  of  accessory  nucleus.  6.  Efferent  fibres  of  tuberculum  acusticum,  forming  the  striae  medullares,  with  6',  their 
direct  bundle  going  to  the  superior  olivary  nucleus  of  the  same  side;  6",  their  decussating  bundles  going  to  the 
superior  olivary  nucleus  of  the  opposite  side.  7.  Superior  oilvary  nucleus.  8.  Trapezoid  body.  9.  Trapezoid  nucleus. 
10.  Central  acoustic  tract  (lateral  lemniscus).  11.  Raph6.  12.  Cerebrospinal  fasciculus.  13.  Fourth  ventricle. 
14.   Restiform  body. 


The  acoustic  nerve  is  soft  in  texture,  and  destitute  of  neurilemma.  After  leaving 
the  medulla  oblongata  it  passes  forward  across  the  posterior  border  of  the  brachium 
pontis,  in  company  with  the  facial  nerve,  from  which  it  is  partially  separated  by 
the  internal  auditory  artery.  It  then  enters  the  internal  acoustic  meatus  wdth  the 
facial  nerve.  At  the  bottom  of  the  meatus  it  receives  one  or  two  filaments  from  the 
facial  nerve,  and  then  divides  into  its  two  branches,  cochlear  and  vestibular,  the 
distribution  of  which  will  be  described  with  the  anatomy  of  the  internal  ear. 

Applied  Anatomy. — The  acoustic  nerve  is  frequently  injured,  together  with  the  facial  nerve, 
in  fracture  of  the  middle  fossa  of  the  base  of  the  skull  implicating  the  internal  acoustic  meatus. 
The  nerve  may  be  either  torn  across,  producing  permanent  deafness,  or  it  may  be  bruised  or 
pressed  upon  by  extravasated  blood  or  inflammatory  exudation,  when  the  deafness  will  in  all 
probability  be  temporary.  The  nerve  may  also  be  injured  by  violent  blows  on  the  head  without 
any  fracture  of  the  bones  of  the  skull  taking  place,  and  deafness  may  arise  from  loud  explosions 
from  dynamite,  etc.,  probably  from  some  lesion  of  this  nerve,  which  is  more  liable  to  be  injured 
than  the  other  cerebral  nerves  on  account  of  its  structure.  "Nerve  deafness"  as  contrasted 
with  deafness  due  to  changes  in  the  middle  ear  or  meatus,  is  suggested  if  (1)  a  sounding  tuning 
fork  placed  on  the  middle  line  of  the  head  is  heard  better  (Weber's  test)  by  the  unaffected  ear; 
or  if  (2)  the  sounding  tuning  fork  is  heard  longer  when  held  before  the  affected  ear  ( =  air  conduc- 
tion) than  when  it  is  stood  on  the  corresponding  mastoid  (  =  bone  conduction,  Rinn^'s  test);  or 
if  (3)  the  sounding  tuning  fork  applied  to  the  vertex  or  mastoid  is  heard  less  well  when  the  air 
in  the  meatus  is  compressed  by  the  use  of  a  Siegle's  speculum  (Gelle's  test) ;  or  if  (4)  the  tuning 
fork  placed  on  the  mastoid  is  heard  for  a  shorter  time  than  its  sound  is  perceptible  to  a  normal 
individual  (  =  evidence  that    bone  conduction  is  diminished,  Schwabach's  test).      It  must  be 


THE  GLOSSOPHARYNGEAL  NERVE 


937 


remembered  tliat  all  these  tests  are  liable  to  anomalies  and  exceptions,  and  are  not  applicable 
to  old  people.  If,  however,  concordant  results  are  yielded  by  the  tests  of  Weber,  Rinn6,  and 
Gelle,  Bezold's  "triad  of  symptoms,"  nerve  deafness  rather  than  deafness  due  to  disease  of  the 
conducting  structures  is  rendered  highly  probable. 

Tinnitus  aurium,  or  the  hearing  of  sounds  in  the  ear  that  have  no  objective  cause  outside  the 
body,  is  said  to  be  present  in  as  many  as  60  per  cent,  of  cases  of  ear  disease  of  all  sorts,  and  is 
commonest  in  disease  of  the  labyrinth  or  of  the  nerve.  It  is  very  variable  in  intensity;  the  worst 
forms  are  purely  subjective  and  due  to  irritation  of  the  nerve  itself.  The  sounds  heard  are  of  the 
most  varied  nature — buzzing,  hissing,  whistling,  rushing,  bell  ringing,  and  so  forth — and  may 
occupy  the  patient's  attention  so  completely  that  he  is  no  longer  able  to  attend-  to  his  business; 
he  may  even  commit  suicide  in  order  to  escape  from  them.  In  the  insane,  tinnitus  is  associated 
with  delusions  and  hallucinations  of  hearing;  cases  of  insanity  have  even  been  recorded  in  which 
cure  was  effected  by  the  removal  of  cerumen  impacted  in  the  meatus  and  giving  rise  to  persistent 
tinnitus. 


THE  GLOSSOPHARYNGEAL  NERVE  (N.  GLOSSOPHARYNGEUS;  NINTH 

NERVE)   (Figs.  792,  793,  794). 


Awricular 


The  glossopharyngeal  nerve  contains  both  motor  and  sensory  fibres,  and  is  dis- 
tributed, as  its  name  implies,  to  the  tongue  and  pharynx.    It  is  the  nerve  of  ordinary 
sensation  to  the  mucous  membrane  of  the  pharynx,  fauces,  and  palatine  tonsil,  and 
the   nerve  of  taste  to  the 
posterior  part  of  the  tongue. 
It  is  attached  by  three  or 
four  filaments  to  the  upper 
part  of  the  medulla  oblon- 
gata, in  the  groove  between 
the  olive  and  the  restiform 
body. 

The  sensory  fibres  arise 
from  the  cells  of  the  supe- 
rior and  petrous  ganglia, 
which  are  situated  on  the 
trunk  of  the  nerve,  and 
Mall  be  presently  described. 
When  traced  into  the  me- 
dulla, some  of  the  sensory 
fibres  end  by  arborizing 
around  the  cells  of  the 
upper  part  of  a  nucleus 
which  lies  beneath  the  ala 
cinera  in  the  lower  part  of 
the  rhomboid  fossa.  Many 
of  the  fibres,  however,  con- 
tribute to  form  a  strand, 
named  the  fasciculus  soli- 
tarius,  which  descends  in  the  medulla  oblongata.  Associated  with  this  strand 
are  numerous  nerve  cells,  and  around  these  the  fibres  of  the  fasciculus  end. 

The  motor  fibres  spring  from  the  cells  of  the  nucleus  ambiguus,  which  lies  some 
distance  from  the  surface  of  the  rhomboid  fossa  in  the  lateral  part  of  the  medulla 
and  is  continuous  below  with  the  anterior  gray  column  of  the  medulla  spinalis. 
From  this  nucleus  the  fibres  are  first  directed  backward,  and  then  they  bend  for- 
ward and  lateralward  to  join  the  fibres  of  the  sensory  root.  The  nucleus  ambiguus 
gives  origin  to  the  motor  branches  of  the  glossopharyngeal  and  vagus  nerves,  and 
to  the  cerebral  part  of  the  accessory  nerve. 


Pharyngeal 


Laryngeal 


Fig.  792. — Plan  of  upper  portions  of  glossopharyngeal,  vagus,  and 
accessory  nerves. 


938 


NEUROLOGY 


From  the  medulla  oblongata,  the  glossopharyngeal  nerve  passes  lateralward 
across  the  flocculus,  and  leaves  the  skull  through  the  central  part  of  the  jugular 
foramen,  in  a  separate  sheath  of  the  dura  mater,  lateral  to  and  in  front  of  the  vagus 
and  accessory  nerves  (Fig.  793).  In  its  passage  through  the  jugular  foramen, 
it  grooves  the  lower  border  of  the  petrous  part  of  the  temporal  bone;  and,  at  its 
exit  from  the  skull,  passes  forward  between  the  internal  jugular  vein  and  internal 
carotid  artery;  it  descends  in  front  of  the  latter  vessel,  and  beneath  the  styloid 
process  and  the  muscles  connected  with  it,  to  the  lower  border  of  the  Stylo- 
pharyngeus.  It  then  curves  forward,  forming  an  arch  on  the  side  of  the  neck 
and  lying  upon  the  Stylopharyngeus  and  Constrictor  pharyngis  medius.  Thence 
it  passes  under  cover  of  the  Hyoglossus,  and  is  finally  distributed  to  the  palatine 
tonsil,  the  mucous  membrane  of  the  fauces  and  base  of  the  tongue,  and  the 
mucous  glands  of  the  mouth. 


Trochlear  verve 

Trigeminal  nerve 
Facial  nerve 
Acoustic  nerve 


Cereb)  al  peduncle 


Bracliiiim  conjunctivitm 
Brachi2i,m  pontis 
Restiform  body 


Glossopharyngeal, 
nerve 

Vagus  nerve 
A  ccessory  nerve 
cerebral  part 
Hypoglossal  nerve 


Accessory  nerve       \ 
{spinal  part) 


Medulkt  spinalis 


Dura  inater 
(laid  open) 


Fasciculus  cuneatus 
Fasciculus  gracilis 


Fig.  793. — Upper  part  of  medulla  spinalis  and  hind-  and  mid-brains;  posterior  aspect,  exposed  in  situ. 

In  passing  through  the  jugular  foramen,  the  nerve  presents  two  ganglia,  the 
superior  and  the  petrous  (Fig.  792). 

The  superior  ganglion  {ganglion  superius;  jugular  ganglion)  is  situated  in  the 
upper  part  of  the  groove  in  which  the  nerve  is  lodged  during  its  passage  through 
the  jugular  foramen.  It  is  very  small,  and  is  usually  regarded  as  a  detached 
portion  of  the  petrous  ganglion. 


THE  GLOSSOPHARYNGEAL  NERVE 


939 


The  petrous  ganglion  (ganglion  petrosum;  inferior  ganglion)  is  larger  than  the 
superior  ami  is  situated  in  a  depression  in  the  lower  border  of  the  petrous  portion 
of  the  temporal  bone. 

ophai yngcal 
Va<jui>      \f 


Glo 


Branches  of  Communication. — 
The  glossopharyngeal  nerve  com- 
munieates  with  the  vagus,  sym- 
pathetic, and  facial. 

The  branches  to  the  vagus  are 
two  filaments  which  arise  from 
the  petrous  ganglion,  one  pass- 
ing to  the  auricular  branch,  and 
the  other  to  the  jugular  gang- 
lion, of  the  vagus.  The  petrous 
ganglion  is  connected  by  a  fila- 
ment with  the  superior  cervical 
ganglion  of  the  sympathetic. 
The  branch  of  communication 
with  the  facial  perforates  the 
posterior  belly  of  theDigastricus. 
It  arises  from  the  trunk  of  the 
glossopharyngeal  below  the  pet- 
rous ganglion,  and  joins  thefacial 
just  after  tKe  exit  of  that  nerve 
from  the  stylomastoid  foramen. 

Branches  of  Distribution. — The 
branches  of  distribution  of  the 
glossopharyngeal  are:  the  tym- 
panic, carotid,  pharyngeal,  mus- 
cular, tonsillar,  and  lingual. 

The  Tympanic  Nerve  {71.  tym- 
yanicus;  nerve  of  Jacohson)  arises 
from  the  petrous  ganglion,  and 
ascends  to  the  tympanic  cavity 
through  a  small  canal  on  the 
under  surface  of  the  petrous 
portion  of  the  temporal  bone  on 
the  ridge  which  separates  the 
carotid  canal  from  the  jugular 
fossa.  In  the  tympanic  cavity 
it  divides  into  branches  which 
form  the  tympanic  plexus  and 
are  contained  in  grooves  upon 
the  surface  of  the  promontory. 
This  plexus  gives  oflF:  (1)  the 
lesser  superficial  petrosal  nerve; 
(2)  a  branch  to  join  the  greater 
superficial  petrosal  nerve;  and (3) 
branches  to  the  tympanic  cavity, 
all  of  which  will  be  described  in 
connection  with  the  anatomy  of 
the  middle  ear. 

The  Carotid  Branches  {n.  caroticofympanicus  superior  and  7i.  caroticotympanicus 
inferior)  descend  along  thje  trunk  of  the  internal  carotid  artery  as  far  as  its  origin, 
communicating  with  the  pharyngeal  branch  of  the  vagus,  and  with  branches  of 
the  sympathetic. 


Fig.  794.- 


-Course  and  distribution  of  the  glossopharyngeal, 
vagus,  and  accessory  nerves. 


940  NEUROLOGY 

The  Pharyngeal  Branches  ()-ami  phuryiigei)  are  three  or  four  hlaraents  which  unite, 
opposite  the  Constrictor  pharyngis  medius,  with  the  pharyngeal  branches  of  the 
vagus  and  sympathetic,  to  form  the  pharyngeal  plexus;  ])ranches  from  this  plexus 
perforate  the  muscular  coat  of  the  pharynx  and  supply  its  muscles  and  mucous 
membrane. 

The  Muscular  Branch  {ramus  stylopharyngeus)  is  distributed  to  the  Stylo- 
pharyngeus. 

The  Tonsillar  Branches  (rami  tonsillares)  supply  the  palatine  tonsil,  forming 
around  it  a  plexus  from  which  filaments  are  distributed  to  the  soft  palate  and 
fauces,  where  they  communicate  with  the  palatine  nerves. , 

The  Lingual  Branches  {rami  linguales)  are  two  in  number;  one  supplies  the  papillae 
vallatae  and  the  mucous  membrane  covering  the  base  of  the  tongue;  the  other 
supplies  the  mucous  membrane  and  follicular  glands  of  the  posterior  part  of  the 
tongue,  and  communicates  with  the  lingual  nerve. 


THE  VAGUS  NERVE  (N.  VAGUS;  TENTH  NERVE;  PNEUMOGASTRIC 
NERVE)  (Figs.  792,  793,  794). 

The  vagus  nerve  is  composed  of  both  motor  and  sensory  fibres,  and  has  a  more 
extensive  course  and  distribution  than  any  of  the  other  cerebral  nerves,  since  it 
passes  through  the  neck  and  thorax  to  the  abdomen. 

The  vagus  is  attached  by  eight  or  ten  filaments  to  the  medulla  oblongata  in  the 
groove  between  the  olive  and  the  restiform  body,  below  the  glossopharyngeal. 
The  sensory  fibres  arise  from  the  cells  of  the  jugular  ganglion  and  ganglion  nodosum 
of  the  nerve,  and,  when  traced  into  the  medulla  oblongata  mostly  end  by  arborizing 
around  the  cells  of  the  inferior  part  of  a  nucleus  which  lie  beneath  the  ala  cinerea 
in  the  lower  part  of  the  rhomboid  fossa.  Some  of  the  sensory  fibres  of  the  glosso- 
pharyngeal nerve  have  been  seen  to  end  in  the  upper  part  of  this  nucleus.  A  few 
of  the  sensory  fibres  of  the  vagus  descend  in  the  fasciculus  solitarius  and  end  around 
its  cells.  The  motor  fibres  arise  from  the  cells  of  the  nucleus  ambiguus,  already 
referred  to  in  connection  with  the  motor  root  of  the  glossopharyngeal  nerve 
(page  937). 

The  filaments  of  the  nerve  unite,  and  form  a  flat  cord,  which  passes  beneath 
the  flocculus  to  the  jugular  foramen,  through  which  it  leaves  the  cranium.  In 
emerging  through  this  opening,  the  vagus  is  accompanied  by  and  contained  in 
the  same  sheath  of  dura  mater  with  the  accessory  nerve,  a  septum  separating 
them  from  the  glossopharyngeal  which  lies  in  front  (Fig.  793).  In  this  situation 
the  vagus  presents  a  well-marked  ganglionic  enlargement,  which  is  called  the  jugular 
ganglion  {ganglion  of  the  root) ;  to  it  the  accessory  nerve  is  connected  by  one  or  two 
filaments.  After  its  exit  from  the  jugular  foramen  the  vagus  is  joined  by  the  cere- 
bral portion  of  the  accessory  nerve,  and  enlarges  into  a  second  gangliform  swelling, 
called  the  ganglion  nodosum  {ganglion  of  the  trunk) ;  through  this  the  fibres  of  the 
cerebral  portion  of  the  accessory  pass  without  interruption,  being  principally 
distributed  to  the  pharyngeal  and  superior  laryngeal  branches  of  the  vagus,  but 
some  of  its  fibres  descend  in  the  trunk  of  the  vagus,  to  be  distributed  with  the 
recurrent  nerve  and  probably  also  with  the  cardiac  nerves. 

The  vagus  nerve  passes  vertically  down  the  neck  within  the  carotid  sheath, 
lying  between  the  internal  jugular  vein  and  internal  carotid  artery  as  far  as  the 
upper  border  of  the  thyroid  cartilage,  and  then  between  the  same  vein  and  the 
common  carotid  artery  to  the  root  of  the  neck.  The  further  course  of  the  nerve 
differs  on  the  two  sides  of  the  body. 

On  the  right  side,  the  nerve  passes  across  the  subclavian  artery  between  it  and 
the  right  innominate  vein,  and  descends  by  the  side  of  the  trachea  to  the  back  of 


THE  VAGUS  NERVE  941 

the  root  of  tlic  lung,  where  it  spreads  out  in  the  posterior  pulmonary  plexus.  From 
the  k)wer  part  of  this  plexus  two  cords  descend  on  tlie  (cs()j)liafjus,  and  divide  to 
form,  with  branches  from  the  opposite  nerve,  the  oesophageal  plexus.  Below,  these 
branches  are  collected  into  a  single  cord,  which  runs  along  the  back  of  the  oesophagus 
enters  the  abdomen,  and  is  distributed  to  the  postero-inferior  surface  of  the  stomach, 
joining  the  left  side  of  the  coeliac  plexus,  and  sending  filaments  to  the  lienal  plexus. 

On  the  left  side,  the  vagus  enters  the  thorax  between  the  left  carotid  and  sub- 
clavian arteries,  behind  the  left  innominate  vein.  It  crosses  the  left  side  of  the 
arch  of  the  aorta,  and  descends  behind  the  root  of  the  left  lung,  forming  there 
the  posterior  pulmonary  plexus.  From  this  it, runs  along  the  anterior  surface  of  the 
oesophagus,  where  it  unites  with  the  nerve  of  the  right  side  in  the  oesophageal 
plexus,  and  is  continued  to  the  stomach,  distributing  branches  over  its  antero- 
superior  surface;  some  of  these  extend  over  the  fundus,  and  others  along  the  lesser 
curvature.  Filaments  from  these  branches  enter  the  lesser  omentum,  and  join  the 
hepatic  plexus. 

The  jugular  ganglion  {ganglion  jugulare;  ganglion  of  the  root)  is  of  a  grayish 
color,  spherical  in  form,  about  4  mm.  in  diameter.    ■ 

Branches  of  Communication. — ^This  ganglion  is  connected  by  several  delicate 
filaments  to  the  cerebral  portion  of  the  accessory  nerve;  it  also  communicates  by 
a  twig  with  the  petrous  ganglion  of  the  glossopharyngeal,  with  the  facial  nerve 
by  means  of  its  auricular  branch,  and  with  the  sympathetic  by  means  of  an  ascend- 
ing filament  from  the  superior  cervical  ganglion. 

The  ganglion  nodosum  (ganglion  of  the  trunk;  inferior  ganglion)  is  cylindrical 
in  form,  of  a  reddish  color,  and  2.5  cm.  in  length.  Passing  through  it  is  the  cerebral 
portion  of  the  accessory  nerve,  which  blends  with  the  vagus  below  the  ganglion. 

Branches  of  Communication. — This  ganglion  is  connected  with  the  hypoglossal, 
the  superior  cervical  ganglion  of  the  sympathetic,  and  the  loop  between  the  first 
and  second  cervical  nerves. 

Branches  of  Distribution. — The  branches  of  distribution  of  the  vagus  are: 

In  the  Jugular  Fossa i  a     •     i 

^  [Auricular. 

^Pharyngeal. 

In  the  Neck i  Superior  laryngeak 

I  Uecurrent. 

[  Superior  cardiac. 
,  f  Inferior  cardiac. 

In  the  Thorax Anterior  bronchial. 

Posterior  bronchial. 

,  Oesophageal. 

f  Gastric. 
In  the  Abdomen I  Coeliac. 

[  Hepatic. 

The  Meningeal  Branch  {ramus  meningeus;  dural  branch)  is  a  recurrent  filament 
given  off  from  the  jugular  ganglion;  it  is  distributed  to  the  dura  mater  in  the 
posterior  fossa  of  the  base  of  the  skull. 

The  Auricular  Branch  {ramus  auricularis;  nerve  of  Arnold)  arises  from  the  jugular 
ganglion,  and  is  joined  soon  after  its  origin  by  a  filament  from  the  petrous  ganglion 
of  the  glossopharyngeal;  it  passes  behind  the  internal  jugular  vein,  and  enters  the 
mastoid  canaliculus  on  the  lateral  wall  of  the  jugular  fossa.  Traversing  the  sub- 
stance of  the  temporal  bone,  it  crosses  the  facial  canal  about  4  mm.  above  the  stylo- 
mastoid foramen,  and  here  it  gives  off  an- ascending  branch  which  joins  the  facial 
nerve.  The  nerve  reaches  the  surface  by  passing  through  the  tympanomastoid 
fissure  between  the  mastoid  process  and  the  tympanic  part  of  the  temporal  bone,. 


942  NEUROLOGY 

and  divides  into  two  branches:  one  joins  the  posterior  auricular  nerve,  the  other 
is  distributed  to  the  skin  of  the  back  of  the  auricuhi  and  to  the  posterior  part  of 
the  external  acoustic  meatus. 

The  Pharyngeal  Branch  {ramus  pharyngeus),  the  principal  motor  nerve  of  the 
pharynx,  arises  from  the  upper  part  of  the  ganglion  nodosum,  and  consists  prin- 
cipally of  filaments  from  the  cerebral  portion  of  the  accessory  nerve.  It  passes 
across  the  internal  carotid  artery  to  the  upper  border  of  the  Constrictor  pharyngis 
medius,  where  it  divides  into  numerous  filaments,  which  join  with  branches  from 
the  glossopharyngeal,  sympathetic,  and  external  laryngeal  to  form  the  pharyngeal 
plexus.  From  the  plexus,  branches  are  distributed  to  the  muscles  and  mucous 
membrane  of  the  pharynx  and  the  muscles  of  the  soft  palate,  except  the  Tensor 
veli  palatini.  A  minute  filament  descends  and  joins  the  hypoglossal  nerve  as  it 
winds  around  the  occipital  artery. 

The  Superior  Laryngeal  Nerve  {n.  laryngeus  superior)  larger  than  the  preceding, 
arises  from  the  middle  of  the  ganglion  nodosum  and  in  its  course  receives  a  branch 
from  the  superior  cervical  ganglion  of  the  sympathetic.  It  descends,  by  the  side  of 
the  pharynx,  behind  the  internal  carotid  artery,  and  divides  into  two  branches, 
external  and  internal. 

The  external  branch  {ramus  externus),  the  smaller,  descends  on  the  larynx,  beneath 
the  Sternothyreoideus,  to  supply  the  Cricothyreoideus.  It  gives  branches  to  the 
pharyngeal  plexus  and  the  Constrictor  pharyngis  inferior,  and  communicates  with 
the  superior  cardiac  nerve,  behind  the  common  carotid  artery. 

The  internal  branch  {ramus  internus)  descends  to  the  hyothyroid  membrane, 
pierces  it  in  company  wdth  the  superior  laryngeal  artery,  and  is  distributed  to  the 
mucous  membrane  of  the  larynx.  Of  these  branches  some  are  distributed  to  the 
epiglottis,  the  base  of  the  tongue,  and  the  epiglottic  glands;  others  pass  backward, 
in  the  ary epiglottic  fold,  to  supply  the  mucous  membrane  surrounding  the  entrance 
of  the  larynx,  and  that  lining  the  cavity  of  the  larynx  as  low  down  as  the  vocal 
folds.  A  filament  descends  beneath  the  mucous  membrane  on  the  inner  surface 
of  the  thyroid  cartilage  and  joins  the  recurrent  nerve. 

The  Recurrent  Nerve  {n.  recurrens;  inferior  or  recurrent  laryngeal  nerve)  arises, 
on  the  right  side,  in  front  of  the  subclavian  artery;  winds  from  before  back- 
ward around  that  vessel,  and  ascends  obliquely  to  the  side  of  the  trachea  behind 
the  common  carotid  artery,  and  either  in  front  of  or  behind  the  inferior  thyroid 
artery.  On  the  left  side,  it  arises  on  the  left  of  the  arch  of  the  aorta,  and  winds 
below  the  aorta  at  the  point  where  the  ligamentum  arteriosum  is  attached,  and  then 
ascends  to  the  side  of  the  trachea.  The  nerve  on  either  side  ascends  in  the  groove 
between  the  trachea  and  oesophagus,  passes  under  the  lower  border  of  the  Con- 
strictor pharyngis  inferior,  and  enters  the  larynx  behind  the  articulation  of  the 
inferior  cornu  of  the  thyroid  cartilage  with  the  cricoid;  it  is  distributed  to  all  the 
muscles  of  the  larynx,  excepting  the  Cricothyreoideus.  It  communicates  with  the 
internal  branch  of  the  superior  laryngeal  nerve,  and  gives  off  a  few  filaments  to 
the  mucous  membrane  of  the  lower  part  of  the  larynx. 

As  the  recurrent  nerve  hooks  around  the  subclavian  artery  or  aorta,  it  gives 
off  several  cardiac  filaments  to  the  deep  part  of  the  cardiac  plexus.  As  it  ascends 
in  the  neck  it  gives  off  branches,  more  numerous  on  the  left  than  on  the  right  side, 
to  the  mucous  membrane  and  muscular  coat  of  the  oesophagus;  branches  to  the 
mucous  membrane  and  muscular  fibres  of  the  trachea;  and  some  pharyngeal 
filaments  to  the  Constrictor  pharyngis  inferior. 

The  Superior  Cardiac  Branches  {rami  cardiaci  superior es;  cervical  cardiac  branches), 
two  or  three  in  number,  arise  from  the  vagus,  at  the  upper  and  lower  parts  of  the 
neck. 

The  upper  branches  are  small,  and  communicate  with  the  cardiac  branches 
of  the  sympathetic.    They  can  be  traced  to  the  deep  part  of  the  cardiac  plexus. 


THE  VAGUS  NERVE  943 

The  lower  branch  arises  at  the  root  of  the  neck,  just  above  the  first  rib.  That 
from  the  right  vagus  passes  in  front  or  by  the  side  of  the  innominate  artery,  and 
proceeds  to  the  deep  part  of  tlie  canUac  plexus;  that  from  the  left  runs  down  across 
the  left  side  of  the  arch  of  the  aorta,  and  joins  the  superficial  part  of  the  cardiac 
plexus. 

The  Inferior  Cardiac  Branches  {rami  cardiaci  inferiores;  thoracic  cardiac  branches), 
on  the  right  side,  arise  from  the  trunk  of  the  vagus  as  it  lies  by  the  side  of  the 
trachea,  and  from  its  recurrent  nerve;  on  the  left  side  from  the  recurrent  nerve  only; 
passing  inward,  they  end  in  the  deep  part  of  the  cardiac  plexus. 

The  Anterior  Bronchial  Branches  (rami  bronchiales  anteriores;  anterior  or  ventral 
pulmonary  branches),  two  or  three  in"  number,  and  of  small  size,  are  distributed 
on  the  anterior  surface  of  the  root  of  the  lung.  They  join  with  filaments  from  the 
sympathetic,  and  form  the  anterior  pulmonary  plexus. 

The  Posterior  Bronchial  Branches  {rami  bronchiales  posteriores;  posterior  or  dorsal 
pulmonary  branches),  more  numerous  and  larger  than  the  anterior,  are  distributed 
on  the  posterior  surface  of  the  root  of  the  lung;  they  are  joined  by  filaments  from 
the  third  and  fourth  (sometimes  also  from  the  first  and  second)  thoracic  ganglia 
of  the  sympathetic  trunk,  and  form  the  posterior  pulmonary  plexus.  Branches  from 
this  plexus  accompany  the  ramifications  of  the  bronchi  through  the  substance  of 
the  lung. 

The  (Esophageal  Branches  {rami  oesophagei)  are  given  off  both  above  and  below 
the  bronchial  branches;  the  lower  are  numerous  and  larger  than  the  upper.  They 
form,  together  with  the  branches  from  the  opposite  nerve,  the  oesophageal  plexus. 
From  this  plexus  filaments  are  distributed  to  the  back  of  the  pericardium. 

The  Gastric  Branches  {rami  gastrici)  are  distributed  to  the  stomach.  The  right 
vagus  forms  tlie  posterior  gastric  plexus  on  the  postero-inferior  surface  of  the  stomach 
and  the  left  the  anterior  gastric  plexus  on  the  antero-superior  surface. 

The  Coeliac  Branches  {rami  coeliaci)  are  mainly  derived  from  the  right  vagus:  they 
join  the  coeliac  plexus  and  through  it  supply  branches  to  the  pancreas,  spleen, 
kidneys,  suprarenal  bodies,  and  intestine. 

The  Hepatic  Branches  {rami  hepatici)  arise  from  the  left  vagus :  they  join  the  hepatic 
plexus  and  through  it  are  conveyed  to  the  liver. 

Applied  Anatomy. — The  trunk  of  the  vagus  is  rarely  injured,  but  the  functions  of  the  nerve 
may  be  interfered  with  by  damage  to  its  nucleus  of  origin  in  the  medulla;  by  thickening  or  growth 
from  the  meninges  or  bones,  or  anem-ism  of  the  basilar  artery,  before  its  exit  from  the  skull; 
injuries  such  as  gimshot  or  pimctured  wounds  in  the  neck,  or  injiu'ies  during  such  operations 
as  Ugatiu-e  of  the  carotid  artery,  removal  of  tuberculous  glands  or  other  deep-seated  tumors. 
The  vagus  may  also  be  compressed  by  aneurisms  of  the  carotid  artery,  and  its  deep  origin  becomes 
affected  in  bulbar  paralysis.  The  symptoms  produced  by  paralysis  of  the  nerve  are  palpitation, 
with  increased  frequency  of  the  pulse,  constant  vomiting,  slowing  of  the  respiration,  and  a  sensa- 
tion of  suffocation. 

"Reflexes"  on  the  branches  of  the  vagus  are  not  at  aU  imcommonly  met  with.  The  "ear 
cough"  is  perhaps  one  of  the  commonest,  where  a  plug  of  wax  in  the  acoustic  meatus  may  by 
irritating  the  filaments  of  the  auricular  (Arnold's)  nerve  be  responsible  for  a  persistent  cough. 
Syringing  the  external  acoustic  meatus  frequently  produces  cough,  and,  in  children,  vomiting 
is  not  uncommon  as  the  result  of  such  a  procedure;  moreover,  in  people  with  weak  hearts,  syringing 
the  ear  has  been  responsible  for  a  sudden  fatal  syncope,  by  reflex  irritation  of  the  cardiac  branches. 
Another  very  common  example  is  the  persistent  cough  which  is  frequently  due  to  enlarged 
bronchial  glands  in  children,  the  irritation  of  which  is  referred  to  the  superior  laryngeal  filaments. 

The  anatomy  of  the  laryngeal  nerves  is  of  importance  in  considering  some  of  the  morbid  condi- 
tions of  the  larynx.  When  the  peripheral  terminations  of  the  superior  laryngeal  nerve  are  irri- 
tated by  some  foreign  body  passing  over  them,  reflex  spasm  of  the  glottis  is  the  result.  When 
its  trunk  is  pressed  upon  by,  for  instance,  a  goitre  or  an  aneiirism  of  the  upper  part  of  the  carotid, 
there  is  a  peculiar  dry,  brassy  cough.  When  the  nerve  is  paralyzed,  there  is  anesthesia  of  the 
mucous  membrane  of  the  larjmx,  so  that  foreign  bodies  can  readily  enter  the  cavity,  and,  as  the 
nerve  also  supplies  the  Cricothyreoideus  muscle,  the  vocal  folds  cannot  be  made  tense,  and  the 
voice  is  deep  and  hoarse.  Paralysis  may  be  the  result  of  bulbar  paralysis;  may  be  a  sequel  to 
diphtheria,  when  both  nerves  are  usually  involved;  or  it  may,  though  less  commonly,  be  caused 


944 


NEUROLOGY 


by  the  pressure  of  tumors  or  aneurisms,  when  the  paralysis  is  generally  unilateral.  Irritation  of 
the  recurrent  nerves  produces  spasm  of  the  muscles  of  the  larynx.  When  both  recurrent  nerves 
are  paralyzed,  the  vocal  folds  are  motionless,  in  the  so-called  "  cadaveric  position"— that  is  to 
say,  in  the  position  in  which  they  are  found  in  ordinary  tranquil  respiration;  neither  closed  as 
in  phonation,  nor  open  as  in  deep  inspiratory  efforts.  When  one  recurrent  nerve  is  paralyzed, 
the  vocal  fold  of  the  same  side  is  motionless,  while  the  opposite  one  crosses  the  middle  line  to 
accommodate  itself  to  the  affected  one;  hence  phonation  is  possible,  but  the  voice  is  altered  and 
weak  in  timbre.  The  nerves  may  be  paralyzed  in  bulbar  paralysis  or  after  diphtheria,  when  the 
paralysis  usually  affects  both  sides;  or  they  may  be  affected  by  the  pressure  of  aneurisms  of  the 
aorta,  innominate,  or  subclavian  arteries;  by  mediastinal  tumors;  by  gummata;  or  by  cancer 
of  the  upper  part  of  the  oesophagus,  when  the  paralysis  is  often  unilateral.  Paralysis  of  the 
adductor  muscles  of  the  larynx  on  both  sides  is  quite  common,  and  is  usually  functional  in  nature. 
The  voice  is  reduced  to  a  whisper,  but  the  power  of  coughing  is  preserved. 


Fig.  795. — Hypoglossal  nerve,  cervical  plexus,  and  their  branches. 


THE   ACCESSORY  NERVE   (N.   ACCESSORIUS;  ELEVENTH  NERVE; 
SPINAL  ACCESSORY  NERVE)    (Figs.  793,  794,  795). 

The  accessory  nerve  consists  of  two  parts :  a  cerebral  and  a  spinal. 

The  cerebral  part  {ramus  internus;  accessory  portion)  is  the  smaller  of  the  two. 
Its  fibres  arise  from  the  cells  of  the  nucleus  ambiguus  and  emerge  as  four  or  five 
delicate  rootlets  from  the  side  of  the  medulla  oblongata,  below  the  roots  of  the 
vagus.  It  runs  lateralward  to  the  jugular  foramen,  where  it  interchanges  fibres 
with  the  spinal  portion  or  becomes  united  to  it  for  a  short  distance;  here  it  is  also 
connected  by  one  or  two  filaments  with  the  jugular  ganglion  of  the  vagus.     It 


THE  HYPOGLOSSAL  NERVE  945 

then  passes  through  the  juguhir  foramen,  separates  from  the  spinal  portion  and 
is  continued  over  the  surface  of  the  ganglion  nodosum  of  the  vagus,  to  the  surface  of 
which  it  is  atlherent,  and  is  distributed  principally  to  the  pharyngeal  and  superior 
laryngeal  branches  of  the  vagus.  Through  the  pharyngeal  branch  it  probably  sup- 
plies the  Musculus  uvulae  and  Levator  veli  palatini.  Some  few  filaments  from  it 
are  continued  into  the  trunk  of  the  vagus  below  the  ganglion,  to  be  distributed  with 
the  recurrent  nerve  and  probably  also  with  the  cardiac  nerves. 

The  spinal  part  (ramus  e.vfernus;  spinal  portion)  is  firm  in  texture,  and  its  fibres 
arise  from  the  motor  cells  in  the  lateral  part  of  the  anterior  column  of  the  gray  sub- 
stance of  the  medulla  spinalis  as  low  as  the  fifth  cervical  nerve.  Passing  through  the 
lateral  funiculus  of  the  medulla  spinalis,  they  emerge  on  its  surface  and  unite  to 
form  a  single  trunk,  which  ascends  between  the  ligamentum  denticulatum  and  the 
posterior  roots  of  the  spinal  nerves,  enters  the  skull  through  the  foramen  magnum, 
and  is  then  directed  to  the  jugular  foramen,  through  which  it  passes,  lying  in  the 
same  sheath  of  dura  mater  as  the  vagus,  but  separated  from  it  by  a  fold  of  the 
arachnoid.  In  the  jugular  foramen,  it  recei^'es  one  or  two  filaments  from  the  cere- 
bral part  of  the  nerve,  or  else  joins  it  for  a  short  dista^nce  and  then  separates  from 
it  again.  iVs  its  exit  from  the  jugular  foramen,  it  runs  backward  in  front  of  the 
internal  jugular  vein  in  66.6  per  cent,  of  cases,  and  behind  in  it  33.3  per  cent. 
(Tandler).  The  nerve  then  descends  obliquely  behind  the  Digastricus  and  Stylo- 
hyoideus  to  the  upper  part  of  the  Sternocleidomastoideus;  it  pierces  this  muscle, 
and  courses  obliquely  across  the  posterior  triangle  of  the  neck,  to  end  in  the  deep 
surface  of  the  Trapezius.  As  it  traverses  the  Sternocleidomastoideus  it  gives  several 
filaments  to  the  muscle,  and  joins  with  branches  from  the  second  cervical  nerve. 
In  the  posterior  triangle  it  unites  with  the  second  and  third  cervical  nerves,  while 
beneath  the  Trapezius  it  forms  a  plexus  with  the  third  and  fourth  cervical  nerves, 
and  from  this  plexus  fibres  are  distributed  to  the  muscle. 

Applied  Anatomy. — The  functions  of  the  accessory  nerve  may  be  interfered  with  either  by 
central  changes;  or  at  its  exit  from  the  skull,  by  fractures  running  across  the  jugular  foramen; 
or  in  the  neck,  by  inflamed  lymph  glands,  etc.  The  acute  wiy-neck  in  children  is  most  commonly 
due  to  inflamed  or  suppurating  glands,  and  rapidly  subsides  with  appropriate  treatment.  Central 
irritation  causes  clonic  spasm  of  the  Sternocleidomastoideus  and  Trapezius  muscles,  or,  as  it  is 
termed,  spasmodic  torticollis.  In  cases  of  this  affection  in  which  all  previous  paUiative  treat- 
ment has  failed,  and  the  spasms  are  so  severe  as  to  undermine  the  patient's  health,  division  or 
excision  of  a  portion  of  the  accessory  nerve  has  been  resorted  to.  This  must  be  done  from  the 
anterior  border  of  the  Sternocleidomastoideus.  The  operation  consists  in  making  an  incision, 
8  cm.  in  length,  from  the  apex  of  the  mastoid  process  along  the  anterior  border  of  the  muscle, 
which  is  defined  and  pulled  backward,  so  as  to  stretch  the  nerve,  which  is  then  to  be  sought  for 
beneath  the  Digastricus,  about  5  cm.  below  the  apex  of  the  mastoid  process.  Unfortunately, 
the  operation  does  not  yield  a  satisfactory  or  permanent  cm-e,  as  the  spasms  tend  to  recm-  after 
an  interval,  either  in  the  same  muscles  or  in  other  groups  of  neck  muscles. 

In  cases  where  extensive  dissections  are  undertaken  for  enlarged  glands  in  the  neck,  it  is  essential 
that  this  nerve  should  be  at  once  sought  for  and  isolated  from  the  mass  of  inflamed  glands  so  as 
to  maintain  its  continuity. 

THE  HYPOGLOSSAL  NERVE  (N.  HYPOGLOSSUS;  TWELFTH  NERVE) 

(Figs.  795,  796). 

The  hypoglossal  nerve  is  the  motor  nerve  of  the  tongue. 

Its  fibres  arise  from  the  cells  of  the  hypoglossal  nucleus,  which  is  an  upward 
prolongation  of  the  base  of  the  anterior  column  of  gray  substance  of  the  medulla 
spinalis.  This  nucleus  is  about  2  cm.  in  length,  and  its  upper  part  corresponds 
with  the  trigonum  hypoglossi,  or  lower  portion  of  the  medial  eminence  of  the  rhom- 
boid fossa  (page  848).  The  lower  part  of  the  nucleus  extends  downward  into  the 
closed  part  of  the  medulla  oblongata,  and  there  lies  in  relation  to  the  ventro-lateral 
aspect  of  the  central  canal.  The  fibres  run  forward  through  the  medulla  oblongata, 
and  emerge  in  the  antero-lateral  sulcus  between  the  pyramid  and  the  olive. 
60 


946 


NEUROLOGY 


The  rootlets  of  this  nerve  are  collected  into  two  bundles,  which  perforate  the 
dura  mater  separately,  opposite  the  hypoglossal  canal  in  the  occipital  bone,  and 
unite  together  after  their  passage  through  it;  in  some  cases  the  canal  is  di\ided 
into  two  by  a  small  bony  spicule.  The  nerve  descends  almost  vertically  to  a  point 
corresponding  with  the  angle  of  the  mandible.  It  is  at  first  deeply  seated  beneath 
the  internal  carotid  artery  and  internal  jugular  vein,  and  intimately  connected  with 
the  vagus  nerve;  it  then  passes  forward  between  the  vein  and  artery,  and  lower 
down  in  the  neck  becomes  superficial  below  the  Digastricus.    The  nerve  then  loops 


To  Dura  uiatc 


To  Lingual  nerve 
TO  GENIOHYOIDEUS 


TO  SUPERIOR  BELLY  OF  OMOHYOIDEUS 


TO   STERNOHYOIDEUS 

TO  STERNOTHYREOIDEUS 
TO  INFERIOR  BELLY  OF  OMOHYOIDEUS 


Fig.   796. — Plan  of  hypoglossal  nerve. 


around  the  occipital  artery,  and  crosses  the  external  carotid  and  lingual  arteries 
below  the  tendon  of  the  Digastricus.  It  passes  beneath  the  tendon  of  the  Digas- 
tricus, the  Stylohyoideus,  and  the  Mylohyoideus,  lying  between  the  last-named 
muscle  and  the  Hyoglossus,  and  communicates  at  the  anterior  border  of  the  Hyo- 
glossus  with  the  lingual  nerve;  it  is  then  continued  forward  in  the  fibres  of  the 
Genioglossus  as  far  as  the  tip  of  the  tongue,  distributing  branches  to  its  muscular 
substance. 

Branches  of  Communication.^ — Its  branches  of  communication  are,  with  the 


Vagus. 
Sympathetic. 


First  and  second  cervical  nerves. 
Lingual. 


The  communications  with  the  vagus  take  place  close  to  the  skull,  numerous 
^laments  passing  between  the  hypoglossal  and  the  ganglion  nodosum  of  the  vagus 


THE  SPINAL  NERVES  947 

through  the  mass  of  connective  tissue  whicli  unites  tlie  two  nerves.    As  the  nerve 
winds  around  the  occipital  artery  it  gives  off  a  filament  to  the  pharyngeal  plexus. 

The  communication  with  the  sympathetic  takes  place  opposite  the  atlas  by 
branches  derived  from  the  superior  cervical  ganglion,  and  in  the  same  situation 
the  nerve  is  joined  by  a  filament  derived  from  the  loop  connecting  the  first  and 
second  cervical  nerves. 

The  communications  with  the  lingual  take  place  near  the  anterior  border  of  the 
Hyoglossus  by  numerous  filaments  which  ascend  upon  the  muscle. 

Branches  of  Distribution. — The  branches  of  distribution  of  the  hypoglossal  nerve 
are: 

^Meningeal.  Thyrohyoid. 

Descending.  .  Muscular. 

Of  these  branches,  the  meningeal,  descending,  thyrohyoid,  and  the  muscular 
twig  to  the  Geniohyoideus,  are  probably  derived  mainly  from  the  branch  which 
passes  from  the  loop  between  the  first  and  second  cervical  to  join  the  hypoglossal 
(Fig.  796). 

Meningeal  Branches  {dural  branches). — As  the  hypoglossal  nerve  passes  through 
the  hypoglossal  canal  it  gives  off,  according  to  Luschka,  several  filaments  to  the 
dura  mater  in  the  posterior  fossa  of  the  skull. 

The  Descending  Ramus  {ramus  descendens;  descendens  hypoglossi),  long  and  slender, 
quits  the  hypoglossal  where  it  turns  around  the  occipital  artery  and  descends  in 
front  of  or  in  the  sheath  of  the  carotid  vessels;  it  gives  a  branch  to  the  superior 
belly  of  the  Omohyoideus,  and  then  joins  the  communicantes  cervicales  from  the 
second  and  third  cervical  nerves;  just  below  the  middle  of  the  neck,  to  form  a  loop, 
the  ansa  hypoglossi.  From  the  convexity  of  this  loop  branches  pass  to  supply 
the  Sternohyoideus,  the  Sternothyreoideus,  and  the  inferior  belly  of  the  Omo- 
hyoideus. According  to  Arnold,  another  filament  descends  in  front  of  the  vessels 
into  the  thorax,  and  joins  the  cardiac  and  phrenic  nerves. 

The  Thyrohyoid  Branch  {ramus  thyreohyoideus)  arises  from  the  hypoglossal  near 
the  posterior  border  of  the  hyoglossus;  it  runs  obliquely  across  the  greater  cornu 
of  the  hyoid  bone,  and  supplies  the  Thyreohyoideus  muscle. 

The  Muscular  Branches  are  distributed  to  the  Styloglossus,  Hyoglossus,  Genio- 
hyoideus, and  Genioglossus.  At  the  under  surface  of  the  tongue  numerous  slender 
branches  pass  upward  into  the  substance  of  the  organ  to  supply  its  intrinsic  muscles. 

Applied  Anatomy. — The  hypoglossal  nerve  is  an  important  guide  in  the  operation  of  ligature 
of  the  lingual  artery  (see  p.  632).  It  runs  forward  on  the  Hyoglossus  just  above  the  greater 
cornu  of  the  hyoid  bone,  and  forms  the  upper  boundary  of  the  triangular  space  in  which  the 
artery  is  to  be  sought  for  by  cutting  through  the  fibres  of  the  Hyoglossus.  In  cases  where  the 
nerve  is  involved  by  gumma  or  new  growth  of  the  base  of  the  skull,  or  where  it  has  been  injured 
on  one  side  of  the  neck,  or  in  some  cases  of  bulbar  paralysis,  unilateral  paralysis,  together  with 
hemiatrophy  of  the  tongue,  results;  the  tongue,  when  protruded,  being  directed  to  the  paralyzed 
side  owing  to  the  unopposed  action  of  the  Genioglossus  of  the  opposite  side.  On  retraction,  the 
wasted  and  paralyzed  side  of  the  tongue  rises  up  higher  than  the  other.  The  larynx  may  deviate 
toward  the  soimd  side  on  swallowing,  from  the  unilateral  paralysis  of  the  depressors  of  the  hyoid 
bone.  If  the  paralysis  is  bilateral,  the  tongue  lies  motionless  in  the  mouth,  while  articulation 
and  mastication  are  much  interfered  with. 

THE  SPINAL  NERVES  (NERVI  SPINALES). 

The  spinal  nerves  spring  from  the  medulla  spinalis,  and  are  transmitted  through 
the  intervertebral  foramina.  They  number  thirty-one  pairs,  which  are  grouped 
as  follows:    Cervical,  8;  Thoracic,  12;  Lumbar,  5;  Sacral,  5;  Coccygeal,  1. 

The  first  cervical  nerve  emerges  from  the  vertebral  canal  between  the  occipital 
bone  and  the  atlas,  and  is  therefore  called  the  suboccipital  nerve;  the  eighth  issues 
between  the  seventh  cervical  and  first  thoracic  vertebrae. 


948 


NEUROLOGY 


Nerve  Roots. — Each  nerve  is  attached  to  the  mecUiHa  spinalis  by  two  roots, 
an  anterior  or  ventral,  and  a  posterior  or  dorsal,  the  hitter  being  characterized  by 
the  presence  of  a  ganghon,  the  spinal  ganglion. 

The  Anterior  Root  {radix  anterior;  ventral  ruut)  emerges  from  the  anterior  surface 
of  the  medulla  spinalis  as  a  number  of  rootlets  or  filaments  (fila  radicularia) , 
which  coalesce  to  form  two  bundles  near  the  intervertebral  foramen. 

The  Posterior  Root  [radix  yosterior;  dorsal  root)  is  larger  than  the  anterior  owing 
to  the  greater  size  and  number  of  its  rootlets;  these  are  attacherl  along  the  postero- 
lateral furrow  of  the  medulla  spinalis  and  unite  to  form  two  bundles  which  join 
the  spinal  ganglion.  The  posterior  root  of  the  first  cervical  nerve  is  exceptional 
in  that  it  is  smaller  than  the  anterior;  it  is  occasionally  wanting. 


Ventral  aspect  Dorsal  aspect 

Fig.  797. — Distribution  of  cutaneous  norvL-.s. 


The  Spinal  Ganglia  (ganglion  spinale)  are  collections  of  nerve  cells  on  the  posterior 
roots  of  the  spinal  nerves.  Each  ganglion  is  oval  in  shape,  reddish  in  color,  and 
its  size  bears  a  proportion  to  that  of  the  nerve  root  on  which  it  is  situated;  it  is 
bifid  medially  where  it  is  joined  by  the  two  bundles  of  the  posterior  nerve  root. 


THE  SPINAL  NERVES  949 

The  ganglia  are  usually  placed  in  the  inter\'ertebral  foramina,  immediately  outside 
the  points  where  the  nerve  roots  perforate  the  dura  mater,  but  there  are  exceptions 
to  this  rule;  thus  the  ganglia  of  the  first  and  second  cervical  nerves  lie  on  the  verte- 
bral arches  of  the  atlas  and  axis  respectively,  those  of  the  sacral  nerves  are  inside 
the  vertebral  canal,  while  that  on  the  posterior  root  of  the  coccygeal  nerve  is  placed 
within  the  sheath  of  dura  mater. 

Structure  (Fig.  679). — The  ganglia  consist  chiefly  of  unipolar  nerve  cells,  and  from  these  the 
fibres  of  the  posterior  root  take  origin — the  single  process  of  each  cell  dividing  after  a  short  course 
into  a  central  fibre  which  enters  the  medulla  spinalis  and  a  peripheral  fibre  which  runs  into  the 
spinal  nerve.  Two  other  forms  of  cells  are,  however,  present,  viz.:  (a)  the  cells  of  Dogiel,  whose 
axons  ramifj^  close  to  the  cell  (type  II,  of  Golgi),  and  are  distributed  entirely  within  the  ganglion; 
and  (b)  multipolar  cells  similar  to  those  found  in  the  sympathetic  ganglia. 

The  ganglia  of  the  first  cervical  nerve  may  be  absent,  while  small  aberrant  ganglia  consisting 
of  groups  of  nerve  cells  are  sometiines  found  on  the  posterior  roots  between  the  spinal  ganglia 
and  the  medulla  spinalis. 

Each  nerve  root  receives  a  covering  from  the  pia  mater,  and  is  loosely  invested 
by  the  arachnoid,  the  latter  being  prolonged  as  far  as, the  points  where  the  roots 
pierce  the  dura  mater.  The  two  roots  pierce  the  dura  mater  separately,  each  receiv- 
ing a  sheath  from  this  membrane;  where  the  roots  join  to  form  the  spinal  nerve 
this  sheath  is  continuous  with  the  epineurium  of  the  nerve. 

Size  and  Direction. — Tlie  roots  of  the  upper  four  cervical  nerves  are  small,  those 
of  the  lower  four  are  large.  The  posterior  roots  of  the  cervical  nerves  bear  a  pro- 
portion to  the  anterior  of  three  to  one,  which  is  greater  than  in  the  other  regions; 
their  individual  filaments  are  also  larger  than  those  of  the  anterior  roots.  The 
posterior  root  of  the  first  cervical  is  an  exception  to  this  rule,  being  smaller  than 
the  anterior  root;  in  eight  per  cent,  of  cases  it  is  wanting.  The  roots  of  the  first 
and  second  cervical  nerves  are  short,  and  run  nearly  horizontally  to  their  points 
of  exit  from  the  vertebral  canal.  From  the  second  to  the  eighth  cervical  they  are 
directed  obliquely  downward,  the  obliquity  and  length  of  the  roots  successively 
increasing;  the  distance,  however,  between  the  level  of  attachment  of  any  of  these 
roots  to  the  medulla  spinalis  and  the  points  of  exit  of  the  corresponding  nerves 
never  exceeds  the  depth  of  one  vertebra. 

The  roots  of  the  thoracic  nerves,  with  the  exception  of  the  first,  are  of  small 
size,  and  the  posterior  only  slightly  exceed  the  anterior  in  thickness.  They  increase 
successively  in  length,  from  above  downward,  and  in  the  lower  part  of  the  thoracic 
region  descend  in  contact  with  the  medulla  spinalis  for  a  distance  equal  to  the  height 
of  at  least  two  vertebrae  before  they  emerge  from  the  vertebral  canal. 

The  roots  of  the  lower  lumbar  and  upper  sacral  nerves  are  the  largest,  and  their 
individual  filaments  the  most  numerous  of  all  the  spinal  nerves,  while  the  roots 
of  the  coccygeal  nerve  are  the  smallest. 

The  roots  of  the  lumbar,  sacral,  and  coccygeal  nerves  rim  vertically  downward 
to  their  respective  exits,  and  as  the  medulla  spinalis  ends  near  the  lower  border 
of  the  first  lumbar  vertebra  it  follows  that  the  length  of  the  successive  roots  must 
rapidly  increase.  As  already  mentioned  (page  806),  the  term  cauda  equina  is  applied 
to  this  collection  of  nerve  roots. 

From  the  description  given  it  Avill  be  seen  that  the  largest  nerve  roots,  and 
consequently  the  largest  spinal  nerves,  are  attached  to  the  cervical  and  lumbar 
swellings  of  the  medulla  spinalis;  these  nerves  are  distributed  to  the  upper  and 
lower  limbs. 

Connections  with  Sympathetic. — Immediately  beyond  the  spinal  ganglion,  the 
anterior  and  posterior  nerve  roots  unite  to  form  the  spinal  nerve  which  emerges 
through  the  intervertebral  foramen.  Each  spinal  nerve  receives  a  branch  (gray 
ramus  communicans)  from  the  adjacent  ganglion  of  the  sympathetic  trunk,  while 
the  thoracic,  and  the  first  and  second  lumbar  nerves  each  contribute  a  branch 


950 


NEUROLOGY 


(white  ramus  communicans)  to  the  adjoining  sympathetic  ganglion.  The  second, 
third,  and  fourth  sacral  nerves  also  supply  white  rami;  these,  however,  are  not 
connected  with  the  ganglia  of  the  sympathetic  trunk,  but  run  directly  into  the 
pelvic  plexuses  of  the  sympathetic. 

Structure. — Each  typical  spinal  nerve  contains  fibres  belonging  to  two  systems,  viz.,  the 
somatic,  and  the  sympathetic  or  splanchnic,  as  well  as  fibres  connecting  these  systems  with  each 
other  (Fig.  798). 

1.  The  somatic  fibres  are  efferent  and  afferent.  The  efferent  fibres  originate  in  the  cells  of  the 
anterior  column  of  the  medulla  spinalis,  and  run  outward  through  the  anterior  nerve  roots  to  the 
spinal  nerve.  They  convey  impulses  to  the  voluntary  muscles,  and  are  continuous  from  their 
origin  to  their  peripheral  distribution.  The  afferent  fibres  convey  impressions  inward  from  the 
skin,  etc.,  and  originate  in  the  unipolar  nerve  cells  of  the  spinal  ganglia.  The  single  processes 
of  these  cells  divide  into  peripheral  and  central  fibres,  and  the  latter  enter  the  medulla  spinalis 
through  the  posterior  nerve  roots. 


Sympathetif 
ganglion 


Spinal  nerve 


Fig.  7£ 


!. — Scheme  showing  structure  of  a  typical  spinal  nerve.    1.  Somatic  efferent. 
Splanchnic  efferent.     6,  7.  Splanchnic  afferent. 


2.  Somatic  afferent.    3,4,5. 


2.  The  sympathetic  fibres  are  also  efferent  and  afferent.  The  efferent  fibres  originate  in  the 
lateral  column  of  the  medulla  spinalis,  and  are  conveyed  through  the  anterior  nerve  root  and  the 
white  ramus  communicans  to  the  corresponding  ganghon  of  the  sympathetic  trunk;  here  they 
may  end  by  forming  synapses  around  its  cells,  or  may  run  through  the  ganglion  to  end  in  another 
of  the  ganglia  of  the  sympathetic  trunk,  or  in  a  more  distally  placed  ganglion  in  one  of  the  sympa- 
thetic plexuses.  In  all  cases  they  end  by  forming  synapses  around  other  nerve  cells.  From  the 
cells  of  the  gangUa  of  the  sympathetic  trunk  other  fibres  take  origin;  some  of  these  run  through 
the  gray  rami  communicantes  to  join  the  spinal  nerves,  along  which  they  are  carried  to  the  blood- 
vessels of  the  trunk  and  limbs,  while  others  pass  to  the  viscera,  either  directly  or  after  interrup- 
tion in  one  of  the  distal  ganglia.  The  afferent  fibres  are  derived  partly  from  the  unipolar  cells 
and  partly  from  the  multipolar  cells  of  the  spinal  gangha.  Their  peripheral  processes  are  carried 
through  the  white  rami  communicantes,  and  after  passing  through  one  or  more  sympathetic 
ganglia  (but  always  without  interruption  in  them)  finally  end  in  the  tissues  of  the  viscera.  The 
central  processes  of  the  unipolar  cells  enter  the  medulla  spinahs  through  the  posterior  nerve 
root  and  form  synapses  around  either  somatic  or  sympathetic  efferent  neurons,  thus  completing 
reflex  arcs.  The  dendrites  of  the  multipolar  nerve  cells  form  synapses  arormd  the  cells  of  type 
II  (cells  of  Dogiel)  in  the  spinal  ganglia,  and  by  this  path  the  original  impulse  is  transferred  from 
the  sympathetic  to  the  somatic  system,  through  which  it  is  conveyed  to  the  sensorium. 


THE  CERVICAL  NERVES  951 

Divisions. — After  emerains  from  the  intervertebral  foramen,  each  spinal  nerve 
gives  olf  a  small  meningeal  branch  which  reenters  the  vertebral  canal  through  the 
intervertebral  foramen  and  supplies  the  ^'erteb^a5  and  their  ligaments,  and  the 
blood^-essels  of  the  medulla  spinalis  and  its  membranes.  The  spinal  nerve  then 
splits  into  a  posterior  or  dorsal,  and  an  anterior  or  ventral  division,  each  recei\'ing 
fibres  from  both  ner^'e  roots. 

POSTERIOR  DIVISIONS   OF   THE   SPINAL   NERVES  (RAMI  POSTERIORES). 

The  posterior  divisions  are  as  a  rule  smaller  than  the  anterior.  They  are  directed 
backward,  and,  with  the  exceptions  of  those  of  the  first  cervical,  the  fourth  and 
fifth  sacral,  and  the  coccygeal,  divide  into  medial  and  lateral  branches  for  the  supply 
of  the  muscles  and  skin  (Figs.  799,  800)  of  the  posterior  part  of  the  trunk. 

The  Cervical  Nerves  (Nn.  Cervicales). 

The  posterior  division  of  the  first  cervical  or  suboccipital  nerve  is  larger  than 
the  anterior  division,  and  emerges  above  the  posterior  arch  of  the  atlas  and  beneath 
the  vertebral  artery.  It  enters  the  suboccipital  triangle  and  supplies  the  muscles 
which  bound  this  triangle,  viz.,  the  Rectus  capitis  posterior  major,  and  the  Obliqui 
superior  and  inferior;  it  gives  branches  also  to  the  Rectus  capitis  posterior  minor 
and  the  Semispinalis  capitis.  A  filament  from  the  branch  to  the  Obliquus  inferior 
joins  the  posterior  division  of  the  second  cervical  nerve. 

The  nerve  occasionally  gives  off  a  cutaneous  branch  which  accompanies  the  occipital  artery 
to  the  scalp,  and  communicates  with  the  greater  and  lesser  occipital  nerves. 

The  posterior  division  of  the  second  cervical  nerve  is  much  larger  than  the 
anterior  division,  and  is  the  greatest  of  all  the  cervical  posterior  divisions.  It 
emerges  between  the  posterior  arch  of  the  atlas  and  the  lamina  of  the  axis,  below 
the  Obliquus  inferior.  It  supplies  a  twig  to  this  muscle,  receives  a  communicating 
filament  from  the  posterior  division  of  the  first  cervical,  and  then  divides  into  a 
large  medial  and  a  small  lateral  branch. 

The  medial  branch  {ramus  medialis;  internal  branch),  called  from  its  size  and 
distribution  the  greater  occipital  nerve  (n.  occipitalis  major;  great  occipital  nerve), 
ascends  obliquely  between  the  Obliquus  inferior  and  the  Semispinalis  capitis,  and 
pierces  the  latter  muscle  and  the  Trapezius  near  their  attachments  to  the  occipital 
bone  (Fig.  799).  It  is  then  joined  by  a  filament  from  the  medial  branch  of  the 
posterior  division  of  the  third  cervical,  and,  ascending  on  the  back  of  the  head 
with  the  occipital  artery,  divides  into  branches  which  communicate  with  the  lesser 
occipital  nerve  and  supply  the  skin  of  the  scalp  as  far  forward  as  the  vertex  of  the 
skull.  It  gives  off  muscular  branches  to  the  Semispinalis  capitis,  and  occasionally 
a  twig  to  the  back  of  the  auricula.  The  lateral  branch  (ramus  lateralis;  external 
branch)  supplies  filaments  to  the  Splenius,  Longus  capitis,  and  Semispinalis  capitis, 
and  is  often  joined  by  the  corresponding  branch  of  the  third  cervical. 

The  posterior  division  of  the  third  cervical  is  intermediate  in  size  between  those 
of  the  second  and  fourth.  Its  medial  branch  runs  between  the  Semispinalis  capitis 
and  cervicis,  and,  piercing  the  Splenius  and  Trapezius,  ends  in  the  skin.  While 
under  the  Trapezius  it  gives  off  a  branch  called  the  third  occipital  nerve,  which  pierces 
the  Trapezius  and  ends  in  the  skin  of  the  lower  part  of  the  back  of  the  head  (Fig. 
799).  It  lies  medial  to  the  greater  occipital  and  communicates  with  it.  The 
lateral  branch  often  joins  that  of  the  second  cervical.   • 

The  posterior  division  of  the  suboccipital,  and  the  medial  branches  of  the  posterior  division 
of  the  second  and  third  cervical  nerves  are  sometimes  joined  by  commvmicating  loops  to  form 
the  -posterior  cervical  -plexus  (Cruveiihier) . 

The  posterior  divisions  of  the  lower  five  cervical  nerves  divide  into  medial 
and  lateral  branches.    The  medial  branches  of  the  fourth  and  fifth  run  between  the 


952 


NEUROLOGY 


Semispinales  cervicis  and  capitis,  and,  lia\ing  reached  the  spinous  processes, 
pierce  the  Splenius  and  Trapezius  to  end  in  the  skin  (Fig.  799).  Sometimes  the 
branch  of  the  fifth  fails  to  reach  the  skin.  Those  of  the  lower  three  ner\'es  are 
small,  and  end  hi  the  Semispinales  cervicis  and  capitis,  Multifidus,  and  Inter- 
spinales.  The  lateral  branches  of  the  lower  five  nerves  supply  the  Iliocostalis 
cervicis,  Longissimus  cervicis,  and  Longissimus  capitis. 


Fig.  799. — Diagram  of  the  distribution  of 
the  cutaneous  branches  of  the  posterior 
divisions  of  the  spinal  nerves. 


Fig.  800. — Areas  of  distribution  of  the  cutaneous  branches  of  the 
posterior  divisions  of  the  spinal  nerves.  (H.  ]M.  Johnston.)  The 
areas  of  the  medial  branches  are  in  black,  those  of  the  lateral  in  red. 


The  Thoracic  Nerves  (Nn.  Thoracalesj. 

The  medial  branches  {ramus  medialis;  internal  branch)  of  the  posterior  divisions  of 
the  upper  six  thoracic  nerves  run  between  the  Semispinalis  dorsi  and  ^lultifidus, 
which  they  supply;  they  then  pierce  the  Rhomboidei  and  Trapezius,  and  reach 
the  skin  by  the  sides  of  the  spinous  processes  (Fig.  799).     The  medial  branches 


THE  SACRAL  XERVES 


953 


of  the  lower  six  are  (listril)ute(l  chiefly  to  the  Muhifi(his  and  Longissimus  dorsi; 
occasionally  they  give  off  filaments  to  the  skin  near  the  middle  line. 

The  lateral  branches  {ra)iim  lateralis;  external  branch)  increase  in  size  from  above 
downward.  They  run  through  or  beneath  the  Longissimus  dorsi  to  the  interval 
between  it  and  the  Iliocostales,  and  supply  these  muscles;  the  lower  five  or  six 
also  give  off  cutaneous  branches  which  pierce  the  Serratus  posterior  inferior  and 
Latissimus  dorsi  in  a  line  with  the  angles  of  the  ribs  (Fig.  799).  The  lateral 
branches  of  a  variable  number  of  the  upper  thoracic  nerves  also  give  filaments 
to  the  skin.  The  lateral  branch  of  the  twelfth  thoracic,  after  sending  a  filament 
medialward  along  the  iliac  crest,  passes  downward  to  the  skin  of  the  buttock. 

The  medial  cutaneous  branches  of  the  posterior  divisions  of  the  thoracic  nerves  descend  for 
some  distance  close  to  the  spinous  processes  before  reaching  the  skin,  while  the  lateral  branches 
travel  downward  for  a  considerable  distance — it  ma}'  be  as  much  as  the  breadth  of  four  ribs — 
before  thej'  become  superficial;  the  branch  from  the  twelfth  thoracic,  for  instance,  reaches  the 
skin  only  a  little  way  above  the  iliac  crest. ^ 

The  Lumbar  Nerves  (Nn.  Lumbales). 

The  medial  branches  of  the  posterior  divisions  of  the  lurnbar  nerves  run  close  to  the 
articular  processes  of  the  vertebrse  and  end  in  the  Multifidus. 

The  lateral  branches  supply  the  Sacrospinalis.  The  upper  three  give  off  cutaneous 
nerves  which  pierce  the  aponeurosis  of  the  Latissimus  dorsi  at  the  lateral  border  of 
the  Sacrospinalis  and  descend  across  the  posterior  part  of  the  iliac  crest  to  the  skin 
of  the  buttock  (Fig.  799),  some  of  their  twigs  running  as  far  as  the  level  of  the 
greater  trochanter. 


■^      Anterio-r    branches 
^     of  lower    sacral  nerves 

J 

Fig.  SOI. — The  posterior  divisions  of  the  sacral  nerves. 


The  Sacral  Nerves  (Nn.  Sacrales). 

The  posterior  divisions  of  the  sacral  nerves  (rami  posteriores)  (Fig.  SQl)  are 
small,  and  diminish  in  size  from  above  downward;  they  emerge,  except  the  last, 

1  See  article  bj-  H.  M.  Johnston,  Journal  of  Anatomj-  and  Phj-siology,  vol.  xliii. 


954  NEUROLOGY 

through  the  posterior  sacral  foramina.  The  upper  three  are  covered  at  their  points 
of  exit  by  the  Miiltifidiis,  and  divide  into  medial  and  lateral  branches. 

The  medial  branches  are  small,  and  end  in  the  Multifidus. 

The  lateral  branches  join  with  one  another  and  with  the  lateral  branches  of  the 
posterior  divisions  of  the  last  lumbar  and  fourth  sacral  to  form  loops  on  the  dorsal 
surface  of  the  sacrum.  From  these  loops  branches  run  to  the  dorsal  surface  of  the 
sacrotuberous  ligament  and  form  a  second  series  of  loops  under  the  Glutaeus  naaxi- 
mus.  From  this  second  series  cutaneous  branches,  two  or  three  in  number,  pierce 
the  Glutaeus  maximus  along  a  line  drawn  from  the  posterior  superior  iliac  spine  to 
the  tip  of  the  coccyx;  they  supply  the  skin  over  the  posterior  part  of  the  buttock. 

The  posterior  divisions  of  the  lower  two  sacral  nerves  are  small  and  lie  below  the 
Multifidus.  They  do  not  divide  into  medial  and  lateral  branches,  but  unite  with 
each  other  and  with  the  posterior  division  of  the  coccygeal  nerve  to  form  loops  on 
the  back  of  the  sacrum;  filaments  from  these  loops  supply  the  skin  over  the  coccyx. 

The  Coccygeal  Nerve  (N.  Coccygeus). 

The  posterior  division  of  the  coccygeal  nerve  {ramus  posterior)  does  not  divide 
into  a  medial  and  a  lateral  branch,  but  receives,  as  already  stated,  a  communicating 
branch  from  the  last  sacral;  it  is  distributed  to  the  skin  over  the  back  of  the  coccyx. 

ANTERIOR  DIVISIONS  OF   THE   SPINAL  NERVES    (RAMI  ANTERIORES). 

The  anterior  divisions  of  the  spinal  nerves  supply  the  antero-lateral  parts  of  the 
trunk,  and  the  limbs;  they  are  for  the  most  part  larger  than  the  posterior  divisions. 
In  the  thoracic  region  they  run  independently  of  one  another,  but  in  the  cervical, 
lumbar,  and  sacral  regions  they  unite  near  their  origins  to  form  plexuses. 

The  Cervical  Nerves  (Nn.  Cervicales). 

The  anterior  divisions  of  the  cervical  nerves  {rami  anteriores) ,  with  the  exception 
of  the  first,  pass  outward  between  the  Intertransversarii  anterior  and  posterior, 
lying  on  the  grooved  upper  surfaces  of  the  transverse  processes  of  the  vertebrae. 
The  anterior  division  of  the  first  or  suboccipital  nerve  issues  from  the  vertebral  canal 
above  the  posterior  arch  of  the  atlas  and  runs  forward  around  the  lateral  aspect 
of  its  superior  articular  process,  medial  to  the  vertebral  artery.  In  most  cases  it 
descends  medial  to  and  in  front  of  the  Rectus  capitis  lateralis,  but  occasionally  it 
pierces  the  muscle. 

The  anterior  divisions  of  the  upper  four  cervical  nerves  unite  to  form  the  cervical 
plexus,  and  each  receives  a  gray  ramus  communicans  from  the  superior  cervical 
ganglion  of  the  sympathetic  trunk.  Those  of  the  lower  four  cervical,  together  with 
the  greater  part  of  the  first  thoracic,  form  the  brachial  plexus.  They  each  receive 
a  gray  ramus  communicans,  those  for  the  fifth  and  sixth  being  derived  from  the 
middle,  and  those  for  the  seventh  and  eighth  from  the  lowest,  cervical  ganglion 
of  the  sympathetic  trunk. 

The  Cervical  Plexus  {plexus  cervicalis)  (Fig.  802). — The  cervical  plexus  is  formed 
by  the  anterior  divisions  of  the  upper  four  cervical  nerves;  each  nerve,  except 
the  first,  divides  into  an  upper  and  a  lower  branch,  and  the  branches  unite  to  form 
three  loops.  The  plexus  is  situated  opposite  the  upper  four  cervical  vertebrae,  in 
front  of  the  Levator  scapulae  and  Scalenus  medius,  and  covered  by  the  Sterno- 
cleidomastoideus. 

Its  branches  are  divided  into  two  groups,  superficial  and  deep,  and  are  here 
given  in  tabular  form;  the  figures  following  the  names  indicate  the  nerves  from 
which  the  different  branches  take  origin: 


THE  CERVICAL  NERVES 


955 


Superficial 


Internal 


Deep 


External 


Smaller  occipital 
Great  auricular  . 
Cutaneous  cervical 
Suprachn-icular 


fCommunicatino; 


''Muscular 


With  hypoglossal 
"    vagus    . 
"     sympathetic 
Rectus  capitis  lateralis 
Rectus  capitis  anterior 
Longus  capitis 
Communicantes  cervi- 

cales 
.Phrenic 
Communicating  with  accessory 

fSternocleidomastoideus 


Muscular 


Trapezius 
1  Levator'  scapulae 
[Scalenus  medius 


2,C. 
2,  3,  C. 

2,  3,  C. 

3,  4,  C. 
1,  2,  C. 
1,  2,  C. 
1,2,3,4,C. 
1,C. 

1,  2,  C. 

1,  2,  3,  C. 

2,  3,  C. 

3,  4,  5,  C. 
2,  3,  4,  C. 

2,  C. 

3,  4,  C. 
3,  4,  C. 
3,  4,  C. 


Smaller  occipital 
To  Vagus 


Great  auricular 
To  Sternocleido- 
mastoideus 


To  Lev.  scapulae 
Cutaneous  cervical 


To  Rectus  lateralis 

To  Rect.  cap.  ant.  and  Long.  cap. 


To  Longus  capitis  and 
Longus  colli 


To  Scalenus  mediu. 


Phrenic 


To  Longus  capitis  and 
Longus  colli 

To  Geniohyoideus 
To  Thyreohyoideus 


Descendens  hypoglossi 
Communicantes 
cervicales 

—  To  Longus  colli 
Ansa  hypoglossi 


Supraclavicular 


Fig.  802. — Plan  of  cervical  plexus. 


956 


NEUROLOGY 


Superficial  Branches  of  the  Cervical  Plexus  (Fig.  803). — The  Smaller  Occipital 
Nerve  {n.  occipifalis  mi  nor;  small  occipital  nerve)  arises  from  the  second  cer\-ical 
ner\'e,  sometimes  also  from  the  third;  it  curves  around  and  ascends  along  the 
posterior  border  of  the  Sternocleidomastoideus,  Near  the  cranium  it  perforates 
the  deep  fascia,  and  is  continued  upward  along  the  side  of  the  head  behind  the 
auricula,  supplying  the  skin  and  communicating  with  the  greater  occipital,  the 
great  auricular,  and  the  posterior  auricular  branch  of  the  facial.  The  smaller 
occipital  varies  in  size,  and  is  sometimes  duplicated. 


Fig.  803. — The  nerves  of  the  scalp,  face,  and  side  of  neck. 

It  gives  off  an  auricular  branch,  which  supplies  the  skin  of  the  upper  and  back 
part  of  the  auricula,  communicating  with  the  mastoid  branch  of  the  great  auricular. 
This  branch  is  occasionally  derived  from  the  greater  occipital  nerve. 

The  Great  Auricular  Nerve  {n.  auricidaris  magnus)  is  the  largest  of  the  ascending 
branches.  It  arises  from  the  second  and  third  cervical  nerves,  winds  around  the 
posterior  border  of  the  Sternocleidomastoideus,  and,  after  perforating  the  deep 
fascia,  ascends  upon  that  muscle  beneath  the  Platysma  to  the  parotid  gland,  where 
it  divides  into  an  anterior  and  a  posterior  branch. 

The  anterior  branch  (ramus  anterior;  facial  branch)  is  distributed  to  the  skin  of 
the  face  over  the  parotid  gland,  and  communicates  in  the  substance  of  the  gland 
with  the  facial  nerve. 


THE  CERVICAL  NERVES  957 

The  posterior  branch  (m/z/z/.v  inhstcrior;  mantuld  branch)  supplies  tlie  skin  o\er  the 
mastoid  process  and  on  the  back  of  the  auricula,  except  at  its  upper  part;  a  fiLament 
pierces  the  auricuhi  to  reach  its  hiteral  surface,  wliere  it  is  distributed  to  the  h)bule 
and  knver  ])art  of  the  concha.  Tlic  posterior  l)ranch  communicates  witli  the  smaller 
occipital,  the  auricular  branch  of  the  vagus,  and  the  posterior  auricular  branch 
of  the  facial. 

The  Cutaneous  Cervical  (//.  ciifaiietts  colli;  .superficial  or  iransverse  cervical  nerve) 
arisc'i  from  the  second  and  third  cervical  nerves,  turns  around  the  posterior  border 
of  the  Sternocleidomastoideus  about  its  middle,  and,  passing  obliquely  forward 
beneath  the  external  jugular  vein  to  the  anterior  border  of  the  muscle,  it  perforates 
the  deep  cervical  fascia,  and  divides  beneath  the  Platysma  into  ascending  and 
descending  branches,  which  are  distributed  to  the  antero-lateral  parts  of  the 
neck. 

The  ascending  branches  {rami  superiores)  pass  upward  to  the  submaxillary  region, 
and  form  a  plexus  with  the  cervical  branch  of  the  facial  nerve  beneath  the  Platysma; 
others  pierce  that  muscle,  and  are  distributed  to  the  skin  of  the  upper  and  front 
part  of  the  neck. 

The  descending  branches  {rami  inferiores)  pierce  the  Platysma,  and  are  distributed 
to  the  skin  of  the  side  and  front  of  the  neck,  as  low  as  the  sternum. 

The  Supraclavicular  Nerves  {nn.  supraclaviculares ;  descending  branches)  arise  from 
the  third  and  fourth  cervical  nerves;  they  emerge  beneath  the  posterior  border 
of  the  Sternocleidomastoideus,  and  descend  in  the  posterior  triangle  of  the  neck 
beneath  the  Platysma  and  deep  cervical  fascia.  Near  the  clavicle  they  perforate 
the  fascia  and  Platysma  to  become  cutaneous,  and  are  arranged,  according  to 
their  position,  into  three  groups — anterior,  middle  and  posterior. 

The  anterior  supraclavicular  nerves  {nn.  supraclaviculares  anteriores;  suprasternal 
nerves)  cross  obliquely  over  the  external  jugular  vein  and  the  clavicular  and  sternal 
heads  of  the  Sternocleidomastoideus,  and  supply  the  skin  as  far  as  the  middle  line. 
They  furnish  one  or  two  filaments  to  the  sternoclavicular  joint. 

The  middle  supraclavicular  nerves  {nn.  supraclaviculares  viedii;  supraclavicular 
nerves)  cross  the  clavicle,  and  supply  the  skin  over  the  Pectoralis  major  and  Del- 
toideus,  communicating  with  the  cutaneous  branches  of  the  upper  intercostal  nerves. 

The  posterior  supraclavicular  nerves  {7in.  supraclaviculares  posteriores;  supra-acromial 
nerves)  pass  obliquely  across  the  outer  surface  of  the  Trapezius  and  the  acromion, 
and  supply  the  skin  of  the  upper  and  posterior  parts  of  the  shoulder. 

Deep  Branches  of  the  Cervicle  Plexus.  Internal  Series. — The  Communicating 
Branches  consist  of  several  filaments,  which  pass  from  the  loop  between  the  first 
and  second  cervical  nerves  to  the  vagus,  hypoglossal,  and  sympathetic.  The  branch 
to  the  hypoglossal  ultimately  leaves  that  nerve  as  a  series  of  branches,  viz.,  the 
descending  ramus,  the  nerve  to  the  Thyreohyoideus  and  the  nerve,  to  the  Genio- 
hyoideus  (see  page  947).  A  communicating  branch  also  passes  from  the  fourth 
to  the  fifth  cervical,  while  each  of  the  first  four  cervical  nerves  receives  a  gray 
ramus  communicans  from  the  superior  cervical  ganglion  of  the  sympathetic. 

Muscular  Branches  supply  the  Longus  capitis,  Rectus  capitis  anterior,  and  Rectus 
capitis  lateralis. 

The  Communicantes  Cervicales  {communicantes  hypoglossi)  (Fig.  802)  consist 
usually  of  two  filaments,  one  derived  from  the  second,  and  the  other  from  the  third 
ce^^'ical.  These  filaments  join  to  form  the  descendens  cervicalis,  which  passes 
downward  on  the  lateral  side  of  the  internal  jugular  vein,  crosses  in  front  of  the 
vein  a  little  below  the  middle  of  the  neck,  and  forms  a  loop  (ansa  hypoglossi)  with 
the  descending  ramus  of  the  hypoglossal  in  front  of  the  sheath  of  the  carotid 
vessels  (see  page  947).    Occasionally,  the  loop  is  formed  within  the  sheath. 

The  Phrenic  Nerve  {n.  phrenicus;  internal  respiratory  nerve  of  Bell)  contains  motor 
and  sensory  fibres  in  the  proportion  of  about  two  to  one.    It  arises  chiefly  from  the 


958  NEUROLOGY 

fourth  cervical  nerve,  but  receives  a  branch  from  the  third  and  another  from  the 
fifth;  the  fibres  from  the  fifth  occasionally  come  through  the  nerve  to  the  Sub- 
clavius.  It  descends  to  the  root  of  the  neck,  running  obliquely  across  the  front 
of  the  Scalenus  anterior,  and  beneath  the  Sternocleidornastoideus,  the  inferior 
belly  of  the  Omohyoideus,  and  the  transverse  cervical  and  transverse  scapular 
vessels.  It  next  passes  in  front  of  the  first  part  of  the  subclavian  artery,  between 
it  and  the  subclavian  vein,  and,  as  it  enters  the  thorax,  crosses  the  internal  mam- 
mary artery  near  its  origin.  Within  the  thorax,  it  descends  nearly  vertically  in 
front  of  the  root  of  the  lung,  and  then  between  the  pericardium  and  the  medias- 
tinal pleura,  to  the  Diaphragma,  where  it  divides  into  branches,  which  pierce 
that  muscle,  and  are  distributed  to  its  under  surface.  In  the  thorax  it  is  accom- 
panied by  the  pericardiacophrenic  branch  of  the  internal  mammary  artery. 

The  two  phrenic  nerves  differ  in  their  length,  and  also  in  their  relations  at  the 
upper  part  of  the  thorax. 

The  right  nerve  is  situated  more  deeply,  and  is  shorter  and  more  vertical  in 
direction  than  the  left;  it  lies  lateral  to  the  right  innominate  vein  and  superior 
vena  cava. 

The  left  nerve  is  rather  longer  than  the  right,  from  the  inclination  of  the  heart 
to  the  left  side,  and  from  the  Diaphragma  being  lower  on  this  than  on  the  right  side. 
At  the  root  of  the  neck  it  is  crossed  by  the  thoracic  duct;  in  the  superior  mediastinal 
cavity  it  lies  between  the  left  common  carotid  and  left  subclavian  arteries,  and 
crosses  superficial  to  the  vagus  on  the  left  side  of  the  arch  of  the  aorta. 

Each  nerve  supplies  filaments  to  the  pericardium  and  pleura,  and  at  the  root 
of  the  neck  is  joined  by  a  filament  from  the  sympathetic,  and,  occasionally,  by 
one  from  the  ansa  hypoglossi.  Branches  have  been  described  as  passing  to  the 
peritoneum. 

From  the  right  nerve,  one  or  two  filaments  pass  to  join  in  a  small  phrenic  ganglion 
with  phrenic  branches  of  the  coeliac  plexus;  and  branches  from  this  ganglion  are 
distributed  to  the  falciform  and  coronary  ligaments  of  the  liver,  the  suprarenal 
gland,  inferior  vena  cava,  and  right  atrium.  From  the  left  nerve,  filaments  pass  to 
join  the  phrenic  branches  of  the  coeliac  plexus,  but  without  any  ganglionic  enlarge- 
ment; and  a  twig  is  distributed  to  the  left  suprarenal  gland. 

Deep  Branches  of  the  Cervical  Plexus.  External  SERiES.^Communicating 
Branches. — The  external  series  of  deep  branches  of  the  cervical  plexus  communi- 
cates with  the  accessory  nerve,  in  the  substance  of  the  Sternocleidomastoideus, 
in  the  posterior  triangle,  and  beneath  the  Trapezius. 

Muscular  Branches  are  distributed  to  the  Sternocleidomastoideus,  Trapezius, 
Levator  scapulae,  and  Scalenus  medius. 

The  branch  for  the  Sternocleidomastoideus  is  derived  from  the  second  cervical ; 
the  Trapezius  and  Levator  scapulae  receive  branches  from  the  third  and  fourth. 
The  Scalenus  medius  receives  twigs  either  from  the  third  or  fourth,  or  occasionally 
from  both. 

Applied  Anatomy, — Pains  referred  to  the  terminal  branches  of  the  cervical  plexus  are  not 
uncommon  in  caries  of  the  cervical  vertebrse,  where  pain  may  be  felt  radiating  over  the  occipital 
bone,  if  the  disease  is  situated  high  up  in  the  vertebral  column. 

The  Brachial  Plexus  {ylexus  brachialis)  (Fig.  804).— The  brachial  plexus  is 
formed  by  the  union  of  the  anterior  divisions  of  the  lower  four  cervical  nerves  and 
the  greater  part  of  the  anterior  division  of  the  first  thoracic  nerve;  the  fourth  cer- 
vical usually  gives  a  branch  to  the  fifth  cervical,  and  the  first  thoracic  frequently 
receives  one  from  the  second  thoracic.  The  plexus  extends  from  the  lower  part 
of  the  side  of  the  neck  to  the  axilla.  The  nerves  which  form  it  are  nearly  equal  in 
size,  but  their  mode  of  communication  is  subject  to  some  variation.    The  following 


THE  CERVICAL  NERVES 


959 


is,  however,  the  most  constant  arrangement.  The  fifth  and  sixth  cervical  unite 
s6on  after  their  exit  from  the  intervertebral  foramina  to  form  a  trunk.  The  eighth 
cervical  and  first  thoracic  also  unite  to  form  one  trunk,  while  the  seventh  cervical 
runs  out  alone.  Three  trunks— upper,  middle,  and  lower— are  thus  formed,  and, 
as  they  pass  beneath  the  clavicle,  each  splits  into  an  anterior  and  a  posterior  divi- 
sion.^ The  anterior  divisions  of  the  upper  and  middle  trunks  unite  to  form  a  cord, 
which  is  situated  on  the  lateral  side  of  the  second  part  of  the  axillary  artery,  and 
is  called  the  lateral  cord  or  fasciculus  of  the  plexus.  The  anterior  division  of  the 
lower  trunk  passes  down  on  the  medial  side  of  the  axillary  artery,  and  forms  the 
medial  cord  or  fasciculus  of  the  brachial  plexus.  The  posterior  divisions  of  all  three 
trunks  unite  to  form  the  posterior  cord  or  fasciculus  of  the  plexus,  which  is  situated 
behind  the  second  portion  of  the  axillary  artery. 


FronYIC. 


To  Rhomboidel- 
Tojoin  the  jjhremc 


Suprascajndar 
To  Subclavius 


Lateral  anteri 
thoracic 


To  Lo'iigus  colli 
and  Scaleni 


—  To  LonnuB  colli 
and  Scaleni 


To  Longus  colli 
and  Scaleni 

Long  thoracic 


To  Longiis  colli 
and  Scaleni 


Median 


Ulnar       J  2ledial  brachial 

Media  I  a  ntibrach  ia  I      cutaneous 
cutaneous 


Fig.  804. — Plan  of  brachial  plexus. 


Relations.— In.  the  neck,  the  brachial  plexus  lies  in  the  posterior  triangle,  being  covered  by  the 
skin,  Platysma,  and  deep  fascia;  it  is  crossed  by  the  supraclavicular  nerves,  the  inferior  belly 
of  the  Omohyoideus,  the  external  jugular  vein,  and  the  transverse  cervical  artery.  It  emerges 
between  the  Scaleni  anterior  and  medius;  its  upper  part  lies  above  the  third  part  of  the  sub- 
clavian artery,  while  the  trunk  formed  by  the  union  of  the  eighth  cervical  and  first  thoracic  is 
placed  behind  the  artery;  the  plexus  next  passes  behind  the  clavicle,  the  Subclavius,  and  the  trans- 
verse scapular  vessels,  and  lies  upon  the  first  digitation  of  the  Serratus  anterior,  and  the  Sub- 
scapularis.  In  the  axilla  it  is  placed  lateral  to  the  first  portion  of  the  axillary  artery;  it  surrounds 
the  second  part  of  the  artery,  one  cord  lying  medial  to  it,  one  lateral  to  it,  and  one  behmd  it; 
at  the  lower  part  of  the  axilla  it  gives  off  its  terminal  branches  to  the  upper  limb. 

1  The  posterior  division  of  the  lower  trunk  is  very  much  smaUer  than  the  others,  and  is  frequently  derived  entirely 
from  the  eighth  cervical  nerve. 


.     5C. 

.     5,  6  C. 

.        .     5,  6  C. 

.     5,  6,  7  C. 

.     5,  6,  7, 8  C 

960  NEUROLOGY 

Branches  of  Communication.- — Close  to  their  exit  from  the  intervertebral  foramina 
the  fifth  and  sixth  cervical  nerves  each  receive  a  gray  ramus  communicans  from 
the  middle  cervical  ganglion  of  the  sympathetic  trunk,  and  the  seventh  and  eighth 
cervical  similar  twigs  from  the  inferior  ganglion.  The  first  thoracic  nerve  receives 
a  gray  ramus  from,  and  contributes  a  white  ramus  to,  the  first  thoracic  ganglion. 
On  the  Scalenus  anterior  the  phrenic  nerve  is  joined  by  a  branch  from  the  fifth 
cervical. 

Branches  of  Distribution. — The  branches  of  distribution  of  the  brachial  plexus 
may  be  arranged  into  two  groups,  viz.,  those  given  oft"  above  and  those  below  the 
clavicle. 

Supraclavicular  Branches. 

Dorsal  scapular    . 

Suprascapular 

Nerve  to  Subclavius 

Long  thoracic 

To  Longus  colli  and  Scaleni 

The  Dorsal  Scapular  Nerve  {n.  dorsaUs  scajmlae;  nerve  to  the  Rhomboidei;  posterior 
scajyular  nerve)  arises  from  the  fifth  cervical,  pierces  the  Scalenus  medius,  passes 
beneath  the  Levator  scapulae,  to  which  it  occasionally  gives  a  twig,  and  ends  in 
the  Rhomboidei. 

The  Suprascapular  (n.  sitprascapidaris)  (Fig.  810)  arises  from  the  trunk  formed 
by  the  union  of  the  fifth  and  sixth  cervical  nerves.  It  runs  lateralward  beneath 
the  Trapezius  and  the  Omohyoideus,  and  enters  the  supraspinatous  fossa  through 
the  suprascapular  notch,  below,  the  superior  transverse  scapular  ligament;  it  then 
passes  beneath  the  Supraspinatus,  and  curves  around  the  lateral  border  of  the 
spine  of  the  scapula  to  the  infraspinatous  fossa.  In  the  supraspinatous  fossa  it 
gives  off  two  branches  to  the  Supraspinatus  muscle,  and  an  articular  filament 
to  the  shoulder-joint;  and  in  the  infraspinatous  fossa  it  gives  off  two  branches 
to  the  Infraspinatous  muscle,  besides  some  filaments  to  the  shoulder-joint  and 
scapula. 

The  Nerve  to  the  Subclavius  (n.  subclavius)  is  a  small  filament,  which  arises  from 
the  point  of  junction  of  the  fifth  and  sixth  cervical  nerves;  it  descends  to  the  muscle 
in  front  of  the  third  part  of  the  subclavian  artery  and  the  lower  trunk  of  the  plexus, 
and  is  usually  connected  by  a  filament  with  the  phrenic  nerve. 

The  Long  Thoracic  Nerve  (n.  thoracalis  longus;  external  respiratory  nerve  of  Bell; 
posterior  thoracic  nerve)  (Fig.  809)  supplies  the  Serratus  anterior.  It  usually  arises 
by  three  roots  from  the  fifth,  sixth,  and  seventh  cervical  nerves;  but  the  root  from 
the  seventh  nerve  may  be  absent.  The  roots  from  the  fifth  and  sixth  nerves  pierce 
the  Scalenus  medius,  while  that  from  the  seventh  passes  in  front  of  the  muscle. 
The  nerve  descends  behind  the  brachial  plexus  and  the  axillary  vessels,  resting 
on  the  outer  surface  of  the  Serratus  anterior.  It  extends  along  the  side  of  the  thorax 
to  the  lower  border  of  that  muscle,  supplying  filaments  to  each  of  its  digitations. 

The  branches  for  the  Longus  colli  and  Scaleni  arise  from  the  lower  four  cervical 
nerves  at  their  exit  from  the  intervertebral  foramina. 


Infraclavicular  Branches. 

The  infraclavicular  branches  are  derived  from  the  three  cords  of  the  brachial 
plexus,  but  the  fasciculi  of  the  nerves  may  be  traced  through  the  plexus  to  the  spinal 
nerves  from  which  thev  originate.    They  are  as  follows: 


THE  CERVICAL  NERVES 


961 


Lateral  cord 


IMedial  cord 


Posterior  cord 


AiusculocutaiieoLis 

Lateral  anterior  thoracic 

Lateral  head  of  median  . 

Medial  anterior  thoracic 

Medial  antihrachial  cutaneous 

Medial  brachial  cutaneous 

Ulnar 

Medial  head  of  median 

Upper  subscapular  . 

Lower  subscapular  . 

Thoracodorsal  . 

Axillary 

Radial 


5,  6,  7  C. 
5,  6,  7  C. 
(),  7  C. 


8  C,  1  T. 


5,  6C. 
5,  6C. 
5,  6,  7  C. 

5,  6C. 

6,  7,  S  C,  1  T. 


The  Anterior  Thoracic  Nerves  {nn.  thoracales  anteriores)  (Fig.  809)  supply  the 
Pectorales  major  and  minor. 

The  lateral  anterior  thoracic  {fasciculus  lateralis)  the;  larger  of  the  two,  arises 
from  the  lateral  cord  of  the  brachial  plexus,  and  through  it  from  the  fifth,  sixth, 
and  seventh  cervical  nerves.  It  passes  across  the  axillary  artery  and  vein,  pierces  the 
coracoclavicular  fascia,  and  is  distributed  to  the  deep  surface  of  the  Pectoralis 
major.  It  sends  a  filament  to  join  the  medial  anterior  thoracic  and  form  with  it 
a  loop  in  front  of  the  first  part  of  the  axillary  artery. 

The  medial  anterior  thoracic  {fasciculus  medialis)  arises  from  the  medial  cord  of 
the  plexus  and  through  it  from  the  eighth  cervical  and  first  thoracic.  It  passes 
behind  the  first  part  of  the  axillary  artery,  curves  forward  between  the  axillary 
artery  and  vein,  and  unites  in  front  of  the  artery  with  a  filament  from  the  lateral 
nerve.  It  then  enters  the  deep  surface  of  the  Pectoralis  minor,  where  it  divides 
into  a  number  of  branches,  which  supply  the  muscle.  Two  or  three  branches  pierce 
the  muscle  and  end  in  the  Pectoralis  major. 

The  Subscapular  Nerves  {nn.  subscajndares) ,  two  in  number,  spring  from  the 
posterior  cord  of  the  plexus  and  through  it  from  the  fifth  and  sixth  cervical  nerves. 

The  upper  subscapular  {short  suhscajmlar) ,  the  smaller  enters  the  upper  part  of 
the  Subscapularis,  and  is  frequently  represented  by  two  branches. 

The  lower  subscapular  supplies  the  lower  part  of  the  Subscapularis,  and  ends  in 
the  Teres  major;  the  latter  muscle  is  sometimes  supplied  by  a  separate  branch. 

The  Thoracodorsal  Nerve  (w.  thoracodorsalis;  middle  or  long  suhscapular  nerve), 
a  branch  of  the  posterior  cord  of  the  plexus,  derives  its  fibres  from  the  fifth,  sixth, 
and  seventh  cervical  nerves;  it  follows  the  course  of  the  subscapular  artery,  along 
the  posterior  wall  of  the  axilla  to  the  Latissimus  dorsi,  in  which  it  ma}^  be  traced 
as  far  as  the  lower  border  of  the  muscle. 

The  Axillary  Nerve  {ii.  axillaris;  circumflex  nerve)  (Fig.  810)  arises  from  the  pos- 
terior cord  of  the  brachial  plexus,  and  its  fibres  are  derived  from  the  fifth  and  sixth 
cervical  nerves.  It  lies  at  first  behind  the  axillary  artery,  and  in  front  of  the 
Subscapularis,  and  passes  downward  to  the  lower  border  of  that  muscle.  It.then 
winds  backward,  in  company  with  the  posterior  humeral  circumflex  artery,  through 
a  quadrilateral  space  bounded  above  by  the  Subscapularis,  below  by  the  Teres 
major,  medially  by  the  long  head  of  the  Triceps  brachii,  and  laterally  by  the 
surgical  neck  of  the  humerus,  and  divides  into  an  anterior  and  a  posterior  branch. 

The  anterior  branch  {upper  branch)  winds  around  the  surgical  neck  of  the  humerus, 
beneath  the  Deltoideus,  with  the  posterior  humeral  circumflex  vessels,  as  far  as 
the  anterior  border  of  that  muscle,  supplying  it,  and  giving  off  a  few  small  cutaneous 
branches,  which  pierce  the  muscle  and  ramify  in  the  skin  covering  its  low^er  part. 

The  posterior  branch  {lower  branch)  supplies  the  Teres  minor  and  the  posterior 
part  of  the  Deltoideus;  upon  the  branch  to  the  Teres  minor  an  oval  enlargement 
61 


962 


NEUROLOGY 


(pseudoganglion)  usually  exists.  The  posterior  branch  then  pierces  the  deep  fascia 
and  is  continued  as  the  lateral  brachial  cutaneous  nerve,  which  sweeps  around  the 
posterior  border  of  the  Deltoideus  and  supplies  the  skin  over  the  lower  two-thirds 
of  the  posterior  part  of  this  muscle,  as  well  as  that  covering  the  long  head  of  the 
Triceps  brachii  (Figs  805,  807). 


Fig.  805. — Cutaneous  nerves  of  right  upper 
extremity.    Anterior  view. 


Fig, 


806. — Diagram  of  segmental  distribution  of  the  cutaneous 
nerves  of  the  right  upper  extremity.    Anterior  view. 


The  trunk  of  the  axillary  nerve  gives  off  an  articular  filament  which  enters 
the  shoulder-joint  below  the  Subscapularis. 

The  Musculocutaneous  Nerve  (n.  musculocutaneus)  (Fig.  809)  arises  from  the 
lateral  cord  of  the  brachial  plexus,  opposite  the  lower  border  of  the  Pectoralis 
minor,  its  fibres  being  derived  from  the  fifth,  sixth,  and  seventh  cervical  nerves. 


THE  CERVICAL  NERVES 


963 


It  pierces  the  Coracobrachialis  muscle  and  passes  obliquely  between  the  Biceps 
brachii  and  the  Brachialis,  to  the  lateral  side  of  the  arm;  a  little  above  the  elbow- 
it  pierces  the  deep  fascia  lateral  to  the  tendon  of  the  liiccps  brachii  and  is  continued 
into  the  forearm  as  the  lateral  antibrachial  cutaneous  nerve.  In  its  course  through 
the  arm  it  supplies  the  Coracobrachialis,  Biceps  brachii,.  and  the  greater  part  of  the 


Fig.  807. — Cutaneous  nerves  of  right  upper 
extremity.     Posterior  view. 


Fig.  808. — Diagram  of  segmental  distribution  ofi'the  cuta- 
neous nerves  of  the  right  upper  extremity.    Posterior    view 


Brachialis.  The  branch  to  the  Coracobrachialis  is  given  off  from  the  nerve  close 
to  its  origin,  and  in  some  instances  as  a  separate  filament  from  the  lateral  cord 
of  the  plexus;  it  is  derived  from  the  seventh  cervical  nerve.  The  branches  to  the 
Biceps  brachii  and  Brachialis  are  given  off  after  the  musculocutaneous  has  pierced 
the  Coracobrachialis;  that  supplying  the  Brachialis  gives  a  filament  to  the  elbow- 


964  NEUROLOGY 

joint.  The  nerve  also  sends  a  small  branch  to  the  bone,  which  enters  the  nntrient 
foramen  with  the  accom})anying  artery. 

The  lateral  antibrachial  cutaneous  nerve  {ii.  cuiaiieus  anfibrachii  cutaneou.s  lateralis; 
branch  of  inusculocidaneous  nerve)  passes  behind  the  cephalic  vein,  and  divides, 
opposite  the  elbow-joint,  into  a  volar  and  a  dorsal  branch  (Figs.  805,  807). 

The  volar  branch  {ramus  volaris;  anterior  branch)  descends  along  the  radial  border 
of  the  forearm  to  the  wrist,  and  supplies  the  skin  over  the  lateral  half  of  its  volar 
surface.  At  the  wrist-joint  it  is  placed  in  front  of  the  radial  artery,  and  some 
filaments,  piercing  the  deep  fascia,  accompany  that  vessel  to  the  dorsal  surface  of 
the  carpus.  The  nerve  then  passes  downward  to  the  ball  of  the  thumb,  where  it 
ends  in  cutaneous  filaments.  It  communicates  with  the  superficial  branch  of  the 
radial  ner\'e,  and  with  the  palmar  cutaneous  branch  of  the  median  nerve. 

The  dorsal  branch  (ramus  dorsalis;  posterior  branch)  descends,  along  the  dorsal 
surface  of  the  radial  side  of  the  forearm  to  the  wrist.  It  supplies  the  skin  of  the 
lower  two-thirds  of  the  dorso-lateral  surface  of  the  forearm,  communicating  with 
the  superficial  branch  of  the  radial  nerve  and  the  dorsal  antibrachial  cutaneous 
branch  of  the  radial. 

The  musculocutaneous  nerve  presents  frequent  irregularities.  It  may  adhere 
for  some  distance  to  the  median  and  then  pass  outward,  beneath  the  Biceps  brachii, 
instead  of  through  the  Coracobrachialis.  Some  of  the  fibres  of  the  median  may 
run  for  some  distance  in  the  musculo-cutaneous  and  then  leave  it  to  join  their 
proper  trunk;  less  frequently  the  reverse  is  the  case,  and  the  median  sends  a  branch 
to  join  the  musculocutaneous.  The  nerve  may  pass  under  the  Coracobrachialis 
or  through  the  Biceps  brachii.  Occasionally  it  gives  a  filament  to  the  Pronator 
teres,  and  it  supplies  the  dorsal  surface  of  the  thumb  when  the  superficial  branch 
of  the  radial  nerve  is  absent. 

The  Medial  Antibrachial  Cutaneous  Nerve  (/i.  cutaneus  antibrachii  medialis;  iniernal 
cutaneous  nerve)  (Fig.  809)  arises  from  the  medial  cord  of  the  brachial  plexus.  It 
derives  its  fibres  from  the  eighth  cervical  and  first  thoracic  nerves,  and  at  its  com- 
mencement is  placed  medial  to  the  axillary  artery.  It  gives  off,  near  the  axilla,  a 
filament,  which  pierces  the  fascia  and  supplies  the  integument  covering  the  Biceps 
brachii,  nearly  as  far  as  the  elbow.  The  nerve  then  runs  down  the  ulnar  side  of  the 
arm  medial  to  the  brachial  artery,  pierces  the  deep  fascia  with  the  basilic  vein, 
about  the  middle  of  the  arm,  and  divides  into  a  volar  and  an  ulnar  branch. 

The  volar  branch  (ramus  volaris;  anterior  branch),  the  larger,  passes  usually  in  front 
of,  but  occasionally  behind,  the  vena  mediana  cubiti  '{inedian  basilic  vein).  It  then 
descends  on  the  front  of  the  ulnar  side  of  the  forearm,  distributing  filaments  to  the 
skin  as  far  as  the  wrist,  and  communicating  with  the  palmar  cutaneous  branch  of 
the  ulnar  nerve  (Fig.  805). 

The  ulnar  branch  (ramus  unlaris;  posterior  branch)  passes  obliquely  downward  on 
the  medial  side  of  the  basilic  vein,  in  front  of  the  medial  epicondyle  of  the  humerus, 
to  the  back  of  the  forearm,  and  descends  on  its  ulnar  side  as  far  as  the  wrist,  dis- 
tributing filaments  to  the  skin.  It  communicates  with  the  medial  brachial  cutaneous, 
the  dorsal  antibrachial  cutaneous  branch  of  the  radial,  and  the  dorsal  branch  of 
the  ulnar  (Fig.  807). 

The  Medial  Brachial  Cutaneous  Nerve  (ii.  cutaneus  brachii  medialis;  lesser  internal 
cutaneous  nerve;  nerve  of  Wrisberg)  is  distributed  to  the  skin  on  the  ulnar  side  of  the 
arm  (Figs.  805,  807).  It  is  the  smallest  branch  of  the  brachial  plexus,  and  arising 
from  the  medial  cord  receives  its  fibres  from  the  eighth  cervical  and  first  thoracic 
nerves.  It  passes  through  the  axilla,  at  first  lying  behind,  and  then  medial  to  the 
axillary  vein,  and  communicates  with  the  intercostobrachial  nerve.  It  descends 
along  the  medial  side  of  the  brachial  artery  to  the  middle  of  the  arm,  where  it  pierces 
the  deep  fascia,  and  is  distributed  to  the  skin  of  the  back  of  the  lower  third  of  the 
arm,  extending  as  far  as  the  elbow,  where  some  filaments  are  lost  in  the  skin  in 


TIIK  CERVICAL  NERVES  965 

front  of  the  medial  epicoiulyle,  and  others  o\'er  the  olecranon.     It  communicates 
with  the  ulnar  branch  of  the  medial  antibrachial  cutaneous  nerve. 

In  some  cases  the  medial  brachial  cutaneous  and  interciostobrachial  are  connected  by  two  or 
three  filaments,  which  form  a  plexus  in  the  axilla.  In  other  cases  the  intercostobrachial  is  of 
large  size,  and  takes  the  place  of  the  medial  bra(!hial  cutaneous,  receiving  merely  a  filament  of 
communication  from  the  brachial  plexus,  which  represents  the  latter  nerve;  in  a  few  cases,  this 
filament  is  wanting. 

The  Median  Nerve  (/?.  mcdianus)  (Fig.  809)  extends  along  the  mifldle  of  the  arm 
and  forearm  to  the  hand.  It  arises  by  two  roots,  one  from  the  lateral  and  one  from 
the  medial  cord  of  the  brachial  plexus;  these  embrace  the  lower  part  of  the  axillary 
artery,  uniting  either  in  front  of  or  lateral  to  that  vessel.  Its  fibres  are  derived 
from  the  sixth,  seventh,  and  eighth  cervical  and  first  thoracic  nerves.  As  it  descends 
through  the  arm,  it  lies  at  first  lateral  to  the  brachial  artery;  about  the  level  of  the 
insertion  of  the  Coracobrachialis  it  crosses  the  artery,  usually  in  front  of,  but  occasion- 
ally behind  it,  and  lies  on  its  medial  side  at  the  bend  of  the  elbow,  where  it  is  situated 
behind  the  lacertus  fibrosus  {bicipital  fascia) ,  and  is  separated  from  the  elbow-joint 
by  the  Brachialis.  In  the  forearm  it  passes  between  the  two  heads  of  the  Pronator 
teres  and  crosses  the  ulnar  artery,  but  is  separated  from  this  vessel  by  the  deep 
head  of  the  Pronator  teres.  It  descends  beneath  the  Flexor  digitorum  sublimis, 
lying  on  the  Flexor  digitorum  profundus,  to  within  5  cm.  of  the  transverse  carpal 
ligament;  here  it  becomes  more  superficial,  and  is  situated  between  the  tendons  of 
the  Flexor  digitorum  sublimis  and  Flexor  carpi  radialis.  In  this  situation  it  lies 
behind,  and  rather  to  the  radial  side  of,  the  tendon  of  the  Palmaris  longus,  and  is 
covered  by  the  skin  and  fascia.  It  then  passes  behind  the  transverse  carpal  liga- 
ment into  the  palm  of  the  hand.  In  its  course  through  the  forearm  it  is  accompanied 
by  the  median  artery,  a  branch  of  the  volar  interroseous  artery. 

Branches. — With  the  exception  of  the  nerve  to  the  Pronator  teres,  which  some- 
times arises  above  the  elbow-joint,  the  median  nerve  gives  off  no  branches  in  the 
arm.    As  it  passes  in  front  of  the  elbow,  it  supplies  one  or  two  twigs  to  the  joint. 

In  the  forearm  its  branches  are :  muscular,  volar  interosseous,  and  palmar. 

The  muscular  branches  (rami  musculares)  are  derived  from  the  nerve  near  the 
elbow  and  supply  all  the  superficial  muscles  on  the  front  of  the  forearm,  except 
the  Flexor  carpi  ulnaris. 

The  volar  interosseous  nerve  {n.  interosseus  [antibrachii]  volaris;  anterior  inter- 
osseous nerve)  supplies  the  deep  muscles  on  the  front  of  the  forearm,  except  the  ulnar 
half  of  the  Flexor  digitorum  profundus.  It  accompanies  the  volar  interosseous 
artery  along  the  front  of  the  interosseous  membrane,  in  the  interval  between  the 
Flexor  pollicis  longus  and  Flexor  digitorum  profundus,  supplying  the  whole  of  the 
former  and  the  radial  half  of  the  latter,  and  ending  below  in  the  Pronator  quadratus 
and  wrist-joint. 

The  palmar  branch  (ramus  cutaneus  palmaris  n.  mediani)  of  the  median  nerve  arises 
at  the  lower  part  of  the  forearm.  It  pierces  the  volar  carpal  ligament,  and  divides  into 
a  lateral  and  a  medial  branch;  the  lateral  branch  supplies  the  skin  over  the  ball  of 
the  thumb,  and  communicates  with  the  volar  branch  of  the  lateral  antibrachial 
cutaneous  nerve;  the  medial  branch  supplies  the  skin  of  the  palm  and  communi- 
cates with  the  palmar  cutaneous  branch  of  the  ulnar. 

In  the  palm  of  the  hand  the  median  nerve  is  covered  by  the  skin  and  the  palmar 
aponeurosis,  and  rests  on  the  tendons  of  the  Flexor  muscles.  Immediately  after 
emerging  from  under  the  transverse  carpal  ligament  the  nerve  becomes  enlarged 
and  flattened  and  splits  into  a  smaller,  lateral,  and  a  larger,  medial  portion.  The 
lateral  portion  supplies  a  short,  stout  branch  to  certain  of  the  muscles  of  the  ball  of 
the  thumb,  viz.,  the  x^bductor  brevis,  the  Opponens,  and  the  superficial  head  of  the 
Flexor  brevis,  and  then  divides  into  three  proper  volar  digital  nerves ;  two  of  these 
supply  the  sides  of  the  thumb,  while  the  third  gives  a  twig  to  the  first  Lumbricalis 


966 


NEUROLOGY 


and  is  distributed  to  the  radial  side  of  the  index  finger.    The  medial  portion  of  the 
nerve  divides  into  two  common  volar  digital  nerves.    The  first  of  these  gives  a  twig 


Lalaal  unto  101  thoracic 

Jlediul  anterior  thoracic 

2Iusculocutaneous 


J — I —  Median 


Radial 

Deep  br.  of  radial 


Superjic.  br.  of  radial 
Volar  interosseous 


Fig.  809, — Nervea  of  the  left  upper  extremity. 


^ 


THE  CERVICAL  NERVES  967 


to  the  second  Lumbricalis  and  runs  toward  the  cleft  between  the  index  and  middle 
fingers,  where  it  divides  into  two  proper  digital  nerves  for  the  adjoining  sides  of 
these  digits;  the  second  runs  toward  the  cleft  between  the  middle  and  ring  fingers, 
and  splits  into  two  proper  digital  nerves  for  the  adjoining  sides  of  these  digits; 
it  communicates  with  a  branch  from  the  ulnar  nerve  and  sometimes  sends  a  twig 
to  the  third  Lumbricalis. 

Each  proper  digital  nerve,  opposite  the  base  of  the  first  phalanx,  gives  off  a 
dorsal  branch  which  joins  the  dorsal  digital  nerve  from  the  superficial  branch  of 
the  radial  nerve,  and  supplies  the  integument  on  the  dorsal  aspect  of  the  last 
phalanx.  At  the  end  of  the  digit,  the  proper  digital  nerve  divides  into  two 
branches,  one  of  which  supplies  the  pulp  of  the  finger,  the  other  ramifies  around 
and  beneath  the  nail.  The  proper  digital  nerves,  as  they  run  along  the  fingers,  are 
placed  superficial  to  the  corresponding  arteries. 

The  Ulnar  Nerve  {n.  ulnaris)  (Fig.  809)  is  placed  along  the  medial  side  of  the  limb, 
and  is  distributed  to  the  muscles  and  skin  of  the  forearm  and  hand.  It  arises 
from  the  medial  cord  of  the  brachial  plexus,  and  derives  its  fibres  from  the  eighth 
cervical  and  first  thoracic  nerves.  It  is  smaller  than  the  median,  and  lies  at  first 
behind  it,  but  diverges  from  it  in  its  course  down  the  arm.  At  its  origin  it  lies 
medial  to  the  axillary  artery,  and  bears  the  same  relation  to  the  brachial  artery 
as  far  as  the  middle  of  the  arm.  Here  it  pierces  the  medial  intermuscular  septum, 
runs  obliquely  across  the  medial  head  of  the  Triceps  brachii,  and  descends  to  the 
groove  between  the  medial  epicondyle  and  the  olecranon,  accompanied  by  the 
superior  ulnar  collateral  artery.  At  the  elbow,  it  rests  upon  the  back  of  the  medial 
epicondyle,  and  enters  the  forearm  between  the  two  heads  of  the  Flexor  carpi 
ulnaris.  In  the  forearm,  it  descends  along  the  ulnar  side,  lying  upon  the  Flexor 
digitorum  profundus;  its  upper  half  is  covered  by  the  Flexor  carpi  ulnaris,  its  lower 
half  lies  on  the  lateral  side  of  the  muscle,  covered  by  the  integument  and  fascia.  In 
the  upper  third  of  the  forearm,  it  is  separated  from  the  ulnar  artery  by  a  consider- 
able interval,  but  in  the  rest  of  its  extent  lies  close  to  the  medial  side  of  the  artery. 
About  5  cm.  above  the  wrist  it  ends  by  dividing  into  a  dorsal  and  a  volar  branch. 

The  branches  of  the  ulnar  nerve  are:  articular  to  the  elbow-joint,  muscular, 
palmar  cutaneous,  dorsal,  and  volar. 

The  articular  branches  to  the  elbow-joint  are  several  small  filaments  which  arise 
from  the  nerve  as  it  lies  in  the  groove  between  the  medial  epicondyle  and  olecranon. 

The  muscular  branches  {rami  musculares)  two  in  number,  arise  near  the  elbow: 
one  supplies  the  Flexor  carpi  ulnaris;  the  other,  the  ulnar  half  of  the  Flexor 
digitorum  profundus. 

The  palmar  cutaneous  branch  {ramus  cutaneus  palmaris)  arises  about  the  middle 
of  the  forearm,  and  descends  on  the  ulnar  artery,  giving  off  some  filaments  to  the 
vessel.  It  perforates  the  volar  carpal  ligament  and  ends  in  the  skin  of  the  palm, 
communicating  with  the  palmar  branch  of  the  median  nerve. 

The  dorsal  branch  {ramus  dorsalis  manus)  arises  about  5  cm.  above  the  wrist;  it 
passes  backward  beneath  the  Flexor  carpi  ulnaris,  perforates  the  deep  fascia,  and, 
running  along  the  ulnar  side  of  the  back  of  the  wrist  and  hand,  divides  into  two 
dorsal  digital  branches;  one  supplies  the  ulnar  side  of  the  little  finger;  the  other, 
the  adjacent  sides  of  the  little  and  ring  fingers.  It  also  sends  a  twig  to  join  that 
given  by  the  superficial  branch  of  the  radial  nerve  for  the  adjoining  sides  of  the 
middle  and  ring  fingers,  and  assists  in  supplying  them.  A  branch  is  distributed 
to  the  metacarpal  region  of  the  hand,  communicating  with  a  twig  of  the  superficial 
branch  of  the  radial  nerve  (Fig.  807) . 

On  the  little  finger  the  dorsal  digital  branches  extend  only  as  far  as  the  base 
of  the  terminal  phalanx,  and  on  the  ring  finger  as  far  as  the  base  of  the  second 
phalanx;  the  more  distal  parts  of  these  digits  are  supplied  by  dorsal  branches  derived 
from  the  proper  volar  digital  branches  of  the  ulnar  nerve. 


968 


NEUROLOGY 


Axillary 


~Radial 


The  volar  branch  (ramus  voJaris  maniis)  crosses  the  transverse  carpal  Hgament 
on  the  hiteral  side  of  the  pisiform  bone,  medial  to  and  a  little  behind  the  ulnar 

artery.    It  ends  by  dividing  into 
Suprascapular  "^^  a  Superficial  and  a  deej)  branch. 

The  superficial  branch  {ramus 
superficialisin.  ulnaris])  supplies 
the  Palmaris  brevis,  and  the 
skin  on  the  ulnar  side  of  the 
hand,  and  divides  into  a  proper 
volar  digital  branch  for  the  ulnar 
side  of  the  little  finger,  and  a 
common  volar  digital  branch 
which  gives  a  communicating 
twig  to  the  median  nerve  and 
divides  into  two  proper  digital 
nerves  for  the  adjoining  sides 
of  the  little  and  ring  fingers 
(Fig.  805).  The  proper  digital 
branches  are  distributed  to  the 
fingers  in  the  same  manner  as 
those  of  the  median. 

The  deep  branch  [ramus  iwo- 
fundus)  accompanied  by  the 
deep  branch  of  the  ulnar  artery, 
passes  between  the  Abductor 
digiti  quinti  and  Flexor  digiti 
quinti  brevis;  it  then  perforates 
the  Opponens  digiti  quinti  and 
follows  the  course  of  the  deejp 
volar  arch  beneath  the  Flexor 
tendons.  At  its  origin  it  sup- 
plies the  three  short  muscles  of 
the  little  finger.  As  it  crosses 
the  deep  part  of  the  hand,  it  sup- 
plies all  the  Interossei  and  the 
third  and  fourth  Lumbricalis; 
it  ends  by  supplying  the  Adduc- 
tores  pollicis  and  the  medial 
head  of  the  Flexor  pollicis  brevis. 
It  also  sends  articular  filaments 
to  the  wrist-joint. 

It  has  been  pointed  out  that 
the  ulnar  part  of  the  Flexor 
digitorum  profundus  is  supplied 
by  the  ulnar  nerve;  the  third 
and  fourth  Lumbricales,  which 
are  connected  with  the  tendons 
of  this  part  of  the  muscle,  are  supplied  by  the  same  nerve.  In  like  manner  the 
lateral  part  of  the  Flexor  digitorum  profundus  and  the  first  and  second  Lumbri- 
cales are  supplied  by  the  median  nerve;  the  third  Lumbricalis  frequently  receives 
an  additional  twig  from  the  median  nerve. 

The  Radial  Nerve  {n.  radialis;  musculospiral  nerve)  (Fig.  810),  the  largest  branch 
of  the  brachial  plexus,  is  the  continuation  of  the  posterior  cord  of  the  plexus.  Its 
fibres  are  derived  from  the  fifth,  sixth,  seventh,  and  eighth  cervical  and  first  thoracic 


Deep  branch 
of  radial 


Fig.  810. — The  suprascapular,  axillary,  and  radial  nerves. 


THE  CERVICAL  NERVES  969 

nerves.  It  descriuls  bt'liind  the  first  part  of  the  axillary  artery  and  the  npper  part 
i)f  the  hraehial  artery,  and  in  front  of  the  tendons  of  the  Latissimus  dorsi  and  Teres 
major.  It  then  winds  around  from  the  medial  to  the  hiteral  side  of  the  humerus  in 
a  groove  with  the  a.  profunda  brachii,  between  the  medial  and  lateral  heads  of  the 
Triceps  brachii.  It  pierces  the  lateral  internuiscular  sejjtum,  and  passes  between 
the  Brachialis  and  Brachioradialis  to  the  front  of  the  lateral  epicond\le,  where 
it  divides  into  a  superficial  and  a  deep  branch. 
The  branches  of  the  musculospiral  nerve  are: 

]\luscular.  Superficial. 

Cutaneous.  Deep. 

The  muscular  branches  (/•(///;/  iiiNscuIarc.-t)  supply  the  Triceps  brachii,  Anconaeus, 
Brachioradialis,  Extensor  carpi  radialis  longus,  and  Brachialis,  and  are  grouped  as 
medial,  posterior,  and  lateral. 

The  medial  muscular  branches  supply  the  medial  and  long  heads  of  the  Triceps 
brachii.  That  to  the  medial  head  is  a  long,  slender  filament,  which  lies  close  to  the 
ulnar  nerve  as  far  as  the  lower  third  of  the  arm,  and  is  therefore  frequently  spoken 
of  as  the  uhiar  collateral  nerve. 

The  posterior  muscular  branch,  of  large  size,  arises  from  the  nerve  in  the  groove 
between  the  Triceps  brachii  and  the  humerus.  It  divides  into  filaments,  which 
supply  the  medial  and  lateral  heads  of  the  Triceps  brachii  and  the  Anconaeus 
muscles.  The  branch  for  the  latter  muscle  is  a  long,  slender  filament,  which  descends 
in  the  substance  of  the  medial  head  of  the  Triceps  brachii. 

The  lateral  muscular  branches  supply  the  Brachioradialis,  Extensor  carpi  radialis 
longus,  and  the  lateral  part  of  the  Brachialis. 

The  cutaneous  branches  are  two  in  number,  the  posterior  brachial  cutaneous 
and  the  dorsal  antibrachial  cutaneous. 

The  posterior  brachial  cutaneous  nerve  (».  cutaneus  brachii  posterior;  internal 
cutaneous  branch  of  musculospiral)  arises  in  the  axilla,  with  the  medial  muscular 
branch.  It  is  of  small  size,  and  passes  through  the  axilla  to  the  medial  side  of 
the  area  supplying  the  skin  on  its  dorsal  surface  nearly  as  far  as  the  olecranon. 
In  its  course  it  crosses  behind,  and  communicates  with,  the  intercostobrachial. 

The  dorsal  antibrachial  cutaneous  nerve  {n.  cutaneus  antibrachii  dorsalis;  external 
cutaneous  branch  of  musculospiral)  perforates  the  lateral  head  of  the  Triceps  brachii  at 
its  attachment  to  the  humerus.  The  upper  and  smaller  branch  of  the  nerve  passes 
to  the  front  of  the  elbow,  lying  close  to  the  cephalic  vein,  and  supplies  the  skin 
of  the  lower  half  of  the  arm  (Fig.  805) .  The  lower  branch  pierces  the  deep  fascia 
below  the  insertion  of  the  Deltoideus,  and  descends  along  the  lateral  side  of  the 
arm  and  elbow,  and  then  along  the  back  of  the  forearm  to  the  wrist,  supplying 
the  skin  in  its  course,  and  joining,  near  its  termination,  with  the  dorsal  branch 
of  the  lateral  antibrachial  cutaneous  nerve  (Fig.  807). 

The  Superficial  Branch  of  the  Radial  Nerve  (ramus  superficialis  radial  nerve) 
passes  along  the  front  of  the  radial  side  of  the  forearm  to  the  commencement  of 
its  lower  third.  It  lies  at  first  slightly  lateral  to  the  radial  artery,  concealed 
beneath  the  Brachioradialis.  In  the  middle  third  of  the  forearm,  it  lies  behind  the 
same  muscle,  close  to  the  lateral  side  of  the  artery.  It  quits  the  artery  about  7  cm. 
above  the  wrist,  passes  beneath  the  tendon  of  the  Brachioradialis,  and,  piercing 
the  deep  fascia,  divides  into  two  branches  (Fig.  807). 

The  lateral  branch,  the  smaller,  supplies  the  skin  of  the  radial  side  and  ball 
of  the  thumb,  joining  with  the  volar  branch  of  the  lateral  antibrachial  cutaneous 
nerve. 

The  medial  branch  communicates,  above  the  wrist,  with  the  dorsal  branch  of  the 
lateral  antibrachial  cutaneous,  and,  on  the  back  of  the  hand,  with  the  dorsal 
branch  of  the  ulnar  nerve.      It  then  di^•ides  into  four  digital  nerves,  which  are 


970  NEUROLOGY 

distributed  as  follows:  the  first  supplies  the  ulnar  side  of  the  thumb;  the  second, 
the  radial  side  of  the  index  finger;  the  third,  the  adjoinino-  sides  of  the  index  and 
middle  fingers;  the  fourth  communicates  with  a  filament  from  the  dorsal  branch 
of  the  ulnar  nerve,  and  supplies  the  adjacent  sides  of  the  middle  and  ring 
fingers.^ 

The  Deep  Branch  of  the  Radial  Nerve  {n.  interosseus  dorsalis;  dorsal  or  posterior 
interosseous  nerve)  winds  to  the  back  of  the  forearm  around  the  lateral  side  of  the 
radius  between  the  two  planes  of  fibres  of  the  Supinator,  and  is  prolonged  down- 
ward between  the  superficial  and  deep  layers  of  muscles,  to  the  middle  of  the 
forearm.  Considerably  diminished  in  size,  it  descends,  as  the  dorsal  interosseous 
nerve,  on  the  interosseous  membrane,  in  front  of  the  Extensor  pollicis  longus,  to  the 
back  of  the  carpus,  where  it  presents  a  gangliform  enlargement  from  which  filaments 
are  distributed  to  the  ligaments  and  articulations  of  the  carpus.  It  supplies  all 
the  muscles  on  the  radial  side  and  dorsal  surface  of  the  forearm,  excepting  the 
Anconaeus,  Brachioradialis,  and  Extenosr  carpi  radialis  longus. 

Applied  Anatomy. — The  brachial  plexus  may  be  injured  by  faUs  from  a  height  on  to  the  side 
of  the  head  and  shoulder,  whereby  the  nerves  of  the  plexus  are  violently  stretched;  the  fifth 
cervical  nerve  sustains  the  greatest  amount  of  injury,  and  the  subsequent  paralysis  may  be  con- 
fined to  the  muscles  supplied  by  this  nerve,  viz.,  the  Deltoideus,  Biceps  brachii,  Brachialis,  and 
Brachioradialis,  with  sometimes  the  Supra-  and  Infraspinatus  and  the  Supinator.  The  position 
of  the  limb,  under  such  conditions,  is  characteristic;  the  arm  hangs  by  the  side  and  is  rotated 
inward;  the  forearm  is  extended  and  pronated.  The  arm  cannot  be  raised  from  the  side;  all 
power  of  flexion  of  the  elbow  is  lost,  as  is  also  supination  of  the  forearm.  This  is  known  as  ErVs 
-paralysis,  and  a  very  similar  condition  is  occasionally  met  with  in  newborn  children,  either  from 
injury  to  the  fifth  nerve  from  the  pressure  of  forceps  used  in  affecting  delivery,  or  from  traction 
of  the  head  in  breech  presentations.  A  second  variety  of  partial  palsy  of  the  brachial  plexus 
is  known  as  Klumpke's  paralysis.  In  this  it  is  the  eighth  cervical  and  first  thoracic  nerves  that 
are  injiu-ed,  either  before  or  after  they  have  joined  to  form  the  lower  trunk.  Atrophy  follows 
in  the  intrinsic  muscles  of  the  hand,  and  in  the  Flexors  of  the  fingers  and  wrist;  the  thenar  and 
hypothenar  eminences  waste  and  flatten;  the  fingers  cannot  be  spread  out  or  approximated,  on 
account  of  the  paralysis  of  the  Interossei,  and  become  clawed.  The  injury  to  the  nerves  may 
follow  direct  violence  or  a  gunshot  wound. 

The  brachial  plexus  may  also  be  injured  by  violent  traction  on  the  arm,  or  by  efforts  at  reduc- 
ing a  dislocation  of  the  shoxilder-joint;  and  the  amoimt  of  paralysis  will  depend  upon  the  amount 
of  injury  to  the  constituent  nerves.  When  the  entire  plexus  is  involved,  the  whole  of  the  upper 
extremity  will  be  paralyzed  and  anesthetic.  In  these  cases  the  injury  appears  to  be  rather  a 
tearing  away  of  the  roots  of  the  nerves  from  the  medulla  spinahs,  than  a  rupture  of  the  nerves 
themselves.  The  brachial  plexus  in  the  axilla  is  often  damaged  from  the  pressure  of  a  crutch, 
producing  the  condition  known  as  crutch  paralysis.  In  these  cases  the  radial  seems  most  fre- 
quently to  be  the  nerve  implicated;  the  ulnar  nerve  suffers  next  in  frequency.  The  median  and 
radial  nerves  often  suffer  from  "sleep  palsies,"  paralysis  from  pressure  coming  on  while  the  patient 
is  profoundly  asleep  under  the  influence  of  alcohol  or  some  narcotic. 

Paralysis  of  the  long  thoracic  nerve  throws  the  Serratus  anterior  out  of  action,  and  may  occur 
in  porters  in  whom  the  nerve  is  exposed  to  injury  as  it  crosses  the  posterior  triangle  of  the  neck. 
The  inferior  angle  of  the  scapula  is  drawn  toward  the  middle  line,  by  the  unopposed  action  of  the 
Rhomboidei  and  Levator  scapulae,  and  tends  to  project  backward  when  the  arm  is  held  hori- 
zontally forward.  The  arm  cannot  be  raised  above  the  horizontal  unless  the  inferior  angle  of 
the  scapula  is  pushed  lateralward  for  the  patient. 

The  axillary  {circumflex)  nerve,  on  account  of  its  course  around  the  surgical  neck  of  the  humerus, 
is  liable  to  be  torn  in  fractures  of  this  part  of  the  bone,  and  in  dislocations  of  the  shoulder-joint; 
paralysis  of  the  Deltoideus,  and  anesthesia  of  the  skin  over  the  lower  part  of  that  muscle,  result. 
According  to  Erb,  inflammation  of  the  shoulder-joint  is  liable  to  be  followed  by  a  nem-itis  of  this 
nerve  from  extension  of  the  inflammation  to  it.  Paralysis  of  the  Deltoideus  renders  abduction 
of  the  arm  to  the  horizontal  level  impossible.  The  associated  paralysis  of  the  Teres  minor  is  not 
easily  demonstrated. 

Hilton  gave  the  axillary  nerve  as  an  illustration  of  a  law  which  he  laid  down,  that  "the  same 
trunks  of  nerves  whose  branches  supply  the  groups  of  muscles  moving  a  joint,  furnish  also  a 

1  According  to  Hutchison,  the  digital  nerve  to  the  thumb  reaches  only  as  high  as  the  root  of  the  nail;  the  one  to  the 
forefinger  as  high  as  the  middle  of  the  second  phalanx;  and  the  one  to  the  middle  and  ring  fingers  not  higher  than  the 
first  phalangeal  joint. — London  Hosp.  Gaz.,  iii,  319. 


THE  CERVICAL  NERVES  971 

distribution  of  iicives  to  the  skin  oxev  the  insertions  of  the  same  muscles,  and  tlie  interior  of  the 
joint  receives  its  nerves  from  the  same  source."  In  this  way  he  explains  the  fact  that  an  inflamed 
joint  becomes  rigid. 

The  median  nerve  is  liable  to  injury  in  wounds  of  the  forearm.  In  such  (tases  there  is  loss  of 
flexion  of  the  second  phalanges  of  all  the  fingers,  and  of  the  terminal  phalanges  of  the  index  and 
middle  fingers.  Flexion  of  the  terminal  plialanges  of  tlie  ring  and  little  fingers  is  effected  by  that 
portion  of  the  Flexor  digitorum  profundus  which  is  supplied  by  the  idnar  nerve.  There  is  power 
to  flex  the  proximal  phalanges  through  the  Interossei.  The  thumb  cannot  be  flexed  or  opposed, 
and  is  maintained  in  a  position  of  extension  and  adduction.  There  is  loss  in  the  power  of  pronat- 
ing  the  forearm;  the  Brachioradialis  has  the  power  of  bringing  the  forearm  into  a  position  of  mid- 
pronation,  but  beyond  this  no  further  pronation  can  be  effected.  The  wrist  can  be  flexed,  if  the 
hand  is  first  adductcd  by  the  action  of  the  Flexor  carpi  ulnaris.  There  is  loss  or  impairment  of 
sensation  on  the  volar  surfaces  of  the  thumb,  index,  middle,  and  radial  half  of  ring  fingers,  and 
on  the  dorsal  surfaces  of  the  same  fingers  over  the  last  two  phalanges;  except  in  the  thumb,  where 
the  loss  of  sensation  would  be  limited  to  the  back  of  the  last  phalanx.  In  old  cases  the  unopposed 
action  of  the  Interossei  produces  backward  dislocation  of  the  interphalangeal  joints.  The  thumb 
is  extended  and  adducted  to  the  index  finger,  cannot  be  flexed  or  abducted,  and  cannot  be  apposed 
to  any  one  of  the  fingers;  in  consequence  an  "ape'-hke"  hand  is  produced.  More  commonly, 
however,  the  nerve  is  injured  just  above  the  annular  ligament  when  the  power  of  flexion  of  the 
fingers  and  pronation  of  the  forearm  remain  intact  unless  the  Flexor  tendons  are  also  divided. 
This  injury  seriously  interferes  with  the  use  of  the  hand,  as,  bfesides  the  wasting  of  the  muscles 
of  the  thenar  eminence,  great  trouble  is  experienced  from  the  trophic  changes  which  result  about 
the  skin  and  nails  of  the  fingers  which  are  anesthetic.  In  order  to  expose  the  median  nerve,  for 
the  purpose  of  uniting  the  divided  ends,  supposing  the  injury  to  be  just  above  the  wrist,  and 
incision  should  be  made  along  the  radial  side  of  the  tendon  of  the  pahnaris  longus,  which  serves 
as  a  guide  to  the  nerve. 

The  ulnar  nerve  is  also  liable  to  be  injured  in  wounds  of  the  forearm,  such  injury  leading  to 
impaired  power  of  ulnar  flexion,  and  upon  an  attempt  being  made  to  flex  the  wrist,  the  hand  is 
drawn  to  the  radial  side  from  paralysis  of  the  Flexor  carpi  ulnaris;  there  is  inability  to  spread 
out  the  fingers  from  paralysis  of  the  Interossei,  and  for  the  same  reason  the  fingers,  especially . 
the  ring  and  little  fingers,  cannot  be  flexed  at  the  metacarpophalangeal  joints  or  extended  at  the 
interphalangeal  joints,  and  the  hand  assumes  a  claw  shape  from  the  action  of  the  opposing  muscles; 
there  is  loss  of  power  of  flexion  in  the  little  and  ring  fingers;  and  there  is  inability  to  adduct  the 
thumb.  The  muscles  of  the  hypothenar  eminence  become  wasted.  Sensation  is  lost,  or  impaired, 
in  the  skin  supplied  by  the  nerve.  In  order  to  expose  the  nerve  in  the  lower  part  of  the  forearm, 
an  incision  should  be  made  along  the  radial  border  of  the  tendon  of  the  Flexor  carpi  ulnaris,  and 
the  nerve  will  be  found  lying  on  the  ulnar  side  of  the  ulnar  artery.  This  nerve  may  be  also  affected 
in  cases  of  dislocation  of  the  shoulder  or  fracture  of  the  svu-gical  neck  of  the  humerus.  Wasting 
of  the  muscles  which  it  suppUes  is  not  imcommonly  seen  where  a  "cervical  rib"  is  present,  the 
lower  end  of  the  plexus  passing  between  this  and  the  first  thoracic  rib. 

The  radial  (musculospiral)  nerve  is  also  frequently  injured.  In  consequence  of  its  close  rela- 
tionship to  the  humerus,  it  is  often  torn  or  injured  in  fractures  of  this  bone,  or  subsequently 
involved  in  the  callus  that  may  be  thrown  out  around  a  fracture,  and  thus  pressed  upon  and  its 
functions  interfered  with.  It  is  also  liable  to  be  contused  against  the  bone  by  kicks  or  blows,, 
or  to  be  divided  in  wounds  of  the  arm.  When  paralyzed,  the  hand  is  flexed  at  the  wrist  and  lies 
flaccid.  This  is  known  as  wrist  drop.  The  fingers  are  also  flexed,  and  on  an  attempt  being  made 
to  extend  them,  the  last  two  phalanges  only  will  be  extended,  through  the  action  of  the  Interossei; 
the  first  phalanges  remaining  flexed.  There  is  no  power  of  extending  the  wrist.  Supination  is 
completely  lost  when  the  forearm  is  extended  on  the  arm,  but  is  possible  to  a  certain  extent  if 
the  forearm  be  flexed  so  as  to  allow  of  the  action  of  the  Biceps  brachii.  The  power  of  extension 
of  the  forearm  is  lost  on  account  of  paralysis  of  the  Triceps  brachii,  if  the  injury  to  the  nerve  has 
taken  place  near  its  origin.  In  cases  due  to  pressure,  sensation  is  hardly  affected;  severe  injury 
to  the  nerve  occasions  anesthesia  over  the  area  supplied  by  the  superficial  branch  of  the  radial 
nerve,  and,  if  the  lesion  be  high  up,  on  the  lateral  side  of  the  upper  arm  and  the  back  of  the 
forearm  (posterior  brachial  and  dorsal  antibrachial  cutaneous  branches)  as  well. 

The  nerve  is  best  exposed  by  making  an  incision  along  the  medial  border  of  the  Brachioradialis, 
just  above  the  level  of  the  elbow-joint.  The  skin  and  superficial  structures  are  to  be  divided 
and  the  deep  fascia  exposed.  The  white  Une  in  the  fascia  indicating  the  border  of  the  muscle 
is  to  be  defined,  and  the  deep  fascia  divided  in  this  line.  On  raising  the  Brachioradiahs,  the 
nerve  will  be  found  lying  between  it  and  the  Brachialis.  The  muscles  supphed  by  the  deep  branch 
of  the  radial  nerve  are  also  particularly  liable  to  be  affected  in  chronic  lead  poisoning;  here  the 
affection  is  probably  in  the  cells  of  the  anterior  column  of  the  medulla  spinalis.  Incisions  down 
to  the  neck  of  the  radius  posteriorly  or  on  the  lateral  side  should  never  be  made,  as  the  deep 
branch  of  the  radial  nerve  would  be  severed. 


972 


NEUROLOGY 


The  Thoracic  Nerves  (Nn.  Thoracales). 

The  anterior  divisions  of  the  thoracic  nerves  {raiui  aiiteriores;  ventral  divisionfi) 
are  twelve  in  iiumber  on  either  side.  Eleven  of  them  are  situated  l)etween  the  ribs, 
and  are  therefore  termed  intercostal;  the  twelfth  lies  below  the  last  rib.  Each  nerve 
is  connected  with  the  adjoining  ganglion  of  the  sympathetic  trunk  by  a  gray  and  a 
white  ramus  communicans.  The  intercostal  nerves  are  distributed  chiefly  to  the 
parietes  of  the  thorax  and  abdomen,  and  differ  from  the  anterior  division's  of  the 
other  spinal  nerves,  in  that  each  pursues  an  independent  course,  i.  e.,  there  is  no 
plexus  formation.  The  first  two  nerves  supply  fibres  to  the  upper  limb  in  addition 
to  their  thoracic  branches;  the  next  four  are  limited  in  their  distribution  to  the 
parietes  of  the  thorax;  the  lower  five  supply  the  parietes  of" the  thorax  and  abdomen. 
The  twelfth  thoracic  is  distributed  to  the  abdominal  wall  and  the  skin  of  the  buttock. 

The  First  Thoracic  Nerve. — The  anterior  division  of  the  first  thoracic  nerve  divides 
into  two  branches :  one,  the  larger,  leaves  the  thorax  in  front  of  the  neck  of  the  first 
rib,  and  enters  the  brachial  plexus;  the  other  and  smaller  branch,  the  first  intercostal 
nerve,  runs  along  the  first  intercostal  space,  and  ends  on  the  front  of  the  chest  as 
the  first  anterior  cutaneous  branch  of  the  thorax.  Occasionally  this  anterior  cuta- 
neous branch  is  wanting.  The  first  intercostal  nerve  as  a  rule  gives  oft'  no  lateral 
cutaneous  branch;  but  sometimes  it  sends  a  small  branch  to  communicate  with 
the  intercostobrachial.  From  the  second  thoracic  nerve  it  frequently  receives  a 
connecting  twig,  which  ascends  over  the  neck  of  the  second  rib. 


Posterior  divisio 


Lateral  cutaneous 


Anterior  cutaneous 
Fig.  811. — Diagram  of  the  course  and  branches  of  a  typical  intercostal  nerve. 


The  Upper  Thoracic  Nerves  {nn.  iniercostales) . — The  anterior,  divisions  of  the 
second,  third,  fourth,  fifth,  and  sixth  thoracic  nerves,  and  the  small  branch  from  the 
first  thoracic,  are  confined  to  the  parietes  of  the  thorax,  and  are  named  thoracic 
intercostal  nerves.  They  pass  forward  (Fig.  811)  in  the  intercostal  spaces  below  the 
intercostal  vessels.  At  the  back  of  the  chest  they  lie  between  the  pleura  and  the 
posterior  intercostal  membranes,  but  soon  pierce  the  latter  and  run  between  the 
two  planes  of  Intercostal  muscles  as  far  as  the  middle  of  the  rib.  They  then  enter 
the  substance  of  the  Intercostales  interni,  and,  running  amidst  their  fibres  as  far  as 


THE  THORACIC  NERVES  973 

the  costal  cartilages,  they  gain  the  inner  surfaces  of  the  muscles  and  lie  l^etween 
them  and  the  pleura.  Near  the  sternum,  they  cross  in  front  of  the  internal  mammary 
artery  and  Transversus  thoracis  muscle,  pierce  the  Intercostales  interni,  the  anterior 
intercostal  membranes,  and  Pectoralis  major,  and  supply  the  integument  of  the 
front  of  the  thorax  and  over  the  mamma,  forming  the  anterior  cutaneous  branches 
of  the  thorax;  the  branch  from  the  second  nerve  unites  with  the  anterior  supra- 
clavicular nerves  of  the  cervical  plexus. 

Branches. — Numerous  slender  muscular  filaments  supply  the  Intercostales,  the 
Subcostales,  the  Levatores  costarum,  the  Serratus  posterior  superior,  and  the  Trans- 
versus thoracis.  x\t  the  front  of  the  thorax  some  of  these  branches  cross  the  costal 
cartilages  from  one  intercostal  space  to  another. 

Lateral  cutaneous  branches  {rami  cutanei  laterales)  are  derived  from  the  intercostal 
nerves,  about  midway  between  the  vertebrae  and  sternum;  they  pierce  the  Inter- 
costales externi  and  Serratus  anterior,  and  divide  into  anterior  and  posterior 
branches.  The  anterior  branches  run  forward  to  the  side  and  the  forepart  of  the 
chest,  supplying  the  skin  and  the  niamma;  those  of  the  fifth  and  sixth  nerves 
supply  the  upper  digitations  of  the  Obliquus  externus  abdominis.  The  posterior 
branches  run  backward,  and  supply  the  skin  over  the  scapula  and  Latissimus  dorsi. 

The  lateral  cutaneous  branch  of  the  second  intercostal  nerve  does  not  divide, 
like  the  others,  into  an  anterior  and  a  posterior  branch;  it  is  named  the  intercosto- 
brachial  nerve  (Fig.  809).  It  pierces  the  Intercostalis  externus  and  the  Serratus 
anterior,  crosses  the  axilla  to  the  medial  side  of  the  arm,  and  joins  with-  a  filament 
from  the  medial  brachial  cutaneous  nerve.  It  then  pierces  the  fascia,  and  supplies 
the  skin  of  the  upper  half  of  the  medial  and  posterior  part  of  the  arm,  communicat- 
ing with  the  posterior  brachial  cutaneous  branch  of  the  radial  nerve.  The  size 
of  the  intercostobrachial  nerve  is  in  inverse  proportion  to  that  of  the  medial  brachial 
cutaneous  nerve.  A  second  intercostobrachial  nerve  is  frequently  given  off  from 
the  lateral  cutaneous  branch  of  the  third  intercostal;  it  supplies  filaments  to  the 
axilla  and  medial  side  of  the  arm. 

The  Lower  Thoracic  Nerves. — Th-e  anterior  divisions  of  the  seventh,  eighth^  ninth, 
tenth,  and  eleventh  thoracic  nerves  are  continued  anteriorly  from  the  intercostal 
spaces  into  the  abdominal  wall;  hence  they  are  named  thoracicoabdominal  inter- 
costal nerves.  They  have  the  same  arrangement  as  the  upper  ones  as  far  as  the 
anterior  ends  of  the  intercostal  spaces,  where  they  pass  behind  the  costal  cartilages, 
and  between  the  Obliquus  internus  and  Transversus  abdominis,  to  the  sheath  of 
the  Rectus  abdominis,  which  they  perforate.  They  supply  the  Rectus  abdominis 
and  end  as  the  anterior  cutaneous  branches  of  the  abdomen;  they  supply  the  skin 
of  the  front  of  the  abdomen.  The  lower  intercostal  nerves  supply  the  Intercostales 
and  abdominal  muscles;  the  last  three  send  branches  to  the  Serratus  posterior 
inferior.  About  the  middle  of  their  course  they  give  off  lateral  cutaneous  branches. 
These  pierce  the  Intercostales  externi  and  the  Obliquus  externus  abdominis,  in  the 
same  line  as  the  lateral  cutaneous  branches  of  the  upper  thoracic  nerves,  and  divide 
into  anterior  and  posterior  branches,  which  are  distributed  to  the  skin  of  the  abdo- 
men and  back;  the  anterior  branches  supply  the  digitations  of  the  Obliquus  externus 
abdominis,  and  extend  downward  and  forward  nearly  as  far  as  the  margin  of  the 
Rectus  abdominis;  the  posterior  branches  pass  backward  to  supply  the  skin  over 
the  Latissimus  dorsi. 

The  anterior  division  of  the  twelfth  thoracic  nerve  is  larger  than  the  others;  it 
runs  along  the  lower  border  of  the  twelfth  rib,  often  gives  a  communicating  branch 
to  the  first  lumbar  nerve,  and  passes  under  the  lateral  lumbocostal  arch.  It  then 
runs  in  front  of  the  Quadratus  lumborum,  perforates  the  Transversus,  and  passes 
forward  between  it  and  the  Obliquus  internus  to  be  distributed  in  the  same  manner 
as  the  lower  intercostal  nerves.  It  communicates  with  the  iliohypogastric  nerve 
of  the  lumbar  plexus,  and  gives  a  branch  to  the  Pyramidalis.    The  lateral  cutaneous 


974  NEUROLOGY 

branch  of  the  last  thoracic  nerve  is  large,  and  does  not  divide  into  an  anterior  and 
a  posterior  branch.  It  perforates  the  Obliqui  internus  and  externus,  descends  over 
the  iliac  crest  in  front  of  the  lateral  cutaneous  branch  of  the  iliohypogastric  (Fig. 
819),  and  is  distributed  to  the  skin  of  the  front  part  of  the  gluteal  region,  some  of 
its  filaments  extending  as  low  as  the  greater  trochanter. 

Applied  Anatomy. — The  lower  seven  thoracic  nerves  and  the  iliohypogastric  from  the  first 
lumbar  nerve  supply  the  skin  of  the  abdominal  wall.  They  run  downward  and  forward  fairly 
equidistant  from  each  other.  The  sixth  and  seventh  supply  the  skin  over  the  "pit  of  the  stomach;" 
the  eighth  corresponds  to  about  the  position  of  the  middle  tendinous  inscription  of  the  Rectus 
abdominis;  the  tenth  to  the  umbihcus;  and  the  ihohypogastric  supphes  the  skin  over  the  pubis 
and  subcutaneous  inguinal  ring.  In  many  diseases  affecting  the  nerve  trunks  at  or  near  their 
origins,  the  pain  is  referred  to  their  peripheral  terminations.  Thus,  in  Pott's  disease  of  the  verte- 
brae, children  often  suffer  from  pain  in  the  abdomen.  When  the  irritation  is  confined  to  a  single 
pair  of  nerves,  the  sensation  complained  of  is  often  a  feeling  of  constriction,  as  if  a  cord  were 
tied  around  the  abdomen,  and  in  these  cases  the  situation  of  the  sense  of  constriction  may  serve 
to  locahze  the  disease  in  the  vertebral  column.  In  other  cases  where  the  bone  disease  is  more  ex- 
tensive, and  two  or  more  nerves  are  involved,  a  more  general,  diffused  pain  in  the  abdomen  is  felt. 

Again,  it  must  be  borne  in  mind  that  the  nerves  which  supply  the  skin  of  the  abdomen  supply 
also  the  planes  of  muscle  which  constitute  the  greater  pai't  of  the  abdominal  wall.  Hence,  any 
irritation  applied  to  the  peripheral  ends  of  the  cutaneous  branches  in  the  skin  of  the  abdomen 
is  immediately  followed  by  reflex  contraction  of  the  abdominal  muscles.  The  supply  of  both 
muscles  and  skin  from  the  same  source  is  of  importance  in  protecting  the  abdominal  viscera 
from  injury.  A  blow  on  the  abdomen,  even  of  a  severe  character,  will  do  no  injury  to  the  viscera 
if  the  muscles  are  in  a  condition  of  firm  contraction;  whereas  in  cases  where  the  muscles  have 
been  taken  unawares,  and  the  blow  has  been  struck  while  they  were  in  a  state  of  rest,  an  injury 
insufficient  to  produce  any  lesion  of  the  abdominal  wall  has  been  attended  with  rupture  of  some 
of  the  abdominal  contents.  The  importance,  therefore,  of  immediate  reflex  contraction  upon 
the  receipt  of  an  injury  cannot  be  overestimated,  and  the  intimate  association  of  the  cutaneous 
and  muscular  fibres  in  the  same  nerve  produces  a  much  more  rapid  response  on  the  part  of  the 
muscles  to  any  peripheral  stimulation  of  the  cutaneous  filaments  than  would  be  the  case  if  the 
two  sets  of  fibres  were  derived  from  independent  sources. 

The  nerves  supplying  the  abdominal  muscles  and  skin,  derived  from  the  lower  intercostal 
nerves,  are  intimately  connected  with  the  sympathetic  supplying  the  abdominal  viscera  through 
the  lower  thoracic  ganglia  from  which  the  splanchnic  nerves  are  derived.  In  consequence  qf  this, 
in  laceration  of  the  abdominal  viscera  and  in  acute  peritonitis,  the  muscles  of  the  belly  wall 
become  firmly  contracted,  and  thus  as  far  as  possible  preserve  the  abdominal  contents  in  a 
condition  of  rest. 

I- 

The  Lumbosacral  Plexus  (Plexus  Lumbosacralis). 

The  anterior  divisions  of  the  lumbar,  sacral,  and  coccygeal  nerves  form  the 
lumbosacral  plexus,  the  first  lumbar  nerve  being  frequently  joined  by  a  branch 
from  the  twelfth  thoracic.  For  descriptive  purposes  this  plexus  is  usually  divided 
into  three  parts — the  lumbar,  sacral,  and  pudendal  plexuses. 

The  Lumbar  Nerves  (Nn.  Lumbales). 

The  anterior  divisions  of  the  lumbar  nerves  {rami  anteriores)  increase  in  size 
from  above  downward.  They  are  joined,  near  their  origins,  by  gray  rami  com- 
municantes  from  the  lumbar  ganglia  of  the  sympathetic  trunk.  These  rami  consist 
of  long,  slender  branches  which  accompany  the  lumbar  arteries  around  the  sides  of 
the  vertebral  bodies,  beneath  the  Psoas  major.  Their  arrangement  is  somewhat 
irregular:  one  ganglion  may  give  rami  to  two  lumbar  nerves,  or  one  lumbar  nerve 
may  receive  rami  from  two  ganglia.  The  first  and  second,  and  sometimes  the 
third  and  fourth  lumbar  nerves  are  each  connected  with  the  lumbar  part  of  the 
sympathetic  trunk  by  a  tvhite  ramus  communicans. 

The  nerves  pass  obliquely  outward  behind  the  Psoas  major,  or  between  its 
fasciculi,  distributing  filaments  to  it  and  the  Quadratus  lumborum.  The  first 
three  and  the  greater  part  of  the  fourth  are  connected  together  in  this  situation 
by  anastomotic  loops,  and  form  the  lumbar  plexus.    The  smaller  part  of  the  fourth 


THE  LUMBAR  NERVES 


975 


joins  with  the  fifth  to  form  the  lumbosacral  trunk,  which  assists  in  the  formation 
of  the  sacral  plexus.  The  fourth  nerve  is  named  the  nervus  furcalis,  from  the  fact 
that  it  is  subdivided  between  the  two  plexuses."^ 

The  Lumbar  Plexus  {plexus  lunihalis)  (Figs.  812,  813). — The  lumbar  plexus  is 
formed  by  the  loops  of  communication  between  the  anterior  divisions  of  the  first 
three  and  the  greater  part  of  the  fourth  lumbar  nerves;  the  first  lumbar  often 
receives  a  branch  from  the  last  thoracic  nerve.  It  is  situated  in  the  posterior  part 
of  the  Psoas  major,  in  front  of  the  transverse  processes  of  the  lumbar  vertebrae. 


— From  12th  thoracic 


—1st  lumbar 


Ilioinguinal 
Iliohypogastric 


Lat.  fe^noral  cutaneous 


To  Psoas  and 
Iliacus 


'2nd  lumbar 


3rd  lumbar 


4:th  lumbar 


oth  lumbar 


Femoral 
Accessory  obturator 

Obturator 


Luvibosacral  trunk 

Fig.  812. — Plan  of  lumbar  plexus. 


The  mode  in  which  the  plexus  is  arranged  varies  in  different  subjects.  It  differs 
from  the  brachial  plexus  in  not  forming  an  intricate  interlacement,  but  the  several 
nerves  of  distribution  arise  from  one  or  more  of  the  spinal  nerves,  in  the  following 
manner:  the  first  lumbar  nerve,  frequently  supplemented  by  a  twig  from  the  last 
thoracic,  splits  into  an  upper  and  lower  branch;  the  upper  and  larger  branch  divides 
into  the  iliohypogastric  and  ilioinguinal  nerves;  the  lower  and  smaller  branch 
unites  with  a  branch  of  the  second  lumbar  to  form  the  genitofemoral  nerve.  The 
remainder  of  the  second  nerve,  and  the  third  and  fourth  nerves,  divide  into  ventral 
and  dorsal  divisions.  The  ventral  division  of  the  second  unites  with  the  ventral 
divisions  of  the  third  and  fourth  nerves  to  form  the  obturator  nerve.  The  dorsal 
divisions  of  the  second  and  third  nerves  divide  into  two  branches,  a  smaller  branch 
from  each  uniting  to  form  the  lateral  femoral  cutaneous  nerve,  and  a  larger  branch 

]  In  most  cases  the  fourth  lumbar  is  the  nermis  furcalis;  but  this  arrangement  is  frequently  departed  from.  The 
third  is  occasionallj'^  the  lowest  nerve  which  enters  the  lumbar  plexus,  giving  at  the  same  time  some  fibres  to  the  sacral 
plexus,  and  thus  forming  the  nervus  furcalis;  or  both  the  third  and  fourth  may  be  f ureal  nerves.  When  this  occurs, 
the  plexus  is  termed  high  or  ■prefixed.  More  frequently  the  fifth  nerve  is  divided  between  the  lumbar  and  sacral  plexuses, 
and  constitutes  the  nervus  furcalis;  and  when  this  takes  place,  the  plexus  is  distinguished  as  a  low  or  postfixed  plexus. 
These  variations  necessarily  produce  corresponding  modifications  in  the  sacral  plexus. 


976 


NEUROLOGY 


from  each  joining  with  the  dorsal  di\'ision  of  the  fourth  ner\'e  to  form  the  femoral 
nerve.  The  accessory  obturator,  when  it  exists,  is  formed  by  the  union  of  two  small 
branches  given  off  from  the  third  and  fourth  nerves. 


Fig.  813. — The  lumbar  ple.xus  and  its  branches. 


The  branches  of  the  lumbar  plexus  may  therefore  be  arranged  as  follows: 


Iliohypogastric 
Ilioinguinal    . 
Genitofemoral 


Lateral  femoral  cutaneous 
Femoral. 


Obturator 
Accessorv  obturator 


1  L. 
1  L. 
1,2L. 

Dorsal  divisions. 
2,  3  L. 

2,  3,  4  L. 

Ventral  divisions. 
.       2,  3,  4  L. 

3,  4  L. 


The  Iliohypogastric  Nerve  (??.  iliohyixjgastricus)  arises  from  the  first  lumbar  nerve. 
It  emerges  from  the  upper  part  of  the  lateral  border  of  the  Psoas  major,  and  crosses 
obliquely  in  front  of  the  Quadratus  lumborum  to  the  iliac  crest.  It  then  perforates 
the  posterior  part  of  the  Transversus  abdominis,  near  the  crest  of  the  ilium,  and 


THE  LUMBAR  NERVES  977 

divides  between  that  muscle  and  the  ObHqims  interniis  abdominis  into  a  lateral 
and  an  anterior  cutaneous  branch. 

The  lateral  cutaneous  branch  (ramus  cutaneus  laieraUs;  iliac  braitch)  pierces  the 
Obhqui  interniis  and  externus  immediately  above  the  iliac  crest,  and  is  distributed 
to  the  skin  of  the  gluteal  region,  behind  the  lateral  cutaneous  branch  of  the  last 
thoracic  nerve  (Fig.  S19) ;  the  size  of  this  branch  bears  an  inverse  proportion  to  that 
of  the  lateral  cutaneous  branch  of  the  last  thoracic  nerve. 

The  anterior  cutaneous  branch  {ramus  cutaneus  anterior;  hypogastric  branch) 
(Fig.  814)  continues  onward  between  the  Obliquus  internus  and  Trans  versus.  It 
then  pierces  the  Obliquus  internus,  becomes  cutaneous  by  perforating  the  aponeu- 
rosis of  the  Obliquus  externus  about  2.5  cm.  above  the  subcutaneous  inguinal  ring, 
and  is  distributed  to  the  skin  of  the  hypogastric  region. 

The  iliohypogastric  nerve  communicates  with  the  last  thoracic  and  ilioinguinal 
nerves. 

The  Ilioinguinal  Nerve  (ji.  ilioinguinalis) ,  smaller  than  the  preceding,  arises  with 
it  from  the  first  lumbar  nerve.  It  emerges  from  the  lateral  border  of  the  Psoas 
major  just  below  the  iliohypogastric,  and,  passing  obliquely  across  the  Quadratus 
lumborum  and  Iliacus,  perforates  the  Transversus  abdominis,  near  the  anterior 
part  of  the  iliac  crest,  and  communicates  with  the  iliohypogastric  nerve  between  the 
Transversus  and  the  Obliquus  internus.  The  nerve  then  pierces  the  Obliquus 
internus,  distributing  filaments  to  it,  and,  accompanying  the  spermatic  cord  through 
the  subcutaneous  inguinal  ring,  is  distributed  to  the  skin  of  the  upper  and  medial 
part  of  the  thigh,  to  the  skin  over  the  root  of  the  penis  and  upper  part  of  the  scrotum 
in  the  male,  and  to  the  skin  covering  the  mons  pubis  and  labium  majus  in  the  female. 
The  size  of  this  nerve  is  in  inverse  proportion  to  that  of  the  iliohypogastric.  Occa- 
sionall}^  it  is  very  small,  and  ends  by  joining  the  iliohypogastric;  in  such  cases,  a 
branch  from  the  iliohypogastric  takes  the  place  of  the  ilioinguinal,  or  the  latter 
nerve  may  be  altogether  absent. 

The  Genitofemoral  Nerve  {n.  genitofevioralis;  genitocrural  nerve)  arises  from  the 
first  and  second  lumbar  nerves.  It  passes  obliquely  through  the  substance  of  the 
Psoas  major,  and  emerges  from  its  medial  border,  close  to  the  vertebral  column, 
opposite  the  fibrocartilage  between  the  third  and  fourth  lumbar  vertebrae;  it 
then  descends  on  the  surface  of  the  Psoas  major,  under  cover  of  the  peritoneum, 
and  divides  into  the  external  spermatic  and  lumboinguinal  nerves.  Occasionally 
these  two  nerves  emerge  separatelj^  through  the  substance  of  the  Psoas. 

The  external  spermatic  nerve  (n.  spermaticus  externus;  genital  branch  of  genito- 
femoral) passes  outward  on  the  Psoas  major,  and  pierces  the  fascia  transversalis,  or 
passes  through  the  abdominal  inguinal  ring;  it  then  descends  behind  the  spermatic 
cord  to  the  scrotum,  supplies  the  Cremaster,  and  gives  a  few  filaments  to  the  skin 
of  the  scrotum.  In  the  female,  it  accompanies  the  round  ligament  of  the  uterus, 
and  is  lost  upon  it. 

The  lumboinguinal  nerve  [n.  lumboinguinalis ;  femoral  or  crural  branch  of  genito- 
femoral) descends  on  the  external  iliac  artery,  sending  a  few  filaments  around  it, 
and,  passing  beneath  the  inguinal  ligament,  enters  the  sheath  of  the  femoral  vessels, 
lying  superficial  and  lateral  to  the  femoral  artery.  It  pierces  the  anterior  layer  of 
the  sheath  of  the  vessels  and  the  fascia  lata,  and  supplies  the  skin  of  the  anterior 
surface  of  the  upper  part  of  the  thigh  (Fig.  814).  On  the  front  of  the  thigh  it 
communicates  with  the  anterior  cutaneous  branches  of  the  femoral  nerve.  A. 
few  filaments  from  the  lumboinguinal  nerve  may  be  traced  to  the  femoral 
artery. 

The  Lateral  Femoral  Cutaneous  Nerve  (?r.  cutaneus  femoralis  lateralis;  external 

cutaneous  nerve)  arises  from  the  dorsal  divisions  of  the  second  and  third  lumbar 

nerves.    It  emerges  from  the  lateral  border  of  the  Psoas  major  about  its  middle, 

and  crosses  the  Iliacus  obliquely,  toward  the  anterior  superior  iliac  spine.    It  then 

62 


978 


NEUROLOGY 


passes  under  the  inguinal  ligament  and  over  the  Sartorius  muscle  into  the  thigh, 
where  it  divides  into  two  branches,  an  anterior  and  a  posterior  (Fig.  814). 


Sural- 


Deep  fcronceal 


Fig.  814. — Cutaneous  nerves  of  right  lower  extremity. 
Front  view. 


Fig.  815. — Diagram  of  segmental  distribution  of 
the  cutaneous  nerves  of  the  right  lower  extremity. 
Front  view. 


THE  LUMBAR  NERVES 


979 


The  anterior  branch  becomes  superficiiil  al)out  10  cm.  below  the  inguinal  ligament, 
and  divides  into  branches  which  are  distributed  to  the  skin  of  the  anterior  and 
lateral  parts  of  the  thigh,  as  far  ,   ,     , 

*  "  Laleral 

femoral 
culuiicuus 


as  the  knee.  The  terminal  fila- 
ments of  this  nerve  frequently 
communicate  with  the  anterior 
cutaneous  branches  of  the  femoral 
nerve,  and  with  the  infrapatellar 
branch  of  the  saphenous  nerve, 
forming  with  them  the  patellar 
plexus. 

The  posterior  branch  pierces  the 
fascia  lata,  and  subdivides  into 
filaments  which  pass  backward 
across  the  lateral  and  posterior 
surfaces  of  the  thigh,  supplying 
the  skin  from  the  level  of  the 
greater  trochanter  to  the  middle 
of  the  thigh. 

The  Obturator  Nerve  (?i.  obtura- 
torius)  arises  from  the  ventral 
divisions  of  the  second,  third, 
and  fourth  lumbar  nerves;  the 
branch  from  the  third  is  the 
largest,  while  that  from  the  sec- 
ond is  often  very  small.  It  de- 
scends through  the  fibres  of  the 
Psoas  major,  and  emerges  from 
its  medial  border  near  the  brim  of 
the  pelvis;  it  then  passes  behind 
the  common  iliac  vessels,  and  on 
the  lateral  side  of  the  hypogastric 
vessels  and  ureter,  which  separate 
it  from  the  ureter,  and  runs  along 
the  lateral  wall  of  the 'lesser  pel- 
vis, above  and  in  front  of  the 
obturator  vessels,  to  the  upper 
part  of  the  obturator  foramen. 
Here  it  enters  the  thigh,  and 
divides  into  an  anterior  and  a 
posterior  branch,  which  are  sepa- 
rated at  first  by  some  of  the 
fibres  of  the  Obturator  externus, 
and  lower  down  by  the  Adductor 
brevis. 

The  anterior  branch  (ramus 
anterior)  (Fig.  816)  leaves  the 
pelvis  in  front  of  the  Obturator 
externus  and  descends  in  front  of 
the  Adductor  brevis,  and  behind 
the  Pectineus  and  Adductor 
longus;  at  the  lower  border  of 
the  latter  muscle  it  communi- 
cates with  the  anterior  cutaneous 


Iliacui) 
rcmoiul 


Psoas  major 


A  nterior  d  ivis  ion 
of  obturator 

Med.  hr.  of  ant. 
cutaneou-s 


Saphenous 


Fig.  816. — Nerves  of  the  right  lower  extremity.     Front  view. 


980  NEUROLOGY 

and  saphenous  branches  of  the  femoral  nerve,  forming  a  kind  of  plexus.  It 
then  descends  upon  the  femoral  artery,  to  which  it  is  finally  distributed.  Near 
the  obturator  foramen  the  nerve  gives  off  an  articular  branch  to  the  hip-joint. 
Behind  the  Pectineus,  it  distributes  branches  to  the  Adductor  longus  and  Gracilis, 
and  usually  to  the  Adductor  brevis,  and  in  rare  cases  to  the  Pectineus;  it  receives 
a  communicating  branch  from  the  accessory  obturator  nerve  when  that  nerve  is 
present. 

Occasionally  the  communicating  branch  to  the  anterior  cutaneous  and  saphenous 
branches  of  the  femoral  is  continued  down,  as  a  cutaneous  branch,  to  the  thigh 
and  leg.  When  this  is  so,  it  emerges  from  beneath  the  lower  border  of  the  Adductor 
longus,  descends  along  the  posterior  margin  of  the  Sartorius  to  the  medial  side  of 
the  knee,  where  it  pierces  the  deep  fascia,  communicates  with  the  saphenous  nerve, 
and  is  distributed  to  the  skin  of  the  tibial  side  of  the  leg  as  low  down  as  its  middle. 

The  posterior  branch  (rarmis  posterior)  pierces  the  anterior  part  of  the  Obturator 
externus,  and  supplies  this  muscle;  it  then  passes  behind  the  Adductor  brevis  on 
the  front  of  the  Adductor  magnus,  where  it  divides  into  numerous  muscular 
branches  which  are  distributed  to  the  Adductor  magnus  and  the  Adductor  brevis 
when  the  latter  does  not  receive  a  branch  from  the  anterior  division  of  the  nerve. 
It  usually  gives  off  an  articular  filament  to  the  knee-joint. 

The  articular  branch  for  the  knee-joint  is  sometimes  absent;  it  either  perforates 
the  lower  part  of  the  Adductor  magnus,  or  passes  through  the  opening  which  trans- 
mits the  femoral  artery,  and  enters  the  popliteal  fossa;  it  then  descends  upon  the 
popliteal  artery,  as  far  as  the  back  part  of  the  knee-joint,  where  it  perforates  the 
oblique  popliteal. ligament,  and  is  distributed  to  the  synovial  membrane.  It  gives 
filaments  to  the  popliteal  artery. 

The  Accessory  Obturator  Nerve  {n.  ohturatoriiis  accessorius)  (Fig.  813)  is  present 
in  about  29  per  cent,  of  cases.  It  is  of  small  size,  and  arises  from  the  ventral  divi- 
sions of  the  third  and  fourth  lumbar  nerves.  It  descends  along  the  medial  border 
of  the  Psoas  major,  crosses  the  superior  ramus  of  the  pubis,  and  passes  under  the 
Pectineus,  where  it  divides  into  numerous  branches.  One  of  these  supplies  the 
Pectineus,  penetrating  its  deep  surface,  another  is  distributed  to  the  hip-joint; 
while  a  third  communicates  with  the  anterior  branch  of  the  obturator  nerve. 
Occasionally  the  accessory  obturator  nerve  is  very  small  and  is  lost  in  the  capsule 
of  the  hip-joint.  When  it  is  absent,  the  hip-joint  receives  two  branches  from  the 
obturator  nerve. 

The  Femoral  Nerve  {n.  femoralis;  anterior  crural  nerve)  (Fig.  816),  the  largest 
branch  of  the  lumbar  plexus,  arises  from  the  dorsal  divisions  of  the  second,  third, 
and  fourth  lumbar  nerves.  It  descends  through  the  fibres  of  the  Psoas  major, 
emerging  from  the  muscle  at  the  lower  part  of  its  lateral  border,  and  passes  down 
between  it  and  the  Iliacus,  behind  the  iliac  fascia;  it  then  runs  beneath  the  inguinal 
ligament,  into  the  thigh,  and  splits  into  an  anterior  and  a  posterior  division.  Under 
the  inguinal  ligament,  it  is  separated  from  the  femoral  artery  by  a  portion  of  the 
Psoas  major. 

Within  the  abdomen  the  femoral  nerve  gives  off  small  branches  to  the  Iliacus, 
and  a  branch  which  is  distributed  upon  the  upper  part  of  the  femoral  artery;  the 
latter  branch  may  arise  in  the  thigh. 

In  the  thigh  the  anterior  division  of  the  femoral  nerve  gives  off  anterior  cuta- 
neous and  muscular  branches.  The  anterior  cutaneous  branches  comprise  the 
intermediate  and  medial  cutaneous  nerves  (Fig.  814). 

The  intermediate  cutaneous  nerve  (ramus  cutaneus  anterior:  middle  cutaneous 
nerve)  pierces  the  fascia  lata  (and  generally  the  Sartorius)  about  7.5  cm.  below^ 
the  inguinal  ligament,  and  divides  into  two  branches  which  descend  in  immediate 
proximity  along  the  forepart  of  the  thigh,  to  supply  the  skin  as  low^  as  the  front 
of  the  knee.     Here  they  communicate  with  the  medial  cutaneous  nerve  and  the 


THE  LUMBAR  XERVES  981 

infrapatellar  branch  of  the  saphenous,  to  form  the  patellar  plexus.  In  the  upper 
part  of  the  thigh  the  lateral  branch  of  the  intermediate  cutaneous  communicates 
with  the  lumboinguinal  branch  of  the  genitofemoral  nerve. 

The  medial  cutaneous  nerve  (ramus  cutaneus  anterior;  internal  cutaneous  nerve) 
passes  obliquely  across  the  upper  part  of  the  sheath  of  the  femoral  artery,  and  divides 
in  front,  or  at  the  nunlial  side  of  that^ vessel,  into  two  branches,  an  anterior  and  a 
posterior.  The  anterior  branch  runs  downward  on  the  Sartorius,  perforates  the 
fascia  lata  at  the  lower  third  of  the  thigh,  and  divides  into  two  branches:  one 
supplies  the  integument  as  low  down  as  the  medial  side  of  the  knee;  the  other 
crosses  to  the  lateral  side  of  the  patella,  communicating  in  its  course  with  the  infra-^ 
patellar  branch  of  the  saphenous  nerve.  The  posterior  branch  descends  along  the 
medial  border  of  the  Sartorius  muscle  to  the  knee,  where  it  pierces  the  fascia  lata, 
communicates  with  the  saphenous  nerve,  and  gives  off  several  cutaneous  branches. 
It  then  passes  down  to  supply  the  integument  of  the  medial  side  of  the  leg.  Beneath 
the  fascia  lata,  at  the  lower  border  of  the  Adductor  longus,  it  joins  to  form  a  plexi- 
form  net-work  (subsartorial  plexus)  with  branches  of  the  saphenous  and^obturator 
nerves.  ^Mien  the  communicating  branch  from  the  obturator  nerve  is  large  and 
continued  to  the  integument  of  the  leg,  the  posterior  branch  of  the  medial  cutaneous 
is  small,  and  terminates  in  the  plexus,  occasionally  giving  off  a  few  cutaneous 
filaments.  The  medial  cutaneous  nerve,  before  dividing,  gives  off  a  few  filaments, 
which  pierce  the  fascia  lata,  to  supply  the  integument  of  the  medial  side  of  the 
thigh,  accompanying  the  long  saphenous  vein.  One  of  these  filaments  passes 
through  the  saphenous  opening;  a  second  becomes  subcutaneous  about  the  middle 
of  the  thigh;  a  third  pierces  the  fascia  at  its  lower  third. 

MuscuL-iE  Bran'CHES  (rami  musculares). — Tlie  nerve  to  the  Pectineus  arises 
immediately  below  the  inguinal  ligament,  and  passes  behind  the  femoral  sheath  to 
enter  the  anterior  surface  of  the  muscle;  it  is  often  duplicated.  The  nerve  to  the 
Sartorius  arises  in  common  with  the  intermediate  cutaneous. 

The  posterior  division  of  the  femoral  nerve  gives  oft'  the  saphenous  nerve,  and 
muscular  and  articular  branches. 

The  Saphenous  Nerve  (n.  sapherius;  long  or  internal  saphenous  nerve)  (Fig.  816) 
is  the  largest  cutaneous  branch  of  the  femoral  nerve.  It  approaches  the  femoral 
artery  where  this  vessel  passes  beneath  the  Sartorius,  and  lies  in  front  of  it,  behind 
the  aponeurotic  covering  of  the  adductor  canal,  as  far  as  the  opening  in  the  lower 
part  of  the  Adductor  magnus.  Here  it  quits  the  artery,  and  emerges  from  behind 
the  lower  edge  of  the  aponeurotic  covering  of  the  canal;  it  descends  vertically 
along  the  medial  side  of  the  knee  behind  the  Sartorius,  pierces  the  fascia  lata, 
between  the  tendons  of  the  Sartorius  and  Gracilis,  and  becomes  subcutaneous. 
The  nerve  then  passes  along  the  tibial  side  of  the  leg,  accompanied  by  the  great 
saphenous  vein,  descends  behind  the  medial  border  of  the  tibia,  and,  at  the  lower 
third  of  the  leg,  divides  into  two  branches:  one  continues  its  course  along  the  margin 
of  the  tibia,  and  ends  at  the  ankle;  the  other  passes  in  front  of  the  ankle,  and  is 
distributed  to  the  skin  on  the  medial  side  of  the  foot,  as  far  as  the  ball  of  the  great 
toe,  com^municating  with  the  medial  branch  of  the  superficial  peroneal  nerve. 

Bk^xches. — The  saphenous  nerve,  about  the  middle  of  the  thigh,  gives  oft'  a 
branch  which  joins  the  subsartorial  plexus. 

At  the  medial  side  of  the  knee  it  gives  oft'  a  large  infrapatellar  branch,  which 
pierces  the  Sartorius  and  fascia  lata,  and  is  distributed  to  the  skin  in  front  of  the 
patella.  This  nerve  communicates  above  the  knee  with  the  anterior  cutaneous 
branches  of  the  femoral  nerve;  below  the  knee,  with  other  branches  of  the  saphenous; 
and,  on  the  lateral  side  of  the  joint,  with  branches  of  the  lateral  femoral  cutaneous 
nerve,  forming  a  plexiform  net-work,  the  plexus  patellae.  The  infrapatellar  branch 
is  occasionally  small,  and  ends  by  joining  the  anterior  cutaneous  branches  of  the 
femoral,  which  supply  its  place  in  front  of  the  knee. 


982  NEUROLOGY 

Below  the  knee,  the  branches  of  the  saphenous  nerve  are  distributed  to  the  skin 
of  the  front  and  medial  side  of  the  leg,  communicating  with  the  cutaneous  branches 
of  the  femoral,  or  with  filaments  from  the  obturator  nerve. 

The  muscular  branches  supply  the  four  parts  of  the  Quadriceps  femoris.  The 
branch  to  the  Rectus  femoris  enters  the  upper  part  of  the  deep  surface  of  the  muscle, 
and  supplies  a  filament  to  the  hip-joint.  The  branch  to  the  Vastus  lateralis,  of 
large  size,  accompanies  the  descending  branch  of  the  lateral  femoral  circumflex 
artery  to  the  lower  part  of  the  muscle.  It  gives  off  an  articular  filament  to  the 
knee-joint.  The  branch  to  the  Vastus  medialis  descends  lateral  to  the  femoral 
vessels  in  company  with  the  saphenous  nerve.  It  enters  the  muscle  about  its  middle, 
and  gives  oft'  a  filament,  which  can  usually  be  traced  downward,  on  the  surface  of 
the  muscle,  to  the  knee-joint.  The  branches  to  the  Vastus  intermedins,  two  or 
three  in  number,  enter  the  anterior  surface  of  the  muscle  about  the  middle  of  the 
thigh;  a  filament  from  one  of  these  descends  through  the  muscle  to  the  Articularis 
genu  and  the  knee-joint.  The  articular  branch  to  the  hip-joint  is  derived  from  the 
nerve  to  the  Rectus  femoris. 

The  articular  branches  to  the  knee-joint  are  three  in  number.  One,  a  long  slender 
filament,  is  derived  from  the  nerve  to  the  Vastus  lateralis;  it  penetrates  the  capsule 
of  the  joint  on  its  anterior  aspect.  Another,  derived  from  the  nerve  to  the  Vastus 
medialis,  can  usually  be  traced  downward  on  the  surface  of  this  muscle  to  near  the 
joint ;  it  then  penetrates  the  muscular  fibres,  and  accompanies  the  articular  branch 
of  the  highest  genicular  artery,  pierces  the  medial  side  of  the  articular  capsule, 
and  supplies  the  synovial  membrane.  The  third  branch  is  derived  from  the  nerve 
to  the  Vastus  intermedins. 

The  Sacral  and  Coccygeal  Nerves  (Nn.  Sacrales  et  Coccygeus). 

The  anterior  divisions  of  the  sacral  and  coccygeal  nerves  {rami  anteriores)  form 
the  sacral  and  pudendal  plexuses.  The  anterior  divisions  of  the  upper  four  sacral 
nerves  enter  the  pelvis  through  the  anterior  sacral  foramina,  that  of  the  fifth 
between  the  sacrum  and  coccyx,  while  that  of  the  coccygeal  nerve  curves  forward 
below  the  rudimentary  transverse  process  of  the  first  piece  of  the  coccyx.  The 
first  and  second  sacral  nerves  are  large;  the  third,  fourth,  and  fifth  diminish  pro- 
gressively from  above  downward.  Each  receives  a  gray  ramus  communicans 
from  the  corresponding  ganglion  of  the  sympathetic  trunk,  while  from  the  third, 
and  frequently  from  the  second  and  the  fourth  sacral  nerves,  a  white  ramus  com- 
municans is  given  to  the  pelvic  plexuses  of  the  sympathetic. 

The  Sacral  Plexus  {plexus  sacralis)  (Fig.  817). — The  sacral  plexus  is  formed  by 
the  lumbosacral  trunk,  the  anterior  division  of  the  first,  and  portions  of  the  anterior 
divisions  of  the  second  and  third  sacral  nerves. 

The  lumbosacral  trunk  comprises  the  whole  of  the  anterior  division  of  the  fifth 
and  a  part  of  that  of  the  fourth  lumbar  nerve;  it  appears  at  the  medial  margin  of 
the  Psoas  major  and  runs  downward  over  the  pelvic  brim  to  join  the  first  sacral 
nerve.  The  anterior  division  of  the  third  sacral  nerve  divides  into  an  upper  and  a 
lower  branch,  the  former  entering  the  sacral  and  the  latter  the  pudendal  plexus. 

The  nerves  forming  the  sacral  plexus  converge  toward  the  lower  part  of  the  greater 
sciatic  foramen,  and  unite  to  form  a  flattened  band,  from  the  anterior  and  posterior 
surfaces  of  w^hich  several  branches  arise.  The  band  itself  is  continued  as  the  sciatic 
nerve,  which  splits  on  the  back  of  the  thigh  into  the  tibial  and  common  peroneal 
nerves;  these  two  nerves  sometimes  arise  separatel}'^  from  the  plexus,  and  in  all 
cases  their  independence  can  be  shown  by  dissection. 

Relations. — The  sacral  plexus  lies  on  the  back  of  the  pelvis  between  the  Piriformis  and  the 
pelvic  fascia  (Fig.  818);  in  front  of  it  are  the  hypogastric  vessels,  the  ureter  and  the  sigmoid  colon. 
The  superior  gluteal  vessels  run  between  the  lumbosacral  trunk  and  the  first  sacral  nerve,  and  the 
inferior  gluteal  vessels  between  the  second  and  third  sacral  nerves. 

All  the  nerves  entering  the  plexus,  with  the  exception  of  the  third  sacral,  split  into  ventral 
and  dorsal  divisions,  and  the  nerves  arising  from  these  are  as  foUows: 


THE  SACRAL  AND  COCCYGEAL  NERVES 


983 


Ventral  divisions. 


Nerve  to  Quadratus  femoris 
and  Gemellus  inferior 

Nerve  to  Obturator  internus 
and  Gemellus  superior 

Nerve  to  Piriformis 

Superior  gluteal 

Inferior  gluteal 

Posterior  femoral  cutaneous 
f  Tibial 


|4,  5L,  1  S. 

I 


i 


5L,  1,2S. 


Sciatic 


2,  3  S     . 

4,  5  L,  1,  2,  3  S. 


\  Common  peroneal 


Superior  gluteal 

Inferior  gluteal 
To  Piriformis 


Sciatic 


J 


Coynmon 
Xieroneat 


Dorsal  divisions. 


(1)  2  S. 
4,  5  L,  1  S. 
5  L,  1,  2  S. 
1,  2  S. 

4,  5  L,  1,  2  S. 

'ah  Lumbar 


To  Quadratus  femoris  and 
Inferior  gemellus 
To  Obturator  internus  and  ■ 
Superior  gemellus 

Post.  fern,  cutaneous ' 
Perforating  cutaneous' 

Pudendal ; 

To  Levator  ani,  Coccygeus  audi 
Sphincter  ani  externus 

Fig.   817. — Plan  of  sacral  and  pudendal  plexuses. 


olh  Lumbar 


\st  Sacral 


Coccygeal 


984 


NEUROLOGY 


The  Nerve  to  the  Quadratus  Femoris  and  Gemellus  Inferior  arises  from  the  ventral 
divisions  of  the  fourth  and  fifth  knnbar  and  first  sacral  nerves:  it  leaves  the  pelvis 
through  the  greater  sciatic  foramen,  below  the  Piriformis,  and  runs  down  in  front  of 
the  sciatic  nerve,  the  Gemelli,  and  the  tendon  of  tlie  Obturator  internus,  and  enters 
the  anterior  surfaces  of  the  muscles;  it  gives  an  articular  branch  to  the  hip-joint. 

The  Nerve  to  the  Obturator  Internus  and  Gemellus  Superior  arises  from  the  ventral 
divisions  of  the  fifth  lumbar  and  first  and  second  sacral  nerves.  It  leaves  the  pelvis 
through  the  greater  sciatic  foramen  below  the  Piriformis,  and  gives  off  the  branch 
to  the  Gemellus  superior,  which  enters  the  upper  part  of  the  posterior  surface  of 
the  muscle.  It  then  crosses  the  ischial  spine,  reenters  the  pelvis  through  the 
lesser  sciatic  foramen,  and  pierces  the  pelvic  surface  of  the  Obturator  internus. 


flortq^ 


Sympathetic 
trunk 


Fig.  818. — Dissection  of  side  wall  of  pelvis  showing  sacral  and  pudendal  plexuses. 

The  Nerve  to  the  Piriformis  arises  from  the  dorsal  division  of  the  second  sacral 
nerve,  or  the  dorsal  divisions  of  the  first  and  second  sacral  nerves,  and  enters 
the  anterior  surface  of  the  muscle;  this  nerve  may  be  double. 

The  Superior  Gluteal  Nerve  {ji.  ghdaetis  superior)  arises  from  the  dorsal  divisions 
of  the  fourth  and  fifth  lumbar  and  first  sacral  nerves:  it  leaves  the  pelvis  through 
the  greater  sciatic  foramen  above  the  Piriformis,  accompanied  by  the  superior 
gluteal  vessels,  and  divides  into  a  superior  and  an  inferior  branch.  The  superior 
branch  accompanies  the  upper  branch  of  the  deep  division  of  the  superior  gluteal 
artery  and  ends  in  the  Glutaeus  minimus.  The  inferior  branch  runs  with  the  lower 
branch  of  the  deep  division  of  the  superior  gluteal  artery  across  the  Glutaeus 


THE  SACRAL  AND  COCCYGEAL  NERVES  .    985 

minimus;  it  gives  filaments  to  the  Glutaei  medius  and  minimus,  and  ends  in  the 
Tensor  fasciae  latae. 

The  Inferior  Gluteal  Nerve  (n.  glidaeus  inferior)  arises  from  the  dorsal  divisions 
of  the  fifth  luml)ar  and  first  and  second  sacral  nerves:  it  leaves  the  pelvis  through 
the  greater  sciatic  foramen,  below  the  Piriformis,  and  divides  into  branches  which 
enter  the  deep  surface  of  the  Glutaeus  maximus. 

The  Posterior  Femoral  Cutaneous  Nerve  (n.  cutaneus  femoralis  posterior;  small 
sciatic  nerve)  is  distributed  to  the  skin  of  the  perineum  and  posterior  surface  of 
the  thigh  and  leg.  It  arises  partly  from  the  dorsal  divisions  of  the  first  and  second, 
and  from  the  ventral  divisions  of  the  second  and  third  sacral  nerves,  and  issues  from 
the  pelvis  through  the  greater  sciatic  foramen  below  the  Piriformis.  It  then  descends 
beneath  the  Glutaeus  maximus  with  the  inferior  gluteal  artery,  and  runs  down  the 
back  of  the  thigh  beneath  the  fascia  lata,  and  over  the  long  head  of  the  Biceps 
femoris  to  the  back  of  the  knee;  here  it  pierces  the  deep  fascia  and  accompanies 
the  small  saphenous  vein  to  about  the  middle  of  the  back  of  the  leg,  its  terminal 
twigs  communicating  with  the  sural  nerve. 

Its  branches  are  all  cutaneous,  and  are  distributed  to  the  gluteal  region,  the  peri- 
neum, and  the  back  of  the  thigh  and  leg. 

The  gluteal  branches  {mi.  chmium  infer  lores) ,  three  or  four  in  number,  turn  upward 
around  the  lower  border  of  the  Glutaeus  maximus,  and  supply  the  skin  covering 
the  lower  and  lateral  part  of  that  muscle. 

The  perineal  branches  (rami  yerineales)  are  distributed  to  the  skin  at  the  upper 
and  medial  side  of  the  thigh.  One  long  perineal  branch,  inferior  pudendal  {long 
scrotal  nerve) ,  curves  forward  below  and  in  front  of  the  ischial  tuberosity,  pierces 
the  fascia  lata,  and  runs  forward  beneath  the  superficial  fascia  of  the  perineum  to 
the  skin  of  the  scrotum  in  the  male,  and  of  the  labium  majus  in  the  female.  It 
communicates  with  the  inferior  hemorrhoidal  and  posterior  scrotal  nerves. 

The  branches  to  the  back  of  the  thigh  and  leg  consist  of  numerous  filaments  derived 
from  both  sides  of  the  nerve,  and  distributed  to  the  skin  covering  the  back  and 
medial  side  of  the  thigh,  the  popliteal  fossa,  and  the  upper  part  of  the  back  of  the 
leg  (Fig.  819). ■ 

The  Sciatic  {n.  ischiadicus;  great  sciatic  nerve)  (Fig.  821)  supplies  nearly  the  whole 
of  the  skin  of  the  leg,  the  muscles  of  the  back  of  the  thigh,  and  those  of  the  leg 
and  foot.  It  is  the  largest  nerve  in  the  body,  measuring  2  cm.  in  breadth,  and  is 
the  continuation  of  the  flattened  band  of  the  sacral  plexus.  It  passes  out  of  the 
pelvis  through  the  greater  sciatic  foramen,  below  the  Piriformis  muscle.  It  descends 
between  the  greater  trochanter  of  the  femur  and  the  tuberosity  of  the  ischium,  and 
along  the  back  of  the  thigh  to  about  its  lower  third,  where  it  divides  into  two  large 
branches,  the  tibial  and  common  peroneal  nerves.  This  division  may  take  place 
at  any  point  between  the  sacral  plexus  and  the  lower  third  of  the  thigh.  When  it 
occurs  at  the  plexus,  the  common  peroneal  nerve  usually  pierces  the  Piriformis. 

In  the  upper  part  of  its  course  the  nerve  rests  upon  the  posterior  surface  of  the 
ischium,  the  nerve  to  the  Quadratus  femoris,  the  Obturator  internus  and  Gemelli, 
and  the  Quadratus  femoris;  it  is  accompanied  by  the  posterior  femoral  cutaneous 
nerve  and  the  inferior  gluteal  artery,  and  is  covered  by  the  Glutaeus  maximus. 
Lower  down,  it  lies  upon  the  Adductor  magnus,  and  is  crossed  obliquely  by  the 
long  head  of  the  Biceps  femoris. 

The  nerve  gives  off  articular  and  muscular  branches. 

The  articular  branches  (rami  articulares)  arise  from  the  upper  part  of  the  nerve 
and  supply  the  hip-joint,  perforating  the  posterior  part  of  its  capsule;  they  are 
sometimes  derived  from  the  sacral  plexus. 

The  muscular  branches  (rami  musculares)  are  distributed  to  the  Biceps  femoris, 
Semitendinosus,  Semimembranosus,  and  iVdductor  magnus.  The  nerve  to  the  short 
head  of  the  Biceps  femoris  comes  from  the  common  peroneal  part  of  the  sciatic, 


986 


NEUROLOGY 


while  the  other  muscuhir  branches  arise  from  the  tibial  portion,  as  may  be  seen  in 
those  cases  where  there  is  a  high  division  of  the  sciatic  nerve. 


\ 


Fig.  819. — Cutaneous  nerves  of  right  lower 
extremity.     Posterior  view. 


Fig.  820. — Diagram  of  the  segmental  distribution  of  the 
cutaneous  nerves  of  the  right  lower  extremity.  Posterior 
view. 


THE  SACRAL  AND  COCCYGEAL  NERVES 


987 


Tlu>  Tibial  Nerve  {n.  tibialis:  inicrnal 
popliteal  iicnr)  (Fig.  S21)  the  larger  of 
the  two  terminal  branches  of  the  sci- 
atic, arises  from  the  anterior  branches 
of  the  fourth  and  fifth  lumbar  and 
first,  second,  and  third  sacral  nerves. 
It  descends  along  the  back  of  the  thigh 
and  through  the  middle  of  the  poj)liteal 
fossa,  to  the  lower  part  of  the  Popliteus 
muscle,  where  it  passes  with  the  pop- 
liteal artery  beneath  the  arch  of  the 
Soleus.  It  then  runs  along  the  back 
of  the  leg  with  the  posterior  tibial 
vessels  to  the  interval  between  the 
medial  malleolus  and  the  heel,  where 
it  divides  beneath  the  laciniate  liga- 
ment into  the  medial  and  lateral 
plantar  nerves.  In  the  thigh  it  is 
overlapped  by  the  hamstring  muscles 
above,  and  then  becomes  more  super- 
ficial, and  lies  lateral  to,  and  some 
distance  from,  the  popliteal  vessels; 
opposite  the  knee-joint,  it  is  in  close 
relation  with  these  vessels,  and  crosses 
to  the  medial  side  of  the  artery.  In  the 
leg  it  is  covered  in  the  upper  part  of 
its  course  by  the  muscles  of  the  calf; 
lower  down  by  the  skin,  the  superficial 
and  deep  fasciae.  It  is  placed  on  the 
deep  muscles,  and  lies  at  first  to  the 
medial  side  of  the  posterior  tibial 
artery,  but  soon  crosses  that  vessel  and 
descends  on  its  lateral  side  as  far  as 
the  ankle.  In  the  lower  third  of  the 
leg  it  runs  parallel  with  the  medial 
margin  of  the  tendo  calcaneus. 

The  branches  of  this  nerve  are :  artic- 
ular, muscular,  medial  sural  cutaneous, 
medial  calcaneal,  medial  and  lateral 
plantar. 

Articular  branches  (rami  articulares) , 
usually  three  in  number,  supply  the 
knee-joint;  two  of  these  accompany 
the  superior  and  inferior  medial  genic- 
ular arteries;  and  a  third,  the  middle 
genicular  artery.  Just  above  the  bi- 
furcation of  the  nerve  an  articular 
branch  is  given  off  to  the  ankle-joint. 

Muscular  branches  {rami  musculares) , 
four  or  five  in  number,  arise  from  the 
nerve  as  it  lies  between  the  two  heads 
of   the   Gastrocnemius   muscle;    thev 


Superior 
gluteal 

Pudendal 

Kervp  to 
obturator  interims 

Po^t.  fern. ^ 

cutaneous 
Perineal 
branch 


Medial 
calcaneal 


Fig.  821. 


-Nerves  of  the  right  lower  extremity.' 
Posterior  view. 


1  N.  B. — In  this  diagram  the  medial  sural    cutaneous  and  peroneal  anastomotic  are  not  in  their  normal  position. 
They  have  been  displaced  by  the  removal  of  the  superficial  muscles. 


988  NEUROLOGY 

supply  that  muscle,  and  the  Plantaris,  Soleus,  and  Popliteus.  The  branch  for  the 
Popliteus  turns  around  the  lower  border  and  is  distributed  to  the  deep  surface  of  the 
muscle.  Lower  down,  muscular  branches  arise  separately  or  by  a  common  trunk  and 
supply  the  Soleus,  Tibialis  posterior.  Flexor  digitorum  longus,  and  Flexor  hallucis 
longus;  the  branch  to  the  last  muscle  accompanies  the  peroneal  artery;  that  to  the 
Soleus  enters  the  deep  surface  of  the  muscle. 

The  medial  sural  cutaneous  nerve  (71.  cutaneus  surae  medialis;  n.  communicans 
tibialis)  descends  bet^veen  the  two  heads  of  the  Gastrocnemius,  and,  about  the 
middle  of  the  back  of  the  leg,  pierces  the  deep  fascia,  and  unites  with  the  anasto- 
motic ramus  of  the  common  peroneal  to  form  the  sural  nerve  (Fig.  819). 

The  sural  nerve  {n.  suralis;  short  saphenous  nerve),  formed  by  the  junction  of  the 
medial  sural  cutaneous  with  the  peroneal  anastomotic  branch,  passes  downward 
near  the  lateral  margin  of  the  tendo  calcaneus,  lying  close  to  the  small  saphenous 
vein,  to  the  interval  between  the  lateral  malleolus  and  the  calcaneus.  It  runs 
forward  below  the  lateral  malleolus,  and  is  continued  as  the  lateral  dorsal  cutaneous 
nerve  along  the  lateral  side  of  the  foot  and  little  toe,  communicating  on  the  dorsum 
of  the  foot  with  the  intermediate  dorsal  cutaneous  nerve,  a  branch  of  the  superficial 
peroneal.  In  the  leg,  its  branches  communicate  with  those  of  the  posterior  femoral 
cutaneous. 

The  medial  calcaneal  branches  {rami  calcanei  mediales;  internal  calcaneal  branches) 
perforate  the  laciniate  ligament,  and  supply  the  skin  of  the  heel  and  medial  side 
of  the  sole  of  the  foot. 

The  medial  plantar  nerve  (?i.  plantaris  medialis;  internal  plantar  nerve)  (Fig.  822), 
the  larger  of  the  two  terminal  divisions  of  the  tibial  nerve,  accompanies  the  medial 
plantar  artery.  From  its  origin  under  the  laciniate  ligament  it  passes  under  cover 
of  the  Abductor  hallucis,  and,  appearing  between  this  muscle  and  the  Flexor  digi- 
torum brevis,  gives  of!  a  proper  digital  plantar  nerve  and  finally  divides  opposite 
the  bases  of  the  metatarsal  bones  into  three  common  digital  plantar  nerves. 

Branches. — The  branches  of  the  medial  plantar  nerve  are:  (1)  cutaneous, 
(2)  muscular,  (3)  articular,  (4)  a  proper  digital  nerve  to  the  medial  side  of  the  great 
toe,  and  (5)  three  common  digital  nerves. 

The  cutaneous  branches  pierce  the  plantar  aponeurosis  between  the  Abductor 
hallucis  and  the  Flexor  digitorum  brevis  and  are  distributed  to  the  skin  of  the  sole 
of  the  foot. 

The  muscular  branches  supply  the  Abductor  hallucis,  the  Flexor  digitorum  brevis, 
the  Flexor  hallucis  brevis,  and  the  first  Lumbricalis;  these  for  the  Abductor  hallucis 
and  Flexor  digitorum  brevis  arise  from  the  trunk  of  the  nerve  near  its  origin  and 
enter  the  deep  surfaces  of  the  muscles;  the  branch  of  the  Flexor  hallucis  brevis 
springs  from  the  proper  digital  nerve  to  the  medial  side  of  the  great  toe,  and  that 
for  the  first  Lumbricalis  from  the  first  common  digital  nerve. 

The  articular  branches  supply  the  articulations  of  the  tarsus  and  metatarsus. 

The  proper  digital  nerve  of  the  great  toe  (nn.  digitales  plantares  proprii;  plantar 
digital  branches)  supplies  the  Flexor  hallucis  brevis  and  the  skin  on  the  medial  side 
of  the  great  toe. 

The  three  common  digital  nerves  {nn.  digitales  plantares  communes)  pass  betw^een 
the  divisions  of  the  plantar  aponeurosis,  and  each  splits  into  two  proper  digital 
nerves — those  of  the  first  common  digital  nerve  supply  the  adjacent  sides  of  the 
great  and  second  toes;  those  of  the  second,  the  adjacent  sides  of  the  second  and 
third  toes;  and  those  of  the  third,  the  adjacent  sides  of  the  third  and  fourth  toes. 
The  third  common  digital  nerve  receives  a  communicating  branch  from  the  lateral 
plantar  nerve;  the  first  gives  a  twig  to  the  first  Lumbricalis.  Each  proper  digital 
nerve  gives  off  cutaneous  and  articular  filaments;  and  opposite  the  last  phalanx 
sends  upward  a  dorsal  branch,  which  supplies  the  structures  around  the  nail, 
the  continuation  of  the  nerve  being  distributed  to  the  ball  of  the  toe.    It  will  be 


THE  SACRAL  AXD  COCCYGEAL  NERVES 


989 


observed  that  these  digital  nerves  are  similar  in  their  distribution  to  those  of  the 
median  nerve  in  the  hand. 

The  Lateral  Plantar  Nerve  (n.  plwitaris  lateralis;  external  lolantar  nerve)  (Fig. 
822)  supphes  the  skin  of  the  fifth  toe  and  lateral  half  of  the  fourth,  as  well  as  most 
of  the  deep  muscles,  its  distribution  being  similar  to  that  of  the  ulnar  nerve  in  the 
hand.  It  passes  obliquely  forward  with  the  lateral  plantar  artery  to  the  lateral 
side  of  the  foot,  lying  between  the  Flexor  digitorum  brevis  and  Quadratus  plantae; 
and,  in  the  interval  between  the  former  muscle  and  the  abductor  digiti  quinti, 
divides  into  a  superficial  and  a  deep  branch.  Before  its  division,  it  supplies  the 
Quadratus  plantae  and  Abductor  digiti  quinti. 

The  superficial  branch  {ramus  superficial  is)  splits  into  a  proper  and  a  common 
digital  nerve;  the  proper  digital  nerve  supplies  the  lateral  side  of  the  little  toe, 

the  Flexor  digiti  quinti  brevis,  and  the  two 
Interossei  of  the  fourth  intermetatarsal  space; 
the  common  digital  nerve  communicates  with 
the  third  common  digital  branch  of  the  medial 
plantar  nerve  and  divides  into  two  proper 
Avv-^^^^^^"^'!  ''W\         mar  digital  nerves   which    supply    the    adjoining 

vlania'-  ^Vv  ''^CAw^A^'f  1  sides  of  the  fourth  and  fifth  toes. 


Deep 
-  branch 


Fig.  822. — The  plantar  nerves. 


Fig.  823. — Diagram  of  the  segmental  distribution  of  the 
cutaneous  nerves, of  the  sole  of  the  foot. 


The  deep  branch  (ramus  profundus;  muscular  hranch)  accompanies  the  lateral 
plantar  artery  on  the  deep  surface  of  the  tendons  of  the  Flexor  muscles  and  the 
Adductor  hallucis,  and  supplies  all  the  Interossei  (except  those  in  the  fourth 
metatarsal  space),  the  second,  third,  and  fourth  Lumbricales,  and  the  Adductor 
hallucis. 

The  Common  Peroneal  Nerve  {n.  peronaeus  communis;  external  popliteal  nerve; 
peroneal  nerve)  (Fig.  821),  about  one-half  the  size  of  the  tibial,  is  derived  from  the 
dorsal  branches  of  the  fourth  and  fifth  lumbar  and  the  first  and  second  sacral 
nerves.  It  descends  obliquely  along  the  lateral  side  of  the  popliteal  fossa  to  the  head 
of  the  fibula,  close  to  the  medial  margin  of  the  Biceps  femoris  muscle.  It  lies 
between  the  tendon  of  the  Biceps  femoris  and  lateral  head  of  the  Gastrocnemius 
muscle,  winds  around  the  neck  of  the  fibula,  between  the  Peronaeus  longus  and  the 
bone,  and  divides  beneath  the  muscle  into  the  superficial  and  deep  peronealnerves. 
Previous  to  its  division  it  gives  off  articular  and  lateral  sural  cutaneous  nerves. 


990  NEUROLOGY 

The  articular  branches  ^rami  articidares)  are  three  in  number;  two  of  these  accom- 
pany the  superior  and  inferior  lateral  genicular  arteries  to  the  knee ;  the  upper  one 
occasionally  arises  from  the  trunk  of  the  sciatic  nerve.  The  third  {recurrent) 
articular  nerve  is  given  off  at  the  point  of  division  of  the  common  peroneal  nerve; 
it  ascends  with  the  anterior  recurrent  tibial  artery  through  the  Tibialis  anterior  to 
the  front  of  the  knee. 

The  lateral  sural  cutaneous  nerve  (n.  cutaneus  surae  lateralis;  lateral  cutaneous 
branch)  supplies  the  skin  on  the  posterior  and  lateral  surfaces  of  the  leg;  one 
branch,  the  peroneal  anastomotic  (m.  comimmicans  fibularis),  arises  near  the  head 
of  the  fibula,  crosses  the  lateral  head  of  the  Gastrocnemius  to  the  middle  of  the 
leg,  and  joins  with  the  medial  sural  cutaneous  to  form  the  sural  nerve.  The 
peroneal  anastomotic  is  occasionally  continued  down  as  a  separate  branch  as  far 
as  the  heel. 

The  Deep  Peroneal  Nerve  {n.  peronaeus  projundus ;  anterior  tibial  nerve)  (Fig. 
816)  begins  at  the  bifurcation  of  the  common  peroneal  nerve,  between  the  fibula 
and  upper  part  of  the  Peronaeus  longus,  passes  obliquely  forward  beneath  the 
Extensor  digitorum  longus  to  the  front  of  the  interosseous  membrane,  and  comes 
into  relation  with  the  anterior  tibial  artery  above  the  middle  of  the  leg;  it  then 
descends  with  the  artery  to  the  front  of  the  ankle-joint,  where  it  divides  into  a  lateral 
and  a  medial  terminal  branch.  It  lies  at  first  on  the  lateral  side  of  the  anterior 
tibial  artery,  then  in  front  of  it,  and  again  on  its  lateral  side  at  the  ankle-joint. 

In  the  leg,  the  deep  peroneal  nerve  supplies  muscular  branches  to  the  Tibialis 
anterior.  Extensor  digitorum  longus,  Peronaeus  tertius,  and  Extensor  hallucis 
proprius,  and  an  articular  branch  to  the  ankle-joint. 

The  lateral  terminal  branch  {external  or  tarsal  branch)  passes  across  the  tarsus, 
beneath  the  Extensor  digitorum  brevis,  and,  having  become  enlarged  like  the  dorsal 
interosseous  nerve  at  the  wrist,  supplies  the  Extensor  digitorum  brevis.  From  the 
enlargement  three  minute  interosseous  branches  are  given  off,  which  supply  the  tarsal 
joints  and  the  metatarsophalangeal  joints  of  the  second,  third,  and  fourth  toes. 
The  first  of  these  sends  a  filament  to  the  second  Interosseus  dorsalis  muscle. 

The  medial  terminal  branch  {internal  branch)  accompanies  the  dorsalis  pedis 
artery  along  the  dorsum  of  the  foot,  and,  at  the  first  interosseous  space,  divides 
into  two  dorsal  digital  nerves  {iin.  digitales  dor  sales  hallucis  lateralis  et  digiti  secundi 
medialis)  which  supply  the  adjacent  sides  of  the  great  and  second  toes,  communicat- 
ing with  the  medial  dorsal  cutaneous  branch  of  the  superficial  peroneal  nerve. 
Before  it  divides  it  gives  off  to  the  first  space  an  interosseous  branch  which  supplies 
the  metatarsophalangeal  joint  of  the  great  toe  and  sends  a  filament  to  the  first 
Interosseous  dorsalis  muscle. 

The  Superficial  Peroneal  Nerve  {n.  perojiaeus  superficialis;  musculocutaneous  nerve) 
(Fig.  816)  supplies  the  Peronei  longus  and  brevis  and  the  skin  over  the  greater  part 
of  the  dorsum  of  the  foot.  It  passes  forward  between  the  Peronaei  and  the  Extensor 
digitorum  longus,  pierces  the  deep  fascia  at  the  lower  third  of  the  leg,  and  divides 
into  a  medial  and  an  intermediate  dorsal  cutaneous  nerve.  In  its  course  between 
the  muscles,  the  nerve- gives  off  muscular  branches  to  the  Peronaei  longus  and  brevis, 
and  cutaneous  filaments  to  the  integument  of  the  lower  part  of  the  leg. 

The  medial  dorsal  cutaneous  nerve  {n.  cutaneus  dorsalis  medialis;  internal  dorsal 
cutaneous  branch)  passes  in  front  of  the  ankle-joint,  and  divides  into  two  dorsal 
digital  branches,  one  of  which  supplies  the  medial  side  of  the  great  tOe,  the  other, 
the  adjacent  side  of  the  second  and  third  toes.  It  also  supplies  the  integument  of 
the  medial  side  of  the  foot  and  ankle,  and  communicates  with  the  saphenous  nerve, 
and  with  the  deep  peroneal  nerve  (Fig.  814). 

The  intermediate  dorsal  cutaneous  nerve  {n.  cutaneus  dorsalis  intermedius;  external 
dorsal  cutaneous  branch),  the  smaller,  passes  along  the  lateral  part  of  the  dorsum 
of  the  foot,  and  divides  into  dorsal  digital  branches,  which  supply  the  contiguous 


THE  SACRAL  AXD  COCCYGEAL  NERVES  991 

sides  of  the  third  and  fourth,  and  of  the  fourth  and  fifth  toes.  It  also  supplies 
the  skin  of  the  lateral  side  of  the  foot  and  ankle,  and  communicates  with  the  sural 
nerve  (Fig.  814). 

The  branches  of  the  superficial  peroneal  nerve  supply  the  skin  of  the  dorsal 
surfaces  of  all  the  toes  excepting  the  lateral  side  of  the  little  toe,  and  the  adjoining 
sides  of  the  great  and  second  toes,  the  former  being  supplied  by  the  lateral  dorsal 
cutaneous  nerve  from  the  sural  nerve,  and  the  latter  by  the  medial  branch  of  the 
deep  peroneal  nerve.  Frequently  some  of  the  lateral  branches  of  the  superficial 
peroneal  are  absent,  and  their  places  are  then  taken  by  branches  of  the  sural  nerve. 

The  Pudendal  Plexus  {plc.vus  pudendus)  (Fig.  817). — The  pudendal  plexus  is 
not  sharply  marked  off  from  the  sacral  plexus,  and  as  a  consequence  some  of  the 
branches  which  spring  from  it  may  arise  in  conjunction  with  those  of  the  sacral 
plexus.  It  lies  on  the  posterior  w^all  of  the  pelvis,  and  is  usually  formed  by  branches 
from  the  anterior  divisions  of  the  second  and  third  sacral  nerves,  the  whole  of  the 
anterior  divisions  of  the  fourth  and  fifth  sacral  nerves,  and  the  coccygeal  nerve. 

It  gives  off'  the  follow:ing  branches: 

Perforating  cutaneous 2,  3  S. 

Pudendal 2,  3,  4  S. 

Visceral 3,  4  S. 

Muscular 4  S. 

Anococcygeal 4,  5  S.  and  Cocc. 

The  Perforating  Cutaneous  Nerve  (n.  dunium  inferior  viedialis)  usually  arises  from 
the  posterior  surface  of  the  second  and  third  sacral  nerves.  It  pierces  the  lower 
part  of  the  sacrotuberous  ligament,  and  winding  around  the  inferior  border  of  the 
Glutaeus  maximus  supplies  the  skin  covering  the  medial  and  lower  parts  of  that 
muscle. 

The  perforating  cutaneous  nerve  may  arise  from  the  pudendal  or  it  may  be  absent;  in  the 
latter  case  its  place  may  be  taken  by  a  branch  from  the  posterior  femoral  cutaneous  nerve  or  by 
a  branch  from  the  third  and  fourth,  or  fourth  and  fifth,  sacral  nerves. 

The  Pudendal  Nerve  (n.  pudendiis;  internal  pudic  rierve)  derives  its  fibres  from  the 
ventral  branches  of  the  second,  third,  and  fourth  sacral  nerves.  It  passes  between 
the  Piriformis  and  Coccygeus  muscles  and  leaves  the  pelvis  through  the  lower  part 
of  the  greater  sciatic  foramen.  It  then  crosses  the  spine  of  the  ischium,  and 
reenters  the  pelvis  through  the  lesser  sciatic  foramen.  It  accompanies  the  internal 
pudendal  vessels  upward  and  forward  along  the  lateral  wall  of  the  ischiorectal 
fossa,  being  contained  in  a  sheath  of  the  obturator  fascia  termed  Alcock's  canal, 
and  divides  into  two  terminal  branches,  viz.,  the  perineal  nerve,  and  the  dorsal  nerve 
of  the  penis  or  clitoris.  Before  its  division  it  gives  off.  the  inferior  hemorrhoidal 
nerve. 

The  inferior  hemorrhoidal  nerve  (?i.  haemorrhoidalis  inferior)  occasionally  arises 
directly  from  the  sacral  plexus;  it  crosses  the  ischiorectal  fossa,  wdth  the  inferior 
hemorrhoidal  vessels,  toward  the  anal  canal  and  the  lower  end  of  the  rectum, 
and  is  distributed  to  the  Sphincter  ani  externus  and  to  the  integument  around  the 
anus.  Branches  of  this  nerve  communicate  with  the  perineal  branch  of  the  posterior 
femoral  cutaneous  and  with  the  posterior  scrotal  nerves  at  the  forepart  of 
the  perineum. 

The  perineal  nerve  {n.  perinei),  the  inferior  and  larger  of  the  tw^o  terminal  branches 
of  the  pudendal,  is  situated  below  the  internal  pudendal  artery.  It  accompanies 
the  perineal  artery  and  divides  into  posterior  scrotal  (or  labial)  and  muscular  branches. 

The  posterior  scrotal  (or  labial)  branches  {nn.  scrotales  (or  lahiales)  posteriores; 
superficial  peroneal  nerves)  are  two  in  number,  medial  and  lateral.  Thej'  pierce 
the  fascia  of  the  urogenital  diaphragm,  and  run  forward  along  the  lateral  part  of 
the  urethral  triangle  in  company  with  the  posterior  scrotal  branches  of  the  perineal 


992  NEUROLOGY 

artery;  the}'  are  distributed  to  the  skin  of  the  scrotum  and  communicate  with  the 
perineal  branch  of  the  posterior  femoral  cutaneous  nerve.  These  nerves  supply  the 
labium  majus  in  the  female. 

The  muscular  branches  are  distributed  to  the  Transversus  perinaei  superficialis, 
Bulbocavernous,  Ischiocavernosus,  and  Constrictor  urethrae.  A  branch,  the 
nerve  to  the  bulb,  given  off  from  the  nerve  to  the  Bulbocavernosus,  pierces  this 
muscle,  and  supplies  the  corpus  cavernosum  urethrae,  ending  in  the  mucous 
membrane  of  the  urethra. 

The  dorsal  nerve  of  the  penis  {71.  dorsalis  penis)  is  the  deepest  division  of  the  puden- 
dal nerve;  it  accompanies  the  internal  pudendal  artery  along  the  ramus  of  the 
ischium;  it  then  runs  forward  along  the  margin  of  the  inferior  ramus  of  the  pubis, 
between  the  superior  and  inferior  layers  of  the  fascia  of  the  urogenital  diaphragm. 
Piercing  the  inferior  layer  it  gives  a  branch  to  the  corpus  cavernosum  penis,  and 
passes  forward,  in  company  with  the  dorsal  artery  of  the  penis,  between  the  layers 
of  the  suspensory  ligament,  on  to  the  dorsum  of  the  penis,  and  ends  on  the  glans 
penis.  In  the  female  this  nerve  is  very  small,  and  supplies  the  clitoris  (n.  dorsalis 
clitoridis). 

The  Visceral  Branches  arise  from  the  third  and  fourth,  and  sometimes  from  the 
second,  sacral  nerves,  and  are  distributed  to  the  bladder  and  rectum  and,  in  the 
female,  to  the  vagina;  they  communicate  with  the  pelvic  plexuses  of  the  sympathetic. 

The  Muscular  Branches  are  derived  from  the  fourth  sacral,  and  supply  the  Levator 
ani,  Coccygeus,  and  Sphincter  ani  externus.  The  branches  to  the  Levator  ani 
and  Coccygeus  enter  their  pelvic  surfaces;  that  to  the  Sphincter  ani  externus 
(perineal  branch)  reaches  the  ischiorectal  fossa  by  piercing  the  Coccygeus  or  by 
passing  between  it  and  the  Levator  ani.  Cutaneous  filaments  from  this  branch 
supply  the  skin  between  the  anus  and  the  coccyx. 

Anococcygeal  Nerves  (nn.  anococcygei) . — The  fifth  sacral  nerve  receives  a  com- 
municating filament  from  the  fourth,  and  unites  with  the  coccygeal  nerve  to  form 
the  coccygeal  plexus.  From  this  plexus  the  anococcygeal  nerves  take  origin;  they 
consist  of  a  few  fine  filaments  which  pierce  the  sacrotuberous  ligament  to  supply 
the  skin  in  the  region  of  the  coccyx. 

Applied  Anatomy. — The  lumbar  plexus  passes  through  the  Psoas  major,  and  therefore  in  psoas 
abscess  any  or  all  of  its  branches  may  be  irritated,  causing  severe  pain  in  the  part  to  which  the 
irritated  nerves  are  distributed.  The  genitofemoral  nerve  is  the  one  which  is  most  frequently 
imphcated.  This  nerve  is  also  of  importance  as  it  is  concerned  in  one  of  the  principal  superficial 
reflexes  employed  in  the  investigation  of  diseases  of  the  medulla  spinahs.  If  the  skin  over  the 
medial  side  of  the  thigh  just  below  the  inguinal  Ugament  (the  part  supphed  by  the  liunboinguinal 
nerve)  be  gently  tickled  in  a  male  chUd,  the  testes  will  be  drawn  upward,  through  the  action 
of  the  Cremaster  muscle,  supplied  by  the  lumboinguinal  nerve.  The  same  result  may  sometimes 
be  noticed  in  adults,  and  can  almost  always  be  produced  by  severe  stimulation.  This  reflex, 
when  present,  shows  that  the  portion  of  the  cord  from  which  the  first  and  second  lumbar  nerves 
are  derived  is  in  a  normal  condition. 

The  femoral  nerve  is  in  danger  of  being  injured  in  fractures  of  the  lesser  pelvis,  since  the  frac- 
ture most  commonly  takes  place  through  the  superior  ramus  of  the  pubis,  at  or  near  the  point 
where  this  nerve  crosses  the  bone.  It  is  also  liable  to  be  pressed  upon,  and  its  functions  impaired, 
by  some  tumors  growing  in  the  pelvis.  Moreover,  on  account  of  its  superficial  position,  it  is 
exposed  to  injury  in  wounds  and  stabs  in  the  groin.  Its  central  origin  is  often  affected  in  cases 
of  infantile  paralysis.  When  this  nerve  is  paralyzed,  the  patient  is  unable  to  flex  his  hip  com- 
pletely, on  account  of  the  paralysis  of  the  Iliacus;  or  to  extend  the  knee  on  the  thigh,  on  account 
of  paralysis  of  the  Quadriceps  femoris;  there  is  complete  paralysis  of  the  Sartorius,  and  partial 
paralysis  of  the  Pectineus.  There  is  loss  of  sensation  down  the  front  and  medial  side  of  the  thigh, 
except  in  that  part  supphed  by  the  lumboinguinal  and  ilioinguinal  nerves.  There  is  also  loss 
of  sensation  down  the  medial  side  of  the  leg  and  foot  as  far  as  the  ball  of  the  great  toe. 

The  obturator  nerve  is  rarely  paralyzed  alone,  but  occasionally  in  association  with  the  femoral. 
The  principal  interest  attached  to  it  is  in  connection  with  its  supply  to  the  knee;  pain  in  the 
knee  being  symptomatic  of  many  diseases  in  which  the  trunk  of  this  nerve,  or  one  of  its  branches, 
is  irritated.  Thus  it  is  well  known  that  in  the  earher  stages  of  hip-joint  disease  the  patient  does 
not  always  complain  of  pain  in  that  articulation,  but  on  the  medial  side  of  the  knee,  or  in  the 
knee-joint  itseK,  both  of  these  articulations  being  supplied  by  the  obturator  nerve,  the  final 


THE  SACRAL  AND  COCCYGEAL  NERVES  993 

distribution  of  the  nerve  being  to  the  knee-joint.  Again,  the  same  thing  occurs  in  sacroiliac 
disease;  pain  is  complained  of  in  the. knee-joint,  or  on  its  medial  side.  The  obturator  nerve  is 
in  close  relationship  with  the  sacroiliac  articulation,  passing  over  it,  and,  according  to  some 
anatomists,  distributing  filaments  to  it.  Further,  in  cancer  of  the  sigmoid  colon,  and  even  in 
cases  where  masses  of  hardened  feces  are  impacted  in  this  portion  of  the  gut,  pain  is  complained 
of  in  the  knee.  The  left  obtui-ator  nerve  hes  beneath  the  sigmoid  colon,  and  is  readily  pressed 
upon  and  irritated  when  disease  exists  in  this  part  of  the  intestine.  Finally,  pain  in  the  knee 
forms  an  important  diagnostic  sign  in  obturator  hernia.  The  hernial  protrusion  as  it  passes 
out  through  the  opening  in  the  obturator  membrane  presses  upon  the  nerve  and  causes  pain  in 
the  parts  suppHed  by  its  peripheral  filaments.  When  the  obturator  nerve  is  paralyzed,  the 
patient  is  unable  to  press  his  knees  together  or  to  cross  one  leg  over  the  other,  on  account  of 
paralysis  of  the  Adductor  muscles.  Rotation  outward  of  the  thigh  is  impaired  from  paralysis 
of  the  Obturator  externus.  Sometimes  there  is  loss  of  sensation  in  the  upper  half  of  the  medial 
side  of  the  thigh. 

The  sciatic  nerve  is  liable  to  be  pressed  upon  by  various  forms  of  pelvic  tumor,  giving  rise  to 
pain  along  its  trunk,  to  which  the  term  sciatica  is  appUed.  Tumors  growing  from  the  pelvic 
viscera,  especially  advanced  cancer  of  the  rectum,  aneurisms  of  some  of  the  branches  of  the 
hypogastric  artery,  calculus  in  the  bladder  when  of  large  size,  accumulation  of  feces  in  the  rectum, 
may  all  cause  pressure  on  the  nerve  inside  the  pelvis,  and  give  rise  to  sciatica.  Outside  the  pelvis 
violent  movements  of  the  hip-joint,  exostoses  or  other  tumors  j^rowing  from  the  margin  of  the 
greater  sciatic  foramen,  may  also  give  rise  to  the  same  condition.  '  Most  cases  of  sciatica,  however, 
are  due  to  neuritis  of  the  sciatic  nerve  from  exposure  to  cold,  and  it  occurs  more  often  in  men  than 
in  women,  in  the  latter  half  of  life,  and  often  in  association  with  rheumatism,  gout,  or  diabetes 
mellitus.  The  inflamed  nerve  is  often  sensitive  to  pressure,  particularly  in  certain  "tender  spots," 
e.  g.,  near  the  posterior  iliac  spine,  at  the  sciatic  notch,  about  the  middle  of  the  back  of  the  thigh, 
in  the  popliteal  fossa,  below  the  head  of  the  fibula,  behind  the  malleoli,  on  the  dorsum  of  the 
foot,  and  pain  is  felt  whenever  extension  of  the  leg  is  attempted,  and  the  nerve  is  stretched. 
Paralysis  of  the  sciatic  nerve  is  rarely  complete;  when  the  lesion  occurs  high  up  there  is  palsy 
of  the  Biceps  femoris,  Semimembranosus,  and  Semitendinosus,  and  of  the  muscles  below  the 
knee.  If  the  lesion  be  lower  down,  there  is  loss  of  motion  in  all  the  muscles  below  the  knee,  and 
loss  of  sensation  in  the  same  situation,  except  the  upper  half  of  the  back  of  the  leg,  which  is  sup- 
pUed  by  the  posterior  femoral  cutaneous,  and  in  the  upper  half  of  the  medial  side  of  the  leg,  when 
the  communicating  branch  of  the  obturator  is  large  (see  p.  980) .  Lesions  of  the  common  peroneal 
nerve  cause  paralysis  of  the  Tibialis  anterior,  the  Peronaei,  the  long  Extensors  of  the  toes,  and 
the  short  Extensor  on  the  dorsum  of  the  foot.  "Foot  drop"  follows,  dorsal  flexion  of  the  toes 
and  abduction  of  the  foot  becoming  impossible.  Later  on  tahpes  results,  largely  by  the  action 
of  gravity  or  by  the  weight  of  the  superincmnbent  bedclothes  when  the  patient  lies  in  bed,  aided 
by  the  contracture  of  the  unopposed  posterior  crural  group  of  muscles. 

The  sciatic  nerve  has  been  frequently  cut  down  upon  and  stretched,  or  has  been  acupunctm-ed, 
for  the  reUef  of  sciatica.  In  order  to  define  it  on  the  surface,  a  point  is  taken  at  the  junction  of 
the  middle  and  lower  thirds  of  a  line  stretching  from  the  posterior  superior  spine  of  the  ilium  to 
the  lateral  part  of  the  ischial  tuberosity,  and  a  line  drawn  from  this  to  the  middle  of  the  upper 
part  of  the  popUteal  fossa.  The  hue  must  be  sUghtly  curved  with  its  convexity  outward,  and 
as  it  passes  downward  to  the  lower  border  of  the  Glutaeus  maximus  is  sHghtly  nearer  to  the 
ischial  tuberosity  than  to  the  greater  trochanter,  as  it  crosses  a  fine  drawn  between  these  two 
points.  The  operation  of  stretching  the  sciatic  nerve  is  performed  by  making  an  incision  over 
the  course  of  the  nerve  beneath  the  fold  of  the  buttock.  The  skin,  superficial  structures,  and 
deep  fascia  having  been  divided,  the  hamstrings  are  defined,  and  pulled  apart  with  retractors. 
The  nerve  will  be  found  lying  on  the  Adductor  magnus  and  covered  by  the  Biceps  femoris.  It 
is  to  be  separated  from  the  surrounding  structm-es,  hooked  up  with  the  finger,  and  stretched 
by  steady  and  continuous  traction  for  two  or  thi'ee  minutes.  The  sciatic  nerve  may  also  be 
stretched  by  what  is  known  as  the  "dry"  plan.  The  patient  is  laid  on  his  back,  the  foot  is  extended, 
the  leg  flexed  on  the  thigh,  and  the  thigh  strongly  flexed  on  the  abdomen.  While  the  thigh  is 
maintained  in  this  position,  the  leg  is  forcibly  extended  to  its  full  extent,  and  the  foot  as  fully 
flexed  on  the  leg. 

The  position  of  the  common  peroneal  nerve,  close  behind  the  tendon  of  the  Biceps  femoris, 
on  the  lateral  side  of  the  popliteal  fossa,  should  be  remembered  in  subcutaneous  division  of  the 
tendon.  After  the  tendon  is  divided,  the  common  peroneal  nerve  rises  up  as  a  cord  and  might 
be  mistaken  for  a  small  undivided  portion  of  the  tendon.  Where  this  nerve  wmds  around  the 
neck  of  the  fibula,  it  is  also  liable  to  be  severed  accidentally  if  its  exact  situation  is  not  kept  in 
mind,  and  especial  care  must  be  used  when  deahng  with  sinuses  leading  down  to  carious  bone 
in  this  situation.  Section  of  the  nerve  results  in  complete  "foot  drop"  from  paralysis  of  the 
anterior  tibial  group  of  muscles  and  inversion  of  the  foot  from  the  unopposed  action  of  the  Tibiahs 
posterior,  the  Peronaei  being  paralyzed,  together  with  anesthesia  of  the  parts  suppUedby  the 
nerve,  and,  owing  to  loss  of  nutrition,  the  limb  frequently  becomes  blue  and  cold,  and  may  develop 
"trophic"  sores. 
63 


994 


NEUROLOGY 


THE   SYMPATHETIC   NERVES. 

The  sympathetic  nerves  (Fig.  824),  sometimes  grouped  under  the  term  sympathetic 
system,  are  distributed  to  the  viscera  and  bloodvessels,  and  are  intimately  connected 
with  the  spinal  and  certain  of  the  cerebral  nerves.    They  are  characterized  by  the 


spmf 

Maxillary  nerve 
Ciliary  ganglion 
Sphenopalatine  ganglion 
Superior  cerricai,  ganglion  of  sympathetic 


Cervical  jdexus 


Brachial  plexus 


Greater  splanchnic 
nerve 

Lesser  splanchnic 
nerve 


Lumbar  plexus 


Sacral  plexus 


Pharyngeal  plexus 

Middle  cervical  ganglion  of 

Hympathetic 
Inferior  cervical  ganglion  nf 

sympathetic 
Recurrent  nerve 

Bronchial  plexus 

■  Cardiac  plexus 


Oesophageal  plexus 
Coronary  plexuses 


Left  vagus  nerve 

Gastric  plexus 
C celiac  plexus    ■ 

Superior  mesenteric 
plexus 


Aortic  plexxis 

Inferior  mesenteric 
plexus 

Hypogastric  plexus 


Pelvic  plexus 


Bladder 
Vesical  plexus 


Fig    824  —The  right  sympathetic  chain  and  its  connections  with  the  thoracic,  abdominal,  and  pelvis  plexuses. 

(After  Schwalbe.) 


THE  CEPHALIC  PORTION  OF  THE  SYMPATHETIC  SYSTEM         995 

presence  of  niiraeroiis  ganglia  wliich  may  be  divided  into  three  groups,  central, 
collateral,  and  terminal  ganglia. 

The  central  ganglia  are  arranged  in  two  vertical  rows,  one  on  either  side  of  the 
middle  line,  situated  i)artly  in  front  and  partly  at  the  sides  of  the  vertebral  column. 
Each  ganglion  is  joined  by  intervening  nervous  cords  to  adjacent  ganglia  so  that 
two  chains,  the  sympathetic  trunks,  are  formed.  The  collateral  ganglia  are  found 
in  connection  with  three  great  prevertebral  plexuses,  placed  within  the  thorax, 
abdomen,  and  pelvis  respectively,  while  the  terminal  ganglia  are  located  in  the  walls 
of  the  viscera.^ 

The  sympathetic  trunks  (tnoicus  sym  path  tens;  gamjliated  cord)  extend  from  the 
base  of  the  skull  to  the  coccyx.  The  cephalic  end  of  each  is  continued  upward 
through  the  carotid  canal  into  the  skull,  and  forms  a  plexus  on  the  internal  carotid 
artery;  the  caudal  ends  of  the  trunks  converge  and  end  in  a  single  ganglion,  the 
ganglion  impar,  placed  in  front  of  the  coccyx.  The  ganglia  of  each  trunk  are  dis- 
tinguished as  cervical,  thoracic,  lumbar,  and  sacral  and,  except  in  the  neck,  they 
closely  correspond  in  number  to  the  vertebrae.    They  are  arranged  thus: 

Cervical  portion  .  ...       3  ganglia 

Thoracic      " 12 

Lumbar       " 4        " 

Sacral  " 4  or  5  " 

In  the  neck  the  ganglia  lie  in  front  of  the  transverse  processes  of  the  vertebrae; 
in  the  thoracic  region  in  front  of  the  heads  of  the  ribs;  in  the  lumbar  region  on  the 
sides  of  the  vertebral  bodies ;  and  in  the  sacral  region  in  front  of  the  sacrum. 

Connections  with  the  Spinal  Nerves. — Communications  are  established  between 
the  sympathetic  and  spinal  nerves  through  what  are  known  as  the  gray  and  white 
rami  communicantes  (Fig.  798);  the  gray  rami  convey  sympathetic  fibres  into  the 
spinal  nerves  and  the  white  rami  transmit  spinal  fibres  into  the  sympathetic. 
Each  spinal  nerve  receives  a  gray  ramus  communicans  from  the  sympathetic 
trunk,  but  white  rami  are  not  supplied  by  all  the  spinal  nerves.  White  rami  are 
derived  from  the  first  thoracic  to  the  first  lumbar  nerves  inclusive,  while  the 
visceral  branches  which  run  from  the  second,  third,  and  fourth  sacral  nerves  directly 
to  the  pelvic  plexuses  of  the  sympathetic  belong  to  this  category.  The  fibres  which 
reach  the  sympathetic  through  the  white  rami  communicantes  are  medullated; 
those  which  spring  from  the  cells  of  the  sympathetic  ganglia  are  almost  entirely 
non-medullated.  The  sympathetic  nerves  consist  of  efferent  and  afferent  fibres,  the 
origin  and  course  of  which  are  described  on  page  950) . 

The  three  great  gangliated  plexuses  {collateral  ganglia)  are  situated  in  front  of 
the  vertebral  column  in  the  thoracic,  abdominal,  and  pelvic  regions,  and  are  named, 
respectively,  the  cardiac,  the  solar  or  epigastric,  and  the  hypogastric  plexuses. 
They  consist  of  collections  of  nerves  and  ganglia;  the  nerves  being  derived  from 
the  sympathetic  trunks  and  from  the  cerebrospinal  nerves.  They  distribute 
branches  to  the  viscera. 


THE   CEPHALIC   PORTION   OF   THE   SYMPATHETIC   SYSTEM    (PARS 
CEPHALICA   S.    SYMPATHICI). 

The  cephalic  portion  of  the  sympathetic  system  begins  as  the  internal  carotid 
nerve,  which  appears  to  be  a  direct  prolongation  of  the  superior  cervical  ganglion. 
It  is  soft  in  texture,  and  of  a  reddish  color.  It  ascends  by  the  side  of  the  internal 
carotid  artery,  and,  entering  the  carotid  canal  in  the  temporal  bone,  divides  into 

1  The  ciliary,  sphenopalatine,  otic,  and  submaxiUarj'  ganglia,  already  described  in  connection  with  the  trigeminal 
nerve,  may  be  regarded  as  belonging  to  the  sjTnpathetic. 


996  NEUROLOGY 

two  branches,  -which  lie  one  on  the  lateral  and  the  other  on  the  medial  side  of  that 
vessel. 

The  lateral  branch,  the  larger  of  the  two,  distributes  filaments  to  the  internal 
carotid  artery,  and  forms  the  internal  carotid  plexus. 

The  medial  branch  also  distributes  filaments  to  the  internal  carotid  artery,  and, 
continuing  onward,  forms  the  cavernous  plexus. 

The  internal  carotid  plexus  (plexus  caroticus  internus;  carotid  plexus)  is  situated 
on  the  lateral  side  of  the  internal  carotid  artery,  and  in  the  plexus  there  occasionally 
exists  a  small  gangliform  swelling,  the  carotid  ganglion,  on  the  under  surface  of 
the  artery.  The  internal  carotid  plexus  communicates  with  the  semilunar  gan- 
glion, the  abducent  nerve,  and  the  sphenopalatine  ganglion;  it  distributes  filaments 
to  the  wall  of  the  carotid  artery,  and  also  communicates  with  the  tympanic  branch 
of  the  glossopharyngeal  nerve. 

The  communicating  branches  with  the  abducent  nerve  consist  of  one  or  two 
filaments  which  join  that  nerve  as  it  lies  upon  the  lateral  side  of  the  internal  carotid 
artery.  The  communication  with  the  sphenopalatine  ganglion  is  effected  by  a 
branch,  the  deep  petrosal,  given  off  from  the  plexus  on  the  lateral  side  of  the  artery; 
this  branch  passes  through  the  cartilage  filling  up  the  foramen  lacerum,  and  joins 
the  greater  superficial  petrosal  to  form  the  nerve  of  the  pterygoid  canal  (Vidian 
nerve),  which  passes  through  the  pterygoid  canal  to  the  sphenopalatine  ganglion. 
The  communication  with  the  tympanic  branch  of  the  glossopharyngeal  nerve  is 
effected  by  the  caroticotympanic,  which  may  consist  of  two  or  three  delicate 
filaments. 

The  cavernous  plexus  (jjlexiis  cavernosus)  is  situated  below  and  medial  to  that 
part  of  the  internal  carotid  artery  which  is  placed  by  the  side  of  the  sella  turcica 
in  the  cavernous  sinus,  and  is  formed  chiefly  by  the  medial  division  of  the  internal 
carotid  nerve.  It  communicates  with  the  oculomotor,  the  trochlear,  the  ophthalmic 
and  the  abducent  nerves,  and  with  the  ciliary  ganglion,  and  distributes  filaments  to 
the  wall  of  the  internal  carotid  artery.  The  branch  of  communication  with  the 
oculomotor  nerve  joins  that  nerve  at  its  point  of  division;  the  branch  to  the  troch- 
lear nerve  joins  it  as  it  lies  on  the  lateral  wall  of  the  cavernous  sinus;  other  filaments 
are  connected  with  the  under  surface  of  the  ophthalmic  nerve;  and  a  second  fila- 
ment joins  the  abducent  nerve. 

The  filaments  of  connection  with  the  ciliar}-  ganglion  arise  from  the  anterior  part 
of  the  cavernous  plexus  and  enter  the  orbit  through  the  superior  orbital  fissure; 
they  may  join  the  nasociliary  branch  of  the  ophthalmic  nerve,  or  be  continued  for- 
ward as  a  separate  branch. 

The  terminal  filaments  from  the  internal  carotid  and  cavernous  plexuses  are 
prolonged  as  plexuses  around  the  anterior  and  middle  cerebral  arteries  and  the 
ophthalmic  artery;  along  the  former  vessels,  they  may  be  traced  to  the  pia  mater; 
along  the  latter,  into  the  orbit,  where  they  accompany  each  of  the  branches  of  the 
vessel.  The  filaments  prolonged  on  to  the  anterior  communicating  artery  connect 
the  sympathetic  nerves  of  the  right  and  left  sides. 


THE    CERVICAL   PORTION    OF    THE    SYMPATHETIC    SYSTEM    (PARS 
CERVICALIS    S.    SYMPATHICI). 

The  cervical  portion  of  the  sympathetic  trunk  consists  of  three  ganglia,  distin- 
guished, according  to  their  positions,  as  the  superior,  middle,  and  inferior  ganglia, 
connected  by  intervening  cords.  This  portion  receives  no  white  rami  communi- 
cantes  from  the  cervical  spinal  nerves;  its  spinal  fibres  are  derived  from  the  white 
rami  of  the  upper  thoracic  nerves,  and  enter  the  corresponding  thoracic  ganglia 
of  the  sympathetic  trunk,  through  which  they  ascend  into  the  neck. 


THE  CERVICAL  PORTION  OF  THE  SYMPATHETIC  SYSTEM         997 

The  superior  cervical  ganglion  (ganglion  cervicale  superius),  the  largest  of  the 
three,  is  phuvd  opijositc  the  second  and  third  cervical  vertebrae.  It  is  of  a  reddish- 
gray  color,  and  usuall.y  fusiform  in  shape;  sometimes  broad  and  flattened,  and  occa- 
sionally constricted  at  intervals;  it  is  believed  to  be  formed  by  the  coalescence 
of  four  ganglia,  corresponding  to  the  upper  four  cervical  nerves.  It  is  in  relation, 
in  front,  with  the  sheath  of  the  internal  carotid  artery  and  internal  jugular  vein; 
behind,  with  the  Longus  capitis  muscle. 

Its  branches  may  be  divided  into  inferior,  lateral,  medial,  and  anterior. 

The  Inferior  Branch  communicates  with  the  middle  cervical  ganglion. 

The  Lateral  Branches  (external  branches)  consist  of  gray  rami  communicantes  to 
the  upper  four  cervical  nerves  and  to  certain  of  the  cerebral  nerves.  Sometimes  the 
branch  to  the  fourth  cervical  nerve  may  come  from  the  trunk  connecting  the 
upper  and  middle  cervical  ganglia.  The  branches  to  the  cerebral  nerves  consist 
of  delicate  filaments,  which  run  to  the  ganglion  nodosum  of  the  vagus,  and  to  the 
hypoglossal  nerve.  A  filament,  the  jugular  nerve,  passes  upward  to  the  base  of 
the  skull,  and  divides  to  join  the  petrous  ganglion  of  the  glossopharyngeal,  and  the 
jugular  ganglion  of  the  vagus. 

The  Medial  Branches  (internal  branches)  are  peripheral,  and  are  the  lamygo- 
pharyngeal  branches  and  the  superior  cardiac  nerve. 

The  laryngopharyngeal  branches  (rami  laryngopharyngei)  pass  to  the  side  of  the 
pharynx,  where  they  join  with  branches  from  the  glossopharyngeal,  vagus,  and 
external  laryngeal  nerves  to  form  the  pharyngeal  plexus. 

The  superior  cardiac  nerve  (n.  cardiacus  superior)  arises  by  two  or  more  branches 
from  the  superior  cervical  ganglion,  and  occasionally  receives  a  filament  from  the 
trunk  between  the  first  and  second  cervical  ganglia.  It  runs  down  the  neck  behind 
the  common  carotid  artery,  and  in  front  of  the  Longus  colli  muscle;  and  crosses 
in  front  of  the  inferior  thyroid  artery,  and  recurrent  nerve.  The  course  of  the  nerves 
on  the  two  sides  then  differ.  The  right  nerve,  at  the  root  of  the  neck,  passes  either 
in  front  of  or  behind  the  subclavian  artery,  and  along  the  innominate  artery  to 
the  back  of  the  arch  of  the  aorta,  where  it  joins  the  deep  part  of  the  cardiac  plexus. 
It  is  connected  with  other  branches  of  the  sympathetic;  about  the  middle  of  the 
neck  it  receives  filaments  from  the  external  laryngeal  nerve;  lower  down,  one  or 
two  twigs  from  the  vagus;  and  as  it  enters  the  thorax  it  is  joined  by  a  filament 
from  the  recurrent  nerve.  Filaments  from  the  nerve  communicate  with  the  thyroid 
branches  from  the  middle  cervical  ganglion.  The  left  nerve,  in  the  thorax,  runs, 
in  front  of  the  left  common  carotid  artery  and  across  the  left  side  of  the  arch  of  the 
aorta,  to  the  superficial  part  of  the  cardiac  plexus. 

The  Anterior  Branches  (nn.  carotid  exierni)  ramify  upon  the  common  carotid 
artery  and  upon  the  external  carotid  artery  and  its  branches,  forming  around  each 
a  delicate  plexus,  on  the  nerves  composing  which  small  ganglia  are  occasionally 
found.  The  plexuses  accompanying  some  of  these  arteries  have  important  com- 
munications with  other  nerves.  That  surrounding  the  external  maxillary  artery 
communicates  with  the  submaxillary  ganglion  by  a  filament;  and  that  accompany- 
ing the  middle  meningeal  artery  sends  an  offset  to  the  otic  ganglion,  and  a  second, 
the  external  petrosal  nerve,  to  the  genicular  ganglion  of  the  facial  nerve. 

The  middle  cervical  ganglion  (ganglion  cervicale  medium)  is  the  smallest  of  the 
three  cervical  ganglia,  and  is  occasionally  wanting.  It  is  placed  opposite  the  sixth 
cervical  vertebra,  usually  in  front  of,  or  close  to,  the  inferior  thyroid  artery.  It 
is  probably  formed  by  the  coalescence  of  two  ganglia  corresponding  to  the  fifth 
and  sixth  cervical  nerves. 

It  sends  gray  rami  communicantes  to  the  fifth  and  sixth  cervical  nerves,  and 
gives  off  the  middle  cardiac  nerve. 

The  Middle  Cardiac  Nerve  (n.  cardiacus  7nedius;  great  cardiac  nerve),  the  largest 
of  the  three  cardiac  nerves,  arises  from  the  middle  cervical  ganglion,  or  from  the 


998  NEUROLOGY 

trunk  between  the  middle  and  inferior  ganglia.  On  the  right  side  it  descends  behind 
the  common  carotid  artery,  and  at  the  root  of  the  neck  runs  either  in  front  of  or 
behind  the  subclavian  artery;  it  then  descends  on  the  trachea,  receives  a  few 
filaments  from  the  recurrent  nerve,  and  joins  the  right  half  of  the  deep  part  of  the 
cardiac  plexus.  In  the  neck,  it  communicates  with  the  superior  cardiac  and  recur- 
rent nerves.  On  the  left  side,  the  middle  cardiac  nerve  enters  the  chest  between 
the  left  carotid  and  subclavian  arteries,  and  joins  the  left  half  of  the  deep  part 
of  the  caridac  plexus. 

The  inferior  cervical  ganglion  (ganglioji  cervicale  inferius)  is  situated  between 
the  base  of  the  transverse  process  of  the  last  cervical  vertebra  and  the  neck  of  the 
first  rib,  on  the  medial  side  of  the  costocervical  artery.  Its  form  is  irregular;  it  is 
larger  in  size  than  the  preceding,  and  is  frequently  fused  with  the  first  thoracic 
ganglion.  It  is  probably  formed  by  the  coalescence  of  two  ganglia  which  corre- 
spond to  the  seventh  and  eighth  cervical  nerves.  It  is  connected  to  the  middle 
cervical  ganglion  by  two  or  more  cords,  one  of  which  forms  a  loop  around  the  sub- 
clavian artery  and  supplies  offsets  to  it.  This  loop  is  named  the  ansa  subclavia 
{Vieussenii). 

The  ganglion  sends  gray  rami  communicantes  to  the  seventh  and  eighth  cervical 
nerves. 

It  gives  off  the  inferior  cardiac  nerve,  and  offsets  to  bloodvessels. 

The  inferior  cardiac  nerve  {n.  cardiacus  inferior)  arises  from  either  the  inferior 
cervical  or  the  first  thoracic  ganglion.  It  descends  behind  the  subclavian  artery 
and  along  the  front  of  the  trachea,  to  join  the  deep  part  of  the  cardiac  plexus.  It 
communicates  freely  behind  the  subclavian  artery  with  the  recurrent  nerve  and 
the  middle  cardiac  nerve. 

The  offsets  to  bloodvessels  form  plexuses  on  the  subclavian  artery  and  its  branches. 
The  plexus  on  the  vertebral  artery  is  continued  on  to  the  basilar,  posterior  cerebral, 
and  cerebellar  arteries.  The  plexus  on  the  inferior  thyroid  artery  accompanies 
the  artery  to  the  thyroid  gland,  and  communicates  with  the  recurrent  and  external 
laryngeal  nerves,  with  the  superior  cardiac  nerve,  and  with  the  plexus  on  the 
common  carotid  artery. 

THE   THORACIC  PORTION   OF   THE   SYMPATHETIC   SYSTEM   (PARS 
THORACALIS   S.  SMYPATHICI)   (Fig.  825). 

The  thoracic  portion  of  the  sympathetic  trunk  consists  of  a  series  of  ganglia, 
which  usually  correspond  in  number  to  that  of  the  vertebrae;  but,  on  account 
of  the  occasional  coalescence  of  two  ganglia,  their  number  is  uncertain.  The 
thoracic  ganglia  rest  against  the  heads  of  the  ribs,  and  are  covered  by  the  costal 
pleura;  the  last  two,  however,  are  more  anterior  than  the  rest,  and  are  placed  on 
the  sides  of  the  bodies  of  the  eleventh  and  twelfth  thoracic  vertebrae.  The  ganglia 
are  small  in  size,  and  of  a  grayish  color.  The  first,  larger  than  the  others,  is  of 
an  elongated  form,  and  frequently  blended  with  the  inferior  cervical  ganglion. 
They  are  connected  together  by  the  intervening  portions  of  the  trunk. 

Two  rami  communicantes,  a  white  and  a  gray,  connect  each  ganglion  with  its 
corresponding  spinal  nerve. 

The  branches  from  the  up-per  five  ganglia  are  very  small;  they  supply  filaments 
to  the  thoracic  aorta  and  its  branches.  Twigs  from  the  second,  third,  and  fourth 
ganglia  enter  the  posterior  pulmonary  plexus. 

The  branches  from  the  lower  seven  ganglia  are  large,  and  white  in  color;  they 
distribute  filaments  to  the  aorta,  and  unite  to  form  the  greater,  the  lesser,  and  the 
lowest  splanchnic  nerves. 

The  greater  splanchnic  nerve  {n.  splanchnicus  major;  great  splanchnic  nerve)  is 
white  in  color,  firm  in  texture,  and  of  a  considerable  size;  it  is  formed  by  branches 


V 


THE  THORACIC  PORTiOS  OF  THE  SYMPATHETIC  SYSTEM 


999 


from  the  fifth  to  the  iiintli  or  tenth  thoracic  ganglia,  hut  tlie  fibres  in  the  higher 
roots  may  be  traced  upward  in  the  synii)athetic  trunk  as  far  as  the  first  or  second 
thoracic  ganghon.  It  descends  obHquely  on  the  IxxHes  of  the  vertebrse,  perforates 
the  cms  of  the  Diaphragma,  and  ends  in  the  ccehac  ganghon.  A  ganglion  (ganglion 
splanchnicum)  exists  on  this  ner\^e  opposite  the  eleventh  or  twelfth  thoracic  vertebra. 


Highest  intercostal  artery 


Highest  intercostal  vein 


Fig.  825. — Thoracic  portion  of  the  sympathetic  trunk. 

The  lesser  splanchnic  nerve  (?i.  splanchiiciis  minor)  is  formed  by  filaments  from 
the  ninth  and  tenth,  and  sometimes  the  eleventh  thoracic  ganglia,  and  from  the 
cord  between  them.  It  pierces  the  Diaphragma  with  the  preceding  nerve,  and 
joins  the  aorticorenal  ganglion. 

The  lowest  splanchnic  nerve  (?i.  splanchnicus  imus;  least  splanchnic  nerve)  arises 
from  the  last  thoracic  ganglion,  and,  piercing  the  Diaphragma,  ends  in  the  renal 
plexus. 


1000 


NEUROLOGY 


A  striking  analogy  exists  between  the  splanchnic  and  the  cardiac  nerves.    The 
cardiac  nerves  are  three  in  number;  they  arise  from  all  three  cervical  ganglia, 


DiaphrayiiMt  ic 
(jaiKjlion 


Swprareiuil  gh 


Aorticorejuil  ganglion- — _  \  \  \ 

Lowest  spanchnic 
nerve 


Hepatic 
ariuy 

,Lcft  codiac  ganglion 

—  v         <*fBsr-:f  unyi'w     Superior  mesenteric 

^1^!^^     ,      %^^  ^y^  Greater  splanchnic  nerve 
-^      ^.^-J^  -^  jg^^     gi      gawjlwu 


Hi  iial  artery 


Lesser  splanchnic 
nerve 


~\  Svperior  tnesenteric 
ganglion 


Blanch  to  aortic  plexus 


Branch  to  aortic  plexus 


JllWi"i    'T Sympathetic  trunk 


—  Inferior  mesenteric  artery 


\  Inferior  mesenteric 
ganglion 


Sacrovertehral  angle 

Common  iliac  vein 
Cmnmon  iliac  artery 


Fig.  826. — Abdominal  portion  of  the  sympathetic  trunk,  -nith  the  cceliac  and  hypogastric  plexuses.     (After  Henle.) 


THE  CARDIAC  PLEXUS  1001 

and  are  distributed  to  a  large  and  important  organ  in  the  thoracic  cavity.  The 
splanchnic  nerves,  also  three  in  number,  are  connected  probably  with  all  the  thoracic 
ganglia,  and  are  distributed  to  important  organs  in  the  abdominal  cavity. 

THE    ABDOMINAL   PORTION    OP    THE    SYMPATHETIC    SYSTEM    (PARS 

ABDOMINALIS    S.    SYMPATHICI;  LUMBAR   PORTION   OF 

GANGLIATED  CORD)  (Fig.  826). 

The  abdominal  portion  of  the  sympathetic  trunk  is  situated  in  front  of  the  ver- 
tebral column,  along  the  medial  margin  of  the  Psoas  major.  It  consists  usually  of 
four  lumbar  ganglia,  connected  together  by  interganglionic  cords.  It  is  continuous 
above  with  the  thoracic  portion  beneath  the  medial  lumbocostal  arch,  and 
below  with  the  pelvic  portion  behind  the  common  iliac  artery.  The  ganglia  are 
of  small  size,  and  placed  much  nearer  the  median  line  than  are  the  thoracic  ganglia. 

Gray  rami  communicantes  pass  from  all  the  ganglia  to  the  lumbar  spinal  nerves. 
The  first  and  second,  and  sometimes  the  third,  lumbar  nerves  send  white  rami 
communicantes  to  the  corresponding  ganglia.  The  rami  communicantes  are  of 
considerable  length,  and  accompany  the  lumbar  arteries  around  the  sides  of  the 
bodies  of  the  vertebrae,  passing  beneath  the  fibrous  arches  from  which  some  of  the 
fibres  of  the  Psoas  major  arise. 

Of  the  branches  of  distribution,  some  pass  in  front  of  the  aorta,  and  join  the  aortic 
plexus;  others  descend  in  front  of  the  common  iliac  arteries,  and  assist  in  forming 
the  hypogastric  plexus. 

THE   PELVIC   PORTION   OF   THE    SYMPATHETIC   SYSTEM    (PARS 
PELVINA    S.    SYMPATHICI). 

The  pelvic  portion  of  each  sympathetic  trunk  is  situated  in  front  of  the  sacrum, 
medial  to  the  anterior  sacral  foramina.  It  consists  of  four  or  five  small  sacral 
ganglia,  connected  together  by  interganglionic  cords,  and  continuous  above  with 
the  abdominal  portion.  Below,  the  two  pelvic  sympathetic  trunks  converge,  and 
end  on  the  front  of  the  coccyx  in  a  small  ganglion,  the  ganglion  impar. 

Gray  rami  communicantes  pass  from  the  ganglia  to  the  sacral  and  coccygeal 
nerves.  No  white  rami  communicantes  are  given  to  this  part  of  the  gangliated 
cord,  but  the  visceral  branches  which  arise  from  the  third  and  fourth,  and  sometimes 
from  the  second,  sacral,  and  run  directly  to  the  pelvic  plexuses,  are  regarded  as 
white  rami  communicantes. 

The  branches  of  distribution  communicate  on  the  front  of  the  sacrum  with  the 
corresponding  branches  from  the  opposite  side;  some,  from  the  first  two  ganglia, 
pass  to  join  the  pelvic  plexus,  and  others  form  a  plexus,  which  accompanies  the 
middle  sacral  artery  and  sends  filaments  to  the  glomus  coccygeum  (coccygeal  body). 

THE    GREAT   PLEXUSES    OF   THE    SYMPATHETIC   SYSTEM. 

The  great  plexuses  of  the  sympathetic  are  aggregations  of  nerves  and  ganglia, 
situated  in  the  thoracic,  abdominal,  and  pelvic  cavities,  and  -named  the  cardiac, 
coeliac,  and  hypogastric  plexuses.  They  consist  not  only  of  sympathetic  fibres 
derived  from  the  ganglia,  but  of  fibres  from  the  medulla  spinalis,  which  are  con- 
veyed through  the  white  rami  communicantes.  From  the  plexuses  branches  are 
given  to  the  thoracic,  abdominal,  and  pelvic  viscera. 

The  Cardiac  Plexus  (Plexus  Cardiacus)  (Fig.  824). 

The  cardiac  plexus  is  situated  at  the  base  of  the  heart,  and  is  divided  into  a  super- 
ficial part,  which  lies  in  the  concavity  of  the  aortic  arch,  and  a  deep  part,  between 
the  aortic  arch  and  the  trachea.    The  two  parts  are,  however,  closely  connected. 


1002  XEUROLOGY 

The  superficial  part  of  the  cardiac  plexus  lies  beneath  the  arch  of  the  aorta, 
in  front  of  the  right  pulmonary  artery.  It  is  formed  by  the  superior  cardiac  branch 
of  the  left  sympathetic  and  the  lower  superior  cervical  cardiac  branch  of  the  left 
vagus.  A  small  ganglion,  the  cardiac  ganglion  of  Wrisberg,  is  occasionally  found 
connected  with  these  nerves  at  their  point  of  junction.  This  ganglion,  when 
present,  is  situated  immediately  beneath  the  arch  of  the  aorta,  on  the  right  side 
of  the  ligamentum  arteriosum.  The  superficial  part  of  the  cardiac  plexus  gives 
branches  (a)  to  the  deep  part  of  the  plexus;  (6)  to  the  anterior  coronary  plexus; 
and  (c)  to  the  left  anterior  pulmonary  plexus. 

The  deep  part  of  the  cardiac  plexus  is  situated  in  front  of  the  bifurcation  of 
the  trachea,  above  the  point  of  di\-ision  of  the  pulmonary  artery,  and  behind  the 
aortic  arch.  It  is  formed  by  the  cardiac  nerves  derived  from  the  cervical  ganglia 
of  the  sympathetic,  and  the  cardiac  branches  of  the  vagus  and  recurrent  nerves. 
The  only  cardiac  nerves  which  do  not  enter  into  the  formation  of  the  deep  part 
of  the  cardiac  plexus  are  the  superior  cardiac  nerve  of  the  left  sympathetic,  and  the 
lower  of  the  two  superior  cervical  cardiac  branches  from  the  left  vagus,  which  pass 
to  the  superficial  part  of  the  plexus. 

The  branches  from  the  right  half  of  the  deep  part  of  the  cardiac  plexus  pass, 
some  in  front  of,  and  others  behind,  the  right  pulmonary  artery;  the  former,  the 
more  numerous,  transmit  a  few  filaments  to  the  anterior  pulmonary  plexus,  and 
are  then  continued  onward  to  form  part  of  the  anterior  coronary  plexus;  those 
behind  the  pulmonary  artery  distribute  a  few  filaments  to  the  right  atrium,  and  are 
then  continued  onward  to  form  part  of  the  posterior  coronary  plexus. 

The  left  half  of  the  deep  part  of  the  plexus  is  connected  with  the  superficial  part 
of  the  cardiac  plexus,  and  gives  filaments  to  the  left  atrium,  and  to  the  anterior 
pulmonary  plexus,  and  is  then  continued  to  form  the  greater  part  of  the  posterior 
coronary  plexus. 

The  Posterior  Coronary  Plexus  (plei-us  coronarius  jxjsterior;  left  coronary  plexus) 
is  larger  than  the  anterior,  and  accompanies  the  left  coronary  artery;  it  is  chiefly 
formed  by  filaments  prolonged  from  the  left  half  of  the  deep  part  of  the  cardiac 
plexus,  and  by  a  few  from  the  right  half.  It  gives  branches  to  the  left  atrium  and 
ventricle. 

The  Anterior  Coronary  Plexus  (jjlexus  coronarius  anterior;  right  coronary  plexus) 
is  formed  partly  from  the  superficial  and  partly  from  the  deep  parts  of  the  cardiac 
plexus.  It  accompanies  the  right  coronary  artery,  and  gives  branches  to  the  right 
atrium  and  ventricle. 


The  Coeliac  Plexus  (Plexus  Coeliacus;  Solar  Plexus)  fFigs.  824,  827). 

The  coeliac  plexus,  the  largest  of  the  three  sympathetic  plexuses,  is  situated  at 
the  level  of  the  upper  part  of  the  first  lumbar  vertebra  and  is  composed  of  two 
large  ganglia,  the  coeliac  ganglia,  and  a  dense  net-work  of  nerve  fibres  uniting  them 
together.  It  surrounds  the  coeliac  artery  and  the  root  of  the  superior  mesenteric 
artery.  It  lies  behind  the  stomach  and  the  omental  bursa,  in  front  of  the  crura 
of  the  Diaphragma  and  the  commencement  of  the  abdominal  aorta,  and  between 
the  suprarenal  glands.  The  plexus  and  the  ganglia  receive  the  greater  and  lesser 
splanchnic  nerves  of  both  sides  and  some  filaments  from  the  right  vagus,  and  give 
off  numerous  secondary  plexuses  along  the  neighboring  arteries. 

The  Coehac  Ganglia  (ganglia  coeliaca;  semilunar  ganglia)  are  two  large  irregularly- 
shaped  masses  having  the  appearance  of  lymph  glands  and  placed  one  on  either 
side  of  the  middle  line  in  front  of  the  crura  of  the  Diaphragma  close  to  the  supra- 
renal glands,  that  on  the  right  side  being  placed  behind  the  inferior  vena  cava.  The 
upper  part  of  each  ganglion  is  joined  by  the  greater  splanchnic  nerve,  while  the 


THE  CCELIAC  PLEXUS 


1003 


lower  part,  which  is  segmented  oil'  and  named  tlie  aorticorenal  ganglion,  receives 
the  lesser  splanchnic  nerve  and  gives  ofi"  the  greater  j)art  of  the  renal  plexus. 


C  celiac     Left 
Phrenic  plexus   vagus 

plexus 


vagus 


Hepatic 
plextis 

Common 
bile-ducf 


Superior 

mesenteric 

plexus 

Aortic 

plexu'' 


<>tric  plexus 

P/irenic 
plexus 

Suprarenal 
plexus 


Lienal 
plexus 

Phrenic 
ganglicn 

Greater 
^^^      splanchnic 

celiac 
nglion 


Renal  plexus 

Superior 
mesenteric 
ganglion 

Spermatic 
plexus 

Lumbar 
ganglia 

Inferior 

\  mesenteric 
plexus 


Fig.  827. — The  coeliac  ganglia  with  the  sympathetic  plexuses  of  the  abdominal  viscera  radiating  from  the  ganglia. 

(Toldt.) 

The  secondary  plexuses  springing  from  or  connected  with  the  coeliac  plexus  are 
the 

Phrenic.  Renal. 

Hepatic.  Spermatic. 

Lienal.  Superior  mesenteric. 

Superior  gastric.  Abdominal  aortic. 

Suprarenal.  Inferior  mesenteric. 

The  phrenic  plexus  {plexus  jjhrenicus)  accompanies  the  inferior  phrenic  artery 
to  the  Diaphragma,  some  filaments  passing  to  the  suprarenal  gland.  It.  arises 
from  the  upper  part  of  the  coeliac  ganglion,  and  is  larger  on  the  right  than  on  the 
left  side.    It  receives  one  or  two  branches  from  the  phrenic  nerve.    At  the  point 


1004  NEUROLOGY 

of  junction  of  the  right  phrenic  plexus  with  the  phrenic  nerve  is  a  small  ganglion 
(ganglion  phrenicum).  This  plexus  distributes  branches  to  the  inferior  vena  cava, 
and  to  the  suprarenal  and  hepatic  plexuses. 

The  hepatic  plexus  {plexus  hepaticvs),  the  largest  offset  from  the  coeliac  plexus, 
receives  filaments  from  the  left  vagus  and  right  phrenic  nerves.  It  accompanies 
the  hepatic  artery,  ramifying  upon  its  branches,  and  upon  those  of  the  portal  vein 
in  the  substance  of  the  liver.  Branches  from  this  plexus  accompan}^  all  the  divisions 
of  the  hepatic  artery.  A  considerable  plexus  accompanies  the  gastroduodenal 
artery  and  is  continued  as  the  inferior  gastric  plexus  on  the  right  gastroepiploic 
arter}'-  along  the  greater  curvature  of  the  stomach,  where  it  unites  with  offshoots 
from  the  lienal  plexus. 

The  lienal  plexus  (plexus  lienalis;  splenic  plexus)  is  formed  by  branches  from  the 
coeliac  plexus,  the  left  coeliac  ganglion,  and  from  the  right  vagus  nerve.  It  accom- 
panies the  lienal  artery  to  the  spleen,  giving  off,  in  its  course,  subsidiary  plexuses 
along  the  various  branches  of  the  artery. 

The  superior  gastric  plexus  {plexus  gastricus  superior;  gastric  or  coronary  plexus) 
accompanies  the  left  gastric  artery  along  the  lesser  curvature  of  the  stomach,  and 
joins  with  branches  from  the  left  vagus. 

The  suprarenal  plexus  {plexus  suprarenalis)  is  formed  by  branches  from  the 
coeliac  plexus,  from  the  coeliac  ganglion,  and  from  the  phrenic  and  greater  splanchnic 
nerves,  a  ganglion  being  formed  at  the  point  of  junction  with  the  latter  nerve. 
The  plexus  supplies  the  suprarenal  gland,  being  distributed  chiefly  to  its  medullary 
portion;  its  branches  are  remarkable  for  their  large  size  in  comparison  with  that 
of  the  organ  they  supply. 

The  renal  plexus  {plexus  renalis)  is  formed  by  filaments  from  the  coeliac  plexus, 
the  aorticorenal  ganglion,  and  the  aortic  plexus.  It  is  joined  also  by  the  smallest 
splanchnic  nerve.  The  nerves  from  these  sources,  fifteen  or  twenty  in  number, 
have  a  few  ganglia  developed  upon  them.  They  accompany  the  branches  of  the 
renal  artery  into  the  kidney;  some  filaments  are  distributed  to  the  spermatic 
plexus  and,  on  the  right  side,  to  the  inferior  vena  cava. 

The  spermatic  plexus  {plexus  spermaticus)  is  derived  from  the  renal  plexus, 
receiving  branches  from  the  aortic  plexus.  It  accompanies  the  internal  spermatic 
artery  to  the  testis.  In  the  female,  the  ovarian  plexus  {plexus  arteriae  ovaricae) 
arises  from  the  renal  plexus,  and  is  distributed  to  the  ovary,  and  fundus  of  the 
uterus. 

Applied  Anatomy. — The  intimate  connection  which  exists  between  the  renal  and  spermatic 
plexuses  serves  to  explain  the  very  frequent  symptom  in  renal  calculus,  of  pain  which  is  referred 
to  the  body  of  the  testis. 

The  superior  mesenteric  plexus  {plexus  mesentericus  superior)  is  a  continuation 
of  the  lower  part  of  the  coeliac  plexus,  receiving  a  branch  from  the  junction  of  the 
right  vagus  nerve  with  the  plexus.  It  surrounds  the  superior  mesenteric  artery, 
accompanies  it  into  the  mesentery,  and  divides  into  a  number  of  secondary  plexuses, 
which  are  distributed  to  all  the  parts  supplied  by  the  artery,  viz.,  pancreatic  branches 
to  the  pancreas;  intestinal  branches  to  the  small  intestine;  and  ileocolic,  right 
colic,  and  middle  colic  branches,  w^hich  supply  the  corresponding  parts  of  the  great 
intestine.  The  nerves  composing  this  plexus  are  white  in  color  and  firm  in  texture; 
in  the  upper  part  of  the  plexus  close  to  the  origin  of  the  superior  mesenteric  artery 
is  a  ganglion  (ganglion  mesentericum  superius) . 

The  abdominal  aortic  plexus  {plexus  aorticus  abdominalis;  aortic  plexus)  is  formed 
by  branches  derived,  on  either  side,  from  the  coeliac  plexus  and  ganglia,  and  receives 
filaments  from  some  of  the  lumbar  ganglia.  It  is  situated  upon  the  sides  and  front  of 
the  aorta,  between  the  origins  of  the  superior  and  inferior  mesenteric  arteries.  From 
this  plexus  arise  part  of  the  spermatic,  the  inferior  mesenteric,  and  the  hypogastric 
plexuses;  it  also  distributes  filaments  to  the  inferior  vena  cava. 


THE  HYPOGASTRIC  PLEXUS  1005 

The  inferior  mesenteric  plexus  {j)lexus  mesentericus  inferior)  is  derived  chiefly 
from  the  aortic  plexus.  It  surrounds  the  inferior  mesenteric  artery,  and  divides 
into  a  number  of  secondary  plexuses,  which  are  distributed  to  all  the  parts  supplied 
by  the  artery,  viz.,  the  left  colic  and  sigmoid  plexuses,  wliich  supply  the  descending 
and  sigmoid  parts  of  the  colon;  and  the  superior  hemorrhoidal  plexus,  which  supplies 
the  rectum  and  joins  in  the  pelvis  with  branches  from  the  pelvic  plexuses. 


The  Hypogastric  Plexus  (Plexus  Hypogastricus)  (Fig.  824). 

The  hypogastric  plexus  is  situated  in  front  of  the  last  lumbar  vertebra  and  the 
promontory  of  the  sacrum,  between  the  two  common  iliac  arteries,  and  is  formed 
by  the  union  of  numerous  filaments,  which  descend  on  either  side  from  the  aortic 
plexus,  and  from  the  lumbar  ganglia;  it  divides,  below,  into  two  lateral  portions 
which  are  named  the  pelvic  plexuses. 

The  Pelvic  Plexuses  (Fig.  824).- — The  pelvic  plexuses  supply  the  viscera  of  the 
pelvic  cavity,  and  are  situated  at  the  sides  of  the  rectum  in  the  male,  and  at  the 
sides  of  the  rectum  and  vagina  in  the  female.  They  are  formed  on  either  side  by 
a  continuation  of  the  hypogastric  plexus,  by  the  visceral  branches  from  the  second, 
third,  and  fourth  sacral  nerves,  and  by  a  few  filaments  from  the  first  two  sacral 
ganglia.  At  the  points  of  junction  of  these  nerves  small  ganglia  are  found.  From 
these  plexuses  numerous  branches  are  distributed  to  the  viscera  of  the  pelvis. 
They  accompany  the  branches  of  the  hypogastric  artery. 

The  Middle  Hemorrhoidal  Plexus  (plexus  haemorrhoidalis  medius)  arises  from  the 
upper  part  of  the  pelvic  plexus.  It  supplies  the  rectum,  and  joins  with  branches 
of  the  superior  hemorrhoidal  plexus. 

The  Vesical  Plexus  (plexus  vesicalis)  arises  from  the  forepart  of  the  pelvic  plexus. 
The  nerves  composing  it  are  numerous,  and  contain  a  large  proportion  of  spinal 
nerve  fibres.  They  accompany  the  vesical  arteries,  and  are  distributed  to  the  sides 
and  fundus  of  the  bladder.  Numerous  filaments  also  pass  to  the  vesiculae  seminales 
and  ductus  deferentes;  those  accompanying  the  ductus  deferens  join,  on  the  sper- 
matic cord,  with  branches  from  the  spermatic  plexus. 

The  Prostatic  Plexus  (plexus  prostaticus)  is  continued  from  the  lower  part  of  the 
pelvic  plexus.  The  nerves  composing  it  are  of  large  size.  They  are  distributed 
to  the  prostate  vesiculae  seminales  and  the  corpora  cavernosa  of  the  penis  and 
urethra.  The  nerves  supplying  the  corpora  cavernosa  consist  of  two  sets,  the 
lesser  and  greater  cavernous  nerves,  which  arise  from  the  forepart  of  the  prostatic 
plexus,  and,  after  joining  with  branches  from  the  pudendal  nerve,  pass  forward 
beneath  the  pubic  arch. 

The  lesser  cavernous  nerves  (nn.  cavernosi  penis  minores;  small  cavernous  nerves) 
perforate  the  fibrous  covering  of  the  penis,  near  its  root. 

The  greater  cavernous  nerve  (n.  cavernosu^  penis  major;  large  cavernous  plexus) 
passes  forward  along  the  dorsum  of  the  penis,  joins  with  the  dorsal  nerve  of  the 
penis,  and  is  distributed  to  the  corpora  cavernosa. 

The  Vaginal  Plexus  arises  from  the  lower  part  of  the  pelvic  plexus.  It  is  distributed 
to  the  walls  of  the  vagina,  to  the  erectile  tissue  of  the  vestibule,  and  to  the  clitoris. 
The  nerves  composing  this  plexus  contain,  like  the  vesical,  a  large  proportion  of 
spinal  nerve  fibres. 

The  Uterine  Plexus  accompanies  the  uterine  artery  to  the  side  of  the  uterus, 
between  the  layers  of  the  broad  ligament;  it  communicates  with  the  ovarian  plexus. 

Applied  Anatomy. — Little  is  known  as  to  the  connection  between  the  numerous  microscopic 
alterations  (pigmentation,  atrophy,  hemorrhage,  fibrosis)  that  have  been  described  in  the  sympa- 
thetic nervous  system,  and  the  fimctional  changes  that  ensue  therefrom.  Grosser  lesions  due 
to  stabs,  bullet  woimds,  or  the  pressm-e  of  new  growths,  may  cause  either  irritative  or  paralytic 


1006  NEUROLOGY 

symptoms.  In  paralysis  of  the  cervical  sympathetic  on  one  side,  the  pupil  is  small  and  does  not 
dilate  when  shaded  or  on  the  instillation  of  cocaine,  although  it  contracts  still  farther  when 
brightly  illumiaated;  it  also  loses  the  cihospinal  reflex,  faihng  to  dilate  when  the  skin  of  the  neck 
is  pinched.  The  palpebral  fissure  narrows  from  paralysis  of  the  involuntary  muscle  of  the  eyelid, 
and  the  eyeball  sinks  backward  into  the  orbit — enophthahnos — either  from  paralysis  of  Miiller's 
orbital  muscle  which  closes  the  inferior  orbital  fissure,  or  from  wasting  of  the  intraorbital  fat. 
The  superficial  vessels  of  the  face  and  scalp  are  at  first  dilated,  but  later  they  contract.  Anidrosis, 
or  absence  of  sweating,  is  often  noted  on  the  afTected  side.  Irritation  of  the  cervical  sympathetic 
produces  signs  mainly  the  converse  of  those  described  above.  We  have  no  definite  knowledge 
of  the  signs  and  symptoms  that  follow  lesions  of  the  thoracic  or  abdominal  sympathetic  systems. 
It  is  Ukely,  however,  that  a  number  of  nervous  disorders  characterized  by  persistent  vascular 
disturbances,  such  as  dilatation  of  the  vessels  with  throbbing,  flushing,  sweating,  and  localized 
oedema,  or  contraction  of  the  vessels  with  pallor,  chilliness,  pain,  and  malnutrition  of  the  affected 
parts,  are  due  to  implication  of  the  sympathetic  nervous  system.  It  is  possible,  too,  that  the  rare 
condition  of  progressive  facial  hemiatro'phy,  coming  on  between  the  ages  of  ten  and  twenty,  and 
producing  marked  unilateral  shrinkage  of  all  the  tissues  of  the  face,  is  primarily  an  affection  of 
the  sympathetic. 


THE  ORGANS  OF  THl^]  SENSES  AND 
THE  COMMON  INTEGUMENT. 


THE  organs  of  the  senses  may  be  divided  into  (a)  those  of  the  special  senses  of 
taste,  smell,  sight,  and  hearing,  and  (6)  those  associated  with  the  general  sensa- 
tions of  heat,  cold,  pain,  pressure,  etc. 


THE  PERIPHERAL   ORGANS   OF   THE   SPECIAL  SENSES. 

THE   ORGAN   OF   TASTE    (ORGANON   GUSTUS). 

The  periphery  gustatory  or  taste  organs  consist  of  certain  modified  epithelial 
cells  arranged  in  flask-shaped  groups  termed  gustatory  calyculi  (taste-buds),  which 
are  found  on  the  tongue  and  adjacent  parts.  They  occupy  nests  in  the  stratified 
epithelium,  and  are  present  in  large  numbers  on  the  sides  of  the  papillae  vallatae 
(Fig.  828),  and  to  a  less  extent  on  their  opposed  walls.    They  are  also  found  on  the 


<a 


Fig.  828. — Vertical  section  of  papilla  f oliata  of  the  rabbit,  crossing  the  folia.  (Ranvier.)  a.  Serous  gland,  g . 
Gustatory  calyculus.  n.  Nerve  bundles,  p.  Central  lamina  of  the  corium.  p'.  Lateral  lamina  m  which  the  nerve 
fibres  run.    z.  Sinus-like  vein  which  traverses  the  whole  length  of  the  folium. 

fungiform  papillse  over  the  back  part  and  sides  of  the  tongue,  and  in  the  general 
epithelial  covering  of  the  same  areas.  They  are  very  plentiful  over  the  fimbriae 
linguae,  and  are  also  present  on  the  under  surface  of  the  soft  palate,  and  on  the 
posterior  surface  of  the  epiglottis. 

Structure.— Each  taste  bud  is  flask-like  in  shape  (Fig.  829),  its  broad  base  resting  on  the  corium, 
and  its  neck  opening  by  an  orifice,  the  gustatory  pore,  between  the  cells  of  the  epithelium.  The 
bud  is  formed  by  two  kinds  of  cells:  supporting  cells  and  gustatory  cells.  The  supporting  cells 
are  mostly  arranged  like  the  staves  of  a  cask,  and  form  an  outer  envelope  for  the  bud.  Some, 
however,  are  foimd  in  the  interior  of  the  bud  between  the  gustatory  cells.    The  gustatory  cells 


1008      ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

occupy  the  central  portion  of  the  bud;  they  are  spindle-shaped,  and  each  possesses  a  large  spherical 
nucleus  near  the  middle  of  the  cell.  The  peripheral  end  of  the  cell  terminates  at  the  gustatory 
pore  in  a  fine  hair-Uke  filament,  the  gustatory  hair.  The  central  process  passes  toward  the  deep 
extremity  of  the  bud,  and  there  ends  in  single  or  bifurcated  varicosities.  The  nerve  fibrils  after 
losing  their  medullary  sheaths  enter  the  taste  bud,  and  end  in  fine  extremities  between  the  gusta- 
tory cells;  other  nerve  fibrils  ramify  between  the  supporting  cells  and  terminate  in  fine  extremities; 
these,  however,  are  beUeved  to  be  nerves  of  ordinary  sensation  and  not  gustatory. 

Oustatory  pore  and 

rjiLstatory  hairs 


Fig.  829. — Taste-bud,  highly  magnified. 

Nerves  of  Taste. — The  chorda  tympani  nerve,  derived  from  the  sensory  root  of  the  facial,  is 
the  nerve  of  taste  for  the  anterior  two-thirds  of  the  tongue;  the  nerve  for  the  posterior  third 
is  the  glossopharyngeal. 


THE  ORGAN  OF  SMELL  (ORGANON  OLFACTORIUS;   THE  NOSE). 

The  peripheral  olfactory  organ  or  organ  of  smell  consists  of  two  parts :  an  outer, 
the  external  nose,  which  projects  from  the  centre  of  the  face;  and  an  internal,  the 
nasal  cavity,  which  is  divided  by  a  septum  into  right  and  left  nasal  chambers. 

The  External  Nose  (Nasus  Externus;  Outer  Nose). 

The  external  nose  is  pyramidal  in  form,  and  its  upper  angle  or  root  is  connected 
directly  with  the  forehead ;  its  free  angle  is  termed  the  apex.  Its  base  is  perforated 
by  two  elliptical  orifices,  the  nares,  separated  from  each  other  by  an  antero-posterior 
septum,  the  columna.  The  margins  of  the  nares  are  provided  with  a  number  of 
stiff  hairs,  or  vibrissse,  which  arrest  the  passage  of  foreign  substances  carried  with 
the  current  of  air  intended  for  respiration.  The  lateral  surfaces  of  the  nose  form, 
by  their  union  in  the  middle  line,  the  dorsum  nasi,  the  direction  of  which  varies 
considerably  in  different  individuals;  the  upper  part  of  the  dorsum  is  supported 
by  the  nasal  bones,  and  is  named  the  bridge.  The  lateral  surface  ends  below  in 
a  rounded  eminence,  the  ala  nasi. 

Structure. — The  frame-work  of  the  external  nose  is  composed  of  bones  and  cartilages;  it  is 
covered  by  the  integument,  and  Uned  by  mucous  membrane. 

The  bony  frame-work  occupies  the  upper  part  of  the  organ;  it  consists  of  the  nasal  bones,  and 
the  frontal  processes  of  the  maxillae. 

The  cartilaginous  frame-work  (cartilagines  nasi)  consists  of  five  large  pieces,  viz.,  the  cartilage 
of  the  septum,  the  two  lateral  and  the  two  greater  alar  cartilages,  and  several  smaller  pieces, 
the  lesser  alar  cartilages  (Figs.  830,  831,  832).  The  various  cartilages  are  connected  to  each  other 
and  to  the  bones  by  a  tough  fibrous  membrane. 

The  cartilage  of  the  septum  {cartilago  septi  nasi)  is  somewhat  quadrilateral  in  form,  thicker  at 
its  margins  than  at  its  centre,  and  completes  the  separation  between  the  nasal  cavities  in  front. 
Its  anterior  margin,  thickest  above,  is  connected  with  the  nasal  bones,  and  is  continuous  with 
the  anterior  margms  of  the  lateral  cartilages;  below,  it  is  connected  to  the  medial  crura  of  the 
greater  alar  cartilages  by  fibrous  tissue.  Its  posterior  margin  is  connected  with  the  perpendicular 
plate  of  the  ethmoid;  its  inferior  margin  with  the  vomer  and  the  palatine  processes  of  the  maxillae. 


THE  EXTERNAL  NOSE 


1009 


It  may  be  pi-olongcd  backward  (especially  in  children)  as  a  narrow  process,  t  ho  sphenoidal  pro- 
cess, for  some  distance  between  the  vomer  and  perpendi(!ular  plate  of  the  ethmoid.    The  septal 
cartilage  does  not  reach  as  far  as  the  lowest  part  of  the  nasal  septum.    This  is  formed  by  the 
medial  crura  of  the  greater  alar  cartilages  and  by  the 
skin;  it  is  freely  movable,  and  hence  is  termed  the 
septum  mobile  nasi. 

The  lateral  cartilage  {cariihtgo  nasi  lateralis;  upper 
lateral  cartilage)  is  situated  below  the  inferior  margin 
of  the  nasal  bone,  and  is  flattened,  and  triangular  in 
shape.  Its  anterior  margin  is  thicker  than  the  pos- 
terior, and  is  continuous  above  with  the  cartilage  of 
the  septum,  but  separated  from  it  below  by  a 
narrow  fissure;  its  superior  margin  is  attached  to 
the  nasal  bone  and  the  frontal  process  of  the  max- 
illa; its  inferior  margin  is  connected  by  fibrous 
tissue  with  the  greater  alar  cartilage. 

The  greater  alar  cartilage  {cartilago  alaris  major; 
lower  lateral  cartilage)  is  a  thin,  flexible  plate,  sit- 
uated immediately  below  the  preceding,  and  bent 
upon  itself  in  such  a  manner  as  to  form  the  medial 
and  lateral  walls  of  the  naris  of  its  own  side.  The 
portion  which  forms  the  medial  wall  (cms  mediale) 
is  loosely  connected  with  the  corresponding  portion 
of  the  opposite  cartilage,  the  two  forming,  together 
with  the  thickened  integument  and  subjacent  tis- 
sue, the  septmn  mobile  nasi.  The  part  which 
forms  the  lateral  wall  {cms  laterale)  is  curved  to 
correspond  with  the  ala  of  the  nose;  it  is  oval  and 

flattened,  narrow  behind,  where  it  is  connected  with  the  frontal  process  of  the  maxilla  by  a  tough 
fibrous  membrane,  in  which  are  found  three  or  four  small  cartilaginous  plates,  the  lesser  alar 
cartilages  {cartilagines  alares  minor es;  sesamoid  cartilages).  Above,  it  is  connected  by  fibrous 
tissue  to  the  lateral  cartilage  and  front  part  of  the  cartilage  of  the  septum;  below,  it  falls  short 
of  the  margin  of  the  naris,  the  ala  being  completed  by  fatty  and  fibrous  tissue  covered  by  skin. 
In  front,  the  greater  alar  cartilages  are  separated  by  a  notch  which  corresponds  with  the  apex 
of  the  nose. 


Gicatei  alar 
caitdage 


Fig.  830. — Cartilages  of  the  nose.     Side  view. 


Lesser  alar 
cartilages 


Fig.  831 . — Cartilages  of  the  nose,  seen  from  below. 


Fig.  832. — Bones  and  cartilages  of  septum  of  nose. 
Right  side. 


The  muscles  acting  on  the  external  nose  have  been  described  in  the  section  on  Myology. 

The  integument  of  the  dorsum  and  sides  of  the  nose  is  thin,  and  loosely  connected  with  the 
subjacent  parts;  but  over  the  tip  and  alse  it  is  thicker  and  more  firmly  adherent,  and  is  fiu-nished 
with  a  large  number  of  sebaceous  foUicles,  the  orifices  of  which  are  usually  very  distinct. 

The  arteries  of  the  external  nose  are  the  alar  and  septal  branches  of  the  external  maxillary, 
which  supply  the  alse  and  septum;  the  dorsum  and  sides  being  supplied  from  the  dorsal  nasal 
branch  of  the  ophthalmic  and  the  infraorbital  branch  of  the  internal  maxillary.  The  veins  end  in 
the  anterior  facial  and  ophthahxiic  veins. 

The  nerves  for  the  muscles  of  the  nose  are  derived  from  the  facial,  while  the  skin  receives 
branches  from  the  infratrochlear  and  nasocihary  branches  of  the  ophthalmic,  and  from  the  infra- 
orbital of  the  maxillary. 
64 


1010        ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

The  Nasal  Cavity  (Cavum  Nasi;  Nasal  Fossa). 

The  nasal  chambers  are  situated  one  on  either  side  of  the  me(Han  plane.  They 
open  in  front  through  the  nares,  and  communicate  behind  through  the  choanse 
with  the  nasal  part  of  the  pharynx.  The  nares  are  somewhat  pear-shaped  apertures, 
each  measuring  about  2.5  cm.  antero-posteriorly  and  1.25  cm.  transversely  at 
its  widest  part.  The  choanae  are  two  oval  openings  each  measuring  2.5  cm. 
in  the  vertical,  and  1.25  cm.  in  the  transverse  direction  in  a  well-developed 
adult  skull. 

For  the  description  of  the  bony  boundaries  of  the  nasal  cavities,  see  pages  292 
to  294. 

Inside  the  aperture  of  the  nostril  is  a  slight  dilatation,  the  vestibule,  bounded 
laterally  by  the  ala  and  lateral  crus  of  the  greater  alar  cartilage,  and  medially  by 
the  medial  crus  of  the  same  cartilage.  It  is  lined  by  skin  containing  hairs  and 
sebaceous  glands,  and  extends  as  a  small  recess  toward  the  apex  of  the  nose.  Each 
nasal  cavity,  above  and  behind  the  vestibule,  is  divided  into  two  parts:  an  olfactory 
region,  consisting  of  the  superior  nasal  concha  and  the  opposed  part  of  the  septum, 
and  a  respiratory  region,  which  comprises  the  rest  of  the  cavity. 


Sphoio-ctJmioidal  recess 


Pharyngeal  o)  ifice  of  audilory  tube        Pharyngeal  recess 
Fig.  833. — Lateral  wall  of  nasal  cavity. 


Lateral  Wall  (Figs.  833,  834). — On  the  lateral  wall  are  the  superior,  middle,  and 
inferior  nasal  conchae,  and  below  and  lateral  to  each  concha  is  the  correspond- 
ing nasal  passage  or  meatus.  Above  the  superior  concha  is  a  narrow  recess, 
the  sphenoethmoidal  recess,  into  wdiich  the  sphenoidal  sinus  opens.  The  superior 
meatus  is  a  short  oblique  passage  extending  about  half-way  along  the  upper  border 
of  the  middle  concha;  the  posterior  ethmoidal  cells  open  into  the  front  part  of  this 
meatus.     The  middle  meatus  is  below  and  lateral  to  the  middle  concha,  and  is 


THE  NASAL  CAVITY 


1011 


contiiiuoil  anteriorly  into  a  slialiow  depression,  situated  above  the  vestibule  and 
named  the  atrium  of  the  middle  meatus.  On  raising  or  removing  the  middle  concha 
the  lateral  wall  of  this  meatus  is  fully  displayed.  On  it  is  a  rounded  elevation, 
the  bulla  ethmoidalis,  and  below  and  in  front  of  this  is  a  curved  cleft,  the  hiatus 
semilunaris. 

The  bulla  ethmoidalis  is  caused  by  the  bulging  of  the  middle  ethmoidal  cells 
which  open  on  or  immediately  abo\'e  it,  and  the  size  of  the  bulla  \'aries  with  that 
of  its  contained  cells. 

Bristle  in  infundibulum 
Cut  edge  of  middle  concha 
Hiatus  semilunaris 
'  Bulla  ethmoidalis 

Opening  of  middle  ethmoidal  cells 
Cut  edge  of  superior  concha 
Openings  of  posterior  ethmoidal  cells 
Bristle  in  opening  of  sphenoidal  si7ius 


Bristle  in  nasclacrimal  car.al 

Bristle  in  opening  of 
maxillary  sinus 


Cut  edge  of       ^jSitlry      P^'^ryngeal  recess 
nfcrior  concha      "  ^^^^^ 


Fig.  834. — Lateral  wall  of  nasal   cavity;   the  three  nasal   conchas  have  been  removed. 


The  hiatus  semilunaris  is  bounded  inferiorly  by  the  sharp  concave  margin  of  the 
uncinate  process  of  the  ethmoid  bone,  and  leads  into  a  curved  channel,  the  infundib- 
ulum, bounded  above  by  the  bulla  ethmoidalis  and  below  by  the  lateral  surface 
of  the  uncinate  process  of  the  ethmoid.  The  anterior  ethmoidal  cells  open  into  the 
front  part  of  the  infundibulum,  and  this  in  slightly  over  50  per  cent,  of  subjects 
is  directly  continuous  with  the  frontonasal  duct  or  passage  leading  from  the  frontal 
air  sinus;  but  when  the  anterior  end  of  the  uncinate  process  fuses  with  the  front 
part  of  the  bulla,  this  continuity  is  interrupted  and  the  frontonasal  duct  then  opens 
directly  into  the  anterior  end  of  the  middle  meatus. 

Below  the  bulla  ethmoidalis,  and  partly  hidden  by  the  inferior  end  of  the  uncinate 
process,  is  the  ostium  maxillare,  or  opening  from  the  maxillary  sinus;  in  a  frontal 
section  this  opening  is  seen  to  be  placed  near  the  roof  of  the  sinus.  An  accessory 
opening  from  the  sinus  is  frequently  present  below  the  posterior  end  of  the  middle 
nasal  concha.  The  inferior  meatus  is  below  and  lateral  to  the  inferior  nasal  concha; 
the  nasolacrimal  duct  opens  into  this  meatus  under  cover  of  the  anterior  part  of 
the  inferior  concha. 


1012       ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

Medial  Wall  (Fig.  832). — The  medial  wall  or  septum  is  frequently  more  or 
less  deflected  from  the  median  plane,  thus  lessening  the  size  of  one  nasal  cavity 
and  increasing  that  of  the  other;  ridges  or  spurs  of  bone  growing  into  one  or  other 
cavity  from  the  septum  are  also  sometimes  present.  Immediately  over  the  incisive 
canal  at  the  lower  edge  of  the  cartilage  of  the  septum  a  depression,  the  nasopalatine 
recess,  is  seen.  In  the  septum  close  to  this  recess  a  minute  orifice  may  be  discerned ; 
it  leads  backward  into  a  l^lind  pouch,  the  rudimentary  vomeronasal  organ  of  Jacobson, 
which  is  supported  by  a  strip  of  cartilage,  the  vomeronasal  cartilage.  This  organ 
is  well-developed  in  many  of  the  lower  animals,  where  it  apparently  plays  a  part 
in  the  sense  of  smell,  since  it  is  supplied  by  twigs  of  the  olfactory  nerve  and  lined 
by  epithelium  similar  to  that  in  the  olfactory  region  of  the  nose. 

The  roof  of  the  nasal  cavity  is  narrow  from  side  to  side,  except  at  its  posterior 
part,  and  may  be  divided,  from  behind  forward,  into  sphenoidal,  ethmoidal,  and 
frontonasal  parts,  after  the  bones  which  form  it. 

The  floor  is  concave  from  side  to  side  and  almost  horizontal  antero-posteriorly; 
its  anterior  three-fourths  are  formed  by  the  palatine  process  of  the  maxilla,  its 
posterior  fourth  by  the  horizontal  process  of  the  palatine  bone.  In  its  antero- 
medial  part,  directly  over  the  incisive  foramen,  a  small  depression,  the  nasopalatine 
recess,  is  sometimes  seen;  it  points  downward  and  forward  and  occupies  the 
position  of  a  canal  which  connected  the  nasal  with  the  buccal  cavity  in  early 
•fetal  life. 

The  Mucous  Membrane  {memhrana  mucosa  nasi). — The  nasal  mucous  membrane 
lines  the  nasal  cavities,  and  is  intimately  adherent  to  the  periosteum  or  perichon- 
drium. It  is  continuous  wdth  the  skin  through  the  nares,  and  with  the  mucous 
membrane  of  the  nasal  part  of  the  pharynx  through  the  choanse.  From  the  nasal 
cavity  its  continuity  with  the  conjunctiva  may  be  traced,  through  the  nasolacrimal 
and  lacrimal  ducts;  and  with  the  frontal,  ethmoidal,  sphenoidal,  and  maxillary 
sinuses,  through  the  several  openings  in  the  meatuses.  The  mucous  membrane 
is  thickest,  and  most  vascular,  over  the  nasal  conchse.  It  is  also  thick  over  the 
septum ;  but  it  is  very  thin  in  the  meatuses  on  the  floor  of  the  nasal  cavities,  and  in 
the  various  sinuses. 

Owing  to  the  thickness  of  the  greater  part  of  this  membrane,  the  nasal  cavities 
are  much  narrower,  and  the  middle  and  inferior  nasal  conchee  appear  larger  and 
more  prominent  than  in  the  skeleton;  also  the  various  apertures  communicating 
wdth  the  meatuses  are  considerably  narrowed. 

Structure  of  the  Mucous  Membrane  (Fig.  835). — The  epithelium  covering  the  mucous  mem- 
brane differs  in  its  character  according  to  the  fimctions  of  the  part  of  the  nose  in  which  it  is  found. 
In  the  respiratory  region  it  is  columnar  and  ciliated.  Interspersed  among  the  columnar  cells 
are  goblet  or  mucin  cells,  while  between  their  bases  are  found  smaller  pyi-amidal  cells.  Beneath 
the  epithelium  and  its  basement  membrane  is  a  fibrous  layer  infiltrated  with  lymph  corpuscles, 
so  as  to  form  in  many  parts  a  diffuse  adenoid  tissue,  and  under  this  a  nearly  continuous  layer 
of  small  and  larger  glands,  some  mucous  and  some  serous,  the  ducts  of  which  open  upon  the 
surface.  In  the  olfactory  region  the  mucous  membrane  is  yellowish  in  color  and  the  epitheUal 
cells  are  columnar  and  non-ciliated;  they  are  of  two  kinds,  supporting  cells  and  olfactory  cells. 
The  supporting  cells  contain  oval  nuclei,  which  are  situated  in  the  deeper  parts  of  the  cells  and 
constitute  the  zone  of  oval  nuclei;  the  superficial  part  of  each  cell  is  columnar,  and  contains 
granules  of  yellow  pigment,  while  its  deep  part  is  prolonged  as  a  delicate  process  which  ramifies 
and  communicates  with  similar  processes  from  neighboring  cells,  so  as  to  form  a  net -work  in  the 
mucous  membrane.  Lying  between  the  deep  processes  of  the  supporting  cells  are  a  number  of 
bipolar  nerve  cells,  the  olfactory  cells,  each  consisting  of  a  small  amount  of  granular  protoplasm 
with  a  large  spherical  nucleus,  and  possessing  two  processes — a  superficial  one  which  runs  between 
the  columnar  epithehal  ceUs,  and  projects  on  the  surface  of  the  mucous  membrane  as  a  fine, 
hair-hke  process,  the  olfactory  hair ;  the  other  or  deep  process  runs  inward,  is  frequently  beaded, 
and  is  continued  as  the  axon  of  an  olfactory  nerve  fibre.  Beneath  the  epithehum,  and  extending 
through  the  thickness  of  the  mucous  membrane,  is  a  layer  of  tubular,  often  branched,  glands, 
the  glands  of  Bowman,  identical  in  structure  with  serous  glands. 


THE  NASAL  CAVITY 


1013 


Vessels  and  Nerves. — The  arteries  of  the  nasal  cavities  are  the  anterior  and  posterior  eth- 
moidal branches  of  the  ophthalmic,  which  suppK-  the  ethmoidal  cells,  frontal  sinuses,  and  roof 
of  the  nose;  the  sphenopalatine  branch  of  the  internal  maxillary,  which  supphes  the  mucous 
membrane  covering  the  conchie,  the  meatuses  and  septum;  the  septal  branch  of  the  superior  labial 
of  the  external  maxillary;  the  infraorbital  and  alveolar  branches  of  the  internal  maxillary,  which 
supply  the  lining  membrane  of  the  maxillary  sua  us;  and  the  pharyngeal  branch  of  the  same  artery, 
distributed  to  the  sphenoidal  sinus.  The  ramifications  of  these  vessels  form  a  close  plexiform 
net-work,  beneath  and  in  the  substance  of  the  mucous  membrane. 


TTTrr^''^T^'^-''Tr[n''^-TF'^ 


Fig.  S35.- 


-Section  of  the  olfactory  mucous  membrane.     (Cadiat.)     a.  Epithelium,     h.  Glands  of  Bowman. 
c.  Xen-e  bundles. 


The  veins  form  a  close  cavernous  plexus  beneath  the  mucous  membrane.    This  plexus  is  especi- 
ally well-marked  over  the  lower  part  of  the  septum  and  over  the  middle  and  inferior  conchse.    Some 
of  the  veins  open  into  the  sphenopalatine  vein;  others  join  the  anterior  facial  vein;  some  accom- 
panj'  the  ethmoidal   arteries,  and  end  in  the 
ophthalmic  veins;  and,  lasth',  a  few  commiini- 
cate  with  the  veins  on  the  orbital  surface  of  the 
frontal  lobe  of  the  brain,  thi'ough  the  foramina 
in  the  cribriform  plate  of  the  ethmoid  bone; 
when  the  foramen  caecum  is  patent  it  transmits 
a  vein  to  the  superior  sagittal  sinus. 

The  l3mapliatics  have  akeadv  been  described 
(p.  776). 

The  nerves  of  ordinary  sensation  are:  the 
nasociUarj-  branch  of  the  ophthalmic,  filaments 
from  the  anterior  alveolar  branch  of  the  max- 
illarj^,  the  nerve  of  the  pterj-goid  canal,  the 
nasopalatine,  the  anterior  palatine,  and  nasal 
branches  of  the  sphenopalatine  ganghon. 

The  nasociharj-  branch  of  the  ophthalmic 
distributes  filaments  to  the  forepart  of  the 
septum  and  lateral  wall  of  the  nasal  caAdty. 
Filaments  from  the  anterior  alveolar  nerve 
supply  the  inferior  meatus  and  inferior  concha. 
The  nerve  of  the  pterj-goid  canal  supplies  the 
upper  and  back  part  of  the  septum,  and  superior 

concha;  and  the  upper  nasal  branches  from  the  sphenopalatine  ganglion  have  a  similar  distri- 
bution. The  nasopalatine  nerve  suppUes  the  middle  of  the  septtmi.  The  anterior  palatine 
nerve  supphes  the  lower  nasal  branches  to  the  middle  and  inferior  conchse. 

The  olfactory,  the  special  nerve  of  the  sense  of  smeU,  is  distributed  to  the  olfactory  region. 
Its  fibres  arise  from  the  bipolar  olfactory  cells  and  are  destitute  of  medullary  sheaths.  They 
unite  in  fascicuh  which  form  a  plexus  beneath  the  mucous  membrane  and  then  ascend  in  grooves 
or  canals  in  the  ethmoid  bone;  they  pass  into  the  skuU  thi-ough  the  foramina  in  the  cribriform 
plate  of  the  ethmoid  and  enter  the  under  sm-face  of  the  olfactory  bulb,  in  which  they  ramify 
and  form  synapses  with  the  dendrites  of  the  mitral  cells  (Fig.  772) . 


Fig.  836. — Xen-es  of  septum  of  nose.     Right  side. 


1014        ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 


The  Accessory  Sinuses  of  the  Nose  (Sinus  Paranasales)  (Figs.  833,  834,  837). 

The  accessory  sinuses  or  air  cells  of  the  nose  arc  the  frontal,  ethmoidal,  sphenoidal, 
and  maxillary;  they  \ary  in  size  and  form  in  different  individuals,  and  are  lined 
by  mucous  membrane  directly  continuous  with  that  of  the  nasal  cavities. 

The  frontal  sinuses  (sinvs  froidales),  situated  behind  the  superciliary  arches, 
are  rarely  symmetrical,  and  the  septum  between  them  frequently  deviates  to  one 
or  other' side  of  the  middle  line.  Their  average  measurements  are  as  follows: 
height,  3  cm.;  breadth,  2.5  cm.;  depth  from  before  backward,  2.5  cm.  Each  opens 
into  the  anterior  part  of  the  corresponding  middle  meatus  of  the  nose  through  the 
frontonasal  duct  which  traverses  the  anterior  part  of  the  labyrinth  of  the  ethmoid. 
Absent  at  birth,  they  are  generally  fairly  well  developed  between  the  seventh  and 
eighth  years,  but  only  reach  their  full  size  after  puberty. 

Superior  concha 

"^      Ethmoidal  air  cell 


Superior 
meatus 

Middle 
concha 

Middle 
meatus 

Septum 

7iasi 
Inferior 
concha 
Maxillary 
sinus 
-  Inferior 
7neatus 


Fig.  837. — Coronal  section  of  nasal  cavities. 

The  ethmoidal  air  cells  (ceUulae  ethmoidales)  consist  of  numerous  thin-w^alled 
cavities  situated  in  the  ethmoidal  labyrinth  and  completed  by  the  frontal,  maxilla, 
lacrimal,  sphenoidal,  and  palatine.  They  lie  between  the  upper  parts  of  the  nasal 
cavities  and  the  orbits,  and  are  separated  from  these  cavities  by  thin  bony 
laminae.  On  either  side  they  are  arranged  in  three  groups,  anterior,  middle,  and 
posterior.  The  anterior  and  middle  groups  open  into  the  middle  meatus  of  the 
nose,  the  former  by  way  of  the  infundibulum,  the  latter  on  or  above  the  bulla 
ethmoidalis.  The  posterior  cells  open  into  the  superior  meatus  under  cover  of 
the  superior  nasal  concha;  sometimes  one  or  more  opens  into  the  sphenoidal  sinus. 
The  ethmoidal  cells  begin  to  develop  during  fetal  life. 

The  sphenoidal  sinuses  (sinus  sphenoidales)  contained  within  the  body  of  the 
sphenoid  vary  in  size  and  shape;  owing  to  the  lateral  displacement  of  the  inter- 
vening septum  they"  are  rarely  symmetrical.  The  following  are  their  average 
measurements:  vertical  height,  2.2  cm.;  transverse  breadth,  2  cm.;  antero-posterior 


THE  ACCESSORY  SINUSES  OF  THE  NOSE  1015 

depth,  2.2  cm.  When  exceptionally  large  they  may  extend  into  the  roots  of  the 
pterygoid  processes  or  great  wings,  and  may  invade  the  basilar  part  of  the  occipital 
bone.  Each  sinus  communicates  with  the  sphenoethmoidal  recess  by  means  of 
an  aperture  in  the  upper  part  of  its  anterior  wall.  They  are  present  as  minute 
cavities  at  birth,  but  their  main  development  takes  place  after  puberty. 

The  maxillary  sinus  {sinus  maxillaris;  antrum  of  Ilighmore),  the  largest  of  the 
accessory  sinuses  of  the  nose,  is  a  pyramidal  cavity  in  the  body  of  the  maxilla. 
Its  base  is  formed  by  the  lateral  wall  of  the  nasal  cavity,  and  its  apex  extends  into 
the  zygomatic  process.  Its  roof  or  orbital  wall  is  frequently  ridged  by  the  infra- 
orbital canal,  while  its  floor  is  formed  by  the  alveolar  process  and  is  usually  on  a 
level  with  the  floor  of  the  nose;  projecting  into  the  floor  are  several  conical  eleva- 
tions corresponding  with  the  roots  of  the  first  and  second  molar  teeth,  and  in  some 
cases  the  floor  is  perforated  by  one  or  more  of  these  roots.  The  size  of  the  sinus 
varies  in  dift'erent  skulls,  and  even  on  the  two  sides  of  the  same  skull.  The  follow- 
ing measurements  are  those  of  an  average-sized  sinus:  vertical  height  opposite 
the  first  molar  tooth,  3.75  cm.;  transverse  breadth,  2.5  cm.;  antero-posterior  depth, 
3  cm.  In  the  antero-superior  part  of  its  base  is  an  opening  through  which  it  com- 
municates with  the  lower  part  of  the  hiatus  semilunaris;  a  second  orifice  is  frequently 
seen  in,  or  immediately  behind,  the  hiatus.  The  maxillary  sinus  appears  as  a  shal- 
low groove  on  the  medial  surface  of  the  bone  about  the  fourth  month  of  fetal  life, 
but  does  not  reach  its  full  size  until  after  the  second  dentition.^ 

Applied  Anatomy. — Instances  of  congenital  deformity  of  the  nose  are  occasionally  met  with, 
such  as  complete  absence  of  the  external  nose,  an  aperture  only  being  present;  or  perfect  develop- 
ment on  one  side,  and  suppression  or  malformation  on  the  other.  Deformities  which  have  been 
acquired  are  much  more  common,  such  as  flattening  of  the  nose,  the  result  of  syphihtic  necrosis; 
or  imperfect  development  of  the  nasal  bones  in  cases  of  congenital  syphihs;  or  a  lateral  deviation 
of  the  nose  may  result  from  fracture. 

The  skin  over  the  alse  and  apex  of  the  nose  is  thick  and  closely  adherent  to  subjacent  parts; 
inflammation  of  this  part  is  therefore  very  painful,  on  account  of  the  tension.  It  is  richly  supphed 
with  blood,  and,  the  circulation  here  being  terminal,  vascular  engorgement  is  liable  to  occur 
especially  in  women  at  the  menopause,  and  in  both  sexes  from  disorders  of  digestion,  exposure 
to  cold,  etc.  The  skin  of  the  nose  also  contains  a  large  number  of  sebaceous  foUicles,  and  these, 
as  the  result  of  intemperance,  are  apt  to  become  affected  and  the  nose  reddened,  congested,  and 
irregularly  swollen.  To  this  the  term  "grog  blossom"  is  popularly  apphed.  In  some  of  these 
cases  there  is  enormous  hypertrophy  of  the  skin  and  subcutaneous  tissues.  Epithehoma  and 
rodent  ulcer  may  attack  the  nose,  the  latter  being  the  more  common  of  the  two.  Lupus  and 
syphihtic  ulceration  frequently  affect  the  nose,  and  may  destroy  the  whole  of  the  cartilaginous 
portion.  In  fact,  lupus  vulgaris  begins  more  frequently  on  the  ala  of  the  nose  than  in  any  other 
situation. 

To  examine  the  nasal  cavities,  the  head  should  be  thrown  back  and  the  nose  drawn  upward, 
the  parts  being  dilated  by  some  form  of  speculum.  The  choanae  can  be  explored  by  reflected 
light  from  the  mouth,  through  which  they  can  be  illuminated.  The  examination  is  very  difficult 
to  carry  out,  and,  as  a  rule,  sufficient  information  regarding  the  presence  of  foreign  bodies  or 
tumors  in  the  nasopharynx  can  be  obtained  by  the  introduction  of  the  finger  behind  the  soft 
palate  through  the  mouth.  The  septum  of  the  nose  may  be  displaced  or  may  deviate  from  the 
middle  line;  this  may  be  the  result  of  an  injury  or  of  some  congenital  defect.  Sometimes  the 
deviation  may  be  so  great  that  the  septum  may  come  into  contact  with  the  lateral  wall  of  the 
nasal  cavity,  and  may  even  become  adherent  to  it,  thus  producing  complete  obstruction.  Per- 
foration of  the  septum  is  not  an  uncommon  affection,  and  may  arise  from  several  causes :  syphihtic 
or  tuberculous  ulceration,  blood  tumor  or  abscess  of  the  septum.  When  small,  the  perforation 
may  cause  a  pecuhar  whistling  sound  during  respiration.  When  large,  it  may  lead  to  the  falling 
in  of  the  bridge  of  the  nose. 

Epistaxis  is  a  very  common  affection  in  children.  It  is  rarely  of  much  consequence,  and  will 
almost  always  subside  without  treatment;  but  in  the  more  violent  hemorrhages  of  later  fife  it 
may  be  necessary  to  plug  the  choanse.  A  ready  method  of  regulating  the  bulk  of  the  plug  to  fit 
the  opening  is  to  make  it  of  the  same  size  as  the  terminal  phalanx  of  the  thumb  of  the  patient 
to  be  operated  on. 

1  The  various  measurements  of  the  accessory  sinuses  of  the  nose  are  based  on  those  given  by  Aldren  Turner  in  his 
Accessory  Sinuses  of  the  Nose. 


lOlG       ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

Foreign  bodies,  such  as  buttons,  are  frequently  inserted  into  the  nostrils  by  children,  and 
require  some  care  in  removal,  as  unskilled  attempts  only  result  in  pushing  the  foreign  body 
farther  into  the  nasal  cavity.  Bodies  which  remain  in  the  nose  for  any  length  of  time  set  up 
ulceration  of  the  mucous  membrane,  sometimes  spreading  to  the  bone,  and  a  profuse  purulent 
discharge  results.  A  condition  of  unilateral  nasal  discharge  in  a  child  is  always  suggestive  of 
the  presence  of  a  foreign  body.  The  removal  of  such  objects  is  best  effected  by  giving  the  child 
an  anesthetic,  opening  the  mouth  with  a  gag,  and  placing  the  left  forefinger  in  the  nasopharynx, 
so  as  to  prevent  the  escape  of  the  body  into  the  air  passages;  the  foreign  body  is  then  removed 
through  the  anterior  naris  by  a  suitable  scoop  or  forceps  manipulated  by  the  right  hand. 

Enlargement  of  the  mucous  membrane  covering  the  inferior  or  middle  nasal  conchs  is  a  very 
frequent  accompaniment  of  chronic  nasal  catarrh.  In  old-standing  cases  the  bones  themselves 
may  become  enlarged,  constituting  the  "  hypertrophied  turbinals"  which  are  so  often  the  cause 
of  nasal  ob.struction.  In  the  case  of  the  inferior  concha  either  the  anterior  or  posterior  end  is 
usually  more  especially  affected,  giving  rise  to  a  reddened  mass  of  tissue  often  confused  with  a 
nasal  polypus;  the  appearances,  however,  are  totally  different,  as  the  true  nasal  polypi  appear 
as  gUstening  grayish-white  bodies  between  the  conchse.  Hypertrophy  of  the  conchae  can  be 
temporarily  reduced  to  a  great  extent  by  the  local  application  of  cocaine,  and  if  the  reduction 
by  this  means  is  to  practically  the  normal  condition,  then  treatment  by  appKcation  of  the  galvano- 
cautery  wiU  be  sufficient;  otherwise  the  enlarged  portion  of  the  bone  or  bones  will  require  removal 
by  a  wire  snare  after  the  attachment  to  the  lateral  wall  of  the  nasal  cavity  has  been  freed,  by  special 
nasal  scissors,  in  the  case  of  enlargement  of  the  anterior  end,  and  by  the  .spokeshave  when  the 
posterior  end  is  enlarged.  It  is  highly  inadvisable  to  remove  more  than  is  necessarj',  as  too  free 
removal  results  in  a  dry  condition  of  the  air  passages,  which  conduces  to  a  chronic  dry  pharyngitis 
and  laryngitis. 

Nasal  polypi  are  of  frequent  occurrence;  in  the  common  gelatinous  form  they  spring  from  the 
lateral  wall  of  the  nasal  cavity  and  project  down  between  the  conchse,  giving  rise  to  obstructed 
nasal  respiration.  They  are  always  accompanied  by  purulent  discharge,  and  are  due  in  all 
instances  to  small  areas  of  carious  bone  in  the  region  of  the  bulla  ethmoidalis,  or  about  the  ethmoidal 
or  sphenoidal  air  cells.  They  appear  as  gUstening  grayish-white  bodies  swinging  on  a  pedicle, 
and  the  larger  ones  can  be  encircled  with  a  cold  wire  snare  and  thus  removed;  usually,  however, 
after  the  extirpation  of  the  larger  ones  has  been  carried  out,  numerous  small  polj^pi  can  be  seen 
springing  from  the  region  of  their  bases,  and  cauterization  of  such  affected  areas  must  be  thor- 
oughly carried  out  if  a  recurrence  of  the  trouble  is  to  be  avoided.  In  bad  cases  a  free  curetting 
of  the  ethmoidal  air  cells  may  be  called  for  after  removal  of  the  middle  concha.  Fibrous  polypi 
are  also  more  rarely  met  with,  and  these  are  of  the  nature  of  new  growths;  they  most  frequently 
spring  from  the  base  of  the  skull  behind  the  choanse  and  form  pedunculated  tumors  occupying 
the  nasopharjmx.  Malignant  polypi  also  occur,  most  commonly  originating  in  the  maxillary 
sinus  and  projecting  through  its  medial  wall  into  the  nasal  cavity;  for  such  cases  removal  of  the 
maxiUa  offers  the  only  hope  of  cure. 

Suppuration  in  the  accessory  nasal  sinuses  is  of  frequent  occurrence,  and  in  connection  with 
this  the  situations  at  which  the  various  sinuses  normally  communicate  with  the  nasal  cavities, 
are  important;  thus  one  finds  they  fall  into  two  main  groups:  the  anterior,  opening  into  the 
middle  meatus,  and  draining  the  maxiUary  sinus,  the  frontal  sinus,  and  the  anterior  ethmoidal 
air  cells;  and  the  posterior  group,  opening  into  the  superior  meatus  and  sphenoethmoidal  recess, 
and  draining  the  posterior  ethmoidal  and  sphenoidal  air  cells.  Suppuration  in  the  anterior  group 
is  the  more  common,  and  the  pus  can  be  seen  running  down  over  the  anterior  end  of  the  inferior 
concha,  whereas  in  the  case  of  the  posterior  group  the  pus  does  not  come  foi-ward,  but  runs  back 
into  the  nasopharynx  over  the  posterior  end  of  the  middle  concha.  Again,  it  is  of  importance  to 
notice  that  the  middle  meatus  is  of  such  a  form  that  pus  running  down  from  the  frontal  sinus  is 
directed  by  the  groove  beneath  the  bulla  ethmoidalis  into  the  ostium  of  the  maxillary-  sinus,  so 
that  the  latter  sinus  may,  in  some  cases,  act  as  a  secondary'  reservoir  for  pus  discharged  from  the 
frontal  sinus.  All  the  accessory  sinuses  can  be  and  are  infected  from  the  nasal  cavity,  but  it  should 
be  noted  that  in  the  case  of  the  maxillary  sinus,  the  infection  is  frequently  conveyed  in  another 
way,  and  that  is  from  the  teeth.  This  sinus  is  the  one  most  frequently  the  seat  of  chronic  suppura- 
tion and  it  often  requires  drainage;  this  can  be  carried  out  b}'  drilling  a  hole  thi-ough  the  alveolus 
after  removal  of  a  tooth,  preferabty  the  fir.st  molar,  or  by  gouging  away  the  anterior  surface  of 
the  maxilla,  after  having  reflected  the  gum,  or  by  removing  bone  from  the  lateral  wall  of  the 
inferior  meatus  of  the  nose.  Simple  drainage,  however,  is  not  usuaUj-  sufficient,  and  more  exten- 
sive operations  have  often  to  be  performed.  Distension  of  the  walls  of  the  maxiUary  antrum 
occurs  as  the  result  of  new-growth  or  cyst  formation  within  its  cavity.  Thus  the  facial  sm-face 
may  be  prominently  bulged  outward,  upward  extension  may  displace  the  eyeball  outward,  or 
the  nasal  cavity  on  that  side  may  be  occluded,  giving  rise  to  unilateral  obstruction.  In  some 
cases  the  disease  wiU  perforate  the  palatine  process  of  the  maxiUa  and  a  soft  spot  will  be  found 
under  the  mucoperiosteum.  If  the  disease  be  malignant  in  nature,  nothing  short  of  excision  of 
the  maxiUa  is  of  any  avaU  (see  p.  300). 


THE  TUNICS  OF  THE  EYE  1017 


THE    ORGAN    OF    SIGHT    (ORG ANON   VISUS;    THE   EYE). 

The  bulb  of  the  eye  {bulbiis  ocuJi;  eyeball),  or  organ  of  sight,  is  contained  in  the 
cavity  of  the  orbit,  where  it  is  protected  from  injury  and  moved  by  the  ocular 
muscles.  Associated  with  it  are  certain  accessory  structures,  viz.,  the  muscles, 
fasciae,  eyebrows,  eyelids,  conjunctiva,  and  lacrimal  apparatus. 

The  bulb  of  the  eye  is  imbedded  in  the  fat  of  the  orbit,  but  is  separated  from  it 
by  a  thin  membranous  sac,  the  fascia  bulbi  (page  1037).  It  is  composed  of  segments 
of  two  spheres  of  different  sizes.  The  anterior  segment  is  one  of  a  small  sphere; 
it  is  transparent,  and  forms  about  one-sixth  of  the  bulb.  It  is  more  prominent 
than  the  posterior  segment,  which  is  one  of  a  larger  sphere,  and  is  opaque,  and  forms 
about  five-sixths  of  the  bulb.  The  term  anterior  pole  is  applied  to  the  central  point 
of  the  anterior  curvature  of  the  bulb,  and  that  of  posterior  pole  to  the  central  point 
of  its  posterior  curvature;  a  line  joining  the  two  poles  forms  the  optic  axis.  The 
axes  of  the  two  bulbs  are  nearly  parallel,  and  therefore  do  not  correspond  to  the 
axes  of  the  orbits,  which  are  directed  forward  and  lateralward.  The  optic  nerves 
follow  the  direction  of  the  axes  of  the  orbits,  and  are  therefore  not  parallel;  each 
enters  its  eyeball  3  mm.  to  the  nasal  side  and  a  little  below^  the  level  of  the  posterior 
pole.  The  bulb  measures  rather  more  in  its  transverse  and  antero-posterior  diame- 
ters than  in  its  vertical  diameter,  the  former  amounting  to  about  24  mm.,  the  latter 
to  about  23.5  mm.;  in  the  female  all  three  diameters  are  rather  less  than  in  the  male; 
its  antero-posterior  diameter  at  birth  is  about  17.5  mm.,  and  at  puberty  from  20 
to  21  mm. 

The  bulb  of  the  eye  is  composed  of  three  tunics,  and  of  three  refracting  media. 

The  Tunics  of  the  Eye  (Fig.  838). 

From  without  inward  the  three  tunics  are:  (1)  A  fibrous  tunic,  consisting  of  the 
sclera  behind  and  the  cornea  in  front;  (2)  a  vascular  pigmented  tunic,  comprising, 
from  behind  forward,  the  choroid,  ciliary  body,  and  iris;  and  (3)  a  nervous  tunic, 
the  retina. 

•  The  Fibrous  Tunic  (tunica  fibrosa  ocidi). — The  sclera  and  cornea  (Fig.  838) 
form  the  fibrous  tunic  of  the  bulb  of  the  eye;  the  sclera  is  opaque,  and  constitutes 
the  posterior  five-sixths  of  the  tunic;  the  cornea  is  transparent,  and  forms  the 
anterior  sixth. 

The  Sclera. — The  sclera  has  received  its  name  from  its  extreme  density  and  hard- 
ness; it  is  a  firm,  unyielding  membrane,  serving  to  maintain  the  form  of  the  bulb. 
It  is  much  thicker  behind  than  in  front;  the  thickness  of  its  posterior  part  is  1  mm. 
Its  external  surface  is  of  white  color,  and  is  in  contact  with  the  inner  surface  of  the 
fascia  of  the  bulb;  it  is  quite  smooth,  except  at  the  points  where  the  Recti  and 
Obliqui  are  inserted  into  it;  its  anterior  part  is  covered  by  the  conjunctival  mem- 
brane. Its  inner  surface  is  brown  in  color  and  marked  by  grooves,  in  which  the 
ciliary  nerves  and  vessels  are  lodged ;  it  is  separated  from  the  outer  surface  of  the 
choroid  by  an  extensive  lymph  space  (spatium  perichorioideale)  which  is  traversed 
by  an  exceedingly  fine  cellular  tissue,  the  lamina  suprachorioidea.  Behind  it  is 
pierced  by  the  optic  nerve,  and  is  continuous  through  the  fibrous  sheath  of  this 
nerve  with  the  dura  mater.  Where  the  optic  nerve  passes  through  the  sclera,  the 
latter  forms  a  thin  cribriform  lamina,  the  lamina  cribrosa  sclerae ;  the  minute  orifices 
in  this  lamina  serve  for  the  transmission  of  the  nervous  filaments,  and  the  fibrous 
septa  dividing  them  from  one  another  are  continuous  with  the  membranous  pro- 
cesses which  separate  the  bundles  of  nerve  fibres.  One  of  these  openings,  larger 
than  the  rest,  occupies  the  centre  of  the  lamina;  it  transmits  the  central  artery 
and  vein  of  the  retina.     Around  the  entrance  of  the  optic  nerve  are  numerous 


1018       ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

small  apertures  for  the  transmission  of  the  ciliary  vessels  and  nerves,  and  about 
midway  between  this  entrance  and  the  sclerocorneal  junction  are  four  or  five 
large  apertures  for  the  transmission  of  veins  (venae  vorticosae).  In  front,  the  sclera 
is  directly  continuous  with  the  cornea,  the  line  of  union  being  termed  the  sclero- 
corneal junction.  In  the  inner  part  of  the  sclera  close  to  this  junction  is  a  Circular 
canal,  the  sinus  venosus  sclerae  {canal  of  ScMemm).  In  a  meridional  section  of  this 
region  this  sinus  presents  the  appearance  of  a  cleft,  the  outer  wall  of  which  consists 
of  the  firm  tissue  of  the  sclera,  while  its  inner  wall  is  formed  by  a  triangular  mass 
of  trabecular  tissue  (Fig.  839) ;  the  apex  of  the  mass  is  directed  forward  and  is  con- 
tinuous with  the  posterior  elastic  lamina  of  the  cornea.  The  sinus  is  lined  by 
endothelium  and  communicates  internally  with  the  anterior  chamber  of  the  eye 
and  externallv  with  the  anterior  ciliarv  veins. 


Sulcus  circularly  corveae 
Posterior  cJianiber 

Conjunctiva 


Rectus 
lateralis 


Sinus  venosus  sclerce 
Ciliary  body 

Zonular  spaces 


Hyaloid  canal 


Rectus 
medial  is 

Sclera 

Choroid 

Retina 


Fovea  centralis  ■^^^'^ 

Nerve  sheath 

Fig.  838. — Horizontal  section  of  the  eyeball. 


A.  centralis  retinm 
Optic  nerve 


Structure. — The  sclera  is  formed  of  white  fibrous  tissue  intermixed  with  fine  elastic  fibres; 
flattened  connective-tissue  corpuscles,  some  of  which  are  pigmented,  are  contained  in  cell  spaces 
between  the  fibres.  The  fibres  are  aggregated  into  bundles,  which  are  arranged  chiefly  in  a 
longitudinal  direction.  Its  vessels  are  not  numerous,  the  capillaries  being  of  small  size,  uniting 
at  long  and  wide  intervals.  Its  nerves  are  derived  from  the  cihary  nerves,  but  their  exact  mode 
of  ending  is  not  known. 

The  Cornea. — The  cornea  is  the  projecting  transparent  part  of  the  external  tunic, 
and  forms  the  anterior  sixth  of  the  surface  of  the  bulb.  It  is  almost  circular  in 
outline,  occasionally  a  little  broader  in  the  transverse  than  in  the  vertical  direction. 
It  is  convex  anteriorly  and  projects  like  a  dome  in  front  of  the  sclera.  Its  degree 
of  curvature  varies  in  different  individuals,  and  in  the  same  individual  at  different 
periods  of  life,  being  more  pronounced  in  youth  than  in  advanced  life.  The  cornea 
is  dense  and  of  uniform  thickness  throughout;  its  posterior  surface  is  perfectly 
circular  in  outline,  and  exceeds  the  anterior  surface  slightly  in  diameter.  Imme- 
diately in  front  of  the  sclerocorneal  junction  the  cornea  bulges  inward  as  a  thickened 


THE  TUNICS  OF  THE  EYE 


1019 


rim,  and  heliiiul  this  there  is  a  distinct  furrow  between  the  attachment  of  the  iris 
and  the  sclerocorneal  junction.  This  furrow  has  been  named  by  Arthur  Thomson^ 
the  sulcus  circularis  corneae;  it  is  bounded  externally  by  the  trabecular  tissue 
already  described  as  forming  the  inner  wall  of  the  sinus  venosus  sclerae.  Between 
this  tissue  anil  the  anterior  surface  of  the  attached  margin  of  the  iris  is  an  angular 
recess,  named  the  iridial  angle  or  filtration  angle  of  the  eye  (Fig.  839).  Immediately 
outside  the  filtration  angle  is  a  projecting  rim  of  scleral  tissue  which  appears  in  a 
meridional  section  as  a  small  triangular  area,  termed  the  scleral  spur.  Its  base 
is  continuous  with  the  inner  surface  of  the  sclera  immediately  to  the  outer  side  of  the 
filtration  angle  and  its  apex  is  directed  forward  and  inward.  To  the  anterior  sloping 
margin  of  this  spur  are  attached  the  bundles  of  trabecular  tissue  just  referred  to; 
from  its  posterior  margin  the  meridional  fibres  of  the  Ciliaris  muscle  arise. 


Cornea 


Iris 


Sinus  venosus  sclerce 
Trabecular  tissue 


Sclera 


Scleral  vein 


Badial  muscular  fibres  of  iris 

Circular  fibres  of  Ciliaris 


Meridional  fibres  of  Ciliaris 
Scleral  spur 
Iridial  angle 

Fig.  839. — Enlarged  general  view  of  the  iridial  angle.      (Arthur  Thomson.) 


Structure  (Fig.  S-tO). — The  cornea  consists  from  before  backward  of  four  layers,  viz.:  (1) 
the  corneal  epithelium,  continuous  with  that  of  the  conjunctiva;  (2)  the  substantia  propria; 
(3)  the  posterior  elastic  lamina;  and  (4)  the  endothelium  of  the  anterior  chamber. 

The  corneal  epitheliimi  (epitheliunj  corneae;  anterior  layer)  covers  the  front  of  the  cornea  and 
consists  of  several  layers  of  cells.  The  cells  of  the  deepest  layer  are  columnar;  then  follow  two  or 
three  layers  of  polyhedral  cells,  the  majority  of  which  are  prickle  cells  similar  to  those  found  in 
the  stratiun  mucosum  of  the  cuticle.  Lastly,  there  are  three  or  four  layers  of  squamous  cells, 
with  flattened  nuclei. 

The  substantia  propria  is  fibrous,  tough,  unjdelding,  and  perfectly  transparent.  It  is  com- 
posed of  about  sixty  flattened  lamellae,  superimposed  one  on  another.  These  lamellae  are  made 
up  of  bundles  of  modified  connective  tissue,  the  fibres  of  which  are  directly  continuous  with  those 


1  Atlas  of  the  Eye,  Clarendon  Press,  Oxford,  1912. 


1020       ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

of  the  sclera.  The  fibres  of  each  lamella  are  for  the  most  part  parallel  with  one  another,  but  at 
right  angles  to  those  of  adjacent  lamellae.  Fibres,  however,  frequently  pass  from  one  lamella 
to  the  next. 

The  lamellse  are  connected  with  each  other  by  an  interstitial  cement  substance,  in  which  are 
spaces,  the  corneal  spaces.  These  are  stellate  in  shape  and  communicate  with  one  another  by 
numerous  offsets.  Each  contains  a  cell,  the  corneal  corpuscle,  resembling  in  form  the  space  in 
which  it  is  lodged,  but  not  entirely  filling  it. 


jji'ji/J^-i^'^^f^i^'SlikfSI^ 


Fig.  840.— Vertical  section  of  human  cornea  from  near  the  margin.  (Waldeyer.)  Magnified.  1.  Epithehum. 
2.  Anterior  elastic  lamina.  3.  substantia  propria.  4.  Posterior  elastic  lamma.  5.  tndothehum  ot  the  anterior 
chamber,  a.  Oblique  fibres  in  the  anterior  layer  of  the  substantia  propria,  b.  Lamellse  the  fibres  of  which  are  cut 
across,  producing  a  dotted  appearance,  c.  Corneal  corpuscles  appearing  fusiform  in  section,  d.  LameUae  the  tibres 
of  which  are  cut  longitudinally,  e.  Transition  to  the  sclera,  with  more  distinct  fibrillation,  and  surmounted  by  a 
thicker  epithelium.    /.  Small  bloodvessels  cut  across  near  the  margin  of  the  cornea. 


The  layer  immediately  beneath  the  corneal  epithehum  presents  certain  characteristics  which 
have  led  some  anatomists  to  regard  it  as  a  distinct  membrane,  and  it  has  been  named  the  anterior 
elastic  lamina  (lamina  elastica  anterior;  anterior  limiting  layer;  Bowman's  membrane).  It  differs, 
however,  from  the  posterior  elastic  lamina,  in  presenting  evidence  of  fibrillar  structure,  and  in 
not  having  the  same  tendency  to  curl  inward,  or  to  undergo  fracture,  when  detached  from  the 
other  layers  of  the  cornea.  It  consists  of  extremely  closely  interwoven  fibrils,  similar  to  those 
found  in  the  substantia  propria,  but  contains  no  corneal  corpuscles.  It  may  be  regarded  as  a 
condensed  part  of  the  substantia  propria. 

The  posterior  elastic  lamina  (lamina  elastica  posterior;  membrane  of  Descemet;  membrane  of 
Demours)  covers  the  posterior  surface  of  the  substantia  propria,  and  is  an  elastic,  transparent 
homogeneous  membrane,  of  extreme  thinness,  which  is  not  rendered  opaque  by  either  water, 


THE  TUNICS  OF  THE  EYE 


1021 


alcohol,  or  acids.      When  stri|)])(Hl  from  the  substantia  i)roi)ria  it  curls  u]),  or  rolls  upon  itself 
with  the  attached  surface  innermost. 

At  the  margin  of  the  cornea  the  posterior  elastic  lamina  breaks  up  into  fil)res  which  form  the 
trabecular  tissue  already  described  (p.  1008);  the  spaces  between  the  trabecula?  are  termed  the 
spaces  of  the  angle  of  the  iris  (sixiccs  of  Fonlana);  they  communicate  with  the  sinus  venosus 
scleriB  and  with  the  anterior  chamber  at  the  filtration  angle.  Some  of  the  fibi-es  of  tliis  trabecular 
tissue  are  continued  into  the  substance  of  the  iris,  forming  the  pectinate  ligament  of  the  iris; 
while  others  are  connected  with  the  forepart  of  the  sclera  and  choroid. 

The  endothelium  of  the  anterior  chamber  {endothelium  camerae  anierioris;  -poslerior  layer; 
corneal  endothelium)  covers  the  posterior  surface  of  the  elastic  lamina,  is  reflected  on  to  the 
front  of  the  iris,  and  also  lines  the  spaces  of  the  angle  of  the  iris;  it  consists  of  a  single  stratum 
of  polygonal,  flattened,  nucleated  cells. 

Vessels  and  Nerves. — The  cornea  is  a  non-vascular  structure,  the  capillary  vessels  ending  in 
loops  at  its  circumference.  Lymphatic  vessels  have  not  yet  been  demonstrated  in  it,  but  are 
represented  by  the  channels  in  which  the  bundles  of  nerves  run;  these  channels  are  lined  by  an 
endothelium.  The  nerves  are  numerous  and  are  derived  from  the  ciliary  nerves.  Around  the 
peripherj^  of  the  cornea  they  form  an  annular  plexus,  from  which  fibres  enter  the  substantia  propria. 
They  lose  their  meduUary  sheaths  and  ramify  throughout  its  substance  in  a  dehcate  net-work, 
and  their  terminal  filaments  form  a  firm  and  closer  plexus  on  the  surface  of  the  cornea  proper, 
beneath  the  epithelium.  This  is  termed  the  subepithelial  plexus,  and  from  it  fibrils  are  given  off 
which  ramify  between  the  epithelial  cells,  forming  an  intraepithelial  plexus. 

Dissection. — In  order  to  separate  the  sclera  and  cornea,  so  as  to  expose  the  second  tunic,  the 
eyeball  should  be  immersed  in  a  small  vessel  of  water  and  held  between  the  finger  and  thumb. 
The  sclera  is  then  carefully  incised,  in  the  equator  of  the  globe,  until  the  choroid  is  exposed.  One 
blade  of  a  pair  of  probe-pointed  scissors  is  now  introduced  through  the  opening  thus  made,  and 
the  sclera  divided  around  its  entire  circumference,  and  removed  in  separate  portions.  The  front 
segment  being  then  drawn  forward,  the 
handle  of  the  scalpel  should  be  pressed 
gently  against  it  at  its  connection  with 
the  iris,  and,  these  being  separated,  a 
quantity  of  perfectly  transparent  fluid  will 

escape;    this   is   the    aqueous   humor.     In  >lff''" "  ^^^  j         ^ 

the   course  of   the   dissection   the   ciliary  -         -  - 

nerves  (Fig.  841)  may  be  seen  lying  in 
the  loose  cellular  tissue  between  the  chor- 
oid and  sclera  or  continued  in  dehcate 
grooves  on  the  inner  surface  of  the  latter 
membrane. 

The  Vascular  Tunic  (tunica  vascu- 
losa  oculi)  (Figs.  841,  842,  843).— 
The  vascular  tunic  of  the  eye  is 
formed  from  behind  forward  by  the 
choroid,  the  cihary  body,  and  the  iris. 

The  choroid  invests  the  posterior 
five-sixths  of  the  bulb,  and  extends 
as  far  forward  as  the  ora  serrata  of 
the  retina.  The  cihary  body  connects 
the  choroid  to  the  circumference  of 
the  iris.  The  iris  is  a  circular  dia- 
phragm behind  the  cornea,  and  pre- 
sents near  its  centre  a  rounded 
aperture,  the  pupil. 

The  Choroid  (chorioidea) . — The  choroid  is  a  thin,  highly  vascular  membrane,  of 
a  dark  brown  or  chocolate  color,  investing  the  posterior  five-sixths  of  the  globe; 
it  is  pierced  behind  by  the  optic  nerve,  and  in  this  situation  is  firmly  adherent  to 
the  sclera.  It  is  thicker  behind  than  in  front.  Its  outer  surface  is  loosely  connected 
by  the  lamina  suprachorioidea  with  the  sclera ;  its  inner  surface  is  attached  to  the 
pigmented  layer  of  the  retina. 

Structure. — The  choroid  consists  mainly  of  a  dense  capillary  plexus,  and  of  small  arteries 
and  veins  carrying  blood  to  and  returning  it  from  this  plexus.    On  its  external  surface  is  a  thin 


Fig.  8-11. — The  choroid  and  iris.      (Enlarged.) 


1022       ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

membrane,  the  lamina  suprachorioidea,  composed  of  delicate  non-vascular  lamella} — each  lamella 
consisting  of  a  net-work  of  fine  elastic  fibres  among  which  are  branched  pigment  cells.  The  spaces 
between  the  lamellae  are  lined  by  endothelium,  and  open  freely  into  the  perichoroidal  Ij-mph 
space,  which,  in  its  turn,  communicates  with  the  periscleral  space  by  the  perforations  in  the 
sclera  through  which  the  vessels  and  nerves  are  transmitted. 


Interior  ciliary  artery 


Short  ciliary  arteri 


Anterior  ciliary  artery 


Fig.  842. — The  arteries  of  the  choroid  and  iris.     The  greater  part  of  the  sclera  has  been  removed.     (Enlarged.) 


Internal  to  this  lamina  is  the  choroid  proper,  consisting  of  two  layers:  an  outer,  composed 
of  small  arteries  and  veins,  with  pigment  cells  interspersed  between  them;  and  an  inner,  consist- 
ing of  a  capillary  plexus.  The  outer  layer  {lanmia  vasculosa)  consists,  in  part,  of  the  larger  branches 
of  the  short  cihary  arteries  which  run  forward  between  the  veins,  before  they  bend  inward  to  end 
in  the  capillaries,  but  is  formed  principally  of  veins,  named,  from  their  arrangement,  the  venae 

vorticosae.  They  converge  to  four  or 
five  equidistant  trunks,  which  pierce  the 
sclera  about  midway  between  the  sclero- 
corneal  junction  and  the  entrance  of  the 
optic  nerve.  Interspersed  between  the 
vessels  are  dark  star-shaped  pigment 
cells,  the  processes  of  which,  communicat- 
ing with  those  of  neighboring  cells,  form 
a  deUcate  net-work  or  stroma,  which 
toward  the  inner  surface  of  the  choroid 
loses  its  pigmentary  character.  The 
inner  layer  {lamina  choriocapillaris)  con- 
sists of  an  exceedingly  fine  capillary 
plexus,  formed  by  the  short  ciliary  vessels; 
the  net-work  is  closer  and  jfiner  in  the  pos- 
terior than  in  the  anterior  part  of  the 
choroid.  About  1.25  cm.  behind  the 
cornea  its  meshes  become  larger,  and  are 
continuous  with  those  of  the  ciliary 
processes.  These  two  laminse  are  con- 
nected by  a  stratum  intermedium  con- 
sisting of  fine  elastic  fibres.  On  the  inner 
surface  of  the  lamina  choriocapillaris  is 
a  very  thin,  structureless,  or  faintly 
fibrous  membrane,  called  the  lamina  basalis;  it  is  closely  connected  with  the  stroma  of  the 
choroid,  and  separates  it  from  the  pigmentary  layer  of  the  retina. 

Tapetum. — This  name  is  applied  to  the  outer  and  posterior  part  of  the  choroid,  which  in  many 
animals  presents  an  iridescent  appearance. 

Dissection. — The  ciliary  body  should  now  be  examined.  It  may  be  exposed,  either  by  detach- 
ing the  iris  from  its  connection  with  the  Ciliaris  muscle,  or  b}'  making  a  transverse  section  of  the 
globe,  and  examining  it  from  behind. 


Fig.  843. — The  veins  of  the  choroid,      (Enlarged.) 


THE  TUNICS  OF  THE  EYE 


1023 


The  Ciliary  Body  {corpus  ciliare). — The  ciliary  body  comprises  the  orbiculus 
ciliaris,  the  ciliary  processes,  and  the  Ciliaris  muscle. 

The  orbiculus  ciliaris  is  a  zone  of  al)()ut  4  miii.  in  width,  directly  continuous 
with  the  anterior  part  of  the  choroid;  it  presents  numerous  ridges  arranged  in  a 
radial  manner  (Fiii'.  S44). 


Ora  ■•icrrata 

Pfirs  cilidrisf  retinae 
hail/  process 


Orbiculus 
ciliaris 


fU—  Eetina 
l-i- —  Ckoroid 
Sclera 


Fig.  844. — Interior  of  anterior  half  of  bulb  of  eye. 

The  ciliary  processes  {processus  ciliares)  are  formed  by  the  inward  folding  of  the 
various  layers  of  the  choroid,  i.  e.,  the  choroid  proper  and  the  lamina  basalis,  and 
are  received  between  corresponding  foldings  of  the  suspensory  ligament  of  the  lens. 
They  are  arranged  in  a  circle,  and  form  a  sort  of  frill  behind  the  iris,  around  the 
margin  of  the  lens  (Fig.  844) .  They  vary  from  sixty  to  eighty  in  number,  lie  side 
by  side/ and  may  be  divided  into  large  and  small;  the  former  are  about  2.5  mm. 
in  length,  and  the  latter,  consisting  of  about  one-third  of  the  entire  number,  are 
situated  in  spaces  between  them,  but  without  regular  arrangement.  They  are 
attached  by  their  periphery  to  three  or  four  of  the  ridges  of  the  orbiculus  ciliaris, 
and  are  continuous  with  the  layers  of  the  choroid:  their  opposite  extremities  are 
free  and  rounded,  and  are  directed  toward  the  posterior  chamber  of  the  eyeball  and 
circumference  of  the  lens.  In  front,  they  are  continuous  with  the  periphery  of  the 
iris.  Their  posterior  surfaces  are  connected  with  the  suspensory  ligament  of  the 
lens. 

Structure. — The  ciliary  processes  (Figs.  845,  846)  are  similar  in  structure  to  the  choroid,  but 
the  vessels  are  larger,  and  have  chiefly  a  longitudinal  direction.  Their  posterior  surfaces  are 
covered  by  a  bilaminar  layer  of  black  pigment  cells,  which  is  continued  forward  from  the  retina, 
and  is  named  the  pars  ciliaris  retinae.  In  the  stroma  of  the  ciliary  processes  there  are  also  stellate 
pigment  cells,  but  these  are  not  so  numerous  as  in  the  choroid  itself. 

The  Ciliaris  muscle  {m.  ciliaris;  Bowman  s  muscle)  consists  of  unstriped  fibres: 
it  forms  a  grayish,  semitransparent,  circular  band,  about  3  mm.  broad,  on  the  outer 
surface  of  the  forepart  of  the  choroid.  It  is  thickest  in  front,  and  consists  of  two 
sets  of  fibres,  meridional  and  circular.  The  meridional  fibres,  much  the  more  numer- 
ous, arise  from  the  posterior  margin  of  the  scleral  spur  (page  1019) ;  they  run  back- 
ward, and  are  attached  to  the  ciliary  processes  and  orbiculus  ciliaris.  One  bundle, 
according  to  Waldeyer,  is  inserted  into  the  sclera.  The  circular  fibres  are  internal 
to  the  meridional  ones,  and  in  a  meridional  section  appear  as  a  triangular  zone 


1024       ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 


behind  the  filtration  angle  and  close  to  the  circumference  of  the  iris.  They  are 
well-developed  in  hypermetropic,  but  are  rudimentary  or  absent  in  myopic  eyes. 
The  Ciliaris  muscle  is  the  chief  agent  in  accommodation,  /.  e.,  in  adjusting  the 
eye  to  the  vision  of  near  objects.  When  it  contracts  it  draws  forward  the  ciliary 
processes,  relaxes  the  suspensory  ligament  of  the  lens,  and  thus  allows  the  lens 
to  become  more  convex. 

The  Iris. — The  iris  has  received  its  name  from  its  various  colors  in  different 
individuals.     It  is  a  thin,  circular,  contractile  disk,  suspended  in  the  aqueous 
humor  between  the  cornea  and 
lens,  and  perforated  a   little  to 
the  nasal  side  of  its  centre  by  a 

circular  aperture,  the  pupil.     By  ^^*\/^^       ^' 

its  periphery  it  is  continuous  with  /--^_  p~ 

the  ciliary  body,  and  is  also  con- 
nected with  the  posterior  elastic 
lamina  of  the  cornea  by  means 

of    the    pectinate   ligament;    its  ^""^^  '-^     \     \  '^ 

surfaces  are  flattened,  and  look 
forward  and  backward,  the  ante- 


FiG.  845. — Vessels  of  the  choroid,  ciliary  pro- 
cesses, and  iris  of  a  child.  (Arnold.)  Magnified 
10  times,  a.  Capillary  net-work  of  the  posterior 
part  of  the  choroid,  ending  at  b,  the  ora  serrata. 
c.  Arteries  of  the  corona  ciliaris,  supplying  the 
ciliary  processes,  d,  and  passing  into  the  iris  e. 
/.  The  capillarj'-  net-work  close  to  the  pupillary 
margin  of  the  iris. 


Fig.  846. — Diagrammatic  representation  of  the  course  of 
the  vessels  in  the  eye.  Horizontal  section.  (Leber.)  Arteries 
and  capillaries  red;  veins  blue.  O.  Entrance  of  optic  nerve. 
a.  Short  posterior  ciliary  arteries.  6.  Long  posterior  ciliary 
arteries,  c.  Anterior  ciliary  vessels,  d.  Posterior  conjunc- 
tival vessels,  d'.  Anterior  conjunctival  vessels,  e.  Central 
vessels  of  the  retina.  /.  Vessels  of  the  inner  sheath  of  the 
optic  nerve,  g.  Vessels  of  the  outer  sheath,  h.  Vorticose 
vein.  i.  Short  posterior  ciliary  vein.  k.  Branches  of  the 
short  posterior  ciliary  arteries  to  the  optic  nerve.  I.  Anasto- 
naosis  of  choroidal  vessels  with  those  of  optic  nerve.  m. 
Choriocapillaris.  ?i.  Episcleral  vessels,  o.  Recurrent  artery 
of  the  choroid,  p.  Circulus  iridis  major  (in  section),  g. 
Vessels  of  iris.  r.  Vessels  of  ciliary  process,  s.  Branch  from 
ciliary  muscle  to  vorticose  vein.  t.  Branch  from  ciliary  muscle 
to  anterior  ciliary  vein.  u.  Sinus  venosus  sclerae.  v.  Capil- 
lary loop  at  margin  of  cornea. 


rior  toward  the  cornea,  the  posterior  toward  the  ciliary  processes  and  lens.  The 
iris  divides  the  space  between  the  lens  and  the  cornea  into  an  anterior  and  a 
posterior  chamber.  The  anterior  chamber  of  the  eye  is  bounded  in  front  by  the  pos- 
terior surface  of  the  cornea;  behind  by  the  front  of  the  iris  and  the  central  part  of 
the  lens.  The  posterior  chamber  is  a  narrow  chink  behind  the  peripheral  part  of 
the  iris,  and  in  front  of  the  suspensory  ligament  of  the  lens  and  the  ciliary  pro- 
cesses. In  the  adult  the  two  chambers  communicate  through  the  pupil,  but  in 
the  fetus  up  to  the  seventh  month  they  are  separated  by  the  viemhrana  pupiUaris. 


THE  TUNICS  OF  THE  EYE 


1025 


Structure. — The  iris  is  composed  of  tlu'  folic iwiiifi  slniclurcs: 

1.  In  front  is  a  layer  of  flattened  endothelial  cells  placed  on  a  delicate  hyaline  basement  mem- 
brane. This  layer  is  continnous  with  the  endothelimn  covering  the  posterior  elastic  lamina  of 
the  cornea,  antl  in  individuals  with  dark-colored  irides  the  cells  contain  pigment  granules. 

2.  The  stroma  (slronin  irtdis)  of  the  iris  consists  of  fibres  and  cells.  The  former  are  made  up 
of  dehcate  bundles  of  fibrous  tissue;  a  few  fibres  at  the  circumference  of  the  iris  have  a  circular 
direction;  but  the  majority  radiate  toward  the  pupil,  forming  by  their  interlacement,  delicate 
meshes,  in  which  the  vessels  and  nerves  are  contained.  Interspersed  between  the  bundles  of 
connecti\'e  tissue  are  numerous  branched  cells  with  fine  processes.  In  dark  eyes  many  of  them 
contain  ])igment  granules,  but  in  blue  eyes  and  the  eyes  of  albinos  they  are  unpigmented. 

3.  The  muscular  fibres  are  involuntary,  and  consist  of  circular  and  radiating  fibres.  The 
circular  fibres  form  the  Sphincter  pupillac;  they  are  arranged  in  a  narrow  band  about  1  mm.  in 
width  which  surrounds  the  margin  of  the  pupil  toward  the  posterior  surface  of  the  iris;  those 
near  the  free  margin  are  closely  aggregated;  those  near  the  periphery  of  the  band  are  somewhat 
separated  and  form  incomplete  circles.  The  radiating  fibres  form  the  Dilatator  pupillae;  they 
converge  from  the  circumference  toward  the  centre,  and  blend  with  the  circular  fibres  near  the 
margin  of  the  pupil. 

4.  The  posterior  surface  of  the  iris  is  of  a  deep  pvu-ple  tint,  being  covered  by  two  layers  of 
pigmented  columnar  epithelium,  continuous  at  the  periphery  of  the  iris  with  the  pars  ciUaris 
retina?.  This  pigmented  epithelium  is  named  the  pars  iridica  retinae,  or,  from  the  resemblance 
of  its  color  to  that  of  a  ripe  grape,  the  uvea. 

The  color  of  the  iris  is  produced  by  the  reflection  of  light  from  dark  pigment  cells  miderlying 
a  translucent  tissue,  and  is  therefore  determined  by  the  amount  of  the  pigment  and  its  distribu- 
tion throughout  the  texture  of  the  iris.  The  number  and  the  situation  of  the  pigment  cells  difi'er 
in  different  irides.  In  the  albino  pigment  is  absent;  in  the  various  shades  of  blue  eyes  the  pigment 
cells  are  confined  to  the  posterior  surface  of  the  iris,  whereas  in  gray,  brown,  and  black  eyes 
pigment  is  found  also  in  the  cells  of  the  stroma  and  in  those  of  the  endothelium  on  the  front  of 
the  iris. 


Fig.  S47. — The  iris,  viewed  from  in  front,  with  its  greater  and  smaller  arterial  circles.  (Testut.)  a.  Choroid. 
b.  Ciliaris  muscle,  c.  Iris.  d.  Pupil.  1  and  1'.  The  two  long  ciliary  arteries,  with  2,  their  ascending  branch  of  bifurca- 
tion; 3,  their  descending  branch  of  bifurcation.  4.  The  anterior  ciliary  arteries.  5.  Circulus  major;  6,  its  branches 
radiating  through  the  iris.    7.  Circulus  minor  around  the  pupil. 


Vessels  and  Nerves. — The  arteries  of  the  iris  are  derived  from  the  long  and  anterior  ciliary 
arteries,  and  from  the  vessels  of  the  ciliary  processes  (see  p.  650).  Each  of  the  two  long  ciliary 
arteries,  having  reached  the  attached  margin  of  the  ii-is,  divides  into  an  upper  and  lower  branch; 
these  anastomose  with  corresponding  branches  from  the  opposite  side  and  thus  encircle  the  iris; 
into  this  Avascular  circle  {circulus  arteriosus  major)  the  anterior  ciliary  arteries  pour  their  blood, 
and  from  it  vessels  converge  to  the  free  margin  of  the  ii'is,  and  there  communicate  and  form  a 
second  circle  {.circulus  arteriosus  minor)  (Figs.  846  and  847). 
65 


1026       ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

The  nerves  of  the  choroid  and  iris  are  the  long  and  short  cihary;  the  former  being  branches 
of  the  nasocihary  nerve,  the  latter  of  the  cihary  ganghon.  They  pierce  the  sclera  around  the 
entrance  of  the  optic  nerv^e,  run  forward  in  the  perichoroidal  space,  and  supply  the  bloodvessels 
of  the  choroid.  After  reaching  the  iris  they  form  a  plexus  around  its  attached  margin;  from  this 
are  derived  non-meduUated  fibres  which  end  in  the  Sphincter  and  Dilatator  pupillae;  their  exact 
mode  of  termination  has  not  been  ascertained.  Other  fibres  from  the  plexus  end  in  a  net-work 
on  the  anterior  surface  of  the  iris.  The  fibres  derived  through  the  motor  root  of  the  ciliary  gangUon 
from  the  oculomotor  nerve,  supply  the  Sphincter,  while  those  derived  from  the  sympathetic  supply 
the  Dilatator. 

Membrana  Pupillaris. — In  the  fetus,  the  pupil  is  closed  by  a  delicate  vascular 
membrane,  the  membrana  pupillaris,  which  divides  the  space  in  which  the  iris  is 
suspended  into  two  distinct  chambers.  The  vessels  of  this  membrane  are  partly 
derived  from  those  of  the  margin  of  the  iris  and  partly  from  those  of  the  capsule 
of  the  lens;  they  have  a  looped  arrangement,  and  converge  toward  each  other  with- 
out anastomosing.  About  the  sixth  month  the  membrane  begins  to  disappear 
by  absorption  from  the  centre  toward  the  circumference,  and  at  birth  only  a  few 
fragments  are  present;  in  exceptional  cases  it  persists. 


Gptic  disc 


Macula  lutea 


Sclera 
Choroid 

Retina 
Fig.  848. — Interior  of  posterior  half  of  bulb  of  left  eye.    The  -veins  are  darker  in  appearance  than  the  arteries. 

The  Retina  {tunica  interna). — The  retina  is  a  delicate  nervous  membrane,  upon 
which  the  images  of  external  objects  are  received.  Its  outer  surface  is  in  contact 
with  the  choroid;  its  inner  with  the  hyaloid  membrane  of  the  vitreous  body.  Be- 
hind, it  is  continuous  with  the  optic  nerve;  it  gradually  diminishes  in  thickness 
from  behind  forward,  and  extends  nearly  as  far  as  the  ciliary  body,  where  it  appears 
to  end  in  a  jagged  margin,  the  ora  serrata.  Here  the  nervous  tissues  of  the  retina 
end,  but  a  thin  prolongation  of  the  membrane  extends  forward  over  the  back  of 
the  ciliary  processes  and  iris,  forming  the  pars  ciliaris  retinae  and  pars  iridica  retinae 
already  referred  to.  This  for^^ard  prolongation  consists  of  the  pigmentary  layer 
of  the  retina  together  with  a  stratum  of  columnar  epithelium.  The  retina  is  soft, 
semitransparent,  and  of  a  purple  tint  in  the  fresh  state,  owing  to  the  presence  of  a 
coloring  material  named  rhodopsin  or  visual  purple;  but  it  soon  becomes  clouded, 
opaque,  and  bleached  when  exposed  to  sunlight.  Exactly  in  the  centre  of  the 
posterior  part  of  the  retina,  corresponding  to  the  axis  of  the  eye,  and  at  a  point 
in  which  the  sense  of  vision  is  most  perfect,  is  an  oval  yellowish  area,  the  macula 
lutea;  in  the  macula  is  a  central  depression,  the  fovae  centralis  (Fig.  848).  At  the 
fovea  centralis  the  retina  is  exceedinglv  thin,  and  the  dark  color  of  the  choroid  is 


THE  TUNICS  OF  THE  EYE 


1027 


distinctly  seen  through  it.  About  )]  mm.  to  the  nasal  side  of  the  mac-ula  hitae 
is  the  entrance  of  the  optic  nerve  {optic  disk),  the  circumference  of  which  is  shghtly 
raised  to  form  an  eminence  {coUiculus  nervi  optici)  (Fig.  849);  the  arteria  centraHs 
retinae  pierces  the  centre  of  the  cHsk.  This  is  the  only  part  of  the  surface  of  the 
retina  which  is  insensitive  to  liuht,  and  it  is  termed  the  blind  spot. 


Lamitia  cnhrosa      CoUiculus  nervi  optici 

ur    ih,a 


Reiiiui 


Choroid  ■ — ; 


Sclera 


Posterior 
short  ciliarti 
arteni  and     ^^ 
vein  ^.J2 

Pial  sheath 

Arachnoid 
sheath 

Dural  sheath 
Iiitcrvaginal  spaces 


Bundles  of 
optic  nerve 


Central  artery  and 
vein  of  retina 


Fig.  849. — The  terminal  portion  of  the  optic  nerve  and  its  entrance  into  the  eyeball,  in  horizontal  section.    (Toldt.) 


Structure   (Figs.  850,  851). — The  retina  consists  of  an  outer  pigmented  laj-er  and  an  inner 
nervous  stratum  or  retina  proper. 

The  pigmented  layer  consists  of  a  single  stratum  of  cells.  When  viewed  from  the  outer  surface 
these  cells  are  smooth  and  hexagonal  in  shape;  when  seen  m  section  each  cell  consists  of  an  outer 
non-pigmented  part  contaioing  a  large  oval  nucleus  and  an  inner 
pigmented  portion  which  extends  as  a  series  of  straight  thread- 
like processes  between  the  rods,  this  being  especially  the  case 
when  the  eye  is  exposed  to  hght.  In  the  eyes  of  albinos  the  cells 
of  this  laj'er  are  destitute  of  pigment. 

Retina  Proper. — The  nervous  structures  of  the  retina  proper 
are  supported  by  a  series  of  non-nervous  or  sustentacular  fibres, 
and,  when  examined  microscopicaUj'  by  means  of  sections  made 
perpendicularly  to  the  surface  of  the  retina,  are  found  to  con- 
sist of  seven  layers,  named  from  within  outward  as  follows: 

1.  Stratum  opticum. 

2.  GangUonic  layer. 

3.  Inner  plexiform  layer. 

4.  Irmer  nuclear  laj-er,  or  layer  of  inner  granules. 

5.  Outer  plexiform  laj^er. 

6.  Outer  nuclear  layer,  or  laj^er  of  outer  granules. 

7.  Layer  of  rods  and  cones. 
1.  The  stratum  opticum  or  layer  of  nerve  fibres  is  formed  by 

the  expansion  of  the  fibres  of  the  optic  nerve;  it  is  tliickest  near 

the  porus  opticus,  gradually  diminishing  toward  the  ora  serrata. 

As  the  nerve  fibres  pass  through  the  lamina  cribrosa  sclerae, 

they  lose  their  medullary  sheaths  and  are  continued  onward 

through  the  choroid  and  retina  as  simple  axis-cy Under s.    When 

they  reach  the  internal  sm-face  of  the  retina  they  radiate  from 

then-  point  of  entrance  over  this  surface  grouped  in  bundles,  and  in  many  places  arranged  ia 

plexuses.    Most  of  the  fibres  are  centripetal,  and  are  the  direct  continuations  of  the  axis-cylinder 

processes  of  the  cells  of  the  ganglionic  layer,  but  a  few  of  them  are  centrifugal  and  ramify  in  the 

inner  plexiform  and  inner  nuclear  laj^ers,  where  they  end  in  enlarged  extremities. 


Fig.  850.  —  Section  of  retina. 
(Magnified.)  a.  Menibrana  liniitans 
interna,  b.  Stratuna  opticum.  c. 
Ganglionic  layer,  d.  Inner  plexiform 
layer.  e.  Inner  nuclear  layer.  /. 
Outer  plexiform  layer,  g.  Outer  nu- 
clear layer,  h.  ^lembrana  liniitans 
externa,  i.  Layer  of  rods  and  cones. 
k.  Pigmented  layer,  m.  Fibres  of 
IMuUer. 


1028       ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

2.  The  ganglionic  layer  consists  of  a  single  layer  of  large  ganglion  cells,  except  in  the  macula 
lutea,  where  there  are  several  strata.  The  cells  are  somewhat  flask-shaped;  the  rounded  internal 
surface  of  each  resting  on  the  stratum  opticum,  and  sending  off  an  axon  which  is  prolonged  into 
it.  From  the  opposite  end  numerous  dendrites  extend  into  the  inner  plexiform  layer,  where 
they  branch  and  form  flattened  arborizations  at  different  levels.  The  gangUon  cells  vary  much 
in  size,  and  the  dendrites  of  the  smaller  ones  as  a  rule  arborize  in  the  inner  plexiform  layer  as  soon 
as  they  enter  it;  while  those  of  the  larger  cells  ramify  close  to  the  inner  nuclear  layer. 

3.  The  inner  plexiform  layer  is  made  up  of  a  dense  reticulum  of  minute  fibrils  formed  by  the 
interlacement  of  the  dendrites  of  the  ganghon  cells  with  those  of  the  cells  of  the  inner  nuclear 
layer;  within  this  reticulmii  a  few  branched  spongioblasts  are  sometimes  imbedded. 

4.  The  inner  nuclear  layer  or  layer  of  inner  granules  is  made  up  of  a  number  of  closely  packed 
cells,  of  which  there  are  three  varieties,  viz.:    bipolar  cells,  horizontal  cells,  and  amacrine  cells. 

Memhrana 
litnitans  interna  ■• 
Stratum  opticum  -  ■\  ^^ 

Ganglionic  layer-— 


Inner  plexiform  .. 
layer 


Centrifugal  fibre  '' 


Inner  nuclear 
layer 

Fibre  of  Mailer  ■ 

Outer  plexiform 

layer 

Outer  nuclear 
layer 

Membrana 
limitans  exterw 


Layer  of  rods 
and  cones 


Diffuse  amacrine 
cell 

''-■  Amacrine  cells 

■-'  Horizontal  cell 


Rod  granules 
Cone  gramdes 


I  o  t-  o:  f  o.  I-  o   1"'-^''^"'''^^^^^^  layer 


Fig.  851. — Plan  of  retinal  neurons.      (After  Cajal.) 


The  bipolar  cells,  by  far  the  most  numerous,  are  round  or  oval  in  shape,  and  each  is  prolonged 
into  an  inner  and  an  outer  process.  They  are  divisible  into  rod  bipolars  and  cone  bipolars.  The 
inner  processes  of  the  rod  bipolars  run  through  the  inner  plexiform  layer  and  arborize  around 
the  bodies  of  the  cells  of  the  ganglionic  layer;  their  outer  processes  end  in  the  outer  plexiform 
layer  in  tufts  of  fibrils  around  the  button-hke  ends  of  the  inner  processes  of  the  rod  granules. 
The  inner  processes  of  the  cone  bipolars  ramify  in  the  inner  plexiform  layer  in  contact  with  the 
dendrites  of  the  ganghonic  cells. 

The  horizontal  cells  he  in  the  outer  part  of  the  inner  nuclear  layer  and  possess  somewhat 
flattened  cell  bodies.  Their  dendrites  divide  into  numerous  branches  in  the  outer  plexiform 
layer,  while  their  axons  run  horizontally  for  some  distance  and  finally  ramifj^  in  the  same  layer. 

The  amacrine  cells  are  placed  in  the  inner  part  of  the  inner  nuclear  layer,  and  are  so  named 
because  they  have  not  yet  been  shown  to  possess  axis-cyhnder  processes.  Their  dendrites  undergo 
extensive  ramification  in  the  inner  plexiform  layer. 

5.  The  outer  plexiform  layer  is  much  thinner  than  the  inner;  but,  like  it,  consists  of  a  dense 
net-work  of  minute  fibrils  derived  from  the  processes  of  the  horizontal  cells  of  the  preceding  layer, 
and  the  outer  processes  of  the  rod  and  cone  bipolar  granules,  which  ramify  in  it,  forming  arboriza- 
tions around  the  enlarged  ends  of  the  rod  fibres  and  with  the  branched  foot  plates  of  the  cone 
fibres. 

6.  The  outer  nuclear  layer  or  layer  of  outer  granules,  hke  the  inner  nuclear  layer,  contains 
several  strata  of  oval  nuclear  bodies;  thej''  are  of  two  kinds,  viz.:     rod  and  cone  granules,  so 


THE  r  CMC'S  OF  THE  EYE  1029 

named  on  account  of  their  being  resix-ctively  connected  with  the  rods  and  cones  of  the  next  layer. 
The  rod  granules  are  much  the  more  nvunerous,  and  are  placed  at  different  levels  throughout 
the  laj'cr.  I'heir  nuclei  present  a  peculiar  cross-striped  appearance,  and  prolonged  from  either 
extremity  of  each  cell  is  a  fine  process;  the  outer  process  is  continuous  with  a  single  rod  of  the 
layer  of  rods  and  cones;  the  inner  ends  in  the  outer  plexiform  layer  in  an  enlarged  extremity,  and 
is  imbedded  in  the  tuft  into  which  the  outer  processes  of  the  rod  bipolar  cells  break  up.  In  its 
course  it  presents  numerous  varicosities.  The  cone  granules,  fewer  in  number  than  the  rod 
granules,  are  placed  close  to  the  membrana  limitans  externa,  through  which  they  are  continuous 
with  the  cones  of  the  layer  of  rods  and  cones.  They  do  not  present  any  cross-striation,  but  con- 
tain a  pj'riform  nucleus,  which  ahnost  completely  fills  the  cell.  From  the  inner  extremity  of  the 
granule  a  thick  process  passes  into  the  outer  plexiform  layer,  and  there  expands  into  a  pyramidal 
enlargement  or  foot  plate,  from  which  are  given  off  numerous  fine  fibrils,  that  come  in  contact 
with  the  outer  processes  of  the  cone  bipolars. 

7.  The  Layer  of  Bods  and  Cones  (Jacob's  membrane) . — The  elements  composing  this  layer  are 
of  two  kinds,  rods  and  cones,  the  former  being  much  more  numerous  than  the  latter  except  in 
the  macula  lutea.  The  rods  are  cylindrical,  of  ncarty  uniform  thickness,  and  are  arranged  per- 
pendicularty  to  the  sm-face.  Each  rod  consists  of  two  segments,  an  outer  and  inner,  of  about 
equal  lengths.  The  segments  differ  from  each  other  as  regards  refraction  and  in  their  behavior 
toward  coloring  reagents;  the  inner  segment  is  stained  by  carmine,  iodine,  etc.;  the  outer  segment 
is  not  stained  bj'  these  reagents,  but  is  colored  j'ellowish  bro'mi  by  osmic  acid.  The  outer  segment 
is  marked  b}^  transverse  striae,  and  tends  to  break  up  into  a  number  of  thin  disks  superimposed 
on  one  another;  it  also  exhibits  faint  longitudinal  markings.  The  deeper  part  of  the  inner  seg- 
ment is  indistinctly  granular;  its  more  superficial  part  presents  a  longitudinal  striation,  being 
composed  of  fine,  bright,  highly  refracting  fibrils.  The  visual  purple  or  rhodopsin  is  found  only 
in  the  outer  segments. 

The  cones  are  conical  or  flask-shaped,  their  broad  ends  resting  upon  the  membrana  limitans 
externa,  the  narrow-pointed  extremity  being  turned  to  the  choroid.  Like  the  rods,  each  is  made 
up  of  two  segments,  outer  and  inner;  the  outer  segment  is  a  short  conical  process,  whiich,  like 
the  outer  segment  of  the  rod,  exliibits  transverse  strise.  The  inner  segment  resembles  the  inner 
segment  of  the  rods  in  structure,  presenting  a  superficial  striated  and  deep  gi'anular  part,  but 
differs  from  it  in  size  and  shape,  being  bulged  out  lateral!}^  and  fiask-shaped.  The  chemical 
and  optical  characters  of  the  two  portions  are  identical  with  those  of  the  rods. 

Supporting  Frame-work  of  the  Retina. — The  nervous  layers  of  the  retina  are  connected  together 
by  a  supporting  frame-work,  formed  bj^  the  sustentacular  fibres  of  Miiller;  these  fibres  pass 
through  all  the  nervous  layers,  except  that  of  the  rods  and  cones.  Each  begins  on  the  inner  surface ' 
of  the  retina  by  an  expanded,  often  forlved  base,  which  sometimes  contains  a  spheroidal  body 
staining  deeply  with  hematoxjdin,  the  edges  of  the  bases  of  adjoining  fibres  being  united  to  form 
the  membrana  limitans  interna.  As  the  fibres  pass  through  the  nerve  fibre  and  ganglionic  laj^ers 
they  give  off  a  few  lateral  branches;  in  the  inner  nuclear  layer  thej'  give  off  numerous  lateral 
processes  for  the  support  of  the  bipolar  cells,  while  in  the  outer  nuclear  layer  they  form  a  net- 
work aroimd  the  rod-  and  cone-fibrils,  and  imite  to  form  the  external  limiting  membrane  at  the 
bases  of  the  rods  and  cones.  At  the  level  of  the  inner  nuclear  layer  each  sustentacular  fibre 
contains  a  clear  oval  nucleus. 

Macula  Lutea  and  Fovea  Centralis. — In  the  macula  lutea  the  nerve  fibres  are  wanting  as  a 
continuous  layer,  the  ganglionic  layer  consists  of  several  strata  of  cells,  there  are  no  rods,  but 
onlj'  cones,  which  are  longer  and  narrower  than  in  other  parts,  and  in  the  outer  nuclear  laj^er 
there  are  only  cone-granules,  the  processes  of  which  are  ^"ery  long  and  arranged  in  curved  lines. 
In  the  fovea  centralis  the  only  parts  present  are  (1)  the  cones;  (2)  the  outer  nuclear  layer,  the 
cone-fibres  of  which  are  almost  horizontal  in  direction;  (3)  an  exceedingly  thin  inner  plexiform 
layer.  The  pigmented  layer  is  thicker  and  its  pigment  more  pronounced  than  elsewhere.  The 
color  of  the  macula  seems  to  imbue  all  the  layers  except  that  of  the  rods  and  cones;  it  is  of  a  rich 
yellow,  deepest  toward  the  centre  of  the  macula,  and  does  not  appear  to  be  due  to  pigment  cells, 
but  simply  to  a  staining  of  the  constituent  parts. 

At  the  era  serrata  the  nervous  layers  of  the  retina  end  abruptly,  and  the  retina  is  continued 
onward  as  a  single  layer  of  colmnnar  cells  covered  by  the  pigmented  layer.  This  double  layer  is 
known  as  the  pars  ciliaris  retinae,  and  can  be  traced  forward  from  the  ciliary  processes  on  to  the 
back  of  the  iris,  -n^ere  it  is  termed  the  pars  iridica  retinae  or  uvea. 

The  arteria  centralis  retinae  (Fig.  848)  and  its  accompanying  vein  pierce  the  optic  nerve,  and 
enter  the  bulb  of  the  eye  through  the  porus  opticus.  The  artery  immediately  bifurcates  into 
an  upper  and  a  lower  branch,  and  each  of  these  again  divides  into  a  medial  or  nasal  and  a  lateral 
or  temporal  branch,  which  at  first  run  between  the  hyaloid  membrane  and  the  nervous  layer; 
but  they  soon  enter  the  latter,  and  pass  forward,  diA'iding  dichotomously.  From  these  branches 
a  minute  capillar}'  plexus  is  given  off,  which  does  not  extend  beyond  the  inner  nuclear  laj'er. 
The  macula  receives  two  small  branches  (superior  and  inferior  macular  arteries)  from  the  tem- 
poral branches  and  small  twigs  dii-ectly  from  the  central  artery;  these  do  not,  however,  reach 
as  far  as  the  fovea  centralis,  which  has  no  bloodvessels.     The  branches  of  the  arteria  centralis 


1030       ORGAXS  OF  THE  SEXSES  AM)  THE  COMMON  INTEGUMENT 

retinae  do  not  anastomose  with  each  other — in  other  words  they  are  tenninal  arteries.  In  the 
fetus,  a  small  vessel,  the  arteria  hj'aloidoa,  passes  forward  as  a  continuation  of  the  arteria  centralis 
retinae  through  the  vitreous  humor  to  the  posterior  surface  of  the  capsule  of  the  lens. 

The   Refracting   Media. 

The  refrac'tinji'  media  are  three,  viz.: 

Aqueous  humor.  Vitreous  body.  Crystalline  lens. 

The  Aqueous  Humor  {hiinwr  aqiieus). — The  aqueous  humor  fills  the  anterior 
and  posterior  chambers  of  the  eyeball.  It  is  small  in  quantity,  has  an  alkaline 
reaction,  and  consists  mainly  of  water,  less  than  one-fittieth  of  its  weight  being 
solid  matter,  chiefly  chloride  of  sodium. 

The  Vitreous  Body  {corpus  xitreum). — The  vitreous  body  forms  about  four- 
fifths  of  the  bulb  of  the  eye.  It  fills  the  concavity  of  the  retina,  and  is  hollowed 
in  front,  forming  a  deep  concavity,  the  hyaloid  fossa,  for  the  reception  of  the  lens. 
It  is  transparent,  of  the  consistence  of  thin  jelly,  and  is  composed  of  an  albuminous 
fluid  enclosed  in  a  delicate  transparent  membrane,  the  hyaloid  membrane.  It  has 
been  supposed,  by  Hannover,  that  from  its  surface  numerous  thin  lamellae  are 
prolonged  inward  in  a  radiating  manner,  forming  spaces  in  which  the  fluid  is  con- 
tained. In  the  adult,  these  lamellae  cannot  be  detected  even  after  careful  micro- 
scopic examination  in  the  fresh  state,  but  in  preparations  hardened  in  weak  chromic 
acid  it  is  possible  to  make  out  a  distinct  lamellation  at  the  periphery  of  the  body. 
In  the  centre  of  the  vitreous  body,  running  from  the  entrance  of  the  optic  nerve 
to  the  posterior  surface  of  the  lens,  is  a  canal,  the  hyaloid  canal,  filled  with  lymph 
and  lined  by  a  prolongation  of  the  hyaloid  membrane.  This  canal,  in  the  embryonic 
vitreous  body,  conveyed  the  arteria  hyaloidea  from  the  central  artery  of  the  retina 
to  the  back  of  the  lens.  The  fluid  from  the  vitreous  body  is  nearly  pure  water;  it 
contains,  however,  some  salts,  and  a  little  albumin. 

The  hyaloid  membrane  envelopes  the  vitreous  body.  The  portion  in  front  of  the 
ora  serrata  is  thickened  by  the  accession  of  radial  fibres  and  is  termed  the  zonula 
ciliaris  (zonule  of  Zinn).  Here  it  presents  a  series  of  radially  arranged  furrows, 
in  which  the  ciliary  processes  are  accommodated  and  to  which  they  adhere,  as  is 
shown  by  the  fact  that  when  they  are  removed  some  of  their  pigment  remains 
attached  to  the  zonula.  The  zonula  ciliaris  splits  into  two  layers,  one  of  which 
is  thin  and  lines  the  hyaloid  fossa;  the  other  is  named  the  suspensory  ligament 
of  the  lens:  it  is  thicker,  and  passes  over  the  ciliary  body  to  be  attached  to  the  cap- 
sule of  the  lens  a  short  distance  in  front  of  its  equator.  Scattered  and  delicate 
fibres  are  also  attached  to  the  region  of  the  equator  itself.  This  ligament  retains 
the  lens  in  position,  and  is  relaxed  by  the  contraction  of  the  meridional  fibres  of 
the  Ciliaris  muscle,  so  that  the  lens  is  allowed  to  become  more  convex.  Behind 
the  suspensory  ligament  there  is  a  sacculated  canal,  the  spatia  zonularis  {canal 
of  Petit),  which  encircles  the  equator  of  the  lens;  it  can  be  easily  inflated  through 
a  fine  blowpipe  inserted  under  the  suspensory  ligament. 

No  bloodvessels  penetrate  the  vitreous  body,  so  that  its  nutrition  must  be  carried 
on  by  vessels  of  the  retina  and  ciliary  processes,  situated  upon  its  exterior. 

The  Crystalline  Lens  (lens  crystallina). — The  crystalline  lens,  enclosed  in  its 
capsule,  is  situated  immediately  behind  the  iris,  in  front  of  the  vitreous  body, 
and  encircled  by  the  ciliary  processes,  which  slightly  overlap  its  margin. 

The  capsule  of  the  lens  {cajysula  lentis)  is  a  transparent,  structureless  membrane 
which  closely  surrounds  the  lens,  and  is  thicker  in  front  than  behind.  It  is  brittle 
but  highly  elastic,  and  when  ruptured  the  edges  roll  up  witli  the  outer  surface 
innermost.  It  rests,  behind,  in  the  hyaloid  fossa  in  the  forepart  of  the  vitreous 
body;  in  front,  it  is  in  contact  with  the  free  border  of  the  iris,  but  recedes  from  it 


THE  REFRACTING  MEDIA 


1031 


at  the  circuniforcMice,  thus  forniing  the  posterior  chain])er  of  the  eye;  it  is  retained 
in  its  i)osition  chiefly  by  the  suspensory  Hgament  of  the  lens,  already  described. 

The  lens  is  a  transparent,  biconvex  body,  the  convexity  of  its  anterior  being 
less  than  that  of  its  posterior  surface.  The  central  points  of  these  surfaces  are 
termed  respectively  the  anterior  and  posterior  poles;  a  line  connecting  the  poles 
constitutes  the  axis  of  the  lens,  while  the  marginal  circumference  is  termed  the 
equator. 

Structure. — The  lens  is  iiiatlc  up  of  soft  cortical  substance  and  a  firm,  central  part,  the  nucleus 
(Fig.  852).  Faint  lines  {radii  lenlia)  radiate  from  the  poles  to  the  equator.  In  the  adult  there 
may  be  six  or  more  of  these  lines,  but  in  the  fetus  they  are  only 
three  in  number  and  diverge  from  each  other  at  angles  of  120° 
(Fig.  853) ;  on  the  anterior  surface  one  line  ascends  vertically 
and  the  other  two  diverge  downward;  on  the  posterior  sur- 
face one  ray  descends  vertically  and  the  other  two  diverge 
upward.  They  correspond  with  the  free  edges  of  an  equal 
number  of  septa  composed  of  an  amorphous  substance,  which 
dip  into  the  substance  of  the  lens.  When  the  lens  has  been 
hardened  it  is  seen  to  consist  of  a  series  of  concentrically 
arranged  laminae,  each  of  which  is  interrupted  at  the  septa 
referred  to.  Each  lamina  is  built  up  of  a  number  of  hexagonal, 
ribbon-like  lens  fibres,  the  edges  of  which  are  more  or  less  ser- 
rated— the  serrations  fitting  between  those  of  neighboring 
fibres,  while  the  ends  of  the  fibres  come  into  apposition  at 
the  septa.    The  fibres  run  in  a  curved  manner  from  the  septa 

on  the  anterior  surface  to  those  on  the  posterior  surface.  No  fibres  pass  from  pole  to  pole; 
they  are  arranged  in  such  a  way  that  those  which  begin  near  the  pole  on  one  surface  of  the 
lens  end  near  the  peripheral  extremity  of  the  plane  on  the  other,  and  vice  versa.  The  fibres  of 
the  outer  layers  of  the  lens  are  nucleated,  and  together  form  a  nuclear  layer,  most  distinct 
toward  the  equator.  The  anterior  surface  of  the  lens  is  covered  by  a  layer  of  transparent, 
colxunnar,  nucleated  epithelium.  At  the  equator  the  cells  become  elongated,  and  their  gradual 
transition  into  lens  fibres  can  be  traced  (Fig.  855). 


Fig.  852 


The  crystalline  lens,   hard- 
ened and  divided.     (Enlarged.) 


Fig.  853. 


-Diagram  to  show  the  direction  and  arrangement  of  the  radiating  hnes  on  the  front  and  back  of  the  fetal 
lens.     A.  From  the  front.     B.  From  the  back. 


In  the  fetus,  the  lens  is  nearly  spherical,  and  has  a  slightly  reddish  tint;  it  is  soft  and  breaks 
down  readily  on  the  slightest  pressure.  A  small  branch  from  the  arteria  centralis  retinae  runs 
forward,  as  ah-eady  mentioned,  through  the  vitreous  body  to  the  posterior  part  of  the  capsule 
of  the  lens,  where  its  branches  radiate  and  form  a  plexiform  network,  which  covers  the  posterior 
surface  of  the  capsule,  and  they  are  continuous  around  the  margin  of  the  capsule  with  the  vessels 
of  the  pupillary  membrane,  and  with  those  of  the  iris.  In  the  adult,  the  lens  is  colorless,  trans- 
parent, firm  in  texture,  and  devoid  of  vessels.  In  old  age  it  "becomes  flattened  on  both  surfaces, 
sHghtly  opaque,  of  an  amber  tint,  and  increased  in  density  (Fig.  854). 

Vessels  and  Nerves. — The  arteries  of  the  bulb  of  the  eye  are  the  long,  short,  and  anterior 
ciliary  arteries,  and  the  arteria  centralis  retinae.    They  have  already  been  described  (see  p.  650). 

The  ciliary  veins  are  seen  on  the  outer  surface  of  the  choroid,  and  are  named,  from  their  arrange- 
ment, the  venae  voriicosae;  they  converge  to  four  or  five  equidistant  trunks  which  pierce  the 
sclera  midway  between  the  sclerocorneal  junction  and  the  porus  opticus.  Another  set  of  veins 
accompanies  the  anterior  ciliary  arteries.    All  of  these  veins  open  into  the  ophthalmic  veins. 

The  ciliary  nerves  are  derived  from  the  nasociliary  nerve  and  from  the  ciliary  ganghon. 

Applied  Anatomy. — From  a  surgical  point  of  view  the  cornea  may  be  regarded  as  consisting 
of  tlu-ee  layers:  (1)  an  external  epithelial  layer,  developed  from  the  ectoderm,  and  continuous 
with  the  epithelial  covering  of  the  rest  of  the  body,  so  that  its  lesions  resemble  those  of  the  epi- 
dermis; (2)  the  cornea  proper,  derived  from  the  mesoderm,  and  associated  in  its  diseases  with 


1032       ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 


the  fibrovascular  structures  of  the  body;  and  (3)  the  posterior  elastic  lamina  with  its  endothe- 
lium, also  derived  from  the  mesoderm  and  having  the  characters  of  a  serous  membrane,  so  that 
inflammation  of  it  resembles  inflammation  of  the  serous  and  synovial  membranes  of  the  body. 

The  cornea  contains  no  bloodvessels  except  at  its  periphery, 
where  numerous  delicate  loops,  derived  from  the  anterior 
cihary  arteries,  may  be  demonstrated  on  its  anterior  surface. 
The  rest  of  the  cornea  is  nourished  by  lymph,  which  gains 
access  to  the  proper  substance  of  the  cornea  and  the  posterior 
layer  through  the  spaces  of  the  angle  of  the  iris.  This  lack 
of  a  direct  blood  supply  renders  the  cornea  very  apt  to 
inflame  in  the  cachectic  and  ill-nourished.  In  cases  of  granular 
lids,  there  is  a  peculiar  affection  of  the  cornea,  called  pannus, 
in  which  the  anterior  layers  of  the  cornea  become  vascular- 
ized, and  a  rich  net-work  of  bloodvessels  may  be  seen  upon  it; 
and  in  interstitial  keratitis  new  vessels  extend  into  the  cornea, 
giving  it  a  pinkish  hue  to  which  the  term  ''salmon  patch" 
is  applied.  In  cases  of  glaucoma  the  cihary  nerves  may  be 
pressed  upon  as  they  course  between  the  choroid  and  sclera, 
and  the  cornea  becomes  anesthetic. 

The  sclera  has  very  few  bloodvessels  and  nerves.  As  the 
bloodvessels  approach  the  corneal  margin  the  arrangement  is 
peculiar.  Some  branches  pass  through  the  sclera  to  the  cihary 
body;  others  become  superficial  and  lie  in  the  episcleral 
tissue,  and  form  arches,  by  anastomosing  with  each  other 
some  httle  distance  behind  the  corneal  margin.  From  these 
arches  numerous  straight  vessels  are  given  off,  which  run 
forward  to  the  cornea,  forming  its  marginal  plexus.  In 
inflammation  of  the  sclera  and  episcleral  tissue  these  vessels 
become  conspicuous,  and  form  a  pinkish  zone  of  straight 
vessels  radiating  from  the  corneal  margin,  commonly  known 
as  the  zone  of  ciliary  injection.  In  inflammation  of  the  iris 
and  cihary  body  this  zone  is  present,  since  the  sclera  speedily 
becomes  involved  when  these  structures  are  inflamed.  But 
in  inflammation  of  the  cornea  the  sclera  is  seldom  much 
affected,  though  the  two  are  structurally  continuous.  This 
would  appear  to  be  due  to  the  fact,  that  the  nutrition  of  the 
cornea  is  derived  from  a  different  source  than  that  of  the 
sclera.  The  sclera  may  be  ruptured  without  any  laceration 
of  the  conjunctiva,  and  the  rupture  usually  ocdu-s  near  the 
corneal  margin.  It  may  be  compUcated  with  lesions  of 
adjacent  parts — laceration  of  the  choroid,  retina,  iris,  or 
suspensory  ligament  of  the  lens — and  is  then  often  attended 
with  hemorrhage  into  the  anterior  chamber,  which  masks 
the  nature  of  the  injury.  In  some  cases  the  lens  has  escaped 
through  the  rent  in  the  sclera  and  has  been  found  under  the 
conjunctiva.  Wounds  of  the  sclera  are  always  dangerous, 
and  are  often  followed  by  inflammation,  suppuration,  and  by 
sympathetic  ophthalmia. 


Fig.  854. — Profile  views  of  the  lens  at  different  periods  of  life. 
1.  In  the  fetus.     2.   In  adult  life.     3.   In  old  age. 


Fig.  855. — Section  through  the  margin 
of  the  lens,  showing  the  transition  of 
the  epithelium  into  the  lens  fibres. 
(Babuchin.) 


One  of  the  functions  of  the  choroid  is  to  provide  nutrition  for  the  retina,  and  to  convey  vessels 
and  nerves  to  the  ciliary  body  and  iris.  Inflammation  of  the  choroid  is  therefore  followed  by 
grave  disturbances  in  the  nutrition  of  the  retina,  and  is  attended  with  early  interference  with 


THE  REFRACTING  MEDIA  1033 

vision.  Its  diseases  boar  a  oonsidenihle  aiuilotiv  U>  tlio-sc  whicli  aiToct.  the  .skin,  and  it  is  one  of 
the  places  from  which  mchmotic  sarcomata  may  grow.  These  tumors  contain  a  large  amount 
of  pigment  in  their  cells,  and  originate  only  in  those  parts  where  i)igm(!nt  is  naturally  present. 

The  iris  may  be  absent,  either  in  part  or  altogether  as  a  congenital  condition,  and  in  some 
instances  the  pupillary  membrane  may  remain  persistent,  though  it  is  rarely  complete.  Again, 
the  iris  may  be  the  seat  of  a  malformation,  termed  colobomd,  which  consists  in  a  deficiency  or 
cleft,  clearl,y  due  in  a  great  number  of  cases  to  an  arrest  in  development.  In  these  cases  the 
cleft  is  found  at  the  lower  aspect,  extending  directly  downward  from  the  pupil,  and  the  gap 
frequently  extends  through  the  choroid  to  the  porus  opticus.  In  some  rarer  cases  the  gap  is 
found  in  other  parts  of  the  iris,  and  is  not  then  associated  with  any  deficiency  of  the  choroid. 
Wounds  of  the  iris,  especially  if  complicated  with  injury  to  the  ciliary  body,  may  be  followed 
by  serious  consequences.  If  septic  matter  is  introduced,  and  a  suppurative  inflammation  is 
set  up,  complete  loss  of  vision  may- result;  and,  what  is  perhaps  of  greater  consequence,  similar 
inflammatory  changes  may  be  set  up  in  the  sound  eye,  from  spreading  of  the  infective  process 
through  the  connective  tissue  surrounding  the  optic  nerve  to  the  chiasma,  and  thence  along  the 
opposite  nerve  to  the  sound  eye.  The  iris  is  abundantly  supphed  with  bloodvessels  and  nerves, 
anil  is  very  prone  to  become  inflamed,  and  when  inflamed,  in  consequence  of  the  intimate  rela- 
tionship which  exists  between  the  vessels  of  the  iris  and  choroid,  this  latter  tunic  is  very  hable 
to  participate  in  the  inflammation.  The  iris  is  covered  with  epithelium,  and  partakes  of  the 
character  of  a  serous  membrane,  and,  like  these  structures,  is  apt  to  pour  out  a  plastic  exudation, 
when  inflamed,  and  contract  adhesions,  either  to  the  cornea  in  front  (synechia  anterior),  or  to 
the  capsule  of  the  lens  behind  (synechia  posterior).  In  iritis  the  lens  may  become  involved,  and 
the  condition  known  as  secondary  cataract  may  be  set  up.  Tumors  occasionally  commence  in 
the  iris;  of  these,  cysts,  which  are  usually  congenital,  and  sarcomatous  tumors,  are  the  most 
common.  Gummata  are  not  infrequently  found  in  this  situation.  In  some  forms  of  injury 
of  the  eyeball,  as  from  the  impact  of  a  spent  shot,  the  rebound  of  a  twig,  or  a  blow  with  a  whip, 
the  iris  may  be  detached  fi-om  the  Ciliaris  muscle. 

The  retina,  with  the  exception  of  its  pigment  layer  and  its  vessels,  is  perfectly  transparent 
when  examined  by  the  ophthalmoscope,  so  that  its  diseased  conditions  are  recognized  by  its 
loss  of  transparency.  In  retinitis,  for  instance,  there  is  more  or  less  dense  and  extensive  opacity 
of  its  structure,  and  not  infi-equently  extravasations  of  blood  into  its  substance.  Hemorrhages 
may  also  take  place  into  the  retina,  from  rupture  of  a  bloodvessel  without  inflammation.  The 
retina  may  become  displaced  from  efl^usion  of  serum  between  it  and  the  choroid,  or  by  blows 
on  the  eyeball,  or  may  occur  without  apparent  cause  in  progressive  myopia,  and  in  this  case 
the  ophthalmoscope  shows  an  opaque,  tremulous  cloud.  GUoma,  a  form  of  sarcoma,  is  occa- 
sionally met  with  in  connection  with  the  retina. 

The  lens  has  no  bloodvessels,  nerves,  or  connective  tissue  in  its  structure,  and  therefore  is  not 
subject  to  those  morbid  changes  to  which  tissues  containing  these  structures  are  Uable.  It  does, 
however,  present  certain  morbid  or  abnormal  conditions  of  various  kinds.  Thus,  variations  in 
shape,  and  displacements,  are  among  its  congenital  defects.  Opacities  may  occur  from  injury, 
senile  changes,  or  malnutrition.  These  opacities  give  rise  to  cataract,  of  which  the  senile  variety, 
is  the  most  common.  They  vary  as  to  the  part  of  the  lens  in  which  the  opacity  commences 
and  are  classified  accordingly,  as  nuclear,  cortical,  lamellar,  anterior,  and  posterior  polar.  Senile 
changes  may  take  place  in  the  lens,  impairing  its  elasticity  and  rendering  it  harder  than  in  youth, 
so  that  it  loses  its  power  of  altering  its  ciu-vature  to  suit  the  requirements  of  near  vision.  This 
condition  is  known  as  presbyopia.  And,  finally,  the  lens  may  be  dislocated  or  displaced  by  blows 
upon  the  eyeball;  and  its  relations  to  surrounding  structures  altered  by  adhesions  or  the  pressure 
of  new  growths. 

There  are  two  particular  regions  of  the  eye  which  require  special  notice :  one  of  these  is  known 
as  the  "filtration  angle,"  and  the  other  as  the  "dangerous  area."  The  filtration  angle  is  the  cu'- 
cumcorneal  zone  immediately  in  front  of  the  iris.  Here  are  situated  the  spaces  of  the  angle  of 
the  iris,  which  communicate  with  the  sinus  venosus  sclerae  through  which  the  chief  transudation 
of  fluid  from  the  eye  is  beheved  to  take  place.  If  any  obstruction  to  this  transudation  occur, 
increased  intra-ocular  tension  is  set  up,  and  the  disease  known  as  glaucoma  results.  The  dayigerous 
area  of  the  eye  is  the  region  in  the  neighborhood  of  the  ciUary  iDody,  and  woimds  or  injuries  in 
this  situation  are  pecuharly  dangerous;  for  inflammation  of  the  cihary  body  is  apt  to  spread  to 
many  of  the  other  structures  of  the  eye,  especially  to  the  iris  and  choroid,  which  are  intimately 
connected  with  it  by  nervous  and  vascular  suppUes. 


1034       ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

The  Accessory  Organs  of  the  Eye   (Organa  Oculi  Accessoria). 

The  accessory  organs  of  the  eye  include  the  ocular  muscles,  the  fasciae,  the  eye- 
brows, the  eyelids,  the  conjunctiva,  and  the  lacrimal  apparatus. 

The  Ocular  Muscles  {imisculi  oculi). — The  ocular  muscles  are  the: 

Levator  palpebrae  superioris.  Rectus  medialis. 

Rectus  superior.  Rectus  lateralis. 

Rectus  inferior.  Obliquus  superior. 

Obliquus  inferior. 

Dissection. — To  open  the  cavity  of  the  orbit,  remove  the  skuU-cap  and  brain;  then  saw  through 
the  frontal  bone  at  the  inner  extremity  of  the  supraorbital  ridge,  and  externally  at  its  junction 
with  the  zygomatic  bone.  Break  in  pieces  the  thin  roof  of  the  orbit  by  a  few  shght  blows  of  the 
hammer,  and  take  it  away;  drive  forward  the  supercihary  portion  of  the  frontal  bone  by  a  smart 
stroke,  but  do  not  remove  it,  as  that  would  destroy  the  pulley  of  the  Obliquus  superior.  When 
the  fragments  are  cleared  away,  the  periosteum  of  the  orbit  will  be  exposed;  this  being  removed, 
together  with  the  fat  which  fills  the  cavity  of  the  orbit,  the  several  muscles  of  this  region  can 
be  examined.  The  dissection  will  be  facilitated  by  distending  the  globe  of  the  eye.  In  order 
to  effect  this,  puncture  the  optic  nerve  near  the  eyeball  with  a  curved  needle,  and  push  the 
needle  onward  into  the  globe;  insert  the  point  of  a  blowpipe  through  this  apertm-e,  and  force  a 
httle  air  into  the  cavity  of  the  eyeball;  then  apply  a  hgature  around  the  nerve  so  as  to  prevent 
the  air  escaping.    The  globe  being  now  drawm  forward,  the  muscles  will  be  put  upon  the  stretch. 


Tendon  of  Ohliquui,  superior 
Otbdal  plate  of  frontal  bone 
Levato7  palpebrae  supei  ions 
Rectus  superior 


Optic  nerve 

Rectus  inferior 
Roof  of  maxillary  sinus 

Obliquus  inferior 

Fig.  8.56. — Sagittal  section  of  right  orbital  cavity. 


Orbic2daris  oculi 
Superior  tarsus 
Upper  eyelid 


Lower  eyelid 
Inferior  tarsus 

Orbicularis  oculi 


The  Levator  palpebrae  superioris  (Fig.  856)  is  thin,  flat,  and  triangular  in  shape. 
It  arises  from  the  under  surface  of  the  small  wing  of  the  sphenoid,  above  and  in 
front  of  the  optic  foramen,  from  which  it  is  separated  by  the  origin  of  the  Rectus 
superior.  At  its  origin,  it  is  narrow  and  tendinous,  but  soon  becomes  broad  and 
fleshy,  and  ends  anteriorly  in  a  wide  aponeurosis  which  splits  into  three  lamellse. 
The  superficial  lamella  blends  with  the  upper  part  of  the  orbital  septum,  and  is  pro- 
longed forward  above  the  superior  tarsus  to  the  palpebral  part  of  the  Orbicularis 
oculi,  and  to  the  deep  surface  of  the  skin  of  the  upper  eyelid.  The  middle  lamella, 
largely  made  up  of  non-striped  muscular  fibres,  is  inserted  into  the  upper  margin 
of  the  superior  tarsus,  while  the  deepest  lamella  blends  with  an  expansion  from 
the  sheath  of  the  Rectus  superior  and  with  it  is  attached  to  the  superior  fornix 
of  the  conjunctiva. 


THE  ACCESSORY  ORGANS  OF  THE  EYE 


1035 


Whitnall'  luis  pointed  out  that  the  upper  i)art  of  the  sheath  of  the  I.evator  palpebrae  becomes 
thickened  in  front  and  forms,  above  the  anterior  part  of  the  muscle,  a  transverse  hgamentous 
band  which  is  attached  to  the  sides  of  the  orbital  cavity.  On  the  medial  side  it  is  mainlj'  fixed 
to  the  pulley  of  ihe  Obliquus  superior,  but  some  fibres  are  attached  to  the  bone  behind  the  pulley 
and  a  slip  passes  forward  and  bridges  over  the  supraorbital  notch;  on  the  lateral  side  it  is  fixed 
to  the  capsule  of  the  lacrimal  gland  and  to  t,he  frontal  bone.  In  front  of  the  transverse  ligament- 
ous band  the  sheath  is  continued  over  the  aponeurosis  of  the  Levator  palpebrae,  as  a  thin  con- 
nective-tissue layer  which  is  fixed  to  the  upper  orbital  margin  immediatly  behind  the  attach- 
ment of  the  orbital  septum.  When  the  Levator  palpebrae  contracts,  the  lateral  and  medial  parts 
of  the  ligamentous  band  are  stretched  and  c-heck  the  action  of  the  muscle;  the  retraction  of  the 
upper  eyelid  is  checked  also  by  the  orbital  septum  coming  into  contact  with  the  transverse  part 
of  the  ligamentous  band. 


Fig.   857. — Muscles  of  the  right  orbit. 

The  four  Recti  (Fig.  857)  arise  from  a  fibrous  ring  (amiuhis  tendineus  communis) 
which  surrounds  the  upper,  medial,  and  lower  margins  of  the  optic  foramen  and 
encircles  the  optic  nerve  (Fig.  858).  The  ring  is  completed  by  a  tendinous  bridge 
prolonged  over  the  lower  and  medial  part  of  the  superior  orbital  fissure  and  attached 
to  a  tubercle  on  the  margin  of  the  great  wing  of  the  sphenoid,  bounding  the  fissure. 
Two  specialized  parts  of  this  fibrous  ring  may  be  made  out:  a  lower,  the  ligament 
or  tendon  of  Zinn,  which  gives  origin  to  the  Rectus  inferior,  part  of  the  Rectus  in- 
ternus,  and  the  lower  head  of  origin  of  the  Rectus  lateralis;  and  an  upper,  which 
gives  origin  to  the  Rectus  superior,  the  rest  of  the  Rectus  medialis,  and  the  upper 
head  of  the  Rectus  lateralis.  This  upper  band  is  sometimes  termed  the  superior 
tendon  of  Lockwood.  Each  muscle  passes  forw^ard  in  the  position  implied  by  its 
name,  to  be  inserted  by  a  tendinous  expansion  into  the  sclera,  about  6  mm.  from  the 
margin  of  the  cornea.  Between  the  two  heads  of  the  Rectus  lateralis  is  a  narrow 
interval,  through  which  pass  the  two  divisions  of  the  oculomotor  nerve,  the  naso- 
ciliary nerve,  the  abducent  nerve,  and  the  ophthalmic  vein.  Although  these 
muscles  present  a  common  origin  and  are  inserted  in  a  similar  manner  into  the 
sclera,  there  are  certain  difl'erences  to  be  observed  in  them  as  regards  their  length 
and  breadth.  The  Rectus  medialis  is  the  broadest,  the  Rectus  lateralis  the  longest, 
and  the  Rectus  superior  the  thinnest  and  narrowest. 

The  Obliquus  oculi  superior  (superior  oblique)  is  a  fusiform  muscle,  placed  at  the 
upper  and  medial  side  of  the  orbit.  It  arises  immediately  above  the  margin  of  the 
optic  foramen,  above  and  medial  to  the  origin  of  the  Rectus  superior,  and,  passing 
forward,  ends  in  a  rounded  tendon,  which  plays  in  a  fibrocartilaginous  ring  or  pulley 
attached  to  the  trochlear  fovea  of  the  frontal  bone.  The  contiguous  surfaces  of 
the  tendon  and  ring  are  lined  by  a  delicate  mucous  sheath,  and  enclosed  in  a  thin 

1  Journal  of  Anatomy  and  Physiologj',  vol.  xlv. 


1036       ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

fibrous  investment.  The  tendon  is  reflected  backward,  lateralward,  and  downward 
beneath  the  Rectus  superior  to  the  lateral  part  of  the  bulb  of  the  eye,  and  is  inserted 
into  the  sclera,  behind  the  ec{uator  of  the  eyeball,  the  insertion  of  the  muscle  lying 
between  the  Rectus  superior  and  Rectus  lateralis. 

The  Obliquus  oculi  inferior  {inferior  oblique)  is  a  thin,  narrow  muscle,  placed  near 
the  anterior  margin  of  the  floor  of  the  orbit.  It  arises  from  the  orbital  surface  of 
the  maxilla,  lateral  to  the  lacrimal  groove.  Passing  lateralward,  backward,  and 
upward,  at  first  between  the  Rectus  inferior  and  the  floor  of  the  orbit,  and  then 
between  the  bulb  of  the  eye  and  the  Rectus  lateralis,  it  is  inserted  into  the  lateral 
part  of  the  sclera  between  the  Rectus  superior  and  Rectus  lateralis,  near  to,  but 
somewhat  behind  the  insertion  of  the  Obliquus  superior. 


Frontal  nerve 
Sup,  ramus  of  oculomotor  nerve 
Sup.  orbital  fissure 
Lacritnal  nerve 


Levator  palpehrce 
Nasociliary  nerve' 
Trochlear  nerve 
Trochlea 

L 


Abducent  nerve 

Inf.  ramus  of  oculomotor     Inf.  orbital         Optic  foramen 
nerve  fissure 

Fig.  858. — Dissection  snowing  origins  of  right  ocular  muscles,  and  nerves  entering  by  the  superior  orbital  fissure. 


Nerves. — The  Levator  palpebrae  superioris,  Obliquus  inferior,  and  the  Recti  superior,  inferior, 
and  medialis  are  supphed  by  the  oculomotor  nerve;  the  ObUquus  superior,  by  the  trochlear 
nerve;  the  Rectus  laterahs,  by  the  abducent  nerve. 

Actions. — The  Levator  palpebrae  raises  the  upper  eyehd,  and  is  the  direct  antagonist  of  the 
Orbicularis  oculi.  The  foiu-  Recti  are  attached  to  the  bulb  of  the  eye  in  such  a  manner  that, 
acting  singly,  they  will  turn  its  corneal  surface  either  upward,  downward,  medialward,  or  lateral- 
ward,  as  expressed  by  their  names.  The  movement  produced  by  the  Rectus  superior  or  Rectus 
inferior  is  not  quite  a  simple  one,  for  inasmuch  as  each  passes  obhquely  lateralward  and  forward 
to  the  bulb  of  the  eye,  the  elevation  or  depression  of  the  cornea  is  accompanied  by  a  certain 
deviation  medialward,  with  a  shght  amount  of  rotation.  These  latter  movements  are  corrected 
by  the  Obhqui,  the  Obhquus  inferior  correcting  the  medial  deviation  caused  by  the  Rectus  superior 
and  the  Obhquus  superior  that  caused  by  the  Rectus  inferior.  The  contraction  of  the  Rectus 
lateralis  or  Rectus  mediahs,  on  the  other  hand,  produces  a  purely  horizontal  movement.  If  any 
two  neighboring  Recti  of  one  eye  act  together  they  carry  the  globe  of  the  eye  in  the  diagonal  of 
these  directions,  viz.,  upward  and  medialward,  upward  and  lateralward,  downward  and  medial- 
ward,  or  downward  and  lateralward.  Sometimes  the  corresponding  Recti  of  the  two  eyes  act 
in  unison,  and  at  other  times  the  opposite  Recti  act  together.  Thus,  in  turning  the  eyes  to  the 
right,  the  Rectus  lateraUs  of  the  right  eye  will  act  in  vmison  with  the  Rectus  mediahs  of  the  left 
ej^e;  but  if  both  ej^es  are  directed  to  an  object  in  the  middle  hne  at  a  short  distance,  the  two  Recti 
mediales  will  act  in  unison.  The  movement  of  circimiduction,  as  in  looking  around  a  room,  is 
performed  by  the  successive  actions  of  the  four  Recti.     The  Obliqui  rotate  the  eyeball  on  its 


THE  ACCESSORY  omiAXS  OF  THE  EYE 


1037 


antero-posterior  axis,  the  superior  directing  the  cornea  downward  and  hiteralward,  and  the 
inferior  directing  it  upward  and  lateralward;  these  movements  are  reciuired  for  the  correct  viewing 
of  an  object  wlien  tlie  head  is  moved  h\terally,  as  from  shoulder  to  shoulder,  in  order  that  the 
picture  may  fall  in  all  respects  on  the  same  part  of  the  retina  of  either  eye. 

A  layer  of  noii-stripcd  muscle,  the  Orbitalis  muscle  of  II.  Miiller,  may  be  seen 
bridging  across  the  inferior  orbital  fissure. 


Optic  nerve  ■ — 


Fascia  bulb/ 


i^jiir'  Superior  tarsus 


vX^,  _  Inferior  tarsxis 


Fig.  S59. — The  right  eye  in  sagittal  section,  showing  the  fascia  buibi  (seniidiagrammatio).     (Testut.) 


The  fascia  bulb  {caysiile  of  Tenon)  (Fig.  859)  is  a  thin  membrane  which  envelops 
the  bulb  of  the  eye  from  the  optic  nerve  to  the  ciliary  region,  separating  it  from 
the  orbital  fat  and  forming  a  socket  in  which  it  plays.  Its  inner  surface  is  smooth, 
and  is  separated  from  the  outer  surface  of  the  sclera  by  the  periscleral  lymph  space. 
This  lymph  space  is  continuous  with  the  subdural  and  subarachnoid  cavities, 
and  is  traversed  by  delicate  bands  of  connective  tissue  which  extend  between  the 
fascia  and  the  sclera.  The  fascia  is  perforated  behind  by  the  ciliary  vessels  and 
nerves,  and  fuses  with  the  sheath  of  the  optic  nerve  and  with  the  sclera  around  the 
entrance  of  the  optic  nerve.  In  front  it  blends  with  the  ocular  conjunctiva,  and 
with  it  is  attached  to  the  ciliary  region  of  the  eyeball.  It  is  perforated  by  the 
tendons  of  the  ocular  muscles,  and  is  reflected  backward  on  each  as  a  tubular 
sheath.  The  sheath  of  the  Obliquus  superior  is  carried  as  far  as  the  fibrous  pulley 
of  that  muscle;  that  on  the  Obliquus  inferior  reaches  as  far  as  the  floor  of  the 
orbit,  to  which  it  gives  off  a  slip.  The  sheaths  on  the  Recti  are  gradually  lost  in 
the  perimysium,  but  they  give  off  important  expansions.  The  expansion  from  the 
Rectus  superior  blends  with  the  tendon  of  the  Levator  palpebrae;  that  of  the 
Rectus  inferior  is  attached  to  the  inferior  tarsus.  The  expansions  from  the  sheaths 
of  the  Recti  lateralis  and  medialis  are  strong,  especially  that  from  the  latter  muscle, 
and  are  attached  to  the  lacrimal  and  zygomatic  bones  respectively.    As  they  prob- 


1038       ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

ably  check  the  actions  of  these  two  Recti  they  have  been  named  the  medial  and 
lateral  check  ligaments.  Lockwood  has  described  a  thickening  of  the  lower  part 
of  the  facia  bulbi,  which  he  has  named  the  suspensory  ligament  of  the  eye.  It  is 
slung  like  a  hammock  below  the  eyeball,  being  expanded  in  the  centre,  and  narrow 
at  its  extremities  which  are  attached  to  the  zygomatic  and  lacrimal  bones 
respectively.^ 

The  orbital  fascia  forms  the  periosteum  of  the  orbit.  It  is  loosely  connected 
to  the  bones  and  can  be  readily  separated  from  them.  Behind,  it  is  united  with 
the  dura  mater  by  processes  which  pass  through  the  optic  foramen  and  superior 
orbital  fissure,  and  with  the  sheath  of  the  optic  nerve.  In  front,  it  is  connected 
with  the  periosteum  at  the  margin  of  the  orbit,  and  sends  off  a  process  which 
assists  in  forming  the  orbital  septum.  From  it  two  processes  are  given  off;  one  to 
enclose  the  lacrimal  gland,  the  other  to  hold  the  pulley  of  the  Obliquus  superior  in 
position. 

Applied  Anatomy. — The  positions  and  exact  areas  of  insertion  of  the  tendons  of  the  Recti 
mediahs  and  lateralis  into  the  bulb  of  the  eye  should  be  carefully  examined  from  the  front, 
as  the  surgeon  is  often  requued  to  divide  one  or  other  of  the  muscles  for  the  cure  of  strabismus. 
In  convergent  strabismus,  which  is  the  more  common  form  of  the  disease,  the  eye  is  turned 
medialward,  requiring  the  division  of  the  Rectus  mediahs.  In  the  divergent  form,  which  is  more 
rare,  the  eye  is  turned  lateralward,  the  Rectus  laterahs  being  especially  implicated.  The  deformity 
produced  in  either  case  may  be  remedied  by  division  of  one  or  the  other  muscle.  The  operation 
is  thus  performed:  the  lids  are  to  be  well  separated;  the  eyeball  is  rotated  lateralward  or  medial- 
ward,  and  the  conjunctiva  raised  by  a  pair  of  forceps,  and  incised  immediately  beneath  the 
lower  border  of  the  tendon  of  the  muscle  to  be  divided,  a  Uttle  behind  its  insertion  into  the  sclera; 
the  submucous  areolar  tissue  is  then  divided,  and  into  the  small  aperture  thus  made,  a  blunt 
hook  is  passed  upward  between  the  muscle  and  the  bulb,  and  the  tendon  of  the  muscle  divided 
by  a  pair  of  blunt-pointed  scissors  passed  between  the  hook  and  the  bulb. 

A  more  recent  operation  is  that  of  advancement  in  which  either  the  Rectus  mediahs  or  Rectus 
lateraUs  (depending  on  the  form  of  strabismus)  is  shortened.  The  muscle  is  exposed  in  the  same 
manner;  a  portion  is  then  cut  out  of  it  and  the  cut  ends  are  sew  together. 

The  eyebrows  {supercilia)  are  two  arched  eminences  of  integument,  which  sur- 
mount the  upper  circumference  of  the  orbits,  and  support  numerous  short,  thick 
hairs,  directed  obliquely  on  the  surface.  The  eyebrows  consist  of  thickened  integu- 
ment, connected  beneath  with  the'  Orbicularis  oculi,  Corrugator,  and  Frontalis 
muscles. 

The  eyelids  (palpebrae)  are  two  thin,  movable  folds,  placed  in  front  of  the  eye, 
protecting  it  from  injury  by  their  closure.  The  upper  eyelid  is  the  larger,  and  the 
more  movable  of  the  two,  and  is  furnished  with  an  elevator  muscle,  the  Levator 
palpebrae  superioris.  When  the  eyelids  are  open,  an  elliptical  space,  the  palpebral 
fissure  (rima  ijolpehraruvi) ,  is  left  between  their  margins,  the  angles  of  which  corre- 
spond to  the  junctions  of  the  upper  and  lower  eyelids,  and  are  called  the  palpebral 
commissures  or  canthi. 

The  lateral  palpebral  commissure  {coimnissura  palpehrarum  lateralis;  external 
canthus)  is  more  acute  than  the  medial,  and  the  eyelids  here  lie  in  close  contact 
with  the  bulb  of  the  eye:  but  the  medial  palpebral  commissure  (commissura 
palpebrarum  viedialis;  internal  canthus)  is  prolonged  for  a  short  distance  toward  the 
nose,  and  the  two  eyelids  are  separated  by  a  triangular  space,  the  lacus  lacrimalis 
(Fig.  860).  At  the  basal  angles  of  the  lacus  lacrimalis,  on  the  margin  of  each 
eyelid,  is  a  small  conical  elevation,  the  lacrimal  papilla,  the  apex  of  which  is  pierced 
by  a  small  orifice,  the  punctum  lacrimale,  the  commencement  of  the  lacrimal  duct. 

The  eyelashes  {cilia)  are  attached  to  the  free  edges  of  the  eyelids;  they  are  short, 
thick,  curved  hairs,  arranged  in  a  double  or  triple  row :  those  of  the  upper  eyelid, 
more  numerous  and  longer  than  those  of  the  lower,  curve  upward ;  those  of  the  lower 

*  C.  B.  Lockwood,  Journal  of  Anatomy  and  Physiology,  vol.  xx. 


THE  ACCESSORY  ORGANS  OF  THE  EYE 


1039 


eyelid  curve  dowmvard,  so  tliat  they  do  not  interlace  in  closing  the  lids.  Near 
the  attachment  of  the  eyelashes  are  the  openings  of  a  number  of  glands,  the  ciliary 
glands,  arranged  in  several  rows  close  to  the  free  margin  of  the  lid;  they  are  regarded 
as  enlarged  and  modified  sudoriferous  glands. 

Structure  of  the  Eyelids. — The  eyelids  are  composed  of  the  following  structures  taken  in  their 
order  from  without  inward;  integument,  areolar  tissue,  fibres  of  the  Orbicularis  oculi,  tarsus, 
orbital  septum,  tarsal  glands  and  conjunctiva.  The  upper  eyehd  has,  in  addition,  the  aponeu- 
rosis of  the  Levator  ])alpebrae  suporioris  (Fig.  S61). 


Piinctum  lacrimale 

I'lica  semilunaris 

Caruncula 

Punctum  lacrimale 

Openings  of  tarsal 

glands 


Fig.  860.- 


-Front  of  left  eye  with  eyelids  separated  to  show 
medial  canthus. 


The  integument  is  extremelj^  thin,  and  contin- 
uous at  the  margins  of  the  eyeUds  with  the 
conjunctiva. 

The  subcutaneous  areolar  tissue  is  very  lax  and 
dehcate,  and  seldom  contains  any  fat. 

The  palpebral  fibres  of  the  Orbicularis  ocuU  are 
thin,  pale  in  color,  and  possess  an  involuntarj'' 
action. 

The  tarsi  (tarsal  plates)  (Fig.  862)  are  two 
thin  elongated  plates  of  dense  connective  tissue, 
about  2.0  cm.  in  length;  one  is  placed  in  each 
eyehd,  and  contributes  to  its  form  and  support. 
The  superior  tarsus  (tarsus  superior;  superior  tarsal 
plate),  the  larger,  is  of  a  semilunar  form,  about  10 
mm.  in  breadth  at  the  centre,  and  gradually  nar- 
rowing toward  its  extremities.  To  the  anterior 
surface  of  this  plate  the  aponeiu-osis  of  the  Levator 
palpebrae  superioris  is  attached.  The  inferior 
tarsus  (tarsus  inferior;  inferior  tarsal  plate),  the 
smaller,  is  thin,  elliptical  in  form,  and  has  a  vertical 
diameter  of  about  5  mm.  The  free  or  ciliary 
margins  of   these   plates  are  thick  and   straight. 

The  attached  or  orbital  margins  are  connected  to  the  circumference  of  the  orbit  by  the  orbital 
septum.  The  lateral  angles  are  attached  to  the  zygomatic  bone  by  the  lateral  palpebral  raphe. 
The  medial  angles  of  the  two  plates  end  at  the  lacus  lacrimalis,  and  are  attached  to  the  frontal 
process  of  the  maxiUa  by  the  medial  palpebral  ligament  (page  468) . 

The  orbital  septum  (septum  orbitale;  palpebral  ligament)  is  a  membranous  sheet,  attached  to 
the  edge  of  the  orbit,  where  it  is  continuous  with  the  periosteum.  In  the  upper  exeMd  it  blends 
by  its  peripheral  circumference  with  the  tendon  of  the  Levator  palpebrae  superioris  and  the 
superior  tarsus,  in  the  lower  eyehd  with  the  inferior  tarsus.  Medially  it  is  thin,  and,  becoming 
separated  from  the  medial  palpebral  Hgament,  is  fixed  to  the  lacrimal  bone  immediateh'  behind 
the  lacrimal  sac.  The  septum  is  perforated  by  the  vessels  and  nerves  which  pass  from  the  orbital 
cavit}'  to  the  face  and  scalp. 


Fig.  S61. — Sagittal  section  through  the  upper 
eyelid.  (After  Waldeyer.)  a.  Skin.  6.  Orbicularis 
oculi.  6'.  Marginal  fasciculus  of  Orbicularis  (ciharj' 
bundle),  c.  Levator  palpebrae.  d.  Conjunctiva. 
e.  Tarsus.  /.  Tarsal  gland,  g.  Sebaceous  gland. 
h.  Eyelashes,  i.  Small  hairs  of  skin.  j.  Sweat 
glands,     k.  Posterior  tarsal  glands. 


1040       ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

The  Tarsal  Glands  [ylandulac  iarsdes  [Meihomi];  Mcihoiniaii  glanch)  (Fig.  8(33). 
— The  tarsal  glands  are  situated  upon  the  inner  surfaces  of  the  eyelids,  between 
the  tarsi  and  conjuncti\a,  and  may  be  distinctly  seen  through  the  latter  on  everting 
the  eyelids,  presenting  an  appearance  like  parallel  strings  of  pearls.  There  are  about 
thirty  in  the  upper  eyelid,  and  somewhat  fewer  in  the  lower.  They  are  imbedded  in 
grooves  in  the  inner  surfaces  of  the  tarsi,  and  correspond  in  length  with  the 
breadth  of  these  plates;  they  are,  consequently,  longer  in  the  upper  than  in  the  lower 
eyelid.    Their  ducts  open  on  the  free  magins  of  the  lids  by  minute  foramina. 


Lacrimal  artery 

and  nerve 


Lateral  'pal- 
pebral raphe 


Supraorbital  vessels 
and  nerve 


Lacrimal  sac 
Medial  palpebral 
ligament 


Fig.  862. — The  tarsi  and  their  ligaments.     Right  eye;  front  view.      (Testut.) 

Structure. — The  tarsal  glands  are  modified  sebaceous  glands,  each  consisting  of  a  single  straight 
tube  or  follicle,  with  numerous  small  lateral  diverticula.  The  tubes  are  supported  by  a  basement 
membrane,  and  are  lined  at  their  mouths  by  stratified  epithehum;  the  deeper  parts  of  the  tubes 
and  the  lateral  offshoots  are  hned  by  a  layer  of  polyhedral  cells. 


Puncta  lacrimalia  - 


Fig.  863. — The  tarsal  glands,  etc.,  seen  from  the  inner  surface  of  the  eyelids. 

The  conjunctiva  is  the  mucous  membrane  of  the  eye.  It  lines  the  inner  surfaces 
of  the  eyelids  or  palpebrse,  and  is  reflected  over  the  forepart  of  the  sclera  and  cornea. 

The  Palpebral  Portion  {tunica  conjimdim  palpehranm)  is  thick,  opaque,  highly 
vascular,  and  covered  with  numerous  papillae,  its  deeper  part  presenting  a 
considerable  amount  of  lymphoid  tissue.    At  the  margins  of  the  lids  it  becomes 


THE  ACCESSORY  ORGANS  OF  TIIK  EYE  1041 

continuous  with  tlie  lining  membrane  of  the  (hicts  of  the  tarsal  glands,  and,  through 
the  lacrimal  ducts,  with  the  lining  membrane  of  the  lacrimal  sac  and  nasolacrimal 
duct.  At  the  lateral  angle  of  the  upper  eyelid  the  ducts  of  the  lacrimal  gland  open 
on  its  free  surface;  and  at  the  me<lial  angle  it  forms  a  semilunar  fold,  the  plica 
semilunaris.  The  line  of  reflection  of  the  conjunctiva  from  the  upper  eyelid  on 
to  the  bulb  of  the  eye  is  named  the  superior  fornix,  and  that  from  the  lower  lid  the 
inferior  fornix. 

The  Bulbar  Portion  {tunica  conjinicfim  buibi). — I "pon  the  .fdera  the  conjunctiva 
is  loosely  connected  to  the  bulb  of  the  eye;  it  is  thin,  transparent,  destitute  of 
papillfe,  and  only  slightly  vascular.  Upon  the  cornea,  the  conjunctiva  consists 
only  of  epithelium,  constituting  the  epithelium  of  the  cornea,  already  described 
(see  page  1019).  Lyniphatics  arise  in  the  conjunctiva  in  a  delicate  zone  around 
the  cornea,  and  run  to  the  ocular  conjunctiva. 

In  and  near  the  fornices,  but  more  plentiful  in  the  upper  than  in  the  lower  eyelid, 
a  number  of  convoluted  tubular  glands  open  on  the  surface  of  the  conjunctiva. 
Other  glands,  analogous  to  lymphoid  follicles,  and  called  by  Henle  trachoma  glands, 
are  found  in  the  conjunctiva,  and,  according  to  Strohmeyer,  are  chiefly  situated 
near  the  medial  palpebral  commissure.  They  were  first  described  by  Brush,  in 
his  description  of  Peyer's  patches  of  the  small  intestine,  as  "identical  structures 
existing  in  the  under  eyelid  of  the  ox." 

The  caruncula  lacrimalis  is  a  small,  reddish,  conical-shaped  body,  situated  at 
the  medial  palpebral  commissure,  and  filling  up  the  lacus  lacrimalis.  It  consists 
of  a  small  island  of  skin  containing  sebaceous  and  sudoriferous  glands,  and  is  the 
source  of  the  whitish  secretion  which  constantly  collects  in  this  region.  A  few 
slender  hairs  are  attached  to  its  surface.  Lateral  to  the  caruncula  is  a  slight  semi- 
lunar fold  of  conjunctiva,  the  concavity  of  which  is  directed  toward  the  cornea; 
it  is  called  the  plica  semilunaris.  Miiller  found  smooth  muscular  fibres  in  this  fold; 
in  some  of  the  domesticated  animals  it  contains  a  thin  plate  of  cartilage. 

The  nerves  in  the  conjunctiva  are  numerous  and  form  rich  plexuses.  According 
to  Krause  they  terminate  in  a  peculiar  form  of  tactile  corpuscle,  which  he  terms 
"terminal  bulb." 

The  Lacrimal  Apparatus  (ajjparatus  lacrimalis)  (Fig.  864)  consists  of  (a)  the 
lacrimal  gland,  which  secretes  the  tears,  and  its  excretory  ducts,  which  convey  the 
fluid  to  the  surface  of  the  eye;  (b)  the  lacrimal  ducts,  the  lacrimal  sac,  and  the  naso- 
lacrimal duct,  by  which  the  fluid  is  conveyed  into  the  cavity  of  the  nose. 

The  Lacrimal  Gland  (glanchda  lacrimalis). — The  lacrimal  gland  is  lodged  in  the 
lacrimal  fossa,  on  the  medial  side  of  the  zygomatic  process  of  the  frontal  bone. 
It  is  of  an  oval  form,  about  the  size  and  shape  of  an  almond,  and  consists  of  two 
portions,  described  as  the  superior  and  inferior  lacrimal  glands.  The  superior 
lacrimal  gland  is  connected  to  the  periosteum  of  the  orbit  by  a  few  fibrous  bands, 
and  rests  upon  the  tendons  of  the  Recti  superior  and  lateralis,  which  separate  it 
from  the  bulb  of  the  eye.  The  inferior  lacrimal  gland  is  separated  from  the  superior 
by  a  fibrous  septum,  and  projects  into  the  back  part  of  the  upper  eyelid,  where 
its  deep  surface  is  related  to  the  conjunctiva.  The  ducts  of  the  glands,  from  six 
to  twelve  in  number,  run  obliquely  beneath  the  conjunctiva  for  a  short  distance, 
and  open  along  the  upper  and  lateral  half  of  the  superior  conjunctival  fornix. 

Structures  of  the  Lacrimal  Gland  (Fig.  865). — In  structiire  and  general  appearance  the  lacrimal 
resembles  the  serous  sahvary  glands  (p.  1137).  In  the  recent  state  the  cells  are  so  crowded  with 
granules  that  their  limits  can  hardly  be  defined.  They  contain  oval  nuclei,  and  the  cell  proto- 
plasm is  finely  fibrillated. 

The  Lacrimal  Ducts  {ductus  lacrimalis;  lacrimal  canals). — The  lacrimal  ducts,  one 

in  each  eyelid,  commence  at  minute  orifices,  termed  puncta  lacrimalia,  on  the 

summits  of  the  papillae  lacrimales,  seen  on  the  margins  of  the  lids  at  the  lateral 

extremity  of  the  lacus  lacrimalis.    The  superior  duct,  the  smaller  and  shorter  of  the 

66 


1042      ORGANS  OF   THE  SENSES  AND   THE   COMMON  INTEGUMENT 


two,  at  first  ascends,  and  tlien  bends  at  an  acnte  angle,  and  passes  medialward 
and  downward  to  the  lacrimal  sac.    The  inferior  duct  at  first  descends,  and  then 

runs  almost  horizontally  to  the  lacri- 
/y  mal  sac.    At  the  angles  they  are  dilated 

into  ampullae;  their  walls  are  dense  in 
structure  and  their  mucous  lining  is 
covered  by  stratified  squamous  epi- 
thelium, placed  on  a  basement  mem- 
brane.     Outside  the  latter  is  a  layer 


Fig.  864. — The  lacrimal  apparatus.     Right  side. 


Fig.  865. — Alveoli  of  lacrimal  gland. 


of  striped  muscle,  continuous  with  the  lacrimal  part  of  the  Orbicularis  oculi;  at 
the  base  of  each  lacrimal  papilla  the  muscular  fibres  are  circularly  arranged  and 
form  a  kind  of  sphincter. 

The  Lacrimal  Sac  (saccus  lacriinalis). — The  lacrimal  sac  is  the  upper  dilated  end 
of  the  nasolacrimal  duct,  and  is  lodged  in  a  deep  groove  formed  by  the  lacrimal  bone 
and  frontal  process  of  the  maxilla.  It  is  oval  in  form  and  measures  from  12  to  15 
mm.  in  length;  its  upper  end  is  closed  and  rounded;  its  lower  is  continued  into  the 
nasolacrimal  duct.  Its  superficial  surface  is  covered  by  a  fibrous  expansion  derived 
from  the  medial  palpebral  ligament,  and  its  deep  surface  is  crossed  by  the  lacrimal 
part  of  the  Orbicularis  oculi  (page  467),  which  is  attached  to  the  crest  on  the 
lacrimal  bone. 

Structure. — The  lacrimal  sac  consists  of  a  fibrous  elastic  coat,  lined  internal^  by  mucous 
membrane:  the  latter  is  continuous,  through  the  lacrimal  ducts,  with  the  conjunctiva,  and 
through  the  nasolacrimal  duct  with  the  mucous  membrane  of  the  nasal  cavity. 

The  Nasolacrimal  Duct  {ductus  nasolacrimalis;  nasal  duct). — The  nasolacrimal 
duct  is  a  membranous  canal,  about  18  mm.  in  length,  which  extends  from  the  lower 
part  of  the  lacrimal  sac  to  the  inferior  meatus  of  the  nose,  where  it  ends  by  a  some- 
what expanded  orifice,  provided  with  an  imperfect  valve,  the  plica  lacrimalis 
( Hasneri),  formed  by  a  fold  of  the  mucous  membrane.  It  is  contained  in  an  osseous 
canal,  formed  by  the  maxilla,  the  lacrimal  bone,  and  the  inferior  nasal  concha; 
it  is  narrower  in  the  middle  than  at  either  end,  and  is  directed  downward,  backward, 
and  a  little  lateralward.  The  mucous  lining  of  the  lacrimal  sac  and  nasolacrimal 
duct  is  covered  with  columnar  epithelium,  which  in  places  is  ciliated. 

Applied  Anatomy. — The  eyelids  are  composed  of  various  tissues,  and  consequently  are  liable 
to  a  variety  of  diseases.  The  skin  covering  them  is  thin  and  dehcate,  and  is  supported  on  a 
quantity  of  loose  areolar  subcutaneous  tissue,  devoid  of  fat.  In  consequence  of  this  it  is  very 
freely  movable,  and  is  liable  to  be  drawn  down  by  the  contraction  of  neighboring  cicatrices, 
and  thus  produce  an  eversion  of  the  lid,  known  as  ectropion.  Inversion  of  the  lids  {entropion) 
from  spasm  of  the  Orbicularis  ocuh  or  from  chronic  inflammation  of  the  palpebral  conjimctiva 
may  also  occur.  The  eyelids  are  richly  supplied  with  blood,  and  are  often  the  seat  of  vascular 
growths,  such  as  n£Evi.  Rodent  ulcer  frequently  commences  about  the  medial  palpebral  com- 
missure. The  loose  cellular  tissue  beneath  the  skin  is  liable  to  become  extensively  infiltrated 
either  with  blood  or  inflammatory  products,  producing  very  great  swelling.  Even  from 
very  shght  injuries  to  this  tissue,  the  extravasation  of  blood  may  be  so  great  as  to  produce  con- 
siderable swelUng  of  the  eyelids  and  complete  closure  of  the  eye,  and  the  same  is  the  case  when 


THE  EXTERNAL  EAR  104:5 

inflammatory  products  arc  puurcd  out.  Tlic  follicles  ol'  tlu'  eyelashes,  or  llic  sebaceous  glands 
associated  witli  these  follicles,  may  be  the  seat  of  inflammation,  constitutinK  the  ordinary  stye. 
The  tarsal  glands  arc  affected  in  the  so-called  larsul  tumor,  which,  according  to  some,  is  caused 
by  the  retained  secretion  of  these  glands;  by  others  it  is  believed  to  be  a  neoplasm  connected 
with^the  gland.  The  ciliary  follicles  arc  liable  to  become  inflamed,  constituting  the  disease 
known  as  blcpharilis  ciliaris.  Irregular  or  disorderly  growth  of  the  eyelashes  not  infrequently 
occurs,  some  of  them  being  turned  toward  the  eyeball  and  producing  inflammation  and  ulcera- 
tion of  the  cornea,  and  possibly  eventually  complete*  destruction  of  the  eye.  The  Orbicularis 
oculi  may  be  the  seat  of  spasm,  either  in  the  form  of  slight  quivering  of  the  lids;  or  repeated 
twitchings,  most  commonly  due  to  errors  of  refraction  in  children;  or  more  continuous  spasms, 
due  to  some  irritation  of  the  trigeminal  or  facial  nerve.  The  Orbicularis  oculi  may  be  para- 
Ij^zed  with  the  other  facial  muscles.  Under  these  circumstances  the  patient  is  unable  to  close 
the  lids,  and,  if  he  attempts  to  do  so,  rolls  the  eyeball  upward  under  the  upper  eyelid.  The 
tears  overflow  from  displacement  of  the  lower  eyelid,  and  the  conjunctiva  and  cornea,  being 
constantly  exposed  and  the  patient  being  unable  to  wink,  become  irritated  from  dust  and  foreign 
bodies.  Ptosis,  or  dropping  of  the  upper  eyelid,  may  be  congenital,  or  may  be  due  to  paralysis 
of  the  Levator  palpebrae  superioris,  in  which  case  there  will  probably  be  other  symptoms  of 
implication  of  the  oculomotor  nerve.  The  eyelids  may  be  the  seat  of  bruises,  wounds,  or  burns. 
Following  burns,  adhesion  of  the  margins  of  the  lids  to  each  other,  or  adhesion  of  the  lids  to 
the  bulb,  may  take  place.  They  are  sometimes  the  seat  of  emphysema,  after  fracture  of  some 
of  the  thin  bones  forming  the  medial  wall  of  the  orbit.  If  shortly  after  such  an  injury  the  patient 
blows  his  nose,  air  is  forced  from  the  nostril  through  the  lacerated  structures  into  the  connective 
tissue  of  the  eyelids,  which  suddenly  swell  up  and  present  the  peculiar  crackhng  characteristic 
of  this  affection. 

Foreign  bodies  frequently  get  into  the  conjunctival  sac  and  cause  great  pain,  especially  if 
they  come  in  contact  with  the  corneal  surface,  during  the  movements  of  the  eyelids  and  the 
eye  on  each  other.  The  conjunctiva  is  often  involved  in  severe  injuries  of  the  eyeball,  but  is 
seldom  ruptured  alone;  the  most  common  form  of  injury  to  the  conjunctiva  alone  is  from  a 
burn,  either  from  fire,  strong  acids,  or  lime.  In  these  cases  union  is  liable  to  take  place  between 
the  eyehd  and  the  eyeball.  The  conjunctiva  is  often  the  seat  of  inflammation  arising  from  many 
different  causes,  and  the  arrangement  of  the  conjunctival  vessels  should  be  remembered  as 
affording  a  means  of  diagnosis  between  this  condition  and  injection  of  the  sclera,  which  is  present 
in  inflammation  of  the  deeper  structures  of  the  bulb  of  the  eye.  The  inflamed  conjunctiva  is 
bright  red;  the  vessels  are  large  and  tortuous,  and  greatest  at  the  circumference,  shading  off 
toward  the  corneal  margin;  they  anastomose  freely  and  form  a  dense  net -work,  and  they  can 
be  emptied  or  displaced  by  gentle  pressure.  Inflammation  of  the  underlying  sclera,  ciliary 
body,  or  iris  is  a  far  more  serious  condition;  the  injection  is  in  the  deeper  vessels  of  the  eye, 
and  as  seen  through  the  sclera  presents  a  diffuse  and  dull  purplish  or  violet  zone  of  circum- 
corneal  discoloration. 

The  lacrimal  gland  is  occasionally,  though  rarely,  the  seat  of  inflammation,  either  acute  or 
chronic;  it  is  also  sometimes  the  seat  of  tumors,  benign  or  malignant,  and  for  these  may  require 
removal.  This  may  be  done  by  an  incision  through  the  skin,  just  below  the  eyebrow;  and  the 
gland,  being  invested  with  a  special  capsule,  may  be  isolated  and  removed,  without  opening  the 
general  cavity  of  the  orbit.  The  lacrimal  ducts  may  be  obstructed,  either  as  a  congenital  defect 
or  by  some  foreign  body,  as  an  eyelash  or  a  dacrj'olith,  causing  the  tears  to  run  over  the  cheek. 
The  lacrimal  ducts  may  also  become  occluded  as  a  result  of  burns  or  injury;  overflow  of  the 
tears  may  in  addition  result  from  deviation  of  the  puncta,  or  from  chronic  inflammation  of  the 
lacrimal  sac.  This  latter  condition  is  set  up  by  some  obstruction  to  the  nasolacrimal  duct, 
frequentlj"  occurring  in  tuberculous  subjects.  In  consequence  of  this  the  tears  and  mucus  accu- 
mulate in  the  lacrimal  sac  and  distend  it.  Suppuration  in  the  lacrimal  sac  is  sometimes  met 
with ;  this  may  be  the  sequel  of  a  chronic  inflammation ;  or  may  occur  after  some  of  the  eruptive 
fevers,  in  cases  where  the  lacrimal  passages  were  previously  quite  healthy.  It  may  lead  to  lacri- 
mal fistula  from  an  abscess  forming  in  the  sac,  which  bursts  or  is  opened  on  the  surface;  the 
condition  is  often  seen  in  badly  nourished,  tuberculous  children. 

THE  ORGAN  OF  HEARING  (ORG ANON  AUDITUS;  THE  EAR). 

The  ear,  or  organ  of  hearing,  is  divisible  into  three  parts:  the  external  ear,  the 
middle  ear  or  tympanic  cavity,  and  the  internal  ear  or  labyrinth. 

The  External  Ear. 

The  external  ear  consists  of  the  expanded  portion  named  the  auricula  or  pinna, 
and  the  external  acoustic  meatus.    The  former  projects  from  the  side  of  the  head 


1044        ORGANS  OF   THE  SENSES  AND   THE  COMMON  INTEGUMENT 


Fig.  866.— The  auricula, 
surface. 


Lateral 


and  serves  to  collect  the  vibrations  of  the  air  by  which  sound  is  produced;  the  latter 
leads  inward  from  the  bottom  of  the  auricula  and  conducts  the  vibrations  to  the 
tympanic  cavity. 

The  Auricula  or  Pinna  (Fig.  800)  is  of  an  ovoid  form,  with  its  larger  end  directed 
upward.  Its  lateral  surface  is  irregularly  concave,  directed  slightly  forward,  and 
presents  numerous  eminences  and  depressions  to  which  names  have  been  assigned. 

The  prominent  rim  of  the  auricula  is  called  the  helix; 
where  the  helix  turns  downward  behind,  a  small  tuber- 
cle, the  auricular  tubercle  of  Darwin,  is  frequently  seen; 
this  tubercle  is  very  evident  about  the  sixth  month 
of  fetal  life  when  the  whole  auricula  has  a  close  re- 
semblance to  that  of  some  of  the  adult  monkeys. 
Another  curved  prominence,  parallel  with  and  in 
front  of  the  helix,  is  called  the  antihelix ;  this  divides 
above  into  two  crura,  between  which  is  a  triangular 
depression,  the  fossa  triangularis.  The  narrow-curved 
depression  betw^een  the  helix  and  the  antihelix  is 
called  the  scapha;  the  antihelix  describes  a  curve 
around  a  deep,  capacious  cavity,  the  concha,  which  is 
partially  divided  into  two  parts  by  the  crus  or  com- 
mencement of  the  helix;  the  upper  part  is  termed  the 
cymba  conchae,  the  lower  part  the  cavum  conchae. 
In  front  of  the  concha,  and  projecting  backward  over 
the  meatus,  is  a  small  pointed  eminence,  the  tragus, 
so  called  from  its  being  generally  covered  on  its  under 
surface  with  a  tuft  of  hair,  resembling  a  goat's  beard. 
Opposite  the  tragus,  and  separated  from  it  by  the  intertragic  notch,  is  a  small 
tubercle,  the  antitragus.  Below  this  is  the  lobule,  composed  of  tough  areolar  and 
adipose  tissues,  and  wanting  the  firmness  and  elasticity  of  the  rest  of  the  auricula. 
The  cranial  surface  of  the  auricula  presents  elevations  which  correspond  to  the 
depressions  on  its  lateral  surface  and  after  which  they  are  named,  e.  g.,  eminentia 
conchae,  eminentia  triangularis,  etc. 

Structure. — The  auricula  is  composed  of  a  thin  plate  of  yellow  fibrocartilage,  covered  with 
integument,  and  connected  to  the  surrounding  parts  by  ligaments  and  muscles;  and  to  the  com- 
mencement of  the  external  acoustic  meatus  by  fibrous  tissue. 

The  skin  is  thin,  closely  adherent  to  the  cartilage,  and  covered  with  fine  hairs  furnished  with 
sebaceous  glands,  which  are  most  numerous  in  the  concha  and  scaphoid  fossa.  On  the  tragus 
and  antitragus  the  hairs  are  strong  and  numerous.  The  skin  of  the  auricula  is  continuous  with 
that  lining  the  external  acoustic  meatus. 

The  cartilage  of  the  auricula  (cartilago  auriculae;  cartilage  of  the  pinna)  (Figs.  867,  868)  con- 
sists of  a  single  piece;  it  gives  form  to  this  part  of  the  ear,  and  upon  its  surface  are  found  the 
eminences  and  depressions  above  described.  It  is  absent  from  the  lobule;  it  is  deficient,  also, 
between  the  tragus  and  beginning  of  the  helix,  the  gap  being  filled  up  by  dense  fibrous  tissue. 
At  the  front  part  of  the  auricula,  where  the  helix  bends  upward,  is  a  small  projection  of  cartilage, 
called  the  spina  helicis,  while  in  the  lower  part  of  the  helix  the  cartilage  is  prolonged  downward 
as  a  tail-like  process,  the  Cauda  helicis;  this  is  separated  from  the  antihelix  by  a  fissure,  the 
fissura  antitragohelicina.  The  cranial  aspect  of  the  cartilage  exhibits  a  transverse  furrow,  the 
sulcus  antihelicis  transversus,  which  corresponds  with  the  inferior  crus  of  the  antihehx  and 
separates  the  eminentia  conchae  from  the  eminentia  triangularis.  The  eminentia  conchae  is 
crossed  by  a  vertical  ridge  {ponticulus) ,  which  gives  attachment  to  the  Auricularis  posterior 
muscle.  In  the  cartilage  of  the  auricula  are  two  fissures,  one  behind  the  crus  helicis  and  another 
in  the  tragus. 

The  ligaments  of  the  auricula  {ligamenti  auricularia  [Valsalva];  ligaments  of  the  pinna)  consist 
of  two  sets:  (1)  extrinsic,  connecting  it  to  the  side  of  the  head;  (2)  intrinsic,  connecting  various 
parts  of  its  cartilage  together. 

The  extrinsic  ligaments  are  two  in  number,  anterior  and  posterior.  The  anterior  ligament 
extends  from  the  tragus  and  spina  helicis  to  the  root  of  the  zygomatic  process  of  the  temporal 
bone.  The  posterior  ligament  passes  from  the  posterior  surface  of  the  concha  to  the  outer  surface 
of  the  mastoid  process. 


THE  EXTERNAL  EAR 


1045 


The  chit'f  intrinsic  ligaments  are:  («)  a  .stionfi  librou.s  baiul,  .strclcliint:;  Iruiii  tlic  tragus  to  the 
eominenccmcnt  of  the  lielix,  completing  the  nioatu.s  in  front,  and  partly  oncirclinp;  the  boundary 
of  the  concha;  and  {b)  a  band  between  the  antihelix  and  the  cauda  helicis.  Other  letis  important 
bands  are  found  on  the  cranial  surface  of  the  pinna. 


Spina  helicis 


Cartilage  of 
meatus 


\ 


helicis  transvcrsus 
Eriiinentin  conchae 


7 

Ponticulus 

Cauda  helicis 


Fig.  867. — Cranial  surface  of  cartilage  of  right  auricula. 


The  muscles  of  the  auricula  (Fig.  868)  consist  of  two  sets:  (1)  the  extrinsic,  which  connect  it 
with  the  skull  and  scalp  and  move  the  auricula  as  a  whole;  and  (2)  the  intrinsic,  which  extend 
from  one  part  of  the  auricle  to  another. 

The  extrinsic  muscles  are  the  Auriculares  anterior,  superior,  and  posterior. 

The  Au7-icularis  anterior  {Attrahens 
aurem),  the  smallest  of  the  three,  is  thin, 
fan-shaped,  and  its  fibers  are  pale  and  in- 
distinct. It  arises  from  the  lateral  edge 
of  the  galea  aponeurotica,  and  its  fibres 
converge  to  be  inserted  into  a  projection 
on  the  front  of  the  hehx. 

The  Auricularis  superior  (Attolens 
aurem),  the  largest  of  the  thi'ee,  is  thin 
and  fan-shaped.  Its  fibres  arise  from  the 
galea  aponem-otica,  and  converge  to  be 
inserted  by  a  thin,  flattened  tendon  into 
the  upper  part  of  the  cranial  surface  of  the 
auricula. 

The  Auricularis  posterior  {Retr  aliens 
aurem)  consists  of  two  or  three  fleshy 
fasciculi,  which  arise  from  the  mastoid 
portion  of  the  temporal  bone  by  short 
aponeurotic  fibres.  They  are  inserted  into 
the  lower  part  of  the  cranial  surface  of 
the  concha. 

Actions. — In  man,  these  muscles  possess 
very  little  action :  the  Auricularis  anterior 
draws  the  amicula  forward  and  upward; 
the  Aimcularis  superior  slightly  raises  it; 
and  the  Auricularis  posterior  draws  it 
backward. 

The  intrinsic  muscles  are  the: 


Hehcis  major. 
Helicis  minor. 
Tragi  cus. 


Antitragicus. 
Transversus  auriculae. 
ObHquus  auriculae. 


Fig.  S6S. — The  muscles  of  the  auricula. 


The  Helicis  major  is  a  narrow  vertical  band  situated  upon  the  anterior  margin  of  the  helix. 
It  arises  below,  from  the  spina  helicis,  and  is  inserted  into  the  anterior  border  of  the  helix, 
just  where  it  is  about  to  curve  backward. 

The  Helicis  minor  is  an  oblique  fasciculus,  covering  the  crus  helicis. 


1046      ORGANS  OF   THE  SENSES  AND   THE   COMMON  INTEGUMENT 

The  Tragicus  is  a  short,  fluttencd  vertical  band  on  the  lateral  surface  of  the  tragus. 

The  Antitragicus  arises  from  the  outer  part  of  the  antitragus,  and  is  inserted  into  the  cauda 
helicis  and  antihelix. 

The  T7'ansversus  auriculae  is  placed  on  the  cranial  surface  of  the  pinna.  It  consists  of  scattered 
fibres,  partly  tendinous  and  pai'tly  muscular,  extending  from  the  eminentia  conchae  to  the  promi- 
nence corresponding  with  the  scapha. 

The  Obliquus  auriculae,  also  on  the  cranial  surface,  consists  of  a  few  fibres  extending  from 
the  upper  and  back  part  of  the  concha  to  the  convexity  immediately  above  it. 

Nerves. — The  Auriculares  anterior  and  superior  and  the  intrinsic  muscles  on  the  lateral  surface 
are  supplied  by  the  temporal  branch  of  the  facial  nerve,  the  Auricularis  posterior  and  the  intrinsic 
muscles  on  the  cranial  surface  by  the  posterior  auricular  branch  of  the  same  nerve. 

The  arteries  of  the  auricula  are  the  posterior  auricular  from  the  external  carotid,  the  anterior 
auricular  from  the  superficial  temporal,  and  a  branch  from  the  occipital  artery. 

The  veins  accompany  the  corresponding  arteries. 

The  sensory  nerves  are:  the  great  auricular,  from  the  cervical  plexus;  the  auricular  branch 
of  the  vagus;  the  auriculotemporal  branch  of  the  mandibular  nerve;  and  the  lesser  occipital 
from  the  cervical  plexus. 

Cartilage  of  amicida 
Attic 
Incus 

Malleus 

Tympanic  cavity 

Tensor  tympani 


Cartilaginous 

part  of  ext. 

acoustic  .meatus 


Bony  part  of 

ext.  acoustic 

meatus 


Fig.  869. — External  and  middle  ear,  opened  from  the  front.     Right  side. 


The  External  Acoustic  Meatus  {meatus  acusticus  externus;  external  auditory  canal 
or  meatus)  extends  from  the  bottom  of  the  concha  to  the  tympanic  membrane  (Figs. 
869,  870).  It  is  about  4  cm.  in  length  if  measured  from  the  tragus;  from  the  bottom 
of  the  concha  its  length  is  about  2.5  cm.  It  forms  an  S-shaped  curve,  and  is  directed 
at  first  inward,  forward,  and  slightly  upward  {pars  externa) ;  it  then  passes  inward 
and  backward  {yars  media),  and  lastly  is  carried  inward,  forward,  and  slightly 
downward  {yars  interna).  It  is  an  oval  cylindrical  canal,  the  greatest  diameter 
being  directed  downward  and  backward  at  the  external  orifice,  but  nearly  hori- 
zontally at  the  inner  end.  It  presents  two  constrictions,  one  near  the  inner  end 
of  the  cartilaginous  portion,  and  another,  the  isthmus,  in  the  osseous  portion,  about 
2  cm.  from  the  bottom  of  the  concha.  The  tympanic  membrane,  which  closes  the 
inner  end  of  the  meatus,  is  obliquely  directed;  in  consequence  of  this  the  floor  and 
anterior  wall  of  the  meatus  are  longer  than  the  roof  and  posterior  wall. 


THE  EXTERNAL  EAR 


104'; 


The  external  acoustic  nieatiis  is  loniicd  partly  by  cartilay'e  and  nienihrane, 
and  partly  by  bone,  and  is  lined  by  skin. 

The  cartilaginous  portion  {iiicdtiis  (icusiicus  c.rtcniN.s  cdrtUaginniH)  is  about  S  mm. 
in  length;  it  is  continuous  with  the  cartilage  of  the  auricula,  and  firmly  attached 
to  the  circumference  of  the  auditory  process  of  the  temporal  bone.  The  cartilage 
is  deficient  at  the  upper  and  back  part  of  the  meatus,  its  place  being  supplied  by 
fibrous  membrane;  two  or  three  deep  fissures  are  present  in  the  anterior  part  of  the 
cartilage. 

The  osseous  portion  {iiicatus  (iriisficus  c.vtcnDi.s'  o.s.seus)  is  about  16  mm.  in  length, 
and  is  narrower  than  the  cartilaginous  portion.  It  is  directed  inward  and  a  little 
forward,  forming  in  its  course  a  slight  curve  the  convexity  of  which  is  upward  and 
backward.    Its  inner  end  is  smaller  than  the  outer,  and  sloped,  the  anterior  wall 

Auditory  tube 

Condyle  of  matulible 


Internal  carotid 
artery 


Internal  acoustic 
meatus 


of  parotid  gland 

xigus 

External  acoustic 
meatus 


Tympanic  cavity  . 
Tympana  memb 
Masto 


Helix 


Transverse  sinus 


Fig.  870. — Horizontal  section  through  left  ear;  upper  half  of  section. 


projecting  beyond  the  posterior  for  about  4  mm. ;  it  is  marked,  except  at  its  upper 
part,  by  a  narrow  groove,  the  tympanic  sulcus,  in  which  the  circumference  of  the 
tympanic  membrane  is  attached.  Its  outer  end  is  dilated  and  rough  in  the  greater 
part  of  its  circumference,  for  the  attachment  of  the  cartilage  of  the  auricula.  The 
front  and  lower  parts  of  the  osseous  portion  are  formed  by  a  curved  plate  of  bone, 
the  tympanic  part  of  the  temporal,  which,  in  the  fetus,  exists  as  a  separate  ring 
(annulus  tympanicus,)  incomplete  at  its  upper  part  (page  245). 

The  skin  lining  the  meatus  is  very  thin;  adheres  closely  to  the  cartilaginous 
and  osseous  portions  of  the  tube,  and  covers  the  outer  surface  of  the  tympanic 
membrane.  After  maceration,  the  thin  pouch  of  epidermis,  when  withdrawn, 
preserves  the  form  of  the  meatus.  In  the  thick  subcutaneous  tissue  of  the  cartil- 
aginous part  of  the  meatus  are  numerous  ceruminous  glands,  which  secrete  the 
ear-wax;  their  structure  resembles  that  of  the  sudoriferous  glands. 

Relations  of  the  Meatus. — In  front  of  the  osseous  part  is  the  condyle  of  the  mandible,  which 
however,  is  frequently  separated  from  the  cartilaginous  part  by  a  portion  of  the  parotid  gland. 
The  movements  of  the  jaw  influence  to  some  extent  the  lumen  of  this  latter  portion.  Behind  the 
osseous  part  are  the  mastoid  air  cells,  separated  from  the  meatus  by  a  thin  layer  of  bone. 

The  arteries  supplying  the  meatus  are  branches  from  the  posterior  auricular,  internal  maxillary, 
and  temporal. 

The  nerves  are  chiefly  derived  from  the  auriculotemporal  branch  of  the  mandibular  nerve 
and  the  auricular  branch  of  the  vagus. 


1048        ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

Applied  Anatomy. — Malformations,  such  as  imperfect  development  of  the  external  parts, 
supernumerary  auricles,  or  absence  of  the  meatus,  are  occasionally  met  with.  The  skin  of  the 
auricula  is  thin  and  richW  suppUed  with  blood,  but  in  spite  of  this  it  is  often  the  seat  of  frost- 
bite, due  to  the  fact  that  it  is  much  exposed  to  cold,  and  lacks  the  usual  underlying  subcutaneous 
fat  found  in  most  other  parts  of  the  body.  A  collection  of  blood  is  sometimes  found  between 
the  cartilage  and  perichondrium  {hematoma  auris),  usually  the  result  of  traumatism,  but  not 
necessarily  due  to  this  cause;  it  is  said  to  occur  most  frequently  in  the  ears  of  the  insane.  Keloid 
sometimes  grows  in  the  auricula  around  the  puncture  made  for  earrings,  and  epithelioma  occa- 
sionally affects  this  part.  Deposits  of  urate  of  soda  are  often  met  with  in  the  auricula  in  gouty 
subjects. 

The  external  acoustic  meatus  can  be  most  satisfactorily  examined  by  Ught  reflected  down  a 
funnel-shaped  speculum;  by  gently  moving  the  latter  in  different  directions  the  greater  part 
of  the  canal  and  tj^mpanic  membrane  can  be  brought  into  view.  In  using  this  instrument,  it  is 
advisable  that  the  auricula  should  be  drawn  upward,  backward,  and  a  httle  outward,  so  as  to 
render  the  meatus  as  straight  as  possible.  The  points  to  be  noted  are:  the  presence  of  wax  or 
foreign  bodies;  the  size  of  the  meatus;  and  the  condition  of  the  tympanic  membrane.  Accumu- 
lation of  wax  is  often  a  cause  of  deafness,  and  may  give  rise  to  very  serious  consequences,  such 
as  ulceration  of  the  membrane;  it  is  best  removed  by  syringing.  Foreign  bodies  are  not  infre- 
quently introduced  into  the  ear  by  children,  and,  when  situated  in  the  first  portion  of  the  meatus, 
may  be  removed  with  tolerable  facility  by  means  of  a  minute  hook  or  loop  of  fine  wire,  aided 
by  reflected  light;  but  when  they  have  slipped  beyond  the  narrow  middle  part  of  the  meatus, 
their  removal  is  in  no  wnse  easy,  and  attempts  to  effect  it,  in  inexperienced  hands,  may  be  fol- 
lowed by  destruction  of  the  tympanic  membrane  and  possibly  the  contents  of  the  tympanic 
cavity.  The  calibre  of  the  external  acoustic  meatus  may  be  narrowed  by  inflammation'  of  its 
lining  membrane;  by  periostitis;  by  polypi;  or  by  exostoses. 

Post,  malltolar  fold 
Long  crus  of  ijiciis  ^        Pars  flaccida 

Lat.  pwc.  of  malleiis 
Ant.  malleolar  fold 

Manubrium 

of  7nalleus 

Postero-superior 

quadrant        Tp^^^^"''''!     _^Antero-supericyr 


Postero-inferior       I  J'^^  f  quadrant 

quadrant        ^ W OfW^  W 


Cone  of  light 


A  7itero- inferior  quadrant 
Fig.  871. — Right  tympanic  membrane  as  seen  through  a  speculum. 

At  the  point  of  junction  of  the  osseous  and  cartilaginous  portions  an  obtuse  angle,  which 
projects  into  the  tube  at  its  antero-inferior  wall,  is  formed;  this  produces  a  sort  of  constriction 
and  renders  it  a  narrow  portion  of  the  meatus — an  important  point  to  be  remembered  in  con- 
nection with  the  presence  of  foreign  bodies  in  the  meatus.  The  shortness  of  the  meatus  in  chil- 
dren should  be  borne  in  mind  in  introducing  the  aural  speculum,  so  that  it  be  not  pushed  in  too 
far,  at  the  risk  of  injuring  the  tympanic  membrane;  indeed,  even  in  the  adult  the  speculum 
should  never  be  introduced  beyond  the  constriction  which  marks  the  junction  of  the  osseous  and 
cartilaginous  portions.  Just  in  front  of  the  membrane  is  a  well-marked  depression,  situated 
on  the  floor  of  the  meatus,  and  bounded  by  a  somewhat  prominent  ridge;  in  this  foreign  bodies 
may  become  lodged.  By  aid  of  the  speculum,  combined  with  traction  of  the  auricle  upward  and 
backward,  the  greater  part  of  the  tympanic  membrane  is  rendered  visible  (Fig.  871).  It  is  a 
pearly-gray  membrane,  slightly  gUstening  in  the  adult,  placed  obhquely,  so  as  to  form  with 
the  floor  of  the  meatus  a  very  acute  angle  (about  fifty-five  degi-ees),  while  with  the  roof  it  forms 
an  obtuse  angle.  At  birth  it  is  more  horizontal,  situated  in  almost  the  same  plane  as  the  base 
of  the  skull.  About  midway  between  the  anterior  and  posterior  margins  of  the  membrane,  and 
extending  from  the  centre  obliquely  upward,  is  a  reddish-yeUow  streak;  this  is  the  handle  of 
the  malleus,  which  is  inserted  into  the  membrane.  At  the  upper  part  of  this  streak,  close  to  the 
roof  of  the  meatus,  a  little  white,  rounded  prominence  is  plainly  to  be  seen;  this  is  the  lateral 
or  short  process  of  the  malleus,  projecting  against  the  membrane.     The  tympanic  membrane 


THE  MIDDLE  EAR  OR  TYMPANIC  CAVITY  1049 

does  not  proscMil,  a  plane  surfac(\;  on  the  eonlrar}',  its  centre  is  drawn  inward,  on  aeeount  of  its 
connection  with  tlie  nuuuibriuni  of  the  malleus,  and  thus  the  external  surface  is  rendered  concave. 
The  connections  of  the  nerves  of  the  meatus  exjilain  the  fact  of  the  occurrence,  in  cases  of 
irritation  of  the  meatus,  of  constant  cou{2;hing  and  sneezing,  from  imjjlication  of  the  vagus,  and 
the  vomiting  wliich  may  follow  syringing  the  ears  of  children,  and  the  occasional  heart  failure 
similarly  induced  in  elderly  people.  No  doubt  also  the  association  of  earache  with  toothache  or 
with  cancer  of  the  tongue  is  due  to  implication  of  the  mandibular  branch  of  the  trigeminal  nerve, 
which  supplies  also  the  teeth  and  the  tongue.  The  upper  half  of  the  tympanic  membrane  is 
much  more  vascular  than  the  lower  half;  for  this  reason,  and  also  to  avoid  the  chorda  tympani 
nerve  and  ossicles,  incisions  through  the  membrane  should  be  made  at  the  lower  and  posterior 
part. 

The  Middle  Ear  or  Tympanic  Cavity  (Cavum  Tympani;  Drum; 

Tympanum). 

The  middle  ear  or  tympanic  cavity  is  an  irregular,  laterally  compressed  space 
within  the  temporal  bone.  It  is  filled  with  air,  which  is  conveyed  to  it  from  the 
nasal  part  of  the  pharynx  through  the  auditory  tube.  It  contains  a  chain  of  mov- 
able bones,  which  connect  its  lateral  to  its  medial  wall,  and  serve  to  conve}^  the 
vibrations  communicated  to  the  tympanic  membrane  across  the  cavity  to  the 
internal  ear. 

The  tympanic  cavity  consists  of  two  parts:  the  tympanic  cavity  proper,  opposite 
the  tympanic  membrane,  and  the  attic  or  epitympanic  recess,  above  the  level  of 
the  membrane;  the  latter  contains  the  upper  half  of  the  malleus  and  the  greater 
part  of  the  incus.  Including  the  attic,  the  vertical  and  antero-posterior  diameters 
of  the  cavity  are  each  about  15  mm.  The  transverse  diameter  measures  about 
6  mm.  above  and  4  mm.  below;  opposite  the  centre  of  the  tympanic  membrane 
it  is  only  about  2  mm.  The  tympanic  cavity  is  bounded  laterally  by  the  tympanic 
membrane;  medially,  by  the  lateral  wall  of  the  internal  ear;  it  communicates, 
behind,  with  the  tympanic  antrum  and  through  it  with  the  mastoid  air  cells,  and 
in  front  with  the  auditory  tube  (Fig.  869) . 

The  Tegmental  Wall  or  Roof  {paries  tegmentalis)  is  formed  by  a  thin  plate  of  bone, 
the  tegmen  tympani,  which  separates  the  cranial  and  tympanic  cavities.  It  is 
situated  on  the  anterior  surface  of  the  petrous  portion  of  the  temporal  bone  close 
to  its  angle  of  junction  with  the  squama  temporalis;  it  is  prolonged  backward  so 
as  to  roof  in  the  tympanic  antrum,  and  forward  to  cover  in  the  semicanal  for  the 
Tensor  tympani  muscle.  Its  lateral  edge  corresponds  with  the  remains  of  the 
petrosquamous  suture. 

The  Jugular  Wall  or  Floor  (paries  jugidaris)  is  narrow,  and  consists  of  a  thin  plate 
of  bone  (fundus  tympani)  which  separates  the  tympanic  cavity  from  the  jugular 
fossa.  It  presents,  near  the  labyrinthic  wall,  a  small  aperture  for  the  passage  of 
the  tympanic  branch  of  the  glossopharyngeal  nerve. 

The  Membranous  or  Lateral  Wall  (paries  membranacea;  outer  wall)  is  formed 
mainly  by  the  tympanic  membrane,  partly  by  the  ring  of  bone  into  which  this 
membrane  is  inserted.  This  ring  of  bone  is  incomplete  at  its  upper  part,  forming 
a  notch  (notch  of  Rivinus),  close  to  which  are  three  small  apertures:  the  iter  chordae 
posterius,  the  petrotympanic  fissure,  and  the  iter  chordae  anterius. 

The  iter  chordae  posterius  (apertura  tympanica  canaliculi  chordae)  is  situated  in 
the  angle  of  junction  between  the  mastoid  and  membranous  wall  of  the  tympanic 
cavity  immediately  behind  the  tympanic  membrane  and  on  a  level  with  the  upper 
end  of  the  manubrium  of  the  malleus;  it  leads  into  a  minute  canal,  which  descends 
in  front  of  the  canal  for  the  facial  nerve,  and  ends  in  that  canal  near  the  stylo- 
mastoid foramen.  Through  it  the  chorda  tympani  nerve  enters  the  tympanic 
cavity. 

The  petrotympanic  fissure  (fissura  petrotympanica;  Glaserian  fissure)  opens  just 
above  and  in  front  of  the  ring  of  bone  into  which  the  tympanic  membrane  is 


1050      ORGANS  OF   THE  SENSES  AND   THE  COMMON  INTEGUMENT 


inserted;  in  this  situation  it  is  a  mere  slit  about  2  mm.  in  length.     It  lodges 

the  anterior  process  and  anterior  ligament  of  the  malleus,  and  gives  passage  to  the 

anterior  tympanic  ])ranch  of  the  internal  maxillary  artery. 

The  iter  chordae  anterius  {canal  of  Iliiguier)  is  placed  at  the  medial  end  of  the 

petrotympanic  fissure;  through  it  the  chorda  tympani  nerve  leaves  the  tympanic 

cavity. 

The  Tympanic  Membrane  (membrana  tympani)  (Figs.  871,  872)  separates  the 

tympanic  cavity  from  the  bottom  of  the  external  acoustic  meatus.    It  is  a  thin, 

semitransparent  membrane,  nearly  oval 
in  form,  somewhat  broader  above  than 
below,  and  directed  very  obliquely  down- 
ward and  inward  so  as  to  form  an  angle 
of  about  fifty-five  degrees  with  the  floor 
of  the  meatus.  Its  longest  diameter  is 
downward  and  forward,  and  measures 
from  9  to  10  mm.;  its  shortest  diameter 
measures  from  8  to  9  mm.  The  greater 
part  of  its  circumference  is  thickened, 
and  forms  a  fibrocartilaginous  ring  which  is 
fixed  in  the  tympanic  sulcus  at  the  inner 
end  of  the  meatus.  This  sulcus  is  defi- 
cient superiorly  at  the  notch  of  Rivinus, 
and  from  the  ends  of  this  notch  two  bands, 
the  anterior  and  posterior  malleolar  folds, 
are  prolonged  to  the  lateral  process  of  the 
malleus.  The  small,  somewhat  triangular 
part  of  the  membrane  situated  above  these 
folds  is  lax  and  thin,  and  is  named  the 
pars  fiaccida;  in  it  a  small  orifice  is  some- 
times seen.  The  manubrium  of  the  malleus 
is  firmly  attached  to  the  medial  surface  of 
the  membrane  as  far  as  its  centre,  which 
it  draws  toward  the  tympanic  cavity;  the 
lateral  surface  of  the  membrane  is  thus 
concave,  and  the  most  depressed  part  of 
this  concavity  is  named  the  umbo. 


Fig.  872. — The  tympanic  membrane  viewed  from 
within.  (Testut.)  The  malleus  has  been  resected 
immediately  beyond  its  lateral  process,  in  order  to 
show  the  tympanomalleolar  folds  and  the  membrana 
flaccida.  1.  Tympanic  membrane.  2.  Umbo.  3. 
Handle  of  the  malleus.  4.  Lateral  process.  5.  Anterior 
tympanomalleolar  fold.  6.  Posterior  tympanomalleolar 
fold.  7.  Pars  fiaccida.  8.  Anterior  pouch  of  Troltsch. 
9.  Posterior  pouch  of  Troltsch.  10.  Fibrocartilaginous 
ring.  11.  Petrotympanic  fissure.  12.  Auditory  tube. 
13.  Iter  chordae  posterius.  14.  Iter  chordae  anterius. 
15.  Fossa  incudis  for  short  crus  of  the  incus.  16.  Pro- 
minentia styloidea. 


Structure. — The  tympanic  membrane  is  com- 
posed of  three  strata:  a  lateral  (cutaneous),  an 
intermediate  (fibrous),  and  a  medial  (^nucous).  The  cutaneous  stratum  is  derived  from  the 
integument  lining  the  meatus.  The  fibrous  stratum  consists  of  two  layers:  a  radiate  stratum, 
the  fibres  of  which  diverge  from  the  manubrium  of  the  malleus,  and  a  circular  stratum,  the 
fibres  of  which  are  plentiful  around  the  circumference  but  sparse  and  scattered  near  the  centre 
of  the  membrane.  Branched  or  dendritic  fibres,  as  pointed  out  by  Grliber,  are  also  present, 
especially  in  the  posterior  half  of  the  membrane. 

Vessels  and  Nerves. — The  arteries  of  the  tympanic  membrane  are  derived  from  the  deep 
auricular  branch  of  the  internal  maxillary,  which  ramifies  beneath  the  cutaneous  stratum;  and 
from  the  stylomastoid  branch  of  the  posterior  auricular,  and  tympanic  branch  of  the  internal 
maxillary,  which  are  distributed  on  the  mucous  surface.  The  superficial  veins  open  into  the 
external  jugular;  those  on  the  deep  surface  drain  partly  into  the  transverse  sinus  and  veins  of 
the  dura  mater,  and  partly  into  a  plexus  on  the  auditory  tube.  The  membrane  receives  its 
nerve  supply  from  the  auriculotemporal  branch  of  the  mandibular,  the  auricular  branch  of  the 
vagus,  and  the  tympanic  branch  of  the  glossopharyngeal. 


The  Labyrinthic  or  Medial  Wall  (paries  lahyrinthica;  inner  loall)  (Fig.  873)  is 
vertical  in  direction,  and  presents  for  examination  the  fenestrae  vestibuli  and 
cochleae,  the  promontory,  and  the  prominence  of  the  facial  canal. 


THE  MIDDLE  EAR  OR  TYMPANIC  CAVITY 


1051 


The  fenestra  vestibuli  {fenestra  ovalis)  is  a  reiiit'orm  opening  leading  from  the 
tympanic  cavity  into  the  \e.stibule  of  the  internal  ear;  its  long  diameter  is  horizontal, 
and  its  convex  border  is  upward.  In  the  recent  state  it  is  occupied  by  the  base  of 
the  stapes,  the  circumference  of  whicli  is  fixed  by  the  annular  ligament  to  the  margin 
of  the  foramen. 

The  fenestra  cochleae  [foiestra  rotunda)  is  situated  below  and  a  little  beiiind  the 
fenestra  Acstibuli.  from  which  it  is  separated  by  a  rounded  elevation,  the  promontory. 
It  is  placed  at  the  bottom  of  a  funnel-shaped  depression  and,  in  the  macerated  bone, 
leads  into  the  cochlea  of  the  internal  ear;  in  the  recent  state  it  is  closed  by  a  mem- 
brane, the  secondary  tympanic  membrane,  which  is  concave  toward  the  tympanic 
cavity,  convex  toward  the  cochlea.  This  membrane  consists  of  three  layers:  an 
external,  or  mucous,  derived  from  the  mucous  lining  of  the  tympanic  cavity;  an 
internal,  from  the  lining  membrane  of  the  cochlea;  and  an  intermediate,  or  fibrous 
laver. 


Tympanic  antrum 


Tegmen  tympani 

Prominence  of  lateral  semicircular  canal 
Pi  eminence  of  facial  canal 
Fenestra  vestibuli 
Bt  istle  in  semicanal  for  Tensor  tympani 
Septum  canalis  vvusculotuharii 

Bristle  in  hiatus  of  facial  canal 


Laiotid  canal 
Bony  part  of  auditory  tithe 
Pi  omontory 
Bustle  in  pyramid 
r finest] a  cochleae 


Sulcus  tympanicus 
Mastoid  cdh     ^^  "^^'^  ^'^  stylomastoid  foramen 

Fig.  873. — Coronal  section  of  right  temporal  bone. 


The  promontory  (promontorium)  is  a  rounded  hollow  prominence,  formed  by  the 
projection  outward  of  the  first  turn  of  the  cochlea;  it  is  placed  between  the  fenestrae, 
and  is  furrowed  on  its  surface  by  small  grooves,  for  the  lodgement  of  branches  of  the 
tympanic  plexus.  A  minute  spicule  of  bone  frequently  connects  the  promontory 
to  tfie  pyramidal  eminence. 

The  prominence  of  the  facial  canal  (prominentia  canalis  facialis;  prominence  of 
aqueduct  of  Fallopius)  indicates  the  position  of  the  bony  canal  in  which  the 
facial  nerve  is  contained;  this  canal  traverses  the  labyrinthic  wall  of  the  tympanic 
cavity  above  the  fenestra  vestibuli,  and  behind  that  opening  curves  nearly 
vertically  downward  along  the  mastoid  wall. 

The  mastoid  or  posterior  wall  (paries  mastoidea)  is  wider  abo^'e  than  below,  and 
presents  for  examination  the  entrance  to  the  tympanic  antrum,  the  pyramidal  eminence, 
and  the  fossa  incudis. 


1052      ORGANS  OF  THE  SENSES  AND   THE   COMMON  INTEGUMENT 

The  entrance  to  the  antrum  is  a  large  irregular  aperture,  which  leads  bac-kward 
from  the  epitympanic  recess  into  a  considerable  air  space,  named  the  tympanic 
or  mastoid  antrum  (see  i^age  240).  The  antrum  communicates  behind  and  below 
with  the  mastoid  air  cells,  which  vary  considerably  in  number,  size,  and  form; 
the  antrum  and  mastoid  air  cells  are  lined  by  mucous  membrane,  continuous  with 
that  lining  the  tympanic  cavity.  On  the  medial  wall  of  the  entrance  to  the  antrum 
is  a  rounded  eminence,  situated  above  and  behind  the  prominence  of  the  facial 
canal;  it  corresponds  with  the  position  of  the  ampullated  ends  of  the  superior  and 
lateral  semicircular  canals. 

The  pyramidal  eminence  (erninentia  'pyraviidalis;  pyraviid)  is  situated  immedi- 
ately behind  the  fenestra  vestibuli,  and  in  front  of  the  vertical  portion  of  the  facial 
canal;  it  is  hollow,  and  contains  the  Stapedius  muscle;  its  summit  projects  forward 
toward  the  fenestra  vestibuli,  and  is  pierced  by  a  small  aperture  which  transmits 
the  tendon  of  the  muscle.  The  cavity  in  the  pyramidal  eminence  is  prolonged 
downward  and  backward  in  front  of  the  facial  canal,  and  communicates  with  it 
by  a  minute  aperture  which  transmits  a  twig  from  the  facial  nerve  to  the  Stapedius 
muscle. 

The  fossa  incudis  is  a  small  depression  in  the  lower  and  back  part  of  the  epi- 
tympanic recess;  it  lodges  the  short  crus  of  the  incus. 

The  Carotid  or  Anterior  Wall  (paries  carotica)  is  wider  above  than  below;  it  corre- 
sponds with  the  carotid  canal,  from  which  it  is  separated  by  a  thin  plate  of  bone 
perforated  by  the  tympanic  branch  of  the  internal  carotid  artery,  and  by  the  deep 
petrosal  nerve  which  connects  the  sympathetic  plexus  on  the  internal  carotid 
artery  with  the  tympanic  plexus  on  the  promontory.  At  the  upper  part  of  the 
anterior  wall  are  the  orifice  of  the  semicanal  for  the  Tensor  tympani  muscle  and 
the  tympanic  orifice  of  the  auditory  tube,  separated  from  each  other  by  a  thin 
horizontal  plate  of  bone,  the  septum  canalis  musculotubarii.  These  canals  run  from 
the  tympanic  cavity  forward  and  downward  to  the  retiring  angle  between  the 
squama  and  the  petrous  portion  of  the  temporal  bone. 

The  semicanal  for  the  Tensor  tympani  {semicanalis  m.  tensoris  tympa7ii)  is  the 
superior  and  the  smaller  of  the  two;  it  is  cylindrical  and  lies  beneath  the  tegmen 
tympani.  It  extends  on  to  the  labyrinthic  wall  of  the  tympanic  cavity  and  ends 
immediately  above  the  fenestra  vestibuli. 

The  septum  canalis  musculotubarii  {processus  cochleariformis)  passes  backward 
below  this  semicanal,  forming  its  lateral  wall  and  floor;  it  expands  above  the  ante- 
rior end  of  the  fenestra  vestibuli  and  terminates  there  by  curving  laterally  so  as 
to  form  a  pulley  over  which  the  tendon  of  the  muscle  passes. 

The  auditory  tube  (tuba  auditiva;  Eustachian  tube)  is  the  channel  through  which 
the  tympanic  cavity  communicates  with  the  nasal  part  of  the  pharynx.  Its  length 
is  about  36  mm.,  and  its  direction  is  downward,  forward,  and  medialward,  forming 
an  angle  of  about  45  degrees  with  the  sagittal  plane  and  one  of  from  30  to  40  degrees 
with  the  horizontal  plane.  It  is  formed  partly  of  bone,  partly  of  cartilage  and  fibrous 
tissue  (Fig.  869). 

The  osseous  portion  (pars  osseo  tubae  auditivae)  is  about  12  mm.  in  length.  It 
begins  in  the  carotid  wall  of  the  tympanic  cavity,  below  the  septum  canalis  musculo- 
tubarii, and,  gradually  narrowing,  ends  at  the  angle  of  junction  of  the  squama  and 
the  petrous  portion  of  the  temporal  bone,  its  extremity  presenting  a  jagged  margin 
which  serves  for  the  attachment  of  the  cartilaginous  portion. 

The  cartilaginous  portion  (pars  cartilaginea  tubae  auditivae),  about  24  mm.  in  length, 
is  formed  of  a  triangular  plate  of  elastic  fibrocartilage,  the  apex  of  which  is  attached 
to  the  margin  of  the  medial  end  of  the  osseous  portion  of  the  tube,  while  its  base 
lies  directly  under  the  mucous  membrane  of  the  nasal  part  of  the  pharynx,  where 
it  forms  an  elevation,  the  torus  tubarius  or  cushion,  behind  the  pharyngeal  orifice  of 
the  tube.   The  upper  edge  of  the  cartilage  is  curled  upon  itself,  being  bent  laterally 


THE  AUDITORY  OSSICLES 


1053 


so  as  to  present  on  transverse  section  the  appearance  of  a  hook;  a  p;roove  or  furrow 
is  thus  prochiced,  wliich  is  open  below  and  hiterally,  and  this  part  of  the  c-anal  is 
completed  by  fibrous  nienibrane.  The  cartila<;e  lies  in  a  is^rooxii  between  the  petrous 
part  of  the  temporal  and  the  great  wing  of  the  sphenoid;  this  groove  ends  oi)posite 
the  middle  of  the  medial  pterygoid  plate.  The  cartilaginous  and  bony  portions  of 
the  tube  are  not  in  the  same  plane,  the  former  inclining  downward  a  little  more 
than  the  latter.  The  diameter  of  the  tube  is  not  uniform  throughout,  being  greatest 
at  the  pharyngeal  orifice,  least  at  the  junction  of  the  l)ony  and  cartilaginous  por- 
tions, and  again  increased  toward  the  tympanic  cavity;  the  narrowest  part  of  the 
tube  is  termed  the  isthmus.  The  position  and  relations  of  the  pharyngeal  orifice 
are  described  with  the  nasal  part  of  the  pharynx.  The  mucous  membrane  of  the 
tube  is  continuous  in  front  with  that  of  the  nasal  part  of  the  pharynx,  and  behind 
with  that  of  the  tympanic  cavity;  it  is  covered  with  ciliated  epithelium  and  is  thin 
in  the  osseous  portion,  while  in  the  cartilaginous  portion  it  contains  many  mucous 
glands  and  near  the  pharyngeal  orifice  a  considerable  amount  of  adenoid  tissue, 
which  has  been  named  by  Gerlach  the  tube  tonsil.  The  tube  is  opened  during  deglu- 
tition by  the  Salpingopharyngeus  and  Dilatator  tubae.  The  latter  arises  from  the 
hook  of  the  catilage  and  from  the  membranous  part  of  the  tube,  and  blends  below 
with  the  Tensor  veli  palatini. 


Head 


The  Auditory  Ossicles  (Ossicula  Auditus). 

The  tympanic  cavity  contains  a  chain  of  three  movable  ossicles,  the  malleus, 
incus,  and  stapes.  The  first  is  attached  to  the  tympanic  membrane,  the  last  to 
the  .circumference  of  the  fenestra  vestibuli,  the  incus  being  placed  between  and 
connected  to  both  by  delicate  articulations. 

The  Malleus  (Fig.  874),  so  named  from  its  fancied  resemblance  to  a  hammer, 
consists  of  a  head,  neck,  and  three  processes,  viz.,  the  manubrium,  the  anterior  and 
lateral  processes. 

The  head  {capitulum  mallei)  is  the  large  upper  extremity  of  the  bone;  it  is  oval 
in  shape,  and  articulates  posteriorly  with  the  incus,  being  free  in  the  rest  of  its 
extent.  The  facet  for  articu- 
lation with  the  incus  is  con- 
stricted near  the  middle,  and 
consists  of  an  upper  larger  and 
lower  smaller  part,  which  form 
nearly  a  right  angle  with  each 
other.  Opposite  the  constric- 
tion the  lower  margin  of  the 
facet  projects  in  the  form  of  a 
process,  the  cog-tooth  or  spur  of 
the  malleus. 

The  neck  (coUiim  mallei)  is 
the  narrow  contracted  part  just 
beneath  the  head ;  below  it,  is  a 
a  prominence,  to  which  the 
various  processes  are  attached. 

The  manubrium  mallei  {handle)  is  connected  by  its  lateral  margin  with  the  tym- 
panic membrane.  It  is  directed  downward,  medialward,  and  backward ;  it  decreases 
in  size  toward  its  free  end,  which  is  curved  slightly  forward,  and  flattened  trans- 
versely. On  its  medial  side,  near  its  upper  end,  is  a  slight  projection,  into  which 
the  tendon  of  the  Tensor  tympani  is  inserted. 

The  anterior  process  (processus  anterior  [Folii];  processus  gracilis)  is  a  delicate 
spicule,  which  springs  from  the  eminence  below  the  neck  and  is  directed  forward 


Fig.  874. — Left  malleus.     .-1.  From  behind.     B.  From  within. 


1054      ORGANS  OF   THE  SENSES  AND   THE   COMMON  INTEGUMENT 

to  the  petrotympanic  fissure,  to  which  it  is  connected  by  ligamentous  fibres.  In 
the  fetus  this  is  the  longest  process  of  the  malleus,  and  is  in  direct  continuity  with 
the  cartilage  of  iNIeckel. 

The  lateral  process  {processus  lateralis;  processus  hrevis)  is  a  slight  conical  projec- 
tion, which  springs  from  the  root  of  the  manubrium;  it  is  directed  laterally,  and  is 
attached  to  the  upper  part  of  the  tympanic  membrane  and,  by  means  of  the  ante- 
rior and  posterior  malleolar  folds,  to  the  extremities  of  the  notch  of  Rivinus. 

The  Incus  (Fig.  875)  has  received  its  name  from  its  supposed  resemblance  to 
an  anvil,  but  it  is  more  like  a  premolar  tooth,  with  two  roots,  which  differ  in 
length,  and  are  widely  separated  from  each  other.  It  consists  of  a  body  and  two 
crura. 

The  body  (corpus  ineudis)  is  somewhat  cubical  but  compressed  transversely. 
On  its  anterior  surface  is  a  deeply  concavo-convex  facet,  which  articulates  with 
the  head  of  the  malleus. 

The  two  crura  diverge  from  one  another  nearly  at  right  angles. 

The  short  crus  (cnis  breve;  short  process),  somewhat  conical  in  shape,  projects 
almost  horizontally  backward,  and  is  attached  to  the  fossa  ineudis,  in  the  lower 
and  back  part  of  the  epitympanic  recess. 

The  long  crus  {crus  longum;  long  process)  descends  nearly  vertically  behind  and 
parallel  to  the  manubrium  of  the  malleus,  and,  bending  medialward,  ends  in  a 
rounded  projection,  the  lenticular  process,  which  is  tipped  with  cartilage,  and 
articulates  with  the  head  of  the  stapes. 


Short  crus 

Body 


Fig.  875. — Left  incus.     A.  From  within.     B.  From 
the  front. 


Head 

Neck       \ 

Anterior  crtis y^^^i 

r ^ 

Posterior  crus ff           ^ 

Base   — ^^Si^^ 

A 

B 

Fig.  876.— .-1.   Left  stapes.     B. 
surface. 

Base 

of  stapes,  medial 

The  Stapes  (Fig.  876),  so  called  from  its  resemblance  to  a  stirrup,  consists  of  a 
head,  neck,  two  crura,  and  a  base. 

The  head  {capjitulum  stapedis)  presents  a  depression,  which  is  covered  by  cartilage, 
and  articulates  wdth  the  lenticular  process  of  the  incus. 

The  neck,  the  constricted  part  of  the  bone  succeeding  the  head,  gives  insertion 
to  the  tendon  of  the  Stapedius  muscle. 

The  two  crura  {crus  anterius  and  crus  posterius)  diverge  from  the  neck  and  are 
connected  at  their  ends  by  a  flattened  oval  plate,  the  base  {basis  stapedis),  which 
forms  the  foot-plate  of  the  stirrup  and  is  fixed  to  the  margin  of  the  fenestra  vestibuli 
by  a  ring  of  ligamentous  fibres.  Of  the  two  crura  the  anterior  is  shorter  and  less 
curved  than  the  posterior. 

Articulations  of  the  Auditory  Ossicles  {articulationes  ossiculonnn  auditus).- — 
The  incudomalleolar  joint  is  a  saddle-shaped  diarthrosis;  it  is  surrounded  by  an 
articular  capsule,  and  the  joint  cavity  is  incompletely  divided  into  two  by  a  wedge- 
shaped  articular  <lisk  or  meniscus.  The  incudostapedial  joint  is  an  enarthrosis, 
surrounded  by  an  articular  capsule;  some  observers  have  described  an  articular 
disk  or  meniscus  in  this  joint;  others  regard  the  joint  as  a  syndesmosis. 

Ligaments  of  the  Ossicles  {Ugainenta  ossiculorum  auditus). — The  ossicles  are 
connected  with  the  walls  of  the  tympanic  cavity  by  ligaments:  three  for  the 
malleus,  and  one  each  for  the  incus  and  stapes. 


THE  AUDITORY  OSSICLES  1055 

The  anterior  ligament  of  the  malleus  (lig.  iiiaUei  anterhis)  is  attached  by  one  end 
to  the  neck  of  the  malleus,  just  abo\e  the  anterior  process,  and  b^^  the  other  to 
the  anterit)r  wall  ol  the  tympanic  cavity,  close  to  the  petrotympanic  fissure,  some 
of  its  fibres  being  prolonged  through  the  fissure  to  reach  the  spina  angularis  of  the 
sphenoid. 

The  superior  ligament  of  the  malleus  {lig.  viaUei  siiperius)  is  a  delicate,  round 
bundle  ^vhich  descends  from  the  roof  of  the  epitympanic  recess  to  the  head  of  the 
malleus. 

The  lateral  ligament  of  the  malleus  (lig.  mallei  laterale;  external  ligament  of  the 
malleus)  is  a  triangular  band  passing  from  the  posterior  part  of  the  notch  of  Rivinus 
to  the  head  of  the  malleus.  Helmholtz  described  the  anterior  ligament  and  the 
posterior  part  of  the  lateral  ligament  as  forming  together  the  axis  ligament  around 
which  the  malleus  rotates. 

The  posterior  ligament  of  the  incus  (lig.  incudis  poster  ins)  is  a  short,  thick  band 
connecting  the  end  of  the  short  crus  of  the  incus  to  the  fossa  incudis. 

A  superior  ligament  of  the  incus  (lig.  incudis  superins)  has  been  described,  but  it 
is  little  more  than  a  fold  of  mucous  membrane. 

The  vestibular  surface  and  the  circumference  of  the  base  of  the  stapes  are  covered 
with  hyaline  cartilage;  that  encircling  the  base  is  attached  to  the  margin  of  the 
fenestra  vestibuli  by  a  fibrous  ring,  the  annular  ligament  of  the  base  of  the  stapes 
(lig.  annulare  haseos  stapedis). 

The  muscles  of  the  tympanic  cavity  (musculi  ossiculorum  anditvs)  are  the  Tensor 
tympani  and  Stapedius. 

The  Tensor  tympani,  the  larger,  is  contained  in  the  bony  canal  above  the  osseous 
portion  of  the  auditory  tube,  from  which  it  is  separated  by  the  septum  canalis 
musculotubarii.  It  arises  from  the  cartilaginous  portion  of  the  auditory  tube 
and  the  adjoining  part  of  the  great  wing  of  the  sphenoid,  as  well  as  from  the  osseous 
canal  in  which  it  is  contained.  Passing  backward  through  the  canal,  it  ends  in  a 
slender  tendon  which  enters  the  tympanic  cavity,  makes  a  sharp  bend  around  the 
extremity  of  the  septum,  and  is  inserted  into  the  manubrium  of  the  malleus,  near 
its  root.  It  is  supplied  by  a  branch  of  the  mandibular  nerve  through  the  otic 
ganglion. 

The  Stapedius  arises  from  the  wall  of  a  conical  cavity,  hollowed  out  of  the  interior 
of  the  pyramidal  eminence;  its  tendon  emerges  from  the  orifice  at  the  apex  of  the 
eminence,  and,  passing  forward,  is  inserted  into  the  posterior  surface  of  the  neck 
of  the  stapes.    It  is  supplied  by  a  branch  of  the  facial  nerve. 

Actions. — The  Tensor  tympani  draws  the  tympanic  membrane  medialward,  and  thus  increases 
its  tension.  The  Stapedius  pulls  the  head  of  the  stapes  backward  and  thus  causes  the  base  of 
the  bone  to  rotate  on  a  vertical  axis  drawn  through  its  own  centre;  the  back  part  of  the  base  is 
pressed  inward  toward  the  vestibule,  while  the  forepart  is  withdrawn  from  it.  By  the  action  of 
the  muscle  the  tension  of  the  fluid  within  the  internal  ear  is  probably  increased. 

The  mucous  membrane  of  the  tympanic  cavity  is  continuous  with  that  of  the  pharynx,  through 
the  auditory  tube.  It  invests  the  auditory  ossicles,  and  the  muscles  and  nerves  contained  in 
the  tympanic  cavity;  forms  the  medial  layer  of  the  tympanic  membrane,  and  the  lateral  layer 
of  the  secondary  tympanic  membrane,  and  is  reflected  into  the  tj^mpanic  antrum  and  mastoid 
cells,  which  it  hues  throughout.  It  forms  several  vascular  folds,  which  extend  from  the  walls 
of  the  tympanic  cavity  of  the  ossicles;  of  these,  one  descends  from  the  roof  of  the 
cavity  to  the  head  of  the  malleus  and  upper  margin  of  the  body  of  the  incus,  a  second 
invests  the  Stapedius  muscle:  other  folds  invest  the  chorda  tympani  nerve  and  the  Tensor 
tympani  muscle.  These  folds  separate  off  pouch-hke  cavities,  and  give  the  interior  of  the  tym- 
panum a  somewhat  honey-combed  appearance.  One  of  these  pouches,  the  pouch  of  Prussak, 
is  well-marked  and  hes  between  the  neck  of  the  maUeus  and  the  membrana  flaccida.  Two  other 
recesses  may  be  mentioned:  they  are  formed  by  the  mucous  membrane  which  envelops  the 
chorda  tjrmpani  nerve  and  are  situated,  one  in  front  of,  and  the  other  behind  the  manubrium  of 
the  malleus;  they  are  named  the  anterior  and  posterior  recesses  of  Troltsch.  In  the  tjonpanic 
cavity  this  membrane  is  pale,  thin,  shghtly  vascular,  and  covered  for  the  most  part  with  colum- 
nar cihated  epithehum,  but  over  the  pyramidal  eminence,  ossicles,  and  tjrmpanic  membrane 


1056      ORGANS  OF   THE  SENSES  AND   THE   COMMON  INTEGUMENT 

it  possesses  a  flattened  non-ciliated  epithelium.  In  the  tympanic  antrum  and  mastoid  cells 
its  epithelium  is  also  non-ciliated.  In  the  osseous  portion  of  the  auditory  tube  the  membrane  is 
thin;  but  in  the  cartilagcinous  portion  it  is  very  thick,  highly  vascular,  and  provided  with  numerous 
mucous  glands;  the  epithelium  which  lines  the  tube  is  columnar  and  ciliated. 

Vessels  and  Nerves. — The  arteries  are  six  in  number.  Two  of  them  are  larger  than  the  others, 
viz.,  the  tympani(!  branch  of  the  internal  maxillary,  which  supphes  the  tj^mpanic  membrane; 
and  the  stylomastoid  branch  of  the  posterior  auricular,  which  supplies  the  back  part  of  the 
tympanic  cavity  and  mastoid  cells.  The  smaller  arteries  are — the  petrosal  branch  of  the  middle 
meningeal,  which  enters  through  the  hiatus  of  the  facial  canal;  a  branch  from  the  ascending 
pharyngeal,  and  another  from  the  artery  of  the  pterj^goid  canal,  which  accompany  the  auditorj^ 
tube;  and  the  tympanic  branch  from  the  internal  carotid,  given  off  in  the  carotid  canal  and 
perforating  the  thin  anterior  wall  of  the  tympanic  cavity.  The  veins  terminate  in  the  pterygoid 
plexus  and  the  superior  petrosal  sinus.  The  nerves  constitute  the  tjanpanic  plexus,  which 
ramifies  upon  the  surface  of  the  promontory.  The  plexus  is  formed  bj^  (1)  the  tympanic  branch 
of  the  glossopharyngeal;  (2)  the  caroticotj^mpanic  nerves;  (3)  the  smaller  superficial  petrosal 
nerve;  and  (4)  a  branch  which  joins  the  greater  superficial  petrosal. 

The  tympanic  branch  of  the  glossopharyngeal  (Jacobson's  nerve)  enters  the  tympanic  cavity 
by  an  aperture  in  its  floor  close  to  the  labyrinthic  wall,  and  divides  into  branches  which 
ramif}'  on  the  promontory  and  enter  into  the  formation  of  the  tympanic  plexus.  The  superior 
and  inferior  caroticotympanic  nerves  from  the  carotid  plexus  of  the  sj^mpathetic  pass  through 
the  wall  of  the  carotid  canal,  and  join  the  branches  of  the  tympanic  branch  of  the  glossopharjm- 
geal.  The  branch  to  the  greater  superficial  petrosal  passes  tkrough  an  opening  on  the  labj"- 
rinthic  wall,  in  front  of  the  fenestra  vestibuli.  The  smaller  superficial  petrosal  nerve,  from 
the  otic  ganglion,  passes  backward  through  a  foramen  in  the  middle  fossa  of  the  base  of  the 
skull  (sometimes  through  the  foramen  ovale),  and  enters  the  anterior  surface  of  the  petrous 
part  of  the  temporal  bone  through  a  small  aperture,  situated  lateral  to  the  hiatus  of  the  facial 
canal;  it  courses  downward  through  the  bone,  past  the  genicular  gangUon  of  the  facial  nerve, 
receiving  a  connecting  filament  from  it,  and  enters  the  tympanic  cavity,  where  it  communicates 
with  the  tympanic  branch  of  the  glossopharyngeal,  and  assists  in  forming  the  tympanic  plexus. 

The  branches  of  distribution  of  the  tympanic  plexus  are  supplied  to  the  mucous  membrane 
of  the  tj^mpanic  caA'ity;  a  branch  passes  to  the  fenestra  vestibuli,  another  to  the  fenestra  cochleae, 
and  a  third  to  the  auditory  tube.  The  smaller  superficial  petrosal  may  be  looked  upon  as  the 
continuation  of  the  tympanic  branch  of  the  glossopharyngeal  through  the  plexus  to  the  otic 
ganglion. 

In  addition  to  the  tympanic  plexus  there  are  the  nerves  supplying  the  muscles.  The  Tensor 
tympani  is  supplied  by  a  branch  from  the  mandibular  through  the  otic  ganglion,  and  the  Stapedius 
by  a  branch  from  the  facial. 

The  chorda  tympani  nerve  crosses  the  tympanic  cavity.  It  is  given  off  from  the  sensory  part 
of  the  facial,  about  6  mm.  before  the  nerve  emerges  from  the  stylomastoid  foramen.  It  runs 
from  below  upward  and  forward  in  a  canal,  and  enters  the  tympanic  cavity  through  the  iter 
chordae  posterius,  and  becomes  invested  with  mucous  membrane.  It  traverses  the  tympanic 
cavity,  crossing  medial  to  the  tj'mpanic  membrane  and  over  the  upper  part  of  the  manubrium 
of  the  malleus  to  the  carotid  wall,  where  it  emerges  through  the  iter  chordae  anterius  {canal 
of  Huguier). 

Applied  Anatomy. — The  tympanic  cavitj^  is  very  frequently  the  seat  of  disease,  both  suppu- 
rative and  non-suppurative,  and  in  practically  every  case  the  inflammation  spreads  upward 
from  the  nose  or  throat  along  the  auditory  tube.  Acute  inflammatory  troubles  spreading  up 
to  the  tympanic  cavity  are  usually  associated  wdth  so  much  inflammatory  swelling  of  the  mucous 
membrane  of  the  auditory  tube  as  to  occlude  it,  and  thus  the  products  of  inflammation  are  pent 
up  in  the  tympanic  cavitj'  and  directly  involve  the  tjmipanic  antrum.  Under  such  circum- 
stances the  only  means  of  escape  for  the  products  is  by  rupture  of  the  tympanic  membrane, 
which  usually  occurs  spontaneously  and  is  followed  by  a  free  discharge  of  pus,  and  relief  to  the 
acute  pain  which  exists  in  these  cases.  Should  the  swelUng  of  the  walls  of  the  auditory  tube 
then  subside,  the  normal  drainage  of  the  cavity  will  be  estabUshed  and  the  perforation  in  the 
drum  will  heal,  but  if  not — as  is  often  the  case  because  the  opening  of  the  tube  may  be  occluded 
by  adenoid  growths  in  the  nasopharynx  or  other  cause — the  pus  will  continue  to  accumulate 
in  the  middle  ear  and  wiU  overflow  through  the  perforation  as  a  chronic  otorrhcea  In  the  course 
of  time  the  disease  spreads  beyond  the  mucous  membrane  to  the  walls  of  the  tympanic  cavitj', 
to  the  ossicles,  or  to  the  mastoid  process,  and  when  this  has  occm-red  the  condition  is  incurable 
except  by  the  removal  of  the  carious  bone.  Further,  severe  intracranial  comphcations  are  at 
this  time  often  produced  owing  to  purulent  material  being  retained;  thus  an  abscess  may  form 
between  the  bone  and  dura  mater,  (a)  about  the  roof  of  the  tj^mpanic  cavity,  and  immediateh' 
beneath  the  dm-a  covering  the  temporal  lobe,  or  (b)  between  the  deep  aspect  of  the  mastoid 
process  and  the  sigmoid  bend  of  the  transverse  sinus,  pos.sibty  extending  widely  and  surrounding 
the  sinus.  In  this  latter  type  of  case,  thrombosis  of  the  transverse  sinus  readily  occurs,  and 
the  clot  being  also  infected  tends  to  disintegrate  and  be  carried  into  the  general  circulation. 


THK   I  STERNAL  EAR  OR  LABYRINTH 


105- 


particles  ol'ten  bocoining  lodged  in  the  fiii)iliarics  of  tJie  lungs  and  sotting  up  abscesses  therein 
Pyemia  from  transverse  sinus  thrombosis  is  more  common  than  from  any  other  focus  of  origin 
In  addition,  bone  tlisease  of  the  tympanic  cavity  or  antrum  may  be  associated  with  severe  and 
fatal  septic  meningitis,  or  with  flu;  formation  of  abscess  in  the  brain,  the  most  common  sites 
being  the  temporal  lobe  and  the  hemisphere  of  the  cerebellum. 

Less  serious,  but  more  conunon,  is  the  formation  of  a  subperiosteal  mastoid  abscess  with 
great  swelling  behind  the  ear,  and  protrusion  outward  of  the  auricula;  such  a  condition  demands 
an  earl}'  incision  down  through  all  the  structures,  including  the  periosteum,  over  the  whole 
length  of  the  mastoid  i)rocess,  aiul  then  it  will  frequently  be  found  that  the  underlying  bone  is 
carious  or  that  a  track  leads  through  the  bone  into  the  tympanic  antrum.  In  such  conditions 
extensive  operations  for  the  removal  of  bone  arc  often  required.  In  many  cases  of  chronic  bone 
disease  in  the  tympanic  cavity  the  facial  nerve  becomes  exposed  as  it  lies  in  its  canal,  and  an 
inflammatory  process  is  set  up  in  the  nerve,  leading  to  facial  paralysis  of  the  intranuclear  type 
(see  page  934).  In  other  cases  localized  areas  of  bone  disease,  most  often  in  the  region  of  the 
epit.ympanic  recess,  form  the  points  from  which  aural  polypi  grow,  and  the  ear  polypus,  like 
the  nasal  jiolypus,  must  be  considered  to  have  originated  in  a  spot  of  carious  bone,  the  removal 
of  which  is  necessary  if  a  cure  is  to  be  established.  Fractures  of  the  middle  fossa  of  the  base  of 
the  skull  almost  invariably  involve  the  tympanic  roof,  and  are  accompanied  by  a  rupture  of 
the  t3'mpanic  membrane  or  fracture  through  the  roof  of  the  bony  meatus.  They  are  associated 
with  iirofuse  continued  bleeding  from  the  ear,  and,  if  the  dura  has  also  been  lacerated,  with 
discharge  of  copious  amounts  of  cerebrospinal  fluid.  Here  the  avoidance  of  infection  from  the 
outside  is  of  the  utmost  importance,  as  should  it  occur  septic  meningitis  must  inevitably  follow 
with  a  fatal  issue. 

Of  the  non-suppurative  conditions  which  affect  the  middle  ear,  chronic  catarrh,  leading  to 
sclerosis  of  the  whole  of  the  tympanic  contents,  is  again  due  to  spread  of  inflammation  from 
some  nasal  or  pharyngeal  condition.  The  progress  is  very  slow,  but  leads  to  ever-increasing 
deafness — this  deafness  in  the  first  instance  is  in  no  way  connected  with  any  defect  in  the  acoustic 
nerve,  and  this  can  be  shown  by  the  fact  that  the  hearing  by  bone  conduction  over  the  mastoid 
process  remains  normal.  In  chronic  non-suppurative  otitis  media,  treatment  must  be  especially 
directed  toward  placing  the  nose  and  pharynx  in  a  healthy  condition;  when  this  has  been  accom- 
plished, the  aural  condition  often  improves  of  itself;  if  not,  however,  improvement  may  be 
induced  by  forcing  air  up  the  auditory  tube  by  means  of  the  Politzer  bag,  or  directly  into  the 
orifice  of  the  tube  by  means  of  a  catheter. 

The  Internal  Ear  or  Labyrinth  (Auris  Interna). 

The  internal  ear  is  the  essential  part  of  the  organ  of  hearing,  receiving  the  ultimate 
distribution  of  the  auditory  nerve.  It  is  called  the  labyrinth,  from  the  complexity 
of  its  shape,  and  consists  of  two  parts:  the  osseous  labyrinth,  a  series  of  cavities 
within  the  petrous  part  of  the  temporal  bone,  and  the  membranous  labyrinth,  a 
series  of  communicating  membranous  sacs  and  ducts,  contained  within  the  bony 
cavities. 


Fig.  877. — Right  osseous  labyrinth.     Lateral  view. 


The   Osseous  Labyrinth   ilabyrinthus  osseus)    (Figs.  877,   878). — The  osseous 
labyrinth  consists  of  three  parts:  the  vestibule,  semicircular  canals,  and  cochlea. 
67 


1058      ORGANS  OF  THE  SENSES  AND   THE   COMMON  INTEGUMENT 

These  are  cavities  hollowed  out  of  the  subs-tance  of  the  bone,  and  lined  by 
periosteum;  they  contain  a  clear  fluid,  the  perilymph,  in  which  the  membranous 
labyrinth  is  situated. 

The  Vestibule  {vestihulum). — The  vestibule  is  the  central  part  of  the  osseous 
labyrinth,  and  is  situated  medial  to  the  tympanic  cavity,  behind  the  cochlea,  and 
in  front  of  the  semicircular  canals.  It  is  somewhat  ovoid  in  shape,  but  flattened 
transversely;  it  measures  about  5  mm.  from  before  backward,  the  same  from  above 
downward,  and  about  3  mm.  across.  In  its  lateral  or  tympanic  wall  is  the  fenestra 
vestibuli,  closed,  in  the  recent  state,  by  the  base  of  the  stapes  and  annular  ligament. 
On  its  medial  wall,  at  the  forepart,  is  a  small  circular  depression,  the  recessus 
sphaericus,  Avhich  is  perforated,  at  its  anterior  and  inferior  part,  by  several  minute 
holes  (macula  cribrosa  media)  for  the  passage  of  filaments  of  the  acoustic  nerve 
to  the  saccule;  and  behind  this  depression  is  an  oblique  ridge,  the  crista  vestibuli, 
the  anterior  end  of  which  is  named  the  pyramid  of  the  vestibule.  This  ridge  bifur- 
cates below  to  enclose  a  small  depression,  the  fossa  cochlearis,  which  is  perforated 
by  a  number  of  holes  for  the  passage  of  filaments  of  the  acoustic  nerve  which  supply 
the  vestibular  end  of  the  ductus  cochlearis.    As  the  hinder  part  of  the  medial  wall 


Recessus  ellipiicus 
Recessus  sfhcericus 


Orifice  of  aquceductus  vestibuli   j 

-,  fi      '■    I       Orifice  of  anuceductus  cocJileae 

Fossa  cochlearis  j  ^        j     i 

Cochlear  fenestra 
Fig.  878. — Interior  of  right  osseous  labyrinth. 


is  the  orifice  of  the  aquaeductus  vestibuli,  which  extends  to  the  posterior  surface  of 
the  petrous  portion  of  the  temporal  bone.  It  transmits  a  small  vein,  and  contains 
a  tubular  prolongation  of  the  membranous  labyrinth,  the  ductus  endolymphaticus, 
which  ends  in  a  cul-de-sac  between  the  layers  of  the  dura  mater  within  the  cranial 
cavity.  On  the  upyer  ivall  or  roof  is  a  transversely  oval  depression,  the  recessus 
ellipticus,  separated  from  the  recessus  sphaericus  by  the  crista  vestibuli  already 
mentioned.  The  pyramid  and  adjoining  part  of  the  recessus  ellipticus  are  perforated 
by  a  number  of  holes  (macula  cribrosa  superior).  The  apertures  in  the  pyramid 
transmit  the  nerves  to  the  utricle;  those  in  the  recessus  ellipticus  the  nerves  to  the 
ampullae  of  the  superior  and  lateral  semicircular  ducts.  Behind  are  the  five  orifices 
of  the  semicircular  canals.  In  front  is  an  elliptical  opening,  which  communicates 
with  the  scala  vestibuli  of  the  cochlea. 

The  Bony  Semicircular  Canals  {canales  semicirculares  ossei). — The  bonj^  semi- 
circular canals  are  three  in  number,  superior,  posterior,  and  lateral,  and  are  situated 
above  and  behind  the  vestibule.  They  are  unequal  in  length,  compressed  from  side 
to  side,  and  each  describes  the  greater  part  of  a  circle.  Each  measures  about 
0.8  mm.  in  diameter,  and  presents  a  dilatation  at  one  end,  called  the  ampulla,  which 


THE  INTERNAL  EAR  OR  LABYRINTH 


1059 


measures  more  than  twice  the  diameter  of  the  tube.  They  oik'u  into  the  vestibule 
by  five  orifices,  one  of  the  apertures  beiii<;-  connnon  to  two  of  the  canals. 

The  superior  semicircular  canal  {canal i.s  .soitieiiriihiris  superior),  15  to  20  mm. 
in  length,  is  vertical  in  direction,  and  is  placed  transversely  to  the  long  axis  of  the 
petrous  portion  of  the  temporal  bone,  on  the  anterior  surface  of  which  its  arch 
forms  a  round  projection.  It  describes  about  two-thirds  of  a  circle.  Its  lateral 
extremity  is  ampullated,  and  opens  into  the  upper  part  of  the  vestibule;  the  oppo- 
site end  joins  with  the  upper  part  of  the  posterior  canal  to  form  the  crus  commune, 
which  opens  into  the  upper  and  medial  part  of  the  vestibule. 

The  posterior  semicircular  canal  {canalis  semicircularis  posterior),  also  vertical,  is 
directed  backward,  nearly  parallel  to  the  posterior  surface  of  the  petrous  bone; 
it  is  the  longest  of  the  three,  measuring  from  IS  to  22  mm.;  its  lower  or  ampullated 
end  opens  into  the  lower  and  back  part  of  the  vestibule,  its  upper  into  the  crus 
commune  already  mentioned. 


j-iG  S79.-The  cochlea  and  vestibule,  viewed  from  above  (Testut )  All  the  hard  parts  which  form  tlie  roof  of 
+hp  Internal  ear  have  been  removed  with  the  saw.  A.  Cochlea.  B.  Vestibule.  C.  Internal  acoustic  meatus.  L>. 
T^pan'rcaXr  Lower  b^d^r  of  vestibular  f^  2.  Fissura  vestibuli     3.  Recessus  sphaericus.    4.   Recessu- 

Jfflcus  5.  Fossa  cochlearis.  6.  Orifice  of  the  aquaeductus  vestibuli  7.  Inferior  °Pening  of  the  posterior  semis 
cSar  canal.  8.  Non-ampullated  end  of  lateral  semicircular  canal  9.  Scala  tympani  of  the  cochlea  10  Sc^a- 
vestibuli.  11.  Cupula.  12.  Lamina  spiralis  ossea,  with  12',  its  vestibular  ongm;  12",  its  external  border.  13.  Hell 
cotrema.     14.  Bony  wall  of  cochlea. 

The  lateral  or  horizontal  canal  (canalis  semicircularis  lateralis;  external  semicircular 
canal)  is  the  shortest  of  the  three.  It  measures  from  12  to  15  mm.,  and  its  arch 
is  directed  horizontally  backward  and  lateralward;  thus  each  semicircular  canal 
stands  at  right  angles  to  the  other  two.  Its  ampullated  end  corresponds  to  the 
upper  and  lateral  angle  of  the  vestibule,  just  above  the  fenestra  vestibuli,  where 
it  opens  close  to  the  ampullated  end  of  the  superior  canal;  its  opposite  end  opens 
at  the  upper  and  back  part  of  the  vestibule.  The  lateral  canal  of  one  ear  is  very 
nearly  in  the  same  plane  as  that  of  the  other;  while  the  superior  canal  of  one  ear 
is  nearly  parallel  to  the  posterior  canal  of  the  other. 

The  Cochlea  (Figs.  878,  879).— The  cochlea  bears  some  resemblance  to  a  common 
snail-shell;  it  forms  the  anterior  part  of  the  labyrinth,  is  conical  in  form,  and  placed 
almost  horizontally  in  front  of  the  vestibule;  its  apex  {cupula)  is  directed  forward 
and  lateralward,  with  a  slight  inclination  downward,  toward  the  upper  and  front 


1060      ORGANS  OF   THE  SENSES  AND  THE   COMMON  INTEGUMENT 

part  of  the  labyrinthic  wall  of  the  tympanic  cavity;  its  base  corresponds  with  the 
bottom  of  the  internal  acoustic  meatus,  and  is  perforated  by  numerous  apertures 
for  the  passage  of  the  cochlear  division  of  the  acoustic  nerve.  It  measures  about 
5  mm.  from  base  to  apex,  and  its  breadth  across  the  base  is  about  9  mm.  It  con- 
sists of  a  conical  shaped  central  axis,  the  modiolus;  of  a  canal,  the  inner  wall  of  which 
is  formed  by  the  central  axis,  wound  spirally  around  it  for  two  turns  and  three- 
quarters,  from  the  base  to  the  apex;  and  of  a  delicate  lamina,  the  osseous  spiral 
lamina,  which  projects  from  the  modiolus,  and,  following  the  windings  of  the  canal, 
partially  subdivides  it  into  two.  In  the  recent  state  a  membrane,  the  basilar 
membrane,  stretches  from  the  free  border  of  this  lamina  to  the  outer  wall  of  the  bony 
cochlea  and  completely  separates  the  canal  into  two  passages,  which,  however, 
communicate  with  each  other  at  the  apex  of  the  modiolus  by  a  small  opening, 
named  the  helicotrema. 

The  modiolus  is  the  conical  central  axis  or  pillar  of  the  cochlea.  Its  base  is  broad, 
and  appears  at  the  bottom  of  the  internal  acoustic  meatus,  where  it  corresponds 
with  the  area  cochleae;  it  is  perforated  by  numerous  orifices,  which  transmit  fila- 
ments of  the  cochlear  division  of  the  acoustic  nerve;  the  nerves  for  the  first  turn 
and  a  half  pass  through  the  foramina  of  the  tractus  spiralis  foraminosus;  those 
for  the  apical  turn,  through  the  foramen  centrale.  The  canals  of  the  tractus 
spiralis  foraminosus  pass  up  through  the  modiolus  and  successiveh'^  bend  outward 
to  reach  the  attached  margin  of  the  lamina  spiralis  ossea.  Here  they  become 
enlarged,  and  by  their  apposition  form  the  spiral  canal  of  the  modiolus,  which 
follows  the  course  of  the  attached  margin  of  the  osseous  spiral  lamina  and  lodges 
the  spiral  ganglion  (ganglion  of  Corti).  The  foramen  centrale  is  continued  into 
a  canal  which  runs  up  the  middle  of  the  modiolus  to  its  apex.  The  modiolus 
diminishes  rapidly  in  size  in  the  second  and  succeeding  coil. 

The  bony  canal  of  the  cochlea  takes  two  turns  and  three-quarters  around  the 
modiolus.  It  is  about  30  mm.  in  length,  and  diminishes  gradually  in  diameter 
from  the  base  to  the  summit,  where  it  terminates  in  the  cupula,  which  forms  the 
apex  of  the  cochlea.  The  beginning  of  this  canal  is  about  3  mm.  in  diameter; 
it  diverges  from  the  modiolus  toward  the  tympanic  cavity  and  vestibule,  and 
presents  three  openings.  One,  the  fenestra  cochleae,  communicates  wuth  the  tym- 
panic cavity — in  the  recent  state  this  aperture  is  closed  by  the  secondary  tympanic 
membrane;  another,  of  an  elliptical  form,  opens  into  the  vestibule.  The  third  is  the 
aperture  of  the  aquaeductus  cochleae,  leading  to  a  minute  funnel-shaped  canal, 
which  opens  on  the  inferior  surface  of  the  petrous  part  of  the  temporal  bone 
and  transmits  a  small  vein,  and  also  forms  a  communication  between  the 
subarachnoid  cavity  and  the  scala  tympani. 

The  osseous  spiral  lamina  (lamina  spiralis  ossea)  is  a  bony  shelf  or  ledge  which  pro- 
jects from  the  modiolus  into  the  interior  of  the  canal,  and,  like  the  canal,  takes  two- 
and  three-quarter  turns  around  the  modiolus.  It  reaches  about  half-way  toward 
the  outer  wall  of  the  tube,  and  partially  divides  its  cavity  into  two  passages  or 
scalse,  of  which  the  upper  is  named  the  scala  vestibuli,  while  the  lower  is  termed 
the  scala  tympani.  Near  the  summit  of  the  cochlea  the  lamina  ends  in  a  hook- 
shaped  process,  the  hamulus  laminae  spiralis;  this  assists  in  forming  the  boundar}- 
of  a  small  opening,  the  helicotrema,  through  which  the  two  scalae  communicate 
with  each  other.  From  the  spiral  canal  of  the  modiolus  numerous  canals  pass  out- 
ward through  the  osseous  spiral  lamina  as  far  as  its  free  edge.  In  the  lower  part 
of  the  first  turn  a  second  bony  lamina,  the  secondary  spiral  lamina,  projects  inward 
from  the  outer  wall  of  the  bony  tube;  it  does  not,  however,  reach  the  primary 
osseous  spiral  lamina,  so  that  if  viewed  from  the  vestibule  a  narrow  fissure,  the 
vestibule  fissure,  is  seen  between  them. 

The  osseous  labyrinth  is  lined  by  an  exceedingly  thin  fibro-serous  membrane; 
its  attached  surface  is  rough  and  fibrous,  and  closely  adherent  to  the  bone;  its 


THE  INTERNAL  EAR  OR   LMiVRISTIl 


I  0(1 


free  surface  is  smoDtli  and  i)al(\  cuvered  witli  a  layer  of  epitlieliuin,  and  secretes 
a  thin,  limpid  fluid,  the  perilymph.  A  delicate  tubular  process  of  this  membrane 
is  prolouii'ed  aloui;-  the  aciucduct  of  the  vestibule  to  the  inner  surface  of  the  dura 
mater. 


ENDOLYMPHATICUS 

Fig.  880. — The  membranous  labyrinth.      (Enlarged.) 


The  Membranous  Labyrinth  {labyrinthvs  inembranaceiis)  (Figs.  880,  881,  882). — 
The  membranous  labyrinth  is  lodged  within  the  bony  cavities  just  described, 
and  has  the  same  general  form  as  these;  it  is,  however,  considerably  smaller,  and 


19181716     15 


Fig.  881. — Right  human  membranous  labyrinth,  removed  from  its  bony  enclosure  and  viewed  from  the  antero-lateral 

aspect.      (G.  Retzius.) 

is  partly-  separated  from  the  bony  walls  by  a  quantity  of  fluid,  the  perilymph.  In 
certain  places  it  is  fixed  to  the  walls  of  the  cavity.  The  membranous  labyrinth 
contains  fluid,  the  endolymph,  and  on  its  walls  the  ramifications  of  the  acoustic 
nerve  are  distributed. 


1062      ORGANS  OF  THE  SENSES  AND  THE  COMMON  INTEGUMENT 

Within  the  osseous  vestibule  the  membranous  hibyrinth  does  not  quite  preserve 
the  form  of  the  bony  cavity,  but  consists  of  two  membranous  sacs,  the  utricle, 
and  tlie  saccule. 

The  Utricle  {idricidus) . — The  utricle,  the  larger  of  the  two,  is  of  an  oblong  form, 
compressed  transversely,  and  occupies  the  upper  and  back  part  of  the  vestibule, 
lying  in  contact  with  the  recessus  ellipticus  and  the  part  below  it.  That  portion 
which  is  lodged  in  the  recess  forms  a  sort  of  pouch  or  cul-de-sac,  the  floor  and  ante- 
rior wall  of  which  are  thickened,  and  form  the  macula  acustica  utriculi,  which  receives 
the  utricular  filaments  of  the  acoustic  nerve.  The  cavity  of  the  utricle  communi- 
cates behind  with  the  semicircular  ducts  by  five  orifices.  From  its  anterior  wall  is 
given  off  the  ductus  utriculosaccularis,  which  opens  into  the  ductus  endolymphaticus. 


Fig.  882. — The  same  from  the  postero-medial  aspect.  (G.  Retzius.)  1.  Latera  semicircular  canal;  1',  its  ampulla. 
2.  Posterior  canal;  2',  its  ampulla.  3.  Superior  canal;  3',  its  ampulla.  4.  Conjoined  limb  of  superior  and  posterior 
canals  (sinus  utriculi  superior).  5.  Utricle.  5'.  Recessus  utriculi.  5".  Sinus  utriculi  posterior.  6.  Ductus  endo- 
lymphaticus. 7.  Canalis  utriculosaccularis.  8.  Nerve  to  ampulla  of  superior  canal.  _  9.  Nerve  to  ampulla  of  lateral 
canal.  10.  Nerve  to  recessus  utriculi  (in  Fig.  881,  the  three  branches  appear  conjoined).  10'.  Ending  of  nerve  in 
recessus  utriculi.  11.  Facial  nerve.  12.  Lagena  cochleae.  13.  Nerve  of  cochlea  within  spiral  lamina.  14.  Basilar 
membrane.  15.  Nerve  fibres  to  macula  of  saccule.  16.  Nerve  to  ampulla  of  posterior  canal.  17.  Saccule.  18. 
Secondary  membrane  of  tympanum.  19.  Canalis  reuniens.  20.  Vestibular  end  of  ductus  cochlearis.  23.  Section 
of  the  facial  and  acoustic  nerves  within  internal  acoustic  meatus  (the  separation  between  them  is  not  apparent  in  the 
section). 


The  Saccule  (sacculus). — The  saccule  is  the  smaller  of  the  two  vestibular  sacs; 
it  is  globular  in  form,  and  lies  in  the  recessus  sphaericus  near  the  opening  of  the 
scala  vestibuli  of  the  cochlea.  Its  anterior  part  exhibits  an  oval  thickening,  the 
macula  acustica  sacculi,  to  which  are  distributed  the  saccular  filaments  of  the 
acoustic  nerve.  Its  cavity  does  not  directly  communicate  wuth  that  of  the  utricle. 
From  the  posterior  wall  a  canal,  the  ductus  endolymphaticus,  is  given  off;  this  duct 
is  joined  by  the  ductus  utriculosaccularis,  and  then  passes  along  the  aquaeductus 
vestibuli  and  ends  in  a  blind  pouch  (saccus  endolymphaticus)  on  the  posterior  sur- 
face of  the  petrous  portion  of  the  temporal  bone,  where  it  is  in  contact  with  the 
dura  mater.  From  the  lower  part  of  the  saccule  a  short  tube,  the  canalis  reuniens 
of  Hensen,  passes  downward  and  opens  into  the  ductus  cochlearis  near  its  vestibular 
extremity  (Fig.  880). 

The  Semicircular  Ducts  {ductus  semicircidares;  membranous  semicircidar  canals), 
(Figs.  881,  882). — The  semicircular  ducts  are  about  one-fourth  of  the  diameter 


THE  INTERNAL  EAR  Oli  LABYRINTH 


1063 


of  the  osseous  canals,  but  in  number,  shape,  and  general  form  they  are  precisely 
similar,  and  each  presents  at  one  end  an  ampulla.  They  open  by  five  orifices  into 
the  utricle,  one  o])cninii;  beinji,-  coiuinon  to  the  medial  end  of  the  superior  and  the 
upper  end  of  the  posterior  duct.  In  the  amj)ulhe  the  wall  is  thickened,  and  projects 
into  the  cavity  as  a  fiddle-shaped,  transversely  i)laced  elevation,  the  septum  trans- 
versum,  in  which  the  nerves  end. 

The  utricle,  saccule,  and  semicircular  ducts  are  held  in  position  by  numerous 
fibrous  bands  which  stretch  across  the  space  between  them  and  the  bony  walls. 

Structure  (Fig.  SS3). — The  walls  of  the  utricle,  saccule,  and  semicircular  ducts  consist  of 
three  layers.  The  outer  layer  is  a  loose  and  flocculent  structure,  apparently  composed  of  ordinary 
fibrous  tissue  containing  bloodvessels  and 
some  pigment-cells.  The  middle  layer, 
thicker  and  more  transparent,  forms  a 
homogeneous  membrana  propria,  and 
presents  on  its  internal  surface,  especially 
in  the  semicircular  ducts,  numerous 
papilliform  projections,  which,  on  the 
addition  of  acetic  acid,  exhibit  an  appear- 
ance of  longitudinal  fibrillation.  The 
inner  layer  is  formed  of  polygonal  nucleat  ed 
epithelial  cells.  In  the  maculae  of  the 
utricle  and  saccule,  and  in  the  transverse 
septa  of  the  ampullee  of  the  semicircular 
ducts,  the  middle  coat  is  thickened  and 
the  epithehum  is  columnar,  and  consists 
of  supporting  cells  and  hair  cells.  The 
former  are  fusiform,  and  their  deep  ends 
are  attached  to  the  membrana  propria, 
while  their  free  extremities  are  united  to 
form  a  thin  cuticle.  The  hair  cells  are 
flask-shaped,  and  their  deep,  rounded 
ends  do  not  reach  the  membrana  propria, 
but  lie  between  the  supporting  cells.  The 
deep  part  of  each  contains  a  large  nucleus, 
while  its  more  superficial  part  is  granular 
and  pigmented.  The  free  end  is  sur- 
mounted by  a  long,  tapering,  hair-like 
filament,  which  projects  into  the  cavity. 
The  filaments  of  the  acoustic  nerve  enter 
these  parts,  and  having  pierced  the  outer 
and  middle  layers,  they  lose  their  medul- 
lary sheaths,  and  their  axis-cyhnders 
ramify  between  the  hair  cells. 

Two     small    rounded  bodies     termed 
otoconia,    and    consisting  of   a   mass   of 

minute  crj'stalline  grains  of  carbonate  of  lime,  held  together  in  a  mesh  of  gelatinous  tissue, 
are  suspended  in  the  endolymph  in  contact  with  the  free  ends  of  the  hairs  projecting  from  the 
maculae.  According  to  Bowman,  a  calcareous  material  is  also  sparingly  scattered  in  the  cells 
lining  the  ampullae  of  the  semicircular  ducts. 

The  Ductus  Cochlearis  (^inemhranous  cochlea;  scala  media). — The  ductus  cochlearis 
consists  of  a  spirally  arranged  tube  enclosed  in  the  bony  canal  of  the  cochlea  and 
lying  along  its  outer  wall. 

As  already  stated,  the  osseous  spiral  lamina  extends  only  part  of  the  distance 
between  the  modiolus  and  the  outer  wall  of  the  cochlea,  while  the  basilar  membrane 
stretches  from  its  free  edge  to  the  outer  wall  of  the  cochlea,  and  completes  the  roof 
of  the  scala  tj^mpani.  A  second  and  more  delicate  membrane,  the  vestibular  mem- 
brane {Reissneri)  extends  from  the  thickened  periosteum  covering  the  osseous 
spiral  lamina  to  the  outer  wall  of  the  cochlea,  w^here  it  is  attached  at  some  little 
distance  above  the  outer  edge  of  the  basilar  membrane.  A  canal  is  thus  shut  off 
between  the  scala  tympani  below  and  the  scala  vestibuli  above;  this  is  the  ductus 


Fig.  883. — Transverse  section  of  a  human  semicircular  canal 
and  duct  (after  Riidinger) .  (Testut.)  1.  Semicircular  canal.  2. 
Periosteum.  3.  Semicircular  duct,  vnth._  4,  papilliforrn  pro- 
cesses on  its  internal  surface.  5.  Connective  tissue  binding  the 
duct  to  the  periosteum.  6,  6.  Fibrous  bands  uniting  the  free 
surface  of  the  duct  to  the  periosteum.  7.  Vessels.  8.  Endo- 
lymphatic space.     9,  9.  Perilymphatic  space. 


1064      ORGANS  OF   THE  SENSES  AND  THE   COMMON  INTEGUMENT 

cochlearis  or  scala  media  (Fig.  884).  It  is  triangular  on  transverse  section,  its  roof 
being  formed  by  the  vestibular  membrane,  its  outer  wall  by  the  periosteum  lining 
the  bony  canal,  and  its  floor  by  the  membrana  basilaris  and  the  outer  part  of  the 
lamina  spiralis  ossea.  Its  extremities  are  closed;  the  upper  is  termed  the  lagena 
and  is  attached  to  the  cupula  at  the  upper  part  of  the  helicotrema;  the  lower  is 
lodged  in  the  recessus  cochlearis  of  the  vestibule.    Near  the  lower  end  the  ductus 


Fig.  884. — Diagrammatic  longitudinal  section  of  the  cochlea. 

cochlearis  is  brought  into  continuity  with  the  saccule  by  a  narrow,  short  canal, 
the  canalis  reuniens  of  Hensen  (Fig.  880).  On  the  membrana  basilaris  is  situated 
the  spiral  organ  of  Corti.  The  vestibular  membrane  is  thin  and  homogeneous, 
and  is  covered  on  its  upper  and  under  surfaces  by  a  layer  of  epithelium.  The 
periosteum,  forming  the  outer  wall  of  the  ductus  cochlearis,  is  greatly  thickened 
and  altered  in  character,  and  is  called  the  spiral  ligament.  It  projects  inward  below 
as  a  triangular  prominence,  the  basilar  crest,  which  gives  attachment  to  the  outer 


Fibres  of  Cochlear  division 
of  Auditory  nerve 


Crista  Basilaris 


Fig.  885. — Floor  of  ductus  cochlearis. 


edge  of  the  basilar  membrane;  immediately  above  the  crest  is  a  concavity,  the 
sulcus  spiralis  externus.  The  upper  portion  of  the  spiral  ligament  contains  numerous 
capillary  loops  and  small  bloodvessels,  and  is  termed  the  stria  vascularis. 

The  osseous  spiral  lamina  consists  of  two  plates  of  bone,  and  between  these  are 
the  canals  for  the  transmission  of  the  filaments  of  the  acoustic  nerve.  On  the  upper 
plate  of  that  part  of  the  lamina  which  is  outside  the  vestibular  membrane,  the  perios- 


Till'.    IXTKUXAL  EAR  Oh'  LMlVh'IM'lf 


1065 


teuiii  is  thickened  to  lonii  the  limbus  laminae  spiralis  ( I'ig.  SS,j),  this  ends  exteriiaUy 
in  a  concavity,  the  sulcus  spiralis  internus,  which  represents,  on  section,  the  form 
of  the  letter  ( ';  the  ii|)|)cr  part,  formed  hy  the  oxcrhanffinfij  extremity  of  the  limbus, 
is  named  the  vestibular  lip;  the  lower  ])art,  prolonfj;ed  and  taperinji^,  is  called  the 
tympanic  lip,  and  is  perforated  hy  nnmerous  foramina  for  the  |)assaji:e  of  the  cochlear 
nerxes.  'J'he  upper  surface  of  tiic  xcstihuhir  \\p  is  intersected  at  ri<j;ht  angles  hy  a 
number  of  furrows,  between  which  are  numerous  elevations;  these  present  the 
appearance  of  teeth  alon<i-  the  free  surface  and  margin  of  the  lip,  and  have  been 
named  b\'  Iluschke  the  auditory  teeth  (Fig.  SSd).  The  hmbus  is  covered  by  a  layer 
of  what  aj)pears  to  be  squamous  epithelium,  but  the  deej)er  parts  of  the  cells  with 
their  contained  nuclei  occupy  the  intervals  between  the  elevations  and  between  the 
auditory  teeth.  This  layer  of  epithelium  is  continuous  on  the  one  hand  with  that 
lining  the  sulcus  spiralis  internus,  and  on  the  other  with  that  covering  the  under 
surface  of  the  vestibular  membrane. 


bed 


Fig.  8S6. — Limbus  laminae  spiralis  and  membrana  basilaris.  (Schematic.)  (Testut.)  1,  1'.  Upper  and  lower 
lamellae  of  the  lamina  spiralis  ossea.  2.  Limbus  laminae  spiralis,  with  a,  the  teeth  of  the  first  row;  b,  b',  the  auditory 
teeth  of  the  other  rows;  c,  c',  the  interdental  grooves  and  the  cells  which  are  lodged  in  them.  3.  Sulcus  spiralis  internus, 
with  3',  its  labium  vestibulare,  and  3",  its  labium  tympanicum.  4.  Foramina  nervosa,  giving  passage  to  the  nerves 
from  the  ganglion  spirale  or  ganglion  of  Corti.  5.  Vas  spirale.  6.  Zona  arcuata,  and  6',  zona  pectinata  of  the  basilar 
membrane,  with  a,  its  hyaline  layer,  ^,  its  connective-tissue  layer.  7.  Arch  of  spiral  organ,  with  7',  its  inner  rod,  and 
7",  its  outer  rod.  8.  Feet  of  the  internal  rods,  from  which  the  cells  are  removed.  9.  Feet  of  the  external  rods.  10. 
Vestibular  membrane,  at  its  origin. 


Basilar  Membrane. — The  basilar  membrane  stretches  from  the  tympanic  lip  of 
the  osseous  spiral  lamina  to  the  basilar  crest  and  consists  of  two  parts,  an  inner 
and  an  outer.  The  inner  is  thin,  and  is  named  the  zona  arcuata :  it  supports  the  spiral 
organ  of  Corti.  The  outer  is  thicker  and  striated,  and  is  termed  the  zona  pectinata. 
The  under  surface  of  the  membrane  is  covered  by  a  layer  of  vascular  connective 
tissue;  one  of  the  vessels  in  this  tissue  is  somewhat  larger  than  the  rest,  and  is 
named  the  vas  spirale;  it  lies  below  Corti's  tunnel. 

The  spiral  organ  of  Corti  (organon  spirale  [Corti];  organ  of  Corti)  (Figs.  887,  888) 
is  composed  of  a  series  of  epithelial  structures  placed  upon  the  inner  part  of  the 
basilar  membrane.  The  more  central  of  these  structures  are  two  rows  of  rod-like 
bodies,  the  inner  and  outer  rods  or  pillars  of  Corti.  The  bases  of  the  rods  are  supported 
on  the  basilar  membrane,  those  of  the  inner  row  at  some  distance  from  those  of  the 
outer;  the  two  rows  incline  toward  each  other  and,  coming  into  contact  above, 
enclose  between  them  and  the  basilar  membrane  a  triangular  tunnel,  the  tunnel 
of  Corti.  On  the  inner  side  of  the  inner  rods  is  a  single  row  of  hair  cells,  and  on  the 
outer  side  of  the  outer  rods  three  or  four  rows  of  similar  cells,  together  with  certain 


10l)()      ORGANS  OF   THE  SEXSES  AM)   THE    COM^VOX   IXTEGL'MEXT 

supporting  cells  termed  the  cells  of  Deiters  and  Ilensen.  The  free  cuds  of  the  outer 
hair  cells  occupy  a  series  of  apertures  in  a  net-like  menihranc,  the  reticular  membrane, 
and  the  entire  organ  is  covered  b\'  the  tectorial  nicnihraiic. 


Membrami  tectoria 


Outer  hair  cclU 


Nerve  fibres  Basilar  membrane 

Fig.  887. — Section  through  the  spiral  organ  of  Corti.     Magnified.      (G.  Retzius.) 


Rods  of  Corti. — Each  of  these  consists  of  a  base  or  foot-plate,  and  elongated 
part  or  bod\',  and  an  upper  end  or  head;  the  body  of  each  rod  is  finely  striated,  but 
in  the  head  there  is  an  oval  non-striated  portion  which  stains  deeply  with  carmine. 


Fig.  888. — The  lamina  reticularis  and  subjacent  structures.  (Schematic)  (Testut.)  A.  Internal  rod  of  Corti, 
with  a,  its  plate.  B.  External  rod  (in  yellow).  C.  Tunnel  of  Corti.  D.  Membrana  basilaris.  E.  Inner  hair  cells. 
1,  1'  Internal  and  external  borders  of  the  membrana  reticularis.  2,  2',  2".  The  three  rows  of  circular  holes  (in  blue). 
3.  First  row  of  phalanges  (in  yellow).  4,  4',  4".  Second,  third,  and  fourth  rows  of  phalanges  (in  red).  6,  6',  (i".  The 
three  rows  of  outer  hair  cells  (in  blue).     7,  7',  7".  Cell?  of  Deiters.     8.  Cells  of  Hensen  and  Claudius. 


Occupying  the  angles  between  the  rods  and  the  basilar  membrane  are  nucleated 
cells  which  partly  envelop  the  rods  and  extend  on  to  the  floor  of  Corti's  tunnel; 
these  may  be  looked  upon  as  the  undifferentiated  i^arts  of  the  cells  from  which  the 
rods  have  been  formed. 


THE  INTERNAL  EAJi  Oli  LAJiYh'/XTII  1007 

The  inner  rods  iiuiiihtT  nearly  (iOOO,  and  their  hases  rest  on  tlie  hasihir  nienil)rune 
close  to  the  t\  nii)anie  lip  of  the  salens  spiralis  internns.  The  shaft  or  body  of  eaeh 
is  sinously  curved  and  forms  an  anf;le  of  ;il)()Ut  00  defj;rees  with  the  basilar  mem- 
brane. The  head  resembles  the  i)roximal  end  of  the  ulna  and  presents  a  deep 
concavity  wliieh  accommodates  a  convexity  on  the  head  of  the  outer  rod.  The 
head-plate,  or  i)ortion  o\i>rhan,iiin,i;-  the  concax'ity,  overlaps  the  licad-plate  of  the 
outer  rod. 

The  outer  rods,  nearly  IOOO  in  number,  are  longer  and  more  obliquely  set  than  the 
inner,  forming  with  the  basilar  membrane  an  angle  of  about  40  degrees.  Their 
heads  are  convex  internally;  they  fit  into  the  concavities  on  the  heads  of  the  inner 
rods  and  are  continued  outward  as  thin  flattened  plates,  termed  phalangeal  processes, 
which  unite  with  the  phalangeal  i)r()cesses  of  Deiters'  cells  to  form  the  reticular 
membrane. 

Hair  Cells. — The  hair  cells  are  short  columnar  cells;  their  free  ends  are  on  a  level 
with  the  heads  of  Corti's  rods,  and  each  is  surmounted  by  about  twenty  hair-like 
processes  arranged  in  the  form  of  a  crescent  Avith  its  concavity  directed  inward. 
The  deep  ends  of  the  cells  reach  about  half-way  along  Corti's  rods,  and  each  con- 
tains a  large  nucleus;  in  contact  w4th  the  deep  ends  of  the  hair  cells  are  the  terminal 
filaments  of  the  cochlear  division  of  the  acoustic  nerve.  The  inner  hair  cells  are 
arranged  in  a  single  row  on  the  medial  side  of  the  inner  rods,  and  their  diameters 
being  greater  than  those  of  the  rods  it  follow^s  that  each  hair  cell  is  supported  by 
more  than  one  rod.  The  free  ends  of  the  inner  hair  cells  are  encircled  by  a  cuticular 
membrane  which  is  fixed  to  the  heads  of  the  inner  rods.  Adjoining  the  inner 
hair  cells  are  one  or  two  rows  of  columnar  supporting  cells,  which,  in  turn,  are  con- 
tinuous with  the  cubical  cells  lining  the  sulcus  spiralis  internus.  The  outer  hair  cells 
number  about  12,000,  and  are  nearly  tw^ice  as  long  as  the  inner.  In  the  basal  coil 
of  the  cochlea  they  are  arranged  in  three  regular  rows;  in  the  apical  coil,  in  four, 
somewhat  irregular,  rows. 

Between  the  rows  of  the  outer  hair  cells  are  rows  of  supporting  cells,  called  the 
cells  of  Deiters;  their  expanded  bases  are  planted  on  the  basilar  membrane,  while 
the  opposite  end  of  each  presents  a  clubbed  extremity  or  phalangeal  process.  Imme- 
diately to  the  outer  side  of  Deiters'  cells  are  five  or  six  row^s  of  columnar  cells,  the 
supporting  cells  of  Hensen.  Their  bases  are  narrow,  while  their  upper  parts  are 
expanded  and  form  a  rounded  elevation  on  the  floor  of  the  ductus  cochlearis. 
The  columnar  cells  lying  outside  Hensen's  cells  are  termed  the  cells  of  Claudius. 
A  space  exists  betw^een  the  outer  rods  of  Corti  and  the  adjacent  hair  cells;  this  is 
called  the  space  of  Nuel. 

The  reticular  lamina  (Fig.  888)  is  a  delicate  frame-work  perforated  by  rounded 
holes  which  are  occupied  by  the  free  ends  of  the  outer  hair  cells.  It  extends  from 
the  heads  of  the  outer  rods  of  Corti  to  the  external  row  of  the  outer  hair  cells,  and 
is  formed  by  several  rows  of  "  minute  fiddle-shaped  cuticular  structures,"  called  pha- 
langes, between  which  are  circular  apertures  containing  the  free  ends  of  the  hair  cells. 
The  inner  most  row  of  phalanges  consists  of  the  phalangeal  processes  of  the  outer 
rods  of  Corti;  the  outer  rows  are  formed  by  the  modified  free  ends  of  Deiters'  cells. 

Covering  the  sulcus  spiralis  internus  and  the  spiral  organ  of  Corti  is  the  tectorial 
membrane,  which  is  attached  to  the  limbus  laminae  spiralis  close  to  the  inner  edge 
of  the  vestibular  membrane.  Its  inner  part  is  thin  and  overlies  the  auditory  teeth 
of  Huschke;  its  outer  part  is  thick,  and  along  its  lower  edge,  opposite  the  inner 
hair  cells,  is  a  clear  band,  named  Hensen's  stripe.  The  lateral  margin  of  the 
membrane  is  much  thinner,  and  is  attached  to  the  outer  row  of  Deiters'  cells 
(Retzius). 

The  acoustic  nerve  (n.  acusticus;  auditory  nerve  or  nerve  of  hearing)  divides  near 
the  bottom  of  the  internal  acoustic  meatus  into  an  anterior  or  cochlear  and  a 
posterior  or  vestibular  branch. 


1068      ORGANS  OF  THE  SENSES  AND  THE   COMMON  INTEGUMENT 

The  vestibular  nerve  (n.  vestibularis)  supplies  the  utricle,  the  saccule,  and  the 
ampullae  of  the  semicircular  ducts.  On  the  trunk  of  the  nerve,  within  the  internal 
acoustic  meatus,  is  a  ganglion,  the  vestibular  ganglion  {ganglion  of  Scarpa);  the 
fibres  of  the  nerve  arise  from  the  cells  of  this  ganglion.  On  the  distal  side  of  the 
ganglion  the  nerve  splits  into  a  superior,  an  inferior,  and  a  posterior  branch.^  The 
filaments  of  the  superior  branch  are  transmitted  through  the  foramina  in  the  area 
vestibularis  superior,  and  end  in  the  macula  of  the  utricle  and  in  the  ampullae 
of  the  superior  and  lateral  semicircular  ducts;  those  of  the  inferior  branch  traverse 
the  foramina  in  the  area  vestibularis  inferior,  and  end  in  the  macula  of  the  saccule. 
The  posterior  branch  runs  through  the  foramen  singulare  at  the  postero-inferior 
part  of  the  bottom  of  the  meatus  and  divides  into  filaments  for  the  supply  of  the 
ampulla  of  the  posterior  semicircular  duct. 

The  cochlear  nerve  (n.  cochlearis)  divides  into  numerous  filaments  at  the  base  of  the 
modiolus;  those  for  the  basal  and  middle  coils  pass  through  the  foramina  in  the 

tractus  spiralis  foraminosis,  those  for 


Ganglion 
spirale 


Spiral 
fibres 


Nerve-fibres  passing  out 
between  the  two  layers  of 
the  lamina  spiralis  ossea 


Fig.  889. — Part  of  the  cochlear  division  of  the  acoustic 
nerve,  highly  magnified.     (Henle.) 


the  apical  coil  through  the  canalis  cen- 
tralis, and  the  nerves  bend  outward  to 
pass  between  the  lamellae  of  the  osseous 
spiral  lamina.  Occupying  the  spiral 
canal  of  the  modiolus  is  the  spiral 
ganglion  of  the  cochlea  (ganglion  of 
Corti)  (Fig.  889),  consisting  of  bipolar 
nerve  cells,  which  constitute  the  cells 
of  origin  of  this  nerve.  Reaching  the 
outer  edge  of  the  osseous  spiral  lamina, 
the  fibres  of  the  nerve  pass  through 
the  foramina  in  the  tympanic  lip ;  some 
end  by  arborizing  around  the  bases  of 
the  inner  hair  cells,  while  others  pass 
between  Corti's  rods  and  across  the  tunnel,  to  end  in  a  similar  manner  in  relation 
to  the  outer  hair  cells.  The  cochlear  nerve  gives  off  a  vestibular  branch  to 
supply  the  vestibular  end  of  the  ductus  cochlearis;  the  filaments  of  this  branch  pass 
through  the  foramina  in  the  fossa  cochlearis  (page  1058). 

Vessels. — The  arteries  of  the  labyrinth  are  the  internal  auditory,  from  the  basilar,  and  the 
stylomastoid,  from  the  posterior  auricular.  The  internal  auditory  artery  divides  at  the  bottom 
of  the  internal  acoustic  meatus  into  two  branches:  cochlear  and  vestibular.  The  cochlear 
branch  subdivides  into  twelve  or  fourteen  twigs,  which  traverse  the  canals  in  the  modiolus, 
and  are  distributed,  in  the  form  of  a  capillary  net-work,  in  the  lamina  spiralis  and  basilar  mem- 
brane.   The  vestibular  branches  are  distributed  to  the  utricle,  saccule,  and  semicircular  ducts. 

The  veins  of  the  vestibule  and  semicircular  canals  accompany  the  arteries,  and,  receiving 
those  of  the  cochlea  at  the  base  of  the  modiolus,  unite  to  form  the  internal  auditory  veins  which 
end  in  the  posterior  part  of  the  superior  petrosal  sinus  or  in  the  transverse  sinus. 

Applied  Anatomy. — The  diseased  conditions  which  may  be  found  in  the  internal  ear  usually 
result  from  the  spread  of  a  suppurative  process  from  the  middle  ear — thus  in  chronic  suppuration 
of  the  latter,  destruction  of  the  internal  ear  may  take  place,  with  necrosis  of  parts  of  the  cochlea 
or  vestibule.  Such  cases  will  be  associated  with  "nerve  deafness,"  and  the  disease  may  spread 
by  means  of  the  sheaths  of  the  facial  and  acoustic  nerves  into  the  posterior  fossa  of  the  skull. 

Hemorrhage  occasionally  occurs  into  the  labyrinth  in  certain  blood  disorders,  resulting  in 
complete  nerve  deafness,  and  such  conditions  may  be  associated  with  symptoms  known  as 
Meniere's  disease,  vertigo,  giddiness,  and  tinnitus.  Nerve  deafness  is  diagnosticated  when  all 
"bone-conduction"  of  sound  is  lost,  and  is  most  commonly  seen  in  patients  suffering  from 
congenital  syphilis,  many  deaf-mutes  being  the  subjects  of  this  condition. 


'  The  nerve  sometimes  splits  on  the  proximal  side  of  the  ganglion,  and  the  latter  is  then  dividfid  into  three  parts, 
one  on  each  branch  of  the  nerve. 


PERIPHERAL  TERMIXATIOXS  OF  NERVES  OF  GEXERAL  SEXSATIOXS    1069 


PERIPHERAL  TERMINATIONS  OF  NERVES  OF  GENERAL  SENSATIONS. 

The  iieriplieral  tenniiuUions  of  tlu>  nerves  us.sociatecl  with  general  sensations,  i.  c,  the  mus- 
cular sense  and  the  senses  of  heat,  cold,  pain,  and  ))ressure,  are  widely  distributed  throughout 
the  body.  These  nerves  may  end /;-ec  among  the  tissue  elements,  or  in  special  end-organs  where 
the  terminal  nerve  filaments  are  enclosed  in  capsules. 

Free  nerve-endings  occur  chiefly  in  the  epidermis  and  in  the  epithelium  covering  certain 
mucous  incinlH:nu>s:  they  are  well  seen  also  in  the  stratified  squamous  epithelium  of  the  cornea, 
and  are  also  Umnd  in  the  root-sheaths  and  papilla?  of  the  hairs,  and  around  the  bodies  of  the 
sudoriferous  glands.  \\'hen  the  nerve  fibre  approaches  its  termination,  the  medullary  sheath 
suddenly  disajipears,  leaving  only  the  axis-cylinder  surrounded  by  the  neurolemma.  After  a  time 
the  fibre  loses  its  neurolemma,  and  consists  only  of  an  axis-cylinder,  which  can  be  seen,  in 
preparations  stained  with  chloride  of  gold,  to  be  made  up  of  fine  varicose  fibrillar.  Finally,  the 
axis-cylinder  breaks  up  into  its  constituent  fibrilla;  which  often  present  regular  varicosities  and 
anastomose  with  one  another,  and  end  in  small  knobs  or  di.sks  between  the  epithehal  cells. 

Under  this  heading  may  be  classed  the  tactile  disks  described  by  Merkel  as  occurring  in  the 
epidermis  of  the  pig's  snout,  where  the  fibrilke  of  the  axis-cylinder  end  in  cup-shaped  di.sks  in 
apposition  with  large  epithelial  cells. 

The  special  end-organs  exhibit  great  variety  in  size  and  shape,  but  have  one  feature  in  common- 
viz.,  the  terminal  nerve  fibrilla;  are  enveloped  by  a  capsule.  Included  in  this  group  are  the  end, 
bulbs  of  Ivi-ause,  the  corpuscles  of  Grandry,  of  Pacini,  of  Golgi  and  INIazzoni,  of  Wagner  and 
Meissner,  and  the  nem-otendinous  and  neuromuscular  spindles. 

The  end-bulbs  of  Krause  (Fig.  890)  are  minute  cylindrical  or  oval  bodies,  consisting  of  a 
capsule  formed  by  the  ex-]3ansion  of  the  connective-tissue  sheath  of  a  medullated  fibre,  and 
containing  a  soft  semifluid  core  in  which  the  axis-cjdinder 
terminates  either  in  a  bulbous  extremity  or  in  a  coiled-up 
plexiform  mass.  End-bulbs  are  found  in  the  conjmictiva 
of  the  eye  (where  they  are  spheroidal  in  shape  in  man,  but 
cylindrical  in  most  other  animals),  in  the  mucous  mem- 
brane of  the  lips  and  tongue,  and  in  the  epinem-ium  of 
nerve  trunks.  They  are  also  found  in  the  penis  and  the 
clitoris,  and  have  received  the  name  of  genital  corpuscles ; 
in  these  situations  they  have  a  mulberrj^-like  appearance, 
being  constricted  bj'  coimective-t issue  septa  into  from  two 
to  six  knob-like  masses.  In  the  synovial  membranes  of 
certain  joints,  e.  g.,  those  of  the  fingers,  rounded  or  oval 
end-bulbs  occur,  and  are  designated  articular  end-bulhs. 

The  tactile  corpuscles  of  Grandry  occur  in  the  papillae  of 
the  beak  and  tongue  of  birds.  Each  consists  of  a  capsule 
composed  of  a  very  delicate,  nucleated  membrane,  and 
contains  two  or  more  granular,  somewhat  flattened  cells; 
between  these  cells  the  axis-cj^linder  ends  in  flattened  disks. 

The  Pacinian  corpuscles  (Fig.  891)  are  found  in  the 
subcutaneous  tissue  on  the  nerves  of  the  palm  of  the  hand 
and  sole  of  the  foot  and  in  the  genital  organs  of  both  sexes; 
the}'  also  occur  in  connection  with  the  nerves  of  the  joints,  and  in  some  other  situations,  as  in 
the  mesentery  and  pancreas  of  the  cat  and  along  the  tibia  of  the  rabbit.  Each  of  these  corpus- 
cles is  attached  to  and  encloses  the  termination  of  a  single  nerve  fibre.  The  corpuscle,  which  is 
perfectly  visible  to  the  naked  e3'e  (and  which  can  be  most  easilj'  demonstrated  in  the  mesentery 
of  a  cat),  consists  of  a  number  of  lamellae  or  capsules  arranged  more  or  less  concentricalh- 
aroimd  a  central  clear  space,  in  which  the  nerve-fibre  is  contained.  Each  lamella  is  composed  of 
bundles  of  fine  connective-tissue  fibres,  and  is  lined  on  its  inner  surface  by  a  single  laj'er  of 
flattened  epithelioid  cells.  The  central  clear  space,  which  is  elongated  or  cj'lindrical  in  shape, 
is  filled  with  a  transparent  core,  in  the  middle  of  which  the  axis-cylinder  traverses  the  space 
to  near  its  distal  extremitj',  where  it  ends  in  one  or  more  small  knobs.  Todd  and  Bowmaii 
have  described  minute  arteries  as  entering  by  the  sides  of  the  nerves  and  forming  capillary 
loops  in  the  intercapsular  spaces,  and  even  penetrating  into  the  central  space. 

Herbst  has  described  a  nerve-ending  somewhat  similar  to  the  Pacinian  corpuscle,  in  the  mucous 
membrane  of  the  tongue  of  the  duck,  and  in  some  other  situations.  It  differs,  however,  from 
the  Pacinian  corpuscle,  in  being  smaller,  in  its  capsules  being  more  closely  approximated,  and 
especiallj'  in  the  fact  that  the  axis  cA'hnder  in  the  central  clear  space  is  coated  N\ith  a  continuous 
row  of  nuclei.    These  bodies  are  known  as  the  corpuscles  of  Herbst. 

The  corpuscles  of  Golgi  and  Mazzoni  are  foimd  in  the  subcutaneous  tissue  of  the  pulp  of 
the  fingers.  The}'  differ  from  Pacinian  corpuscles  in  that  their  capsules  are  thinner,  their  con- 
tained cores  thicker,  and  in  the  latter  the  axis-cjdinders  ramifj-  more  extensively  and  end  in 
flat  expansions. 


Fig.  S90.  —  End-bulb  of  Krause.  a. 
Medullated  nerve  fibre.  6.  Capsule  of 
corpuscle.     (Klein.) 


1070       ORGANS  OF  THE  SENSES  AND  THE   COMMON  INTEGUMENT 


The  tactile  corpuscles  of  Wagner  and  Meissner  (Fig.  892)  are  oval-shaped  bodies.     Each 
is  enveloped  }jy  a  connective-tissue  capsule,  and  imperfect  membranous  septa  derived  from  this 

penetrate  the  interior.  The  axis-cylinder 
passes  through  the  capsule,  and  after  making 
several  spiral  turns  around  the  body  of  the 
corpuscle  ends  in  small  globular  or  pyriform 
enlargements.  These  tactile  corpuscles  occur 
in  the  papillse  of  the  corium  of  the  hand  and 
foot,  the  front  of  the  forearm,  the  skin  of  the 
lips,  the  mucous  membrane  of  the  tip  of  the 
tongue,  the  palpebral  conjunctiva,  and  the 
skin  of  the  mammary  papilla. 

Corpuscles  of  Ruffini.^Ruffini  described  a 
special  variety  of  nerve-ending  in  the  subcuta- 


4*'* 


iMh 


Fig.  891. — Pacinian  corpuscle,  with  its  system  of 
capsules  and  central  cavity,  a.  Arterial  tnig,  end- 
ing in  capillaries,  which  form  loops  in  some  of  the 
intercapsular  spaces,  and  one  penetrates  to  the  cen- 
tral capsule.  6.  The  fibrous  tissue  of  the  stalk,  n. 
Nerve  tube  advancing  to  the  central  capsule,  there 
losing  its  white  matter,  and  stretching  along  the 
axis  to  the  opposite  end,  where  it  ends  by  a  tubercu- 
lated  enlargement. 


Fig.  892. — Papilla  of  the  hand,  treated  with  acetic 
acid.  Magnified  350  times.  A.  Side  view  of  a  papilla 
of  the  hand.  a.  Cortical  layer,  h.  Tactile  corpuscle,  c. 
Small  ner-ve  of  the  papilla,  with  neurolemma,  d.  Its  two 
nervous  fibres  running  with  spiral  coils  around  the  tactile 
corpuscle,  e.  Apparent  termination  of  one  of  these  fibres. 
B.  A  tactile  papilla  seen  from  above  so  as  to  show  its 
transverse  section,  a.  Cortical  layer.  6.  Nerve  fibre,  c. 
Outer  layer  of  the  tactile  body,  with  nuclei,  d.  Clear 
interior  substance. 


neous  tissue  of  the  human  finger  (Fig.  893);  they  are  principally  situated  at  the  junction  ot  the 
corium  with  the  subcutaneous  tissue.  They  are  oval  in  shape,  and  consist  of  strong  connective- 
tissue  sheaths,  inside  which  the  nerve-fibres  divide  into  numerous  branches,  which  show  vari- 
cosities and  end  in  small  free  knobs. 


Nerve  fibres 


Terminal  ramific/iUons 
of  axis  cylinders 


Connective  tissue  sheath 


Fig.  893. — Nerve  ending  of  Ruffini.      (After  A.  Rufiini.) 


The  neurotendinous  spindles  {organs  of  Golgi)  are  chiefly  found  near  the  junctions  of  tendons 
and  muscles.  Each  is  enclosed  in  a  capsule  which  contains  a  number  of  enlarged  tendon  fascicuh 
{intrafusal  fasciculi).  One  or  more  nerve  fibres  perforate  the  side  of  the  capsule  and  lose  their 
meduUary  sheaths;  the  axis-cylinders  subdivide  and  end  between  the  tendon  fibres  in  irregular 
disks  or  varicosities  (Fig.  894). 


THE  COM M OX   IXTEaUMEXT 


1U71 


The  neuromuscular  spindles  arc  present  in  the  majority  of  voluntary  muscles,  and  consist 
of  small  hmullcs  of  peculiar  muscular  fibres  (intrafusal  fibres),  embryonic  in  type,  invested  by 
capsules,   willun   wliicli   iicrxc  fibres,  cxpci-iiiicntallN'  slinwii   to  be  sensory  in  origin,   terminate. 


Nenr  fibre 


Tendon 
bundles 


Oigan.  of  Golcji,  showing 
ramification  of  nerve-fibrils 


Muscular  fibres 
Fig.  S94. — Organ  of  Golgi   (neurotendinous  spindle)   from  the  human  tendo  calcaneus.     (After  Ciaccio.) 

These  neuromuscular  spindles  vary  in  length  from  0.8  mm.'  to  5  mm.,  and  have  a  distinctly 
fusiform  appearance.  The  large  meduUated  nerve  fibres  passing  to  the  end-organ  are  from 
one  to  three  or  four  in  number;  entering  the  fibrous  capsule,  they  divide  several  times,  and. 


Fig.  895. — Middle  third  of  a  terminal  plaque  in  the  muscle  spindle  of  an  adult  oat.     (After  RufSni.) 

losing  their  medullary  sheaths,  ultimately  end  in  naked  axis-cylinders  encircling  the  intrafusal 
fibres  by  flattened  expansions,  or  irregular  ovoid  or  rounded  disks  (Fig.  895).  Neuromuscular 
spindles  have  not  yet  been  demonstrated  in  the  tongue  muscles,  and  only  a  few  exist  in  the 
ocular  muscles. 


THE  COMMON  INTEGUMENT  (INTEGUMENTUM  COMMUNE;   SKIN). 

The  integument  (Fig.  896)  covers  the  body  and  protects  the  deeper  tissues; 
it  contains  the  peripheral  endings  of  many  of  the  sensory  nerves;  it  plays  an  impor- 
tant part  in  the  regulation  of  the  body  temperature,  and  has  also  limited  excretory 
and  absorbing  powers.  It  consists  principally  of  a  layer  of  vascular  connective 
tissue,  named  the  corium  or  cutis  vera,  and  an  external  covering  of  epithelium, 
termed  the  epidermis  or  cuticle.  On  the  surface  of  the  former  layer  are  sensitive 
and  vascular  papillae  within,  or  beneath  it,  are  certain  organs  with  special  func- 
tions: namely,  the  sudoriferous  and  sebaceous  glands,  and  the  hair  follicles. 

The  epidermis,  cuticle,  or  scarf  skin  is  non-vascular,  and  consists  of  stratified 
epithelium  (Fig.  897),  and  is  accurately  moulded  on  the  papillary  layer  of  the  corium. 
It  varies  in  thickness  in  different  parts.  In  some  situations,  as  in  the  palms  of  the 
hands  and  soles  of  the  feet,  it  is  thick,  hard,  and  horny  in  texture.    This  may  be  in 


1072       ORGANS  OF   THE  SENSES  AND   THE   COMMON  INTEGUMENT 

a  measure  due  to  the  fact  that  these  parts  are  exposed  to  intermittent  pressure, 
but  that  this  is  not  the  onl.>-  cause  is  proved  by  the  fact  that  the  comhtion  exists 
to  a  very  considerable  extent  at  birth.  The  more  superficial  layers  of  cells,  called 
the  horny  layer  {stratum  corncum),  may  be  separated  by  maceration  from  a  deeper 
stratum  which  is  called  the  stratum  mucosum,  and  which  consists  of  several  layers 
of  dift'er'enth'  shaped  cells.  The  free  surface  of  the  epidermis  is  marked  by  a 
net-work  of  linear  furrows  of  variable  size,  dividing  the  surface  into  a  number  ot 
polyo-onal  or  lozenge-shaped  areas.  Some  of  these  furrows  are  large,  as  opposite  the 
flexures  of  the  joints,  and  correspond  to  the  folds  in  the  corium  produced  by  move- 


Duct  of 

sudoriferous 

gland 


Tactile 
corpuscle 

Duct  of 

sudoriferous , 

gland 


Adipose  tissue  < 
Artery  • 


Pacinian  _ 
corpuscle 


Stratum, 
'  corneum 


Stratum 

lucidum 
'  Stratum 

granulosum 
'  Stratum 

■mucosum 

.  Stratum 
germinativum 


~  —  Dermis 


Sudoriferous 
gland 


, -Nerve 


PiQ    896.— A  diagrammatic  sectional  view  of  the  skin  (magnified). 

ments.  In  other  situations,  as  upon  the  back  of  the  hand,  they  are  exceedingly 
fine,  and  intersect  one  another  at  various  angles.  Upon  the  palmar  surfaces  ot  the 
hands  and  fingers,  and  upon  the  soles  of  the  feet,  these  lines  are  very  distinct, 
and  are  disposed  in  curves;  they  depend  upon  the  large  size  and  peculiar  arrange- 
ments of  the  papilte  upon  which  the  epidermis  is  placed.  In  each  individual  the 
lines  on  the  tips  of  the  fingers  and  thumbs  form  distinct  patterns  un  ike  those  ot 
any  other  person.  A  method  of  determining  the  identity  of  a  criminal  is  based  on 
this  fact,  impressions  ''finger-prints"  of  these  lines  being  made  on  paper  covered 
with  soot,  or  on  white  paper  after  first  covering  the  fingers  with  ink.     Ihe  deep 


THE  COMMON  INTEGUMKXT 


1073 


surface  of  the  epidermis  is  accurately  moulded  upon  the  papiUary  layer  of  the 
corium,  the  papillie  being  covered  by  a  basement  membrane;  so  that  when  the 
epidermis  is  removed  by  maceration,  it  i)resents  on  its  under  surface  a  number  of 
pits  or  depressions  corresponding  to  the  papilla?,  and  ridges  corresi)onding  to  the 
intervals  between  them.  Fine  tubular  prolongations  are  continued  from  this 
laver  into  tlie  ducts  of  the  sudoriferous  and  sebaceous  glands. 


Si  rat  urn  corncum 


Stratum  liicidum  ■'. 
Stratum  granulosum  ( 


.Stratum  mucostion  < 


Stratum  gcr7ninativum 


mwfS 


erve  fibrils 


Fig.  897. — Section  of  epidermis.     (Ranvier.) 

The  epidermis  consists  of  stratified  epithelium  which  is  arranged  in  four  layers 
from  within  outward  as  follows:  (a)  stratum  mucosum,  (6)  stratum  granulosum,  (c) 
stratum  lucidum,  and  (c/)  stratum  corneum. 

The  stratum  mucosum  {mucous  layer)  is  composed  of  several  layers  of  cells;  those 
of  the  deepest  layer  are  columnar  in  shape  and  placed  perpendicularly  on  the 
surface  of  the  basement  membrane,  to  which  they  are  attached  by  toothed  extrem- 
ities ;  this  deepest  layer  is  sometimes  termed  the  stratum  germinativum ;  the  succeed- 
ing strata  consist  of  cells  of  a  more  rounded  or  polyhedral  form,  the  contents  of 
which  are  soft,  opaque,  granular,  and  soluble  in  acetic  acid.  These  are  known  as 
prickle  cells  because  of  the  bridges  by  which  they  are  connected  to  one  another 
(see  page  39) .  They  contain  fine  fibrils  which  are  continuous  across  the  connecting 
processes  with  corresponding  fibrils  in  adjacent  cells.  Bet^veen  the  bridges  are 
fine  intercellular  clefts  serving  for  the  passage  of  lymph,  and  in  these,  lymph 
corpuscles  or  pigment  granules  may  be  found. 

The  stratum  granulosum  comprises  two  or  three  layers  of  flattened  cells  which 
contain  granules  of  eleidin,  a  substance  readily  stained  by  hematoxylin  or  carmine, 
and  probably  an  intermediate  substance  in  the  formation  of  keratin.  They  are 
supposed  to  be  cells  in  a  transitional  stage  between  the  protoplasmic  cells  of  the 
stratum  mucosum  and  the  horny  cells  of  the  superficial  layers. 

The  stratum  lucidum  appears  in  section  as  a  homogeneous  or  dimly  striated  mem- 
brane, composed  of  closely  packed  cells  in  which  traces  of  flattened  nuclei  may  be 
found,  and  in  which  minute  granules  of  a  substance  named  kerotohi/alin  are  present. 

The  stratum  corneum  (horny  layer)  consists  of  several  layers  of  horny  epithelial 
68 


1074       ORGANS  OF   THE  SENSES  AND   THE  COMMON  INTEGUMENT 

scales  in  which  no  nuclei  are  discernible,  and  which  are  unaffected  by  acetic  acid,  the 
protoplasm  having  become  changed  into  horny  material  or  keratin.  According  to 
Ranvier  they  contain  granules  of  a  material  which  has  the  characteristics  of  beeswax. 

The  black  color  of  the  skin  in  the  negro,  and  the  tawny  color  among  some  of 
the  white  races,  is  due  to  the  presence  of  pigment  in  the  cells  of  the  epidermis. 
This  pigment  is  more  especially  distinct  in  the  cells  of  the  stratum  mucosum,  and 
is  similar  to  that  found  in  the  cells  of  the  pigmentary  layer  of  the  retina.  As  the 
cells  approach  the  surface  and  desiccate,  the  color  becomes  partially  lost;  the 
disappearance  of  the  pigment  from  the  superficial  layers  of  the  epidermis  is, 
however,  difficult  to  explain. 

The  Corium,  Cutis  Vera,  Dermis,  or  True  Skin  is  tough,  flexible,  and  highly 
elastic.  It  ^'a^ies  in  thickness  in  difi'erent  parts  of  the  body.  Thus  it  is  very 
thick  in  the  palms  of  the  hands  and  soles  of  the  feet;  thicker  on  the  posterior  aspect 
of  the  body  than  on  the  front,  and  on  the  lateral  than  on  the  medial  sides  of  the 
limbs.    In  the  eyelids,  scrotum,  and  penis  it  is  exceedingly  thin  and  delicate. 

It  consists  of  felted  connective  tissue,  with  a  varying  amount  of  elastic  fibres 
and  numerous  bloodvessels,  lymphatics,  and  nerves.  The  connective  tissue  is 
arranged  in  two  layers:  a  deeper  or  reticular,  and  a  superficial  or  papillary.  Un- 
striped  muscular  fibres  are  found  in  the  superficial  layers  of  the  corium,  wherever 
hairs  are  present,  and  in  the  subcutaneous  areolar  tissue  of  the  scrotum,  penis, 
labia  majora,  and  nipples.  In  the  nipples  the  fibres  are  disposed  in  bands,  closely 
reticulated  and  arranged  in  superimposed  laminse. 

The  reticular  layer  (stratum  reticulare;  deep  layer)  consists  of  strong  interlacing 
bands,  composed  chiefly  of  white  fibrous  tissue,  but  containing  some  fibres  of  yellow 
elastic  tissue,  w^hich  vary  in  number  in  different  parts;  and  connective-tissue  cor- 
puscles, which  are  often  to  be  found  flattened  against  the  white  fibrous  tissue  bundles 
Toward  the  attached  surface  the  fasciculi  are  large  and  coarse,  and  the  areolae 
left  by  their  interlacement  are  large,  and  occupied  by  adipose  tissue  and  sweat 
glands.  Below  the  reticular  layer  is  the  subcutaneous  areolar  tissue,  which,  except 
in  a  few  situations,  contains  fat. 

The  papillary  layer  (stratum  papillare;  superficial  layer;  corpus  papiUare  of  the 
corium)  consists  of  numerous  small,  highly  sensitive,  and  vascular  eminences, 
the  papillae,  which  rise  perpendicularly  from  its  surface.  The  papillae  are  minute 
conical  eminences,  having  rounded  or  blunted  extremities,  occasionally  divided 
into  two  or  more  parts,  and  are  received  into  corresponding  pits  on  the  under 
surface  of  the  cuticle.  On  the  general  surface  of  the  body,  more  especially  in  parts 
endowed  with  slight  sensibility,  they  are  f ew^  in  number,  and  exceedingly  minute ;  but 
in  some  situations,  as  upon  the  palmar  surfaces  of  the  hands  and  fingers,  and  upon 
the  plantar  surfaces  of  the  feet  and  toes,  they  are  long,  of  large  size,  closely  aggre- 
gated together,  and  arranged  in  parallel  curved  lines,  forming  the  elevated  ridges 
seen  on  the  free  surface  of  the  epidermis.  Each  ridge  contains  two  rows  of  papillae, 
between  which  the  ducts  of  the  sudoriferous  glands  pass  outward  to  open  on  the 
summit  of  the  ridge.  Each  papilla  consists  of  very  small  and  closely  interlacing 
bundles  of  finely  fibrillated  tissue,  w4th  a  few  elastic  fibres;  within  this  tissue  is  a 
capillary  loop,  and  in  some  papillae,  especially  in  the  palms  of  the  hands  and  the 
fingers,  there  are  tactile  corpuscles. 

The  arteries  supplying  the  skin  form  a  net-work  in  the  subcutaneous  tissue,  and  from  this 
net-work  branches  are  given  off  to  supply  the  sudoriferous  glands,  the  hair  foUicles,  and  the 
fat.  Other  branches  imite  in  a  plexus  immediately  beneath  the  corium;  from  this  plexus,  fine 
capillary  vessels  pass  into  the  papillse,  forming,  in  the  smaller  ones,  a  single  capillary  loop,  but 
in  the  larger,  a  more  or  less  convoluted  vessel.  The  lymphatic  vessels  of  the  skin  form  two 
net-works,  superficial  and  deep,  which  communicate  with  each  other  and  with  those  of  the  sub- 
cutaneous tissue  by  oblique  branches. 

The  nerves  of  the  skin  terminate  partly  in  the  epidermis  and  partly  in  the  corium;  their  different 
modes  of  ending  are  described  on  pages  1069  to  1071. 


THE  APFEXDAGES  OF  THE  SKIX  1075 

THE  APPENDAGES   OF  THE  SKIN. 

The  appen(laii;es  of  tlie  skin  are  the  nails,  the  hairs,  .iiid  the  sudoriferous  and 
sebaceous  glands  with  tlieir  (hiets. 

The  Nails  (NNiiiics-)  (Fig.  89S)  are  Hattened,  elastic  structures  of  a  horny  texture, 
])hiced  upon  the  chirsal  surfaces  of  the  terminal  phalanges  of  the  fingers  and  toes. 
Each  luiil  is  con\ex  on  its  outer  surface,  concave  within,  and  is  implanted  })y  a 
portion,  called  the  root,  into  a  groove  in  the  skin;  the  exposed  portion  is  called  the 
body,  and  the  distal  extremity  the  free  edge.  The  nail  is  firmly  adherent  to  the 
corium,  being  accurately  moulded  u])on  its  surface;  the  part  beneath  the  body  and 
root  of  the  nail  is  called  the  nail  matrix,  because  from  it  the  nail  is  produced.  Under 
the  greater  ])art  of  the  body  of  the  nail,  the  matrix  is  thick,  and  raised  into  a  series 
of  longitudinal  ridges  which  are  very  vascular,  and  the  color  is  seen  through  the 
transparent  tissue.  Near  the  root  of  the  nail,  the  papillae  are  smaller,  less  vascular, 
and  have  no  regular  arrangement,  and  here  the  tissue  of  the  nail  is  more  opaque; 
hence  this  portion  is  of  a  whiter  color,  and  is  called  the  lunula  on  account  of  its 
shape. 

Stratnm 

Euotui-l'i  ^-^  "^  •  ^^^^.^^_„^^i-.i  i-i.r— r  — ,1^  ^    'corueuin 

■..   ..""""" ^y^    ^.-iss""^-** "^''"'^'°°^^7"~^^ ■ '  ■/ ■'^''■'n  A'A'^'    v'x^v ''r\T\--'K'r\  ■■, l-■^^\C' ^-^    Stratuin 

-''"*'  ___      ~^— =~A  V  C        "     ■  ^       ^  ^^    L^  >"-'     ^  I,  V  granulosum 


Stratum    ^-JS^ 
inucoisum  " 

Stratum  cor-       .'I?;-.  ^^;^\\^Or  •'- Corium 

nail  nrooce  -_ .:        .-•-        ~  -~.~".,        "^-<^-^ 


i-:".'.-^ —  Blood-vessel 


Fig.  S9S. — Longitudinal  section  through  nail  and  its  nail  groove  (sulcus). 

The  cuticle  as  it  passes  forw^ard  on  the  dorsal  surface  of  the  finger  or  toe  is 
attached  to  the  surface  of  the  nail  a  little  in  advance  of  its  root;  at  the  extremity 
of  the  finger  it  is  connected  with  the  under  surface  of  the  nail  a  little  behind  its 
free  edge.  The  cuticle  and  horny  substance  of  the  nail  (both  epidermic  structures) 
are  thus  directh'  continuous  with  each  other.  The  superficial,  horny  part  of  the 
nail  consists  of  a  greatly  thickened  stratum  lucidum,  the  stratum  corneum  forming 
merely  the  thin  cuticular  fold  (eponychium)  which  overlaps  the  lunula;  the  deeper 
part  consists  of  the  stratum  mucosum.  The  cells  in  contact  with  the  papillae  of  the 
matrix  are  columnar  in  form  and  arranged  perpendicularly  to  the  surface;  those 
which  succeed  them  are  of  a  rounded  or  polygonal  form,  the  more  superficial  ones 
becoming  broad,  thin,  and  flattened,  and  so  closely  packed  as  to  make  the  limits 
of  the  cells  very  indistinct.  The  nails  grow  in  length  by  the  proliferation  of  the 
cells  of  the  stratum  mucosum  at  the  root  of  the  nail,  and  in  thickness  from  that 
part  of  the  stratum  mucosum  w-hich  underlies  the  lunula. 

Hairs  {pili)  are  found  on  nearly  every  part  of  the  surface  of  the  bod}',  but  are 
absent  from  the  palms  of  the  hands,  the  soles  of  the  feet,  the  dorsal  surfaces  of  the 
terminal  phalanges,  the  glans  penis,  the  inner  surface  of  the  prepuce,  and  the 
inner  surfaces  of  the  labia.  They  vary  much  in  length,  thickness,  and  color  in 
different  parts  of  the  body  and  in  different  races  of  mankind.  In  some  parts,  as 
in  the  skin  of  the  eyelids,  they  are  so  short  as  not  to  project  beyond  the  follicles 
containing  them;  in  others,  as  upon  the  scalp,  they  are  of  considerable  length; 
again,  in  other  parts,  as  the  eyelashes,  the  hairs  of  the  pubic  region,  and  the  whiskers 
and  beard,  they  are  remarkable  for  their  thickness.  Straight  hairs  are  stronger 
than  curly  hairs,  and  present  on  transverse  section  a  cylindrical  or  oval  outline; 
curly  hairs,  on  the  other  hand,  are  flattened.  A  hair  consists  of  a  root,  the  part  im- 
planted in  the  skin;  and  a  shaft  or  scapus,  the  portion  projecting  from  the  surface. 

The  root  of  the  hair  {radix  pili)  ends  in  an  enlargement,  the  hair  bulb,  which  is 


1076     ORGANS  OF   THE  SENSES  AND   THE  COMMON  INTEGUMENT 


whiter  in  color  and  softer  in  texture  than  the  shaft,  and  is  kxlged  in  a  foIHcular 
invohition  of  the  epidermis  called  the  hair  follicle  (Fig.  899).  When  the  hair  is  of 
considerable  length  the  follicle  extends  into  the  subcutaneous  cellular  tissue.  The 
hair  follicle  commences  on  the  surface  of  the  skin  with  a  funnel-shaped  opening, 
and  passes  inward  in  an  oblique  or  curved  direction — the  latter  in  curly  hairs — to 
become  dilated  at  its  deep  extremity,  where  it  corresponds  with  the  hair  bulb. 
Opening  into  the  follicle,  near  its  free  extremity,  are  the  ducts  of  one  or  more 
sebaceous  glands.  At  the  bottom  of  each  hair  follicle  is  a  small  conical,  vascular 
eminence  or  papilla,  similar  in  every  respect  to  those  found  upon  the  surface  of  the 
skin;  it  is  continuous  with  the  dermic  layer  of  the  follicle,  and  is  supplied  with 
nerve  fibrils.  The  hair  follicle  consists  of  two  coats — an  outer  or  dermic,  and  an 
inner  or  epidermic. 


Slraium  corneum 

,^~  Stratum  lucidum 
"  Stratum  granulosum 
■'  Stratum  mucosum 
'  Stratum 

germinativinn 
Dermis 


Sebaceous  gland  ^  — 

Cortex  of  hair  '^ 

Vessel  '^ 

Dermic  coat  *= 

Inner  root  sheath  - 

Outer  root  sheath  ~ 


Arrector  pili 
muscle 


Dermic  coat 
Medulla  of  hair 


Bulb  of  hair  - 
Papilla  of  hair  -"--^ 


Fig. 


899. — Section  of  skin,  shiowing  the  epidermis  and  dermis;  a  hair  in  its  follicle;  the  Arrector  pili  muscle; 

sebaceous  glands. 


The  outer  or  dermic  coat  is  formed  mainly  of  fibrous  tissue;  it  is  continuous 
with  the  corium,  is  highly  vascular,  and  supplied  by  numerous  minute  nervous 
filaments.  It  consists  of  three  layers  (Fig.  900).  The  most  internal  is  a  hyaline 
basement  membrane,  which  is  well-marked  in  the  larger  hair  follicles,  but  is  not 
very  distinct  in  the  follicles  of  minute  hairs;  it  is  limited  to  the  deeper  part  of  the 
follicle.  Outside  this  is  a  compact  layer  of  fibres  and  spindle-shaped  cells  arranged 
circularly  around  the  follicle;  this  layer  extends  from  the  bottom  of  the  follicle 
as  high  as  the  entrance  of  the  ducts  of  the  sebaceous  glands.  Externally  is  a  thick 
layer  of  connective  tissue,  arranged  in  longitudinal  bundles,  forming  a  more 
open  texture  and  corresponding  to  the  reticular  part  of  the  corium;  in  this  are 
contained  the  bloodvessels  and  nerves. 


THE  Al'PKXDAdKS  OF  TlIK  SKIS 


10 


/  ( 


Hijalme  layer -jpi 

I  u 
Cortex  ___  Vi^l// 
of  hair         """" 


Medulla 
■  of  hair 

Huxleifs 

layer 


Henle's  layer   "-  -  "'xn 


Outer  or 
dermic  coat 


The  inner  or  epidermic  coat  is  closely  adherent  to  the  root  of  the  hair,  and  con- 
sists of  two  strata  named  respectively  the  outer  and  inner  root  sheaths;  the  former 
of  these  corresponds  with  the 
stratum  mucosum  of  the  epider- 
mis, and  resembles  it  in  the 
rounded  form  and  soft  character 
of  its  cells;  at  the  bottom  of  the 
hair  follicle  these  cells  become 
continuous  with  those  of  the  root 
of  the  hair.  The  inner  root  sheath 
consists  of  (1)  a  delicate  cuticle 
next  the  hair,  composed  of  a 
single  layer  of  imbricated  scales 
with  atrophied  nuclei;  (2)  one  or 
two  layers  of  horny,  flattened, 
nucleated  cells,  known  as  Huxley's 
layer;  and  (3)  a  single  layer  of 
cubical  cells  wdth  clear  flattened 
nuclei,  called  Henle's  layer. 

The  hair  bulb  is  moulded  over 
the  papilla  and  composed  of  poly- 
hedral epithelial  cells,  which  as 
they  pass  upward  into  the  root 
of  the  hair  become  elongated  and 
spindle-shaped,  except  some  in  the 
centre  which  remain  polyhedral. 
Some  of  these  latter  cells  contain 
pigment  granules  w^hich  give  rise 
to  the  color  of  the  hair.  It  occa- 
sionally happens  that  these  pig- 
mr  it  granules  completely  fill  the 

cells  in  the  centre  of  the  bulb;  this  gives  rise  to  the  dark  tract  of  pigment  often 
found,  of  greater  or  less  length,  in  the  axis  of  the  hair.  • 

The  shaft  of  the  hair  (scapus  pili)  consists,  from  within  outward,  of  three  parts, 
the  medulla,  the  cortex,  and  the  cuticle.  The  medulla  is  usually  w-anting  in  the 
jBne  hairs  covering  the  surface  of  the  body,  and  commonly  in  those  of  the  head. 
It  is  more  opaque  and  deeper  colored  than  the  cortex  when  viewed  by  transmitted 
light;  but  when  view^ed  by  reflected  light  it  is  white.  It  is  composed  of  rows  of 
polyhedral  cells,  containing  granules  of  eleidin  and  frequently  air  spaces.  The 
cortex  constitutes  the  chief  part  of  the  shaft;  its  cells  are  elongated  and  united 
to  form  flattened  fusiform  fibres  which  contain  pigment  granules  in  dark  hair, 
and  air  in  white  hair.  The  cuticle  consists  of  a  single  layer  of  flat  scales  which 
overlap  one  another  from  below^  upward. 

Connected  with  the  hair  follicles  are  minute  bundles  of  involuntary  muscular 
fibres,  termed  the  Arrectores  pilorum.  They  arise  from  the  superficial  layer  of  the 
corium,  and  are  inserted  into  the  hair  follicle,  below  the  entrance  of  the  duct  of 
the  sebaceous  gland.  They  are  placed  on  the  side  toward  w^hich  the  hair  slopes, 
and  by  their  action  diminish  the  obliquity  of  the  follicle  and  elevate  the  hair 
(Fig.  899).^  The  sebaceous  gland  is  situated  in  the  angle  which  the  Arrector 
muscle  forms  with  the  superficial  portion  of  the  hair  follicle,  and  contraction  of  the 
muscle  thus  tends  to  squeeze  the  sebaceous  secretion  out  from  the  duct  of  the  gland. 

The  Sebaceous  Glands   (glandidae  sebaceae)  are   small,  sacculated,  glandular 


Fig.  900. — Transverse  section  of  hair  follicle. 


1  Professor  Arthur  Thomson  of  O-xford  suggests  that  the  contraction  of  these  muscles  on  follicles  which  contain 
weak,  flat  hairs  will  tend  to  produce  a  ptrmanent  curve  in  the  follicle,  and  this  curve  will  be  impressed  on  the  hair 
which  is  moulded  ^\-ithin  it,  so  that  the  hair,  on  emerging  through  the  skin,  will  be  curled.  Curved  hair  follicles  are 
characteristic  of  the  scalp  of  the  Bushman. 


1078     ORGANS  OF   THE  SENSES  AND   THE  COMMON  JNTEGLMENT 


organs,  lodged  in  the  substance  of  the  corium.  They  are  found  in  most  parts  of 
the  skin,  but  are  especially  abundant  in  the  scalp  and  face;  they  are  also  very 
numerous  around  the  apertures  of  the  anus,  nose,  mouth,  and  external  ear,  but  are 
wanting  in  the  palms  of  the  hands  and  soles  of  the  feet.  Each  gland  consists  of  a 
single  duct,  more  or  less  capacious,  which  emerges  from  a  cluster  of  oval  or  flask- 
shaped  alveoli  which  vary  from  two  to  five  in  number,  but  in  some  instances  there 
may  be  as  many  as  twenty.  Each  alveolus  is  composed  of  a  transparent  basement 
membrane,  enclosing  a  number  of  epithelial  cells.  The  outer  or  marginal  cells 
are  small  and  polyhedral,  and  are  continuous  with  the  cells  lining  the  duct.  The 
remainder  of  the  alveolus  is  filled  with  larger  cells,  containing  fat,  except  in  the 
centre,  where  the  cells  have  become  broken  up,  leaving  a  cavity  filled  witli  their 
debris  and  a  mass  of  fatty  matter,  which  constitutes  the  sebum  cutaneum.  The 
ducts  open  most  frequently  into  the  hair  follicles,  but  occasionally  upon  the  general 
surface,  as  in  the  labia  minora  and  the  free  margin  of  the  lips.  On  the  nose  and  face 
the  glands  are  of  large  size,  distinctly  lobulated,  and  often  become  much  enlarged 
from  the  accumulation  of  pent-up  secretion.  The  tarsal  glands  of  the  eyelids  are 
elongated  sebaceous  glands  with  numerous  lateral  diverticula. 

The  Sudoriferous  or  Sweat  Glands  (glandidae  sudoriferae)  are  found  in  almost 
every  part  of  the  skin,  and  are  situated  in  small  pits  on  the  under  surface  of  the 
corium,  or,  more  frequently,  in  the  subcutaneous  areolar  tissue,  surrounded  by  a 
quantity  of  adipose  tissue.  Each  consists  of  a  single  tube,  the  deep  part  of  which 
is  rolled  into  an  oval  or  spherical  ball,  named  the  body  of  the  gland,  while  the  super- 
ficial part,  or  duct,  traverses  the  corium 
and  cuticle  and  opens  on  the  surface  of 
the  skin  by  a  funnel-shaped  aperture. 
In  the  superficial  layers  of  the  corium 
the  duct  is  straight,  but  in  the  deeper 
layers  it  is  convoluted  or  even  twisted; 
where  the  epidermis  is  thick,  as  in  the 
palms  of  the  hands  and  soles  of  the  feet, 
the  part  of  the  duct  which  passes  through 
it  is  spirally  coiled.  The  size  of  the 
glands  varies.  They  are  especially  large 
in  those  regions  where  the  amount  of 
perspiration  is  great,  as  in  the  axillse, 
where  they  form  a  thin,  mammillated 
layer  of  a  reddish  color,  which  corre- 
sponds exactly  to  the  situation  of  the 
hair  in  this  region;  they  are  large  also 
in  the  groin.  Their  number  varies. 
They  are  very  plentiful  on  the  palms 
of  the  hands,  and  on  the  soles  of  the  feet,  where  the  orifices  of  the  ducts  are  exceed- 
ingly regular,  and  open  on  the  curved  ridges;  they  are  least  numerous  in  the  neck 
and  back.  The  tube,  both  in  the  body  of  the  gland  and  in  the  duct,  consists  of 
two  layers — an  outer,  of  fine  areolar  tissue,  and  an  inner  of  epithelium  (Fig.  901). 
The  outer  layer  is  thin  and  is  continuous  with  the  superficial  stratum  of  the  corium. 
In  the  body  of  the  gland  the  epithelium  consists  of  a  single  layer  of  cubical  cells, 
between  the  deep  ends  of  which  and  the  basement  membrane  is  a  layer  of  longi- 
tudinally or  obliquely  arranged  non-striped  muscular  fibres.  The  ducts  are  desti- 
tute of  muscular  fibres  and  are  composed  of  a  basement  membrane  lined  by  two 
or  three  layers  of  polyhedral  cells;  the  lumen  of  the  duct  is  coated  by  a  thin  cuticle. 
When  the  cuticle  is  carefully  remo^-ed  from  the  surface  of  the  corium,  the  ducts 
may  be  drawn  out  in  the  form  of  short,  thread-like  processes  on  its  under  surface. 
The  ceruminous  glands  of  the  external  acoustic  meatus,  and  the  ciliary  glands  at 
the  margins  of  the  eyelids,  are  modified  sudoriferous  glands. 


Fig.  901. — Body  of  a  sudoriferous-gland  cut  in  various 
directions,  a.  Longitudinal  section  of  the  pro-\imal  part 
of  the  coiled  tube.  b.  Transverse  section  of  the  same. 
c.  Longitudinal  section  of  the  distal  part  of  the  coiled 
tube.  rl.  Transverse  section  of  the  same.  (Klein  and 
Noble  Smith.) 


S?LANCHN( )!.()( ;V. 


TTNDEK    this   headinfj   arc   included   the   respiratory,    digestive,    and    urogenital 
organs,  and  tlic  ductless  glands. 


THE  RESPIRATORY  APPARATUS  (APPARATUS  RESPIRATORIUS; 
RESPIRATORY  SYSTEM). 

The  respiratory  apparatus  consists  of  the  larynx,  trachea,  bronchi,  lungs,  and 
pleura. 

THE    LARYNX. 

The  larynx  or  organ  of  voice  is  placed  at  the  upper  part  of  the  air  passage. 
It  is  situated  between  the  trachea  and  the  root  of  the  tongue,  at  the  upper  and 
forepart  of  the  neck,  where  it  presents  a  considerable  projection  in  the  middle 
line.  It  forms  the  lower  part  of  the  anterior  wall  of  the  pharynx,  and  is  covered 
behind  by  the  mucous  lining  of  that  cavity;  on  either  side  of  it  lie  the  great  vessels 
of  the  neck.  Its  vertical  extent  corresponds  to  the  fourth,  fifth,  and  sixth  cervical 
vertebrae,  but  it  is  placed  somewhat  higher  in  the  female  and  also  during  childhood. 
Symington  found  that  in  infants  between  six  and  twelve  months  of  age  the  tip 
of  the  epiglottis  was  a  little  above  the  level  of  the  fibrocartilage  between  the 
odontoid  process  and  body  of  the  axis,  and  that  between  infancy  and  adult  life 
the  larynx  descends  for  a  distance  equal  to  two  vertebral  bodies  and  tw^o  inter- 
vertebral fibrocartilages.  According  to  Sappey  the  average  measurements  of  the 
adult  larynx  are  as  follows: 

In  males.  In  females. 

Length 44  mm.  36  mm. 

Transverse  diameter 
Antero-posterior  diameter 
Circumference     .... 


43     "  41 

36     "  26 

1.36     "  112 


Until  pubert}'  the  larj^nx  of  the  male  differs  little  in  size  from  that  of  the  female.  In  the 
female  its  increase  after  pubertj'  is  only  slight;  in  the  male  it  undergoes  considerable  increase; 
all  the  cartilages  are  enlarged  and  the  thyroid  cartilage  becomes  prominent  in  the  middle  line  of 
the  neck,  while  the  length  of  the  rima  glottidis  is  nearly  doubled. 

The  larynx  is  broad  above,  where  it  presents  the  form  of  a  triangular  box  flattened 
behind  and  at  the  sides,  and  bounded  in  front  by  a  prominent  vertical  ridge. 
Below,  it  is  narrow  and  cylindrical.  It  is  composed  of  cartilages,  which  are  con- 
nected together  by  ligaments  and  moved  by  numerous  muscles.  It  is  lined  by 
mucous  membrane  continuous  above  with  that  of  the  pharynx  and  below  with 
that  of  the  trachea. 

The  Cartilages  of  the  Larynx  {carfilagines  laryngis)  (Fig.  902)  are  nine  in  number, 
three  single  and  three  paired,  as  follows: 

Thyroid.  Two  Corniculate. 

Cricoid.  Two  Cuneiform. 

Two  Arytenoid.  Epiglottis. 


1080 


SPLANCHNOLOGY 


EPIGLOTTIS 


The  Thyroid  Cartilage  (cartilago  thyreoidea)  is  the  lar^^est  cartilage  of  the  hirynx. 
It  consists  of  two  lamina?  the  anterior  borders  of  which  are  fused  with  each  other 
at  an  acute  angle  in  the  niiddl(>  line  of  the  neck,  and  form  a  subcutaneous  projec- 
tion named  the  laryngeal  prominence  {pomuin  Adaiiii).  This  prominence  is  most 
distinct  at  its  upper  part,  and  is  larger  in  the  male  than  in  the  female.  Immediately 
above  it  the  lamiucie  are  separated  by  a  V-shaped  notch,  the  superior  thyroid  notch. 

The  laminae  are  irregularly  quadri- 
lateral in  shape,  and  their  posterior 
angles  are  prolonged  into  processes 
termed  the  superior  and  inferior 
cornua. 

The  outer  surface  of  each  lamina 
presents  an  oblique  line  wdiich  runs 
downward  and  forward  from  the 
superior  thyroid  tubercle  situated 
near  the  root  of  the  superior  cornu, 
to  the  inferior  thyroid  tubercle  on 
the  lower  border.  This  line  gives 
attachment  to  the  Sternothyreoid- 
eus,  Thyreohyoideus,  and  Constric- 
tor pharyngis  inferior. 

The  inner  surface  is  smooth;  above 
and  behind,  it  is  slightly  concave  and 
covered  by  mucous  membrane.  In 
front,  in  the  angle  formed  by  the 
junction  of  the  laminee,  are  attached 
the  stem  of  the  epiglottis,  the  ven- 
tricular and  vocal  ligaments,  the 
Thyreoarytaenoidei,  Thyreoepiglot- 
tici  and  Vocales  muscles,  and  the 
thyroepiglottic  ligament. 

The  upper  border  is  concave  behind 
and  convex  in  front;  it  gives  attach- 
ment to  the  corresponding  half  of 
the  hyothyroid  membrane. 

The  lower  border  is  concave  be- 
hind, and  nearly  straight  in  front, 
the  two  parts  being  separated  by 
the  inferior  thyroid  tubercle.  A 
small  part  of  it  in  and  near  the 
middle  line  is  connected  to  the  cri- 
coid cartilage  by  the  middle  crico- 
thyroid ligament. 

The  posterior  border,  thick  and 
rounded,  receives  the  insertions  of 
the  Stylopharyngeus  and  Pharyngopalatinus.  It  ends  above,  in  the  superior  cornu, 
and  below,  in  the  inferior  cornu.  The  superior  cornu  is  long  and  narrow,  directed 
upward,  backward,  and  medialward,  and  ends  in  a  conical  extremity,  which  gives 
attachment  to  the  lateral  hyothyroid  ligament.  The  inferior  cornu  is  short  and 
thick;  it  is  directed  downward,  with  a  slight  inclination  forward  and  medialward, 
and  presents,  on  the  medial  side  of  its  tip,  a  small  oval  articular  facet  for  articula- 
tion with  the  side  of  the  cricoid  cartilage. 

During  infancy  the  laminae  of  the  thyroid  cartilage  are  joined  to  each  other 
by  a  narrow,  lozenge-shaped  strip,  named  the  intrathyroid  cartilage.     This  strip 


Corniculate  cartilages 


Cuneiform  cartilage 


ARYTENOID 


Insertion  of 

Cricoarytcenoidcus 

posterior 


P ^ 

Arytenoid  cartilages,  base 


Posterior 
surface 


Articular  facet  fo) 

arytenoid  cartilage 

Articular  facet  foi 
inferior  cornu  of 
thyroid  cartilage 


Fig.  902.- — The  cartilages  of  the  larynx.     Posterior  view. 


THE  LAinXX  1081 

extends  from  thr  ii|)|H>r  to  the  lower  honler  of  the  cartilage  in  the  middle  line, 
and  is  distinj^nislied  from  the  himina^  hy  hein<>;  more  transparent  and  more  (iexihle. 

The  Cricoid  Cartilage  [rarfihigo  cricoidca)  is  smaller,  hut  thicker  and  stron^^er 
than  the  thyroid,  and  forms  the  lower  and  posterior  parts  of  the  wall  of  the  larynx. 
It  consists  of  two  parts:  a  posterior  quadrate  lamina,  and  a  narrow  anterior  arch, 
one-fonrth  or  one-fifth  of  th(>  depth  of  the  lamina. 

The  lamina  {lainiiia  cartUag'tiui^  crirDidcac;  pij.slcrlnr  jjuiiloii)  is  deej)  and  hroad, 
and  measures  from  above  downward  about  2  to  3  cm.;  on  its  posterior  surface,  in 
the  middle  line,  is  a  vertical  ridge  to  the  lower  part  of  which  are  attached  the 
longitudinal  fibres  of  the  oesophagus;  and  on  either  side  of  this  a  broad  depression 
for  the  Cricoarytaenoideus  posterior. 

The  arch  (arcus  carfilaginhs  cricoideae;  anterior  ■portion)  is  narrow  and  convex, 
and  measures  vertically  from  5  to  7  mm, ;  it  affords  attachment  externally  in  front 
and  at  the  sides  to  the  CricothjTeiodei,  and  behind,  to  part  of  the  Constrictor 
pharyngis  inferior. 

On  either  side,  at  the  junction  of  the  himina  with  the  arch,  is  a  small  round 
articular  surface,  for  articulation  with  the  inferior  cornu  of  the  thyroid  cartilage. 

The  lower  border  of  the  cricoid  cartilage  is  horizontal,  and  connected  to  the 
highest  ring  of  the  trachea  by  the  cricotracheal  ligament. 

The  upper  border  runs  obliquely  upward  and  backward,  owing  to  the  great 
depth  of  the  lamina.  It  gives  attachment,  in  front,  to  the  middle  cricothyroid 
ligament;  at  the  side,  to  the  conus  elasticus  and  the  Cricoarytaenoidei  laterales; 
behind,  it  presents,  in  the  middle,  a  shallow  notch,  and  on  either  side  of  this  is  a 
smooth,  oval,  convex  surface,  directed  upward  and"  lateralward,  for  articulation 
wdth  the  base  of  an  arytenoid  cartilage. 

The  inner  surface  of  the  cricoid  cartilage  is  smooth,  and  lined  by  mucous 
membrane. 

The  Arytenoid  Cartilages  (cartilagines  arytenoideae)  are  two  in  number,  and  sit- 
uated at  the  upper  border  of  the  lamina  of  the  cricoid  cartilage,  at  the  back  of 
the  larynx.  Each  is  pyramidal  in  form,  and  has  three  surfaces,  a  base,  and  an 
apex. 

The  posterior  surface  is  a  triangular,  smooth,  concave,  and  gives  attachment 
to  the  Arytaenoidei  obliquus  and  trans  versus. 

The  antero-lateral  surface  is  somewhat  convex  and  rough.  On  it,  near  the  apex 
of  the  cartilage,  is  a  rounded  elevation  (colliculus)  from  which  a  ridge  (crista  arcuata) 
curves  at  first  backward  and  then  downward  and  forward  to  the  vocal  process. 
The  lower  part  of  this  crest  intervenes  between  two  depressions  or  foveae,  an 
upper,  triangular,  and  a  lower  oblong  in  shape;  the  latter  gives  attachment  to  the 
Vocalis  muscle. 

The  medial  surface  is  narrow,  smooth,  and  flattened,  covered  by  mucous  mem- 
brane, and  forms  the  lateral  boundary  of  the  intercartilaginous  part  of  the  rima 
glottidis. 

The  base  of  each  cartilage  is  broad,  and  on  it  is  a  concave  smooth  surface, 
for  articulation  with  the  cricoid  cartilage.  Its  lateral  angle  is  short,  rounded, 
and  prominent;  it  projects  backward  and  lateralward,  and  is  termed  the  muscular 
process;  it  gives  insertion  to  the  Cricoarytaenoideus  posterior  behind,  and  to  the 
Cricoarytaenoideus  lateralis  in  front.  Its  anterior  angle,  also  prominent,  but  more 
pointed,  projects  horizontally  forward;  it  gives  attachment  to  the  vocal  ligament, 
and  is  called  the  vocal  process. 

The  apex  of  each  cartilage  is  pointed,  curved  backward  and  medialward,  and 
surmounted  by  a  small  conical,  cartilaginous  nodule,  the  corniculate  cartilage. 

The  Corniculate  Cartilages  (cartilagines  cornicidatae;  cartilages  of  Santorini)  are 
two  small  conical  nodules  consisting  of  yellow  elastic  cartilage,  which  articulate 
Avith  the  summits  of  the  arytenoid  cartilages  and  serve  to  prolong  them  backward 


1082  SPLANCHNOLOGY 

and  medialward.  They  are  situated  in  the  posterior  parts  of  the  ar^^epiglottic 
folds  of  mucous  membrane,  and  are  sometimes  fused  with  the  arytenoid  eartihiges. 

The  Cuneiform  Cartilages  {cartilagines  cuneifornies;  cartiJages  of  Wrisherg)  are  two 
small,  elongated  pieces  of  yellow  elastic  cartilage,  placed  one  on  either  side,  in  the 
aryepiglottic  fold,  where  they  give  rise  to  small  whitish  elevations  on  the  surface 
of  the  mucous  membrane,  just  in  front  of  the  arytenoid  cartilages. 

The  Epiglottis  {cartilago  e-piglottica)  is  a  thin  lamella  of  fibrocartilage  of  a  yel- 
lowish color,  shaped  like  a  leaf,  and  projecting  obliquely  upward  behind  the  root 
of  the  tongue,  in  front  of  the  entrance  to  the  larynx.  The  free  extremity  is  broad 
and  rounded;  the  attached  part  or  stem  is  long,  narrow,  and  connected  by  the 
thyroepiglottic  ligament  to  the  angle  formed  by  the  two  laminae  of  the  thyroid 
cartilage,  a  short  distance  below  the  superior  thyroid  notch.  The  lower  part  of 
its  anterior  surface  is  connected  to  the  upper  border  of  the  body  of  the  hyoid 
bone  by  an  elastic  ligamentous  band,  the  hyoepiglottic  ligament. 

The  anterior  or  lingual  surface  is  curved  forward,  and  covered  on  its  upper,  free 
part  by  mucous  membrane  which  is  reflected  on  to  the  sides  and  root  of  the  tongue, 
forming  a  median  and  two  lateral  glossoepiglottic  folds;  the  lateral  folds  are  partly 
attached  to  the  wall  of  the  pharynx.  The  depressions  between  the  epiglottis  and 
the  root  of  the  tongue,  on  either  side  of  the  median  fold,  are  named  the  valleculse. 
The  lower  part  of  the  anterior  surface  lies  behind  the  hyoid  bone,  the  hyothyroid 
membrane,  and  upper  part  of  the  thyroid  cartilage,  but  is  separated  from  these 
structures  by  a  mass  of  fatty  tissue. 

The  posterior  or  laryngeal  surface  is  smooth,  concave  from  side  to  side,  concavo- 
convex  from  above  downward;  its  lower  part  projects  backward  as  an  elevation, 
the  tubercle  or  cushion.  When  the  mucous  membrane  is  removed,  the  surface  of 
the  cartilage  is  seen  to  be  indented  by  a  number  of  small  pits,  in  which  mucous 
glands  are  lodged.    To  its  sides  the  aryepiglottic  folds  are  attached. 

Structure. — The  corniculate  and  cuneiform  cartilages,  the  epiglottis,  and  the  apices  of  the 
arytenoids  at  first  consist  of  hyaline  cartilage,  but  later  elastic  fibres  are  deposited  in  the  matrix, 
converting  them  into  yellow  fibrocartilage,  which  shows  little  tendency. to  calcification.  The 
thyroid,  cricoid,  and  the  greater  part  of  the  arytenoids  consist  of  hyaline  cartilage,  and  become 
more  or  less  ossified  as  age  advances.  Ossification  commences  about  the  twenty-fifth  year  in 
the  thyroid  cartilage,  and  somewhat  later  in  the  cricoid  and  arytenoids;  by  the  sixty-fifth  year 
these  cartilages  may  be  completely  converted  into  bone. 

Ligaments. — The  ligaments  of  the  larynx  (Figs.  903,  904)  are  extrinsic,  i.  e.,  those 
connecting  the  thyroid  cartilage  and  epiglottis  with  the  hyoid  bone,  and  the  cricoid 
cartilage  with  the  trachea;  and  intrinsic,  those  which  connect  the  several  cartilages 
of  the  larynx  to  each  other. 

Extrinsic  Ligaments. — The  ligaments  connecting  the  thyroid  cartilage  with  the 
hyoid  bone  are  the  hyothyroid  membrane,  and  a  middle  and  two  lateral  hyo- 
thyroid ligaments. 

The  Hyothyroid  Membrane  (membrana  hyothyreoidea;  thyrohyoid  membrane)  is 
a  broad,  fibro-elastic  layer,  attached  below  to  the  upper  border  of  the  thyroid 
cartilage  and  to  the  front  of  its  superior  cornu,  and  above  to  the  upper  margin  of 
the  posterior  surface  of  the  body  and  greater  cornua  of  the  hyoid  bone,  thus  passing 
behind  the  posterior  surface  of  the  body  of  the  hyoid,  and  being  separated  from  it 
by  a  mucous  bursa,  which  facilitates  the  upward  movement  of  the  larynx  during 
deglutition.  Its  middle  thicker  part  is  termed  the  middle  hyothyroid  ligament 
{ligamentinn  hyothyreoideum  medium;  middle  thyrohyoid  ligament),  its  lateral  thinner 
portions  are  pierced  by  the  superior  laryngeal  vessels  and  the  internal  branch  of 
the  superior  laryngeal  nerve.  Its  anterior  surface  is  in  relation  with  the  Thyreo- 
hyoideus,  Sternohyoideus,  and  Omohyoideus,  and  with  the  body  of  the  hyoid 
bone. 


TIIK  LAUYXX 


1083 


T\w  Lateral  Hyothyroid  Ligament  {JUjamcuttuii  lii/oflii/iroidrinii  latrntle;  lateral 
iht/rolii/oid  lifidiiiciit)  is  a  rouiul  clastic  cord,  which  forms  the  posterior  border 
of  the  hyotliyroiil  iiicmhranc  and  passes  l)ct\vcen  the  tip  of  the  superior  cornu  of 
the  thyroid  cartihi,u-c  and  tlie  extremity  of  the  iireater  cornu  of  the  liyoid  hone. 
A  small  cartilafi'inous  luxhiie  (rartilddo  trillrcd),  sometimes  bony,  is  frecpicntly 
found  in  it. 

The  Epiglottis  is  connected  with  the  Jiyoid  bone  by  an  elastic  band,  the  hyo- 
epiglottic  ligament  {ligamcntum,  hiiocpiglotticuni),  which  extends  from  the  anterior 
surface  of  the  epiglottis  to  the  upper  border  of  the  body  of  the  hyoid  bone.1  The 
glossoepiglottic  folds  of  mucous  membrane  (page  1082)  may  also  be  considered 
as  extrinsic  ligaments  of  the  epiglottis. 


Lateral  hyothyrtiul  llr/ament 
J iiltimal  lariimjeal  nei  ce 
Cartilago  tnUcca 

Svperior  lannvjral  artenj 

Superior  cnniii 
Thyroid  notch 


Oblique  line 

Conan  cla.tticuK  {lateral  part.f) 

Middle  cricothyroid  ligamevt 
Inferior  cornii 


Fig.  903. — The  ligaments  of  the  larynx.     Antero-lateral  view. 

The  Cricotracheal  Ligament  (ligamenhim  cricoiracheale)  connects  the  cricoid  car- 
tilage with  the  first  ring  of  the  trachea.  It  resembles  the  fibrous  membrane  which 
connects  the  cartilaginous  rings  of  the  trachea  to  each  other. 

Intrinsic  Ligaments. — Beneath  the  mucous  membrane  of  the  larynx  is  a  broad 
sheet  of  fibrous  tissue  containing  many  elastic  fibres,  and  termed  the  elastic  membrane 
of  the  larynx.  It  is  subdivided  on  either  side  by  the  interval  betw^een  the  ven- 
tricular and  vocal  ligaments,  the  upper  portion  extends  between  the  arytenoid 
cartilage  and  the  epiglottis  and  is  often  poorly  defined;  the  lower  part  is  a  well- 
marked  membrane  forming,  with  its  fellow  of  the  opposite  side,  the  conus  elasticus 
wdfich  connects  the  thyroid,  cricoid,  and  arytenoid  cartilages  to  one  another. 
In  addition  the  joints  between  the  indiA'idual  cartilages  are  provided  with  ligaments. 

The  Conus  Elasticus  (cricothyroid  membrane)  is  composed  mainly  of  yellow  elastic 
tissue.  It  consists  of  an  anterior  and  two  lateral  portions.  The  anterior  part  or 
middle  cricothyroid  ligament  (ligamentum  cricothyreoideum  medium;  central  part  of 


1084 


SPLAXCHXOLOGY 


cricothyroid  membrane)  is  thick  and  strong,  narrow  above  and  broad  below.  It 
connects  together  the  front  parts  of  the  contiguous  margins  of  the  thyroid  and 
cricoid  cartilages.  It  is  overlapped  on  either  side  by  the  Cricothyreoideus,  but 
between  these  is  subcutaneous;  it  is  crossed  horizontally  by  a  small  anastomotic 
arterial  arch,  formed  by  the  junction  of  the  two  cricothyroid  arteries,  branches 
of  which  pierce  it.  The  lateral  portions  are  thinner  and  lie  close  under  the  mucous 
membrane  of  the  larynx;  they  extend  from  the  superior  border  of  the  cricoid  carti- 
lage to  the  inferior  margin  of  the  vocal  ligaments,  with  which  they  are  continuous. 
These  ligaments  may  therefore  be  regarded  as  the  free  borders  of  the  lateral  por- 
tions of  the  conus  elasticus,  and  extend  from  the  vocal  processes  of  the  arytenoid 
cartilages  to  the  angle  of  the  thyroid  cartilage  about  midway  between  its  upper 
and  lower  borders.  The  lateral  portions  are  lined  medially  by  mucous  membrane, 
and  covered  bv  the  Cricoarytaenoideus  lateralis  and  Th}Teoarytaenoideus. 


Hyoid  horn 


Carniculf.de  caiiiluge 


Posterior  crico-arytenoid 
ligament 


Cricoihyroid 
artirulution 


Fig.  904. — Ligaments  of  the  larynx.     Posterior  view. 


An  articular  capsule,  strengthened  posteriorly  by  a  well-marked  fibrous  band, 
encloses  the  articidation  of  the  inferior  cornu  of  the  thyroid  with  the  cricoid  car- 
tilage on  either  side. 

Each  arytenoid  cartilage  is  connected  to  the  cricoid  b}-  a  capsule  and  a  posterior 
cricoarytenoid  ligament.  The  capsule  (capsula  articidaris  cricoarytenoidea)  is  thin 
and  loose,  and  is  attached  to  the  margins  of  the  articular  surfaces.  The  posterior 
cricoarytenoid  ligament  ilig amentum  cricoarytenoideum  posterins)  extends  from  the 
cricoid  to  the  medial  and  back  part  of  the  base  of  the  arytenoid. 

The  thyroepiglottic  ligament  (ligamentum  thyreoepiglotticum)  is  a  long,  slender, 
elastic  cord  which  connects  the  stem  of  the  epiglottis  with  the  angle  of  the  thyroid 


THE  LAh'YXX 


1085 


cartilage,  immediately  heneath  the  superior  thyroid  uotcii,  al)o\'e  the  attachment 
of  the  ventricular  ligaments. 

Movements. — Tlie  artic-ulation  hotween  tlie  inferior  cormi  of  tlio  thjToid  cartilage  and  the 
cricoid  cartilage  on  either  side  is  a  iliarthrodial  one,  and  permits  of  rotatory  and  gliding  move- 
ments. The  rotatory  movement  is  one  in  which  the  cricoid  cartilage  rotates  upon  the  inferior 
cornua  of  the  thyroid  cartilage  around  an  axis  passing  transversely  through  both  joints. 
The  gliding  movement  consists  in  a  Limited  shifting  of  the  cricoid  on  the  thyroid  in  different 
directions. 

The  articulation  between  the  arytenoid  cartilages  and  the  cricoid  is  also  a  diarthrodial  one, 
and  permits  of  two  varieties  of  movement:  one  is  a  rotation  of  the  arytenoid  on  a  vortical  axis, 
whereb}'  the  vocal  process  is  moved  lateralward  or  medialward,  and  the  rima  glottidis  increased 
or  diminished ;  the  other  is  a  gliding  movement,  and  allows  the  arj^tonoid  cartilages  to  approach 
or  recede  from  each  other;  from  the  direction  and  slope  of  the  articular  surfaces  lateral  gUding 
is  accompanied  by  a  forward  and  downward  movement.  The  two  movements  of  gliding  and 
rotation  are  associated,  the  medial  gliding  being  connected  with  medialward  rotation,  and  the 
lateral  gliding  with  lateralward  rotation.  The  posterior  cricoarytenoid  ligaments  limit  the 
forward  movement  of  the  arytenoid  cartilages  on  the  cricoid. 


Glossoe  pi  glottic 
fold 


A)  l/rp) glottic 

fold 


^Arytenoid 
cartilage 


Au/taenoideiLs 

'4        mtiscle 


Interior  of  the  Larynx  (Figs.  905,  907). — The  cavity  of  the  larynx  (cavum 
laryngis)  extends  from  the  laryngeal  entrance  to  the  lower  border  of  the  cricoid 
cartilage  where  it  is  continuous  with 
that  of  the  trachea.  It  is  divided 
into  two  parts  by  the  projection  of 
the  vocal  folds,  between  which  is  a 
narrow  triangular  fissure  or  chink, 
the  rima  glottidis.  The  portion  of 
the  cavity  of  the  larynx  above  the 
vocal  folds  is  called  the  vestibule;  it 
is  wide  and  triangular  in  shape,  its 
base  or  anterior  wall  presenting, 
however,  about  its  centre  the  back- 
ward projection  of  the  tubercle  of 
the  epiglottis.  It  contains  the  ven- 
tricular folds,  and  between  these 
and  the  vocal  folds  are  the  ventricles 
of  the  larynx.  The  portion  below  the 
vocal  folds  is  at  first  of  an  elliptical- 
form,  but  lower  down  it  widens  out, 
assumes  a  circular  form,  and  is  con- 
tinuous with  the  tube  of  the  trachea. 

The  entrance  of  the  larynx  (Fig. 
906)  is  a  triangular  opening,  wide 
in  front,  narrow  behind,  and  sloping 
obliquely  downward  and  backward. 
It  is  bounded,  in  front,  by  the  epi- 
glottis; behind,  by  the  apices  of  the 
arytenoid  cartilages,  the  corniculate 
cartilages,  and  the  interarytenoid  notch;  and  on  either  side,  by  a  fold  of  mucous 
membrane,  enclosing  ligamentous  and  muscular  fibres,  stretched  between  the  side 
of  the  epiglottis  and  the  apex  of  the  arytenoid  cartilage;  this  is  the  aryepiglottic 
fold,  on  the  posterior  part  of  the  margin  of  which  the  cuneiform  cartilage  forms  a 
more  or  less  distinct  whitish  prominence,  the  cuneiform  tubercle. 

The  Ventricular  Folds  (plicae  ventricular es;  superior  or  false  vocal  cords)  are  two 
thick  folds  of  mucous  membrane,  each  enclosing  a  narrow  band  of  fibrous  tissue, 
the  ventricular  ligament  which  is  attached  in  front  to  the  angle  of  the  thyroid  car- 
tilage immediately  below  the  attachment  of  the  epiglottis,  and  behind  to  the  antero- 


Middle 

cricothyroid 

ligament 


Fig. 


905. — Sagittal  section  of  the  larj^nx  and  upper  part  of  the 
trachea. 


1086 


SPLANCHNOLOGY 


lateral  surface  of  the  arytenoid  cartilage,  a  short  distance  above  the  vocal  process. 
The  lower  border  of  this  ligament,  enclosed  in  mucous  membrane,  forms  a  free 
crescentic  margin,  which  constitutes  the  upper  l)oundary  of  the  ventricle  of  the 
larj'nx. 

Sulcus  terminalis 


Median  glosso- 
epiglottic  fold 


Greater  cornu  of  ^i_^r\\ 

hjoid  bone,      Vlji"i'  l\\\"^ 

Sup.  corna  of  _j^^}^}\\ 
thyroid  cart.       jjUi  j  ,, 

Ventricidar  fold     7^       --"'^i. 

Ventricle '■'^\\    '  |  _^  fjlmj, 
\  ocal  joLd       ^  luiHiiiw,, 

Pyriform  sinus 


Foramen  cecum 


Vallecula 

Lateral  glasso- 
epiglottic  fold 


Tubercle 

Aryepiglottic  fold 

Glottis 

Cuneiform  cartilage 


Corniculate  cartilage 


Fig.  906. — The  entrance  to  the  larynx,  viewed  from  behind. 

The  Vocal  Folds  (plicae  vocales;  inferior  or  true  vocal  cords)  are  concerned  in  the 
production  of  sound,  and  enclose  two  strong  bands,  named  the  vocal  ligaments 
{ligamenta  vocales;  inferior  thyroarytenoid).  Each  ligament  consists  of  a  band  of 
yellow  elastic  tissue,  attached  in  front  to  the  angle  of  the  thyroid  cartilage,  and 
behind  to  the  vocal  process  of  the  arytenoid.  Its  lower  border  is  continuous  w4th 
the  thin  lateral  part  of  the  conus  elasticus.  Its  upper  border  forms  the  lower 
boundary  of  the  ventricle  of  the  larynx.  Laterally,  the  Vocalis  muscle  lies  parallel 
with  it.  It  is  covered  medially  by  mucous  membrane,  which  is  extremely  thin  and 
closely  adherent  to  its  surface. 

The  Ventricle  of  the  Larynx  (ventriculus  laryngis  [Morgagnii];  laryngeal  sinus) 
is  a  fusiform  fossa,  situated  between  the  ventricular  and  vocal  folds  on  either  side, 
and  extending  nearly  their  entire  length.  The  fossa  is  bounded,  above,  by  the  free 
crescentic  edge  of  the  ventricular  fold;  belo7V,  by  the  straight  margin  of  the  vocal 
fold;  laterally,  by  the  mucous  membrane  covering  the  corresponding  Thyreoary- 
taenoideus.  The  anterior  part  of  the  ventricle  leads  up  by  a  narrow  opening 
into  a  cecal  pouch  of  mucous  membrane  of  variable  size  called  the  appendix. 

The  appendix  of  the  laryngeal  ventricle  {appendix  ventricuU  laryngis;  laryngeal 
saccule)  is  a  membranous  sac,  placed  between  the  ventricular  fold  and  the  inner 
surface  of  the  thyroid  cartilage,  occasionally  extending  as  far  as  its  upper  border 
or  even  higher;  it  is  conical  in  form,  and  curved  slightly  backward.    On  the  surface 


THE  LARYNX 


108- 


Jlyoid  hone 


of  its  mucous  nu'inhraiic  arc  the  oi)ciiuigs  of  sixty  or  seventy  mucous  glands,  which 
are  lodged  in  the  submucous  areolar  tissue.  This  sac  is  enclosed  in  a  fibrous  capsule, 
continuous  below  with  the  ventricular 
ligament.  Its  medial  surface  is  covered 
by  a  few  delicate  muscular  fasciculi,  which 
arise  from  the  apex  of  the  arytenoid  car- 
tilage and  become  lost  in  the  aryepiglottic 
fold  of  mucous  membrane;  laterally  it  is 
separated  from  the  thyroid  cartilage  b}' 
the  Thyreoepiglotticus.  These  muscles 
compress  the  sac,  and  express  the  secre- 
tion it  contains  upon  the  vocal  folds  to 
lubricate  their  surfaces. 

The  Rima  Glottidis  (Fig.  908)  is  the  elon- 
gated fissure  or  chink  between  the  vocal 
folds  in  front,  and  the  bases  and  vocal 
processes  of  the  arytenoid  cartilages  be- 
hind. It  is  therefore  subdivided  into  a 
larger  anterior  intramembranous  part 
(glottis  meal  is),  which  measures  about 
three-fifths  of  the  length  of  the  entire 
aperture,  and  a  posterior  intercartilaginous 
part  (glottis  respiratoria).  Posteriorly  it  is 
limited  by  the  mucous  membrane  passing 
between  the  arytenoid  cartilages.  The 
rima  glottidis  is  the  narrowest  part  of  the 
cavity  of  the  larynx,  and  its  level  corre- 
sponds with  the  bases  of  the  arytenoid  car- 
tilages. Its  length,  in  the  male,  is  about  23 
mm.;  in  the  female  from  17  to  18  mm. 

The  width  and  shape  of  the  rima  glottidis  vary  with  the  movements  of  the  vocal 
folds  and  arytenoid  cartilages  during  respiration  and  phonation.  In  the  condition 
of  rest,  i.  e.,  when  these  structures  are  uninfluenced  by  muscular  action,  as  in 


nokleuti  muscle 


Fig.  907. — Corona!  section  of   larynx  and   upper   part 
of  trachea. 


Vallecula 


Median  glosso  einglottic  fold 
Epiglottis 

.Tnheicle  of  epiglottis 
Vocal  fold 

■  Ventricular  fold 


Aryepiglottic  fold 
Cuneiform  cartilage 


udate  cartilage 
Trachea 
Fig.  90S. — Laryngoscopic  view  of  interior  of  larynx. 


quiet  respiration,  the  intramembranous  part  is  triangular,  with  its  apex  in  front 
and  its  base  behind — the  latter  being  represented  by  a  line,  about  8  mm.  long, 
connecting  the  anterior  ends  of  the  vocal  processes,  while  the  medial  surfaces  of 


1088 


SPLANCHNOLOGY 


the  arytenoids  are  parallel  to  each  other,  and  hence  the  intercartilaginous  part 
is  rectangular.  During  extreme  adduction  of  the  vocal  folds,  as  in  the  emission 
of  a  high  note,  the  intramembranous  part  is  reduced  to  a  linear  slit  by  the  ap- 
position of  the  vocal  folds,  while  the  intercartilaginous  part  is  triangular,  its  apex 
corresponding  to  the  anterior  ends  of  the  vocal  processes  of  the  arytenoids,  which 
are  approximated  by  the  medial  rotation  of  the  cartilages.  Conversely  in  extreme 
abduction  of  the  vocal  folds,  as  in  forced  inspiration,  the  arytenoids  and  their 
vocal  processes  are  rotated  lateralward,  and  the  intercartilaginous  part  is  trian- 
gular in  shape  but  with  its  apex  directed  backward.  In  this  condition  the  entire 
glottis  is  somewhat  lozenge-shaped,  the  sides  of  the  intramembranous  part 
diverging  from  before  backward,  those  of  the  intercartilaginous  part  diverging 
from  behind  forward— the  widest  part  of  the  aperture  corresponding  with  the 
attachments  of  the  vocal  folds  to  the  vocal  processes. 

Muscles.— The  muscles  of  the  larynx  are  extrinsic,  passing  between  the  larynx 
and  parts  around— these  have  been  described  in  the  section  on  Myology;  and 
intrinsic,  confined  entirely  to  the  larynx. 

The  intrinsic  muscles  are: 

Cricothyreoideus.  Cricoarytaenoideus  lateralis. 

Cricoarytaenoideus  posterior.  Arytaenoideus. 

Thyroarytaenoideus. 

The  Cricothyreoideus  (Cricothyroid)  (Fig.  909),  triangular  in  form,  arises  from  the 
front  and  lateral  part  of  the  cricoid  cartilage;  its  fibres  diverge,  and  are  arranged 

in  two  groups.  The  lower  fibres  constitute  a 
pars  obliqua  and  slant  backward  and  lateral- 
ward  to  the  anterior  border  of  the  inferior 
cornu;  the  anterior  fibres,  forming  a  pars  recta, 
run  upward,  backward,  and  lateralward  to  the 
posterior  part  of  the  lower  border  of  the  lamina 
of  the  thyroid  cartilage. 

The  medial  borders  of  the  two  muscles  are 
separated  by  a  triangular  interval,  occupied 
by  the  middle  cricothyroid  ligament. 

The  Cricoarytaenoideus  posterior  {posterior 
cricoarytenoid)  (Fig.  910)  arises  from  the  broad 
depression  on  the  corresponding  half  of  the  pos- 
terior surface  of  the  lamina  of  the  cricoid  carti- 
lage; its  fibres  run  upward  and  lateralward, 
and  converge  to  be  inserted  into  the  back  of 
the  muscular  process  of  the  arytenoid  carti- 
lage. The  uppermost  fibres  are  nearly  hori- 
zontal, the  middle  oblique,  and  the  lowest 
almost  vertical. 

The  Cricoarytaenoideus  lateralis  {lateral 
cricoarytenoid)  (Fig.  911)  is  smaller  than  the 
preceding,  and  of  an  oblong  form.  It  arises 
from  the  upper  border  of  the  arch  of  the 
cricoid  cartilage,  and,  passing  obliquely  up- 
ward and  backward,  is  inserted  into  the  front  of  the  muscular  process  of  the 
arytenoid  cartilage. 

The  Arytaenoideus  (Fig.  910)  is  a  single  muscle,  filling  up  the  posterior  concave 
surfaces  of  the  arytenoid  cartilages.  It  arises  from  the  posterior  surface  and  lateral 
border  of  one  arytenoid  cartilage,  and  is  inserted  into  the  corresponding  parts  of 
the  opposite  cartilage.    It  consists  of  oblique  and  transA'erse  parts.     The  Arytae- 


FiG.  909. — Side  view  of  the  larynx,  showing 
muscular  attachments. 


THE  LARYNX 


1089 


noideus  obliquus,  the  more  superfifial,  forms  two  fasciculi,  which  pass  from  the  base 
of  one  cartilage  to  the  apex  of  the  opposite  one,  and  therefore  cross  eacli  otlier 


Tubercle  of 
epiglottis 

Cuneiform 

iiirtilfKje 

<  nniiridate 

cdililayc 

:'l—\Ar')/lae- 
- — j  noidens 


Cricodrylar- 
noideas 
posterior 


Cornicidiii, 
cartilage 


Articular  facet  fui  \w[  i 
inferior  cornu  of^X} 
thyreoid  cartilage 


Fig.  910. — Muscles  of  larynx.     Posterior  view. 


Fig.  911. — Muscles  of  larynx.     Side  view.     Right  lamina 
of  thyroid  cartilage  removed. 


like  the  limbs  of  the  letter  X;  a  few  fibres 
are  continued  around  the  lateral  margin 
of  the  cartilage,  and  are  prolonged  into 
the  aryepiglottic  fold ;  they  are  sometimes 
described  as  a  separate  muscle,  the  Ary- 
epiglotticus.  The  Arytaenoideus  trans- 
versus  crosses  transversely  between  the 
two  cartilages. 

The  Thyreoarytaenoideus  ( Thyroary- 
tenoid) (Figs.  911,  912)  is  a  broad,  thin, 
muscle  which  lies  parallel  wdth  and  lateral 
to  the  vocal  fold,  and  supports  the  wall  of 
the  ventricle  and  its  appendix.  It  arises 
in  front  from  the  lower  half  of  the  angle 
of  the  thyroid  cartilage,  and  from  the 
middle  cricothyroid  ligament.  Its  fibres 
pass  backward  and  lateralward,  to  be  in- 
serted into  the  base  and  anterior  surface 
of  the  arytenoid  cartilage.  The  lower  and 
deeper  fibres  of  the  muscle  can  be  differ- 
entiated  as   a  triangular  band  which  is 

inserted  into  the  vocal  process  of  the  arytenoid  cartilage,  and  into  the  adjacent 
portion  of  its  anterior  surface;  it  is  termed  the  Vocalis,  and  lies  parallel  with  the 
vocal  ligament,  to  which  it  is  adherent. 
69 


Fig.  912. 


-Muscles  of  the  larynx,  seen  from  above. 
(Enlarged.) 


1090  SPLANCHNOLOGY 

A  considerable  number  of  the  fibres  of  the  Thyreoarytaenoideus  are  prolonged 
.  into  the  ary epiglottic  fold,  where  some  of  them  become  lost,  while  others  are  con- 
tinued to  the  margin  of  the  epiglottis.     They  have  received  a  distinctive  name, 
Thyreoepiglotticus,  and  are  sometimes  described  as  a  separate  muscle. 

Actions. — In  considering  the  actions  of  the  muscles  of  the  larynx,  they  may  be  conveniently 
divided  into  two  groups,  vix. :  1.  Those  which  open  and  close  the  glottis.  2.  Those  which  regu- 
late the  degree  of  tension  of  the  vocal  folds. 

1 .  The  muscles  which  open  the  glottis  are  the  Cricoarytaenoidei  posteriores ;  and  those  which 
close  it  are  the  Cricoarytaenoidei  laterales  and  the  Arytaenoideus.  2.  The  muscles  which 
regulate  the  tension  of  the  vocal  folds  are  the  Cricothyreoidei,  which  elongate  and  render  them 
tense;  and  the  ThjTCoarytaenoidei,  which  relax  and  shorten  them. 

The  Cricoarytaenoidei  posteriores  separate  the  vocal  folds,  and,  consequently,  open  the  glottis, 
by  rotating  the  arjrtenoid  cartilages  outward  around  a  vertical  axis  passing  through  the  crico- 
arytenoid joints;  so  that  their  vocal  processes  and  the  vocal  folds  attached  to  them  become 
widely  separated. 

The  Cricoarytaenoidei  laterales  close  the  glottis  by  rotating  the  arytenoid  cartilages  inward, 
so  as  to  approximate  their  vocal  processes. 

The  Arytaenoideus  .approximates  the  arytenoid  cartilages,  and  thus  closes  the  opening  of 
the  glottis,  especially  at  its  back  part. 

The  Cricothyreodei  produce  tension  and  elongation  of  the  vocal  folds  by  drawing  up  the  arch 
of  the  cricoid  cartilage  and  tilting  back  the  upper  border  of  its  lamina;  the  distance  between  the 
vocal  processes  and  the  angle  of  the  thyroid  is  thus  increased,  and  the  folds  are  consequently 
elongated. 

The  Thyreoaryiaenoidei,  consisting  of  two  parts  having  different  attachments  and  different 
directions,  are  rather  complicated  as  regards  their  action.  Their  main  use  is  to  draw  the  aryte- 
noid cartilages  forward  toward  the  thyroid,  and  thus  shorten  and  relax  the  vocal  folds.  But, 
owing  to  the  connection  of  the  deeper  portion  with  the  vocal  fold,  this  part,  if  acting  separately, 
is  supposed  to  modify  its  elasticity  and  tension,  while  the  lateral  portion  rotates  the  arytenoid 
cartilage  inward,  and  thus  narrows  the  rima  glottidis  by  bringing  the  two  vocal  folds  together. 

The  manner  in  which  the  entrance  of  the  larynx  is  closed  during  deglutition  is  referred  to 
on  page  1114. 

Mucous  Membrane. — The  mucous  membrane  of  the  larynx  is  continuous  above  with  that 
lining  the  mouth  and  pharynx,  and  is  prolonged  through  the  trachea  and  bronchi  into  the  lungs. 
It  lines  the  posterior  surface  and  the  upper  part  of  the  anterior  surface  of  the  epiglottis,  to  which 
it  is  closely  adherent,  and  forms  the  aryepiglottic  folds  which  bound  the  entrance  of  the  larynx. 
It  lines  the  whole  of  the  cavity  of  the  larynx;  forms,  by  its  reduplication,  the  chief  part  of  the 
ventricular  fold,  and,  from  the  ventricle,  is  continued  into  the  ventricular  appendix.  It  is  then 
reflected  over  the  vocal  ligament,  where  it  is  thin,  and  very  intimately  adherent;  covers  the 
inner  sm-face  of  the  con  us  elasticus  and  cricoid  cartilage;  and  is  ultimately  continuous  with  the 
lining  membrane  of  the  trachea.  The  anterior  surface  and  the  upper  half  of  the  posterior  surface 
of  the  epiglottis,  the  upper  part  of  the  aryepiglottic  folds  and  the  vocal  folds  are  covered  by 
stratified  squamous  epithelium;  all  the  rest  of  the  laryngeal  mucous  membrane  is  covered  by 
columnar  ciliated  cells,  but  patches  of  stratified  squamous  epithelium  are  found  in  the  mucous 
membrane  above  the  glottis. 

Glands. — The  mucous  membrane  of  the  larynx  is  furnished  with  numerous  mucous  secreting 
glands,  the  orifices  of  which  are  found  in  nearly  every  part;  they  are  very  plentiful  upon  the 
epiglottis,  being  lodged  in  little  pits  in  its  substance;  they  are  also  found  in  large  numbers  along 
the  margin  of  the  aryepiglottic  fold,  in  front  of  the  arytenoid  cartilages,  where  they  are  termed 
the  arytenoid  glands.  They  exist  also  in  large  numbers  in  the  ventricular  appendages.  None 
are  found  on  the  free  edges  of  the  vocal  folds. 

Vessels  and  Nerves. — The  chief  arteries  of  the  larynx  are  the  laryngeal  branches  derived 
from  the  superior  and  inferior  thyroid.  The  veins  accompany  the  arteries;  those  accompanying 
the  superior  laryngeal  artery  join  the  superior  thyroid  vein  which  opens  into  the  internal  jugular 
vein;  while  those  accompanying  the  inferior  laryngeal  artery  join  the  inferior  thyroid  vein 
which  opens  into  the  innominate  vein.  The  lymphatic  vessels  consist  of  two  sets,  superior 
and  inferior.  The  former  accompany  the  superior  laryngeal  artery  and  pierce  the  hyothyroid 
membrane,  to  end  in  the  glands  situated  near  the  bifurcation  of  the  common  carotid  artery.  Of 
the  latter,  some  pass  through  the  middle  cricothyroid  ligament  and  open  into  a  gland  lying  in 
front  of  that  ligament  or  in  front  of  the  upper  part  of  the  trachea,  while  others  pass  to  the  deep 
cervical  glands  and  to  the  glands  accompanying  the  inferior  thyroid  artery.  The  nerves  are 
derived  from  the  internal  and  external  branches  of  the  superior  laryngeal  nerve,  from  the 
recurrent  nerve,  and  from  the  sympathetic.  The  internal  laryngeal  branch  is  almost  entirely 
sensory,  but  some  motor  filaments  are  said  to  be  carried  by  it  to  the  Arytaenoideus.  It  enters 
tlie  larynx   by  piercing   the  posterior   part  of    the    hyothyroid  membrane  above  the  superior 


rill':   Th'Aclll'A    AM)   liUOXCIII 


1091 


laryngeal  \"('.ssi'l.s,  ami  dixidi's  iuUi  a  hiaiirh  which  is  (list  ril)U(('(l  to  hoth  surlaccs  of  the  opi- 
glottis,  a  sc'coiul  to  lli(>  aryopiglottic  fold,  and  a  third,  liic  largest,  which  sujjplies  tho  imicous 
membrane  over  (ho  hack  of  tlie  larynx  and  (•()niiiiuni('atc;s  with  tlu;  recurrent  nerve.  The  external 
larj'ngoal  branch  supplies  the  Cricothyreoideus.  The  recurrent  nerve  i)asses  uj)ward  beneath 
the  lower  bonier  of  the  Constrictor  ])haryngi.s  inferior  inunediately  behind  the  cricothyroid  joint. 
It  sui)plies  all  the  muscles  of  the  larynx  except  the  Cri(Hj(hyrcoideus,  and  perliaj)s  a  part  of  the 
Arytaenoideus.  The  sensory  branches  of  the  laryngeal  nerves  form  subejjithelial  plexuses,  from 
which  fibres  pass  to  end  between  the  cells  covering  the  nmcous  membrane. 

Over  the  posterior  surface  of  the  epiglottis,  in  the  arycpiglottic  folds,  and  less  r(>gulaily  in 
some  other  parts,  taste-buds,  similar  to  those  in  the  tongue,  are  found. 

THE  TRACHEA  AND  BRONCHI  (Fig.  913). 

The   trachea  or  windpipe  is  a  cartilaginous  and  membranous  tube,  extending 
from  the  k)\ver  part  of  the  Larynx,  on  a  level  with  the  sixth  cervical  vertebra,  to  the 


Superior 
C'ornu. 


Fig.  913. — Front  view  of  cartilages  of  larynx,  trachea,  and  bronchi. 


upper  border  of  the  fifth  thoracic  vertebra,  where  it  diN'ides  into  the  two  bronchi, 
one  for  each  lung.  The  trachea  is  nearly  but  not  quite  cylindrical,  being  flattened 
posteriorly;  it  measures  about  11  cm.  in  length;  its  diameter,  from  side  to  side. 


1092 


SPLANCHNOLOGY 


is  from  2  to  2.5  cm.,  being  always  greater  in  the  male  than  in  the  female.  In 
the  child  the  trachea  is  smaller,  more  deeply  placed,  and  more  movable  than 
in  the  adnlt. 

Relations. — The  anieHor  surface  of  the  trachea  is  convex,  and  covered,  in  the  neck,  from 
above  downward,  by  the  isthmus  of  the  thjToid  gland,  the  inferior  thyroid  veins,  the  arteria 
thyroidea  ima  (when  that  vessel  exists),  the  Sternothyreoideus  and  Sternohyoideus  muscles, 
the  cervical  fascia,  and,  more  superficially,  by  the  anastomosing  branches  between  the  anterior 
jugular  veins;  in  the  thorax,  it  is  covered  from  before  backward  by  the  manubrium  sterni, 
the  remains  of  the  thymus,  the  left  innominate  vein,  the  aortic  arch,  the  innominate  and  left 
common  carotid  arteries,  and  the  deep  cardiac  plexus.  Posteriorly  it  is  in  contact  with  the 
oesophagus.  Laterally,  in  the  neck,  it  is  in  relation  with  the  common  carotid  arteries,  the  right 
and  left  lobes  of  the  thjToid  gland,  the  inferior  thyroid  arteries,  and  the  recurrent  nerves;  in  the 
thorax,  it  lies  in  the  superior  mediastinal  cavity,  and  is  in  relation  on  the  right  side  with  the 
pleura  and  right  vagus,  and  near  the  root  of  the  neck  with  the  innominate  artery;  on  its  left  side 
are  the  left  recurrent  nerve,  the  aortic  arch,  and  the  left  common  carotid  and  subclavian  arteries. 

The  right  bronchus  (bronchus  dexter),  wider,  shorter,  and  more  vertical  in  direc- 
tion than  the  left,  is  about  2.5  cm.  long,  and  enters  the  right  lung  nearly  opposite 
the  fifth  thoracic  vertebra.  The  az^-gos  vein  arches  over  it  from  behind;  and  the 
right  pulmonar}'  artery  lies  at  first  below  and  then  in  front  of  it.  About  2  cm. 
from  its  commencement  it  gives  off  a  branch  to  the  upper  lobe  of  the  right  lung. 
This  is  termed  the  eparterial  branch  of  the  bronchus,  because  it  arises  above  the  right 
pulmonary  artery.  The  bronchus  now  passes  below  the  artery,  and  is  known  as  the 
hyparterial  branch;  it  divides  into  two  branches  for  the  middle  and  lower  lobes. 

The  left  bronchus  (bronchus  sinister)  is  smaller  in  calibre  but  longer  than  the 
right,  being  nearly  5  cm.  long.  It  enters  the  root  of  the  left  lung  opposite  the  sixth 
thoracic  vertebra.  It  passes  beneath  the  aortic  arch,  crosses  in  front  of  the  oeso- 
phagus, the  thoracic  duct,  and  the  descending  aorta,  and  has  the  left  pulmonary 
artery  lying  at  first  above,  and  then  in  front  of  it.  The  left  bronchus  has  no 
eparterial  branch,  and  therefore  it  has  been  supposed  by  some  that  there  is  no 

upper  lobe  to  the  left  lung,  but  that  the 
so-called  upper  lobe  corresponds  to  the 
middle  lobe  of  the  right  lung. 
_^  The  further  subdivisions  of  the  bronchi 

i  'II  i  ,1,/        '     ^"^ "  f''/^^v\    I  \     "^vill  be  considered  with  the  anatomy  of 

W*'')'  H      1'  '1     the  lung. 

If  a  transverse  section  be  made  across 
the  trachea  a  short  distance  above  its 
point  of  bifurcation,  and  a  bird's-eye  view 
taken  of  its  interior  (Fig.  914),  the  septum 
placed  at  the  bottom  of  the  trachea  and 
separating  the  two  bronchi  will  be  seen 
to  occupy  the  left  of  the  median  line,  and  the  right  bronchus  appears  to  be  a  more 
direct  continuation  of  the  trachea  than  the  left,  so  that  any  solid  body  dropping 
into  the  trachea  would  naturally  be  directed  toward  the  right  bronchus.  This 
tendency  is  aided  by  the  larger  diameter  of  the  right  tube  as  compared  with 
its  fellow.  This  fact  serves  to  explain  why  a  foreign  body  in  the  trachea  more 
frequently  falls  into  the  right  bronchus.^ 

Structure  (Fig.  915)  — The  trachea  and  extrapulmonary  bronchi  are  composed  of  imperfect 
rings  of  hyaline  cartilage,  fibrous  tissue,  muscular  fibres,  mucous  membrane,  and  glands. 

The  cartilages  of  the  trachea  vary  fi-om  sixteen  to  twenty  in  number:  each  forms  an  imperfect 
ring,  which  occupies  the  anterior  two-thirds  or  so  of  the  circumference  of  the  trachea,  being 
deficient  behind,  where  the  tube  is  completed  by  fibrous  tissue  and  imstriped  muscular  fibres. 
The  cartilages  are  placed  horizontally  above  each  other,  separated  by  narrow  intervals.  They 
measiire  about  4  mm.  in  depth  and  1  mm.  in  thickness.  Their  outer  surfaces  are  flattened  in 
a  vertical  direction,  but  the  internal  are  convex,  the  cartilages  being  thicker  in  the  middle  than 

'  Reigel  asserts  that  the  entrj'  of  a  foreign  body  into  the  l-'ft  bronchus  is  by  no  means  so  infrequent  as  is  generally 
supposed.     See  also  Med.-Chi.  Trans.,  Ixx',  121. 


Fig  .  914. — Transverse  section  of  the  trachea,  just 
above  its  bifurcation,  with  a  bird's-eye  view  of  the 
interior. 


77//-;  TRACHEA  AM)  liROXClU 


1093 


Stratified 
ciliated 
epitJielium 
LoTigittidinal 
elastic  fibres 


Svbmucous 
layer 

M-wcous 
glands 


at  the  margins.  Two  or  more  of  the  cai-liUiges  often  unite,  partiallj'  or  completely,  and  they 
are  sometimes  bifurcated  at  their  extremities.  They  are  highly  elastic;,  but  may  become  calcified 
in  advanced  life  In  the  right  bronchus  the  cartilages  vary  in  number  from  six  to  eight;  in  the 
left,  from  nin(>  to  twelve.  They  are  shorter  and  narrower  than  those  of  the  trachea,  but  have 
the  same  shape  and  arrangement.  The  i)eculiar  tracheal  cartilages  are  the  first  and  the  last 
(Fig.  913). 

mho  first  carlilagc  is  broailer  than  the  rest,  and  often  divided  at  one  end;  it  is  connected  by 
the  cricotracheal  ligament  with  the  lower  border  of  the  cricoid  cartilage,  with  which,  or  with 
the  succeeding  cartilage,  it  is  sometimes  blended. 

The  last  cartilage  is  thick  and  broad  in  the  middle,  in  consequence  of  its  lower  border  being 
prolonged  into  a  triangular  hook-shaped  process,  which  curves  downward  and  backward  between 
the  two  bronchi.  It  ends  on  each  side  in 
an  imperfect  ring,  which  encloses  the  com- 
mencement of  the  bronchus.  The  cartilage 
above  the  last  is  somewhat  broader  than 
the  others  at  its  centre. 

The  Fibrous  Membrane. — The  cartilages 
are  enclo.-^ed  in  an  elastic  fibrous  mem- 
brane, which  consists  of  two  layers;  one, 
the  thicker,  passing  over  the  outer  surface 
of  the  ring,  the  other  over  the  inner  sur- 
face: at  the  upper  and  lower  margins  of 
the  cartilages  the  two  layers  blend  together 
to  form  a  single  membrane,  which  connects 
the  rings  one  with  another.  They  are  thus 
invested  by  the  membrane.  In  the  space 
behind,  between  the  ends  of  the  rings,  the 
membrane  forms  a  single  layer. 

The  muscular  tissue  consists  of  two 
layers  of  non-striated  muscle,  longitudinal 
and  transverse.  The  longitudinal  fibers 
are  external,  and  consist  of  a  few  scattered 
bundles.  The  transverse  fibres  {Trachealis 
muscle)  are  internal,  and  form  a  thin  layer 
which  extends  transversely  between  the 
ends  of  the  cartilages. 

Mucous  Membrane. — The  mucous  mem- 
brane is  continuous  above  with  that  of  the 
larynx,  and  below  with  that  of  the  bron- 
chi. It  consists  of  areolar  and  lymphoid 
tissue,  and  presents  a  well-marked  base- 
ment membrane,  supporting  a  stratified 
epithehum,  the  surface  layer  of  which  is 
columnar  and  ciliated,  while  the  deeper 
laj^ers  are  composed  of  oval  or  rounded 
cells.  Beneath  the  basement  membrane 
there   is    a   distinct   layer  of   longitudinal 

elastic  fibres  with  a  small  amount  of  intervening  areolar  tissue.  The  submucous  layer  is  com- 
posed of  a  loose  mesh-work  of  connective  tissue,  containing  large  bloodvessels,  nerves,  and 
mucous  glands;  the  ducts  of  the  latter  pierce  the  overlying  layers  and  open  on  the  sm-face 
(Fig.  915). 

Vessels  and  Nerves. — The  trachea  is  supplied  with  blood  by  the  inferior  thyroid  arteries. 
The  veins  end  in  the  thjToid  venous  plexus.  The  nerves  are  derived  from  tjie  vagus  and  the 
recurrent  nerves,  and  from  the  sjonpathetic ;  they  are  distributed  to  the  TracheaHs  muscles  and 
between  the  epitheUal  cells. 

Applied  Anatomy. — Foreign  bodies  often  find  their  way  into  the  air  passages.  These  may 
consist  of  large  soft  substances,  as  pieces  of  meat,  which  may  become  lodged  in  the  entrance  of 
the  larynx,  or  in  the  rima  glottidis,  and  cause  speedy  suffocation  unless  rapidly  got  rid  of,  or  unless 
an  opening  is  made  into  the  air  passages  below,  so  as  to  enable  the  patient  to  breathe.  Smaller 
bodies,  frequently  of  a  hard  nature,  such  as  cherry  or  plum  stones,  small  pieces  of  bone,  buttons, 
etc.,  may  find  their  way  through  the  rima  glottidis  into  the  trachea  or  bronchus,  or  may  become 
lodged  in  the  ventricle  of  the  larynx.  The  dangers  then  depend  not  so  much  upon  the  mechanical 
obstruction  as  upon  the  spasm  of  the  glottis  which  they  excite  from  reflex  irritation.  When 
lodged  in  the  ventricle  of  the  larynx,  they  may  produce  very  few  symptoms,  be5rond  sudden 
loss  of  voice  or  alteration  in  the  voice  sounds  immediately  after  the  inhalation  of  the  foreign 
body.     When,  however,  thej'  are  situated  in  the  trachea,  they  are  constanth^  striking  against 


Fibrous 
membrane 


Hyaline 
cartilage 


Fibrous 
membrane 


Fig.  915. — Transverse  section  of  trachea. 


1 094  SPLA  XrjIXOJ^OGY 

the  vocal  folds  during  expiratory  efforts,  and  produce  attacks  of  dyspnoea  from  spasm  of  the 
glottis.  When  lodged  in  the  bronchus,  they  usually  become  fixed  there,  and,  occluding  the 
lumen  of  the  tube,  cause  a  loss  of  the  respiratory  nuu'mur  on  the  affected  side,  and  maj'  subse- 
quently lead  to  purulent  broncliitis  and  gangrene  of  the  lung.  Foreign  bodies  in  the  air  passages 
should  always  be  removed  as  soon  as  possible. 

Beneath  the  mucous  membrane  of  the  upper  part  of  the  air  passages  there  is  a  considei'able 
amount  of  submucous  tissue,  which  is  liable  to  become  much  swollen  from  effusion  in  inflam- 
matory affections,  constituting  the  condition  known  as  oedema  of  the  glottis.  This  effusion  does 
not  extend  below  the  level  of  the  vocal  folds,  on  account  of  the  fact  that  the  mucous  membrane 
is  closely  adherent  to  these  structures  without  the  intervention  of  any  submucous  tissue.  So 
that,  in  cases  of  oedema  of  the  glottis,  in  which  it  is  necessary  to  open  the  air  passages  to  prevent 
suffocation,  the  operation  of  laryngotomy  is  sufficient.  Laryngeal  or  glottidean  oedema  may 
be  secondary  to  some  local  inflammatory  affection,  such  as  acute  septic  laryngitis,  syphilitic 
laryngeal  perichondritis,  or  to  malignant  disease.  Or  the  oedema  may  be  passive  (non-inflam- 
matory), consequent  upon  renal  or  cardiac  mischief,  angioneurotic  ccdema;  or,  in  unusually 
susceptible  persons,  the  administration  of  potassium  iodide. 

Chronic  laryngitis  is  an  inflammation  of  the  mucous  glands  of  the  larynx,  which  occurs  in 
those  who  speak  much  in  public,  and  is  known  as  clergyman's  sore  throat.  It  is  due  to  the  dryness 
induced  by  the  large  amount  of  cold  air  drawn  into  the  air  passages  during  prolonged  speaking, 
which  excites  increased  activity  of  the  mucous  glands  to  keep  the  parts  moist,  and  this  eventually 
terminates  in  inflammation  of  these  structures. 

Ulceration  of  the  larynx  may  occur  from  syphilis,  either  as  a  superficial  ulceration,  or  from 
the  softening  of  a  gumma;  from  tuberculous  disease  (laryngeal  phthisis),  or  from  malignant 
disease  (epithelioma) . 

The  air  passages  may  be  opened  in  three  different  situations:  by  a  vertical  incision  through 
the  centre  of  the  thja-oid  cartilage  (thyrotomy) ;  through  the  middle  cricothyroid  ligament  {laryn- 
gotomy), or  in  some  part  of  the  trachea  {tracheotomy). 

Thyrotomy  is  usually  performed  for  the  purpose  of  removing  growths  from  the  vocal  folds  or 
for  extracting  foreign  bodies  from  the  ventricle  of  the  larynx.  A  median  incision  is  made  from 
the  upper  border  of  the  body  of  the  hyoid  bone  to  the  lower  border  of  the  cricoid  cartilage,  and 
is  carried  through  the  subcutaneous  tissues  and  deep  fascia  between  the  margins  of  the  Sterno- 
hyoidei.  An  incision  is  then  made  in  the  middle  cricothyroid  ligament,  and  one  blade  of  a  stout, 
sharp-pointed  pair  of  scissors  is  introduced  beneath  the  lower  border  of  the  thyi-oid  cartilage, 
and  this  structure  is  divided  from  below  upward.  Great  care  must  be  taken  to  cut  exactly  in 
the  middle  line  to  avoid  wounding  the  vocal  folds.  If  the  two  halves  of  the  cartilage  are  now 
drawn  apart,  a  very  good  view  of  the  interior  of  the  larynx  will  be  obtained. 

Laryngotomy  is  anatomically  a  simple  operation:  it  can  readily  be  performed,  and  should 
be  employed  in  those  eases  where  the  air  passages  require  opening  in  an  emergency  for  the  relief 
of  some  sudden  obstruction  to  respiration.  The  middle  cricothyroid  membrane  is  very  super- 
ficial, being  covered  only  in  the  middle  fine  by  the  skin,  superficial  fascia,  and  the  deep  fascia. 
On  either  side  of  the  middle  line  it  is  also  covered  by  the  Sternohyoideus  and  Sternothyreoideus, 
which  diverge  from  each  other  at  their  upper  parts,  leaving  a  shght  interval  between  them.  On 
these  muscles  rest  the  anterior  jugular  veins.  The  only  vessel  of  any  importance  in  connection 
with  this  operation  is  the  cricothyroid  artery,  which  crosses  the  middle  cricothyi-oid  ligament, 
and  may  be  wounded,  but  rarely  gives  rise  to  any  trouble.  The  operation  is  performed  thus:  the 
head  being  thrown  back  and  steadied  by  an  assistant,  the  finger  is  passed  over  the  front  of  the 
neck,  and  the  cricothyroid  depression  felt  for.  A  vertical  incision  is  then  made  through  the  skin 
in  the  middle  line  over  this  spot,  and  carried  down  through  the  fascia  until  the  middle  crico- 
thyroid ligament  is  exposed.  A  cross-cut  is  then  made  through  the  Hgament  close  to  the  upper 
border  of  the  cricoid  cartilage,  so  as  to  avoid,  if  possible,  the  cricothyroid  artery,  and  a  laryn- 
gotomy tube  inserted.  It  has  been  recommended,  as  a  more  rapid  way  of  performing  the  opera- 
tion, to  make  a  transverse  instead  of  a  longitudinal  cut  through  the  superficial  structures,  and 
thus  to  open  at  once  the  air  passages.  It  will  be  seen,  however,  that  in  operating  in  this  way 
the  anterior  jugular  veins  are  in  danger  of  being  wounded. 

Tracheotomy  may  be  performed  either  above  or  below  the  isthmus  of  the  thyroid  gland,  or 
this  structm-e  may  be  divided  and  the  trachea  opened  behind  it. 

From  the  relations  already  described,  it  must  be  evident  that  the  trachea  can  be  more  readily 
opened  above  than  below  the  isthmus  of  the  thyroid  gland. 

Tracheotomy  above  the  isthmus  is  performed  thus:  the  patient  should,  if  possible,  be  laid 
on  his  back  on  a  table  in  a  good  light.  A  pillow  is  to  be  placed  under  the  shoulders  and  the 
head  thrown  back  and  steadied  by  an  assistant.  The  surgeon  standing  on  the  right  side  of  his 
patient  makes  an  incision  from  4  to  5  cm.  long  in  the  median  fine  of  the  neck  from  the  top  of 
the  cricoid  cartilage.  The  incision  must  be  made  exactl}'^  in  the  middle  fine  so  as  to  avoid  the 
anterior  jugular  veins,  and  after  the  superficial  structures  have  been  divided,  the  interval  between 
the  Sternohyoidei  must  be  found,  the  raphe  divided,  and  the  muscles  drawn  apart.  The  lower 
border  of  the  cricoid  cartilage  must  now  be  felt  for,  and  the  upper  part  of  the  trachea  exposed 


THE  piJ'A'R.E  \m:i 

from  this  point  downward  in  th(>  middle  line.  Bose  has  recommended  that  the  layer  of  fascia 
in  front  of  the  trachea  should  l)e  di\ided  transversely  at  the  level  of  the  lower  border  of  the 
cricoid  cartilafxe,  and,  havinp;  been  seized  with  a  i)air  of  forcejjs,  i)ressed  downward  with  the 
handle  of  the  scalix'l.  Hy  this  means  the  isthmus  of  the  thyroid  gland  is  dei)ressed  and  is  saved 
from  all  danger  of  being  wounded,  and  the  trachea  (deaidy  exposed.  The  trachea  is  now  trans- 
fixed with  a  sharj)  hook  and  drawn  forward  in  order  to  steady  it,  and  is  then  opened  by  inserting 
the  knife  into  it  and  dividing  the  ui)i)er  two  or  three  rings  by  cutting  upward.  If  the  trachea  is 
to  be  opened  beneath  the  isthnuis,  the  incision  mu.st  be  made  from  a  little  below  the  cricoid 
cartilage  to  the  top  of  the  sternum. 

A  portion  of  the  larynx  or  the  whole  of  it  may  be  removed  for  nialignanl  di.scasc.  The  results 
which  have  been  obtained  from  the  removal  of  the  whole  of  it  have  not  been  very  satisfactory, 
and  the  cases  in  which  the  operation  is  justifiable  arc  very  few.  It  may  be  removed  by  a  median 
incision  through  the  soft  parts,  freeing  the  cartilages  from  the  nuiscles  and  other  structures- 
in  front,  sejiarat ing  the  larynx  from  the  trachea  below,  and  dissecting  off  the  deeper  structure 
from  below  ui)ward. 

THE   PLEURA. 

Each  lung  is  invested  by  an  exceedingly  delicate  serous  membrane,  the  pleura, 
which  is  arranged  in  the  form  of  a  closed  invaginated  sac.  A  portion  of  the  serous 
membrane  covers  the  surface  of  the  lung  and  dips  into  the  fissures  between  its 
lobes;  it  is  called  the  pulmonary  pleura.  The  rest  of  the  membrane  lines  the  inner 
surface  of  the  chest  wall,  covers  the  Diaphragma,  and  is  reflected  over  the  structures 
occupying  the  middle  of  the  thorax;  this  portion  is  termed  the  parietal  pleura.  The 
two  layers  are  continuous  with  one  another  around  and  below  the  root  of  the  lung; 
in  health  they  are  in  actual  contact  with  one  another,  but  the  potential  space 
between  them  is  known  as  the  pleural  cavity.  When  the  lung  collapses  or  when 
air  or  fluid  collects  between  the  two  layers  the  cavity  becomes  apparent.  The  right 
and  left  pleural  sacs  are  entirely  separate  from  one  another;  between  them  are  all 
the  thoracic  viscera  except  the  lungs,  and  they  onh'  touch  each  other  for  a  short 
distance  in  front;  opposite  the  second  and  third  pieces  of  the  sternum  the  interval 
between  the  two  sacs  is  termed  the  mediastinal  cavity. 

Different  portions  of  the  parietal  pleura  have  received  special  names  which 
indicate  their  position:  thus,  that  portion  which  lines  the  inner  surfaces  of  the 
ribs  and  Intercostales  is  the  costal  pleura;  that  clothing  the  convex  surface  of  the 
Diaphragma  is  the  diaphragmatic  pleura;  that  which  rises  into  the  neck,  over  the 
summit  of  the  lung,  is  the  cupula  of  the  pleura  {cenical  pleura) ;  and  that  which  is 
applied  to  the  other  thoracic  viscera  is  the  mediastinal  pleura. 

Reflections  of  the  Pleura  (Figs.  916,  917).— Commencing  at  the  sternum,  the 
pleura  passes  lateralward,  lines  the  inner  surfaces  of  the  costal  cartilages,  ribs, 
and  Intercostales,  and  at  the  back  part  of  the  thorax  passes  over  the  sympathetic 
trunk  and  its  branches,  and  is  reflected  upon  the  sides  of  the  bodies  of  the  vertebrae, 
where  it  is  separated  by  a  narrow  interval,  the  posterior  mediastinal  cavity,  from 
the  opposite  pleura.  From  the  vertebral  column  the  pleura  passes  to  the  side  of  the 
pericardium,  which  it  covers  to  a  slight  extent;  it  then  covers  the  back  part  of  the 
root  of  the  lung,  from  the  lower  border  of  which  a  triangular  sheet  descends  verti- 
cally toward  the  Diaphragma.  This  sheet  is  the  posterior  layer  of  a  wide  fold, 
known  as  the  pulmonary  ligament.  From  the  back  of  the  lung  root,  the  pleura 
may  be  traced  over  the  costal  surface  of  the  lung,  the  apex  and  base,  and  also  o^•er 
the  sides  of  the  fissures  between  the  lobes,  on  to  its  mediastinal  surface  and  the  front 
part  of  its  root.  It  is  continued  from  the  lower  margin  of  the  root  as  the  anterior 
layer  of  the  pulmonary  ligament,  and  from  this  it  is  reflected  on  to  the  pericardium 
(pericardial  pleura),  and  from  it  to  the  back  of  the  sternum.  Abo^'e  the  le^el  of 
the  root  of  the  lung,  however,  the  mediastinal  pleura  passes  uninterruptedly  from 
the  vertebral  column  to  the  sternum  over  the  structures  in  the  superior  media- 
stinal cavity.  Beloic,  it  covers  the  upper  surface  of  the  Diaphragma  and  extends, 
in  front,  as  low  as  the  costal  cartilage  of  the  seventh  rib;  at  the  side  of  the  chest, 


1096 


SPLANCHNOLOGY 


to  the  lower  border  of  the  tenth  rib  on  the  left  side  and  to  the  upper  border  of  the 
same  rib  on  the  right  side ;  and  behind,  it  reaches  as  low  as  the  twelfth  rib,  and  some- 
times even  to  the  transverse  process  of  the  first  lumbar  vertebra.  Above,  its  cupula 
projects  through  the  superior  opening  of  the  thorax  into  the  neck,  extending  from 
2.5  to  5  cm.  above  the  sternal  end  of  the  first  rib;  this  portion  of  the  sac  is  strength- 
ened by  a  dome-like  expansion  of  fascia  (Sibson's  fascia),  attached  in  front  to  the 
inner  border  of  the  first  rib,  and  behind  to  the  anterior  border  of  the  transverse 
process  of  the  seventh  cervical  vertebra.  This  is  covered  and  strengthened  by  a 
few  spreading  muscular  fibres  derived  from  the  Scaleni. 


Lower  margin  of  'pleura 


Fig.  916. — Front  view  of  thorax,  showing  the  relations  of  the  pleurae  and  lungs  to  the  chest  wall. 
Pleura  in  blue;  lungs  in  purple. 

In  the  front  of  the  chest,  where  the  parietal  pleura  is  reflected  backward  to  the 
pericardium,  the  two  pleural  sacs  are  in  contact  for  a  short  distance.  At  the  upper 
part  of  the  chest,  behind  the  manubrium,  they  are  separated  by  an  angular  interval; 
the  line  of  reflection  being  represented  by  a  line  drawn  from  the  sternoclavicular 
articulation  to  the  mid-point  of  the  junction  of  the  manubrium  with  the  bod}^ 
of  the  sternum.  From  this  point  the  two  pleurae  descend  in  close  contact  to  the 
level  of  the  fourth  costal  cartilages,  and  the  line  of  reflection  on  the  right  side  is 
continued  downward  in  nearly  a  straight  line  to  the  xiphoid  process,  and  then 
turns  lateralward,  while  on  the  left  side  the  line  of  reflection  diverges  lateralward 
and  is  continued  downward,  close  to  the  left  border  of  the  sternum,  as  far  as  the 
sixth  costal  cartilage.  The  inferior  limit  of  the  pleura  is  on  a  considerably  lower 
level  than  the  corresponding  limit  of  the  lung,  but  does  not  extend  to  the  attach- 
ment of  the  Diaphragma,  so  that  below  the  line  of  reflection  of  the  pleura  from  the 
chest  wall  on  to  the  Diaphragma  the  latter  is  in  direct  contact  with  the  rib  cartilages 


THE  PLEURA 


1097 


Trachea 

R,  subclavian  art. 
B.  innominate  vein 


and  the  lutereostales  iuterui.  Moreover,  in  ordinary  inspiration  the  tliin  inferior 
margin  of  the  lung  does  not  extend  as  low  as  the  line  of  the  pleural  reflection,  with 
the  result  that  the  costal  and  diaphragmatic  pleura^  arc  here  in  contact,  the  inter- 
vening narrow  slit  being  termed  the  phrenicocostal  sinus.  A  similar  condition 
exists  behind  the  sternum  and  rib 
cartilages,  where  the  anterior  thin 
margin  of  the  lung  falls  short  of 
the  line  of  i)lcural  reflection,  and 
where  the  slit-like  ca^'ity  between 

the    two   layers    of    i)lcura    forms  M /V  \     ^*^i: 

what  is  called  the  costamediastinal 
sinus. 

The  line  along  which  the  right 
pleura  is  reflected  from  the  chest- 
wall  to  the  Diaphragma  starts  in 
front,  immediately  below  the 
seventh  sternocostal  joint,  and 
runs  downward  and  backward 
behind  the  seventh  costal  carti- 
lage so  as  to  cross  the  tenth  rib  in 
the  mid-axillary  line,  from  which 
it  is  prolonged  to  the  spinous  pro- 
cess of  the  twelfth  thoracic  verte- 
bra. The  reflection  of  the  left 
pleura  follows  at  first  the  ascending 
part  of  the  sixth  costal  cartilage, 
and  in  the  rest  of  its  course  is 
slightly  lower  than  that  of  the  right 
side. 

The  free  surface  of  the  pleura  is 
smooth,  polished,  and  moistened 
bj''  a  serous  fluid;  its  attached  sur- 
face is  intimately  adherent  to  the 
lung,  and  to  the  pulmonary  vessels 
as  they  emerge  from  the  pericar- 
dium; it  is  also  adherent  to  the  upper  surface  of  the  Diaphragma:  throughout  the 
rest  of  its  extent  it  is  easily  separable  from  the  adjacent  parts. 

The  right  pleural  sac  is  shorter,  wider,  and  reaches  higher  in  the  neck  than  the 
left. 

Pulmonary  Ligament  (ligamentum  pulmonale;  Ugamentum  latum  pulmonis). — 
From  the  above  description  it  will  be  seen  that  the  root  of  the  lung  is  covered  in 
front,  above,  and  behind  by  pleura,  and  that  at  its  lower  border  the  investing 
layers  come  into  contact.  Here  they  form  a  sort  of  mesenteric  fold,  the  pulmonary 
ligament,  which  extends  between  the  lower  part  of  the  mediastinal  surface  of  the 
lung  and  the  pericardium.  Just  above  the  Diaphragma  the  ligament  ends  in  a  free 
falciform  border.    It  serves  to  retain  the  lower  part  of  the  lung  in  position. 

Structure  of  Pleura. — Like  other  serous  membranes,  the  pleura  is  covered  by  a  single  layer 
of  flattened,  nucleated  cells,  vmited  at  their  edges  by  cement  substance.  These  cells  are  modified 
connective-tissue  corpuscles,  and  rest  on  a  basement  membrane.  Beneath  the  basement  mem- 
brane there  are  net-works  of  yellow  elastic  and  white  fibres,  unbedded  in  ground  substance  which 
also  contains  connective-tissue  cells.  Bloodvessels,  lymphatics,  and  nerves  are  distributed  in 
the  substance  of  the  pleura,  and  the  lymphatics  communicate  with  the  pleural  cavity  by  means 
of  stomata  or  openings  between  the  cells  of  the  superficial  laj^er. 

Vessels  and  Nerves. — ^The  arteries  of  the  pleura  are  derived  from  the  intercostal,  internal 
mammary,  musculophrenic,  thymic,  pericardiac,  and  bronchial  vessels.     The  veins  correspond 


Lo-wer  margin 

of  pleura 

Lower  margin  of  lung 


Fig.  917. — Lateral  view  of  thorax,  showing  the  relations  of 
the  pleurae  and  lungs  to  the  chest  wall.  Pleura  in  blue;  lungs  in 
purple. 


1098  SPLANCHNOLOGY 

to  the  arteries.  The  lymphatics  are  described  on  page  800.  Tlie  nerves  are  derived  from  the 
phrenic  and  sympatlietic  (Luschka).  Kolhker  states  that  nerves  accompany  the  ramifications 
of  the  bronchial  arteries  in  the  pulmonary  pleura. 

Applied  Anatomy. — Acute  inflammation  of  the  pleura  or  pleurisy  may  be  either  dry  or  wet, 
and,  if  wet,  either  serous  or  purulent.  Dry  pleurisy  is  common  in  pneumonia,  and  is  often  an 
early  manifestation  of  tuberculosis.  It  gives  rise  to  much  pain,  and  to  friction  sounds  due  to 
the  scraping  to  and  fro  over  one  another  of  the  inflamed  and  roughened  parietal  and  pulmonary 
pleurae.  Wet  pleurisy  occm's  if  the  inflammation  causes  the  effusion  of  serum  into  the  pleural 
cavity.  The  two  pleural  layers  are  now  separated  by  the  fluid  effusion,  so  the  friction  sounds 
are  no  longer  produced.  Room  is  found  for  the  fluid  by  shrinkage  of  the  supernatant  lung  due 
to  the  retraction  of  its  elastic  tissue,  and  later,  when  the  quantity  of  serum  exceeds  about  1.5 
litre,  by  shifting  over  of  the  heart  and  vmaffected  lung  toward  the  sound  side.  This  shifting 
may  be  so  extensive  that  the  apex  beat  of  the  heart  comes  to  lie  under  the  right  mammary  papilla. 
Any  pleural  effusion  that  is  large  enough  to  embarrass  respiration  seriously,  or  has  remained 
unabsorbed  for  two  or  three  weeks,  should  be  removed  by  tapping  (paracentesis  thoracis) .  The 
trocar  is  pushed  through  the  chest  wall  into  the  fluid,  in  the  sixth  or  seventh  intercostal  space 
in  the  mid-axillary  Une,  or  in  the  eighth  or  ninth  space  just  outside  the  angle  of  the  scapula. 
Aspiration  is  then  performed,  and  as  much  fluid  as  possible  drawn  off;  it  must  be  stopped,  how- 
ever, if  the  patient  shows  signs  of  collapse,  or  if  fits  of  coughing  occur  and  threaten  to  wound 
the  expanding  lung  against  the  sharp  end  of  the  trocar.  Non-inflammatory  or  passive  effusion 
into  the  pleura,  called  hydrothorax,  is  often  seen  in  the  later  stages  of  chronic  renal  or  cardiac 
disease,  and  demands  treatment  on  hues  similar  to  the  above. 

Purulent  pleural  effusion,  or  empyema,  often  occurs  after  such  diseases  as  pneumonia  or  measles. 
This  condition  requires  drainage  of  the  cavity,  which  usually  necessitates  excision  of  a  portion 
of  the  rib.  An  incision  is  made  down  to  the  seventh  or  eighth  rib  in  the  mid-  or  posterior  axillary 
line  and  the  periosteum  is  incised,  and  separated  from  the  shaft  of  the  rib,  carrying  with  it  the 
structures  in  the  costal  groove.  With  bone-cutting  forceps  about  4  or  5  cm.  of  the  rib  are  sepa- 
rated and  removed,  and  the  underlying  pleura  is  incised.  The  pus  having  been  evacuated,  a  large 
drainage-tube  is  inserted  into  the  cavity.  The  pleura  should  never  be  irrigated,  as  sudden  death 
has  followed  this  proceeding,  and  great  care  should  be  taken  to  prevent  the  tube  from  slipping 
into  the  cavity,  an  occurrence  which  is  far  from  uncommon. 

Pneumothorax,  or  the  presence  of  gas  in  the  pleural  cavity,  is  a  common  terminal  event  in 
tuberculosis  of  the  lungs;  less  often  it  is  due  to  trauma — ruptiu-e  of  the  lung,  for  example,  when 
the  chest  is  crushed,  or  tearing  of  the  lung  tissue  by  the  sharp  projecting  end  of  a  broken  rib. 
Air  escapes  from  the  lung  into  the  pleural  cavity;  the  elastic  tissue  of  the  lung  at  once  contracts, 
and  finally  that  organ  shrinks  away  to  a  dark  rounded  mass  the  size  of  a  fist,  lying  close  against 
the  vertebral  column.  The  symptoms  of  pneumothorax  are  often  very  severe;  cyanosis,  intense 
dyspnoea,  great  pain  on  the  affected  side,  and  cardiac  failure.  Their  severity  is  increased  by 
the  fact  that  the  bloodvessels  of  the  collapsed  lung  offer  less  resistance  to  the  circulation  of 
the  blood  than  do  those  of  the  other  lung.  Not  only,  therefore,  does  the  sound  lung  suddenly 
have  to  take  over  the  work — the  aeration  of  the  blood — normally  performed  by  both  lungs,  but 
it  has  to  do  so  at  the  moment  when  the  circulation  of  blood  through  it  is  partially  short-circuited 
by  the  collapsed  lung,  If  the  patient  survives  for  a  few  days,  empyema  often  complicates  the 
pneumothorax,  setting  up  the  condition  called  pyopneumothorax. 

In  operations  upon  the  kidney,  it  must  be  borne  in  mind  that  the  pleura  usually  extends 
below  the  level  of  the  medial  portion  of  the  last  rib,  and  may  therefore  be  opened  in  these  opera- 
tions, especially  when  the  last  rib  is  removed  in  order  to  give  more  room. 

THE   MEDIASTINAL    CAVITY    (INTERPLEURAL    SPACE). 

The  mediastinal  cavity  is  the  space  between  the  right  and  left  pleurae  in  and  near 
the  median  sagittal  plane  of  the  chest.  It  extends  from  the  sternum  in  front 
to  the  vertebral  column  behind,  and  contains  all  the  thoracic  viscera  excepting 
the  lungs.  The  cavity  may  be  divided  for  purposes  of  description  into  two  parts: 
an  upper  portion,  above  the  upper  level  of  the  pericardium,  which  is  named  the 
superior  mediastinal  cavity;  and  a  lower  portion,  below  the  upper  level  of  the 
pericardium.  This  lower  portion  is  again  subdivided  into  three  parts,  viz.,  that 
in  front  of  the  pericardium,  the  anterior  mediastinal  cavity;  that  containing  the 
pericardiurn  and  its  contents,  the  middle  mediastinal  cavity;  and  that  behind 
the  pericardium,  the  posterior  mediastinal  cavity. 

The  superior  mediastinal  cavity  (Fig.  918)  is  that  portion  of  the  interpleural 
space  which  lies  between  the  manubrium  sterni  in  front,  and  the  upper  thoracic 


THE  MK  1)1  AST  ISM.  CAVITY 


1099 


vertebni"  lu'liind.     It  is  Ixxiiuk-d  lu'low  l)y  a  sli<ilitly  ohliquc  plane  i)assiii^r  backward 
from  the  jiiiicli.ni  of  (lie  iiianiihriiim  and  body  of  tJic  sttTniun  to  tlie  lower  part 


Ll.  raroliil 
Lift  innominate  vein  „ri.        Thi/mMs         \'agi(.,  nerve 


Vagn-s  netve 


w     ■      I  -^  ^ '    inno- 

/^^^   ZX^ luinute  V. 


1  u   I  )  llj 


Trachea 


Third  rib 
Fig.  918. — Transverse  section  through  the  upper  margin  of  the  second  thoracic  vertebra.      (Braune.) 


Transvcisuii  fJiomcis 
Internal  mamman/  i-exnelx 


Left  phreni 
nerve 


Puhnotmry  pleura 
Costal  pleura 


Sympathetic  trunk  /  \J  \  -■'^~I/9os  vein 

Thoracic  duct  Vagus  nerves 

Fig.  919. — A  transverse  section  of  the  thorax,  showing  the  contents  of  the  middle  and  posterior  mediastinal  cavities. 


1100 


SPLANCHNOLOGY 


ofthe  body  of  the  fourth  thoracic  vertebra,  and  hiterally  by  the  pleura.  It  con- 
tains the  origins  of  the  Sternohyoidei  and  SternothyreoJdei'and  the  lower  ends  of 
the  Longi  colli;  the  aortic  arch;  the  innominate  artery  and  the  thoracic  portions 
of  the  left  common  carotid  and  the  left  subclavian  arteries;  the  innominate  veins 
and  the  upper  half  of  the  superior  vena  cava;  the  left  highest  intercostal  vein;  the 
vagus,  cardiac,  phrenic,  and  left  recurrent  nerves;  the  trachea,  esophagus,  and 
thoracic  duct;  the  remains  of  the  thymus,  and  some  lymph  glands. 


Highest  inUrco'^ial  artery 

Highest  intercostal  vein 
Bami  communicantes 


Fig.  920. — The  middle  and  posterior  mediastiua.     Left  side.     . 

The  anterior  mediastinal  cavity  (Fig.  919)  exists  onh-  on  the  left  side  where 
the  left  pleura  diverges  from  the  mid-sternal  line.  It  is  bounded  in  front  by  the 
sternum,  laterally  by  the  pleurse,  and  behind  by  the  pericardium.  It  is  narrow, 
above,  but  widens  out  a  little  below.  Its  anterior  wall  is  formed  by  the  left  Trans- 
versus  thoracis  and  the  fifth,  sixth,  and  seventh  left  costal  cartilages.    It  contains 


THE  LUNGS  1101 

a  quantity  of  loose  areolar  tissue,  some  lymphatic  vessels  which  ascend  from  the 
convex  surface  of  the  liver,  two  or  three  anterior  mediastinal  lymph  glands,  and 
the  small  mediastinal  branches  of  the  internal  mammary  artery. 

The  middle  mediastinal  cavity  (Fig-.  919)  is  the  broadest  part  of  the  interpleural 
space.  It  contains  the  heart  enclosed  in  the  pericardium,  the  ascending  aorta, 
the  lower  half  of  the  superior  vena  cava  with  the  azygos  vein  opening  into  it, 
the  bifurcation  of  the  trachea  and  the  two  bronchi,  the  pulmonary  artery  dividing 
into  its  two  branches,  the  right  and  left  pulmonary  veins,  the  phrenic  nerves, 
and  some  bronchial  lymph  glands. 

The  posterior  mediastinal  cavity  (Figs.  919,  920)  is  an  irregular  triangular 
space  running  parallel  with  the  vertebral  column;  it  is  bounded  in  front  by  the 
pericardium  above,  and  by  the  posterior  surface  of  the  Diaphragma  below,  behind 
by  the  vertebral  column  from  the  lower  border  of  the  fourth  to  the  twelfth  thoracic 
vertebra,  and  on  either  side  by  the  mediastinal  pleura.  It  contains  the  thoracic 
part  of  the  descending  aorta,  the  azygos  and  the  two  hemiazygos  veins,  the  vagus 
and  splanchnic  nerves,  the  oesophagus,  the  thoracic  duct,  and  some  lymph  glands. 

Applied  Anatomy. — Primary  tumors  of  the  mediastinum  are  usually  lymphoma  or  lympho- 
sarcoma arising  from  the  thymus  or  from  the  bronchial  or  posterior  mediastinal  lymph  glands 
sarcomata,  dermoid  cysts,  and  embryomata  occur  more  rarely.  These  tumors  give  rise  to  pain, 
deformity  of  the  chest,  and  symptoms  of  pressure  on  the  various  nerves,  bloodvessels,  air  passages, 
lymphatics,  and  on  the  oesophagus,  as  these  various  structures  pass  through  the  thorax.  They 
may  produce  physical  signs  very  much  Uke  those  of  an  aortic  aneurism,  so  that  diagnosis  between 
the  two  is  often  difficult.  The  prognosis  is  bad,  the  condition  usually  proving  fatal  within  a  few 
months  or  a  year  of  the  onset  of  the  symptoms. 

Inflammation  of  the  mediastinum  due  to  wounds,  or  to  the  spread  of  inflammation  from  adja- 
cent parts,  e.  g.,  the  oesophagus,  the  pericardiimi,  is  sometimes  acute,  leading  to  abscess  forma- 
tion. A  more  chronic  form  associated  with  adhesions  and  inflammation  of  the  pericardium — 
the  so-called  chronic  adhesive  mediastinopericarditis — gives  rise  to  obscure  symptoms  suggesting 
gradual  heart -failure,  and  leads  to  death  slowly  but  surely. 


THE   LUNGS    (PULMONES). 

The  lungs  are  the  essential  organs  of  respiration;  they  are  two  in  number,  placed 
one  on  either  side  within  the  thorax,  and  separated  from  each  other  by  the  heart 
and  other  contents  of  the  mediastinal  cavity  (Fig.  921).  The  substance  of  the  lung 
is  of  a  light,  porous,  spongy  texture;  it  floats  in  water,  and  crepitates  when  handled, 
owing  to  the  presence  of  air  in  the  alveoli;  it  is  also  highly  elastic;  hence  the  retracted 
state  of  these  organs  when  they  are  removed  from  the  closed  cavity  of  the  thorax. 
The  surface  is  smooth,  shining,  and  marked  out  into  numerous  polyhedral  areas, 
indicating  the  lobules  of  the  organ:  each  of  these  areas  is  crossed  by  numerous 
lighter  lines. 

At  birth  the  lungs  are  pinkish  w^hite  in  color;  in  adult  life  the  color  is  a  dark 
slaty  gray,  mottled  in  patches;  and  as  age  advances,  this  mottling  assumes  a  black 
color.  The  coloring  matter  consists  of  granules  of  a  carbonaceous  substance 
deposited  in  the  areolar  tissue  near  the  surface  of  the  organ.  It  increases  in  quan- 
tity as  age  advances,  and  is  more  abundant  in  males  than  in  females.  As  a  rule, 
the  posterior  border  of  the  lung  is  darker  than  the  anterior. 

The  right  lung  usually  weighs  about  625  gm.,  the  left  567  gm.,  but  much  varia- 
tion is  met  with  according  to  the  amount  of  blood  or  serous  fluid  they  may  contain. 
The  lungs  are  heavier  in  the  male  than  in  the  female,  their  proportion  to  the  body 
being,  in  the  former,  as  1  to  37,  in  the  latter  as  1  to  43. 

Each  lung  is  conical  in  shape,  and  presents  for  examination  an  apex,  a  base, 
three  borders,  and  two  surfaces. 

The  apex  (apex  pulmonis)  is  rounded,  and  extends  into  the  root  of  the  neck, 
reaching  from  2.5  to  4  cm.  above  the  level  of  the  sternal  end  of  the  first  rib.    A 


1102 


SPLAXCHXOLOGY 


sulcus  produced  by  the  subclavian  artery  as  it  curves  in  front  of  the  pleura  runs 
upward  and  laterahvard  immediately  below  the  apex. 

The  base  (basis  puhnouis)  is  broad,  concave,  and  rests  upon  the  convex  surface 
of  the  Diaphragma,  which  separates  the  right  lung  from  the  right  lobe  of  the  liver, 
and  the  left  lung  from  the  left  lobe  of  the  liver,  the  stomach,  and  the  spleen.  Since 
the  Diaphragma  extends  higher  on  the  right  than  on  the  left  side,  the  concavity 
on  the  base  of  the  right  lung  is  deeper  than  that  on  the  left.  Laterally  and  behind, 
the  base  is  bounded  by  a  thin,  sharp  margin  which  projects  for  some  distance 
into  the  phrenicocostal  sinus  of  the  pleura,  between  the  lower  ribs  and  the  costal 
attachment  of  the  Diaphragma.  The  base  of  the  lung  descends  during  inspiration 
and  ascends  during  expiration. 


fencaidhim 


Fig.  921. — Front  view  of  heart  and  lungs. 


Surfaces. — The  costal  surface  ( fades  costalis;  external  or  thoracic  surface)  is 
smooth,  convex,  of  considerable  extent,  and  corresponds  to  the  form  of  the  cavity 
of  the  chest,  being  deeper  behind  than  in  front.  It  is  in  contact  with  the  costal 
pleura,  and  presents,  in  specimens  which  have  been  hardened  in  situ,  slight  grooves 
corresponding  Avith  the  overlying  ribs. 

The  mediastinal  surface  (fades  mediastinalis ;  inner  surface)  is  in  contact  with 
the  mediastinal  pleura.  It  presents  a  deep  concavity,  the  cardiac  impression, 
which  accommodates  the  pericardium;  this  is  larger  and  deeper  on  the  left  than 
on  the  right  lung,  on  account  of  the  heart  projecting  farther  to  the  left  than  to  the 
right  side  of  the  median  plane.  Above  and  behind  this  concavity  is  a  triangular 
depression  named  the  hilus,  where  the  structures  which  form  the  root  of  the  lung 
enter  and  leave  the  viscus.    These  structures  are  invested  by  pleura,  which,  below 


THE  LrXCrS 


1103 


the  hilus  and  hcliiiid  the  pericardial  impression,  lurnis  the  i)uhuonary  ligament. 
On  the  ridlit  luui;-  (h\.  922),  immediately  above  the  hilus,  is  an  arched  furrow 
which  accomnioihites  the  azygos  vein;  while  running  ui)ward,  and  then  arching 
lateralward  some  little  distance  below  the  apex,  is  a  wide  groove  for  the  superior 
vena  cava  and  right  innominate  vein;  behind  this,  and  nearer  the  apex,  is  a  furrow 
for  the  innominate  artery.  Behind  the  hilus  and  the  attachment  of  the  pulmonary 
ligament  is  a  vertical  groove  for  the  oesophagus;  this  groove  becomes  less  distinct 
below,  owing  to  the  inclination  of  the  lower  part  of  the  (x'sophagus  to  the  left  of 
the  middle  line.  In  front  and  to  the  right  of  the  lower  part  of  the  oesophageal 
groove  is  a  deep  conca^•ity  for  the  extrapericardiac  portion  of  the  thoracic  part 
of  the  inferior  vena  ca\a.  On  the  left  lung  (Fig.  923),  immediately  above  the  hilus, 
is  a  well-marked  curNcd  furrow  produced  by  the  aortic  arch,  and  running  upward 


Groove  for 
innominate  artery 

Groove  foi       y^ 

sup.  vena  cava 


P  uhnonary 
artery 


G wove  for  azygos 

vein 

\ Eparterial 

bro7ichus 

Hyparlcrial 
bronchus 
^^  P  ulmonary 

veins 

Groove  for 

cesopltagus 


Pidmonary 
ligament 


Fig.  922. — Mediastinal  surface  of  right  lung. 

from  this  toward  the  apex  is  a  groove  accommodating  the  left  subclavian  artery; 
a  slight  impression  in  front  of  the  latter  and  close  to  the  margin  of  the  lung  lodges 
the  left  innominate  vein.  Behind  the  hilus  and  pulmonary  ligament  is  a  vertical 
furrow  produced  by  the  descending  aorta,  and  in  front  of  this,  near  the  base  of 
the  lung,  the  lower  part  of  the  oesophagus  causes  a  shallow  impression. 

Borders. — The  inferior  border  {margo  inferior)  is  thin  and  sharp  where  it  sepa- 
rates the  base  from  the  costal  surface  and  extends  into  the  phrenicocostal  sinus; 
medially  where  it  divides  the  base  from  the  mediastinal  surface  it  is  blunt  and 
rounded. 

The  posterior  border  {margo  posterior)  is  broad  and  rounded,  and  is  received  into 
the  deep  concavity  on  either  side  of  the  vertebral  column.  It  is  much  longer 
than  the  anterior  border,  and  projects,  below,  into  the  phrenicocostal  sinus. 


1104 


SPLANCHNOLOGY 


The  anterior  border  {)nargu  anterior)  is  thin  and  sharp,  and  overlaps  the  front 
of  the  pericardium.  The  anterior  border  of  the  right  knig  is  almost  vertical,  and 
projects  into  the  costoniediastinal  sinus;  that  of  the  left  presents^  below,  an  angular 
notch,  the  cardiac  notch,  in  which  the  pericardium  is  exposed.  Opposite  this 
notch  the  anterior  margin  of  the  left  lung  is  situated  some  little  distance  lateral 
to  the  line  of  reflection  of  the  corresponding  part  of  the  pleura. 

Gwoicfoi  left  •subclavian  artery 
Gioobcfoi  left  innominate  vein 


Bronchus 


Posterior 
border 


Pulmonary 
I  ifjaiiient 


Pulmonary 
artery 

"4-      I'ti  '.monary 
1 ,1  ^  veins 

V 


-—     yJardiac  notch 


Fig.  923. — Mediastinal  surface  of  left  lung. 


Fissures  and  Lobes  of  the  Lungs. — The  left  lung  is  divided  into  two  lobes, 
an  upper  and  a  lower,  by  an  interlobular  fissure,  which  extends  from  the  costal 
to  the  mediastinal  surface  of  the  lung  both  above  and  below  the  hilus.  As  seen 
on  the  surface,  this  fissure  begins  on  the  mediastinal  surface  of  the  lung  at  the 
upper  and  posterior  part  of  the  hilus,  and  runs  backward  and  upward  to  the  pos- 
terior border,  which  it  crosses  at  a  point  about  6  cm.  below  the  apex.  It  then 
extends  downward  and  forward  over  the  costal  surface,  and  reaches  the  lower 
border  a  little  behind  its  anterior  extremity,  and  its  further  course  can  be  followed 
upward  and  backward  across  the  mediastinal  surface  as  far  as  the  lower  part  of 
the  hilus.  The  superior  lobe  lies  above  and  in  front  of  this  fissure,  and  includes  the 
apex,  the  anterior  border,  and  a  considerable  part  of  the  costal  surface  and  the 
greater  part  of  the  mediastinal  surface  of  the  lung.  The  inferior  lobe,  the  larger 
of  the  two,  is  situated,  below  and  behind  the  fissure,  and  comprises  almost  the 
whole  of  the  base,  a  large  portion  of  the  costal  surface,  and  the  greater  part  of 
the  posterior  border. 

The  right  lung  is  divided  into  three  lobes,  superior,  middle,  and  inferior,  by 
two  interlobular  fissures.  One  of  these  separates  the  inferior  from  the  middle 
and  superior  lobes,  and  corresponds  closely  with  the  fissure  in  the  left  lung.    Its 


THE  LUNGS  1105 

direction  is,  however,  more  vertical,  and  it  cuts  the  lower  border  about  7.5  cm. 
behind  its  anterior  extremity.  The  otiier  fissure  separates  the  superior  from  the 
middle  lobe.  It  begins  in  the  previous  fissure  near  the  posterior  border  of  the  lung, 
and,  running  horizontally  forward,  cuts  the  anterior  border  on  a  level  with  the 
sternal  end  of  the  fourth  costal  cartilage;  on  the  mediastinal  surface  it  may  be 
traced  backward  to  the  hilus.  The  middle  lobe,  the  smallest  lobe  of  the  right 
lung,  is  wedge-shaped,  and  includes  the  lower  part  of  the  anterior  border  and  the 
anterior  part  of  the  base  of  the  lung. 

The  right  lung,  although  shorter  by  2.5  cm.  than  the  left,  in  consequence  of  the 
Diaphragma  rising  higher  on  the  right  side  to  accommodate  the  liver,  is  broader, 
owing  to  the  inclination  of  the  heart  to  the  left  side;  its  total  capacity  is  greater 
and  it  weighs  more  than  the  left  lung. 

The  Root  of  the  Lung  {radix  yulmoms). — A  little  above  the  middle  of  the  medias- 
tinal surface  of  each  lung,  and  nearer  its  posterior  than  its  anterior  border,  is  its 
root,  by  which  the  lung  is  connected  to  the  heart  and  the  trachea.  The  root  is 
formed  by  the  bronchus,  the  pulmonary  artery,  the  pulmonary  veins,  the  bronchial 
arteries  and  veins,  the  pulmonary  plexuses  of  nerves,  lymphatic  vessels,  bronchial 
lymph  glands,  and  areolar  tissue,  all  of  which  are  enclosed  by  a  reflection  of  the 
pleura.  The  root  of  the  right  lung  lies  behind  the  superior  vena  cava  and  part 
of  the  right  atrium,  and  below  the  azygos  vein.  That  of  the  left  lung  passes 
beneath  the  aortic  arch  and  in  front  of  the  descending  aorta;  the  phrenic  nerve, 
the  pericardiacophrenic  artery  and  vein,  and  the  anterior  pulmonary  plexus,  lie 
in  front  of  each,  and  the  vagus  and  posterior  pulmonary  plexus  behind  each; 
below  each  is  the  pulmonary  ligament. 

The  chief  structures  composing  the  root  of  each  lung  are  arranged  in  a  similar 
manner  from  before  backward  on  both  sides,  viz.,  the  upper  of  the  two  pulmonary 
veins  in  front;  the  pulmonary  artery  in  the  middle;  and  the  bronchus,  together 
with  the  bronchial  vessels,  behind.  From  above  downward,  on  the  two  sides, 
their  arrangement  differs,  thus: 

On  the  right  side  their  position  is — eparterial  bronchus,  pulmonary  artery, 
hyparterial  bronchus,  pulmonary  veins,  but  on  the  left  side  their  position  is — 
pulmonary  artery,  bronchus,  pulmonary  veins.  The  lower  of  the  two  pulmonary 
veins,  is  situated  below  the  bronchus,  at  the  apex  or  lowest  part  of  the  hilus 
(Figs.  922,  923). 

Divisions  of  the  Bronchi. — Just  as  the  lungs  differ  from  each  other  in  the  number 
of  their  lobes,  so  the  bronchi  differ  in  their  mode  of  subdivision. 

The  right  bronchus  gives  off,  about  2.5  cm.  from  the  bifurcation  of  the  trachea, 
a  branch  for  the  superior  lobe.  This  branch  arises  above  the  level  of  the  pulmonary 
artery,  and  is  therefore  named  the  eparterial  bronchus.  All  the  other  divisions 
of  the  main  stem  come  off  below  the  pulmonary  artery,  and  consequently  are 
termed  hyparterial  bronchi.  The  first  of  these  is  distributed  to  the  middle  lobe, 
and  the  main  tube  then  passes  downward  and  backward  into  the  inferior  lobe, 
giving  off  in  its  course  a  series  of  large  ventral  and  small  dorsal  branches.  The 
ventral  and  dorsal  branches  arise  alternately,  and  are  usually  eight  in  number — 
four  of  each  kind.  The  branch  to  the  middle  lobe  is  regarded  as  the  first  of  the 
ventral  series. 

The  left  bronchus  passes  below  the  level  of  the  pulmonary  artery  before  it  divides, 
and  hence  all  its  branches  are  hyparterial;  it  may  therefore  be  looked  upon  as 
equivalent  to  that  portion  of  the  right  bronchus  w^hich  lies  on  the  distal  side  of  its 
eparterial  branch.  The  first  branch  of  the  left  bronchus  arises  about  5  cm.  from 
the  bifurcation  of  the  trachea,  and  is  distributed  to  the  superior  lobe.  The  main 
stem  then  enters  the  inferior  lobe,  w'here  it  divides  into  ventral  and  dorsal  branches 
similar  to  those  in  the  right  lung.  The  branch  to  the  superior  lobe  of  the  left  lung 
is  regarded  as  the  first  of  the  ventral  series. 
70 


1106 


SPLANCHNOLOGY 


Structure. — The  lungs  are  composed  of  an  external  serous  coat,  a  subserous  areolar  tissue, 
and  the  puhnonary  substance  or  parenchyma. 

The  serous  coat  is  the  pulmonarj^  pleura  (page  1097);  it  is  thin,  transparent,  and  invests  the 
entire  organ  as  far  as  the  root. 

The  subserous  areolar  tissue  contains  a  large  proportion  of  elastic  fibres;  it  invests  the  entire 
surface  of  the  lung,  and  extends  inward  between  the  lobules. 

The  parenchyma  is  composed  of  lobules  which,  although  closely  connected  together  by  an 
interlobular  areolar  tissue,  are  quite  distinct  from  one  another,  and  may  be  teased  asunder 
without  much  difficulty  in  the  fetus.  The  lobules  vary  in  size;  those  on  the  surface  are  large, 
of  pyramidal  form,  the  base  turned  toward  the  surface;  those  in  the  interior  smaller,  and  of 
various  forms.  Each  lobule  is  composed  of  a  lobular  bronchiole  and  its  terminal  air  cells,  and 
of  the  ramifications  of  the  pulmonary  and  bronchial  vessels,  lymphatics,  and  nerves;  all  of  these 
structures  being  connected  together  by  areolar  tissue. 

The  intrapulmonary  bronchi  di^-ide  and  subdivide  throughout  the  entire  organ,  the  smallest 
subdivisions  constituting  the  lobular  bronchioles.  The  larger  divisions  consist  of:  (1)  an  outer 
coat  of  fibrous  tissue  in  which  are  found  at  intervals  irregular  plates  of  hyaline  cartilage,  most 
developed  at  the  points  of  division;  (2)  internal  to  the  fibrous  coat,  a  layer  of  circularly  disposed 
smooth  muscle  fibres,  the  bronchial  muscle;  and  (3)  most  internally,  the  mucous  membrane, 
lined  by  columnar  ciliated  epithelium  resting  on  a  basement  membrane.  The  corium  of  the 
mucous  membrane  contains  numerous  elastic  fibres  running  longitudinally,  and  a  certain  amount 
of  IjTnphoid  tissue;  it  also  contains  the  ducts  of  mucous  glands,  the  acini  of  which  lie  in  the 
fibrous  coat.  The  lobular  bronchioles  differ  from  the  larger  tubes  in  containing  no  cartilage 
and  in  the  fact  that  the  ciliated  epithelial  cells  are  cubical  in  shape.  The  lobular  bronchioles 
are  about  0.2  mm.  in  diameter. 

TnfnnrUbuhim 
Vestibule  \    ^ff\^\ 


Caiiilfige  plates 

Fig.  924. — Section  of  lung  of  cat,  shon-ing  termination  of  bronchus.     X  50. 


Each  bronchiole  terminates  at  a  jjoint  called  the  vestibule  by  dividing  into  from  three  to  six 
wider  ii-regular  passages  called  atria.  These  are  fined  by  flattened  non-ciUated  epithelium;  at 
the  vestibule  the  bronchial  muscle  forms  a  definite  circular  band.  From  each  atrimn  arise  two 
or  more  infundibula,  elongated,  blind  passages,  lined  by  simple  squamous  epitheUum,  and  beset 
on  all  sides  by  hemispherical  alveofi  or  air  ceUs  (Fig.  924). 

The  alveoli  are  lined  by  a  delicate  layer  of  simple  squamous  epithelium,  the  cells  of  which 
are  imited  at  their  edges  by  cement  substance.  Between  the  squames  are  here  and  there  smaller, 
polygonal,  nucleated  cells.  Outside  the  epithelial  fining  is  a  little  dehcate  connective  tissue, 
containing  nimierous  elastic  fibres  and  a  close  net-work  of  blood  capillaries,  and  forming  a  common 
wall  to  adjacent  alveoli  (Fig.  925). 

The  fetal  lung  resembles  a  gland  in  that  the  alveofi  haA-e  a  small  lumen  and  are  lined  by 
cubical  epithelium  (Fig.  926) .  After  the  first  respiration  the  alveoli  become  distended,  and  the 
epithelium  takes  on  the  characters  described  above. 


THE  LUNGS 


1107 


Vessels  and  Nerves. — The  pulmonary  artery  conveys  tlic  venous  blood  to  the  lungs;  it  divides 
into  branches  which  accompany  the  bronchial  tubes  and  end  in  a  dense  capillary  net-work  in 


Epithelium 


Alveoli 


\         Injundibulum 


Fig.  925. — Section  of  lung  tissue. 

the  walls  of  the  alveoli.     In  the  lung  the  branches  of  the  pulmonary  artery  are  usually  above 
and  in  front  of  a  bronchial  tube,  the  vein  below. 


Fig.  92(3. — Section  of  lung  of  pig  embryo,  13  cm.  long,  showing  the  glandular  character  of  the  developing  alveoli. 
(J.  M.  Flint.)  X  70.  o.  Interstitial  connective  tissue.  6.  A  bronchial  tube.  c.  An  Alveolus.  I.  lymphatic  clefts. 
p.  Pleura. 


The  pulmonary  capillaries  form  plexuses  which  he  immediately  beneath  the  lining  epithe- 
lium, in  the  walls  and  septa  of  the  alveoli  and  of  the  infundibula.     In  the  septa  between  the 


IIOS  SPLANCHNOLOGY 

alveoli  the  capillary  net-work  forms  a  single  layer.  The  capillaries  form  a  very  minute  net-work, 
the  meshes  of  which  are  smaller  than  the  vessels  themselves;  their  walls  are  also  exceedingly 
thin.  The  arteries  of  neighboring  lobules  are  independent  of  each  other,  but  the  veins  freely 
anastomose. 

The  pulmonary  veins  commence  in  the  pulmonary  capillaries,  the  radicles  coalescing  into 
larger  branches  which  run  through  the  substance  of  the  lung,  independently  of  the  pulmonary 
arteries  and  bronchi.  After  freely  communicating  with  other  branches  they  form  large  vessels, 
which  ultimately  come  into  relation  with  the  arteries  and  bronchial  tubes,  and  accompany 
them  to  the  hilus  of  the  organ.  Finally  they  open  into  the  left  atrium  of  the  heart,  conveying 
oxygenated  blood  to  be  distributed  to  all  parts  of  the  body  by  the  aorta. 

The  bronchial  arteries  supply  blood  for  the  nutrition  of  the  lung;  they  are  derived  from  the 
thoracic  aorta  or  from  the  upper  aortic  intercostal  arteries,  and,  accompanying  the  bronchial 
tubes,  are  distributed  to  the  bronchial  glands  and  upon  the  walls  of  the  larger  bronchial  tubes 
and  pulmonary  vessels.  Those  supplying  the  bronchial  tubes  form  a  capillary  plexus  in  the 
muscular  coat,  from  which  branches  are  given  off  to  form  a  second  plexus  in  the  mucous  coat; 
this  plexus  communicates  with  branches  of  the  pulmonary  artery,  and  empties  itself  into  the 
pulmonary  veins.  Others  are  distributed  in  the  interlobular  areolar  tissue,  and  end  partly  in 
the  deep,  partly  in  the  superficial,  bronchial  veins.  Lastly,  some  ramify  upon  the  surface  of 
the  lung,  beneath  the  pleura,  where  they  form  a  capillary  network. 

The  bronchial  vein  is  formed  at  the  root  of  the  lung,  receiving  superficial  and  deep  veins  corre- 
sponding to  branches  of  the  bronchial  artery.  It  does  not,  however,  receive  all  the  blood  supplied 
by  the  artery,  as  some  of  it  passes  into  the  pulmonary  veins.  It  ends  on  the  right  side  in  the 
azygos  vein,  and  on  the  left  side  in  the  highest  intercostal  or  in  the  accessory  hemiazygos  vein. 

The  Ijrmphatics  are  described  on  page  799. 

Nerves. — The  lungs  are  supplied  from  the  anterior  and  posterior  pulmonary  plexuses,  formed 
chiefly  by  branches  from  the  sympathetic  and  vagus.  The  filaments  from  these  plexuses  accom- 
pany the  bronchial  tubes,  supplying  efferent  fibres  to  the  bronchial  muscle  and  afferent  fibres 
to  the  bronchial  mucous  membrane  and  to  the  alveoli  of  the  lung.  Small  gangha  are  found 
upon  these  nerves. 

Applied  Anatomy. — The  hmgs  may  be  wounded  or  torn  in  three  ways;  (1)  by  compression 
of  the  chest,  without  any  injur}^  to  the  ribs;  (2)  by  a  fractured  rib  penetrating  the  lung;  (3)  by 
stabs,  gunshot  wounds,  etc. 

The  first  form,  where  the  lung  is  ruptured  by  external  compression  without  any  fracture  of 
the  ribs,  is  very  rare,  and  usually  occurs  in  young  children,  and  affects  the  root  of  the  lung,  i.  e., 
the  most  fixed  part,  and  thus,  implicating  the  great  vessels,  is  frequently  fatal.  It  would  seem 
a  priori  a  most  unusual  injin-y,  and  its  exact  mode  of  causation  is  difficult  to  interpret. 

In  the  second  variety,  when  the  wound  in  the  lung  is  produced  by  the  penetration  of  a  broken 
rib,  both  the  costal  pleura  and  pulmonary  pleura  must  necessarily  be  injured,  and  consequently 
the  air  taken  into  the  wounded  alveoli  may  find  its  way  through  these  wounds  into  the  cellular 
tissue  of  the  parietes  of  the  chest,  producing  surgical  emphysema.  This  it  may  do  without  col- 
lecting in  the  pleural  cavity;  the  two  layers  of  the  pleura  are  so  intimately  in  contact  that  the 
air  passes  straight  through  from  the  wounded  lung  into  the  subcutaneous  tissue.  Emphysema 
constitutes  therefore  the  most  important  sign  of  injury  to  the  lung  in  cases  of  fracture  of  the 
ribs.  Pneumothorax,  or  air  in  the  pleural  cavity,  is  much  more  likely  to  occur  in  injmies  of 
the  third  variety — that  is  to  say,  from  external  woimds,  from  stabs,  gunshot  injuries,  and  such 
like — in  which  case  air  passes  either  from  the  wound  of  the  lung  or  from  the  external  wound 
into  the  cavity  of  the  pleura  during  the  respiratory  movements.  In  these  cases  there  is  generally 
no  emphysema  of  the  subcutaneous  tissue  unless  the  external  wound  is  small  and  valvular,  so 
that  the  air  is  drawn  into  the  wound  during  inspiration,  and  then  forced  into  the  cellular  tissue 
around  during  expiration  because  it  cannot  escape  from  the  external  wound.  Occasionally  in 
wounds  of  the  parietes  of  the  chest  no  air  finds  its  way  into  the  cavity  of  the  pleura,  because 
the  lung  at  the  time  of  the  accident  protrudes  through  the  wound  and  blocks  the  opening.  This 
takes  place  where  the  wound  is  large,  and  constitutes  one  form  of  hernia  of  the  lung.  Another 
form  of  hernia  of  the  lung  occurs,  though  very  rarely,  after  wounds  of  the  chest  wall,  when 
the  wound  has  healed  and  the  cicatrix  subsequently  yields  from  the  pressure  of  the  viscus  behind. 
It  forms  a  globular,  elastic,  crepitatmg  swelling,  which  enlarges  during  expiratory  efforts,  falls 
in  during  inspiration,  and  disappears  on  holding  the  breath. 

An  incision  into  the  lung  is  occasionally  required  in  cases  of  abscess  the  result  of  pneumonia 
or  the  presence  of  a  foreign  body,  and  from  an  abscess  in  the  liver  which  has  made  its  way  through 
the  Diaphragma  into  the  lung  substance,  and  also  in  cases  of  hydatid  disease.  In  these  cases 
there  is  always  risk  of  hemorrhage,  and  it  has  been  recommended  that  the  lung  tissue  should 
be  penetrated  by  the  actual  cautery,  rather  than  with  the  knife.  Unless  adhesions  have  formed 
between  the  two  layers  of  the  pleura,  the  pleural  cavity  must  necessarily  be  opened,  and  there 
is  the  further  risk  of  pneumothorax,  and  possibly  of  septic  infection.  It  is  therefore  advisable 
to  suture  the  lung  to  the  opening  in  the  thoracic  wall,  and  wait  for  adhesions  to  form  before 
perforating  the  lung. 


THE  DIGESTIVE  APPARATUS  1109 

The  routine  metliods  of  pliysical  examination — inspection,  palpation,  percussion,  and  auscul- 
tation— are  nowhere  more  important  than  they  are  in  the  diagnosis  of  diseases  of  the  lungs. 
It  is  essential,  too,  that  in  every  case  the  two  sides  of  the  chest  should  be  compared  with  one 
another,  and  that  the  wide  variations  that  may  be  met  with  under  normal  conditions  in  different 
persons  and  at  different  ages  should  be  kept  in  mind  when  the  chest  is  being  examined.  On 
inspection  the  thorax  will  be  seen  to  be  enlarged  and  barrel-shaped  in  emphysema,  in  which 
the  volume  of  the  lungs  is  increased  by  dilatation  of  their  alveoU,  or  in  an  acute  attack  of  asthma, 
or  when  a  large  pleural  effusion  or  mediastinal  tumor  is  present.  The  chest  wall  will  be  flattened 
or  sunken,  on  the  other  hand,  over  an  area  of  lung  that  has  collapsed  or  become  fibrosed,  as 
often  happens  in  chronic  pulmonary  tuberculosis.  The  respiratory  movements  of  the  chest  wall 
will  be  lessened,  or  even  absent,  over  a  part  of  the  whole  of  the  affected  side  in  such  acute  dis- 
orders as  pleurisy,  pneumonia,  or  pleural  effusion,  or  in  more  chronic  diseases  where  the  under- 
lying lung  is  fibrosed,  or  is  crushed  to  one  side  by  a  mediastinal  tumor;  and  by  the  use  of  the 
x-rays  a  corresponding  loss  of  movement  or  displacement  of  the  Diaphragma  on  the  affected 
side  can  often  be  observed.  Under  normal  conditions  the  intercostal  spaces  are  a  httle  depressed; 
but  they  may  be  obUterated  or  even  bulging  on  that  side  when  a  large  effusion  or  new-  growth 
fills  up  one  of  the  pleural  cavities. 

On  palpation  the  hand  can  be  used  to  verify  the  eye's  impressions  as  to  the  degree  of  move- 
ment on  respiration  of  any  part  of  the  chest  w^all.  The  facihty  with  which  the  vibrations- produced 
by  the  voice  are  conducted  from  the  larynx  by  the  underlying  lung  to  the  hand  (in  the  form  of 
vocal  fremitus)  can  also  be  tested.  The  vocal  fremitus,  is  commonly  much  increased  over  the 
consolidated  area  in  pneumonia  or  in  fibrosis  of  the  lung,  and  much  diminished  over  a  pleural 
effusion  when  the  lung  is  pushed  up  by  the  fluid  toward  the  top  of  the  pleural  cavity.  It  is  also 
diminished, .but  to  a  less  extent,  in  emphysema,  and  in  bronchitis  when  the  bronchi  are  blocked 
by  secretion.  In  bronchitis  the  bubbling  of  the  secretion  in  the  tubes  can  often  be  felt  by  a  hand 
placed  on  the  chest  wall  as  the  patient  breathes;  and  in  chronic  pleiu-isy  the  friction  of  the  two 
roughened  pleural  surfaces  against  one  another  can  sometimes  be  felt  in  the  same  way. 

On  percussion,  the  normal  resonance  of  the  pulmonary  tissue  is  found  to  be  increased  in  emphy- 
sema, and  in  pneumothorax  (page  1098)  this  hj^perresonance  may  be  still  further  increased. 
The  resonance  is  lessened  in  any  condition  causing  collapse  or  sohdification  of  the  lung  tissue, 
or  when  its  place  is  taken  by  fluid  (pleural  effusion)  or  some  solid  growth  (mediastinal  tumor). 
Thus  duhiess  on  percussion  at  the  bases  of  the  lungs  is  common  in  the  hjrpostatic  congestion  of 
the  bases  seen  in  heart  failure;  duhiess  at  the  right  base  is  often  due  to  compression  of  the  lung 
by  enlargement  of  the  liver;  some  duhiess  at  the  apex  of  a  lung  is  frequently  met  with  in  tuber- 
culosis of  the  part,  before  the  disease  has  progressed  very  far.  Complete  dulness  over  one  side 
of  the  chest,  back  and  front  alike,  except  at  the  apex,  is  common  when  a  large  plem-al  effusion 
has  taken  the  lung's  place.  Von  Koranyi,  Grocco,  and  others  have  drawn  attention  to  a  tri- 
angular patch  of  dulness  along  the  vertebral  column  (the  paravertebral  triangle  of  dulness)  on 
the  imaffected  side  in  plem-al  effusion;  this  triangle  of  dulness  is  said  to  be  absent  in  other  con- 
ditions, causing  loss  of  pulmonary  resonance  on  percussion,  and  is  due  to  shifting  over  of  the 
contents  of  the  posterior  mediastinal  cavity  toward  the  soimd  side.  The  apex  of  this  triangle  is  in 
the  middle  line  at  the  upper  level  of  the  fluid  effusion;  its  base,  some  5  to  10  cm.  in  length,  runs 
horizontally  outward  from  the  middle  line  at  the  level  where  the  pulmonary  resonance  normally 
comes  to  an  end. 

On  auscultation  of  the  lungs,  both  in  health  and  disease,  the  variety  of  sounds  to  be  heard 
is  very  gi-eat.  It  is  impossible  to  give  adequate  consideration  to  them  here,  and  for  further 
information  reference  should  be  made  to  text-books  dealing  with  the  subject.^ 

THE  DIGESTIVE  APPARATUS   (APPARATUS  DIGESTORIUS;  ORGANS 

OF  DIGESTION). 

The  apparatus  for  the  digestion  of  the  food  consists  of  the  digestive  tube  and  of 
certain  accessory  organs. 

The  Digestive  Tube  (alimenatry  canal)  is  a  musculomembranous  tube,  about 
9  metres  long,  extending  from  the  mouth  to  the  anus,  and  Hned  throughout  its 
entire  extent  by  mucous  membrane.  It  has  received  different  names  in  the  various 
parts  of  its  course:  at  its  commencement  is  the  mouth,  where  provision  is  made 
for  the  mechanical  division  of  the  food  {mastication),  and  for  its  admixture  with 
a  fluid  secreted  by  the  salivary  glands  (insalivation) ;  beyond  this  are  the  organs 
of  deglutition,  the  pharynx  and  the  oesophagus,  which  convey  the  food  into  the 
stomach,  in  which  it  is  stored  for  a  time  and  in  which  also  the  first  stages  of  the 

'  See  especially  Auscultation  and  Percussion,  by  Austin  Flint,  JvI.D.,  6th  ed.,  1912. 


1110  SPLANCHNOLOG  Y 

digestive  process  take  place;  the  stomach  is  followed  by  the  small  intestine,  which 
is  divided  for  purposes  of  description  into  three  parts,  the  duodenum,  the  jejimum, 
and  ileum.  In  the  small  intestine  the  process  of  digestion  is  completed  and  the 
resulting  products  are  absorbed  into  the  blood  and  lacteal  vessels.  Finally  the 
small  intestine  ends  in  the  large  intestine,  which  is  made  up  of  cecum,  colon,  rectum, 
and  anal  canal,  the  last  terminating  on  the  surface  of  the  body  at  the  anus. 

The  accessory  organs  are  the  teeth,  for  purposes  of  mastication;  the  three  pairs 
of  salivary  glands — the  parotid,  submaxillary,  and  sublingual — the  secretion  from 
which  mixes  with  the  food  in  the  mouth  and  converts  it  into  a  bolus  and  acts 
chemically  on  one  of  its  constituents;  the  liver  and  pancreas,  two  large  glands 
in  the  abdomen,  the  secretions  of  which,  in  addition  to  that  of  numerous  minute 
glands  in  the  walls  of  the  alimentary  canal,  assist  in  the  process  of  digestion, 

THE  MOUTH   (CAVUM   ORIS;   ORAL   OR  BUCCAL  CAVITY). 

The  cavity  of  the  mouth  is  placed  at  the  commencement  of  the  digestive  tube 
(Fig.  927) ;  it  is  a  nearly  oval-shaped  cavity  which  consists  of  two  parts :  an  outer, 
smaller  portion,  the  vestibule,  and  an  inner,  larger  part,  the  mouth  cavity  proper. 

The  Vestibule  (vestibulum  oris)  is  a  slit-like  space,  bounded  externally  by  the 
lips  and  cheeks;  internally  by  the  gums  and  teeth.  It  communicates  with  the 
surface  of  the  body  by  the  rima  or  orifice  of  the  mouth.  Above  and  below,  it  is 
limited  by  the  reflection  of  the  mucous  membrane  from  the  lips  and  cheeks  to 
the  gum  covering  the  upper  and  lower  alveolar  arch  respectively.  It  receives  the 
secretion  from  the  parotid  salivary  glands,  and  communicates,  when  the  jaws  are 
closed,  with  the  mouth  cavity  proper  by  an  aperture  on  either  side  behind  the 
wisdom  teeth,  and  by  narrow  clefts  between  opposing  teeth. 

The  Mouth  Cavity  Proper  (cavum  oris  proyrium)  (Fig.  943)  is  bounded  laterally 
and  in  front  by  the  alveolar  arches  with  their  contained  teeth;  behind,  it  communi- 
cates with  the  pharynx  by  a  constricted  aperture  termed  the  isthmus  faucium. 
It  is  roofed  in  by  the  hard  and  soft  plates,  while  the  greater  part  of  the  floor  is 
formed  by  the  tongue,  the  remainder  by  the  reflection  of  the  mucous  membrane 
from  the  sides  and  under  surface  of  the  tongue  to  the  gum  lining  the  inner  aspect 
of  the  mandible.  It  receives  the  secretion  from  the  submaxillary  and  sublingual 
salivary  glands. 

Structure. — The  mucous  membrane  lining  the  mouth  is  continuous  with  the  integument  at 
the  free  margin  of  the  hps,  and  with  the  mucous  lining  of  the  pharynx  behind;  it  is  of  a  rose- 
pink  tinge  during  life,  and  very  thick  where  it  overlies  the  hard  parts  bounding  the  cavity.  It 
is  covered  by  stratified  squamous  epitheUum. 

The  Lips  {labia  oris),  the  two  fleshy  folds  which  surround  the  rima  or  orifice  of 
the  mouth,  are  formed  externally  of  integument  and  internally  of  mucous  mem- 
brane, between  which  are  found  the  Orbicularis  oris  muscle,  the  labial  vessels, 
some  nerves,  areolar  tissue,  and  fat,  and  numerous  small  labial  glands.  The  inner 
surface  of  each  lip  is  connected  in  the  middle  line  to  the  corresponding  gum  by  a 
fold  of  mucous  membrane,  the  frenulum — the  upper  being  the  larger. 

The  Labial  Glands  {glajidulae  labiates)  are  situated  between  the  mucous  membrane 
and  the  Orbicularis  oris,  around  the  orifice  of  the  mouth.  They  are  circular  in  form, 
and  about  the  size  of  small  peas;  their  ducts  open  by  minute  orifices  upon  the 
mucous  membrane.     In  structure  they  resemble  the  salivary  glands. 

The  Cheeks  (buccae)  form  the  sides  of  the  face,  and  are  continuous  in  front  with 
the  lips.  They  are  composed  externally  of  integument;  internally  of  mucous 
membrane;  and  between  the  two  of  a  muscular  stratum,  besides  a  large  quantity 
of  fat,  areolar  tissue,  vessels,  nerves,  and  buccal  glands. 

Structure. — The  mucous  membrane  hning  the  cheek  is  reflected  above  and  below  upon  the 
gums,  and  is  continuous  behind  with  the  lining  membrane  of  the  soft  palate.     Opposite  the 


rill':  MoiTii 


nil 


second  inolai-  tooth  of  the  iiiaxilhi  is  ;i  i);ii)ilhi,  on  lUn  .suiuuiil  of  which  is  the  apertui-e  of  the 
parotid  duct.  The  priiiciijal  muscle  of  tlio  check  is  the  Huccinator;  but  other  muscles  enter  into 
its  formation,  viz.,  the  Zygoinaticus,  Ri.sorius,  and  Platysnia. 

The  buccal  ylcinds  are  placed  het\v(>(Mi  tlie  mucous  meinl)rane  and  Buccinator  nm.scle:  they 
are  similar  in  structure  to  the  lal)ial  shuuls,  l)ut  smaller.  About  five,  of  a  larger  size  than  the 
rest,  are  placed  between  the  Alasseter  and  Buccinator  muscles  around  the  distal  extremity  of 
the  parotid  duct;  (heir  ducts  open  in  the  mouth  opi)Osite  the  l;ist  molar  tooth.  'J'hey  are  called 
molar  glands. 


Hypophysh. 


Pharyngeal 
to7isil 

Orifice  of 
atulitory  htbe 

Nasal  part  of 
pharynx 

Anterior  arch  of  _. 
alias 

Odo)vtoid  process 
of  axis 

Oral  part  of 

pharynx 

Body  of  axis 


Epiglottis  — 

Laryngeal  part 
of  pharynx 
Aryepiglottic  fold 


Cricoid  cartilage 


(Esophagiis 


Frenulum  linguoe 
)//\    /   \  2Iylohyoideus  muscle 

•-  '    ^  Hyoid  hone 


t    V       Thywid  cartilage 
I  Ny       Venn  icidai  fold 


J  DC  a  I  fold 
Cricoid  cartilage 

Isthmus  of  thyroid  gland 
Fig.  927. — Sagittal  section  of  nose,  mouth,  pharynx,  and  larynx. 

The  Gums  {gingivae)  are  composed  of  dense  fibrous  tissue,  closely  connected  to 
the  periosteum  of  the  alveolar  processes,  and  surrounding  the  necks  of  the  teeth. 
They  are  covered  by  smooth  and  vascular  mucous  membrane,  which  is  remark- 
able for  its  limited  "^ sensibility.     Around  the  necks  of  the  teeth  this  membrane 


1 1 12  SPLANCHNOLOGY 

presents  numerous  fine  papillae,  and  is  reflected  int(;  the  alveoli,  where  it  is  con- 
tinuous with  the  periosteal  membrane  lining  these  cavities. 

Applied  Anatomy. — The  gums  are  occasionally  the  seat  of  considerable  hypertrophy,  forming 
a  lobulated  vascular  fold  growing  up  in  front  of  and  behind  the  teeth,  so  as  almost  to  bury  them. 
They  may  also  become  swollen  and  congested,  bleeding  freely,  and  often  becoming  ulcerated. 
The  condition  is  known  as  spongy  gums,  and  maj'  occur  in  scurvy,  in  stomatitis  and  dyspepsia,  in 
ill-fed  tuberculous  children,  and  from  the  administration  of  mercury;  the  gums  are  very  tender, 
mastication  is  painful,  and  there  is  often  considerable  fetor.  The  margin  of  the  gum  presents 
an  interrupted  blue  Line  in  cases  of  lead  poisoning.  The  collection  of  tartar,  which  consists  of 
the  secretion  from  the  gums,  mixed  with  fragments  of  food  and  salivarj^  salts,  may  give  rise  to 
a  condition  known  as  pyorrhoea  alveolaris,  which  is  an  inflammatory  condition  of  the  gums, 
followed  by  the  gradual  absorption  of  the  alveolus  and  the  falling  out  of  the  teeth.  Fibrous 
tumors  (epulis),  mj^eloid  growths,  and  epitheliomata  are  met  with  in  the  gums. 

The  Palate  (palatum)  forms  the  roof  of  the  mouth;  it  consists  of  two  portions, 
the  hard  palate  in  front,  the  soft  palate  behind. 

The  Hard  Palate  (palatum  durum)  (Fig.  943)  is  bounded  in  front  and  at  the  sides 
by  the  alveolar  arches  and  gums;  behind,  it  is  continuous  with  the  soft  palate. 
It  is  covered  by  a  dense  structure,  formed  by  the  periosteum  and  mucous  mem- 
brane of  the  mouth,  W'hich  are  intimately  adherent.  Along  the  middle  line  is  a 
linear  raphe,  which  ends  anteriorly  in  a  small  papilla  corresponding  with  the 
incisive  canal.  On  either  side  and  in  front  of  the  raphe  the  mucous  membrane 
is  thick,  pale  in  color,  and  corrugated;  behind,  it  is  thin,  smooth,  and  of  a  deeper 
color;  it  is  covered  with  stratified  squamous  epithelium,  and  furnished  with 
numerous  palatal  glands,  which  lie  between  the  mucous  membrane  and  the  surface 
of  the  bone. 

The  Soft  Palate  (palatum  molle)  (Fig.  943)  is  a  movable  fold,  suspended  from  the 
posterior  border  of  the  hard  palate,  and  forming  an  incomplete  septum  between 
the  mouth  and  pharynx.  It  consists  of  a  fold  of  mucous  membrane  enclosing 
muscular  fibres,  an  aponeurosis,  vessels,  nerves,  adenoid  tissue,  and  mucous  glands. 
"\^Tien  occupjdng  its  usual  position,  i.  e.,  relaxed  and  pendent,  its  anterior  surface 
is  concave,  continuous  with  the  roof  of  the  mouth,  and  marked  by  a  median  raphe. 
Its  posterior  surface  is  convex,  and  continuous  with  the  mucous  membrane  covering 
the  floor  of  the  nasal  cavities.  Its  upper  border  is  attached  to  the  posterior  margin 
of  the  hard  palate,  and  its  sides  are  blended  with  the  pharynx.  Its  low^er  border 
is  free.  Its  lower  portion,  which  hangs  like  a  curtain  between  the  mouth  and 
pharynx  is  termed  the  palatine  velum. 

Hanging  from  the  middle  of  its  lower  border  is  a  small,  conical,  pendulous 
process,  the  palatine  uvula;  and  arching  lateralward  and  downward  from  the  base 
of  the  uvula  on  either  side  are  two  curved  folds  of  mucous  membrane,  containing 
muscular  fibres,  called  the  arches  or  pillars  of  the  fauces. 

The  glossopalatine  arch  (arcus  glossojjalatinus ;  anterior  pillar  of  fauces)  on  either 
side  runs  downward,  lateralward,  and  forward  to  the  side  of  the  base  of  the  tongue, 
and  is  formed  by  the  projection  of  the  Glossopalatinus  with  its  covering  mucous 
membrane. 

The  pharsoigopalatine  arch  (arcus  'pharyncjopalatinus ;  pjosterior  pillar  of  fauces)  is 
larger  and  projects  farther  toward  the  middle  line  than  the  anterior;  it  runs  down- 
ward, lateralward,  and  backward  to  the  side  of  the  pharynx,  and  is  formed  by  the 
projection  of  the  Pharyngopalatinus,  covered  by  mucous  membrane.  On  either  side 
the  two  arches  are  separated  below  by  a  triangular  interval,  in  which  the  palatine 
tonsil  is  lodged. 

The  aperture  by  which  the  mouth  communicates  with  the  pharynx  is  called 
the  isthmus  faucium.  It  is  bounded,  above,  by  the  soft  palate;  below,  by  the  dorsum 
of  the  tongue;  and  on  either  side,  by  the  glossopalatine  arch. 

Palatine  Aponeurosis. — ^Attached  to  the  posterior  border  of  the  hard  palate  is 
a  thin,  firm  fibrous  lamella  which  supports  the  muscles  and  gives  strength  to  the 


77/ A'  .\ii)(  ru 


in; 


soft  palate.    It  is  tliickrr  al)<)Vt>  than  helow.  wluTf  it  l)rc..iiics  vc-ry  tliiii  and  (lifheult 
to  define.    Laterally  it  is  continnous  with  the  pharyngeal  aponeurosis. 
Muscles  of  the  Palate,     'riic  nuisclcs  of  the  palate  (Fi^-  02S)  are: 


Levator  veli  i)alatini. 
Tensor  veli  pahitini. 
Musculus  uvulae. 


Glossopalatinus. 
Pharyngopalatinus. 


Styloid  process 

J.tvalor  veli 
palalini 

Pltri/goid  hamulus 

V — Slijlo  pluiryngeus 

~^~Salp  i  iifjophn  rij  iiyeus 


Musculus  uvulce 


Entrance  to  larynx 


Fig.  928.— Dissection  of  the  muscles  of  the  palate  from  behind. 


The  Levator  veli  palatini  {Levator  palati)  is  a  thick,  rounded  muscle  situated 
lateral  to  the  choauEe.  It  arises  from  the  under  surface  of  the  apex  of  the  petrous 
part  of  the  temporal  bone  and  from  the  medial  lamina  of  the  cartilage  of  the  audi- 
tory tube.  After  passing  above  the  upper  concave  margin  of  the  Constrictor 
pharvngis  superior  it  spreads  out  in  the  palatine  velum  its  fibres  extending 
obliquety  downward  and  medialward  to  the  middle  line,  where  they  blend  with 

those  of  the  opposite  side.  i  n      ^   .^i^ 

The  Tensor  veU  palatini  {Tensor  palati)  is  a  broad,  thin,  riband-ike  muscle 
placed  lateral  to  the  Levator  veli  palatini.  It  arises  by  a  flat  lamella  from  the 
scaphoid  fossa  at  the  base  of  the  medial  pterygoid  plate,  from  the  spina  angularis 
of  the  sphenoid  and  from  the  lateral  wall  of  the  cartilage  of  the  auditory  tube. 
Descending  vertically  between  the  medial  pterygoid  plate  and  the  Pterygoideus 
internus  it  ends  in  a  tendon  which  winds  around  the  pterygoid  hamulus,  being 
retained  in  this  situation  by  some  of  the  fibres  of  origin  of  the  Pterygoideus  internus. 


1114  SPLANCHNOLOG  Y 

Between  the  tendon  and  the  hamulus  is  a  small  bursa.  The  tendon  then  passes 
medialward  and  is  inserted  into  the  palatine  aponeurosis  and  into  the  surface 
behind  the  transverse  ridge  on  the  horizontal  part  of  the  palatine  bone. 

The  Musculus  uvulae  (Azygos  uvulae)  arises  from  the  posterior  nasal  spine  of 
the  palatine  bones  and  from  the  palatine  aponeurosis;  it  descends  to  be  inserted 
into  the  uvula. 

The  Glossopalatinus  (Palatoglossus)  is  a  small  fleshy  fasciculus,  narrower  in 
the  middle  than  at  either  end,  forming,  with  the  mucous  membrane  covering 
its  surface,  the  glossopalatine  arch.  It  arises  from  the  anterior  surface  of  the 
soft  palate,  where  it  is  continuous  with  the  muscle  of  the  opposite  side,  and  passing 
downward,  forward,  and  lateralward  in  front  of  the  palatine  tonsil,  is  inserted 
into  the  side  of  the  tongue,  some  of  its  fibres  spreading  over  the  dorsum,  and 
others  passing  deeply  into  the  substance  of  the  organ  to  intermingle  with  the 
Transversus  linguae. 

The  Pharyngopalatinus  (Palatopharyngeus)  is  a  long,  fleshy  fasciculus  narrower 
in  the  middle  than  at  either  end,  forming,  with  the  mucous  membrane  covering 
its  surface,  the  pharyngopalatine  arch.  It  is  separated  from  the  Glossopalatinus 
by  an  angular  interval,  in  which  the  palatine  tonsil  is  lodged.  It  arises  from  the 
soft  palate,  where  it  is  divided  into  two  fasciculi  by  the  Levator  veli  palatini  and 
Musculus  uvulae.  The  posterior  fasciculus  lies  in  contact  with  the  mucous  mem- 
brane, and  joins  with  that  of  the  opposite  muscle  in  the  middle  line;  the  anterior 
fasciculus,  the  thicker,  lies  in  the  soft  palate  between  the  Levator  and  Tensor, 
and  joins  in  the  middle  line  the  corresponding  part  of  the  opposite  muscle.  Passing 
lateralward  and  downward  behind  the  palatine  tonsil,  the  Pharyngopalatinus 
joins  the  Stylopharyngeus,  and  is  inserted  with  that  muscle  into  the  posterior 
border  of  the  thyroid  cartilage,  some  of  its  fibres  being  lost  on  the  side  of  the 
pharynx  and  others  passing  across  the  middle  line  posteriorly,  to  decussate  with 
the  muscle  of  the  opposite  side. 

Dissection. — In  a  dissection  of  the  soft  palate  from  its  posterior  or  pharyngeal  surface  to  its 
anterior  or  oral  surface,  the  muscles  would  be  exposed  in  the  following  order:  viz.,  the  posterior 
fasciculus  of  the  Pharyngopalatinus,  covered  by  a  continuation  of  the  mucous  membrane  of 
the  floor  of  the  nasal  cavities;  the  Musculus  uvulae;  the  Levator  veli  palatini;  the  anterior 
fasciculus  of  the  Pharyngopalatinus;  the  aponeurosis  of  the  Tensor  veli  palatini,  and  the  Glosso- 
palatinus covered  by  a  continuation  of  the  oral  mucous  membrane. 

Nerves. — The  Tensor  veli  palatini  is  supphed  by  a  branch  from  the  otic  ganglion;  the  remain- 
ing muscles  of  this  group  are  in  all  probability  supplied  by  the  accessory  nerve  through  the 
pharyngeal  plexus.-^ 

Actions. — During  the  first  stage  of  deglutition,  the  bolus  of  food  is  driven  back  into  the  fauces 
by  the  pressure  of  the  tongue  against  the  hard  palate,  the  base  of  the  tongue  being,  at  the  same 
time,  retracted,  and  the  larynx  raised  with  the  pharynx.  During  the  second  stage  the  entrance 
to  the  larynx  is  closed  by  the  drawing  forward  of  the  arytenoid  cartilages  toward  the  cushion 
of  the  epiglottis — a  movement  produced  by  the  contraction  of  the  Thyreoarytaenoidei,  the 
Aiytaenoidei,  and  the  Arytaenoepiglottidei. 

After  leaving  the  tongue  the  bolus  passes  on  to  the  posterior  or  laryngeal  surface  of  the  epi- 
glottis, and  glides  along  this  for  a  certain  distance;  then  the  Glossopalatini,  the  constrictors  of 
the  fauces,  contract  behind  it;  the  palatine  velum  is  slightly  raised  by  the  Levator  veli  palatini, 
and  made  tense  by  the  Tensor  veli  palatini;  and  the  Pharyngopalatini,  by  their  contraction, 
puU  the  pharynx  upward  over  the  bolus,  and  come  nearly  together,  the  uvula  filling  up  the 
slight  interval  between  them.  By  these  means  the  food  is  prevented  from  passing  into  the  nasal 
part  of  the  pharynx;  at  the  same  time,  the  Pharyngopalatini  form  an  inclined  plane,  directed 
obliquely  downward  and  backward  along  the  under  surface  of  which  the  bolus  descends  into, 
the  lower  part  of  the  pharynx.  The  Salpingopharyngei  raise  the  upper  and  lateral  parts  of  the 
pharynx — i.  e.,  those  parts  which  are  above  the  points  where  the  Stylopharyngei  are  attached 
to  the  pharynx. 

Mucous  Membrane. — The  mucous  membrane  of  the  soft  palate  is  thin,  and  covered  with  strati- 
fied squamous  epithelium  on  both  surfaces,  excepting  near  the  pharyngeal  ostium  of  the  auditory 
tube,  where  it  is  columnar  and  ciliated.     According  to  Klein,  the  mucous  membrane  on  the 

'  "The  Innervation  of  the  Soft  Palate,"  by  Aldren  Turner,  Journal  of  Anatomy  and  Physiology,  xxiii,  523. 


nil':  MOLT  11 


1115 


nasal  surface  of  the  soft  palate  in  the  fetus  is  covered  ihrounliout  by  cohiiiinar  cihalcd  epithelium, 
which  subsequently  becomes  scjuamous;  some  anatomists  state  that  it  is  covered  with  columnar 
ciliated  epitlielium,  except  at  its  free  margin,  throughout  life,  lieneath  the  mucous  membrane 
on  the  oral  surface  of  the  soft  plate  is  a  consideralile  amount  of  adenoitl  tissue.  The  palatine 
glands  form  a  contiiuious  layer  on  its  i)osterior  sui'face  and  around  the  uvula. 

Vessels  and  Nerves.  'i1ie  arteries  supi)lying  tlie  palate  are  the  descending  palatine  branch 
of  the  internal  maxillary,  the  ascending  i)alatine  brancii  of  the  external  maxillary,  and  the  pala- 
tine branch  of  the  ascending  i)haryngeal.  The  veins  end  chiefly  in  the  pterygoid  and  tonsillar 
plexuses.  Tlie  lymphatic  vessels  jiass  to  the  dee])  cervical  glands.  The  sensory  nerves  are 
derived  from  the  jialatine  and  nasopalatine  nerves  and  from  the  glo.ssopharyngeal. 

Applied  Anatomy. — The  occurrence  of  a  congenital  cleft  in  the  ])alate  has  been  aheady  referred 
to  as  a  defect  in  development  (page  299).  After  the  operation  for  the  closure  of  a  cleft  in  the 
palate,  the  palatine  muscles,  especially  the  Tensor  and  Levator  veli  palatini,  have  a  tendency 
to  retard  the  healing  process  by  active  traction  upon  the  line  of  suture.  To  obviate  tliis,  it  is 
necessary  to  divide  tliem.  This  is  best  done  bj'  making  longitudinal  incisions,  on  either  side, 
parallel  to  the  cleft  and  just  medial  to  the  pterygoid  hamulus,  in  such  a  position  as  to  avoid 
the  descending  palatine  artery.  Acquired  perforations  of  the  palate  are  almost  invariably  the 
result  of  the  breaking  down  of  sj'philitic  gummata.  The  ensuing  ulceration  may  continue  until 
practically  the  whole  palate,  both  hard  and  soft,  has  been  destroyed.  Tumors  of  the  palate, 
both  innocent  and  malignant,  are  occasionally  seen. 

Parah'sis  of  the  soft  palate  often  occurs  after  diphtheria.  It  gives  rise  to  a  change  in  the 
voice,  which  becomes  nasal,  and  to  the  regurgitation  of  fluids  down  the  nose  when  their  swal- 
lowing is  attempted.  On  inspection,  the  palate  is  seen  to  hang  flaccid  and  motionless  when 
phonation  or  deglutition  are  attempted;  it  is  also  anesthetic. 


^->  riTp.- 


Fig.  929. — Side  view  of  the  teeth  and  jaws. 


The  Teeth  (denies)  (Figs.  929  to  931). — Man  is  provided  with  two  sets  of  teeth, 
which  make  their  appearance  at  different  periods  of  life.  Those  of  the  first  set 
appear  in  childhood,  and  are  called  the  deciduous  or  milk  teeth.  Those  of  the  second 
set,  which  also  appear  at  an  early  period,  may  continue  imtil  old  age,  and  are 
named  permanent. 

The  deciduous  teeth  are  twenty  in  number:  four  incisors,  two  canines,  and  four 
molars,  in  each  jaw. 

The  permanent  teeth  are  thirty-two  in  number:  four  incisors,  two  canines,  four 
premolars,  and  six  molars,  in  each  jaw. 


1116 


SPLANCHNOLOGY 


The  dental  formulae  may  be  represented  as  follows: 

Deciduous   Teeth. 


Upper  jaw 


lol. 

can. 

in. 

in. 

can. 

mol 

2 

1 

2 

2 

1 

2 

Total  20 


Lower  jaw 
Upper  jaw 


2         1         2  12 
Permanent  Teeth. 


mol. 

pr.  mol. 

can. 

in. 

in. 

can. 

pr.  mol. 

mol 

3 

2 

1 

2 

2 

1 

2 

3 

Lower  jaw 


2      2 


1 


3j 


I-  Total  32 


General  Characteristics.  —  Each  tooth  consists  of  three  portions:  the  crown, 
projecting  above  the  gum;  the  root,  imbedded  in  the  alveolus;  and  the  neck,  the 
constricted  portion  between  the  crown  and  root. 


Incisive  cmials 


Incisive  foramen 


Foramina  cf  Scarpa 


Pxrniolars 


Palatine  process  of  maxilla 
Horizontal  part  of  palatine  bo7ie. 


Greater  palatine  foramen 
Lesser  palatine  foramina 


'\Iclars 


Fig.  930. — Permanent  teeth  of  upper  dental  arch, 
seen  from  below. 


Fig.   931. — Permanent  teeth  of  right  half  of 
lower  dental  arch,  seen  from  above. 


The  roots  of  the  teeth  are  firmly  implanted  in  depressions  within  the  alveoli; 
these  depressions  are  lined  with  periosteum  which  invests  the  tooth  as  far  as  the 
neck.  At  the  margins  of  the  alveoli,  the  periosteum  is  continuous  with  the  fibrous 
structure  of  the  gums. 

In  consequence  of  the  curve  of  the  dental  arch,  terms  such  as  anterior  and 
posterior,  as  applied  to  the  teeth,  are  misleading  and  confusing.  Special  terms 
are  therefore  used  to  indicate  the  different  surfaces  of  a  tooth :  the  surface  directed 
toward  the  lips  or  cheek  is  known  as  the  labial  or  buccal  surface;  that  directed 
toward  the  tongue  is  described  as  the  lingual  surface;  those  surfaces  which  touch 


THE   MOiril 


1117* 


neighboring  teeth  arc  termed  surfaces  of  contact.  In  tlu'  case  of  the  incisor  and 
canine  teeth  the  surfaces  of  contact  are  medial  ;ind  lateral;  in  the  premolar  and 
molar  teeth  they  are  anterior  and  posterior. 

The  superior  dental  arch  is  larger  than  the  inferior,  so  that  in  the  normal  ccjndi- 
tion  the  teeth  in  the  maxilhe  slightly  overlap  those  of  the  manrlihle  hoth  in  front 
and  at  the  sides.  Since  the  upper  central  incisors  are  wider  than  the  lower,  the 
other  teeth  in  the  upper  arch  are  thrown  somewhat  distally,  and  the  two  sets  do 
not  quite  correspond  to  each  other  when  the  mouth  is  closed:  thus  the  upper 
canine  tooth  rests  partly  on  the  lower  canine  and  partly  on  the  first  premolar, 
and  the  cusps  of  the  upper  molar  teeth  lie  behind  the  corresponding  cusps  of  the 
lower  molar  teeth.  The  two  series,  however,  end  at  nearly  the  same  point  behind; 
this  is  mainly  because  the  molars  in  the  upper  arch  are  the  smaller. 

The  Permanent  Teeth  {denies  permanentes)  (Fig.  932). — The  Incisors  {denies 
incisivi;  incisive  or  cutting  teeth)  are  so  named  from  their  presenting  a  sharp  cutting 
edge,  adapted  for  biting  the  food.  They  are  eight  in  number,  and  form  the  four 
front  teeth  in  each  dental  arch. 


Fig.  932. — Permanent  teeth.     Right  side.      (Burchard.) 

The  crown  is  directed  vertically,  and  is  chisel-shaped,  being  bevelled  at  the  expense 
of  its  lingual  surface,  so  as  to  present  a  sharp  horizontal  cutting  edge,  w^hich, 
before  being  subjected  to  attrition,  presents  three  small  prominent  points  separated 
by  two  slight  notches.  It  is  convex,  smooth,  and  highly  polished  on  its  labial 
surface;  concave  on  its  lingual  surface,  where,  in  the  teeth  of  the  upper  arch,  it  is 
frequently  marked  by  an  inverted  V-shaped  eminence,  situated  near  the  gum. 
This  is  known  as  the  basal  ridge  or  cingulum.  The  neck  is  constricted.  The  root 
is  long,  single,  conical,  transversely  flattened,  thicker  in  front  than  behind,  and 
slightly  grooved  on  either  side  in  the  longitudinal  direction. 

The  upper  incisors  are  larger  and  stronger  than  the  lower,  and  are  directed 
obliquely  downward  and  forward.  The  central  ones  are  larger  than  the  lateral, 
and  their  roots  are  more  rounded. 

The  lower  incisors  are  smaller  than  the  upper:  the  central  ones  are  smaller  than 
the  lateral,  and  are  the  smallest  of  all  the  incisors.  They  are  placed  vertically 
and  are  somewhat  bevelled  in  front,  wdiere  they  have  been  worn  down  by  contact 
with  the  overlapping  edge  of  the  upper  teeth.    The  cingulum  is  absent. 

The  Canine  Teeth  {denies  canini)  are  four  in  number,  two  in  the  upper,  and  two 
in  the  lower  arch,  one  being  placed  laterally  to  each  lateral  incisor.  They  are  larger 
and  stronger  than  the  incisors,  and  their  roots  sink  deeply  into  the  bones,  and 
cause  well-marked  prominences  upon  the  surface. 


1118 


SPLANCHNOLOGY 


The  crown  is  large  and  conical,  very  convex  on  its  labial  surface,  a  little  hollowed 
and  uneven  on  its  lingual  surface,  and  tapering  to  a  blunted  point  or  cusp,  which 
projects  beyond  the  level  of  the  other  teeth.  The  root  is  single,  but  longer  and 
thicker  than  that  of  the  incisors,  conical  in  form,  compressed  laterally,  and  marked 
by  a  slight  groove  on  each  side. 

The  upper  canine  teeth  (popularly  called  eye  teeth)  are  larger  and  longer  than 
the  lower,  and  usually  present  a  distinct  basal  ridge. 

The  lower  canine  teeth  (popularly  called  stomach  teeth)  are  placed  nearer  the 
middle  line  than  the  upper,  so  that  their  summits  correspond  to  the  intervals 
between  the  upper  canines  and  the  lateral  incisors. 

The  Premolars  or  Bicuspid  teeth  (dentes  praemolares)  are  eight  in  number,  four 
in  each  arch.  They  are  situated  lateral  to  and  behind  the  canine  teeth,  and  are 
smaller  and  shorter  than  them. 

The  crown  is  compressed  antero-posteriorly,  and  surmounted  by  two  pyramidal 
eminences  or  cusps,  a  labial  and  a  lingual,  separated  by  a  groove;  hence  their  name 
bicuspid.  Of  the  two  cusps  the  labial  is  the  larger  and  more  prominent.  The 
neck  is  oval.  The  root  is  generally  single,  compressed,  and  presents  in  front  and 
behind  a  deep  groove,  which  indicates  a  tendency  in  the  root  to  become  double. 
The  apex  is  generally  bifid. 

The  upper  premolars  are  larger,  and  present  a  greater  tendency  to  the  division 
of  their  roots  than  the  lower;  this  is  especially  the  case  in  the  first  upper  premolar. 
The  Molar  Teeth  {denies  molares)  are  the  largest  of  the  permanent  set,  and  their 
broad  crowns  are  adapted  for  grinding  and  pounding  the  food.  They  are  twelve 
in  number;  six  in  each  arch,  three  being  placed  posterior  to  each  of  the  second 
premolars. 

The  crown  of  each  is  nearly  cubical  in  form,  convex  on  its  buccal  and  lingual 
surfaces,  flattened  on  its  surfaces  of  contact;  it  is  surmounted  by  four  or  five  tuber- 
cles, or  cusps,  separated  from  each  other  by  a  crucial  depression;  hence  the  molars 
are  sometimes  termed  multicuspids.    The  neck  is  distinct,  large,  and  rounded. 

Upper  Molars. — As  a  rule  the  first  is  the  largest,  and  the  third  the  smallest  of 
the  upper  molars.  The  crown  of  the  first  has  usually  four  tubercles;  that  of  the 
second,  three  or  four;  that  of  the  third,  three.  Each  upper  molar  has  three  roots, 
and  of  these  two  are  buccal  and  nearly  parallel  to  one  another;  the  third  is  lingual 
and  diverges  from  the  others  as  it  runs  upward.  The  roots  of  the  third  molar 
{dens  serotinus  or  wisdom-tooth)  are  more  or  less  fused  together. 

Loiver  Molars. — The  lower  molars  are  larger  than  the  upper.  On  the  crown 
of  the  first  there  are  usually  five  tubercles;  on  those  of  the  second  and  third,  four 

or  five.  Each  lower  molar  has  two  roots,  an 
anterior,  nearly  vertical,  and  a  posterior, 
directed  obliquely  backward;  both  roots  are 
grooved  longitudinally,  indicating  a  tendency 
to  division.  The  two  roots  of  the  third  molar 
{dens  serotinus  or  wisdom  tooth)  are  more  or 
less  united. 

The  Deciduous  Teeth  {denies  decidui;  tem- 
porary or  milk  teeth)  (Fig.  933). — The  decid- 
uous are  smaller  than,  but,  generally  speak- 
ing, resemble  in  form,  the  teeth  which  bear 
the  same  names  in  the  permanent  set.  The 
hinder  of  the  two  molars  is  the  largest  of  all 
the  deciduous  teeth,  and  is  succeeded  by  the 
second  premolar.  The  first  upper  molar  has  only  three  cusps — two  labial,  one 
lingual;  the  second  upper  molar  has  four  cusps.  The  first  lower  molar  has  four 
cusps;  the  second  lower  molar  has  five.    The  roots  of  the  deciduous  molars  are 


Fig.  933. — Deciduous  teeth.     Left  side. 


THE  MOUTH 


1119 


smaller  and   more  divcTgent  than  those   of  the  permanent  molars,  but  in  other 
respects  hear  a  strong  resemblance  to  them. 

Structure  of  the  Teeth. — On  making  a  vertical  section  of  a  tooth  (Fig.  934),  a  cavity  will  be 
found  ill  tlie  inlcrior  oi  the  crown  and  the  centre  of  each  root;  it  opens  by  a  minute  orifice  at 
the  extremity  of  the  latter.  This  is  called  the  pulp  cavity,  and  contains  the  dental  pulp,  a  loose 
connective  tissue  richly  supplied  with  vessels  and  nerves,  which  enter  the  (-avity  lln-ough  the 
small  aperture  at  the  point  of  each  root.  Some  of  the  cells  of  llu;  pulp  ;uo  arranged  as  a  layer 
on  the  wall  of  the  pulp  cavity;  they  are  named  the  odontoblasts  of  Waldeyer,  and  during  the 
development  of  the  tooth,  are  colunmar  in  shape,  but  later  on,  after  the  dentin  is  fully  formed, 
they  become  flattened  and  resemble  osteoblasts.  Each  has  two  fine  processes,  the  outer  one 
passing  into  a  dental  canaliculus,  the  inner  being  continuous  with  the  processes  of  the  connective- 
tissue  cells  of  the  pulp  matrix. 


Fig.  935. — Vertical  section  of  a  molar  tooth. 


Fig.  934. — Vertical  section  of  a  tooth  in  situ.  X  15. 
c  is  placed  in  the  pulp  cavity,  opposite  the  neck  of  the 
tooth;  the  part  above  it  is  the  crown,  that  below  is  the 
root.  1.  Enamel  with  radial  and  concentric  markings. 
2.  Dentin  with  tubulesand  incremental  lines.  3.  Cement 
or  crusta  petrosa,  with  bone  corpuscles.  4.  Dental 
periosteum.    5.  Mandible. 


Croii'i 


Neck 


Boot 


Fig.  936.- 


-  Vertical  section  of  a  premolar  tooth. 
(iSIagmfied  ) 


The  solid  portion  of  the  tooth  consists  of  (1)  the  ivory  or  dentin,  which  forms  the  bulk  of  the 
tooth;  (2)  the  enamel,  which  covers  the  exposed  part  of  the  crown;  and  (3)  a  thin  layer  of  bone, 
the  cement  or  crusta  petrosa,  which  is  disposed  on  the  surface  of  the  root. 

The  dentin  (substantia  eburnea;  ivory)  (Fig.  936)  forms  the  principal  mass  of  a  tooth.  It  is 
a  modification  of  osseous  tissue,  from  which  it  differs,  however,  in  structure.  On  microscopic 
examination  it  is  seen  to  consist  of  a  number  of  minute  wavy  and  branching  tubes,  the  dental 
canaliculi,  imbedded  in  a  dense  homogeneous  substance,  the  matrix. 


1120 


SPLANCHNOLOGY 


Cemen„ 


Interglobular 
spaces 


Dentin 


The  dental  canaliculi  {dentinal  lubules)  (Fig.  937j  are  placed  parallel  with  one  another,  and 
open  at  their  inner  ends  into  the  pulp  cavity.  In  their  course  to  the  periphery  they  present  two 
or  three  curves,  and  are  twisted  on  themselves  in  a  spiral  direction.  These  canaUcuh  vary  in 
direction:  thus  in  a  tooth  of  tlie  mandible  they  are  vertical  in  the  upper  portion  of  the  crown, 
becoming  oblique  and  then  horizontal  in  the  neck  and  upper  part  of  the  root,  while  toward  the 
lower  part  of  the  root  they  are  inclined  downward.  In  their  course  they  divide  and  subdivide 
dichotomously,  and,  especially  in  the  root,  give  off  minute  branches,  which  join  together  in 
loops  in  the  matri.x,  or  end  blindlj'.  Near  the  jieriphery  of  the  dentin,  the  finer  ramifications 
of  the  canaliculi  terminate  imperceptiblj-  by  free  ends.  The  dental  canalicuU  have  definite  walls, 
consisting  of  an  elastic  homogeneous  membrane,  the  dentinal  sheath  of  Neumann,  which  resists 
the  action  of  acids;  they  contain  slender  cylindrical  prolongations  of  the  odontoblasts,  first 
described  by  Tomes,  and  named  Tomes'  fibres  or  dentinal  fibres. 

The  matrix  (interlubular  dentin)  is  translucent,  and  contains  the  chief  part  of  the  earthy 
matter  of  the  dentin.     In  it  are  a  number  of  fine  fibrils,  which  are  continuous  with  the  fibrik 

of  the  dental  pulp.     After   the  earthy  matter  has 

__— — r===s=^^  been  removed  by   steeping   a  tooth  in  weak  acid, 

the  animal  basis  remaining  may  be  torn  into  laminae 
which  run  parallel  with  the  pulp  cavity,  across  the 
direction  of  the  tubes.  A  section  of  dry  dentin  often 
display's  a  series  of  somewhat  parallel  lines — the 
incremental  lines  of  Salter.  These  lines  are  com- 
posed of  imperfectly  calcified  dentin  arranged  in 
layers.  In  consequence  of  the  imperfection  in  the 
calcifying  process,  little  irregular  cavities  are  left, 
termed  interglobular  spaces  (Fig.  937).  Normally 
a  series  of  these  spaces  is  found  toward  the  outer 
surface  of  the  dentin,  where  they  form  a  layer  which 
is  sometimes  known  as  the  granular  layer.  They 
have  received  their  name  from  the  fact  that  they 
are  surrovmded  bj-  minute  nodules  or  globules  of 
dentin.  Other  curved  lines  maj^  be  seen  parallel  to 
the  surface.  These  are  the  lines  of  Schreger,  and 
are  due  to  the  optical  effect  of  simultaneous  cmn^a- 
tme  of  the  dentinal  fibres. 

Chemical  Composition.  —  According  to  BerzeUus 
and  von  Bibra,  dentin  consists  of  28  parts  of  animal 
and  72  parts  of  earth}^  matter.  The  animal  matter 
is  converted  by  boiling  into  gelatin.  The  earthy 
matter  consists  of  phosphate  of  lime,  carbonate  of 
lime,  a  trace  of  fluoride  of  calcimn,  phosphate  of 
magnesium,  and  other  salts. 

The  enamel  (substantia  adaviantiiia)  is  the  hardest 
and  most  compact  part  of  the  tooth,  and  forms  a 
thin  crust  over  the  exposed  part  of  the  crown,  as  far 
as  the  commencement  of  the  root.  It  is  thickest  on 
the  grinding  surface  of  the  crown,  imtil  worn  away 
by  attrition,  and  becomes  thiimer  toward  the  neck. 
It  consists  of  minute  hexagonal  rods  or  columns 
termed  enamel  fibres  or  enamel  prisms  (prismata  adamantina) .  They  he  parallel  with  one 
another,  resting  by  one  extremity  upon  the  dentin,  which  presents  a  nmnber  of  minute  depres- 
sions for  their  reception;  and  forming  the  free  surface  of  the  crown  by  the  other  extremity. 
The  columns  are  directed  vertically  on  the  summit  of  the  cro-mi,  horizontally  at  the  sides;  they 
are  about  4/^  in  diameter,  and  pm-sue  a  more  or  less  wavj^  course.  Each  column  is  a  six-sided 
prism  and  presents  numerous  dark  transverse  shadings;  these  shadings  are  probably  due  to  the 
manner  in  which  the  columns  are  developed  in  successive  stages,  producing  shallow  constric- 
tions, as  will  be  subsequently  explained.  Another  series  of  fines,  having  a  bro'mi  appearance, 
the  parallel  striae  or  colored  lines  of  Retzius,  is  seen  on  section.  According  to  Ebner,  they  are 
produced  by  air  in  the  interjDrismatic  spaces;  others  believe  that  thej^  are  the  result  of  true 
pigmentation. 

Numerous  minute  interstices  intervene  between  the  enamel  fibres  near  their  dentinal  ends, 
a  provision  calculated  to  allow  of  the  permeation  of  fluids  from  the  dental  canalicuh  into  the 
substance  of  the  enamel. 

Chemical  Composition. — ^According  to  von  Bibra,  enamel  consists  of  96.5  per  cent,  of  earthy 
matter,  and  3.5  per  cent  of  animal  matter.  The  earthy  matter  consists  of  phosphate  of  hme, 
with  traces  of  fluoride  of  calcimn,  carbonate  of  hme,  phosphate  of  magnesium,  and  other  salts. 
According  to  Tomes,  the  enamel  contains  the  merest  trace  of  organic  matter. 


Fig.  937. — Transverse  section  of  a  portion  of  the 
root  of  a  canine  tooth.     X  300. 


THE  MOITH  1121 

Tlic  crusta  petrosa  or  cement  {substantia  ossca)  is  disposed  as  a  thin  layer  on  Ihe  roots  of  the 
teeth,  from  the  terniiiiatioii  of  the  enamel  to  the  a])ex  of  each  root,  where  it  is  usually  very  thick. 
In  structure  and  chemical  composition  it  resembles  bone.  It  contains,  sparingly,  the  lacunae 
juid  canaliculi  which  characterize  true  bone;  the  lacunie  i)laced  near  the  surface  receive  the 
canaliculi  radiating  from  the  side  of  the  lacuna-  toward  the  periodontal  membrane;  and  those 
more  deeply  placed  join  with  the  adjacent  dental  canaliculi.  In  the  thicker  jjortions  of  the 
crusta  petrosa,  the  lamelkr  and  Haversian  canals  peculiar  to  bone  are  also  found. 


Ik 
L.E.L. 


M  E. 


Fig.  938. — Sagittal  section  through  the  first  lower  deciduous  molar  of  a  human  embryo  30  mm.  long.  (Rose.) 
X  100.  L.E.L.  Labiodental  lamina,  here  separated  from  the  dental  lamina.  Z.L.  Placed  over  the  shallow  dental 
furrow,  points  to  the  dental  lamina,  which  is  spread  out  below  to  form  the  enamel  germ  of  the  future  tooth.  P.p. 
Bicuspidate  papilla,  capped  by  the  enamel  germ.     Z.S.  Condensed  tissue  forming  dental  sac.     M.E.  Mouth  epitheUum. 

As  age  advances,  the  cement  increases  in  thickness,  and  gives  rise  to  those  bony  growths  or 
e.xostoses  so  common  in  the  teeth  of  the  aged;  the  pulp  cavity  also  becomes  partially  filled  up  by 
a  hard  substance,  intermediate  in  structure  between  dentin  and  bone  {osteodentin,  Owen;  second- 
ary dentin,  Tomes).  It  appears  to  be  formed  by  a  slow  conversion  of  the  dental  pulp,  which 
shrinks,  or  even  disappears. 

Development  of  the  Teeth  (Figs.  938  to  941). — In  describing  the  development  of  the  teeth, 
the  mode  of  formation  of  the  deciduous  teeth  must  fii'st  be  considered,  and  then  that  of  the 
permanent  series. 


L.F. 


Z.L.  ''■^- 


/S.  I^,  ^^^^__t 


L.E.L.~>1 


Fig.  939. — Similar  section  through  the  canine  tooth  of  an  embrj^o  40  mm.  long.     (Rose.)      X  100.     L.F.  Labio- 
dental furrow.     The  other  lettering  as  in  Fig.  938. 

Development  of  the  Deciduous  Teeth. — The  development  of  the  deciduous  teeth  begins 
about  the  sixth  week  of  fetal  hfe  as  a  thickening  of  the  epitheUum  along  the  hne  of  the  future 
jaw,  the  thickening  being  due  to  a  rapid  multiplication  of  the  more  deeply  situated  epithehal 
cells.  As  the  cells  multiply  they  extend  into  the  subjacent  mesoderm,  and  thus  form  a  ridge 
or  strand  of  cells  imbedded  in  mesoderm.  About  the  seventh  week  a  longitudinal  spUtting  or 
cleavage  of  this  strand  of  cells  takes  place,  and  it  becomes  divided  into  two  strands;  the  separa- 
tion begins  in  front  and  extends  laterally,  the  process  occupying  four  or  five  weeks.  Of  the  two 
strands  thus  formed,  the  labial  forms  the  labiodental  lamina;  while  the  other,  the  lingual, 
is  the  ridge  of  cells  in  connection  with  which  the  teeth,  both  deciduous  and  permanent,  are 
developed.  Hence  it  is  known  as  the  dental  lamina  or  common  dental  germ.  It  forms  a  flat 
71 


1122 


SPLANCHNOLOGY 


band  of  cells,  which  grows  into  the  substance  of  the  embryonic  jaw,  at  first  horizontally- 
inward,  and  then,  as  the  teeth  develop,  vertically,  i.  e.,  upward  in  the  upper  jaw,  and 
downward  in  the  lower  jaw.     While  still  maintaining  a  horizontal  direction  it  has  two  edges 


Dental  Jiurow 


Betnains  of  enamel  germ 


Secondary  enamel  germ 


Meckel's  cartilage  — -_i 


—  Enamel  organ 

Dental  papilla 


I     Mandible 


Fig.  940. — Vertical  section  of  the  mandible  of  an  early  human  fetus.      X  25. 


P 


— an  attached  edge,  continuous  with  the  epithelium  lining  the  mouth,  and  a  free  edge,  projecting 
inward,  and  imbedded  in  the  mesodermal  tissue  of  the  embryonic  jaw.  Along  its  hne  of 
attachment  to  the  buccal  epithelium  is  a  shallow  groove,  the  dental  furrow. 

About  the  ninth  week  the  dental  lamina  begins 
to  develop  enlargements  along  its  free  border. 
These  are  ten  in  number  in  each  jaw,  and  each 
corresponds  to  a  future  deciduous  tooth.  They 
consist  of  masses  of  epithelial  eeUs;  and  the  cells 
of  the  deeper  part — that  is,  the  part  farthest  from 
the  margin  of  the  jaw — increase  rapidly  and  spread 
out  in  all  dii-ections.  Each  mass  thus  comes  to 
assume  a  club  shape,  connected  with  the  general 
epithelial  lining  of  the  mouth  by  a  narrow  neck, 
embraced  by  mesoderm.  They  are  now  kno'mi  as 
special  dental  germs.  After  a  time  the  lower  ex- 
panded portion  incUnes  outward,  so  as  to  form  an 
angle  with  the  superficial  constricted  portion,  which 
is  sometimes  known  as  the  neck  of  the  special 
dental  germ.  About  the  tenth  week  the  meso- 
dermal tissue  beneath  these  special  dental  germs 
becomes  differentiated  into  papiUse;  these  grow 
upward,  and  come  in  contact  with  the  epithelial 
cells  of  the  special  dental  germs,  which  become 
folded  over  them  hke  a  hood  or  cap.  There  is, 
then,  at  this  stage  a  papilla  (or  papillae)  which 
has  already  begun  to  assume  somewhat  the  shape 
of  the  crown  of  the  future  tooth,  and  from  which 
the  dentin  and  pulp  of  the  tooth  are  formed,  sur- 
mounted by  a  dome  or  cap  of  epitheUal  cells  from 
which  the  enamel  is  derived. 

In  the  meantime,  while  these  changes  have  been 
going  on,  the  dental  lamina  has  been  extending 
backward  behind  the  special  dental  germ  corre- 
sponding to  the  second  deciduous  molar  tooth, 
and  at  about  the  seventeenth  week  it  presents  an 
enlai'gement,  the  special  dental  germ,  for  the  first 
permanent  molar,  soon  followed  by  the  formation 
of  a  papilla  in  the  mesodermal  tissue  for  the  same  tooth.  This  is  followed,  about  the  sixth 
month  after  birth,  by  a  further  extension  backward  of  the  dental  lamina,  with  the  formation 


ep.sch. -^:'-i^:-': 


'm^- 


Fig.  941. — Longitudinal  section  of  the  lower  part 
of  a  growing  tooth,  showing  the  extension  of  the  layer 
of  adamantoblasts  bej-ond  the  crown  to  mark  off 
the  limit  of  formation  of  the  dentin  of  the  root. 
(Rose.)  ad.  Adamantoblasts,  continuous  below  with 
ep.sch.,  the  epithelial  sheath  of  Hertwig.  d.  Dentin. 
en.  Enamel,    od.  Odontoblasts,    p.  Pulp. 


THE  MOCTIl  1123 

of  another  enlarjj;ciiK'iit  ami  its  corroyi)i)ii(ling  papilla  fur  the  sccoiul  molar.  And  linallj-  the  pro- 
cess is  repeated  for  the  third  molar,  its  papilla  appearing  about  the  fifth  year  of  life. 

After  the  formation  of  the  special  dental  germs,  the  denial  lamina  undergoes  atrophic  changes 
and  becomes  cribriform,  except  on  the  hngual  and  lateral  aspects  of  each  of  the  special  germs 
of  the  temporarj-  teeth,  where  it  imdorgoes  a  local  thickening  forming  the  special  dental  germ 
of  each  of  the  successional  permanent  teeth — i.  e.,  the  ten  anterior  ones  in  each  jaw.  Here  the 
same  process  goes  on  as  has  been  described  in  connection  with  those  of  the  deciduous  teeth: 
that  is,  they  recede  into  the  substance  of  the  gimi  bchiml  the  germs  of  the  deciduous  teeth.  As 
they  recetle  they  become  club-shaped,  form  expansions  at  their  distal  extremities,  and  finally 
meet  papilla\  which  have  been  formed  in  the  mesoderm,  just  in  the  same  manner  as  was  the 
case  in  the  deciduous  teeth.  The  apex  of  each  papilla  indents  the  dental  germ,  which  encloses 
it,  and,  forming  a  cap  for  it,  becomes  converted  into  the  enamel,  while  the  papilla  forms  the 
dentin  and  pulp  of  the  permanent  tooth. 

The  special  dental  germs  consist  at  first  of  rounded  or  j^olyhcdral  epithelial  cells;  after  the 
formation  of  the  papillae,  these  cells  undergo  a  dilTcrentiation  into  three  laj'ers.  Those  which 
are  in  immediate  contact  with  the  papilla  become  elongated,  and  form  a  layer  of  well-marked 
columnar  epithelium  coating  the  papilla.  They  are  the  cells  which  form  the  enamel  fibres, 
and  are  therefore  termed  enamel  cells  or  adamantoblasts.  The  cells  of  the  outer  layer  of  the 
special  dental  germ,  which  are  in  contact  with  the  inner  surface  of  the  dental  sac,  presently  to 
be  described,  are  much  shorter,  cubical  in  form,  and  are  named  the  external  enamel  epithelium. 
All  the  intermediate  romad  cells  of  the  dental  germ  between  these  two  layers  undergo  a  pecuhar 
change.  They  become  stellate  in  shape  and  develop  -processes,  which  unite  to  form  a  net-work 
into  which  fluid  is  secreted;  this  has  the  appearance  of  a  jelly,  and  to  it  the  name  of  enamel  pulp 
is  given.  This  transformed  special  dental  germ  is  now  kno^ii  under  the  name  of  enamel  organ 
(Fig.  940). 

"VMiile  these  changes  are  going  on,  a  sac  is  formed  around  each  enamel  organ  from  the  sur- 
rounding mesodermal  tissue.  This  is  known  as  the  dental  sac,  and  is  a  vascular  membrane 
of  connective  tissue.  It  grows  up  from  below,  and  thus  encloses  the  whole  tooth  germ;  as  it 
grows  it  causes  the  neck  of  the  enamel  organ  to  atrophy  and  disappear;  so  that  all  communi- 
cation between  the  enamel  organ  and  the  superficial  epithelium  is  cut  off.  At  this  stage  there 
are  vascular  papillae  surmoimted  by  caps  of  epithelial  cells,  the  whole  being  smi-oimded  by 
by  membranous  sacs. 

Formation  of  the  Enamel. — The  enamel  is  formed  exclusiveh'  from  the  enamel  ceUs  or  adaman- 
toblasts of  the  special  dental  germ,  either  by  duect  calcification  of  the  columnar  cells,  which 
become  elongated  into  the  hexagonal  rods  of  the  enamel;  or,  as  is  more  generaUj-  beUeved,  as 
a  secretion  from  the  adamantoblasts,  within  which  calcareous  matter  is  subsequenth'  deposited. 

The  process  begins  at  the  apex  of  each  cusp,  at  the  ends  of  the  enamel  cells  in  contact  with 
the  dental  papilla.  Here  a  fine  globular  deposit  takes  place,  being  apparenth'  shed  from  the  end 
of  the  adamantoblasts.  It  is  known  bj^  the  name  of  the  enamel  droplet,  and  resembles  keratin 
in  its  resistance  to  the  action  of  mineral  acids.  This  droplet  then  becomes  fibrous  and  calcifies 
and  forms  the  first  layer  of  the  enamel;  a  second  cboplet  now  appears  and  calcifies,  and  so  on; 
successive  droplets  of  keratin-like  material  are  shed  from  the  adamantoblasts  and  form  successive 
layers  of  enamel,  the  adamantoblasts  gradually  receding  as  each  layer  is  produced,  until  at  the 
termination  of  the  process  thej-  have  almost  disappeared.  The  intermediate  cells  of  the  enamel 
pulp  atrophj'  and  disappear,  so  that  the  newty  formed  calcified  material  and  the  external  enamel 
epitheUum  come  into  apposition.  This  latter  laj^er,  however,  soon  disappears  on  the  emergence 
of  the  tooth  beyond  the  gum.  After  its  disappearance  the  crown  of  the  tooth  is  still  covered 
by  a  distinct  membrane,  which  persists  for  some  time.  This  is  known  as  the  cuticula  dentis,  or 
Nasmytb's  membrane,  and  is  beUeved  to  be  the  last-formed  layer  of  enamel  derived  from  the 
adamantoblasts,  which  has  not  become  calcified.  It  forms  a  horny  layer,  which  maj^  be  separ- 
ated from  the  subjacent  calcified  mass  bj'  the  action  of  strong  acids.  It  is  marked  bj^  the  hexagonal 
impressions  of  the  enamel  prisms,  and,  when  stained  bj'  nitrate  of  silver,  shows  the  characteristic 
appearance  of  epitheUum. 

Formation  of  the  Dentin. — While  these  changes  are  taking  place  in  the  epithehimi  to  form 
the  enamel,  contemporaneous  changes  occm'ring  in  the  differentiated  mesoderm  of  the  dental 
papillae  result  in  the  formation  of  the  dentin.  As  before  stated,  the  first  germs  of  the  dentin  are 
the  papiUs;  corresponding  in  number  to  the  teeth,  formed  from  the  soft  mesodermal  tissue 
which  bounds  the  depressions  containing  the  special  enamel  germs.  The  papillae  grow  upward 
into  the  enamel  germs  and  become  covered  by  them,  both  being  enclosed  in  a  vascular  connective 
tissue,  the  dental  sac,  in  the  manner  above  described.  Each  papilla  then  constitutes  the  forma- 
tive pulp  from  which  the  dentin  and  permanent  pidp  are  developed;  it  consists  of  rounded  cells 
and  is  XQvy  vascular,  and  soon  begins  to  assume  the  shape  of  the  futiu-e  tooth.  The  next  step 
is  the  appearance  of  the  odontoblasts,  which  have  a  relation  to  the  development  of  the  teeth 
similar  to  that  of  the  osteoblasts  to  the  fonnation  of  bone.  Thej-  are  formed  from  the  cells 
of  the  periphery  of  the  papilla — that  is  to  say,  from  the  cells  in  immediate  contact  with  the 
adamantoblasts  of  the  special   dental  germ.      These   cells   become  elongated,  one  end  of  the 


1124  SPLANCHNOLOGY 

elongated  cell  resting  against  the  epithelium  of  the  special  dental  germs,  the  other  being  tapered 
and  oftened  branched.  By  the  direct  transformation  of  tlie  periplieral  ends  of  these  cells,  or 
by  a  secretion  from  them,  a  layer  of  uncalcified  matrix  (predentin)  is  formed  which  caps  the 
cusp  or  cusps,  if  there  are  more  than  one,  of  the  papilla?.  This  matrix  becomes  fibrillated,  and 
in  it  islets  of  calcification  make  their  appearance,  and  coalescing  give  rise  to  a  continuous  layer 
of  calcified  material  which  covers  each  cusp  and  constitutes  the  first  layer  of  dentin.  The  odon- 
toblasts, having  thus  formed  the  first  layer,  retire  toward  the  centre  of  the  papilla,  and,  as  they 
do  so,  produce  successive  layers  of  dentin  from  their  peripheral  extremities — that  is  to  say, 
they  form  the  dentinal  matrix  in  which  calcification  subsequently  takes  place.  As  they  thus 
recede  from  the  periphery  of  the  papilla,  they  leave  behind  them  filamentous  processes  of  cell 
protoplasm,  provided  with  finer  side  processes;  these  are  surrounded  by  calcified  material,  and 
thus  form  the  dental  canahculi,  and,  by  their  side  branches,  the  anastomosing  canaliculi:  the 
processes  of  protoplasm  contained  within  them  constitute  the  dentinal  fibres  (Tomes'  fibres). 
In  this  way  the  entire  thickness  of  the  dentin  is  developed,  each  canahculus  being  completed 
throughout  its  whole  length  by  a  single  odontoblast.  The  central  part  of  the  papilla  does  not 
undergo  calcification,  but  persists  as  the  pulp  of  the  tooth.  In  this  process  of  formation  of  dentin 
it  has  been  shown  that  an  uncalcified  matrix  is  first  developed,  and  that  in  this  matrix  islets  of 
calcification  appear  which  subsequently  blend  together  to  form  a  cap  to  each  cusp :  in  hke  manner 
successive  layers  are  produced,  which  ultimately  become  blended  with  each  other.  In  certain 
places  this  blending  is  not  complete,  portions  of  the  matrix  remaining  uncalcified  between  the 
successive  layers;  this  gives  rise  to  little  spaces,  which  are  the  interglobular  spaces  alluded  to 
above. 

Formation  of  the  Cement. — The  root  of  the  tooth  begins  to  be  formed  shortly  before  the  crown 
emerges  through  the  gum,  but  is  not  completed  until  some  time  afterward.  It  is  produced  by  a 
downgrowth  of  the  epithelium  of  the  dental  germ,  which  extends  almost  as  far  as  the  situation 
of  the  apex  of  the  future  root,  and  determines  the  form  of  this  portion  of  the  tooth.  This  fold 
of  epithelium  is  known  as  the  epithelial  sheath,  and  on  its  papillary  surface  odontoblasts  appear, 
which  in  turn  form  dentin,  so  that  the  dentin  formation  is  identical  in  the  crown  and  root  of  the 
tooth.  After  the  dentin  of  the  root  has  been  developed,  the  vascular  tissues  of  the  dental  sac 
begin  to  break  through  the  epithehal  sheath,  and  spread  over  the  surface  of  the  root  as  a  layer 
of  bone-forming  material.  In  this  osteoblasts  make  their  appearance,  and  the  process  of  ossi- 
fication goes  on  in  identically  the  same  manner  as  in  the  ordinary  intramembranous  ossification 
of  bone.  In  this  way  the  cement  is  formed,  and  consists  of  ordinary  bone  containing  canaUculi 
and  lacunae. 

Formation  of  the  Alveoli. — About  the  fourteenth  week  of  embryonic  life  the  dental  lamina 
becomes  enclosed  in  a  trough  or  groove  of  mesodermal  tissue,  which  at  first  is  common  to  all  the 
dental  germs,  but  subsequently  becomes  divided  by  bony  septa  into  locuH,  each  loculus  con- 
taining the  special  dental  germ  of  a  deciduous  tooth  and  its  corresponding  permanent  tooth. 
After  birth  each  cavity  becomes  subdivided,  so  as  to  form  separate  locuh  (the  future  alveoli) 
for  the  deciduous  tooth  and  its  corresponding  permanent  tooth.  Although  at  one  time  the  whole 
of  the  growing  tooth  is  contained  in  the  cavity  of  the  alveolus,  the  latter  never  completely  encloses 
it,  since  there  is  always  an  aperture  over  the  top  of  the  crown  filled  by  soft  tissue,  by  which  the 
dental  sac  is  connected  with  the  surface  of  the  gum,  and  which  in  the  permanent  teeth  is  caUed 
the  gubernaculum  dentis. 

Development  of  the  Permanent  Teeth. — The  permanent  teeth  as  regards  their  development 
may  be  divided  into  two  sets:  (1)  those  which  replace  the  deciduous  teeth,  and  which,  like  them, 
are  ten  in  number  in  each  jaw:  these  are  the  successional  permanent  teeth;  and  (2)  those  which 
have  no  deciduous  predecessors,  but  are  superadded  distal  to  the  temporary  dental  series.  These 
are  three  in  number  on  either  side  in  each  jaw,  and  are  termed  superadded  permanent  teeth. 
They  are  the  three  molars  of  the  permanent  set,  the  molars  of  the  deciduous  set  being  replaced 
by  the  premolars  of  the  permanent  set.  The  development  of  the  successional  permanent  teeth — 
the  ten  anterior  ones  in  either  jaw — has  akeady  been  indicated.  During  their  development  the 
permanent  teeth,  enclosed  in  their  sacs,  come  to  be  placed  on  the  lingual  side  of  the  deciduous 
teeth  and  more  distant  from  the  margin  of  the  futm-e  gum,  and,  as  already  stated,  are  separated 
from  them  by  bony  partitions.  As  the  crown  of  the  permanent  tooth  grows,  absorption  of  these 
bony  partitions  and  of  the  root  of  the  deciduous  tooth  takes  place,  through  the  agency  of  osteo- 
clasts, which  appear  at  this  time,  and  finally  nothing  but  the  crown  of  the  deciduous  tooth  remains. 
This  is  shed  or  removed,  and  the  permanent  tooth  takes  its  place. 

The  superadded  permanent  teeth  are  developed  in  the  manner  akeady  described,  by  extensions 
backward  of  the  posterior  part  of  the  dental  lamina  in  each  jaw. 

Eruption  of  the  Teeth. — When  the  calcification  of  the  different  tissues  of  the  tooth 
is  sufficiently  advanced  to  enable  it  to  bear  the  pressure  to  which  it  will  be  afterward 
subjected,  eruption  takes  place,  the  tooth  making  its  way  through  tlie  gum.  The 
gum  is  absorbed  by  the  pressure  of  the  crown  of  the  tooth  against  it,  which  is 


THE  MOUTH 


1125 


itself  pressed  up  l)y  the  iiiereasinn'  size  of  the  root.  At  the  same  time  the  septa 
between  the  dental  saes  ossifiy,  and  eonstitute  the  alveoli;  these  firmly  embrace 
the  necks  of  the  teeth,  and  afford  them  a  solid  basis  of  support. 

The  eruption  of  the  deciduous  teeth  commences  about  the  seventh  month  after 
birth,  and  is  com])leted  about  th(>  end  of  the  second  year,  the  teeth  of  the  h)wer 
jaw  precedin<i-  those  of  the  upjxT. 

The  followiiiii',  accordin*;'  to  (\  S.  Tomes,  are  the  most  usual  times  of  eruption: 

Lower  central  incisors 0  to    9  months. 

Upper  incisors 8  to  10  months. 

Lower  lateral  incisors  and  first  molars                  .  15  to  21  months. 

Canines 16  to  20  months. 

Second  molars     .                20  to  24  months. 

There  are,  however,  considerable  variations  in  these  times;  thus,  according 
to  Holt: 

At  the  age  of  1    year   a  child  should  ha^•e     6  teeth. 
"     U  years       "  "  12      " 

a  "9  "  ' '  -  "  \(\         " 


Calcification  of  the  permanent  teeth  proceeds  in  the  following  order  in  the 
lower  jaw  (in  the  upper  jaw  it  takes  place  a  little  later) :  the  first  molar,  soon 
after  birth;  the  central  and  lateral  incisors,  and  the  canine,  about  six  months 
after  birth;  the  premolars,  at  the  second  year,  or  a  little  later;  the  second  molar, 
about  the  end  of  the  second  year;  the  third  molar,  about  the  twelfth  year. 

The  eruption  of  the  permanent  teeth  takes  place  at  the  following  periods,  the 
teeth  of  the  lower  jaw  preceding  those  of  the  upper  by  short  intervals: 


First  molars    . 
Two  central  incisors 
Two  lateral  incisors 
First  premolars 
Second  premolars 
Canines    . 
Second  molars 
Third  molars 


6th  3  ear. 

7th  year. 

8th  year. 

9th  year. 
.  10th  year. 
11th  to  12th  year. 
12th  to  13th  year. 
17th  to  25th  vear. 


Toward  the  sixth  year,  before  the  shedding  of  the  deciduous  teeth  begins,  there 
are  twenty-four  teeth  in  each  jaw,  viz.,  the  ten  deciduous  teeth  and  the  crowns 
of  all  the  permanent  teeth  except  the  third  molars. 

Applied  Anatomy. — As  a  consequence  of  local  irritation  or  of  chronic  digestive  disturbances 
occurring  during  their  eruption,  both  the  deciduous  and  the  permanent  teeth  may  show  defective 
development  or  irregular  transverse  furrowing  and  erosions;  this  is  particularly  the  case  with 
the  incisors.  Quite  distinct  from  and  much  less  common  than  this  is  a  characteristic  malforma- 
tion of  the  two  upper  central  permanent  incisors  seen  in  patients  with  inherited  syphiUs,  and» 
first  described  by  Hutchinson.  Here  there  is  a  crescentic  notch  in  the  anterior  surface  and  at 
the  cutting  edge  of  the  tooth,  which  is  peg-shaped,  stunted,  and  often  also  set  obliquely  in  the 
gum,  pointing  either  inward  or  outward.  Numerous  forms  of  innocent  tumor  arising  from  the 
teeth,  or  from  their  constituent  layers,  have  been  described  under  the  general  name  of  odontoma. 
Infection  of  the  pulp  of  a  tooth  by  bacteria  gaining  access  thereto  in  consequence  of  dental  caries 
gives  rise  to  the  common  and  very  painful  alveolar  abscess;  starting  in  the  apical  space  between 
the  root  of  the  tooth  and  its  alveolar  socket,  the  pus  from  such  an  abscess  may  make  its  way 
into  the  maxillary  antrum,  or  burst  through  the  hard  palate  or  cheek.  A  more  superficial  abscess 
forming  between  the  root  of  a  tooth  and  the  gum  is  known  as  a  guvi-boil. 

The  Tongue  (lingua). — The  tongue  is  the  principal  organ  of  the  sense  of  taste, 
and  an  important  organ  of  speech;  it  also  assists  in  the  mastication  and  deglutition 


112G 


SPLANCHNOLOGY 


of  the  food.  It  is  situated  in  the  floor  of  the  mouth,  within  the  curve  of  the 
body  of  the  mandible. 

Its  Root  (radix  linguae;  base)  (Fig.  906)  is  directed  backward,  and  connected 
with  the  hyoid  bone  by  the  Hyoglossi  and  Genioglossi  muscles  and  the  hyoglossal 
membrane;  with  the  epiglottis  by  three  folds  (glossoe  pi  glottic)  of  mucous  membrane; 
with  the  soft  palate  by  the  glossopalatine  arches;  and  with  the  pharynx  by  the 
Constrictores  pharyngis  superiores  and  the  mucous  membrane. 

Its  Apex  (apex  linguae;  tip),  thin  and  narrow,  is  directed  forward  against  the 
linsual  surfaces  of  the  lower  incisor  teeth. 


Anterior  lingual  gland 

Lingual  nerve 

Art.  profunda  linguce 

Vena  com  n.  liypoglossi 

Longitudinalis  inferior 


.Plica  fimhriatot 
\         Vena  com.  n  liypoglossi 
■Frenulum 


Orifice  of  suhmax.  dud 
Plica  sitblingualis 


Fig.  942. — The  mouth  cavity.    The  apex  of  the  tongue  is  turned  upward,  and  on  the  right  side  a  superficial 
dissection  of  its  under  surface  has  been  made. 


Its  Inferior  Surface  (fades  inferior  linguae;  under  surface)  (Fig.  942)  is  connected 
with  the  mandible  by  the  Genioglossi;  the  mucous  membrane  is  reflected  from  it 
to  the  lingual  surface  of  the  gum  and  on  to  the  floor  of  the  mouth,  where,  in  the 
jniddle  line,  it  is  elevated  into  a  distinct  vertical  fold,  the  frenulum  linguae.  On 
either  side  lateral  to  the  frenulum  is  a  slight  fold  of  the  mucous  membrane,  the 
plica  fimbriata,  the  free  edge  of  which  occasionally  exhibits  a  series  of  fringe-like 
processes. 

The  apex  of  the  tongue,  part  of  the  inferior  surface,  the  sides,  and  dorsum  are 
free. 

The  Dorsum  of  the  Tongue  (dorsum  linguae)  (Fig.  943)  is  convex  and  marked  by 
a  median  sulcus,  which  divides  it  into  symmetrical  halves;  this  sulcus  ends  behind, 
about  2.5  cm.  from  the  root  of  the  organ,  in  a  depression,  the  foramen  cecum, 
from  which  a  shallow  groove,  the  sulcus  terminalis,  runs  lateralward  and  forward 
on  either  side  to  the  margin  of  the  tongue.    The  part  of  the  dorsum  of  the  tongue 


THE  MO r Til 


112- 


in  front  of  this  groove,  forming  about  two-thirds  of  its  surface,  looks  upward,  and 
is  rough  and  covered  with  papilhe;  the  posterior  third  looks  backward,  and  is 
smoother,  and  contains  numerous  muciparous  glands  and  lymph  follicles  {lingual 
tonsil).  The  foramen  cecum  is  the  remains  of  the  ujiper  part  of  the  thyroglossal 
duct  or  diverticulum  from  which  the  thyroid  gland  is  developed;  the  pyramidal 
lobe  of  the  thyroid  gland  indicates  the  jiosition  of  the  lower  part  of  the  duct. 


Phdryiujoixdatine  arch 
Palatine  Imisil 


Glossopalatitie  arch 
Buccinator 


]'allate  papillae 


IstJitmis 
faitciwn 


Fungiform  papillae 


Fig.  943. — The  mouth  cavity.     The  cheeks  have  been  slit  transversely  and  the  tongue  pulled  forward. 


The  Papillae  of  the  Tongue  (Fig.  943)  are  projections  of  the  corium.  They  are 
thickly  distributed  over  the  anterior  two-thirds  of  its  dorsum,  giving  to  this  surface 
its  characteristic  roughness.  The  varieties  of  papillae  met  with  are  the  papillae 
vallatae,  papillae  fungiformes,  papillae  filiformes,  and  papillae  simplices. 

The  papillae  vallatae  (circumvaUate  papillae)  (Fig.  944)  are  of  large  size,  and  vary 
from  eight  to  twelve  in  number.  They  are  situated  on  the  dorsum  of  the  tongue 
immediately  in  front  of  the  foramen  cecum  and  sulcus  terminalis,  forming  a  row 
on  either  side;  the  two  rows  run  backward  and  medialward,  and  meet  in  the  middle 
line,  like  the  limbs  of  the  letter  V  inverted.  Each  papilla  consists  of  a  projection 
of  mucous  membrane  from  1  to  2  mm.  wide,  attached  to  the  bottom  of  a  circular 
depression  of  the  mucous  membrane;  the  margin  of  the  depression  is  elevated  to 
form  a  wall  (vallum),  and  between  this  and  the  papilla  is  a  circular  sulcus  termed 


1128 


SPLANCHNOLOGY 


the  fossa.  The  papiHa  is  shaped  like  a  truncated  cone,  the  smaller  end  being 
directed  downward  and  attached  to  the  tongue,  the  broader  part  or  base  projecting 
a  little  above  the  surface  of  the  tongue  and  being  studded  with  numerous  small 
secondary  papillse  and  covered  by  stratified  squamous  epithelium. 


n    ■-  ^**     u 


Fig.  944. — Vertical  section  of  vallate  papilla  from 
the  calf.  (Engelmann.)  A.  The  papilla.  B.  The 
surrounding  wall.  n.  Nerves,  d.  Duct  of  a  lingual 
gland. 


Artenj  "Yj^  Vein 
Fig.  945. — A  filiform  papilla.   Magnified 


Secondary 
papillce 


Artery 
Vein 


Fig.  946. — Section  of  a  fungiform 
papilla.     Magnified. 


The  papillae  fungiformes  {fungiform  papilloe)  (Fig.  946),  more  numerous  than  the 
preceding,  are  found  chiefly  at  the  sides  and  apex,  but  are  scattered  irregularly 
and  sparingly  over  the  dorsum.  They  are  easil}'  recognized,  among  the  other 
papillse,  by  their  large  size,  rounded  eminences,  and  deep  red  color.     They  are 

narrow  at  their  attachment  to  the  tongue,  but 
broad  and  rounded  at  their  free  extremities,  and 
covered  with  secondary  papillae. 

The  papillae  filiformes  {filiform  or  conical papillcB) 
(Fig.  945)  cover  the  anterior  two-thirds  of  the 
dorsum.  They  are  very  minute,  filiform  in  shape, 
and  arranged  in  lines  parallel  with  the  two  rows  of 
the  papillae  vallatae,  excepting  at  the  apex  of  the 
organ,  where  their  direction  is  transverse.  Pro- 
jecting from  their  apices  are  numerous  filamentous 
processes,  or  secondary  papillse;  these  are  of  a 
whitish  tint,  owing  to  the  thickness  and  density  of 
the  epithelium  of  w^hich  they  are  composed,  and  which  has  here  undergone  a 
peculiar  modification,  the  cells  having  become  cornified  and  elongated  into  dense, 
imbricated,  brush-like  processes.  They  contain  also  a  number  of  elastic  fibres, 
which  render  them  firmer  and  more  elastic  than  the  papillae  of  mucous  membrane 
generally.  The  larger  and  longer  papillse  of  this  group  are  sometimes  termed 
papillae  conicae. 

The  papillae  simplices  are  similar  to  those  of  the  skin,  and  cover  the  whole  of 
the  mucous  membrane  of  the  tongue,  as  well  as  the  larger  papillse.  They  consist 
of  closely  set  microscopic  elevations  of  the  corium,  each  containing  a  capillary 
loop,  covered  by  a  layer  of  epithelium. 

Muscles  of  the  Tongue. — The  tongue  is  divided  into  lateral  halves  by  a  median 
fibrous  septum  which  extends  throughout  its  entire  length  and  is  fixed  below  to  the 
hyoid  bone.  In  either  half  there  are  two  sets  of  muscles,  extrinsic  and  intrinsic; 
the  former  have  their  origins  outside  the  tongue,  the  latter  are  contained  entirely 
within  it. 


"^ 


THE  MOLT II 


1129 


The  extrinsic  muscles  (Fig.  947)  are: 

Geiiioglossus.  Choiulroglossus. 

Hyoglossus.  Styloglossus. 

Glu.ssopalatinu.s.' 


Fig.   94/ . — Extrinsic  muscles  of  the  tongue.     Left  side. 

The  Genioglossus  (Geniohyoglossiis)  is  a  flat  triangular  muscle  close  to  and  par- 
allel with  the  median  plane,  its  apex  corresponding  with  its  point  of  origin  from  the 
mandible,  its  base  with  its  insertion  into  the  tongue  and  hyoid  bone.  It  arises 
by  a  short  tendon  from  the  superior  mental  spine  on  the  inner  surface  of  the  sym- 
physis menti,  immediately  above  the  Geniohyoideus,  and  from  this  point  spreads 
out  in  a  fan-like  form.  The  inferior  fibres  extend  downward,  to  be  attached  by  a 
thin  aponeiu-osis  to  the  upper  part  of  the  body  of  the  hyoid  bone,  a  few  passing 
between  the  Hyoglossus  and  Chondroglossus  to  blend  with  the.Constrictores 
pharyngis;  the  middle  fibres  pass  backward,  and  the  superior  ones  upward  and  for- 
ward, to  enter  the  whole  length  of  the  under  surface  of  the  tongue,  from  the  root 
to  the  apex.  The  muscles  of  opposite  sides  are  separated  at  their  insertions  by  the 
median  fibrous  septum  of  the  tongue;  in  front,  they  are  more  or  less  blended  owing 
to  the  decussation  of  fasciculi  in  the  median  plane. 

The  Hyoglossus,  thin  and  quadrilateral,  arises  from  the  side  of  the  body  and 
from  the  whole  length  of  the  greater  cornu  of  the  hyoid  bone,  and  passes  almost 
vertically  upward  to  enter  the  side  of  the  tongue,  between  the  Styloglossus  and 
Longitudinalis  inferior.  The  fibres  arising  from  the  body  of  the  hyoid  bone  overlap 
those  from  the  greater  cornu. 

Relations. — The  Hj^oglossus  is  in  relation  bj^  its  superficial  surface  with  the  Digastricus,  the 
Stj'lohyoideus,   Styloglossus,   and   Mylohyoideus,   the  submaxillary  gangUon,   the  lingual  and 

1  The  Glossopalatinus  (Palatoglossus) ,  although  one  of  the  muscles  of  the  tongue,  is  more  closely  associated  with  the 
soft  palate  both  in  situation  and  function;  it  has  consequently  been  described  with  the  muscles  of  that  structure 
(p.  1114). 


1130 


SPLANCHNOLOGY 


hypoglossal  nerves,  the  raniiie  vein,  the  sublingual  gland,  llie  deep  portion  of  the  submaxillary 
gland,  and  the  submaxillary  duct.  By  its  deep  surface  it  is  in  relation  with  the  stylohyoid  liga- 
ment, the  Genioglossus,  Longitudinahs  inferior,  and  Constrictor  pharyngis  medius,  the  lingual 
vessels,  and  the  glossopharyngeal  nerve. 

The  Chondroglossus  is  sometimes  described  as  a  part  of  the  Hyoglossus,  but  is 
separated  from  it  by  fibres  of  the  Genioglossus,  which  pass  to  the  side  of  the 
pharynx.  It  is  about  2  cm.  long,  and  arises  from  the  medial  side  and  base  of  the 
lesser  cornu  and  contiguous  portion  of  the  body  of  the  hyoid  bone,  and  passes 
directly  upward  to  blend  with  the  intrinsic  muscular  fibres  of  the  tongue,  between 
the  Hyoglossus  and  Genioglossus. 

A  small  slip  of  muscular  fibres  is  occasionally  found,  arising  from  the  cartilago 
triticea  in  the  lateral  hyothyroid  ligament  and  entering  the  tongue  with  the  hinder- 
most  fibres  of  the  Hyoglossus. 

The  Styloglossus,  the  shortest  and  smallest  of  the  three  styloid  muscles,  arises 
from  the  anterior  and  lateral  surfaces  of  the  styloid  process,  near  its  apex,  and 
from  the  stylomandibular  ligament.  Passing  downward  and  forward  between  the 
internal  and  external  carotid  arteries,  it  divides  upon  the  side  of  the  tongue 
into  two  portions:  one,  longitudinal,  enters  the  side  of  the  tongue  near  its 
dorsal  surface,  blending  wdth  the  fibres  of  the  Longitudinahs  inferior  in  front  of 
the  Hyoglossus;  the  other,  oblique,  overlaps  the  Hyoglossus  and  decussates  with 
its  fibres. 

The  intrinsic  muscles  (Fig.  948)  are : 


Longitudinahs  superior. 
Longitudinahs  inferior. 


Trans  versus. 
Verticalis. 


P^j^j\fvvuuinA| 


.jwiAAnfoWn 


The  Longitudinalis  linguae  superior  {Suxjerior  lingualis)  is  a  thin  stratum  of  oblique 
and  longitudinal   fibres  immediately  underlying  the  mucous  membrane  on  the 

dorsum  of  the  tongue.  It  arises  from 
/  g  the  submucous  fibrous  layer  close  to 

the  epiglottis  and  from  the  median 
fibrous  septum,  and  runs  forward  to 
the  edges  of  the  tongue. 

The  Longitudinalis  linguae  inferior 
{Inferior  lingualis)  is  a  narrow  band 
situated  on  the  under  surface  of  the 
tongue  between  the  Genioglossus  and 
Hyoglossus.  It  extends  from  the  root 
to  the  apex  of  the  tongue:  behind, 
some  of  its  fibres  are  connected  wdth 
the  body  of  the  hyoid  bone;  in  front 
it  blends  with  the  fibres  of  the  Stylo- 
glossus. 

The  Transversus  linguae  ( Transverse 
lingualis)  consists  of  fibres  which  arise 
from  the  median  fibrous  septum  and 
pass  lateralward  to  be  inserted  into 
the  submucous  fibrous  tissue  at  the 
sides  of  the  tongue. 

The  Verticalis  linguae  (Vertical  lin- 
gualis) is  found  only  at  the  borders  of 
Its  fibres  extend  from  the  upper  to  the  under  surface 


J  Mil  I 


Fig.  948. — Coronal  section  of  tongue,  showing  intrinsic 
muscles.  (Altered  from  Krause.)  a.  Lingual  artery,  b. 
Longitudinalis  inferior,  c.  Hyoglossus.  d.  Styloglossus,  e. 
Insertion  of  Transversus.  /.  Longitudinalis  superior,  g. 
Papillse  of  tongue,  h.  Vertical  fibres  of  Genioglossus  inter- 
secting Transversus.     i.  Septum. 


the  forepart  of  the  tongue, 
of  the  organ. 

Applied  Anatomy. — The  median  fibrous  septimi  of  the  tongue  is  very  complete,  so  that  the 
anastomosis  between  the  two  hngual  arteries  is  not  very  free.     This  is  a  point  of  considerable 


THE  MOUTH  1131 

importance  in  connection  with  removal  of  onc-lialf  of  the  tongue  for  cancer,  an  operation  fre- 
quently resorted  to  when  the  disease  is  strictly  confined  to  one  side  of  the  organ.  If  the  nmcous 
membrane  be  divided  exactly  in  the  middle  line,  the  tongue  can  be  split  into  lialves,  without  any 
appreciable  hemorrhage,  and  the  diseased  half  can  then  be  removed. 

Nerves. — The  nniscles  of  the  tongue  ilcscribed  al)ove  arc  supplied  by  the  hypoglossal  nerve. 

Actions.- — The  movements  of  the  tongue,  although  numerous  and  complicated,  may  be  under- 
stood by  carefully  considering  the  direction  of  tlie  fibres  of  its  muscles.  The  Genioglossi,  by  means 
of  their  ]iosterior  fibres,  draw^  the  root  of  the  tongue  forward,  and  protrude  the  apex  from  the 
mouth.  The  anterior  fibres  draw  the  tongue  back  into  the  mouth.  The  two  muscles  acting  in 
their  entire tj-^  draw  the  tongue  downward,  so  as  to  make  its  superior  surface  concave  from  side 
to  side,  forming  a  channel  along  which  fluids  may  pass  toward  the  pharynx,  as  in  sucking.  The 
Hyoglossi  depress  the  tongue,  and  draw  down  its  sides.  The  Styloglossi  draw  the  tongue  upward 
and  backward.  The  Glossoi)alatini  draw  the  root  of  the  tongue  upward.  The  intrinsic  muscles 
are  mainly  concerned  in  altering  the  shape  of  the  tongue,  whereby  it  becomes  shortened,  nar- 
rowed, or  curved  in  different  directions;  thus,  the  Longitudinalis  superior  and  inferior  tend  to 
shorten  the  tongue,  but  the  former,  in  addition,  turn  the  tip  and  sides  upward  so  as  to  render 
the  dorsum  concave,  while  the  latter  pull  the  tip  downward  and  render  the  dorsum  convex. 
The  Transversus  narrows  and  elongates  the  tongue,  and  the  VerticaUs  flattens  and  broadens  it. 
The  complex  arrangement  of  the  muscular  fibres  of  the  tongue,  and  the  various  directions  in 
which  they  run,  give  to  this  organ  the  power  of  assuming  the  forms  necessary  for  the  enuncia- 
tion of  the  different  consonantal  sounds;  and  Macalister  states  "there  is  reason  to  believe  that 
the  musculature  of  the  tongue  varies  in  different  races  owing  to  the  hereditary  practice  and 
habitual  use  of  certain  motions  required  for  enunciating  the  several  vernacular  languages." 

Structure  of  the  Tongue.- — The  tongue  is  partly  invested  by  mucous  membrane  and  a  sub- 
mucous fibrous  layer. 

The  mucous  membrane  (tunica  mucosa  linguae)  differs  in  different  parts.  That  covering  the 
under  surface  of  the  organ  is  thin,  smooth,  and  identical  in  structure  with  that  lining  the  rest 
of  the  oral  cavity.  The  mucous  membrane  of  the  dorsum  of  the  tongue  behind  the  foramen 
cecum  and  sulcus  terminahs  is  thick  and  freely  movable  over  the  subjacent  parts.  It  contains 
a  large  number  of  lymphoid  folhcles,  which  together  constitute  what  is  sometimes  termed  the 
lingual  tonsil.  Each  follicle  forms  a  rounded  eminence,  the  centre  of  which  is  perforated  by  a 
minute  orifice  leading  into  a  funnel-shaped  cavity  or  recess;  around  this  recess  are  grouped 
nmnerous  oval  or  rounded  nodules  of  lymphoid  tissue,  each  enveloped  by  a  capsule  derived  from 
the  submucosa,  while  opening  into  the  bottom  of  the  recesses  are  also  seen  the  ducts  of  mucous 
glands.  The  mucous  membrane  on  the  anterior  part  of  the  dorsum  of  the  tongue  is  thin,  inti- 
mately adherent  to  the  muscular  tissue,  and  presents  numerous  minute  surface  eminences,  the 
papillae  of  the  tongue.  It  consists  of  a  layer  of  connective  tissue,  the  corium  or  mucosa,  covered 
with  epithelium. 

The  epithelium  is  of  the  stratified  squamous  variety,  similar  to  but  much  thinner  than  that 
of  the  skin:  and  each  papilla  has  a  separate  investment  from  root  to  summit.  The  deepest  cells 
may  sometimes  be  detached  as  a  separate  layer,  corresponding  to  the  rete  mucosum,  but  they 
never  contain  coloring  matter. 

The  corium  consists  of  a  dense  felt-work  of  fibrous  connective  tissue,  with  numerous  elastic 
fibres,  fijmly  connected  with  the  fibrous  tissue  forming  the  septa  between  the  muscular  bimdles 
of  the  tongue.  It  contains  the  ramifications  of  the  numerous  vessels  and  nerves  from  which 
the  papillae  are  suppHed,  large  plexuses  of  lymphatic  vessels,  and  the  glands  of  the  tongue. 

Structure  of  the  Papillce. — The  papillse  apparently  resemble  in  structure  those  of  the  cutis, 
consisting  of  cone-shaped  projections  of  connective  tissue,  covered  with  a  thick  layer  of  stratified 
squamous  epithelium,  and  containing  one  or  more  capillary  loops  among  which  nerves  are  dis- 
tributed in  great  abundance.  If  the  epitheliima  be  removed,  it  will  be  found  that  they  are  not 
simple  elevations  like  the  papiUse  of  the  skin,  for  the  surface  of  each  is  studded  with  minute 
conical  processes  which  form  secondary  papillse.  In  the  papillae  vallatae,  the  nerves  are  numer- 
ous and  of  large  size;  in  the  papillae  fungiformes  they  are  also  numerous,  and  end  in  a  plexiform 
net-work,  from  which  brush-like  branches  proceed;  in  the  papillae  filiformes,  their  mode  of 
termination  is  uncertain. 

Glands  of  the  Tongue. — The  tongue  is  provided  with  mucous  and  serous  glands. 

The  mucous  glands  are  similar  in  structure  to  the  labial  and  buccal  glands.  They  are  foimd 
especially  at  the  back  part  behind  the  vallate  papiUse,  but  are  also  present  at  the  apex  and  mar- 
ginal parts.  In  this  connection  the  anterior  Ungual  glands  (Blandin  or  Nuhn)  requii-e  special 
notice.  They  are  situated  on  the  under  surface  of  the  apex  of  the  tongue  (Fig.  942),  one  on  either 
side  of  the  frenulum,  where  they  are  covered  by  a  fasciculus  of  muscular  fibres  derived  from  the 
Styloglossus  and  Longitudinalis  inferior.  They  are  from  12  to  25  mm.  long,  and  about  8  mm. 
broad,  and  each  opens  by  three  or  fovu-  ducts  on  the  under  surface  of  the  apex. 

The  serous  glands  occur  only  at  the  back  of  the  tdngue  in  the  neighborhood  of  the  taste-buds, 
their  ducts  opening  for  the  most  part  into  the  fossae  of  the  vallate  papillse.  These  glands  are 
racemose,  the  duct  of  each  branching  into  several  minute  ducts,  which  end  in  alveoli,  lined  by 


1132 


SPLANCHNOLOGY 


a  single  laj'^cr  of  more  or  less  columnar  epithelium.  Their  secretion  is  of  a  watery  nature,  and 
probably  assists  in  the  distribution  of  the  substance  to  be  tasted  over  the  taste  area.     (Ebner.) 

The  septum  consists  of  a  vertical  layer  of  fibrous  tissue,  extending  throughout  the  entire 
length  of  the  median  plane  of  the  tongue,  though  not  quite  reaching  the  dorsum.  It  is  thicker 
behind  than  in  front,  and  occasionally  contains  a  small  fibrocartilage,  about  6  mm.  in  length. 
It  is  well  disi)layed  by  making  a  vertical  section  across  the  organ. 

The  hyoglossal  membrane  is  a  strong  fibrous  lamina,  which  connects  the  under  surface  of 
the  root  of  the  tongue  to  the  body  of  the  hyoid  bone.  This  membrane  receives,  in  front,  some 
of  the  fibres  of  the  Genioglossi. 

Taste-buds,  the  end-organs  of  the  gustatory  sense,  are  scattered  over  the  mucous  membrane 
of  the  mouth  and  tongue  at  irregular  intervals.  They  occur  especially  in  the  sides  of  the  vallate 
papilla*.  In  the  rabbit  there  is  a  localized  area  at  the  side  of  the  base  of  the  tongue,  the  papilla 
f  oliata,  in  which  they  are  especially  abundant  (Fig.  949) .  They  are  described  under  the  organs 
of  the  senses  (page  1007). 


Fig.  949. — ^Vertical  section  of  papilla  foliata  of  the  rabbit,  passing  across  the  folia.  (Ranvier.)  a.  Serous  gland. 
g.  Gustatory  calyculus.  n.  Nerve  bundles,  p.  Central  lamina  of  corium.  p'.  Lateral  lamina,  z.  Section  across  a 
sinus-like  vein,  which  traverses  the  whole  length  of  the  folium. 


Vessels  and  Nerves. — The  main  artery  of  the  tongue  is  the  Ungual  branch  of  the  external 
carotid,  but  the  external  maxillary  and  ascending  pharyngeal  also  give  branches  to  it.  The 
veins  open  into  the  internal  jugular. 

The  lymphatics  of  the  tongue  have  been  described  on  page  778. 

The  sensory  nerves  of  the  tongue  are:  (1)  the  lingual  branch  of  the  mandibular,  w^hich  is. 
distributed  to  the  papillae  at  the  forepart  and  sides  of  the  tongue,  and  forms  the  nerve  of  ordinary 
sensibility  for  its  anterior  two-thirds;  (2)  the  chorda  tympani  branch  of  the  facial,  which  rims 
in  the  sheath  of  the  lingual,  and  is  generally  regarded  as  the  nerve  of  taste  for  the  anterior  two- 
thirds;  this  nerve  is  a  continuation  of  the  sensory  root  of  the  facial  (nervus  intermedius) ;  (3)  the 
lingual  branch  of  the  glossopharyngeal,  which  is  distributed  to  the  mucous  membrane  at  the 
base  and  sides  of  the  tongue,  and  to  the  papillae  vaUatae,  and  which  supplies  both  gustatory 
filaments  and  fibres  of  general  sensation  to  this  region;  (4)  the  superior  laryngeal,  which  sends 
some  fine  branches  to  the  root  near  the  epiglottis. 

Applied  Anatomy. — The  diseases  to  which  the  tongue  is  liable  are  numerous,  and  any  or  all  of 
the  structures  of  which  it  is  composed — muscles,  connective  tissue,  mucous  membrane,  glands, 
vessels,  nerves,  and  lymphatics — may  be  the  seat  of  morbid  changes.  It  is  not  often  the  seat 
of  congenital  defects,  though  a  few  cases  of  vertical  cleft  have  been  recorded,  and  it  is  occasionally, 
though  much  more  rarely  than  is  commonly  supposed,  the  seat  of  "tongue-tie,"  from  shortness 
of  the  frenulum. 

There  is  one  condition  which  may  be  regarded  as  congenital,  the  so-called  macroglossia,  though 
sometimes  it  does  not  evidence  itself  vmtil  a  year  or  two  after  birth.  This  is  an  enlargement 
of  the  tongue  which  is  due  primarily  to  a  dilatation  of  the  lymph  channels  and  a  greatly  increased 
development  of  the  lymphatic  tissue  throughout  the  organ.  This  is  often  aggravated  by  inflam- 
matory changes  induced  by  inj  ury  or  exposure,  and  the  tongue  may  assume  enormous  dimensions 
and  hang  out  of  the  mouth,  giving  the  child  an  imbecile  expression.  The  treatment  consists  in 
excising  a  V-shaped  portion  and  bringing  the  cut  surfaces  together  with  deeply  placed  sutures. 

Acute  inflammation  of  the  tongue;  which  may  be  caused  by  injury  and  the  introduction  of 
some  septic  or  irritating  matter,  is  attended  by  great  swelling  from  infiltration  of  its  connective 


THE  MOUTH  1133 

tissue,  which  is  in  considerable  quantity.  This  renders  the  patient  incapable  of  swallowing  or 
speaking,  and  may  seriouslj'  impede  respiration.  It  may  run  on  to  suppuration,  and  the  forma- 
tion of  an  acute  abscess. 

In  all  ages  the  mucous  membrane  of  the  tongue  has  received  much  sedulous  consideration  in 
disease,  and  it  is  certain  that  the  amoimt  and  the  distribution  of  the  "fur"  with  which  it  may 
be  co\-ere(l  often  give  valuable  help  in  diagnosis.  The  fur  consists  of  proliferating  or  desquamated 
epitliehum,  bound  up  with  inspissated  nuicus,  the  debris  of  food,  and  bacteria  of  all  sorts.  The 
mucous  membrane  of  the  tongue  may  become  chronically  inflamed,  and  presents  different  appear- 
ances in  the  various  stages  of  the  disease,  to  which  the  terms  leucoplakia  and  psoriasis  lingua; 
have  been  given.     They  are  usually  the  result  of  syphilis. 

The  tongue  is  frequently  the  seat  of  ulceration,  which  may  arise  from  many  causes,  as  from 
the  irritation  of  jagged  teeth,  dyspepsia,  tuberculosis,  syphilis,  and  cancer.  Of  these  the  can- 
cerous ulcer  is  the  most  important  and  also  the  most  common.  The  variety  is  the  squamous 
epithelioma,  which  soon  develops  into  an  ulcer  with  an  indurated  edge.  It  causes  great  pain, 
which  speedily  extends  to  all  parts  supplied  with  sensation  by  the  trigeminal  nerve,  especially 
to  the  region  of  the  ear  (auriculotemporal  nerve). 

Cancer  of  the  tongue  may  necessitate  removal  of  a  part  or  the  whole  of  the  organ,  and  many 
different  methods  have  been  adopted  for  its  excision.  It  may  be  removed  from  the  mouth  by 
the  scissors;  this  is  usually  knoNNTi  as  Whitehead's  method.  The  mouth  is  widely  opened  with 
a  gag,  the  tongue  transfixed  with  a  stout  silk  ligature,  by  which  to  hold  and  make  traction  on  it; 
the  reflection  of  mucous  membrane  from  the  tongue  to  the  jaw,  and  the  insertion  of  the  Genio- 
glossus,  are  first  divided  with  a  pair  of  curved,  blunt-pointed  scissors.  The  Glossopalatinus  is 
also  divided.  The  tongue  can  now  be  pulled  well  out  of  the  mouth.  The  base  of  the  tongue  is  cut 
through  by  a  series  of  short  snips,  each  bleeding  vessel  being  dealt  with  as  soon  as  divided,  mitil 
the  situation  of  the  main  arterj^  is  reached.  The  remaining  undivided  portion  of  tissue  is  to  be 
seized  with  a  pair  of  Wells'  forceps,  the  tongue  removed,  and  the  vessel  secm-ed.  In  the  event 
of  the  artery  being  accidentally  injm-ed,  hemorrhage  can  be  at  once  controlled  by  passing  the 
forefinger  over  the  tongue  till  it  touches  the  epiglottis,  and  then  tm-ning  it  toward  the  side  on 
which  the  artery  is  to  be  compressed,  and  pushing  it  forcibly  against  the  jaw  (Heath).  In  cases 
where  the  disease  is  confined  to  one  side  of  the  tongue,  this  operation  va&y  be  modified  by  spHtting 
the  tongue  down  the  centre  and  removing  only  the  affected  half. 

In  cases  where  the  submaxillary  lymph  glands  are  involved,  Kocher's  operation  should  be 
resorted  to.  Having  performed  a  preliminary  tracheotomy,  Kocher  removes  the  tongue  from 
the  neck  by  an  incision  from  near  the  lobule  of  the  am-icula,  down  the  anterior  border  of  the 
Sternocleidomastoideus  to  the  level  of  the  greater  cornu  of  the  hyoid  bone,  then  forward  to  the 
body  of  the  hj'oid  bone,  and  upward  to  near  the  symphysis  menti.  The  hngual  artery  is  now- 
secured,  and  by  a  careful  dissection  the  submaxillary  lymph  glands  and  the  tongue  are  removed. 
If  the  l}Tnph  glands  in  the  submaxillary  region  are  in  any  way  affected,  an  extensive  dissection 
of  these  will  be  required  if  there  is  any  chance  of  eradicating  the  disease,  and  for  this  piu-pose 
it  will  be  found  necessary  to  remove  the  submaxillary  sahvary  gland. 

The  more  recent  operations  aim  at,  first,  clearing  the  neck  thoroughly  of  affected  glands, 
both  in  the  submaxillary  region  and  along  the  carotid  sheath,  and  secondly,  removal  of  the 
tongue  from  within  the  mouth,  leaving  if  possible  the  mucous  membrane  of  the  floor  of  the 
mouth  intact,  so  as  to  avoid  soiling  the  large  wound  in  the  neck  by  discharges  from  the  mouth. 

The  Salivary  Glands  (Fig.  952). — Three  large  pairs  of  salivary  glands  communi- 
cate with  the  mouth,  and  pour  their  secretion  into  its  cavity;  they  are  the  parotid, 
submaxillary,  and  sublingual. 

Parotid  Gland  {cjlandidae  parotis). — The  parotid  gland  (Figs.  950,  951),  the  largest 
of  the  three,  varies  in  weight  from  14  to  28  gm.  It  lies  upon  the  side  of  the  face, 
immediately  below  and  in  front  of  the  external  ear.  The  main  portion  of  the  gland 
is  superficial,  somewhat  flattened  and  quadrilateral  in  form,  and  is  placed  between 
the  ramus  of  the  mandible  in  front  and  the  mastoid  process  and  Sternocleido- 
mastoideus behind,  overlapping,  however,  both  boundaries.  Above,  it  is  broad 
and  reaches  nearly  to  the  zygomatic  arch;  below,  it  tapers  somewhat  to  about 
the  level  of  a  line  joining  the  tip  of  the  mastoid  process  to  the  angle  of  the  mandible. 
The  remainder  of  the  gland  is  irregularly  wedge-shaped,  and  extends  deeply 
inward  toward  the  pharyngeal  wall. 

The  gland  is  enclosed  within  a  capsule  continuous  with  the  deep  cervical  fascia ; 
the  layer  covering  the  superficial  surface  is  dense  and  closely  adherent  to  the 
gland;  a  portion  of  the  fascia,  attached  to  the  styloid  process  and  the  angle  of  the 
mandible,  is  thickened  to  form  the  stylomandibular  ligament  which  intervenes 
between  the  parotid  and  submaxillary  glands. 


1134 


SPLANCHNOLOGY 


The  anterior  surface  of  the  gland  is  moulded  on  the  posterior  border  of  the 
ramus  of  the  mandible,  clothed  by  the  Pterygoideus  internus  and  Masseter.  The 
inner  lip  of  the  groove  dips,  for  a  short  distance,  between  the  two  Pterygoid  muscles, 


Superficial  temporal  an. 


Parotid  dud 


Portion  in  front  of  styloid  pr 

Impression  for  styloid  process 

Ext.  carotid  art 


Posterior  facial  vein 


Impression  for  ext.  acoustic 
vieatus 


Portion  behind  styloid  process 

Impression  for  mastoid  pro- 
^iJ  cess  and  Sternocleidomas- 
"*'  ioideiis 

Impression  for  Digastricus 


Fig.  950. — Right  parotid  gland.     Posterior  and  deep  aspects. 


while  the  outer  lip  extends  for  some  distance  over  the  superficial  surface  of  the 
Masseter;  a  small  portion  of  this  lip  immediately  below  the  zygomatic  arch  is 
usually  detached,  and  is  named  the  accessory  part  {soda  forotidis)  of  the  gland. 


Superfic.  temp,  artery 
Int.  max.  artery 

Portion  in  front  of  styloid 
process 
Portion  behind  styloid 
process 

Impression  for  styloid 
process 


'  ja External  carotid  artery 


Posterior  facial  vein 


Fig.  951. — Right  parotid  gland.     Deep  and  anterior  aspects. 

The  posterior  surface  is  grooved  longitudinally  and  abuts  against  the  external 
acoustic  meatus,  the  mastoid  process,  and  the  anterior  border  of  the  Sterno- 
cleidomastoideus . 


THE  MOUTH  1135 

The  superficial  surface,  slightly  lobulated,  is  covered  by  the  integument,  the 
superficial  fascia  containing  the  facial  branches  of  the  great  auricular  nerve  and 
some  small  lymph  glands,  and  the  fascia  which  forms  the  capsule  of  the  gland. 

The  deep  surface  extends  inward  by  means  of  two  processes,  one  of  which  lies 
on  the  Digastricus,  styloid  process,  and  the  styloid  group  of  muscles,  and  projects 
under  the  mastoid  process  and  Sternocleidomastoideus;  the  other  is  situated  in 
front  of  the  styloid  process,  and  sometimes  passes  into  the  posterior  part  of  the 
mandibular  fossa  behind  the  temporomandibular  joint.  The  deep  surface  is  in 
contact  with  the  internal  and  external  carotid  arteries,  the  internal  jugular  vein, 
and  the  vagus  and  glossopharyngeal  nerves. 

The  gland  is  separated  from  the  pharyngeal  wall  by  some  loose  connective 
tissue. 

Structures  within  the  Gland. — The  external  carotid  artery  lies  at  first  on  the  deep 
surface,  and  then  in  the  substance  of  the  gland.  The  artery  gives  oft'  its  posterior 
auricular  branch  which  emerges  from  the  gland  behind;  it  then  divides  into  its 
terminal  branches,  the  internal  maxillary  and  superficial  temporal;  the  former  runs 
forward  deep  to  the  neck  of  the  mandible;  the  latter  runs  upward  across  the  zygo- 
matic arch  and  gives  off  its  transverse  facial  branch  which  emerges  from  the  front 
of  the  gland.  Superficial  to  the  arteries  are  the  superficial  temporal  and  internal 
maxillary  wins,  uniting  to  form  the  posterior  facial  vein ;  in  the  lower  part  of  the 
gland  this  vein  splits  into  anterior  and  posterior  divisions.  The  anterior  division 
emerges  from  the  gland  and  unites  with  the  anterior  facial  to  form  the  common 
facial  vein;  the  posterior  unites  in  the  gland  with  the  posterior  auricular  to  form 
the  external  jugular  vein.  On  a  still  more  superficial  plane  is  the  facial  nerve,  the 
branches  of  which  emerge  from  the  borders  of  the  gland.  Branches  of  the  great 
auricular  nerve  pierce  the  gland  to  join  the  facial,  while  the  auriculotemporal  nerve 
issues  from  the  upper  part  of  the  gland. 

The  parotid  duct  {ductus  parotideus;  Stensen's  duct)  is  about  7  cm.  long.  It 
begins  by  numerous  branches  from  the  anterior  part  of  the  gland,  crosses  the  Masse- 
ter,  and  at  the  anterior  border  of  this  muscle  turns  inward  nearly  at  a  right  angle, 
passes  through  the  corpus  adiposum  of  the  cheek  and  pierces  the  Buccinator;  it 
then  runs  for  a  short  distance  obliquely  forward  between  the  Buccinator  and  mucous 
membrane  of  the  mouth,  and  opens  upon  the  oral  surface  of  the  cheek  by  a  small 
orifice,  opposite  the  second  upper  molar  tooth.  While  crossing  the  Masseter, 
it  receives  the  duct  of  the  accessory  portion;  in  this  position  it  lies  between  the 
branches  of  the  facial  nerve;  the  accessor}^  part  of  the  gland  and  the  transverse 
facial  artery  are  above  it. 

Structure. — The  parotid  duct  is  dense,  its  wall  being  of  considerable  thickness;  its  canal  is 
about  the  size  of  a  crow-quill,  but  at  its  orifice  on  the  oral  surface  of  the  cheek  its  lumen  is 
greatly  reduced  in  size.  It  consists  of  a  thick  external  fibrous  coat  which  contains  contractile 
fibres,  and  of  an  internal  or  mucous  coat  lined  with  short  columnar  epithelium. 

Vessels  and  Nerves. — The  arteries  supplying  the  parotid  gland  are  derived  from  the  external 
carotid,  and  from  the  branches  given  off  by  that  vessel  in  or  near  its  substance.  The  veins 
empty  themselves  into  the  external  jugular,  through  some  of  its  tributaries.  The  lymphatic 
end  in  the  superficial  and  deep  cervical  lymph  glands,  passing  in  their  course  through  two  of 
three  glands,  placed  on  the  surface  and  in  the  substance  of  the  parotid.  The  nerves  are  derived 
from  the  plexus  of  the  sjmapathetic  on  the  external  carotid  artery,  the  facial,  the  auriculotem- 
poral, and  the  great  auricular  nerves.  It  is  probable  that  the  branch  from  the  auriculotemporal 
nerve  is  derived  from  the  glossopharyngeal  through  the  otic  gangUon.  At  all  events,  in  some  of 
the  lower  animals  this  has  been  proved  experimentally  to  be  the  case. 

Submaxillary  Gland  (glandtda  suhmaxillaris) . — The  submaxillary  gland  (Fig. 
952)  is  irregular  in  form  and  about  the  size  of  a  walnut.  A  considerable  part  of 
it  is  situated  in  the  submaxillary  triangle,  reaching  forward  to  the  anterior  belly 
of  the  Digastricus  and  backward  to  the  stylomandibular  ligament,  which, inter- 
venes between  it  and  the  parotid  gland.    Above,  it  extends  under  cover  of  the 


1136 


SPLANCHNOLOGY 


body  of  the  mandible;  below,  it  usually  overlaps  the  intermediate  tendon  of 
the  Digastricus  and  the  insertion  of  the  Stylohyoideus,  while  from  its  deep  surface 
a  tongue-like  deep  process  extends  forward  above  the  ]\Iylohyoideus  muscle. 

Its  superficial  surface  consists  of  an  upper  and  a  lower  part.  The  upper  part 
is  directed  outward,  and  lies  partly  against  the  submaxillary  depression  on  the 
inner  surface  of  the  body  of  the  mandible,  and  partly  on  the  Pterygoideus  internus. 
The  lower  part  is  directed  downward  and  outward,  and  is  covered  by  the  skin, 
superficial  fascia,  Platysma,  and  deep  cervical  fascia;  it  is  crossed  by  the  anterior 
facial  vein  and  by  filaments  of  the  facial  nerve;  in  contact  with  it,  near  the  mandible, 
are  the  submaxillary  lymph  glands. 


Opening  of  parotid 
duct 
—  Suhmaxillary  duct 


Anterior  facial  vein 


Fig.  952. — Dissection,  showing  salivary  glands  of  right  side. 

The  deep  surface  is  in  relation  with  the  Mylohyoideus,  Hyoglossus,  Styloglossus, 
Stylohyoideus,  and  posterior  belly  of  the  Digastricus;  in  contact  with  it  are  the 
mylohyoid  nerve  and  the  mylohyoid  and  submental  vessels. 

The  external  maxillary  artery  is  imbedded  in  a  groove  in  the  posterior  border 
of  the  gland. 

The  deep  process  of  the  gland  extends  forward  between  the  jMylohyoideus 
below  and  externally,  and  the  Hyoglossus  and  Styloglossus  internally;  above 
it,  is  the  lingual  nerve  and  submaxillary  ganglion ;  below  it,  the  hypoglossal  nerve 
and  its  accompanying  vein. 

The  submaxillary  duct  {ductus  suhmaxillaris;  Wharton''s  duct)  is  about  5  cm.  long, 
and  its  wall  is  much  thinner  than  that  of  the  parotid  duct.  It  begins  by  numerous 
branches  from  the  deep  surface  of  the  gland,  and  runs  forward  between  the  jMylo- 
hyoideus and  the  Hyoglossus  and  Genioglossus,  then  between  the  sublingual 
gland  and  the  Genioglossus,  and  opens  by  a  narrow  orifice  on  the  summit  of  a  small 
papilla,  at  the  side  of  the  frenulum  linguae.    On  the  Hyoglossus  it  lies  between  the 


THE  MOUTH  1137 

lin.nual  and  li\  j)()i;i()s.sal  nerves,  hut  at  tlii>  anterior  border  of  the  muscle  it  is  crossed 
laterally  by  the  Jinuual  ntT\e;  the  terminal  branches  of  the  lingual  nerve  ascend 
on  its  m(Mlial  side. 

Vessels  and  Nerves.  —'I'he  arteries  supplying  the  submaxillary  gland  are  branches  of  the 
external  maxillary  and  lingual,  its  veins  follow  the  course  of  the  arteries.  The  nerves  are 
deri\ed  from  the  submaxillary  ganglion,  through  wliich  it  receives  filaments  from  the  chorda 
tympani  of  the  facial  nerve  and  the  lingual  branch  of  the  mandibular,  sometimes  from  the 
mylohyoid  branch  of  the  inferior  alveolar,  and  from  the  sympathetic. 

Sublingual  Gland  (glundula  sublingualis) . — The  sublingual  gland  (Fig.  952)  is  the 
smallest  of  the  three  glands.  It  is  situated  beneath  the  mucous  membrane  of 
the  floor  of  the  mouth,  at  the  side  of  the  fremdum  linguae,  in  contact  with  the 
sublingual  depression  on  the  inner  surface  of  the  mandible,  close  to  the  symphysis. 
It  is  narrow,  flattened,  shaped  somewhat  like  an  almond,  and  weighs  nearly  2  gm. 
It  is  in  relation,  above,  with  the  mucous  membrane;  beloic,  with  the  IMylohyoideus; 
in  front,  with  its  fellow  of  the  opposite  side;  behind,  with  the  deep  part  of  the  sub- 
maxillary gland;  laterally,  with  the  mandible;  and  medially,  with  the  Genioglossus, 
from  which  it  is  separated  by  the  lingual  nerve  and  the  submaxillary  duct.  Its 
excretory  ducts  are  from  eight  to  twenty 'in  number.  Of  the  smaller  sublingual 
ducts  {dnds  of  Rivinus),  some  join  the  submaxillary  duct;  others  open  separately 
into  the  mouth,  on  the  elevaterd  crest  of  mucous  membrane  {plica  sublingualis), 
caused  b}-  the  projection  of  the  gland,  on  either  side  of  the  frenulum  linguae.  One 
or  more  join  to  form  the  larger  sublingual  duct  {duct  of  Bartholin),  which  opens  into 
the  submaxillary  duct. 

Vessels  and  Nerves. — The  subungual  gland  is  supplied  with  blood  from  the  sublingual  and 
submental  arteries.  Its  nerves  are  derived  from  the  lingual,  the  chorda  tympani,  and  the 
sympathetic. 

Structure  of  the  Salivary  Glands. — The  salivary  glands  are  compound  racemose  glands, 
consisting  of  nvmierous  lobes,  which  are  made  up  of  smaller  lobules,  connected  together  by 
dense  areolar  tissue,  vessels,  and  ducts.  Each  lobule  consists  of  the  ramifications  of  a  single 
duct,  the  branches  ending  in  dilated  ends  or  alveoli  on  which  the  capillaries  are  distributed. 
The  alveoli  are  enclosed  by  a  basement-membrane,  which  is  continuous  with  the  membrana 
propria  of  the  duct  and  consists  of  a  net-work  of  branched  and  flattened  nucleated  cells. 

The  alveoli  of  the  salivary  glands  are  of  two  kinds,  which  differ  in  the  appearance  of  their 
secreting  cells,  in  their  size,  and  in  the  nature  of  their  secretion.  (1)  The  mucous  variety  secretes 
a  viscid  fluid,  which  contains  mucin;  (2)  the  serous  variety  secretes  a  thinner  and  more  watery 
fluid.  The  subhngual  gland  consists  of  mucous,  the  parotid  of  serous  alveoli.  The  submaxillary 
contains  both  mucous  and  serous  alveoli,  the  latter,  however,  preponderating. 

The  cells  in  the  mucous  alveoli  are  columnar  in  shape.  In  the  fresh  condition  they  contain 
large  granules  of  mucinogen.  In  hardened  preparations  a  delicate  protoplasmic  net-work  is  seen, 
and  the  cells  are  clear  and  transparent.  The  nucleus  is  usually  situated  near  the  basement- 
membrane,  and  is  flattened. 

In  some  alveoli  are  seen  pecuHar  crescentic  bodies,  lying  between  the  cells  ,and  the  mem- 
brana propria.  They  are  termed  the  crescents  of  Gianuzzi,  or  the  demilunes  of  Heidenhain 
(Fig.  953),  and  are  composed  of  polyhedral  granular  cells,  which  Heidenhain  regards  as  young 
epithehal  ceUs  destined  to  supply  the  place  of  those  sahvary  cells  which  have  undergone 
disintegration.  This  view,  however,  is  not  accepted  by  Klein.  Fine  canaUculi  pass  between 
the  mucus-secreting  cells  to  reach  the  demilimes  and  even  penetrate  the  cells  forming  these 
structures. 

In  the  serous  alveoli  the  cells  almost  completely  fill  the  cavity,  so  that  there  is  hardly  any 
lumen  perceptible;  they  contain  secretory  granules  imbedded  in  a  closely  I'eticulated  protoplasm 
(Fig.  954).  The  cells  are  more  cubical  than  those  of  the  mucous  type;  the  nucleus  of  each  is 
spherical  and  placed  near  the  centre  of  the  cell,  and  the  granules  are  smaller. 

Both  mucous  and  serous  cells  vary  in  appearance  according  to  whether  the  gland  is  in  a  resting 
condition  or  has  been  i-ecently  active.  In  the  former  case  the  cells  are  large  and  contain  many 
secretory  granules;  in  the  latter  case  they  are  shrunken  and  contain  few  granules,  cliiefly  collected 
at  the  inner  ends  of  the  cells.    The  granules  are  best  seen  in  fresh  preparations. 

The  ducts  are  lined  at  their  origins  by  epithelium  which  differs  little  from  the  pavement  form. 
As  the  ducts  enlarge,  the  epithelial  cells  change  to  the  columnar  type,  and  the  part  of- the  cell 
next  the  basement-membrane  is  finely  striated. 
72 


1138 


SPLANCHNOLOGY 


The  lobules  of  the  salivary  glands  are  richly  supplied  with  bloodvessels  which  form  a  dense 
net-work  in  the  interalveolar  spaces.  Fine  plexuses  of  nerves  are  also  found  in  the  interlobular 
tissue.  The  nerve  fibrils  pierce  the  basement-membrane  of  the  alveoli,  and  end  in  branched 
varicose  filaments  between  the  secreting  cells.  In  the  hilus  of  the  submaxillary  gland  there  is 
a  collection  of  nerve  cells  termed  Langley's  ganglion 


Demilune 


Fig.  953. — Section  of  submaxillary  gland  of  kitten, 
semidiagrammatic.     X  200. 


Duct 


Fig.  954. — Human  submaxillary  gland.  (R.  Heiden- 
hain.)  To  the  right  of  the  figure  is  a  group  of  mucous 
alveoli,  to  the  left  a  group  of  serous  alveoli. 


Accessory  Glands. — Besides  the  sahvary  glands  proper,  numerous  other  glands  are  found 
in  the  mouth.  Many  of  these  glands  are  found  at  the  posterior  part  of  the  dorsum  of  the  tongue 
behind  the  vallate  papiUse,  and  also  along  its  margins  as  far  forward  as  the  apex.  Others  he 
around  and  in  the  palatine  tonsil  between  its  crypts,  and  large  numbers  are  present  in  the  soft 
palate,  the  lips,  and  cheeks.  These  glands  are  of  the  same  structure  as  the  larger  saHvary  glands, 
and  are  of  the  mucous  or  mixed  type. 

Applied  Anatomy. — The  parotid  glands,  and  much  less  often  the  other  salivary  glands,  are 
liable  to  an  acute  infectious  inflammation,  known  in  the  case  of  the  parotid  as  mumps.  The 
affected  glands  swell  up,  becoming  tense,  tender,  and  painful;  much  pain  is  felt  when  swallowing 
or  mastication  is  attempted,  and  salivation  may  or  may  not  occur.  The  inflammation  goes 
down  after  a  few  days;  suppiu-ation  in  the  affected  glands  is  very  rare. 


THE   PHARYNX. 


The  pharynx  is  that  part  of  the  digestive  tube  which  is  placed  behind  the  nasal 
cavities,  mouth,  and  larynx.  It  is  a  musculomembranous  tube,  somewhat  conical 
in  form,  with  the  base  upward,  and  the  apex  downward,  extending  from  the  under 
surface  of  the  skull  to  the  level  of  the  cricoid  cartilage  in  front,  and  that  of  the 
sixth  cervical  vertebra  behind. 

The  cavity  of  the  pharynx  is  about  12.5  cm.  long,  and  broader  in  the  transverse 
than  in  the  antero-posterior  diameter.  Its  greatest  breadth  is  immediately  below 
the  base  of  the  skull,  where  it  projects  on  either  side,  behind  the  pharyngeal  ostium 
of  the  auditory  tube,  as  the  pharyngeal  recess  (fossa  of  RosenmiiUer) ;  its  narrowest 
point  is  at  its  termination  in  the  oesophagus.  It  is  limited,  ahom,  by  the  body 
of  the  sphenoid  and  basilar  part  of  the  occipital  bone;  heloio,  it  is  continuous  with 
the  oesophagus;  ijosteriorly ,  it  is  connected  by  loose  areolar  tissue  with  the  cervical 
portion  of  the  vertebral  column,  and  the  prevertebral  fascia  covering  the  Longus 
colli  and  Longus  capitis  muscles;  anteriorly,  it  is  incomplete,  and  is  attached  in 


THE  PHARYNX 


1139 


succession  to  tlu-  iiicdial  ptrrvi^oid  plate,  ptLTyy-oinaiulihular  rai)lie,  mandible, 
tongue,  hyoid  hone,  and  tliyroid  and  cricoid  cartilages;  laicrnlhi,  it  is  connected  to 
the  styloid  processes  and  their  muscles,  and  is  in  contact  with  the  common  and 
internal  carotid  arteries,  the  internal  jugular  veins,  the  glossopharyngeal,  vagus, 
and  hypoglossal  nerves,  and  the  sympathetics  trunks,  and  above  with  small  parts 
of  the  Pterygoidei  interni.  wSeven  cavities  communicate  with  it,  viz.,  the  two 
nasal  cavities,  the  two  tympanic  cavities,  the  mouth,  the  larynx,  and  the  oesophagus. 
The  cavity  of  the  pharynx  may  be  subdivided  from  above  downward  into  three 
parts:  nasal,  oral,  and  laryngeal  (Fig.  927). 

Nasal  septum 

"'.-   '     ■:    .' '       ■■      '     / 

^  Nasal  conchas 


riiuryngeal  recess 


^^m__ Torus  of  auditory 


Pharyngeal  ostium  of 
auditory  tube 


Fig.  955. — Front  of  nasal  part  of  pharynx,  as  seen  with  the  larj-ngoscope. 


The  Nasal  Part  of  the  Pharynx  [pars  nasalis  pharyngis;  nasopharynx)  lies  behind 
the  nose  and  above  the  level  of  the  soft  palate:  it  differs  from  the  oral  and  laryn- 
geal parts  of  the  pharynx  in  that  its  cavity  always  remains  patent.  In  front  (Fig. 
955)  it  communicates  through  the  choanse  with  the  nasal  cavities.  On  its  lateral 
wall  is  the  pharyngeal  ostium  of  the  auditory  tube,  somewhat  triangular  in  shape, 
and  bounded  behind  by  a  firm  prominence,  the  torus  or  cushion,  caused  by  the 
medial  end  of  the  cartilage  of  the  tube  which  elevates  the  mucous  membrane. 
A  vertical  fold  of  mucous  membrane,  the  salpingopharyngeal  fold,  stretches  from 
the  lower  part  of  the  torus;  it  contains  the  Salpingopharyngeus  muscle.  A  second 
and  smaller  fold,  the  salpingopalatine  fold,  stretches  from  the  upper  part  of  the  torus 
to  the  palate.  Behind  the  ostium  of  the  auditory  tube  is  a  deep  recess,  the  pharyn- 
geal recess  (fossa  of  Rosenmiiller) .  On  the  posterior  wall  is  a  prominence,  best 
marked  in  childhood,  produced  by  a  mass  of  lymphoid  tissue,  w^hich  is  known  as  the 
pharyngeal  tonsil.  Above  the  pharyngeal  tonsil,  in  the  middle  line,  an  irregular 
flask-shaped  depression  of  the  mucous  membrane  sometimes  extends  up  as  far 
as  the  basilar  process  of  the  occipital  bone;  it  is  known  as  the  pharyngeal  bursa. 

The  oral  part  of  the  pharynx  {pars  oralis  pharyngis)  reaches  from  the  soft  palate 
to  the  level  of  the  hyoid  bone.  It  opens  anteriorly,  through  the  isthmus  faucium, 
into  the  mouth,  while  in  its  lateral  wall,  between  the  two  palatine  arches,  is  the 
palatine  tonsil. 

The  Palatine  Tonsils  {tonsillae  palatinae;  tonsil)  are  two  prominent  masses  situated 
one  on  either  side  between  the  glossopalatine  and  pharyngopalatine  arches.  Each 
tonsil  consists  fundamentally  of  an  aggregation  of  lymphoid  tissue  underlying 
the  mucous  membrane  between  the  palatine  arches.  The  lymphoid  mass,  however, 
does  not  completely  fill  the  interval  between  the  two  arches,  so  that  a  small  depres- 
sion, the  supratonsillar  fossa,  exists  at  the  upper  part  of  the  interval.     Further, 


1140  SPLANCHNOLOGY 

the  tonsil  extends  for  a  variable  distance  under  cover  of  the  glossopalatine  arch, 
and  is  here  covered  by  a  reduplication  of  mucous  membrane;  the  upper  part  of  this 
fold  reaches  across  the  supratonsillar  fossa,  between  the  two  arches,  as  a  thin 
fold  sometimes  termed  the  plica  semilunaris ;  the  remainder  of  the  fold  is  called  the 
plica  triangularis.  Between  the  plica  triangularis  and  the  surface  of  the  tonsil  is 
a  space  known  as  the  tonsillar  sinus;  in  many  cases,  however,  this  sinus  is  obliterated 
by  its  walls  becoming  adherent.  From  this  description  it  will  be  apparent  that  a 
portion  of  the  tonsil  is  below  the  level  of  the  surrounding  mucous  membrane,  i.  e.,  is 
imbedded,  while  the  remainder  projects  as  the  visible  tonsil.  In  the  child  the 
tonsils  are  relatively  (and  frequently  absolutely)  larger  than  in  the  adult,  and  about 
one-third  of  the  tonsil  is  imbedded.  After  puberty  the  imbedded  portion  diminishes 
considerably  in  size  and  the  tonsil  assumes  a  disk-like  form,  flattened  from  side 
to  side;  the  shape  and  size  of  the  tonsil,  however,  vary  considerably  in  different 
individuals. 


m 


Fig.  956.-ySectiqn  through  one  of  the  crypts  of  the  tonsil.  (Stohr.)  Magnified,  e.  Stratified  epithelium  of  general 
surface,  continued  into  crypt.  /,  /.  Nodules  of  lymphoid  tissue — opposite  each  nodule  numbers  of  lymph  cells  are 
passing  into  or  through  the  epithelium,    s,  s.  Cells  which  have  thus  escaped  to  mix  with  the  saliva  as  salivary  corpuscles. 

The  medial  surface  of  the  tonsil  is  free  except  anteriorly,  where  it  is  covered  by 
the  plica  triangularis;  it  presents  from  twelve  to  fifteen  orifices  leading  into  small 
crypts  or  recesses  from  which  numerous  follicles  branch  out  into  the  tonsillar 
substance. 

The  lateral  or  deep  surface  is  adherent  to  a  fibrous  capsule  which  is  continued 
into  the  plica  triangularis.  It  is  separated  from  the  inner  surface  of  the  Constrictor 
pharyngis  superior  usually  by  some  loose  connective  tissue;  this  muscle  intervenes 
between  the  tonsil  and  the  external  maxillary  artery  with  its  tonsillar  and  ascend- 
ing palatine  branches.  The  internal  carotid  artery  lies  behind  and  lateral  to  the 
tonsil  at  a  distance  of  20  to  25  mm.  from  it. 

The  tonsils  form  part  of  a  circular  band  of  adenoid  tissue  which  guards  the 
opening  into  the  digestive  and  respiratory  tubes.  The  anterior  part  of  the  ring 
is  formed  by  the  submucous  adenoid  collections  (lingual  tonsil)  on  the  posterior 
part  of  the  tongue;  the  lateral  portions  consist  of  the  palatine  tonsils  and  the  ade- 
noid collections  in  the  vicinity  of  the  auditory  tubes,  while  the  ring  is  completed 


THE  PUARYSX  1141 

behintl  by  the  pharyngeal  tonsil  on  the  posterior  wall  of  the  pharynx.     In  the 
intervals  between  these  main  masses  are  smaller  collections  of  adenoid  tissue. 

Structure  (Fig.  956). — The  follicles  of  the  tonsil  are  lined  by  a  continuation  of  the  mucous 
membrane  of  the  pharynx,  covered  with  stratified  squamous  epithelium';  around  each  follicle 
is  a  laj'er  of  closed  capsules  consisting  of  lyinjjhoid  tissue  imbedded  in  the  submucous  tissue. 
Lymph  corpuscles  arc  found  in  large  numbers  invatling  the  stratified  epithehum.  It  is  probable 
that  ihoy  pass  into  the  mouth  and  form  the  so-called  salivary  corpuscles.  Surrounding  each 
follicle  is  a  close  plexus  of  lymphatics,  from  which  the  lymphatic  vessels  pass  to  the  deep  cervical 
glands  in  the  neighborhood  of  the  greater  cornu  of  the  hyoid  bone,  behind  and  below  the  angle 
of  the  mandible. 

Vessels  and  Nerves. — The  arteries  supplj-ing  the  tonsil  are  the  dorsalis  linguae  from  the 
lingual,  the  ascending  palatine  and  tonsillar  from  the  external  maxillary,  the  ascending  pharyn- 
geal from  the  external  carotid,  the  descending  palatine  branch  of  the  internal  maxiUary,  and  a 
twig  from  the  small  meningeal. 

The  veins  end  in  the  tonsillar  plexus,  on  the  lateral  side  of  the  tonsil. 

The  nerves  are  derived  from  the  sphenopalatine  ganglion,  and  from  the  glossopharj'ngeal. 

Applied  Anatomy. — The  palatine  tonsils  can  be  easilj-  inspected  bj-  instructing  the  patient 
to  throw  tlie  head  back  and  open  his  mouth  widely;  the  tongue  at  the  same  time  being  depressed 
by  a  spatula  or  tongue-depressor.  The  normal  tonsil  should  not  project  bej-ond  the  plane  of 
the  glossopalatine  arch.  They  are  prone  to  become  enlarged,  especiallj-  in  tuberculous  children; 
and  when  much  increased  in  size  they  cause  great  trouble,  owing  to  obstruction  to  respiration 
and  deglutition.  The  tonsils  may  be  the  seat  of  acute  inflammation,  which  may  run  on  to  sup- 
puration, requiring  evacuation  of  the  pus.  The  incision  into  the  tonsil  should  always  be  made 
from  in  front  backward  and  medialward.  Another  form  of  acute  inflammation  of  the  tonsil 
is  follicular  tonsillitis,  due  to  the  lodgement  of  microorganisms  in  the  cr^-pts  of  the  tonsil.  The 
removal  of  an  enlarged  tonsil  is,  as  a  rule,  a  very  simple  operation,  and  is  not  usually  attended 
with  much  hemon-hage,  unless  the  patient  is  suffering  from  hemophilia.  The  tonsil  maj-  be  the 
seat  of  malignant  growth,  either  an  epithelioma  or  a  lymphosarcoma. 

The  Laryngeal  Part  of  the  Pharynx  (pars  laryngea  pharyngis)  reaches  from  the 
hyoid  bone  to  the  lower  border  of  the  cricoid  cartilage,  where  it  is  continuous  with 
the  oesophagus.  In  front  it  presents  the  triangular  entrance  of  the  larynx,  the  base 
of  which  is  directed  forward  and  is  formed  by  the  epiglottis,  while  its  lateral  boun- 
daries are  constituted  by  the  aryepiglottic  folds.  On  either  side  of  the  laryngeal 
orifice  is  a  recess,  termed  the  sinus  piriformis,  which  is  bounded  medially  by  the 
aryepiglottic  fold,  laterally'  by  the  thyroid  cartilage  and  hyothyroid  membrane. 

Muscels  of  the  Pharynx. — ^The  muscles  of  the  pharynx  (Fig.  957)  are: 

Constrictor  inferior.  Stylopharyngeus. 

Constrictor  medius.  Salpingopharyngeus. 

Constrictor  superior.  Pharyngopalatinus.^ 

Dissection. — In  order  to  examine  the  muscles  of  the  phai^yTix,  cut  through  the  trachea  and 
cESophagus  just  above  the  sternum,  and  draw  them  upward  by  dividing  the  loose  areolar  tissue 
connecting  the  pharj-nx  with  the  front  of  the  vertebral  column.  The  parts  being  drawn  well 
forward,  apply  the  edge  of  the  saw  immediately  behind  the  styloid  processes,  and  saw  the  base 
of  the  skull  through  from  below  upward.  The  phai-jTix  and  mouth  should  then  be  stuffed  with 
tow,  in  order  to  distend  its  cavit}'  and  render  the  muscles  tense  and  easier  of  dissection. 

The  Constrictor  pharyngis  inferior  {Inferior  constrictor),  the  thickest  of  the 
three  constrictors,  arises  from  the  sides  of  the  cricoid  and  th^Toid  cartilage. 
From  the  cricoid  cartilage  it  arises  in  the  interval  between  the  Cricothyreoideus 
in  front,  and  the  articular  facet  for  the  inferior  cornu  of  the  thyroid  cartilage 
behind.  On  the  thyroid  cartilage  it  arises  from  the  oblique  line  on  the  side  of  the 
lamina,  from  the  surface  behind  this  nearly  as  far  as  the  posterior  border  and  from 
the  inferior  cornu.  From  these  origins  the  fibres  spread  back^vard  and  medialward 
to  be  inserted  with  the  muscle  of  the  opposite  side  into  the  fibrous  raphe  in  the 
posterior  median  line  of  the  pharynx.  The  inferior  fibres  are  horizontal  and  con- 
tinuous with  the  circular  fibres  of  the  oesophagus;  the  rest  ascend,  increasing  in 
obliquity,  and  overlap  the  Constrictor  medius. 

1  The  Pharyngopalatinus  is  described  with  the  muscles  of  the  palate  (p.  1114). 


1142 


SPLANCHNOLOGY 


Relations.— The  Constrictor  inferior  is  covered  by  the  thin  membrane  which  surrounds  the 
entire  jjhaiynx  (buccopharyngeal  fascia).  Behind,  it  is  in  relation  with  the  vertebral  column  and 
the  prevertebral  fascia  and  muscles;  laterally,  with  the  thyroid  gland,  the  common  carotid  artery, 
and  the  SternothjTeoideus;  by  its  internal  surface,  with  the  Constrictor  medius,  the  Stylopharj-n- 
geus  the  Pharyngopalatinus,  the  pharj-ngeal  aponeurosis  and  the  mucous  membrane  of  the 
'  '  pharynx.    The  internal  branch  of  the  superior  laryn- 

geal nerve  and  the  laryngeal  branch  of  the  superior 
thyroid  artery  run  near  the  upper  border,  and  the 
recurrent  nerve  and  the  larj-ngeal  branch  of  the 
inferior  thjToid  arterj'  pass  beneath  the  lower  border 
of  this  muscle,  before  they  enter  the  larjiix. 

The  Constrictor  pharyngis  medius  (Middle 
constrictor)  is  a  fan-shaped  muscle,  smaller 
than  the  preceding.  It  arises  from  the  whole 
length  of  the  upper  border  of  the  greater 
cornu  of  the  hyoid  bone,  from  the  lesser 
cornu,  and  from  the  stylohyoid  ligament. 
The  fibres  diverge  from  their  origin:  the 
lower  ones  descend  beneath  the  Constrictor 
inferior,  the  middle  fibres  pass  transversely, 
and  the  upper  fibres  ascend  and  overlap  the 
Constrictor  superior.  It  is  inserted  into  the 
posterior  median  fibrous  raphe,  blending 
in  -the  middle  line  with  the  muscle  of  the 
opposite  side. 

Relations. — This  muscle  is  separated  from  the 
Constrictor  superior  by  the  glossopharjiigeal  ner\-e, 
the  StylopharjTigeus  and  the  stylohyoid  ligament; 
and  from  the  Constrictor  inferior  by  the  internal 
branch  of  the  superior  larjiigeal  ner^-e  and  larjmgeal 
branch  of  the  superior  thjToid  artery.  Behind,  it 
lies  on  the  prevertebral  fascia,,  the  Longus  coUi, 
and  the  Longus  capitis.  Laterally  it  is  in  relation 
with  the  carotid  vessels,  the  pharjTigeal  plexus,  and 
some  Ij-mph  glands.  Xear  its  origin  it  is  covered  by  the  Hyoglossus,  from  which  it  is  separated 
by  the  lingual  vessels.  It  Ues  upon  the  Constrictor  superior,  the  Stj-lopharjiigeus,  the  Pharyngo- 
palatinus, the  phar>Tigeal  aponeurosis,  and  the  mucous  membrane  of  the  pharj-nx. 

The  Constrictor  pharyngis  superior  (Superior  constrictor)  is  a  quadrilateral  muscle, 
thinner  and  paler  than  the  other  two.  It  arises  from  the  lower  third  of  the  posterior 
margin  of  the  medial  pterygoid  plate  and  its  hamulus,  from  the  pterygomandibular 
raphe,  from  the  alveolar  process  of  the  mandible  above  the  posterior  end  of  the 
mylohyoid  line,  and  by  a  few  fibres  from  the  side  of  the  tongue.  The  fibres  curve 
backward  to  be  inserted  into  the  median  raphe,  being  also  prolonged  by  means  of 
an  aponeurosis  to  the  pharyngeal  spine  on  the  basilar  part  of  the  occipital  bone. 
The  superior  fibres  arch  beneath  the  Levator  veli  palatini  and  the  auditory  tube. 
The  interval  between  the  upper  border  of  the  muscle  and  the  base  of  the  skull  is 
closed  by  the  pharyngeal  aponeurosis,  and  is  known  as  the  sinus  of  Morgagni. 

Relations. — The  Constrictor  superior  is  in  relation  by  its  outer  surface  with  the  prevertebral 
fascia  and  muscles,  the  vertebral  column,  the  internal  carotid  and  ascending  pharj-ngeal  arteries, 
the  internal  jugular  vein  and  pharjTigeal  venous  plexus,  and  the  glossopharjmgeal,  vagus,  hj'po- 
glossal,  and  lingual  nerves,  the  s>-mpathetic  trunks,  the  Constrictor  medius  and  Pterj'goideus 
intemus,  the  stj^loid  process,  the  stylohyoid  ligament,  and  the  Stj-lopharj-ngeus.  By  its  internal 
surface  it  is  in  relation  with  the  Phai-j-ngopalatinus,  the  capsule  of  the  palatine  tonsil,  the  pharyn- 
geal aponeuro.sis,  and  the  mucous  membrane  of  the  pharjTix.  Its  lover  border  is  separated  from 
the  Constrictor  medius  by  the  Stj-lophai-j-ngeus  and  the  glossopharj-ngeal  nerve. 

The  Stylopharyngeus  (Fig.  947)  is  a  long,  slender  muscle,  cylindrical  above, 
flattened  below.    It  arises  from  the  medial  side  of  the  base  of  the  styloid  process. 


Fig 


— Muscles  of  the  pharj-nx  and  cheek. 


THE  PHARYNX  1143 

passes  downwurd  alun^"  the  side  of  the  pluirynx  between  tlie  Constrietores  superior 
and  medius,  and  spreads  out  beneath  the  mucous  membrane.  Some  of  its  fibres 
are  lost  in  tlie  Constrictor  muscles,  while  others,  joining-  with  the  Pharyn<i;o})alatinus, 
are  inserted  into  the  posterior  border  of  the  thyroid  (•artilaf2;e.  The  ti;lossopharyn- 
geal  nerve  runs  on  tlu>  hitcral  side  of  this  nuiscle,  and  crosses  over  it  to  reach  the 
tongue. 

The  Salpingopharyngeus  (Fig.  928)  arises  from  the  inferior  part  of  the  auditory 
tube  near  its  orifice;  it  passes  downward  and  blends  with  the  j)osterior  fasciculus 
of  the  Pharyngt)palatinus. 

Nerves. — The  Constrietores  and  Salpingopharyngeus  are  suppUed  by  branches  from  the 
pharyngeal  plexus,  the  Constrictor  inferior  by  additional  branches  from  the  external  laryngeal 
and  recurrent  nerves,  and  the  Stylopharyngeus  by  the  glossopharyngeal  nerve. 

Actions. — ^When  deglutition  is  about  to  be  performed,  the  pharynx  is  drawn  upward  and 
dilated  in  different  directions,  to  receive  the  food  propelled  into  it  from  the  mouth.  TheStylo- 
pharyngei,  which  are  much  farther  removed  from  one  another  at  their  origin  than  at  their  inser- 
tion, draw  the  sides  of  the  pharynx  upward  and  lateralward,  and  so  increase  its  transverse 
diameter;  its  breadth  in  the  antero-posterior  direction  is  increased  by  the  larynx  and  tongue 
being  carried  forward  in  their  ascent.  As  soon  as  the  bolus  of  food  is  received  in  the  pharynx, 
the  elevator  muscles  relax,  the  pharynx  descends,  and  the  Constrietores  contract  upon  the 
bolus,  and  convey  it  downward  into  the  oesophagus. 

Structure. — The  pharynx  is  composed  of  thi-ee  coats:  mucous,  fibrous,  and  muscular. 

The  pharyngeal  aponeurosis,  or  fibrous  coat,  is  situated  between  the  mucous  and  muscular 
layers.  It  is  thick  above  where  the  muscular  fibres  are  wanting,  and  is  firmly  connected  to  the 
basilar  portion  of  the  occipital  and  the  petrous  portions  of  the  temporal  bones.  As  it  descends 
it  diminishes  in  thickness,  and  is  gradually  lost.  It  is  strengthened  posteriorly  by  a  strong  fibrous 
band,  which  is  attached  above  to  the  pharyngeal  spine  on  the  under  surface  of  the  basilar  portion 
of  the  occipital  bone,  and  passes  downward,  forming  a  median  raphe,  which  gives  attachment 
to  the  Constrietores  pharyngis. 

The  mucous  coat  is  continuous  with  that  fining  the  auditory  tubes,  the  nasal  cavities,  the 
mouth,  and  the  larynx.  In  the  nasal  part  of  the  pharynx  it  is  covered  by  columnar  cihated 
epithelium;  in  the  oral  and  laryngeal  portions  the  epithelium  is  stratified  squamous.  Beneath 
the  mucous  membrane  are  found  racemose  mucous  glands;  they  are  especially  numerous  at  the 
upper  pa  t  of  the  pharynx  around  the  orifices  of  the  auditory  tubes. 

Applied  Anatomy. — Hypertrophy  of  the  lymphatic  tissue  in  the  nasal  part  of  the  pharynx 
commonly  known  as  "adenoids,"  is  a  frequent  cause  of  mouth-breathing  and  all  its  attendant 
disadvantages  and  dangers  in  children.  It  entails  a  proneness  to  inflammation  of  all  parts  of 
the  air  passages  and  the  auditory  tubes,  and  leads  to  deformed  development  of  the  palate  and 
dental  arch.  In  many  cases  adenoids  tend  to  atrophy  about  the  age  of  puberty,  by  which  time 
their  presence  is  likely  to  have  caused  permanent  injury  to  the  health  and  development  of  the 
patient. 

The  pharynx  is  sometimes  the  seat  of  a  pouch-like  dilatation  of  its  walls,  in  which  the  food 
collects  when  the  patient  swallows.  A  cure  is  effected  by  removing  the  diverticulima  and  accu- 
rately  suturing  the  opening  which  has  been  made  in  the  pharynx.  The  internal  carotid  artery  is 
in  close  relation  with  the  pharynx,  so  that  its  pulsations  can  be  felt  through  the  mouth.  It  has 
been  occasionally  wounded  by  sharp-pointed  instruments,  introduced  into  the  mouth  and  thrust 
through  the  waU  of  the  pharynx.  In  aneurism  of  this  vessel  in  the  neck,  the  tiunor  necessarily 
bulges  into  the  pharynx,  as  this  is  the  direction  in  which  it  meets  with  the  least  resistance,  nothing 
lying  between  the  vessel  and  the  mucous  membrane  except  the  thin  Constrictor  muscles,  whereas 
on  the  lateral  side  there  are  the  dense  cervical  fascia,  the  muscles  descending  from  the  styloid 
process,  and  the  margin  of  the  Sternocleidomastoideus. 

The  mucous  membrane  of  the  pharynx  is  very  vascular,  and  is  often  the  seat  of  inflammation, 
frequently  of  a  septic  character,  since  the  numerous  recesses  are  prone  to  lodge  microorganisms. 
And,  in  addition,  owing  to  its  exposed  situation,  the  mucous  membrane  is  fiable  to  be  ii-ritated 
by  agents  introduced  during  inspiration.  The  inflammation  may  be  attended  with  serious 
consequences:  it  may  extend  up  the  auditory  tube  and  involve  the  middle  ear;  it  may  spread 
to  the  entrance  of  the  larynx,  causing  oedema  and  seriously  interfering  with  respiration;  or, 
invading  the  lymphatics,  it  may  spread  to  the  loose  areolar  tissue  surrounding  the  i^haryngeal 
wall;  and  may  extend  far  and  wide,  sometimes  into  the  posterior  mediastinal  cavity  along  the 
oesophagus.  Abscess  may  form  in  the  connective  tissue  behind  the  pharynx,  between  it  and 
the  vei'tebral  column,  constituting  what  is  known  as  retropharyngeal  abscess.  This  may  be  due 
to  caries  of  the  cervical  vertebr£e  or  may  be  caused  by  suppuration  of  the  lymph  glands,  which 
are  situated  in  this  position  opposite  the  axis,  and  which  receive  the  lymphatics  from  the  nasal 
cavities.     In  these  cases  the  pus  may  be  easily  evacuated  by  incision  with  a  guarded  bistoury, 


1144  SPLANCHNOLOGY 

through  the  mouth,  but,  for  aseptic  reasons,  it  is  desirable  that  the  abscess  should  be  opened 
from  the  neck.  In  some  instances  this  is  perfectly  easy:  the  abscess  can  be  felt  bulging  at  the 
side  of  the  neck,  and  merely  requires  an  incision  for  its  reUef ;  but  this  is  not  always  so,  and  then 
an  incision  should  be  made  along  the  posterior  border  of  the  Sternocleidomastoideus  and  the 
deep  fascia  divided.  A  director  is  now  to  be  inserted  into  the  wound,  the  forefinger  of  the  left 
hand  being  introduced  into  the  mouth  and  pressure  made  upon  ihe  swelling.  This  acts  as  a 
guide,  and  the  director  is  to  be  pushed  onward  until  pus  appears  in  the  groove.  A  pair  of  sinus 
forceps  is  now  inserted  along  the  director  and  the  opening  into  the  cavity  dilated. 

Abscess  also  occvu-s  in  children,  underneath  the  mucous  membrane,  between  it  and  the  pharyn- 
geal aponeurosis.  The  condition  usually  arises  from  a  peritonsillar  inflammation,  which  spreads 
backward.  In  some  cases  an  enormous  swelhng  may  form,  which  pushes  forward  the  soft  palate 
and  gives  rise  to  respiratory  obstruction.  In  such  the  abscess  should  be  opened  through  the 
mouth  with  the  child  in  the  inverted  positions,  so  as  to  prevent  the  first  gush  of  pus  from  entering 
the  superior  opening  of  the  larynx. 

Foreign  bodies  not  infrequently  become  lodged  in  the  pharynx,  and  most  usually  at  its  termina- 
tion at  about  the  level  of  the  cricoid  cartilage,  just  beyond  the  reach  of  the  finger,  as  the  distance 
from  the  arch  of  the  teeth  to  the  commencement  of  the  oesophagus  is  about  15  cm. 


THE  (ESOPHAGUS  (Fig.  958). 

The  oesophagus  or  gullet  is  a  muscular  canal,  about  23  to  25  cm.  long,  extending 
from  the  pharynx  to  the  stomach.  It  begins  in  the  neck  at  the  lower  border  of 
the  cricoid  cartilage,  opposite  the  sixth  cervical  vertebra,  descends  along  the  front 
of  the  vertebral  column,  through  the  superior  and  posterior  mediastinal  cavities, 
passes  through  the  Diaphragma,  and,  entering  the  abdomen,  ends  at  the  cardiac 
orifice  of  the  stomach,  opposite  the  eleventh  thoracic  vertebra.  '  The  general  direc- 
tion of  the  oesophagus  is  vertical;  but  it  presents  two  slight  curves  in  its  course. 
At  its  commencement  it  is  placed  in  the  middle  line;  but  it  inclines  to  the  left  side 
as  far  as  the  root  of  the  neck,  gradually  passes  to  the  middle  line  again  at  the  level 
of  the  fifth  thoracic  vertebra,  and  finally  deviates  to  the  left  as  it  passes  forward 
to  the  oesophageal  hiatus  in  the  Diaphragma.  The  oesophagus  also  presents 
antero-posterior  flexures  corresponding  to  the  curvatures  of  the  cervical  and 
thoracic  portions  of  the  vertebral  column.  It  is  the  narrowest  part  of  the  diges- 
tive tube,  and  is  most  contracted  at  its  commencement,  and  at  the  point  where 
it  passes  through  the  Diaphragma. 

Relations. — The  cervical  portion  of  the  oesophagus  is  in  relation,  in  front,  with  the  trachea; 
and  at  the  lower  part  of  the  neck,  where  it  projects  to  the  left  side,  with  the  thyroid  gland;  behind, 
it  rests  upon  the  vertebral  column  and  Longus  coUi  muscles;  on  either  side  it  is  in  relation  with 
the  common  carotid  artery  (especially  the  left,  as  it  inchnes  to  that  side),  and  parts  of  the  lobes 
of  the  thyroid  gland;  the  recurrent  nerves  ascend  between  it  and  the  trachea;  to  its  left  side  is 
the  thoracic  duct. 

The  thoracic  portion  of  the  CEsophagus  is  at  first  situated  in  the  superior  mediastinal  cavity 
between  the  trachea  and  the  vertebral  column,  a  httle  to  the  left  of  the  median  hne.  It  then 
passes  behind  and  to  the  right  of  the  aortic  arch,  and  descends  in  the  posterior  mediastinal 
cavity,  along  the  right  side  of  the  descending  aorta,  then  runs  in  front  and  a  httle  to  the  left 
of  the  aorta,  and  enters  the  abdomen  through  the  Diaphragma  at  the  level  of  the  tenth  thoracic 
vertebra.  Just  before  it  perforates  the  Diaphragma  it  presents  a  distinct  dilatation.  It  is  in 
relation,  in  front,  with  the  trachea,  the  left  bronchus,  the  pericardium,  and  the  Diaphragma; 
behind,  it  rests  upon  the  vertebral  column,  the  Longus  colU  muscles,  the  right  aortic  intercostal 
arteries,  the  thoracic  duct,  and  the  hemiazygos  veins;  and  below,  near  the  Diaphragma,  upon 
the  front  of  the  aorta.  On  its  left  side,  in  the  superior  mediastinal  cavity,  are  the  terminal  part 
of  the  aortic  arch,  the  left  subclavian  artery,  the  thoracic  duct,  and  left  pleura,  while  running 
upward  in  the  angle  between  it  and  the  trachea  is  the  left  recurrent  nerve;  below,  it  is  in  relation 
with  the  descending  thoracic  aorta.  On  its  right  side  are  the  right  pleura,  and  the  azygos  vein 
which  it  overlaps.  Below  the  roots  of  the  lungs  the  vagi  descend  in  close  contact  with  it,  the 
right  nerve  passing  down  behind,  and  the  left  nerve  in  front  of  it;  the  two  nerves  uniting  to 
form  a  plexus  around  the  tube. 

In  the  lower  part  of  the  posterior  mediastinal  cavity  the  thoracic  duct  hes  to  the  right  side 
of  the  oesophagus;  higher  up,  it  is  placed  behind  it,  and,  crossing  about  the  level  of  the  fom'th 
thoracic  vertebra,  is  continued  upward  on  its  left  side. 


THE  (KSOrilAdL'S 


n-io 


The  abdominal  portion  of  the  (i'S()])h;igus  Ues  in  the  a?sophageal  groove  on  the  posterior  surface 
of  the  left  lobe  of  the  liver.  It  measures  about  1.25  cm.  in  length,  and  only  its  front  and  left 
aspects  are  covered  by  peritoneum.  It  is  somewhat  conical  with  its  base  appUed  to  the  upper 
orifice  of  the  stomach,  and  is  known  as  the  antrum  cardiacum. 

Structure  (l''ig.  959).— The  (rsophagus  has  four  coals:  an  external  or  fibrous,  a  muscular, 
a    submucous    or    areolar,    and    an    internal    or   mucous    coat. 

The  muscular  coat  {tunica  muscularis) 
is  composed  of  two  planes  of  consider- 
able thickness:  an  external  of  longitu- 
dinal and  an  internal  of  circular  fibres. 
The  longiiudinal  fibres  are  arranged, 
at  the  commencement  of  the  tube,  in 
three  fasciculi:  one  in  front,  which  is 
attached  to  the  vertical  ridge  on  the 
posterior  surface  of  the  lamina  of  the 
cricoid  cartilage;  and  one  at  either 
side,  which  is  continuous  with  the 
muscular  fibres  of  the  pharynx:  as 
they  descend  they  blend  together,  and 
form  a  uniform  layer,  which  covers  the 
outer  surface  of  the  tube. 

Accessoi-y    slips    of  muscular    fibres 
pass  between  the  oesophagus  and  the 


^"^^ 


Fig.  958. — The  CESophagus. 


Fig.  959. — Section  of  the  human  oesophagus. 
(From  a  drawing  by  V.  Horsley.)  Moderately 
magnified.  The  section  is  transverse  and  from 
near  the  middle  of  the  guUet.  a.  Fbrous  cover- 
ing, b.  Divided  fibres  of  longitudinal  muscular 
coat.  c.  Transverse  muscular  fibres,  d.  Sub- 
mucous or  areolar  layer,  e.  Muscularis  mucosae. 
/.  Mucous  membrane,  with  vessels  and  part  of  a 
"lymphoid  nodule,  g.  Stratified  epitheUal  lining. 
h.  Mucous  gland,  i.  Gland  duct.  m'.  Striated 
muscular  fibres  cut  across. 


left  pleura,  where  the  latter  covers  the  thoracic  aorta,  or  the  root  of  the  left  bronchus,  or  the 
back  of  the  pericardium. 

The  circular  fibres  are  continuous  above  with  the  Constrictor  pharyxigis  inferior;  their  direction 
is  transverse  at  the  upper  and  lower  parts  of  the  tube,  but  obUque  in  the  intermediate  part. 

The  muscular  fibres  in  the  upper  part  of  the  oesophagus  are  of  a  red  color,  and  consist  chiefly 
of  the  striped  variety;  but  below,  they  consist  of  the  most  part  of  involuntary  fibres. 

The  areolar  or  submucous  coat  {tela  submucosa)  connects  loosety  the  mucous  and  muscular 
coats.     It  contains  bloodvessels,  nerves,  and  mucous  glands. 


,A.i  i  SPLANCHNOLOGY 

The  mucous  coat  ilunica  mucosa)  is  thick,  of  a  reddish  color  above,  and  pale  below.  It  is 
disposed  in  longitudinal  folds,  which  disappear  on  distension  of  the  tube.  Its  surface  is  studded 
with  minute  papilla,  and  it  is  covered  throughout  with  a  thick  laj'er  of  stratified  squamous 
epithelium.  Beneath  the  mucous  membrane,  between  it  and  the  areolar  coat,  is  a  layer  of  longi- 
tudinally arranged  non-striped  muscular  fibres.  This  is  the  muscularis  mucosae.  At  the  com- 
mencement of  the  oesophagus  it  is  absent,  or  only  represented  by  a  few  scattered  bundles;  lower 
down  it  forms  a  considerable  stratum. 

The  oesophageal  glands  (glandulae  oesophageae)  are  small  compound  racemose  glands  of  the 
mucous  tA-pe;  they  are  lodged  in  the  submucous  tissue,  and  each  opens  upon  the  surface  by  a 
long  e.xcretcr\'  duct. 

Vessels  and  Nerves. — The  arteries  suppl}'ing  the  oesophagus  are  derived  from  the  inferior 
thyroid  branch  of  the  thjTOcervical  trunk,  from  the  descending  thoracic  aorta,  from  the  left 
gastric  branch  of  the  coeUac  arterj',  and  from  the  left  inferior  phrenic  of  the  abdominal  aorta. 
Thej'  have  for  the  most  part  a  longitudinal  direction. 

The  nerves  are  derived  from  the  vagi  and  from  the  sjTnpathetic  tnmks;  they  form  a  plexus. 
in  which  are  groups  of  ganglion  cells,  between  the  two  laj'ers  of  the  muscular  coats,  and  also  a 
second  ple.xus  in  the  submucous  tissue. 

Applied  Anatomy. — The  oesophagus  may  be  obstructed  by  foreign  bodies,,  and  also  by  changes 
in  its  coats  producing  strictiire,  or  by  pressure  on  it  from  without  of  new  growths  or  aneuri.sm. 
etc.  The  different  forms  of  strictm-e  are:  (Ij  the  fibrous,  due  to  cicatrization  following  destruc- 
tion of  tissue,  the  result  of  swallowing  boiling  or  corrosive  fluids — here  dilatation  of  the  stricture 
may  be  carried  out;  and  (2)  maUgnant,  usually  epitheUomatous  iu  its  nature.  This  may  be 
situated  either  at  the  upper  end  of  the  tube,  opposite  the  cricoid  cartilage,  or  at  its  lower  end 
at  the  cardiac  orifice,  but  is  most  commonlly  found  in  that  part  of  the  tube  which  is  crossed  by 
the  left  bronchus.  In  these  cases,  if  the  patient  is  losing  weight  from  insufficient  nourishment, 
the  operation  of  gastrostomj-  may  be  performed  in  order  to  avoid  death  from  starvation;  death, 
however,  most  commonly  occurs  from  ulceration  of  the  growth  into  the  mediastinal  cavity  or 
air  passages.  In  cases  of  stricture  of  the  oesophagus  it  may  be  necessary  to  dilate  the  canal  by 
a  bougie,  when  it  is  of  importance  that  the  direction  of  the  oesophagus  and  its  relations  to  sur- 
rounding parts  should  be  remembered.  In  cases  of  malignant  disease  of  the  oesophagus,  where 
its  tissues  have  become  softened  from  infiltration  of  the  growth,  the  greatest  care  is  requisite 
in  directing  the  bougie  through  the  strictured  part,  as  a  false  passage  maj^  easily  be  made,  and 
the  instrmnent  maj'  pass  into  the  mediastinal  ca^-itj'  or  into  one  or  other  pleural  cavity,  or  even 
into  the  pericardium. 

In  cases  of  obstruction  of  the  oesophagus,  and  consequent  .sj-mptoms  of  stricture,  produced 
by  an  aneurism  of  some  part  of  the  aorta  pressing  upon  this  tube,  the  passage  of  a  bougie  wiU 
only  hasten  the  fatal  is.sue. 

In  passing  a  bougie,  the  left  forefinger  should  be  introduced  into  the  mouth,  and  the  epiglottis 
felt  for,  care  being  taken  not  to  throw  the  head  too  far  backward.  The  bougie  is  then  to  be 
passed  bej'ond  the  finger  until  it  touches  the  posterior  wall  of  the  pharj-nx.  The  patient  is  now 
asked  to  swallow,  and  at  the  moment  of  swallowing  the  bougie  is  passed  gently  onward,  all 
■\dolence  being  carefuUy  avoided. 

It  occasionally  happens  that  a  foreign  body  becomes  impacted  in  the  oesophagus,  and  can 
neither  be  brought  upward  nor  moved  downward.  When  all  ordinarj'  means  for  its  removal 
have  failed,  excision  is  the  only  resource.  This,  of  course,  can  only  be  performed  when  it  is  not 
verj'  low  down.  If  the  foreign  bodj-  is  allowed  to  remain,  extensive  inflammation  and  ulceration 
of  the  oesophagus  may  ensue.  In  one  case  the  foreign  body  ultimately  penetrated  the  inter- 
vertebral fibrocartilage.  and  destroj-ed  life  by  inflammation  of  the  membranes  and  substance 
of  the  medulla  spinalis. 

THE  ABDOMEN. 

The  abdomen  is  the  largest  cavity  in  the  body.  It  is  of  an  oval  shape,  the  extrem- 
ities of  the  oval  being  directed  upward  and  do^^Tiward.  The  upper  extremity  is 
formed  by  the  Diaphragma  which  extends  as  a  dome  over  the  abdomen,  so  that  the 
cavity  extends  high  into  the  bony  thorax,  reaching  on  the  right  side,  in  the  mammary 
line,  to  the  upper  border  of  the  fifth  rib;  on  the  left  side  it  falls  below  this  level  by 
about  2.5  cm.  The  lower  extremity  is  formed  by  the  structures  which  clothe  the 
inner  surface  of  the  bony  pelvis,  principally  the  Levator  ani  and  Coccygeus  on 
either  side.  These  muscles  are  sometimes  termed  the  diaphragm  of  the  pelvis. 
The  cavity  is  wider  above  than  below,  and  measures  more  in  the  vertical  than  in 
the  transverse  diameter.  In  order  to  facilitate  description,  it  is  artificially  divided 
into  two  parts :  an  upper  and  larger  part,  the  abdomen  proper;  and  a  lower  and  smaller 


THE  ABDOMEN  1147 

part,  the  pelvis.     These  two  eavities  are  not  separated  from  each  other,  but  the 
limit  between  them  is  marked  by  the  superior  aperture  of  the  lesser  pelvis. 

The  abdomen  proper  differs  from  the  other  great  cavities  of  the  body  in  being 
bounded  for  the  most  i)art  by  muscles  and  fasciae,  so  that  it  can  vary  in  capacity 
and  shape  according  to  the  condition  of  the  viscera  which  it  contains;  but,  in  addi- 
tion to  this,  the  abdomen  varies  in  form  and  extent  with  age  and  sex.  In  the  adult 
male,  with  moderate  distension  of  the  viscera,  it  is  oval  in  shape,  but  at  the  same 
time  flattened  from  before  backward.  In  the  adult  female,  with  a  fully  developed 
peh'is,  it  is  ovoid  with  the  narrower  pole  upward,  and  in  young  children  it  is  also 
ovoid  but  with  the  narrower  pole  downward. 

Boundaries. — It  is  boimded  in  front  and  at  the  sides  by  the  abdominal  muscles 
and  the  Iliacus  muscles;  behind  by  the  vertebral  column  and  the  Psoas  and 
Quadratus  lumborum  muscles;  a6o?)e  by  the  Diaphragma;  belotv  by  the  plane  of 
the  superior  aperture  of  the  lesser  pelvis.  The  muscles  forming  the  boundaries 
of  the  cavity  are  lined  upon  their  inner  surfaces  by  a  layer  of  fascia. 

The  abdomen  contains  the  greater  part  of  the  digestive  tube;  some  of  the 
accessory  organs  to  digestion,  viz.,  the  liver  and  pancreas;  the  spleen,  the  kidneys, 
and  the  suprarenal  glands.  Most  of  these  structures,  as  well  as  the  wall  of  the 
cavity  in  which  they  are  contained,  are  more  or  less  covered  by  an  extensive  and 
complicated  serous  membrane,  the  peritoneum. 

The  Apertures  in  the  Walls  of  the  Abdomen. — The  apertures  in  the  walls  of  the 
abdomen,  for  the  transmission  of  structures  to  or  from  it,  are,  in  front,  the  mnbilical 
(in  the  fetus),  for  the  transmission  of  the  umbilical  vessels,  the  allantois,  and  vitel- 
line duct;  above,  the  vena  caval  opening,  for  the  transmission  of  the  inferior  vena 
cava,  the  aortic  hiatus,  for  the  passage  of  the  aorta,  azygos  vein,  and  thoracic  duct, 
and  the  oesophageal  hiatus,  for  the  oesophagus  and  vagi.  Below,  there  are  two 
apertures  on  either  side:  one  for  the  passage  of  the  femoral  vessels  and  lumbo- 
inguinal  nerve,  and  the  other  for  the  transmission  of  the  spermatic  cord  iri  the  male, 
and  the  round  ligament  of  the  uterus  in  the  female. 

Regions. — For  convenience  of  description  of  the  viscera,  as  well  as  of  reference 
to  the  morbid  conditions  of  the  contained  parts,  the  abdomen  is  artificially  divided 
into  nine  regions  by  imaginary  planes,  two  horizontal  and  two  sagittal,  passing 
through  the  cavity,  the  edges  of  the  planes  being  indicated  by  lines  drawn  on  the 
surface  of  the  body.  Of  the  horizontal  planes  the  upper  or  transpyloric  is  indicated 
by  a  line  encircling  the  body  at  the  level  of  a  point  midway  between  the  jugular 
notch  and  the  symphysis  pubis,  the  lower  by  a  line  carried  around  the  trunk  at  the 
level  of  a  point  midway  between  the  transpyloric  and  the  symphysis  pubis.  The 
latter  is  practically  the  intertubercular  plane  of  Cunningham,  who  pointed  out^ 
that  its  level  corresponds  with  the  prominent  and  easily  defined  tubercle  on  the 
iliac  crest  about  5  cm.  behind  the  anterior  superior  iliac  spine.  By  means  of  these 
imaginary  planes  the  abdomen  is  divided  into  three  zones,  which  are  named  from 
above  downward  the  subcostal,  umbilical,  and  hypogastric  zones.  Each  of  these  is 
further  subdivided  into  three  regions  by  the  two  sagittal  planes,  which  are  indi- 
cated on  the  surface  by  lines  drawn  vertically  through  points  half-way  between 
the  anterior  superior  iliac  spines  and  the  symphysis  pubis. ^ 

The  middle  region  of  the  upper  zone  is  called  the  epigastric ;  and  the  two  lateral 
regions,  the  right  and  left  hypochondriac.  The  central  region  of  the  middle  zone 
is  the  umbiUcal;  and  the  two  lateral  regions,  the  right  and  left  lumbar.  The  middle 
region  of  the  lower  zone  is  the  hypogastric  or  pubic  region;  and  the  lateral  regions 
are  the  right  and  left  iliac  or  inguinal  (Fig.  960). 

The  pelvis  is  that  portion  of  the  abdominal  cavity  which  lies  below  and  behind 
a  plane  passing  through  the  promontory  of  the  sacrum,  lineae  terminales  of  the 
hip  bones,  and  the  pubic  crests.    It  is  bounded  behind  by  the  sacrum,  coccyx, 

'  Journal  of  Anatomy  and  Physiology,  vol.  xxvii.  ^  Ibid.,  vols,  xxxiii,  xxxiv,  xxxv. 


1148 


SPLANCHNOLOGY 


Piriformes,   and   the   sacrospinous   and   sacrotuberous  ligaments;    in    front    and 
laterally  by  the  piibes  and  ischia  and  Obturatores  interni;  above  it  communicates 


Fig.  960. — Front  view  of  the  thoracic  and  abdominal  viscera,     a.  Median  plane,     b  b.  Lateral  planea.    c  c.  Trans 
tubercular  plane,     d  d.  Subcostal  plane,     e  e.  Transpyloric  plane. 


77/ A'  PKRITOXEIM  'ij^y 

with  the  abdomen  projxT;  hclow  it  is  closed  by  tlie  Lovatores  ani  and  Coccygei  and 
the  urogenital  diaphratiin.  The  pelvis  contains  the  urinary  bladder,  the  sigmoid 
colon  and  rectum,  a  few  coils  of  the  small  intestine,  and  some  of  the  generative 
organs. 

When  the  anterior  abdominal  wall  is  removed,  the  viscera  are  partly  exposed 
as  follows:  above  and  to  the  right  side  is  the  liver,  situated  chiefly  under  the  shelter 
of  the  right  ribs  and  their  cartilages,  but  extending  across  the  middle  line  and  reach- 
ing for  some  distance  below  the  level  of  the  xiphoid  process.  To  the  left  of  the  liver 
is  the  stomach,  from  the  lower  border  of  which  an  apron-like  fold  of  peritoneum, 
the  greater  omentum,  descends  for  a  varying  distance,  and  obscures,  to  a  greater 
or  lesser  extent,  the  other  viscera.  Below  it,  however,  some  of  the  coils  of  the  small 
intestine  can  generally  be  seen,  while  in  the  right  and  left  iliac  regions  respectively 
the  cecum  and  the  iliac  colon  are  parth'  exposed.  The  bladder  occupies  the  ante- 
rior part  of  the  pelvis,  and,  if  distended,  will  project  above  the  symphysis  pubis; 
the  rectimi  lies  in  the  concavity  of  the  sacrum,  but  is  usually  obscured  by  the  coils 
of  the  small  intestine.    The  sigmoid  colon  lies  between  the  rectum  and  the  bladder. 

When  the  stomach  is  followed  from  left  to  right  it  is  seen  to  be  continuous  with 
the  first  part  of  the  small  intestine,  or  duodenum,  the  point  of  continuity  being 
marked  by  a  thickened  ring  which  indicates  the  position  of  the  pyloric  valve. 
The  duodenum  passes  toward  the  under  surface  of  the  liver,  and  then,  curving 
downward,  is  lost  to  sight.  If,  however,  the  greater  omentum  be  thrown  upward 
over  the  chest,  the  inferior  part  of  the  duodenum  will  be  observed  passing  across 
the  vertebral  column  toward  the  left  side,  where  it  becomes  continuous  with  the 
coils  of  the  jejunum  and  ileum.  These  measure  some  6  metres  in  length,  and  if 
followed  downward  the  ileum  will  be  seen  to  end  in  the  right  iliac  fossa  by  opening 
into  the  cecum,  the  commencement  of  the  large  intestine.  From  the  cecum  the 
large  intestine  takes  an  arched  course,  passing  at  first  upward  on  the  right  side, 
then  across  the  middle  line  and  downward  on  the  left  side,  and  forming  respectively 
the  ascending  transverse,  and  descending  parts  of  the  colon.  In  the  pelvis  it 
assumes  the  form  of  a  loop,  the  sigmoid  colon,  and  ends  in  the  rectum. 

The  spleen  lies  behind  the  stomach  in  the  left  hypochondriac  region,  and  may 
be  in  part  exposed  by  pulling  the  stomach  over  toward  the  right  side. 

The  glistening  appearance  of  the  deep  surface  of  the  abdominal  wall  and  of  the 
surfaces  of  the  exposed  viscera  is  due  to  the  fact  that  the  former  is  lined,  and  the 
latter  are  more  or  less  completely  covered,  by  a  serous  membrane,  the  peritoneum. 

The  Peritoneum  (Tunica  Serosa). 

The  peritoneum  is  the  largest  serous  membrane  in  the  body,  and  consists,  in  the 
male,  of  a  closed  sac,  a  part  of  which  is  applied  against  the  abdominal  parietes, 
while  the  remainder  is  reflected  over  the  contained  viscera.  In  the  female  the 
peritoneum  is  not  a  closed  sac,  since  the  free  ends  of  the  uterine  tubes  open  directly 
into  the  peritoneal  cavity.  The  part  which  lines  the  parietes  is  named  the  parietal 
portion  of  the  peritoneum;  that  which  is  reflected  over  the  contained  viscera  con- 
stitutes the  visceral  portion  of  the  peritoneum.  The  free  surface  of  the  membrane 
is  smooth,  covered  by  a  layer  of  flattened  endothelium,  and  lubricated  by  a  small 
quantity  of  serous  fluid.  Hence  the  viscera  can  glide  freely  against  the  wall  of  the 
cavity  or  upon  one  another  with  the  least  possible  amount  of  friction.  The  attached 
surface  is  rough,  being  connected  to  the  viscera  and  inner  surface  of  the  parietes  by 
means  of  areolar  tissue,  termed  the  subserous  areolar  tissue.  The  parietal  portion 
is  loosely  connected  with  the  fascial  lining  of  the  abdomen  and  pelvis,  but  is  more 
closely  adherent  to  the  under  surface  of  the  Diaphragma,  and  also  in  the  middle 
line   of   the   abdomen. 

The  space  between  the  parietal  and  visceral  layers  of  the  peritoneum  is  named 
the  peritoneal  cavity;  but  under  normal  conditions  this  cavity  is  merely  a  potential 


ll.!)0 


SPLANCHNOLOGY 


one,  since  the  parietal  and  visceral  layers  are  in  contact.  The  peritoneal  cavity 
gives  off  a  large  diverticulum,  the  omental  bursa,  which  is  situated  behind  the 
stomach  and  adjoining  structures;  the  neck  of  communication  between  the  cavity 
and  the  bursa  is  termed  the  epiploic  foramen  (foramen  of  Winsloiv).  Formerly  the 
main  portion  of  the  cavity  was  described  as  the  greater,  and  the  omental  bursa 
as  the  lesser  sac. 

The  peritoneum  differs  from  the  other  serous  membranes  of  the  body  in  pre- 
senting a  much  more  complex  arrangement,  and  one  that  can  only  be  clearly  under- 
stood by  following  the  changes  which  take  place  in  the  digestive  tube  during  its 
development;  the  student  therefore  is  advised  to  preface  his  study  of  the  peri- 
toneum by  reviewing  the  chapter  dealing  with  this  subject  in  the  section  on 
Embryology  (page  162). 

To  trace  the  membrane  from  one  viscus  to  another,  and  from  the  viscera  to  the 
parietes,  it  is  necessary  to  follow  its  continuity  in  the  vertical  and  horizontal 
directions,  and  it  will  be  found  simpler  to  describe  the  main  portion  of  the  cavity 
and  the  omental  bursa  separately. 


Superior  layer  oj 
corotmry  ligament 

Bare  area  of  liver 

Inferior  layer  of 
coronary  ligament 


Bristle  in  epiploic 
foramen 

Stomach 


Transverse  colon 

Greater  omentum 

Small  intestine 


Uterovesical 
excavation 

Bladder 
Urethra 


Pancreas 
Duodenum 
A  or  la 
Mesentery 


-. —  Uterus 

]_ Rectovaginal 

^      /        excavation 
Rectum 


Fig.  961. — Vertical  disposition  of  the  peritoneum.     Main  cavity,  red;  omental  bursa,  blue. 

Vertical  Disposition  of  the  Main  Peritoneal  Cavity  {greater  sac)  (Fig.  961). — It 
is  convenient  to  trace  this  from  the  back  of  the  abdominal  wall  at  the  level  of  the 
umbilicus.  On  following  the  peritoneum  upward  from  this  level  it  is  seen  to  be 
reflected  around  a  fibrous  cord,  the  ligamentum  teres  (obliterated  umbilical  vein), 
which  reaches  from  the  umbilicus  to  the  under  surface  of  the  liver.  This  reflection 
forms  a  somewhat  triangular  fold,  the  falciform  ligament  of  the  liver,  attaching  the 
upper  and  anterior  surfaces  of  the  liver  to  the  Diaphragma  and  abdominal  wall. 
With  the  exception  of  the  line  of  attachment  of  this  ligament  the  peritoneum 
covers  the  whole  of  the  under  surface  of  the  anterior  part  of  the  Diaphragma, 
and  is  continued  from  it  on  to  the  upper  surface  of  the  right  lobe  of  the  liver  as 


THE  PERITONEUM  1151 

tilt'  superior  layer  of  the  coronary  ligament,  and  on  to  the  upper  surface  of  the  left 
lobe  as  the  superior  layer  of  the  left  triangular  ligament  of  the  liver.  Coverin*;-  the 
upper  and  anterior  surfaces  of  the  liver,  it  is  continued  around  its  sharj)  margin 
on  to  the  under  surface,  where  it  presents  the  following  relations:  (a)  It  covers  the 
under  surface  of  the  right  lobe  and  is  reflected  from  the  back  part  of  this  on  to  the 
right  sui)rarenal  gland  and  ui)per  extremity  of  the  right  kidney,  forming  in  this 
situation  the  inferior  layer  of  the  coronary  ligament;  a  special  fold,  the  hepatorenal 
ligament,  is  frecjuently  present  between  the  inferior  surface  of  the  liver  and  the 
front  of  the  kidney.  From  the  kidney  it  is  carried  downward  to  the  duodenum 
and  right  colic  Hexure  and  medialward  in  front  of  the  inferior  vena  cava,  where  it 
is  continuous  with  the  posterior  wall  of  the  omental  bursa.  Between  the  two  layers 
of  the  coronary  ligament  there  is  a  large  triangular  surface  of  the  liver  devoid  of 
peritoneal  covering;  this  is  named  the  bare  area  of  the  liver,  and  is  attached  to  the 
Diaphragma  by  areolar  tissue.  Toward  the  ^  right  margin  of  the  liver  the  two 
layers  of  the  coronary  ligament  gradually  approach  each  other,  and  ultimately 
fuse  to  form  a  small  triangular  fold  connecting  the  right  lobe  of  the  liver  to  the 
Diaphragma,  and  named  the  right  triangular  ligament  of  the  liver.  The  apex  of 
the  triangular  bare  area  corresponds  with  the  point  of  meeting  of  the  two  layers 
of  the  coronary  ligament,  its  base  with  the  fossa  for  the  inferior  vena  cava.  (6) 
It  covers  the  lower  surface  of  the  quadrate  lobe,  the  under  and  lateral  surfaces 
of  the  gall-bladder,  and  the  under  surface  and  posterior  border  of  the  left  lobe;  it  is 
then  reflected  from  the  upper  surface  of  the  left  lobe  to  the  Diaphragma  as  the 
inferior  layer  of  the  left  triangular  ligament,  and  from  the  porta  of  the  liver  and  the 
fossa  for  the  ductus  venosus  to  the  lesser  curvature  of  the  stomach  and  the  first 
2.5  cm.  of  the  duodenum  as  the  anterior  layer  of  the  hepatogastric  and  hepatoduodenal 
ligaments,  wliich  together  constitute  the  lesser  omentum.  If  this  layer  of  the  lesser 
omentum  be  fpllowed  to  the  right  it  will  be  found  to  turn  around  the  hepatic  artery, 
bile  duct,  and^  portal  vein,  and  become  continuous  with  the  anterior  wall  of  the 
omental  bursa;>  forming  a  free  folded  edge  of  peritoneum.  Traced  downward,  it 
covers  the  anterp-superior  surface  of  the  stomach  and  the  commencement  of  the 
duodenum,  and  is  icarried  down  into  a  large  free  fold,  known  as  the  gastrocolic 
ligament  or  greater  omentum.  Reaching  the  free  margin  of  this  fold,  it  is  reflected 
upward  to  cover  th6,  under  and  posterior  surfaces  of  the  transverse  colon,  and  thence 
to  the  posterior  abdominal  wall  as  the  inferior  layer  of  the  transverse  mesocolon. 
It  reaches  the  abdominal  wall  at  the  head  and  anterior  border  of  the  pancreas, 
is  then  carried  down  over  the  lower  part  of  the  head  and  over  the  inferior  surface 
of  the  pancreas  on  the  superior  mesenteric  vessels,  and  thence  to  the  small  intestine 
as  the  anterior  layer  of  the  mesentery.  It  encircles  the  intestine,  and  subsequently 
may  be  traced,  as  the  posterior  layer  of  the  mesentery,  upward  and  backward 
to  the  abdominal  wall.  From  this  it  sweeps  down  over  the  aorta  into  the  pelvis, 
where  it  invests  the  sigmoid  colon,  its  reduplication  forming  the  sigmoid  mesocolon. 
Leaving  first  the  sides  and  then  the  front  of  the  rectum,  it  is  reflected  on  to  the  semi- 
nal vesicles  and  fundus  of  the  urinary  bladder  and,  after  covering  the  upper  surface 
of  that  viscus,  is  carried  along  the  medial  and  lateral  umbilical  ligaments  (Fig. 
962)  on  to  the  back  of  the  abdominal  wall  to  the  level  from  which  a  start  was  made. 
Between  the  rectum  and  the  bladder  it  forms,  in  the  male,  a  pouch,  the  recto- 
vesical excavation,  the  bottom  of  which  is  slightly  below  the  level  of  the  upper 
ends  of  the  vesiculae  seminales — i.  e.,  about  7.5  cm.  from  the  orifice  of  the  anus. 
When  the  bladder  is  distended,  the  peritoneum  is  carried  up  with  the  expanded 
viscus  so  that  a  considerable  part  of  the  anterior  surface  of  the  latter  lies  directly 
against  the  abdominal  wall  without  the  intervention  of  peritoneal  membrane. 
In  the  female  the  peritoneum  is  reflected  from  the  rectum  over  the  posterior  vaginal 
fornix  to  the  cervix  and  body  of  the  uterus,  forming  the  rectouterine  excavation 
{■pouch  of  Douglas).    It  is  continued  over  the  intestinal  surface  and  fundus  of  the 


1152 


SPLANCHNOLOGY 


uterus  on  to  its  vesical  surface,  which  it  covers  as  far  as  the  junction  of  the  body 
and  cervix  uteri,  and  then  to  the  bladder,  forming  here  a  second,  but  shallower, 
pouch,  the  vesicouterine  excavation.  It  is  also  reflected  from  the  sides  of  the  uterus 
to  the  lateral  walls  of  the  j^elvis  as  two  expanded  folds,  the  broad  ligaments  of  the 
uterus,  in  the  free  margin  of  each  of  which  is  the  uterine  tube. 


M.  ilinrna 


Lateral 
buitdnal 
fossa 


Infci  iial 

ihac 

artery 


Supravesical 
fovea 


Femoral 
'^  fovea, 

~\^>il)erinr 
filial 
rtcry 
Medial 
inguinal 
fovea 


Fig.  962.- 


-Posterior  view  of  the  anterior  abdominal  wall  in  its  lower  half.    The  peritoneum  is  in  place,  and  the  various 
cords  are  shining  through.     (After  Joessel.) 


Vertical  Disposition  of  the  Omental  Bursa  {lesser  'peritoneal  sac)  (Fig.  961). — A 
start  may  be  made  in  this  case  on  the  posterior  abdominal  wall  at  the  anterior 
border  of  the  pancreas.  From  this  region  the  peritoneum  may  be  followed  upward 
over  the  pancreas  on  to  the  inferior  surface  of  the  Diaphragma,  and  thence  on  to  the 
caudate  lobe  and  caudate  process  of  the  liver  to  the  fossa  from  the  ductus  venosus 
and  the  porta  of  the  liver.  Traced  to  the  right,  it  is  continuous  over  the  inferior 
vena  cava  with  the  posterior  wall  of  the  main  cavity.  From  the  liver  it  is  carried 
downward  to  the  lesser  curvature  of  the  stomach  and  the  commencement  of  the 
duodenum  as  the  posterior  layer  of  the  lesser  omentum,  and  is  continuous  on  the 
right,  around  the  hepatic  artery,  bile  duct,  and  portal  vein,  with  the  anterior  layer 
of  this  omentum.  The  posterior  layer  of  the  lesser  omentum  is  carried  down  as  a 
covering  for  the  postero-inferior  surfaces  of  the  stomach  and  commencement  of  the 
duodenum,  and  is  continued  downward  as  the  deep  layer  of  the  gastrocolic  ligament 
or  greater  omentum.  From  the  free  margin  of  this  fold  it  is  reflected  upward  on 
itself  to  the  anterior  and  superior  surfaces  of  the  transverse  colon,  and  thence  as 
the  superior  layer  of  the  transverse  mesocolon  to  the  anterior  border  of  the  pancreas, 
the  level  from  which  a  start  was  made.     It  will  be  seen  that  the  loop  formed  by 


THE  PERITONEUM 


1153 


the  wall  of  the  omental  bursa  below  the  transverse  eolon  follows,  and  is  closely 
applied  to,  the  deep  surface  of  that  formed  by  the  peritoneum  of  the  main  cavity, 
and  that  the  jjreater  omentum  or  large  fold  of  peritoneum  which  hangs  in  front 
of  the  small  intestine  therefore  consists  of  four  layers,  two  anterior  and  two  posterior 
separatetl  by  the  |)otential  c-nity  of  the  omental  bursa. 

Horizontal  Disposition  of  the  Peritoneum. — Below  the  transverse  colon  the 
arrangement  is  simi)le,  as  it  includes  only  the  main  cavity;  above  the  level  of  the 
transverse  colon  it  is  more  complicated  on  accoiuit  of  the  existence  of  the  omental 
bursa.  Below  the  transverse  colon  it  may  be  considered  in  the  two  regions,  viz., 
in  the  pelvis  and  in  the  abdomen  proper. 


Jledial 
umbilical  ligament 


Fig.  963. — The  peritoneum  of  the  male  pelvis.      (Dixon  and  Birmingham.) 

(1)  In  the  Pelvis. — The  peritoneum  here  follows  closely  the  surfaces  of  the 
pelvic  viscera  and  the  inequalities  of  the  pelvic  walls,  and  presents  important 
differences  in  the  two  sexes,  {a)  In  the  male  (Fig.  963)  it  encircles  the  sigmoid 
colon,  from  which  it  is  reflected  to  the  posterior  wall  of  the  pelvis  as  a  fold,  the 
sigmoid  mesocolon.  It  then  leaves  the  sides  and,  finally,  the  front  of  the  rectum, 
and  is  continued  on  to  the  upper  ends  of  the  seminal  vesicles  and  the  bladder; 
on  either  side  of  the  rectum  if  forms  a  fossa,  the  pararectal  fossa,  which  varies  in 
size  with  the  distension  of  the  rectum.  In  front  of  the  rectum  the  peritoneum  forms 
the  rectovesical  excavation,  which  is  limited  laterally  by  peritoneal  folds  extending 
from  the  sides  of  the  bladder  to  the  rectum  and  sacrum.  These  folds  are  known 
from  their  position  as  the  rectovesical  or  sacrogenltal  folds.  The  peritoneum  of 
the  anterior  pelvic  wall  covers  the  superior  surface  of  the  bladder,  and  on  either 
side  of  this  viscus  forms  a  depression,  termed  the  paravesical  fossa,  which  is  limited 
laterally  by  the  fold  of  peritoneum  covering  the  ductus  deferens.  The  size  of  this 
fossa  is. dependent  on  the  state  of  distension  of  the  bladder;  when  the  bladder  is 
empty,  a  variable  fold  of  peritoneum,  the  plica  vesicalis  transversa,  divides  the  fossa 
into  two  portions.  On  the  peritoneum  between  the  paravesical  and  pararectal 
fossae  the  only  elevations  are  those  produced  by  the  ureters  and  the  hj^DOgastric 
vessels.  (6)  In  the  female,  pararectal  and  paravesical  fossae  similar  to  those  in  the 
73 


1154 


SPLANCHNOLOGY 


male  are  present :  the  lateral  limit  of  the  paravesical  fossa  is  the  peritoneum  invest- 
ing the  round  ligament  of  the  uterus.  The  rectovesical  excavation  is,  however, 
divided  by  the  uterus  and  vagina  into  a  small  anterior  vesicouterine  and  a  large, 
deep,  posterior  rectouterine  excavation.  The  sacrogenital  folds  form  the  margins 
of  the  latter,  and  are  continued  on  to  the  back  of  the  uterus  to  form  a  transverse 
fold,  the  torus  uterinus.  The  broad  ligaments  extend  from  the  sides  of  the  uterus 
to  the  lateral  walls  of  the  pelvis;  they  contain  in  their  free  margins  the  uterine 
tubes,  and  in  their  posterior  layers  the  ovaries.  Below,  the  broad  ligaments  are 
continuous  with  the  peritoneum  on  the  lateral  walls  of  the  pelvis.  On  the  lateral 
pelvic  wall  behind  the  attachment  of  the  broad  ligament,  in  the  angle  between 
the  elevations  produced  by  the  diverging  hypogastric  and  external  iliac  vessels  is 
a  slight  fossa,  the  ovarian  fossa,  in  which  the  ovary  normally  lies. 


Rectus 


Small  intestine 

Mesentery 


A  orta 


I  nferior  vena  cava 


Ascending  colon 


DesceTiding  colon 

Quadrattus  himhorum 

Psoas  major     I,  .     ,. 

■'.        jSacrospi7ialis 

Fig.  964. — Horizontal  disposition  of  the  peritoneum  in  the  lower  part  of  the  abdomen. 


(2)  In  the  Lower  Abdomen  (Fig.  964). — Starting  from  the  linea  alba,  below  the 
level  of  the  transverse  colon,  and  tracing  the  continuity  of  the  peritoneum  in  a 
horizontal  direction  to  the  right,  the  membrane  covers  the  inner  surface  of  the 
abdominal  wall  almost  as  far  as  the  lateral  border  of  the  Quadratus  lumborum; 
it  encloses  the  cecum  and  vermiform  process,  and  is  reflected  over  the  sides  and  front 
of  the  ascending  colon;  it  may  then  be  traced  over  the  duodenum,  Psoas  major, 
and  inferior  vena  cava  toward  the  middle  line,  whence  it  passes  along  the  mesen- 
teric vessels  to  invest  the  small  intestine,  and  back  again  to  the  large  vessels^  in 
front  of  the  vertebral  column,  forming  the  mesentery,  between  the  layers  of  which 
are  contained  the  mesenteric  bloodvessels,  lacteals,  and  glands.  It  is  then  con- 
tinued over  the  left  Psoas;  it  covers  the  sides  and  front  of  the  descending  colon, 
and,  reaching  the  abdominal  wall,  is  carried  on  it  to  the  middle  line. 

(3)  In  the  Upper  Abdomen  (Fig.  965) . — Above  the  transverse  colon  the  omental 
bursa  is  superadded  to  the  general  sac,  and  the  communication  of  the  two. cavities 
with  one  another  through  the  epiploic  foramen  can  be  demonstrated. 

(a)  Main  Cavity. — Commencing  on  the  posterior  abdominal  wall  at  the  inferior 
vena  cava,  the  peritoneum  may  be  followed  to  the  right  over  the  front  of  the 
suprarenal  gland  and  upper  part  of  the  right  kidney  on  to  the  antero-lateral 


THE  PElilTOSELM 


1155 


abdominal  wall.  From  the  middle  line  of  the  anterior  wall  a  hackwardly  directed 
fold  encircles  the  ohliterated  umhilical  vein  and  forms  the  falciform  ligament 
of  the  liver.  Continning  to  the  left,  the  peritoneum  lines  the  antero-lateral 
abdominal  wall  and  covers  the  lateral  part  of  the  front  of  the  left  kidney,  and  is 
reflected  to  the  posterior  border  of  the  hilus  of  the  spleen  as  the  posterior  layer 
of  the  phrenicolienal  ligament.  It  can  then  be  traced  around  the  surface  of  the  spleen 
to  the  front  of  the  lulus,  and  thence  to  the  cardiac  end  (jf  the  greater  curvature 
of  the  stomach  as  the  anterior  layer  of  the  gastrolienal  ligament.  It  covers  the 
antero-superior  surfaces  of  the  stomach  and  commencement  of  the  duodenum, 
and  extends  up  from  the  lesser  curvature  of  the  stomach  to  the  liver  as  the  anterior 
layer  of  the  lesser  omentum. 

Lesser  omentum 

Falciform  ligament  of  liver 


Gastrolienal 
ligament 


Hepatic  artery 
bile  dtict,and 
portal  vein 


Epiploic 
foramen 

Inferior 
vena  cava 


Phrenicolienal  ligament 

Aorta 
Fig.   965. — Horizontal  disposition  of  the  peritoneum  in  the  upper  part  of  the  abdomen. 


(6)  Omental  Bursa  (bursa  omentalis;  lesser  'peritoneal  sac). — On  the  posterior 
abdominal  wall  the  peritoneum  of  the  general  cavity  is  continuous  with  that  of 
the  omental  bursa  in  front  of  the  inferior  vena  cava.  Starting  from  here,  the 
bursa  may  be  traced  across  the  aorta  and  over  the  medial  part  of  the  front  of 
the  left  kidney  and  Diaphragma  to  the  hilus  of  the  spleen  as  the  anterior  layer 
of  the  phrenicolienal  ligament.  From  the  spleen  it  is  reflected  to  the  stomach  as 
the  posterior  layer  of  the  gastrosplenic  ligament.  It  covers  the  postero-inferior 
surfaces  of  the  stomach  and  commencement  of  the  duodenum,  and  extends 
upward  to  the  liver  as  the  posterior  layer  of  the  lesser  omentum;  the  right  margin 
of  this  layer  is  continuous  around  the  hepatic  artery,  bile  duct,  and  portal  vein, 
with  the  wall  of  the  general  cavity. 

The  epiploic  foramen  (foramen  epiploicum;  foramen  of  Winslow)  is  the  passage  of 
communication  between  the  general  cavit}'  and  the  omental  bursa.  It  is  bounded 
in  front  by  the  free  border  of  the  lesser  omentum,  with  the  common  bile  duct, 
hepatic  artery,  and  portal  vein  between  its  tw^o  layers;  behind  by  the  peritoneum 
covering  the  inferior  vena  cava;  above  by  the  peritoneum  on  the  caudate  process 
of  the  liver,  and  below  by  the  peritoneum  covering  the  commencement  of  the 
duodenum  and  the  hepatic  artery,  the  latter  passing  forward  below  the  foramen 
before  ascending  between  the  two  layers  of  the  lesser  omentum. 

The  boundaries  of  the  omental  bursa  will  now  be  evident.    It  is  bounded  in  front 


1156  SPLANCHNOLOGY 

from  above  downward,  by  the  caudate  lobe  of  the  liver,  the  lesser  omentum,  the 
stomach,  and  the  anterior  two  layers  of  the  greater  omentum.  Behind,  it  is  limited, 
from  below  upward,  by  the  two  posterior  layers  of  the  greater  omentum,  the  trans- 
verse colon,  and  the  ascending  layer  of  the  transverse  mesocolon,  the  upper  surface 
of  the  pancreas,  the  left  suprarenal  gland,  and  the  upper  end  of  the  left  kidney. 
To  the  right  of  the  oesophageal  opening  of  the  stomach  it  is  formed  by  that  part 
of  the  Diaphragma  which  supports  the  caudate  lobe  of  the  liver.  Laterally,  the 
bursa  extends  from  the  epiploic  foramen  to  the  spleen,  where  it  is  limited  by 
the  phrenicolienal  and  gastrolienal  ligaments. 

The  omental  bursa,  therefore,  consists  of  a  series  of  pouches  or  recesses  to  which 
the  following  terms  are  applied:  (1)  the  vestibule,  a  narrow  channel  continued 
from  the  epiploic  foramen,  over  the  head  of  the  pancreas  to  the  gastropancreatic 
fold;  this  fold  extends  from  the  omental  tuberosity  of  the  pancreas  to  the  right 
side  of  the  fundus  of  the  stomach,  and  contains  the  left  gastric  artery  and  coronary 
vein;  (2)  the  superior  omental  recess,  between  the  caudate  lobe  of  the  liver  and  the 
Diaphragma;  (3)  the  lienal  recess,  between  the  spleen  and  the  stomach;  (4)  the 
inferior  omental  recess,  which  comprises  the  remainder  of  the  bursa. 

In  the  fetus  the  bursa  reaches  as  low  as  the  free  margin  of  the  greater  omentum, 
but  in  the  adult  its  vertical  extent  is  usually  more  limited  owing  to  adhesions 
between  the  layers  of  the  omentum.  During  a  considerable  part  of  fetal  life  the 
transverse  colon  is  suspended  from  the  posterior  abdominal  wall  by  a  mesentery 
of  its  own,  the  two  posterior  layers  of  the  greater  omentum  passing  at  this  stage 
in  front  of  the  colon.  This  condition  occasionally  persists  throughout  life,  but  as 
a  rule  adhesion  occurs  between  the  mesentery  of  the  transverse  colon  and  the  pos- 
terior layer  of  the  greater  omentum,  with  the  result  that  the  colon  appears  to  receive 
its  peritoneal  covering  by  the  splitting  of  the  two  posterior  layers  of  the  latter  fold. 
In  the  adult  the  omental  bursa  intervenes  between  the  stomach  and  the  structures 
on  which  that  viscus  lies,  and  performs  therefore  the  functions  of  a  serous  bursa 
for  the  stomach. 

Numerous  peritoneal  folds  extend  between  the  various  organs  or  connect  them 
to  the  parietes;  they  serve  to  hold  the  viscera  in  position,  and,  at  the  same  time, 
enclose  the  vessels  and  nerves  proceeding  to  them.  They  are  grouped  under  the 
three  headings  of  ligaments,  omenta,  and  mesenteries. 

The  ligaments  will  be  described  with  their  respective  organs. 

There  are  two  omenta,  the  lesser  and  the  greater. 

The  lesser  omentum  {omentum  minus;  small  omentum;  gasirohepatic  omentum)  is  the 
duplicature  which  extends  to  the  liver  from  the  lesser  curvature  of  the  stomach  and 
the  commencement  of  the  duodenum.  It  is  extremely  thin,  and  is  continuous  with  the 
two  layers  of  peritoneum  which  cover  respectively  the  antero-superior  and  postero- 
inferior  surfaces  of  the  stomach  and  first  part  of  the  duodenum.  When  these 
two  layers  reach  the  lesser  curvature  of  the  stomach  and  the  upper  border  of  the 
duodenum,  they  join  together  and  ascend  as  a  double  fold  to  the  porta  of  the  liver ; 
to  the  left  of  the  porta  the  fold  is  attached  to  the  bottom  of  the  fossa  for  the  ductus 
venosus,  along  which  it  is  carried  to  the  Diaphragma,  where  the  two  layers  separate 
to  embrance  the  end  of  the  oesophagus.  At  the  right  border  of  the  omentum  the 
two  layers  are  continuous,  and  form  a  free  margin  which  constitutes  the  anterior 
boundary  of  the  epiploic  foramen.  The  portion  of  the  lesser  omentum  extending 
between  the  liver  and  stomach  is  termed  the  hepatogastric  ligament,  while  that 
between  the  liver  and  duodenum  is  the  hepatoduodenal  ligament.  Between  the  two 
layers  of  the  lesser  omentum,  close  to  the  right  free  margin,  are  the  hepatic 
artery,  the  common  bile  duct,  the  portal  vein,  lymphatics,  and  the  hepatic  plexus  of 
nerves — all  these  structures  being  enclosed  in  a  fibrous  capsule  (Glisson's  capsule). 
Between  the  layers  of  the  lesser  omentum,  where  they  are  attached  to  the 
stomach,  run  the  right  and  left  gastric  vessels. 


THE  PERITONEUM  1157 

Tlie  greater  omentum  (oiitcntinii  iiiajua;  great  omentum;  gastrocolic  omentu in)  is  the 
largest  peritoneal  fold.  It  consists  of  a  double  sheet  of  peritoneum,  folded  on  itself 
so  that  it  is  made  up  of  four  layers.  The  two  layers  which  descend  from  the  stomach 
and  commencement  of  the  duodenum  pass  in  front  of  the  small  intestines,  sometimes 
as  low  down  as  the  i)elvis;  they  tlien  turn  upon  themselves,  and  ascend  again  as 
far  as  the  transverse  colon,  where  they  separate  and  enclose  that  part  of  the  intes- 
tine. These  individual  layers  may  be  easily  demonstrated  in  the  young  subject, 
but  in  the  adult  they  are  more  or  less  inseparably  blended.  The  left  border  of  the 
greater  omentum  is  continuous  with  the  gastrolienal  ligament;  its  right  border 
extends  as  far  as  the  commencement  of  the  duodenum.  The  greater  omentum  is 
usually  thin,  presents  a  cribriform  appearance,  and  always  contains  some  adipose 
tissue,  which  in  fat  people  accumulates  in  considerable  quantit3\  Between  its 
two  anterior  layers,  a  short  distance  from  the  greater  curvature  of  the  stomach, 
is  the  anastomosis  between  the  right  and  left  gastroepiploic  vessels. 

The  mesenteries  are:  the  mesentery  proper,  the  transverse  mesocolon,  and  the 
sigmoid  mesocolon.  In  addition  to  these  there  are  sometimes  present  an  ascending 
and  a  descending  mesocolon. 

The  mesentery  proper  {mesenterium)  is  the  broad,  fan-shaped  fold  of  peritoneum 
which  connects  the  convolutions  of  the  jejunum  and  ileum  with  the  posterior  wall 
of  the  abdomen.  Its  root — the  part  connected  wdth  the  structures  in  front  of  the 
vertebral  column — is  narrow,  about  15  cm.  long,  and  is  directed  obliquely  from  the 
duodenojejunal  flexure  at  the  left  side  of  the  second  lumbar  vertebra  to  the  right 
sacroiliac  articulation  (Fig.  966).  Its  intestinal  border  is  about  6  metres  long;  and 
here  the  two  layers  separate  to  enclose  the  intestine,  and  form  its  peritoneal  coat. 
It  is  narrow  above,  but  widens  rapidly  to  about  20  cm.,  and  is  thrown  into  numerous 
plaits  or  folds.  It  suspends  the  small  intestine,  and  contains  between  its  layers 
the  intestinal  branches  of  the  superior  mesenteric  artery,  with  their  accompanying 
veins  and  plexuses  of  nerves,  the  lacteal  vessels,  and  mesenteric  lymph  glands. 

The  transverse  mesocolon  {mesocolon  transversum)  is  a  broad  fold,  which  connects 
the  transverse  colon  to  the  posterior  wall  of  the  abdomen.  It  is  continuous  with 
the  two  posterior  layers  of  the  greater  omentum,  which,  after  separating  to  surround 
the  transverse  colon,  join  behind  it,  and  are  continued  backward  to  the  vertebral 
column,  where  the}^  diverge  in  front  of  the  anterior  border  of  the  pancreas.  This 
fold  contains  between  its  layers  the  vessels  which  supply  the  transverse  colon. 

The  sigmoid  mesocolon  {mesocolon  sigmoideum)  is  the  fold  of  peritoneum  which 
retains  the  sigmoid  colon  in  connection  with  the  pelvic  wall.  Its  line  of  attachment 
forms  a  V-shaped  curve,  the  apex  of  the  curve  being  placed  about  the  point  of 
division  of  the  left  common  iliac  artery.  The  curve  begins  on  the  medial  side  of 
the  left  Psoas  major,  and  runs  upward  and  backward  to  the  apex,  from  which  it 
bends  sharply  downward,  and  ends  in  the  median  plane  at  the  level  of  the  third 
sacral  vertebra.  The  sigmoid  and  superior  hemorrhoidal  vessels  run  between  the 
two  layers  of  this  fold. 

In  most  cases  the  peritoneum  covers  only  the  front  and  sides  of  the  ascending 
and  descending  parts  of  the  colon.  Sometimes,  however,  these  are  surrounded 
by  the  serous  membrane  and  attached  to  the  posterior  abdominal  wall  by  an 
ascending  and  a  descending  mesocolon  respectively.  A  fold  of  peritoneum,  the 
phrenicocolic  ligament,  is  continued  from  the  left  colic  flexure  to  the  Diaphragma 
opposite  the  tenth  and  eleventh  ribs;  it  passes  below  and  serves  to  support  the 
spleen,  and  therefore  has  received  the  name  of  sustentaculum  lienis. 

The  appendices  epiploicae  are  small  pouches  of  the  peritoneum  filled  wdth  fat 
and  situated  along  the  colon  and  upper  part  of  the  rectum.  They  are  chiefly 
appended  to  the  transverse  and  sigmoid  parts  of  the  colon. 

Peritoneal  Recesses  or  Fossae  {retroperitoneal  fossae). — In  certain  parts  of  the 
abdominal  cavit}''  there  are  recesses  of  peritoneum  forming  culs-de-sac  or  pouches. 


1158 


SPLANCHNOLOGY 


which  are  of  surgical  interest  in  connection  with  the  possibihty  of  the  occurrence 
of  "retroperitoneal"  hernise.  The  hirgest  of  these  is  the  omental  bursa  (already 
described),  but  several  others,  of  smaller  size,  require  mention,  and  may  be  divided 
into  three  groups,  viz.:  duodenal,  cecal,  and  inter  sigmoid. 


Jli<lld  Iriangultir   Falciform  ligament 
I  lyament  oj  huLr  oj  hiicr 


Lift  Iriangulnr 
ligament  vj  liotr 


Inferior  vena  cava  .    ~^j '. 

(Esophagus  . 
Bight  phrenic  artery  . 

Left  gastric  artery  ■ 
Hepatic  artery 

Lienal  artery  ■ 
Fancreas  ' 

Inf.  panciiuo.  artery  - 

Middle  colic  ■ 

Superior  mesenteric  - 

Duodenum  (horiz.  part)  .- 

Aorta  - 

Duodenum  (desc.  part)  - 

Right  and  left  kidneys  ■ 

Superior  mesenteric  ' 

Aorta  - 

Left  colic 

Right  colic  —   ~ 

Intestinal  arteries  <  ;; 


Si {nnoid  artery  • 

Su2).  hemorrhoidal  artery 

Common  iliac  artery  —     - 


Hypogastric  artery  -~ 

External  iliac  artery  .  ■ 

Inf.  epigastric  artery  '— 
Bladder  ' 


Peritoneum, 

"'  '  Extraperitoneal  tissue 

\].,  ^.  ( Diaphragmatic  end  of 
•    i      lesser  omentum 
"  Gastrophrenic  ligariuni 


Phrenicoliemtl  ligament 
J'l/iploic  foramen 
Duodenum  (sup.  part) 


Phrevicocolic  ligament 
I  Dot  between  two  anterior 
i  layers  of  greater  omentum 

Transverse  mesocolon 


( Bare  surface  for  descend- 
\  ing  colon 


/  The  tivo  layers  of  tlie 
(,     mesetitery  proper 


<  Bare  surface  for  ascend- 
I  ing  Colon 


Iliac  mesocolon 


Sigmoid  mesocolon 

Bare  surface  for  rectum 

f  Cut  edge  of  peritoneum 
(.  on  bladder 


Fig.  966. — Diagram  devised  by  Del6pine  to  show  the  Knes  along  which  the  peritoneum  leaves  the  wall  of  the  abdomen 

to  invest  the  viscera. 


1.  Duodenal  Fossae  (Figs.  967,  968). — Three  are  fairly  constant,  viz.:  (a)  The 
inferior  duodenal  fossa,  present  in  from  70  to  75  per  cent,  of  cases,  is  situated 
opposite  the  third  lumbar  vertebra  on  the  left  side  of  the  ascending  portion  of 
the  duodenum.  Its  opening  is  directed  upward,  and  is  bounded  by  a  thin  sharp 
fold  of  peritoneum  with  a  concave  margin,  called  the  duodenomesocolic  fold.  The 
tip  of  the  index  finger  introduced  into  the  fossa  under  the  fold  passes  some 
little  distance  behind  the  ascending  portion  of  the  duodenum.  (6)  The  superior 
duodenal  fossa,  present  in  from  40  to  50  per  cent,  of  cases,  often  coexists  with  the 
inferior  one,  and  its  orifice  looks  downward.  It  lies  on  the  left  of  the  ascending 
portion  of  the  duodenum,  in  front  of  the  second  lumbar  vertebra,  and  behind  a 


THE  PERITONEUM 


1159 


sickle-shaped  fold  of  peritoneum,  the  duodenojejunal  fold,  and  has  a  depth  of  about 
2  cm.  (c)  The  duodenojejunal  fossa  exists  in  from  15  to  20  per  cent,  of  cases, 
but  has  never  yet  been  found  in  conjunction  with  the  other  forms  of  duodenal 
fossse;  it  can  be  seen  by  pulling  the  jejunum  downward  and  to  the  right,  after  the 


\         Inferior 
Tnenenteric 


Duode  no  jejunal 
"j  fold 

Superior 
duodenal  fossa 


Inferior 


juj  _/     dvjodenal  fossa 

~^^-^»iL.__/__  Du ode nomesocol  ic 
-        ^//  fold 

.'    y~~~~-~  Left  colic  artery 
Fig.  967. — Superior  and  inferior  duodenal  fossae.     (Poirier  and  Charpy.) 

transverse  colon  has  been  pulled  upward.  It  is  bounded  above  by  the  pancreas, 
to  the  right  by  the  aorta,  and  to  the  left  by  the  kidney;  beneath  is  the  left  renal 
vein.  It  has  a  depth  of  from  2  to  3  cm.,  and  its  orifice,  directed  downward  and  to 
the  right,  is  nearly  circular  and  will  admit  the  tip  of  the  little  finger. 


Duodenum 


Right 
duodeno- 
mesocolic 

fold 


Inferior 

'mesenteric  vein 

Left 

duode  nomesocol  ic 

fold 

Left  colic  artery 


Inferior  mesenteric  artery 
Fig.  968. — Duodenojejunal  fossa.     (Poirier  and  Charpy.) 

2.  Cecal  Fossae  (pericecal  folds  or  fossce). — There  are  three  principal  pouches 
or  recesses  in  the  neighborhood  of  the  cecum  (Figs.  969  to  971) :  (a)  The  superior 
ileocecal  fossa  is  formed  by  a  fold  of  peritoneum,  arching  over  the  branch  of  the 


1160 


SPLANCHNOLOGY 


Siiperiw 

ileocrral 

Jvld 


Anterior 
ileocecal 
ai  tei  y 


ileocolic  artery  which  supplies  the  ileocolic  junction.  The  fossa  is  a  narrow  chink 
situated  between  the  mesentery  of  the  small  intestine,  the  ileum,  and  the  small 
portion  of  the  cecum  behind.  (6)  The  inferior  ileocecal  fossa  is  situated  behind  the 
angle  of  junction  of  the  ileum  and  cecum.  It  is  formed  by  the  ileocecal  fold  of 
peritoneum  (bloodless  fold  of  Treves),  the  upper  border  of  which  is  fixed  to  the  ileum, 

opposite  its  mesenteric  attach- 
ment, while  the  lower  border, 
passing  over  the  ileocecal  junc- 
tion, joins  the  mesenteriole  of  the 
vermiform  process,  and  some- 
times the  process  itself.  Between 
this  fold  and  the  mesenteriole 
of  the  vermiform  process  is  the 
inferior  ileocecal  fossa.  It  is 
bounded  above  by  the  posterior 
surface  of  the  ileum  and  the  me- 
sentery; in  front  and  below  by  the 
ileocecal  fold,  and  behind  by  the 
upper  part  of  the  mesenteriole 
of  the  vermiform  process,  (c) 
The  cecal  fossa  is  situated  im- 
mediately behind  the  cecum, 
which  has  to  be  raised  to  bring 

Fig.  969.— Superior  Ueocecal  fossa.     (Poirier  and  Charpy.)  it   luto   VlCW.      It  VariCS    mUCh   in 

size  and  extent.  In  some  cases 
it  is  sufficiently  large  to  abmit  the  index  finger,  and  extends  upward  behind  the 
ascending  colon  in  the  direction  of  the  kidney;  in  others  it  is  merely  a  shallow 
depression.  It  is  bounded  on  the  right  by  the  cecal  fold,  which  is  attached  by 
one  edge  to  the  abdominal  wall  from  the  lower  border  of  the  kidney  to  the  iliac 
fossa  and  by  the  other  to  the  postero-lateral  aspect  of  the  colon.  In  some 
instances  additional  fossse,  the  retrocecal  fossae,  are  present. 


—  Mesentery 


Superior 

ileocecal 

fosna 

Inferior 
ileocecal 

fold 
Ileum 


Inferior 
leocecal  fos^a 


Mesentery 


5|—  '\  Artery  to 

■^    J  vermiform  process 


Mesenteriole  of 
vermiform  process 


Fig.  970. — Inferior  ileocecal  fossa.     The  cecum  and  ascending  colon  have  been  drawn  lateralward  and  downward, 
the  ileum  upward  and  backward,  and  the  vermiform  process  downward.    (Poirier  and  Charpy.) 


3.  The  intersigmoid  fossa  (recessus  intersigmoideus)  is  constant  in  the  fetus  and 
during  infancy,  but  disappears  in  a  certain  percentage  of  cases  as  age  advances. 
Upon  drawing  the  sigmoid  colon  upward,  the  left  surface  of  the  sigmoid  mesocolon 
is  exposed,  and  on  it  will  be  seen  a  funnel-shaped  recess  of  the  peritoneum,  lying 
on  the  external  iliac  vessels,  in  the  interspace  between  the  Psoas  and  Iliacus  muscles. 
This  is  the  orifice  leading  to  the  intersigmoid  fossa,  which  lies  behind  the  sigmoid 


THE  STOMACH 


1161 


mesocolon,  and  in  front  of  the  parietal  peritoneum.  The  fossa  varies  in  size;  in 
some  instances  it  is  a  mere  dimple,  whereas  in  others  it  will  admit  the  whole  of  the 
index  finger. 

Inferior  Ueoca'cal 
fold 


Inferior  ileoccecal  fossa 

Mesenteriole  of 
vermiform  'process 


Mesentericoparietal 
fold 


C cecal  fossa 
Fig.  971. — The  cecal  fossa.      The  ileum  and  cecum  are  drawn  backward  and  upward.     (SouUgoux.) 

Applied  Anatomy. — Any  of  these  fossae  may  be  the  site  of  a  "retroperitoneal"  hernia.  The 
cecal  fossae  are  of  special  interest,  because  hernia  of  the  vermiform  process  frequently  takes 
place  into  one  of  them,  and  it  may  there  become  strangulated.  The  presence  of  these  pouches 
also  explains  the  course  which  pus  has  been  known  to  take  in  cases  of  perforation  of  the  vermi- 
form process,  where  it  travels  upward  behind  the  ascending  colon  as  far  as  the  Diaphragma.^ 


The  Stomach  ( Ventriculus ;  Gaster). 

The  stomach  is  the  most  dilated  part  of  the  digestive  tube,  and  is  situated  between 
the  end  of  the  oesophagus  and  the  beginning  of  the  small  intestine.  It  lies  in  the 
epigastric,  umbilical,  and  left  hypochondriac  regions  of  the  abdomen,  and  occupies 
a  recess  bounded  by  the  upper  abdominal  viscera,  and  completed  in  front  and  on 
the  left  side  by  the  anterior  abdominal  wall  and  the  Diaphragma. 

The  shape  and  position  of  the  stomach  are  so  greatly  modified  by  changes  within 
itself  and  in  the  surrounding  viscera  that  no  one  form  can  be  described  as  typical. 
The  chief  modifications  are  determined  by  (1)  the  amount  of  the  stomach  contents, 
(2)  the  stage  which  the  digestive  process  has  reached,  (3)  the  degtee  of  develop- 
ment of  the  gastric  musculature,  and  (4)  the  condition  of  the  adjacent  intestines. 
It  is,  however,  possible  by  comparing  a  series  of  stomachs  to  determine  certain 
markings  more  or  less  common  to  all  (Figs.  972,  973). 

The  stomach  presents  two  openings,  two  borders  or  curvatures,  and  two  surfaces. 

Openings. — The  opening  by  which  the  oesophagus  communicates  with  the 
stomach  is  known  as  the  cardiac  orifice,  and  is  situated  on  the  left  of  the  middle 
line  at  the  level  of  the  tenth  thoracic  vertebra.  The  short  abdominal  portion  of  the 
oesophagus  {antrum  cardiacum)  is  conical  in  shape  and  curved  sharply  to  the  left, 
the  base  of  the  cone  being  continuous  with  the  cardiac  orifice  of  the  stomach. 
The  right  margin  of  the  oesophagus  is  continuous  with  the  lesser  curvature  of  the 


1  On  the  anatomy  of  these  fossse,  see  the  Arris  and  Gale  Lectures  by  Moynihan,  1899. 


1162 


SPLANCHNOLOGY 


stomach,  while  the  left  margin  joins  the  greater  curvature  at  an  acute  angle,  termed 
the  incisura  cardiaca. 

The  pyloric  orifice  communicates  with  the  duodenum,  and  its  position  is  usually 
indicated  on  the  surface  of  the  stomach  by  a  circular  groove,  the  duodenopyloric 
constriction.  This  orifice  lies  to  the  right  of  the  middle  line  at  the  level  of  the  upper 
border  of  the  first  lumbar  vertebra. 

Curvatures. — The  lesser  curvature  (curvatura  ventriculi  minor),  extending  between 
the  cardiac  and  pyloric  orifices,  forms  the  right  or  posterior  border  of  the  stomach. 
It  descends  as  a  continuation  of  the  right  margin  of  the  oesophagus  in  front  of  the 
fibres  of  the  right  crus  of  the  Diaphragma,  and  then,  turning  to  the  right,  it  crosses 
the  first  lumbar  vertebra  and  ends  at  the  pylorus.  Nearer  its  pyloric  than  its 
cardiac  end  is  a  well-marked  notch,  the  incisura  angularis,  which  varies  somewhat 
in  position  with  the  state  of  distension  of  the  viscus;  it  serves  to  separate  the 
stomach  into  a  right  and  a  left  portion.  The  lesser  curvature  gives  attachment 
to  the  two  layers  of  the  hepatogastric  ligament,  and  between  these  two  layers  are 
the  left  gastric  artery  and  the  right  gastric  branch  of  the  hepatic  artery. 


Antrum, 


Incisur 


Pyloroduodenal 
openini) 

Pyloric  antrum 
Sulcus  intermedius 


Pyloric  part 

Fig.  972. — Outline  of  stomach,  showing  its  anatomical 
landmarks. 


Incisura 
angularis 


Pylorus  Mttscvlnr  constriction  oetween 

cardiac  and  pyloric  portions 


Fig.  973. — Outline  of  stomach  at  an  early  stage  of 
gastric  digestion. 


The  greater  curvature  (curvatura  ventriculi  major)  is  directed  mainly  forward, 
and  is  four  or  five  times  as  long  as  the  lesser  curvature.  Starting  from  the  cardiac 
orifice  at  the  incisura  cardiaca,  it  forms  an  arch  backward,  upward,  and  to  the  left; 
the  highest  point  of  the  convexity  is  on  a  level  with  the  sixth  left  costal  cartilage. 
From  this  level  it  may  be  followed  downward  and  forward,  with  a  slight  convexity 
to  the  left  as  low  as  the  cartilage  of  the  ninth  rib ;  it  then  turns  to  the  right,  to  the 
end  of  the  pylorus.  Directly  opposite  the  incisura  angularis  or  the  lesser  curva- 
ture the  greater  curvature  presents  a  dilatation,  which  is  the  left  extremity  of  the 
pyloric  part;  this  dilatation  is  limited  on  the  right  by  a  slight  groove,  the  sulcus 
intermedius,  which  is  about  2.5  cm,  from  the  duodenopyloric  constriction.  The 
portion  between  the  sulcus  intermedius  and  the  duodenopyloric  constriction  is 
termed  the  pyloric  antrum.  At  its  commencement  the  greater  curvature  is  covered 
by  peritoneum  continuous  with  that  covering  the  front  of  the  organ.  The  left 
part  of  the  curvature  gives  attachment  to  the  gastrolienal  ligament,  while  to  its 
anterior  portion  are  attached  the  two  layers  of  the  greater  omentum,  separated 
from  each  other  by  the  gastroepiploic  vessels. 

Surfaces. — When  the  stomach  is  in  the  contracted  condition,  its  surfaces  are 
directed  upward  and  downward  respectively,  but  when  the  viscus  is  distended  they 
are  directed  forward,  and  backward.  They  may  therefore  be  described  as  antero- 
superior  and  postero-inferior. 

Antero-superior  Surface. — The  left  half  of  this  surface  is  in  contact  with  the 
Diaphragma,  which  separates  it  from  the  base  of  the  left  lung,  the  pericardium. 


THE  STOMACH  1163 

and  the  seventh,  eighth,  and  ninth  ribs,  and  intercostal  spaces  of  the  left  side.  The 
right  hah'  is  in  relation  witli  the  left  and  quadrate  lobes  of  the  liver  and  with  the 
anterior  abdominal  wall.  When  the  stomach  is  empty,  the  transverse  colon  may 
lie  on  the  front  part  of  this  surface.  The  whole  surface  is  covered  by  peritoneum. 
The  Postero-inferior  Surface  is  in  relation  with  the  Diaphragma,  the  spleen, 
the  left  sui)rarenal  gland,  the  upper  part  of  the  front  of  the  left  kidney,  the  anterior 
surface  of  the  pancreas,  the  left  colic  flexure,  and  the  upper  layer  of  the  transverse 
mesocolon.  These  structures  form  a  shallow  bed,  the  stomach  bed,  on  wdiich  the 
viscus  rests.  The  transverse  mesocolon  separates  the  stomach  from  the  duodeno- 
jejunal flexure  and  small  intestine.  The  postero-inferior  surface  is  covered  by 
peritoneum,  except  over  a  small  area  close  to  the  cardiac  orifice;  this  area  is  limited 
by  the  lines  of  attachment  of  the  gastrophrenic  ligament,  and  lies  in  apposition 
with  the  Diaphragma,  and  frequently  w^ith  the  upper  portion  of  the  left  supra- 
renal gland. 

Component  Parts  of  the  Stomach. — The  stomach  is  capable  of  subdivision  into  distinctive 
parts,  and  the  divisions  may  be  made  on  either  anatomical  or  chnical  grounds. 

Anatomical  Subdivisions. — A  plane  passing  through  the  incisura  angularis  on  the  lesser  curva- 
ture and  the  left  limit  of  the  opposed  dilatation  on  the  greater  curvature  divides  the  stomach 
into  a  left  portion  or  body  and  a  right  or  pyloric  portion.  The  left  portion  of  the  body  is  known 
as  the  fundus,  and  is  marked  off  from  the  remainder  of  the  body  by  a  plane  passing  horizon- 
tally through  the  cardiac  orifice.  The  pyloric  portion  is  divided  by  a  plane  through  the  sulcus 
intermedius  at  right  angles  to  the  long  axis  of  this  portion;  the  part  to  the  right  of  this  plane 
is  the  pyloric  antrum  (Fig   972). 

Clinical  Subdivisions. — If  the  stomach  be  examined  during  the  process  of  digestion  it  will  be 
found  divided  by  a  muscular  constriction  into  a  large  dilated  left  portion,  arid  a  narrow  con- 
tracted tubular  right  portion.  The  constriction  is«in  the  body  of  the  stomach,  and  does  not 
follow  any  of  the  anatomical  landmarks;  indeed,  it  shifts  gradually  toward  the  left  as  digestion 
progresses,  i.  e.,  more  of  the  body  is  gradually  absorbed  into  the  tubular  part.  These  two  por- 
tions are  known  as  the  fundus  and  pyloric  portions.  It  will  be  seen  therefore  that  the  clinical 
fundus  includes  the  anatomical  fundus  and  the  proximal  part  of  the  body,  while  the  chnical 
pyloric  portion  comprises  the  distal  p^rt  of  the  body,  and  the  anatomical  pyloric  part  (Fig.  973). 

Position  of  the  Stomach. — The  position  of  the  stomach  varies  with  the  posture,  with  the 
amount  of  the  stomach  contents  and  with  the  condition  of  the  intestines  on  which  it  rests.  In 
the  erect  postm'e  the  empty  stomach  is  somewhat  J-shaped;  the  part  above  the  cardiac  orifice 
is  usually  distended  with  gas;  the  pylorus  descends  to  the  level  of  the  second  Imnbar  vertebra 
and  the  most  dependent  part  of  the  stomach  is  at  the  level  of  the  umbilicus.  Variation  in  the 
amount  of  its  contents  affects  mainly  the  cardiac  portion,  the  pyloric  portion  remaining  in  a  more 
or  less  contracted  condition  during  the  process  of  digestion.  As  the  stomach  fills  it  tends  to 
expand  forward  and  downward  in  the  direction  of  least  resistance,  but  when  this  is  interfered 
with  by  a  distended  condition  of  the  colon  or  intestines  the  fundus  presses  upward  on  the  hver 
and  Diaphragma  and  gives  rise  to  the  feelings  of  oppression  and  palpitation  complaiaed  of  in 
such  cases.  His^  and  Cimningham^  have  shown  by  hardening  the  viscera  in  situ  that  the  con- 
tracted stomach  has  a  sickle  shape,  the  fundus  looking  du'ectly  backward.  The  surfaces  are 
directed  upward  and  downward,  the  upper  siurface  having,  however,  a  gi'adual  downward  slope 
to  the  right.    The  greater  curvature  is  in  front  and  at  a  slightly  higher  level  than  the  lesser. 

The  position  of  the  full  stomach  depends,  as  aheady  indicated,  on  the  state  of  the  intestines; 
when  these  are  empty  the  fimdus  expands  vertically  and  also  forward,  the  pylorus  is  displaced 
toward  the  right  and  the  whole  organ  assumes  an  oblique  position,  so  that  its  surfaces  are  directed 
more  forward  and  backward.  The  lowest  part  of  the  stomach  is  at  the  pyloric  vestibule,  which 
reaches  to  the  region  of  the  mnbilicus.  Where  the  intestines  iaterfere  with  the  downward 
expansion  of  the  fundus  the  stomach  retains  the  horizontal  position  which  is  characteristic  of 
the  contracted  viscus. 

Examination  of  the  stomach  during  Ufe  by  a;-rays  has  confirmed  these  findings.,  and  has 
demonstrated  that,  in  the  erect  posture,  the  full  stomach  usually  presents  a  hook-hke  appear- 
ance, the  long  axis  of  the  clinical  fundus  being  directed  downward,  medialward,  and  forward 
toward  the  umbiUcus,  while  the  pyloric  portion  curves  upward  to  the  duodenopyloric  junction. 

Interior  of  the  Stomach. — When  examined  after  death,  the  stomach  is  usually  fixed  at  some 
temporary  stage  of  the  digestive  process.  A  common  form  is  that  shown  in  Fig.  974.  If  the 
viscus  be  laid  open  by  a  section  through  the  plane  of  its  two  curvatures,  it  is  seen  to  consist  of 
two  segments:    (a)  a  large  globular  portion  on  the  left  and  (&)  a  narrow  tubular  part  on  the 

^  Archiv  fiir  Anatomie  und  Physiologie,  anat.  Abth.,  1903. 

-  Transactions  of  the  Royal  Society  of  Edinburgh,  vol.  xlv,  part  i. 


1164 


SPLANCHNOLOGY 


right.  These  correspond  to  the  clinical  subdivisions  of  fundus  and  pjdoric  portions  already 
described,  and  are  separated  by  a  constriction  which  indents  the  body  and  greater  curvature, 
but  does  not  involve  the  lesser  curv^ature.  To  the  left  of  the  cardiac  orifice  is  the  incisura 
cardiaca:  the  projection  of  this  notch  into  the  cavity  of  the  stomach  increases  as  the  organ 
distends,  and  has  been  supposed  to  act  as  a  valve  preventing  regurgitation  into  the  oesophagus. 
In  the  pyloric  portion  are  seen:  (a)  the  elevation  corresponding  to  the  incisura  angularis,  and 
(6)  the  circular  projection  from  the  duodenopyloric  constriction  which  forms  the  pyloric  valve; 
the  separation  of  the  pyloric  antrum  from  the  rest  of  the  pyloric  part  is  scarcely  indicated. 

The  pyloric  valve  (valmla  pylori)  is  formed  by  a  reduplication  of  the  mucous 
membrane  of  the  stomach,  covering  a  muscular  ring  composed  of  a  thickened  por- 
tion of  the  circular  layer  of  the  muscular  coat.  Some  of  the  deeper  longitudinal 
fibres  turn  in  and  interlace  with  the  circular  fibres  of  the  valve. 


Pylor 
Pylor, 


Fig.  974. — Interior  of  the  stomach. 


Structure. — The  wall  of  the  stomach  consists  of  fom-  coats:  serous,  muscular,  areolar,  and 
mucous,  together  with  vessels  and  nerves. 

The  serous  coat  (tunica  serosa)  is  derived  from  the  peritoneum,  and  covers  the  entire  surface 
of  the  organ,  excepting  along  the  greater  and  lesser  curvatures  at  the  points  of  attachment  of 
the  greater  and  lesser  omenta;  here  the  two  layers  of  peritoneum  leave  a  small  triangular  space, 
along  which  the  nutrient  vessels  and  nerves  pass.  On  the  posterior  surface  of  the  stomach, 
close  to  the  cardiac  orifice,  there  is  also  a  small  area  uncovered  by  peritoneum,  where  the  organ 
is  in  contact  with  the  under  surface  of  the  Diaphragma. 

The  muscular  coat  (tunica  muscularis)  (Figs.  975,  976)  is  situated  immediately  beneath  the 
serous  covering,  with  which  it  is  closely  connected.  It  consists  of  three  sets  of  fibres:  longi- 
tudinal, circular,  and  obhque. 

The  longitudinal  fibres  (stratum  lonqitudinale)  are  the  most  superficial,  and  are  arranged  in 
two  sets.  The  first  set  consists  of  fibres  continuous  with  the  longitudinal  fibres  of  the  oesophagus; 
they  radiate  in  a  stellate  manner  from  the  cardiac  orifice  and  are  practically  all  lost  before  the 
pyloric  portion  is  reached.  The  second  set  commences  on  the  body  of  the  stomach  and  passes 
to  the  right,  its  fibres  becoming  more  thickly  distributed  as  they  approach  the  pylorus.  Some 
of  the  more  superficial  fibres  of  this  set  pass  on  to  the  duodenum,  but  the  deeper  fibres  dip  inward 
and  interlace  with  the  circular  fibres  of  the  pyloric  valve. 

The  circular  fibres  (stratum  circulare)  form  a  imiform  layer  over  the  whole  extent  of  the  stomach 
beneath  the  longitudinal  fibres.  At  the  pylorus  they  are  most  abundant,  and  are  aggregated  into 
a  circular  ring,  which  projects  into  the  limien,  and  forms,  with  the  fold  of  mucous  membrane 
covering  its  surface,  the  pyloric  valve.  They  are  continuous  with  the  circular  fibres  of  the 
oesophagus,  but  are  sharply  marked  off  from  the  circular  fibres  of  the  duodenimi. 

The  oblique  fibres  (fibrae  obliquae)  internal  to  the  circular  layer,  are  Limited  chiefly  to  the 
cardiac  end  of  the  stomach,  where  they  are  disposed  as  a  thick  uniform  layer,  covering  both 
surfaces,  some  passing  obhquely  from  left  to  right,  others  from  right  to  left,  around  the  cardiac 
end. 


THE  STOMACH 


1165 


The  areolar  or  submucous  coat  (tela  sttbyimcosn)  consists  of  a  loose,  areolar  tissue,  connecting 
the  mucous  anil  muscular  layers. 

The  mucous  membrane  {tunica  mucosa)  is  thick  and  its  surface  is  smooth,  soft,  and  velvety. 
In  the  fresh  state  it  is  of  a  pinkish  tinge  at  the  pyloric  end,  and  of  a  red  or  reddish-brown  color 


CEsophagius- — 


Fig.  975. — The  longitudinal  and  circular  muscular  fibres  of  the  stomach,  viewed  from  above  and  in  front.  (Spalteholz .) 

over  the  rest  of  its  surface.  In  infancy  it  is  of  a  brighter  hue,  the  vascular  redness  being  more 
marked.  It  is  thin  at  the  cardiac  extremity,  but  thicker  toward  the  pylorus.  During  the  con- 
tracted state  of  the  organ  it  is  thrown  into  numerous  plaits  or  rugae,  which,  for  the  most  part, 


(EsopJiagu 


Fig.  976. — The  oblique  niuscula 


\iewed  from  above  and  in  front.      (Spalteholz.) 


have  a  longitudinal  direction,  and  are  most  marked  toward  the  pyloric  end  of  the  stomach, 
and  along  the  greater  cur^^ature  (Fig.  974).  These  folds  are  entirely  obliterated  when  the  organ 
becomes  distended. 


1166  SPLAXCHXOLOGY 

Structure  of  the  Mucous  Membrane.- — When  examined  with  a  lens,  the  inner  surface  of  the 
mucous  membrane  presents  a  pecuhar  honeycomb  appearance  from  being  covered  with  small 
shallow  depressions  or  alveoh,  of  a  polygonal  or  hexagonal  form,  which  vary  from  0.12  to  0.25 
mm.  in  diameter.  These  are  the  ducts  of  the  gastric  glands,  and  at  the  bottom  of  each  may  be 
seen  one  or  more  minute  orifices,  the  openings  of  the  gland  tubes.  The  surface  of  the  mucous 
membrane  is  covered  by  a  single  layer  of  colmnnar  epithehmn  with  occasional  goblet  cells.  This 
epithelium  commences  very  abruptly  at  the  cardiac  orifice,  where  there  is  a  sudden  transition 
from  the  stratified  epitheUum  of  the  esophagus.  The  epithehal  lining  of  the  gland  ducts  is  of 
the  same  character  and  is  continuous  with  the  general  epithelial  lining  of  the  stomach  (Fig.  979). 

The  Gastric  Glands. — The  gastric  glands  are  of  three  kinds:  (a)  pyloric,  (fe)  cardiac,  and  (c) 
fundus  or  oxjoitic  glands.  They  are  tubular  in  character,  and  are  formed  of  a  delicate  basement- 
membrane,  consisting  of  flattened  transparent  endothehal  cells  lined  by  epithelium.  The  pyloric 
glands  (Fig.  978)  are  found  in  the  pyloric  portion  of  the  stomach.  They  consist  of  two  or 
three  short  closed  tubes  opening  into  a  common  duct  or  mouth.  These  tubes  are  wavy,  and 
are  about  one-half  the  length  of  the  duct.  The  duct  is  lined  by  columnar  cells,  continuous 
with  the  epithehmn  lining  the  surface  of  the  mucous  membrane  of  the  stomach,  the  tubes 
by  shorter  and  more  cubical  cell  which  are  finely  granular.  The  cardiac  glands  (Fig.  977), 
few  in  number,  occur  close  to  the  cardiac  orifice.    They  are  of  two  kinds:    (1)  simple  tubular 

w  or 


Fig.  977. — Section  of  mucous  membrane  of  human  stomach,  near  the  cardiac  orifice,  (v.  Ebner,  after  J.  Schaffer.) 
X  45.  c.  Cardiac  glands,  d.  Their  ducts,  cr.  Gland  similar  to  the  intestinal  glands,  with  goblet  cells,  mm.  Mucoua 
membrane,    m.  Muscularis  mucosae,    m'.  Muscular  tissue  within  the  mucous  membrane. 

glands  resembUng  those  of  the  pyloric  end  of  the  stomach,  but  with  short  ducts;  ^2)  com- 
pound racemose  glands  resembling  the  duodenal  glands.  The  fundus  glands  (Fig.  979)  are 
found  in  the  body  and  fundas  of  the  stomach;  they  are  simple  tubes,  two  or  more  of  which 
open  into  a  single  duct.  The  duct,  however,  in  these  glands  is  shorter  than  in  the  pyloric 
variety,  sometimes  not  amounting  to  more  than  one-sixth  of  the  whole  length  of  the  gland; 
it  is  lined  throughout  by  columnar  epithelium.  The  gland  tubes  are  straight  and  parallel  to  each 
other.  At  the  point  where  they  open  into  the  duct,  which  is  termed  the  neck,  the  epitheUum 
alters,  and  consists  of  short  columnar  or  polyhedral,  granular  cells,  which  almost  fill  the  tube, 
so  that  the  lumen  becomes  suddenly  constricted  and  is  continued  down  as  a  very  fine  channel. 
They  are  known  as  the  chief  or  central  cells  of  the  glands.  Between  these  cells  and  the  basement- 
membrane,  larger  oval  cells,  which  stain  deeply  with  eosin,  are  found;  these  cells  are  studded 
throughout  the  tube  at  intervals,  giving  it  a  beaded  or  varicose  appearance.  These  are  known 
as  the  parietal  or  oxyntic  cells,  and  they  are  connected  with  the  lumen  by  fine  channels  which  run 
into  their  substance.  Between  the  glands  the  mucous  membrane  consists  of  a  connective-tissue 
frame-work,  with  lymphoid  tissue.  In  places,  this  latter  tissue,  especially  in  early  hfe,  is  collected 
into  httle  masses,  which  to  a  certain  extent  resemble  the  sohtary  nodules  of  the  intestine,  and  are 
termed  the  lenticular  glands  of  the  stomach.  They  are  not,  however,  so  distinctly  circumscribed 
as  the  sohtary  nodules.  Beneath  the  mucous  membrane,  and  between  it  and  the  submucous 
coat,  is  a  thin  stratum  of  involuntary  muscular  fibre  {inuscularis  mucosae),  which  in  some  parts 


THE  STOMACH 


1167 


consists  only  of  a  single  longitudinal  layer;  in  others  of  two  layers,  an  inner  circular  and  an  outer 
longitudinal. 

Vessels  and  Nerves. — ^The  arteries  supplying  the  stomach  are:  the  left  gastric,  the  right 
gastric  and  right  gastroepiploic  branches  of  the  hepatic,  and  the  left  gastroepiploic  and  short 
gastric  branches  of  the  lienal.  They  supply  the  muscular  coat,  ramify  in  the  submucous  coat,  and 
are  finally  distributed  to  the  mucous  membrane.  The  arrangement  of  the  vessels  in  the  mucous 
membrane  is  somewhat  peculiar.  The  arteries  break  up  at  the  base  of  the  gastric  tubules  into 
a  plexus  of  fine  capillaries  which  run  upward  between  the  tubules,  anastomosing  with  each  other, 
and  ending  in  a  plexus  of  larger  capillaries,  which  sm-round  the  mouths  of  the  tubes,  and  also 
form  hexagonal  meshes  around  the  ducts.  From  these  the  veins  arise,  and  pursue  a  straight 
course  downward,  between  the  tubules,  to  the  submucous  tissue;  they  end  either  in  the  Uenal 
and  superior  mesenteric  veins,  or  directly  in  the  portal  vein.  The  lymphatics  are  numerous: 
they  consist  of  a  superficial  and  a  deep  set,  and  pass  to  the  lymph  glands  found  along  the  two 
curvatures  of  the  organ  (page  792) .     The  nerves  are  the  terminal  branches  of  the  right  and  left 


0J3  feOQQ  0  0  OOQoiOO 
_J^oq3O0OOot)o0«3oe^ 


Fig.  978. — A  pyloric  gland,  from  a  section  of  the 
dog's  stomach.  (Ebstein.)  m.  Mouth,  n.  Neck.  tr. 
A  deep  portion  of  a  tubule  cut  transversely. 


Fig.  979. — A  fundus  gland.     A.  Transverse  section 
of  gland. 


vagi,  the  former  being  distributed  upon  the  back,  and  the  latter  upon  the  front  part  of  the  organ. 
A  great  number  of  branches  from  the  coeliac  plexus  of  the  sympathetic  are  also  distributed  to 
it.  Nerve  plexuses  are  found  in  the  submucous  coat  and  between  the  layers  of  the  muscular  coat 
as  in  the  intestine.  From  these  plexuses  fibrils  are  distributed  to  the  muscular  tissue  and  the 
mucous  membrane. 

Applied  Anatomy. — Operations  on  the  stomach  are  frequently  performed.  By  gastrotomy  is 
meant  an  incision  into  the  stomach  for  the  removal  of  a  foreign  body,  the  opening  being  imme- 
diately afterward  closed — in  contradistinction  to  gastrostomy,  the  making  of  a  more  or  less  per- 
manent fistulous  opening.  Gastrotomy  is  probably  best  performed  by  an  incision  in  the  linea  alba, 
especially  if  the  foreign  body  be  large,  but  may  be  performed  by  an  incision  over  the  foreign 
body  itself,  where  this  can  be  felt,  or  by  one  of  the  incisions  for  gastrostomy  mentioned  below. 
The  peritoneal  cavity  is  opened,  and  the  pomt  at  which  the  stomach  is  to  be  incised  decided 
upon.  This  portion  is  then  brought  out  of  the  abdominal  wound,  and  gauze  is  carefully  packed 
around  it.  The  stomach  is  now  opened  by  a  transverse  incision  and  the  foreign  body  extracted. 
The  wound  in  the  stomach  is  then  closed  by  Lembert's  sutures,  i.  e.,  by  sutures  passed  through 


1 1 68  SPLANCHNOLOG  Y 

the  peritoneal  and  muscular  coats  in  such  a  way  that  the  peritoneal  surfaces  on  each  side  of  the 
wound  ai'e  brouf>;ht  into  apposition.  In  gastrostomy,  the  incision  is  commenced  opposite  the  eighth 
left  intercostal  space,  5  cm.  from  the  median  line,  and  carried  downvv'ard  for  7.5  cm.  By  this 
incision  the  fibres  of  the  Rectus  abdominis  are  exposed,  and  these  are  separated  in  the  same 
hne.  The  posterior  layer  of  the  sheath,  the  Transversus  muscle  and  transversaUs  fascia,  and 
the  peritoneum  are  then  divided,  and  the  peritoneal  cavity  opened.  The  anterior  wall  of  the 
stomach  is  now  seized  and  drawn  out  of  the  wound,  and  a  silk  suture  passed  through  its  mus- 
cular and  serous  coats  at  the  point  selected  for  opening  the  viscus.  This  is  held  by  an  assistant 
so  that  a  long  conical  diverticulum  of  the  stomach  protrudes  from  the  external  wound,  and  the 
parietal  peritoneum  and  the  posterior  layer  of  the  sheath  of  the  Rectus  are  sutured  to  it.  A 
second  incision  is  made  through  the  skin,  over  the  margin  of  the  costal  cartilage,  above  and  a 
little  to  the  outer  side  of  the  first  incision.  A  tract  is  made  under  the  skin  through  the  subcu- 
taneous tissue  from  the  one  opening  to  the  other,  and  the  diverticulum  of  the  stomach  is  drawn 
along  this  tract  by  means  of  the  suture  inserted  into  it,  so  that  its  apex  appears  at  the  second 
opening.  A  small  perforation  is  now  made  into  the  stomach  through  this  protruding  apex,  and 
its  margins  are  carefully  and  accurately  sutured  to  the  edge  of  the  external  wound.  The  remainder 
of  this  incision  and  the  whole  of  the  first  incision  are  then  closed  in  the  ordinary  way  and  the 
wound  dressed. 

In  cases  of  gasti'ic  ulcer  perforation  sometimes  takes  place,  and  this  was  formerly  regarded 
as  an  almost  fatal  compUcation.  In  the  present  day,  by  opening  the  abdomen  and  closing  the 
perforation,  which  is  generally  situated  on  the  anterior  surface  of  the  stomach,  a  considerable 
number  of  cases  are  cured,  provided  the  operation  is  done  not  longer  than  twelve  or  fifteen 
hours  after  the  perforation  has  taken  place.  The  opening  is  best  closed  by  bringing  the  peritoneal 
surfaces  on  either  side  into  apposition  by  means  of  Lembert's  sutures.  Free  drainage  of  the 
peritoneal  cavity  should  be  established  at  the  same  time. 

Excision  of  the  pylorus  has  occasionally  been  performed,  but  the  results  of  this  operation  are 
by  no  means  favorable,  and,  in  cases  of  cancer  of  the  pylorus,  before  operative  proceedings  are 
undertaken,  the  tumor  has  become  so  fixed  and  has  so  far  imphcated  surrounding  parts  that 
removal  of  the  pylorus  is  impossible  and  gastroenterostomy  has  to  be  substituted.  The  object 
of  this  operation  is  to  make  a  fistulous  communication  between  the  stomach,  on  the  cardiac  side 
of  the  disease,  and  the  small  intestine,  as  high  up  as  is  possible.  In  cases  of  cancer  of  the  stomach 
involving  other  parts  than  the  pylorus,  the  question  of  removing  the  whole  or  greater  part  of 
the  stomach  has  to  be  considered.  This  operation  has  been  performed  by  Schlatter  and  others 
with  success. 

Hypertrophy  and  spasm  of  the  circumferential  muscular  coat  of  the  pylorus  coming  on  during 
the  first  few  weeks  or  months  of  hfe,  and  somewhat  erroneously  described  as  congenital  hyper- 
trophic stenosis  of  the  pylorus,  is  a  serious  disorder  of  infancy.  It  is  characterized  by  abdominal 
pains  and  obstinate  vomiting  coming  on  after  food  has  been  given.  Gastric  peristalsis  can  be 
observed  by  inspection  of  the  child's  epigastrium  after  it  has  been  fed  and  before  vomiting  has 
occurred.  Progressive  wasting  for  want  of  nourishment  and  death  from  exhaustion  tend  to 
ensue.  Treatment  should  be  by  washing  out  the  stomach,  and  the  administration  at  frequent 
intervals  of  small  quantities  of  easily  digested  food,  so  as  to  minimize  irritation  of  the  gastric 
mucous  membrane.  Surgical  interference  entailing  a  severe  operation,  gives  favorable  results 
in  a  small  proportion  of  cases. 

The  stomach  is  seldom  ruptured  from  external  violence  on  account  of  its  protected  position. 
If  it  occurs,  it  is  when  the  organ  is  distended  with  food.  The  stomach  is  sometimes  injured  in 
gunshot  wounds.  There  is  intense  shock  and  severe  pain,  localized  at  first  at  the  seat  of  the 
injury,  but  soon  radiating  over  the  whole  abdomen.  The  treatment  consists  of  opening  the 
peritoneal  cavity,  clearing  away  all  the  extruded  contents  of  the  stomach,  and  repairing  the 
rent. 

The  Small  Intestine  (Intestinum  Tenue). 

The  small  intestine  is  a  convoluted  tube,  extending  from  the  pylorus  to  the  colic 
valve,  where  it  ends  in  the  large  intestine.  It  is  about  6  metres  long,^  and  gradually 
diminishes  in  size  from  its  commencement  to  its  termination.  It  is  contained  in 
the  central  and  lower  part  of  the  abdominal  cavity,  and  is  surrounded  above  and 
at  the  sides  by  the  large  intestine;  a  portion  of  it  extends  below  the  superior 
aperture  of  the  pelvis  and  lies  in  front  of  the  rectum.  It  is  in  relation,  in  front,  with 
the  greater  omentum  and  abdominal  parietes,  and  is  connected  to  the  vertebral 

'  Treves  states  that,  in  one  hundred  cases,  the  average  length  of  the  small  intestine  in  the  adult  male  was  22  feet 
6  inches,  and  in  the  adult  female  23  feet  4  inches;  but  that  it  varies  very  much,  the  extremes  in  the  male  being  31  feet 
10  inches,  and  15  feet  6  inches.  He  states  that  in  the  adult  the  length  of  the  bowel  is  independent  of  age,  height ,  and 
weight. 


THE  SMALL  INTESTINE 


1169 


coluinu  hy  a  told  of  pcritoiieuni,  the  mesentery.  The  small  intestine  is  divisible 
into  three  portions:  the  duodenum,  the  jejunum,  and  the  ileum. 

The  Duodenum  (Fiji".  UiSO)  has  reeei\ed  its  name  from  being  about  equal  in 
length  to  the  breadth  of  twelve  fingers  (25  cm.).  It  is  the  shortest,  the  widest, 
and  the  most  fixed  i)art  of  the  small  intestine,  and  has  no  mesentery,  being  only 
partially  covered  by  j)eritoneum.  Its  course  presents  a  remarkable  curve,  some- 
what of  the  shape  of  an  imperfect  circle,  so  that  its  termination  is  not  far  removed 
from  its  starting-point. 

In  the  adult  the  course  of  the  duodenum  is  as  follows:  commencing  at  the  pylorus 
it  passes  backward,  ui)ward,  and  to  the  right,  })cneath  the  quadrate  lobe  of  the 
liver  to  the  neck  of  the  gall-bladder,  varying  slightly  in  direction  according  to  the 
degree  of  distension  of  the  stomach:  it  then  takes  a  sharp  curve  and  descends 
along  the  right  margin  of  the  head  of  the  pancreas,  for  a  variable  distance,  generally 
to  the  level  of  the  upper  border  of  the  body  of  the  fourth  lumbar  vertebra.  It 
now  takes  a  second  bend,  and  passes  from  right  to  left  across  the  vertebral  column, 


Fig.  980. — The  duodenum  and  pancreas. 


having  a  slight  inclination  upward;  and  on  the  left  side  of  the  vertebral  column 
it  ascends  for  about  2.5  cm.,  and  then  ends  opposite  the  second  lumbar  vertebra 
in  the  jejunum.  As  it  unites  with  the  jejunum  it  turns  abruptly  forward,  forming 
the  duodendojejunal  flexure.  From  the  above  description  it  will  be  seen  that  the 
duodenum  may  be  divided  into  four  portions:  superior,  descending,  horizontal, 
and  ascending. 

Relations. — The  superior  portion  {pars  superior;  first  portion)  is  about  5  cm.  long. 
Beginning  at  the  pylorus,  it  ends  at  the  neck  of  the  gall-bladder.  It  is  the  most 
movable  of  the  four  portions.  It  is  almost  completely  covered  by  peritoneum,  but  a 
small  part  of  its  posterior  surface  near  the  neck  of  the  gall-bladder  and  the  inferior 
vena  cava  is  uncovered;  the  upper  border  of  its  first  half  has  the  hepatoduodenal 
ligament  attached  to  it,  while  to  the  lower  border  of  the  same  segment  the  greater 
omentum  is  connected.  It  is  in  such  close  relation  with  the  gall-bladder  that  it 
is  usually  found  to  be  stained  by  bile  after  death,  especially  on  its  anterior  surface, 
It  is  in  relation  above  and  in  front  with  the  quadrate  lobe  of  the  liver  and  the  gall- 
74 


1170 


SPLANCHNOLOGY 


bladder;  behind  with  the  gastroduodenal  artery,  the  common  bile  duct,  and  the 
portal  vein;  and  below  and  behind  with  the  head  and  neck  of  the  pancreas. 

The  descending  portion  (pars  descendens ;  second  j)ortion)  is  from  7  to  10  cm.  long,  and 
extends  from  the  neck  of  the  gall-bladder,  on  a  level  with  the  first  lumbar  vertebra, 
along  the  right  side  of  the  vertebral  column  as  low  as  the  upper  border  of  the  body 
of  the  fourth  lumbar  vertebra.  It  is  crossed  in  its  middle  third  by  the  transverse 
colon,  the  posterior  surface  of  which  is  uncovered  by  peritoneum  and  is  connected 
to  the  duodenum  by  a  small  quantity  of  connective  tissue.  The  supra-  and  infra- 
colic  portions  are  covered  in  front  by  peritoneum,  the  infracolic  part  by  the  right 
leaf  of  the  mesentery.  Posteriorly  the  descending  portion  of  the  duodenum  is  not 
covered  by  peritoneum.  The  descending  portion  is  in  relation,  in  front,  from  above 
downward,  with  the  duodenal  impression  on  the  right  lobe  of  the  liver,  the  trans- 
verse colon,  and  the  small  intestine;  behind,  it  has  a  variable  relation  to  the  front 
of  the  right  kidney  in  the  neighborhood  of  the  hilus,  and  is  connected  to  it  by 
loose  areolar  tissue;  the  renal  vessels,  the  inferior  vena  cava,  and  the  Psoas  below, 
are  also  behind  it.    At  its  medial  side  is  the  head  of  the  pancreas,  and  the  common 


Probe  in  pancreatic  duct 

Probe  in  common  bile-duct 
Fig.  981. — Interior  of  the  descending  portion  of  the  duodenum,  showing  bile  papilla. 

bile  duct;  to  its  lateral  side  is  the  right  colic  flexure.  The  common  bile  duct  and 
the  pancreatic  duct  together  perforate  the  medial  side  of  this  portion  of  the  intestine 
obliquely  (Figs.  981  and  1014),  some  7  to  10  cm.  below  the  pylorus;  the  accessory 
pancreatic  duct  sometimes  pierces  it  about  2  cm.  above  and  slightly  in  front  of  these. 
The  horizontal  portion  {pars  horizontalis;  third  or  jjreaortic  or  transverse  portion)  is 
from  5  to  7.5  cm.  long.  It  begins  at  the  right  side  of  the  upper  border  of  the  fourth 
lumbar  vertebra  and  passes  from  right  to  left,  with  a  slight  inclination  upward, 
in  front  of  the  great  vessels  and  crura  of  the  Diaphragma,  and  ends  in  the  ascending 
portion  in  front  of  the  abdominal  aorta.  It  is  crossed  by  the  superior  mesenteric 
vessels  and  the  mesentery.  Its  front  surface  is  covered  by  peritoneum,  except 
near  the  middle  line,  where  it  is  crossed  by  the  superior  mesenteric  vessels.  Its 
posterior  surface  is  uncovered  by  peritoneum,  except  toward  its  left  extremity, 
where  the  posterior  layer  of  the  mesentery  may  sometimes  be  found  covering  it 
to  a  variable  extent.  This  surface  rests  upon  the  right  crus  of  the  Diaphragma, 
the  inferior  vena  cava,  and  the  aorta.  The  upper  surface  is  in  relation  with  the 
head  of  the  pancreas. 


THE  SMALL  IXTESTIXE  1171 

The  ascending  portion  {pan-  cuiccmlens;  fourth  portion)  of  the  duodenum  is  about 
2.5  em  loiii;.  It  ascends  on  the  left  side  of  the  aorta,  as  far  as  the  level  of  the  upper 
border  of  the  second  lunihar  \tTtcl)ra,  w here  it  turns  abruptly  forward  to  become 
the  jejunum,  fonninii;  the  duodenojejunal  flexure.  It  lies  in  front  of  the  left  Psoas 
major  and  left  renal  vessels,  and  is  covered  in  front,  and  partly  at  the  sides,  by 
peritoneum  continuous  with  the  left  portion  of  the  mesentery. 

The  superior  part  of  the  duodenum,  as  stated  above,  is  somewhat  movable, 
but  the  rest  is  practically  fixed,  and  is  bound  down  to  neighboring  viscera  and  the 
posterior  abdominal  wall  by  the  peritoneum.  In  addition  to  this,  the  ascending 
part  of  the  duodenum  and  the  duodenojejunal  flexure  are  fixed  by  a  structure 
to  which  the  name  of  Muscuhis  susyensorius  duoden  i  has  been  given.  This  structure 
commences  in  the  connective  tissue  around  the  coeliac  artery  and  left  cms  of  the 
Diaphragma,  and  passes  downward  to  be  inserted  into  the  superior  border  of  the 
duodenojejunal  curve  and  a  part  of  the  ascending  duodenum,  and  from  this  it  is 
continued  into  the  mesentery.  It  possesses,  according  to  Treitz,  plain  muscular 
fibres  mixed  with  the  fibrous  tissue  of  which  it  is  principally  made  up.  It  is  of 
little  importance  as  a  muscle,  but  acts  as  a  suspensory  ligament. 

Vessels  and  Nerves. — The  arteries  supplying.-the  duodenum  are  the  right  gastric  and  superior 
pancreaticoduodenal  branches  of  the  hepatic,  and  the  interior  pancreaticoduodenal  branch  of 
the  superior  mesenteric.  The  veins  end  in  the  henal  and  superior  mesenteric.  The  nerves  are 
derived  from  the  coeliac  plexus. 

Jejunum  and  Ileuni. — The  remainder  of  the  small  intestine  from  the  end  of  the 
duodenum  is  named  jejunum  and  ileum;  the  former  term  being  given  to  the  upper 
two-fifths  and  the  latter  to  the  lower  three-fifths.  There  is  no  morphological  line 
of  distinction  between  the  two,  and  the  division  is  arbitrary;  but  at  the  same  time 
the  character  of  the  intestine  gradually  undergoes  a  change  from  the  commence- 
ment of  the  jejunum  to  the  end  of  the  ileum,  so  that  a  portion  of  the  bowel  taken 
from  these  two  situations  would  present  characteristic  and  marked  differences. 
These  are  briefly  as  follows : 

The  Jejunum  (intestinum  jejunum)  is  wider,  its  diameter  being  about  4  cm., 
and  is  thicker,  more  vascular,  and  of  a  deeper  color  than  the  ileum,  so  that  a  given 
length  weighs  more.  The  circular  folds  (valvulae  connivenies)  of  its  mucous  mem- 
brane are  large  and  thickly  set,  and  its  villi  are  larger  than  in  the  ileum.  The  aggre- 
gated lymph  nodules  are  almost  absent  in  the  upper  part  of  the  jejunum,  and  in 
the  lower  part  are  less  frequently  found  than  in  the  ileum,  and  are  smaller  and  tend 
to  assume  a  circular  form.  By  grasping  the  jejunum  between  the  finger  and  thumb 
the  circular  folds  can  be  felt  through  the  walls  of  the  gut;  these  being  absent  in 
the  lower  part  of  the  ileum,  it  is  possible  in  this  way  to  distinguish  the  upper 
from  the  lower  part  of  the  small  intestine. 

The  Ileum  {intestinum  ileum)  is  narrow,  its  diameter  being  3.75  cm.,  and  its 
coats  thinner  and  less  vascular  than  those  of  the  jejunum.  It  possesses  but  few 
circular  folds,  and  they  are  small  and  disappear  entirely  toward  its  lower  end, 
but  aggregated  h'mph  nodules  (Peyer's  patches)  are  larger  and  more  numerous. 
The  jejunum  for  the  most  part  occupies  the  umbilical  and  left  iliac  regions,  while 
the  ileum  occupies  chiefly  the  umbilical,  hypogastric,  right  iliac,  and  pelvic  regions. 
The  terminal  part  of  the  ileum  usually  lies  in  the  pelvis,  from  w^hich  it  ascends  over 
the  right  Psoas  and  right  iliac  vessels;  it  ends  in  the  right  iliac  fossa  by  opening 
into  the  medial  side  of  the  commencement  of  the  large  intestine.  The  jejunum 
and  ileum  are  attached  to  the  posterior  abdominal  wall  b}'  an  extensive  fold  of 
peritoneum,  the  mesentery,  which  allow^s  the  freest  motion,  so  that  each  coil  can 
accommodate  itself  to  changes  in  form  and  position.  The  mesentery  is  fan-shaped; 
its  posterior  border  or  root,  about  15  cm.  long,  is  attached  to  the  posterior  abdominal 
wall  from  the  left  side  of  the  body  of  the  second  lumbar  vertebra  to  the  right  sacro- 
iliac articulation,  crossing  successively  the  horizontal  part  of  the  duodenum,  the 


1172 


SPLANCHNOLOGY 


aorta,  the  inferior  vena  cava,  the  ureter,  and  right  Psoas  miisde  (Fig.  966).  Its 
breadth  between  its  vertebral  and  intestinal  borders  averages  about  20  cm.,  and  is 
areater  in  the  middle  than  at  its  upper  and  lower  ends.  According  to  Lockwood  it 
tends  to  increase  in  breadth  as  age  advances.  Between  the  two  layers  of  which  it  is 
composed  are  contained  bloodvessels,  nerves,  lacteals,  and  lymph  glands,  together 
with  a  variable  amount  of  fat. 


Villi 


Intestinal  glands 


Mtiscularis  mucoscB 


Duodenal  glands  in 
suhmiKOsa 


Circular  muscular  layer 


Longitudinal  muscular 
layer 


C  f     Serous  coat 


Fig.  982.— Section  of  duodenum  of  cat.     (After  Schiifer.)      X  60. 

Meckel's  Diverticulum  {diverticulum  ilei). -This  consists  of  a  pouch  which  projects  from  the 
lower  part  of  the  ileum  in  about  2  per  cent,  of  subjects.  Its  average  position  is  ^boutl  meter 
above  the  colic  valve,  and  its  average  length  about  5  cm.  Its  cahbre  is  g^^^^^^ll^  !^?^^^^!  ^^^  '^^^ 
of  the  ileum,  and  its  bhnd  extremity  may  be  free  or  may  be  connected  with  the  ^bdominaljaU 
or  with  som^  other  portion  of  the  intestine  by  a  fibrous  band.  It  represents  the  ^e™ams  of 
the  proximal  part  of  the  viteUine  duct,  the  duct  of  communication  between  the  yolk-sac  and  the 
primitive  digestive  tube  in  early  fetal  hfe.  ,     cc  ^-o■■     oormi<! 

Structure  -The  wall  of  the  small  intestine  (Fig.  982)  is  composed  of  four  coats,  serous, 
muscular,  areolar,  and  mucous.  .         f  .-, 

The  serous  coat  {tunica  serosa)  is  derived  from  the  peritoneum.  The  superior  POition  of  the 
duodenum  is  almost  completely  surrounded  by  this  membrane  near  its  pyloric  end,  but  is  only 


THE  SMALL  INTESTINE  1173 

« 

covered  in  front  at  the  other  extremity;  the  descending  portion  is  covered  by  it  in  front,  except 
where  it  is  carried  off  by  the  transverse  colon;  and  the  inferior  portion  lies  behind  the  peritoneum 
which  passes  over  it  without  being  closely  incorporated  with  the  other  coats  of  this  part  of  the 
intestine,  and  is  separated  from  it  in  and  near  the  middle  line  b}^  the  superior  mesenteric  vessels. 
The  rest  of  the  small  intestine  is  surrounded  by  the  peritoneum,  excepting  along  its  attached 
or  mesenteric  border;  licre  a  space  is  left  for  the  vessels  and  nerves  to  pass  to  the  gut. 

The  muscular  coat  {tunica  muscularis)  consists  of  two  layers  of  fibres:  an  external,  longi- 
tudinal, and  an  internal,  circular  layer.  The  longiludinal  fibres  are  thinly  scattered  over  the 
surface  of  the  intestine,  and  are  more  distinct  along  its  free  border.  The  circular  fibres  form  a 
thick,  uniform  layer,  and  are  composed  of  plain  muscle  cells  of  considerable  length.  The  mus- 
cular coat  is  thicker  at  the  upper  than  at  the  lower  part  of  the  small  intestine. 

The  areolar  or  submucous  coat  {tela  submucosa)  connects  together  the  mucous  and  muscular 
layers.  It  consists  of  loose,  filamentous  areolar  tissue  containing  bloodvessels,  lymphatics,  and 
nerves. 

The  mucous  membrane  {tunica  mucosa)  is  thick  and  highly  vascular  at  the  upper  part  of 
the  small  intestine,  but  somewhat  paler  and  thinner  below.  It  consists  of  the  following  structures: 
next  the  areolar  or  submucous  coat  is  a  double  layer  of  unstriped  muscular  fibres,  outer  longi- 
tudinal and  inner  circular,  the  muscularis  mucosae;  internal  to  this  is  a  quantity  of  retiform 
tissue,  enclosing  in  its  meshes  lymph  corpuscles,  and  in  this  the  bloodvessels  and  nerves  ramify; 
lastly,  a  basement-membrane,  supporting  a  single  layer  of  epithelial  cells,  which  throughout  the 
intestine  are  columnar  in  character.  The  cells  are  granular  in  appearance,  and  each  possesses 
a  clear  oval  nucleus.  At  their  superficial  or  unattached  ends  they  present  a  distinct  layer  of 
highly  refracting  material,  marked  by  vertical  strise,  the  striated  border. 

The  mucous  membrane  presents  for  examination  the  following  structures,  contained  within 
it  or  belonging  to  it: 

Circular  folds.  Duodenal  glands. 

Villi.  Solitary  lymphatic  nodules. 

Intestinal  glands.  Aggregated  Ijanphatic  nodules. 

The  circular  folds  {plicae  circulares  [Kerkringi];  valvulae  conniventes ;  valves  of  Kerkring)  are  large 
valvular  flaps  projecting  into  the  lumen  of  the  bowel.  They  are  composed  of  reduplications  of  the 
mucous  membrane,  the  two  layers  of  the  fold  being  bound  together  by  submucous  tissue;  unlike  the 
folds  in  the  stomach,  they  are  permanent,  and  are  not  obliterated  when  the  intestine  is  distended. 
The  majority  extend  transversely  around  the  cylinder  of  the  intestine  for  about  one-half  or  two- 
thirds  of  its  circumference,  but  some  form  complete  cii-cles,  and  others  have  a  spiral  direction; 
the  latter  usually  extend  a  Uttle  more  than  once  around  the  bowel,  but  occasionally  two  or  three 
times.  The  larger  folds  are  about  8  mm.  in  depth  at  their  broadest  part;  but  the  greater  number 
are  of  smaller  size.  The  larger  and  smaller  folds  alternate  with  each  other.  They  are  not  found 
at  the  commencement  of  the  duodenum,  but  begin  to  appear  about  2.5  or  5  cm.  beyond  the 
pylorus.  In  the  lower  part  of  the  descending  portion,  below  the  point  where  the  bile  and  pan- 
creatic ducts  enter  the  intestine,  they  are  very  large  and  closely  approximated.  In  the  hori- 
zontal and  ascending  portions  of  the  duodemun  and  upper  half  of  the  jejunum  they  are  large 
and  numerous,  but  from  this  point,  down  to  the  middle  of  the  ileum,  they  diminish  considerably 
in  size.  In  the  lower  part  of  the  ileum  they  almost  entirely  disappear;  hence  the  comparative 
thinness  of  this  portion  of  the  intestine,  as  compared  with  the  duodenum  and  jejunum.  The 
circular  folds  retard  the  passage  of  the  food  along  the  intestines,  and  afford  an  increased  sm'face 
for  absorption. 

The  intestinal  villi  {nlli  intestinales)  are  highly  vascular  processes,  projecting  from  the  mucous 
membrane  of  the  small  intestine  throughout  its  whole  extent,  and  giving  to  its  surface  a  velvety 
appearance.  They  are  largest  and  most  numerous  in  the  duodenum  and  jejunum,  and  become 
fewer  and  smaller  in  the  ileum. 

Structure  of  the  villi  (Figs.  983,  984). — The  essential  parts  of  a  villus  are:  the  lacteal  vessel, 
the  bloodvessels,  the  epithehum,  the  basement-membrane,  and  the  muscular  tissue  of  the  mucosa, 
all  being  supported  and  held  together  by  retiform  lymphoid  tissue. 

The  lacfeals  are  in  some  cases  double,  and  in  some  animals  multiple,  but  usually  there  is  a 
single  vessel.  Situated  in  the  axis  of  the  villus,  each  commences  by  dilated  cecal  extremities 
near  to,  but  not  quite  at,  the  summit  of  the  villus.  The  walls  are  composed  of  a  single  layer  of 
endothelial  cells. 

The  muscular  fibres  are  derived  from  the  muscularis  mucosae,  and  are  arranged  in  longitudinal 
bundles  around  the  lacteal  vessel,  extending  from  the  base  to  the  summit  of  the  villus,  and  giving 
off,  laterally,  individual  muscle  cells,  which  are  enclosed  by  the  reticulum,  and  by  it  are  attached 
to  the  basement-membrane  and  to  the  lacteal. 

The  bloodvessels  (Fig.  985)  form  a  plexus  under  the  basement  membrane,  and  are  enclosed 
in  the  reticular  tissue. 

These  structures  are  surrounded  by  the  basement-membrajie,  which  is  made  up  of  a  stratum 
of  endotheUal  ceUs,  and  upon  this  is  placed  a  layer  of  columnar  epithelium,  the  characteristics 


1174 


SPLANCHXOLOGY 


of  which  have  been  described.    The  retiform  tissue  forms  a  net-work  fFig.  984)  in  the  meshes 
of  which  a  number  of  leucocytes  are  found. 


Central  lacteal 

Smooth  muscle  fibres  ^     ' 

r 

~  Reticular  tissue 

Columnar  epithelium         i 


Ftg.  983. — Vertical  section  of  a  villus  from  the 
dog's  small  intestine.      X  80. 


Fig.  984. — Transverse  section  of  a  villus,  from  the  human  intes- 
tine, (v.  Ebner.)  X  3.50.  o.  Basement  membrane,  here  some- 
■vvhat  shrunken  away  from  the  epithelium.  6.  Lacteal,  c. 
Columnar  epithelium,  d.  Its  striated  border,  e.  Goblet  cells. 
/.  Leucocytes  in  epithelium.  /'.  Leucocytes  below  epitheUum. 
g.  Bloodvessels,    h.  Muscle  cells  cut  across. 


The  intestinal  glands  (glarululae  intestinales  [Lieherkuhni] ;  crypts  of  Lieberkuhn)  (Fig.  986)  are 
found  in  considerable  numbers  over  every  part  of  the  mucous  membrane  of  the  small  intestine. 


Capillaries 
Lymphatic  vessel 


Capillaries 


■  Lymphatic  vessel 


Small  artery        LympJuitic  plexus 
Fig.  985. — Villi  of  small  intestine,  showing  bloodvessels  and  lymphatic  vessels.      (Cadiat.) 

They  consist  of  minute  tubular  depressions  of  the  mucous  membrane,  arranged  perpendicularly  to 
the  surface,  upon  which  they  open  by  small  circular  apertm-es.    They  maj-  be  seen  vdth  the  aid 


THE  SMALL  INTESTINE 


1175 


of  a  lens,  their  orifiees  a])iH'arins  as  minute  dots  scattered  between  the  villi.  Their  walls  are 
thui,  consisting  of  a  basement  membrane  lined  bj-  columnar  epithelium,  and  covered  on  their 
exterior  by  capillary  vessels. 

The  duodenal  glands  (glandidac  duodenalcs  [Bruiuieri];  Brunncr'ti  c/lands)  arc  limited  to  the 
duodenum  [Viy:..  9S2,),  and  are  found  in  the  submucous  areolar  tissue.  They  are  largest  and  most 
numerous  near  the  pylorus,  forming  an  almost  comj^lete  layer  in 
the  superior  portion  and  upper  half  of  the  descending  jiortions  of 
the  duodenum.  They  then  begin  to  diminish  in  number,  and 
practically  disappear  at  the  junction  of  the  duodenum  and  jeju- 
num. They  are  small  compound  acinotubular  glands  consisting 
of  a  number  of  ah-eoli  lined  by  short  columnar  epithelium  and 
opening  bj-  a  single  duct  on  the  inner  surface  of  the  intestine. 

The  solitary  lymphatic  nodules  {noduli  lyvi-phatici  solitarii;  soli- 
tary glands)  are  found  scattered  throughout  the  mucous  mem- 
brane of  the  small  intestine,  but  are  most  numerous  in  the  lower 
part  of  the  ileum.  Their  free  surfaces  are  covered  with  rudimen- 
tary villi,  except  at  the  summits,  and  each  gland  is  surrounded  bj- 
the  openings  of  the  intestinal  glands.  Each  consists  of  a  dense 
interlacing  retiform  tissue  closety  packed  with  lymph-corpuscles, 
and  permeated  with  an  abundant  capillary  network.  The  inter- 
spaces of  the  retiform  tissue  are  continuous  with  larger  IjTnph 
spaces  which  surround  the  gland,  through  which  they  communi- 
cate with  the  lacteal  system.  They  are  situated  partly  in  the 
submucous  tissue,  partly  in  the  mucous  membrane,  where  they 
form  slight  projections  of  its  epithelial  layer  (see  Fig.  998). 

The  aggregated  lymphatic  nodules  {noduli  lymphatici  aggregati; 
Peyer's  patches;  Peyers  glands;  agminated  follicles;  tonsillae  intes- 
tinales)  (Fig.  987)  form  circular  or  oval  patches,  from  twenty  to 
thirty  in  number,  and  varying  in  length  from  2  to  10  cm.  They  are 
largest  and  most  mmierous  in  the  ileum.  In  the  lower  part  of  the 
jejunum  they  are  small,  circular,  and  few  in  number.  They  are 
occasionally  seen  in  the  duodenum.  They  are  placed  lengthwise 
in  the  intestine,  and  are  situated  in  the  portion  of  the  tube  most 
distant  from  the  attachment  of  the  mesentery.  Each  patch  is 
formed  of  a  group  of  solitary  lymphatic  nodules  covered  with  mucous  membrane,  but  the 
patches  do  not,  as  a  rule,  possess  vilh  on  their  free  surfaces.    They   are  best   marked   in  the 


Fig.  986. — An  intestinal  gland 
from  the  human  intestine.  (Flem- 
ming.) 


Fig.  987. — Vertical  section  of  a  human  aggregated  lymphatic  nodule,  injected  through  its  lymphatic  canals,  a. 
Villi  with  their  chyle  passages.  6.  Intestinal  glands,  c.  Muscularis  mucosae,  d.  Cupola  or  apex  of  solitarj' nodule. 
e.  Mesial  zone  of  nodule.  /.  Base  of  nodule,  g.  Points  of  exit  of  the  lacteals  from  the  villi,  and  entrance  into  the  true 
naucous  membrane,  h.  Retiform  arrangement  of  the  lymphatics  in  the  mesial  zone.  i.  Course  of  the  latter  at  the 
base  of  the  nodule,  k.  Confluence  of  the  lymphatics  opening  into  the  vessels  of  the  submucous  tissue.  I.  Follicular 
tissue  of  the  latter. 


young  subject,    become    indistinct    in  middle    age,    and    sometimes    disappear    altogether  in 
advanced  life.     They  are  freely  supphed  with  bloodvessels  (Fig.  988),  which  form  an  abundant 


1176 


SPLAXCIIXOLOGY 


plexus  around  each  follicle  and  give  off  fine  branches  permeating  the  lymphoid  tissue  in  the 
interior  of  the  follicle.    The  lymphatic  plexuses  are  especially  abundant  around  these  patches. 

Vessels  and  Nerves. — The  jejunum  and  ileum  are  supplied  b}-  the  superior  mesenteric  artery, 
the  intc.-^tinal  branches  of  which,  having  reached  the  attached  border  of  the  b(nvel,  run  between 
the  serous  and  muscular  coats,  with  frequent  inosculations  to  the  free  border,  where  tliey  also 
anastomose  with  other  branches  running  around  the  opposite  surface  of  the  gut.     From  these 


'JU 


...Capillary  network 


Fig.  988. — Transverse  section  through  the  equatorial 
plane  of  three  aggregated  lymphatic  nodules  from  the 
rabbit. 


Fig.  989. — The  myenteric  plexus  from  the  rabbit. 
X  50. 


vessels  numerous  branches  are  given  off,  which  pierce  the  muscular  coat,  supplying  it  and  forming 
an  intricate  plexus  in  the  submucous  tissue.  From  this  plexus  minute  vessels  pass  to  the  glands 
and  vilU  of  the  mucous  membrane.  The  veins  have  a  similar  com'se  and  arrangement  to  the 
arteries.  The  lymphatics  of  the  small  intestine  (lacteals)  are  arranged  in  two  sets,  those  of  the 
mucous  membrane  and  those  of  the  muscular  coat.  The  lymphatics  of  the  villi  commence  in 
these  structures  in  the  manner  described  above.  They  form  an  intricate  plexus  in  the  mucous 
and  submucous  tissue,  being  joined  by  the  lymphatics  from  the 
lymph  spaces  at  the  bases  of  the  sohtary  nodules,  and  from  this  pass 
to  larger  vessels  at  the  mesenteric  border  of  the  gut.  The  Ij'mphatics 
of  the  muscular  coat  are  situated  to  a  great  extent  between  the  two 
la3^ers  of  muscular  fibres,  where  they  form  a  close  plexus;  thi'ough- 
out  their  course  they  commimicate  freelj-  with  the  IjTnphatics  from 
the  mucous  membrane,  and  empty  themselves  in  the  same  manner 
as  these  into  the  origins  of  the  lacteal  vessels  at  the  attached  border 
of  the  gut. 

The  nerves  of  the  small  intestines  are  derived  from  the  plexuses  of 
sympathetic  nerves  around  the  superior  mesenteric  arter}\  From 
this  source  they  run  to  the  mesenteric  plexus  (Aiwrbach' s  plexus) 
(Fig.  989)  of  nerves  and  gangha  situated  between  the  circular  and 
longitudinal  muscular  fibres  from  which  the  nervous  branches  are 
distributed  to  the  muscular  coats  of  the  intestine.  From  this  a 
secondarjr  plexus,  the  pleuxs  of  the  submucosa  iMeus7ier's  plexus) 
(Fig.  990)  is  derived,  and  is  formed  bj'  branches  which  have  per- 
forated the  circular  muscular  fibres.  This  plexus  hes  in  the  submucous  coat  of  the  intestine;  it 
also  contains  ganglia  from  which  nerve  fibres  pass  to  the  muscularis  mucosae  and  to  the  mucous 
membrane.  The  nerve  bundles  of  the  submucous  plexus  are  finer  than  those  of  the  mj'enteric 
plexus. 

The  Large  Intestine  (Intestinum  Crassum). 

The  large  intestine  extends  from  the  end  of  the  ileum  to  the  anus.  It  is  about 
1.5  metres  long,  being  one-fifth  of  the  whole  extent  of  the  intestinal  canal.  Its 
calibre  is  largest  at  its  commencement  at  the  cecum,  and  gradually  diminishes 


Fig.  990.— The  plexus  of  the 
submucosa  from  the  rabbit. 
X  50. 


THE  LAh'CI-:  IXTESriM': 


ir 


as  far  as  the  rectum,  where  there  is  a  dihitatiou  of  considerable  size  just  above 
the  anal  canal.  It  differs  from  the  small  intestine  in  its  ^^reater  calibre,  its  more 
fixed  position,  its  sacculated  form,  and  in  possessinj;-  certain  ai)i)enda<;es  to  its 
external  coat,  the  appendices  epiploicae.  Inirther,  its  longitudinal  muscular  fibres 
do  not  form  a  continuous  layer  around  the  gut,  but  are  arranged  in  three  longitudinal 
bands  or  tsenise.  The  large  intestine,  in  its  course,  describes  an  arch  which  sur- 
rounds the  convolutions  of  the  small  intestine.  It  commences  in  the  right  iliac 
region,  in  a  dilated  part,  the  cecum.  It  ascends  through  the  right  lumbar  and  hypo- 
chondriac regicms  to  the  under  surface  of  the  liver;  it  here  takes  a  bend,  the  right 
colic  flexure,  to  the  left  and  passes  transversely  across  the  abdomen  on  the  confines 
of  the  epigastric  and  umbilical  regions,  to  the  left  hypochondriac  region;  it  then 
bends  again,  the  left  colic  flexure,  and  descends  through  the  left  lumbar  and  iliac 
regions  to  the  pelvis,  where  it  forms  a  bend  called  the  sigmoid  flexure;  from  this  it 
is  continued  along  the  posterior  wall  of  the  pelvis  to  the  anus.  The  large  intestine 
is  divided  into  the  cecum,  colon,  rectum,  and  anal  canal. 


Terminal  part  oj  ileocolic  artery 


Cecal  brandies 


Ileal  branches 


Appendicular 
artery 


'■^''^'TjyJocess 


Fig.  991. — The  cecum  and  vermiform  process,  with  their  arteries. 


Tlie  Cecum  {intestinum  caecum)  (Fig.  991),  the  commencement  of  the  large 
intestine,  is  the  large  blind  pouch  situated  below  the  colic  valve.  Its  blind  end 
is  directed  downward,  and  its  open  end  upward,  communicating  directly  with  the 
colon,  of  which  this  blind  pouch  appears  to  be  the  beginning  or  head,  and  hence  the 
old  name  of  caput  caecum  coli  was  applied  to  it.  Its  size  is  variously  estimated  by 
different  authors,  but  on  an  average  it  may  be  said  to  be  6.25  cm.  in  length  and  7.5  in 
breadth.  It  is  situated  in  the  right  iliac  fossa,  above  the  lateral  half  of  the  inguinal 
ligament :  it  rests  on  the  Iliacus  and  Psoas  major,  and  usually  lies  in  contact  with  the 
anterior  abdominal  wall,  but  the  greater  omentum  and,  if  the  cecum  be  empty, 
some  coils  of  small  intestine  may  lie  in  front  of  it.  As  a  rule,  it  is  entirely  enveloped 
by  peritoneum,  but  in  a  certain  number  of  cases  (5  per  cent.,  Berry)  the  peritoneal 
covering  is  not  complete,  so  that  the  upper  part  of  the  posterior  surface  is  imcovered 
and  connected  to  the  iliac  fascia  by  connective  tissue.  The  cecum  lies  quite  free 
in  the  abdominal  cavity  and  enjoys  a  conside'rable  amount  of  movement,  so  that 


1 1 78  SPLANCHXOLOa  Y 

it  may  become  herniated  down  the  rij^ht  inguinal  canal,  and  has  occasionally 
been  found  in  an  inguinal  hernia  on  the  left  side.  The  cecum  varies  in  shape,  but, 
according  to  Treves,  in  man  it  may  be  classified  under  one  of  four  typ^s.  In  early 
fetal  life  it  is  short,  conical,  and  broad  at  the  base,  with  its  apex  turned  upward 
and  mediahvard  toward  the  ileocolic  junction.  It  then  resembles  the  cecum  of  some 
monkeys,  e.  g.,  mangabey  monkey.  As  the  fetus  grows  the  cecum  increases  in 
length  more  than  in  breadth,  so  that  it  forms  a  longer  tube  than  in  the  primitive 
form  and  without  the  broad  base,  but  with  the  same  inclination  of  the  apex  toward 
the  ileocolic  junction.  This  form  is  seen  in  other  monkeys,  e.  g.,  the  spider  monkey. 
As  development  goes  on,  the  lower  part  of  the  tube  ceases  to  grow  and  the  upper 
part  becomes  greatly  increased,  so  that  at  birth  there  is  a  narrow  tube,  the  vermi- 
form process,  hanging  from  a  conical  projection,  the  cecum.  This  is  the  infantile 
form,  and  as  it  persists  throughout  life  in  about  2  per  cent,  of  eases,  it  is  regarded 
by  Treves  as  the  first  of  his  four  types  of  human  ceca.  The  cecum  is  conical  and 
the  appendix  rises  from  its  apex.  The  three  longitudinal  bands  start  from  the 
appendix  and  are  equidistant  from  each  other.  In  the  second  type,  the  conical 
cecum  has  become  quadrate  by  the  growing  out  of  a  saccule  on  either  side  of  the 
anterior  longitudinal  band.  These  saccules  are  of  equal  size,  and  the  appendix 
arises  from  between  them,  instead  of  from  the  apex  of  a  cone.  This  type  is  found 
in  about  3  per  cent,  of  cases.  The  third  type  is  the  normal  type  of  man.  Here 
the  two  saccules,  which  in  the  second  type  were  uniform,  have  grown  at  unequal 
rates:  the  right  with  greater  rapidity  than  the  left.  In  consequence  of  this  an 
apparently  new  apex  has  been  formed  by  the  growing  downward  of  the  right  sac- 
cule, and  the  original  apex,  with  the  appendix  attached,  is  pushed  over  to  the  left 
toward  the  ileocolic  junction.  The  three  longitudinal  bands  still  start  from  the 
base  of  the  vermiform  process,  but  they  are  now  no  longer  equidistant  from  each 
other,  because  the  right  saccule  has  grown  between  the  anterior  and  postero- 
lateral bands,  pushing  them  over  to  the  left.  This  type  occurs  in  about  90  per 
cent,  of  cases.  The  fourth  type  is  merely  an  exaggerated  condition  of  the  third; 
the  right  saccule  is  still  larger,  and  at  the  same  time  the  left  saccule  has  become 
atrophied,  so  that  the  original  apex  of  the  cecum,  with  the  vermiform  process,  is 
close  to  the  ileocolic  junction,  and  the  anterior  band  courses  medialward  to  the 
same  situation.    This  type  is  present  in  about  4  per  cent,  of  cases. 

The  Vermiform  Process  or  Appendix  (processus  vermiformis)  (Fig.  991)  is  a  long, 
narrow,  worm-shaped  tube,  which  starts  from  what  was  originally  the  apex  of  the 
cecum,  and  may  pass  in  one  of  several  directions:  upward  behind  the  cecum;  to 
the  left  behind  the  ileum  and  mesentery;  or  downward  into  the  lesser  pelvis.  It 
varies  from  2  to  20  cm.  in  length,  its  average  being  about  8.3  cm.  It  is  retained 
in  position  by  a  fold  of  peritoneum  (mesenteriole),  derived  from  the  left  leaf  of 
the  mesentery.  This  fold,  in  the  majority  of  cases,  is  more  or  less  triangular  in 
shape,  and  as  a  rule  extends  along  the  entire  length  of  the  tube.  Between  its  two 
layers  and  close  to  its  free  margin  lies  the  appendicular  artery  (Fig.  991) .  The  canal 
of  the  vermiform  process  is  small,  extends  throughout  the  whole  length  of  the  tube, 
and  communicates  with  the  cecum  by  an  orifice  which  is  placed  below  and  behind 
the  ileocecal  opening.  It  is  sometimes  guarded  by  a  semilunar  valve  formed  by  a 
fold  of  mucous  membrane,  but  this  is  by  no  means  constant. 

Structure. — The  coats  of  the  vermiform  process  are  the  same  as  those  of  the  intestine:  serous, 
muscular,  submucous,  and  mucous.  The  serous  coat  forms  a  complete  investment  for  the  tube, 
except  along  the  narrow  line  of  attachment  of  its  mesenteriole  in  its  proximal  two-thirds.  The 
longitudinal  muscular  fibres  do  not  form  three  bands  as  in  the  greater  part  of  the  large  intestine, 
but  invest  the  whole  organ,  except  at  one  or  two  points  where  both  the  longitudinal  and  circular 
fibres  are  deficient  so  that  the  peritoneal  and  submucous  coats  are  contiguous  over  small  areas. 

The  circular  muscle  fibres  form  a  much  thicker  layer  than  the  longitudinal  fibres,  and  are 
separated  from  them  by  a  small  amoimt  of  connective  tissue.  The  submucous  coat  is  well 
marked,  and  contains  a  large  number  of  masses  of  lymphoid  tissue  which  cause  the  mucous 


77/ A'  L.lAVr'A'  IXTESTIXE 


1179 


membrane  to  hulj;e  into  tlie  luiiion  uikI  so  render  (he  latter  of  small  size  and  irregular  shape. 
The  mucous  membrane  is  lined  by  ecjlunmar  ei)itlieliuni  and  resembles  that  of  the  rest  of  the 
large  intestine,  Iml  I  lie  intestinal  glands  are  fewer  in  nuin!)er  (Fig.  992). 


;-^iJ^V_J Gland-^ 


Miisculur  coat 

Columnar 
epithelhim 


Lymph  nodvle 


Fig.  992. — Transverse  section  of  human  vermiform  process.      X  20. 

The  Colic  Valve  (mhula  coli;  ileocecal  valve)  (Fig.  993). — The  lower  end  of  the  ileum 
ends  by  opening  into  the  medial  and  back  part  of  the  large  intestine,  at  the  point 
of  junction  of  the  cecum  with  the  colon.  The  opening  is  guarded  by  a  valve, 
consisting  of  two  segments  or  lips,  which  project  into  the  lumen  of  the  large  intes- 
tine. If  the  intestine  has  been  inflated  and  dried,  the  lips  are  of  a  semilunar  shape. 
The  upper  one,  nearly  horizontal  in  direction,  is  attached  by  its  convex  border 


Upper  segment 
of  colic  valve.  _^ 

Opening  of  ileum— i—^D^ 


Lower  segment 
of  colic  valve 


P)obe  in  vermiform 
jjrocess 


Fig.  993. — Interior  of  the  cecum  and  lower  end  of  ascending  colon,  showing  colic  valve. 


to  the  line  of  junction  of  the  ileum  with  the  colon;  the  lower  lip,  which  is  longer 
and  more  concave,  is  attached  to  the  line  of  junction  of  the  ileum  with  the  cecum. 
At  the  ends  of  the  aperture  the  two  segments  of  the  valve  coalesce,  and  are  continued 
as  narrow  membranous  ridges  around  the  canal  for  a  short  distance,  forming  the 
frenula  of  the  valve.  The  left  or  anterior  end  of  the  aperture  is  rounded;  the  right 
or  posterior  is  narrow  and  pointed.    In  the  fresh  condition,  or  in  specimens  which 


IISO  SPLANCHNOLOGY 

have  been  hardened  in  situ,  the  lips  project  as  thick  cushion-like  folds  into  the  lumen 
of  the  large  gut,  while  the  opening  between  them  may  present  the  appearance  of  a 
slit  or  may  be  somewhat  oval  in  shape. 

Each  lip  of  the  valve  is  formed  by  a  reduplication  of  the  mucous  membrane 
and  of  the  circular  muscular  fibres  of  the  intestine,  the  longitudinal  fibres  and 
peritoneum  being  continued  uninterruptedly  from  the  small  to  the  large  intestine. 

The  surfaces  of  the  valve  directed  toward  the  ileum  are  co^T^ed  with  villi,  and 
present  the  characteristic  structure  of  the  mucous  membrane  of  the  small  intestine; 
while  those  turned  toward  the  large  intestine  are  destitute  of  villi,  and  marked 
with  the  orifices  of  the  numerous  tubular  glands  peculiar  to  the  mucous  membrane 
of  the  large  intestine.  These  differences  in  structure  continue  as  far  as  the  free 
margins  of  the  valve.  It  is  generally  maintained  that  this  valve  prevents  reflux 
from  the  cecum  into  the  ileum,  but  in  all  probability  it  acts  as  a  sphincter  around 
the  end  of  the  ileum  and  prevents  the  contents  of  the  ileum  from  passing  too 
quickly  into  the  cecum. 

The  Colon  is  divided  into  four  parts:  the  ascending,  transverse,  descending,  and 
sigmoid. 

The  Ascending  Colon  {colon  ascendens)  is  smaller  in  calibre  than  the  cecum,  with 
which  it  is  continuous.  It  passes  upward,  from  its  commencement  at  the  cecum, 
opposite  the  colic  valve,  to  the  under  surface  of  the  right  lobe  of  the  liver,  on  the 
right  of  the  gall-bladder,  where  it  is  lodged  in  a  shallow^  depression,  the  coUc  impres- 
sion; here  it  bends  abruptly  forward  and  to  the  left,  forming  the  right  colic  {hepatic) 
flexure  (Fig.  980).  It  is  retained  in  contact  with  the  posterior  wall  of  the  abdomen 
by  the  peritoneum,  which  covers  its  anterior  surface  and  sides,  its  posterior  surface 
being  connected  by  loose  areolar  tissue  with  the  Iliacus,  Quadratus  lumborum, 
aponeurotic  origin  of  Transversus  abdominis,  and  with  the  front  of  the  lower  and 
lateral  part  of  the  right  kidney.  Sometimes  the  peritoneum  completely  invests 
it,  and  forms  a  distinct  but  narrow  mesocolon.^  It  is  in  relation,  in  front,  with  the 
convolutions  of  the  ileum  and  the  abdominal  parietes. 

The  Transverse  Colon  {colon  transversum)  the  longest  and  most  movable  part  of 
the  colon,  passes  with  a  dow^nward  convexity  from  the  right  hypochondriac  region 
across  the  abdomen,  opposite  the  confines  of  the  epigastric  and  umbilical  zones, 
into  the  left  hypochondriac  region,  where  it  curves  sharply  on  itself  beneath  the 
lower  end  of  the  spleen,  forming  the  left  colic  {splenic)  flexure.  In  its  course  it 
describes  an  arch,  the  concavity  of  which  is  directed  backward  and  a  little  upward ; 
toward  its  splenic  end  there  is  often  an  abrupt  U-shaped  curve  which  may  descend 
lower  than  the  main  curve.  It  is  almost  completely  invested  by  peritoneum,  and 
is  connected  to  the  inferior  border  of  the  pancreas  by  a  large  and  wide  duplicature 
of  that  membrane,  the  transverse  mesocolon.  It  is  in  relation,  by  its  upper  surface, 
w^ith  the  liver  and  gall-bladder,  the  greater  curvature  of  the  stomach,  and  the 
lower  end  of  the  spleen;  by  its  under  surface,  with  the  small  intestines;  by  its  ante- 
rior surface,  with  the  anterior  layers  of  the  greater  omentum  and  the  abdominal 
parietes;  its  posterior  surface  is  in  relation  from  right  to  left  with  the  descending 
portion  of  the  duodenum,  the  head  of  the  pancreas,  and  some  of  the  convolutions 
of  the  jejunum  and  ileum. 

The  left  colic  or  splenic  flexure  (Fig.  980)  is  situated  at  the  junction  of  the  trans- 
verse and  descending  parts  of  the  colon,  and  is  in  relation  with  the  lower  end  of  the 
spleen  and  the  tail  of  the  pancreas;  the  flexure  is  so  acute  that  the  end  of  the  trans- 
verse colon  usually  lies  in  contact  with  the  front  of  the  descending  colon.    It  lies 

1  Treves  states  that,  after  a  careful  examination  of  one  hundred  subjects,  he  found  that  in  fifty-two  there  was  neither 
an  ascending  nor  a  descending  mesocolon.  In  twenty-two  there  was  a  descending  mesocolon,  but  no  trace  of  a  corre- 
sponding fold  on  the  other  side.  In  fourteen  subjects  there  was  a  mesocolon  to  both  the  ascending  and  the  descending 
segments  of  the  bowel;  while  in  the  remaining  twelve  there  was  an  ascending  mesocolon,  but  no  corresponding  fold 
on  the  left  side.  It  follows,  therefore,  that  in  performing  lumbar  colotomy  a  mesocolon  may  be  expected  upon  the  left 
side  in  36  per  cent,  of  all  cases,  and  on  the  right  in  26  per  cent. — The  Anatomy  of  the  Intestinal  Canal  and  Peritoneum 
in  Man,  1885,  p.  .55. 


THE  LARGE  INTESTINE 


1181 


at  a  higher  level  than,  and  on  a  plane  posterior  to,  the  right  eolic  flexure,  and  is 
attaehed  to  the  Diaphragma,  opposite  the  tenth  and  eleventh  ribs,  by  a  peritoneal 
fold,  named  the  phrenicocolic  ligament,  which  assists  in  supporting  the  lower  end 
of  the  spleen  (see  page  lloTj. 

The  Descending  Colon'  {colon  descendens)  passes  downward  through  the  left 
hypochondriac-  and  lumbar  regions  along  the  lateral  border  of  the  left  kidney. 
At  the  lower  end  of  the  kidney  it  turns  medialward  toward  the  lateral  border  of 
the  Psoas,  and  then  descends,  in  the  angle  between  Psoas  and  Quadratuslumborum, 
to  the  crest  of  the  ilium,  where  it  ends  in  the  iliac  colon.  The  peritoneum  covers 
its  anterior  surface  and  sides,  while  its  posterior  surface  is  connected  by  areolar 
tissue  with  the  loAver  and  lateral  part  of  the  left  kidney,  the  aponeurotic  origin  of 
the  Transversus  abdominis,  and  the  Quadratus  lumborum  (Fig.  980) .  It  is  smaller 
in  calibre  and  more  deeply  placed  than  the  ascending  colon,  and  is  more  frequently 
covered  with  peritoneum  on  its  posterior  surface  than  the  ascending  colon  (Treves). 
In  front  of  it  are  some  coils  of  small  intestine. 


FeTnoral  nerve 
Femoral  vessels 
Peritoneuvi 

Levator  ani  muscle 


Fig.  994.     Iliac  colon,  sigmoid  or  pelvic  colon,  and  rectum  seen  from  the  front,  after  removal  of  pubic  bones 

and  bladder. 

_The  lUac  Colon  (Fig.  994)  is  situated  in  the  left  iliac  fossa,  and  is  about  12  to 
15  cm.  long.  It  begins  at  the  level  of  the  iliac  crest,  w^here  it  is  continuous  wath 
the  descending  colon,  and  ends  in  the  sigmoid  colon  at  the  superior  aperture  of  the 
lesser  pelvis.  It  curves  downward  and  medialward  in  front  of  the  Iliacus  and  Psoas, 
and,  as  a  rule,  is  covered  by  peritoneum  on  its  sides  and  anterior  surface  only. 

The  Sigmoid  Colon  {colon  sigmoideum;  pelvic  colon;  sigmoid  flexure)  (Fig.  994) 
forms  a  loop  which  averages  about  40  cm.  in  length,  and  normally  lies  within  the 
pelvis,  but  on  account  of  its  freedom  of  movement  it  is  liable  to  be  displaced  into 

1  In  the  Basle  nomenclature  the  descending  colon  is  the  portion  between  the  left  colic  flexure  and  the  superior  aper- 
ture ot  the  lesser  pelvis;  it  is,  however,  convenient  to  still  describe  its  lowest  part  as  the  iliac  colon. 


1182 


SPLANCHNOLOGY 


the  abdominal  cavity.  It  begins  at  the  superior  aperture  of  the  lesser  pelvis, 
where  it  is  continuous  with  the  iliac  colon,  and  passes  transversely  across  the  front 
of  the  sacrum  to  the  right  side  of  the  pelvis;  it  then  curves  on  itself  and  turns 
toward  the  left  to  reach  the  middle  line  at  the  level  of  the  third  piece  of  the  sacrum, 
where  it  bends  downward  and  ends  in  the  rectum.  It  is  completely  surrounded  by 
peritoneum,  which  forms  a  mesentery  (sigmoid  mesocolon),  which  diminishes  in 
length  from  the  centre  toward  the  ends  of  the  loop,  where  it  disappears,  so  that  the 
loop  is  fixed  at  its  junctions  with  the  iliac  colon  and  rectum,  but  enjoys  a  consider- 
able range  of  movement  in  its  central  portion.  Behind  the  sigmoid  colon  are  the 
external  iliac  vessels,  the  left  Piriformis,  and  left  sacral  plexus  of  nerves ;  in  front, 
it  is  separated  from  the  bladder  in  the  male,  and  the  uterus  in  the  female,  by  some 
coils  of  the  small  intestine. 


k/ 


Fig.  995. — The  posterior  aspect  of  the  rectum  exposed  by  removing  the  lower  part  of  the  sacrum  and  the  coccy.x. 

The  Rectum  {intestinum  rectum)  (Fig.  995)  is  continuous  above  with  the  sigmoid 
colon,  while  below  it  ends  in  the  anal  canal.  From  its  origin  at  the  level  of  the 
third  sacral  vertebra  it  passes  downw^ard,  lying  in  the  sacrococcygeal  curve,  and 
extends  for  about  2.5  cm.  in  front  of,  and  a  little  below,  the  tip  of  the  coccyx, 
as  far  as  the  apex  of  the  prostate.  It  then  bends  sharply  backward  into  the  anal 
canal.    It  therefore  presents  two  antero-posterior  curves:  an  upper,  with  its  con- 


THE  LARGE  INTESTINE 


1183 


vexity  backwartl,  aiul  a  lower,  with  its  convexity  forward.  Two  lateral  cur\es  are 
also  described,  one  to  the  right  opposite  the  junction  of  the  third  and  fourth  sacral 
vertebrae,  and  the  other  to  the  left,  opposite  the  left  sacrococcygeal  articulation; 
they  are,  however,  of  little  inij)ortance.  The  rectum  is  about  12  cm.  long,  and  at 
its  commencement  its  calibre  is  similar  to  that  of  the  sigmoid  colon,  but  near  its 
termination  it  is  dilated  to  form  the  rectal  ampulla.  The  rectum  has  no  sacculations 
comparable  to  those  of  the  colon,  but  when  the  lower  part  of  the  rectum  is  con- 
tracted, its  mucous  membrane  is  thrown  into  a  number  of  folds,  which  are  longitudi- 
nal in  direction  and  are  effaced  by  the  distension  of  the  gut.  Besides  these  there 
are  certain  permanent  transverse  folds,  of  a  semilunar  shape,  known  as  Houston's 
valves  (Fig.  996).  They  are  usually  three  in  number;  sometimes  a  fourth  is  found, 
and  occasionally  only  two  are  present.  One  is 
situated  near  the  commencement  of  the  rectum, 
on  the  right  side;  a  second  extends  inward  from 
the  left  side  of  the  tube,  opposite  the  middle  of 
the  sacrum;  a  third,  the  largest  and  most  con- 
stant, projects  backward  from  the  forepart  of 
the  rectum,  opposite  the  fundus  of  the  urinary 
bladder.  When  a  fourth  is  present,  it  is  situated 
nearly  2.5  cm.  above  the  anus  on  the  left  and 
posterior  wall  of  the  tube.  These  folds  are  about 
12  mm.  in  width,  and  contain  some  of  the 
circular  fibres  of  the  gut.  In  the  empty  state  of 
the  intestines  thej'  overlap  each  other,  as  Houston 
remarks,  so  effectually  as  to  require  considerable 
manoeuvering  to  conduct  a  bougie  or  the  finger 
along  the  canal.  Their  use  seems  to  be,  "to 
support  the  weight  of  fecal  matter,  and  prevent 
its  urging  toward  the  anus,  where  its  presence 
always  excites  a  sensation  demanding  its  dis- 
charge.^ 

The  peritoneum  is  related  to  the  upper  two- 
thirds  of  the  rectum,  covering  at  first  its  front 
and  sides,  but  lower  down  its  front  only;  from 
the  latter  it  is  reflected  on  to  the  seminal  vesicles 
in  the  male  and  the  posterior  vaginal  wall  in  the 
female. 

The  level  at  which  the  peritoneum  leaves  the  anterior  wall  of  the  rectum  to  be 
reflected  on  to  the  viscus  in  front  of  it  is  of  considerable  importance  from  a  surgical 
point  of  view^,  in  connection  with  the  removal  of  the  lower  part  of  the  rectum.  It 
is  higher  in  the  male  than  in  the  female.  In  the  former  the  height  of  the  recto- 
vesical excavation  is  about  7.5  cm.,  i.  e.,  the  height  to  which  an  ordinary  index 
finger  can  reach  from  the  anus.  In  the  female  the  height  of  the  rectouterine  excava- 
tion is  about  5.5  cm.  from  the  anal  orifice.  The  rectum  is  surrounded  by  a  dense 
tube  of  fascia  derived  from  the  fascia  endopelvina,  but  fused  behind  with  the  fascia 
covering  the  sacrum  and  coccyx.  The  facial  tube  is  loosely  attached  to  the  rectal 
wall  by  areolar  tissue  in  order  to  allow  of  distension  of  the  viscus. 

Relations  of  the  Rectum. — The  upper  part  of  the  rectum  is  in  relation,  behind,  \sdth  the  superior 
hemorrhoidal  vessels,  the  left  Piriformis,  and  left  sacral  plexus  of  nerves,  which  separate  it  from 
the  pelvic  sm-faces  of  the  sacral  vertebrae;  in  its  lower  part  it  hes  directly  on  the  sacrum,  coccyx, 
and  Levatores  ani,  a  dense  fascia  alone  intervening;  in  front,  it  is  separated  above,  in  the  male, 
from  the  fundus  of  the  bladder;  in  the  female,  from  the  intestinal  sm-face  of  the  uterus  and  its 

I  Paterson  ("The  Form  of  the  Rectum,"  Journal  of  Anatomy  and  Physiology,  vol.  xhii)  utilizes  the  third  fold  for 
the  purpose  of  dividing  the  rectum  into  an  upper  and  a  lower  portion ;  he  considers  the  latter  "to  be  just  as  much  a 
duct  as  the  narrower  anal  canal  below, "  and  maintains  that,  under  normal  conditions,  it  does  not  contain  feces  except 
during  the  act  of  defecation. 


Fig.  996. 


Rectal  columns 

Sphincter  ani 

internus 
Sphincter  ani 

externus 


-Coronal  section  of  rectum  and 
anal  canal. 


1184 


SPLANCHXOLOGY 


appendages,  by  some  convolutions  of  the  small  intestine,  and  frequently  by  the  sigmoid  colon; 
beloiv,  it  is  in  relation  in  the  male  with  the  triangular  portion  of  the  fundus  of  the  bladder,  the 
vesiculae  seminales,  and  ductus  deferentes,  and  more  anteriorly  with  the  posterior  surface  of 
the  prostate;  in  the  female,  with  the  posterior  wall  of  the  vagina. 

The  Anal  Canal  (jxirs  analis  recti)  (Fig.  997),  or  terminal  portion  of  the  large 
intestine,  begins  at  the  level  of  the  apex  of  the  prostate,  is  directed  downward  and 

backward,  and  ends  at  the  anus.  It 
forms  an  angle  Avith  the  lower  part  of 
the  rectum,  and  measures  from  2.5  to 
4  cm.  in  length.  It  has  no  peritoneal 
covering,  but  is  invested  by  the  Sphinc- 
ter ani  internus,  supported  by  the 
Levatores  ani,  and  surrounded  at  its 
termination  by  the  Sphincter  ani  ex- 
ternus.  In  the  empty  condition  it  pre- 
sents the  appearance  of  an  antero- 
posterior longitudinal  slit.  Behind  it 
is  a  mass  of  muscular  and  fibrous 
tissue,  the  anococcygeal  body  (Syming- 
ton); in  front  of  it,  in  the  male,  but 
separated  by  connective  tissue  from  it, 
are  the  membranous  portion  and  bulb 
of  the  urethra,  and  the  fascia  of  the  uro- 
genital diaphragm;  and  in  the  female 
it  is  separated  from  the  lower  end  of 
the  vagina  by  a  mass  of  muscular  and 
fibrous  tissue,  named  the  perineal  body. 
The  lumen  of  the  anal  canal  pre- 
sents, in  its  upper  half,  a  number  of 
vertical  folds,  produced  by  an  infolding 
of  the  mucous  membrane  and  some  of 
the  muscular  tissue.  They  are  known  as  the  rectal  columns  [Morgagni]  (Fig.  996), 
and  are  separated  from  one  another  by  furrows  (rectal  sinuses),  which  end  below 
in  small  valve-like  folds,  termed  anal  valves,  which  join  together  the  lower  ends 
of  the  rectal  columns. 

Structure  of  the  Colon. — The  large  intestine  has  four  coats:  serous,  muscular,  areolar,  and 
mucous. 

The  serous  coat  (tunica  serosa)  is  derived  from  the  peritoneum,  and  iuA^ests  the  different 
portions  of  the  large  intestine  to  a  variable  extent.  The  cecum  is  completely  covered  by  the , 
serous  membrane,  except  in  about  5  per  cent,  of  cases  where  the  upper  part  of  the  posterior 
surface  is  im covered.  The  ascending,  descending,  and  iliac  parts  of  the  colon  are  usually  covered 
only  in  front  and  at  the  sides;  a  A'ariable  amount  of  the  posterior  surface  is  uncovered.^  The 
transverse  colon  is  almost  completely  invested,  the  parts  corresponding  to  the  attachment  of 
the  greater  omentum  and  transverse  mesocolon  being  alone  excepted.  The  sigmoid  colon  is 
entirely  surrounded.  The  rectum  is  covered  above  on  its  anterior  surface  and  sides;  below, 
on  its  anterior  aspect  only;  the  anal  canal  is  entirely  devoid  of  any  serous  covering.  In  the 
course  of  the  colon  the  peritoneal  coat  is  thi'own  into  a  number  of  small  pouches  filled  with  fat, 
called  appendices  epiploicae.     They  are  most  niunerous  on  the  transverse  colon. 

The  muscular  coat  {tunica  nmscularis)  consists  of  an  external  longitudinal,  and  an  internal 
circular,  layer  of  non-striped  muscular  fibres. 

The  longitudinal  fibres  do  not  form  a  continuous  layer  over  the  whole  surface  of  the  large  intes- 
tine. In  the  cecum  and  colon  they  are  especially  collected  into  thi-ee  flat  longitudinal  bands 
{taeniae  coli),  each  of  about  12  mm.  in  width;  one,  the  posterior,  is  placed  along  the  attached 
border  of  the  intestine;  the  anterior,  the  largest,  corresponds  along  the  arch  of  the  colon  to  the 
attachment  of  the  greater  omentum,  but  is  in  front  in  the  ascending,  descending,  and  ihac  parts 
of  the  colon,  and  in  the  sigmoid  colon;  the  third,  or  lateral  band,  is  found  on  the  medial  side  of 
the  ascending  and  descending  parts  of  the  colon,  and  on  the  under  aspect  of  the  transverse  colon. 

1  See  footnote,  p.  1180. 


Fig.  997. — Coronal  section  through  the  anal  canal. 
(Symington.)  B.  Cavity  of  urinary  bladder.  V.D.  Ductus 
deferens.  .S.T'.  Seminal  vesicle.  R.  Second  part  of 
rectum.  A.C.  Anal  canal.  L.A.  Levator  ani.  /.S. 
Sphincter  ani  internus.    E.S.  Sphincter  ani  externus. 


Till':  LARGE  IXTESTIXE 


1185 


These  bands  arc  shorlci-  tlian  I  lie  oilier  coats  of  ilic  intestine,  and  serve  to  produce  the  sacculi 
which  are  cliaracteristic  of  the  cecum  and  colon;  accordingly,  when  they  are  dissected  off,  the 
tube  can  be  lengthened,  and  its  sacculated  character  becomes  lost.  In  the  sigmoid  colon  the  longi- 
tudinal fibres  become  more  scattered;  and  around  the  rectum  they  spread  out  and  form  a  layer, 
which  completely  encircles  this  portion  of  the  gut,  but  is  thicker  on  the  anterior  and  posterior 
surfaces,  where  it  forms  two  bands,  than  on  the  lateral  surfaces.  In  addition,  two  bands  of  plain 
muscular  tissue  arise  from  the  se(^ond  and  third  coccygeal  vertebrae,  and  pass  downward  and 
forward  to  blend  with  the  longitudinal  nnisculur  fibres  on  the  posterior  wall  of  the  anal  canal. 
These  are  known  as  the  Rectococcygeal  muscles. 

The  circular  fibres  form  a  thin  laj'cr  over  the  cecum  and  colon,  being  especially  accumulated 
in  the  intervals  between  the  sacculi;  in  the  rectum  they  form  a  thick  layer,  and  in  the  anal  canal 
they  become  numerous,  and  constitute  the  Sphincter  ani  internus. 

The  areolar  coat  {tcln  submucosa;  submucous  coat)  connects  the  muscular  and  mucous  layers 
closely  together. 

The  mucous  membrane  (tunica  viucosa)  in  the  cecum  and  colon,  is  pale,  smooth,  destitute  of 
villi,  and  raised  into  numerous  crescentic  folds  which  correspond  to  the  intervals  between  the 
sacculi.  In  the  rectum  it  is  thicker,  of  a  darker  color,  more  vascular,  and  connected  loosely  to 
the  muscular  coat,  as  in  the  a?sophagus. 


Leucocytes  in 
epilheliuvi 


Gland 


M^iscularis 
mucosce 


«j-,..-.v-.-.-.A.....-.'.,.~...-:.vj:-..y:feiv,,K,,!g='    Uerm-centre 
Solitary  lympJialic  nodule 


Fig.  998. — Section  of  mucous  membrane  of  human  rectum.      (Sobotta.)      X  60. 


As  in  the  small  intestine,  the  mucous  membrane  (Fig.  998)  consists  of  a  muscular  layer,  the 
muscularis  mucosae ;  a  quantity  of  retif orm  tissue  in  which  the  vessels  ramify ;  a  basement-mem- 
brane and  epithelium  which  is  of  the  columnar  variety,  and  resembles  the  epithelitim  found  in 
the  small  intestine.  The  mucous  membrane  of  the  large  intestine  presents  for  examination  glands 
and  sohtary  Ijonphatic  nodules. 

The  glands  of  the  great  intestine  are  minute  tubular  prolongations  of  the  mucous  membrane 
arranged  perpendicularly,  side  by  side,  over  its  entire  surface;  they  are  longer,  more  numerous, 
and  placed  in  much  closer  apposition  than  those  of  the  small  intestine;  and  they  open  by  minute 
roimded  orificeiS  upon  the  surface,  giving  it  a  cribriform  appearance.  Each  gland  is  lined  by 
short  cohunnar  epithelium  and  contains  niunerous  goblet  cells. 

The  solitary  lymphatic  nodules  {noduU  lymphatic  solitarii)  (Fig.  998)  of  the  large  intestine 
are  most  abundant  in  the  cecum  and  vermiform  process,  but  are  irregularly  scattered  also  over 
the  rest  of  the  intestine.    They  are  similar  to  those  of  the  small  intestine. 

Vessels  and  Nerves. — The  arteries  supplying  the  colon  are  derived  from  the  cohc  and  sigmoid 
branches  of  the  mesenteric  arteries.  They  give  off  large  branches,  which  ramify  between  and 
supply  the  muscular  coats,  and  after  dividing  into  small  vessels  in  the  submucous  tissue,  pass 
to  the  mucous  membrane.  The  rectum  is  supplied  by  the  superior  hemorrhoidal  branch  of  the 
inferior  mesenteric,  and  the  anal  canal  by  the  middle  hemorrhoidal  from  the  hj^ogastric,  and 
the  inferior  hemorrhoidal  from  the  internal  pudendal  artery.  The  superior  hemorrhoidal,  the 
continuation  of  the  superior  mesenteric,  divides  into  two  branches,  which  run  down  either  side 
of  the  rectum  to  within  about  12.5  cm.  of  the  anus;  they  here  spht  up  into  about  six  branches, 
which  pierce  the  muscular  coat  and  descend  between  it  and  the  mucous  membrane  in  a  longi- 
75 


1186  SPLA  NCHNOLOG  Y 

tiidinal  direction,  parallel  with  each  other  as  far  as  the  Sphincter  ani  internus,  where  they  anas- 
tomose with  the  other  hemorrhoidal  arteries  and  form  a  series  of  loops  around  the  anus.  The 
veins  of  the  rectum  commence  in  a  plexus  of  vessels  which  surrounds  the  anal  canal.  In  the 
vessels  forming  this  plexus  are  smaller  saccular  dilatations  just  within  the  margin  of  the  anus; 
from  the  plexus  about  six  vessels  of  considerable  size  are  given  off.  These  ascend  between  the 
muscular  and  mucous  coats  for  about  12.5  cm.-,  running  parallel  to  each  other;  they  then 
pierce  the  muscular  coat,  and,  by  their  union,  form  a  single  trunk,  the  superior  hemorrhoidal 
vein.  This  arrangement  is  termed  the  hemorrhoidal  plexus;  it  communicates  with  the  tribu- 
taries of  the  middle  and  inferior  hemorrhoidal  veins,  at  its  commencement,  and  thus  a  communi- 
cation is  established  between  the  systemic  and  portal  circulations.  The  lymphatics  of  the  large 
intestine  are  described  on  page  792.  The  nerves  are  derived  from  the  sympathetic  plexuses 
around  the  branches  of  the  superior  and  inferior  mesenteric  arteries.  They  are  distributed  in 
a  similar  way  to  those  found  in  the  small  intestine. 

Applied  Anatomy. — The  small  intestine  is  much  exposed  to  injury,  but,  in  consequence  of 
elasticity  and  the  ease  with  which  one  coil  glides  over  another,  it  is  not  so  frequently  ruptured 
as  would  otherwise  be  the  case.  Any  part  of  it  may  be  ruptured,  but  probably  the  most  common 
situation  is  the  horizontal  portion  of  the  duodenum,  on  account  of  its  being  more  fixed  than 
other  portions  of  the  bowel,  and  because  it  is  situated  in  front  of  the  bodies  of  the  vertebrae, 
so  that  if  this  portion  of  the  intestine  is  struck  by  a  sharp  blow,  as  from  the  kick  of  a  horse,  it  is 
unable  to  glide  out  of  the  way,  but  is  compressed  against  the  bone  and  so  lacerated.  Wounds 
of  the  intestine  sometimes  occur.  If  the  wound  is  a  small  puncture,  under,  it  is  said,  6  mm.  in 
length,  no  extravasation  of  the  contents  of  the  bowel  takes  place;  the  mucous  membrane  becomes 
everted  and  plugs  the  little  opening.  The  small  intestine,  and  most  frequently  the  ileum,  may 
become  strangulated  by  internal  bands,  or  through  apertures,  normal  or  abnormal.  The  bands 
may  be  formed  in  several  different  ways:  they  may  be  old  peritoneal  adhesions  from  previous 
attacks  of  peritonitis:  or  an  adherent  omentum  from  the  same  cause;  or  the  band  may  be  formed 
by  Meckel's  diverticulum,  which  has  contracted  adhesions  at  its  distal  extremity;  or  it  may  be 
the  result  of  the  abnormal  attachment  of  some  normal  structure,  as  the  adhesion  of  two  appen- 
dices epiploicae,  or  an  adherent  vermiform  process  or  uterine  tube.  Intussusception,  most  com- 
monly an  invagination  of  the  small  intestine  into  the  large,  may  take  place;  it  may  attain  great 
size,  and  it  is  not  uncommon  in  these  cases  to  find  the  cohc  valve  projecting  from  the  anus. 
Stricture,  the  impaction  of  foreign  bodies,  and  twisting  of  the  gut  (volvulus)  may  also  lead  to 
intestinal  obstruction. 

Resection  of  a  portion  of  the  intestine  may  be  required  in  cases  of  gangrene;  for  the  removal 
of  new  growth  in  the  bowel;  in  dealing  with  artificial  anus;  and  in  cases  of  rupture.  The  opera- 
gion  is  termed  enteredomy,  and  is  performed  as  foUows:  the  abdomen  having  been  opened  and 
the  amount  of  bowel  requiring  removal  having  been  determined  upon,  the  intestine  must  be 
clamped  on  either  side  of  this  portion  in  order  to  prevent  the  escape  of  any  of  its  contents  during 
the  operation.  The  portion  of  the  bowel  is  then  separated  above  and  below  by  means  of  scissors. 
If  the  portion  resected  is  small,  it  may  be  simply  removed  from  the  mesentery  at  its  attachment, 
and  the  bleeding  vessels  tied ;  but  if  it  be  large  it  will  be  necessary  to  take  away  a  triangular  piece 
of  the  mesentery,  and,  having  secured  the  vessels,  suture  the  cut  edges  of  this  structure  together. 
In  doing  this,  care  must  be  taken  not  to  leave  any  intestine  projecting  beyond  the  line  of  the 
section  of  mesentery,  as  gangrene  is  very  likely  to  occur  in  the  projecting  part  if  this  is  done. 
The  surgeon  then  proceeds  to  unite  the  cut  ends  of  the  bowel  together  by  what  is  termed  end-to- 
end  anastomosis.  There  are  many  ways  of  doing  this,  which  may  be  divided  into  two  classes, 
one  where  the  anastomosis  is  made  by  means  of  some  mechanical  appliance,  such  as  Murphy's 
button,  or  one  of  the  forms  of  decalcified  bone  bobbin;  and  the  other,  where  the  operation  is 
performed  by  suturing  the  ends  of  the  bowel  in  such  a  manner  that  the  peritoneum  covering  the 
two  divided  ends  is  brought  into  contact,  so  that  speedy  union  may  ensue. 

The  vermiform  process  is  very  Uable  to  become  inflamed,  because  it  contains  a  relatively 
large  amount  of  lymphoid  tissue,  which  is  prone  to  bacterial  infection.  In  many  cases  the  inflam- 
mation is  set  up  by  the  impaction  in  it  of  a  solid  mass  of  feces  or  a  foreign  body,  or  by  the  inspis- 
sation  of  its  mucous  secretion  in  catarrhal  conditions.  The  inflammation  may  result  in  ulceration 
and  perforation,  or  if  very  acute  in  gangrene  of  the  process.  These  conditions  generally  require 
immediate  operative  interference,  and  in  chronic  cases  with  recurring  attacks  of  inflammation 
it  is  always  advisable  to  remove  this  diverticulum  of  the  bowel.  In  incising  the  abdominal  wall 
for  this  operation,  the  muscles  should  be  split  in  the  direction  of  their  fibres  rather  than  cut 
across  in  order  to  prevent  subsequent  weakening  of  the  abdominal  parietes  and  the  occurrence 
of  a  ventral  hernia.  After  the  process  has  been  removed  it  is  better  to  suture  the  planes  of  the 
abdominal  wall  separately. 

In  external  hernia  the  ileum  is  the  portion  of  bowel  most  frequently  herniated.  When  a  part 
of  the  large  intestine  is  involved  it  is  usually  the  cecum,  and  this  may  occur  even  on  the  left  side. 
In  some  few  cases  the  vermiform  process  has  been  the  part  implicated  in  strangulated  hernia. 

Chronic  ulcer  of  the  duodenum  is  sometimes  met  with,  probably  produced  by  the  same  causes 
as  chronic  ulcer  of  the  stomach.     It  may  perforate  and  set  up  a  rapidly  fatal  peritonitis,  or  it 


THE  LARGE  INTESTINE  1187 

may  open  into  one  of  tlic  largo  duotloiml  nosscIs  and  cause  dcalli  I'roni  licnioiThagc.  An  acute 
ulcer  sometimes,  but  rarely,  follows  extensive  burns  of  the  skin. 

The  calibre  of  the  large  intestine  gradually  diminishes  from  the  cecum,  which  has  the  greatest 
diameter  of  any  part  of  the  bowel,  to  the  point  of  junction  of  the  sigmoid  colon  with  the  rectum. 
At  or  a  little  below  this  point  stricture  most  commonly  occurs,  and  diminishes  in  frequency  as 
one  proceeds  upward  to  the  cecum.  When  distended  by  some  obstruction  low  down,  the  outline 
of  the  large  intestine  can  be  defined  throughout  nearly  the  whole  of  its  course — all,  in  fact,  except 
the  rigiit  and  left  colic  flexures,  which  are  more  deeply  placed;  the  distension  is  most  obvious  in 
the  flanks  and  on  tiie  front  of  the  abdomen  just  above  the  umbilicus.  The  cecum,  however, 
is  the  portion  of  tiie  bowel  wliich  becomes  most  distended.  It  may  assume  enormous  dimensions, 
and  has  been  known  to  give  way  from  the  distension,  causing  fatal  peritonitis.  The  right  colic 
flexure  and  the  right  extremity  of  the  transverse  colon  are  in  close  relationship  with  the  liver, 
and  abscess  of  this  viscus  sometimes  bursts  into  the  gut  in  this  situation.  The  gall-bladder  may 
become  adherent  to  the  colon,  and  gallstones  may  find  their  way  into  the  latter  and  may  become 
impacted,  or  may  be  discharged  per  anum.  The  mobihty  of  the  sigmoid  colon  renders  it  more 
liable  to  become  the  seat  of  a  volvulus  or  twist  than  any  other  part  of  the  intestine.  It  generally 
occurs  in  patients  who  have  been  the  subjects  of  habitual  constipation,  and  in  whom,  therefore, 
the  mesocolon  is  elongated.  The  gut  at  this  part,  being  loaded  with  feces,  falls  over  the  part 
below,  and  so  gives  rise  to  the  twist. 

Hernia. — The  two  chief  sites  at  which  external  hernia  may  take  place  are  the  inguinal  region 
and  the  femoral  canal.  The  description  of  the  inguinal  canal  and  its  relations  will  be  found  on 
page  508,  and  that  of  the  femoral  canal  on  page  712.  Some  points  in  regard  to  the  disposition 
of  the  peritoneum  in  these  regions  may,  hoWever,  be  recapitulated  here. 

Between  the  upper  margin  of  the  front  of  the  pelvis  and  the  umbilicus,  the  peritoneum,  when 
viewed  from  behind,  will  be  seen  to  be  raised  into  five  folds,  with  intervening  depressions,  by 
more  or  less  prominent  bands  which  converge  to  the  umbihcus  (Fig.  962).  The  middle  umbihcal 
ligament,  situated  in  the  middle  Une,  is  covered  by  a  fold  of  peritoneum  known  as  the  middle 
umbilical  fold.  On  either  side  of  this  a  fold  of  peritoneimi  around  the  obhterated  umbilical  artery 
forms  the  lateral  umbilical  fold.  To  either  side  of  these  tlrree  cords  is  the  inferior  epigastric 
artery  covered  by  the  epigastric  fold.  Between  these  raised  folds  are  depressions  constituting 
the  so-called  foveas.  The  most  medial,  between  the  middle  and  lateral  umbihcal  folds,  is  known 
as  the  supravesical  fovea.  The  intermediate  one  is  situated  medial  to  the  plica  epigastrica,  and 
is  termed  the  medial  inguinal  fovea.  The  third  is  lateral  to  the  pUca  epigastrica,  and  is  known 
as  the  lateral  inguinal  fovea.  Occasionally  the  inferior  epigastric  artery  corresponds  in  position 
to  the  obhterated  hypogastric  artery,  and  then  there  is  but  one  fold  on  each  side  of  the  middle 
hne.  In  the  usual  position  of  the  parts,  the  floor  of  the  lateral  inguinal  fovea  corresponds  to  the 
abdominal  inguinal  ring,  and  into  this  fovea  an  oblique  inguinal  hernia  descends.  Medial  to 
the  epigastric  fold  are  the  medial  inguinal  and  the  supravesical  fovese,  and  through  either  of 
these  a  direct  hernia  may  descend.  The  whole  of  the  space  between  the  inferior  epigastric  artery, 
the  margin  of  the  Rectus  abdominis,  and  the  inguinal  Ugament  is  known  as  Hesselbach's  triangle. 
Below  the  level  of  the  inguinal  hgament  is  a  small  depression  corresponding  to  the  position  of  the 
femoral  rmg.    It  is  known  as  the  femoral  fovea,  and  into  it  a  femoral  hernia  descends. 

Inguinal  Hernia. — Inguinal  hernia  is  that  form  of  protrusion  which  makes  its  way  through 
the  abdominal  wall  in  the  inguinal  region.  There  are  two  principal  varieties  of  it:  lateral  or 
obhque,  and  medial  or  direct. 

In  oblique  inguinal  hernia  the  intestine  escapes  from  the  abdominal  cavity  at  the  abdominal 
inguinal  ring,  pushing  before  it  a  pouch  of  peritoneum  which  forms  the  hernial  sac.  As  it  enters 
the  inguinal  canal  it  receives  an  investment  from  the  extraperitoneal  tissue  and  is  enclosed  in 
the  infundibuhform  fascia.  In  passing  along  the  inguinal  canal  it  displaces  upward  the  arched 
fibres  of  the  Transversus  and  ObUquus  internus,  and  receives  a  covering  of  Cremaster  muscle 
and  cremasteric  fascia.  It  then  passes  along  the  front  of  the  spermatic  cord  and  escapes  from 
the  inguinal  canal  at  the  subcutaneous  inguinal  ring,  becoming  invested  by  intercrural  fascia. 
Lastty  it  descends  into  the  scrotum,  receiving  coverings  from  the  superficial  fascia  and  the 
integument . 

The  seat  of  stricture  in  oblique  inguinal  hernia  is  at  either  the  abdominal  or  the  subcutaneous 
inguinal  ring;  most  frequently  in  the  latter  situation.  If  it  is  situated  at  the  subcutaneous  ring, 
the  division  of  a  few  fibres  at  one  point  of  the  circumference  is  all  that  is  necessary  for  the  replace- 
ment of  the  hernia.  If  at  the  abdominal  ring,  it  is  necessary  to  divide  the  aponeurosis  of  the 
Obliquus  externus  so  as  to  lay  open  the  inguinal  canal,  in  dividing  the  aponeurosis  the  incision 
should  be  directed  parallel  to  the  mguinal  hgament,  and  the  constriction  at  the  abdominal  ring 
should  then  be  divided  directly  upward. 

When  the  intestine  passes  along  the  inguinal  canal  and  escapes  from  the  subcutaneous  ring 
into  the  scrotum,  it  is  called  complete  oblique  inguinal  or  scrotal  hernia.  If  the  intestine  does  not 
escape  from  the  subcutaneous  ring,  but  is  retained  in  the  inguinal  canal,  it  is  called  incomplete 
inguinal  hernia  or  bubonocele.  In  each  of.  these  cases  the  coverings  which  invest  it  will  depend 
upon  the  e.xtent  to  which  it  descends  in  the  inguinal  canal. 


1188 


SPLANCHNOLOGY 


Complete  oblique  inguinal 


Complete  congenital 


Incomplete  congenital 
Fig.  999. — Varieties  of  oblique  inguinal  hernia. 


There  are  some  other  varieties  of  obhqiie  inguinal  hernia  (Fig.  999)  depending  upon  congenital 
defects  in  the  saccus  vaginalis,  the  pouch  of  peritoneum  which  precedes  the  descent  of  the  testis. 
Normally  this  pouch  is  closed  before  birth,  closure  commencing  at  two  points,  viz.,  at  the  abdomi- 
nal inguinal  ring  and  at  the  top  of  the  epididymis,  and  gradually  extending  until  the  whole  of 
the  intervening  portion  is  converted  into  a  fibrous  cord.    From  failure  in  the  completion  of  this 

process,  variations  in  the  relation  of  the 
hernial  protrusion  to  the  testis  and 
tunica  vaginahs  are  produced;  these 
constitute  distinct  varieties  of  inguinal 
hernia,  viz.,  the  hernia  of  the  funicular 
process  and  the  complete  congenital 
variety. 

Where  the  saccus  vaginalis  remains 
patent  throughout,  the  cavity  of  the 
tunica  vaginalis  communicates  directly 
with  that  of  the  peritoneum.  The  in- 
testine descends  along  this  pouch  into 
the  cavity  of  the  tunica  vaginalis  which 
constitutes  the  sac  of  the  hernia,  and 
the  gut  hes  in  contact  with  the  testis. 
Though  this  form  of  hernia  is  termed 
complete  congenital,  the  term  does  not 
imply  that  the  hernia  existed  at  birth, 
but  merely  that  a  condition  is  present 
which  may  allow  of  the  descent  of  the 
hernia  at  any  moment.  As  a  matter  of 
fact,  congenital  hernise  frequently  do 
not  appear  until  adult  hfe. 

Where  the  processus  vaginaUs  is 
occluded  at  the  lower  point  only,  i.  e., 
just  above  the  testis,  the  intestine 
descends  into  the  pouch  of  peritoneum 
as  far  as  the  testis,  but  is  prevented 
from  entering  the  sac  of  the  tunica  vaginahs  by  the  septum  which  has  formed  between  it  and  the 
pouch.  This  is  knowTi  as  hernia  iiito  the  funicular  process  or  incomplete  congenital  hernia;  it 
differs  from  the  former  in  that  instead  of  enveloping  the  testis  it  lies  above  it. 

In  direct  inguinal  hernia  the  protrusion  makes  its  way  through  some  part  of  Hesselbach's 
triangle,  either  through  (a)  the  lateral  part,  where  only  extraperitoneal  tissue  and  transversahs 
fascia  intervene  between  the  peritoneixm  and  the  aponeurosis  of  the  Obliquus  externus;  or  through 
(b)  the  inguinal  aponeurotic  falx  which  stretches  across  the  medial  two-thirds  of  the  triangle 
between  the  artery  and  the  middle  line.  In  the  former  the  hernial  protrusion  escapes  from 
the  abdomen  on  the  lateral  side  of  the  inguinal  falx,  pushes  before  it  the  peritoneum,  extra- 
peritoneal tissue,  and  transversahs  fascia,  and  enters  the  inguinal  canal.  It  passes  along  nearly 
the  whole  length  of  the  canal  and  finally  emerges  from  the  subcutaneous  ring,  receiving  an  invest- 
ment from  the  intercrural  fascia.  The  coverings  of  this  form  of  hernia  are  similar  to  those  of 
the  obhque  form,  except  that  a  portion  derived  from  the  general  layer  of  transversahs  fascia 
replaces  the  infundibuhform  fascia. 

In  the  second  form,  which  is  the  more  frequent,  the  hernia  is  either  forced  through  the  fibres 
of  the  inguinal  falx,  or  the  falx  is  gradually  distended  in  front  of  it  so  as  to  form  a  complete 
investment  for  it.  The  intestine  then  enters  the  lower  end  of  the  inguinal  canal,  escapes  at  the 
subcutaneous  ring,  lying  on  the  medial  side  of  the  cord,  and  receives  additional  coverings  from 
the  intercrxiral  fascia,  the  superficial  fascia  and  the  integument.  The  coverings  of  this  form 
therefore  differ  from  those  of  the  obhque  form  in  that  the  inguinal  falx  is  substituted  for  the 
Cremaster,  and  the  infundibuhform  fascia  is  replaced  by  a  portion  of  the  general  layer  of  the 
transversahs  fascia. 

The  seat  of  stricture  in  both  varieties  of  direct  hernia  is  usually  foimd  either  at  the  neck  of  the 
sac  or  at  the  subcutaneous  ring.  In  that  form  which  perforates  the  inguinal  fabc  it  not  infrequently 
occurs  at  the  edges  of  the  fissure  through  which  the  gut  passes.  In  all  cases  of  inguinal  hernia, 
whether  direct  or  oblique,  it  is  proper  to  divide  the  stricture  directly  upward;  by  cutting  in  this 
direction  the  incision  is  made  paraUel  to  the  inferior  epigastric  artery — lateral  to  it  in  the  oblique 
variety,  medial  to  it  in  the  direct  form  of  hernia;  all  chance  of  wounding  the  vessel  is  thus  avoided. 
Direct  inguinal  hernia  is  of  much  less  frequent  occm-rence  than  oblique,  and  is  found  more  often 
in  men  than  in  women.  The  main  diiTerences  in  position  between  it  and  the  obhque  form  are: 
(a)  it  is  placed  over  the  pubis  and  not  in  the  course  of  the  inguinal  canal;  (6)  the  inferior  epi- 
gastric artery  runs  on  the  lateral  or  iliac  side  of  the  neck  of  the  sac;  and  (c)  the  spermatic  cord 
lies  along  its  lateral  and  posterior  sides,  not  directly  behind  it  as  in  oblique  inguinal  hernia. 


THE  LARGE  INTESTINE  1189 

Femoral  Hernia. — In  femoral  hernia  the  protrusion  of  the  intestine  takes  place  througli  the 
femoral  riii};.  As  already  described  (page  712),  this  ring  is  closed  by  the  femoral  septum,  a 
partition  of  modified  extraperitoneal  tissue;  it  is  therefore  a  weak  spot  in  the  abdominal  wall, 
and  especially  in  tlic  female,  where  the  ring  is  larger  and  where  profound  changes  are  produced 
in  the  tissues  of  the  abdomen  by  pregnancy.  Femoral  licrnia  is  therefore  more  common  in 
women  than  in  men. 

When  a  portion  of  intestine  is  forced  tlu'ough  the  femoral  ring,  it  carries  before  it  a  pouch  of 
peritoneum,  which  forms  the  hernial  sac.  It  receives  an  investment  from  the  extraperitoneal 
tissue  or  femoral  septum,  and  descends  along  the  femoral  canal,  or  inner  compartment  of  the 
sheath  of  the  femoral  vessels,  as  far  as  the  fossa  ovalis;  at  this  point  it  changes  its  course,,  being 
prevented  from  extending  farther  down  the  sheath  on  account  of  the  narrowing  of  the  latter, 
and  its  close  contact  with  the  vessels,  and  also  the  close  attachment  of  the  superficial  fascia 
and  femoral  sheath  to  the  lower  part  of  the  circmnference  of  the  fossa  ovahs.  The  tumor  is 
consequentlj'^  directed  forward,  pushing  before  it  the  fascia  cribrosa,  and  then  curves  upward 
over  tlie  inguinal  ligament  and  the  lower  part  of  the  aponeurosis  of  the  Obliquus  externus.  being 
covered  by  the  superficial  fascia  and  integument.  While  the  hernia  is  contained  in  the  femoral 
canal  it  is  usually  of  small  size,  owing  to  the  resisting  nature  of  the  surrounding  parts,  but  when 
it  escapes  from  the  fossa  ovahs  into  the  loose  areolar  tissue  of  the  groin  it  becomes  considerably 
enlarged.  The  direction  taken  by  a  femoral  hernia  is  at  first  downward,  then  forward  and  up- 
ward; in  the  application  of  taxis  for  the  reduction  of  a  femoral  hernia  therefore,  pressure  should 
be  directed  in  the  reverse  order. 

The  coverings  of  a  femoral  hernia  from  within  outward  are:  peritoneum,  femoral  septmn, 
femoral  sheath,  fascia  cribrosa,  superficial  fascia,  and  integument.  Sir  Astley  Cooper  has  described 
an  investment  for  femoral  hernia  under  the  name  of  fascia  -propria,  lying  immediately  external 
to  the  peritoneal  sac  but  frequently  separated  from  it  by  some  adipose  tissue.  Surgically  it  is 
important  to  remember  the  frequent  existence  of  this  layer  on  account  of  the  ease  with  which  an 
inexperienced  operator  may  mistake  the  fascia  for  the  peritoneal  sac  and  the  contained  fat  for 
omentum,  as  there  is  often  a  great  excess  of  subperitoneal  fatty  tissue  enclosed  in  the  "fascia 
propria."  In  many  cases  it  resembles  a  fatty  tumor,  but  on  further  dissection  the  true  hernial 
sac  will  be  found  in  the  centre  of  the  mass  of  fat.  The  fascia  propria  is  merely  modified  extra- 
peritoneal tissue  which  has  been  thickened  to  form  a  membranous  sheet  by  the  pressure  of  the 
hernia. 

When  the  intestine  descends  along  the  femoral  canal  only  as  far  as  the  fossa  ovahs  the  con- 
dition is  known  as  incomplete  femoral  hernia.  The  small  size  of  the  protrusion  in  this  form  of 
hernia,  on  account  of  the  firm  and  resisting  nature  of  the  canal  in  which  it  is  contained,  renders 
it  an  exceedingly  dangerous  variety  of  the  disease,  from  the  extreme  difficulty  of  detecting  the 
existence  of  the  sweUing,  especially  in  corpulent  subjects.  The  coverings  of  an  incomplete 
femoral  hernia  would  be  from  without  inward:  integiunent,  superficial  fascia,  superior  cornu  of 
falciform  max'gin  of  the  fossa  ovalis,  femoral  sheath,  femoral  septum,  and  peritoneum. 

The  seat  of  stricture  of  a  femoral  hernia  varies:  it  may  be  in  the  peritoneum  at  the  neck  of 
the  hernial  sac;  in  the  greater  nimiber  of  cases  it  is  at  the  point  of  junction  of  the  falciform  margin 
of  the  fossa  ovahs  with  the  free  edge  of  the  lacunar  ligament;  or  it  may  be  at  the  margin  of  the 
fossa  ovalis.  The  stricture  should  in  every  case  be  divided  in  a  direction  upward  and  medialward 
for  a  distance  of  about  4  to  6  mm.  All  vessels  or  other  structures  of  importance  in  relation  to 
the  neck  of  the  sac  will  thus  be  avoided. 

The  pubic  tubercle  forms  an  important  landmark  in  serving  to  differentiate  the  inguinal  from 
the  femoral  variety  of  hernia.  The  inguinal  protrusion  is  above  and  medial  to  the  tubercle,  while 
the  femoral  is  below  and  lateral  to  it. 

There  are  several  details  of  practical  interest  in  connection  with  the  mesentery  which  merit 
notice.  (1)  The  depth  of  the  mesentery — that  is  to  say,  the  distance  from  its  parietal  to  its 
intestinal  attachment — is  normally  less  than  20  cm.,  generally  nearer  15  cm.;  but  under  certain 
abnormal  conditions  it  may  become  elongated,  and  this  would  appear  to  favor  the  occurrence  of 
hernia  of  the  intestine.  (2)  Not  only  may  the  depth  of  the  mesentery  be  increased,  but  its  point 
of  attachment  to  the  posterior  abdominal  wall  may  yield,  and  descend  over  the  lumbar  vertebrae. 
This  condition,  which  is  knowTi  under  the  name  of  enteroptosis,  usually  occurs  in  women  who 
have  borne  many  children,  and  is  attended  with  general  relaxation  of  the  abdominal  parietes. 
It  produces  a  characteristic  appearance,  the  abdomen  being  prominent  and  pendulous  below, 
while  above,  it  is  flattened  and  constricted.  (3)  Holes  are  sometimes  present  in  the  mesentery, 
and  these  may  be  congenital,  or  may  be  the  result  of  injury.  They  are  of  practical  importance, 
since  a  knuckle  of  intestine  may  become  herniated  into  one  of  them,  causing  acute  strangulation. 
(4)  The  lymph  glands  contained  between  the  two  layers  of  the  mesentery  are  frequently  the 
seat  of  tuberculous  deposit,  especially  in  children. 

The  colon  frequently  requires  opening  in  cases  of  intestinal  obstruction,  and  by  some  sui'geons 
this  operation  is  performed  in  cases  of  cancer  of  the  rectum  as  soon  as  the  disease  is  recognized, 
in  the  hope  that  the  symptoms  may  be  reheved  by  removing  the  irritation  produced  by  the 
passage  of  fecal  matter  over  the  diseased  surface.    The  operation  of  colostomy  may  be  performed 


1190  SPLANCHNOLOGY 

either  in  the  ihae  or  himbar  region;  but  iliac  colostomy  has  in  the  present  day  entirelj'  super- 
seded the  lumbar  operation.  The  main  reason  for  preferring  this  operation  is  that  a  spur-shaped 
process  of  the  mesocolon  can  be  formed,  which  prevents  any  fecal  matter  finding  its  way  past 
the  artificial  anus,  and  the  greater  ease  in  maintaining  cleanliness.  The  sigmoid  colon  being 
entirely  surrounded  by  peritoneum,  a  coil  can  be  drawn  out  of  the  wound  and  opened,  leaving  the 
attachment  of  the  mesocolon  to  form  a  spur,  much  as  it  does  in  an  artificial  anus  caused  by 
.  sloughing  of  the  intestine  after  a  strangulated  hernia,  and  this  prevents  any  fecal  matter  finding 
its  way  from  the  gut  above  the  opening  into  that  below.  The  operation  is  performed  by  making 
an  incision  5  to  7  cm.  long  from  a  point  2.5  cm.  medial  to  the  anterior  superior  iliac- spine,  parallel 
to  the  inguinal  ligament.  The  various  muscular  layers  are  cut  through,  and  the  peritonemn 
opened;  the  sigmoid  colon  is  now  sought  for,  pulled  out  of  the  wound,  and  fixed  by  passing  a 
needle  threaded  with  carbolized  silk  first  thi'ough  the  mesocolon  close  to  the  gut,  and  then  through 
the  abdominal  wall.  The  wound  is  dressed,  and  about  the  second  day  the  protruding  coil  of 
intestine  is  opened. 

The  surgical  anatomy  of  the  rectum  is  of  considerable  importance.  There  may  be  congenital 
maKormations  due  to  arrest  of,  or  imperfection  in,  development.  Thus,  there  may  be  no  proc- 
todoeal  invagination  (see  page  174),  and  consequently  a  complete  absence  of  the  anus;  or  the 
hind-gut  may  be  imperfectly  developed,  and  there  may  be  an  absence  of  the  rectum,  though  the 
anus  is  developed;  or  the  ectodermal  invagination  may  not  communicate  with  the  termination 
of  the  hind-gut  from  want  of  solution  of  continuity  in  the  septum  which  in  early  fetal  life  exists 
between  the  two.  The  mucous  membrane  is  thick  and  but  loosely  connected  to  the  muscular 
coat  beneath,  and  thus  favors  prolapse,  especially  in  children.  The  vessels  of  the  rectum  are 
arranged,  as  mentioned  above,  longitudinally,  and  are  contained  in  the  loose  cellular  tissue 
between  the  mucous  and  muscular  coats,  and  receive  no  support  from  surromiding  tissues,  and 
this  favors  varicosity.  Moreover,  the  veins,  after  running  upward  in  a  longitudinal  direction  for 
about  12.5  cm.  in  the  submucous  tissue,  pierce  the  muscular  coats,  and  are  hable  to  become 
constricted  at  this  spot  by  the  contraction  of  the  muscular  wall  of  the  gut.  In  addition  to  this 
there  are  no  valves  in  the  superior  hemorrhoidal  veins,  and  the  vessels  of  the  rectum  are  placed 
in  a  dependent  position,  and  are  liable  to  be  pressed  upon  and  obstructed  by  hardened  feces. 
The  anatomical  arrangement,  therefore,  of  the  hemorrhoidal  vessels  explains  the  great  tendency 
to  the  occurrence  of  piles.  The  presence  of  the  Sphincter  ani  externus  is  of  surgical  importance, 
since  it  is  the  constant  contraction  of  this  muscle  which  prevents  an  ischiorectal  abscess  from 
healing,  and  causes  it  to  become  a  fistula.  Also  the  reflex  contraction  of  this  muscle  is  the  cause 
of  the  severe  pain  complained  of  in  fissure  of  the  anus.  The  relations  of  the  peritoneum  to  the 
bowel  are  of  importance  in  connection  with  the  operation  of  removal  of  the  rectum  for  malignant 
disease.  This  membrane  gradually  leaves  the  rectum  as  it  descends  into  the  pelvis;  first  leaving 
its  posterior  surface,  then  the  sides,  and  then  the  anterior  surface,  to  become  reflected,  in  the 
male  on  to  the  posterior  wall  of  the  bladder,  forming  the  rectovesical  excavation,  and  in  the 
female  on  to  the  posterior  wall  of  the  vagina,  forming  rectouterine  excavation.  The  recto- 
vesical excavation  extends  to  within  7.5  cm.  from  the  anus.  Within  recent  years  much  more 
extensive  operations  have  been  done  for  the  removal  of  cancer  of  the  rectum,  and  in  these  the 
peritoneal  cavity  has  necessarily  been  opened.  If,  in  these  cases,  the  opening  is  plugged  with 
antiseptic  gauze  imtil  the  operation  is  completed  and  then  the  edges  of  the  wound  in  the  peri- 
toneum are  accurately  brought  together  with  sutures,  no  evil  result  appears  to  follow.  For  cases 
of  cancer  of  the  rectum  which  are  too  low  to  be  reached  by  abdominal  section,  and  too  high  to 
be  removed  by  the  perineum,  Kraske  has  devised  an  operation  which  goes  by  his  name.  The 
patient  is  placed  on  his  right  side  and  an  incision  is  made  from  the  last  piece  of  the  sacrum  to 
the  anus.  The  soft  parts  are  now  separated  from  the  back  of  the  sides  of  the  sacrum  and  coccyx, 
and  the  sacrotuberous  and  sacrospinous  ligaments  are  separated.  The  coccyx  is  removed,  and 
if  necessary  a  small  piece  of  the  sacrum,  and  the  edges  of  the  wound  being  now  forcibly  drawn 
outward,  a  considerable  length  of  the  rectum  is  brought  into  view,  and  the  diseased  portion  can 
be  removed,  leaving  the  anal  portion  of  the  gut,  if  healthy.  The  two  diAdded  ends  of  the  gut 
can  sometimes  be  approximated  and  sutured  together,  the  posterior  part  being  left  open  for 
drainage. 

The  loose  connective  tissue  around  the  rectum  is  occasionally  the  site  of  an  abscess,  the  active 
focus  of  which,  however,  may  be  located  elsewhere.  This  form  of  abscess  may  be  described  as 
the  superior  pelvic  rectal;  it  is  placed  above  the  pelvic  diaphragm  but  beneath  the  peritoneum. 
The  acute  variety  is  generally  due  to  ulceration  or  perforation  of  the  bowel  (possibly  produced 
by  a  foreign  body)  above  the  level  of  attachment  of  the  Levator  ani.  The  abscess  may  also  occur 
above  a  stricture  (simple  or  mahgnant)  of  the  rectum;  occasionally  it  arises  from  suppuration 
around  the  prostate,  and  more  rarely  follows  abscess  of  the  vesiculae  seminales.  Chronic  abscesses 
also  appear  in  the  same  region  either  from  caries  of  the  anterior  surface  of  the  sacrum  or  from 
caseation  of  the  presacral  lymph  glands,  while  in  other  cases  an  abscess  finds  its  way  down  into 
the  pelvis  from  disease  of  the  anterior  surfaces  of  the  bodies  of  the  lumbar  vertebrae. 


THE  LIVER  1191 

The  Liver  (Hepar). 

The  liver  is  the  hirgest  gland  in  the  body,  and  is  sitnated  in  the  npper  and  riglit 
parts  of  the  abdominal  cavity,  occupying  almost  the  whole  of  the  right  h}'pochon- 
drium,  the  greater  part  of  the  epigastrium,  and  not  uncommonly  extending  into 
the  left  h,\i)()clu)ndrium  as  far  as  the  mammary  line.  In  the  male  it  weighs  from 
1.4  to  l.G  kilogm.,  in  the  female  from  1 .2  to  1.4  kilogm.  It  is  relatively  much  larger. 
in  the  fetus  than  in  the  adult,  constituting,  in  the  former,  about  one-eighteenth, 
and  in  the  latter  about  one  thirty-sixth  of  the  entire  body  weight.  Its  greatest 
transverse  measurement  is  from  20  to  22.5  cm.  Vertically,  near  its  lateral  or  right 
surface,  it  measures  about  15  to  17.5  cm.,  while  its  greatest  antero-posterior  diame- 
ter is  on  a  level  with  the  upper  end  of  the  right  kidney,  and  is  from  10  to  12.5  cm. 
Opposite  the  vertebral  column  its  measurement  from  before  backward  is  reduced 
to  about  7.5  cm.  Its  consistence  is  that  of  a  soft  solid ;  it  is,  however,  friable  and 
easily  lacerated;  its  color  is  a  dark  reddish  brown,  and  its  specific  gravity  is  1.05. 

To  obtain  a  correct  idea  of  its  shape  it  must  be  hardened  in  situ,  and  it  will 
then  be  seen  to  present  the  appearance  of  a  wedge,  the  base  of  which  is  directed 
to  the  right  and  the  thin  edge  toward  the  left.  Symington  describes  its  shape 
as  that  "of  a  right-angled  triangular  prism  with  the  right  angle  rounded  off." 

Surfaces. — ^The  liver  possesses  five  surfaces,  viz.,  superior,  inferior,  anterior,  pos- 
terior, and  right  lateral.  A  sharp,  well-defined  margin  divides  the  inferior  from 
the  superior,  anterior,  and  right  lateral  surfaces,  but  the  other  surfaces  are  separated 
from  one  another  by  rounded  borders.  The  superior  and  anterior  surfaces  are 
attached  to  the  Diaphragma  and  anterior  abdominal  wall  by  a  triangular  or  falci- 
form fold  of  peritoneum,  the  falciform  ligament,  in  the  free  margin  of  which  is  a 
rounded  cord,  the  ligamentum  teres  (obliterated  umbilical  vein).  The  line  of  attach- 
ment of  the  falciform  ligament  divides  the  liver  into  two  parts,  termed  the  right 
and  left  lobes,  the  right  being  much  the  larger.  The  inferior  and  posterior  surfaces 
are  divided  into  five  lobes  by  five  fossae,  which  are  arranged  in  the  form  of  the  letter 
H.  The  left  limb  of  the  H  marks  on  these  surfaces  the  division  of  the  liver  into 
right  and  left  lobes ;  it  is  known  as  the  left  sagittal  fossa,  and  consists  of  two  parts, 
viz.,  the  fossa  for  the  umbilical  vein  in  front  and  the  fossa  for  the  ductus  venosus 
behind.  The  right  limb  of  the  H  is  formed  in  front  by  the  fossa  for  the  gall-bladder, 
and  behind  by  the  fossa  for  the  inferior  vena  cava;  these  tw^o  fossse  are  separated 
from  one  another  by  a  band  of  liver  substance,  termed  the  caudate  process.  The 
bar  connecting  the  two  limbs  of  the  H  is  the  porta  (transverse  fissure) ;  in  front  of  it 
is  the  quadrate  lobe,  behind  it  the  caudate  lobe. 

The  superior  surface  (fades  superior)  (Fig.  1000)  comprises  a  part  of  both  lobes, 
and,  as  a  whole,  is  convex,  and  fits  under  the  vault  of  the  Diaphragma;  its  central 
part,  however,  presents  a  shallow  depression,  which  corresponds  w^ith  the  position 
of  the  pericardium  on  the  upper  surface  of  the  Diaphragma.  It  is  separated  from 
the  anterior,  posterior,  and  right  lateral  surfaces  by  rounded  borders.  Its  left 
extremity  is  separated  from  the  under  surface  by  a  prominent  sharp  margin. 
Except  along  the  lines  of  attachment  of  the  falciform  ligament  it  is  completely 
covered  by  peritoneum. 

The  anterior  surface  is  large,  triangular  in  shape,  and  also  comprises  a  part  of 
both  lobes.  It  is  directed  forward,  and  the  greater  part  of  it  is  in  contact  with 
the  Diaphragma,  which  separates  it  on  the  right  from  the  sixth  to  the  tenth  ribs 
and  their  cartilages,  and  on  the  left  from  the  seventh  and  eighth  costal  cartilages. 
Its  middle  part  lies  behind  the  xiphoid  process,  and,  in  the  angle  between  the  diverg- 
ing rib  cartilage  of  opposite  sides,  is  in  contact  with  the  abdominal  wall.  It  is 
separated  from  the  inferior  surface  by  a  sharp  margin,  and  from  the  superior  and 
right  lateral  surfaces  by  rounded  borders,  It  is  completely  covered  by  peritoneum 
except  along  the  line  of  attachment  of  the  falciform  ligament. 


1192 


SPLANCUXOLOGY 


The  right  lateral  surface  is  covered  by  peritoneum,  and  is  convex  from  before 
backward  and  slightly  so  from  above  downward.  It  is  directed  toward  the  right 
side,  forming  the  base  of  the  wedge,  and  lies  against  the  lateral  portion  of  the  Dia- 
phragma,  which  separates  it  from  the  lower  part  of  the  pleura  and  lung,  outside 
which  are  the  right  costal  arches  from  the  seventh  to  the  eleventh  inclusive. 


Caudate  lobe 
Left  triangular  ligament 

Fig.   1000. — The  superior,  anterior,  and  right  lateral  surfaces  of  the  liver.     (From  model  by  His.) 


Right  triangular 
ligament 


The  inferior  surf  ace  {fades  inferior;  visceral  surface)  (Figs.  1001  1002)  is  uneven, 
concave,  directed  downward,  backward,  and  to  the  left,  and  is  in  relation  with 
the  stomach  and  duodenum,  the  right  colic  flexure,  and  the  right  kidney  and  supra- 
renal gland.  The  surface  is  almost  completely  invested  by  peritoneum;  the  only 
parts  devoid  of  this  covering  are  where  the  gall-bladder  is  attached  to  the  liver, 
and  at  the  porta  hepatis  where  the  two  layers  of  the  lesser  omentum  are  separated 
from  each  other  by  the  bloodvessels  and  ducts  of  the  liver.  The  inferior  surface 
of  the  left  lobe  presents  behind  and  to  the  left  the  gastric  impression,  moulded 
over  the  antero-superior  surface  of  the  stomach,  and  to  the  right  of  this  a  rounded 
eminence,  the  tuber  omentale,  which  fits  into  the  concavity  of  the  lesser  curvature 
of  the  stomach  and  lies  in  front  of  the  anterior  layer  of  the  lesser  omentum.  The 
under  surface  of  the  right  lobe  is  divided  into  two  unequal  portions  by  the  fossa 
for  the  gall-bladder;  the  portion  to  the  left,  the  smaller  of  the  two,  is  the  quadrate 
lobe,  and  is  in  relation  with  the  pyloric  end  of  the  stomach,  the  superior  portion 
of  the  duodenum,  and  the  transverse  colon.  The  portion  of  the  under  surface  of 
the  right  lobe  to  the  right  of  the  fossa  for  the  gall-bladder  presents  two  impressions, 
one  situated  behind  the  other,  and  separated  by  a  ridge.  The  anterior  of  these 
two  impressions,  the  colic  impression,  is  shallow  and  is  produced  by  the  right  colic 
flexure;  the  posterior,  the  renal  impression,  is  deeper  and  is  occupied  by  the  upper 
part  of  the  right  kidney  and  lower  part  of  the  right  suprarenal  gland.  Medial 
to  the  renal  impression  is  a  third  and  slightly  marked  impression,  lying  between  it 
and  the  neck  of  the  gall-bladder.  This  is  caused  by  the  descending  portion  of  the 
duodenum,  and  is  known  as  the  duodenal  impression.  Just  in  front  of  the  inferior 
vena  cava  is  a  narrow  strip  of  liver  tissue,  the  caudate  process,  which  connects 
the  right  inferior  angle  of  the  caudate  lobe  to  the  under  surface  of  the  right  lobe. 
It  forms  the  upper  boundary  of  the  epiploic  foramen  of  the  peritoneum. 


THE  LIVER 


1193 


The  posterior  surface  (fades  posterior)  (Fi^-.  1002)  is  rounded  and  broad  behind 
the  rii^lit  lobe,  but  narrow  on  the  left.  Over  a  hirge  part  of  its  extent  it  is  not 
covered  by  pei-itoiicuui;  this  uncox-ered  portion  is  about  7.5  eiu.  l)road  at  its  widest 


Fossa  jor  (heel us  veiio. 
(Esophayial  gioot'e 


Papillary 
process 

Hepatic  artenj 

Portal  vein    /  ^  Bound  ligament 

Common  bile  duct 

Fig.   1001. — Inferior  surface  of  the  liver.     (From  modol  by  His.) 

part,  and  is  in  direct  contact  with  the  Diaphragma.  It  is  marked  oflf  from  the  upper 
surface  by  the  line  of  reflection  of  the  upper  layer  of  the  coronary  ligament,  and 
from  the  under  surface  by  the  line  of  reflection  of  the  lower  layer  of  the  coronary 


(Esophageal  groove 


Fossa  f  01 
diutui  veiioi>us 


Papillcoy      Fossa  fo)  iimhilicul  veil 
process 


Fig.   1002. — Posterior  and  inferior  surfaces  of  the  liver.     (From  model  by  His.) 

ligament.  The  central  part  of  the  posterior  surface  presents  a  deep  concavity 
which  is  moulded  on  the  vertebral  column  and  crura  of  the  Diaphragma.  To  the 
right  of  this  the  inferior  vena  cava  is  lodged  in  its  fossa  between  the  uncovered 


1 1 94  SPLA  Xf'IfXnLOG  Y 

area  and  the  caudate  lobe.  Close  to  the  right  of  this  fossa  and  immediately  above 
the  renal  impression  is  a  small  triangular  depressed  area,  the  suprarenal  impression, 
the  greater  part  of  which  is  devoid  of  peritoneum;  it  lodges  the  right  suprarenal 
gland.  To  the  left  of  the  inferior  vena  cava  is  the  caudate  lobe,  which  lies  between 
the  fossa  for  the  vena  cava  and  the  fossa  for  the  ductus  \cnosus.  Its  lower  end 
projects  and  forms  part  of  the  posterior  boundary  of  the  porta;  on  the  right,  it 
is  connected  with  the  under  surface  of  the  right  lobe  of  the  liver  by  the  caudate 
process,  and  on  the  left  it  presents  an  elevation,  the  papillary  process.  Its  posterior 
surface  rests  upon  the  Diaphragma,  being  separated  from  it  merely  by  the  upper 
part  of  the  omental  bursa.  To  the  left  of  the  fossa  for  the  ductus  venosus  is  a 
groove  in  which  lies  the  antrum  cardiacum  of  the  oesophagus. 

The  anterior  border  {margo  anterior)  is  thin  and  sharp,  and  marked  opposite 
the  attachment  of  the  falciform  ligament  by  a  deep  notch,  the  umbilical  notch, 
and  opposite  the  cartilage  of  the  ninth  rib  by  a  second  notch  for  the  fundus  of  the 
gall-bladder.  In  adult  males  this  border  generally  corresponds  with  the  lower 
margin  of  the  thorax  in  the  right  mammary  line;  but  in  women  and  children  it 
usually  projects  below  the  ribs. 

The  left  extremity  of  the  liver  is  thin  and  flattened  from  above  downward. 

Fossae. — The  left  sagittal  fossa  {fossa  sagittalis  sinistra;  longihidinal  fissure) 
is  a  deep  groove,  which  extends  from  the  notch  on  the  anterior  margin  of  the  liver 
to  the  upper  border  of  the  posterior  surface  of  the  organ;  it  separates  the  right  and 
left  lobes.  The  porta  joins  it,  at  right  angles,  and  divides  it  into  two  parts.  The 
anterior  part,  or  fossa  for  the  umbilical  vein,  lodges  the  umbilical  vein  in  the  fetus, 
and  its  remains  (the  ligamentum  teres)  in  the  adult;  it  lies  between  the  quadrate 
lobe  and  the  left  lobe  of  the  liver,  and  is  often  partially  bridged  over  by  a  pro- 
longation of  the  hepatic  substance,  the  pons  hepatis.  The  posterior  part,  or  fossa 
for  the  ductus  venosus,  lies  between  the  left  lobe  and  the  caudate  lobe;  it  lodges  in 
the  fetus,  the  ductus  venosus,  and  in  the  adult  a  slender  fibrous  cord,  the  ligamentum 
venosum,  the  obliterated  remains  of  that  vessel. 

The  porta  or  transverse  fissure  {porta  hepatis)  is  a  short  but  deep  fissure,  about 
5  cm.  long,  extending  transversely  across  the  under  surface  of  the  left  portion  of  the 
right  lobe,  nearer  its  posterior  surface  than  its  anterior  border.  It  joins  nearly 
at  right  angles  with  the  left  sagittal  fossa,  and  separates  the  quadrate  lobe  in 
front  from  the  caudate  lobe  and  process  behind.  It  transmits  the  portal  vein, 
the  hepatic  artery  and  nerves,  and  the  hepatic  duct  and  lymphatics.  The  hepatic 
duct  lies  in  front  and  to  the  right,  the  hepatic  artery  to  the  left,  and  the  portal 
vein  behind  and  between  the  duct  and  artery. 

The  fossa  for  the  gall-bladder  {fossa  vesicae  felleae)  is  a  shallow,  oblong  fossa, 
placed  on  the  under  surface  of  the  right  lobe,  parallel  with  the  left  sagittal  fossa. 
It  extends  from  the  anterior  free  margin  of  the  liver,  which  is  notched  by  it,  to  the 
right  extremity  of  the  porta. 

The  fossa  for  the  inferior  vena  cava  {fossa  venae  cavae)  is  a  short  deep  depression, 
occasionally  a  complete  canal  in  consequence  of  the  substance  of  the  liver  surround- 
ing the  vena  cava.  It  extends  obliquely  upward  on  the  posterior  surface  between 
the  caudate  lobe  and  the  bare  area  of  the  liver,  and  is  separated  from  the  porta 
by  the  caudate  process.  On  slitting  open  the  inferior  vena  cava  the  orifices  of 
the  hepatic  veins  will  be  seen  opening  into  this  vessel  at  its  upper  part,  after 
perforating  the  floor  of  this  fossa. 

Lobes. — The  right  lobe  {lohus  hepatis  dexter)  is  much  larger  than  the  left;  the 
proportion  between  them  being  as  six  to  one.  It  occupies  the  right  hypochon- 
drium,  and  is  separated  from  the  left  lobe  on  its  upper  and  anterior  surfaces  by 
the  falciform  ligament;  on  its  under  and  posterior  surfaces  by  the  left  sagittal 
fossa;  and  in  front  by  the  umbilical  notch.  It  is  of  a  somewhat  quadrilateral  form, 
its  under  and  posterior  surfaces  being  marked  by  three  fossse:  the  porta  and  the 


THE  LIVER  1195 

fossae  for  the  gall-bladder  and  inferior  vena  cava,  wliich  separate  its  left  part 
into  two  smaller  lohes;  the  quadrate  and  caudate  lobes.  The  impressions  on  the 
ri»ht  lobe  liave  already  l)een  described. 

The  quadrate  lobe  {lobus  quadratus)  is  situated  on  the  under  surface  of  the  right 
lobe,  bounded  in  front  by  the  anterior  margin  of  the  liver;  behind  by  the  porta; 
on  the  right,  by  the  fossa  for  the  gall-bladder;  and  on  the  left,  by  the  fossa  for  the 
umbilical  vein.  It  is  oblong  in  shape,  its  antero-posterior  diameter  being  greater 
than  its  transverse. 

The  caudate  lobe  {lubus  candatus;  Spigelian  lobe)  is  situated  upon  the  posterior 
surface  of  the  right  lobe  of  the  liver,  opposite  the  tenth  and  eleventh  thoracic 
vertebra^.  It  is  bounded,  below,  by  the  porta;  on  the  right,  by  the  fossa  for  the 
inferior  vena  cava;  and,  on  the  left,  by  the  fossa  for  the  ductus  venosus.  It  looks 
backward,  being  nearh'  vertical  in  position;  it  is  longer  from  above  downward 
than  from  side  to  side,  and  is  somewhat  concave  in  the  transverse  direction.  The 
caudate  process  is  a  small  elevation  of  the  hepatic  substance  extending  obliciuely 
lateral  ward,  from  the  lower  extremity  of  the  caudate  lobe  to  the  under  surface  of 
the  right  lobe.  It  is  situated  behind  the  porta,  and  separates  the  fossa  for  the  gall- 
bladder from  the  commencement  of  the  fossa  for  the  inferior  vena  cava. 

The  left  lobe  (lobus  hepatis  sinister)  "is  smaller  and  more  flattened  than  the  right. 
It  is  situated  in  the  epigastric  and  left  hypochondriac  regions.  Its  upper  surface 
is  slightly  convex  and  is  moulded  on  to  the  Diaphragma;  its  under  surface  presents 
the  c«*4«ke  impression  and  omental  tuberosity,  already  referred  to  page  1192. 

Ligaments. — The  liver  is  connected  to  the  under  surface  of  the  Diaphragma 
and  to  the  anterior  wall  of  the  abdomen  by  five  ligaments;  four  of  these — the 
falciform,  the  coronary,  and  the  two  lateral — are  peritoneal  folds;  the  fifth,  the 
round  ligament,  is  a  fibrous  cord,  the  obliterated  umbilical  vein.  The  liver  is  also 
attached  to  the  lesser  curvature  of  the  stomach  by  the  hepatogastric  and  to  the 
duodenum  by  the  hepatoduodenal  ligament  (see  page  1156). 

The  falciform  ligament  {Ugamentnm  falciforme  Jiepatis)  is  a  broad  and  thin  antero- 
posterior peritoneal  fold,  falciform  in  shape,  its  base  being  directed  downward 
and  backward,  its  apex  upward  and  backward.  It  is  situated  in  an  antero-posterior 
plane,  but  lies  obliquely  so  that  one  surface  faces  forward  and  is  in  contact  with 
the  peritoneum  behind  the  right  Rectus  and  the  Diaphragma,  while  the  other  is 
directed  backward  and  is  in  contact  with  the  left  lobe  of  the  liver.  It  is  attached 
by  its  left  margin  to  the  under  surface  of  the  Diaphragma,  and  the  posterior  surface 
of  the  sheath  of  the  right  Rectus  as  low  down  as  the  umbilicus;  by  its  right  margin 
it  extends  from  the  notch  on  the  anterior  margin  of  the  liver,  as  far  back  as  the 
posterior  surface.  It  is  composed  of  two  layers  of  peritoneum  closely  united 
together.  Its  base  or  free  edge  contains  between  its  layers  the  round  ligament 
and  the  parumbilical  veins. 

The  coronary  ligament  (ligamentum  coronarium  hepatis)  consists  of  an  upper 
and  a  lower  layer.  The  upper  layer  is  formed  by  the  reflection  of  the  peritoneum 
from  the  upper  margin  of  the  bare  area  of  the  liver  to  the  under  surface  of  the  Dia- 
phragma, and  is  continuous  with  the  right  layer  of  the  falciform  ligament.  The 
lower  layer  is  reflected  from  the  lower  margin  of  the  bare  area  on  to  the  right  kidney 
and  suprarenal  gland,  and  is  termed  the  hepatorenal  ligament. 

The  triangular  ligaments  {lateral  ligaments)  are  two  in  number,  right  and  left. 
The  right  triangular  ligament  (ligamentum  triangidare  dextrum)  is  situated  at  the 
right  extremity  of  the  bare  area,  and  is  a  small  fold  w^hich  passes  to  the  Diaphragma, 
being  formed  by  the  apposition  of  the  upper  and  lower  layers  of  the  coronary 
ligament.  The  left  triangular  ligament  (ligamentum  triangulare  sinistrum)  is  a  fold 
of  some  considerable  size,  which  connects  the  posterior  part  of  the  upper  surface 
of  the  left  lobe  to  the  Diaphragma;  its  anterior  layer  is  continuous  with  the  left 
layer  of  the  falciform  ligament. 


1196 


SPLANCHNOLOGY 


The  round  ligament  (ligamentum  teres  hepatis)  is  a  fibrous  cord  resulting  from  the 
obhteration  of  the  umbilical  vein.  It  ascends  from  the  umbilicus,  in  the  free  margin 
of  the  falciform  ligament,  to  the  umbilical  notch  of  the  liver,  from  which  it  may  be 
traced  in  its  proper  fossa  on  the  inferior  surface  of  the  liver  to  the  porta,  where 
it  becomes  continuous  with  the  ligamentum  venosum. 


^^^«^^^^^/'^""'' 


Orifices  of  intialobular  veins 

Fig.  1003. — Longitudinal  section  of  a  hepatic  vein. 
(After  Kieman.) 


/  oin  ul  ich 

ve  n  hwi  been 

removed. 


Fig.   1004. — Longitudinal  section  of  a  small  portal  vein 
and  canal.     (After  Kiernan.) 


Vessels  and  Nerves. — The  vessels  connected  with  the  Uver  are:  the  hepatic  artery,  the  portal 
vein,  and  the  hepatic  veins. 

The  hepatic  artery  and  portal  vein,  accompanied  by  numerous  nerves,  ascend  to  the  porta, 
between  the  layers  of  the  lesser  omentmn.  The  hile  duct  and  the  lymphatic  vessels  descend 
from  the  porta  between  the  layers  of  the  same  omentum.  The  relative  positions  of  the  three 
structures  are  as  follows:    the  bile  duct  lies  to  the  right,  the  hepatic  artery  to  the  left,  and  the 


Intralobular  vein  — -, 


Intralobular  vein 


Fig.   1005. — Section  of  injected  liver  (dog). 

portal  vein  behind  and  between  the  other  two.  They  are  enveloped  in  a  loose  areolar  tissue,  the 
fibrous  capsule  of  Glisson,  which  accompanies  the  vessels  in  their  course  through  the  portal 
canals  ia  the  interior  of  the  organ  (Fig.  1004). 

The  hepatic  veins  (Fig.  1003)  convey  the  blood  from  the  liver,  and  are  described  on  page  764. 
They  have  very  little  cellular  investment,  and  what  there  is  binds  their  parietes  closely  to  the 


THE  LIVER 


1197 


walls  of  the  canals  tluougli  which  thej-  run;  so  that,  on  section  of  the  organ,  they  remain  widely 
open  and  arc  solitary,  and  may  be  easily  distinguished  from  the  branches  of  the  portal  vein, 
which  are  more  or  less  collapsed,  and  always  accompanied  by  an  artery  and  duct. 

The  Ijraiphatic  vessels  of  the  liver  are  described  on  page  792. 

The  nerves  of  tlu^  li\er,  derived  from  the  left  vagus  and  sympathetic,  enter  at  the  porta  and 
accompany  the  vessels  anil  ducts  to  the  interlobular  spaces.  Here,  according  to  Korollcow,  the 
meduUated  fibres  are  distributed  almost  exclusively  to  the  coats  of  the  bloodvessels;  while  the 
non-medullated  enter  the  lobules  and  ramify  between  the  cells. 

Structure  of  the  Liver. — The  substance  of  the  liver  is  composed  of  lobules,  held  together  by 
an  extremely  line  areolar  tissue,  in  which  ramify  the  portal  vein,  hepatic  ducts,  hepatic  artery, 
hepatic  veins,  lymphatics,  and  nerves;  the  whole  being  invested  by  a  serous  and  a  fibrous  coat. 

The  serous  coat  {tunica  serosa)  is  derived  from  the  peritoneum,  and  invests  the  greater  part 
of  the  surface  of  the  organ.    It  is  intimately  adherent  to  the  fibrous  coat. 

The  fibrous  coat  (capsula  fibrosa  [Glissoni];  areolar  coat)  lies  beneath  the  serous  investment, 
and  covers  the  entire  sm-face  of  the  organ.  It  is  difficult  of  demonstration,  excepting  where 
the  serous  coat  is  deficient.  At  the  porta  it  is  continuous  with  the  fibrous  capsule  of  Ghsson, 
and  on  the  sm-face  of  the  organ  with  the  areolar  tissue  separating  the  lobules. 

The  lobules  {lohuli  hepatis)  form  the  chief  mass  of  the  hepatic  substance;  they  may  be  seen 
either  on  the  sm-face  of  the  organ,  or  by  making  a  section  through  the  gland,  as  small  granular 
bodies,  about  the  size  of  a  miUet-seed,  measuring  from  1  to  2.5  mm.  in  diameter.  In  the  human 
subject  their  outlines  are  very  irregular;  but  in  some  of  the  lower  animals  (for  example,  the  pig) 
they  are  well-defined,  and,  when  divided  transversely,  have  polygonal  outhnes.  The  bases  of 
the  lobules  are  clustered  around  the  smallest  radicles  (suhlobular)  of  the  hepatic  veins,  to  which 
each  is  connected  (Fig.  1003)  by  means  of  a  small  branch  which  issues  from  the  centre  of  the 
lobule  {intralobular).  The  remaining  part  of  the  surface  of  each  lobule  is  imperfectly  isolated 
from  the  surrounding  lobules  by  a  thin  stratum  of  areolar  tissue,  in  which  is  contained  a  plexus 
of  vessels,  the  interlobular  plexus,  and  ducts.  In  some  animals,  as  the  pig;  the  lobules  are  com- 
pletely isolated  from  one  another  by  the  interlobular  areolar  tissue  (Fig.  1006). 

If  one  of  the  sublobular  veins  be  laid  open,  the  bases  of  the  lobules  may  be  seen  through  the 
thin  wall  of  the  vein  on  which  they  rest,  arranged  in  a  form  resembling  a  tesselated  pavement, 
the  centre  of  each  polygonal  space  presenting  a  minute  aperture,  the  mouth  of  an  intralobular 
vein  (Fig.  1003). 

Microscopic  Appearance  (Fig.  1006). — Each  lobule  consists  of  a  mass  of  cells,  hepatic  cells, 
arranged  in  irregular  radiating  columns  between  which  are  the  blood  channels  {sinusoids).  These 
convey  the  blood  from  the  circum- 
ference to  the  centre  of  the  lobule, 
and  end  in  the  intralobular  vein, 
which  runs  through  its  centre,  to 
open  at  its  base  into  one  of  the  sub- 
lobular veins.  Between  the  ceUs  are 
also  the  minute  bile  capillaries. 
Therefore,  in  the  lobule  there  are  all 
the  essentials  of  a  secreting  gland; 
that  is  to  say:  (1)  cells,  by  which 
the  secretion  is  formed;  (2)  blood- 
vessels, in  close  relation  with  the 
cells,  containing  the  blood  from 
which  the  secretion  is  derived;  (3) 
ducts,  by  which  the  secretion,  when 
formed,  is  carried  away. 

1.  The  hepatic  cells  are  polyhedral 
in  form.  They  vary  in  size  from  12 
to  25/^  in  diameter.  They  contain 
one  or  sometimes  two  distinct  nuclei. 
The  nucleus  exhibits  an  intranuclear 
net-work  and  one  or  two  refractile 
nucleoli.  The  cells  usually  contain 
granules;  some  of  which  are  proto- 
plasmic, while  others  consist  of  glycogen,  fat,  or  an  iron  compound.  In  the  lower  vertebrates, 
e.  g.,  frog,  the  cells  are  arranged  in  tubes  with  the  bile  duct  forming  the  lumen  and  bloodvessels 
externally.  According  to  Delepine,  evidences  of  this  arrangement  can  be  found  in  the  human 
liver. 

2.  The  Bloodvessels.- — The  blood  in  the  capillary  plexus  around  the  hver  cells  is  brought  to 
the  liver  principally  by  the  portal  vein,  but  also  to  a  certain  extent  by  the  hepatic  artery. 

The  hepatic  artery,  entering  the  hver  at  the  porta  with  the  portal  vein  and  hepatic  duct, 
ramifies  with  these  vessels  thi-ough  the  portal  canals.    It  gives  off  vaginal  branches,  which  ramify 


Sinusoii 


Column  of  liver- 
cells 
Interlobular  vein 


Intralobular  vein 


Sublobular  vein 


Fig.   1006. — A  single  lobule  of  the  liver  of  a  pi? 


X  60. 


1198 


SPLANCHNOLOGY 


in  the  fibrous  capsule  of  Glisson,  and  appear  to  be  destinod  chiefly  for  the  nutrition  of  the  coats 
of  the  vessels  and  ducts.  It  also  gives  off  capsular  branches,  which  reach  the  surface  of  the 
organ,  ending  in  its  fibrous  coat  in  stellate  plexuses.  Finally,  it  gives  off  interlobular  branches, 
which  form  a  plexus  outside  each  lobule,  to  supply  the  walls  of  the  interlobular  veins  and  the 
accompanying  bile  ducts.  From  this  plexus  lobular  branches  enter  the  lobule  and  end  in  the 
net-work  of  sinusoids  between  the  cells. 

The  portal  vein  also  enters  at  the  porta,  and  runs  through  the  portal  canals  (Fig.  1007), 
enclosed  in  Glisson 's  capsule,  dividing  in  its  course  into  branches,  which  finally  break  up  into  a 
plexus,  the  interlobular  plexus,  in  the  interlobular  spaces.     These  branches  receive  the  vaginal 

and  capsular  veins,  correspond- 
Bile-duct        hepatic  arter/j  jng  to  the  vaginal  and  capsular 

branches  of  the  hepatic  artery. 
Thus  it  will  be  seen  that  all  the 
blood  carried  to  the  hver  by  the 
portal  vein  and  hepatic  artery 
finds  its  way  into  the  interlob- 
ular plexus.  From  this  plexus 
the  blood  is  carried  into  the  lobule 
by  fine  branches  which  converge 
from    the  circumference   to  the 


Lymphatic 

vessel 


Fig.   1007. — Section  across  portal  canal  of  pig.     X  250. 


Fig.   1008. — Bile   capillaries  of  rabbit, 
shown  by  Golgi's  method.     X  460. 


centre  of  the  lobule,  and  are  connected  by  transverse  branches  (Fig.  1005).  The  walls  of  these 
small  vessels  are  incomplete  so  that  the  blood  is  brought  into  direct  relationship  with  the  liver 
cells.  The  lining  endotheUum  consists  of  irregularly  branched,  disconnected  cells  {stellate  cells  of 
Kupffer).  Moreover,  according  to  Herring  and  Simpson,  minute  channels  penetrate  the  fiver  cells 
themselves,  conveying  the  constituents  of  the  blood  into  their  substance.  It  will  be  seen  that  the 
blood  capillaries  of  the  hver  lobule  differ  structurally  from  capillaries  elsewhere.  Developmentally 
they  are  formed  by  the  growth  of  the  columns  of  liver  cells  into  large  blood  spaces  or  sinuses, 
and  hence  they  have  received  the  name  of  "sinusoids."  Arrived  at  the  centre  of  the  lobule, 
the  sinusoids  empty  themselves  into  one  vein,  of  considerable  size,  which  runs  down  the 
centre  of  the  lobule  from  apex  to  base,  and  is  called  the  intralobular  vein.  At  the  base  of 
the  lobule  this  vein  opens  directly  into  the  sublobular  vein,  with  which  the  lobule  is  con- 
nected. The  sublobular  veins  unite  to  form  larger  and  larger  trunks,  and  end  at  last  in  the 
hepatic  veins,  these  converge  to  form  three  large  trunks  which  open  into  the  inferior  vena  cava 
wlule  that  vessel  is  situated  in  its  fossa  on  the  posterior  surface  of  the  liver. 

3.  The  bile  ducts  commence  by  little  passages  in  the  hver  cells  which  communicate  with 
canahcuU  termed  intercellular  biliary  passages  {bile  capillaries).  These  passages  are  merely 
httle  channels  or  spaces  left  between  the  contiguous  surfaces  of  two  cells,  or  in  the  angle  where 
three  or  more  liver  cells  meet  (Fig.  1008),  and  they  are  always  separated  from  the  blood  capil- 
laries by  at  least  half  the  width  of  a  liver  cell.  The  channels  thus  formed  radiate  to  the  circum- 
ference of  the  lobule,  and  open  into  the  interlobular  bile  ducts  which  run  in  Glisson's  capsule, 
accompanying  the  portal  vein  and  hepatic  artery  (Fig.  1007).  These  join  with  other  ducts  to 
form  two  main  trunks,  which  leave  the  hver  at  the  transverse  fissure,  and  by  their  union  form 
the  hepatic  duct. 

Structure  of  the  Ducts. — The  walls  of  the  biliary  ducts  consist  of  a  connective-tissue  coat,  in 
which  are  muscle  cells,  arranged  both  circularly  and  longitudinally,  and  an  epithelial  layer, 
consisting  of  short  columnar  cells  resting  on  a  distinct  basement-membrane. 

Excretory  Apparatus  of  the  Liver. — The  excretory  apparatus  of  the  hver  con- 
sists of  (1)  the  hepatic  duct,  formed  by  the  junction  of  the  two  main  ducts,  which 


THE  LIVER 


1199 


pass  out  of  the  livor  at  the  porta;  (2)  the  gall-bladder,  which  serves  as  a  reservoir 
for  the  bik';  (3)  the  cystic  duct,  or  the  duct  of  the  gall-hhidder;  and  (4)  the  common 
bile  duct,  formed  by  tlie  junction  of  the  hepatic  and  cystic  (hicts. 

The  Hepatic  Duct  {ductus  hepaticus). — Two  main  trunks  of  nearly  equal  size 
issue  from  the  liver  at  the  porta,  one  from  the  right,  the  other  from  the  left  lobe; 
these  unite  to  form  the  hepatic  duct,  which  passes  downward  and  to  the  right  for 
about  4  cm.,  between  the  layers  of  the  lesser  omentum,  where  it  is  joined  at  an 
acute  angle  by  the  cystic  duct,  and  so  forms  the  common  bile  duct.  The  hepatic 
duct  is  accompanied  by  the  hepatic  artery  and  portal  vein. 

•The  Gall-bladder  (^vesica  felled)  (Fig.  1009). — The  gall-bladder  is  a  conical  or 
pear-shaped  nuisculomembranous  sac,  lodged  in  a  fossa  on  the  under  surface 
of  the  right  lobe  of  the  liver,  and  extending 
from  near  the  right  extremity  of  the  porta  to 
the  anterior  border  of  the  organ.  It  is  from 
7  to  10  cm.  in  length,  2.5  cm.  in  breadth  at  its 
widest  part,  and  holds  from  30  to  35  c.c.  It  is 
divided  into  a  fundus,  body,  and  neck.  The 
fundus,  or  broad  extremity,  is  directed  down- 
ward, forward,  and  to  the  right,  and  projects 
beyond  the  anterior  border  of  the  liver;  the 
body  and  neck  are  directed  upward  and  back- 
ward to  the  left.  The  upper  surface  of  the  gall- 
bladder is  attached  to  the  liver  by  connective 
tissue  and  vessels.  The  under  surface  is 
covered  by  peritoneum,  which  is  reflected  on  to 
it  from  the  surface  of  the  liver.  Occasionally 
the  whole  of  the  organ  is  invested  by  the 
serous  membrane,  and  is  then  connected  to 
the  liver  h\  a  kind  of  mesenterv. 


Gall- 
bladder 


Hepatic 
duct 


Common  bile- 
dtict 


Fig.   1009.— The  gall-bladder  and  bile  ducts 
laid  open.     (Spalteholz.) 


Relations. — The  body  is  in  relation,  by  its  upper 
surface,  with  the  liver;  by  its  under  surface,  with  the 
commencement  of  the  transverse  colon;  and  farther 
back  usually  with  the  upper  end  of  the  descending 
portion  of  the  duodenum,  but  sometimes  with  the 
superior  portion  of  the  duodenum  or  pyloric  end  of 
the  stomach.  The  fundus  is  completely  invested  by 
peritoneum;  it  is  in  relation,  m  front,  with  the  abdom- 
inal parietes,  immediately  below  the  ninth  costal  car- 
tilage; behind  with  the  transverse  colon.  The  neck  is 
narrow,  and  curves  upon  itself  hke  the  letter  S;  at  its 
point  of  connection  with  the  cystic  duct  it  presents  a 
weU-marked  constriction. 

Structure  (Fig.  1010). — The  gall-bladder  consists  of 
three  coats:   serous,  fibromuscular,  and  mucous. 

The  external  or  serous  coat  {tunica  serosa  vesicae  felleae)  is  derived  from  the  peritoneum;  it 
completely  invests  the  fundus,  but  covers  the  body  and  neck  only  on  their  imder  surfaces. 

The  fibromuscular  coat  {tunica  muscularis  vesicae  felleae),  a  thin  but  strong  layer  forming  the 
frame-work  of  the  sac,  consists  of  dense  fibrous  tissue,  which  interlaces  in  all  directions,  and  is 
mixed  with  plain  muscular  fibres,  disposed  chiefly  in  a  longitudinal  direction,  a  few  running 
trans"\'erselJ^ 

The  internal  or  mucous  coat  {tunica  mucosa  vesicae  felleae)  is  loosely  connected  with  the  fibrous 
layer.  It  is  generally  of  a  yellowish-brown  color,  and  is  elevated  into  minute  rugae.  Opposite 
the  neck  of  the  gall-bladder  the  mucous  membrane  projects  inward  in  the  form  of  obhque  ridges 
or  folds,  forming  a  sort  of  spiral  valve. 

The  mucous  membrane  is  continuous  through  the  hepatic  duct  with  the  mucous  membrane 
lining  the  ducts  of  the  hver,  and  through  the  common  bile  duct  with  the  mucous  membrane  of 
the  duodeniuu.^  It  is  covered  with  columnar  epithehum,  and  secretes  mucin;  in  some  animals 
it  secretes  a  nucleoprotein  instead  of  mucin. 


1200 


SPLANCHNOLOGY 


The  Cystic  Duct  (ductus  cijsticus). — The  cystic  duct  aVjout  4  cm.  long,  runs  back- 
ward, dc)\vin\  ard,  and  to  the  left  from  the  neck  of  the  gall-bladder,  and  joins  the 
hepatic  duct  to  form  the  common  bile  duct.  The  mucous  membrane  lining  its 
interior  is  thrown  into  a  series  of  crescentic  folds,  from  five  to  twelve  in  number, 
similar  to  those  found  in  the  neck  of  the  gall-bladder.  They  project  into  the  duct 
in  regular  succession,  and  are  directed  obliquely  around  the  tube,  presenting 
much  the  appearance  of  a  continuous  spiral  valve.  When  the  duct  is  distended, 
the  spaces  between  the  folds  are  dilated,  so  as  to  give  to  its  exterior  a  twisted 
appearance. 


Columnar  epitJielium 


Fibro-muscular 

coat 


71  '^M^ 

'^        ^-  Liver-cells 


ffiffiC^'^ 


Oh* 


Fig.   1010. — Transverse  section  of  gall-bladder. 

The  Common  Bile  Duct  {ductus  choledochus) . — The  common  bile  duct  is  formed 
by  the  junction  of  the  cystic  and  hepatic  ducts;  it  is  about  7.5  cm.  long,  and  of  the 
diameter  of  a  goose-quill. 

It  descends  along  the  right  border  of  the  lesser  omentum  behind  the  superior 
portion  of  the  duodenum,  in  front  of  the  portal  vein,  and  to  the  right  of  the  hepatic 
artery;  it  then  runs  in  a  groove  near  the  right  border  of  the  posterior  surface  of  the 
head  of  the  pancreas;  here  it  is  situated  in  front  of  the  inferior  vena  cava,  and  is 
occasionally  completely  imbedded  in  the  pancreatic  substance.  At  its  termination 
it  lies  for  a  short  distance  along  the  right  side  of  the  terminal  part  of  the  pancreatic 
duct  and  passes  with  it  obliquely  between  the  mucous  and  muscular  coats.  The 
two  ducts  unite  and  open  by  a  common  orifice  upon  the  summit  of  the  duodenal 
papilla,  situated  at  the  medial  side  of  the  descending  portion  of  the  duodenum,  a 
little  below  its  middle  and  about  7  to  10  cm.  from  the  pylorus  (Fig.  1015).  The 
short  tube  formed  by  the  union  of  the  two  ducts  is  dilated  into  an  ampulla,  the 
ampulla  of  Vater. 

Structure. — The  coats  of  the  large  biUary  ducts  are  an  external  or  fibrous,  and  an  internal  or 
mucous.  The  fibrous  coat  is  composed  of  strong  fibroareolar  tissue,  with  a  certain  amount  of 
muscular  tissue,  arranged,  for  the  most  part,  in  a  circular  manner  around  the  duct.  The  mucous 
coat  is  continuous  with  the  Uning  membrane  of  the  hepatic  ducts  and  gall-bladder,  and  also  with 
that  of  the  duodeniun;  and,  like  the  mucous  membrane  of  these  structures,  its  epithelium  is  of 
the  columnar  variety.  It  is  provided  with  numerous  mucous  glands,  which  are  lobulated  and 
open  by  minute  orifices  scattered  irregularly  in  the  larger  ducts. 

Applied  Anatomy. — On  account  of  its  large  size,  its  fixed  position,  and  its  friability,  the  liver 
is  more  frequently  ruptured  than  any  of  the  other  abdominal  viscera.  The  rupture  may  vary 
from  a  slight  scratch  to  an  extensive  and  complete  laceration  of  its  substance,  dividing  it  into 
two  parts.  Sometimes  an  internal  rupture,  without  laceration  of  the  peritoneal  covering,  takes 
place,  and  such  injuries  are  most  susceptible  of  repair;  but  small  tears  of  the  surface  may  also 
heal;  when,  however,  the  laceration  is  extensive,  death  usually  takes  place  from  hemorrhage, 
on  account  of  the  fact  that  the  hepatic  veins  are  contained  in  rigid  canals  in  the  liver  substance 
and  are  unable  to  contract,  and  are  moreover  unprovided  with  valves.  The  hver  may  also  be 
torn  by  the  end  of  a  broken  rib  perforating  the  Diaphragma.     It  may  be  injured  by  stabs  or 


THE  PANCREAS  1201 

other  punctured  wounds,  luid  when  tliese  arc  inflicted  throufi;li  Uie  chest  wall  the  pleural  and 
peritoneal  cavities  may  both  be  opened  up,  and  both  lung  and  liver  wounded.  In  cases  of  wound 
of  the  liver  from  the  front,  hernia  of  a  part  of  this  viscus  may  take  place,  but  generally  can  be 
easily  replaced.  In  cases  of  laceration  of  the  liver,  when  tliere  is  evidence  that  bleeding  is  going 
on,  the  abdomen  must  be  opened,  the  laceration  sought  for,  and  the  bleeding  arrested.  This 
may  be  done  temporarily  by  introducing  the  forefinger  into  the  epiploic  foramen  and  placing  the 
thumb  on  the  lesser  omentum,  and  compressing  the  hepatic  artery  and  portal  vein  between  the 
two.  The  margins  of  the  laceration,  if  small,  can  be  brought  together  and  sutured  by  means 
of  a  blunt  curved  needle  passed  from  one  side  of  the  wound  to  the  other.  All  sutures  must  be 
passed  before  any  are  tied,  and  this  must  be  done  with  the  greatest  gentleness,  as  the  liver  sub- 
stance is  very  friable.  When  the  laceration  is  extensive  it  must  be  packed  with  gauze,  the  end 
of  which  is  allowed  to  hang  out  of  the  external  wound. 

Abscess  of  the  liver  is  of  not  infrequent  occurrence.  The  so-called  tropical  abscess  is  due  to 
absorption  from  the  intestine  of  the  amoeba  of  dysentery,  which  reaches  the  liver  through  the 
portal  system  and  causes  the  formation  of  a  large  chronic  abscess;  this  may  open  in  many  different 
w-ays  on  account  of  the  relations  of  the  liver  to  other  organs.  Thus  it  has  been  known  to  burst 
into  the  lungs  when  the  pus  is  coughed  up,  or  into  the  stomach  when  the  pus  is  vomited;  it  may 
burst  into  the  colon,  or  duodenum;  or,  by  perforating  the  Diaphragma,  it  may  empty  itself  into 
the  pleural  cavity.  It  often  makes  its  way  forward,  and  points  on  the  anterior  abdominal  wall, 
and  finally  it  may  burst  into  the  peritoneal  or  pericardial  cavities.  Abscesses  of  the  liver  fre- 
quently require  opening,  and  this  must  be  done  by  an  incision  in  the  abdominal  wall,  in  the 
thoracic  wall,  or  in  the  lumbar  region,  according  to  the  direction  in  which  the  abscess  is  tracking. 
The  incision  through  the  abdominal  wall  is  to  be  preferred  when  possible.  The  abdominal  wall 
is  incised  over  the  swelling,  and,  unless  the  peritoneum  is  adherent,  gauze  is  packed  all  around 
the  exposed  liver  surface,  the  abscess  opened,  and  a  large  drainage-tube  inserted. 

Hydatid  cysts  are  more  often  found  in  the  liver  than  in  any  of  the  other  viscera.  The  reason 
of  this  is  not  far  to  seek.  The  embryo  of  the  egg  of  the  taenia  echinococcus,  being  liberated  in 
the  stomach  by  the  disintegration  of  its  shell,  bores  its  way  through  the  gastric  walls  and  usually 
enters  a  bloodvessel,  and  is  carried  by  the  blood  stream  to  the  hepatic  capillaries,  where  its  onward 
coui'se  is  arrested,  and  where  it  undergoes  development  mto  the  fully  formed  hydatid. 

Ptosis  of  the  liver,  or  hepatoptosis,  from  abnormal  laxity  of  its  ligaments  and  failure  of  the 
support  it  usually  receives  from  the  subjacent  viscera,  is  an  occasional  cause  of  various  nervous 
and  gastro-intestinal  disturbances.  It  has  been  very  fully  described  by  Glenard  and  his  pupils. 
In  women  who  have  used  very  tight  corsets  and  in  men  who  have  worn  tightly  buckled  belts, 
the  lower  margin  of  the  right  lobe  may  become  elongated  by  the  pressure,  producing  an  abnormal 
lobe  known  as  the  linguiform  or  Riedel's  lobe.  This  may  cause  indefinite  abdominal  symptoms 
suggesting  dyspepsia  or  disease  of  the  gall-bladder;  and  if  discovered  accidentally,  a  Riedel's 
lobe  may  be  mistaken  for  a  tumor  of  the  right  kidney,  of  the  right  suprarenal  gland,  of  the 
transverse  colon  or  pancreas,  or  even  of  the  vermiform  process. 

The  gall-bladder  may  become  distended  in  cases  of  obstruction  of  its  duct  or  the  common 
bile  duct,  or  from  a  collection  of  gall-stones  in  its  interior,  thus  forming  a  large  tumor.  The 
swelHng  is  pear-shaped,  and  projects  downward  and  forward  to  the  imibiUcus.  It  moves  with 
respiration,  since  it  is  attached  to  the  liver.  To  reheve  this  condition,  the  gall-bladder  must  be 
opened  {cJiolecystotovnj)  and  the  gall-stones  removed.  The  operation  is  performed  by  an  incision, 
5  to  7  cm.  long,  thcrough  the  lateral  part  of  the  right  Rectus,  commencing  at  the  costal  margin. 
The  peritoneal  cavity  is  opened,  and,  the  tumor  having  been  found,  gauze  is  packed  around  it 
to  protect  the  peritoneal  cavity,  and  it  is  aspirated.  When  the  contained  fluid  has  been  evacu- 
ated the  flaccid  bladder  is  drawn  out  of  the  abdominal  wound  and  its  wall  incised;  any  gall- 
stones m  the  bladder  are  now  removed.  If  the  case  is  one  of  obstruction  of  the  duct,  an  attempt 
must  be  made  to  dislodge  the  stone  by  manipulation  through  the  wall  of  the  duct;  or  it  may  be 
crushed  from  without  by  the  fingers  or  carefully  padded  forceps.  If  this  does  not  succeed,  the 
safest  plan  is  to  incise  the  duct,  extract  the  stone,  and  close  the  incision  by  fine  sutures  in  two 
layers.  After  all  obstruction  has  been  removed,  the  edges  of  the  incision  in  the  gall-bladder  may 
be  sutured  to  the  posterior  sheath  of  the  Rectus  and  a  fistulous  communication  established 
between  the  gall-bladder  and  the  exterior,  a  drainage-tube  being  inserted  mto  the  cavity;  this 
fistulous  opening  usually  closes  in  the  course  of  a  few  weeks.  The  gall-bladder  may  be  com- 
pletely removed  if  it  be  quite  certain  that  no  cause  for  bihary  obstruction  remain ;  this  is  also 
done  for  primary  malignant  growth  of  the  viscus. 

The  Pancreas  (Figs.  1011,  1012). 

Dissection. — The  pancreas  may  be  exposed  for  dissection  in  three  different  ways:     (1)  By 

raising  the  Uver,  drawing  down  the  stomach,  and  tearing  thi-ough  the  gastrohepatic  omentum, 

and  the  ascending  layer  of  the  transverse  mesocolon.     (2)  By  raising  the  stomach;  the  arch  of 

the  colon,  and  greater  omentum,  and  then  dividing  the  inferior  layer  of  the  transverse  mesocolon 

76 


1202 


SPLANCHNOLOGY 


and  raising  its  ascending  layer.  (3)  By  dividing  the  two  layers  of  peritoneum,  which  descend 
from  the  greater  curvature  of  the  stomach  to  form  the  greater  omentum ;  turning  the  stomach 
upward,  and  then  cutting  through  the  ascending  layer  of  the  transverse  mesocolon  (see  Fig.  961). 


Rectus  abdominis 


Eighth  costal  cartilage 

Seventh  costal  cartilage 


Seventli  rib 


Eighth 


Abdominal  aorta 


Twelfth  rib 


Eleventh  rib 


Fig.  1011. — Transverse  section  through  the  middle  of  the  first  lumbar  vertebra,  showing  the  relations  of  the  pancreas. 

(Braune. 


Fig.   1012. — The  duodenum  and  pancreas. 


The  pancreas  is  a  compound  racemose  gland,  analogous  in  its  structures  to  the 
salivary  glands,  though  softer  and  less  compactly  arranged  than  the  se  organs. 


THK  PA \C RE AS 


]2{):] 


It  is  lono-  and  iriTj;ularly  i)risiiiaTic  in  shape;  its  ri[;lit  extremity,  Wein^  hroad,  is 
called  the  head,  and  is  connected  to  the  main  portion  of  the  organ,  or  body,  by  a 
slight  constriction,  tiie  neck;  while  its  left  extremity  gradually  tapers  to  form  the 
tail.  It  is  situated  trans\(Tsely  across  the  posterior  wall  of  the  abdomen,  at  the 
back  of  the  epigastric  and  left  hypochondriac  regions.  Its  length  varies  from  12.5 
to  1.")  cm.,  and  its  weight  from  (JU  to  100  gm. 

Relations. — The  Head  {caput  pancreatis)  is  flattened  from  before  backward,  and 
is  lodged  within  the  curve  of  the  duodenum.  Its  upper  border  is  overlapped  by  the 
superior  part  of  the  duodenum  and  its  lower  overlai)s  the  horizontal  part;  its  right 
and  left  borders  overlap  in  front,  and  insinuate  themselves  behind,  the  descending 
and  ascending  parts  of  the  duodenum  respectively.  The  angle  of  junction  of  the 
lower  and  left  lateral  borders  forms  a  prolongation,  termed  the  uncinate  process.  In 
the  groove  between  the  duodenum  and  the  right  lateral  and  lower  borders  in  front 
are  the  anastomosing  superior  and  inferior  pancreaticoduodenal  arteries;  the  com- 
mon bile  duct  descends  behind,  close  to  the  right  border,  to  its  termination  in  the 
descending  part  of  the  duodenum. 


SUP-    MESENTERIC  ARTERY 


CCELIAC    ftXIS 


AREA  FOR  Diaphragm 


Fig.   1013. — The  pancreas  and  duodenum  from  behind.     (From  model  by  His.) 

Anterior  Surface. — The  greater  part  of  the  right  half  of  this  surface  is  in  contact 
with  the  transverse  colon,  only  areolar  tissue  inter\'ening.  From  its  upper  part 
the  neck  springs,  its  right  limit  being  marked  by  a  groove  for  the  gastroduodenal 
artery.  The  lower  part  of  the  right  half,  below^  the  transverse  colon,  is  covered 
by  peritoneum  continuous  with  the  inferior  layer  of  the  transverse  mesocolon, 
and  is  in  contact  with  the  coils  of  the  small  intestine.  The  superior  mesenteric 
artery  passes  down  in  front  of  the  left  half  across  the  uncinate  process;  the  superior 
mesenteric  vein  runs  upward  on  the  right  side  of  the  artery  and,  behind  the  neck, 
joins  with  the  lienal  vein  to  form  the  portal  vein. 

Posterior  Surface. — The  posterior  surface  is  in  relation  with  the  inferior  vena 
cava,  the  common  bile  duct,  the  renal  veins,  the  right  cms  of  the  Diaphragma, 
and  the  aorta. 

The  Neck  springs  from  the  right  upper  portion  of  the  front  of  the  head.  It  is 
about  2. .5  cm.  long,  and  is  directed  at  first  upward  and  forward,  and  then  upward 


1204  SPLANCHNOLOGY 

and  to  the  left  to  join  the  body;  it  is  somewhat  flattened  from  above  downward 
and  backward.  Its  antero-superior  surface  supports  the  pylorus;  its  postero- 
inferior  surface  is  in  relation  with  the  commencement  of  the  portal  vein;  on  the 
right  it  is  grooved  by  the  gastroduodenal  artery. 

The  Body  (corpus  pancreatis)  is  somewhat  prismatic  in  shape,  and  has  three 
surfaces:  anterior,  posterior,  and  inferior. 

The  anterior  surface  (fades  anterior)  is  somewhat  concave;  and  is  directed  for- 
ward and  upward:  it  is-  covered  by  the  postero-inferior  surface  of  the  stomach 
which  rests  upon  it,  the  two  organs  being  separated  by  the  omental  bursa.  Where 
it  joins  the  neck  there  is  a  well-marked  prominence,  the  tuber  omentale,  which 
abuts  against  the  posterior  surface  of  the  lesser  omentum. 

The  posterior  surface  (jades  posterior)  is  devoid  of  peritoneum,  and  is  in  contact 
with  the  aorta,  the  lienal  vein,  the  left  kidney  and  its  vessels,  the  left  suprarenal 
gland,  the  origin  of  the  superior  mesenteric  artery,  and  the  crura  of  the  Diaphragma. 

The  inferior  surface  (jades  inferior)  is  narrow  on  the  right  but  broader  on  the  left, 
and  is  covered  by  peritoneum;  it  lies  upon  the  duodenojejunal  flexure  and  on  some 
coils  of  the  jejunum;  its  left  extremity  rests  on  the  left  colic  flexure. 

The  superior  border  {margo  superior)  is  blunt  and  flat  to  the  right;  narrow  and 
sharp  to  the  left,  near^the  tail.  It  commences  on  the  right  in  the  omental  tuber- 
osity, and  is  in  relation  with  the  coeliac  artery,  from  which  the  hepatic  artery 
courses  to  the  right  just  above  the  gland,  while  the  lienal  arterj'  runs  toward  the 
left  in  a  groove  along  this  border. 

The  anterior  border  (margo  anterior)  separates  the  anterior  from  the  inferior 
surface,  and  along  this  border  the  two  layers  of  the  transverse  mesocolon  diverge 
from  one  another;  one  passing  upward  over  the  anterior  surface,  the  other 
backward  over  the  inferior  surface. 

The  inferior  border  {margo  inferior)  separates  the  posterior  from  the  inferior 
surface;  the  superior  mesenteric  vessels  emerge  under  its  right  extremity. 

The  Tan  {cauda  pancreatis)  is  narrow;  it  extends  to  the  left  as  far  as  the  lower 
part  of  the  gastric  surface  of  the  spleen,  lying  in  the  phrenicolienal  ligament, 
and  it  is  in  contact  with  the  left  colic  flexure. 

Birmingham  described  the  body  of  the  pancreas  as  projecting  forward  as  a  promi- 
nent ridge  into  the  abdominal  cavit}'  and  forming  part  of  a  shelf  on  which  the 
stomach  lies.  "The  portion  of  the  pancreas  to  the  left  of  the  middle  line  has  a 
very  considerable  antero-posterior  thickness;  as  a  result  the  anterior  surface  is  of 
considerable  extent;  it  looks  strongly  upward,  and  forms  a  large  and  important 
part  of  the  shelf.  As  the  pancreas  extends  to  the  left  toward  the  spleen  it  crosses 
the  upper  part  of  the  kidney,  and  is  so  moulded  on  to  it  that  the  top  of  the  kidney 
forms  an  extension  inward  and  backw^ard  of  the  upper  surface  of  the  pancreas 
and  extends  the  bed  in  this  direction.  On  the  other  hand,  the  extremity  of  the 
pancreas  comes  in  contact  with  the  spleen  in  such  a  way  that  the  plane  of  its 
upper  surface  runs  with  little  interruption  upward  and  backward  into  the  concave 
gastric  surface  of  the  spleen,  which  completes  the  bed  behind  and  to  the  left,  and, 
running  upward,  forms  a  partial  cap  for  the  wide  end  of  the  stomach.^ 

The  Pancreatic  Duct  {ductus  pancreaticus  [Wirsimgi];  duct  of  Wirsung)  extends 
transversely  from  left  to  right  through  the  substance  of  the  pancreas  (Fig.  1014).  It 
commences  by  the  junction  of  the  small  ducts  of  the  lobules  situated  in  the  tail  of  the 
pancreas,  and,  running  from  left  to  right  through  the  body,  it  receives  the  ducts  of  the 
various  lobules  composing  the  gland.  Considerably  augmented  in  size,  it  reaches  the 
neck,  and  turning  downward,  backward,  and  to  the  right,  it  comes  into  relation  with 
the  common  bile  duct,  which  lies  to  its  right  side;  leaving  the  head  of  the  gland, 
it  passes  very  obliquely  through  the  mucous  and  muscular  coats  of  tk'?  duodenum, 

1  Journal  of  Anatomy  and  Physiology,  pt.  1,  xxxi,  102. 


THE  PANCREAS 


1205 


and  ends  by  an  oriticc  common  to  it  and  the  connuon  bile  duct  upon  the  summit 
of  the  duodenal  i)apilla,  situated  at  the  medial  side  of  the  descending  portion 
of  the  (huxlenum,  7.5  to  10  cm.  below  the  pylorus.  The  pancreatic  duct,  near  the 
duodenum,  is  about  the  size  of  an  ordinary  quill.  Sometimes  the  pancreatic  duct 
and  the  common  bile  duct  open  separately  into  the  duodenum.  Frequently  there 
is  an  additional  duct,  which  is  given  off  from  the  pancreatic  duct  in  the  neck  of 
the  pancreas  and  opens  into  the  duodenum  about  2.5  cm.  above  the  duodenal 
papilla.  It  recei^■cs  the  ducts  from  the  lower  part  of  the  head,  and  is  known  as 
the  accessory  pancreatic  duct  (duct  of  Saniorini). 

Hepatic  artery 
Portal  vein     \ 
Common  bile-duct      \     \ 
Orifice    of    comtnoii  \^  VW\l 

bile-duct  and  pan-  '^  J V     'I   -     Accessory  pancreatic  duct 

creatic  duct  ■ltSl^ll>:T~'"rA  '  /   Pancreatic  duct 


*l*lilili^' 


Fig.   1014. — The  pancreatic  duct. 


Structure  (Fig.  1015).- — In  structure,  the  pancreas  resembles  the  saUvary  glands.  It  differs 
from  them,  however,  in  certain  particulars,  and  is  looser  and  softer  in  its  texture.  It  is  not 
enclosed  in  a  distinct  capsule,  but  is  surrounded  by  areolar  tissue,  which  dips  into  its  interior, 
and  connects  together  the  various  lobules  of  which  it  is  composed.  Each  lobule,  like  the  lobules 
of  the  sahvary  glands,  consists  of  one  of  the  ultimate  ramifications  of  the  main  duct,  ending  in  a 
number  of  cecal  pouches  or  alveoli,  which  are  tubular  and  somewhat  convoluted.  The  minute 
ducts  connected  with  the  alveoli  are  narrow  and  lined  with  flattened  cells.  The  alveoU  are 
almost  completely  filled  \\ath  secreting  cells,  so  that  scarcely  any  Imnen  is  visible.  In  some 
animals  spindle-shaped  cells  occupy  the  centre  of  the  alveolus  and  are  known  as  the  centro- 
acinar  cells  of  Langerhans.  These  are  prolongations  of  the  terminal  ducts.  The  true  secreting 
ceUs  which  line  the  wall  of  the  alveolus  are  very  characteristic.  They  are  columnar  in  shape 
and  present  two  zones :  an  outer  one,  clear  and  finely  striated  next  the  basement-membrane,  and 
an  inner  granular  one  next  the  lumen.  In  hardened  specimens  the  outer  zone  stains  deeply  with 
various  dyes,  whereas  the  inner  zone  stains  slightly.  Druing  activity  the  granular  zone  gradually 
diminishes  in  size,  and  when  exhausted  is  only  seen  as  a  small  area  next  to  the  Imnen.  During 
the  resting  stages  it  gradually  increases  until  it  forms  nearly  three-fourths  of  the  cell.  In  some 
of  the  secreting  cells  of  the  pancreas  is  a  spherical  mass,  staining  more  easily  than  the  rest  of 
the  cell;  this  is  termed  the  paranucleus,  and  is  beheved  to  be  an  extension  from  the  nucleus. 
The  connective  tissue  between  the  alveoli  presents  in  certain  parts  collections  of  ceUs,  which  are 
termed  interalveolar  cell  islets  {islands  of  Langerhans).  The  cells  of  these  stain  lightly  with 
hematoxylin  or  carmine,  and  are  more  or  less  polyhedral  in  shape,  forming  a  net-work  in  which 
ramify  many  capillaries.  There  are  two  main  types  of  cell  in  the  islets,  distinguished  as  A-cells 
and  B-cells  according  to  the  special  staining  reactions  of  the  granules  they  contain.     The  cell 


1206 


SPLANCHNOLOGY 


islets  have  been  supposed  to  produce  the  internal  secretion  of  the  pancreas  which  is  necessary 
for  carbohydrate  metabolism,  but  numerous  researches  have  so  far  failed  to  elucidate  their 
real  function. 

The  walls  of  the  pancreatic  duct  are  thin,  consisting  of  two  coats,  an  external  fibrous  and  an 
internal  mucous;  the  latter  is  smooth,  and  fm-nished  near  its  termination  with  a  few  scattered 
follicles. 

Vessels  and  Nerves.  —  The  arteries  of  the  pancreas  are  derived  from  the  lienal,  and  the 
pancreaticoduodenal  branches  of  the  hepatic  and  superior  mesenteric.    Its  veins  open  into  the 

lienal   and   superior   mesenteric    veins.     Its 
Alveolus  lymphatics    are  described  on  page  793.    Its 

nerves  are  filaments  from  the  lienal  plexus. 
Applied  Anatomy. — Inflammation  of  the 
pancreas  has  of  late  years  received  con- 
siderable attention.  It  appears  to  be  due 
to  infection  of  the  pancreatic  ducts  by 
microorganisms  from  the  duodenum  in 
cases  of  gastroduodenal  catarrh,  or  from 
the  biUary  passages  in  which  a  gall-stone 
is  lodged.  Acute  cases  usually  terminate 
fatally  and  are  frequently  of  the  hemor- 
rhagic type;  chronic  inflammation  of  the 
pancreas  produces  few  symptoms  of  disease 
unless  it  is  extensive,  when  attacks  of 
abdominal  pain,  loss  of  appetite,  progressive 
weakness  and  wasting,  and  the  passage  of 
whitish  fatty  motions,  are  hkely  to  follow. 
Extensive  fibrosis  of  the  pancreas  also  one 
of  the  commonest  lesions  found  post  mortem 
in  cases  of  diabetes  melhtus.  Cysts  of  the 
pancreas  are  sometimes  met  with.  They 
may  be  the  result  of  traumatism,  when  they 
generally  contain  blood,  or  they  may  be  due  to  retention  from  obstruction  of  a  duct,  or  from 
pressure  on  the  main  duct  by  a  gall-stone.  They  may  attain  a  large  size,  and  cause  symptoms 
by  pressing  on  the  stomach,  Diaphragma,  or  common  bile  duct.  They  generally  push  their 
way  forward  between  the  stomach  and  transverse  colon,  and  may  then  be  felt  as  a  definite  tumor 
in  the  middle  line  of  the  upper  part  of  the  abdomen.  The  tumor  is  fixed  and  does  not  move 
with  respiration.  The  treatment  consists  in  opening  the  abdomen  in  the  middle  line,  incising 
the  cyst,  evacuating  its  contents,  and  fixing  its  walls  to  the  deeper  layers  of  the  abdominal  wall. 
Drainage  in  the  left  loin,  just  below  the  last  rib,  can  sometimes  be  estabhshed.  When  they 
are  situated  in  the  tail  of  the  pancreas  they  have  been  removed.  The  pancreas  is  often  the  seat 
of  cancer;  this  usually  affects  the  head,  and  therefore  speedily  involves  the  common  bile  duct, 
leading  to  persistent  jaundice;  or  it  may  press  upon  the  portal  vein,  causing  ascites,  or  involve 
the  stomach,  causing  pyloric  obstruction.  It  has  been  said  that  the  pancreas  is  the  only  abdominal 
viscus  which  has  never  been  found  in  a  hernial  protrusion;  but  even  this  organ  has  been  found 
in  company  with  other  viscera,  in  rare  cases  of  diaphragmatic  hernia. 


Fig.   1015. — Section  of  pancreas  of  dog.      X  250. 


THE  UROGENITAL  APPARATUS    (APPARATUS  UROGENITALIS ; 
UROGENITAL   ORGANS). 

The  urogenital  apparatus  consists  of  (a)  the  urinary  organs  for  the  secretion 
and  discharge  of  the  urine,  and  (6)  the  genital  organs,  which  are  concerned  with 
the  process  of  reproduction. 

THE   URINARY    ORGANS. 

The  urinary  organs  comprise  the  kidneys,  which  secrete  the  urine,  the  ureters, 
or  ducts,  which  convey  urine  to  the  urinary  bladder,  where  it  is  for  a  time  retained; 
and  the  urethra,  through  which  it  is  discharged  from  the  body. 


The  Kidneys  (Renes). 

The  kidneys  are  situated  in  the  posterior  part  of  the  abdomen,  one  on  either  side 
of  the  vertebral  column,  behind  the  peritoneum,  and  surrounded  by  a  mass  of  fat 


THE  KIDXEYS 


1207 


and  loose  areolar  tissue.  Their  upi)iT  extremities  are  on  a  le\el  with  the  upper 
border  of  the  twelfth  thoracie  vertebra,  tluMr  lower  extremities  on  a  level  with  the 
third  lumbar.  The  riyht  kidne,\-  is  usually  sli<):htly  lower  than  the  left,  probably 
on  aeeount  of  the  \iciuity  of  the  lixcr.  The  \()u^  axis  of  each  kidney  is  directed 
downward  and  lateralward;  the  transverse  axis  backward  and  lateralward. 

Each  kidney  is  about  1  1.20  cm.  in  length,  5  to  7.5  cm.  in  breadth,  and  rather 
more  than  2.5  cm.  in  thickness.  The  left  is  somewhat  longer,  and  narrower,  than 
the  right.  The  weight  of  the  kidney  in  the  adult  male  varies  from  125  to  170  gm., 
in  the  adult  female  from  115  to  155  gm.  The  combined  weight  of  the  two 
kidneys  in  proportion  to  that  of  the  body  is  about  1  to  240. 

The  kidney  has  a  characteristic  form,  and  presents  for  examination  two  surfaces, 
two  borders,  and  an  upper  and  lower  extremity. 


U  PRAREN AL   AF 


SUPRARENAL    AREA 


Fig.   1016. — The  anterior  surfaces  of  the  kidneys,  showing  the  areas  of  contact  of  neighboring  viscera. 

Relations. — The  anterior  surface  (fades  anterior)  (Figs.  1012  and  1016)  of 
each  kidney  is  convex,  and  looks  forward  and  lateralward.  Its  relations  to 
adjacent  viscera  differ  so  completely  on  the  two  sides  that  separate  descriptions 
are  necessary. 

Anterior  Surface  of  Right  Kidney. — A  narrow^  portion  at  the  upper  extremity  is  in 
relation  with  the  right  suprarenal  gland.  A  large  area  just  below  this  and  involv- 
ing about  three-fourths  of  the  surface,  lies  in  the  renal  impression  on  the  inferior 
surface  of  the  liver,  and  a  narrow  but  somewhat  variable  area  near  the  medial 
border  is  in  contact  with  the  descending  part  of  the  duodentmi.  The  lower  part  of 
the  anterior  surface  is  in  contact  laterally  with  the  right  colic  flexure,  and  medially, 
as  a  rule,  with  the  small  intestine.  The  areas  in  relation  with  the  liver  and  small 
intestine  are  covered  by  peritoneum;  the  suprarenal,  duodenal,  and  colic  areas 
are  devoid  of  peritoneum. 

Anterior  Surface  of  Left  Kidney. — A  small  area  along  the  upper  part  of  the  medial 
border  is  in  relation  with  the  left  suprarenal  gland,  and  close  to  the  lateral 
border  is  a  long  strip  in  contact  with  the  renal  impression  on  the  spleen.  A 
somewhat  quadrilateral  field,  about  the  middle  of  the  anterior  surface,  marks  the 
site  of  contact  with  the  body  of  the  pancreas,  on  the  deep  surface  of  which  are  the 
lienal  vessels.  Above  this  is  a  small  triangular  portion,  betw^een  the  suprarenal 
and  splenic  areas,  in  contact  with  the  postero-inferior  surface  of  the  stomach. 
Below  the  pancreatic  area  the  lateral  part  is  in  relation  w  ith  the  left  colic  flexure, 


1208 


SPLANCHNOLOGY 


the  medial  with  the  small  intestine.    The  areas  in  contact  with  the  stomach  a,nd 
spleen  are  covered  ]\v  the  peritoneum  of  the  omental  bursa,  while  that  in  relation 


:leventh  rib 


TWELFTH    RIB 


TRANSVERSE  PROCESSES 
OF  FIRST  LUMBAR  VERTEBRA 


( 

TRANSVERSE  PROCESS 
OFSECOND  LUMBAR 
VERTEBRA 


Fig.   1017. — The  posterior  surfaces  of  the  kidneys,  showing  areas  of  relation  to  the  parietes. 

to  the  small  intestine  is  covered  by  the  peritoneum  of  the  general  cavity;  behind 
the  latter  are  some  branches  of  the  left  colic  vessels.  The  suprarenal,  pancreatic, 
and  colic  areas  are  devoid  of  peritoneum. 


Fig.   1018. — The  relations  of  the  kidneys  from  behind. 


The  Posterior  Surface  (fades  posterior)  (Figs.  1017,  1018).— The  posterior  surface 
of  each  kidney  is  directed  backward  and  medialward.    It  is  imbedded  in  areolar 


7 •///•;  KIDM'JYS 


1209 


and  fatty  tissue  and  entirely  devoid  of  peritoneal  eovering.  It  lies  upon  the  Dia- 
plira<i:ma,  the  medial  and  lateral  lunihoeostal  arelies,  the  Psoas  major,  the  Qnadratus 
lumhorum,  and  the  tendon  of  tlu;  Traiisversus  abdominis,  the  subcostal,  and  one 
or  two  of  the  upper  lumbar  arteries,  and  the  last  thoracic,  iliohypo^^astrie,  and 
ilioinguinal  nerves.  The  right  kidney  rests  Upon  the  twelfth  rib,  the  left  usually 
on  the  eleventh  and  twelfth.  The  Diaphragma  separates  the  kidney  from  the 
pleura,  Avhieli  dips  down  to  form  the  phrenicocostal  sinus,  but  frequently  the 
muscular  fibres  of  the  Dinphragma  are  defective  or  a})sent  over  a  triangular  area 
immediately  above  the  lateral  lumbocostal  arch,  and  when  this  is  the  case  the 
perinephric  areolar  tissue  is  in  contact  with  the  diaphragmatic  pleura. 

Borders. — The  lateral  border  {margo  lafcralis;  external  border)  is  convex,  and  is 
directed  toward  the  j)oster()-lateral  wall  of  the  abdomen.  On  the  left  side  it  is  in 
contact  at  its  upper  part,  with  the  spleen. 

The  medial  border  {margo  medialis;  internal  border)  is  concave  in  the  centre  and 
convex  toward  either  extremity;  it  is  directed  forward  and  a  little  downward. 
Its  central  part  presents  a  deep  longitudinal  fissure,  bounded  by  prominent  over- 
hanging anterior  and  posterior  lips.  This  fissure  is  named  the  hilus,  and  transmits 
the  vessels,  nerves,  and  ureter.  Above  the  hilus  the  medial  border  is  in  relation 
with  the  suprarenal  gland;  below  the  hilus,  with  the  ureter. 

Extremities. — ^The  superior  extremity  (extremitas  superior)  is  thick  and  rounded, 
and  is  nearer  the  median  line  than  the  lower;  it  is  surmounted  by  the  suprarenal 
gland,  which  covers  also  a  small  portion  of  the  anterior  surface. 

The  inferior  extremity  (extremitas  inferior)  is  smaller  and  thinner  than  the  supe- 
rior and  farther  from  the  median  line.    It  extends  to  within  5  cm.  of  the  iliac  crest. 

The  relative  position  of  the 
main  structures  in  the  hilus  is  as 
follows:  the  vein  is  in  front,  the 
artery  in  the  middle,  and  the 
ureter  behind  and  directed  down- 
ward. Frequentl}',  however, 
branches  of  both  artery  and 
vein  are  placed  behind  the  ureter. 

Fixation  of  the  Kidney  (Figs. 
1019,  1020).— The  kidney  and  its 
vessels  are  imbedded  in  a  mass 
of  fatt}^  tissue,  termed  the  adipose 
capsule,  which  is  thickest  at  the 
margins  of  the  kidney  and  is  pro- 
longed through  the  hilus  into  the 
renal  sinus.  The  kidney  and  the 
adipose  capsule  are  enclosed  in  a 
sheath  of  fibrous  tissue  continuous 
with  the  subperitoneal  fascia,  and 
named  the  renal  fascia.  At  the 
lateral  border  of  the  kidney  the 
renal  fascia  splits  into  an  anterior 
and  a  posterior  layer.  The  ante- 
rior layer  is  carried  medialward 
in  front  of  the  kidney  and  its 
vessels,  and   is   continuous   over 

the  aorta  with  the  corresponding  layer  of  the  opposite  side.  The  posterior  layer 
extends  medialward  behind  the  kidney  and  blends  with  the  fascia  on  the  Quad- 
ratus  lumborum  and  Psoas  major,  and  through  this  fascia  is  attached  to  the  verte- 
bral column.   Above  the  suprarenal  gland  the  two  layers  of  the  renal  fascia  fuse. 


Eleventh  rih 


Twelfth  rih  -r— 


Posterior 

lamella  of 

renal  fascia 


Paranephr  u 
body 


Peritoneum 

Vessels  of  hilus 
of  kidney 

I  Section  of 

riqht  colic 

flexure 


Fig.   1019. — Sagittal  section  through  posterior  abdominal  wall, 
showing  the  relations  of  the  capsule  of  the  kidney.  (After  Gerota) . 


1210 


SPLANCHNOLOGY 


and  unite  with  the  fascia  of  the  Diaphragma;  below  they  remain  separate,  and  are 
gradually  lost  in  the  subperitoneal  fascia  of  the  iliac  fossa.  The  renal  fascia  is 
connected  to  the  fibrous  tunic  of  the  kidney  by  numerous  trabeculse,  which  traverse 
the  adipose  capsule,  and  are  strongest  near  the  lower  end  of  the  organ.  Behind 
the  fascia  renalis  is  a  considerable  quantity  of  fat,  which  constitutes  the  paranephric 
body.  The  kidney  is  held  in  position  partly  through  the  attachment  of  the  renal 
fascia  and  partly  by  the  apposition  of  the  neighboring  viscera. 


Suh-peritoneal  fascia 


l__    Anterior  lamella  of 
//  renal  fascia 


Peritoneum 
Adipose  capsule 


nephric  body 
Quadratus  lumborum, 
Saciospinahs 
1020. — Transverse  section,  showing  the  relations  of  the  capsule  of  the  kidney.     (After  Gerota.) 


General  Structure  of  the  Kidney. — The  kidney  is  invested  by  a  fibrous  tunic,  which  forms 
a  firm,  smooth  covering  to  the  organ.  The  tunic  can  be  easily  stripped  off,  but  in  doing  so 
numerous  fine  processes  of  connective  tissue  and  small  bloodvessels  are  torn  through.  Beneath 
this  coat  a  thin  wide-meshed  net-work  of  unstriped  muscular  fibre  forms  an  incomplete  covering 
to  the  organ.  When  the  capsule  is  stripped  ofT,  the  surface  of  the  kidney  is  found  to  be  smooth 
and  even  and  of  a  deep  red  color.  In  infants  fissures  extending  for  some  depth  may  be  seen  on 
the  surface  of  the  organ,  a  remnant  of  the  lobular  construction  of  the  gland.  The  kidney  is 
dense  in  texture,  but  is  easily  lacerable  by  mechanical  force.  If  a  vertical  section  of  the  kidney 
be  made  from  its  convex  to  its  concave  border,  and  the  loose  tissue  and  fat  removed  from  around 
the  vessels  and  the  excretory  duct,  it  will  be  seen  that  the  kidney  consists  of  a  central  cavity  sur- 
rounded at  all  parts  but  one  by  the  proper  kidney  substance  (Fig.  1021).  This  central  cavity 
is  called  the  renal  sinus,  and  is  lined  by  a  prolongation  of  the  fibrous  tunic,  which  is  continued 
around  the  lips  of  the  hilus.  Through  the  hilus  the  bloodvessels  of  the  kidney  and  its  excretory 
duct  pass,  and  therefore  these  structures,  upon  entering  or  leaving  the  kidney,  are  contained  within 
the  sinus.  The  excretory  duct  or  ureter  begins  by  several  short  truncated  branches  termed 
calcies,  which  unite  to  form  two  or  three  short  tubes;  these  in  turn  expand  into  a  wide  funnel- 
shaped  sac  named  the  renal  pelvis,  from  the  neck  of  which  the  ureter  issues.  The  calices  and 
pelvis  he  within  the  sinus;  the  bloodvessels  of  the  kidney,  after  passing  through  the  hilus,  are 
also  contained  in  the  sinus,  lying  between  its  lining  membrane  and  the  excrelory  apparatus. 

The  kidney  is  composed  of  an  internal  medullary  and  an  external  cortical  substance. 

The  medullary  substance  (substantia  medidlaris)  consists  of  a  series  of  red-colored  striated 
conical  masses,  termed  the  renal  pyramids,  the  bases  of  which  are  directed  toward  the  circum- 
ference of  the  kidney,  while  their  apices  converge  toward  the  renal  sinus,  where  they  form  promi- 
nent papillae  projecting  into  the  interior  of  the  calices;  each  calyx  receives  from  one  to  three 
papiUse. 


TJIE  KIDXEYS 


1211 


Tho  cortical  substance  (snhsta)itia  coHicalis)  is  rodtiish  brown  in  color  and  soft  and  gi'anul 
in  consistence.  It  lies  iniincdiatoly  beneath  the  fibrous  tunic,  arclies  over  the  bases  of  tl 
pyramids,  and  dijjs  in  bct\ve(>n  adjacent  pyramids 
toward  the  renal  sinus.  The  i)arts  dipijins  in  between 
the  i)yramids  are  named  tlie  renal  columns  (Bertini), 
while  the  portions  which  coniuM't  the  renal  columns  to 
each  other  and  intervene  lietween  the  bases  of  the 
pyramids  and  the  fibrous  tunic  are  called  the  cortical 
arches  (indicated  between  A  and  A'  in  Fig.  1021). 
If  the  cortex  be  examined  with  a  lens,  it  will  be  seen 
to  consist  of  a  series  of  lighter-colored,  conical  areas, 
termed  the  radiate  part,  and  a  darker-colored  inter- 
vening substance,  which  from  the  complexity  of  its 
structure  is  named  the  convoluted  part.  The  rays 
gradually  taper  toward  the  circumference  of  the  kidney, 
and  consist  of  a  series  of  outward  prolongations  from 
the  base  of  each  renal  pyramid. 

The  cortical  and  medullary  substances,  so  dissimilar 
in  appearance,  are  very  similar  in  structure,  being  made 
up  of  renal  tubules  and  bloodvessels,  united  and  bound 
together  by  a  connecting  stroma. 

Minute  Anatomy. — The  renal  tubules  (Fig.  1022), 
of  which  the  kidney  is  for  the  most  p'art  made  up, 
commence  in  the  cortical  substance,  and  after  pursuing 
a  verj'  circuitous  course  through  the  cortical  and  medul- 
lary substances,  finally  end  at  the  apices  of  the  renal 
pyramids  bj'  open  mouths,  so  that  the  fluid  which 
they  contain  is  emptied,  through  the  calices,  into  the 
pelvis  of  the  kidney.  If  the  surface  of  one  of  the 
papiUse  be  examined  with  a  lens,  it  will  be  seen  to  be 
studded  over  with  minute  openings,  the  orifices  of  the  Fig.  io21.— Vertical  section  of  kidney. 


Boicmcm's  capsule     Neck         ist  convoluted  tubule 


A jf event  vessel 
Efferent  vessel 

Intertiibular  capillaries 
Interlobular  vein 

Interlobular  artery 
Spiral  tubule 


Henle'sf  Ascending  limb 
loop   \Descending  limb 


Arterial  arch 
Venous  arch 


Cortical  substance 


-Bouiidaiy  zone 


Medullary 
substance 


Duct  of  Bell 


Fig.  1022. — Scheme  of  renal  tubule  and  its  vascular  supply. 


1212 


SPLANCHNOLOGY 


renal  tubules,  from  sixteen  to  twenty  in  number,  and  if  pressure  be  made  on  a  fresh  kidney, 
urine  will  be  seen  to  exude  from  these  orifices.  The  tubules  commence  in  the  convoluted  part 
and  renal  columns  as  the  Malpighian  bodies,  which  are  small  rounded  masses  of  a  deep  red 
color,  varying  in  size,  but  of  an  average  of  about  0.2  mm.  in  diameter.  Each  of  these  httle 
bodies  is  composed  of  two  parts:  a  central  glomerulus  of  vessels,  called  a  Malpighian  tuft, 
and  a  membranous  envelope,  the  Malpighian  capsule  {capsule  of  Bowman),  which  is  the  small 
pouch-like  commencement  of  a  renal  tubule. 

The  Malpighian  tuft  (vascula  glomerulus)  is  a  lobulated  net-work  of  convoluted  capillary 
bloodvessels,  held  together  by  scanty  connective  tissue.  This  capillary  net-work  is  derived  from 
a  small  arterial  twig,  the  afferent  vessel,  which  enters  the  capsule,  generally  at  a  point  opposite 
to  that  at  which  the  latter  is  connected  with  the  tubule;  and  the  resulting  vein,  the  efferent 
vessel,  emerges  from  the  capsule  at  the  same  point.  The  afferent  vessel  is  usually  the  larger  of 
the  two  (Fig.  1023).  The  Malpighian  or  Bowman's  capsule,  which  sun-ounds  the  glomerulus, 
is  formed  of  a  hyahne  membrane,  supported  by  a  small  amoimt  of  connective  tissue,  which  is 
continuous  with  the  connective  tissue  of  the  tube.  It  is  hned  on  its  inner  surface  by  a  layer  of 
squamous  epitheUal  cells,  which  are  reflected  from  the  lining  membrane  on  to  the  glomerulus, 
at  the  point  of  entrance  or  exit  of  the  afferent  and  efferent  vessels.  The  whole  surface  of  the 
glomerulus  is  covered  with  a  continuous  layer  of  the  same  cells,  on  a  dehcate  supporting  mem- 
brane (Fig.  1024).  Thus  between  the  glomerulus  and  the  capsule  a  space  is  left,  forming  a  cavity 
Uned  by  a  continuous  layer  of  squamous  cells;  this  cavity  varies  in  size  according  to  the  state 
of  secretion  and  the  amount  of  fluid  present  in  it.  In  the  fetus  and  yoimg  subject  the  lining 
epitheUal  cells  are  polyhedral  or  even  columnar. 


Fig.  1023. — Distribution  of  bloodvessels  in  cortex  of  kidney. 


Fig.  1024. — Malpighian  body. 


The  renal  tubules,  commencing  in  the  Malpighian  bodies,  present,  during  their  course,  many 
changes  in  shape  and  direction,  and  are  contained  partly  in  the  medullary  and  partly  in  the 
cortical  substance.  At  their  jimction  with  the  Malpighian  capsule  they  exhibit  a  somewhat 
constricted  portion,  which  is  termed  the  neck.  Beyond  this  the  tubule  becomes  convoluted, 
and  pm-sues  a  considerable  course  in  the  cortical  substance  constituting  the  proximal  convoluted 
tube.  After  a  time  the  convolutions  disappear,  and  the  tube  approaches  the  meduUary  sub- 
stance in  a  more  or  less  spiral  manner;  this  section  of  the  tubule  has  been  called  the  spiral  tube. 
Throughout  this  portion  of  their  course  the  renal  tubules  are  contained  entirely  in  the  cortical 
substance,  and  present  a  fairly  uniform  calibre.  They  now  enter  the  medullary  substance, 
suddenly  become  much  smaller,  quite  straight  in  direction,  and  dip  down  for  a  variable  depth 
into  the  pyramids,  constituting  the  descending  limb  of  Henle's  loop.  Bending  on  themselves, 
they  form  what  is  termed  the  loop  of  Henle,  and  reascending,  they  become  suddenly  enlarged, 
forming  the  ascending  limb  of  Henle's  loop,  and  reenter  the  cortical  substance.  This  portion 
of  the  tubule  ascends  for  a  short  distance,  when  it  again  becomes  dilated,  irregular,  and  angular. 
This  section  is  termed  the  zigzag  tubule;  it  ends  in  a  convoluted  tube,  which  resembles  the 
proximal  convoluted  tubule,  and  is  called  the  distal  convoluted  tubule.  This  again  terminates 
in  a  narrow  jimctional  tube,  which  enters  the  straight  or  collecting  tube. 

The  straight  or  collecting  tubes  commence  in  the  radiate  part  of  the  cortex^  where  they  receive 
the  curved  ends  of  the  distal  convoluted  tubules.  They  unite  at  short  intervals  with  one  another, 
the  resulting  tubes  presenting  a  considerable  increase  in  calibre,  so  that  a  series  of  comparatively 
large  tubes  passes  from  the  bases  of  the  rays  into  the  renal  pyramids.  In  the  medulla  the  tubes 
of  each  pjrramid  converge  to  join  a  central  tube  (duct  of  Bellini)  which  finally  opens  on  the  summit 
of  one  of  the  papiUse;  the  contents  of  the  tube  are  therefore  discharged  into  one  of  the  calices. 

Structure  of  the  Renal  Tubules. — The  renal  tubules  consist  of  a  basement  membrane  lined  with 
epitheUmn.    The  epitheUum  varies  considerably  in  different  sections  of  the  tubule.    In  the  neck 


THE  KIDNEYS 


1213 


the  epitlieliuin  is  continuous  with  that  Uning  the  Malpighian  capsule,  and  like  it  consists  of 
flattened  cells  each  containing  an  oval  nucleus  (Fig.  102Gj.  The  two  convoluted  tubules,  the 
spiral  and  zigzag  tubules  and  the  ascending  limb  of  Henle's  loop,  are  lined  by  a  type  of  epithelium 
which  is  histologically  the  same  in  all.  The  cells  are  somewhat  columnar  in  shape  and  dovetail 
into  one  another  of  their  lateral  aspect.  Each  has  a  striated  border  next  the  lumen  of  the  tube, 
its  inner  part  is  granular  and  its  outer  portion  vertically  striated.  The  nucleus  is  spherical  and 
situated  about  the  centre  of  the  cell.  In  the  descend- 
ing limb  of  Henle's  loop  the  epithelium  resembles  that  }\  ^ 
found  in  the  Malpighian  capsule  and  the  commence- 
ment of  the  tube,  consisting  of  flat,  clear  epithelial 
plates,  each  with  an  oval  nucleus  (Fig.  1025).  The 
nuclei  alternate  on  opposite  surfaces  of  the  tubule  so 
that  the  lumen  remains  fairly  constant. 

In  the  straight  tube  the  epitheUum  is  clear  and 
cubicftl:  in  its  papillarj^  portion  the  cells  are  distinctly 
columnar  and  transparent  (Fig.  1026). 

The  Renal  Bloodvessels. — The  kidney  is  plentifully 
supplied  with  blood  (Fig.  1027)  by  the  renal  artery,  a 
large  offset  of  the  abdominal  aorta.  Before  it  enters 
the  kidney,  each  artery  divides  into  four  or  jfive 
branches  which  at  the  hilus  lie  mainly  between  the 
renal  vein  and  m-eter,  the  vein  being  in  front,  the 
ureter  behind;  one  branch  usually  hes  behind  the 
ureter.  Each  vessel  gives  off  some  small  branches  to 
the  suprarenal  glands,  to  the  iireter,  and  to  the  sur- 
rounding cellular  tissue  and  muscles.  Frequently  a 
second  renal  artery,  termed  the  inferior  renal,  is  given 
off  from  the  abdominal  aorta  at  a  lower  level,  and  supplies  the  lower  portion  of  the  kidney, 
while  occasionally  an  additional  artery  enters  the  upper  part  of  the  kidney.  The  branches 
of  the  renal  artery,  while  in  the  sinus,  give  off  a  few  twigs  for  the  nutrition  of  the  surround- 
ing tissues,  and  end  in  the  arteriae  propriae  renales,  which  enter  the  kidney  proper  in  the 
renal  columns.  Two  of  these  pass  to  each  renal  pyramid,  and  run  along  its  sides  for  its 
entire  length,  giving  off  in  their  course  the  afferent  vessels  of  the  Malpighian  bodies  in  the  renal 


Fig.  1025.  —  Loogitudinal  section  of  de- 
scending limb  of  Henle's  loop.  a.  Membrana 
propria,    b.  Epithelium. 


Convoluted  tubule 


p^T —  Malpighian  tuft 


Neck  of  tubule 


Fig.   1026. — Section  of  cortex  of  human  kidney. 

columns.  Having  arrived  at  the  bases  of  the  pyramids,  they  form  arterial  arches  or  arcades 
which  lie  in  the  boundary  zone  between  the  bases  of  the  pyramids  and  the  cortical  arches,  and 
break  up  into  two  distinct  sets  of  branches  devoted  to  the  supply  of  the  remaining  portions 
of  the  kidney. 

The  first  set,  the  interlobular  arteries  (Fig.  1022),  are  given  off  at  right  angles  from  the  side 
of  the  arterial  arcade  looking  toward  the  cortical  substance,  and  pass  directly  outward  between 


1214 


SPLANCHNOLOGY 


the  medullary  rays  to  reach  the  fibrous  tunic,  where  they  end  in  the  capillary  net-work  oi  this 
part.  These  vessels  do  not  anastomose  with  each  other,  but  form  what  are  called  end-arteries. 
In  their  outward  course  thej'  give  off  lateral  branches;  these  are  the  afferent  vessels  for  the  Mal- 
pighian  bodies  (see  page  1212) ;  they  enter  the  capsule,  and  end  in  the  Malpighian  tufts.  From 
each  tuft  the  corresponding  efferent  vessel  arises,  and,  having  made  its  egress  from  the  capsule 
near  to  the  point  where  the  different  vessel  enters,  breaks  up  into  a  number  of  branches,  which 
form  a  dense  plexus  around  the  adjacent  urinary  tubes. 

The  second  set  of  branches  from  the  arterial  arcades  supply  the  renal  pyramids,  which  they 
enter  at  their  bases;  and,  passing  straight  through  their  substance  to  their  apices,  terminate 
in  the  venous  plexuses  found  in  that  situation.  They  are  called  the  arteriae  rectae.  The  efferent 
vessels  from  the  glomeruli  nearest  the  medulla  break  up  into  leashes  of  straight  vessels  {false 
arteriae  rectae)  which  pass  down  into  the  medulla  and  join  the  plexus  of  vessels  there  (Fig.  1022). 

The  renal  veins  arise  from  three  sources,  viz.,  the  veins  beneath  the  fibrous  tunic,  the  plexuses 
around  the  convoluted  tubules  in  the  cortex,  and  the  plexuses  situated  at  the  apices  of 
the  renal  pyramids.  The  veins  beneath  the  fibrous  tunic  (venae  stellatae)  are  stellate  in 
arrangement,  and  are  derived  from  the  capillary  net-work,  into  which  the  terminal  branches  of 
the  interlobular  arteries  break  up.  These  join  to  form  the  interlobular  veins,  which  pass  inward 
between  the  rays,  receive  branches  from  the  plexuses  around  the  convoluted  tubules,  and,  having 
arrived  at  the  bases  of  the  renal  pyramids,  join  with  the  venae  rectae,  next  to  be  described. 


Fig.  1027. — Transverse  section  of  pyramidal  substance  of  kidney  of  pig,  the  bloodvessels  of  which  are  injected. 
a.  Large  collecting  tube,  cut  across,  lined  with  cylindrical  epitheUum.  h.  Branch  of  collecting  tube,  cut  across,  lined 
with  cubical  epithelium,  c,  d.  Henle's  loops  out  across,  e:  Bloodvessels  cut  across.  D.  Connective  tissue  ground 
substance. 


The  venae  rectae  are  branches  from  the  plexuses  at  the  apices  of  the  medullary  pyramids, 
formed  by  the  terminations  of  the  arteriae  rectae.  They  run  outward  in  a  straight  course  between 
the  tubes  of  the  medullary  substance,  and  joining,  as  above  stated,  the  interlobular  veins,  form 
venous  arcades;  these  in  turn  unite  and  form  veins  which  pass  along  the  sides  of  the  pyramids 
(Fig.  1022). 

These  vessels,  venae  propriae  renales,  accompany  the  arteries  of  the  same  name,  running 
along  the  entire  length  of  the  sides  of  the  pyramids,  and  quit  the  kidney  substance  to  enter  the 
sinus.  In  this  cavity  they  join  the  corresponding  veins  from  the  other  pyramids  to  form  the 
renal  vein,  which  emerges  from  the  kidney  at  the  hilus  and  opens  into  the  inferior  vena  cava; 
the  left  vein  is  longer  than  the  right,  and  crosses  in  front  of  the  abdominal  aorta. 

The  lymphatics  of  the  kidney  are  described  on  page  793. 

Nerves  of  the  Kidney. — The  nerves  of  the  kidney,  although  small,  are  about  fifteen  in  number. 
They  have  small  ganglia  developed  upon  them,  and  are  derived  from  the  renal  plexus,  which  is 
formed  by  branches  from  the  coeliac  plexus,  the  lower  and  outer  part  of  the  ca?Uac  ganglion  and 
aortic  plexus,  and  from  the  lesser  and  lowest  splanchnic  nerves.  They  communicate  with  the 
spermatic  plexus,  a  circumstance  which  may  explain  the  occurrence  of  pain  in  the  testis  in  affec- 
tions of  the  kidney.  They  accompany  the  renal  artery  and  its  branches,  and  are  distributed  to 
the  bloodvessels  and  to  the  cells  of  the  urinary  tubules. 

Connective  Tissue  {intertubular  stroma) .  —  Although  the  tubules  and  vessels  are  closely 
packed,  a  small  amount  of  connective  tissue,  continuous  with  the  fibrous  tunic,  binds  them 
firmly  together  and  supports  the  bloodvessels,  lymphatics,  and  nerves. 

Applied  Anatomy. — Malformations  of  the  kidney  are  not  uncommon.  There  may  be  an 
entire  absence  of  one  kidney,  but,  according  to  Morris,  the  number  of  these  cases  is  "excessively 
small":  or  there  may  be  congenital  atrophy  of  one  kidney,  when  the  kidney  is  very  small,  but 
usually  healthy  in  structure.    These  cases  are  of  great  importance,  and  must  be  duly  taken  into 


rilh:  KIDNKYS  ^  1215 

account  wIhmi  iicplirectomy  is  contcmijlatcil.  A  more  {•oiiiiiioii  iiiaUoriiiiitioii  is  where  the  two 
kidneys  are  fused  togetlu>r.  They  may  hv  jointul  tof^cther  only  at.  th(!ii-  lower  ends  by  means 
of  a  thick  mass  of  renal  tissue,  so  as  to  form  a  horseshoe-shaped  body,  or  they  may  be  completely 
united,  forming  a  disk-like  kidney,  from  which  two  ureters  ilescend  into  the  bladder.  These  fused 
kidneys  are  t^enerally  situated  in  the  middle  line  of  the  abdomen,  but  may  be  misplaced  as  well. 
In  some  mammals,  e.  g.,  ox  and  bear,  the  kidney  consists  of  a  number  of  distinct  lobules;  this 
lobulated  condition  is  characteristic  of  the  kidney  of  the  human  fetus,  and  traces  of  it  may  persist 
in  the  adult.  Sometimes  the  pelvis  is  duplicated,  while  a  douljje  ureter  is  not  very  uncommon. 
In  sonre  rare  instances  a  third  kidney  may  be  jiresent. 

One  or  both  kidneys  may  be  misplaced  as  a  congenital  condition,  and  remain  fixed  in  this 
abnormal  position.  They  are  then  very  often  misshapen.  They  may  be  situated  higher,  though 
this  is  very  uncommon,  or  lower  than  normal  or  removed  farther  from  the  vertebral  column 
than  usual;  or  they  may  be  displaced  into  the  iliac  fossa,  over  the  sacroiliac  joint,  on  to  the 
promontory'  of  the  sacrum,  or  into  the  pelvis  between  the  rectum  and  bladder  or  by  the  side  of 
the  uterus.  In  these  latter  cases  they  may  give  rise  to  very  serious  trouble.  The  kidney  may  also 
be  misplaced  as  a  congenital  condition,  but  maj^  not  be  fixed;  it  is  then  known  as  a  floating  kidney. 
It  is  believed  to  be  due  to  the  fact  that  the  kidney  is  completely  enveloped  by  peritoneum  which 
then  passes  backward  to  the  vertebral  column  as  a  double  layer,  forming  a  mesonephron  which 
permits  of  movement  taking  place.  The  kidney  may  also  be  misplaced  as  an  acquired  condition; 
in  these  cases  the  kidney  is  mobile  in  the  tissues  by  which  it  is  surrounded,  moving  with  the 
capsule  in  the  perinephric  tissues.  This  condition  is  known  as  movable  kidney,  and  is  more  common 
in  the  female  than  in  the  male.  It  occurs  in  badly  nourished  people,  or  in  those  who  have  become 
emaciated  from  anj'  cause.  It  must  not,  be  confounded  with  the  floating  kidney,  which  is  a 
congenital  condition  due  to  the  development  of  a  mesonephron.  The  two  conditions  cannot, 
however,  be  distinguished  until  the  abdomen  is  opened  or  the  kidney  explored  from  the  loin. 

Injuries  of  the  kidney  are  generally  due  to  some  severe  crushing  force,  as  from  being  run  over 
by  a  heavy  wagon  or  cart,  or  from  the  abdomen  being  compressed  between  the  buffers  of  two 
railway  carriages.  When  a  laceration  occurs  on  the  posterior  surface  of  the  organ,  infiltration 
of  blood  and  urine  takes  place  into  the  retroperitoneal  connective  tissue;  this  is  often  followed 
by  suppiu'ation,  and  death  maj^  ensue  from  septic  poisoning.  When  the  laceration  is  in  front, 
the  peritoneum  may  be  torn  and  extravasation  of  blood  and  urine  take  place  into  the  peritoneal 
cavity.  Death  may  occm'  from  hemorrhage  or  peritonitis.  Occasionally,  when  ruptm-e  involves 
the  pelvis  of  the  kidney  or  the  commencement  of  the  ureter,  this  duct  may  become  blocked,  and 
hj^dronephrosis  follow.  Sometimes  the  kidney  may  be  bruised  by  blows  in  the  loin,  or  by  being 
compressed  between  the  lower  ribs  and  the  ilium  when  the  body  is  violently  bent  forward.  This 
is  followed  by  a  little  transient  hematuria,  which,  however,  speedily  passes  off. 

The  loose  cellular  tissue  around  the  kidney  may  be  the  seat  of  suppuration,  constituting 
perinephric  abscess.  This  may  be  due  to  injury,  to  disease  of  the  kidney  itself,  or  to  extension 
of  inflammation  from  neighboring  parts.  The  abscess  tends  to  point  externally  in  the  groin  or 
loin. 

Tumors  of  the  kidney,  of  which  perhaps  sarcoma  is  the  most  common,  may  be  recognized 
by  their  position;  by  the  resonant  colon  lying  in  front  of  them;  and  by  their  rounded  outline 
not  presenting  a  notched  anterior  margin  like  the  spleen,  with  which,  they  are  most  hkely  to  be 
confounded. 

The  hypernephroma,  a  benign  or  malignant  tumor  arising  from  the  suprarenal  gland,  or  from 
suprarenal  "rests"  or  inclusions  in  the  cortex  or  medulla  of  the  kidney,  is  not  infrequent.  When 
occurring  in  children  it  is  often  associated  with  precocious  growth  of  the  body  generally  and  of 
the  hair  and  sexual  organs  in  particular.  Arising,  as  it  often  does,  in  the  kidney,  a  hypernephroma 
maj'  be  indistinguishable  from  a  true  renal  tumor  so  far  as  the  physical  signs  and  symptoms  go; 
it  is  reallj',  however,  a  tumor  of  the  suprarenal  gland  substance. 

The  examination  of  the  kidney  should  be  bimanual;  that  is  to  say,  one  hand  should  be  placed 
in  the  flank  and  firm  pressure  made  forward;  while  the  other  hand  is  bm'ied  in  the  abdominal 
wall,  over  the  situation  of  the  organ.  Manipulation  of  the  kidney  frequently  produces  a  peculiar 
sickening  sensation,  sometimes  with  faintness. 

The  kidney  may  require  exposure  for  exploration  or  the  evacuation  of  pus  {nephrotomy);  it 
may  be  incised  for  the  removal  of  stone  (nephrolithotomy) ;  it  may  be  sutured  when  movable  or 
floating  (nephrorrhaphy);  or  it  may  be  removed  {nephrectomy).  It  may  be  exposed  either  by  a 
lumbar  or  an  abdominal  incision;  except  in  cases  of  very  large  tumors,  a  lumbar  incision  is  best, 
as  it  has  the  advantages  of  not  opening  the  peritoneum,  and  of  affording  admirable  drainage. 
An  oblique  incision  should  be  made,  starting  at  the  lateral  border  of  the  Sacrospinahs,  1.25  cm. 
below  the  last  rib  and  directed  downward  and  forward  toward  a  point  2.5  cm.  in  front  of  the 
anterior  superior  spine  of  the  ilium.  The  structures  divided  are  the  skin,  the  superficial  fascia 
with  the  cutaneous  nerves,  the  deep  fascia,  the  posterior  border  of  the  Obhquus  externus  ab- 
dominis, and  the  outer  border  of  the  Latissimus  dorsi;  the  Obliquus  internus  and  the  posterior 
aponeurosis  of  the  Transversus  abdominis;  the  lateral  border  of  the  Quadratus  lumborum;  the 
deep  layer  of  the  lumbodorsal  fascia  and  the  transversalis  fascia.     The  fatty  tissue  around  the 


1216  .  SPLAXCHXOLOGY 

kidney  is  now  exposed  to  view,  and  must  be  separated  by  the  fingers,  or  a  director,  in  order  to 
reach  the  kidney.  The  operations  of  nephrolithotomy,  for  the  removal  of  calculi  from  the  kidney, 
and  nephrotomy,  or  incision  of  the  kidney  for  abscess,  etc.,  are  generally  performed  by  the  lumbar 
incision.  This  route  is  also  generally  chosen  for  nephrectomy,  especially  if  the  organ  is  thought 
to  contain  pus.  The  abdominal  operation  is  best  performed  by  an  incision  through  the  lateral 
part  of  the  Rectus  abdominis  on  the  side  of  the  kidney  to  be  removed;  the  kidney  is  then  reached 
from  the  lateral  side  of  the  colon,  ascending  or  descending,  as  the  case  may  be,  and  thus  the 
vessels  of  the  colon  are  not  interfered  with.  The  incision  commencing  just  below  the  costal  arch 
is  made  of  varj-ing  length,  according  to  the  size  of  the  kidney.  The  abdominal  cavity  having 
been  opened,  the  intestines  are  dra'mi  medialward  and  the  peritoneum  covering  the  kidney  to 
the  lateral  side  of  the  colon  is  incised,  so  that  the  fingers  can  be  introduced  behind  the  peritoneum. 
The  kidnej^  must  now  be  enucleated,  and  the  vessels  firmly  ligatured  and  divided,  the  ureter 
being  tied  separately.  The  particular  advantage  of  the  abdominal  operation  is  that  the  con- 
dition of  the  other  kidne}'  can  be  ascertained  by  manual  examination,  before  the  removal  of  the 
diseased  kidney  is  fiinaUy  decided  upon;  and  further,  involvement  of  neighboring  structure  by 
a  new-growth,  rendering  removal  impossible,  can  only  be  discovered  by  the  abdominal  route. 

Nephrorrhaphy  is  the  name  given  to  the  operation  for  fixing  a  movable  kidney.  The  kidney 
is  reached  by  the  lumbar  incision,  and  its  posterior  surface  denuded  of  its  adipose  capsule.  Three 
stitches  of  medium  thickness  are  passed  through  the  transversalis  fascia  and  muscles  and  through 
the  cortical  substance  of  the  kidney,  seeming  a  good  hold  of  it.  When  these  sutures  are  tied, 
the  kidney  is  tightly  anchored  in  position;  cases  which  are  seen  sometime  afterward  seem,  however, 
to  show  that  it  does  not  always  remain  fixed. 

The  Ureters. 

The  ureters  are  the  two  tubes  which  convey  the  urme  from  the  kidneys  to  the 
urinary  bladder.  Each  commences  within  the  sinus  of  the  corresponding  kidney 
as  a  number  of  short  cup-shaped  tubes,  termed  calices,  which  encircle  the  renal 
papillee.  Since  a  single  calyx  may  enclose  more  than  one  papilla  the  calices  are 
generally  fewer  in  number  than  the  pyramids — the  former  varying  from  seven  to 
thirteen,  the  latter  from  eight  to  eighteen.  The  calices  join  to  form  two  or  three 
short  tubes,  and  these  unite  to  form  a  funnel-shaped  dilatation,  wide  above  and 
narrow  below,  named  the  renal  pelvis,  which  is  situated  partly  inside  and  partly 
outside  the  renal  sinus.  It  is  usually  placed  on  a  leA'el  with  the  spinous  process  of 
the  first  lumbar  vertebra. 

The  Ureter  Proper  measures  from  25  to  30  cm.  in  length,  and  is  a  thick-walled 
narrow  cylindrical  tube  which  is  directly  continuous  near  the  lower  end  of  the 
kidney  with  the  tapering  extremity  of  the  renal  pelvis.  It  runs  downward  and 
medialward  in  front  of  the  Psoas  major  and,  entering  the  pelvic  cavity,  finally 
opens  into  the  fundus  of  the  bladder. 

The  abdominal  part  (pars  ahdominalis)  lies  behind  the  peritoneum  on  the  medial 
part  of  the  Psoas  major,  and  is  crossed  obliquely  b}^  the  internal  spermatic  vessels. 
It  enters  the  pelvic  cavity  by  crossing  either  the  termination  of  the  common,  or 
the  commencement  of  the  external,  iliac  vessels. 

At  its  origin  the  right  ureter  is  usualh'  covered  by  the  descending  part  of  the 
duodenum,  and  in  its  course  downward  lies  to  the  right  of  the  inferior  vena  cava, 
and  is  crossed  by  the  right  colic  and  ileocolic  vessels,  while  near  the  superior  aperture 
of  the  pelvis  it  passes  behind  the  lower  part  of  the  mesentery  and  the  terminal 
part  of  the  ileum.  The  left  lu-eter  is  crossed  by  the  left  colic  vessels,  and  near  the 
superior  aperture  of  the  pelvis  passes  behind  the  sigmoid  colon  and  its  mesenterj'. 

The  pelvic  part  {ijars  pehina)  runs  at  first  downward  on  the  lateral  wall  of  the 
pelvic  cavity,  along  the  anterior  border  of  the  greater  sciatic  notch  and  under 
cover  of  the  peritoneum.  It  lies  in  front  of  the  hypogastric  artery  medial  to  the 
obturator  nerve  and  the  umbilical,  obturator,  inferior  vesical,  and  middle  hemor- 
rhoidal arteries.  Opposite  the  lower  part  of  the  greater  sciatic  foramen  it  inclines 
medialward,  and  reaches  the  lateral  angle  of  the  bladder,  where  it  is  situated  in 
front  of  the  upper  end  of  the  seminal  vesicle  and  at  a  distance  of  about  5  cm. 
from  the  opposite  ureter;  here  the  ductus  deferens  crosses  to  its  medial  side,  and 


THE  URETERS 


1217 


the  vesical  veins  surroiiiul  it.  Finally,  the  ureters  run  obliquely  for  about  2  cm. 
through  the  wall  of  the  bladder  and  open  by  slit-like  apertures  into  the  cavity 
of  the  viscus  at  the  lateral  angles  of  the  trigone.  When  the  bladder  is  distended 
the  openings  of  the  ureters  are  about  5  cm.  ai)art,  but  when  it  is  empty  and  con- 
tracted the  distance  between  them  is  diminished  by  one-half.  Owing  to  their 
oblique  course  through  the  coats  of  the  bladder,  the  upper  and  lower  walls  of  the 
terminal  portions  of  the  ureters  become  closely  applied  to  each  other  when  the  viscus 
is  distended,  and,  acting  as  valves,  prevent  regurgitation  of  urine  from  the  bladder. 
In  the  female,  the  ureter  forms,  as  it  lies  in  relation  to  the  wall  of  the  pelvis, 
the  posterior  boundary  of  a  shallow  depression  named  the  ovarian  fossa,  in  which 
the  ovary  is  situated.  It  then  runs  medialward  and  forward  on  the  lateral  aspect 
of  the  cervix  uteri  and  upper  part  of  the  vagina  to  reach  the  fundus  of  the  bladder. 
In  this  part  of  its  course  it  is  accompanied  for  about  2.5  cm.  by  the  uterine  artery, 
which  then  crosses  in  front  of  the  ureter  and  ascends  between  the  two  layers  of  the 
broad  ligament.  The  ureter  is  distant  about  2  cm.  from  the  side  of  the  cervix  of 
the  uterus.  The  ureter  is  sometimes  duplicated  on  one  or  both  sides,  and  the 
two  tubes  may  remain  distinct  as  far  as  the  fundus  of  the  bladder.  On  rare 
occasions  they  open  separately  into  the  bladder  cavity. 

Structure  (Fig.  1028). — The  ureter  is  cbmposed  of  three  coats:   fibrous,  muscular,  and  mucous 
coats. 

The  fibrous  coat  {tunica  adventitia)  is  continuous  at  one  end  with  the  fibrous  tunic  of  the  kidney 
on  the  floor  of  the  sinus;  while  at  the  other  it  is  lost  in  the  fibrous  structure  of  the  bladder. 

In  the  renal  pelvis  the  muscular  coat 
{tunica  muscularis)  consists  of  two 
layers,  longitudinal  and  circular:  the 
longitudinal  fibres  become  lost  upon  the 
sides  of  the  papillee  at  the  extremities 
of  the  cahces;  the  cu'cular  fibres  may 
be  traced  surrounding  the  medullary 
substance  in  the  same  situation.  In 
the  lu-eter  proper  the  muscular  fibres 
ai'e  very  distinct,  and  are  arranged  in 
thi-ee  layers:  an  external  longitudinal, 
a  middle  circular,  and  an  internal,  less 
distinct  than  the  other  two,  but  having 
a  general  longitudinal  direction.  Ac- 
cording to  KoUiker  this  internal  layer  is 
found  only  in  the  neighborhood  of  the 
bladder. 

The  mucous  coat  {tunica  mucosa)  is 
smooth,  and  presents  a  few  longitudinal 
folds  which  become  effaced  by  disten- 
sion. It  is  continuous  with  the  mucous 
membrane  of  the  bladder  below,  while 
it  is  prolonged  over  the  papillae  of  the 
kidney  above.  Its  epithelium  is  of  a 
transitional  character,  and  resembles 
that  found  in  the  bladder  (see  Fig. 
1034).  It  consists  of  several  layers  of 
ceUs,  of  which  the  innermost — that  is  to 
say,  the  cells  in  contact  with  the  urine — 

are  somewhat  flattened,  with  concavities  on  their  deep  sm-faces  into  which  the  rounded  ends 
of  the  ceUs  of  the  second  layer  fit.  These,  the  intermediate  cells,  more  or  less  resemble  coliunnar 
epitheUum,  and  are  pear-shaped,  with  roimded  internal  extremities  which  fit  into  the  concavities 
of  the  cells  of  the  first  layer,  and  narrow  external  extremities  which  are  wedged  in  between  the 
cells  of  the  third  layer.  The  external  or  third  layer  consists  of  conical  or  oval  cells  varying  in 
number  in  different  parts,  and  presenting  processes  which  extend  down  into  the  basement- 
membrane.  Beneath  the  epithelium,  and  separating  it  from  the  muscular  coats,  is  a  dense  layer 
of  fibrous  tissue  containing  many  elastic  fibres. 

Vessels  and  Nerves. — The  arteries  supplying  the  ureter  are  branches  from  the  renal,  internal 
spermatic,  hypogastric,  and  inferior  vesical. 

The  nerves  are  derived  from  the  inferior  mesenteric,  spei-matic,  and  pelvic  plexuses. 


—  Fibrous  tissue 

Longitudinal 

muscular  fibres 

—  Circular  muscular 
fibres 

^     Subepithelial 
connective  tissue 

Transitional 
epithelium 


Fig.   1028. — Transverse  section  of  ureter. 


1218 


SPLANCHNOLOGY 


Applied  Anatomy. — Rupture  of  the  lu-eter  is  not  a  common  accident,  but  occasionally  occurs. 
If  it  be  torn  completely  across,  the  urine  collects  in  the  retroi)eritoneal  tissues;  if  it  be  not  com- 
pletely divided,  the  lumen  of  the  tube  may  become  strictm-ed  and  hydronephrosis  or  pyonephrosis 
result.  The  ureter  may  be  accidentally  wounded  in  some  pelvic  operations;  such  as  removal  of 
the  uterus;  if  this  should  happen  the  divided  ends  must  be  sutured  together,  or  failing  to  accom- 
plish this  an  attempt  may  be  made  to  implant  the  upper  end  into  the  bladder  or  rectum.  If  this 
cannot  be  carried  out  the  only  alternative  is  to  remove  the  kidney  immediately. 

Stones  not  uncommonly  become  impacted  in  the  m-eter.  These  may  occur  at  any  part,  but 
most  commonly  either  at  the  point  where  the  tube  is  crossing  the  pelvic  brim  or  at  the  termina- 
tion, where  it  is  passing  obliquely  through  the  muscular  wall  of  the  bladder.  In  the  former  case, 
an  incision  with  its  centre  opposite,  and  2.5  cm.  internal  to,  the  anterior  superior  iUac  spine, 
dividing  all  the  structm-es  down  to  the  peritoneum,  enables  the  operator  to  reach  the  ureter  by 
pushing  the  unopened  peritoneum  inward;  the  stone  can  then  be  felt  in  the  ureter,  the  wall  of 
which  is  incised,  and  the  stone  extracted,  free  di-ainage  being  provided  for  the  escaping  urine. 
When  the  stone  is  impacted  at  the  vesical  end  of  the  tube  a  preliminary  incision  into  the  bladder 
is  required,  and  by  scratching  through  the  mucous  membrane  overlying  it  the  calculus  can  be 
removed. 

The  Urinary  Bladder  (Vesica  Urinaria;  Bladder)  (Fig.  1029). 

The  urinary  bladder  is  a  musculomembranous  sac  which  acts  as  a  reservoir 
for  the  urine;  and  as  its  size,  position,  and  relations  vary  according  to  the  amount 
of  fluid  it  contains,  it  is  necessary  to  study  it  as  it  appears  (a)  when  empty,  and  (b) 


Ureter 


Ductus  deferens 


Urethra 


Sacrum 


Rectovesical 
excavation 


Coccyx 

Ejaculatory  duct 
—  Anal  canal 


External  urethral      » 
orifice 


Fig.   1029. — Median  sagittal  section  of  male  pelvis. 


when  distended.  In  both  conditions  the  position  of  the  bladder  varies  with  the 
condition  of  the  rectum,  being  pushed  upward  and  forward  when  the  rectum  is 
distended. 

The  Empty  Bladder. — When  hardened  in  situ,  the  empty  bladder  has  the 
form  of  a  flattened  tetrahedron,  with  its  vertex  tilted  forward.    It  presents  a  fundus, 


THE  URINARY  BLADDER  1219 

a  vertex,  a  superior  and  an  inferior  surfaee.  The  fundus  (Fig.  1041)  is  triangular 
in  shape,  and  is  direeted  downward  and  baekward  toward  the  rectum,  from  which 
it  is  separated  by  the  rectovesical  fascia,  the  vesiculae  seminales,  and  the  terminal 
portions  of  the  ductus  deferentes.  The  vertex  is  directed  forward  toward  the  upper 
part  of  the  symphysis  pubis,  and  from  it  the  middle  umbilical  ligament  is  continued 
upward  on  the  back  of  the  anterior  abdominal  wall  to  the  umbilicus.  The  peri- 
toneum is  carried  by  it  from  the  vertex  of  the  bladder  on  to  the  abdominal  wall 
to  form  the  middle  umbilical  fold.  The  superior  surface  is  triangular,  bounded 
on  either  side  by  a  lateral  border  wdiich  separates  it  from  the  inferior  surface,  and 
behind  by  a  posterior  border,  represented  by  a  line  joining  the  tw^o  ureters,  which 
intervenes  between  it  and  the  fundus.  The  lateral  borders  extend  from  the  ureters 
to  the  vertex,  and  from  them  the  peritoneum  is  carried  to  the  walls  of  the  pelvis. 
On  either  side  of  the  bladder  the  peritoneum  shows  a  depression,  named  the  para- 
vesical fossa  (Fig.  963).  The  superior  surface  is  directed  upward,  is  covered  by  peri- 
toneum, and  is  in  relation  with  the  sigmoid  colon  and  some  of  the  coils  of  the  small 
intestine.  When  the  bladder  is  empty  and  firmly  contracted,  this  surface  is  convex 
and  the  lateral  and  posterior  borders  are  rounded;  whereas  if  the  bladder  be  relaxed 
it  is  concave,  and  the  interior  of  the  viscus,  as  seen  in  a  median  sagittal  section, 
presents  the  appearance  of  a  V-shaped  slit  with  a  shorter  posterior  and  a  longer 
anterior  limb — the  apex  of  the  V  corresponding  with  the  internal  orifice  of  the 
urethra.  The  inferior  surface  is  directed  downw-ard  and  is  uncovered  by  peritoneum. 
It  may  be  divided  into  a  posterior  or  prostatic  area  and  two  infero-lateral  surfaces. 
The  prostatic  area  is  somewhat  triangular :  it  rests  upon  and  is  in  direct  continuity 
with  the  base  of  the  prostate;  and  from  it  the  urethra  emerges.  The  infero-lateral 
portions  of  the  inferior  surface  are  directed  downward  and  lateralward:  in  front, 
they  are  separated  from  the  symphysis  pubis  by  a  mass  of  fatty  tissue  w^hich  is 
named  the  retropubic  pad;  behind,  they  are  in  contact  with  the  fascia  which  covers 
the  Levatores  ani  and  Obturatores  interni. 

When  the  bladder  is  empty  it  is  placed  entirely  wdthin  the  pelvis,  below  the  level 
of  the  obliterated  hypogastric  arteries,  and  below  the  level  of  those  portions  of  the 
ductus  deferentes  which  are  in  contact  with  the  lateral  wall  of  the  pelvis;  after 
they  cross  the  ureters  the  ductus  deferentes  come  into  contact  with  the  fundus 
of  the  bladder.  As  the  viscus  fills,  its  fundus,  being  more  or  less  fixed,  is  only 
slightly  depressed;  while  its  superior  surface  gradually  rises  into  the  abdominal 
cavity,  carrying  with  it  its  peritoneal  covering,  and  at  the  same  time  rounding 
of?  the  posterior  and  lateral  borders. 

The  Distended  Bladder. — When  the  bladder  is  moderately  full  it  contains 
about  0.5  litre  and  assumes  an  oval  form;  the  long  diameter  of  the  oval  measures 
about  12  cm.  and  is  directed  upward  and  forward.  In  this  condition  it  presents 
a  postero-superior,  an  antero-inferior,  and  two  lateral  surfaces,  a  fundus  and  a 
summit.  The  postero-superior  surface  is  directed  upward  and  backward,  and  is  cov- 
ered by  peritoneum:  behind,  it  is  separated  from  the  rectum  by  the  rectovesical 
excavation,  while  its  anterior  part  is  in  contact  with  the  coils  of  the  small  intestine. 
The  antero-inferior  surface  is  devoid  of  peritoneum,  and  rests,  below,  against  the 
pubic  bones,  above  which  it  is  in  contact  w-ith  the  back  of  the  anterior  abdominal 
w^all.  The  lower  parts  of  the  lateral  surfaces  are  destitute  of  peritoneum,  and  are 
in  contact  with  the  lateral  walls  of  the  pelvis.  The  line  of  peritoneal  reflection 
from  the  lateral  surface  is  raised  to  the  level  of  the  obliterated  hypogastric  artery. 
The  fundus  undergoes  little  alteration  in  position,  being  only  slightly  lowered. 
It  exhibits,  however,  a  narrow  triangular  area,  wdiich  is  separated  from  the  rectum 
merely  by  the  rectovesical  fascia.  This  area  is  bounded  below  by  the  prostate, 
above  by  the  rectovesical  fold  of  peritoneum,  and  laterally  by  the  ductus  deferentes. 
The  ductus  deferentes  frequently  come  in  contact  with  each  other  above  the  pros- 
tate, and  under  such  circumstances  the  loW'Cr  part  of  the  triangular  area  is  obliter- 


1220 


SPLANCHNOLOGY 


ated.  The  line  of  reflection  of  the  peritoneum  from  the  rectum  to  the  bladder 
appears  to  undergo  little  or  no  change  when  the  latter  is  distended;  it  is  situated 
about  10  cm.  from  the  anus.  The  summit  is  directed  u])\vard  and  forward  above 
the  point  of  attachment  of  the  middle  umbilical  ligament,  and  hence  the  peritoneum 
which  follows  the  ligament,  forms  a  pouch  of  varying  depth  between  the  summit 
of  the  bladder,  and  the  anterior  abdominal  wall. 


Saci-um 

Eectum 
Coccyx  ^<:^^ 

Anal  canal' — - 


Symphysis  pubis 
Uteihra 


Fig.   1030. — Sagittal  section  through  the  pelvis  of  a  newly  born  male  child. 

The  Bladder  in  the  Child  (Figs.  1030, 1031).— In  the  newborn  child  the  internal 
urethral  orifice  is  at  the  level  of  the  upper  border  of  the  symphysis  pubis;  the 
bladder  therefore  lies  relatively  at  a  much  higher  level  in  the  infant  than  in  the 


Uterine  tube 


Cavity  of  uterus 
Sigmoid  colon 

Rectum — ^ 


Anal  canal 


Round  ligament  of 

uterus 
Bladder 

Symphysis  pubis 

Urethra 
Vagina 


Fig.   1031. — Sagittal  section  through  the  pelvis  of  a  newly  born  female  child. 

adult.  Its  anterior  surface  "is  in  contact  with  about  the  lower  two-thirds  of  that 
part  of  the  abdominal  wall  which  lies  between  the  symphysis  pubis  and  the  umbili- 
cus" (Symington^).      Its  fundus  is  clothed  with  peritoneum  as  far  as  the  level 

1  The  Anatomj^  of  the  Child. 


THE  URINARY  BLADDER 


1221 


of  tlio  internal  orificr  of  tlio  nrothra.  Althoii<>h  the  l)la(l(ler  of  the  infant  is  usually 
deserihed  as  an  alnioniinal  oryan,  Symington  has  pointed  out  that  only  about 
one-half  of  it  lies  above  the  plane  of  the  superior  aperture  of  the  pelvis.  Disse 
maintains  that  the  internal  urethral  orifice  sinks  rapidly  during  the  first  three 
years,  and  then  more  slowly  until  the  ninth  year,  after  which  it  remains  stationary 
until  puberty,  wlieu  it  again  slowly  descends  and  reaches  its  adult  position. 

The  Female  Bladder  (Fig.  1032). — In  the  female,  the  bladder  is  in  relation 
behind  with  the  uterus  and  tlie  upper  part  of  the  vagina.  It  is  separated  from  the 
anterior  surface  of  the  body  of  the  uterus  by  the  vesicouterine  excavation,  but 
below  the  level  of  this  excavation  it  is  connected  to  the  front  of  the  cervix  uteri 
and  the  upper  part  of  the  anterior  wall  of  the  vagina  by  areolar  tissue.  When 
the  bladder  is  empty  the  uterus  rests  upon  its  superior  surface.  The  female  bladder 
is  said  by  some  to  be  more  capacious  than  that  of  the  male,  but  probably  the 
opposite  is  the  case. 


Sacrum 


Coccyx 

Rectovaginal 
excavation      I       T 
External  tUerine     I       \ 
orifice 


Anal  canal  A 


Fig.   1032. — Median  sagittal  section  of  female  pelvis. 


Ligaments. — The  bladder  is  connected  to  the  pehic  wall  by  the  fascia  endo- 
pelvina.  In  front  this  fascial  attachment  is  strengthened  by  a  few  muscular  fibres, 
the  Pubovesicales,  which  extend  from  the  back  of  the  pubic  bones  to  the  front 
of  the  bladder;  behind,  other  muscular  fibres  run  from  the  fundus  of  the  bladder 
to  the  sides  of  the  rectum,  in  the  sacrogenital  folds,  and  constitute  the  Rectovesicales. 

The  vertex  of  the  bladder  is  joined  to  the  umbilicus  b}'  the  remains  of  the  urachus 
which  forms  the  middle  umbilical  ligament,  a  fibromuscular  cord,  broad  at  its 
attachment  to  the  bladder  but  narrowing  as  it  ascends. 

From  the  superior  surface  of  the  bladder  the  peritoneum  is  carried  off  in  a  series 
of  folds  which  are  sometimes  termed  the  false  ligaments  of  the  bladder.  Anteriorly 
there  are  three  folds:  the  middle  umbilical  fold  on  the  middle  umbilical  ligament, 


1222 


SPLANCHNOLOGY 


and  two  lateral  umbilical  folds  on  the  obliterated  hypogastric  arteries.  The  reflec- 
tions of  the  peritoneum  on  to  the  side  walls  of  the  pelvis  form  the  lateral  false 
ligaments,  while  the  sacrogenital  folds  constitute  posterior  false  ligaments. 

Interior  of  the  Bladder  (Fig.  1033). — The  mucous  membrane  lining  the  bladder 
is,  over  the  greater  part  of  the  viscus,  loosely  attached  to  the  muscular  coat,  and 
appears  wrinkled  or  folded  when  the  bladder  is  contracted:  in  the  distended  condi- 
tion of  the  bladder  the  folds  are  effaced.  Over  a  small  triangular  area,  termed  the 
trigonum  vesicae,  immediately  above  and  behind  the  internal  orifice  of  the  urethra, 
the  mucous  membrane  is  firmly  bound  to  the  muscular  coat,  and  is  always  smooth. 
The  anterior  angle  of  the  trigonum  vesicae  is  formed  by  the  internal  orifice  of  the 
urethra:  its  postero-lateral  angles  by  the  orifices  of  the  ureters.  Stretching  behind 
the  latter  openings  is  a  slightly  curved  ridge,  the  torus  uretericus,  forming  the  base 
of  the  trigone  and  produced  by  an  underlying  bundle  of  non-striped  muscular 

Vertex 


urethral 
orifice 

idae  vesicae 

Trigonum 
vesicae 

Torus 
uretericus 

Orifice  of 
ureter 


Fig.   1033. — The  interior  of  bladder. 


fibres.  The  lateral  parts  of  this  ridge  extend  beyond  the  openings  of  the  ureters, 
and  are  named  the  plicae  uretericae ;  they  are  produced  by  the  terminal  portions  of 
the  ureters  as  they  traverse  obliquely  the  bladder  wall.  When  the  bladder  is 
illuminated  the  torus  uretericus  appears  as  a  pale  band  and  forms  an  important 
guide  during  the  operation  of  introducing  a  catheter  into  the  ureter. 

The  orifices  of  the  ureters  are  placed  at  the  postero-lateral  angles  of  the  trigonum 
vesicae,  and  are  usually  slit-like  in  form.  In  the  contracted  bladder  they  are  about 
2.5  cm.  apart  and  about  the  same  distance  from  the  internal  urethral  orifice;  in 
the  distended  viscus  these  measurements  may  be  increased  to  about  5  cm. 

The  internal  urethral  orifice  is  placed  at  the  apex  of  the  trigonum  vesicae,  in  the 
most  dependent  part  of  the  bladder,  and  is  usually  somewhat  crescentic  in  form; 
the  mucous  membrane  immediately  behind  it  presents  a  slight  elevation,  the 
uvula  vesicae,  caused  by  the  middle  lobe  of  the  prostate. 


THE  URINARY  BLADDER 


1223 


Transitional 
epithelium 

Submucous  coat 


Inner  layer  of 
longitudinal 
vwscle  fibres 


Hrcular  muscle 
fibres 


Outer  layer  of 
longitudinal 
muscle  fibres 


Fig.   1034. — Vertical  section  of  bladder  wall. 


Kr 


Structure  (Fig.  1034).— The  bladder  is  composed  of  the  four  coats:  serous,  muscular,  sub- 
mucous, and  mucous  coats. 

The  serous  coat  (tunica  serosa)  is  a  partial  one,  and  is  derived  from  the  peritoneum.  It  invests 
the  superior  surface  and  the  upper  parts  of  the  lateral  surfaces,  and  is  reflected  from  these  on 
to  the  abdominal  and  pelvic  walls. 

The  muscular  coat  (tunica  muscularis)  consists  of  three  layers  of  unstriped  muscular  fibres: 
an  external  layer,  composed  of  fibres  having  for  the  most  part  a  longitudinal  arrangement;  a 
middle  layer,  in  which  the  fibres  are  arranged,  more 
or  less,  in  a  circular  manner;  and  an  internal  layer, 
in  which  the  fibres  have  a  general  longitudinal  ar- 
rangement. 

The  fibres  of  the  external  layer  arise  from  the  pos- 
terior surface  of  the  body  of  the  pubis  in  both  sexes 
(musculi  pubovesicales) ,  and  in  the  male  from  the 
adjacent  part  of  the  prostate  and  its  capsule. 
Thej'  pass,  in  a  more  or  less  longitudinal  manner,  up 
the  inferior  surface  of  the  bladder,  over  its  vertex, 
and  then  descend  along  its  fundus  to  become  at- 
tached to  the  prostate  in  the  male,  and  to  the  front 
of  the  vagina  in  the  female.  At  the  sides  of  the 
bladder  the  fibres  are  arranged  obliquely  and  inter- 
sect one  another.  This  layer  has  been  named  the 
Detrusor  urinae  muscle. 

The  fibres  of  the  middle  circular  layer  are  very 
thinly  and  irregularly  scattered  on  the  body  of  the 
organ,  and,  although  to  some  extent  placed  trans- 
versely to  the  long  axis  of  the  bladder,  are  for  the 
most  part  arranged  obliquely.  Toward  the  lower 
part  of  the  bladder,  around  the  internal  urethral 
orifice,  thej'  are  disposed  in  a  thick  circular  layer, 
forming  the  Sphincter  vesicae,  which  is  continuous 
with  the  muscular  fibres  of  the  prostate. 

The  internal  longitudinal  layer  is  thin,  and  its 
fasciculi  have  a  reticular  arrangement,  but  with  a 

tendency  to  assume  for  the  most  part  a  longitudinal  direction.  Two  bands  of  oblique  fibres, 
originating  behind  the  orifices  of  the  ureters,  converge  to  the  back  part  of  the  prostate,  and 
are  inserted  by  means  of  a  fibrous  process,  into  the  middle  lobe  of  that  organ.  They  are  the 
muscles  of  the  ureters,  described  by  Sir  C.  Bell,  who  supposed  that  during  the  contraction  of 
the  bladder  they  serve  to  retain  the  oblique  direction  of  the  ureters,  and  so  prevent  the  reflux  of 
the  luine  into  them. 

The  submucous  coat  (tela  submucosa)  consists  of  a  layer  of  areolar  tissue,  connecting  together 
the  muscular  and  mucous  coats,  and  intimately  luiited  to  the  latter. 

The  mucous  coat  (tunica  mucosa)  is  thin,  smooth,  and  of  a  pale  rose  color.  It  is  continuous 
above  through  the  ureters  with  the  lining  membrane  of  the  renal  tubules,  and  below  with  that 
of  the  urethra.  The  loose  texture  of  the  submucous  layer  allows  the  mucous  coat  to  be  thrown 
into  folds  or  rugoe  when  the  bladder  is  empty.  Over  the  trigonum  vesicae  the  mucous  mem- 
brane is  closely  attached  to  the  muscular  coat,  and  is  not  thrown  into  folds,  but  is  smooth  and 
flat.  The  epitheUum  covering  it  is  of  the  transitional  variety,  consisting  of  a  superficial  layer 
of  polyhedral  flattened  cells,  each  with  one,  two,  or  three  nuclei;  beneath  these  is  a  stratum 
of  large  club-shaped  cells,  with  their  narrow  extremities  directed  downward  and  wedged  in 
between  smaller  spindle-shaped  cells,  containing  oval  nuclei  (Fig.  1034).  The  epithelium  varies 
according  as  the  bladder  is  distended  or  contracted.  In  the  former  condition  the  superficial  cells 
are  flattened  and  those  of  the  other  layers  are  shortened;  in  the  latter  they  present  the  appear- 
ance described  above.  There  are  no  true  glands  in  the  mucous  membrane  of  the  bladder,  though 
certain  mucous  follicles  which  exist,  especially  near  the  neck  of  the  bladder,  have  been  regarded 
as  such. 

Vessels  and  Nerves. — The  arteries  supplying  the  bladder  are  the  superior,  middle,  and  inferior 
vesical,  derived  from  the  anterior  trunk  of  the  hypogastric.  The  obturator  and  inferior  gluteal 
arteries  also  supply  small  visceral  branches  to  the  bladder,  and  in  the  female  additional  branches 
are  derived  from  the  uterine  and  vaginal  arteries. 

The  veins  form  a  compHcated  plexus  on  the  inferior  surface,  and  fundus  near  the  prostate,  and 
end  in  the  hypogastric  veins. 

The  lymphatics  are  described  on  page  793. 

The  nerves  of  the  bladder  are  (1)  fine  medullated  fibres  from  the  third  and  fom-th  sacral  nerves, 
and  (2)  non-medullated  fibres  from  the  hypogastric  plexus.  They  are  connected  with  ganglia 
in  the  outer  and  submucous  coats  and  are  finally  distributed,  all  as  non-meduUated  fibres,  to  the 
muscular  layer  and  epitheUal  lining  of  the  viscus. 


1224  SPLANCHNOLOGY 

Applied  Anatomy. — -A  defect  of  development,  in  which  the  bladder  is  implicated,  is  known 
under  the  name  of  extroversion  of  the  bladder.  In  this  condition  the  lower  part  of  the  abdominal 
wall  and  the  anterior  wall  of  the  bladder  are  wanting,  so  that  the  fundus  of  the  bladder  presents 
on  the  abdominal  surface,  and  is  pushed  forward  by  the  pressure  of  the  viscera  within  the  abdomen, 
forming  a  red  vascular  tumor  on  which  the  openings  of  the  ureters  are  visible.  The  penis,  except 
the  glans,  is  rudimentary  and  is  cleft  on  its  dorsal  surface,  exposing  the  floor  of  the  urethra,  a 
condition  known  as  epispadias .    The  pelvic  bones  are  also  arrested  in  development  (see  page  344). 

The  bladder  may  be  ruptured  by  violence  applied  to  the  abdominal  wall,  when  the  viscus  is 
distended,  without  any  injury  to  the  bony  pelvis,  or  it  may  be  torn  in  cases  of  fracture  of  the 
pelvis.  The  rupture  may  be  either  intraperitoneal  or  extraperitoneal:  that  is,  may  implicate 
the  superior  surface  of  the  bladder  in  the  former  case,  or  one  of  the  other  surfaces  in  the  latter. 
Until  recently  intraperitoneal  rupture  was  uniformly  fatal,  but  now  abdominal  section  and 
suturing  the  rent  with  Lembert's  suture  is  resorted  to,  with  a  very  considerable  amount  of  success. 
The  sutures  are  inserted  only  through  the  peritoneal  and  muscular  coats  in  such  a  way  as  to 
bring  the  serous  surfaces  at  the  margins  of  the  wound  into  apposition,  and  one  is  inserted  just 
beyond  each  end  of  the  woimd.  The  bladder  should  be  tested  as  to  whether  it  is  water-tight 
before  closing  the  external  incision. 

The  muscular  coat  of  the  bladder  undergoes  hypertrophy  in  cases  in  which  there  is  any  obstruc- 
tion to  the  flow  of  urine.  Under  these  cii-cumstances  the  bundles  of  which  the  muscular  coat 
consists  become  much  increased  in  size,  and,  interlacing  in  all  directions,  give  rise  to  what  is 
known  as  the  fasciculated  bladder.  Between  these  muscular  bundles  the  mucous  membrane 
may  bulge  out,  forming  sacculi,  constituting  the  sacculated  bladder,  and  in  these  little  pouches 
phosphatic  concretions  may  collect,  forming  encysted  calculi.  The  mucous  membrane  is  very 
loosely  attached,  except  over  the  trigone,  to  allow  of  the  distension  of  the  viscus. 

Various  forms  of  tumor  have  been  found  springing  from  the  wall  of  the  bladder.  The  com- 
monest innocent  tumor  is  the  viUous  papilloma.  Of  the  malignant  tumors,  epithelioma  is  the 
most  common,  but  sarcoma  is  occasionally  found  in  the  bladder  of  children. 

In  doubtful  cases  the  cystoscope  proves  a  valuable  aid  in  diagnosis.  This  instrument  consists 
of  a  tube  in  which  is  fixed  a  small  electric  light,  the  wires  of  which  run  through  the  shaft  of  the 
instrument.  Upon  introducing  this  down  the  urethra,  the  bladder  can  be  examined  with  the  eye 
and  a  viUous  growth  or  other  tumor,  a  calculus,  or  an  ulcer  can  be  detected;  or  the  orifices  of 
the  ureters  can  be  examined,  and  renal  hematuria  diagnosticated,  and  it  can  be  definitely  settled 
from  which  kidney  the  blood  comes.  Again,  the  presence  of  minute  tuberculous  ulceration  near 
the  mouth  of  the  ureter  on  the  affected  side  may  estabhsh  the  diagnosis,  not  only  of  tuberculous 
kidney,  but  also  of  the  side  in  which  the  disease  is  located.  The  cystoscope  can  be  used  to 
catheterize  the  ureter,  for  the  purpose  of  obtaining  a  specimen  of  urine  from  either  kidney,  or  to 
ascertain  the  condition  of  both  kidneys  where  it  is  proposed  to  remove  one.  Ureteric  bougies 
opaque  to  .r-rays  can  be  passed  up  and  photographed. 

Puncture  of  the  bladder  may  be  performed  either  above  the  symphysis  pubis  or  through 
the  rectum,  in  both  cases  without  wounding  the  peritoneum.  The  former  plan  is  generally  to 
be  preferred,  since  in  puncture  by  the  rectum  a  permanent  fistula  may  be  left  from  abscess  forming 
between  the  rectum  and  the  bladder;  or  pelvis  celluhtis  may  be  set  up;  moreover,  it  is  exceedingly 
inconvenient  to  keep  a  cannula  in  the  rectum.  In  some  cases,  in  performing  this  operation  the 
rectovesical  excavation  of  the  peritoneum  has  been  wounded,  inducing  fatal  peritonitis.  Puncture 
through  the  rectum,  therefore,  has  been  almost  completely  abandoned  in  favor  of  the  suprapubic 
route. 

Access  to  the  bladder,  for  the  purpose  of  removing  calculi  or  an  enlarged  prostate,  is  almost 
always  efl'ected  by  the  suprapubic  route,  the  old  perineal  operation  being  now  rarely  resorted 
to.  In  the  female,  owing  to  the  shortness  of  the  urethra,  and  its  ready  dilatabihty,  calculi  and 
foreign  bodies  and  new  growths,  when  of  small  size,  may  be  removed  by  the  urethral  route. 

Suprapubic  cystotomy  is  performed  by  first  injecting  ten  or  twelve  ounces  of  some  weak  anti- 
septic fluid  into  the  bladder.  Then,  with  or  without  distending  the  rectum,  a  vertical  median 
incision,  from  7  to  10  cm.  in  length,  is  made  in  the  hypogastric  region  immediately  above  the 
symphysis,  and  extended  between  the  Pyramidales  and  Recti  until  the  transversalis  fascia  is 
reached.  This  is  divided  and  some  fatty  tissue  exposed  (space  of  Retzius).  Upon  separating 
this,  the  inferior  surface  of  the  bladder  wiU  be  exposed  and  will  be  recognized  by  its  muscular 
fibres.  A  needle  should  be  passed  through  its  coat  on  either  side  of  the  spot  selected  for  the 
opening,  and  two  long  pieces  of  silk  inserted.  The  bladder  is  incised  between  these  stays,  which 
are  held  by  an  assistant  and  form  a  useful  guide  to  the  opening  in  the  bladder  when  the  fluid 
has  escaped. 

It  is  important  that  the  bladder  should  be  emptied  by  catheter  as  a  routine  measure  in  women, 
prior  to  operations  on  the  lower  part  of  the  abdomen  or  pelvis.  Neglect  of  this  precaution  has, 
not  uncommonly,  led  to  that  viscus  being  opened  by  accident.  Women  especially  are  apt  to 
acquire  an  atonic  distension  of  the  bladder,  and  the  fact  that  some  quantity  of  urine  has  been 
passed  immediately  before  operation  is  no  guarantee  that  the  viscus  is  not  distended.  If  the 
accident  should  occur,  the  bladder  wall  must  be  carefuUy  sutured  before  the  peritoneum  is 
opened. 


THE  MALE  URETHRA 


1225 


The  Male  Urethra  (Urethra  Virilis)  (] 


10:^5). 


Urethral  crest 

Openings  of  prostatic  utricle 

atul  ejaculatory  ducts 
Prostatic  joart  of  urethra 

Membranous  part  of  urethra 


The  male  urethra  extends  from  the  internal  nretliral  orifiee  in  the  nrinary  hhulder 
to  the  external  nrethral  orifiee  at  the  end  of  the  i)enis.  It  presents  a  douhle  enrve 
in  the  ordinary  rchixed  state  of  the  penis  (Fig.  1030).  Its  length  varies  from  17.5 
to  20  cm.;  and  it  is  divided  into  three  portions,  the  prostatic,  membranous,  and 
cavernous,  the  strneture  and  rela- 
tions of  which  are  essentially  Bladder 
difterent.  Except  during  the 
passage  of  the  urine  or  semen, 
the  greater  part  of  the  urethral 
canal  is  a  mere  transverse  cleft 
or  slit,  with  its  upper  and  under 
surfaces  in  contact;  at  the  external 
orifice  the  slit  is  vertical,  in  the 
membranous  portion  irregular  or 
stellate,  and  in  the  prostatic  por- 
tion somewhat  arched. 

The  prostatic  portion  {pars  pros- 
taiica),  the  widest  and  most  dila- 
table part  of  the  canal,  is  about 
3  cm.  long,  It  runs  almost  ver- 
tically through  the  prostate  from 
its  base  to  its  apex,  lying  nearer 
its  anterior  than  its  posterior 
surface;  the  form  of  the  canal 
is  spindle-shaped,  being  wilder  in 
the  middle  than  at  either  extrem- 
ity, and  narrowest  below,  where 
it  joins  the  membranous  portion. 
A  transverse  section  of  the  canal 
as  it  lies  in  the  prostate  is  horse- 
shoe-shaped, with  the  convexity 
directed  forward. 

Upon  the  posterior  wall  or 
floor  is  a  narrow^  longitudinal 
ridge,  the  urethral  crest  {veru- 
montanum),  formed  by  an  eleva- 
tion of  the  mucous  membrane 
and  its  subjacent  tissue.  It  is 
from  15  to  17  mm.  in  length, 
and  about  3  mm.  in  height,  and 

contains,  according  to  Kobelt,  muscular  and  erectile  tissue.  When  distended, 
it  may  serve  to  prevent  the  passage  of  the  semen  backward  into  the  bladder. 
On  either  side  of  the  crest  is  a  slightly  depressed  fossa,  the  prostatic  sinus,  the  floor 
of  which  is  perforated  by  numerous  apertures,  the  orifices  of  the  prostatic  ducts 
from  the  lateral  lobes  of  the  prostate;  the  ducts  of  the  middle  lobe  open  behind 
the  crest.  At  the  forepart  of  the  urethral  crest,  below  its  summit,  is  a  median 
elevation,  the  colliculus  seminalis,  upon  or  within  the  margins  of  which  are  the 
orifices  of  the  prostatic  utricle  and  the  slit-like  openings  of  the  ejaculatory  ducts. 
The  prostatic  utricle  {sinus  pocularis)  forms  a  cul-de-sac  about  6  mm.  long,  which 
runs  upward  and  backward  in  the  substance  of  the  prostate  behind  the  middle 
lobe.    Its  w^alls  are  composed  of  fibrous  tissue,   muscular  fibres,   and    mucous 


Small  lacwia 


Lacuna  magna 


Ext  111 ethal  onfice 


Fig.   1035. — The  male  urethra  laid  open  on  its  anterior  (upper) 
surface. 


1226  SPLANCHNOLOGY 

membrane,  and  numerous  small  glands  open  on  its  inner  surface.  It  was  called 
by  Weber  the  uterus  masculinus,  from  its  being  developed  from  the  united 
lower  ends  of  the  atrophied  jMiillerian  ducts,  and  therefore  homologous  with  the 
uterus  and  vagina  in  the  female. 

The  membranous  portion  (pars  membranacea)  is  the  shortest,  least  dilatable, 
and,  with  the  exception  of  the  external  orifice,  the  narrowest  part  of  the  canal. 
It  extends  downward  and  forward,  with  a  slight  anterior  concavity,  between  the 
apex  of  the  prostate  and  the  bulb  of  the  urethra,  perforating  the  urogenital  dia- 
phragm about  2.5  cm.  below  and  behind  the  pubic  symphysis.  The  hinder  part 
of  the  urethral  bulb  lies  in  apposition  with  the  inferior  fascia  of  the  urogenital 
diaphragm,  but  its  upper  portion  diverges  somew^hat  from  this  fascia :  the  anterior 
wall  of  the  membranous  urethra  is  thus  prolonged  for  a  short  distance  in  front 
of  the  urogenital  diaphragm;  it  measures  about  2  cm.  in  length,  while  the  posterior 
wall  which  is  between  the  two  fasciae  of  the  diaphragm  is  only  1.25  cm.  long. 

The  membranous  portion  of  the  urethra  is  completely  surrounded  by  the  fibres 
of  the  Sphincter  urethrae  membranaceae.  In  front  of  it  the  deep  dorsal  vein  of 
the  penis  enters  the  pelvis  between  the  transverse  ligament  of  the  pelvis  and  the 
arcuate  pubic  ligament;  on  either  side  near  its  termination  are  the  bulbourethral 
glands. 

The  cavernous  portion  {pars  cavernosa;  penile  or  spongy  portion)  is  the  longest 
part  of  the  urethra,  and  is  contained  in  the  corpus  cavernosum  urethrae.  It  is 
about  15  cm.  long,  and  extends  from  the  termination  of  the  membranous  portion 
to  the  external  urethral  orifice.  Commencing  below  the  inferior  fascia  of  the 
urogenital  diaphragm  it  passes  forward  and  upward  to  the  front  of  the  symphysis 
pubis;  and  then,  in  the  flaccid  condition  of  the  penis,  it  bends  downward  and 
forward.  It  is  narrow,  and  of  uniform  size  in  the  body  of  the  penis,  measur- 
ing about  6  mm.  in  diameter;  it  is  dilated  behind,  within  the  bulb,  and  again 
anteriorly  within  the  glans  penis,  where  it  forms  the  fossa  navicularis  urethrae. 

The  external  urethral  orifice  (orificium  urethrae  externum;  meatus  urinarius)  is 
the  most  contracted  part  of  the  urethra;  it  is  a  vertical  slit,  about  6  mm.  long, 
bounded  on  either  side  by  two  small  labia. 

The  lining  membrane  of  the  urethra,  especially  on  the  floor  of  the  cavernous 
portion,  presents  the  orifices  of  numerous  mucous  glands  and  follicles  situated 
in  the  submucous  tissue,  and  named  the  urethral  glands  (Littre).  Besides  these 
there  are  a  number  of  small  pit-like  recesses,  or  lacunae,  of  varying  sizes.  Their 
orifices  are  directed  forward,  so  that  they  may  easily  intercept  the  point  of  a 
catheter  in  its  passage  along  the  canal.  One  of  these  lacunae,  larger  than  the  rest, 
is  situated  on  the  upper  surface  of  the  fossa  navicularis;  it  is  called  the  lacuna 
magna.  The  bulbo-urethral  glands  open  into  the  cavernous  portion  about  2.5  cm. 
in  front  of  the  inferior  fascia  of  the  urogenital  diaphragm. 

Structure. — The  urethra  is  composed  of  mucous  membrane,  supported  by  a  submucous  tissue 
which  connects  it  with  the  various  structures  through  which  it  passes. 

The  mucous  coat  forms  part  of  the  genito-iuinary  mucous  membrane.  It  is  continuous  with 
the  mucous  membrane  of  the  bladder,  ureters,  and  kidneys;  externally,  with  the  integument 
covering  the  glans  penis;  and  is  prolonged  into  the  ducts  of  the  glands  which  open  into  the  urethra, 
viz.,  the  bulbo-urethral  glands  and  the  prostate;  and  into  the  ductus  deferentes  and  vesiculae 
seminales,  through  the  ejaculatory  ducts.  In  the  cavernous  and  membranous  portions  the  mucous 
membrane  is  arranged  in  longitudinal  folds  when  the  tube  is  empty.  Small  papillae  are  found 
upon  it,  near  the  external  iu:ethral  orifice;  its  epithehal  Uning  is  of  the  columnar  variety  except 
near  the  external  orifice,  where  it  is  squamous  and  stratified. 

The  submucous  tissue  consists  of  a  vascular  erectile  layer;  outside  this  is  a  layer  of  unstriped 
muscular  fibres,  arranged  in  a  circular  direction,  which  separates  the  mucous  membrane  and 
submucous  tissue  from  the  tissue  of  the  corpus  cavernosum  urethrae. 

Applied  Anatomy. — The  urethra  may  be  ruptured  by  the  patient  falling  astride  of  any  hard 
substance  and  striking  his  perineum,  so  that  the  urethra  is  crushed  against  the  pubic  arch. 
Bleeding  will  at  once  take  place  from  the  urethra,  and  this,  together  with  the  bruising  in  the 


THE  MALE  URETHRA  1227 

perineum  and  the  history  of  the  accident,  will  point  to  the  nature  of  the  injury.  Rupture  of 
the  urethra  is  due  in  other  cases  to  the  perforation  of  a  periurethral  abscess.  Extravasation  of 
urine  most  fretpiontly  takes  place  into  the  perineum  in  front  of  the  inferior  fascia  of  the  urogenital 
diaphragm,  i.  e.,  under  the  fascia  of  CoUes.  Hoth  these  layers  of  fascia  are  attached  firndy  to 
the  ischiopuhic  rami.  It  is  clear,  therefore,  that  when  extravasation  of  fluid  takes  place  between 
them,  it  cannot  pass  backward,  because  the  two  layers  are  continuous  with  each  other  around 
the  Transversus  pcrinaei  muscles;  it  cannot  extend  laterally,  on  account  of  the  connection  of 
both  these  layers  to  the  rami  of  the  pubis  and  ischium;  it  cannot  find  its  way  into  the  pelvis, 
because  the  opening  info  this  cavity  is  closed  by  the  m-ogenital  diaphragm,  and,  therefore,  so 
long  as  these  two  layers  remain  intact,  the  only  direction  in  which  the  fluid  can  make  its  way 
is  forward  into  the  areolar  tissue  of  the  scrotum  and  penis,  and  thence  on  to  the  anterior  wall  of 
the  abdomen. 

Gonorrhtva  is  an  acute  and  very  prevalent  inflammatory  infection  of  the  mucous  membrane 
of  the  urethra.  The  causative  organisms  (gonococci)  pass  through  the  mucous  membrane  into 
the  submucous  tissue,  and  most  serious  complications  and  results  may  follow.  In  most  cases 
the  disease  remains  limited  to  the  part  of  the  urethra  in  front  of  the  urogenital  diaphragm,  but 
in  some  (about  10  per  cent.)  the  "posterior  urethra"  becomes  involved  in  the  process,  leading  to 
an  inflanunation  of  the  openings  of  the  prostatic  foUiclcs.  Such  a  condition  is  apt  to  continue 
as  a  very  chronic  form  of  prostatitis,  and  in  many  cases  the  infection  will  spread  along  the  ductus 
deferens,  giving  rise  to  epididymitis. 

The  anatomy  of  the  urethra  is  of  considerable  importance  in  connection  with  the  passage  of 
instrmnents  into  the  bladder.  Otis  was  the  first  to  point  out  that  the  urethra  is  capable  of  great 
dilatability,  so  that,  excepting  through  the  external  urethral  orifice,  an  instrument  corresponding 
to  IS  EngUsh  gauge  (29  French)  can  usually  be  passed  without  damage.  The  external  orifice 
of  the  m-etlii-a  is  not  so  dilatable,  and  therefore  may  require  slitting.  A  recognition  of  this  dila- 
tabiUty  caused  Bigelow  to  very  considerably  modify  the  operation  for  crushing  a  stone  in  the 
bladder.  In  passing  catheters,  especially  fine  ones,  the  point  of  the  instrument  should  be  kept 
as  far  as  possible  along  the  upper  wall  of  the  canal,  as  otherwise  it  is  very  liable  to  enter  one  of 
the  lacunae. 

Strictm-e  of  the  urethi-a  is  a  disease  of  very  common  occurrence,  and  is  generally  situated  in 
the  cavernous  part  of  the  urethra,  just  in  front  of  the  membranous  portion,  but  in  a  very  con- 
siderable number  of  cases  in  the  antescrotal  part  of  the  canal.  The  stricture  usually  results  from 
the  contraction  of  inflammatory  products  in  the  submucous  tissue,  the  result,  in  the  vast  majority 
of  all  cases,  of  a  prolonged  gleet  following  gonorrhoea.  Urethral  stricture,  however,  follows 
ruptm-e  of  that  tube  resulting  from  falls  on  the  perineum,  and  in  this  variety  is  very  dense, 
and  is  a  most  unsatisfactory  condition  with  regard  to  treatment.  Congenital  stricture  is  also 
occasionally  met  with,  and  in  such  cases  multiple  strictures  may  be  present  throughout  the 
whole  length  of  the  cavernous  portion. 

Congenital  defects  of  the  urethra  occur  occasionally.  The  one  most  frequently  met  with  is 
where  there  is  a  cleft  on  the  floor  of  the  urethra  owing  to  an  arrest  of  union  in  the  middle  line. 
This  is  known  as  hypospadias,  and  the  cleft  may  vary  in  extent.  The  simplest  and  by  far  the 
most  common  form  is  where  the  deficiency  is  confined  to  the  glans  penis.  The  urethra  ends  at 
the  point  where  the  extremity  of  the  prepuce  joins  the  body  of  the  penis,  in  a  small  valve-Uke 
opening.  The  prepuce  is  also  cleft  on  its  under  surface  and  forms  a  sort  of  hood  over  the  glans. 
There  is  a  depression  on  the  glans  in  the  position  of  the  normal  meatus.  This  condition  produces 
no  disabihty  and  requires  no  treatment.  In  more  severe  cases  the  cavernous  portion  of  the 
urethra  is  cleft  thi-oughout  its  entire  length,  and  the  opening  of  the  urethra  is  at  the  point  of 
junction  of  the  penis  and  scrotum.  The  under  surface  of  the  penis  in  the  middle  fine  presents  a 
fm-row  lined  by  a  moist  mucous  membrane,  on  either  side  of  which  is  often  more  or  less  dense 
fibrous  tissue  stretching  from  the  glans  to  the  opening  of  the  urethra,  which  prevents  conaplete 
erection  taking  place.  Great  discomfort  is  induced  during  micturition,  and  sexual  connection  is 
impossible.  The  condition  may  be  remedied  by  a  series  of  plastic  operations.  The  worst  form 
of  this  condition  is  where  the  urethra  is  deficient  as  far  back  as  the  perineum,  and  the  scrotum 
is  cleft.  The  penis  is  small  and  bound  down  between  the  two  halves  of  the  scrotum,  so  as  to 
resemble  an  hypertrophied  clitoris.  The  testes  are  often  retained.  The  condition  of  parts, 
therefore,  very  much  resembles  the  exi;ernal  organs  of  generation  of  the  female,  and  many  chil- 
dren the  victims  of  this  malformation  have  been  brought  up  as  girls.  The  halves  of  the  scrotum, 
deficient  of  testes,  resemble  the  labia,  the  cleft  between  them  looks  Hke  the  orifice  of  the  vagina, 
and  the  diminutive  penis  is  taken  for  an  enlarged  cUtoris.    There  is  no  remedy  for  this  condition. 

A  much  more  uncommon  form  of  malformation  is  where  there  is  an  apparent  deficiency  of  the 
upper  wall  of  the  urethra;  this  is  named  epispadias.  The  deficiency  may  vary  in  extent;  when 
it  is  complete  the  condition  is  associated  with  extroversion  of  the  bladder.  In  less  extensive  cases, 
where  there  is  no  extroversion,  there  is  an  infundibuliform  opening  into  the  bladder.  The 
penis  is  usually  dwarfed  and  turned  upward,  so  that  the  glans  Ues  over  the  opening. 


1228  SPLANCHNOLOGY 

The  Female  Urethra  (Urethra  Muliebris)  (Fig.  1032). 

The  female  urethra  is  a  narrow  membranous  canal,  about  4  cm.  long,  extending 
from  the  internal  to  the  external  urethral  orifice.  It  is  placed  behind  the  sym- 
physis pubis,  imbedded  in  the  anterior  wall  of  the  vagina,  and  its  direction  is  ob- 
liquely downward  and  forward;  it  is  slightly  curved  with  the  concavity  directed 
forward.  Its  diameter  when  undilated  is  about  6  mm.  It  perforates  the  fasciae 
of  the  urogenital  diaphragm,  and  its  external  orifice  is  situated  directly  in  front 
of  the  vaginal  opening  and  about  2.5  cm.  behind  the  glans  clitoridis.  The  lining 
membrane  is  thrown  into  longitudinal  folds,  one  of  which,  placed  along  the  floor 
of  the  canal,  is  termed  the  urethral  crest.  ]Many  small  urethral  glands  open  into 
the  urethra. 

Structiire. — The  urethra  consists  of  three  coats:   muscular,  erectile,  and  mucous. 

The  muscular  coat  is  continuous  with  that  of  the  bladder;  it  extends  the  whole  length  of  the 
tube,  and  consists  of  circular  fibres.  In  addition  to  this,  between  the  superior  and  inferior  fasciee 
of  the  urogenital  diaphragm,  the  female  urethra  is  surrounded  by  the  Sphincter  urethrse  mem- 
branaceae,  as  in  the  male. 

A  thin  layer  of  spongy  erectile  tissue,  containing  a  plexus  of  large  veins,  intermixed  with 
bundles  of  unstriped  muscular  fibres,  lies  immediately  beneath  the  mucous  coat. 

The  mucous  coat  is  pale;  it  is  continuous  externally  with  that  of  the  AOilva,  and  internally  with 
that  of  the  bladder.  It  is  hned  by  stratified  squamous  epitheUum,  which  becomes  transitional 
near  the  bladder.    Its  external  orifice  is  surrounded  by  a  few  mucous  folUcles. 


THE   MALE    GENITAL    ORGANS   (ORGANA   GENITALIA   VIRILIA). 

The  male  genitals  include  the  testes,  the  ductus  deferentes,  the  vesiculae  semi- 
nales,  the  ejaculatory  ducts,  and  the  penis,  together  with  the  following  accessory 
structures,  viz.,  the  prostate  and  the  bulbourethral  glands. 

The  Testes  and  Their  Coverings  (Fig.  1036). 

The  testes  are  two  glandular  organs,  which  secrete  the  semen ;  they  are  suspended 
in  the  scrotum  by  the  spermatic  cords.  At  an  early  period  of  fetal  life  the  testes 
are  contained  in  the  abdominal  cavity,  behind  the  peritoneum.  Before  birth  they 
descend  to  the  inguinal  canal,  along  which  they  pass  with  the  spermatic  cord, 
and,  emerging  at  the  subcutaneous  inguinal  ring,  they  descend  into  the  scrotum, 
becoming  invested  in  their  course  by  coverings  derived  from  the  serous,  muscular, 
and  fibrous  layers  of  the  abdominal  parietes,  as  well  as  by  the  scrotum. 

The  coverings  of  the  testes  are,  the 

Dartos  tunic  /  Scrotum.  Infundibuliform  fascia. 

Intercrural  fascia.  ■  Tunica  vaginalis. 

The  Scrotum  is  a  cutaneous  pouch  wdiich  contains  the  testes  and  parts  of  the 
spermatic  cords.  It  is  divided  on  its  surface  into  two  lateral  portions  by  a  ridge 
or  raphe,  which  is  continued  forward  to  the  under  surface  of  the  penis,  and  backward, 
along  the  middle  line  of  the  perineum  to  the  anus.  Of  these  two  lateral  portions 
the  left  hangs  lower  than  the  right,  to  correspond  with  the  greater  length  of  the 
left  spermatic  cord.  Its  external  aspect  varies  under  different  circumstances: 
thus,  under  the  influence  of  warmth,  and  in  old  and  debilitated  persons,  it  becomes 
elongated  and  flaccid;  but,  under  the-  influence  of  cold,  and  in  the  young  and 
robust,  it  is  short,  corrugated,  and  closely  applied  to  the  testes. 

The  scrotum  consists  of  two  layers,  the  integument  and  the  dartos  tunic. 

The  Integument  is  very  thin,  of  a  brownish  color,  and  generally  thrown  into 
folds  or  rugse.    It  is  provided  with  sebaceous  follicles,  the  secretion  of  which  has  a 


THE  TESTES  AND  THEIR  COVERINGS 


1229 


peculiar  ucIdf,  iiiul  is  beset  with  thinly  scattered,  crisp  hairs,  the  ro(>ts  of  which 
are  seen  through  the  skin. 

The  Dartos  Tunic  (tunica  darton)  is  a  thin  layer  of  non-striped  muscular  fibres, 
continuous,  around  the  base  of  the  scrotum,  with  the  two  layers  of  the  superficial 
fascia  of  the  groin  and  the  perineum;  it  sends  inward  a  septum,  which  divides 
the  scrotal  pouch  into  two  cavities  for  the  testes,  and  extends  betw'een  the  raphe 
and  the  under  surface  of  the  penis,  as  far  as  its  root. 

The  dartos  tunic  is  closely  united  to  the  skin  externally,  but  connected  with 
the  subjacent  parts  by  delicate  areolar  tissue,  upon  which  it  glides  with  the 
greatest  facility. 


Skill 

Dartog  tunic 

fntercru  ml  fascia 

Crem  ai;teric  fascia 

I  nfttndibuliform  fascia 

Parietal  tunica  vaginalis 

Visceral  tunica  vaginal/ •> 

Tunica  allnigmca 
A  lobtile  (if  the  teiti^ 


A  sex>tum 

Mediastinum  testis 

Sinus  of  epididymis 

Spermatic  xem 

Epididymis 

Ductus  dejeiens 

Artery  to  ductus 

Internal  spermatic  artci  y 

Internal  muscular  tunic 


Fig.   1036. — Transverse  section  through  the  left  side  of  the  scrotum  and  the  left  testis.     The  sac  of  the  tunica 
vaginalis  is  represented  in  a  distended  condition.     (Diagrammatic.)     (Del^pine.) 

The  Intercmral  Fascia  (intercolumnar  or  external  spermatic  fascia)  is  a  thin 
membrane,  prolonged  downward  around  the  surface  of  the  cord  and  testis  (see 
page  501).    It  is  separated  from  the  dartos  tunic  by  loose  areolar  tissue. 

The  Cremaster  consists  of  scattered  bundles  of  muscular  fibres  connected 
together  into  a  continuous  covering  by  intermediate  areolar  tissue  (see  page  504). 

The  Infundibuliform  Fascia  (tunica  vaginalis  communis  [testis  et  funiculi  sper- 
matid]) is  a  thin  layer,  which  loosely  invests  the  cord;  it  is  a  continuation 
dow^nward  of  the  transversalis  fascia  (see  page  508). 

The  Tunica  Vaginalis  is  described  with  the  testes. 

Vessels  and  Nerves. — The  arteries  supplying  the  coverings  of  the  testes  are:  the  superficial 
and  deep  external  pudendal  branches  of  the  femoral,  the  superficial  perineal  branch  of  the 
internal  pudendal,  and  the  cremasteric  branch  from  the  inferior  epigastric.  The  veins  follow 
the  course  of  the  corresponding  arteries.  The  lymphatics  end  in  the  inguinal  Ijonph  glands. 
The  nerves  are  the  ihoinguinal  and  lumboinguinal  branches  of  the  lumbar  plexus,  the  two 
superficial  perineal  branches  of  the  internal  pudendal  nerve,  and  the  pudendal  branch  of  the 
posterior  femoral  cutaneous  nerve. 

The  Inguinal  Canal  (canalis  inguinalis)  is  described  on  page  508. 

The  Spermatic  Cord  (funiculus  spermaticus)  extends  from  the  abdominal 
inguinal  ring,  where  the  structures  of  which  it  is  composed  converge,  to  the  back 
part  of  the  testis.  In  the  abdominal  wall  the  cord  passes  obliquely  along  the 
inguinal  canal,  lying  at  first  beneath  the  Obliquus  internus,  and  upon  the  fascia 


1230  SPLANCHNOLOGY 

transversalis;  but  nearer  the  pubis,  it  rests  upon  the  inguinal  and  lacunar  liga- 
ments, having  the  aponeurosis  of  the  Obliquus  externus  in  front  of  it,  and  the 
inguinal  falx  behind  it.  It  then  escapes  at  the  subcutaneous  ring,  and  descends 
nearly  vertically  into  the  scrotum.  The  left  cord  is  rather  longer  than  the  right, 
consequently  the  left  testis  hangs  somewhat  lower  than  its  fellow. 

Structure  of  the  Spermatic  Cord.- — The  spermatic  cord  is  composed  of  arteries,  veins,  lymphatics, 
nerves,  and  the  excretory  duct  of  the  testis.  These  structures  are  connected  together  by  areolar 
tissue,  and  invested  by  the  layers  brought  down  by  the  testis  in  its  descent. 

The  arteries  of  the  cord  are :  the  internal  and  external  spermatics ;  and  the  artery  to  the  ductus 
deferens. 

The  internal  s-permatic  artery,  a  branch  of  the  abdominal  aorta,  escapes  from  the  abdomen 
at  the  abdominal  inguinal  ring,  and  accompanies  the  other  constituents  of  the  spermatic  cord 
along  the  inguinal  canal  and  through  the  subcutaneous  inguinal  ring  into  the  scrotum.  It  then 
descends  to  the  testis,  and,  becoming  tortuous,  divides  into  several  branches,  two  or  three  of 
which  accompany  the  ductus  deferens  and  supply  the  epididymis,  anastomosing  with  the  artery 
of  the  ductus  deferens:  the  others  supply  the  substance  of  the  testis. 

The  external  spermatic  artery  is  a  branch  of  the  inferior  epigastric  artery.  It  accompanies  the 
spermatic  cord  and  suppUes  the  coverings  of  the  cord,  anastomosing  with  the  internal  spermatic 
artery. 

The  artery  of  the  ductus  deferens,  a  branch  of  the  superior  vesical,  is  a  long,  slender  vessel,  which 
accompanies  the  ductus  deferens,  ramifying  upon  its  coats,  and  anastomosing  with  the  internal 
spermatic  artery  near  the  testis. 

The  spermatic  veins  emerge  from  the  back  of  the  testis,  and  receive  tributaries  from  the  epi- 
didymis: they  unite  and  form  a  convoluted  plexus,  the  plexus  pampiniformis,  which  forms  the 
chief  mass  of  the  cord;  the  vessels  composing  this  plexus  are  very  numerous,  and  ascend  along 
the  cord  in  front  of  the  ductus  deferens;  below  the  subcutaneous  inguinal  ring  they  unite  to  form 
three  or  four  veins,  which  pass  along  the  inguinal  canal,  and,  entering  the  abdomen  through  the 
abdominal  inguinal  ring,  coalesce  to  form  two  veins.  These  again  unite  to  form  a  single  vein, 
which  opens  on  the  right  side  into  the  inferior  vena  cava,  at  an  acute  angle,  and  on  the  left  side 
into  the  left  renal  vein,  at  a  right  angle. 

The  lymphatic  vessels  are  described  on  page  794. 

The  nerves  are  the  spermatic  plexus  from  the  sympathetic,  joined  by  filaments  from  the  pelvic 
plexus  which  accompany  the  artery  of  the  ductus  deferens. 

Applied  Anatomy. — The  scrotum  forms  an  admirable  covering  for  the  protection  of  the  testes. 
These  bodies,  lying  suspended  and  loose  in  the  cavity  of  the  scrotima  and  svirrounded  by  serous 
membrane,  are  capable  of  great  mobility,  and  can  therefore  easily  shp  about  within  the  scrotum 
and  thus  avoid  injuries  from  blows  or  squeezes.  The  skin  of  the  scrotum  is  very  elastic  and 
capable  of  great  distension,  and  on  accoimt  of  the  looseness  and  amount  of  subcutaneous  tissue, 
the  scrotum  becomes  greatly  enlarged  in  cases  of  oedema,  to  which  this  part  is  especially  liable 
as  a  result  of  its  dependent  position.  The  scrotum  is  occasionally  the  seat  of  epithehoma;  this  is 
no  doubt  due  to  the  rugae  on  its  sm-face,  which  favor  the  lodgement  of  dirt,  and  this,  producing 
irritation,  is  the  exciting  cause  of  the  disease.  The  disease  is  very  much  less  common  than  it 
used  to  be;  this  is  probably  due  to  the  better  hygienic  conditions  of  the  working  classes.  The 
scrotum  is  also  the  part  most  frequently  affected  by  elephantiasis. 

On  accoimt  of  the  looseness  of  the  subcutaneous  tissue,  large  extravasations  of  blood  may  take 
place  from  very  sUght  injuries.  It  is  therefore  generally  recommended  never  to  apply  leeches  to 
the  scrotum,  since  they  may  lead  to  ecchymosis,  but  rather  to  puncture  one  or  more  of  the  super- 
ficial veins  of  the  scrotum  in  cases  where  local  blood-letting  from  this  part  is  judged  to  be  desirable. 
The  muscular  fibre  in  the  dartos  tunic  causes  contraction  and  considerable  diminution  in  the  size 
of  a  wound  of  the  scrotima,  as  after  the  operation  of  castration,  and  are  of  assistance  in  keeping 
the  edges  together,  and  covering  the  exposed  parts. 

The  Testes  are  suspended  in  the  scrotum  by  the  spermatic  cords,  the  left  testis 
hanging  somewhat  lower  than  its  fellow.  The  average  dimensions  of  the  testis 
are  from  4  to  5  cm.  in  length,  2.5  cm.  in  breadth,  and  3  cm.  in  the  antero-posterior 
diameter;  its  weight  varies  from  10.5  to  14  gm.  Each  testis  is  of  an  oval  form 
(Fig.  1037),  compressed  laterally,  and  having  an  oblique  position  in  the  scrotum; 
the  upper  extremity  is  directed  forward  and  a  little  lateralward;  the  lower, 
backward  and  a  little  medialward;  the  anterior  convex  border  looks  forward  and 
downward,  the  posterior  or  straight  border,  to  which  the  cord  is  attached, 
backward  and  upward. 

The  anterior  border  and  lateral  surfaces,  as  well  as  both  extremities  of  the  organ. 


THE  TESTES  AM)  Til  KIR  COY  E  RINGS 


]2;]i 


are  convex,  free,  smooth,  aiul  invested  by  the  \'iscenil  hiyer  ol'  the  tunica  ^•^l<;■inalis. 
The  posterior  border,  to  which  the  cord  is  attached,  receives  only  a  partial  invest- 
ment from  that  membrane.  Lying  upon  the  hiteral  edge  of  this  posterior  border 
is  a  long,  narrow,  flattened  body,  named  the  epididymis. 

The  epididymis  consists  of  a  central  portion  or  body;  an  upper  enlarged  extremity, 
the  head  {(/lobits  major);  and  a  lower  pointed  extremity,  the  tail  (globus  minor), 
which  is  continuous  with  the  ductus  deferens,  the  duct  of  the  testis.  The  head 
is  intimately  connected  with  the  upper  end  of  the  testis  by  means  of  the  efferent 
ductules  of  the  gland;  the  tail  is  connected  with  the  lower  end  by  cellular  tissue, 
and  a  reflection  of  the  tunica  vaginalis.  The  lateral  surface,  head  and  tail  of  the 
epididymis  are  free  and  covered  by  the  serous  membrane;  the  body  is  also  com- 
pletely invested  by  it,  excepting  along  its  posterior  border;  while  between  the 
body  and  the  testis  is  a  pouch,  named  the  sinus  of  the  epididymis  (digital  fossa). 
The  epididymis  is  connected  to  the  back  of  the  testis  by  a  fold  of  the  serous 
membrane. 


Tail  of 
epididymis 


Cremaster 

Tunica  vaginalis 

Appendix  of  epididymis 
Head  of  epididymis 

Appeyidix  of  testis 


Fig.   1037. — The  right  testis,  exposed  by  laying  open  the  tunica  vaginalis. 


Appendages  of  the  Testis  and  Epididymis. — On  the  upper  extremity  of  the  testis, 
just  beneath  the  head  of  the  epididymis,  is  a  minute  oval,  sessile  body,  the  appendix 
of  the  testis  (hydatid  of  Morgagni) ;  it  is  the  remnant  of  the  upper  end  of  the  Miillerian 
duct.  On  the  head  of  the  epididymis  is  a  second  small  stalked  appendage  (some- 
times duplicated) ;  it  is  named  the  appendix  of  the  epididymis  (^pedunculated  hydatid), 
and  is  usually  regarded  as  a  detached  eft'erent  duct. 

The  testis  is  invested  by  three  tunics:  the  tunica  vaginalis,  tunica  albuginea, 
and  tunica  vasculosa. 

The  Tunica  Vaginalis  (tunica  vaginalis  propria  testis)  is  the  serous  covering  of 
the  testis.  It  is  a  pouch  of  serous  membrane,  derived  from  the  saccus  vaginalis 
of  the  peritoneum,  which  in  the  fetus  preceded  the  descent  of  the  testis  from  the 
abdomen  into  the  scrotum.  After  its  descent,  that  portion  of  the  pouch  which 
extends  from  the  abdominal  inguinal  ring  to  near  the  upper  part  of  the  gland 
becomes  obliterated;  the  lower  portion  remains  as  a  shut  sac,  which  invests  the 
surface  of  the  testis,  and  is  reflected  on  to  the  internal  surface  of  the  scrotum; 
hence  it  may  be  described  as  consisting  of  a  visceral  and  parietal  lamina. 

The  visceral  lamina  (lamina  visceralis)  covers  the  greater  part  of  the  testis  and 
epididymis,  connecting  the  latter  to  the  testis  by  means  of  a  distinct  fold.    From 


1232  SPLANCHNOLOGY 

the  posterior  border  of  the  gland  it  is  reflected  on  to  the  internal  surface  of  the 
scrotum. 

The  parietal  lamina  {laviina  iMrietalis)  is  far  more  extensive  than  the  visceral, 
extending  upward  for  some  distance  in  front  and  on  the  medial  side  of  the  cord, 
and  reaching  below  the  testis.  The  inner  surface  of  the  tunica  vaginalis  is 
smooth,  and  covered  by  a  layer  of  endothelial  cells.  The  interval  between  the 
visceral  and  parietal  laminae  constitutes  the  cavity  of  the  tunica  vaginalis. 

The  obliterated  portion  of  the  saccus  vaginalis  may  generalh'  be  seen  as  a  fibro- 
cellular  thread  lying  in  the  loose  areolar  tissue  around  the  spermatic  cord;  some- 
times this  may  be  traced  as  a  distinct  band  from  the  upper  end  of  the  inguinal 
canal,  where  it  is  connected  with  the  peritoneum,  down  to  the  tunica  vaginalis; 
sometimes  it  gradually  becomes  lost  on  the  spermatic  cord.  Occasionally  no  trace 
of  it  can  be  detected.  In  some  cases  it  happens  that  the  pouch  of  peritoneum  does 
not  become  obliterated,  but  the  sac  of  the  peritoneum  communicates  with  the 
tunica  vaginalis.  This  may  give  rise  to  one  of  the  varieties  of  oblique  inguinal 
hernia  (page  1187).  In  other  cases  the  pouch  may  contract,  but  not  become 
entirely  obliterated;  it  then  forms  a  minute  canal  leading  from  the  peritoneum  to 
the  tunica  vaginalis. 

The  Tunica  Albuginea  is  the  fibrous  covering  of  the  testis.  It  is  a  dense  membrane, 
of  a  bluish-white  color,  composed  of  bundles  of  white  fibrous  tissue  which  interlace 
in  every  direction.  It  is  covered  by  the  tunica  vaginalis,  except  at  the  points  of 
attachment  of  the  epididjTnis  to  the  testis,  and  along  its.  posterior  border,  where 
the  spermatic  vessels  enter  the  gland.  It  is  applied  to  the  tunica  vasculosa  over 
the  glandular  substance  of  the  testis,  and,  at  its  posterior  border,  is  reflected 
into  the  interior  of  the  gland,  forming  an  incomplete  vertical  septum,  called  the 
mediastinum  testis  {corjpus  Highmori) . 

The  mediastinum  testis  extends  from  the  upper  to  near  the  lower  extremity 
of  the  gland,  and  is  wider  above  than  below.  From  its  front  and  sides  numerous 
imperfect  septa  (trabecidcB)  are  given  off,  which  radiate  toward  the  surface  of  the 
organ,  and  are  attached  to  the  tunica  albuginea.  They  divide  the  interior  of  the 
organ  into  a  number  of  incomplete  spaces  which  are  somewhat  cone-shaped,  being 
broad  at  their  bases  at  the  surface  of  the  gland,  and  becoming  narrower  as  they 
converge  to  the  mediastinum.  The  mediastinum  supports  the  vessels  and  duct 
of  the  testis  in  their  passage  to  and  from  the  substance  of  the  gland. 

The  Tunica  Vasculosa  is  the  vascular  layer  of  the  testis,  consisting  of  a  plexus 
of  bloodvessels,  held  together  by  delicate  areolar  tissue.  It  clothes  the  inner  sur- 
face of  the  tunica  albuginea  and  the  different  septa  in  the  interior  of  the  gland, 
and  therefore  forms  an  internal  investment  to  all  the  spaces  of  which  the  gland  is 
composed. 

Structure. — The  glandular  structure  of  the  testis  consists  of  numerous  lobules.  Their  number, 
in  a  single  testis,  is  estimated  by  Berres  at  250,  and  by  Ivrause  at  400.  They  differ  in  size 
according  to  theii'  position,  those  in  the  middle  of  the  gland  being  larger  and  longer.  The 
lobules  CFig.  1038J  are  conical  in  shape,  the  base  being  du-ected  toward  the  circumference  of  the 
organ,  the  apex  toward  the  mediastinum.  Each  lobule  is  contained  in  one  of  the  intervals  between 
the  fibrous  septa  which  extend  between  the  mediastinum  testis  and  the  tunica  albuginea,  and 
consists  of  from  one  to  three,  or  more,  minute  convoluted  tubes,  the  tubuli  seminiferi.  The 
tubules  may  be  separately  unravelled,  by  careful  dissection  under  water,  and  maj'  be  seen  to 
commence  either  by  free  cecal  ends  or  by  anastomotic  loops.  They  are  supported  by  loose  con- 
nective tissue  which  contains  here  and  there  groups  of  "interstitial  cells"  containing  yellow 
pigment  granules.  The  total  number  of  tubules  is  estimated  by  Lauth  at  840,  and  the  average 
length  of  each  is  70  to  80  cm.  Their  diameter  varies  from  0.12  to  0.3  mm.  The  tubules  are  pale 
in  color  in  early  life,  but  in  old  age  they  acquire  a  deep  yeUow  tinge  from  containing  much  fatty 
matter.  Each  tubule  consists  of  a  basement  laj^er  fbmied  of  laminated  connective  tissue  con- 
taining numerous  elastic  fibres  with  flattened  cells  between  the  layers  and  covered  externally  bj' 
a  layer  of  flattened  epithelioid  ceUs.  Within  the  basement-membrane  are  epitheUal  cells  arranged 
in  several  irregular  laj-ers,  which  are  not  alwaj's  clearly  separated,  but  which  may  be  arranged 
in  three  different  groups  (Fig.  1039j.    Among  these  cells  may  be  seen  the  spermatozoa  in  different 


THE  TESTES  AXD  THEIR  COVEIUXGS 


1233 


Tunica  va/jiruilis 
Tunica  alhuginca 
Its  septa 


stages  of  development.  (1)  Lining  the  basement  membrane  and  forming  llie  outer  zone  is  a 
layer  of  cubical  cells,  with  small  nuclei;  some  of  these  enlarge  to  become  spermatogoiua.  The 
nucleus  of  some  of  the  spermatogonia  may  be  seen  to  be  in  process  of  indirect  division  {karyn- 
kincses,  page  34),  and  in  consequence  of  this  daughter  cells  are  formed,  which  constitute  the  second 
zone.  (2)  Within  this  fii'st  layer  is  to  be  seen  a  numljcr  of  larger  polyhwh-al  cells,  with  clear 
nuclei,  arranged  in  two  or  three  layers;  these  are  the  intermediate  cells  or  spermatocytes.  Most 
of  these  cells  are  in  a  condition  of  karj^okinetic  division, 
and  the  cells  which  result  from  this  division  form  those 
of  the  next  layer,  the  spermatoblasts  or  spermatids, 
(3)  The  third  layer  of  cells  consists  of  the  spermato- 
blasts or  spermatids,  and  each  of  these,  without  further 
subdivision,  becomes  a  spermatozoon.  The  spermatids 
are  small  polyhedral  cells,  the  nucleus  of  each  of  which 
contains  half  the  usual  number  of  chromosomes.  In 
addition  to  these  three  laj'ers  of  cells  others  are  seen, 
which  are  termed  the  supporting  cells  (cells  of  Sertoli). 
They  are  elongated  and  columnar,  and  project  inward 
from  the  basement  membrane  toward  the  lumen  of  the 
tube.  As  development  of  the  spermatozoa  proceeds 
the  latter  group  themselves  around  the  inner  extremi- 
ties of  the  supporting  cells.  The  nuclear  portion  of 
the  spermatid,  which  is  partly  imbedded  in  the  sup- 
porting cell,  is  differentiated  to  form  the  head  of  the 
spermatozoon,  while  part  of  the  cell  protoplasm  forms 
the  middle  piece  and  the  tail  is  produced  by  an  out- 
growth from  the  double  centriole  of  the  cell.  Ultimately 
the  heads  are  liberated  and  the  spermatozoa  are  set 
free.  The  structure  of  the  spermatozoa  is  described  on 
pages  80,  81. 

In  the  apices  of  the  lobules,  the  tubules  become  less 
convoluted,  assume  a  nearly  straight  com-se,  and  unite 
together  to  form  frbm  twenty  to  thirty  larger  ducts, 
of  about  0.5  mm.  in  diameter,  and  these,  from  their 
straight  course,  are  called  tubuli  recti  (Fig.  1038) . 

The  tubuli  recti  enter  the  fibrous  tissue  of  the  mediastinmn,  and  pass  upward  and  backward, 
forming,  in  their  ascent,  a  close  net-work  of  anastomosing  tubes  which  are  merely  channels  in 
the  fibrous  stroma,  lined  by  flattened  epitheliiun,  and  having  no  proper  walls;  this  constitutes  the 
rete  testis.  At  the  upper  end  of  the  mediastinum,  the  vessels  of  the  rete  testis  terminate  in  from 
twelve  to  fifteen  or  twenty  ducts,  the  ductuli  efferentes;  thej^  perforate  the  tunica  albuginea, 
and  carry  the  seminal  fluid  from  the  testis  to  the  epididymis.  Their  course  is  at  first  straight; 
they  then  become  enlarged,  and  exceedingly  convoluted,  and  form  a  series  of  conical  masses, 


Fig.  1038. — Vertical  section  of  the  testis,  to 
show  the  arrangement  of  the  ducts. 


Spermatocyte  Spermatid 

V 


Cell  of  Sertoli  -fe^^:^;^::^^^,^  ^f~^H 

Spermatogoniuvi  ^\^^^J/^^yy^        /  ^ 

Spermatozoon         ^^^^m§MMB 

Fig.   1039. — Transverse  section  of  a  tubule  of  the  testis  of  a  rat.     X  250. 


the  coni  vasculosi,  which  together  constitute  the  head  of  the  epididymis.  Each  cone  consists 
of  a  single  convoluted  duct,  from  15  to  20  cm.  in  length,  the  diameter  of  which  gradually  decreases 
from  the  testis  to  the  epididymis.  Opposite  the  bases  of  the  cones  the  efferent  vessels  open,  at 
narrow  inter\^als  into  a  single  duct,  which  constitutes,  by  its  complex  convolutions,  the  body 
and  tad  of  the  epididjonis.  When  the  convolutions  of  this  tube  are  unravelled,  it  measures 
upward  of  6  metres  in  length;  it  increases  in  diameter  and  thickness  as  it  approaches  the  ductus 
78 


1234 


SPLANCHNOLOGY 


deferens.  The  convolutions  are  held  together  by  fine  areolar  tissue,  and  by  bands  of  fibrous 
tissue. 

The  tubuli  recti  have  very  thin  walls;  like  the  channels  of  the  rete  testis  they  are  lined  by  a 
single  layer  of  flattened  epithelium.  The  ductuli  efferentes  and  the  tube  of  the  epididymis  have 
walls  of  considerable  thickness,  on  account  of  the  presence  in  them  of  muscular  tissue,  which  is 
principally  arranged  in  a  circular  manner.  These  tubes  are  lined  by  columnar  ciliated  epithe- 
lium (Fig.  1040). 

Applied  Anatomy. — The  testis,  developed  in  the  lumbar  region,  may  be  arrested  or  delayed 
in  its  transit  to  the  scrotum.  It  may  be  retained  in  the  abdomen;  or  it  may  be  arrested  at  the 
abdominal  inguinal  ring,  or  in  the  inguinal  canal;  or  it  may  just  pass  out  of  the  subcutaneous 
inguinal  ring  without  finding  its  way  to  the  bottom  of  the  scrotum.  When  retained  in  the  abdo- 
men it  gives  rise  to  no  sjinptoms,  other  than  the  absence  of  the  testis  from  the  scrotum;  but 
when  it  is  retained  in  the  inguinal  canal  it  is  subjected  to  pressure  and  may  become  inflamed 
and  painful.  The  retained  testis  is  probably  functionally  useless;  so  that  a  man  in  whom  both 
testes  are  retained  (anorchistn)  is  sterile,  though  he  maj^  not  be  impotent.  The  absence  of  one 
testis  is  termed  monorchism.  When  a  testis  is  retained  in  the  inguinal  canal  it  is  often  compli- 
cated with  a  congenital  hernia,  the  funicular  process  of  the  peritoneum  not  being  obliterated. 
In  addition  to  the  cases  above  described,  where  there  is  some  arrest  in  the  descent  of  the  testis, 
this  organ  maj-  descend  through  the  inguinal  canal,  but  may  miss  the  scrotum  and  assume  some 
abnormal  position.  The  most  common  form  is  where  the  testis,  emerging  at  the  subcutaneous 
inguinal  ring,  slips  dowm  between  the  scrotum  and  thigh  and  comes  to  rest  in  the  perineum. 
This  is  known  as  perineal  ectopia  testis.  With  all  varieties  of  abnormality  in  the  position  of  the 
testis,  it  is  very  common  to  find  concurrently  a  congenital  hernia,  or,  if  a  hernia  be  not  actuallj'' 
present,  the  funicular  process  is  usually  patent,  and  almost  invariably  so  if  the  testis  is  in  the 
inguinal  canal. 


Ciliated 
epithelium 

Spermatozoa 
in  lumen 


Fig.   1040. — Section  of  epididymis  of  guinea-pig.     X  255. 

The  testis,  finally  reaching  the  scrotum,  may  occupy  an  abnormal  position  in  it.  It  may  be 
inverted,  so  that  its  posterior  or  attached  border  is  directed  forward  and  the  tunica  vaginaUs  is 
situated  behind.  Should  a  hydrocele  occm-,  and  tapping  be  resorted  to,  the  trocar  may  be  thrust 
into  the  testis,  if  the  operation  is  performed  in  the  ordinary  way,  and  care  is  not  taken  beforehand 
to  ascertain  the  position  of  the  gland. 

A  number  of  instances  of  torsion  of  the  spermatic  cord,  resulting  in  acute  strangulation  of  the 
testis,  have  been  recorded.  In  some  it  has  been  attributed  to  a  strain  or  twist,  and  in  several 
patients  the  condition  has  been  associated  with  a  late  descent  of  the  organ.  Symptoms  of  this 
condition  closely  simulate  those  of  a  strangulated  hernia.  In  consequence  of  the  torsion  the 
circulation  is  partly  arrested  and  the  organ  swells  and  becomes  acutely  painful,  and  the  condition 
may  be  accompanied  with  shock  and  vomiting.  Gangrene  of  the  testis,  however,  rarely  follows, 
and  the  condition,  if  left  without  operation,  ends  in  atrophy  of  the  organ.  Torsion  of  the  bod}^ 
of  the  testis  also  sometimes  occurs  within  the  tunica  vaginalis  in  those  cases  in  which  a  persistent 
mesorchium  is  present. 

Fluid  collections  of  a  serous  character  are  very  frequently  found  in  the  scrotum.  To  these  the 
term  hydrocele  is  applied.  The  most  common  form  is  the  ordinary  vaginal  hydrocele,  in  which 
the  fluid  is  contained  in  the  sac  of  the  tunica  vaginalis,  which  is  separated,  in  its  normal  condition, 
from  the  peritoneal  cavity  by  the  whole  extent  of  the  inguinal  canal.  In  another  form,  the 
congenital  hydrocele,  the  fluid  is  in  the  sac  of  the  tunica  vaginalis,  but  this  cavity  communicates 
with  the  general  peritoneal  cavity,  its  tubular  process  remaining  pervious.     A  third  variety, 


THE  DUCTUS  DEFERENS  1235 

known  as  an  infantile  hydrocele,  occurs  in  those  cases  where  llie  tubular  i)rucess  becomes  obliter- 
ated only  at  its  ui)i)er  part,  at  or  near  the  abdoniiiuil  iufijuinal  ring.  It  resembles  the  vaginal 
hydrocele,  excejit  as  regards  its  shape,  the  collection  of  fiuitl  extending  up  the  cord  into  the  inguinal 
canal.  Fourthly,  the  funicular  process  may  become  obliterated  both  at  the  abdominal  inguinal 
ring  and  above  the  epididymis,  leaving  a  central  unobliterated  portion,  which  may  become 
distended  with  fluid,  giving  rise  to  a  condition  known  as  the  encysted  hydrocele  of  the  cord. 

Encysted  hydrocele  of  the  epididymis  or  spermatocele  is  the  name  given  to  a  cj'st  found  in  con- 
nection with  the  head  of  the  epididymis.  Among  its  contents  are  found,  in  many  instances,  a 
varj'ing  number  of  spermatozoa,  and  it  is  probably  a  retention  cyst  of  one  of  the  tubules. 

The  testis  frequently  requires  removal  for  malignant  disease;  in  tuberculous  disease;  in  cases 
of  large  hernia  testis,  and  in  some  instances  of  incompletely  descended  or  misplaced  testes.  The 
operation  of  castration  was  formerly  performed  for  enlargement  of  the  prostate,  but  has  now 
been  entirelj"  abandoned  in  favor  of  the  direct  operation  of  the  enlarged  prostate.  Castration 
is  in  most  cases  best  carried  out  by  the  "high"  operation,  an  incision  being  made  through  the 
skin  and  fascia  in  the  region  of  the  subcutaneous  inguinal  ring.  The  testis,  with  its  deeper  cover- 
ings, is  then  pushed  up  into  the  wound  and  separated  from  the  scrotal  tissues.  The  cord  is  then 
isolated,  and  an  aneurism  needle,  armed  with  a  ligature,  passed  through  it,  as  high  as  it  is  thought 
necessary',  and  the  cord  tied  and  divided.  In  cases  of  malignant  and  tuberculous  disease,  it  is 
desirable  to  open  the  inguinal  canal  and  tie  the  cord  as  near  the  abdominal  ring  as  possible. 
When  removing  the  testis  in  this  manner  the  tunica  vaginalis  is  not  opened  and  its  folds  of  reflec- 
to  the  scrotal  tissues  do  not  need  division.  The  whole  of  the  tunica  vaginalis  is  thus  removed 
with  the  cord  and  its  coverings. 

Acute  inflammation  of  the  testjs,  or  orchitis,  is  common  in  gonorrhoea;  a  chronic  fibrosing 
form  of  orchitis  is  frequent  in  syphilis,  and  leads  to  shrinkage  and  hardening  of  the  testis.  In 
tabes  dorsalis  the  testis  often  becomes  quite  insensitive  to  pressure,  which,  in  the  healthy  adult, 
readily  produces  a  severe  and  peculiar  sickening  sensation. 


The  Ductus  Deferens  (Vas  Deferens;  Seminal  Duct). 

The  ductus  deferens,  the  excretory  duet  of  the  testis,  is  the  continuation  of  the 
canal  of  the  epidi(l}'mis.  Commencing  at  the  lower  part  of  the  tail  of  the  epididymis 
it  is  at  first  very  tortuous,  but  gradually  becoming  less  twisted  it  ascends  along 
the  posterior  border  of  the  testis  and  medial  side  of  the  epididymis,  and,  as  a  con- 
stituent of  the  spermatic  cord,  traverses  the  inguinal  canal  to  the  abdominal 
inguinal  ring.  Here  it  separates  from  the  other  structures  of  the  cord,  curves 
around  the  lateral  side  of  the  inferior  epigastric  artery,  and  ascends  for  about 
2.5  cm.  in  front  of  the  external  iliac  artery.  It  is  next  directed  backward  and  slightly 
downward,  and,  crossing  the  external  iliac  vessels  obliquely,  enters  the  pelvic 
cavity,  where  it  lies  between  the  peritoneal  membrane  and  the  lateral  wall  of  the 
pelvis,  and  descends  on  the  medial  side  of  the  obliterated  umbilical  artery  and  the 
obturator  nerve  and  vessels.  It  then  crosses  in  front  of  the  ureter,  and,  reaching 
the  medial  side  of  this  tube,  bends  to  form  an  acute  angle,  and  runs  medialward 
and  slightly  forward  between  the  fundus  of  the  bladder  and  the  upper  end  of 
the  seminal  vesicle.  Reaching  the  medial  side  of  the  seminal  vesicle,  it  is  directed 
downward  and  medialward  in  contact  with  it,  gradualh^  approaching  the  opposite 
ductus.  Here  it  lies  between  the  fundus  of  the  bladder  and  the  rectum,  where  it 
is  enclosed,  together  with  the  seminal  vesicle,  in  a  sheath  derived  from  the  recto- 
vesical portion  of  the  fascia  endopelvina.  Lastly,  it  is  directed  downward  to  the 
base  of  the  prostate,  where  it  becomes  greatly  narrowed,  and  is  joined  at  an  acute 
angle  by  the  duct  of  the  seminal  vesicle  to  form  the  ejaculatory  duct,  which  tra- 
verses the  prostate  behind  its  middle  lobe  and  opens  into  the  prostatic  portion 
of  the  urethra,  close  to  the  orifice  of  the  prostatic  utricle.  The  ductus  deferens 
presents  a  hard  and  cord-like  sensation  to  the  fingers,  and  is  of  cylindrical  form;  its 
walls  are  dense,  and  its  canal  is  extremely  small.  At  the  fundus  of  the  bladder 
it  becomes  enlarged  and  tortuous,  and  this  portion  is  termed  the  ampulla.  A  small 
triangular  area  of  the  fundus  of  the  bladder,  between  the  ductus  deferentes  laterally 
and  the  bottom  of  the  rectovesical  excavation  of  peritoneum  above,  is  in  contact 
with  the  rectum. 


1236 


SPLANCHNOLOGY 


Ductuli  Aberrantes. — A  long  narrow  tube,  the  ductulus  aberrans  inferior  (vas  aberrans  of 
Holler),  is  occasionally  found  connected  with  the  lower  part  of  the  canal  of  the  epididymis,  or 
with  the  commencement  of  the  ductus  deferens.  Its  length  varies  from  3.5  to  35  cm.,  and  it 
may  become  dilated  toward  its  extremity;  more  commonly  it  retains  the  same  diameter  through- 
out. Its  structure  is  similar  to  that  of  the  ductus  deferens.  Occasionally  it  is  found  unconnected 
with  the  epididymis.  A  second  tube,  the  ductulus  aberrans  superior,  occurs  in  the  head  of  the 
epididymis;  it  is  connected  with  the  rete  testis. 

Paradidymis  {organ  of  Giraldes). — This  term  is  applied  to  a  small  collection  of  convoluted 
tubules,  situated  in  front  of  the  lower  part  of  the  cord  above  the  head  of  the  epididymis.  These 
tubes  are  lined  with  columnar  ciliated  epithelium,  and  probably  represent  the  remains  of  a  part 
of  the  Wolffian  body. 

Structure. — The  ductus  deferens  consists  of  three  coats:  (1)  an  external  or  areolar  coat;  (2)  a 
muscular  coat  which  in  the  greater  part  of  the  tube  consists  of  two  layers  of  unstriped  muscular 
fibre:  an  outer,  longitudinal  in  direction,  and  an  inner,  circular;  but  in  addition  to  these,  at  the 
commencement  of  the  ductus,  there  is  a  third  layer,  consisting  of  longitudinal  fibres,  placed 
internal  to  the  circular  stratum,  between  it  and  the  mucous  membrane;  (3)  an  internal  or  mucous 
coat,  which  is  pale,  and  arranged  in  longitudinal  folds.  The  mucous  coat  is  lined  by  columnar 
epithelium  which  is  non-ciliated  throughout  the  greater  part  of  the  tube;  a  variable  portion  of 
the  testicular  end  of  the  tube  is  lined  by  two  strata  of  columnar  cells  and  the  cells  of  the 
superficial  layer  are  ciliated. 

The  Vesiculae  Seminales  (Seminal  Vesicalesj  (Fig.  1041). 

The  vesiculae  seminales  are  two  lobulated  membranous  pouches,  placed  between 
the  fundus  of  the  bladder  and  the  rectum,  serving  as  reservoirs  for  the  semen, 
and  secreting  a  fluid  to  be  added  to  the  secretion  of  the  testes.    Each  sac  is  somewhat 


Fig.   1041. — Fundus  of  tlie  bladder  with  the  vesiculae  seminales. 


pyramidal  in  form,  the  broad  end  being  directed  backward,  upward  and  lateralward. 
It  is  usually  about  7.5  cm.  long,  but  varies  in  size,  not  only  in  different  individuals, 
but  also  in  the  same  individual  on  the  two  sides.  The  anterior  surface  is  in  contact 
with  the  fundus  of  the  bladder,  extending  from  near  the  termination  of  the  ureter 
to  the  base  of  the  prostate.  The  posterior  surface  rests  upon  the  rectum,  from  which 
it  is  separated  by  the  rectovesical  fascia.  The  upper  extremities  of  the  two  vesicles 
diverge  from  each  other,  and  are  in  relation  with  the  ductus  deferentes  and  the 
terminations  of  the  ureters,  and  are  partly  covered  by  peritoneum.     The  lower 


THE  PENIS 


1237 


extremities  are  pointed,  and  converge  toward  the  base  of  tlie  prostate,  where  each 
joins  with  the  corresponding  diictns  deferens  to  form  the  ejaciilatory  duct.  Along 
the  medial  margin  of  each  vesicle  runs  the  ampulla  of  the  ductus  deferens. 

Each  vesicle  consists  of  a  single  tube,  coiled  u{K)n  itself,  and  giving  ofi'  several 
irregular  cecal  diverticula;  the  separate  coils,  as  well  as  the  diverticula,  are  connected 
together  by  fibrous  tissue.  When  uncoiled,  the  tube  is  about  the  diameter  of  a 
quill,  and  varies  in  length  from  10  to  15  cm.;  it  ends  posteriorly  in  a  cul-de-sac; 
its  anterior  extremity  becomes  constricted  into  a  narrow  straight  duct,  which 
joins  with  the  corresponding  ductus  deferens  to  form  the  ejaculatory  duct. 

Structure. — The  vesiculae  seminales  are  composed  of  three  coats:  an  external  or  areolar  coat; 
a  middle  or  muscular  coat  thinner  than  in  the  ductus  deferens  and  arranged  in  two  layers,  an 
outer  longitudinal  and  inner  circular;  an  internal  or  mucous  coat,  which  is  pale,  of  a  whitish 
brown  color,  and  presents  a  delicate  reticular  structure.  The  epithelium  is  columnar,  and  in 
the  diverticula  goblet  cells  are  present,  the  secretion  of  which  increases  the  bulk  of  the  seminal 
fluid. 

Vessels  and  Nerves. — The  arteries  supplying  the  vesiculae  seminales  are  derived  from  the 
middle  and  inferior  vesical  and  middle  hemorrhoidal.  The  veins  and  lymphatics  accompany 
the  arteries.    The  nerves  are  derived  from  the  pelvic  plexuses. 

Applied  Anatomy. — The  vesiculae  seminales  are  often  the  seat  of  an  extension  of  the  disease 
in  cases  of  tuberculosis  of  the  testis,  and  should  always  be  examined  from  the  rectum,  before 
deciding  to  perform  castration  in  this  affection.  They  also  become  afifected  in  chronic  posterior 
urethritis  of  gonorrhoeal  origin. 


The  Ejaculatory  Ducts  (Ductus  Ejaculatorii)  (Fig.  1042). 

The  ejaculatory  ducts  are  two  in  number,  one  on  either  side  of  the  middle  line. 
Each  is  formed  by  the  union  of  the  duct  from  the  vesicula  seminalis  with  the  ductus 
deferens,  and  is  about  2  cm.  long. 
They  commence  at  the  base  of 
the  prostate,  and  run  forward 
and  downward  between  its  mid- 
dle and  lateral  lobes,  and  along 
the  sides  of  the  prostatic  utricle, 
to  end  by  separate  slit-like  ori- 
jQces  close  to  or  just  within  the 
margins  of  the  utricle.  The  ducts 
diminish  in  size,  and  also  converge, 
toward  their  terminations. 

Structure. — The  coats  of  the  ejacula- 
tory ducts  are  extremely  thin.  They 
are:  an  outer  fibrous  layer,  which  is 
almost  entirely  lost  after  the  entrance 
of  the  ducts  into  the  prostate;  a  layer 
of  muscular  fibres  consisting  of  a  thin 
outer  circular,  and  an  inner  longitu- 
dinal, layer;  and  mucous  membrane. 


Ejaculatory  duct 


Prostatic  utricle 
Urethral  crest 

-Prostatic  urethra 


Fig.  1042. — ^Vesiculae  seminales  and  ampullae  of  ductus  defer- 
entes,  seen  from  the  front.  The  anterior  walls  of  the  left  ampulla, 
left  seminal  vesicle,  and  prostatic  urethra  have  been  cut  away. 


The  Penis. 

The  penis  is  a  pendulous  organ  suspended  from  the  front  and  sides  of  the  pubic 
arch  and  containing  the  greater  part  of  the  urethra.  In  the  flaccid  condition  it  is 
cylindrical  in  shape,  but  when  erect  assumes  the  form  of  a  triangular  prism  with 
rounded  angles,  one  side  of  the  prism  forming  the  dorsum.  It  is  composed  of 
three  cylindrical  masses  of  cavernous  tissue  bound  together  by  fibrous  tissue  and 
covered  with  skin.  Two  of  the  masses  are  lateral,  and  are  known  as  the  corpora 
cavernosa  penis;  the  third  is  median,  and  is  termed  the  corpus  cavernosum  urethrae 
(Figs.  1043,  1044). 


1238 


SPLANCHNOLOGY 


The  Corpora  Cavernosa  Penis  form  the  greater  part  of  the  substance  of  the 
penis.  For  their  anterior  three-fourths  they  lie  in  intimate  apposition  with  one 
another,  but  behind  they  diverge  in  the  form  of  two  tapering  processes,  known 
as  the  crura,  which  are  firmly  connected  to  the  rami  of  the  pubic  arch.  Traced 
from  behind  forward,  each  crus  begins  by  a  bhmt-pointed  process  in  front  of  the 
tuberosity  of  the  ischium.  Just  before  it  meets  its  fehow  it  presents  a  shght  enlarge- 
ment, named  by  Kobelt  the  bulb  of  the  corpus  cavernosum  penis.  Beyond  this  point 
the  crus  undergoes  a  constriction  and  merges  into  the  corpus  cavernosum  proper, 

which  retains  a  uniform  diameter  to  its 
anterior  end.  Each  corpus  cavernosum 
penis  ends  abruptly  in  a  rounded  ex- 
tremity some  distance  from  the  point  of 
the  penis. 

The  corpora  cavernosa  penis  are  sur- 
rounded by  a  strong  fibrous  envelope 
consisting  of  superficial  and  deep  fibres. 
The  superficial  fibres  are  longitudinal  in 
direction,  and  form  a  single  tube  w^hich 
encloses  both  corpora;  the  deep  fibres  are 
arranged  circularly  around  each  corpus, 
and  form  by  their  junction  in  the  median 
plane  the  septum  of  the  penis.  This  is 
thick  and  complete  behind,  but  is  imper- 
fect in  front,  where  it  consists  of  a  series 
of  vertical  bands  arranged  like  the  teeth 
of  a  comb;  it  is  therefore  named  the  sep- 
tum pectiniforme. 

The  Corpus  Cavernosum  Urethrae 
{corpus  spongiosum)  contains  the  urethra. 


Dorsal  veins 


Dorsal  artery  and  nerve 
Integument 


Fig.  1043. — The  constituent  cavernous  cylinders  of 
the  penis.  The  glans  and  anterior  part  of  the  corpus 
cavernosum  urethrae  are  detached  from  the  corpora 
cavernosa  penis  and  turned  to  one  side. 


Fibrous  envelope 

Corpora  cavernosa  penis 
Septum  pectiniforme 

Urethra 


Corpus  cavernosum,  uretliroe 
Fig.   1044. — Transverse  section  of  the  penis. 


Behind,  it  is  expanded  to  form  the  urethral  bulb,  and  lies  in  apposition  with  the 
inferior  fascia  of  the  urogenital  diaphragm,  from  which  it  receives  a  fibrous  invest- 
ment. The  urethra  enters  the  bulb  nearer  to  the  upper  than  to  the  lower  surface. 
On  the  latter  there  is  a  median  sulcus,  from  which  a  thin  fibrous  septum  projects 
into  the  substance  of  the  bulb  and  divides  it  imperfectly  into  two  lateral  lobes  or 
hemispheres. 

The  portion  of  the  corpus  cavernosum  urethrae  in  front  of  the  bulb  lies  in  a 
groove  on  the  under  surface  of  the  conjoined  corpora  cavernosa  penis.  It  is  cylin- 
drical in  form  and  tapers  slightly  from  behind  forward.  Its  anterior  end  is  expanded 
in  the  form  of  an  obtuse  cone,  flattened  from  above  downward.  This  expansion, 
termed  the  glans  penis,  is  moulded  on  the  rounded  ends  of  the  corpora  cavernosa 


THE  PEXIS  12:^9 

penis,  exteiitliug-  fartlicr  011  their  uj^pcr  than  on  tlicir  lower  surfaces.  At  the  .summit 
of  the  glans  is  the  slit-like  vertical  external  urethral  orifice.  The  circumference 
of  the  base  of  the  iilans  forms  a  rounded  projcctinfi;  border,  the  corona  glandis, 
overhanging'  a  deep  retroglandular  sulcus,  behind  which  is  the  neck  of  the  i)enis. 

For  descripti\'e  purposes  it  is  con^■enient  to  (HvicU'  the  jjenis  into  tiiree  regions: 
the  root,  the  body,  and  the  extremity. 

The  root  (radix  j)enis)  of  the  penis  is  triradiate  in  form,  consisting  of  the 
diverging  crura,  one  on  either  side,  and  the  median  urethral  bull).  Each  crus 
is  covered  by  the  Ischiocavernosus,  ^vhile  the  bulb  is  surrounded  by  the  Bulbo- 
cavernosus.  The  root  of  the  penis  lies  in  the  perineum  between  the  inferior  fascia 
of  the  urogenital  diaphragm  and  the  fascia  of  Colles.  In  addition  to  being  attached 
to  the  fascia?  and  the  pubic  rami,  it  is  bound  to  the  front  of  the  symphysis  pubis 
by  the  fundiform  and  suspensory  ligaments.  The  fundiform  ligament  springs  from 
the  front  of  the  sheath  of  the  Rectus  abdominis  and  the  linea  alba;  it  splits  into  two 
fasciculi  which  encircle  the  root  of  the  penis.  The  upper  fibres  of  the  suspensory 
ligament  pass  downward  from  the  lower  end  of  the  linea  alba,  and  the  lower  fibres 
from  the  symphysis  pubis;  together  they  form  a  strong  fibrous  band,  which  extends 
to  the  upper  surface  of  the  root,  where  it  blends  with  the  fascial  sheath  of  the  organ. 

The  body  (corpus  penis-)  extends  from  the  root  to  the  ends  of  the  corpora  caver- 
nosa penis,  and  in  it  these  corpora  cavernosa  are  intimately  bound  to  one  another. 
A  shallow  groove  which  marks  their"  junction  on  the  upper  surface  lodges  the 
deep  dorsal  vein  of  the  penis,  while  a  deeper  and  wider  groove  between  them 
on  the  under  surface  contains  the  corpus  cavernosum  urethrae.  The  body  is 
ensheathed  by  fascia,  which  is  continuous  above  with  the  fascia  of  Scarpa,  and 
below  with  the  dartos  tunic  of  the  scrotum  and  the  fascia  of  Colles. 

The  extremity  is  formed  by  the  glans  penis,  the  expanded  anterior  end  of  the 
corpus  cavernosum  urethrae.  It  is  separated  from  the  body  by  the  constricted 
neck,  which  is  overhung  by  the  corona  glandis. 

The  integument  covering  the  penis  is  remarkable  for  its  thinness,  its  dark  color, 
its  looseness  of  connection  with  the  deeper  parts  of  the  organ,  and  its  absence  of 
adipose  tissue.  At  the  root  of  the  penis  it  is  continuous  with  that  over  the  pubes, 
scrotum,  and  perineum.  x\t  the  neck  it  leaves  the  surface  and  becomes  folded 
upon  itself  to  form  the  prepuce  or  foreskin.  The  internal  layer  of  the  prepuce  is 
directly  continuous,  along  the  line  of  the  neck,  with  the  integument  over  the  glans. 
Immediately  behind  the  external  urethral  orifice  it  forms  a  small  secondary  redu- 
plication, attached  along  the  bottom  of  a  depressed  median  raphe,  which  extends 
from  the  meatus  to  the  neck;  this  fold  is  termed  the  frenulum  of  the  prepuce.  The 
integument  covering  the  glans  is  continuous  with  the  urethral  mucous  membrane 
at  the  orifice;  it  is  devoid  of  hairs,  but  projecting  from  its  free  surface  are  a  number 
of  small,  highly  sensitive  papillse.  On  the  corona  and  neck  numerous  small  glands, 
the  preputial  glands,  have  been  described.^  They  secrete  a  sebaceous  material 
of  very  peculiar  odor,  which  probably  contains  casein,  and  readily  undergoes 
decomposition. 

The  prepuce  covers  a  variable  amount  of  the  glans,  and  is  separated  from  it 
by  a  potential  sac — the  preputial  sac — which  presents  two  shallow  fossae,  one  on 
either  side  of  the  frenulum. 

Structure  of  the  Penis. — From  the  internal  surface  of  the  fibrous  envelope  of  the  corpora 
cavernosa  penis,  as  well  as  from  the  sides  of  the  septum,  numerous  bands  or  cords  are  given  off, 
which  cross  the  interior  of  these  corpora  cavernosa  in  all  directions,  subdividing  them  into  a 
number  of  separate  compartments,  and  giving  the  entire  structure  a  spongy  appearance  (Fig. 
1044).  These  bands  and  cords  are  called  trabeculse,  and  consist  of  white  fibrous  tissue,  elastic 
fibres,  and  plain  muscular  fibres.  In  them  are  contained  numerous  arteries  and  nerves.  The 
component  fibres  which  form  the  trabeculse  are  larger  and  stronger  around  the  circumference  than 

1  Stieda  (Comptes-rendus  du  XII  Congr^s  International  de  JM^dicine,  Moscow,  1897)  asserts  that  glands  are  never 
found  on  the  corona  glandis,  and  that  what  have  hitherto  been  mistaken  for  glands  are  really  large  papillae. 


1240 


SPLANCHNOLOGY 


..£' 


at  the  centres  of  the  corpora  cavernosa;  they  are  also  thicker  behind  than  in  front.  The  inter- 
spaces (cavernous  spaces),  on  the  contrary,  are  larger  at  the  centre  than  at  the  circumference, 
their  long  diameters  being  directed  transversely.  They  are  filled  with  blood,  and  are  lined  by  a 
layer  of  flattened  cells  similar  to  the  endothelial  lining  of  veins. 

The  fibrous  envelope  of  the  corpus  cavernosum  urethrae  is  thinner,  whiter  in  color,  and  more 
elastic  than  that  of  the  corpora  cavernosa  penis.  The  trabeculse  are  more  delicate,  nearly  uniform 
in  size,  and  the  meshes  between  them  smaller  than  in  the  corpora  cavernosa  penis:  their  long 
diameters,  for  the  most  part,  corresponding  with  that  of  the  penis.  The  external  envelope  or 
outer  coat  of  the  corpus  cavernosum  urethrae  is  formed  partly  of  unstriped  muscular  fibres,  and 
a  layer  of  the  same  tissue  immediately  surrounds  the  canal  of  the  urethra. 

Vessels  and  Nerves. — The  arteries  bringing  the  blood  to  the  cavernous  spaces  are  the  deep 
arteries  of  the  penis  and  branches  from  the  dorsal  arteries  of  the  penis,  which  perforate  the  fibrous 
capsule,  along  the  upper  surface,  especially  near  the  forepart  of  the  organ.  On  entering  the 
cavernous  structure  the  arteries  divide  into  branches,  which  are  supported  and  enclosed  by  the 
trabeculse.    Some  of  these  arteries  end  in  a  capillary  net-work,  the  branches  of  which  open  directly 

into  the  cavernous  spaces;  others  as- 
sume a  tendril-like  appearance,  and 
form  convoluted  and  somewhat  dilated 
vessels,  which  were  named  by  Mtiller 
helicine  arteries.  They  open  into  the 
spaces,  and  from  them  are  also  given  off 
small  capillary  branches  to  supply  the 
trabecular  structure.  They  are  bound 
down  in  the  spaces  by  fine  fibrous  pro- 
cesses, and  are  most  abundant  in  the 
back  part  of  the  corpora  cavernosa 
(Fig.  1045). 

The  blood  from  the  cavernous  spaces 
is  returned  by  a  series  of  vessels,  some 
of  which  emerge  in  considerable  num- 
bers from  the  base  of  the  glans  penis 
and  converge  on  the  dorsum  of  the 
organ  to  form  the  deep  dorsal  vein; 
others  pass  out  on  the  upper  surface  of 
the  corpora  cavernosa  and  join  the  same 
vein;  some  emerge  from  the  under  sur- 
face of  the  corpora  cavernosa  penis  and 
receiving  branches  from  the  corpus  cav- 
ernosum urethi-ae,  wind  around  the  sides 
of  the  penis  to  end  in  the  deep  dorsal 
vein;  but  the  greater  nmnber  pass  out 
at  the  root  of  the  penis  and  join  the 
prostatic  plexus. 
The  lymphatic  vessels  of  the  penis  are  described  on  page  794. 

The  nerves  are  derived  from  the  pudendal  nerve  and  the  pelvic  plexuses.  On  the  glans  and 
bulb  some  filaments  of  the  cutaneous  nerves  have  Pacinian  bodies  connected  with  them,  and, 
according  to  Krause,  many  of  them  end  in  peculiar  end-bulbs  (see  page  1069). 

Applied  Anatomy. — The  penis  occasionally  requires  removal  for  malignant  disease.  Usually, 
removal  of  the  antescrotal  portion  is  all  that  is  necessary,  but  sometimes  it  is  requisite  to  remove 
the  whole  organ  from  its  attachment  to  the  rami  of  the  pubes  and  ischia.  The  former  operation 
is  performed  by  cutting  through  the  corpora  cavernosa  penis  from  the  dorsum,  and  then  separ- 
ating the  corpus  cavernosum  urethrae  from  them,  dividing  it  at  a  level  nearer  the  glans  penis. 
The  mucous  membrane  of  the  urethra  is  then  slit  up,  and  the  edges  of  the  flap  attached  to  the 
external  skin,  in  order  to  prevent  contraction  of  the  orifice,  which  might  otherwise  take  place. 
The  vessels  which  require  ligature  are  the  deep  and  the  dorsal  arteries  of  the  penis,  and  the  artery 
of  the  septum.  When  the  entire  organ  requires  removal,  the  patient  is  placed  in  the  lithotomy 
position,  and  an  incision  is  made  through  the  skin  and  subcutaneous  tissue  around  the  root  of 
the  penis,  and  carried  down  through  the  median  line  of  the  scrotum  as  far  as  the  perineum.  The 
two  halves  of  the  scrotum  are  then  separated  from  each  other,  and  a  catheter  having  been  intro- 
duced into  the  bladder  as  a  guide,  the  corpus  cavernosum  urethrae  below  the  urogenital  diaphragm 
is  separated  from  the  corpora  cavernosa  penis  and  divided,  the  catheter  having  been  withdrawn. 
The  suspensory  ligament  is  now  severed  and  the  crura  separated  from  the  bone  with  a  perios- 
teum scraper,  and  the  whole  penis  removed.  The  membranous  portion  of  the  urethra,  which 
has  not  been  removed,  is  now  to  be  attached  to  the  skin  at  the  posterior  extremity  of  the  incision 
in  the  perineum.    The  remainder  of  the  wound  is  closed,  free  drainage  being  provided  for. 


Fig.  1045. — Section  of  corpus  cavernosum  penis  in  a  non-dis- 
tended condition.  (Cadiat.)  a.  Trabeculse  of  connective  tissue, 
with  many  elastic  fibres  and  bundles  of  plain  muscular  tissue, 
some  of  which  are  cut  across  (c).     6.  Blood  sinuses. 


rilK  J'h'OSTATM  1241 

The  Prostate  (Prostata;  Prostate  Gland). 

The  prostate  is  a  firm,  ])artly  ylaiKliihir  and  partly  muscular  body,  which  is 
placed  immediately  below  the  iuternal  urethral  orifice  aud  arouud  the  commence- 
ment of  the  urethra.  It  is  situated  in  the  pelvic  cavity,  below  the  lower  part 
of  the  symphysis  pubis,  above  the  superior  fascia  of  the  urogenital  diaphragm, 
and  in  front  of  the  rectum,  through  which  it  may  be  distinctly  felt,  especially 
when  enlarged.  It  is  about  the  size  of  a  chestnut  and  somewhat  conical  in  shape, 
and  presents  for  examination  a  base,  an  apex,  an  anterior,  a  posterior,  and  two 
lateral  surfaces. 

The  base  (basis  prostatac)  is  directed  upward,  and  is  applied  to  the  inferior 
surface  of  the  bladder.  The  greater  part  of  this  surface  is  directly  continuous 
with  the  bladder  wall;  the  urethra  penetrates  it  nearer  its  anterior  than  its 
posterior  border. 

The  apex  (apex  prostatae)  is  directed  downward,  and  is  in  contact  with  the 
superior  fascia  of  the  urogenital  diaphragm. 

Surfaces. — The  posterior  surface  {fades  posterior)  is  flattened  from  side  to  side 
and  slightly  convex  from  above  downward;  it  is  separated  from  the  rectum  by  its 
sheath  and  some  loose  connective  tissue,  and  is  distant  about  4  cm.  from  the  anus. 
Near  its  upper  border  there  is  a  depression  through  which  the  two  ejaculatory 
ducts  enter  the  prostate.  This  depression  serves  to  divide  the  posterior  surface 
into  a  lower  larger  and  an  upper  smaller  part.  The  upper  smaller  part  constitutes 
the  middle  lobe  of  the  prostate  and  intervenes  between  the  ejaculatory  ducts  and 
the  urethra;  it  varies  greatly  in  size,  and  in  some  cases  is  destitute  of  glandular  tissue. 
The  lower  larger  portion  sometimes  presents  a  shallow  median  furrow,  which 
imperfectly  separates  it  into  a  right  and  a  left  lateral  lobe:  these  form  the  main 
mass  of  the  gland  and  are  directly  continuous  with  each  other  behind  the  urethra. 
In  front  of  the  urethra  they  are  connected  by  a  band  which  is  named  the  isthmus: 
this  consists  of  the  same  tissues  as  the  capsule  and  is  devoid  of  glandular  substance. 

The  anterior  surface  {fades  anterior)  measures  about  2.5  cm.  from  above  downward 
but  is  narrow  and  convex  from  side  to  side.  It  is  placed  about  2  cm.  behind  the 
pubic  symphysis,  from  which  it  is  separated  by  a  plexus  of  veins  and  a  quantity 
of  loose  fat.  It  is  connected  to  the  pubic  bone  on  either  side  by  the  puboprostatic 
ligaments.  The  urethra  emerges  from  this  surface  a  little  above  and  in  front  of  the 
apex  of  the  gland. 

The  lateral  surfaces  are  prominent,  and  are  covered  by  the  anterior  portions  of 
the  Levatores  ani,  which  are,  however,  separated  from  the  gland  by  a  plexus 
of  veins. 

The  prostate  measures  about  4  cm.  transversely  at  the  base,  2  cm.  in  its  antero- 
posterior diameter,  and  3  cm.  in  its  vertical  diameter.  Its  weight  is  about  8  gm. 
It  is  held  in  its  position  by  the  puboprostatic  ligaments;  by  the  superior  fascia  of 
the  urogenital  diaphragm,  which  invests  the  prostate  and  the  commencement 
of  the  membranous  portion  of  the  urethra;  and  by  the  anterior  portions  of  the 
Levatores  ani,  which  pass  backward  from  the  pubis  and  embrace  the  sides  of 
the  prostate.  These  portions  of  the  Levatores  ani,  from  the  support  they  afford 
to  the  prostate,  are  named  the  Levatores  prostatae. 

The  prostate  is  perforated  by  the  urethra  and  the  ejaculatory^  ducts.  The 
urethra  usually  lies  along  the  junction  of  its  anterior  with  its  middle  third.  The 
ejaculatory  ducts  pass  obliquely  downward  and  forward  through  the  posterior 
part  of  the  prostate,  and  open  into  the  prostatic  portion  of  the  urethra. 

Structure  (Fig.  1046). — The  prostate  is  immediately  enveloped  by  a  thin  but  firm  fibrous 
capsule,  distinct  from  that  derived  from  the  fascia  endopelvina,  and  separated  from  it  by  a  plexus 
of  veins.  This  capsule  is  firmly  adherent  to  the  prostate  and  is  structurally  continuous  with 
the  stroma  of  the  gland,  being  composed  of  the  same  tissues,  viz. :  non-striped  muscle  and  fibrous 


1242 


SPLANCHNOLOGY 


tissue.    The  substance  of  the  prostate  is  of  a  pale  reddish-gray  color,  of  great  density,  and  not 
easily  torn.     It  consists  of  glandular  substance  and  muscular  tissue. 

The  muscular  tissue  according  to  Kolliker,  constitutes  the  proper  stroma  of  the  prostate; 
the  connective  tissue  being  very  scanty,  and  simply  forming  between  the  muscular  fibres,  thin 
trabecuke,  in  which  the  vessels  and  nerves  of  the  gland  ramify.  The  muscular  tissue  is  arranged 
as  follows:  immediately  beneath  the  fibrous  capsule  is  a  dense  layer,  which  forms  an  investing 
sheath  for  the  gland;  secondly,  around  the  urethra,  as  it  lies  in  the  prostate,  is  another  dense 
layer  of  circular  fibres,  continuous  above  with  the  internal  layer  of  the  muscular  coat  of  the 
bladder,  and  blending  below  with  the  fibres  surrounding  the  membranous  portion  of  the  urethra. 
Between  these  two  layers  strong  bands  of  muscular  tissue,  which  decussate  freely,  form  meshes 
in  which  the  glandular  structure  of  the  organ  is  imbedded.  In  that  part  of  the  gland  which  is 
situated  in  front  of  the  urethra  the  muscular  tissue  is  especially  dense,  and  there  is  here  little  or 
no  gland  tissue;  while  in  that  part  which  is  behind  the  urethra  the  muscular  tissue  presents  a 
wide-meshed  structure,  which  is  densest  at  the  base  of  the  gland — that  is,  near  the  bladder- — 
becoming  looser  and  more  sponge-like  toward  the  apex  of  the  organ. 


.,^-a 


^a&Afc-^ 


ic^V4^-.£ro^|^. 


f^%'l^.^ 


<^c 


-  Oi 


%-y^^ 


■^^P^-^  .^jv  ,^  re  '^'s 


Fig  1046  — Transverse  section  of  normal  prostate  through  the  middle  of  the  urethral  crest,  from  a  subject  aged 
nineteen  j  ears  (Taj  lor  )  a  Longitudinal  section  of  ductb  leading  from  the  lobules  of  the  prostatic  glands  b  L  rethral 
crest,  c.  Prostatic  utricle,  d.  Urethra,  e.  Ejaculatory  ducts.  /.  Arteries,  veins,  and  venous  sinuses  in  sheath  of 
prostate,  g.  Nerve  trunks  in  sheath,  h.  Point  of  origin  of  fibromuscular  bands  encircling  urethra,  i.  Zone  of  striated 
voluntary  muscle  on  superior  surface. 


The  glandular  substance  is  composed  of  numerous  follicular  pouches  the  lining  of  which  fre- 
quently shows  papillary  elevations.  The  follicles  open  into  elongated  canals,  which  join  to  form 
from  twelve  to  twenty  small  excretory  ducts.  They  are  connected  together  by  areolar  tissue, 
supported  by  prolongations  from  the  fibrous  capsule  and  muscular  stroma,  and  enclosed  in  a 
delicate  capillary  plexus.  The  epithelium  which  lines  the  canals  and  the  terminal  vesicles  is  of 
the  columnar  variety.  The  prostatic  ducts  open  into  the  floor  of  the  prostatic  portion  of  the 
urethra,  and  are  lined  by  two  layers  of  epithelium,  the  inner  layer  .consisting  of  columnar  and 
the  outer  of  small  cubical  cells.  Small  colloid  masses,  known  as  amyloid  bodies  are  often  found 
in  the  gland  tubes. 

Vessels  and  Nerves. — The  arteries  supplying  the  prostate  are  derived  from  the  internal 
pudendal,  inferior  vesical,  and  middle  hemorrhoidal.  Its  veins  form  a  plexus  around  the  sides 
and  base  of  the  gland;  they  receive  in  front  the  dorsal  vein  of  the  penis,  and  end  in  the  hypogastric 
veins.     The  nerves  are  derived  from  the  pelvic  plexus. 

Applied  Anatomy. — By  means  of  the  finger  introduced  into  the  rectum,  the  surgeon  detects 
enlargement  or  other  disease  of  the  prostate;  he  can  feel  the  apex  of  the  gland,  which  is  the  guide 
to  Cock's  operation  for  stricture;  he  is  enabled  also  by  the  same  means  to  direct  the  point  of  a 
catheter,  when  its  introduction  is  attended  with  difficulty  either  from  injmy  or  disease  of  the 
membranous  or  prostatic  portions  of  the  urethra.  When  the  finger  is  introduced  into  the  bowel 
the  surgeon  may,  in  some  cases,  especially  in  boys,  learn  the  position,  as  well  as  the  size,  of  a 


THE  OVARIES  1243 

calculus  in  the  bladder;  and  in  the  operation  for  its  removal,  if,  as  is  not  infrequently  the  case, 
it  should  be  lodj^ed  Ix'hind  an  enlarjfed  prostate,  it  may  be  displaced  from  its  position  by  pressing 
upward  the  fundus  of  the  bladder  from  the  rectum.  The  i)rostate  is  occasionally  the  seat  of  sup- 
puration,, due  to  either  f2;onorrhea  or  tubercidous  disease.  The  gland  is  enveloped  in  a  dense, 
unyielding  capsule,  which  determines  the  course  of  the  abscess,  and  also  explains  the  great  pain 
which  is  present  in  the  acute  form  of  the  disease.  The  abscess  most  frequently  bursts  into  the 
urethra,  the  direction  in  whicih  there  is  least  resistance,  but  may  burst  into  the  rectum,  or  more 
rarely  in  the  jierineum.  In  advanced  life  the  prostate  sometimes  becomes  considerably  enlarged 
and  projects  into  the  bladder  so  as  to  impede  the  passage  of  the  urine.  According  to  Messer's 
researches,  conducted  at  Greenwich  Hospital,  it  would  seem  that  such  obstruction  exists  in  20 
per  cent,  of  all  men  over  sixty  .years  of  age.  In  some  cases  the  condition  affects  principally  the 
lateral  lobes,  which  may  undergo  considerable  enlargement  without  causing  much  inconvenience. 
In  other  cases  it  would  seem  that  the  middle  lobe  enlarges  most,  and  even  a  small  enlargement 
of  this  lobe  ma,y  act  injuriously,  by  forming  a  sort  of  valve  over  the  internal  urethral  orifice, 
preventing  the  passage  of  the  urine;  and  the  more  the  patient  strains,  the  more  completel}''  will 
it  block  the  opening  into  the  urethra.  In  consequence  of  the  enlargement  of  the  prostate,  a 
pouch  is  formed  at  the  base  of  the  bladder  behind  the  projection,  in  which  urine  collects,  and 
from  which  it  cannot  be  entirely  expelled.  For  this  condition  prosialeciomy  is  sometimes  done. 
The  bladder  is  opened  by  an  incision  above  the  symphysis  pubis,  the  mucous  membrane  of  the 
post-prostatic  pouch  is  scratched  through,  and  the  finger  is  then  introduced  into  the  space  between 
the  true  capsule  of  the  prostate  and  outer  capsule  formed  by  the  fascia  endopelvina.  Separation 
in  this  plane  is  then  carried  out  below  and  laterally  until  the  apex  of  the  gland  is  reached.  The 
whole  of  the  work  is  done  with  the  finger,  which  is  gradually  swept  around  the  sides  until  the 
anterior  surface  is  reached  and  freed.  The  gland  is  then,  by  traction,  displaced  into  the  bladder 
and  removed,  usually  carrying  with  it  the  greater  portion  of  the  mucous  membrane  of  the  pros- 
tatic urethi-a.  Hemorrhage,  which  may  be  considerable  at  times,  is  checked  by  hot  irrigations, 
and  the  bladder  is  temporarily  drained.  Very  satisfactory  results  have  followed  this  operation. 
The  prostate  can  be  reached  from  the  perineum,  and  in  some  cases  the  enlarged  gland  has 
been  removed  by  this  route,  but  the  perineal  approach  is  not  usually  employed  except  in  the 
case  of  abscess  of  or  about  the  gland. 

The  Bulbourethral  Glands  (Glandulae  Bulbourethrales ;  Cowper's  Glands). 

The  bulbourethral  glands  are  two  small,  rounded,  and  somewhat  lobulated  bodies, 
of  a  yellow  color,  about  the  size  of  peas,  placed  behind  and  lateral  to  the  membran- 
ous portion  of  the  urethra,  between  the  two  layers  of  the  fascia  of  the  urogenital 
diaphragm.  They  lie  close  above  the  bulb,  and  are  enclosed  by  the  transverse  fibres 
of  the  Sphincter  urethrae  membranaceae.  Their  existence  is  said  to  be  constant: 
they  gradually  diminish  in  size  as  age  advances. 

The  excretory  duct  of  each  gland,  nearlj^  2.5  cm.  long,  passes  obliquely  forward 
beneath  the  mucous  membrane,  and  opens  by  a  minute  orifice  on  the  floor  of  the 
cavernous  portion  of  the  urethra  about  2.5  cm.  in  front  of  the  urogenital  diaphragm. 

Structure. — Each  gland  is  made  up  of  several  lobules,  held  together  by  a  fibrous  investment. 
Each  lobule  consists  of  a  number  of  acini,  lined  by  columnar  epithelial  cells,  opening  into  one 
duct,  which  joins  with  the  ducts  of  other  lobules  outside  the  gland  to  form  the  single  excretory 
duct. 

THE  FEMALE  GENITAL  ORGANS  (ORGANA  GENITALIA  MULIEBRIA) . 

The  female  genital  organs  consist  of  an  internal  and  an  external  group.  The 
internal  organs  are  situated  within  the  pelvis,  and  consist  of  the  ovaries,  the  uterine 
tubes,  the  uterus,  and  the  vagina.  The  external  organs  are  placed  below  the  urogenital 
diaphragm  and  below  and  in  front  of  the  pubic  arch.  They  comprise  the  mons 
pubis,  the  labia  majora  et  minora  pudendi,  the  clitoris,  the  bulbus  vestibuli,  and  the 
greater  vestibular  glands. 

The  Ovaries  (Ovaria). 

The  ovaries  are  homologous  with  the  testes  in  the  male.  They  are  two  nodular 
bodies,  situated  one  on  either  side  of  the  uterus  in  relation  to  the  lateral  wall  of 
the  pelvis,  and  attached  to  the  back  of  the  broad  ligament  of  the  uterus,  behind 


1244 


SPLAXCHXOLOGY 


and  below  the  uterine  tubes  (Fig.  1047).  The  ovaries  are  of  a  grayish-pink  color, 
and  present  either  a  smooth  or  a  puckered  uneven  surface.  They  are  each  about 
4  cm.  in  length,  2  cm.  in  width,  and  about  8  mm.  in  thickness,  and  weigh  from  2 
to  3.5  gm.  Each  ovary  presents  a  lateral  and  a  medial  surface,  an  upper  or  tubal 
and  a  lower  or  uterine  extremity,  and  an  anterior  or  meso^'arion  and  a  posterior 
free  border.  It  lies  in  a  shallow  depression,  named  the  ovarian  fossa,  on  the  lateral 
wall  of  the  pelvis;  this  fossa  is  bounded  above  by  the  external  iliac  vessels,  in  front 
by  the  obliterated  umbilical  artery,  and  behind  by  the  ureter.  The  exact  position 
of  the  ovary  has  been  the  subject  of  considerable  difference  of  opinion,  and  the 
description  here  given  applies  to  the  ovary  of  the  nulliparous  woman.  The  ovary 
becomes  displaced  during  the  &st  pregnancy,  and  probably  never  again  returns 
to  its  original  position.  In  the  erect  posture  the  long  axis  of  the  ovary  is  vertical. 
The  tubal  extremity  is  near  the  external  iliac  vein;  to  it  is  attached  the  ovarian 
fimbria  of  the  uterine  tube  and  a  fold  of  peritoneum,  the  suspensory  ligament  of 
the  ovary,  which  is  directed  upward  over  the  iliac  vessels  and  contains  the  ovarian 


Epoophoron 


Ligament  of  ovaiy 


Ovarian  fimbria 


Ovarian 
vessels 


External  uterine  orifice 


Fig.  1047. — Uterus  and  right  broad  ligament,  seen  from  behind.     The  broad  ligament  has  been  spread  out  and  the 

ovarj^  drawn  downward. 


vessels.  The  uterine  end  is  directed  downward  toward  the  pelvic  floor,  it  is  usually 
narrower  than  the  tubal,  and  is  attached  to  the  lateral  angle  of  the  uterus,  immedi- 
ately behind  the  uterine  tube,  by  a  rounded  cord  termed  the  ligament  of  the  ovary, 
which  lies  within  the  broad  ligament  and  contains  some  non-striped  muscular 
fibres.  The  lateral  surface  is  in  contact  with  the  parietal  peritoneum,  which  lines 
the  OA' arian  fossa ;  the  medial  surface  is  to  a  large  extent  covered  by  the  fimbriated 
extremity  of  the  uterine  tube.  The  mesovarian  border  is  straight  and  is  directed 
toward  the  obliterated  umbilical  artery,  and  is  attached  to  the  back  of  the  broad 
ligament  by  a  short  fold  named  the  mesovarium.  Between  the  two  layers  of  this 
fold  the  bloodvessels  and  nerves  pass  to  reach  the  hilus  of  the  ovary.  The  free 
border  is  convex,  and  is  directed  toward  the  ureter.  The  uterine  tube  arches  over 
the  ovary,  running  upward  in  relation  to  its  mesovarian  border,  then  curving  over 
its  tubal  pole,  and  finally  passing  downward  on  its  free  border  and  medial  surface. 
Epoophoron  {parovarium;  orga7i  of  Rosenmilller)  (Figs.  1047,  1048).- — The 
epoophoron  lies  in  the  mesosalpinx  between  the  ovary  and  the  uterine  tube,  and 
consists  of  a  few  short  tubules  (ductuli  transversi)  which  converge  toward  the  ovary 


THE  OVARIES 


1245 


while  their  opposite  ends  open  into  a  rudinicntary  dnet,  the  ductus  longitudinalis 
epoophori  (duct  of  Gartner). 

Paroophoron. — The  paroophoron  consists  of  a  few  scattered  rudimentary 
tubules,  best  seen  in  the  child,  situated  in  the  broad  lijjjament  between  the  epo- 
ophoron  and  the  uterus. 


Fig.  1048. — Adult  ovary,  epoophoron,  and  uterine  tube.  (From  Farre,  after  Kobelt.)  a,  a.  Epoophoron  formed 
from  the  upper  part  of  the  Wolffian  body.  6.  Remains  of  the  uppermost  tubes  sometimes  forming  hydatids,  c.  Middle 
set  of  tubes,  d.  Some  lower  atrophied  tubes,  e.  Atrophied  remains  of  the  Wolffian  duct.  /.  The  terminal  bulb  or 
hydatid,     h.  The  uterine  tube.     i.  Hydatid  attached  to  the  extremity.     I.  The  ovary. 

The  ductuli  transversi  of  the  epoophoron  and  the  tubules  of  the  paroophoron 
are  remnants  of  the  tubules  of  the  Wolffian  body  or  mesonephros;  the  ductus 
longitudinalis  epoophori  is  a  persistent  portion  of  the  Wolffian  duct. 

In  the  fetus,  the  ovaries  are  situated,  like  the  testes,  in  the  lumbar  region,  near 
the  kidneys,  but  they  gradually  descend  into  the  pelvis  (page  187). 

Structure  (Fig.  1049). — The  surface  of  the  ovary  is  covered  by  a  layer  of  columnar  cells  which 
constitutes  the  germinal  epithelium  of  Waldeyer.  This  epithelium  gives  to  the  ovary  a  dull 
gray  color  as  compared  with  the  shining 
smoothness  of  the  peritoneum;  and  the 
transition  between  the  squamous  epithelium 
of  the  peritoneum  and  the  columnar  cells 
which  cover  the  ovary  is  usually  marked 
by  a  line  around  the  anterior  border  of  the 
ovary.  The  ovary  consists  of  a  number  of 
vesicular  ovarian  follicles  imbedded  in  the 
meshes  of  a  stroma  or  frame-work. 

The  stroma  is  a  peculiar  soft  tissue,  abun- 
dantly suppUed  with  bloodvessels,  consist- 
ing for  the  most  part  of  spindle-shaped  cells 
with  a  small  amount  of  ordinary  connective 
tissue.  These  cells  have  been  regarded  by 
some  anatomists  as  unstriped  muscle  cells, 
which,  indeed,  they  most  resemble;  by 
others  as  cormective-tissue  cells.  On  the 
surface  of  the  organ  this  tissue  is  much 
condensed,  and  forms  a  layer  (tunica  albu- 
ginea)  composed  of  short  connective-tissue 
fibres,  with  fusiform  cells  between  them. 
The  stroma  of  the  ovary  may  contain  inter- 
stitial cells  resembUng  those  of  the  testis. 

Vesicular  Ovarian  Follicles  (Graafian  follicles) .—V-pon  making  a  section  of  an  ovary,  numerous 
round  transparent  vesicles  of  various  sizes  are  to  be  seen;  they  are  the  follicles,  or  ovisacs  con- 
taining the  ova.  Immediately  beneath  the  superficial  covering  is  a  layer  of  stroma,  in  which  are 
a  large  number  of  minute  vesicles,  of  uniform  size,  about  0.25  mm.  in  diameter.  These  are  the 
folhcles  in  their  earhest  condition,  and  the  layer  where  they  are  found  has  been  termed  the 
cortical  layer.  They  are  especially  numerous  in  the  ovary  of  the  young  child.  After  puberty, 
and  during  the  whole  of  the  child-bearing  period,  large  and  mature,  or  ahnost  mature  folhcles 
are  also  found  in  the  cortical  layer  in  small  numbers,  and  also  "corpora  lutea,"  the  remains  of 


Fig.  1049. — Section  of  the  ovary.  (After  Schron.)  1. 
Outer  covering.  1'.  Attached  border.  2.  Central  stroma. 
3.  Peripheral  stroma.  4.  Bloodvessels.  5.  Vesicular  follicles 
in  their  earliest  stage.  6,  7,  8.  More  advanced  folhcles.  9. 
An  almost  mature  follicle.  9'.  FoUicle  from  which  the  ovum 
has  escaped.     10.  Corpus  luteum. 


1246 


SFLAXCHXOLOGY 


Fibro-vascular  coal 


Mevibraiia  granulos 


Zona  siriala 
Germinal  vesicle 


Discus  froligervM  — — * 


\S. 


/. 


Fig.    1050. — Section  of  vesicular  ovarian  follicle  of  cat.     X  50. 


follicle.s  which  have  burst  and  are  undergoing  atrophj^  and  absorption.  Beneath  this  superficial 
stratum,  other  large  and  more  or  less  mature  follicles  are  found  imbedded  in  the  ovarian  stroma. 
These  increase  in  size  as  they  recede  from  the  surface  toward  a  highly  vascular  stroma  in  the 
centre  of  the  organ,  termed  the  medullary  substance  {zona  vasculosa  of  Waldeyer).  This  stroma 
forms  the  tissue  of  the  hilus  by  which  the  ovarj^  is  attached,  and  through  which  the  bloodvessels 
enter:    it  does  not  contain  anj^  follicles. 

The  larger  follicles  (Fig.  lOoOj  consist  of  an  external  fibrovascular  coat,  connected  with  the 
surrounding  stroma  of  the  ovary  by  a  net-work  of  bloodvessels;  and  an  internal  coat,  which  con- 
sists of  several  layers  of  nucleated 
cells,  called  the  membrana  granulosa. 
At  one  part  of  the  mature  follicle  the 
cells  of  the  membrana  granulosa  are 
collected  into  a  mass  which  projects 
into  the  cavity  of  the  follicle.  This 
is  termed  the  discus  proligerus,  and 
in  it  the  o"vum  is  imbedded.^  The 
follicle  contains  a  transparent  albumi- 
nous fluid. 

The  development  and  maturation 
of  the  follicles  and  ova  continue  un- 
interruptedly from  puberty  to  the  end 
of  the  fruitful  period  of  woman's  life, 
while  their  formation  commences  be- 
fore birth.  Before  puberty  the  ovaries 
are  small  and  the  follicles  contained 
in  them  are  disposed  in  a  compara- 
tively thick  layer  in  the  cortical  sub- 
stance; here  thej^  present  the  appear- 
ance of  a  large  number  of  minute 
closed  vesicles,  constituting  the  early 
condition  of  the  follicles;  many, 
however,  never  attain  full  develop- 
ment, but  shrink  and  disappear.  At  puberty  the  ovaries  enlarge  and  become  more  vascular, 
the  follicles  are  developed  in  gi'eater  abundance,  and  their  ova  are  capable  of  fecundation. 

Discharge  of  the  Ovum. — The  foUicles,  after  attauiing  a  certain  stage  of  development,  gradu- 
ally approach  the  surface  of  the  ovary  and  burst;  the  ovum  and  fluid  contents  of  the  follicle 
are  liberated  on  the  exterior  of  the  ovary,  and  carried  into  the  uterine  tube  by  cm-rents  set  up 
by  the  movements  of  the  cilia  covering  the  mucous  membrane  of  the  fimbrite. 

Corpus  Luteum. — After  the  discharge  of  the  ovum  the  lining  of  the  folUcle  is  thrown  into 
folds,  and  vascular  processes  grow  inward  from  the  siu-rounding  tissue.  In  this  way  the  space 
is  filled  up  and  the  corpus  luteum  formed.  It  consists  at  first  of  a  radial  arrangement  of  yellow 
cells  with  bloodvessels  and  lymphatic  spaces,  and  later  it  merges  with  the  surroundiag  stroma. 
Vessels  and  Nerves. — The  arteries  of  the  ovaries  and  uterine  tubes  are  the  ovarian  from 
the  aorta.  Each  anastomoses  freely  in  the  mesosalpinx,  with  the  uterine  artery,  gives  some 
branches  to  the  uterine  tube,  and  others  which  traverse  the  mesovarimn  and  enter  the  hilus  of 
the  ovary.  The  veins  emerge  from  the  hilus  in  the  form  of  a  plexus,  the  pampiniform  plexus ; 
the  ovarian  vein  is  formed  from  this  plexus,  and  leaves  the  pelvis  iu  company  with  the  artery. 
The  nerves  are  derived  from  the  hypogastric  or  pelvic  plexus,  and  from  the  ovarian  plexus,  the 
uterine  tube  receiving  a  branch  from  one  of  the  uterine  nerves. 

Applied  Anatomy. — The  inflammations  which  affect  the  ovarj'  are  merely  an  extension  of 
those  from  the  tube.  Ovarian  new  formations  are  of  common  occurrence,  and  are  either  solid 
or  cystic;  the  former  being  the  less  common.  The  ovarian  cysts  in  the  majority  of  cases  are 
cj'stadenomata  which  maj^  assume  enormous  dimensions;  in  rarer  instances  they  form  from 
the  tubules  at  the  hilus  of  the  ovary  or  those  of  the  organ  of  Rosenmiiller;  ia  other  instances  a 
clear  waterj^  c^^st  forms  between  the  layers  of  the  broad  ligament.  An  ovarian  cj^st,  once  diag- 
nosticated, should  always  be  removed,  as  it  is  hable  to  become  affected  by  suppuration,  torsion 
of  its  pedicle,  or  other  serious  comphcations.  The  operation  for  its  removal,  badly  termed 
ovariotomy,  consists  in  opening  the  abdomen,  and  reducing  the  size  of  the  cyst  when  large  by 
tapping  it  before  its  withdrawal  from  the  abdomen;  the  pedicle  is  then  clamped  with  a  large 
forceps,  and  the  cyst  is  cut  free.  This  pedicle  must  then  be  transfixed  and  securely  ligatured 
by  an  interlocking  ligature,  which  will  not  slip  off.  The  pedicle  consists  of  an  elongated  part  of 
the  broad  hgament,  including  the  uterine  tube  and  ovarian  artery,  and  a  great  number  of  large 
veins.  Ovariotomy  for  a  simple  uncomplicated  cj^st  presents  no  special  difficulties,  but,  in  cases 
where  there  are  old  adhesions  implicating  the  small  intestines,  it  may  present  very  great  difficulties. 


1  For  a  description  of  the  ovum,  see  page  77. 


THE  UTERINE  TUBE 


1247 


The  Uterine  Tube  (Tuba  Uterina  IFallopii];  Fallopian  Tube;  Oviduct). 

(Fife's.    1047,    K).")!). 

The  uterine  tubes  convey  the  ova  from  the  ovaries  to  the  cavity  of  the  uterus. 
They  are  two  in  nnmher,  one  on  either  side,  situated  in  tlie  upper  margin  of  the 
broad  lijiament,  and  extencHng  from  the  superior  angle  of  the  uterus  to  the  side  of 
the  pelvis.  Eacli  tube  is  about  10  cm.  long,  and  is  described  as  consisting  of  three 
portions:  (1)  the  isthmus,  or  medial  constricted  third;  (2)  the  ampulla,  or  inter- 
mediate dilated  portion,  which  curves  over  the  ovary;  and  (3)  the  infundibulum, 
with  its  abdominal  ostium,  surrounded  by  fimbriae,  one  of  wliicli,  the  ovarian  fimbria. 


/ 
Urete'i 
Sacrogenital  jdd      ,      "^^^^^^^^\C^  \  \  '   Ligament  of  ovary 

Utenne  tube 
Punt) edalf 0390  /  ^   Bound  ligament  of  uteriis 

Fig.   1051. — Female  pelvis  and  its  contents,  seen  from  above  and  in  front. 

is  attached  to  the  ovar}-.  The  uterine  tube  is  directed  lateralward  as  far  as  the 
uterine  pole  of  the  ovary,  and  then  ascends  along  the  mesovarian  border  of  the 
ovary  to  the  tubal  pole,  over  which  it  arches;  finally  it  turns  downward  and  ends 
in  relation  to  the  free  border  and  medial  surface  of  the  ovary.  The  uterine  opening 
is  minute,  and  will  onl}-  admit  a  fine  bristle;  the  abdominal  opening  is  somewhat 
larger.  In  connection  with  the  fimbriae  of  the  uterine  tube,  or  with  the  broad  liga- 
ment close  to  them,  there  are  frequently  one  or  more  small  pedunculated  vesicles. 
These  are  termed  the  appendices  vesiculosae  {hydatids  of  Morgagni). 

Structure. — The  uterine  tube  consists  of  three  coats:  serous,  muscular,  and  mucous.  The 
external  or  serous  coat  is  peritoneal.  The  middle  or  muscular  coat  consists  of  an  external  longi- 
tudinal and  an  internal  circular  layer  of  non-striped  muscular  fibres  continuous  with  those  of 
the  uterus.  The  internal  or  mucous  coat  is  continuous  with  the  mucous  lining  of  the  uterus,  and, 
at  the  abdominal  ostium  of  the  tube,  with  the  peritoneum.  It  is  thi'own  into  longitudinal  folds, 
which  in  the  ampulla  are  much  more  extensive  than  in  the  isthmus.  The  hning  epithelium  is 
columnar  and  ciliated.  This  form  of  epithelium  is  also  found  on  the  inner  surface  of  the  fimbriae, 
while  on  the  outer  or  serous  surfaces  of  these  processes  the  epithelium  gradually  merges  into 
the  endothelium  of  the  peritoneum. 

Applied  Anatomy. — The  majority  of  the  diseases  of  the  uterine  tube  are  due  to  infection 
which  have  spread  by  way  of  the  vagina  and  uterus,  and  the  disease  often  does  not  stop  at  the 
uterine  tube,  but  passes  on  to  the  peritoneum,  giving  rise  to  acute  general  peritonitis,  or  a  local- 
ized condition  termed  ■perimetritis  that  may  be  acute  or  chronic.  Perimetritis  is  often  followed 
b}-  various  painful  conditions,  which  are  due  to  the  peritoneal  adhesions  resulting  from  the 


1248 


SPLANCHNOLOGY 


inflammation  of  the  serous  membrane,  and  which  persist  throughout  life.  Tubal  inflammation 
(salpingitis)  is  usually  the  result  of  an  infection  either  by  the  gonococcus  or  by  septic  organisms 
implanted  at  the  time  of  labor  or  abortion.  In  many  cases  the  fimbriated  ends  of  the  tubes 
become  closed  by  adhesions,  pus  collects  in  the  tubes,  and  a  pyosalpinx  results. 

Fertilization  of  the  ovum  is  believed  (page  82)  to  occur  in  the  tube,  and  the  fertilized  ovum 
is  then  normallj^  passed  on  into  the  uterus;  the  ovum,  however,  may  adhere  to  an  undergo  develop- 
ment in  the  uterine  tube,  giving  rise  to  the  commonest  variety  of  ectopic  gestation.  In  such  cases 
the  amnion  and  chorion  are  formed,  but  a  true  decidua  is  never  present;  and  the  gestation  usually 
ends  by  extrusion  of  the  ovum  through  the  abdominal  ostium,  although  it  is  not  uncommon  for 
the  tube  to  rupture  into  the  peritoneal  cavity,  this  being  accompanied  by  severe  hemorrhage, 
and  needing  surgical  interference. 

The  Uterus  (Womb)  (Figs.  1047,  1051,  1052). 

The  uterus  is  a  hollow,  thick-walled,  muscular  organ  situated  deeply  in  the 
pelvic  cavity  between  the  bladder  and  rectum.  Into  its  upper  part  the  uterine 
tubes  open,  one  on  either  side,  while  below,  its  cavity  communicates  with  that  of 


SacruVi 


Coccyx 

Recto-uterine 
excavation      /       T 
External  uterine    j       \ 
orifice 


Anal  canal 


Vesico-uterine 
excavation 


Urethra 


Fig.   1052. — A'ledian  sagittal  section  of  female  pelvis. 


the  vagina.  When  the  ova  are  discharged  from  the  ovaries  they  are  carried  to  the 
uterine  cavity  through  the  uterine  tubes.  If  an  ovum  be  fertilized  it  imbeds  itself 
in  the  uterine  wall  and  is  normally  retained  in  the  uterus  until  prenatal  develop- 
ment is  completed,  the  uterus  undergoing  changes  in  size  and  structure  to  accom- 
modate itself  to  the  needs  of  the  growing  embryo  (see  page  98).  After  parturition 
the  uterus  returns  almost  to  its  former  condition,  but  certain  traces  of  its  enlarge- 
ment remains.  It  is  necessary,  therefore,  to  describe  as  the  type-form  the  adult 
virgin  uterus,  and  then  to  consider  the  modifications  which  are  effected  as  a  result 
of  pregnancy. 


THE  UTERUS  1249 

III  the  virgin  state  the  uterus  is  flattened  antero-posteriorly  and  is  pyriform 
in  shape,  with  the  apex  directed  downward  and  backward.  It  Hcs  between  the 
bUidder  in  front  and  the  ])elvic  or  si<i;nioid  colon  and  rectum  behind,  and  is  com- 
pletely within  the  pelvis,  so  that  its  base  is  below^  the  level  of  the  superior  pelvic 
aperture.  Its  upper  part  is  suspended  by  the  broad  and  the  round  ligaments, 
while  its  lower  portion  is  imbedded  in  the  fibrous  tissue  of  the  pelvis. 

The  long  axis  of  the  uterus  usually  lies  approximately  in  the  axis  of  the  superior 
pelvic  aperture,  but  as  the  organ  is  freely  movable  its  position  varies  with  the 
state  of  distension  of  the  bladder  and  rectum.  Except  when  much  displaced  by  a 
fully  distended  bladder,  it  forms  a  forward  angle  with  the  vagina,  since  the  axis 
of  the  vagina  corresponds  to  the  axes  of  the  cavity  and  inferior  aperture  of  the 
pelvis. 

The  uterus  measures  about  7.5  cm.  in  length,  5  cm.  in  breadth,  at  its  upper 
part,  and  nearly  2.5  cm.  in  thickness;  it  weighs  from  30  to  40  gm.  It  is  divisible 
into  two  portions.  On  the  surface,  about  midway  between  the  apex  and  base, 
is  a  slight  constriction,  known  as  the  isthmus,  and  corresponding  to  this  in  the 
interior  is  a  narrowing  of  the  uterine  cavity,  the  internal  orifice  of  the  uterus.  The 
portion  above  the  isthmus  is  termed  the  body,  and  that  below,  the  cervix.  The 
part  of  the  body  which  lies  above  a  plane  passing  through  the  points  of  entrance 
of  the  uterine  tubes  is  known  as  the  fundus. 

Body  (corpus  uteri) .  —  The  body  gradually  narrows  from  the  fundus  to  the 
isthmus. 

The  vesical  or  anterior  surface  (fades  vesicalis)  is  flattened  and  covered  by 
peritoneum,  which  is  reflected  on  to  the  bladder  to  form  the  vesicouterine 
excavation.     The  surface  lies  in  apposition  with  the  bladder. 

The  intestinal  or  posterior  surface  (fades  intestinalis)  is  convex  transversely  and 
is  covered  by  peritoneum,  which  is  continued  down  on  to  the  cervix  and  vagina. 
It  is  in  relation  with  the  sigmoid  colon,  from  which  it  is  usually  separated  by  some 
coils  of  small  intestine. 

The  fundus  (fundus  uteri)  is  convex  in  all  directions,  and  covered  by  peritoneum 
continuous  with  that  on  the  vesical  and  intestinal  surfaces.  On  it  rest  some  coils 
of  small  intestine,  and  occasionally  the  distended  sigmoid  colon. 

The  lateral  margins  (margo  lateralis)  are  slightly  convex.  At  the  upper  end  of 
each  the  uterine  tube  pierces  the  uterine  wall.  Below  and  in  front  of  this  point 
the  round  ligament  of  the  uterus  is  fixed,  while  behind  it  is  the  attachment  of  the 
ligament  of  the  ovary.  The§e  three  structures  lie  within  a  fold  of  peritoneum 
which  is  reflected  from  the  margin  of  the  uterus  to  the  wall  of  the  pelvis,  and  is 
named  the  broad  ligament. 

Cervix  (cervix  uteri;  neck).— The  cervix  is  the  lower  constricted  segment  of 
the  uterus.  It  is  somewhat  conical  in  shape,  with  its  truncated  apex  directed 
downward  and  backward,  but  is  slightly  wider  in  the  middle  than  either  above  or 
below.  Owang  to  its  relationships,  it  is  less  freely  movable  than  the  body,  so  that 
the  latter  may  bend  on  it.  The  long  axis  of  the  cervix  is  therefore  seldom  in  the 
same  straight  line  as  the  long  axis  of  the  body.  The  long  axis  of  the  uterus  as  a 
w^hole  presents  the  form  of  a  curved  line  with  its  concavity  forward,  or  in  extreme 
cases  may  present  an  angular  bend  at  the  region  of  the  isthmus. 

The  cervix  projects  through  the  anterior  wall  of  the  vagina,  which  divides  it 
into  an  upper,  supravaginal  portion,  and  a  lower,  vaginal  portion. 

The  supravaginal  portion  (portio  supravaginalis  [cervids])  is  separated  in  front 
from  the  bladder  by  fibrous  tissue  (parametrium),  which  extends  also  on  to  its  sides 
and  lateralward  between  the  layers  of  the  broad  ligaments.  The  uterine  arteries 
reach  the  margins  of  the  cervix  in  this  fibrous  tissue,  while  on  either  side  the  ureter 
runs  downward  and  forward  in  it  at  a  distance  of  about  2  cm.  from  the  cervix. 
Posteriorly,  the  supravaginal  cervix  is  covered  by  peritoneum,  which  is  prolonged 
79 


1250 


SPLANCHNOLOGY 


below  on  to  the  posterior  vaginal  wall,  when  it  is  reflected  on  to  the  rectum, 
forming  the  rectouterine  excavation.  It  is  in  relation  with  the  rectum,  from 
which  it  may  be  separated  by  coils  of  small  intestine. 

The  vaginal  portion  {portio  vaginalis  [cervicis])  of  the  cervix  projects  free  into  the 
anterior  wall  of  the  vagina  between  the  anterior  and  posterior  fornices.  On  its 
rounded  extremity  is  a  small,  depressed,  somewhat  circular  aperture,  the  external 
orifice  of  the  uterus,  through  which  the  cavity  of  the  cervix  communicates  with 
that  of  the  vagina.  The  external  orifice  is  bounded  by  two  lips,  an  anterior  and  a 
posterior,  of  which  the  anterior  is  the  shorter  and  thicker,  although,  on  account 
of  the  slope  of  the  cervix,  it  projects  lower  than  the  posterior.  Normally,  both  lips 
are  in  contact  with  the  posterior  vaginal  wall. 

Interior  of  the  Uterus  (Fig.  1053). — The  cavity  of  the  uterus  is  small  in 
comparison  with  the  size  of  the  organ. 

The  Cavity  of  the  Body  (caimm  uteri)  is  a  mere  slit,  flattened  antero-posteriorly. 
It  is  triangular  in  shape,  the  base  being  formed  by  the  internal  surface  of  the 

fundus  between  the  orifices  of  the  uterine 
tubes,  the  apex  by  the  internal  orifice  of  the 
uterus  through  which  the  cavity  of  the  body 
communicates  with  the  canal  of  the  cervix. 

The  Canal  of  the  Cervix  {canalis  cervicis 
uteri)  is  somewhat  fusiform,  flattened  from 
before  backward,  and  broader  at  the  middle 
than  at  either  extremity.  It  communicates 
above  through  the  internal  orifice  with  the 
cavity  of  the  body,  and  below  through  the 
external  orifice  with  the  vaginal  cavity.  The 
wall  of  the  canal  presents  an  anterior  and  a 
posterior  longitudinal  ridge,  from  each  of 
which  proceed  a  number  of  small  oblique 
columns,  the  palmate  folds,  giving  the  appear- 
ance of  branches  from  the  stem  of  a  tree; 
to  this  arrangement  the  name  arbor  vitae 
uterina  is  applied.  The  folds  on  the  two 
walls  are  not  exactly  opposed,  but  fit  between  one  another  so  as  to  close  the 
cervical  canal. 

The  total  length  of  the  uterine  cavity  from  the  external  orifice  to  the  fundus 
is  about  6.25  cm. 

Ligaments. — The  ligaments  of  the  uterus  are  eight  in  number:  one  anterior; 
one  posterior;  two  lateral  or  broad;  two  uterosacral;  and  two  round  ligaments. 

The  anterior  ligament  consists  of  the  vesicouterine  fold  of  peritoneum,  which 
is  refiected  on  to  the  bladder  from  the  front  of  the  uterus,  at  the  junction  of  the 
cervix  and  body. 

The  posterior  ligament  consists  of  the  rectovaginal  fold  of  peritoneum,  which  is 
reflected  from  the  back  of  the  posterior  fornix  of  the  vagina  on  to  the  front  of  the 
rectum.  It  forms  the  bottom  of  a  deep  pouch  called  the  rectouterine  excavation, 
which  is  bounded  in  front  by  the  posterior  wall  of  the  uterus,  the  supravaginal 
cervix,  and  the  posterior  fornix  of  the  vagina;  behind,  by  the  rectum;  and  laterally 
by  two  crescentic  folds  of  peritoneum  which  pass  backward  from  the  cervix  uteri 
on  either  side  of  the  rectum  to  the  posterior  wall  of  the  pelvis.  These  folds  are 
named  the  sacrogenital  or  rectouterine  folds.  They  contain  a  considerable  amount 
of  fibrous  tissue  and  non-striped  muscular  fibres  which  are  attached  to  the  front 
of  the  sacrum  and  constitute  the  uterosacral  ligaments. 

The  two  lateral  or  broad  ligaments  {ligamentum  latum  uteri)  pass  from  the  sides  of 
the  uterus  to  the   lateral  walls  of  the  pelvis.    Together  with  the  uterus  they  form. 


Fig.  1053. 


Internal 
orifice 


External 
orifice 


-Posterior  half  of  uterus  and  upper 
part  of  vagina. 


THE  UTERUS 


1251 


a  septum  across  the  female  pehis,  divitliug  that  cavity  into  two  portions.  In  the 
anterior  part  is  contained  the  bhidder;  in  the  posterior  part  the  rectum,  and  in 
certain  conditions  some  coils  ol"  the  small  intestine  and  a  part  of  the  sigmoid  colon. 
Between  the  two  layers  of  each  broad  ligament  are  contained:  (1)  the  uterine 
tube  superiorly;  (2)  the  round  ligament  of  the  uterus;  (3)  the  ovary  and  its  ligament; 
(4)  the  epoophoron  and  paro6j)horon;  (5)  connective  tissue;  (6)  unstriped  muscular 
fibre;  and  (7)  bloodvessels  and  nerves.  The  portion  of  the  broad  ligament  which 
stretches  from  the  uterine  tube  to  the  level  of  the  ovary  is  known  by  the  name 
of  the  mesosalpinx.  Between  the  fimbriated  extremity  of  the  tube  and  the  lower 
attachment  of  the  broad  ligament  is  a  concave  rounded  margin,  called  the  infun- 
dibulopelvic  ligament. 

Tlie  round  ligaments  {ligamentuvi  teres  vteri)  are  two  flattened  bands  between 
10  and  12  cm.  in  length,  situated  between  the  layers  of  the  broad  ligament  in  front 
of  and  below  the  uterine  tubes.  Commencing  on  either  side  at  the  lateral  angle 
of  the  uterus,  this  ligament  is  directed  forward,  upward,  and  lateralward  over  the 
external  iliac  vessels.  It  then  passes  through  the  abdominal  inguinal  ring  and  along 
the  inguinal  canal  to  the  labium  majus,  in  which  it  becomes  lost.  The  round 
ligaments  consists  principally  of  muscular  tissue,  prolonged  from  the  uterus;  also 
of  some  fibrous  and  areolar  tissue,  besides  bloodvessels,  lymphatics;  and  nerves, 
enclosed  in  a  duplicature  of  peritoneum,  which,  in  the  fetus,  is  prolonged  in  the 
form  of  a  tubular  process  for  a  short  distance  into  the  inguinal  canal.  This  process 
is  called  the  canal  of  Nuck.  It  is  generally  obliterated  in  the  adult,  but  sometimes 
remains  pervious  even  in  advanced  life.  It  is  analogous  to  the  saccus  vaginalis, 
which  precedes  the  descent  of  the  testis. 

In  addition  to  the  ligaments  just  described,  there  is  a  band  named  the  ligamentum  trans- 
versalis  colli  (Mackenrodt)  on  either  side  of  the  cervix  uteri.  It  is  attached  to  the  side  of  the 
cervix  uteri  and  to  the  vault  and  lateral  fornix  of  the  vagina,  and  is  continuous  externally  with 
the  fibrous  tissue  which  surrounds  the  pelvic  bloodvessels. 

The  form,  size,  and  situation  of  the  uterus  vary  at  different  periods  of  life  and  under  different 
circumstances. 


Uterine  tube. 


Cavity  of  uterus 
Sigmoid  colon 

Rectum 


Anal  canal  - 


Round  ligament  of 
uterus 

Bladder- 


Sympliysis  pubis 
Urethra, 


—  Vagina, 


Fig.   1054. — Sagittal  section  through  the  pelvis  of  a  newly  born  female  child. 


In  the  fetus  the  uterus  is  contained  in  the  abdominal  cavity,  projecting  beyond  the  superior 
aperture  of  the  pelvis  (Fig.  1054).    The  cervix  is  considerably  larger  than  the  body. 

At  pubcriy  the  uterus  is  pyriform  in  shape,  and  weighs  from  14  to  17  gm.  It  has  descended 
into  the  pelvis,  the  fundus  being  just  below  the  level  of  the  superior  aperture  of  this  cavity.  The 
palmate  folds  are  distinct,  and  extend  to  the  upper  part  of  the  cavity  of  the  organ. 


1252  SPLANCHNOLOGY 

The  position  of  the  uterus  in  the  adult  is  liable  to  considerable  variation,  depending  chiefly 
on  the  condition  of  the  bladder  and  rectum.  When  the  bladder  is  empty  the  entire  uterus  is 
directed  forward,  and  is  at  the  same  time  bent  on  itself  at  the  junction  of  the  body  and  cervix, 
so  that  the  body  lies  upon  the  bladder.  As  the  latter  fills,  the  uterus  gradually  becomes  more 
and  more  erect,  until  with  a  fully  distended  bladder  the  fundus  may  be  directed  backward  toward 
the  sacrum. 

During  menstruation  the  organ  is  enlarged,  more  vascular,  and  its  surfaces  rounder;  the  external 
orifice  is  rounded,  its  labia  swollen,  and  the  lining  membrane  of  the  body  thickened,  softer,  and 
of  a  darker  color.  According  to  Sir  J.  Williams,  at  each  recurrence  of  menstruation,  a  mole- 
cular disintegration  of  the  mucous  membrane  takes  place,  which  leads  to  its  complete 
removal,  only  the  bases  of  the  glands  imbedded  in  the  muscle  being  left.  At  the  cessation  of 
menstruation,  a  fresh  mucous  membrane  is  formed  by  a  proliferation  of  the  remaining 
structures. 

During  pregnancy  the  uterus  becomes  enormously  enlarged,  and  in  the  eighth  month  reaches 
the  epigastric  region.  The  increase  in  size  is  partly  due  to  growth  of  preexisting  muscle,  and 
partly  to  development  of  new  fibres. 

After  parturition  the  uterus  nearly  regains  its  usual  size,  weighing  about  42  gm.;  but  its  cavity 
is  larger  than  in  the  virgin  state,  its  vessels  are  tortuous,  and  its  muscular  layei's  are  more  defined; 
the  external  orifice  is  more  marked,  and  its  edges  present  one  or  more  fissures. 

In  old  age  the  uterus  becomes  atrophied,  and  paler  and  denser  in  texture;  a  more  distinct 
constriction  separates  the  body  and  cervix.  The  internal  orifice  is  frequently,  and  the  external 
orifice  occasionally,  obliterated,  while  the  lips  almost  entirely  disappear. 

Structure. — ^The  uterus  is  composed  of  three  coats:  an  external  or  serous,  a  middle  or 
muscular,  and  an  internal  or  mucous. 

The  serous  coat  {tunica  serosa)  is  derived  from  the  peritoneum;  it  invests  the  fundus  and 
the  whole  of  the  intestinal  surface  of  the  uterus;  but  covers  the  vesical  surface  only  as  far  as 
the  junction  of  the  body  and  cervix.  In  the  lower  fourth  of  the  intestinal  surface  the  peritoneum, 
though  covering  the  uterus,  is  not  closely  connected  with  it,  being  separated  from  it  by  a  layer 
of  loose  cellular  tissue  and  some  large  veins. 

The  muscular  coat  {tunica  muscularis)  forms  the  chief  bulk  of  the  substance  of  the  uterus. 
In  the  virgin  it  is  dense,  firm,  of  a  grayish  color,  and  cuts  almost  like  cartilage.  It  is  thick  opposite 
the  middle  of  the  body  and  fundus,  and  thin  at  the  orifices  of  the  uterine  tubes.  It  consists  of 
bundles  of  unstriped  muscular  fibres,  disposed  in  layers,  intermixed  with  areolar  tissue,  blood- 
vessels, lymphatic  vessels,  and  nerves.  The  layers  are  three  in  number:  external,  middle,  and 
internal.  The  external  and  middle  layers  constitute  the  muscular  coat  proper,  while  the  inner 
layer  is  a  greatly  hypertrophied  muscularis  mucosae.  Dm-ing  pregnancy  the  muscular  tissue 
becomes  more  prominently  developed,  the  fibres  being  greatly  enlarged. 

The  external  layer,  placed  beneath  the  peritoneum,  is  disposed  as  a  thin  plane  on  the  vesical 
and  intestinal  sm-faces.  It  consists  of  fibres  which  pass  transversely  across  the  fundus,  and, 
converging  at  each  lateral  angle  of  the  uterus,  are  continued  on  to  the  uterine  tube,  the  round 
ligament,  and  the  ligament  of  the  ovary:  some  passing  at  each  side  into  the  broad  ligament, 
and  others  running  backward  from  the  cervix  into  the  sacrouterine  ligaments.  The  middle 
layer  of  fibres  presents  no  regularity  in  its  arrangement,  being  disposed  longitudinally,  obliquely, 
and  transversely.  It  contains  most  bloodvessels.  The  internal  or  deep  layer  consists  of  circular 
fibres  arranged  in  the  form  of  two  hollow  cones,  the  apices  of  which  surround  the  orifices  of  the 
uterine  tubes,  their  bases  intermingling  with  one  another  on  the  middle  of  the  body  of  the  uterus. 
At  the  internal  orifice  these  circular  fibres  form  a  distinct  sphincter. 

The  mucous  membrane  {tunica  mucosa)  (Fig.  1055)  is  smooth,  and  closely  adherent  to  the 
subjacent  tissue.  It  is  continuous  through  the  fimbriated  extremity  of  the  uterine  tubes,  with 
the  peritoneum;  and,  through  the  external  uterine  orifice,  with  the  Uning  of  the  vagina. 

In  the  body  of  the  uterus  the  mucous  membrane  is  smooth,  soft,  of  a  pale  red  color,  lined  by 
columnar  ciliated  epithelium,  and  presents,  when  viewed  with  a  lens,  the  orifices  of  numerous 
tubular  folUcles,  arranged  perpendicularly  to  the  surface.  The  structure  of  the  corium  differs 
from  that  of  ordinary  mucous  membranes,  and  consists  of  an  embryonic  nucleated  and  highly 
cellular  form  of  connective  tissue  in  which  run  numerous  large  lynaphatics.  In  it  are  the  tube- 
Uke  uterine  glands,  lined  by  ciliated  columnar  epithelium.  They  are  of  small  size  in  the  unim- 
pregnated  uterus,  but  shortly  after  impregnation  become  enlarged  and  elongated,  presenting 
a  contorted  or  waved  appearance  (see  page  98). 

In  the  cervix  the  mucous  membrane  is  sharply  differentiated  from  that  of  the  uterine  cavity. 
It  is  thi'own  into  numerous  oblique  ridges,  which  diverge  from  an  anterior  and  posterior  longi- 
tudinal raphe.  In  the  upper  two-thirds  of  the  canal,  the  mucous  membrane  is  provided  with 
numerous  deep  glandular  follicles,  which  secrete  a  clear  viscid  alkahne  mucus;  and,  in  addition, 
extending  through  the  whole  length  of  the  canal  is  a  variable  number  of  little  cysts,  presumably 
foUicles  which  have  become  occluded  and  distended  with  retained  secretion.  They  are  called 
the  ovula  Nabothi.  The  mucous  membrane  covering  the  lower  half  of  the  cervical  canal  presents 
numerous  papillae.    The  epithelium  of  the  upper  two-thirds  is  cylindrical  and  ciliated,  but  below 


THE  UTERUS 


1253 


this  it  loses  its  cilia,  and  graduallj-  changes  to  stratified  scinanious  epithelium  close  to  the  external 
orifice.  On  the  vaginal  surlace  of  the  cervix  the  epithelium  is  similar  to  that  lining  the  vagina, 
viz.,  stratified  squamous. 

Ciliated  epithelium 


/-.--N 


Glands 


Cimilar 

mitscular 

Jlbres 


Gland        Stroma 
Fig.  1055. — Vertical  section  of  mucous  membrane  of  human  uterus.     (Sobotta.) 

Vessels  and  Nerves.^ — The  arteries  of  the  uterus  are  the  uterine,  from  the  hypogastric;  and 
the  ovarian,  from  the  abdominal  aorta  (Fig.  1056).     They  are  remarkable  for  their  tortuous 


Branches  to  tube 


Branches  to  fundus 


Fig.  1056. — The  arteries  of  the  internal  organs  of  generation  of  the  female,  seen  from  behind.    (After  Hyrtl.) 

coui'se  in  the  substance  of  the  organ,  and  for  theii'  frequent  anastomoses.  The  termination  of 
the  ovarian  arterj^  meets  that  of  tlie  uterine  artery,  and  forms  an  anastomotic  trunk  from  which 
branches  are  given  off  to  supply  the  uterus,  their  disposition  being  cu'cular.     The  veins  are  of 


1254  SPLANCHNOLOGY 

large  size,  and  correspond  with  the  arteries.  They  end  in  the  uterine  plexuses.  In  the  impreg- 
nated uterus  the  arteries  carry  the  blood  to,  and  the  veins  convey  it  away  from,  the  intervillous 
space  of  the  placenta  (see  page  100).  The  lymphatics  are  described  on  page  795.  The  nerves 
are  derived  from  the  hypogastric  and  ovarian  plexuses,  and  from  the  third  and  fourth  sacral 
nerves. 

Applied  Anatomy. — A  certain  amount  of  anteversion  and  retroversion  of  the  uterus  can  take 
place  without  the  condition  being  regarded  as  pathological,  but  when  the  degree  of  flexion  becomes 
considei-able  it  must  be  regarded  as  a  morbid  condition.  This  is  especially  true  of  retroversion  and 
retroflexion.  The  former  is  a  falling  back  of  the  whole  uterus,  so  that  the  cervix  points  upward 
toward  the  pubes,  and  the  latter  is  a  bending  backward  of  the  body,  the  cervix  remaining  in  its 
normal  position.  The  two  conditions  are  usually  combined.  Prolapse  of  the  uterus  is  another 
common  infirmity.  The  organ  sinks  to  an  abnormally  low  level  in  the  pelvis,  and  sometimes 
protrudes  beyond  the  vulva.  This  is  due  to  the  supporting  mechanism  of  the  uterus  being 
insufficient  to  sustain  the  strain  thrown  upon  it. 

The  uterus  may  require  removal  in  cases  of  malignant  disease  or  for  fibroid  tumors.  Carcinoma 
is  the  most  common  form  of  malignant  disease  of  the  uterus,  though  cases  of  sarcoma  do  occur. 
It  may  show  itself  either  as  a  columnar  carcinoma  or  as  a  squamous  carcinoma;  the  former  com- 
mencing either  in  the  cervix  or  body  of  the  uterus,  the  latter  always  commencing  in  the  epithelial 
cells  of  the  mucous  covering  of  the  vaginal  surface  of  the  cervix.  Cancer  of  the  body  or  of  the 
cervix  may  be  treated  in  the  early  stage,  before  fixation  has  taken  place,  by  removal  of  the  uterus, 
either  through  the  vagina  or  by  means  of  abdominal  section,  but  if  the  body  be  much  enlarged 
the  former  operation  is  impossible.  Vaginal  hysterectomy  is  performed  by  placing  the  patient 
in  the  hthotomy  position  and  introducing  a  large  duck-bill  speculum.  The  cervix  is  then  seized 
with  a  volsellum  and  pulled  down  as  far  as  possible,  and  the  mucous  membrane  of  the  vagina 
incised  around  the  cervix  and  as  near  to  it  as  the  disease  will  allow,  especially  in  front,  where  the 
•ureters  are  in  danger  of  being  wounded.  The  rectouterine  excavation  is  then  opened  sufficiently 
to  allow  of  the  introduction  of  the  two  forefingers,  by  means  of  which  the  opening  is  dilated 
laterally  as  far  as  the  sacro-uterine  ligaments.  A  somewhat  similar  proceeding  is  adopted  in 
front,  but  here  the  bladder  has  to  be  separated  from  the  wall  of  the  uterus  for  about  2.5  cm. 
before  the  vesicouterine  fold  of  peritoneum  can  be  reached.  This  is  done  by  carefully  bm-rowing 
upward  with  a  director  and  stripping  the  tissues  off  the  uterine  wall.  When  the  vesicouterine 
pouch  has  been  opened  and  the  aperture  dilated  laterally,  the  uterus  remains  attached  only  bj^ 
the  broad  ligaments,  in  which  are  contained  the  vessels  that  supply  the  uterus.  Before  division 
of  the  ligaments,  these  vessels  have  to  be  dealt  with.  The  forefinger  of  the  left  hand  is  introduced 
into  the  rectouterine  excavation,  and  an  aneurism  needle,  armed  with  a  long  silk  ligature,  is 
inserted  into  the  vesicouterine  pouch,  and  is  pushed  through  the  broad  hgament  about  2.5  cm. 
above  its  lower  level  and  at  some  distance  from  the  uterus.  One  end  of  the  hgature  is  now 
pulled  through  the  anterior  opening,  and  in  this  way  we  have  the  lowest  2.5  cm.  of  the  broad 
ligament,  in  which  is  contained  the  uterine  artery  (Fig.  1056),  enclosed  in  a  ligatm"e.  This  is  tied 
tightly,  and  the  operation  is  repeated  on  the  other  side.  The  broad  ligament  is  then  divided  on 
either  side,  between  the  Hgature  and  the  uterus,  to  the  extent  to  which  it  has  been  constricted. 
By  traction  on  the  volsellum  which  grasps  the  cervix,  the  uterus  can  be  pulled  considerably 
further  down  in  the  vagina,  and  a  second  2.5  cm.  of  the  broad  ligament  is  treated  in  a  similar 
way.  This  second  ligature  will  embrace  the  pampiniform  plexus  of  veins,  and,  when  the  broad 
hgament  has  been  divided  on  either  side,  it  will  be  found  that  a  third  hgature  can  be  made  to 
pass  over  the  uterine  tube  and  top  of  the  broad  ligament,  after  the  uterus  has  been  dragged  down 
as  far  as  possible.  After  the  thu'd  ligature  has  been  tied  and  the  structures  between  it  and  the 
uterus  divided,  this  organ  wiU  be  freed  from  all  its  connections  and  can  be  removed  from  the 
vagina.  The  third  ligature  will  contain  the  ovarian  artery,  between  the  ovary  and  the  uterus, 
as  it  lies  below  the  uterine  tube.  The  vagina  is  then  sponged  out  and  lightly  dressed  with  gauze; 
no  sutures  being  used. 

In  the  treatment  of  uterine  fibroids  which  require  operative  interference,  removal  of  the 
whole  of  the  uterus,  together  with  the  tumors,  through  an  abdominal  incision  gives  the  most 
satisfactory  results;  for,  if  the  tumor  is  large,  its  size  acts  as  a  barrier  to  its  safe  dehvery  through 
the  pelvis  and  genital  passages.  After  the  abdomen  has  been  opened  the  uterine  vessels  are 
secured  and  the  broad  ligaments  divided  in  a  manner  similar  to  that  employed  in  vaginal  hysterec- 
tomy, except  that  the  proceeding  is  commenced  from  above.  When  the  first  two  ligatures  have 
been  tied,  and  the  broad  ligament  divided,  it  will  be  found  that  the  uterus  can  be  raised  out  of 
the  pelvis.  A  transverse  incision  is  now  made  through  the  peritoneum,  where  it  is  reflected 
from  the  front  of  the  uterus  on  to  the  back  of  the  bladder,  and  the  serous  membrane  peeled 
from  the  surface  of  the  uterus  until  the  vagina  is  reached.  The  anterior  wall  of  this  canal  is 
then  cut  across.  The  uterus  is  now  turned  forward  and  the  peritoneum  at  the  bottom  of  the 
rectouterine  excavation  incised  transversely,  and  the  posterior  wall  of  the  vagina  cut  across, 
until  it  meets  the  incision  on  the  anterior  wall.  The  uterus  is  now  almost  free,  and  is  held  only 
by  the  lower  part  of  the  broad  hgament  on  either  side,  containing  the  uterine  artery.  A  third 
ligature  is  made  to  encircle  this  as  close  to  the  uterus  as  possible,  the  position  of  the  ureter 


THE  VAGINA  1255 

being  always  kept  in  mind,  and,  after  havin<!;  been  lied,  tlio  structures  are  divided  between  the 
ligature  and  the  uterus.  The  organ  can  now  be  reniuvcd.  The  vagina  is  plugg(>d  with  gauze, 
and  the  external  wound  closed  in  the  usual  way.  The  vagina  acts  as  a  drain,  and  therefore  the 
opening  into  it  is  not  sutured. 

Inflannnation  of  the  ccUular  tissue  surrounding  the  cervix  occasionally  takes  place.  Laceration 
of  the  cervix  bj-^  instruments  or  by  the  fetal  head  frequently  occurs,  opening  up  the  cellular 
planes  and  so  exposing  them  to  any  infection  that  may  be  present.  An  infianunatory  mass 
forms  in  the  cellular  tissue  between  the  layers  of  the  broad  ligament  or  of  the  uterosacral  liga- 
ments, and  the  condition  is  termed  pelvic  cellulUis  or  parametritis.  This  condition  is  usually  con- 
fined to  one  side  of  the  pelvis,  forming  a  large  inflammator.y  mass  which  pushes  the  uterus  over 
to  the  opposite  side.  It  does  not  always  remain  localized,  however,  but  may  spread  widely, 
surrounding  the  rectum  or  the  neck  of  the  bladder,  or  mounting  into  the  iUac  fossa,  or  even  to 
the  perinephric  cellular  tissue.  The  condition  may  resolve  or  an  abscess  may  form.  In  the 
former  condition  the  cicatrization  of  the  inflammatory  products  often  produces  displacements 
of  the  uterus  toward  the  affected  side  of  the  pelvis,  or  stricture  of  the  rectum  when  that  viscus 
has  been  surrounded  by  the  process.  When  suppuration  ensues,  the  pus  may  burst  into  the 
bladder,  vagina,  or  rectum,  or  it  may  present  above  the  inguinal  hgament,  or  it  may  mount 
to  the  anterior  abdominal  wall  in  front  of  the  bladder  or  to  the  posterior  abdominal  wall  between 
the  iliac  crest  and  last  rib.  The  abscess  may,  moreover,  make  its  way  into  the  buttock  by  passing 
out  of  the  pelvis  through  the  greater  sciatic  foramen,  or  it  may  pass  down  between  the  fibres  of 
the  Levator  ani  and  appear  as  a  secondary  ischiorectal  abscess. 

The  Vagina  (Fig.  1052). 

The  vagina  extends  from  the  vestibule  to  the  uterus,  and  is  situated  behind  the 
bladder  and  in  front  of  the  rectum;  it  is  directed  upward  and  backward,  its  axis 
forming  with  that  of  the  uterus  an  angle  of  over  90°,  opening  forward.  Its  walls 
are  ordinarily  in  contact,  and  the  usual  shape  of  its  lower  part  on  transverse  section 
is  that  of  an  H,  the  transverse  limb  being  slightly  curved  forward  or  backward, 
while  the  lateral  limbs  are  somewhat  convex  toward  the  median  line;  its  middle 
part  has  the  appearance  of  a  transverse  slit.  Its  length  is  6  to  7.5  cm.  along  its 
anterior  wall,  and  9  cm.  along  its  posterior  wall.  It  is  constricted  at  its  commence- 
ment, dilated  in  the  middle,  and  narrowed  near  its  uterine  extremity ;  it  surrounds 
the  vaginal  portion  of  the  cervix  uteri,  a  short  distance  from  the  external  orifice 
of  the  uterus,  its  attachment  extending  higher  up  on  the  posterior  than  on  the 
anterior  wall  of  the  uterus.  To  the  recess  behind  the  cervix  the  term  posterior 
fornix  is  applied,  while  the  smaller  recesses  in  front  and  at  the  sides  are  called  the 
anterior  and  lateral  fornices. 

Relations. — The  anterior  surface  of  the  vagina  is  in  relation  with  the  fundus  of  the  bladder, 
and  vnth  the  urethra.  Its  posterior  surface  is  separated  from  the  rectum  by  the  rectouterine 
excavation  in  its  upper  fourth,  and  by  the  rectovesical  fascia  in  its  middle  two-fourths;  the  lower 
fourth  is  separated  from  the  anal  canal  by  the  perineal  body.  Its  sides  are  enclosed  between 
the  Levatores  ani  muscles.  As  the  terminal  portions  of  the  ureters  pass  forward  and  medial- 
ward  to  reach  the  fundus  of  the  bladder,  they  run  close  to  the  lateral  fornices  of  the  vagina,  and 
as  they  enter  the  bladder  are  slightly  in  front  of  the  anterior  fornix. 

Structure. — The  vagina  consists  of  an  internal  mucous  lining  and  a  muscular  coat  separated 
by  a  layer  of  erectile  tissue. 

The  mucous  membrane  (tunica  mucosa)  is  continuous  above  with  that  lining  the  uterus.  Its 
inner  sm-face  presents  two  longitudinal  ridges,  one  on  its  anterior  and  one  on  its  posterior  w^all. 
These  ridges  are  called  the  columns  of  the  vagina  and  from  them  numerous  transverse  ridges 
or  rugfe  extend  outward  on  either  side.  These  rugae  are  divided  by  furrows  of  variable  depth, 
giving  to  the  mucous  membrane  the  appearance  of  being  studded  over  -ndth  conical  projections 
or  papillae;  thej'  are  most  numerous  near  the  orifice  of  the  vagina,  especially  before  parturition. 
The  epithelium  covering  the  mucous  membrane  is  of  the  stratified  squamous  variety.  The  sub- 
mucous tissue  is  very  loose,  and  contains  numerous  large  v-eins  which  by  their  anastomoses  form 
a  plexus,  together  with  smooth  muscular  fibres  derived  from  the  muscular  coat;  it  is  regarded 
by  Gussenbauer  as  an  erectile  tissue.    It  contains  a  number  of  mucous  crypts,  but  no  true  glands. 

The  muscular  coat  (tunica  muscularis)  consists  of  two  layers:  an  external  longitudinal,  which 
is  by  far  the  stronger,  and  an  internal  circular  layer.  The  longitudinal  fibres  are  continuous 
with  the  superficial  muscular  fibres  of  the  uterus.  The  strongest  fasciculi  are  those  attached 
to  the  rectovesical  fascia  on  either  side.  The  two  layers  are  not  distinctly  separable  from  each 
other,  but  are  connected  by  obhque  decussating  fascicuh,  which  pass  from  the  one  layer  to  the 


1256 


SPLANCHNOLOGY 


other.  In  addition  to  this,  the  vagina  at  its  lower  end  is  surrounded  by  a  band  of  striped  muscular 
fibres,  the  Bulbocavernosus  (see  page  520). 

External  to  the  muscular  coat  is  a  layer  of  comiective  tissue,  containing  a  large  plexus  of 
bloodvessels. 

The  erectile  tissue  consists  of  a  layer  of  loose  connective  tissue,  situated  between  the  mucous 
membrane  and  the  muscular  coat;  imbedded  in  it  is  a  plexus  of  large  veins,  and  numerous  bundles 
of  unstriped  muscular  fibres,  derived  from  the  circular  muscular  layer.  The  arrangement  of  the 
veins  is  similar  to  that  found  in  other  erectile  tissues. 


The  External  Genital  Organs  (Partes  Genitales  Externae  Muliebres) 

(Fig.  1057). 

The  external  genital  organs  of  the  female  are:  the  mons  pubis,  the  labia  majora 
et  minora  pedundi,  the  clitoris,  the  vestibule  of  the  vagina,  the  bulb  of  the  vestibule, 
and  the  greater  vestibular  glands.  The  term  pudendum  or  vulva,  as  generally  applied, 
includes  all  these  parts. 


Clitoris 


Vestibule 

External  urethral 
orifice 


Vaginal  orifice 
Hymen 


Fig.  1057. — External  genital  organs  of  female.    The  labia  minora  have  been  drawn  apart. 

The  Mons  Pubis  {commissura  labiorum  anterior;  mons  Veneris),  the  rounded 
eminence  in  front  of  the  pubic  symphysis,  is  formed  by  a  collection  of  fatty  tissue 
beneath  the  integument.    It  becomes  covered  with  hair  at  the  time  of  puberty. 

The  Labia  Majora  {labia  majora  pudendi)  are  two  prominent  longitudinal  cuta- 
neous folds  which  extend  downward  and  backward  from  the  mons  pubis  and  form 
the  lateral  boundaries  of  a  fissure  or  cleft,  the  pudendal  cleft  or  rima,  into  which 
the  vagina  and  urethra  open.  Each  labium  has  two  surfaces,  an  outer,  pigmented 
and  covered  with  strong,  crisp  hairs;  and  an  inner,  smooth  and  beset  with  large 
sebaceous  follicles.  Between  the  two  there  is  a  considerable  quantity  of  areolar 
tissue,  fat,  and  a  tissue  resembling  the  dartos  tunic  of  the  scrotum,  besides  vessels, 


THE  EXTERNAL  GENITAL  ORGANS  1257 

nerves,  and  glands.  The  labia  are  thicker  in  front,  Avhere  they  form  b}'  their 
meeting  the  anterior  labial  commissm-e.  Posteriorly  they  are  not  really  joined,  but 
appear  to  become  lost  in  the  neighboring  integument,  ending  close  to,  and  nearly 
parallel  with,  each  other.  Together  ^\•ith  the  connecting  skin  between  them, 
they  form  the  posterior  labial  commissure  or  posterior  boundary  of  the  pudendum. 
The  interval  between  the  j)osterior  connnissure  and  the  anus,  from  2.5  to  3  cm. 
in  length,  constitutes  the  perineum.  The  labia  majora  correspond  to  the  scrotum 
in  the  male. 

The  Labia  Minora  (labia  minora  pudendi;  nympJuje)  are  two  small  cutaneous 
folds,  situated  between  the  labia  majora,  and  extending  from  the  clitoris  obliquelj'^ 
downward,  lateralward,  and  backward  for  about  4  cm.  on  either  side  of  the  orifice 
of  the  vagina,  between  which  and  the  labia  majora  they  end;  in  the  virgin  the  pos- 
terior ends  of  the  labia  minora  are  usually  joined  across  the  middle  line  by  a  fold 
of  skin,  named  the  frenulum  of  the  labia  or  fourchette.  Anteriorly,  each  labium 
minus  divides  into  two  portions:  the  upper  division  passes  above  the  clitoris  to 
meet  its  fellow  of  the  opposite  side,  forming  a  fold  which  overhangs  the  glans 
clitoridis,  and  is  named  the  preputium  clitoridis ;  the  lower  division  passes  beneath 
the  clitoris  and  becomes  united  to  its  under  surface,  forming,  with  its  fellow  of  the 
opposite  side,  the  frenulum  of  the  clitoris.  On  the  opposed  surfaces  of  the  labia 
minora  are  numerous  sebaceous  follicles. 

The  Clitoris  is  an  erectile  structure,  homologous  w^ith  the  penis.  It  is  situated 
beneath  the  anterior  labial  commissure,  partially  hidden  between  the  anterior 
ends  of  the  labia  minora.  It  consists  of  two  corpora  cavernosa,  composed  of 
erectile  tissue  enclosed  in  a  dense  layer  of  fibrous  membrane,  united  together  along 
their  medial  surfaces  by  an  incomplete  fibrous  pectiniform  septum;  each  corpus 
is  connected  to  the  rami  of  the  pubis  and  ischium  by  a  crus;  the  free  extremity 
(glans  clitoridis)  is  a  small  rounded  tubercle,  consisting  of  spongy  erectile  tissue, 
and  highly  sensitive.  The  clitoris  is  provided  like  the  penis,  wdth  a  suspensory 
ligament,  and  with  two  small  muscles,  the  Ischiocavernosi,  which  are  inserted 
into  the  crura  of  the  clitoris. 

The  Vestibule  {vestihidum  vaginae). — The  cleft  between  the  labia  minora  and 
behind  the  glans  clitoridis  is  named  the  vestibule  of  the  vagina:  in  it  are  seen  the 
urethral  and  vaginal  orifices  and  the  openings  of  the  ducts  of  the  greater  vestibular 
glands. 

The  external  urethral  orifice  (orificiiim,  urethrae  externum;  urinary  meatus)  is 
placed  about  2.5  cm.  behind  the  glans  clitoridis  and  immediately  in  front  of  that 
of  the  vagina;  it  usually  assumes  the  form  of  a  short,  sagittal  cleft  with  slightly 
raised  margins. 

The  vaginal  orifice  is  a  median  slit  below  and  behind  the  opening  of  the  urethra; 
its  size  varies  inversely  with  that  of  the  hymen. 

The  hymen  is  a  thin  fold  of  mucous  membrane  situated  at  the  orifice  of  the  vagina ; 
the  inner  surfaces  of  the  fold  are  normally  in  contact  with  each  other,  and  the 
vaginal  orifice  appears  as  a  cleft  between  them.  The  hymen  varies  much  in  shape. 
When  stretched,  its  commonest  form  is  that  of  a  ring,  generally  broadest  posteriorly; 
sometimes  it  is  represented  by  a  semilunar  fold,  with  its  concave  margin  turned 
toward  the  pubes.  Occasional!}'  it  is  cribriform,  or  its  free  margin  forms  a  mem- 
branous fringe.  It  may  be  entirely  absent,  or  may  form  a  complete  septum  across 
the  lower  end  of  the  vagina;  the  latter  condition  is  known  as  an  imperforate  hymen. 
It  may  persist  after  copulation,  so  that  it  cannot  be  considered  as  a  test  of 
virginity.  When  the  hymen  has  been  ruptured,  small  rounded  elevations  known 
as  the  carunculae  hymeneales  are  found  as  its  remains.  Between  the  hymen  and 
the  frenulum  of  the  labia  is  a  shallow  depression,  named  the  navicular  fossa. 

The  Bulb  of  the  Vestibule  (hulhus  vestihuli;  vaginal  bulb)  is  the  homologue  of 
the  bulb  and  adjoining  part  of  the  corpus  cavernosum  urethrae  of  the  male,  and 


1258  SPLANCHNOLOGY 

consists  of  two  elongated  masses  of  erectile  tissue,  placed  one  on  either  side  of  the 
vaginal  orifice  and  united  to  each  other  in  front  by  a  narrow  median  band  termed 
the  pars  intermedia.  Each  lateral  mass  measures  a  little  over  2.5  cm.  in  length. 
Their  posterior  ends  are  expanded  and  are  in  contact  with  the  greater  vestibular 
glands;  their  anterior  ends  are  tapered  and  joined  to  one  another  by  the  pars 
intermedia;  their  deep  surfaces  are  in  contact  with  the  inferior  fascia  of  the  uro- 
genital diaphragm;  superficially  they  are  covered  by  the  Bulbocavernosus. 

The  Greater  Vestibular  Glands  (glandida  vestibularis  major  [Bartholini];  Bar- 
tholin s  glands)  are  the  homologues  of  the  bulbo-urethral  glands  in  the  male.  They 
consist  of  two  small,  roundish  bodies  of  a  reddish-yellow  color,  situated  one  on  either 
side  of  the  vaginal  orifice  in  contact  with  the  posterior  end  of  each  lateral  mass  of 
the  bulb  of  the  vestibule.  Each  gland  opens  by  means  of  a  duct,  about  2  cm.  long, 
immediately  lateral  to  the  hymen,  in  the  groove  between  it  and  the  labium  minus. 

The  Mammae  (Mammary  Gland;  Breasts). 

The  mammae  secretes  the  milk,  and  are  accessory  glands  of  the  generative  system* 
They  exist  in  the  male  as  well  as  in  the  female;  but  in  the  former  only  in  the  rudi- 
mentary state,  unless  their  growth  is  excited  by  peculiar  circumstances.  In  the 
female  they  are  tw^o  large  hemispherical  eminences  lying  within  the  superficial 
fascia  and  situated  on  the  front  and  sides  of  the  chest;  each  extends  from  the  second 
rib  above  to  the  sixth  rib  below,  and  from  the  side  of  the  sternum  to  near  the  mid- 
axillary  line.  Their  weight  and  dimensions  differ  at  different  periods  of  life,  and 
in  different  individuals.  Before  puberty  they  are  of  small  size,  but  enlarge  as  the 
generative  organs  become  more  completely  developed.  They  increase  during  preg- 
nancy and  especially  after  delivery,  and  become  atrophied  in  old  age.  The  left 
mamma  is  generally  a  little  larger  than  the  right.  The  deep  surface  of  each  is 
nearly  circular,  flattened,  or  slightly  concave,  and  has  its  long  diameter  directed 
upward  and  lateralward  toward  the  axilla;  it  is  separated  from  the  fascia  covering 
the  Pectoralis  major,  Serratus  anterior,  and  Obliquus  externus  abdominis  by  loose 
connective  tissue.  The  subcutaneous  surface  of  the  mamma  is  convex,  and  presents, 
just  below  the  centre,  a  small  conical  prominence,  the  papilla. 

The  Mammary  Papilla  or  Nipple  {papilla  mammae)  is  a  cylindrical  or  conical 
eminence  situated  about  the  level  of  the  fourth  intercostal  space.  It  is  capable 
of  undergoing  a  sort  of  erection  from  mechanical  excitement,  a  change  mainly 
due  to  the  contraction  of  its  muscular  fibres.  It  is  of  a  pink  or  brownish  hue,  its 
surface  wrinkled  and  provided  with  secondary  papillae;  and  it  is  perforated  by  from 
fifteen  to  twenty  orifices,  the  apertures  of  the  lactiferous  ducts.  The  base  of  the 
mammary  papilla  is  surrounded  by  an  areola.  In  the  virgin  the  areola  is  of  a  delicate 
rosy  hue;  about  the  second  month  after  impregnation  it  enlarges  and  acquires  a 
darker  tinge,  and  as  pregnancy  advances  it  may  assume  a  dark  brown  or  even  black 
color.  This  color  diminishes  as  soon  as  lactation  is  over,  but  is  never  entirely 
lost  throughout  life.  These  changes  in  the  color  of  the  areola  are  of  importance 
in  forming  a  conclusion  in  a  case  of  suspected  first  pregnanc3^  Near  the  base  of 
the  papilla,  and  upon  the  surface  of  the  areola,  are  numerous  large  sebaceous  glands, 
the  areolar  glands,  which  become  much  enlarged  during  lactation,  and  present 
the  appearance  of  small  tubercles  beneath  the  skin.  These  glands  secrete  a  pecu- 
liar fatty  substance,  which  serves  as  a  protection  to  the  integument  of  the  papilla 
during  the  act  of  sucking.  The  mammary  papilla  consists  of  numerous  vessels, 
intermixed  with  plain  muscular  fibres,  which  are  principally  arranged  in  a  circular 
manner  around  the  base :  some  few  fibres  [radiating  from  base  to  apex. 

Structure  (Figs.  1058,  1059). — The  mamma  consists  of  gland  tissue;  of  fibrous  tissue,  con- 
necting its  lobes;  and  of  fatty  tissue  in  the  intervals  between  the  lobes.  The  gland  tissue,  when 
freed  from  fibrous  tissue  and  fat,  is  of  a  pale  reddish  color,  firm  in  texture,  flattened  from  before 


THE  MAMMAE 


1259 


backward  and  thicker  in  the  centre  tluin  at  the  circumference.  The  subcutaneous  surface  of 
the  mamma  presents  numerous  irregular  processes  which  })roject  toward  the  skin  and  are  joined 
to  it  by  bands  of  connective  tissue.  It  consists  of  numerous  lobes,  and  these  are  com])osed  of 
lobules,  connected  together  by  areolar  tissue,  bloodvessels,  and  ducts.  The  smallest  lobules 
consist  of  a  cluster  of  rounded  alveoli,  which  open  into  the  smallest  branches  of  the  lactiferous 
ducts;  these  ducts  unite  to  form  larger  ducts,  and  these  end  in  a  single  canal,  corresponding  with 


Lobule  unravelled    ^&^J^^ 


Lactiferou 
Hihule 


A  tujntUa 


Lobules  ■  ^^ 

Loculi  xn  connective  tissue 
Fig.   1058. — Dissection  of  the  lower  half  of  the  mamma  during  the  period  of  lactation.     (Luschka.) 

one  of  the  chief  subdivisions  of  the  gland.  The  number  of  excretory  ducts  varies  from  fifteen 
to  twenty;  they  are  termed  the  tubuli  lactiferi.  They  converge  toward  the  areola,  beneath 
which  they  form  dilatations  or  ampullae,  which  serve  as  reservoirs  for  the  milk,  and,  at  the  base 
of  the  papillae,  become  contracted,  and  pursue  a  straight  course  to  its  summit,  perforating  it 
by  separate  orifices  considerably  narrower  than  the  ducts  themselves.  The  ducts  are  composed 
of  areolar  tissue  containing  longitudinal  and  transverse  elastic  fibres;  muscular  fibres  are  entirely 
absent;  they  are  lined  bj''  columnar  epithe- 
lium resting  on  a  basement-membrane. 
The  epithehum  of  the  mamma  differs  ac- 
cording to  the  state  of  activit}'  of  the 
organ.  In  the  gland  of  a  woman  who  is 
not  pregnant  or  suckling,  the  alveoli  are 
very  small  and  soUd,  being  filled  with  a 
mass  of  granular  polyhedral  cells.  During 
pregnane}^  the  alveoli  enlarge,  and  the  cells 
undergo  rapid  multiplication.  At  the  com- 
mencement of  lactation,  the  cells  in  the 
centre  of  the  alveolus  undergo  fatty  degen- 
eration, and  are  eliminated  in  the  fii'st  milk, 
as  colostrum  corpuscles.  The  peripheral 
cells  of  the  alveolus  remain,  and  form  a 
single  laj'er  of  gi-anular,  short  columnar 
ceUs,  with  spherical  nuclei,  lining  the  base- 
ment  membrane.     The   cells,   during   the 

state  of  acti\'ity  of  the  gland,  are  capable  of  forming,  in  their  interior,  oil  globules,  which  are 
then  ejected  into  the  lumen  of  the  alveolus,  and  constitute  the  milk  globules.  \ATien  the  acini 
are  distended  bj'  the  accumulation  of  the  secretion  the  lining  epithelium  becomes  flattened. 

The  fibrous  tissue  invests  the  entire  surface  of  the  mamma,  and  sends  down  septa  between 
its  lobes,  connecting  them  together. 

The  fatty  tissue  covers  the  surface  of  the  gland,  and  occupies  the  interval  between  its  lobes. 
It  usually  exists  in  considerable  abundance,  and  determines  the  form  and  size  of  the  gland.  There 
is  no  fat  immediately  beneath  the  areola  and  papilla. 


Alveoli 


Fat 


Duct 


Fig.   1059. — Section  of  portion  of  mamma. 


1260  SPLANCHNOLOGY 

Vessels  and  Nerves. — The  arteries  supplying  the  mammae  are  derived  from  the  thoracic 
branches  of  the  axillary,  the  intercostals,  and  the  internal  mammary.  The  veins  describe  an 
anastomotic  circle  around  the  base  of  the  papilla,  called  by  Haller  the  circulus  venosus.  From 
this,  large  branches  transmit  the  blood  to  the  circumference  of  the  gland,  and  end  in  the  axillary 
and  internal  mammary  veins.  The  lymphatics  are  described  on  page  797.  The  nerves  are 
derived  from  the  anterior  and  lateral  cutaneous  branches  of  the  fourth,  fifth,  and  sixth  thoracic 
nerves. 

Applied  Anatomy. — The  ducts  descending  from  the  mammary  papilla  radiate  through  the 
gland,  and  when  an  incision  is  made  into  the  breast  the  scalpel  should  be  directed  radially,  from 
the  centre  to  the  periphery,  so  that  it  may  not  pass  across  the  ducts.  A  milk  duct  may  become 
obstructed  and  distended,  forming  a  tumor  known  as  a  galadocele.  Abscess  frequently  occurs 
about  the  mamma,  and  most  often  in  women  who  are  lactating,  especially  those  who  have  cracks 
or  fissures  about  the  papilla.  The  abscess  may  lie  between  the  septa,  in  the  gland  tissue  itself; 
or  it  may  lie  beneath  the  skin  by  the  side  of  the  papilla  and  superficial  to  the  mamma  or  it  may 
form  beneath  it,  between  the  mamma  and  the  deep  fascia.  Free  incision,  radiating  from  the 
papilla,  is  required  in  such  cases. 

Cystic  formation  of  many  different  kinds  is  commonly  seen  in  the  mamma;  in  some  cases  it  is 
due  to  dilatation  of  the  larger  ducts  or  of  the  lymph  spaces  throughout  the  gland;  in  others  the 
cysts  occur  in  new  growths  of  the  mamma,  or  as  the  result  of  obstruction  of  the  smaller  ducts  by 
chronic  inflammatory  processes. 

Malignant  growths  are  seen  more  often  in  the  mamma  than  in  any  other  organ;  they  are  of 
great  variety,  but  the  commonest  is  the  spheroidal-celled  cancer,  the  cells  of  which  are  inter- 
mingled with  a  varying  amount  of  fibrous  tissue.  A  hard  contracting  tumor  mass  results,  which 
drags  on  the  fibrous  septa  between  the  lobes  so  that  fixation  or  retraction  of  the  papilla  ensues, 
and  sooner  or  later  the  malignant  infiltration  invades  the  surrounding  gland  tissues,  the  skin, 
the  deep  fascia  and  Pectorales,  and  even  the  chest  wall  and  pleura.  The  lymph  glands  beneath 
the  Pectorales  and  those  situated  toward  the  apex  of  the  axilla  become  early  involved  with 
secondary  malignant  deposit,  and  later  the  supraclavicular  glands  enlarge.  In  other  cases  the 
mediastinal  glands  may  be  involved,  when  the  disease  is  situated  on  the  medial  side  of  the 
papUla. 

The  operation  for  removal  of  a  mamma  affected  with  malignant  disease  should  be  an  extensive 
procedure,  with  the  object  of  extirpating  all  fascial  planes  and  lymphatic  structures  that  may  be 
infected.  The  incision  commences  below,  over  the  upper  part  of  the  sheath  of  the  Rectus,  encloses 
the  mamma  by  an  ellipse,  and  is  then  continued  on  toward  the  apex  of  the  axilla.  The  skin  is 
reflected  on  both  sides  of  the  incision;  anteriorly,  until  the  sternum  is  reached,  and  posteriorly 
to  the  posterior  boundary  of  the  axilla.  The  origin  of  the  sternal  portion  of  the  Pectoralis  major 
is  then  divided  and  turned  outward.  The  Pectoralis  minor  is  next  seen,  and  its  origin  is  then 
divided  in  a  similar  manner.  The  whole  of  the  muscular  and  fascial  planes  of  the  front  of  the 
chest  are  thus  separated  en  masse,  carrying  with  them  the  mamma  and  the  skin  covering  it.  The 
insertions  of  the  two  Pectorales  have  next  to  be  divided,  and  finally  the  axillary  lymph  glands 
and  fat  are  removed  from  the  axillary  vessels  in  one  piece  with  the  mass  of  tissue  already  detached. 
This  is  done  by  first  freely  exposing  the  whole  length  of  the  axillary  vein  and  then,  with  a  blunt 
instrument,  peeling  the  structures  ofT  the  vein  from  above  downward,  from  the  point  where  they 
are  crossed  by  the  Subclavius  muscle  to  the  lower  border  of  the  axQla.  In  this  part  of  the  opera- 
tion many  branches  of  both  vein  and  artery  require  ligature.  The  only  thing  which  then  remains 
to  be  divided  is  the  deep  fascia  along  the  posterior  axillary  wall.  The  wound  is  then  closed, 
drainage  is  provided,  and  firm  pressure  is  applied  with  the  dressings.  It  will  be  noted  that  the 
clavicular  portion  of  the  Pectoralis  major  is  left  intact,  as  it  is  of  considerable  service  for 
the  subsequent  movements  of  the  arm,  the  utility  of  which  is  but  slightly  impaired. 


THE  DUCTLESS  GLANDS. 

There  are  certain  organs  which  are  very  similar  to  secreting  glands,  but  differ 
from  them  in  one  essential  particular,  viz.,  they  do  not  possess  any  ducts  by  which 
their  secretion  is  discharged.  These  organs  are  known  as  ductless  glands.  They 
are  capable  of  internal  secretion — that  is  to  say,  of  forming,  from  materials  brought 
to  them  in  the  blood,  substances  which  have  a  certain  influence  upon  the  nutritive 
and  other  changes  going  on  in  the  body.  This  secretion  is  carried  into  the  blood 
stream,  either  directly  by  the  veins  or  indirectly  through  the  medium  of  the 
lymphatics. 

These  glands  include  the  thyroid  and  the  parathyroids,  the  thymus,  the  spleen, 
the  suprarenal  glands,  and  the  glomus  caroticum  and  glomus  coccygeum,  which  will 


THE  TffVh'OfD  (HAND 


1261 


be  described  in  this  section.  They  also  include  the  lymph  glands,  whicli  have 
already  been  described  in  the  section  on  Angiology;  and  the  pineal  gland  and 
hypophysis  cerebri  described  in  the  section  on  Neurology. 

THE  THYROID  GLAND   (GLANDULA  THYREIODEA;   THYROID  BODY) 

(Kig.  lOGOJ. 

The  thyroid  gland  is  a  highly  vascular  organ,  situated  at  the  front  and  sides  of 
the  neck;  it  consists  of  right  and  left  lobes  connected  across  the  middle  line  by  a 
narrow  portion,  the  isthmus.  Its  weight  is  somewhat  variable,  but  is  usually  about 
30  grams.  It  is  slightly  heavier  in  the  female,  in  whom  it  becomes  enlarged  during 
menstruation  and  pregnancy. 


Vagus  nerve 


External  carotid  artery 

Superior  thyroid  artery 
Swperior  thyroid  vein 


ddle  thyroid  vein 


■^tM- 


Fig.   1060. — The  thyroid  gland  and  its  relations. 

The  lobes  (lobuli  gl.  thyreoideae)  are  conical  in  shape,  the  apex  of  each  being 
directed  upward  and  lateralward  as  far  as  the  junction  of  the  middle  with  the  lower 
third  of  the  thyroid  cartilage;  the  base  looks  downward,  and  is  on  a  level  with  the 
fifth  or  sixth  tracheal  ring.  Each  lobe  is  about  5  cm.  long;  its  greatest  width  is 
about  3  cm.,  and  its  thickness  about  2  cm.  The  lateral  or  superficial  surface  is  con- 
vex, and  covered  by  the  skin,  the  superficial  and  deep  fasciae,  the  Sternocleido- 
mastoideus,  the  superior  belly  of  the  Omohyoideus,  the  Sternohyoideus  and  Sterno- 
thyreoideus,  and  beneath  the  last  muscle  by  the  pretracheal  layer  of  the  deep 
fascia,  which  forms  a  capsule  for  the  gland.  The  deep  or  medial  surface  is  moulded 
over  the  underlying  structures,  viz.,  the  thyroid  and  cricoid  cartilages,  the  trachea, 
the  Constrictor  pharyngis  inferior  and  posterior  part  of  the  Cricothj^eoideus, 
the  oesophagus  (particularly  on  the  left  side  of  the  neck),  the  superior  and  inferior 
thyroid  arteries,  and  the  recurrent  nerves.  The  anterior  border  is  thin,  and  inclines 
obliquely  from  above  downward  toward  the  middle  line  of  the  neck,  while  the 


1262  SPLANCHNOLOGY 

posterior  border  is  thick  and  overlaps  the  common  carotid  artery,  and,  as  a  rule, 
the  parathyroids. 

The  isthmus  {isthmus  gl.  thyreoidea)  connects  together  the  lower  thirds  of  the 
lobes;  it  measures  about  1.25  cm.  in  breadth,  and  the  same  in  depth,  and  usually 
covers  the  second  and  third  rings  of  the  trachea.  Its  situation  and  size  present, 
however,  many  variations.  In  the  middle  line  of  the  neck  it  is  covered  by  the  skin 
and  fascia,  and  close  to  the  middle  line,  on  either  side,  by  the  Sternothyreoideus. 
Across  its  upper  border  runs  an  anastomotic  branch  uniting  the  two  superior 
thyroid  arteries;  at  its  lower  border  are  the  inferior  thyroid  veins.  Sometimes  the 
isthmus  is  altogether  wanting. 

A  third  lobe,  of  conical  shape,  called  the  pyramidal  lobe,  frequently  arises  from 
the  upper  part  of  the  isthmus,  or  from  the  adjacent  portion  of  either  lobe,  but 
most  commonly  the  left,  and  ascends  as  far  as  the  hyoid  bone.  It  is  occasionally 
quite  detached,  or  may  be  divided  into  two  or  more  parts. 

A  fibrous  or  muscular  band  is  sometimes  found  attached,  above,  to  the  body 
of  the  hyoid  bone,  and  below  to  the  isthmus  of  the  gland,  or  its  pyramidal  lobe. 
AMien  muscular,  it  is  termed  the  Levator  glandulae  thyreoideae. 

Small  detached  portions  of  thyroid  tissue  are  sometimes  found  in  the  vicinity 
of  the  lateral  lobes  or  above  the  isthmus;  they  are  called  accessory  thyroid  glands 
{glandulae  thyreoideae  accessoriae) . 


Colloid  material __  _ 

Colloid  in       G ^A'   ,  — 

lymphatic  vessel 

Cubical 
epithelium  ^ 

Fig.   1061. — Section  of  thjToid  gland  of  sheep.     X  160. 

Structure. — The  thyroid  gland  is  invested  by  a  thin  capsule  of  connective  tissue,  which  pro- 
jects rato  its  substance  and  imperfectly  divides  it  into  masses  of  irregular  form  and  size.  When 
the  organ  is  cut  into,  it  is  of  a  brownish-red  color,  and  is  seen  to  be  made  up  of  a  number  of 
closed  vesicles,  containing  a  yellow  glairy  fluid,  and  separated  from  each  other  by  intermediate 
coimective  tissue  (Fig.  1061). 

The  vesicles  of  the  thjToid  of  the  adult  animal  are  generally  closed  spherical  sacs;  but  in  some 
young  animals,  e.  g.,  young  dogs,  the  vesicles  are  more  or  less  tubular  and  branched.  This 
appearance  is  supposed  to  be  due  to  the  mode  of  gro-n-th  of  the  gland,  and  merely  indicates  that 
an  increase  in  the  number  of  vesicles  is  taking  place.  Each  vesicle  is  lined  by  a  single  layer  of 
cubical  epitheUum.  There  does  not  appear  to  be  a  basement-membrane,  so  that  the  epithelial 
cells  are  in  direct  contact  with  the  connective-tissue  reticulum  which  supports  the  acini.  The 
vesicles  are  of  various  sizes  and  shapes,  and  contain  as  a  normal  product  a  viscid,  homogeneous, 
semifluid,  shghth'  yellowish,  colloid  material;  red  corpuscles  are  found  in  it  in  various  stages 
of  disintegration  and  decolorization,  the  yellow  tinge  being  probablj'  due  to  the  hemoglobin, 
which  is  thus  set  free  from  the  colored  corpuscles.  The  colloid  material  contains  an  iodine  com- 
poimd,  iodothyrin,  and  is  readily  stained  b}'  eosin.  It  passes  out  between  the  cubical  cells  and 
is  absorbed  into  the  blood  or  Ij-mph. 

Vessels  and  Nerves. — The  arteries  supphdng  the  thjToid  gland  are  the  superior  and  inferior 
thyroids  and  sometimes  an  additional  branch  (thjToidea  imaj  from  the  innominate  artery  or  the 
arch  of  the  aorta,  which  ascends  upon  the  front  of  the  trachea.  The  arteries  are  remarkable 
for  their  large  size  and  frequent  anastomoses.     The  veins  form  a  plexus  on  the  surface  of  the 


THE  PARATHYROID  G LANDS  1263 

gland  and  on  the  front  of  the  trachea;  from  tliis  plexus  the  superior,  middle,  and  inferior  thyroid 
veins  arise;  the  superior  and  middle  end  in  the  internal  jugular,  the  inferior  in  the  innominate 
vein.  The  capillary  bloodvessels  form  a  dense  plexus  in  the  connective  tissue  around  the  vesicles, 
between  the  epithelium  of  the  vesicles  and  the  endothelium  of  the  Ij'mphatics,  which  surround 
a  greater  or  smaller  part  of  the  circumference  of  the  vesicle.  The  lymphatic  vessels  run  in  the 
interlobular  connective  tissue,  not  uncommonly  surrounding  the  arteries  w  Inch  liiey  accompany, 
and  communicate  with  a  net-work  in  the  capsule  of  the  gland;  the}-  may  contain  colloid  material. 
They  end  in  the  thoracic  and  right  lymphatic  trunks.  The  nerves  are  derived  from  the  middle 
and  inferior  cervical  ganglia  of  the  sympathetic. 

Applied  Anatomy. — An  enlargement  of  the  thyroid  gland  is  called  a  goitre.  The  swelling  may 
take  the  form  of  a  diffuse  hypertrophy  of  the  whole  gland,  giving  rise  to  the  parenchy7natous  goitre, 
this  being  mainly  due  to  the  hypertrophj-  of  the  thyroid  follicles  themselves;  in  other  cases  a 
fibroid  form  of  goitre  is  produced  owing  to  the  increase  in  the  interstitial  connective  tissue;  in 
others,  again,  the  vascular  changes  may  preponderate,  and  many  large  pulsating  vessels  may 
be  present.  Much  more  commonly,  however,  the  enlargement  is  due  to  adenomatous  new  growth 
in  the  substance  of  the  thyroid;  these  tumors  are  always  innocent,  and  tend  to  destroy  life  only 
bj'  pressure  on  the  air  passages.  A  single  tumor  is  the  rule,  but  in  some  instances  a  very  large 
number  may  be  present.  They  tend  to  show  marked  mucoid  degeneration,  and  so  become  con- 
verted into  c3^st-adenomata,  and  finally  into  what  appear  to  be  simple  cysts.  These  tumors 
may  attain  an  enormous  size  and  may  involve  practically  the  whole  gland.  Malignant  tumor- 
growth  more  rarely  attacks  the  organ. 

When,  in  spite  of  treatment,  a  goitre  continues  to  grow,  and  especially  when  there  are  com- 
mencing symptoms  of  tracheal  pressure,  operative  interference  becomes  necessary.  This  is  not 
difficult,  if  an  encapsuled  tumor  is  to  be  dealt  with,  provided  the  anatomical  layers  covering 
it  are  remembered.  In  such  a  case  it  is  necessary  to  make  an  incision  suited  to  the  size  and 
situation  of  the  tumor,  and  having  divided  the  deep  cervical  fascia,  to  retract  the  Sternocleido- 
mastoideus  or  divide  it  if  necessary.  The  Sternohyoideus  and  Sternothyreoideus  next  require 
division,  or  in  some  cases  their  fibres  may  be  separated  and  drawn  asunder,  and  beneath  is  found 
the  ensheathing  capsule  derived  from  the  pretracheal  fascia;  this  requii-es  division,  and  exposes 
the  true  capsule  of  the  thyroid  gland.  In  the  case  of  an  adenoma  or  cyst,  this  true  capsule  then 
needs  incision  before  the  tumor  can  be  effectually  shelled  out,  and  this  is  usually  accomplished 
^ath  verj'  little  hemorrhage,  and  without  any  of  the  main  vessels  of  the  gland  requii'ing  hgature. 

Partial  extu-pation  of  the  thya-oid,  viz.,  the  removal  of  one  lateral  lobe  with  division  of  the 
isthmus,  may  be  required  in  cases  of  parenchymatous  goitre,  and  in  the  diffuse  form  of  adenoma- 
tous disease.  It  is  a  more  radical  proceeding,  and  carries  with  it  a  much  greater  risk  from  hemor- 
rhage; there  is  also  a  danger  of  wounding  the  recurrent  nerve.  The  whole  gland  must  never  be 
removed,  as  such  a  procedure  is  followed  by  the  development  of  myxedema.  In  hemith;yToid- 
ectomy  a  free  incision  is  indicated — dividing  muscles,  if  necessary — to  expose  the  triie  gland  cap- 
sule, but  at  the  same  time  avoiding  injury  to  the  large  vessels  which  he  beneath  it.  The  superior 
and  inferior  pedicles  containing  the  respective  thyroid  arteries  are  then  isolated  and  clamped 
on  either  side  and  divided  between  the  clamps.  The  half  gland  is  then  turned  over  toward  the 
middle  line,  and  the  isthmus  ligatured  and  divided.  Some  venous  bleeding  is  apt  to  occur  from 
connections  with  the  tracheal  veins,  and  must  be  stopped.  The  pedicles  are  then  securely  liga- 
tured and  the  wound  closed.  In  dealing  with  the  inferior  thjToid  artery,  the  position  of  the 
recun-ent  nerve  must  be  borne  in  mind,  so  as  not  to  hgature  or  divide  it.  Temporary  aphonia 
not  uncommonly  follows  from  bruising  of  the  nerve,  and  if  nothing  more  serious  has  occurred 
soon  passes  off. 

THE   PARATHYROID    GLANDS. 

The  parathyroid  glands  are  small  brownish-red  bodies,  situated  as  a  rule  between 
the  posterior  borders  of  the  lateral  lobes  of  the  thyroid  gland  and  its  capsule. 
They  differ  from  it  in  structure,  being  composed  of  masses  of  cells  arranged  in  a 
more  or  less  columnar  fashion  with  numerous  intervening  capillaries.  They  meas- 
ure on  an  average  about  6  mm.  in  length,  and  from  3  to  4  mm.  in  breadth,  and 
usually  present  the  appearance  of  flattened  oval  disks.  They  are  divided,  accord- 
ing to  their  situation,  into  superior  and  inferior.  The  superior,  usually  two  in  number, 
are  the  more  constant  in  position,  and  are  situated,  one  on  either  side,  at  the  level 
of  the  lower  border  of  the  cricoid  cartilage,  behind  the  junction  of  the  pharynx 
and  oesophagus.  The  inferior,  also  usually  two  in  number,  may  be  applied  to  the 
lower  edge  of  the  lateral  lobes,  or  placed  at  some  little  distance  below  the  thyroid 
gland,  or  found  in  relation  to  one  of  the  inferior  thyroid  veins. ^ 

1  Consult  an  article  "Concerning  the  Parathyroid  Glands,"  by  D.  A.  Welsh,  Journal  of  Anatomy  and  Physiology, 
vol.  xxxii. 


1264 


SPLAXCHXOLOGY 


In  man,  they  number  four  as  a  rule;  fewer  than  four  were  found  in  less  than  1 

per  cent,  of  over  a  thousand  persons  (Pepere^),  but  more  than  four  in  over  33  per 
cent,  of  122  bodies  examined  by  Civalleri.  In  addition,  numerous  minute  islands 
of  parathyroid  tissue  may  be  found  scattered  in  the  connective  tissue  and  fat  of 
the  neck  around  the  parathyroid  glands  proper,  and  quite  distinct  from  them. 

Structure. — Microscopically  the  parathyroids  consist  of  intercommunicating  columns  of 
cells  supported  by  connective  tissue  containing  a  rich  supply  of  blood  capillaries.  Most  of  the 
cells  are  clear,  but  some,  larger  in  size,  contain  ox}-phil  granules.  Vesicles  containing  colloid 
have  been  described  as  occurring  in  the  parathjToid,  but  the  observation  has  not  been  confirmed. 

Applied  Anatomy. — Xo  doubt  the  parathjToid  glands  produce  an  internal  secretion  essential 
to  the  well-being  of  the  human  economy-;  but  it  is  still  a  matter  of  dispute  what  symptoms  of 
disease  are  produced  hy  their  removal  and  suppression  of  their  secretion.  Pepere  beheves  that 
they  show  signs  of  exceptional  activity  during  pregnane}-,  and  that  parathjToid  insufficiency 
is  a  main  factor  in  the  production  of  tetany-  in  infants  and  adults,  of  eclampsia,  and  of  certain 
sorts  of  fits. 

THE  THYMUS   (THYMUS  GLANDS)  (Fig.  1062). 

The  thymus  is  a  temporary  organ,  attaining  its  largest  size  at  the  time  of 
puberty  (Hammar),  when  it  ceases  to  grow,  gradually  dwindles,  and  almost 
disappears.  If  examined  when  its  growth  is  most  active,  it  will  be  found  to  con- 
sist of  two  lateral  lobes  placed  in  close  contact  along  the  middle  line,  situated 
partly  in  the  thorax,  partly  in  the  neck,  and  extending  from  the  fourth  costal 
cartilage  upward,  as  high  as  the  lower  border  of  the  th\Toid  gland.  It  is  covered 
by  the  sternum,  and  by  the  origins  of  the  Sternohyoidei  and  Sternothyreoidei. 


Ihiiioidrjland 

Left  common 
caiotul  artery 
Lejt  internal 
jugular  vein 

~::^  Left  ii/bclavian  vesS' 


Fig.   1062. — The  thymus  of  a  full-time  fetus,  exposed  in  situ. 

Below,  it  rests  upon  the  pericardium,  being  separated  from  the  aortic  arch  and 
great  vessels  by  a  layer  of  fascia.  In  the  neck  it  lies  on  the  front  and  sides  of  the 
trachea,  behind  the  Sternohyoidei  and  Sternothyreoidei.  The  two  lobes  generally 
differ  in  size;  they  are  occasionally  united,  so  as  to  form  a  single  mass;  and  some- 
times separated  by  an  intermediate  lobe.  The  thymus  is  of  a  pinkish-gray  color, 
soft,  and  lobulated  on  its  surfaces.  It  is  about  o  cm.  in  length,  4  cm.  in  breadth 
below,  and  about  6  mm.  in  thickness.    At  birth  it  weighs  about  15  grams. 

Structure. — Each  lateral  lobe  is  composed  of  mmierous  lobules  held  together  by  deUcate 
areolar  tissue;  the  entire  gland  being  enclosed  in  an  investing  capsule  of  a  similar  but  denser 
structure.  The  primarj-  lobules  varj-  in  size  from  that  of  a  pin's  head  to  that  of  a  small  pea,  and 
are  made  up  of  a  number  of  small  nodules  or  foUicles,  which  are  irregular  in  shape  and  are  more 
or  less  fused  together,  especially  toward  the  interior  of  the  gland.    Each  follicle  is  from  1  to  2  mm. 

1  Consult  Le  Ghiandole  paratiroidee,  by  A.  Pepere,  Turin,  1906. 


THE  THYMCS 


1265 


in  diameter  and  eonsists  of  a  nicdullarv  ami  a  cortical  portion,  and  these  dilTcr  in  nianj-  essential 
particulars  from  each  other.  The  cortical  portion  is  niainl}'  composed  of  lymjjhoid  cells,  supported 
by  a  network  of  linely  braneheil  cells,  which  is  continuous  with  a  similar  network  in  the  nie(lullarj' 
portion.  This  network  forms  an  adventitia  to  the  bloodvessels.  In  the  medullary  portion  the 
reticulum  is  coarser  than  in  the  cortex,  the  lymphoitl  cells  are  relativelj'  fewer  in  numb(;r,  and 
there  are  found  peculiar  nest-like  bodies,  the  concentric  corpuscles  of  llassall.  These  concentric 
corpuscles  are  composed  of  a  central  mass,  consisting  of  one  or  more  granular  cells,  and  of  a 
capsule  which  is  formed  of  epithelioid  cells  (P'ig.  10G3).  Thej'  are  the  remains  of  tlie  epithelial 
tubcs^which  grow  out  from  the  third  branchial  pouches  of  the  embrj'o  to  form  the  thymus. 


Arte) 


Vein 


Fig.  1063. — Minute  structure  of  thymus.  Follicle  of  injected  thymus  from  calf,  four  days  old,  slightly  diagram- 
matic, magnified  about  50  diameters.  The  large  vessels  are  disposed  in  two  rings,  one  of  which  surrounds  the  follicle, 
the  other  lies  just  within  the  margin  of  the  medulla.  (Watnej-.)  A  and  B.  From  thymus  of  camel,  examined  without 
addition  of  any  reagent.  Magnified  about  400  diameters.  A.  Large  colorless  cell,  containing  small  oval  masses  of 
hemoglobin.    Similar  cells  are  found  in  the  lymph  glands,  spleen,  and  medulla  of  bone.    B.  Colored  blood  corpuscles. 

Each  follicle  is  surrounded  by  a  vascular  plexus,  from  which  vessels  pass  into  the  interior, 
and  radiate  from  the  periphery  toward  the  centre,  forming  a  second  zone  just  within  the  margin 
of  the  medullary  portion.  In  the  centre  of  the  medullary  portion  there  are  very  few  vessels,  and 
they  are  of  minute  size. 

Wa1;ney  has  made  the  important  observation  that  hemoglobin  is  found  in  the  thjnnus,  either 
in  cj'sts  or  in  cells  situated  near  to,  or  forming  part  of,  the  concentric  corpuscles.  This  hemo- 
globin occurs  as  gi'anules  or  as  circular  masses  exactly  resembling  colored  blood  corpuscles.  He 
has  also  discovered,  in  the  lymph  issuing  from  the  thjTnus,  similar  cells  to  those  found  in  the 
gland,  and,  like  them,  containing  hemoglobin  in  the  form  of  either  granules  or  masses.  From 
these  facts  he  arrives  at  the  conclusion  that  the  gland  is  one  source  of  the  colored  blood  corpuscles. 
INIore  recently  Schaffer  has  observed  actual  nucleated  red-blood  corpuscles  in  the  thymus. 

Vessels  and  Nerves. — The  arteries  supptying  the  th3'mus  are  derived  from  the  internal 
mammary,  and  from  the  superior  and  inferior  thjToids.  The  veins  end  in  the  left  innominate 
vein,  and  in  the  thyi'oid  veins.  The  lymphatics  are  described  on  page  779.  The  nerves  are 
exceedingl}^  minute;  they  are  derived  from  the  vagi  and  .sj-mpathetic.  Branches  from  the  descen- 
dens  hypoglossi  and  pln-enic  reach  the  investing  capsule,  but  do  not  penetrate  into  the  substance 
of  the  gland. 
80 


1266 


SPLANCHNOLOGY 


Applied  Anatomy. — Sudden  death — thymus  death — with  heart-failure,  and  with  or  without 
acute  respiratory  embarrassment,  has  been  recorded  in  a  number  of  infants  and  children  in 
whom  the  thjonus  was  considerablj^  enlarged  and  the  lymphatic  tissues  throughout  the  bodj^ 
showed  general  hj-pertrophy,  but  who  showed  no  other  e\'idence  of  disease.  Such  deaths  have 
often  occurred  dm-ing  the  administration  of  anesthetics,  particularly  chloroform.  How  far  the 
enlarged  thjonus  was  responsible  for  the  death  of  these  patients,  and,  if  it  was  responsible,  how 
far  its  action  was  mechanical,  are  points  that  have  been  much  disputed.  Short  of  producing 
this  sudden  death,  it  appears  that  thjonic  enlargement  may  cause  attacks  of  respiratory  stridor, 
or  noisy  and  difficult  breathing,  and  spasmodic  attacks  of  asthma — thymic  asthma — which  may 
be  frequently  repeated  and  may  even  result  ta  death.  Primary  tumors  of  the  thymus  are  rare 
forms  of  mediastinal  new  growth,  and  are  usually  dermoids  or  lymphosarcomas. 

THE    SPLEEN    (LIEN). 

The  spleen  is  situated  principally  in  the  left  hypochondriac  region,  but  its  supe- 
rior extremity  extends  into  the  epigastric  region;  it  lies  between  the  fundus  of  the 
stomach  and  the  Diaphragma.  It  is  the  largest  of  the  ductless  glands,  and  is  of 
an  oblong,  flattened  form,  soft,  of  very  friable  consistence,  highly  vascular,  and 
of  a  dark  purplish  color. 

Relations. — The  diaphragmatic  surface  (fades  diajphragmatica;  external  or  phrenic  surface)  is 
convex,  smooth,  and  is  directed  upward,  backward,  and  to  the  left,  except  at  its  upper  end, 
where  it  is  directed  slightly  medialward.  It  is  in  relation  with  the  under  surface  of  the  Dia- 
phragma, which  separates  it  from  the  ninth,  tenth,  and  eleventh  ribs  of  the  left  side,  and  the 
intervening  lower  border  of  the  left  limg  and  pleura. 

The  visceral  surface  (Fig.  1064)  is  divided  by  a  ridge  into  an  anterior  or  gastric  and  a  posterior 
or  renal  portion. 


Vein 
leaving  — - 
hilus        j 


Fig.   1064. — The  visceral  surface  of  the  spleen. 


The  gastric  surface  (fades  gastrica),  which  is  directed  forward,  upward,  and  medialward,  is 
broad  and  concave,  and  is  in  contact  with  the  posterior  wall  of  the  stomach;  and  below  this 
with  the  tail  of  the  pancreas.  It  presents  near  its  medial  border  a  long  fissure,  termed  the  hilus. 
This  is  pierced  by  several  irregular  apertures,  for  the  entrance  and  exit  of  vessels  and  nerves. 

The  renal  surface  (fades  renalis)  is  directed  medialward  and  downward.  It  is  somewhat 
flattened,  is  considerably  narrower  than  the  gastric  surface,  and  is  in  relation  with  the  upper 
part  of  the  anterior  surface  of  the  left  kidney  and  occasionally  with  the  left  suprarenal  gland. 


THE  SPLEEN  1267 

The  superior  extremity  {cxtremitas  superior)  is  directed  toward  the  vertebral  column,  where 
it  lies  on  a  level  with  the  eleventh  thoracic  vertebra.  The  lower  extremity  or  colic  surface 
{extrcmitos  inferior)  is  flat,  triangular  in  shape,  and  rests  upon  the  left  flexure  of  the  colon  and 
the  phrenicocolic  ligament,  and  is  generally  in  contact  with  the  tail  of  the  pancreas.  The  anterior 
border  {margo  onlerior)  is  free,  sharp,  and  thin,  and  is  often  notched,  especial^  below;  it  separ- 
ates the  diaphragmatic  from  the  gastric  surface.  The  posterior  border  {margo  posterior),  more 
rounded  and  blunter  than  the  anterior,  separates  the  renal  from  the  diaphragmatic  surface; 
it  corresponds  to  the  lower  border  of  the  eleventh  rib  and  lies  between  the  Diaphragma  and  left 
kidney.  The  intermediate  margin  is  the  ridge  wliich  separates  the  renal  and  gastric  surfaces. 
The  inferior  border  {internal  border)  separates  the  diaphragmatic  from  the  colic  surface. 

The  spleen  is  almost  entirely  surrounded  by  peritoneum,  which  is  firmlj-  adherent  to  its  cap- 
sule. It  is  held  in  position  bj'  two  folds  of  this  membrane.  One,  the  phrenicolienal  ligament, 
is  derived  from  the  peritoneum,  where  the  wall  of  the  general  peritoneal  cavity  comes  into  contact 
with  the  omental  bm-sa  between  the  left  kidnej-  and  the  spleen;  the  lienal  vessels  pass  between  its 
two  layers  (Fig.  965).  The  other  fold,  the  gastrolienal  ligament,  is  also  formed  of  two  layers, 
derived  from  the  general  peritoneal  cavity  and  the  omental  bursa  respectivelj-,  where  they  meet 
between  the  spleen  and  stomach  (Fig.  965);  the  short  gastric  and  left  gastroepiploic  branches 
of  the  lienal  arterj'  run  between  its  two  layers.  The  lower  end  of  the  spleen  is  supported  by  the 
phrenicocolic  ligament  (see  page  1157). 

The  size  and  weight  of  the  spleen  are  liable  to  very  extreme  variations  at  different  periods 
of  life,  in  different  individuals,  and  in  the  same  individual  under  different  conditions.  In  the 
adult,  it  is  usually  about  12  cm.  in  length,  7  cm.  in  breadth,  and  3  or  4  cm.  in  thickness,  and 
weighs  about  200  grams.  At  birth,  its  weight,  in  proportion  to  the  entire  body,  is  almost  equal 
to  what  is  observed  iu  the  adult,  being  as  1  to  350;  while  in  the  adult  it  varies  from  1  to  320  and 
400.  In  old  age,  the  organ  not  only  diminishes  in  weight,  but  decreases  considerably  in  propor- 
tion to  the  entire  body,  being  as  1  to  700.  The  size  of  the  spleen  is  increased  during  and  after 
digestion,  and  varies  according  to  the  state  of  nutrition  of  the  body,  being  large  in  highly  fed, 
and  small  in  starved  animals.  In  malarial  fever  it  becomes  much  enlarged,  weighing  occasionally 
as  much  as  9  kilos. 

Frequently  in  the  neighborhood  of  the  spleen,  and  especiallj^  in  the  gastroKenal  ligament  and 
greater  omentum,  small  nodules  of  splenic  tissue  may  be  found,  either  isolated  or  connected 
to  the  spleen  b}^  thin  bands  of  splenic  tissue.  Thej'  are  known  as  accessory  spleens  {lien  acces- 
sorius;  supernumerary  spleen).    They  vary  in  size  from  that  of  a  pea  to  that  of  a  plum. 

Structiue. — The  spleen  is  invested  by  two  coats:  an  external  serous  and  an  internal  fibro- 
elastic  coat. 

The  external  or  serous  coat  (tunica  serosa)  is  derived  from  the  peritoneum;  it  is  thin,  smooth, 
and  in  the  himian  subject  intimately  adherent  to  the  fibroelastic  coat.  It  invests  the  entire 
organ,  except  at  the  hilus  and  along  the  lines  of  reflection  of  the  phrenicohenal  and  gastrolienal 
ligaments. 

The  fibroelastic  coat  (tunica  albuginea)  invests  the  organ,  and  at  the  hilus  is  reflected  inward 
upon  the  vessels  in  the  form  of  sheaths.  From  these  sheaths,  as  well  as  from  the  inner  sm-face 
of  the  fibroelastic  coat,  numerous  small  fibrous  bands,  trabeculae  (Fig.  1065),  are  given  off  in  all 
directions;  these  uniting,  constitute  the  frame-work  of  the  spleen.  The  spleen  therefore  consists 
of  a  number  of  small  spaces  or  areolse,  formed  by  the  trabeculae;  in  these  areolae  is  contained 
the  splenic  pulp. 

The  fibroelastic  coat,  the  sheaths  of  the  vessels,  and  the  trabeculae,  are  composed  of  white  and 
yellow  elastic  fibrous  tissues,  the  latter  predominating.  It  is  owing  to  the  presence  of  the  elastic 
tissue  that  the  spleen  possesses  a  considerable  amount  of  elasticitj',  which  allows  of  the  very 
great  variations  in  size  that  it  presents  imder  certain  circumstances.  In  addition  to  these 
constituents  of  this  tunic,  there  is  found  in  man  a  small  amount  of  non-striped  muscular  fibre; 
and  in  some  mammaha,  e.  g.,  dog,  pig,  and  cat,  a  large  amount,  so  that  the  trabeculae  appear 
to  consist  chiefly  of  muscular  tissue. 

The  splenic  pulp  {pidpa  lienis)  is  a  soft  mass  of  a  dark  reddish-brown  color,  resembling  grimious 
blood;  it  consists  of  a  fine  reticulum  of  fibres,  continuous  with  those  of  the  trabeculae,  to  which 
are  apphed  flat,  branching  cells.  The  meshes  of  the  reticulum  are  filled  with  blood,  in  which, 
however,  the  white  corpuscles  are  found  to  be  in  larger  proportion  than  thej'  are  in  ordinar}- 
blood.  Large  rounded  cells,  termed  splenic  cells,  are  also  seen;  these  are  capable  of  amoeboid 
movement,  and  often  contain  pigment  and  red-blood  corpuscles  in  then-  interior.  The  cells  of 
the  reticulum  each  possess  a  roimd  or  oval  nucleus,  and  Hke  the  splenic  cells,  they  may  contain 
pigment  granules  in  their  c^-toplasm;  they  do  not  stain  deeph*  with  carmine,  and  in  this  respect 
differ  from  the  cells  of  the  Malpighian  bodies.  In  the  young  spleen,  giant  cells  may  also  be  found, 
each  containing  numerous  nuclei  or  one  compound  nucleus.  Nucleated  red-blood  corpuscles 
have  also  been  found  in  the  spleen  of  young  animals. 

Bloodvessels  of  the  Spleen. — The  lienal  artery  is  remarkable  for  its  large  size  in  proportion 
to  the  size  of  the  organ,  and  also  for  its  tortuous  com*se.  It  di\ddes  into  sLx  or  more  branches, 
which  enter  the  hilus  of  the  spleen  and  ramify  throughout  its  substance  (Fig.  1066),  receiving 


1268 


SPLANCHNOLOGY 


sheaths  from  an  involution  of  the  external  fibrous  tissue.    Similar  sheaths  also  invest  the  nerves 
and  veins. 

Each  branch  runs  in  the  transverse  axis  of  the  organ,  from  within  outward,  diminishing  in 
size  during  its  transit,  and  giving  off  in  its  passage  smaller  branches,  some  of  which  pass  to  the 
anterior,  others  to  the  posterior  part.  These  ultimately  leave  the  trabecular  sheaths,  and  ter- 
minate in  the  proper  substance  of  the  spleen  in  small  tufts  or  pencils  of  minute  arterioles,  which 
open  into  the  interstices  of  the  reticulum  formed  by  the  branched  sustentacular  cells.  Each  of 
the  larger  branches  of  the  arterj^  supplies  chiefly  that  region  of  the  organ  in  which  the  branch 
ramifies,  having  no  anastomosis  with  the  majority  of  the  other  branches. 


Fig.  1065. — Transverse  section  of  the  sjjleen,  showing  the  trabecular  tissue  and  the  splenic  vein  and  its  tributaries. 

The  arterioles  supported  by  the  minute  trabeculse,  traverse  the  pulp  in  all  directions  in  bundles 
(pencilli)  of  straight  vessels.  Their  trabecular  sheaths  gradually  undergo  a  transformation, 
become  much  thickened,  and  converted  into  adenoid  tissue;  the  bundles  of  connective  tissue 
becoming  looser  and  their  fibrils  more  delicate,  and  containing  in  their  interstices  an  abundance 
of  lymph  corpuscles  (W.  Mtiller). 


Fig.  1066. — Transverse  section  of  the  human  spleen,  showing  the  distribution  of  the  splenic  artery  and  its  branches. 


The  altered  coat  of  the  arterioles,  consisting  of  adenoid  tissue,  presents  here  and  there  thick- 
enings of  a  spheroidal  shape,  the  lymphatic  nodules  {Malpighian  bodies  of  (he  spleen).  These 
bodies  vary  in  size  from  about  0.25  mm.  to  1  mm.  in  diameter.  They  are  merely  local  expansions 
or  hj^erplasise  of  the  adenoid  tissue,  of  which  the  external  coat  of  the  smaller  arteries  of  the  spleen 


THE  SPLEEN 


1269 


is  formed.  They  are  most  fnHiuontly  found  surrounding  the  arteriole,  which  thus  seems  to 
tunnel  them,  but  occasionally  (h(>y  grow  from  one  .sidi;  of  the  vessel  only,  and  i)resent  the  appear- 
ance of  a  sessile  bud  growing  from  the  arterial  wall.  In  transverse  sections,  the  artery,  in  the 
majority  of  cases,  is  found  in  an  excentric  jjosition.  These  bodies  are  visible  to  the  naked  eye 
on  the  surface  of  a  fresh  section  of  the  organ,  appearing  as  minute  dots  of  a  semiopaque  whitish 


Fig.   1067. — Transverse  section  of  a  portion  of  the  spleen. 


Trabecula 


Lymphatic 
nodule 


Spleen  pulp 


color  in  the  dark  substance  of  the  pulp.  In  minute  structure  they  resemble  the  adenoid  tissue 
of  IjTnph  glands,  consisting  of  a  delicate  reticulum,  in  the  meshes  of  which  lie  ordinary  lymphoid 
cells  (Fig.  1067).  The  reticulum  is  made  up  of  extremely  fine  fibrils,  and  is  comparatively  open 
in  the  centre  of  the  corpuscle,  becoming  closer  at  its  periphery.  The  cells  which  it  encloses 
are  possessed  of  amoeboid  movement.  When  treated  with  carmine  they  become  deeply  stained, 
and  can  be  easily  distinguished  from  those  of  the  pulp. 


Branching  cell 


Small 
artery 


Vessel  continuous 
"^    ivith  processes  of 
network  cells 


■Branching  cell 


cell      '    ^J^^K.    '        ( 
Fig.  106S. — Section  of  the  spleen,  showing  the  termination  of  the  small  bloodvessels. 


The  arterioles  end  by  opening  freely  into  the  splenic  pulp;  their  walls  become  much  attenuated, 
they  lose  their  tubular  character,  and  the  endothelial  cells  become  altered,  presenting  a  branched 
appearance,  and  acquiring  processes  which  are  directly  connected  with  the  processes  of  the 
reticular  cells  of  the  pulp  (Fig.  1068).  In  this  manner  the  vessels  end,  and  the  blood  flowing 
through  them  finds  its  way  into  the  interstices  of  the  reticulated  tissue  of  the  splenic  pulp.    Thus 


1270  SPLANCHNOLOGY 

the  blood  passing  throufi;h  the  spleen  is  brought  into  intimate  relation  with  the  elements  of  the 
pulp,  and  no  doubt  undergoes  important  changes. 

After  these  changes  have  taken  place  the  blood  is  collected  from  the  interstices  of  the  tissue 
by  the  rootlets  of  the  veins,  which  begin  much  in  the  same  way  as  the  arteries  end.  The  con- 
nective-tissue corpuscles  of  the  pulp  arrange  themselves  in  rows,  in  such  a  way  as  to  form  an 
elongated  space  or  sinus.  They  become  elongated  and  spindle-shaped,  and  overlap  each  other 
at  their  extremities,  and  thus  form  a  sort  of  endothelial  lining  of  the  path  or  sinus,  which  is  the 
radicle  of  a  vein.  On  the  outer  surfaces  of  these  cells  are  seen  delicate  transverse  lines  or  markings, 
which  are  due  to  minute  elastic  fibrillae  arranged  in  a  circular  manner  around  the  sinus.  Thus 
the  channel  obtains  an  external  investment,  and  gradually  becomes  converted  into  a  small 
vein,  which  after  a  short  course  acquu-es  a  coat  of  ordinary  connective  tissue,  lined  by  a  layer  of 
flattened  epithelial  cells  which  are  continuous  with  the  supporting  cells  of  the  pulp.  The  smaller 
veins  unite  to  form  larger  ones;  these  do  not  accompany  the  arteries,  but  soon  enter  the  tra- 
becular sheaths  of  the  capsule,  and  by  their  junction  form  six  or  more  branches,  which  emerge 
from  the  hilus,  and,  uniting,  constitute  the  lienal  vein,  the  largest  radicle  of  the  portal  vein. 

The  veins  are  remarkable  for  their  numerous  anastomoses,  while  the  arteries  hardly  anastomose 
at  all. 

The  lymphatics  are  described  on  page  793. 

The  nerves  are  derived  from  the  coeliac  plexus  and  are  chiefly  non-medullated.     They  are 
distributed  to  the  bloodvessels  and  to  the  smooth  muscle  of  the  capsule  and  trabeculse. 

Applied  Anatomy. — Injury  of  the  spleen  is  less  common  than  that  of  the  liver,  on  account  of 
its  protected  situation  and  connections.  It  may  be  ruptured  by  direct  or  indirect  violence;  torn 
by  a  broken  rib;  or  injured  by  a  punctured  or  gunshot  wound.  When  the  organ  is  enlarged,  the 
chance  of  rupture  is  increased.  The  great  risk  is  hemorrhage,  owing  to  the  vascularity  of  the 
organ,  and  the  absence  of  a  proper  system  of  capillaries.  The  injury  is  not,  however,  necessarily 
fatal,  and  this  would  appear  to  be  due,  in  a  great  measure,  to  the  contractile  power  of  the  cap- 
sule, which  narrows  the  wound  and  prevents  the  escape  of  blood.  In  cases  where  the  diagnosis 
is  clear,  and  the  symptoms  indicate  danger  to  life,  laparotomy  must  be  performed,  and  if  the 
hemorrhage  cannot  be  stayed  by  ordinary  surgical  methods,  the  spleen  must  be  removed. 

The  spleen  may  become  enormously  enlarged  in  certain  diseased  conditions,  such  as  ague, 
leukemia,  syphilis,  valvular  disease  of  the  heart,  or  without  any  obtainable  history  of  previous 
disease.  It  may  also  become  enlarged  in  lymphadenoma,  as  a  part  of  a  general  blood-disease. 
In  these  cases  the  tumor  may  fill  a  considerable  part  of  the  abdomen  and  extend  into  the  pelvis, 
and  may  be  mistaken  for  ovarian  or  uterine  new  growth. 

The  spleen  is  sometimes  the  seat  of  cystic  tumors,  especially  hydatids,  and  of  abscess.  These 
cases  require  treatment  by  incision  and  drainage;  and  in  abscess  great  care  must  be  taken,  if 
there  are  no  adhesions  between  the  spleen  and  abdominal  wall,  to  prevent  the  escape  of  any  of 
the  pus  into  the  peritoneal  cavity.  If  possible  the  operation  should  be  performed  in  two  stages. 
Sarcoma  and  carcinoma  are  occasionally  found  in  the  spleen,  but  very  rarely  as  primary  diseases. 

Extirpation  of  the  spleen  has  been  performed  for  wounds  or  injuries,  in  floating  spleen,  in 
simple  hypertrophy,  in  leukemic  enlargement  (but  the  operation  is  now  considered  unjustifiable 
in  this  condition),  and  in  the  case  of  enlargement  due  to  certain  obscure  parasitic  infections  met 
with  in  hot  climates.  The  incision  is  best  made  in  the  left  semilunar  line;  the  spleen  is  isolated 
from  its  surroundings  and  delivered  from  the  abdomen;  the  pedicle  is  then  transfixed  and  ligatured 
in  two  portions. 


THE  SUPRARENAL  GLANDS  (GLANDULAE  SUPRARENALIS ;  ADRENAL 
CAPSULE)  (Figs.  1069,  1070). 

The  suprarenal  glands  are  two  small  flattened  bodies  of  a  yellowish  color,  situated 
at  the  back  part  of  the  abdomen,  behind  the  peritoneum,  and  immediately  above 
and  in  front  of  the  upper  end  of  each  kidney;  hence  their  name.  The  right  one  is 
somewhat  triangular  in  shape,  bearing  a  resemblance  to  a  cocked  hat;  the  left  is 
more  semilunar,  usually  larger,  and  placed  at  a  higher  level  than  the  right.  They 
vary  in  size  in  different  individuals,  being  sometimes  so  small  as  to  be  scarcely 
detected :  their  usual  size  is  from  3  to  5  cm.  in  length,  rather  less  in  width,  and  from 
4  to  6  mm.  in  thickness.    Their  average  weight  is  from  1.5  to  2.5  gm.  each. 

Relations. — The  relations  of  the  suprarenal  glands  differ  on  the  two  sides  of  the  body. 

The  right  suprarenal  is  situated  behind  the  inferior  vena  cava  and  right  lobe  of  the  liver,  and 
in  front  of  the  Diaphragma  and  upper  end  of  the  right  kidney.  It  is  roughly  triangular  in  shape; 
its  base,  directed  downward,  is  in  contact  with  the  medial  and  anterior  aspects  of  the  upper  end 


THE  Si'PRAREXAL  C'LAXDS 


1271 


of  the  right  kidney.  It  iiresents  two  surfaces  for  examination,  an  anterior  and  a  posterior.  The 
anterior  surface  looks  forward  and  latcralward,  and  has  two  areas:  a  medial,  narrow,  and  non- 
peritoneal,  which  lies  beliind  the  inferior  vena  cava;  and  a  lateral,  somewhat  triangular,  in 
contact  with  the  liver.  The  upper  part  of  the  latter  surface  is  devoid  of  peritoneum,  and  is  in 
relation  witii  the  bare  area  of  the  liver  near  its  lower  and  mcnlial  angle,  while  its  inferior  portion 
is  covered  bj-  peritoneum,  reflected  on  to  it  from  the  inferior  layer  of  the  coronary  ligament; 
occasionally  the  duodenum  overlaps  the  inferior  portion.  A  little  below  the  apex,  and  near 
the  anterior  border  of  the  gland,  is  a  short  furrow  termed  the  hilus,  from  which  the  suprarenal 
vein  emerges  to  join  the  inferior  vena  cava.  The  posterior  surface  is  divided  into  upper  and 
lower  parts  by  a  curved  ridge:  the  upper,  slightly  convex,  rests  upon  the  Diaphragma;  the 
lower,  concave,  is  in  contact  with  the  upper  end  and  the  adjacent  part  of  the  anterior  surface 
of  the  kidney. 


Suprarenal  lein 


Hepatic  area 

Area  in  con- 
tact with  in- 

ferior    vena 
cava 


—  Gastric  area 


Pancreatic  area 


Suprarenal  vein 
Right.  Left. 

Fig.   1069. — Suprarenal  glands  viewed  from  the  front. 


The  left  suprarenal,  slightly  larger  than  the  right,  is  crescentic  in  shape,  its  concavity  being 
adapted  to  the  medial  border  of  the  upper  part  of  the  left  kidney.  It  presents  a  medial  border, 
which  is  convex,  and  a  lateral,  which  is  concave;  its  upper  end  is  narrow,  and  its  lower  rounded. 
Its  anterior  surface  has  two  areas:  an  upper  one,  covered  by  the  peritoneum  of  the  omental 
bursa,  which  separates  it  from  the  cardiac  end  of  the  stomach,  and  sometimes  from  the  superior 
extremity  of  the  spleen;  and  a  lower  one,  which  is  in  contact  with  the  pancreas  and  lienal 
artery,  and  is  therefore  not  covered  by  the  peritoneum.  On  the  anterior  surface,  near  its  lower 
end,  is  a  fmTow  or  hilus,  dnected  downward  and  forward,  from  which  the  suprarenal  vein 
emerges.  Its  posterior  surface  presents  a  vertical  ridge,  which  divides  it  into  two  areas;  the 
lateral  area  rests  on  the  kidney,  the  medial  and  smaller  on  the  left  crus  of  the  Diaphragma. 


Diaphrag- 
maiic  area 


Renal  area 


D  iaphragmat  ic 
area 


Renal  area 


Right.  Left. 

Fig.  1070. — Suprarenal  glands  viewed  from  behind. 

The  surface  of  the  suprarenal  gland  is  surrounded  by  areolar  tissue  containing  much  fat,  and 
closely  invested  by  a  thin  fibrous  capsule,  which  is  difficult  to  remove  on  account  of  the  numerous 
fibrous  processes  and  vessels  entering  the  organ  thi-ough  the  furrows  on  its  anterior  snrface  and 
base. 

Small  accessory  suprarenals  (glandulae  suprarenales  accessoriae)  are  often  to  be  found  in  the 
connective  tissue  around  the  suprarenals.  The  smaller  of  these,  on  section,  show  a  uniform 
surface,  but  in  some  of  the  larger  a  distinct  meduUa  can  be  made  out. 

Structure. — On  section,  the  suprarenal  gland  is  seen  to  consist  of  two  portions  (Fig.  1071): 
an  external  or  cortical  and  an  internal  or  medullary.  The  former  constitutes  the  chief  part  of 
the  organ,  and  is  of  a  deep  yellow  color;  the  medullary  substance  is  soft,  pulpy,  and  of  a  dark  red 
or  brown  color. 


1272  SPLANCHNOLOGY 

The  cortical  portion  (substantia  corlicalis)  consists  of  a  fine  connective-tissue  net-work,  in 
which  is  imbedded  the  glandular  epithelium.  The  epithelial  cells  are  polyhedral  in  shape  and 
possess  rounded  nuclei;  many  of  the  cells  contain  coarse  granules,  others  hpoid  globules.  Owing 
to  differences  in  the  arrangement  of  the  cells,  three  distinct  zones  can  be  made  out:  (1)  the  zona 
glomerulosa,  situated  beneath  the  capsule,  consists  of  cells  arranged  in  rounded  groups,  with 
here  and  there  indications  of  an  alveolar  structure;  the  cells  of  this  zone  are  verj-  granular,  and 
stain  deeply.  (2j  The  zona  fasciculata,  continuous  with  the  zona  glomerulosa,  is  composed  of 
columns  of  cells  arranged  in  a  radial  manner;  these  cells  contain  finer  granules  and  in  many 
instances  globules  of  hpoid  material.  (3)  The  zona  reticularis,  in  contact  with  the  medulla, 
consists  of  cylindrical  masses  of  cells  irregularly  arranged;  these  cells  often  contain  pigment 
granules  which  give  this  zone  a  darker  appearance  than  the  rest  of  the  cortex. 

The  medullary  portion  {substantia  medullaris)  is  extremely  vascular,  and  is  composed  of  a 
loose  mesh-work  of  connective  tissue  sm^rounding  a  large  plexus  of  sinusoidal  venous  spaces  and 
containing  non-striped  muscular  fibres.  In  addition  to  the  veins,  multinucleated  masses  of 
protoplasm  are  scattered  throughout  the  meduUa  as  well  as  many  irregular-shaped  cells  con- 
taining pigment.  The  cell  protoplasm  has  an  especial  affinity  for  chromic  salts,  which  stain  it 
a  brown  color.  Such  cells  are  therefore  termed  chromaffin  cells  (see  page  133 j.  This  portion 
of  the  gland  is  richly  supplied  with  non-medullated  nerve  fibres,  and  here  and  there  sjonpathetic 
ganglia  are  found. 


1 


—  Capsule 

^  I  Zona  glomerulosa 


'  \  Zona  fasciculata 

I  Zona  reticidaris 

^  '  ilidtinucleated  mass 
of  protoplasm. 


h 


>  Medulla 


^^.SC 


Ganglion 
Fig.   1071. — Section  of  a  part  of  a  suprarenal  gland.     (Magnified.) 

Vessels  and  Nerves. — The  arteries  supplj'ing  the  suprarenal  glands  are  numerous  and  of 
comparatively  large  size;  they  are  derived  from  the  aorta,  the  inferior  phrenic,  and  the  renal. 
They  subdivide  into  minute  branches  previous  to  entering  the  cortical  part  of  the  gland,  where 
they  break  up  into  capillaries  which  end  in  the  venous  plexus  of  the  meduUarj'  portion. 

The  suprarenal  vein  returns  the  blood  from  the  medullary  venous  plexus  and  receives  several 
branches  from  the  cortical  substance;  it  emerges  from  the  hilus  of  the  gland  and  on  the  right 
side  opens  into  the  inferior  vena  cava,  on  the  left  into  the  renal  vein. 

The  lymphatics  end  in  the  lumbar  glands. 

The  nerves  are  exceedingly  numerous,  and  are  derived  from  the  cceUac  and  renal  plexuses, 
and,  according  to  Bergmann,  from  the  phrenic  and  vagus  ner\^es.  They  enter  the  lower  and 
medial  part  of  the  capsule,  traverse  the  cortex,  and  end  around  the  cells  of  the  meduUa.  They 
have  numerous  small  gangUa  developed  upon  them  in  the  meduUarj'  portion  of  the  gland. 

In  cormection  with  the  development  of  the  medulla  from  the  sjTnpathochromaffin  tissue,  it  is 
to  be  noted  that  this  portion  of  the  gland  secretes  a  substance,  adrenalin,  which  has  a  powerful 
influence  on  those  muscular  tissues  which  are  supphed  bj'  sj-mpathetic  fibres. 

Applied  Anatomy. — The  suprarenal  cortex  is  derived  from  the  coelomic  epitheUum  of  the 
Wolffian  ridge,  and  is  coimected  with  the  sexual  glands;  it  is  related  to  growth  and  development 
in  some  way,  and  is  often  found  to  be  hj'pertrophied  in  patients  with  chronic  kidney  disease 
and  high  blood-pressure.     The  meduUa,  on  the  other  hand,  is  neuro-ectodermal  in  origin,  and 


THE  COCCYGEAL  SKEIN  1273 

closelj''  connected  with  the  synipathctic  nervous  system.  When  the  suprarenal  medulla  is 
destroj^ed  by  tuberculosis,  to  wliicli  the  glands  arc  prone,  or  by  the  pressure  of  a  new  growth, 
the  secretion  of  adrenalin  becomes  inadequate,  and  Addison's  disease  develops.  Patients  with 
Addison's  disease  become  pigmented  in  various  parts  of  the  body,  possibly  from  irritation  of 
the  sympathetic,  and  complain  of  great  weakness,  lack  of  energy,  nausea,  and  severe  attacks  of 
vomiting.  Their  blood-pressure  is  low,  the  whole  nervous  system  is  depressed,  and  death  follows 
after  a  period  of  months  or  years,  usually  from  asthenia.  Tumors  derived  from  the  suprarenal 
itself,  or  from  misi^laced  suprarenal  "rests"  occurring  in  such  organs  as  the  kidney  or  hver,  may 
be  either  benign  or  malignant,  and  are  classed  together  under  the  name  "hypernephroma." 
In  children  the  malignant  hjqaernephroma  is  often  associated  with  obesity  and  precocity.  The 
benign  hypernephroma,  or  suprarenal  adenoma,  appears  to  produce  no  symptoms  except  those 
due  to  its  slow  enlargement. 


THE  CAROTID  SKEINS   (GLOMERA  CAROTICA;  CAROTID  GLANDS; 

CAROTID  BODIES.) 

The  carotid  skeins,  two  in  number,  are  situated  one  on  either  side  of  the  neck, 
behind  the  common  carotid  artery  at  its  point  of  bifurcation  into  the  external 
and  internal  carotid. trunks.  They  are  reddish  brown  in  color  and  oval  in  shape, 
the  long  diameter  measuring  about  5  mm. 


^-  Ol  ^:-v-^ 


Fig.   1072. — Section  of  part  of  human  glomus  caroticum.     (Schaper.)     Highly  magnified.    Numerous  bloodvessels  are 

seen  in  section  among  the  gland  cells. 

Each  is  invested  by  a  fibrous  capsule  and  consists  largely  of  spherical  or  irregular 
masses  of  cells  (Fig.  1072),  the  masses  being  more  or  less  isolated  from  one  another 
by  septa  which  extend  inward  from  the  deep  surface  of  the  capsule.  The  cells 
are  polyhedral  in  shape,  and  each  contains  a  large  nucleus  imbedded  in  finely 
granular  protoplasm,  which  is  stained  yellow  by  chromic  salts.  Numerous  nerve 
fibres,  derived  from  the  sympathetic  plexus  on  the  carotid  artery,  are  distributed 
throughout  the  organ,  and  a  net-work  of  large  sinusoidal  capillaries  ramifies  among 
the  cells. 


THE  COCCYGEAL  SKEIN  (GLOMUS  COCCYGEUM;  COCCYGEAL   GLAND 
OR  BODY;  LUSCHKA'S  GLAND). 

The  coccygeal  skein  is  placed  in  front  of,  or  immediately  below,  the  tip  of  the 
coccjTC.  It  is  about  2.5  mm.  in  diameter  and  is  irregularly  oval  in  shape;  several 
smaller  nodules  are  found  around  or  near  the  main  mass. 

It  consists  of  irregular  masses  of  round  or  polyhedral  cells  (Fig.  1073),  the  cells 
of  each  mass  being  grouped  around  a  dilated  sinusoidal  capillary  vtsssel.    Each  cell 


1274  SPLANCHNOLOGY 

contains  a  large  round  or  oval  nucleus,  the  protoplasm  surrounding  which  is  clear, 
and  is  not  stained  by  chromic  salts. ^ 


M' 


\;;- 


Fig.    1073. — Section  of  an  irregular  nodule  of  the  glomus  coccygeum.     (Sertoli.)      X  85.     The  section  shows  the 
fibrous  covering  of  the  nodule,  the  bloodvessels  within  it,  and  the  epithelial  cells  of  which  it  is  constituted. 

Besides  the  ductless  glands  mentioned,  reference  may  be  made  to  a  pair  of  small 
bodies,  the  aortic  bodies  of  Zuckerkandl.  These  are  found  in  the  embryo,  and  persist 
until  shortly  after  birth;  they  lie  one  on  either  side  of  the  abdominal  aorta  between 
the  superior  mesenteric  and  common  iliac  arteries  (see  page  133).  They  consist 
essentially  of  masses  of  polygonal  or  cuboidal  chromaffin  cells  imbedded  in  a 
wide-meshed  capillary  plexus. 

1  Consult  the  following  article:  "Uber  die  menschliche  Steissdruse,"  von  J.  W.  Thomson  Walker,  Archiv  fur  mikro- 
skopische  Anatomie  und  Entwickelungsgeschichte,  Band  64,  1904. 


SURFACE  ANATOMY  AND  SURFACE 

MARKINGS. 


SURFACE  ANATOMY  OF  THE  HEAD  AND  NECK. 

Bones  (Fig.  1074), — Various  bony  surfaces  and  prominences  on  the  skull  can  be 
easily  identified  by  palpation.  The  external  occipital  protuberance  is  situated 
behind,  in  the  middle  line,  at  the  junction  of  the  skin  of  the  neck  with  that  of  the 
head.  The  superior  nuchal  line  runs  lateralward  from  it  on  either  side,  while  extend- 
ing downward  from  it  is  the  median  nuchal  crest,  situated  deeply  at  the  bottom 
of  the  nuchal  furrow.     Above  the  superior  nuchal  lines  the  vault  of  the  cranium 


Zygomatic  Uihercle^ 
Zygomaticofrontal     ^l 

suture  ^"/  /x 

Supraorbital  foramen  ~  j^ 
Glabella 
Nasion  __ 


Inion 
Reid's  hose 
line 


Median  nuchal  crest 


t  Auricular  point 
Prce-auricular  point 


Fig.  1074. — Side  view  of  head,  showing  surface  relations  of  bones. 

is  thinly  covered  with  soft  structures,  so  that  the  form  of  this  part  of  the  head  is 
almost  that  of  the  upper  portion  of  the  occipital,  the  parietal,  and  the  frontal 
bones.  The  superior  nuchal  line  can  be  followed  lateralward  to  the  mastoid  por- 
tion of  the  temporal  bone,  from  which  the  mastoid  process  projects  downward 
and  forward  behind  the  ear.  The  anterior  and  posterior  borders,  the  apex,  and 
the  external  surface  of  this  process  are  all  available  for  superficial  examination  the 
anterior  border  lies  immediately  behind  the  concha,  and  the  apex  is  on  a  level 


1276  SURFACE  ANATOMY  AND  SURFACE  MARKINGS 

with  the  lobule  of  the  auricula.  Aljout  1  ciu.  below  and  in  front  of  the  apex  of 
the  mastoid  process,  the  transverse  process  of  the  atlas  can  be  distinguished.  In 
front  of  the  ear  the  zygomatic  arch  can  be  felt  throughout  its  entire  length;  its 
posterior  end  is  narrow  and  is  situated  a  little  above  the  level  of  the  tragus;  its 
anterior  end  is  broad  and  is  continued  into  the  zygomatic  bone.  The  lower  border 
of  the  arch  is  more  distinct  than  the  upper,  which  is  obscured  by  the  attachment 
of  the  temporal  fascia.  In  front,  and  behind,  the  upper  border  of  the  arch  can  be 
followed  into  the  superior  temporal  line.  In  front,  this  line  begins  at  the  zygomatic 
process  of  the  frontal  bone  as  a  curved  ridge  which  runs  at  first  forward  and 
upward  on  the  frontal  bone,  and  then  curving  backward  separates  the  forehead 
from  the  temporal  fossa.  It  can  then  be  traced  across  the  parietal  bone,  where, 
though  less  marked,  it  can  generally  be  recognized.  Finally,  it  curves  downward, 
and  forward,  and  passing  above  the  external  acoustic  meatus,  ends  in  the  posterior 
root  of  the  zygomatic  arch.  Near  the  line  of  the  greatest  transverse  diameter  of 
the  head  are  the  parietal  eminences,  one  on  either  side  of  the  middle  line;  further 
forward,  on  the  forehead,  are  the  frontal  eminences,  which  vary  in  prominence  in 
different  individuals  and  are  frequently  uns}'mmetrical.  Below  the  frontal  emi- 
nences the  superciliary  arches,  which  indicate  the  position  of  the  frontal  sinuses, 
can  be  recognized;  as  a  rule  they  are  small  in  the  female  and  absent  in  children. 
In  some  cases  the  prominence  of  the  superciliary  arches  is  related  to  the  size  of 
the  frontal  sinuses,  but  frequently  there  is  no  such  relationship.  Situated  between, 
and  connecting  the  superciliary  ridges,  is  a  smooth,  somewhat  triangular  area,  the 
glabella,  below  which  the  nasion  {frontonasal  suture)  can  be  felt  as  a  slight  depres- 
sion at  the  root  of  the  nose. 

Below  the  nasion  the  nasal  bones,  scantily  covered  by  soft  tissues,  can  be  traced 
to  their  junction  with  the  nasal  cartilages,  and  on  either  side  of  the  nasal  bone 
the  complete  outline  of  the  orbital  margin  can  be  made  out.  At  the  junction  of 
the  medial  and  intermediate  thirds  of  the  supraorbital  margin  the  supraorbital 
notch,  when  present,  can  be  felt;  close  to  the  medial  end  of  the  infraorbital  margin 
is  a  little  tubercle  which  serves  as  a  guide  to  the  position  of  the  lacrimal  sac.  Below 
and  lateral  to  the  orbit,  on  either  side,  is  the  zygomatic  bone  forming  the  prominence 
of  the  cheek;  its  posterior  margin  is  easily  palpable,  and  on  it  just  above  the  level 
of  the  lateral  palpebral  commissure  is  the  zygomatic  tubercle.  A  slight  depression, 
about  1  cm.  above  this  tubercle,  indicates  the  position  of  the  zygomaticofrontal 
suture.  Directly  below  the  orbit  a  considerable  part  of  the  anterior  surface  of  the 
maxilla  and  the  whole  of  its  alveolar  process  can  be  palpated.  The  outline  of  the 
mandible  can  be  recognized  throughout  practically  its  entire  extent;  in  front  of 
the  tragus  and  below  the  zygomatic  arch  is  the  condyle,  and  from  this  the  posterior 
border  of  the  ramus  can  be  followed  to  the  angle;  from  the  angle  to  the  symph3'sis 
the  lower  rounded  border  of  the  mandible  can  be  easily  traced;  the  lower  part  of 
the  anterior  border  of  the  ramus  and  the  alveolar  process  can  be  made  out  without 
difficulty.  In  the  receding  angle  below  the  chin  is  the  hyoid  bone,  and  the  finger 
can  be  carried  along  the  bone  to  the  tip  of  the  greater  cornu,  which  is  on  a  level 
with  the  angle  of  the  mandible:  the  greater  cornu  is  most  readily  appreciated 
by  making  pressure  on  one  side,  when  the  cornu  of  the  opposite  side  will  be  rendered 
prominent  and  can  be  felt  distinctly  beneath  the  skin. 

Joints  and  Muscles. — The  temporomandibular  articulation  is  quite  superficial,  and 
is  situated  below  the  posterior  end  of  the  zygomatic  arch,  in  front  of  the  external 
acoustic  meatus.  Its  position  can  be  ascertained  by  defining  the  condyle  of  the 
mandible;  when  the  mouth  opens,  the  condyle  advances  out  of  the  mandibular 
fossa  on  to  the  articular  tubercle,  and  a  depression  is  felt  in  the  situation  of  the 
joint. 

The  outlines  of  the  muscles  of  the  head  and  face  cannot  be  traced  on  the  surface 
except  in  the  case  of  the  Masseter  and  Temporalis.     The  muscles  of  the  scalp 


SURFACE  AX  ATOMY  OF  THE  HEAD  AXD  XECK 


1277 


are  so  thin  that  the  outline  of  the  bone  is  perceptible  beneath  them.  Those  of 
the  face  are  small,  covered  by  soft  skin,  and  often  })y  a  considerable  layer  of  fat, 
and  their  outlines  are  therefore  concealed;  they  serve,  however,  to  round  off  and 
smooth  prominent  borders,  and  to  fill  up  what  would  otherwise  be  unsightly 
angular  depressions.  Thus  the  Orbicularis  oculi  rounds  off  the  prominent  margin 
of  the  orbit,  and  the  Procerus  fills  in  the  sharp  depression  below  the  glabella.  In 
like  manner  the  labial  muscles  converging  to  the  lips,  and  assisted  by  the  super- 
imposed fat,  fill  up  the  sunken  hollow  of  the  lower  part  of  the  face.  When  in 
action  the  facial  muscles  produce  the  various  expressions,  and  in  addition  through 
the  skin  into  numerous  folds  and  wrinkles.  The  Masseter  imparts  fulness  to  the 
hinder  part  of  the  cheek;  if  firmly  contracted,  as  when  the  teeth  are  clenched,  its 
quadrilateral  outline  is  plainly  visible;  the  anterior  border  forms  a  prominent 
vertical  ridge,  behind  which  is  a  considerable  fulness  especially  marked  at  the 


v|       Sternodeidomastoideus 


Submaxillary  triangle 
Hyoid  hone 

Thyroid  cartilage 
Cricoid  cartilage 


Supraclavicular  fossa 


Clavicle 


'  Infraclavicular  fossa 

Clavicular  head 
Sternal  head 


Jugular  notch 

Fig.   1075. — Anterolateral  view  of  head  and  neck. 


of  Sternocleidoraastoideus 


lower  part  of  the  muscle.  The  Temporalis  is  fan-shaped  and  fills  the  temporal 
fossa,  substituting  for  the  concavity  a  somewhat  convex  swelling,  the  anterior 
part  of  which,  on  account  of  the  absence  of  hair  on  the.  overlying  skin,  is  more 
marked  than  the  posterior,  and  stands  out  in  strong  relief  when  the  muscle  is  in 
action. 

In  the  neck,  the  Platysma  when  contracted  throws  the  skin  into  oblique  ridges 
parallel  with  the  fasciculi  of  the  muscle.  The  Stemocleidomastoideus  has  the  most 
important  influence  on  the  surface  form  of  the  neck  (Figs.  1075,  1076).  When  the 
muscle  is  at  rest  its  anterior  border  forms  an  oblique  rounded  edge  ending  below  in 
the  sharp  outline  of  the  sternal  head;  the  posterior  border  is  only  distinct  for  about 
2  or  3  cm,  above  the  middle  of  the  clavicle.  During  contraction,  the  sternal  head 
stands  out  as  a  sharply  defined  ridge,  while  the  clavicular  head  is  flatter  and  less 
prominent;  between  the  two  heads  is  a  slight  depression:  the  fleshy  middle  portion 


1278 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


of  the  muscle  appears  as  an  oblique  elevation  with  a  thick,  rounded,  anterior  border, 
best  marked  in  its  lower  part.  The  sternal  heads  of  the  two  muscles  are  separated 
by  a  V-shaped  depression,  in  which  are  the  Sternohyoideus  and  Sternothyreoideus. 

Above  the  hyoid  bone,  near  the  middle  line,  the  anterior  belly  of  the  Digastricus 
produces  a  slight  convexity. 

The  anterior  border  of  the  Trapezius  presents  as  a  faint  ridge  running  from  the 
superior  nuchal  line,  downward  and  forward  to  the  junction  of  the  intermediate 
and  lateral  thirds  of  the  clavicle.  Between  the  Sternocleidomastoideus  and  the 
Trapezius  is  the  posterior  triangle  of  the  neck,  the  lower  part  of  which  appears  as 
a  shallow  concavity — the  supraclavicular  fossa.  In  this  fossa,  the  inferior  belly  of 
the  Omohyoideus,  when  in  action,  presents  as  a  rounded  cord-like  elevation  a  little 
above,  and  almost  parallel  to,  the  clavicle. 


Anterior  helly  of  Digastricus 
2IyloTiyoideus 

Hyoid  hone 
Thyroid  cartilage 
Cricoid  cartilage 
Sternochidomastoideus 
Supraclavicular  fossa 
/  Trapezius 


Fig. 


I  Clavicle 

Clavicular  head  )  of  Sternocleido- 
Sternal  head  )      mastoideus 

1076. — Front  view  of  neck. 


Arteries.- — The  positions  of  several  of  the  larger  arteries  can  be  ascertained 
from  their  pulsations. 

The  subclavian  artery  can  be  felt  by  making  pressure  downward,  backward,  and 
medialward  behind  the  clavicular  head  of  the  Sternocleidomastoideus;  its  transverse 
cervical  branch  may  be  detected  parallel  to,  and  about  a  finger's  breadth  above, 
the  clavicle.  The  common  and  external  carotid  arteries  can  be  recognized  immediately 
beneath  the  anterior  edge  of  the  Sternocleidomastoideus.  The  external  maxillary 
artery  can  be  traced  over  the  border  of  the  mandible  just  in  front  of  the  anterior 
border  of  the  Masseter,  then  about  1  cm.  lateral  to  the  angle  of  the  mouth,  and 
finally  as  it  runs  up  the  side  of  the  nose.  The  pulsation  of  the  occipital  artery 
can  be  distinguished  about  3  or  4  cm.  lateral  to  the  external  occipital  protuberance; 
that  of  the  posterior  auricular  in  the  groove  between  the  mastoid  process  and  the 
auricula.  The  course  of  the  superficial  temporal  artery  can  be  readily  followed 
across  the  posterior  end  of  the  zygomatic  arch  to  a  point  about  3  to  5  cm.  above 
this,  where  it  divides  into  its  frontal  and  parietal  branches;  the  pulsation  of  the 
frontal  branch  is  frequently  visible  on  the  side  of  the  forehead.  The  supraorbital 
artery  can  usually  be  detected  immediately  above  the  supraorbital  notch  or  foramen. 


SURFACE  MARKINGS  OF  SPECIAL  REGIONS  OF  HEAD  AND  NECK     1279 


SURFACE  MARKINGS  OF  SPECIAL  REGIONS  OF  HEAD  AND  NECK. 

The  Cranium. — Scalp.— The  soft  parts  covering  the  upper  surface  of  the  skull 
form  the  scalp  and  comprise  the  following  layers  (Fig.  1077):  (1)  skin,  (2)  subcuta- 
neous tissue,  (3)  Occipitalis  frontalis  and  galea  aponeurotica,  (4)  subaponeurotic  tissue, 
(5)  pericranium.  The  subcutaneous  tissue  consists  of  a  close  mesh-work  of  fibres, 
the  meshes  of  which  contain  fatty  tissue;  the  fibres  bind  the  skin  and  galea  aponeu- 
rotica firmly  together,  so  that  when  the  Occipitalis  or  the  Frontalis  is  in  action 
the  skin  moves  with  the  aponeurosis.  The  subaponeurotic  tissue,  which  intervenes 
between  the  galea  aponeurotica  and  the  pericranium,  is  much  looser  in  texture, 
and  permits  the  movement  of  the  aponeurosis  over  the  underlying  bones. 


Suhcutaneous  tissue 

Galea  aponeurotica 
Pericranium 


Superior  sagittal  sinus 


Fig.  1077. — Diagrammatic  section  of  scalp. 

Bony  Landmarks  (Fig.  1074). — In  addition  to  the  bony  points  already  described 
which  can  be  determined  by  palpation,  the  following  are  utilized  for  surface 
markings : 

Auricular  Point. — ^The  centre  of  the  orifice  of  the  external  acoustic  meatus. 

Preauricular  Point. — A  point  on  the  posterior  root  of  the  zygomatic  arch  imme- 
diately in  front  of  the  external  acoustic  meatus. 

Asterion. — The  point  of  meeting  of  the  lambdoidal,  mastooccipital,  and  masto- 
parietal  sutures;  it  lies  4  cm.  behind  and  12  mm.  above  the  level  of  the  auricular 
point. 

Pterion. — ^The  point  where  the  great  wdng  of  the  sphenoid  joins  the  sphenoidal 
angle  of  the  parietal;  it  is  situated  35  mm.  behind,  and  12  mm.  above,  the  level 
of  the  frontozygomatic  suture. 

Inion. — The  external  occipital  protuberance. 

Lambda. — The  point  of  meeting  of  the  lambdoidal  and  sagittal  sutures;  it  is 
in  the  middle  line  about  6.5  cm.  above  the  inion. 

Bregma. — The  meeting-point  of  the  coronal  and  sagittal  sutures;  it  lies  at  the 
point  of  intersection  of  the  middle  line  of  the  scalp  with  a  line  drawn  vertically 
upward  through  the  preauricular  point. 

K  line  passing  through  the  inferior  margin  of  the  orbit  and  the  auricular  point 
is  known  as  Reid's  base  line.     The  lambdoidal  suture  can  be  indicated  on  either 


1280 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


side  by  the  upper  two-thirds  of  a  line  from  the  lambda  to  the  tip  of  the  mastoid 
process.  The  sagittal  suture  is  in  the  line  joining  the  lambda  to  the  bregma.  The 
position  of  the  coronal  suture  on  either  side  is  sufficiently  represented  by  a  line 
joining  the  bregma  to  the  centre  of  the  zygomatic  arch. 

The  floor  of  the  middle  fossa  of  the  skull  is  at  the  level  of  the  posterior  three- 
fourths  of  the  upper  border  of  the  zygomatic  arch;  the  articular  eminence  of  the 
temporal  bone  is  opposite  the  foramen  spinosum  and  the  semilunar  ganglion. 


Fig.   1078. — Drawing  of  a  cast  by  Cunningham  to  illustrate  the  relations  of  the  brain  to  the  skull. 


Brain  (Figs.  1078,  1079). — ^The  general  outline  of  the  cerebral  hemisphere,  on 
either  side,  may  be  mapped  out  on  the  surface  in  the  following  manner.  Starting 
from  the  nasion,  a  line  drawn  along  the  middle  of  the  scalp  to  the  inion  represents 
the  superior  border.  The  line  of  the  lower  margin  behind  is  that  of  the  transverse 
sinus  (see  page  1282),  or  more  roughly  a  line  convex  upward  from  the  inion  to  the 
posterior  root  of  the  zygomatic  process  of  the  temporal  bone;  thence  along  the 
posterior  two-thirds  of  the  upper  border  of  the  zygomatic  arch  where  the  line  turns 
up  to  the  pterion;  the  front  part  of  the  lower  margin  extends  from  the  pterion  to 
the  glabella  about  1  cm.  above  the  supraorbital  margin.  The  cerebellum  is  so  deeply 
situated  that  there  is  no  reliable  surface  marking  for  it;  a  point  4  cm.  behind  and 
1.5  cm.  below  the  level  of  the  auricular  point  is  situated  directly  over  it. 

The  relations  of  the  principal  fissures  and  gyri  of  the  cerebral  hemispheres  to 
the  surface  of  the  scalp  are  of  considerable  practical  importance,  and  several 
methods  of  indicating  them  have  been  devised.    Necessarily  these  methods  can 


SURFACE  MARKINGS  OF  SPECIAL  REGIONS  OF  HEAD  AND  NECK     1281 

onl\'  be  regarded  as  approximately  correct,  yet  they  are  all  sufficiently  accurate 
for  surgical  purposes.  The  longitudinal  fissure  corresponds  to  the  medial  line  of 
the  scalp  between  the  nasion  and  inion.  In  order  to  mark  out  the  lateral  cerebral 
(Sylvian)  fissure  a  i)oint,  termed  the  Sylvian  point,  which  practically  corresponds 
to  the  pterion,  is  defined  35  mm.  behind  and  12  mm.  above  the  level  of  the  fronto- 
zygomatic  suture;  this  point  marks  the  spot  where  the  lateral  fissure  divides. 
Another  method  of  defining  the  Sylvian  point  is  to  divide  the  distance  betwjeen 
the  nasion  and  inion  into  four  equal  parts;  from  the  junction  of  the  third  and 
fourth  parts  (reckoning  from  the  front)  draw  a  line  to  the  frontozygomatic  suture; 
from  the  junction  of  the  first  and  second  parts  a  line  to  the  auricular  point.  These 
two  lines  intersect  at  the  Sylvian  point  and  the  portion  of  the  first  line  behind 
this  point  overlies  the  posterior  ramus  of  the  lateral  cerebral  fissure.    The  position 


Fig.  1079. — Relations  of  the  brain  and  middle  meningeal  artery  to  the  surface  of  the  skull.  1.  Nasion.  2.  Inion. 
3.  Lambda.  4.  Lateral  cerebral  fissure.  5.  Central  sulcus.  AA.  Reid's  base  line.  JS.  Point  for  trephining  the  anterior 
branch  of  the  middle  meningeal  artery.  C.  Suprameatal  triangle.  D.  Sigmoid  bend  of  the  transverse  sinus.  E. 
Point  for  trephining  over  the  straight  portion  of  the  transverse  sinus,  exposing  dura  mater  of  both  cerebrum  and 
cerebellum.     Outline  of  cerebral  hemisphere  indicated  in  blue;  course  of  middle  meningeal  artery  in  red. 


of  the  posterior  ramus  can  otherwise  be  obtained  by  joining  the  Sylvian  point  to  a 
point  2  cm.  below  the  summit  of  the  parietal  eminence.  The  anterior  ascending 
ramus  can  be  marked  out  by  drawing  a  line  upward  at  right  angles  to  the  line 
of  the  posterior  ramus  for  2  cm.  and  the  anterior  horizontal  ramus  by  a  line  of  the 
same  length  drawn  horizontally  forward — both  from  the  Sylvian  point.  To  define 
the  central  sulcus  {fissure  of  Rolando)  two  points  are  taken;  one  is  situated  1.25 
cm.  behind  the  centre  of  the  line  joining  the  nasion  and  inion;  the  second  is  at 
the  intersection  of  the  line  of  the  posterior  ramus  of  the  lateral  cerebral  fissure 
with  a  line  through  the  preauricular  point  at  right  angles  to  Reid's  base  line.  The 
upper  9  cm.  of  the  line  joining  these  two  points  overlies  the  central  sulcus  and  forms 
an  angle,  opening  forward,  of  about  70°  with  the  middle  line  of  the  scalp.  An 
alternative  method  is  to  draw  two  perpendicular  lines  from  Reid's  base  lin€  to  the 
top  of  the  head;  one  from  the  preauricular  point  and  the  other  from  the  posterior 
81 


1282  SURFACE  AX  ATOMY  AXD  SURFACE  MARKINGS 

border  of  the  mastoid  process  at  its  root.  A  line  from  the  upper  end  of  the  posterior 
line  to  the  point  Avhere  the  anterior  intersects  the  line  of  the  posterior  ramus  of  the 
lateral  fissure  indicates  the  position  of  the  central  sulcus.  The  precentral  and 
postcentral  sulci  are  practically  parallel  to  the  central  sulcus;  they  are  -ituated 
respectively  about  15  mm.  in  front  of,  and  behind,  it.  The  superior  frontal  sulcus 
can  be  mapped  out  by  a  line  drawn  from  the  junction  of  the  upper  and  middle 
thirds  of  the  precentral  sulcus,  in  a  direction  parallel  with  the  longitudinal  sulcus, 
to  a  point  midway  between  the  middle  line  of  the  forehead  and  the  temporal  line, 

4  cm.  above  the  supraorbital  notch.  The  inferior  frontal  sulcus  begins  at  the  junc- 
tion of  the  middle  and  lower  thirds  of  the  precentral  sulcus,  and  follows  the  course 
of  the  superior  temporal  line. 

The  horizontal  limb  of  the  intraparietal  sulcus  begins  from  the  junction  of  the 
lower  with  the  middle  third  of  the  postcentral  sulcus  and  curves  backward  parallel 
to  the  longitudinal  fissure,  midway  between  it  and  the  parietal  eminence;  it  then 
curves  downward  to  end  midway  between  the  lambda  and  the  parietal  eminence. 
The  external  part  of  the  parietooccipital  fissure  runs  lateralward  at  right  angles 
to  the  longitudinal  fissure  for  about  2.-5  cm.  from  a  point  5  mm.  in  front  of  the 
lambda.  If  the  line  of  the  posterior  ramus  of  the  lateral  cerebral  fissure  be 
continued  back  to  the  longitudinal  fissure,  the  last  2.5  cm.  of  it  will  indicate  the 
position  of  the  parietooccipital  fissure. 

The  lateral  ventricle  may  be  circumscribed  by  a  quadrilateral  figure.  The  upper 
limit  is  a  horizontal  line  5  cm.  above  the  zygomatic  arch;  this  defines  the  roof  of 
the  ventricle.  The  lower  limit  is  a  horizontal  line  1  cm.  above  the  zygomatic  arch; 
it  indicates  the  level  of  the  end  of  the  inferior  horn.  Two  vertical  lines,  one  through 
the  junction  of  the  anterior  and  middle  thirds  of  the  zygomatic  arch,  and  the  other 

5  cm.  behind  the  tip  of  the  mastoid  process,  indicate  the  extent  of  the  anterior 
horn  in  front  and  the  posterior  horn  behind. 

Vessels. — The  line  of  the  anterior  division  of  the  middle  meningeal  artery  is 
equidistant  from  the  frontozygomatic  suture  and  the  zygomatic  arch;  it  is  obtained 
by  joining  up  the  following  points:  (1)  2.5  cm.,  (2)  4  cm.,  and  (3)  5  cm.  from 
these  two  landmarks.  The  posterior  division  can  be  reached  2.5  cm.  above  the 
auricular  point. 

The  position  of  the  transverse  sinus  is  obtained  by  taking  two  lines:  the  first 
from  the  inion  to  a  point  2.5  cm.  behind  the  auricular  point;  the  second  from  the 
anterior  end  of  the  first  to  the  tip  of  the  mastoid  process.  The  second  line  corre- 
sponds roughly  to  the  line  of  reflection  of  the  skin  of  the  auricula  behind,  and  its 
upper  two-thirds  represents  the  sigmoid  part  of  the  sinus.  The  first  part  of  the 
sinus  has  a  slight  upward  convexity,  and  its  highest  point  is  about  4  cm.  behind 
and  1  cm.  above  the  level  of  the  auricular  point.  The  width  of  the  sinus  is 
about  1  cm. 

The  Face. — Air  Sinuses  (Fig.  lOSOj. — The  frontal  and  maxillary  sinuses  vary 
so  greatly  in  form  and  size  that  their  surface  markings  must  be  regarded  as  only 
roughly  approximate.  To  mark  out  the  position  of  the  frontal  sinus  three  points 
are  taken:  (1)  the  nasion,  (2)  a  point  in  the  middle  line  3  cm.  above  the  nasion, 
(3)  a  point  at  the  junction  of  the  lateral  and  intermediate  thirds  of  the  supraorbital 
margin.  By  joining  these  a  triangular  field  is  described  which  overlies  the  greater 
part  of  the  sinus.  The  outline  of  the  maxillary  sinus  is  irregularly  quadrilateral 
and  is  obtained  by  joining  up  the  following  points:  (1)  the  lacrimal  tubercle,  (2) 
a  point  on  the  zygomatic  bone  at  the  level  of  the  inferior  and  lateral  margins  of  the 
orbit,  (3)  and  (4)  points  on  the  alveolar  process  above  the  last  molar  and  the  second 
premolar  teeth  respectively. 

External  Maxillary  Artery. — The  course  of  this  artery  on  the  face  may  be  indicated 
by  a  line  starting  from  the  lower  border  of  the  mandible  at  the  anterior  margin 
of  the  Masseter,  and  running  at  first  forward  and  upward  to  a  point  1  cm.  lateral 


SURFACE  MARKINGS  OF  SPECIAL  REGIONS  OF  HEAD  AND  NECK     12S3 

to  the  angle  of  the  mouth,  thence  to  the  ahi  of  the  nose  and  upward  to  the  medial 
commissure  of  the  eye  (Fig.  1081). 

Trigeminal  Nerve.— Terminal  branches  of  this  nerve,  viz.,  the  supraorbital  branch 
of  the  ophthalmic, the  int'raorbitalof  the  maxillary, and  the  mentalof  the  mandibular 
emerge  from  corresponding  foramina  on  the  face  (Fig.  1081).  The  supraorbital 
foramen  is  situated  at  the  junction  of  the  medial  and  intermediate  thirds  of  the 
supraorbital  margin.  A  line  drawn  from  this  foramen  to  the  lower  border  of  the 
mandible,  through  the  interval  between  the  two  lower  premolar  teeth,  passes  over 
the  infraorbital  and  mental  foramina;  the  former  lies  about  1  cm.  below  the  margin 
of  the  orbit,  while  the  latter  varies  in  position  according  to  the  age  of  the  individual; 
in  the  adult  it  is  midway  between  the  upper  and  lower  borders  of  the  mandible, 
in  the  child  it  is  nearer  the  lower  border,  while  in  the  edentulous  jaw  of  old  age 
it  is  close  to  the  upper  margin. 


Frontal  sinus 


Line  of  no.solacrimal 
duct 


Maxillary  sinus 


Fig.  lOSO. — Outline  of  bones  of  face,  shcn-ing  position  of 


air  sinuses. 


Fig.   1081. — Outline    of    side  of    face,    showing    chief 
surface  markings. 


The  position  of  the  sphenopalatine  ganglion  is  indicated  from  the  side  by  a 
point  on  the  upper  border  of  the  zygomatic  arch,  6  mm.  from  the  margin  of  the 
zygomatic  bone. 

Parotid  Gland  (Fig.  1081).— The  upper  border  of  the  parotid  gland  corresponds  to 
the  posterior  two-thirds  of  the  lower  border  of  the  zygomatic  arch;  the  posterior 
border  to  the  front  of  the  external  acoustic  meatus,  the  mastoid  process,  and  the 
anterior  border  of  Sternocleidomastoideus.  The  inferior  border  is  indicated  by  a 
line  from  the  tip  of  the  mastoid  process  to  the  junction  of  the  body  and  greater 
cornu  of  the  hyoid  bone.  In  front,  the  anterior  border  extends  for  a  variable  dis- 
tance on  the  superficial  surface  of  the  ]Masseter.  The  surface  marking  for  the  parotid 
duct  is  a  line  drawn  across  the  face  about  a  finger's  breadth  below  the  zygomatic 
arch,  i.  e.,  from  the  lower  margin  of  the  concha  to  midway  between  the  red  margin 


1284 


SURFACE  AX  ATOMY  AND  SURFACE  MARKINGS 


of  the  lip  and  the  ala  of  the  nose;  the  duct  ends  opposite  the  second  upper  molar 
tooth  and  measures  about  5  cm.  in  length. 

The  Nose. — The  outlines  of  the  nasal  bones  and  the  cartilages  forming  the  exter- 
nal nose  can  be  easily  felt.  The  mobile  portion  of  the  nasal  septum,  formed  by 
the  medial  crura  of  the  greater  alar  cartilages  and  the  skin,  is  easily  distinguished 
between  the  nares.  AYhen  the  head  is  tilted  back  and  a  speculum  introduced 
through  the  naris,  the  floor  of  the  nasal  cavity,  the  lower  part  of  the  nasal  septum, 
and  the  anterior  ends  of  the  middle  and  inferior  nasal  conchae  can  be  examined. 
The  opening  of  the  nasolacrimal  duct,  which  lies  under  cover  of  the  front  of  the 
inferior  nasal  concha,  is  situated  about  2.5  cm.  behind  the  naris  and  2  cm.  above 
the  level  of  the  floor  of  the  nasal  cavitv. 


Pliaryngopalatitie  arch 

Palatine  tonsil 

lossopalaiine  arch 
Buccinatcr 


Vallate  papillce 


Isthrmis 
faucium 


Fungiform  papillce 


Fig.   1082. — The  mouth  cavity.     The  cheeks  have  been  slit  transversely  and  the  tongue  pulled  forward. 


The  Mouth. — The  orifice  of  the  mouth  is  bounded  by  the  lips,  which  are  covered 
externally  by  the  whitish  skin  and  internally  by  the  red  mucous  membrane.  The 
size  of  the  orifice  varies  considerably  in  dift'erent  individuals,  but  seems  to  bear  a 
close  relationship  to  the  size  and  prominence  of  the  teeth;  its  angles  usually  corre- 
spond to  the  lateral  borders  of  the  canine  teeth.  Running  down  the  centre  of  the 
outer  surface  of  the  upper  lip  is  a  shallow  groove — the  philtrum.  If  the  lips  be 
everted  there  can  be  seen,  in  the  middle  line  of  each,  a  small  fold  of  mucous  mem- 
brane— the  frenulum — passing  from  the  lip  to  the  gum.    By  pulling  the  angle  of  the 


SURFACE  MARKINGS  OF  SPECIAL  REaWNS  OF  HEAD  AND  NECK     1285 

mouth  outward  the  mucous  membrane  of  the  cheek  can  be  inspected,  and  on  this, 
opposite  the  second  molar  tooth  of  the  maxilla,  is  the  little  papilla  which  marks 
theorificeof  the  parotid  duct. 

In  the  floor  of  the  mouth  is  the  tongue  a\.  10S2).  Its  upper  surface  is  convex 
and  is  marked  along  the  middle  line  by  a  shallow  sulcus;  the  anterior  two-thirds 
are  rough  and  studded  with  papillae;  the  posterior  third  is  smooth  and  tuberculated 
The  division  between  the  anterior  two-thirds  and  the  posterior  third  is  marked 
by  a  V-shaped  furrow,  the  sulcus  terminalis,  which  is  situated  immediately  behind 
the  line  of  the  vallate  papillte. 


Anterior  lingual  gland 

Lingual  nerve 

Art.  profunda  linguos 

Vena  com.  n.  liijpoglossi 
Longituditialis  inferior    ^    )[ 


Plica  fimhriata 
Vena  com.  n.  hypoglo-ssi 
y^  Frenulum 

Orifice  of  submax.  duct 
Plica  sublingualis 


Fig    1083.-The  mouth  cavity.     The  apex  of  the  tongue  is  turned  upward    and  on  the  right  side  a  superficial 
dissection  of  its  under  surface  has  been  made. 


On  the  under  surface  of  the  tongue  (Fig.  1083)  the  mucous  membrane  is  smooth 
and  devoid  of  papilla?.  In  the  middle  line,  the  mucous  membrane  extends  to  the 
floor  of  the  mouth  as  a  distinct  fold— the  frenulum— the  free  edge  of  which  runs 
forward  to  the  symphvsis  menti.  Sometimes  the  ranine  vein  can  be  seen  immedi- 
ately beneath  the  mucous  membrane,  a  little  lateral  to  the  frenulum.  Close  to  the 
attachment  of  the  frenulum  to  the  floor  of  the  mouth,  the  slit-hke  orihce  of  the 
submaxillary  duct  is  visible  on  either  side.  Running  backward  and  lateralward 
from  the  orifice  of  the  submaxillary  duct  is  the  plica  sublingualis,  produced  by 
the  projection  of  the  sublingual  gland  which  lies  immediately  beneath  the  mucous 
membrane.  The  plica  serves  also  to  indicate  the  line  of  the  submaxillary  duct 
and  of  the  lingual  nerve.  At  the  back  of  the  mouth  is  the  isthmus  faucmm,  bounded 
above  by  the  palatine  velum,  from  the  free  margin  of  which  the  uvula  projects 
downward  in  the  middle  line.  On  either  side  of  the  isthmus  are  the  two  palatine 
arches,  the  anterior  formed  by  the  Glossopalatinus  and  the  posterior  by  the  Tharyn- 


1286 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


gopalatinus.  Between  the  two  arches  of  either  side  is  the  palatine  tonsil,  above 
which  is  the  small  supratonsillar  recess;  the  position  of  the  tonsil  corresponds  to 
the  angle  of  the  mandible.  When  the  mouth  is  opened  widely,  a  tense  band — 
the  pterygomandibular  raphe — can  be  seen  and  felt  lateral  to  the  glossopalatine 
arch.  Its  lower  end  is  attached  to  the  mandible  behind  the  last  molar  tooth, 
and  immediately  below  and  in  front  of  this  the  lingual  nerve  can  be  felt;  the  upper 


Naml  sefUim 

/ 

/ 


Nasal  conchce 


Pharyngeal  recess 

Torus  of  auditory 
tube 


Fhu)  yngcal  ostium  oj 
auditory  tube 

Fig.-  1084. — Front  of  nasal  part  of  pharynx,  as  seen  with  the  laryngoscope. 

end  of  the  ligament  can  be  traced  to  the  pterygoid  hamulus.  About  1  cm.  in  front 
of  the  hamulus  and  1  cm.  medial  to  the  last  molar  tooth  of  the  maxilla  is  the  greater 
palatine  foramen  through  which  the  descending  palatine  vessels  and  the  anterior 
palatine  nerve  emerge.  Behind  the  last  molar  tooth  of  the  maxilla  the  coronoid 
process  of  the  mandible  is  palpable. 


Vallecula 


Median  glossoepiglottic  fold 
I  Epiglottis 

, Tubercle  of  epiglottii 
Vocal  fold 

Ventricular  fold 


Aryeintjlottic  fold 
Cuneiform  cartilage 


Corniculate  cartilage 


Fig.  1085.- 


Trachea 
-Laryngosoopic  vieiv"  of  interior  of  larynx. 


By  tilting  the  head  well  back  a  portion  of  the  po.sterior  pharyngeal  wall,  corre- 
sponding to  the  site  of  the  second  and  third  cervical  vertebrae,  can  be  seen  through 
the  isthmus  faucium.  On  introducing  the  finger  the  anterior  surfaces  of  the  upper 
cervical  vertebrse  can  be  felt  through  the  thin  muscular  wall  of  the  pharynx; 
if  the  finger  be  hooked  round  the  palatine  velum,  the  choanae  can  be  distinguished  in 
front,  and  the  pharyngeal  ostium  of  the  auditory  tube  on  either  side.  The  level 
of  the  choanse  is  that  of  the  atlas,  while  the  palatine  velum  is  opposite  the  body 
of  the  axis. 


SURFACE  MARKINGS  OF  SPECIAL  REGIONS  OF  HEAD  AND  NECK     1287 


With  the  laryngoscope  many  other  structures  can  be  seen.  In  the  nasal  part 
of  the  pharynx  (Fig.  1084),  the  choanae,  the  nasal  septum,  the  nasal  conchse,  and 
the  pharyngeal  ostia  of  the  auditory  tubes  can  all  be  examined.  Further  down,  the 
base  of  the  tongue,  the  anterior  surface  of  the  epiglottis  with  the  glossoepiglottic 
and  pharyngoepiglottic  folds  bounding  the  valleculai,  and  the  pyriform  sinuses,  are 
readily  distinguished.  Beyond  these  is  the  entrance  to  the  larynx,  bounded  on 
either  side  by  the  aryepiglottic  folds,  in  each  of  which  are  two  rounded  eminences 
corresponding  to  the  corniculate  and  cuneiform  cartilages. 

Within  the  larynx  (Fig.  1085)  on  either  side  are  the  ventricular  and  vocal  folds 
(false  and  true  vocal  cords)  with  the  ventricle  between  them.  Still  deeper  are 
seen  the  cricoid  cartilage  and  the  anterior  parts  of  some  of  the  cartilaginous  rings 
of  the  trachea,  and  sometimes,  during  deep  inspiration,  the  bifurcation  of  the 
trachea. 

The  Eye. — The  palpebral  fissure  is  elliptical  in  shape,  and  varies  in  form  in  dif- 
ferent individuals  and  in  different  races  of  mankind;  normally  it  is  oblique,  in  a 
direction  upward  and  lateralward,  so  that  the  lateral  commissure  is  on  a  slightly 
higher  level  than  the  medial.  When  the  eyes  are  directed  forward  as  in  ordinary 
vision  the  upper  part  of  the  cornea  is  covered  by  the  upper  eyelid  and  its  lower 
margin  corresponds  to  the  level  of  the  free  margin  of  the  lower  eyelid,  so  that 
usually  the  lower  three-fourths  are  exposed. 

At  the  medial  commissure  (Fig.  1086)  are  the  caruncula  lacrimalis  and  the  plica 
semilunaris.  When  the  lids  are  everted,  the  tarsal  glands  appear  as  a  series  of 
nearly  straight  parallel  rows  of 
light  yellow  granules.  On  the 
margins  of  the  lids  about  5  mm. 
from  the  medial  commissure  are 

two  small  openings — the  lacrimal  '''^H1IIIIIP&  "^^ '  \^^ 

puncta;  in  the   natural  condition  "^^^^Mmw///. ,  \ 

they  are  in  contact  with  the  con- 
junctiva  of  the   bulb   of   the   eye,     PrinctumlacnmaU- 

so  that  it  is  necessary  to  evert 
the  eyelids  to  expose  them.  The 
position  of  the  lacrimal  sac  is  indi- 
cated by  a  little  tubercle  which 
can  be  plainly  felt  on  the  lower 
margin  of  the  orbit;  the  sac  lies 
immediately  above  and  medial  to 
the  tubercle.  If  the  eyelids  be 
drawn  lateralward  so  as  to  tighten 
the  skin  at  the  medial  commissure 
a  prominent  core  can  be  felt  be- 
neath the  tightened  skin;  this  is  the  medial  palpebral  ligament,  which  lies  over 
the  junction  of  the  upper  with  the  lower  two-thirds  of  the  sac,  thus  forming  a 
useful  guide  to  its  situation.  The  direction  of  the  nasolacrimal  duct  is  indicated 
by  a  line  from  the  lacrimal  sac  to  the  first  molar  tooth  of  the  maxilla;  the  length 
of  the  duct  is  about  12  or  13  mm. 

On  looking  into  the  eye,  the  iris  with  its  opening,  the  pupil,  and  the  front  of  the 
lens  can  be  examined,  but  for  investigation  of  the  retina  an  ophthalmoscope  is  neces- 
sary. With  this  the  lens,  the  vessels  of  the  retina  the  optic  disk,  and  the  macula 
lutea  can  all  be  inspected  (Fig.  1087). 

On  the  lateral  surface  of  the  nasal  part  of  the  frontal  bone  the  pulley  of  the 
Obliquus  superior  can  be  easily  reached  by  pushing  the  finger  backward  along  the 
roof  of  the  orbit;  the  tendon  of  the  muscle  can  be  traced  for  a  short  distance  back- 
ward and  lateralward  from  the  pulley. 


Plica  semihinaris 

Caruncula  — 

Punctum  lacrimale 
Openings  of  tarsal 


Fig.  1086.- 


-Front  of  left  eye  with  eyelids  separated  to  show 
medial  canthus. 


1288 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


Optic  disc ' 


Macula  lutea 


Sclera 
Choroid 

Retina 
Fig.   1087. — The  interior  of  the  posterior  half  of  the  left  eyeball. 


The  Ear. — The  various  prominences  and  fossae  of  the  auricula  (see  page  1044) 
are  visible  (Fig.  1088).    The  opening  of  the  external  acoustic  meatus  is  exposed  by" 

drawing  the  tragus  forward;  at  the  orifice  are  a  few 
short  crisp  hairs  which  serve  to  prevent  the  entrance 
of  dust  or  of  small  insects;  beyond  this  the  secretion 
of  the  ceruminous  glands  serves  to  catch  an}'  small 
particles  which  may  find  their  way  into  the  meatus. 
The  interior  of  the  meatus  can  be  examined  through 
a  speculum.  At  the  line  of  junction  of  its  bony 
and  cartilaginous  portions  an  obtuse  angle  is  formed 
which  projects  into  the  antero-inferior  wall  and 
produces  a  narrowing  of  the  lumen  in  this  situation. 
The  cartilaginous  part,  however,  is  connected  to  the 
bony  part  by  fibrous  tissue  which  renders  the  outer 
part  of  the  meatus  very  movable,  and  therefore  by 
drawing  the  auricula  upward,  backward,  and  slightly 
outward,  the  canal  is  rendered  almost  straight.  In 
children  the  meatus  is  very  short,  and  this  should 
be  remembered  in  introducing  the  speculum. 

Through  the  speculum  the  greater  part  of  the  tym- 
panic membrane  (Fig.  1089)  is  visible.  It  is  a  pearly- 
gray  membrane  slightly  glistening  in  the  adult,  placed 
obliquely  so  as  to  form  with  the  floor  of  the  meatus  an  angle  of  about  55°.  At 
birth  it  is  more  horizontal  and  situated  in  almost  the  same  plane  as  the  base  of  the 
skull.  The  membrane  is  concave  outward,  and  the  point  of  deepest  concavity — 
the  umbo — is  slightly  below  the  centre.  Running  upward  and  slightly  forward 
from  the  umbo  is  a  reddish-yellow  streak  produced  by  the  manubrium  of  the 
malleus.  This  streak  ends  above  just  below  the  roof  of  the  meatus  at  a  small 
white  rounded  prominence  which  is  caused  by  the  lateral  process  of  the  malleus 
projecting  against  the  membrane.  The  anterior  and  posterior  malleolar  folds 
extend  from  the  prominence  to  the  circumference  of  the  membrane  and  enclose 
the  pars  flaccida.  Behind  the  streak  caused  by  the  manubrium  of  the  malleus  a 
second  streak,  shorter  and  very  faint,  can  be  distinguished;  this  is  the  long  eras 


Fig. 


1088. — The  auricula  or  pinna. 
Lateral  surface. 


SURFACE  MARKINGS  OF  SPECIAL  REGIONS  OF  HEAD  AND  NECK     1289 


of  the  incus.  A  narrow  triangular  patch  extending  downward  and  forward  from  the 
umbo  reflects  the  Hght  more  brightly  than  any  other  part,  and  is  usually  described 
as  the  cone  of  light. 

Post,  mallcnlar  fold 

Long  cms  of  incus  /         n        „        , 

'         Fars  jlacctda 

I  Lnt.  proc.  of  malleus 

I  /  Ant.  vuilleolar  fold 

Manuhrium 
of  malleus 
Postero-superior 
quadrant 

Postero-inferior 
quadrant 


Antero- superior 

quadrant 
Utnbo 


Cone  of  light 


A ntero-inferior  quadrant 
F:g.  1089. — The  right  tympanic  membrane  as  seen  through  a  speculum. 


Groove  for  middle 
temporal  artery 


Parietal  notch 


Suprameatal 
ri  angle 

Occipitalis 

/ 


Articular  tubercle 
Postglenoid  process 

Mandibular  fusi,a 


Petrotympanic  fissure 
Vaginal  process 


-^    f' V   >\-'^   y  o^>"  ^V3 


Occipital  groove 


Tyvipanic  part 

Stylohyoideus 


Styloid  process 


Fig.   1090. — Left  temporal  bone  showing  surface  markings  for  the  tympanic  antrum  (red),  transverse  sinus  (blue), 

and  facial  nerve  (yellow). 

Tympanic  Antrum. — The  site  of  the  tympanic  antrum  is  indicated  by  the  supra- 
meatal triangle  (Fig.  1090).  This  triangle  is  bounded  above  by  the  posterior  root 
of  the  zygomatic  arch;  behind  by  a  vertical  line  from  the  posterior  border  of  the 
external  acoustic  meatus;  in  front  and  below  by  the  upper  margin  of  the  meatus. 

The  Neck  (Fig.  1091). — Larynx  and  Trachea. — In  the  receding  angle  below  the 
chin,  the  hyoid  bone  (page  1276),  situated  opposite  the  fourth  cervical  vertebra,  can 
easily  be  made  out.    A  finger's  breadth  below  it  is  the  laryngeal  prominence  of  the 


1290 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


thyroid  cartilage;  the  space  inte^^'ening  between  the  hyoid  bone  and  the  thyroid 
cartilage  is  occupied  by  the  hyothyroid  membrane.  The  outUnes  of  the  thyroid 
cartilage  are  readily  palpated;  below  its  lower  border  is  a  depression  corresponding 
to  the  middle  cricothyroid  ligament.  The  level  of  the  vocal  folds  corresponds  to 
the  middle  of  the  anterior  margin  of  the  thyroid  cartilage.  The  anterior  part  of 
the  cricoid  cartilage  forms  an  important  landmark  on  the  front  of  the  neck;  it 
lies  opposite  the  sixth  cervical  vertebra,  and  indicates  the  junctions  of  pharynx 
with  oesophagus,  the  larynx  with  trachea.  Below  the  cricoid  cartilage  the  trachea 
can  be  felt,  though  it  is  only  in  thin  subjects  that  the  separate  rings  can  be  distin- 
guished; as  a  rule  there  are  seven  or  eight  rings  above  the  jugular  notch  of  the 
sternum,  and  of  these  the  second,  third,  and  fourth  are  covered  by  the  isthmus 
of  the  thyroid  gland. 


Ext.  max.  art.  - 


Lingual  art. 
Sup.  thyroid  art. 
Point  of  bifurcation  --' 
of  com.  carotid  art. 


Com.  carotid  art. 
Subclavian  art 


'  Facial  nerve 


Ext.  carotid  art. 

Occipital  art. 

Lesser  occip.  nerve 


Great  auric,  nerve 
Cervical  eutan.  nerve 
Accessory  nerve 
Supraclavic.  nerves 

Line  of  tipper  margin 
of  brachial  plexus 


ra.\^^^^w\r////^v////r/} 


Fig.   1091. — Side  of  neck,  showing  chief  surface  markings. 


Muscles. — ^The  posterior  belly  of  Digastricus  is  marked  out  by  a  line  from  the  tip 
of  the  mastoid  process  to  the  junction  of  the  greater  cornu  and  body  of  the  hyoid 
bone;  a  line  from  this  latter  point  to  a  point  just  lateral  to  the  symphysis  menti 
indicates  the  position  of  the  anterior  belly.  The  line  of  Omohyoideus  begins  at 
the  lower  border  of  the  hyoid  bone,  curves  downward  and  lateral  ward  to  cross 
Sternocleidomastoideus  at  the  junction  of  its  middle  and  lower  thirds,  i.  e.,  opposite 
the  cricoid  cartilage,  and  then  runs  more  horizontally  to  the  acromial  end  of  the 
clavicle. 

Arteries. — The  position  of  the  common  carotid  arterj^  in  the  neck  is  indicated 
by  a  line  drawn  from  the  upper  part  of  the  sternal  end  of  the  clavicle  to  a  point 
midw^ay  between  the  tip  of  the  mastoid  process  and  the  angle  of  the  mandible. 
From  the  clavicle  to  the  upper  border  of  the  thyroid  cartilage  this  line  overlies 
the  common  carotid  artery,  beyond  this  it  is  over  the  external  carotid.  The 
external  carotid  artery  may  otherwise  be  marked  out  by  the  upper  part  of  a  line 
from  the  side  of  the  cricoid  cartilage  to  the  front  of  the  external  acoustic  meatuS; 
arching  the  line  slightly  forward. 

The  points  of  origin  of  the  main  branches  of  the  external  carotid  in  the  neck 
are  all  related  to  the  tip  of  the  greater  cornu  of  the  hj'oid  bone  as  follows:  (1)  the 
superior  thyroid,  immediately  below^  it;  (2)  the  lingual,  on  a  level  with  it;  (3)  the 
facial,  and  (4)  the  occipital  a  little  above  and  behind  it. 


SURFACE  AXATOMY  OF  THE  BACK  1291 

The  subclavian  artery  is  indicated  on  the  surface  by  a  curved  Hne,  convex  upward, 
from  the  sternoclavicular  articulation  to  the  middle  of  the  clavicle.  The  highest 
point  of  the  convexity  is  from  1  to  3  cm.  above  the  clavicle. 

Veins. — The  surface  marking  for  the  internal  jugular  vein  is  slighth'  lateral 
and  parallel  to  that  for  the  common  carotid  artery.  The  position  of  the  external 
jugular  vein  is  marked  out  by  a  line  from  the  angle  of  the  mandible  to  the  middle 
of  the  clavicle.  A  point  on  this  line  about  4  cm.  above  the  clavicle  indicates  the 
spot  where  the  vein  pierces  the  deep  fascia.  The  line  of  the  anterior  jugular  vein 
begins  close  to  the  symphysis  menti,  runs  downward  parallel  with  and  a  little 
to  one  side  of  the  middle  line  and,  at  a  variable  distance  above  the  jugular  notch, 
turns  lateralward  to  the  external  jugular. 

Nerves. — ^The  facial  nerve  at  its  exit  from  the  stylomastoid  foramen  is  situated 
about  2.5  cm.  from  the  surface,  opposite  the  middle  of  the  anterior  border  of  the 
mastoid  process;  a  horizontal  line  from  this  point  to  the  ramus  of  the  mandible 
overlies  the  stem  of  the  nerve.  To  mark  the  site  of  the  accessory  nerve  a  line  is 
drawn  from  the  angle  of  the  mandible  to  a  point  on  the  anterior  border  of  Sterno- 
cleidomastoideus  about  3  to  4  cm.  below  the  apex  of  the  mastoid  process,  or  to  the 
midpoint  of  the  posterior  border  of  the  muscle;  the  line  is  continued  across  the 
posterior  triangle  to  Trapezius. 

The  cutaneous  branches  of  the  cervical  plexus  as  they  emerge  from  the  posterior 
border  of  Sternocleidomastoideus  may  be  indicated  as  follows:  the  lesser  occipital 
begins  immediately  above  the  midpoint  of  the  border  and  runs  along  the  border  to 
the  scalp;  the  great  auricular  and  cervical  cutaneous  both  start  from  the  middle 
of  the  border,  the  former  running  upward  toward  the  lobule  of  the  auricula,  the 
latter  crossing  Sternocleidomastoideus  at  right  angles  to  its  long  axis;  the  supra- 
clavicular nerves  emerge  from  immediately  below^  the  middle  of  the  posterior  border 
and  run  down  over  the  clavicle.  The  phrenic  nerve  begins  at  the  level  of  the  middle 
of  the  thyroid  cartilage  and  runs  behind  the  clavicle  about  midway  between  the 
anterior  and  posterior  borders  of  Sternocleidomastoideus. 

The  upper  border  of  the  brachial  plexus  is  indicated  by  a  line  from  the  side  of 
the  cricoid  cartilage  to  the  middle  of  the  clavicle. 

Submaxillary  Gland. — On  either  side  of  the  neck  the  superficial  portion  of  the 
submaxillary  gland,  as  it  lies  partly  under  cover  of  the  mandible,  can  be  palpated. 

SURFACE  ANATOMY  OF  THE  BACK. 

Bones. — ^The  only  subcutaneous  parts  of  the  vertebral  column  are  the  apices 
of  the  spinous  processes.  These  are  distinguishable  at  the  bottom  of  a  furrow 
which  runs  down  the  middle  line  of  the  back  from  the  external  occipital  protuber- 
ance to  the  middle  of  the  sacrum.  In  the  cervical  region  the  furrow  is  broad  and 
ends  below  in  a  conspicuous  projection  caused  by  the  spinous  processes  of  the 
seventh  cervical  and  first  thoracic  vertebra.  Above  this,  the  spinous  process  of  the 
sixth  cervical  vertebra  sometimes  forms  a  projection;  the  other  cervical  spinous 
processes  are  sunken,  but  that  of  the  axis  can  be  felt.  In  the  thoracic  region  the 
furrow  is  shallow  and  during  stooping  disappears,  and  then  the  spinous  processes 
become  more  or  less  visible;  the  markings  produced  by  them  are  small  and  close 
together.  In  the  lumbar  region  the  furrow  is  deep  and  the  situations  of  the  spinous 
processes  are  frequently  indicated  by  little  pits  or  depressions,  especially  when  the 
muscles  in  the  loins  are  well-developed.  In  the  sacral  region  the  furrow  is  shallower, 
presenting  a  flattened  area  which  ends  below  at  the  most  prominent  part  of  the 
dorsal  surface  of  the  sacrum,  i.  e.,  the  spinous  process  of  the  third  sacral  vertebra. 
At  the  bottom  of  the  sacral  furrow  the  irregular  dorsal  surface  of  the  bone  may  be 
felt,  and  below  this,  in  the  deep  groove  running  to  the  anus,  the  coccyx. 

The  only  other  portions  of  the  vertebral  column  which  can  be  felt  from  the 
sm-face  are  the  transverse  processes  of  the  first,  sixth,  and  seventh  cervical  vertebrae. 


1292 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


Muscles. — The  muscles  proper  of  the  back  are  so  obscured  by  those  of  the  upper 
extremity  (Fig.  1092)  that  they  have  very  little  influence  on  surface  form.  The 
Splenii  b}'  their  divergence  serve  to  broaden  out  the  upper  part  of  the  back  of  the 
neck  and  produce  a  fulness  in  this  situation.    In  the  loin  the  Sacrospinales,  bound 


Trapezius 

Spine  of  scapula 

Ehomboideus  major 
Ttres  major 


Delloideus 


Inf.  angle  of  scapula 


Sacrospinalis 
Iliac  crest 

Laiissimus  dor  si 


Glutaeus  medius 


— .  Glutaeus  maximus 


Fig.   1092. — Surface  anatomy  of  the  back. 


down  by  the  lumbodorsal  fascia,  form  rounded  vertical  eminences  which  determine 
the  depth  of  the  spinal  furrow  and  taper  below  to  a  point  on  the  dorsal  surface  of 
the  sacrum.  The  continuations  of  the  Sacrospinales  in  the  lower  thoracic  region 
form  flattened  planes  which  are  gradually  lost  on  passing  upward. 


SURFACE  MARKINGS  OF  THE  BACK 


1293 


SURFACE  MARKINGS  OF  THE  BACK. 

Bony  Landmarks. — In  order  to  identify  any  particular  spinous  process  it  is 
customary  to  count  from  the  prominence  caused  by  the  seventh  cervical  and  first 


Fig.  1093. — Diagram  showing  the  relation  of  the  medulla  spinaUs  to  the  dorsal  surface  of  the  trunk.        The  bones 

are  outlined  in  red. 

Level  of 

No.  of 

Level  of  tip       Level  of         No.  of 

Level  of  tip 

body  of 

nerve. 

of  spine  of        body  of          nerve. 

of  spine  of 

C.  1 

C.  1 

F    T.  8 

T.  9 

7  T. 

2 

i2 

9 

10 

8 

13 

1  C. 

i        10 

11 

9 

3 

4 

2 

12 

10 

•4 

5 

3 

11 

L.  1 

11 

5 

6 

4 

2 
^3^ 

6 

7 

5 

12 

8 

6               '         .. 

14J 

12 

7 

T.  1 

7 

r      5) 

T.  1 

2 

1  T. 

1 

S.  1/ 

2 

3 

L.  1 

■ 

21 

3 

4 

2 

3 

4 

5 

3 

4 

1  L. 

5 

6 

4                                             5 

6 

7 

5 

C.  Ij 

7 

8 

6 

1  L.  2     1      . : 

~ 

1294 


SURFACE  ANATOMY  AXD  SURFACE  MARKINGS 


thoracic;  of  these  the  latter  is  the  more  prominent.    The  root  of  the  spine  of  the 
scapula  is  on  a  level  with  the  tip  of  the  spinous  process  of  the  third  thoracic  vertebra, 
and  the  inferior  angle  with  that  of  the  seventh.     The  highest  point  of  the  iliac 
crest  is  on  a  level  with  the  spinous 
process  of  the  fourth  lumbar,  and  the 
posterior  superior  iliac  spine  with  that 
of  the  second  sacral. 

The  transverse  process  of  the  atlas 
is  about  1  cm.  below  and  in  front  of 
the  apex  of  the  mastoid  process.  The 
transverse  process  of  the  sixth  cervical 
vertebra  is  opposite  the  cricoid  carti- 
lage; below  it  is  the  transverse  pro- 
cess of  the  seventh  and  occasionally 
a  cervical  rib. 


Fig.  1094. — Sagittal  section  of  vertebral  canal  to 
show  the  lower  end  of  the  nriedulla  spinalis  and  the 
filum  terminale.  (Testut.)  Li,  Lv.  First  and  fifth 
lumbar  vertebrae.  Sii.  Second  sacral  vertebra.  1. 
Dura  mater.  2.  Lower  part  of  subarachnoid  cavity. 
3.  Lower  extremity  of  medulla  spinalis.  4.  Filum  ter- 
minale internum,  and  5,  FUum  terminale  externum. 
6.  Attachment  of  filum  terminale  to  first  segment  of 
coccyx. 


z  ^Cervical}  (T) 

^~^>  3''.'^ Cervical 

5'^^'Cervical 


r'-^Cervical 


^^^Thorac 


j^.t  Thoracic 


'^Thoracic 


t'-h  Thoracic 


6thfy,QTacic< 


b<^hTh 


>5'--'Thoracic 


\bj  '>-9^I>'Thoracic 

i^^Thoracic   <  ^^ 


yvi-'-lhoracic 


',thTh. 


izv^ltboractc 


z'^t^Lurnbar  <  /^ 


:thTh 


>i^PLii'nhhar 


Sacral  z< 

5 

Coccygeal 


>  s.'^-'^Lumhar 
s'-^LvMbhar 


© 
© 


Fig.  1095. — Scheme  showing  the  relations  of  the 
regions  of  attachment  of  the  spinal  nerves  to  the  verte- 
bral spinous  recesses.     (After  Reid.) 


Medulla  Spinalis. — The  po.sition  of  the  lower  end  of  the  medulla  spinalis  varies 
slightly  with  the  movements  of  the  vertebral  column,  but,  in  the  adult,  in  the 
upright  posture  it  is  usually  at  the  level  of  the  spinous  process  of  the  second  lumbar 
vertebra  (Fig.  109.3) ;  at  birth  it  lies  at  the  level  of  the  fourth  lumbar. 

The  subdural  and  subarachnoid  cavities  end  below  opposite  the  spinous  process 
of  the  third  sacral  vertebra  (Fig.  1094). 


SURFACE  ANATOMY  OF  THE  THORAX  1295 

Spinal  Nerves  (Fig.  1095).— The  table  on  page  1293,  after  Macalister,  shows  the 
rehitions  which  the  pL^ces  of  attachment  of  the  nerves  to  the  medulla  spinalis 
present  to  the  bodies  and  spinous  processes  of  the  vertebrae. 


SURFACE   ANATOMY  OF  THE  THORAX. 

Bones. — The  skeleton  of  the  thorax  is  to  a  very  considerable  extent  covered  by 
muscles,  so  that  in  the  strongly  developed  muscular  subject  it  is  for  the  most  part 
concealed.  In  the  emaciated  subject,  however,  the  ribs,  especially  in  the  lower  and 
lateral  regions,  stand  out  as  prominent  ridges  with  the  sunken  intercostal  spaces 
between  them. 

In  the  middle  line,  in  front,  the  superficial  surface  of  the  sternum  can  be  felt 
throughout  its  entire  length  at  the  bottom  of  a  furrow,  the  sternal  furrow,  situated 
between  the  Pectorales  majores.  These  muscles  overlap  the  anterior  surface 
somewhat,  so  that  the  whole  width  of  the  sternum  is  not  subcutaneous,  and  this 
overlapping  is  greatest  opposite  the  middle  of  the  bone;  the  furrow,  therefore,  is 
wide  at  its  upper  and  lower  parts  but  narrow  in  the  middle.  At  the  upper  border 
of  the  manubrium  sterni  is  the  jugular  notch:  the  lateral  parts  of  this  notch  are 
obscured  by  the  tendinous  origins  of  the  Sternocleidomastoidei,  which  appear  as 
oblique  cords  narro\\-ing  and  deepening  the  notch.  Lower  down  on  the  subcu- 
taneous surface  is  a  well-defined  transverse  ridge,  the  sternal  angle ;  it  denotes  the 
junction  of  the  manubrium  and  body.  From  the  middle  of  the  sternum  the  sternal 
furrow  spreads  out  and  ends  at  the  junction  of  the  body  with  the  xiphoid  process. 
Immediately  below  this  is  the  infrastemal  notch;  between  the  sternal  ends  of  the 
seventh  costal  cartilages,  and  below  the  notch,  is  a  triangular  depression,  the 
epigastric  fossa,  in  which  the  xiphoid  process  can  be  felt. 

On  either  side  of  the  sternum  the  costal  cartilages  and  ribs  on  the  front  of  the 
thorax  are  partly  obscured  by  the  Pectoralis  major,  through  which,  however,  they 
can  be  felt  as  ridges  with  yielding  intervals  between  them  corresponding  to  the 
intercostal  spaces.  Of  these  spaces,  that  between  the  second  and  third  ribs  is  the 
widest,  the  next  two  are  somewhat  narrower,  and  the  remainder,  with  the  exception 
of  the  last  tw^o,  are  comparatively  narrow. 

Below  the  lower  border  of  the  Pectoralis  major  on  the  front  of  the  chest,  the 
broad  flat  outlines  of  the  ribs  as  they  descend,  and  the  more  rounded  outlines  of  the 
costal  cartilages,  are  often  visible.  The  lower  boundary  of  the  front  of  the  thorax, 
which  is  most  plainly  seen  by  bending  the  body  backward,  is  formed  by  the  xiphoid 
process,  the  cartilages  of  the  seventh,  eighth,  ninth,  and  tenth  ribs,  and  the  ends  of 
the  cartilages  of  the  eleventh  and  twelfth  ribs. 

On  either  side  of  the  thorax,  from  the  axilla  downward,  the  flattened  external 
surfaces  of  the  ribs  may  be  defined.  Although  covered  by  muscles,  all  the  ribs, 
with  the  exception  of  the  first,  can  generally  be  followed  without  difficulty  over  the 
front  and  sides  of  the  thorax.  The  first  rib  being  almost  completely  covered  by 
the  clavicle  can  only  be  distinguished  in  a  small  portion  of  its  extent. 

At  the  back,  the  angles  of  the  ribs  lie  on  a  slightly  marked  oblique  line  on  either 
side  of,  and  some  distance  from,  the  spinous  processes  of  the  vertebrae.  The  line 
diverges  somewhat  as  it  descends,  and  lateral  to  it  is  a  broad  convex  surface  caused 
by  the  projection  of  the  ribs  beyond  their  angles.  Over  this  surface,  except  where 
covered  by  the  scapula,  the  individual  ribs  can  be  distinguished. 

Muscles. — ^The  surface  muscles  covering  the  thorax  belong  to  the  musculature 
of  the  upper  extremity  (Figs.  1096,  1100),  and  wall  be  described  in  that  section 
(page  1319).  There  is,  however,  an  area  of  practical  importance  bounded  by  these 
muscles.  It  is  limited  above  by  the  lower  border  of  Trapezius,  below  by  the  upper 
border  of  Latissimus  dorsi,  and  laterally  by  the  vertebral  border  of  the  scapula;  the 


1296 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


floor  is  partly  formed  by  Rliomboideus  major.  If  the  scapula  be  drawn  forward  by 
folding  the  arms  across  the  chest,  and  the  trunk  bent  forward,  parts  of  the  sixth 
and  seventh  ribs  and  the  interspace  between  them  become  subcutaneous  and  avail- 
able for  ausculation.    The  space  is  therefore  known  as  the  triangle  of  ausculation. 


•  Trapezius 


Pectoral  is  major 


Serratus  anterior    -J 


Ohliquus  extemus- 
Rectus  abdominis " 


Latissimus  dor  si 


Fig.   1096. — The  left  side  of  the  thorax. 

Mamma. — The  size  of  the  mamma  is  subject  to  great  variations.  In  the  adult 
nulliparous  female,  it  extends  vertically  from  the  second  to  the  sixth  rib,  and 
transversely  from  the  side  of  the  sternum  to  the  midaxillary  line.  In  the  male  and 
in  the  nulliparous  female  the  mammary  papilla  is  situated  in  the  fourth  interspace 
about  9  or  10  cm.  from  the  middle  line,  or  2  cm.  from  the  costochondral  junction. 


SURFACE  MARKINGS   OF  THE  THORAX. 

Bony  Landmarks. — ^The  second  costal  cartilage  corresponding  to  the  sternal 
angle  is  so  readily  found  that  it  is  used  as  a  starting-point  from  which  to  count  the 
ribs.  The  lower  border  of  the  Pectoralis  major  at  its  attachment  corresponds  to 
the  fifth  rib;  the  uppermost  visible  digitation  of  Serratus  anterior  indicates  the 
sixth  rib. 

The  jugular  notch  is  in  the  same  horizontal  plane  as  the  lower  border  of  the  body 
of  the  second  thoracic  vertebra;  the  sternal  angle  is  at  the  level  of  the  fifth  thoracic 
vertebra,  while  the  junction  between  the  body  and  xiphoid  process  of  the  sternum 
corresponds  to  the  fibrocartilage  between  the  ninth  and  tenth  thoracic  vertebrae. 

The  influence  of  the  obliquity  of  the  ribs  on  horizontal  levels  in  the  thorax  is 
well  shown  by  the  following  line.  "  If  a  horizontal  line  be  drawn  around  the  body 
at  the  level  of  the  inferior  angle  of  the  scapula,  while  the  arms  are  at  the  sides,  the 


SURFACE  MARKINGS  OF  THE  THORAX 


1297 


line  would  cut  the  sternum  in  front  between  tiie  fourth  and  fifth  ribs,  the  fifth  rib 
in  the  ni])j)le  line,  and  the  ninth  rib  at  the  vertebral  column."     (Treves). 

Diaphragma. — The  shape  and  variations  of  the  Diaphragma  as  seen  by  skia- 
graphx'  ha\c  already  been  described  (i)age  497). 

Surface  Lines. — For  clinical  purposes,  and  for  convenience  of  description,  the 
surface  of  the  thorax  has  been  mapped  out  by  arbitrary  lines  (Fig.  1101).  On  the 
front  of  the  thorax  the  most  important  vertical  lines  are  the  midsternal,  the  middle 
line  of  the  sternum;  and  the  mammary,  which  runs  vertically  downward  from  a 
point  midway  between  the  centre  of  the  jugular  notch  and  the  tip  of  the  acromion. 
This  latter  line,  if  prolonged,  is  practically  continuous  with  the  lateral  line  on  the 
front  of  the  abdomen.  Other  vertical  lines  on  the  front  of  the  thorax  are  the  lateral 
sternal  along  the  sternal  margin,  and  the  parasternal  midway  between  the  lateral 
sternal  and  the  mammary. 

On  either  side  of  the  thorax  the  anterior  and  posterior  axillary  lines  are  drawn 
vertically  from  the  corresponding  axillary  folds;  the  midaxillary  line  runs  down- 
ward from  the  apex  of  the  axilla. 

On  the  posterior  surface  of  the  thorax  the  scapular  line  is  drawn  vertically 
through  the  inferior  angle  of  the  scapula. 


■//  / 


^S> 


Fig.   1097. — Front  of  thorax,  showing  surface  relations  of  bones,  lungs  (purple),  pleura  (blue),  and  heart  (red 
outline).     P.  Pulmonary  valve.     A.  Aortic  valve.     B.  Bicuspid  valve.     T.  Tricuspid  valve. 


Pleurae  (Figs.  1097,  1098). — The  lines  of  reflection  of  the  pleurae  can  be  indicated 
on  the  surface.  On  the  right  side  the  line  begins  at  the  sternoclavicular  articulation 
and  runs  downward  and  medialward  to  the  midpoint  of  the  junction  between  the 
manubrium  and  body  of  the  sternum.  It  then  follows  the  midsternal  line  to  the 
lower  end  of  the  body  of  the  sternum  or  on  to  the  xiphoid  process,  where  it  turns 
lateral  ward  and  downward  across  the  seventh  sternocostal  articulation.  It  crosses 
the  eighth  costochondral  junction  in  the  mammary  line,  the  tenth  rib  in  the  mid- 
axillary  line,  and  is  prolonged  thence  to  the  spinous  process  of  the  twelfth  thoracic 
vertebra. 
82 


1298 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


On  the  left  side,  beginning  at  the  sternoclavicular  articulation,  it  reaches  the 
midpoint  of  the  junction  between  the  manubrium  and  body  of  the  sternum,  and 
extends  down  the  midsternal  line  in  contact  with  that  of  the  opposite  side  to  the 
level  of  the  fourth  costal  cartilage.  It  then  diverges  lateralward  and  is  continued 
downward  slightly  lateral  to  the  sternal  border,  as  far  as  the  sixth  costal  cartilage. 
Running  downward  and  lateralward  from  this  point  it  crosses  the  seventh  costal 
cartilage,  and  from  this  onward  it  is  similar  to  the  line  on  the  right  side,  but  at  a 
slightly  lower  level. 

Lungs  (Figs.  1097,  1098). — The  apex  of  the  lung  is  situated  in  the  neck  above  the 
medial  third  of  the  clavicle.  The  height  to  which  it  rises  above  the  clavicle  varies 
very  considerably,  but  is  generally  about  2.5  cm.  It  may,  however,  extend  as 
high  as  4  or  5  cm.,  or,  on  the  other  hand,  may  scarcely  project  above  the  level 
of  this  bone. 


Fig.   1098. — Side  of  thorax,  showing  surface  markings   for  bones,  lungs  (purple),  pleura    (blue),   and  spleen  (green). 


In  order  to  mark  out  the  anterior  borders  of  the  lungs  a  line  is  drawn  from  each 
apex  point — 2.5  cm.  above  the  clavicle  and  rather  nearer  the  anterior  than  the 
posterior  border  of  Sternocleidomastoideus — downward  and  medialward  across  the 
sternoclavicular  articulation  and  manubrium  sterni  until  it  meets,  or  almost  meets, 
its  fellow  of  the  other  side  at  the  midpoint  of  the  junction  between  the  manubrium 
and  body  of  the  sternum.  From  this  point  the  tw^o  lines  run  downward,  prac- 
tically along  the  midsternal  line,  as  far  as  the  level  of  the  fourth  costal  cartilages. 
The  continuation  of  the  anterior  border  of  the  right  lung  is  marked  by  a  prolonga- 
tion of  its  line  vertically,  dowmward  to  the  lerel  of  the  sixth  costal  cartilage,  and 
then  it  turns  lateralward  and  downward.  The  line  on  the  left  side  curves  laterahvard 
and  downward  across  the  fourth  sternocostal  articulation  to  reach  the  parasternal 
line  at  the  fifth  costal  cartilage,  and  then  turns  medialward  and  downward  to  the 
sixth  sternocostal  articulation. 


SURFACE  MAia<I.\(;s  OF  THE  THORAX  1299 

In  the  position  of  expiration  the  lower  border  of  the  kmg  may  be  marked  by  a 
shghtly  enrved  Hne  with  its  convexity  downward,  from  the  sixth  sternocostal 
jnnction  to  the  tenth  thoracic  s])inons  process.  This  hne  crosses  the  mammary 
Hne  at  the  sixth,  and  the  midaxihary  hne  at  the  eighth  rib. 

The  posterior  borders  of  the  lungs  are  indicated  by  hnes  drawn  from  the  Ie\'el 
of  the  spinous  process  of  the  seventh  cervical  vertebra,  down  either  side  of  the 
vertebral  cohunn,  across  the  costo\-ertebral  joints,  as  low  as  the  spinous  process 
of  the  tenth  thoracic  vertebra. 

The  position  of  the  oblique  fissure  in  either  lung  can  be  shown  by  a  line  drawn 
from  the  spinous  process  of  the  second  thoracic  vertebra  around  the  side  of  the 
thorax  to  the  sixth  rib  in  the  mammary  line;  this  line  corresponds  roughly  to  the 
line  of  the  vertebral  border  of  the  scapula  when  the  hand  is  placed  on  the  top  of 
the  head.  The  horizontal  fissure  in  the  right  lung  is  indicated  by  a  line  drawn  from 
the  midpoint  of  the  preceding,  or  from  the  point  where  it  cuts  the  midaxillary  line, 
to  the  midsternal  line  at  the  level  of  the  fourth  costal  cartilage. 

Trachea. — This  may  be  marked  out  on  the  back  by  a  line  from  the  spinous 
process  of  the  sixth  cervical  to  that  of  the  fourth  thoracic  vertebra  where  it  bifur- 
cates; from  its  bifurcation  the  two  bronchi  are  directed  downward  and  lateralward. 
In  front,  the  point  of  bifurcation  corresponds  to  the  sternal  angle. 

(Esophagus. — The  extent  of  the  oesophagus  may  be  indicated  on  the  back  by  a 
line  from  the  sixth  cervical  to  the  level  of  the  ninth  thoracic  spinous  process, 
2.5  cm.  to  the  left  of  the  middle  line. 

Heart. — The  outline  of  the  heart  in  relation  to  the  front  of  the  thorax  (Figs 
1097,  1099)  can  be  represented  by  a  quadrangular  figure.  The  apex  of  the  heart 
is  first  determined,  either  by  its  pulsation  or  as  a  point  in  the  fifth  interspace, 
9  cm.  to  the  left  of  the  midsternal  line.  The  other  three  points  are:  (a)  the  seventh 
right  sternocostal  articulation;  (6)  a  point  on  the  upper  border  of  the  third  right 
costal  cartilage  1  cm.  from  the  right  lateral  sternal  line;  (c)  a  point  on  the  lower 
border  of  the  second  left  costal  cartilage  2.5  cm.  from  the  left  lateral  sternal  line. 
A  line  joining  the  apex  to  point  (a)  and  traversing  the  junction  of  the  body  of  the 
sternum  with  the  xiphoid  process  represents  the  lowest  limit  of  the  heart — its 
acute  margin.  The  right  and  left  borders  are  represented  respectively  by  lines 
joining  (a)  to  ih)  and  the  apex  to  (c);  both  lines  are  convex  lateralward,  but  the 
convexity  is  more  marked  on  the  right  where  its  summit  is  4  cm.  distant  from  the 
midsternal  line  opposite  the  fourth  costal  cartilage. 

A  portion  of  the  area  of  the  heart  thus  mapped  out  is  uncovered  by  lung,  and 
therefore  gives  a  dull  note  on  percussion;  the  remainder  being  overlapped  by  lung 
gives  a  more  or  less  resonant  note.  The  former  is  known  as  the  area  of  superficial 
cardiac  dulness,  the  latter  as  the  area  of  deep  cardiac  dulness.  The  area  of  super- 
ficial cardiac  dulness  is  somewhat  triangular;  from  the  apex  of  the  heart  two  lines 
are  drawn  to  the  midsternal  line,  one  to  the  level  of  the  fourth  costal  cartilage, 
the  other  to  the  junction  between  the  body  and  xiphoid  process;  the  portion  of  the 
midsternal  line  between  these  points  is  the  base  of  the  triangle.  Latham  lays 
down  the  following  rule  as  a  sufficient  practical  guide  for  the  definition  of  the  area 
of  superficial  dulness.  "Make  a  circle  of  two  inches  in  diameter  around  a  point 
midway  between  the  nipple  and  the  end  of  the  sternum." 

The  coronary  sulcus  can  be  indicated  by  a  line  from  the  third  left,  to  the  sixth 
right,  sternocostal  joint.  The  anterior  longitudinal  sulcus  is  a  finger's  breadth  to 
the  right  of  the  left  margin  of  the  heart. 

The  position  of  the  various  orifices  is  as  follows:  The  pulmonary  orifice  is  sit- 
uated in  the  upper  angle  of  the  third  left  sternocostal  articulation;  the  aortic 
orifice  is  a  little  below  and  medial  to  this,  close  to  the  articulation.  The  left  atrio- 
ventricular opening  is  opposite  the  fourth  costal  cartilage,  and  rather  to  the  left 
of  the  midsternal  line;  the  right  atrioventricular  opening  is  a  little  lower,  opposite 


1300 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


the  fourth  interspace  of  the  right  side.    The  lines  indicating  the  atrioventricular 
openings  are  slightly  below  and  parallel  to  the  line  of  the  coronary  sulcus. 

Arteries.^ — The  line  of  the  ascending  aorta  begins  slightly  to  the  left  of  the  mid- 
sternal  line  opposite  the  third  costal  cartilage  and  extends  upward  and  to  the 
right  to  the  upper  border  of  the  second  right  costal  cartilage.  The  beginning  of 
the  aortic  arch  is  indicated  by  a  line  from  this  latter  point  to  the  midsternal  line 
about  2.5  cm.  below  the  jugular  notch.  The  point  on  the  midsternal  line  is  oppo- 
site the  summit  of  the  arch,  and  a  line  from  it  to  the  right  sternoclavicular  articu- 
lation represents  the  site  of  the  innominate  artery,  while  another  line  from  a  point 
slightly  to  the  left  of  it  and  passing  through  the  left  sternoclavicular  articulation 
indicates  the  position  of  the  left  common  carotid  artery  in  the  thorax. 


Fig.  1099. — Diagram  showing  relations  of  opened  heart  to  front  of  thoracic  wall.  A?if..  Anterior  segment  of  tri- 
cuspid valve.  A.O.  Aorta.  A.P.  Anterior  papillary  muscle.  Iv.  Innominate  artery.  L.C.C.  Left  comrnon  carotid 
artery.  L.S.  Left  subclavian  artery.  L.V.  Left  ventricle.  P. 4.  Pulmonary  artery,  fi. A.  Right  atrium.  R.V. 
Right  ventricle.     V.S.  Ventricular  septum. 


The  internal  mammary  artery  descends  behind  the  first  six  costal  cartilages 
about  1  cm.  from  the  lateral  sternal  line. 

Veins. — The  line  of  the  right  innominate  vein  crosses  the  right  sternoclavicular 
joint  and  the  upper  border  of  the  first  right  costal  cartilage  about  1  cm.  from  the 
lateral  sternal  line;  that  of  the  left  innominate  vein  extends  from  the  left  sterno- 
clavicular articulation  to  meet  the  right  at  the  upper  border  of  the  first  right 
costal  cartilage.  The  junction  of  the  two  lines  indicates  the  origin  of  the  superior 
vena  cava,  the  line  of  which  is  continued  vertically  down  to  the  level  of  the  third 
right  costal  cartilage.  The  end  of  the  inferior  vena  cava  is  situated  opposite  the 
upper  margin  of  the  sixth  right  costal  cartilage  about  2  cm.  from  the' mid- 
sternal line. 


SURFACE  ANATOMY  OF  THE  ABDOMEN  1301 


SURFACE   ANATOMY  OF  THE   ABDOMEN. 

Skin. — The  skin  of  the  front  of  tlie  abdomen  is  thin.  In  the  male  it  is  often 
thickly  hair-clad,  especially  toward  the  lower  part  of  the  middle  line;  in  the  female 
the  hairs  are  confined  to  the  pubes.  Just  below  the  line  of  the  iliac  crest,  especially 
marked  in  fat  subjects,  is  a  shallow  groove  termed  the  iliac  furrow,  while  in  the 
site  of  the  inguinal  ligament  a  sharper  fold  known  as  the  fold  of  the  groin  is  easily- 
distinguishable. 

After  distension  of  the  abdomen  from  pregnancy  or  other  causes  the  skin  com- 
monly presents  transverse  white  lines  which  are  quite  smooth,  being  destitute 
of  papilla?;  these  are  known  as  striae  gravidarum  or  striae  albicantes.  The  linea 
nigra  of  pregnancy  is  often  seen  as  a  pigmented  brow-n  streak  in  the  middle  line 
between  the  umbilicus  and  symphysis  pubis. 

In  the  middle  line  of  the  front  of  the  abdomen  is  a  shallow  furrow  which  extends 
from  the  junction  between  the  body  of  the  sternum  with  the  xiphoid  process  to  a 
short  distance  below  the  umbilicus;  it  corresponds  to  the  linea  alba.  The  umbilicus 
is  situated  in  the  middle  line,  but  it  varies  in  position  as  regards  its  height;  in  an 
adult  subject  it  is  always  placed  above  the  middle  point  of  the  body,  and  in  a  nor- 
mal well-nourished  subject  is  from  2  to  2.5  cm.  above  the  level  of  the  tubercles 
of  the  iliac  crests. 

Bones. — The  bones  in  relation  with  the  surface  of  the  ^bdomen  are  (1)  the  lower 
part  of  the  vertebral  column  and  the  lower  ribs  and  (2)  the  pelvis;  the  former 
have  already  been  described  (page  1291),  the  latter  will  be  considered  with  the 
lower  limb. 

Muscles  (Fig.  1100). — The  only  muscles  of  the  abdomen  which  have  any  consider- 
able influence  on  surface  form  are  the  Obliquus  externus  and  the  Rectus.  The 
upper  digitations  of  origin  of  Obliquus  externus  are  well-marked  in  a  muscular  sub- 
ject, interdigitating  with  those  of  Serratus  anterior;  the  lower  digitations  are  cov- 
ered by  the  border  of  Latissimus  dorsi  and  are  not  visible.  The  attachment  of  the 
Obliqui  externus  and  internus  to  the  crest  of  the  ilium  forms  a  thick  oblique  roll 
which  determines  the  iliac  furrow.  Sometimes  on  the  front  of  the  lateral  region  of 
the  abdomen  an  undulating  line  marks  the  passing  of  the  muscular  fibres  of  the 
Obliquus  externus  into  its  aponeurosis.  The  lateral  margin  of  the  Obliquus  externus 
is  separated  from  that  of  the  Latissimus  dorsi  by  a  small  triangular  interval — the 
lumbar  triangle^ — the  base  of  which  is  formed  by  the  iliac  crest,  and  its  floor  by 
Obliquus  internus. 

The  lateral  margin  of  Rectus  abdominis  is  indicated  by  the  linea  semilunaris, 
which  may  be  exactly  defined  by  putting  the  muscle  into  action.  The  surface  of 
the  Rectus  presents  three  transverse  furrows,  the  tendinous  inscriptions :  the  upper 
two  of  these,  viz.,  one  opposite,  or  a  little  below,  the  tip  of  the  xiphoid  process, 
and  the  other  midway  betw-een  this  point  and  the  umbilicus,  are  usually  well- 
marked;  the  third,  opposite  the  umbilicus,  is  not  so  distinct.  Between  the  two 
Recti  the  linea  alba  can  be  palpated  from  the  xiphoid  process  to  a  point  just  below 
the  umbilicus;  it  is  represented  by  a  distinct  dip  between  the  muscles:  beyond 
this  the  muscles  are  in  apposition. 

Vessels. — In  thin  subjects  the  pulsation  of  the  abdominal  aorta  can  be  readily 
felt  by  making  deep  pressure  in  the  middle  line  above  the  umbilicus. 

Viscera. — Under  normal  conditions  the  various  portions  of  the  digestive  tube 
cannot  be  identified  by  simple  palpation.  Peristalsis  of  the  coils  of  small  intestine 
can  be  observed  in  some  persons  with  extremely  thin  abdominal  walls  when  some 
degree  of  constipation  exists.  In  cases  of  constipation  it  is  sometimes  possible  to 
trace  portions  of  the  great  intestine  by  feeling  the  fecal  masses  within  the  gut. 
In  thin  persons  w-ith  relaxed  abdominal  walls  the  iliac  colon  can  be  felt  in  the  left 


1302 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


iliac  region— rolling  under  the  fingers  when  empty  and  forming  a  distinct  tumor 
when  distended. 

The  greater  part  of  the  liver  lies  under  cover  of  the  lower  ribs  and  their  cartilages, 
but  in  the  epigastric  fossa  it  comes  in  contact  with  the  abdominal  wall.     The 


Infrasternal  nctch 

Pectoralis  tmijor 


iScrratus 
anterior 
—  Rechis  abdcminis 

Linea  alba 
Aponeurosis  of 
Oblinuus  externus 

jI  use  ular  fibres  of 
Ohliquiis  externus 

Anterior  superior 

iliac  spine 


Inguivxil  ligament 


Fig.   1100. — Surface  anatomy  of  the  front  of  the  thorax  and  abdomen. 

position  of  the  liver  varies  according  to  the  posture  of  the  body.  In  the  erect 
posture  in  the  adult  male  the  edge  of  the  liver  projects  about  1  cm.  below  the 
lower  margin  of  the  right  costal  cartilages,  and  its  inferior  margin  can  often  be  felt 
in  this  situation  if  the  abdominal  wall  is  thin.    In  the  supine  position  the  Iner 


SURFACE  MARKINGS  OF  THE  ABDOMEN  1303 

recedes  above  the  margin  of  the  ribs  and  cannot  then  be  detected  b}'  the  finger; 
in  the  prone  position  it  falls  forward  and  is  then  generally  palpable  in  a  patient 
with  loose  and  lax  abdominal  walls.  Its  position  varies  with  the  respiratory 
movements;  during  a  deep  inspiration  it  descends  below  the  ribs;  in  expiration 
it  is  raised.  Pressure  from  without,  as  in  tight  lacing,  by  compressing  the  lower 
part  of  the  chest,  displaces  the  liver  considerably,  its  anterior  edge  frequently 
extending  as  low  as  the  crest  of  the  ilium.  Again  its  position  varies  greatly  with 
the  state  of  the  stomach  and  intestines;  when  these  are  empty  the  liver  descends, 
when  they  are  distended  it  is  pushed  upward. 

The  pancreas  can  sometimes  be  felt,  in  emaciated  subjects,  when  the  stomach 
and  colon  are  empty,  by  making  deep  pressure  in  the  middle  line  about  7  or  8  cm. 
above  the  umbilicus. 

The  kidneys  being  situated  at  the  back  of  the  abdominal  cavity  and  deeply 
placed  cannot  be  palpated  unless  enlarged  or  misplaced. 


SURFACE  MARKINGS  OF  THE  ABDOMEN. 

Bony  Landmarks.- -Above,  the  chief  bony  markings  are  the  xiphoid  process, 
the  lower  six  costal  cartilages,  and  the  anterior  ends  of  the  lower  six  ribs.  The 
junction  betAveen  the  body  of  the  sternum  and  the  xiphoid  process  is  on  the  level 
of  the  tenth  thoracic  vertebra.  Below,  the  main  landmarks  are  the  symphysis 
pubis  and  the  pubic  crest  and  tubercle,  the  anterior  superior  iliac  spine,  and  the 
iliac  crest. 

Muscles  (Fig.  1106). — The  Rectus  lies  between  the  linea  alba  and  the  linea  semi- 
lunaris; the  former  is  indicated  by  the  middle  line,  the  latter  by  a  curved  line, 
convex  lateralward,  from  the  tip  of  the  cartilage  of  the  ninth  rib  to  the  pubic 
tubercle;  at  the  level  of  the  umbilicus  the  linea  semilunaris  is  about  7  cm.  from  the 
middle  line.  The  line  indicating  the  junction  of  the  muscular  fibres  of  Obliquus 
externus  with  its  aponeurosis  extends  from  the  tip  of  the  ninth  costal  cartilage 
to  a  point  just  medial  to  the  anterior  superior  iliac  spine. 

The  umbilicus  is  at  the  level  of  the  fibrocartilage  between  the  third  and  fourth 
lumbar  vertebrse. 

The  subcutaneous  inguinal  ring  is  situated  1  cm.  above  and  lateral  to  the  pubic 
tubercle;  the  abdominal  inguinal  ring  lies  1  to  2  cm.  above  the  middle  of  the  inguinal 
ligament.  The  position  of  the  inguinal  canal  is  indicated  by  a  line  joining  these 
two  points. 

Surface  Lines. — For  convenience  of  description  of  the  viscera  and  of  reference 
to  morbid  conditions  of  the  contained  parts,  the  abdomen  is  divided  into  nine 
regions,  by  imaginary  planes,  two  horizontal  and  two  sagittal,  the  edges  of  the  planes 
being  indicated  by  lines  drawn  on  the  surface  of  the  bodj^  (Fig.  1101).  In  the  older 
method  the  upper,  or  subcostal,  horizontal  line  encircles  the  body  at  the  level  of  the 
lowest  points  of  the  tenth  costal  cartilages;  the  lower,  or  intertubercular,  is  a  line 
carried  through  the  highest  points  of  the  iliac  crests  seen  from  the  front,  i.  e., 
through  the  tubercles  on  the  iliac  crests  about  5  cm.  behind  the  anterior  superior 
spines.   An  alternative  method  is  that  of  Addison,  w^ho  adopts  the  following  lines: 

(1)  An  upper  transverse,  the  transpyloric,  halfway  between  the  jugular  notch 
and  the  upper  border  of  the  symphysis  pubis;  this  indicates  the  margin  of  the 
transpyloric  plane,  which  in  most  cases  cuts  through  the  pylorus,  the  tips  of  the 
ninth  costal  cartilages  and  the  low^er  border  of  the  first  lumbar  vertebra;  (2)  a 
low^er  transverse  line  midw^ay  between  the  upper  transverse  and  the  upper  border 
of  the  symphysis  pubis;  this  is  termed  the  transtubercular,  since  it  practically  corre- 
sponds to  that  passing  through  the  iliac  tubercles;  behind,  its  plane  cuts  the  body 
of  the  fifth  lumbar  vertebra. 


1304 


SURFACE  AXATOMY  AXD  SURFACE  MARKIXGS 


By  means  of  these  horizontal  planes  the  abdomen  is  di^-ided  into  three  zones 
named  from  above,  the  subcostal,  umbilical,  and  hypogastric  zones.  Each  of  these 
is  further  subdivided  into  three  regions  by  the  two  sagittal  planes,  which  are  indi- 
cated on  the  surface  by  a  right  and  a  left  lateral  line  drawn  vertically  through 
points  halfway  between  the  anterior  superior  iliac  spines  and  the  middle  line.  The 
middle  region  of  the  upper  zone  is  called  the  epigastric,  and  the  two  lateral  regions 


Lateral  sternal  line 

,  ParasterrMl  line 
Mammary  line 


TranspyloT^c 
plane 


^ans  tubercular 
plane 


-  Left  lateral  line 


Fig.   1101. — ^Surface  Unes  of  the  front  of  the  thorax  and  abdomen. 


the  right  and  left  hypochondriac.  The  central  region  of  the  middle  zone  is  the 
umbiUcal,  and  the  two  lateral  regions  the  right  and  left  lumbar.  The  middle  region 
of  the  lower  zone  is  the  hypogastric  or  pubic,  and  the  lateral  are  the  right  and  left 
iliac  or  inguinal.  The  middle  regions,  viz.,  epigastric,  umbilical,  and  pubic,  can  each 
be  divided  into  right  and  left  portions  by  the  middle  line.  In  the  following  descrip- 
tion of  the  viscera  the  regions  marked  out  by  Addison's  lines  are  those  referred  to. 


SURFACE  MARKIXGS  OF  THE  ABDOMEN 


1305 


Stomach  (Fig.  1103). — The  shape  of  the  stomach  is  constantly  undergoing  altera- 
tion; it  is  affected  by  the  particular  i:»hase  of  the  process  of  gastric  digestion,  by 


B 


Fig.   1102. — Radiographs  of  a  moderately  distended  stomach,  showing   the   influence  of   posture.      (^Modified    from 
Hertz.)     A.  With  the  patient  in  the  erect  posture.     B.  With  the  patient  lying  down. 

the  state  of  the  surrounding  viscera,  and  by  the  amount  and  character  of  its  con- 
tents.    Its  position  also  varies  with  that  of  the  body  (Fig.  1102),  so  that  it  is 


.■' ,!     /  Transpy iortc 
plane 


Orifice  of 
vermiform  process 


>     '  '•    {       '\TTarts tuber ciolar' 
p  lan,e 


Fig.   1103. — Front  of  abdomen,  showing  surface  markings  for  liver,  stomach,  and  great  intestine. 


impossible  to  indicate  it  on  the  surface  with  any  degree  of  accuracy.  The  measure- 
ments given  refer  to  a  moderately  filled  stomach  with  the  body  in  the  supine 
position. 


1306 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


The  cardiac  orifice  is  opposite  the  seventh  left  costal  cartilage  about  2.5  cm. 
from  the  side  of  the  sternum;  it  corres])on(ls  to  the  level  of  the  tenth  thoracic  verte- 
bra. The  pyloric  orifice  is  on  the  transpyloric  line  about  1  cm.  to  the  rifilit  of  the 
middle  line,  or  alternately  5  cm.  below  the  seventh  right  sternocostal  articulation; 
it  is  at  the  level  of  the  first  lumbar  vertebra.  A  curved  line,  convex  downward  and 
to  the  left,  joining  these  points  indicates  the  lesser  curvature.  In  the  left  lateral 
line  the  fundus  of  the  stomach  reaches  as  high  as  the  fifth  interspace  or  the  sixth 
costal  cartilage,  a  little  below  the  apex  of  the  heart.  To  indicate  the  greater  cur- 
vature a  curved  line  is  drawn  from  the  cardiac  orifice  to  the  summit  of  the  fundus, 
thence  downward  and  to  the  left,  finally  turning  medialward  to  the  pyloric  orifice, 
but  passing,  on  its  way,  through  the  intersection  of  the  left  lateral  with  the  trans- 
pyloric line.  The  portion  of  the  stomach  which  is  in  contact  with  the  abdominal 
wall  can  be  represented  roughly  by  a  triangular  area  the  base  of  which  is  formed  by 
a  line  draw^n  from  the  tip  of  the  tenth  left  costal  cartilage  to  the  tip  of  the  ninth 
right  cartilage,  and  the  sides  by  two  lines  drawn  from  the  end  of  the  eighth  left 
costal  cartilage  to  the  ends  of  the  base  line. 


'/'  :.--':V 


Tt'\'\     '- 


A.^^^- 


m 


'■H-L\.„ 


YTrans  tuherctblar 
plane. 


Fig.  1104. — Front  of  abdomen,  showing  surface  markings  for  duodenum,  pancreas,  and  kidneys.  A  A'.  Plane 
through  joint  between  body  and  xiphoid  process  of  sternum.  B  B'.  Plane  midway  between  .4  A'  and  transpyloric 
plane.     C  C.  Plane  midway  between  transpjdoric  and  transtubercular  planes. 


Transpylori  c 
plane 


A  space  of  some  clinical  importance — the  space  of  Traube — overlies  the  stomach 
and  may  be  thus  indicated.  It  is  semilunar  in  outline  and  lies  within  the  following 
boundaries:  the  lower  edge  of  the  left  lung,  the  anterior  border  of  the  spleen,  the 
left  costal  margin  and  the  inferior  margin  of  the  left  lobe  of  the  liver. 

Duodenum  (Fig.  1104). — The  superior  part  is  horizontal  and  extends  from  the 
pylorus  to  the  right  lateral  line;  the  descending  part  is  situated  medial  to  the 
right  lateral  line,  from  the  transpyloric  line  to  a  point  midway  between  the  trans- 
pyloric and  transtubercular  lines.  The  horizontal  part  runs  with  a  slight  upward 
slope  from  the  end  of  the  descending  part  to  the  left  of  the  middle  line;  the  ascending 
part  is  vertical,  and  reaches  the  transpyloric  line,  where  it  ends  in  the  duodeno- 
jejunal flexure,  about  2.5  cm.  to  the  left  of  the  middle  line. 

Small  Intestine. — The  coils  of  small  intestine  occupy  the  front  of  the  abdomen. 
For  the  most  part  the  coils  of  the  jejunum  are  situated  on  the  left  side,  i.  e.,  in  the 
left  lumbar  and  iliac  regions,  and  in  the  left  half  of  the  umbilical  region.  The  coils 
of  the  ileum  lie  toward  the  right  in  the  right  lumbar  and  iliac  regions,  in  the  right 


SURFACE  MARKINGS  OF  THE  ABDOMEN  1307 

half  of  the  umbilical  region,  and  in  the  hypogastric  region;  a  i)ortion  of  the  ileum 
is  within  the  pelvis.  The  end  of  the  ileum,  i.  e.,  the  ileocolic  junction,  is  slightly 
belo\v  and  medial  to  the  intersection  of  the  right  lateral  and  traiistubereular  lines. 

Cecum  and  Vermiform  Process. — The  cecum  is  in  the  right  iliac  and  hypo- 
gastric regions;  its  position  varies  with  its  degree  of  distension,  but  the  midpoint 
of  a  line  drawn  from  the  right  anterior  superior  iliac  spine  to  the  upper  margin  of 
the  symphysis  pubis  will  mark  approximately  the  middle  of  its  lower  border. 

The  position  of  the  base  of  the  vermiform  process  is  indicated  by  a  point  on  the 
lateral  line  on  a  level  with  the  anterior  superior  iliac  spine. 

Ascending  Colon. — The  ascending  colon  passes  upward  through  the  right 
lumbar  region,  lateral  to  the  right  lateral  line.  The  right  colic  flexure  is  situated  in 
the  upper  and  right  angle  of  intersection  of  the  subcostal  and  right  lateral  lines. 

Transverse  Colon. — The  transverse  colon  crosses  the  abdomen  on  the  confines 
of  the  umbilical  and  epigastric  regions,  its  lower  border  being  on  a  level  slightly 
above  the  umbilicus,  its  upper  border  just  below  the  greater  curvature  of  the 
stomach. 

Descending  Colon. — The  left  colic  flexure  is  situated  in  the  upper  left  angle  of 
the  intersection  between  the  left  lateral  and  transpyloric  lines.  The  descending 
colon  courses  down  through  the  left  lumbar  region,  lateral  to  the  left  lateral  line, 
as  far  as  the  iliac  crest  (see  footnote  p.  1181). 

Hiac  Colon. — The  line  of  the  iliac  colon  is  from  the  end  of  the  descending  colon 
to  the  left  lateral  line  at  the  level  of  the  anterior  superior  iliac  spine. 

Liver  (Fig.  1103). — The  upper  limit  of  the  right  lobe  of  the  liver,  in  the  middle 
line,  is  at  the  level  of  the  junction  between  the  body  of  the  sternum  and  the  xiphoid 
process;  on  the  right  side  the  line  must  be  carried  upward  as  far  as  the  fifth  costal 
cartilage  in  the  mammary  line,  and  then  downward  to  reach  the  seventh  rib  at 
the  side  of  the  thorax.  The  upper  limit  of  the  left  lobe  can  be  defined  by  continuing 
this  line  downward  and  to  the  left  to  the  sixth  costal  cartilage,  5  cm.  from  the 
middle  line.  The  lower  limit  can  be  indicated  by  a  line  drawn  1  cm.  below  the 
lower  margin  of  the  thorax  on  the  right  side  as  far  as  the  ninth  costal  cartilage, 
thence  obliquely  upward  to  the  eighth  left  costal  cartilage,  crossing  the  middle 
line  just  above  the  transpyloric  plane  and  finally,  with  a  slight  left  convexity,  to 
the  end  of  the  line  indicating  the  upper  limit. 

According  to  Birmingham  the  limits  of  the  normal  liver  may  be  marked  out 
on  the  surface  of  the  body  in  the  following  manner.  Take  three  points:  (a)  1.25 
cm.  below  the  right  nipple;  (b)  1.25  cm.  below  the  tip  of  the  tenth  rib;  (c)  2.5  cm. 
below  the  left  nipple.  Join  (a)  and  (c)  by  a  line  slightly  convex  upward;  (a)  and 
(6)  by  a  line  slightly  convex  lateralward;  and  (6)  and  (c)  by  a  line  slightly  convex 
downward. 

The  fundus  of  the  gall-bladder  approaches  the  surface  behind  the  anterior 
end  of  the  ninth  right  costal  cartilage  close  to  the  lateral  margin  of  the  Rectus 
abdominis. 

Pancreas  (Fig.  1104). — The  pancreas  lies  in  front  of  the  second  lumbar  vertebra. 
Its  head  occupies  the  curve  of  the  duodenum  and  is  therefore  indicated  by  the  same 
lines  as  that  viscus;  its  neck  corresponds  to  the  pylorus.  Its  body  extends  along 
the  transpyloric  line,  the  bulk  of  it  lying  above  this  line  to  the  tail  which  is  in  the 
left  hypochondriac  region  slightly  to  the  left  of  the  lateral  line  and  above  the 
transpyloric. 

Spleen  (Figs.  1098,  1105). — To  map  out  the  spleen  the  tenth  rib  is  taken  as 
representing  its  long  axis;  vertically  it  is  situated  between  the  upper  border  of  the 
ninth  and  the  lower  border  of  the  eleventh  ribs.  The  highest  point  is  4  cm.  from 
the  middle  line  of  the  back  at  the  level  of  the  tip  of  the  ninth  thoracic  spinous 
process;  the  lowest  point  is  in  the  midaxillary  line  at  the  level  of  the  first  lumbar 
.spinous  process. 


1308 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


Kidneys  (Figs.  1104,  1105). — The  right  kichiey  usually  lies  about  1  cm.  lower 

than  the  left,  but  for  practical  purposes  similar  surface  markings  are  taken  for  each. 

On  the  front  of  the  abdomen  the  upper  pole  lies  midway  between  the  plane  of 

the  lower  end  of  the  body  of  the  sternum  and  the  transpyloric  plane,  5  em.  from 

the  middle  line.  The  lower  pole 
is  situated  midway  between  the 
transpyloric  and  intertubercular 
planes,  7  cm.  from  the  middle  line. 
The  hilus  is  on  the  transpyloric 
plane,  5  cm.  from  the  middle  line. 
Round  these  three  points  a  kidney- 
shaped  figure  4  cm.  to  5  cm.  broad 
is  drawn,  two  thirds  of  which  lie 
medial  to  the  lateral  line.  To  indi- 
cate the  position  of  the  kidney 
from  the  back,  the  parallellogram 
of  Morris  is  used;  two  vertical  lines 
are  drawn,  the  first  2.5  cm.,  the 
second  9.5  cm.  from  the  middle 
line;  the  parallelogram  is  completed 
by  two  horizontal  lines  drawn  re- 
spectively at  the  levels  of  the  tips 
of  the  spinous  process  of  the 
eleventh  thoracic  and  the  lower 
border  of  the  spinous  process  of  the 
The  hilus  is  5  cm.  from  the  middle  line  at  the  level  of  the 


Fig.  1105. — Back  of  lumbar  region,  showing  surface  markings 
for  kidneys,  ureters,  and  spleen.  The  lower  portions  of  the  lung 
and  pleura  are  shown  on  the  right  side. 


third  lumbar  vertebra 

spinous  process  of  the  first  lumbar  vertebra 


Transpyloria 
plane. 


Abdominal  inguinal  ring 
Subcutaneous  inguinal  ring 

Fpfnoral  ring 
Fig.   1106. — Front  of  abdomen,  showing  surface  markings  for  arteries  and  inguinal  canal. 

Ureters. — On  the  front  of  the  abdomen,  the  line  of  the  ureter  runs  from  the 
hilus  of  the  kidney  to  the  pubic  tubercle;  on  the  back,  from  the  hilus  vertically 
downward,  passing  practically  through  the  posterior  superior  iliac  spine  (Fig.  1105). 


SURFACE  M.\h'KI.\(;S  OF  THE  I'KRINEUM  1309 

Vessels  (Fig.  11  ()()). — The  inferior  epigastric  artery  can  be  marked  out  hy  a  line 
from  a  i)oint  muhvay  between  the  anterior  superior  iliae  spine  and  the  pubie  sym- 
pliysis  to  the  umbiUeus.  This  line  also  indicates  the  lateral  boundarx-  of  He?sel- 
bach's  triangle — an  area  of  importance  in  connection  with  inguinal  hernia;  the  other 
boundaries  are  the  lateral  edge  of  Rectus  abdominis,  and  the  medial  half  of  the 
inguinal  ligament.  The  line  of  the  abdominal  aorta  begins  in  the  middle  line  about 
4  cm.  above  the  transpyloric  line  and  extends  to  a  ]K)int  2  cm.  below  and  to  the 
left  of  the  umbilicus — or  more  accurately  to  a  point  2  cm.  to  the  left  of  the  middle 
line  on  a  line  which  passes  through  the  highest  points  of  the  iliac  crests  (.1  A', 
Fig.  1106).  The  point  of  termination  of  the  abdominal  aorta  corresponds  to  the 
level  of  the  fourth  lumbar  vertebra;  a  line  drawn  from  it  to  a  point  midway 
between  the  anterior  superior  iliac  spine  and  the  symphysis  pubis  indicates  the 
common  and  external  iliac  arteries.  The  common  iliac  is  represented  by  the  upper 
third  of  this  line,  the  external  iliac  by  the  remaining  two-thirds. 

Of  the  larger  branches  of  the  abdominal  aorta,  the  coeliac  artery  is  4  cm.,  the 
superior  mesenteric  2  cm.  above  the  transpyloric  line;  the  renal  arteries  are  2  cm. 
below  the  same  line.  The  inferior  mesenteric  artery  is  4  cm.  above  the  bifurcation 
of  the  abdominal  aorta. 

Nerves. — The  thoracic  nerves  on  the  anterior  abdominal  wall  are  represented  by 
lines  continuing  those  of  the  bony  ribs.  The  termination  of  the  seventh  nerve  is 
at  the  level  of  the  xiphoid  process,  the  tenth  reaches  the  vicinity  of  the  umbilicus, 
the  twelfth  ends  about  midway  between  the  umbilicus  and  the  upper  border  of 
the  symphysis  pubis.  The  first  lumbar  is  parallel  to  the  thoracic  nerves;  its  ilio- 
hypogastric branch  becomes  cutaneous  above  the  subcutaneous  inguinal  ring;  its 
ilioinguinal  branch  at  the  ring. 

SURFACE   ANATOMY  OF  THE  PERINEUM. 

Skin. — In  the  middle  line  of  the  posterior  part  of  the  perineum  and  about  4  cm. 
in  front  of  the  tip  of  the  coccyx  is  the  anal  orifice.  The  junction  of  the  mucous 
membrane  of  the  anal  canal  with  the  skin  of  the  perineum  is  marked  by  a  white 
line  which  indicates  also  the  line  of  contact  of  the  external  and  internal  Sphincters. 
In  the  anterior  part  of  the  perineum  the  external  genital  organs  are  situated. 
The  skin  covering  the  scrotum  is  rough  and  corrugated,  but  over  the  penis  it  is 
smooth;  extending  forward  from  the  anus  on  to  the  scrotum  and  penis  is  a  median 
ridge  which  indicates  the  scrotal  raphe.  In  the  female  are  seen  the  skin  reduplica- 
tions forming  the  labia  majora  and  minora  laterally,  the  frenulum  of  the  labia 
behind,  and  the  prepuce  of  the  clitoris  in  front;  still  more  anteriorly  is  the  mons 
pubis. 

Bones. — In  the  antero-lateral  boundaries  of  the  perineum,  the  whole  outline 
of  the  pubic  arch  can  be  readily  traced  ending  in  the  ischial  tuberosities.  Behind 
in  the  middle  line  is  the  tip  of  the  coccyx. 

Muscles  and  Ligaments. — The  margin  of  the  Glutaeus  maximus  forms  the  postero- 
lateral boundary,  and  in  thin  subjects,  by  pressing  deeply,  the  sacrotuberous 
ligament  can  be  felt  through  the  muscle.  The  only  other  muscles  influencing 
surface  form  are  the  Ischiocavernosus  covering  the  crus  penis,  which  lies  on  the  side 
of  the  pubic  arch,  and  the  Sphincter  ani  externus,  which,  in  action,  closes  the  anal 
orifice  and  causes  a  puckering  of  the  skin  around  it. 

SURFACE  MARKINGS  OF  THE  PERINEUM. 

A  line  drawn  transversely  across  in  front  of  the  ischial  tuberosities  divides  the 
perineum  into  a  posterior  or  rectal,  and  an  anterior  or  urogenital,  triangle.  This 
line  passes  through  the  central  point  of  the  perineum,  which  is  situated  about 


1310 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


2.5  cm.  in  front  of  the  centre  of  the  anal  aperture  or,  in  the  male,  midway  between 
the  anus  and  the  reflection  of  the  skin  on  to  the  scrotum. 

Rectum  and  Anal  Canal. — A  finger  inserted  through  the  anal  orifice  is  grasped 
by  the  Sphincter  ani  externus,  passes  into  the  region  of  the  Sphincter  ani  internus, 
and  higher  up  encounters  the  resistance  of  the  Puborectalis;  beyond  this  it  may 
reach  the  lowest  of  the  transverse  rectal  folds.  In  front,  the  urethral  bulb  and 
membranous  part  of  the  urethra  are  first  identified,  and  then  about  4  cm.  abo\-e 
the  anal  orifice  the  prostate  is  felt;  beyond  this  the  vesiculae  seminales,  if  enlarged, 
and  the  fundus  of  the  bladder,  when  distended,  can  be  recognized.  On  either  side 
is  the  ischiorectal  fossa.  Behind  are  the  anococcygeal  body,  the  pelvic  surfaces 
of  the  coccvx  and  lower  end  of  the  sacrum,  and  the  sacrospinous  ligaments  (Fig 
1107). 


Ureffi 


Ductus  deferen  i 


Urethra 


External  urethral 
orifice 


'Sacrum 


Rectovesical 
excavation 


Coccyx 


Ejaculatory  duct 
Anal  canal 


Fig.   1107. — Median  sagittal  section  of  male  pelvis. 


In  the  female  the  posterior  w^all  and  fornix  of  the  vagina,  and  the  cervix  and 
body  of  the  uterus  can  be  felt  in  front,  while  somewhat  laterally  the  ovaries  can 
just  be  reached. 

Male  Urogenital  Organs. — The  corpora  cavernosa  penis  can  be  followed  backward 
to  the  crura  which  are  attached  to  the  sides  of  the  pubic  arch.  The  glans  penis, 
covered  by  the  prepuce,  and  the  external  urethral  orifice  can  be  examined,  and  the 
course  of  the  urethra  traced  along  the  under  surface  of  the  penis  to  the  bulb  which 
is  situated  immediately  in  front  of  the  central  point  of  the  perineum.  Through 
the  wall  of  the  scrotum  on  either  side  the  testis  can  be  palpated;  it  lies  toward 
the  back  of  the  scrotum,  and  along  its  posterior  border  the  epididymis  can  be  felt; 
passing  upward  along  the  medial  side  of  the  epididymis  is  the  spermatic  cord, 
which  can  be  traced  upward  to  the  subcutaneous  inguinal  ring. 

By  means  of  a  sound  the  general  topography  of  the  urethra  and  bladder  can 


SURFACE  MARKINGS  OF  THE  PERINEUM 


1311 


be  investigated;  with  the  urethroscope  the  interior  of  the  urethra  can  be  illuminated 
and  viewed  directly;  with  the  cystoscope  the  interior  of  the  bladder  is  in  a  similar 
manner  illuminated  for  visual  examination.  In  the  bladder  the  main  points  to 
which  attention  is  directed  are  the  trigone,  the  torus  uretericus,  the  plicae  uretericae, 
and  the  openings  of  the  ureters  and  urethra  (see  Fig.  l()o3). 


/'  ,  ;  V- 


Clitoris 


Vestibule 


External  urethral 
orifice 


Vaginal  orifice 
Hymen 


Fig.   1108. — External  genital  organs  of  female.     The  labia  minora  have  been  drawn  apart. 

Female  Urogenital  Organs. — In  the  pudendal  cleft  (Fig.  1108)  between  the  labia 
minora  are  the  openings  of  the  vagina  and  urethra.  In  the  virgin  the  vaginal  open- 
ing is  partly  closed  by  the  hymen — after  coitus  the  remains  of  the  hymen  are  rep- 
resented by  the  carunculae  hymeneales.  Between  the  hymen  and  the  frenulum  of 
the  labia  is  the  fossa  navicularis,  while  in  the  groove  between  the  hymen  and  the 
labium  minus,  on  either  side,  the  small  opening  of  the  greater  vestibular  (Bartholin's) 
gland  can  be  seen.  These  glands  when  enlarged  can  be  felt  on  either  side  of  the 
posterior  part  of  the  vaginal  orifice.  By  inserting  a  finger  into  the  vagina  the  fol- 
lowing structures  can  be  examined  through  its  wall  (Fig:  1109).  Behind,  from 
below  upward,  are  the  anal  canal,  the  rectum,  and  the  rectouterine  excavation. 
Projecting  into  the  roof  of  the  vagina  is  the  vaginal  portion  of  the  cervix  uteri 
with  the  external  uterine  orifice;  in  front  of  and  behind  the  cervix  the  anterior 
and  posterior  vaginal  fornices  respectively  can  be  examined.  With  the  finger  in  the 
vagina  and  the  other  hand  on  the  abdominal  wall  the  whole  of  the  cervix  and 
body  of  the  uterus,  the  uterine  tubes,  and  the  ovaries  can  be  palpated.  If  a  speculum 
be  introduced  into  the  vagina,  the  walls  of  the  passage,  the  vaginal  portion  of  the 
cervix,  and  the  external  uterine  orifice  can  all  be  exposed  for  visual  examination. 

The  external  urethral  orifice  lies  in  front  of  the  vaginal  opening;  the  angular 
gap  in  which  it  is  situated  between  the  two  converging  labia  minora  is  termed  the 


1312 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


vestibule.  The  urethral  canal  in  the  female  is  very  dilatable  and  can  be  explored 
with  the  finger.  About  2.5  cm.  in  front  of  the  external  orifice  of  the  urethra  are 
the  glans  and  prepuce  of  the  clitoris,  and  still  farther  forward  is  the  mons  pubis. 


Sacruvi 


Coccyx 


Recto-uterine 
excavation 
External  uteriu' 
orifice 


Anal  canal-^ 


Vesicouterine 

-^.^54,  /      /     '  xcavation 


Urethra 


Fig.   1109. — Median  sagittal  section  of  female  pelvis. 


SURFACE  ANATOMY  OF  THE  UPPER  EXTREMITY. 


Skin. — The  skin  covering  the  shoulder  and  arm  is  smooth  and  very  movable 
on  the  underlying  structures.  In  the  axilla  there  are  numerous  hairs  and  many 
sudoriferous  and  sebaceous  glands.  Over  the  medial  side  and  front  of  the  forearm 
the  skin  is  thin  and  smooth,  and  contains  few  hairs  but  many  sudoriferous  glands; 
over  the  lateral  side  and  back  of  the  arm  and  forearm  it  is  thicker,  denser,  and 
contains  more  hairs  but  fewer  sudoriferous  glands.  In  the  region  of  the  olecranon 
it  is  thick  and  rough,  and  is  very  loosely  connected  to  the  underlying  tissue  so 
that  it  falls  into  transverse  wrinkles  when  the  forearm  is  extended.  At  the  front 
of  the  wrist  there  are  three  transverse  furrows  in  the  skin;  they  correspond  respec- 
tively from  above  downward  to  the  positions  of  the  styloid  process  of  the  ulna, 
the  wrist-joint,  and  the  midcarpal  joint. 

The  skin  of  the  palm  of  the  hand  differs  considerably  from  that  of  the  forearm. 
At  the  wrist  it  suddenly  becomes  hard  and  dense  and  covered  with  a  thick  layer  of 
epidermis;  on  the  thenar  eminence  these  characteristics  are  less  marked  than  else- 
where. In  spite  of  its  hardness  and  density  the  skin  of  the  palm  is  exceedingly 
sensitive  and  very  vascular,  but  it  is  destitute  of  hairs  and  sebaceous  glands.  It 
is  tied  down  by  fibrous  bands  along  the  lines  of  flexion  of  the  digits,  exhibiting 
certain  furrows  of  a  permanent  character.    One  of  these,  starting  in  front  of  the 


SURFACE  ANATOMY  OF  THE  UPPER  EXTREMITY  1313 

wrist  at  the  tuberosity  of  the  naviciiliir  hone,  eurves  Hroiiiid  the  thenar  eminence 
and  ends  on  the  radial  border  of  the  hand  a  little  above  the  metacarpophalangeal 
joint  of  the  index  finger.  A  second  line  begins  at  the  end  of  the  first  and  extends 
obliquely  across  the  palm  to  reach  the  ulnar  border  about  the  middle  of  the  fifth 
metacarpal  bone.  A  third  line  begins  at  the  ulnar  border  about  2.5  cm.  distal  to 
the  end  of  the  second  and  extends  across  the  heads  of  the  hfth,  fourth,  and  third 
metacarpal  bones.  The  proximal  segments  of  the  fingers  are  joined  to  one  another 
on  the  volar  aspect  by  folds  of  skin  constituting  the  "web"  of  the  fingers;  these 
folds  extend  across  about  the  level  of  the  centres  of  the  proximal  phalanges  and  their 
free  margins  are  continuous  with  the  transverse  furrows  at  the  roots  of  the  fingers. 
Since  the  web  is  confined  to  the  volar  aspect  the  fingers  appear  shorter  when  viewed 
from  in  front  than  from  behind. 

Over  the  fingers  and  thumb  the  skin  again  becomes  thinner,  especially  at  the 
flexures  of  the  joints  (where  it  is  crossed  by  transverse  furrows)  and  over  the  ter- 
minal phalanges;  it  is  disposed  on  numerous  ridges  in  consequence  of  the  arrange- 
ment of  the  papilloe  in  it.  These  ridges  form,  in  different  individuals,  distinctive 
and  permanent  patterns  which  can  be  used  for  purposes  of  identification.  The 
superficial  fascia  in  the  palm  of  the  hand  is  made  up  of  dense  fibro-fatty  tissue  which 
binds  the  skin  so  firmly  to  the  palmar  aponeurosis  that  very  little  movement  is 
permitted  between  the  two. 

On  the  back  of  the  hand  and  fingers  the  subcutaneous  tissue  is  lax,  so  that  the 
skin  is  freely  movable  on  the  underlying  parts.  Over  the  interphalangeal  joints 
the  skin  is  very  loose  and  is  thrown  into  transverse  wrinkles  when  the  fingers 
are  extended. 

Bones.— The  clavicle  can  be  felt  throughout  its  entire  length.  The  enlarged 
sternal  extremity  projects  above  the  upper  margin  of  the  sternum  at  the  side  of 
the  jugular  notch,  and  from  this  the  body  of  the  bone  can  be  traced  lateral  ward 
immediately  under  the  skin.  The  medial  part  is  convex  forward,  but  the  surface 
is  partially  obscured  by  the  attachments  of  Sternocleidomastoideus  and  Pectoralis 
major;  the  lateral  third  is  concave  forward  and  ends  at  the  acromion  of  the  scapula 
in  a  slight  enlargement.  The  clavicle  is  almost  horizontal  when  the  arm  is  lying 
by  the  side,  although  in  muscular  subjects  it  may  incline  a  little  upward  at  its 
acromial  end,  which  is  on  a  plane  posterior  to  the  sternal  end. 

The  only  parts  of  the  scapula  that  are  truly  subcutaneous  are  the  spine  and 
acromion,  but  the  coracoid  process,  the  vertebral  border,  the  inferior  angle,  and  to 
a  lesser  extent  the  axillary  border  can  also  be  readily  defined.  The  acromion  and 
spine  are  easily  recognizable  throughout  their  entire  extent,  forming  with  the 
clavicle  the  arch  of  the  shoulder.  The  acromion  forms  the  point  of  the  shoulder; 
it  joins  the  clavicle  at  an  acute  angle — ^the  acromial  angle — slightly  niedial  to,  and 
behind  the  tip  of  the  acromion.  The  spine  can  be  felt  as  a  distinct  ridge,  marked 
on  the  surface  as  an  oblique  depression  which  becomes  less  distinct  and  ends  in  a 
slight  dimple  a  little  lateral  to  the  spinous  processes  of  the  vertebrae.  Below  this 
point  the  vertebral  border  can  be  traced  downward  arid  lateralward  to  the  inferior 
angle,  which  can  be  identified  although  covered  by  Latissimus  dorsi.  From  the 
inferior  angle  the  axillary  border  can  usually  be  traced  upward  through  its  thick 
muscular  covering,  forming  wdth  its  enveloping  muscles  the  posterior  fold  of  the 
axilla.  The  coracoid  process  is  situated  about  2  cm.  below  the  junction  of  the 
intermediate  and  lateral  thirds  of  the  clavicle;  it  is  covered  by  the  anterior  border 
of  Deltoideus,  and  thus  lies  a  little  lateral  to  the  infraclavicular  fossa  or  depression 
which  marks  the  interval  betAveen  the  Pectoralis  major  and  Deltoideus. 

The  humerus  is  almost  entirely  surrounded  by  muscles,  and  the  only  parts 

which  are  strictly  subcutaneous  are  small  portions  of  the  medial  and  lateral  epi- 

condyles;  in  addition  to  these,  however,  the  tubercles  and  a  part  of  the  head  of  the 

bone  can  be  felt  under  the  skin  and  muscles  by  which  they  are  covered.    Of  these, 

83 


1314  SURFACE  ANATOMY  AND  SURFACE  MARKINGS 

the  greater  tubercle  forms  the  most  prominent  bony  point  of  the  shoulder,  extending 
beyond  the  acromion;  it  is  best  recognized  when  the  arm  is  lying  passive  by  the 
side,  for  if  the  arm  be  raised  it  recedes  under  the  arch  of  the  shoulder.  The  lesser 
tubercle,  directed  forward,  is  medial  to  the  greater  and  separated  from  it  by  the 
intertubercular  groove,  which  can  be  made  out  by  deep  pressure.  When  the  arm 
is  abducted  the  lower  part  of  the  head  of  the  humerus  can  be  examined  by  pressing 
deeply  in  the  axilla.  On  either  side  of  the  elbow-joint  and  just  above  it  are  the 
medial  and  lateral  epicondyles.  Of  these,  the  former  is  the  more  prominent,  but  the 
medial  supracondylar  ridge  passing  upward  from  it  is  much  less  marked  than  the 
lateral,  and  as  a  rule  is  not  palpable;  occasionally,  however,  the  hook-shaped  supra- 
condylar process  (page  312)  is  found  on  this  border.  The  position  of  the  lateral 
epicondyle  is  best  seen  during  semiflexion  of  the  forearm,  and  is  indicated  by 
a  depression;  from  it  the  strongly  marked  lateral  supracondylar  ridge  runs 
upward. 

The  most  prominent  part  of  the  ulna,  the  olecranon,  can  always  be  identified  at 
the  back  of  the  elbow-joint.  When  the  forearm  is  flexed  the  upper  quadrilateral 
surface  is  palpable,  but  during  extension  it  recedes  into  the  olecranon  fossa.  During 
extension  the  upper  border  of  the  olecranon  is  slightly  above  the  level  of  the  medial 
epicondyle  and  nearer  to  this  than  to  the  lateral;  when  the  forearm  is  fully  flexed 
the  olecranon  and  the  epicondyles  form  the  angles  of  an  equilateral  triangle.  On 
the  back  of  the  olecranon  is  a  smooth  triangular  subcutaneous  surface,  and  running 
down  the  back  of  the  forearm  from  the  apex  of  this  triangle  the  prominent  dorsal 
border  of  the  ulna  can  be  felt  in  its  whole  length:  it  has  a  sinuous  outline,  and  is 
situated  in  the  middle  of  the  back  of  the  limb  above;  but  below,  where  it  is  rounded 
off,  it  can  be  traced  to  the  small  subcutaneous  surface  of  the  styloid  process  on  the 
medial  side  of  the  wrist.  The  stjdoid  process  forms  a  prominent  tubercle  continuous 
above  with  the  dorsal  border  and  ending  below  in  a  blunt  apex  at  the  level  of  the 
wrist-joint;  it  is  most  evident  when  the  hand  is  in  a  position  midway  between 
supination  and  pronation.  When  the  forearm  is  pronated  another  prominence, 
the  head  of  the  ulna,  appears  behind  and  above  the  styloid  process. 

Below  the  lateral  epicondyle  of  the  humerus  a  portion  of  the  head  of  the  radius 
is  palpable;  its  position  is  indicated  on  the  surface  by  a  little  dimple,  which  is  best 
seen  when  the  arm  is  extended.  If  the  finger  be  placed  in  this  dimple  and  the 
semiflexed  forearm  be  alternately  pronated  and  supinated  the  head  of  the  radius 
will  be  felt  distinctly,  rotating  in  the  radial  notch.  The  upper  half  of  the  body  of 
the  bone  is  obscured  by  muscles;  the  lower  half,  though  not  subcutaneous,  can  be 
readily  examined,  and  if  traced  downward  is  found  to  end  in  a  lozenge-shaped  con- 
vex surface  on  the  lateral  side  of  the  base  of  the  styloid  process;  this  is  the  only 
subcutaneous  part  of  the  bone,  and  from  its  lower  end  the  apex  of  the  styloid  process 
bends  medialward  toward  the  wrist.  About  the  middle  of  the  dorsal  surface  of 
the  lower  end  of  the  radius  is  the  dorsal  radial  tubercle,  best  perceived  when  the 
wrist  is  slightly  flexed;  it  forms  the  lateral  boundary  of  the  oblique  groove  for  the 
tendon  of  Extensor  pollicis  longus. 

On  the  front  of  the  wrist  are  two  subcutaneous  eminences,  one,  on  the  radial 
side,  the  larger  and  flatter,  produced  by  the  tuberosity  of  the  navicular  and  the  ridge 
on  the  greater  multangular;  the  other,  on  the  ulnar  side,  by  the  pisiform.  The  tuber- 
osity of  the  navicular  is  distal  and  medial  to  the  styloid  process  of  the  radius,  and 
is  most  clearly  visible  w^hen  the  w^ist-joint  is  extended;  the  ridge  on  the  greater 
multangular  is  about  1  cm.  distal  to  it.  The  pisiform  is  about  1  cm.  distal  to  the 
lower  end  of  the  ulna  and  just  distal  to  the  level  of  the  styloid  process  of  the  radius; 
it  is  crossed  bj'  the  uppermost  crease  which  separates  the  front  of  the  forearm  from 
the  palm  of  the  hand.  The  rest  of  the  volar  surface  of  the  bony  carpus  is  covered 
by  tendons  and  the  transverse  carpal  ligament,  and  is  entirely  concealed,  with 
the  exception  of  the  hamulus  of  the  hamate  bone,  which,  however,  is  difficult  to 


SURFACE  ANATOMY  OF  THE  UPPER  EXTREMITY  1815 

define.  On  the  dorsal  surface  of  {\\v  (■ar])iis  only  the  triangular  bone  can  l)c  clearly 
made  out. 

Distal  to  the  carpus  the  dorsal  surfaces  of  the  metacarpal  bones,  eovered  by  the 
P^xtensor  tendons,  except  the  fifth,  are  visible  only  in  \'ery  thin  hands;  the  dorsal 
surface  of  the  fifth  is,  however,  subcutaneous  throuji,h()ut  almost  its  whole  length. 
Slightly  lateral  to  the  middle  line  of  the  hand  is  a  prominence,  frequently  well- 
marked,  but  occasionally  indistinct,  formed  by  the  styloid  process  of  the  third 
metacarpal  bone;  it  is  situated  about  4  cm.  distal  to  the  dorsal  radial  tubercle. 
The  heads  of  the  metacarpal  bones  can  be  plainly  seen  and  felt,  rounded  in  contour 
and  standing  out  in  bold  relief  under  the  skin  when  the  fist  is  clenched;  the  head 
of  the  third  is  the  most  prominent.  In  the  palm  of  the  hand  the  metacarpal  bones 
are  covered  by  muscles,  tendons,  and  aponeuroses,  so  that  only  their  heads  can  be 
distinguished.  The  base  of  the  metacarpal  bone  of  the  thumb,  however,  is  promi- 
nent dorsally,  distal  to  the  styloid  process  of  the  radius;  the  body  of  the  bone  is 
easily  palpable,  ending  at  the  head  in  a  flattened  prominence,  in  front  of  which 
are  the  sesamoid  bones. 

The  enlarged  ends  of  the  phalanges  can  be  easily-  felt.  When  the  digits  are 
bent  the  proximal  phalanges  form  prominences,  which  in  the  joints  between  the 
first  and  second  phalanges  are  slightly  hollow,  but  flattened  and  square-shaped  in 
those  between  the  second  and  third. 

Articulations. — The  sternoclavicular  joint  is  subcutaneous,  and  its  position  is 
indicated  by  the  enlarged  sternal  extremity  of  the  clavicle,  lateral  to  the  long 
cord-like  sternal  head  of  Sternocleidomastoideus.  If  this  muscle  be  relaxed  a 
depression  between  the  end  of  the  clavicle  and  the  sternum  can  be  felt,  defining 
the  exact  position  of  the  joint. 

The  position  of  the  acromioclavicular  joint  can  generally  be  ascertained  by 
determining  the  slightly  enlarged  acromial  end  of  the  clavicle  which  projects  above 
the  level  of  the  acromion;  sometimes  this  enlargement  is  so  considerable  as  to 
form  a  rounded  eminence. 

The  shoulder- joint  is  deeply  seated  and  cannot  be  palpated."  If  the  forearm 
be  slightly  flexed  a  curved  crease  or  fold  with  its  convexity  downward  is  seen  in 
front  of  the  elbow,  extending  from  one  epicondyle  to  the  other;  the  elbow-joint 
is  slightly  distal  to  the  centre  of  the  fold.  The  position  of  the  radiohumeral  joint 
can  be  ascertained  by  feeling  for  a  slight  groove  or  depression  between  the  head 
of  the  radius  and  the  capitulum  of  the  humerus,  at  the  back  of  the  elbow-joint. 

The  position  of  the  proximal  radioulnar  joint  is  marked  on  the  surface  at  the 
back  of  the  elbow  by  the  dimple  which  indicates  the  position  of  the  head  of  the 
radius.  The  site  of  the  distal  radioulnar  joint  can  be  defined  by  feeling  for  the 
slight  groove  at  the  back  of  the  wrist  between  the  prominent  head  of  the  ulna 
and  the  lower  end  of  the  radius,  when  the  forearm  is  in  a  state  of  almost  complete 
pronation. 

Of  the  three  transverse  skin  furrows  on  the  front  of  the  wrist,  the  middle  corre- 
sponds fairly  accurately  with  the  wrist-joint,  while  the  most  distal  indicates  the 
position  of  the  midcarpal  articulation. 

The  metacarpophalangeal  and  interphalangeal  joints  are  readily  available  for 
surface  examination;  the  former  are  situated  just  distal  to  the  prominences  of  the 
knuckles,  the  latter  are  sufficiently  indicated  by  the  furrows  on  the  volar,  and  the 
wrinkles  on  the  dorsal  surfaces. 

Muscles  (Figs.  1075, 1110, 1111). — The  anterior  border  of  the  Trapezius  presents  as 
a  slight  ridge  running  downward  and  forward  from  the  superior  nuchal  line  of  the 
occipital  bone  to  the  junction  of  the  intermediate  and  lateral  thirds  of  the  clavicle. 
The  inferior  border  of  the  muscle  forms  an  undulating  ridge  passing  downward 
and  medialward  from  the  root  of  the  spine  of  the  scapula  to  the  spinous  process 
of  the  twelfth  thoracic  vertebra. 


1316 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


The  lateral  border  of  the  Latissimus  dorsi  (Fig.  1096)  may  be  traced,  when  the 
muscle  is  in  action,  as  a  rounded  edge  starting  from  the  ihac  crest  and  slanting 
obliquely  forward  and  upward  to  the  axilla,  where  it  takes  part  with  the  Teres 
major  in  forming  the  posterior  axillary'  fold. 


Flex.  carp.  rod. 
Ahd.  i)oll  lomj. 
Ext.  pull.  breu. 


Lateral  group  of 
antibrachial  muscles 

I         Brachialis 

Biceps  hrachii 


Flex.  carp,  ulnaris   \ 
Palmaris  longus 


Medial  grovp  of      /     ,        Tnceps  hrachii 
antibrachial  timscies    i       /  ^ 

Anticubital  fossa     ■''^«'^»«^  epicondyle 

Coracobrachialis 

Axilla 

Pectoralis  major 


Serratus  anterior 


Fig.  1110. — Front  of  right  upper  extremity. 

The  Pectoralis  major  (Fig.  1100)  conceals  a  considerable  part  of  the  thoracic  wall 
in  front.  Its  sternal  origin  presents  a  border  which  bounds,  and  determines  the 
width  of  the  sternal  furrow.  The  upper  margin  is  generally  well-marked  medially 
and  forms  the  medial  boundary  of  a  triangular  depression,  the  infraclavicular  fossa, 
which  separates  the  Pectoralis  major  from  the  Deltoideus;  it  gradually  becomes 
less  marked  as  it  approaches  the  tendon  of  insertion  and  is  closely  blended  with 
the  Deltoideus.  The  lower  border  of  Pectoralis  major  forms  the  rounded  anterior 
axillary  fold.  Occasionally  a  gap  is  visible  between  the  clavicular  and  sternal  parts 
of  the  muscle. 


Deltoideus  Medial  eminence 

I  T,  •         ,        ,  . .  I  Abd.  poll.  long. 

I  Biceps  brachii  \  i^xt.  poll.  brev. 

■^,^  I  Lateral  eminence  j  I 


Medial  epicondyle 


-  ',  Bead  of  ulna 

I  ,  J-:j't .  rarp.  tilnaris 

1  Flex.  carp,  ulnaris 

Olecranon        Anconaeus 


Fig.   1111. — Back  of  right  upper  extremity. 


When  the  arm  is  raised  the  lowest  slip  of  origin  of  Pectoralis  minor  produces  a 
fulness  just  below  the  anterior  axillary  fold  and  serves  to  break  the  sharp  outline 
of  the  lower  border  of  Pectoralis  major. 

The  origin  of  the  Serratus  anterior  (Figs.  1096,  1100)  causes  a  very  characteristic 
surface  marking.  When  the  arm  is  abducted  the  lower  five  or  six  serrations  form 
a  zigzag  line  with  a  general  convexity  forward;  when  the  arm  is  by  the  side  the 
highest  visible  serration  is  that  attached  to  the  fifth  rib. 

The  Deltoideus  with  the  prominence  of  the  upper  end  of  the  humerus  produces 
the  rounded  contour  of  the  shoulder;  it  is  rounded  and  fuller  in  front  than  behind,. 


SURFACE  ANATOMY  OF  THE  UPPER  EXTREMITY  1317 

where  it  presents  a  somewhat  flattened  form.  Above,  its  anterior  border  presents 
a  shghtly  curved  eminence  which  forms  the  lateral  boundary  of  the  infraclavicular 
fossa;  below,  it  is  closel.y  united  with  the  Pectoralis  major.  Its  posterior  border 
is  thin,  flattened,  and  scarcely  marked  above,  but  is  thicker  and  more  prominent 
below.  The  insertion  of  Deltoideus  is  marked  by  a  depression  on  the  lateral  side 
of  the  middle  of  the  arm. 

Of  the  scapular  muscles  the  only  one  which  influences  surface  form  is  the  Teres 
major;  it  assists  the  Latissimus  dorsi  in  forming  the  thick,  rounded,  posterior 
axillary  fold. 

When  the  arm  is  raised  the  Coracobrachialis  reveals  itself  as  a  narrow  elevation 
emerging  from  under  cover  of  the  anterior  axillary  fold  and  running  medial  to  the 
body  of  the  humerus. 

On  the  front  and  medial  aspects  of  the  arm  is  the  prominence  of  the  Biceps 
brachii,  bounded  on  either  side  by  an  intermuscular  depression.  It  determines  the 
contour  of  the  front  of  the  arm  and  extends  from  the  anterior  axillary  fold  to  the 
bend  of  the  elbow;  its  upper  tendons  are  concealed  by  the  Pectoralis  major  and 
Deltoideus,  and  its  lower  tendon  sinks  into  the  anticubital  fossa.  When  the  muscle 
is  fully  contracted  it  presents  a  globular  form,  and  the  lacertus  fibrosus  attached 
to  its  tendon  of  insertion  becomes  prominent  as  a  sharp  ridge  running  downward 
and  medialward. 

On  either  side  of  the  Biceps  brachii  at  the  lower  part  of  the  arm  the  Brachialis 
is  discernible.  Laterally  it  forms  a  narrow  eminence  extending  some  distance  up 
the  arm;  medially  it  exhibits  only  a  little  fulness  above  the  elbow. 

On  the  back  of  the  arm  the  long  head  of  the  Triceps  brachii  may  be  seen  as  a 
longitudinal  eminence,  emerging  from  under  cover  of  Deltoideus  and  gradually 
passing  into  the  flattened  plane  of  the  tendon  of  the  muscle  at  the  lower  part  of 
the  back  of  the  arm.  When  the  muscle  is  in  action  the  medial  and  lateral  heads 
become  prominent. 

On  the  front  of  the  elbow  are  two  muscular  elevations,  one  on  either  side,  sep- 
arate above  but  converging  below  so  as  to  form  the  medial  and  lateral  boundaries 
of  the  anticubital  fossa.  The  medial  elevation  consists  of  the  Pronator  teres  and 
the  Flexors,  and  forms  a  fusiform  mass,  pointed  above  at  the  medial  epicondyle 
and  gradually  tapering  off  below.  The  Pronator  teres  is  the  most  lateral  of  the 
group,  while  the  Flexor  carpi  radialis,  lying  to  its  medial  side,  is  the  most  prominent 
and  may  be  traced  downward  to  its  tendon,  which  is  situated  nearer  to  the  radial 
than  to  the  ulnar  border  of  the  front  of  the  wrist  and  medial  to  the  radial  artery. 
The  Palmaris  longus  presents  no  surface  marking  above,  but  below,  its  tendon 
stands  out  when  the  muscle  is  in  action  as  a  sharp,  tense  cord  in  front  of  the  middle 
of  the  wrist.  The  Flexor  digitorum  sublimis  does  not  directly  influence  surface 
form;  the  position  of  its  four  tendons  on  the  front  of  the  lower  part  of  the  forearm 
is  indicated  by  an  elongated  depression  between  the  tendons  of  Palmaris  longus 
and  Flexor  carpi  ulnaris.  The  Flexor  carpi  ulnaris  determines  the  contour  of  the 
medial  border  of  the  forearm,  and  is  separated  from  the  Extensor  group  of  muscles 
by  the  ulnar  furrow  produced  by  the  subcutaneous  dorsal  border  of  the  ulna;  its 
tendon  is  evident  along  the  ulnar  border  of  the  lower  part  of  the  forearm,  and  is 
most  marked  when  the  hand  is  flexed  and  adducted. 

The  elevation  forming  the  lateral  side  of  the  anticubital  fossa  consists  of  the 
Brachioradialis,  the  Extensors  and  the  Supinator;  it  occupies  the  lateral  and  a 
considerable  part  of  the  dorsal  surface  of  the  forearm  in  the  region  of  the  elbow, 
and  forms  a  fusiform  mass  which  is  altogether  on  a  higher  level  than  that  produced 
by  the  medial  elcA^ation.  Its  apex  is  between  the  Triceps  brachii  and  Brachialis 
some  distance  above  the  elbow-joint;  it  acquires  its  greatest  breadth  opposite  the 
lateral  epicondyle,  and  below  this  shades  off  into  a  flattened  surface.  About  the 
middle  of  the  forearm  it  divides  into  two  diverging  longitudinal  eminences.    The 


1318  SURFACE  ANATOMY  AND  SURFACE  MARKINGS 

lateral  eminence  consists  of  the  Brachioradialis  and  the  Extensores  carpi  radiales 
longus  and  brevis,  and  descends  from  tlie  lateral  snj)rac{)ndy]ar  ridge  in  the  direction 
of  the  styloid  process  of  the  radius.  The  medial  eminence  comprises  the  Extensor 
digitorum  communis,  Extensor  digiti  quinti  proprius,  and  the  Extensor  carpi  ulnaris; 
it  begins  at  the  lateral  epicondyle  of  the  humerus  as  a  tapering  mass  which  is  sep- 
arated above  from  the  Anconaeus  by  a  well-marked  furrow,  and  below  from  the 
Pronator  teres  and  Flexor  group  by  the  ulnar  furrow.  The  medial  border  of  the 
Brachioradialis  starts  as  a  rounded  elevation  above  the  lateral  epicondyle;  lower 
down  the  muscle  forms  a  prominent  mass  on  the  radial  side  of  the  upper  part  of 
the  forearm;  below  it  tapers  to  its  tendon,  which  may  be  traced  to  the  styloid 
process  of  the  radius.  The  Anconaeus  presents  as  a  triangular  slightly  elevated 
area,  immediately  lateral  to  the  subcutaneous  surface  of  the  olecranon  and  differ- 
entiated from  the  Extensor  group  by  an  oblique  depression;  the  upper  angle  of 
the  triangle  is  at  the  dimple  over  the  lateral  epicondyle. 

At  the  lower  part  of  the  back  of  the  forearm  in  the  interval  between  the  two 
diverging  eminences  is  an  oblique  elongated  swelling;  full  above  but  flattened 
and  partially  subdivided  below;  it  is  caused  by  the  Abductor  pollicis  longus 
and  the  Extensor  pollicis  brevis.  It  crosses  the  dorsal  and  lateral  surfaces  of 
the  radius  to  the  radial  side  of  the  wrist-joint,  whence  it  is  continued  on  to 
the  dorsal  surface  of  the  thumb  as  a  ridge  best  marked  when  the  thumb  is 
extended. 

The  tendons  of  most  of  the  Extensor  muscles  can  be  seen  and  felt  on  the  back 
of  the  wrist.  Laterally  is  the  oblique  ridge  produced  by  the  Extensor  pollicis 
longus.  The  Extensor  carpi  radialis  longus  is  scarcely  palpable,  but  the  Extensor 
carpi  radialis  brevis  can  be  identified  as  a  vertical  ridge  emerging  from  under  the 
ulnar  border  of  the  tendon  of  the  Extensor  pollicis  longus  when  the  wrist  is  extended. 
Medial  to  this  the  Extensor  tendons  of  the  fingers  can  be  felt,  the  Extensor  digiti 
quinti  proprius  being  separated  from  the  tendons  of  the  Extensor  digitorum 
communis  by  a  slight  furrow. 

The  muscles  of  the  hand  are  principally  concerned,  as  regards  surface  form,  in 
producing  the  thenar  and  hypothenar  eminences,  and  cannot  be  individually  dis- 
tinguished; the  thenar  eminence,  on  the  radial  side,  is  larger  and  rounder  than  the 
hypothenar,  which  is  a  long  narrow  elevation  along  the  ulnar  side  of  the  palm. 
When  the  Palmaris  brevis  is  in  action  it  produces  a  wrinkling  of  the  skin  over  the 
hypothenar  eminence  and  a  dimple  on  the  ulnar  border.  On  the  back  of  the  hand 
the  Interossei  dorsales  give  rise  to  elongated  swellings  between  the  metacarpal 
bones;  the  first  forms  a  prominent  fusiform  bulging  when  the  thumb  is  adducted, 
the  others  are  not  so  marked. 

Arteries.^ — Above  the  middle  of  the  clavicle  the  pulsation  of  the  subclavian  artery 
can  be  detected  by  pressing  downward,  backward,  and  medialward  against  the 
first  rib.  The  pulsation  of  the  axillary  artery  as  it  crosses  the  second  rib  can  be 
felt  below  the  middle  of  the  clavicle  just  medial  to  the  coracoid  process;  along  the 
lateral  wall  of  the  axilla  the  course  of  the  artery  can  be  easily  followed  close  to  the 
medial  border  of  Coracobrachialis.  The  brachial  artery  can  be  recognized  in  practi- 
cally the  whole  of  its  extent,  along  the  medial  margin  of  the  Biceps;  in  the  upper 
two-thirds  of  the  arm  it  lies  medial  to  the  humerus,  but  in  the  lower  third  is  more 
directly  on  the  front  of  the  bone.  Over  the  lower  end  of  the  radius,  between  the 
styloid  process  and  Flexor  carpi  radialis,  a  portion  of  the  radial  artery  is  superficial 
and  is  used  clinically  for  observations  on  the  pulse. 

Veins.^ — The  superficial  veins  of  the  upper  extremity  are  easily  rendered  visible 
by  compressing  the  proximal  trunks;  their  arrangement  is  described  on  pages  747 
to  749. 

Nerves. — The  uppermost  trunks  of  the  brachial  plexus  are  palpable  for  a  short 
distance  above  the  clavicle  as  they  emerge  from  under  the  lateral  border  of  Sterno- 


SURFACE  MARKINGS  OF  THE  UPPER  EXTREMITY  1319 

cleidomastoideus;  the  larger  nerves  derived  from  the  plexus  can  be  rolled  under  the 
finger  against  the  lateral  axillary  wall  but  cannot  be  identified.  The  ulnar  nerve 
can  be  detected  in  the  groove  behind  the  medial  epicondyle  of  tlie  humerus. 


SURFACE    MARKINGS    OF    THE    UPPER   EXTREMITY. 

Bony  Landmarks. — The  bony  landmarks  as  described  above  are  so  readily  avail- 
able for  surface  recognition  that  no  special  measurements  are  required  to  indicate 
them.  It  may  be  noted,  however,  that  the  medial  angle  of  the  scapula  is  applied 
to  the  second  rib,  while  the  inferior  angle  lies  against  the  seventh.  The  intertuber- 
cular  groove  of  the  humerus  is  vertically  below  the  acromioclavicular  joint  when 
the  arm  hangs  by  the  side  with  the  palm  of  the  hand  forward. 

Articulations. — The  acromioclavicular  joint  is  situated  in  a  plane  passing  sagit- 
tally  through  the  middle  line  of  the  front  of  the  arm.  The  line  of  the  elbow-joint 
is  not  straight;  the  radiohumeral  portion  is  practically  at  right  angles  to  the  long 
axis  of  the  humerus  and  is  situated  about  2  cm.  distal  to  the  lateral  epicondyle; 
the  ulnohumeral  portion  is  oblique,  and  its  medial  end  is  about  2.5  cm.  distal  to  the 
medial  epicondyle.  The  position  of  the  wrist-joint  can  be  indicated  by  drawing  a 
curved  line,  with  its  convexity  upward,  between  the  styloid  processes  of  the  radius 
and  ulna;  the  summit  of  the  convexity  is  about  1  cm.  above  the  centre  of  a  straight 
line  joining  the  two  processes. 

Muscles. — The  only  muscles  of  the  upper  extremity  which  occasionally  require 
definition  by  surface  lines  are  the  Trapezius,  the  Latissimus  dorsi,  and  the  Pectorales 
major  and  minor.  The  antero-superior  border  of  Trapezius  is  indicated  by  a  line 
from  the  superior  nuchal  line  about  3  cm.  lateral  to  the  external  occipital  protuber- 
ance to  the  junction  of  the  intermediate  and  lateral  thirds  of  the  clavicle;  the  line 
of  the  lower  border  extends  from  the  spinous  process  of  the  twelfth  thoracic  vertebra 
to  the  vertebral  border  of  the  scapula  at  the  root  of  the  spine.  The  upper  border 
of  Latissimus  dorsi  is  almost  horizontal,  running  from  the  spinous  process  of  the 
seventh  thoracic  vertebra  to  the  inferior  angle  of  the  scapula  and  thence  somewhat 
obliquely  to  the  intertubercular  sulcus  of  the  humerus;  the  lower  border  corresponds 
roughly  to  a  line  drawn  from  the  iliac  crest  about  2  cm.  from  the  lateral  margin  of 
the  Sacrospinalis  to  the  intertubercular  sulcus.  The  upper  margin  of  Pectoralis 
major  extends  from  the  middle  of  the  clavicle  to  the  surgical  neck  of  the  humerus; 
its  lower  border  is  practically  in  the  line  of  the  fifth  rib  and  reaches  from  the  fifth 
costochondral  junction  to  the  middle  of  the  anterior  border  of  Deltoideus.  The 
two  lines  indicating  the  borders  of  Pectoralis  minor  begin  at  the  coracoid  process 
of  the  scapula  and  extend  to  the  third  and  fifth  ribs  respectively,  just  lateral  to  the 
corresponding  costal  cartilages.  On  the  front  of  the  elbow-joint  a  triangular  space 
— ^the  anticubital  fossa — is  mapped  out  for  convenience  of  reference.  The  base  of 
the  triangle  is  a  line  joining  the  medial  and  lateral  epicondyles,  while  the  sides  are 
formed  respectively  by  the  salient  margins  of  the  Brachioradialis  and  Pronator 
teres. 

Mucous  Sheaths. — On  the  volar  surfaces  of  the  wrist  and  hand  the  mucous 
sheaths  of  the  Flexor  tendons  (Fig.  1112)  can  be  indicated  as  follows.  The  sheath 
for  Flexor  pollicis  longus  extends  from  about  3  cm.  above  the  upper  edge  of  the 
transverse  carpal  ligament  to  the  terminal  phalanx  of  the  thumb.  The  common 
sheath  for  the  Flexores  digitorum  reaches  about  3.5  to  4  cm.  above  the  upper  edge 
of  the  transverse  carpal  ligament  and  extends  on  the  palm  of  the  hand  to  about 
the  level  of  the  centres  of  the  metacarpal  bones.  The  sheath  for  the  tendons  to  the 
little  finger  is  continued  from  the  common  sheath  to  the  base  of  the  terminal  phalanx 
of  this  finger;  the  sheaths  for  the  tendons  of  the  other  fingers  are  separated  from 
the  common  sheath  by  an  interval;  they  begin  opposite  the  necks  of  the  meta- 


1320 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


carpal  bones  and  extend  to  the  terminal  phalanges.    The  mucous  sheaths  of  the 
Extensor  tendons  are  shown  in  Fig.  1113  (see  also  page  550). 


Sheaths  of  terminal 
farts  of  Flexores 
digitorum 


Muscles  of  thenar  ,^\ 


Sheath  of  Flexor 
poinds  longus 


Sheath  of  Flexor  carpi 
radialis 


Muscles  of  hypo- 
thenar  eminence 


mi 

^  ^       Gonvmon  sheath  of 
Flexores  digitorum, 

IjIL^         sid>limis  and 


profundus 


Flexor  carpi  ulnaris 


Fig.   1112. — The  mucous  sheaths  of  the  tendons  on  the  front  of  the  wrist  and  digits. 

Arteries  (Fig.  1114). — The  course  of  the  axillary  artery  can  be  marked  out  by 
abducting  the  arm  to  a  right  angle  and  drawing  a  line  from  the  middle  of  the 
clavicle  to  the  point  where  the  tendon  of  the  Pectoralis  major  crosses  the  promi- 
nence of  the  Coracobrachialis.  Of  the  branches  of  the  axillary  artery,  the  origin 
of  the  thoracoacromial  corresponds  to  the  point  where  the  artery  crosses  the 
upper  border  of  Pectoralis  minor;  the  lateral  thoracic  takes  practically  the  line  of 
the  lower  border  of  Pectoralis  minor;  the  subscapular  is  sufficiently  indicated  by 


SURFACE  MARKINGS  OF  THE  UPPER  EXTREMITY 


1321 


the  axillan^  border  of  the  scapula;  the  scapular  circumflex  is  given  off  the  sub- 
scapular opposite  the  midpoint  of  a  line  joining  the  tip  of  the  acromion  to  the 
lower  edge  of  the  deltoid  tuberosity,  while  the  humeral  circumflex  arteries  arise 
from  the  axillary  about  2  cm.  above  this.     The  position  of  the  brachial  artery  is 


Abd.  poll,  long. 


Ext  carp.  rod.  long, 
Ext   carp.  rad.  brev. 


Fig.   1113. — The  mucous  sheaths  of  the  tendons  on  the  back  of  the  wrist. 


marked  by  a  line  draM'n  from  the  junction  of  the  anterior  and  middle  thirds  of  the 
distance  between  the  anterior  and  posterior  axillary  folds  to  a  point  midway 
between  the  epicondyles  of  the  humerus  and  continued  distally  for  2.5  cm.,  at 
which  point  the  artery  bifurcates.  With  regard  to  the  branches  of  the  brachial 


1322 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


artery — the  profunda  crosses  the  back  of  the  humerus  at  the  level  of  the  insertion 
of  Deltoideus;  the  nutrient  is  given  off  opposite  the  middle  of  the  body  of  the 
humerus;  a  line  from  this  point  to  the  back  of  the  medial  condyle  represents 
the  superior  uhiar  collateral;  the  inferior  ulnar  collateral  is  given  off  about  5  cm. 
above  the  fold  of  the  elbow-joint  and  runs  directly  medialward. 


Fig.   1114. — Front  of  right  upper  extremity,  shoxvang  surface  markings  for  bones,  arteries,  and  nerves. 

The  position  of  the  radial  artery  in  the  forearm  is  represented  by  a  line  from  the 
lateral  margin  of  the  Biceps  tendon  in  the  centre  of  the  anticubital  fossa  to  the 
medial  side  of  the  front  of  the  styloid  process  of  the  radius  when  the  limb  is 
in  the  position  of  supination.  The  situation  of  the  distal  portion  of  the  artery 
is  indicated  by  continuing  this  line  around  the  radial  side  of  the  wrist  to  the 
proximal  end  of  the  first  intermetacarpal  space. 


Fig.   1115. — Back  of  right  upper  extremity,  showing  surface  markings  for  bones  and  nerves. 

On  account  of  the  curved  direction  of  the  ulnar  artery,  two  lines  are  required  to 
indicate  its  course;  one  is  drawn  from  the  front  of  the  medial  epicondyle  to  the 
radial  side  of  the  pisiform  bone;  the  lower  two-thirds  of  this  line  represents  two- 
thirds  of  the  artery;  the  upper  third  is  represented  by  a  second  line  from  the  centre 
of  the  hollow  in  front  of  the  elbow-joint  to  the  junction  of  the  upper  and  middle 
thirds  of  the  first  line. 

The  superficial  volar  arch  (Fig.  1116)  can  be  indicated  by  a  line  starting  from 
the  radial  side  of  the  pisiform  bone  and  curving  distalward  and  lateralward  as 
far  as  the  base  of  the  thumb,  with  its  convexity  toward  the  fingers.  The  summit 
of  the  arch  is  usually  on  a  level  with  the  ulnar  border  of  the  outstretched  thumb . 
The  deep  volar  arch  is  practically  transverse,  and  is  situated  about  1  cm.  nearer  to 
the  carpus. 


SURFACE  AX  ATOMY  OF  THE  LOWER  EXTREMITY 


132J 


Nerves  (Figs.  1114,  1115). — In  the  arm  the  line  of  the  median  nerve  is  practically 
the  same  as  that  for  the  brachial  artery;  at  the  bend  of  the  elbow  the  nerve  is 
medial  to  the  artery.    The  course  of  . 

the  nerve  in  the  forearm  is  marked 
by  a  line  starting  from  a  point  just 
medial  to  the  centre  of  one  joining 
the  epicondyles,  and  extending  to  the 
lateral  margin  of  the  tendon  of  Pal- 
maris  longus  at  the  wrist. 

The  ulnar  nerve  follows  the  line  of 
the  brachial  artery  in  the  upper  half 
of  the  arm,  but  at  the  middle  of  the 
arm  it  diverges  and  descends  to  the 
back  of  the  medial  epicondyle.  In  the 
forearm  it  is  represented  by  a  line 
from  the  front  of  the  medial  epi- 
condyle to  the  radial  side  of  the  pisi- 
form bone. 

The  course  of  the  radial  nerve  can 
be  indicated  by  a  line  from  just 
below  the  posterior  axillary  fold,  to 
the  lateral  side  of  the  humerus  at 
the  junction  of  its  middle  and  lower 
thirds;  thence  it  passes  vertically 
downward  on  the  front  of  the  arm 
to  the  level  of  the  lateral  epicondyle. 
The  course  of  the  superficial  radial 
nerve  is  represented  by  a  continua- 
tion of  this  line  downward  to  the 
junction  of  the  middle  and  lower 
thirds  of  the  radial  artery;  it  then 
crosses  the  radius  and  runs  distal- 
ward  to  the  dorsum  of  the  base  of 
the  first  metacarpal  bone. 

The  axillary  nerve  crosses  the  humerus  about  2  cm.  above  the  centre  of  a  line 
joining  the  tip  of  the  acromion  to  the  lower  edge  of  the  deltoid  tuberosity. 


Fig.  1116. — Palm  of  left  hand,  shovdng  position  of  skin 
creases  and  bones,  and  surface  markings  for  the  volar 
arches. 


SURFACE   ANATOMY   OF    THE   LOWER  EXTREMITY, 


Skin. — The  skin  of  the  thigh,  especially  in  the  hollow  of  the  groin  and  on  the 
medial  side,  is  thin,  smooth  and  elastic,  and  contains  few  hairs  except  on  the  neigh- 
borhood of  the  pubis.  Laterally  it  is  thicker  and  the  hairs  are  more  numerous. 
The  junction  of  the  skin  of  the  thigh  with  that  on  the  front  of  the  abdomen  is 
marked  by  a  well-defined  furrow  which  indicates  the  site  of  the  inguinal  ligament; 
the  furrow  presents  a  general  convexity  downward,  but  its  medial  half,  which  is 
the  better  marked,  is  nearly  straight.  The  skin  over  the  buttock  is  fairly  thick 
and  is  characterized  by  its  low  sensibility  and  slight  vascularity;  as  a  rule  it  is 
destitute  of  conspicuous  hairs  except  toward  the  post-anal  furrow,  where  in  some 
males  they  are  abundantly  developed.  An  almost  transverse  fold — the  gluteal 
fold — crosses  the  lower  part  of  the  buttock;  it  practically  bisects  the  lower  margin 
of  the  Glutaeus  maximus  and  is  most  evident  during  extension  of  the  hip-joint. 
The  skin  over  the  front  of  the  knee  is  covered  by  thickened  epidermis;  it  is  loose 
and  thrown  into  transverse  wrinkles  when  the  leg  is  extended.    The  skin  of  the  leg 


1324  SURFACE  ANATOMY  AND  SURFACE  MARKINGS 

is  thin,  especially  on  the  medial  side,  and  is  covered  with  numerous  larc;e  hairs. 
On  the  dorsum  of  the  foot  the  skin  is  thin,  loosely  connected  to  subjacent  parts, 
and  contains  few  hairs,  on  the  plantar  surface,  and  especially  over  the  heel,  the 
epidermis  is  of  great  thickness,  and  here,  as  in  the  palm  of  the  hand,  there  are 
neither  hairs  nor  sebaceous  glands. 

Bones. — The  hip  bones  are  largely  covered  with  muscles,  so  that  only  at  a  few 
points  do  they  approach  the  surface.  In  front  the  anterior  superior  iliac  spine  is 
easily  recognized,  and  in  thin  subjects  stands  out  as  a  prominence  at  the  lateral 
end  of  the  fold  of  the  groin;  in  fat  subjects  its  position  is  indicated  by  an  oblique 
depression,  at  the  bottom  of  which  the  bony  process  can  be  felt.  Proceeding 
upward  and  backward  from  this  process  the  sinuously  curved  iliac  crest  can  be 
traced  to  the  posterior  superior  iliac  spine,  the  site  of  which  is  indicated  by  a  slight 
depression;  on  the  outer  lip  of  the  crest,  about  5  cm.  behind  the  anterior  superior 
spine,  is  the  prominent  iliac  tubercle.  In  thin  subjects  the  pubic  tubercle  is  very 
apparent,  but  in  the  obese  it  is  obscured  by  the  pubic  fat;  it  can,  however,  be 
detected  by  following  up  the  tendon  of  origin  of  Adductor  longus.  Another  part 
of  the  bony  pelvis  which  is  accessible  to  touch  is  the  ischial  tuberosity,  situated 
beneath  the  Glutaeus  maximus,  and,  when  the  hip  is  flexed,  easily  felt,  as  it  is  then 
uncovered  by  muscle. 

The  femur  is  enveloped  by  muscles,  so  that  in  fairly  muscular  subjects  the  only 
accessible  parts  are  the  lateral  surface  of  the  greater  trochanter  and  the  lower 
expanded  end  of  the  bone.  The  site  of  the  greater  trochanter  is  generally  indicated 
by  a  depression,  owing  to  the  thickness  of  the  Glutaei  medius  and  minimus  which 
project  above  it;  when,  however,  the  thigh  is  flexed,  and  especially  if  it  be  crossed 
over  the  opposite  one,  the  trochanter  produces  a  blunt  eminence  on  the  surface. 
The  lateral  condyle  is  more  easily  felt  than  the  medial;  both  epicondyles  can  be 
readily  identified,  and  at  the  upper  part  of  the  medial  condyle  the  sharp  adductor 
tubercle  can  be  recognized  without  difficulty.  When  the  knee  is  flexed  a  portion 
of  the  patellar  surface  is  uncovered  and  is  palpable. 

The  anterior  surface  of  the  patella  is  subcutaneous.  When  the  knee  is  extended 
the  medial  border  of  the  bone  is  a  little  more  prominent  than  the  lateral,  and  if 
the  Quadriceps  femoris  be  relaxed  the  bone  can  be  moved  from  side  to  side.  When 
the  joint  is  flexed  the  patella  recedes  into  the  hollow  between  the  condyles  of  the 
femur  and  the  upper  end  of  the  tibia,  and  becomes  firmly  applied  to  the  femur. 

A  considerable  portion  of  the  tibia  is  subcutaneous.  At  the  upper  end  the  con- 
dyles can  be  felt  just  below  the  knee;  the  medial  condyle  is  broad  and  smooth, 
and  merges  into  the  subcutaneous  surface  of  the  body  below;  the  lateral  is  narrower 
and  more  prominent,  and  on  it,  about  midway  between  the  apex  of  the  patella 
and  the  head  of  the  fibula,  is  the  tubercle  for  the  attachment  of  the  iliotibial  band. 
In  front  of  the  upper  end  of  the  bone,  between  the  condyles,  is  an  oval  eminence, 
the  tuberosity,  which  is  continuous  below  with  the  anterior  crest  of  the  bone.  This 
crest  can  be  identified  in  the  upper  two-thirds  of  its  extent  as  a  flexuous  ridge, 
but  in  the  lower  third  it  disappears  and  the  bone  is  concealed  by  the  tendons  of 
the  muscles  on  the  front  of  the  leg.  Medial  to  the  anterior  crest  is  the  broad 
surface,  slightly  encroached  on  by  muscles  in  front  and  behind.  The  medial 
malleolus  forms  a  broad  prominence,  situated  at  a  higher  level  and  somewhat 
farther  forward  than  the  lateral  malleolus;  it  overhangs  the  medial  border  of  the 
arch  of  the  foot;  its  anterior  border  is  nearly  straight,  its  posterior  presents  a  sharp 
edge  which  forms  the  medial  margin  of  the  groove  for  the  tendon  of  Tibialis 
posterior. 

The  only  subcutaneous  parts  of  the  fibula  are  the  head,  the  lower  part  of  the 
body,  and  the  lateral  malleolus.  The  head  lies  behind  and  lateral  to  the  lateral 
condyle  of  the  tibia,  and  presents  as  a  small  prominent  pyramidal  eminence  slightly 
above  the  level  of  the  tibial  tuberosity;  its  position  can  be  readily  located  by 


SURFACE  ANATOMY  OF  THE  LOWER  EXTREMITY 


1325 


following  downward  the  tendon  of  Biceps  femoris.  Tiie  lateral  malleolus  is  a 
narrow  elongated  prominence,  from  which  the  lower  third  or  half  of  the  lateral 
surface  of  the  body  of  the  bone  can  be  traced  upward. 

On  the  dorsum  of  the  tarsus  the  individual  bones  cannot  be  distinguished,  with 
the  exception  of  the  head  of  the  talus,  which  forms  a  rounded  projection  in  front 
of  the  ankle-joint  when  the  foot  is  forcibly  extended.  The  whole  dorsal  surface  of 
the  foot  has  a  smooth  convex  outline,  the  summit  of  which  is  the  ridge  formed  by 
the  head  of  the  talus,  the  navicular,  the  second  cuneiform,  and  the  second  meta- 
tarsal bone;  from  this  it  inclines  gradually  lateralward,  and  rapidly  medialward. 
On  the  medial  side  of  the  foot  the  medial  process  of  the  tuberosity  of  the  calcaneus 
and  the  ridge  separating  the  posterior  from  the  medial  surface  of  the  bone  are 
distinguishable;  in  front  of  this,  and  below  the  medial  malleolus,  is  the  susten- 
taculum tali.  The  tuberosity  of  the  navicular  is  palpable  about  2.5  to  3  cm.  in 
front  of  the  medial  malleolus. 

Farther  forward,  the  ridge  formed  by  the  base  of  the  first  metatarsal  bone  can 
be  obscurely  felt,  and  from  this  the  body  of  the  bone  can  be  traced  to  the  expanded 
head;  beneath  the  base  of  the  first  phalanx  is  the  medial  sesamoid  bone.    On  the 
lateral  side  of  the  foot,  the  most 
posterior  bony  point  is  the  lateral  , 

process  of    the    tuberosity   of  the  { 

calcaneus,  with  the  ridge  separating  f 

the  posterior  from  the  lateral  sur- 
face of  the  bone.  In  front  of  this 
the  greater  part  of  the  lateral  sur- 
face of  the  calcaneus  is  subcuta- 
neous; on  it,  below  and  in  front  of 
the  lateral  malleolus,  the  trochlear 
process,  when  present,  can  be  felt. 
Farther  forward  the  base  of  the 
fifth  metatarsal  bone  is  prominent, 
and  from  it  the  body  and  expanded 
head  can  be  traced. 

As  in  the  case  of  the  meta- 
carpals, the  dorsal  surfaces  of  the 
metatarsal  bones  are  easily  defined, 
although  their  heads  do  not  form 
prominences;  the  plantar  surfaces 
are  obscured  by  muscles.  The 
phalanges  in  their  w^hole  extent  are 
readily  palpable. 

Articulations.  —  The  hip-joint  is 
deeply  seated  and  cannot  be  pal- 
pated. 

The  interval  between  the  tibia 
and  femur  can  always  be  easily 
felt;  if  the  knee-joint  be  extended 
this  interval  is  on  a  higher  level 
than  the  apex  of  the  patella,  but 
if  the  joint  be  slightly  flexed  it  is 
directly  behind  the  apex.  When 
the  knee  is  semiflexed,  the  medial 

borders  of  the  patella  and  of  the  medial  condyle  of  the  femur,  and  the  upper 
border  of  the  medial  condyle  of  the  tibia,  bound  a  triangular  depressed  area  which 
indicates  the  position  of  the  joint. 


Tensor  fasciae  latae— 


Femoral  triangle 


Sartoritis 


Quadriceps  femoris 


Addv£tores 


Patella 


Tuberosity  of  tibia 


Fig.  1117. — Front  and  medial  aspect  of  right  tliigh. 


1326 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


Tensor  fasciae 
latae 


Hamstrings  • 


Gluteal  fold 


Semimembranosus 
Semitendinosus 


Popliteal  fossa 


Gastrc 


Peronae  lonr/us  and  brevis 


Medial  onalleolus 


Tendo  calcaneus 


Lateral  malleolus 
Fig.  1118. — Back  of  left  lower  extremity. 


The  ankle-joint  can  be  felt 
on  either  side  of  the  Ex- 
tensor tendons,  and  during 
extension  of  the  joint  the 
superior  articular  surface  of 
the  tahis  presents  below  the 
anterior  border  of  the  lower 
end  of  tlie  tibia. 

Muscles. — Of  the  muscles 
of  the  thigh,  those  of  the 
anterior  femoral  region  (Fig. 
1117)  contribute  largely  to 
surface  form.  The  Tensor 
fasciae  latae  produces  a  broad 
elevation  immediately  below 
the  anterior  part  of  the  iliac 
crest  and  behind  the  ante- 
rior superior  iliac  spine;  from 
its  lower  border  a  groove 
caused  by  the  iliotibial  band 
extends  downward  to  the 
lateral  side  of  the  knee-joint. 
The  upper  portion  of  Sarto- 
rius  constitutes  the  lateral 
boundary  of  the  femoral  tri- 
angle, and,  when  the  muscle 
is  in  action,  forms  a  promi- 
nent oblique  ridge  which  is 
continued  below  into  a  flat- 
tened plane  and  then  grad- 
ually merges  into  a  general 
fulness  on  the  medial  side 
of  the  knee-joint.  When 
the  Sartorius  is  not  in  action, 
a  depression  exists  between 
the  Quadriceps  femoris  and 
the  Adductors,  and  extends 
obliquely  downward  and 
medialward  from  the  apex 
of  the  femoral  triangle  to 
the  side  of  the  knee.  In 
the  angle  formed  by  the 
divergence  of  Sartorius  and 
Tensor  fasciae  latae,  just 
below  the  anterior  superior 
iliac  spine,  the  Rectus  femoris 
appears,  and  in  a  muscular 
subject  its  borders  can  be 
clearly  defined  when  the 
muscle  is  in  action.  The 
Vastus  lateralis  forms  a  long 
flattened  plane  traversed  by 
the  groove  of  the  iliotibial 
band.  The  Vastus  medialis 
gives  rise  to  a  considerable 


SURFACE  ANATOMY  OF  THE  LOWER  EXTREMITY 


1327 


Biceps  femoris 
Popliteal  fossa 


Quadriceps 
femoris 


Patella 


Tuberosity 
of  tibia 


Gastrocnemius 

Peronaeus 
longus 


Tibialis  anterior 


prominence  on  the  medial  side  of  the  lower  half  of  the  thi^li;  this  prominence  in- 
creases toward  the  knee  and  ends  somewhat  al)ru})tl\'  witii  a  full  curved  outline. 
The  Vastus  intermedius  is  comi)letely  hidden.  The  Adduetores  cannot  be  differ- 
entiated from  one  another,  with  the  exception  of  the  upper  tendon  of  Adductor 
lonijus  and  the  lower  tendon  of  Adductor  magnus.  When  the  Adductor  longus  is  in 
action  its  upper  tendon  stands  out  as  a  prominent  ridge  running  ohliquel\-  down- 
ward and  lateralward  from  the  neighborhood  of  the  pubic  tubercle,  and  forming 
the  medial  border  of  the  femoral  triangle.  The  lower  tendon  of  Adductor  magnus 
can  be  distinctly  felt  as  a  short  ridge  extending  downward  between  the  Sartorius 
and  ^\astus  medialis  to  the  adductor  tubercle.  The  adduetores  fill  in  the  tri- 
angular space  at  the  upper  part  of 
the  thigh,  between  the  femur  and 
the  pelvis,  and  to  them  is  due  the 
contour  of  the  medial  border  of 
the  thigh,  the  Gracilis  contributing 
largely  to  the  smoothness  of  the 
outline. 

The  Glutaeus  maximus  (Fig.  1118) 
forms  the  full  rounded  outline  of  the 
buttock;  it  is  more  prominent  be- 
hind, compressed  in  front,  and  ends 
at  its  tendinous  insertion  in  a  de- 
pression immediately'  behind  the 
greater  trochanter;  its  lower  border 
crosses  the  gluteal  fold  obliquely 
downward  and  lateralward.  The 
upper  part  of  Glutaeus  medius  is 
visible,  but  its  lower  part  with  Glu- 
taeus minimus  and  the  external 
rotators  are  completely  hidden. 
From  beneath  the  lower  margin  of 
Glutaeus  maximus  the  hamstrings 
appear;  at  first  they  are  narrow 
and  not  well-defined, .  but  as  they 
descend  they  become  more  promi- 
nent and  eventually  divide  into  two 
well-marked  ridges  formed  by  their 
tendons;  these  constitute  the  upper 
boundaries  of  the  popliteal  fossa. 
The  tendon  of  Biceps  femoris  is  a 
thick  cord  running  to  the  head  of 
the  fibula;  the  tendons  of  the  Semi- 
membranosus and  Semitendinosus  as 

they  run  medialward  to  the  tibia  are  separated  by  a  slight  furrow;  the  Semitendi- 
nosus is  the  more  medial,  and  can  be  felt  in  certain  positions  of  the  limb  as  a  sharp 
cord,  while  the  Semimembranosus  is  thick  and  rounded.  The  Gracilis  is  situated  a 
little  in  front  of  them. 

The  Tibialis  anterior  (Fig.  1119)  presents  a  fusiform  enlargement  at  the  lateral 
side  of  the  tibia  and  projects  beyond  the  anterior  crest  of  the  bone;  its  tendon  can 
be  traced  on  the  front  of  the  tibia  and  ankle-joint  and  thence  along  the  medial  side 
of  the  foot  to  the  base  of  the  first  metatarsal  bone.  The  fleshy  fibres  of  Peronaeus 
longus  are  strongly  marked  at  the  upper  part  of  the  lateral  side  of  the  leg;  it  is 
separated  by  furrows  from  Extensor  digitorum  longus  in  front  and  Soleus  behind. 
Below,  the  fleshy  fibres  end  abruptly  in  a  tendon  which  overlaps  the  more  flattened 


Lateral 
m,alleolus 


Fig.   1119. — Lateral  aspect  of  right  leg. 


1328 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


elevation  of  Peronaeus  brevis;  below  the  lateral  malleolus  the  tendon  of  Peronaeus 
brevis  is  the  more  marked. 

On  the  dorsum  of  the  foot  (Fig.  1120)  the  tendons  emerging  from  beneath  the 
transverse  and  cruciate  crural  ligaments  spread  out  and  can  be  distinguished  as 
follows:  the  most  medial  and  largest  is  Tibialis  anterior,  the  next  is  Extensor 
hallucis  proprius,  then  Extensor  digitorum  longus  dividing  into  four  tendons,  to 
the  second,  third,  fourth,  and  fifth  toes,  and  lastly  Peronaeus  tertius.  The  Extensor 
digitorum  brevis  produces  a  rounded  outline  on  the  dorsum  of  the  foot  and  a  fulness  in 
front  of  the  lateral  malleolus.  The  Interossei  dorsales  bulge  between  the  metatarsal 
bones. 


Tibialis  anteuor 

Extensor  dig.  Icngus 


Ext.  hall.  long. 

Ext.  dig.  breiis 


Tendo  calcaneits 

Peronceus  longus 


Peronaeus  brevis  Peronaeus  teriius 

Fig.   1120. — The  mucous  sheaths  of  the  tendons  around  the  ankle.     Lateral  aspect. 


At  the  back  of  the  knee  is  the  popliteal  fossa,  bounded  above  by  the  tendons  of 
the  hamstrings  and  below  by  the  Gastrocnemius.  Below  this  fossa  is  the  prominent 
fleshy  mass  of  the  calf  of  the  leg  produced  by  Gastrocnemius  and  Soleus  (Fig.  1118). 
When  these  muscles  are  in  action  the  borders  of  Gastrocnemius  form  two  well- 
defined  curved  lines  which  converge  to  the  tendocalcaneus ;  the  medial  border  is  the 
more  prominent.  At  the  same  time  the  edges  of  Soleus  can  be  seen  forming,  on 
either  side  of  Gastrocnemius,  curved  eminences,  of  which  the  lateral  is  the  longer. 
The  fleshy  mass  of  the  calf  ends  somewhat  abruptly  in  the  tendocalcaneus,  which 
tapers  in  the  upper  three-fourths  of  its  extent  but  widens  out  slightly  below. 
Behind  the  medial  border  of  the  lower  part  of  the  tibia  (Fig.  1121)  a  well-defined 
ridge  is  produced  by  the  tendon  of  Tibialis  posterior  during  contraction  of  the 
muscle. 

On  the  sole  of  the  foot  the  Abductor  digiti  quinti  forms  a  narrow  rounded  eleva- 
tion on  the  lateral  side,  and  the  Abductor  hallucis  a  lesser  elevation  on  the  medial 
side.  The  Flexor  digitorum  brevis,  bound  down  by  the  plantar  aponeurosis,  is  not 
very  apparent;  it  produces  a  flattened  form,  and  the  thickened  skin  underlying 
it  is  thrown  into  numerous  wrinkles. 

Arteries. — The  femoral  artery  as  it  crosses  the  brim  of  the  pelvis  is  readily  felt; 
in  its  course  down  the  thigh  its  pulsation  becomes  gradually  more  difficult  of  recog- 
nition. When  the  knee  is  flexed  the  pulsation  of  the  popliteal  artery  can  easily  be 
detected  in  the  popliteal  fossa. 


SURFACE  MARKINGS  OF  THE  LOWER  EXTREMITY 


1329 


On  the  lower  part  of  the  front  of  the  tibia  the  anterior  tibial  artery  becomes 
superficial  and  can  be  traced  over  the  ankle  into  the  dorsalis  pedis;  the  latter  can 
be  followed  to  tlie  proximal  end  of  the  first  intermetatarsal  space.  The  pulsation 
of  the  posterior  tibial  artery  becomes  evident  near  the  lower  end  of  the  back  of  the 
tibia,  and  is  easily  detected  behind  the  medial  malleolus. 


Tibialis  posterior 


Ext.  hall.  long.  \ 


Flexor  liallucis  longus 


Plantar  is 

Ten  do  calcaneus 


Fig.  1121. — The  mucous  sheaths  of  the  tendons  around  the  ankle.    Medial  aspect. 

Veins. — By  compressing  the  proximal  trunks,  the  venous  arch  on  the  dorsum 
of  the  foot,  together  with  the  great  and  small  saphenous  veins  leading  from  it  (see 
page  756),  are  rendered  visible. 

Nerves. — ^The  only  nerve  of  the  lower  extremity  which  can  be  located  by  palpa- 
tion is  the  common  peroneal  as  it  winds  around  the  lateral  side  of  the  neck  of  the 
fibula. 

SURFACE   MARKINGS    OF   THE   LOWER   EXTREMITY. 

Bony  Landmarks. — The  anterior  superior  iliac  spine  is  at  the  level  of  the  sacral 
promontory — the  posterior  at  the  level  of  the  spinous  process  of  the  second  sacral 
vertebra.  A  horizontal  line  through  the  highest  points  of  the  iliac  crests  passes 
also  through  the  spinous  process  of  the  fourth  lumbar  vertebra,  while,  as  alread}^ 
pointed  out  (page  1303),  the  transtubercular  plane  through  the  tubercles  on  the 
iliac  crests  cuts  the  body  of  the  fifth  lumbar  vertebra.  The  upper  margin  of  the 
greater  sciatic  notch  is  opposite  the  spinous  process  of  the  third  sacral  vertebra, 
and  slightly  below  this  level  is  the  posterior  inferior  iliac  spine.  The  surface  mark- 
ings of  the  posterior  inferior  iliac  spine  and  the  ischial  spine  are  both  situated  in  a 
line  which  joins  the  posterior  superior  iliac  spine  to  the  outer  part  of  the  ischial 
tuberosity;  the  posterior  inferior  spine  is  5  cm.  and  the  ischial  spine  10  cm.  below 
the  posterior  superior  spine;  the  ischial  spine  is  opposite  the  first  piece  of  the 
coccyx. 

With  the  body  in  the  erect  posture  the  line  joining  the  pubic  tubercle  to  the  top 
of  the  greater  trochanter  is  practically  horizontal;  the  middle  of  this  line  overlies 
the  acetabulum  and  the  head  of  the  femur. 

A  line  used  for  clinical  purposes  is  that  of  Nelaton  (Fig.  1122),  which  is  drawn 
from  the  anterior  superior  iliac  spine  to  the  most  prominent  part  of  the  ischial 
tuberosity;  it  crosses  the  centre  of  the  acetabulum  and  the  upper  border  of  the 
84 


1330 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


greater  trochanter.  Another  surface  marking  of  chnical  importance  is  Bryant's 
triangle,  which  is  mapped  out  thus:  a  line  from  the  anterior  superior  ihac  spine 
to  the  top  of  the  greater  trochanter  forms  the  base  of  the  triangle;  its  sides  are 
formed  respectively  by  a  horizontal  line  from  the  anterior  superior  iliac  spine  and 
a  vertical  line  from  the  top  of  the  greater  trochanter. 


Sacrotuberous  ligament 
Sacrospinous  ligament 


Greater  trochanter 
of  femur 


Ischial  tuberosity 


Fig.   1122. — N^laton's  line  and  Bryant's  triangle. 

Articulations. — The  posterior  superior  iliac  spine  overlies  the  centre  of  the  sacro- 
iliac articulations. 

The  hip-joint  may  be  indicated,  as  described  above,  by  the  centre  of  a  horizontal 
line  from  the  pubic  tubercle  to  the  top  of  the  greater  trochanter;  or  more  generally, 
it  is  below  and  slightly  lateral  to  the  middle  of  the  inguinal  ligament.  The  knee-joint 
is  superficial  and  requires  no  surface  marking.  The  level  of  the  ankle-joint  is  that 
of  a  transverse  line  about  1  cm.  above  the  level  of  the  tip  of  the  medial  malleolus. 
If  the  foot  be  forcibly  extended,  the  head  of  the  talus  appears  as  a  rounded  promi- 
nence on  the  medial  side  of  the  dorsum;  just  in  front  of  this  prominence  and  behind 
the  tuberosity  of  the  navicular  is  the  talonavicular  joint.  The  calcaneocuboid  joint 
is  situated  midway  between  the  lateral  malleolus  and  the  prominent  base  of  the 
fifth  metatarsal  bone;  the  line  indicating  it  is  parallel  to  that  of  the  talonavicular 
joint.  The  line  of  the  fifth  tarsometatarsal  joint  is  very  oblique;  it  starts  from  the 
projection  of  the  base  of  the  fifth  metatarsal  bone,  and  if  continued  would  pass 
through  the  head  of  the  first  metatarsal.  The  lines  of  the  fourth  and  third  tarso- 
metatarsal joints  are  less  oblique.  The  first  tarsometatarsal  joint  corresponds  to  a 
groove  which  can  be  felt  by  making  firm  pressure  on  the  medial  border  of  the  foot 
2.5  cm.  in  front  of  the  tuberosity  of  the  navicular  bone;  the  position  of  the  second 
tarsometatarsal  joint  is  1.25  cm.  behind  this.  The  metatarsophalangeal  joints  are 
about  2.5  cm.  behind  the  webs  of  the  corresponding  toes. 

Muscles. — None  of  the  muscles  require  any  special  surface  lines  to  indicate 
them,  but  there  are  three  intermuscular  spaces  which  occasionally  require  defini- 
tion, viz.,  the  femoral  triangle,  the  adductor  canal,  and  the  popliteal  fossa. 


SURFACE  MARKINGS  OF  THE  LOWER  EXTREMITY 


1331 


The  femoral  triangle  is  bounded  abo\'e  by  the  inguinal  ligament,  laterally  by  the 
medial  border  of  Sartorius,  and  medially  by  the  medial  border  of  Adductor  longus. 
In  the  triangle  is  the  fossa  ovalis,  through  which  the  great  saphenous  vein  dips  to 
join  the  femoral;  the  centre  of  this  fossa  is  about  4  cm.  below  and  lateral  to  the 
pubic  tubercle,  its  vertical  diameter  measures  about  4  cm.  and  its  transverse  about 
1.5  cm.    The  femoral  ring  is  about  1.25  cm.  lateral  to  the  pubic  tubercle. 

The  adductor  canal  occupies  the  medial  part  of  the  middle  third  of  the  thigh;  it 
begins  at  the  a])ex  of  the  femoral  triangle  and  lies  deep  to  the  vertical  part  of 
Sartorius.  The  popliteal  fossa  is  bounded:  above  and  medially  by  the  tendons 
of  Semimembranosus  and  Semitendinosus;  above  and  laterally  b}^  the  tendon  of 
Biceps  femoris;  below  and  medially  by  the  medial  head  of  Gastrocnemius;  below 
and  laterally  by  the  lateral  head  of  Gastrocnemius  and  the  Plantaris. 

Mucous  Sheaths. — The  positions  of  the  mucous  sheaths  around  the  tendons 
about  the  ankle-joints  are  sufficiently  indicated  in  Figs.  1120,  1121  (see  also  page 
586). 


Superior  gluteal 
artery 


Inferior  gluteal 

artery 
Internal  pudendal 

artery 


Fig.  1123. — Left  gluteal  region,  showing  surface  markings  for  arteries  and  sciatic  nerve. 


Arteries. — The  points  of  emergence  of  the  three  main  arteries  on  the  buttock, 
viz.,  the  superior  and  inferior  gluteals  and  the  internal  pudendal,  maybe  indicated 
in  the  following  manner  (Fig.  1123).  With  the  femur  slightly  flexed  and  rotated 
inw^ard,  a  line  is  drawn  from  the  posterior  superior  iliac  spine  to  the  posterior  supe- 
rior angle  of  the  greater  trochanter;  the  point  of  emergence  of  the  superior  gluteal 
artery  from  the  upper  part  of  the  greater  sciatic  foramen  corresponds  to  the  junction 
of  the  upper  and  middle  thirds  of  this  line.  A  second  line  is  drawn  from  the  poste- 
rior superior  iliac  spine  to  the  outer  part  of  the  ischial  tuberosity;  the  junction 
of  its  lower  with  its  middle  third  marks  the  point  or  emergence  of  the  inferior 
gluteal  and  internal  pudendal  arteries  from  the  lower  part  of  the  greater  sciatic 
foramen.  The  course  of  the  femoral  artery  (Fig.  1124)  is  represented  by  the  upper 
two-thirds  of  a  line  from  a  point  midw^ay  between  the  anterior  superior  iliac  spine 
and  the  symphysis  pubis  to  the  adductor  tubercle,  with  the  thigh  abducted  and 
rotated  outward;  the  profunda  femoris  arises  from  it  about  1  to  5  cm.  below  the 
inguinal  ligament.  The  course  of  the  upper  part  of  the  popliteal  artery  (Fig.  1126) 
is  indicated  by  a  line  from  the  lateral  margin  of  Semimembranosus  at  the  junction 
of  the  middle  and  low^er  thirds  of  the  thigh,  obliquely  downward  to  the  middle  of 


1332 


SURFACE  ANATOMY  AND  SURFACE  MARKINGS 


the  popliteal  fossa;  from  this  point  it  runs  vertically  downward  for  about  2.5  cm. 
or  to  the  level  of  a  line  through  the  lower  part  of  the  tibial  tuberosity.  The  line 
indicating  the  anterior  tibial  artery  (Fig.  1125)  is  drawn  from  the  medial  side  of 
the  head  of  the  fibula  to  a  point  midway  between  the  malleoli;  the  artery  begins 
about  3  cm.  below  the  head  of  the  fibula.  The  dorsalis  pedis  artery  is  represented 
on  the  dorsum  of  the  foot  by  a  line  from  the  centre  of  the  interval  between  the 
malleoli  to  the  proximal  end  of  the  first  intermetatarsal  space. 


Femoral  nerve 
Femoral  artery 


Adductor  tubercle 


A  nterior  tibial  artery 
Deep  peronceal  nerve 


Fig.  1124. —  Front  of  right  thigh,   showing   surface 
markings  for  bones,  femoral  artery  and  femoral  nerve. 


Fig.  1125. — Lateral  aspect  of  right  leg,  showing 
surface  markings  for  bones,  anterior  tibial  and 
dorsalis  pedis  arteries,  and  deep  peroneal  nerve. 


The  course  of  the  posterior  tibial  artery  (Fig.  1126)  can  be  shown  by  a  line  from 
the  end  of  the  popliteal  artery,  i.  e.,  2.5  cm.  below  the  centre  of  the  popliteal  fossa, 
to  midway  between  the  tip  of  the  medial  malleolus  and  the  centre  of  the  convexity 
of  the  heel;  its  main  branch,  the  peroneal  artery,  begins  about  7  or  8  cm.  below  the 
level  of  the  knee-joint  and  follows  the  line  of  the  fibula  to  the  back  of  the  lateral 
malleolus.  The  medial  and  lateral  plantar  arteries  begin  from  the  end  of  the  poste- 
rior tibial;  the  medial  extends  to  the  middle  of  the  plantar  surface  of  the  ball  of  the 
great  toe,  the  lateral  to  within  a  finger's  breadth  of  the  tuberosity  of  the  fifth 
metatarsal  bone;  from  this  latter  point  the  plantar  arch  crosses  the  foot  trans- 
versely to  the  proximal  end  of  the  first  intermetatarsal  space. 

Veins. — The  line  of  the  great  saphenous  vein  is  from  the  front  of  the  medial 
malleolus  to  the  centre  of  the  fossa  ovalis;  the  small  saphenous  vein  runs  from  the 
back  of  the  lateral  malleolus  to  the  centre  of  the  popliteal  fossa. 


SURFACE  MARKINGS  OF  THE  LOWER  EXTREMITY 


1  ooo 

iooo 


-Sciatic  nerve 


-Popliteal  artery 


Comjnon 
peroneal, 
nerve 

A  nterior 
tibial' 
artery 


-Tibial  nerve 

Posterior  tibial 
artery 


1  '' 


Fig.   I126.-Back  of  left  lower  extremity,  showing  surface  markings  for  bones,  vessels,  and  nerves. 


1334  SURFACE  ANATOMY  AND  SURFACE  MARKINGS 

Nerves. — The  course  of  the  sciatic  nerve  (Fig.  1126)  can  be  indicated  by  a  Hne 
from  a  point  midway  between  the  outer  border  of  the  ischial  tuberosity  and  the 
posterior  superior  angle  of  the  greater  trochanter  to  the  upper  angle  of  the  popliteal 
fossa.  The  continuation  of  this  line  vertically  through  the  centre  of  the  popliteal 
fossa  represents  the  position  of  the  tibial  nerve,  while  the  common  peroneal  nerve 
follows  the  line  of  the  tendon  of  Biceps  femoris.  The  lines  for  the  deep  peroneal 
nerve  and  the  continuation  of  the  tibial  nerve  corresponds  respectively  to  those  for 
the  anterior  and  posterior  tibial  arteries. 


A  GLOSSARY  (IF  THE  INTERNATIONAL  OR  liASLE 
ANATOMICAL  NOMENCLATURE. 


TERMINOLOGY  ADOPTED  IN  TEXT 

Vertebral  Column 


OSTEOLOGY. 

BASLE    TERMINOLOGY 

Columna  Vertebralis 


QhD    TERMINOLOGY 

Spinal  Column 


Vertebrae 

Vertebral  arch 
Vertebral  foramen 
Pedicle 

Vertebral  notch 
Costal  demifacet 
Facet  for  tiibercle  of  rib 


Vertebrae 

Arcus  vertebrae 
Foramen  vertebrale 
Radix  arcus  vertebrae 
Incisura  vertebralis 
Fovea  costalis 
Fovea  costalis  transversalis 


Vertebrae 

Neural  arch 
Spinal  foramen 
Pedicle 

Intervertebral  notch 
Demifacet  for  head  of  rib 
Facet  for  tubercle  of  rib 


Atlas 

Facet  for  odontoid  process 


Atlas 

Fovea  dentis 


Atlas 

Facet  for  odontoid  process 


Axis 

Odontoid  process 


Epistropheus 

Dens 


Axis 

Odontoid  process 


Sacrum 

Lateral  part 
Sacral  tuberosity 

Middle  sacral  crest 

Lateral  sacral  crests 

Sacral  articular  crests 

Vertebral  canal 


Sternum 

Jugular  notch 

Body 

Sternal  angle 

Xiphoid  process 

Anterior  surface  of  sternum 


Os  Sacrum 

Pars  lateralis 
Tuberositas  sacralis 

Crista  sacralis  media 

Cristae  sacrales  laterales 

Cristae  sacrales  articulares 

Canalis  sacralis 


Sternum 

Incisura  jugularis 
Corpus 

Angulus  sterni 
Processus  xiphoideus 
Planum  sternale 


Sacrum 

Lateral  mass 

Rough     surface     for     posterior 

sacroiliac   ligament 
Spinous     processes     of     sacral 

vertebrae 
Transverse   processes   of   sacral 

vertebrae 
Articular    processes    of    sacral 

vertebrae 
Sacral  canal 


Sternum  (Breast  bone) 

Suprasternal  notch 
Gladiolus 
Angulus  Ludovici 
Ensiform  or  xiphoid  process 
Anterior  surface  of  sternum 


Ribs 

Costal  groove 


Costae 

Sulcus  costae 


Ribs 

Subcostal  groove 


Cranial  Bones 
Occipital  bone 

Squama 

Highest  nuchal  line 
Superior  nuchal  line 
Inferior  nuchal  line 
Sagittal  sulcus 

Lateral  part 

Hj^poglossal  canal 

Condyloid  canal 

Basilar  part 

Superior  border 

Upper  half  of  inferior  border 


Ossa  Cranii 
Os  occipitale 

Squama  occipitalis 
Linea  nuchae  suprema 
Linea  nuchae  superior 
Linea  nuchae  inferior 
Sulcus  sagittalis 

Pars  lateralis 
Canalis  hypoglossi 
Canalis  condjdoideus 
Pars  basilaris 
Margo  lambdoideus 
Margo  mastoideus 


Cranial  Bones 
Occipital  bone 

Tabular  portion 
Highest  curved  line 
Superior  curved  line 
Inferior  curved  line 
Groove    for    superior    longitu- 
dinal sinus 
Condylic  portion 
Anterior  condyloid  foramen 
Posterior  cond5doid  foramen 
Basilar  process 
Superior  border 
Upper  half  of  inferior  border 


1336 


A  GLOSSARY  OF  THE  INTERNATIONAL 


TERMIXOLOGY  ADOPTED  IN  TEXT 

Parietal  bone 

External  surface 
Parietal  eminence 
Temporal  lines 
Internal  surface 
Sagittal  sulcus 

Sagittal  border 
Squamous  border 
Frontal  border 
Occipital  border 
Frontal  angle 
Sphenoidal  angle 
Occipital  angle 
Mastoid  angle 
Groove  for  transverse  sinus 

Frontal  bone 

Squama 

External  surface 
Orbital  part 
Frontal  eminence 
Zygomatic  process 
Nasal  part 
Frontal  spine 
Internal  surface 
Sagittal  sulcus 

Temporal  bone 

Squama 

Articiilar  tubercle 
Mandibular  fossa 
Petrotympanic  fissure 
Mastoid  notch 
Sigmoid  sulcus 
Eminentia  arcuata 

Hiatus  of  facial  canal 
Trigeminal  impression 

Internal  acoustic  meatus 
Canal  for  facial  nerve 
Tympanic  canaliculxxs 

Mastoid  canaliculus 

Vaginal  process 

Tympanomastoid  fissure 
Angles  of  petrous  part 
Septum  canalis  nausculotubarii 
Semicanalis  m.  tensoris  tj-mpani 
Semicanalis  tubae  auditivae 
Tjinpanic  part 
External  acoustic  meatus 

Sphenoidal  bone 

Chiasmatic  groove 
Tuberculum  sellae 
Fossa  hypophyseos 
Sphenoidal  crest 
Great  vrings 
Spina  angularis 
Small  ■«-ing8 
Infratemporal  crest 
Pterygoid  canal 
Lateral  pterj'goid  plate 

Medial  pterygoid  plate 

Sphenoidal  conchae 
Pterygoid  hamulus 
Pharyngeal  canal 

Ethmoidal  bone 

Cribriform  plate 
Perpendicular  plate 
Ethmoidal  labyrinth 
Lamina  papyracea 
Uncinate  process 
Middle  nasal  concha 
Superior  nasal  concha 


BASLE    TERMINOLOGY 

Os  parietale 

Facies  parietalis 
Tuber  parietale 
Lineae  temporales 
Facies  cerebralis 
Sulcus  sagittalis 

Margo  sagittalis 
Margo  squamosus 
Margo  frontalis 
Margo  occipitalis 
Angulus  frontalis 
Angulus  sphenoidaUs 
Angulus  occipitalis 
Angulus  mastoideus 
Sulcus  transversus 

Os  frontale 

Squama  frontalis 
Facies  frontalis 
Pars  orbitalis 
Tuber  frontale 
Processus  zj'gomaticus 
Pars  nasalis 
Spina  frontalis 
Facies  cerebralis 
Sulcus  sagittalis 

Os  temporale 

Squama  temporalis 
Tuberculum  artictdare 
Fossa  mandibularis 
Fissura  petrotjTnpanica 
Incisura  mastoidea 
Sulcus  sigmoideus 
Eminentia  arcuata 

Hiatus  canalis  facialis 
Impressio  trigemini 

Meatus  acusticus  intemus 
Canalis  facialis  [FaUopii] 
Canalicxilus  tympanicus 

Canaliculus  mastoideus 

Vagina  processus  styloidei 

Fissura  tjTupanomastoidea 

Anguli  pjTramidis 

Septum  canalis  musculotubarii 

Semicanalis  m.  tensoris  tj^mpani 

Semicanalis  tubae  auditivae 

Pars  tympanica 

Meatus  acusticus  extemus 

Os  sphenoidale 

Sulcus  chiasmatis 

Tuberculum  sellae 

Fossa  hj'pophj-seos 

Crista  sphenoidalis 

Alae  magna 

Spina  angularis 

AJae  par\'a 

Crista  infratemporalis 

Canalis  pterj'goideus  [Vidii] 

Lamina    lateralis    processus 

pterygoidei 
Lamina    medialis    processus 

pterygoidei 
Conchae  sphenoidales 
Hamulus  pterygoideus 
Canalis  pharyngeus 

Os  ethmoidale 

Lamina  cribrosa 
Lamina  perpendicularis 
Labyrinthus  ethmoidalis 
Lamina  papyracea 
Processus  uncinatus 
Concha  nasalis  media 
Concha  nasalis  superior 


OLD    TERMIN-OLOGY 

Parietal  bone 

External  surface 
Parietal  eminence 
Temporal  ridges 
Internal  surface 

Groove    for    superior    longitu- 
dinal sinus 
Superior  border 
Inferior  border 
Anterior  border 
Posterior  border 
Antero-superior  angle 
Antero-inferior  an^e 
Postero-superior  angle 
Postero-inferior  angle 
Groove  for  lateral  sinus 

Frontale  bone 

Frontal  or  vertical  portion 

External  surface 

Horizontal  part 

Frontal  eminence 

External  angular  process 

Internal  angular  process 

Xasal  spine 

Internal  surface 

Groove  for  superior  longitudinal 
sinus 
Temporal  bone 

Squamous  portion 

Eminentia  articularis 

Glenoid  ca-vity 

Glaserian  fissure 

Digastric  fossa 

Fossa  sigmoidea 

Eminence     for     superior     semi- 
circular canal 

Hiatus  Fallopii 

Impression  for  Gasserian 
ganglion 

Internal  auditory  meatus 

Aqueduct  of  FaUopius 

Canal  for  tympanic  branch  of 
glossopharyngeal  nerve 

Canal  for   auricular  branch  of 
vagus 

Vaginal    process    of     temporal 
bone 

Auricular  fissure 

Borders  of  petrous  part  _ 

Processus  cochleariformis 

Canal  for  Tensor  tympani 

Bony  part  of  Eustachian  tube 

Tympanic  plate 

External  auditory  meatus 

Sphenoid  bone 

Optic  groove 

Olivary  eminence 

Pituitarj-  fossa 

Ethmoidal  crest 

Great  wings 

Spinous  process 

Small  -w-ings 

Pterygoid  ridge  » 

Vidian  canal 

External  pterygoid  plate 

Internal  pterygoid  plate 

Sphenoidal  turbinated  processes 
Hamular  process 
Pterygopalatine  canal 

Ethmoid  bone 

Horizontal  lamina 

Vertical  plate 

Lateral  mass 

Os  planum 

Unciform  process 

Middle  turbinated  process 

Superior  turbinated  process 


OR  BASLE  ANATOMICAL  NOMENCLATURE 


1337 


TERMINOLOGY  ADOPTED  IN  TEXT         BASLE  TERMINOLOGY 

Facial  Bones  Ossa  Faciei 

Nasal  bones  Ossa  nasalia 

Groove  for  branch  of  ntisociliary      Sulcus  ethmoidalis 
nerve 


Maxilla 

Anterior  surface 
Infratemporal  surface 
Alveolar  canals 
Conchal  crest 
Maxillary  sinus 
Zygomatic  process 
Frontal  process 
Ethmoidal  crest 
Palatine  process 
Incisive  foramen 
Incisive  canal 
Os  incisivum  or  premaxilla 

Lacrimal  bone 

Posterior  lacrimal  crest 
Lacrimal  hamulus 

Zygomatic  bone 

Malar  surface 
Temporal  surface 
Zygomaticofacial  foramen 
Zygomaticotemporal  foramen 

Frontosph-anoidal  process 
Zygomaticoorbital  foramen 

Palatine  bone 

Horizontal  part 
Vertical  part 
Conchal  crest 
Ethmoidal  crest 
Pterygopalatine  canal 
Pyramidal  process 
Lesser  palatine  foramina 

Inferior  nasal  concha 

Mandible 

Oblique  line 
Mental  spine 
Mylohyoid  line 
Ramus 

Mandibular  foramen 
Mandibular  canal 
Mandibular  notch 

Hyoid  bone 

Body 

Greater  cornua 

Lesser  cornua 

Skull 

Sutural  bones 

Greater  palatine  foramen 

Foramen  lacerum 

Infratemporal  fossa 

Inferior  orbital  fissure 

Pterygopalatine  fossa 

Superior  orbital  fissure 

Nasal  cavity 

Anterior  nasal  aperture 

Choanse 

Bones  of  Upper  Extremity 
Shoulder  girdle 

Clavicle 

Coracoid  tuberosity 
Costal  tuberosity 
Sternal  extremity 
Acromial  extremity 


Maxilla 

Facics  anterior 
Facies  infrateniporalis 
Canales  alveolares 
Crista  conchalis 
Sinus  maxillaris 
Processus  zygomaticus 
Processus  frontalis 
Crista  ethmoidalis 
Processus  palatinus 
Foramen  incisivum 
Canalis  incisivum 
Os  incisivum 

Os  lacrimale 

Crista  lacrimalis  posterior 
Hamulus  lacrimalis 

Os  zygomaticum 

Facies  malaris 
Facies  temporalis 
Foramen  zygomaticofaciale      ") 
Foramen  zygomaticotem-   > 
porale  J 

Processus  frontosphenoidalis 
Foramen  zygomaticoorbitale 

Os  palatinimi 

Pars  horizontalis 
Pars  perpendicularis 
Crista  conchalis 
Crista  ethmoidalis 
Canalis  pterygopalatinus 
Processus  pyramidalis 
Foramina  palatina  minora 

Concha  nasalis  inferior 

Mandibula 

Linea  obliqua 
Spina  mentalis 
Linea  mylohyoidea 
Ramus  mandibulae 
Foramen  mandibulare 
Canalis  mandibulae 
Incisura  mandibulae 

Os  hyoideum 

Corpus  ossei  hyoidei 
Cornua  majora 
Cornua  minora 

Cranium 

Ossa  saturarum 
Foramen  palatinum  majus 
Foramen  lacerum 
Fossa  infratemporalis 
Fissura  orbitalis  inferior 
Fossa  pterygopalatina 
Fissura  orbitalis  superior 
Cavum  nasi 
Apertura  piriformis 
Choanae 


OLD    TERMINOLOGY 

Facial  Bones 
Nasal  bones 

Groove  for  nasal  nerve 

Superior  maxillary  bone ;  Upper  jaw 

Facial  or  external  surface 
Zygomatic  surface 
Posterior  dental  canals 
Inferior  turbinated  crest 
Antrum  of  Highmore 
Malar  process 
Nasal  process 
Superior  turbinated  crest 
Palatal  process 
Anterior  palatine  foramen 
Foramen  of  Stensen 
Premaxilla 

Lacrimal  bone 

Lacrimal  crest 
Hamular  process 

Malar  bone 

External  surface 
Internal  surface 

Malar  foramina 

Frontal  process 
Temporomalar  canal 

Palate  bone 

Horizontal  plate 

Perpendicular  plate 

Inferior  turbinated  crest 

Superior  turbinated  crest 

Posterior  palatine  canal 

Tuberosity 

Accessory  palatine  foramina 

Turbinated  bone 

Inferior  maxillary  bone ;  Lower  jaw 

External  oblique  line 
Genial  tubercle 
Internal  oblique  line 
Perpendicular  portions 
Inferior  dental  foramen 
Inferior  dental  canal 
Sigmoid  notch 

Lingual  bone 

Basihyal 

Thyrohyals 

Ceratohyals 


Skull 

Wormian  bones 
Posterior  palatine  foramen 
Foramen  lacerum  medium 
Zygomatic  fossa 
Sphenomaxillary  fissure 
Sphenomaxillary  fossa 
Sphenoidal  fissure 
Nasal  fossa 

Anterior  aperture  of  nose 
Posterior  nares 


Ossa  Extremitatis  Superioris  Bones  of  Upper  Extremity 

Cingulum  extremitatis  superioris    Shoulder  girdle 


Clavicula 

Tuberositas  coracoidea 
Tuberositas  costalis 
Extremitas  sternalis 
Extremitas  acromialis 


Clavicle ;  Collar  bone 

Conoid  tubercle 
Rhomboid  impression 
Internal  extremity 
Outer  extremity 


1338 


A  GLOSSARY  OF   THE  INTERNATIONAL 


TERMINOLOGY  ADOPTED  IN  TEXT 

Scapula 

Supraspinatous  fossa 
Infraspinatous  fossa 
Scapular  notch 
Medial  angle 
Lateral  angle 

Humerus 

Greater  tubercle 
Lesser  tubercle 
Intertubercular  groove 
Crest  of  greater  tubercle 
Crest  of  lesser  tubercle 
Body 

Lateral  border 
Radial  sulcus 
Medial  border 
Antero-lateral  surface 
Antero-medial  surface 
Capitulum 
Lateral  epicondyle 
Medial  epicondyle 

Ulna 

Olecranon 
Tuberosity 
Semilunar  notch 
Radial  notch 
Body 

Volar  border 
Dorsal  border 
Interosseous  crest 
Volar  surface 
Dorsal  surface 
Medial  surface 

Radius 

Radial  tuberosity 
Body 

Volar  border 
Dorsal  border 
Interosseous  crest 
Volar  surface 
Dorsal  surface 
Lateral  surface 
Ulnar  notch 


BASLE    TERMINOLOGY 

Scapula 

Fossa  supraspinata 
Fossa  infraspinata 
Incisura  scapulae 
Angulus  medialis 
Angulus  lateralis 

Humerus 

Tuberculum  majus 
Tuberculum  minus 
Sulcus  intertubercularis 
Crista  tuberculi  majoris 
Crista  tuberculi  minoris 
Corpus 

Margo  lateralis 
Sulcus  nervi  radialis 
Margo  medialis 
Facies  anterior  lateralis 
Facies  anterior  medialis 
Capitulum 
Epicondylus  lateralis 
Epicondylus  medialis 

Ulna 

Olecranon 
Tuberositas  ulnae 
Incisura  semilunaris 
Incisura  radialis 
Corpus 
Margo  volaris 
Margo  dorsalis 
Crista  interossea 
Facies  volaris 
Facies  dorsalis 
Facies  medialis 

Radius 

Tuberositas  radii 
Corpus 
Margo  volaris 
Margo  dorsalis 
Crista  interossea 
Facies  volaris 
Facies  dorsalis 
Facies  lateralis 
Incisura  ulnaris 


OLD    TERMINOLOGY 

Scapula;  Shoulder  blade 

Supraspinous  fo«sa 
Infraspinous  fossa 
Suprascapular  notch 
Superior  angle 
External  angle 

Humerus ;  Arm  bone 

Creator  tuberosity 

Lesser  tuberosity 

Bicipital  groove 

External  lip  of  bicipital  groove 

Internal  lip  of  bicipital  groove 

Shaft 

External  border 

Musculospiral  groove 

Internal  border 

External  surface 

Internal  surface 

Capitellum 

External  condyle 

Internal  condyle 

Ulna;  Elbow  bone 

Olecranon  process 

Tubercle 

Greater  sigmoid  cavity 

Lesser  sigmoid  cavity 

Shaft 

Anterior  border 

Posterior  border 

External  or  interosseous  border 

Anterior  surface 

Posterior  surface 

Internal  surface 

Radius 

Bicipital  tuberosity 
Shaft 

Anterior  border 
Posterior  border 
Medial  border 
Anterior  surface 
Posterior  surface 
External  surface 
Sigmoid  cavity 


Carpus 

Navicular  bone 
Lunate  bone 
Triangular  bone 
Greater  multangular  bone 
Lesser  multangular  bone 
Capitate  bone 
Hamate  bone 
Hamulus 


Ossa  Carpi 

Os  naviculare  manus 
Os  lunatum 
Os  triquetrum 
Os  multangulum  majus 
Os  multangulum  minor 
Os  capitatum 
Os  hamatum 
Hamulus  oss.  hamati 


Carpus 

Scaphoid 

Semilunar 

Cuneiform 

Trapezium 

Trapezoid 

Os  magnum 

Unciform 

Unciform  process 


Bones  of  Lower  Extremity 
Pelvic  girdle 

Hip-bone 

Posterior  gluteal  line 
Anterior  gluteal  line 
Inferior  gluteal  line 
Arcuate  line 
Iliac  tuberosity 

Ischial  spine 
Greater  sciatic  notch 
Lesser  sciatic  notch 
Superior  ramus 
Inferior  ramus 
Pubic  tubercle 
Superior  ramus 
Inferior  ramus 
Acetabulum 
Obturator  foramen 
Pectineal  line 
Glenoidal  labrum 
Acetabular  notch 


Ossa  Extremitatis  Inferioris  Bones  of  Lower  Extreynity 

Cingulum  extremitatis  inferioris     Pelvic  girdle 


Os  coxae 

Linea  glutaea  posterior 
Linea  glutaea  anterior 
Linea  glutaea  inferior 
Linea  arcuata 
Tuberositas  iliaca 

Spina  ischiadica 
Incisura  ischiadica  major 
Incisura  ischiadica  minor 
Ramus  superior  ossis  ischii 
Ramus  inferior  ossis  ischii 
Tuberculum  pubicum 
Ramus  superior  ossis  pubis 
Ramus  inferior  ossis  pubis 
Acetabulum 
Foramen  obturatum 
Pecten  ossis  pubis 
Labrum  glenoidale 
Incisura  acetabuli 


Os  innominatum 

Superior  curved  line 

Middle  curved  line 

Inferior  curved  line 

Iliac  part  of  iliopectineal  line 

Rough     surface     for     posterior 

sacroiliac   ligament 
Spine  of  ischium 
Greater  sacrosciatic  notch 
Lesser  sacrosciatic  notch 
Descending  ramus 
Ascending  ramus 
Spine  of  pubis 
Ascending  ramus 
Descending  ramus 
Cotyloid  cavity 
Thyroid  foramen 
Pubic  part  of  iliopectineal  line 
Cotyloid  ligament 
Cotyloid  notch 


OR  BASLE  ANATOMICAL  NOMENCLATURE 


1339 


TERMINOLOGY  ADOPTED  IN  TEXT         BASLE  TERMINOLOGY 

Pelvis  Pelvis 


OLD  TERMINOLOGY 


Pelvis 


Linea  terminalis 

Greater  pelvis 

Lesser  pelvis 

Superior  aperture  of  pelvis 

Inferior  aperture  of  pelvis 

Femur 

Greater  trochanter 
Trochanteric  fossa 
Lesser  trochanter 
Intertrochanteric  line 

Intertrochanteric  crest 
Body 

Gluteal  tuberosity 
Lateral  condyle 
Medial  condyle 
Intercondyloid  fossa 
Medial  epicondyle 
Lateral  epicondyle 
Patellar  surface 


Linea  terminalis 

Pelvis  major 

Pelvis  minor 

Apertura  pelvis  niinoris  superior 

Apertura  pelvis  minoris  inferior 

Femur 

Trochanter  major 
Fossa  trochanterica 
Trochanter  minor 
Linea  intertrochanterica 

Crista  intertrochanterica 
Corpus 

Tuberositas  glutaea 
Condylus  lateralis 
Condylus  medialis 
Fossa  intercondylea 
Epicondylus  medialis 
Epicondylus  lateralis 
Facies  patellaris 


Circumference   of  inlet   of   true 

pelvis 
False  pelvis 
True  pelvis 
Pelvic  inlet 
Pelvic  outlet 


Femur ;  Thigh  bone 

Great  trochanter 

Digital  fossa 

Small  trochanter 

Anterior     intertrochanteric     or 

spiral  line 
Posterior  intertrochanteric  line 
Shaft 

Gluteal  ridge 
External  condyle 
Internal  condyle 
Intercondyloid  notch 
Inner  tuberosity 
Outer  tuberosity 
Trochlea 


Tibia 

Medial  condyle 
Lateral  condyle 
Intercondyloid  eminence 
Tuberosity 
Body 

Anterior  crest 
Medial  border 
Interosseous  crest 
Medial  surface 
Lateral  surface 
Popliteal  line 
Malleolar  sulcus 


Tibia 

Condylus  medialis 

Condylus  lateralis 

Eminentia  intercondyloidea 

Tuberositas  tibiae 

Corpus 

Crista  anterior 

Crista  medialis 

Crista  interossea 

Facies  medialis 

Facies  lateralis 

Linea  poplitea 

Sulcus  malleolaris 


Tibia;  Shin  bone 

Inner  tuberosity 

Outer  tuberosity 

Spine  of  tibia 

Tubercle 

Shaft 

Anterior  border 

Internal  border 

External  border 

Internal  surface 

External  surface 

Oblique  line  of  tibia 

Groove  for  tendons  of  Tibialis 

posterior    and     Flexor     digi- 

torum  longus 


Fibula 

Apex  of  head 
Body 

Interosseous  crest 
Lateral  malleolus 


Tarsus 

Calcaneus 

Tuberosity 

Medial  process 
Lateral  process 

Trochlear  process 
Talus 

NaAdcular  bone 
First  cuneiform  bone 
Second  cuneiform  bone 
Third  cuneiform  bone 


Fibula 

Apex  capituli  fibulae 

Corpus 

Crista  interossea 

Malleolus  lateralis 


Ossa  Tarsi 

Calcaneus 

Tuber  calcanei 

Processus  medialis 
Processus  lateralis 

Processus  trochlearis 
Talus 

Os  naviculare  pedis 
Os  cuneiforme  primum 
Os  cuneiforme  secundum 
Os  cuneiforme  tertium 


Fibula;  Calf  bone 

Styloid  process 
Shaft 

Antero-internal  border 
External  malleolus  or  distal  ex- 
tremity 

Tarsus 

Os  calcis 

Tuberosity 
Inner  tubercle 
Outer  tubercle 

Peroneal  tubercle 
Astragalus  or  ankle  bone 
Scaphoid  bone 
Internal  cuneiform 
Middle  cuneiform 
External  cuneiform 


SYNDESMOLOGY. 


Synarthrosis 

Amphiarthrosis 

Diarthrosis 

Ginglymus 

Trochoid  or  Pivot  joint 

Condyloid  articulation 

Articulation     by     reciprocal 

reception 
Enarthrosis 
Arthrodia 


Synarthrosis 
Amphiarthrosis 
Diarthrosis 
Ginglymus 

Articulatio  trochoidea 
Articulatio  ellipsoidea 
Articulatio  sellaris 

Enarthrosis 
Arthrodia 


Immovable  articulations 

Slightly  movable  articulations 

Freely  movable  articulations 

Hinge-joint 

Rotary  joint 

Condyloid  articulation 

Saddle-joint 

Ball-and-socket  joints 
Gliding  joints 


1340 


A  GLOSSARY  OF  THE  INTERNATIONAL 


TERMINOLOGY  ADOPTED  IN  TEXT 

Articulations    of    the    vertebral 
column  and  cranium 

Anterior  longitudinal  ligament 
Posterior  longitudinal  ligament 
Intervertebral  fibrocartilages 

Ligamenta  flava 

Supraspinal  ligament 

Interspinal  ligaments 

Cruciate  ligament  of  the  atlas 

Anterior  atlantooccipital  mem- 
brane 

Posterior  atlantooccipital  mem- 
brane 

Membrana  tectoria 

Alar  ligaments 

Articulation  of  the  mandible 

Temporomandibular  ligament 
Sphenomandibular  ligament 
Articular  disk 
Stylomandibular  ligament 

Articulations  of  the  heads  of 
the  ribs 
Radiate  ligament 

Interarticular  ligament 


Costotransverse  articulations 

Anterior  costotransverse  liga- 
ment 
Ligament  of  the  neck  of  the  rib 
Ligament  of  the  tubercle  of  the 
rib 

Sternocostal  articulations 

Radiate  sternocostal  ligaments 

Interarticular  sternocostal  liga- 
ment 
Costoxiphoid  ligaments 

Interchondral  articulations 
Articulations  of  the  pelvis 

Sacrotuberous  ligament 

Sacrospinous  ligament 

Sacrococcygeal  symphysis 

Lateral  sacrococcygeal  ligament 
Pubic  symphysis 
Greater  sciatic  foramen 
Lesser  sciatic  foramen 
Pubic  arcuate  ligament 
Interpubic      fibrocartilaginous 
lamina 

Sternoclavicular  articulation 

Costoclavicular  ligament 
Articular  disk 

Acromioclavicular  articulation 

Ligaments  of  the  scapula 

Superior  transverse  ligament 
Inferior  transverse  ligament 

Humeral  articulation 

Glenoidal  labrum 

Elbow- joint 

Ulnar  collateral  ligament 
Radial  collateral  ligament 


BASLE    TEHMINOLOGY 

Ligamenta  columnae  vertebralis 
et  cranii 

Lig.  longitudinale  anterius 
Lig.  longitudinale  posterius 
Fibrocartilagines  interverte- 

brales 
Ligg.  flava 
Lig.  supraspinale 
Ligg.  interspinalia 
Lig.  cruciatum  atlantis 
Membrana    atlantooccipitalis 

anterior 
Membrana    atlantooccipitalis 

posterior 
Membrana  tectoria 
Ligg.  alaria 

Articulatio  mandibularis 

Lig.  temporomandibulare 
Lig.  sphenomandibulare 
Discus  articularis 
Lig.  stylomandibulare 

Articulationes  capitulorum 

Lig.  capituli  costae  radiatum 

Lig.  capituli  costae  interarticu- 
lare 

Articulationes  costotransversariae 

Lig.     costotransversarium      an- 
terius 
Lig.  colli  costae 
Lig.  tuberculi  costae 

Articulationes  sternocostales 

Ligg.  sternocostalia  radiata 

Lig.  sternocostale  interarticu- 
lar e 
Ligg.  costoxiphoidea 

Articulationes  interchondrales 

Ligg.  cinguli  extremitatis  inferi- 
oris 

Lig.  sacrotuberosum 

Lig.  sacrospinosum 

Symphysis  sacrococcygea 

Lig.  sacrococcygeum  laterale 
Symphysis  ossium  pubis 
Foramen  ischiadicum  majus 
Foramen  ischiadicum  minus 
Lig.  arcuatum  pubis 
Lamina  fibrocartilaginea  inter- 
pubica 

Articulatio  sternoclaviculars 

Lig.  costoclaviculare 
Discus  articularis 

Articulatio  acromioclavicularis 

Ligg.   cinguli   extremitatis 
superioris 

Lig.    transversum    scapulae 

superius 
Lig.  transvers  um  scapulae 

inferius 


OLD    TERMINOLOGY 

Articulations    of    the    spine    and 
cranium 

Anterior  common  ligament 
Posterior  common  ligament 
Intervertebral  disks 

Ligamenta  subfiava 

Supraspinous  ligament 

Interspinous  ligaments 

Cruciform  ligament  _ 

Anterior  atlantooccipital  liga- 
ment 

Posterior  atlantooccipital  liga- 
ment 

Occipitoaxial  ligament 

Odontoid  or  check  ligaments 

Temporomandibular  articulation 

External  lateral  ligament 
Internal  lateral  ligament 
Articular  meniscus 
Stylomaxillary  ligament 

Costocentral  articulations 

Anterior  costovertebral  or 

stellate  ligament 
Intraarticular  ligament 


Articulatio  humeri 

Labrum  glenoidale 

Articulatio  cubiti 

Lig.  collaterale  ulnare 
Lig.  collaterale  radiale 


Costotransverse  articulations 

Anterior  superior  ligament 

Middle  costotransverse  ligament 
Posterior    costotransverse    liga- 
ment 

Chondrosternal  articulations 

Chondrosternal    or  sternocostal 

ligaments 
Intraarticular    chondrosternal 

ligament 
Chondroxiphoid  ligaments 

Articulations  of  the  cartilages  of 
the  ribs  with  each  other 

Articulations  of  the  pelvis 

Great   or   posterior    sacrosciatic 

ligament 
Small    or    anterior    sacrosciatic 

ligament 
Articulation  of  the  sacrum  and 

coccyx 
Intertransverse  ligament 
Articulation  of  the  pubic  bones 
Great  sacrosciatic  foramen 
Small  sacrosciatic  foramen 
Subpubic  ligament 
Interpubic  disk 

Sternoclavicular  articulation 

Rhomboid  ligament 
Interarticular  fibrbcartilage 

Scapuloclavicular  articulation 

Ligaments  of  the  scapula 

Suprascapular  ligament 
Spinoglenoid  ligament 

Shoulder-joint 

Glenoid  ligament 

Elbow-joint 

Internal  lateral  ligament 
External  lateral  ligament 


OR  BASLE  AX  ATOMIC  AL  XOMEXCLATURE 


1341 


TERMINOLOGY  ADOPTED  IN  TEXT 


BASLE  TERMINOLOGY 


Proxiinal  radioulnar  articulation     Articulatio   radioulnaris   proxi- 

maUs 


Annular  ligament 
Oblique  cord 

Distal  radioulnar  articulation 

Articular  disk 

Radiocarpal  articulation 

Volar  radiocarpal  ligament 

Dorsal  radiocarpal  ligament 

Ulnar  collateral  ligament 
Radial  collateral  ligament 

Intercarpal  articulations 

Volar  ligaments 

Intermetacarpal  articulations 


Lig.  annulare  radii 
Chorda  obliqua 

Articulatio  radioulnaris  distalis 

Discus  articularis 

Articulatio  radiocarpea 

Lig.  radiocarpeum  volare 

Lig.  radiocarpeum  dorsale 

Lig.  collaterale  carpi  vilnare 
Lig.  collaterale  carpi  radiale 

Articulationes  intercarpeae 

Ligg.  intercarpea  volaria 

Articulationes  intermetacarpeae 


Transverse  metacarpal  ligament      Lig.  capitulorum  (oss.  metacar- 

palium)  transversa 


OLD    TERMINOLOGY 

Superior  radioulnar  joint 

Orbicular  ligament 
Oblique  ligament 

Inferior  radioulnar  joint 

Triangular  articular  disk 

Wrist- joint 

Anterior  ligament  of  the  radio- 
carpal joint 

Posterior  ligament  of  the  radio- 
carpal joint 

Internal  lateral  ligament 

External  lateral  ligament 

Carpal  joints 

Palmar  ligaments 

Articulations  of  metacarpal  bones 
with  each  other 

Transverse  metacarpal  ligament 


Metacarpophalangeal    articula-     Articulationes      metacarpopha- 
tions  langeae 

Volar  ligaments  Ligg.  metacarpophalangeae 

volaria 
Collateral  ligaments  Ligg.coUateralia 


Metacarpophalangeal  joints 

Glenoid  ligament  of  Cruveilhier ; 

palmar  or  vaginal  ligaments 
Lateral  ligaments 


Articulation  of  the  digits 

Coxal  articulation 

Articular  capsule 
Iliofemoral  ligament 
Pubocapsular  ligament 
Ischiocapsular  ligament 
Glenoidal  labrum 


Articulationes  digitorum  manus      Articulation  of  the  phlanges 


Articulatio  coxae 

Capsula  articularis 
Lig.  iliofemorale 
Lig.  pubocapsulare 
Lig.  ischiocapsulare 
Labrum  glenoidale 


Transverse  acetabular  ligament      Lig.  transversum  acetabuli 


Hip-joint 

Capsular  ligament 
Y-ligament ;  ligament  of  Bigelow 
Pubofemoral  band 
Ligament  of  Bertin 
Cotj'loid  ligament 
Transverse  ligament 


Knee-joint 

Articular  capsule 
Patellar  retinacula 
Oblique  popliteal  ligament 
Tibial  collateral  ligament 
Fibular  collateral  ligament 

Cruciate  ligaments 

Anterior  cruciate  ligament 

Posterior  cruciate  ligament 

Menisci 

Medial  meniscus 

Lateral  meniscus 

Alar  folds 

Patellar  fold 

Tibiofibular  articulation 

Articular  capsule 
Ligaments  of  head  of  fibula 


Interosseous  membrane 


Articulatio  genu 

Capsula  articularis 
Retinacula  patellae 
Lig.  popliteum  obliquum 
Lig.  collaterale  tibiale 
Lig.  collaterale  fibulare 

Ligg.  cruciata  genu 
Lig.  cruciatum  anterius 
Lig.  cruciatum  posterius 
Menisci 

Meniscus  medialis 
Meniscus  lateralis 
Plicae  alares 
Plica  synovalis  patellaris 

Articulatio  tibiofibularis 

Capsula  articularis 
Ligg.  capituli  fibulae 


Membrana  interossea  cruris 


Knee-joint 

Capsular  ligament 
Lateral  patellar  ligaments 
Posterior  ligament 
Internal  lateral  ligament 
External  lateral  or  long  external 

lateral  ligament 
Crucial  ligaments 
External  crucial  ligament 
Internal  crucial  ligament 
Semilunar  fibrocartilages 
Internal  semilunar  cartilage 
External  semilunar  cartilage  . 
Ligamenta  alaria 
Ligamentum  mucosum 

Superior  tibiofibular  articulation 

Capsular  ligament 
Anterior  and  posterior  superior 
tibiofibular  ligaments 

Middle  tibiofibular  ligament 


Tibiofibular  syndesmosis 

Anterior  ligament 
Posterior  ligament 

Talocrural  articulation 

Articular  capsule 

Deltoid  ligament 

Anterior  talofibular  ligament 

Posterior  talofibular  ligament 

Calcaneofibular  ligament 


Syndesmosis  tibiofibulare 

Lig.  malleoli  lateralis  anterius 
Lig.  malleoli  lateralis  posterius 

Articulatio  talocruralis 

Capsula  articularis 
Lig.  deltoideum 
Lig.  talofibulare  anterius 
Lig.  talofibulare  posterius 
Lig.  calcaneofibulare 


Inferior  tibiofibular  articulation 

Anterior  inferior  ligament 
Posterior  inferior  ligament 

Ankle-joint;  tibiotarsal  articulation 

,    Capsular  ligament 
Internal  lateral  ligament 
Anterior  fasciculus    "i  of  external 
Posterior  fasciculus   > lateral 
Middle  fasciculus      J  ligament 


Intertarsal  articulations 


Articulationes  intertarseae 


Articulations  of  the  tarsus 


1342 


A  GLOSSARY  OF  THE  INTERNATIONAL 


TERMIXOLOGY  ADOPTED  IN  TEXT         BASLE  TERMINOLOGY 

Talocalcaneal  articulation  Articulatio  talocalcanea 


Articular  capsule 

Anterior  talocalcaneal  ligament 


Capsula  articularis 

Lig.  talocalcaneum  anterius 


Posterior  talocalcaneal  ligament     Lig.  talocalcaneum  posterius 


Lateral  talocalcaneal  ligament 
Medial  talocalcaneal  ligament 


Talocalcaneonavicular  articula- 
tion 

Articular  capsule 

Dorsal  talonavicular  ligament 


Calcaneocuboid  articulation 

Articular  capsule 

Dorsal    calcaneocuboid    liga- 
ment 

Bifurcated  ligament 

Calcaneonavicular  part  of 

Calcaneocuboid  part  of 

Long  plantar  ligament 


Lig.  talocalcaneum  laterale 
Lig.  talocalcaneum  mediale 


Articulatio    talocalcaneonavicu- 
laris 

Capsula  articularis 

Lig.  talonaviculare  dorsale 


Articulatio  calcaneocuboidea 

Capsula  articularis 

Lig.  calcaneocuboideum  dorsale 

Lig.  bifurcatum 

Pars  calcaneonavicularis 

Pars  calcaneocuboid 

Lig.  plantare  longum 


OLD     TERMINOLOGY 

Articulation  of  calcalcaneus  and 
astragalus ;  calcaneo-astraga- 
loid  articulation 

Caijsular  ligament 

Anterior    calcaneo-astragaloid 

ligament 
Posterior     calcaneoastragaloid 

ligament 
External     calcaneoastragaloid 

ligament 
Internal      calcaneoastragaloid 

ligament 

Talocalcaneonavicular  articula- 
tion 

Capsular  ligament 
Superior  astragalonavicular  liga- 
ment 

Articulation  of  calcaneus  with 
cuboid 

Capsular  ligament 
Superior     calcaneocuboid     liga- 
ment 

Superior  calcaneonavicular  liga- 
ment 

Internal  calcaneocuboid  liga- 
ment 

Long  calcaneocuboid  or  super- 
ficial long  plantar  ligament 

Short  plantar  ligament 


Plantar  calcaneocuboid  ligament     Lig.  calcaneocaboideum 

plantare 

Plantar  calcaneona\'icular  liga-     Lig.  calcaneonaviculare  plantare     Inferior  calcaneonavicular  liga- 
ment ment 


Cuneonavicular    articulation 


Articulation  of  the  digits 


Articulatio  cuneonavicularis 


Articulation    of    navicular    with 
cuneiform  bone 


Articulationes  digitorum  pedis  Articulations  of  the  phalanges 


Epicranius 

Galea  aponeurotica 

Orbicularis  oculi 

Lacrimal  part 
Corrugator 
Procerus 
Nasalis 

Depressor  septi 
Quadratus  labii  superioris 

Zygomatic  head 

Infraorbital  head 
■  Angular  head 

Caninus 

Zygomaticus 

Mentalis 

Quadratus  labii  inferioris 

Triangularis 

Pterygomandibular  raphe 

Parotideomasseteric  fascia 

Temporalis 

Pterygoideus  externus 

Pterygoideus  internus 

Fascia  colli 

Sternocleidomastoideus 

Digastricus 

Stylohyoideus 

Mjdohyoideus 

Geniohyoideus 

Sternohyoideus 

Omohyoideus 

Sternothyreoideus 

Thyreohyoideus 

Longus  capitis 

Rectus  capitis  anterior 


MYOLOGY. 

Epicranius 

Galea  aponeurotica 

Orbicularis  oculi 

Pars  lacrimalis 
Corrugator 
Procerus 
Nasalis 

Depressor  septi 
Quadratus  labii  superioris 

Caput  zygomaticum 

Caput  infraorbitale 

Caput  angulare 

Caninus 

Zygomaticus 

Mentalis 

Quadratus  labii  inferioris 

Triangularis 

Fascia  parotideomasseterica 

Temporalis 

Pterygoideus  externus 

Pterygoideus  internus 

Fascia  colli 

Sternocleidomastoideus 

Digastricus 

Stylohyoideus 

Mylohyoideus 

Geniohyoideus 

Sternohyoideus 

Omohj'oideus 

Sternothyreoideus 

Thyreohyoideus 

Longus  capitis 

Rectus  capitis  anterior 


Occipitofrontalis 
Epicranial  aponeurosis 
Orbicularis  palpebrarum 

Tensor  tarsi 
Corrugator  supercilii 
Pyramidalis  nasi 
Compressor  naris 
Depressor  alae  nasi 

Zygomaticus  minor 
Levator  labii  superioris 
Levator  labii  superioris 
alaeque  nasi 

Levator  anguli  oris 

Zygomaticus  major 

Levator  menti 

Depressor  labii  inferioris ;  Quad- 
ratus menti 

Depressor  anguli  oris 

Pterygomandibular  ligament 

Masseteric  fascia 

Temporal 

External  pterygoid 

Internal  pterygoid 

Deep  cervical  fascia 

Sternomastoid 

Digastric 

Stylohyoid 

Mylohyoid 

Geniohyoid 

Sternohyoid 

Omohj'oid 

Sternothyroid 

Thyrohyoid 

Rectus  capitis  anticus  major 

Rectus  capitis  anticus  minor 


OR  BASLE  ANATOMICAL  NOMENCLATURE 


1343 


TERMINOLOGY    ADOl'TKD    IN    TEXT 

Scalenus  anterior 
Scalenus  posterior 
Lumbodorsal  fascia 

Splenius  cervicis 

Sacrospinalis 

Iliocostalis 

"  luniborum 

"  dorsi 

"  cervicis 

Longissimus 

"  dorsi 

"  cervicis 

"  capitis 

Spinalis  dorsi 
"        cervicis 
capitis 
Semispinalis  dorsi 

cervicis 
capitis 
Multifidus 
Rotatores 
Intertransversarii 
Rectus  capitis  posterior  major 
Rectus  capitis  posterior  minor 
Obliquus  capitis  inferior 
Obliquus  capitis  superior 
Intercostales 
Intercostales  externi 
Intercostales  interni 
Subcostales 
Transversus  thoracis 
Serratus  posterior  superior 
Serratus  posterior  inferior 
Diaphragma 

Medial  crus  "i 

Intermediate  crus  > 

Lateral  crus  J 

Medial  lumbocostal  arch 

Lateral  lumbocostal  arch 

Obliquus  externus  abdominis 
Subcutaneous  inguinal  ring 

Superior  crus 

Inferior  crus 
Intercrural  fibres 
Inguinal  ligament 

Lacunar  ligament 

Reflected  inguinal  ligament 

Obliquus  internus  abdominis 
Transversus  abdominis 
Inguinal  aponeurotic  falx 

Tendinous  inscriptions 

Linea  semicircularis 

Abdominal  inguinal  ring 

Inguinal  canal 

Superior  fascia  of  pelvic  dia- 
phragm 

Inferior  fascia  of  pelvic  dia- 
phragm 

Tendinous  arch  of  pelvic  fascia 

Sphincter  ani  externus 

Sphincter  ani  internus 

Transversus  perinae  superficialis 

Bulbocavernosus 

Ischiocavernosus 
Urogenital  diaphragm 
Superior    fascia    of    urogenital 

diaphragm 
Inferior     fascia     of     urogenital 

diaphragm 
Transversus  perinaei  pro-   -| 

fundus 
Sphincter  urethrae   mem- 

branaceae 
Levator  scapulae 
Pectoral  fascia 


BASLE    TIOUMINOLOGY 

Scalenus  anterior 
Scalenus  posterior 
Fascia  lumbodorsalis 

Splenius  cervicis 

Sacrospinalis 

Iliocostalis 

"  lumborum 

"  dorsi 

"  cervicis 

Longissimus 

"  dorsi 

"  cervicis 

"  capitis 

Spinalis  dorsi 
"        cervicis 
"        capitis 
Semispinalis  dorsi 

"  cer\dcis 

"  capitis 

Multifidus 
Rotatores 
Intertransversarii 
Rectus  capitis  posterior  major 
Rectus  capitis  posterior  minor 
Obliquus  capitis  inferior 
Obliquus  capitis  superior 
Intercostales 
Intercostales  externi 
Intercostales  interni 
Subcostales 
Transversus  thoracis 
Serratus  posterior  superior 
Serratus  posterior  inferior 
Diaphragma 

Crus  mediale  ^ 

Crus  intermedium  > 

Crus  laterale  ) 

Arcus     lumbocostalis     medialis 

[Halleri] 
Arcus     lumbocostalis     lateralis 

[Halleri] 
Obliquus  externus  abdominis 
Annulus  inguinalis  subcutaneus 

Crus  superior 

Crus  inferior 
Fibrae  intercrurales 
Ligamentum     inguinale      [Pou- 

parti] 
Ligamentum  lacunare  [Gimber- 

nati] 
Ligamentum  inguinale  refiexum 

[Collesi] 
Obliquus  internus  abdominis 
Transversus  abdominis 
Falx  aponeurotica  inguinalis 

Inscriptiones  tendineae 
Linea  semicircularis  [Douglasi] 
Annulus  inguinalis  abdominalis 
Canalis  inguinalis 
Fascia  diaphragmatis  pelvis 

superior 
Fascia  diaphragmatis  pelvis 

inferior 
Arcus  tendineus  fasciae  pelvis 
Sphincter  ani  externus 
Sphincter  ani  internus 
Transversus  perinaei  superficialis 
Bulbocavernosus 

Ischiocavernosus 
Diaphragma  urogenitale 
Fascia    diaphragmatis    urogeni- 

talis  superior 
Fascia    diaphragmatis    urogeni- 

talis  inferior 
Transversus  perinaei  pro-    -i 

fundus  ' 

Sphincter   urethrae    mem-    I 

branaceae  J 

Levator  scapulae 
Fascia  pectoralis 


OLD    TERMINOLOGY 

Scalenus  anticus 

Scalenus  posticus 

Lumbar    aponeurosis    and    ver- 
tebral fascia 

Splenius  colli 

Erector  spina; 

Iliocostalis 
Sacrolumbalis 
Musculus  accessorius 
Cervicalis  ascondens 

Longissimus  dorsi 
"  dorsi 

Transversalis  cervicis 
Trachelomastoideus 

Spinalis  dorsi 
"        colli 

Biventer  cervicis 

Semispinalis  dorsi 
"  colli 

Complexus 

Multifidus  spinae 

Rotatores  spinae 

Intertransversales 

Rectus  capitis  posticus  major 

Rectus  capitis  posticus  minor 

Obliquus  inferior 

Obliquus  superior 

Intercostal 

External  intercostal 

Internal  intercostal 

Infracostales 

Triangularis  sterni 

Serratus  posticus  superior 

Serratus  posticus  inferior 

Diaphragm 

Crura     and      origins     from 
arcuate    ligaments 

Internal  arcuate  ligament 

External  arcuate  ligament 

External  or  descending  oblique 
External  abdominal  ring 

Internal  pillar 

External  pillar 
Intercolumnar  fibres 
Poupart's  ligament 

Gimbernat's  ligament 

Triangular  fascia 

Internal  or  ascending  oblique 
Transversalis  abdominis 
Conjoined    tendon    of    Internal 

oblique  and  Transversalis 
Lineae  transversae 
Fold  of  Douglas 
Internal  or  deep  abdominal  ring 
Spermatic  canal 
Visceral  layer  of  pelvic  fascia 

Anal  fascia 

White  line  of  pelvic  fascia 

External  sphincter  ani 

Internal  sphincter  ani 

Transversus  perinaei 

Ejaculator  urinae  or  Sphincter 
vaginae 

Erector  penis  vel  clitoridis 

Constrictor  urethrae 

Deep  layer  of  triangular  liga- 
ment 

Superficial  layer  of  triangular 
ligament 

Constrictor  urethrae 


Levator  anguli  scapulae 
Deep  fascia  of  anterior  thoracic 
region 


1344 


A  GLOSSARY  OF  THE  INTERNATIONAL 


TERMINOLOGY  ADOPTED  IN  TEXT 

Coracoclavicular  fascia 
Serratus  anterior 
Deltoideus 
Brachial  fascia 
Biceps  brachii 

Lacertus  fibrosus 
Brachialis 
Triceps  brachii 

Medial  head 

Long  head 

Lateral  head 
Antibrachial  fascia 
Pronator  teres 

Humeral  head 

Ulnar  head 
Brachioradialis 
Extensor  carpi  radialis  longus 
Extensor  carpi  radialis  brevis 
Extensor  digiti  quinti  proprius 
Supinator 

Abductor  pollicis  longus 
Extensor  pollicis  brevis 

Extensor  pollicis  longus 

Extensor  indicis  proprius 
Transverse  carpal  ligament 
Dorsal  carpal  ligament 
Mucous  sheaths 
Palmar  aponeurosis 

Superficial  transverse 
ligament 
Abductor  pollicis  brevis 
Abductor  digiti  quinti 
Flexor  digiti  quinti  brevis 
Opponens  digiti  quinti 
Interopsei  dorsales 
Interossei  volares 
Psoas  major 
Psoas  minor 
Fascia  cribrosa 
Fossa  ovalis 
Iliotibial  band 
Tensor  fasciae  latae 
Quadriceps  femoris 

Pectus  femoris 

Vastus  lateralis 

Vastus  medialis 

Vastus  intermedius 

Articularis  genu 
Biceps  femoris 
Tibialis  anterior 
Extensor  hallucis  longus 
Tendo  calcaneus 
Tibialis  posterior 
Transverse  crural  ligament 

Cruciate  crural  ligament 

Laciniate  ligament 

Superior  peronaeal  retinaculum 

Plantar  aponeurosis 
Quadratus  plantae 
Adductor  hallucis 
Abductor  digiti  quinti 
Flexor  digiti  quinti  brevis 
Interossei  dorsales 
Interossei  plantares 


BASLE    TERMINOLOGY 

Fascia  coracoclavicularis 
Serratus  anterior 
Deltoideus 
Fascia  brachii 
Biceps  brachii 

Lactcrtus  fibrosus 
Brachialis 
Triceps  brachii 

Caput  mediale 

Caput  longum 

Caput  laterale 
Fascia  antibrachii 
Pronator  teres 

Caput  humerale 

Caput  ulnare 
Brachioradialis 
Extensor  carpi  radialis  longus 
Extensor  carpi  radialis  brevis 
Extensor  digiti  quinti  proprius 
Supinator 

Abductor  pollicis  longus 
Extensor  pollicis  brevis 

Extensor  pollicis  longus 

Extensor  indicis  proprius 
Lig.  carpi  transversum 
Lig.  carpi  dorsale 
Vaginae  ipucosae 
Aponeurosis  palmaris 
Fasciculi  transversi 

Abductor  pollicis  bre\ds 
Abductor  digiti  quinti 
Flexor  digiti  quinti  brevis 
Opponens  digiti  quinti 
Interossei  dorsales 
Interossei  volares 
Psoas  major 
Psoas  minor 
Fascia  cribrosa 
Fossa  ovalis 
Tractus  iliotibialis 
Tensor  fasciae  latae 
Quadriceps  femoris 

Rectus  femoris 

Vastus  lateralis 

Vastus  medialis 

Vastus  mtermedius 

Articularis  genu 
Biceps  femoris 
Tibialis  anterior 
Extensor  hallucis  longus 
Tendo  calcaneus  [Achillis] 
Tibialis  posterior 
Lig.  transversum  cruris 

Lig.  cruciatum  cruris 

Lig.  laciniatum 

Retinaculum  mm.  peronaeoruni 

superius 
Aponeurosis  plantaris 
Quadratus  plantae 
Adductor  hallucis 
Abductor  digiti  quinti 
Flexor  digiti  quinti  brevis 
Interossei  dorsales 
Interossei  plantares 


OLD    TERMINOLOGY 

Costocoracoid  membrane 

Serratus  magnus 

Deltoid 

Deep  fascia  of  arm 

Biceps;  Biceps  flexor  cubiti 

Bicipital  fascia 
Brachialis  anticus 
Triceps;  Triceps  extensor  cubiti 

Inner  head 

Long  head 

Outer  head 
Deep  fascia  of  forearm 
Pronator  radii  teres 

Humeral  head 

Coronoid  head 
Supinator  longus 
Extensor  carpi  radialis  longior 
Extensor  carpi  radialis  bre^^or 
Extensor  minimi  digiti 
Supinator  brevis 
Extensor  ossis  metacarpi  pollicis 
Extensor    primi    internodii 

pollicis 
Extensor    secundi   internodii 

pollicis 
Extensor  indicis 
Anterior  annular  ligament 
Posterior  annular  ligament 
Synovial  sheaths 
Palmar  fascia 

Superficial  transverse 
ligament 
Abductor  pollicis 
Abductor  minimi  digiti 
Flexor  brevis  minimi  digiti 
Opponens  minimi  digiti 
Dorsal  interossei 
Palmar  interossei 
Psoas  magnus 
Psoas  parvus 
Cribriform  fascia 
Saphenous  opening 
Iliotibial  band 
Tensor  fasciae  femoris 
Quadriceps  extensor 

Rectus  femoris 

Vastus  externus 

Vastus  internus 

Crureus 

Subcrureus 
Biceps 

Tibialis  anticus 
Extensor  proprius  hallucis 
Tendo  Achillis 
Tibialis  posticus 
Upper  part  of  anterior  annular 

ligament 
Lower  part  of  anterior  annular 

ligament 
Internal  annular  ligament 
External  annular  ligament 

Plantar  fascia 
Flexor  accessorius 
Adductor  obliquus  hallucis 
Abductor  minimi  digiti 
Flexor  breads  minimi  digiti 
Dorsal  interossei 
Plantar  interossei 


Heart 

Coronary  sulcus 

Anterior  longitudinal  sulcus 

Posterior  longitudinal  sulcus 

Atrium 

Sinus  venarum 


ANGIOLOGY. 

Cor 

Sulcus  coronarius 

Sulcus  longitudinalis  anterior 

Sulcus  longitudinalis  posterior 

Atrium 

Sinus  venarum 


Heart 

Auriculoventricular  groove 
Anterior  interventricular  groove 
Posterior  interventricular 

groove 
Auricle 
Sinus  venosus 


OR  BASLE  ANATOMICAL  NOMENCLATURE 


1345 


TERMINOLOGY  ADOPTED  IN  TEXT 

Heart  {continued) 
Auricula 
Valve  of  inferior  vena  cava 

Valve  of  coronary  sinus 

Limbus  fossae  ovalis 
Intervenous  tubercle 
Tricuspid  valve 

Anterior  cusp 

Posterior  cusp 

Medial  cusp 
Trabcculae  carncae 
Nodules  of  semilunar  valves 


Bicuspid  vah'c 
Aortic  sinuses 
Ventricular  septum 

Arteries 

Pulmonary  artery 
Ascending  aorta 
Risht  coronary  artery 
Left  coronary  artery 
Arch  of  aorta 
Innominate  artery 
Common  carotid  artery 
External  carotid  artery 
Superior  thyroid  artery 

Hyoid  branch 

Sternocleidomastoid  branch 
Lingual  artery 

Hyoid  branch 

A.  dorsalis  linguae 

A.  profunda  linguae 

External  maxillary  artery 

Inferior  labial  artery 

Superior  labial  artery 
Sternocleidomastoid  artery 
Descending  branch  of  occipital 

artery 
Anterior  tympanic  artery 
Accessory  meningeal  branch 
Inferior  alveolar  artery 
Buccinator  artery 
Posterior  superior  alveolar 

artery 
Caroticotympanic  branch 

Artery  of  pterygoid  canal 
Sphenopalatine  artery 
Medial  palpebral  arteries 
Anterior  choroidal  artery 
Dorsal  nasal  artery 
Arterial  circle  of  Willis 
Meningeal  branch  of  vertebrae 
Posterior  spinal  artery 
Anterior  spinal  artery 
Internal  auditory  artery 
Thyrocervical  trunk 
Transverse  scapular  artery 
Transverse  cervical  artery 

Ascending  branch 

Descending  branch 
Pericardiacophrenic  artery 
Costocervical  trunk  "i 

Highest  intercostal  artery  | 
Highest  thoracic  artery 
Thoracoacromial  artery 

Deltoid  branch 
Lateral  thoracic  artery 
Scapular  circumflex  artery 
Posterior  humeral  circumflex 

artery 
Anterior  humeral  circumflex 

artery 
A.  profunda  brachii 

Radial  collateral  artery 

Superior  ulnar  collateral  arterj' 
Inferior  ulnar  collateral  artery 

85 


liASLE    TKHMINGLOOY 

Cor  {conliniied) 
Auricula 
Valvula   venae    cavac   inferior! 

[Eustacliii] 
Valvula  sinus  coi'onarii 

[Thci)esiil 
Limiius  fossae  ovalis 
Tuberculum  intervenosum 
Valvula  tricuspidalis 

Cuspus  anterior 

Cuspus  pijslrrior 

("uspiis  inc(li:ilis 
Trabcculae  cMru(.'ae 
Noduli  valvularum  semi- 

lunarium  [Ariintii] 
Valvula  bicuspidalis  [mitralis] 
Sinus  aortae  [Valsalvae] 
Septum  ventriculorum 

Arteriae 


OLD    TERMINOLOGY 

Heart  (continued) 

Auricular  appendix 
s     Eustachian  valve 

Thebesian  valve 

Annulus  ovalis 
Tubercle  of  Lower 
Tricuspid  valve 

Infundibular  cusp 

Marginal  cusp 

Septal  cusp 
Columnae  carneae 
Corpora  Arantii 

Mitral  valve 
Sinuses  of  Valsalva 
Interventricular  septum 

Arteries 


A.  pulmonalis 

Aorta  ascendens 

A.  coronaria  (cordis)  dextra 

A.  coronaria  (cordis)  sinistra 

Arcus  aortae 

A.  anonym  a 

A.  carotis  communis 

A.  carotis  externa 

A.  thyreoidea  superior 

Ramus  hyoideus 

Ramus  ster-nocleidomastoideus 
A.  lingualis 

Ramus  hyoideus 

A.  dorsalis  linguae 

A.  profunda  linguae 

A.  maxillaris  externa 

A.  labialis  inferior 

A.  labialis  superior 
A.  sternomastoidea 
Ramus  descendens  a.  occipitalis 

A.  tympanica  anterior 

Ramus  meningeus  accessorius 

A.  alveolaris  inferior 

A.  buccinatoria 

A.  alveolaris  superior  posterior 

Ramus  caroticotympanicus 

A.  canalis  pterygoidei  [Vidii] 

A.  sphenopalatina 

Aa.  palpebrales  mediales 

A.  chorioidea 

A.  dorsalis  nasi 

Circulus  arteriosus  [Willisi] 

Ramus  meningeus 

A.  spinalis  posterior 

A.  spinalis  anterior 

A.  auditiva  interna 

Truncus  thyreocervicalis 

A.  transversa  scapulae 

A.  transversa  colli 

Ramus  ascendens 

Ramus  descendens 
A.  pericardiacophrenica 
Truncus  costocervicalis  i^ 
A.  intercostalis  supremaj 
A.  thoracalis  supi'ema 
A.  thoracoacromialis 

Ramus  deltoideus 
A.  thoracalis  lateralis 
A.  circumflexa  scapulae 
A.  circumflexa  humeri  posterior 


Pulmonary  artery 

Ascending  aorta 

Right  coronary  artery 

Left  coronary  artery 

Transverse  aorta 

Brachiocephalic  artery 

Common  carotid  artery 

External  carotid  artery 

Superior  thyroid  arterj^ 
Infrahyoid  branch 
Sternomastoid  branch 

Lingual  artery 

Suprahyoid  branch 
Rami  dorsalis  linguae 
Ranine  artery;  deep  lingual 
artery 

Facial  artery- 
Inferior  coronary  artery 
Superior  coronary  artery 

Sternomastoid  artery 

Arteria  princeps  cervicis 

Tympanic  artery 

Small  meningeal  artery 

Inferior  dental  artery 

Buccal  arterjr 

Alveolar     or    posterior    dental 

artery 
Tympanic    branch    of    internal 

carotid  artery 
Vidian  artery 
Nasopalatine  artery 
Internal  palpebral  arteries 
Choroid  artery 
Nasal  artery 
Circle  of  Willis 
Posterior  meningeal  branch 
Dorsal  spinal  artery 
Ventral  spinal  artery 
Auditory  artery 
Thyroid  axis 
Suprascapular  artery 
Transversalis  colli  artery 

Superficial  cervical  artery 

Posterior  scapular  artery 
A.  comes  nervi  phrenici 

Superior  intercostal  artery 

Superior  thoracic  artery 
Acromiothoracic  artery ;  thoracic 
axis 
Humeral  branch 
Long  thoracic  artery 
Dorsalis  scapulae  artery 
Posterior  circumflex  artery 


A.  circumflexa  humeri  anterior       Anterior  circumflex  artery 


A.  profunda  brachii 
A.  coUateralis  radialis 

A.  coUateralis  ulnaris  superior 
A.  coUateralis  ulnaris  inferior 


Superior  profunda  artery 

Ant.   branch  of  sup.   profunda 

artery 
Inferior  profunda  artery 
Anastomotica  magna  artery 


1346 


A  GLOSSARY  OF  THE  INTERNATIONAL 


TERMINOLOGY  ADOPTED  IN  TEXT 

Arteries  {continued) 
Volar  carpal  branch 
Superficial  volar  branch 
Dorsal  carpal  branch 
Dorsal  metacarpal  arteries 
A.  volaris  indicis  radialis 
Deep  volar  arch 
Volar  metacarpal  arteries 
Volar  interosseous  artery 
Dorsal  interosseous  artery 
Volar  carpal  branch  of  ulnar 
Dorsal  carpal  branch  of  ulnar 
Deep  volar  branch  of  ulnar 
Superficial  volar  arch 
Common  volar  digital  arteries 
Proper  volar  digital  arteries 
Cceliac  artery 

Left  gastric  artery 

Right  gastric  artery 

Lienal  artery 

Short  gastric  arteries 
Intestinal  arteries 
Middle  suprarenal  artery 
Internal  spermatic  arteries 
Hypogastric  artery 
Internal  pudendal  artery 

Perineal  artery 

Posterior  scrotal  arteries 

Deep  artery  of  penis 
Inferior  gluteal  artery 
Superior  gluteal  artery 
Inferior  epigastric  artery 

External  spermatic  artery 
Femoral  canal 
Femoral  ring 
Femoral  septum 
Femoral  triangle 


BASLE    TERMINOLOGY 


Adductor  canal 

Superficial  external  pudendal 

artery 
Deep  external  pudendal  artery 
Profunda  femoris  artery 
Lateral  femoral  circumflex  artery 
Medial  femoral  circumflex  artery 
Highest  genicular  artery 
Sural  arteries 
Superior  genicular  arteries 
Middle  genicular  artery- 
Inferior  genicular  arteries 
Anterior  medial  malleolar  artery 
Anterior  lateral  malleolar  artery 
Lateral  tarsal  artery 
Arcuate  artery 
Dorsal  metatarsal  arteries 
Deep  plantar  artery 
Peroneal  artery 

Perforating  branch 

Lateral  calcaneal 

Posterior  medial  malleolar  artery 

Medial  calcaneal 
Medial  plantar  artery 
Lateral  plantar  artery 
Plantar  metatarsal  arteries 
Plantar  digital  arteries 


Arteriae  (continued) 
Ramus  carpeus  volaris 
Ramus  volaris  superficialis 
Ramus  carpens  dorsalis 
Aa.  metacarpeae  dorsales 
A.  volaris  indicis  radialis 
Arcus  volaris  profundus 
Aa.  metacarpeae  volares 
A.  interossea  volaris 
A.  interossea  dorsalis 
Ramus  carpeus  volaris 
Ramus  carpeus  dorsalis 
Ramus  volaris  profundus 
Arcus  volaris  superficialis 
Aa.  digitales  volares  communes 
Aa.  digitales  volares  propriae 
A.  coeliaca 

A.  gastrica  sinistra 

A.  gastrica  dextra 

A.  lienalis 

Aa.  gastricae  breves 
Aa.  intestinales 
A.  suprarenalis  media 
A.  spermaticae  internae 
A.  hypogastrica 
A.  pudenda  interna 

A.  perinei 

Aa.  scrotales  posteriores 

A.  profunda  penis 
A.  glutaea  inferior 
A.  glutaea  superior 
A.  epigastrica  inferior 

A.  spermatica  externa 
Canalis  femoralis 
Annulus  feinoralis 
Septum  femorale  [Cloqueti] 
Trigonum     femorale     [fossa 

Scarpae  major] 
Canalis  adductorius  [Hunteri] 
A.    pudenda    externa    super- 
ficialis 
A.  pudenda  externa  profunda 
A.  profunda  femoris 
A.  circumflexa  femoris  lateralis 
A.  circumflexa  femoris  medialis 
A.  genu  suprema 
Aa.  surales 
Aa.  genu  superiores 
A.  genu  media 
Aa.  genu  inferiores 
A.  malleolaris  anterior  medialis 
A.  malleolaris  anterior  lateralis 
A.  tarsea  lateralis 
A.  arcuata 

Aa.  metatarseae  dorsales 
Ramus  plantaris  profundus 
A.  peronaea 

Ramus  perforans 

Ramus  calcaneus  lateralis 

A.  malleolaris  posterior  medialis 

Rami  calcanei  mediales 


OLD    TERMINOLOGY 

Arteries  (continued) 
Anterior  radial  carpal  artery 
Superficialis  volae  artery 
Posterior  radial  carpal  artery 
Dorsal  interosseous  arteries 
Radialis  indicis  artery 
Deep  palmar  arch 
Palmar  interosseous  arteries 
Anterior  interosseous  artery 
Posterior  interosseous  artery 
Anterior  ulnar  carpal  artery 
Posterior  ulnar  carpal  artery 
Profunda  branch 
Superficial  palmar  arch 
Palmar  digital  arteries 
Collateral  digital  arteries 
Cceliac  axis 

Gastric  or  coronary  artery 

Pyloric  artery 

Splenic  artery 

Vasa  brevia 
Vasa  intestini  tenuis 
Middle  capsular  artery 
Spermatic  arteries 
Internal  iliac  artery 
Internal  pudic  artery 

Superficial  perineal  artery 

Superficial  perineal  arteries 

Artery  to  corpus  cavernosum 
Sciatic  artery 
Gluteal  artery 
Deep  epigastric  artery 

Cremasteric  artery 
Crural  canal 
Crural  ring 
Septum  crurale 
Scarpa's  triangle 


A.  plantaris  medialis 
A.  plantaris  lateralis 
Aa.  metatarseae  plantares 
Aa.  digitales  plantares 


Hunter's  canal 

Superficial  external  pudic  arterj'^ 

Deep  external  pudic  arterj^ 
Deep  femoral  artery 
External  circumflex  artery 
Internal  circumflex  artery 
Anastomotica  magna  artery 
Inferior  muscular  arteries 
Superior  articular  arteries 
Azygos  articular  artery 
Inferior  articular  arteries 
Internal  malleolar  artery 
External  malleolar  artery 
Tarsal  artery 
Metatarsal  arterj^ 
Dorsal  interosseous  arteries 
Communicating  artery 
Peroneal  artery 

Anterior  peroneal  artery 

External  calcaneal 

Internal  malleolar  artery 

Internal  calcaneal 
Internal  plantar  artery 
External  plantar  artery 
Digital  branches 
Collateral  digital  branches 


Veins 

Great  cardiac  vein 
Small  cardiac  vein 
Oblique  vein  of  left  atrium 

Ligament  of  left  vena  cava 
Smallest  cardiac  veins 
Anterior  facial  vein 
Posterior  facial  vein 
Deep  cervical  vein 

Middle  cerebral  vein 
Internal  cerebral  veins 
Great  cerebral  vein 
Terminal  vein 
Superior  sagittal  sinus 


Venae 

V.  cordis  magna 

V.  cordis  parva 

V.   obliqua   atrii   sinistri 

shalli] 
Lig.  venae  cavae  sinistrae 
Vv.  cordis  minimae 
V.  facialis  anterior 
V.  facialis  posterior 
V.  cer^dcalis  profunda 

V.  cerebri  media 

Vv.  cerebri  internae 

V.  cerebri  magna  [Galeni] 

V.  terminalis 

Sinus  sagittalis  superior 


Veins 

Left  coronary  vein 
Right  coronary  vein 
[Mar-     Oblique  vein  of  Marshall 

Vestigial  fold  of  Marshall 
Veins  of  Thebesius 
Facial  vein 

Temporomaxillary  vein 
Posterior  vertebral  or  posterior 

deep  cer\dcal  vein 
Superficial  Sylvian  vein 
Veins  of  Galen 
Great  vein  of  Galen 
Vein  of  corpus  striaturn 
Superior  longitudinal  sinus 


OR  BASLE  ANATOMICAL  NOMENCLATURE 


1347 


TERMINOLOGY  ADOPTED  IN  TEXT 

Veins  {continued) 


BASLE    TEUMINOLOGY 


Venae  {continued) 


Inferior  sagittal  sinus 
Transverse  sinus 
Conflucnee  of  the  sinuses 
Basilar  plexus 
Innominate  veins 
Highest  intercostal  \-eiu 
Az.\-gos  vi'in 
Hcniiazygos  vein 
Accessory  hemiazygos  vein 
External  vertebral  venous  plexus 

Internal  vertebral  venous  plexus 
Great  saphenous  vein 
Small  saphenous  vein 
Inferior  epigastric  vein 
Hypogastric  vein 
Superior  gluteal  veins 
Inferior  gluteal  veins 
Pudendal  plexus 
Lienal  vein 
Coronary  vein 


Lymphatic  vessels 

Cisterna  chj'li 

Posterior  auricular  glands 

Anterior  auricular  glands 

Deep  facial  glands 

Hypogastric  glands 
Inferior  gastric  glands 

Pancreaticolienal  glands 

Sternal  glands 


Sinus  sagittalis  inferior 

Sinus  transversus 

Confluens  sinuuni 

Plexus  basilaris 

Vv.  anonymae 

V.  intercostalis  suprema 

V.  azygos 

V.  hemiazygos 

V.  hemiazygos  accesoria 

Plexus     venosi     vertebralis 

externi 
Plexus  venosi  vertebralis  inter: 
V.  saphena  magna 
V.  saphena  parva 
V.  epigastrica  inferior 
V.  hypogastrica 
Vv.  glutaeae  superiores 
Vv.  glutaeae  inferiores 
Plexus  pudendalis 
V.  lienalis 
V.  coronaria  ventriculi 


OLD   TERMINOLOGY 

Veins  {continued) 

Inferior  longitudinal  sinus 
Lateral  sinus 
Torcular  ll(;rophili 
Transverse  or  basilar  sinus 
Brachiocephalic  veins 
Superior  intercostal  vein 
Vena  azygos  major 
Vena  azygos  minor  inferior 
Vena  azygos  minor  superior 
Extraspinal  veins 

li     Intraspinal  veins 

Internal  or  long  saphenous  vein 
External  or  short  saphenous  vein 
Deep  epigastric  vein 
Internal  iliac  vein 
Gluteal  veins 
Sciatic  veins 
Vesicoprostatic  plexus 
Splenic  vein 
Gastric  vein 


Vasa  lymphatici 

Cisterna  chyli 
Lymphoglandulae 

posteriores 
Lymphoglandulae 

anteriores 
Lymphoglandulae 

funda 
Lymphoglandulae 
Lymphoglandulae 

inferiores 
Lymphoglandulae 

lienales 
Lymphoglandulae 


Lymphatic  vessels 

Receptaculum  chyli 
auriculares       Mastoid  glands 

auriculares       Superficial  parotid  or  preauricu- 
lar glands 
faciales  pro-       Internal  maxillary  glands 

hypogastricae    Internal  iliac  glands 
gastricae  Right  gastroepiploic  gland 

pancreatico-     Splenic  glands 

sternales  Internal  mammary  glands 


NEUROLOGY. 


Medulla  spinalis 

Funiculi  of  medulla  spinalis 
Columns  of  gray  substance 
Anterior  column 
Lateral  column 
Posterior  column 
Dorsal  nucleus 


Anterior  cerebrospinal  fasciculus 
Anterior  proper  fasciculus 

■  Lateral  cerebrospinal  fasciculus 
Cerebellospinal  fasciculus 
Superficial  antero-lateral  fascic- 
ulus 
Lateral  proper  fasciculus 

Fasciculus  gracilis 
Fasciculus  cuneatus 

Rhombencephalon 

Medulla  oblongata 

Anterior  median  fissure 

Posterior  median  fissure 

Olive 

Tubercle  of  Rolando 

Spinal  tract  of  trigeminal  nerve 

Lemniscus 

Decussation  of  lemniscus 

Cerebellospinal  fasciculus 

Medial  longitudinal  fasciculus 

Horizontal    sulcus    [of    cerebel- 
lum] 
Quadrangular  lobule 
Folium  vermis 


Medulla  spinalis 

Funiculi  medullae  spinalis 
Columnae  griseae 
Columna  anterior 
Columna  lateralis 
Columna  posterior 
Nucleus  dorsalis  [Stillingi, 

Clarkii] 
Fasciculus  cerebrospinalis  anterior 
Fasciculus  anterior  proprius 

[Flechsigi] 
Fasciculus  cerebrospinalis  lateralis 
Fasciculus  cerebellospinalis 
Fasciculus  anterolateralis  super- 

ficialis  [Gowersi] 
Fasciculus  lateralis  proprius 

[Flechsigi] 
Fasciculus  gracilis  [GoUi] 
Fasciculus  cuneatus  [Burdachi] 


Spinal  cord 

Columns  of  spinal  cord 
Horns  of  gray  matter 
Anterior  cornu 
Lateral  cornu 
Posterior  cornu 
Clarke's  column 

Direct  pyramidal  tract 
Anterior  basis  bundle 

Crossed  pyramidal  tract 
Direct  cerebellar  tract 
Gowers'  tract. 

Lateral  basis  bundle 

Column  of  Goll 
Column  of  Burdach 


Rhombencephalon 

Medulla  oblongata 

Fissura  mediana  anterior 

Fissura  mediana  posterior 

Oliva 

Tuber  cinereum 

Tractus  spinalis  n.  trigemini 

Lemniscus 

Decussatio  lemniscorum 

Fasciculus  cerebellospinalis 

Fasciculus  longitudinalis  medi 

alls 
Sulcus  horizontalis  [cerebelli] 

Lobulus  quadrangularis 
Folium  vermis 


Hind-brain 

Spinal  bulb 

Ventral  or  ventromedian  fissure 
Dorsal  or  dorsomedian  fissure 
Olivary  body 
Tubercle  of  Rolando 
Spinal  root  of  fifth  cranial  nerve 
Fillet 

Sensory  decussation 
Direct  cerebellar  tract 
-     Posterior  longitudinal  bundle 

Great  horizontal  fissure 

Ant.  and  post,  crescentic  lobes 
Folium     cacuminis ;     cacuminal 
lobe 


1348 


A  GLOSSARY  OF  THE  INTERN  AT  lOXAL 


TERMIXOLOGY  ADOPTED  IX  TEXT 

Rhombencephalon  {continued) 
Superior  semilunar  lobule 
Nodule 
U\'ula 
Tonsillae 
Tuber  vermis 
Inferior  semilunar  lobule 

Brachia  conjunctiva 
Brachia  pontis 
Restiform  bodies 
Anterior  medullary  velura 

Posterior  medullary  velum 
Taenia  of  fourth  ventricle 

Rhomboid  fossa 
Medial  eminence 
Colliculus  facialis 
Area  acustica 
Medullary  striae 
Ala  cinerea 

Mesencephalon 

Cerebral  peduncle 
Base  of  peduncle 
Substantia  nigra 
Inferior  colliculus 
Superior  colliculus 
Cerebral  aqueduct 

Prosencephalon 

Thalami 

Intermediate  mass 
Medial  geniculate  body 

Lateral  geniculate  body 

Pineal  body 

Corpus  subthalamicum 

Corpora  mamillaria 

Hypophysis 

Optic  chiasma 

Cerebral  hemisphere 

Longitudinal  fissure 
Lateral  cerebral  fissure 
Central  sulcus 
Cingulate  sulcus 
Anterior  central  gj-rus 

Superior  frontal  gyrus 
Middle  frontal  gj^rus 
Inferior  frontal  gyrus 
Intraparietal  sulcus 
Posterior  central  gyrus 

Inferior  parietal  lobule 

Fusiform  gyrus 

Transverse  temporal  gjTi 

Insula 

Cingulate  gjTus 

Callosal  sulcus 

Hippocampal  fissure 

Subcallosal  gjjus 

Supracallosal  gj-rus 

Fascia  dentata  hippocampi 

Body  of  corpus  callosum 

Calcar  a^^s 

Anterior     cornu      of     lateral 
ventricle 

Posterior     cornu     of     lateral 
ventricle 

Inferioi  cornu  of  lateral  ven- 
tricle 

Hippocampus 

Caudate  nucleus 

Lentiform  nucleus 

Frontal  part  of  internal  capsule 

Occipital  part  of  internal  cap- 
sule 

Stria  terminaHs 


BASLE    TERMIXOLOGY 

Rhombencephalon  (continued) 
Lobulus  semilunaris  superior 
Xodulus  vermis 
Uvula  vermis 
TonsOla  cerebelli 
Tuber  vermis 
Lobulus  semilunaris  inferior 

Brachia  conjunctiva  [cerebelli] 
Brachia  pontis 
Corpus  restiformes 
Velum  medullare  anterius 

Velum  meduUare  posterius 
Taenia  ventriculi  quarti 
Fossa  rhomboidea 
Eminentia  medialis 
Colliculus  facialis 
Area  acustica 
Striae  medullares 
Ala  cinerea 

Mesencephalon 

Pedunculus  cerebri 
Basis  pedunculi 
Substantia  nigra 
Colliculus  inferior 
Colliculus  superior 
Aquaeductus  cerebri 

Prosencephalon 

Thalami 

Massa  intermedia 

Corpus  geniculatum  mediale 

Corpus  geniculatum  laterals 

Corpus  pineale 
Corpus  subthalamicum 
Corpora  mamillaria 
Hypophysis 
Chiasma  opticum 

Hemisphaerium 

Fissura  cerebri  longitudinalis 
Fissura  cerebri  lateralis  [Sjd%-ii] 
Sulcus  centralis  [Rolandi] 
Sulcus  cinguli 
Gyrus  centralis  anterior 

Gyrus  frontalis  superior 
GjTus  frontalis  medius 
Gyrus  frontalis  inferior 
Sulcus  interparietalis 
G5TUS  centralis  posterior 

Lobulus  parietalis  inferior 

Gj^rus  fusiformis 

Gyri  temporales  transversi 

Insula 

GjTus  cinguli 

Sulcus  corporis  callosi 

Fissura  hippocampi 

GjTus  subcallosus 

Indusium  giiserum 

Fascia  dentata  hippocampi 

Truncus  corporis  callosi 

Calcar  a^-is 

Cornu  anterius 

Cornu  posterius 

Cornu  inferior 

Hippocampus 

Nucleus  caudatus 

Nucleus  lentiformis 

Pars  frontalis  capsulae  internae 

Pars  occipitalis  capsulae  internae 

Stria  terminalis 


OLD    TERMIXOLOGY 

Hind-brain  {continued) 
Postero-superior  lobule 
Nodular  lobe 
L'\'ular  lobe 
Amygdaline  nucleus 
Tuber  val\Tilae 
Slender   and  postero-inferior 

lobules 
Superior  cerebellar  peduncles 
Middle  cerebellar  peduncles 
Inferior  cerebellar  peduncles 
Valve    of    Vieussens;    superior 

medullarj'  velura 
Inferior  medullary  velum 
Ligula 

Floor  of  fourth  ventricle 
Fasciculus  teres 
Eminentia  teres 
Trigonum  acusticum 
Striae  acusticae 
Trigonum  vagi 

Mid-brain 

Crus  cerebri 

Crusta  or  pes 

Intercalatum 

Inferior  quadrigeminal  body 

Superior  quadrigeminal  body 

Aqueduct  of  Syhdus 

Fore-brain 

Optic  thalamus 

Middle  commissure 

Internal  geniculate  body;  post- 

geniculatum 
External  geniculate  body;    pre- 

geniculatum 
Epiphysis 
Nucleus  of  Luys 
Corpus  albicantia 
Pituitary  body 
Optic  commissure 

Cerebral  heinisphere 

Great  longitudinal  fissure 
Fissure  of  Sjd-vius 
Fissure  of  Rolando 
Callosomarginal  fissure 
Ascending  frontal   convolution; 

precentral  gj're 
Suprafrontal  gj're 
^Medifrontal  gj're 
Subfrontal  gjTe 
Intraparietal  fissure 
Ascending  parietal  convolution; 

postcentral  gjTe 
Subparietal  district  or  lobule 
Occipitotemporal  convolution 
Gyri  of  Heschl 
Island  of  Reil 
Callosal  convolution 
Callosal  sulcus 
Dentate  fissure 
Peduncle  of  corpus  callosum 
GjTus  epicallosus 
Gjrrus  dentatus 
Body  of  corpus  callosum 
Hippocampus  minor 
Anterior  horn;  precornu 

Postcornu 

Descending  horn ;  medicornu 

Hippocampus  major 
Caudatum 
Lenticular  nucleus 
Anterior  limb  of  internal  capsule 
Posterior  limb  of  internal  cap- 
sule 
Taenia  semicircularis 


OR  BASLE  ANATOMICAL  NOMENCLATURE 


1349 


TERMIXOLOGY  ADOPTED  IN  TEXT 

Prosencephalon  (continued) 
Cerebral  hemisphere 

Optic  radiation 

Column  of  fornix 

Thalamomamillary  fasciculus 

Crura  of  fornix 

Septum  pelluciclum 

Cavity  of  septum  pelluciduni 

Tela    chorioidea    of    third    ven- 
tricle 

Tela  chorioidea  of  fourth  ven- 
tricle 

(^horoid     plexus     of     lateral 
ventricle 


BASLE    TEUMINOLOGY 

Prosencephalon  {continued) 
Hemisphaerium 
Radiatio  occipitothalamica 
Columna  fornicis 
Fasciculus  thalamoniamillaris 
Crus  fornicis 
Septum  pcllucidum 
Cavum  septi  pellucidi 
Tela  chorioidea  ventriculi  tertii 


OLD  TERMINOLOGY 

Fore-brain  (continued) 

Cerebral  hemisphere 
Optic  radiation 
Anterior  pillar  of  fornix 
Bundle  of  Vicq  d'Azyr 
Posterior  pillar  of  fornix 
Septum  lucidum 
Pseudocole;  fifth  ventricle 
Velum  interpositum 


Tela  chorioidea  ventriculi  quarti     Tela  chorioidea  inferior 

Plexus  chorioideus  ventriculus       Paraplexus 
lateralis 


Meninges 

Cerebral  dura  mater 
Spinal  dura  mater 
Subarachnoid  cavity 
Cisterna  cerebellomedullaris 
Cisterua  interpeduncularis 
Arachnoid  granulations 
Cerebral  pia  mater 
Spinal  pia  mater 

Cerebral  nerves 

Olfactory  nerves 
Optic  nerve 
Oculomotor  nerve 
Trochlear  nerve 
Trigeminal  nerve 

Semilunar  ganglion 

Nasociliary  nerve 

Ciliary  ganglion 

MaxUlary  nerve 
Middle  meningeal  nerve 
Zygomatic  nerve 
Zygomaticotemporal  branch 

Zygomaticofacial  branch 

Posterior     superior     alveolar 
branches 

Middle    superior    alveolar 
branch 

Anterior   superior   alveolar 
branch 

Inferior  palpebral  branches 

Superior  labial  branches 

Sphenopalatine  ganglion 

Greater    superficial    petrosal 
nerve 

Deep  petrosal  nerve 

Nerve  of  pter5-goid  canal 

Orbital  branches 

Palatine  nerves 

Mandibular  nerve 

Nervus  spinosus 

Buccinator  nerve 

Inferior  alveolar  nerve 
Abducent  nerve 
Facial  nerve 

Sensory  part  of  facial  nerve 

Genicular  ganglion 

Nerve  to  Stapedius 

Z5'gomatic  branches 

Buccal  branches 
Acoustic  nerve 

Vestibular  root 

Cochlear  root 
Glossopharyngeal  nerve 

Superior  ganglion 

Petrous  ganglion 

Tympanic  nerve 
Vagus  nerve 

Jugular  ganglion 
Ganglion  nodosum 

Meningeal  branch 
Auricular  branch 


Meninges 

Dura  mater  encephali 
Dura  mater  spinalis 
Cavum  subarachnoideale 
Cisterna  cerebellomedullaris 
Cisterna  interpeduncularis 
Granulationes  arachnoidales 
Pia  mater  encephali 
Pia  mater  spinalis 

Nervi  cerebrales 

Nn.  olfactorii 
N.  opticus 
N.  oculomotorius 
N.  trochlearis 
N.  trigeminus 

Ganglion  semilunare  [Gasseri] 

N.  nasocUiaris 

Ganglion  ciliare 

N.  maxillaris 

N.  meningeus  medius 

N.  zygomaticus 

Ramus  zygomaticotemporalis 

Ramus  zygomaticofacialis 
Rami     alveolares     superiores 

posteriores 
Ramus    alveolaris    superior 

medius 
Ramus    alveolaris  superior 

anteriores 
Rami  palpebrales  inferiores 
Rami  labiales  superiores 
Ganglion  sphenopalatinum 
N.  petrosus  superficialis  major 

N.  petrous  profundus 

N.  canalis  pterygoidei  [Vidii] 

Rami  orbitales 

Nn.  palatini 

N.  mandibularis 

N. spinosus 

N.  buccinatorius 

N.  alveolaris  inferior 
N.  abducens 
N.  facialis 

N.  intermedins 

Ganglion  geniculi 

N.  stapedius 

Rami  zygomatic! 

Rami  buccales 
N.  acusticus 

Radix  vestibularis 

Radix  cochlearis 
N.  glossopharyngeus 

Ganglion  superius 

Ganglion  petrosum 

N.  tympanicus 
N.  vagus 

Ganglion  jugulare 
Ganglion  nodosum 

Ramus  meningeus 
Ramus  auricularis 


Meninges 

Dura  of  brain 
Spinal  dura 
Subarachnoid  space 
Cisterna  magna 
Cisterna  basalis 
Pacchionian  bodies 
Pia  of  brain 
Pia  of  cord 

Cranial  nerves 

First  nerve 
Second  nerve 
Third  nerve 
Fourth  nerve 
Fifth  nerve 

Gasserian  ganglion 

Nasal  nerve 

Ophthalmic  or  lenticular 
ganglion 

Superior  maxillary  nerve 

Meningeal  or  dural  branch 

Temporomalar  nerve 

Temporal      branch;       orbital 
nerve 

Malar  branch 

Posterior     superior     dental 
branches 

Middle  superior  dental  branch 

Anterior    superior     dental 
branch 

Palpebral  branches 

Labial  branches 

Ganglion  of  Meckel 

Large    superficial     petrosal 
nerve 

Large  deep  petrosal  nerve 

Vidian  nerve 

Ascending  branches 

Descending  branches 

Inferior  maxillary  nerve 

Recurrent  or  meningeal  branch 

Long  buccal  nerve 

Inferior  dental  nerve 
Sixth  nerve 
Seventh  nerve 

Pars  intermedia  of  Wrisberg 

Geniculate  ganglion 

Tympanic  branch 

Malar  branches 

Infraorbital  branches 
Eighth  nerve;  auditory  nerve      * 

Vestibular  nerve 

Cochlear  nerve 
Ninth  nerve 

Jugular  ganglion 

Inferior  ganglion 

Nerve  of  Jacobson 
Tenth     nerve ;      pneumogastric 
nerve 

Ganglion  of  root 

Ganglion   of    trunk;    inferior 
ganglion 

Dural  branch 

Nerve  of  Arnold  , 


1350 


A  GLOSSARY  OF  THE  INTERNATIONAL 


TERMIXOLOGY  ADOPTED  IN  TEXT 

Cerebral  nerves  (continued) 
Vagus  nerve 

Recurrent  nerve 

Superior  cardiac  branches 
Inferior  cardiac  branches 
Anterior  bronchial  branches 

Posterior  bronchial  branches 


BASLE    TERMINOLOGY 

Nervi  cerebrales  (continued) 

N. vagus 


(Esophageal  plexus 
Accessory  nerve 

Cerebral  part 
Spinal  part 
Hypoglossal  nerve 

Spinal  nerves 

Posterior  di^asions 

Medial  branch 

Lateral  branch 
Greater  occipital  nerve 
Anterior  divisions 
Smaller  occipital  nerve 

Anterior  branch 

Posterior  branch 
Cutaneous  cer%dcal  nerve 

Supracla\dc\ilar  nerves 
Anterior  supraclavicular  nerves 
Middle  supracla-\-icular  nerv^es 
Posterior  supraclaviciilar  nerves 

Brachial  plexus 

Lateral  cord 

Medial  cord 

Posterior  cord 
Dorsal  scapular  nerve 

Long  thoracic  nerve 


N.  recurrens 

Rami  cardiaci  superiores 
Rami  cardiaci  inferiores 
Rami  bronchiales  anteriores 

Rami  bronchiales  posteriores 

f  Plexus  oesophageus  anterior 
t  Plexus  oesophageus  posterior 
N.  accessorius 

Ramus  internus 
Ramus  externus 
N.  hypoglossi 

Nervi  spinales 

Rami  posteriores 

Ramus  medialis 

Ramus  lateralis 
N.  occipitalis  major 
Rami  anteriores 
X.  occipitalis  minor 

Ramus  anterior  ■ 

Ramus  posterior 
N.  cutaneus  colli 

Nn.  supracla^dculares 
Nn.  supraclaviculares  anteriores 
Nn.  supraclaviculares  medii 
Nn.    supracia-^dculares    pos- 
teriores 
Plexus  brachialis 
Fasciculus  lateralis 
Fasciculus  medialis 
Fasciculus  posterior 
N.  dorsalis  scapulae 


OLD    TERMINOLOGY 

Cranial  nerves  (continued) 

Tenth      nerve;     pneumogastric 
nerve 
Inferior  or  recurrent  laryngeal 

nerve 
Cervical  cardiac  branches 
Thoracic  cardiac  branches 
Anterior  or  ventral  pulmonary 

branches 
Posterior  or  dorsal  pulmonary 
branches 


Lateral     and     medial     anterior 

thoracic  nerves 
Thoracodorsal  nerve 
Axillary  nerve 
Lateral  brachial  cutaneous  nerve 

Lateral   antibrachial   cutaneous 
nerve 

Volar  branch 

Dorsal  branch 
Medial    antibrachial    cutaneous 
nerve 

Volar  branch 

Ulnar  branch 
Medial  brachial  cutaneous  nerve 
Volar  interosseous  nerve 
Proper  volar  digital  nerves 

Radial  nerve 

Posterior     brachial     cutaneous 

nerve 
Dorsal    antibrachial    cutaneous 

nerve 
Superficial     branch     of     radial 

nerve 
Deep  branch  of  radial  nerve  < 
Dorsal  interosseous  nerve       f 
Lumbosacral  trunk 
Iliohypogastric  nerve 

Lateral  cutaneous  branch 

Anterior  cutaneous  branch 
Genitofemoral  nerve 

External  spermatic  nerve 

Lumboinguinal  nerve 
Lateral  femoral  cutaneous  nerve 
Femoral  nerve 

Intermediate  cutaneous  nerve 
Saphenous  nerve 

Infrapatellar  branch 


N.  thoracalis  longus 

Nn.  thoracales  anteriores 

N.  thoracodorsalis 

N.  axillaris 

N.  cutaneus  brachii  lateralis 

N.  cutaneus  antibrachii  lateralis 

Ramus  volaris 
Ramus  dorsalis 
N.  cutaneus  antibrachii  medialis 

Ramus  volaris 

Ramus  ulnaris 
N.  cutaneus  brachii  medialis 
N.  interosseus  volaris 
Nn.  digitales  volares  proprii 

N.  radialis 

N.  cutaneus  brachii  posterior 

N.  cutaneus  antibrachii  dorsalis 

Ramus  superficialis 

Ramus  profundus  \ 
N.  interosseus  dorsalis  j 
Truncus  lumbosacralis 
N.  iliohypogastricus 

Ramus  cutaneus  lateralis 

Ramus  cutaneus  anterior 
N.  genitofemoralis 

N.  spermaticus  externus 

N.  lumboinguinalis 
N.  cutaneus  femoralis  lateralis 
N.  femoralis 

Ramus  cutaneus  anterior 
N.  saphenus 

Ramus  infrapatellaris 


Plexus  guise 

Eleventh  nerve ;  spinal  accessory 
nerv-e 

Accessory  portion 

Spinal  portion 
Twelfth  nerve 

Spinal  nerves 

Posterior  divisions 

Internal  branch 

External  branch 
Great  occipital  nerve 
Anterior  di\asions 
Small  occipital  nerve 

Facial  branch 

Mastoid  branch 
Superficial  or  transverse  cer\'ical 

nerve 
Descending  branches 
Suprasternal  nerves 
Supracla\-icular  nerves 
Supra-acromial  nerves 

Brachial  plexus 

Outer  cord 

Inner  cord 

Posterior  cord 
Nerve  to  Rhomboidei;  posterior 

scapular,  nerve 
External    respiratorj-    nerve    of 

Bell 
Internal   and   external   anterior 

thoracic  nerves 
Long  subscapular  ner^'e 
Circumflex  nerve 
Cutaneous  branch  of  circumflex 

nerve 
Cutaneous  branch  of  musculo- 
cutaneous nerve 

Anterior  branch 

Posterior  branch 
Internal  cutaneous  nerve 

Anterior  branch 

Posterior  branch 
Lesser  internal  cutaneous  nerve 
Anterior  interosseous  nerve 
Collateral    branches    of    digital 

nerves 
Musculosptral  nerve 
Internal    cutaneous    branch    of 

musculospiral  nerve 
External  cutaneous  branches  of 

musculospiral  nerve 
Radial  nerve 

Posterior  interosseous  nerve 

Lumbosacral  cord 
Iliohypogastric  nerve 

Iliac  branch 

Hypogastric  branch 
Genitocrural  nerve 

Genital  branch 

Femoral  or  crural  branch 
External  cutaneous  nerve 
Anterior  crural  nerve 
Middle  cutaneous  nerve 
Long  or  internal  saphenous  nerve 

Patellar  branch 


OR  BASLE  ANATOMICAL  NOMENCLATURE 


1351 


TERMINOLOGY  ADOPTED  IN  TEXT        BASLE  TERMINOLOGY 

Spinal  nerves  (continued)  Nervi  spinales  {continued) 

cutaneous     N.  cutancus  fcnioralis  posterior 


Posterior      femoral 
nerve 

Sciatic  nerve 

Tibial  norvc 

Medial  sural  cutaneous  nerve 

Sural  nerve 

Medial  plantar  nerve 

Lateral  plantar  nerve 

Common  peroneal  nerve 

Lateral  sural  cutaneous  nerve 
Peroneal  anastomotic  branch 

Deep  peroneal  nerve 
Superficial  peroneal  nerve 
Medial  dorsal  cutaneous  nerve 

Intermediate  dorsal  cutaneous 

nerve 
Pudendal  nerve 

Posterior  scrotal  nerves 


Sympathetic  system 

Sj-mpathetic  trunks 
Internal  carotid  plexus 
Ansa  subclavia  [Vieussenii] 
Middle  cardiac  nerve 
Greater  splanchnic  nerve 
Lowest  splanchnic  nerve 
Cardiac  plexus 

Posterior  coronary  plexus 
Anterior  coronary  plexus 
Cceliac  plexus 
Coeliac  ganglia 
Superior  gastric  plexus 
Abdominal  aortic  plexus 
Lesser  cavernous  nerves 
Greater  cavernous  nerve 


N.  ischiadicus 

N.  tibialis 

N.  cutaneus  surae  medialis 

N.  suralis 

N.  plantaris  medialis 

N.  plantaris  lateralis 

N.  peronaeus  communis 
N.  cutaneus  surae  lateralis 
Ramus  anastomoticus  per- 
onaeus 

N.  peronaeus  profundus 

N.  peronaeus  superficialis 

N.  cutaneus  dorsalis  medialis 

N.    cutaneus    dorsalis    inter- 
medins 

N.  pudendus 

Nn.  scrotales  posteriores 


OLD    TERMINOLOGY 

Spinal  nerves  (continued) 
Small  sciatic  nerve 

Great  sciatic  nerve 
Internal  popliteal  nerve 
Nervus  communicans  tibialis 
Short  saphenous  nerve 
Internal  plantar  nerve 
External  plantar  nerve 
External  popliteal  nerve 
Lateral  cutaneous  branch 
Nervus  communicans  fibularis 

Anterior  tibial  nerve 
Musculocutaneous  nerve 
Internal     dorsal     cutaneous 

branch 
External    dorsal    cutaneous 

branch 
Internal  pudic  nerve 

Superficial  peroneal  nerves 


nervorum    sympathi-     Sympathetic  system 


Systema 
cum 

Truncus  sympathicus 
Plexus  caroticus  internus 
Ansa  subclavia  [Vieussenii] 
N.  cardiacus  medius 
N.  splanchnicus  major 
N.  splanchnicus  imus 
Plexus  cardiacus 

Plexus  coronarius  posterior 
Plexus  coronarius  anterior 
Plexus  coeliacus 
Ganglia  coeliaca 
Plexus  gastricus  superior 
Plexus  aorticus  abdominis 
Nn.  cavernosi  penis  minores 
N.  cavernosus  penis  major 


Gangliated  cord 
Carotid  plexus_ 
Ansa  Vieussenii 
Great  cardiac  nerve 
Great  splanchnic  nerve 
Least  splanchnic  nerve 
Superficial  and  deep  cardiac 

plexuses 
Left  coronary  plexus 
Right  coronary  plexus 
Solar  plexus 
Semilunar  ganglia 
Gastric  or  coronarj^  plexus 
Aortic  plexus 
Small  cavernous  nerves 
Large  cavernous  plexus 


PERIPHERAL  ORGANS  OF  THE  SPECIAL  SENSES. 


Organ  of  Taste 

Gustatory  calj-culi 

Organ  of  smell 

External  nose 

Lateral  cartilage 

Greater  alar  cartilage 

Lesser  alar  cartilages 

Nasal  ca\at'y 

Choanse 

Accessory  sinuses  of  nose 

Maxillary  sinus 

Organ  of  sight 

Bulb  of  ej-e 
Sinus  venosus  sclerae 
Corneal  epithelium 
Anterior  elastic  lamina 

Posterior  elastic  lamina 

Spaces  of  the  angle  of  the  iris 
Endothelium   of  the   anterior 

chamber 
Zonula  ciliaris 
Spatia  zonularis 
Rectus  medialis 
Rectus  lateralis 
Ligament  or  tendon  of  Zinn 

Fascia  bulbi 

Lateral  palpebral  commissure 

Medial  palpebral  commissure 


Organon  gustus 

Calyculi  gustatorii 

Organon  olfactus 

Nasus  externus 
Cartilago  nasi  lateralis 
Cartilage  alaris  major 
Cartilagines  alares  minores 
Cavum  nasi 
Choanae 

Sinus  paranasales 
Sinus  maxillaris 

Organon  visus 

Bulbus  oculi 
Sinus  venosus  sclerae 
Epithelium  corneae 
Lamina  elastica  anterior 

Lamina  elastica  posterior 

Spatia  anguli  iridis 
Endothelium    camerae    ante- 

rioris 
Zonula  ciliaris  [Zinni] 
Spatia  zonularis 
M.  rectus  medialis 
M.  rectus  lateralis 
Annulus  tendineus  communis 

[Zinni] 
Fascia  bulbi  [Tenoni] 
Commissura  palpebrarum  later 

alls 
Commissura  palpebrarum 

medialis 


Organs  of  taste 

Taste-buds 

The  nose 

Outer  nose 

Upper  lateral  cartilage 
Lower  lateral  cartilage 
Sesamoid  cartilages 
Nasal  fossa 
Posterior  nares 
Accessory  sinuses  of  nose 
Antrum  of  Highmore 

The  eye 

Eyeball 

Canal  of  Schlemm 

Anterior  layer 

Anterior  limiting  layer;  Bow- 
man's membrane 

Membrane  of  Descemet;  mem- 
brane of  Demours 

Spaces  of  Fontana 

Posterior  layer;  corneal  endo- 
thelium 

Zonule  of  Zinn 

Canal  of  Petit 

Rectus  internus 

Rectus  externus 

Ligament  or  tendon  of  Zinn 

Capsule  of  Tenon 
External  canthus 

Internal  canthus 


1352 


A  GLOSSARY  OF  THE  INTERNATIONAL 


TERMINOLOGY  ADOPTED  IN  TEXT 

Organ  of  sight  (continued) 
Superior  tarsus 
Inferior  tarsus 
Orbital  septum 
Medial  palpebral  ligament 
Lateral  palpebral  raph6 
Tarsal  glands 
Lacrimal  ducts 
Nasolacrimal  duct 

Organ  of  hearing 

Auricula 

Fossa  triangularis 
Scapha 

Auricularis  anterior 
Auricularis  superior 
Auricularis  posterior 
External  acoustic  meatus 
Tegmental  wall 
Jugular  wall 
Membranous  wall 
Petrotympanic  fissure 
Labyrinthic  wall 

Fenestra  vestibuli 

Fenestra  cochleae 

Prominence  of  facial  canal 

Mastoid  wall 

Tympanic  antrum 
Pyramidal  eminence 

Carotid  wall 

Auditory  tube 

Anterior  process  [of  malleus] 

Lateral  process  [of  malleus] 

Short  crus  [of  incus] 

Long  crus  [of  incus] 

Lenticular  process  [of  incus] 

Recessus  sphaericus 

Recessus  ellipticus 

Lateral  semicircular  canal 

Ductus  reuniens 

Semicircular  ducts 

Ductus  cochlearis 

Vestibular  membrane 

Spiral  organ  of  Corti 

Vestibular  ganglion 

Spiral  ganglion  of  cochlea  * 

Common  integument 


BASLE    TERMINOLOGY 

Organon  visus  {continued) 
Tarsus  superior 
Tarsus  inferior 
Septum  orbitale 
Lig.  palpebrale  mediale 
Raphe  palpebralis  lateralis 
Glandulae  tarsales  [Meibomi] 
Ductus  lacrimales 
Ductus  nasolacrimalis 

Organon  auditus 

Auricula 

Fossa  triangularis 

Scapha 

M.  auricularis  anterior 

M.  auricularis  superior 

M.  auricularis  posterior 

Meatus  acusticus  externus 

Paries  tegmentalis 

Paries  jugularis 

Paries  membranacea 

Fissura  petrotympanicus 

Paries  labyrinthica 

Fenestra  vestibuli 

Fenestra  cochleae 

Prominentia  canalis  facialis 

Paries  mastoidea 

Antrum  tympanicurn 

Eminentia  pyramidalis 
Paries  carotica 
Tuba  auditiva 
Processus  anterior  [Folii] 
Processus  lateralis 
Crus  breve 
Crus  longum 
Processus  lenticularis 
Recessus  sphaericus 
Recessus  ellipticus 
Canalis  semicircularis  lateralis 
Ductus  reuniens 
Ductus  semicirculares 
Ductus  cochlearis 

Membrana    vestibularis    [Reiss- 

neri] 
Organon  spirale  [Cortii] 
Ganglion  vestibulare 
Ganglion  spirale  cochleae 

Integumentum  commune  Skin 


OLD    TERMINOLOGY 

The  eye  (continued) 
Superior  tarsal  plate 
Inferior  tarsal  plate 
Palpebral  ligaments 
Internal  tarsal  ligament 
External  tarsal  ligament 
Meibomian  glands 
Lacrimal  canals 
Nasal  duct 

The  ear 

Pinna 

Fossa  of  antihelix 
Fossa  of  helix 
Attrahens  aurem 
Attollens  aurem 
Retrahens  aurem 
External  auditory  meatus 
Roof  of  tympanic  cavity 
Floor  of  tympanic  cavit>- 
Outer  wall 
Glaserian  fissure 
Inner  wall 

Fenestra  ovalis 

Fenestra  rotunda  ^ 
Prominence  of  aqueduct  of 

Fallopius 
Posterior  wall 

Mastoid  antrum 

Pyramid 
Anterior  wall 
Eustachian  tube 
Processus  gracilis 
Processus  brevis 
Short  process 
Long  process 
Os  orbiculare 
Recessus  hemisphericus 
Recessus  hemiellipticus 
External  semicircular  canal 
Canalis  reuniens 
Membranous  semicircular  canals 
Membranous    cochlea    or    scala 

media 
Reissner's  membrane 

Organ  of  Corti 
Ganglion  of  Scarpa 
Ganglion  of  Corti 


SPLANCHNOLOGY. 


Respiratory  apparatus 

Laryngeal  prominence 
Corniculate  cartilages 

Cuneiform  cartilages 
Tubercle  of  epiglottis 
Hyothyroid  membrane 
Lateral  hyothyroid  ligament 
Conus  elasticus 
Middle  cricothyroid  ligament 

Ventricular  folds 
Ventricular  ligament 

Vocal  folds 
Vocal  ligament 

Ventricle  of  the  larynx 

Appendix  of  laryngeal  ventricle 

Rima  glottidis 

Intermembranous  part 
Intercartilaginous  part 

Vocalis  muscle 


Apparatus  respiratorius 

Prominentia  laryngea 
Cartilagines  corniculatae    [San- 

torini] 
Cartilagines  cuneiformes 
Tuberculum  epiglotticum 
Membrana  hyothyreoidea 
Lig.  hyothyreoideum  laterale 
Conus  elasticus 
Lig.  cricothyreoideum  medium 

Plicae  ventriculares 
Lig.  ventriculare 


Plicae  vocales 
Lig.  vocale 


[Mor- 


Ventriculus     laryngis 
gagnii] 

Appendix  ventriculi  laryngis 

Rima  glottidis 

Pars  intermembranacca 
Pars  intercartilaginea 

M.  vocalis 


Respiratory  system 

Pomum  Adami 
■     Cartilages  of  Santorini 

Cartilages  of  Wrisberg 
Cushion  of  epiglottis 
Thyrohyoid  membrane 
Lateral  thyrohyoid  ligament 
Cricothyroid  membrane 
Central     part     of     cricothyroid 

membrane 
Superior  or  false  vocal  cords 
Superior    thyroarytenoid      liga- 
ment 
Inferior  or  true  vocal  cords 
Inferior    thyroarytenoid      liga- 
ment 
Laryngeal  sinus 

Laryngeal  saccule 
Rima  glottidis 

Glottis  vocalis 

Glottis  respiratoria 
Inner  portion  of  Thyroarj'tenoid 


OR  BASLE  ANATOMICAL  NOMENCLATURE 


1353 


BASLli  TEUMINOLOGY 


OLD  TERMINOLOGY 


TERMINOLOGY  ADOPTED  IN  TEXT 

Respiratory  apparatus  {continued)  Apparatus  respiratorius  {continued)  Respiratory  system  {continued) 
Cricothyrcoidcus 
Cricoaryteuoidciis  posterior 
Cricoarytonoidous  latei'alis 
Thyreoaiy  t  acuoidous 
Cupula  of  pleura 
Pulmonary  ligament 
Costal  surface 
Mediastinal  surface 


I\'I.  cricothyreoideus 

M.  cricoarytenoideus  posterior 

M.  cricoarytenoideus  lateralis 

M.  thyreoarytaonoideus 

Cupula  pleurae 

Lig.  pulmonale 

Facios  costalis 

Facios  mediastinalls 


Cricothyroid 
Posterior  cricoarytenoid 
Lateral  cricoarytenoid 
Thyroarytenoid 
Cervical  pleura 
Ligamentum  latum  pulmonis 
External  or  thoracic  surface 
Inner  surface 


Digestive  apparatus 

Mouth 

Glossopalatine  arch 

Pharyngopalatine  arch 

Levator  veli  palatini 

Tensor  veli  i)alatini 

Musculus  uvulae 

Glossopalatinus 

Pharyngopalatinus 

Incisor  teeth 

Premolar  teeth 

Dens  serotinus 

Deciduous  teeth 

Dentin 

Crusta  petrosa 

Root  of  tongue 

Papillae  vallatae 

Apex  of  tongue 

Inferior  surface  of  tongue 

Genioglossus 

Longitudinalis  linguae  superior 

Longitudinalis  linguae  inferior 

Transversus  linguae 

^'erticalis  linguae 

Anterior  lingual  gland 

Accessory  parotid  gland 
Parotid  duct 
Submaxillary  duct 
Smaller  sublingual  duct 
Lai-ger  sublingual  ducts 
Nasal  part  of  pharj-nx 
Pharyngeal  recess 

Palatine  tonsil 
Pterygomandibular  raphe 
Constrictor  pharyngis  inferior 

Constrictor  pharyngis  medius 

Constrictor  pharyngis  superior 


Apparatus  digestorius 

Cavum  oris 
Arcus  glossopalatinus 
Arcus  pharyngopalatinus 
M.  levator  veli  palatini 
M.  tensor  veli  palatini 
M.  uvulae 
M.  glossopalatinus 
M.  pharyngopalatinus 
Dentes  incisivi 
Dentes  praemolares 
Dens  serotinus 
Dentes  decidui 
Substantia  eburnea 
Substantia  ossea 
Radix  linguae 
Papillae  vallatae 
Apex  linguae 
Facies  inferior  linguae 
M.  genioglossus 


Organs  of  digestion 

Oral  or  buccal  cavity 
Anterior  pillar  of  fauces 
Posterior  pillar  of  fauces 
Levator  palati 
Tensor  palati 
Azygos  uvulae 
Palatoglossus 
Palatopharyngcus 
Incisive  or  cutting  teeth 
Biscupid  teeth 
Wisdom  tooth 
Temporary  or  milk-teeth 
Ivory  of  teeth 
Cement  of  teeth 
Base  of  tongue 
Circumvallate  papillae 
Tip  of  tongue 
Under  surface  of  tongue 
Geniohyoglossus 


M.  longitudinalis  linguae  superior  Superior  lingualis 

M.  longitudinalis  linguae  inferior     Inferior  lingualis 

M.  transversus  linguae 

M.  verticalis  linguae 

Gl.  lingualis  anterior  [Blandini, 

Nuhni] 
Glandula  parotis  accessoria 
Ductus  parotideus  [Stenonis] 
Ductus  submaxillaris 
Ductus  sublingualis  major 
Ductus  sublinguales  minores 
Pars  nasalis  pharyngis 
Recessus    pharyngeus     [Rosen- 

muelleri] 
Tonsilla  palatina 
Raphe  pterygomandibularis 
M.    constrictor    pharyngis 

inferior 
M.    constrictor    pharyngis 

medius 
M.    constrictor    pharyngis 

superior 


Transverse  lingualis 
Vertical  lingualis 
Gland  of  Nuhn 

Socia  parotidis 
Stensen's  duct 
Wharton's  duct 
Bartholin's  duct 
Ducts  of  Ri\T[nus 
Nasopharynx 
Fossa  of  Rosenmuller 

Tonsil 

Pterygomandibular  ligament 

Inferior  constrictor 

Middle  constrictor 

Superior  constrictor 


Peritoneum 
Omental  bursa 
Rectouterine  excavation 

Epiploic  foramen 
Lesser  omentum 

Greater  omentum 

Vesicouterine  excavation 
Gastrolienal  ligament 
Phrenicolienal  ligament 
Phrenicocolic  ligament 
Mesenteriole    of    vermiform 
process 

Digestive  tube 
Stomach 
Circular  folds 

Intestinal  glands 

Duodenal  glands 

Solitary  lymphatic  nodules 
Aggregated  Ij-mphatic  nodules 

Vermiform  process 


Peritonaeum 
Bursa  omentalis 
Excavatio  rectouterina  [cavum 

Douglasi] 
Foramen  epiploicum  [Winslowi] 
Omentum  minus 

Omentum  majus 

Excavatio  vesicouterina 
Lig.  gastrolienale 
Lig.  phrenicolienale 
Lig.  phrenicocolicum 
Mesenteriolum  processus  vermi- 
formis 

Tubus  digestorius 
Ventriculus 
Plicae  circulares 

Glandulae  intestinales  [Lieber- 

kuhn] 
Glandulae  duodenales 

(Brunneri) 
Noduli  lymphatici  solitarii 
Noduli   lymphatici   aggregati 

[Peyeri] 
Processus  vermiformis 


Perito7ieum 
Lesser  peritoneal  sac 
Pouch  of  Douglas 

Foramen  of  Winslow 

Small    omentum;    gastrohepatic 

omentum 
Great      omentum;      gastrocolic 

omentuni 
Uterovesical  pouch 
Gastrosplenic  omentum 
Lienorenal  ligament 
Phreno-  or  costocolic  ligament 
Mesoappendix 


Alimentary  canal 
Stomach;  Gaster 
Valvulae  conniventes;  valves  of 

Kerkring 
Crypts  of  Lieberkuhn) 

Brunner's  glands 

Solitarj^  glands 

Beyer's  patches  or  glands 

Vermiform  appendix 


1354    THE  INTERNATIONAL  OR  BASLE  ANATOMICAL  NOMENCLATURE 


TERMINOLOGY  ADOPTED  IN  TEXT 

Digestive  apparatus  (cojilinued) 
Digestive  tube 
Colic  valve 
Right  colic  flexure 
Left  colic  flexure 
Descending  colon   | 
Iliac  colon  j" 

Sigmoid  colon 
Transverse  rectal  folds 
Anal  canal 
Rectal  columns 
Liver 

Inferior  surface 
Left  sagittal  fossa 
Porta  hepatis 
Caudate  lobe 
Caudate  process 
Fibrous  coat 
Pancreatic  duct 
Accessory  pancreatic  duct 

Urogenital  apparatus 

Kidnej's 

Urinary  bladder 

Urethral  crest 

Prostatic  utricle 

Urethral  glands 

Head  of  epididymis 

Tail  of  epididymis 

Sinus  of  epididymis 

Appendix  of  testis 

Appendix  of  epididymis 

Ductus  deferens 

Corpus  cavernosum  urethrae 

Prostate 

Bulbourethral  gland 

Epoophoron 

Vesicular  ovarian  follicles 

Uterine  tube 

Internal  uterine  orifice 

External  uterine  orifice 

Pudendum 

Mons  pubis 

Labia  minora 

External  urethral  orifice 

Bulb  of  the  vestibule 

Greater  vestibular  gland 

Mammae 

Ductless  glands 
Thyroid  gland 
Thymus 
Spleen 

Suprarenal  glands 
Carotid  skeins 
Coccygeal  skein 


BASLE    TERMINOLOGY 

Apparatus  digestorius  (continued) 
Tubus  digestorius 
Valvula  coli 
Flexura  colica  dextra 
Flexura  colica  sinistra 

Colon  descendens 

Colon  sigmoideum 
Plicae  transversales  recti 
Pars  analis  recti 
Columnae  rectales  [Morgagni] 
Hepar 

Fades  inferior 
Fossa  sagittalis  sinistra 
Porta  hepatis 
Lobus  caudatus 
Processus  caudatus 
Capsula  fibrosa  [Glissoni] 
Ductus  pancreaticus  [Wirsungi] 
Ductus  pancreaticus  accessorius 
[Santorini] 

Apparatus  urogenitalis 

Renes 

Vesica  urinaria 
Crista  urethralis 
Utriculus  prostaticus 
Glandulae  urethrales 
Caput  epididymis 
Cauda  epididymis 
Sinus  epididymis 
Appendix  testis  [Morgagni] 
Appendix  epididymis 
Ductus  deferens 
Corpus  cavernosum  urethrae 
Prostata 

Glandula  bulbourethralis  [Cow- 
peri] 
Epoophoron 

Folliculi       oophori       vesiculosi 

[Graafi] 
Tuba  uterina  [Fallopii] 
Orificium  internum  uteri 
Orificium  externum  uteri 
Pudendum  muliebre 
Mons  pubis 
Labia  minora  pudendi 
Orificium  urethrae  externum 
Bulbus  vestibuli 
Glandula  vestibularis  major 

[Bartholini] 
Mammae 


OLD    TERMINOLOGY 

Organs  of  digestion  (continued) 
Alimentary  canal 

Iliocecal  valve 

Hepatic  flexure 

Splenic  flexure 
J  Descending  colon 
(Iliac  colon 

Pelvic  colon 

Houston's  valves 

Anal  canal 

Columns  of  Morgagni 

Liver 

Visceral  surface 

Longitudinal  fissure 

Transverse  fissure  of  liver 

Spigelian  lobe 

Caudate  lobe 

Areolar  coat 

Duct  of  Wirsung 

Duct  of  Santorini 


Glandula  thyreoidea 

Thymus 

Lien 

Glandulae  suprarenalis 

Glomera  carotica 

Glomus  coccygeum 


Urogenital  organs 

Kidneys 

Bladder 

Verumontanum 

Sinus  pocularis 

Glands  of  Littre 

Globulus  major 

Globus  minor 

Digital  fossa 

Hydatid  of  Morgagni 

Pedunculated  hydatid 

Vas  deferens;  seminal  duct 

Corpus  spongiosum 

Prostate  gland 

Cowper's  gland 

Parovarium;    organ    of    Rosen- 

miiller 
Graafian  follicles 

Fallopian  tube;  oviduct 

Internal  os 

External  os 

Vulva 

Mons  Veneris 

Nymphse 

Urinary  meatus 

Vaginal  bulb 

Bartholin's  gland;    commissura 

labiorum  anterior 
Mammary  glands;  breasts 

Ductless  glands 
Thyroid  body 
Thymus  gland 
Spleen 

Adrenal  capsule 
Carotid  body  or  glands 
Coccygeal    gland     or     body; 
Luschka's  gland 


INDEX. 


A 


Abdomen, 1140 

apertures  iu  walls  of,  1147 
boundaries  of,  1147 
fascia  of,  498 

triangular,  502 
lymph  glands  of,  785 
muscles  of,  498 

dissection  of,  498,   503,   504, 
505 
regions  of,  1147 
surface  anatomy  of,  1301 
markings  of,  1303 
Abdominal  aorta,  686 

applied  anatomy  of,  687 
branches  of,  689,  690 
surface  markings  of,  1309 
aortic  plexus,  1004 
muscles,  498 
ring,  deep,  508 
external,  500 
inguinal,  508 
internal,  508 
■wall,  lymphatic  vessels  of,  787 
Abducent  nerve,  927 

applied  anatomy  of,  929 
Abductor    digiti    quinti    muscle 
(foot),  588 
(hand),  554 
hallucis  muscle,  587 
indicis  muscle,  556 
minimi  digiti  muscle,  554 
pollicis  bre^^s  muscle,  552 
longus  muscle,  545 
muscle,  552 
Aberrant  ducts  of  testis,  1236 
Accelerator  urinae  muscle,  518 
Accessory  hemiazygos  vein,  753 
nerve,  944 

applied  anatomj^  of,  945 
cerebral  part  of,  944 
spinal  part  of,  945 
obturator  nerve,  980 
olivary  nuclei,  830 
organs  of  digestive  tube,  1109 

of  eye,  1034 
pancreatic  duct,  1205 
part  of  parotid  gland,  1133 
processes,  205 
pudendal  artery,  704 
sinuses  of  nose,  1014 

applied  anatomy  of,  1015 
spleens,  1267 
thjToid  glands,  1263 
Acetabular  fossa,  339 

notch,  339 
Acetabulum,  340 
Achromatic  spindle,  36 
Acoustic   meatus,    external,    244, 
283,  1046 
development  of,  141 
internal,  241,  291 
nerve,  934,  1046 

applied  anatomy  of,  936 
development  of,  141 
nuclei  of,  836,  935 
Acromiocla^-icular  joint,  411 
applied  anatomy  of,  413 
movements  of,  413 


Acromioclavicular   joint,    surface 

anatomy  of,  1315,  1319 
Acromion,  306 
Acromiothoracic  artery,  670 
Adamantoblasts,  1123 
Adductor  brevis  muscle,  568 

canal,  713  ! 

hallucis  muscle,  589 

longus  muscle,  567 

magnus  muscle,  568 

obliquus  hallucis  muscle,  589 
pollicis  muscle,  554 

pollicis  obliquus  muscle,  554 
transversus  muscle,  554 

transversus  pollicis  muscle,  554 

tubercle,  348 
Adenoid  tissue,  45 
Adipose  capsule  of  kidney,  1209 

tissue,  42 
Adminieulum  lineae  albae,  507 
Adrenal  capsule,  1270 
Adrenalin,  1272 
Afferent  nerves,  803 

vessels  of  kidney,  1214 
After-birth,  101 
Agger  nasi,  260 
Aggregated    Ivmphatic    nodules, 

1175 
Agminated  follicles,  1175 
Air  cells,  ethmoidal,  253,  1014 

mastoid,  240 
Air  sinuses  of  nose,  1014 

of  skull,  196 
Ala  cinerea,  848 

lobuli  centralis,  838 

7iasi,  1008 

OSS.  ilii,  333 
Alae  of  ethmoid,  252 

of  sacrum,  208 

of  vomer,  269 
Alar  cartilages  of  nose,  1009 

lamina,  119 
Alcock,  canal  of,  511 
Alimentary  canal,  1109 
Allantoic  vessels,  93 
Allantois,  93 
Alveolar  arch,  260 

arteries,  640,  641 

border  of  mandible,  272 

canals,  257 

index,  296 

nerves,  918,  923 

point,  260,  296 

process  of  maxilla,  260 
Alveoli,  formation  of,  1124 
j  Alveus,  881,  887 
I  Amacrine  cells  of  retina,  1028 
Amnion,  96 

false,  96 
■  Amniotic  cavity,  96 

ectoderm,  95 

fold,  96 
Amphiarthroses,  381 
Ampulla  of  ductus  deferens,  1235 

rectal,  1183 

of  uterine  tube,  1247 

of  Vater,  1200 
Ampullfe   of  semicircular  canals, 
1058 

of  tubuli  lactiferi,  1259 


Amygdala,  883 
Amygdaline  nucleus,  839 
Anal  canal  or  anal  part  of  rectum, 
1184 
development  of,  172 
lymphatic  vessels  of,  792 
membrane  of,  174 
valves  of,  1184 
fascia,  511 
Anaphase  of  karyokinesis,  36 
Anastomoses  of  arteries,  619 
around  elbow-joint,  675 

knee-joint,  721 
crucial,  717 
Anastomotic    branch    of    inferior 

gluteal  artery,  706 
Anastomotica  magna  of  brachial 
artery,  675 
of  femoral  artery,  718 
Anatomical  neck  of  humerus,  309 
Anconaeus  muscle,  544 
Angiology,  595 
Angle  of  Louis,  218  note 
iridial  or  filtration,  1019 
of  mandible,  273 
of  pubis,  338 
of  rib,  222 
sacro vertebral,  206 
of  sternum,  218 
subscapular,  305 
Angular  arterj^  635 
gyrus,  871 
movement,  383 
vein,  733 
Angulus  Ludovici,  218 
Animal  cell,  33 
Ankle  bone,  366 
Ankle-joint,  449 

applied  anatomj'  of,  452 

movements  of,  451 

relations  of  tendons  and  vessels 

to,  451 
surface  anatomy  of,  1326 
markings  of,  1330 
Annular  ligament,  547,  550 
of  ankle,  584,  585 
of  radius,  422 
of  wrist,  anterior,  547 
posterior,  550 
Annulus  fihrosus  [of  intervertebral 
fibrocartilage],  335,  386 
inguinalis  abdominis,  508 

subcutaneiis,  500 
ovalis,  608 

tendineus  communis,  1035 
Anococcj-geal  body,  1184 
nerves,  992 
raphe,  516 
Ansa  hypoglossi,  957 
lentiformis,  882,  884 
subclavia  [Vieusse^ii],  998 
Anterior    annular  ligament,   547, 
584 
basis  bundle,  815 
calcaneoastragaloid     ligament, 

452 
circumflex  artery,  672 
common  ligament,  384 
condyloid  foramen,  229 
cornu  of  medulla  spinalis,  809 


1356 


INDEX 


Anterior  costovertebral  ligament, 
396 
crural  nerve,  9S0 
inferior  ligament,  448 
intercostal  arteries,  664 
interosseous  artery,  680 

nerve,  965 
ligament,  426 
peroneal  artery,  726 
pillar  of  fauces,  1112 
pillars  of  fornix,  886 
pulmonary  nerves,  943 
radial  carpal  artery,  678 
radioulnar  ligament,  424 
superior  dental  nerve,  919 

ligament,  398,  448 
talotibial  ligament,  450 
temporal  artery.  638 
tibial  nerve,  990 
ulnar  carpal  arterjs  682 
Anteror-lateal  ganglionic  arteries' 
653 
muscles  of  abdomen,  498 
Antero-medial  ganglionic  arteries, 

652 
Antibrachial  fascia,  536 

cutaneous  nerve,  dorsal,  969 
lateral,  963 
medial,  964 
Anticlinal  vertebra,  202  note 
Anticubital  fossa,  672 
Antihelix,  1044 
Antitragicus  muscle,  1046 
Antitragus,  1044,  1145 
Antrum  cardiacum,  1145,  1161 
of  Highmore,  259,  1015 
pyloric,  1162,  1163 
tympanic,  240,  1052 
entrance  to,  1052 
Anus,  1110 

lymphatic  vessels  of,  792 
Aorta,  621    ■ 
abdominal,  686 

applied  anatomy  of,  687 
branches  of,  688 
abdominalis,  686 
arch  of,  623 

applied  anatomy  of,  624 
branches  of,  625 
peculiarities  of,  624 
of  branches  of,  625 
ascendens,  621 
ascending,  621 
bulb  of,  622    ■ 
coarctation  of,  624 
descending,  683 
thoracalis,  683 

rami  mediastinales ,  685 
pericardiaci,  685 
thoracic,  683 

applied  anatomy  of,  683 
branches  of,  685 
transverse,  623 
Aortas,  anterior  ventral,  152 
dorsal,  154 
primitive.  144 
Aortic  arches,  1.52 
bodies,  133,  1274 
hiatus,  495 
isthmus,  154,  623 
lymph  glands,  787 
opening  of  heart,  612 
plexus,  1004 
semilunar  valves,  612 
septum,  150 
sinuses,  612 
spindle,  624 
.    vestibule,  612 
Aorticorenal  ganglion,  1003 
Apertura  pelvis  [minoris]  inferior, 
341 
superior,  340 
tympanica     canaliculi    chordae, 
1049 
Aperture,  anterior  nasal,  294 


Apertures  in  walls  of  abdomen 

1147 
Apex  cordis,  605 
of  fibula,  359 
of  heart,  605 
linguae,  1126 
of  nose,  1008 
OSS.  sacri,  208 
prostatae,  1241 
puhnonis,  1101 
Aponeurosis,  463 
epicranial,  466 
lumbar,  486 

of  obliquus  externus,  499 
palatine,  1112 
palmar,  550 
palmar  is,  550 
pharyngeal,  1143 
plantar,  586 
plantaris,  586 
suprahyoid,  481 
Apparatus  dig estorius,  1109 
lacrimalis,  1041 
respiralorius,  1079 
urogenitalis,  1206 
Appendages  of  testis,  1231 
Appendices  epiploicae,  1157 

vesiculosae,  1247 
Appendicular  artery,  693 

skeleton,  195 
Appendix,  auricular,  left,  610 
right,  606 
ensiform,  220 
of  epididvmis,  1231 
of  testis,  1231 
of  ventricle  of  larynx,  1086 
ventriculi  laryngis,  1086 
vermiform,  1178 
xiphoid,  220 
Applied    anatomy   of  abdominal 
aorta,  687 
of  abducent  nerve,  929 
of  accessory  nerve,  945 
of  acoustic  nerve,  936 
of    acromioclavicular    joint, 

413 
of  adductor  longus  muscle, 

569 
of  ankle-joint,  452 
of  anterior  facial  vein,  733 

tibial  artery,  722 
of  arch  of  aorta,  624 
of  arteries,  619 
of  ascending  pharyngeal  ar- 
tery, 638 
of    atrioventricular    bundle, 

614 
of  auditory  tube,  1056 
of  axilla,  667 
of  axillary  artery,  670 
fascia,  526 
glands,  781 
vein,  750 
of  azygos  veins,  754 
of  biceps  brachii  muscle,  535 
of  bone,  59 
of  bones  of  foot,  375 
of  forearm,  321 
of  hand,  332 
of  leg,  361 
of  pelvis,  344 
of  skull,  297 
of  brachial  artery,  673 

plexus,  970 
of  brain,  899 
of  branches  of  hypogastric  or 

internal  iliac  artery,  708 
of  bulb  of  eye,  1031 
of  carpal  bones,  332 
of  cavernous  sinus,  745 
of  cerebellum,  844 
of  cervical  fascia,  478 
glands,  779 
plexus,  958 
ribs,  226 


Applied  anatomy  of  clavicle,  303 
of   common    carotid    artery 
627 
iliac  artery,  700 
peroneal  nerve,  993 
of  conjunctiva,  1043 
of  coronary  art(!ries,  623 
of  deltoid  muscle,  531 
of  descending  aorta,  683 

palatine  artery,  642 
of  dorsalis  pedis  artery,  724 
of  elbow-joint,  421 
of  emissary  veins,  747 
of   extensor   tendons   of   fin- 
gers, 546 
of  external  acoustic  meatus, 
1048 
carotid  artery,  630 
ear,  1048 
iliac  artery,  708 
jugular  vein,  736 
maxillary  artery,  635 
of  eyelids,  1042 
of  facial  artery,  635 
nerve,  933 
vein,  anterior,  733 
of  fascia  of  axilla,  526 

of  psoas  and  iliacus,  562 
of  femoral  artery,  715 
of  femur,  352 
of  fibula,  361 
of  fingers,  551 

flexor  sheaths  of,  552 
of  gall-bladder,  1116 
of  gluteal  arteries,  70S 
of  gums,  1112 
of  hamstring  tendons,  575 
of  heart,  614 
of     hemorrhoidal     venous 

plexus,  761 
of  hip-joint,  437 
of  humerus,  313 
of  hyoid  bone,  277 
of  hypogastric  artery,  701 
of  hj'poglossal  nerve,  947 
of  iliac  fascia,  562 
of  inferior  epigastric  artery, 
710 
vena  cava,  762 
of  inguinal  and  subinguinal 

glands,  784 
of  innominate  artery,  626 
of  intercostal  arteries,  686 

nerves,  974 
of  internal  capsule,  895 
carotid  artery,  647 
ear,  1068 
iliac  artery,  701 
jugular  vein,  737 
mammary  artery,  666 
of  intervertebral    fibrocartil- 

ages,  386 
of  intestines,  1186 
of  ischiorectal  fossa,  516 
of  kidneys,  1214 
of  knee-joint,  446 
of  labyrinth  of  ear,  1068 
of  lacrimal  apparatus,  1043 
of  laryngeal  nerves,  943 
of  larynx,  1093 
of  lineal  artery,  691 
of  lingual  artery,  6.': 2 
of  liver,  1200 
of  lumbar  plexus,  992 
of  lungs.  1108 
of  lymphatic  system,  770 
of  mammte,  1260 
of  mediastinal  cavitj-,  1101 
of  medulla  oblongata,  833 

spinalis,  820 
of  meninges,  907 
of  mesenteric  arteries,  696 

lymph  glands,  789 
of  metacarpal  bones,  332 
of  metatarsal  bones,  375 


INDEX 


1357 


Applied    anatomy  of   mctatarso- 
phalanseal    joint   of  great  ; 
toe,  459  I 

of  middle  meningeal  artery. 

G40 
of  motor  and  sensory  traets. 

899 
of  muscles,  462 

of  lower  oxtrcmity,  592 
ocular.  1U3.S  1 

of  palate,  1115 
of  upper  extremity,  556 
of  vertebral  column,  492 
of  nasal  cavities,  1015 
of  nose,  1015  | 

of  oculomotor  nerve,  913         ; 
of  a^sophagus,  1146 
of  olfactory  nerves,  909 
of  optic  nerve,  911 
of  ovaries,  1246 
of  palate.  299,  1115 
of  palatine  tonsils,  1141 
of  palmar  aponeurosis,  551 

arches,  682 
of  pancreas,  1206 
of  parametrium,  1255 
of  parathyroid  glands,  1264 
of  patella,  355 
of  pelvis,  344 
of  penis,  1240 
of  pericardium,  603 
of  peritoneal  fossce,  1161 
of  pharynx,  1143 
of  pigment,  46 
of  plantar  arch,  728 

calcaneonavicular         liga- 
ment, 456 
of  pleura,  1098 
of  pons,  836 
of  popliteal  artery,  719 

lymph  glands,  784  _ 
of  portal  system  of  veins,  767 
of  posterior  tibial  artery,  725 
of  pronator  teres  muscle,  537 
of  prostate,  1242 
of   prostatic  venous   plexus, 

761 
of  proximal  radioulnar  artic- 
ulation, 423 
of  psoas  major  muscle,  562 
of  pulmonary  artery,  621 
of  quadriceps  femoris  muscle, 

567 
of  radial  artery,  676 

nerve,  970 
of  radius,  321 

of  recti  muscles  of  eye,  1038 
of  rectus  femoris  muscle,  567 
of  ribs,  225 
of  sacral  plexus,  993 
of  salivary  glands,  1138 
of  saphenous  veins,  747 
of  scalp,  466 
of  scapula,  309 
of  sciatic  or  inferior  gluteal 
artery,  708 
nerve,  993 
of  scrotum,  1230 
of  serratus  anterior  muscle, 

530 
of   sheath   of  psoas  muscle, 

562 
of  shoulder-joint,  417 
of  skull,  297 
of  spermatic  veins,  762 
of  spinal  arteries,  661 
of  spleen,  1270 
of    splenic    or   lienal    artery, 

691 
of  sternoclavicular  joint,  411 
of        sternocleidomastoideus 

muscle,    479 
of  sternum,  225 
of  stomach,  1167 
of  subclavian  artery,  657 


Applied  anatoi^iy  of  .-iuperior  thy- 
roid artery,  631 
vena  cava,  754 
of  suprarenal  glands,  1272 
of  svmpatlietic  nervous  sys- 

tiMu,    1005 
of  tarsal  bones,  375 

j(jints,  457 
of  teeth,  1125 
of  temporal  artery,  63S 
of  temporomandibular  joint, 

39()  I 

of   tendons  of  leg  ami   foot, 
583 
I  of  testis,  1234  | 

'■  of  thoracic  aorta,  683 

duct,  773 
!  nerves,  974 

of  thorax,  226 
of  thymus,  1266 
of  thyroid  gland,  1263 
of  tibia,  361 
of  tongue,  1130,  1132 
of  trachea,  1093 
of    tracheobronchial    glands, 

798 
of  triceps  brachii  muscle,  536 
of  trigeminal  nerve,  925 
of  trochlear  nerve,  914 
of  tvmpanic  cavity,  1056 
of  ulna,  321 
of  ulnar  artery,  680 
of  ureter,  1218 
of  urethra,  1226 
of  urinary  bladder,  1224 
of  uterus,  1254 
of  vagus  nerve,  943 
of  veins  in  front  of  elbow,  749 
of  vena  cava,  inferior,  762 
superior,  754 
mediana  cubiti,  749 
of  vertebral  column,  214 

joints,  393 
of  vesiculae  seminales,  1237 
of  volar  arches,  682 
of  wrist-joint,  426 
Aquaeductus  cerebri,  854 
cochleae,  243,  1060 
Fallojni,  242,  1058 
vestibuli,  242,  280 
Aqueduct,  cerebral,  854 
of  cochlea,  243,  1060 
of  Sylvius,  821,  854 
Aqueous  humor,  1030 
Arachnoid,  903 
granulations,  905 
structure  of,  906 
villi,  905 
Arachnoidea  encephali,  903 

spinalis,  903 
Arantii,  corpus,  610,  612 
Arbor  vitae  [of  cerebellum],  839 

uterina,  1250 
Arch,  alveolar,  260 
of  aorta,  623 

applied  anatomy  of,  624 
branches  of,  625 
peculiarities  of,  625 
of  atlas,  anterior,  199 
axillary,  524 
carotid,  153 
I       crural,  deep,  509 
glossopalatine,  1112 
lumbocostal,  495 
palmar,  deep,  679 
superficial,  682 
pharyngopalatine,  1112 
plantar,  727 
pubic,  341 
of  a  vertebra,  197 
volar,  deep,  679 

superficial,  682 
zygomatic,  282 
Arches,  aortic,  144,  153 
branchial  or  visceral,  108 


Arches  of  fauces,  1112 
of  foot,  459 
of  soft  palate,  1112 
superciliary,  234,  278,  282 
Arcuate  artery,  724 
fibres,  831,  832 
ligaments,  495 
line  of  ilium,  335 
nucleus,  831 
Arcus  aorlae,  623 

cartilaginis  cricoideae,  1081 
glossopalatinus,  1112 
lumbocoslalis  lateralis  [Halleri], 
1  495 

I  medialis  [Halleri],  495 

parieiooccipitalis,  871 
pharyngopalatinus,  1112 
volaris  profundus,  679 
superficialis,  682 
Area  acustica,  848,  935 
cribrosa  media,  241 

superior,  242 
facialis,  242 
olfactory.  111 
oval,  of  Flechsig,  818 
parolfactoria,  875 
pericardial,  87 
postrema,  848 
proamniotic,  87 
Areas  of  cerebral  cortex,  894 
of  Cohnheim,  66 
vascular,  141 
Areola  of  mamma,  1258 
Areolae  of  bone,  57,  58 
Areolar  glands,  1258 

tissue,  40 
Arm  bone,  309 
fascia  of,  534 
muscles  of,  533 
dissection  of.  533 
Arnold's  nerve,  941 
Arrectores  pilorum  muscle,  1077 
Arteria  alveolaris  inferior,  640 
superior  posterior,  641 
angularis,  635 
anonyma,  625 
arcuata,  724' 
auditiva  witerna,  661 
auricularis  posterior,  636 
ramus  auricularis,  636 
occipitalis,  637 
profundus,  640 
axillaris,  668 
basilaris,  661 

rami  ad  pontem,  661 
brachialis,  672 

rami  muscular es,  675 
buccinator ia,  641 
bulbi  urethrae,  705 
canalis  pterygoidei,  642,  648 
carotis  communis,  627 
externa,  630 
interna,  645 

ramus    caroticotympanicus, 
648 
centralis  retinae,  650,  1029 
cerebelli  inferior  anterior,  661 
posterior,  661 
superior,  661 
cerebri  anterior,  651 
media,  652 
posterior,  662 
cervicalis  ascendens,  663 

profunda,  666 
chorioidea,  653 

circumfiexa     femoris     lateralis, 
716 
medialis,  717 
humeri  anterior,  672 

posterior,  671 
ilium  profunda,  710 
superficialis,  716 
scapulae,  671 
coeliaca,  688 
colica  dextra,  694 


1358 


INDEX 


Arteria  colica  media,  694 
sinistra,  695 
collateralis  ulnaris  inferior,  675 

superior,  674 
comes  nervi  phrenici,  664 
comitans  nervi  ischiadici,  706 
communicans  anterior,  652 

posterior,  653 
coronaria  [cordis]  dextra,  622 

sinistra,  623 
cystica,  691 
dorsalis  haUucis,  724 
nasi,  650 
pedis,  724 

ramus  plantaris  profundus, 
725 
epigastrica  inferior,  709 
super jicialis,  715 
superior,  666 
femoralis,  710 

ramz  muscular es,  716 
frontalis,  650 
gastrica  dextra,  689 

sinistra,  688 
gastroduodenalis,  690 
gastroepiploica  dextra,  690 

sinistra,  691 
grenw  media,  720 
suprema,  718 
glutaea  inferior,  706 
ramus  iliacus,  707 
lumbalis,  707 
superior,  707 
haemorrhoidalis  inferior,  704 
media,  701 
swperior,  696 
hepatica,  689 
hypogastrica,  700 
ileocolica,  693 
iliaca  externa,  708 
iliolumhalis,  706 
infraorbitalis,  641 
interossea  communis,  680 
dorsalis.  681 
volar  is,  680 
lahialis  inferior.  634 

superior,  634 
lacrimalis,  649 
laryngea  inferior,  662 

superior,  631 
lienalis,  691 

rami  pancreatici,  691 
lingualis,  631 

rami  dorsales  linguae,  632 
ramus  hyoideus,  632 
malleolaris     anterior     lateralis, 
723 
medialis,  723 
posterior  medialis,  727 
mammaria  interna,  664 
rami  inter costales,  664 
perforantes,  666 
sternales,  664 
masseterica,  641 
maxillaris  externa,  633 

rami  glandulares,  634 
ramus  tonsillaris,  634 
interna,  638 

rami  pterygoidei,  641 
ramus     meningeus     acces- 
sorius,  640 
mediana,  680 
meningea  anterior,  648 

media,  640 
mesenterica  inferior,  694 

superior,  691 
musculophrenica,  666 
nutricia  fibulae,  726 
humeri,  672 
tibiae,  726 
obturatoria,  702 
occipitalis,  635 

rami  musculares,  636 
raynus  auricularis,  636 
descendens,  636 


Arteria   occipitalis,,  ramus  menin- 
geus, 636 
ophthalmica,  648 
palatinu  nsn ndvns,  634 

desa  iiilms,  (142 
pancreulicd  uiagna,  691 
pancreaticoduodenalis  inferior, 
690 
superior,  690 
perforans  prima,  717 
secunda,  717 
<eriia,  717 
pericardiophreiiica,  664 
perinei,  705 
peronaea,  726 

ramus  calcaneus  lateralis,  726 
communicans,  726 
perforans,  726 
pharyngea  ascendens,  637 
rami  pharyngei,  637 
plantaris  lateralis,  727 

medialis,  727 
poplitea,  718 
princeps  cervicis,  636 
hallucis,  728 
poinds,  678 
profunda  brachii,  674 

fe^noris.  716  I 

penis,  705  I 

pudenda  externa  profunda,  716 
super ficialis,  716 
interna,  703 
pulmonalis,  620 
ramus  dexter,  620 
sinister,  621 
radialis,  676 

ra?Mi  musculares,  678 

perforantes,  679 
ramws  carpeus  dorsalis,  678 
volaris,  678 
volaris  super  ficialis,  678 
recurrens  radialis,  678 
tibialis  anterior,  723 
posterior,  724 
recurrentes  ulnaris  anterior,  680 

posterior,  680 
sacralis  lateralis,  707 

media,  698 
sphenopalatina,  642 
spinalis  anterior,  660 

posterior,  660 
sternocleidomastoidea,  636 
stylomastoidea,  636 
subclavia,  655 
sublingualis,  632 
submentalis,  634 
sub  scapular  is,  671 
supraorbitalis,  649 
tarsea  lateralis,  724 
temporalis  media,  638 
superficialis,  637 

rami  auriculares  anteriores, 

638 
ramus  frontalis,  638 
parietalis,  638 
thoracalis  lateralis,  671 

suprema,  670 
thoracoacrornialis ,  670 
thyreoidea  ima,  626 
inferior,  662 

rami  oesophagei,  663 
tracheales,  662 
superior,  631 

ramus      cricothyreoideus , 
631 
hyoideus,  631 
sternocleidomastoideus. 
631 
tibialis  anterior,  722 

rami  musculares,  723 
posterior,  725 

rami  calcanei  medialis,  727 
ramus  communicans,  727 
transversa  colli,  663 

ramus  ascendens,  664 


Arteria     transversa    colli,    ramus 
descendens,  664 

faciei,  638 

scapulae,  663 
tympanica  anterior,  639 

inferior,  637 
ulnaris,  679 

ra?ni  musculares,  682 

ramus   carpeus  dorsalis,  682 
volaris,  682 
volaris  prefundus,  682 
urethralis,  705 
uterina,  701 
vaginalis,  702 
vertebralis,  659 

rami  spinales,  660 

ramus  meningeus,  660 
vesicalis  inferior,  701 

medialis,  701 

superior,  701 
volaris  indicis  radialis,  679 
Arteriae  bronchiales,  685 
ciliares,  650 
digitales  volares  communes,  682 

propriae,  682 
gastricae  breves,  691 
genw  inferiores,  721 

superior  es,  720 
iliacae  communes,  698 
inter  costales,  685 
intestinales,  692 
lumbales,  698 
metacarpeae  volares,  679 
metatarseae  plantares,  728 
oesophageae,  685 
ovaricae,  697 
palpebrales  jnediales,  650 
phrenicae  inferiores,  697 
propriae  renales,  1213 
rectae,  1214 
renales,  696 
sigmoideae,  695 
spermaticae  internae,  697 
suprarenales  media,  696 
surales,  720 
tarseae  mediates,  724 
tunica  adventitia,  597 

intitna,  596 

media,  596 
Arterial  mesocardium,  603 
Artery    or   Arteries,     abdominal 

aorta,  686 
accessory  pudendal,  704 

meningeal,  640 
acromiothoracic.  670 
alveolar,  640,  641 
anastomoses  of,  619 
anastomotic  branch  of  inferior 

gluteal,  706 
anastomotica    magna,  of    bra- 
chial, 675 
of  femoral,  718 
angular,  635 
anterior  cerebral,  651 

choroidal,  653 

ciliary,  650 

communicating,  651 

humeral  circumflex,  672 

inferior  cerebellar,  661 

meningeal,  648 

spinal,  660 

tibial,  722 

tympanic.  639 
antero-lateral  ganglionic,  653 
antero-medial  ganglionic,  652 
aorta,  622 

abdominal,  686 

arch  of,  623 

ascending,  622 

descending.  683 

thoracic,  683 
appendicular,  693 
applied  anatomy  of,  619 
arcuate,  724 
articular,  720,  721 


INDEX 


1359 


Artery  or  Arteries,  ascending  cer- 
vical, 6(53 

palatine,  634 

pharyngeal,  637 
auditory,  661 

internal,  661 
auricular,  anterior,  638 
deep,  6-40 

of  occipital,  637 

posterior,  636 
axillary,  668 
azygos,  of  knee,  720 

of  vagina,  702 
basilar,  661 
brachial,  672 
brachiocephalic,  625 
of  brain,  653 
bronchial,  685,  1108 
buccal,  641 
buccinator,  641 
bulbar,  661 
calcaneal,  726,  727 
calcanean,  726,  727 
capsular,  middle,  696 
caroticotympanic,  648 
carotid,  common,  627 

external,  630 

internal,  645 
carpal,  dorsal,  678 

radial,  678 

ulnar,  682 

volar,  678,  682 
cavernous,  648 
cecal,  of  ileocolic,  693 
central",  of  retina,  650,  1029 
cerebellar,  661 
cerebral,  anterior,  651 

middle,  652 

posterior,  662 
of  cerebral  hemorrhage,  653 
cer\dcal,  ascending,  663 

deep,  666 

superficial,  664 

transverse,  663 
choroid,  653 
choroidal,  653,  662 
ciliary,  650 
circle  of  Willis,  653 
circumflex,  femoral,  716,  717 

humeral,  671,  672 
coccygeal    of    inferior    gluteal, 

706 
cochlear,  1068 
coeliac,  688 
colic,  694,  695 
comitans  ner\a  ischiadici,  706 

plirenici,  664 
common  carotid,  627 

iliac,  698 

interosseous,  680 
communicating,  anterior,  651 

of  dorsalis  pedis,  725 

posterior,   653 
coronary,  of  heart,  622 

of  lips,  634 

of  stomach,  688 
of   corpus   cavernosum,    penis, 

705 
costocervical  trunk,  666 
cremasteric,  709 
cricothyroid,  631 
cjrstic,  691 
deep  auricular,  640 

epigastric,  709 

external  pudendal,  716 

iliac  circumflex,  710 

palmar  arch,  679 

of  penis,  703 

plantar,  725 

temporal,  641 

volar  branch  of  ulnar,  682 
dental,  inferior,  640 

posterior,  641 
descending  aorta,  683 

development  of,  141,  151 


Artery    or    Arteries,    descending 
liranch  of  occipital,  636 

palatine,  642 
digital,  foot,  728 

hand,  682 

volar,  682 
distribution  of,  619 
dorsal  carpal  of  radial,  678 
of  ulnar,  682 

interosseous,  681 

metacarpal,  678 

nasal,  650 

of  penis,  706 
dorsales  linguae,  632 
dorsalis  hallucis,  724 

pedis,  724 

scapulae,  671 
of  ductus  defei'ens,  701 
epigastric,  deep  or  inferior,  709 

superficial,  715 

superior,  666 
ethmoidal,  650 
external  carotid,  630 

iliac,  708 

maxillary,  633 

plantar,  727 

pudendal,  716 
facial,  633 

transverse,  638 
femoral,  710 

circumflex,  716,  717 
fibular,  723 
frontal,  650 

ganglionic,  652,  653,  662 
gastric,  688,  689,  691 
gastroduodenal,  690 
gastroepiploic,  690,  691 
genicular,  718,  720,  721 
gluteal,  706,  707 
of  head  and  neck,  626 
helicine,  1240 
hemorrhoidal,  inferior,  704 

middle,  701 

superior,  696 
hepatic,  688 
highest  genicular,  718 

intercostal,  666 

thoracic,  670 
humeral  circumflex,  671,  672 
hypogastric,  700 

obliterated,  700 
ileal,  of  ileocolic,  693 
ileocolic,  693 

iliac  circumflex,  deep,  710 
superficial,  716 

common,  698 

external,  70S 

internal,  700 
iliolumbar,  706 
inferior  alveolar,  640 

articular  of  knee,  721 

cerebellar,  661 

epigastric,  709 

gluteal,  706 

hemorrhoidal,  704 

labial,  634 

laryngeal,  662 

mesenteric,  694 

pancreaticoduodenal,  692 

phi'enic,  697 

profunda,  674 

thyroid,  662 

tympanic,  637 

ulnar  collateral,  675 
infrahyoid,  631 
infraorbital,  641 
infrascapular,  671 
innominate,  625 
intercostal,  685,  686 

branches    of   internal    mam- 
mary, 664 

highest,  666 

superior,  666 
interlobular,  of  kidney,  1213 
internal  auditory;  661,  1068 


Artery  or  Arteries,  internal  caro- 
tid, 645 

iliac,  700 

mammary,  664 

maxillary,  638 

plantar,  727 

pudendal  or  pudic,  703 

spermatic,  697 
interosseous,  common,  680 

anterior,  680 

dorsal,  681 

palmar,  679 

posterior,  681 

volar,  680 
intestinal.  692 
labial,  634 
of  labyrinth,  1068 
lacrimal,  649 
laryngeal,  inferior,  662 

superior,  631 
lateral  calcaneal,  726 

femoral  circumflex,  716 

nasal,  635 

palpebral,  649 

sacral,  707 

tarsal,  724 
left  colic,  695 

gastric,  688 

gastroepiploic,  691 
lienal,  691 
lingual,  631 

deep,  632 
long  ciliary,  650 

thoracic,  671 
of  lower  extremitj^  710 
lumbar,  698 
malleolar,  723 

internal,  727 
mammary,  internal,  664 
masseteric,  641 
maxillary,  external,  633 

internal,  638 
medial  palpebral,  650 
mediana,  680 
mediastinal,  from  aorta,  685 

from  internal  mammarj%i664 
medidural,  640 
medullarj-,  661 
meningeal,  accessory,  640 

anterior,  648 

of  ascending  pharj^ngeal,  637 

middle,  640 

of  occipital,  636 

small,  640 

of  vertebral,  660 
mesenteric,  inferior,  694 

superior,  691 
metatarsal,  724 
middle  cerebral,  652 

genicular,  720 

hemorrhoidal,  701 

meningeal,  640 

sacral,  698 
mode  of  division  of,  619 

of  origin  of  branches,  619 
musculophrenic,  664 
mylohyoid,  641 
nasal,  650 

dorsal,  650 

lateral,  635 
nasopalatine,  642 
nerves  of,  598 
obturator,  702 
occipital,  635 
oesophageal  of  aorta,  685 

of  inferior  thjToid,  663 
•    ophthalmic,  648 
ovarian,  697 
palatine,  ascending,  634 

of  ascending  pharyngeal,  637 

descending,  642 
palmar  arch,  deep.  679 

superficial,  682 
palpebral,  649,  650 
internal,  650 


1360 


INDEX 


Artery  or  Arteries,  pancreatic,  of 
lienal,  G91 
pancreaticoduodenal,  690 
pai-\ddural,  G40 
perforating,  of  foot,  728 
of  hand,  679 

of  internal     mammary,    666 
of  thigh,  717 
pericardiac,  064,  085 
pericardiacophrenic,  004 
perineal,  705 

superficial,  705 
pei'oneal,  726 

anterior,  726 
pharyngeal,  ascending,  637 

of  internal  maxillary,  642 
phrenic,  inferior,  697 

superior,  686 
plantar,  727 

deep,  725 

lateral  (external),  727 

medial  (internal),  727 

metatarsal,  728 
pontine,  661 
popliteal,  718 
posterior  auricular,  636 

cerebral,  662 

communicating,  653 

humeral  circumflex,  671 

inferior  cerebellar,  661 

meningeal,    from    vertebral, 
660 

scapular,  604 

scrotal,  705 

superior  alveolar,  641 

tibial,  725 
postero-medial  ganglionic,  653, 

662 
princeps  cervicis,  636 

pollicis,  678 
profunda,  674 

brachii,  674 

cervicalis,  666 

femoris,  716 

linguae,  632 

superior,  674 
of  pterygoid  canal,  642,  648 
pudendal,  external,  716 

internal,  703 

in  female,  706 

in  male,  703 
pudic,  external,  710 

internal,  703 
pulmonary,  620 
pyloric,  089 
radial,  676 

recurrent,  678 
radialis  indicis,  679 
ranine,  632 
recurrent,  of  hand,  679 

interosseous,  682 

radial,  078 

tibial,  722,  723 

ulnar,  680 
renal,  696 
right  colic,  094 

gastric,  689 

gastroepiploic,  691 
sacral,  lateral,  707 

middle,  698 
scapular  circumflex,  671 

posterior,  664 

transverse,  663 
sciatic,  706 
scrotal,  posterior,  705 
sheaths  of,  597 
short  ciliary,  650 

gastric,  691 
sigmoid,  095 
spermatic,  097 

external,  709 

internal,  097 
sphenopalatine,  042 
spinal,  660 
splenic,  691 


Artery  or  Arteries,  sternal,  660 
sternocleidomastoid,  631,  636 
steniouKif^toid,  631,  636 
striate,  653 
structure  of,  596 
stylomastoid,  636 
subclavian,  655 
subcostal,  086 
sublingual,  632 
submaxillary,  634 
submental,  634 
subscapular,  671 
superficial  cervical,  004 
epigastric,  715 
external  pudendal,  710 
iliac  circumflex,  716 
palmar  arch,  682 
temporal,  637 
volar,  678 
arch,  682 
superior     articular,    of    knee 
720 
cerebellar,  661 
epigastric,  666 
gluteal,  707 
hemorrhoidal,  696 
intercostal,  666 
labial,  634 
laryngeal,  631 
mesenteric,  691 
phrenic,  686 
profunda,  674 
thoracic,  670 
thyroid,  031 
tympanic,  640 
ulnar  collateral,  674 
vesical,  701 
superhyoid,  632 
supraorbital,  049 
suprarenal,  696,  697,  698 
suprascapular,  663 
sural,  720 

systemic  distribution  of,  619 
tarsal,  724 
temporal,  038 
deep,  041 
middle,  638 
superficial,  037 
thoracic,  670,  671 
aorta,  683 
axis,  670 
highest,  670 
lateral,  671 
superior,  670 
thoracoacromial,  670 
thyreoidea  ima,  626 
thyrocervical  trunk,  662 
thyroid  axis,  662 
inferior,  662 
superior,  631 
tibial,  anterior,  722 
posterior,  725 
recurrent,  723 
tonsillar,  634 
transversa  colli,  063 
transverse  cervical,  663 
facial,  638 
perineal,  705 
scapular,  603 
transversalis  colli,  663 
of  trunk,  683 
tympanic,  037,  639,  640 
ulnar,  679 

recurrent,  680 
umbilical,  in  fetus,  616 
of  upper  extremity,  055 
urethral,  705 
of  urethral  bulb,  705 
uterine,  701 
vaginal,  702 
vasa  aberrantia,  673 
brevia,  691 
intestini  tenuis,  692 
vertebral,  059 
vesical,  701 


Artery    or    Arteries,    vestibular, 
1008 
Vidian,  642,  648 
volar  arch,  deep,  679 
superficial,  682 
carpal,  678 
digital,  common,  682 
interosseous,  680 
metacarpal,  679 
proper,  682 
volaris  indicis  radialis,  679 
Arterioles,  595 
Arthrodia,  382 
Articular  arteries,  720,  721 
capsules,  379 
cartilage,  48 

disk  of  acromioclavicular  joint, 
412 
of  distal  radioulnar  joint,  377 
of  sternoclavicular  joint,  410 
of  temporomandibular  joint, 
395 
end  bulbs,  1069 
lamella  of  bone,  379 
meniscus,  395 
processes  of  vertebrae,  197 
tubercle  of  temporal  bone,  237, 
280 
Articulatio    acromioclavicularis, 
411 
atlantoepistrophica,  388 
calcaneocuboidea,  454 
coxjue,  432 
cubiti,  418 

cuneonavicular  is,  456 
ellipsoidea,  382 
genu,  438 
humeri,  414 
mandibularis ,  393 
radiocarpea,  425 
radioulnaris,  422 
distalis,  423 
proximalis;  422 
sacroiliaca,  404 
sellaris,  382 
sternoclavicularis,  409 
talocalcanea,  452 
talocalcaneonavicular  is,  454 
talocruralis ,  449 
tibiofibularis ,  448 
trochoidea,  382 
Articulation  or  Articulations,  379 
acromiocla-vricular,  411 
amphiarthroses,  381 
of  ankle,  449 
atlantooccipital,  392 
of  atlas  with  axis  or  epistro- 
pheus, 388 
with  occipital  bone,  392 
calcaneocuboid,  454 
calcaneonavicular,  455 
of    calcaneus    and    astragalus, 
452 
with  the  cuboid,  454 
carpometacarpal,  429 
of  carpus,  427 
of  cartilages  of  ribs  with  each 

other,  401 
classification  of,  380 
condyloid,  382 
costocentral,  396 
costochondral,  401 
costosternal,  399 
costotransverse,  397 
costovertebral,  396 
coxal,  432 

cuboideonavicular,  455 
cuueocuboid,  457 
cuneonavicular,  450 
diarthroses,  381 
of  digits,  431,  549 
of  elbow,  418 
gomphosis,  381 
of  hip,  432 
humeral,  414 


INDEX 


1361 


Articulation  or  Art  icul;it  ions,  im- 
movable, 3S0 

inferior,  423 

iatercari)al,  -427 

intcrchondral,  -101 

intercuneiform,  457 

intermetacarpal,  430 

intermctatarsal,  45S 

inter  tarsal,  452 

of  knee,  438 

of  lower  extri'mity,  432 

of  mandilile,  393 

metacarpophalangeal,  430 

metatarsophalangeal,  459 

movable,  381 
freely,  381 
slightly,  381 

movements  of,  383 

of    navicular    with    cuneiform 
bones,  456 

of  pelvis,  404 

with  vertebral  column,  403 

of  phalanges  of  foot,  459 
of  hand,  431 

of  pubic  bones,  406 
symphysis,  406 

radiocarpal,  425 

radioulnar,  distal,  423 
proximal,  422 

by  reciprocal  reception,  382 

sacrococcygeal  symphysis,  406 

sacroiliac,  404 

of  sacrum  and  coccyx,  406 

scapuloclavicular,  411 

schindylesis,  381 

shoulder,  414 

sternoclavicular,  409 

sternocostal,  399 

of  sternum,  401 

sutura,  380,  381 

symphysis,  381 
pubis,  406 

synarthroses,  380 

synchondrosis,  381 

syndesmosis,  381 

talocalcaneal,  453 

talocalcaneonavicular,  454 

talocrural,  449 

tarsometatarsal,  457 

of  tarsus,  452 

temporomandibular,  393 

tibiofibular,  448 
syndesmosis,  448 

tibiotarsal,  449 

of  trunk,  384 

of  upper  extremity,  409 

of  vertebra)  arches,  386 
bodies,  384 
column,  384 

with  cranium,  392 
with  pelvis,  403 

of  wrist,  425 
Articulationes  capitulorum,  396 

carpometacarpeae,  429 
pollicis,  429 

costotransversariae,  397 

costovertebrales,  396 

digitorum  manus,  431 
pedis,  459 

intercarpeae,  427 

interchondrales,  401 

intermetacarpeae,  430 

intermetatarseae,  458 

intertarseae,  452 

tnetatarsophalangeae,  459 

ossiculorum  auditus,  1054 

sternorostaleis,  399 

tarsometatanieae,  457 
Aryepiglottic  fold,  1085 
Aryepiglotticus  muscle,  1089 
Ar\-taenoideus  muscle,  1088 
Ar\-tenoid  cartilages,  1081 

glands,  1090 

swellings,  177 
Ascending  aorta,  621 

86 


Ascending  cervical  artery,  664 
colon,  ilSO 

frontal  convolution,  869 
lumbar  vein,  753 
oblique  muscle,  503 
palatine  artery,  634 
parietal  convolution,  871 
pharyngeal  artery,  637 

applied  anatomy  of,  638 
ramus  of  ischium,  337 
of  OS  pubis,  337 
Association     fibres     of     cerebral 
hemispheres,  890 
neurons,  811 
Asterion,  282,  296 
Astragalus,  366 

ossification  of,  374 
Atavistic  epiphyses,  59 
Atlantooccipital  articulation,  392 
Atlas,  199 

development  of   anterior  arch 

of,  104 
ossification  of,  210 
Atresia,  congenital,,  of  pupil,  136 
Atria  of  bronchi,  1106 
Atrial  canal,  145 
Atrioventricular   bundle   of   His, 
614 
groove  of  heart,  604 
opening,  left,  611 
right,  609 
Atrium  dextrum,  606 
of  heart,  left,  610 
primitive,  145 
right,  606 
of  nasal  fossa,  1011 
sinistrum,  610 
Attic  or  epitympanic  recess,  240, 

1049 
Attolens  aurem  muscle,  1045 
Attraction  sphere,  34 
Attrahens  aurem  muscle,  1045 
Auditory  artery,  661 
internal,  661 
canal,  external,  1046 
meatus,  external,  1046 
nerve,  934 
ossicles,  1053 

development  of,  140 
pit,  138 
plate,  138 

teeth  of  Huschke,  1065 
tube,  1052 

cartilaginous  portion  of,  1052 
isthmus  of,  1053 
osseous  portion  of,  1052 
pharyngeal  ostium  of,  1189 
tonsil  of,  1053 

torus  tubarius  or  cushion  of, 
1052,  1140 
veins,  1068 
vesicle,  138 
Auerbach's  plexus,  1176 
Auricle,  left,  610 

right,  606 
Auricula  dextra,  606 
of  ear,  1044 

cartilage  of,  1044 
development  of,  141 
ligaments  of,  1044 
muscles  of,  1045 
vessels  and  nerves  of,  1046 
of  heart,  left,  610 

right,  606 
sinistra,  610 
Auricular  appendix,  left,  610 
right,  606 
artery,  anterior,  638 
deep,  640 
of  occipital,  636 
posterior,  636 
lymph  glands,  774 
nerves,  anterior,  923 
great,  956 
posterior,  933 


Auricular  nerves  of  vagus,  941 

point,  296 

surface  of  ilium,  335 
of  sacrum,  208 

tubercle  of  E)arwin,  1044 

vein,  jiosterior,  734 
Auricuhiris  inustdes,  1045 
Auriculotemporal  nerve,  923 
Auriculoventricular  groove,  604 
Auris  interna,  1057 
Auscultation,  triangle  of,  524 
Axes  of  pelvis,  342 
Axial  filament  of  spermatozoon, 
81 

skeleton,  195 
Axilla,  667 

applied  anatomy  of,  667 

dissection  of,  525 

fascia  of,  526 
Axillary  arch,  524 

artery,  668 

applied  anatomy  of,  669 

branches  of,  670 

surface  markings  of,  1318 

lymph  glands,  780 

nerve,  961 

sheath,  668 

vein,  750 

applied  anatomy  of,  750 
Axis,  cojliac,  688 

of  lens,  1031 

optic,  1017 

thoracic,  670 

thyroid,  662 

vertebra,  200 

ossification  of,  210 
Axis-cylinder  process,  71 
Axon  of  nerve  cells,  71 
Azj^gos  arteries  of  vagina,  702 

artery,  articular,  720 

uvulae  muscle,  1114 

vein,  753 

applied  anatomy  of,  754 


B 


Back,  muscles  of,  deep,  485 

dissection  of,  485 
Baillarger,  band  of,  883,  891 
Ball-and-socket  joint,  382 
Band  of  Baillarger,  883,  891 

of  Bechterew,  893 

of  Gennari,  893 

of  Giacomini,  875 

iliotibial,  563 

moderator,  610 
Bare  area  of  liver,  1151 
Bartholin,  duct  of,  1137 

glands  of,  190,  1258 
Basal  column,  posterior,  813 

knobs  of  Englemann,  38 

lamina,  119 

optic  nucleus  of  Meynert,  861 

plate  of  placenta,  100 

ridge,    or    cingulum    of    tooth, 
1117 

vein,  740 
Base  of  cerebral  peduncle,  849 

of  heart,  605 

of  sacrum,  208 

of  skull,  inferior  surface,  278 
upper  surface  of,  288 
Basement  membranes,  45 
Basiphromatin,  34 
Basihyal  of  hyoid  bone,  275 
Basilar  artery,  661 

crest,  1064 

membrane,  1065 

part  of  occipital  bone,  230 

plexus,  746 

sinus,  746 
Basilic  vein,  748 
median,  747 
Basion,  281,  296 


1362 


INDEX 


Basis  bundle,  anterior,  815 
lateral,  817 
cordis,  605 
OSS.  sacri.  208 
pedunculi,  849 
prostatae,  1241 
pulmonis,  1102 
Basivertebral  veins,  755 
Basket  cells  of  cerebellum,  642 
Bechterew,  band  of,  893 

nucleus  of,  836,  935 
Bed  of  stomach.  1163 
Bell,  nerve  of,  957,  960 
Bellini,  duct  of,  1212 
Bertin,  ligament  of,  433 
Betz,  giant  cells  of,  891 
Biceps  brachii  muscle,  534 
femoris  muscle,  574 
flexor  cubiti  muscle,  534 
muscle,  534 
Bicipital  fascia,  535 
groove,  311 
ridges,  311 
Bicuspid  teeth,  1118 

valve,  612 
Bigelow,   Y-shaped  ligament  of, 

433 
Bile  capillaries,  1198 
ducts,  1198,  1200 
structure  of,  1200 
Bipolar  cells  of  retina,  1028 
Bird's  nest  of  cerebellum,  839 
Biventer  cervicis  muscle,  489 
Biventral  lobes  of  cerebellum,  839 
Bladder,  1218 
gall,  1199 
urinary,  1218 

applied  anatomy  of,  1224 
in  child,  1220 
development  of,  188 
distended,  1219 
empty,  1218 
female,  1221 
interior  of,  1222 
ligaments  of,  1221 
lymphatic  vessels  of,  793 
structure  of,  1223 
trigone  of,  1222 
vessels  and  nerves  of,  1223 
Blandin,  glands  of,  1131 
Blastodermic  vesicle,  85 
Blastopore,  86 
Blood,  composition  of,  61 
corpuscles,  61 

development  of,  141 
origin  of,  192 
course  of,  in  an  adult,  595 

in  fetus,  616 
liquor  sanguinis,  61 
plasma,  61 
platelets,  64 
Blood  islands,  142 
Bochdalek,  cornucopia  of,  846 
Body    or    Bodies,    anococcygeal, 
1184 
aortic,  of  Zuckerkandl,  1274 
carotid,  1273 

cavities,  development  of,  178 
ciliary,  1023 
coccygeal,  1273 
geniculate,  858 
Malpighian,  of  kidney,  1212 

of  spleen,  1268 
olivary,  824 
of  penis,  1239 
perineal,  1184 
pituitary,  861 
polar,  79 
restiform,  841 
of  stomach,  1163 
thyroid,  1261 
trapezoid,  835 
of  uterus,  1249 
of  a  vertebra,  197 
Body-stalk,  92,  96 


Bone  or  Bones,  50 
ankle,  366 

applied  anatomy  of,  59 
arm,  309 

articular  lamella  of,  379 
astragalus,  366 
atlas,  199 
axis,  200 
breast,  216 
calcaneus,  362 
calf,  359 
canaliculi  of,  54 
cancellous  tissue  of,  50 
capitate,  327 
carpal,  323 
cells,  55 

chemical  composition  of,  55 
classes  of,  viz  ,  long,  flat,  mixed 

or  irregular,  short,  195 
clavicle,  307 
coccyx,  209 
collar,  301 

compact  tissue  of,  50 
cranial,  227 
cuboid,  367 
cuneiform,  of  carpus,  324 

of  tarsus,  369 
diploe  of,  196 
of  ear,  1053 
of  elbow,  314 
eminences  and  depressions  of, 

196 
epistropheus,  200 
ethmoid,  251 
ethmoidal,  251 
facial,  255 
femur,  345 
fibula,  359 
flat,  196 
of  foot,  362 
frontal,  233 
hamate,  328 
of  hand,  323 
Haversian  canals  of,  53 

systems  of,  53 
hip,  333 
humerus,  309 
hyoid,  275 
ilium,  333 
incus,  1054 

inferior  nasal  conchse,  268 
innominate,  333 
interparietal,  231 
ischium,  336 
lacrimal,  263 

lesser,  263 
lacunae  of,  54 
lamellae  of,  54 
lingual,  275 
long,  195 
of  lower  extremity,  333 

jaw,  271 
lunate,  323 
lymphatics  of,  53 
malar,  263 
malleus,  1053 
mandible,  271 
marrow  of,  51 
maxillae,  256 
medullarj'^  artery  of,  52 

membrane  of,  51 
metacarpal,  329 
metatarsal,  371 
minute  anatomy  of,  53 
multangular,  greater,  326 

lesser,  327 
nasal,  255 
navicular,  of  carpus,  323 

of  tarsus,  368 
nerves  of,  52 
number  of,  in  body,  195 
nutrient  artery  of,  52 
occipital,  227 
OS  calcis,  362 

coxae,  333 


Bone  or  Bones,  os  magnum,  327 

ossification  of,  56 

palate,  265 

palatine,  265 

parietal,  231 

patella,  354 

pelvic,  340 

perforating  fibres  of,  54 

periosteum  of,  51 

phalanges  of  foot,  373 
of  hand,  337 

pisiform,  326 

pubis,  337 

radius,  319 

ribs,  220 

sacrum,  206 

scaphoid,  323,  368 

scapula,  304 

semilunar,  323 

sesamoid,  376 

shin,  355 

short,  196 

sphenoid,  245 

sphenoidal,  245 
conchae,  250 

stapes,  1054 

sternum,  216 

structure    and    physical    prop- 
erties of,  50 

surfaces  of,  196 

sutural,  255 

talus,  366 

tarsal,  362 

temporal,  237 

thigh,  345 

tibia,  355 

trapezium,  326 

trapezoid,  327 

triangular,  324 

turbinated,  268 

ulna,  314 

unciform,  328 

of  upper  extremity,  301 
jaw,  256 

vertebra  prominens,  201 

vertebrae,  cervical,  198 
lumbar,  204 
thoracic,  201 
sacral  and  coccygeal,  205 

vessels  of,  52 

vomer,  269 

Wormian,  255 

zygomatic,  263 
Bowman,  capsule  of,  1212 

glands  of,  1012 

membrane  of,  1020 

muscle  of,  1023 
Brachia     conjunctiva     of     cere- 
bellum, 841 

of  corpora  quadrigemina,  853 

pontis,  841 
Brachial  artery,  672 

applied  anatomy  of,  673 
branches  of,  674 
peculiarities  of,  672 
surface  marking  of,  1321 

cutaneous  nerve,  lateral,  962 
medial,  964 
posterior,  969 

fascia,  534 

plexus,  958 

applied  anatomy  of,  970 

veins,  750 
Brachialis  anticus  muscle,  535 

muscle,  535 
Brachiocephalic  artery,  625 

veins,  751 
Brachioradialis  mxiscle,  542 
Brain;  arteries  of,  653 

commissures  of,  856 

development  of,  120 

dissection  of,  821 

divisions  of,  821 

dura  of,  900 

meninges  of,  900 


INDEX 


1363 


1154, 


Brain,  pia  of,  906 

surface  inarkings  of,  1280 

veins  of.  789 

weight  of,  894 
Branchial  arches,  108 

Kruoves,  108 
Breadth  index  of  skull,  296 
Breast  bone,  216 
Breasts  or  manima\  1258 

development  of,  116 
Bregma,  238,  277,  296 
Bregmatic  fontanelle,  294 
Bridge  of  nose,  1008 
Brim  of  pelvis,  340 
Broad  ligaments  of  uterus, 

1250 
Broca,  cap  of,  870 

gyrus  of,  870 

limbic  lobe  of,  873 

parolfactory  area  of,  874 
Bronchi,  1091 
Bronchial  arteries,  685,  1108 

nerves,  943 

veins,  754,  1108 
Bronchomediastinal  trunks,  798 
Bronchus  dextra,  1092 

divisions  of,  1105 

eparterial,  1105 

hyparterial,  1105 

intrapulmonarv,  1106 

left,  1092 

right,  1092 

sinister,  1092 
Brunner's  glands,  1175 
Bryant's  triangle,  1330 
Buccal  artery,  641 

branches  of  facial  nerve,  933 

cavity,  1110 

glands,  1111 

nerve,  long,  922 
Buccinator  artery,  641 

muscle,  470 

nerve,  922 
Bucconasal  membrane,  112 
Buccopharyngeal  fascia,  477 

membrane,  86 
Bulb  of  aorta,  622 

of  corpus cavernosum  penis,  1238 

of  eye,  1017 

olfactory,  874,  893 

of  posterior  cornu,  879 

spinal,  822 

vaginal,  1257 

of  vestibule,  1257 
Bulbar  arteries,  661 
Bulbocavernosus  muscle,  518,  520 
Bulbourethral  glands  of  Cowper, 

190,  1243 
Bulbs  of  internal  jugular  vein,  736 
Bulbus  cordis,  145 

oculi,  1017 

olfactorius,  874 

vestibuli,  1257 
Bulla  ethmoidalis,  294,  1011 
Bundle  of  His,  69 

oval,  119 

of  Vicq  d'Azyr,  857,  860,  886 
Burdach,  tract  of,  808,  817 
Burns'  space,  477 
Bursa,  omental,  1152,  1155 
development  of,  170 

omenialis,  1155 

pharyngeal,  1139 

prepatellar,  566 
Bursce    beneath     glutaeus    maxi- 
mus,  570 

mucosae,  380 

near  knee-joint,  443 
shoulder-joint,  415 


Cacuminal  lobe,  838 
Calamus  scriptorius,  847,  726 


Calcaneal  arteries,  726,  727 
Calcanean  arteries,  lateral,  726 
medial,  727 

nerve,  medial,  988 

sulcus,  365 

tuberosity,  365 
Calcaneoastragaloid  articulation, 
452 

ligaments,  452,  453 
Calcaneocuboid  ligaments,  454 
Calcaneonavicular  ligaments,  455 
Calcaneotibial  ligament,  450 
Calcaneus,  362 

ossification  of,  374 
Calcar  avis,  879 

femorale,  351 
Calcarine  fissure,  869 
Calf  bone,  359 

Caliccs  of  kidney,  1210,  1216 
Callosal  convolution,  873 

fissure,  873,  876 
Callosomarginal  fissure,  869 
Camper,  fascia  of,  498 
Canaliculi  of  bone,  53 

dental,  1119 
Canaliculus,    inferior    tvmpanic, 
243,  280 

mastoid,  243,  2S0 
Canalis  centralis  cochleae,  242 

craniopharynqeus,  251 

reuniens  [of  Hensen],  1062,  1064 
Canal  or  Canals,  adductor,  713 

Alcock's,  511 

alimentary,  1109 

alveolar,  257 

atrial,  145 

auditory,  external,  1046 

carotid,  242,  280 

central,  of  medulla  spinalis,  810 

of  cervix  of  uterus,  1250 

condyloid,  230 

craniopharvngeal,  166,  251 

ethmoidal,  235,  253 

femoral,  712 

Haversian,  of  bone,  53 
i      of  Huguier,  238,  932,  1050 
'      Hunter's,  713 

hyaloid,  1030 

hypoglossal,  229 

incisive,  261,  278 

infraorbital,  258 

inguinal,  508 

lacrimal,  1041 

mandibular,  273 

neural,  88 

neurenteric,  88 

of  Nuck,  187,  1251 

of  Petit,  1030 

pharyngeal,  278 

pterj'goid,  280 

pterj'gopalatine,  258,  267 

sacral,  208 

of  Schlemm,  1018 

semicircular,  1058 
membranous,  1062 

spermatic,  508 

spiral,  of  modiolus,  1060 

vertebral,  208 
Canales  semicirculares  ossei,  1058 
Canaliculus  innominatus  of  Ar- 
nold, 248,  note 
Canalis  adductorius,  713 

centralis  [niedulla  spinalis],  810 

cervicis  uteri,  1250 

inguinalis,  508,  1229 

sacralis,  208 

semicircularis  lateralis,  1059 
posterior,  1059 
superior,  1059 
Cancellous  tissue  of  bone,  50 
Canine  eminence,  257 

fossa,  257 

teeth,  1117 
Caninus  muscle,  470 
Canthi  of  eyelids,  1038 


Cap  of  Broca,  870 
Capillaries,  598 
bile,  1198 
structure  of,  598 
Capitate  bone,  327 
Capitulum  fibulae,  359 
humeri,  312 
mallei,  1053 
stapedis,  1054 
Capsula    articularis.       See    Indi- 
vidual joints. 
cricoarylaenoidea,  1084 
externa,  884 
extrema,  883 
interna,  883 
lentis,  1030 
vasculosa  lentis,  136 
Capsular  artery,  middle,  696 
Capsule,  adipose,  of  kidney,  1209 
adrenal,  1270 
of  Bowman,  1212 
of  brain,  883,  884 
of  Glisson,  1156,  1196 
of  lens,  1030 
of  Tenon,  1037 
Caput  caecian  coli,  1177 
femoris,  345 
humeri,  309 
pancreaiis,  1203 
tali,  367 
Cardiac  cycle,  615 

ganglion  of  Wrisberg,  1002 
glands  of  stomach,  1166 
muscular  tissue,  68 
nerves,  cer^n.cal,  942 
great,  997 

from  sj^mpathetic,  997 
thoracic,  943 
from  vagus,  942 
notch,  1104 

orifice  of  stomach,  1161 
plexus  of  nerves,  1001 
veins,  730 
Cardinal  veins,  157 
Caroticoclinoid  foramen,  249,  290 

ligament,  251 
Caroticotympanic  arterj-,  648 

nerve,  946,  1056 
Carotid  arch,  153 

artery,  common,  627 

applied  anatomy  of,  629 
branches    of    (occasional), 

629 
peculiarities  of,  628 
surface  markings  of,  1290 
external,  630 

applied  anatomy  of,  630 
branches  of,  630 
surface  markings  of,  1290 
internal,  645 

applied  anatomy  of,  647 
branches  of,  648 
peculiarities  of,  647 
bodies,  1273 
canal,  242,  280 
ganglion,  996 
glands,  1273 
groove,  247,  290 
nerve,  internal,  995 
nerves  from  glossopharyngeal, 

939 
plexus,  996 

internal,  996 
sheath,  477 
skeins,  134,  1273 
triangles,  643 
tubercle,  199 
Carpal  arteries  from  radial,  678 
from  ulnar,  682 
bones,  323 
net-work,  678 
Carpometacarpal   articulations, 

429 
Carpus,  323 

applied  anatomy  of,  332 


1364 


INDEX 


Carpus,  articulations  of,  427 

ossification  of,  331 

surface  form  of,  1315 
Cartilage  or  Cartilages,  articular, 
48 

arytenoid,  1081 

of  auricula,  1044 

cells,  47 

cellular,  47 

corniculate,  1081 

costal,  48,  224 

cricoid,  1081 

cuneiform,  1082 

of  epiglottis,  1082 

epiphysial,  57 

ethmovomerine,  270 

histology  of,  47 

hyaline.  47 

intrathyroid,  1080 

lacuniB,  47 

of  larynx,  1079 
structure  of,  1082 

lateral,  lower,  1009 
upper,  1009 

of  nose,  1008,  1009 

Meckel's,  109,  273 

parachordal,  106 

permanent,  47 

of  pinna,  1044 

of  Santorini,  1081 

of  septum  of  nose,  1009 

sesamoid,  1009 

temporary,  47 

thyroid,  iOSO 

trabeculae  cranii,  106 

of  trachea,  1092 

vomeronasal,  1012 

white  fibro-,  49 

of  Wrisberg,  1082 
Cartilagines  alares  niinores,  1009 

arytaenoideae,  1081 

corniculatae,  1081 

costales,  224 

cuneifornies,  1082 

laryngis,  1079 

nasi,  1008 
Cartilaginous  ear  capsules,  107 

vertebral  column,  104 
Cartilago  alaris  major,  1009 
crus  laterale,  1009 
mediale,  1009 

auriculae,  1044 

cricoidea,  1081 

epiglottica,  1082 

nasi  lateralis,  1009 

septi  nasi,  1008 

thyreoidea,  1080 

triticea,  1083 
Caruncula  lacrimalis,  1041 
Carunculae  hymeneales,  1257 
Cauda  equina,  806 

helicis,  1044 

pancreatis,  1204 
Caudal  fold  of  embryo,  92 
Caudate  lobe  of  liver,  1195 

nucleus,  881 

process  of  liver,  1195 
Caudatum,  881 
Cavernous  arteries,  648 

nerves  of  penis,  1005 

plexus,  996 

portion  of  urethra,  1226 

sinuses,  744 

applied  anatomy  of,  745 
nerves  in,  928 

spaces  of  penis,  1240 
Cavity  or  Cavities,  amniotic,  96 

bodj^  or  coelom,  88 

buccal,  1110 

cotyloid,  339 

glenoid,  307 

of  lesser  pelvis,  341 

mediastinal,  1098,  1100,  1101 

of  mouth  proper,  1110 

nasal,  292,  1010 


Cavity  or  Cavities,  oral,  1110 

peritoneal,  1149 

of  septum  pellucidum,  887 

sigmoid,  of  radius,  321 
of  ulna,  313,  318 

subarachnoid,  904 

subdural,  903 

of  thorax,  600 

tympanic,  1049 

of  uterus,  1250 
Cavum  conchae,  1044 

laryngis,  1085 

Meckelii,  914 

nasi,  292,  1010 

oris,  1110 

proprium,  1110 

septi  pellucidi,  887 

subarachnoideale,  904 

tympani,  paries  carotica,  1052 
labyrinthica,  1050 
mastoidea,  1051 

tympanum,  1049 

paries  jugular  is,  1049 
membranacea,  1049 
tegmentalis,  1049 

uteri,  1250 
Cecal  arteries,  693 

fossae,  1159 
Cecum,  1177 

lymphatic  vessels  of,  792 
Cell  or  Cells,  animal,  33 

basket,  of  cerebellum,  842 

of  Betz,  891 

of  bone,  55 

centro-acinar    of    Langerhans, 
1205 

chalice,  37 

chromaffin,  1272 

clasmatocytes,  41 

of  Claudius,  1067 

definition  of,  33 

of  Deiters,  1067 

divisions  of,  34 

of  Dogiel,  950 

enamel,  1123 

fat,  42 

germinal,  of    medulla  spinalis, 
117 

giant,  51 

of  Betz,  891 

goblet,  37 

of  Golgi,  892 

granule,  41 

gustatory,  1007 

of  Hensen,  1067 

lamellar,  41 

of  Martinotti,  892 
intermediate,  88 

Mastzellen,  41 

membrane,  34 

mesamceboid,  142 

nerve,  70 

nucleus  of,  34 

olfactory,  1012 

pigment,  42 

plasma,  41 

prickle,  39 

of  Purkinje,  842 

reproduction  of,  34 

of  Sertoli,  1233 

of  spinal  ganglia,  803,  949 

splenic,  1267 

structure  of,  33 

wandering,  42 
Cell  mass,  inner,  84 
Cella,  877 

Cellulae  ethinoidales,  1014 
Cellular  cartilage,  47 
Cement  of  teeth,  1121 
formation  of,  1124 
Central  artery  of  retina,  650 

canal      of      medulla     spinalis, 
810 

cells  of  fundus  glands,  1166 

fissure,  868 


Central  gray  stratum  of  cerebral 
aqueduct,  854 
ligament   of   medulla    spinalis, 

907 
lobe,  873 

nervous  system,  801 
part  of  lateral  ventricle,  877 
sulcus,  868 
tendinous  point   of  perineum, 

518 
tendon  of  diaphragma,  495 
Centres,  higher  visual,  864,  909 
lower  visual,  909 
of  ossification,  57,  864 
Centrifugal  nerve  fibres,  803 
Centriole,  34 

bodies  of  ovum,  78 

of  spermatozoon,  80,  81 
Centripetal  nerve  fibres,  803 
Centroacinar  cells  of  Langerhans, 

1205 
Centrosome,  34 
Centrosphere,  34 
Centrum  ovale  majus,  876 

minus,  876 
Cephalic     flexure,     ventral,     of 
embryonic  brain,  121 
fold  of  embryo,  92 
index,  296 
portion  of  sympathetic  system, 

995 
vein,  747 

accessory,  748 
Ceratohyal  of  hj'oid  bone,  277 
Cerebellar    artery,     anterior    in- 
ferior, 661 
posterior  inferior,  661 
superior,  661 
fasciculus,  direct,  813 
notches,  837 
peduncles,  841 
tract,  direct,  816 

of  Flechsig,  816,  828 
veins,  739 
Cerebelloolivary  fasciculus,  830 
Cerebellospinal  tract  of   Lowen- 

thal,  815 
Cerebellum,  836 

applied  anatomy  of,  844 
brachia,  conjunctiva,  841 

pontis,  840 
development  of,  124 
fibrae  propriae,  842 
gray  substance  of,  842 
lobes  of,  836 
nucleus  dentatus,  844 
peduncles  of,  841 
structure  of,  839 
surfaces  of,  837,  838 
vermis  of,  836 
white  substance  of,  839 
Cerebral  arteries,  anterior,  651 
middle,  652 
posterior,  662 
aqueduct,  854 
cortex,  nerve  cells  of,  891 
nerve  fibres  of,  892 
structure  of,  891 
types  of,  893 
dura  mater,  900 
fissure,  lateral,  867 
hemispheres,  865 
borders  of,  866,  867 
development  of,  128 
fibers  of,  association,  890 
commissural,  890 
projection,  890 
transverse,  890 
fissures  of,  867 
gray  substance  of,  891 
gyri  of,  869 
interior  of,  875 
lobes  of,  869 
localization  of,  894 
poles  of,  867 


INDEX 


1365 


Cerebral    hemispheres,    structure 
of,  889 
sulci  of,  867 
surfaces  of,  SG7 
white  substance  of,  889 
peduncles,  848 

structure  of,  848 
nerves,  907 
abducent,  927 
accessory,  944 
acoustic,  934 
development  of,  131 
facial,  929 

glossopharyngeal,  937 
hj'poglossal,  945 
oculomotor,  911 
olfactory,  90S 
optic,  909 
trigeminal,  914 
trochlear,  913 
vagus,  940 
veins,  739 

ventricles,  845,  864,  877 
vesicles,  88,  120 
Cerebroolivary  fasciculus,  830 
Cerebrospinal  fasciculus,  815 
fibres  of  internal  capsule,  884 
fluid,  905 
Ceruminous  glands,  1047 
Cer%'ical  artery,  ascending,  663 
deep,  666 
superficial,  664 
transverse,  663 
branrh  of  facial  nerve,  933 
cardiac  nerves,  942 
enlargement         of         medulla 

spinalis,  808 
fascia,  476 

applied  anatomy  of,  478 
flexure  of  embryonic  brain,  121 
ganglion,  997,  998 
lymph  glands,  778 

applied  anatomy  of,  780 
muscles,  lateral,  475 

superficial,  dissection  of,  475 
•   nerve,  957 

cutaneous  or  transverse,  957 
of  facial,  933 
ner^'es,  951 

di-\dsions  of,  anterior,  954 
posterior,  951 
pleura,  1095 
plexus,  954 

applied  anatomy  of,  958 
branches  of,  956,  957 
posterior,  957 
portion  of  svmpathetic,  996 
rib,  201 

appUed  anatomj'  of,  226 
vein,  deep,  738 

posterior,  738 
vertebrae,  198 
Cervicalis  ascendens  muscle,  488 
Cervix  uteri,  1249 

portio  supravaginalis,  1249 
vaginalis,  1250 
of  uterus,  1249 
Chalice  cells,  37 
Chambers  of  ej'e,  1024 
Chassaignac's  tubercle,  199 
Check  ligaments,  393 

of  eve,  1038 
Cheeks,  1110 
Chest,  216 
Chiasma,  optic,  862,  909 

opticum,  862,  909 
Chiasmatic  groove,  246,  290 
Choana;,  278,  294,  1010 
Chondrin,  50 
Chondrocranium,  106 
Chondroglossus  muscle,  1129 
Chondromucoid,  50 
Chondrosternal  ligament,  399 

intra-articular,  400 
Chondroxiphoid  ligaments,  401 


Chorda  ohliquii,  423 

tj'mpani  nerve,  932 
Chordae  tendineae  [left  ventricle], 
612 
[right  ventricle],  610 

Willisi,  741 
Chordal  furrow,  91 

portion  of  base  of  skull,  106 
Chorioidca,  1021 

lamina  choriocapiUaris,  1022 
vasculosa,  1022 
Chorion,  99 

frondosum,  100 

laeve.  99 
Chorionic  villi,  99 
Choroid  artery,  653 

coat  of  eyeball,  1021 
structure  of,  1021 

plexuses    of    fourth    ventricle, 
846 
of  lateral  ventricle,  887 
of  third  ventricle,  864 

vein,  740 
Choroidal  artery,  anterior,  653 
posterior,  662 

fissure,  135,  888 
Chromaffin  cells, 1272 

organs,  133 
Chromatin,  34 
Chromatolysis,  72 
Chromosomes,  34 
Chyle,  768 

Chyliferous  vessels,  768 
Cilia,  1038 
Ciliaris  muscle,  1023 
Ciliarv  arteries,  650 

body, 1023 

ganglion,  917 

glands,  1039 

muscle,  1023 

nerves,  916,  917 

processes,  1023 
Ciliated  epithelium,  37 
Cingulate  gyrus,  873 

sulcus,  869 
Cingulum  of  cerebral  hemisphere. 
890 

of  teeth,  1125 
Circle,  arterial,  of  Willis,  653 
Circular  folds  of  small  intestine, 
1173 

sinus,  746 

sulcus,  869,  873 
Circulating  fluids,  61 

blood,  61 

Ij-mph,  64 
Circulation  of  blood  in  adult,  595 

in  fetus,  616,  650 
Circulus  arteriosus  major,  1025 
minor,  1025 

major  [iris],  650,  1025 

m,inor  [iris],  650,  1025 

venosus  [mamma],  1260 
Circumduction,  3S3 
Circumferential  fibrocartilage,  50 
Circumflex  artery,  femoral, lateral, 
716 
medial,  717 
humeral,  anterior,  672 
posterior,  671 

nerve,  961 
Circuminsular  fissure,  869 
Circumvallate  papillae,  1127 
Cister?ia  basalis,  904 

chyli,  772 

cerebellomedullaris ,  904 

chiasmatis,  904 

fossae  cerebri  lateralis,  905 

interpeduncularis,  904 

magna,  904 

ponfis,  904 

venae  magnae  cerebri,  905 
Cisternae  subarachnoid,  904 

subarachnoidales ,  904 
Clarke's  column,  813 


Clasmatocytes,  41 
Claudius,  cells  of,  1067 
Claustrum,  882 
Clava,  824 
Clavicle,  301 

applied  anatomy  of,  303 

ossification  of,  303 

peculiarities  of,  in  sexes,  303 

structure  of,  303 

surface  anatomy  of,  1313 
Clavicula,  301 
Clavipcctoral  fascia,  528 
Cleft  palate,  299 

Clinging  fil^res  of  cerebellum,  844 
Clinoid  processes,  anterior,   249, 
290 
middle,  246,  290 
posterior,  246,  290 
Clitoris,  1257 

frenulum  of,  1257 

glans  of,  1257 

prepuce  of,  1257 
Clivus  of  sphenoid,  246 

monticuli  of  cerebellum,  838 
Cloaca,  ectodermal,  172 

entodermal,  172 

pelvic  portion  of,  188 

phallic  portion  of,  188 

vesicourethral  portion  of,  188 
Cloacal  niembrane,  172 

duct,  172 

tubercle,  190 
Cloquet,  lj"mph  gland  of,  783 
Closing  membranes,  108 
Coarctation  of  aorta,  624 
Coccvgeal  arteries,  706 

body, 1273 

cornua,  209 

gland,  1273 

nerve,  division  of,  anterior,  982 
posterior,  954 

plexus,  992 

skein,  1273 
Coccj'geus  muscle,  514 
Coccyx,  209 

ossification  of,  212 
Cochlea,  1059 

aqueduct  of,  243,  280,  1060 

cupula  of,  1059,  1060 

hatyiulus  laminae  spiralis,  1060 

helicotrema  of,  1060 

modiolus  of,  1060 

scalse  of,  1060 

spiral  canal  of,  1060 

lamina  of,  osseous,  1060 
secondary,  1060 

vessels  of,  1068 
Cochlear  arterv,  1068 

nerve,  935,  1068 

nuclei,  836,  935 

root  of  acoustic  nerve,  935 
Cochleariform  process,  243,  1052 
Ccfiliac  artery,  688 

axis,  688 

branches  of  vagus  nerve,  943 

ganglion,  1002 

plexus,  1002 
Cog-tooth  of  malleus,  1053 
Cohnheim,  areas  of,  66 
Colic  arteries  of  ileocolic,  794 
arterv,  left,  695 
middle,  694 
right,  694 

flexures,  right  and  left,  1180 

impression,  1192 

valve,  1179 
Collagen,  44 
Collar  bone,  301 
Collateral  circulation,  619 

eminence,  881 

fissure,  869 

ganglia,  995 
Collecting  tubes  of  kidney,  1212 
CoUes,  fascia  of,  337.  499,  517 
Colliculi,  inferior,  853,  854 


1366 


INDEX 


Colliculi,  superior,  853,  854; 
CoUiculus  of  arytenoid  cartilage, 
1081 

facialis,  848 

inferior,  854 

nervi  optici,  1027 

superior,  854 
Colluni  anatomicum,  309 

femoris,  345 

mallei,  1053 

tali,  367 
Coloboma,  135 
Colon,  1180 

ascendens,  1180 

ascending,  1180 

descendens,  1181 

descending,  1181 

iliac,  1181 

left  or  splenic  flexure  of,  1180 

pelvic,  1181 

right  or  hepatic  flexure  of,  1180 

sigmoid,  1181 

sigmoideum,  1181 

structure  of,  1184 

tela  submucosa,  1185 

iransversum,  1180 

tunica  mucosa,  1185 
■muscularis ,  1184 
serosa,  1184 

vessels  and  nerves  of,  1185 
Colored  lines  of  Retzius,  1120 

or  red  corpuscles,  61 
Colorless  corpuscles,  62 
Colostrum  corpuscles,  1259 
Columna  anterior  [medulla  spin- 
alis]. 809 

fornicis,  886 

lateralis  [medulla  spinalis],  809 

nasi,  1008 

posterior  [medulla  spinalis],  890 

vertebralis.  196 
Columnae  carneae,  610 
Columnar  epithelium,  37 
Columns  of  Clarke,  813 

of  fornix,  886 

of  medulla  spinalis,  811,  812, 
813 

rectal,  of  Morgagni,  1184 

renal,  1211 

of  vagina,  1255 

vertebral,  196,  212 
Comes  nervi  phrenici,  664 
Comitans  nervi  ischiadici,  706 
Comma-shaped  fasciculus,  817 
Commissura    labiorum    anterior, 
1256 

palpebrarum  lateralis,  1038 
medialis,  1038 
Commissural    fibres    of    cerebral 

hemispheres,  890 
Commissure  of  brain,  856 
anterior,  131,  887 
middle  or  gray,  856 
posterior,  127,  860 

of  corpus  callosum,  131 

habenular,  859 

hippocampal,  886 

of  Gudden,  909 
■    of  labia  majora,  1257 

of    medulla    spinalis,    anterior 
and  posterior  gray,  810 
anterior  white,  808 

optic,  862 
Commissures,  palpebral,  1038 
Common  bile  duct,  1200 
lymphatics  of,  793 

carotid  artery,  627 

dental  germ,  1121 

iliac  arteries,  698 
glands,  786 
veins,  763 

integument,  1071 

interosseous  artery.  680 

peroneal  nerve,  989 
Communicans  fibularis  nerve,  990 


Communicans  tibialis  nerve,  988 
Communicantcs    cervicales, 

nerves,  957 
Communicating  artery,  anterior, 
651 
from  dorsalis  pedis,  725 
posterior,  653 
Compact  tissue  of  bone,  50 
Comparison  of  bones  of  hand  and 

foot,  375 
Complexus  muscle,  489 
Compressor  naris  muscle,  469 
Concha  of  auricula,  1044 
cavum  conchae,  1044 
cymba  conchae,  1044 
nasal,  inferior,  268 

articulations  of,  269 
ossiffication  of,  269 
middle,  254 
superior,  254 
nasalis  inferior,  268 
Conchse,  sphenoidal,  250 

sphenoidales,  250 
Conchal  crest,  258,  266 
Condyle  of  mandible,  293 
Condyles  of  femur,  349 
occipital,  230 
of  tibia,  355 
Condyloid  articulation,  382 
canal,  230 

foramen,  anterior,  229 
fossa,  230,  287 
process  of  mandible,  273 
Cone  of  attraction,  83 
bipolars  of  retina,  1028 
granules  of  retina,  1029 
of  origin  of  axon,  72 
Cones  of  retina,  1029 
Confluence  of  sinuses,  229,  743 
Confluens  sinuum,  743 
Coni  vasculosi,  1233 
Conical  papillae,  1128 
Conjoined     tendon     of     internal 
oblique        and        transversalis 
muscles,  505 
Conjugate  diameter  of  pelvis,  341 
Conjunctiva,  1040 

applied  anatomy  of,  1042 
Connecting  fibrocartilages,  50 
Connective  tissues,  40 
adipose,  42 
areolar,  40 
development  of,  47 
lymphatics  of,  46 
mucous,  44 
nerves  of,  46 
proper,  40 
retiform,  40 
vessels  of,  46 
white  fibrous,  40 
yellow  elastic,  40 
Connective  tissue  corpuscles,  40 

extraperitoneal,  509 
Conoid  ligament,  412 

tubercle,  301 
Constriction,     duodenopyloric, 

1162 
Constrictor  muscles,  1141,  1142 
pharyngis  inferior  muscle,  1141 
medius  muscle,  1142 
superior  muscle,  1142 
urethrae  muscle,  520,  521 
Contractile  fibre-cells,  68 
Conus  arteriosus,  608 
elasticus  [larynx],  1083 
medullaris,  806 
Convoluted  tubes  of  kidney,  1212 
Convolution,  callosal,  873 
frontal,  ascending,  869 
occipitotemporal,  871 
parietal,  ascending,  871 
Cooper,  ligament  of,  502 
Copula,  164 
Cor,  603 
Coracoacromial  ligament,  413 


Coracol)rachialis  muscle,  534 
Coracoclavicular  fascia,  528 
Coracohumeral  ligament,  414 
Coracoid  process,  307 

tuberosity,  301 
Cord,  gangliated,  995 
spermatic,  1229 
spinal,  805 
umbilical,  96 
vocal,  false,  1085 
inferior,  1086 
superior,  1085 
true,  1086 
Corium  or  cutis  vera,  1074 
layers  of,  1074 
stratum  papillare,  1074 
reticular  e,  1074 
Cornea,  1018 

structure  of,  1019 
Corneal  corpuscles,  1020 
endothelium,  1021 
epithelium,  1019 
spaces,  1020 
Corniculate  cartilages,  1081 
Cornu  anterius,  878 
inferior,  879 
of  medulla  spinalis,  809 
posterius,  879 
Cornua  of  coccyx,  209 
of  hyoid  bone,  275 
of  lateral  ventricles,  878,  879 
majora  [os  hyoidei],  275 
minora  [os  hyoidei],  277 
of  sacrum,  207 
of  thyroid  cartilage,  1080 
Cornucommissural  fasciculus,  817 
Cornucopia  of  Bochdalek,  846 
Corona  glandis,  1239 
radiata  [brain],  884 
[ovum],  79 
Coronal  suture,  277,  282 
Coronary  artery  of  heart,  622 
applied  anatomy  of,  623 
peculiarities  of,  623 
of  lips,  634 
of  stomach,  688 
ligament  of  liver,  1151 
ligaments  of  knee,  442 
plexuses,  1002,  1004 
sinus,  730 

opening  of,  608 
sulcus  of  heart,  604 
veins,  730 

of  stomach,  766 
Coronoid  fossa,  313 

process  of  mandible,  273 
of  ulna,  315 
Corpora  cavernosa  clitoridis,  1257 
penis,  1238 
bulbs  of,  1238 
crura  of,  1238 
mamillaria,  860 
quadrigemina,  853 
brachia  of,  853 
structure  of,  854 
Corpus  albicantia,  860 
Arantii,  610,  612 
callosum,  865,  876 
development  of,  131 
genu  of,  876 
peduncle  of,  875 
rostrum  of,  876 
splenium  of,  876 
cavernosum,  artery  to,  705 

urethrae,  1237 
ciliare,  1023 
femoris,  348 
fibulae,  359 
fornicis,  886 
geniculatum  laterale,  858 

mediate,  858 
Highmori,  1232 
humeri,  311 
incudis,  1054 
luteum,  1246 


INDEX 


1367 


Corpus  maxillae,  250 

OSS.  hijoidci,  275 
ilii,  333 
ischii,  336 
pubis,  337 

pancreatis,  1204 

fades  anterior,  1204 
inferior,  1204 
posterior,  1204 
margo  anterior,  1204 
inferior,  1204 
superior,  1204 

papillare  [corium],  1074 

penis,  1239 

pincale,  S59 

radii,  320 

restiformcs,  830,  S41 

sphenoidal  is,  24G 

spongiosum,  1238 

sterni,  218 

striatum,  729,  SSI 
vein  of,  SS5 

subthalamicum,  860 

/aii,  367 

tibiae,  356 

ulnae,  318 

wterj:,  1249 
fades  intestinalis,  1249 

vesicalis,  1249 
margo  lateralis,  1249 

vertebrae,  197 

vitreum,  1030 
Corpuscles,  colored,  61 
development  of,  142 

colorless,  62 

connective  tissue,  40 

genital.  1069 

of  Golgi  and  Mazzoni,  1069 

of  Grandry.  1069 

of  Hassall,  1265 

of  Herbst,  1069 

Pacinian,  1069 

of  Ruffini,  1070 

of  Wagner  and  Meissner,  1070 
Corrugator  cutis  ani  muscle,  516 

muscle,  468 

supercilii  muscle,  468 
Cortex  of  cerebellum,  842 

of  cerebrum,  891 
Corti,  ganglion  of,  1060,  1068 

organs  of,  1065 

pillars  or  rods  of,  1065 

spiral  organ  of,  1065 

tunnel  of,  1065 
Cortical  arches  of  kidney,  1211 

arterial  system  of  brain,  654 

portion    of    suprarenal    gland, 
1272 

substance  of  kidney,  1211 
of  lens,  1031 

visual  centre,  909 
Corticostriate  fibres,  882 
Costae,  220 
Costal  cartilages,  48,  224 

element  or  process,  199 

groove,  222 

pleura,  1095 

tuberosity,  303 
Costocentral  articulation,  396 
Costocervical  trunk,  666 
Costoehondral  articulations,  401 
Costocoracoid  ligament,  528 

membrane,  528 
Costomediastinal  sinus,  1097 
Costosternal  articulations,  399 
Costotransverse     articulations, 
397 

ligaments,  399 
Costovertebral  articulations,  396 

ligament,  anterior,  396 
Cotyloid  cavity,  339 

ligament,  339,  434 
Covering  bones,  107 
Coverings      of      direct     inguinal 

hernia,  1188 


Coverings  of  fe'inoral  hernia,  1189 

of  obli(iue  inguinal  hernia,  1187 

of  ovum,  79 

of  teslcs,  1228 
Cowper's  glands,  190,  1243 
Coxal  articulation,  432 

applied  anatomy  of,  437 
movements  of,  435 
muscles  in  relation  to,  435 
Cranial  bones,  227 

fossa,  anterior,  288 
middle,  290 
posterior,  291 

nerve,  907 
Craniology,  295 
Craniopharyngeal  canal,  166 
Cranium,  227 

bones  of,  227 

breadth  of,  296 

development  of,  105 

fissures  in,  congenital,  255 

height  of,  296 

horizontal     circumference     of, 
296 

length  of,  296 

longitudinal  arc  of,  296 
Cremaster  muscle,  504 
Cremasteric  artery,  709 

fascia.  504 
Crescents  of  Gianuzzi,  1137 
Crest  or  Crests,  basilar,  1064 

conchal,  258,  266 

ethmoidal,  260,  267 

frontal,  235 

of  ilium,  336 

incisor,  261 

infratemporal,  248,  282 

internal  occipital,  228,  292 

intertrochanteric,  348 

lacrimal,  260,  263 

nasal,  261,  266 

neural,  88,  120 

obturator,  338 

of  pubis,  338 

of  right  atrium,  606,  607 

sphenoidal,  247 

supramastoid,  237 

of  tibia,  356 

of  tubercles  of  humerus,  309 

urethral,  in  female,  1228 
in  male,  1225 
Cribriform  plate  of  ethmoid,  252 
Cricoarytaenoideus    lateralis 
muscle,  1088 

posterior  muscle,  1088 
Cricoarytenoid  ligament,  1084 

muscles,  1088 
Cricoid  cartilage,  1081 
Cricothyreoideus  muscle,  1088 
Cricothyroid  artery,  631 

ligament,  middle,  1083 

membrane,  1083 

muscle,  1088 
Cricotracheal  ligament,  1083 
Crista     arcuata     [arytenoid    car- 
tilage], 1081 

colli  costae,  222 

faldformis,  241 

gain,  252 

terminalis  [of  His],  146 

vestibuli,  1058 
Crossed  commissural  fibres,  811 

pyramidal  tract,  815 
Crosses  of  Ranvier,  75 
Crown  of  a  tooth,  1118 
Crucial  anastomosis,  717 

ligaments,  441 
Cruciate  crural  ligament,  584 

eminence  of  occipital  bone,  228 

ligament  of  atlas,  390 

ligaments  of  knee,  441 
Crura  cerebri,  848 

of  diaphragma,  495 

of  fornix,  887 

of  penis,  1238 


Crura  of  stapes,  1054 

of  subcutaneous  inguinal  ling, 
500 
Crural  arch,  deep,  509 

muscles,  anterior,  dissection  of, 
578 
lateral,  dissection  of,  582 
posterior,  dissection  of,  578, 
579,  581 
nerve,  anterior,  980 
septum,  712 
sheath,  710 
Crureus  muscle,  566 
Crus  cerebri,  848 

commune  [semicircular  canals], 

1059 
fornicis,  887 
helicis,  1044 
penis,  1238 
Crusta  or  pes  of  cerebral  peduncle, 
849 
petrosa  of  teeth,  1121 
formation  of,  1121 
Cruveilhier,  glenoid  ligaments  of, 

430,  459 
Crypts  of  Lieberkuhn,  1174 
Crystalline  lens,  1030 

cortical  substance  of,  1031 
development  of,  136 
nucleus  of,  1031 
Cuboid  bone,  367 
Cuboideonavicular  articulation, 

457 
Culmen  monticuli  [cerebellum]  ,838 
Cuneate  nucleus,  825 

tubercle,  825 
Cuneiform  bone  of  carpus,  324 
of  tarsus,  first,  369 
second,  369 
third,  370 
cartilages,  1082 
tubercle,  1085 
Cuneocuboid  articulation,  457 
Cuneonavicular  articulation,  456 
Cuneus,  871 
Cup,  optic,  134 
Cupula  of  cochlea,  1060 

of  pleura,  1095 
Curvatura  ventriculi  major,  1162 

minor,  1162 
Curvatures  of  stomach,  1161 
Curved  lines  of  ilium,  333 
Curves     of     vertebral     column, 

212 
Cushion  of  auditory  tube,  1139 

of  epiglottis,  1082 
Cushions,  endocardial,  148 
Cusps  of  bicuspid  valve,  612 

of  tricuspid  valve,  609 
Cutaneous  cervical  nerve,  957 
nerve,  external,  977 
internal,  964,  981 

lesser,  964 
middle,  980 
Cuticle,  1071 
Cuticula  dentis,  1123 
Cutis  plate,  102 

vera  or  corium,  1074 
Cutting  teeth,  1117 
Cuvier,  ducts  of,  157 
Cycle,  cardiac,  615 
Cylindrical  epithelium,  37 
Cymba  conchas,  1044 
Cystic  artery,  691 
duct,  1200 
vein,  767 
Cyton,  72 
Cytoplasm,  33 
Cytotrophoblast,  85 


D 


Dacryon,  287,  296 
Dartos  tunic,  1228 


1368 


INDEX 


Darwin,    auricular    tubercle    of, 

1044 
Daughter  chromosomes,  36 
Decidua,  98 

basalis,  98 

capsularis,  98 

parietalis,  98 

placentalis,  98 

stratum  compactum  of,  98 
spongiosum  of,  98 

unaltered  or  boundary  layer  of, 
.  98 
Decidual  cells,  98 
Decussation  of  lemniscus,  827 

partial,  of  optic  nerves,  909 

pyramidal,  822 
Deep  abdominal  ring,  508 

artery  of  penis,  703 

auricular  artery,  640 

cerebral  veins,  740 

cer\'ical  artery,  666 
fascia,  476 
•lymph  glands,  778 
vein,  738 

crural  arch,  509 

epigastric  artery,  709 
vein,  760 

external  pudic  artery,  716 

fascia  of  arm,  534 
of  forearm,  536 

femoral  artery,  716 

iliac  circumflex  vein,  760 

lingual  artery,  632 

muscles  of  back,  485 

palmar  arch,  679 

peroneal  nerve,  990 

petrosal  nerve,  919 

plantar  artery,  725 

Sylvian  vein,  740 

temporal  arteries,  641 
nerves,  922 

transverse  fascia  of  leg,  580 
Degeneration,  Wallerian,  815 
Deglutition,  1114 
Deiters,  cells  of,  1067 

nucleus  of,  836,  935 
Deltoid  ligament,  450 

muscle,  530 

tubercle,  302 

tuberosity,  312 
Deltoideus  muscle,  530 
Demilunes  of  Heidenhain,  1137 
Demours,  membrane  of,  1020 
Dendrons  of  nerve  cells,  72 
Dens,  or  odontoid  process  of  axis, 
199 

serotinus,  1118 
Dental  artery,  inferior,  640 
posterior,  641 

canaliculi,  1120 

formulte,  1116 

furrow,  1122 

germs,  1121 

lamina,  1121 

nerve,  inferior,  923 

pulp,  1119 

sac,  1123 
Dentate  fissure,  874 

gyrus,  874 

ligament,  907 
Denies,  1115 

canini,  1117 

decidui,  1118 

incisivi,  1117 

■molar  es,  1118 

permanentes,  1117 

praemolares,  1118 
Dentin,  1119 

formation  of,  1123 

intertubular,  1120 

secondary,  1121 
Dentinal  canaliculi,  1120 

fibres,  1120 

matrix,  1120 

sheath  of  Neumann,  1120 


Dentinal  tubules,  1120 
Depressions  for  arachnoid  granu- 
lations, 232 
Depressor  alae  nasi  muscle,  469 

anguli  oris  muscle,  470 
labii  inferioris  muscle,  470 

septi  muscle,  469 
Dermal  bones,  107 
Dermic  coat  of  hair  follicle,  1076 
Dermis,  1074 

Descemet,  membrane  of,  1020 
Descendens  cervicalis  nerve,  957 
Descending  aorta,  683 

colon,  1181 

comma-shaped  fasciculus,  817 

oblique  muscle,  499 

palatine  artery,  642 

process  of  lacrimal  bone,  263 

ramus  of  hypoglossal  nerve,  947 
of  ischium,  337 
of  OS  pubis,  338 
Descent  of  testis,  186 
Detrusor  urinae  muscle,  1223 
Deutoplasm,  78 
Development  of  adipose  tissue,  42 

of  allantois,  93 

of  amnion,  94 

of  anal  canal,  172 

of  arteries,  152 

of  body  cavities,  178 

of  brain,  120 

of  branchial  or  visceral  arches, 
108 

of  cerebral  nerves,  132 

of  chorion,  99 

of  chromaffin  organs,  133 

of  deciduous  teeth,  1121 

of  digestive  tube,  162 

of  ear,  138 

of   external   organs   of   genera- 
tion, 190 

of  eye,  134 

of  face,  111 

of  fetal  membranes,  93 

of  glands  of  skin,  116 

of  heart,  143 

of  hypophysis  cerebri,  166 

of  joints,  115 

of  kidney,  187 

of  limbs,  113 

of  liver,  174 

of  lymphatic  system,  161 

of  mammae,  116 

of  medulla  spinalis,  117 

of  mouth,  163 

of  muscles,  116 

of  nervous  system,  117 

of  neural  groove  and  tube,  88 

of  nose,  111 

of  notochord,  90 

of  ovaries,  184 

of  palate,  112 

of  palatine  tonsils,  165 

of  pancreas,  175 

of  parathyroid  glands,  166 

of  parietes,  102 

of  permanent  teeth,  1124 

of  pharyngeal  pouches,  108 

of  placenta,  100 

of  primitive  segments,  91 
streak,  86 

of  prostate,  189 

of  rectum,  172 

of  respiratory  organs,  176 

of  ribs,  104 

of  salivary  glands,  164 

of  skeleton,  102 

of  skin,  116 

of  skull,  105 

of  spinal  nerves,  119 

of  spleen,  176 

of  sternum,  105 

of  suprarenal  glands,  134 

of  sympathetic  system,  133 

of  teeth,  1121 


Development  of  testis,  186 
of  thymus,  165 
of  thyroid  gland,  165 
of  tongue,  104 
of  umbilical  cord,  96 
of  urethra,  190 
of  urinary  bladder,  188 

and  generative  organs,  180 
of  vascular  system,  141 
of  veins,  155 
of  vertebral  column,  102 
of  visceral  arches,  108 
of  yolk-sac,  93 
Diameters  of  pelvis,  341,  342 
Diaphragm,  muscles  of,  493 
pelvic,  510,  1146 
urogenital,  519 
Diaphragma,  493 

lymphatic  vessels  of,  798 
sellae,  901 
Diaphragmatic  lymph  glands,  796 
part  of  pelvic  fascia,  511 
pleura,  1095 
surface  of  heart,  605 
Diaphysis,  59 
Diarthroses,  381 
Diaster,  36 

Diencephalon,  126,  855 
Digastric  fossa,  239 
muscle,  480 
nerve,  from  facial,  933 
triangle,  644 
Digastricus  muscle,  480 
Digestion,  organs  of,  1109 
Digestive  apparatus,  1109 
development  of,  162,  168 
tube,  1109 
Digital  arteries,  foot,  728 

from   superficial   volar   arch, 
hand,  682 
682 
fossa  of  epididymis,  1231 

of  femur,  347 
nerves  of  lateral  plantar,  989 
of  medial  plantar,  988 
of  median,  965 
of  musculocutaneous.  964 
of  radial,  969 
of  ulnar,  967 
vaginal  ligaments,  540 
veins  of  foot,  756 
of  hand,  747 
Digits,  articulations  of,  431 
Dilatator  naris  anterior  muscle, 
469 
posterior  muscle,  469 
pupillae  muscle,  1025 
tubae  muscle,  1053 
Diploe,  196 
Diploic  veins,  738 
frontal,  738 
occipital,  739 
temporal,  738 
Direct  cerebellar  fasciculus,  813 
tract,  828 

of  Flechsig,  816,  828 
inguinal  hernia,  1188 
pyramidal  tract,  815 
Discharge  of  ovum,  1246 
Discus  articularis,  395 

proligerus,  1246 
Disk,  interpubic,  407 

optic,  1027 
Disks,  tactile,  of  Merkel,  1069 
Dissection  of  axilla,  525 
of  brain,  821 
of  crural  muscles,  578,  579,  581, 

582 
of  encephalon,  821 
of  femoral  muscles,  medial,  567 

posterior,  574 
of  geniohyoideus  muscle,  481 
of  infrahyoid  muscles,  482 
of  left  atrium,  610 
ventricle,  611 


INDEX 


1869 


Di!=section    of    humIuIUi    .siiinalisi, 
805 
of  nicscnteric  arterj^   inferior, 
695 
superior,  692 
of   muscles    of   al)donien,    498, 
503,  504,  505 
of  arm,  533 
of  back,  485 
of  eyelids,  467 
of  foot,  587,  588 
of  forearm,  53(),  539,  542 
of  Kluti-al  resioii,  569,  572 
of  iliac  region,  559 
of   leg,  576,    578,    579,  581, 

582 
of  mouth,  469 
of  palate,  1114 
of  scalp,  464 
of  shoulder,  530,  531 
of  thigh,  562 
of  pectoral  region,  525 
of  popliteal  fossa,  718 
of  pterygoidei  muscles,  474 
of    rectus    abdominis    muscle, 

505 
of  right  auricle,  607 

ventricle,  609 
of   superficial   cervical   muscle, 

475 
of  suprahyoid  muscles,  480 
of  temporal  muscle,  473 
Diverticulum  ilei,  1172 

Meckel's,  93,  1172 
Divisions  of  bronchi,  1105 

of  cells,  34 
Dobie's  line,  66 
Dogiel,  cells  of,  950 
Dorsal  aortse,  154 
artery  of  penis,  706 
carpal      artery,      of      radial, 
678 
of  ulnar,  682 
ligament,  550 
cutaneous  nerve,  intermediate, 
990 
lateral,  988 
medial,  990 
fissure   of   medulla   oblongata, 

822 
interossei  muscles,  555,  591 
interosseous  artery,  681 

nerve,  970 
lamina,  119 
mesogastrium,  168 
metacarpal  arteries,  678 

veins,  750 
nasal  artery,  650 
nerve  of  penis,  992 
peripheral  band,  818 
pulmonary  nerves,  943 
scapular  nerve,  960 
spinal  artery,  660 
veins  of  penis,  761 
venous  arch  of  foot,  756 
net-work  of  hand,  747 
vestibular  nucleus,  836 
Dorsalis  hallucis  artery,  724 
linguae  artery,  632 
pedis  artery,  724 

applied  anatomy  of,  724 
branches  of,  724 
peculiarities  of,  724 
surface  markings  of,  1332 
scapulae  artery,  671 
Dorsoepitrochlearis     brachii 

muscle,  524 
Dorsomedian  fissure  of  medulla 

oblongata,  822 
Dorsum  ilii,  333 
linguae,  1126 
nasi,  1008 
scapulae,  305 
sellae,  246,  290 
Douglas,  pouch  of,  1151 


Drum,  1049 

Duct    or    Ducts,   accessory    pan- 
creatic, 1205 
of  liartholin,  1137 
of  Bellini,  1212 
of  bulbourethral  glands,  1243 
cloacal,  172 
common  bile,  1200 
of  Cuvier,  157 
cystic,  1200 
ejaculatory,  1237 
frontonasal,  236 
of  Gartner,  1245 
hepatic,  1199 
lacrimal,  1041 
lactiferous,  1258 
of  liver,  1198 
lymphatic,  right,  772 
Miillerian,  182 
nasolacrimal  or  nasal,  1042 
pancreatic,  1204,  1205 
parotid,  1135 
pronephric,  180 
prostatic,  1241 

orifices  of,  1225 
of  Rivinus,  1137 
of  Santo rini,  1205 
semicircular,  1062 
seminal,  1235 
Skene's,  190 
Stensen's,  1135 
sublingual,  1137 
submaxillary,  1136 
thoracic,  771 
thyroglossal,  165,  1127 
vitelline,  92 
Wharton's,  1136 
of  Wirsung,  1204 
Wolffian,  ISO 
Ductless  glands,  1260 

aortic  bodies  of  Zuckerkandl, 
1274 

carotid  skeins,  1273 

coccygeal  skein,  1273 

lien,  1266 

parathyroids,  1263 

spleen,  1266 

suprarenals,  1270 

thvmus,  1264 

thyroid,  1261 
Ductuli  aberrantes  [testis],  1236 
efferentes  [testis],  1233 
transversilepoophoTon],  1244 
Ductus  arteriosus,  616 
choledochus,  1200 
cochlearis,  1063 
cysticus.  1200 
deferens,  1235 

ampulla  of,  1235 

structure  of,  1236 
ejaculatorii,  1237 
endolymphaticus ,  1058,  1062 
hepaticus,  1199 
lacrimalis,  1041 
longitudinalis  epoophori,  1245 
lymphaticus  dexter,  772 
nasolacrimalis ,  1042 
pancreaticus  [Wirsungi],  1204 
parotideus,  1135 
Santorini,  1205 
semicircular  es,  1062 
suhmaxillaris ,  1136 
thoracicus,  771 
utriculosaccularis,  1062 
venosus,  156,  618 

development  of,  156 

fossa  for,  1194 

obliterated,  765 
Duodenal  fossae,  1158 
glands,  1175 
impression,  1192  ^ 

Duodenojejunal  flexure,  1171 
fold,  1159 
fossa,  1159 
Duodenomesocolic  fold,  1158 


Duodcn()p\  loiic     constriction, 

1162 
Duodenum,  1169 

ascending  portion,  1171 
d(;scending  portion,  1170 
hori;!ontal  portion,  1170 
lymphatic  vessels  of,  792 
superior  jjortion,  1169 
suspensory  muscle  of,  1171 
vessels  and  nerves  of,  1171 
Dura  of  brain,  900 
mater,  cerebral,  900 
arteries  of,  902 
endosteal  layer  of,  902 
meningeal  layer  of,  902 
nerves  of,  902 
processes  of,  900 
veins  of,  902 
encephali,  900 
spinal,  902 

structure  of,  903 
spinalis,  902 
Dural  nerve,  941 


E 


Eab,  1043 

auricula  of,  1044 
muscles  of,  1045 

cartilaginous  capsules  of,  107 

cochlea,  1059 

development  of,  138 

external,  1043 

internal,  or  labyrinth,  1057 
applied  anatomy  of,  1068 

meatus   acusticus   externus, 
1046 

membranous  labyrinth,  1061 

middle,  1049 

osseous  labyrinth,  1057 

pinna  of,  1044 

semicircular  canals  of,  1058 

tympanic  cavity  of,  1049 

applied  anatomy  of,  1056 
muscles  of,  1055 
ossicles  of,  1053 
vessels  and  nerves  of,  1056 

vestibule  of,  1058 
Eberstaller,  medial  frontal  sulcus 

of,  870 
Ectoderm,  86,  87 
Ectodermal  cloaca,  172 
Efferent  nerves,  803 
Eighth  nerve,  934 
Ejaculator  urinae  muscle,  518 
Ejaculatory  ducts,  1237 
Elastic  fibrocartilage,  50 

laminae  of  cornea,  1020 

membrane  of  larynx,  1083 

tissue,  yellow,  44 
Elastin,  44 
Elbow  bone,  314 
Elbow-joint,  418 

anastomoses  around,  675 

applied  anatomy  of,  421 

movements  of,  420 

surface  anatomy  of,  1315 
markings  of,  1319 

vessels  and  nerves  of,  420 
Eleidin,  39 
Eleventh  nerve,  944 
Embryo,    form    of,    at    different 
stages,   191 

separation  of,  92 
Embryology,  77 
Embryonic  disk,  86 

pole,  85 
Eminence,  canine,  257 

collateral,  881 

cruciate,  228 

frontal,  234,  278,  282 

hypothenar,  546 

iliopectineal,  336. 

intercondyloid,  of  tibia,  355 


1370 


INDEX 


Eminence,    medial,  of    rhoujboid 
fossa,  847 

parietal,  231,  277,  282 

pyramidal,  of  pons,  833 
of  tympanic  cavity,  1052 

thenar,  546 
Eminences    and    depressions    of 

bones,  196 
Eminentia  arcuata,  241 

articularis,  237 

coUateralis,  881 

pyramidalis,  1052 

saccularis,  861 
Emissary  veins,  746 
Enamel  cells,  1123 

droplet,  1123 

epithelium,  1123 

fibres  or  prisms,  1120 

organ, 1123 

of  teeth,  1120 

formation  of,  1123 
Enarthrosis,  382 
Encephalon,  821 

dissection  of,  821 
End-arteries,  1214 
End-bulbs  of  Krause,  1069 
End-plates,  motor,  of  Kiihne,  803 
Endocardial  cushions,  148 
Endocardium,  613 
Endognathion,  299 
Endolymph,  1061 
Endomysium,  64 
Endoneurium,  802 
Endoskeleton,  195 
Endosteal  laver  of  dura  mater, 

902 
Endothelium,  37 

camerae  anterioris,  1021 

corneal,  1021 
Engelmann,  basal  knobs  of,  38 
Enlargements  of  medulla  spinalis, 

808 
Ensiform  appendix,  220 
Entoderm,  85 
Entodermal  cloaca,  172 
Entrance  of  larynx,  1085 
Eosinophil  corpuscles,  63 
Eparterial  branch  of  right  bron- 
chus, 1092,  1105 
Ependymal  layer,  117 
Epicardium,  613 
Epicondyles  of  humerus,  313 
Epicranial  aponeurosis,  466 
Epidermic    coat   of   hair   follicle, 

1077 
Epidermis,  development  of,  116 

structure  of,  1071 
Epididymis,  1231 
Epidural  space,  903 
Epigastric    artery,    deep    or    in- 
ferior, 709 
applied  anatomy  of,  710 
peculiarities,  709 
surface  markings  of,  1309 
superficial,  717 
superior,  666 

fold,  1187 

lymph  glands,  786 

region,  1147 

vein,  deep,  760 
superficial,  756 
Epiglottis,  1082 

tubercle  or  cushion  of,  1082 
Epimysium,  64 
Epineurium,  801 
Epiotic  centre  of  temporal  bone, 

245 
Epiphyses,  atavistic,  59 

pressure,  59 

traction,  59 
Epiphysial  cartilage,  57 
Epiphysis,  59,  859 
Epiploic  foramen,  176,  1155 

glands,  right,  788 
Epistropheus,,  200 


Epilhalamus,  127,  859 

fasciculus  relrojlexus   [of   Mey- 

nert],  859 
ganglion  habenulae,  859 
pineal  bod.^^  859 

structure  of,  860 
posterior  commissure,  860 

nucleus  of,  860 
trigonum  habenulae,  859 
Epithelial  cells,  36 
Epithelium,  36 
ciliated,  37 
columnar,  37 
corneae,  1019 
cylindrical,  37 
enamel,  1123 
germinal,    of    Waldeyer,    184, 

1245 
glandular,  37 
pavement,  37 
simple,  37 
stratified,  39 

of  cornea,  1019 
transitional,  40,  1223 
Epitympanic  recess,  240,  1049 
Eponychium,  1075 
Epoophoron,  181,  1244 
Equator  of  lens,  1031 
Erector  clitoridis  muscle,  521 
penis  muscle,  518 
spinae  or  sacrospinalis  muscle, 
488 
Eruption  of  teeth,  1124 
Erythroblasts,  51 
Erythrocytes,  61 
Ethmoid  bone,  251 
Ethmoidal  arteries,  650 
bone,  251 

articulations  of,  255 
cribriform  plate  of,  252 
crest,  260,  267 
foramina,  287 
horizontal  lamina,  252 
labso-inth  or  lateral  mass  of, 

253 
lamina  papyracea  of,  253 
OS  planum  of,  253 
ossification  of,  254 
perpendicular        plate        of, 

252 
uncinate  process  of,  253 
vertical  plate,  252 
canals,  235,  253 
cells,  253,  1014 
notch,  235 
plate,  107 
process  of  inferior  nasal  concha, 

268 
spine,  246,  290 
Ethmovomerine  cartilage,  270 
Eustachian  tube,  1052 

valve,  607,  608 
Excavation,  rectouterine,  1151 

vesicouterine,  1152 
Exner,  plexus  of,  893 
Exognathion,  299 
Exoskeleton,  195 
Extensor     carpi    radialis    brevis 
muscle,  542 
longus  muscle,  542 
ulnaris  muscle,  544 
coccygis  muscle,  490 
digiti   quinti   proprius   muscle, 

544 
digitorum  brevis  muscle,  586 
communis  muscle,  544 
longus  muscle,  577 
hallucis  longus  muscle,  577 
indicis  muscle,  546 

proprius  muscle,  546 
minimi  digiti  muscle,  544 
ossis  metacarpi  pollicis  muscle, 

545 
pollicis  brevis  muscle,  545 
longus  muscle,  545 


Extensor  jiriiiii  internodii   jjollicis 
muscle,  545 

proprius  hallucis  muscle,  577 

secundi    internodii    pollicis 
muscle,  545 
Exterior  of  skull,  277 
External  abdominal  ring,  500 

arcuate  ligament,  495 

auditory  canal,  1040 
meatus,  1046 

calcaneal  artery,  726 

calcaneoastragaloid     ligament, 
453 

canthus  of  eyelids.  1038 

circumflex  artery,  716 

cutaneous  nerve,  977 

geniculate  body,  858 

intercostal  muscles,  492 

lateral     ligament,     394,     419, 
426 

ligament  of  malleus,  1055 

malleolar  artery,  723 

oblique  muscle,  499 

plantar  artery,  727 
nerve,  989 

popliteal  nerve,  989 

pterygoid  muscle,  474 

pudic  arteries,  716 

respiratory  nerve  of  Bell,  960 

saphenous  vein,  757 

semilunar  fibrocartilage,  442 

spermatic  fascia,  1229 

sphincter  ani  muscle,  516 
Extraspinal  veins,  754 
Extremitas   acromialis   [clavicula], 
303 

sternalis  [clavicula],  303 
Extremity  of  penis,  1239 
Extrinsic      muscles     of     tongue, 

1129 
Eye,  1017 
Eyeball  or  bulb  of  eye,  1017 

accessory  organs  of,  1034 

applied  anatomy  of,  1031 

aqueous  humor,  1030 

capsule  of  Tenon,  1037 

chambers  of,  1024 

choroid,  1021 

ciliary  body,  1023 
muscle,  1023 
processes,  1023 

conjunctiva,  1040 

cornea,  1018 

crystalline  lens,  1030 

development  of,  134 

fascia  bulbi,  1037 

fibrous  tunic,  1017 

hyaloid  membrane,  1030 

iris,  1024 

7nembrana  pupillaris,  136 

orbiculus  ciliaris,  1023 

pupil,  1024 

refracting  media,  1030 

retina,  1026 

pigmented  layer  of,  1027 
proper,  1027 

supporting    frame-work     of, 
1029 

sclera,  1017 

tunics  of,  1017 
vascular,  1021 

uvea,  1025 

vessels  and  nerves  of,  1031 

■vitreous  body,  1030 
Eyebrows,  1038 
Eyelashes,  1038 
Eyelids,  1038 

applied  anatomy  of,  1042 

canthus  of,  1038 

development  of,  137 

muscles  of,  dissection  of,  467 

structure  of,  1039 

surface  anatomy  of,  1287 

tarsi  of,  1039 
Eye-teeth,  1118 


INDEX 


1371 


Face,  bones  of,  255 
development  of,  111 
lymphatics  of,  774 
surface  anatomy  of,  1282 
Facial  artery,  033 

transverse,  638 
bones,  255 
canal,  241 

hiatus  of,  241 

prominence  of,  1052 
lymph  jilands,  775 
nerve,  929 

applied  anatomy  of,  933 
vein,  anterior,  733 

applied  anatomy  of,  733 

common,  733 

deep,  733 

posterior,  734 

transverse,  734 
Falciform  ligament  of  liver,  1150 

1195 
margin  of  fossa  ovalis,  564 
process  of  sacrotuberous  liga- 
ment, 405 
Fallopian  tubes,  1247 
Fallopius,    aqueduct    of,    promi- 
nence of,  1051 
False  ligaments  of  bladder,  1221 
pehas,  340 
ribs,  220 

vocal  cords,  1085 
Falx  aponeurntica  inguinalis,  505 
cerebelli,  900 
cerebri,  900 
Fascia  or  Fascise,  463 
of  abdomen,  498 

triangular,  502 
anal,  511 
of  ankle,  584 
antibrachial,  536 
antibrachii,  536 
of  arm,  534 
axillarj-,  526 
bicipital,  535 
brachial,  534 
brachii,  534 
buccopharyngeal,  477 
bulbi,  1037 
of  Camper,  498 
cervical,  475,  476 
clavipectoral,  528 
of  Colles,  337,  499,  517 
colli,  476 

applied  anatomy  of,  478 
coracoclavicular,  528 
coracoclavicularis,  528 
cremasteric,  504 
cribrosa,  563 
cruris,  576 
deep,  464 
of  deltoideus,  530 
dentata  hippoca?npi,  875 
diaphragmatic  part  of  pelvic, 

511 
dorsal,  of  foot,  586 
endopehdc,  512 
of  forearm,  536 
general  description  of,  463 
of  hand,  546 
iliaca,  560 
iliopectineal,  560 
infraspinata,  533 
infraspinatous,  533 
infundibuliform,  508 
intercolumnar,  1229 
intercostal,  492 
intercrural,  501 
lata,  563 

falciform  margin  of,  564 

fossa  ovalis  of,  564 

iliotibial  tract  or  band  of,  563 
of  leg,  576 

deep  transverse,  580 


Fascia  or  Fascia-,  lumbar,  486 
masseteric,  472 
of  obturator  internus,  510 
orbital,   1038 
palmar,  550 

parotidcomassetei"ic,  472 
pectoral,  526 
pelvic,  510 
plantar,  586 
pretracheal,  477 
prevertebral,  477 
propria  of  femoral  hernia,  1189 
of  piriformis,  511 
of  psoas  and  iliacus,  559 
of  quadratus  lumborimi,  510 
rectal,  518 
rectovesical,  512 
renal,  1209 
of  Scarpa,  499 
Sibson's,  1096 

spermatic,  external,  501,  1229 
subscapular,  531 
subscapularis.  531 
superficial,  463 
supraspinala,  532 
supraspinatous,  532 
temporal,  473 
of  thigh,  562 
of  thoracic  region,  526 
transversalis ,  508 
triangular,  of  abdomen,  502 
of  upper  extremity,  522 
of  urogenital  diaphragm,  519, 
520,  521 

region,  517 
vesical,  512 
Fasciculi,  intrafusal,  1071 

longitudinales,  834 
Fasciculus,  anterior  proper,  815 
cerebelloolivary,  830 
cerebellospinal,  816,  828 
cerebroolivary,  830 
cerebrospinal,  815 
cerebrospinalis  anterior,  815 

lateralis,  815 
comma-shaped,  817 
cornucommissural,  817 
cuneatus,  817 
gracilis,  817 
lateral  proper,  817 
lateralis  proprius,  817 
of  Lissauer,  817 
longitudinal,  inferior,  891 

medial,  851 

posterior,  851 

superior,  891 
occipitofrontal,  891 
olfactory,  887 
olivospinal,  816 
perpendicular,  891 
retroflexus  of  Meynert,  859 
rubrospinal,  816 
secondary  sensory,  817 
solitarius,  833 
spinocerebellar,  816 

ventral,  817 
spinoolivary,  830 
spinotectal,  817 
spinothalamic,  817 
superficial  antero-lateral,  816 
tectospinal,  815,  816 
thalamomamillary,  886 
uncinate,  890 
vestibulospinal,  815 
Fasciola  cinerea,  875 
Fat  or  adipose  tissue,  42 

cells,  42 
Fauces,  arches  or  pillars  of,  1112 

isthmus  of,  1112 
Female  genital  organs,  1243 
bulb  of  vestibule,  1256 
carunculae       hymeneales, 
j  1257 

clitoris,  1257 
'  development  of,  180 


epo- 


Female     genital      organs, 
ophoron,  1244 
fourchette,  1257 
glands  of  Bartholin,  1258 
greater  vestibular,  1257 
hymen,  1257 
labia  majora,  1256 

minora,  1257 
mons  pubis,  1256 
navicular  fossa,  1257 
ovaries,  1243 
uterine  tubes,  1247 
uterus  or  womb,  1248 
vagina,  1255 
vestibule,  1257 
pronucleus,  80 
urethra,  1228 
Femoral  artery,  710 

applied  anatomy  of,  715 
branches  of,  715 
deep,  716 

peculiarities  of,  714 
surface  marking  of,  1331 
canal,  712 

circumflex  arteries,  716,  717 
cutaneous  nerve,  anterior,  981 
lateral,  977 
posterior,  985 
fossa,  712 
fovea,  1187 
hernia,  1189 

muscles,  medial,  dissection  of, 
567 
posterior,  dissection  of,  594 
nerve,  980 

applied  anatomy  of,  992 
ring,  712 
septum,  712 
sheath,  710 
triangle,  565,  712 
vein,  758 
Femur,  345 

applied  anatomy  of,  852 
articulations  of,  352 
condyles  of,  349 
head  of,  345 
neck  of,  345 
ossification  of,  352 
spiral  line  of,  348 
structure  of,  350 
surface  anatomy  of,  1324 
trochanters  of,  346,  347 
Fenestra  cochleae,  1051 
ovalis,  1051 
rotunda,  1051 
vestibuli,  1051 
Fenestrated  membrane  of  Henle, 

44 
Fertilization  of  ovum,  82 
Fetal  heart,  peculiarities  of,  161 

membranes,  93 
Fetus,  circulation  in,  616 
foramen  ovale  in,  149,  616 
valve  of  inferior  vena  cava  in, 

616 
vascular     system     in,     peculi- 
arities of,  615 
Fibrae  inter crurales,  501 
pontis  profundae,  834 

super ficiales ,  834 
propriae  [cerebellum],  842 
Fibre  cells,  contractile,  68 
Fibres,  arcuate,  831 
dentinal,  1120 
intercolumnar,  501 
intercrural,  501 
intrafusal,  1071 
of  muscles,  64 
nerve,  70 
of  Purkinje,  69 
of  Remak,  76 

sustentacular,  of  Miiller,  1029 
of  Tomes,  1120 
Fibrocartilage,  49 
circumferential,  50 


1372 


INDEX 


Fibrocartilage,  connecting,  50 
interarticular,  49 
intervertebral,  385 
semilunar,  of  knee,  442 
stratiform,  50 
yellow  or  elastic,  50 
Fibrocartilaginous  lamina,  inter- 
pubic,  407 
Fibrous  capsule  of  Glisson,  1196 
pericardium,  601 
rings  of  heart,  613 
sheaths    of    flexor    tendons    of 
fingers,  540 
of  toes,  588 
tissue,  white,  43 
tunic  of  kidnev,  1210 
Fibula,  359 

applied  anatomy  of,  361 
articulations  of,  361 
ossification  of,  361 
surface  form  of,  1324 
Fibular  artery,  723 

collateral    ligament    of    knee- 
joint,  440 
Fifth  metacarpal  bone,  330 
metatarsal  bone,  372 
nerve.  914 
ventricle,  887 
Filiform  papillse  of  tongue,  1128 
Fillet,  852 
lateral,  853 
mesial,  853 
Filtration  angle  of  eye,  1019 
Filum  terminale,  807 
Fimbria  hippocatnpi,  887 

ovarian,  1247 
Fimbriae  of  uterine  tube,  1247 
Fimbriodentate  fissure,  875,  887 
First  cuneiform  bone,  369 

dorsal  metacarpal  artery,  678 

metatarsal  artery,  724 
metacarpal  bone,  329 
metatarsal  bone,  371 
nerve,  908 
Fissura  antitragohelicina,  1044 
calcarina,  869 
cerebri  lateralis  [Sylvii],  867 

longitudinalis,  865 
collateralis,  869 
hippocampi,  874 
mediana  anterior  [mednllae  ob- 
longatae]    822 
spinalis],  808 
posterior   [meduUae   oblonga- 
tae],  822 
parietooccipitalis,  868 
petrotympanica,  1049 
priyna  [cerebellum],  124 
[rhinencephalon],  875 
secunda  [cerebellum],  124 
Fissure  or  Fissures,  anterior  me- 
dian of  medulla  spinalis,  808 
callosomarginal,  869 
central,  868 
of  cerebellum,  837,  838 
development  of,  125 
floccular,  125 
horizontal,  837 
postcentral,  838 
postnodular,  838 
postpyramidal,  839 
precentral,  838 
preclival,  838 
prepyraniiidal,  838 
of  cerelarum,  867 
calcarine,  869 
callosal,  873,  876 
collateral,  869 
development  of,  131 
external  rhinal,  128 
fimbriodentate,  875,  887 
hippocampal,  130,  814 
interlobular,  867 
lateral,  130,  867 
longitudinal,  865 


Fissure  or  Fissures  of  cerebrum, 
parietooccipital,  868 
of  Rolando,  868 
of  Sylvius,  867 
transverse,  889 
choroidal,  135,  888 
circuminsular,  869 
congenital,  of  cranium,  255 
dentate,  874 
Glascrian.  238,  1040 
of  liver,  longitudinal,  1194 

transverse,  1194 
longitudinal,  great,  865 
of  lungs,  1104 
of  medulla  oblongata,  822 
orbital,  inferior,  284,  288 
superior,  249,  288,  290 
petrooccipital,  280,  291 
petrosphenoidal,  280 
petrotympanic,  238,  280,  1049 
pterygoid,  250 
ptervgomaxillary,  284 
of  Rolando,  868 
sphenomaxillarj^  284 
of  Sylvius,  867 
tympanomastoid,  280 
vestibular,  1060 
Fixation  of  kidney,  1209 

of  muscles,  462 
Flat  b9nes,  196 

Flechsig,  cerebellar  tract  of,  816, 
828 
oval  area  of,  818 
Flexor  accessorius  muscle,  589 
brevis    minimi    digiti    muscle, 

554,  590. 
carpi  radiaiis  muscle,  537 

ulnaris  muscle,  538 
digiti  quinti   brevis  muscle   of 
foot,  590 
of  hand,  554 
digitorum  brevis  muscle,  588 
longus  muscle,  581 
profundus  muscle,  540 
sublimis  muscle,  539 
hallucis  brevis  muscle,  589 

longus  muscle,  581 
pollicis  brevis  muscle,  553 
longus  muscle,  540 
Flexure,  cervical,  121 
colic,  left,  1180 

right,  1180 
hepatic,  1180 
pontine,  121 
splenic,  1180 
ventral  cephalic,  121 
Floating  ribs,  221 
Floccular  fissure,  125 
Flocculus,  839 

Floor  of  fourth  ventricle,  847 
Floor-plate,  117 
Fluid,  cerebrospinal,  905 
Fluids,  circulating.  61 
Fold  or  Folds,  amniotic,  96 
aryepiglottic,  1085 
caudal,  92 
cephalic,  92 
duodenojejunal,  1159 
epigastric,  1187 
gastropancreatic,  1156 
glossoepiglottic,  1082,  1126 
ileocecal,  1160 
malleolar,  1050 
rectouterine,  1250 
sacrogenital,  1153,  1250 
salpingopalatine,  1139 
salpingopharyngeal,  1139 
transverse,  of  rectum,  1183 
of  Treves,  1160 
umbilical,  1187,  1221,  1222 
ventricular,  of  larynx,  1085 
vestigial,  of  Marshall,  159,  603 
vocal,  of  larynx,  1086 
Folium  cacumirus,  838 
vermis,  838 


Follicle  of  hair,  1076 
Follicles,  agminated,  1175 

Graafian,  or  vesicular  (jvarian, 
1245 
Fontana,  spaces  of,  1021 
Fontanellcs,  294 
Foot,  arches  of,  459 

fascia  of,  586 

muscles  of,  586 

dissection  of,  587,  588 

ossification  of  bones  of,  374 

phalanges  of,   articulations  of, 
459 

skeleton  of,  362 

applied  anatomy  of,  375 

surface  anatomy  of,  1325 

Foramen,  caroticoclinoid,  249,  290 

cecum  of  frontal  bone,  2.35 
of  medulla  oblongata,  822 
of  tongue,  165,  1126 

condyloid,  anterior,  229 

epiploicum,  170,  1155 

of  Huschke,  244,  245 

incisive,  261,  278 

infraorbital,  257,  286 

interventricular,  865,  887 

intervertebral,  197 

jugular,  280,  291 

lacerum,  280,  291 

magnum,  227,  230,  288,  291 

Majendii,  847 

mandibular,  272 

mastoid,  239,  282 

mental,  271,  286 

of  Monro,  865,  887 

obturator,  339 

optic,  246,  250,  290 

ovale  of  heart,  149,  616 
of  sphenoid,  248,  280,  291 

palatine,  278 

parietal,  277 

rotundum,  248,  291 

sciatic,  406 

singulare,  242 

sphenopalatine,  267 

spinosum,  248,  280,  291 

sternal,  220 

stylomastoid,  243,  280 

supraorbital,  235,  286,  2S8 

supratrochlear,  313 

•thj^Toid,  339 

transversarium,  198 

vena-caval,  497 

vertebral,  197 

Vesalii,  248,  291 

of  Winslow,  170,  689,  1155 

zygomaticofacial,  263,  286 

zygomatico5rbital,  264 

zygomaticotemporal,  263,  282 
Foramina,  ethmoidal,  287 

intervertebral,  197 

for  olfactory  nerves,  252 

in  roof  of  fourth  ventricle,  847 

sacral,  206,  208 

of  Scarpa,  261,  278 

of  Stensen,  261,278 

Thebesii,  608 

venarum  niinimarum,  608 
Forceps,  anterior,  877 

posterior,  877 
Forearm,  fascia  of,  536, 

muscles  of,  536 

dissection  of,  536,  539,  542 
Forebrain,  90,  125,  855 
Foregut,  92,  162 
Foreskin,  1239 
Form     of    embrj^o    at     different 

stages,  191 
Formatio  grisea,  833 

of  medulla  spinalis,  809 

reticularis  alba,  833 
Fornicolumns,  886 
Fornix  of  brain,  885 
body  of,  886 
columns  of,  886 


INDEX 


1373 


Fornix  of  brain,  crura  of,  887 

(levcloimR'nt  of,  131 

pillars  of,  880,  887 
of  conjunctiva,  1041 
Fossa  or  Fossio,  acetabular,  339 
anticubital,  (572 
canine,  257 
cecal,  1159,  1100 
cochlearis,  1058 
condyloid,  230,  281 
coronoid,  313 
cranii  anterior,  288 

media,  290 

posterior,  291 
digastric,  239 
digital,  of  epididymis,  1231 

of  femur,  347 
for  ductus  venosus,  1194 
duodenal,  1158 
duodenojejunal,  1159 
femoral,  712 
for  gall-bladder,  1194 
glenoid,  238 
hyaloid,  1030 
hypophvseos,  246,  290 
ileocecal,  1159,  1160 
iliac,  335 
incisive,  256,  271 
iucudis,  1052 

for  inferior  vena  cava,  1194 
infraspinatous,'305 
infratemporal,  283 
infratcmporalis,  283 
intercondvloid,  of  femur,  349 

of  tibia,  356 
interpeduncular,  848,  865 
intersigmoid,  1160 
ischiorectal,  515 
ischiorectalis,  515 
jugular,  243 
lacrimal,  235,  286 
of  liver,  1194 
mandibular,  238,  280,  283 
mastoid,  238 
nasal,  1010 
navicularis  [urethra],  1226 

[^Tilva],  1257 
occipital,  inferior,  292 
olecranon,  313 
ovalis  of  fascia  lata,  564 

of  heart,  60S 
ovarian,  1154,  1244 
pararectal,  1153 
paravesical,  1153 
pericecal,  1159 
peritoneal.  1157 
popliteal,  718 
pterygoid,  250 
pterygopalatina,  284 
ptervgopalatine,  284 
radial,  312 
retrocecal,  1160 
retroperitoneal,  1157 
rhomboid,  847 
rhomhaidea,  847 
of  Rosenmuller,  1138,  1139 
sagit talis  sinistra  [liver],  1194 
scaphoid,  250,  278 
of  skull,  anterior,  288 

middle,  290 

posterior,  291 
sphenomaxillary,  284 
subarcuate,  242 
subscapular,  304 
supraspinatous,  305 
supratonsillar,  1139 
Sj-lvian,  131 
temporal,  282 
temporalis,  282 
triangularis,  1044 
trochanteric,  347 
for  umbilical  vein,  1194 
venae  cavae,  1194 
vermian,  228 
vesicae  felleae,  1194 


Fossa     or     Fossa;,     zygomatic, 

272 
Fountain  decussation  of  Meynert, 

854 
Fourchctte,   1257 
Fourth  metacarpal  bone,  330 

metatarsal  bone,  372 

nerve,  913 

ventricle,  845 
floor  of,  847 
Fovea  capitis  fcmoris,  345 

centralis  retinae,  1020,  1029 
structure  of,  1029 

dentis,  199 

femoral,  1187 

inguinal,  1187 

of  rhomboid  fossa,  84S 

supravesical,  1187 

trochlear,  235,  286 
FoveoliE,  Howship's,  52 
Fracture  of  bones  of  foot,  375 
of  hand,  332 

of  clavicle,  303 

of  femur,  353,  592 

of  fibula,  593 

of  humerus,  313,  557 

of  mandible,  300 

of  maxilla,  300 

of  nasal  bone,  300 

of  olecranon,  321,  558 

of  patella,  355,  593 

of  pelvis,  344 

Pott's,  593 

of  radius,  321,  558 

of  ribs,  225 

of  scapula,  309 

of  skull,  297 

of  sternum,  225 

of  tibia,  361,  593 

of  ulna,  321,  558 

of  zygomatic  arch,  300 
Free  nerve-endings,  1069 
Freely  movable  joints,  381 
Frenula  of  colic  valve,  1179 

of  lips,  1110  _ 
Frenulum  of  clitoris,  1257 

of  labia  minora,  1257 

linguae,  1126 

of  prepuce,  1239 

veli,  853 
Frontal  air  sinuses,  235,  1014 

artery,  650 

bone,  233 

articulations  of,  237 

orbital  or  horizlintal  part  of, 

235 
ossification  of,  237 
squama  of,  234 
structure  of,  236 

convolution,  ascending,  -869 

crest,  235 

eminences,  234,  278,  282 

gvri,  869,  870 

lobe,  869 

nerve,  916 

operculum,  873 

process  of  maxilla,  260 

sulci,  869 

suture,  234,  278 

vein,  732 
Frontoethmoidal  suture,  288 
Frontomaxillary  suture,  287 
Frontonasal  duct,  236 

process,  111 
Frontopontine  fibres,  850 
Frontosphenoidal  process  of  zj^go- 

matic  bone,  264 
Fundiform     ligament     of     penis, 

1239 
Fundus      glands      of      stomach, 
1163 

tympani,  1049 

of  uterus,  1249 
Fungiform    papillse    of    tongue, 

1128 


Funinculi  of  medulla  spinalis,  814, 

815 
Funiculus  separans,  848 

spermaticus,  1229 
Furcal  nerve,  975 
Furcula,  164,177 
Furrow,  chordal,  91 

dental,  1122 

iliac,  1213 

nasooptic,  112,  137 

sternal,  1208 
Furrowed  band  of  cerebellum,  839 
Fusiform  gyrus,  871,  872 


G 


Galea  aponeurotica,  466 
Galen,  veins  of,  740 
Gall-bladder,  1199 

applied  anatomy  of,  1201 

fossa  for,  1194 

lymphatic  vessels  of,  793 

structure  of,  1199 
Gangliated  cord,  995 
Ganglion  or  Ganglia,  803 

aorticorenal,  1003 

cardiac,  of  Wrisberg,  1002 

carotid,  996 

cervical,  997,  998 

cenicale  inferius,  998 
medium,  997 
superius,  997 

ciliare,  917 

ciliarv,  917 

coeliac,  1002 

coeliaca,  1002 

collateral,  995 

of  Corti,  1060,  1068 

Gasserian,  914 

genicular,  930 

geniculi,  930 

of  glossopharyngeal,  937 

habemdae,  859 

impar,  1001 

inferior,  939 

interpeduncular,  848,  851 

jugular,  938,  941 

jugular e,  941 

Langley's,  1138 

lenticular,  917 

Meckel's,  919 

nodosum,  941 

ophthalmic,  917 

otic,  924 

oticum,  924 

petrosum,  939 

petrous,  939 

phrenicum,  1004 

ridge  or  neural  crest,  88,  120 

of  Scarpa,  1068 

semilunar,  of  abdomen,  1002 
of  trigeminal  nerve,  914 

semihinare  [Gasseri],  914 

sphenopalatine,  919 

sphenopalaiimim ,  919 

rami  nasales    posteriores   in- 
feriores,  921 
superiores,  921 
orbitales,  920 

spinal,  948 

spinale,  948 

spiral,  of  cochlea,  1068 

splanchnicum,  999 

suhmaxillare,  925 

submaxillary,  925 

superior,  of    glossopharyngeal, 
938 
mesenteric,  1004 

superius,  938 

of  vagus,  940 

vestibular,  1068 

of  Wrisberg,  1002 
Ganglionic     arterial     sj'stem    of 
brain,  654 


1374 


INDEX 


Ganglionic        arteries,        antero- 
lateral, 653 
antero-medial,  652 
postero-lateral,  662 
postero-mcdial,  653,  662 

layer  of  retina,  1028 
Gartner,  duct  of,  1S2,  1245 
Gasserian  ganglion,  914 
Gaster,  1161 
Gastric  arteries,  short,  691 

artery,  left,  688 
right,  689 

glands,  1166 

impression,  1192 

lymph  glands,  788 

nerves  from  vagus,  943 

plexuses      from      sj^mpathetic, 
1004 
from  vagus,  943 

veins,  short,  766 
Gastrocnemius  muscle,  578 
Gastrocolic  ligament,  1152 

omentum,  1157 
Gastroduodenal  artery,  690 
Gastroepiploic  arteries,  690,  691 

veins,  766 
Gastrohepatic  omentum,  1156 
Gastrolienal  ligament,  1155 
Gastrophrenic  ligament,  1163 
Gemellus  inferior  muscle,  573 

superior  muscle,  573 
General     sensations,     peripheral 

terminations  of  nerve  of,  1069 
Generation,   development  of  ex- 
ternal organs  of,  190 
Genicular  arteries,  718,  720,  721 

ganglion  of  facial  nerve,  930 
Geniculate  bodies,  858 
Geniculum  of  facial  nerve,  930 

of  internal  capsule,  883 
Genioglossus  muscle,  1129 
Geniohyoglossus  muscle,  1129 
Geniohyoid  muscle,  481 
Geniohyoideus  muscle,  481 

dissection  of,  481 
Genital  cord,  184 

corpuscles,  1069 

organs  of  female,  1243 
external,  1256 
of  male,  1228 

glands,  184 

ridge,  184 

swellings,  190 

tubercle,  190 
Genitocrural  nerve,  977 
Genitofemoral  nerve,  977, 
Gennari,  band  of,  891,  893 
Genu  of  corpus  callosum,  876 

of  internal  capsule,  883 
Gerlach,  tube  tonsil  of,  1053 
Germ,  dental,  1121,  1122 
Germ  centres,  770 
Germinal  cells,  77 

epithelium,  184,  1245 

path,  185 

spot,  77 

vesicle,  77 
Giacomini,  band  of,  875 
Giant  cells,  51 

of  Betz,  891 
Gianuzzi,  crescents  of,  1137 
Gimbernat's  ligament,  502 
Gingivae,  1111 
Ginglymus,  382 
Giraldes,  organ  of,' 1236 
Girdle  of  inferior  extremity,  301 

pelvic,  301 

shoulder,  301 

of  superior  extremity,  301 
Glabella,  234,  278,  296 
Gladiolus,  218 

Gland    or    Glands,    accessory,   of 
mouth,  1138 
part  of  parotid,  1134 

anterior  lingual,  1131 


Gland  or  Glands,  areolar,  1258 

arytenoid,  1091 

of  Bartholin,  1258 

of  Blandin,  1131 

of  Bowman,  1012 

Brunner's,  1175 

buccal,  1111 

bulbourethral,  1243 

carotid,  1273 

ceruminous,  1047 

ciliary,  1039 

coccygeal,  1273 

Cowper's,  1243 

ductless,  1260 

duodenal,  1175 

gastric,  1166 

genital,  184 

intestinal,  1174 

labial,  1110 

lacrimal,  1041 

of  larynx,  1090 

lenticular,  of  stomach,  1166 

of  Littre,  1226 

Luschka's,  1273 

mammae,  1258 

mammary,  1258 

Meibomian,  1040 

molar,  1111 

of  Nuhn,  1131 

oesophageal,  1146 

palatal,  1112 

parathyroid,  1263 

parotid,  1133 

Peyers,  1175 

preputial,  1239 

prostate,  1241 

salivary,  1133 

sebaceous,  1078 

solitary,  1175 

sublingual,  1137 

submaxillary,  1135 

sudoriferous,  1078 

suprarenal,  1270 

sweat,  1078 

tarsal,  1040 

thymus,  1264 

thyroid,  1261 

of  tongue,  1131 

trachoma,  1041 

urethral,  1226 

uterine,  1252 

vestibular,  greater,  1258 
Glandula  lacrimalis,  1041 

sublingualis,  1137 

submaxillar  is,  1135 

thyreoidea,  1261 

vestibularis   major    [Bartholini], 
1258 
Glandulae  bulbourethrales,  1243 

duodenales  [Brunneri],  1175 

intestinales  [Lieberkuhni],  1174 

labiales,  1110 

oesophageae,  1146 

Pacchioni,  905 

parotis,  1133 

sebaceae,  1078 

sudoriferae,  1078 

suprarenales  accessoriae,  1271 

suprarenalis,  1270 

tarsales  [Meibomi],  1040 

thyreoideae  accessoriae,  1262 
Glandular  epithelium,  37 
Glans  clitoridis,  1257 

penis,  1238 
Glaserian  fissure,  238,  1049 
Glenohumeral  ligaments,  415 
Glenoid  cavity,  307 

fossa,  238 

ligament    of    CruveUhier,    430, 
459 
of  shoulder,  415 
Glenoidal    labrum    of    hip-joint, 
434 
of  shoulder-joint,  415 
Gliding  joints,  382 


Gliding  movement,  383 
Glisson's  capsule,  1156,  1196 
Globular  processos  of  His,  111 
Globus  major  [o)iididymis],  1231 

minor  [epididymis],  1231 

pallidus,  882 
Glom.era  carolica,  1273 
Glomus  coccijgeum,  1273 
Glossoopiglottic  folds,  1082,  1126 
Glossojjalatine  arch,  1112 
Glossopalatinus     muscle,      1114, 

1129  note 
Glossopharyngeal  nerve,  937 
Glottis  respiratoria,  1087 
vocalis,  1087 

rima  of,  1087 
Gluta,eus  maximus  muscle,  569 

medius  muscle,  570 

minimus  muscle,  570 
Gluteal  artery,  inferior,  706 
superior,  707 

lines  of  ilium,  333 

muscles,  569 

nerve,  inferior,  985 
superior,  984 

region,    muscles    of,    dissection 
of,  569,  572 

tuberosity,  348 

veins,  760 
Gnathic  index,  296 
Goblet  cells,  37 
Golgi,  cells  of,  892 

organs  of,  1070 
Golgi  and  Mazzoni,  corpuscles  of, 

1069 
GoU,  tract  of,  808,  817 
Gomphosis,  381 
Gonion,  296 
Gower's,  tract  of,  816 
Graafian  follicles,  1245 
structure  of,  1245 
Gracile  nucleus,  824 
Gracilis  muscle,  567 
Grandry,    tactile    corpuscles    of, 

1069 
Granular  layer  of  dentin,  1119 
Granulationes  arar.hnoideales,  905 
Granulations,  arachnoid,  905 
Granule  cells,  41 
Gray  commissure  of  brain,  856 

commissures  of  medulla  spinalis, 
810 

or  gelatinous  nerve  fibres,  76 

substance  of  cerebellum,  842 
of  cerebral  hemispheres,  891 
of  medulla  oblongata,  829 
spinalis,  809 
Great  auricular  nerve,  956 

cardiac  nerve,  997 
vein,  730 

cerebral  vein,  740 

longitudinal  fissure,  865 

omentum,  1157 

sacrosciatic  ligament,  404 

saphenous  vein,  656 

splanchnic  nerve,  998 

transverse  fissure  of  brain,  889 

wings  of  sphenoid,  248 
Greater  cavernous  nerve,  1005 

curvature  of  stomach,  1162 

multangular  bone,  326 

occipital  nerve,  951 

omentum,  1157 

palatine  foramen,  278 

pelvis,  340 

peritoneal  sac,  1150 

sciatic  foramen,  406 
notch,  336 

sigmoid  cavity,  315 

superficial  petrosal  nerve,  919, 
931 

trochanter,  347 

vestibular  glands,  190,  1258 
Groove,  atrioventricular,  604 

auriculoventricular,  604 


L\DEX 


1375 


Groove,  liicipital,  311 
carotid,  247,  290 
chiasinutic,  216,  290 
costal,  222 
infraorbital,  258 
interatrial,  604 

intertubercular,  of  hunuuus,311 
lacrimal,  258,  287 
musculospiral,  311 
mj'lohyoid,  272 
neural,  88 
obturator,  339 
occipital,  239 
optic,  246 
primitive,  SO 
pterygopalatine,  250 
for  radial  nerve,  311 
vertebral,  214 
Guhenmculum  denlis,  1124 

testis,  18G 
Ciudden,  commissure  of,  909 
(JiUlct,  1140 
Gums,  nil 

applied  anatomy  of,  1112 
Gustatorv  calyculi,  1007 
cells,  1007 
hair,  1008 
pore,  1007 
Gyre,  medifrontal,  870 
precentral,  869 
subfrontal,  870 
superfrontal,  869 
Gyri  of  .brain,  869 
angular,  871 
of  Broca,  870 
central,  anterior,  869 

posterior,  871 
cingulate,  874 
cuneus,  871 
dentate,  875 
frontal,  869,  870 
fusiform,  871,  872 
hippocampal,  874 
of  insula,  873 
of  limbic  lobe,  873 
lingual,  871 
occipital,  871 
orbital,  870 
precuneus,  871 
quadrate,  871 
straight,  870 
subcallosal,  875 
superior  parietal  lobule,  871 
supracallosal,  875 
supramarginal,  871 
temporal,  872 

transverse,  of  Heschl,  872 
uncus,  874 
Gyrus  centralis  anterior,  869 
posterior,  871 
cinguli,  873 
dentatus,  875 
epicallosus,  875 
frontalis  inferior,  870 
medius,  870 
superior,  869 
hippocampi,  874 
marginal,  870 
subcallosus,  875 


Habenttlar  commissure,  859 
Hair  cells  of  spiral  organ  of  Corti, 

1067 
Hairs,  1075 

cuticle  of,  1077 

follicle  of,  1076 

gustatory,  1008 

olfactory,  1012 

roots  of,  1076 

scapus  or  shaft  of,  1077 

structure  of,  1077 
Haller,  vas  aberrans  of,  1236 


Hamate  bone,  32S 
Hamstring  muscles,  574 

tendons,    ap])lied    anatomy    of, 
575 
Hamulus  of  hamate  bone,  328 
lacrimal,  263 
laviinae  spiralis,  1060 
pterygoid,  250,  278 
Hand,  muscles  of,  540 
dissection  of,  546 
phalanges  of,  articulations  of, 

431 
skeleton  of,  323 
surface  anatomy  of,  1315   • 
markings  of,  1318 
Hard  palate,  1112 
Harrison's  sulcus,  226 
Hasner,  plica  lacrimalis  of,  1042 
Hassal,  corpuscles  of,  1265 
Haversian  canals  of  bone,  53 

systems  of  bone,  53 
Head,  arteries  of,  626 
lymphatics  of,  774 
muscles  of,  464 
veins  of.  732 
Head-cap  of  spermatozoon,  81 
Hearing,  organ  of,  1043 
Heart,  603 

applied  anatomy  of,  614 
arteries  of,  614 

atrioventricular  bundle  of  His, 
614 
node,  614 
atrium,  left,  610 

right,  606 
component  parts  of,  604 
development  of,  143-145 
endocardium,  613 
fibres  of  atria,  614 

of  ventricles,  614 
fibrous  rings  of,  613 
lymphatic  vessels  of,  798 
nerves  of,  615 
sinoatrial  node  of,  614 
size  and  weight  of,  604 
structure  of,  613 
surface  marking  of,  1299 
trigonum  fibrosum,  613 
veins  of,  730 
ventricle,  left,  611 
right,  608 
Heidenhain,  demilunes  of,  1137 
Height  index  of  skull,  296 
Helicine  arteries,  1240 
Helicis  major  muscle,  1045 

minor  muscle,  1045 
Helicotrema,  1060 
Helix,  1044 
Hemiazygos  vein,  753 

accessory,  753 
Hemispheres,  cerebellar,  836 

cerebral,  865 
Hemorrhoidal     arterj',     inferior, 
704 
middle,  701 
superior,  696 
nerve,  inferior,  991 
plexuses  of  nerves,  1005 
vein,  middle,  760 

superior,  766 
venous  plexus,  761 

applied  anatomy  of,  761 
Henle,  loop  of,  1212 
Henle's  layer  of  hair  follicle,  1077 
Hensen,  canalis  reuniens  of,  1064 
knot  of,  86 
lines  of,  66 
stripe  of,  1067 
supporting  cells  of,  1067 
Hepar,  1191 

capsula  fibrosa  [Glissoni],  1197 

fades  inferior,  1192 

posterior,  1193 

superior,  1192 

margo  anterior,  1194 


Hepar,  tunica  serosa,  1197 
Plepatic  artery,  689 

branches  of  vagus  nerve,  943 
cells,  1197 
cylinders,  174 
duct,  1199 

flexure  of  colon,  1180 
lymph  glands,  788 
plexus,  1004 
veins,  764 
Hepatoduodenal  ligament,    1151, 

1156 
Hepatogastric     ligament,      1151, 

1156 
Hepatorenal  ligament,  1151 
Herbst,  corpuscles  of,  1069 
Hernia,  complete  congenital,  1188 
femoral,  1189 
into  funicular  process,  1188 
inguinal,  1187 
direct,  1188 
oblique,  1187 
scrotal,  1187 
HerophUus,  torcular  of,  743 
Heschl,  gyri  of,  872 
Hesselbach,     interfoveolar     liga- 
ment of,  505 
triangle  of,  1187,  1309 
Hiatus,  aortic,  495 
of  facial  canal,  241 
oesophageal,  496 
semilunaris,  293,  1011 
Higher  or  cortical  visual  centres, 

864,  909 
Highest  intercostal  arterj%  666 
veins,  753 
nuchal  line,  227 
thoracic  artery,  670 
Highmore,  antrum  of,  259,  1015 
Hilus  of  kidney,  1209 
of  lung,  1102 
of  spleen,  1266 
Hind-brain,  122,  821 
Hind-gut,  92,  162 
Hinge-joint,  382 
Hip  bone,  333 

articulations  of,  340 
ossification  of,  340 
structure  of,  340 
surface  anatomy  of,  1324 
Hip-joint,  432 

applied  anatomy  of,  437 
movements  of,  435 
muscles  in  relation  with,  435 
I       surface  marking  of,  1330 
Hippocampal  commissure,  886 
fissure,  130,  874 
gyrus,  874 
Hippocampus,  130,  880 

major,  880 
His,   atrioventricular   bundle   of, 
614 
globular  processes  of.  111 
Holoblastic  ova,  84 
Horizontal  cells  of  retina,  1028 
part  of  palatine  bone,  266 
semicircular  canal,  1059 
sulcus  of  cerebellum,  837 
Houston's  valves  of  rectum,  1183 
Howship's  foveolse,  52 
Huguier,  canal  of,  238,  932,  1050 
Humeral  articulation,  414 
applied  anatomy  of,  417 
bursiE  in  relation  to,  415 
movements  of,  416 
vessels  and  nerves  of,  416 
circumflex  arteries,  671,  672 
Humerus,  309 

applied  anatomy  of,  313 
articulations  of,  313 
ossification  of,  313 
structure  of,  313 
surface  anatomy  of,  1313 
Humor,  aqueous,   1030 
Hunter's  canal,  713 


1376 


INDEX 


Hnschke,  auditory  teeth  of,  1065 

I'oiaiiien  of,  244,  245 
Huxley's    layer    of    hair   follicle , 

1077 
Hvaline  cartilage,  47 

cell,  63 
Hyaloid  canal,  1030 
fossa,  1030 

membrane  of  eye,  1030 
Hyaloplasm,  34 

Hydatid  of  Morgagni,  182,  1231, 
1247 
pedunculated,    of     epididymis, 
1231 
Hymen,  1257 

Hj'-oepifflottic  ligament,  1083 
Hyoglossal  membrane,  1132 
Hyoglossus  muscle,  1129 
Hvoid  arch,  109 
arteries,  631,  632 
bone,  275 

applied  anatomv  of,  277 
body  of,  275 
cornua  of,  275 
ossification  ofj  277 
Hyothyroid  ligaments,  1082 

membrane,  1082 
Hyparterial  bronchi,  1092,  1105 
Hypochondriac  regions,  1147 
Hypochordal  bar  or  brace,  104 
Hypogastric  artery,  700 

applied  anatomy  of,  701 
branches  of.  701 
in  fetus,  616 
obliterated,  700 
peculiarities  of,  700 
lymph  glands,  786 
plexus,  1005 
region,  1147 
vein,  760 
zone,  1147 
Hypoglossal  nerve,  945 

applied  anatomy  of,  947 
nucleus  of,  829 
Hypophysis  cerebri,  166,  861 
applied  anatomy  of,  862 
development  of,  166 
lobes  of,  862 
structure  of,  861 
Hypothalami,  pars  ma^nillaria,  127 

optica,  128 
Hypothalamus,  860 

corpora  m,a77iillaria,  860 
hypophysis   or   pituitary  body, 

861 
infundihuluyn,  861 
optic  chiasma,  862 
subthalamic  tegmental  region, 
860 
corpus  subthalaniicum,,   or 

nucleus  of  Luys,  860 
stratum  dorsale,  860 
zona  incerta,  860 
tuber  cinerum,,  861 
Hypothenar  eminence,  546 


Ileocecal  fossse,  1159 

fold,  1160 
Ileocolic  artery,  693 
lymph  glands,  789 
valve,  1179 
Ileum,  1171 

lymphatic  vessels  of,  792 
Iliac  arteries,  common,  698 

applied  anatomy  of,  700 
peculiarities  of,  700 
surface  markings  of,  1309 
external,  708 

applied  anatomy  of,  708 
surface  markings  of,  1309 
internal,  700 

applied  anatomj'  of,  701 


Iliac  arteries,  internal,   peculiar- 
ities of,/00 

circumflex  artery,  deep,  710 
applied  anatomy  of,  710 
peculiarities  of,  709 

superficial,  716 
vein,  deep,  760 
superficial,  750 

colon,  1181 

fascia,  560 

fossa,  335 

furrow,  1301 

lymph  glands,  786 

region,  1147 

muscles  of,  dissection  of,  559 

spines,  336 

tuberosity,  335 

vein,  common,  762 

peculiarities  of,  762 
external,  759 
internal,  760 
Iliacus  muscle,  561 

fascia  of,  560 
Iliococcj^geus  muscle,  513 
Iliocostalis  cervicis  muscle,  488 

dorsi  muscle,  488 

lumborum  muscle,  488 
Iliofemoral  ligament,  433 
Iliohypogastric  nerve,  976 
Ilioinguinal  nerve,  977 
Iliolumbar  artery,  706 

ligament,  404 

vein,  762 
Iliopectineal  eminence,  336 

fascia,  560  . 
Iliosacralis  muscle,  514 
Iliotibial  band  or  tract,  563 
Iliotrochanteric  ligament,  433 
Ilium,  333 

ala  of,  333 

body  of,  333 

crest  of,  336 

dorsum  of,  333 

gluteal  lines  of,  333 

spines  of,  336 
Imbedding    or    implantation    of 

ovum,  97 
Immovable  articulations,  380 
Impression,  colic,  1192 

duodenal,  1192 

gastric,  1192 

renal,  1192 

rhomboid,  303 

suprarenal,  1194 

trigeminal,  241 
Incisive  bone,  262 

canals,  261,  278 

foramen,  261,  278 

fossa,  256,  271 

teeth,  1117 
Incisor  crest,  261 

teeth,  1117 
Incisura  angularis,  1162 

apicis  cordis,  605 

cardiaca,  1162 

fastigii,  125 

radialis,  318 

semilunaris,  315 

temporalis,  874 

tentorii,  901 
Incremental  lines  of  Salter,  1120 
Incus,  1054 

crus  breve,  1054 
longum,  1054 

development  of,  141 

ligaments  of,  1055 

process  of,  long,  1054 
short,  1054 
Index,  cephalic  or  breadth,  296 

gnathic  or  alveolar,  296 

nasal,  296 

orbital,  296 

vertical  or  height,  296 
Indusiuin  griseum,  875 
Inferior  articular  arteries,  721 


Inferior  articulation,  423 

calcaneonavicular     ligament, 
455 

cerebellar  peduncles,  841 
,  constrictor  muscle,  1141 

dental  artery,  040 
nerve,  923 

ganglion,  939,  941 

laryngeal  nerve,  942 

longitudinal  sinus,  741 

maxillary  nerve,  921 

medullary  velum,  842 

oblique  muscle,  1036 

profunda  artery,  674 

pubic  ligament,  407 

quadrigeminal  body,  854 

tarsal  plate,  1039 

thyroarytenoid  ligaments,  1086 

vocal  cords,  1086 
Infraclavicular  branches  of  bra- 
chial plexus,  960 
Infracostales  muscle,  492 
Infraglenoid  tuberosity,  307 
Infrahyoid  artery,  631 

muscles,  480 

dissection  of,  482 
Infraorbital  artery,  641 

canal,  258 

foramen,  257,  286 

groove,  258 

nerve,  917  note 

plexus  of  nerves,  919 
Infrapatellar  pad  of  fat,  443 
Infrascapular  artery,  671 
Infraspinatous  fascia,  533 

fossa,  305 
Infraspinatus  muscle,  533 
Infrasternal  notch,  129,5 
Infratemporal  crest,  248,  282 

fossa,  283 

surface  of  maxilla,  257 
Infratrochlear  nerve,  916 
Infundibuliform  fascia,  508 
Infundibulopelvic  ligament,  1251 
Infundibulum  of  brain,  861 

of  ethmoid  bone,  254,  294, 101 1 
Inguinal  aponeurotic  falx,  505 

canal,  508 

glands,  783 

applied  anatomy  of,  784 

hernia,  1187 

ligament,  502 
reflected,  502 

regions,  1147 

ring,  abdominal,  508 
subcutaneous,  499 
Inion, 284,  296 
Inlet  of  pelvis,  340 
Inner  cell-mass,  84 
Innominate  artery,  625 

applied  anatomy  of,  626 

bone,  333 

articulations  of,  340 
ossification  of,  340 

veins,  751 

peculiarities  of,  751 
Inscriptions,  tendinous,  of  rectus 

abdominis,  506 
Insertion  of  muscles,  462 
Insula,  873 

circular  sulcus  of,  873 

development  of,  873 

gyri  of,  873 

opercula  of,  873 
Integument,  common,  1071 
Interalveolar  cell-islets,  1205 
Interarticular    costocentral    liga- 
ments, 397 

fibrocartilages,  49 

sternocostal  ligaments,  400 
Interatrial  groove,  604 
Intercalatum,  850 
Intercapitular  veins,  747,  756 
Intercarpal  articulations,  427 
movements  of,  428 


INDEX 


i;]77 


Intercavurnous  sinuses,  7-16 
Intercelluliir  biliary   passages, 

119^ 
Intcrcentnil  ligaments,  384 
Interchondral  ligaments,  4t)l 
luterclavic-ular  ligament,  410 
Interclinoid  ligament,  251 
Inteicolunuiar  fascia,  1229 

fibres,  oUl 
Intereondyloid  eminence  of  tibia, 
355 
fossa  of  femur,  349 
of  tibia,  posterior,  35G 
Intercostal    arteries    from    aorta, 
6S5 
■highest,  G(it) 

from  internal  mammar\-,  ()G4 
superior,  600 
fasciae,  492 
lymph  glands,  790 
membranes,  492,  493 
muscles,  492 
nerves,  972 
spaces,  221 
veins,  753 
Intercostales  externi  muscles,  492 

interni  muscles,  492 
Intercostobrachial  nerve,  973 
Intercrural  fascia,  501 

fibres,  501 
Intercuneiform  articulations,  457 
Interfoveolar  ligament  of  Hessel- 

bach, 505 
Interglobular  spaces,  1120 
Interior  of  bladder,  1222 
of  larynx,  1085 
of  skull,  288 
of  uterus,  1250 
Interlobular    arteries    of    kidnev, 

1214 
Intermediate  cell-mass,  88 
Intermetacarpal  articulations,  430 
Intermetatarsal  articulations,  458 
Internal  abdominal  ring,  508 
acoustic  meatus,  241 
arcuate  ligament,  495 
calcaneal  arteries,  727 
calcaneoastragaloid     ligament, 

453 
calcaneonavicular      ligament. 

495 
canthus  of  eyelids,  1038 
capsule  of  brain,  883 

applied  anatomy  of,  895 
circumflex  arterj^  717 
cutaneous  nerve,  904,  981 

lesser,  904 
geniculate  body,  858 
iliac  artery,  700 
glands,  786 
vein,  700 
intercostals  muscle,  492 
lateral  hgament,  395,  418,  420 
malleolar  artery,  723,  727 
mammary  artery,  064 

applied  anatomy  of,  000 
gland,  790 
maxillarj'  glands.  775 
oblique  muscle,  503 
palpebral  arteries,  050 
plantar  artery,  727 

nerve,  988 
popliteal  nerve,  987 
pterygoid  muscle,  474 
pudic  artery.  703 
nerve,  991 
veins,  700 
respiratory  nerve  of  Bell,  957 
saphenous  nerve,  981 

vein,  756 
semilunar  fibrocartilage,  442 
sphincter  ani  muscle,  516 
Internodal  segments  of  nerves,  75 
Interossei  muscles  of  foot,  590 
of  hand, 555 

87 


Interosseous  artcr\-,  anterior,  680 
common,  (i.so 
dorsal,  (iM 
l)alniar,  ()79 
posterior,  681 
recurrtMit,  682 
volar,  080 
ligament,  399 
membrane  of  forearm,  423 

of  leg,  448 
nerve,  dorsal  or  posterior,  970 
volar  or  anterior,  905 
Interparietal  bone,  231 
Interpeduncular  fossa,  805 

ganglion,  848,  850 
Interphalangcal       articulations, 

431,  459 
Interpleural  space,  1098 
Interpubic  disk,  407 

fibrocartilaginous  lamina,  407 
Intersegmental  neurons,  811 

septa,  102 
Intersigmoid  fossa,  1100 
Interspinal  ligaments,  3S7 
Interspinales  muscles,  490 
Interspinous  ligament,  387 
Intersternal  ligaments,  401 
Intertarsal  articulations,  452 
Intertragic  notch,  1044 
Intertransversales  muscle,  490 
Intertransversarii  muscles,  490 
Intertransverse  ligaments,  387 
Intertrochanteric  crest,  348 

line,  348 
Intertubercular  plane,  1147 
Intertubular  dentin,  1120 
Intervenous  tubercle,  608 
Interventricular     foramen,     865, 
887 
septum,  012 
Intervertebral  fibrocartilages,  380 
foramina,  197 
veins,  755 
Intervillous  space,  98 
Intestinal  arteries,  092 
glands,  1174 
vUli,  1173 
Intestine,    aggregated   lymphatic 
nodules  of,  1175 
applied  anatomy  of,  1186 
development  of,  102 
large,  1170 
Ivmphatics  of,  791 
small,  1108 

structure  of,  1172 
vessels  and  nerves  of,  1170 
solitary  lymphatic  nodules  of, 

1175 
surface  markings  of,  1300 
Inteslinum  caecum,  1177 
crassum,  1176 
ileum,  1171 
jejunum,  1171 
rectum,  1182 
tenue,  1168 

tela  submucosa,  1173 
tunica  mucosa,  1173 
muscularis,  1173 
serosa,  1172 
Intra-articular      chondrosternal 
ligament,  400 
ligament,  397 
Intracartilaginous  ossification,  57 
Intraepithelial  plexus  of  cornea, 

1021 
Intrafusal  fasciculi,  1071 

fibres,  1071 
Intrajugular  process,  230 
Intralobular  veins,  1197 
Intramembranous  ossification,  56 
Intraparietal  sulcus,  870 
Intrapulmonai-y  bronchi,  1106 
Intraspinal  veins,  755 
Intrathyroid  cartilage,  1080 
Intrinsic  niuscles  of  tongue,  1130 


Involuntar\-  niusi'le,  67 
lodothvrin.  1202 
Iridial  angle,  1019 
Iris,  1024 

structure  of,  1025 

vessels  and  nerves  of,  1025 
Irregular  bones,  190 
Ischiocapsular  ligament,  433 
Ischioca\-crnosus  naiscle,  .518,  521 
Ischiorectal  fossa^  515 

ap])lied  anatomy  of,  510 
Ischium,  330 

bodj'  of,  336 

rami  of,  337 

spine  of,  336 

tuberosit\-  of,  337 
Island  of  Reil,  873 
Islands,  blood,  142 

of  Langerhans,  1205 
Isthmus,  aortic,  154,  623 

of    external    acoustic    meatus, 
1053 

faucium,  112 

glandula  thyreoidea.  1202 

of  limbic  lobe,  873 

rhombencephali,  122 

of  thjroid  gland,  1261 

of  uterine  tube,  1247 
Iter  chordae  anterius,  1050 

posterius,  1049 
Ivory  of  teeth,  1119 


Jacob's  membrane,  1029 
Jacobson,  nerve  of,  939,  1056 
vomeronasal  organs  of,  113 
1012 
Jejunum,  1171 

lymphatic  vessels  of,  792 
Jelly  of  Wharton,  97 
Joints.    See  Articulations. 
Jugular  foramen,  280,  291 
fossa,  243 

ganglion  of  glossopharyngeal 
nerve,  938 
of  vagus  nerve,  941 
nerve,  997 
notch,  217,  230 
process,  230,  281 
surface  of  temporal  bone,  243 
tubercle,  230 
vein,  anterior,  736 
external,  734 

applied  anatomy  of,  736 
internal,  736 

applied  anatomv  of,  737 
bulbs  of,  736 
posterior  external,  736 
Jugum  sphenoidale,  251 
Junctional  tube,  1212 


Karokinesis,  34 
Karj-omitome,  34 
Karyomitosis,  34 
Karyoplasm,  34 
Keratin,  39 

Kerckring,  ossific  centre  of,  231 
Kerkring,  valves  of,  1173 
Kidneys,  1206 

applied  anatomv  of,  1214 

calicesof,  1210,'l216 

cortical  substance  of,  1210 

development  of,  187 

fixation  of,  1209 

hilus  of,  1209 

lymphatic  vessels  of,  793 

Malpighian  bodies  of,  1212 
tufts  of,  1212 

medullary  substance  of,  1210 

minute  anatomy  of,  1211 


1378 


IXDEX 


Kidneys,  nerves  of,  1214 
paranephric  body,  1210 
renal  artery,  696 
fascia,  1209 
pelvis,  1210,  1216 
sinus,  1210 
tubules,  1212 
structure  of,  1210 
surface  marking  of,  1308 
veins  of,  764,  1214 
weight  and  dimensions  of,  1207 
Knee  cap,  354 
Knee-joint,  438 

applied  anatomy  of,  446 
bursse  of,  443 
movements  of,  444 
surface  anatomy  of,  1325 
Kxause,  end-bulbs  of,  1069 

membrane  of,  66 
Kiihne,  motor  end-plates  of,  803 


Labbe,      posterior     anastomotic, 

vein  of,  739 
Labia  cerebri,  875  | 

majora,  1256  | 

minora,  1257  I 

oris,  1110 
Labial  arteries,  634 
commissures,  1257 
glands,  1110 
grooves,  163,  164 
Labiodentallamina,  1121 
Labrum  glenoidale,  415,  434 
LabjTinth,  membranous,  1061 
development  of,  140 
vessels  of,  1068 
osseous,  1057 
Labyrinthus  ethmoidalis ,  253 
meynbranaceus,  1061 
osseus,  1057 
Lacertus  fibrosus,  535 
Laciniate  ligament,  585 
Lacrimal  apparatus,  1041 

applied  anatomy  of,  1042 
arterj',  649 
bone,  263 

articulations  of,  263 
lesser,  263 
ossification  of,  263 
canals,  1041 
caruncula,  1041 
crest,  posterior,  263 
ducts  or  canals,  1041 

ampullae  of,  1042 
fossa,  235,  286 
glands,  1041 
groove,  258,  287 
hamulus,  263 
nerve,  915 
notch,  257 
papilla,  1038 
process  of  inferior  nasal  concha, 

268 
punctum,  1038 
sac,  1042 
sulcus,  1042 
tubercle,  260 
Lacteals,  768 
Lactiferous  ducts,  1259 
Lacuna  magna  [of  urethra],  1226 
Lacunse  of  bone,  53,  54 
of  cartilage,  47 
of  urethra,  1226 
venous,  741 
Lacunar  ligament,  502 
Lacus  lacrimalis,  1038,  1041 
Lagena,  1064 
Lambda,  277,  296 
Lambdoidal  suture,  230,  232,  282 
Lamellse  of  bone,  53 
articular,  379 
circumferential,  53 


Lamellie    circumferential,     inter- 
stitial, 53 
primary  or  fundamental,  53 
secondary  or  special,  53 
Lamellar  cells,  41 
Lamina  affixia,  885 

anterior  elastic,  of  cornea,  1020 

basalis,  1022 

cartilaginis  cricoideae,  1081 

chorioca  pillar  is,  1022 

cribrosa  sclerae,  1017 

dorsal  or  alar,  119 

elastica  anterior,  1020 

posterior,  1020 
fibrocartilaQimo  interpubica,  407 
labiodental,  1121 
lingual,  1121 
medullarj-,  856,  857 
nasal.  111 
posterior     elastic,     of     cornea, 

1020 
reticular,  1067 
spiral,  of  cochlea,  osseous,  1060 

secondary,  1060 
spiralis  ossea,  1060 
suprachorioidea,  1017,  1022 
terminalis,  126,  864 
vasculosa,  1022 
ventral  or  basal,  119 
of  vertebrge,  197 
Langerhans,     centro-acinar    cells 
of,  1205 
islands  of,  1205 
Langhans,  layer  of,  85 
Langley's  ganglion,  1138 
Lantermann,  segments  of,  75 
Lanugo,  116 

Large  deep  petrosal  nerve,  919 
intestine,  1176 
cecum,  1177 
cohc  valve,  1179 
colon,  1180 

ascending,  1180 
descending,  1181 
iliac,  1181 

sigmoid  or  pehn^c,  1181 
transverse,  1180 
rectum,  1182 
superficial  petrosal  nerve,  919, 
931 
Larj'ngeal  artery,  inferior,  662 
superior,  631 
nerves,  942 
part  of  pharj^nx,  1141 
prominence,  1080 
saccule,  1086 
sinus,  1086 
Laryngotomy,  1094 
Laryngotracheal  tube^  176 
Larj'nx,  1079 

applied  anatomy  of,  1093 

cartilages  of,  1079 

conus  elasticus  of,  1083 

elastic  membrane  of.  1083 

entrance  of,  1083 

glands  of,  1090 

interior  of,  1085 

ligaments  of,  1082 

Ijonphatic  vessels  of,  779,  1090 

mucous  membrane  of,  1090 

muscles  of,  10S8 

actions  of,  1090 
nerves  of,  1090 
rima  glottidis  of,  1087 
surface  marking  of,  1289 
ventricle  of,  1086 
ventricular  folds  of ,  1085 
vessels  of,  1090 
vestibule  of,  1085 
vocal  folds  of,  1086 
Lateral  basis  bundle,  817 
cartilage,  lower,  1009 

upper,  1009 
cornu  of  medulla  spinalis,  809 
cricoarytenoid  muscle,  1088 


Lateral  sinuses,  742 

thyrohyoid  ligament,  1083 
Latissimus  dorsi  muscle,  524 
Layer  of  Langhans,  85 

of  rods  and  cones,  1029 
Layers  of  cerebral  cortex,  891 
Least  splanchnic  nerve,  999 
Left  atrium,  dissection  of,  610 

auricle,  610 

auricular  appendix,  610 

coronary  plexus,  1002 
vein,  730 

lobe  of  liver,  1195 

ventricle,  dissection  of,  611 
Leg,  fascia  of,  576 

deep  transverse,  580 

muscles  of,  570 

dissection  of,  576,  578,  579, 
581,  582 
Lemniscus,  lateral,  853 

lateralis,  853 

medial,  853 

medialis,  853 
Lens,  capsule  of,  1030 
vascular,  136 

changes  produced  in,   by  age, 
1031 

crystallina,  1030 

crystalline,  1030 

development  of.  136 

equator  of,  1031 

poles  of,  1031 

structure  of.  1031 

suspensorj-  ligament  of,  1030 

vesicle,  134 
Lenticula,  881 
Lenticular  ganglion,  917 

glands  of  stomach,  1166 

nucleus,  881 

process  of  incus,  1054 
Lentiform  nucleus,  881 
Lesser  cavernous  nerve,  1005 

curvature  of  stomach,  1162 

internal  cutaneous  nerve,  964 

lacrimal  bone,  263 

multangular  bone,  327 

omentum,  1156 

pelvis,  340 

peritoneal  sac,  1152,  1155 

sac  or  omental  bursa  of  peri- 
toneum, 1155 
boundaries  of,  1155,  1156 

sciatic  foramen,  406 
notch,  336 

sigmoid  cavity,  318 

trochanter,  348 
Leucocytes,  62 

Levator  anguli  oris  muscle,  470 
scapulae  muscle,  525 

ani  muscle,  513 

glandulae  th\Teoideae  muscle, 
1262 

menti  muscle,  470 

palati  muscle,  1113 

palpebrae     superioris     muscle, 
1034 

prostatae  muscle,  514 

scapulae  muscle,  525 

veli  palatini  muscle,  1113 
Levatores  costarum  muscle,  493 
Lieberkijhn,  crvpts  of,  1174 
Lien,  1266 

acccssorius,  1267 

extremitas  inferior,  1267 
superior,  1267 

fades  gasirica,  1266 
renalis,  1266 

margo  anterior,  1267 
posterior,  1267 
Lienal  artery,  691 

plexus  of  nerves,  1004 

vein,  765 
Ligament  or  Ligaments,  acromio- 
cla^^cula^,  inferior,  412 
superior,  411 


INDEX 


1379 


Lij^aiuent  or  Ligaments,  alar,  393    L 
of  anklo,  45U,  451     ^ 
annular,  of  ankle,  584,  585 
of  radius,  422 
of  stapes,  1055 
of  wrist,  547,  550 
anterior,  42() 
inferior,  44S 
lonuiit'uliiial,  384 
superior,  3U8,  448 
apical  i)clontoicl,  393 
arcuate,  495 
atlantoaxial,  389 
atlantoooeipital,  392 

membrane,  posterior,  392 
of  auricula  or  pinna,  1044 
of  Bertin,  433 
bifurcated,  454,  455 
of  Bigelow,  433 
of  bladder,  1221 
broad,  of  uterus,  1250 
calcaneoastragaloid,  452,  453 
calcaneocuboid,  454 
calcaneofibular,  451 
calcaneonavicular,  plantar,  455 
calcaneotibial,  450 
capsular.  See  Individual  Joints, 
cai'oticoclinoid,  251 
carpometacarpal,  429 
of  carpus,  427,  428 
central,  of  medulla  spinalis,  907 
check,  393 

of  eye,  1038 
chondrosternal,  399 

intra-articular,  400 
chondroxiphoid,  401 
common,  anterior,  384 

posterior,  385 
conoid,  412 
of  Cooper,  502 
coracoacromial,  413 
coracoclavicular,  412 
coracohumeral,  415 
coronarv,  of  knee,  442  1 

of  liver,  1150,  1151,  1195  j 

costoclavicular,  410  1 

costocoracoid,  528  j 

costotransverse,  397,  398 
middle,  399 

posterior,  399  _  j 

costovertebral,  anterior,  396 
costoxiphoid,  401  i 

cotyloid,  339,  434 
cricoarytenoid,  posterior,   1084 
cricotracheal,  1083 
crucial,  441 
cruciate,  of  atlas,  390 
crural,  584 
of  knee,  441 
cuboideonavicular,  457 
cuneocuboid,  457 
cuneona\'icular,  455 
deltoid,  of  ankle-joint,  450 
dentate,  907 
digital  vaginal,  540 
dorsal  carpal,  550 
radiocarpal,  425 
radioulnar,  424 
of  elbow,  418,419 
falciform,  of  liver,  1150,  1195 
fibular  collateral,  of  knee-joint, 

440 
fundiform,  of  penis,  1239 
gastrocolic,  1151 
gastrolienal,  1155 
gastrophrenic,  1163 
Gimbernat's,  502 
glenohumeral,  415 
glenoid,  414 

of  Cruveilhier,  430,  459 
of  shoulder-joint,  415 
glenoidal  labrum  of  hip-joint, 
434 
of  shoulder-joint,  415 
hepatoduodenal,  1151,  1156 


igament  or  Ligaments,    hepato- 
gastric, 1151,  1156 
hepatorenal,  1151,  1195 
of  liesselbach,  505 
of  hip-joint,  432 
hyoepiglottic,  1083 
iliofemoral,  432 
iliolumliar,  404 
iliotrochantcric,  433 
of  incus,  1055 
inferior  transverse  of  scapula, 

413 
infundibulopelvic,  1251 
inguinal,  502 

reflected,  502 
interarticular,  of  ribs,  397 

sternocostal,  400 
intercarpal,  427 
intercentral,  384 
interchondral,  401 
interclavicular,  410 
interclinoid,  251 
intercuneiform,  457 
interfoveolar,  505 
intermetacarpal,  430 
intermetatarsal,  458 
interosseous,  399  . 
interphalangeal,  431,  459 
interpubic       fibrocartilaginous 

lamina,  407 
interspinal,  387 
interspinous,  387 
intersternal,  401 
intertarsal,  452 
intertransverse,  387,  406 
intra-articular,  397 
ischiocapsular,  433 
of  knee-joint,  438 
laciniate,  585 
lacunar,  502 
of  larynx,  1082 

lateral  atlanto5ccipital,  392         I 
external,  394,  419,  426 
internal,  395,  418,  426 
of  uterus,  1250 
left  triangular,  of  liver,  1151 
of  left  vena  cava,  603 
long  plantar,  454 
of  Mackenrodt,  1251 
of  malleus,  1055 
medial  palpebral,  468 
metacarpoph'alangeal,  430 
metatarsophalangeal,  459 
middle  cricothjToid,  1083 
mucosum,  of  knee,  443 
of  neck  of  rib,  399 
nuchae,  387 
oblique  cord,  423 
popliteal,  439 
sacroiliac,  404 
occipitoaxial,  393 
odontoid,  393 
orbicular,  422 
of  ovary,  1244 
palmar,  427,  429 
palpebral,  1039 
pectinate,  of  iris,  1021 
of  pelvis,  404 
phrenicocolic,  1157 
phrenicolienal,  1155 
phrenicopericardiac,  right,  762 
of  pinna  or  auricula,  1044 
plantar,  long,  454 
posterior,  426 

cricoarytenoid,  1084 
inferior,  448 
of  knee,  439 
longitudinal,  385 
superior,  448 
Poupart's,  502 
pterygomandibular,  471 
ptervgospinous,  251,  477 
pubic,  407 
pubocapsular,  433 
pubofemoral,  433 


Ligament  or    Ligaments,    pulmo- 
nary, 1095,  1097 
quadrate,  423 

radial  collateral,  of  elbow-joint, 
419 
of  wrist-joint,  425 
radiate,  396 

sternocostal,  399 
of  radiocarpal  joint,  425 
radioulnar,  424 
i-eflectcd  inguinal,  502 
rhoml)oid,  410 
round,  of  liver,  1195 

of  uterus,  1251 
sacrococcygeal,  406 
sacroiliac,  404 
sacrosciatic,  404,  405 
sacrospinous,  405 
sacrotuberous,  404 
of  scapula,  413 
of  shoulder-joint,  414 
sphenomandibular,  395,  477 
spinoglenoid,  413 
spiral,    of    ductus    cochlearis, 

1064 
stellate,  396 
sternoclavicular,  410 
sternocostal,  399 
sternopericardiac,  602 
of  sternum,  400 
structure  of,  379 
stylohyoid,  481 
stylomandibular,  395,  477 
subpubic,  407 
superficial     transverse     of 

fingers,  551 
superior  transverse  of  scapula, 

413 
suprascapular,  413 
supraspinal,  387 
supraspinous,  387 
suspensory,  of  axilla,  526 
of  eye,  1038 
of  lens,  1030 
of  liver,  1195 
of  mamma,  526 
of  ovary,  1244 
of  penis,  1239 
talocalcaneal,  452,  453 
talonavicular,  dorsal,  454 
talotibial,  450 
tarsometatarsal,  457 
of  tarsus,  452  _ 
temporomandibular,  393 
tendo  oculi,  468 
teres,  of  hip,  454 
thyroarytenoid,  inferior,  1086 
thyroepiglottic,  1084 
thyrohyoid,  1082,  1083 
tibial  collateral,  of  knee-joint, 

439 
tibiofibular,  448 
tibionavicular,  450 
transversalis  colli  uteri,  1251 
transverse  acetabular,  434 
of  atlas,  389 
carpal,  547 
crural,  584 
humeral,  415 
inferior,  449 
of  knee,  442 
metacarpal,  430 
metatarsal,  458 
of  pelvis,  520 
of  scapula,  413 
trapezoid,  412 
triangular,  of  liver,  1195 

of  urethra,  519 
of  tubercle  of  rib,  399 
ulnar  collateral,  of  elbow-joint, 
418 
of  wrist-joint,  426 
uterosacral,  1250 
of  uterus,  1250 
ventricular,  of  larjmx",  1085 


1380 


INDEX 


Ligament  or  Ligaments  of  verte-  l 

braj,  384 
volar  carpal,  547 

metacarpophalangeal,  430 

radiocarpal,  42(j 

radioulnar,  424 
of  Wrisberg,  442 
of  wrist-joint,  425,  426 
Y-shaped,  of  Bigelow,  433 
of  Zinn, 1035 
Ligamenta     accessoria     plantaria, 

459 
alaria,  393 

auricularia  [Valsalva],  1044 
basium  [oss.  metacarp.]  dorsalia, 
430 
interossea,  430 
volaria,  430 

[oss.  metatars.]  dorsalia,  458 
interossea,  458 
plantaria,  458 
carpometacarpeae  dorsalia,  429 

volaria,  429 
collateralia,  459 
costoxiphoidea,  401 
cruciata  gejiu,  441 
cuneo7netatarsea  interossea,  458 
intercarpea  dorsalia,  427 

interossea,  427 

volaria,  427 
inter cuneif or mia  interossea,  457 

plantaria,  457 
inter spinalia,  387 
intertransversaria,  387 
navicularicuneiformia    dorsalia, 
456 

plantaria,  456 
ossiculorum  auditus,  1054 
sternocostalia  radiata,  399 
suspensoria  [of  mamma], -526 
tarsometatarsea  dorsalia,  457 

plantaria,  458 
vocales,  1086 
Ligamentous  action   of  muscles, 
383 
applied  anatomy  of,  383 
Ligamentujn  acromioclaviculare, 

411 
annulare  baseos  stapedis,  1055 

radw,  422 
arcuatum  pubis,  407 
arteriosum,  621 
bifurcatuin,  454 
calcaneocuboideum  dorsale,  454 

plantare,  454 
calcaneofibulare,  451 
calcaneonaviculare  plantare,  455 
capituli    costae    interarticulare, 
397 
radiatum,  396 
capitulorum     [oss .     metacarpa- 

lium]  interosseum,  430 
carpi  dorsale,  550 

transversum,  547 

volare,  547 
collaterale  fibulare,  440 

radiate,  419,  426 

a'biaZe,  439 

ulnare,  418,  426 
coZZi  costae,  399 
conoideum,  412 
coracoacromiale,  413 
coracoclaviculare,  412 
coracohumerale,  414 
coronarium  hepatis,  1195 
costodaviculare,  410 
costotransversarium  anterius, 
398 

posterius,  398 
cricoarytaenoideumposterius, 

1084 
cricolhyreoideum  medium,  1083 
cricotracheale,  1083 
cruciatum  anterius,  441 
posterius,  441 


Ligamcntum     cuboideonaviculare 
dorsale,  457 
plantare,  457 

drlloidrmN,  450 

(I,  iiliriihiliim,  907 
/(itclfiinHc  hepatis,  1195 
hyuoj)njl(illicin)/ ,  1083 
hyothi/ii  iiit/i mil  laleralc,  1083 

medium,  1U82 
iliofenwrale,  433 
iliolurnbale,  404 
incudis  jwsterius,  1055 

superius,  1055 
inguinale  [Pourparti],  502 

reflexuni  [Colleri],  502 
interclaviculare,  410 
ischiuai psiihirc,  433 
lacuniin  \(!iiiiliernati],  502 
latum  put  mo  I  lis,  1097 

uteri,  1250 
longitudinale  anterius,  384 

posterius,  385 
tnallei  anterius,  1055 

laterals,  1055 

superius,  1055 
malleoli       lateralis       anterius, 
448 
posterius,  448 
mucosum,  443 
nuchae,  587 
patellae,  439 
plantare  longum,  454 
popliteum  obliquum,  439 
pubicum  superius,  407 
pubocapsulare,  433 
pubnonale,  1097 
radiocarpeum  dorsale,  426 

volare,  426 
sacrococcygeum  anterius,  406 

laterale,  406 

posterius,  406 
.sacroiliacum  anterius,  404 

inter osseus,  404 

posterius,  404 
sacrospinosum,  405 
sacroiuberosum,  404 
sphenomandibulare,  395 
sterna  clavicular  e,  410 
sternocostale  interarticulare,  400 
stylomandibular e,  395 
supraspinale,  387 
talocalcaneum  anterius,  452 

interosseum,  453 

laterale,  453 

mediale,  453 

posterius,  453 
talofibulare  anterius,  450 

posterius,  451 
talonaviculare  dorsale,  454 
temporomandibular e,  394 
teres  femoris,  434 

hepatis,  1196 

Mteri,  1251 
thyroepiglotticum,  1084 
transversalis  colli  uteri,  1251 
transversum  acetabuli,  434 

atlantis,  389 

crws  inferius,  390 
superius,  390 

cruris,  584 

genu,  442 

scapulae  inferius,  413 
superius,  413 
trapezoideum,  412 
triangular e  dextrum,  1195 

sinistrum,  1195 
tuberculi  costae,  399 
venosum,  1196 
Ligature    of    arteries.    *See   each 

Artery. 
Ligulae,  846 
Limbic  lobe,  873 
Limbs,  development  of,  113 
Linibus  fossae  oralis,  608 
laminae  spiralis,  1065 


Limiting    nicnihi-ancs    of    rclina, 

1029 
Line  or  Lines,  arcuate,  of  ilium, 
335 

colored,  of  Retzius,  1120 

curved,  of  ilium,  333 

gluteal,  of  ilium,  333 

incremental,  of  Salter,  1120 

intercondyloid,  350 

intertrochanteric,  348 

mylohyoid,  272 

Nelaton's,  1239 

nuchal,  227,  281 

oblique,  of  fibula,  360 
of  mandible,  271 
of  radius,  320 

pectineal,  348 

popliteal,  of  tibia,  357 

of  Schreger,  1120 

spiral,  of  femur,  348 

temporal,  231,  235,  278,  282 
Linea  alba,  507 

aspera,  348 

quadrata,  348 

semicircularis,  507 

splendens,  907 
Lineae  semilunar es,  507 
Lingua,  1125 

fades  inferior,  1126 

tunica  mucosa,  1131 
Lingual  artery,  631 

applied  anatomy  of,  632 
deep,  632 

bone,  275 

branches    of    glossopharyngeal 
nerve,  939 

gyrus,  871 

lamina,  1121 

lymph  glands,  775 

nerve,  923 

tonsil,  1131 

veins,  736 
Lingula  of  cerebellum,  837 

of  mandibulae,  272 

of  sphenoid,  247,  290 
Linin,  34 
Lip,  tympanic,  1065 

vestibular,  1065 
Lips,  1110 
Liquor  amnii,  95 

sanguinis,  61 
Lissauer,  fasciculus  of,  817 
Littre,  urethral  glands  of,  1226 
Liver,  1191 

applied  anatomy  of,  1200 

bare  area  of,  1151 

bile  ducts  of,  1198 
common,  1200 

cystic  duct,  1200 

development  of,  174 

excretory  apparatus  of,  1198 

fissures  of,  longitudinal,  1194 

fossiB  of,  1194 

gall-bladder,  1199 

hepatic  artery,  689,  1197 
cells,  1197 
duct,  1198 
veins,  764 

ligaments  of,  1195 

lobes  of,  1194,  1195 

lobules  of,  1197 

lymphatic  vessels  of,  792 

nerves  of,  1196 

portal  vein,  764,  1198 

structure  of,  1197 

surface  markings  of,  1307 

surfaces  of,  1191 

vessels  of,  1196 
Lobe  or  Lobes,  cacuminal,  838 

of  cerebellum,  836 

of  cerebral  hemisphere,  869 
frontal,  869 
insula,  873 
limbic,  873 
occipital,  871 


INDEX 


1381 


Lobe  or  Lobes  of  cerebral  hemis- 
phere, olfactory,  874 
parietal,  S70 
prepuneus,  871 
quadrate,  .S71 
temporal,  S7l 
ofliver,  1191, 1195 
of  lung,  1105 
nodular,  839 
Spigelian,  1195 
of  lh\iHus,  I2(J4 
of  thyroid  uland,  12(J1 
tub(n-al,  839 
uvular,  839 
Lobule  of  auricula,  10-14 
paracentral,  870 
parietal,  871 
postero-inferior,  839 
l)ostero-superior,  838 
Lobules  of  liver,  1195 

of  testes,  1232 
Lobuli  glnndulae  thyreoideae,  1261 

hepatis,  1197 
Lobulus  centralis,  838 
parietalis  inferior,  871 

superior,  871 
semilunaris  inferior,  839 
superior,  838 
Lohus  caudalus,  1195 
clivi,  838 
culminis,  838 
frontalis,  869 
hepatis  dexter,  1194 

sinister,  1195 
noduli,  839 
occipitalis,  871 
olfactorius,  874 
parietalis,  870 
pyramidis,  839 
quadratus,  1195 
semilunaris,  838 
temporalis,  871 
tuberus,  839 
uvulae,  839 
Localization,  cerebral,  894 
Lockwood,  tendon  of,  1035 
Locus  coeruleus,  848 
Long  bones,  195 
buccal  nerve,  922 
calcaneocuboid  ligament,  454 
ciliary  nerves,  916 
external  lateral  ligament,  440 
or    internal    saphenous    nerve, 

981 
root  of  ciliary  ganglion,  916 
saphenous  nerve,  981 

vein,  756 
subscapular  nerve,  961 
thoracic  artery,  671 
nerve,  960 
Longissimus  capitis  muscle,  489 
cervicis  muscle,  488 
dorsi  muscle,  488 
Longitudinal  fasciculus,  inferior, 
891 
posterior,  851 
superior,  891 
fissure,  cerebral,  865 
great,  865 
of  liver,  1194 
sinuses,  740,  741 
strise,  lateral  and  medial,  875 
sulci  of  heart,  604 
Longitudinalis     linguae     inferior 
muscle,  1130 
superior  muscle,  1130 
Longus  capitis  muscle,  484 

colli  muscle,  403 
Loop  of  Henle,  1212 
Lowenthal,    cerebellospinal   tract 

of,  815 
Lower  extremity,  arteries  of,  710 
articulations  of,  432 
bones  of,  333 
lymphatic  vessels  of,  782 


Lower  extremity,  muscles  of,  559 
surface  anatomy  of,  1323 

markings  of,  1329 
veins  of,  755 
jaw,  bones  of,  271 
lateral  cartilage,  1009 
visual  centres,  8()4,  909 
Lower,  tubercle  of,  608 
Lumbar  aponeunjsis,  486 
arteries,  698 

enlargement    of    m(?dulla    spi- 
nalis, 808 
fascia,  486 
lymph  glands,  787 
nerves,    divisions  of,   anterior, 
974- 
posterior,  953 
plexus  of  nerves,  975 

applied  anatomy  of,  992 
regions  of  abdomen,  1147 
triangle,  524 
vein,  ascending,  753,  763 
veins,  763 
vertebriE,  204 
Lumbocostal  arch,  495 
Lumbodorsal  fascia,  486 
Lumbosacral  plexus,  974 

trunk,  975 
Lumbricales  muscles  of  foot,  589 

of  hand, 555 
Lunate  bone,  323 

surface  of  acetabulum,  339 
Lung-buds,  177 
Lungs,  1101 

applied  anatomy  of,  1108 
development  of,  177 
fissures  and  lobes  of,  1104 
nerves  of,  1107 
root  of,  1105 
structure  of,  1106 
surface  markings  of,  1298 
vessels  of,  1107 
Lunulse  of  nails,  1075 

of  semilunar  valves,  610 
Luschka's  gland,  1273 
Luys,  nucleus  of,  860 
Lymph,  64 
capillaries,  64 
path,  770 
sacs,  161 
sinus,  770 
Lymph  Gland  or  Glands  of  abdo- 
men, 785 
aortic,  787 

applied  anatomy  of,  770 
auricular,  774,  775 
axillary,  780 
buccinator,  775 
cervical,  anterior,  778,  779 
of  Cloquet,  783 
deltoideopectoral,  779 
diaphragmatic,  797 
epigastric,  786 
facial,  775 

deep,  775 
gastric,  788 

gastroepiploic,  right,  788 
of  head,  774 
hepatic,  788 
hypogastric,  786 
iliac,  786 
ileocolic,  789 
infraorbital,  775 
inguinal,  783 

applied  anatomy  of,  784 
intercostal,  797 
lingual,  775 

of  lower  extremity,  782 
lumbar,  787 

mammary,  internal,  796 
mastoid,  774 
maxillary,  775 
mediastinal,  798 
mesenteric,  789,  791 
mesocolic,  789 


Lymph  Gland  or  Glands  of  neck, 

778 
obturator,  787 
occipital,  774 
pancreaticoduodenal,  792 
pancreaticolicnal,  768 
pararectal,  791 
paratracheal,  779 
parietal     of     abdomen     and 

pelvis,  786 
parotid,  775 
of  pelvis,  785 
popliteal,  782 

applied  anatomy  of,  784 
preauricular,  775 
principal    gland    of    tongue, 

778 
retropharyngeal,  776 
of  Rosenmlillcr,  783 
sacral,  787 
splenic,  788 

Stahr,  middle  gland  of,  778 
sternal,  796 
structure  of,  769 
subinguinal,  783 
submaxillary,  778 
submental,  778 
suprahyoid,  778 
supramandibular,  775 
supratrochlear,  779 
of  thorax,  796 
tibial,  anterior,  782 
tracheobronchial,  798 
of  upper  extremity,  779,  780 
visceral     of     abdomen     and 
pelvis,  787 
Lymphatic  duct,  right,  772 
nodules,  aggregated,  1175 
solitary,  1175 

of  spleen,  1268 
system,  768 

trunk,  bronchomediastinal,  798 
intestinal,  772 

jugular,  772,  773 

lumbar,  772 

subclavian,  772,  773 
vessels,  768 

of  abdominal  viscera,  791 
wall,  787 

of  anal  canal  and  anus,  792 

applied  anatomy  of,  770 

of     auricula     and     external 
acoustic  meatus,  776 

of  cecum,  792 

of  colon,  792 

of  common  bile-duct,  793 

development  of,  161 

of  diaphragma,  798 

of  ductus  deferens,  794 

of  duodenum,  792 

of  external  genitals,  787 

of  face,  776 

of  gall-bladder,  793 

of  gluteal  region,  784 

of  heart,  798 

of  ileum,  792 

of  jejunum,  792 

of  kidney,  793 

lacteals,  768 

of  larvnx,  779 

of  liver,  792 

of  lower  extremity,  784 

of  lungs,  799 

of  mamma,  797 

of  mouth,  777 

of  nasal  cavities,  776 

of  neck,  779 

of  oesophagus,  800 

of  ovary,  795 

of  palatine  tonsil,  777 

of  pancreas,  793 

of  pelvis,  787 

of  perineum,  787 

of  pharj'nx,  779 

of  pleura,  800       ' 


1382 


INDEX 


Lympathic    vessels  of    prostate, 
794 

of  rectum,  792 

of  reproductive  organs,  794 

of  scalp,  776 

of  spleen,  793 

of  stomach,  792 

structure  of,  768 

of  suprarenal  glands,  793 

of  testes,  794 

of  thoracic  viscera,  799 
wall,  797 

of  thymus,  800 

of  thyroid  gland,  779 

of  tongue,  778 

of  upper  extremity,  781 

of  ureter,  793 

of  urethra,  794 

of  urinary  organs,  793 

of  uterine  tubes,  795 

of  uterus,  795 

of  vagina,  795 

of  vermiform  process,  792 

of  vesiculae  seminales,  795 
Lymphocyte,  63 
Lymphoglandulae,  768 

auriculares  anteriores,  775 

posteriores,  774 
axillares,  780 
cervicales  profundae,  778 

superficiales ,  778 
epigastricae,  786 
faciales  profundae,  775 
gastricae  inferiores,  788 

superiores,  788 
hepaticae,  788 
hypogastricae,  786 
inguinales,  783 
inter costales,  797 
linguales,  775 
lumhales,  787 
mediastinales  anteriores,  798 

posteriores,  798 
■mesentericae,  789 
mesocolicae,  791 
occipitales,  774 
pancreaticolienales,  788 
popliteae,  782 
sternales,  796 
subinguinales  profundae,  783 

superficiales,  783 . 
submaxillar es,  778 
tibialis  anterior,  782 
Lymphoid  tissue,  45 
Lyra  of  fornix,  886 


M 

Macewen,  suprameatal  triangle 

of,  238 
Mackenrodt,  ligament  of,  1251   • 
Macula  acustica  sacculi,  1062 
utriculi,  1062 
cribrosa  media,  1058 

superior,  1058 
lutea,  1026,  1029 
structure  of,  1029 
Majendie,  foramen  of,  847,  905 
Malar  bone,  263 

process  of  inaxilla,  260 
Male  genital  organs,  1228 

bulbourethral  glands,  190, 

1243    ■ 
ductus  deferens,  1235 
ejaculatory  duct,  1237 
penis,  1237 
prostate,  1241 
testes  and  their  coverings, 

1228 
vesiculae  seminales,  1236 
pronucleus,  83 
urethra,  1225 
Malleolar  arteries,  723 
internal,  727 


Malleolar  folds,  anterior  and  pos- 
terior, 1050 
sulcus,  360 
Malleolus,  lateral,  360 

medial,  358,  359 
Malleus,  1053 

development  of,  141 
ligaments  of,  1055 
Malpighian    bodies    of    kidney, 
1212 
of  spleen,  1268 
capsules  of  kidnev,  1212 
tufts  of  kidney,  1212 
Mamillary  process,  205 
Mammae,  1258 

applied  anatomy  of,  1260 
development  of,  116 
lymphatic  vessels  of,  797 
nerves  of,  1260 
papilla  or  nipple  of,  1258 
structure  of,  1258 
vessels  of,  1260 
Mammary  artery,  external,  671 
internal,  664 
gland,  1258 

internal,  796 
veins,  internal,  751 
Mandible,  271 
angle  of,  273 
articulations  of,  274 
body  of,  271 

changes  in,  due  to  age,  275 
condyloid  process  of,  273 
coronoid  process  of,  273 
ossification  of,  273 
ramus  of,  272 
Mandibula,  271 
Mandibular  arch,  109, 

branches  of  facial  nerve,  933 
canal,  273 
foramen,  272 
fossa,  238,  280,  283 
nerve,  921 
notch,  273 
Mantle  layer,  117 
Manubrium  of  malleus,  1053 

of  sternum,  216 
Margin,  supraorbital,  234 
Marginal  gyrus,  870 
layer,  117 
veins  of  foot,  756 
j  Margins  of  heart,  606 
Marrow  of  bone,  51 
Marshall,    oblique   vein   of,    159, 
603,  731 
vestigial  fold  of,  159,  603,  731 
Martinotti,  cells  of,  892, 
Massa  intermedia,  856,  865 
Masses,  lateral,  of  atlas,  200 
Masseter  muscle,  472 
Masseteric  artery,  641 
fascia,  472 
nerve,  921 
Mastoid  canaliculus,  243,  280 
cells,  240 
foramen,  239,  282 
fossa,  238 
glands,  774 
notch,  239,  280 
portion  of  temporal  bone,  239 
process,  239 
Mastzellen,  41 
Matrix  of  nail,  1075 
Maturation  of  ovum,  79 
Maxilla,  256 

articulations  of,  262 
changes  in,  due  to  age,  262 
ossification  of,  262 
Maxillary  artery,  external,  633 
applied  anatomy  of,  635 
peculiarities  of,  635 
internal,  638 
glands,  internal,  775 
nerve,  917 
inferior,  921 


Maxillary  process  of  inferior  nasa 
concha,  268 
of  palatine  bone,  267 
of  zygomatic  bone,  205 
processes  of  fetus,  109 
sinus,  259,  1015 
tuberosity,  257 
vein,  internal,  734 
Meatus  acusticus  externa,  1046 
externus  cartilagineus ,  1047 
osseus,  1047 
auditory,  external,  1046 
external     acoustic,     244.     283, 
1046 
applied  anatomy  of,  1048 
internal,  244,  291 
urinarius,  1226 
urinary,  1257 
Meatuses  of  nose,  293,  1010,  1011 
Mechanism  of  pelvis,  408 
of  respiration,  497 
of  thorax,  401 
Meckel's  cartilages,  109,  273 
diverticulum,  93,  1172 
ganglion,  919 
Media,  refracting,  of  bulb  of  ej^e, 

1030 
Medial  geniculate  body,  858 
longitudinal  fasciculus,  851 
wall  of  nasal  cavity,  1012 
Median  antibrachial  vein,  749 
basilic  vein,  747 
nerve,  965 
Mediastinal  arteries  from  aorta, 
685 
from  internal  mammary,  664 
cavity,  1098 
anterior,  1100 
applied  anatomy  of,  1101 
middle,  1101 
posterior,  1101 
superior,  1098 
lymph  glands,  798 
pleura,  1095 
Mediastinum  testis,  1232 
Medicornu,  879 
Medidural  artery,  640 
Medifrontal  gyre,  870 
Medulla  of  hair,  1077 
oblongata,  822 

anterior  district  of,  822 
applied  anatomy  of  ,  833 
arcuate  fibres  of,  830 
development  of,  123 
fasciculus  cuneatus,  827 

gracilis,  827 
fissures  and  sulci  of,  822 
gray  substance  of,  829 
formatio  reticularis,  832 
lateral  district  of,  823 
olive  of,  824 
posterior  district  of,  824 
pyramid  of,  823 
restiform  bodies  of,  830 
structure  of,  826 
spinalis,  805 

anterior    white    commissure 

of,  808 
applied  anatomy  of,  820 
central  canal  of,  810 
columns  of,  809 
development  of,  805 
dissection  of,  805 
distribution  of  nerve  cells  in, 

811 
enlargements  of,  808 
fissures  of,  808 
gray  commissures  of,  810 

substance  of,  809 
ligamentum  denticulatum ,  905 
meninges  of,  900 

applied  anatomy  of,  907 
neuroglia  of,  809 
sulci  of,  808 
veins  of,  755 


INDEX 


1383 


Medulla  spinalis,  wliitc  substance 

of,  814 
Medullary  artery  of  bono,  52 
lamina,  lateral,  856 

medial,  857 
laiuiiue    of    Icntii'in'in    nucleus, 

881 
membrane  of  bone,  51 
portion    of    suprarenal    gland, 

1272 
segments  of  nerves,  75 
sheath  of  nerve-fibres,  73 
spaces  of  bone,  58 
substance  of  kidney,  1210 
velum,  842,  845 
MeduUated  nerve-fibres,  73 
Meibomian  glands,  1040 
Meissner's  plexus,  1176 

tactile  corpuscles,  1070 
Melanin,  46 

Membrana   atlantooccipitalis    an- 
terior, 392 

jMstcrior,  392 
granulosa  [of  Graafian  follicle], 

1246 
hyolhyreoidea,  1082 
interossea  antebrachii,  423 

cruris,  448 
pupillaris ,  1026 
tectorias  [of  atlas  and  occipital 

bone],  393 
Membrane,  anal,  174 
arachnoid,  903 
atlan-oooccipital,  392 
basilar,  1063,  1065 
of  Bowman,  1020 
costocoracoid,  528 
cricothyroid,  1083 
of  Demours,  1020 
of  Descemet,  1020 
elastic,  of  larynx,  1083 
fenestrated,!  596 
hyaloid,  1030 
hyoglossal,  1132 
hyothyroid,  1082 
intercostal,  492 
interosseous,  of  forearm,  423 

of  leg,  448 
Jacob's,  1029 
of  Krause,  66 
limiting,  1029 
medullary,  of  bone,  51 
of  Nasmyth,  1123 
nuclear,  34 
obturator,  572 
pharyngeal,  163 
pupillary,  136,  1026 
of  Reissner,  1063 
tectorial,  of  ductus  cochlearis, 

1067 
thyrohyoid,  1082 
tympanic,  1050 

structure  of,  1050 
vestibular,  1063 
vitelline,  83 
Membranes,  basement,  45 

of  brain  and  medulla  spinalis, 

900 
fetal,  93 
synovial,  379 
Membranous  cochlea,  1063 
cranium,  106 
labyrinth,  1061 
portion  of  urethra,  1226 
semicircular  canals,  1062 
vertebral  column,  102 
Meningeal  arterj^  accessory,  640 

anterior,  648 

from  ascending  pharyngeal, 
637 

middle,  640 

applied  anatomy  of,  640 
surface  marking  of,  1281 

from  occipital,  636 

from  vertebral,  660 


Meningeal  branch  of  spinal  nerve, 
951 
layer  of  dura  mater,  902 
nerve  from  hypoghjssal,  947 
from  maxillary,  917 

Meninges  of   brain   and   medulla 
spinalis,  900 

Menisci,  49 

of  knee-joint,  441 

Meniscus,  articular,  395 
lateralis,  442 
7nedialis,  442 

Mental  foramen,  271,  280 
nerve,  924 
point,  296 
protuberance,  271 
spines,  271 
tubercle,  271 

Mentalis  muscle,  470 

Merkel,  tactile  disks  of,  1069 

Meroblastic  ova,  84 

Mesamoeboid  cells,  142 

Mesencephalon,  90,  125,  848 

Mesenteric  artery,  inferior,  694 
dissection  of,  695 
superior,  691 

dissection  of,  692,  695 
lymph  glands,  789 
plexuses  of  nerves,  1004,  1005 
veins,  766 

Mesenteries,  1156 

mesentery  proper,  1157 
sigmoid  mesocolon,  1153,  1157 
transverse  mesocolon,  1157 

Mesenteriole  of  vermiform  pro- 
cess, 1178 

Mesenterium,  1157 

Mesocardium,  arterial,  603 
venous,  603 

Mesocolic  lymph  glands,  789 

Mesocolon,  sigmoid,  1153,  1157 
transverse,  1157 
signioideum  ,1157 
transversum,  1157 

Mesoderm,  88 
■  formation  of,  86 

Mesogastrium,  168 

Mesognathion,  299 

Mesonephros,  180 

Mesorchium,.  184 

Mesosalpinx,  1251 

Mesovarium,  184,  1244 

Metacarpal  bones,  329 

applied  anatomy  of,  332 
articulations  of,  331 
characteristics  of,  329 
ossification  of,  332 

Metacarpophalangeal    articula- 
tions, 430 

Metacarpus,  329 

Metanephros,  187 

Metaphase  of  karyokinesis,  36 

Metatarsal  arteries,  724 
bones,  371 

characteristics  of,  371 
veins,  758 

Metatarsophalangeal       articula- 
tions, 459 

Metatarsus,  371 
ossification  of,  374 

Metathalamus,  127,  858 

Metencephalon,  122 

Metopic  suture,  234 

Meynert,  basal  optic  nucleus  of, 
861 
fasciculus  retroflexus  of,  859 
fountain  decussation  of,  854 
substantia  innominata  of,  884 

Microcvtes,  62 

Mid-brain,  90,  126,  848 

Mid-carpal  joint,  427 

Middle  capsular  artery,  696 
cerebellar  peduncles,  841 
commissure  of  brain,  856 
constrictor  muscle,  1142 


Middle  costotransverse  ligament, 
399 
cutaneous  nerve,  980 
dental  nerve,  919 
subscapular  nerve,  961 
th.\n)li.\  old  ligament,  1082 
tibiofibular  ligament,  448 
Milk  teeth,  1118 
Mitochondria  sheath,  81 
Mitral  cells,  894,  1013 
orifice,  611 
valve,  612 
Moderator  band,  610 
Modiolus  of  cochlea,  1060 
Molar  glands,  1111 

teeth,  1118 
Molecular    layer    of    cortex    of 
cerebellum,  842 
of  cerebrum,  891 
Monakow,  rubrospinal,  tract  of, 

816 
Monaster  or  mother  star,  36 
Monro,  foramen  of,  865,  887 

sulcus  of,  125,  865 
Mons  pubis,  1256 

Veneris,  1256 
Morgagni,  hydatid  of,  182,  1231, 
1247 
rectal  columns  of,  1184 
sinus  of,  1142 
Morula,  84 
Moss  fibres,  844 
Mother  star  or  monaster,  36 
Motor  areas  of  cerebral  cortex, 
894 
end-plates,  803 
nerves,  803 
neurons,  lower  and  upper,  896, 

897 

tract,  896 

Mouth,  1110 

development  of,  163 
lymphatics  of,  777 
mucous  membrane  of,  1110 
muscles  of,  dissection  of,  469 
Movable  articulations,  381 
Movements   admitted   in  joints, 

383 
Mucigen,  37 

Mucous  glands  of  tongue,  1131 
sheaths,  380 

of  tendons  around  ankle,  586 
on  back  of  wrist,  550 
on  front  of  wrist,  548 
tissue,  44 
Mtiller,     orbitalis     muscle     of, 
1037 
sustentacular  fibres  of,  1029 
Mullerian  duct,  182 

eminence,  182 
Multangular  bone,  greater,  326 

lesser  327 
Multicuspid  teeth,  1118 
Multifidus  muscle,  489 

spinae  muscle,  489 
Muscle  or  Muscles  of  abdomen, 
498 
abductor  hallucis,  587 
digiti  quinti  (foot),  588 

(hand),  554 
indicia,  556 
minimi  digiti,  554 
poinds,  552 
brevis,  553 
longus,  545 
transversus,  554 
accelerator  urinae,  518 
accessorius,  488 

of  foot,  589 
adductor  brevis,  568 
hallucis,  589 
longus,  567 
jnagnus,  568 
obliquus  hallucis,  589 
pollicis,  554 


1384 


INDEX 


Muscle  or  Muscles,    adductor  pol- 
licis  obliguus,  554 
transversus,  554 
of  anal  region,  515 
ancotiaeux,  544 
anterior  crural,  576 

femoral,  562 

vertebral,  483 
anterolateral,  of  abdomen,  498 
antiiragicus,  1046 
applied  anatomy  of,  410 
of  arm,  533 

arreciores  pilortim,  1077 
articularis  genu  or  subcrureus, 

566 
aryepiglotticus,  1089 
arytaenoideus,  1088 
attoUens  aurem,  1045 
attrahens  aurem,  1045 
of  auricula  or  pinna,  1045 
auricularis,  1045 
axillary  arch,  524 
azygos  uvulae,  1114 
biceps,  534 

brachii,  534 

femoris,  574 

flexor  cubiti,  534 
hiventer  cervicis,  489 
Bowman's,  1023 
brachialis,  535 

anticus,  535 
brachioradialis,  bA2 
buccinator,  470 
bulbocavernosus,  518,  520 
caninus,  470 
cardiac,  68 
cervical,  475 
cervicalis  ascendens,  488 
chondroglossus,  1130 
ciliaris,  1023 
coccygeus,  514 
columns,  65 
complexus,  489 
compressor  naris,  469 

urethrae,  520 
constrictors,  1141,  1142 

pharyngis  inferior,  1141 
medius,  1142 
superior,  1142 

urethrae,  521 
coracobrachialis ,  534 
corrugator,  468 

CMh's  am,  516 

supercilii,  468 
creynaster,  504 
cricoarytaenoideus,  1088 
cricoarytenoid,  1088 
cricothyreoideus,  1088 
cricothyroid,  1088 
crureus,  566 
deep,  of  back,  485 
deltoid,  530 
deltoideus,  530 
depressor  alae  nasi,  469 

anguli  oris,  470 

labii  inferioris,  470 

septi,  469 
detrusor  urinae,  1223 
development  of,  69,  116 
diaphragma,  493 
digastric,  480 
digastricus,  480 
dilatator  naris,  469 

pupillae,  1025 

tubae,  1053 
dorsal  antibrachial,  542 
dorsoepitrochlearis  brachii,  524 
ejaculator  urinae,  518 
epicranius,  465 
erector  clitoridis,  521 

penis,  518 
spinae,  488 
extensor  carpi  radialis  bre\'ior, 
542 
brevis,  542 


Muscle  or  Muscles,  extensor  carpi 
radialis  longior,  542 
longus,  542 
ulnar  is,  544 
coccygis,  490 

digiti  quinti  proprius,  544 
digitorum  brevis,  586 
communis,  544 
longus,  577 
hallucis  longus,  577 
indicis,  546 

proprius,  546 
minimi  digiti,  544 
osst's  metacarpi  pollicis,  545 
poinds  brevis,  545 

longus,  545 
primi  internodii  pollicis,  545 
proprius  hallucis,  577 
secunda    internodii    pollicis, 
545 
external  sphincter  ani,  516 

of  eyelids,  467 
fasciculi  of,  64 
fibres  of,  64 
fixation,  462 
flexor  accessorius,  589 

brevis  minimi  digiti,  554,  590 
carpi  radialis,  537 

ulnaris,  539 
digiti  quinti  brevis  [of  foot], 
590 
[of  hand],  554 
digitorum  brevis,  5^8 
longus,  581 
profundus,  540 
sublimis,  539 
hallucis  brevis,  589 

longus,  581 
pollicis  brevis,  553 
longus,  540 
of  foot,  586 
of  forearm,  536 
form  of,  461 
frontalis,  466 
gastrocnemius,  578 
gemellus,  573 
genioglossus,  1129 
geniohyoglossus,  1129 
geniohyoid,  481 
geniohyoideus ,  481 
glossopalatinus,  1114,  1129  no/e 
glutaeus  maximus,  569 
medius,  570 
minimus,  570 
of  gluteal  region,  569 
gracilis,  567 
hamstring,  574 
of  hand,  546 

dissection  of,  546 
of  head,  464 
helicis  major,  1045 

minor,  1045 
hyoglossus,  1129 
of  iliac  region,  559 
iliacus,  561 
iliococcygeus,  514 
iliocostalis,  488 
cervices,  488 
dorsi,  488 
lumborum,  488 
iliosacralis,  514 
incisivus  labii  inferioris,  472 

superioris,  472 
infracostal,  492 
infrahyoid,  480 
infraspinatus,  533 
insertion  of,  462 
intercostal,  492 
inter costales,  492 
intermediate  volar,  555 
internal  sphincter  ani,  516 
interossei,  dorsal,  591 
of  foot,  590 
of  hand,  555 
plantar,  591 


Muscle  or  Muscles,  inter spinales, 
490 
intertransversales,  490 
intertransversarii,  490 
involuntary,  67 
ischiocavernosus,  518,  520 
of  larynx,  1088 
lateral  cervical,  475 

crural,  582 
vertebral,  484 
volar,  552 
latissi7nus  dorsi,  524 
of  leg,  576 

levator  anguli  oris,  470 
scapulae,  525 

ani,  513 

glandulae  thyreoideae,  1262 
,    menti,  470 

palati,  1113 

palpebrae  superioris,  1034 

prostatae,  514 

scapulae,  525 

wZi  palatini,  1113 
levatores  costarum,  493 
lingualis,  1130 
longissimus  capitis,  489 

cervicis,  488 

dorsi,  488 
longitudinalis  linguae,  1130 
longus  capitis,  484 

coZZi,  483 
of  lower  extremity,  559 
lumbricales  [of  foot],  589 

[of  hand],  555 
lymphatics  of,  67 
masseter,  472 
of  mastication,  472 
medial  femoral,  567 

volar,  554 
mentalis,  470 
of  mouth,  469 
multifidus,  489 

spinae,  489 
mylohyoid,  481 
mylohyoideus,  481 
nasalis,  469 
nasolabialis ,  472 
nerves  and  vessels  of,  67 
of  nose,  468 
oblique,  499,  503 

inferior,  1036 

superior,  1035 
obliquus  auriculae,  1046 

capitis,  491 

externus  abdominis,  499 

inferior,  491 

internus  abdominis,  503 

oculi  inferior,  1036 
superior,  1035 

superior,  491 
obturator  externus,  573 

internus,  572 
occipitalis,  466 
occipitofrontalis,  465 
ocular,  1034 
omohyoid,  482 
omohyoideus,  482 
opponens  digiti  quinti  [of  foot], 
590 
[of  hand],  555 

minimi  digiti,  555 

pollicis,  553 
orbicularis  oculi,  467 

oris,  471 

palpebrarum,  467 
orbitalis  of  H    Midler,  1037 
origin  of,  462 
of  palate,  1113 

palatoglossus,  1114,  1129  ?ioie  . 
palatopharyngeus ,  1114 
palmaris  brevis,  554 

longus,  538 
pectineus,  567 
pectoralis  major,  526 

minor,  528 


INDEX 


1385 


Muscle  or  Muscles  of  pelvis,  510 
perineal,  superficial  transverse, 

518,  520 
of  perineum,  514 
peronaeus  brcoin,  583 

longus,  582 

lerliufi,  578 
phari/niio  palal  Inus ,  11 14 
of  phar.Niix,  1 141 
of  pinna  or  auricula,  1045 
piri/orDiis,  571 
plain,  67 
plantar,  first  layer,  587 

foiu-th  layer,  590 

second  layer,  589 

third  layer,  589 
plantar  is,  579 
plate,  102 
platysma,  475 
popliteus,  581 
posterior  crural,  578 

femoral,  574 
procerus,  469 
pronator  quadratus,  540 

teres,  537 
psoas  magnus,  560 

major,  560 

minor,  561 

parvus,  561 
pterygoid,  474 
pterygoideus  externus,  474 

internus,  474 
pubococcygeus,  514 
puborcctalis,  514 
pubovesicales,  1221 
pyramidalis  abdominis,  507 

nasi,  469 
quadratus  femoris,  573 

labii  superioris,  469 
inferioris,  470 

lumborum,  510 

menti,  470 

plantae,  589 
quadriceps  extensor,  565 

femoris,  565 
rec/i  [of  eyeball],  1035 
rectococcygeal,  1185 
rectovesicales,  1221 
rectus  abdominis,  506 

capitis  anterior,  484 
lateralis,  484 
posterior  major,  491 
minor,  491 
anticus  major,  484 

minor,  484 
posticus  major,  491 
minor,  491 

femoris,  565 
retrahens  aurem,  1045 
rhomboideus  major,  525 

tninor,  525 
risorius,  472 
rotatores,  490 

spinae,  490 
sacrospinalis,  488 
salpingopharyngeus,  1143 
sarcous  elements  of,  66 
sartorius,  565 
scalenus  anterior,  484 

anticus,  484 

medius,  484 

posterior,  485 

posticus,  485 
of  scalp,  464 
semimembranosus,  575 
semispinalis  capitis,  489 

cervicis,  489 

colli,  489 

dorsi,  489 
semitendinosus,  575 
serratus  anterior,  529 

magnus,  529 

posterior  inferior,  493 
superior,  493 

posticus  inferior,  493 


Muscle  or  Muscles,  serratus  pos- 
ticus sui)erior,  493 
soleus,  579 
sphincter  ani,  516 
externus,  516 
internus,  516 

pupillae,  1025 

rec/j,  514 

urethrae  memhranaceae,  520, 
521 

vaginae,  520 

vesicae,  1223 
spinalis  capitis,  489 

cervicis,  489 

colli,  489 

dorsi,  489 
splenius  capitis,  486 

cervicis,  487 

colli,  487 
stapedius,  1055 
sternocleidomastoideus,  478 
sternohyoid,  482 
sternohyoideus ,  482 
sternomastoid,  478 
sternothyreoideus,  482 
sternothyroid,  482 
striped,  64 

structure  of,  64 
styloglossus,  1130 
stylohyoid,  481 
stylohyoideus ,  481 
stylopharyngeus,  1142 
subanconeus,  536 
subclavius,  528 
subcostales,  492 
subcrureus,  566 
suboccipital,  490 
sub  scapular  is,  531     , 
superficial  cervical,  475 
supinator,  544 

brevis,  544 

longus,  542 
suprahyoid,  480 
supraspinatus ,  532 
suspensory,  of  duodenum,  1171 
synergic,  462 
temporal,  473 
temporalis,  473 
tendons  of,  463 
tensor  fasciae  femoris,  565 
latae,  565 

palati,  1113 

torsi,  468 

tympani,     1055 

veZt  palatini,  1113 
fej'es  major,  533 

minor,  533 
of  thigh,  562 
of  thorax,  492 
thyreoarytaenoideus,  1089 
thyreoepiglotticus,  1090 
thyrohyoideus ,  482 
thyroarytenoid,  1089 
thyrohyoid,  482 
■tibialis  anterior,  576 

anticus,  576 

posterior,  582 
of  tongue,  1044 
trachealis,  1093 
trachelomastoideus,  489 
tragicus,  1046 
transversalis,  504 

cervicis,  488 
transversus  auriculae,  1046 

abdominis,  504 

linguae,  1130 

menti,  470 

nuchae,  466 

pedis,  589 

perinaei,  518,  520 
profundus,  521,  522 

superficialis  [in  female],  520 
[in  male],  518 

thoracis,  492 
trapezius,  522 


Muscle  or   Muscles,    triangularis, 
470 
sterni,  492 
triceps,  535 
brachii,  535 
extensor  cubiti,  535 
surae,  579 
of  trunk,  485 
of  tympanic  cavity,  1055 
of  upper  extremity,  522 
of  ureters,  1222 
unstriped,  67 

structure  of,  67 
urogenital  region  [female],  520 

[male],  517 
of  uvula,  1114 
vastus  externus,  566 
intermedius,  566 
internus,  566 
lateralis,  566 
medialis,  566 
vertebral,  anterior,  483 

lateral,  484 
verticalis  lingxiae,  1130 
vocalis,  1089 
volar  antibrachial,  537 
voluntary,  64 
zygomaticus,  470 
major,  470 
Muscular  fibres  of  heart,  613 
process  of  arytenoid  cartilage, 

_  1081 
tissue,  64,  68 
triangle,  483,  643 
Muscularis  mucosae,  1173 
Musculi  oculi,  1034 

ossiculorum  auditus,  1055 
papillares  [of  left  ventricle],  612 

[of  right  ventricle],  610 
pecti?iati  [of  left  auricle],  611 

[of  right  auricle],  607 
pubovesicales,  1223 
Musculocutaneous  nerve  of  arm, 
962 
of  leg,  990 
Musculophrenic  artery,  666 
Musculospiral  groove,  311 

nerve,  968 
Musculus  accessorius,  488 
ciliaris,  1023 
incisivus  labii  inferioris,  472 

superioris,  472 
nasolabialis ,  472 
suspensorius  duodeni,  1 171 
uvulae,  1114 
Myelencephalon,  122 
Myelocytes,  51 
Myeloplaxes,  51 
Mylohyoid  artery,  641 
groove,  272 
line,  272 
muscle,  481 
nerve,  924 
Mylohyoideus  muscle,  481 
Myocardium,  613 
Myocoel,  91 
Myology,  461 


N 

Nails,  1075 
Nares,  1008,  1009 
Nasal  aperture,  anterior,  294 
artery,  650 

lateral,  635 
bones,  255 

articulations  of,  256 
ossification  of,  256 
cartilages,  1008 
cavities,  292,  1010 

applied  anatomy  of,  1015 
arteries  of,  1012 
lymphatic  vessels  of,  776 
mucous  membrane  of,  1012 


1386 


INDEX 


Nasal   ca\-ities,    nerves  of,    1012, 
1013 
veins  of,  1013 
vestibule  of,  1010 
concha,  inferior,  268 
middle,  254 
superior,  254 
crest,  261,  266 
duct,  1042 
fossa,  1010 
index,  296 
laminae.  111 
mucous  membrane,  1012 
nerve  from  ophthalmic,  916 
nerves  from  nasopalatine  gan- 
glion, 921 
notch  of  frontal  bone,  235 

of  maxilla,  257 
part  of  frontal  bone,  235 
of  pharynx,  1138,  1139 
process  of  frontal  bone,  235 

of  maxilla,  260 
processes  of  fetus,  111 
septum,  293,  1012 
spine,  anterior,  257,  262 
of  frontal  bone,  235 
posterior,  266,  278 
Nasalis  muscle,  469 
Nasion,  235,  285,  296 
Nasmj^h's  membrane,  1123 
Nasociliary  nerve,  916 
Nasofrontal  vein,  745 
Nasolabialis  muscle,  472 
Nasolacrimal  duct,  1042 
Nasooptic  furrow,  112,  137 
Nasopalatine  nerve,  921 

recess,  1012 
Nasopharynx,  1139 
Nasus  extemns,  1008 
Navicular  bone  of  carpus,  323 
of  tarsus,  368 
fossa,  1257 
Neck,  lymphatic  glands  of,  778 
vessels  of,  779 
muscles  of,  475 
triangles  of,  642 
veins  of,  734 
Nelaton's  line,  1329 
Neopallium,  128 
Nerve  cells,  70 

of  cerebellar  cortex,  842 
of  cerebral  cortex,  891 
of  medulla  spinalis,  811,  812 
endings,  free,  813,  1069 
fasciculi    of    medulla    spinalis, 

814 
fibres    of    cerebral    cortex, 
892 
medullated,  73 
non-medullated,  76 
posterior,  948 
roots,  anterior,  948 
Nerve  or  Nerves,  abducent,  927 
accessory,  944 
acoustic,  934,  1067 
alveolar,  anterior  superior,  919 
middle,  919 
posterior,  918 
inferior,  922  j 

anococcygeal,  992 
anterior  crural,  979  ' 

interosseous,  965 
superior  alveolar,  919 
thoracic,  961 
tibial,  990 
antibrachial     cutaneous,     963, 

964 
Arnold's,  941  i 

auditory,  934  ' 

auricular,  great,  956 

of  auriculotemporal,  923 
posterior,  933 
of  vagus,  941 
auriculotemporal,  923 
axillary,  961  ' 


Nerve  or  Nerves  of  Bell,  960 
brachial  cutaneous,  lateral,  962 
medial,  964 
posterior,  969 
bronchial,  943 
buccal,  of  facial,  933 

long,  922 
buccinator,  922 
calcaneau,  medial,  988 
cardiac,  cerWcal,  942 

great,  997 

of  sympathetic,  997 

thoracic,  943 

of  vagus,  942 
caroticotympanic,  996,  1056 
carotid     of     glossopharyngeal, 

939 
cavernous,  of  penis,  1005 
cerebral,  907 

abducent,  927 

accessory,  944 

acoustic,  934 

facial,  929 

glossopharyngeal,  937 

hypoglossal,  945 

oculomotor,  911 

olfactorv,  908 

optic,  959 

trigeminal,  914 

trochlear,  913 

vagus,  940 
cerebrospinal,  structure  of,  801 
cervical,  957 

cutaneous,  957 

divisions  of,  anterior,  954 
posterior,  951 

of  facial,  933 

transverse,  957 
chorda  tympani,  932,  1056 
ciliary,  916,  917 
circumflex,  961 

coccygeal,  division  of,  anterior, 
982  _ 
posterior,  954 
cochlear,  935,  1068 
coeliac,  of  vagus,  943 
cranial,  907 
crural,  anterior,  980 
cutaneous  cervical,  957 

external,  977 

internal,  964,  981 
lesser,  964 

middle,  980 
deep  branch  of  radial,  970 
of  ulnar,  968 

peroneal,  990 

petrosal,  919 

temporal,  921 
descending     ramus     of     hypo- 
glossal, 947 
development  of,  119,  131 
digastric,  from  facial,  933 
digital,  of  lateral  plantar,  988 

of  medial  plantar,  988 

of  median,  966 

of  radial,  970 

of  superficial  peroneal,  990 

of  ulnar,  968 
dorsal  antibrachial  cutaneous, 
969 

branch  of  ulnar,  967 

cutaneous,  lateral,  988 
medial,  990 

of  penis,  992 

scapular,  960 
of  dura  mater,  902 
dural,  941 
eighth,  934 
eleventh,  944 
end-organs  of,  1069 
endoneurium  of,  802 
epineurium  of,  801 
external  nasal,  919 

plantar,  989 

popliteal,  989 


Nerve  or  Nerves,  external  saphe- 
nous, 988 

spermatic,  977 
facial,  929 
femoral,  980 

cutaneous,  anterior,  980 
lateral,  977 
posterior,  985 
fifth,  914 
first,  908 
fourth,  913 
frontal,  916    • 
ganglia  of,  803 

gastric  branches  of  vagus,  943 
genitocrural,  977 
genitofemoral,  977 
glossopharyngeal,  937 
gluteal,  984,  985 
great  auricular,  956 
greater  occipital,  951 

splanchnic,  998 

superficial  petrosal,  919 
hemorrhoidal,  inferior,  991 
hepatic  branches  of  vagus,  943 
hypoglossal,  945 
iliohypogastric,  976 
ilioinguinal,  977 
incisive,  924 
inferior  dental,  924 
infraorbital,  917  note 
infrapatellar,  981 
infratrochlear,  916 
intercostal,  972 
intercostobrachial,  973 
intermedins  of  Wrisberg,  929 
internal  cutaneous,  of  arm,  964 

carotid,  995 

plantar,  998 

popliteal,  987 

saphenous,  981 
interosseous,  dorsal,  970 

volar,  965 
Jacobson's,  939,  1056 
jugular,  997 
labial,  superior,  919 
lacrimal,  915 
laryngeal,  942 

larvngopharyngeal    of    sympa- 
thetic, 997 
lateral  antibrachial  cutaneous, 
963,  964 

brachial  cutaneous,  962 

femoral  cutaneous,  977 

plantar,  984 
lesser  splanchnic,  999 
lingual,  923 

of  glossopharyngeal,  940 
long  ciliary,  916 

saphenous,  981 

subscapular,  961 

thoracic,  960 
lowest  splanchnic,  999 
lumbar,  di\dsions  of,  anterior, 
974 
posterior,  953 
lumboinguinal,  977 
lumbosacral  trunk,  975 
mandibular,  921 

of  facial,  933 
masseteric,  921 
maxillary,  917 

inferior,  921 
medial  antibrachial  cutaneous, 
964 

brachial  cutaneous,  964 

sural  cutaneous,  998 

plantar,  998 
median,  965 
meningeal,  of  hypoglossal,  947 

of  maxillary,  917 

middle,  917 

of  spinal  nerves,  947 

of  vagus,  941 
mental,  924 
motor,  803 


INDEX 


1387 


Nerve   or  Nerves,    musculocuta- 
neous, of  arm,  962 
of  log,  990 
musculospii"al,  968 
mylohyoid,  924 
uasal,  of  ophthalniic,  916 

from     sphonopalatine     gan- 
glion,   921 
nasociliary,  916 
nasopalatine,  921 
ninth,  937 
obturator,  979 

accessory,  980 
occipital,  greater,  951 
smaller,  956 
third,  951 
oculomotor,  911 
oesophageal,  943 
olfactory,  908 
ophthalmic,  915 
optic,  909 
orbital,  917 

their  relation,   in   cavernous 
sinus,  928 
in  orbit,  928 
in   superior   orbital    fis- 
sure, 928 
origins  of,  803 
palatine,  920,  921 
palmar  cutaneous,  of  median, 
965 
of  ulnar,  967 
palpebral,  inferior,  919 
perforating  cutaneous,  991 
pei'ineurium  of,  801 
plexus  of,  802 
peroneal,  989,  990 
petrosal,  deep,  919,  996 
external,  997 

greater  superficial,  919 
smaller  superficial,  1056 
large,  deep,  919 

superficial,  919,  931 
pharyngeal,    of    glossopharyn- 
geal, 940 
of  sphenopalatine   ganglion, 

921 
of  vagus,  942 
phrenic,  957 
plantar,  988,  989 
pneumogastric,  940 
popliteal,  external,  989 

internal,  987 
of  pterygoid  canal,  920,  996 
to  pterygoideus  internus,  921 

externus,  922 
pterygopalatine,  921 
pudendal,  991 
inferior,  985 
pudic,  991 

internal,  991 
pulmonary,  943 
radial,  970 
rami  communicantes,  gray  and 

white,  949,  950,  995 
recurrent,  942 
respiratory,  of  Bell,  957 
to  rhomboids,  960 
roots,  818,  948 
sacral,  982 
saphenous,  981 
internal,  981 
short,  988 
sciatic,  985 
scrotal,  posterior,  991 
second,  909 
seventh,  929 
short  ciliary,  917 
sixth,  927 

smaller  occipital,  956 
spermatic,  external,  977 
sphenopalatine      branches      of 

maxillary,  918 
spinal,  947 

accessory,  944 


Nerve  or  Nerves,  spinal,  develop- 
ment of,  119 

divisions    of,    anterior    pri- 
mary, 954  I 
posterior  primary,  951  I 
roots  of,  818,  948 
spinosus,  921 
splanchnic,  998,  999 
to  stapedius,  932 
stylohyoid,  933 
to  subclavius,  960 
suboccipital,  951,  954 
subscapular,  961 
superior  labial,  919 
superficial  branch  of  radial,  969 

of  ulnar,  968 
supra-acromial,  957 
supraclavicular,  957 
supraorbital,  916 
suprascapular,  960 
suprasternal,  957 
supratrochlear,  916 
sural,  998 
sympathetic,  994 

structure  of,  803 
of  taste,  1008 
1      temporal,  deep,  922 

of  facial,  933 
I      temporomalar,  917 

tenth,  940 
1       terminations  of,  803 
1       third,  911 

I       thoracic,  divisions  of,  anterior, 
i  972 

1  posterior,  952 

lateral  anterior,  961 
medial  anterior,  961 
thoracodorsal,  961 
thyrohyoid,  947 
1      tibial,  987 

anterior,  990 
of  tongue,  1132 
tonsillar,  940 
transverse  cervical,  957 
trifacial,  914 
trigeminal,  914 
trochlear,  913 
twelfth,  945 
tympanic,  of  glossopharyngeal 

939,  1056 
ulnar,  967 

collateral,  969 
of  urethral  bulb,  992 
vagus,  940 
vestibular,  935,  1068 
Vidian,  920,  996 
volar  digital,  966 

interosseous,  965,  968 
of  Wrisberg,  964 
zygomatic,  917 
of  facial,  933 
zygomaticofacial,  918 
zygomaticotemporal,  918 
Nervi  anococcygei,  992 

auriculares  anterior es,  923 
carotid  externi,  997 
cavernosi  penis  minores,  1005 
cerebral  es,  907 
cervicales,  951,  954 
rainus  lateralis,  951 
medialis,  951 
ciliares  longi,  916 
clunium  inferiores,  985 
coccygeus,  954,  982 
communicantes  cervicales,  957 
digitales  dorsales  hallucis,  990 
■plantar es  communes,  988 
proprii,  988 
ethmoidales,  916 
inter costales,  972 

rami  cutanei  laterales,  973 
labiales  anterior  es,  974 

posteriores,  953 
lumbales,  953 
nervorum,  802 


Nervi  olfactorii,  90S 
palatini,  920 
sacrales,  953,  982 
spheno palatini,  918 
spinales,  947 

radix  anterior,  948 

posterior,  948 
rami  anteriores,  954 
posteriores,  957 
subscapular  es,  961 
supraclaviculares  anteriores,  957 
medii,  957 
posteriores,  957 
temporales  profundi,  922 
thoracales,  952 

anteriores,  961,  972 
ramus  lateralis,  953 
medialis,  952 
Nervous  system,  description  of, 
801 
development  of,  117 
tissue,  69 
Nervus  abducens,  927 
accessorius,  944 

ramus  externus,  945 
internus,  944 
acusticus,  934,  1067 
radix  cochlearis,  935 
vestibularis,  935 
alveolaris  inferior,  923 
i      auricularis  magnus,  956 
posterior,  933 
auriculotemporalis,  923 
7'ami  parotidei,  923 

temporales      super  ficiales, 
923 
axillaris,  961 
buccinatorius ,  922 
canalis  pterygoidei,  920 
cardiacus  inferior,  998 
medius,  997 
superior,  997 
caroticotympanicus  inferior,  939 

superior,  939 
cavernous  penis  major,  1005 
cochlearis,  1068 
clunium  inferior  medialis,  991 
communicans  fibularis,  990 

tibialis,  988 
cutaneus     antebrachii    dorsalis, 
969 
lateralis,  964 
medialis,  964 

ramus  ulnaris,  964 
volaris,  964 
brachii  medialis,  964 

posterior,  969 
colli,  957 

rami  inferiores,  957 

ramus  superior,  957 

dorsalis  intermedius,  990 

medialis,  990 
femoris  lateralis,  977 
posterior,  985 

rami  perineales,  985 
surae  lateralis,  990 
medialis,  988 
descendens  cervicales,  957 
dorsalis  penis,  992 

scapulae,  960 
facialis,  929 

ra7ni  buccales,  933 
temporales,  933 
zygomatici,  933 
ramus  colli,  933 
digastricus.  933 
marginalis  mandibulae,  933 
stylohyoideus,  933 
femoralis,  980 
frontalis,  916 
furcalis,  975 
genitofemoralis,  977 
glossopharyngeus,  937 
ganglion  inferius,  939 
superius,  938 


1388 


INDEX 


Nervus   glossojjharyngcus,   rami 
linguales,  940 
pharyngei,  940 
tonsillares,  940 
ramus  stylopharyngeus ,  940 
glutaeus  inferior,  985 

superior,  984 
haemorrhoidalis  inferior,  991 
hyoglossus,  945 

rajnus  descendens,  947 
ihyreohyoideus,  947 
iliohypogastricxts,  976 
ramus  lateralis,  977 
ilioinguinalis,  977 
infratrochlearis,  916 
intermedins  [of  Wrisborg],  929 
interosseus  dorsalis,  970 

volaris,  965 
ischiadicus,  985 

rami  articulares,  985 
musculares,  985 
lacrimalis,  915 
laryngeus  superior,  942 
ramus  externus,  942 
internus,  942 
lingualis,  923 
lumboinguinalis,  977 
mandibularis,  921 
massetertcus,  921 
mazillaris,  917 

rami      alveolares      superiores 
posteriores,  917 
lahialis  superiores,  919 
nasales  externi,  919 
palpebrales  inferiores,  919 
ramus  alveolaris  superior  an- 
terior es,  919 
medius,  919 
meatus  auditorii  externi,  923 
medianus,  965 

rami  inusculares,  965 
ramus  cutaneus  palmaris  n. 
mediani,  965 
meningeus  medius,  917 
musculocutaneus,  962 
ramus  dorsalis,  964 
volaris,  964 
mylohyoideus,  923 
nasociliaris ,  916 
ohturatorius ,  979 
accessorius,  980 
ramus  anterior,  979 
posterior,  980 
occipitalis  major,  951 

minor,  956 
oculomotorius,  911 
ophthalmicus,  915 
opticus,  909 
palatinus  anterior,  920 
medius,  920 
posterior,  921 
perinei,  991 

peronaeus  communis,  989 
rami  articulares,  990 
profundus,  990 
petrosus  profundus,  919 

superficialis  major,  919 
phrenicus ,  957 
plantaris  lateralis,  989 

ramus  profundus,  989 
superficialis,  989 
medialis,  988 
pterygoideus  externus,  922 

internus,  921 
pudendus,  991 
radialis,  968 

rami  musculares,  969 
ramus  superficialis,  969 
recurrens,  942 
saphenus,  981 
spermaticus  exter^ius,  977 
spinosus,  921 
splanchnicus  imus,  999 
major,  998 
minor,  999 


Nervus  stapedius,  932 
subscapularis,  960 
supraorlritalis,  916 
supratrochlearis,  916 
thoracalis  longus,  960 
thoracodorsalis,  961 
tibialis,  987 

rami  articulares,  987 
calcanei  mediales,  988 
musculares,  987 
trigeminus,  914 
trochlearis,  913 
tympanicus,  939 
ulnaris,  967 

?'a??ii  musculares,  967 
ramus  cutaneus  palmaris,  967 
dorsalis  manus,  967 
profundus,  968 
superficialis,  968 
volaris  manus,  968 
vagus,  940 

rami    bronchiales    anteriores, 
943 
posteriores,  943 
cardiaci  inferiores,  943 

superiores,  942 
coeliaci,  943 
gastrici,  943 
hepatica,  943 
oesophagei,  943 
ramus  auricularis,  941 
meningeus,  941 
pharyngeus,  942 
vestibularis,  1068 
zygomaticus,  917 

ramus  zygomaticofacialis,  918 
zygomaticotemporalis,  918 
Net-work,  carpal,  dorsal,  678 
volar,  678 
malleolar  lateral,  724 
medial,  723 
Neumann,    dentinal    sheath    of, 

1120 
Neural  arch,  197 
canal,  88    . 
crest,  88,  120 
folds,  88 
groove,  88 
tube,  88 
Neurenterie  canal,  88 
Neuroblasts,  118 
Neurocentral  synchondrosis,  210 
Neuroglia,  70 
of  cord,  810 
Neurokeratin,  75 
Neurolemma,  75 
Neurology,  801 
Neuromeres,  806 
Neuromuscular  spindles,  1071 
Neuron  theory,  805 
Neurons,  motor,  lower,  897 
upper,  896 
sensory,  highest,  899 
intermediate,  899 
lowest,  899 
Neurotendinous  spindles,  1070 
Neutrophil    colorless    corpuscles, 

62 
Nidus  avis  of  cerebellum,  839 
Ninth  nerve,  937 
Nipple  or  papilla  of  mamma,  1258 
Nissl's  granules,  72 
Node,  atrioventricular,  614 

sinoatrial,  614 
Nodes  of  Ranvier,  75 
Nodular  lobe,  839 
Nodule  of  cerebellum,  839 
Noduli  lymphatici  aggregati,  1175 

solitarii,  1175,  1185 
Modulus  vermis,  839 
Non-medullated  nerve  fibres,  76 
Normse  of  skull,  basalis,  278 
frontalis,  285 
lateralis,  281 
occipitalis,  284 


Normi3e  of  skull,  vcrticalis,  277 
Normoblasts,  51 
Nose,  1008 

accessory  sinuses  of,  1014 
alar  cartilages  of,  1009 
applied  anatomy  of,  1015 
arteries  of,  1009,  1012 
cartilage  of  septum  of,  1008 
cartilaginous    frame-work  [of, 

1008 
cavities  of,  1010 
development  of.  111 
external,  1008 
lateral  cartilage  of,  1009 
lymphatics  of,  776 
mucous  membrane  of,  1012 
muscles  of,  468 
nerves  of,  1013 
veins  of,  1013 
Notch,  acetabular,  339 
cardiac,  1104 
cerebellar,  anterior,  837 

posterior,  837 
ethmoidal,  235 
intertragic,  1044 
jugular,  230 
lacrimal,  257 
mandibular,  273 
mastoid,  239,  280 
nasal,  of  frontal,  235 

of  maxilla,  257 
parietal,  239 
preoccipital,  867 
presternal,  217 
of  Rivinus,  1049 
scapular,  306 
sciatic,  336 
sphenopalatine,  268 
superior  thj^roid,  1080 
supraorbital,  235,  286,  288 
ulnar,  of  radius,  321  ? 
umbilical,  of  liver,  1194 
vertebral,  197 
Notochord,  90 
Nuchal  line,  227,  281 
Nuck,  canal  of,  187,  1251 
Nuclear  layer  of  cerebellar  cortex, 
843 
layers  of  retina,  1028 
matrix,  34 
membrane,  34 
substance,  34 
Nucleated    sheath    of    Schwann, 

73 
Nuclei  of  cochlear  nerve,  836,  935 
of  glossopharyngeal  and  vagus 

nerves,  829 
of  oculomotor  nerve,  911 
olivary,  830 

of  origin  of  motor  nerves,  908 
pontis,  835,  908 
of      termination      of      sensory 

nerves,  908 
of  trigeminal  nerve,  835,  855 
of  vestibular  nerve,  836,  935 
Nucleoli,  34 

Nucleus  of  abducent  nerve,  835 
of  accessory  nerve,  830,  944 
ambiguus,  829 
amygdalae,  883 
amygdaline,  839 
arcuatus,  831 
of  Bechterew,  836,  935 
caudate,  881 
caudatus,  881 
of  a  cell,  34 

of  Darkschewitsch,  860 
of  Deiters,  836,  935 
dentatus  [of  cerebellum],  844 
dorsalis,  813 
emboliformis,  844 
of  facial  nerve,  836,  929 
fastigii,  844 
globosus,  844 
of  hypoglossal  nerve,  829 


INDEX 


1389 


Nucleus,  inferior  central,  S33 

intercalatus,  848 

of  lateral  lenniiscus,  935 

lateralis,  833 

of  lens,  1031 

lenticular,  881 

lentiforni,  881 

lentiformis,  8M 

of  Lays,  8(j() 

of  medial  longitudinal  fascicu- 
lus, 851 

nervus  abducenlis,  835 
acuniici,  836 
facialis,  836 
tri(]cmini,  835 

of  oculomotor  nerve,  855,  911 

olivaris  superior,  835 

olivary,  830,  835 

of  posterior  commissure,  860 

pulposus,  104 

red,  850 

of  Roller,  833 

segmentation,  84 

sensorj',  930 

trapezoid,  835 

of  trochlear  nerve,  855,  913 

of  vagus  nerve,  829 
Nuel,  space  of,  1067 
Nuhn,  glands  of,  1131 
Nutrient  artery  of  bone,  52 
Nutritive  yolk,  78 
Nj'mphae,  1257 


Obelion,  278,  296 
Obex,  846 
Oblique  cord,  423 

inguinal  hernia,  1187 
ligament,  423 
line  of  fibula,  360 

of  mandible,  271 

of  radius,  320 
muscles,  499,  503 

inferior,  1036 

superior,  1035 
.     popliteal  ligament,  439 
ridge  of  clavicle,  302 
sinus  of  pericardium,  603 
vein  of  left  atrium,  603,  731 

of  Marshall,  603,  731 

Obliquus  auriculae  muscle,  1046 

capitis  inferior  muscle,  491 

superior  muscle,  491 
externus  abdominis  muscle,  499 
inferior  muscle,  491 
internus     abdominis      muscle, 

503 
oculi  inferior  muscle,  1036 

superior  muscle,  1035 
superior  muscle,  491 
Obliterated  ductus  venosus,  765 
hypogastric  artery,  700 
umbilical  vein,  765,  1150 
Obturator  artery,  702 

peculiarities  of,  703 
crest,  338 

externus  muscle,  573 
foramen,  339 
groove,  339 
internus  muscle,  572 

fascia  of,  510 
lymph  gland,  787 
membrane,  572 
nerve,  979 

accessory,  980 

applied  anatomy  of,  992 
tubercle,  339 
vein,  760 
Occipital  artery,  635 
bone,  227 

articulations  of,  231 

basilar  part  of,  230 

lateral  parts  of,  229 


Occipital  bono,  ossification  of,  231 
squama  of,  227 
structure  of,  231 

condyles,  229 

crest,  internal,  228,  292 

fossa;,  228 

groove,  239,  280 

lobe,  871 

lyniph  glands,  774 

nerve,  951,  956 

point,  296 

protuberance,  227,  228,  282 

sinus,  743 

sulcus,  871 

triangle,  483,  645 

vein,  734 
Occipitoaxial  ligaments,  393 
Occipitofrontal  fasciculus,  891 
Occipitofrontalis  muscle,  465 
Occipitomastoid  suture,  282 
Occipitotemporal       convolution, 

871 
Ocular  muscles,  1034 

applied  anatomy  of,  1038 
Oculomotor  sulcus,  849 

nerve,  911 

applied  anatomy  of,  913 
OdontoJDlasts,  1119,  1123 
Odontoid  ligaments,  393 

process  of  axis,  200 
CEsophageal  arteries,  663,  685 

glands,  1146 

hiatus  in  diaphragm,  496 

nerves,  943 
.  plexus,  943 
(Esophagus,  1144 

abdominal  portion  of,  1145 

applied  anatomy  of,  1146 

cervical  portion  of,  1144 

lymphatic  vessels  of,  800 

nerves  of,  1146 

structure  of,  1145 

tela  submucosa,  1145 

thoracic  portion  of,  1144 

tunica  mucosa,  1146 
muscularis,  1145 

vessels  of,  1146 
Olecranon,  315 

fossa,  313 
Olfactory  areas.  111 

bulb,  874,  893 
structure  of,  894 

cells,  1012 

fasciculus,  887 

hair,  1012 

lobe,  874 

nerves,  908 

applied  anatomy  of,  909 
development  of,  134 

pits.  111 

sulcus,  870 

tract,  874 

trigone,  875 
Oliva,  824 
Olive,  824 

peduncle  of,  830 
Olivary  body,  824 

nucleus,  830,  835 
Omental  bursa,  1152,  1155 
boundaries  of,  1155,  1156 

recess,  1156 
Omentum,  gastrocolic,  1157 

gastrohepatic,  1156 

greater,  1157 

lesser,  1156 

niajus,  1157 

minus,  1156 

small,  1156 
Omohyoid  muscle,  482 
Omohyoideus  muscle,  482 
Ontogeny,  77 
Oocytes,  primary,  77 

secondary,  80 
Oogonia,  77 
Ooplasm,  77 


Opening  of  aorta  in  left  ventricle, 
612 

aortic,  in  diaphragma,  495 

atrioventricular,  left,  611 
right,  609 

caval,  in  diaphragma,  495 

of  coroiuiry  sinus,  608 

of  inferior  vena  cava,  607 

oesophageal,     in     diaphragma, 
496 

of  pulmonary  artery,  609 
veins,  611 

saphenous,  562 

of  superior  cava,  607 

of  thorax,  601 
Openings  in  diaphragma,  495 

in  roof  of  fourth  ventricle,  847 
Opercula  of  insula,  873 
Ophryon,  296 
Ophthalmic  artery,  648 

ganglion,  917 

nerve,  915 

veins,  745 
Opisthion,  281,  296 
Opisthotic    centre    of    temporal 

bone,  244 
Opponens    digiti    quinti    muscle, 
555 

minimi  digiti  muscle,  555 

pollicis  muscle,  553 
Optic  axis,  1017 

chiasma,  862,  909 

commissure,  862 

cup, 134 

disk,  1027 

foramen,  246,  250,  290 

groove,  246 

nerve,  909 

applied  anatomy  of,  911 

radiations,  857,  864 

recess,  865 

stalk,  126,  134 

thalamus,  855 

tracts,  863,  909 

vesicle,  126,  134 
Ora  serrata,  1026,  1029 
Oral  cavity,  1110 

part  of  pharynx,  1139 
Orbicular  ligament,  422 
Orbicularis  oculi  muscle,  467 
lacrimal  part,  468 
orbital  part,  468 
palpebral  part,  468 

oris  muscle,  471 

palpebrarum  muscle,  467 
Orbiculus  ciliaris  muscle,  1023 
Orbitae,  286 
Orbits,  286 

relation  of  nerves  in,  928 
Orbital  fascia,  1038 

fissure,  inferior,  284,  288 
superior,  249,  288,  290 

gyri,  870 

index,  296 

nerve,  917 

operculum,  873 

plates,  235 

process  of  palatine  bone,  267 
of  zygomatic  bone,  264 

septum,  1039 

sulcus,  870 

vein,  734 
Orbitalis  muscle   of   H.    Miiller, 

1037 
Orbitosphenoids,  249 
Organ,  enamel,  1123 

of  Girald^s,  1236 

of  hearing,  1043 

of  Rosenmiiller,  181,  1244 

of  sight,  1017 

of  smell,  1008 

spiral,  of  Corti,  1065 
Organa  genitalia  inuliehria,  1243 
virilia,  1228 

oculi  accessoria,  1034 


1390 


INDEX 


Organon  aiulilus,  1043 
gustus,  1007 
ol/aclorius,  lOOS 
spirale  [Corti\,  1065 
visus,  1017 
Organs  of  digestion,  110!) 
genital,  of  female,  1243 

of  male,  122S 
of  Golgi,  1069 
of  the  senses,  1007 
of  taste,  1007 
urogenital,  1206 
vomeronasal,  of  Jacobson,  113, 
1012 
Orifice,  atrioventricular,  left,  611 
right,  609 
cardiac,  of  stomach,  1161 
mitral,  611 
of  mouth,  1110 
pyloric,  of  stomach,  1162 
urethral,  external,  1226,  1257 

internal,  1222 
of  uterus,  external,  1250 

internal,  1249 
vaginal,  1257 
Orifices  of  ureters,  1222 
Orificium  urethrae  externum,  1226, 

1257 
Origin  of  muscles,  462 
Os  acetabuli,  340 
calcis,  362 
capitatum,  327 
coccygis,  209 
cordis,  613 
coxae,  333 

articulations  of,  340 
ossification  of,  340 
structure  of,  340 
cuboideum,  367 
cuneifortne  prinium,  369 
secundum,  369 
tertium,  370 
ethmoidale,  251 

lamina  crihrosa,  252 
perpendicularis,  252 
frontale,  233 
hamatum,  328 
hyoideum,  275 
ilii,  333 
incisiviun,  261 
innominatum,  333 
ischii,  336 
lacrimale,  263 
lunatum,  323 
magnum,  327 
multangulum  majus,  326 

minus,  327 
naviculare  manus,  323 

pedis,  368 
occipitale,  227 
palatinu?n,  265 

pars  horizontalis,  266 
perpendicularis,  266 
parietale,  231 
pisiforme,  326 
planum,  253 
pubis,  337 
sacrum,  206 

fades  dorsalis,  207 
pelvina,  206 
sphenoidale,  245 
aZae  magna,  248 
parva,  249 
temporale,  237 
trigonum,  367 
triquetum,  324 
zygoynaticum,  263 
Ossa  carpi,  323 
cranii,  227 
exiremitatis  inferioris,  333 

superioris,  301 
faciei,  255 
metacarpalia,  329 
tnetatarsalia,  371 
nasalia,  255 


Ossa  sesumoidca,  376 

torsi,  362 
Ossein,  56 

Ossicles,  auditory,  1053 
development  of,  141 
ligaments  of,  1054 
Ossicula  audilus,  1053 
Ossification  of  atlas,  210 
of  axis,  210 
of  clavicle,  303 
of  coccyx,  212 
of  ethmoidal,  254 
of  femur,  352 
of  fibula,  361 
of  foot,  374 
I      of  frontal,  237 
of  hand, 331 
of  hip  bone,  340 
of  humerus,  313 
of  hyoid,  277 

of  inferior  nasal  concha,  269 
intracartilaginous,  57 
intramembranous,  56 
of  lacrimal,  263 
of  lumbar  vertebrae,  212 
of  mandible,  270 
of  maxilla,  262 
of  nasal,  256 
of  occipital,  231 
of  OS  coxae  or  innominatum,  340 
of  palatine,  268 
of  parietal,  233 
of  patella,  355 
of  radius,  321 
of  ribs,  224 
of  sacrum,  212 
of  scapula,  308 
of    seventh    cervical    vertebra, 

211 
of  sphenoidal,  251 
of  sternum,  220 
of  temporal,  244 
of  tibia,  359 
of  ulna,  319 

of  vertebral  column,  210 
of  vomer,  270 
of  zygomatic,  265 
Osteoblasts,  51 
Osteoclasts,  51,  1124 
Osteodentin,  1121 
Osteogenetic  fibres,  56 
Osteology,  195 

Ostium,    abdominal,    of    uterine 
tube,  1247 
maxillare,  1011 
pharyngeal,   of  auditory  tube, 

1139 
primitive  urogenital,  190 
prim,um  [heart],  149 
secundum  [heart],  149 
Otic  ganglion,  924 
Otoconia,  1063 
Outlet  of  pelvis,  341 
Ova,  primitive,  184 
Oval  area  of  Flechsig,  818 

bundle,  119 
Ovaria,  1243 
Ovarian  arteries,  697 
fossa,  1154,.  1244 
plexus  of  nerves,  1004 
veins,  764 
Ovaries,   1243 

applied  anatomy  of,  1246 
descent  of,  184 
development  of,  184 
ligaments  of,  1244 
lymphatic  vessels  of,  795 
nerves  of,  1246 

structure  of,  1245  i 

vesicular   or   Graafian   follicles  I 

of,  1245 
vessels  of,  1246 
Oviduct,  1247 
Ovula  Nabothi,  1252 
Ovum,  77 


Ovum,  corona  radiata  of.  7S 

coverings  of,  77 

discharge  of,  1246 

fertilization  of,  82 

germinal  spot  of,  79 
vesicle  of,  79 

implantation  or  imbedding  of, 
97 

maturation  of,  79 

mature,  80 

segmentation  of,  84 

structure  of,  77 

yolk  of,  77 

zona   pellucida   or   radiata   of. 
79 
Oxyntic  cells,  1166 

glands,  1166 
Oxyphil  colorless  corpuscles,  62 


!  Pacchionian  glands,  905 
Pacinian  corpuscles,  1069 
Pad,  retropubic,  1219 
Palatal  process  of  maxilla,  260 
Palate,   1112 

applied  anatomy  of,  1115 

arches  of,  1112 

bone,  265 

development  of,  112 

hard,  1112 

muscles  of,  dissection  of,  1114 

soft,  1112 

aponeurosis  of,  1112 
muscles  of,  1113 
Palatine  aponeurosis,  1112 
artery,  ascending,  634 

of  ascending  pharyngeal,  637 
descending,   642 
bone,  265 

articulations  of,  268 
horizontal  part  of,  266 
orbital  process  of,  267 
ossification  of,  268 
pyramidal  process  or  tuber- 
osity of,  267 
sphenoidal  process  of,  268     . 
vertical  part  of,  266 
foramen,  278 
nerves,  920 
process  of  maxilla,  260 
processes  of  fetus,  112 
tonsils,  1139 
uvula,  1112 
velum,  1112 
Palatoglossus  muscle,  1114,  1129 

note 
Palatopharyngeus  muscle,  1114 
Palatum,  1112 
durum,  1112 
molle,  1112 
Palmar  aponeurosis,  550 
arch,  deep,  679 

superficial,  682 
cutaneous    branch    of    median 
nerve,  965 
of  ulnar  nerve,  967 
fascia,  550 

interossei  muscles,  556 
interosseous  arteries,  679 
ligaments,  427,  429 
nerve  of  ulnar,  deep,  968 
superficial,  968 
Palmaris  breads  muscle,  554 

longus  muscle,  538 
Palpehrae,  1038 

Palpebral  arteries,  internal,  650 
lateral,  649 
medial,  650 
commissures  or  canthi,  1038 
fissure,  1038 
ligaments,  1039 

medial,  468 
nerves  from  maxillary,  919 


INDEX 


1391 


Palpebral  raphe,  lateral,  468 
Pampiniform     plexus     of     sper- 
matic cord,  703 
Pancreas,  1202 

accessory  duct  of,  175,  1205 

applied  anatomy  of,  1206 

body  of,  1204 

development  of,  175 

duct  of,  175,  1204 

head  of,  1203 

lymph'atic  vessels  of,  793 

lieck  of,  1203 

nerves  of,  1204 

structure  of,  1205 

surface  marking;  of,  1307 

tail  of,  1203 

uncinate  process  of,  1203 

vessels  of,  1204 
Pancreatic  arteries,  691 

duct,  1206 

accessory,  175,  1205 

veins,  766 
Pancreatica  magna  artery,  691 
Pancreaticoduodenal    artery, 
inferior,  692 
superior,  690 

lymph  glands,  792 

veins,  766 
Pancreaticolienal   lymph   glands, 

788 
Papilla,  lacrimal,  1038 

foliata,  1132 

mammae,  1258 
Papillse, -circumvallate,  1127 

conical,  1128 

filiform,  1128 

fungiform,   1128 

of  skin,  1074 

of  tongue,  1127 
Papillary  layer  of  skin,  1074 

process,  1194 
Paracentral  lobule,  870 
Parachordal  cartilages,  106 
Paradidymis,  1236 
Parallel  strise  of  Retzius,  1120 
Paramastoid  process,  230 
Paramedial  sulcus,  870 
Parametrium,   1249 
Paranephric  body,  1210 
Paranucleus,  1205 
Paraplasm,  34 
Paraplexus,  887 
Pararectal  fossa,  1153 

lymph  glands,  791 
Parathyroid  glands,  1263 

applied  anatomy  of,  1264 
development  of,  166 
structure  of,  1264 
Paravesical  fossa,  1153 
Paraxial  mesoderm,  88 
Parietal  bone,  231 

articulations  of,  233 
ossification  of,  233 

cells  of  fundus  glands,  1166 

convolution,  ascending,  871 

eminence,  231,  277,  282 

foramen,  231,  277 

lobe,  870 
gyri  of,  871 

notch,  239 

operculum,  873 

pleura,    1095 

veins,  157 
Parietomastoid  suture,  282 
Parietooccipital  fissure,  868 
Parietotemporal  artery,  653 
Parolfactory  area  of  Broca,  875 
Paroophoron,  181,  1245 
Parotid  duct,  1135 

gland,  1133 

accessory  part  of,  1134 
applied  anatomy  of,  1138 
nerves  of,  1135 
structure  of,  1135 
surface  marking  of,  1283 


Parotid  gland,  vessels  of,  1135 

lymph  glands,  775 

plexus,  930 
Parotideomasseteric  fascia,  472 
Parovarium,  1244 
Pars   ahdotninalin   s.    sympathici, 
1001 

(ii/iilis  recti.,  1184 

liii.-iiliiri.^  pontis,  833 

ccphulicu  s.  sympathici,  995 

cervicalis  s.  sympathici,  996 

ciliaris  retinae,  135,  1023,  1026 

dorsalis  pontis,  834 

endopelvina  fasciae  pelvis,  512 

externa,  interna  et  media  [ex- 
ternal acoustic  meatus) , 
1046 

flaccida  [tympanic  membrane]* 
1050 

intermedia  [vestibular  bulb], 
1258 

iridica  retinae,  135,  1025,  1029 

laryngrn  pharyngis,  1141 

mamilldiiii  liypothalami,  127 

nasatis  phuryiigis,  1139' 

optica  hypothalami,  127 

oralis  pharyngis,  1139 

pelvina  s.  sympathici,  1001 

thoracalis  s.  sympathici,  998 
Partes   genitales    externae   mulei- 

bres,  1256 
Parumbilical  veins,  767 
Patella,  354 

applied  anatomy  of,  355 

articulations  of,  355 

movements  of,  444 

ossification  of,  355 

structure  of,  355 

surface  anatomy  of,  1324 
Patellar  plexus,  979,  981 

retinacula,  439 

surface  of  femur,  350 
Pavement  epithelium,  37 
Pectinate  ligament  of  iris,  1021 
Pectineal  line,  348 
Pectineus  muscle,  567 
Pectiniforme  septum,  1238 
Pectoral  region,  dissection  of,  525 
Pectoralis  major  muscle,  426 

minor  muscle,  428 
Peculiar  thoracic  vertebrae,  203, 

204 
Peculiarities  of  fetal  heart,  161 
Pedicles  of  a  vertebra,  197 
Peduncle  of  carpus  callosum,  875 

of  olive,  830 
Peduncles  of  cerebellum,  841 

cerebral,  848 
Pedunculus  cerebri,  848 
Pelvic  colon,  1181 

diaphragm,  510 
fascia  of,  510 

fascia,  510 

endopelvic  part  of,  512 

girdle,  301 

plexuses,  1005 

portion    of    sympathetic    cord, 
1001 
Pelvis,  340,  1147 

applied  anatomy  of,  344 

articulations  of,  404 

axes  of,  342 

boundaries  of,  340 

brim  of,  340 

cavity  of  lesser,  341 

diameters,  341,  342 

in  fetus,  344 

greater  or  false,  340 

inferior  aperture  or  outlet  of, 
341 

lesser  or  true,  340 

ligaments  of,  404 

linea  terminalis  of,  340 

lymph  glands  of,  785 

major,  340 


Pelvis,  male  and   female,   differ- 
ences between,  343 
mechanism  of,  408 
minor,  340 
position  of,  342 
renal,  1210 
superior  aperture  or  inlet  of, 

340 
surface  anatomy  of,  1324 
Penis,  1237 

applied  anatomy  of,  1240 
body  of,  1239 
coronu  (jldiidis,  1239 
corjiiirii  ran  rnosa,  1238 
Corpus  i-drcraosum  urethrae,  or 

corpus  spongiosum,  238 
crura  of,  1238 
deep  artery  of,  705 
dorsal  artery  of,  706 

veins  of,  761 
extremity  of,  1239 
fundiform  ligament  of,  1239 
glands,   1238 
nerves  of,  1240 
prepuce  or  foreskin  of,  1239 
root  of,  1239 

septum  pectinifo7-me,  1238 
structure  of,  1239 
suspensory  ligament  of,  1239 
Perforated    substance,     anterior, 
875 
posterior,  848 
Perforating     arteries,     of    hand, 
679 
from  internal  mammary,  666 
from  plantar,  728 
from  profunda  femoris,  717 
cutaneous  nerve,  991 
fibres  of  Sharpey,  54 
Perforator  of  spermatozoon,  81 
Pericardiac  arteries,  664,  685 
Pericardiacophrenic  artery,  664 
Pericardial  area,  87 

pleura,    1095 
Pericardium,  601 

applied  anatomy  of,  603 
diverticula  of,  602 
fibrous,  601 
nerves  of,  603 
oblique  sinus  of,  603 
relations  of,  601 
serous,  602 
structure  of,  601 
transverse  sinus  of,  603 
vessels  of,  602 
vestigial  fold  of,  603 
Pericecal  folds,  1159 

possse,  1159 
Perichondrium,  47 
Perilymph,  1061 
Perimysium,  64 
Perineal  arteries,  705 
body, 1184 
branch  of  fourth  sacral  nerve, 

992 
muscle,   superficial  transverse, 

518,  520 
nerve,  991 
Perineum,  boundaries  of,  514 
central  tendinous  point  of,  518 
lymphatic  vessels  of,  787 
muscles  of,  514 
Perineurium,  801 
Periosteum,  51 
Peripheral  end-organs,  1069 
nervous  system,  801 
organs  of  special  senses,  1007 
terminations   of   nerves   of 
general  sensations,  1069 
Periscleral  lymph  space,  1037 
Peritoneal  cavity,  1149 
fossae  or  recesses,  1057 

applied  anatomy  of,  1161 
sac,  greater,  1150 
lesser,  1152,  1155 


1392 


INDEX 


Peritoneum,  1149 

epiploic  foramen  of,  1155 
lesser  sac  of,  1155 
ligaments,  1156 

main  ca\-ity  or  greater  sac  of, 
1150 
horizontal    disposition    of, 
in  lower  abdomen,  1154 
in  pelvis,  1153 
in  upper  abdomen,  1154 
vertical  disposition  of,  1150 
'mesenteries,  1157 
omenta,   1156 
omental  bursa  of,  1155 

vertical  disposition  of,  1152 
parietal  portion  of,  1149 
visceral  portion  of,  1149   • 
Permanent  cartilage,  47 
choance,   113 
kidney,  187 
teeth,    1117 

development  of,  1124 
Peronaeus  bre\'is  muscle,  583 
longus  muscle,  582 
tertius  muscle,  578 
Peroneal  artery,  726 
anterior,  726 
peculiarities  of,  726 
nerve,  common,  989 

applied  anatomy  of,  993 
deep,  990 
superficial,  990 
retinacula,  585  ' 

septa,  576 
tubercle,  165 
Perpendicular  fasciculus,  891 
line  of  ulna,  318 
plate  of  ethmoid,  252 
Pes  or  base  of  cerebral  peduncle, 
849  j 

hippocaniTpi,  881 
Petit,  canal  of,  1030  ' 

triangle  of,  524 
Petrooccipital  fissure,  280 
Petrosal  nerve,  deep,  919 
external,  997 
large  deep,  919 

superficial,  919,  931  | 

superficial,  greater,  919,  931 

smaller,   1056 
process,  246  1 

sinuses,  736,  746  i 

Petrosphenoidal  fissure,  280 
Petrosquamous  sinus,  743 

suture,  241,  243 
Petrotympanic  fissure,  238,  280 
Petrous  ganglion,  938 

portion  of  temporal  bone,  241 
Peyer's  glands,   1175 

patches,  1175 
Phalangeal    processes    of    Corti's 

rods,  1067 
Phalanges  digitoritm  manus,  331 
pedis,  373 
of  foot,  373  I 

articulations  of,  459 
ossification  of,  374 
of  hand,  331  ; 

articulations  of,  431 
ossification  of,  332  i 

Pharyngeal  aponeurosis,  1143 
arterj^  ascending,  637 
bursa,  1139  I 

grooves,  108  I 

membrane,  163 

nerve   from    glossopharyngeal, 
940 
from     sphenopalatine     gan- 
glion, 921 
from  vagus,  942 
ostium  of  auditorv  tube,  1139 
plexus  of  nerves,  940,  942,  997 
pouches,  108 

recess,  1139  i 

tonsU,  1139  ' 


PharjTigeal  tubercle,  230,  280 

veins,   737 
Pharyngojjalatine  arch,  1112 
Pharyngopalatinus  muscle,  1114 
Pharynx,  1138 

aponeurosis  of,  1143 

applied  anatomy  of,  1143 

development  of,  168 

laryngeal  part  of,  1141 

lymphatic  vessels  of,  779 

mucous  coat  of,  1143 

muscles  of,  1141 

nasal  part  of,  1139 

oral  part  of,  1139 

structure  of,  1143 
Philtrum,  472 

Phrenic  artery,  inferior,  697 
superior,  686 

nerve,  957 

plexus  of  nerves,  1003 

vein,  inferior,  764 
superior,  751 
Phrenicocolic  ligament,  1157 
Phrenicocostal  sinus,  1097 
Phrenicolienal  ligament,  1155 
Phrenicopericardiac  ligament, 

right,  762 
Phylogenv,  77 
Pia  of  brain,  906 

of  cord,  906 

mater,  cerebral,  906 
encephali,  906 
spinalis,  906 

spinal,  906 
Pigment,  46 

of  iris,  1025 

of  skin,  1074 
Pigmentary  layer  of  retina,  1027 
Pigmented    connective-tissue 
cells,  46 

epithelial  cells,  46 
Pill,   1075 
Pillars  of  Corti,  1065 

of  external  abdominal  ring,  500 

of  fauces,  1112 

of  fornix,  886,  887 
Pineal  body,  859 

development  of,  859 
structure  of,  860 

eye  of  lizards,  860 

recess,  127,  865 
Pinna,  1044 

cartilage  of,  1044 

ligaments  of,  1044 
Piriformis  muscle,  571 

fascia  of,  511 
Pisiform  bone,  326 
Pisohamate  ligament,  427 
Pisometacarpal  ligament,  427 
Pits,  olfactory,  111 
Pituitarv  bodv,  861 
Pivot-joint,  3S2 
Placenta,  100 

circulation  through,  101,  616 

cotyledons  of,  101 

fetal  portion  of,  100 

maternal  portion  of,  100 

pre\'ia,   101 

separation  of,  101 
Plain  muscle,  67 
Plane,  intertubercular,  1147 

subcostal,  1147 

transpyloric,   1147 
Plantar  aponeurosis,  586 

arch,  727 

applied  anatomy  of,  728 

arteries,  727 

cutaneous  venous  arch,  756 
net-work,  756 

digital  veins,  759 

fascia,  586 

interossei  muscles,  591 

ligament,  long,  454 

metatarsal  arteries,  728 

nerves,  988,  989 


Plantaris  muscle,  579 
Planum  nuchale,  'I'll 

occipitale,  227 
Plasma  cells,  41 

Plate  or  Plates,  criijriform,  of  eth- 
moidal, 252 

ethmoidal,  107 

orbital,  of  frontal,  235 

perpendicular,    of     ethmoidal, 
252 

pterygoid,  of  sphenoidal,  250 

tarsal,  1039 
Platelets  of  blood,  64 
Plat5'sma  muscle,  475 
Pleura,  1095 

ai^plied  anatomj-  of,  1098 

ca\aty  of,  1095 

cervical,  1095 

costal.  1095 

cupula  of,  1095 

diaphragmatic,  1095 

lymphatic  vessels  of,  800 

mediastinal,  1095 

nerves  of,  1097 

parietal,  1095 

pericardial,  1095 

pulmonary,   1095 

reflections  of,  1095 

structure  of,  1097 

surface  markings  of,  1297 

vessels  of,  1097 
Plexiform  layers  of  retina,  1028 
Plexus,  aortic  abdominal,  1004 

Auerbach's,  1176 

basilar,  746 

brachial,  958 

cardiac,  1001 

carotid,  internal,  996 

cavernous,  996 

cer^aca!,  954 
posterior,  951 

choroid  of  fourth  ventricle,  846 
of  lateral  ventricle,  887 
of  third  ventricle,  864 

coccvgeal,  992 

cceliac,   1002 

of  cornea,  1021 

coronary,  1002,  1004 

of  Exner,  893 

gastric,  1004 

hemorrhoidal,  1005 
venous,  761 

hepatic,    1004 

hypogastric,  1005 

infraorbital,  919 

lienal,  1004 

lumbar,  975 

lumbosacral,  974 

Aleissner's,  1176 

mesenteric,  1004,  1005 

myenteric,   1176 

oesophageal,  943 

ovarian,  1004 

parotid,  930 

patellar,  979,  981 

pehdc,  1005 

pharyngeal,  940,  942,  997 

phrenic,   1003 

prostatic,  1005 

pudendal,  991 
venous,  761 

pulmonarv,  941,  943 

renal,    1004 

sacral,  982 

solar,  1002 

spermatic,   1004 

splenic,  1004 

of  submucosa,  1176 

subsartorial,  981 

suprarenal,  1004 

tonsillar,  940 

tympanic,  1056 

uterine,  1005 
venous,  761 

vaginal,   1005 


IXDEX 


1893 


Plexus  of    veins,   vesicoprostatit-, 
761 
vesical,  1005 
venous,  761 
Plej^us  aorticus  abclominali.i,  1004 
arleriae  ovaricae,  1004 
brachiali>!,  9o.S 
cardiacus,  1001 
caroticus  iriternus,  996 
cavernosus,  996 
cervicalin,  954 

ramus  anterior.  956 
posterior,  957 
chorioideus   ventriculi   lateralis, 
887 
<er<z!',  888 
coeliacus,   1002 
coronarius  anterior,  1002 

posterior,  1002 
gastricus  superior,  1004 
hcpaticus,  1004 
hypogastricus,   1005 
lienalis,  1004 
lumbalis,  975 
lumbosacralis,  974 
mesentericua  inferior,  1005 
phrenicus,  1003 
prostaticus,  1005 
pudendus,  991 
renalis,  1004 
sacralis,  982 
spermaticus,  1004 
suprareiialis,  -1004 
venosi  basilaris  746 
haemorrhoidalis,  761 
pterygoideus,  734 
pudendalis,  761 
vertebrates  externi,  754 

interni,  755 
vesicalis,  781 
Plica  circular es  [Kerkringi],  1173 
fimbriata  [tongue],  1126 
gubernatrix,    186 
lacrimalis  of  Hasner,  1042 
•  semilunaris  [conjunctiva],  1041 
[tonsil],  1140 
sublingualis,  1137 
triangularis  [tonsil],  1140 
vascularis,  186 
ventriculares  [laryngis],  1085 
vesicalis  transversa,  1153 
Plicae  uretericae,  1222 

vocales,  1086 
Pneumogastrie  nerve,  940 
Polar  bodies  or  polocytes,  79 
Poles    of    cerebral    hemispheres, 
867 
of  eyeball,  1017 
of  lens,  1031 
Polvmorphonuclear   leucocvtes, 

62 
Polyspermy,   83 
Pomum  Adami,  1080 
Por^s,  833 

applied  anatomy  of,  836 
development  of,  124 
hepatis,  1194 
structure  of,  834 
Varoli,  833 
Ponticulus  [auricula],  1044 
Pontine  arteries,  661 
Popliteal  artery,  718 

applied  anatomy  of,  719 
branches  of,  720 
peculiarities  of,  719 
surface  marking  of,  1331 
fossa  or  space,  718 
dissection  of,  718 
line  of  tibia,  357 
Ij'mph  glands,  782 
nerve,  external,  989 

internal,  987 
surface  of  femur,  348 
vein,  758 
Popliteus  muscle,  581 

88 


Pore,  gustatory,  1007 

Porta  of  liver,  1194 

Portal  vein,  7()4 

applied  anatomy  of,  7()7 
develoinnent  of,  764 

Position  of  pelvis,  342 

Postanal  gut,  174 

Postaxial  borders  of  limbs,  1 14 

Postcentral  sulcus,  870 

Postcornu,  879 

Posterior*annular  ligament,  550 
calcaneoastragaloid     ligament, 

453 
circumflex  artery,  671 
common  ligament,  385 
cornu  of  medulla  spinalis,  809 
costotransverse  ligament,  399 
cricoarytenoid  muscle,  1088 
deep  cervical  vein,  738 
dental  arterj%  641 
inferior  ligament,  448 
interosseous  artery,  681 

nerve,  970 
ligament,  426 
pillar  of  fauces,  1112 
pulmonary  nerves,  943 
radial  carpal  artery,  678 
radioulnar  ligament,  424 
sacrosciatic  ligament,  404 
scapular  artery,  664 

nerve,  960 
superior  ligament,  448 
talotibial  ligament,  450 
temporal  artery,  638 
ulnar  carpal  artery,  682 
vertebral  vein,  738 

Postero-inferior  lobule,  839 

Postero-lateral  ganglionic  arteries, 
662 

Postero-medial    ganglionic    arte- 
ries, 653, 662 

Postero-superior  lobule,  838 

Postgemina,  854 

Postnodular  fissure,  838 

Postpartum  hemorrhage.  101 

Postpj-ramidal  fissure,  839 

Postsphenoid  part  of   sphenoid, 
251 

Pott's  fracture,  593 

Pouch  of  Douglas,  1151 
of  Prussak,  1055 
of  Rathke,  166 

Pouches,  pharyngeal,  108 

Poupart's  ligament,  502 

Praeputium  clitoridis,  1257 

Preauricular  lymph  glands,  775 
point,  1279 
sulcus  of  ilium,  335,  336 

Preaxial  borders  of  limbs,  1 14 

Precentral  gyre,  869 
sulcus,   869 

Prechordal    portion    of    base    of 
fetal  skull,  106 

Preclival  fissure,  869 

Precommissure,  887 

Precornu,  878 

Precuneus,  871 

Pregemina,  854 

Pregnancy,  abdominal,  S3 
ovarian,  83 
tubal,  83 

Premaxilla,  261 

Premolar  teeth,  1118 

Preoccipital  notch,  867 

Prepatellar  bursa,  566 

Prepuce  of  clitoris,  1257 
of  penis,  1239 

development  of.  190 

Preputial  glands,  1239 
sac,  1239 

Prepyramidal  fissure,  838,  839 
tract,  816 

Presphenoid,  251 

Pressure  epiphyses,  59 

Presternal  notch,  217 


Pretracheal  fascia,  477 
Prevertel>ral  fascia,  477 

part  of  base  of  skull,  106 
Prickle  cells,  39 
Primary  areolae  of  bone,  59 
oocytes,  77 
spermatocytes,  82 
Primitive  aortas,  143 
atrium,  145,  149 
costal  arches,  104 
digestive  tube,  92 
fibrillaj  of  Schultze,  74 
groove,  86 
jugular  veins,  157 
ova,  184 
palate,   112 
segments,  91 
sheath  of  nerve  fibre,  75 
streak,  86 

urogenital  ostium,  190 
ventricle  of  heart,  145 
Princeps  cer^^cis  artery,  636 

pollicis  arterj-,  678 
Prismata  adamantina,  1120 
Proamnion,  87 
Procerus  muscle,  469 
Process  or  Processes,  accessory, 

of  vertebrae,  205 
alveolar,  260 

articular,  of  vertebrae,  197 
ciliary,   1023 
clinoid,  anterior,  249,  290 

middle,  246,  290 

posterior,  246,  290 
condyloid,  of  mandible,  273 
coracoid,  307 
coronoid,  of  mandible,  273 

of  ulna,  315 
costal,  199 

descending,  of  lacrimal,  263 
of  dura  mater,  900 
ethmoidal,    of  inferior   nasal 

concha,  268 
frontal,  of  maxilla,  260 
frontonasal.  111 
frontosphenoidal,  of  zygomatic, 

264 
globular,  of  His,  111 
intrajugular,  230 
jugular,  230,  281 
lacrimal,      of      inferior      nasal 

concha,  268 
lateral  nasal.  111 
lenticular,  of  incus,  1055 
malar,  of  maxilla,  260 
mamillary,  of  vertebrae,  205 
mastoid,  239 
maxillary,  of  fetus,  112 

of  inferior  nasal  concha,  268 

of  palatine  bone,  267 

of  zygomatic  bone,  265 
muscular,  of  arytenoid.  1081 
nasal,  of  frontal  bone,  235 

of  maxilla,  260 
odontoid,  of    axis   or   epistro- 
pheus, 200 
orbital,  of  palatine  bone,  267 

of  zygomatic  bone,  264    • 
palatal,  of  maxilla,  260 
palatine,  of  fetus,  112 

of  maxilla,  260 
papillary,  of  liver,  1194 
paramastoid,  230 
petrosal,  246 

phalangeal,  of  Corti'srods,  1067 
ptervgoid,  of  sphenoidal  bone, 
•     250 
pyramidal,    of   palatine   bone, 

^267,  278 
sphenoidal,   of  palatine    bone, 
268 

of  septal   cartilage  of  nose. 
1009 

turbinated,   250 
spinous,  of  ilium,  336  ^ 


1394 


INDEX 


Process  or  Processes,  spinous,  of 
vertebrae,  197 

styloid,  of  fibula,  359 
of  radius,  321 
of  temporal  bono,  244,  280 
of  ulna,  319 

temporal,  of  zygomatic,  265 

transverse,  of  vertebra;,  197 

trochlear,  of  calcaneus,  365 

uncinate,  of  ethmoid,  253 

vaginal,  of  sphenoid,  250 
of  temporal,  243,  244 

vermiform,  1178 

vocal,  of  arvtenoid,  1081    ■ 

xiphoid,  220 

zygomatic,  of  frontal,  235 
of  maxilla,  260 
of  temporal  bone,  237 
Processus     alveolaris     [maxillae], 
260 

brevis  [malleus],  1054 

ciliares,  1023 

cochleariformis,  243,  1052 

condyloideuf:  [mandibulae],  273 

coracoideus  [scapulae],  307 

coronoideus  [majidibulae],  273 
[ulnare],  315 

frontalis  [^maxillae],  260 

gracilis  [malleus],  1053 

orbitalis  [os  palatinum],  267 

palatinus  [maxillae],  260 

pterygoidei,  250 

pyramidalis  [os  palatinum],  267 

spinosus,  197 

splenoidalis  [os  palatinum],  268 

transversi,  197 

tubarius,  250 

vermiformis,  1178 

xiphoideus,  220 

zygomaticus,  260 
Proctodeum,  174 
Predentin,  1124 
Profunda  arteries,  674 

brachii  artery,  674 

cervicalis  arterj',  666 

femoris  artery,  716 
vein,  759 

linguae  artery,  632 
Projection  fibres  of  cerebral  hemi- 

sheres,  889 
Prominence  of  aqueduct  of  Fal- 
lopius,  1051 

of  facial  canal,  1051 

laryngeal,  1080 
Prominentia  canalis  facialis,  1051 
Promontorium,  1051 
Promontory  of  tympanic  cavity, 

1051 
Pronator  quadratus  muscle,  540 

teres  muscle,  537 
Pronephric  duct,  180 
Pronephros,  ISO 
Pronucleus,  female,  80 

male,  83 
Prootic  centre  of  temporal  bone, 

244 
Prophase  of  karyokinesis,  35 
Prosencephalon,  88,  125,  855 
Prostata,  1241 

fades  anterior,  1241 
posterior,  1241 
Prostate,   1241 

applied  anatomy  of,  1242 

development  of,  189 

gland,  1241 

lobes  of,  1241 

lymphatic  vessels  of,  794 

nerves  of,  1242 

structure  of,  1241 

vessels  of,  1242 
Prostatic  ducts,  orifices  of,  1225 

plexus  of  nerves,  1005 

portion  of  urethra,  1225 

sinus,    1225 

utricle,  1225 


Prosthion,  296 

Prothrombin,    04 

Protoplasm,  33 

Protoplasmic     process    of    nerve 

cells,  72 
Protuberance,  mental,  271 

occipital,  227,  228,  282 
Prussak,  pouch  of,  1055 
Psalterium,  886 
Pseudocele,  887 
Pseudonucleoli,  34 
Pseudopodium,  63 
Psoas  magnus  muscle,  560 

major  muscle,  560 

applied  anatomy  of,  562 
fascia  covering,  559 

minor  muscle,  561 

parvus  muscle,  561 
Pterion,  249,  282,  296 

ossicle,  255 
Pterotic  centre  of  temporal  bone, 

245 
Pterygoid  canal,  250,  278 

fissure,  250 

fossa  of  sphenoid,  250 

hamulus,  250,  278 

muscles,  474 

plates,   250 

plexus  of  veins,  734 

processes  of  sphenoid,  250 

tubercle,  250 
Pterygoidei    muscles,    dissection 

of,  474 
Pterj^goideus     externus     muscle, 
474 

internus  muscle,  474 
,  Pterygomandibular  ligament,  471 

raphe,  471 
Pterj'gomaxillary  fissure,  284 
Pterygopalatine  canal,  258,  267 

fossa,  284 

groove,  250 

nerve,  921 
Pterygospinous     ligament,     251, 

477 
Pubic  arch,  341 

bones,  articulation  of,  406 

ligaments,  407 

region,    1147 
i      tubercle  or  spine,  338 
'       vein,  760 
Pubis,  337 

angle  of,  338 

body  of,  337 

crest  of,  338 

iliopectineal  eminence  of,  338 

obturator  crest  of,  338 

rami  of,  337 

sj-mphysis  of,  406 
\      tubercle  or  spine  of,  338 
1  Pubocapsular  ligament,  433 
Pubococcygeus  muscle,  514 
Pubofemoral  ligament,  433 
Puborectalis  muscle,  514 
Pubovesicales  muscles,  1221 
Pudendal  artery,  accessory,  704 
external,  761 
internal,  in  female,  706 
in  male,  703 

cleft  or  rima,  1170 

nerve,  991 
inferior,   985 

plexus,  nervous,  991 
venous,  761 

veins,  internal,  760 
Pudendum,   1256 
Pudic  arteries,  external,  716 
internal,  703 

nerve,  internal,  991 

veins,  internal,  760 
Pulmonary  artery,  620 

applied  anatomj-  of,  621 
opening  of,  in  right  ventricle, 
609 

ligaments,  1095,  1097 


Pulmonary  nerves,  943 
pleura,  1095 
semilunar  vah-es,  610 
veins,  730 

openings  of,  in  left  atrium, 
611 
Pulmones,  1101 

fades  coslalis,  1102 

mediastinalis,  1102 
margo  anterior,  1104 
inferior,  1103 
posterior,  1103 
Pulp  cavity  of  teeth,  1119 
dental,  1119 
of  spleen,  1207 
Pulvinar,  855 
Puncta  lacrimalia,  1041 
vasculosa,  875 
i  Pupil,  1024 

congenital  atresia  of,  136 
Pupillarj'  membrane,  130,  1026 
Purkinje,  cells  of,  842 

fibres  of,  69 
Putamen,  882 
Pyloric  antrum,  1162,  1163 
artery,  689 
glands,  1166 
orifice  of  stomach,  1162 
part  of  stomach,  1162,  1163 
valve,  1164 
vein,  766 
Pyramid,  1052 
of  cerebellum,  839 
of  medulla  oblongata,  823 
of  temporal  bone,  241 
of  vestibule,  1058 
Pyramidal  cells  of  cerebral  cortex, 
891 
decussation,  823 
eminence  of  tjonpanic  cavitv, 

1052 
lobe  of  thyroid  gland,  1261 
process  of  palatine  bone,  267, 
278 
!      tract,  crossed,  815 
direct,  815 
Pyramidalis  muscle,  507 

nasi  muscle,  469 
Pyramids,  renal,  1210 
i  Pyramis  medullae  obl.ongatae,  823 


Quadrate  lobe  of  liver,  1195 
Quadratus  femoris  muscle,  573 

labii  inferioris  muscle,  470 
superioris  muscle,  469 

lumborum  muscle,  510 
fascia  covering,  510 

menti  muscle,  470 

plantae    muscle,  589 
Quadriceps  extensor  muscle,  565 

femoris  muscle,  565 
Quadrigefiinal  bodies,  853 


R 


Radial  artery,  676 

applied  anatomy  of,  676 
branches  of,  678 
carpal,   678 
peculiarities  of,  676 
recurrent,  678 
surface  marking  of,  1322 
fibres  of  cerebral  cortex.  893 
fossa,  312 
nerve,  96'^ 
sulcus,  311 
tuberosity,  320 
Radialis  indicis  artery,  679 
Radiate  ligament,  396 

sternocostal  ligaments,  399 
Radiocarpal  articulation,  425 


INDEX 


1395 


Radiocarpal  articulation,  api)lied 
anatomy  of,  42G 
movements  of,  -12G 
Uadioulnar    articulation,    distal, 
423 
movements  of,  425 
proximal,  422 
movements,  423 

ligaments,  424 

union,  middle,  423 
Radius,  319 

applied  anatomy  of,  321 

articulations  of,  321 

grooves  on  lower  end  of.  321 

oblique  line  of,  320 

ossification  of,  321 

sigmoid  cavity  of,  321 

structure  of,  321 

surface  anatomv  of,  1314 

tuberosity  of,  320 

ulnar  notch  of,  321 
Radix  ai-cus  vertebrae,  197 

linguae,  1126 

penis.  1239 

pili,  1075 

pulmonis,  1105 
Rami    communicantes,   949,    950, 
995 

of  ischium,  337 

of  pubis,  337 
Ramus  inferior  ossis  ischii,  337 
pubis,  338 

of  mandible,  272 

mandibulae,  272 

superior  oss.  ischii,  337 
pubis,  337 
Ranine  artery,  632 

vein,  736 
Ran%der,  crosses  of,  75 

nodes  of,  75 
Raphe,  anococcygeal,  516 

lateral  palpebral,  468 

of  medulla,  822 

of  palate,  1112 

pterygomandibular,  471 

of  scrotum,  1228 
Rathke,  pouch  of,  166 
Receptaculum  chyli,  772 
Recess,  epitympanic,  240,  1049 

nasopalatine,  1012 

omental,  1156 

optic,  865 

pharj-ngeal.  1139 

pineal,  127,  865 

sphenoethmoidal,  293,  1010 
Recesses,  lateral,  of  fourth  ven- 
tricle, 845 

peritoneal,  1157 

of  Troltsch,  1055 
Recessus  ellipticus,  1058 

infundibuli,  864 

inter  sigmoideus,  1160 

pinealis,  127,  865 

sacciformis,  425 

sphaericus ,  1058 

suprapinealis,  865 
Reciprocal  reception,  articulation 

by,  382 
Rectal  ampulla,  1183 

columns  of  Morgagni,  1184 

laj'er  of  pelvic  fascia,  513 
Rectococcygeal  muscles,  1185 
Rectouterine  folds,  1250 
Rectovesical  excavation,  1151 

folds,  1153 

layer  of  pehdc  fascia,  512 
Rectovesicales  muscles,  1221 
Rectum,  1182 

ampulla  of,  1183 

anal  part  of,  1184 

development  of,  172 

Houston's  valves  of,  1183 

lymphatic  vessels  of,  792 

relations  of,  1183 

surgical  anatomy  of,  1190 


Rectus  abdominis  muscle,  506 
dissection  of,  505 
sheath  of,  506 
capitis  anterior  muscle,  484 
anticiis  major  muscle,  484 

minor  muscle,  484 
lateralis  muscle,  484 
posterior  major  muscle,  491 
minor  muscle.  491 
femoris  muscle,  565 
muscles  of  eyeball,  1035 
Recurrent    arterv,    interosseous, 
682 
radial,  678 
tibial,  722,  723 
ulnar,  680 
branches  from  deep  volar  arch, 

679 
larj-ngeal  nerve,  942 
nerve,  942 
Red  corpuscles,  61 

nucleus,  850 
Reflected  inguinal  ligament.  502 
Reflections  of  pleurte,  1095 
Refracting  media  of  eye,  1030 
Region,  iliac,  1147 
lumbar,  1147 
pubic,  1147 
Regions  of  abdomen,  1147 
Reil,  island  of,  873 
Reissner,    vestibular    membrane 

of,  1063 
Renal  arteries,  696 
columns,  1211 
fascia,  1209 
impression,  1192 
pehds,  1210,  1216 
plexus,   1004 
p^Tamids,  1210 
sinus,   1210 
tubules,   1212 
veins,   764 

vessels,    afferent   and   efferent, 
1212,  1214 
Renes,  1206 

extremitas  inferior,  1209 

superior,  1209 
fades  anterior,  1207 

posterior,  1208 
margo  lateralis,  1209 

medialis,  1209 
substantia  corticalis,  1211 

medullaris,  1210 
vascula  glomerulus,  1212 
Reproduction  of  cells,  34 
Respiration,  mechanism  of,  497 
Respiratorj-  apparatus,  1079 
development  of,  177 
nerve  of  Bell,  957,  960 
system,  1079 
Restiform  bodies  of  medulla,  841 
Rete  canalis  hypoglossi,  746 
foraminis  ovalis,  747 
testis,  1233 
Retia  venosa  vertebrarum,  755 
Reticular  lamina,  1067 
layer  of  skin,  1074 
tissue,  44 
Reticularis  alba,  833 

grisea,  833 
Retiform  tissue,  44 
Retina,  1026 

central  artery  of,  650 
development  of,  135 
fovea  centralis,  1026 
layers  of,  1027 
macula  lutea,  1026 
membrana      limitans     interna, 
1029 
externa,  1029 
ora  serrata,  1026 
structure  of,  1027 
supporting  frame-work  of,  1029 
Retinacula  of  hip-joint,  432 
patellar,  439 


Retinacula  peroneal,  585 
Retrahens  aurem  muscle,  1045 
Retrocecal  fossa,  1160 
Retroglandular  sulcus   of  penis, 

1239 
Retroperitoneal  fossa?,  1157 
Retropharyngeal    Ivmph    glands, 
776 

space,  477 
Retropubic  pad,  1219 
Retzius,  colored  lines  of.  1121 
Rhinal  fissure,  external,  128 
Rhinencephalon,  128,  874 
Rhodopsin,  or  casual  purple,  46, 

1026 
Rhombencephalon,  90,  122.  821 
Rhombic  grooves,  124 

lip:  123 
Rhomboid  fossa,  847 

impression,  303 

ligament,  410 
Rhomboideus  major  muscle,  525 

minor  muscle,  525 
Rhomboids,  nerve  to,  960 
Ribs,  220 

applied  anatomy  of,  179 

common  characteristics  of,  221 

development  of,  104 

false,  220 

floating  or  vertebral,  221 

ossification  of,  224 

peculiar,  223 

structure  of,  224 

true,  220 

vertebrochondral,  221 

vertebrosternal,  220 
Ridge,  ganglion,  88,  120 

supracondylar,  lateral,  311 
medial.  312 

trapezoid  or  oblique,  302 
Ridges,  bicipital,  311 
Right  atrium,  dissection  of,  607 

auricle,  606 

auricular  appendix,  606 

coronarj-  plexus,  1002 
veins,  730 

gastroepiploic  glands,  788 

ventricle,  dissection  of,  609 
Rinta  glottidis,  1087 

of  mouth,  1110 

palpebrarum,  1038 

pudendal,    1256 
Ring,  abdominal,  external,  500 
internal,  508 

femoral,  712 

inguinal,  abdominal,  508 

subcutaneous,  500 

tjTnpanic,  245 
Rings,  fibrous,  of  heart,  613 
Risorius  muscle,  472 
Ri^-inus,  ducts  of,  1137 

notch  of,  1049 
Rod-bipolars  of  retina,  1028 
Rod-granules  of  retina,  1029 
Rods  and  cones,  laver  of,  1029 

of  Corti,  1065 

of  retina,  1029 
Rolando,  fissure  of,  868 

substantia  gelatinosa  of,  809 

tubercle  of,  825 
Roller,  nucleus  of,  833 
Roof  plate,  117 
Root  of  lung.  1105 

of  penis,  1239 
Root-sheaths  of  hair,  1077 
Roots  of  spinal  nerves,  818,  948 

of  teeth,    1116 

of  zygomatic  process,  237 
Rosenmliller,  fossa  of,  1138,  1139 

IjTuph  gland  of,  783 

organ  of.  181,  1244 
Rostrum  of  corpus  callosum,  876 

sphenoidal,  247 
Rotary  joint,  382 
Rotation,  movement  of,  383 


1396 


INDEX 


Rotatores  muscles,  490 

spinae  muscle,  490 
Round  ligament  of  liver,  1195 

of  uterus,  1251 
Ruffini,  corpuscles  of,  1070 
Rust-colored  layer  of  cerebellar 

cortex,  843 


Sac,  dental,  1123 
lacrimal,  1041 
of  peritoneum,  greater,  1150 

lesser,  1152 
preputial,  1239 
Saccule,  laryngeal,  1086 

of  vestibule,  1062 
Sacculus,  1062 
Saccus  lacrimalis,  1042 

vaginalis,  186 
Sacral  arteries,  lateral,  707 
artery,  middle,  698 
canal,  208 
cornua,  207 
crests,  207,  208 
foramina.  206,  208 
groove,  207 
hiatus,  207 
lymph  glands,  787 
nerves,    divisions  of,    anterior, 
982 
posterior,  953 
nucleus  of  medulla  spinalis,  813 
plexus,  982  • 

applied  anatomy  of,  992 
tuberosity,  208 
veins,  760,  762 
Sacrococcygeal  ligaments,  406 
Sacrogenital  folds,  1153,  1250 
Sacroiliac  articulation,  404 

ligaments,  404,  405 
Sacrosciatic  ligaments,  404,  405 
Sacrospinalis  muscle,  480 
Sacro vertebral  angle,  206 
Sacrum,  206 
ala  of,  208 
apex  of,  208 
articulations  of,  208 
auricular  surface  of,  208 
base  of,  208 
ossification  of,  212 
structure  of,  208 
variations  of,  209 
Saddle-joint,  382 
Sagittal  fossa  of  liver,  1194 
sinus,  inferior,  741 

superior,  740 
sulcus,  228,  232,  235 
suture,  232,  277 
Salivary  glands,  1133 

development  of,  164 
parotid,   1133 
structure  of,  1137 
sublingual,  1135 
submaxillary,  1135 
Salpingopalatine  fold,  1139 
Salpingopharyngeal  fold,  1139 
Salpingopharyngeus  muscle,  1143 
Salter,  incremental  lines  of,  1120 
Santorini,  cartilages  of,  1081 

duct  of,  1205 
Saphenous  nerve,  981 
external,  988 
internal,  981 
long,  981 
short,  988 
opening,  564 
veins,  756,  757 

applied  anatomy  of,  757 
Sarcolemma,  64 
Sarcomere,  66 
Sarcoplasm,  65 
Sarcostyles,  65 
Sarcous  elements  of  muscles,  66 


Sartorius  muscle,  565 
Scala  media  [cochlea],  1063 
tympani,  1060 
vestihuli,  1060 
Scalene  tubercle,  224 
Scalenus  anterior  muscle,  484 
anticus  muscle,  484 
medius  muscle,  484 
posterior  muscle,  485 
posticus  muscle,  485 
Scalp,  applied  anatomy  of,  466 
lymphatic  vessels  of,  776 
muscles  of,  dissection  of,  464 
skin  of,  465 
Scapha, 1044 
Scaphoid  bone,  323,  368 

fossa  of  sphenoid,  250,  278 
Scapula,  304 

acromion  of,  306 
applied  anatomy  of,  309 
articulations  of:  309 
coracoid  process  of,  307 
glenoid  canity  of,  307 
ligaments  of,  412 
ossification  of,  308 
spine  of,  306 
structure  of,  308 
surface  anatomy  of,  1313 
surfaces  of,  304,  305 
Scapular  arteries,  663,  664 
circumflex  artery,  671 
nerve,  posterior,  960 
notch,  307 
Scapuloclavicular    articulation, 

411 
Scapus  or  shaft  of  hair,  1077 

pili,  1077 
Scarpa,  fascia  of,  499 
foramina  of,  261,  278 
ganglion  of,  1068 
triangle  of,  712 
Schindylesis,  381 
Schlemm,  canal  of,  1018 
Schreger,  lines  of,  1120 
Schultze,  primitive  fibrUlse  of,  74 
Schwann,  white  matter  of,  75 
Sciatic  artery,  706 
foramen,  406 
nerve,  985 

applied  anatomj'  of,  993 
small,  985 
notch, 336 
veins,   760 
Sclera,  1017 

structure  of,  1018 
Scleral  spur,  1019 
Scleratogenous  layer,  102 
Sclerocorneal  junction,  1018 
Sclerotome,  102 
Scrotal  arteries,  posterior,  705 

nerves,  posterior,  991 
Scrotum,  1228 

applied  anatomy  of,  1230 
dartos  tunic  of,  1229 
integument  of,  1228 
nerves  of,  1229 
raphe  of,  1228 
vessels  of,  1229 
Sebaceous  glands,  1078 
Second  cuneiform  bone,  369 
metacarpal  bone,  329 
metatarsal  bone,  372 
nerve,  909 
Secondary  areola  of  bone,  58 
dentin,   1121 
oocytes,  80 

sensory  fasciculus.  817 
spermatocytes,  82 
tympanic  membrane,  1051 
Secretion,  internal,  1260 
Segment,  internodal,  75 
of  Lantermann,  75 
medullary,  75 
Segmentation  of  cells,  34 
of  fertilized  ovum,  84 


Segmentation  nucleus,  84 
Segments,  primitive,  91 

spinal,  806 
Sella  turcica,  246,  290 
Semicanalis  m.  iensoris  tympani, 
243,  1052 
tuhae  auditivae,  243,  1052 
Semicircular  canals,  bony,  1058 
membranous,  1062 
ducts,  1062 

structure  of,  1063 
Semilunar  bone,  323 

fibrocartilages  of  knee,  441,  442 
ganglion  of  abdomen,  1002 
of  trigeminal  nerve,  914 
lobules  of  cerebellum,  838,  839 
Semimembranosus  muscle,  575 
Seminal  duct.  1235 

vesicles,  .1236 
Semispinalis  capitis  muscle,  489 
cervicis  muscle,  489 
colli  muscle,  489 
dorsi  muscle,  489 
Semitendinosus  muscle,  575 
Sensations,     general,     peripheral 
terminations    of    nerves    of, 
1069 
Senses,  organs  of,  1007 
development  of,  117 
special,    peripheral   organs   of, 
1007 
Sensory  areas  of  cerebral  cortex, 
894 
decussation,  827 
neurons,  lower  and  upper,  896, 

897 
tract,   897 
Separation  of  embryo,  92 
Septum,  aortic,  150 

canalis     m,usculoiuharii,      243, 

1052 
crural,  712 
femorale,  712 
inferius  of  heart,  149 
intermedium,,  148 
interventricular,  612 
lucidum,  887 
mobile  nasi,  1009 
Tiasi,  293 

of  nose,  293,  1012 
orbital,  1039 
pectiniforme  penis,  1238 
pellucidum,  887 
cavity  of,  887 
primum,  149 
secundum,  149 
spurium,  146 
subarachnoid,  905 
of  tongue,  1132 
transversum,  178 

of  semicircular  ducts,  1063 
urorectal,  172 
ventricular,  149,  612 
ventriculorum,  612 
Serosa,  or  false  amnion,  96 
Serous  glands  of  tongue,  1131 

pericardium,  602 
Serratus  anterior  muscle,  529 
magnus  muscle,  529 
posterior  inferior  muscle,  493 

superior  muscle,  493 
posticus  inferior  muscle,  493 
superior  muscle,  493 
Sertoli,  cells  of,  1233 
Sesamoid  bones,  376 

cartilages,  1009 
Seventh  nerve,  929 
Shaft  of  hair,  1077 
Sheath  or  Sheaths  of  arteries,  597 
carotid,  477 
crural,  710 

dentinal,  of  Neumann,  1120 
femoral,  710 

fibrous,  of  flexor  tendons,  540 
of  flexor  tendons  of  fingers,  540 


INDEX 


1397 


Sheath  or  Sheaths  of   flexor    ten- 
dons of  toos,  588 

miK'ous,  380 

of  tendons  around  anklo,  58G 
on  buck  of  wrist,  550 
in  front  of  wrist,  548 

of  rectus  abdominis  muscle,  500 
Shin  bone,  355 
Short  bones,  196 

calcaneocuboid  liKaraent,  454 

gastric  veins,  7G6 

plantar  ligament,  454- 

saphenous  nerve,  988 
vein,  757 
Shoulder  lilade,  304 

girdle,  301 

muscles  of,  530 

dissection  of,  530,  531 
Shoulder-joint,  414 

applied  anatomy  of,  417 
burstB  near,  415 
movements  of,  416 
vessels  and  nerves  of,  416 
Sibson's  fascia,  1096 
Sight,  organ  of,  1017 
Sigmoid  arteries,  695 

cavity  of  radius,  321 
of  ulna,  315,  318 

colon,   1181 

flexure,  1181 

mesocolon,  1153 

sinus,  743 

sulcus,  240 
Simple  epithelium,  36 

papilltE  of  tongue,  1128 
Sinuses  or  Sinuses,  accessory,  of 
nose,  1014 

aortic,  612 

basilar,  746 

cavernous,  744 

cervicalis,  110 

circular,  746 

confluence  of,  743 

coronary,  730 

costomediastinal,   1097 

cranial,  234  note 

of  dura  mater,  740 

of  epididymis,  1231 

of  external  jugular  vein,  735 

frontal,  235,  1014 

intercavernous,  746 

laryngeal,  1086 

lateral,  742 

longitudinal,  superior,  740,  741 

maxillary,  259,  1015 

of  Morgagni,  1142 

occipital,  743 

of  pericardium,  603 

petrosal,  746 

petrosquamous,  743 

phrenicocostal,   1097 

pocularis,  1225 

prostatic,  1225 

pyriformis,  1141 

renal,  1210 

rhomboidalis,  88 

sagittal,  740,  741 

septum,  146 

sigmoid,  743 

sphenoidal,  247,  1014 

sphenoparietal,  744 

straight,  741 

tentorial,  742 

tonsillaris,  111 

transverse,  742,  746 

urogenital,  188 

of  Valsalva,  610,  612 

venarum,  606 

venosus,  145 
Sinus  or  Sinuses,  cavernosus,  744 

coronarius,  730 

durae  niatris,  740 

frontales,  1014 

intercavernosi,  746 

maxillaris,  295,  1015 


Sinus  or  Sinuses,  occipitalis,  743 
paranasalcs,  1014 
pelrosus  inferior,  736,  746 

superior,  746 
rectus,  741 
sagittalis  inferior,  741 

superior,  740 
sphenoidales,  1014 
tarsi,  362,  367 
transversus,  742 
ve7iosus,  606 
sclerae,  1018 
Sinusoids  of  Minot,  599 
Sixth  nerve,  927 
Skein,  or  spirem,  35 

coccygeal,  1273 
Skeins,  carotid,  1273 
Skeletal  muscular  tissue,  64 
Skeleton,   195 

development  of,  102 
Skene's  duct,  190 
Skin,  1071 

appendages  of,  1075 
hairs,  1075 
nails,  1075 

sebaceous  glands,  1078 
sudoriferous  or  sweat  glands, 
1078 
arteries  of,  1074 
corium  or  cutis  vera,  1074 
development  of,  116 
epidermis  or  cuticle,  1071 
fuiTows  of,  1072 
nerves  of,  1074 
papillary  layer  of,  1074 
reticular  layer  of,  1074 
of  scalp,  dissection  of,  465 
stratum  corneum,  1072 

mucosum,  1072 
true  1074 
Skull,   226 

applied  anatomy  of,  297 
development  of,  105 
differences  in.  due  to  age,  294 
diseases  of,  298 
exterior  of,  277 
fossa  of,  anterior,  288 
middle,  290 
posterior,  291 
interior  of,  288 
norma  basalis,  278 
frontalis,  285 
lateralis,  281 
occipitalis,  284 
verticalis,  277 
sexual  differences  in,  295 
surface  anatomy  of,  1275 
tables  of,  196 

upper  surface  of  base  of,  288 
Skull-cap,  inner  surface  of,  288" 
Slightly  movable  joints,  381 
Small  cardiac  vein,  730 
cavernous  nerves,  1005 
intestine,  1168 

areolar    or    submucous    coat 

of,  1173 
circular  folds  of,  1173 
duodenum,  1169 
glands  of,  1175 
ileum,  1171 
jejunum,  1171 

lymphatic  nodules  of,  aggre- 
gated, 1175 
solitary,  1175 
vessels  of,  792 
Meckel's     diverticulum     of, 

1178 
mucous  membrane  of,  1173 
muscular  coat  of,  1173 
nerves  of,  1176 
Peyer's  glands  of,  1175 
serous  coat  of,  1172 
valvulae  conniventes  of,  1173 
vessels  of,  1176 
villi  of,  1173 


Small  saphenous  vein,  757 
sciatic  nerve,  985 
wings  of  sphenoid,  249 
Smaller  occipital  nerve,  956 
Smallest  cardiac  veins,  731 
Smell,  organ  of,  1008 
Soft  palate,  1 1 12 

aponeurosis  of ,  1112 
arches  or  pillars  of,  1112 
muscles  of,  1113 
Solar  plexus,  1002 
Sole    of    foot,    muscles    of,    first 
laj^er,  587 
fourth  layer,  590 
second  layer,  589 
third  layer,  589 
Soleus  muscle,  579 
Solitary  cells  of  medulla  spinalis, 
813 
glands,  1175 
Somatic  cells,  77 

fibres  of  spinal  nerves,  950 
layer  of  mesoderm,  88 
Somatopleure,  88 
Space  or  Spaces,  of  angle  of  iris, 
1021 
of  Burns,  477 
corneal,  1020 
epidural,  993 
interpleural,  1098 
of  Fontana,  1021 
intercostal,  221 
interglobular,  1120 
of  Nuel,  1067 
popliteal,  718 
retropharyngeal,  477 
of  Retzius,  1224 
subarachnoid,  904 
suprasternal,  477 
Spatia  zonularis,  1030 
Spatium  perichorioideale,  1017 
Special  dental  germ,  1122 

end-organs  of  nerves,  1069 
Spermatic  artery,  internal,  697 
canal,  508 
cord,  1229 

applied  anatomy  of,  1230 
structure  of,  1230 
fascia,  external,  501,  1229 
plexus,  of  nerves,  1004 

applied  anatomy  of,  1004 
veins,  763 

applied  anatomy  of,  763 
Spermatids,  82,  1233 
Spermatoblasts,  1233 
Spermatocytes,  82,  1233 
Spermatogonia,  82,  1233 
Spermatozoon    80,  1233 

body  or  connecting  piece  of,  81 
formation  of,  1233 
head  of,  80 
neck  of,  80 
perforator  of,  81 
tail  of,  82 
Sphenoethmoidal  recess,   293, 
1010 
suture,  288 
Sphenofrontal  suture,  282,  288 
Sphenoid  bone,  245 
Sphenoidal  air  sinuses,  247,  1014 
bone,  245 

articulations  of,  251 
body  of,  246 
ossification  of,  251 
pterygoid  processes  of,  250 
wings  of,  great,  248 
small,  249 
conchcB,  250 
crest,  247 

process  of  palatine  bone,  268 
of  septal  cartilage  of  nose, 
1009 
rostrum,  247 
spine,  248,  280 
turbinated  processes,  250 


1398 


INDEX 


SphenomaQclibular  ligament,  395, 

477 
Sphenomaxillary  fissure,  284 

fossa,  284 
Sphenopalatine  artery,  642 
foramen,  267 
ganglion,  919 
nerves,  918 
notch,  268 
Sphenoparietal  sinus,  744 

suture,   282 
Sphenosquamosal  suture,  282 
Sphenozygomatic  suture,  282 
Sphincter    ani    externus    muscle, 
516 
internus  muscle,  516 
pupillae  muscle,  1025 
recti  muscle,  514 
urethrae  membranaceae    mus- 
cle, 520, 521 
vaginae  muscle,  520 
Spigelian  lobe  of  liver,  1195 
Spina  angular  is  [sphenoid],  248, 
280 
helicis,  1044 
scapulae,'30Q 
vestibuli,  146 
Spinal,  accessory  nerve,  944 
arteries,   660 
bulb,  822 
column,  196 
cord,  805 
dura  of,  902 
pia  of,  906 
ganglia,  948 

structure  of,  949 
nerves,  947 

arrangement     into     groups, 

947 
connections  with   sympa- 
thetic, 949 
development  of,  81 
divisions  of,  951 
anterior,  954 
posterior,  951 
points  of  emergence  of,  947 
roots  of,  818,  948 
size  and  direction  of,  949 
somatic  fibres  of,  950 
structure  of,  950 
sympathetic  fibres  of,  950 
segments,  806 
Spinalis  capitis  muscle,  489 
cervicis  muscle,  489 
colli  muscle,  489 
dorsi  muscle,  489 
Spindle,  achromatic,  36 
aortic,  624 
neuromuscular,  1071 
neurotendinous,  1070 
Spine  or  Spines,  ethmoidal,  246, 
290 
of  frontal  bone,  235 
iliac,  336 
ischial,  336 
mental,  271 
nasal,  anterior,  257,  262,  286 

posterior,  266,  278 
pubic,  338 
of  scapula,  306 
sphenoidal,  248,  280 
suprameatal,  244,  283 
of  tibia,  355 
trochlear.  235 
Spinoglenoid  ligament,  413 
Spinoolivary  fasciculus,  830 
Spinotectal  fasciculus,  817 
Spinothalamic  fasciculus,  817 
Spinous  process  of.a  vertebra,  197 
Spiral  canal  of  modiolus,  1060 
ligament,  1064 
line  of  femur,  348 
organ  of  Corti,  1065 
thread  of  spermatozo5n,  81 
tube  of  kidney,  1212 


Spirem  or  skein,  35 
Splanchnic   fibres   of   spinal 
nerves,  950 

layer  of  mesoderm,  88 

nerves,  998,  999 
Splanchnology,  979 
Splanchnoplcure,  88 
Spleen  or  lien,  1266 

accessory,  1267 

applied  anatomy  of,  1270 

bloodvessels  of,  1267 

development  of,  176 

lymphatic  nodules  of,  1268 
vessels  of,  793 

Malpighian  bodies  of,  1268 

relations  of,  1266 

size  and  weight  of,  1267 

structure  of,  1267 

supernumerary,  1267 

surf  ace  marking  of ,  1307 
Splenial  centre  of  ossification,  274 
Splenic  artery,  691 

distribution  of,  1267 

cells,  1267 

glands,  788 

flexure  of  colon,  1180 

plexus,  1004 

pulp,  1267 

vein,  765 
Splenium  of  corpus  callosum,  876 
Splenius  capitis  muscle,  486 

cervicis  muscle,  487 

colli  muscle,  487 
Spongioblasts,  118 
Spongioplasm,  34 
Spring  ligament;  456 
Spur  of  malleus,  1053 

scleral,  1019 
Squama,  frontal,  233 

frontalis,  234 

occipital,  227 

occipitalis,  227 

temporal,  237 

temporalis,  237 
Squamosal  suture,  282 
Squamous  epithelium,  37 
Stahr,  middle  gland  of,  778 
Stalks,  optic,  126,  134 
^  of  thalamus,  857,  858 
Stapedius  muscle,  1055 
Stapes,  1054 

annular  liganaent  of,'  1055 

cms  anterius,  1054 
posterius,   1054 

development  of,  141 
Stellate  ligament,  396 

veins  of  kidney,  1214 
Stensen,  duct  of,  1135 

foramina  of,  261,  278 
Stephanion,  282,  296 
Sternal  angle,  218 

end  of  clavicle,  303 

foramen,  220 

furrow,  1295 

glands,  796 

plate,  105 
Sternebrse,  216 

Sternoclavicular  articulation,  409 

applied  anatomy  of,  411 

movements  of,  411 

surface  anatomy  of,  1315 

Sternocleidomastoid  artery,  631, 

636 
Sternocleidomastoideus  muscle, 

478 
Sternocostal  ligaments,  399 

surface  of  heart,  605 
Sternohyoid  muscle,  482 
Sternohyoideus  muscle,  482 
Sternomastoid  artery,  631,  636 

muscle,  478 
Sternopericardiac  ligaments,  602 
Sternothyreoideus  muscle,  482 
Sternothyroid  muscle,  482 
Sternum,  216 


Sternum,  applied  anatomy  of,  225 

articulations  of,  220 

development  of,  105 

ossification  of,  220 

structure  of,  220 
Stomach,   1101 

applied  anatomy  of,  1167 

bed,  1163 

body  of,  1163 

cardiac  glands  of,  1166 
orifice  of,  1161 

component  parts  of,  1163 

curvatures  of,  1162 

development  of,  168 

fundus  of,  1163 
glands  of,  1166 

incisura  angularis,  1162 

interior  of,  1163 

lymphatic  vessels  of,  792 

mucous  membrane  of,  1165 

muscular  coat  of,  1164 

nerves  of,  1167 

openings  of,  1161 

position  of,  1163 

pyloric  antrum,  1162,  1163 
glands,   1166 
orifice,  1162 
valve,  1164 

serous  coat  of,  1164 

shape  and  position  of,  1161 

structure  of,  1164 

subdivisions     of,     anatomical, 
1163 
clinical,  1163 

sulcus  intermedins,  1162 

surface  marking  of,  1295 

surfaces  of,  1161 

teeth,   1118 

vessels  of,  1167 
Stomodeum,  163 
Straight  gyrus,  870 

sinus,  741 

tubes  of  kidney,  1212 
Strands  of   posterior  nerve  root, 

819 
Stratified  epithelium,  39 
Stratiform  fibrocartilage,  50 
Stratum  cinereum,  854 

compactum  [decidua],  98 

corneum,  1072 

dorsale,  860 

germinativum,   1073 

granulosum,  1073 

intermedium  [choroid],  1022 

lemnisci,  854 

lucidum,  1073 

mucosuni,  1072,  1073 

opticum  [retina],  1027 
[superior  coUiculus],  854 

spongiosum  [decidua],  98 

zonale,  854,  855 
Streak,  primitive,  86 
Stria  terminalis,  855,  885 

vascularis,  1064 
Striae  acusticae,  935 

gravidarum,  1301 

longitudinal, lateral  and  medial, 
875 

medullar  es     [rhomboid    fossa], 
848, 935 
Striate  arteries,  653 

veins,  inferior,  740 
Stripe  of  Hensen,  1067 
Striped  muscle,  64 
Stroma,  intertubular,  of  kidney, 
1214 

of  iris,  1025 

of  ovary,  1245 
Styloglossus  muscle,  1130 
Stylohyal  part  of  styloid  process, 

244 
Stylohyoid  ligament,  481 

muscle,  481 

nerve,  from  facial,  933 
Stylohyoideus  muscle,  481 


INDEX 


1399 


Styloid  process  of  fibula,  359 
of  radius,  321 
of  temporal  bone,  244,  280 
of  ulna,  319 
Stylomandibular  ligament,  477 
Stylomastoid  artery,  636 

foramen,  243,  2S0 
Stylopharyngeus  muscle,  1142 
Subanconcus  muscle,  530 
Subarachnoid  cavity,  904 
cisteriiiP,  904 
septum,  905 
space,  904 
Subarcuate  fossa,  242 
Subcallosal  gyrus,  875 
Subcardinal  veins,  157 
Subclavian  arteries,  655 

applied  anatomy  of,  657 
branches  of,  659 
first  part  of  left,  655 

of  right,  655 
peculiarities  of,  657 
second  portion  of,  656 
surface  anatomy  of,  127S 

marldng  of,  1291 
third  portion  of,  656 
triangle,  483,  645 
vein,  750 
Subclavius  muscle,  528 

nerve  to,  960 
Subcostal  arteries,  686 

zone,  1147 
Subcostales  muscles,  492 
Subcrureus    or    articularis    genu 

muscle,  566 
Subcutaneous  inguinal  ring,  500 
Subdural  cavity,  903 
Subepithelial    plexus    of    cornea, 

1021 
Subfrontal  gyre,  870 
Subinguinal  lymph  glands,  783 
Sublingual  arterv,  632 
gland,  1137 

vessels  and  nerves  of,  1137 
Sublobular  veins,  1197 
Submaxillarv  arterv,  634 
duct,  1136 
ganglion,  925 
gland.  1135 

vessels  and  nerves  of,  1137 
lymph  glands,  778 
triangle.  481.  644 
Submental  artery,  634 
lymph  glands,  778 
triangle.  481 
Subnasal  point,  296 
Suboccipital  muscles,  490 
nerve,  951 
triangle,  491,  660 
Subparietal  sulcus,  871 
Subperitoneal   connective   tissue, 

509 
Subpleural    mediastinal     plexus, 

664 
Subpubic  ligament,  407 
Subsartorial  plexus,  981 
Subscapular  angle,  305 
artery.  671 
fascia,  531 
fossa.  304 
nerves,  961 
Subscapularis  muscle,  531 
Subserous  areolar  tissue,  1149 
Substance,    perforated,    anterior, 
874 
posterior,  848 
Substantia  adamantina,  1120 
alba,  814 
eburnea,  1119 
fe'rruginea,  848 
gelatinosa  centralis,  810 
of  Rolando,  809 
nerve  cells  in,  813 
grisea  centralis,  809 
innominata  of  Meynert,  884 


Substantia  nigra,  850 
ossea,   1121 
perforata  anterior,  875 
propria  [cornea],  1019 
Subthalamic    tegmental    region, 
-.  860 
Successional     permanent     teeth, 

1124 
Suctorial  pad,  471 
Sudoriferous  glands,  1078 
Sulci    and    fissures    of    cerebral 
hemisphere,  867 

development  of,  131 
of  medulla,  oblongata,  822 

spinalis,  808 
Sulcus,  anterior  longitudinal,  of 

heart,  604 
antihelicis  transversus,  1044 
arteria  vertebralis,  199 
basilaris,  833 
calcaneal,  365 
central,  868 
centralis  [Rolandi],  868 
cingulate,  869 
cinguli,  809 
circular,  869,  873 
circularis  corneae,  1019 
coronarv,  of  heart,  604 
frontal,  "869 

horizontal,  of  cerebellum,  837 
intermedius  [stomach],  1162 
intraparietal,  870 
lateral  cerebral,  849 

of  cerebral  peduncle,  849 
limitans  [rhomboid  fossa],   847, 

848 
lunatus,  871  note 
malleolar,  360 
medial  frontal,   of  Eberstaller, 

870 
median,  of  rhomboid  fossa,  847 

of  tongue,  1126 
medianus  posterior,  808 
of  Monro,  125,  865 
occipital,  871 
oculomotor,  849 
olfactory,  870 
orbital,  870 
paramedial,  870 
postcentral,  870 
posterior    longitudinal,     of 

heart,  604 
preauricular,  of  ilium,  335,  336 
precentral,  869 
radial,  311 
retroglandular,   1239 
sagittalis,  228,  232,  235 
sigmoid,  240 
spiralis  externus,  1064 

internus,  1065 
subparietal,  871 
taU,  367 
temporal,  inferior,  872 

middle,  872 

superior,  872 
terminal,  of  right  atrium,  606 

of  tongue,  1126 
tubae  auditivae,  249,  280 
tympanic,  243,  1050 
valleculae,  838 
Superadded      permanent      teeth. 

1124 
Supercilia,  1038 

Superciliary  arches,  278,  234,  282 
Superficial  cervical  artery,  664 

lymph  glands  778 

muscle,  475 

dissection  of,  475 

nerve,  957 
epigastric  artery,  715 
external  pudendal  artery,  716 

pudic  artery,  716 
iliac  circumflex  artery,  716 
long  plantar  ligament,  454 
palmar  arch,  682 


Superficial  perineal  artery,  705 

peroneal  nerve,  990, 991 

Sylvian  vein,  739 

temporal  artery,  637 

applied  anatomy  of,  638 
vein,  733 

transverse   ligament   of   hand, 
551 
perineal  muscle,  518,  520 

volar  artery,  678 
Superficialis  volae  artery,  678 
Superfrontal  gyre,  869 
Superior  articular  arteries,  720 

calcaneocuboid  ligament,  454 

cerebellar  peduncles,  841 

constrictor  muscle,  1142 

dental  nerve,  918 

intercostal  artery,  666 

lingualis  muscle,  1130 

longitudinal  sinus,  740 

maxillary  nerve,  917 

medullary  velum,  842 

nasal  concha,  254 

nuchal  line,  227 

oblique  muscle,  1035 

orbital  fissure,  249,  288 

petrosal  sinus,  746 

profunda  artery,  674 

sagittal  sinus,  740 

semicircular  canal,  1059 

tarsal  plate,  1039 

thoracic  artery,  670 

tibiofibular  articulation,  448 

tympanic  artery,  640 

vesical  artery,  701 

vocal  cords,  1085 
Supernumerary  spleen,  1267 
Supinator  )>revis  muscle,  544 

longus  muscle,  542 

muscle,  544 
Supra-acromial  nerves,  957 
Supporting  cells  of  Hensen,  1067 
of  Sertoli,  1233 

frame-work  of  retina,  1029 
Supracallosal  gyrus,  875 
Supraclavicular    branches    of 
brachial  plexus,  960 

nerves,  957 
Supracondvlar  process,  312  note 

ridges,  311,  312 
Supraglenoid  tuberosity,  307 
Suprahyoid  Aponeurosis,  481 

artery,  632 

lymph  glands,  778 

muscles,  480 

dissection  of,  480 

triangle,  481,  644 
Supramarginal  gyrus,  871 
Supramastoid  crest,  237 
Suprameatal  spine,  244,  283 

triangle,  238,  283 
Supraorbital  arterv.  649 

foramen,  235,  286,  288 

margin,  234 

nerve,  916 

notch, 235, 286, 288 

vein,  732 
Suprarenal  arteries,  inferior,  697 
middle,  696 
superior,  698 

glands,   1270 

applied  anatomy  of,  1272 
development  of,  134 
lymphatic  vessels  of,  793 
nerves  of,  1272 
structure  of,  1271 
vessels  of,  1272 

impression,  1194 

plexus,    1004 

veins,  764 
Suprascapular  arterj-,  663 

ligament,  413 

nerve,  960 
Supraspinal  ligament,  387 
Supraspinatous  fascia',  532 


1400 


INDEX 


Supraspinatous  fossa,  305 
Supraspinatus  muscle,  532 
Supraspinous  ligament,  3S7 
Suprasternal  nerves,  957 

space,  477 
Supratonsillar  fossa,  1139 
Supratrochlear  foramen,  313 

nerve,  916 
Sural  arteries,  720 

cutaneous  nerve,  medial,  988 
nerve,  988 
Surface    anatomy     and     surface 
markings    of    abdomen, 
1303 

regions  of,  1303 

surface  lines  of,  1303 
accessory  nerve,  1291 
acoustic     meatus,     external, 

1228 
acromioclavicular  joint, 1315, 

1319 
adductor  canal,  1331 
ankle-joint,  1326,  1330 
anterior  tibial  artery,    1329, 

1332 
aorta,  abdominal  1301,  1309 

ascending,  1300 
aortic  arch,  1300 
auscultation,    triangle   of, 

1296 
axillary  artery,  1318,  1320 

nerve,  1323 
back,  1291 
bones  of  craniuni,  1279 

of  lower  extremity,  1324 

of  thorax,  1296 

of  upper  extremitv,  1312 
brachial  arterv,  1318,  1321 

plexus,  1291,  1318 
brain,   1280 

Bryant's  triangle,  1330 
calcaneus,  1325 
carpal  bones,  1315 
caruncular  lacrimalis,  1287 
cecum,   1307 
cerebellum,  1280 
cerebral  hemisphere,  1280 
cervical     cutaneous     nerve, 

1291 
clavicle,  1313 
coeliac  artery,  1309 
colon,  ascending*  1307 

descending,  1307 

iliac,  1307 

transverse,  1307 
common  carotid  artery,  1290 

iliac  arterv,  1309 

peroneal  nerve,  1329,  1334 
deep  peroneal  nerve,  1334 
deltoideus  muscle,  1316 
diaphragma,  1297 
dorsalis   pedis   artery,    1329, 

1332 
duodenum,  1306 
ear,  1288 
elbow-joint,  1319 
epigastric     arterv,     inferior, 

1309 
external  carotid  artery,  1290 
main   branches   of, 
1290 

iliac  arterj'^;  1309 
eye,  1287 
facial  nerve,  1291 
femoral  artery,  1328,  1331 

triangle  1331 
femur,  1324 
fibula,  1324 
fissures  of  brain,  1281 
fold  of  groin,  1301 
frontal  sinus,  1282 
gall-bladder,  1307 
gluteal,  arteries,  1331 

fold,  1323 
great  auricular  nerve,  1291 


Surface     anatomy    and     surface 

markings  of  head  and  neck, 

1275 
heart,  1299 

coronary  sulcus,  1299 

longitudinal     sulcus,     an- 
terior, 1299 

orifices  of,  1299 
Hesselbach's  triangle,  1309 
hip  bones,  1324 
hip-joint,  1325,  1330 
humeral    circumflex    artery, 

1321 
humerus,   1313 
hyoid  bone,  1289 
ileocolic  junction,  1307 
iliac  artery,  common,  1309 
external,  1309 

furrow,  1301 
infrasternal  notch,  1295 
inguinal     rings     and      canal 

1303 
innominate  artery,  1300 

veins,    1300 
internal  pudendal   arterv, 

1331 
intestines,  1306,  1307 
joints  of  fingers,  1315 

of  foot,  1330 
jugulai  notch,  1295,  1297 

veins,   1291 
kidnevs,  1308 
knee-joint,  1300,  1325 
lacrimal  puncta,  1287 

sac,  1187 
larjmx,  1287,  1289 
lateral  plantar  artery,  1332 

thoracic  artery,  1320 

ventricle  of  brain,  1282 
latissimus  dorsi,  1316,  1319 
left  common  carotid  artery, 

in  thorax,  1300 
lesser  occipital  nerve,  1291 
linea  semilunaris,  1301 
liver,  1302,  1307 
lower  extremity,  1323 
lumbar  triangle,  1301 
lungs,  1298 
mamma,  1296 
mammary    artery,    internal, 

1300 
maxillary    arterv,    external, 
1282 

sinus,  1282 
medial  plantar  artery,  1332 
median  nerve,  1323 
medulla  spinalis,  1294 
mesenteric  arteries,  1309 
metacarpal  bones,  1315 
middle     meningeal      arterv, 

1282 
mouth,  1284 
mucous    sheaths    around 
ankle,  1331 
of  wrist  and  hand,  1319 
muscles  of  abdomen,  1303 

of  arm,  1316 

of  buttock,  1326 

of  foot,  1327,  1328 

of  forearm,  1317 

of  head  and   neck,    1276, 
1277,  1289 

of  hand,  1318 

of  leg,  1328 

of  thigh,  1326 
nasal  part  of  pharynx,  1287 
nasolacrimal  duct,  1287 
neck,  1291 
Nelaton's  line,  1329 
nose,  1284 
oesophagus,   1299 
palatine  arches,  1285 
palmar  or  volar  arches,  1322 
palpebral  fissure,  1287 
pancreas,  1303,  1307 


Surface  anatomy  and  surface 
markings  of  parotid  duct, 
1283 

gland,  1283 
patella,  1324 

pectoralis      major      muscle, 
1316,  1319 

minor  nmsclc,  1310,  1319 
pelvis,  1324 
perineum,  1309 
peroneal  artery,  1332 

nerves,   1334 
phalanges  of  foot,  1325 

of  hand,  1315 
phrenic  nerve,  1291 
plantar  arch,  1332 

arteries,  1332 
pleura;,  1297 
plica  semilunaris,  1287 
popliteal  artery,  1328 

fossa,  1331 
posterior  tibial  artery,  1329, 

1332 
profunda  brachii  artery,  1321 

femoris  artery,  1331 
pupil,  1287 
radial  artery,  1318,  1322 

nerve,  1323 
radioulnar  joints,  1315 
radius,  1314 

rectum  and  anal  canal,  1310 
Reid's  base  line,  1279 
renal  arteries,  1309 
sacroiliac  joint,  1330 
saphenous  veins,  1334 
scapula,  1313 
scapular   "circumflex    artery, 

1321 
sciatic  nerve,  1334 
serratusanteriormuscle,1316 
shoulder-joint,  1315 
spinal  nerves,  1295 
spleen,  1307 

sternal  angle,  1295,  1297 
sternoclavicular  joint,  1315 
sternocleidomastoideus 

muscle,  1277 
stomach,  1305 
striae    gravidarum    or    albi- 

cantes,  1301 
subclavian  artery,  1291,  1318 
subdural    and    subarachnoid 

cavities,  1294 
submaxillary  gland,  1291 
subscapular  artery,  1320 
supraclavicular  nerves,  1291 
talus,  1325 
tarsus  and  foot,  1325 
temporomandibular       joint, 

1276 
tendinous  inscriptions  of  rec- 
tus abdominis,  1301 
thoracoacromial  arterv,  1320 
thorax,  1295 

surface  lines  of,  1296 
tibia,  1324 
tibial  nerve,  1334 
tongue,  1285 
tonsil,  1286 
trachea,  1289,  1299 
transverse  sinus,  1282 
trapezius,  1319 
trigeminal  nerve,  1283 
tympanic  antrum,  1289 

membrane,  1288 
,  ulna,  1314 
ulnar  artery,  1322 
•  collateral  arteries,  1322 

nerve,  1319,  1323 
umbilicus,  1301,  1303 
upper  extremity,  1312 
urogenital     organs,     female, 
1311 
male,  1310 
vena  cava,  inferior,  1300 


INDEX 


1401 


Surface     auatonij-    and     surface 
nuirkiiigs    of    vena    cava, 
superior,  1300 
verniifonn  process,  1307 
vertel)ral  column,  1291 
volar  or  palmar  arches,  1322 
wrist  and  hand,  1314 
wrist-joint,  1314,  1319 
Suspensory  li{i;ament  of  axilla,  520 
of  eve,  1038 
of  lens,  1030 
of  ovary,  1244 
of  penis,  1239 
Sustcntacular    fibres    of    Midler, 

1029 
Sustentaculum  lienis,  1157 

tali,  365 
Sutura  dentala,  381 
harmonia,  381 
limbosa,  381 
notha,  381 
se^rata,  381 
squamosa,  381 
vera,  38 1 
Sutural  bones,  255 

applied  anatomy  of,  255 
Suture,  coronal,  277,  282 
frontal,  278 
frontoetlimoidal,  288 
frontomaxillary,  287 
frontozygomatic,  282 
interparietal,  233 
lambdoidal,  230,  232,  277,  282 
metopjc,  234 
occipitomastoid,  282 
parietomastoid,  282 
petrooccipital,  291 
petrosquamous,  241,  243 
sagittal,  277 
sphenoethmoidal,  288 
sphenofrontal,  282,  288 
sphenoparietal,  282 
sphenopetrosal,  290 
sphenosquamosal,  282 
sphenozygomatic,  282 
squamosal,  282 
zygomaticofrontal,  282 
zygomaticomaxillary,  288 
zygomaticotemporal,  282 
Sweat  glands,  1078 
Swellings,  genital,  190 
Sylvian  fossa,  131 
veins,  739,  740 
Sylvius,  aqueduct  of,  821,  854 

fissure  of,  867 
Sympathetic     fibres     of     spinal 
nerves,  949 
nerves,  994 

connections        with      spinal 
nerves,  995 
plexuses,  1001 

cardiac,  1001 
cceliac,  1002 
hypogastric,  1005 
pelvic,  1005 
solar,  1002 
system,  abdominal  portion  of, 
1001 
applied  anatomy  of,  1005 
cephalic  portion  of,  995 
cervical  portion  of,  996 
development  of,  133 
pelvic  portion  of,  1001 
thoracic  portion  of,  998 
trunks,  995 
Symphysis  of  mandible,  271 
ossiurn  pubis,  406 
pubis,  406 
sacrococcygea,  406 
Synarthroses,  380 
Synchondrosis,  381 
neurocentral,  210 
Syncytiotrophoblast,  85 
Sj-ncytium,  85 
Syndesmology,  379 


Syndesmosis,  381 

tibiufibularis,  448 
Synergic  nniscles,  462 
Synovia,  380 
Synovial    membrane,    380.       See 

also  Individual  Joints. 
Systemic  circulation,  595 

veins,  729 
Systcmis,  Haversian,  53 


Tables  of  the  skull,  196 
Tactile  corpuscles  of  Golgi   and 
Mazzoni,  1069 
of  Grandry,  1069 
of  Pacini,  1069 
of  Ruffini,  1070 
of    Wagner    and    Meissner, 
1070 
Taenia  pontis,  833 

semicircularis,  885 

thalami,  856 

ventriculi  quarti,  846 
Taeniae  coli,  1184 

of  fourth  ventricle,  846 

of  muscular  coat  of  large  intes- 
tine, 1177 
Talocalcaneal  articulation,  452 
Talocalcaneonavicular      articula- 
tion, 454 
Talotibial  ligaments,  450 
Talus,  366 

ossification  of,  374 
Tangential     fibres     of     cerebral 

cortex,  892 
Tapetum  of  choroid,  1022 

of  corpus  callosum,  877 
Tarsal  arteries,  724 

bones,  362 

glands,  1040 

plates,  1039 
Tarsi  of  eyelids,  1039 
Tarsometatarsal       articulations, 

457 
Tarsus,  362 

applied  anatomy  of,  375 

articulations  of,  452 

inferior,  1039 

ossification  of,  374 

superior,  1039 

surface  markings  of,  1330 

synovial  membranes  of,  458 
Taste,  nerves  of,  1008 

organ  of,  1007 
Taste-buds,  1007 
Tectorial    membrane    of    ductus 

cochlearis,  1067 
Teeth,  11 15 

applied  anatomy  of,  1125 

bicuspid,  1118 

canine,  117,  1118 

cement   or   crusta  petrosa   of, 
1121 

crown  of,  1117 

cutting,  1117 

deciduous,  1118 

dental  canaliculi  of,  1120 

dentin  of,  1119 

development  of,  1121 

enamel  of,  1120 

eruption  of,  1124 

eye,  1118 

general  characters  of,  1113 

incisive,  1117 

incisors,  1117 

ivory  of,  1119 

milk,  1118 

molar,  1118 

multicuspid,  1118 

necks  of,  1116 

permanent,  1117 
successional,  1124 
superadded,  1124 


Teeth,  premolar,  1118 
pulp  cavity  of,  1119  ' 
roots  of,  1116 
stomach,  1118 
structure  of,  1119 
substantia  adainantina  of,  1120 
eburnea  of,  1119 
ossea  of,  1121 
temporary,  1118 
wisdom,  1118 
Tegmen  tympani,  240,  1049 
Tegmental  part  of  pons,  835 
Tegmentum,  850 
Tela  chorioidea  [fourth  ventricle], 
846 
[third  ventricle],  888 
Telencephalon,  126,  127,  865 
Telopihase  of  karyokinesis,  36 
Temporal  artery,  deep,  641 
middle,  638 
superficial,  637 
bone,  237 

articulations  of,  245 
mastoid  portion  of,  239 
ossification  of,  244 
petrous  portion  of,  241 
pyramid  of,  241 
squama  of,  237 
structure  of,  244 
tympanic  part  of,  243 
fascia,  473 
fossa,  282 
gyri,  872 

lines,  231,  235,  278,  282 
lobe,  871 
muscle,  473 

dissection  of,  473 
nerves  of  auriculotemporal,  923 
deep,  922 
of  facial,  933 
operculum,  873 

process  of  zygomatic  bone,  265 
veins,  733 
Temporalis  muscle,  473 
Temporary  teeth,  1118 
Temporomalar  nerve,  917 
Temporomandibular  articulation, 
393 
applied  anatomy  of,  396 
surface  anatomy  of,  1276 
Temporomaxillary  vein,  734 
Tendinous  arch  of  pelvic  fascia, 
512 
inscriptions  of  rectus  abdomi- 
nis muscle,  506 
Tendo  Achillis,  579 
calcaneus,  579 
oculi,  468 

ligament,  468 
Tendon,  central,  of  diaphragma, 
495 
conjoined,   of  internal  oblique 
and  transversalis  muscles, 504 
of  conus  arteriosus,  608 
structure  of,  44 
superior,  of  Lockwood,  1035 
of  Zinn,  1035 
Tendons,  463 

on  back  of  wrist,  relations  of, 
550 
Tendril  fibres  of  cerebellum,  844 
Tenon,  capsule  of,  1037 
Tensor    fasciae    femoris    muscle, 
565 
latae  muscle,  565 
palati  muscle,  1113 
tarsi  muscle,  468 
tympani  muscle,  1055 

semicanal  for,  243,  1052 
veil  palatini  muscle,  1113 
Tenth  nerve,  940 
Tentorial  sinus,  741 
Tentorium,  cerebelli,  901 
Teres  major  muscle,  533 
minor  muscle,  533 


1402 


INDEX 


Terminal   crost  of  right  iitrium, 
606,  607 
sulcus  of  right  atrium,  (506, 
vein,  740 

ventricle,  119,  810 
Terminations    of    motor    nerves, 
803 
of  nerves  of  general  sensations, 
1069 
Testes,  1228,  1230 
appendages  of,  1231 
applied  anatomy  of,  1234 
coni  vasculosi  of,  1233 
coverings  of,  1228 
descent  of,  186 
development  of,  186 
ducluli  efferentes,  1233 
ductus  deferens,  1235 
gubernaculum  testis,  186 
lobules  of,  1232 
Ij-mphatic  vessels  of,  794 
mediastinum  testis,  1232 
rete  testis,  1233 
structure  of,  1232 
tubuli  recti,  1233 

se?niniferi,  1232 
tunica  albuginea,  1232 
vaginalis,  1231 
vasculosa,  1232 
Thalamencephalon,  855 
Thalami,  126,  855 
connections  of,  857 
development  of,  126 
intermediate  mass  of,  126,  856 
stalks  of,  857,  858 
structure  of,  856 
surfaces  of,  855,  856 
Thalamomamillary  fasciculus,  886 
Thebesius.  foramina  of,  608 
valve  of,  608,  730 
veins  of,  731 
Thenar  eminence,  546 
Thigh  bone,  345 
fascia  lata  of,  563 
superficial,  562 
muscles  of,  562 
dissection  of,  562 
Third  cuneiform  bone,  370 
metacarpal  bone,  330 
metatarsal  bone,  372 
nerve,  911 
trochanter,  348 
ventricle  of  brain,  864 
choroid  plexuses  of,  864 
Thoracic  aorta,  683 

applied  anatomy  of,  683 
peculiarities  of,  683 
arteries,  670,  671 
axis,  670 

cardiac  nerves,  943 
duct,  771 

applied  anatomy  of,  773 
nerves,  anterior,  961 

applied  anatomy  of,  974 
divisions  of,  anterior,  972 
posterior,  952 
portion  of  gangliated  cord,  998 
vertebrae,  201 
Thoracoacromial  artery,  670 
Thoracodorsal  nerve,  961 
Thoracoepigastric  vein,  756 
Thorax,  216' 

boundaries  of,  216 
cavity  of,  600 
lower  opening  of,  216,  601 
lymph  glands  of,  796 
lymphatic  vessels  of,  797,  798 
mechanism  of,  401 
muscles  of,  492 

parts    passing    through    lower 
opening  of,  601 
upper  opening  of,  601 
skeleton  of,  216 
surface  anatomy  of,  1295 
markings  of,  1296 


Thorax,    upper    opening  of,    210, 

601 
Thromboplastin,  64 
Thunil),  carpometacarpal  articu- 
lation of,  429 
Thymus,  1264 

applied  anatomy  of,  1266 
development  of,  165 
glands,  1264 
lymphatic  vessels  of,  800 
nerves  of,  1265 
structure  of,  1264 
vessels  of,  1265 
Thyreoarytaenoideus      muscle, 

1089 
Thyreohyoideus  muscle,  482 

nerve  to,  947 
Thyreoidea  ima  artery,  626 
Thyroarytenoid   ligaments,   infe- 
rior, 1086 
muscle,  1089 
Thyrocervical  trunk,  662 
Thyroepiglottic  ligament,  1084 

muscle,  1090 
Thyroglossal  duct,  165,  1127 
Thyrohyals  of  hyoid  bone,  275 
Thyrohyoid     ligament,      lateral, 
1083 
middle,  1082 
membrane,  1082 
muscle,  482 
Thyroid  artery,  inferior,  662 
superior,  631 

applied  anatomy  of,  631 
axis,  662 
body, 1261 
cartilage,  1080 
foramen,  339 
gland,  1261 

applied  anatomy  of,  1263 
development  of,  165 
isthmus  of.  1261 
lobes  of,  1261 
lymphatic  vessels  of,  779 
nerves  of,  1262 
pyramidal  lobe  of,  1262 
structure  of,  1262 
vessels  of,  1262 
notch,  superior,  1080 
veins,  inferior,  751 
middle,  737 
superior,  737 
Thyroids,  accessory,  1262 
Tibia,  355 

applied  anatomy  of,  361 
articulations  of,  359 
condyles  of,  355 
ossification  of,  359 
spine  of,  355 

surface  anatomy  of,  1324 
tuberoaitj'  of,  356 
Tibial  artery,  anterior,  722 

applied  anatomy  of,  722 
branches  of,  722 
peculiarities  of,  722 
surface  marking  of,  1332 
posterior,  725 

applied  anatomy  of,  725 
branches  of,  72'') 
peculiarities  of,  725 
surface  marking  of,  1332 
recurrent,  anterior,  723 
posterior,  722 
collateral    liganient    of    knee- 
joint,  439 
nerve,  987 

anterior.  990 
surfaces  of  femur,  350 
veins,  758 
Tibialis  anterior  muscle,  576 
anticus  muscle,  576 
posterior  muscle,  582 
Tibiofibular  articulation,  448 
ligament,  middle,  448 
syndesmosis,  448 


Tibionavicular  ligament,  4.">0 
Tibiotarsal  articulation,  449 
Tissue,  adenoid,  45 

adipose,  42 

areolar,  40 

connective,  40 

Ij'mphoid,  45 

mucous,  44 

muscular,  64 

nervous,  09 

retiform  or  reticular,  44 

white  fibrous,  43 

yellow  elastic,  44 
Tomes'  fibres,  1120 
Tongue,  1125 

applied  anatomy  of,  11^52 

development  of,  164 

frenulum  of,  1126 

glands  of,  1131 

lymph  gland  of,  778 

lymphatic  vessels  of,  778 

mucous  membrane  of,  1131 

muscles  of,  1128 

nerves  of,  1132 

papilla  of,  1127 

septum  of,  1132 

structure  of,  1131 

vessels  of,  1132 
Tonsil,  1139 

lingual,  1131 

pharyngeal,  1139 
Tonsilla  cerebelli,  839 
Tonsillae  intestinales,  1175 

jjalatinae,  1139 
Tonsillar  artery,  634 

nerves  from  glossopharvngeal, 
940 

sinus,  1140 
Tonsils,  palatine,  1139 

applied  anatomy  of,  1141 
development  of,  165 
lymphatic  vessels  of,  777 
nerves  of,  1141 
structure  of,  1141 
vessels  of,  1141 
Torcular  Herophili,  229,  743 
Torus  of  auditory  tube,  1139 

ureiericus,  1222 

uterinus,  1154 
Trabeculae  carneae  [left  ventricle], 
612 
[right  ventricle],  610 

cranii,  106 

of  penis,  1239 

of  spleen,  1267 

of  testis,  1232 
Trachea,  1091 

applied  anatomy  of,  1093 

nerves  of,  1093 

relations  of,  1092 

structure  of,  1092 

vessels  of,  1093 
Trachealis  muscle,  1093 
Trachelomastoideus  muscle,  489 
Tracheobronchial  glands,  798 
Tracheotomy,  1094 
Trachoma  glands,  1041 
Tract    or    Tracts,   anterior    basis 
bundle,  815 

of  Burdach,  808,  817 

cerebellar,  of  Flechsig,  816 

cerebellospinal,  815 

comma,  817 

dorsal  peripheral  band,  818 

of  Goll,  808.  817 

of  Gowers,  816 

lateral  basis  bundle,  817 

of  Lowenthal,  815 

motor,  896 

olfactory,  874 

optic,  863,  909 

prepyramidal,  816 

pyramidal,  crossed,  815 
direct,  815 

sensory,  897 


INDEX 


1403 


Traction  epiphyses,  59 
Tracius  iliotibialiii,  563 
olfactorius,  87-1 
peduncular  is    transversus,     850 

note 
solitarius,  128 

spiralis  forum i nosus,  242,  1060 
Tragic-US  muscle,  10-16 
Tragus,  1044 

Transitioual  epithelium,  40 
Trauspyloric  plane,  1147 
Transversa  colli  artery,  663 
Transversalis  ccrvicis  muscle,  488 
colli  arter.\',  663 
fascia,  508 
muscle,  504 
Transverse    acetabular    ligament 
of  hip-joint,  434 
aorta,  623 

carpal  ligament,  547 
cervical  arteries,  663,  664 

nerve,  957 
colon,  11  SO 
crural  ligament,  584 
facial  artery,  638 

vein,  734 
fibres  of  cerebral  hemispheres, 

890 
fissure  of  brain,  889 

of  liver,  1194 
folds  of  rectum,  1183 
ligament  of  atlas,  389 
of  fingers,  o51 
humeral,  415 
of  knee,  442 
metacarpal,  430 
metatarsal,  458 
of  pelvis,  520 
ligaments  of  scapula,  413 
lingualis  muscle,  1130 
mesocolon,  1157 
occipital  sulcus,  871 
process  of  a  vertebra,  197 
scapular  artery,  663 
sinus,  746 

of  pericardium,  603 
temporal  gyri,  872 
Transversus    abdominis    muscle, 
504 
auriculae  muscle,  1046 
linguae  muscle,  1130 
menti  muscle,  470 
nuchae  muscle,  466 
pedis  muscle,  589 
perinaei  muscle,  518 

profundus  muscle  in  female, 
521 
in  male,  520 
superficialis    muscle,    in    fe- 
male, 520 
in  male,  518 
thoracis  muscle,  492 
Trapezium,  326 
Trapezius  muscle,  522 
Trapezoid,  327 
body, 835 
ligament,  412 
nucleus,  835 
ridge,  302 
Treves,  bloodless  fold  of,  1160 
Triangle  of  auscultation,  524 
Bryant's,  1330 
carotid,  481,  483,  643 
digastric,  480,  644 
femoral,  565,  712 
of  Hesselbach,  1187,  1309 
lumbar,  524 
muscular,  483,  643 
of  neck,  642,  644 
occipital,  483,  645 
of  Petit,  524 
Scarpa's,  712 
subclavian,  483,  645 
submaxiLlary,  481,  644 
submental,  481 


Triangle,  suboccipital,  491,  660 
suprahyoid,  481,  644 
suprameatal,  238,  283 
Triangular  articular  disk,  424 
bone,  324 

fascia  of  abdomen,  502 
ligament,  519 
of  liver,  1151 
Triangularis  muscle,  470 

stcrni  muscle,  492 
Triceps  brachii  muscle,  535 
extensor  cubiti  muscle,  535 
muscle,  535 
surae  muscle,  579 
Tricuspid  valve,  609 
Trifacial  nerve,  914 
Trigeminal  impression,  241 
nerve,  914 

applied  anatomy  of,  925 
surface  marking  of,  1283 
Trigone,  olfactory,  875 
Trigonum  collaterale,  881 
femorale,  712 
habcnulae,  859 
hypoglossi,  848 
olfactorixcm,  875 
vagi,  829 
vesicae,  1222 
Trochanter,  greater,  347 
lesser,  348 
major,  347 
minor,  348 
third,  348 
Trochanteric  fossa,  347 
Troclilea  of  humerus,  312 
Trochlear  fovea,  235,  286 
nerve,  913 

applied  anatomy  of,  914 
process  of  calcaneus,  365 
spine,  235 
Trochoid  joint,  382 
Trolard,  anastomotic  vein  of,  739 
Troltsch,  recess  of,  1055 
Trophoblast,  84 
True  nucleoli,  34 
pelvis,  340 
skin,  1074 
vocal  cords,  1086 
Trvncus  arteriosus,  145,  150 
costocervicalis,  666 
synipathicus ,  995 
thyreocervicalis,  662 
Trunk,  arteries  of,  683 
articulations  of,  384 
costocervical,  666 
thyrocervical,  662 
Tuba  auditiva,  1052 

par  cartilaginea ,  1052 
ossea,  1052 
uterina  [Fallopii],  1247 
Tube,  auditory,  1052 
tonsil  of,  1053 
digestive,  1109 
Eustachian,  1052 
Fallopian,  1247 
neural,  88 
uterine,  1247 
Tiiber  cinereum,  825 
frontale,  234 
onientale  [liver],  1192 

[pancreas],  1204 
parietale,  231 
valvulae,  839 
vermis  [cerebellum],  839 
Tuberal  lobe,  839 
Tubercle,  adductor,  348 

articular,    of    temporal    bone, 

237,  280 
auricular,  of  Darwin,  1044 
carotid,  or  Chassaignac's,  199 
conoid,  301 
cuneate,  825 
cuneiform,  1085 
deltoid,  302 
of  epiglottis,  1082 


Tubercle  of  feumr,  348 

of  humerus,  309 

intervenous,  60S 

jugular,  230 

lacrimal,  260 

of  Lower,  608 

mental,  271 

obturator,  339 

peroneal,  365 

pharyngeal,  230,  280 

pterygoid,  250 

pubic,  338 

of  rib,  222 

of  Rolando,  825 

scalene,  224 
Tuberculum  acusticum,  848,  935 

anterius,  199 

caroticum,  199 

impar,  164 

intervenosum,  608 

majus  [humeri],  309 

minus  [humeri],  309 

posterius,  199 

sellae,2i6,  290 
Tuberosity,  calcaneal,  365 

coracoid,  301 

costal,  303 

of  cuboid,  368 

deltoid,  312 

of  fifth  metatarsal  bone,  372 

gluteal,  348 

iliac,  335 

infraglenoid,  307 

of  ischium,  337 

maxillary,  257 

of  navicular  bone,  369 

of  palatine  bone,  267 

radial,  320 

supraglenoid,  307 

of  tibia,  356 

of  ulna,  315 
Tubules,  renal,  1212 
Tuhuli  lactiferi,  1259 

recti  [testis],  1233 

seminiferi,  1232 
Tuft,  Malpighian,  1212 
Tunic,  dartos,  1228 

fibrous,  of  kidney,  1210 
Tunica  adventitia,  597 

albuginea  [ovary],  1245 
[testis],  1232 

conjunctiva  bulbi,  1041 

dartos,  1229 

elastica  externa,  597 

fibrosa  oculi,  1017 

intima,  596 

media,  596 

serosa,  1149 

vaginalis,  1231 

communis  [testis    et   funiculi 

spermatid],  1229 
development  of,  187 
propria  testis,  1231 

lamina  parietalis,  1232 
visceralis,  1231 

vasculosa  [testis],  1232 
oculi,  1021 
Tunics  of  eveball,  1017 
Tunnel  of  Corti,  1065 
Turbinated  bone,  268 

processes,  sphenoidal,  250 
Turner,    intraparietal    sulcus    of, 

870 
Twelfth  nerve,  945 
Tympanic  antrum,  240 
entrance  to,  1051 

artery,  639 

from   ascending  pharyngeal, 

637 
from      internal       maxillary, 
639 

canaliculus,  inferior,  243,  280 

cavity,  1049 

applied  anatomy  of,  1056 
arteries  of,  1056 


1404 


IXDEX 


Tympanic     cavity,    attic  or  epi- 
tympanio  recess  of,  1049 
carotid  or  anterior  wall  of, 

1052 
development  of,  141 
jugular  wall  or  floor  of,  1049 
lab\rintliine  or  medial  wall 

of,  1050 
mastoid  or  posterior  wall  of, 

1051 
membranous  or  lateral  wall 

of,  1049 
mucous  membrane  of,  1055 
muscles  of,  1055 
nerves  of,  1056 
ossicles  of,  1053 
tegmental    wall    or    roof    of, 

1049 
vessels  of,  1056 
lip,  1065 
membrane,  1050 
nerves  of,  1050 
pars  flaccida,  1050 
secondary,  1051 
structure  of,  1050 
vessels  of,  1050 
nerve  (Jacobson's),  939,  1056 
plexus,  939,  1056 
ring,  245 

sulcus,  243,  1047,  1050 
Tympanohyal     part     of     styloid 

process,  244 
Tympanomastoid     fissure,     243, 

280 
Tympanum,  1049 


Ulna,  314 

applied  anatomy  of,  321 
articulations  of,  321 
coronoid  process  of,  315 
olecranon  of,  315 
ossification  of,  319 
radial  notch  of,  318 
semilunar  notch  of,  315 
sigmoid  cavities  of,  318 
structure  of,  319 
styloid  process  of,  319 
surface  anatomy  of,  1314 
tuberosity  of,  315 
Ulnar  arterj-,  679 

applied  anatomy  of,  680 
branches  of,  680 
carpal,  682 
collateral,  674,  675 

branch  of  radial  nerve,  969 
peculiarities  of,  679 
recurrent,  680 
surface  marking  of,  1322 
notch  of  radius,  321 
Ultimobranchial  bodies,  166 
Umbilical    arteries   in   fetus,    99, 
616 
cord,  96 

folds,  1187,  1221,  1222 
fossa  of  liver,  1194 
notch  of  liver,  1194 
veins,  100,  145,  156 

obliterated,  765,  1150 
zone,  1147 
Umbilicus,  507 
Umbo    of    membrana    tympani, 

1050 
Unciform  bone,  328 
Uncinate  fasciculus,  890 

process   of  head   of  pancreas, 
1203 
Uncus,  874 

Ungual  phalanges,  331,  373 
Ungues,  1075 
Unstriped  muscle,  67 
Upper  extremity,  arteries  of,  655 
articulations  of,  409 


Upper  extremity,  bones  of,  301 
lymphatics  of,  779 
muscles  and  fasciae  of,  522 
surface  markings  of,  1319 
veins  of,  747 
jaw,  bones  of,  256 
lateral  cartilage,  1009 
motor  neurons,  896 
Urachus,  189 
Ureter,  1216 

abdominal  part  of,  1216 
arteries  of,  1217 
lymphatic  vessels  of,  793 
muscles  of,  1>223 
nerves  of,  1217 
orifices  of,  1222 
pars  abdominalis,  1216 

pehina,  1216 
pelvic  part  of,  1216 
structure  of,  1217 
tunica  adcenlitia,  1217 
mucosa,  1217 
Urethra,  development  of,  190 
female,  1228 
male,  1225 

applied  anatomy  of,  1226 
cavernous  portion  of,  1226 
crest    or  verumontanum   of, 

1225 
lymphatic  vessels  of,  794 
membranous  portion  of,  1226 
prostatic  portion  of,  1225 

sinus  of,  1225 
structure  of,  1226 
muliebris,  1228 
virilis,  1225 

pars  cavernosa,  1226 
I  7ne)nbranace.a ,  1226 

'    ^  prostatica,  1225 

Urethral  arterv,  705 
bulb,  1226 
crest,  in  female,  1228 

in  male,  1225 
glands,  1226 
orifice,  external,  1226,  1257 

internal,  1222 
plate,  190 
Urinary  bladder,  male,  1218 
female,  1221 
meatus,  1257 
organs,  1206 

development  of,  180 
lymphatic  vessels  of,  793 
Urogenital  apparatus,  1206 
diaphraem,  519 
fold,  181 
organs,  1206 
ostium,  primitive,  190 
Urorectal  septum.  172 
Uterine  artery-,  701 
glands,  1252 
plexus  of  nerves,  1005 
plexuses  of  veins,  761 
tube,  1247 

abdominal  ostium  of,  1247 
ampulla  of,  1247 
appendices  vesiculosae,  1247 
applied  anatomy,  1247 
development  of,  182 
fimbriae,  1247 
infundibulum  of,  1247 
isthmus  of,  1247 
Uterosacral  ligaments,  1250 
Uterus,  1248 
in  adult,  1252 
after  parturition,  1252 
applied  anatomy  of,  1254 
body  of,  1249 
cervix  of,  1249 
development  of,  182 
during  menstruation,  1252 

pregnancy,  1252 
in  fetus,  1251 

form,    size,    and   situation    of, 
1251 


Uterus,  fundus  of,  1249 

interior  of,  1250 

isthmus  of,  1249 

ligaments  of,  1250 

lymphatic  vessels  of,  795 

masculinus,  or  prostatic  utricle, 
1225,  1226 

nerves  of,  1253 

in  old  age,  1252 

at  puberty,  1251 

structure  of,  1252 

tunica  mucosa,  1252 
muscularis,  1252 

vessels  of,  1253 

•virgin  state  of,  1249 
Utricle,  prostatic,  1226 

of  vestibule,  1062 
Utriculus,  1062 
Uvea,   1025 
Uvula  of  cerebellum,  839 

palatine,  1112 

vermis,  839 

vesicae,  1222 
Uvular  lobe,  839 


I  Vagina,  1255 

columns  of,  1255 
fornices  of,  1255 
lymphatic  vessels  of,  795 
structure  of,  1255 
tunica  mucosa,  1255 
m,uscularis,  1255 
Vaginae  mucosae,  380 
Vaginal  arterv,  702 
bulb,  1257  ' 
orifice,  1257 
plexus  of  nerves,  1005 
plexuses  of  veins,  762 
process  of  temporal  bone,  243, 

244 
processes  of  sphenoid  bone,  250 
Vagus  nerve,  940 

applied  anatomy  of,  943 
ganglion  of  root  of,  941 

of  trunk  of,  941 
nuclei  of,  829,  940 
Vallecula  cerebelli,  837 
Valleculse  of  tongue,  10S2 
Vallum,  1128 

Valsalva,  sinuses  of,  610,  612 
Valve,  bicuspid,  612 
colic,  1179 

of  coronary  sinus,  608,  730 
Eustachian,  607,  608 
ileocolic,  1179 

of  inferior  vena  cava,  607,  762 
mitral,  612 
pyloric,  1164 
Thebesian,  608,  730 
tricuspid,  609 
of  Vieussens,  842 
Valves,  anal,  1184 

of  heart,  development  of,  151 

of  Houston,  1183 

of  Kerkring,  1173 

of  lymphatics,  768,  769 

right  and  left  venous,  146 

semilunar  aortic,  612 

pulmonary,  610 
of  veins,  599 
Vahulabicuspidalis  [metralis],  612 
coli,  1179 

sinus  coronarii  [Thebesii],  608 
tricuspidalis,  609 
venae  cavae  inferioris,  608 
Valvulae  conniventes,  1173 
Vas  aberrans  of  Haller,  1236 
deferens,  1235 
spirale,  1065 
Vasa    aberraniia    [from    brachial 
artery],  673 
afferentia  [lymph  glands],  770 


Iv 


asa  brcvia  arteries,  691 
effereniin  [lymph  <;lauds],  770 
intcstini  tenuis  arteries,  692 
vasoruin  (arteries],  597 

[veins],  600 
ascular  areas  of  >olk-sae,  HI 
capsule  of  lens,  136 
system,    ehanjies   in,    at    birth, 
618 

development  of,  141 

peculiarities  in  fetus,  615 
asomotor  nerve  fibres,  802 
astus  exteruus  muscle,  566 
intermedius  muscle,  566 
internus  muscle,  566 
lateralis  muscle,  566 
medialis  muscle,  566 
ater,  ampulla  of,  1200 
ein  or  ^'eins,  of  abdomen,  759 
anastomotic,  of  Labbe,  739 
angular,  733 
auditory,  internal,  1067 
auricular,  posterior,  734 
axillary,  750 
azygos,  753 
basal,  740 
basilic.  748 

median,  747 
basivertebral,  755 
brachial,  750 
brachiocephalis,  751 
of  brain,  739 
bronchial,  754,  llOS 
cardiac,  730' 

anterior,  731 

great,  730 

small,  730 

smallest,  731 
cardinal,  157 
cava,  inferior,  762 

superior,  753 
cephalic,  747 

accessory,  748 
cerebellar.  740 
cerebral,  739,  740 

anterior,  740 

choroid.  740 

deep  middle,  740 

external,  739 

great,  740 

inferior,  739 

internal,  740 

middle,  739 

superior,  739 

terminal,  740 
cervical,  deep,  738 
choroid.   740 
coats  of,  599 
comitans,  of  hypoglossal  nerve, 

736 
common  facial,  733 

iliac,  762 

peculiarities  of,  762 
coronary,  730 

of  stomach,  766 
of  corpus  striatum,  885 
cystic,  767 
deep  cerebral,  740 

facial,  733 

of  forearm,  750 

of  hand,  750 

of  lower  extremity,  758 

of  upper  extremity,  750 
development  of,  154 
digital,  of  foot,  756 

of  hand,  747 
diploic,  738 
dorsal  digital,  747 

metacarpal,  747,  750 

of  penis,  761 
emissary,  746 

applied  anatomy  of,  747 
epigastric,  760 

deep,  760 

superficial,  756 


INDEX 


Vein  or  Veins,  extrastiinal.  754 
facial.  733 

anterior,  733 

common,  733 

dei'p,  733 

posterior,  734 

transverse,  734 
femoral,  758 
frontal,  732 
of  Galen,  740 
gastric,  short,  766 
gastroepiploic,  766 
gluteal,  760 
of  hand, 747,  750 
of  head  and  neck,  731 
of  heart,  730 
hemiazygos,  753 
hemorrhoidal,  inferior,  761 

middle,  760 

superior,  766 
hepatic,  764 
highest  intercostal,  753 
histology  of,  599 
hypogastric.  760 
iliac,  circumflex,  deep,  760 
superficial,  756 

common,  762 

external,  759 

internal,  760 
iliolumbar,  762 
inferior  cava,  762 

thyroid.  751 
innominate,  751 
intercapitular,  747,  756 
intercostal,  highest,  753 
interlobular,  of  kidnev,  1214 

of  liver,  119S 
internal  mammary,  751 
intervertebral,  755 
intralobular,  of  liver,  1198 
intraspinal,  755 
jugular,  anterior,  736 

external,  734 
posterior,  736 

internal,  736 

primitive,  157 
of    Labbe,     posterior     anasto- 
motic. 739 
labial,  733 
lateral  sacral,  760 
of  left  atrium,  603 
lienal  or  splenic,  765 
lingual,  736 

of  lower  extremity,  755 
lumbar,  763 

ascending,  753 
mammary,  internal,  751 
marginal,  of  foot,  756 
masseteric,  733 
maxillary,  internal,  734 
median  antibrachial,  749 

basilic,  747 
of  medulla  spinalis,  755 
mesenteric,  766 
metatarsal,  758 
middle  cardiac,  731 

sacral,  762 
nasofrontal.  745 
of  neck,  734 
oblique,   of  left    atrium  [JNIar- 

shalli],  159,  603,  731 
obturator,  760 
occipital,  734 
ophthalmic,  745 
orbital,  734 
ovarian,  764 
palpebral,  733 
pancreatic,  766 
pancreaticoduodenal,  766 
parumbilical,  767 
of  pelvis,  759 
penis,  dorsal  of,  761 
peroneal,  758 
pharyngeal,  737 
phrenic,  inferior,  764 


1405 


Vein  or  \'eins,  phrenic,   superior, 

751 
plantar,  758 
popliteal.  758 
portal,  764 

applied  anatomy  of,  707 
posterior  of  left  ventricle,  731 
primitive  jugular,  157 
profunda  femoris,  759 
prostatic  plexus,  761 
pterygoid  plexus,  734 
pubic,  760 
pudendal  internal,  760 

plexus,  761. 
pudic,  750,  700 
pulmonary,  730 
pyloric,  766 
ranine.  736 
renal,  764,  1214 
sacral,  760,  762 
saphenous,  757 

applied  anatomy  of,  757 
sciatic,  760 
short  gastric,  766 
spermatic,  763 
of  spinal  cord,  755 
splenic  or  lienal,  765 
striate,  inferior,  740 
structure  of,  599 
stylomastoid,  734 
subcardinal,  157 
subcla\'ian,  750 
sublobular,  of  liver,  1198 
submaxillary,  733 
submental,  733 
superficial,  729 

of  lower  extremity,  756 

applied  anatomy  of,  757 

of  upper  extremity,  747 

applied  anatomy  of,  749 
superior  cava,  753 

mesenteric,  766 

phrenic,  751 
supraorbital,  733 
suprarenal,  764 
Syh-ian,  739,  740 
systemic,  730 
temporal,  733 
temporomaxillary,  734 
terminal,  740 
of  Thebesius,  731 
thoracoepigastric,  756 
of  thorax,  751 
thyroid,  inferior,  751 

middle,  737 

superior,  737 
tibial,  758 
transverse  cervical,  735 

facial,  734 

scapular,  735 
Trolard,  great  anastomotic  of, 

739 
umbUical,  100,  145 

obliterated,  765,  1150 
of  upper  extremity,  747 
uterine  plexuses,  761 
vaginal  plexuses,  762 
valves  of,  599 
vena  azygos  major,  753 
minor  inferior,  753 

cava,  inferior,  762 

superior,  753 

vertebral  anterior,  738 

plexuses,  754 

posterior,  738 
of  vertebral  column,  754 
vesical  plexus,  761 
vesicoprostatic  plexus  of,  761 
visceral,  155 
vitelline,  144.  155 
volar  digital,  747,  750 

metacarpal,  750 
Velamentous    insertion    of    um- 
bilical cord,  102 
Velum  inter positum,  888 


1406 


INDEX 


Velum  medullare  anterius,  842 
posterius,  842 
medullary,  842,  845 
palatine,  1112 
Vena  angularis,  733 
anonyma  dextra,  751 

siniMra,  751 
auricularis  posterior,  734 
axillaris,  750 
azygos,  753 
major,  753 
minor  inferior,  753 
superior,  753 
basilica,  74S 
capitis  lateralis,  160 

medialis.,  160 
ca^Ja  inferior,  762 

applied  anatomy  of,  762 
development  of,  157 
fossa  for.  1194 
peculiarities  of,  762 
valve  of,  762 
superior,  753 

applied  anatomy  of,  754 
development  of,  157 
surface  marking  of,  1300 
caval  foramen  in  diaphragm,496 
cephalica  accessoria,  748 
cerebri  magna,  740 

media,  739 
cervicalis  profunda,  738 
circumjlexa  ilium  profunda,  760 
comitans  of  hypoglossal  nerve, 

733,  736 
cordis  magna,  730 
media,  731 
parva,  736 
coronaria  ventriculi,  766 
corporis  striata,  740 
cystica,  767 

epigasfrica  inferior,  760 
facialis  anterior,  733 

posterior,  734 
femoralis,  758 
frontalis,  732 
gastroepiploica  dextra,  766 

sinistra,  766 
haemorrhoidalis  media,  760 
hemiazygos,  753 
accessoria,  753 
hypogastrica,  760 
iliaca,  externa,  759 
intercostalis     suprema     dextra, 
753 
sinister,  753 
jugularis  anterior,  736 
externa,  734 
interna,  736 
posterior,  736 
linealis,  765 

magna  [Galeni],  740,  889 
maxillaris  interna,  734 
mediana  antibrachii,  749 

cuhiti,  747 
mesenterica  inferior,  766 

superior,  766 
obliqua  atrii  sinistri  [Marshalli], 

731 
obturatoria,  760 
occipitalis,  734 
ophthalmica,  inferior,  746 

superior,  745 
poplitea,  758 
portae,  764 

posterior  ventriculi  sinistri,  731 
profunda  femoris,  759 
saphena  magna,  756 

parva,  757 
subclavia,  750 
supraorbitalis,  733 
temporalis  superficialis ,  733 
terminalis,  740 
thyreoidea  superioris,  737 
vertebralis,  738 
Venae  advehentes,   155 


Fenae  ano7iymae,  751 
liasivertebrales ,  755 
brachiales,  750,  754 
cerebelli  inferiores,  740 

superior es,  740 
cerebri,  739 
inferiores,  739 
internae,  740 
superiores,  739 
comitantes,  729 
cordis,  730 

minimae,  608 
digitales  plantar  es,  758 
diploicae,  73S 
dorsales  penis,  761 
Galeni,  889 
gastricac  breves,  766 
glutaeae  inferiores,  760 

superiores,  760 
hepaticae,  764 
iliacae  communes,  762 
intervertebrales ,  755 
linguales,  736 
lumbales,  763 
mammariae  ijiternae,  751 
ovariacae,  764 
pancreaticae,  766 
pancreaticoduodenales,  766 
parumbilicales,  767 
pharyngeae,  737 
phrenicae  inferiores,  764 
propriae  renales,  1214 
pulmonales,  736 
rectae  [kidney],  1214 
renales,  764 
revehenies,  156 
sacrales  laterales,  760 

mediales,  762 
spermaticae,  763 
spinales,  755 
stellatae  [kidneyl,  1214 
suprarenales,  764 
thyreoideae  inferiores,  751 
tibialis  anteriores,  758 

posteriores,  758 
vorficosae,  1022,  1031 
Venesection,  749 
Venous  arch,  dorsal,  756 
plantar  cutaneous,  756 
lacunae  of  dura  mater,  741 
mesocardium,  603 
plexus,  ovarian,  764,  1246 
pampiniform,  763, 1230, 1246 
pharyngeal,  737 
pterygoid,  734 
pudendal,  761 
spermatic,  763,  1230 
uterine,  761 
vaginal,  762 
sinuses,  727 

of  dura  mater,  740 
valves,  right  and  left,  146 
Ventral  aorta?,  145 
cochlear  nucleus,  836 
fissure    of   medulla    oblongata, 

822 
lamina,  119 
mesogastrium,  168 
pulmonary  nerves,  943 
spinal  artery,  660 
Ventricle  of  fornix,  886 
fourth,  floor  of,  847 
of  mid-brain,  854 
terminal,  of    medulla  spinalis, 

810 
of  Verga,  886 
Ventricles  of  brain,  fourth,  845 
lateral,  877 
third,  864 
of  heart,  left,  611 
pi'imitive,  145 
right,  608 
of  larynx,  1086 
Ventricular  folds  ot  larynx,  1085 
ligament  of  larynx,  1085 


Ventricular  septum,  149,  612 
Ventriculus,  1161 
dea-/er,  60S 

laryngis  [Morgagni],  1086 
lateralis,  877 

pars  centralis,  877 
quartus,  845 
tela  submucosa,  1165 
terlius,  864 
tunica  mucosa ,  1165 
muscularis,  1164 
fibrae  obliquae,  1164 
stratum  circularis,  1164 
longitudinale,  1164 
serosa,  1164 
Ventromedian  fissure  of  medHlla 

oblongata,  822  ^ 

Verga,  ventricle  of,  886 
Vermian  fossa,  228 
Vermiform  process  or  appendix, 
1178 
structure  of,  1178 
Verinis  of  cerebellum,  837 
Vernix  caseosa,  116 
Vertebra,  anticlinal,  202  ?io/e 
prominens,  201 
ossification  of,  211 
Vertebras,  196 
cervical,  198 
cervicales,  198 
characteristics  of,  197 
coccygeal,  205 
ligaments  of,  384-386 
lumbales,  204 
lumbar,  204 
ossification  of,  210 
sacral,  205 
sacrales,  205 
structure  of.  197 
thoracales,  201 
thoracic,  201 
Vertebral  arch,  197 

arches,  articulations  of,  386 
artery,  659 
canal,  214 
column,  196,  212 

applied  anatomy  of.  214 
articulations  of,  384 
curves  of,  212 
ossification  of,  210 
surface  form  of,  1293 
veins  of,  754 
foramen,  197 
groove,  214 
notches,  197 

part  of  base  of  skull,  106 
ribs,  221 
vein.  738 

venous  plexuses.  754 
Vertical  index  of  skull,  290 
lingualis  muscle,  1130 
part  of  palatine  bone,  266 
Verticalis  linguae  muscle,  1130 
Verumontanum.  1225 
Vesica  fellea,  1199 

tunica  mucosa,  1199 
muscularis,  1199 
serosa,  1199 
urinaria,  1218 

ieZa  submucosa,  1223 
tunica  mucosa,  1223 
muscularis,  1223 
.serosa,  1223 
Vesical  artery,  701 

layer  of  pelvic  fascia,  512 
plexus  of  nerves,  1005 
of  veins,  761 
Vesicle,  auditory,  138 
blastodermic,  85' 
germinal,  78 
lens,  134 
optic,  126,  134 
Vesicles,  cerebral,  88,  120 
Vesicoprostatic   plexus   of   veins, 
761 


COLUMBIA  UNIVERSITY   LIBRAKIES 

^  ^  ^p.f\r.ite  nenod  after  tr 


COLUMBIA  UNIVERSITY  LIBRARIES  (hsi.stx) 

QM23G79  1913C.1 

.'■ ';  ':  rtppliet! 


2002153319 


DATE  DUE 

OCT  \  -  iQo<  r 

n  p  p  i9< 

'6 

u 

' 

Demco,  Inc.  38-293 

G79 

1913a 


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